HYSYS 3.2 Operations Guide

HYSYS 3.2 Operations Guide
®
HYSYS 3.2
Operations Guide
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OGH3.2-B5025-OCT03-O
Table of Contents
1
2
3
4
5
Operations Overview.................................................. 1-1
1.1
Engineering.......................................................................1-2
1.2
Operations ........................................................................1-5
Sub-Flowsheet Operations......................................... 2-1
2.1
Introduction .......................................................................2-2
2.2
Sub-Flowsheet Property View...........................................2-3
2.3
Adding a Sub-Flowsheet.................................................2-10
2.4
MASSBAL Sub-Flowsheet ..............................................2-12
2.5
Adding a MASSBAL Sub-Flowsheet...............................2-13
Streams ...................................................................... 3-1
3.1
Material Stream Property View .........................................3-2
3.2
Energy Stream Property View.........................................3-30
Heat Transfer Equipment........................................... 4-1
4.1
Air Cooler ..........................................................................4-3
4.2
Cooler/Heater..................................................................4-37
4.3
Heat Exchanger ..............................................................4-55
4.4
Fired Heater (Furnace) .................................................4-125
4.5
LNG...............................................................................4-152
4.6
References....................................................................4-198
Piping Equipment ....................................................... 5-1
5.1
Mixer .................................................................................5-3
5.2
Pipe Segment .................................................................5-10
5.3
Compressible Gas Pipe ..................................................5-71
5.4
Tee..................................................................................5-82
5.5
Valve ...............................................................................5-89
5.6
Relief Valve...................................................................5-109
5.7
References....................................................................5-121
iii
6
7
8
9
Rotating Equipment ................................................... 6-1
6.1
Centrifugal Compressor or Expander ...............................6-2
6.2
Reciprocating Compressor .............................................6-37
6.3
Pump...............................................................................6-50
6.4
References......................................................................6-69
Separation Operations ............................................... 7-1
7.1
Separator, 3-Phase Separator, & Tank.............................7-2
7.2
Shortcut Column .............................................................7-36
7.3
Component Splitter .........................................................7-41
Column........................................................................ 8-1
8.1
Column Sub-Flowsheet.....................................................8-4
8.2
Column Theory ...............................................................8-10
8.3
Column Installation .........................................................8-21
8.4
Column Property View ....................................................8-32
8.5
Column Specification Types .........................................8-103
8.6
Column-Specific Operations .........................................8-116
8.7
Running the Column .....................................................8-166
8.8
Column Troubleshooting...............................................8-169
8.9
References....................................................................8-175
Reactors ..................................................................... 9-1
9.1
CSTR/General Reactors ...................................................9-2
9.2
CSTR/General Reactors Property View............................9-5
9.3
Plug Flow Reactor (PFR) ................................................9-40
9.4
Plug Flow Reactor (PFR) Property View.........................9-42
10 Solid Separation Operations .................................... 10-1
iv
10.1
Simple Solid Separator (Simple Filter)............................10-3
10.2
Cyclone ...........................................................................10-7
10.3
Hydrocyclone ................................................................10-16
10.4
Rotary Vacuum Filter ....................................................10-23
10.5
Baghouse Filter.............................................................10-29
11 Electrolyte Operations ............................................. 11-1
11.1
Introduction .....................................................................11-2
11.2
Neutralizer Operation......................................................11-3
11.3
Precipitator Operation ...................................................11-10
11.4
Crystalizer Operation ....................................................11-17
12 Logical Operations ................................................... 12-1
12.1
Adjust ..............................................................................12-4
12.2
Balance .........................................................................12-19
12.3
Boolean Operations ......................................................12-28
12.4
Control Ops...................................................................12-54
12.5
Digital Point.................................................................12-164
12.6
Parametric Unit Operation ..........................................12-171
12.7
Recycle .......................................................................12-182
12.8
Selector Block .............................................................12-195
12.9
Set...............................................................................12-203
12.10 Spreadsheet................................................................12-206
12.11 Stream Cutter..............................................................12-226
12.12 Transfer Function........................................................12-242
12.13 Controller Face Plate ..................................................12-257
12.14
ATV Tuning Technique ..............................................12-262
13 Optimizer .................................................................. 13-1
13.1
Optimizer.........................................................................13-2
13.2
Original Optimizer ...........................................................13-4
13.3
Hyprotech SQP Optimizer.............................................13-16
13.4
Selection Optimization ..................................................13-21
13.5
Example: Original Optimizer .........................................13-31
13.6
Example: MNLP Optimization .......................................13-40
13.7
References....................................................................13-55
v
14 Utilities ..................................................................... 14-1
14.1
Introduction .....................................................................14-4
14.2
Boiling Point Curves........................................................14-6
14.3
CO2 Solids....................................................................14-14
14.4
Cold Properties .............................................................14-17
14.5
Composition Curves Utility............................................14-21
14.6
Critical Properties..........................................................14-28
14.7
Data Recon Utility .........................................................14-32
14.8
Derivative Utility ............................................................14-33
14.9
Dynamic Depressuring..................................................14-33
14.10 Envelope Utility .............................................................14-58
14.11 Hydrate Formation Utility ..............................................14-65
14.12 Parametric Utility...........................................................14-75
14.13 Pipe Sizing ....................................................................14-91
14.14 Property Balance Utility.................................................14-95
14.15 Property Table ............................................................14-106
14.16 Tray Sizing ..................................................................14-114
14.17 User Properties ...........................................................14-145
14.18 Vessel Sizing ..............................................................14-149
14.19 References..................................................................14-156
Index............................................................................I-1
vi
Operations Overview
1-1
1 Operations Overview
1.1 Engineering ......................................................................................2
1.2 Operations........................................................................................5
1.2.1 Installing Operations.................................................................5
1.2.2 Unit Operation Property View...................................................8
1.2.3 Worksheet Tab .........................................................................9
1-1
1-2
Engineering
1.1 Engineering
As explained in the User Guide and Simulation Basis manuals, HYSYS
has been uniquely created with respect to the program architecture,
interface design, engineering capabilities, and interactive operation.
The integrated steady state and dynamic modeling capabilities, where
the same model can be evaluated from either perspective with full
sharing of process information, represent a significant advancement in
the engineering software industry.
The various components that comprise HYSYS provide an extremely
powerful approach to steady state process modeling. At a fundamental
level, the comprehensive selection of operations and property methods
allows you to model a wide range of processes with confidence. Perhaps
even more important is how the HYSYS approach to modeling
maximizes your return on simulation time through increased process
understanding. The key to this is the Event Driven operation. By using a
‘degrees of freedom’ approach, calculations in HYSYS are performed
automatically. HYSYS performs calculations as soon as unit operations
and property packages have enough required information.
Any results, including passing partial information when a complete
calculation cannot be performed, is propagated bi-directionally
throughout the flowsheet. What this means is that you can start your
simulation in any location using the available information to its greatest
advantage. Since results are available immediately - as calculations are
performed - you gain the greatest understanding of each individual
aspect of your process.
The multi-flowsheet architecture of HYSYS is vital to this overall
modeling approach. Although HYSYS has been designed to allow the use
of multiple property packages and the creation of pre-built templates,
the greatest advantage of using multiple flowsheets is that they provide
an extremely effective way to organize large processes. By breaking
flowsheets into smaller components, you can easily isolate any aspect
for detailed analysis. Each of these sub-processes is part of the overall
simulation, automatically calculating like any other operation.
1-2
Operations Overview
1-3
The design of the HYSYS interface is consistent, if not integral, with this
approach to modeling. Access to information is the most important
aspect of successful modeling, with accuracy and capabilities accepted
as fundamental requirements. Not only can you access whatever
information you need when you need it, but the same information can
be displayed simultaneously in a variety of locations. Just as there is no
standardized way to build a model, there is no unique way to look at
results. HYSYS uses a variety of methods to display process information
- individual property views, the PFD, Workbook, Databook, graphical
Performance Profiles, and Tabular Summaries. Not only are all of these
display types simultaneously available, but through the object-oriented
design, every piece of displayed information is automatically updated
whenever conditions change.
The inherent flexibility of HYSYS allows for the use of third party design
options and custom-built unit operations. These can be linked to HYSYS
through OLE Extensibility.
This Engineering section covers the various unit operations, template
and column sub-flowsheet models, optimization, utilities, and
dynamics. Since HYSYS is an integrated steady state and dynamic
modeling package, the steady state and dynamic modeling capabilities
of each unit operation are described successively, thus illustrating how
the information is shared between the two approaches. In addition to
the Physical operations, there is a chapter for Logical operations, which
are the operations that do not physically perform heat and material
balance calculations, but rather, impart logical relationships between
the elements that make up your process.
The following is a brief definition of categories used in this volume:
Term
Definition
Physical Operations
Governed by thermodynamics and mass/energy balances, as
well as operation-specific relations.
Logical Operations
The Logical Operations presented in this volume are primarily
used in Steady State mode to establish numerical relationships
between variables. Examples include the Adjust and Recycle.
There are, however, several operations such as the
Spreadsheet and Set operation which can be used in steady
state and Dynamic mode.
1-3
1-4
Engineering
Term
Definition
Sub-flowsheets
You can define processes in a sub-flowsheet, which can then
be inserted as a “unit operation” into any other flowsheet. You
have full access to the operations normally available in the
main flowsheet.
Columns
Unlike the other unit operations, the HYSYS Column is
contained within a separate sub-flowsheet, which appears as a
single operation in the main flowsheet.
Integrated into the steady state modeling is multi-variable optimization.
Once you have reached a converged solution, you can construct
virtually any objective function with the Optimizer. There are five
available solution algorithms for both unconstrained and constrained
optimization problems, with an automatic backup mechanism when
the flowsheet moves into a region of non-convergence.
HYSYS offers an assortment of utilities which can be attached to process
streams and unit operations. These tools interact with the process and
provide additional information.
In this manual, each operation is explained in its respective chapters for
steady state and dynamic modeling. A separate manual has been
devoted to the principles behind dynamic modeling. HYSYS is the first
simulation package to offer dynamic flowsheet modeling backed up by
rigorous property package calculations.
HYSYS has a number of unit operations, which can be used to assemble
flowsheets. By connecting the proper unit operations and streams, you
can model a wide variety of oil, gas, petrochemical, and chemical
processes.
Included in the available operations are those which are governed by
thermodynamics and mass/energy balances, such as Heat Exchangers,
Separators, and Compressors, and the logical operations like the Adjust,
Set, and Recycle. A number of operations are also included specifically
for dynamic modeling, such as the Controller, Transfer Function Block,
and Selector. The Spreadsheet is a powerful tool, which provides a link
to nearly any flowsheet variable, allowing you to model “special” effects
not otherwise available in HYSYS.
1-4
Operations Overview
1-5
In modeling operations, HYSYS uses a Degrees of Freedom approach,
which increases the flexibility with which solutions are obtained. For
most operations, you are not constrained to provide information in a
specific order, or even to provide a specific set of information. As you
provide information to the operation, HYSYS calculates any unknowns
that can be determined based on what you have entered.
For instance, consider the Pump operation. If you provide a fullydefined inlet stream to the pump, HYSYS immediately passes the
composition and flow to the outlet. If you then provide a percent
efficiency and pressure rise, the outlet and energy streams is fully
defined. If, on the other hand, the flowrate of the inlet stream is
undefined, HYSYS cannot calculate any outlet conditions until you
provide three parameters, such as the efficiency, pressure rise, and work.
In the case of the Pump operation, there are three degrees of freedom,
thus, three parameters are required to fully define the outlet stream.
All information concerning a unit operation can be found on the tabs
and pages of its property view. Each tab in the property view contains
pages which pertain to a certain aspect of the operation, such as its
stream connections, physical parameters (for example, pressure drop
and energy input), or dynamic parameters such as vessel rating and
valve information.
For information on the
Upstream operations refer to
the Upstream Option Guide.
1.2 Operations
1.2.1 Installing Operations
There are a number of ways to install unit operations into your
flowsheet. The operations which are available depends on where you are
currently working (main flowsheet, template sub-flowsheet or column
sub-flowsheet). If you are in the main flowsheet or template
environments, all operations are available, except those associated
specifically with the column, such as reboilers and condensers. A
smaller set of operations is available within the column sub-flowsheet.
1-5
1-6
Operations
For detailed information on installing unit operations, refer to Section
8.1 - Installing Objects or Section 7.24.2 - Installing Streams or
Operations in the User Guide.
The two primary areas from which you can install operations are the
UnitOps view and the Object Palette.
The operations are divided into categories with each category
containing a number of individual operations. For the main flowsheet,
the available operations are categorized in the following table.
Operation Category
1-6
Types
All
• All Unit Operations
Vessels
•
•
•
•
•
•
•
•
•
•
3-Phase Reboiler
3-Phase Separator
Cont. Stirred Tank Reactor
Conversion Reactor
Equilibrium Reactor
General Reactor
Gibbs Reactor
Reboiler
Separator
Tank
Heat Transfer Equipment
•
•
•
•
•
Air Cooler
Cooler
Heat Exchanger
Heater
LNG
Rotating Equipment
• Compressor
• Expander
• Pump
Piping Equipment
•
•
•
•
•
Mixer
Pipe Segment
Relief Valve
Tee
Valve
Solids Handling
•
•
•
•
•
Baghouse Filter
Cyclone
Hydrocyclone
Rotary Vacuum Filter
Simple Solid Separator
Reactors
•
•
•
•
•
•
Continuous-Stirred Tank Reactor (CSTR)
Conversion Reactor
Equilibrium Reactor
General Reactor
Gibbs Reactor
Plug Flow Reactor (PFR)
Operations Overview
Operation Category
1-7
Types
Prebuilt Columns
•
•
•
•
•
•
•
•
•
•
3 Stripper Crude
4 Stripper Crude
Absorber
Distillation
FCCU Main Fractionator
Liquid-Liquid Extractor
Reboiled Absorber
Refluxed Absorber
Three Phase Distillation
Vacuum Resid Tower
Shortcut Columns
• Component Splitter
Sub-flowsheets
•
•
•
•
•
•
•
•
•
•
•
•
3 Stripper Crude
4 Stripper Crude
Absorber
Column sub-flowsheet
Distillation
FCCU Main Fractionator
Liquid-Liquid Extractor
Reboiled Absorber
Refluxed Absorber
Standard sub-flowsheet
Three Phase Distillation
Vacuum Resid Tower
Logicals
•
•
•
•
•
•
•
•
•
•
Adjust,
Balance
Digital Control Point
PID Controller
Recycle
Selector Block
Set
Spreadsheet
Surge Controller
Transfer Function Block
Extensions
• User Defined
User Ops
• User Defined
Prior to describing each of the unit operations, a quick overview of the
material and energy streams is provided, as they are the means of
transferring process information between operations.
1-7
1-8
Operations
1.2.2 Unit Operation Property View
Although each Unit Operation differs in functionality and operation, in
general, the Unit Operation property view remains fairly consistent in its
overall appearance. The figure below shows a generic property view for a
Unit Operation.
Figure 1.1
The Name
of the Unit
Operation.
The various
pages of the
active tab.
The active
tab of the
property
view.
Deletes the Unit
Operation from the
flowsheet.
Displays the calculation status of the
Unit Operation. It may also display
what specifications are required.
Ignores the Unit
Operation.
The Operation property view can contain several different tabs which
are operation specific, however the Design, Ratings, Worksheet, and
Dynamics tabs can usually be found in each Unit Operation property
view and have similar functionality.
1-8
Tab
Description
Design
Connects the feed and product streams to the Unit Operation. Other
parameters such as pressure drop, heat flow, and solving method
are also specified on the various pages of this tab.
Ratings
Rates and Sizes the Unit Operation vessel. Specification of the tab
is not always necessary in Steady State mode, however it can be
used to calculate vessel hold up.
Worksheet
Displays the Conditions, Properties, Composition, and Pressure
Flow values of the streams entering and exiting the Unit Operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Dynamics
Sets the dynamic parameters associated with the Unit Operation
such as valve sizing and pressure flow relations. Not relevant to
steady state modeling. For information on dynamic modeling
implications of this tab, refer to the Dynamic Modeling manual.
Operations Overview
1-9
1.2.3 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the air cooler.
The Conditions and Composition pages contain selected information
from the corresponding pages of the Worksheet tab for the stream
property view.
The Properties page displays the property correlations of the inlet and
outlet streams of the unit operations. The following is a list of the
property correlations:
The Heat of Vapourisation for
a stream in HYSYS is defined
as the heat required to go
from saturated liquid to
saturated vapour.
• Vapour / Phase Fraction
• Vap. Frac. (molar basis)
• Temperature
• Vap. Frac. (mass basis)
• Pressure
• Vap. Frac. (volume basis)
• Actual Vol. Flow
• Molar Volume
• Mass Enthalpy
• Act. Gas Flow
• Mass Entropy
• Act. Liq. Flow
• Molecular Weight
• Std. Liq. Flow
• Molar Density
• Std. Gas Flow
• Mass Density
• Watson K
• Std. Ideal Liquid Mass Density
• Kinematic Viscosity
• Liquid Mass Density
• Cp/Cv
• Molar Heat Capacity
• Lower Heating Value
• Mass Heat Capacity
• Mass Lower Heating Value
• Thermal Conductivity
• Liquid Fraction
• Viscosity
• Partial Pressure of CO2
• Surface Tension
• Avg. Liq. Density
• Specific Heat
• Heat of Vap.
• Z Factor
• Mass Heat of Vap.
The PF Specs page contains a summary of the stream property view
Dynamics tab.
1-9
1-10
1-10
Operations
Sub-Flowsheet Operations
2-1
2 Sub-Flowsheet Operations
2.1 Introduction......................................................................................2
2.2 Sub-Flowsheet Property View ........................................................3
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
Connections Tab......................................................................4
Parameters Tab .......................................................................6
Transfer Basis Tab...................................................................7
Mapping Tab ............................................................................8
Variables Tab ...........................................................................9
Notes Tab ..............................................................................10
2.3 Adding a Sub-Flowsheet...............................................................10
2.3.1 Read an Existing Template.................................................... 11
2.3.2 Start with a Blank Flowsheet ................................................. 11
2.3.3 Paste Exported Objects......................................................... 11
2.4 MASSBAL Sub-Flowsheet ............................................................12
2.5 Adding a MASSBAL Sub-Flowsheet ............................................13
2.5.1
2.5.2
2.5.3
2.5.4
2.5.5
2.5.6
Connections Tab....................................................................14
Parameters Tab .....................................................................18
Transfer Basis Tab.................................................................21
Mapping Tab ..........................................................................22
Notes Tab ..............................................................................23
Results Tab............................................................................23
2-1
2-2
Introduction
2.1 Introduction
The sub-flowsheet operation uses the multi-level flowsheet architecture
and provides a flexible, intuitive method for building the simulation.
Suppose you are simulating a large processing facility with a number of
individual process units and instead of installing all process streams and
unit operations into a single flowsheet, you can simulate each process
unit inside its own compact sub-flowsheet.
Once a sub-flowsheet operation is installed in a flowsheet, its property
view becomes available just like any other flowsheet object. Think of this
view as the “outside” view of the “black box” that represents the subflowsheet. Some of the information contained on this view is the same
as that used to construct a Template type of Main flowsheet. Naturally
this is due to the fact that once a Template is installed into another
flowsheet, it becomes a sub-flowsheet in that simulation.
Whether the flowsheet is the Main flowsheet of a simulation case, or it is
contained in a sub-flowsheet operation, it possesses the following
components:
•
•
•
•
•
2-2
Fluid Package. An independent fluid package, consisting of a
Property Package, Components, etc. It is not necessary that
every flowsheet in the simulation have its own separate fluid
package. More than one flowsheet can share the same fluid
package.
Flowsheet Objects. The inter-connected topology of the
flowsheet. Unit operations, material and energy streams, utilities
etc.
A Dedicated PFD. A HYSYS view presenting a graphical
representation of the flowsheet, showing the inter-connections
between flowsheet objects.
A Dedicated Workbook. A HYSYS view of tabular information
describing the various types of flowsheet objects.
A Dedicated Desktop. The PFD and Workbook are home views
for this Desktop, but also included are a menu bar and a tool bar
specific to either regular or Column Sub-flowsheets.
Sub-Flowsheet Operations
2-3
2.2 Sub-Flowsheet Property View
The Sub-flowsheet property view consists of the following six tabs:
•
•
•
•
•
•
Connections
Parameters
Transfer Basis
Mapping
Variables
Notes
Figure 2.1
Click this button to delete
the sub-flowsheet.
Click this button to enter the
sub-flowsheet environment.
2-3
2-4
Sub-Flowsheet Property View
2.2.1 Connections Tab
You can enter the name of the sub-flowsheet, as well as its Tag name, on
the Connections tab. All feed and product connections appear on the
Connections tab.
Figure 2.2
Flowsheet Tags
These short names are used by HYSYS to identify the flowsheet
associated with a stream or operation when that flowsheet object is
being viewed outside of its native flowsheet scope. The default Tag name
for a sub-flowsheet operation is TPL1 (for Template).
When more than one sub-flowsheet operation is installed, HYSYS
ensures unique tag names by incrementing the numerical suffix; the
sub-flowsheets are numbered sequentially in the order they were
installed. For example, if the first sub-flowsheet added to a simulation
contained a stream called Comp Duty, it would appear as Comp
[email protected] when viewed from the Main flowsheet of the simulation.
2-4
Sub-Flowsheet Operations
2-5
Feed and Product Connections
Internal streams are the boundary streams within the sub-flowsheet that
can be connected to external streams in the Parent flowsheet. Internal
streams cannot be specified on this tab, they are automatically
determined by HYSYS. Basically, any streams in the sub-flowsheet that
are not completely connected (i.e.,”open ended”) can serve as a feed or
product.
Sub-flowsheet streams that are not connected to any unit operations in
the sub-flowsheet appear in the view as well (and are termed “dangling
streams”).
Figure 2.3
To connect the sub-flowsheet, specify the appropriate name of the
external streams, which are in the Parent flowsheet, in the matrix
opposite the corresponding internal streams, which are in the subflowsheet. The stream conditions are passed across the flowsheet
boundary via these connections.
It is not necessary to specify an external stream for each internal
stream.
2-5
2-6
Sub-Flowsheet Property View
2.2.2 Parameters Tab
You can view the exported sub-flowsheet variables on the Parameters
tab, which allows you to keep track of several key variables without
entering the sub-flowsheet environment or adding the variables to the
global DataBook. It is also useful when dealing with a sub-flowsheet as a
“black box”. The user who created the sub-flowsheet can set up an
appropriate Parameters tab, and another user of the sub-flowsheet can
be unaware of the complexities within the sub-flowsheet.
Figure 2.4
These variables display values, which have been calculated or specified
by the user. If changes to the specified values are made here, the subflowsheet is updated accordingly. For each variable, the description,
value, and units are shown.
The Ignore checkbox is used to bypass the sub-flowsheet during
calculations, just as with all HYSYS unit operations.
These variables are actually added on the Variables tab of the property
view, but are viewed in full detail on the Parameters tab.
2-6
Sub-Flowsheet Operations
2-7
2.2.3 Transfer Basis Tab
The Transfer Basis is also
useful in controlling VF, T or P
calculations in column subflowsheet boundary streams
with close boiling or nearly
pure compositions.
The transfer basis for each Feed and Product Stream is listed on the
Transfer Basis tab. The transfer basis only becomes significant when the
sub-flowsheet and Parent flowsheet’s fluid packages consist of different
property methods. The transfer basis is used to provide a consistent
means of switching between the different basis of the various property
methods.
Transfer Basis
Description
T-P Flash
The Pressure and Temperature of the Material stream are passed
between flowsheets. A new Vapour Fraction is calculated.
VF-T Flash
The Vapour Fraction and Temperature of the Material stream are
passed between flowsheets. A new Pressure is calculated.
VF-P Flash
The Vapour Fraction and Pressure of the Material stream are
passed between flowsheets. A new Temperature is calculated.
P-H Flash
The Pressure and Enthalpy of the Material stream are passed
between flowsheets.
User Specs
You define the properties passed between flowsheets for a Material
stream.
None Required
No calculation is required for an Energy stream. The heat flow is
simply passed between flowsheets.
Figure 2.5
2-7
2-8
Sub-Flowsheet Property View
2.2.4 Mapping Tab
Component Maps can be
created and edited in the
Basis environment.
The Mapping tab allows you to map fluid component composition
across fluid package boundaries. Composition values for individual
components from one fluid package can be mapped to a different
component in an alternate fluid package. Mapping is especially useful
when dealing with hypothetical oil components where like components
from one fluid package can be mapped across the sub-flowsheet
boundary to another fluid package.
Refer to Section 6.2 Component Maps Tab in
the Simulation Basis
manual for more
information.
For every pairing of different fluid packages, a collection of maps exists.
Component maps can be added to each collection on the Component
Maps tab in the Simulation Basis Manager view.
Figure 2.6
To attach a component map to inlet and outlet streams, select the name
of the inlet component map in the In to Sub-Flowsheet field and the
name of the outlet component map in the Out of Sub-Flowsheet field of
the desired stream.
Click the Overall Imbalance Into Sub-Flowsheet button or Overall
Imbalance Out of Sub-Flowsheet button to open the Untransferred
Component Info view. The Untransferred Component Info view allows
you to confirm that all of the components have been transferred into or
out of the sub-flowsheet.
2-8
Sub-Flowsheet Operations
2-9
2.2.5 Variables Tab
The Variables tab of the Main flowsheet property view allows you to
create and maintain the list of Externally Accessible Variables.
Figure 2.7
Although you can access any information inside the sub-flowsheet using
the Variable Navigator, the features on the Variables tab allow you to
target key process variables inside the sub-flowsheet and display their
values on the property view. Then, you can conveniently view this whole
group of information directly on the sub-flowsheet property view in the
Parent flowsheet.
Refer to Section 11.21 Variable Navigator in the
User Guide for details on the
Variable Navigator.
To add variables:
1.
Click the Add button. The Variable Navigator appears.
2.
On the Variable Navigator view, select the flowsheet object and
variable you want.
You can also over-ride the default variable description displayed in
the Variable Description field of the Variable Navigator view.
The sub-flowsheet variables appear on the Parameters tab.
2-9
2-10
Adding a Sub-Flowsheet
2.2.6 Notes Tab
For more information, refer to
Section 7.20 - Notes
Manager in the User Guide.
The Notes tab provides a text editor where you can record any
comments or information regarding the material stream or to your
simulation case in general.
2.3 Adding a Sub-Flowsheet
You can also add a subflowsheet by clicking the F12
hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways you can add a sub-flowsheet to your simulation.
1.
From the Flowsheet menu, select the Add Operation command. The
UnitOps view appears.
2.
Click the Sub-Flowsheets radio button.
3.
From the list of available unit operations, select Standard SubFlowsheet.
4.
Click the Add button. The Sub-Flowsheet Option view appears.
OR
Sub-Flowsheet icon
5.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
6.
Double-click on the Sub-Flowsheet icon on the Object Palette.
7.
The Sub-Flowsheet Option view appears.
Figure 2.8
The Sub-Flowsheet Option view contains the following options:
•
•
•
•
2-10
Read an Existing Template
Start with a Blank Flowsheet
Paste exported objects
Cancel
Sub-Flowsheet Operations
2-11
2.3.1 Read an Existing Template
If you want to use a previously constructed Template that has been
saved on disk, click the Read an Existing Template button on the SubFlowsheet Option view. For more information, refer to Section 3.5.2 Creating a Template Style Flowsheet in the User Guide.
2.3.2 Start with a Blank Flowsheet
If you click the Start with a Blank Flowsheet button on the SubFlowsheet Option view, HYSYS installs a sub-flowsheet operation
containing no unit operations or streams. The property view of the subflowsheet appears, and on the Connections tab, there are no feed or
product connections (boundary streams) to the sub-flowsheet. You can
connect feed streams in the External Stream column by either typing in
the name of the stream to create a new stream or selecting a pre-defined
stream from a drop-down list. When an external feed connection is
made by selecting a pre-defined stream from the drop-down list, a
stream similar to the pre-defined stream is created inside the subflowsheet environment.
In order to fully define the flowsheet, you have to enter the subflowsheet environment. Click the Sub-Flowsheet Environment button
on the property view to transition to the sub-flowsheet environment
and its dedicated Desktop. You construct the sub-flowsheet in the same
way as the main flowsheet. When you return to the Parent environment,
you can connect the sub-flowsheet boundary streams to streams in the
Parent flowsheet.
2.3.3 Paste Exported Objects
If you click the Paste Exported Objects button on the Sub-Flowsheet
Option view, HYSYS imports previously exported objects into a new subflowsheet. The objects that are selected and exported via the PFD can be
imported back into a flowsheet without creating a new sub-flowsheet
first. You can copy and paste selected objects inside the same
subflowsheet or another sub-flowsheet. You can also copy and paste
Sub-flowsheets and column sub-flowsheets. Objects can also be moved
into or out of a sub-flowsheet.
2-11
2-12
MASSBAL Sub-Flowsheet
2.4 MASSBAL Sub-Flowsheet
HYSYS solves as a sequential modular solver. Unit operations must have
specific degrees of freedom in order for the unit operation to solve.
MASSBAL is a simultaneous solver. In MASSBAL, a completely specified
problem requires that there be no degrees of freedom remaining for the
flowsheet, however, the specifications are restricted on a unit by unit
basis and can be specified anywhere in the flowsheet.
The task is to allow you to use MASSBAL within a HYSYS interface. The
design has two modes of operation:
•
Generating Cases via the MASSBAL flowsheet. Within the
MASSBAL flowsheets in HYSYS, you can create HYSYS unit
operations that can either be solved sequentially or
simultaneously. You can select unit operations and streams from
the Object Palette and create the PFD in the MASSBAL
flowsheet. You can also make a list of specifications within the
MASSBAL flowsheet. Upon calculating simultaneously,
MASSBAL uses the specifications to create results files.
Reading in Previously Created Cases. You also have the option
of reading in previously created cases into HYSYS. You can run
previously created cases but cannot modify the cases through the
HYSYS interface. You have to modify the *.dat files directly.
•
Other important information:
•
•
2-12
Solving Backwards. All source streams in the MASSBAL
flowsheet have to be fully specified (Phase Rule has to be
satisfied for each stream). Specifications can be made
elsewhere in the flowsheet.
Thermo Interfaces. MASSBAL has many different possible
stream definitions (e.g., Chemical, VLE, Fluid, Food, Pulp).
The only one used in HYSYS, however, is the VLE stream
type. Thus, in order for MASSBAL to use HYSYS to perform
its thermodynamic calculations, callback functions have been
set up to deal with flashes and property calculations of
individual components and streams.
Sub-Flowsheet Operations
2-13
2.5 Adding a MASSBAL SubFlowsheet
You can also add a
MASSBAL sub-flowsheet by
clicking the F12 hot key.
There are two ways you can add a MASSBAL sub-flowsheet to your
simulation.
You can also open the
Object Palette by clicking the
F4 hot key.
1.
From the Flowsheet menu, select the Add Operation command. The
UnitOps view appears.
2.
Click the Sub-Flowsheets radio button.
3.
From the list of available unit operations, select MassBal
SubFlowsheet.
4.
Click the Add button. The MASSBAL property view appears.
OR
MassBal icon
5.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
6.
Double-click on the MassBal icon on the Object Palette.
7.
The MASSBAL property view appears.
Figure 2.9
You can enter
the MASSBAL
sub-flowsheet
environment
by clicking this
button.
You can delete the MASSBAL operation by clicking this button.
2-13
2-14
Adding a MASSBAL Sub-Flowsheet
The MASSBAL property view consists of six tabs:
•
•
•
•
•
•
Connections
Parameters
Transfer Basis
Mapping
Notes
Results.
The following sections describe each tab.
2.5.1 Connections Tab
The Connections tab allows you to choose between opening a
previously created case or generating a case in the MASSBAL flowsheet.
The table below briefly describes the four groups on the Connections
tab.
The Solving Mode group is
only available if you select
the Read from Flowsheet
radio button in the Mode
group.
Group
Description
Mode
Click on one of the radio buttons to select the mode you
want to use. There are two radio buttons:
• Read from File. Select this radio button if you want to
use an existing case. For more information, refer to the
section on Reading in Previously Created Cases.
• Read from Flowsheet. Select this radio button if you
want to generate a case in the MASSBAL flowsheet.
For more information refer to the section on
Generating Cases via the MASSBAL Flowsheet.
Solving Mode
Select one of the radio buttons to choose the mode you want
to use:
• MASSBAL
• Sequential Modular
Feed Connections to
Sub-Flowsheet
Allows you to select the external stream you want to enter
the MASSBAL sub-flowsheet. In the External Stream
column, you can either type in the name of the stream or you
can select a pre-defined stream from the drop-down list.
Product Connections
to Sub-Flowsheet
Allows you to select the external stream you want to exit the
MASSBAL sub-flowsheet. In the External Stream column,
you can either type in the name of the stream or you can
select a pre-defined stream from the drop-down list.
You can change the name of the MASSBAL operation or the Tag name by
typing the new name in the Name field or Tab field respectively.
2-14
Sub-Flowsheet Operations
2-15
Reading in Previously Created Cases
To read a previously created case in the MASSBAL flowsheet, a *.dat file
must be provided containing information of a case.
1.
On the Connections tab of the MASSBAL property view, click the
Read From File radio button in the Mode group.
Figure 2.10
The File Name
display field shows
the path and the
name of file being
used.
The Sub-Flowsheet
Environment button
appears greyed
because you are
not allowed to
modify the case
within the HYSYS
interface.
2.
Click the Open Model button. The Choose a MASSBAL File view
appears.
3.
From the list of file names, select the *.dat file containing the
information you want
4.
Click the OK button.
The name of the file and path appears in the File Name field of the
MASSBAL property view.
2-15
2-16
Adding a MASSBAL Sub-Flowsheet
Generating Cases via the MASSBAL Flowsheet
To generate cases via the MASSBAL flowsheet, the MASSBAL flowsheet is
like a sub-flowsheet or template. You can enter the MASSBAL flowsheet
environment and build the simulation case just like a flowsheet.
1.
On the Connections tab of the MASSBAL property view, select the
Read From Flowsheet radio button in the Mode group.
Figure 2.11
The Solving Mode
group contains the
two solving modes.
Select one of the
modes using the
radio button.
The Create
Initialize File button
is only available
when Sequential
Modular radio
button is selected.
2.
In the Solving Mode group, select one of the radio buttons to set how
you want to write out to streams:
•
•
MASSBAL. The MASSBAL flowsheet writes out calculated
values to streams and pertinent unit operations. You can also
view the MASSBAL results for the PH1 and PH2 files on the
Results tab.
Sequential Modular. The MASSBAL flowsheet solves using the
HYSYS solver. You have the option of running MASSBAL on the
existing operations. The only difference is that the stream results
of MASSBAL won’t be printed to any of the streams in Sequential
Modular mode.
Click the Create Initialize File button to create a *.sav file
containing initial estimates for the solver calculations. The *.sav
file can be accessed using the Use Initialize File checkbox in the
Parameters tab.
2-16
Sub-Flowsheet Operations
3.
2-17
Click the Sub-Flowsheet Environment button to enter the
MASSBAL flowsheet environment.
A MASSBAL Object in HYSYS is a flowsheet object (similar to a template
object) that holds all streams or unit operations subject to the equation
based solver.
Refer to Chapter 8 - HYSYS
Objects in the User Guide
for more information
regarding installing streams
and operations.
4.
Enter the material streams and unit operations in the MASSBAL PFD
to create the simulation case.
The stand alone MASSBAL application uses a graphical interface to
create a *.dat file. The .dat file is a text file containing the streams,
unit operations, connections, and any specifications the case may
have. The *.dat file is used by HYSYS to generate simulation results.
HYSYS is able to translate the following unit operations: Separator,
Heat Exchanger, Valve, Heater, Cooler, Compressor, Expander,
Pump, Mixer, Tee, Recycle, Adjust, and Set.
The concept of the stream in HYSYS is different from that in
MASSBAL. HYSYS streams are flowsheet objects with properties/
characteristics (and can exist without unit operations) whereas
MASSBAL streams are connections between unit operations. Special
streams known as Sources feed into unit operations and are fully
defined for VLE cases. Streams that exit the flowsheet are known as
Sinks.
In MASSBAL, convention dictates that streams are defined as either
feeds to a unit operation, or products of a unit operation. In
generating identifiers for streams, HYSYS has associated each
stream as the product of the immediate upstream unit operation.
This works for all streams except Source streams, which are fully
defined.
Refer to Section 2.5.2 Parameters Tab for more
information.
5.
On the Parameters tab:
•
•
•
Select the option for the convergence process.
Enter specifications used for the MASSBAL equation-based
solver.
Manipulate the solving behaviour of the MASSBAL flowsheet.
2-17
2-18
Adding a MASSBAL Sub-Flowsheet
2.5.2 Parameters Tab
The Parameters tab allows you to specify variables used for the
MASSBAL equation-based solver, select derivative options to help the
calculations converge, and manipulate the solving behaviour.
Figure 2.12
MASSBAL Specifications Group
The MASSBAL Specifications group contains a table and four buttons
that allows you to manipulate the specifications for the MASSBAL
equation-based solver.
The table contains the list of variables that are used for the
specifications. The Value column allows you to specify the variables
value. The Units column allows you to specify the units for the variable
values entered.
Clicking the Populate Specifications button tells HYSYS to check for unit
operations or streams (except SOURCE streams) with specified values
and adds them to the list of specifications.
The Degrees of Freedom field displays the number of degrees of
freedom available. The number of degrees of freedom is not applicable
to the Sequential Modular solving mode.
2-18
Sub-Flowsheet Operations
2-19
Adding a Specification
To add a MASSBAL specification, do the following:
1.
On the Parameters tab of the MASSBAL property view, click the Add
Specification button in the MASSBAL Specifications group. The Add
Variable To Mass view appears.
Figure 2.13
The Add Variable To Mass
view is similar to the
Variable Navigator view.
Refer to Section 11.21 Variable Navigator in the
User Guide on how to
select variables from the
Variable Navigator view.
2.
Select the variable you want to specify.
3.
Click the OK button.
You are automatically returned to the Parameters tab. The table in
the MASSBAL Specifications group displays the variable selected
from the Add Variable To Mass view.
Editing a Specification
To edit a MASSBAL specification:
The Add Variable To Mass
view is similar to the
Variable Navigator view.
Refer to Section 11.21 Variable Navigator in the
User Guide on how to
select variables from the
Variable Navigator view.
1.
On the Parameters tab of the MASSBAL property view, select the
variable you want to edit from the table.
2.
Click on the Edit Specification button in the MASSBAL
Specifications group. The Add Variable To Mass view appears.
3.
Select the new variable you want to specify and click the OK button.
You are automatically returned to the Parameters tab. The table in
the MASSBAL Specifications group displays the new variable
selected from the Add Variable To Mass view.
2-19
2-20
Adding a MASSBAL Sub-Flowsheet
Deleting a Specification
To delete a MASSBAL specification:
1.
On the Parameters tab of the MASSBAL property view, select the
variable you want to delete from the table.
2.
Click on the Delete Specification button in the MASSBAL
Specifications group. The selected variable is removed from the
table.
Solving Behaviour Group
All options, except Ignored,
in the Solving Behaviour
group are only available if
the Read From Flowsheet
and MASSBAL radio buttons
are selected.
The derivative options are located in the Solving Behaviour group. To
activate the derivative options click their respective checkbox and radio
buttons.
•
•
•
•
Analytical Derivatives
Use Constraints
Forward Finite Difference
Central Finite Difference
The Solving Behaviour group also contains options to manipulate the
solving behaviour of the MASSBAL flowsheet.
•
•
The Create Initial File button
is only available when the
solving mode is Sequential
Modular.
•
Calculate with every Solve. When this checkbox is activated,
the solver behaves like a regular HYSYS case. If there are
changes upstream of the MASSBAL operation, then it
automatically resolves. When the checkbox is deactivated, you
are required to click the Calculate button to get MASSBAL to
recalculate each time.
The Calculate button is greyed out and made unavailable when
the Calculated with every Solve checkbox is activated.
Maximum Iterations. The value in this field sets the maximum
number of iterations that the solver is allowed to perform
regardless if the solution is converged or not. You can change the
value in this field.
Use Initialize File. When this checkbox is activated, a *.sav file is
used as initial estimates for the Mass solver. The *.sav file is
created when you click the Create Initial File button on the
Connections tab. Activating this option can aid in the
convergence of cases by providing the solver with better initial
values.
Activate the Ignored checkbox to ignore the options and settings in the
Solving Behaviour group.
2-20
Sub-Flowsheet Operations
2-21
If the Read From File radio button is selected, the specifications and
degrees of freedom on the Parameters tab are not applicable. You are not
allowed to modify the cases within the HYSYS interface.
Figure 2.14
2.5.3 Transfer Basis Tab
The Transfer Basis is also
useful in controlling VF, T or P
calculations in column subflowsheet boundary streams
with close boiling or nearly
pure compositions.
The transfer basis for each feed and product stream is listed on the
Transfer Basis tab.
Figure 2.15
2-21
2-22
Adding a MASSBAL Sub-Flowsheet
The transfer basis becomes significant only when the sub-flowsheet and
Parent flowsheet fluid packages consist of different property methods.
Refer to Section 2.2.3 - Transfer Basis Tab for more Information.
2.5.4 Mapping Tab
Refer to Chapter 6 Component Maps in the
Simulation Basis manual
for more information.
The Mapping tab allows you to map fluid component composition
across fluid package boundaries. Refer to Section 2.2.4 - Mapping Tab
for information.
Figure 2.16
To attach a component map to inlet and outlet streams, specify the
name of the inlet component map in the In to Sub-Flowsheet field and
the name of the outlet component map in the Out of Sub-Flowsheet
field of the desired stream.
Component Maps can be created and edited in the Basis environment.
Click the Overall Imbalance Into Sub-Flowsheet or Overall Imbalance
Out of Sub-Flowsheet button to open the Untransferred Component
Info view. The Untransferred Component Info view allows you to
confirm that all of the components have been transferred into or out of
the sub-flowsheet.
2-22
Sub-Flowsheet Operations
2-23
2.5.5 Notes Tab
For more information, refer to
Section 7.20 - Notes
Manager in the User Guide.
The Notes tab provides a text editor where you can record any
comments or information regarding the material stream or your
simulation case in general.
2.5.6 Results Tab
The calculated result from MASSBAL appears on the Results tab.
Figure 2.17
2-23
2-24
2-24
Adding a MASSBAL Sub-Flowsheet
Streams
3-1
3 Streams
3.1 Material Stream Property View .......................................................2
3.1.1 Worksheet Tab.........................................................................4
3.1.2 Attachments Tab ....................................................................24
3.1.3 Dynamics Tab ........................................................................27
3.2 Energy Stream Property View ......................................................30
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
Stream Tab ............................................................................32
Unit Ops Tab ..........................................................................32
Dynamics Tab ........................................................................33
Stripchart Tab.........................................................................33
User Variables Tab.................................................................33
3-1
3-2
Material Stream Property View
3.1 Material Stream Property View
Material streams are used to simulate the material travelling in and out
of the simulation boundaries and passing between unit operations. For
the material stream you must define their properties and composition
so HYSYS can solve the stream.
You can also add a new
material stream by pressing
the F11 hot key.
You can also open the
Object Palette by pressing
the F4 hot key.
There are two ways that you can add a Material stream to your
simulation:
1.
In the Flowsheet menu, select the Add Stream command. The
Material Stream property view appears.
OR
Material Stream icon
2.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
3.
Double-click the Material Stream icon. The Material Stream
property view appears.
The Material Stream property view contains three tabs and associated
pages that allow you to define parameters, view properties, add utilities,
and specify dynamic information.
The three tabs on the Material Stream property view are:
•
•
•
3-2
Worksheet
Attachments
Dynamics
Streams
3-3
The figure below shows the initial view of a new material stream after it
has been added to a simulation.
Figure 3.1
If you want to copy properties or compositions from existing streams
within the flowsheet, click the Define from Other Stream button. The
Spec Stream As view appears, which allows you to select the stream
properties and/or compositions you want to copy to your stream.
View Upstream Operation
icon
View Downstream Operation
icon
The left green arrow is the View Upstream Operation icon, which
indicates the upstream position. The right green arrow is the View
Downstream Operation icon, which indicates the downstream position.
If the stream you want is attached to an operation, clicking these icons
opens the property view of the nearest upstream or downstream
operation. If the stream is not connected to an operation at the
upstream or downstream end, then these icons open a Feeder Block or a
Product Block.
3-3
3-4
Material Stream Property View
3.1.1 Worksheet Tab
The Worksheet tab has seven pages that display information relating to
the stream properties:
The Electrolytes page is
only available if the stream is
in an electrolyte system.
•
•
•
•
•
•
•
Conditions
Properties
Compositions
K Value
Electrolytes
User Variables
Notes
The figure below shows the Worksheet tab of a solved material stream
within a simulation.
Figure 3.2
The green
status bar
containing OK
indicates a
completely
solved stream.
3-4
Streams
3-5
Conditions Page
In the electrolyte system, the
Conditions page contains an
extra column. This column
displays the property
parameters of the stream
after electrolyte flash
calculations.
The Conditions page displays all of the default stream information as it
is shown on the Material Streams tab of the Workbook view. The names
and current values for the following parameters appear below:
•
•
•
•
•
•
•
•
•
•
•
•
Stream Name
Vapour/Phase Fraction
Temperature
Pressure
Molar Flow
Mass Flow
Std Ideal LiqVol Flow
Molar Enthalpy
Molar Entropy
Heat Flow
LiqVol Flow @ Std Cond
Fluid Package
HYSYS uses degrees of freedom in combination with built-in
intelligence to automatically perform flash calculations. In order for a
stream to “flash”, the following information must be specified, either
from your specifications or as a result of other flowsheet calculations:
•
Stream Composition
Two of the following properties must also be specified; at least one of
the specifications must be temperature or pressure:
At least one of the
temperature or pressure
properties must be specified
for the material stream to
solve.
In the electrolyte system, the
entropy (S) is always a
calculated property.
•
•
•
•
•
Temperature
Pressure
Vapour Fraction
Entropy
Enthalpy
If you specify a vapour fraction of 0 or 1, the stream is assumed to be at
the bubble point or dew point, respectively. You can also specify vapour
fractions between 0 and 1.
3-5
3-6
Material Stream Property View
Depending on which of the state variables are known, HYSYS
automatically performs the correct flash calculation.
For an electrolyte material
stream, HYSYS conducts a
simultaneous phase and
reaction equilibrium flash on
the stream. For the reactions
involved in the flash and the
model used for the flash
calculation, refer to Section
1.6.9 - Electrolyte Stream
Flash in the HYSYS OLI
Interface manual.
Once a stream has flashed, all other properties about the stream are
calculated as well. You can examine these properties through the
additional pages of the property view. A flowrate is required to calculate
the Heat Flow.
The stream parameters can be specified on the Conditions page or in
the Workbook view. Changes in one area are reflected throughout the
flowsheet.
While the Workbook displays the bulk conditions of the stream, the
Conditions page, Properties page, and Compositions page also show the
values for the individual phase conditions. HYSYS can display up to five
different phases.
•
•
•
•
•
•
The Mixed Liquid phase does
not add its composition or
molar flow to the stream it is
derived from. This phase is
only another representation
of existing liquid components.
3-6
•
Overall
Vapour
Liquid. If there is only one hydrocarbon liquid phase, that phase
is referred to as liquid.
Liquid 1. This phase refers to the lighter liquid phase.
Liquid 2. This phase refers to the heavier liquid phase.
Aqueous. In the absence of an aqueous phase, the heavier
hydrocarbon liquid is treated as aqueous. When there is only one
aqueous phase, that phase is labelled as aqueous.
Mixed Liquid. This phase combines the Liquid phases of all
components in a specified stream, and calculates all liquid phase
properties for the resulting fluid.
Streams
3-7
For instance, if you expand the width of the default stream view of
Figure 3.2, you can view the hidden phase properties (as shown in the
figure below). In this case, the vapour phase and liquid phase properties
appear beside the overall stream properties. If there were another liquid
phase, it would appear as well.
Figure 3.3
In HYSYS, the liquid phase,
and aqueous phase are
internally recognized as
Liquid 1, and Liquid 2,
respectively. Liquid 1 refers to
the lighter phase whereas the
heavier phase is recognized
as Liquid 2. In the absence of
an aqueous phase, the
heavier hydrocarbon liquid is
treated as aqueous. If there is
only one hydrocarbon liquid
phase, that phase is referred
to as liquid. When there is
only one aqueous phase, that
phase is labelled as aqueous.
Rather than expanding the view, you can use the horizontal scroll bar to
view the hidden phase properties.
When you are viewing a stream property view in the column subflowsheet, there is an additional Create Column Stream Spec button on
the Conditions page. For more information on the functionality of the
Create Column Stream Spec button, refer to Section 8.5.29 - Column
Stream Specifications.
3-7
3-8
Material Stream Property View
Dynamic Mode
This feature can be used on
streams that feed into the
flowsheet (sits on the
boundary) and those that
connect operations together.
If the stream being changed
flows out of a unit operation,
its contents are likely
overwritten by the upstream
operation as soon as you
start the integrator.
If the downstream operation
is new or had problems
solving, changing its feed
stream may allow HYSYS to
solve the downstream
operation or initialize and
solve a replacement unit
operation.
In Dynamic mode, the Initialize Stream Conditions button appears on
the Conditions page of the Material Stream property view.
The Initialize Stream Conditions button allows you to change the values
in a stream if you want to provide a different set of values for when the
integrator is started. Normally, you would not have to use this feature.
The Initialize Stream Conditions button is an advanced troubleshooting
feature that you can use when you encounter problems, and you want to
change the stream values temporarily to affect a downstream operation.
You can use this feature, for example, if you ran the simulation and you
got really cold temperatures out of a heat exchanger that is causing
problems downstream.
If you click the Initialize Stream Conditions button, the stream values in
the table appear in red. You can then enter in a new temperature (even if
the stream had no specifications before). The Initialize Stream
Conditions button is also replaced by the Accept Stream Conditions
button.
If you click the Accept Stream Conditions button, HYSYS performs flash
calculations again with the initial values you provided. The stream
values in the table appear in black as before.
3-8
Streams
3-9
Properties Page
You can manipulate the
property correlations shown
on this view by using the
Property Correlation
Controls group, or by using
the Correlation Manager.
Refer to Section 11.18 Correlation Manager in the
User Guide for more
information.
The Properties page displays the properties for each stream phase. You
can manipulate the property correlations displayed on this page for an
individual stream. The properties from the Conditions page are not
available on this page.
The Properties page contains a table, a Preference Option field, and a
group of icons. The table displays the property correlations you select
for the stream. The Preference Option field is ‘Active’ if the Activate
Property Correlations checkbox is checked. This checkbox can be found
on the Options page, Simulation tab of the Session Preferences view.
The Property Correlation Controls group contains ten icons. These
icons are used to manipulate the property correlations displayed in the
table.
Name
You can modify and overwrite any existing correlation
set using the stream’s
Property Correlation
Controls.
Icon
Description
View Correlation Set List
Allows you to select a correlation set. Refer to
the section on Displaying a Correlation Set
for more information.
Append New Correlation
Allows you to add a property correlation to
the end of the table. Refer to the section on
Adding a Property Correlation for more
information.
Move Selected
Correlation Down
Allows you to move the selected property
correlation one row down the table.
Move Selected
Correlation Up
Allows you to move the selected property
correlation one row up the table.
Sort Ascending
Allows you to sort the property correlations in
the table by ascending alphabetic order.
Remove Selected
Correlation
Allows you to remove the selected property
correlation from the table. Refer to the section
on Removing a Property Correlation from
the table for more information.
Remove All Correlations
Allows you to remove all the property
correlations from the table.
3-9
3-10
Material Stream Property View
Name
Icon
Description
Save Correlation Set to
File
Allows you to save a set of property
correlations. Refer to the section on Creating
a Correlation Set for more information.
View Selected
Correlation
Allows you to view the parameters and status
of the selected property correlation. Refer to
the section on Viewing a Property
Correlation for more information.
View All Correlation
Plots
Allows you to view all correlation plots for the
selected stream. Refer to the section on
Viewing All Correlation Plots for more
information.
Adding a Property Correlation
To add a property correlation to the table:
1.
Append New Correlation icon
Click the Append New Correlation icon. The Correlation Picker view
appears.
Figure 3.4
HYSYS property
correlations have
been grouped into
categories which
target the specific
reporting needs of
the various process
industries.
Select Material Stream to
Append icon
3-10
2.
Select a property correlation that you want to view from the branch
list. Click the ‘+’ symbol to expand the available correlations list.
3.
Click the Apply button to append the selected property correlation
to the stream. The selected stream name is shown to the right of the
Select Material Stream to Append icon. If the selected correlation
cannot be calculated by that stream’s fluid, a message will be sent to
the trace window informing the user that this property correlation
cannot be added to the stream.
Streams
4.
Repeat steps #2 to #3 to add another property correlation.
5.
When you have completed appending property correlations to the
stream, click the Close button to return to the stream property view.
3-11
To select a different stream to append the property correlations to:
1.
Click the Select Material Stream to Append icon. The Select
Material Stream view appears.
2.
Select the appropriate stream from the object list.
3.
Click the OK button to return to the Correlation Picker view. You
can now add a property correlation to the selected stream.
Removing a Property Correlation from the table
To remove property correlations from the table:
Remove Selected Correlation
icon
1.
Select the property correlation you want to remove in the table.
2.
Click the Remove Selected Correlation icon. HYSYS removes the
selected property correlation from the table.
You can remove all property correlations in the table by clicking the
Remove All Correlations icon.
Remove All Correlations icon
Creating a Correlation Set
To save the property correlations in the table as a set:
1.
Add all the property correlations you want to the table.
2.
Click the Save Correlation Set to File icon. The Save Correlation Set
Name view appears.
Save Correlation Set to File
icon
Figure 3.5
For the stream called AGO, HYSYS
automatically enters the default
name AGO-CorrelationSet for the
property list.
HYSYS automatically
enters a name for the
property list based on the
stream name.
3.
Enter the name you want for the property list in the Set Name
(Global) field. Each correlation set name must be unique.
3-11
3-12
Material Stream Property View
4.
Click the Save button to save the property list.
If this is the first time you are creating a correlation set, you are also
creating the default file (Support\StreamCorrSets.xml) which will hold all
these sets. You can change the name of the file on the Locations page,
Files tab of the Session Preferences view.
The saved correlation set can then be added to other streams using the
View Correlation Set List icon displayed in each stream view. You can
also add the saved correlation set to all of the streams within the case by
using the Correlation Manager.
Displaying a Correlation Set
To display a correlation set:
1.
Click the View Correlation Set List icon.
2.
The Correlation Set Picker view appears.
View Correlation Set List icon
Figure 3.6
The location and
name of the file
that contains the
correlation set is
shown in the File
Path field. The xml
path and file name
can be changed
using the Session
Preferences view.
Refer to Section
12.5.2 Locations Page.
If the xml file does not exist (you have never created a correlation set
before) the window will display “File has not been created.” If the xml file
does exist but all previous sets have been deleted, the window will
display “File is empty.”
3.
3-12
Select the correlation set you want from the view. Click the ‘+’
symbol to expand the list of correlations the correlation set
contains.
Streams
HYSYS will check each
correlation’s type against the
fluid type of the stream. If
there is a problem
encountered while appending
a correlation from the set, a
warning will be sent to the
trace window.
4.
Click the Apply button. The Correlation Set Picker view will close,
and the property correlations contained in the selected correlation
set will appear in that streams properties table.
5.
Repeat steps #1 to #4 to apply additional correlation sets to your
stream.
3-13
You can expand the view or use the scroll bar to view any property
correlation phase values, as shown in the figure below.
Figure 3.7
3-13
3-14
Material Stream Property View
Deleting a Correlation Set
To delete a correlation set:
1.
Click the View Correlation Set List icon.
2.
The Correlation Set Picker view appears.
Figure 3.8
3-14
3.
Select the correlation set you want to delete.
4.
Click the Delete button. A window will appear asking you if you are
sure you want to delete the set because it cannot be undone.
5.
Click the Yes button and the Correlation Set Picker view appears
with the chosen set deleted from the list.
6.
Click the Cancel button to return to the stream property view.
Streams
3-15
Viewing a Property Correlation
When you select a property correlation from the table and click the View
Selected Correlation icon, the following view appears.
View Selected Correlation
icon
Figure 3.9
The values shown on
this view cannot be
edited. Any configuration
parameters available to
each property
correlation can only be
edited using the
Correlation Manager
view.
The following table describes the six status bars contained in the Status
group.
Status Bar
Description
Stream
Indicates that the correlation can only be applied to material
streams.
Point/Plottable
Indicates whether the property correlation is a point or
plottable property.
Black Oil/Electrolyte/
Gas/RVP/Solid/
Standard/User/Clone
Indicates which correlation type the property correlation
resides within in the Available Correlations list.
Active/Inactive
Indicates whether the property correlation has been
activated by the correlation manager.
If the status bar is green, any new stream added to the
flowsheet with the same fluid type as the correlation will
automatically have the property correlation added.
In Use/Not in Use
Indicates whether the property correlation is being used by a
stream in the case.
Available/Unavailable
Indicates whether the property correlation exists in the
window registry of the system.
In the Stream Connections group, a list of all the material streams
currently using the property correlation is displayed.
3-15
3-16
Material Stream Property View
In the Parameters group, you can view the parameters used to calculate
the property correlation.
The Correlation Manager view allows you to manipulate the
parameters. Refer to Section 11.18 - Correlation Manager in the User
Guide for more information.
Viewing All Correlation Plots
The Correlation Plots view is a separate view which displays all plottable
properties for the stream.
View All Correlation Plots
icon
Figure 3.10
Only plottable properties appear on the plots view, while both point and
plot properties appear on the stream properties view. The plot view can
show only one plot property at a time.
3-16
Streams
3-17
Composition Page
You cannot change the
composition of streams
calculated by HYSYS. The
default colour for specified
stream values is blue, and
black for those calculated by
HYSYS.
There are two ways you can specify or change the stream composition:
1.
Click the Edit button. The Input Composition view appears.
OR
2.
Type a value in a component cell and press ENTER. The Input
Composition view appears.
Refer to the section on the Input Composition View for more
information.
The figure below shows the mole fractions for each component in the
overall phase, vapour phase, and aqueous phase. You can view the
composition in a different basis by clicking the Basis button, which
opens the Stream view.
Figure 3.11
3-17
3-18
Material Stream Property View
Stream View
On the Stream view, click one of the radio buttons to choose a new
compositional basis.
Figure 3.12
Click the Close icon to return to the Composition page. HYSYS
displays the stream compositions using the selected basis.
Input Composition View
The Input Composition view allows you to edit the stream
compositions.
Figure 3.13
3-18
Streams
For fractional bases, clicking
the OK button automatically
normalizes the composition
if all compositions contain a
value. The Cancel button
closes the view without
accepting any changes.
The Normalize button does
not apply to flow
compositional bases, since
there is no restriction on the
total flowrate.
3-19
In the Composition Basis group, select the radio button that
corresponds to the basis for your stream. In the list of available
components, specify the composition of the stream.
The Composition Controls group has two buttons that can be used to
manipulate the compositions.
Button
Action
Erase
Clears all compositions.
Normalize
Allows you to enter any value for fractional compositions and have
HYSYS normalize the values such that the total equals 1. This
button is useful when many components are available, but you want
to specify compositions for only a few. When you enter the
compositions, click the Normalize button and HYSYS ensures the
Total is 1.0, while also specifying any <empty> compositions as
zero. If compositions are left as <empty>, HYSYS cannot perform
the flash calculation on the stream.
You cannot edit the compositions for a stream that is calculated by
HYSYS. When you move to the Composition page for such a stream, the
Edit button is greyed out.
K Value Page
Figure 3.14
3-19
3-20
Material Stream Property View
The K Value page displays the K values or distribution coefficients for
each component in the stream. A distribution coefficient is a ratio
between the mole fraction of component i in the vapour phase and the
mole fraction of component i in the liquid phase:
yi
K i = ---xi
where:
(3.1)
Ki = distribution coefficient
yi = mole fraction of component i in the vapour phase
xi = mole fraction of component i in the liquid phase
Electrolytes Page
The Electrolytes page is
available only if the stream is
in an electrolyte system.
Refer to Section 1.2.4 Adding Electrolyte
Components in the
Simulation Basis manual
for more information on
electrolytes.
If the stream is associated with an OLI-Electrolyte property package, the
Electrolytes page displays electrolytic information.
Figure 3.15
You can view the electrolyte stream properties or the electrolyte stream
composition for aqueous or solid phase. In the True Species Info group,
select the appropriate radio button to view the electrolyte stream
properties.
3-20
Streams
3-21
The Properties radio button displays the stream fluid phase properties
for an electrolyte system. Use the radio buttons in the Phase group to
switch between the aqueous phase and the solid phase.
When you click the Aqueous phase radio button, the following aqueous
phase related properties appear:
•
•
•
•
•
pH value
Osmotic Pressure
Ionic Strength
Heat Capacity
Viscosity
For more information, refer to Section 1.6 - HYSYS OLI_Electrolyte
Property Package in the HYSYS OLI Interface manual.
To globally include or
exclude particular solids in
all electrolyte streams, refer
to the section on the
OLI_Electrolyte Options in
the Simulation Basis
manual.
When you click the Solid phase radio button, you can include or exclude
a particular solid in the current stream equilibrium flash calculation.
Figure 3.16
The value of Scale Tendency Index as
shown in the table is a measure of the
tendency of a solid species forming at
the specified conditions. Solid with a
scaling tendency greater than one forms
if the solid formation is governed by
equilibrium (as opposed to kinetics), and
if there are no other solids with a
common cation or anion portion which
also has a scaling tendency greater than
one.
3-21
3-22
Material Stream Property View
The Composition radio button displays the component name, molar
fraction, molar flow, or molality and molarity of all the components in
the stream for aqueous or solid phase in a table.
Figure 3.17
If you select the
Aqueous radio
button, the
component list
including ionic
component(s)
appears in the
table.
If you select the Solid radio
button, a component list
including precipitate (PPT) and
hydrated (-nH2O) solid appears
with only mole fraction and mole
flow.
User Variables Page
You can create and implement your own User Variables for use in a
HYSYS simulation on the User Variables page. For more information on
the User Variables refer to Chapter 5 - User Variables in the
Customization Guide.
3-22
Streams
3-23
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor that allows you to record any
comments or information regarding the material stream or the
simulation case in general.
Cost Parameters Page
For more information
regarding cost parameters,
refer to the Economix
manual.
You can enter a cost factor value for the stream in the Cost Parameters
page. You can also choose the flow basis associated with the cost factor
from the Flow Basis drop-down list.
Figure 3.18
3-23
3-24
Material Stream Property View
3.1.2 Attachments Tab
Unit Ops Page
The Unit Ops page allows you to view the names and types of unit
operations and logicals to which the stream is attached.
Figure 3.19
The view uses three groups:
•
•
•
The units from which the stream is a product.
The units to which the stream is a feed.
The logicals to which the stream is connected.
You can access the property view for a specific unit operation or logical
by double-clicking in the Name cell or Type cell.
3-24
Streams
3-25
Utilities Page
Refer to Chapter 14 Utilities for more
information on the utilities
available in HYSYS.
The Utilities page allows you to view and manipulate the utilities
attached to the stream.
Figure 3.20
The Utilities page allows you to do the following:
Refer to Section 7.27 Utilities in the User Guide
for more information on
adding, viewing, and
deleting utilities.
•
•
•
Attach Utilities to the current stream.
View existing Utilities that are attached to the stream.
Delete existing Utilities that are attached to the stream.
Only the Create button is available all the time.
The View button and Delete button are greyed out until you select a
utility from the list.
3-25
3-26
Material Stream Property View
DRU Stream Page
The DRU stream is
applicable for data
reconciliation problems.
The DRU stream facilitates running a given set of unit operations under
different stream conditions (which are stored within the DRU stream,
and can be either user input, or acquired from the RTO system directly).
Figure 3.21
When the Add
Transfer Stream
button is enabled,
the Delete Transfer
Stream button is
disabled, and viceversa.
The DRU stream is used for data reconciliation to hold different states of
streams. During data reconciliation, measured data of DCS tags can be
obtained under different stream states (e.g., temperature or pressure).
The DRU stream can also perform flash calculations as other HYSYS
streams do.
Each data set behaviour as
a stream (e.g., can
automatically flash
calculation and have
freedom control).
If you want to use the DRU stream to hold data, the number of data sets
needs to be equal to the number of data sets of DCS tags. You can create
data sets for streams and set values to stream states.
The Data Rec utility controls the updating of its associated streams with
the correct data corresponding to the data set being evaluated at that
point in time.
The Add Transfer Stream button and Delete Transfer Stream button are
solely for On-Line applications. Clicking the Add Transfer Stream
button creates a DRU Stream (Data Reconciliation Stream) such that
you can move the information for the stream as a block between HYSYS
cases, or instances of HYSYS. Clicking the Delete Transfer Stream button
removes the DRU Stream.
3-26
Streams
3-27
3.1.3 Dynamics Tab
You must be in dynamic
mode for any of these
specifications to have an
effect on the simulation.
The Dynamics tab displays the pressure and flow specifications for the
material stream, allows you to generate the stripchart for a set of
variables. The view for the Specs page on the Dynamics tab appears in
the figure below.
Figure 3.22
Feeder block or
Product block
button appears
only when the
stream is a
flowsheet
boundary
stream.
Specs Page
The Specs page allows you to add a pressure and a flow specification for
the stream. If the Active checkbox is activated for a specification, the
value of the specification appears in blue and you can modify the value.
If the active checkbox is not activated, the value is appears in black and
is calculated by HYSYS. Default stream conditions are shown in red.
3-27
3-28
Material Stream Property View
Feed and Product Blocks
A flowsheet boundary stream is a stream which has only one unit
operation attached to it. If a material stream is a flowsheet boundary
stream, a Feeder block button or Product block button appears in the
Dynamics tab. A flowsheet boundary stream can be the feed or product
of the model. Depending on whether the flowsheet boundary stream is a
feed or a product, the Dynamics tab view displays either a Feeder block
button or a Product block button.
The figure below shows a Product Block view of a material stream.
Figure 3.23
To ignore the Feed or Product block operations, activate
the Ignored checkbox.
View Upstream Operation
icon
View Downstream Operation
icon
3-28
You can also access the Feeder Block view by clicking the View
Upstream Operation icon on the stream view. Similarly, you can also
access the Product Block view by clicking the View Downstream
Operation icon.
The Product Block view displays flow reversal conditions of the material
stream which you can specify. If simulation conditions are such that the
product stream flow becomes negative, HYSYS recalls the stream
conditions stored in the Product block and performs a rigorous flash on
the product stream to determine the other stream conditions.
Streams
3-29
When process conditions in the simulation cause the feed flow to
reverse, the feed stream conditions are calculated by the downstream
operation. The Feeder Block view is used to restore desired feed
conditions and compositions if the feed stream reverses and then
becomes feed again.
The Feeder Block and Product Block have similar views. You can specify
the stream conditions as follows:
Required Feed and Product Block Specifications
Conditions Tab
Specify one of the following:
•
•
•
•
Composition Tab
Temperature
Vapour Fraction
Entropy
Enthalpy
Specify the stream composition.
Since the pressure of the stream remains the same after the product
stream flow reverses, the pressure value does not need to be specified.
With this information, the stream is able to perform flash calculations
on the other stream properties.
Both the Feeder Block view and Product Block view have three buttons
that allow you to manipulate the direction of stream conditions
between the material stream and the block. The table below briefly
describes each button.:
Block Button
Action
Export Conditions to
Stream
Copies stream conditions stored in the block to the
material stream.
Update From Stream
Copies the current stream conditions from the material
stream to the block.
Update from Current
Composition
Copies only the stream composition from the material
stream to the block.
3-29
3-30
Energy Stream Property View
Stripchart Page
Refer to Section 11.7.3 Strip Chartsin the User
Guide for more information
about strip charts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Figure 3.24
3.2 Energy Stream Property View
You can also open the
Object Palette by pressing
the F4 hot key.
Energy Stream icon
Energy streams are used to simulate the energy travelling in and out of
the simulation boundaries and passing between unit operations.
1.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
2.
Double-click the Energy Stream icon. The Energy Stream property
view appears.
OR
3.
In the Workbook view, click the Energy Streams tab.
4.
Double-click on the name of the stream you want to view.
The Energy Stream property view appears.
3-30
Streams
3-31
The Energy Stream property view contains the following five tabs that
allow you to define stream parameters, view objects to which the stream
is attached, and specify dynamic information:
•
•
•
•
•
Streams
Unit Ops
Dynamics
Stripchart
User Variables
Figure 3.25
View Upstream Operation
icon
As with the material streams, the energy stream view has the View
Upstream Operation icon and the View Downstream Operation icon
that allow you to view the unit operation to which the stream is
connected. Energy streams differ from material streams in that if there is
no upstream or downstream connection on the stream (which is often
the case for the energy stream) the associated icon is not active.
View Downstream Operation
icon
3-31
3-32
Energy Stream Property View
3.2.1 Stream Tab
When converting an energy
stream to a material stream,
all material stream properties
are unspecified, except for the
stream name.
The Stream tab allows you to specify the Stream Name and Heat Flow
for the stream. The figure below shows the Stream tab of the Energy
Stream property view.
Figure 3.26
3.2.2 Unit Ops Tab
You can double-click on
either the Product From or
Feed To cell to access the
property view of the
operation attached to the
stream.
3-32
The Unit Ops tab displays the Names and Types of all objects to which
the energy stream is attached. Both unit operations and logicals are
listed. The Unit Ops tab either shows a unit operation in the Product
From cell or in the Feed To cell, depending on whether the energy
stream receives or provides energy respectively.
Figure 3.27
Streams
3-33
3.2.3 Dynamics Tab
The options on the Dynamics tab allow you to set the dynamic
specifications for a simulation in dynamic mode.
Figure 3.28
In dynamic mode, two different heating methods can be chosen for an
energy stream. When the Direct Q radio button is selected, you can
specify a duty value. When the Utility Fluid radio button is selected, the
duty is calculated from specified properties of a utility fluid.
The Utility Valve button opens the Flow Control Valve (FCV) view for the
energy stream. For a detailed description of the Direct Q and Utility
Fluid Heating methods, refer to Section 5.5 - Valve.
3.2.4 Stripchart Tab
The Stripchart tab currently does not have any functions. Refer to
Section 11.7.3 - Strip Charts in the User Guide for more information
about strip charts.
3.2.5 User Variables Tab
The User Variables tab allows you to create and implement User
Variables for use in your HYSYS simulation. For more information on
working with User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
3-33
3-34
3-34
Energy Stream Property View
Heat Transfer Equipment
4-1
4 Heat Transfer Equipment
4.1 Air Cooler .........................................................................................3
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6
4.1.7
4.1.8
Theory......................................................................................3
Air Cooler Property View .........................................................6
Design Tab...............................................................................7
Rating Tab................................................................................9
Worksheet Tab.......................................................................12
Performance Tab ...................................................................12
Dynamics Tab ........................................................................13
HTFS - ACOL Tab..................................................................18
4.2 Cooler/Heater .................................................................................37
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
Theory....................................................................................37
Heater or Cooler Propety View ..............................................40
Design Tab.............................................................................41
Rating Tab..............................................................................43
Worksheet Tab.......................................................................45
Performance Tab ...................................................................45
Dynamics Tab ........................................................................49
4.3 Heat Exchanger..............................................................................55
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.6
4.3.7
4.3.8
Theory....................................................................................56
Heat Exchanger Property View..............................................59
Design Tab.............................................................................60
Rating Tab..............................................................................73
Worksheet Tab.......................................................................89
Performance Tab ...................................................................89
Dynamics Tab ........................................................................93
HTFS-TASC Tab ..................................................................102
4-1
4-2
Heat Transfer
4.4 Fired Heater (Furnace) ................................................................ 125
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6
4.4.7
Theory ................................................................................. 126
Fired Heater Property View ................................................. 134
Design Tab .......................................................................... 135
Rating Tab ........................................................................... 137
Worksheet Tab..................................................................... 143
Performance Tab ................................................................. 144
Dynamics Tab ...................................................................... 149
4.5 LNG ............................................................................................... 152
4.5.1
4.5.2
4.5.3
4.5.4
4.5.5
4.5.6
4.5.7
4.5.8
Theory ................................................................................. 153
LNG Property View.............................................................. 156
Design Tab .......................................................................... 157
Rating Tab ........................................................................... 164
Worksheet Tab..................................................................... 170
Performance Tab ................................................................. 170
Dynamics Tab ...................................................................... 175
HTFS-MUSE Tab................................................................. 182
4.6 References ................................................................................... 198
4-2
Heat Transfer Equipment
4-3
4.1 Air Cooler
In dynamics, the Air Cooler
tube is capable of storing
inventory like other dynamic
unit operations. The
direction of the material
flowing through the Air
Cooler operation is
governed by the pressures
of the surrounding unit
operations.
The Air Cooler unit operation uses an ideal air mixture as a heat transfer
medium to cool (or heat) an inlet process stream to a required exit
stream condition. One or more fans circulate the air through bundles of
tubes to cool process fluids. The air flow can be specified or calculated
from the fan rating information. The Air Cooler can solve for many
different sets of specifications including the:
•
•
•
Overall heat transfer coefficient, UA
Total air flow
Exit stream temperature
4.1.1 Theory
Steady State
The Air Cooler uses the same basic equation as the Heat Exchanger unit
operation, however, the Air Cooler operation can calculate the flow of air
based on the fan rating information.
The Air Cooler calculations are based on an energy balance between the
air and process streams. For a cross-current Air Cooler, the energy
balance is calculated as follows:
Mair(Hout - Hin)air = Mprocess(Hin - Hout)process
where:
(4.1)
Mair = air stream mass flow rate
Mprocess = process stream mass flow rate
H = enthalpy
The Air Cooler duty, Q, is defined in terms of the overall heat transfer
coefficient, the area available for heat exchange, and the log mean
temperature difference:
Q = – UA∆T LM F t
(4.2)
4-3
4-4
Air Cooler
where:
U = overall heat transfer coefficient
A = surface area available for heat transfer
∆T LM = log mean temperature difference (LMTD)
Ft = correction factor
The LMTD correction factor, Ft, is calculated from the geometry and
configuration of the Air Cooler.
ACOL Functionality
In Steady State mode, you can also access certain ACOL functions on the
HTFS-ACOL tab.
You must install and license ACOL 6.4 before you can access the ACOL
functions.
Dynamic
Heat Transfer
The Air Cooler uses the same basic energy balance equations as the Heat
Exchanger unit operation. The Air Cooler calculations are based on an
energy balance between the air and process streams. For a cross-current
Air Cooler, the energy balance is shown as follows:
d ( VH out ) process
M process ( H in – H out ) process – M air ( H in – H out ) air = ρ ---------------------------------------dt
where:
Mair = air stream mass flow rate
Mprocess = process stream mass flow rate
ρ = density
H = enthalpy
V = volume of Air Cooler tube
4-4
(4.3)
Heat Transfer Equipment
4-5
Pressure Drop
The pressure drop of the Air Cooler can be determined in one of two
ways:
•
•
Specify the pressure drop.
Define a pressure flow relation in the Air Cooler by specifying a kvalue.
If the pressure flow option is chosen for pressure drop determination in
the Air Cooler, a k value is used to relate the frictional pressure loss and
flow through the exchanger. This relation is similar to the general valve
equation:
flow =
density × k P 1 – P 2
(4.4)
This general flow equation uses the pressure drop across the Heat
Exchanger without any static head contributions. The quantity, P1 - P2, is
defined as the frictional pressure loss which is used to “size” the Air
Cooler with a k value.
Dynamic Specifications
In general, three specifications are required by HYSYS in order for the Air
Cooler unit operation to fully solve:
Dynamic Specifications
Description
Overall UA
The product of the Overall Heat Transfer Coefficient, and
the total area available for heat transfer. The Overall UA
must be specified in Dynamic mode. You can specify the
value of UA on the Parameters page of the Design tab.
Fan Rating Information
You must specify the following information on the Sizing
page of the Rating tab:
•
•
•
•
Demanded Speed
Design Speed
Design Flow
Max Acceleration (optional)
or
• Current Air Flow
Pressure Drop
Either specify an Overall Delta P or an Overall K-value for
the Air Cooler. These pressure drop specifications can be
made on the Specs page of the Dynamics tab.
4-5
4-6
Air Cooler
4.1.2 Air Cooler Property View
Add an Air Cooler to your simulation by doing the following:
1.
From the Flowsheet menu, select Add Operation [or press F12]. The
UnitOps view appears.
2.
Click the Heat Transfer Equipment radio button.
3.
From the list of available unit operations, select Air Cooler.
4.
Click the Add button. The Air Cooler property view appears.
OR
1.
From the Flowsheet menu, select Palette [or press F4]. The Object
Palette appears.
2.
Double-click the Air Cooler icon.
The Air Cooler property view appears.
Air Cooler icon
Figure 4.1
To ignore the Air Cooler
during calculations, click the
Ignored checkbox. HYSYS
completely disregards the
operation (and cannot
calculate the outlet stream)
until you restore it to an active
state by deactivating the
checkbox.
4-6
Heat Transfer Equipment
4-7
4.1.3 Design Tab
The Design tab contains four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
On the Connections page, you can specify the feed and product streams
attached to the Air Cooler. You can change the name of the operation in
the Name field.
Figure 4.2
4-7
4-8
Air Cooler
Parameters Page
On the Parameters page, the following information appears:
Air Cooler Parameters
Description
Air Cooler Model
Allows you to select HYSYS-Engines or HTFS-Engines. The
HTFS-Engines options appears only if you have ACOL6.4
installed and licensed. The HTFS-Engines option allows you
to access ACOL functions on the HTFS-ACOL tab.
Delta P
Allows you to specify the pressure drops (DP) for the
process side of the Air Cooler. The pressure drop can be
calculated if both the inlet and exit pressures of the process
stream are specified. There is no pressure drop associated
with the air stream. The air pressure through the Cooler is
assumed to be atmospheric.
Overall UA
The product of the Overall Heat Transfer Coefficient, and the
Total Area available for heat transfer. The Air Cooler duty is
proportional to the log mean temperature difference, where
UA is the proportionality factor. The UA can either be
specified or calculated by HYSYS.
Configuration
Displays the possible tube pass arrangements in the Air
Cooler. There are seven different Air Cooler configurations
to choose from. HYSYS determines the correction factor, Ft,
based on the Air Cooler configuration.
Air Intake/Outlet
Temperatures
The inlet and exit air stream temperatures can be specified
or calculated by HYSYS.
Air Intake Pressure
The inlet air stream pressure has a default value of 1 atm.
Figure 4.3
4-8
Heat Transfer Equipment
4-9
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation or the
simulation case in general. For more information, refer to Section 7.20 Notes Manager in the User Guide.
4.1.4 Rating Tab
In dynamics, the air flow
must be calculated using the
fan rating information.
The Rating tab allows you to specify the fan rating information. The
steady state and dynamic Air Cooler operations share the same fan
rating information.
The Rating tab contains the Sizing page. The content of this page differs
depending on which option you selected in the Air Cooler Model dropdown list on the Parameters page of the Design tab. If you selected
HTFS-Engines, this page displays only one field: Air Mass Flow Rate.
The Nozzles page appears only if the HYSYS Fidelity license is activated.
4-9
4-10
Air Cooler
Sizing Page HYSYS-Engines
Figure 4.4
In the Sizing page, the following fan rating information appears for the
Air Cooler operation when the HYSYS-Engines option is selected on the
Parameters page of the Design tab.
The Fan Is On checkbox has
the same function as setting
the Speed to 0 rpm.
4-10
Fan Data
Description
Number of Fans
Number of fans in the Air Cooler.
Speed
Actual speed of the fan in rpm (rotations per minute).
Demanded speed
Desired speed of the fan.
• Steady State mode. The demanded speed is always
equal the speed of the fan. The desired speed is either
calculated from the fan rating information or userspecified.
• Dynamic mode. The demanded speed should either be
specified directly or from a Spreadsheet operation. If a
control structure uses the fan speed as an output signal,
it is the demanded speed which should be manipulated.
Max Acceleration
Applicable only in Dynamic mode. It is the rate at which the
actual speed moves to the demanded speed.
Design speed
The reference Air Cooler fan speed. It is used in the calculation
of the actual air flow through the Cooler.
Design air flow
The reference Air Cooler air flow. It is used in the calculation of
the actual air flow through the Cooler.
Current air flow
This can be calculated or user-specified. If the air flow is
specified no other fan rating information needs to be specified.
Fan Is On
By default, this checkbox is checked. You have the option to
turn on or off the air cooler as desired. When you uncheck the
checkbox, the temperature of the outlet stream of the air cooler
will be identical to that of the inlet stream.
Heat Transfer Equipment
4-11
The air flow through the fan is calculated using a linear relation:
Speed
Fan Air Flow = ------------------------------------ × Design Flow
Design Speed
(4.5)
In dynamic mode only, the actual speed of the fan is not always equal to
the demanded speed. The actual fan speed after each integration time
step is calculated as follows:
Actual Speed = ( Max Acceleration )∆t + Actual Speed o
until Actual Speed = Demanded Speed
(4.6)
Each fan in the Air Cooler contributes to the air flow through the Cooler.
The total air flow is calculated as follows:
Total Air Flow =
∑ Fan Air Flow
(4.7)
Sizing Page HTFS-Engines
HYSYS air coolers can have
multiple fans, and HYSYS
calculates the airflow from the
sum of the airflows of each
fan.
The following page appears when the HTFS-Engines option is selected
on the Parameters page of the Design tab.
Figure 4.5
When you select HYSYSEngines on the Parameters
page of the Design tab,
HYSYS allows you to define
the parameters for each fan on
this page.
When you select HTFSEngines, however, you can
only enter the total air mass
flow rate for the air cooler on
this page.
Here you enter the total airflow for the air cooler.
4-11
4-12
Air Cooler
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. The information provided in the Nozzles page is
applicable only in Dynamic mode. Refer to Section 1.6.2 - Nozzles in the
Dynamic Modeling manual for more information.
4.1.5 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Air Cooler.
Refer to Section 1.2.3 - Worksheet Tab for more information.
4.1.6 Performance Tab
The Profiles page is relevant
to dynamics cases only.
The Performance tab contains pages that display the results of the Air
Cooler calculations.
Results Page
Figure 4.6
4-12
Heat Transfer Equipment
4-13
The information from the Results page is shown as follows:
Results
Description
Working Fluid Duty
This is defined as the change in duty from the inlet to the exit
process stream:
H process, in + Duty = H process, out
LMTD Correction
Factor, Ft
The correction factor is used to calculate the overall heat
exchange in the Air Cooler. It accounts for different tube pass
configurations.
UA
The product of the Overall Heat Transfer Coefficient, and the
Total Area available for heat transfer. The UA can either be
specified or calculated by HYSYS.
LMTD
The LMTD is calculated in terms of the temperature
approaches (terminal temperature difference) in the exchanger,
using the following uncorrected LMTD equation:
∆T 1 – ∆T 2
∆T LM = --------------------------------------ln ( ∆T 1 ⁄ ( ∆T 2 ) )
where: ∆T 1 = T hot, out – T cold, in
∆T 2 = T hot, in – T cold, o ut
Inlet/Outlet Process
Temperatures
The inlet and outlet process stream temperatures can be
specified or calculated in HYSYS.
Inlet/Outlet Air
Temperatures
The inlet and exit air stream temperatures can be specified or
calculated in HYSYS.
Air Inlet Pressure
The inlet air stream pressure has a default value of 1 atm.
Total Air flow
The total air flowrate appears in volume and mass units.
4.1.7 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any of the values
on the pages accessible
through this tab.
The Dynamics tab contains four pages:
•
•
•
•
Model
Specs
Holdup
Stripchart
In dynamics, the air flow must be calculated using the fan rating
information.
4-13
4-14
Air Cooler
Model Page
The Model page allows you to define how UA is defined in Dynamic
mode. The value of UA is calculated as follows:
UA dynamic = F × UA steadystate
where:
UAsteadystate = UA value entered on the Parameters page of the Design
tab.
2 × f1 × f2
F = ------------------------( f1 + f2 )
where:
(4.8)
the flow scale factor
(4.9)
f1 = (mass flowrate / reference flowrate)^0.8 for air.
(4.10)
f2 = (mass flowrate / reference flowrate)^0.8 for fluid.
(4.11)
The page consists of one group, the UA Calculation.
Figure 4.7
The group contains four fields, which are described in the table below.
4-14
Field
Description
UA
The steady state value of UA. This should be the same as the
value entered on the Parameters tab.
Reference air flow
The reference flowrate for air. It is used to calculate the value of
f1 as shown in Equation (4.10).
Heat Transfer Equipment
Field
Description
Reference fluid flow
The reference flowrate for the fluid. It is used to calculate the
value of f2 as shown in Equation (4.11).
Minimum flow scale
factor
The minimum scale factor used. If the value calculated by
Equation (4.9) is smaller than this value, this value is used.
4-15
Specs Page
The Specs page contains information regarding the calculation of
pressure drop across the Air Cooler:
Figure 4.8
You can specify how the pressure drop across the Air Cooler is
calculated in the Dynamic Specifications group.
The Air Cooler operations, like
other dynamic unit operations,
should use the k-value
specification option as much
as possible to simulate actual
pressure flow relations in the
plant.
Dynamic Specifications
Description
Overall Delta P
A set pressure drop is assumed across the valve operation
with this specification. The flow and the pressure of either
the inlet or exit stream must be specified or calculated from
other operations in the flowsheet. The flow through the
valve is not dependent on the pressure drop across the Air
Cooler. To use the overall delta P as a dynamic
specification, activate the corresponding checkbox.
Overall k Value
The k-value defines the relationship between the flow
through the Air Cooler and the pressure of the surrounding
streams. You can either specify the k-value or have it
calculated from the stream conditions surrounding the Air
Cooler. You can “size” the Cooler with a k-value by clicking
the Calculate K button. Ensure that there is a non zero
pressure drop across the Air Cooler before the Calculate K
button is clicked. To use the k-value as a dynamic
specification, activate the corresponding checkbox.
4-15
4-16
Air Cooler
Dynamic Specifications
Description
Pressure Flow
Reference Flow
The reference flow value results in a more linear
relationship between flow and pressure drop. This is used
to increase model stability during startup and shutdown
where the flows are low.
If the pressure flow option is chosen the k value is
calculated based on two criteria. If the flow of the system is
larger than the k Reference Flow the k value remains
unchanged. It is recommended that the k reference flow is
taken as 40% of steady state design flow for better pressure
flow stability at low flow range. If the flow of the system is
smaller than the k Reference Flow the k value is given by:
k used = k specified × Factor
where Factor is determined by HYSYS internally to take
into consideration the flow and pressure drop relationship at
low flow regions.
The Dynamic Parameters group contains information about the holdup
of the Air Cooler, which is described in the table below.
4-16
Dynamic Parameters
Description
Fluid Volume
Specify the Air Cooler holdup volume.
Mass Flow
The mass flow of process stream through the Air Cooler is
calculated.
Exit Temperature
The exit temperature of the process stream.
Heat Transfer Equipment
4-17
Holdup Page
The Holdup page contains information regarding the properties,
composition, and amount of the holdup.
Figure 4.9
For each phase contained within the volume space of the unit
operation, the following is specified:
Holdup Details
Description
Phase
The phase of the substance in the holdup volume.
Accumulation
The rate of change of material in the holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The Stripchart page allows you to setup the strip chart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the strip chart.
4-17
4-18
Air Cooler
4.1.8 HTFS - ACOL Tab
For more information about
ACOL data input, refer to the
ACOL Reference Guide.
Also, refer to the ACOL Online
Help for information about
specific input fields.
This tab allows you to access certain ACOL functions. To access the
functions on this tab, you must do the following:
•
•
Install and license ACOL6.4.
Select HTFS-Engines from the Air Cooler Model drop-down list
on the Parameters page of the Design tab.
The HTFS-Engines option runs only in Steady State mode.
If you provide more data than is required, ACOL will perform
consistency checks and warn you of any discrepancies.
ACOL Simulation Modes
ACOL has eight different simulation modes, four of which are
recognized by HYSYS. Each mode calculates a different variable based
on the data you supply. HYSYS checks the data entered for the air-cooler
to determine if ACOL can run, then which mode ACOL will run based on
the supplied data. HYSYS then sends the data to ACOL.
The following tables list and describe the criteria used by HYSYS to
determine the air cooler status messages, whether or not ACOL can run,
and which mode ACOL will run.
All simulation modes
The following applies unless specified differently:
4-18
Criteria
Value
Air inlet temperature
specified
Air outlet temperature
not specified
Pressure drop
not specified
Process inlet temperature
specified
Process outlet temperature
not specified
Heat Transfer Equipment
4-19
ACOL Simulation 9: Calculation of the outlet temperature:
Criteria
Value
Process inlet temperature
specified
Process outlet temperature
not specified
Airflow
specified
Process flow rate
specified
ACOL Simulation 1: Calculation of the inlet temperature:
Criteria
Value
Process inlet temperature
not specified
Process outlet temperature
specified
Airflow
specified
Process flow rate
specified
Process inlet temperature
not specified
Process outlet temperature
specified
ACOL Simulation 3: Calculation of the process mass flow rate:
Criteria
Value
Process inlet temperature
specified
Process outlet temperature
specified
Airflow
specified
Process flow rate
not specified
ACOL Simulation 4: Calculation of the air mass flow rate:
Criteria
Value
Process inlet temperature
specified
Process outlet temperature
specified
Airflow
not specified
Process flow rate
specified
4-19
4-20
Air Cooler
Importing and Exporting ACOL Input Files
Import and Export buttons appears on every page of the HTFS-ACOL
tab. These buttons allow you to import existing ACOL data or export the
current data. The file format used is ACOL Input files [*.aci].
Bundle Geometry Page
The Bundle Geometry page content changes depending on the radio
button you select.
Headers/Nozzles Radio Button
Figure 4.10
4-20
Heat Transfer Equipment
4-21
The following table describes the fields that appear when you click the
Headers/Nozzles radio button.
Object
Description
Number of Inlet Nozzles
Enter the number of inlet nozzles per bundle. Too
few nozzles can cause excessive pressure losses
and possibly erosion of the nozzles and headers.
Default value is 1.
Number of Outlet Nozzles
Enter the number of outlet nozzles per bundle. If a
phase change occurs through the bundle then it may
be appropriate to have a different number of nozzles
of different size to the inlet nozzles. Default value is
1.
Inside Diameter of Inlet
Nozzle
Enter the inside diameter of the inlet nozzles.
Defaults to the highest preferred diameter which
gives a momentum flux (rV2) less than 6000 kg/m
s2. Preferred sizes are; 50mm, 100mm, 150mm,
200mm etc.
Inside Diameter of Outlet
Nozzle
Enter the inside diameter of the outlet nozzles.
Defaults to the highest preferred diameter which
gives a momentum flux (rV2) less than 6000 kg/m
s2. Preferred sizes are; 50mm, 100mm, 150mm,
200mm etc.
Type of Header
Type of Header options: Box, D-header, Plug, Cover
Plate, or Manifold.
U-Bend Configuration
U-Bend Configuration options: No-bends, U-bends in
alternate passes, or U-bends in every pass.
Depth of Inlet Header
Enter the depth of the header at the tubeside fluid
inlet. For a D-header, this will be the maximum depth
of the D-section. Default is 300mm (11.8 in) for Aircooled Heat Exchangers.
Depth of Other Header
Enter the depth of the other header. The other
header is at the side opposite to the inlet header. For
an odd number of passes, this will be the outlet
header. For a D-header, the depth will be the
maximum depth of the D-section. Default is 150mm
(5.9 in) for Air-cooled Heat Exchangers.
Perf. Pass Plates
Enter the average number of velocity heads lost
through each perforated plate in the headers.
Perforated pass plates are usually fitted to
strengthen the header in high-pressure applications.
Default value is 0.0
4-21
4-22
Air Cooler
Bundle Radio Button
Figure 4.11
Required Fields
Number of Passes:
Must be <= 50.
Number of Rows:
Must be <= 100.
Number of Tubes:
Must be <1000.
The following table describes the fields that appear when you click the
Bundle radio button.
Object
Description
Number of Passes
Required. Must be <= 50. With four or more number
of passes, the exchanger tends towards the ideal of
a pure counter current or co-current exchanger.
Number of Rows
Required. Must be <= 100.
Number of Tubes
Required. Must be < 1000.
Type of Bundle
There are five types of bundle layouts available from
the drop-down list; the bundle layout affects the
allowable number of tubes.
NumberOfTubesInARow = NumberOfTubes/
NumberOfRows
If the NumberOfTubesInARow does not have a
remainder, then only these bundles can be used:
• Inline
• Staggered - even rows to the right
• Staggered - even rows to the left
If the NumberofTubesInARow has a remainder, then
only two bundles can be used:
• Staggered - extra tubes in odd rows
• Staggered - extra tube in even rows
Tube Side Flow Orientation
Select the orientation of the tubeside flow with
respect to the X-side flow. This item is used only to
correctly set up a symmetrical bundle. It does not
apply to a non-symmetrical bundle as the tubeside
flow orientation is explicitly set when the bundle is
defined using the Pass Layout Window.
Select from Counter-current (default), Cross-flow,
Co-current
4-22
Heat Transfer Equipment
Object
Description
Rows per Pass
Enter the number of tube rows occupied by each
tubeside pass. Only to be used when specifying
symmetrical bundles. When specifying nonsymmetrical bundles use the Pass Layout Window to
specify the bundle.
Max. No. Tubes per Row per
Pass
Enter the maximum number of tubes in each row
occupied by each pass. Only to be used when
specifying symmetrical bundles. When specifying
non-symmetrical bundles use the interactive bundle
specification feature.
X-Side Stream Mass Flow
Orientation
Defines the X-side flow orientation relative to the
Bundle direction. Enter 0 (vertical-up), 45, 90
(horizontal) or 180 (vertical-down). Default value is 0.
Bundle Relative Direction
Defines the angle of orientation of the bundle relative
to the X-side Stream Mass Flow Direction (XSFD) in
the range -90° to +90°. If 0° (default) is entered the
tubes are always horizontal regardless of the X-side
Stream Mass Flow Direction.
Number of Circuits
Enter the number of times a basic pass layout
pattern appears in the bundle.
4-23
The repeat facility is used when a basic pass layout
pattern is to be repeated a number of times across
the bundle. This feature is most likely to be of use in
air-conditioning coils with U tube circuits. It may only
be used:
a) with inline bundles and staggered bundles with the
same number of tubes per row or,
b) when X-side stream inlet conditions do not vary
across the bundle.
When using the repeat facility, count the original
section as 1 (Default).
Shape of Tubes
Select from Round (default), Oval, or Flat. If Oval or
Flat tubes are selected, the geometric data for the
tube should be entered for each tube type on the
Non-circular Tubes page (click the Tubes radio
button).The geometric data for each fin type can be
entered on the Extended Surfaces page.
Pass Layout Diagram button
Displays a Pass Layout diagram that allows you to
specify the pass arrangement according to your
requirements.
4-23
4-24
Air Cooler
Tubes Radio Button
Figure 4.12
The following table lists and describes the fields that appear when you
click the Tubes radio button.
Object
Description
Common Options
4-24
Add Tube button
Adds a tube to the air cooler.
Remove Tube button
Removes a tube from the air cooler.
Effective Length
This is the length of tube that is transferring heat.
Inactive parts of a tube are where it fits into the
tubesheets and comes into contact with tube
supports. Include these parts in the Total Tube
Length. Default is 6000mm (19.7 ft) for Air-cooled
Heat Exchangers.
Total Length
This is the total length of tube including the ends
fitted into the tubesheets and where the tube comes
into contact with tube supports.This is used for
tubeside pressure drop calculations only. Default
value is the Effective tube length.
Transverse Pitch
This is the distance between the centre-lines of
consecutive tubes in the same tube row. Default is
2.3 times Tube OD for Air-cooled Heat Exchangers
Heat Transfer Equipment
Object
Description
Longitudinal Pitch
If you have a standard TEMA tube layout, i.e.
triangular (30°), rotated square (45°), rotated
triangular (60°) or square (90°) then use the layout
angle.
4-25
If you have a non-standard tube layout then use this
item. The plain tube correlations are only valid for the
standard TEMA tube layout given above so use
layout angle in this case.
For uncommonly large longitudinal pitches, you may
have to allow for a reduction in the heat transfer
coefficient separately from ACOL. Currently ACOL
does not allow for this effect.
There is no default value. The value will be
calculated from the Transverse Pitch and the Layout
Angle.
Layout Angle
If you have more than one
tube type defined, then
corresponding input cells
appear on the Extended
Surfaces and Materials
pages.
Use this field to enter the layout angle for a standard
TEMA tube layout.
• 30° – triangular arrangement (default)
• 45° – rotated square arrangement
• 60° – rotated triangular arrangement
• 90° – square arrangement (for in-line banks
only)
If you have a non-standard tube layout, i.e. one,
which would give a layout angle not in the above list
then, input longitudinal pitch instead of this item. Use
this item for plain tubes, as the correlations are only
valid for the standard TEMA tube layouts. Default
Value is 30°.
Tube Details group options
Tube Number
Displays the system defined tube number.
Tube ID
Up to 4 Tube Diameters may be specified.
Default values for Tube ID(1): Tube ID(1) = Tube
OD(1) – 3.3mm (0.13in) for Air-cooled Heat
Exchangers. Other tube types default to Tube ID(1).
Tube OD
Up to 4 Tube Diameters may be specified. API661
recommends 25.4 mm or 1 inch as the minimum
outside diameter.
Non-Circular Tube Details group options
Non-Circular Tubes checkbox
Check this checkbox to specify non-circular tube
parameters. When you click this checkbox, the fields
listed below appear.
Tube Number
Displays the system defined tube number.
Major Axis on Outside of Tube
Allows you to specify the length of the flatter side of
the tube.
Minor Axis on Outside of
Tube
Allows you to specify the length of ‘short’ side of the
tube.
Tube Wall Thickness
Allows you to specify the tube wall thickness.
4-25
4-26
Air Cooler
Extended Surfaces Page
Figure 4.13
The following table lists and describes the objects on this page.
If you have finned tubes, you
will need to supply tube and
fin details on the Bundle
Geometry and Extended
Surfaces pages.
4-26
Object
Description
Add Fin
Click this button to add a fin. The fin parameter set
appears in the Fin Details table.
Remove Fin
Click this button to remove the select fin parameter
set.
Fin ID
Displays the system generated Fin number.
Fin Type
Allows you to select a fin type from a drop-down list:
• Integral
• G-fin (embedded) (default)
• Modified G-fin
• L-finned
• Bi-metallic or extruded
• Shoulder-grooved
• Tube-in-plate
• Plain tubes
• Serrated fins
• Low fins
• Circular studs
• Rectangular studs
• Elliptical studs
• Lenticular studs
• Chamfered studs
Heat Transfer Equipment
Object
Description
Tip Diameter or Plate Length
For a finned or studded tube, enter the fin (or stud)
tip diameter. Default is 2.25 times Tube OD for Aircooled Heat Exchangers.
4-27
For tube-in-plate fins, enter the plate length in the
direction of the X-side flow (from the leading edge to
the trailing edge of the plate). This will be calculated
if left blank.
Frequency
This is the number of fins per unit length or the
number of stud crowns per unit length. Default is 433
fins/m (11 fins/inch) for Air-cooled Heat Exchangers.
Mean Fin Thickness
For fins made by wrapping ribbon around the base
tube, the fin thickness is usually thinner than the
ribbon thickness. Default is 0.28mm (0.011in) for Aircooled Heat Exchangers
Fin Root Diameter
Enter the root diameter for Integral, L-finned,
Extruded tubes or Shoulder-grooved fins. For other
fin types, the fin root diameter is the base tube
outside diameter. The Common Fin Root Diameter
applies to the whole bundle unless a local values is
used. Defaults to the tube outside diameter.
Number of Studs per Crown
This is the number of studs making up a crown.
Stud Width
This item is not required for circular studs.
Major Axis of Fin
This is the length of the ‘long’ side of the tube.
Default is 54 mm (2.13 in).
Minor Axis of Fin
This is the length of the ‘short’ side of the tube.
Default value is 34 mm (1.34 in).
Fin Root Thickness
For L shape or bimetallic fins. Fin Root Thickness is
used in place of Fin Root Diameter for round fins.
Default value is 0.0.
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4-28
Air Cooler
ACHE Geometry Page
Figure 4.14
The following table lists and describes some of the objects on the ACHE
Geometry page.
Object
Description
Number of Bays per Unit
Required. Range 1-99. Default is 1.
Number of Bundles per Bay
Required. Range 1-12. Default is 1.
Number of Fans per Bay
Required. Range 1-6. Default is 2.
Fan Configuration
Select from Forced Draught, Induced Draught, or No
fans.
Type of Louvres
Select the type of louvres required for the air cooler.
Options appear in the image to the left.
Louvre Angle or Loss
Coefficient
Enter either the louvre opening angle (for louvre
types A-D) or the loss coefficient (for louvre type K).
An angle of 0° is fully open and 90° is fully closed.
4-28
Steam Coils
Select Yes or No (default) depending on whether a
steam coil is fitted. This item is used only in the
calculation of the X-side pressure drop. Steam coils
are assumed to consist of one row of tubes with the
same tube geometry as the first type of fin but with
twice the transverse pitch.
Plenum Depth
This is distance from the bundle side of the fan ring
to the bundle. Defaults to 0.4 times the exchanger
fan diameter.
Heat Transfer Equipment
Object
Description
Ground Clearance
This is the distance from the ground to the fan inlet
for a forced draught exchanger or to the bundle entry
for an induced draught exchanger. Defaults to1.5
times the exchanger fan diameter.
Height Above Bundle
This is the distance from the top of the bundle to the
exchanger exit. Use only with the Natural Convection
simulation option. The hardware height acts as a
’chimney’ filled with hot air.
4-29
For forced draught exchangers this will typically be
the height of a wind skirt above the bundle. For
induced draught exchangers it will be the distance to
the top of the fan casing.
Default value is 0.0.
Exchanger Fan Diameter
This is used to calculate fan related pressure losses
and fan noise levels. The fan diameter cannot be
larger than the bay width. Default calculated to give
40% bundle coverage per fan.
A or V Frame
The default is (None).
Process Data Page
Figure 4.15
Refer to “ACOL Simulation
Modes” on page 18.
HYSYS uses information in the first six fields to determine if ACOL can
run, and what mode it will use.
4-29
4-30
Air Cooler
The following table lists and describes the objects on this page.
Object
Description
Process Steams group
You cannot edit the values in
black text. These values are
determined using input on
other tabs in the Air Cooler
view.
Total Mass Flow
Displays the process stream mass flow calculated by
HYSYS.
Inlet Mass Quality
Displays the default value.
Outlet Mass Quality
Displays the system defined outlet mass quality.
Inlet Temperature
Displays the stream inlet temperature as defined on
the Worksheet tab.
Outlet Temperature
Displays the stream outlet temperature, if available.
Inlet Pressure
Displays the stream inlet pressure as defined on the
Worksheet tab.
Heat Load
You may enter the heat load directly, or omit it and
leave ACOL to calculate it from the stream flowrate
and inlet and outlet conditions.
ACOL will use the input heat load to calculate the
duty ratio (heat load calculated/heat load input),
otherwise it will use the input tubeside stream
conditions.
Fouling Resistance
Allows you to specify the fouling resistance of the
process stream.
Air Stream Conditions group
4-30
Inlet Dry Bulb Design
Temperature
This is the temperature of the incoming air; it has a
significant effect on the overall heat transfer area
required. This is a useful parameter for helping to
determine Annual Fan Power Consumption.
Inlet Gauge Pressure
This is the gauge pressure of the air at entry to the
bundle. This item is intended primarily for ducted
systems where there may be a slight positive air inlet
pressure. Negative values may also be used.The
default air pressure is the International Standard
Atmosphere at sea level, 1013mbar. Use either or
both inlet gauge pressure and altitude to specify the
actual inlet air pressure.
Inlet Humidity Parameter
Select the way in which the Inlet Humidity Value will
be expressed:
• Humidity ratio (default)
• Relative humidity
The only two-phase system that ACOL can handle on
the X-side is the condensation of water vapour from a
humid air stream. Important note: If you want to use
this parameter, ensure that you have selected Humid
Air for the X-side Option
Inlet Humidity Value
This is the value of the air inlet humidity in the way
selected by the Inlet Humidity Parameter.
Winter Des. Temperature for
Fans Only
This is the value for the X-side Stream Winter Inlet
Temperature (or Minimum Ambient Temperature) and
is used for calculating maximum fan power
consumption only. Only relevant to forced draught
exchangers. Default value is 0°C (32°F).
Heat Transfer Equipment
For ACOL to run, it must have
initial values for this group.
Only the estimate that applies
to the current calculation will
be used.
Object
Description
Altitude
This is the height of the unit above sea level. You can
use either or both inlet gauge pressure and altitude to
specify the actual inlet air pressure.The default air
pressure is the International Standard Atmosphere at
sea level, 1013mbar.
Fouling Resistance
Allows you to specify the fouling resistance of the air
stream.
X-Side Option
This is the fluid you wish to use on the X-side. Select
from Dry Air (default), Humid Air, or Dry Gas. Dry Air
is appropriate for air-cooled heat exchangers and
other heat exchangers where air is being heated. Dry
Gas is appropriate for waste heat recovery units
where gases such as flue gases are being cooled.
Also for any exchanger where gases other than or
including air are handled. ACOL cannot handle
condensation of any of the components of the gas
stream.
Air Mass Flow Rate
Allows you to specify the air mass flow rate for the air
stream. You can also edit this value on the Rating tab.
4-31
Solution Estimates - Optional group[
Process Stream Flow Rate
Estimate
Provides an initial value for ACOL calculations. If you
do not enter a value, the following estimates are used.
When calculating the process mass flow rate:
Process Mass Flow = 5kg/s
When calculating the air mass flow rate:
No estimate required
Delta T Estimate
Provides an initial value for ACOL calculations. If you
do not enter a value, the following estimates are used.
When calculating the outlet process temperature:
Outlet Process temp = Inlet Process temp - 10°C
When calculating the inlet process temperature:
Inlet Process temp = Outlet Process temp +
10°C
4-31
4-32
Air Cooler
Materials Page
Figure 4.16
On this page you can define the tube, header and fin materials and
material properties. The default material for tubes and headers is
carbon steel; the default for fins is aluminium.
4-32
Heat Transfer Equipment
4-33
Enhanced Surfaces Page
This page changes depending on which radio button you select.
Specific Enhancements Radio Button
Figure 4.17
The following table lists and describes some of the objects available for
the Specific Enhancements option.
Object
Description
Enhancement Specification
Select the type of enhancement specification from
the drop-down list. Available options appear in the
image to the left.
Pass Number Enhancement
Starts
Enter the pass number from which (and including)
the tube enhancement is to take effect. This allows
you to specify tubeside enhancement where it might
be most effective.
Pass Number Enhancement
Stops
Enter the pass number at which (and including) the
tube enhancement is to stop.
If this item is left blank and tubeside enhancement
has been specified, then the enhancement will stop
at the last pass.
Twisted Tape Thickness
This is the thickness of the twisted tape insert.
Default value is 0.5 mm (0.02 in).
180 Degree Twist Pitch
This is the pitch of the twisted tape insert as it
completes one 180-degree twist. Default value is 50
mm (2 in).
4-33
4-34
4-34
Air Cooler
Object
Description
Wet Wall Desuperheating
Select YES for wet wall (or NO for dry wall)
desuperheating. Wet wall desuperheating occurs
when the bulk temperature of a stream is above the
dew point, but the local wall temperature is below the
dew point. If the wet wall calculation is selected, the
program corrects the heat transfer rate in the
desuperheating zone to allow for condensation
occurring at the wall. When the alternative dry wall
calculation is selected the program uses the single
phase gas coefficient until the bulk vapour
temperature reaches the dew point. As a rule, dry
wall coefficients are usually lower than wet wall
coefficients, and more conservative. Default is Yes
Reynolds Number
This field allows you to enter values of Reynolds
Number for the first and second points which
correspond with input values of tubeside heat
transfer j factors and friction factors. The reference
diameter is the tube inside diameter. A log-log
interpolation is performed between two points.
Extrapolation is not permitted.
Heat Transfer J Factor
This field allows you to enter values of the heat
transfer j factor corresponding to the values of the
Reynolds Number for Points 1 and 2. This is
particularly useful for specifying the performance of
tube inserts. A log-log interpolation is performed
between two points. Extrapolation is not permitted.
Friction Factor
This field allows you to enter values of the friction
factor corresponding to the values of the Reynolds
Number for Points 1 and 2. This is particularly useful
for specifying the performance of tube inserts. A loglog interpolation is performed between two points.
Extrapolation is not permitted.
Heat Transfer Equipment
4-35
General Enhancements Radio Button
Figure 4.18
The following table lists and describes some of the objects available for
the General Enhancements option.
Object
Description
Surface Identification group
Add Surface button
Adds another surface set to the matrix.
Remove Surface button
Removes a surface set from the matrix.
Enhanced Surface Name
Displays the system generated set name. Maximum
number of surfaces = 20.
Where Used
Defines where the enhanced surface is used.
Surface Performance Data group
Set list
Displays the list of available sets.
Reynolds Number
Allows you to specify the Reynolds Number for the
selected set. You can enter up to four values.
Friction Factor
Allows you to specify the friction factor for the
selected set. You can enter up to four values.
Colburn J Factor
Allows you to specify the Colburn J Factor for the
selected set. You can enter up to four values.
4-35
4-36
Air Cooler
Options Page
Figure 4.19
This page determines what appears on the Results page.
Object
Description
Main Output Options group
The Monitor Output group is
used for debugging purposes
only. Use the default settings.
4-36
Units of Output
Determines the output data units. Choose from S.I.,
British/US, and Metric.
Physical Properties Package
Determines where the output data goes: line printer,
separate file, or no output
Detailed Table Output
Determines the output table format.
Lines per Page for Line
Printer Output
Sets the number of lines on a page for printed
output.
Units of Repeat Output
Sets the units for repeated output on the Results
page; contains the same options as Units of Output.
Final Output Page
Select Yes if you require the final output page in the
lineprinter output.
Header Output
Select Yes to show headers in the lineprinter output.
Temperature Table
Select Yes to show the temperature table in the
lineprinter output.
Pressure Tables
Select Yes to show the pressure tables in the
lineprinter output.
Monitor Output group
Input Data
Use the default setting.
Representative Tube Details
Use the default setting.
Heat Transfer Equipment
4-37
Results Page
This page displays the result of the ACOL calculations. Set the format of
the Results page on the Options page.
Figure 4.20
4.2 Cooler/Heater
The difference between the
Cooler and Heater is the
energy balance sign
convention.
The Cooler and Heater operations are one-sided heat exchangers. The
inlet stream is cooled (or heated) to the required outlet conditions, and
the energy stream absorbs (or provides) the enthalpy difference
between the two streams. These operations are useful when you are
interested only in how much energy is required to cool or heat a process
stream with a utility, but you are not interested in the conditions of the
utility itself.
4.2.1 Theory
The Cooler and Heater use the same basic equation.
4-37
4-38
Cooler/Heater
Steady State
The primary difference between a cooler and a heater is the sign
convention. You specify the absolute energy flow of the utility stream,
and HYSYS then applies that value as follows:
•
For a Cooler, the enthalpy or heat flow of the energy stream is
subtracted from that of the inlet stream:
Heat Flowinlet - Dutycooler = Heat Flowoutlet
•
(4.12)
For a Heater, the heat flow of the energy stream is added:
Heat Flowinlet + Dutycooler = Heat Flowoutlet
(4.13)
Dynamic
The Cooler duty is subtracted from the process holdup while the Heater
duty is added to the process holdup.
For a Cooler, the enthalpy or heat flow of the energy stream is removed
from the Cooler process side holdup:
d ( VH out )
M ( H in – H out ) – Q cooler = ρ ----------------------dt
(4.14)
For a Heater, the enthalpy or heat flow of the energy stream is added to
the Heater process side holdup:
d ( VH out )
M ( H in – H out ) + Q heater = ρ ----------------------dt
where:
M = process fluid flow rate
ρ = density
H = enthalpy
Qcooler = cooler duty
Qheater = heater duty
V = volume shell or tube holdup
4-38
(4.15)
Heat Transfer Equipment
4-39
Pressure Drop
The pressure drop of the Cooler/Heater can be determined in one of
two ways:
•
•
Specify the pressure drop manually.
Define a pressure flow relation in the Cooler or Heater by
specifying a k-value.
If the pressure flow option is chosen for pressure drop determination in
the Cooler or Heater, a k value is used to relate the frictional pressure
loss and flow through the Cooler/Heater.
The relation is similar to the general valve equation:
flow =
density × k P 1 – P 2
(4.16)
This general flow equation uses the pressure drop across the heat
exchanger without any static head contributions. The quantity, P1 - P2, is
defined as the frictional pressure loss which is used to “size” the Cooler
or Heater with a k-value.
Dynamic Specifications
In general, two specifications are required by HYSYS in order for the
Cooler/Heater unit operation to fully solve in Dynamic mode:
Dynamic Specifications
Description
Duty Calculation
The duty applied to the Cooler/Heater can be calculated
using one of three different models:
• Supplied Duty
• Product Temp Spec
• Duty Fluid
Specify the duty model in the Model Details group on the
Specs page of the Dynamics tab.
Pressure Drop
Either specify an Overall Delta P or an Overall K-value.
Specify the Pressure Drop calculation in the Dynamic
Specifications group on the Specs page of the Dynamics
tab.
4-39
4-40
Cooler/Heater
4.2.2 Heater or Cooler Propety View
You can also add a new
heater or cooler by pressing
the F12 hot key.
You can also open the
Object Palette by pressing
the F4 hot key.
There are two ways that you can add a Heater or Cooler to your
simulation:
1.
In the Flowsheet menu, select the Add Operation command. The
UnitOps view appears.
2.
Click the Heat Transfer Equipment radio button.
3.
From the list of available unit operations, select Cooler or Heater.
4.
Click the Add button. The Cooler or Heater property view appears.
OR
Cooler icon
5.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
6.
Double-click the Cooler icon or the Heater icon. The Cooler or
Heater property view appears.
Figure 4.21
Heater icon
To ignore the Cooler/Heater during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation (and cannot
calculate the outlet stream) until you restore it to an active state by
deactivating the checkbox.
4-40
Heat Transfer Equipment
4-41
4.2.3 Design Tab
The Design tab contains four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
The Connections page is used to define all of the connections to the
Cooler/Heater. You can specify the inlet, outlet, and energy streams
attached to the operation on this page. The name of the operation can
be changed in the Name field.
Figure 4.22
4-41
4-42
Cooler/Heater
Parameters Page
Remember that HYSYS
uses the proper sign
convention for the unit you
have chosen, so you can
always enter a positive duty
value.
The applicable parameters are the pressure drop (Delta P) across the
process side, and the duty of the energy stream. Both the pressure drop
and energy flow can be specified directly or can be determined from the
attached streams.
Figure 4.23
You can specify a negative duty value, however, be aware of the
following:
•
•
For a Cooler, a negative duty means that the unit is heating the
inlet stream.
For a Heater, a negative duty means that the unit is cooling the
inlet stream.
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
4-42
The Notes page provides a text editor that allows you to record any
comments or information regarding the specific unit operation, or the
simulation case in general.
Heat Transfer Equipment
4-43
4.2.4 Rating Tab
You must specify the rating information only when working with a
dynamics simulation.
Nozzles Page
The Fidelity license is
required to use the nozzle
features found on the
Nozzles page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
On the Nozzles page, you can specify nozzle parameters on both the
inlet and outlet streams connected to a Cooler or Heater. The addition
of nozzles to Coolers and Heaters is relevant when creating dynamic
simulations.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. Refer to Section 1.6.2 - Nozzles in the Dynamic
Modeling manual for more information.
Heat Loss Page
Rating information regarding heat loss is relevant only in Dynamic
mode. The Heat Loss page contains heat loss parameters that
characterize the amount of heat lost across the vessel wall.
You can choose either a Simple or Detailed heat loss model or no heat
loss through the vessel walls.
Simple Model
The Simple model allows you to either specify the heat loss directly, or
have the heat loss calculated from the specified values:
•
•
Overall U value
Ambient Temperature
The heat transfer area, A, and the fluid temperature, Tf, are calculated by
HYSYS using the following equation:
Q = UA(Tf - Tamb)
(4.17)
4-43
4-44
Cooler/Heater
For a Cooler, the parameters available for the Simple model appear in
the figure below.
Figure 4.24
The simple heat loss parameters are as follows:
•
•
•
•
Overall Heat Transfer Coefficient
Ambient Temperature
Overall Heat Transfer Area
Heat Flow
The heat flow is calculated as follows:
Heat Flow = UA(TAmb - T)
where:
(4.18)
U = overall heat transfer coefficient
A = heat transfer area
TAmb = ambient temperature
T = holdup temperature
Heat flow is defined as the heat flowing into the vessel. The heat transfer
area is calculated from the vessel geometry. The ambient temperature,
TAmb, and overall heat transfer coefficient, U, can be modified from their
default values shown in red.
4-44
Heat Transfer Equipment
4-45
Detailed Model
The Fidelity license is
required to use the Detailed
Heat Loss model.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The PF Specs page is
relevant to dynamics cases
only.
The Detailed model allows you to specify more detailed heat transfer
parameters. Refer to Section 1.6.1 - Detailed Heat Model in the
Dynamic Modeling manual for more information.
4.2.5 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the unit
operation. Refer to Section 1.2.3 - Worksheet Tab for more information.
4.2.6 Performance Tab
The Performance tab contains pages that display calculated stream
information. By default, the performance parameters include the
following stream properties:
•
•
•
•
Pressure
Temperature
Vapour Fraction
Enthalpy
Other stream properties can be viewed by adding them to the Viewing
Variables group on the Setup page.
All information appearing on the Performance tab is read-only. The
Performance tab contains the following pages:
•
•
•
•
Profiles
Plots
Tables
Setup
4-45
4-46
Cooler/Heater
Profiles Page
In Steady State mode, HYSYS calculates the zone conditions for the inlet
zone only, regardless of the number of zones specified.
Figure 4.25
Plots Page
In Steady State mode, stream
property readings are taken
only from the inlet and outlet
streams for the plots. As such,
the resulting graph is always a
straight line.
On the Plots page, you can graph any of the default performance
parameters to view changes that occur across the operation. In Steady
State mode, this is always a straight line because the calculated stream
properties are taken only from the inlet and outlet streams. These values
are not calculated incrementally through the operation. All default
performance parameters are listed in the X Variable and Y Variable
drop-down lists below the graph. Select the axis and variables you want
to compare, and the plot is displayed.
To graph other variables, you need to go to the Setup page and add them
to the Selected Viewing Variables group from the Available Variables
listed.
4-46
Heat Transfer Equipment
Right-click on the graph area
to access the graph controls.
Refer to Section 10.4 Graph Control in the User
Guide for more information.
4-47
A temperature - pressure graph for a Cooler, with 5 specified intervals is
displayed in the following figure.
Figure 4.26
You can specify the number of
calculation intervals you want
calculated across the graph in
the Interval field. This divides the
plot line into equally spaced
intervals with the values
displayed as described on the
Tables page.
Tables Page
Information on the Tables
page is read-only, except the
Intervals value.
The Tables page displays the results of the Cooler/Heater in a tabular
format. All default values for the pressure, temperature, vapour fraction,
and enthalpy calculated for each interval are listed here.
Figure 4.27
You can select what phase
options to view by clicking on
the checkbox. For some options
you need to add variables via
the Setup page.
You can specify the number of
calculation intervals you want
calculated across the data in
the Interval field. This divides
the data up into equally
spaced intervals.
4-47
4-48
Cooler/Heater
Setup Page
The Setup page allows you to filter and add variables to be viewed on the
Plots and Tables pages.
Figure 4.28
The variables that are listed in the Selected Viewing Variables group are
available in the X and Y drop down list for plotting on the Plots page.
The variables are also available for tabular plot results on the Tables
page based on the Phase Viewing Options selected.
4-48
Heat Transfer Equipment
4-49
4.2.7 Dynamics Tab
If you are working exclusively
in Steady State mode, you do
not need to change any of the
values on the pages
accessible on the Dynamics
tab.
In the Dynamic mode, the values you enter in the Dynamics tab affects
the calculation. The Dynamics tab contains four pages:
•
•
•
•
Specs
Duty Fluid
Holdup
Stripchart
Specs Page
The Specs page contains information regarding the calculation of
pressure drop across the Cooler or Heater:
Figure 4.29
Zone Information
HYSYS has the ability to partition the Cooler and Heater into discrete
sections called zones. By dividing this unit operation into zones, you can
make different heat transfer specifications for individual zones, and
therefore more accurately model the physical process. Specifying the
Cooler/Heater with one zone provides optimal speed conditions, and is
usually sufficient in modeling accurate exit stream conditions.
4-49
4-50
Cooler/Heater
Model Details
The Model Details group must be completed before the simulation case
solves. The number of zones and the volume of a Cooler/Heater can be
specified in this group. HYSYS can calculate the duty applied to the
holdup fluid using one of the three different methods described in the
table below.
4-50
Model
Description
Supplied Duty
If you select the Supplied Duty radio button, you must specify
the duty applied to the Cooler/Heater. It is recommended that
the duty supplied to the unit operation be calculated from a PID
Controller or a Spreadsheet operation that can account for zero
flow conditions.
Product Temp Spec
If you select the Product Temp Spec radio button, you must
specify the desired exit temperature. HYSYS back calculates
the required duty to achieve the specified desired temperature.
This method does not run as fast as the Supplied Duty model.
Duty Fluid
If you select the Duty Fluid radio button, you can model a
simple utility fluid to heat or cool your process stream. The
following parameters must be specified for the utility fluid on the
Duty Fluid page of the Dynamics tab:
• Mass Flow
• Holdup Mass
• Mass Cp
• Inlet temperature
• Average UA
Heat Transfer Equipment
4-51
Dynamic Specifications
The Cooler or Heater unit
operation, like other dynamic
unit operations, should use
the k-value specification
option as much as possible to
simulate actual pressure flow
relations in the plant.
The Dynamic Specifications group allows you to specify how the
pressure drop is calculated across the Cooler or Heater unit operation.
The table below describes the specifications.
Specification
Description
Overall Delta P
A set pressure drop is assumed across the Cooler or Heater
operation with this specification. The flow and the pressure of
either the inlet or exit stream must be specified, or calculated from
other unit operations in the flowsheet. The flow through the valve is
not dependent on the pressure drop across the Cooler or Heater.
To use the overall delta P as a dynamic specification, activate the
corresponding checkbox in the Dynamic Specifications group
Overall k Value
The k-value defines the relationship between the flow through
Cooler or Heater and the pressure of the surrounding streams. You
can either specify the k-value, or have it calculated from the
stream conditions surrounding the unit operation. You can “size”
the Cooler or Heater with a k-value by clicking the Calculate k
button. Ensure that there is a non zero pressure drop across the
Cooler or Heater before the Calculate k button is clicked. To use
the k-value as a dynamic specification, activate the corresponding
checkbox in the Dynamic Specifications group.
Zone Dynamic Specifications
If the Cooler or Heater operation is specified with multiple zones, you
can click the Spec Zones button to define dynamic specifications for
each zone.
Figure 4.30
4-51
4-52
Cooler/Heater
In the Delta P Specs and Duties group, you can specify the following
parameters:
Dynamic Specification
Description
dP Value
Allows you to specify the fixed pressure drop value.
dP Option
Allows you to either specify or calculate the pressure drop
across the Cooler or Heater. Specify the dP Option with
one of the following options:
• user specified. The pressure drop across the zone
is specified by you in the dP Value field.
• non specified. Pressure drop across the zone is
calculated from a pressure flow relationship. You
must specify a k-value, and activate the specification
for the zone in the Zone Conductance Specifications
group.
Duty
A fixed duty can be specified across each zone in the
Cooler or Heater unit operation.
In the Zone Conductance Specifications group, you can specify the
following parameters:
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Dynamic Specification
Description
k
The k-value for individual zones can be specified in this
field. You can either specify the k-value, or have it
calculated by clicking the Calculate k button
Specification
Activate the specification if the k-value is to be used to
calculate pressure across the zone.
Heat Transfer Equipment
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Duty Fluid Page
The Duty Fluid page becomes visible if the Duty Fluid radio button is
selected on the Specs page.
Figure 4.31
The Duty Fluid page allows you to enter the following parameters to
define your duty fluid:
•
•
•
•
•
Mass Flow
Holdup mass
Mass Cp
Inlet Temperature
Average UA
The Counter Flow checkbox allows you to specify the direction of flow
for the duty fluid. When the checkbox is active, you are using a counter
flow.
The View Zones button displays the duty fluid parameters for each of
the zones specified on the Specs page.
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Cooler/Heater
Holdup Page
The Holdup page contains information regarding the Cooler or Heater
holdup properties, composition, and amount.
Figure 4.32
The Overall Holdup Details group contains information regarding the
Cooler or Heater holdup parameters. For each phase contained within
the volume space of the unit operation, the following is specified:
Holdup Details
Description
Accumulation
The rate of change of material in the holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
The Individual Zone Holdups group contains detailed holdup
properties for each holdup in the Cooler or Heater. In order to view the
advanced properties for individual holdups, you must first choose the
individual zone in the Zone drop-down list.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
The Zone Holdup view appears, and provides more detailed
information about the holdup of that unit operation.
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Heat Transfer Equipment
4-55
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
4.3 Heat Exchanger
Additional Heat Exchanger
models, such as TASC and
STX, are also available.
Contact your local
AspenTech representative for
details.
The Heat Exchanger performs two-sided energy and material balance
calculations. The Heat Exchanger is very flexible, and can solve for
temperatures, pressures, heat flows (including heat loss and heat leak),
material stream flows, or UA.
In HYSYS, you can choose the Heat Exchanger Model for your analysis.
Your choices include an End Point analysis design model, an ideal
(Ft=1) counter-current Weighted design model, a steady state rating
method, and a dynamic rating method for use in dynamic simulations.
The dynamic rating method is available as either a Basic or Detailed
model, and can also be used in Steady State mode for Heat Exchanger
rating. The unit operation also allows the use of third party Heat
Exchanger design methods via OLE Extensibility.
In Dynamic mode, the shell
and tube of the Heat
Exchanger is capable of
storing inventory like other
dynamic vessel operations.
The direction of flow of
material through the Heat
Exchanger is governed by
the pressures of the
surrounding unit operations.
The following are some of the key features of the dynamic Heat
Exchanger operation:
•
•
•
•
A pressure-flow specification option which realistically models
flow through the Heat Exchanger according to the pressure
network of the plant. Possible flow reversal situations can
therefore be modeled.
The choice between a Basic and Detailed Heat Exchanger
model. Detailed Heat Exchanger rating information can be used
to calculate the overall heat transfer coefficient and pressure drop
across the Heat Exchanger.
A dynamic holdup model which calculates level in the Heat
Exchanger shell based on its geometry and orientation.
A heat loss model which accounts for the convective and
conductive heat transfer that occurs across the Heat Exchanger
shell wall.
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Heat Exchanger
4.3.1 Theory
The Heat Exchanger calculations are based on energy balances for the
hot and cold fluids.
Steady State
In the following general relations, the hot fluid supplies the Heat
Exchanger duty to the cold fluid:
(Mcold(Hout - Hin)cold - Qleak) - (Mhot(Hin - Hout)hot - Qloss) =
Balance Error
where:
(4.19)
M = fluid mass flow rate
H = enthalpy
Qleak = heat leak
Qloss = heat loss
The Heat Exchanger
operation allows the heat
curve for either side of the
exchanger to be broken into
intervals. Rather than
calculating the energy
transfer based on the
terminal conditions of the
exchanger, it is calculated for
each of the intervals, then
summed to determine the
overall transfer.
The Balance Error is a Heat Exchanger Specification that equals zero for
most applications.
The subscripts hot and cold designate the hot and cold fluids, while in
and out refer to the inlet and outlet.
The total heat transferred between the tube and shell sides (Heat
Exchanger duty) can be defined in terms of the overall heat transfer
coefficient, the area available for heat exchange, and the log mean
temperature difference:
Q = UA∆T LM F t
where:
U = overall heat transfer coefficient
A = surface area available for heat transfer
∆T TM = log mean temperature difference (LMTD)
Ft = LMTD correction factor
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(4.20)
Heat Transfer Equipment
4-57
The heat transfer coefficient and the surface area are often combined for
convenience into a single variable referred to as UA. The LMTD and its
correction factor are defined in the Performance section.
Dynamic
The following general relation applies to the shell side of the Basic
model Heat Exchanger.
d ( VH out ) shell
M shell ( H in – H out ) shell – Q loss + Q = ρ --------------------------------dt
(4.21)
For the tube side:
d ( VH out ) tube
M tube ( H in – H out ) tube – Q = ρ -------------------------------dt
where:
(4.22)
Mshell = shell fluid flow rate
Mtube = tube fluid flow rate
ρ = density
H = enthalpy
Qloss = heat loss
Q = heat transfer from the tube side to the shell side
V = volume shell or tube holdup
The term Qloss represents the heat lost from the shell side of the dynamic
Heat Exchanger. For more information regarding how Qloss is calculated,
refer to Section 1.3.4 - Heat Loss Model in the Dynamic Modeling
manual.
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Heat Exchanger
Pressure Drop
The pressure drop of the Heat Exchanger can be determined in one of
three ways:
•
•
•
Specify the pressure drop.
Calculate the pressure drop based on the Heat Exchanger
geometry and configuration.
Define a pressure flow relation in the Heat Exchanger by
specifying a k-value.
If the pressure flow option is chosen for pressure drop determination in
the Heat Exchanger, a k value is used to relate the frictional pressure loss
and flow through the exchanger. This relation is similar to the general
valve equation:
f =
density × k P 1 – P 2
(4.23)
This general flow equation uses the pressure drop across the Heat
Exchanger without any static head contributions. The quantity, P1 - P2,
is defined as the frictional pressure loss which is used to “size” the Heat
Exchanger with a k-value.
Dynamic Specifications
The following tables list the minimum specifications required for the
Heat Exchanger unit operation to solve in Dynamic mode.
The Basic Heat Exchanger model requires the following specifications:
Dynamic Specifications
Description
Volume
The tube and shell volumes must be specified.
Overall UA
The Overall UA must be specified.
Pressure Drop
Either specify an Overall Delta P or an Overall K-value for
the Heat Exchanger.
Specify the Pressure Drop calculation method in the
Dynamic Specifications group on the Specs page of the
Dynamics tab. You can also specify the Overall Delta P
values for the shell and tube sides on the Sizing page of
the Rating tab.
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Heat Transfer Equipment
4-59
The Detailed Heat Exchanger model requires the following
specifications:
The overall tube/shell
volumes, and the heat
transfer surface area are
calculated from the shell and
tube ratings information.
Dynamic Specifications
Description
Sizing Data
The tube and shell sides of the Heat Exchanger must be
completely specified on the Sizing page of the Rating tab.
Overall UA
Either specify an Overall UA or have it calculated from the
Shell and Tube geometry.
Specify the U calculation method on the Parameters page
of the Rating tab. The U calculation method can also be
specified on the Model page of the Dynamics tab.
Pressure Drop
Either specify an Overall Delta P or an Overall K-value for
the Heat Exchanger.
Specify the Pressure Drop calculation method on the
Parameters page of the Rating tab. You can also specify
the Pressure Drop calculation method in the Pressure
Flow Specifications group on the Specs page of the
Dynamics tab.
4.3.2 Heat Exchanger Property View
You can also add a new
heat exchanger by pressing
the F12 hot key.
You can also open the
Object Palette by pressing
the F4 hot key.
There are two ways that you can add a Heat Exchanger to your
simulation:
1.
In the Flowsheet menu, select the Add Operation command. The
UnitOps view appears.
2.
Click the Heat Transfer Equipment radio button.
3.
From the list of available unit operations, select Heat Exchanger.
4.
Click the Add button. The Heat Exchanger property view appears.
OR
1.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
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4-60
Heat Exchanger
2.
Double-click the Heat Exchanger icon. The Heat Exchanger
property view is displayed.
Figure 4.33
Heat Exchanger icon
To ignore the Heat Exchanger during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation (and cannot
calculate the outlet stream) until you restore it to an active state by
deactivating the checkbox.
4.3.3 Design Tab
The Design tab contains five pages:
•
•
•
•
•
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Connections
Parameters
Specs
User Variables
Notes
Heat Transfer Equipment
4-61
Connections Page
The Connections page allows you to specify the operation name, and
the inlet and outlet streams of the shell and tube.
Figure 4.34
The main flowsheet is the default flowsheet for the Tube and Shell side.
You can select a sub-flowsheet on the Tube and/or Shell side which
allows you to choose inlet and outlet streams from that flowsheet. This
is useful for processes such as the Refrigeration cycle, which require
separate fluid packages for each side. You can define a sub-flowsheet
with a different fluid package, and then connect to the main flowsheet
Heat Exchanger.
Parameters Page
The Parameters page allows you to select the Heat Exchanger Model and
specify relevant physical data. The parameters appearing on the
Parameters page depend on which Heat Exchanger Model you select.
When a heat exchanger is installed as part of a column sub-flowsheet
(available when using the Modified HYSIM Inside-Out solving method)
these Heat Exchanger Models are not available. Instead, in the column
sub-flowsheet, the heat exchanger is “Calculated from Column” as a
simple heat and mass balance.
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Heat Exchanger
From the Heat Exchanger Model drop-down list, select the calculation
model for the Heat Exchanger. The following Heat Exchanger models
are available:
The HTFS - Engine and
TASC Heat Exchanger
options are only available if
you have installed TASC.
•
•
•
•
•
•
Exchanger Design (Endpoint)
Exchanger Design (Weighted)
Steady State Rating
Dynamic Rating
HTFS - Engine
TASC Heat Exchanger (Refer to the TASC Thermal Reference
manual for more information.)
For both the Endpoint and Weighted models, you can specify whether
your Heat Exchanger experiences heat leak/loss.
•
•
Heat Leak. Loss of cold side duty due to leakage. Duty gained to
reflect the increase in temperature.
Heat Loss. Loss of hot side duty due to leakage. Duty lost to
reflect the decrease in temperature.
The table below describes the radio buttons in the Heat Leak/Loss
group of the Endpoint and Weighted models.
Radio Button
Description
None
By default, the None radio button is selected.
Extremes
On the hot side, the heat is considered to be “lost” where the
temperature is highest. Essentially, the top of the heat curve is being
removed to allow for the heat loss/leak. This is the worst possible
scenario. On the cold side, the heat is gained where the temperature
is lowest.
Proportional
The heat loss is distributed over all of the intervals.
All Heat Exchanger models allow for the specification of either Counter
or Co-Current tube flow. Refer to Section 4.3.4 - Rating Tab for further
details.
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Heat Transfer Equipment
4-63
End Point Model
The End Point model is based on the standard Heat Exchanger duty
equation (Equation (4.20)) defined in terms of overall heat transfer
coefficient, area available for heat exchange, and the log mean
temperature difference (LMTD).
The main assumptions of the model are as follows:
•
•
Overall heat transfer coefficient, U is constant.
Specific heats of both shell and tube side streams are constant.
The End Point model treats the heat curves for both Heat Exchanger
sides as linear. For simple problems where there is no phase change and
Cp is relatively constant, this option may be sufficient to model your
Heat Exchanger. For non-linear heat flow problems, the Weighted
model should be used instead.
Figure 4.35
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4-64
Heat Exchanger
The following parameters are available when the End Point model is
selected:
Parameters
Description
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides of the
exchanger can be specified here. If you do not specify the
Delta P values, HYSYS calculates them from the attached
stream pressures.
UA
The product of the Overall Heat Transfer Coefficient, and the
Total Area available for heat transfer. The Heat Exchanger duty
is proportional to the log mean temperature difference, where
UA is the proportionality factor. The UA can either be specified,
or calculated by HYSYS.
Exchanger
Geometry
The Exchanger Geometry is used to calculate the Ft Factor
using the End Point Model. It is not available for the weighted
model. Refer to the Rating tab for more information on the
Exchanger Geometry.
Weighted Model
The Weighted model is an excellent model to apply to non-linear heat
curve problems such as the phase change of pure components in one or
both Heat Exchanger sides. With the Weighted model, the heating
curves are broken into intervals, and an energy balance is performed
along each interval. A LMTD and UA are calculated for each interval in
the heat curve, and summed to calculate the overall exchanger UA.
The Weighted model is available only for counter-current exchangers,
and is essentially an energy and material balance model. The geometry
configurations which affect the Ft correction factor are not taken into
consideration in this model.
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Heat Transfer Equipment
4-65
When you select the Weighted model, the Parameters page appears as
shown in the figure below.
Figure 4.36
The following table describes the parameters available on the
Parameters page when the Weighted model is selected:
Parameters
Description
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides of the
exchanger can be specified here. If you do not specify the DP
values, HYSYS calculates them from the attached stream
pressures.
UA
The product of the Overall Heat Transfer Coefficient and the
Total Area available for heat transfer. The Heat Exchanger duty
is proportional to the log mean temperature difference, where
UA is the proportionality factor. The UA can either be specified,
or calculated by HYSYS.
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4-66
Heat Exchanger
Parameters
Description
Individual Heat
Curve Details
For each side of the Heat Exchanger, the following parameters
appear (all but the Pass Names can be modified).
• Pass Name.Identifies the shell and tube side according
to the names you provided on the Connections page.
• Intervals.The number of intervals can be specified. For
non-linear temperature profiles, more intervals are
necessary.
• Dew/Bubble Point.Activate this checkbox to add a point
to the heat curve for the dew and/or bubble point. If there
is a phase change occurring in either pass, the
appropriate checkbox should be activated.
There are three choices for the Step Type:
• Equal Enthalpy. All intervals have an equal enthalpy
change.
• Equal Temperature. All intervals have an equal
temperature change.
• Auto Interval. HYSYS determines where points should
be added to the heat curve. This is designed to minimize
error using the least number of intervals.
The Pressure Profile is updated in the outer iteration loop,
using one of the following methods:
• Constant dPdH.Maintains constant dPdH during
update.
• Constant dPdUA.Maintains constant dPdUA during
update.
• Constant dPdA. Maintains constant dPdA during
update. This is not currently applicable to the Heat
Exchanger, as the area is not predicted.
• Inlet Pressure.Pressure is constant and equal to the
inlet pressure.
• Outlet Pressure. Pressure is constant and equal to the
outlet pressure.
Steady State Rating Model
The Steady State Rating model is an extension of the End Point model to
incorporate a rating calculation, and uses the same assumptions as the
End Point model. If you provide detailed geometry information, you can
rate the exchanger using this model. As the name suggests, this model is
only available for steady state rating.
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Heat Transfer Equipment
4-67
When dealing with linear or nearly linear heat curve problems, the
Steady State Rating model should be used. Due to the solver method
incorporated into this rating model, the Steady State Rating model can
perform calculations exceptionally faster than the Dynamic Rating
model.
Figure 4.37
The following parameters are available on the Parameters page when
the Steady State Rating model is selected:
Parameters
Description
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides of the
exchanger can be specified here. If you do not specify the
Delta P values, HYSYS calculates them from the attached
stream pressures.
UA
The product of the Overall Heat Transfer Coefficient, and the
Total Area available for heat transfer. The Heat Exchanger duty
is proportional to the log mean temperature difference, where
UA is the proportionality factor. The UA can either be specified,
or calculated by HYSYS.
Dynamic Rating
Two models are available for Dynamic Rating using the Heat Exchanger
unit operation: a Basic and a Detailed model. If you specify three
temperatures or two temperatures and a UA, you can rate the exchanger
with the Basic model. If you provide detailed geometry information, you
can rate the exchanger using the Detailed model.
The Specs page no longer appears when Dynamic Rating is selected.
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4-68
Heat Exchanger
The Basic model is based on the same assumptions as the End Point
model, which uses the standard Heat Exchanger duty equation
(Equation (4.20)) defined in terms of overall heat transfer coefficient,
area available for heat exchange, and the log mean temperature
difference. The Basic model is actually the counterpart of the End Point
model for dynamics and dynamic rating. The Basic model can also be
used for steady state Heat Exchanger rating.
The Detailed model is based on the same assumptions as the Weighted
model, and divides the Heat Exchanger into a number of heat zones,
performing an energy balance along each interval. This model requires
detailed geometry information about your Heat Exchanger. The
Detailed model is actually the counterpart of the Weighted model for
dynamics and dynamic rating, but can also be used for steady state Heat
Exchanger rating.
The Basic and Detailed Dynamic Rating models share rating
information with the Dynamics Heat Exchanger model. Any rating
information entered using these models is observed in Dynamic mode.
Once the Dynamic Rating model is selected, no further information is
required on the Parameters page of the Design tab. You can choose the
model (Basic or Detailed) on the Parameters page of the Rating tab.
Figure 4.38
4-68
Heat Transfer Equipment
4-69
HTFS - Engine
The figure below shows the Parameters page of the Design tab, if you
select the HTFS - Engine model. Notice that the values in the fields
appear in black, indicating that they are HYSYS calculated values, and
you cannot change them in the current fields.
Figure 4.39
To change the variable values shown on this page, you have to go to the
HTFS - TASC tab on the Heat Exchanger property view. Refer to Section
4.3.8 - HTFS-TASC Tab for more information.
Specs Page
If you are working with a
Dynamic Rating model, the
Specs page does not appear
on the Design tab.
The Specs page includes three groups that organize various
specifications and solver information. The information provided on the
Specs page is only valid for the Weighted, Endpoint, and Steady State
Rating models.
Figure 4.40
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4-70
Heat Exchanger
Solver Group
The following parameters are listed in the Solver group:
Parameters
Details
Tolerance
The calculation error tolerance can be set.
Current Error
When the current error is less than the calculation tolerance, the
solution is considered to have converged.
Iterations
The current iteration of the outer loop appears. In the outer loop, the
heat curve is updated and the property package calculations are
performed. Non-rigorous property calculations are performed in the
inner loop. Any constraints are also considered in the inner loop.
Unknown Variables Group
HYSYS lists all unknown Heat Exchanger variables according to your
specifications. Once the unit has solved, the values of these variables
appear.
Specifications Group
Without the Heat Balance
specification, the heat
equation is not balanced. For
this reason, it is considered a
heat exchanger constraint.
Notice the Heat Balance (specified at 0 kJ/h) is considered to be a
constraint. This is a Duty Error spec, which you cannot turn off. Without
the Heat Balance specification, you could, for example, completely
specify all four Heat Exchanger streams, and have HYSYS calculate the
Heat Balance error which would be displayed in the Current Value
column of the Specifications group.
The UA is also included as a default specification. HYSYS displays this as
a convenience, since it is a common specification. You can either use
this spec or deactivate it.
You can View or Delete highlighted specifications by using the buttons
at the right of the group. A specification view appears automatically
each time a new spec is created via the Add button. Figure 4.41 shows a
typical view of a specification, which is accessed via the View or Add
button.
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Heat Transfer Equipment
4-71
Each specification view has two tabs:
•
•
Parameters
Summary
For example, defining the Delta Temp spec requires two stream names
and a value for the specification.
Figure 4.41
The Summary page is used to define whether the specification is Active
or an Estimate. The Spec Value is also shown on this page.
Information specified on the specification view also appears in the
Specifications group.
All specifications are one of the following three types:
An Active specification is one
that the convergence
algorithm is trying to meet. An
Active specification is on
when both checkboxes are
activated.
An Estimate is used as an
initial “guess” for the
convergence algorithm, and is
considered to be an inactive
specification.
A Completely Inactive
specification is one that is
ignored completely by the
convergence algorithm, but
can be made Active or an
Estimate at a later time.
Specification Type
Description
Active
An active specification is one that the convergence algorithm is
trying to meet. An active specification always serves as an
initial estimate (when the Active checkbox is checked, HYSYS
automatically activates the Estimate checkbox). An active
specification exhausts one degree of freedom.
Estimate
An Estimate is considered an Inactive specification because
the convergence algorithm is not trying to satisfy it. To use a
specification as an estimate only, uncheck the Active checkbox.
The value then serves only as an initial estimate for the
convergence algorithm. An estimate does not use an available
degree of freedom.
Completely Inactive
To disregard the value of a specification entirely during
convergence, deactivate both the Active and Estimate
checkboxes. By ignoring rather than deleting a specification, it
remains available if you want to use it later.
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4-72
Heat Exchanger
The specification list allows you to try different combinations of the
above three specification types. For example, suppose you have a
number of specifications, and you want to determine which ones should
be active, which should be estimates and which ones should be ignored
altogether. By manipulating the checkboxes among various
specifications, you can test various combinations of the three types to
see their effect on the results.
The available specification types include the following:
The Hot Inlet Equilibrium
temperature is the
temperature of the inlet hot
stream minus the heat loss
temperature drop.
The Cold Inlet Equilibrium
temperature is the
temperature of the inlet cold
stream plus the heat leak
temperature rise.
Specification
Description
Temperature
The temperature of any stream attached to the Heat
Exchanger. The hot or cold inlet equilibrium temperature can
also be defined.
Delta Temp
The temperature difference at the inlet or outlet between any
two streams attached to the Heat Exchanger. The hot or cold
inlet equilibrium temperatures (which incorporate the heat loss/
heat leak with the inlet conditions) can also be used.
Minimum Approach
Minimum internal temperature approach. The minimum
temperature difference between the hot and cold stream (not
necessarily at the inlet or outlet).
UA
The overall UA (product of overall heat transfer coefficient and
heat transfer area).
LMTD
The overall log mean temperature difference.
Duty
The overall duty, duty error, heat leak or heat loss. The duty
error should normally be specified as 0 so that the heat
balance is satisfied. The heat leak and heat loss are available
as specifications only if the Heat Loss/Leak is set to Extremes
or Proportional on the Parameters page.
Duty Ratio
A duty ratio can be specified between any two of the following
duties: overall, error, heat loss, and heat leak.
Flow
The flowrate of any attached stream (molar, mass or liquid
volume).
Flow Ratio
The ratio of the two inlet stream flowrates. All other ratios are
either impossible or redundant (i.e., - the inlet and outlet
flowrates on the shell or tube side are equal).
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
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Heat Transfer Equipment
4-73
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor that allows you to record any
comments or information regarding the specific unit operation or the
simulation case in general.
4.3.4 Rating Tab
The Parameters page is
used exclusively by the
dynamics Heat Exchanger,
and only becomes active
either in Dynamic mode or
while using the Dynamic
Rating model.
The Rating tab contains four pages:
•
•
•
•
Sizing
Parameters
Nozzles
Heat Loss
Sizing Page
The Sizing page provides Heat Exchanger sizing related information.
Based on the geometry information, HYSYS is able to calculate the
pressure drop and the convective heat transfer coefficients for both
Heat Exchanger sides and rate the exchanger.
The information is grouped under three radio buttons:
•
•
•
Overall
Shell
Tube
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4-74
Heat Exchanger
Overall
When you select the Overall radio button, the overall Heat Exchanger
geometry appears:
Figure 4.42
Tube flow
direction can
be defined as
either Counter
or Co-Current
for all heat
exchanger
calculation
models.
In the Configuration group, you can specify whether multiple shells are
used in the Heat Exchanger design.
The following fields appear, and can be modified in, the Configuration
group.
For n shell passes, HYSYS
solves the heat exchanger on
the basis that at least 2n tube
passes exist. Charts for Shell
and Tube Exchanger LMTD
Correction Factors, as found
in the GPSA Engineering Data
Book, are normally in terms of
n shell passes and 2n or more
tube passes.
4-74
Field
Description
Number of
Shell Passes
You have the option of HYSYS performing the calculations for
Counter Current (ideal with Ft = 1.0) operation, or for a specified
number of shell passes. Specify the number of shell passes to be
any integer between 1 and 7. When the shell pass number is
specified, HYSYS calculates the LMTD correction factor (Ft) for the
current exchanger design. A value lower than 0.8 generally
corresponds to inefficient design in terms of the use of heat transfer
surface. More passes or larger temperature differences should be
used in this case.
Number of
Shells in Series
If a multiple number of shells are specified in series, the
configuration is shown as follows:
Heat Transfer Equipment
Field
Description
Number of
Shells in
Parallel
If a multiple number of shells are specified in parallel, the
configuration is shown as follows:
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Currently, multiple shells in parallel are not supported in HYSYS.
The Shell Feed at Bottom
checkbox is only visible for
the vertical oriented
exchanger.
Tube Passes
per Shell
The number of tube passes per shell. The default setting is 2 (i.e.,
the number of tubes equal to 2n, where n is the number of shells.)
Exchanger
Orientation
The exchanger orientation defines whether or not the shell is
horizontal or vertical. Used only in dynamic simulations.
When the shell orientation is vertical, you can also specify whether
the shell feed is at the top or bottom via the Shell Feed at Bottom
checkbox.
First Tube Pass
Flow Direction
Specifies whether or not the tube feed is co-current or countercurrent.
Elevation
(base)
The height of the base of the exchanger above the ground. Used
only in dynamic simulations.
You can specify the number of shell and tube passes in the shell of the
Heat Exchanger. In general, at least 2n tube passes must be specified for
every n shell pass. The exception is a counter-current flow Heat
Exchanger which has 1 shell pass and one tube pass. The orientation
can be specified as a vertical or horizontal Heat Exchanger. The
orientation of the Heat Exchanger does not impact the steady state
solver, however, it is used in the Dynamics Heat Exchanger Model in the
calculation of liquid level in the shell.
For a more detailed
discussion of TEMA-style
shell-and-tube heat
exchangers, refer to page 1133 of the Perry’s Chemical
Engineers’ Handbook (1997
edition).
The shape of Heat Exchanger can be specified using the TEMA-style
drop-down lists. The first list contains a list of front end stationary head
types of the Heat Exchanger. The second list contains a list of shell types.
The third list contains a list of rear end head types.
Figure 4.43
4-75
4-76
Heat Exchanger
In the Calculated Information group, the following Heat Exchanger
parameters are listed:
•
•
•
•
•
•
•
•
•
Shell HT Coeff
Tube HT Coeff
Overall U
Overall UA
Shell DP
Tube DP
Heat Trans. Area per Shell
Tube Volume per Shell
Shell Volume per Shell
Shell
Selecting the Shell radio button allows you to specify the shell
configuration and the baffle arrangement in each shell.
Figure 4.44
In the Shell and Tube Bundle Data group, you can specify whether
multiple shells are used in the Heat Exchanger design. The following
fields appear, and can be modified in, the Shell and Tube Bundle Data
group.
4-76
Field
Description
Shell Diameter
Diameter of the shell(s).
Number of Tubes
per Shell
Number of tubes per shell. You can change the value in this field.
Tube Pitch
Shortest distance between the centres of two adjacent tubes.
Heat Transfer Equipment
Field
Description
Tube Layout Angle
In HYSYS, the tubes in a single shell can be arranged in four
different symmetrical patterns:
• Triangular (30°)
• Triangular Rotated (60°)
• Square (90°)
• Square Rotated (45°)
For more information regarding the benefits of different tube
layout angles, refer to page 139 of Process Heat Transfer by
Donald Q. Kern (1965)
Shell Fouling
The shell fouling factor is taken into account in the calculation of
the overall heat transfer coefficient, UA.
4-77
The following fields appear, and can be modified in, the Shell Baffles
group:
Field
Description
Shell Baffle Type
You can choose from four different baffle types:
•
•
•
•
Single
Double
Triple
Grid
Shell Baffle
Orientation
You can choose whether the baffles are aligned horizontally or
vertically along the inner shell wall.
Baffle cut (Area%)
You can specify the percent area where the liquid flows through
relative to the cross sectional area of the shell. The baffle cut is
expressed as a percent of net free area. The net free area is
defined as the total cross-sectional area in the flow direction
parallel to the tubes minus the area blocked off by the tubes
(essentially the percentage of open area).
Baffle Spacing
You can specify the space between each baffle.
4-77
4-78
Heat Exchanger
Tube
Selecting the Tube radio button allows you to specify the tube geometry
information in each shell.
Figure 4.45
The Dimensions group allows you to specify the following tube
geometric parameters:
Field
Description
Outer Tube Diameter (OD)
Two of the three listed parameters must be specified to
characterize the tube width dimensions.
Inner Tube Diameter (ID)
Tube Thickness
This value is not the actual
tube length.
Tube Length
Heat transfer length of one tube in a single Heat
Exchanger shell.
In the Tube Properties group, the following metal tube heat transfer
properties must be specified:
•
•
•
•
4-78
Tube Fouling Factor
Thermal Conductivity
Wall Specific Heat Capacity, Cp
Wall Density
Heat Transfer Equipment
4-79
Parameters Page
The Parameters page of the Rating tab is used to define rating
parameters for the Dynamic Rating model. On the Parameters page, you
can specify either a Basic model or a Detailed model. For the Basic
model, you must define the Heat Exchanger overall UA and pressure
drop across the shell and tube. For the Detailed model, you must define
the geometry and heat transfer parameters of both the shell and tube
sides in the Heat Exchanger operation. In order for either the Basic or
Detailed Heat Exchanger Model to completely solve, the Parameters
page must be completed.
Basic Model
When you select the Basic model radio button on the Parameters page
in Dynamic mode, the following view appears.
Figure 4.46
The Dimensions group contains the following information:
•
•
•
Tube Volume
Shell Volume
Elevation (Base)
The tube volume, shell volume, and heat transfer area are calculated
from Shell and Tube properties specified by selecting the Shell and Tube
radio buttons on the Sizing page. The elevation of the base of the Heat
Exchanger can be specified but does not impact the steady state solver.
The Prevent Temperature Cross checkbox is used to activate additional
model options when checked. These additional model options prevent
temperature crosses by automatically reducing the heat transfer rate
slowly.
4-79
4-80
Heat Exchanger
The Parameters group includes the following Heat Exchanger
parameters. All but the correction factor, F, can be modified:
Field
Description
Overall UA
The product of the Overall Heat Transfer Coefficient, and the
Total Area available for heat transfer. The Heat Exchanger duty
is proportional to the log mean temperature difference, where
UA is the proportionality factor. The UA can either be specified,
or calculated by HYSYS.
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides of the
exchanger can be specified here. If you do not specify the DP
values, HYSYS calculates them from the attached stream
pressures.
Detailed Model
The Detailed model option allows you to specify the zone information,
heat transfer coefficient, and Delta P details. When you select the
Detailed model radio button on the Parameters page, the following view
appears.
Figure 4.47
Zone Information
HYSYS can partition the Heat Exchanger into discrete multiple sections
called zones. Because shell and tube stream conditions do not remain
constant across the operation, the heat transfer parameters are not the
same along the length of the Heat Exchanger. By dividing the Heat
Exchanger into zones, you can make different heat transfer
specifications for individual zones, and therefore more accurately
model an actual Heat Exchanger.
4-80
Heat Transfer Equipment
4-81
In the Zone Information group you can specify the following:
Field
Description
Zones per Shell Pass
Enter the number of zones you want for one shell. The total
number of zones in a Heat Exchanger shell is calculated as:
Total Zones = Total Shell Passes ⋅ Zones
Zone Fraction
The fraction of space the zone occupies relative to the total
shell volume. HYSYS automatically sets each zone to have
the same volume. You can modify the zone fractions to
occupy a larger or smaller proportion of the total volume.
Click the Normalize Zone Fractions button in order to adjust
the sum of fractions to equal one.
Heat Transfer Coefficients
The Heat Transfer Coefficients group contains information regarding
the calculation of the overall heat transfer coefficient, UA, and local heat
transfer coefficients for the fluid in the tube, hi, and the fluid
surrounding the tube, ho. The heat transfer coefficients can be
determined in one of two ways:
•
•
The heat transfer coefficients can be specified using the rating
information provided on the Parameters page and the stream
conditions.
You can specify the heat transfer coefficients.
For fluids without phase change, the local heat transfer coefficient, hi, is
calculated according to the Sieder-Tate correlation:
0.027k m D i G i 0.8 C p, i µ i 1 ⁄ 3  µ i  0.14
---------h i = --------------------  ------------  ---------------
 µ i, w
Di  µi   km 
where:
(4.24)
Gi = mass velocity of the fluid in the tubes (velocity*density)
µ i = viscosity of the fluid in the tube
µ i, w = viscosity of the fluid inside tubes, at the tube wall
Cp,i = specific heat capacity of the fluid inside the tube
4-81
4-82
Heat Exchanger
The relationship between the local heat transfer coefficients, and the
overall heat transfer coefficient is shown in Equation (4.25).
1
U = --------------------------------------------------------------------Do
1
1
----- + r o + r w + ------  r i + ----
Di 
ho
h i
where:
(4.25)
U = overall heat transfer coefficient
ho = local heat transfer coefficient outside tube
hi = local heat transfer coefficient inside tube
ro = fouling factor outside tube
ri = fouling factor inside tube
rw = tube wall resistance
Do = outside diameter of tube
Di = inside diameter of tube
The Heat Transfer coefficients group contains the following
information:
Field
Description
Shell/Tube Heat
Transfer Coefficient
The local Heat Transfer Coefficients, ho and hi, can be
specified or calculated.
Shell/Tube HT
Coefficient
Calculator
The Heat Transfer Coefficient Calculator allows you to either
specify or calculate the local Heat Transfer Coefficients.
Specify the cell with one of following options:
• Shell & Tube. The local heat transfer coefficients, ho and
hi, are calculated using the heat exchange rating
information and correlations.
• U specified. The local heat transfer coefficients, ho and hi,
are specified by you.
4-82
Heat Transfer Equipment
4-83
Delta P
The Delta P group contains information regarding the calculation of the
shell and tube pressure drop across the exchanger. In Steady State
mode, the pressure drop across either the shell or tube side of the Heat
Exchanger can be calculated in one of two ways:
•
•
The pressure drop can be calculated from the rating information
provided in the Sizing page and the stream conditions.
The pressure drop can be specified.
The Delta P group contains the following information:
Field
Description
Shell/Tube Delta P
The pressure drop across the Shell/Tube side of the Heat
Exchanger can be specified or calculated.
Shell/Tube Delta P
Calculator
The Shell/Tube Delta P Calculator allows you to either specify
or calculate the shell/tube pressure drop across the Heat
Exchanger. Specify the cell with one of following options:
• Shell & Tube Delta P Calculator. The pressure drop is
calculated using the Heat Exchanger rating information
and correlations.
• User specified. The pressure drop is specified by you.
• Non specified. This option is only applicable in Dynamic
mode. Pressure drop across the Heat Exchanger is
calculated from a pressure flow relation.
Detailed Heat Model Properties
When you click the Specify Parameters for Individual Zones button, the
Detailed Heat Model Properties view appears. The Detailed Heat Model
Properties view displays the detailed heat transfer parameters and
holdup conditions for each zone. HYSYS uses the following terms to
describe different locations within the Heat Exchanger.
Location Term
Description
Zone
HYSYS represents the zone using the letter “Z”. Zones are
numbered starting from 0. For instance, if there are 3 zones in a
Heat Exchanger, the zones are labeled: Z0, Z1, and Z2.
4-83
4-84
Heat Exchanger
Location Term
Description
Holdup
HYSYS represents the holdup within each zone with the letter “H”.
Holdups are numbered starting from 0. “Holdup 0” is always the
holdup of the shell within the zone. Holdups 1 through n represents
the n tube holdups existing in the zone.
Tube Location
HYSYS represents tube locations using the letters “TH”. Tube
locations occur at the interface of each zone. Depending on the
number of tube passes per shell pass, there can be several tube
locations within a particular zone. For instance, 2 tube locations
exist for each zone in a Heat Exchanger with 1 shell pass and 2 tube
passes. Tube locations are numbered starting from 1.
Consider a shell and tube Heat Exchanger with 3 zones, 1 shell pass, and
2 tube passes. The following diagram labels zones, tube locations, and
hold-ups within the Heat Exchanger:
Figure 4.48
4-84
Heat Transfer Equipment
4-85
Heat Transfer (Individual) Tab
Information regarding the heat transfer elements of each tube location
in the Heat Exchanger appears on the Heat Transfer (Individual) tab.
Figure 4.49
Heat transfer from the fluid in the tube to the fluid in the shell occurs
through a series of heat transfer resistances or elements. There are two
convective elements, and one conductive element associated with each
tube location.
This tab organizes all the heat transfer elements for each tube location
in one spreadsheet. You can choose whether Conductive or Convective
elements will appear by selecting the appropriate element type in the
Heat Transfer Type drop-down list.
The following is a list of possible elements for each tube location:
Heat Transfer Element
Description
Convective Element
The Shell Side element is associated with the local heat
transfer coefficient, ho, around the tube. The Tube Side is
associated with the local heat transfer coefficient, hi, inside
the tube.These local heat transfer coefficients can be
calculated by HYSYS or modified by you.
Conductive Element
This element is associated with the conduction of heat
through the metal wall of the tube. The conductivity of the
tube metal, and the inside and outside metal wall
temperatures appear. You can modify the conductivity.
4-85
4-86
Heat Exchanger
Heat Transfer (Global) Tab
The Heat Transfer (Global) tab displays the heat transfer elements for
the entire Heat Exchanger. You can choose whether the overall
Conductive or Convective elements are to appear by selecting the
appropriate element type in the Heat Transfer Type drop-down list.
Tabular Results Tab
You can choose whether the
flow path is shell or tube
side by selecting the
appropriate flow path in the
Display which flow path?
drop-down list.
The Tabular Results tab displays the following stream properties for the
shell and tube fluid flow paths. The feed and exit stream conditions
appear for each zone.
•
•
•
•
•
•
•
•
Temperature
Pressure
Vapour Fraction
Molar Flow
Enthalpy
Cumulative UA
Cumulative Heat Flow
Length (into Heat Exchanger)
Specs (Individual) Tab
You can choose whether the
shell or tube side appears by
selecting the appropriate
flow path in the Display
which flow path? drop-down
list.
4-86
The Specs (Individual) tab displays the pressure drop specifications for
each shell and tube holdup in one spreadsheet.
Figure 4.50
Heat Transfer Equipment
4-87
The Pressure Flow K and Use Pressure Flow K columns are applicable
only in Dynamic mode.
Specs (Global) Tab
The Specs (Global) tab displays the pressure drop specifications for the
entire shell and tube holdups. The Pressure Flow K and Use Pressure
Flow K columns are applicable only in Dynamic mode.
You can choose whether the shell or tube side appears by selecting the
appropriate flow path in the Display which flow path? drop-down list.
Plots Tab
The information displayed on the Plots tab is a graphical representation
of the parameters provided on the Tabular Results tab. You can plot the
following variables for the shell and tube side of the Heat Exchanger:
•
•
•
•
•
•
Vapour Fraction
Molar Flow
Enthalpy
Cumulative UA
Heat Flow
Length
Nozzles Page
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. The Fidelity license is required to use the
Nozzle features found on this page. Refer to Section 1.6 - Fidelity in the
Dynamic Modeling manual for more information.
The placement of feed and product nozzles on the Detailed Dynamic
Heat Exchanger operation has physical meaning. The exit stream’s
composition depends on the exit stream nozzle’s location and diameter
in relation to the physical holdup level in the vessel. If the product
nozzle is located below the liquid level in the vessel, the exit stream
draws material from the liquid holdup. If the product nozzle is located
above the liquid level, the exit stream draws material from the vapour
holdup.
4-87
4-88
Heat Exchanger
If the liquid level sits across a nozzle, the mole fraction of liquid in the
product stream varies linearly with how far up the nozzle the liquid is.
Essentially, all vessel operations in HYSYS are treated the same. The
compositions and phase fractions of each product stream depend solely
on the relative levels of each phase in the holdup and the placement of
the product nozzles, so a vapour product nozzle does not necessarily
produce pure vapour. A 3-phase separator may not produce two distinct
liquid phase products from its product nozzles.
Heat Loss Page
The Heat Loss page contains heat loss parameters which characterize
the amount of heat lost across the vessel wall. You can choose either to
have no heat loss model, a Simple heat loss model or a Detailed heat loss
model.
Simple Heat Loss Model
Figure 4.51
4-88
Heat Transfer Equipment
4-89
When you select the Simple radio button, the following parameters
appear:
•
•
•
•
Overall U
Ambient Temperature
Overall Heat Transfer Area
Heat Flow
Detailed Heat Loss Model
The Detailed model allows you to specify more detailed heat transfer
parameters. The Fidelity license is required to use the Detailed Heat
Loss model found on this page. Refer to Section 1.6 - Fidelity in the
Dynamic Modeling manual for more information.
4.3.5 Worksheet Tab
To view the stream
parameters broken down per
stream phase, open the
Worksheet tab of the stream
property view.
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Heat
Exchanger unit operation. Refer to Section 1.2.3 - Worksheet Tab for
more information.
4.3.6 Performance Tab
The Performance tab has pages that display the results of the Heat
Exchanger calculations in overall performance parameters, as well as
using plots and tables.
The Performance tab contains the following pages:
•
•
•
•
•
Details
Plots
Tables
Setup
Error Msg
4-89
4-90
Heat Exchanger
Details Page
The information from the Details page appears in the figure below.
Figure 4.52
The appearance of this page
is slightly different for the
Dynamic Rating model.
Dynamic Rating.
Steady State Rating.
Overall Performance Group
The Overall and Detailed performance groups contain the following
parameters that are calculated by HYSYS:
4-90
Parameter
Description
Duty
Heat flow from the hot stream to the cold stream.
Heat Leak
Loss of cold side duty due to leakage. Duty gained to reflect
the increase in temperature.
Heat Loss
Loss of the hot side duty to leakage. The overall duty plus the
heat loss is equal to the individual hot stream duty defined on
the Tables page.
UA
Product of the Overall Heat Transfer Coefficient, and the Total
Area available for heat transfer. The UA is equal to the overall
duty divided by the LMTD.
Minimum Approach
The minimum temperature difference between the hot and cold
stream.
Mean Temp Driving
Force
The average temperature difference between the hot and cold
stream.
LMTD
The uncorrected LMTD multiplied by the Ft factor. For the
Weighted Rating Method, the uncorrected LMTD equals the
effective LMTD.
UA Curvature Error
The LMTD is ordinarily calculated using constant heat capacity.
An LMTD can also be calculated using linear heat capacity. In
either case, a different UA is predicted. The UA Curvature Error
reflects the difference between these UAs.
Heat Transfer Equipment
4-91
Parameter
Description
Hot Pinch
Temperature
The hot stream temperature at the minimum approach.
Cold Pinch
Temperature
The cold stream temperature at the minimum approach.
Ft Factor
The LMTD (log mean temperature difference) correction factor,
Ft, is calculated as a function of the Number of Shell Passes
and the temperature approaches. For a counter-current Heat
Exchanger, Ft is 1.0. For the Weighted rating method, Ft = 1.
Uncorrected LMTD
(Applicable only for the End Point method) - The LMTD is
calculated in terms of the temperature approaches (terminal
temperature differences) in the exchanger, using the Equation
(4.26).
Uncorrected LMTD equation:
∆T 1 – ∆T 2
∆T LM = --------------------------------------ln ( ∆T 1 ⁄ ( ∆T 2 ) )
where:
(4.26)
∆T 1 = T hot, out – T cold, in
∆T 2 = T hot, in – T cold, o ut
Plots Page
You can modify the
appearance of the plot via the
Graph Control view. Refer to
Section 10.4 - Graph
Control in the User Guide for
more information.
You can plot curves for the hot and/or cold fluid. Use the Plot
checkboxes to specify which side(s) of the exchanger should be plotted.
Figure 4.53
4-91
4-92
Heat Exchanger
The following default variables can be plotted along either the X or Yaxis:
•
•
•
•
•
•
Temperature
UA
Delta T
Enthalpy
Pressure
Heat Flow
Select the combination from the Plot Type drop-down list. To Plot other
available variables, you need to add them on the Setup page. Once the
variables are added, they are available in the X and Y drop-down lists.
Tables Page
On the Tables page, you can view (default variables) interval
temperature, pressure, heat flow, enthalpy, UA, and vapour fraction for
each side of the Exchanger in a tabular format. Select either the Shell
Side or Tube Side radio button.
To view other available variables, you need to add them on the Setup
page. Variables are displayed based on Phase Viewing Options selected.
Setup Page
The Setup page allows you to filter and add variables to be viewed on the
Plots and Tables pages .
The variables that are listed in the Selected Viewing Variables group are
available in the X and Y drop down list for plotting on the Plots page.
The variables are also available for tabular plot results on the Tables
page based on the Phase Viewing Options selected.
Error Msg Page
The Error Msg page contains a list of the warning messages on the Heat
Exchanger. You cannot add comments to this page. Use it to see if there
are any warnings in modeling the Heat Exchanger.
4-92
Heat Transfer Equipment
4-93
4.3.7 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Dynamics tab.
The Dynamics tab contains four pages:
•
•
•
•
Model
Specs
Holdup
Stripchart
Any information specified on the Rating tab also appears in the
Dynamics tab.
Model Page
In the Model page, you can specify whether HYSYS uses a Basic or
Detailed model.
Figure 4.54
4-93
4-94
Heat Exchanger
Basic Model
The Model Parameters group contains the following information for the
Heat Exchanger unit operation:
Field
Description
Tube/Shell Volume
The volume of the shell and tube must be specified in the Basic
model.
Elevation
The elevation is significant in the calculation of static head
around and in the Heat Exchanger.
Overall UA
Product of the Overall Heat Transfer Coefficient and the Total
Area available for heat transfer. The Heat Exchanger duty is
proportional to the log mean temperature difference, where UA
is the proportionality factor. The UA must be specified if the
Basic model is used.
Shell/Tube UA
Reference Flow
Since UA depends on flow, these parameters allow you to set a
reference point that uses HYSYS to calculate a more realistic
UA value. If no reference point is set then UA is fixed.
If the UA is specified, the specified UA value does not change
during the simulation. The UA value that is used, however,
does change if a Reference Flow is specified. Basically, as in
most heat transfer correlation’s, the heat
transfer coefficient is
0.8
proportional to the ( mass flow ratio ) . The equation below is
used to determine the UA used:
mass flow current 0.8
UA used = UA specified ×  ------------------------------------------
 mass flow reference
(4.27)
Reference flows generally help to stabilize the system when
you do shut downs and startups as well.
In some cases you can use
a negative value for
minimum flow scale factor. If
you use -0.1, then if the
scale factor goes below 0.1,
the Minimum Flow Scale
Factor uses 0.
Minimum Flow Scale
Factor
The ratio of mass flow at time t to reference mass flow is also
known as flow scaled factor. The minimum flow scaled factor is
the lowest value which the ratio is anticipated at low flow
regions. This value can be expressed in a positive value or
negative value.
• A positive value ensures that some heat transfer still
takes place at very low flows.
• A negative value ignores heat transfer at very low flows.
A negative factor is often used in shut downs if you are not
interested in the results or run into problems shutting down an
exchanger.
If the Minimum Flow Scale Factor is specified, the Equations
(4.27) uses the mass flow current 0.8 ratio if the ratio is
 ------------------------------------------
 mass flow reference
greater than the Min Flow Scale Factor. Otherwise the Min
Flow Scale Factor is used.
The Summary group contains information regarding the duty of the
Heat Exchanger shell and tube sides.
4-94
Heat Transfer Equipment
4-95
Detailed Model
When you select the Detailed radio button, a summary of the rating
information specified on the Rating tab appears.
Figure 4.55
The Model Data group contains the following information:
Field
Description
Tube/Shell Volume
The volume of the shell and tube is calculated from the Heat
Exchanger rating information.
Heat Transfer Area
The heat transfer area is calculated from the Heat
Exchanger rating information.
Elevation
The elevation is significant in the calculation of static head
around and in the Heat Exchanger.
Shell/Tube Passes
You can specify the number of tube and shell passes in the
shell of the Heat Exchanger. In general, at least 2n tube
passes must be specified for every n shell pass. The
exception is a counter-current flow Heat Exchanger which
has 1 shell pass and one tube pass
Orientation
The orientation may be specified as a vertical or horizontal
Heat Exchanger. The orientation of the Heat Exchanger
does not impact the steady state solver. However, it used in
the dynamic Heat Exchanger in the calculation of liquid level
in the shell.
Zones per Shell Pass
Enter the number of zones you would like for one shell pass.
The total number of zones in a Heat Exchanger shell is
calculated as:
Zones
Total Zones = # of Shells ⋅ ---------------------------Shell Pass
4-95
4-96
Heat Exchanger
The Model Parameters group contains the local and overall heat transfer
coefficients for the Heat Exchanger. Depending on how the Heat
Transfer Coefficient Calculator is set on the Parameters page of the
Rating tab, the local and overall heat transfer coefficients can either be
calculated or specified in the Model Parameters group.
HT Coefficient Calculator Setting
Description
Shell & Tube
Overall heat transfer coefficient, U, is calculated
using the exchanger rating information.
U Specified
Overall heat transfer coefficient, U, is specified
by you.
The Startup Level group appears only if the Heat Exchanger is specified
with a single shell and/or tube pass having only one zone. The Startup
level cannot be set for multiple shell and/or tube pass exchangers for
multiple shell or tube passes. You can specify an initial liquid level
percent for the shell or tube holdups. This initial liquid level percent is
used only if the simulation case re-initializes.
Specs Page
The information displayed on
the Specs page depends on
the model (Basic or Detailed)
selected on the Model page.
4-96
The Specs page contains information regarding the calculation of
pressure drop across the Heat Exchanger.
Heat Transfer Equipment
4-97
Basic Model
When you select the Basic model radio button on the Model page, the
Specs page appears as follows.
Figure 4.56
The pressure drop across any pass in the Heat Exchanger operation can
be determined in one of two ways:
•
•
Specify the pressure drop.
Define a pressure flow relation for each pass by specifying a k
value.
The following parameters are used to specify the pressure drop for the
Heat Exchanger.
Dynamic Specification
Description
Shell/Tube Delta P
The pressure drop across the Shell/Tube side of the Heat
Exchanger may be specified (checkbox active) of
calculated (checkbox inactive).
4-97
4-98
Heat Exchanger
Dynamic Specification
Description
k
Activate this option if to have the Pressure Flow k values
used in the calculation of pressure drop.
k Reference Flow
If the pressure flow option is chosen the k value is
calculated based on two criteria. If the flow of the system
is larger than the k Reference Flow the k value remains
unchanged. It is recommended that the k reference flow is
taken as 40% of steady state design flow for better
pressure flow stability at low flow range. If the flow of the
system is smaller than the k Reference Flow the k value is
given by:
k used = k specified × Factor
where:Factor = value is determined by HYSYS internally
to take into consideration the flow
and pressure drop relationship at low
flow regions.
Effectively, the k Reference Flow results in a more linear relationship
between flow and pressure drop, and this is used to increase model
stability during startup and shutdown where the flows are low.
Use the Calculate k button to calculate a k value based on the Delta P
and k Reference flow. Ensure that there is a non zero pressure drop
across the Heat Exchanger before you click the Calculate k button.
Detailed Model
When you select the Basic model radio button on the Model page, the
Specs page appears as follows.
Figure 4.57
4-98
Heat Transfer Equipment
4-99
The following parameters are used to specify the pressure drop for the
Heat Exchanger.
Dynamic Specification
Description
Pressure Flow k
The k-value defines the relationship between the flow
through the shell or tube holdup and the pressure of the
surrounding streams. You can either specify the k-value or
have it calculated from the stream conditions surrounding
the Heat Exchanger. you can “size” the exchanger with a
k-value by clicking the Calculate K’s button. Ensure that
there is a non zero pressure drop across the Heat
Exchanger before the Calculate k button is clicked.
Pressure Flow Option
Activate this option to have the Pressure Flow k values
used in the calculation of pressure drop. If the Pressure
Flow option is selected, the Shell/Tube Delta P calculator
must also be set to non specified.
Shell/Tube Delta P
The pressure drop across the Shell/Tube side of the Heat
Exchanger may be specified or calculated.
Shell/Tube Delta P
Calculator
The Shell/Tube Delta P calculator allows you to either
specify or calculate the shell/tube pressure drop across
the Heat Exchanger. Specify the cell with one of the
following options:
• Shell & Tube Delta P Calculator. The pressure drop
is calculated using the Heat Exchanger rating
information and correlations.
• user specified. The pressure drop is specified by
you.
• not specified. This option is only applicable in
Dynamic mode. Pressure drop across the Heat
Exchanger is calculated from a pressure flow
relationship. You must specify a k-value and activate
the Pressure Flow option to use this calculator.
Clicking the K Summary button opens the Detailed Heat Model
Properties view, refer to the section on the Detailed Heat Model
Properties for more information.
Holdup Page
The Holdup page contains information regarding the shell and tube
holdup properties, composition, and amount.
4-99
4-100
Heat Exchanger
Basic Model
When you select the Basic model radio button on the Model page, the
Holdup page appears as follows.
Figure 4.58
The Shell Holdup group and Tube Holdup group contain information
regarding the shell and tube side holdup parameters. For each phase
contained within the volume space of the unit operation, the following
is specified:
Holdup Details
Description
Accumulation
Rate of change of material in the holdup for each phase.
Moles
Amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
4-100
Heat Transfer Equipment
4-101
Detailed Model
When you select the Detailed model radio button on the Model page,
the Holdup page appears as follows.
Figure 4.59
The Overall Holdup Details group contains information regarding the
shell and tube side holdup parameters. For each phase contained within
the volume space of the unit operation, the following is specified:
Holdup Details
Description
Accumulation
Rate of change of material in the holdup for each phase.
Moles
Amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
The Individual Zone Holdups group contains detailed holdup
properties for every layer in each zone of the Heat Exchanger unit
operation.
In order to view the advanced properties for individual holdups, you
must first choose the individual holdup.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
To choose individual holdups you must specify the Zone and Layer in
the corresponding drop-down lists.
4-101
4-102
Heat Exchanger
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
4.3.8 HTFS-TASC Tab
When you select the HTFS - Engine model on the Parameters page of the
Design tab, the HTFS-TASC tab appears as shown in the figure below:
Figure 4.60
The HTFS-TASC tab contains eight pages:
•
•
•
•
•
•
•
•
4-102
Exchanger
Process
Bundle
Nozzles
Enhanced Surfaces
Design and Material
Methods
Results
Heat Transfer Equipment
4-103
The HTFS-TASC tab also consists of two button:
•
•
Import. Allows you to import values from TASC into the pages of
the tab.
Export. Allows you to export the information provided within this
tab to TASC.
Exchanger Page
The Exchanger page allows you to input parameters that define the
geometric configuration of the Heat Exchanger.
Figure 4.61
After entering a basic configuration of the Heat Exchanger, you can
specify detailed information.
Basics Data
For the Basics data, you can enter the following information:
Refer to the TASC Thermal
Reference manual for more
information about the
selections available.
Entry
Description
Front End Head Type
You can select the type of front end head for your heat
exchanger using the drop-down list.
The type of head selected has no significant effect on the
heat exchanger thermal or pressure drop performance, as
calculated by TASC. It only affects the heat exchanger
weight.
Shell Type
You can select the type of shells for the heat exchanger
using the drop-down list.
4-103
4-104
If you did not enter any value
in this cell, TASC derives an
exact tube count while
setting up the Tube Bundle
Layout.
Heat Exchanger
Entry
Description
Rear End Head Type
You can select the type of rear end head for your heat
exchanger using the drop-down list.
Shell Internal Diameter
You can enter the internal diameter of the shell in this cell.
Tube Outside Diameter
You can enter the outside diameter of the tube in this cell.
Tube Length (Straight)
You can enter the length of the tube in this cell.
Effective Tube Count
You can enter the number of tubes in the heat exchanger
in this cell.
Orientation
You can select from three types of orientation for your
heat exchanger in the drop-down list:
• Default (Horiz.)
• Horizontal
• Vertical
Hot Side
You can select which side is the hot side in your heat
exchanger from the drop-down list. There are three
selections:
• Not yet set
• Tubeside hot
• Shell-side hot
Countercurrent in 1st
Pass
You can select whether countercurrent occurs in the first
pass from the drop-down list. There are three selections:
• Not set
• Yes
• No (co-current)
No. Exchangers in
Parallel
You can specify how many heat exchangers are parallel to
the current heat exchanger in this cell.
No. Exchangers in Series
You can specify how many heat exchangers are in series
to the current heat exchanger in this cell.
No. of Tubeside Passes
You can specify how many tubeside passes occur in the
heat exchanger in this cell.
Details Data
For the Details data, you can enter the following information:
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
4-104
Entry
Description
Tubeplate Thickness
You can specify the tubeplate thickness in this cell.
Shell Thickness
You can specify the shell thickness in this cell.
FFE/Reflux
You can select the special type of exchanger using the
drop-down list. There are four selections:
• Default (normal)
• Normal exchanger
• Falling Film Evap
• Reflux Condenser
Heat Transfer Equipment
Entry
Description
Fixed Head (Vert Exchgr)
You can select the location of the fixed end head from the
drop-down list. There are three selections:
• Default/horiz
• Top
• Bottom
The Top and Bottom selections only apply to vertical
shells.
Area Fraction
Submerged
You can enter the area fraction on the tubes that may be
submerged under condensate in this cell.
4-105
This value only applies to horizontal shellside condensers
and if there is a lute or geometric feature that causes
tubes to be submerged.
If no value is entered,
HYSYS assumes the value
is zero. The top of the weir is
assumed to be level with the
top of the outer tube limit
circle of the bundle.
M Shell Pitch
You can enter the shell pitch for double-pipe U-tube
exchangers or Multitube hairpin exchangers in this cell.
The value is used to determine the U-bend heat transfer
area.
Kettle Large Shell
Diameter
You can enter the internal diameter of the larger part of
the shell of a kettle reboiler in this cell.
Weir Height Over Bundle
You can enter the height of the weir above the top of the
bundle in this cell. This value is used to define the head of
liquid providing the driving force for re-circulation within a
kettle.
Process Page
The Process page allows you to specify the estimate pressure drop,
fouling resistance, and heat load.
Figure 4.62
4-105
4-106
Heat Exchanger
The estimated heat load is used as a starting point to do the simulation
calculation.
Bundle Page
The Bundle page allows you to specify the bundle, tube, and baffles
configurations. The radio buttons in the Bundle Data group controls
which configuration appears on the page.
•
•
•
Bundle
Tubes
Baffles
Bundle Configuration
If you select the Bundle radio button in the Bundle Data group, the
Bundle page appears as shown in the figure below:
Figure 4.63
The configuration information you can specify for the bundle is sorted
into four groups:
•
•
•
•
4-106
Size
U-Tubes
Layout
Pass Partitions
Heat Transfer Equipment
4-107
Size Group
The Size group allows you to specify information used to calculate the
size of the bundle.
The Effective Tube Count
field is linked to the Effective
Tube Count field on the
Exchanger page. Any
changes in either fields
propagates to the other.
Specification
Description
Effective Tube Count
Number of tubes in the heat exchanger.
No of Blocked Off Tubes
Number of blocked off tubes.
Bundle-Shell DIam Clear
Diametral clearance between the tube bundle (outer limit
diameter) and the shell wall. This value is used to
determine the fraction of the shellside flow which by
passes around the bundle. For zero clearance, enter 0.
First Row to Shell
Number of tubes in the bundle for the first row to the shell.
Last Row to Shell
Number of tubes in the bundle for the last row to the shell.
U-Tubes Group
The U-tubes group allows you to select the configuration of the U-tubes.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
U-Bend Orientation
You can select the type of U-bend orientation from the
drop-down list. There are three selections:
• Default
• Horizontal
• Vertical
U-Bend Heat Transfer
You can select whether to include or exclude the heat
transfer that occurs in the U-tube using the drop-down list.
There are three selections:
• Default
• Allow for U-bend
• Ignore U-bend
4-107
4-108
Heat Exchanger
Layout Group
The Layout group allows you to specify information used to design the
layout of the bundle.
Refer to TASC Thermal
Reference manual for
information about the
selections available.
4-108
Specification
Description
Normal/Full Bundle
You can select what type of bundle to use from the dropdown list. There are three selections:
• Default (Normal)
• Normal Bundle
• Full Bundle
Tubes in Window
You can select whether you want tubes in the window or
not from the drop-down list. There are three selections:
• Default (Yes)
• Yes
• No
Bundle Band Orientation
You can select the bundle band orientation from the dropdown list. There are three selections:
• Default (horizontal)
• Horizontal
• Vertical
Tube Alignment
You can select the tube alignment from the drop-down list.
There are four selections:
• Default (if yes 45 90)
• Fully aligned
• Unaligned
• Part aligned
Layout Symmetry
You can select the layout symmetry from the drop-down
list. There are four selections:
• Default (sym.case 1)
• Symmetry (case 1)
• Symmetry (case 2)
• Not enforced
Pairs of Sealing Strips
Number of pairs of sealing strips.
Heat Transfer Equipment
4-109
Pass Partitions Group
The Pass Partitions group allows you to specify information used to
configure the pass partition.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Pass Partition Layout
You can select the type of pass partition from the dropdown list. There are four selections:
• Not set
• H Banded
• Double Banded
• Ribbon Banded
Vertical PP Lane Width
Vertical pass partition lane width.
Horizontal PP Lane
Width
Horizontal pass partition lane width.
Tubes Configuration
If you select the Tubes radio button in the Bundle Data group, the
Bundle page appears as shown in the figure below:
Figure 4.64
The configuration information you can specify for the tubes is sorted
into two groups:
•
•
Tube Characteristics
Lengths Along Tube
4-109
4-110
Heat Exchanger
Tube Characteristics Group
The Tube Characteristics group allows you to specify the configuration
for the tube.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Tube Type
You can select the type of tube you want from the dropdown lists:
• Default (Plain)
• Plain Tubes
• Lowfin Tubes
• Longitudinal Tubes
Tube Outside Diameter
Outside diameter of the tube.
Tube Wall Thickness
Thickness of the tube’s wall.
Tube Pitch
The tube’s pitch.
Tube Pattern (Angle)
You can select the pattern of the tube from the drop-down
list:
• Default (Triangular)
• Triangular (30 deg)
• Rotated square (45)
• Roated triang. (60)
• Square (90 deg)
Lengths Along Tube Group
The Lengths Along Tube group allows you to specify the lengths of each
tube section.
Specification
Description
Tube Length
Length of the tube.
Endlength (Front Head)
Length of the front head of the tube.
Endlength (Rear Head)
Length of the rear head of the tube.
Tube Outstand (Inlet)
The distance the tube inlet end protrudes beyond the face
of a tube sheet.
Tube Outstand (Other)
The distance the tube rear end protrudes beyond the face
of a tube sheet.
HYSYS assumes the two
baffle spacings are equal if
no value is entered.
Central Entry/Exit Length
The distance between the centres of the Flow Baffles on
either side of a central inlet or outlet nozzle.
Dist. After Blank Baffle
The distance between the tube and the blank baffle.
HYSYS assumes the value
to be double the mean
length of the end spaces at
the ends of the exchanger if
no value is entered.
H-Shell Central Length
Length of the central region in an H-shell. This value is the
distance between two halves of the axial baffle in an Hshell.
4-110
Heat Transfer Equipment
4-111
Baffles Configuration
If you select the Baffles radio button in the Bundle Data group, the
Bundle page appears as shown in the figure below:
Figure 4.65
The configuration information you can specify for the baffles is sorted
into two groups:
•
•
Baffles
Intermediate Supports
Baffles Group
The Baffles group allows you to specify the configuration of the baffles.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Number of Baffles
Number of baffles.
Baffle Type
Select the baffle type from the drop-down list:
• Default (Sing.Seg.)
• Single Segmental
• Double Segmental
• Unbar/Low pr.drop
• Rodbaffled
Baffle Pitch
The value of the baffle pitch. The baffle pitch is the baffle
spacing plus the baffle thickness.
Baffle Thickness
The baffle thickness.
Baffle Cut
The percentage of baffle cut.
Inner Cut (Double Seg)
The percentage of inner cut. This is only applicable to
Double Segmental baffle type.
4-111
4-112
Heat Exchanger
Specification
Description
Baffle Cut Orientation
Select the orientation of the baffle cut using the dropdown list:
• Default (horizontal)
• Vertical
• Horizontal
Diam. Clearance - Tube
Diametral clearance between the tube and the baffle hole.
For a zero clearance, enter 0.
Diam. Clearance - Shell
Diametral clearance between the baffles and the shell
wall. For a zero clearance, enter 0.
Intermediate Support Group
The Intermediate Support group allows you to specify the tube
supports, other than flow baffles, that help remove the risk of vibration
damage.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Intermediate Supports
(Inlet)
Number of intermediate supports in the inlet endspace.
This endspace corresponds to the inlet endlength.
Intermediate Supports/
Baffle
Number of intermediate supports between each pair of
flow baffles.
Intermediate Supports
(Return)
Number of intermediate supports in the endspace
corresponding to the outlet (return) endlength.
U-bend Extra Supports
Number of tube supports on the U-bend.
Int. Supports (Central
Nozzle)
Number of intermediate supports for nozzles (not over
inlet or return endspace).
Support/Blanking Baffle
Select whether there is a support of blanking baffle at the
rear end head:
• Default (Yes for S T)
• Yes
• No
Longitudinal Baffle
Leakage
An estimate of the percentage of the shellside flow which
leaks across the longitudinal baffle. This value is only
relevant to the F, G, or H shell types.
Nozzles Page
The Nozzles page allows you to specify the nozzles in the shellside and
tubeside. The radio buttons in the Side Data group controls which side
appears on the page.
4-112
Heat Transfer Equipment
4-113
Shellside Configuration
If you select the Shellside radio button in the Size group, the Nozzles
page appears as shown in the figure below:
Figure 4.66
The following table lists and describes the configuration information
that you can specify for the nozzles in shellside.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Vapour Belt Diam
Clearance
Diametral annular clearance (difference in diameters)
between the outside of the shell and the vapour belt.
Vapour Belt Slot Area
The total flow area of all the slots leading through the shell
wall (from the vapour belt into the shell).
Vapour Belt Axial Length
The axial length of the exchanger occupied by (the inside
of) the belt.
Impingement Plate
Thickness
The thickness of the impingement plate.
Nozzle Function
You can specify up to three types of nozzle function.
Select the nozzle function from the drop-down list:
• Unset
• Inlet
• Outlet
• Intermediate
• Liquid Outlet
• Vapour Outlet
Nozzle Type
Select the nozzle types from the drop-down list:
• Default (Plain)
• Plain
• Plain + Imp Plate
• Vapour Belt
4-113
4-114
Heat Exchanger
Specification
Description
Nozzle Inside Diameter
The inside diameter of the nozzle.
Number In Parallel
Number of nozzles in parallel on one shell.
Nozzle Orientation
Select the nozzle orientation from the drop-down list:
• Default
• Top of Shell
• RHSide of Shell
• Bottom of Shell
• LHSide of Shell
Distance to Nozzle
The axial distance along the shell to the nozzle centre
line, measured from the inner surface of the tubesheet at
the front (fixed) head.
Nozzle Wall Thickness
The wall thickness of the nozzle.
Tubeside Configuration
If you select the Tubeside radio button in the Size group, the Nozzles
page appears as shown in the figure below:
Figure 4.67
4-114
Heat Transfer Equipment
4-115
The configuration information you can specify for the nozzles in
tubeside is described in the table below:
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Nozzle Function
You can specify up to three types of nozzle function.
Select the nozzle function from the drop-down list:
• Unset
• Inlet
• Outlet
• Intermediate
• Liquid Outlet
• Vapour Outlet
Nozzle Inside Diameter
The inside diameter of the nozzle.
Nozzle Orientation
Select the nozzle orientation from the drop-down list:
• Default
• Top of Shell
• RHSide of Shell
• Bottom of Shell
• LHSide of Shell
Vel Head Lost/FFE Inlet
Number of velocity heads lost in a device (used to achieve
uniform flow distribution of the liquid in-flow to all the
tubes of a falling film evaporator).
Nozzle Wall Thickness
The wall thickness of the nozzle.
Enhanced Surface Page
The Enhanced Surface page allows you to perform model calculations
on the exchanger that are not explicitly modeled by TASC. There are two
enhanced options on the page, and you can select which enhanced
option you want using the radio buttons in the Enhanced Surface Data
group.
4-115
4-116
Heat Exchanger
Specific Enhanced Option
If you select the Specific Enhanced radio button in the Enhanced
Surface Data group, the Enhanced Surface page appears as shown in the
figure below.
Figure 4.68
The variables you can specify for the Specific Enhanced option are
sorted into three groups:
•
•
•
Longitudinal Fins
Lowfin Tubes
Tube Inserts
Longitudinal Fins Group
The Longitudinal Fins group allows you to specify the configuration of
the longitudinal fins.
4-116
Specification
Description
Fins Per Tube
Number of fins are on each tube.
Fin Height
Height of each fin.
Fin Thickness
Thickness of each fin.
Fin Root Spacing
The root spacing of each fin.
Cut and Twist Length
The cut and twist length.
Heat Transfer Equipment
4-117
Lowfin Tubes Group
The Lowfin Tubes group allows you to specify the configuration of the
lowfin tubes.
Specification
Description
Fin Pitch
The lowfin fin pitch.
Fin Height
The height of each fin.
Fin Thickness
The thickness of each fin.
Root Diameter
The lowfin tube root diameter.
Wall Thickness
The lowfin tube wall thickness.
Unfinned at Baffle
Length of unfinned tubing at a baffle.
Tube Inserts Group
The Tube Inserts group allows you to specify the configuration of the
tube inserts.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Tube Insert
Select the type of tube inserts from the drop-down list:
• Default (plain tubes)
• None (plain tubes)
• Twisted tape
Twisted Tape Thickness
The twisted tape thickness. The value only applies if you
selected twisted tape for the tube insert.
360 Degree Twisted Pitch
The distance between each 360 degree twist of a twisted
tape insert.
4-117
4-118
Heat Exchanger
Specific Enhanced Option
If you select the General Enhanced radio button in the Enhanced
Surface Data group, the Enhanced Surface page appears as shown in the
figure below:
Figure 4.69
The variables you can specify for the General Enhanced option is sorted
into two groups:
•
•
Identity of Surface
Surface Performance
Identity of Surface Group
The Identity of Surface group allows you to create surfaces for both the
shellside and tubeside.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
4-118
Specification
Description
Add Surface
Allows you to add/create a surface.
Remove Surface
Allows you to remove the last surface.
Name of Enhanced
Surface
Contains the name of the surface created. HYSYS
automatically names the surface as “Set” followed by a
number. The number value is incremented by 1 for each
new surface created.
Shellside or Tubeside
Select which side the surface created on from the dropdown list:
• Not used
• Shellside
• Tubeside
Heat Transfer Equipment
4-119
Surface Performance Group
The Surface Performance group allows you to specify the configuration
of each surface.
Specification
Description
Surface
Contains the list of surfaces created.
Any values entered in the table located at the right of the
list apply only to the surface you selected in the list.
Re
The Reynolds Number for the corresponding surface.
f
The friction factor for the corresponding surface.
Cj
The heat transfer factor (Colburn j factor) for the
corresponding surface.
Design and Material Page
The Design and Material page allows you to specify design values,
material types, and some properties for the Heat Exchanger. The
information on this page is sorted into three groups:
•
•
•
Design Data
Materials
User Defined Properties
Figure 4.70
4-119
4-120
Heat Exchanger
Design Data Group
The Design Data group allows you to specify the following variables:
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Specification
Description
Shellside Design
Temperature
Design temperature on the shellside.
Shellside Design
Pressure
Design pressure on the shellside.
Tubeside Design
Temperature
Design temperature on the tubeside.
Tubeside Design
Pressure
Design pressure on the tubeside.
TEMA Class
Select the TEMA class from the drop-down list:
• Default (R)
• R
• C
• B
• Not TEMA
Crossflow Fraction for
Vibration
The fraction from the shellside flow in the cross flow which
causes vibration.
Materials Group
The Materials group allows you to select the material type for the heat
exchanger. HYSYS lets you select the material for four parts of the heat
exchanger: Tubes, Shell, Tubeplate, and Channel. You can select the
material type from the drop-down list provided for each part.
User Defined Properties Group
The User Defined Properties group allows you to specify values for the
following properties:
4-120
Specification
Description
Thermal Conductivity
The thermal conductivity of the tube material. This value
overrides the calculated value based on the tube material
selected.
Heat Transfer Equipment
Specification
Description
Density
Density for all the exchanger materials. This value
overrides the calculated value based on the selected
materials for each part of the exchanger.
Youngs Modulus
The Young’s Modulus. This value overrides the calculated
value based on the tube material selected.
4-121
Methods Page
The Methods page allows you to specify the process methods and
constraints of the heat exchanger. The Methods and Constraints group
contains three radio buttons:
•
•
•
Process Methods
Process Constraints
Other
The variables displayed on this page depend on the radio button you
selected in the Methods and Constraints group.
Process Methods Variables
If you select the Process Methods radio button from the Methods and
Constraints group, the Methods page appears as shown in the figure
below:
Figure 4.71
4-121
4-122
Heat Exchanger
The table below lists the variables available for the process method:
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
4-122
Method
Description
Vapour Shear
Enhancement
Select whether the process stream has vapour shear
enhancement from the drop-down list:
• Default (Yes)
• Yes
• No
Wet Wall Desuperheating
Select whether the process stream has wet wall
desuperheating from the drop-down list:
• Default (Yes)
• Yes
• No
Number of Points on
Curve
Specify the number of points on the TASC stream heat
load curve in this field. The minimum value is 6 and the
maximum value is 12.
Fit to Property Curve
Select whether the results fit the property curve from the
drop-down list:
• Default
• A input / calc.
• Use best fit
Subcooled Boiling
Select whether there is subcooled boiling from the dropdown list:
• Default(ht.tr&pr.drop)
• Allow in heat.tr&pr.drop
• Allow in heat tran. only
• Allow in press. drop only
• Not allowed for
Post Dryout Heat
Transfer
Select whether there is post dryout heat transfer from the
drop-down list:
• Default (allow)
• Allow for
• Assume Boiling
Pressure Drop
Calculations
Select the type of pressure drop calculations from the
drop-down list:
• Default (fric+acc)
• Frict+Acc+Gravitation
• Friction+Accel
HTFS Colburn-Hougen
Method
Select whether to apply HTFS Colburn-Hougen method
from the drop-down list:
• Default (no)
• Yes
• No
Downflow Condensate
Cooling
Select the type of downflow condensate cooling from the
drop-down list:
• Default (standard)
• Falling Film
• Standard Method
Heat Transfer Equipment
4-123
Process Constraints Variables
If you select the Process Constraints radio button from the Methods and
Constraints group, the Methods page appears as shown in the figure
below:
Figure 4.72
The table below contains a list of the constraints available in the
operation:
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Constraints
Description
Revise for Heat Balance
Select the type of revise for heat balance from the dropdown list:
• Default (h.load)
• Heat Load
• Outlet Temp.
• Inlet Temp.
• Flowrate
Liquid Heat Transfer
Coefficient
Amount of liquid heat transfer coefficient.
Two Phase Heat Transfer
Coefficient
Amount of two phase heat transfer coefficient.
Vapour Heat Transfer
Coefficient
Amount of vapour heat transfer coefficient.
Liquid Heat Transfer
Coefficient Multiplier
The liquid heat transfer coefficient multiplier.
Two Phase Heat Transfer
Coefficient Multiplier
The two phase heat transfer coefficient multiplier.
Vapour Heat Transfer
Coefficient Multiplier
The vapour heat transfer coefficient multiplier.
Pressure Drop Multiplier
The pressure drop multiplier.
4-123
4-124
Heat Exchanger
Other Variables
If you select the Other radio button from the Methods and Constraints
group, the Methods page appears as shown in the figure below.
Figure 4.73
The table below contains a list of variables available in the operation.
Refer to the TASC Thermal
Reference manual for
information about the
selections available.
Variables
Description
Units of Output
Select the type of unit for the output from the drop-down
list:
• Default (as Input)
• SI
• British/US
• Metric
• unused option
Physical Property
Package
Select the type of physical property package from the
drop-down list:
• Default (Sep.File)
• In Lineprinter O/p
• Separate File
• No Output
Tube Layout Data
Select the type of tube layout data from the drop-down list:
• Default (use if available)
• Use if available
• Revise from input
• Ignore layout data
Results Page
The Heat Exchanger results appear on this page. The results are created
in a text format that can be exported to HTFS-TASC.
4-124
Heat Transfer Equipment
4-125
4.4 Fired Heater (Furnace)
The Fired Heater operation
is available as a dynamic
unit operation only.
The dynamic Fired Heater (Furnace) operation performs energy and
material balances to model a direct Fired Heater type furnace. This type
of equipment requires a large amount of heat input. Heat is generated
by the combustion of fuel and transferred to process streams. A
simplified schematic of a direct Fired Heater is illustrated in the figure
below.
Figure 4.74
To define the number of
zones required by the Fired
Heater, enter the number in
#External Passes field on
Connections page of the
Design tab.
In general, a Fired Heater can be divided into three zones:
•
•
•
Radiant zone
Convective zone
Economizer zone
The Fired Heater operation allows multiple stream connections at tube
side in each zone and optional economizer, and convection zone
selections. The operation incorporates a single burner model, and a
single feed inlet and outlet on the flue gas side.
4-125
4-126
Fired Heater (Furnace)
The following are some of the major features of the dynamic Fired
Heater operation:
•
•
•
•
•
Flexible connection of process fluid associated in each Fired
Heater zone, e.g., radiant zone, convective zone or economizer
zone. Different Fired Heater configurations can be modeled or
customized using tee, mixer, and heat exchanger unit operations.
A pressure-flow specification option on each side and pass
realistically models flow through Fired Heater operation according
to the pressure gradient in the entire pressure network of the
plant. Possible flow reversal situations can therefore be modeled.
A comprehensive heat calculation inclusive of radiant,
convective, and conduction heat transfer on radiant zone enables
the prediction of process fluid temperature, Fired Heater wall
temperature, and flue gas temperature.
A dynamic model which accounts for energy and material
holdups in each zone. Heat transfer in each zone depends on the
flue gas properties, tube and Fired Heater wall properties,
surface properties of metal, heat loss to the ambient, and the
process stream physical properties.
A combustion model which accounts for imperfect mixing of fuel,
and allows automatic flame ignition or extinguished based on the
oxygen availability in the fuel air mixture.
4.4.1 Theory
Combustion Reaction
The combustion reaction in the burner model of the Fired Heater
performs pure hydrocarbon (CxHy) combustion calculations only. The
extent of the combustion depends on the availability of oxygen which is
usually governed by the air to fuel ratio.
Air to fuel ratio (AF) is defined as follows:
Mass of flow O 2 
 -------------------------------------------------- Σ Mass flow of fuel
AF = ---------------------------------------------------------------Mass Ratio of O 2 in Air
4-126
(4.28)
Heat Transfer Equipment
4-127
You can set the combustion boundaries, such as the maximum AF and
the minimum AF, to control the burner flame. The flame cannot light if
the calculated air to fuel ratio falls below the specified minimum air to
fuel ratio. The minimum air to fuel ratio and the maximum air to fuel
ratio can be found on the Parameters page of the Design tab.
The heat released by the combustion process is the product of molar
flowrate, and the heat of formation of the products minus the heat of
formation of the reactants at combustion temperature and pressure. In
the Fired Heater unit operation, a traditional reaction set for the
combustion reactions is not required. You can choose the fuels
components (the hydrocarbons and hydrogen) to be considered in the
combustion reaction. You can see the mixing efficiency of each fuel
component on the Parameter page of the Design tab.
Heat Transfer
The Fired Heater heat transfer calculations are based on energy
balances for each zone. The shell side of the Fired Heater contains five
holdups:
•
•
•
three in the radiant zone
a convective zone
an economizer zone holdup as outlined previously in Figure
4.74.
For the tube side, each individual stream passing through the respective
zones is considered as a single holdup.
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4-128
Fired Heater (Furnace)
Major heat terms underlying the Fired Heater model are illustrated in
the figure below.
Figure 4.75
4-128
Heat Transfer Equipment
4-129
The heat terms related to the tubeside are illustrated in the figure below.
Figure 4.76
Taking Radiant zone as an envelope, the following energy balance
equation applies:
d ( M rad H rad ) d ( M RPFTube H RPFTube )
-------------------------------- + ---------------------------------------------------------dt
dt
= ( M RPF H RPF ) IN – ( M RPF H RPF ) OUT + ( M FG H FG ) IN
– ( M FG H FG ) OUT – Q RadToCTube – Q rad
+ Q rad
where:
wall to tube
– Q con
to wall
wall sur
– Q con
(4.29)
wall sur
+ Q reaction
d ( M rad H rad )
-------------------------------- = energy accumulation in radiant zone holdup shell
dt
side
d ( M RPFTube H RPFTube )
---------------------------------------------------------- = energy accumulation in radiant zone
dt
process fluid holdup (tube side)
4-129
4-130
Fired Heater (Furnace)
(MRPFHRPF)IN = total heat flow of process fluid entering radiant zone
tube
(MRPFHRPF)OUT = total heat flow of process fluid exiting radiant zone
tube
(MFGHFG)IN = total heat flow of fuel gas entering radiant zone
(MFGHFG)OUT = total heat flow of fuel gas exiting radiant zone
QRadToCTube = radiant heat of radiant zone to convective zone’s tube
bank
Qrad_wall_sur = radiant heat loss of Fired Heater wall in radiant zone to
surrounding
Qcon_wall_sur = convective heat loss of Fired Heater wall in radiant
zone to surrounding
Qrad_wall_to_tube = radiant heat from inner Fired Heater wall to
radiant zone’s tube bank
Qrad_flame_wall = radiant heat from flue gas flame to inner Fired Heater
wall
Qcon_to_wall = convective heat from flue gas to Fired Heater inner wall
Qreaction = heat of combustion of the flue gas
Radiant Heat Transfer
For a hot object in a large room, the radiant energy emitted is given as:
4
4
Q radiative = δAε ( T 1 – T 2 )
where:
δ = Stefan-Boltzmann constant, 5.669x10-8 W/m2K4
ε = emissivity, (0-1), dimensionless
A = area exposed to radiant heat transfer, m2
T1 = temperature of hot surface 1, K
T2 = temperature of hot surface 2, K
4-130
(4.30)
Heat Transfer Equipment
4-131
Convective Heat Transfer
The convective heat transfer taking part between a fluid and a metal is
given in the following:
Q convective = UA ( T 1 – T 2 )
where:
(4.31)
U = overall heat transfer coefficient, W/m2K
A = area exposed to convective heat transfer, m2
T1 = temperature of hot surface 1,K
T2 = temperature of surface 2, K
The U actually varies with flow according to the following flow-U
relationship if this Flow Scaled method is used:
Mass flow at time t
U used = U specified  --------------------------------------------------------
 Reference Mass flow
where:
0.8
(4.32)
Uspecified = U value at steady state design conditions.
The ratio of mass flow at time t to reference mass flow is also known as
flow scaled factor. The minimum flow scaled factor is the lowest value,
which the ratio is anticipated at low flow region. For the Fired Heater
operation, the minimum flow scaled factor can be expressed only as a
positive value.
For example, if the minimum flow scaled factor is +0.001 (0.1%), when
this mass flow ratio is achieved, the Uused stays as a constant value.
Therefore,
U used = U specified ( 0.001 )
0.8
(4.33)
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4-132
Fired Heater (Furnace)
Conductive Heat Transfer
Conductive heat transfer in a solid surface is given as:
( T1 – T2 )
Q conductive = – kA ---------------------∆t
where:
(4.34)
k = thermal conductivity of the solid material, W/mK
∆t = thickness of the solid material, m
A = area exposed to conductive heat transfer, m2
T1 = temperature of inner solid surface 1, K
T2 = temperature of outer solid surface 2, K
Pressure Drop
The pressure drop across any pass in the Fired Heater unit operation
can be determined in one of two ways:
•
•
Specify the pressure drop - delta P.
Define a pressure flow relation for each pass by specifying a kvalue
If the pressure flow option is chosen for pressure drop determination in
the Fired Heater pass, a k value is used to relate the frictional pressure
drop and molar flow, F through the Fired Heater. This relation is similar
to the general valve equation:
F = k ρ ( P1 – P2 )
(4.35)
This general flow equation uses the pressure drop across the Fired
Heater pass without any static head contribution. The quantity, (P1-P2)
is defined as the frictional pressure loss which is used to “size” the flow.
The k value is calculated based on two criteria:
•
4-132
If the flow of the system is larger than the value at kref (k
reference flow), the k value remain unchanged. It is
recommended that the k reference flow is taken as 40% of steady
state design flow for better pressure flow stability at low flow
range.
Heat Transfer Equipment
•
If the flow of the system is smaller than the kref, the k value is
given by:
k used = k user
where:
4-133
specified
× Factor
(4.36)
Factor = value is determined by HYSYS internally to take into
consideration the flow and pressure drop relationship for low
flow regions.
The effect of kref is to increase the stability by modeling a more linear
relationship between flow and pressure. This is also more realistic at low
flows.
Dynamic Specifications
The following is a list of the minimum specifications required for the
Fired Heater operation to solve:
Dynamic Specifications
Description
Connections
At least one radiant zone inlet stream and the respective
outlet zone, one burner fuel/air feed stream and one
combustion product stream must be defined. There is a
minimum of one inlet stream and one outlet stream
required per zone. Complete the connections group for
each zone of the Design tab.
(Zone) Sizing
The dimensions of the tube and shell in each zone in the
Fired Heater must be specified. All information in the
Sizing page of the Rating tab must be completed.
Heat Transfer
For each zone, almost all parameters in the Radiant Zone
Properties group and Radiant/Convective/Economizer
Tube Properties groups are required except the Inner/
Outer Scaled HX Coefficient.
Nozzle
Nozzle elevation is defaulted to 0. Elevation input is
required when static head contribution in Integrator view
is checked.
Pressure Drop
Either specify an overall delta P or an overall K value for
the Fired Heater. Specify the pressure drop calculation
method on the Tube Side PF page and Flue Gas PF page
of the Dynamics tab.
4-133
4-134
Fired Heater (Furnace)
4.4.2 Fired Heater Property View
You can also add a new
fired heater by pressing the
F12 hot key.
You can also open the
Object Palette by pressing
the F4 hot key.
There are two ways that you can add a Fired Heater to your simulation:
1.
In the Flowsheet menu, select the Add Operation command. The
UnitOps view appears.
2.
Click the Heat Transfer Equipment radio button.
3.
From the list of available unit operations, select Fired Heater.
4.
Click the Add button. The Fired Heater property view appears.
OR
Fired Heater icon
1.
In the Flowsheet menu, select the Palette command. The Object
Palette appears.
2.
Double-click the Fired Heater icon. The Fired Heater property view
appears.
Figure 4.77
To ignore the Fired Heater during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation (and cannot
calculate the outlet stream) until you restore it to an active state by
deactivating the checkbox.
4-134
Heat Transfer Equipment
4-135
4.4.3 Design Tab
The Design tab consists of four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
On the Connections page, you can specify the name of the operation,
and inlet and outlet streams.
Figure 4.78
Object
Description
Econ Zone Inlet/Outlet
You can specify multiple inlet and outlet streams for the
Economizer zone.
Conv Zone Inlet/Outlet
You can specify multiple inlet and outlet streams for the
Convective zone.
Radiant Zone Inlet/Outlet
You can specify multiple inlet and outlet streams for the
Radiant zone.
Burner Fuel/Air Feed
Specifies the stream to be used for the burner fuel.
Combustion Product
The stream that contains the products from the
combustion.
# External Passes
You can define the number of zones required by the Fired
Heater
4-135
4-136
Fired Heater (Furnace)
Parameters Page
The Parameters page is used to specify the Fired Heater combustion
options.
Figure 4.79
This page is divided into four groups. The Flame Status group, along
with displaying the flame status, allows you to toggle between a lit flame
and an extinguished flame. The Oxygen group simply allows you to
specify the oxygen mixing efficiency. The Combustion Boundaries
group is used to set the combustion boundary based on a range of air
fuel ratios. The checkbox, when active, allows you to auto-light the
flame if your calculated air fuel ratio is within the boundary. Finally the
Fuels group allows you to select the components present in your fuel as
well as set their mixing efficiencies.
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
4-136
Heat Transfer Equipment
4-137
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor that allows you to record any
comments or information regarding the specific unit operation, or the
simulation case in general.
4.4.4 Rating Tab
The Rating tab contains three pages:
•
•
•
Sizing
Nozzles
Heat Transfer
Each page is discussed in the following sections.
Sizing Page
On the Sizing page, you can specify the geometry of the radiant,
convective, and economizer zones in the Fired Heater.
Figure 4.80
4-137
4-138
Fired Heater (Furnace)
From the Zone group on the Sizing page, you can choose between
Radiative, Convective, and Economizer zone views by selecting the
appropriate radio button. These views contain information regarding
the tube and shell properties. To edit or enter parameters within these
views, click the individual cell and make the necessary changes.
The figure below shows an example of the Fired Heater setup with one
radiant zone/firebox only with four tube passes. This is the simplest
type.
Figure 4.81
4-138
Heat Transfer Equipment
4-139
The figure below shows an example of the Fired Heater setup with a
radiant, convective and economizer section.
Figure 4.82
Tube Properties Group
The Tube Properties group displays the following information regarding
the dimension of the tube:
•
•
•
•
•
•
•
•
•
stream pass
tube inner diameter, Din
tube outer diameter, Dout
tube thickness
# tubes per external pass
tube length, L
tube inner area
tube outer area
tube inner volume
A pass in the Fired Heater is defined as a path where the process fluid
flows through a distinctive inlet nozzle and outlet nozzle.
4-139
4-140
Fired Heater (Furnace)
The figure below illustrates the various dimensions of the tube and
shell.
Figure 4.83
Shell Properties Group
The Shell Properties group displays the following information regarding
the dimension of the shell:
•
•
•
•
•
•
•
•
4-140
shell inner diameter, Dsin
shell outer diameter, Dsout
wall thickness, ts
zone height, H
shell inner area
shell outer area
shell net volume
shell total volume
Heat Transfer Equipment
4-141
Nozzles Page
Figure 4.84
The information provided in the Nozzles page is applicable only in
Dynamic mode. You can define the base elevation to ground level of the
Fired Heater in the Nozzles page.
Heat Transfer Page
The information provided in the Heat Loss page is applicable only in
Dynamic mode. This page displays the radiant heat transfer properties,
heat transfer coefficients of the Fired Heater wall and tube, and shell
area, tube area, and volume in each individual zone.
Figure 4.85
HYSYS accounts for the convective, conduction, and radiative heat
transfer in the radiant zone. For the convective heat transfer calculation,
you have two options:
•
•
User Specified. You can specify the heat transfer coefficient of
the inner tube and the outer tube.
Flow Scaled. The heat transfer coefficient is scaled based on a
specified flow.
The scaled heat transfer coefficient is defined by Equation (4.32).
4-141
4-142
Fired Heater (Furnace)
The same equation applies to the outer tube heat transfer coefficient
calculation. Currently, the heat transfer coefficient U must be specified
by the user. HYSYS calculates the heat transfer coefficient from the
geometry/configuration of the Fired Heater. The radiant box or the fire
box is assumed cylindrical in geometry.
Radiant Zone Properties Group
The following table describes each the parameters listed in the Radiant
Zone group.
Radiant Zone Parameter
Description
Zone to Wall Emissivity
Emissivity of flue gas. HYSYS uses a constant value.
Zone to Wall U
Convective heat transfer coefficient of the radiative zone
to the Fired Heater inner wall.
Outer Wall to
Surrounding Emissivity
Emissivity of the Fired Heater outer wall.
Outer Wall to
Surroundings U
Convective heat transfer coefficient of the Fired Heater
outer wall to ambient.
Furnace Wall
Conductivity/Specific
Heat/Wall Density
These are user specified properties of a single layer of
Fired Heater wall.
The Radiant, Convective, and Economizer Tube Properties groups all
contain similar parameters, which are described in the following table.
Tube Properties
Description
Zone to Tube Emissivity
Emissivity of flue gas at radiant/convective zone to the
tube in radiant/convective zone respectively.
Wall to Tube Emissivity
Radiant zone Fired Heater wall emissivity to the radiant
zone tubes.
Inner HX Coeff Method
There are two options to calculate the Heat transfer
coefficient in the tube: User Specified or Flow Scaled.
Flow Scaled provides a more realistic HX calculation
where:
mass 0.8
U used = U specified  -------------------
 mass ref
4-142
Tube to Fluid HX
Coefficient
Heat transfer coefficient of the tube to the process fluid.
Tube to Fluid HX
Reference Flow
Mass flow at which the tube to fluid HX coefficient is
based on. Usually the ideal steady state flow is
recommended as input.
Heat Transfer Equipment
If the process flow in the
tubes is less than this value,
the HX coefficient used is set
to zero.
Tube Properties
Description
Tube to Fluid HX
Minimum Scale Factor
The ratio of mass flow of the process fluid to the reference
mass flow in the tube. The valve ranges from a value of
zero to one. If the process flow in the tube becomes less
than the scale factor, the heat transfer coefficient used is
smaller than U specified.
Inner Scaled HX
Coefficient
The HX coefficient obtained if the Flow Scaled (Uused)
method is applied to perform the calculation.
Tube Cp, Density,
Conductivity
Metal properties of the tube in their respective zones.
Outer HX Coefficient
Method
Method used to calculate the shell side HX coefficient.
Two options available: User Specified or Flow Scaled.
Zone to Tube HX
Coefficient
HX coefficient in the radiative/convective/ economizer or
flue gas zones to the respective tubes.
Zone to Tube HX
Reference Flow
Mass flow of the flue gas at which the outer HX coefficient
is based upon. This is usually designed using the ideal
steady state flow of the flue gas.
Zone to Tube HX
Minimum Scale Factor
Mass ratio of flue gas flow to the flue gas reference mass
flow. This value ranges from zero to one.
Outer Scaled U
The actual HX coefficient used in the calculation if the
Flow Scaled option is selected.
4-143
In general the Tube to Fluid HX Coefficient is always shown in a
common Fired Heater flowsheet, however, the Zone to Wall U and
Outer Wall to Surroundings U are usually unknown. The Outer wall to
Surroundings U can be easily estimated from the Fired Heater
convective heat loss calculation, Equation (4.31) if the total heat loss via
Fired Heater wall is known. The total heat loss is normally expressed as a
percentage of total Fired Heater duty. A 3-5% heat loss is an acceptable
estimate.
Estimating Zone to Wall U requires trial and error techniques. Enter a
value of U then observe the temperature profile of the flue gas exiting
the radiant zone.
4.4.5 Worksheet Tab
To view the stream
parameters broken down per
stream phase, open the
Worksheet tab of the stream
property view.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the heat
exchanger unit operation. Refer to Section 1.2.3 - Worksheet Tab for
more information.
The PF Specs page is
relevant to dynamics cases
only.
4-143
4-144
Fired Heater (Furnace)
4.4.6 Performance Tab
The performance tab contains three pages which highlight the
calculated temperature, duty, and pressure of the Fired Heater
operation.
Figure 4.86
Duty Page
The Duty page displays the results of the Fired Heater energy balance
calculation. The Duty page contains three levels/branches: Radiant
Zone, Convective Zone, and Economizer Zone.
4-144
Heat Transfer Equipment
•
4-145
If you select Radiant Zone from the tree browser, the following
four levels/branches containing information regarding the Tube
Duty results and Zone Duty results appear:
Overall:
Figure 4.87
Holdup:
Figure 4.88
4-145
4-146
Fired Heater (Furnace)
Tubes:
Figure 4.89
Wall:
Figure 4.90
4-146
Heat Transfer Equipment
•
4-147
If you select the Convective Zone from the tree browser, the
following parameters from the Tube Duty Results group and the
Zone Duty Results group appear:
Figure 4.91
•
If you select the Economizer Zone from the tree browser, the
following parameters from the Tube Duty results group and Zone
Duty results group appear:
Figure 4.92
4-147
4-148
Fired Heater (Furnace)
Process Fluid Page
The Process Fluid page contains two sub-pages:
•
•
Temperatures
Pressures
In the Temperatures sub-page, the following parameters appear:
Sub pages on the Process
Fluid page.
•
•
•
Inlet Temp, Inlet stream process fluid temperature
Outlet Temp, Outlet stream process fluid temperature
Tube Inner Temp, Tube inner wall temperature
In the Pressures sub-page, the following parameters appear:
•
•
•
•
Inlet pressure, inlet stream pressure
Friction Delta P, friction pressure drop across the tube
Static Head Delta P, static pressure of the stream
Outlet Pressure, outlet stream pressure
Flue Gas Page
The Flue Gas page consists of three sub pages:
•
•
•
Temperatures
Pressures
Flows
On the Temperatures sub-page, you can view your flue gas temperature
and Fired Heater inner/outer wall temperatures.
Figure 4.93
4-148
Heat Transfer Equipment
4-149
Similarly, the Pressures sub-page displays the flue gas pressures,
frictional delta P, and static head delta P. The Flow sub-page displays
the flue gas molar/mass flow.
4.4.7 Dynamics Tab
The Dynamics tab contains information pertaining to pressure
specifications for he dynamic calculations. The information is sorted
into three pages:
•
•
•
Tube Side PF
Flue Gas PF
Holdup
Tube Side PF Page
The Tube Side PF page allows you to specify how the pressure drop in
each pass is calculated.
Figure 4.94
4-149
4-150
Fired Heater (Furnace)
The following table outlines the tube side PF options available on this
page.
Option
Description
Use K’s?
If this checkbox is activated, the K method is used to calculate
Delta P across the pass.
Use Delta P Spec?
If this checkbox is activated, the pressure drop is fixed at this
specified value.
Calculate K’s
If this button is clicked, HYSYS calculates the K required to
maintain a specified Delta P across a defined flow condition.
Flue Gas PF Page
On the Flue Gas PF page, you can specify how the pressure drop in each
pass is calculated.
Figure 4.95
The following table outlines the tube side PF options available on this
page.
4-150
Option
Description
Use PF K’s
If this checkbox is activated, the K method is used to calculate Delta
P across the pass.
Use Delta P
If this checkbox is activated, the pressure drop is fixed at this
specified value.
Calculate K’s
If this button is clicked, HYSYS calculates the K required to maintain
a specified Delta P across a defined flow condition.
Heat Transfer Equipment
4-151
Holdup Page
The Holdup page contains information regarding each stream’s holdup
properties and composition.
Figure 4.96
The Overall Stream Holdup Details group contains information
regarding the stream’s holdup with its associated phases. For each
phase contained within the volume space of the unit operation, the
following is specified:
Holdup Details
Description
Accumulation
The rate of change of material in the holdup for each phase.
Moles
Amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
4-151
4-152
LNG
4.5 LNG
To ignore the LNG during
calculations, activate the
Ignored checkbox. HYSYS
completely disregards the
operation (and cannot
calculate the outlet stream)
until you restore it to an
active state by deactivating
the checkbox.
The LNG (Liquefied Natural Gas) exchanger model solves heat and
material balances for multi-stream heat exchangers and heat exchanger
networks. The solution method can handle a wide variety of specified
and unknown variables.
For the overall exchanger, you can specify various parameters, including
heat leak/heat loss, UA or temperature approaches. Two solution
approaches are employed; in the case of a single unknown, the solution
is calculated directly from an energy balance. In the case of multiple
unknowns, an iterative approach is used that attempts to determine the
solution that satisfies not only the energy balance, but also any
constraints, such as temperature approach or UA.
The LNG allows for multiple streams, while the heat exchanger allows
only one hot side stream and one cold side stream.
The dynamic LNG exchanger model performs energy and material
balances for a rating plate-fin type heat exchanger model. The dynamic
LNG is characterized as having a high area density, typically allowing
heat exchange even when low temperature gradients and heat transfer
coefficients exist between layers in the LNG operation.
Some of the major features in the dynamic LNG operation include:
•
•
•
•
4-152
A pressure-flow specification option which realistically models
flow through the LNG operation according to the pressure
network of the plant. Possible flow reversal situations can
therefore be modeled.
A dynamic model, which accounts for energy holdup in the metal
walls and material stream layers. Heat transfer between layers
depends on the arrangement of streams, metal properties, and
fin and bypass efficiencies.
Versatile connections between layers in a single or multiple zone
LNG operation. It is possible to model cross and counter flow,
and multipass flow configurations within the LNG operation.
A heat loss model, which accounts for the convective and
conductive heat transfer that occurs across the wall of the LNG
operation.
Heat Transfer Equipment
4-153
4.5.1 Theory
Heat Transfer
The LNG calculations are based on energy balances for the hot and cold
fluids. The following general relation applies any layer in the LNG unit
operation.
d ( VH out )
M ( H in – H out ) + Q internal + Q external = ρ ----------------------dt
where:
(4.37)
M = fluid flow rate in the layer
ρ = density
H = enthalpy
Qinternal = heat gained from the surrounding layers
Qexternal = heat gained from the external surroundings
V = volume shell or tube holdup
Pressure Drop
The pressure drop across any layer in the LNG unit operation can be
determined in one of two ways:
•
•
Specify the pressure drop.
Define a pressure flow relation for each layer by specifying a kvalue.
If the pressure flow option is chosen for pressure drop determination in
the LNG, a k value is used to relate the frictional pressure loss and flow
through the exchanger. This relation is similar to the general valve
equation:
f =
density × k P 1 – P 2
(4.38)
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4-154
LNG
This general flow equation uses the pressure drop across the heat
exchanger without any static head contributions. The quantity, P1 - P2, is
defined as the frictional pressure loss which is used to “size” the LNG
with a k-value.
Convective (U) & Overall (UA) Heat Transfer Coefficients
Several of the pages in the
LNG view indicate whether
the information applies to
steady state or dynamics.
It is important to understand the differences between steady state and
dynamics LNG models. The Steady State model is based on heat
balances, and a number of specifications related to temperatures and
enthalpy. In this model, the UA values are calculated based on heat
curves. Whereas, the dynamic LNG model is a rating model, which
means the outlet streams are determined by the physical layout of the
exchanger.
In steady state the order of the streams given to the LNG is not
important but in the dynamics rating model the ordering of streams
inside layers in each zone is an important consideration. The U value on
the dynamics page of LNG refers to the convective heat transfer
coefficient for that stream in contact with the metal layer.
For convenience, you can also specify a UA value in Dynamic mode for
each layer, and it is important to note that this value is not an overall UA
value as it is in steady state but accounts merely for the convective heat
transfer of the particular stream in question with its immediate
surroundings. These UA values are thus not calculated in the same way
as in Steady State mode.
If you specify the convective
UA values in Dynamic
mode, than the size and
metal holdup of the LNG are
still considered.
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In Dynamic mode the U and UA value refers to the convective heat
transfer (only) contribution between a stream and the metal that
immediately surrounds it. The overall duty of each stream, in dynamic
mode, is influenced by the presence of metal fins, fin efficiencies, direct
heat flow between metal layers, and other factors, as it would be in a real
plate-fin exchanger.
Heat Transfer Equipment
4-155
Ideally in Dynamic mode the convective heat transfer coefficient, U, for
each stream is specified. An initial value can be estimated from
correlations commonly available in the literature or from the steady
state UA values. The values specified can be manipulated by a spread
sheet if desired. If the shut down and start up of the LNG is to be
modeled, then the U flow scaled calculator should be selected on the
Heat Transfer page, of the Rating tab, as it correctly scales the U values
based on the flow.
If the streams in the rating model are properly laid to optimize heat
transfer (i.e., arranged in the fashion hot, cold, hot, cold and not hot,
hot, cold, cold on the Model page of the Dynamics tab), and the metal
resistance is not significant and significant phase change is not taking
place, then the UA values reported by steady state approximates the
convective UA values that can be specified in Dynamic mode for the
same results.
Dynamic Specifications
The following table lists the minimum specifications required for the
LNG unit operation to solve:
Dynamic Specifications
Description
Zone Sizing
The dimensions of each zone in the LNG operation must
be specified. All information in the Sizing page of the
Rating tab must be completed. You can modify the
number of zones in the Model page of the Dynamics tab.
Layer Rating
The individual layer rating parameters for each zone must
be specified. All information on the Layers page of the
Rating tab must be completed.
Heat Transfer
Specify an Overall Heat Transfer Coefficient, U, or Overall
UA.
These specifications can be made on the Heat Transfer
page of the Rating tab.
Pressure Drop
Either specify an Overall Delta P or an Overall K-value for
the LNG.
Specify the Pressure Drop calculation method on the
Specs page of the Dynamics tab.
Layer Connections
Every layer in each zone must be specified with one feed
and one product. Complete the Connections group for
each zone on the Model page of the Dynamics tab.
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LNG
4.5.2 LNG Property View
You can also add a new
LNG by clicking the F12 hot
key.
You can also open the
Object Palette by clicking
the F4 hot key.
There are two ways to add a LNG Exchanger to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Heat Transfer Equipment radio button.
3.
From the list of available unit operations, select LNG.
4.
Click the Add button. The LNG property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the LNG icon. The LNG property view appears.
Figure 4.97
LNG icon
To ignore the LNG during calculations, activate the Ignored checkbox.
HYSYS completely disregards the operation (and cannot calculate the
outlet stream) until you restore it to an active state by deactivating the
checkbox.
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Heat Transfer Equipment
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4.5.3 Design Tab
There are five pages on the Design tab:
•
•
•
•
•
Connections
Parameters
Specs
User Variables
Notes
Connections Page
The Connections page is shown in the figure below.
Figure 4.98
Any number of Sides can be
added simply by clicking the
Add Side button. To remove
a side, select the side to be
deleted and click the Delete
Side button.
For each exchanger side:
•
•
•
•
An inlet stream and outlet stream are required.
A Pressure Drop is required.
The Hot/Cold designation can be specified. This is used as an
estimate for calculations and is also used for drawing the PFD. If
a designated hot pass is actually cold (or vice versa), the
operation still solves properly. The actual Hot/Cold designation
(as determined by the LNG) can be found on the Side Results
page.
The main flowsheet is the default shown in the flowsheet column.
The LNG status appears on the bottom of the property view, regardless
of which page is currently shown. It displays an appropriate message
such as Under Specified, Not Converged, or OK.
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LNG
Parameters Page
On the Parameters page, you have access to the exchanger parameters,
heat leak/loss options, the exchanger details, and the solving behaviour.
Figure 4.99
Exchanger Parameters Group
If there are more than two
LNG sides, then only the
Weighted rating method
can be used.
Parameters
Description
Rating Method
For the Weighted method, the heating curves are broken into
intervals, which then exchange energy individually. An LMTD and
UA are calculated for each interval in the heat curve and summed to
calculate the overall exchanger UA.
Shell Passes
You have the option of having HYSYS perform the calculations for
Counter Current (ideal with Ft = 1.0) operation or for a specified
number of shell passes. You can specify the number of shell passes
to be any integer between 1 and 7.
In Steady State mode, you can select either an End Point or Weighted
Rating Method.
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Heat Transfer Equipment
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Heat Leak/Loss Group
Heat Leak/Loss group is
available only when the
Rating Method is Weighted.
By default, the None radio button is selected. The other two radio
buttons incorporate heat loss/heat leak:
Radio Button
Description
Extremes
The heat loss and heat leak are considered to occur only
at the end points (inlets and outlets) and are applied to the
Hot and Cold Equilibrium streams.
Proportional
The heat loss and heat leak are applied over each
interval.
Exchange Details Group
The LNG Exchange Details appear as follows:
Figure 4.100
For each side, the following parameters can be specified:
Parameter
Description
Intervals
The number of intervals, applicable only to the Weighted Rating
Method, can be specified. For non-linear temperature profiles,
more intervals are necessary.
Dew/Bubble Point
Activate this checkbox to add a point to the Heat curve for a
phase change. Figure 4.101 illustrates the effect of the number
of intervals and inclusion of the dew and bubble points on the
temperature / heat flow curves. Temperature is on the y-axis, and
heat flow is on the x-axis
Equilibrate
All sides that are checked comes to thermal equilibrium before
entering into the UA and LMTD calculations. If only one hot
stream or cold stream is checked, then that stream is by
definition in equilibrium with itself and the results are not
affected. If two or more hot or cold streams are checked, then the
effective driving force is reduced. All unchecked streams enter
the composite curve at their respective temperatures.
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LNG
Parameter
Description
Step Type
There are three choices, which are described below.
• Equal Enthalpy. All intervals have an equal enthalpy
change.
• Equal Temperature. All intervals have an equal
temperature change.
• Auto Interval. HYSYS determines where points should be
added to the heat curve. This is designed to minimize the
error, using the least amount of intervals.
Pressure Profile
The Pressure Profile is updated in the outer iteration loop, using
one of the following methods described below.
• Constant dPdH. Maintains constant dPdH during update.
• Constant dPdUA. Maintains constant dPdUA during
update.
• Constant dPdA. Maintains constant dPdA during update.
This is not currently applicable to the LNG Exchanger in
steady state, as the area is not predicted.
• Inlet Pressure. The pressure is constant and equal to the
inlet pressure.
• Outlet Pressure. The pressure is constant and equal to the
pressure.
Figure 4.101
10 Intervals; Dew Bubble Points included
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3 Intervals; Dew Bubble Points not included
Heat Transfer Equipment
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Specs Page
On the Specs page, there are three groups which organize the various
specification and solver information.
Figure 4.102
Solver Group
The Solver group includes the solving parameters used for LNG’s:
Solver Parameter
Specification Description
Tolerance
You can set the calculation error tolerance.
Current Error
When the current error is less than the calculation tolerance,
the solution is considered to have converged.
Maximum Iterations
You can specify the maximum number of iteration before
HYSYS stops the calculations.
Iteration
The current iteration of the outer loop appears. In the outer
loop, the heat curve is updated and the property package
calculations are performed. Non-rigorous property calculations
are performed in the inner loop. Any constraints are also
considered in the inner loop.
Unknown Variables
Displays the number of unknown variables in the LNG.
Constraints
Displays the number specifications you have placed on the
LNG.
Degrees of Freedom
Displays the number of Degrees of Freedom on the LNG.
To help reach the desired solution, unknown parameters (flows,
temperatures) can be manipulated in the attached streams.
Each parameter specification reduces the Degrees of Freedom
by one.
The number of Constraints (specs) must equal the number of
Unknown Variables. When this is the case, the Degrees of
Freedom is equal to zero, and a solution is calculated.
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LNG
Unknown Variables Group
HYSYS lists all unknown LNG variables according to your specifications.
Once the unit has solved, the values of these variables appear.
Specifications Group
The Heat Balance
specification is a default LNG
specification that must be
active for the heat equation to
balance.
Notice the Heat Balance (specified at 0 kJ/h) is considered to be a
constraint. This is a Duty Error spec; if you turn it off, the heat equation
cannot balance. Without the Heat Balance spec, you can, for example,
completely specify all four heat exchanger streams, and have HYSYS
calculate the Heat Balance error, which would be displayed in the
Current Value column of the Specifications group.
You can view or delete selected specifications by using the buttons that
align the right of the group. A specification view appears automatically
each time a new spec is created via the Add button. In the figure below is
a typical view of a specification, which is accessed via the View or Add
button.
Figure 4.103
As an example,
defining the Delta
Temp Spec requires
two stream names,
and a value for the
specification.
Each specification view has two tabs:
•
•
Parameters
Summary
The Summary page is used to define whether the specification is Active
or an Estimate. The Spec Value is also shown on this page.
Information specified on the Summary page of the specification view
also appears in the Specifications group.
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Heat Transfer Equipment
4-163
All specifications are one of the following three types:
An Active specification is one
which the convergence
algorithm is trying to meet.
Both checkboxes are
selected for this specification.
Specification Type
Action
Active
An active specification is one which the convergence algorithm
is trying to meet. Notice an active specification always serves
as an initial estimate (when the Active checkbox is activated,
HYSYS automatically activates the Estimate checkbox). An
active specification exhausts one degree of freedom.
An Estimate is used as an
“initial guess” for the
convergence algorithm, and
is considered to be an
Inactive specification.
Estimate
An estimate is considered an Inactive specification because
the convergence algorithm is not trying to satisfy it. To use a
specification as an estimate only, deactivate the Active
checkbox. The value then serves only as an initial estimate for
the convergence algorithm. An estimate does not use an
available degree of freedom.
A Completely Inactive
specification is one which is
ignored completely by the
convergence algorithm, but
can be made Active or an
Estimate at a later time.
Completely Inactive
To disregard the value of a specification entirely during
convergence, deactivate both the Active and Estimate
checkboxes. By ignoring rather than deleting a specification, it
is available if you want to use it later or simply view its current
value.
The specification list allows you to try different combinations of the
above three specification types. For example, suppose you have a
number of specifications, and you want to determine which ones should
be active, which should be estimates and which ones should be ignored
altogether. By manipulating the checkboxes among various
specifications, you can test various combinations of the three types to
see their effect on the results.
The available specification types are:
The Hot Inlet Equilibrium
temperature is the
temperature of the inlet hot
stream minus the heat loss
temperature drop. The Cold
Inlet Equilibrium temperature
is the temperature of the
inlet cold stream plus the
heat leak temperature rise.
Specification
Description
Temperature
The temperature of any stream attached to the LNG. The
hot or cold inlet equilibrium temperature can also be
defined.
Delta Temp
The temperature difference at the inlet or outlet between
any two streams attached to the LNG. The hot or cold
inlet equilibrium temperatures can also be used.
Minimum Approach
The minimum temperature difference between the
specified pass and the opposite composite curve. For
example, if you select a cold pass, this is the minimum
temperature difference between that cold pass and the
hot composite curve.
UA
The overall UA (product of overall heat transfer coefficient
and heat transfer area).
LMTD
The overall log mean temperature difference. It is
calculated in terms of the temperature approaches
(terminal temperature differences) in the exchanger. See
Equation (4.39).
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4-164
LNG
Specification
Description
Duty
The overall duty, duty error, heat leak or heat loss. The
duty error should normally be specified as 0 so that the
heat balance is satisfied. The heat leak and heat loss are
available as specifications only if Heat Loss/Leak is set to
Extremes or Proportional on the Parameters page.
Duty Ratio
A duty ratio can be specified between any two of the
following duties: overall, error, heat loss, heat leak or any
pass duty.
Flow
The flowrate of any attached stream (molar, mass or liquid
volume).
Flow Ratio
The ratio of any two inlet stream flowrates.
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
4.5.4 Rating Tab
You are not required to
change any information on
the pages accessible
through this tab, while
working exclusively in
Steady State mode.
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The Rating tab contains three pages:
•
•
•
Sizing (dynamics)
Layers (dynamics)
Heat Transfer (dynamics)
Heat Transfer Equipment
4-165
Sizing (dynamics) Page
On the Sizing (dynamics) page, you can specify the geometry of each
zone in the LNG unit operation.
Figure 4.104
You can partition the exchanger into a number of zones along its length.
Each zone features a stacking pattern with one feed and one product
connected to each representative layer in the pattern.
In practice, a plate-fin heat exchanger may have a repeating pattern of
layers in a single exchanger block. A set is defined as a single pattern of
layers that are repeated over the height of an exchanger block. Each
zone can be characterized with a multiple number of sets each with the
same repeating pattern of layers.
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4-166
LNG
The figure below displays an LNG exchanger block (zone) with 3 sets,
each containing 3 layers:
Figure 4.105
The Zone Sizing and Configuration group contains information
regarding the geometry, heat transfer properties, and configuration of
each zone in the LNG unit operation. To edit a zone, select the
individual zone in Zone group, and make the necessary changes to the
other groups.
The Zone Geometry group displays the following information regarding
the dimensions of each zone:
•
•
Width
Length
This length refers to the actual length of the exchanger, which is used for
heat transfer. The remainder is taken up by the flow distributors. The
flow of material travels in the direction of the length of the exchanger
block. The fins within each layer are situated across the width of the
exchanger block.
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Heat Transfer Equipment
4-167
The Zone Metal Properties group contains information regarding the
metal heat transfer properties:
•
•
•
Thermal Conductivity
Specific Heat Capacity, Cp
Density
The Zone Layers group contains the following information regarding
the configuration of layers in the zone:
•
•
Number of Layers in a Set
Repeated Sets
Layers (dynamic) Page
The Layers (dynamics) page contains information regarding the plate
and fin geometry:
Figure 4.106
The Copy First Layer Properties to All button can be clicked if you want to
specify all the layers in the zone with the same plate and fin properties.
Each of the following plate and fin properties should be specified for
every layer in each zone if the LNG operation is to solve:
Plate and Fin Property
Description
Fin Perforation
The perforation percentage represents the area of
perforation relative to the total fin area. Increasing the Fin
Perforation decreases the heat transfer area.
Height
The height of the individual layers. This affects the volume
of each layer holdup.
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4-168
LNG
Plate and Fin Property
Description
Pitch
The pitch is defined as the fin density of each layer. The
pitch can be defined as the number of fins per unit width
of layer.
Fin thickness
The thickness of the fin in the layer.
Plate thickness
The thickness of the plate.
Heat Transfer (dynamics) Page
The Heat Transfer (dynamics) page displays the heat transfer
coefficients associated with the individual layers of the LNG unit
operation.
Figure 4.107
If you select the Internal radio button, the internal heat transfer
coefficient associated with each layer appears as shown in the figure
above.
HYSYS accounts for the heating and cooling of the metal fins and plates
in the LNG unit operation. The calculation of heat accumulation in the
metal is based on the conductive heat transfer properties, fin
efficiencies, and various other correction factors. An initial metal
temperature can be specified for each zone in the Initial Metal
Temperature field.
Since a repeating stacking pattern is used, the top most layer of a set is
assumed to exchange heat with the bottom layer of the set above.
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Heat Transfer Equipment
4-169
Currently, the internal heat transfer coefficient, U, or the overall UA
must be specified for the LNG unit operation. HYSYS cannot calculate
the heat transfer coefficient from the geometry/configuration of the
plates and fins. The Internal Heat Transfer group contains the following
parameters:
Internal Heat Transfer
Parameter
Description
U Calculator
The heat transfer calculator currently available in HYSYS
are U specified and U flow scaled. If U specified is
selected, you must specify the internal heat transfer
coefficient, U. Alternatively, you can select U flow scaled
calculator and a reference flow rate is used to calculate U.
U
The internal heat transfer coefficient is specified in this
cell.
Ref. Flow
The Reference Flow is used to calculate U when the U
Flow Scaled calculator is selected.
Min Scale
The minimum scale factor is applied to U by the U Flow
Scaled calculator when the flow changes.
Override UA
The overall UA can be specified if the Override UA
checkbox is activated. The specified UA value is used
without the consideration or back calculation of the
internal heat transfer coefficient, U.
Convective UA
The overall UA is specified in this cell.
If you select the External radio button, the overall UA associated with
heat loss to the atmosphere appears.
Figure 4.108
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4-170
LNG
Like the internal heat transfer coefficients, the external overall UA must
be specified.The External Heat Transfer group contains the following
parameters:
External Heat Transfer Parameter
Description
External T
The ambient temperature surrounding the
plate-fin heat exchanger. This parameter may
be specified or can remain at its default value.
UA
The overall UA is specified in this field. The
heat gained from the ambient conditions is
calculated using the overall UA.
Q1
Q1 is calculated from the overall UA and the
ambient temperature. If heat is gained in the
holdup, Q1 is positive; if heat is lost, Q1 is
negative.
Qfixed
A fixed heat value can be added to each layer
in the LNG unit operation. Since Qfixed does
not vary, a constant heat source or sink is
implied (e.g., electrical tracing). If heat is
gained in the holdup, Qfixed is positive; if heat
is lost, Qfixed is negative.
4.5.5 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the LNG unit
operation. Refer to Section 1.2.3 - Worksheet Tab for more information.
4.5.6 Performance Tab
The Performance tab contains detail performance results of the LNG
exchanger.
Only the first three pages are relevant to Steady State mode simulation:
•
•
•
Results
Plots
Tables
The last two pages pertain to the dynamic simulation of the LNG unit
operation:
•
•
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Summary
Layers
Heat Transfer Equipment
4-171
Results Page
The Results page displays the calculated values generated by HYSYS.
These values are split into three groups for your convenience.
Figure 4.109
Overall Performance Group
Parameter
Description
Duty
Combined heat flow from the hot streams to the cold streams minus
the heat loss. Conversely, this is the heat flow to the cold streams
minus the heat leak.
Heat Leak
Loss of cold side duty to leakage.
Heat Loss
Loss of hot side duty to leakage.
UA
Product of the Overall Heat Transfer Coefficient and the Total Area
available for heat transfer. The LNG Exchanger duty is proportional
to the overall log mean temperature difference, where UA is the
proportionality factor. That is, the UA is equal to the overall duty
divided by the LMTD.
Minimum
Approach
The minimum temperature difference between the hot and cold
composite curves.
LMTD
The LMTD is calculated in terms of the temperature approaches
(terminal temperature differences) in the exchanger, using Equation
(4.39).
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LNG
The equation used to calculate LMTD is:
∆T 1 – ∆T 2
∆T LM = ---------------------------------ln ( ∆T 1 ⁄ ∆T 2 )
where:
(4.39)
∆T 1 = T hot, out – T cold, in
∆T 2 = T hot, in – T cold, o ut
Detailed Performance Group
Parameter
Description
Estimated UA Curvature
Error
The LMTD is ordinarily calculated using constant heat
capacity. An LMTD can also be calculated using linear
heat capacity. In either case, a different UA is predicted.
The UA Curvature Error reflects the difference between
these UAs.
Hot Pinch Temperature
The hot stream temperature at the minimum approach
between composite curves.
Cold Pinch Temperature
The cold stream temperature at the minimum approach
between composite curves.
Cold Inlet Equilibrium
Temperature
The Equilibrium Temperature for the cold streams. When
streams are not equilibrated (see the Parameters page),
the Equilibrium temperature is the coldest temperature of
all cold inlet streams.
Hot Inlet Equilibrium
Temperature
The Equilibrium Temperature for the hot streams. When
streams are not equilibrated (see the Parameters Page),
the Equilibrium temperature is the hottest temperature of
all hot inlet streams.
Side Results Group
The Side Results group displays information on each Pass. For each side,
the inlet and outlet temperatures, molar flow, duty, UA, and the hot/
cold designation appear.
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Heat Transfer Equipment
4-173
Plots Page
You can modify the
appearance of the plot via the
Graph Control view. Refer to
Section 10.4 - Graph
Control in the User Guide for
more information.
You can plot composite curves or individual pass curves for the LNG.
Use the Plot checkboxes to specify which curve(s) you want displayed.
To view the plot area only,
click the View Plot button.
The following variables can be used for either the x or y-axis:
Figure 4.110
•
•
•
•
•
•
Temperature
UA
Delta T
Enthalpy
Pressure
Heat Flow
Select the combination from the Plot Type drop-down list.
Tables Page
On the Table page, you can examine the interval Temperature, Pressure,
Heat Flow, Enthalpy, UA, Vapour Fraction, and Delta T for each side of
the Exchanger in a tabular format. Choose the side, Cold Composite or
Hot Composite, by making a selection from the drop-down list above
the table.
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LNG
Summary (dynamics) Page
The Summary (dynamics) page displays the results of the dynamic LNG
unit operation calculations.
Figure 4.111
On this page, the following zone properties appear for each layer:
•
•
•
•
•
•
•
Inlet Temperature
Exit Temperature
Inlet Enthalpy
Exit Enthalpy
Fluid Duty
Fluid Volume
Surface Area
The Fluid Duty is defined as the energy specified to the holdup. If the
fluid duty is positive, the layer gains energy from its surroundings; if the
fluid duty is negative, the layer loses energy to its surroundings.
If the Combine Layers checkbox is activated in the Model page of the
Dynamics tab, some parameters in the Summary page of the
Performance tab include contributions from multiple layers.
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Heat Transfer Equipment
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Layers (dynamics) Page
The Layers (dynamics) page displays information regarding local heat
transfer and fluid properties at endpoint locations in each layer. The
information displayed on this page is not central to the performance of
the LNG operation.
4.5.7 Dynamics Tab
If you are working
exclusively in steady state
mode, you are not required
to change any information
on the pages accessible
through this tab.
The Dynamics tab contains five pages:
•
•
•
•
Model
Specs
Holdup Estimates
Stripchart
Model Page
On the Model page, you can specify how each layer in a multi-zone LNG
unit operation is connected.
Figure 4.112
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LNG
Main Settings
The Main Settings group displays the following LNG model parameters:
Parameter
Description
Number of Zones
The number of zones in a LNG unit operation can be
specified in this field.
Elevation
You can specify the elevation of the LNG in this field.
The elevation is significant in the calculation of static
head in and around the LNG unit operation.
Combine Layers Checkbox
With the Combine Layers checkbox activated, individual
layers (holdups) carrying the same stream in a single
zone is calculated using a single holdup. The Combine
Layers option increases the speed of the dynamic
solver, and usually yields results that are similar to a
case not using the option.
The Connections group displays the feed and product streams of each
layer for every zone in the LNG unit operation. Every layer must have
one feed stream and one product stream in order for the LNG operation
to solve. A layer’s feed or product stream can originate internally (from
another layer) or externally (from a material stream in the simulation
flowsheet). Thus, various different connections can be made allowing
for the modeling of multi-pass streams in a single zone.
Figure 4.113
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Heat Transfer Equipment
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Connections Group
Every zone in the LNG unit operation is listed in the Zone drop-down
list in the Connections group. All the layers in the selected zone in one
set appear. For every layer’s feed and product, you must specify one of
the following:
•
•
An external material stream.
The zone and layer of an internal inlet or exit stream.
You can specify the relative direction of flow in each layer in the zone.
Layers can flow counter (in the opposite direction) or across the
direction of a reference stream. The reference stream is defined as a
stream which does not have either the Counter or Cross checkbox
activated in the Connections group.
The following table lists three possible flow configurations:
Description
Flow Direction
Flow Setting
Counter Current Flow
Parallel Flow
Cross Flow
To implement counter current flow for two streams in a single exchanger
block, ensure that the Counter checkbox is activated for only one of the
streams. If the Counter checkbox is activated for both streams, the flow
configuration is still parallel, and in the opposite direction.
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4-178
LNG
Specs Page
The Specs page contains information regarding the calculation of
pressure drop across the LNG unit operation.
Figure 4.114
The following parameters appear for every layer in each zone in the LNG
unit operation in the Dynamic Specification groups.
Dynamic Specification
Description
Delta P Calculator
The Delta P Calculator allows you to either specify or
calculate the pressure drop across the layer in the LNG
operation. Specify the cell with one of following options:
• user specified. You specify the pressure drop.
• not specified. Pressure drop across the layer is
calculated from a pressure flow relationship. You
must specify a k-value, and activate the Flow Eqn
checkbox if you want to use this non specified Delta P
calculator.
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Delta P
The pressure drop across the layer of the LNG operation
can be specified or calculated.
Flow eqn
Activate this option, if you want to have the Pressure Flow
k value used in the calculation of pressure drop. If the
Flow Eqn checkbox is activated, the Delta P calculator
must also be set to not specified.
Heat Transfer Equipment
The LNG unit operation, like
other dynamic unit
operations, should use the kvalue specification option as
much as possible to simulate
actual pressure flow relations
in the plant.
Dynamic Specification
Description
Laminar
HYSYS is able to model laminar flow conditions in the
layer. Activate the Laminar checkbox if the flow through
the layer is in the laminar flow regime.
Pressure Flow k Value
The k-value defines the relationship between the flow
through layer and the pressure of the surrounding
streams. You can either specify the k-value or have it
calculated from the stream conditions surrounding the
layer. You can “size” each layer in the zone with a k-value
by clicking the Calculate k’s button. Ensure that there is a
non zero pressure drop across the LNG layer before the
Calculate k button is clicked. Each zone layer can be
specified with a flow and set pressure drop by clicking the
Generate Estimates button.
4-179
When you click the Generate Estimates button, the initial pressure flow
conditions for each layer are calculated. HYSYS generates estimates
using the assumption that the flow of a particular stream entering the
exchanger block (zone) is distributed equally among the layers. The
generated estimates appear on the Estimates page of the Dynamics tab.
It is necessary to complete the Estimates page in order for the LNG unit
operation to solve.
It is strongly recommended that you specify the same pressure drop
calculator for layers that are connected together in the same exchanger
block or across adjacent exchanger blocks. Complications arise in the
pressure flow solver if a stream’s flow is set in one layer, and calculated
in the neighbouring layer.
4-179
4-180
LNG
Holdup Page
The Holdup page contains information regarding each layer’s holdup
properties, composition, and amount.
Figure 4.115
The Details group contains detailed holdup properties for every layer in
each zone of the LNG. For each phase contained within the volume
space of the unit operation, the following is specified:
Holdup Details
Description
Accumulation
The rate of change of material in the holdup for each phase.
Moles
Amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
In order to view the advanced properties for individual holdups, you
must first select the individual holdup.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
To choose individual holdups you must specify the Zone and Layer in
the corresponding drop-down lists.
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Heat Transfer Equipment
4-181
Estimates Page
The Estimates page contains pressure flow information surrounding
each layer in the LNG unit operation:
Figure 4.116
The following pressure flow information appears on the Estimates page:
•
•
•
•
•
Delta P
Inlet Pressure
Outlet Pressure
Inlet Flow
Outlet Flow
It is necessary to complete the Estimates page in order for the LNG unit
operation to completely solve. The simplest method of specifying the
Estimates page with pressure flow values is having HYSYS estimate
these values for you. This is achieved by clicking the Generate Estimates
button on the Specs page of the Dynamics tab. HYSYS generates
estimates using the assumption that the flow of a particular stream
entering the exchanger block (zone) is distributed equally among the
layers.
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
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4-182
LNG
4.5.8 HTFS-MUSE Tab
The HTFS-MUSE tab integrates the HTFS’ MUSE application into the
HYSYS LNG unit Calculation. HYSYS can use the MUSE and MULE
calculation Engines.
MUSE can perform a range of calculations on plate-fin heat exchangers,
either simple two-stream exchangers, or complex ones with multiple
streams. The basic calculation options are described in the table below.
MUSE Calculation Modes
Description
Simulation
Determines the heat load, pressure changes and outlet
conditions for each stream in the exchanger, based on an
exchanger you specify, and given stream inlet conditions.
Layer by Layer
Simulation
For the simulation of a plate fin heat exchanger on a layer
by layer basis. It must be specified with a layer pattern. It
predicts temperature profiles through the layer pattern,
which can be used to assess how good the layer pattern
is.
Thermosyphon
Determines the performance of an exchanger, with a
geometry you specify, with one stream operating as a
thermosyphon. The exchanger can either be internal to
the column or outside it and connected via pipe work. You
can specify either the head of liquid driving the
thermosyphon flow, or the thermosyphon stream flowrate,
leaving the program to calculate the one you do not
specify.
Design
Produces a “first shot” design of a heat exchanger to meet
a heat load duty and pressure drop limits, which you
specify for each stream. This should be a useful indication
of what a specialist manufacturer would provide. A final
design of a plate-fin exchanger must, however, come from
a manufacturer, who can use proprietary finning and
specialist design and manufacturing techniques.
These calculation types all relate to co- or counter-current exchangers.
The HTFS-MUSE tab is made up of nine pages:
•
•
•
•
•
•
•
•
•
4-182
Exchanger
Process
Distributors
Layer Pattern
Fins
Design Limits
Stream Details
Methods
Results
Heat Transfer Equipment
4-183
The HTFS-MUSE tab also consists of two buttons:
•
•
Import. Allows you to import values from MUSE into the pages of
the tab.
Export. Allows you to export the information provided within this
tab to MUSE.
Exchanger Page
The Exchanger page allows you to specify parameters that define the
geometric configuration of the exchanger, as well as the stream.
Figure 4.117
4-183
4-184
LNG
The group located on the top of the page is for specifying the stream
geometry and consists of the following fields:
Field
Description
Flow Direction
There are two options that you can choose from to
define the Flow direction of the stream.
• flow away from end A, Up (B to A).
• flow towards end A, Down (A to B).
Normal design practice is for hot streams to flow away
from end A (which is at the top of the exchanger),
while cold streams flow towards end A.
Number of Layers
Allows you to enter the total number of layers a stream
occupies in the exchanger. If there is more than one
exchanger in parallel, enter the number for one
exchanger only.
This item can be omitted if a layer pattern is specified.
If you specify both, however, they are cross-checked,
which can be useful in detecting errors in a layer
pattern input. When they are inconsistent, a warning is
produced.
If a stream is re-distributed, and occupies extra layers
for part of its length, enter the basic number of layers
only here, and specify the additional layers on the
Distributors page.
Distance to Start of Main Fin
Allows you to enter the distance to the start of a
stream's main finning from the fixed reference point. If
omitted, the default is zero.
If this distance is less than the distance to the start of
the effective length, then there is a region of main fin
where pressure drop, but no heat transfer is evaluated.
If this distance is greater than that to the start of the
effective length, then the stream has a draw-on or
draw-off point part way along the exchanger.
The remainder of the groups located on this page are for specifying the
exchangers geometry and consists of the following fields:
4-184
Field
Description
Orientation
Plate Fin heat exchangers are normally vertical, with
flow up or down. Enter 1.0 for vertical exchangers with
the reference end, A, at the top. For horizontal or
inclined exchangers, refer to the MUSE help file.
Exchangers in Parallel
More than one exchanger in parallel can be used
when stream flowrates, or thermal duties are too large
to be handled by a single exchanger. In all cases the
exchangers are assumed to be identical, and no
calculations are performed on pressure losses in
connecting pipe work.
Effective Width
The effective flow width is the total width of the
exchanger less the widths of the two side bars.
Heat Transfer Equipment
Field
Description
Exchanger Metal
Plate Fin exchangers for LNG and other cryogenic
duties are made of aluminium. For other exchangers,
you can select from:
4-185
• aluminium
• stainless steel
• titanium
Parting Sheet Thickness
The thickness of the separating plates (parting sheets)
between layers is used to determine the exchanger
stack height, and also has an effect on the metal
resistance to heat transfer.
Side Bar Width
Side bars form the sides and ends of each layer. This
item does not usually affect the calculated results, with
the exception of longitudinal conduction calculations.
Cap Sheet Thickness
The stack height is the sum of the fin heights and
parting sheet thicknesses for every layer in the
exchanger, plus the thickness of the two side plates
(cap sheets).
Fin Number for Empty Layer
If you specify a layer pattern with some layers
containing no streams enter the fin number to identify
the fins used in such layers.
Process Page
Figure 4.118
4-185
4-186
LNG
The Process page allows you to specify the following process
information for the streams attached to your exchanger:
•
•
•
•
Estimated Pressure Drop
Fouling Resistance
Heat Load
Design Pressure
Distributors Page
Distributors are special regions of finning, usually laid at an angle, that
directs the flow between a header (inlet or outlet) and the main heat
transfer finning. A low frequency perforated fin is usually used - for
example 6fpi, 25% perforated. Distributor data is optional for each
stream. If omitted the distributor pressure drop for that stream is
ignored.
Heat transfer in inlet and outlet distributors is not considered, but if all
streams have distributor data specified, an estimate is made of the heat
transfer margin associated with each distributor. When distributor
pressure drops are calculated, an estimate is made of the risk of
maldistribution across the width of each layer.
When Redistribution is used, you should specify the Redistributor, and
corresponding re-inlet distributor. Redistributors associated with
partial draw-off of streams can also be specified.
4-186
Heat Transfer Equipment
4-187
Each distributor type consists of a set of inputs as shown in the figure
below.
Figure 4.119
Inlet/Outlet Distributor Type
Field
Description
Type
Allows you to specify the redistributor type, and the side
of the exchanger on which the associated header is
located. You have seven options:
•
•
•
•
•
•
•
Header Location
Allows you to specify the side of the exchanger that the
header is located. You have four options:
•
•
•
•
Fin Number for Pad 1 and 2
Full End
End-Side
Central
Diagonal
Mitred
Indirect
Hardway
Right side
Left side
Central
Twin
Numbers to identify the fins used in the inlet/outlet
distributor pads. Distributors typically use 6fpi 255
perforated finning. The same fin is usually used in both
pads, so only pad 1 need normally be specified. Pad 1
is adjacent to the header.
4-187
4-188
LNG
Field
Description
Dimension a (axial length)
Dimension a for the inlet/outlet distributor. Dimension a
is the length along the exchanger occupied by the
distributor.
Dimension b
Dimension b for the inlet/outlet distributor. This is the
header diameter for End Side, Central, Indirect and
Hardway distributors, and the Pad 1 length for Mitred
distributors. It is not needed for Full End of Diagonal
distributors.
Nozzle DIameter
The internal diameter of the inlet/outlet nozzle. If
omitted the inlet/outlet nozzle pressure loss is not
calculated.
Redistributor Type
Field
Description
Type
Allows you to specify the redistributor type, and the side
of the exchanger on which the associated header is
located. You have four options:
•
•
•
•
Header Location
Standard
Twin
Hardway
Hardway Twin
Allows you to specify the side of the exchanger that the
header is located. You have three options:
• Right side
• Left side
• Twin
4-188
Distance to Redistributor
Allows you to specify the distance to the redistributor
from the inlet.
Fin Number for Pad 1, 2,
and 3
Numbers to identify the fins used in the redistributor.
The same fin is usually used in all pads, so only pad 1
need normally be specified. In a dividing redistributor,
flow that remains in the layers flows through Pad 1 then
Pad 2, while Pad 3 carries the flow that goes to other
layers.
Dimension a (axial length)
Dimension a, the length along the exchanger occupied
by the redistributor.
Dimension b
Dimension b for the redistributor. In a conventional
dividing redistributor, this is the entry width associated
with the flow that remains in the same layer.
Heat Transfer Equipment
4-189
Re-Inlet Distributor Type
Field
Description
Type
Allows you to specify the re-inlet distributor type. This
can be in any form of side entry/exit distributor. You
have five options:
•
•
•
•
•
None
Diagonal
Mitred
Indirect
Hardway
Fin Number for Pad 1 and
2
Numbers to identify the fins used in the re-inlet
distributor pads. The same fin is usually used in both
pads, so only pad 1 need normally be specified. Pad 1
is adjacent to the header.
Dimension a (axial length)
Dimension a, the length along the exchanger occupied
by the re-inlet distributor.
Dimension b
Dimension b for the re-inlet distributor.
Extra Layers/Draw Off
Fraction
For a re-inlet distributor that directs flow to a number of
extra layers, enter the number of extra layers.
For a re-inlet distributor that collects from the extra
layers, to direct it back to the basic number of layers,
enter the number of extra layers with a minus sign.
If there are no extra layers, but the stream is partially
drawn off, enter the fraction of the stream that is drawn
off.
4-189
4-190
LNG
Layer Pattern Page
The Layer Pattern page allows you to define the sequence of stream
numbers that comprise the exchanger. The layer pattern itself gives the
sequence of layers, while the Layer Definition table lets you define the
sequence of streams in each layer. The layer pattern is mandatory input
for Layer-by-Layer simulations, but optional for stream by stream. If no
layer pattern is provided, the number of layers for each stream must be
specified.
Figure 4.120
Layer Pattern
Enter the sequence of layers forming the layer pattern (stacking
pattern). The pattern can be identified as a sequence of layer
identifiers, each identified by a letter, such as ABABABCAB. Though in
simple cases, for example when there is only one stream per layer, the
layer pattern can be specified as sequence of streams, for example
121213412.
Repeated sequences can be written in brackets, for example (121213/
5)1312 means that the sequence 121213 occurs five times, followed by
1312. Spaces in the pattern are ignored, and brackets cannot be
embedded in brackets. A stream number’s sequence can contain zeros
to indicate completely empty layers.
4-190
Heat Transfer Equipment
4-191
A layer pattern can terminate in M or MM to indicate that the pattern
has central symmetry. MM indicates that the central layer is repeated, M
that the symmetry is about the centre of the final layer. When The
pattern is defined in terms of letters, use | or ||, not M’s, to indicate
mirror symmetry.
Layer Definition
The Layer Definition facility
is only available in MUSE
3.20 and later versions.
For each (alphabetic) layer identifier in the pattern specify the stream or
sequence of streams along the exchanger from end A, within each layer
type. This is only needed when a pattern is defined in terms of layer
types (A,B,C etc.) rather than streams, 1, 2, 4 etc.
Fins Page
The Fins page allows you to specify data on fin geometry.
Figure 4.121
When a fin is specified, the corresponding fin performance data from
the fin manufacturer (friction factors and Colburn j factors over a range
of Reynolds numbers) should be input when available. If they are not
available, they are estimated using generalized HTFS correlations for
particular fin types.
4-191
4-192
LNG
Fin numbers are used to identify the particular fin used as main fin or
distributor fin for each stream. Fin numbers up to 20 identify fins that
data is specified in the program input.
The Fin Geometry groups consists of two buttons and a table. The two
buttons allows you to add and remove fins from the heat exchanger,
while the table allows you to specify each fin’s geometry.
The table consists of the following fields.
Field
Description
Fin Type
There are four main types of fin
• Plain
• Perforated
• Serrated, or offset-strip
• Wavy or herringbone
For details of when each type should be used, refer to the MUSE
Help file.
Prandtl No.
Correlation to
Cj
This parameter is important for high viscosity fluids in plain or
perforated fins.
The Colburn j factor assumes that Cj is a function of Re only, but this
is not true at low Reynolds numbers (below 1000), where there is
also Prandtl number dependence.
If you specify the Re-f-Cj data at a Pr appropriate to the fluids used,
omit this item. If you specify the Pr=1 data, specify 1 for a full
correction, or a value between 0 and 1 for a partial correction. Refer
to the MUSE Help file for more details.
Fin Height
Distance between the separating plates (parting sheets). This
applies to all fin types.
All the fins (main fin and distributor) for a stream must have the
same height. A warning is issued if this is not so.
Fin Thickness
The fin thickness.
Fin Frequency
Number of fins per unit of length. This item can be zero if no fins are
present.
Common fin frequencies are 16, 18 or 21 ft/in for main fins, and 6 or
8 ft/in for distributor fins.
Fin Porosity
For perforated fins, enter the fin porosity as a fraction of the metal
lost as holes.
Fin Serration
Length
For serrated fins enter the fin serration length. The default is 3 mm
(approximately 1/8 inch), which is typical of values used by most
manufacturers.
This input item is only needed for long-serration length serrated fins.
As mentioned above the corresponding fin performance data from the
fin manufacturer, if available, should be entered into the Fin
Performance group. To specify the data, select the fin number from the
list of fins, and enter the data in the appropriate fields.
4-192
Heat Transfer Equipment
4-193
Design Limits Page
In the future version of HYSYS, the HTFS design capability will be
available on the Design Limits page.
Stream Details Page
Figure 4.122
The Stream Details page allows you to specify more stream geometry
data that supplements the data that was entered on the Exchanger page.
The following table defines each of the fields on this page.
Field
Description
Same Layer as Stream
The Same Layer as Stream parameter is one way of
specifying that two streams occupy the same set of layers
in an exchanger. It is not needed, if you specify a layer
pattern in terms of Layer Identifiers A,B,C etc., with Layer
Definition information.
If you specify a layer pattern in terms of stream numbers,
then one stream in each layer is used to identify that layer.
For other streams in that layer give the number of the
stream in the layer pattern that identifies the layer.
Fraction of Double
Banking
The Fraction of Double Banking parameter is not needed
if you specify a layer pattern, and is estimated if you do
not. Refer to the MUSE Help for a definition and more
details.
4-193
4-194
LNG
Field
Description
Number of Cross Flow
Passes
For streams in multipass crossflow, enter the number of
crossflow passes.
Fin Number of (first)
Main Fin
Number to identify the main heat transfer fin for the
stream. The number must correspond to one of the fin
data blocks in the Fins page, or to a fin in a User
Databank.
If the stream uses more than one type of main fin, this
item is the first fin, counting from the stream inlet.
Length of (first) Main Fin
The length of the main fin for the stream.
Fin Number for Second
to Sixth Fins
For a stream that uses more than one type of main fin,
enter the fin numbers. The sequence is from stream inlet
to outlet.
Length of Fins for
Second to Sixth Fins
The length of each main fin for the stream.
Methods Page
The Methods page consists of three groups:
•
•
•
Calculation Options
Calculation Parameters
Process Constraints
Figure 4.123
4-194
Heat Transfer Equipment
4-195
Calculation Options
The Calculation Options group is used to configure the data that
appears on the Results page. Only the Output Units need normally be
set, as defaults are usually acceptable for all other items. The group
consists of the following fields.
Field
Description
Calculation Type
The Calculation Type should not be set. It gives access to
a deprecated calculation facility, Length estimation, as an
alternative to Normal simulation. Refer to the MUSE help
file for more information.
Units of Output
Allows you to specify the set of units you want to use for
the output data. There are five options to choose from:
•
•
•
•
•
SI / deg C
British
Metric / C
SI / deg K
Metric / K
Output of Input Data
Specifies where the output of input data appears in the
main Results page (lineprinter output). Refer to the MUSE
help for more information.
Physical Properties
Package
Allows you to send the Physical Properties of the
exchanger to the Results page or to a specific file.
Convergence Parameter
Use only if MUSE shows convergence problems. Refer to
the MUSE help for more information.
Stream by Stream or
Layer by Layer
Normally leave this item unset. Use it only with the
(MULE) layer-by-layer calculation engine to enforce a
reduced stream-by-stream calculation. Refer to the MUSE
help for more information.
Longitudinal Conduction
You can specify that in addition to heat transfer between
streams, allowance can be made for heat conducted in
the exchanger metal from the hot to cold end of the
exchanger. This can be important for exchangers used in
liquefying hydrogen or helium. Refer to the MUSE help for
more information.
Number of Calculation
Steps
Calculations in MUSE use a number of equal length steps
along the exchanger. The default is 100, the maximum
200. Refer to the MUSE help file for more information.
1st Est. Heat Load
(fraction of max)
Use this item only if there are convergence problems. It
lets you change the initial estimate of exchanger duty.
Refer to the MUSE help file for more information.
Distributor Calculations
Gives you control over when distributor pressure losses
are calculated. The default is that losses are calculated if
you specify distributor data. Refer to the MUSE help for
more information.
Maximum Number of
Iterations
Enter a value if you want to restrict the number of
iterations. Refer to the MUSE help file for more
information.
4-195
4-196
LNG
Calculation Parameters
The Calculation Parameters group allows you to specify process
exchanger parameters. The group consists of the following fields:
Field
Description
Heat Leak
It is possible to specify a net heat leak into the exchanger,
or out of the exchanger, if a negative value is specified.
Heat Leak Skewness
For heat leaks that are not uniform along the exchanger
length. Refer to the MUSE help for more information.
Effective Length,
Distance to Effective
Length
These two fields should normally be omitted, and left to
the program to calculate. The effective length is that
region of the exchanger where heat transfer is assumed
to occur. It is determined from the exchanger geometry
data, but you can override the program if you want. Refer
to the MUSE help for more information.
A Stream - B Stream
Load
A deprecated input. It is possible to specify the heat load
across the exchanger for end A to end B.
Process Constraints
The Process Constraints group allows you to specify sets of stream
constraints for over-riding, or scaling values normally calculated by the
program. These should not be used, unless you have a good reason for
doing so.
Field
Description
Liquid Phase HTC
You can enter a value for the liquid heat transfer
coefficient here to override the calculated value.
It is recommended that the program calculated values be
used.
Two Phase HTC
You can enter a value for the two phase (boiling or
condensing) heat transfer coefficient here to override the
calculated value.
It is recommended that the program calculated values be
used.
Vapour Phase HTC
You can enter a value for the vapour heat transfer
coefficient here to override the calculated value.
It is recommended that the program calculated values be
used.
Multiplier for Liquid
Coefficient
A value entered here can be used to increase or decrease
the calculated liquid heat transfer coefficient. It also
scales any pre-set coefficient you input.
It is recommended that the program calculated values be
used.
4-196
Heat Transfer Equipment
Field
Description
Multiplier for Two Phase
Coefficient
A value entered here can be used to increase or decrease
the calculated boiling or condensing heat transfer
coefficient. It also scales any pre-set coefficient you input.
4-197
It is recommended that the program calculated values be
used.
Multiplier for Vapour
Coefficient
A value entered here can be used to increase or decrease
the calculated vapour or gas heat transfer coefficient. It
also scales any pre-set coefficient you input.
It is recommended that the program calculated values be
used.
Pressure Drop Multiplier
Enter the number that the calculated frictional pressure
gradient (liquid, two phase or vapour) should be
multiplied. It is not possible to scale the pressure drops of
each phase separately.
It is recommended that the program calculated values be
used.
Precalculated Arrays
Flag
Allows you to override an internal calculation flag, it is
best left unset. See the MUSE help for more details.
Preset deltaT for Boiling
Provides a variant on the boiling method, it is best left
unset. See the MUSE help for more details.
Results Page
The exchanger results appear on this page. The results are created in a
text format that can be exported to HTFS-MUSE.
4-197
4-198
References
4.6 References
4-198
1
Perry, R.H. and D.W. Green. Perry’s Chemical Engineers’ Handbook (Seventh
Edition) McGraw-Hill (1997) p. 11-33
2
Perry, R.H. and D.W. Green. Perry’s Chemical Engineers’ Handbook (Seventh
Edition) McGraw-Hill (1997) p. 11-42
3
Kern, Donald Q. Process Heat Transfer McGraw-Hill International Editions:
Chemical Engineering Series, Singapore (1965) p. 139
Piping Equipment
5-1
5 Piping Equipment
5.1 Mixer .................................................................................................3
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
Mixer Property View.................................................................4
Design Tab...............................................................................5
Rating Tab................................................................................7
Worksheet Tab.........................................................................8
Dynamics Tab ..........................................................................8
5.2 Pipe Segment .................................................................................10
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
5.2.6
5.2.7
5.2.8
5.2.9
Pipe Segment Property View.................................................16
Design Tab.............................................................................17
Rating Tab..............................................................................32
Worksheet Tab.......................................................................47
Performance Tab ...................................................................48
Dynamics Tab ........................................................................53
Deposition Tab .......................................................................54
Profes Wax Method ...............................................................57
Modifying the Fittings Database ............................................66
5.3 Compressible Gas Pipe.................................................................71
5.3.1
5.3.2
5.3.3
5.3.4
5.3.5
5.3.6
5.3.7
Compressible Gas Pipe Property View..................................73
Design Tab.............................................................................74
Rating Tab..............................................................................76
Worksheet Tab.......................................................................78
Performance Tab ...................................................................78
Properties Tab........................................................................79
Dynamics Tab ........................................................................81
5-1
5-2
Piping
5.4 Tee................................................................................................... 82
5.4.1
5.4.2
5.4.3
5.4.4
5.4.5
Tee Property View ................................................................. 82
Design Tab ............................................................................ 83
Rating tab .............................................................................. 86
Worksheet Tab....................................................................... 86
Dynamics Tab ........................................................................ 87
5.5 Valve ............................................................................................... 89
5.5.1
5.5.2
5.5.3
5.5.4
5.5.5
Valve Property View .............................................................. 90
Design Tab ............................................................................ 91
Rating Tab ............................................................................. 93
Worksheet Tab....................................................................... 99
Dynamics Tab ........................................................................ 99
5.6 Relief Valve .................................................................................. 109
5.6.1
5.6.2
5.6.3
5.6.4
5.6.5
Relief Valve Property View .................................................. 109
Design Tab .......................................................................... 110
Rating tab ............................................................................ 113
Worksheet Tab..................................................................... 117
Dynamics Tab ...................................................................... 117
5.7 References ................................................................................... 121
5-2
Piping Equipment
5-3
5.1 Mixer
The Mixer operation combines two or more inlet streams to produce a
single outlet stream. A complete heat and material balance is performed
with the Mixer. That is, the one unknown temperature among the inlet
and outlet streams is always calculated rigorously. If the properties of all
the inlet streams to the Mixer are known (temperature, pressure, and
composition), the properties of the outlet stream is calculated
automatically since the composition, pressure, and enthalpy is known
for that stream.
The mixture pressure and temperature are usually the unknowns to be
determined. However, the Mixer also calculates backwards and
determine the missing temperature for one of the inlet streams if the
outlet is completely defined. In this latter case, the pressure must be
known for all streams.
The resultant temperature of the mixed streams may be quite different
than those of the feed streams due to mixing effects.
The Mixer flashes the outlet stream using the combined enthalpy. Notice
that when the inlet streams are completely known, no additional
information needs to be specified for the outlet stream. The problem is
completely defined; no degrees of freedom remain.
The dynamic Mixer operation functions very similarly to the steady state
Mixer operation. However, the enhanced holdup model and the concept
of nozzle efficiencies can be applied to the dynamic Mixer. Flow reversal
is also possible in the Mixer depending on the pressure-flow conditions
of the surrounding unit operations.
5-3
5-4
Mixer
5.1.1 Mixer Property View
You can also add a mixer by
clicking the F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Mixer to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Piping Equipment radio button.
3.
From the list of available unit operations, select Mixer.
4.
Click the Add button. The Mixer property view appears.
OR
1.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
2.
Double-click the Mixer icon. The Mixer property view appears.
Figure 5.1
Mixer icon
To ignore the Mixer during calculations, activate the Ignored checkbox.
HYSYS disregards the operation until you deactivate the checkbox.
5-4
Piping Equipment
5-5
5.1.2 Design Tab
The Design tab provides access to four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
On the Connections page, you can specify any number of inlet streams
to the Mixer; a single outlet stream is also required.
Figure 5.2
5-5
5-6
Mixer
Parameters Page
The Parameters page allows you to indicate the type of Automatic
Pressure Assignment, HYSYS should use for the streams attached to the
Mixer.
Figure 5.3
The default is Set Outlet to Lowest Inlet, in which case all but one
attached stream pressure must be known. HYSYS assigns the lowest inlet
pressure to the outlet stream pressure.
If you specify Equalize All, HYSYS gives all attached streams the same
pressure once one of the attached stream pressures are known. If you
want to specify all of the inlet stream pressures, ensure first that all
pressures have been specified before installing the Mixer, then choose
Set Outlet to Lowest Inlet. In this case, there is no automatic pressure
assignment since all the stream pressures are known.
If you select Equalize All and two or more of the attached streams have
different pressures, a pressure inconsistency message appears.
In this case, you must either remove the pressure specifications for all
but one of the attached streams, or select Set Outlet to Lowest Inlet. If
you specify Set Outlet to Lowest Inlet, you can still set the pressures of
all the streams.
5-6
Piping Equipment
5-7
If you are uncertain of which pressure assignment to use, choose Set
Outlet to Lowest Inlet. Only use Equalize All if you are completely sure
that all the attached streams should have the same pressure. While the
pressure assignment seems to be extraneous, it is of special importance
when the Mixer is being used to simulate the junction of multiple pipe
nodes.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
5.1.3 Rating Tab
You need HYSYS dynamics to specify any rating information for the
Mixer operation. The Rating tab consists of the Nozzles page.
Nozzles Page
The Fidelity license is
required to use the nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. Refer to Section 1.6.2 - Nozzles in Dynamic
Modeling manual for more information.
It is strongly recommended that the elevation of the inlet and exit
nozzles are equal for this unit operation. If you want to model static
head, the entire piece of equipment can be moved by modifying the
Base Elevation relative to Ground Elevation field.
5-7
5-8
Mixer
5.1.4 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
5.1.5 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Dynamics tab.
The Dynamics tab provides access to two pages:
•
•
Specs
Holdup
In Dynamic mode, changes in inlet streams to the Mixer are seen
instantaneously in the outlet stream; the Mixer has no holdup.
Specs Page
In dynamic mode, there are
two possible dynamic
specifications you can
choose to characterize the
Mixer operation.
5-8
The dynamic specifications of the Mixer can be specified on the Specs
page.
Figure 5.4
Piping Equipment
5-9
If you select the Equalize All radio button, the pressure of the
surrounding streams of the Mixer are equal if static head contributions
are not considered. This is a realistic situation since the inlet stream
pressures to a Mixer in an actual plant must be the same. With this
specification, flow to and from the Mixer is determined by the pressure
flow network. The “one PF specification per flowsheet boundary stream”
rule applies to the Mixer operation if the Equalize All option is chosen. It
is strongly recommended that you use the Equalize All option in order to
realistically model flow behaviour in a dynamic simulation case.
If you select the Set Outlet to Lowest Inlet radio button, HYSYS sets the
pressure of the exit stream of the Mixer to the lowest inlet stream
pressure. This situation is not recommended since two or more streams
can enter the Mixer at different pressures which is not realistic. With this
specification, flow to and from the Mixer is determined from upstream
flow specifications, and not from the surrounding pressure network of
the simulation case. If this option is used, n more pressure-flow
specifications are required by the PF solver than if the Equalize All
option is used. The variable, n, is the number of inlet streams to the
Mixer.
Reverse flow conditions can occur in the Mixer operation if the Equalize
All checkbox is deactivated. If flow reverses in the Mixer, it essentially
acts like a dynamic Tee with the Use Splits as Dynamic Specs checkbox
inactive. In dynamics, these two unit operations are very similar.
Holdup Page
The volume of the Mixer is
assumed to be zero.
Each unit operation in HYSYS has the capacity to store material and
energy. Typical Mixers in actual plants usually have significantly less
holdup than other unit operations in a plant. Therefore, the volume of
the Mixer operation in HYSYS cannot be specified and is assumed to be
zero. Since there is no holdup associated with the Mixer operation, the
holdup’s quantity and volume are shown as zero in the Holdup page.
Refer to Section 1.3.7 Advanced Holdup
Properties in the Dynamic
Modeling manual for more
information.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation.
5-9
5-10
Pipe Segment
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about stripcharts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
5.2 Pipe Segment
OLGAS is a third-party option
which can be purchased
through AspenTech or
SCANDPOWER. Contact your
AspenTech agent for more
information, or e-mail us at
[email protected]
The Pipe Segment is used to simulate a wide variety of piping situations
ranging from single or multiphase plant piping with rigorous heat
transfer estimation, to a large capacity looped pipeline problems. It
offers several pressure drop correlations:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Aziz, Govier, and Fogarasi
Baxendell and Thomas
Beggs and Brill
Duns and Ros
Gregory Aziz Mandhane
Hagedorn and Brown
HTFS, Liquid Slip
HTFS, Homogeneous Flow
OLGAS2000_2P
OLGAS2000_3P
Orkiszewski
Poettmann and Carpenter
Tacite Hydrodynamic Module
Tulsa 99
Another option, OLGAS, is also available as a gradient method. Four
levels of complexity in heat transfer estimation allow you to find a
solution as rigorous as required while allowing for quick generalized
solutions to well-known problems.
The Pipe Segment offers four calculation modes:
•
•
•
•
5-10
Diameter
Pressure Drop
Flow
Length
Piping Equipment
5-11
The appropriate mode is automatically selected depending on the
information specified. In order to solve the pipe, you must specify
enough information to completely define both the material balance and
energy balance.
Calculation Modes
HYSYS checks for sonic flow
if indicated by the option in
the Calculation page of the
Design tab.
There are four calculation modes:
•
•
•
•
Pressure Drop
Length
Flow
Diameter
The mode is automatically assigned depending on what information is
specified.
Regardless of which mode you use, you must specify the number of
increments in the pipe. Calculations are performed in each increment;
for instance, in the determination of the pressure drop, energy, and
mass balances are performed in each increment, and the outlet pressure
in that increment is used as the inlet pressure to the next increment.
This continues down the length of the pipe until the pipe outlet pressure
is determined.
The Pipe can solve in either direction. The solution procedure generally
starts at the end where the temperature is known (temperature is
typically not known on both ends). HYSYS then begins stepping through
the pipe from that point, using either the specified pressure, or
estimating a starting value. If the starting point is the pipe outlet, HYSYS
steps backwards through the pipe. At the other end of the pipe, HYSYS
compares the calculated solution to other known information and
specifications, and if necessary, restarts the procedure with a new set of
starting estimates.
Some specifics of each calculation mode are provided below in the
sections below.
5-11
5-12
Delta P Method 1:
1. At the end where
temperature and pressure
are specified, solve for the
outlet temperature and
pressure in the first
segment.
2. Move to the next segment,
using the outlet conditions
of the previous segment
as the new inlet
conditions.
3. Continue down the pipe
until the outlet pressure
and temperature are
solved.
Delta P Method 2:
1. Estimate a pressure for the
stream which has a
specified temperature.
2. At the end where the
pressure is estimated,
solve for the outlet
temperature and pressure
in the first segment.
3. Move to the next segment,
using the outlet conditions
of the previous segment as
the new inlet conditions.
4. Continue down the pipe
until the outlet pressure
and temperature are
solved.
5. If the calculated outlet
pressure is not equal to
the actual pressure, a new
estimate is made for
pressure (Return to 1).
Pipe Segment
Pressure Drop
Assuming that a feed, product, and energy stream are attached to the
pipe, the following information is required:
•
•
•
•
Flow
Pipe length, diameter, and elevation change
Heat transfer information
At least one stream temperature and one pressure
There are two different methods for calculating the pressure drop, which
are discussed in the sections below.
Method 1
If you specify the temperature and pressure at the same end of the pipe,
then energy and mass balances are solved for each increment, and the
temperature and pressure of the stream at the opposite end of the pipe
are determined.
Method 2
If you specify temperature for one stream and pressure for the other, an
iterative loop is required outside of the normal calculation procedure:
•
•
•
First, a pressure is estimated for the stream which has the
temperature specified.
Second, the pressure and temperature for the stream at the
opposite end of the pipe are determined from incremental energy
and mass balances as in the first method.
If the calculated pressure and user-specified pressure are not the
same (within a certain tolerance), a new pressure is estimated
and the incremental energy and mass balances are re-solved.
This continues until the absolute difference of the calculated and
user-specified pressures are less than a certain tolerance.
The calculated pressure drop accounts for fittings, frictional, and
hydrostatic effects.
5-12
Piping Equipment
Length Calculation:
1. Estimate a Length. At the
end where temperature is
specified, solve for the
outlet temperature and
pressure in the first
segment.
2. Move to the next segment,
using the outlet conditions
of the previous segment as
the new inlet conditions.
3. Continue down the pipe
until the outlet pressure
and temperature are
solved.
4. If the calculated outlet
pressure is not equal to
the actual pressure, a new
estimate is made for
length. (Return to 1).
5-13
Length
Assuming that the feed, product, and energy stream are attached, the
following information is required:
•
•
•
•
•
•
Flow
Heat transfer information
Pipe diameter
Inlet and Outlet Pressure (or one stream Pressure and Pressure
Drop)
One stream temperature
Initial estimate of Length
For each segment, the Length estimate, along with the known stream
specifications, are used to solve for the unknown stream temperature
and pressure. If the calculated pressure is not equal to the actual
pressure (within the user-specified tolerance), a new estimate is made
for the length, and calculations continue.
A good initial guess and step size greatly decreases the solving time.
The Pipe also solves for the length if you provide one pressure, two
temperature specifications and the duty.
Diameter
Information required in this calculation mode is the same as Length,
except HYSYS requires the length instead of the diameter of the pipe.
Initial estimate of diameter can be given on the Calculation page of the
Design tab.
Both length and diameter calculations can only be done for pipes with a
single segment.
5-13
5-14
Pipe Segment
Flow
Flow Calculation:
1. Estimate Flow. At the end
where temperature is
specified, solve for the
outlet temperature and
pressure in the first
segment.
2. Move to the next segment,
using the outlet conditions
of the previous segment as
the inlet conditions.
3. Continue down the pipe
until the outlet pressure
and temperature are
solved.
4. If the calculated outlet
pressure is not equal to
the actual pressure, a new
estimate is made for the
flow. (Return to 1).
Assuming that a feed, product, and energy stream are attached to the
pipe, the following information is required:
•
•
•
•
•
Pipe length and diameter
Heat transfer information
Inlet and Outlet Pressure (or one stream Pressure and Pressure
Drop)
One stream temperature
Initial estimate of Flow
Using the flow estimate and known stream conditions (at the end with
the known temperature), HYSYS calculates a pressure at the other end. If
the calculated pressure is not equal to the actual pressure (within the
user-specified tolerance), a new estimate is made for the flow, and
calculations continue.
Again, a good initial guess decreases the solving time significantly.
Incremental Material and Energy Balances
The overall algorithm consists of three nested loops. The outer loop
iterates on the increments (Pressure, Length or Flow Mode), the middle
loop solves for the temperature, and the inner loop solves for pressure.
The middle and inner loops implement a secant method to speed
convergence. The pressure and temperature are calculated as follows:
5-14
1.
The inlet temperature and pressure are passed to the material/
energy balance routine.
2.
Using internal estimates for temperature and pressure gradients, the
outlet temperature and pressure are calculated.
3.
Average fluid properties are calculated based on the inlet and
estimated outlet conditions.
4.
These properties, along with the inlet pressure, are passed to the
pressure gradient algorithm.
5.
With the pressure gradient, the outlet pressure can be calculated.
6.
The calculated pressure and estimate pressure are compared. If
their difference exceeds the tolerance (default value 0.1 kPa), a new
outlet pressure is estimated, and steps #3 to #6 are repeated. The
tolerance is specified in the Calculation page of the Design tab.
Piping Equipment
7.
5-15
Once the inner pressure loop has converged, the outlet temperature
is calculated:
•
where:
If U and the ambient temperature are specified, then the outlet
temperature is determined from the following equations:
Q = U × A × ∆T LM
(5.1)
Q = Q in – Q out
(5.2)
Q = amount of heat transferred
U = overall heat transfer coefficient
A = outer heat transfer area
∆T LM = log mean temperature difference
Qin = heat flow of inlet stream
Qout = heat flow of outlet stream
•
•
If both the inlet and outlet Pipe temperatures are known, the
outlet temperature of the increment is calculated by linear
interpolation. The attached duty stream then completes the
energy balance.
If duty is known, the outlet temperature is calculated from a
Pressure-Enthalpy flash.
When the Increment outlet temperature is calculated, it is
compared with the estimated outlet temperature. If their difference
exceeds the tolerance (default value 0.01oC), a new outlet
temperature is estimated, and new fluid properties are calculated
(return to step #3). The tolerance is specified in the Calculation page
of the Design tab.
8.
When both the temperature and pressure converge, the outlet
results are passed to the inlet of the next increment, where
calculations continue.
5-15
5-16
Pipe Segment
5.2.1 Pipe Segment Property View
You can also add a pipe
segment by clicking the F12
hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Pipe Segment to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Piping Equipment radio button.
3.
From the list of available unit operations, select Pipe Segment.
4.
Click the Add button. The Pipe Segment property view appears.
OR
Pipe Segment icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Pipe Segment icon. The Pipe Segment property
view appears.
Figure 5.5
To ignore the Pipe Segment during calculations, activate the Ignored
checkbox. HYSYS disregards the operation until you deactivate the
checkbox.
5-16
Piping Equipment
5-17
5.2.2 Design Tab
The Design tab provides access to five pages:
•
•
•
•
•
Connections
Parameters
Calculation
User Variables
Notes
Connections Page
In the Inlet, Outlet and
Energy drop-down lists
either type in the name of
the stream or if you have
pre-defined your stream
select it from the drop-down
list.
On the Connections page, you must specify the feed and product
material streams.
Figure 5.6
In addition to the material stream connections, you also have the option
of attaching an energy stream to the Pipe Segment, and selecting the
fluid package for the Pipe Segment. You can also edit the operation
name on this page.
5-17
5-18
Pipe Segment
Parameters Page
In the Pipe Flow Correlation group, you can select the correlation
method used for Two Phase (VL) flow calculations.
Figure 5.7
The options are:
OLGAS is a third-party option
that can be purchased
through AspenTech or
SCANDPOWER.
5-18
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Aziz, Govier, and Fogarasi
Baxendell and Thomas
Beggs and Brill
Duns and Ros
Gregory Aziz Mandhane
Hagedorn and Brown
HTFS, Liquid Slip
HTFS, Homogeneous Flow
OLGAS2000_2P
OLGAS2000_3P
Orkiszewski
Poettmann and Carpenter
Tacite Hydrodynamic Module
Tulsa 99
Piping Equipment
5-19
Summary of Methods
The methods above have all been developed for predicting two-phase
pressure drops. Some methods were developed exclusively for flow in
horizontal pipes, others exclusively for flow in vertical pipes while some
can be used for either. Some of the methods define a flow regime map
and can apply specific pressure drop correlations according to the type
of flow predicted. Some of the methods calculate the expected liquid
holdup in two-phase flow while others assume a homogeneous mixture.
The table below summarizes the characteristics of each model. More
detailed information on each model is presented later in this section.
Model
Horizontal Flow
Vertical Flow
Liquid Holdup
Flow Map
Aziz, Govier & Fogarasi
No
Yes
Yes
Yes
Baxendell & Thomas
Use with Care
Yes
No
No
Beggs & Brill
Yes
Yes
Yes
Yes
Duns & Ros
No
Yes
Yes
Yes
Gregory, Aziz, Mandhane
Yes
Use with Care
Yes
Yes
Hagedorn & Brown
No
Yes
Yes
No
HTFS Homogeneous
Yes
Yes
No
No
HTFS Liquid Slip
Yes
Yes
Yes
No
Olgas2000
Yes
Yes
Yes
Yes
Orkisewski
No
Yes
Yes
Yes
Poettman & Carpenter
No
Yes
No
No
Tacite Hydrodynamic
Module
Yes
Yes
Yes
Yes
Tulsa
No
Yes
Yes
Yes
For Single Phase streams, the Darcy equation is used for pressure drop
predictions. This equation is a modified form of the mechanical energy
equation, which takes into account losses due to frictional effects as well
as changes in potential energy.
The total heat loss from the Pipe Segment is indicated in the Duty field.
The total heat loss can be calculated using estimated heat transfer
coefficients or specified on the Heat Transfer page of the Rating tab.
5-19
5-20
Pipe Segment
You can also specify the overall pressure drop for the operation. The
pressure drop includes the losses due to friction, static head, and
fittings. If the overall pressure drop is not specified on the Parameters
page, it is calculated by HYSYS, provided all other required parameters
are specified.
The Gravitational Energy Change field displays the change in potential
energy experienced by the fluid across the length of the pipe. It is
determined for the overall elevation change, based on the sum of the
elevation change specified for each segment on the Sizing page of the
Rating tab.
When the pressure drop is specified, the Pipe Segment can be used to
calculate either the length of the Pipe Segment or the flow of the
material through the length of pipe.
The overall pressure drop,
which can be specified or
calculated by HYSYS, is the
sum of the friction, static
head, and fittings pressure
drops. When two liquid
phases are present,
appropriate volume based
empirical mixing rules are
implemented to calculate a
single pseudo liquid phase.
Therefore, caution should
be exercised in interpreting
the calculated pressure
drops for three-phase
systems. Actual pressure
drops can vary dramatically
for different flow regimes,
and for emulsion systems.
5-20
Notice the calculation type (i.e., pressure drop, length, flow) is not
explicitly specified. HYSYS determines what is to be calculated by the
information that you provide.
Piping Equipment
5-21
Aziz, Govier & Fogarasi
In developing their model1 Aziz, Govier & Fogarasi argue that flow
regime is independent of phase viscosities and pipe diameters but is
1⁄3
proportional to the gas density to the one third power ( ρ g ). From this,
then the calculate modified superficial gas and liquid velocities on
which they base the following flow regime map.
Figure 5.8
Once the flow regime has been determined a range of correlations is
used to determine the frictional pressure gradient and slip velocity or
void fraction applicable to that regime.
5-21
5-22
Pipe Segment
Baxendell & Thomas
The Baxendell & Thomas model2 is an extension of the Poettman &
Carpenter model to include higher flow rates. It is based on a
homogeneous model using a two-phase friction factor obtained from
correlation based on experimental results relating friction factor to the
parameter Dρυ . Baxendell & Thomas fitted a smooth curve for values of
the Dρυ parameter greater than 45 x103 cp. Below this value they
propose that original correlation of Poettman & Carpenter be used.
Baxendell & Thomas claim the correlation is suitable for use in
calculating horizontal flow pressure gradients in addition to the vertical
flow pressure gradients for which the original Poettman & Carpenter
approach was developed although the correlation takes no account of
the very different flow regimes that can occur. Like the Poettman &
Carpenter model this model assumes that the pressure gradient is
independent of viscosity.
Beggs and Brill Pressure Gradient
The Beggs and Brill3 method is based on work done with an air-water
mixture at many different conditions, and is applicable for inclined flow.
Figure 5.9
Beggs and Brill Flow Regimes
1000
Distributed
Froude Number
100
10
Intermittent
Segregated
1
Transition
0.0001
0.001
0.01
Input Liquid Content
5-22
0.1
1
Piping Equipment
5-23
In the Beggs and Brill correlation, the flow regime is determined using
the Froude number and inlet liquid content. The flow map used is based
on horizontal flow and has four regimes: segregated, intermittent,
distributed, and transition. The types of flow in the first three regime are
listed as follows:
•
•
•
Segregated Flow: Stratified, Wavy, and Annular.
Intermittent Flow: Plug and Slug.
Distributed Flow: Bubble and Mist.
Once the flow regime has been determined, the liquid holdup for a
horizontal pipe is calculated, using the correlation applicable to that
regime. A factor is applied to this holdup to account for pipe inclination.
From the holdup, a two-phase friction factor is calculated and the
pressure gradient determined.
Duns & Ros
The Duns and Ros model6 is based on a large scale laboratory
investigation of upward vertical flow of air / hydrocarbon liquid and air /
water systems. The model identifies three flow regions, outlined below.
•
•
•
Region I. Where the liquid phase is continuous (i.e., bubble and
plug flow, and part of froth flow regimes).
Region II. Where the phases of liquid and gas alternate (i.e.,
remainder of froth flow regime and slug flow regime).
Region III. Where gas phase is continuous (i.e., mist flow and
annular flow regime).
5-23
5-24
Pipe Segment
The flow region map is shown in the figure below:
Figure 5.10
The regions are distinguished using functions of four dimensionless
groups namely a gas velocity number, a liquid velocity number, a
diameter number, and a liquid viscosity number. Separate frictional
pressure drop correlations and liquid slip velocity (liquid holdup)
correlations are defined for each region in terms of the same
dimensionless groups.
5-24
Piping Equipment
5-25
Gregory Aziz Mandhane Pressure Gradient
For the Gregory Aziz Mandhane correlation8, an appropriate model is
used for predicting the overall pressure drop in two-phase flow.
Figure 5.11
Gregory Aziz Mandhane Flow Regimes
Superficial Liquid Velocity (m/sec)
Dispersed Flow
Bubble,
Elongated
Bubble Flow
Slug Flow
Annular,
Annular
Mist Flow
Wave
Flow
Stratified Flow
Superficial Gas Velocity (m/sec)
Regime
Model
Slugflow
Mandhane, et. al. modification #1 of Lockhart-Martinelli
Dispersed
Bubble Mandhane, et. al. modification #2 of Lockhart-Martinelli
Annular Mist
Lockhart-Martinelli
Elongated Bubble
Mandhane, et. al. modification #1 of Lockhart-Martinelli
Stratified
Lockhart-Martinelli
Wave
Lockhart-Martinelli
5-25
5-26
Pipe Segment
Hagedorn & Brown
Hagedorn & Brown based their model9 on experimental data on upward
flow of air / water and air / oil mixtures. The frictional pressure drop is
calculated using a friction factor derived from a single phase Moody
curve using a two phase Reynolds number that reduces to the
appropriate single phase Reynolds number when the flow becomes
single phase. For the void fraction required to calculate the two phase
Reynolds number and the static pressure loss, Hagedorn & Brown
developed a single curve relating the void fraction to the same
dimensionless parameters proposed by Duns & Ros.
HTFS Models
The two HTFS models10, 15 share a common method for calculating the
frictional pressure gradient and acceleration pressure gradient while
differing in the method used to calculate static pressure gradient.
The frictional pressure gradient method is adapted from that of Claxton
et. al. (1972). The method first calculates the frictional pressure drop for
the gas and liquid phases assuming that they are flowing alone in the
pipe based on Fanning friction factors for each phase that are again
calculated by assuming the fluid is flowing alone in the pipe. The
frictional pressure drop is then calculated from the formula:
∆p F = ∆p l + C c ( ∆p l ∆p g ) + ∆p g
where:
(5.3)
∆p F = frictional pressure drop
∆p l = liquid phase pressure drop
Cc = correction factor calculated from the properties of the liquid and
gas phases and the superficial mass velocities of the phases
∆p g = gas phase pressure drop
The static pressure gradient is calculated from a separated model of two
phase flow. In the HTFS Homogeneous model the void fraction required
by this model is assumed to be the homogeneous void fraction. In the
HTFS Liquid Slip model the void fraction is calculated using a method
published by Whalley and Ward (1981).
5-26
Piping Equipment
5-27
The accelerational gradient term is calculated from a homogeneous
equation model.
The HTFS models have been validated for horizontal, and both upward
and downward vertical flow using a wide range of data held by the
Harwell data bank.
OLGAS2000 (2-Phase & 3-Phase)
OLGAS2000 employs mechanistic models for each of the four major flow
regimes: stratified, annular, slug, and dispersed bubble flow. It is based
in large part on data from the SINTEF multiphase flow laboratory in
Norway.
Multiphase Flow is a dynamic physical process between the phases. It
includes fluid properties, complex geometry and interaction between
reservoir, well, flowline and process plant. OLGAS 2000 can handle 2phase and 3-phase flow. For instance, the elements involved can consist
of water droplets, oil, gas, sand, wax, and hydrates.
OLGAS2000 predicts the pressure gradient, liquid holdup, and flow
regime. It has been tested in one degree increments for all angles from
horizontal to vertical. OLGAS2000 gives one of the best overall
predictions of pressure drop and liquid holdup of any currently
available method.
Contact your AspenTech agent for more information on OLGAS2000 and
the licensing on OLGAS2000 3-Phase.
Orkisewski
Orkisewski13 composed a composite correlation for vertical upward flow
based on a combination of methods developed by Griffith (1962),
Griffith & Wallis(1961), and Duns & Ros (1963)6. Four flow regimes are
defined and the methods proposed for each region are:
•
•
•
•
Bubble flow—Griffith correlation
Slug/Plug flow—Griffith & Wallis correlation modified by
Orkisewski
Churn flow—Duns & Ros
Mist/Annular flow—Duns & Ros
5-27
5-28
Pipe Segment
Orkisewski proposed that the method of Griffith and Wallis be used to
determine the boundary between the bubble and plug flow regime and
the methods of Duns & Ros be used to determine the remaining flow
regime boundaries.
Poettman & Carpenter
The Poettman & Carpenter model14 assumes that the contribution of the
acceleration term to the total pressure loss is small and that the
frictional pressure drop can be calculated using a homogeneous model.
The model further assumes that the static head loss can be calculated
using a homogeneous two phase density. Poettman & Carpenter varies
from a standard homogeneous method in its calculation of a two phase
friction factor. The model proposes a correlation for the friction factor
based on experimental results from 49 flowing and gas lift wells
operating over a wide range of conditions. The two-phase friction factor
is plotted against the parameter Dρυ (D= diameter, ρ = homogeneous
density, and υ = homogeneous superficial velocity). Effectively therefore
the model assumes that the pressure gradient is independent of
viscosity.
Tacite Hydrodynamic Module
The Tacite Hydrodynamic
Module is designed for twophase flow computation, thus
water and the oil phase are
defined as the same liquid
phase.
5-28
The Tacite Hydrodynamic Module is a transient multi-component twophase flow simulator for the design and control of oil and gas pipelines.
This module provides two modelling options, full gas-liquid modeling
and Zuber-Findlay, for predicting the flow behaviour, pressure drop,
Barycentric velocity, gas slug fraction, frictional heat transfer coefficient,
and volume fraction of a fluid in a horizontal, or inclined pipeline.
Piping Equipment
5-29
The model identifies three flow patterns: stratified, intermittent, and
dispersed.
•
•
•
Stratified flow. The model assumes a momentum balance
between the phases present in the pipe segment.
Intermittent flow. The intermittent flow regime is solved as a
two-region problem. The gas pocket is considered as a stratified
flow, whereas the liquid slug is considered as the dispersed flow.
The Tacite Hydrodynamic Module can predict the propagation of
liquid slug flow that occurs during transient flow conditions in a
pipeline. Liquid slugs are created during flow rate changes,
pipeline depressurization, shutdown, and startup operations or
variations in pipeline topography. Closure laws are used for
calculating the slug velocity and gas fraction in the slug.
Dispersed flow. The regime is a particular case of intermittent
flow.
Tulsa
The Tulsa model16 proposes a comprehensive mechanistic model
formulated to predict flow patterns, pressure drop, and liquid holdup in
vertical upward two-phase flow. The model identifies five flow patterns:
bubble, dispersed bubble, slug, churn, and annular. The flow pattern
prediction models used are Ansari et. al. (1994) for dispersed bubble and
annular flows, Chokshi (1994) for bubbly flow and a new model for
churn flow. The resulting flow pattern map is shown below.
Figure 5.12
5-29
5-30
Pipe Segment
Separate hydrodynamic models for each flow pattern are used. A new
hydrodynamic model is proposed for churn flow and a modified version
of Chokshi’s model is proposed for slug flow. Chokshi and Ansari et. al.
models are adopted for bubbly and annular flows respectively.
The model has been evaluated using the Tulsa University Fluid Flow
Projects well data back of 2052 wells covering a wide range of field data.
The model has been compared with Ansari et. al. (1994), Chokshi (1994),
Hasan & Kabir (1994), Aziz et. al. (1972), and Hagedorn and Brown
(1964) methods, and is claimed to offer superior results.
All methods account for static head losses, while Aziz, Beggs and Brill,
and OLGAS methods account for hydrostatic recovery. Beggs and Brill
calculate the hydrostatic recovery as a function of the flow parameters
and pipe angle.
Calculation Page
Figure 5.13
You can specify any of the calculation parameters on this page. The
table below describes the parameters.
5-30
Field
Description
Pressure Tolerance
Tolerance used to compare pressures in the calculation loop.
Temperature
Tolerance
Tolerance used to compare temperatures in the calculation
loop.
Heat Flow Tolerance
Tolerance used to compare heat flow in the calculation loop.
Piping Equipment
Field
Description
Length Initial Guess
Used in the algorithm when length is to be calculated.
Length Step Size
Used in the algorithm when length is to be calculated.
Flow Initial Guess
Used in the algorithm when flow of material is to be calculated.
Flow Step Size
Used in the algorithm when flow of material is to be calculated
Diameter Initial
Guess
Optional estimate when diameter is to be calculated.
Default Increments
The increment number which appears for each segment on the
Dimensions page
Always PH Flash
Activating this checkbox, force HYSYS’ calculations to be done
using PH flashes rather than PT flashes. Slower but more
reliable for pure component or narrow boiling range systems.
Check Choked Flow
When this checkbox is active, HYSYS checks for choked flow.
The default setting is inactive because the command slows
down calculations.
5-31
This check is carried out only on pipe segments not on fitting or
swage segments.
Do Deposition Calcs
When this checkbox is inactive, HYSYS turns off deposition
calculations. This checkbox is a duplicate of the checkbox on
the Deposition tab
Do Slug Tool
Calculations
When this checkbox is active, HYSYS performs slug
calculations.
When calculating Flow or Length, good initial guesses and step sizes
can greatly reduce solution time.
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
5-31
5-32
Pipe Segment
5.2.3 Rating Tab
The Rating tab provides access to two pages:
•
•
Sizing
Heat Transfer
On the Sizing page, you can specify information regarding the
dimensions of sections in the Pipe Segment. In the Heat Transfer page,
the heat loss of the Pipe Segment can either be specified or calculated
from various heat transfer parameters.
Sizing Page
On the Sizing page, the length-elevation profile for the Pipe Segment is
constructed. You can provide details for each fitting or pipe section that
is contained in the Pipe Segment that you are modeling. An unlimited
number of pipe sections or fittings can be added on this page.
Figure 5.14
For a given length of pipe which is modelled in HYSYS, the parameters
of each segment is entered separately, as they are for each fitting.
5-32
Piping Equipment
5-33
The procedure for modeling a length of pipe is illustrated using the
diagram shown below. In the diagram, the pipe length AD is represented
by segments A, B, C, D, and three fittings.
Figure 5.15
Fittings
D
Y2
C
F2
Y1
A
X2
B
F1
X1
The horizontal pipe sections
have an Elevation of 0. A
positive elevation indicates
that the outlet is higher than
the inlet.
Number
F3
X3
Example of Pipe Sections
and Fittings Modelled in the
Pipe Segment Operation
The table shown below displays the fitting/pipe, length, and elevation
input that you require to represent the pipe length AD. Each pipe
section and fitting is labelled as a segment.
1
2
3
4
5
6
7
Represented by
A
F1
B
F2
C
F3
D
Fitting/Pipe
Pipe
Fitting
Pipe
Fitting
Pipe
Fitting
Pipe
Length
x1
N/A
y1
N/A
x2
N/A
Elevation
0
N/A
y1
N/A
0
N/A
x 32 + y 22
y2
To fully define the pipe section segments, you must also specify pipe
schedule, diameters (nominal or inner and outer), a material, and a
number of increments. The fittings require an inner diameter value.
When you have only one pipe segment HYSYS calculates the inner
diameter of the pipe when a pressure difference and pipe length is
specified.
5-33
5-34
Pipe Segment
Adding Segments
You can add segments to the length-elevation profile by clicking the
Append Segment button.
Figure 5.16
The pipe segment report
has been updated to include
dedicated detail sections for
both fittings and swage
fittings. These sections
appear in the parameters
datablock.
For each segment that you add, you must specify the following:
Field
Description
Pipe/Fitting/Swage
Select a pipe section, swage or one of the available fittings from
the drop-down list. If the list does not contain the fitting
required, you can modify the fittings and change its K-factor for
these calculations.
You can modify the Fittings Database, which is contained in file
FITTING.DB. For more information, refer to Section 5.2.9 Modifying the Fittings Database.
Length
The actual length of the Pipe Segment. Not required for fittings.
Elevation Change
The change in vertical distance between the outlet and inlet of
the pipe section. Positive values indicate that the outlet is
higher than the inlet. Not required for fittings.
Outer Diameter
Outside diameter of the pipe or fitting.
Inner Diameter
Inside diameter of the pipe or fitting.
Material
Select one of the available default materials or choose User
Specified for the pipe section. Not required for fittings.
Increments
The number of increments the pipe section is divided for
calculation purposes.
Once you have selected the segment type (pipe, swage or fitting), you
can specify detailed information concerning the highlighted segment.
With the cursor located on a segment, click the View Segment button.
When you click the View Segment button, the Pipe Fittings, Pipe
Swages, or Pipe Info view appears. The view that appears depends on
the type of Fitting/Pipe option you selected from the drop-down list.
5-34
Piping Equipment
5-35
Viewing Segments
Figure 5.17
The Pipe Info view appears for pipe sections. On this view, the following
information is shown:.
HYSYS contains a pipe
database for three pipe
schedules (40, 80, 160). If a
schedule is specified, a
popup menu appears
indicating the possible
nominal pipe diameters that
can be specified.
The roughness factor is
automatically specified for
pipe material chosen from
this list. You can also specify
the roughness factor
manually.
Field
Description
Pipe Schedule
Select one of the following:
• Actual. The nominal diameter cannot be specified. The inner
diameter can be specified.
• Schedule 40
• Schedule 80
• Schedule 160
Nominal
Diameter
Provides the nominal diameter for the pipe section.
Inner Diameter
For Schedule 40, 80, or 160, this is referenced from the database.
For Actual Pipe Schedule, this can be specified directly by the user.
Pipe Material
Select a pipe material or choose User Specified. The pipe material
type can be selected from the drop-down list in the field. A table of
pipe materials and corresponding Absolute Roughness factors is
shown in the next table.
Roughness
A default value is provided based on the Pipe Material. You can
specify a value if you want.
Pipe Wall
Conductivity
Thermal conductivity of pipe material in W/m.K to allow calculation
of heat transfer resistance of pipe wall.
Defaults provided for standard pipe materials are as follows:
• All steel and coated iron pipes: 45.0
• Cast iron: 48.0
• Concrete: 1.38
• Wood: 0.173
• PlasticTubing: 0.17
• RubberHose: 0.151
5-35
5-36
Pipe Segment
Pipe Material Type
Absolute Roughness, m
Drawn Tube
0.0000015
Mild Steel
0.0000457
Asphalted Iron
0.0001220
Galvanized Iron
0.0001520
Cast Iron
0.0002590
Smooth Concrete
0.0003050
Rough Concrete
0.0030500
Smooth Steel
0.0009140
Rough Steel
0.0091400
Smooth Wood Stave
0.0001830
Rough Wood Stave
0.0009140
Fitting Pressure Loss
The fittings pressure loss is characterised by a two constant equation as
shown below.
K = A + B × fT
where:
(5.4)
A = constant, also known as velocity head factor
B = constant, also known as FT factor
fT = fully turbulent friction factor
The fittings pressure loss constant K is then used to obtain the pressure
drop across the fitting from the equation shown below.
2
ρν
∆P = K --------2
where:
(5.5)
∆P = pressure drop
ρ = density
ν = velocity
Calculation of the fully turbulent friction factor fT needed in the method
requires knowledge of the relative roughness of the fitting. This is
calculated from user entered values for roughness and fitting diameter.
5-36
Piping Equipment
5-37
The Pipe Segment’s standard friction factor equation (Churchill) is then
called repeatedly with the calculated relative roughness at increasing
Reynolds numbers until the limiting value of friction factor is found.
In general a fitting is characterised by either a velocity head factor (A) or
a FT factor (B) but not both. HYSYS does not enforce this restriction
however and you are free to define both factors for a fitting if required.
Pipe Fittings View
You can customize the pipe in the Pipe Fitting view.
Figure 5.18
The above view shows a standard fitting as it would be retrieved from
the fittings database (refer to Section 5.2.9 - Modifying the Fittings
Database). If you customize a fitting by changing either the VH Factor or
FT Factor, the word “User” is added to the fitting name to denote the
fact that it is now user defined, and the Data Source field becomes
updateable to allow you to describe the source of the new data.
Default data for FT Factor and Data Source is provided for cases
retrieved from earlier versions of HYSYS. Specifically the FT Factor is set
to 0.0 and the Data Source is set to “HYSYS, pre V2.3”. The VH Factor is
the same as the K Factor used in earlier versions.
5-37
5-38
Pipe Segment
Swage Fittings
A new capability has been added to the Pipe Segment to allow the
pressure drop across reductions or enlargements in the pipe line to be
calculated. The feature has been added as a new fitting type called a
swage. The swage fitting automatically uses the upstream and
downstream pipe/fitting diameters to calculate the K factor for the
fitting. Once the K factor is known the pressure loss across the reducer/
enlarger can be calculated. The equations used are as follows.
2
2
2
ρ out υ out ρ in ν in
ρ out ν out
∆P = K out ----------------------- – ----------------- + ----------------------2
2
2
(5.6)
∆P = static pressure loss
where:
ρ = density
ν = velocity
K = reducer/enlarger K factor
The K factor from the above equation is calculated from the following
equations:
For reducers
θ
2
K out = 0.8 sin --- ( 1 – β )
2
for ( θ ≤ 45° )
2
θ
K out = 0.5 ( 1 – β ) sin --2
for ( 45 ° < θ ≤ 180° )
where:
d out
β = --------d in
5-38
(5.7)
Piping Equipment
5-39
For enlargers
K out
θ
2 2
2.6 sin --- ( 1 – β )
2
= ----------------------------------------4
β
2 2
(1 – β )
K out = --------------------4
β
for ( θ ≤ 45° )
for ( 45° < θ ≤ 180° )
(5.8)
where:
d in
β = --------d out
θ in the equations above is known as swage angle. Swage angle is shown
in the figure below:
Figure 5.19
Equations for K above are taken from Crane, Flow of Fluids, Publication
410M, Appendix A-26.
As stated above a swage segment automatically considers the upstream
(din) and downstream (dout) diameters to work out whether the swage is
a reducer or an enlarger and calculate the appropriate K value. In
addition the following special cases are detected and a fixed K value is
used.
•
•
•
The swage is the first segment in the pipe and an entrance K
value of 0.5 is used.
The swage is the last segment in the pipe and an exit K value of
1.0 is used.
din = dout the swage is a simple coupling and a K value of 0.04 is
used.
5-39
5-40
Pipe Segment
Pipe Swages View
A new swage fitting view has been created to allow you to update the
swage angle for a swage fitting. It also displays the upstream and
downstream diameters that are used in the calculation as shown in the
figure below.
Figure 5.20
The automatic detection of upstream and downstream diameters by the
swage segment means that there cannot be two consecutive swage
segments in a pipe. This restriction is enforced by HYSYS which
prevents you from specifying two adjacent segments to be swages. In
addition, if two adjacent swage segments would result from deletion of
an intervening pipe or fitting segment, the second swage segment is
automatically converted to a default Pipe Segment. An explanatory
message appears in both cases.
Removing a Segment
No confirmation is given by
HYSYS before segments are
removed.
To remove a segment from the Length-Elevation Profile group, select
one of its parameters and click the Delete Segment button.
You can remove all input from the Length-Elevation Profile group by
clicking the Clear Profile button.
5-40
Piping Equipment
5-41
Heat Transfer Page
The Heat Transfer page is used to enter data for defining the heat
transfer. The Specify By group, at the top of the view, contains four radio
buttons. Selecting one of the radio buttons displays one of the four ways
of defining heat transfer:
•
•
•
•
Specified heat loss
Overall Heat Transfer Coefficient (HTC)
HTC specified by segment
Estimated HTC
The radio button does not force the pipe segment to use that method of
calculation – it only provides access to the views.
HYSYS works out which method to use from the data provided.
Heat Loss
HYSYS selects the Heat Loss radio button as the default setting, when
you select the Heat Transfer page for the first time. The view appears as
shown in the figure below:
Figure 5.21
5-41
5-42
Pipe Segment
If the Overall heat duty of the pipe is known, the energy balance can be
calculated immediately. Each increment is assumed to have the same
heat loss. You enter the heat loss for the pipe in the Heat Loss field. This
assumption is valid when the temperature profile is flat, indicating low
heat transfer rates compared to the heat flows of the streams. This is the
fastest solution method.
The value in the Heat Loss
field is black in colour,
signifying that the value was
generated by HYSYS.
If both inlet and outlet temperatures are specified, a linear profile is
assumed and HYSYS can calculate the overall heat duty. This method
allows fast calculation when stream conditions are known. Select the
Heat Loss radio button to see the calculated overall heat duty.
Overall HTC
When you select the Overall HTC radio button, the Heat Transfer page
changes to the view shown in the figure below.
Figure 5.22
If the overall HTC (Heat Transfer Coefficient) and a representative
ambient temperature are known, rigorous heat transfer calculations are
performed on each increment.
5-42
Piping Equipment
5-43
Segment HTC
When you select the Segment HTC radio button, the Heat Transfer page
changes to the view shown in the figure below.
Figure 5.23
If the heat transfer coefficient and a representative ambient
temperature are known for each segment. You can specify the ambient
temperature and HTC for each pipe segment that was created on the
Sizing page. HYSYS performs rigorous heat transfer calculations on each
increment.
Estimate HTC
When you select the Estimate HTC radio button, the Heat Transfer page
changes to the view shown in the figure below.
The Overall HTC and
Estimate HTC can be used
together to define the heat
transfer information for the
pipe.
If you only know the Ambient
Temperature, you can supply
it in the Overall HTC section
and have the Overall HTC
value calculated by the
Estimate HTC section.
Likewise, you need to specify
the Ambient Temperature in
the Estimate HTC section for
the pipe segment to have
enough heat transfer
information to solve.
Figure 5.24
You can select
whether the ambient
temperature used in
the heat transfer
calculations is for the
entire pipe or for
each segment of the
pipe.
If the pipe’s HTC is unknown, you can enter information in this view
and HYSYS calculates the HTC for the pipe.
5-43
5-44
Pipe Segment
Inside Film Convection
You can prompt HYSYS to estimate the inside film heat transfer
coefficient using one of the five correlations provided.
The Petukov, Dittus, and Sieder methods for calculation of inner HTC
are limited to single phase applications and essentially turbulent flow
only. Two and three phase systems are modeled using the single phase
equations with “averaged” fluid properties. A correction for laminar
flow is applied but this is not particularly effective. It is recommended
that these three methods be used only for single phase pipelines
operating at high Reynolds numbers (> 10000).
The Profes and HTFS methods should provide much better results for
two and three phase systems, and in the laminar flow region at the cost
of some increase in calculation time. In general the Profes option is
recommended for most pipeline applications since it takes into full
account the flow regime in the pipe and is reasonably efficient in
calculation. The HTFS option is more calculation intensive, particularly
in two phase applications where additional flash calculations are
required. It is recommended for use in cases with a high heat flux with
high delta temperatures between the pipe contents and ambient
conditions.
The five correlations provided are:
•
Petukov (1970)
( f ⁄ 8 )Re d Pr
k
h = --- ----------------------------------------------------------------------------d 1.07 + 12.7 ( f ⁄ 8 ) 1 ⁄ 2 ( Pr 2 ⁄ 3 – 1 )
•
Dittus and Boelter (1930)
k
h = --- 0.023Re d0.8 Pr n
d
where:
5-44
(5.9)
0.4 → for heating
n = 0.3 → for cooling
(5.10)
Piping Equipment
•
5-45
Sieder and Tate (1936)
For two-phase flow:
µ b 0.14
k
h 2-phase = --- 0.027Re d0.8 Pr 1 ⁄ 3  ------
 µ w
d
(5.11)
For single phase flow:
h 1-phase = [ ( h lam )
12
1
-----12 12
+ ( h 2-phase ) ]
(5.12)
where:
d
Pr
h lam = 3.66 + 0.0668 --- × R e × ---------------------------------------------2
L
--3
d
1 + 0.04  --- RePr
L

Refer to the Profes
Reference manual for more
information.
•
•
Profes. Implements the methods used by the Profes Pipe
Simulation program (formerly PLAC). The methods are based on
the Profes flow maps for horizontal and vertical flow, and
appropriate correlations are used to determine the HTC in each
region of the flow map.
HTFS. Implements the methods used by HTFS programs.
Separate correlations are used for boiling and condensing heat
transfer, and for horizontal and vertical flow. The methods used
are documented in the HTFS Handbook11.
You can choose to include the pipe’s thermal resistance in your HTC
calculations by activating the Include Pipe Wall checkbox. Activating
this option requires that the thermal conductivity be defined for the
pipe material on the detail view of each Pipe Segment. Default values of
thermal conductivity are provided for the standard materials that can be
selected in the Pipe Segment.
5-45
5-46
Pipe Segment
Outside Conduction/Convection
Outside convection to either Air, Water or Ground can be included by
activating the Include Outer HTC checkbox. For air and water, the
velocity of the ambient medium is defaulted to 1 m/s and is usermodifiable. The outside convection heat transfer coefficient correlation
is for flow past horizontal tubes (J.P. Holman, 1989):
k
h = --- 0.25Re 0.6 Pr 0.38
d
(5.13)
If Ground is selected as the ambient medium, the Ground type can then
be selected. The thermal conductivity of this medium appears but is also
modifiable by typing over the default value.
The Ground types and their corresponding conductivities are tabulated
below:
Ground Type
Conductivity
Ground Type
Conductivity
Dry Peat
0.17 W/mK
Frozen Clay
2.50 W/mK
Wet Peat
0.54 W/mK
Gravel
1.10 W/mK
Icy Peat
1.89 W/mK
Sandy Gravel
2.50 W/mK
Dry Sand
0.50 W/mK
Limestone
1.30 W/mK
Moist Sand
0.95 W/mK
Sandy Stone
1.95 W/mK
Wet Sand
2.20 W/mK
Ice
2.20 W/mK
Dry Clay
0.48 W/mK
Cold Ice
2.66 W/mK
Moist Clay
0.75 W/mK
Loose Snow
0.15 W/mK
Wet Clay
1.40 W/mK
Hard Snow
0.80 W/mK
In HYSYS, the surrounding heat transfer coefficient value is based on the
following heat transfer resistance equation:
5-46
1
H surroundings = --------------------------------------------R surroundings ⋅ D ot
(5.14)
2
D ot 2Z b + 4Z b2 – D ot
R surroundings = -------- ln -------------------------------------------2k s
D ot
(5.15)
Piping Equipment
where:
5-47
Hsurroundings = surrounding heat transfer coefficient
Rsurroundings = surrounding heat transfer resistance
Zb = depth of cover to centreline of pipe
ks = thermal conductivity of pipe-surrounding material (Air, Water,
Ground)
Dot = outer diameter of pipe, including insulation
Conduction Through Insulation
Conduction through the insulation or any other pipe coating can also be
specified. Several representative materials are provided, with their
respective thermal conductivities. You must specify a thickness for this
coating.
Insulation / Pipe
Conductivity
Insulation / Pipe
Conductivity
Evacuated Annulus
0.005 W/mK
Asphalt
0.700 W/mK
Urethane Foam
0.018 W/mK
Concrete
1.000 W/mK
Glass Block
0.080 W/mK
Concrete Insulated
0.500 W/mK
Fiberglass Block
0.035 W/mK
Neoprene
0.250 W/mK
Fiber Blanket
0.070 W/mK
PVC Foam
0.040 W/mK
Fiber Blanket-Vap Barr
0.030 W/mK
PVC Block
0.150 W/mK
Plastic Block
0.036 W/mK
PolyStyrene Foam
0.027 W/mK
5.2.4 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
5-47
5-48
Pipe Segment
5.2.5 Performance Tab
The Performance tab consists of three pages:
•
•
•
Profiles
Slug Options
Slug Results
Profiles Page
The Profiles page allows you to access information about the fluid
stream conditions for each specified increment in the Pipe Segment.
Figure 5.25
The page contains a summary table for the segments which make up the
Pipe Segment. The distance (length), elevation, and number of
increments appear for each segment. You cannot modify the values on
this page.
By clicking the View Profile button, the Pipe Profile view appears, which
consists of a Table tab and a Plot tab. The Table tab displays the
following information for each increment along the Pipe Segment:
•
•
•
•
•
5-48
Length
Elevation
Pressure
Temperature
Heat Transferred
Piping Equipment
•
•
•
•
•
•
•
•
•
•
•
5-49
Flow Regime
Liquid Holdup
Friction Gradient
Static Gradient
Accel Gradient
Liquid Reynolds Number
Vapour Reynolds Number
Liquid Velocity
Vapour Velocity
Deposit Thickness
Deposit Volume
Figure 5.26
The Plot tab graphically displays the profile data that is listed on the
Table page. Select one of the radio buttons to view a profile with Length
as the x-axis variable:
Figure 5.27
5-49
5-50
Refer to Section 10.4 Graph Control of the User
Guide for information
regarding the customization of
plots.
Pipe Segment
You can modify the plot by right-clicking on the plot area, and selecting
Graph Control from the menu.
Slug Tool
The Slug Tool predicts slug properties for horizontal and inclined twophase flows in each Pipe Segment. Travelling wave solutions of the onedimensional averaged mass and momentum equations are found and
analysed to obtain slug flow properties. Stratified flow is tested for
instability to small disturbances and then analysed in the unstable
region to find if slug flow is possible. If large amplitude waves can bridge
the pipe then slug flow is deemed to be possible. In this slug flow region
a range of frequencies is possible with a maximum slug frequency
occurring for slugs of zero length. Up to this maximum there is a
relationship between frequency and slug length with maximum lengths
occurring for the lowest frequencies. The other slug properties such as
bubble length, average film holdup, slug transitional velocity, average
pressure gradient can all be found over the range of allowable slug
frequencies.
The detailed methodology used to predict slug formation and slug
properties was developed within AspenTech and is described in the
paper “The modelling of slug flow properties” by M Watson17.
Slug Options Page
Figure 5.28
5-50
Piping Equipment
5-51
The entries on the Slug Options page control the models and
parameters used by the slug tool in its calculations as follows:
•
Translational Model. You can select the option to be used for
calculating the translational velocity of the slugs in the pipeline.
The general form of the translational velocity is of the form:
c = C0 VM + U0
where:
(5.16)
c = translation velocity of slug
VM = superficial velocity of two phase mixture
C0, U0 = constants
You have the option to select the Bendikson (1984) model to predict
values of C0 and U0 or to select User Specified to enter values
manually.
•
•
•
Holdup Model. You can select the option to be used to calculate
the liquid holdup in the pipe. Two options are available: Gregory
et. al. uses the methods published by Gregory et. al. (1978) or
User Specified to enter a user defined value for the holdup
fraction.
Friction Factor. Two options are available to select the friction
factor model to be used in the slug tool calculations: Smooth pipe
or Colebrook equation.
Frequency Option. The slug tool evaluates slug flow
characteristics at a particular slug frequency. This frequency can
either be predicted by the Hill & Wood correlation or specified by
the user.
5-51
5-52
Pipe Segment
Slug Results Page
Figure 5.29
The Slug Results page presents the result from the slug tool analysis as a
table with the following entries.
5-52
Column
Description
Position
Distance along the pipe.
Status
Result of the slug calculations. Possible results are Single
Phase, Stable two phase, Slug flow, Annular flow, Bubble flow
or Unknown. Any error in the calculation is also reported here.
Frequency
Slug frequency used to calculate the slug properties. This is
normally the value calculated by the Hill & Wood correlation or
the user specified slug frequency according to the settings on
the Slug Options page. When the correlation or user specified
frequency lies outside the predicted range of slug frequencies
this field shows either the minimum or maximum slug
frequency which is indicated by the entry in the next column.
Slug Length
Average length of a slug at the indicated frequency.
Bubble Length
Average length of a bubble at the indicated frequency.
Film Holdup
Film holdup as a fraction.
Velocity
Translational velocity of the slug.
Pressure Gradient
Pressure drop over the slug/bubble unit.
Slug/Bubble ratio
Ratio of lengths of slug and bubble.
Piping Equipment
5-53
Cell Details
When you click the View Cell Plot button on the Slug Results page, the
Cell Details view appears.
Figure 5.30
The view shows the slug properties for a single position in the pipe
across the full range of possible slug frequencies in both tabular and
graphical form. A further graph shows the flow regime map for the cell
indicating the region of possible slug formation at different vapour and
liquid flowrates.
The Next button and Previous button on the view allow you to move
along the pipe to inspect the detailed results at any point.
5.2.6 Dynamics Tab
This unit operation is currently not available for dynamic simulation.
5-53
5-54
Pipe Segment
5.2.7 Deposition Tab
Deposition is a general capability that can be used to model deposition
of material that affects pressure drop or heat transfer to or from the
pipe. Possible deposits include wax, asphaltenes, hydrates, sand etc.
The Deposition tab consists of four pages:
•
•
•
•
Methods
Properties
Profile
Limits
HYSYS provides a model for one type of deposit namely Wax deposition
modeled using the Profes methods. Other third party methods can be
added as plug-in extensions.
Methods Page
When solving with its default
data, the model displays a
warning message in the
status bar of the Pipe
Segment.
For more information about
the Profes Wax method, refer
to Section 5.2.8 - Profes
Wax Method.
The Methods page displays the available deposition methods. Profes
Wax is the only standard one at present. Registered third party plug-in
methods also appear on this page.
Figure 5.31
The Profes Wax model is installed by selecting it from the Deposition
Correlation list. On installation the Pipe Segment is not able to solve
until the initial deposition thickness is defined on the Profile page. Once
the initial deposition thickness is defined the model solves using the
default values provided for the other deposition data properties.
5-54
Piping Equipment
5-55
The Max. Time field allows you to specify the maximum amount of time
wax deposits on the pipe. The Timestep field allows you to specify the
timestep that the deposition rate is integrated over.
Properties Page
The Properties page allows you to specify deposit properties required by
the deposition calculations.
Figure 5.32
The page consists of three properties:
•
•
•
Density of the deposit.
Thermal Conductivity of the deposit.
Yield Strength of the deposit.
5-55
5-56
Pipe Segment
Profile Page
The Profile page consists of the Deposition Profile table.
Figure 5.33
This table has two purposes:
•
•
Is used to specify the initial deposition thickness, required by the
deposition calculations.
Displays the profile of the deposit on the pipe.
Limits Page
Figure 5.34
5-56
Piping Equipment
5-57
The Limits page allows you to specify the maximum limits for the
following parameters.
•
•
•
•
•
Max. Deposit Thickness
Overall Pressure Drop
Total Deposit Volume
Plug Pressure Drop
Simulation Time
5.2.8 Profes Wax Method
The deposition of the wax from the bulk oil onto the pipe wall is
assumed to only be due to mass transfer, shear dispersion is not
considered to be a significant factor. The rate of deposition is described
by:
m’= k ( C wall – C bulk )AMw wax
where:
(5.17)
m’ = deposition rate (kg/s)
k = mass transfer coefficient (mole/m2 s mole Fraction)
C = local concentration of wax forming components (mole fraction)
Mwwax = molecular weight of wax (kg/mole)
A = cross-sectional area (m2)
The mass transfer coefficient is calculated using the following
correlation:
Sh = 0.015 × Re
where:
Sc =
0.88
Sc
1
--3
(5.18)
µl
--------ρl D
Vl ρl DH
Re = ----------------µl
Sh =
kD H
---------cD
D = diffusivity of wax in oil (m2/s)
5-57
5-58
Pipe Segment
µ = liquid viscosity (kg/ms)
ρ l = liquid density (kg/m2)
k = mass transfer coefficient (mole/m2 s mole fraction)
DH = hydraulic radius (m)
Vl = liquid velocity (m/s)
c = liquid molar density (mole/m3).
The Reynolds number that is used in these calculations is based on the
local liquid velocity and liquid hydraulic radius. Physical properties are
taken as the single phase liquid values. The viscosity used is based on
the fluid temperature and shear rate at the wall.
The difference in concentration of wax forming species between the
bulk fluid and the wall, which is the driving force for the deposition of
wax is obtained from calculating the equilibrium wax quantities at the
two relevant temperatures.
These calculations provide a wax deposition rate which is integrated
over each timestep to give the total quantity of wax laid down on the
pipe wall.
Profes Wax View
When you click the View Method button, the Profes Wax view appears.
You can change the default data in the Profes Wax model, and tune it to
your specific application in this view. The Profes Wax view consists of
three tabs:
•
•
•
Wax Data
Tuning Data
Ref. Comp
The Calculate wax formation temperature checkbox allows you to select
whether the deposition model is to calculate the initial wax formation
temperature or cloud point for each pipe element when performing the
deposition calculations. If activated the results appear in the Profile
page of the Deposition tab.
5-58
Piping Equipment
5-59
The Tune button initiates the tuning calculations and is only active
when there is sufficient data to allow tuning calculation to take place
(i.e., cloud point is defined, at least one temperature or wax mass
percent pair is defined and reference composition defined).
Wax Data Tab
The Wax Data tab allows you to select the wax model to be used for the
wax equilibrium calculations.
Figure 5.35
The Wax Model drop-down list provides you with four thermodynamic
models for wax formation:
•
•
•
•
Chung
Pederson
Conoco
AEA (default)
All models are based on the following equation for the equilibrium
constant, Ki, which is the ratio of concentrations of a particular
component in the solid and liquid phase:
S
L L
L
S
ζi fi
xi
 P Vi – Vi 
exp
K i = ----L- = -------- ∫ ------------------ ∂P
S S
 0 RT 
ζi fi
xi
(5.19)
5-59
5-60
Pipe Segment
where:
xi = mol fraction
ζ i = activity coefficient
f = standard state fugacity
P = pressure
V = molar volume
T = temperature
R = gas constant
S, L = denote solid and liquid phases
Once the equilibrium constant for each component has been
calculated, they are used to determine the quantities and composition
of each phase. The differences between the various thermodynamic
models depend on how the terms in the equilibrium constant equation
are evaluated. The four models available in the Profes method are
described by the following equations:
•
AEA:
f
L
f
f
PV – V
∆h i 
Ti
T
T  ∆C p
i
i
ln K i = --------  1 – ----f + ---------- 1 – ---- + ln ----i + ∫ ----------------- ∂P
RT 
R
RT
T
T

0
Ti
•
(5.20)
Chung:
f
L
L
L
∆h i 
Vi
Vi
L 2
T  Vi L
ln K i = --------  1 – ----f + ------- ( δ m – δ i ) + ln ------- + 1 – ------RT 
RT
Vm
Vm
T
(5.21)
i
•
Conoco (Erikson):
f
∆h i 
T
ln K i = --------  1 – ----f
RT 
T i
5-60
(5.22)
Piping Equipment
•
Pederson:
L
L
L 2
f
f
f
∆h i 
Vi ( δm – δi )
Ti
T
T  ∆C p
ln K i = -------------------------------2- + --------  1 – ----f + ---------- 1 – ---- + ln ----i
R
RT 
T
S S
S
T
T i
Vi ( δm – δi )
where:
5-61
(5.23)
f
∆h i = enthalpy of melting
Ti f = melting temperature
V = molar volume
δ = solubility parameter
∆C p = heat capacity difference between solid and liquid
m = denotes mixture properties
i = component
All the models require a detailed compositional analysis of the fluid in
order to be used effectively and for the Conoco model Erickson et al
proposed that the hydrocarbon analysis should distinguish between
normal and non normal paraffin components as there is a substantial
difference in melting points between these two groups. The melting
temperatures make a very significant impact on the predicted cloud
point for any given composition. In Pederson model the Ki values
depend on the composition of the liquid and solid phases; this is unlike
normal equilibrium calculations, where the Ki ’s are fixed for any
temperature and pressure, and can lead to unstable or incorrect
numerical solutions.
The AEA model is the only model which incorporates a term for the
effect of pressure on the liquid-solid equilibrium, the result of this is to
counteract the increased solubility of wax forming components at high
pressures which is due to more light ends entering the liquid phase.
Using this model, the predicted cloud point and wax quantities can both
increase or decrease with increasing pressure, depending on the fluid
composition.
5-61
5-62
Pipe Segment
The table allows you to select which components in the system are able
to form wax. The default criteria for the components in this table are as
follows:
•
•
Components with a mole weight less than 140 or inorganic
component types can never form wax. The check box for these
components is set to a grey check box that cannot be modified.
Hydrocarbon component types form wax. The check box is
automatically activated for these components, but you can
deactivate it.
Hypothetical components generally fall into this category.
•
Other organic component types do not form wax. The check box
is inactive but you can activate it.
The ability to select whether a particular component forms wax gives
you additional control when defining the wax formation characteristics
of a system. For example, you can define two hypothetical components
with common properties, and by setting one as a wax former you could
vary the quantity of wax produced in the boiling range covered by the
hypotheticals by varying their proportions.
5-62
Piping Equipment
5-63
Tuning Data Tab
The Tuning Data tab allows you to define the observed wax formation
characteristics of a system to tune the wax model.
Figure 5.36
Calculated values for
the Cloud Point and
Wax Mass Percent
appear in the
calculated field and
column after the
tuning process is run.
The Cloud Point Input field allows you to specify the temperature at
which the first wax appears i.e., the phase transition temperature
between single liquid phase and the two phase wax/liquid mixture.
To remove a point from the
table both the temperature
and the wax mass percent
values must be deleted.
The table of Temperature vs. Wax Mass Percent allows you to define the
quantity of wax deposit observed as a function of temperature. New
points can be added to the table in any order; they are sorted by
temperature when the tuning process is run. To run the tuning
calculations a minimum of one pair of data points is required. Up to 10
pairs of data points can be specified.
5-63
5-64
Pipe Segment
Ref Comp Tab
The Ref Comp tab allows you to specify the reference composition of the
fluid that is used for tuning calculations.
Figure 5.37
The composition is
entered in a table
as either a mole or
mass fraction
depending on
which radio button
is selected.
The Normalise
button allows
you to normalise
the composition
entered and
setting any
unspecified
fractions to zero.
Tuning Process
The tuning process is a series of calculations that is initiated as a task by
clicking the Tune button. The first step validates the tuning data
specified as follows:
•
•
•
•
that there is at least one component identified as a wax former.
a valid reference composition has been entered.
sorting the pairs of temperature/wax mass percent in order of
descending temperature.
ensure cloud point temperature is greater than any temperature
in table of temperature/wax mass percent pairs.
If any problem is found the tuning process stops, and an appropriate
error message appears on the tuning status bar.
If the tuning data is valid then the tuning process first does a VLE flash at
15°C and 100 kPa to calculate the liquid composition of the reference
stream. This is used as the base composition for all subsequent tuning
calculations. If a liquid phase cannot be found in the reference stream at
these conditions the tuning calculations fail.
5-64
Piping Equipment
5-65
The tuning process then continues using an iterative least squares
solution method. Progress of the tuning process is output to the main
HYSYS status bar. When complete the tuning process checks for
convergence and displays the result on the tuning status bar. If the
tuning process converged then the calculated results on the Tuning data
tab are updated. If the tuning process failed to converge the tuning
parameters are set to the best values that were obtained. Tuning
parameters can be reset to their original values by re-selecting the wax
model.
There are three tuning parameters available for the Chung, Pederson,
and Conoco wax models, and four tuning parameters for the AEA
model. The tuning process only attempts to tune as many parameters as
is possible from the specified data (i.e., cloud point + one pair of
temperature/wax percent data allows tuning of two parameters - more
pairs of temperature/wax percent data points are required to tune
additional parameters). In cases where an attempt to tune three or four
parameters fails to converge, a second tuning attempt is made
automatically for just two tuning parameters.
The convergence of the tuning process is checked by looking at the
cloud point result since this is the most critical parameter. Generally
convergence is achieved when there are one or two pairs of
temperature/wax percent data. Given the emphasis placed on achieving
the cloud point the calculated results for wax percent can often show
greater errors, particularly when there are multiple temperature/wax
percent points.
You should realise that the degree to which the tuning parameters can
adjust the temperature/wax percent curve predicted by the models is
limited, and that hand tuning by changing the number and proportion
of wax forming components in the system may be required in some
cases.
5-65
5-66
Pipe Segment
5.2.9 Modifying the Fittings Database
The fittings data base contains VH Factor and FT Factor data taken from
Perry. Some of the Factor data are taken from Crane.
The following table details the values in the database. The Data Source
column displays the source of the data values.
5-66
Description
VH Factor
FT Factor
Swage Angle
Data Source
Pipe
0
0
0
Swage: Abrupt
0
0
180
Swage: 45 degree
0
0
45
Elbow: 45 Std
0
16
0
Elbow: 45 Long
0.2
0
0
Perry 5th ed, Table 5-19
Elbow: 90 Std
0
30
0
Crane 410M, A-29
Elbow: 90 Long
0.45
0
0
Perry 5th ed, Table 5-19
Bend: 90, r/d 1
0
20
0
Crane 410M, A-29
Bend: 90, r/d 1.5
0
14
0
Crane 410M, A-29
Bend: 90, r/d 2
0
12
0
Crane 410M, A-29
Bend: 90, r/d 3
0
12
0
Crane 410M, A-29
Bend: 90, r/d 4
0
14
0
Crane 410M, A-29
Bend: 90, r/d 6
0
17
0
Crane 410M, A-29
Bend: 90, r/d 8
0
24
0
Crane 410M, A-29
Bend: 90, r/d 10
0
30
0
Crane 410M, A-29
Bend: 90, r/d 12
0
34
0
Crane 410M, A-29
Bend: 90, r/d 14
0
38
0
Crane 410M, A-29
Bend: 90, r/d 16
0
42
0
Crane 410M, A-29
Bend: 90, r/d 20
0
50
0
Crane 410M, A-29
Elbow: 45 Mitre
0
60
0
Crane 410M, A-29
Elbow: 90 Mitre
0
60
0
Crane 410M, A-29
180 Degree Close Return
0
50
0
Crane 410M, A-29
Tee: Branch Blanked
0
20
0
Crane 410M, A-29
Tee: As Elbow
0
60
0
Crane 410M, A-29
Coupling/Union
0.04
0
0
Perry 5th ed, Table 5-19
Gate Valve: Open
0.17
0
0
Perry 5th ed, Table 5-19
Gate Valve: Three Quarter
0.9
0
0
Perry 5th ed, Table 5-19
Gate Valve: Half
4.5
0
0
Perry 5th ed, Table 5-19
Gate Valve: One Quarter
24
0
0
Perry 5th ed, Table 5-19
Gate Valve, Crane: Open
0
8
0
Crane 410M, A-27
Diaphram Valve: Open
2.3
0
Perry 5th ed, Table 5-19
Crane 410M, A-29
Piping Equipment
5-67
Description
VH Factor
FT Factor
Swage Angle
Data Source
Diaphram Valve: Three Quarter
2.6
0
0
Perry 5th ed, Table 5-19
Diaphram Valve: Half
4.3
0
0
Perry 5th ed, Table 5-19
Diaphram Valve: One Quarter
21
0
0
Perry 5th ed, Table 5-19
Globe Valve: Open
6
0
0
Perry 5th ed, Table 5-19
Globe Valve: Half
9.5
0
0
Perry 5th ed, Table 5-19
Globe Valve, Crane: Open
0
340
0
Crane 410M, A-27
Angle Valve: Open
2
0
0
Perry 5th ed, Table 5-19
Angle Valve, 45 deg: Open
0
55
0
Perry 5th ed, Table 5-19
Angle Valve, 90 deg: Open
0
150
0
Crane 410M, A-27
Blowoff Valve: Open
3
0
0
Perry 5th ed, Table 5-19
Plug Cock: Angle 5
0.05
0
0
Perry 5th ed, Table 5-19
Plug Cock: Angle 10
0.29
0
0
Perry 5th ed, Table 5-19
Plug Cock: Angle 20
1.56
0
0
Perry 5th ed, Table 5-19
Plug Cock: Angle 40
17.3
0
0
Perry 5th ed, Table 5-19
Plug Cock: Angle 60
206
0
0
Perry 5th ed, Table 5-19
Plug Cock: Open
0
18
0
Crane 410M, A-29
Butterfly Valve: Angle 5
0.24
0
0
Perry 5th ed, Table 5-19
Butterfly Valve: Angle 10
0.52
0
0
Perry 5th ed, Table 5-19
Butterfly Valve: Angle 20
1.54
0
0
Perry 5th ed, Table 5-19
Butterfly Valve: Angle 40
10.8
0
0
Perry 5th ed, Table 5-19
Butterfly Valve: Angle 60
118
0
0
Perry 5th ed, Table 5-19
Butterfly Valve: 2-8in, Open
0
45
0
Crane 410M, A-28
Butterfly Valve: 10-14in, Open
0
35
0
Crane 410M, A-28
Butterfly Valve: 16-24in, Open
0
25
0
Crane 410M, A-28
Ball Valve: Open
0
3
0
Crane 410M, A-28
Check Valve: Swing
2
0
0
Perry 5th ed, Table 5-19
Check Valve: Disk
10
0
0
Perry 5th ed, Table 5-19
Check Valve: Ball
70
0
0
Perry 5th ed, Table 5-19
Check Valve: Lift
0
600
0
Crane 410M, A-27
Check Valve: 45 deg Lift
0
55
0
Crane 410M, A-27
Foot Valve
15
0
0
Perry 5th ed, Table 5-19
Foot Valve: Poppet disk
0
420
0
Crane 410M, A-28
Foot Valve: Hinged disk
0
75
0
Crane 410M, A-28
Water Meter: Disk
7
0
0
Perry 5th ed, Table 5-19
Water Meter: Piston
15
0
0
Perry 5th ed, Table 5-19
Water Meter: Rotary
10
0
0
Perry 5th ed, Table 5-19
Water Meter: Turbine
6
0
0
Perry 5th ed, Table 5-19
User Defined
0
0
0
User specified
5-67
5-68
Pipe Segment
A few sections from the “fittings.db” file are shown below:
FittingType elbow45std
VHFactor 0.0
Desc “Elbow: 45 Std”
FTFactor 16.0
Data Source “Crane 410M, A-29”
end
FittingType swage2
VHFactor 0.0
Desc “Wage: 45 degree”
Sweating 45.0
end
...
FittingTypeGroup FTG
AddFitt elbow45std
...
end
This can be broken down, line by line:
1.
FittingType elbow45std
What this does is define an object “elbow45std” of type
“FittingType”. “FittingType” has three members (parameters): a VH
Factor (K-Factor), FT factor or Swage angle, and a description.
The object name “elbow45std” is only an internal name; it doesn't
appear in any lists or views.
2.
VHFactor 0.0
This is the K-Factor for the fitting. When you add a fitting to the
fittings list, this is the number that is put in the K-Factor column.
3.
Desc “Elbow: 45 Std”
This assigns a label (description) to the fitting “elbow45std”. It is
this label that is used in the fittings window to select fittings.
5-68
Piping Equipment
4.
5-69
This line contains one of the following two possible command lines:
•
FTFactor 16.0
This is the FT factor for the fitting. When you add a fitting to the
fittings list, this is the number that is put in the FT factor column.
•
Swage Angle 45
This command is used to assign the value for the swage angle fitting
calculation method.
5.
DataSource “Crane 410M, A-29”
This tells you where the data source was taken from.
6.
end
This tells HYSYS that the description of “elbow45std” is done.
So, you have a definition of a fitting. But, that's not quite enough. All the
fittings are gathered into one group - a “FittingTypeGroup”- to make it
easier for HYSYS to determine what should go where.
1.
FittingTypeGroup FTG
Same as line 1 above. This defines an object “FTG” of type
“FittingTypeGroup”. “FTG” can have many parameters, but they
must all be of the same type - FittingType. The FittingTypeGroup is
like a container for all the pipe fittings.
2.
AddFitt elbow45std
This adds the previously defined fitting to the group. Notice that the
fitting MUST be defined before it is added to the group. All new
fittings should be added last in the database file. When the fittings
appear in the drop-down list, they are sorted alphabetically by their
Desc parameter.
New fittings should be added
as the last entry in the
database.
3.
end
This tells HYSYS that you have added all the fittings you want to the
fitting group. Notice that HYSYS does not automatically put fittings
in the group just because they are defined beforehand. For example,
if we had defined “elbow45std” as above, but forgot to add it to the
fittings group, there would be no way to access it in the fittings
window.
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5-70
Pipe Segment
Also, the “end” command is very important. If you forget to put an “end”
in somewhere in the middle of the fittings.db file, you can get errors that
may or may not tell you what is actually wrong.
Adding a Fitting
So, now you can add your own fitting. Open the “fitting.db” file in an
ASCII editor and move somewhere in the middle of the file (but make
sure that you are above the definition of the fittings group).
Now, add the following lines:
FittingType loopdeloop
VHFactor 10.0
Desc “Loop-de-loop!”
FT Factor 0.0
DataSource “Add fitting demo”
end
You have now created a fitting. You don't have to indent the VHFactor,
Desc, FTFactor, and DataSource lines, it just makes for neater and easier
to read files. Next, the fitting needs to be added to the fittings group.
Find the line in the file that says “FittingTypeGroup FTG”. Now, go
anywhere between this line and the “end” line and type the following:
AddFitt loopdeloop
Now all you have to do is run HYSYS and make a Pipe Segment. The new
fitting “Loop-de-loop!” appears in the fittings drop-down list, and if you
add a “Loop-de-loop!” to the fittings list, it comes up with a K-Factor of
10.0.
To take out the fitting, just delete the lines that were previously added.
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Piping Equipment
5-71
5.3 Compressible Gas Pipe
The Compressible Gas Pipe (CGP) model uses an algorithm that solves a
vector system using the Two-Step Lax-Wendroff method with Boris &
Book anti-diffusion.
The CGP unit operation is primarily designed for transient calculations
with streams. Steady state calculations have been implemented
primarily for initialization of the Pipe State prior to transient
calculations.
The following calculation modes are supported in steady sate mode:
•
•
•
Specify Inlet Pressure, Temperature, and Mass Flow
Specify Inlet Temperature, Mass Flow, and Outlet Pressure
Specify Inlet Pressure and Temperature, and Outlet Pressure.
Alternatively the pressure drop may be used with either boundary
pressure.
Model for a Single Phase Compressible Flow
The following equations are used in HYSYS to model a single phase
compressible flow.
Governing Equations
Mass:
∂( Aρ ) ∂( Aρu )
--------------- + ------------------ = 0
∂x
∂t
(5.24)
Momentum:
2
1
S
2 1 dA
∂( ρu ) ∂( ρu + p )
-------------- + -------------------------- = ρgsinθ – --- fρu u --- – ρu --- -----A dx
2
A
∂x
∂t
(5.25)
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5-72
Compressible Gas Pipe
Energy:
S
S
1
1 dA
2
∂( ρE ) ∂( ρHu )
--------------- + ------------------- = k ( T wall – T ) --- – ρ gsinθ – --- fρu u --- – ρHu --- -----A
A
2
A dx
∂t
∂x
where:
(5.26)
1 2
--- πD , pipe cross-sectional area
4
1 2
E = e + --- u , total internal energy
2
1 2
H = h + --- u , total enthalpy
2
πD , the pipe perimeter
S=
A=
D = pipe diameter
e = internal energy
f = friction factor
g = acceleration due to gravity
h = enthalpy
k = heat transfer coefficient
p = pressure
t = time
T = temperature
Twall = wall temperature
u = velocity
x = distance
θ = pipe inclination
ρ = density
Algorithm
∂U ∂D
------- + ------- = G
∂t ∂x
(5.27)
The algorithm solves the vector system by the Two-Step Lax-Wendroff
method with Boris & Book anti-diffusion.
5-72
Piping Equipment
5-73
5.3.1 Compressible Gas Pipe Property View
You can also add a
compressible gas pipe by
clicking the F12 hot key.
There are two ways that you can add a Compressible Gas Pipe to your
simulation:
You can also open the
Object Palette by clicking the
F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Piping Equipment radio button.
3.
From the list of available unit operations, select Compressible Gas
Pipe.
4.
Click the Add button. The Compressible Gas Pipe property view
appears.
OR
Compressible Gas Pipe icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Compressible Gas Pipe icon. The Compressible
Gas Pipe property view appears.
Figure 5.38
To ignore the CGP operation during calculations, activate the Ignored
checkbox. HYSYS disregards the operation until you deactivate the
checkbox.
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5-74
Compressible Gas Pipe
5.3.2 Design Tab
The Design tab consists of four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
On the Connections page, you must specify the Feed and Product
material streams.
Figure 5.39
You can specify the streams by either typing the name of the new stream
or selecting existing streams in the Inlet and Outlet drop-down lists. You
can also edit the name of the operation on this page.
The Compressible Gas Pipe does not support an energy stream.
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Piping Equipment
5-75
Parameters Page
The Parameters page allows you to specify the pressure drop across the
pipe as well as the name of the operation.
Figure 5.40
There are also three calculated values that are displayed on the page.
•
•
•
Max. Mach Number. For steady state calculations this is always
at the outflow from the pipe. During dynamic calculations this can
be at any location within the pipe.
Max. Pressure. For steady state calculations this is always at the
outflow from the pipe. During dynamic calculations this can be at
any location within the pipe.
Max. Velocity. For steady state calculations this is always at the
outflow from the pipe. During dynamic calculations this can be at
any location within the pipe.
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
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5-76
Compressible Gas Pipe
Notes Page
For more information, refer to
Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
5.3.3 Rating Tab
The Rating tab consists of two pages:
•
•
Sizing. you provide information regarding the dimensions of
sections in the pipe segment
Heat Transfer. the heat loss of the pipe segment can either be
specified or calculated from various heat transfer parameters.
Sizing Page
On the Sizing page, the length-elevation profile for the CGP is
constructed. You can provide details for each fitting or pipe section that
is contained in the CGP that you are modeling. An unlimited number of
pipe sections or fittings can be added on this page.
Figure 5.41
5-76
Piping Equipment
5-77
For a given length of pipe which is modeled in HYSYS, the parameters of
each section is entered separately. To fully define the pipe section, you
must also specify pipe schedule, diameters (nominal or inner and
outer), a material, and a number of cells.
There are two ways that you can add sections to the length-elevation
profile:
1.
Click the Add Section button, which allows you to add the new
section after the currently selected section.
OR
2.
Click the Insert Section button, which allows you to add the new
section before the currently selected section
For each segment that you add, you must specify the following:
•
•
•
Length. The physical length of the pipe. Notice that it is not
appropriate to enter an equivalent length and attempt to model
fittings.
Elevation Change. The elevation change of the pipe.
Cells. Number of cells within the pipe (10 - 1000).
When modeling multiple sections, faster and more stable convergence
can be obtained if all cell sizes are similar. For a stable solution, the
number of cells should be selected such that the following constraint is
met:
Cell Length
---------------------------- < 0.5 Sonic Velocity
Time Step
(5.28)
To delete a section, click on the section you want to delete and click the
Delete button. The Clear Profile button deletes all sections except for the
first section, however, all data for the first section is cleared.
The Overall Dimensions group manages the pipe diameter and material
data. This works in the same fashion as the standard Pipe Segment unit
operation (refer to Section 5.2 - Pipe Segment).
The external diameter is not currently used by the calculations. It has
been added so that the heat transfer models can be more easily
enhanced in future versions.
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5-78
Compressible Gas Pipe
Heat Transfer Page
The Ambient Temperature is
the bulk ambient temperature,
and Overall HTC is the overall
heat transfer coefficient based
upon the inside diameter of
the pipe.
A simplified heat transfer model is used that allows you to specify the
ambient temperature and an overall heat transfer coefficient.
Figure 5.42
5.3.4 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
5.3.5 Performance Tab
This tab is functionally similar to the Performance tab on the standard
Pipe Segment unit operation (refer to Section 5.2 - Pipe Segment).
Figure 5.43
5-78
Piping Equipment
5-79
You can view a complete profile by clicking on the View Profile button.
The properties displayed on the Table tab of the Profile View are listed
below:
•
•
•
•
•
•
•
•
•
•
Axial Length
Pressure
Temperature
Mass Flow
Velocity
Mach Number
Mass Density
Internal Energy
Enthalpy
Speed Of Sound
5.3.6 Properties Tab
Due to the number of physical property calculations, an acceptable
calculation speed is not possible by directly calling the current property
package for the flowsheet. Three alternative methods are available from
the drop-down list:
•
•
•
Perfect Gas
Compressible Gas
Table Interpolation
The methods are described in the sections below.
Perfect Gas
H = C p ∆T
(5.29)
PMW
ρ = -------------RT
(5.30)
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5-80
Compressible Gas Pipe
Compressible Gas
Same as for perfect gas, but
PMW
ρ = -------------ZRT
(5.31)
The compressibility factor, Z is calculated from the current property
package for the flow sheet at the average conditions within the pipe.
Table Interpolation
A neural network calculates physical properties. This neural network
uses a Radial Basis Function to train the network from physical
properties, predicted from the current property package of the
flowsheet.
Care must be taken to train
over the full extent of the
expected range of operating
conditions since
extrapolation always yield
unpredictable results.
5-80
Prior to calculations, you must train the neural network. The Table
Generation group manages the extent of the training.
Figure 5.44
Piping Equipment
5-81
5.3.7 Dynamics Tab
The Dynamics tab consist of two pages:
•
•
Specs
StripChart.
Figure 5.45
Specs Page
For transient compressible flow calculations, the solution of pressure/
flow equations is inappropriate since the boundary pressure is not
directly related to flow. It is however critical that the compressible gas
solve simultaneously with the other flow sheet equations. This is
achieved by making perforations at each end of the pipe for each time
step and re-evaluating the change in state over the time step. These
changes are the fit to an equation of the following form, which is passed
to the Pressure Flow solver:
2
A.Pres + BFlow + CFlow + D = 0
(5.32)
The Pressure Flow Equations group displays the values for the
coefficients in the above equation, which are continuously updated at
each time step.
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5-82
Tee
Stripchart Page
Refer to Section 11.7.3 Strip Chartsin the User
Guide for more information
about stripcharts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
5.4 Tee
The Tee operation splits one feed stream into multiple product streams
with the same conditions and composition as the feed stream, and is
used for simulating pipe tees and manifolds.
The dynamic Tee operation functions very similarly to the steady state
Tee operation. However, the enhanced holdup model and the concept
of nozzle efficiencies can be applied to the dynamic Tee. Flow reversal is
also possible in the Tee depending on the pressure-flow conditions of
the surrounding unit operations.
5.4.1 Tee Property View
You can also add a tee by
clicking the F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Tee to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Piping Equipment radio button.
3.
From the list of available unit operations, select Tee.
4.
Click the Add button. The Tee property view appears.
OR
5.
5-82
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
Piping Equipment
6.
5-83
Double-click the Tee icon. The Tee property view appears.
Figure 5.46
Tee icon
To ignore the Tee operation during calculations, activate the Ignored
check box. HYSYS disregards the operation until you deactivate the
check box.
5.4.2 Design Tab
The Design tab consists of four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
5-83
5-84
Tee
Connections Page
On the Connections page, you can specify the feed stream as well as any
number of product streams, all of which are assigned the conditions and
composition of the feed.
Figure 5.47
The only difference among the products are the flow rates, determined
by the flow ratios, which you specify on the Parameters page (Steady
State mode) or the outlet valve openings, which you specify on the
Dynamics page (Dynamic mode).
Parameters Page
For steady state calculations, specify the desired flow ratio (the ratio of
the outlet stream flow to the total inlet flow).
Figure 5.48
5-84
Piping Equipment
5-85
A flow ratio is generally between 0 and 1; however, a ratio greater than
one may be given. In that case, at least one of the outlet streams have a
negative flow ratio and a negative flow (backflow). For N outlet streams
attached to the Tee, you must specify N-1 flow ratios. HYSYS then
calculates the unknown stream flow ratio and the outlet flow rates.
N
∑ ri
= 1.0
(5.33)
1=i
fi
r i = --F
where:
(5.34)
ri = flow ratio of the ith stream
fi = outlet flow of the ith stream
F = feed flow rate
N = number of outlet streams
For example, if you have four outlet streams attached to the Tee, you
must give three flow ratios and HYSYS calculates the fourth. If you
switch to Dynamic mode, the flow ratio values do not change if the
values are between 0 and 1 (they are equal to the dynamic flow
fractions).
Figure 5.49
F
1
f1
2
f2
3
f3
.....
N
•
•
•
•
Inlet flow F
N outlet streams
Specify N-1 flow ratios ri
Outlet stream flows f1 = r1F
fN
5-85
5-86
Tee
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
5.4.3 Rating tab
You need HYSYS dynamics to specify any rating information for the Tee
operation.
Nozzles Page
The Fidelity license is
required to use the nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. Refer to Section 1.6.2 - Nozzles in the Dynamic
Modeling manual for more information.
It is strongly recommended that the elevation of the inlet and exit
nozzles are equal for this unit operation. If you want to model static
head, the entire piece of equipment can be moved by modifying the
Base Elevation relative to the Ground Elevation field.
5.4.4 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
5-86
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Piping Equipment
5-87
5.4.5 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Dynamic tab.
The Dynamics tab consists of three pages:
•
•
•
Specs
Holdup
Stripchart
Specs Page
The dynamic specifications of the Tee can be specified on the Specs
page:
Figure 5.50
In Dynamic mode, there are
two specifications you can
choose to characterize the
Tee operation.
If the Use Splits as Dynamic Flow Specs checkbox is activated, the exit
flows streams from the Tee are user-defined. You can define the molar
flow for each exit stream by specifying the specific valve openings for
each exit stream from the Tee. This situation is not recommended since
the flow from the Tee is determined from split fractions and not from the
surrounding pressure network of the simulation case. If this option is
used, the valve opening fields should be specified all Tee exit streams. In
addition a single pressure and single flow specification are required by
the PF solver.
5-87
5-88
Tee
If the Use Splits as Dynamic Flow Specs checkbox is inactive, the flow
rates of the exit streams are determined from the pressure network. If
this option is set, the dynamic Tee acts similar to a Mixer set with the
Equalize All option. The “one PF specification per flowsheet boundary
stream” rule applies to the Tee operation if the Use Splits checkbox is
inactive. It is strongly recommended that you deactivate the Use Splits
checkbox in order to realistically model flow behaviour in your dynamic
simulation case.
Reverse flow conditions can occur in the Tee operation if the Use Splits
checkbox is inactive. If flow reverses in the Tee, it acts essentially like a
dynamic Mixer with the Equalize All option. In dynamics, these two unit
operations are very similar.
Holdup Page
Each unit operation in HYSYS has the capacity to store material and
energy. Typical Tees in actual plants usually have significantly less
holdup than other unit operations in a plant. Therefore, the volume of
the Tee operation in HYSYS cannot be specified and is assumed to be
zero. Since there is no holdup associated with the Tee operation, the
holdup’s quantity and volume are shown as zero in the Holdup page.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
Stripchart Page
Refer to Section 11.7.3 Strip Chartsin the User
Guide for more information
about stripcharts.
5-88
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Piping Equipment
5-89
5.5 Valve
HYSYS performs a material and energy balance on the inlet and exit
streams of the Valve operation. HYSYS performs a flash calculation
based on equal material and enthalpy between the two streams. It is
assumed that the Valve operation is isenthalpic.
The following is a list of variables that can be specified by the user in the
Valve operation.
•
•
•
•
•
Inlet temperature
Inlet pressure
Outlet temperature
Outlet pressure
Valve Pressure Drop
A total of three specifications are required before the Valve operation
solves. At least one temperature specification and one pressure
specification are required. HYSYS calculates the other two unknowns.
There are also a number of new features that are available with the Valve
operation. The Valve is a basic building block in HYSYS dynamic cases.
The new Valve operation models control valves much more realistically.
The direction of flow through a Valve is dependent on the pressures of
the surrounding unit operations. Like the steady state Valve, the
dynamics Valve operation is isenthalpic.
Some of the new features in the Valve operation include:
•
•
•
•
•
•
A pressure-flow specification option that realistically models flow
through the valve according to the pressure network of the plant.
Possible flow reversal situations can therefore be modeled.
A pipe segment contribution that can model pressure losses
caused by an attached pipe’s roughness and diameter.
A new valve equation that incorporates static head and frictional
losses from the valve and/or pipe segment.
A model incorporating Valve dynamics such as the stickiness in
the valve and dynamic behaviour in the actuator.
Different valve types such as linear, equal percentage, and quick
opening valves.
Built-in sizing features that determine valve parameters used in
the valve equation.
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5-90
Valve
The total valve pressure drop refers to the total pressure difference
between the inlet stream pressure and the exit stream pressure. The
total pressure drop across the Valve is calculated from the frictional
pressure loss of the Valve, and the pressure loss from static head
contributions.
5.5.1 Valve Property View
You can also add a valve by
clicking the F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Valve to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Piping Equipment radio button.
3.
From the list of available unit operations, select Valve.
4.
Click the Add button. The Valve property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Valve icon. The Valve property view appears.
Figure 5.51
Valve icon
To ignore the Valve operation during calculations, activate the Ignored
checkbox. HYSYS disregards the operation until you deactivate the
checkbox.
5-90
Piping Equipment
5-91
5.5.2 Design Tab
The Design tab consists of four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
The Connections page allows you to specify the name of the operation,
as well as the inlet stream and outlet stream.
Figure 5.52
5-91
5-92
Valve
Parameters Page
The pressure drop of the Valve operation can be specified on the
Parameters page.
Figure 5.53
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
5-92
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Piping Equipment
5-93
5.5.3 Rating Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Rating tab.
The Rating tab consists of two pages:
•
•
Sizing
Nozzles
Sizing (dynamics) Page
The Sizing (dynamics) page contains the:
•
•
•
sizing conditions
valve type
sizing method
Figure 5.54
Sizing Conditions
The current stream conditions of the Valve appears by clicking on the
Current radio button. HYSYS uses the stream conditions provided in this
field to calculate valve parameters, which are used in the valve equation.
If you want to specify your own sizing conditions, the User Input radio
button should be selected.
5-93
5-94
Valve
The following stream conditions appear and cannot be modified:
•
•
Inlet Pressure
Molecular Weight
The following valve and stream conditions appear and can be modified
in the sizing calculation:
•
•
•
Valve % Opening
Delta P
Mass Flow Rate
Valve Type
In HYSYS, three different types of valves can be specified using the Valve
operation:
•
•
•
Linear
Quick Opening
Equal Percentage
The flow rate through a control valve depends on the actual valve
position. If the flow can be expressed in terms of %Cv,(0% representing
no flow conditions and 100% representing the maximum flow
conditions) then the valve characteristics of a control valve is defined as
the dependence on the quantity of %Cv as a function of the actual valve
percent opening.
In HYSYS, you can specify three different valve characteristics for any
control valve in the simulation case. The table below describes the valve
types.
5-94
Valve Type
Description
Linear
A control valve with linear valve characteristics has a flow which is
directly proportional to the valve % opening.
Quick Opening
A control valve with quick opening valve characteristics obtains
larger flows initially at lower valve openings. As the valve opens
further, the flow increases at a smaller rate.
Equal Percentage
A control valve with equal percentage valve characteristics initially
obtains very small flows at lower valve openings. However, the
flow increases rapidly as the valve opens to its full position.
Piping Equipment
5-95
The valve characteristics are shown graphically in the figure below.
Figure 5.55
CONTROL VALVE FLOW CHARACTERISTICS
10
Quick
Opening
80
Linear
60
% Cv
40
Equal
Percentage
20
0
0
20
40
60
80
10
% Valve Position
The mathematical relationship of Cv (%) and Valve Position (%) for each
type of valve are as follows:
Linear
%C = ( %Valve Opening )
v
(5.35)
Quick Opening
%C = ( %Valve Opening )
v
0.5
(5.36)
5-95
5-96
Valve
Equal percentage
%C = (%Valve Opening)
v
3
(5.37)
Sizing Method
Three different sizing methods can be implemented in HYSYS. You can
use either a Cv, Cg, or k-type resistance equation to calculate flow.
If the Cv or Cg method is chosen, two of the following parameters can be
specified in order to fully define the Valve
•
Cv Method Parameters
C1, Km, Cv, and Cg
C1 and Km cannot both be specified by the user.
If desired, a single valve parameter can be specified while HYSYS
calculates the remaining parameters from the stream and valve
conditions displayed in the Sizing Conditions group. This is achieved by
clicking the Size Valve button. HYSYS provides a C1 default value of 25.
The Cv and Cg methods calculate the vapour flow through the valve
using the following equation:
P2
 59.64

f ( lb ⁄ hr ) = υ fracfac 1.06C g ρ ( lb ⁄ ft 3 ) × P 1 × sin  ------------- 1 – ------ × cp fac
P1
 C1

(5.38)
where:
5-96
Cg
C1 = ------Cv
(5.39)
Km = 0.001434C1
(5.40)
Piping Equipment
cp fac =
5-97
0.4839
--------------------------------------- γ 
2  ---------γ – 1
1 –  -----------
 1 + γ
γ = Cp ⁄ Cv
(5.41)
(5.42)
P1 = pressure of the inlet stream
P2 = pressure of the exit stream without static head contributions
vfrac fac = 1, outlet molar vapour fraction vfrac > 0.1
= 0, outlet molar vapour fraction vfrac = 0
= vfrac/0.1, otherwise
For the liquid flow through the valve, the equation is as follows:
f ( lb ⁄ hr ) = υ fracfac × 63.338 × C v × ρ ( lb ⁄ ft 3 ) × P 1 – P 2
(5.43)
HYSYS reports the full Cv (at 100% open, which remains fixed) plus the
valve opening. If the Valve is 100% open then you get a smaller Valve
than if the Valve was only 50% open for the same conditions. This is just
one way of sizing a Valve as some sources report an effective Cv (varies
with the valve opening) versus the value opening.
The above equations are not rigorous for two-phase flow.
5-97
5-98
Valve
If the k method is chosen, you can either specify k or have it calculated
from the stream and valve conditions displayed in the Sizing Conditions
field. HYSYS can calculate k by clicking the Size Valve button. The k
method calculates the flow through the Valve using the following
equation:
f = k density × valveopening × ( P 1 × P 2 )
(5.44)
The general valve flow equation uses the pressure drop across the Valve
without any static head contributions. The quantity, P1 - P2, is defined as
the frictional pressure loss, which is used in the valve sizing calculation.
The valve opening term is dependant on the type of Valve and the
percentage that it is open. For a linear valve:
% valve open
valveopening =  --------------------------------


100
2
(5.45)
The inverse relationship between the percentage of valve opening, and
Cg can be shown as follows:
( % valve open ) × C g = Flow
(5.46)
When the valve size is fixed (i.e., Cg), the percentage of valve opening
increases with the flow through the valve. However, when the sizing a
valve, the Cg is not fixed. The Cg is inversely dependent on the flow, and
the percentage of valve opening.
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
5-98
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. Refer to Section 1.6.2 - Nozzles in the Dynamic
Modeling manual for more information.
Piping Equipment
5-99
5.5.4 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
5.5.5 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Dynamics tab.
The Dynamics tab consists of six pages:
•
•
•
•
•
•
Specs
Pipe
Holdup
Actuator
Flow Limits
Stripchart
Specs Page
The dynamic specifications and parameters of the Valve can be
specified on the Specs page.
Figure 5.56
5-99
5-100
Valve
Dynamic Specifications
In Dynamic mode, there are
two possible dynamic
specifications you can
choose to characterize the
Valve operation.
If the Total Delta P checkbox is activated, a set pressure drop is assumed
across the Valve operation. With this specification, the flow and the
pressure of either the inlet or exit stream must be specified or calculated
from other operations in the flowsheet. The flow through the Valve is
not dependent on the pressure drop across the Valve.
If the Pressure Flow Relation checkbox is activated, two of the following
pressure-flow specifications must either be specified or calculated by
the other unit operations in the flowsheet:
•
•
•
Inlet Stream Pressure
Exit Stream Pressure
Flow through the Valve
The flow rate through the Valve is calculated from the valve equation,
and the pressure of the streams entering and exiting the Valve.
In dynamics, the suggested mode of operation for the Valve is the
Pressure Flow specification. The pressure drop option is provided for
steady state compatibility mostly, and to allow difficult simulations to
converge more easily. However, it usually is not a sensible specification
since it allows a pressure drop to exist with zero flow.
Dynamic Parameters
The Dynamic Parameters group lists the same stream and valve
conditions required to size the Valve as in the Sizing Conditions group.
The Valve Opening % and the Conductance (Cv or k) appear and can be
modified in the section. The conductance of the Valve can be calculated
by clicking the Size Valve button.
The Check Valve checkbox can be activated if you do not want flow
reversal to occur in the Valve.
5-100
Piping Equipment
5-101
Pipe Page
The pipe calculations for a
valve are not rigorous for
multiphase flow and are only
approximations.
The Valve module supports a pipe contribution in the pressure flow
equation.
Figure 5.57
A pipe contribution DOES NOT contribute to any holdup. You have to
enter the holdup separately in the Holdup Page.
This can be used to model a pipe segment in the feed to the Valve, but it
is also possible to disable the valve contribution and have the Valve unit
operation act as a simple pipe segment only. The pressure flow
specification has to be enabled in order for the pipe segment to be
modeled.
The following pipe modeling parameters appear in this section:
•
•
•
•
•
•
•
•
•
Friction Factor Equation
Material
Roughness
Pipe length
Feed diameter
Darcy friction factor
Pipe k
Velocity
Reynolds number
5-101
5-102
Valve
The Friction Factor Equation option allows you to choose between two
different equations:
•
•
Assume Complete Turbulence (f is fixed)
Full-Range Churchill (covers all flow regimes)
The default equation, Assume Complete Turbulence, is fast and simple.
This method calculates the friction factor once and uses that value
irrespective of the Reynolds number (this number is not correct if the
flow is laminar). The Full-Range Churchill method calculates the friction
factor as a function of the Reynolds number. This method is slower but
calculates a unique friction factor for the turbulent, lamiar and
transtitional regions. If the flow through the Valve is too low HYSYS uses
a low limit of 10 for the Reynolds number.
HYSYS suggests a typical pipe roughness if the pipe material is specified.
The pipe roughness may also be directly specified. The feed diameter
and pipe length must be specified as well. These specifications are used
to determine the Darcy friction factor.
The friction factor is calculated as follows:
The pipe segments only
calculate frictional losses.
They do not automatically
calculate holdup volume. You
must enter this on the Holdup
page of the Dynamics tab.
where:
3.707D
1
---------------------- = 2.457 ln  ------------------
 ε 
f friction
(5.47)
f Darcy = 8 × f friction
(5.48)
fDarcy = Darcy friction factor
D = pipe diameter
ε = pipe roughness
A pipe k-value is calculated from the Darcy friction factor and the pipe
diameter. The pipe k value is incorporated into the general valve
equation. Notice that this pipe k is independent of the flow rate or
pressure of the fluid in the Valve.
5-102
Piping Equipment
5-103
Holdup Page
Each unit operation in
HYSYS has the capacity to
store material and energy.
Typical Valves usually have
significantly less holdup than
other unit operations in a
plant. Therefore, the volume
of the Valve operation in
HYSYS is defaulted to be
zero.
The Holdup page contains information regarding the holdup properties,
composition, and amount.
Holdup occurs after the
valve, whereas the pipe
contribution occurs before
the valve.
The Holdup page also allows you to disable any flashes that may occur
in the Valve.
Figure 5.58
For each phase contained within the volume space of the unit
operation, the following is specified:
You will need a Fidelity
license, and to have Fidelity
enabled in the Integrator
control panel to set a nonzero holdup.
Holdup Details
Description
Holdup Volume
The holdup volume can be specified in this field.
Accumulation
The accumulation refers to the rate of change of material in the
holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
5-103
5-104
Valve
Actuator Page
The Actuator page allows you to model valve dynamics in the Valve
operation. The Fidelity license is required to use the Actuator features
found on this page. Refer to Section 1.6.3 - Control Valve Actuator in
the Dynamic Modeling manual for more information.
Flow Limits Page
The Flow Limits page allows you to monitor the status of the vapour and
liquid flow passing through the valve. The page consists of two groups:
•
•
Vapour Choking
Liquid Choking
Figure 5.59
Vapour Choking Group
By default, the Vapour Choking status is always monitored whenever it
is applicable. You can view the current condition of the vapour flow in
the Vapour Choking Status group. The active status is shown in black
whereas the inactive status is greyed out. The two statuses available are
Critical Flow and No Choking.
5-104
Piping Equipment
5-105
Critical flow or vapour choking refers to the crowding condition when
the gas flowing through the valve has exceeded the designed limit and
reaches the sonic velocity. Critical flow is calculated by the Fisher
equation for gases.
f = V
where:
frac
P
 59.64

2
× 1.06 × C × ρ × P × sin  ------------- × 1 – ------ × C

g
1
p
C
P
 1
fac
1
(5.49)
f = flow (lb/hr)
Vfrac = vapour fraction
Cg = Fisher’s valve vapour coefficient
C1 = critical flow factor, Cg/Cv (between 33 - 38)
Cpfac = theoretical correction factor for the ratio of specific heats
ρ = density (lb/ft3)
P1 = pressure at valve inlet (psia)
P2 = pressure at valve outlet (psia)
As the Sine function approaches to 1, the flow through the valve
becomes choked and under this condition, the vapour through the valve
undergoes critical flow.
Liquid Choking Group
Liquid choked modeling is optional in HYSYS. You can turn it on or off
for the associated valve by checking the Model Liquid Choking
checkbox.
5-105
5-106
Valve
You can also activate the Model Liquid Choking checkbox on the
Options tab of the Integrator view.
Figure 5.60
There are three flow conditions in the Liquid Choking Status group:
•
•
•
No choking. Normal flow condition. An increase in pressure drop
across the valve results in an increased flow. The No choking
condition holds for a limited range.
Flashing. When the pressure of the valve outlet falls below the
vapour pressure of the liquid.
Cavitating. When the pressure of valve outlet raises above the
vapour pressure of the liquid.
The presence of these flow conditions can significantly affect the valve
performance and the overall process. During flashing, liquid starts to
vapourize, and the change in phase from liquid to vapour causes
bubbles to form. This creates congestion across the valve (liquid
choking), and the flow is severely limited. At this point, increase in
pressure drop will not result in increased flow. When cavitation occurs,
the pressure of the liquid recovers and raises above its vapour pressure.
This causes vapour bubbles to collapse and burst, producing a great
amount of noise and vibrations that can damage the valve.
5-106
Piping Equipment
5-107
Since the regular Fisher liquid flow equation does not predict liquid
choked flow, a different equation is used to take into account the effects
of flashing and cavitation.
Figure 5.61
Flow equation
prediction
q, gpm
Choked flow
∆P allowable
∆P max
∆P
Km (the pressure recovery coefficient) predicts flashing and cavitation
for a valve. By default, the pressure recovery coefficient is set at a
conservative value of 0.9. You can specify the Km value to adjust the flow
condition.
The liquid choked-flow condition is shown in Figure 5.61. As pressure
drop increases, the liquid flow becomes choked. The allowable pressure
drop (∆Pallowable) indicates when the liquid choked-flow occurs and it is
defined as:
∆P allowable = K m ( P 1 – r c P v )
where:
(5.50)
Km = pressure recovery value
rc = critical pressure ratio
Pv = vapour pressure of liquid
5-107
5-108
Valve
The values of these parameters are displayed in the table. The Frictional
Delta P shows the current pressure drop across the valve. As you adjust
the pressure recovery coefficient, the Frictional Delta P allowable
changes according to Equation (5.50). If the Frictional Delta P allowable
is below the Frictional Delta P, then cavitation occurs. The Liquid Vapour
pressure and the Critical Pressure Ratio are also displayed for reference.
Figure 5.62
If the flow is vapour
dominant, HYSYS
displays this
message even if the
Model Liquid
Choking checkbox is
checked.
No message is displayed when the flow consists of vapour and liquid.
Figure 5.63
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about stripcharts.
5-108
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Piping Equipment
5-109
5.6 Relief Valve
The Relief Valve unit operation can be used to model several types of
spring loaded Relief Valves. Relief Valves are used quite frequently in
many different industries in order to prevent dangerous situations
occurring from pressure buildups in a system. Its purpose is to avert
situations that occur in a dynamic environment. The flow through the
Relief Valve can be vapour, liquid, liquid with precipitate or any
combination of the three.
5.6.1 Relief Valve Property View
You can also add a relief
valve by clicking the F12 hot
key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Relief Valve to your simulation:
1.
In the Flowsheet menu, click the Add Operation. The UnitOps view
appears.
2.
Click the Piping Equipment radio button.
3.
From the list of available unit operations, select Relief Valve.
4.
Click the Add button. The Relief Valve property view appears.
OR
5.
In the Flowsheet menu, click the Palette. The Object Palette
appears.
5-109
5-110
Relief Valve
6.
Double-click the Relief Valve icon. The Relief Valve property view
appears.
Figure 5.64
Relief Valve icon
To ignore the Relief Valve operation during calculations, activate the
Ignored checkbox. HYSYS disregards the operation until you deactivate
the checkbox.
5.6.2 Design Tab
The Design tab of the Relief Valve property view consists of four pages:
•
•
•
•
5-110
Connections
Parameters
User Variables
Notes
Piping Equipment
5-111
Connections Page
The Connections page is where the inlet and outlet streams of the Relief
Valve are specified.
Figure 5.65
The page contains three fields, which are described in the table below:
Field
Description
Inlet
Stream entering Relief Valve. You can either select a pre-existing stream
from the drop-down list associated with this field or you can create a new
stream by selecting this field and typing the stream name.
Outlet
Relief Valve exit stream. Like the Inlet field, you can either select a preexisting stream from the drop-down list associated with this field or you
can create a new stream by selecting this field and typing the stream
name.
Name
The name of the Relief Valve. HYSYS provides a default designation for
the unit operation, however, you can edit this name at any time by
entering a new name in this field.
5-111
5-112
Relief Valve
Parameters Page
Figure 5.66
The Parameters page contains only two fields, which are described in
the table below:
Object
Description
Set Pressure
The pressure that the Relief Valve begins to open.
Full Open Pressure
The pressure that the Relief Valve is fully open.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer to
Section 7.20 - Notes
Manager in the User Guide.
5-112
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Piping Equipment
5-113
5.6.3 Rating tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Rating tab.
The Rating tab consists of two pages:
•
•
Sizing
Nozzles
Sizing Page
On the Sizing page, you can specify the Valve Type, and the Capacity
Correction Factors and Parameters.
Figure 5.67
Valve Type
In HYSYS, you can specify three different valve characteristics for any
Relief Valve in the simulation case.
Valve Type
Description
Quick Opening
A Relief Valve with quick opening valve characteristics obtains
larger flows initially at lower valve openings. As the valve opens
further, the flow increases at a smaller rate.
Linear
A Relief Valve with linear valve characteristics has a flow, which
is directly proportional to the valve % opening.
Equal Percentage
A Relief Valve with equal percentage valve characteristics initially
obtains very small flows at lower valve openings. However, the
flow increases rapidly as the valve opens to its full position.
5-113
5-114
Relief Valve
Capacity Correction Factors and Parameters
The Capacity Correction Factors and Parameters group consists of five
parameters of the flow equations. You can set:
•
•
•
•
•
Viscosity Coefficient (KV)
Discharge Coefficient (KD)
Back Pressure Coefficient (KB)
Valve Head Differential Coefficient
Orifice Area (A)
For more information on the function of these parameters, consult the
following section on flow through the Relief Valve.
Flow Through Relief Valve
The mass flowrate through the Relief Valve varies depending on the
vapour fraction and the pressure ratio across the valve. For two phase
flow, the flows are proportional to the vapour fraction and can be
calculated separately and then combined for the total flow.
Vapour Flow In Valve
For gases and vapours, flow may be choked or non-choked. If the
pressure ratio is greater than the critical, the flow is NOT choked:
P2
2
------ ≥ ------------P1
K+1
where:
P1 = upstream pressure
P2 = downstream pressure
K = ratio of Specific Heats
5-114
K
------------K–1
(5.51)
Piping Equipment
5-115
For Choked vapour flow, the mass flowrate is given by the following
relationship:
W = AK L K D K B
where:
P1 K 2
---------- ------------V1 K + 1
1
K + 1 --------------- 2
K–1
(5.52)
W = mass flow rate
A = relief valve orifice area
KL = capacity correction factor for valve lift
KD = coefficient of discharge
KB = back pressure coefficient
V1 = specific volume of the upstream fluid
For non-Choked vapour flow, the mass flowrate is given by:
2
K+1
---------------P
P2 K P2 K
1 2K
W = AK L K D  ------  -------------  ------ –  ------
 V 1  K – 1  P 1
 P 1

1
---
2



(5.53)
Liquid Flow In Valve
Liquid Flow through the valve is calculated using the following equation:
W = AK L K D K V [ 2 ( P 1 – P 2 )ρ 1 ]
where:
1
--2
(5.54)
ρ 1 = density of upstream fluid
KV = viscosity correction factor
5-115
5-116
Relief Valve
Capacity Correction Factor (KL)
The Capacity Correction Factor for back pressure is typically linear with
increasing back pressure. The correct value of the factor should be userspecified. It may be obtained from the valve manufacturer. The capacity
correction factor for valve lift compensates for the conditions when the
Relief Valve is not completely open. Increasing-sensitivity valves have
the following flow characteristics:
2
L
K L = -------------------------------------------4 1⁄2
[ a + ( 1 – a )L ]
(5.55)
Linear and decreasing-sensitivity valves have the following flow
characteristics:
L
K L = -------------------------------------------2 1⁄2
[ a + ( 1 – a )L ]
(5.56)
valve head differential a maximum flow
a = ----------------------------------------------------------------------------------------------valve head differential at zero flow
(5.57)
where:
The valve head differential term allows for customization of the flow
characteristics with respect to stem travel. Its value can range between 0
and 1.
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
5-116
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. Refer to Section 1.6.2 - Nozzles for more
information.
Piping Equipment
5-117
5.6.4 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
5.6.5 Dynamics Tab
If you are working exclusively
in Steady State mode, you are
not required to change any
information on the pages
accessible through the
Dynamics tab.
The Dynamics tab contains four pages:
•
•
•
•
Specs
Holdup
Advanced
Stripchart
Specs Page
The Specs page consists of two groups:
•
•
Dynamic Parameters
Hysterysis Parameters
Figure 5.68
5-117
5-118
Relief Valve
Dynamic Parameters Group
The Dynamic Parameters group consists of three parameters.
Parameter
Descriptions
Delta P
Pressure drop across the valve.
Valve Lift
The Relief Valve lift. It is calculated using one of the two
following formulas:
If inlet pressure is increasing:
P 1 – P OPEN
L = --------------------------------------P FULL – P OPEN
(5.58)
where: P1 = upstream pressure
POPEN = set pressure
PFULL = full open pressure
If inlet pressure is decreasing:
P 1 – P RESEAT
L = -----------------------------------------P CLOSE – P OPEN
(5.59)
where: P1 = upstream pressure
PRESEAT = reseating pressure
PCLOSE = closing pressure
Percentage Open
The Valve Lift in percentage.
Hysterysis Parameters Group
When the Enable Valve Hysterysis checkbox is activated, the Hysterysis
Parameters group appears. This group contains two fields, which are
described in the table below:
5-118
Field
Descriptions
Closing Pressure
Pressure that the valve begins to close after reaching the full lift
pressure (i.e., the value entered in the full pressure field on the
Parameters page of the Design tab).
Reseating Pressure
The pressure that the valve reseats after discharge.
Piping Equipment
5-119
Holdup Page
For more information on the Holdup page, refer to the valve operation
Holdup Page in the Chapter 5.5.5 - Dynamics Tab.
Advanced Page
The fail-safe function in Relief Valve is used to prevent pipeline and
equipment from physical damages due to escalation in pressure. The
plant operator can either apply this feature to relief the pressure builtup from affecting other parts of the plant or it can be used in their
training to simulate valve stickiness or failure.
The Relief Valve has five fail modes. The way that these fail modes
interact with the relief valve is somewhat different from the ones of the
control valve discussed in Chapter 1.6.3 - Control Valve Actuator.
Refer to Chapter 1.6 Fidelity in the Dynamic
Modeling manual for more
information on how to run the
integrator with
HYSYS.Fidelity.
To activate the relief valve fail mode option, ensure that the Integrator is
running with HYSYS.Fidelity. To set the Relief Valve in fail state, you can
check the Valve has Failed checkbox on the Advanced page. You can now
specify one of the following fail modes:
•
•
•
•
•
None. Relief valve operates as it is designed to be (same as the
operating condition when the Valve has Failed checkbox is not
active).
Fail Open. The valve lift completely opens. The valve lift remains
at maximum opening position even when the inlet pressure is not
longer above the opening (set) pressure. The Relief Valve
continues to fully open until it is reset.
Fail Shut. The valve lift completely closes. The valve life stays
shut even when the inlet pressure is above the opening (set)
pressure. The Relief Valve remains fully shut until it is reset.
Fail Hold. Allows you to simulate the valve lift stickiness by
holding the valve lift to the last failed position. The Relief Valve lift
will not move even when the inlet pressure is no longer above the
opening pressure.
Fail Specified. Allows you to manually specify the fail position
when the Relief Valve has failed. The fail position is expressed in
terms of percentage of the valve opening, and it is used to define
the amount of valve lift.
5-119
5-120
Relief Valve
Figure 5.69
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about stripcharts.
5-120
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Piping Equipment
5-121
5.7 References
1
Aziz, K., Govier, G.A., and Fogarasi, M., Pressure Drop in Wells Producing Oil
and Gas, Journal of Canadian Petroleum Technology, July-September 1972,
pp 38-48.
2
Baxendell, P.B., and Thomas, R., The Calculation of Pressure Gradients in HighRate Flowing Wells, J. Pet. Tech., October 1961, pp 1023-1028.
3
Beggs, H.D., and Brill, J.P., A Study of Two-Phase Flow in Inclined Pipes, J.
Petrol. Technol., p. 607, May (1973).
4
Brill, J.P., and Beggs, H.D., Two Phase Flow in Pipes, Sixth Ed, July 1989.
5
Brill, J.P., and Mukherjee, H., Multiphase Flow in Wells, SPE Monograph,
Volume 17.
6
Duns, H.Jr., and Ros, N.C.J., Vertical Flow of Gas and Liquid Mixtures in Wells,
6th World Petroleum Congress, Frankfurt, June 1963, pp 451-465.
7
Eckert, E.R.G. & Drake, R.M., “Analysis of heat and mass transfer”, HTFS
Reference Number 60167, 1972.
8
Gregory, G.A., Mandhane, J. and Aziz, K., Some Design Considerations for TwoPhase Flow in Pipes, J. Can. Petrol. Technol., Jan. - Mar. (1975).
9
Hagedorn, A.R., and Brown, K.E., Experimental Study of Pressure Gradients
Occurring During Continuous Two-Phase Flow in Small-Diameter Vertical
Conduits, Journal of Petroleum Technology, April 1965, pp 475-484.
10
HTFS Handbook, Volume 2, Methods TP3, TM4, TM5
11
HTFS Handbook, Volume 2, Two Phase Flow.
12 Multiphase
Flow and Subsea Separation. Special report by Smith Rea
Energy Associates and UKAEA, April 1989.
13 Orkisewski,
J., Predicting Two-Phase Pressure Drops in Vertical Pipe, Journal of
Petroleum Technology, June 1967, pp 829-839.
14
Poettmann, F.H., and Carpenter, P.G., The Multiphase Flow of Gas, Oil and
Water Through Vertical Flow Strings with Application to the Design of GasLift Installations, Drill and Prod. Practice, API, pp. 257-317, March 1952.
15
Smith, R.A. et al, Two Phase Pressure Drop, HTFS Design Report 28 (Revised),
1981 (8 parts, 2 Appendices).
16 Tengesdal,
J.Ø, Sarica, C., Schmidt, Z., and Doty, D., A Mechanistic Model for
Predicting Pressure Drop in Vertical Upward Two-Phase Flow, Journal of
Energy Resources Technology, March 1999, Vol 121.
17
Watson, M., The modelling of slug flow properties, 10th International
Conference Multiphase '01, Cannes, France, 13-15 June 2001.
5-121
5-122
5-122
References
Rotating Equipment
6-1
6 Rotating Equipment
6.1 Centrifugal Compressor or Expander............................................2
6.1.1
6.1.2
6.1.3
6.1.4
6.1.5
6.1.6
6.1.7
Theory......................................................................................4
Compressor or Expander Property View ...............................10
Design Tab............................................................................. 11
Rating Tab..............................................................................15
Worksheet Tab.......................................................................26
Performance Tab ...................................................................27
Dynamics Tab ........................................................................27
6.2 Reciprocating Compressor...........................................................37
6.2.1
6.2.2
6.2.3
6.2.4
6.2.5
6.2.6
6.2.7
Theory....................................................................................38
Reciprocating Compressor Property View.............................43
Design Tab.............................................................................44
Rating Tab..............................................................................48
Worksheet Tab.......................................................................49
Performance Tab ...................................................................49
Dynamics Tab ........................................................................50
6.3 Pump...............................................................................................50
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.3.7
Theory....................................................................................51
Pump Property View ..............................................................53
Design Tab.............................................................................54
Rating Tab..............................................................................58
Worksheet Tab.......................................................................64
Performance Tab ...................................................................64
Dynamics Tab ........................................................................65
6-1
6-2
Centrifugal Compressor or Expander
6.1 Centrifugal Compressor or
Expander
The Centrifugal Compressor operation is used to increase the pressure
of an inlet gas stream with relative high capacities and low compression
ratios. Depending on the information specified, the Centrifugal
Compressor calculates either a stream property (pressure or
temperature) or a compression efficiency.
A Centrifugal Compressor can also be used to represent a Pump
operation when a more rigorous pump calculation is required. The
Pump operation in HYSYS assumes that the liquid is incompressible.
Therefore, if you want to pump a fluid near its critical point (where it
becomes compressible), you can do so by representing the Pump with a
Centrifugal Compressor. The Centrifugal Compressor operation takes
into account the compressibility of the liquid, thus performing a more
rigorous calculation.
The Expander operation is used to decrease the pressure of a high
pressure inlet gas stream to produce an outlet stream with low pressure
and high velocity. An expansion process involves converting the internal
energy of the gas to kinetic energy and finally to shaft work. The
Expander calculates either a stream property or an expansion efficiency.
The operating
characteristics curves of a
compressor is usually
expressed as a set of
polytropic head and
efficiency curves made by
manufacturers.
6-2
There are several methods for the Centrifugal Compressor or Expander
to solve, depending on what information has been specified, and
whether or not you are using the compressor’s characteristic curves. In
general, the solution is a function of flow, pressure change, applied
energy, and efficiency. The Centrifugal Compressor or Expander
provides a great deal of flexibility with respect to what you can specify
and what it then calculates. You must ensure that you do not enable too
many of the solution options or inconsistencies may result.
Rotating Equipment
6-3
Some of the features in the dynamic Centrifugal Compressor and
Expander operations include:
•
•
•
•
•
•
•
Dynamic modeling of friction loss and inertia in the Centrifugal
Compressor or Expander.
Dynamic modeling which supports shutdown and startup
behaviour.
Multiple head and efficiency curves.
Modeling of Stonewall and Surge conditions of the Centrifugal
Compressor or Expander.
A dedicated surge controller which features quick opening
capabilities.
Handling of phase changes that may occur in the unit operation
(e.g. Expanders producing liquid).
Linking capabilities with other rotational equipment operating at
the same speed with one total power.
Typical Solution Methods
Without Curves
With Curves
1. Flow rate and inlet pressure are known.
1. Flow rate and inlet pressure are known.
2. Specify outlet pressure.
2. Specify operating speed.
3. Specify either Adiabatic or Polytropic efficiency.
3. HYSYS uses curves to determine efficiency and head.
4. HYSYS calculates the required energy, outlet
temperature, and other efficiency.
4. HYSYS calculates outlet pressure, temperature, and
applied duty.
1. Flow rate and inlet pressure are known.
1. Flow rate, inlet pressure, and efficiency are known.
2. Specify efficiency and duty.
2. HYSYS interpolates curves to determine operating speed
and head.
3. HYSYS calculates outlet pressure, temperature, and
other efficiency.
3. HYSYS calculates outlet pressure, temperature, and
applied duty.
The thermodynamic principles governing the Centrifugal Compressor
and Expander operations are the same, but the direction of the energy
stream flow is opposite. Compression requires energy, while expansion
releases energy.
6-3
6-4
Centrifugal Compressor or Expander
6.1.1 Theory
Steady State
Throughout this chapter you
will see “isentropic” and
“adiabatic” used
interchangeably. This is
because they are the same.
For a Centrifugal Compressor, the isentropic efficiency is given as the
ratio of the isentropic (ideal) power required for compression to the
actual power required:
Power Required isentropic
Efficiency ( % ) = ----------------------------------------------------------------- × 100%
Power Required actual
(6.1)
For an Expander, the efficiency is given as the ratio of the actual power
produced in the expansion process to the power produced for an
isentropic expansion:
Fluid Power Produced actual
Efficiency ( % ) = ----------------------------------------------------------------------------------- × 100%
Fluid Power Produced isentropic
(6.2)
For an adiabatic Centrifugal Compressor and Expander, HYSYS
calculates the centrifugal compression (or expansion) rigorously by
following the isentropic line from the inlet to outlet pressure. Using the
enthalpy at that point, as well as the specified efficiency, HYSYS then
determines the actual outlet enthalpy. From this value and the outlet
pressure, the outlet temperature is determined.
For a polytropic Centrifugal Compressor or Expander, the path of the
fluid is neither adiabatic nor isothermal. For a 100% efficient process,
there is only the condition of mechanical reversibility. For an
irreversible process, the polytropic efficiency is less than 100%.
Depending on whether the process is an expansion or compression, the
work determined for the mechanically reversible process is multiplied
or divided by an efficiency to give the actual work. The form of the
polytropic efficiency equations are the same as Equation (6.1) and
Equation (6.2).
6-4
Rotating Equipment
6-5
Notice that all intensive quantities are determined thermodynamically,
using the specified Property Package. In general, the work for a
mechanically reversible process can be determined from:.
W =
where:
∫ V dP
(6.3)
W = work
V = volume
dP = pressure difference
As with any unit operation, the calculated information depends on the
information which is specified by the user. In the case where the inlet
and outlet pressures and temperatures of the gas are known, the ideal
(isentropic) power of the Operation is calculated using one of the above
equations, depending on the Centrifugal Compressor or Expander type.
The actual power is equivalent to the heat flow (enthalpy) difference
between the inlet and outlet streams.
For the Centrifugal Compressor:
Power Requiredactual = Heat Flowoutlet - Heat Flowinlet
(6.4)
where the efficiency of the Centrifugal Compressor is then determined
as the ratio of the isentropic power to the actual power required for
compression.
For the Expander:
Power Producedactual = Heat Flowinlet - Heat Flowoutlet
(6.5)
The efficiency of the Expander is then determined as the ratio of the
actual power produced by the gas to the isentropic power.
In the case where the inlet pressure, the outlet pressure, the inlet
temperature and the efficiency are known, the isentropic power is once
again calculated using the appropriate equation. The actual power
required by the Centrifugal Compressor (enthalpy difference between
the inlet and outlet streams) is calculated by dividing the ideal power by
the compressor efficiency. The outlet temperature is then rigorously
6-5
6-6
Centrifugal Compressor or Expander
determined from the outlet enthalpy of the gas using the enthalpy
expression derived from the property method being used. For an
isentropic compression or expansion (100% efficiency), the outlet
temperature of the gas is always lower than the outlet temperature for a
real compression or expansion.
Dynamic
An essential concept associated with the Centrifugal Compressor and
Expander operations is the isentropic and polytropic power. The
calculation of these parameters and other quantities are taken from
“Compressors and Exhausters - Power Test Codes” from the American
Society of Mechanical Engineers.
The isentropic or polytropic power, W, can be calculated from:
-
P 2  ----------P1
n
n 
W = F 1 ( MW )  ------------ CF  ------ ×  ------
–1
 n – 1
 ρ 1
 P 1
n–1
where:
(6.6)
n = volume exponent
CF = correction factor
P1 =pressure of the inlet stream
P2 = pressure of the exit stream
ρ 1 = density of the inlet stream
F1 =molar flow rate of the inlet stream
MW = molecular weight of the gas
Isentropic power is calculated by defining the volume exponent as:
ln ( P 2 ⁄ P 1 )
n = --------------------------ln ( ρ’2 ⁄ ρ 1 )
where:
6-6
(6.7)
ρ′ 2 = density of the exit stream corresponding to the inlet entropy
Rotating Equipment
6-7
Polytropic power is calculated by defining the volume exponent as:
ln ( P 2 ⁄ P 1 )
n = -------------------------ln ( ρ 2 ⁄ ρ 1 )
where:
(6.8)
ρ 2 = density of the exit stream
The correction factor is calculated as:
h’2 – h 1
CF = ------------------------------------------n   P 2 P 1
 ----------- ------ – ----- n – 1  ρ' 2 ρ 1
where:
(6.9)
h′ 2 = enthalpy of the exit stream corresponding to the inlet entropy
h1 = enthalpy of the inlet stream
An isentropic flash is performed to calculate the values of h′ 2 and ρ′ 2 .
HYSYS calculates the compression (or expansion) rigorously by
following the isentropic line from the inlet to the exit pressure. The path
of a polytropic process is neither adiabatic nor isothermal. The only
condition is that the polytropic process is reversible.
Equations Used
The Centrifugal Compressor equations are used for the Centrifugal
Compressor. The Expander equations are used for the Expander.
Compressor Efficiencies
The Adiabatic and Polytropic Efficiencies are included in the Centrifugal
Compressor calculations. An isentropic flash (Pin and Entropyin) is
performed internally to obtain the ideal (isentropic) properties.
6-7
6-8
Centrifugal Compressor or Expander
Expander Efficiencies
For an Expander, the efficiencies are parts of the Expander calculations,
and an isentropic flash is performed as well. The flash is done on the
Expander fluid, and the results are not stored.
Efficiencies
Compressor
Expander
Adiabatic
( H out – H in )
Work Required
( ideal )
( ideal )
---------------------------------------------------------- = -------------------------------------------------------Work Required ( actual )
( H out – H in )
( actual )
Polytropic
 P out
 ------------
 P in 
–1
n
------------
 n 
( H out – H in )
Work Produced
( actual )
( actual )
------------------------------------------------------------ = -------------------------------------------------------Work Produced ( ideal )
( H out – H in )
( ideal )
 P out
 ------------
 P in 
n
k–1
– 1 ×  ---------------- ×  -----------
 ( n – 1 )  k 
------------------------------------------------------------------------------------------------------------ × AdiabaticEff
– 1
 k--------- k 
 P out
–1
 ------------
 P in 
where:
– 1
 k--------- k 
–1
------------------------------------------------------------------------------------------------------------ × AdiabaticEff
–1
n
------------
 n 
 P out
n
k–1
– 1 ×  ---------------- ×  -----------
 ------------
 ( n – 1 )  k 
 P in 
where:
log ( P out ⁄ P in )
n = ---------------------------------------------------------log ( ρ
⁄ρ )
out, actual in
log ( P out ⁄ P in )
n = ---------------------------------------------------------log ( ρ
⁄ρ )
out, actual in
log ( P
⁄P )
out in
k = -----------------------------------------------------log ( ρ
⁄ρ )
out, ideal in
log ( P
⁄P )
out in
k = -----------------------------------------------------log ( ρ
⁄ρ )
out, ideal in
where: H = mass enthalpy
P = pressure
out = product discharge
ρ = mass density
in = feed stream
n = polytropic exponent
k = isentropic exponent
Compressor Heads
The Adiabatic and Polytropic Heads are performed after the Centrifugal
Compressor calculations are completed, only when the Results page of
the Centrifugal Compressor is selected. The Work Required (actual) is
the compressor energy stream (heat flow). The Polytropic Head is
calculated based on the ASME method (“The Polytropic Analysis of
Centrifugal Compressors”, Journal of Engineering for Power, J.M.
Schultz, January 1962, p. 69-82).
6-8
Rotating Equipment
6-9
Expander Heads
The Adiabatic and Polytropic Heads are performed after the Expander
calculations are completed, only when the Results page of the Expander
is selected. The Work Produced (actual) is the Expander energy stream
(heat flow).
Head
Compressor
Expander
Adiabatic
Work Required ( actual )
1
---------------------------------------------------------- × AdiabaticEff × ----------------MassFlowRate
(g ⁄ g )
c
Polytropic
P

  P in
n
1
out
f ×  ------------ ×  ------------------------------- –  --------- × ---------------- n – 1
ρ
(g ⁄ g )
 out ,actual  ρ in
c
where:
Work Produced ( actual )
1
1
------------------------------------------------------------ × ----------------------------------- × ----------------MassFlowRate
AdiabaticEff ( g ⁄ g )
c
n 
- ×
– f ×  n----------– 1
P

  P in
1
out
 ------------------------------- –  --------- × ----------------ρ
(g ⁄ g )
 out ,actual  ρ in
c
where:
H
–H
out ,ideal
in
f = ----------------------------------------------------------------------------------P
P 


out
in
k
 ----------- ×  --------------------------- –  --------
 k – 1
 ρ out ,ideal  ρ in
log ( P
⁄P )
out in
n = ---------------------------------------------------------log ( ρ out, actual ⁄ ρ in )
log ( P
⁄P )
out in
k = -----------------------------------------------------log ( ρ out, ideal ⁄ ρ in )
where: H = mass enthalpy
H
–H
out ,ideal
in
f = ----------------------------------------------------------------------------------P

k 
out   P in
 ---------- ×  --------------------------- –  ---------
 k – 1
 ρ out ,ideal  ρ in
log ( P
⁄P )
out in
n = ---------------------------------------------------------log ( ρ out, actual ⁄ ρ in )
log ( P
⁄P )
out in
k = -----------------------------------------------------log ( ρ out, ideal ⁄ ρ in )
ρ = mass density
out = product discharge
f = polytropic head factor
in = feed stream
n = polytropic exponent
P = pressure
k = isentropic exponent
6-9
6-10
Centrifugal Compressor or Expander
6.1.2 Compressor or Expander Property View
You can also add a
compressor or expander by
clicking the F12 hot key.
There are two ways that you can add a Compressor or Expander to your
simulation:
You can also open the
Object Palette by clicking
the F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Rotating Equipment radio button.
3.
From the list of available unit operations, select Compressor or
Expander.
4.
Click the Add button. The Compressor or Expander property view
appears.
OR
Compressor icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Compressor icon or Expander icon. The
Compressor or Expander property view appears.
The figure below shows the Expander property view.
Figure 6.1
Expander icon
To ignore the Centrifugal Compressor or Expander during calculations,
activate the Ignored checkbox. HYSYS completely disregards the
operation until you restore it to an active state by deactivating the
checkbox.
6-10
Rotating Equipment
6-11
6.1.3 Design Tab
The Design tab contains five pages:
•
•
•
•
•
Connections
Parameters
Links
User Variables
Notes
Connections Page
The information required on
the Connections page of the
Expander is identical; the
only difference is that the
Expander icon is shown
rather than the Compressor
icon.
The figure below shows the Connections page for the Centrifugal
Compressor property view.
Figure 6.2
The Connections page allows you to specify the name of the operation,
as well as the inlet stream, outlet stream, and energy stream.
6-11
6-12
Centrifugal Compressor or Expander
Parameters Page
You can specify the duty of the attached energy stream on the
Parameters page, or allow HYSYS to calculate it.
Figure 6.3
The adiabatic and polytropic efficiencies appear on this page as well.
You can specify only one efficiency, either adiabatic or polytropic. If you
specify one efficiency and a solution is obtained, HYSYS back
calculates the other efficiency, using the calculated duty and stream
conditions.
The only difference between the Parameters page for the Compressor
and the Expander are the Operating Mode group and MW Operation
Mode group that are present in the compressor view. In the compressor
view you can switch between a Centrifugal and Reciprocating
Compressor by selecting the corresponding radio button. If you choose
the Centrifugal radio button, the radio buttons in the MW Operation
Mode group are enabled. From the MW Operation Mode group, choose
either the Single MW (molecular weight) or Multiple MW radio button
based on the amount of information you have regarding the molecular
weight of the components within your streams.
6-12
Rotating Equipment
6-13
Links Page
The rotational equipment
linker operates both in
Steady State and Dynamic
mode.
Compressors and expanders modeled in HYSYS can have shafts that are
physically connected to the unit operation. Linking compressors and
expanders in HYSYS means the:
•
•
Speed of each linked unit operation is the same.
Sum of the duties of each linked Compressor or Expander and
the total power loss equals zero.
The figure below shows compressor K-100 linked to compressor K-101.
It is not significant which order the Compressors or Expanders are
linked. The notion of upstream and downstream links is arbitrary and
determined by the user.
Figure 6.4
A list of available compressors or expanders can be displayed by clicking
the down arrow in the Downstream Link field. In most cases, one
additional specification for any of the linked operations is required to
allow the simulation case to completely solve. Ideally, you should
specify one of the following for any of the linked unit operations.
•
•
•
Duty
Speed
Total Power Loss
It is also possible to link an Expander to a Compressor, and use the
Expander to generate kinetic energy to drive the Compressor. If this
option is chosen, the total power loss is typically specified as zero.
6-13
6-14
Centrifugal Compressor or Expander
Dynamics Mode
In Dynamics mode, at least one curve must be specified in the Curves
page of the Rating tab for each linked unit operation. Ideally, a set of
linked compressor or expanders should only have the Use Characteristic
Curves checkbox activated in the Specs page of the Dynamics tab. In
addition, the total power loss for the linked operations should be
specified. Usually, total power input to the linked compressors or
expanders is calculated in a Spreadsheet operation and specified by you
in the Total Power Loss field.
If you want to provide the total power input to a set of linked
compressors or expanders, the total power input to the linked
operations is defined in terms of a total power loss. The relationship is
as follows:
Total Power Input = - Total Power Loss
(6.10)
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
6-14
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Rotating Equipment
6-15
6.1.4 Rating Tab
The Rating tab contains four pages:
The Nozzles page is only
visible if you have the
Fidelity license.
•
•
•
•
Curves
Flow Limits
Nozzles
Inertia
Curves Page
One or more Centrifugal Compressor or Expander curves can be
specified on the Curves page. You can create adiabatic or polytropic
plots for values of efficiency and head. The efficiency and head for a
specified speed can be plotted against the capacity of the Centrifugal
Compressor or Expander. Multiple curves can be plotted to show the
dependence of efficiency and head on the speed of Centrifugal
Compressors or Expanders.
Figure 6.5
6-15
6-16
Centrifugal Compressor or Expander
If you do not use curves, specify four of the following variables, and the
fifth is calculated, along with the duty:
•
•
•
•
•
Inlet Temperature
Inlet Pressure
Outlet Temperature
Outlet Pressure
Efficiency
It is assumed that you have specified the composition and flow.
Single MW
If you choose the Single MW (molecular weight) radio button on the
Parameters page of the Design Tab, the only group visible on the Curves
page is the Compressor Curves group.
Figure 6.6
Entering Curve Data
The following are steps to add a curve to the compressor or expander:
1.
6-16
Select either the Adiabatic or Polytropic radio button in the
Efficiency group. This determines the basis of your input efficiency
values. The efficiency type must be the same for all input curves.
Rotating Equipment
2.
6-17
Click the Add Curve button and the Curve view appears.
Figure 6.7
3.
HYSYS can interpolate values
for the efficiency and head of
the Centrifugal Compressor or
Expander for speeds that are
not plotted.
Close icon
You can specify the following data in the Curve view.
Curve Data
Description
Name
Name of the curve.
Speed
The rotational speed of the Centrifugal Compressor or
Expander. This is optional if you specify only one curve.
Flow Units/Head Units
Units for the flow and head.
Flow/Head/% Efficiency
One row of data is equivalent to one point on the curve. For
better results, you should enter data for at least three (or
more) points on the curve.
4.
Click the Close icon to return to the Curves page.
5.
Click the corresponding Activate checkbox to use that curve in
calculations.
6.
For each additional curve, repeat steps #2 to #5.
7.
Click the Enable Curves checkbox.
You can remove a specific curve from the calculation by disabling its
Activate checkbox.
HYSYS uses the curve(s) to determine the appropriate efficiency for your
operational conditions. If you specify curves, ensure the efficiency
values on the Parameters page are empty or a consistency error will be
generated.
6-17
6-18
Centrifugal Compressor or Expander
Once a curve has been created, the following three buttons on the
Curves page are enabled:
•
•
•
View Curve. Allows you to view or edit your input data in the
Curve view.
Delete Curve. Allows you to delete the selected curve from the
simulation.
Plot Curves. Allows you to view a graph of activated curves.
You can access the Curve view of an existing curve by clicking the View
Curve button or by double-clicking the curve name.
Deleting Curve Data
The following are two ways you can delete information within a curve:
1.
Double-click the curve name to open the Curve view.
2.
Highlight the data you want to delete and click the Erase Selected
button.
OR
3.
Select the curve within the table and click the View Curve button.
4.
Click the Erase All button to delete all of the information within the
Curve view.
Single Curve
When you have a single curve, the following combinations of input
allow the operation to completely solve (assuming the feed composition
and temperature are known):
•
•
•
•
6-18
Inlet Pressure and Flow Rate
Inlet Pressure and Duty
Inlet Pressure and Outlet Pressure
Inlet Pressure and Efficiency corresponding to the Curve type
(e.g., if the Curve is Adiabatic, provide an Adiabatic Efficiency).
Rotating Equipment
6-19
Multiple Curves
If multiple curves have been installed, an operating speed is specified on
the Curves page, and one of the multiple curves’ speed equals the
operating speed, then only the curve with the corresponding speed is
used. For example, if you provide curves for two speeds (1000/min and
2000/min), and you specify an operating speed of 1000/min, then only
the curve with the speed of 1000/min is used within the calculation.
If multiple curves have been installed, an operating speed has been
specified, and none of the multiple curves’ speed equals the operating
speed, then all of the curves will be used within the calculation. For
example, if you provide curves for two speeds (1000/min and 2000/
min), and you specify an operating speed of 1500/min, HYSYS
interpolates between the two curves to obtain the solution. You must
also provide an inlet pressure and one of the following variables: flow
rate, duty, outlet pressure, or efficiency, as explained above.
HYSYS can calculate the appropriate speed based on your input. In this
case, you need to provide the feed composition, pressure, and
temperature as well as two of the following four variables:
•
•
•
•
Flow rate
Duty
Efficiency
Outlet Pressure
Once you provide the necessary information, the appropriate speed is
determined, and the other two variables are then calculated.
6-19
6-20
Centrifugal Compressor or Expander
Dynamics Mode
In order to run a stable and realistic dynamics model, HYSYS requires
you to input reasonable curves. If compressors or expanders are linked,
it is a good idea to ensure that the curves plotted for each unit operation
span a common speed and capacity range. Typical curves are plotted in
Figure 6.8 and Figure 6.9.
Figure 6.8
6-20
Rotating Equipment
6-21
For an Expander, the head is only zero when the speed and capacity are
zero.
Figure 6.9
Multiple MW
This option is only relevant for
compressors and not
expanders.
The Multiple MW (molecular weight) option is for more advanced users
of HYSYS. This option provides your case with an example scenario if
the molecular weight of the components within the stream get heavier
or lighter.
6-21
6-22
Centrifugal Compressor or Expander
When you choose the Multiple MW radio button on the Parameters
page of the Design tab, the MW Curve Collections group is added to the
Curves page.
Figure 6.10
The following is a brief description of the fields and buttons found
within the MW Curve Collections group.
6-22
Fields
Description
Curve Collections
Each curve collection holds data for the curves in the adjacent
table.
Design MW
The Design MW is the designed average molecular weight for
the compressor. Its default value is the same as the value for
the Actual MW.
Curve MW
Each curve collection has its corresponding Curve MW. The
following are descriptions of three potential Curve MW
situations:
• If the value is the same as the Design MW, it means the
compressor is operating with components at your
designed MW.
• If the value is less than the Design MW value, it means
the compressor is operating with lighter components.
• If the value is more than the Design MW value, it means
the compressor is operating with heavier components.
Actual MW
This value is calculated by HYSYS. The field displays the
actual MW of the stream within your case.
Buttons
Description
Add Curve Collection
Adds another curve collection to the Curve Collections field
Rotating Equipment
Buttons
Description
Del. Curve Collection
Deletes the selected curve collection in the Curve Collections
field.
Set Simple Curves
Once data has been entered for CurveCollection-1, clicking
this button will add two more curve collections. The data
within these curve collections are based on the data of
CurveCollection-1. These estimated values for
CurveCollection-2 and 3 are for testing purposes only. You
need to modify these data accordingly to determine the
definite curve values.
6-23
Creating Multiple Curve Collections
The following two ways are how you can create multiple curve
collections:
1.
Enter the data for the curve(s). (Refer to Entering Curve Data for
more information.) All of these values will be stored under
CurveCollection-1.
2.
Click the Set Simple Curves button.
3.
Two hypothetical curve collections will appear (named
CurveCollection-2 and CurveCollection-3). These two new
collections will provide you with rough data for curves generated
with lighter or heavier components. These estimated values are
based on the values entered for CurveCollection-1.
The values given in CurveCollection-2 and CurveCollection-3 are for
testing purposes only. You need to modify the data accordingly in order
to determine the definite curve values.
OR
4.
Enter the data for the curve(s). (Refer to Entering Curve Data for
more information.) All of these values will be stored under
CurveCollection-1.
5.
Click the Add Curve Collection button.
6.
Repeat step #4 to enter the data for the new curve collection.
7.
Repeat steps #5 to #6 for each additional curve collection.
6-23
6-24
Centrifugal Compressor or Expander
Flow Limits Page
If you are working exclusively
in Steady State mode, you
are not required to change
any information on the Flow
Limits page.
There is a certain range that the dynamic Centrifugal Compressors or
Expanders can operate in depending on its operating speed. The lower
flow limit of a Centrifugal Compressor is called the surge limit, whereas
the upper flow limit is called the stonewall limit. In HYSYS, you can
specify the flow limits of a Centrifugal Compressor or Expander by
plotting surge and stonewall curves.
Figure 6.11
From the Flow Limits page, it is possible to add Surge or Stonewall
curves for the Centrifugal Compressor.
Adding a Surge Curve
To add or edit a Surge curve, follow this procedure:
6-24
1.
Click the Surge Curve button. The Surge flow curve view appears.
2.
From the Speed Units drop-down list, select the units you want to
use for the speed measurements.
3.
From the Flow Units drop-down list, select the units you want to use
for the flow measurements.
4.
Specify the speed and flow data points for the curve.
Rotating Equipment
5.
6-25
Once you have entered all the data points, click the Close icon to
return to the Compressor or Expander property view.
Figure 6.12
Close icon
6.
Activate the Use Surge Curve checkbox to use the surge curve for
the compressor or expander calculations.
Editing a Surge Curve
To edit the information within a surge curve, do the following:
1.
Click the Surge Curve button. The Surge flow curve view appears.
2.
To remove a certain data point, select either the speed cell or flow
cell, and click the Erase Selected button.
OR
3.
To remove all the data points, click the Erase All button.
The procedure for adding or editing a Stonewall curve is similar to the
procedure for adding or editing a Surge curve.
When a dynamic Centrifugal Compressor reaches its stonewall limit,
HYSYS fixes the flow at that Centrifugal Compressor speed. When a
Centrifugal Compressor reaches the surge limit, the flow reverses and
cycles continuously causing damage to the Centrifugal Compressor.
This phenomenon is modeled in HYSYS by causing the flow rate
through the Centrifugal Compressor to fluctuate randomly below the
surge flow.
6-25
6-26
Centrifugal Compressor or Expander
Nozzles Page
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the Nozzles page.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. The Fidelity license is required to use the
Nozzle features found on this page. Refer to Section 1.6 - Fidelity in the
Dynamic Modeling manual for more information.
For a Centrifugal Compressor or Expander unit operation it is strongly
recommended that the elevation of the inlet and exit nozzles are equal.
If you want to model static head, the entire piece of equipment can be
moved by modifying the Base Elevation relative to Ground Elevation
field.
Inertia Page
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the Inertia page.
The inertia modeling parameters and the friction loss associated with
the impeller in the Centrifugal Compressor can be specified on the
Inertia page. The Fidelity license is required to use the Inertia features
found on this page. Refer to Section 1.6 - Fidelity in the Dynamic
Modeling manual for more information.
6.1.5 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
6-26
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Centrifugal
Compressor or Expander. Refer to Section 1.2.3 - Worksheet Tab for
more information.
Rotating Equipment
6-27
6.1.6 Performance Tab
The Performance page consists of the Results page.
Results Page
On the Results page, you can view a table of calculated values for the
Centrifugal Compressor or Expander:
•
•
•
•
•
•
•
•
•
•
•
•
Adiabatic Head
Polytropic Head
Adiabatic Efficiency
Polytropic Efficiency
Power Consumed (Power Produced for Expander)
Friction Loss
Rotational Inertia
Fluid Power
Polytropic Head Factor
Polytropic Exponent
Isentropic Exponent
Speed
6.1.7 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through this tab
The Dynamics tab contains the following three pages:
•
•
•
Specs
Holdup
Stripchart
6-27
6-28
Centrifugal Compressor or Expander
Specs Page
The dynamic specifications of the Centrifugal Compressor or Expander
can be specified on the Specs page.
Figure 6.13
In general, two specifications are required in the Dynamics
Specifications group. You should be aware of specifications which may
cause complications or singularity in the pressure flow matrix. Some
examples of such cases are:
•
•
6-28
The Pressure Increase checkbox should not be activated if the
inlet and exit stream pressures are specified.
The Speed checkbox should not be activated if the Use
Characteristic Curves checkbox is not activated.
Rotating Equipment
6-29
The possible dynamic specifications are as follows:
Duty
The duty is defined, in the case of the Centrifugal Compressor
operation, as the power required to rotate the shaft and provide energy
to the fluid. The duty has three components:
Duty = Power imparted to the fluid + Power required to
change the rotational speed of the shaft + Power
lost due to mechanical friction loss
(6.11)
The duty in a Centrifugal Compressor should be specified only if there is
a fixed power available to be used to drive the shaft.
Efficiency (Adiabatic and Polytropic)
For a dynamic Centrifugal Compressor, the efficiency is given as the
ratio of the isentropic power required for compression to the actual
energy imparted to the fluid. The efficiency, η , is defined as:
W ( to system )
η = ----------------------------------------F 1 ( MW ) ( h 2 – h 1 )
where:
(6.12)
W = isentropic power
F1 = molar flow rate of the inlet gas stream
MW = molecular weight of the gas
h1 = inlet head
h2 = outlet head
For a dynamic Expander, the efficiency, η , is defined as:
F 1 ( MW ) ( h 1 – h 2 )
η = -----------------------------------------W ( from system )
(6.13)
6-29
6-30
Centrifugal Compressor or Expander
If a polytropic efficiency definition is required, the polytropic work
should be provided in Equation (6.12) or Equation (6.13). If an adiabatic
efficiency definition is required, the isentropic work should be provided.
The general definition of the efficiency does not include the losses due
to the rotational acceleration of the shaft and seal losses. Therefore, the
efficiency equations in dynamics are not different from the general
efficiency equations defined in Section 6.1.1 - Theory. This is true since
the actual work required by a steady state Centrifugal Compressor is the
same as the energy imparted to the fluid.
If the Centrifugal Compressor or Expander curves are specified in the
Curves page of the Rating tab, the adiabatic or polytropic efficiency can
be interpolated from the flow of gas and the speed of the Centrifugal
Compressor or Expander.
Pressure Increase
A Pressure Increase specification can be selected if the pressure drop
across the Centrifugal Compressor is constant.
Head
The isentropic or polytropic head, h, can be defined as a function of the
isentropic or polytropic work. The relationship is:
W = ( MW )F 1 ( CF )gh
where:
(6.14)
W = isentropic or polytropic power
MW = molecular weight of the gas
CF = correction factor
F1 = molar flow rate of the inlet gas stream
g = gravity acceleration
If the Centrifugal Compressor or Expander curves are provided in the
Curves page of the Rating tab, the isentropic or polytropic head can be
interpolated from the flow of gas and the speed of the Centrifugal
Compressor or Expander.
6-30
Rotating Equipment
6-31
Capacity
The capacity is defined as the actual volumetric flow rate entering the
Centrifugal Compressor or Expander. A capacity specification can be
selected if the volumetric flow to the unit operation is constant.
Speed
The rotational speed of the shaft, ω , driving the Centrifugal Compressor
or being driven by the Expander can be specified.
Shift to Reciprocating Compressor (Positive Displacement)
Activate the Reciprocating (Positive Displacement) checkbox if you
want to change the Centrifugal Compressor to a Reciprocating
Compressor. You can change the Centrifugal Compressor to a
Reciprocating Compressor at any time. The reciprocating checkbox
option is only available with the compressor unit operation, refer to
Section 6.2 - Reciprocating Compressor for more information.
Use Characteristic Curves
Activate the Use Characteristic Curves checkbox, if you want to use the
curve(s) specified in the Curves page of the Rating tab. If a single curve is
specified in a dynamics Centrifugal Compressor, the speed of the
Centrifugal Compressor is not automatically set to the speed of the
curve (unlike the steady state Centrifugal Compressor or Expander unit
operation). A different speed can be specified and HYSYS extrapolates
values for head and efficiency.
6-31
6-32
Centrifugal Compressor or Expander
Surge Controller
The Create Surge Controller button on the Specs page of the Dynamics
tab opens a Surge Controller view (which is owned by the Centrifugal
Compressor). If you decide to delete the Centrifugal Compressor, the
surge controller associated with the Centrifugal Compressor is deleted
as well. The surge controller also works exclusively with Centrifugal
Compressor and Expander unit operations.
Figure 6.14
As mentioned, a Centrifugal Compressor surges if its capacity falls
below the surge limit. The surge controller determines a minimum
volumetric flow rate that the Centrifugal Compressor should operate at
without surging. This is called the surge flow. The surge controller then
attempts to control the flow to the Centrifugal Compressor at some
percent above the surge flow (this is typically 10%). The surge controller
essentially acts like PID Controller operations. The control algorithms
used to prevent Centrifugal Compressors from surging are extensions of
the PID algorithm. There are two major differences which distinguish a
surge controller and a regular controller:
•
•
6-32
The setpoint of the surge controller is calculated and not set.
More aggressive action is taken by the surge controller if the
Centrifugal Compressor is close to surging.
Rotating Equipment
6-33
Connections Tab
For more information on the
individual parameters which
make up the Connections
tab, refer to Chapter 12 Logical Operations
The Connections tab is very similar to a PID controller’s Connections
tab. The inlet volumetric flow to the Centrifugal Compressor is
automatically defaulted as the process variable (PV) to be measured.
You must select a Control Valve operation as an operating variable (OP),
which has a direct effect on the inlet flow to the Centrifugal Compressor.
The Upstream Surge Controller Output field contains a list of the other
surge controllers in the simulation flowsheet. If you select an upstream
surge controller using the Upstream Surge Controller Output field,
HYSYS ensures that the output signal of the Centrifugal Compressor’s
surge controller is not lower than an upstream surge controller’s output
signal.
Consider a situation in which two compressors are connected in series.
Figure 6.15
As shown in the figure above, both surge controllers must use the same
valve for surge control. If the surge controllers are connected in this
manner HYSYS autoselects the largest controller output. This is done to
ensure that surge control is adequately provided for both compressors.
6-33
6-34
Centrifugal Compressor or Expander
Parameters Tab
The parameters tab consists of two pages:
•
•
Configuration
Surge Control
Configuration Page
If the process variable (PV) is operating above a certain margin over the
surge flow limit, the surge controller operates exactly as a PID
Controller. Therefore, PID control parameters should be set on the
Configuration page. The process variable range, the controller action,
operation mode, and the tuning parameters of the controller can be set
in this page. For more information on the individual fields in the
Configuration page, refer to Section 12.4.4 - PID Controller.
Surge Control Page
Various surge control parameters can be specified on the Surge Control
page.
Figure 6.16
6-34
Rotating Equipment
6-35
A head versus quadratic flow expression relates the surge flow to the
head of the Centrifugal Compressor. The surge flow, FS, is calculated as
follows:
FS ( m 3 ⁄ s ) =
where:
h(m) – A
---------------------B
(6.15)
h(m) = head of the Centrifugal Compressor
A, B = parameters used to characterize the relationship between surge
flow and head
You can enter surge flow parameters A and B in order to characterize the
relationship between the surge flow and head.
The next three parameters in the Surge Control Parameters section are
defined as follows:
Surge Control Parameter
Description
Control Line (%)
The primary setpoint for the surge controller. This line is
defaulted at 10% above the surge flow. If the flow is
above the backup line then the surge controller acts as a
normal PID controller.
Backup Line (%)
Set somewhere between the control line and the surge
flow. This line is defaulted at 5% above the surge flow. If
the flow to the Centrifugal Compressor falls below the
backup line, more aggressive action is taken by the
controller to prevent a surge condition.
Quick Opening (%/sec)
Aggressive action is taken by increasing the desired
actuator opening at a rate specified in this field until the
volumetric flow to the Centrifugal Compressor rises above
the backup line.
Monitor Tab
The Monitor tab displays a chart that graphs the three variables (PV, SP,
and OP) of the surge controller
6-35
6-36
Centrifugal Compressor or Expander
User Variables Tab
You can create and implement you own User Variables for use in a
HYSYS simulation on the User Variables tab. For more information on
the User Variables refer to Chapter 5 - User Variables in the
Customization Guide.
Holdup Page
Typical Centrifugal Compressors and Expanders in actual plants usually
have significantly less holdup than most other unit operations in a
plant. Therefore, the volume of the Centrifugal Compressor or Expander
operation in HYSYS cannot be specified and is assumed to be zero on
the Holdup page.
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about stripcharts.
6-36
The Stripchart page allows you to set up the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Rotating Equipment
6-37
6.2 Reciprocating Compressor
In Section 6.1 - Centrifugal Compressor or Expander a Centrifugal
Compressor type is presented. The following section discusses a
Reciprocating Compressor. A Reciprocating Compressor is just another
type of compressor used for applications where higher discharge
pressures and lower flows are needed. It is known as a positive
displacement type. Reciprocating Compressors have a constant volume
and variable head characteristics, as compared to the Centrifugal
Compressor that has a constant head and variable volume.
For Reciprocating
Compressors there is no
direct relationship between
the head and flow capacity.
In HYSYS, Centrifugal and Reciprocating Compressors are accessed via
the same compressor unit operation. However, the solution methods
differ slightly as a Reciprocating Compressor does not require a
compressor curve and the required geometry data. The present
capability of Reciprocating Compressors in HYSYS is focused on a single
stage compressor with a single or double acting piston. A typical
solution method for a Reciprocating Compressor is as follows:
•
•
•
•
Always start with a fully defined inlet stream, e.g., inlet pressure,
temperature, flow rate, and compositional data are known.
Specify compressor geometry data, i.e., number of cylinders,
cylinder type, bore, stroke, and piston rod diameter. HYSYS
provides default values too.
Compressor performance data, i.e, adiabatic efficiency or
polytropic efficiency, and constant volumetric efficiency loss are
specified.
HYSYS calculates the duty required, outlet temperature if the
outlet pressure is specified.
Some of the features in the dynamic Reciprocating Compressor unit
operation include:
•
•
•
•
Dynamic modeling of friction loss and inertia.
Dynamic modeling which supports shutdown and startup
behaviour.
Dynamic modeling of the cylinder loading.
Linking capabilities with other rotational equipment operating at
the same speed with one total power.
6-37
6-38
Reciprocating Compressor
6.2.1 Theory
In a single stage Reciprocating Compressor, it comprises of the basic
components like the piston, the cylinder, head, connecting rod,
crankshaft, intake valve, and exhaust valve. This is illustrated in Figure
6.17. HYSYS is capable of modeling a multi-cylinder in one
Reciprocating Compressor with a single acting or double acting piston.
A single acting compressor has a piston that is compressing the gas
contained in the cylinder using one end of the piston only. A double
acting compressor has a piston that is compressing the gas contained in
the cylinder using both ends of the piston. The piston end that is close to
the crank is called crank end, while the other is named as outer.
Figure 6.17
The thermodynamic calculations for a Reciprocating Compressor are
the same as a Centrifugal Compressor. Basically, there are two types of
compression being considered:
•
•
Isentropic/adiabatic reversible path. A process during which
there is no heat added to or removed from the system, and the
entropy remains constant. PVk=constant, where k is the ratio of
the specific heat (Cp/Cv).
Polytropic reversible path. A process in which changes in the
gas characteristic during compression are considered.
Details of the equation are found in Section 6.1.1 - Theory. Reference1
has the information about the operation of the Reciprocating
Compressor.
The performance of the Reciprocating Compressor is evaluated based
on the volumetric efficiency, cylinder clearance, brake power, and duty.
6-38
Rotating Equipment
6-39
Cylinder clearance, C, is given as
Sum of all clearance volume for all cylinders
C = -----------------------------------------------------------------------------------------------------------PD
where:
(6.16)
PD = positive displacement volume
The sum of all clearance volume for all cylinders includes both fixed and
variable volume. C is normally expressed in a fractional or percentage
form.
The piston displacement, PD, is equal to the net piston area multiplied
by the length of piston sweep in a given period of time. This
displacement can be expressed as follows:
For a single-acting piston compressing on the outer end only:
2
π ⋅ D ⋅ stroke
PD = --------------------------------4
(6.17)
For a single-acting piston compressing on the crank end only:
2
2
π ⋅ ( D – d ) ⋅ stroke
PD = -------------------------------------------------4
(6.18)
For double-acting piston (other than tail rod type):
2
2
π ⋅ ( 2D – d ) ⋅ stroke
PD = ----------------------------------------------------4
(6.19)
For a double-acting piston (tail rod type):
2
2
π ⋅ ( 2D – 2d ) ⋅ stroke
PD = --------------------------------------------------------4
where:
(6.20)
d = piston rod diameter
D = piston diameter
6-39
6-40
Reciprocating Compressor
PD includes the contributions from all cylinders and both ends of any
double acting. If a cylinder is unloaded then its contribution does not
factor in.
The volumetric efficiency is one of the important parameters used to
evaluate the Reciprocating Compressor’s performance. Volumetric
efficiency, VE, is defined as the actual pumping capacity of a cylinder
compared to the piston displacement volume. VE is given by:
1
---
Zs Pd k
VE = ( 1 – L ) – C -----  ------ – 1
Zd  Ps
where:
(6.21)
Pd = discharge pressure
Ps = suction pressure
L = effects of variable such as internal leakage, gas friction, pressure
drop through valves, and inlet gas preheating
k = heat capacity ratio, Cp/Cv
Zd = discharge compressibility factor
Zs = suction compressibility factor
C = clearance volume
To account for losses at the suction and discharge valve, an arbitrary
value about 4% VE loss is acceptable. For a non-lubricated compressor,
an additional 5% loss is required to account for slippage of gas. If the
compressor is in propane, or similar heavy gas service, an additional 4%
should be subtracted from the volumetric efficiency. These deductions
for non-lubricated and propane performance are both approximate,
and if both apply, cumulative. Thus, the value of L varies from (0.04 to
0.15 or more) in general.
6-40
Rotating Equipment
6-41
Rod Loading
Rod loads are established to limit the static and inertial loads on the
crankshaft, connecting rod, frame, piston rod, bolting, and projected
bearing surfaces.
Figure 6.18
It can be calculated as follows:
Load in compression, Lc
Lc = Pd Ap – Ps ( Ap – Ar )
(6.22)
Lt = Pd ( Ap – Ar ) – Ps Ap
(6.23)
Load in tension, Lt
Maximum Pressure
The maximum pressure that the Reciprocating Compressor can achieve
is:
P max = P s ⋅ PR max
(6.24)
6-41
6-42
Reciprocating Compressor
where the maximum discharge pressure ratio, PRmax, is calculated from:
Zd
PR max = ------------- ( 1 – L – VE + C )
Zs ⋅ C
k
(6.25)
Flow
Flow into the Reciprocating Compressor is governed by the speed of the
compressor. If the speed of the compressor is larger than zero then the
flow rate is zero or larger then zero (but never negative). The molar flow
is then equal to:
1
---
Zs Pd k
L
F =  1 – --------- – C -----  ------ – 1

Zd  Ps
100
where:
N
------ ⋅ PD ⋅ ρ
60
-------------------------MW
(6.26)
N = speed, rpm
ρ = gas density
MW = gas molecular weight
If the speed of the compressor is exactly zero, then the flow through the
unit is governed by a typical pressure flow relationship, and you can
specify the resistance in zero speed flow resistance, kzero speed.
The flow equation is as follows:
F = k zero speed ⋅ ρ ⋅ ∆P friction
where:
6-42
∆P friction = frictional pressure drop across the compressor
(6.27)
Rotating Equipment
6-43
6.2.2 Reciprocating Compressor Property View
You can also add a
compressor by clicking the
F12 hot key.
You can also open the
Object Palette by clicking
the F4 hot key.
There are two ways that you can add a Compressor to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Rotating Equipment radio button.
3.
From the list of available unit operations, select Compressor.
4.
Click the Add button. The Compressor property view appears.
OR
Compressor icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Compressor icon. The Compressor property view
appears.
You can also toggle from a Centrifugal Compressor to a Reciprocating
Compressor:
1.
On the Design tab, click the Parameters page.
2.
Select the Reciprocating radio button in the Operating Mode group.
Figure 6.19
OR
3.
On the Dynamics tab, click on the Specs page.
6-43
6-44
Reciprocating Compressor
4.
Activate the Reciprocating (Positive Displacement) checkbox in the
Dynamic Specifications group.
To ignore the Reciprocating Compressor during calculation, activate the
Ignored checkbox. HYSYS completely disregards the operation until you
restore it to an active state by deactivating the checkbox.
6.2.3 Design Tab
The Design tab consists of six pages:
•
•
•
•
•
•
Connections
Parameters
Links
Settings
User Variables
Notes
Connections Page
The Connections page is
identical to the Connections
page for the Centrifugal
Compressor property view.
Refer to the section on the
Centrifugal Compressor or
Expanders Connections
Page for more information.
6-44
The Connections page allows you to specify the inlet stream, outlet
stream, and energy stream.
Figure 6.20
Rotating Equipment
6-45
Parameters Page
You can switch between
Centrifugal and
Reciprocating Compressor
by selecting one of the radio
buttons in the Operating
Mode group.
The Parameters pages is identical to the Centrifugal Compressor as
shown in the figure below.
Figure 6.21
The only difference is the MW Operation Mode group is not visible.
You can specify the duty of the attached energy stream on this page, or
allow HYSYS to calculate it. The adiabatic and polytropic efficiencies
appear as well.
You can specify only one efficiency, either adiabatic or polytropic. If you
specify one efficiency and a solution is obtained, HYSYS back
calculates the other efficiency, using the calculated duty and stream
conditions.
The Reciprocating Compressor has a higher adiabatic efficiency than
the Centrifugal Compressor, normally in the range of 85% - 95%.
Maximum pressure ratio can be achieved at zero volume efficiency.
6-45
6-46
Reciprocating Compressor
Links Page
Refer to the section on the
Links Page in Section 6.1 Centrifugal Compressor
or Expander for more
information regarding the
Links page.
The Links page is identical to the Centrifugal Compressor as shown in
the figure below.
Figure 6.22
Settings Page
The Settings page is only
visible when you have
activated the Reciprocating
Compressor option either
from the Parameters page
on the Design tab or the
Specs page on the
Dynamics tab.
6-46
The Settings page is used to size the Reciprocating Compressor.
Figure 6.23
Rotating Equipment
6-47
A Reciprocating Compressor does not require a characteristic curve,
however the following compressor geometry information is required:
Bore is the diameter of the
cylinder.
Stroke is the distance head
of piston travels.
Typical Design Speed is the
estimated speed for the
rotor.
Speed is the actual speed
of the rotor.
•
•
•
•
•
•
•
•
•
•
•
Depending on the cylinder type selected, you have four parameters that
can be specified. If the cylinder type is of double action, you need to
specify the fixed clearance volume for the crank side and the outer side.
•
•
•
•
The variable clearance
volume is used when
additional clearance volume
(external) is intentionally
added to reduce cylinder
capacity.
Number of Cylinders
Cylinder Type
Bore
Stroke
Piston Rod Diameter
Constant Volumetric Efficiency Loss
Default Fixed Clearance Volume
Zero Speed Flow Resistance (k) - dynamics only
Typical Design Speed
Volumetric Efficiency
Speed
Fixed Clearance Volume
Variable Clearance Volume
Variable Volume Enabled
Cylinder is Unloaded - dynamics only
If the Variable Volume Enabled checkbox is activated, you need to
specify a variable clearance volume.
If the Cylinder is Unloaded checkbox is activated, the total displacement
volume is not considered and is essentially zero.
The Size k button allows you to specify a pressure drop and mass flow
rate that is used to calculate the zero speed flow resistance of the
Reciprocating Compressor.
Figure 6.24
6-47
6-48
Reciprocating Compressor
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
6.2.4 Rating Tab
The Rating tab contains two pages:
•
•
Nozzles
Inertia
Nozzles Page
If you are working exclusively in Steady State mode, you are not
required to change any information on the Nozzles page. The Nozzles
page is identical to the Centrifugal Compressor, refer to the section on
the Nozzles Page for more information.
Inertia Page
If you are working exclusively in Steady State mode, you are not
required to change any information on this page. The Reciprocating
Compressor Inertia page is identical to the one for the Centrifugal
Compressor. (Refer to the section on the Inertia Page for more
information.)
6-48
Rotating Equipment
6-49
6.2.5 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
6.2.6 Performance Tab
The Performance tab consists of the Results page.
Results Page
On the Results page, you can view a table of calculated values for the
Compressor.
In the Results group you will find the following fields:
•
•
•
•
•
•
•
•
•
•
•
•
Adiabatic Head
Polytropic Head
Adiabatic Efficiency
Polytropic Efficiency
Power Consumed
Friction Loss
Rational Inertia
Fluid Power
Polytropic Head Factor
Polytropic Exponent
Isentropic Exponent
Speed
In the Reciprocating group you will find the following fields:
•
•
•
•
•
Total Effective Piston Displacement Volume
Total Effective Fractional Clearance Volume
Maximum Pressure Ratio
Load in Compression
Load in Tension
6-49
6-50
Pump
6.2.7 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Dynamics tab.
The Dynamics tab is identical to the one for the Centrifugal
Compressor. (Refer to Section 6.1.7 - Dynamics Tab for more
information.) However, when using a Reciprocating Compressor you
cannot use the Characteristic Curves specification or create a Surge
Controller.
6.3 Pump
The Pump operation is used to increase the pressure of an inlet liquid
stream. Depending on the information specified, the Pump calculates
either an unknown pressure, temperature or pump efficiency.
The dynamics Pump operation is similar to the Compressor operation
in that it increases the pressure of its inlet stream. The Pump operation
assumes that the inlet fluid is incompressible.
Some of the features in the dynamic Pump include:
•
•
•
•
•
6-50
Dynamic modeling of friction loss and inertia.
Dynamic modeling which supports shutdown and startup
behaviour.
Multiple head and efficiency curves.
Modeling of cavitation if Net Positive Suction Head (NPSH) is
less than a calculated NPSH limit.
Linking capabilities with other rotational equipment operating at
the same speed with one total power.
Rotating Equipment
6-51
6.3.1 Theory
Calculations are based on the standard pump equation for power,
which uses the pressure rise, the liquid flow rate, and density:
( P out – P in ) × Flow Rate
Power Required ideal = --------------------------------------------------------------Liquid Density
where:
(6.28)
Pout = pump outlet pressure
Pin = pump inlet pressure
The previous equation defines the ideal power needed to raise the liquid
pressure.
The actual power requirement of the Pump is defined in terms of the
Pump Efficiency:
Power Required ideal
Efficiency ( % ) = --------------------------------------------------------- × 100%
Power Required actual
(6.29)
When the efficiency is less than 100%, the excess energy goes into
raising the temperature of the outlet stream.
Combining the above equations leads to the following expression for the
actual power requirement of the Pump:
( P out – P in ) × Flow Rate × 100%
Power Required actual = ----------------------------------------------------------------------------------Liquid Density × Efficiency ( % )
(6.30)
Finally, the actual power is equal to the difference in heat flow between
the outlet and inlet streams:
Power Requiredactual = (Heat Flowoutlet - Heat Flowinlet)
(6.31)
6-51
6-52
Pump
If the feed is fully defined, only two of the following variables need to be
specified for the Pump to calculate all unknowns:
•
•
•
Outlet Pressure or Pressure Drop
Efficiency
Pump Energy
HYSYS can also back-calculate the inlet Pressure.
For a pump, an efficiency of 100% does not correspond to a true
isentropic compression of the liquid. Pump calculations are performed
by HYSYS with the assumption that the liquid is incompressible; that is,
the density is constant (liquid volume is independent of pressure). This
is the usual assumption for liquids well removed from the critical point,
and the standard pump equation given above is generally accepted for
calculating the power requirement. However, if you want to perform a
more rigorous calculation for pumping a compressible liquid (i.e., one
near the critical point), you should instead install a compressor to
represent the pump.
If you choose to represent a Pump by installing a Compressor in HYSYS,
the power requirement and temperature rise of the Compressor is
always greater than those of the Pump (for the same fluid stream),
because the compressor treats the liquid as a compressible fluid. When
the pressure of a compressible fluid increases, the temperature also
increases, and the specific volume decreases. More work is required to
move the fluid than if it were incompressible, exhibiting little
temperature rise, as is the case with a HYSYS Pump.
The ideal power required, W, to increase the pressure of an
incompressible fluid is:
( P 2 – P 1 )F ( MW )
W = -----------------------------------------ρ
where:
P1 = pressure of the inlet stream
P2 = pressure of the exit stream
ρ = density of the inlet stream
F = molar flow rate of the stream
MW = molecular weight of the fluid
6-52
(6.32)
Rotating Equipment
6-53
For a Pump, it is assumed that the entering liquid stream is
incompressible. Therefore, the ideal work defined in Equation
(6.32)does not correspond to a true isentropic compression of the
liquid. Despite this, the pump efficiency is defined in terms of the ideal
work and not the isentropic work.
Incompressibility is the usual assumption for liquids well removed from
the critical point, and the standard pump equation provided in
Equation (6.32) is generally accepted for calculating the power
requirement. However, if you want to perform a more rigorous
calculation for pumping a compressible liquid (i.e., one near the critical
point), you should install a Compressor operation instead of a Pump.
6.3.2 Pump Property View
You can also add a pump by
clicking the F12 hot key.
You can also open the
Object Palette by clicking
the F4 hot key.
There are two ways that you can add a Pump to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Rotating Equipment radio button.
3.
From the list of available unit operations, select Pump.
4.
Click the Add button. The Pump property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6-53
6-54
Pump
6.
Double-click the Pump icon. The Pump property view appears.
Figure 6.25
Pump icon
The On checkbox activates and deactivates the Pump.
If you specify a Delta P, this
value is simply ignored
when you turn the Pump off.
On the other hand, if you
specify the pressures of the
inlet stream and outlet
stream, you get a
consistency error when you
turn the Pump off, as
HYSYS attempts to pass the
inlet stream conditions to the
outlet stream.
If the On checkbox is activated, the Pump is “on”, and works as normal.
If this checkbox is deactivated, HYSYS passes the inlet stream
unchanged; that is, the outlet stream is exactly the same as the inlet
stream. When you use the On option, you should specify a pressure rise
rather than specify the pressures of the inlet stream and outlet stream.
To ignore the Pump during calculations, activate the Ignored checkbox.
HYSYS completely disregards the operation (and cannot calculate the
outlet stream) until you restore it to an active state by deactivating the
checkbox.
6.3.3 Design Tab
The Design tab consists of six pages:
•
•
•
•
•
•
6-54
Connections
Parameters
Curves
Links
User Variables
Notes
Rotating Equipment
6-55
Connections Page
On the Connections page, you can specify the inlet stream, outlet
stream, and energy stream attached to the Pump.
Figure 6.26
Parameters Page
You can specify the adiabatic efficiency, Delta P, and pump energy
(power) parameters on the Parameters page.
Figure 6.27
On the Parameters page, you can specify both the inlet stream pressure
and outlet stream pressure, in which case HYSYS calculates Delta P.
Alternatively, you can specify one stream pressure and a Delta P value;
in this case, the other stream pressure is calculated by HYSYS.
6-55
6-56
Pump
Curves Page
The Curves page allows you to specify a pump curve.
Figure 6.28
If you want to specify a pump curve:
1.
On the Design tab, click on the Curves page.
2.
Enter the coefficients for the quadratic pump equation, as well as
the units for pressure and flow.
3.
Activate the Activate Curves checkbox, and HYSYS determines the
pressure rise across the Pump for the given flowrate.
To avoid a consistency error, ensure that you have not specified the
pressure rise across the Pump, either in the attached streams or in the
operation itself.
6-56
Rotating Equipment
6-57
Links Page
In HYSYS, Pumps can have shafts which are physically connected. The
rotational equipment linker operates both in Steady State and Dynamic
mode.
Figure 6.29
A list of available Pumps can be displayed by clicking the Downstream
Link drop-down list. It is not significant which order the Pumps are
linked. The notion of upstream and downstream links is arbitrary and
determined by the user.
Linked Pump operations require curves. To fully define a set of linked
Pumps, you must activate the Use the Characteristic Curves checkbox
for each of the linked Pumps in the Specs page of the Dynamics tab. One
additional dynamic specification is required for the set. Usually, the
total power loss from the linked operations is specified. For a series of
linked Pumps, it is desired to input a total power:
Total Power Input = - Total Power Loss
(6.33)
Total power loss or input to the linked Pump operations can be
specified by you in the Total Power Loss field.
It is possible to link a Pump to a Compressor and use the Pump as a
turbine to generate kinetic energy to drive the Compressor. If this
option is selected, the total power loss is typically specified as zero.
6-57
6-58
Pump
User Variables Page
The User Variables page allows you to create and implement variables
in the HYSYS simulation case. For more information on implementing
the User Variables, refer to Chapter 5 - User Variables in the
Customization Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
6.3.4 Rating Tab
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through the
Rating tab. The Rating tab consists of five pages:
•
•
•
•
•
6-58
Curves
NPSH
Nozzles
Inertia
Startup
Rotating Equipment
6-59
Curves Page
The curves used on this
page work exclusively in
dynamic mode. Pump
curves for steady state
operation are specified in
the Curves page of the
Design tab.
One or more Pump curves can be specified on the Curves page.
Figure 6.30
The efficiency and head for a specified speed can be plotted against the
capacity of the Pump. Multiple curves can be plotted to show the
dependence of efficiency and head on the speed of Pump.
To specify data for a curve, use the following the procedure:
1.
Click the Add Curve button, the Curve view appears.
2.
On the Curve view, you can specify the flow, head, and %efficiency
data points, as well as the speed value for a single curve.
Figure 6.31
6-59
6-60
When you click the Erase
Selected button, the current
row (Flow, Head or
Efficiency) is deleted. Click
the Erase All button to
delete all Flow, Head, and
Efficiency data for the curve.
Close View icon
Pump
3.
For each additional curve, repeat step #1 and #2.
4.
After entering all your curve data, click the Close View icon to return
to the Pump property view.
HYSYS uses the curve(s) to determine the appropriate efficiency for your
operational conditions. If you specify curves, ensure the Efficiency
values on the Parameters page are empty or a consistency error is
generated.
Once a curve has been created, the View Curve, Delete Curve, and Plot
Curves buttons become available. The View Curve button allows you to
edit your input data in the Curve view. The Delete Curve button allows
you to delete the highlighted curve from the simulation.
You can access the Curve view by clicking the Add Curve button or View
Curve button. You can specify the following data in the Curve view:
•
•
•
•
Name. Name of the Curve.
Speed. The rotation speed of the Pump. This is optional if you
specify only one curve.
Flow Units/Head Units. Units for the Flow and Head (In Volume/
Time and Length units, respectively).
Flow/Head/Efficiency. Enter any number of data points for the
Curve.
HYSYS can interpolate values for the efficiency and head of the
Compressor or Expander for speeds that are not plotted
In order to run a stable and realistic dynamic model, HYSYS requires
you to input reasonable curves. If Compressors or Expanders are linked,
it is a good idea to ensure that the curves plotted for each unit operation
span a common speed and capacity range. Typical curves are plotted in
the figure below.
6-60
Rotating Equipment
6-61
Figure 6.32
NPSH Page
Net Positive Suction Head (NPSH) is an important factor to consider
when choosing a Pump. Sufficient NPSH is required at the inlet of the
Pump to prevent the formation of small bubbles in the pump casing
which can damage the Pump. This is known as cavitation. For a given
Pump, the net positive suction head required to prevent cavitation,
NPSHrequired, is a function of the capacity (volumetric flowrate) and
speed of the Pump.
6-61
6-62
Pump
In HYSYS, NPSH curves can be specified like regular pump curves on the
NPSH page.
Figure 6.33
To add or edit a NPSH curve from the NPSH page:
1.
Activate the Enable NPSH curves checkbox.
2.
Click the Add Curve button, the NPSHCurve view appears.
3.
Specify the speed for each curve.
4.
Enter a capacity and NPSH for two points on the curve. Only two
points are required for the NPSH curves since:
log ( NPSH required ) ∝ log ( capacity )
5.
To remove all the data points, click the Erase All button.
Figure 6.34
6.
6-62
For each additional curve, repeat steps #2 to #4.
(6.34)
Rotating Equipment
6-63
The NPSHrequired value can either be taken from the NPSH curves or
specified directly in the NPSH required field. To directly specify the
NPSHrequired, you must first deactivate the Enable NPSH curves
checkbox.
NPSHavailable can be explicitly calculated from the flowsheet conditions
by clicking the Calculate Head button. The NPSHavailable is calculated as
follows:
V1 2
P 1 – P vap
NPSH available = ----------------------- +  ------ 

2g 
ρg
where:
(6.35)
P1 = inlet stream pressure to the pump
Pvap = vapour pressure of the inlet stream
ρ = density of the fluid
V1 = velocity of the inlet stream
g = gravity constant
To prevent pump cavitation the NPSHavailable must be above the
NPSHrequired. If a pump cavitates in HYSYS, it is modeled by scaling the
density of the fluid, ρ , randomly between zero and one.
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. For more information on the Nozzles page,
refer to Section 1.6.2 - Nozzles in the Dynamic Modeling manual.
For a Pump unit operation it is strongly recommended that the
elevation of the inlet and exit nozzles are equal. If you want to model
static head, the entire piece of equipment can be moved by modifying
the Base Elevation relative to Ground Elevation field.
6-63
6-64
Pump
Inertia Page
The inertia modeling parameters and the frictional loss associated with
the impeller in the Pump can be specified on this page. The Fidelity
license is required to use the Inertia features. Refer to Section 1.6 Fidelity in the Dynamic Modeling manual for more information.
Startup Page
The Startup page allows you to specify the Typical operating capacity.
The Fidelity license is required to use the Startup feature. Refer to
Section 1.6 - Fidelity in the Dynamic Modeling manual for more
information.
6.3.5 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
6.3.6 Performance Tab
The Performance tab consists of the Results page.
Results Page
The Results page contains pump head information. The values for total
head, pressure head, velocity head, Delta P excluding static head, total
power, friction loss, rotational inertia, and fluid power are calculated
values.
The Total Head field is used only for dynamic simulation.
6-64
Rotating Equipment
6-65
6.3.7 Dynamics Tab
If you are working exclusively
in Steady State mode, you
are not required to change
any of the values on the
pages accessible through the
Dynamics tab.
The Dynamics tab is used only for dynamic simulation. The Dynamic
tab consists of three pages:
•
•
•
Specs
Holdup
Stripchart
Specs Page
The dynamic specifications of the Pump can be specified on the Specs
page.
Figure 6.35
In general, two specifications should be selected in the Dynamics
Specifications group in order for the Pump operation to fully solve. You
should be aware of specifications, which may cause complications or
singularity in the pressure flow matrix. Some examples of such cases
are:
•
•
The Pressure Increase checkbox should not be activated if the
inlet and exit stream pressures are specified.
The Speed checkbox should not be activated if the Use
Characteristic Curves checkbox is not activated.
6-65
6-66
Pump
The possible dynamic specifications are as follows:
Head
The ideal head, h, can easily be defined as a function of the isentropic or
polytropic work. The relationship is:
W = ( MW )Fgh
where:
(6.36)
W = ideal pump power
MW = molecular weight of the gas
F = molar flow rate of the inlet stream
g = gravity acceleration
or using Equation (6.32), the head is defined as:
P2 – P1
h = -----------------ρg
(6.37)
If pump curves are provided in the Curves page of the Rating tab, the
ideal head can be interpolated from the flow of gas and the speed of the
pump.
Speed
The rotational speed of the shaft, ω , driving the Pump can be specified.
Efficiency
The efficiency is given as the ratio of the ideal power required by the
pump to the actual energy imparted to the fluid. The efficiency, η , is
defined as:
W
η = --------------------------------------F ( MW ) ( h 2 – h 1 )
6-66
(6.38)
Rotating Equipment
6-67
The ideal power required by the pump is provided in Equation (6.32).
The general definition of the efficiency does not include the losses due
to the rotational acceleration of the shaft and seal losses. Therefore, the
efficiency equations in dynamics are not different at all from the general
efficiency equations defined in Section 6.3.1 - Theory.
If pump curves are provided in the Curves page of the Rating tab, the
efficiency can be interpolated from the flow of gas and the speed of the
Pump.
Pressure Rise
A Pressure Rise specification can be selected, if the pressure drop across
the Pump is constant.
Power
The duty is defined as the power required to rotate the shaft and provide
energy to the fluid. The duty has three components:
Duty = Power supplied to the fluid + Power required to
change the rotational speed of the shaft + Power
lost due to mechanical friction loss
(6.39)
The duty should be specified only if there is a fixed rate of energy
available to be used to drive the shaft.
Capacity
The capacity is defined as the actual volumetric flow rate entering the
Pump.
6-67
6-68
Pump
Use Characteristic Curves
Activate the Use Characteristic Curves checkbox, if you want to use the
curve(s) specified in the Curves page of the Rating tab. If a single curve is
specified in a dynamics Pump, the speed of the Pump is not
automatically set to the speed of the curve. A different speed can be
specified, and HYSYS extrapolates values for head and efficiency.
Holdup Page
Typical pumps in actual plants usually have significantly less holdup
than most other unit operations in a plant. Therefore, the volume of the
Pump operation in HYSYS cannot be specified, and is assumed to be
zero on the Holdup page.
Stripchart Page
Refer to Section 11.7.3 Strip Chartsin the User
Guide for more information
about stripcharts.
6-68
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Rotating Equipment
6-69
6.4 References
1
Gas Processors Association. Gas Processors Suppliers Association (1998) p.131 to p13-20
2
Campbell M.John. Gas Conditioning and Processing (vol2) 7th edi. 1994,
p213-221
6-69
6-70
6-70
References
Separation Operations
7-1
7 Separation Operations
7.1 Separator, 3-Phase Separator, & Tank ...........................................2
7.1.1
7.1.2
7.1.3
7.1.4
7.1.5
7.1.6
7.1.7
Theory .....................................................................................4
Separator General Property View............................................4
Design Tab ..............................................................................6
Reactions Tab..........................................................................9
Rating Tab .............................................................................10
Worksheet Tab.......................................................................28
Dynamics Tab ........................................................................28
7.2 Shortcut Column............................................................................36
7.2.1
7.2.2
7.2.3
7.2.4
7.2.5
7.2.6
Shortcut Column Property View ............................................36
Design Tab ............................................................................37
Rating Tab .............................................................................40
Worksheet Tab.......................................................................40
Performance Tab ...................................................................40
Dynamics Tab ........................................................................41
7.3 Component Splitter .......................................................................41
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.3.6
Theory ...................................................................................42
Component Splitter Property View ........................................43
Design Tab ............................................................................44
Rating Tab .............................................................................48
Worksheet Tab.......................................................................48
Dynamics Tab ........................................................................48
7-1
7-2
Separator, 3-Phase Separator, & Tank
7.1 Separator, 3-Phase Separator, &
Tank
All information in this section
applies to the Separator, the
3-Phase Separator, and the
Tank operation, unless
indicated otherwise.
The property views for the Separator, 3-Phase Separator, and Tank are
similar, therefore, the three unit operations are discussed together in
this section. There is an Operation Toggle on the Parameters page of the
Design tab that allows you to easily switch from one of these operations
to another. For example, you may want to change a fully defined
Separator to a 3-Phase Separator. Simply, select the appropriate radio
button using the operation toggle. The only additional information
required would be to identify the additional liquid stream. All of the
original characteristics of the operation (Parameters, Reactions, etc.) are
retained. The key differences in these operations are the stream
connections (related to the feed separation), which are described in the
table below.
Unit Operation
Description
Separator
Multiple feeds, one vapour and one liquid product stream. In
Steady State mode, the Separator divides the vessel contents
into its constituent vapour and liquid phases.
3-Phase Separator
Multiple feeds, one vapour and two liquid product streams. The
3-Phase Separator operation divides the vessel contents into
its constituent vapour, light liquid, and heavy liquid phases.
Tank
Multiple feeds, one liquid and one vapour product stream. The
Tank is generally used to simulate liquid surge vessels.
In Dynamic mode, the following unit operations all use the holdup
model and therefore, have many of the same properties. Vessel
operations in HYSYS have the ability to store a significant amount of
holdup. The key differences in the vessel operations are outlined in the
table below.
7-2
Separation Operations
Unit Operation
Description
Separator
The Separator can have multiple feeds. There are two product
nozzles:
• liquid
• vapour.
3-Phase Separator
The 3-Phase Separator can have multiple feeds. There are 3
product nozzles:
• light liquid
• heavy liquid
• vapour.
Tank
The Tank can have multiple feeds. There are two product
nozzles which normally removes liquid and vapour from the
Tank.
Condenser
The condenser has one vapour inlet stream. The number and
phase of each exit stream depends on the type of condenser.
The condenser has a unique method of calculating the duty
applied to its holdup.
Reboiler
The reboiler has one liquid inlet stream. The reboiler can have
a number of liquid and vapour exit streams.
Reactors
Reactor operations can have multiple inlet and exit streams.
Heat Exchanger
(Simple Rating
Model, Detailed)
A shell or tube with a single pass in the heat exchanger unit
operation can be modeled with a liquid level. Both the shell and
tube sides of the heat exchanger have one inlet and one exit
stream.
7-3
Every dynamic vessel operation in HYSYS has some common features
including:
•
•
•
•
The geometry of the vessel and the placement and diameter of
the attached feed and product nozzles have physical meaning.
A heat loss model which accounts for the convective and
conductive heat transfer that occurs across the vessel wall.
Various initialization modes which allow you to initialize the
vessel at user-specified holdup conditions before running the
integrator.
Various Heater types which determine the way in which heat is
transferred to the vessel operation.
7-3
7-4
Separator, 3-Phase Separator, & Tank
7.1.1 Theory
A P-H flash is performed to determine the product conditions and
phases. The pressure at which the flash is performed is the lowest feed
pressure minus the pressure drop across the vessel. The enthalpy is the
combined feed enthalpy plus or minus the duty (for heating, the duty is
added; for cooling, the duty is subtracted).
As well as standard forward applications, the Separator and 3-Phase
Separator have the ability to back-calculate results. In addition to the
standard application (completely defined feed stream(s) being
separated at the vessel pressure and enthalpy), the Separator can also
use a known product composition to determine the composition(s) of
the other product stream(s), and by a balance the feed composition.
In order to back-calculate with the Separator, the following information
must be specified:
•
•
•
One product composition.
The temperature or pressure of a product stream.
Two (2-phase Separators) or three (3-phase Separators) flows.
If you are using multiple feed streams, only one feed stream can have an
unknown composition in order for HYSYS to back-calculate.
7.1.2 Separator General Property View
You can also add a
separator or 3-phase
separator or tank by clicking
the F12 hot key.
You can also open the
Object Palette by clicking
the F4 hot key.
7-4
There are two ways that you can add a Separator or 3 -Phase Separator
or Tank to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Vessels radio button.
3.
From the list of available unit operations, select the Separator or 3
Phase Separator or Tank.
Separation Operations
4.
7-5
Click the Add button. The Separator or 3 Phase Separator or Tank
property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Separator icon or 3 Phase Separator icon or Tank
icon. The Separator or 3 Phase Separator or Tank property view
appears.
Separator icon
If you want to use the Separator as a reactor, you can either install a
Separator or choose General Reactor from the UnitOps view.
3-Phase Separator icon
The figure below shows the Parameters page for the Separator.
Figure 7.1
Tank icon
To ignore a vessel
operation, activate the
Ignored checkbox. HYSYS
disregards the operation
(and cannot calculate the
outlet stream) until you
restore it to an active state
by deactivating the
checkbox.
Click one of the radio buttons to toggle between the
operations.
In the Type group, you can toggle between the Separator, 3-Phase
Separator, and Tank by clicking the appropriate radio button.
If you toggle from a Separator operation to a Tank operation, you
permanently lose the vapour stream connection. If you change back to
the Separator, you have to reconnect the vapour stream.
7-5
7-6
Separator, 3-Phase Separator, & Tank
7.1.3 Design Tab
The Design tab consist of four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes.
You must specify information on the Connections page and Parameters
page of the Design tab.
Connections Page
You must provide names for
the outlet/product streams in
the Connections page.
Any of the available separation operations accept multiple feed streams,
as well as an optional energy stream. The figure below shows the
Connections pages for the three operations:
Figure 7.2
7-6
Separation Operations
7-7
You can specify the optional energy input to the vessel by providing the
name of the energy stream on the Connections page. The Steady State
mode Separator energy balance is defined below:
H feed ± Duty = H vapour + H heavy + H light
where:
(7.1)
Hfeed = heat flow of the feed stream(s)
Hvapour = heat flow of the vapour product stream
Hlight = heat flow of the light liquid product stream
Hheavy = heat flow of the heavy liquid product stream
Parameters Page
The Parameters page allows you to specify the pressure drop across the
vessel.
Figure 7.3
The following vessel parameters appear:
Vessel Parameter
Description
Vessel Volume
A user-specified parameter.
Liquid Level SP
Expressed as a percentage of the Full (Vessel) Volume. This is
a user-specified parameter.
Liquid Volume
Not set by the user. The Liquid Volume is calculated from the
product of the Vessel Volume and Liquid Level fraction.
7-7
7-8
Separator, 3-Phase Separator, & Tank
Physical Parameters
The default pressure drop
across the vessel is zero.
The Physical Parameters associated with this operation are the pressure
drop across the vessel (Delta P) and the vessel volume. The pressure
drop is defined as:
P = P v = P 1 = P feed – ∆P
where:
(7.2)
P = vessel pressure
Pv = pressure of vapour product stream (not applicable for Tank)
Pl = pressure of liquid product stream(s)
Pfeed = pressure of feed stream (assumed to be the lowest pressure of all
the feed streams)
Pfeed is assumed to be the
lowest pressure of all the
feed streams.
∆P = pressure drop in vessel (Delta P)
The Vessel Volume is
necessary in steady state
when modeling a Reactor
(CSTR), as it determines the
residence time.
The vessel volume, together with the set point for liquid level/flow,
defines the amount of holdup in the vessel. The amount of liquid
volume, or holdup, in the vessel at any time is given by the following
expression
PV ( %Full )
Holdup = Vessel Volume × ----------------------------100
where:
(7.3)
PV(%Full) = liquid level in the vessel at time t
The default vessel volume is 2 m3.
User Variables Page
You can create and implement your own User Variables for use in a
HYSYS simulation on the User Variables page. For more information on
the User Variables refer to Chapter 5 - User Variables in the
Customization Guide.
If you select an alternate unit, your value appears in the face plate using
HYSYS display units.
7-8
Separation Operations
7-9
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
7.1.4 Reactions Tab
The Reactions tab consists of the Results page.
Results Page
The Results page allows you to attach a reaction set to the Separator, 3Phase Separator, or Tank Operations. In the Reaction Set drop-down
list, select the reaction set you want to use.
Figure 7.4
Reaction and component information can also be examined in the
Reaction Results group. Select the Reaction Balance radio button to
view the total inflow, total reaction, and total outflow for all of the
components in the reaction.
7-9
7-10
Separator, 3-Phase Separator, & Tank
Select the Reaction Extents radio button to view the Percent Conversion,
Base Component, Equilibrium Constant, and Reaction Extent. You can
also view information for specific reactions by clicking the View Global
Rxn button.
7.1.5 Rating Tab
You must provide rating
information only when working
with a dynamic simulation.
The Rating tab includes the Sizing and Heat Loss pages. The
information on the three pages is not relevant when working exclusively
in Steady State mode.
Sizing Page
You can define the geometry of the unit operation on the Sizing page.
Also, you can indicate whether or not the unit operation has a boot
associated with it. If it does, then you can specify the boot dimensions.
Figure 7.5
Vessel Geometry
In the Geometry group, you can specify the vessel volume and shape.
The geometry of the vessel is important in determining the liquid height
in the vessel.
7-10
Separation Operations
7-11
There are two possible vessel shapes as described in the table below.
Vessel Shape
Description
Sphere
The shape of the vessel is a sphere. You can either specify the total
volume or the diameter of the sphere.
Cylinder
A horizontal or vertical cylindrical vessel can be specified. You can
either specify the total volume or any two of the following for the
vessel:
• total volume
• diameter
• height (length)
If only the total cylindrical volume of the vessel is specified, the height
to diameter ratio is defaulted as 3:2.
The liquid height in a vertical cylindrical vessel varies linearly with the
liquid volume. There is a nonlinear relationship between the liquid
height, and the liquid volume in horizontal cylindrical and spherical
vessels.
Weir
A weir can be specified for any horizontal separator by clicking the Weir
button.
Figure 7.6
This view allows
you to specify the
weir height and
position. HYSYS
calculates the
Levels and Phase
Moles in each
chamber using the
specified values
for the weir height
and position.
7-11
7-12
Separator, 3-Phase Separator, & Tank
When HYSYS simulates, the weir has two volumes inside the Separator,
called chamber 1 and chamber 2; but there is still only one enhanced
holdup volume and moles as far as the pressure flow solver is
concerned. This means that the compositions and properties of the
phases in the two volumes are the same.
Figure 7.7
Boot Geometry
Any vessel operation can be specified with a boot. A boot is typically
added when two liquid phases are present in the holdup. Normally, the
heavy liquid exits from the boot exit nozzle. The lighter liquid can exit
from another exit nozzle attached to the vessel itself. In HYSYS, a boot
can be added to the vessel geometry by activating the This Separator has
a Boot checkbox. The boot height is defaulted to one third the vessel
height. The boot diameter is defaulted to one third the vessel diameter.
7-12
Separation Operations
7-13
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. Unlike steady state vessel operations, the
placement of feed and product nozzles on a dynamic vessel operation
has physical meaning. The composition of the exit stream depends on
the exit stream nozzle location and diameter in relation to the physical
holdup level in the vessel. If the product nozzle is located below the
liquid level in the vessel, the exit stream draws material from the liquid
holdup. If the product nozzle is located above the liquid level, the exit
stream draws material from the vapour holdup. If the liquid level sits
across a nozzle, the mole fraction of liquid in the product stream varies
linearly with how far up the liquid is in the nozzle.
Essentially, all vessel operations in HYSYS are treated the same. The
compositions and phase fractions of each product stream depend solely
on the relative levels of each phase in the holdup and the placement of
the product nozzles. So, a vapour product nozzle does not necessarily
produce pure vapour. A 3-Phase Separator may not produce two
distinct liquid phase products from its product nozzles.
Figure 7.8
7-13
7-14
Separator, 3-Phase Separator, & Tank
Heat Loss Page
The Heat Loss page contains heat loss parameters which characterize
the amount of heat lost across the vessel wall.
Figure 7.9
In the Heat Loss Model group, you can select one of the radio buttons to
use as a model:
•
•
•
Simple
Detailed
None (no heat loss through the vessel walls).
The Simple and Detailed heat loss models are discussed in the following
sections.
Simple Model
The Simple model allows you to either specify the heat loss directly or
have the heat loss calculated from specified values:
•
•
7-14
Overall U value
Ambient Temperature
Separation Operations
7-15
The heat transfer area, A, and the fluid temperature, Tf, are calculated by
HYSYS. The heat loss is calculated using:
Q = UA(Tf - Tamb)
(7.4)
For a Separator, the parameters available for the Simple model are
shown in the figure below:
Figure 7.10
The simple heat loss parameters are:
•
•
•
•
Overall Heat Transfer Coefficient
Ambient Temperature
Overall Heat Transfer Area
Heat Flow
The Heat Flow is calculated as follows:
Heat Flow = UA(TAmb - T)
where:
(7.5)
U = overall heat transfer coefficient
A = heat transfer area
TAmb = ambient temperature
T = holdup temperature
As shown, Heat Flow is defined as the heat flowing into the vessel. The
heat transfer area is calculated from the vessel geometry. The ambient
temperature, TAmb, and overall heat transfer coefficient, U, can be
modified from their default values shown in red.
7-15
7-16
Separator, 3-Phase Separator, & Tank
Detailed Model
The Detailed model allows you to specify more detailed heat transfer
parameters. The Fidelity license is required to use the Detailed Heat
Loss model found on the Heat Loss page. Refer to Section 1.6 - Fidelity
in the Dynamic Modeling manual for more information.
Level Taps Page
The information available on this page is relevant only to dynamics
cases. Since the contents in a vessel can be distributed in different
phases, the Level Taps page allows you to monitor the level of liquid and
aqueous contents that coexist within a specified zone in a tank or
separator.
Figure 7.11
7-16
Separation Operations
7-17
Level Taps Specifications (Dynamics)
The Level Tap Specifications (Dynamics) group allows you to specify the
boundaries to be monitored within the vessel, and to normalize that
section in a desired scale.
New Level Tap
A level tap can be specified for any horizontal or vertical vessel by
clicking the New Level Tap button. To set the boundaries of the section
concerned, specify the following fields:
The normalization scale can
be negative values. In some
cases, the output
normalization scale is
manually set between -7% to
100% or -15%-100% so that
there is a cushion range
before the level of the content
becomes unacceptable (i.e.,
too low, or too high).
Field
Description
Level Tap
Name of the level tap.
PV High (m)
Upper limit of the section to be monitored. It is expressed
in meters.
PV Low (m)
Lower limit of the section to be monitored. It is expressed
in meters.
OP High
Upper limit of the output of the normalization scale.
OP Low
Lower limit of the output of the normalization scale.
By default, a new level tap is set to the total height of the vessel, and the
height is normalized in percentage (100-0).
All the upper limit specifications should not be smaller than or equal to
the lower limit specifications and vice versa; otherwise no calculations
will be performed.
Calculated Level Taps Values (Dynamics)
The level of liquid and aqueous are displayed in terms of the output
normalization scale you specified. Whenever the level of a content
exceeds PV High, HYSYS automatically outputs the OP High value as the
level of that content. If the level is below the PV Low, HYSYS outputs the
OP Low value. The levels displayed are always entrained within the
normalized zone.
7-17
7-18
Separator, 3-Phase Separator, & Tank
Option Page
The Options page allows you to specify and enable the PV Work Term
Contribution. The PV Work Term Contribution is expressed in percent.
It is approximately the isentropic efficiency. A high PV work term
contribution value results in lower pressures, and temperatures. The PV
work term contribution value should be between 87% to 98%.
Figure 7.12
C. Over Setup Page
The C. Over Setup page
information is also available
in Dynamic mode.
7-18
The C. Over Setup page allows you to model the carryover effect in the
separator, three-phase separator, and tank. Carryover refers to the
conditions when the liquid gets entrained in the vapour phase and/or
when the gas gets entrained in the liquid phase. The effect is mainly
caused by the disturbances created as the inlet stream enters the vessel.
In HYSYS, you can model the carryover effect by specifying the
entrainment fraction in the feed or product stream, or by using the
available correlations that calculate carryover based on the vessel
configuration.
Separation Operations
7-19
The C. Over Setup page allows you to model six types of carryover flow
in the feed, and product stream:
•
•
•
•
•
•
Light liquid in gas
Heavy liquid in gas
Gas in light liquid
Heavy liquid in light liquid
Gas in heavy liquid
Light liquid in heavy liquid
The terms light liquid, and heavy liquid refer to oil and water,
respectively. No assumptions are made as to the actual composition of
the two liquid phases.
On the Carry Over Setup page, you can select the type of carryover
calculation model by clicking one of the following four radio buttons:
•
•
•
•
None (indicates that there is currently no Carry Over Model
applied to the associated vessel).
Feed Basis
Product Basis
Correlation Based
The Feed Basis, Product Basis, and Correlation Based models are
discussed in the following sections.
7-19
7-20
Separator, 3-Phase Separator, & Tank
Feed Basis Model
The Feed Basis Model allows you to specify the entrainment of each
phase in each product as a fraction of the feed flow of the phase.
Figure 7.13
There are two checkboxes available at the bottom of the page:
•
•
Carry Over to Zero Flow Streams. When you check the Carry
Over to Zero Flow Streams, the calculated carryover will be
added to the product stream even if it has no flow.
Use PH Flash for Product Streams. When you check the Use
PH Flash for Product Streams, you apply a PH flash calculation
to the product streams. This option is slower but it may be
required to eliminate inconsistencies when one product flow is
much less than the others.
These two checkboxes are also available in the Product Basis, and
Correlation Based model.
7-20
Separation Operations
7-21
Product Basis Model
The Product Basis model allows you to specify the carryover
entrainment in the product streams on fraction or flow basis. You can
select the desired basis by clicking on one of the following radio buttons
in the Specification By group:
•
•
Fraction. Allows you to specify the entrainment in the product
stream as a fraction. The fraction basis is selected from the Basis
drop-down list and may be either Mole, Mass, Liq.Volume or
Actual Volume.
Flow. Allows you to specify the entrainment in the product
streams as a flow. The flow basis may be specified using the
Flow Basis drop-down list. The options are Mole, Mass,
Liq.Volume or Actual volume.
You can check the Use 0.0 as product spec if phase feed flow is zero
checkbox to prevent errors, and thus allows the separator to continue to
calculate the carryover effect when a phase is missing in the feed
stream.
Figure 7.14
7-21
7-22
Separator, 3-Phase Separator, & Tank
Correlation Based Model
The Correlation Based model allows you to calculate the expected
carryover based on the configuration of the vessel, the feed conditions,
and the operating conditions. The Correlation Based model allows you
to setup the type of the correlation, dimensions and geometry of vessel,
pressure drop methods, and nozzle location. You can specify these
parameters on the Correlation Setup, Dimensions Setup, and DP/
Nozzle Setup groups.
Correlation Setup
The Correlation Setup group allows you to select the Correlation
Calculation Type, and how you want to apply the correlation. You can
apply one correlation for all of the carryover calculations by clicking on
the Overall Correlation radio button. If you want to select a different
correlation for the Inlet Device, Gas/Liq Separation, Liq/Liq Separation,
and Vapour Exit Device, you can select the Sub Calculations radio
button, which allows you to select a different correlation type for each of
them.
Figure 7.15
There are three correlations available: Generic, Horizontal Vessel, and
ProSeparator. After you have selected the type of correlation, you can
click on the View Correlation button to view its calculation parameters.
7-22
Separation Operations
7-23
Generic
The Generic correlation provides a general correlation for generating
the phase dispersions in the feed and defining the separation criteria. It
is a generic calculation that is independent of the vessel dimensions,
geometry, and operating levels.
For the inlet calculations, you must define the percentage of each feed
phase dispersed in each other phase. You must also define the
maximum droplet sizes and Rosin Rammler index for each dispersion.
The dispersions are then calculated using Rosin Rammler methods to
give the amount of each phase in each droplet size range.
The Generic correlation can be used for gas/liquid, liquid/liquid, and
gas exit separation calculations. You must define the critical droplet size
for each type of separation. Any droplets that are smaller than the
specified critical droplet size will be carried over; the droplets that are
larger than the critical droplet size will be separated.
Horizontal Vessel
The Horizontal Vessel correlation is based on an inlet calculation that
calculates the six types of carryovers according to an assumed efficiency
of a user-defined inlet device, and user-defined carryover fractions. The
carryover fluid is then distributed using a Rossin Rammler distribution
according to the user-specified d95 droplet diameters, and Rossin
Rammler index.
The primary separation is calculated from settling velocities and the
calculated residence time for each fluid. The correction factors for the
residence time can be user defined. The settling velocities are calculated
by using the GPSA correlation for all separations, except for the water in
oil settling velocity, where the sedimentation velocity is calculated by
using the method of Barnea and Mizrahi. In all cases a droplet would get
carried over if the vertical distance travelled during its residence in the
vessel is less than the distance required to join its bulk phase.
The secondary separation calculations for the gas phase are defined by
the critical droplet size. The gas loading factor for each device type is
used to calculate the size of the secondary device.
7-23
7-24
Separator, 3-Phase Separator, & Tank
ProSeparator
The ProSeparator correlation only calculates the liquid separation from
the gas phase. There are no calculations for liquid/liquid separation or
gas separation from liquid. The ProSeparator correlation includes a
primary gravity separation followed by a secondary separation with
mesh pads or vane pack. Two alternate mesh pad correlations and two
alternate vane pack correlations are provided in the algorithm.
The ProSeparator first determines a maximum and minimum droplet
diameter at the inlet. The diameters are then used in a Rossin Rammler
method. The primary and secondary separation calculations are carried
out once for the light liquid phase, and once for the heavy liquid phase.
The total carryover is the sum of the separate light and heavy liquid
carryover calculations.
Dimensions Setup
The Dimensions Setup group allows you to set the orientation, and the
geometry of the vessel. You can also set the operating levels for the light
and heavy liquid in the vessel. You have the option to model the
horizontal vessel with weir or a boot by checking the Has Weir checkbox
and Has Boot checkbox, respectively.
Figure 7.16
7-24
Separation Operations
7-25
DP/Nozzle Setup
The Pressure Drop/Nozzle Setup group allows you to model the method
of DP (pressure drop), and the geometry of the nozzles.
Figure 7.17
Since the dynamic pressure
and the pressure drop of the
feed stream and vessel are
specified in the Specs page
of the Dynamics tab, the
Pressure Drop table is not
available when the separator
is operating in dynamics
mode.
In the Pressure Drop table, after you have selected a DP method from
the drop-down list, you can activate the Inlet Device DP Method, and
the Vapour Exit DP Method by checking the Active checkbox. You can
click on the View Method button to view the parameters of the DP
method you have selected.
In the Nozzle Diameter/Location table, you can set the diameter,
height, and location for all the streams connected to the vessel.
7-25
7-26
Separator, 3-Phase Separator, & Tank
C. Over Results Page
The C. Over Results page
information is also available
in Dynamic mode.
The C. Over Results page allows you to view the carryover results in the
feed, and product streams based on what you specified in the C. Over
Setup page. There are four columns of data in the Carry Over Results
table:
•
•
•
•
Frac. of Feed
Frac. in Product
Product Flow
Prod. Mass/Vol
The units for Frac. of Feed, and Prod. Mass/Vol are set by default. You
can change the unit for the Frac. in Product and Product Flow column
by selecting one of the four units from the Product Basis drop-down list
(Mole, Mass, Liq. Volume, and Actual Volume).
Figure 7.18
You can view the carryover dispersion results by clicking on the View
Dispersion Results button.
7-26
Separation Operations
7-27
The Carry Over Dispersion Results view has two tabs:
•
Table. Displays the dispersion results for a single phase at a
given point in the vessel. The radio buttons allow you to select the
results of the corresponding phase. You can select the unit to be
displayed from the Dispersion Basis drop-down list.
Figure 7.19
•
Plot. Provides a graphically interpretation of the dispersed
quantity against the droplet size for a single dispersion. The
Select Plot checkboxes allow you to select one or more
dispersions to be plotted. You can select the dispersion basis
from the Dispersion Basis drop-down list.
Figure 7.20
7-27
7-28
Separator, 3-Phase Separator, & Tank
7.1.6 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
7.1.7 Dynamics Tab
Information available on this page is relevant only to cases in Dynamic
mode.
The tab consists of four pages:
•
•
•
•
Spec
Holdup
StripChart
Duty
Each of the pages are discussed in the following sections.
Specs Page
The Specs page contains information regarding initialization modes,
vessel geometry, and vessel dynamic specifications.
Figure 7.21
7-28
Separation Operations
7-29
Model Details
You can determine the composition and amount of each phase in the
vessel holdup by specifying different initialization modes. HYSYS forces
the simulation case to re-initialize whenever the initialization mode is
changed. The radio buttons in the Model Details group are briefly
described in the table below.
The vessel geometry
parameters can be
specified in the same
manner as those specified
in the Geometry group for
the Sizing page of the
Rating tab.
Initialization Mode
Description
Initialize from
Products
The composition of the holdup is calculated from a weighted
average of all products exiting the holdup. A PT flash is
performed to determine other holdup conditions. The liquid
level is set to the value indicated in the Liq Volume Percent
field.
Dry Startup
The composition of the holdup is calculated from a weighted
average of all feeds entering the holdup. A PT flash is
performed to determine other holdup conditions. The liquid
level in the Liq Volume Percent field is set to zero.
Initialize from User
The composition of the liquid holdup in the vessel is user
specified. The molar composition of the liquid holdup can be
specified by clicking the Init Holdup button. The liquid level is
set to the value indicated in the Liq Volume Percent field.
In the Model Details group, you can specify the vessel geometry
parameters.
•
•
•
•
Vessel Volume
Vessel Diameter
Vessel Height (Length)
Vessel Geometry (Level Calculator)
Liquid Volume Percent
You can modify the level in the vessel at any time. HYSYS then uses that
level as an initial value when the integrator is run.
7-29
7-30
Separator, 3-Phase Separator, & Tank
Fraction Calculator
The Fraction Calculator
defaults to the correct mode
for all unit operations and
does not typically require
any changing.
The Fraction Calculator determines how the levels in the tank, and the
elevation and diameter of the nozzles affect the product composition.
The following is a description of the Fraction Calculator options:
•
•
Use Levels and Nozzles. The nozzle location and vessel phase
(liquid/vapour) level determines how much of each phase, inside
the vessel, will exit through that nozzle. For example, if a vessel
contained both liquid and vapour phases and the nozzle is below
the liquid level, then liquid will flow out through it. If the nozzle is
above the liquid level, then vapour will flow out through it. For
more information, see the section on Nozzles Page.
Emulsion Liquids. This behaves like the Use Levels and
Nozzles option, except it simulates a mixer inside the vessel that
mixes two liquid phases together so they do not separate out. For
example, if a nozzle is below the lighter liquid level and the vessel
has two liquid phases, the product is a mixture of both liquid
phases.
Dynamic Specifications
It is recommended that you
enter a value of zero in the
Feed Delta P field because
a fixed pressure drop in the
vessel is not realistic for all
flows.
The frictional pressure loss at the feed nozzle is a dynamic specification
in HYSYS. It can be specified in the Feed Delta P field. The frictional
pressure losses at each product nozzle are automatically set to zero by
HYSYS.
If you want to model friction loss at the inlet and exit stream, it is
suggested you add valve operations. In this case, flow into and out of the
vessel is realistically modeled.
The vessel pressure can also be specified. This specification can be
made active by activating the checkbox beside the Vessel Pressure field.
This specification is typically not set since the pressure of the vessel is
usually a variable and determined from the surrounding pieces of
equipment.
7-30
Separation Operations
7-31
Holdup Page
The Holdup page contains information regarding the properties,
composition, and amount of the holdup.
Figure 7.22
For each phase contained within the volume space of the unit
operation, the following is specified:
Holdup Details
Description
Accumulation
The accumulation refers to the rate of change of material in the
holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
Stripchart Page
Refer to Section 11.7.3 Strip Chartsin the User
Guide for more information
about strip charts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
7-31
7-32
Separator, 3-Phase Separator, & Tank
Duty Page
The Duty page is only visible
if a duty stream has been
attached to the vessel on the
Connections page of the
Design tab.
The Duty page opens a list of available heating methods for the vessel
operation.
Figure 7.23
Duty Source
In the Source group, you can choose whether HYSYS calculates the duty
applied to the vessel from a Direct Q or a Utility.
If you select the Direct Q radio button, you can directly specify the duty
applied to the holdup in the SP field. If you select the Utility radio
button, you can specify the flow of the utility fluid. The duty is then
calculated using the local overall heat transfer coefficient, the inlet fluid
conditions, and the process conditions. The calculated duty is then
displayed in the SP field or the Heat Flow field. For more information
regarding how the utility option calculates duty, refer to Chapter 12 Logical Operations.
If you select the Heating radio button, the duty shown in the SP field or
Heat Flow field is added to the holdup. If you select the Cooling radio
button, the duty is subtracted from the holdup.
7-32
Separation Operations
7-33
Heater Type
In the Heater Type group, there are two heating methods available to
the general vessel operation:
•
•
Vessel Heater
Liquid Heater
If you select the Vessel Heater radio button, 100% of the duty specified
or calculated in the SP field is applied to the vessel’s holdup.
Q = QTotal
where:
(7.6)
Q = total heat applied to the holdup
QTotal = duty calculated from the Duty Source
If you select the Liquid Heater radio button, the duty applied to the
vessel depends on the liquid level in the tank. You must specify the
heater height. The heater height is expressed as a percentage of the
liquid level in the vessel operation. The default values are 5% for the Top
of the Heater and 0% for the Bottom of the Heater.
These values are used to scale the amount of duty that is applied to the
vessel contents.
where:
Q = 0
(L < B)
L–B
Q = ------------- Q Total
T–B
(B ≤ L ≤ T)
Q = Q Total
(L > T)
(7.7)
L = liquid percent level (%)
T = top of heater (%)
B = bottom of heater (%)
The Percent Heat Applied may be calculated as follows:
Q
Percent Heat Applied = --------------- × 100%
Q Total
(7.8)
7-33
7-34
Separator, 3-Phase Separator, & Tank
It is shown that the percent of heat applied to the vessel’s holdup
directly varies with the surface area of liquid contacting the heater.
Figure 7.24
Percent of Heat Applied
100
80
60
40
20
B
T
0
0
20
40
60
80
100
Liquid Percent Level, L
Percent Heat Applied for a Liquid Heater
A Liquid Heater, however, is not suitable in the Condenser operation.
This is because the heat transfer to the condenser depends more on the
surface area of the vapour contacting the cooling coils than the liquid.
Therefore, in the Condenser operation, the heat applied to the vessel
holdup is expressed as follows:
Q = ( 2 – 0.02L )Q Total
where:
7-34
L = liquid percent level
(7.9)
Separation Operations
7-35
The heat applied to the Condenser operation directly varies with the
surface area of vapour contacting the vessel wall.
Figure 7.25
Percent of Heat Applied
200
160
120
80
40
0
0
20
40
60
80
100
Liquid Percent Level, L
Percent Heat Applied to Condenser
The following is a summary of the heating parameters for each vessel
operation:
Vessel Operation
Description
Reboiler
The reboiler can only use a liquid heater.
Condenser
The condenser uses its own method of calculating the
heat applied to the holdup.
Separators/ Tank/ Reactors
These unit operations can use a vessel heater or a
liquid heater.
7-35
7-36
Shortcut Column
7.2 Shortcut Column
The Shortcut Column performs Fenske-Underwood short cut
calculations for simple refluxed towers. The Fenske minimum number
of trays and the Underwood minimum reflux are calculated. A specified
reflux ratio can then be used to calculate the vapour and liquid traffic
rates in the enriching and stripping sections, the condenser duty and
reboiler duty, the number of ideal trays, and the optimal feed location.
The Shortcut Column is only an estimate of the Column performance
and is restricted to simple refluxed Columns. For more realistic results
the rigorous Column operation should be used. This operation can
provide initial estimates for most simple Columns.
7.2.1 Shortcut Column Property View
You can also add a shortcut
column by clicking the F12
hot key.
There are two ways that you can add a Shortcut Column to your
simulation:
You can also open the
Object Palette by clicking
the F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Short Cut Columns radio button.
3.
From the list of available unit operations, select the Shortcut
Column model.
4.
Click the Add button. The Shortcut Column property view appears.
OR
5.
7-36
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
Separation Operations
6.
7-37
Double-click the Short Cut Distillation icon. The Shortcut Column
property view appears.
Figure 7.26
Short Cut Distillation icon
7.2.2 Design Tab
The Design tab consists of four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Each of the pages are discussed in the following sections.
7-37
7-38
Shortcut Column
Connections Page
You must specify the feed stream, overhead product, bottoms product,
condenser, and reboiler duty name on the Connections page.
Figure 7.27
You can specify the top
product to be either liquid or
vapour using the radio
buttons in the Top Product
Phase group.
7-38
The overhead product can either be an overhead vapour or a distillate
stream, depending on the radio button selected in the Top Product
Phase group. The operation name can also be changed on this page.
Separation Operations
7-39
Parameters Page
The composition of the light
key in the bottoms and the
heavy key in the overhead
are the only composition
specifications required.
The Shortcut Column requires the light key and heavy key components
to be defined. The light key is the more volatile component of the two
main components that are to be separated. The compositions of the
keys are used to specify the distillation products.
Figure 7.28
In the Components group, select the light key in bottoms and heavy key
in distillation component from the drop-down list in the component
cell, and specify their corresponding mole fraction. The specification
must be such that there is enough of both keys to be distributed in the
bottoms and overhead. It is possible to specify a large value for the light
key composition such that too much of the light key is in the bottoms,
and the overhead heavy key composition spec cannot be met. If this
problem occurs, one or both of the key specs must be changed.
In the Pressures group, you can define the column pressure profile by
specifying a value in the Condenser Pressure field and a Reboiler
Pressure field.
In the Reflux Ratios group, the calculated minimum reflux ratio appears
once streams are attached on the Connections page, and the required
parameters are specified in the Components group and Pressures
group.
7-39
7-40
Shortcut Column
You can then specify an external reflux ratio, which is used to calculate
the tray traffic, the condenser and reboiler duties, the ideal number of
trays, and the optimum tray location. The external reflux ratio must be
greater than the minimum reflux ratio.
7.2.3 Rating Tab
You currently cannot provide any rating information for the Shortcut
Column.
7.2.4 Worksheet Tab
The Worksheet tab displays a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
7.2.5 Performance Tab
The Performance tab allows you to examine the results of the Shortcut
Column calculations. The results correspond to the external reflux ratio
value that you specified on the Parameters page.
Figure 7.29
7-40
Separation Operations
7-41
The following results are available on the:
Column Result
Description
Minimum Number of Trays
The Fenske minimum number of trays, which is not
affected by the external reflux ratio specification.
Actual Number of Trays
Calculated using a using the Gilliland method.
Optimal Feed Stage
Top down feed stage for optimal separation.
Condenser and Reboiler
Temperatures
These temperatures are not affected by the external
reflux ratio specification.
Rectifying Section Vapour
and Liquid traffic flow rates
The estimated average flow rates above the feed
location.
Stripping Section Vapour
and Liquid traffic flow rates
The estimated average flow rates below the feed
location.
Condenser and Reboiler
Duties
The duties, as calculated by HYSYS.
7.2.6 Dynamics Tab
The Shortcut Column currently runs only in Steady State mode. As such,
there is no information available on the Dynamics tab.
7.3 Component Splitter
With a Component Splitter, a material feed stream is separated into two
component streams based on the parameters and split fractions that
you specify. You must specify the fraction of each feed component that
exits the Component Splitter into the overhead product stream. Use it to
approximate the separation for proprietary and non-standard
separation processes that are not handled elsewhere in HYSYS.
7-41
7-42
Component Splitter
7.3.1 Theory
The Component Splitter satisfies the material balance for each
component:
fi = ai + bi
where:
(7.10)
fi = molar flow of the ith component in the feed
ai = molar flow of the ith component in the overhead
bi = molar flow in the ith component in the bottoms
The molar flows going to the overhead and bottoms are calculated as:
where:
ai = xi fi
(7.11)
bi = (1-xi ) fi
(7.12)
xi = split, or fraction of component i going to the overhead
Once the composition, vapour fraction, and pressure of the outlet
streams are know, a P-VF flash is performed to obtain the temperatures
and heat flows.
An overall heat balance is performed to obtain the energy stream heat
flow:
hE = hF - hO - hB
where:
hE = enthalpy of unknown energy stream
hF = enthalpy of feed stream
hO = enthalpy of overhead stream
hB = enthalpy of bottoms stream
7-42
(7.13)
Separation Operations
7-43
7.3.2 Component Splitter Property View
You can also add a
component splitter by
clicking the F12 hot key.
There are two ways that you can add a Component Splitter to your
simulation:
You can also open the
Object Palette by clicking
the F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Short Cut Columns radio button.
3.
From the list of available unit operations, select the Component
Splitter model.
4.
Click the Add button. The Component Splitter property view
appears.
OR
Component Splitter icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Component Splitter icon. The Component Splitter
property view appears.
Figure 7.30
Click the Ignored checkbox to tell HYSYS to ignore the unit operation
when solving the simulation. HYSYS completely disregards the
operation (and cannot calculate the outlet stream) until you restore it to
an active state by deactivating the checkbox.
7-43
7-44
Component Splitter
7.3.3 Design Tab
The Design tab consists of six pages:
•
•
•
•
•
•
Connections
Parameters
Splits
TBP Cut Point
User Variables
Notes
Each of the pages are discussed in the following sections.
Connections Page
You can specify an unlimited number of inlet streams to the
Component Splitter on the Connections page. You must specify the
overhead outlet stream, bottoms outlet stream, and an unlimited
number of energy streams.
Figure 7.31
One of the attached energy streams should have an unspecified energy
value to allow the operation to solve the energy balance.
7-44
Separation Operations
7-45
Parameters Page
The Parameters page displays the stream parameters. You must specify
the stream parameters, which include the vapour fraction, pressure of
the overhead stream, and pressure of the bottoms stream.
Figure 7.32
Splits Page
The Splits page allows you to specify the separation fraction of the outlet
streams.
Figure 7.33
7-45
7-46
For example, if the majority
of your components are
going overhead, simply click
the All 1 button, rather than
repeatedly entering fractions
of 1. Then, correct the splits
appropriately for the
components not leaving
entirely in the overhead.
You can specify a
temperature cut point of 0 K
and higher.
The TBP Cut Point Page is
designed for streams with
hypothetical components.
Component Splitter
The Splits, or separation fractions ranging from 0 to 1, must be specified
for each component in the overhead stream exiting the Component
Splitter. The quantity in the bottoms product is set once the overhead
fraction is known.
The two buttons on the Splits page, All 1 and All 0, allow you to specify
overhead fractions of one (100%) or zero (0%), respectively, for all
components. These buttons are useful if many components are leaving
entirely in either the overhead stream or bottoms stream.
TBP Cut Point Page
The TBP Cut Point page allows you to specify the compositions of the
product streams by providing the TBP Cut Point between the streams,
and assuming that there is sharp separation at the cut point.
Figure 7.34
On the TBP Cut Point page, the upper table allows you to specify the
initial TBP Cut Point on the Feed for each product stream except for the
overhead. The Initial Cut Point values are expressed in temperature and
they are listed in ascending order. Consecutive streams can have the
same Initial Cut Point value, implying that the second or subsequent
stream has zero flow.
The bottom table allows you to specify the split fraction for each
component in the stream. The split fraction values are also available on
the Splits page of the Design tab.
7-46
Separation Operations
7-47
Pure components are distributed according to their NBP (Natural
Boiling Point) while the TBP (True Boiling Point) of the pure
components defines the boundaries of distribution. The NBP for each
component is displayed in the NBP table for reference.
The TBP Cut Point page is designed for handling streams that carry
hypocomponents. The hypocomponents are treated as a continuum
and they are distributed according to their FBP (Final Boiling Point).
The FBP of each hypocomponent is first calculated by sorting the NBP
of the hypocomponents in ascending order. Then with the sorted order,
the FBP of the last hypocomponent is calculated as follows:
FBP
last
= NBP
last
+ ( NBP
last
– NBP
last – 1
)
(7.14)
The FBPs for other hypocomponents is calculated by:
NBP + NBP
i
i+1
FBP = ------------------------------------------i
2
(7.15)
The hypocomponents are then distributed according to where the cut
point lies. The boiling range for each hypocomponent is defined by the
FBP of the previous component to the FBP of the current component.
The boiling range for each product stream is from its Initial TBP Cut
Point to the Initial TBP Cut Point of the next stream.
User Variables Page
You can create and implement your own User Variables for use in a
HYSYS simulation on the User Variables page. For more information on
the User Variables refer to Chapter 5 - User Variables in the
Customization Guide.
7-47
7-48
Component Splitter
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
7.3.4 Rating Tab
You cannot provide any information for the Component Splitter on the
Rating tab when in steady state.
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. For more information about the Nozzles page,
refer to Section 1.6.2 - Nozzles in the Dynamics Modeling manual.
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
7.3.5 Worksheet Tab
7.3.6 Dynamics Tab
Information available on this page is relevant only to cases in Dynamic
mode. The Dynamics tab consists of the Specs page.
7-48
Separation Operations
7-49
Specs Page
The Specs page contains information regarding pressure specifications
of the streams.
Figure 7.35
The Equal Pressures checkbox allows you to propagate the pressure
from one stream to all others. If you want to equalize the pressures you
have to free up the pressure specs on the streams that you want the
pressure to be propagated to.
The Vessel Volume is also specified on this page.
7-49
7-50
7-50
Component Splitter
Column
8-1
8 Column
8.1 Column Sub-Flowsheet...................................................................4
8.2 Column Theory ..............................................................................10
8.2.1
8.2.2
8.2.3
8.2.4
Three Phase Theory..............................................................13
Detection of Three Phases ....................................................13
Initial Estimates .....................................................................14
Pressure Flow .......................................................................17
8.3 Column Installation .......................................................................21
8.3.1 Input Experts .........................................................................23
8.3.2 Templates ..............................................................................23
8.4 Column Property View ..................................................................32
8.4.1 Design Tab ............................................................................34
8.4.2 Parameters Tab .....................................................................48
8.4.3 Side Ops Tab .........................................................................68
8.4.4 Rating Tab .............................................................................72
8.4.5 Worksheet Tab.......................................................................75
8.4.6 Performance Tab ...................................................................76
8.4.7 Flowsheet Tab .......................................................................87
8.4.8 Reactions Tab........................................................................92
8.4.9 Dynamics Tab ........................................................................99
8.4.10 Perturb Tab ........................................................................101
8-1
8-2
Column
8.5 Column Specification Types....................................................... 103
8.5.1 Cold Property Specifications ............................................... 103
8.5.2 Component Flow Rate ........................................................ 104
8.5.3 Component Fractions.......................................................... 104
8.5.4 Component Ratio ................................................................ 105
8.5.5 Component Recovery ......................................................... 105
8.5.6 Cut Point ............................................................................. 106
8.5.7 Draw Rate ........................................................................... 106
8.5.8 Delta T (Heater/Cooler)....................................................... 106
8.5.9 Delta T (Streams)................................................................ 107
8.5.10 Duty................................................................................... 107
8.5.11 Duty Ratio.......................................................................... 107
8.5.12 Feed Ratio......................................................................... 108
8.5.13 Gap Cut Point.................................................................... 108
8.5.14 Liquid Flow ........................................................................ 109
8.5.15 Physical Property Specifications ....................................... 109
8.5.16 Pump Around Specifications ............................................. 109
8.5.17 Reboil Ratio....................................................................... 110
8.5.18 Recovery ........................................................................... 110
8.5.19 Reflux Feed Ratio ............................................................. 111
8.5.20 Reflux Fraction Ratio......................................................... 111
8.5.21 Reflux Ratio....................................................................... 112
8.5.22 Tee Split Fraction .............................................................. 112
8.5.23 Tray Temperature .............................................................. 112
8.5.24 Transport Property Specifications ..................................... 113
8.5.25 User Property .................................................................... 113
8.5.26 Vapor Flow ........................................................................ 114
8.5.27 Vapor Fraction ................................................................... 114
8.5.28 Vapor Pressure Specifications .......................................... 114
8.5.29 Column Stream Specifications .......................................... 115
8.6 Column-Specific Operations ...................................................... 116
8.6.1
8.6.2
8.6.3
8.6.4
8-2
Condenser........................................................................... 117
Reboiler............................................................................... 134
Tray Section ........................................................................ 147
Tee ...................................................................................... 165
8-3
Column
8.7 Running the Column ................................................................... 166
8.7.1 Run...................................................................................... 167
8.7.2 Reset................................................................................... 168
8.8 Column Troubleshooting ............................................................ 169
8.8.1 Heat and Spec Errors Fail to Converge .............................. 170
8.8.2 Equilibrium Error Fails to Converge .................................... 174
8.8.3 Equilibrium Error Oscillates................................................. 174
8.9 References ................................................................................... 175
8-3
8-4
Column Sub-Flowsheet
8.1 Column Sub-Flowsheet
For detailed information about
sub-flowsheet manipulation,
refer to Chapter 3 - Flowsheet
in the User Guide.
The Column is a special type of sub-flowsheet in HYSYS. A subflowsheet contains equipment and streams, and exchanges information
with the parent flowsheet through the connected internal and external
streams. From the main simulation environment, the Column appears
as a single, multi-feed multi-product operation. In many cases, you can
treat the column in exactly that manner.
You can also work inside the Column sub-flowsheet. You can do this to
“focus” your attention on the Column. When you move into the Column
build environment, the main simulation is “cached.” All aspects of the
main environment are paused until you exit the Column build
environment. When you return to the Main Environment, the Desktop
re-appears as it was when you left it.
You can also enter the Column build environment when you want to
create a custom column configuration. Side equipment such as pump
arounds, side strippers, and side rectifiers can be added from the
Column property view in the main simulation. However, if you want to
install multiple tray sections or multiple columns, you need to enter the
Column build environment. Once inside, you can access the Columnspecific operations (Tray Sections, Heaters/Coolers, Condensers,
Reboilers, etc.) and build the column as you would any other flowsheet.
In this chapter, the use of the
Column property view and
Column Templates are
explained. Section 8.6 Column-Specific Operations,
describes the unit operations
available in the Column build
environment.
If you want to create a custom column template for use in other
simulations, on the File menu select the New command, and then select
the Column sub-command. Since this is a column template, you can
access the Column build environment directly from the Basis
environment. Once you have created the template, you can store it on
disk. Before you install the template in another simulation, ensure that
the Use Input Experts checkbox in the Session Preferences view is
unchecked.
Having a Column sub-flowsheet provides a number of advantages:
•
•
•
•
8-4
isolation of the Column Solver.
optional use of different Property Packages.
construction of custom templates.
ability to solve multiple towers simultaneously.
Column
8-5
Isolation of the Column Solver
One advantage of the Column build environment is that it allows you to
make changes, and focus on the Column without requiring a
recalculation of the entire flowsheet. When you enter the Column build
environment, HYSYS clears the Desktop by caching all views that were
open in the parent flowsheet. Then the views that were open when you
were last in the Column build environment are re-opened.
While in the Column subflowsheet, you can view the
Workbook or PFD for both
the Parent flowsheet or subflowsheet by using the
Workbooks option or PFDs
option in the Tools menu.
PFD icon
Once inside the Column build environment, you can access profiles,
stage summaries, and other data, as well as make changes to Column
specifications, parameters, equipment, efficiencies, or reactions. When
you have made the necessary changes, simply run the Column to
produce a new converged solution. The parent flowsheet cannot
recalculate until you return to the parent build environment.
The sub-flowsheet environment permits easy access to all streams and
operations associated with your column. Click the PFD icon to view the
sub-flowsheet. If you want to access information regarding column
product streams, click the Workbook icon to view the Column
workbook, which displays the Column information exclusively.
Independent Fluid Package
Workbook icon
HYSYS allows you to specify a unique fluid package for the Column subflowsheet. Here are some instances where a separate fluid package is
useful:
•
•
•
If a column does not use all of the components used in the main
flowsheet, it is often advantageous to define a new fluid package
with only the components that are necessary. This speeds up the
column solution.
In some cases, a different fluid package can be better suited to
the column conditions. For example, if you want to redefine
Interaction Parameters such that they are applicable for the
operating range of the column.
In Dynamic mode, different columns can operate at very different
temperatures and pressures. With each fluid package, you can
define a different dynamic model whose parameters can be
regressed in the appropriate temperature and pressure range,
thus, improving the accuracy and stability of the dynamic
simulation.
8-5
8-6
Column Sub-Flowsheet
Ability to construct Custom Column Configurations
Complex custom columns
and multiple columns can be
simulated within a single subflowsheet using various
combinations of subflowsheet equipment.
Column arrangements are
created in the same way that
you build the main flowsheet:
• accessing various
operations.
• making the appropriate
connections.
• defining the
parameters.
Custom column configurations can be stored as templates, and recalled
into another simulation. To create a custom template, on the File menu
select the New command, and then select the Column sub-command.
When you store the template, it has a .col extension.
There exists a great deal of freedom when defining column
configurations, and you can define column setups with varying degrees
of complexity. You can use a wide array of column operations in a
manner which is straightforward and flexible.
Use of Simultaneous Solution Algorithm
The Column sub-flowsheet uses a simultaneous solver whereby all
operations within the sub-flowsheet are solved simultaneously. The
simultaneous solver permits you to install multiple unit operations
within the sub-flowsheet (interconnected columns, for example)
without the need for Recycle blocks.
Dynamic Mode
There are several major differences between the dynamic column
operation and the steady state column operation. One of the main
differences is the way in which the Column sub-flowsheet solves. In
steady state if you are in the Column sub-flowsheet, calculations in the
main flowsheet are put on Hold until the focus is returned to the main
flowsheet. When running in dynamics, calculations in the main
flowsheet proceed at the same time as those in the Column subflowsheet.
Another difference between the steady state column and the dynamic
column is with the column specifications. Steady state column
specifications are ignored in dynamics. To achieve the column
specifications when using dynamics, control schemes must be added to
the column.
8-6
Column
8-7
Finally, although it is possible to turn off static head contributions for
the rest of the simulation, this option does not apply to the column.
When running a column in Dynamic mode, the static head
contributions are always used in the column calculations.
Column Property View
Side equipment (pump
arounds, side strippers, etc.)
is added from the Column
property view.
The Column property view (the representation of the Column within the
main or parent flowsheet) essentially provides you with complete access
to the Column. You can enter the Column sub-flowsheet to add new
pieces of equipment, such as additional Tray Sections or Reboilers.
Figure 8.1
From the Column property view, you can change feed and product
connections, specifications, parameters, pressures, estimates,
efficiencies, reactions, side operations, and view the Profiles, Work
Sheet, and Summary. You can also run the column from the main
flowsheet just as you would from the Column sub-flowsheet. This is
described in Section 8.4 - Column Property View.
8-7
8-8
Column Sub-Flowsheet
If you want to make a minor change to a column operation (for instance,
resize a condenser) you can call up that operation using the Object
Navigator without entering the Column sub-flowsheet. Major changes,
such as adding a second tray section, require you to enter the Column
sub-flowsheet. To access to the Column build environment, click the
Column Environment button at the bottom of the Column property
view.
Main/Column Sub-flowsheet Relationship
If you make a change to the
Column while you are
working in the parent, or
main build environment, both
the Column and the parent
flowsheets are automatically
recalculated.
Unlike other unit operations, the Column contains its own subflowsheet, which in turn, is contained in the Parent (usually the main)
flowsheet. When you are working in the parent flowsheet, the Column
appears just as any other unit operation, with multiple input and output
streams, and various adjustable parameters. If changes are made to any
of these basic column parameters, both the Column sub-flowsheet and
parent flowsheet are recalculated.
When you install a Column, HYSYS creates a sub-flowsheet containing
all operations and streams associated with the template you have
chosen. This sub-flowsheet operates as a unit operation in the main
flowsheet. Figure 8.2 shows this concept of a Column sub-flowsheet
within a main flowsheet.
Main Flowsheet / Sub-flowsheet Concept
Consider a simple absorber in which you want to remove CO2 from a gas
stream using H2O as the solvent. A typical approach to setting up the
problem would be as follows:
8-8
1.
Create the gas feed stream, FeedGas, and the water solvent stream,
WaterIn, in the main flowsheet.
2.
Click the Absorber icon from the Object Palette, and specify the
stream names, number of trays, pressures, estimates, and
specifications. You must also specify the names of the outlet
streams, CleanGas and WaterOut.
3.
Run the Column from the main flowsheet Column property view.
Column
A sub-flowsheet stream that
is connected to a stream in
the main flowsheet is
automatically given the
same name with “@Subflowsheet tag” attached at
the end of the name. An
example is the stream
named “WaterIn” has the
sub-flowsheet stream
named “[email protected]”.
8-9
When you connected the streams to the tower, HYSYS created internal
streams with the same names. The Connection Points or “Labels” serve
to connect the main flowsheet streams to the sub-flowsheet streams
and facilitate the information transfer between the two flowsheets. For
instance, the main flowsheet stream WaterIn is “connected” to the subflowsheet stream WaterIn.
Figure 8.2
The connected streams do not necessarily have the same values. All
specified values are identical, but calculated stream variables can be
different depending on the fluid packages and transfer basis (defined on
the Flowsheet tab).
When working in the main build environment, you “see” the Column
just as any other unit operation, with a property view containing
parameters such as the number of stages, and top and bottom
pressures. If you change one of these parameters, the sub-flowsheet
recalculates (just as if you had clicked the Run button); the main
flowsheet also recalculates once a new column solution is reached.
8-9
8-10
If you delete any streams
connected to the column in
the main flowsheet, these
streams are also deleted in
the Column sub-flowsheet.
Column Theory
However, if you are inside the Column sub-flowsheet build
environment, you are working in an entirely different flowsheet. To
make a major change to the Column such as adding a reboiler, you must
enter the Column sub-flowsheet build environment. When you enter
this environment, the main flowsheet is put on “hold” until you return.
8.2 Column Theory
For information regarding the
electrolyte column theory,
refer to Section 1.6.8 HYSYS Column Operation
in the HYSYS OLI Interface
manual.
Multi-stage fractionation towers, such as crude and vacuum distillation
units, reboiled demethanizers, and extractive distillation columns, are
the most complex unit operations that HYSYS simulates. Depending on
the system being simulated, each of these towers consists of a series of
equilibrium or non-equilibrium flash stages. The vapour leaving each
stage flows to the stage above and the liquid from the stage flows to the
stage below. A stage can have one or more feed streams flowing onto it,
liquid or vapour products withdrawn from it, and can be heated or
cooled with a side exchanger.
The following figure shows a typical stage j in a Column using the topdown stage numbering scheme. The stage above is j-1, while the stage
below is j+1. The stream nomenclature is shown in the figure below.
Figure 8.3
Lj-1
Vj
F = Stage feed stream
VSDj
Fj
Stage j
Qj
Rj
LSDj
Vj+1
8-10
Lj
L = Liquid stream travelling
to stage below
V = Vapor stream travelling
to stage above
LSD = Liquid side draw from
stage
VSD = Vapor side draw from
stage
Q = Energy stream entering
stage
Column
8-11
More complex towers can have pump arounds, which withdraw liquid
from one stage of the tower and typically return it to a stage farther up
the column. Small auxiliary towers, called sidestrippers, can be used on
some towers to help purify side liquid products. With the exception of
Crude distillation towers, very few columns have all of these items, but
virtually any type of column can be simulated with the appropriate
combination of features.
It is important to note that the Column operation by itself is capable of
handling all the different fractionation applications. HYSYS has the
capability to run cryogenic towers, high pressure TEG absorption
systems, sour water strippers, lean oil absorbers, complex crude towers,
highly non-ideal azeotropic distillation columns, etc. There are no
programmed limits for the number of components and stages. The size
of the column which you can solve depends on your hardware
configuration and the amount of computer memory you have available.
The column is unique among the unit operations in the methods used
for calculations. There are several additional underlying equations
which are used in the column.
The Francis Weir equation is the starting point for calculating the liquid
flowrate leaving a tray:
L N = Cρl w h
where:
1.5
(8.1)
LN = liquid flowrate leaving tray N
C = units conversion constant
ρ = density of liquid on tray
lw = weir length
h = height of liquid above weir
8-11
8-12
Column Theory
The vapour flowrate leaving a tray is determined by the resistance
equation:
F vap = k ∆P friction
where:
For columns the
conductance, k, is
proportional to the square of
the column diameter.
The pressure drop across a
stage is determined by
summing the static head
and the frictional losses.
(8.2)
Fvap = vapour flowrate leaving tray N
k = conductance, which is a constant representing the reciprocal of
resistance to flow
∆P friction = dry hole pressure drop
It is possible to use column stage efficiencies when running a column in
dynamics. The efficiency is equivalent to bypassing a portion of the
vapour around the liquid phase, as shown in the figure below, where n is
the specified efficiency.
Figure 8.4
HYSYS has the ability to model both weeping and flooding inside the
column. If ∆P friction is very small, the stage exhibits weeping. Therefore it
is possible to have a liquid flow to the stage below even if the liquid
height over the weir is zero.
8-12
Column
8-13
For the flooding condition, the bulk liquid volume approaches the tray
volume. This can be observed on the Holdup page in the Dynamics tab,
of either the Column Runner or the Tray Section property view.
8.2.1 Three Phase Theory
For non-ideal systems with more than two components, boundaries can
exist in the form of azeotropes, which a simple distillation system
cannot cross. The formation of azeotropes in a three phase system
provides a thermodynamic barrier to separating chemical mixtures.
Distillation schemes for non-ideal systems are often difficult to
converge without very accurate initial guesses. To aid in the
initialization of towers, a Three Phase Input Expert is available to
initialize temperatures, flows, and compositions. Refer to Section 8.3.2 Templates for further details on the three phase capabilities in HYSYS.
For non-ideal multicomponent systems, DISTIL is an excellent tool for
determining process viability. This conceptual design software
application also determines the optimal feed tray location and allows
direct export of column specifications to HYSYS for use as an initial
estimate. Contact your local AspenTech representative for details.
8.2.2 Detection of Three Phases
Look at the Trace Window for
column convergence
messages.
Whenever your Column converges, HYSYS automatically performs a
Three Phase Flash on the top stage. If a second liquid phase is detected,
and no associated water draw is found, a warning message appears.
If there is a water draw, HYSYS checks the next stage for a second liquid
phase, with the same results as above. This continues down the Tower
until a stage is found that is two phase only.
If there is a three phase stage below a stage that was found to be two
phase, the three phase stage is not detected because the checking
would have ended in the previous two phase stage.
HYSYS always indicates the existence of the second liquid phase. This
continues until the Column reverts to VLE operation, or all applicable
stages have water draws placed on them.
8-13
8-14
Column Theory
8.2.3 Initial Estimates
Initial estimates are optional values that you provide to help the HYSYS
algorithm converge to a solution. The better your estimates, the quicker
HYSYS converges.
There are three ways for you to provide the column with initial
estimates:
•
•
Refer to Section 8.3.2 Templates for more
information regarding
default specifications.
•
Provide the estimate values when you first build the column.
Go to the Profiles or Estimates page on the Parameters tab to
provide the estimate values.
Go to the Monitor or Specs page on the Design tab to provide
values for the default specifications or add your own
specifications.
It is important to remember, when the column starts to solve for the first
time or after the column has been reset, the specification values are also
initial estimates. So if you replaced one of the original default
specifications (overhead vapour flow, side liquid draw or reflux ratio)
with a new active specification, the new specification value is used as
initial estimates. For this reason it is recommended you provide
reasonable specification values initially even if you can replace them
while the column is solving or after the column has solved.
Although HYSYS does not require any estimates to converge to a
solution, reasonable estimates help in the convergence process.
Temperatures
Temperature estimates can be given for any stage in the column,
including the condenser and reboiler, using the Profiles page in the
Parameters tab of the Column property view. Intermediate temperatures
are estimated by linear interpolation. When large temperature changes
occur across the condenser or bottom reboiler, it would be helpful to
provide an estimate for the top and bottom trays in the tray section.
If the overhead product is a subcooled liquid, it is best to specify an
estimated bubble-point temperature for the condenser rather than the
subcooled temperature.
8-14
Column
8-15
Mixing Rules at Feed Stages
When a feed stream is introduced onto a stage of the column, the
following sequence is employed to establish the resulting internal
product streams:
1.
The entire component flow (liquid and vapour phase) of the feed
stream is added to the component flows of the internal vapour and
liquid phases entering the stage.
2.
The total enthalpy (vapour and liquid phases) of the feed stream is
added to the enthalpies of the internal vapour and liquid streams
entering the stage.
3.
HYSYS flashes the combined mixture based on the total enthalpy at
the stage Pressure. The results of this process produce the
conditions and composition of the vapour and liquid phases leaving
the stage.
In most physical situations, the vapour phase of a feed stream does not
come in close contact with the liquid on its feed stage. However if this is
the case, the column allows you to split all material inlet streams into
their phase components before being fed to the column. The Split Inlets
checkbox can be activated in the Setup page of the Flowsheet tab. You
can also set all the feed streams to a column to always split, by activating
the appropriate checkbox in the Options page from the Simulation tab
of the Session Preferences view.
Basic Column Parameters
Regardless of the type of column, the Basic Column Parameters remain
at their input values during convergence.
Pressure
The pressure profile in a Column Tray Section is calculated using your
specifications. You can either explicitly enter all stage pressures or enter
the top and bottom tray pressures (and any intermediate pressures)
such that HYSYS can interpolate between the specified values to
determine the pressure profile. Simple linear interpolation is used to
calculate the pressures on stages which are not explicitly specified.
8-15
8-16
Column Theory
You can enter the condenser and reboiler pressure drops explicitly
within the appropriate operation view. Default pressure drops for the
condenser and reboiler are zero, and a non-zero value is not necessary
to produce a converged solution.
If the pressure of a Column product stream (including side vapour or
liquid draws, side stripper bottom streams, or internal stream
assignments) is set (either by specification or calculation) prior to
running the Column, HYSYS “backs” this value into the column and
uses this value for the convergence process. If you do specify a stream
pressure that allows HYSYS to calculate the column pressure profile, it is
not necessary to specify another value within the column property view.
If you later change the pressure of an attached stream, the Column is
rerun.
Recall that whenever a change is made in a stream, HYSYS checks all
operations attached to that stream and recalculates as required.
Number of Stages
The number of stages that you specify for the tray section does not
include the condenser and bottom reboiler, if present. If sidestrippers
are to be added to the column, their stages are not included in this
number. By default, HYSYS numbers stages from the top down. If you
want, you can change the numbering scheme to bottom-up by selecting
this scheme on the Connections page of the Design tab.
HYSYS initially treats the stages as being ideal. If you want your stages to
be treated as real stages, you must specify efficiencies on the Efficiencies
page of the Parameters tab. Once you provide efficiencies for the stages,
even if the value you specify is 1, HYSYS treats the stages as being real.
Stream
The feed stream and product stream location, conditions, and
composition are treated as Basic Column Parameters during
convergence.
8-16
Column
8-17
8.2.4 Pressure Flow
In the following sections, the pressure flow specifications presented are
the recommended configurations if no other equipment, such as side
strippers, side draws, heat exchanger, etc., are connected. Other
combinations of pressure flow specifications are possible, however they
can lead to less stable configurations.
Regardless of the pressure flow specification configuration, when
performing detailed dynamic modeling it is recommended that at least
valves be added to all boundary streams. Once valves have been added,
the resulting boundary streams can all be specified with pressure
specifications, and, where necessary, flow controlled with flow
controllers.
Absorber
The basic Absorber column has two inlet and two exit streams. When
used alone, the Absorber has four boundary streams and so requires
four Pressure Flow specifications. A pressure specification is always
required for the liquid product stream leaving the bottom of the column.
A second pressure specification should be added to the vapour product
of the column, with the two feed streams having flow specifications.
The column
shows the recommended
pressure flow
specifications for a stand
alone absorber column.
If there are down stream unit operations attached to the liquid product
stream, then a column sump needs to be simulated. There are several
methods for simulating the column sump. A simple solution is to use a
reboiled absorber, with the reboiler duty stream specified as zero in
place of the absorber. Another option is to feed the liquid product
stream directly into a separator, and return the separator vapour
product to the bottom stage of the column.
8-17
8-18
Column Theory
Refluxed Absorber
The basic Refluxed Absorber column has a single inlet and two or three
exit streams, depending on the condenser configuration. When used
alone, the Refluxed Absorber has three or four boundary streams
(depending on the condenser) and requires four or five pressure-flow
specifications; generally two pressure and three flow specifications. A
pressure specification is always required for the liquid product stream
leaving the bottom of the column. The extra specification is required
due to the reflux stream and is discussed in Section 8.6 - ColumnSpecific Operations.
The column shows the
recommended pressure
flow specifications for a
stand alone refluxed
absorber with a partial
condenser.
If there are down stream unit operations attached to the liquid product
stream, then a column sump needs to be simulated. There are several
methods for simulating the column sump. A simple solution is to use a
distillation column, with the reboiler duty stream specified as zero in
place of the refluxed absorber. Another option is to feed the liquid
product stream directly into a separator, and return the separator
vapour product to the bottom stage of the column.
Reboiled Absorber
A Reboiled Absorber column has a single inlet and two exit streams.
When used alone, the Reboiled Absorber has three boundary streams
and so requires three Pressure Flow specifications; one pressure and two
flow specifications. A pressure specification is always required for the
vapour product leaving the column.
The column shows the
recommended pressure
flow specifications for a
stand alone reboiled
absorber.
8-18
Column
8-19
Distillation Column
The basic Distillation column has one inlet and two or three exit
streams, depending on the condenser configuration. When used alone,
the Distillation column has three or four boundary streams but requires
four or five pressure-flow specifications; generally one pressure and
three or four flow specifications. The extra pressure-flow specification is
required due to the reflux stream, and is discussed in Section 8.6 Column-Specific Operations.
The column shows the
recommended pressureflow specifications for a
stand alone distillation
column with a partial
condenser.
The Three Phase Distillation column is similar to the basic Distillation
column except it has three or four exit streams. So when used alone, the
Three Phase Distillation column has four to five boundary streams, but
requires five or six pressure-flow specifications; generally one pressure
and four to five flow specifications.
Condenser and Reboiler
The following sections provide some recommended pressure-flow
specifications for simple dynamic modeling only. The use of flow
specifications on reflux streams is not recommended for detailed
modeling. If the condenser liquid level goes to zero, a mass flow
specification results in a large volumetric flow because the stream is a
vapour.
The column shows the
recommended pressureflow specifications for a
stand alone three phase
distillation column with a
partial condenser.
It is highly recommended that the proper equipment be added to the
reflux stream (e.g., pumps, valves, etc.). In all cases, level control for the
condenser should be used to ensure a proper liquid level.
Partial Condenser
The partial condenser has three exit streams:
•
•
•
overhead vapour
reflux
distillate
8-19
8-20
Column Theory
All three exit streams must be specified when attached to the main tray
section. One pressure specification is recommended for the vapour
stream, and one flow specification for either of the liquid product
streams. The final pressure flow specification can be a second flow
specification on the remaining liquid product stream, or the Reflux
Flow/Total Liquid Flow value on the Specs page of the Dynamics tab of
the condenser can be specified.
Fully-Refluxed Condenser
The Fully-Refluxed condenser has two exit streams:
•
•
overhead vapour
reflux
A pressure specification is required for the overhead vapour stream, and
a flow specification is required for the reflux stream.
Total Condenser
A Total condenser has two exit streams:
•
•
reflux
distillate
There are several possible configurations of pressure flow specifications
for this type of condenser. A flow specification can be used for the reflux
stream and a pressure flow spec can be used for the distillate stream.
Two flow specifications can be used, however, it is suggested that a
vessel pressure controller be setup with the condenser duty as the
operating variable.
Reboiler
The Reboiler has two exit streams:
•
•
boilup vapour
bottoms liquid
Only one exit stream can be specified. If a pressure constraint is
specified elsewhere in the column, this exit stream must be specified
with a flow rate.
8-20
Column
8-21
8.3 Column Installation
The first step in installing a Column is deciding which type you want to
install. Your choice depends on the type of equipment (for example,
reboilers and condensers) your Column requires. HYSYS has several
basic Column templates (pre-constructed column configurations)
which can be used for installing a new Column. The most basic Column
types are described in the table below.
Basic Column Types
Icon
Description
Absorber
Tray section only.
Liquid-Liquid Extractor
Tray section only.
Reboiled Absorber
Tray section and a bottom stage reboiler.
Refluxed Absorber
Tray section and an overhead condenser.
Distillation
Tray section with both a reboiler and
condenser.
Three Phase
Distillation
Tray section, three-phase condenser,
reboiler. Condenser can be either chemical
or hydrocarbon specific.
8-21
8-22
You can also add a basic
Column type by pressing the
F12 hot key.
You can also open the
Object Palette by pressing
the F4 hot key.
Column Installation
There are two ways that you can add a basic Column type to your
simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Prebuilt Columns radio button.
3.
From the list of available unit operations, select the column type.
4.
Click the Add button. The Input Expert view appears. Refer to
Section 8.3.1 - Input Experts for more information.
OR
1.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
2.
Double-click the column type icon, as described in the table above.
The Input Expert view appears.
There are also more complex Column types, which are described in the
table below.
You can also add a complex
Column type by pressing the
F12 hot key.
8-22
Complex Column Types
Description
3 Sidestripper Crude Column
Tray section, reboiler, condenser, 3 sidestrippers,
and 3 corresponding pump around circuits.
4 Sidestripper Crude Column
Tray section, reboiler, condenser, an uppermost
reboiled sidestripper, 3 steam-stripped lower
sidestrippers, and 3 corresponding pump around
circuits.
FCCU Main Fractionator
Tray section, condenser, an upper pump around
reflux circuit and product draw, a mid-column twoproduct-stream sidestripper, a lower pump around
reflux circuit and product draw, and a quench pump
around circuit at the bottom of the column.
Vacuum Reside Tower
Tray section, 2 side product draws with pump around
reflux circuits and a wash oil-cooled steam stripping
section below the flash zone.
To add a complex column type to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Prebuilt Columns radio button.
3.
From the list of available unit operations, select the column type.
4.
Click the Add button. The column property view appears.
Column
8-23
8.3.1 Input Experts
Input Experts guide you through the installation of a Column. The Input
Experts are available for the following six standard column templates:
•
•
•
•
•
•
Absorber
Liquid-Liquid Extractor
Reboiled Absorber
Refluxed Absorber
Distillation
Three Phase Distillation
Details related to each column template are outlined in Section 8.3.2 Templates. Each Input Expert contains a series of input pages whereby
you must specify the required information for the page before
advancing to the next one. When you have worked through all the pages,
you have specified the basic information required to build your column.
You are then placed in the Column property view which gives
comprehensive access to most of the column features.
Refer to Chapter 12 Session Preferences in the
User Guide for details on how
to access the Session
Preferences view.
It is not necessary to use the Input Experts to install a column. You can
disable and enable the use of Input Experts on the Options page in the
Simulation tab of the Session Preferences view. If you do not use the
Input Experts, you move directly to the Column property view when you
install a new column.
8.3.2 Templates
Press F12 to access the
UnitOps view, which allows
you to add a column
template.
HYSYS contains a number of column templates which have been
designed to simplify the installation of columns.
A Column Template is a pre-constructed configuration or “blueprint” of
a common type of Column, including Absorbers, Reboiled and Refluxed
Absorbers, Distillation Towers, and Crude Columns. A Column Template
contains the unit operations and streams that are necessary for defining
the particular column type, as well as a default set of specifications.
8-23
8-24
Column Installation
Figure 8.5
All Column templates can be viewed by selecting the Prebuilt Columns
radio button.
When you add a new Column, HYSYS gives you a choice of the available
templates. Simply select the template that most closely matches your
column configuration, provide the necessary input in the Input Expert
view (if applicable), and HYSYS installs the equipment and streams for
you in a new Column sub-flowsheet. Stream connections are already in
place, and HYSYS provides default names for all internal streams and
equipment. You can then make modifications by adding, removing or
changing the names of any streams or operations to suit your specific
requirements.
Clicking the Side Ops button on the final page of the Column Input
Expert opens the Side Operations Input Expert wizard, which guides you
through the process of adding a side operation to your column.
In addition to the basic Column Templates which are included with
HYSYS, you can create custom Templates containing Column
configurations that you commonly use.
8-24
Column
8-25
HYSYS Column Conventions
Column Tray Sections, Overhead Condensers, and Bottom Reboilers are
each defined as individual unit operations. Condensers and Reboilers
are not numbered stages, as they are considered to be separate from the
Tray Section.
By making the individual
components of the column
separate pieces of
equipment, there is easier
access to equipment
information, as well as the
streams connecting them.
The following are some of the conventions, definitions, and descriptions
of the basic columns:
Column Component
Description
Tray Section
A HYSYS unit operation that represents the series of
equilibrium trays in a Column.
Stages
Stages are numbered from the top down or from the
bottom up, depending on your preference. The top tray is
1, and the bottom tray is N for the top-down numbering
scheme. The stage numbering preference can be
selected on the Connections page of the Design tab on
the Column property view.
Overhead Vapor Product
The overhead vapour product is the vapour leaving the
top tray of the Tray Section in simple Absorbers and
Reboiled Absorbers. In Refluxed Absorbers and
Distillation Towers, the overhead vapour product is the
vapour leaving the Condenser.
Overhead Liquid Product
The overhead liquid product is the Distillate leaving the
Condenser in Refluxed Absorbers and Distillation
Towers. There is no top liquid product in simple
Absorbers and Reboiled Absorbers.
Bottom Liquid Product
The bottom liquid product is the liquid leaving the bottom
tray of the Tray Section in simple Absorbers and Refluxed
Absorbers. In Reboiled Absorbers and Distillation
Columns, the bottom liquid product is the liquid leaving
the Reboiler.
Overhead Condenser
An Overhead Condenser represents a combined Cooler
and separation stage, and is not given a stage number.
Bottom Reboiler
A Bottom Reboiler represents a combined heater and
separation stage, and is not given a stage number.
8-25
8-26
Column Installation
Default Replaceable Specifications
Replaceable specifications are the values, which the Column
convergence algorithm is trying to meet. When you select a particular
Column template, or as you add side equipment, HYSYS creates default
specifications. You can use the specifications that HYSYS provides, or
replace these specifications with others more suited to your
requirements.
The available default replaceable specifications are dependent on the
Basic Column type (template) that you have chosen. The default
specifications for the four basic column templates are combinations of
the following:
The pressure for a tray
section stage, condenser or
reboiler can be specified at
any time on the Pressures
page of the Column
property view.
The specifications in
HYSYS can be set as
specifications or changed
to estimates. Refer to the
Monitor Page and Specs
Page in Section 8.4.1 Design Tab for more
information.
8-26
•
•
•
•
•
Overhead vapour flowrate
Distillate flowrate
Bottoms flowrate
Reflux ratio
Reflux rate
The provided templates contain only pre-named internal streams
(streams which are both a feed and product). For instance, the Reflux
stream, which is named by HYSYS, is a product from the Condenser and
a feed to the top tray of the Tray Section.
In the following schematics, you specify the feed and product streams,
including duty streams.
Column
8-27
Absorber Template
The only unit operation contained in the Absorber is the Tray Section,
and the only streams are the overhead vapour and bottom liquid
products.
A schematic
representation of the
Absorber.
The Liquid-Liquid Extraction
Template is identical to the
Absorber Template.
There are no available specifications for the Absorber, which is the base
case for all tower configurations. The conditions and composition of the
column feed stream, as well as the operating pressure, define the
resulting converged solution. The converged solution includes the
conditions and composition of the vapour and liquid product streams.
The remaining Column templates have additional equipment, thus
increasing the number of required specifications.
Reboiled Absorber Template
The Reboiled Absorber template consists of a tray section and a bottom
reboiler. Two additional streams connecting the Reboiler to the Tray
Section are also included in the template.
Figure 8.6
When you install a Reboiled Absorber (i.e., add only a Reboiler to the
Tray Section), you increase the number of required specifications by one
over the Base Case. As there is no overhead liquid, the default
specification in this case is the overhead vapour flow rate.
8-27
8-28
Column Installation
Refluxed Absorber Template
The Refluxed Absorber template contains a Tray Section and an
overhead Condenser (partial or total). Additional material streams
associated with the Condenser are also included in the template. For
example, the vapour entering the Condenser from the top tray is named
to Condenser by default, and the liquid returning to the Tray Section is
the Reflux.
Figure 8.7
When you install a Refluxed Absorber, you are adding only a Condenser
to the base case. Specifying a partial condenser increases the number of
required specifications by two over the Base Case. The default
specifications are the overhead vapour flow rate, and the side liquid
(Distillate) draw. Specifying a total condenser results in only one
available specification, since there is no overhead vapour product.
Either of the overhead vapour or distillate flow rates can be specified as
zero, which creates three possible combinations for these two
specifications. Each combination defines a different set of operating
conditions. The three possible Refluxed Absorber configurations are
listed below:
•
•
•
8-28
Partial condenser with vapour overhead but no side liquid
(distillate) draw.
Partial condenser with both vapour overhead and distillate draws.
Total condenser with distillate but no vapour overhead draw.
Column
8-29
Distillation Template
If you select the Distillation template, HYSYS creates a Column with
both a Reboiler and Condenser. The equipment and streams in the
Distillation template are therefore a combination of the Reboiled
Absorber and Refluxed Absorber Templates
Figure 8.8
Reflux Ratio
The number of specifications for a column with both a Reboiler and
Condenser depends on the condenser type. For a partial condenser, you
must specify three specifications. For a total condenser, you must
specify two specifications. The third default specification (in addition to
Overhead Vapor Flow Rate and Side Liquid Draw) is the Reflux Ratio.
Figure 8.9
8-29
8-30
Column Installation
The Reflux Ratio is defined as the ratio of the liquid returning to the tray
section divided by the total flow of the products (see the figure above). If
a water draw is present, its flow is not included in the ratio.
As with the Refluxed Absorber, the Distillation template can have either
a Partial or Total Condenser. Choosing a Partial Condenser results in
three replaceable specifications, while a Total Condenser results in two
replaceable specifications.
The pressure remains fixed
during the Column
calculations.
The pressure in the tower is, in essence, a replaceable specification, in
that you can change the pressure for any stage from the Column
property view.
The following table gives a summary of replaceable column (default)
specifications for the basic column templates.
Templates
Vapour Draw
Reboiled Absorber
X
Distillate Draw
Reflux Ratio
Refluxed Absorber
Total Condenser
Partial Condenser
X
X
X
Distillation
Total Condenser
Partial Condenser
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X
X
X
X
X
Column
8-31
Three Phase Distillation Template
The same standard column
types exist for a three phase
system that are available for
the “normal” two phase
(binary) systems.
If you select the Three Phase Distillation template, HYSYS creates a
Column based on a three phase column model.
Figure 8.10
Using the Three Phase Column Input Expert, the initial view allows you
to select from the following options:
•
•
•
•
Distillation
Refluxed Absorber
Reboiled Absorber
Absorber
Each choice builds the appropriate column based on their respective
standard (two phase) system templates.
If the Input Expert is turned off, installing a Three Phase column
template opens a default Column property view for a Distillation type
column equipped with a Reboiler and Condenser.
The key difference between using the standard column templates and
their three phase counterparts lies in the solver that is used. The default
solver for three phase columns is the “Sparse Continuation” solver
which is an advanced solver designed to handle three phase, non ideal
chemical systems, that other solvers cannot.
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Column Property View
When using the Three Phase Column Input Expert some additional
specifications can be required when compared with the standard
(binary system) column setups.
Figure 8.11
It requires some expertise to set up,
initialize, and solve three phase
distillation problems. Additional
modeling software applications such
as DISTIL, use residue curve maps
and distillation region diagrams to
determine feasible designs, and can
greatly assist in the initial design
work. Contact your local AspenTech
representative for details.
Clicking the Side Ops button on the final page of the Three Phase
Column Input Expert opens the Side Operations Input Expert wizard,
which guides you through the process of adding a side operation to your
column.
8.4 Column Property View
Column Runner icon
Column Runner is another
name for the sub-flowsheet
Column property view.
The column property view is sectioned into tabs containing pages with
information pertaining to the column. The column property view is
accessible from the main flowsheet or Column sub-flowsheet. In the
Column sub-flowsheet, the column property view is also known as the
Column Runner, and can be accessed by clicking the Column Runner
icon.
The column property view is used to define specifications, provide
estimates, monitor convergence, view stage-by-stage and product
stream summaries, add pump-arounds and side-strippers, specify
dynamic parameters and define other Column parameters such as
convergence tolerances, and attach reactions to column stages.
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Column
There are some differences
in the Column property view;
in the main flowsheet, and in
the Column sub-flowsheet.
These differences are noted.
8-33
The column property view is essentially the same when accessed from
the main flowsheet or Column sub-flowsheet. However, there are some
differences:
•
•
•
The Connections page in the main flowsheet column property
view displays and allows you to change all product and feed
stream connections. In addition, you can specify the number of
stages and condenser type.
The Connections page in the sub-flowsheet Column property
view (Column Runner) allows you to change the product and feed
stream connections, and gives more flexibility in defining new
streams.
In the main flowsheet Column property view, the Flowsheet
Variables and Flowsheet Setup pages allow you to specify the
transfer basis for stream connections, and permit you to view
selected column variables.
In order to make changes or additions to the Column in the main
simulation environment, the Solver should be active. Otherwise HYSYS
cannot register your changes.
Column Convergence
The Run and Reset buttons are used to start the convergence algorithm
and reset the Column, respectively. HYSYS first performs iterations
toward convergence of the inner and outer loops (Equilibrium and
Heat/Spec Errors), and then checks the individual specification
tolerances (refer to the section on the Specification Tolerances for
Solver for more information).
The Monitor page displays a summary of the convergence procedure for
the Equilibrium and Heat/Spec Errors. An example of a converged
solution is shown in the following figure:
Figure 8.12
A summary of each of the tabs in the Column property view are in the
following sections.
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Column Property View
8.4.1 Design Tab
Column Runner is another
name for the sub-flowsheet
Column property view.
The following sections detail information regarding the Column
property view pages. All pages are common to both the Main Column
property view and the Column Runner, unless stated otherwise.
Connections page (Main Flowsheet)
If you have modified the
Column Template (e.g., added an additional Tray
Section), the Connections
page appears differently
than what is shown in
Figure 8.13.
The main flowsheet Connections page allows you to specify the name
and location of feed streams, the number of stages in the tray section,
the stage numbering scheme, condenser type, names of the Column
product streams, and Condenser/Reboiler energy streams.
Figure 8.13
The streams shown in this view reside in the parent or main flowsheet;
they do not include Column sub-flowsheet streams, such as the Reflux
or Boilup. In other words, only feed and product streams (material and
energy) appear on this page.
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Column
8-35
The appearance of the Connections page varies depending on the
template you are using. See Figure 8.14 for the Connections page of a
Stripper Crude.
When the column has complex connections, the Connections page
changes to the view shown in the figure below.
Figure 8.14
You can also split the feed streams by activating the Split checkbox
associated to the stream.
Click the Edit Trays button to open the Tray Section Details view. You
can edit the number of trays in the column, and add or delete trays after
or before the tray number of your choice in this view.
Figure 8.15
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Column Property View
Connections page (Column Runner)
If you specify a new stream
name in any of the cells, this
creates the stream inside
the Column. This new
stream is not automatically
transferred into the main
flowsheet.
The Connections page displayed in the Column Runner (inside the
Column sub-flowsheet) appears as shown in the following figure.
You can connect or
disconnect streams from this
page, as well as change the
stream location.
All feed and energy streams, as well as the associated stage, appear in
the left portion of the Connections page. Liquid, vapour, and water
product streams and locations appear on the right side of the page.
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Figure 8.16
Column
8-37
Monitor Page
The Monitor page is primarily used for editing specifications,
monitoring Column convergence, and viewing Column profile plots. An
input summary, and a view of the initial estimates can also be accessed
from this page.
Figure 8.17
HYSYS displays the iteration number, step size, and Equilibrium
and Heat/Spec errors in this area during the iteration process.
Profiles are where plots of
column temperatures,
flows, and pressures
appear during
convergence.
The Current checkbox
shows the current specs
that are being used in the
column solution. You
cannot activate or
deactivate this checkbox.
Specification types, the
value of each
specification, the current
calculated value and the
weighted error appear
here.
Buttons for working with specifications.
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Column Property View
Optional Checks Group
In the Optional Checks group, you find the following two buttons:
Refer to Section 1.3 - Object
Status Window/Trace
Window in the User Guide
for details concerning the
Trace Window.
Button
Function
Input Summary
Provides a column input summary in the Trace Window. The
summary lists vital tower information including the number of
trays, the attached fluid package, attached streams, and
specifications.
You can click the Input Summary button after you make a
change to any of the column parameters to view an updated
input summary. The newly defined column configuration
appears.
View Initial Estimates
Opens the Summary page of the Column property view, and
displays the initial temperature and flow estimates for the
column. You can then use the values generated by HYSYS to
enter estimates on the Estimates page.
These estimates are generated by performing one iteration
using the current column configuration. If a specification for
flow or temperature has been provided, it is honoured in the
displayed estimates.
Profile Group
During the column calculations, a profile of temperature, pressure or
flow appears, and is updated as the solution progresses. Select the
appropriate radio button to display the desired variable versus tray
number profile.
Specifications Group
New specifications can also be
added via the Specs page.
Each specification, along with its specified value, current value,
weighted error, and status is shown in the Specifications group.
You can change a specified value by typing directly in the associated
Specified Value cell. Specified values can also be viewed and changed on
the Specs and Specs Summary pages. Any changes made in one location
are reflected across all locations. Refer to Section 8.5 - Column
Specification Types for a description of the available specification types.
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Column
8-39
Double-clicking on a cell within the row for any listed specification
opens its property view. In this view, you can define all the information
associated with a particular specification. Each specification view has
three tabs:
•
•
•
Parameters
Summary
Spec Type
This view can also be accessed from both the Specs and Specs Summary
pages. Further details are outlined in the section on the Specification
Property View.
Spec Status Checkboxes
Spec Status checkboxes
An Active specification is one
which the convergence
algorithm is trying to meet
initially. An Active
specification has the Estimate
checkbox activated also.
An Estimate is used as an
initial “guess” for the
convergence algorithm, and
is considered to be an
Inactive specification.
The status of listed specifications are one of the following types:
Status
Description
Active
The active specification is one that the convergence algorithm is
trying to meet. An active specification always serves as an initial
estimate (when the Active checkbox is activated, HYSYS
automatically activates the Estimate and Current checkboxes). An
active specification always exhausts one degree of freedom.
Estimate
An Estimate is considered an Inactive specification because the
convergence algorithm is not trying to satisfy it. To use a
specification as an estimate only, deactivate the Active checkbox.
The value then serves only as an initial estimate for the convergence
algorithm. An estimate does not exhaust an available degree of
freedom.
Current
This checkbox shows the current specs being used by the column
solution. When the Active checkbox is activated, the Current
checkbox automatically activates. You cannot alter this checkbox.
A Current specification is one
which is currently being used
in the column solution.
A Completely Inactive
specification is ignored
completely by the
convergence algorithm, but
can be made Active or an
Estimate at a later time.
When Alternate specs are used and an existing hard to solve spec
has been replaced with an Alternate spec, this checkbox shows you
the current specs used to solve the column.
Completely
Inactive
To disregard the value of a specification entirely during
convergence, deactivate both the Active and Estimate checkboxes.
By ignoring a specification rather than deleting it, you are always
able to use it later if required. The current value appears for each
specification, regardless of its status. An Inactive specification is
therefore ideal when you want to monitor a key variable without
including it as an estimate or specification.
The degrees of freedom value appears in the Degrees of Freedom field
on the Monitor page. When you make a specification active, the degrees
of freedom is decreased by one. Conversely, when you deactivate a
specification, the degrees of freedom is increased by one. You can start
column calculations when there are zero degrees of freedom.
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Column Property View
Variables such as the duty of the reboiler stream, which is specified in
the Workbook, or feed streams that are not completely known can offset
the current degrees of freedom. If you feel that the number of active
specifications is appropriate for the current configuration, yet the
degrees of freedom is not zero, check the conditions of the attached
streams (material and energy).You must provide as many specifications
as there are available degrees of freedom. For a simple Absorber there
are no available degrees of freedom, therefore no specifications are
required. Distillation columns with a partial condenser have three
available degrees of freedom.
Specification Group Buttons
The four buttons which align the bottom of the Specifications group
allow you to manipulate the list of specs. The table below describes the
four buttons.
You can also double-click in
a specification cell to open
its property view.
Button
Action
View
Move to one of the specification cells and click the View button to
display its property view. You can then make any necessary
changes to the specification. Refer to the section on the
Specification Property View for more details.
To change the value of a specification only, move to the Specified
Value cell for the specification you want to change, and type in the
new value.
Add Spec
Opens the Column Specifications menu list, from which you can
select one or multiple (by holding the CTRL key while selecting)
specifications, and then click the Add Spec(s) button.
The property view for each new spec is shown and its name is
added to the list of existing specifications. Refer to Section 8.5 Column Specification Types for a description of the available
specification types.
8-40
Update Inactive
Updates the specified value of each inactive specification with its
current value.
Group Active
Arranges all active specifications together at the top of the
specifications list.
Column
8-41
Specs Page
Remember that the active
specification values are
used as initial estimates
when the column initially
starts to solve.
Adding and changing Column specifications is straightforward. If you
have created a Column based on one of the templates, HYSYS already
has default specifications in place. The type of default specification
depends on which of the templates you have chosen (refer to the
Default Replaceable Specifications in Section 8.3.2 - Templates for
more details).
Figure 8.18
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Column Property View
Column Specifications Group
The following buttons are available:
Button
Action
View
Opens the property view for the highlighted specification. Alternatively,
you can object inspect a spec name and select View from the menu.
Refer to the section on the Specification Property View for more
details.
Add
Opens the Column Specifications menu list, from which you can select
one or multiple (by holding the CTRL key while selecting) specifications,
and then click the Add Spec(s) button.
The property view for each new spec is shown, and its name is added to
the list of existing specifications. Refer to Section 8.5 - Column
Specification Types for a description of the available specification types.
Delete
Removes the highlighted specification from the list.
From the Default Basis drop-down list, you can choose the basis for the
new specifications to be Molar, Mass or Volume.
Available Specification Types
view
The Update Specs from Dynamics button replaces the specified value of
each specification with the current value (lined out value) obtained from
Dynamic mode.
Specification Property View
Figure 8.19 is a typical property view of a specification. In this view, you
can define all the information associated with a particular specification.
Each specification property view has three tabs:
•
•
•
Parameters
Summary
Spec Type
This example shows a component recovery specification which requires
the stage number, spec value, and phase type when a Target Type of
Stage is chosen.
Specification information is shared between this property view, and the
specification list on both the Monitor and Specs Summary pages.
Altering information in one location automatically updates across all
other locations.
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Column
8-43
For example, you can enter the spec value in one location, and the
change is reflected across all other locations.
Figure 8.19
Provide the name of
the component(s) to
which the
specification applies.
Provide basic spec
information on the
Parameters tab.
Specify the stage to
which the
specification
applies.
Specify Liquid or
Vapor phase for
the specification.
The Summary tab is used to specify tolerances, and define whether the
specification is Active or simply an Estimate.
Figure 8.20
Specify the interval for use with a
Ranged Spec Value.
Define as either a Fixed or Ranged
Spec. A Ranged Spec allows the
solver to meet a Spec over an
interval (defined according to the
Upper and Lower spec values).
Define as either a Primary or
Alternate Spec. An Alternate Spec
can replace another hard to solve
spec in situations where the
column is not converging.
The Spec Type tab (as shown in Figure 8.20) can be used to define
specifications as either Fixed/Ranged and Primary/Alternate. By
default, all specifications are initially defined as Fixed and Primary.
Advanced solving options available in HYSYS allow the use of both
Alternate and Ranged Spec types.
The following section further details the advanced solving options
available in HYSYS.
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Column Property View
Ranged and Alternate Specs
The reliability of any solution method depends on its ability to solve a
wide group of problems. Some specs like purity, recovery, and cut point
are hard to solve compared to a flow or reflux ratio spec. The use of
Alternate and/or Ranged Specs can help to solve columns that fail due
to difficult specifications.
If the Column solves on an
Alternate or Ranged Spec,
the status bar reads
“Converged - Alternate
Specs” highlighted in purple.
Configuration of these advanced solving options are made by selecting
the Advanced Solving Options button located on the Solver page. The
advanced solving options are only available for use with either the
Hysim I/O or Modified I/O solving methods. Refer to Advanced Solving
Options Button in Section 8.4.2 - Parameters Tab for further details.
Fixed/Ranged Specs
When the solver attempts to
meet a Ranged spec, the Wt.
Error becomes zero when the
Current Value is within the
Ranged interval (as shown on
the Monitor page).
For a Fixed Spec, HYSYS attempts to solve for a specific value. For a
Ranged Spec, the solver attempts to meet the specified value, but if the
rest of the specifications are not solved after a set number of iterations,
the spec is perturbed within the interval range provided for the spec
until the column converges. Any column specification can be specified
over an interval. A Ranged Spec requires both lower and upper
specification values to be entered. This option (when enabled), can help
solve columns where some specifications can be varied over an interval
to meet the rest of the specifications.
Primary/Alternate Specs
When an existing spec is
replaced by an alternate spec
during a column solution, the
Current checkbox becomes
deactivated for the original
(not met) spec and is
activated for the alternate
spec.
The number of active
Alternate specs must always
equal the number of inactive
Alternate specs.
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A Primary Spec must be met for the column solution to converge. An
Alternate Spec can be used to replace an existing hard to solve
specification during a column solution. The solver first attempts to meet
an active Alternate spec value, but if the rest of the specifications are not
solved after a minimum number of iterations, the active Alternate spec
is replaced by an inactive Alternate spec. This option (when enabled),
can help solve columns where some specifications can be ignored
(enabling another) to meet the rest of the specifications and converge
the column.
Column
8-45
Both Ranged or Alternate Specs must be enabled and configured using
the Advanced Solving Options Button located on the Solver page of the
Parameters tab before they can be applied during a column solution.
Specification Tolerances for Solver
The Solver Tolerances feature allows you to specify individual tolerances
for your Column specifications. In addition to HYSYS converging to a
solution for the Heat/Spec and Equilibrium Errors, the individual
specification tolerances must also be satisfied. HYSYS first performs
iterations until the Heat/Spec (inner loop), and Equilibrium (outer loop)
errors are within specified tolerances (described in Section 8.4.2 Parameters Tab).
The Column specifications do not have individual tolerances during this
initial iteration process; the specification errors are “lumped” into the
Heat/Spec Error. Once the Heat/Spec and Equilibrium conditions are
met, HYSYS proceeds to compare the error with the tolerance for each
individual specification. If any of these tolerances are not met, HYSYS
iterates through the Heat/Spec, and Equilibrium loops again to produce
another converged solution. The specification errors and tolerances are
again compared, and the process continues until both the inner/outer
loops and the specification criteria are met.
Specific Solver Tolerances can be provided for each individual
specification. HYSYS calculates two kinds of errors for each
specification:
•
•
an absolute error
a weighted error
The absolute error is simply the absolute value of the difference between
the calculated and specified values:
Errorabsolute = |Calculated Value - Specified Value|
When the Weighted and
Absolute Errors are less than
their respective tolerances, an
Active specification has
converged.
(8.3)
The Weighted Error is a function of a particular specification type. When
a specification is active, the convergence algorithm is trying to meet the
Weighted Tolerances (Absolute Tolerances are only used if no Weighted
Tolerances are specified, or the weighted tolerances are not met).
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Column Property View
Therefore, both the weighted and absolute errors must be less than their
respective tolerances for an active specification to converge. HYSYS
provides default values for all specification tolerances, but any tolerance
can be changed. For example, if you are dealing with ppm levels of
crucial components, composition tolerances can be set tighter (smaller)
than the other specification tolerances. If you delete any tolerances,
HYSYS cannot apply the individual specification criteria to that
specification, and Ignore appears in the tolerance input field.
The specification tolerance feature is simply an “extra” to permit you to
work with individual specifications and change their tolerances if
desired.
Specification Details Group
You can edit any specification
values (in the Column
property view) shown in blue.
For a highlighted specification in the Column Specifications group, the
following information appears:
•
•
•
•
•
•
•
8-46
Spec Name
Convergence Condition. If the weighted and absolute errors are
within their tolerances, the specification has converged and Yes
appears.
Status. You can manipulate the Active and Use As Estimate
checkboxes. Refer to the Monitor Page for further details
concerning the use of these checkboxes.
Dry Flow Basis. Draw specifications are calculated on a dry flow
basis by activating the Dry Flow Basis checkbox. This option is
only available for draw specifications. The checkbox is greyed out
if it does not apply to the specification chosen.
Spec Type. You can select between Fixed/Ranged and Primary/
Alternate specs. Refer to the section on the Ranged and
Alternate Specs for more details.
Specified and Current Calculated Values.
Weighted/Absolute Tolerance and Calculated Error.
Column
8-47
Specs Summary Page
You can edit any specification
details shown in blue.
You can double-click in a
specification cell to open its
property view. Refer to the
section on the Specification
Property View for more
details.
The Specs Summary page lists all Column specifications available along
with relevant information. This specification information is shared with
the Monitor page and Specs page. Altering information in one location
automatically updates across all other locations.
Figure 8.21
Subcooling Page
The Subcooling page is not
available for Liquid-Liquid
Extractor.
The Subcooling page allows you to specify subcooling for products
coming off the condenser of your column. You can specify the
condenser product temperature or the degrees to subcool. For columns
without condensers, such as absorbers, this page requires no additional
information.
Notes Page
For more information, refer to
Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
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Column Property View
8.4.2 Parameters Tab
The Parameters tab shows the column calculation results, and is used to
define some basic parameters for the Column solution. The Parameters
tab consists of six pages:
•
•
•
•
•
•
Profiles
Estimates
Efficiencies
Solver
2/3 Phase
Amines
Profiles Page
The Profiles page shows the column pressure profile, and provides
estimates for the temperature, net liquid and net vapour flow for each
stage of the column. You can specify tray estimates in the Temperature
column, Net Liquid column and Net Vapour column, or view the values
calculated by HYSYS.
The graph in Figure 8.22 depicts the pressure profile across the column.
Figure 8.22
8-48
Column
At least one iteration must
have occurred for HYSYS to
convert between bases. In
this way, values for the
compositions on each tray
are available.
8-49
Use the radio buttons in the Flow Basis group to select the flow type you
want displayed in the Net Liquid and Net Vapour columns. The Flow
Basis group contains three radio buttons:
•
•
•
Molar
Mass
Volume
The buttons in the Steady State Profiles group are defined as follows:
Button
Function
Update from Solution
Transfers the current values that HYSYS has calculated for the
trays into the appropriate cells. Estimates that have been
Locked (displayed in blue) are not updated. The Column
Profiles page on the Performance tab allows you to view all
the current values.
Clear
Deletes values for the selected tray.
Clear All Trays
Deletes values for all trays.
Lock
Changes all red values (unlocked estimates, current values,
interpolated values) to blue (locked), which means that they
cannot be overwritten by current values when the Update from
Solution button is clicked.
Unlock
Changes all blue values (locked) to red (unlocked). Unlocked
values are overwritten by current values when the Update
from Solution button is clicked.
Stream Estimates
Displays the temperature, molar flow, and enthalpy of all
streams attached to the column operation.
Although the Profiles page is mainly used for steady state simulation, it
does contain vital information for running a column in dynamics. One
of the most important aspects of running a column in dynamics is the
pressure profile. While a steady state column can run with zero pressure
drop across a tray section, the dynamic column requires a pressure
drop. In dynamics, an initial pressure profile is required before the
column can run. This profile can be from the steady state model or can
be added in dynamics. If a new tray section is created in Dynamic mode,
the pressure profile can be obtained from the streams if not directly
specified. In either case, the closer the initial pressure profile is to the
one calculated while running in dynamics, the fewer problems you
encounter.
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Column Property View
Estimates Page
To see the initial estimates
generated by HYSYS, click
the View Initial Estimates
button on the Monitor page.
The Estimates page allows you to view and specify composition
estimates.
When you specify estimates on stages that are not adjacent to each
other, HYSYS cannot interpolate values for intermediate stages until the
solution algorithm begins.
Estimates are NOT required
for column convergence.
You can specify tray by tray component composition estimates for the
vapour phase or liquid phase. Each composition estimate is on a mole
fraction basis, so values must be between 0 and 1.
Figure 8.23
HYSYS interpolates intermediate tray component values when you
specify compositions for non-adjacent trays. The interpolation is on a
log basis. Unlike the temperature estimates, the interpolation for the
compositions does not wait for the algorithm to begin. Select either the
Vap or Liq radio button in the Phase group to display the table for the
vapour or liquid phase, respectively.
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Column
8-51
The Composition Estimates group has the following buttons:
HYSYS does not ask for
confirmation before deleting
estimates.
Button
Action
Clear Tray
Deletes all values, including user specified (blue) and HYSYS
generated (red), for the selected tray.
Clear All Trays
Deletes all values for all trays.
Update
Transfers the current values which HYSYS has calculated for tray
compositions into the appropriate cells. Estimates that have been
locked (shown in blue) cannot be updated.
Restore
Removes all HYSYS updated values from the table, and replaces
them with your estimates and their corresponding interpolated
values. Any cells that did not contain estimates or interpolated
values are shown as <empty>. This button essentially reverses the
effect of the Update button.
If you had entered some estimate values, click the Unlock
Estimates button, and click the Update button. All the values in the
table appear in red. You can restore your estimated values by
clicking the Restore button.
Normalize Trays
Normalizes the values on a tray so that the total of the composition
fractions equals 1. HYSYS ignores <empty> cells, and normalizes
the compositions on a tray provided that there is at least one cell
containing a value.
Lock Estimates
Changes all red values (unlocked estimates, current values,
interpolated values) to blue (locked), which means that they
cannot be overwritten by current values when the Update button is
clicked.
Unlock Estimates
Changes all blue values (locked) to red (unlocked). Unlocked
values are overwritten by current values when the Update button
is clicked.
Efficiencies Page
Fractional efficiencies cannot
be given for the condenser or
reboiler stages, nor should
they be set for feed or draw
stages.
The Efficiencies page allows you to specify Column stage efficiencies on
an overall or component-specific basis. Efficiencies for a single stage or
a section of stages can easily be specified.
The functionality of this page is slightly different when working with the
Amines Property Package. Refer to the section on Special Case Amines Property Package for more information.
HYSYS uses a modified Murphree stage efficiency. All values are initially
set to 1.0, which is consistent with the assumption of ideal equilibrium
or theoretical stages. If this assumption is not valid for your column, you
have the option of specifying the number of actual stages, and changing
the efficiencies for one or more stages.
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Column Property View
Figure 8.24
To specify an efficiency to
multiple cells, highlight the
desired cells, enter a value in
the Eff. Multi-Spec field, and
click the Specify button.
The data table on the Efficiency page gives a stage-by-stage efficiency
summary.
The efficiencies are fractional, i.e., an efficiency of 1.0 corresponds to
100% efficiency.
Overall stage efficiencies can be specified by selecting the Overall radio
button in the Efficiency Type group, and entering values in the
appropriate cells.
Component-specific efficiencies can be specified by selecting the
Component radio button, and entering values in the appropriate cells.
Special Case - Amines Property Package
When solving a column for a case using the Amines Property Package,
HYSYS always uses stage efficiencies for H2S and CO2 component
calculations. If these are not specified on the Efficiencies page of the
Column property view, HYSYS calculates values based on the tray
dimensions. Tray dimensions can be specified on the Amines page of
the Parameters tab. If column dimensions are not specified, HYSYS uses
its default tray values to determine the efficiency values.
8-52
Column
The Reset H2S, CO2 button,
and the Transpose checkbox
are available only if the
Efficiency Type is set to
Component.
8-53
If you specify values for the CO2 and H2S efficiencies, these are the
values that HYSYS uses to solve the column. If you want to solve the
column again using efficiencies generated by HYSYS, click the Reset
H2S, CO2 button, which is available on this page. Run the column again,
and HYSYS calculates and displays the new values for the efficiencies.
Activate the Transpose checkbox to change the component efficiency
matrix so that the rows list components and the columns list the stages.
For more information on the Amines Property Packages, refer to
Appendix C - Amines Property Package of the Simulation Basis manual.
Solver Page
You can manipulate how the column solves the column variables on the
Solver page.
Figure 8.25
The Solving Method Group,
Acceleration Group, and
Damping Group will have
different information
displayed according to the
options selected within the
group. Refer to the
corresponding sections for
more information.
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8-54
Column Property View
Solving Options Group
Specify your preferences for the column solving behaviour in the Solving
Options group.
Figure 8.26
Maximum Number of Iterations
The Column convergence process terminates if the maximum number
of iterations is reached. The default value is 10000, and applies to the
outer iterations. If you are using Newton’s method, and the inner loop
does not converge within 50 iterations, the convergence process
terminates.
Equilibrium and Heat/Spec Tolerances
Convergence tolerances are pre-set to very tight values, thus ensuring
that regardless of the starting estimates (if provided) for column
temperatures, flow rates, and compositions, HYSYS always converges to
the same solution. However, you have the option of changing these two
values if you want. Default values are:
•
•
Inner Loop. Heat and Spec Error: 5.000e-04
Outer Loop. Equilibrium Error: 1.000e-05
Because the default values are already very small, you should use
caution in making them any smaller. You should not make these
tolerances looser (larger) for preliminary work to reduce computer time.
The time savings are usually minor, if any. Also, if the column is in a
recycle or adjust loop, this could cause difficulty for the loop
convergence.
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Column
8-55
Equilibrium Error
The value of the equilibrium error printed during the column iterations
represents the error in the calculated vapour phase mole fractions. The
error over each stage is calculated as one minus the sum of the
component vapour phase mole fractions. This value is then squared; the
total equilibrium error is the sum of the squared values. The total
equilibrium error must be less than 0.00001 to be considered a
converged column.
Heat and Spec Error
The heat and specification error is the sum of the absolute values of the
heat error and the specification error, summed over each stage in the
tower.
This total value is divided by the number of inner loop equations. The
heat error contribution is the heat flow imbalance on each tray divided
by the total average heat flow through the stage.
The specification error contribution is the sum of each individual
specification error divided by an appropriate normalization factor.
For component(s) flow, the normalization factor is the actual
component(s) flow; for composition, it is the actual mole fraction; for
vapour pressure and temperature it is a value of 5000; etc. The total sum
of heat and spec errors must be less than 0.0005 to be considered a
converged column.
The allowed equilibrium error and heat and spec error are tighter than
in most programs, but this is necessary to avoid meta-stable solutions,
and to ensure satisfactory column heat and material balances.
Save Solution as Initial Estimate
This option is on by default, and it saves converged solutions as
estimates for the next solution.
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8-56
Column Property View
Super Critical Handling Model
Supercritical phase behaviour occurs when one or more Column stages
are operating above the critical point of one or more components.
During the convergence process, supercritical behaviour can be
encountered on one or more stages in the Column. If HYSYS encounters
supercritical phase behaviour, appropriate messages appear in the
Trace Window.
HYSYS cannot use the equation of state or activity model in the
supercritical range, so an alternate method must be used. You can
specify which method you want HYSYS to use to model the phase
behaviour. There are three choices for supercritical calculations:
Refer to Section 1.3 - Object
Status Window/Trace
Window in the User Guide
for details on the Trace
Window.
Model
Description
Simple K
The default method. HYSYS calculates K-values for the
components based on the vapour pressure model being used.
Using this method, the K-values which are calculated are ideal
K-values.
Decrease Pressure
When supercritical conditions are encountered, HYSYS
reduces the pressure on all trays by an internally determined
factor, which can be seen in the Trace Window when the
Verbose option is used. This factor is gradually decreased until
supercritical conditions no longer exist on any tray, at which
point, the pressure in the column is gradually increased to your
specified pressure. If supercritical conditions are encountered
during the pressure increase, the pressure is once again
reduced and the process is repeated.
Adjacent Tray
When supercritical conditions are encountered on a tray,
HYSYS searches for the closest tray above which does not
have supercritical behaviour. The non-supercritical conditions
are substituted in the phase calculations for the tray with
supercritical conditions.
Trace Level
The Trace Level defines the level of detail for messages displayed in the
Trace Window, and can be set to Low, Medium, or High. The default is
Low.
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Column
8-57
Initialize from Ideal K’s
When this checkbox is checked, HYSYS initializes its column solution
using ideal K values which are calculated from vapour pressure
correlations. The ideal K-value option, which is also used by HYSIM,
increases the compatibility between HYSIM and HYSYS.
By default, the Initialize from Ideal K’s checkbox is deactivated. HYSYS
uses specified composition estimates or generates estimates to
rigorously calculate K-values.
Two Liquids Check Based on
This option allows you to specify a check for two liquid phases in the
column. The check is based on one of the following criteria:
•
•
•
No 2 Liq Check. Disables the two liquid check.
Tray Liquid Fluid. The calculation is based on the composition of
the liquid in the column.
Tray Total Fluid. The calculation is based on the overall
composition of the fluid in the column.
Tighten Water Tolerance
When this checkbox is checked, HYSYS increases the contribution of the
water balance error to the overall balance error in order to solve
columns with water more accurately. The default setting for this
checkbox is unchecked.
Solving Method Group
The Solving Method drop-down list allows you to select the column
solution method.
Figure 8.27
8-57
8-58
Column Property View
The display field, which appears below the drop-down list, provides
explanations for each method, and is restated here:
Only a simple Heat
Exchanger Model
(Calculated from Column) is
available in the Column subflowsheet. The Simple
Rating, End-Point, and
Weighted models are not
available.
Method
Explanation
HYSIM Inside-Out
General purpose method, which is good for most problems.
Modified HYSIM
Inside-Out
General purpose method, which allows mixer, tee, and heat
exchangers inside the column sub-flowsheet.
Newton Raphson
Inside-Out
General purpose method, which allows liquid-phase kinetic
reactions inside the Column sub-flowsheet.
Sparse Continuation
Solver
An equation based solver. It supports two liquid phases on the
trays, and its main use is for solving highly non-ideal chemical
systems and reactive distillation.
Simultaneous
Correction
Simultaneous method using dogleg methods. Good for
chemical systems. This method also supports reactive
distillation.
OLI Solver
Only used to calculate the column unit operation in an
electrolyte system.
Inside-Out
Open the Trace Window at
the bottom of the HYSYS
Desktop to view messages
regarding the convergence
of the column.
With the “inside-out” based algorithms, simple equilibrium and
enthalpy models are used in the inner loop to solve the overall
component and heat balances as well as any specifications. The outer
loop updates the simple thermodynamic models with rigorous model
calculations.
General Features of the Solving Methods
The following table displays the general features of all the HYSYS
column solving methods.
8-58
HYSIM
I/O
Modified
HYSIM I/O
Newton
Raphson I/O
Sparse
Continuation
Simultaneous
Correction
OLI
Component Efficiency
Handling
Yes
Yes
No
Yes
No
Yes
Total Efficiency Handling
Yes
Yes
No
Yes
No
Yes
Additional Side Draw
Yes
Yes
Yes
Yes
Yes
Yes
Vapour Bypass
Yes
Yes
No
Yes
No
No
Pump Arounds
Yes
Yes
No
Yes
No
Yes
Side Stripper
Yes
Yes
No
Yes
No
No
Side Rectifier
Yes
Yes
No
Yes
No
No
Mixer & Tee in Subflowsheet
No
Yes
No
No
No
No
Column
8-59
HYSIM
I/O
Modified
HYSIM I/O
Newton
Raphson I/O
Sparse
Continuation
Simultaneous
Correction
OLI
Three Phase
Yes
(water
draw)
Yes (water
draw)
No
Yes
No
Yes
Chemical (reactive)
No
No
Yes
Yes
Yes
Internal
reactions
Acceleration Group
By default, the Accelerate K
value & H Model Parameters
checkbox is deactivated.
When activated, the Accelerate K value & H Model Parameters checkbox
displays two fields, which relate to an acceleration program called the
Dominant Eigenvalue Method (DEM).
Figure 8.28
The DEM is a numerical solution program, which accelerates
convergence of the simple model K values and enthalpy parameters. It is
similar to the Wegstein accelerator, with the main difference being that
the DEM considers all interactions between the variables being
accelerated. The DEM is applied independently to each stage of the
column.
Use the acceleration option if you find that the equilibrium error is
decreasing slowly during convergence. This should help to speed up
convergence. Notice that the Accelerate K value & H Model Parameters
checkbox should NOT be activated for AZEOTROPIC columns, as
convergence tends to be impeded.
The listed DEM parameters include:
Parameter
Description
Acceleration Mode
Select either Conservative or Aggressive. With the
Conservative approach, smaller steps are taken in the iterative
procedure, thus decreasing the chance of a bad step.
Maximum Iterations
Queued
Allows you to choose the number of data points from previous
iterations that the accelerator program uses to obtain a
solution.
8-59
8-60
Column Property View
Damping Group
Choose the Damping method by selecting either the Fixed or Adaptive
radio button.
Figure 8.29
Fixed Damping
If you select the Fixed radio button, you can specify the damping factor.
The damping factor controls the step size used in the outer loop when
updating the simple thermodynamic models used in the inner loop. For
the vast majority of hydrocarbon-oriented towers, the default value of
1.0 is appropriate, which permits a full adjustment step. However,
should you encounter a tower where the heat and specification errors
become quite small, but the equilibrium errors diverge or oscillate and
converge very slowly, try reducing the damping factor to a value
between 0.3 and 0.9. Alternatively, you could enable Adaptive Damping,
allowing HYSYS to automatically adjust this factor.
Changing the damping factor has an effect on problems where the heat
and spec error does not converge.
There are certain types of columns, which definitely require a special
damping factor.
Use the following table as a guideline in setting up the initial value.
8-60
Type of Column
Damping Factor
All hydrocarbon columns from demethanizers to
debutanizers to crude distillation units
1.0
Non-hydrocarbon columns including air separation,
nitrogen rejection
1.0
Most petrochemical columns including C2= and C3=
splitters, BTX columns
1.0
Amines absorber
1.0
Column
Type of Column
The Azeotropic checkbox on
the Solver page of the
Parameters tab must be
activated for an azeotropic
column to converge.
8-61
Damping Factor
Amines regenerator, TEG strippers, sour water strippers
0.25 to 0.50
Highly non-ideal chemical columns without azeotropes
0.25 to 0.50
Highly non-ideal chemical columns with azeotropes
0.50 to -1.0*
As shown in the table above, an azeotropic column requires the
azeotrope checkbox to be enabled. There are two ways to indicate to
HYSYS that you are simulating an azeotropic column:
•
Enter a negative damping factor, and HYSYS automatically
activates the Azeotropic checkbox.
The absolute value of the damping factor is always displayed.
•
Enter a positive value for the damping factor, and activate the
Azeotropic checkbox.
Adaptive Damping
If you select the Adaptive radio button, the Damping matrix displays
three fields. HYSYS updates the damping factor as the column solution
is calculated, depending on the Damping Period and convergence
behaviour.
Damping Period
Description
Initial Damping Factor
Specifies the starting point for adaptive damping.
Adaptive Damping Period
The default Adaptive Damping Period is ten. In this
case, after the tenth iteration, HYSYS looks at the
last ten errors to see how many times the error
increased rather than decreased. If the error
increased more than the acceptable tolerance, this
is an indication that the convergence is likely
cycling, and the current damping factor is then
multiplied by 0.7. Every ten iterations, the same
analysis is done to see if the damping factor should
be further decreased. Alternatively, if the error
increased only once in the last period, the damping
factor is increased to allow for quicker convergence.
Reset Initial Damping Factor
If this checkbox is activated, the current damping
factor is used the next time the column is solved. If it
is deactivated, the damping factor before adaptive
damping was applied is used.
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8-62
Column Property View
Initialization Algorithm Radio Buttons
There are two types of method for the initialization algorithm
calculation:
•
•
Standard Initialization radio button uses the tradition
initialization algorithm in Hysys.
Program Generates Estimations radio button uses a new
functionality that handles the cases where the traditional
initialization does not.
Figure 8.30
The following list situations when the Program Generates Estimations
(PGE) initialization method is used:
•
•
The PGE initialization handles systems with more than 25
components while the standard initialization does not handle
systems with more than 25 components without the user’s initial
estimation.
When column does not converge with the standard initialization
method (default), switching to PEG may converge the column.
The new algorithm eliminates the discrepancy in the temperature
and component estimates, which may exist in standard
initialization.
Initial Estimate Generator Parameters
You can enable the initial estimate generator (IEG) by activating the
Dynamic Integration for IEG checkbox. The IEG then performs iterative
flash calculations (NRSolver, PV, and PH) to provide initial estimates for
the temperature and composition profiles. No user estimates are
required when the Dynamic Integration for IEG checkbox is activated.
Figure 8.31
8-62
Column
8-63
Click the Dynamic Estimates Integrator button, and the Col Dynamic
Estimates view appears as shown in the figure below.
Col Dynamic Estimates View
The Col Dynamic Estimates view allows you to further define the
dynamic estimates parameters.
Figure 8.32
You can set parameters for the time period over which the dynamic
estimates are calculated, as well as set the calculation tolerance. An
activated Active checkbox indicates that the Dynamic Integration for
IEG is on. Select either the Adiabatic or Isothermal radio button to set
the dynamic initialization flash type.
If you want to generate the dynamic estimates without running the
column, you can do so from this view by clicking the Start button. If you
want to stop calculations before the specified time has elapsed, click the
Stop button. You do not have to manually click the Start button to
generate the estimates; if the Dynamic Integration for IEG option is
active, HYSYS generates them automatically whenever the column is
running.
If you are running
simulation with an iterative
solving procedure where the
column has to be calculated
several times, it is a good
idea to select this option to
save on calculation time.
The Shortcut Mode checkbox allows you to bypass this step once a set of
estimates is generated, that is, once the column has converged.
8-63
8-64
Column Property View
Advanced Solving Options Button
When you click the Advanced Solving Options button, the Advanced
Solving Options property view appears.
Figure 8.33
If the Column converges
on an Alternate or Ranged
Spec, the status bar reads
“Converged - Alternate
Specs” highlighted in
purple.
The “use” checkboxes must be
selected in order to enable a
particular option.
These checkboxes are only
enabled if the corresponding
spec type exists.
All the Alternate active specs
can be replaced on an individual
spec basis or all specs
simultaneously. The alternative
(active) spec with the larger error
is replaced with an alternative
inactive spec with minimum
error.
The order in which the solving options are executed is based on the priority.
On the Advanced Solving Options property view, each solving option
(i.e., Alternate, Ranged, and Autoreset) has a solving priority and also a
checkbox option. To use a particular solving option, you have to activate
the corresponding checkbox. You must also specify the priority of the
solving method. This is the order in which the solving options are
executed (either first, second or third).
When a column is in recycle,
by default, the solver
switches to the original set of
specs after each recycle
iteration or the next time the
column solves.
8-64
Advanced solving options cannot be used until the minimum number of
iterations are met. If the column is not solved after the minimum
number of iterations, the solver switches to an advanced solving option
according to the solving priority. This process is repeated until all the
solving options have been attempted or the column converges.
Column
8-65
2/3 Phase Page
This page is not available for
Liquid-Liquid Extractor.
The 2/3 Phase page is relevant only when you are working with threephase distillation. On this page, you can check for the presence of two
liquid phases on each stage of your column.
Figure 8.34
The Liquid Phase Detection table lists the liquid molar flow rates on
each tray of the tray section, including the reboiler and the condenser.
In order for HYSYS to check for two liquid phases on any given stage,
activate the checkbox in the Check column. If a second liquid phase is
calculated, this is indicated in the Detected column, and by a calculated
flowrate value in the L2Rate column. The buttons in the Liquid Phase
Detection group serve as aids in selecting and de-selecting the trays you
want to check.
By default, HYSYS selects
Pure for all hydrocarbon, and
Rigorous for all chemical
based distillations. This
default selection criteria is
based on the type of fluid
package used but you can
always change it.
The 2nd Liquid Type group allows you to specify the type of calculation
HYSYS performs when checking for a second liquid phase. When the
Pure radio button is selected, HYSYS checks only for pure water as the
second phase. This helps save calculation time when working with
complex hydrocarbon systems. When you want a more rigorous
calculation, select the Rigorous radio button.
8-65
8-66
Column Property View
Checking for liquid phases in a three phase distillation tower greatly
increases the solution time. Typically, checking the top few stages only,
provides reasonable results.
Auto Water Draws Button
The Auto Water Draws facility
is available for IO and MIO
solvers.
The Auto Water Draws (AWD) option allows for the automatic adding
and removing of total aqueous phase draws depending on the
conditions in the converged column.
The Two Liquids Check Based
on drop-down list is located in
the Parameters tab of the
Solver page in the Solving
Options group.
AWD updating process is based on direct check of stage fluid phases.
The direct check follows the Two Liquids Check Based on control criteria
for detecting the aqueous phase. AWD mode is not available if No 2 Liq
Check option is selected.
To manipulate the AWD option, click the Auto Water Draws button to
open the Auto Water Draws view.
Figure 8.35
The Auto Water Draws
button is available in both
column sub-flowsheet and
main flowsheet.
The Auto Water Draws view contains the following objects:
Object
Description
On
Check this checkbox to activate the Auto Water Draws mode.
Threshold
The threshold value allows variation of the condition for 2nd
liquid phase. The default value in this cell is 0.001 (same as for
Two Liquids Check based on control).
If you delete the value in this cell, the threshold is set to
minimum possible value.
8-66
Keep draws
If this checkbox is checked, the added draws are not removed.
Preserve estimates
If this checkbox is checked, the converged values are
preserved as estimates for the next column run.
Column
The All option results
typically in multiple water
draws with small flows, and
the From Top or From
Bottom option results
typically in fewer water
draws.
Object
Description
Reset
If this checkbox is checked, the column Reset option is
performed before each column run.
Strategy
There are three options of strategy to select from in the
Strategy group:
• All. All required changes in water draw configuration are
done simultaneously.
• From Top.Updates on the topmost stage from required is
performed.
• From Bottom. Updates on the bottommost stage from
required is performed.
To AWD
All existing water draws are converted to AWDs.
From AWD
Converts all AWDs to regular draws.
Restore
Restores the last successful (i.e., column equation were
solved) AWD configuration.
Delete
Deletes all AWDs.
8-67
Two more columns are added in the table on the 2/3 Phase page when in
Auto Water Draws mode. These two columns are called AWD and No
AWD
•
•
Set AWD mode for attached water draw by checking the
checkboxes under the AWD column.
If the checkbox in the No AWD column is checked, no AWD will
be attached to corresponding stage.
Amines Page
The Amines Property
Package is an optional
property package that must
be purchased in addition to
the base version of HYSYS.
For more information on the
Amines Property Package,
refer to the Appendix C Amines Property Package
in the Simulation Basis
manual.
The Amines page appears on the Parameters tab only when working
with the Amines Property Package.
When solving the column using the Amines package, HYSYS always
takes into account the tray efficiencies, which can either be userspecified, on the Efficiencies page, or calculated by HYSYS. Calculated
efficiency values are based on the tray dimensions specified. The
Amines page lists the tray section dimensions of your column, where
you can specify these values that are used to determine the tray
efficiencies. The list includes:
•
•
•
•
•
Tray Section
Weir Height
Weir Length
Tray Volume
Tray Diameter
8-67
8-68
Column Property View
If tray dimensions are not specified, HYSYS uses the default tray
dimensions to determine the efficiency values.
8.4.3 Side Ops Tab
The Side Ops tab is not
available in the Liquid-Liquid
Extractor.
Some solver methods do not
allow side ops. Refer to the
table in the section on the
General Features of the
Solving Methods for more
information.
Side strippers, side rectifiers, pump arounds, and vapour bypasses can
be added to the Column from this tab. To install any of these Side
Operations, click the Side Ops Input Expert button or on the appropriate
Side Ops page, click the Add button.
•
•
If you are using the Side Ops Input Expert, a wizard guides you
through the entire procedure of adding a side operation to your
column.
If you are using the Add button, complete the form which
appears, and then click the Install button. Specifications that are
created when you add a side operation are automatically added
to the Monitor page and Specs page. For instance, when you add
a side stripper, product draw and boilup ratio specs are added. As
well, all appropriate operations are added; for example, with the
side stripper (reboiled configuration), a side stripper tray section
and reboiler are installed in the Column sub-flowsheet.
You can view or delete any Side Operation simply by positioning the
cursor in the same line as the Operation, and clicking the View or Delete
button.
If you are specifying Side Operations while in the Main simulation
environment, make sure that the Solver is Active. Otherwise, HYSYS
cannot register your changes.
Side Strippers Page
You can install a reboiled or steam-stripped side stripper on this page.
You must specify the number of stages, the liquid draw stage (from the
Main Column), the vapour return stage (to the Main Column), and the
product stream and flow rate (on a molar, mass or volume basis).
For the reboiled configuration, you must specify the boilup ratio, which
is the ratio of the vapour to the liquid leaving the reboiler. For the steamstripped configuration it is necessary to specify the steam feed.
8-68
Column
8-69
The property view of the side stripper is shown in the figure below.
Figure 8.36
To change the side stripper
draw and return stages from
the Column property view,
the Solver must be Active in
the Main simulation
environment.
When you click the Install button, a side stripper tray section is installed,
as well as a reboiler if you selected the Reboiled configuration.
By default, the tray section is named SS1, the reboiler is named SS1_Reb,
and the reboiler duty stream is named SS1_Energy. As you add
additional Side strippers, the index increases (e.g., - SS2, SS3, etc.).
Side Rectifiers Page
As with the side stripper, you must specify the number of stages, the
liquid draw stage, and the vapour return stage.
Figure 8.37
8-69
8-70
Column Property View
The vapour and liquid product rates, as well as the reflux ratio are also
required. These specifications are added to the Monitor page and Specs
page of the Column property view.
When you install the side rectifier, a side rectifier tray section and partial
condenser are added. By default, the tray section is named SR_1, the
condenser is named SR_1_Cond, and the condenser duty stream is
named SR_1_Energy.
Pump Arounds Page
When you install the pump around, a Cooler is also installed. The
default pump around specifications are the pump around rate and
temperature drop. These are added on the Monitor page and Specs page
of the Column property view.
When installing a Pump
Around, it is necessary to
specify the draw stage, return
stage, molar flow, and duty.
After you click the Install button, the Pump Around property view
changes significantly, as shown in the figure below, allowing you to
change pump around specifications, and view pump around calculated
information.
Figure 8.38
8-70
Column
8-71
Vap Bypasses Page
As with the Pump Around, it is necessary to specify the draw and return
stage, as well as the molar flow and duty for the vapour bypass. When
you install the vapour bypass, the draw temperature and flowrate
appear on the vapour bypass view.
The vapour bypass flowrate is automatically added as a specification.
The figure below shows the vapour bypass view once the side operation
has been installed.
Figure 8.39
Side Draws Page
The Side Draws page allows you to view, and edit information regarding
the side draw streams in the column. The following is the information
included on this page:
•
•
•
•
•
•
Draw Stream
Draw Stage
Type (Vapour, Liquid or Water)
Mole Flow
Mass Flow
Volume Flow
8-71
8-72
Column Property View
8.4.4 Rating Tab
The Rating tab has four pages, which are described in the table below.
Page
Description
Tray Sections
Provides information regarding tray sizing. On this page, you can
specify the following:
• Tray Section (Name)
• Uniform Section. When checked all tray stages have the same
physical setup (diameter, tray type, etc.).
• Internal Type (tray type)
• Tray Diameter
• Tray Space
• Tray Volume
• Disable Heat Loss Calcs
• Heat Model
• Rating Calculations
• Hold Up (ft3). If you delete the weir height, you can then enter
the hold up value, and the weir height is back-calculated.
• Weeping Factor. The value is used to adjust the weeping in
dynamic mode for low pressure drops.
Vessels
Provides information regarding vessel sizing. On this page, you can
specify the following:
• Vessel (Name)
• Diameter
• Length
• Volume
• Orientation
• Vessel has a Boot
• Boot Diameter
• Boot Length
• Hold Up (ft3)
Equipment
Contains a list of Other Equipment in the Column flowsheet.
Pressure Drop
Contains information regarding pressure drop across the column.
On this page you can specify the following information:
•
•
•
•
•
8-72
Pressure Tolerance
Pressure Drop Tolerance
Damping Factor
Maximum Pressure Iterations
Top and Bottom column pressures
Column
8-73
Tray Sections Page
The required size information
for the tray section can be
calculated using the Tray
Sizing utility.
The Tray Sections page contains all the required information for
correctly sizing the column tray sections. The tray section diameter, weir
length, weir height, and the tray spacing are required for an accurate
and stable dynamic simulation. You must specify all the information on
this page. With the exception of the tray volume, no other calculations
are performed on this page.
Figure 8.40
For multipass trays, simply enter the column diameter and the
appropriate total weir length.
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Column Property View
Vessels Page
The Vessels page contains the necessary sizing information for the
different vessels in the column sub-flowsheet.
Figure 8.41
Equipment Page
This page is not available in
the Liquid-Liquid Extractor.
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The Equipment page contains a list of all the additional equipment,
which is part of the column sub-flowsheet. The list does not contain
equipment, which is part of the original template. Any extra equipment,
which is added to the sub-flowsheet (pump arounds, side strippers, etc.)
is listed here. Double-clicking on the equipment name opens its
property view on the Rating tab.
Column
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Pressure Drop Page
This page is not available in
the Liquid-Liquid Extractor.
The Pressure Drop page allows you to specify the pressure drop across
individual trays in the tray section. The pressure at each individual stage
can also be specified. The Pressure Solving Options group allows you to
adjust the following parameters:
•
•
•
•
Pressure Tolerance
Pressure Drop Tolerance
Damping Factor
Maximum Pressure Iterations
Figure 8.42
8.4.5 Worksheet Tab
The Column Environment
also has its own Workbook.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the unit
operation. The PF Specs page contains a summary of the stream
property view’s Dynamics tab. Refer to Section 1.2.3 - Worksheet Tab for
more information.
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Column Property View
8.4.6 Performance Tab
You can view the results in
molar, mass or liquid volume,
by selecting the appropriate
basis radio button.
On the Performance tab, you can view the results of a converged column
on the Summary page, Column Profiles page, and Feeds/Products page.
You can also view the graphical and tabular presentation of the column
profile on the Plots page.
Summary Page
The Summary page gives a tabular summary of the feed and product
stream compositions, flows or the % recovery of the components in the
product streams. When you select the Recovery radio button, the feed
table displays the feed stream flowrate.
Figure 8.43
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Column
8-77
Column Profiles Page
The liquid and vapour flows
are net flows for each stage.
The Column Profiles page gives a tabular summary of Column stage
temperatures, pressures, flows, and duties.
Figure 8.44
The Heat Loss column is
empty unless you select a
heat flow model in the column
sub-flowsheet of Main TS
view on the Rating tab.
You can change the basis for which the data appears by selecting the
appropriate radio button from the Basis group.
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8-78
Column Property View
Feeds/Products Page
The Feeds/Products page gives a tabular summary of feed and product
streams tray entry/exit, temperatures, pressures, flows, and duties.
Figure 8.45
You can split a feed stream
into its phase components
either on the Setup page of
the Flowsheet tab in the
column view or on the
Options page of the
Simulation tab in the Session
Preference view.
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You can change the basis of the data by selecting the appropriate radio
button from the Basis group. For the feeds and draw Streams, the VF
column to the right of each flow value indicates whether the flow is
vapour (V) or liquid (L). If the feed has been split, a star (*) follows the
phase designation. If there is a duty stream on a stage, “Energy” appears
in the Type column. The direction of the energy stream is indicated by
the sign of the duty.
Column
8-79
Plots Page
On the Plots page, you can view various column profiles or assay curves
in a graphical or tabular format.
Figure 8.46
Activate the Live Updates checkbox to update the profiles with every
pass of the solver (i.e., a dynamic update). It is deactivated by default,
and performance of the column can be a bit slower if the checkbox is on
and a profile is open.
Tray by Tray Properties Group
To view a column profile, follow this generalized procedure:
Electrolyte Properties are
only available for cases with
an electrolyte system.
The main tray section along
with the condenser and
reboiler are considered one
section, as is each side
stripper.
1.
Select a profile from the list in the Tray by Tray Properties group. The
choices include: Temperature, Pressure, Flow, Transport Properties,
Composition, K Value, Light/Heavy Key, and Electrolyte Properties.
2.
In the Column Tray Ranges group, select the appropriate radio
button:
Radio Button
Action
All
Displays the selected profile for all trays connected to the column
(i.e., main tray section, side strippers, condenser, reboiler, etc.).
Single Tower
From the drop-down list, select a tray section.
From/To
Use the drop-down lists to specify a specific range of the column.
The first field contains the tray that is located at a higher spot in the
tower (i.e., for top to bottom tray numbering, the first field could be
tray 3 and the second tray 6).
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Plots and tables are
expandible views that can
remain open without the
column property view.
Column Property View
3.
After selecting a tray range, click either the View Graph button or the
View Table button to display a plot or table respectively.
Figure 8.47
To make changes to the plot,
right-click in the plot area,
and select Graph Control
from the menu. Refer to
Section 10.4 - Graph
Control in the User Guide.
Depending on the profile selected, you have to make further
specifications. For certain profiles, there is a Properties button on both
the profile plot and table. By clicking this button, the Properties view
appears, where you can customize the display of your profile. Changes
made on the Properties view affect both the table and plot.
A description of the specifications available for each profile type are
outlined in the following table.
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Profile Type
Description
Temperature Profile
Displays the temperature for the tray range selected. No further
specification is needed.
Pressure Profile
Displays the pressure of each tray in the selected range. No
further specification is needed.
Column
Profile Type
Description
Flow Profile
Displays the flow rate of each tray in the selected range. You
can customise the data displayed using the Properties view.
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In the Basis group, select molar, mass or liquid volume for your
flow profile basis.
In the Phase group, activate the checkbox for the flow of each
phase that you want to display. Multiple flows can be shown. If
three phases are not present in the column, the Heavy Liquid
checkbox is not available, and thus, the Light Liquid checkbox
represents the liquid phase.
In the Tray Flow Basis group, you can specify the stage tray
flow basis by selecting the appropriate radio button:
• Net. The net basis option only includes interstage flow.
• Total. The total basis option includes draw and pump
around flow.
The Properties Profile table
displays all of the properties
for the phase(s) selected.
Transport
Properties Profile
Displays the selected properties from each tray in the selected
range. You can customise the data displayed using the
Properties view:
In the Basis group, select molar or mass for the properties
profile basis.
In the Phase group, activate the checkbox for the flow of each
phase that you want to display on the graph. Multiple flows can
be shown. If three phases are not present in the column, the
Heavy Liquid checkbox is not available.
In the Axis Assignment group, by selecting a radio button under
Left, you assign the values of the appropriate property to the
left y-axis. To display a second property, choose the radio
button under Right. The right y-axis then shows the range of
the second property. If you want to display only one property on
the plot, select the None radio button under Right.
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Column Property View
Profile Type
Description
Composition
Displays the selected component’s mole fraction of each tray in
the selected range. You can customise the data displayed
using the Properties view.
In the Basis group, select molar, mass or liquid volume for the
composition profile basis.
In the Phase group, activate the checkbox for the flow of each
phase that you want to display. Multiple flows can be shown. If
the three phases are not present in the column, the Heavy
Liquid checkbox is not available, and thus, the Light Liquid
checkbox represents the liquid phase.
Choose either Fractions or Flows in the Comp Basis group by
selecting the appropriate radio button.
The Components group displays a list of all the components
that enter the tower. You can display the composition profile of
any component by activating the appropriate checkbox. The
plot displays any combination of component profiles.
K Values Profile
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Displays the K Values of each tray in the selected range. You
can select which components you want included in the profile
using the Properties view.
Column
Profile Type
Description
Light/Heavy Key
Profile
Displays the fraction ratio for each stage. You can customise
the data displayed using the Properties view.
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In the Basis group, select molar, mass or liquid volume for the
profile basis.
In the Phase group, select Vapour, Light Liquid or Heavy Liquid
for the profile phase.
In the Light Key(s) and Heavy Key(s) groups, you can select
the key component(s) to include in your profile.
Electrolyte
Properties Profile
Displays the pH and ionic strength or the scale index
depending on which radio button you select in the Graph Type
group.
When you select the pH, Ionic Strength radio button, you can
see how the pH value and ionic strength decrease or increase
from tray to tray.
The Solid Components group displays a list of the solids that
could form in the distillation column. You can activate or
deactivate the checkboxes to display or hide the scale
tendency index value for the solid components in the table or
graph.
The scale tendency index value refers to its tendency to form at
the given tray conditions. Solids with a scale tendency index
greater than 1 form, if the solid formation is governed by
equilibrium (as oppose to kinetics), and if there are no other
solids with a common cation or anion portion which also has
scale tendency greater than 1.
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Column Property View
Assay Curves Group
Figure 8.48
From the Assay Curves group, you can create plots and tables for the
following properties:
•
•
•
•
Boiling Point Assay
Molecular Weight Assay
Density Assay
User Properties
For each of the options, you can display curves for a single tray or
multiple trays. To display a plot or table, make a selection from the list,
and click either the View Graph button or the View Table button. The
figure below is an example of how a Boiling Point Properties plot
appears.
Figure 8.49
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Column
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Data Control View
Click the Profile Data Control button, which is located on bottom left
corner of every plot and table, to open the Data Control property view.
This view is common to all plots and tables on the Curves page. For a
selected curve, all changes made on the Data Control property view
affect the data of both the plot and table.
The Data Control property view consists of five groups as shown in the
figure below.
Figure 8.50
The following table describes each data control option available
according to group name.
Group
Description
Style
Select either the Multi Tray or Single Tray radio button. The layout of
the Data Control property view differs slightly for each selection.
For the Single Tray selection, you must open the drop-down list and
select one tray.
If you select Multi Tray, the drop-down list is replaced by a list of all
the trays in the column. Each tray has a corresponding checkbox,
which you can activate to display the tray property on the plot or
table.
Refer to Chapter 4 - HYSYS
Oil Manager in the
Simulation Basis manual
for details on boiling point
curves.
Properties
Displays the properties available for the plot or table. Each Curve
option has its own distinct Properties group. For a single tray
selection, you can choose as many of the boiling point curves as
required. Activate the checkbox for any of the following options:
TBP,ASTM D86,D86 Crack Reduced, D1160 Vac, D1160 ATM, and
D2887. When multiple trays have been chosen in the Style group,
the checkbox list is replaced by a drop-down list. You can only
choose one boiling point curve when displaying multiple trays.
Basis
Select molar, mass or liquid volume for the composition basis.
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Column Property View
Group
Description
Phase
Activate the checkbox for the flow of each phase that you want
displayed. Multiple flows can be shown. If there are not three phases
present in the column, the Heavy Liquid checkbox is not available,
and thus, the Light Liquid checkbox represents the liquid phase.
Visible Points
The radio buttons in the Visible Points group apply to the plots only.
Select either the 15 Points or 31 Points option to represent the
number of data points which appear for each curve.
TBP Envelope Group
The curve allows you to
view product stream
distillation overlaid on the
column feed distillation. This
gives a visual representation
of how sharp the
separations are for each
product. The sharpness of
separation is adjusted using
section and stripper
efficiencies and front and
back end shape factors.
The TBP Envelope group contains only the View Graph button. You can
click the View Graph button to display a TBP Envelope curve as shown
in the figure below.
Figure 8.51
Click the Profile Data Control button located on the view above to open
a view for customizing your TBP Envelope curve.
Figure 8.52
Select either a wet or dry
basis. Dry basis is the
default selection.
Select a basis to define
your TBP profile here.
Select from either 100 or
200 data points for your
TBP plot.
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Column
8-87
8.4.7 Flowsheet Tab
The Flowsheet tab consists of four pages:
•
•
•
•
Setup
Variables
Internal Streams
Mapping
Setup Page
The Setup page defines the connections between the internal (subflowsheet) and external (Parent) flowsheets.
Figure 8.53
To split all material inlet
streams into their phase
components before being
fed to the column, activate
the Split All Inlets checkbox.
If one of the material feed
stream Split checkbox is
deactivated, the Split All
Inlets checkbox deactivates
too.
If you deactivate the Split All
Inlets checkbox, none of the
material inlet stream Split
checkboxes are affected.
The Labels, as noted previously, attach the external flowsheet streams to
the internal sub-flowsheet streams. They also perform the transfer (or
translation) of stream information from the property package used in
the parent flowsheet into the property package used in the Column subflowsheet (if the two property packages are different). The default
transfer basis used for material streams is a P-H Flash.
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Column Property View
The Transfer Basis is significant only when the sub-flowsheet and parent
flowsheet Property Packages are different.
See the Summary page of the
Performance tab to verify the
split feed streams. An asterisk
(*) following the phase
indicator in the VF column
indicates a split stream.
Flash Type
Action
T-P Flash
The pressure and temperature of the material stream are passed
between flowsheets. A new vapour fraction is calculated.
VF-T Flash
The vapor fraction and temperature of the material stream are
passed between flowsheets. A new Pressure is calculated.
VF-P Flash
The vapor fraction and pressure of the material stream are passed
between flowsheets. A new temperature is calculated.
P-H Flash
The pressure and enthalpy of the material stream is passed
between flowsheets. This is the default transfer basis.
User Specs
You can specify the transfer basis for a material Stream.
None Required
No calculation is required for an energy stream. The heat flow is
simply passed between flowsheets.
When the Split checkbox for any of the inlet material streams is
activated, the stream is split into its vapour and liquid phase
components. The liquid stream is then fed to the specified tray, and the
vapour phase to the tray immediately above the specified feed tray.
Energy streams and material streams connected to the top tray
(condenser) cannot be split. The checkboxes for there variables appear
greyed out.
Figure 8.54
The Flowsheet Topology group provides stage information for each
element in the flow sheet.
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Column
8-89
Flowsheet Variables Page (Main)
The Variables page allows you to select and monitor any flowsheet
variables from one location. You can examine sub-flowsheet variables
from the outside Column property view, without actually having to enter
the Column sub-flowsheet environment.
You can also use the
Specifications page to view
certain variables. Select the
variable by adding a
specification, and ensure that
the Active and Estimate
checkboxes are not activated.
The value of this variable
appears in the Current value
column, and this “pseudospecification” do not affect the
solution.
You can add, edit or delete variables in the Selected Column flowsheet
Variables group.
Figure 8.55
Adding a Variable
Refer to Section 11.21 Variable Navigator in the
User Guide for information on
the Variable Navigator.
To add a variable in the Selected Column Flowsheet Variables group:
1.
Click the Add button.
2.
From the Variable Navigator, select each of the parameters for the
variable.
3.
Click the OK button.
4.
The variable is added to the Selected Column Flowsheet Variables
group.
Editing a Variable
If you decide that you do not
want to keep the changes
made in the variable
navigator, click the Cancel
button.
You can edit a variable in the Selected Column Flowsheet Variables
group as follows:
1.
Highlight a variable.
2.
Click the Edit button.
3.
Make changes to the selections in the Variable Navigator.
4.
Click the OK button.
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Column Property View
Deleting a Variable
You can remove a variable in any of the following ways:
1.
Select a variable, and click the Delete button.
OR
2.
Select a variable, click the Edit button, and then click the
Disconnect button on the Variable Navigator.
Internal Streams Page
On the Internal Streams page, you can create a flowsheet stream that
represents any phase leaving any tray within the Column. Streams
within operations attached to the main tray section (i.e., side strippers,
the condenser, the reboiler, etc.) can also be targeted. Each time changes
occur to the column, new information is automatically transferred to
the stream which you have created.
Figure 8.56
To demonstrate the addition of an internal stream, a stream
representing the liquid phase flowing from tray 7 to tray 8 in the main
tray section of a column is added:
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1.
Click the Add button.
2.
In the Stream drop-down list, type the name of the stream named
Liquid.
3.
In the Stage drop-down list, select tray 6 or simply type 6, which
locates the selection in the list.
4.
In the Type drop-down list, select the phase that you want to
represent. The options include Vapor, Liquid or Aqueous. Select
Liquid in this case.
Column
5.
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From the Net/Total drop-down list, select either Net or Total. For the
stage 6 liquid, select Net.
•
•
Net represents the material flowing from the Stage you have
selected to the next stage (above for vapour, below for liquid or
aqueous) in the column.
Total represents all the material leaving the stage (i.e., includes
draws, pump around streams, etc.).
Mapping Page
The Mapping page contains a table that displays the inlet and outlet
streams from the column sub-flowsheet, and component maps for each
boundary stream.
Figure 8.57
For more detail on the actual
map collections and
component maps
themselves, refer to
Chapter 6 - Component
Maps in the Simulation
Basis manual.
If the fluid package of the column is the same as the main flowsheet,
component maps are not needed (because components are the same on
each side of the column boundary). None Req’d is the only option in the
drop-down list of the Into Sub-Flowsheet and Out of Sub-Flowsheet
columns. If the fluid packages are different, you can choose a map for
each boundary stream. HYSYS lists appropriate maps based on the fluid
package of each stream across the boundary.
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Column Property View
Click the Overall Imbalance Into Sub-Flowsheet button or Overall
Imbalance Out of Sub-Flowsheet button to view any mole, mass of
liquid volume imbalance due to changes in fluid package. If there are no
fluid package changes, then there are no imbalances.
8.4.8 Reactions Tab
This tab is not available for
the Liquid-Liquid Extractor.
Reactive distillation has been used for many years to carry out chemical
reactions, in particular esterification reactions. The advantages of using
distillation columns for carrying out chemical reactions include:
•
•
•
•
the possibility of driving the reaction to completion (break down of
thermodynamic limitations for a reversible reaction), and
separating the products of reactions in only one unit, thus
eliminating recycle and reactor costs.
the elimination of possible side reactions by continuous
withdrawal of one of the products from the liquid phase.
the operation at higher temperatures (boiling liquid), thus
increasing the rate of reaction of endothermic reactions.
the internal recovery of the heat of reaction for exothermic
reactions, thereby replacing an equivalent amount of external
heat input required for boil-up.
For any column in an electrolyte flowsheet, there is no option to add any
reaction (reaction set) to the column. Conceptually, electrolyte thermo
conducts a reactive and phase flash all together. HYSYS does not
provide options to allow you to add external reactions to the unit
operation.
The Reactions tab allows you to attach multiple reactions to the column.
The tab consists of two pages:
•
•
8-92
Stages. Allows you select the reaction set, and its scope across
the column.
Results. Displays the reaction results stage by stage.
Column
8-93
Before adding a reaction to a column, you must first ensure that you are
using the correct column Solving Method. HYSYS provides three solving
methods which allow for reactive distillation.
Solving Method
Reaction Type
Reaction Phase
Sparse Continuation Solver
Kinetic Rate, Simple Rate,
Equilibrium Reaction
Vapor, Liquid
Newton Raphson Inside-Out
Kinetic Rate, Simple Rate
Liquid
Simultaneous Correction
Kinetic Rate, Simple Rate,
Equilibrium Reaction
Vapor, Liquid,
Combined Phase
The Sparse Continuation Solver method allows you to attach a reaction
set to your column, which combines reaction types. Other solvers
require that the attached reactions are of a single type.
Stages Page
The Stages page consists of the Column Reaction Stages group. The
group contains the Column Reaction Stages table and three buttons.
Figure 8.58
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8-94
Column Property View
Column Reaction Stages Table
The table consists of four columns, which are described in the table
below.
Column
Description
Column Reaction
Name
The name you have associated with the column reaction. This is
not the name of the reaction set you set in the fluid package
manager.
First Stage
The highest stage of the stage range over which the reaction is
occurring.
Last Stage
The lowest stage of the stage range over which the reaction is
occurring.
Active
Activates the associated reaction thereby enabling it to occur
inside the column.
The view also contains three buttons that control the addition,
manipulation, and deletion of column reactions.
8-94
Button
Description
New
Allows you to add a new column reaction set via the Column
Reaction view. For more information of the Column Reaction view
and adding new reactions, refer to the section on the Column
Reaction View.
Edit
Allows you to edit the column reaction set whose name is
currently selected in Column Reaction Stages table. The selected
reaction’s Column Reaction view opens. For more information on
the Column Reaction view, refer to the section on the Column
Reaction View.
Delete
Allows you to delete the column reaction set whose name is
currently selected in the Column Reaction Stages table.
Column
8-95
Column Reaction View
The Column Reaction view allows you to add and revise column
reactions.
Figure 8.59
The Reaction Set
Information group allows you
to select the reaction set,
and the scope of its
application.
The Reaction Information
group contains
thermodynamic and
stoichiometric information
about the reaction you are
applying to the selected
section of the column.
The Column Reaction view shown in the above figure consists of two
groups:
•
•
Reaction Set Information
Reaction Information
Reaction Set Information Group
The Reaction Set Information group consists of six objects:
Objects
Description
Name
The name you would like to associate with the column reaction. This is
the name that appears in the Column Reaction Name column of the
Column Reaction Stages table.
Reaction Set
Allows you to select a reaction set from a list of all the reaction sets
attached to the fluid package.
First Stage
The upper limit for the reaction that is to occur over a range of stages.
Last Stage
The lower limit for the reaction that is to occur over a range of stages.
Delete
Deletes the Column Reaction from the column.
Active
Allows you to enable and disable the associated column reaction.
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Column Property View
Reaction Information Group
The Reaction Information group contains the Reaction field, which
allows you to select a reaction from the reaction set selected in the
Reaction Set field. Click the View Reaction button to open the selected
reaction’s Reaction view. This group also contains three sub-groups,
which allow you to view or specify the selected reactions properties:
Sub-group
Description
Stoichiometry
Allows you to view and make changes to the stoichiometric formula
of the reaction currently selected in the Reaction drop-down list. The
group contains three columns:
• Components. Displays the components involved in the
reaction.
• Mole Wt. Displays the molar weight of each component
involved in the reaction.
• Stoich Coeff. Stoichiometric coefficients associated with the
reaction.
You can make changes to the
fields in these groups.
These changes affect all the
unit operations associated
with this reaction. Click the
View Reactions button for
more information about the
attached reaction.
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Basis
Consists of two fields:
• Base Component. Displays the reactant to which the reaction
extent is calculated. This is often the limiting reactant.
• Reaction Phase. Displays the phase for which the kinetic rate
equations for different phases can be modeled in the same
reactor. To see the possible reactions, click the Reaction
Information button in the View Reaction group.
Heat and
Balance Error
Consists of two fields:
• Reaction Heat. Displays the reaction heat.
• Balance Error. Displays any error in the mass balance around
the reaction.
Column
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Results Page
The Results page displays the results of a converged column.
Figure 8.60
The page consists of a table containing six columns. The first column
contains the column stage. The remaining columns are as follows:
Column
Description
Rxn Name
The name of the reaction occurring at this stage.
Base Comp
The name of the reactant component to which the calculated
reaction extent is applied.
Rxn Extent
The consumption or production of the base component in the
reaction.
Spec % Conv
Displays the percentage of conversion specified by you.
Act % Conv
Displays the percentage of conversion calculated by HYSYS.
If you have more than one reaction occurring at any particular stage,
each reaction appears simultaneously.
The Rxn Extent results appear only if the Sparse Continuation Solver is
chosen as the Solving Method.
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Column Property View
Design Tips for Reactive Distillation
1
Although the column unit operations allows for multiple column
reactions and numerous column configurations, a general column
topography can be subdivided into three sections:
•
•
•
Rectifying Section
Reactive Section
Stripping Section
Figure 8.61
Rectifying
Section
Reactive
Section
Stripping
Section
While the Rectifying and Stripping Sections are similar to ordinary
distillation, a reactive distillation column also has a Reactive Section.
The Reactive Section of the column is where the main reactions occur.
There is no particular requirement for separation in this section.
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Column
8-99
There are several unique operational considerations when designing a
reactive distillation column:
•
•
•
•
The operating pressure should be predicated on the indirect
effects of pressure on reaction equilibrium.
The optimum feed point to a reactive distillation column is just
below the reactive section. Introducing a feed too far below the
reactive section reduces the stripping potential of the column and
results in increased energy consumption.
Reflux has a dual purpose in reactive distillation. Increasing the
reflux rate enhances separation and recycles unreacted
reactants to the reaction zone thereby increasing conversion.
Reboiler Duty is integral to reactive distillation as it must be set to
ensure sufficient recycle of unreacted, heavy reactant to the
reaction zone without excluding the light reactant from the
reaction zone, if the reboiler duty is too high or too low,
conversion, and purity can be compromised.
8.4.9 Dynamics Tab
The Dynamics tab has three related pages:
•
•
•
Vessels
Equipment
Holdup
If you are working exclusively in Steady State mode or your version of
HYSYS does not support dynamics, you are not required to change any
information on the pages accessible through this tab.
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8-100
Column Property View
Vessels Page
The Vessels page contains a summary of the sizing information for the
different vessels contained in the column sub-flowsheet. In addition, it
contains the possible dynamic specifications for these vessels.
Figure 8.62
Equipment Page
This page is not available for
the Liquid-Liquid Extractor.
8-100
The Equipment page displays the same information as the Equipment
page on the Rating tab. The difference is that double-clicking on the
equipment name opens its property view on the Dynamics tab.
Column
8-101
Holdup Page
The Holdup page contains a summary of the dynamic information
calculated by HYSYS.
Column
Description
Pressure
Displays the calculated stage pressure.
Total Volume
Displays the stage volume.
Bulk Liq Volume
Displays the liquid volume occupying the stage.
8.4.10 Perturb Tab
The Perturb tab is only available in the Column Runner view. The
Perturb tab allows you to control the way column solver calculates the
partial derivatives. There are two types of independent controls.
Control
Description
Low Level Analytic
The Analytic property derivatives checkbox allows you to
turn On and Off low level analytic derivatives support (i.e.,
derivatives of thermodynamic properties like Fugacity,
Enthalpy, and Entropy by Temperature, Pressure, and
Composition).
At present this facility is available for Peng Robinson or
Soave-Redlich-Kwong property packages in Sparse
Continuation Solver context.
Optimizer Level Analytic
HYSYS Optimizer (RTO+) allows calculation of column
analytic derivatives by stream Temperature, Pressure,
Component Flow, Column Spec specified value, and Tear
Variables.
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8-102
Column Property View
The Sparse analytic page allows you to select a particular method of
column analytic derivatives calculation.
Figure 8.63
The Perturb method parameters group provides tuning parameters for
analytic column derivatives calculator.
•
•
•
8-102
Rigorous properties checkbox. If active, rigorous
thermodynamic properties are applied in Jacobi matrix
calculation. If inactive, simple models (controlled by Control panel
of Sparse solver) are applied instead for Enthalpy and Fugacity of
thermodynamic phases. The last option may expedite derivative
calculations.
Warm restart checkbox. If active, additional Sparse linear solver
information is preserved between Analytic derivative calculator
calls (faster solution of linear system). If inactive, no Sparse linear
solver information is stored (memory economy).
Skip Sparse Solve checkbox. If active, Column solution phase is
skipped (may allow faster execution).
Column
8-103
8.5 Column Specification Types
This section outlines the various Column specification (spec) types
available along with relevant details. Specs are added and modified on
the Specs Page or the Monitor Page of the Design tab.
Adding and changing Column specifications is straightforward. If you
have created a Column based on one of the templates, HYSYS already
has default specifications in place. The type of default specification
depends on which of the templates you have chosen (refer to the
Default Replaceable Specifications in Section 8.3.2 - Templates for
more details).
8.5.1 Cold Property Specifications
Figure 8.64
Cold Property
Description
Flash Point
Allows you to specify the Flash Point temperature (ASTM D93 flash
point temperature closed cup) for the liquid or vapour flow on any
stage in the column.
Pour Point
Allows you to specify the ASTM Pour Point temperature for the liquid
or vapour flow on any stage in the column.
RON
Allows you to specify the Research Octane Number for the liquid or
vapour flow on any stage.
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8-104
Column Specification Types
8.5.2 Component Flow Rate
The flow rate (molar, mass or volume) of any component, or the total
flow rate for any set of components, can be specified for the flow leaving
any stage. If a side liquid or vapour draw is present on the selected stage,
these are included with the internal vapour and liquid flows.
Figure 8.65
8.5.3 Component Fractions
The mole, mass or volume fraction can be specified in the liquid or
vapour phase for any stage. You can specify a value for any individual
component, or specify a value for the sum of the mole fractions of
multiple components.
Figure 8.66
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Column
8-105
8.5.4 Component Ratio
The ratio (molar, mass or volume fraction) of any set of components
over any other set of components can be specified for the liquid or
vapour phase on any stage.
Figure 8.67
8.5.5 Component Recovery
Component recovery is the molar, mass or volume flow of a component
(or group of components) in any internal or product stream draw
divided by the flow of that component (or group) in the combined tower
feeds. As the recovery is a ratio between two flows, you specify a
fractional value. Also, there is no need to specify a Flow Basis since this is
a ratio of the same component between specified stream and the
combined tower feeds.
Figure 8.68
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8-106
Column Specification Types
8.5.6 Cut Point
While initial and final cut
points are permitted, it is
often better to use 5 and 95
percent cut points to
minimize the errors
introduced at the extreme
ends of boiling point curves.
This option allows a cut point temperature to be specified for the liquid
or vapour leaving any stage. The types are TBP, ASTM D86, D1160 Vac,
D1160 ATM, and ASTM D2887. For D86, you are given the option to use
ASTM Cracking Factor. For D1160, you are given an Atmospheric
Pressure option. The cut point can be on a mole, mass or volume
fraction basis, and any value from 0 to 100 percent is allowed.
Figure 8.69
8.5.7 Draw Rate
The molar, mass or volume flowrate of any product stream draw can be
specified.
Figure 8.70
8.5.8 Delta T (Heater/Cooler)
The temperature difference across a Heater or Cooler unit operation can
be specified. The Heater/Cooler unit must be installed in the Column
sub-flowsheet, and the HYSIM Inside-Out, Modified HYSIM Inside-Out
or Sparse Continuation solving methods must be selected on the Solver
page of the Parameters tab.
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Column
8-107
8.5.9 Delta T (Streams)
The temperature difference between two Column sub-flowsheet
streams can be specified.
Figure 8.71
8.5.10 Duty
You can specify the duty for an energy stream.
Figure 8.72
8.5.11 Duty Ratio
You can specify the duty ratio for any two energy streams. In addition to
Column feed duties, the choice of energy streams also includes pump
around duties (if available).
Figure 8.73
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Column Specification Types
8.5.12 Feed Ratio
This type of specification is
useful for turn down or
overflash of a crude feed.
The Feed Ratio option allows you to establish a ratio between the flow
rate on or from any stage in the column, and the external feed to a stage.
You are prompted for the stage, flow type (Vapor, Liquid, Draw), and the
external feed stage.
Figure 8.74
8.5.13 Gap Cut Point
The Gap Cut Point is defined as the temperature difference between a
cut point (Cut Point A) for the liquid or vapour leaving one stage, and a
cut point (Cut Point B) on a different stage.
Figure 8.75
This specification is best
used in combination with at
least one flow specification;
using this specification with a
Temperature specification
can produce non-unique
solutions.
You have a choice of specifying the distillation curve to be used:
•
•
•
•
•
TBP
ASTM D86
D1160 Vac
D1160 ATM
ASTM D2887
You can define Cut Point A and Cut Point B, which together must total
100%. The cut points can be on a mole, mass or volume basis.
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Column
8-109
8.5.14 Liquid Flow
The net molar, mass or volume liquid (Light or Heavy) flow can be
specified for any stage.
Figure 8.76
8.5.15 Physical Property Specifications
The mass density can be specified for the liquid or vapour on any stage.
Figure 8.77
8.5.16 Pump Around Specifications
Figure 8.78
The Pump Around Rate, as
well as the Pump Around
Temperature Drop are the
default specifications HYSYS
requests when a pump
around is added to the
column.
Specification
Description
Flow Rate
The flow rate of the Pump Around can be specified in
molar, mass or liquid volume units.
Temperature Drop
Allows you to specify the temperature drop across a Pump
Around exchanger. The conditions for using this
specification are the same as that stated for the Pump
Around return temperature.
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Column Specification Types
Specification
Description
Return Temperature
The return temperature of a Pump Around stream can be
specified. Ensure that you have not also specified both the
pump around rate and the duty. This would result in the
three associated variables (flow rate, side exchanger duty,
and temperature) all specified, leaving HYSYS with nothing
to vary in search of a converged solution.
Duty
You can specify the duty for any Pump Around.
Return Vapor Fraction
You can specify the return vapour fraction for any Pump
Around.
Duty Ratio
To specify a Pump Around duty ratio for a Column
specification, add a Column Duty Ratio spec instead, and
select the Pump Around energy streams to define the duty
ratio. Refer to Section 8.5.11 - Duty Ratio for further
details.
8.5.17 Reboil Ratio
You can specify the molar, mass or volume ratio of the vapour leaving a
specific stage to the liquid leaving that stage.
Figure 8.79
8.5.18 Recovery
The Recovery spec is the recovery of the total feed flow in the defined
outlet streams (value range between 0 and 1).
molar flow of draw stream
---------------------------------------------------------------- = % recovery
total molar feed flow
Figure 8.80
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(8.4)
Column
8-111
8.5.19 Reflux Feed Ratio
The Reflux Feed Ratio spec is the fraction of the reflux flow divided by
the reference flow for the specified stage and phase.
reflux flow
---------------------------------- = reflux feed ratio
reference flow
(8.5)
Figure 8.81
8.5.20 Reflux Fraction Ratio
The Reflux Fraction Ratio spec is the fraction or % of liquid that is being
refluxed on the specified stage (value range between 0 and 1).
Figure 8.82
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Column Specification Types
8.5.21 Reflux Ratio
The Reflux Ratio specification
is normally used only for top
stage condensers, but it can
be specified for any stage.
For a Partial Condenser:
The Reflux Ratio is the molar, mass or volume flow of liquid (Light or
Heavy) leaving a stage, divided by the sum of the vapour flow from the
stage plus any side liquid flow.
Figure 8.83
• Checking the Include
Vapour checkbox, gives
the following equation
for the reflux ratio: R
Reflux Ratio = -------------V+D
• Unchecking the Include
Vapour checkbox, gives
the following equation
for the reflux ratio: R
Reflux Ratio = ---D
Reflux Ratio view for general
column
Reflux Ratio view for three
phase distillation column
where:
R = liquid reflux to
column
V = vapour product
8.5.22 Tee Split Fraction
D = distillate product
The split fraction for a Tee operation product stream can be specified.
The Tee must be installed within the Column sub-flowsheet and directly
attached to the column i.e., to a draw stream, in a pump around circuit,
etc. Also, the Modified HYSIM Inside-Out solving method must be
selected.
Refer to Section 5.4 - Tee for
details on the Tee operation.
Tee split fraction specifications are automatically installed as you install
the tee operation in the Column sub-flowsheet; however, you can select
which specifications become active on the Monitor page or Specs page.
Changes made to the split fraction specification value are updated on
the Splits page of the tee operation.
8.5.23 Tray Temperature
The temperature of any stage can be specified.
Figure 8.84
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Column
8-113
8.5.24 Transport Property Specifications
The viscosity, surface tension or thermal conductivity can be specified
for the liquid leaving any stage. The viscosity or thermal conductivity
can be specified for the vapour leaving any stage. A reference
temperature must also be given.
The computing time required to satisfy a vapour viscosity specification
can be considerably longer than that needed to meet a liquid viscosity
specification.
Figure 8.85
8.5.25 User Property
A User Property value can be specified for the flow leaving any stage. You
can choose any installed user property in the flowsheet, and specify its
value. The basis used in the installation of the user property is used in
the spec calculations.
Figure 8.86
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Column Specification Types
8.5.26 Vapor Flow
The net molar, mass or volume vapor flow can be specified for any stage.
Feeds and draws to that tray are taken into account.
Figure 8.87
8.5.27 Vapor Fraction
The vapour fraction of a stream exiting a stage can be specified.
Figure 8.88
8.5.28 Vapor Pressure Specifications
Two types of vapour pressure specifications are available:
•
•
true vapour pressure (@100°F)
Reid vapour pressure.
Figure 8.89
8-114
Vapor Type
Description
Vapor Pressure
The true vapour pressure at 100°F can be specified for the vapour or
liquid leaving any stage.
Reid Vapor
Pressure
Reid vapour pressure can be specified for the vapour or liquid
leaving any stage. The specification must always be given in
absolute pressure units.
Column
8-115
8.5.29 Column Stream Specifications
Column stream specifications must be created in the Column subflowsheet. Unlike other specifications, the stream specification is
created through the stream’s property view, and not the Column Runner
Specs page. To be able to add a specification to a stream:
Only one stream
specification can be created
per draw stream.
•
•
The Modified HYSIM Inside-out solving method must be chosen
for the solver.
The stream must be a draw stream.
The Create Column Stream Spec button on the Conditions page of the
Worksheet tab is available only on Stream property views within the
Column sub-flowsheet. When you click on the Create Column Stream
Spec button, the Stream Spec view appears.
Figure 8.90
Creating a new stream
specification for a stage, or
activating a specification
automatically deactivates all
other existing draw stream
specifications for that stage.
For draw streams from a separation stage (tray section stage, condenser
or reboiler) only a stream temperature specification can be set. For a
non-separation stage streams (from pumps, heaters etc.) either a
temperature or a vapour fraction specification can be set. For any given
stage, only one draw stream specification can be active at any given
time.
Once a specification is added for a stream, the button on the Conditions
page of the Worksheet tab changes from Create Column Stream Spec to
View Column Stream Spec, and can be clicked to view the Stream
Specification view.
You can only add Column Stream Specifications via the Stream property
view of a draw stream within the Column sub-flowsheet.
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Column-Specific Operations
8.6 Column-Specific Operations
Only the operations which are
applicable to a Column
operations are available within
the Column sub-flowsheet.
The procedure for installing unit operations in a Column sub-flowsheet
is the same as in the main flowsheet (refer to Section 1.2.1 - Installing
Operations for details). The UnitOps view for the Column is activated by
selecting the Add Operation command from the Flowsheet menu in the
menu bar, or by pressing F12.
Figure 8.91
The unit operations available within the Column sub-flowsheet are
listed in the following table. Most operations shown here are identical to
those available in the main flowsheet in terms of specified and
calculated information, property view structure, etc.
There are also additional unit operations which are not available in the
main flowsheet. They are:
•
•
•
8-116
Condenser (Partial, Total, 3-Phase)
Reboiler
Tray Section
Column
8-117
The Bypasses and Side Operations (side strippers, pump arounds, etc.)
are available on the Side Ops page of the Column property view.
Available unit operations in the Column sub-flowsheet are:
Operation Category
Types
Vessels
3-Phase Condenser, Partial Condenser, Reboiler,
Separator, Total Condenser, Tray Section
Heat Transfer Equipment
Cooler, Heater, Heat Exchanger
Rotating Equipment
Pump
Piping Equipment
Valve
Logicals
Balance, Digital Pt, PID Controller, Selector Block,
Transfer Function Block
You can open a view of the Column PFD from the main build
environment (refer to Section 7.25.4 - Access Column or Sub-Flowsheet
PFDs in the User Guide for more information). This PFD only provides
you with the ability to modify stream and operation parameters. You
cannot add and delete operations or break stream connections. These
tasks can only be performed in the Column sub-flowsheet environment.
8.6.1 Condenser
The Condenser is used to condense vapour by removing its latent heat
with a coolant. In HYSYS, the condenser is used only in the Column
Environment, and is generally associated with a Column Tray Section.
There are four types of Condensers:
The Partial Condenser can be
used as a Total Condenser
simply by specifying the
vapour flowrate to be zero.
Condenser Type
Description
Partial
Feed is partially condensed; there are vapour and
liquid product streams. The Partial Condenser can be
operated as a total condenser by specifying the
vapour stream to have zero flowrate.
Total
Feed is completely condensed; there is a liquid
product only.
Three-Phase - Chemical
There are two liquid product streams and one vapour
product stream.
Three-Phase - Hydrocarbon
There is a liquid product streams and a water product
stream and one vapour product stream.
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8-118
Column-Specific Operations
The Condenser property view uses a Type drop-down list, which allows
you to switch between condenser types without having to delete and reinstall a new piece of equipment.
Figure 8.92
Partial Condenser icon
Total Condenser icon
Three-Phase Condenser icon
When you switch between the condenser types, the pages change
appropriately. For instance, the Connections page for the Total
Condenser does not show the vapor stream. If you switch from the
Partial to Total Condenser, the vapor stream is disconnected. If you then
switch back, you have to reconnect the stream.
When you add a Column to the simulation using a pre-defined template,
there can be a condenser attached to the tower (this is the case for a
Distillation Column, for example). To manually add a Condenser, press
F12, and make the appropriate selection from the UnitOps view, or click
a Condenser icon from the Column Palette.
The Condenser property view has the same basic five tabs that are
available on any unit operation:
•
•
•
•
•
8-118
Design
Rating
Worksheet
Performance
Dynamics
Column
8-119
It is necessary to specify the connections and the parameters for the
Condenser. The information on the Rating tab and Dynamics tab are not
relevant in steady state.
Design Tab
The Design tab contains five pages:
•
•
•
•
•
Connections
Parameters
Estimate
User Variables
Notes
Connections Page
On the Connections page, you can specify the operation name, as well as
the feed(s), vapour, water, reflux, product, and energy streams. The Total
Condenser does not have a vapour stream, as the entire feed is liquefied.
Neither the Partial nor the Total Condenser has a water stream. The
Connections page shows only the product streams, which are
appropriate for the selected condenser.
The Condenser is typically used with a tray section, where the vapour
from the top tray of the column is the feed to the condenser, and the
reflux from the condenser is returned to the top tray of the column.
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8-120
Column-Specific Operations
Parameters Page
Figure 8.93
It is better to use a duty spec
than specifying the heat flow
of the duty stream.
The condenser parameters that can be specified are:
•
•
•
Pressure Drop
Duty
Subcooling Data
Pressure Drop
The Pressure Drop across the condenser (Delta P) is zero by default. It is
defined in the following expression:
P = P v = P l = P feed – ∆P
where:
(8.6)
P = vessel pressure
Pv = pressure of vapour product stream
Pl = pressure of liquid product stream
Pfeed = pressure of feed stream to condenser
∆P = pressure drop in vessel (Delta P)
You typically specify a pressure for the condenser during the column
setup, in which case the pressure of the top stage is the calculated
value.
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Column
8-121
Duty
If you specify the duty, it is
equivalent to installing a duty
spec, and a degree of
freedom is used.
The Duty for the energy stream can be specified here, but this is better
done as a column spec (defined on the Monitor page or Specs page of
the Column property view). This allows for more flexibility when
adjusting specifications, and also introduces a tolerance.
The Duty should be positive, indicating that energy is being removed
from the Condenser feed.
The steady state condenser energy balance is defined as:
Hfeed - Duty = Hvapour + Hliquid
where:
(8.7)
Hfeed = heat flow of the feed stream to the condenser
Hvapour = heat flow of the vapour product stream
Hliquid = heat flow of the liquid product stream(s)
SubCooling
In steady state, SubCooling
applies only to the Total
Condenser. There is no
SubCooling in dynamics.
In some instances, you want to specify Condenser SubCooling. In this
situation, either the Degrees of SubCooling or the SubCooled
Temperature can be specified. If one of these fields is set, the other is
calculated automatically.
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8-122
Column-Specific Operations
Estimate Page
On the Estimate page you can estimate the flows and phase
compositions of the streams exiting the Condenser.
Figure 8.94
You can enter any value for fractional compositions, and click the
Normalize Composition button to have HYSYS normalize the values
such that the total equals 1. This button is useful when many
components are available, but you want to specify compositions for
only a few. HYSYS also specifies any <empty> compositions as zero.
HYSYS re-calculates the phase composition estimates when you click
the Update Comp. Est. button. Clicking this button also removes any of
the estimated values you entered for the phase composition estimates.
Click the Clear Comp. Est. button to clear the phase compositions
estimated by HYSYS. This button does not remove any estimate values
you entered. You can clear the all estimate values by clicking the Clear
All Comp. Est. button.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
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Column
8-123
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Rating Tab
You are not required to
modify information on the
Condenser’s Rating tab or
Dynamics tab when working
in Steady State mode.
The Rating tab contains three pages:
•
•
•
Sizing
Nozzles
Heat Loss
Sizing Page
Figure 8.95
The Sizing page contains all the required information for correctly sizing
the condenser. You can select either vertical or horizontal orientation,
and cylinder or sphere. You can either enter the volume or dimensions
for your condenser. You can also indicate whether or not the condenser
has a boot associated with it. If it does, then you can specify the boot
dimensions.
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8-124
Column-Specific Operations
Nozzles Page
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. The information provided in the Nozzles page is
applicable only in Dynamic mode. The Plant+ license is required to use
the Nozzle features found on this page.
Figure 8.96
8-124
Column
8-125
Heat Loss Page
The Heat Loss page allows you to specify the heat loss from individual
trays in the tray section. You can choose either a Direct Q, Simple or
Detailed heat loss model or no heat loss from the Heat Loss Mode group.
Figure 8.97
Direct Q Heat Loss Model
The Direct Q model allows you to either specify the heat loss directly, or
have the heat loss calculated from the Heat Flow for the condenser.
Figure 8.98
8-125
8-126
Column-Specific Operations
Simple Heat Loss Model
The Simple model allows you to calculate the heat loss from these
specified values:
•
•
Overall U value
Ambient Temperature
Figure 8.99
Detailed Heat Loss Model
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Detailed model allows you to specify more detailed heat transfer
parameters. The Plant+ license is required to use the Detailed Heat Loss
model.
Figure 8.100
Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
8-126
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Condenser.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Column
8-127
Performance Tab
In steady state, the displayed
plots are all straight lines.
Only in Dynamic mode, when
the concept of zones is
applicable, do the plots show
variance across the vessels.
The Performance tab has two pages:
•
•
Plots
Tables
From these pages you can view the calculated values, and plot any
combination of the calculated temperature, pressure, heat flow,
enthalpy or vapor fraction. At the bottom of either page, you can specify
the interval size over which the values should be calculated and plotted.
Dynamics Tab
You are not required to
modify information on the
Condenser’s Rating tab or
Dynamics tab when working
in Steady State mode.
The Dynamics tab contains four pages:
•
•
•
•
Specs
Holdup
StripChart
Duty
Specs Page
The Specs page contains information regarding initialization modes,
condenser geometry, and condenser dynamic specifications.
Figure 8.101
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8-128
Column-Specific Operations
Model Details
In the Model Details group, you can specify the initial composition and
amount of liquid that the separator should start with when you start
dynamics. This is done via the initialization mode which is discussed in
the table below.
The Initialization Mode can
be changed any time when
the integrator is not running.
The changes cause the
vessel to re-initialize when
the integrator is started
again.
Initialization Mode
Description
Initialize from Products
The composition of the holdup is calculated from a
weighted average of all products exiting the holdup. A PT
flash is performed to determine other holdup conditions.
The liquid level is set to the value indicated in the Liq
Volume Percent field.
Dry Startup
The composition of the holdup is calculated from a
weighted average of all feeds entering the holdup. A PT
flash is performed to determine other holdup conditions.
The liquid level in the Liq Volume Percent field is set to
zero.
Initialize from User
The composition of the liquid holdup in the condenser is
user specified. The molar composition of the liquid holdup
can be specified by clicking the Init Holdup button. The
liquid level is set to the value indicated in the Liq Volume
Percent field.
The condenser geometry can be specified in the Model Details group.
The following condenser geometry parameters can be specified in the
same manner as the Geometry group on Sizing page of the Rating tab:
•
•
•
•
Volume
Diameter
Height (Length)
Geometry (Level Calculator)
The Liquid Volume Percent value is also displayed in this group. You can
modify the level in the condenser at any time. HYSYS then uses that level
as an initial value when the integrator is run.
The Fraction Calculator determines how the level in the condenser and
the elevation and diameter of the nozzle affects the product
composition.
There is only one Fraction Calculation mode available, it is called Use
Levels and Nozzles. The calculations are based on how the nozzle
location and vessel liquid level affect the product composition. Refer to
the section on the Nozzles Page for more details.
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Column
8-129
Dynamic Specifications
The Dynamic Specifications group contains fields, where you can
specify what happens to the pressure and reflux ratio of the condenser
when you enter dynamic mode.
The Fixed Pressure Delta P field allows you to impose a fixed pressure
drop between the vessel and all of the feed streams. This is mostly
supported for compatibility with Steady State mode. In Dynamic mode,
you are advised to properly account for all pressure losses by using the
appropriate equipment such as valves or pumps or static head
contributions. A zero pressure drop should preferably be used here
otherwise you may get unrealistic results such as material flowing from a
low to a high pressure area.
The Fixed Vessel Pressure field allows you to fix the vessel pressure in
Dynamic mode. This option can be used in simpler models where you
do not want to configure pressure controllers etc., or if the vessel is open
to the atmosphere. In general the specification should not be used,
because the pressure should be determined by the surrounding
equipment.
The Reflux Flow/Total Liquid Flow field provides you with a simple
reflux ratio control option, and the ratio determines the reflux flow rate
divided by the sum of the reflux and distillate flow rates.
This option allows you to set up simple models without having to add
the valves, pumps, and controller that would normally be present. This
option does not always give desirable results under all conditions such
as very low levels or reversal of some of the streams.
The Add/Configure Level Controller button installs a level controller on
the distillate (liquid) outlet stream if one is not already present. If this
stream has a valve immediately downstream of the vessel, the controller
is configured to control the valve rather than the stream directly. In any
case, the controller is configured with some basic tuning parameters,
but you can adjust those. The default tuning values are as follows:
•
•
Kp = 1.8
Ti = 4 * Residence time / Kp
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Column-Specific Operations
Holdup Page
The Holdup page contains information regarding the properties,
composition, and amount of the holdup.
Figure 8.102
For each phase contained within the volume space of the unit
operation, the following is specified:
Holdup Details
Description
Accumulation
The rate of change of material in the holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
StripChart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
8-130
The StripChart page allows you to setup the strip chart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the strip chart.
Column
8-131
Duty Page
The Duty page opens a list of available heating methods for the unit
operation.This page contains different objects depending on which
radio button you select in the Heater Type and Duty Source group.
Figure 8.103
Heater Type Group
The Heater Type group has two radio buttons:
The Gas Heater method is
available only for
condensers, because the
heat transfer depends more
on the surface area of the
vapour contacting the
cooling coils than the liquid.
•
Gas Heater. When you select this radio button, the duty is
linearly reduced so that it is zero at liquid percent level of 100%,
unchanged at liquid percent level of 50%, and doubled at liquid
percent level of 0%. The following equation is used:
Q = ( 2 – 0.02L )Q Total
where:
(8.8)
Q = total heat applied to the holdup
L= liquid percent level
QTotal = duty calculated from the duty source
The Vessel Heater method
is a non-scaling method.
•
Vessel Heater. When you select this radio button, 100% of the
duty specified or calculated in the SP cell is applied to the
vessel’s holdup. That is:
Q = QTotal
where:
(8.9)
Q = total heat applied to the holdup
QTotal = duty calculated from the duty source
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8-132
Column-Specific Operations
Duty Source Group
The Duty Source group has two radio buttons:
•
•
Direct Q
From Utility
When you select the Direct Q radio button, the Direct Q Data group
appears. The following table describes the purpose of each object in the
group.
Object
Description
SP
The heat flow value in this cell is the same value specified in the
Duty field on the Parameters page of the Design tab. Any changes
made in this cell are reflected on the Duty field on the Parameters
page of the Design tab.
Min. Available
Allows you to specify the minimum amount of heat flow.
Max. Available
Allows you to specify the maximum amount of heat flow.
When you select the From Utility radio button, the Utility Flow
Properties group appears.
Figure 8.104
8-132
Column
The cells containing:
• black text indicates the
value is calculated by
HYSYS and cannot be
changed.
• blue text indicates the
value is entered by
you, and you can
change the value.
• red text indicates the
value is calculated by
HYSYS, and you can
change the value.
8-133
The following table describes the purpose of each object that appears
when the From Utility radio button is selected.
Object
Description
Heat Flow
Displays the heat flow value.
UA
Displays the overall heat transfer coefficient.
Holdup
Displays the amount of holdup fluid in the condenser.
Flow
Displays the amount of fluid flowing out of the condenser.
Min. Flow
Displays the minimum amount of fluid flowing out of the
condenser.
Max. Flow
Displays the maximum amount of fluid flowing out of the
condenser.
Heat Capacity
Displays the heat capacity of the fluid.
Inlet Temp.
Displays the temperature of the stream flowing into the
condenser.
Outlet Temp.
Displays the temperature of the stream flowing out of the
condenser.
Temp Approach
Displays the value of the operation outlet temperature minus
the outlet temperature of the Utility Fluid. It is only used when
one initializes the duty valve via the Initialize Duty Valve button.
Initialize Duty Valve
Allows you to initialize the UA, flow, and outlet temperature to
be consistent with the duty for purposes of control.
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8-134
Column-Specific Operations
8.6.2 Reboiler
If you choose a Reboiled Absorber or Distillation template, it includes a
Reboiler which is connected to the bottom tray in the tray section with
the streams to reboiler and boilup.
Reboiler icon
The Reboiler is a column operation, where the liquid from the bottom
tray of the column is the feed to the reboiler, and the boilup from the
reboiler is returned to the bottom tray of the column.
Figure 8.105
The Reboiler is used to partially or completely vapourize liquid feed
streams. You must be in a Column sub-flowsheet to install the Reboiler.
To install the Reboiler operation, press F12 and select Reboiler. From the
UnitOps view or click the Reboiler icon in the Column Palette.
The Reboiler property view has the same basic five tabs that are
available on any unit operation:
•
•
•
•
•
8-134
Design
Rating
Worksheet
Performance
Dynamics
Column
8-135
It is necessary to specify the connections, and the parameters for the
Reboiler. The information on the Rating tab and Dynamics tab are not
relevant in steady state.
Design Tab
The Design tab contains four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
On the Connections page, you must specify the Reboiler name, as well
as the feed(s), boilup, vapor draw, energy, and bottoms product streams.
The vapor draw stream is optional.
Figure 8.106
8-135
8-136
Column-Specific Operations
Parameters Page
On the Parameter page, you can specify the pressure drop and energy
used by the Reboiler. The pressure drop across the Reboiler is zero by
default.
Figure 8.107
It is better to use a duty spec
rather than specifying the
heat flow of the duty stream.
The Duty for the energy Stream should be positive, indicating that
energy is being added to the Reboiler feed(s). If you specify the duty, a
degree of freedom is used. However, it is preferable to define a duty
specification on the Monitor page or Specs page of the Column property
view, instead of specifying this value here.
The steady state reboiler energy balance is defined as:
Hfeed + Duty = Hvapour + Hbottom + Hboilup
(8.10)
where:
Hfeed = heat flow of the feed stream to the reboiler
Hvapour = heat flow of the vapour draw stream
Hbottoms = heat flow of the bottoms product stream
Hboilup = heat flow of the boilup stream
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
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Column
8-137
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Rating Tab
Rating tab and Dynamics tab
for a Reboiler is the same as
the Rating tab and Dynamics
tab for the Condenser.
You are not required to modify
information on the Reboiler’s
Rating tab or Dynamics tab
when working in Steady State
mode.
The Rating tab contains three pages:
•
•
•
Sizing
Nozzles
Heat Loss
Sizing Page
Figure 8.108
The Sizing page contains all the required information for correctly sizing
the reboiler. You can select either vertical or horizontal orientation, and
cylinder or sphere. You can either enter the volume or dimensions for
your reboiler. You can also indicate whether or not the reboiler has a
boot associated with it. If it does, you can specify the boot dimensions.
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8-138
Column-Specific Operations
Nozzles Page
The Plant+ license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. The information provided in the Nozzles page is
applicable only in Dynamic mode.
Figure 8.109
Heat Loss Page
The Heat Loss page allows you to specify the heat loss from individual
trays in the tray section. You can choose either a Direct Q, Simple or
Detailed heat loss model or no heat loss from the Heat Loss Mode group.
Direct Q Heat Loss Model
The Direct Q model allows you to either specify the heat loss directly, or
have the heat loss calculated from the Heat Flow for the reboiler.
Figure 8.110
8-138
Column
8-139
Simple Heat Loss Model
The Simple model allows you to calculate the heat loss from these
specified values:
•
•
Overall U value
Ambient Temperature
Figure 8.111
Detailed Heat Loss Model
The Detailed model allows you to specify more detailed heat transfer
parameters. The Plant+ license is required to use the Detailed Heat Loss
model. Refer to Section 1.6 - Fidelity in the Dynamic Modeling manual
for more information.
Figure 8.112
8-139
8-140
Column-Specific Operations
Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Reboiler.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Performance Tab
The Performance tab has two pages:
•
•
Plots
Tables
At the bottom of either page, you can specify the interval size over which
the values should be calculated and plotted.
Dynamics Tab
The Rating tab and Dynamics
tab for a Reboiler is the same
as the Rating tab and
Dynamics tab for the
Condenser.
You are not required to modify
information on the Reboiler’s
Rating tab or Dynamics tab
when working in Steady State
mode.
8-140
The Dynamics tab contains four pages:
•
•
•
•
Specs
Holdup
StripChart
Duty
Column
8-141
Specs Page
The Specs page contains information regarding initialization modes,
reboiler geometry, and reboiler dynamic specifications.
Figure 8.113
Model Details
The Initialization Mode can
be changed any time when
the integrator is not running.
The changes cause the
vessel to re-initialize when
the integrator is started
again.
In the Model Details group, you can specify the initial composition and
amount of liquid that the separator should start with when you start
dynamics. This done via the initialization mode which is discussed in
the table below.
Initialization Mode
Description
Initialize from
Products
The composition of the holdup is calculated from a weighted
average of all products exiting the holdup. A PT flash is
performed to determine other holdup conditions. The liquid
level is set to the value indicated in the Liq Volume Percent
field.
Dry Startup
The composition of the holdup is calculated from a weighted
average of all feeds entering the holdup. A PT flash is
performed to determine other holdup conditions. The liquid
level in the Liq Volume Percent field is set to zero.
Initialize from User
The composition of the liquid holdup in the reboiler is user
specified. The molar composition of the liquid holdup can be
specified by clicking the Init Holdup button. The liquid level is
set to the value indicated in the Liq Volume Percent field.
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8-142
Column-Specific Operations
The reboiler geometry can be specified in the Model Details group. The
following reboiler geometry parameters can be specified in the same
manner as the Geometry group on the Sizing page of the Rating tab:
•
•
•
•
Volume
Diameter
Height (Length)
Geometry (Level Calculator)
The Liquid Volume Percent value is also displayed in this group. You can
modify the level in the condenser at any time. HYSYS then uses that level
as an initial value when the integrator is run.
The Fraction Calculator determines how the level in the condenser, and
the elevation and diameter of the nozzle affects the product
composition.
There is only one Fraction Calculation mode available, it is called Use
Levels and Nozzles. The calculations are based on how the nozzle
location and vessel liquid level affect the product composition. Refer to
the section on the Nozzles Page for more information.
Dynamic Specifications
The Dynamic Specifications group contains fields where you can specify
what happens to the pressure of the reboiler when you enter dynamic
mode.
The Feed Delta P field allows you to impose a fixed pressure drop
between the vessel and all of the feed streams. This is mostly supported
for compatibility with Steady State mode. In Dynamic mode, you are
advised to properly account for all pressure losses by using the
appropriate equipment such as valves or pumps or static head
contributions. A zero pressure drop should preferably be used here
otherwise you may get unrealistic results such as material flowing from a
low to a high pressure area.
The Fixed Vessel Pressure field allows you to fix the vessel pressure in
Dynamic mode. This option can be used in simpler models where you
do not want to configure pressure controllers etc., or if the vessel is open
to the atmosphere. In general the specification should not be used,
because the pressure should be determined by the surrounding
equipment.
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Column
8-143
Holdup Page
The Holdup page contains information regarding the properties,
composition, and amount of the holdup.
Figure 8.114
For each phase contained within the volume space of the unit
operation, the following is specified:
Holdup Details
Description
Accumulation
The rate of change of material in the holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
StripChart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The StripChart page allows you to setup the strip chart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the strip chart.
8-143
8-144
Column-Specific Operations
Duty Page
The Duty page opens a list of available heating methods for the unit
operation. This page contains different objects depending on which
radio button you select in the Heater Type and Duty Source group.
Figure 8.115
Heater Type Group
The Heater Type group has two radio buttons:
•
•
When you select the Liquid
Heater radio button, the
Heater Height as % Vessel
Volume group appears. This
group contains two cells:
• Top of Heater
• Bottom of Heater
These cells are used to
specify the heater height.
Liquid Heater
Vessel Heater
For the Liquid Heater method, the duty applied to the vessel depends on
the liquid level in the tank. The heater height value must be specified.
The heater height is expressed as a percentage of the liquid level in the
vessel operation. The default values are 5% for the top of the heater, and
0% for the bottom of the heater. These values are used to scale the
amount of duty that is applied to the vessel contents.
where:
Q = 0
(L < B)
L–B
Q = ------------- Q Total
T–B
(B ≤ L ≤ T)
Q = Q Total
(L > T)
L = liquid percent level (%)
T = top of heater (%)
B = bottom of heater (%)
8-144
(8.11)
Column
8-145
The Percent Heat Applied may be calculated as follows:
Q
Percent Heat Applied = --------------- × 100%
Q Total
(8.12)
It is shown that the percent of heat applied to the vessel’s holdup directly
varies with the surface area of liquid contacting the heater.
Figure 8.116
Percent of Heat Applied
100
80
60
40
20
B
T
0
0
20
40
60
80
100
Liquid Percent Level, L
Percent Heat Applied for a Liquid Heater
When you select the Vessel Heater radio button, 100% of the duty
specified or calculated in the SP cell is applied to the vessel’s holdup:
Q = QTotal
where:
(8.13)
Q = total heat applied to the holdup
QTotal = duty calculated from the duty source
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8-146
Column-Specific Operations
Duty Source Group
The Duty Source group has two radio buttons:
•
•
Direct Q
From Utility
When you select the Direct Q radio button, the Direct Q Data group
appears. The following table describes the purpose of each object in the
group.
Object
Description
SP
The heat flow value in this cell is the same value specified in the
Duty field of the Parameters page on the Design tab. Any changes
made in this cell is reflected on the Duty field of the Parameters
page on the Design tab.
Min. Available
Allows you to specify the minimum amount of heat flow.
Max. Available
Allows you to specify the maximum amount of heat flow.
When you select the From Utility radio button, the Utility Flow
Properties group appears.
Figure 8.117
8-146
Column
The cells containing:
• black text indicates the
value is calculated by
HYSYS and cannot be
changed.
• blue text indicates the
value is entered by
you, and you can
change the value.
• red text indicates the
value is calculated by
HYSYS, and you can
change the value.
8-147
The following table describes the purpose of each object that appears
when the From Utility radio button is selected.
Object
Description
Heat Flow
Displays the heat flow value.
Available UA
Displays the overall heat transfer coefficient.
Utility Holdup
Displays the amount of holdup fluid in the reboiler.
Mole Flow
Displays the amount of fluid flowing out of the reboiler.
Min Mole Flow
Displays the minimum amount of fluid flowing out of the
reboiler.
Max Mole Flow
Displays the maximum amount of fluid flowing out of the
reboiler.
Heat Capacity
Displays the heat capacity of the fluid.
Inlet Temp.
Displays the temperature of the stream flowing into the
condenser.
Outlet Temp.
Displays the temperature of the stream flowing out of the
condenser.
Initialize Duty Valve
Allows you to initialize the UA, flow, and outlet temperature to
be consistent with the duty for purposes of control.
8.6.3 Tray Section
At the very minimum, every Column Templates includes a tray section.
An individual tray has a vapour feed from the tray below, a liquid feed
from the tray above, and any additional feed, draw or duty streams to or
from that particular tray.
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8-148
Column-Specific Operations
The property view for the tray section of a Distillation Column template
is shown in the figure below.
Figure 8.118
The tray section property view contains the five tabs that are common to
most unit operations:
•
•
•
•
•
Design
Rating
Worksheet
Performance
Dynamics
You are not required to change anything on the Rating tab and
Dynamics tab, if you are operating in Steady State mode.
Design Tab
The Design tab contains six pages:
•
•
•
•
•
•
8-148
Connections
Side Draws
Parameters
Pressures
User Variables
Notes
Column
8-149
Connections Page
The Connections page of the Tray Section is used for specifying the
names and locations of vapour and liquid inlet and outlet streams, feed
streams, and the number of stages (see Figure 8.118). When a Column
template is selected, HYSYS inserts the default stream names associated
with the template into the appropriate input cells. For example, in a
Distillation Column, the Tray Section vapour outlet stream is To
Condenser and the Liquid inlet stream is Reflux.
A number of conventions exist for the naming and locating of streams
associated with a Column Tray Section:
•
•
When you select a Tray Section feed stream, HYSYS by default
feeds the stream to the middle tray of the column (for example, in
a 20-tray column, the feed would enter on tray 10). The location
can be changed by selecting the desired feed tray from the dropdown list, or by typing the tray number in the appropriate field.
Streams entering and leaving the top and bottom trays are
always placed in the Liquid or Vapor Inlet/Outlet fields.
Specifying the location of a column feed stream to be either the top tray
(tray 1 or tray N, depending on your selected numbering convention) or
the bottom tray (N or 1) automatically results in the stream becoming the
Liquid Inlet or the Vapour Inlet, respectively. If the Liquid Inlet or Vapour
Inlet already exists, your specified feed stream is an additional stream
entering on the top or bottom tray, displayed with the tray number (1 or
N). A similar convention exists for the top and bottom tray outlet
streams (Vapour Outlet and Liquid Outlet).
Side Draws Page
On the Side Draws page, you can specify the name and type of side
draws taken from the tray section of your column. Use the radio buttons
to select the type of side draw:
•
•
•
Vapor
Liquid
Water
Select the cells to name the side draw stream, and specify the tray from
which it is taken.
8-149
8-150
Column-Specific Operations
Parameters Page
By default, the Use Tray
Section Name for Stage
Name checkbox is activated.
You can input the number of trays on the Parameters page. The trays are
treated as ideal if the fractional efficiencies are set to 1. If the efficiency
of a particular tray is less than 1, the tray is modeled using a modified
Murphree Efficiency.
Figure 8.119
You can add or delete trays anywhere in the column by clicking the
Customize button, and entering the appropriate information in the
Custom Modify Number of Trays group. This feature makes adding and
removing trays simple, especially if you have a complex column, and
you do not want to lose any feed or product stream information. The
figure below shows the view that appears when the Customize button is
clicked.
Figure 8.120
8-150
Column
8-151
You can add and remove trays in the following way:
When you are adding or
deleting trays, all Feeds
remain connected to their
current trays.
•
Specify a new number of trays in the Current Number of Trays
field. This is the same as changing the number of theoretical
trays on the Connections page. All inlet and outlet streams move
appropriately; for example, if you are changing the number of
trays from 10 to 20, a stream initially connected to tray 5 is now at
tray 10, and a stream initially connected at stream 10 is now at
tray 20.
Adding Trays
To add trays to the tray section:
1.
Enter the number of trays you want to add in the Number of Trays to
Add/Delete field.
2.
Specify the tray number after, which you want to add the trays in the
Tray to Add After or Delete First field.
3.
Click the Add Trays button, and HYSYS inserts the trays in the
appropriate place according to the tray numbering sequence you
are using. All streams (except feeds) and auxiliary equipment below
(or above, depending on the tray numbering scheme) the tray where
you inserted is moved down (or up) by the number of trays that were
inserted.
Removing Trays
To remove trays from the tray section:
1.
Enter the number of trays you want to delete in the Number of Trays
to Add/Delete field.
2.
Enter the first tray in the section you want to delete in the Tray to
Add After or Delete First field.
3.
Click the Remove Trays button. All trays in the selected section are
deleted. If you are using the top-down numbering scheme, the
appropriate number of trays below the first tray (and including the
first tray) you specify are removed. If you are using the bottom-up
scheme, the appropriate number of trays above the first tray (and
including the first tray) you specify are removed.
4.
Streams connected to a higher tray (numerically) are not affected;
for example, if you are deleting 3 trays starting at tray number 6, a
side draw initially at tray 5 remains there, but a side draw initially
connected to tray 10 is now at tray 7. Any draw streams connected to
trays 6,7 or 8 are deleted with your confirmation to do so.
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8-152
Column-Specific Operations
If you select the Side Stripper radio button or Side Rectifier radio button
at the bottom of the view, this affects the pressure profile. The pressure
of the main tray section stage from which the liquid feed stream is
drawn is used as the side stripper pressure, which is constant for all
stages. The pressure of the main tray section stage from which the
vapour feed stream is drawn is used as the Side Rectifier pressure, which
is constant for all stages.
Pressures Page
The Pressures page displays the pressure on each tray. Whenever two
pressures are known for the tray section, HYSYS interpolates to find the
intermediate pressures. For example, if you enter the Condenser and
Reboiler Pressures through the Column Input Expert or Column
property view, HYSYS calculates the top and bottom tray pressures
based on the Condenser and Reboiler pressure drops. The intermediate
tray pressures are then calculated by linear interpolation.
Figure 8.121
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
8-152
Column
8-153
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Rating Tab
The Rating tab consists of five pages:
•
•
•
•
•
Sizing
Nozzles
Heat Loss
Efficiencies
Pressure Drop
Sizing Page
The Sizing page contains the required information for correctly sizing
column tray and packed sections. If the Sieve, Valve, Bubble Cap radio
button with the Uniform Tray Data are selected, the following view is
shown.
Figure 8.122
8-153
8-154
Column-Specific Operations
The required size information
for the tray section can be
calculated using the Tray
Sizing utility. Each parameter is
also discussed in Section
14.16 - Tray Sizing of the
Operations Guide.
The tray section diameter, weir length, weir height, and the tray spacing
are required for an accurate and stable dynamic simulation. You must
specify all of the information on this page. The Quick Size button allows
you to automatically and quickly size the tray parameters. The Quick
Size calculations are based on the same calculations that are used in the
Tray Sizing Utility.
HYSYS only calculates the tray volume, based on the weir length, tray
spacing, and tray diameter. For multipass trays, simply enter the column
diameter and the appropriate total weir length.
When you select the Packed radio button and the Uniform Tray Data
section, the Sizing page changes to the view shown below.
Figure 8.123
The stage packing height, stage diameter, packing type, void fraction,
specified surface area, and Robbins factor are required for the simple
dynamic model. HYSYS uses the stage packing dimensions and packing
properties to calculate the pressure flow relationship across the packed
section.
8-154
Packing Properties
(Dynamics)
Description
Void Fraction
Packing porosity, i.e., m 3 void space/ m3 packed bed.
Specific Surface
Area
Packing surface area per unit volume of packing (m-1).
Column
Packing Properties
(Dynamics)
8-155
Description
Robbins Factor
A packing-specific quantity used in the Robbins correlation,
which is also called the dry bed packing factor (m-1). The
Robbins correlation is used to predict the column vapour
pressure drop. For the dry packed bed at atmospheric pressure,
2
the Robbins or packing factor is proportional to the vapour
pressure drop.
Static Holdup
Static liquid, hst, is the m 3 liquid/ m 3 packed bed remaining on
the packing after it has been fully wetted and left to drain. The
static liquid holdup is a constant value.
Include Loading
Regime Term
Loading regime term is the second term in the Robbins pressure
drop equation, which is limited to atmospheric pressure and
under vacuum but not at elevated pressures. When pressure is
high, (i.e., above 1 atm), inclusion of the loading regime term
may cause an unrealistically high pressure drop prediction.
To specify Chimney and Sump tray types, the Non Uniform Tray Data
Option must be selected from the Section Properties group. The Non
Uniform Tray Data Option allows you to model a column with high
fidelity by adjusting tray rating parameters on a tray by tray basis.
Figure 8.124
For a Trayed section of a column, you can adjust the Internal Type of
tray, Tray Spacing, Diameter, Weir Height, Weir Length, DC Volume,
Flow Path and Weeping factor. For a Packed section of a column, you can
adjust the Stage Packing Height, and Diameter.
8-155
8-156
Column-Specific Operations
From the Internal Type drop-down list in the Detailed Sizing
Information group, you can select alternative internal tray types on a
tray by tray basis. The Chimney and Sump internals along with the
weeping factor details are mentioned below.
Detailed Sizing Information
Description
Internal Type
Chimney - This allows a higher liquid level and
does not have any liquid going down to the tray
below. Although vapor can go up through it but it
does not contact the liquid. The Chimney tray type
can be designated on any tray. By default, the
weeping factor is set to 0 and the stage efficiency
is set to 5% on the Efficiencies page. The weir
height and tray spacing is increased for a tray
section. For a packed section stage packing height
is increased.
Sump - Only the bottom tray can be designated as
a sump. By default, the efficiency is set to 5%. The
tray spacing for a tray section and the stage
packing height in a packed section are increased
when using a Sump.
Weeping Factor
The weeping factor can be adjusted on a tray by
tray basis. It is used to scale back or turn off
weeping. By default the weeping factor is set to 1
for all internal types except the sump.
Nozzles Page
The Nozzles page contains the elevations at which vapour and liquid
enter or leave the tray section. The Plant+ license is required to use the
Nozzles features found on this page. Refer to Section 1.6 - Fidelity in the
Dynamic Modeling manual for more information.
Heat Loss Page
The Heat Loss page allows you to specify the heat loss from individual
trays in the tray section. You can select from either a Direct Q, Simple or
Detailed heat loss model or have no heat loss from the tray sections.
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Column
8-157
Direct Q Heat Flow Model
The Direct Q model allows you to input the heat loss directly where the
heat flow is distributed evenly over each tray section. Otherwise you
have the heat loss calculated from the Heat Flow for each specified tray
section.
Figure 8.125
Using the checkbox, you can temporarily disable heat loss calculations
without losing any Heat Loss data that is entered.
Simple Heat Flow Model
The Simple model allows you to calculate the heat loss by specifying:
•
•
The Overall U value
The Ambient Temperature°C
Figure 8.126
8-157
8-158
Column-Specific Operations
Detailed Heat Flow Model
The Plant+ license is required to use the Detailed Heat Loss model. Refer
to Section 1.6 - Fidelity in the Dynamic Modeling manual for more
information.
The Detailed model allows you to specify more detailed heat transfer
parameters. The detailed properties can be used on a tray to tray basis
based on the temperature profile, conduction, and convection data
specified.
Figure 8.127
8-158
Column
8-159
Efficiencies Page
As with steady state, you can specify tray efficiencies for columns in
dynamics. However, you can only specify the overall tray efficiency;
component tray efficiencies are only available in steady state.
Figure 8.128
Pressure Drop Page
The Pressure Drop page
uses the same calculation in
the Tray Sizing utility to
calculate the pressure drop
for the tray sections when
the column is running (i.e.,
using the traffics and
geometries to determine
what the pressure drop is).
The Pressure Drop page displays the information associated with the
pressure drops (or pressures) across the tray section.
Activating the Rating Enabled checkbox turns on the pressure drop
calculations as part of the column solution.
The tray sizing utility calculates a pressure drop across each tray, you
need to fix one end of the column (top or bottom), allowing the other
trays to float with the calculations. You can select which end of the
column to be fixed by selecting the appropriate radio button in the Fix
Tray group.
8-159
8-160
Column-Specific Operations
The Tray Section Pressure Drop field displays the absolute overall
pressure change between the fixed tray and the last tray at the other end.
Figure 8.129
Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Tray Section.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Performance Tab
The Performance tab has five pages:
•
•
•
•
•
8-160
Pressure
Temperature
Flow
Summary
Hydraulics
Column
8-161
Pressure Page
The Pressure page contains a table that lists all the pressure for each tray.
The table also includes the names of any inlet streams associated to a
tray and the inlet streams’ pressure.
Temperature Page
The Temperature page contains a table that lists all the temperature for
each tray. The table also includes the names of any inlet streams
associated to a tray and the inlet streams’ temperature.
Flow Page
The Flow page contains a table that lists all the liquid and vapour flow
rates for each tray. The table also includes the names of any inlet
streams associated to a tray and the inlet streams’ flow rate. You can also
change the unit of the flow rates displayed by selecting the unit from the
Flow Basis drop-down list. There are four possible units:
•
•
•
•
Molar
Mass
Standard Liquid Volume
Actual Volume
Summary Page
The Summary page contains a table that displays the flow rates,
temperature, and pressure for each tray.
Hydraulics Page
The Hydraulics page is only
available in dynamic mode.
The Hydraulics page contains a table that displays the height and
pressure of Dry Hole DP, Static Head, and Height over Weir.
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8-162
Column-Specific Operations
Dynamics Tab
The Dynamics tab contains four pages:
•
•
•
•
Specs
Holdup
Static Head
StripChart
Specs Page
The Specs page contains the Nozzle Pressure Flow k Factors for all the
trays in the tray section. You can select to have HYSYS calculate the k
value for all the trays by clicking the All Stages button. If you want HYSYS
to calculate the k values for certain trays only, select the desired trays
and click the Selected Stages button. HYSYS only calculates the k values
for the selected stages.
Figure 8.130
The Use tower diameter method checkbox, when activated, calculates
the k values for the column based on the column diameter. When the
checkbox is deactivated the k values are calculated using the results
obtained from the steady state model, providing a smoother transition
between your steady state model and dynamic model.
8-162
Column
Weeping can start to occur
on a tray when the dry hole
pressure loss drops below
0.015 kPa. It allows liquid to
drain to the stage below
even if the liquid height is
below the weir height.
8-163
The Model Weeping checkbox, when activated, takes into account any
weeping that occurs on the tray sections and add the effects to your
model.
The Perform dry start up checkbox allows you to simulate a dry start up.
Activating this checkbox removes all the liquid from all the trays when
the integrator starts.
The Initialize From User checkbox allows you to start the simulation
from conditions you specify. Activating this checkbox, activates the Init
HoldUp button. Click this button to enter the initial liquid mole
fractions of each component and the initial flash conditions.
The Fixed Pressure Profile checkbox allows you to simulate the column
based on the fixed pressure profile.
Pressure Profile
You do not have to configure
pressure control systems
with this option. This option
is not recommended for
rigorous modeling work
where the pressure can
typically change on
response to other events.
The Fixed Pressure Profile checkbox allows you to run the column in
Dynamic mode using the steady state pressure profile. This option
simplifies the column solution for inexperienced users, and makes their
transition from the steady state to dynamics simulation a bit easier.
The pressure profile of a tray section is determined by the static head,
which is caused mostly by the liquid on the trays, and the frictional
pressure losses, which are also known as dry hole pressure loses.
The frictional pressure losses are associated with vapour flowing
through the tray section. The flowrate is determined by Equation (8.14).
flow = k × density × friction pressure losses
(8.14)
In HYSYS, the k-value is calculated by assuming:
kα ( Tray diameter )
2
(8.15)
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8-164
Column-Specific Operations
However, if the Fixed Pressure Profile option is selected, then the static
head contribution can be subtracted and hence the vapour flow and the
frictional pressure loss is known. This allows the k-values to be directly
calculated to match steady state results more closely.
Holdup Page
The Holdup page contains a summary of the dynamic simulation results
for the column. The holdup pressure, total volume and bulk liquid
volume results on a tray basis are contained in this view. Doubleclicking on a stage name in the Holdup column opens the stage property
view.
You can double-click on any cell within each row to view the advanced
holdup properties for each specific tray section.
Static Head Page
Since static head
contributions are often
essential for proper column
modeling, internal static
head contributions are
generally considered for the
column model in any case,
and should only be disabled
under special
circumstances.
The Plant+ license is required to use the Static Head features. Refer to
Section 1.6 - Fidelity in the Dynamic Modeling manual for more
information.
Figure 8.131
StripChart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
8-164
The StripChart page allows you to setup the strip chart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the strip chart.
Column
8-165
8.6.4 Tee
Refer to Chapter 5 - Piping
Equipment for more details
on the property view of the
TEE.
The property view for the Tee operation in the Column sub-flowsheet
has all of the pages and inherent functionality contained by the Tee in
the Main Environment with one addition, the Estimates page.
Refer to the section on the
General Features of the
Solving Methods for
information on which method
supports Tee operation.
Figure 8.132
On the Estimates page, you can help the convergence of the Column
sub-flowsheet’s simultaneous solution by specifying flow estimates for
the tee product streams. To specify flow estimates:
1.
Select one of the Flow Basis radio buttons: Molar, Mass or Volume.
2.
Enter estimates for any of the product streams in the associated
fields next to the stream name.
There are four buttons on the Estimates page, which are described in the
table below.
Button
Related Setting
Update
Replaces all estimates except user specified estimates (in
blue) with values obtained from the solution.
Clear Selected
Deletes the highlighted estimate.
Clear Calculated
Deletes all calculated estimates.
Clear All
Deletes all estimates.
If the Tee operation is attached to the column, i.e., via a draw stream,
one tee split fraction specification is added to the list of column
specifications for each tee product stream that you specify. As you
specify the split fractions for the product streams, these values are
transferred to the individual column specifications on the Monitor page
and Specs page of the column property view.
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8-166
Running the Column
The additional pieces of equipment available in the Column subflowsheet are identical to those in the main flowsheet. For information
on each piece of equipment, refer to its respective chapter (e.g., for
information on the Heat Exchanger, refer to Section 4.3 - Heat
Exchanger). All operations within the Column sub-flowsheet
environment are solved simultaneously.
8.7 Running the Column
Once you are satisfied with the configuration of your Column subflowsheet and you have specified all the necessary input, the next step is
to run the Column solution algorithm.
The Run/Reset buttons can
be accessed from any page
of the Column property view.
Run icon
Stop icon
On the toolbar, the Run icon
and Stop icon are two
separate icons. Whichever
icon is toggled on has light
grey shading.
The iterative procedure begins when you click the Run button on the
Column property view. The Run/Reset buttons can be accessed from
any page of the Column property view. When you are inside the Column
build environment, a Run icon also appears on the toolbar, which has
the same function as the Run button on the Column property view.
When the Run button on the Column property view is clicked, the Run/
Reset buttons are replaced by a Stop button which, when clicked,
terminates the convergence procedure. The Run button can then be
clicked again to continue from the same location. Similarly, the Stop
icon switches to a grey shading with the Run icon on the toolbar after it
is activated.
When you are working inside the Column build environment, the
Column runs only when you click the Run button on the Column
property view, or the Run icon on the toolbar. When you are working
with the Column property view in the Main build environment, the
Column automatically runs when you change:
•
•
8-166
A specification value after a converged solution has been
reached.
The Active specifications, such that the Degrees of Freedom
return to zero.
Column
8-167
8.7.1 Run
The Run command begins the iterative calculations necessary to
simulate the column described by the input. On the Monitor page of the
Column property view, a summary showing the iteration number,
equilibrium error, and the heat and specification errors appear. Detailed
messages showing the convergence status are shown in the Trace
Window (Refer to Section 8.4.1 - Design Tab).
The default basis for the calculation is a modified “inside-out”
algorithm. In this type of solution, simple equilibrium and enthalpy
models are used in the inner loop, which solve the overall component
and heat balances, vapour-liquid equilibrium, and any specifications.
The outer loop updates the simple thermodynamic models with
rigorous calculations.
When the simulation is running, the status line at the bottom of the
screen first tracks the calculation of the initial properties used to
generate the simple models. Then the determination of a Jacobian
matrix appears, which is used in the solution of the inner loop. Next, the
status line reports the inner loop errors and the relative size of the step
taken on each of the inner loop iterations. Finally, the rigorous
thermodynamics is again calculated and the resulting equilibrium, heat,
and spec errors reported. The calculation of the inner loop and the outer
loop properties continues until convergence is achieved, or you
determine that the column cannot converge and click Stop to terminate
the calculation.
If difficulty is encountered in converging the inner loop, the program
occasionally recalculates the inner loop Jacobian. If no obvious
improvement is being made with the printed equilibrium and heat and
spec errors, press Stop to terminate the calculations and examine the
available information for clues (Refer to Section 8.8 - Column
Troubleshooting) if trouble is encountered achieving the desired
solution).
Any estimates which appear in the Column Profile page and Estimates
page are used as initial guesses for the convergence algorithm. If no
estimates are present, HYSYS begins the convergence procedure by
generating initial estimates (Refer to Section 8.4.2 - Parameters Tab for
more information on the Estimates page).
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8-168
Running the Column
8.7.2 Reset
The Reset command clears the current Column solution, and any
estimates appearing on the Estimates page of the Column view. If you
make major changes after getting a converged Column, it is a good idea
to Reset to clear the previous solution. This allows the Column solver to
start fresh and distance itself from the previous solution. If you make
only minor changes to the Column, try clicking Run before Resetting.
Once the column calculation has started it continues until it has either
converged, has been terminated due to a mathematically impossible
condition, (e.g., being unable to invert the Jacobian matrix), or it has
reached the maximum number of iterations. Other than these three
situations, calculations continue indefinitely in an attempt to solve the
column unless the Stop button is clicked. Unconverged results can be
analysed, as discussed in Section 8.8 - Column Troubleshooting.
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Column
8-169
8.8 Column Troubleshooting
Although HYSYS does not require any initial estimates for convergence,
good estimates of top and bottom temperatures and one product
accelerate the convergence process. Detailed profiles of vapour and
liquid flow rates are not required.
However, should the column have difficulty, the diagnostic output
printed during the iterations provides helpful clues on how the tower is
performing. If the equilibrium errors are approaching zero, but the heat
and spec errors are staying relatively constant, the specifications are
likely at fault. If both the equilibrium errors and the heat and spec errors
do not appear to be getting anywhere, then examine all your input (e.g.,
initial estimates, specifications, and tower configuration).
In running a column, keep in mind that the Basic Column Parameters
cannot change. By this, it is meant that column pressure, number of
trays, feed tray locations, and extra attachments such as side exchanger
and pump around locations remain fixed. To achieve the desired
specifications the Column only adjusts variables which have been
specified as initial estimates, such as reflux, side exchanger duties, or
product flow rates. This includes values that were originally
specifications but were replaced, thereby becoming initial estimates. It
is your responsibility to ensure that you have entered a reasonable set of
operating conditions (initial estimates) and specifications (Basic
Column Parameters) that permit solution of the column. There are
obviously many combinations of column configurations and
specifications that makes convergence difficult or impossible. Although
all these different conditions could not possibly be covered here, some
of the more frequent problems are discussed in the following sections.
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8-170
Column Troubleshooting
8.8.1 Heat and Spec Errors Fail to Converge
This is by far the most frequent situation encountered when a column is
unable to satisfy the allowable tolerance. The following section gives the
most common ailments and remedies.
Poor Initial Estimates
To see the initial estimates,
click the View Initial Estimates
button on the Monitor page of
the column property view.
Initial estimates are important only to the extent that they provide the
initial starting point for the tower algorithm. Generally, poor guesses
simply cause your tower to converge more slowly. However, occasionally
the effect is more serious. Consider the following:
•
•
•
8-170
Check product estimates using approximate splits. A good
estimate for the tower overhead flow rate is to add up all the
components in your feed which are expected in the overheads,
plus a small amount of your heavy key component. If the tower
starts with extremely high errors, check to see that the overhead
estimate is smaller than the combined feed rates.
Poor reflux estimates usually do not cause a problem except in
very narrow boiling point separations. Better estimates are
required if you have high column liquid rates relative to vapour
rates, or vice versa.
Towers containing significant amounts of inert gases, e.g., H2,
N2, etc., require better estimates of overhead rates to avoid initial
bubble point problems. A nitrogen rejection column is a good
example.
Column
8-171
Input Errors
Clicking the Input Summary
button on the Monitor page of
the column property view
displays the column input in
the Trace Window.
It is good practice to check all of your input just before running your
column to ensure that all your entries, such as the stage temperatures
and product flow rates, appear reasonable:
•
•
•
•
Check to ensure that your input contains the correct values and
units. Typical mistakes are entering a product flow rate in moles/
hr when you really meant to enter it in barrels/day, or a heat duty
in BTU/hr instead of E+06 BTU/hr.
When specifying a distillate liquid rate, make sure you have
specified the Distillate rate for the condenser, not the Reflux rate.
If you change the number of trays in the column, make sure you
have updated the feed tray locations, pressure specifications,
and locations of other units such as side exchangers on the
column.
If the tower fails immediately, check to see if all of your feeds are
known, if a feed was entered on a non-existent tray, or if a
composition specification was mistakenly entered for a zero
component.
Incorrect Configuration
For more complex tower configurations, such as crude columns, it is
more important that you always review your input carefully before
running the tower. It is easy to overlook a stripping feed stream, side
water draw, pump around or side exchanger. Any one of these omissions
can have a drastic effect on the column performance. As a result, the
problem is not immediately obvious until you have reviewed your input
carefully or tried to change some of the specifications.
•
•
Check for trays which have no counter-current vapour-liquid
traffic. Examples of this are having a feed stream on a tray that is
either below the top tray of an un-refluxed tower or a tower
without a top lean oil feed, or placing a feed stream above the
bottom stage of a tower that does not have a bottom reboiler or a
stripping feed stream below it. In both cases the trays above or
below the feed tray become single phase. Since they do not
represent any equilibrium mass transfer, they should be removed
or the feed should be moved. The tower cannot converge with
this configuration.
The tower fails immediately if any of the sidestrippers do not have
a stripping feed stream or a reboiler. If this should occur, a
message is generated stating that a reboiler or feed stream is
missing in one of the sidestrippers.
8-171
8-172
Column Troubleshooting
•
•
Make sure you have installed a side water draw if you have a
steam-stripped hydrocarbon column with free water expected on
the top stage.
Regardless of how you have approached solving crude columns
in the past, try to set up the entire crude column with your first
run, including all the side strippers, side exchangers, product side
draws, and pump arounds attached. Difficulties arise when you
try to set up a more simplified tower that does not have all the
auxiliary units attached to the main column, then assign product
specs expected from the final configuration.
Impossible Specifications
Impossible specifications are normally indicated by an unchanging heat
and spec error during the column iterations even though the
equilibrium error is approaching zero. To get around this problem you
have to either alter the column configuration or operating pressure or
relax/change one of the product specifications.
•
•
•
•
•
8-172
You cannot specify a temperature for the condenser if you are
also using subcooling.
If you have zero liquid flows in the top of the tower, either your top
stage temperature spec is too high, your condenser duty is too
low, or your reflux estimate is too low.
If your tower shows excessively large liquid flows, either your
purity specs are too tight for the given number of trays or your
Cooler duties are too high.
Dry trays almost always indicate a heat balance problem. Check
your temperature and duty specifications. There are a number of
possible solutions: fix tray traffic and let duty vary; increase steam
rates; decrease product makes; check feed temperature and
quality; check feed location.
A zero product rate could be the result of an incorrect product
spec, too much heat in the column which eliminates internal
reflux, or the absence of a heat source under a total draw tray to
produce needed vapour.
Column
8-173
Conflicting Specifications
This problem is typically the most difficult to detect and correct. Since it
is relatively common, it deserves considerable attention.
•
•
•
•
•
•
•
•
•
You cannot fix all the product flow rates on a tower.
Avoid fixing the overhead temperature, liquid and vapour flow
rates because this combination offers only a very narrow
convergence envelope.
You cannot have subcooling with a partial condenser.
A cut point specification is similar to a flow rate spec; you cannot
specify all flows and leave one unspecified and then specify the
cut point on that missing flow.
Only two of the three optional specifications on a pump around
can be fixed, i.e., duty and return temperature, duty and pump
around rate, etc.
Fixing column internal liquid and vapour flows, as well as duties
can present conflicts since they directly affect each other.
The bottom temperature spec for a non-reboiled tower must be
less than that of the bottom stage feed.
The top temperature for a reboiled absorber must be greater than
that of the top stage feed unless the feed goes through a valve.
The overhead vapour rate for a reboiled absorber must be
greater than the vapour portion of the top feed.
Heat and Spec Error Oscillates
While less common, this situation can also occur. It is often caused by
poor initial estimates. Check for:
•
•
•
Water condensation or a situation where water alternately
condenses and vapourizes.
A combination of specifications that do not allow for a given
component to exit the column, causing the component to cycle in
the column.
Extremely narrow boiling point separations can be difficult since a
small step change can result in total vapourization. First, change
the specifications so that the products are not pure components.
After convergence, reset the specifications and restart.
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8-174
Column Troubleshooting
8.8.2 Equilibrium Error Fails to Converge
This is almost always a material balance problem. Check the overall
balance.
•
•
Check the tower profile. If the overhead condenser is very cold
for a hydrocarbon-steam column, you need a water draw.
Normally, a side water draw should be added for any stage below
200oF.
If the column almost converges, you may have too many water
draws.
8.8.3 Equilibrium Error Oscillates
This generally occurs with non-ideal towers, such as those with
azeotropes. Decreasing the damping factor or using adaptive damping
should correct this problem (Refer to Section 8.4.2 - Parameters Tab).
8-174
Column
8-175
8.9 References
1
Sneesby, Martin G., Simulation and Control of Reactive Distillation, Curtin
University of Technology, School of Engineering, March 1998.
2
Henry, Kister., Distillation Design, (1992), pp 497-499.
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8-176
8-176
References
Reactors
9-1
9 Reactors
9.1 CSTR/General Reactors ..................................................................2
9.1.1 Adding a CSTR/General Reactors ..........................................3
9.2 CSTR/General Reactors Property View .........................................5
9.2.1
9.2.2
9.2.3
9.2.4
9.2.5
9.2.6
9.2.7
9.2.8
Design Tab ..............................................................................5
Conversion Reactor Reactions Tab .........................................9
CSTR Reactions Tab .............................................................14
Equilibrium Reactor Reactions Tab .......................................19
Gibbs Reactor Reactions Tab................................................24
Rating Tab .............................................................................28
Worksheet Tab.......................................................................32
Dynamics Tab ........................................................................33
9.3 Plug Flow Reactor (PFR)...............................................................40
9.3.1 Adding a Plug Flow Reactor (PFR) .......................................41
9.4 Plug Flow Reactor (PFR) Property View......................................42
9.4.1
9.4.2
9.4.3
9.4.4
9.4.5
9.4.6
PFR Design Tab ....................................................................43
Reactions Tab........................................................................50
Rating tab ..............................................................................58
Work Sheet Tab .....................................................................60
Performance Tab ...................................................................60
Dynamics Tab ........................................................................63
9-1
9-2
CSTR/General Reactors
9.1 CSTR/General Reactors
With the exception of the Plug Flow Reactor (PFR), all of the reactor
operations share the same basic property view. The primary differences
are the functions of the reaction type (conversion, kinetic, equilibrium,
heterogeneous catalytic or simple rate) associated with each reactor. As
opposed to a separator or general reactor with an attached reaction set,
specific reactor operations can only support one particular reaction
type. For instance, a conversion reactor only functions properly with
conversion reactions attached. If you try to attach an equilibrium or a
kinetic reaction to a conversion reactor, an error message appears. The
GIBBS reactor is unique in that it can function with or without a reaction
set.
You have a great deal of flexibility in defining and grouping reactions.
You can:
•
•
•
Refer to Chapter 5 Reactions of the Simulation
Basis manual or Section 5.3
- Reaction Package of the
User Guide for details on
installing reactions and
Reaction Sets.
9-2
Define the reactions inside the Basis Manager, group them into a
set and then attach the set to your reactor.
Create reactions in the Reaction Package in the main flowsheet,
group them into a set, and attach the set to the reactor.
Create reactions and reaction sets in the Basis Environment and
make changes in the Main Environment's Reaction Package.
Regardless of the approach, the reactions you define are visible to the
entire flowsheet, i.e., a reaction set can be attached to more than one
reactor.
However, there are some subtleties of which you must be aware. When
you make a modification to a reaction via a reactor, the change is only
seen locally, in that particular reactor. Modifications made to a reaction
in the Basis Environment or in the Reaction Package are automatically
reflected in every reactor using the reaction set, provided you have not
made changes locally. Local changes are always retained. To override
local changes and return the global parameters to a reaction, you must
press the DELETE key when the cursor is in the cell which contains the
local change.
Reactors
9-3
The four reactors which share common property views include:
•
•
•
•
To remove local changes,
move to the appropriate cell
and press the DELETE key.
CSTR (Continuous-Stirred Tank Reactor)
GIBBS Reactor
Equilibrium Reactor
Conversion Reactor
The last three reactors are referred to as General Reactors. In order to
avoid redundancy, these operations are discussed co-currently. In areas
of the property view where there are differences, such as the Reactions
tab, the differences are clearly noted.
The PFR has a different property view from the other reactors. As a result
it is discussed in Section 9.3 - Plug Flow Reactor (PFR).
9.1.1 Adding a CSTR/General Reactors
You can also add a reactor
by clicking the F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a reactor operation to your
simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Reactors radio button.
3.
From the list of available unit operations, select the Cont. Stirred
Tank Reactor or Conversion Reactor or Equilibrium Reactor or
Gibbs Reactor.
4.
Click the Add button. The CSTR or Conversion Reactor or
Equilibrium Reactor or Gibbs Reactor property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
9-3
9-4
CSTR/General Reactors
6.
Double-click the CSTR icon. The CSTR property view appears.
Figure 9.1
CSTR (Continuous-Stirred
Tank Reactor) icon
For Conversion, Equilibrium, and Gibbs reactors, click the General
Reactors icon to open the General Reactors object palette.
Double-click on the appropriate reactor operation icon from the
General Reactors object palette.
Figure 9.2
Gibbs Reactor
icon
Equilibrium
Reactors icon
General Reactors
icon
General Reactors
object palette
Conversion
Reactors icon
The property view for the selected general reactor operation appears.
9-4
Reactors
9-5
9.2 CSTR/General Reactors Property
View
The CSTR and General Reactors property view consists of five tabs:
•
•
•
•
•
Design
Reactions
Rating
Worksheet
Dynamics
9.2.1 Design Tab
The Design tab contains four pages, which are briefly described in the
table below.
For more information on the
Notes page, refer to Section
7.20 - Notes Manager in the
User Guide.
Page
Description
Connections
Connects the feed, product, and energy streams to the reactor. For
more information, refer to the section below.
Parameters
Sets heat transfer and pressure drop parameters for the reactor. For
more information, refer to the section on the Parameters Page.
User Variables
Allows you to create and implement User Variables.
Notes
Allows you to add relevant comments which are exclusively
associated with the unit operation.
9-5
9-6
CSTR/General Reactors Property View
Connections Page
The Connections page, is the same for both the CSTR and the three
General Reactors.
Figure 9.3
To ignore the reactor
operation entirely during
calculations, click the
Ignored checkbox. HYSYS
disregards the operation
entirely until you restore it to
an active state.
The Connections page consists of five objects, which are described in
the table below.
At least one product stream
is required.
9-6
Object
Input Required
Name
Contains the name of the reactor. You can edit the name of the
reactor at any time by typing in a new name in the Name field.
Inlets
Connects a single feed or multiple feed streams to the reactor.
You can either type in the name of the stream or if you have predefined your stream select it from the drop-down list.
Vapour Outlet
Connects the vapour product stream to the reactor. You can
either type in the name of the stream or if you have pre-defined
your stream select it from the drop-down list.
Liquid Outlet
Connects the liquid product stream to the reactor. You can either
type in the name of the stream or if you have pre-defined your
stream select it from the drop-down list.
Energy (Optional)
Connects or creates an energy stream if one is required for the
operation.
Reactors
9-7
Parameters Page
The Parameters page allows you to specify the pressure drop, vessel
volume, duty, and solving behaviour.
Figure 9.4
Object
Description
Delta P
Contains the pressure drop across the vessel. The pressure
drop is defined as:
∆P = P feed – P v = P feed – P l
(9.1)
P = Pv = Pl
Pfeed is assumed to be the
lowest pressure of all the
feed streams.
where:P = vessel pressure
Pv = pressure of vapour product stream
Pl = pressure of liquid product stream
The vessel pressure is used
in the reaction calculations.
Pfeed = pressure of feed stream
∆P = pressure drop in vessel (Delta P)
The default pressure drop across the vessel is zero.
9-7
9-8
CSTR/General Reactors Property View
The enthalpy basis used by
HYSYS is equal to the ideal
gas enthalpy of formation at
25°C and 1 atm. As a result,
the heat of reaction
calculation is amalgamated
into any product/reactant
enthalpy difference.
Object
Description
Duty
If you have attached an energy stream, you can specify
whether it is to be used for heating or for cooling by selecting
the appropriate radio button. You also have a choice of
specifying the applied duty, or having HYSYS calculate the
duty. For the latter case, you must specify an outlet
temperature for a reactor product stream.
The steady state Reactor energy balance is defined below:
Duty = H vapour + H liquid – H feed
(9.2)
where:Duty = heating (+ve) or cooling (-ve) by the optional
energy stream
Hvapour = heat flow of the vapour product stream
Hliquid = heat flow of the liquid product stream
Hfeed = heat flow of the feed stream(s)
The vessel volume is
necessary when modeling
reactors in steady state, as it
determines the residence
time.
Heating /Cooling
If you change from Heating to Cooling (or vice versa), the
magnitude of the energy stream does not change. However,
the sign changes in the energy balance. For Heating, the duty
is added. For Cooling, the duty is subtracted.
Volume
The total volume of the vessel and is user specified. While not
necessarily required for solving Conversion, GIBBS or
Equilibrium reactors in Steady State mode, this value must be
entered for CSTR.
The vessel volume, together with the liquid level set point,
define the amount of holdup in the vessel. The amount of liquid
volume or holdup in the vessel at any time is given by the
following expression:
PV ( %Full )
Holdup = Vessel Volume × ----------------------------100
(9.3)
where:PV(%Full) = liquid level in the vessel
Liquid Level
Displays the liquid level of the reactor expressed as a
percentage of the Full Vessel Volume.
Liquid Volume
Not set by the user, this value is calculated from the product of
the volume (vessel volume) and liquid level fraction. It is only
active when the Volume field contains a valid entry.
Act as a Separator
When Cannot Solve
Only available for Conversion and Equilibrium reactors, this
option allows you to operate the reactor as a simple 2 phase
separator whenever the reactor does not solve.
Single Phase
Allows you to specify a single phase reaction. Otherwise
HYSYS considers it a vapour-liquid reaction.
Type
Only available for the Gibbs reactor, you have two options for
the type of reactor you want:
• Separator. A two phase Gibbs Reactor.
• Three Phase. A three phase Gibbs Reactor.
9-8
Reactors
9-9
9.2.2 Conversion Reactor Reactions Tab
Conversion Reactor icon
Refer to Section 5.3.2 Conversion Reaction in the
Simulation Basis manual
for details on creating
Conversion Reaction Sets
and Conversion Reactions.
The Conversion Reactor is a vessel in which conversion reactions are
performed. You can only attach reaction sets that contain conversion
reactions. Each reaction in the set proceeds until the specified
conversion is attained or until a limiting reactant is depleted.
The Reactions tab, consists of two pages:
•
•
Details
Results.
Details Page
You can attach the reaction set to the operation and specify the
conversion for each reaction in the set on the Details page. The reaction
set can contain only conversion reactions.
Figure 9.5
9-9
9-10
CSTR/General Reactors Property View
The Details page consists of four objects as described in the table below.
Object
Description
Reaction Set
Allows you to select the appropriate conversion reaction set.
Reaction
You must select the appropriate conversion reaction from the
selected Reaction Set.
View Reaction button
Opens the Reaction property view for the reaction currently
selected in the Reaction drop-down list. The Reaction
property view allows you to edit the reaction.
[Radio buttons]
The three radio buttons on the Details page are:
• Stoichiometry
• Basis
• Conversion
The three radio buttons allow you to toggle between the
Stoichiometry group, the Basis group or the Conversion
group (each group is described in the following sections).
Stoichiometry Radio Button
The Balance Error (for the
reaction stoichiometry) and
the Reaction Heat (Heat of
Reaction at 25°C) are also
shown for the current
reaction.
When you select the Stoichiometry radio button, the Stoichiometry Info
group appears. The Stoichiometry Info group allows you to examine the
components involved in the selected reaction, their molecular weights
as well as their stoichiometric coefficients.
Figure 9.6
9-10
Reactors
9-11
Basis Radio Button
When you select the Basis radio button, the Basis group appears. In the
Basis group, you can view the base component, the conversion, and the
reaction phase for each reaction in the reaction set.
Figure 9.7
Conversion Radio Button
In the Fractional Conversion
Equation group, parameters
shown in red or blue colour
indicate that the variable
can be cloned.
When you select the Conversion radio button, the Fractional Conversion
Equation group appears. The Fractional Conversion Equation group
allows you to implement a conversion model based on the
Conversion(%) equation listed.
Figure 9.8
The parameters for the attached conversion reaction(s) can be cloned as
local variables belonging to the Conversion Reactor. Therefore, you can
either use the parameters specified in the reaction(s) from the attached
reaction set by clicking the Use Default checkbox or specifying locally
the values within the Fractional Conversion Equation group.
9-11
9-12
CSTR/General Reactors Property View
View Reaction Button
When you click the View Reaction button, the Conversion Reaction
property view of the reaction currently selected in the Reaction dropdown list appears.
Figure 9.9
Any changes made to the Conversion Reaction property view are made
globally to the selected Reaction and any Reaction Sets which contain
the Reaction. For example, if any change is made to the reaction shown
in the figure above, the change is carried over to every other instance in
which this Reaction is used. It is therefore recommended that changes
which are Reactor specific (i.e., changes which are only meant to affect
one Reactor) are made within the Reactions tab.
Results Page
You can change the specified
conversion for a reaction
directly on this page.
The Results page displays the results of a converged reactor. The page
consists of the Reactor Results Summary group which contains two
radio buttons:
•
•
Reaction Extents
Reaction Balance.
The type of results displayed on the Results page depend on the radio
button selected.
9-12
Reactors
9-13
Reaction Extents Radio Button
When the Reaction Extents radio button is selected, the Results page
appears as shown in the figure below.
Figure 9.10
When there are multiple
reactions in a Reaction Set,
HYSYS automatically ranks
the reactions. A reaction
with a lower ranking value
occurs first. Each group of
reactions of equal rank can
have an overall specified
conversion between 0% and
100%.
Any changes made to the
global reaction affect all
Reaction Sets to which the
reaction is attached,
provided local changes have
not been made.
The Reactor Results Summary group displays the following results for a
converged reactor:
Result Field
Description
Rank
Displays the current rank of the reaction. For multiple
reactions, lower ranked reactions occur first.
Actual % Conversion
Displays the percentage of the base component in the feed
stream(s) which has been consumed in the reaction.
Base Component
The reactant to which the calculation conversion is based
on.
Rxn Extent
Lists the molar rate consumption of the base component.
Notice that the actual conversion values do not match the specified
conversion values. Rxn-3 proceeds first and is halted when a limiting
reactant is exhausted. The sum of the specified conversions for Rxn-1
and Rxn-2 is 100%, so all of the remaining base component can be
consumed, provided a limiting reactant is not fully consumed
beforehand. All of the base component is consumed, and this is
reflected in the actual conversion totalling 100%.
9-13
9-14
CSTR/General Reactors Property View
Reaction Balance Radio Button
When the Reaction Balance radio button is selected, the Reaction
Balance option provides an overall component summary for the
Conversion Reactor. All components which appear in the fluid package
are shown here.
Figure 9.11
Values appear after the solution of the reactor has converged. The Total
Inflow rate, the Total Reacted rate and the Total Outflow rate for each
component are provided on a molar basis. Negative values indicate the
consumption of a reactant, while positive values indicate the
appearance of a product.
9.2.3 CSTR Reactions Tab
For more information on
Kinetic, Heterogeneous
Catalytic and Simple Rate
reactions, refer to Chapter 5
- Reactions in the
Simulation Basis manual.
CSTR icon
9-14
The CSTR is a vessel in which Kinetic, Heterogeneous Catalytic, and
Simple Rate reactions can be performed. The conversion in the reactor
depends on the rate expression of the reactions associated with the
reaction type. The inlet stream is assumed to be perfectly (and
instantaneously) mixed with the material already in the reactor, so that
the outlet stream composition is identical to that of the reactor contents.
Given the reactor volume, a consistent rate expression for each reaction
and the reaction stoichiometry, the CSTR computes the conversion of
each component entering the reactor.
Reactors
9-15
On the Reactions tab, you can select a reaction set for the operation. You
can also view the results of the solved reactor including the actual
conversion of the base component. The actual conversion is calculated
as the percentage of the base component that was consumed in the
reaction.
NA – NA
in
out
- × 100%
X = --------------------------NA
(9.4)
in
where:
X = actual % conversion
NAin = base component flowrate into the reactor
NAout = base component flowrate (same basis as the inlet rate) out of
the reactor
The Reactions tab consists of two pages:
•
•
Details
Results
Details Page
The Details page allows you to attach the appropriate reaction set to the
operation.
Figure 9.12
9-15
9-16
CSTR/General Reactors Property View
As mentioned earlier in this section, the selected reaction set can
contain only Kinetic, Heterogeneous Catalytic, and Simple Rate
reactions.
The page consists of four objects, which are described in the table below.
Object
Description
Reaction Set
Allows you to select the reaction set you want to use in the reactor.
Reaction
Allows you to select the reaction you want to use in the reactor.
View Reaction
Opens the Reaction property view for the selected Reaction. This
allows you to edit the reaction globally.
Specifics
Toggles between the Stoichiometry group or the Basis group (the
groups are described in the following sections).
Stoichiometry Radio Button
The Balance Error (for the
reaction stoichiometry) and
the Reaction Heat (Heat of
Reaction at 25°C) are also
shown for the current
reaction.
When you select the Stoichiometry radio button, the Stoichiometry
group appears. The Stoichiometry group allows you to examine the
components involved in the currently selected reaction, their molecular
weights as well as their stoichiometric coefficients.
Figure 9.13
9-16
Reactors
9-17
Basis Radio Button
When you select the Basis radio button, the Basis group appears. In the
Basis group, you can view the base component, the reaction rate
parameters (e.g., A, E, ß, A’, E’, and ß’) and the reaction phase for each
reaction in the attached set.
Figure 9.14
You can view the properties for a specific reaction by selecting the
reaction from the Reaction drop-down list, and its data appears in the
Basis group.
Changes can be made to the reaction rate parameters (frequency factor,
A, activation energy, E, and ß), but these changes are reflected only in
the active reactor. The changes do not affect the global reaction.
To return the global reaction values, select the appropriate Use Default
checkbox. For instance, if you have made a change to the forward
reaction activation energy (E), the Use Default E checkbox is inactive.
Activate this checkbox to return to the global E value.
Results Page
The Results page displays the results of a converged reactor. The page is
made up of the Reaction Results Summary group which contains two
radio buttons:
•
•
Reaction Extents
Reaction Balance
9-17
9-18
CSTR/General Reactors Property View
Reaction Extents Radio Button
Figure 9.15
When you select the Reaction Extents radio button, the Reaction Extents
option displays the following results for a converged reactor:
Result Field
Description
Actual %
Conversion
Displays the percentage of the base component in the feed
stream(s) which has been consumed in the reaction.
Base Component
The reactant to which the conversion is applied.
Rxn Extent
Lists the molar rate of consumption of the base component.
Reaction Balance Radio Button
When you select the Reaction Balance radio button, the Reaction
Balance option provides an overall component summary for the CSTR.
All components which appear in the fluid package are shown here.
Figure 9.16
9-18
Reactors
9-19
Values appear after the solution of the reactor has converged. The Total
Inflow rate, the Total Reacted rate and the Total Outflow rate for each
component are provided on a molar basis. Negative values indicate the
consumption of a reactant, while positive values indicate the
appearance of a product.
9.2.4 Equilibrium Reactor Reactions Tab
Refer to Section 5.3.3 Equilibrium Reaction in the
Simulation Basis manual
for details on creating and
installing Equilibrium
Reactions.
Equilibrium Reactor icon
Any changes made to the
global reaction affect all
reaction sets to which the
reaction is attached,
provided local changes have
not been made.
The Equilibrium reactor is a vessel which models equilibrium reactions.
The outlet streams of the reactor are in a state of chemical and physical
equilibrium. The reaction set which you attach to the Equilibrium
Reactor can contain an unlimited number of equilibrium reactions,
which are simultaneously or sequentially solved. Neither the
components nor the mixing process need be ideal, since HYSYS can
compute the chemical activity of each component in the mixture based
on mixture and pure component fugacities.
You can also examine the actual conversion, the base component, the
equilibrium constant, and the reaction extent for each reaction in the
selected reaction set. The conversion, the equilibrium constant and the
extent are all calculated based on the equilibrium reaction information
which you provided when the reaction set was created.
The Reactions tab consists of two pages:
•
•
Details
Results
Details Page
The Details page consists primarily of four radio buttons:
•
•
•
•
Stoichiometry
Basis
Ln[K]
Table
9-19
9-20
CSTR/General Reactors Property View
Stoichiometry Radio Button
Changes made to the global
reaction affect all reaction
sets which contain the
reaction, and thus all
operations to which the
reaction set is attached.
When you select the Stoichiometry radio button, the Stoichiometry Info
group appears. The Stoichiometry group allows you to view the
stoichiometric formula of the reaction currently selected in the Reaction
drop-down list.
Figure 9.17
The Balance Error (for the reaction stoichiometry) and the Reaction
Heat (Heat of Reaction at 25°C) are also shown for the current reaction.
Basis Radio Button
Refer to Section 5.3.3 Equilibrium Reaction of
Simulation Basis for
details on Equilibrium
Constant source.
When you select the Basis radio button, Basis group appears.
Figure 9.18
The Basis group allows you to view or edit (locally) various information
for each reaction in the reaction set including the:
•
•
•
Basis for the equilibrium calculations.
Phase in which the reaction occurs.
Temperature Approach of the equilibrium composition.
The temperature range for the equilibrium constant, and the source for
the calculation of the equilibrium constant is also shown.
9-20
Reactors
9-21
Keq Radio Button
Refer to Section 5.3.3 Equilibrium Reaction of
Simulation Basis for
details on the Equilibrium
Constant source.
When you select the Keq radio button, the Ln(keq) group and K Table
appears. The Ln(keq) group displays the Ln(Keq) relationship which
may vary depending upon the Ln(K) Source value selected for the
reaction (refer to the section on the Basis Radio Button for more
information).
Figure 9.19
When you select the Ln(Keq) Equation radio button in the Ln(K) Source
group, the parameters of the equilibrium constant equation appear.
These values are either specified when the reaction was created or are
calculated by HYSYS. If a fixed equilibrium constant was provided, it is
shown here.
Any of the parameters in the Ln(K) Equation group can be modified on
this page. Changes made to the parameters only affect the selected
reaction in the current reactor. After a change has been made, you can
have HYSYS return the original calculated value by activating the
appropriate Use Default checkbox.
9-21
9-22
CSTR/General Reactors Property View
Approach Radio Button
When you select the Approach radio button, the Fractional Approach
group and the Temperature Approach group appear.
Figure 9.20
For each reaction in the reaction set, a fractional approach equation as a
function of temperature is provided. Any of the parameters in the
Approach % equation can be modified on this page. Changes made to
the parameters only affect the selected reaction in the current reactor.
After a change has been made, you can have HYSYS return the original
calculated value by activating the appropriate Use Default checkbox.
For more detailed information
on equilibrium reactions, refer
to Chapter 5 - Reactions in
the Simulation Basis
manual.
You can edit a reaction by clicking the View Reaction button. The
property view for the highlighted reaction appears.
You can change the specified
conversion for a reaction
directly on this page.
The Results page displays the results of a converged reactor. The page is
made up of the Results Summary group which contains two radio
buttons:
Results Page
•
•
9-22
Reaction Extents
Reaction Balance
Reactors
9-23
Reaction Extents
Figure 9.21
When you select the Reaction Extents radio button, the option displays
the following results for a converged reactor:
Result Field
Description
Actual % Conversion
Displays the percentage of base component in the feed
stream(s) which has been consumed in the reaction.
The actual conversion is calculated as the percentage of the
base component that was consumed in the reaction.
NA – NA
in
out
- × 100%
X = --------------------------NA
(9.5)
in
where:X = actual % conversion
NAin = base component flowrate into the reactor
NAout = base component flowrate (same basis as the
inlet rate) out of the reactor
The four parameters for
each equilibrium equation
are listed on the Rxn Ln(K)
page.
Base Component
The reactant to which the conversion is applied.
Eqm Const.
The equilibrium constant is calculated at the reactor
temperature by the following:
B
ln K = A + --- + C ln T + DT
T
(9.6)
where:T = reactor temperature, K
A, B, C, D = equation parameters
The four parameters in Equation (9.6) are calculated by
HYSYS if they are not specified during the installation of the
equilibrium reaction.
Rxn Extent
Lists the molar rate consumption of the base component.
9-23
9-24
CSTR/General Reactors Property View
Reaction Balance
Figure 9.22
When you select the Reaction Balance radio button, the Reaction
Balance option provides an overall component summary for the
Equilibrium Reactor. All components which appear in the component
list related to the fluid package are shown here.
Values appear after the solution of reactor has converged. The Total
Inflow rate, the Total Reacted rate, and the Total Outflow rate for each
component are provided on a molar basis. Negative values indicate the
consumption of a reactant, while positive values indicate the
appearance of a product.
9.2.5 Gibbs Reactor Reactions Tab
Gibbs Reactor icon
9-24
The Gibbs Reactor calculates the exiting compositions such that the
phase and chemical equilibria of the outlet streams are attained.
However, the Gibbs Reactor does not need to make use of a specified
reaction stoichiometry to compute the outlet stream composition. The
condition that the Gibbs free energy of the reacting system is at a
minimum at equilibrium is used to calculate the product mixture
composition. As with the Equilibrium Reactor, neither pure components
nor the reaction mixture are assumed to behave ideally.
Reactors
9-25
Figure 9.23
The versatility of the Gibbs Reactor allows it to function solely as a
separator, as a reactor which minimizes the Gibbs free energy without
an attached reaction set or as a reactor which accepts equilibrium
reactions. When a reaction set is attached, the stoichiometry involved in
the reactions is used in the Gibbs Reactor calculations.
The Reactions tab consists of two pages:
•
•
Overall
Details
Overall Page
You must first select the reactor type on the Overall page. The objects
that appear depend on the radio button you selected in the Reactor Type
group. You can then attach a reaction set if necessary, and you can
specify the vessel parameters on the Rating tab.
9-25
9-26
CSTR/General Reactors Property View
Reactor Type Group
In the Reactor Type group, select the radio button to define the method
which HYSYS uses to solve the Gibbs Reactor. The table below describes
the radio buttons.
Radio Button
Description
Gibbs Reactions
Only
No reaction set is required as HYSYS solves the system by
minimizing the Gibbs free energy while attaining phase and
chemical equilibrium. You can also customize the maximum
iteration number and equilibrium error tolerance in the Solving
Option group.
Specify Equilibrium
Reactions
Displays the Equilibrium Reaction Sets group. When a reaction
set is attached, the Gibbs Reactor is solved using the
stoichiometry of the reactions involved. The Gibbs minimization
function uses the extents of the attached reactions while setting
any unknowns to zero.
NO Reactions
(=Separator)
The Gibbs Reactor is solved as a separator operation,
concerned only with phase equilibrium in the outlet streams.
Details Page
The Details page consists of one group, the Gibbs Reaction Details
group. The group consists of two radio buttons:
•
•
Flow Specs
Atom Matrix
The information that is viewable on the page depends on which of the
two radio buttons is selected.
9-26
Reactors
9-27
Flow Specs Option
When you select the Flow Specs radio button, a view similar to the one
in the figure below appears.
Figure 9.24
You can view the component feed and product flowrates on a molar
basis. You can also designate any of the components as inert or specify a
rate of production for a component.
Inert species are excluded from the Gibbs free energy minimization
calculations. When the Inerts checkbox is activated for a component,
values of 1 and 0 appear respectively in the associated Frac Spec and
Fixed Spec cells, which indicates that the component feed flowrate
equals the product flowrate.
You may want to specify the rate of production of any component in
your reactor as a constraint on the equilibrium composition. The
component product flowrate is calculated as follows, based on your
input of a Frac Spec value and a Fixed Spec value:
Total Prod = FracSpec x Total Feed + FixedSpec
(9.7)
The Gibbs Reactor attempts to meet that flowrate in calculating the
composition of the outlet stream. If the constraint cannot be met, a
message appears alerting you to that effect.
9-27
9-28
CSTR/General Reactors Property View
Atom Matrix Option
When you select the Atom Matrix radio button, you can specify the
atomic composition of any species for which the formula is unknown or
unrecognized.
Figure 9.25
The atomic matrix input form displays all components in the case with
their atomic composition as understood by HYSYS. You have the option
to enter the composition of an unrecognized compound or to correct
the atomic composition of any compound.
9.2.6 Rating Tab
You are required to specify
the rating information only
when working with a
dynamics simulation.
9-28
The Rating tab includes the Sizing, Nozzles, and Heat Loss pages.
Although most of the information on the three pages is not relevant
when working in the Steady State mode, sizing a reactor plays an
important role in calculating the holdup time. For information on
specifying information on the Sizing Page, refer to the Dynamic
Modeling manual.
Reactors
9-29
Sizing Page
You can define the geometry of the unit operation on the Sizing page.
Also, you can indicate whether or not the unit operation has a boot
associated with it. If it does, then you can specify the boot dimensions.
Figure 9.26
The page consists of three main objects, which are described in the table
below.
Object
Description
Geometry
Allows you to specify the vessel geometry.
This Reactor has a Boot
When activated, the Boot Dimensions group appears.
Boot Dimensions
Allows you to specify the boot dimensions of the vessel.
9-29
9-30
CSTR/General Reactors Property View
Geometry Group
The Geometry group contains five objects which are described in the
table below.
Object
Description
Cylinder /
Sphere
Toggles the shape of the vessel between Sphere and Cylinder. This
affects the number of specifications required as well as the method
of volume calculation.
If you select the Cylinder, and you have specified the diameter and
height; the vessel volume is calculated as:
2
Diameter
V reactor =  ---------------------------π × Height + V boot


4
(9.8)
If you select Sphere, and you have specified either the height or
diameter; the vessel volume is calculated as:
3
( Height or Diameter ) π
V reactor = ---------------------------------------------------------- + V boot
6
(9.9)
where:Vreactor = volume of the reactor
Vboot = volume of the boot
Height, Diameter = values taken from the respective fields
Orientation
Allows you to select the orientation of the vessel. There are two
options:
• Horizontal. The ends of the vessels are horizontally orientated.
• Vertical. The ends of the vessel are vertically orientated.
Volume
Contains the total volume of the vessel.
There are three possibilities for values in this field:
• If the height and/or diameter have been entered, this field
displays the value calculated using either Equation (9.8) or
Equation (9.9).
• If you enter a value into this field and either the height (length)
or diameter is specified, HYSYS back calculates the other
parameter using either Equation (9.8) or Equation (9.9). This
is only possible with cylindrical vessels as spherical vessels
have the height equal to the diameter.
• If you enter a value into this field (and only this field) both the
height (length) and diameter are calculated assuming a ratio of
3/2 (i.e., Height: Diameter).
9-30
Diameter
Holds the diameter of the vessel. If the vessel is a Sphere, then it is
the same value as the Height (Length).
Height / Length
Holds the height or length of the vessel depending on the vessels
orientation (vertical or horizontal). If the vessel is a Sphere, then it is
the same value as the diameter.
Reactors
If you specify the Volume
then you are not required to
specify the other two
parameters as HYSYS
calculates a Height (or
Length) and Diameter
assuming a ratio of Height to
Diameter of 3/2. You can
however specify one of the
two parameters (either
Height or Diameter) and the
third is automatically
calculated using either
Equation (9.8) or Equation
(9.9).
9-31
The Geometry group contains three fields:
•
•
•
Volume
Diameter
Height (or Length depending on orientation)
Boot Dimensions
If the reactor you are rating has a boot, you can include its volume in the
total vessel volume by activating the This Reactor has a Boot checkbox.
The Boot Dimensions group appears. The Boot Dimensions group
consists of two fields, which are described in the table below.
Field
Description
Boot Diameter
The diameter of the boot. The default value is usually 1/3 the reactor
diameter.
Boot Height
The height of the boot which is defaulted at 1/3 the reactor diameter
(sphere) or 1/3 the reactor height or length (cylinder).
The volume of the boot is calculated using a simple cylindrical volume
calculation:
Boot Diameter 2
V Boot = π  ----------------------------------- × ( Boot Height or Boot Length )


2
(9.10)
and the default boot volume is:
Diameter 2 Diameter
V Boot = π  ------------------------- × ------------------------

3
6
3
π ( Diameter )
= -----------------------------------72
(9.11)
The total Reactor volume can estimated using the boot diameter, boot
height or the default boot volume.
9-31
9-32
CSTR/General Reactors Property View
Nozzles Page
The Fidelity license is
required to use the Nozzle
features found on this page.
Refer to Section 1.6 Fidelity in the Dynamic
Modeling manual for more
information.
The Nozzles page contains information regarding the elevation and
diameter of the nozzles.
A vapour product nozzle
does not necessarily
produce pure vapour and a
3-phase separator may not
produce two distinct liquid
phase products from its
product nozzles.
Essentially, all vessel operations in HYSYS are treated similarly. The
composition and phase fractions (i.e., fraction of each phase) of every
product stream depends solely on the relative levels of each phase in the
holdup and the location the product nozzles.
Unlike steady state vessel operations, the placement of feed and product
nozzles on a dynamic reactor operation has physical meaning. The
composition of the exit stream depends on the exit stream nozzle’s
location and diameter in relation to the physical holdup level in the
vessel. If the product nozzle is located below the liquid level in the
vessel, the exit stream draws material from the liquid holdup. If the
product nozzle is located above the liquid level, the exit stream draws
material from the vapour holdup. If the liquid level lies across a nozzle,
the phase fraction of liquid in the product stream varies linearly with
how far up the liquid is in the nozzle.
Heat Loss Page
The Heat Loss page allows you to specify which Heat Loss Model you
want to implement, and to define the parameters associated with each
model. For information on specifying information on this page, refer to
the section on the Heat Loss Page in Chapter 7 - Separation Operations.
9.2.7 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
9-32
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Reactors
9-33
9.2.8 Dynamics Tab
If you are working exclusively in Steady State mode, you are not required
to change any information on the pages accessible through this tab.
Figure 9.27
Specs Page
The Specs page contains information regarding initialization modes,
vessel geometry, and vessel dynamic specifications.
Figure 9.28
9-33
9-34
CSTR/General Reactors Property View
Model Details
You can determine the composition and amount of each phase in the
vessel holdup by specifying different initialization modes. HYSYS forces
the simulation case to re-initialize whenever the initialization mode is
changed. The radio buttons in the Model Details group are described in
the table below.
Initialization Mode
Description
Initialize from
Products
The composition of the holdup is calculated from a weighted
average of all products exiting the holdup. A PT flash is
performed to determine other holdup conditions. The liquid
level is set to the value indicated in the Liq Volume Percent
field.
Dry Startup
The composition of the holdup is calculated from a weighted
average of all feeds entering the holdup. A PT flash is
performed to determine other holdup conditions. The liquid
level in the Liq Volume Percent field is set to zero.
Initialize from User
The composition of the liquid holdup in the vessel is user
specified. The molar composition of the liquid holdup can be
specified by clicking the Init Holdup button. The liquid level is
set to the value indicated in the Liq Volume Percent field.
The Enable Explicit Reaction Calculations is defaulted to be used for
dynamic run reaction solver.
The Lag Rxn Temperature is designed to speed up the dynamic run for
the reaction solver when the run has to invoke the steady state reaction
solver. Mathematically, when you activate the Lag Rxn Temperature
checkbox, the reaction solver flashes with the explicit Euler method.
Otherwise, for a dynamic run, the steady state reaction solver always
flashes with the implicit Euler methods which could be slow with many
iterations.
The Lag Rxn Temperature may cause some instability due to the nature
of the explicit Euler method. But it must compromise with the dynamic
step size.
The vessel geometry
parameters can be
specified in the same
manner as those specified
in the Geometry group for
the Sizing page of the
Rating tab.
9-34
In the Model Details group, you can specify the vessel geometry
parameters.
•
•
•
•
Vessel Volume
Vessel Diameter
Vessel Height (Length)
Vessel Geometry (Level Calculator)
Reactors
9-35
Liquid Volume Percent
You can modify the level in the vessel at any time. HYSYS then uses that
level as an initial value when the Integrator has started, depending on
the initialization mode you selected.
Fraction Calculator
The Fraction Calculator
defaults to the correct mode
for all unit operations and
does not typically require
any changing.
The Fraction Calculator determines how the level in the tank, and the
elevation and diameter of the nozzle affects the product composition.
The following is a description of the Fraction Calculator option:
•
Use Levels and Nozzles.The nozzle location and vessel liquid
level affect the product composition as detailed in the Nozzles
Page of Section 9.2.6 - Rating Tab.
Dynamic Specifications
It is recommended that you
enter a value of zero in the
Feed Delta P field because
a fixed pressure drop in the
vessel is not realistic for all
flows.
The frictional pressure loss at the feed nozzle is a dynamic specification
in HYSYS. It can be specified in the Feed Delta P field. The frictional
pressure losses at each product nozzle are automatically set to zero by
HYSYS.
If you want to model friction loss at the inlet and exit stream, it is
suggested you add valve operations. In this case, flow into and out of the
vessel is realistically modeled.
The vessel pressure can also be specified. This specification can be
made active by activating the checkbox beside the Vessel Pressure field.
This specification is typically not set since the pressure of the vessel is
usually a variable and determined from the surrounding pieces of
equipment.
9-35
9-36
CSTR/General Reactors Property View
Holdup Page
The Holdup page contains information regarding the properties,
composition, and amount of the holdup.
Figure 9.29
Vessel Levels Group
For each possible phase in the vessel (vapour, aqueous, and liquid), the
Vessel Levels group displays:
9-36
Vessel Levels
Description
Level
The cumulative height of the phase.
Percentage Level
The cumulative height of the phase as percentage of the vessel
height.
Volume
The cumulative volume of the phase.
Reactors
9-37
Details Group
For each phase contained within the volume space of the unit
operation, the following is specified:
Details
Description
Phase
The phase of the holdup volume.
Accumulation
The accumulation refers to the rate of change of material in the
holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
Stripchart Page
Refer to Section 11.7.3 Strip Chartsin the User
Guide for more information
about stripcharts.
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
9-37
9-38
CSTR/General Reactors Property View
Duty Page
The Duty page is only
available if you had entered
a name for the Energy
(Optional) field in the
Connections Page on the
Design tab, and the
flowsheet is in dynamic
mode.
The Duty page opens a list of available heating methods for the vessel
operation.
Figure 9.30
Duty Source
In the Source group, you can choose whether HYSYS calculates the duty
applied to the vessel from a Direct Q or a Utility.
If you select the Direct Q radio button, you can directly specify the duty
applied to the holdup in the SP field. If you select the Utility radio
button, you can specify the flow of the utility fluid. The duty is then
calculated using the local overall heat transfer coefficient, the inlet fluid
conditions, and the process conditions. The calculated duty is then
displayed in the SP field or the Heat Flow field. For more information
regarding how the utility option calculates duty, refer to Chapter 12 Logical Operations.
If you select the Heating radio button, the duty shown in the SP field or
Heat Flow field is added to the holdup. If you select the Cooling radio
button, the duty is subtracted from the holdup.
9-38
Reactors
9-39
Heater Type
In the Heater Type group, there are two heating methods available to the
general vessel operation:
•
•
Vessel Heater
Liquid Heater
If you select the Vessel Heater radio button, 100% of the duty specified or
calculated in the SP field is applied to the vessel’s holdup
Q = QTotal
where:
(9.12)
Q = total heat applied to the holdup
QTotal = duty calculated from the duty source
If you select the Liquid Heater radio button, the duty applied to the
vessel depends on the liquid level in the tank. You must specify the
heater height. The heater height is expressed as a percentage of the
liquid level in the vessel operation. The default values are 5% for the Top
of the Heater and 0% for the Bottom of the Heater. These values are used
to scale the amount of duty that is applied to the vessel contents.
where:
Q = 0
(L < B)
L–B
Q = ------------- Q Total
T–B
(B ≤ L ≤ T)
Q = Q Total
(L > T)
(9.13)
L = liquid percent level (%)
T = top of heater (%)
B = bottom of heater (%)
The Percent Heat Applied may be calculated as follows:
Q
Percent Heat Applied = --------------- × 100%
Q Total
(9.14)
9-39
9-40
Plug Flow Reactor (PFR)
It is shown that the percent of heat applied to the vessel’s holdup directly
varies with the surface area of liquid contacting the heater.
Figure 9.31
Percent of Heat Applied
100
80
60
40
20
B
T
0
0
20
40
60
80
100
Liquid Percent Level, L
Percent Heat Applied for a Liquid Heater
9.3 Plug Flow Reactor (PFR)
The PFR (Plug Flow Reactor, or Tubular Reactor) generally consists of a
bank of cylindrical pipes or tubes. The flow field is modeled as plug flow,
implying that the stream is radially isotropic (without mass or energy
gradients). This also implies that axial mixing is negligible.
Figure 9.32
As the reactants flow the length of the reactor, they are continually
consumed, hence, there is an axial variation in concentration. Since
reaction rate is a function of concentration, the reaction rate also varies
axially (except for zero-order reactions).
9-40
Reactors
9-41
To obtain the solution for the PFR (axial profiles of compositions,
temperature, etc.), the reactor is divided into several subvolumes.
Within each subvolume, the reaction rate is considered to be spatially
uniform. A mole balance is done in each subvolume j:
dN j
F j0 – F j + ∫ r j dV = -------dt
V
(9.15)
Because the reaction rate is considered spatially uniform in each
subvolume, the third term reduces to rjV. At steady state, the right side of
this balance equals zero, and the equation reduces to:
F j = F j0 + r j V
(9.16)
9.3.1 Adding a Plug Flow Reactor (PFR)
You can also add a reactor
by clicking the F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a PFR to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Reactors radio button.
3.
From the list of available unit operations, select Plug Flow Reactor.
4.
Click the Add button. The PFR property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
9-41
9-42
Plug Flow Reactor (PFR) Property View
6.
Double-click the Plug Flow Reactor icon. The PFR property view
appears.
Figure 9.33
Plug Flow Reactor icon
To ignore the PFR during calculations, click the Ignored checkbox.
HYSYS completely disregards the operation until you restore the
operation to an active state by deactivating the checkbox.
9.4 Plug Flow Reactor (PFR)
Property View
The Plug Flow Reactor (PFR) property view consists of six tabs:
•
•
•
•
•
•
9-42
Design
Reactions
Rating
Worksheet
Performance
Dynamics
Reactors
9-43
9.4.1 PFR Design Tab
The Design tab of the PFR consists of five pages, which are briefly
described in the table below.
Page
Input Required
Connections
Attaches the feed and product streams to the reactor. Refer to the
section below for more information.
Parameters
Allows you to specify the parameters for the pressure drops and
energy streams. Refer to the section on the Parameters Page for
more information.
Heat Transfer
Allows you to specify the heat transfer parameters. Refer to the
section on the Heat Transfer Page for more information.
User Variables
Allows you to create and implement User Variables. Refer to the
section on the User Variables Page for more information.
Notes
Allows you to add relevant comments which are exclusively
associated with the unit operation. Refer to the section on theNotes
Page for more information.
Connections Page
You can specify the name of the reactor, the feed(s) stream, product
stream, and energy stream on the Connections page.
Figure 9.34
9-43
9-44
Plug Flow Reactor (PFR) Property View
Notice that if you do not provide an energy stream, the operation is
considered to be adiabatic. The table below describes the objects on the
Connections page.
Object
Input Required
Inlets
The reactor feed stream.
Outlet
The reactor product stream.
Energy (Optional)
You are not required to provide an energy stream, however
under those circumstances HYSYS assumes that the operation
is adiabatic.
Parameters Page
You can instruct HYSYS on the calculations for the pressure drop and
heat transfer, and also decide whether the operation is included in the
calculation on the Parameters page.
Figure 9.35
9-44
Reactors
9-45
Delta P
In the Pressure Drop Parameters group, you can select one of the
available radio buttons for the determination of the total pressure drop
across the reactor. The radio buttons are described in the table below.
When you select the Ergun
Equation radio button, the
pressure drop (Delta P) field
changes colour from blue to
black, indicating a value
calculated by HYSYS.
Radio Button
Description
User Specified
You must specify a pressure drop in the pressure drop (Delta P)
field.
Ergun Equation
HYSYS uses the Ergun equation to calculate the pressure drop
across the PFR. The equation parameters include values which you
specify for the PFR dimensions and feed streams:
∆Pg c ϕ s D p ε 3
150 ( 1 – ε )
------------- ---------------------- = ---------------------------- + 1.75
L ρV 2 1 – ε
ϕ s D p Vρ ⁄ µ
(9.17)
where: ∆P = pressure drop across the reactor
If you select the Ergun
Equation radio button for a
PFR with no catalyst (solid),
HYSYS sets ∆P = 0.
gc = Newton’s-law proportionality factor for the gravitational
force unit
L = reactor length
ϕ s = particle sphericity
Dp = particle (catalyst) diameter
ρ = fluid density
V = superficial or empty tower fluid velocity
ε = void fraction
µ = fluid viscosity
Duty
For the PFR heat transfer calculations, you can select one of the radio
buttons described in the table below.
Radio Button
Description
Formula
HYSYS calculates the energy stream duty after you specify further
heat transfer information on the Heat Transfer Page. The two fields
below the radio buttons show the Energy Stream, which is attached
on the Connections page, and the Calculated Duty value.
Direct Q Value
You can directly specify a duty value for the energy stream.
9-45
9-46
Plug Flow Reactor (PFR) Property View
You can specify whether the energy stream is Heating or Cooling by
selecting the appropriate radio button. This does not affect the sign of
the duty stream. Rather, if the energy stream is Heating, then the duty is
added to the feed. If Cooling is chosen, the duty is subtracted.
Heat Transfer Page
Your selection in the SS Duty
Calculation Option group is
also transferred to the Heat
Transfer group on the
Parameters page.
The format of the Heat Transfer page depends on your selection in the
SS Duty Calculation Option group. There are two radio buttons:
•
•
Formula
Direct Q Value.
Direct Q Value Option
Figure 9.36
When you select the Direct Q Value radio button, the Heat Transfer
group appears. It consists of three objects, which are described in the
table below.
9-46
Object
Description
Energy Stream
The name of the duty stream.
Duty
The duty value to be specified in the energy stream.
Heating \ Cooling
Selecting one of these radio buttons does not affect the sign of the
duty stream. Rather, if the energy stream is Heating, then the duty
is added to the feed. If Cooling is chosen, the duty is subtracted.
Reactors
9-47
Formula Option
For the Formula option, you
must have an energy stream
attached to the PFR. You
cannot use this option while
operating adiabatically.
When you select the Formula radio button, you instruct HYSYS to
rigorously calculate the duty of each PFR subvolume using local heat
transfer coefficients for the inside and the outside of each PFR tube
using Equation (9.18) and Equation (9.19).
Figure 9.37
Qj = UjA(Tbulkj - Toutj)
Resistance of the tube wall to
heat transfer is neglected.
where:
(9.18)
Qj = heat transfer for subvolume j
Uj = overall heat transfer coefficient for subvolume j
A = surface area of the PFR tube
Tbulkj = bulk temperature of the fluid
Toutj = temperature outside of the PFR tube (utility fluid)
The final term in Equation
(9.19), which represents the
thickness of the tube divided
by the thermal conductivity of
the tube material, is deemed
negligible and is ignored in
the PFR calculations.
1
1
1 xw
---- = --------- + ------ + -----U
h out h w k m
where:
(9.19)
U = overall heat transfer coefficient
hout = local heat transfer coefficient for the outside (utility fluid)
hw = local heat transfer coefficient inside the PFR tube
xw
------ = heat transfer term for the tube wall (ignored in calculations)
km
9-47
9-48
Plug Flow Reactor (PFR) Property View
In each subvolume, heat is being transferred radially between the PFR
fluid and the utility fluid. The two groups available on the Heat Transfer
page allow you to specify parameters which are used in the
determination of the duty.
Heat Medium Side Heat Transfer Infos Group
If you specify a heat flow on
the Energy Stream property
view and select the Formula
radio button on the Heat
Transfer page,
inconsistencies appear in
the solution. You cannot
specify a duty and have
HYSYS calculate the same
duty.
Figure 9.38
In the Heat Medium Side Heat Transfer Infos group, you can modify the
parameters which are used to calculate the duty (Qj) for the outside of
each PFR subvolume. The table below describes the parameters.
Parameter
Formula Variable
Input Required
Wall Heat
Transfer
Coefficient
hout
Specify a value for the local heat transfer
coefficient. Since the UA value, in this case
the U being the local heat transfer
coefficient, is constant, changes made to
the specified length, diameter or number of
tubes (on the Dimensions page) affects
hout.
Mole Flow
m
Molar flow of the energy stream utility fluid.
Heat Capacity
Cp
Heat capacity of the energy stream utility
fluid.
Inlet Temperature
T
The temperature of the utility fluid entering
the PFR.
Calculated Duty
Qj
Duty calculated for each PFR subvolume.
The equation used to determine the temperature of the utility fluid
entering each subvolume j is:
Q j = mρC p ( T j – T j + 1 )
9-48
(9.20)
Reactors
9-49
Tube Side Heat Transfer Info Group
In the Tube Side Heat Transfer Info group, you can select the method for
determining the inside local heat transfer coefficient (hw) by selecting
one of the radio buttons and specifying the required parameters. The
radio buttons are described in the table below.
Radio Button
Description
User
Specify a value for the local heat transfer coefficient in the User
Specified input field.
View
Empirical
Specify coefficients for the empirical equation which relates the
heat transfer coefficient to the flowrate of the PFR fluid via the
following equation:
h w = A × Flow
B
(9.21)
You can also choose the basis for the equation as Molar, Mass
or Volume.
Standard
Specify coefficients for the calculation of the Nusselt number,
which is then used to calculate the local heat transfer
coefficient:
N u = A × Re B × Pr C
Nu kg
h w = -----------Dp
(9.22)
(9.23)
User Variables Page
HYSYS uses the following
defaults:
A = 1.6, B = 0.51,C = 0.33
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
9-49
9-50
Plug Flow Reactor (PFR) Property View
9.4.2 Reactions Tab
You can add a reaction set to the PFR on the Reactions tab. Notice that
only Kinetic, Heterogeneous Catalytic, and Simple Rate reactions are
allowed in the PFR. The tab consists of three pages:
•
•
•
Overall
Details
Results
Overall Page
You can specify the reaction set and calculation information on the
Overall page.
Figure 9.39
The Overall page consists of three groups:
•
•
•
9-50
Reaction Info
Integration Information
Catalyst Data
Reactors
9-51
Reaction Info Group
In the Reaction Info group, you specify the following information:
•
•
The reaction set to be used.
The segment initialization method.
Figure 9.40
From the Reaction Set drop-down list, select the reaction set you want to
use for the PFR.
The reaction set you want to use must be attached to the fluid package
you are using in this environment.
As described earlier in this section, the PFR is split into segments by the
reactor solver algorithm; HYSYS obtains a solution in each segment of
the reactor. The segment reactions may be initialized using the following
methods:
Initialization Option
Description
Current
Initializes from the most recent solution of the current segment.
Previous
Initializes from the most recent solution of the previous
segment.
Re-init
Re-initializes the current segment reaction calculations.
9-51
9-52
Plug Flow Reactor (PFR) Property View
Integration Information Group
The Integration Information group consists of three fields:
•
•
•
Number of Segments
Minimum Step Fraction
Minimum Step Length
Figure 9.41
The table below briefly describes the fields.
The length of each segment
stays constant during the
calculations. However, if a
solution cannot be obtained
for an individual segment, it
is divided into smaller
sections until a solution is
reached. This does not affect
the other segments.
9-52
Field
Description
Number of Segments
The number of segments you want to split the PFR into.
Minimum Step Fraction
The minimum fraction an unresolved segment splits too.
Minimum Step Length
The product of the Reactor Length and the Minimum Step
Fraction.
During each segment calculation, HYSYS attempts to calculate a
solution over the complete segment length. If a solution cannot be
obtained, the current segment is halved, and HYSYS attempts to
determine a solution over the first half of the segment. The segment
continues to be halved until a solution is obtained, at which point the
remaining portion of the segment is calculated. If the segment is divided
to the point where its length is less than the minimum step length,
calculations stop.
Reactors
9-53
Catalyst Data Group
If you specified a void fraction less than one on the Rating tab, the
Catalyst Data group appears.
Figure 9.42
The following information must be specified:
Field
Description
Particle Diameter
The mean diameter of the catalyst particles. The default particle
diameter is 0.001 m.
Particle Sphericity
This is defined as the surface area of a sphere having the same
volume as the particle divided by the surface area of the
particle. A perfectly spherical particle has a sphericity of 1.The
Particle Diameter and Sphericity are used to calculate the
pressure drop (in the Ergun pressure drop equation) if it is not
specified.
Solid Density
The density of the solid portion of the particle, including the
catalyst pore space (microparticle voidage).This is the mass of
the particle divided by the overall volume of the particle, and
therefore includes the pore space.The default is 2500 kg/m3.
Bulk Density
Equal to the solid density multiplied by one minus the void
fraction.
ρ b = ρ s ( 1 – ε ma )
(9.24)
where: ρ b = bulk density
ρ s = solid density
ε ma = macroparticle voidage (void fraction)
Solid Heat Capacity
Used to determine the solid enthalpy holdup in dynamics.The
bulk density is also required in this calculation.
9-53
9-54
Plug Flow Reactor (PFR) Property View
Details Page
You can manipulate the reactions attached to the selected reactions set
on the Details page.
Figure 9.43
The Details page consists of three objects, which are briefly described in
the table below.
9-54
Object
Description
Reaction
Allows you to select the reaction you want to use in the reactor.
View Reaction
Opens the Reaction property view for the selected reaction. This
allows you to edit the reaction. Editing the Reaction propety view
affects all other implementations of the selected reaction.
Specifics
Toggles between the Stoichiometry group or the Basis group (the
groups are described in the following sections).
Reactors
9-55
Stoichiometry Group
To affect change in the
reaction over the entire
simulation you must click the
View Reaction button and
make the changes in the
Reaction property view.
When you select the Stoichiometry radio button, the Stoichiometry
group appears. The Stoichiometry group allows you to examine the
components involved in the currently selected reaction, their molecular
weights as well as their stoichiometric coefficients.
Figure 9.44
The Balance Error (for the reaction stoichiometry) and the Reaction
Heat (Heat of Reaction at 25°C) are also shown for the current reaction.
Basis Group
When you select the Basis radio button, the Basis group appears. In the
Basis group, you can view the base component, and the rate expression
parameters.
Figure 9.45
You can make changes to these parameters, however these changes only
affect the current implementation of the reaction and are not affected by
other reactors using the reaction set or reaction.
9-55
9-56
Plug Flow Reactor (PFR) Property View
View Reaction Button
Click the View Reaction button to open the Reaction property view of
the reaction currently selected in the Reaction drop-down list.
Any changes made to the Conversion Reaction property view are made
globally to the selected reaction and any reaction sets which contain the
reaction.
Results Page
You can change the
specified conversion for a
reaction directly on this
page.
The Results page displays the results of a converged reactor. The page
consists of the Reaction Balance group which contains two radio
buttons:
•
•
Reaction Extents
Reaction Balance
The type of results displayed depend on the radio button selected.
Reaction Extents
When you select the Reaction Extents radio button, the Results page
appears as shown in the figure below.
Figure 9.46
9-56
Reactors
9-57
The Reaction Balance group displays the following results for a
converged reactor:
Result Field
Description
Actual % Conversion
Displays the percentage of the base component in the feed
stream(s) which has been consumed in the reaction.
Base Component
The reactant to which the conversion is applied.
Rxn Extent
Lists the molar rate consumption of the base component.
Reaction Balance
Any changes made to the
global reaction affect all
reaction sets to which the
reaction is attached,
provided local changes have
not been made.
When you select the Reaction Balance radio button, the option provides
an overall component summary for the PFR. All components which
appear in the connected component list are shown.
Figure 9.47
Values appear after the solution of the reactor has converged. The Total
Inflow rate, the Total Reacted rate and the Total Outflow rate for each
component are provided on a molar basis. Negative values indicate the
consumption of a reactant, while positive values indicate the
appearance of a product.
9-57
9-58
Plug Flow Reactor (PFR) Property View
9.4.3 Rating tab
The Rating tab consists of two pages:
•
•
Sizing
Nozzles
Sizing Page
You can specify the tube dimensions and the tube packing information
on the Sizing page.
Figure 9.48
Tube Dimensions
For the tube dimensions, you need to specify any three of the following
four parameters:
9-58
Tube Dimension
Description
Total Volume
Total volume of the PFR.
Length
Total length of the individual tube.
Diameter
Diameter of an individual tube.
Number of tubes.
Total number of tubes required. This is always calculated to the
nearest integer value.
Reactors
9-59
When three of these dimensions are specified, the fourth is
automatically calculated. Notice that the Total Volume refers to the
combined volumes of all tubes.
By default, the number of tubes is set to 1. Although the number of tubes
is generally specified, you can set this parameter as a calculated value by
selecting the Number of Tubes field and pressing the DELETE key. The
number of tubes are always calculated as an integer value. It is possible
to obtain a rounded value of 0 as the number of tubes, depending on
what you specified for the tube dimensions. In this case, you have to respecify the tube dimensions.
The Tube Wall Thickness can also be specified.
Tube Packing
The Void Volume is used to
calculate the spatial velocity,
which impacts the rate of
reaction.
The Tube Packing group consists of two fields:
•
•
Void Fraction
Void Volume
The Void Fraction is by default set to 1, in which case there is no catalyst
present in the reactor. The resulting Void Volume is equal to the reactor
volume.
At Void Fractions less than 1, the Void Volume is the product of the Total
Volume and Void Fraction. In this case, you are also required to provide
information on the Overall page of the Reactions tab. This information is
used to calculate pressure drop, reactor heat capacity and spatial
velocity of the fluid travelling down the reactor.
Nozzles Page
The Nozzles page contains information regarding the elevation and
diameter of the nozzles. The Fidelity license is required to use the Nozzle
features found on this page. Refer to Section 1.6 - Fidelity in the
Dynamic Modeling manual for more information.
9-59
9-60
Plug Flow Reactor (PFR) Property View
9.4.4 Work Sheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
9.4.5 Performance Tab
The Performance tab allows you to examine various axial profiles in the
PFR. The tab consists of five pages each containing a general type of
profile:
•
•
•
•
•
Conditions
Flows
Reaction Rates (Rxn Rates)
Transport
Compositions
Figure 9.49
Each page consists of a table containing the relevant performance data
and a Plot button which converts the data to a graphical form.
The Reactor Length is always plotted on the x-axis.
9-60
Reactors
9-61
The data points are taken in the middle of each reactor segment, and
correspond to the number of reactor segments you specified.
Conditions Page
Physical Parameters
Temperature
Pressure
Enthalpy
The Conditions page allows you to view a table of the various physical
parameters including Temperature, Pressure, Vapour Fraction, Duty,
Enthalpy, Entropy, Inside HTC, and Outside HTC as a function of the
Reactor Length.
Entropy
Duty
Vapour Fraction
If you click the Plot button, a plot similar to the one shown in the figure
below appears. It shows the selected Physical parameter as a function of
the Reactor Length.
Figure 9.50
Flows Page
There are four overall flow types which can be viewed in a table or
plotted as a function of the Reactor Length:
•
•
Material Flow: Molar, Mass or Volume
Energy: Heat
If you click the Plot button, the table appears in a graphical form.
9-61
9-62
Plug Flow Reactor (PFR) Property View
Reaction Rates Page
Although only one reaction
set can be attached to the
PFR, it can contain multiple
reactions.
You can view either Reaction Rate or Component Production Rate data
as a function of the Reactor Length on the Rxn Rates page. You can
toggle between the two data sets by selecting the appropriate radio
button.
You can view the data in graphical form by clicking the Plot button.
Transport Page
Transport Properties:
•
•
•
•
•
•
Viscosity
Molar Weight
Mass Density
Heat Capacity
Surface Tension
Z Factor
The overall Transport properties appear in a tabular form as a function
of the Reactor Length on the Transport page.
You can view the data in a graphical form by clicking the Plot button.
Select the appropriate radio button to display the selected plot.
Compositions Page
You can view individual component profiles using one of six
composition bases:
•
•
•
•
Molar Flow
Mass Flow
Liquid Volume Flow
Fraction:
•Mole Fraction
•Mass Fraction
•Liquid Volume Fraction
You can display the data in a plot form by clicking the Plot button.
9-62
Reactors
9-63
9.4.6 Dynamics Tab
If you are working
exclusively in Steady State
mode, you are not required
to change any information
on the pages accessible
through the Dynamics tab.
The Dynamics tab contains four pages:
•
•
•
•
Specs
Holdup
Duty
Stripchart
Specs Page
Figure 9.51
Dynamic Specifications Group
The Dynamic Specifications group consists of eleven objects, which are
described in the table below.
Objects
Description
Initialize from Products
The composition of the holdup is calculated from a
weighted average of all products exiting the holdup. A PT
flash is performed to determine other holdup conditions.
Initialize from First Feed
The composition of the holdup is calculated from the first
feed entering the PFR reactor.
9-63
9-64
Plug Flow Reactor (PFR) Property View
Objects
Description
Dry Startup
The calculations based on the holdup starts with no fluid in
it.
Steady State
Uses steady state results to initialize the holdup.
Single Phase
Allows you to specify a single phase reaction. Otherwise
HYSYS considers it a vapour-liquid reaction.
Laminar Flow
Assumes laminar flow in the PFR.
Flow Equation
Uses the flow equation to calculate the pressure gradient
across the PFR. You are required to either estimate k
values in steady state (by clicking the Calculate K’s button)
or specifying your own values in the Pressure Flow
Relation group.
Fixed Delta P
Assumes a constant pressure drop across the PFR. Does
not require k values.
PFR Elevation
The height above ground that the PFR is currently
positioned.
Lag Rxn Temperature
Refer to the section on the Model Details for more
information.
Enable Explicit Rxn
Calc.
The Enable Explicit Reaction Calculations is defaulted to
be used for dynamic run reaction solver. The explicit
reaction solver is quick, but can introduce instability. You
can deactivate this option. The implicit reaction solver is
used instead.
Pressure Flow Relation Group
The Pressure Flow Relation group consists mainly of a table of the k
values for each segment in the PFR. You can enter your own k values into
this table or, while you are in Steady State mode, you can click the
Calculate K’s button and HYSYS calculates the k values using the steady
state data.
9-64
Reactors
9-65
Holdup Page
The Holdup page contains information regarding the properties,
composition, and amount of the holdup in each phase in the PFR.
Figure 9.52
The Holdup page consists of two groups:
•
•
Overall Holdup Detail
Segment Holdup Details
Overall Holdup Details Group
For each phase contained within the volume space of the PFR, the
following appears:
Holdup Details
Description
Phase
The phase of the holdup volume.
Accumulation
The accumulation refers to the rate of change of material in the
holdup for each phase.
Moles
The amount of material in the holdup for each phase.
Volume
The holdup volume of each phase.
Click the Advanced button to access the view that provides more
detailed information about the holdup of that unit operation. Refer to
Section 1.3.7 - Advanced Holdup Properties in the Dynamic Modeling
manual for more information.
9-65
9-66
Plug Flow Reactor (PFR) Property View
Duty Page
In the Source group, you can choose whether HYSYS calculates the duty
applied to the vessel from a Direct Q or a Utility.
Figure 9.53
If you select the Direct Q radio button, you can directly specify the duty
applied to the holdup in the SP field. If you select the Utility radio
button, you can specify the flow of the utility fluid. The duty is then
calculated using the local overall heat transfer coefficient, the inlet fluid
conditions, and the process conditions. The calculated duty is then
displayed in the SP field or the Heat Flow field. For more information
regarding how the utility option calculates duty, refer to Chapter 12 Logical Operations.
If you select the Heating radio button, the duty shown in the SP field or
Heat Flow field is added to the holdup. If you select the Cooling radio
button, the duty is subtracted from the holdup.
Stripchart Page
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about stripcharts.
9-66
The Stripchart page allows you to setup the stripchart for various
variable sets. You can select the variable set by clicking the Variable Set
drop-down list, and then clicking the Create Stripchart button to display
the stripchart.
Solid Separation Operations
10-1
10 Solid Separation
Operations
10.1 Simple Solid Separator (Simple Filter) ........................................3
10.1.1
10.1.2
10.1.3
10.1.4
10.1.5
Simple Solid Separator Property View.................................3
Design Tab ...........................................................................4
Rating Tab............................................................................7
Worksheet Tab .....................................................................7
Dynamics Tab ......................................................................7
10.2 Cyclone...........................................................................................7
10.2.1
10.2.2
10.2.3
10.2.4
10.2.5
10.2.6
Cyclone Property View.........................................................8
Design Tab ...........................................................................9
Rating tab...........................................................................12
Worksheet Tab ...................................................................14
Performance Tab................................................................15
Dynamics Tab ....................................................................15
10.3 Hydrocyclone ...............................................................................16
10.3.1
10.3.2
10.3.3
10.3.4
10.3.5
10.3.6
Hydrocyclone Property View..............................................16
Design Tab .........................................................................17
Rating tab...........................................................................20
Worksheet Tab ...................................................................21
Performance Tab................................................................22
Dynamics Tab ....................................................................22
10.4 Rotary Vacuum Filter...................................................................23
10.4.1
10.4.2
10.4.3
10.4.4
10.4.5
Rotary Vacuum Filter Property View ..................................23
Design Tab .........................................................................24
Rating tab...........................................................................27
Worksheet Tab ...................................................................29
Dynamics Tab ....................................................................29
10-1
10-2
Solid
10.5 Baghouse Filter ........................................................................... 29
10.5.1
10.5.2
10.5.3
10.5.4
10.5.5
10.5.6
10-2
Baghouse Filter Property View .......................................... 29
Design Tab......................................................................... 31
Rating Tab ......................................................................... 33
Worksheet Tab................................................................... 33
Performance Tab ............................................................... 34
Dynamics Tab .................................................................... 34
Solid Separation Operations
10-3
10.1 Simple Solid Separator (Simple
Filter)
The Simple Solid Separator performs a non-equilibrium separation of a
stream containing solids. This operation does not perform an energy
balance, as the separation is based on your specified carry over of solids
in the vapour and liquid streams, and liquid content in the solid
product. It should be used when you have an existing operation with
known carry over or entrainment in the product streams. The solids
being separated must be previously specified and installed as
components in the stream attached to this operation.
10.1.1 Simple Solid Separator Property View
You can also add a simple
solid separator by clicking
the F12 hot key.
There are two ways that you can add a Simple Solid Separator to your
simulation:
You can also open the
Object Palette by clicking the
F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Solids Handling radio button.
3.
From the list of available unit operations, select Simple Solid
Separator.
4.
Click the Add button. The Simple Solid Separator property view
appears.
OR
Solid Ops
icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Click on the Solid Ops icon. The Solid Operations Palette appears.
Simple Solid Separator icon
10-3
10-4
Simple Solid Separator (Simple Filter)
7.
Double-click the Simple Solid Separator icon. The Simple Solid
Separator property view appears.
Figure 10.1
You can also delete a
Simple Solid Separator by
clicking on the Simple Solid
Separator icon on the PFD
and pressing the DELETE
key.
You can delete the operation by clicking the Delete button. HYSYS will
ask you to confirm the deletion.
To ignore the Simple Solid Separator during calculations, activate the
Ignored checkbox. HYSYS completely disregards the operation until you
restore it to an active state by deactivating the checkbox.
10.1.2 Design Tab
The Design tab contains five pages:
•
•
•
•
•
10-4
Connections
Parameters
Splits
User Variables
Notes
Solid Separation Operations
10-5
Connections Page
You can specify the name of the operation, feed stream, and product
streams (Vapour, Liquid, Solids) on the Connections page.
Figure 10.2
Parameters Page
You can specify the pressure drop on the Parameters page.
Figure 10.3
10-5
10-6
Simple Solid Separator (Simple Filter)
Splits Page
Figure 10.4
On the Splits page, you must choose the split method by defining a Type
of Fraction. The types of fraction are described in the table below.
Object
Definition
Split Fractions
Specify the fractional distribution of solids from the feed into the
vapour and liquid product streams. The solids fraction in the
bottoms are calculated by HYSYS. You must also specify the
fraction of liquid in the bottoms (solid product).
Stream Fractions
Enter the mole, mass or liquid volume fraction specification for
each of the following:
• Total vapour product solids fraction on the specified basis.
• Total liquid product solids fraction on the specified basis.
• Liquid phase fraction in the bottom product.
In the flowsheet, the streams are not reported as single phase, due to the
solid content in the vapour and liquid streams, and the liquid content in
the solid product stream.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
10-6
Solid Separation Operations
10-7
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
10.1.3 Rating Tab
This unit operation currently does not have rating features.
10.1.4 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
10.1.5 Dynamics Tab
This unit operation is currently not available for dynamic simulation.
10.2 Cyclone
The Cyclone is used to separate solids from a gas stream and is
recommended only for particle sizes greater than 5 microns. The
Cyclone consists of a vertical cylinder with a conical bottom, a
rectangular inlet near the top, and an outlet for solids at the bottom of
the cone. It is the centrifugal force developed in the vortex which moves
the particles toward the wall. Particles which reach the wall, slide down
the cone, and so become separated from the gas stream. The solids
being separated must be previously specified and installed as
components in the stream attached to this operation.
10-7
10-8
Cyclone
10.2.1 Cyclone Property View
You can also add a cyclone
by clicking the F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Cyclone to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Solids Handling radio button.
3.
From the list of available unit operations, select Cyclone.
4.
Click the Add button. The Cyclone property view appears.
OR
Solid Ops
icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Click on the Solid Ops icon. The Solid Operations Palette appears.
7.
Double-click the Cyclone icon. The Cyclone property view appears.
Figure 10.5
Cyclone icon
You can also delete a
Cyclone by clicking on the
Cyclone icon on the PFD
and pressing the DELETE
key.
10-8
You can delete the operation by clicking the Delete button. HYSYS will
ask you to confirm the deletion.
To ignore the Cyclone during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation until you restore
it to an active state by deactivating the checkbox.
Solid Separation Operations
10-9
10.2.2 Design Tab
The Design tab contains five pages:
•
•
•
•
•
Connections
Parameters
Solids
User Variables
Notes
Connections Page
You can specify the name of the operation, as well as the feed, vapour
product, and solid product streams on the Connections page.
Figure 10.6
10-9
10-10
Cyclone
Parameters Page
Figure 10.7
On the Parameters page, you can specify the following parameters:
Parameter
Description
Configuration
Select either High Efficiency, High Output or User Defined.
Efficiency Method
Select either the Lapple or the Leith/Licht method. The latter is
a more rigorous calculation as it considers radial mixing effects.
Particle Efficiency
The percent recovery of the specified solid in the bottoms
stream.
The diameter provided, either from the selected component or from the
particle characteristics, is used in the efficiency calculations. For
example, if you select an 85% efficiency, 85% of the solids of the
specified diameter is recovered. All other solids in the inlet stream are
removed at an efficiency related to these parameters.
10-10
Solid Separation Operations
10-11
Solids Page
You can specify the solid characteristics on the Solids page. This page
contains two different views, depending on the radio button you
selected in the Efficiency Basis group.
Figure 10.8
When you select the Single Particle Diameter radio button, the following
solids information can be specified:
Parameter
Description
Solid Name
You must provide either the name of a solid already
installed in the case, or provide a particle diameter and
density.
Particle Diameter and
Particle Density
If you do not choose a solid component, provide the
particle diameter and density.
When you select the Particle Size Distribution radio button, the
following solids information can be specified:
Parameter
Description
Solid Name
You must provide either the name of a solid already
installed in the case, or provide a particle diameter and
density.
Particle Density
If you do not choose a solid component, provide the
particle density.
Particle Size Distribution
If you do not choose a solid component, provide the
minimum or maximum particle size.
10-11
10-12
Cyclone
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
10.2.3 Rating tab
The Rating tab contains two pages:
•
•
Sizing
Constraints
Sizing Page
Select the On radio button to
turn on the Design Mode
option. Select the Off radio
button to turn off the Design
Mode option.
The Sizing page contains two groups:
•
•
Design Mode.Contains two radio buttons: On and Off.
Sizing Ratios. Contains a table.
Figure 10.9
10-12
Solid Separation Operations
10-13
When you select the Off radio button, the Specify Number of Parallel
Cyclones checkbox appears in the Sizing page. Activate the checkbox if
you want to specify the number of parallel Cyclones in the flowsheet.
The table below describes the parameters available on the page:
Parameter
Description
Configuration
Select High Output, High Efficiency, or User Defined. This
is also defined on the Parameters page.
Inlet Width Ratio
The ratio of the inlet width to the body diameter (must be
between 0 and 1).
The value must be less than the Total Height Ratio
Inlet Height Ratio
The ratio of the inlet height to the body diameter.
Cyclone Height Ratio
The ratio of the Cyclone height to the body diameter. The
Cyclone is the conical section at the bottom of the entire
operation.
Gas Outlet Length Ratio
The ratio of the gas outlet length to the body diameter.
Gas Outlet Diameter
Ratio
The ratio of the gas outlet diameter to the body diameter
(must be between 0 and 1).
The value must be less than the Total Height Ratio
Total Height Ratio
The ratio of the total height of the apparatus to the body
diameter.
Solids Outlet Diameter
Ratio
The ratio of the solids outlet diameter to the body diameter.
Body Diameter
If Design Mode is on, this is automatically calculated,
within the provided constraints. If Design Mode is off, then
you can specify this value.
# Parallel Cyclones
If Design Mode is on, this field displays the number of
parallel Cyclones (if any) attached to the unit operation. If
Design Mode is off and the Specify Number of Parallel
Cyclones checkbox is activated, you can specify this value.
10-13
10-14
Cyclone
Constraints Page
On the Constraints page, you can specify the minimum and maximum
diameter for the Cyclone. The page is also applicable only when the On
radio button is selected in the Design Mode group.
Figure 10.10
The Maximum Pressure Drop and Maximum Number of Cyclones is set
on this page. These are used in the calculations to determine the
minimum number of Cyclones needed to complete the separation.
10.2.4 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
10-14
Solid Separation Operations
10-15
10.2.5 Performance Tab
The Performance tab contains the Results page.
Results Page
The Results page displays the calculated pressure drop, overall
efficiency, and the number of parallel Cyclones.
Figure 10.11
10.2.6 Dynamics Tab
This unit operation is currently not available for dynamic simulation.
10-15
10-16
Hydrocyclone
10.3 Hydrocyclone
The Hydrocyclone is essentially the same as the cyclone, the primary
difference being that this operation separates the solid from a liquid
phase, rather than a gas phase. The solids being separated must be
previously specified and installed as components in the stream attached
to this operation.
10.3.1 Hydrocyclone Property View
You can also add a
hydrocyclone by clicking the
F12 hot key.
You can also open the
Object Palette by clicking the
F4 hot key.
There are two ways that you can add a Hydrocyclone to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Solids Handling radio button.
3.
From the list of available unit operations, select Hydrocyclone.
4.
Click the Add button. The Hydrocyclone property view appears.
OR
Solid Ops
icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Click on the Solid Ops icon. The Solid Operations Palette appears.
7.
Double-click the Hydrocyclone icon. The Hydrocyclone property
view appears.
Figure 10.12
Hydrocyclone icon
10-16
Solid Separation Operations
You can also delete a
Hydrocyclone by clicking on
the Hydrocyclone icon on
the PFD and pressing the
DELETE key.
10-17
You can delete the operation by clicking the Delete button. HYSYS will
ask you to confirm the deletion.
To ignore the Hydrocyclone during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation until you restore
it to an active state by deactivating the checkbox.
10.3.2 Design Tab
The Design tab contains five pages:
•
•
•
•
•
Connections
Parameters
Solids
User Variables
Notes
Connections Page
On the Connections page, you can specify the name of the operation, as
well as the feed, liquid product, and solid product streams.
Figure 10.13
10-17
10-18
Hydrocyclone
Parameters Page
Figure 10.14
On the Parameters page, you can specify the following parameters:
Parameter
Description
Configuration
Select either Mode 1, Mode 2 or User Defined.
Particle Efficiency
The percent recovery of the specified solid in the bottoms
stream.
The diameter provided, either from the selected component or from the
particle characteristics, is used in the efficiency calculations. For
example, if you select an 85% efficiency, 85% of the solids of the
specified diameter are recovered. All other solids in the inlet stream are
removed at an efficiency related to these parameters.
10-18
Solid Separation Operations
10-19
Solids Page
Figure 10.15
On the Solids page, the following solids information can be specified:
Parameter
Description
Solid Name
You must provide either the name of a solid already installed in
the case, or provide a particle diameter and density.
Particle Diameter
and Particle Density
If you do not specify a Solid Name, provide the particle
diameter and density.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
10-19
10-20
Hydrocyclone
10.3.3 Rating tab
The Rating tab contains two pages
•
•
Sizing
Constraints
Sizing Page
Select the On radio button to
turn on the Design Mode
option. Select the Off radio
button to turn off the Design
Mode option.
The Sizing page contains two groups.
•
•
Design Mode. Contains two radio buttons: On and Off.
Sizing Ratio. Contains a table.
Figure 10.16
The table below describes the parameters available on the page:
10-20
Parameter
Description
Configuration
Select Mode 1, Mode 2 or User Defined. This is also
defined on the Parameters page.
Inlet Diameter Ratio
The ratio of the inlet diameter to the body diameter.
Included Angle (Degrees)
The angle of the cyclone slope to the vertical.
Overflow Length Ratio
The ratio of the overflow length to the body diameter.
Overflow Diameter Ratio
The ratio of the overflow diameter to the body diameter.
Total Height Ratio
The ratio of the total height of the apparatus to the body
diameter.
Underflow Diameter
Ratio
The ratio of the underflow diameter to the body diameter.
Body Diameter
If Design Mode is on, then this is automatically calculated,
within the provided constraints. If Design Mode is off, then
you can specify this value.
Solid Separation Operations
10-21
Constraints Page
You can specify the minimum and maximum diameter for the Cyclone,
applicable only when the On radio button is selected in the Design
Mode group.
Figure 10.17
The Maximum Pressure Drop and Maximum Number of Cyclones can
also be set on this page.
10.3.4 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
10-21
10-22
Hydrocyclone
10.3.5 Performance Tab
The Performance tab consists of the Results page.
Results Page
The calculated pressure drop, overall efficiency, and the number of
parallel cyclones appear on this page.
Figure 10.18
10.3.6 Dynamics Tab
This unit operation is currently not available for dynamic simulation.
10-22
Solid Separation Operations
10-23
10.4 Rotary Vacuum Filter
The Rotary Vacuum Filter assumes that there is 100% removal of the
solid from the solvent stream. This operation determines the retention
of solvent in the particle cake, based on the particle diameter and
sphericity of your defined solid(s). The diameter and sphericity
determines the capillary space in the cake and thus the solvent
retention. The solids being separated must be previously specified and
installed as components in the stream attached to this operation.
10.4.1 Rotary Vacuum Filter Property View
You can also add a rotary
vacuum filter by clicking the
F12 hot key.
There are two ways that you can add a Rotary Vacuum Filter to your
simulation:
You can also open the
Object Palette by clicking the
F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Solids Handling radio button.
3.
From the list of available unit operations, select Rotary Vacuum
Filter.
4.
Click the Add button. The Rotary Vacuum Filter property view
appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Click on the Solid Ops icon. The Solid Operations Palette appears.
Solid Ops
icon
Rotary Vacuum Filter icon
10-23
10-24
Rotary Vacuum Filter
7.
Double-click the Rotary Vacuum Filter icon. The Rotary Vacuum
Filter property view appears.
Figure 10.19
You can also delete a Rotary
Vacuum Filter by clicking on
the Rotary Vacuum Filter
icon on the PFD and
pressing the DELETE key.
You can delete the operation by clicking the Delete button. HYSYS will
ask you to confirm the deletion.
To ignore the operation during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation until you restore
it to an active state by deactivating the checkbox.
10.4.2 Design Tab
The Design tab contains four pages:
•
•
•
•
10-24
Connections
Parameters
User Variables
Notes
Solid Separation Operations
10-25
Connections Page
On the Connections page, you can define the operation name, as well as
the feed, liquid product, and solids product streams.
Figure 10.20
Parameters Page
Figure 10.21
10-25
10-26
Rotary Vacuum Filter
The Rotary Vacuum Filter parameters are described in the table below:
Parameter
Description
Cycle Time
The complete time for a cycle (one complete revolution of the
cylinder).
Dewatering
The portion of the cycle between the time the cake comes out of the
liquid to the time it is scraped, expressed as a percentage of the
overall cycle time.
Submergence
The percentage of the overall cycle for which the cake is
submerged.
Pressure Drop
Pressure drop across the filter.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
10-26
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Solid Separation Operations
10-27
10.4.3 Rating tab
The Rating tab contains two pages:
•
•
Sizing
Cake
Sizing Page
Figure 10.22
You can specify the following filter size parameters:
Parameter
Description
Filter Radius
The radius of the filter. This defines the circumference of the drum.
Filter Width
The horizontal filter dimension.
Filter Area
The area of the filter.
10-27
10-28
Rotary Vacuum Filter
Cake Page
The Cake page consists of two groups:
•
•
Cake Properties
Resistance.
Figure 10.23
You can define the cake properties in the Cake Properties group.
Property
Description
Mass Fraction of Cake
The final solid mass fraction.
Thickness
The thickness of the cake.
Porosity
The overall void space in the cake.
Irreducible Saturation
The solvent retention at infinite pressure drop.
Permeability
If you do not provide a value, HYSYS calculates this from
the sphericity and diameter of the solid.
You can define the resistance or use a resistance equation in the
Resistance group. Activating the Use Resistance Equation checkbox,
which allows HYSYS to calculate the resistance value based on the
Filtration Resistance equation.
The Filtration Resistance equation is as follows:
Resistance = a(dP)s
where:
a, s = constants
dP = pressure drop
10-28
(10.1)
Solid Separation Operations
10-29
10.4.4 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
10.4.5 Dynamics Tab
This unit operation is currently not available for dynamic simulation.
10.5 Baghouse Filter
The Baghouse Filter model is based on empirical equations. It contains
an internal curve relating separation efficiency to particle size. Based on
your particle diameter, the reported separation efficiency for your solids
is determined from this curve. The solids being separated must be
previously specified and installed as components in the stream attached
to this operation.
10.5.1 Baghouse Filter Property View
You can also add a
baghouse filter by clicking
the F12 hot key.
There are two ways that you can add a Baghouse Filter to your
simulation:
You can also open the
Object Palette by clicking the
F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Solids Handling radio button.
3.
From the list of available unit operations, select Baghouse Filter.
4.
Click the Add button. The Baghouse Filter property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
10-29
10-30
Baghouse Filter
6.
Click on the Solid Ops icon. The Solid Operations Palette appears.
7.
Double-click the Baghouse Filter icon. The Baghouse Filter property
view appears.
Figure 10.24
Solid Ops
icon
Baghouse Filter icon
To ignore the Baghouse Filter during calculations, activate the Ignored
checkbox. HYSYS completely disregards the operation until you restore
it to an active state by deactivating the checkbox.
You can also delete a
Baghouse Filter by clicking
on the Baghouse Filter icon
on the PFD and pressing the
DELETE key.
10-30
You can delete the operation by clicking the Delete button. HYSYS will
ask you to confirm the deletion
Solid Separation Operations
10-31
10.5.2 Design Tab
The Design tab contains four pages:
•
•
•
•
Connections
Parameters
User Variables
Notes
Connections Page
On the Connections page, you can specify the name of the operation, as
well as the feed, vapour product, and solid product streams.
Figure 10.25
10-31
10-32
Baghouse Filter
Parameters Page
Figure 10.26
On the Parameters page, you must specify the following information:
Parameter
Description
Configuration
When you make a change to any of the parameters, the
configuration changes to User Defined. Select Default to
revert to the HYSYS defaults.
Clean Bag Pressure Drop
The pressure drop across a clean bag.
Dirty Bag Pressure Drop
The pressure drop across a dirty bag. This value must
be greater than the Clean Bag Pressure Drop.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
10-32
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
Solid Separation Operations
10-33
10.5.3 Rating Tab
The Rating tab consists of the Sizing page.
Sizing Page
Figure 10.27
On the Sizing page, the following parameters can be specified:
Parameter
Description
Maximum Gas Velocity
Maximum velocity of gas in the Baghouse Filter.
Bag Filter Area
Filter Area for each bag.
Bag Diameter
Bag Diameter.
Bags per Cell
Number of bags per filter cell.
Bag Spacing
Spacing between the bags.
10.5.4 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the operation.
Refer to Section 1.2.3 - Worksheet Tab for more information.
10-33
10-34
Baghouse Filter
10.5.5 Performance Tab
The Performance tab consists of the Results page.
Results page
The following Filtration results appear on this page:
•
•
•
•
•
Filtration Time
Number of Cells
Area/Cell
Total Cell Area
Particle Diameter
Figure 10.28
10.5.6 Dynamics Tab
This unit operation is currently not available for dynamic simulation.
10-34
Electrolyte Operations
11-1
11 Electrolyte Operations
11.1 Introduction ....................................................................................2
11.1.1 Adding Electrolyte Operations..............................................3
11.2 Neutralizer Operation ....................................................................3
11.2.1
11.2.3
11.2.3
11.2.4
Design Tab ...........................................................................6
Worksheet Tab .....................................................................9
Worksheet Tab .....................................................................9
Dynamic Tab ......................................................................10
11.3 Precipitator Operation .................................................................10
11.3.1
11.3.2
11.3.3
11.3.4
Design Tab .........................................................................12
Rating Tab ..........................................................................16
Worksheet Tab ...................................................................16
Dynamic Tab ......................................................................16
11.4 Crystalizer Operation...................................................................17
11.4.1
11.4.2
11.4.3
11.4.4
Design Tab .........................................................................19
Rating Tab ..........................................................................22
Worksheet Tab ...................................................................23
Dynamic Tab ......................................................................23
11-1
11-2
Introduction
11.1 Introduction
Press F4 to open the Object
Palette. The Object Palette
shows the unit operations
available in OLI Electrolyte
property package by active
icons.
Most HYSYS unit operations can be used when working with the OLI
Electrolyte property package.
The following HYSYS unit operations are not available in the OLI
Electrolyte property package:
•
•
•
•
•
The electrolyte operations
are only available if your
case is an electrolyte system
(the selected fluid package
must support electrolyte).
Pipe Segment
Reactors
Short Cut Column
Three Phase Distillation
Compressible Gas Pipe
In addition to the typical HYSYS unit operations, three new electrolyte
simulations, specific to OLI Electrolyte property package have been
added. The table below describes the three new electrolyte simulations.:
Operation
11-2
Icon
Description
Neutralizer
Neutralizer operation is used to control PH value for
a process material stream.
Precipitator
Precipitator operation is used to achieve a specified
aqueous ionic species concentration in its product
stream.
Crystalizer
Crystallizer operation is used to estimate and control
solid concentration in a product stream.
Electrolyte Operations
11-3
11.1.1 Adding Electrolyte Operations
You can also add an
electrolyte operation by
clicking the F12 hot key.
There are two ways you can add an electrolyte operation to your
simulation:
You can also open the
Object Palette by clicking the
F4 hot key.
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Electrolyte Equipment radio button.
3.
From the list of available unit operations, select the electrolyte
operation you want.
4.
Click the Add button. The property view for the selected electrolyte
operation appears.
OR
Electrolyte Ops icon
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Click the Electrolyte Ops icon. The electrolyte object palette
appears.
7.
Double-click the electrolyte operation you want. The property view
for the selected electrolyte operation appears.
The following sections describe the function of each electrolyte unit
operation.
11.2 Neutralizer Operation
The Neutralizer operation models the neutralization of a fully defined
inlet stream, and allows you to adjust the pH value in the effluent
stream. The Neutralizer property view contains four tabs:
•
•
•
•
Design
Rating
Worksheet
Dynamics
11-3
11-4
Neutralizer Operation
Theory
The figure below represents the neutralizer model. Through adjusting
the Reagent Stream variables (flow rate), the PH value for the targeting
stream (Liquid Stream) could be controlled at the level as required.
Figure 11.1
•
•
•
•
•
Inlet Stream. At least one inlet stream.
Reagent Stream. Reagent stream must be a free stream, that is,
not attached to any other unit operations.
Product Stream. A Neutralizer has two product streams, a
vapour stream and a liquid stream. The liquid stream controls the
pH value.
pH. The liquid stream’s pH value that is to be controlled must fall
in the range between the pH values of the Reagent and inlet
streams to guarantee the solution.
Q. The energy stream is optional. When no energy stream is
attached, an adiabatic operation is assumed.
The Neutralizer vessel is modeled as perfect mixing. Heat can be added
or removed from the Neutralizer, and a simple constant duty model is
assumed.
Boundary Condition
Since the electrolyte flow sheet implements a forward calculation only,
the Neutralizer does not solve until both inlet and Reagent streams are
defined. If the energy stream is not specified, the neutralizer is treated as
an adiabatic one. If the energy stream is specified, you must specify
either the Neutralizer temperature or the duty of the energy stream.
Pressure drop of the neutralizer must be specified or can be calculated
out from the inlet and product streams.
11-4
Electrolyte Operations
11-5
Solving Options
The Neutralizer has two different solving options, depending on what
you specify.
Option 1 (Targeting pH Value is Not Specified)
If the targeting pH value is not specified, the Neutralizer operates as a
mixer for the inlet and Reagent streams. The product stream accepts the
mixed result as is.
Option 2 (Targeting pH Value is Specified)
If the targeting pH value is specified, the flow rate of the Reagent stream
must be left unspecified. The Reagent stream is used as an adjusting
variable for neutralizer solver to search for a solution to meet the
targeting pH value at the outlet stream.
Equations
The Neutralizer solves under the constraint of the following equations.
where:
pH product stream – pH specified = 0
(11.1)
pH specified ⊂ { pH inlet stream, pH Reagent stream }
(11.2)
E product stream = E inlet stream + E Reagent stream + E duty
(11.3)
M product stream = M inlet stream + M Reagent stream
(11.4)
E = energy/heat transfer rate
M = mass flow rate
11-5
11-6
Neutralizer Operation
11.2.1 Design Tab
The Design tab contains five pages:
•
•
•
•
•
Connections
Parameters
Solver
User Variables
Notes
Connections Page
You can specify the inlet stream, outlet stream, and energy stream on the
Connections page.
Figure 11.2
To ignore the electrolyte
operations during
calculations, activate the
Ignored checkbox. HYSYS
completely disregards the
operation until you restore it
to an active state by
deactivating the checkbox.
11-6
Object
Description
Name
You can change the name of the operation by typing a new name
in the field.
Inlet
You can enter one or more inlet streams in this table, or use the
drop-down list to select the streams you want.
Reagent Stream
You can enter a name for the reagent stream or use the dropdown list. Reagent stream must be a free stream, that is, not
attached to any other unit operations.
Vapour Outlet
You can type the name of the vapour product stream or use the
drop-down list to select a pre-defined stream.
Liquid Outlet
You can type the name of the product stream in this field or use
the drop-down list to select a pre-defined stream.
Electrolyte Operations
11-7
Object
Description
Energy (Optional)
You can add an energy stream to the operation by selecting an
energy stream from the drop-down list or typing the name for a
new energy stream.
Fluid Package
Displays the fluid package currently being used by the operation.
You can select a different fluid package from the drop-down list.
Parameters Page
On the Parameters page, you can specify the pressure drop and an initial
pH value. This page also displays the degrees of freedom for the
operation at the current setting, and the actual pH balance in the
operation when the operation reaches a solution.
Figure 11.3
Object
Description
Delta P
You must specify the pressure drop for the Neutralizer or specify inlet and
product streams with known pressure.
pH Spec
You can specify the product stream’s pH value in this field.
The pH value that is to be controlled must fall in the range between the pH
values of the Reagent and Inlet Streams for calculations to converge.
The pH value in a solution is defined in a mathematical format:
pH = – log
where:
10 [ H
+
]
(11.5)
[H+] = concentration of H+ in a solution, mol/l
11-7
11-8
Neutralizer Operation
According to Equation (11.2), the pH (specified) value must be specified
between the pH values of the inlet and the Reagent streams. An
adjustment of Reagent Stream’s variables, for example, temperature,
pressure, and compositions, can bracket the pH (specified) value to
meet the constraint Equation (11.2). As soon as the specified pH value is
bracketed according to Equation (11.2), the pH value of the product
stream in Equation (11.1) can be obtained by adjusting the flow rate of
the Reagent stream.
Solver Page
On the Solver page, you can specify the upper and lower bounds of the
manipulated variable, the tolerance of specified variable, and the
maximum iterations/steps of calculations the solver performs before
stopping.
Figure 11.4
Currently only the flow rate of a defined Reagent stream is used as an
adjustable variable to the solver. Here a defined Reagent stream means
that the stream can be flashed to get a solution with the specified
variables meeting the degree of freedom. According to HYSYS, a defined
stream can have the following variables:
•
•
•
•
•
•
11-8
T. Stream Temperature
P. Stream Pressure
F. Stream Flow Rate
x. Stream Component Compositions
H. Stream Enthalpy
V. Stream Vapor Fraction
Electrolyte Operations
11-9
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
11.2.2 Rating Tab
Neutralizer operation currently does not support any rating
calculations.
11.2.3 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Neutralizer.
Refer to Section 1.2.3 - Worksheet Tab for more information.
Figure 11.5
11-9
11-10
Precipitator Operation
11.2.4 Dynamic Tab
Neutralizer operation currently does not support dynamic mode.
11.3 Precipitator Operation
The Precipitator models the precipitation of a selected ion in a stream
entering the operation to achieve a specified target concentration in the
effluent stream. The Precipitator operation contains four tabs:
•
•
•
•
Design
Rating
Worksheet
Dynamics
Theory
The figure below represents the precipitator model. Through adjusting
the flow rate of the Reagent stream, the concentration of the targeting
ion could be controlled at the desired level as you require in the outlet
stream. To ensure that the Precipitator functions properly, the ions in
the Reagent stream must be capable of reacting with the target ion
under the specified operation condition. The formation of a precipitate
in the outlet stream reduces the target ion concentration that entered
the operation in the inlet stream.
Figure 11.6
11-10
Electrolyte Operations
•
•
•
•
•
11-11
Inlet Stream. At least one inlet stream.
Reagent Stream. Reagent stream must be a free stream, that is,
not attached to any other unit operations.
Liquid Stream. A Precipitator must have one liquid stream
(contains liquid and solid) that is a targeting stream for the control
of ion concentration through precipitation.
Ion Concentration. The product stream’s ion concentration
value can be controlled by dilution or precipitation.
Q. The energy stream is optional.
The Precipitator is modeled as a perfect mixing in HYSYS. Heat can be
added or removed from the precipitator through a duty stream, and a
simple constant duty model is assumed.
Boundary Condition
Since the electrolyte flow sheet implements a forward calculation only,
the Precipitator does not solve until both inlet and Reagent streams are
defined. If the energy stream is not specified, the precipitator is treated
as an adiabatic one. If the energy stream is specified, you must specify
either the Precipitator temperature or the duty of the energy stream.
Pressure drop of the Precipitator must be either specified or can be
calculated from the inlet and product streams.
Solving Options
The Precipitator has two different solving options, depending on what
you specify.
Option 1 (Targeting Ionic Species Not Specified)
If the targeting ionic species is not specified, the Precipitator simply
mixes the inlet stream with the Reagent stream. The product stream
accepts the mixed result as is.
Option 2 (Targeting Ionic Species is Specified)
If the targeting ionic species is specified for the control of its
concentration, the flow rate of the Reagent stream is used as iterative
variables for the precipitator solver to search for a solution.
11-11
11-12
Precipitator Operation
Equations
The precipitator solves under the constraint of the following equations:
C ion ( product stream ) < C ion ( specified )
(11.6)
E product stream + E vapour stream + E duty = E inlet stream + E Reagent stream
(11.7)
M product stream + M vapour stream = M inlet stream + M Reagent stream
(11.8)
where:
Cion = concentration of the targeting ion species
E = energy/heat transfer rate
M = mass flow rate
11.3.1 Design Tab
The Design tab contains five pages:
•
•
•
•
•
11-12
Connections
Parameters
Solver
User Variables
Notes
Electrolyte Operations
11-13
Connections Page
You can specify the inlet stream, outlet stream, and energy stream on the
Connections page.
Figure 11.7
To ignore the electrolyte
operations during
calculations, activate the
Ignored checkbox. HYSYS
completely disregards the
operation until you restore it
to an active state by
deactivating the checkbox.
Object
Description
Name
You can change the name of the operation by typing a new
name in the field.
Inlet
You can enter one or more inlet streams in this table, or use the
drop-down list to select the streams you want.
Reagent Stream
You can enter a name for the reagent stream or use the dropdown list. Reagent stream must be a free stream, that is, not
attached to any other unit operations.
Vapour Outlet
You can enter the name of the vapour product stream or use
the drop-down list to select a pre-defined stream.
Liquid Outlet
You can enter the name of the product stream in this field or
use the drop-down list to select a pre-defined stream.
Energy (Optional)
You can add an energy stream to the operation by selecting an
energy stream from the drop-down list or typing the name for a
new energy stream.
Fluid Package
Displays the fluid package currently being used by the
operation. You can select a different fluid package from the
drop-down list.
11-13
11-14
Precipitator Operation
Parameters Page
On the Parameters page, you can specify the pressure drop, select the
ion to be controlled, and specify the ion concentration in the liquid
stream. This page also displays the degrees of freedom for the operation
at the current setting, and the actual ion concentration value in the
operation when the operation has reached a solution.
Figure 11.8
11-14
Object
Description
Delta P
You must specify the pressure drop for the Precipitator or specify
inlet and product streams with known pressure.
Controlled Ion
Select the ion component you want to control from the drop-down
list, or type the name of the ion component in the field.
Ion Spec
The concentration of ion from the inlet stream can be controlled via
the following exercises:
• Dilution. If the mixing of reagent and inlet streams does not
produce the ion to be controlled and the ion concentration in
the Reagent stream is less than that in the inlet stream, an
increase of flow rate of the Reagent stream can achieve the
target. In this case, the Chemistry Model does not have to
include Solid.
• Precipitation. Form precipitator by mixing inlet and Reagent
streams. The change of Regent stream variables:
temperature, pressure, flow rate or composition may achieve
the target. To form precipitator, OLI chemistry model must
include Solid.
Electrolyte Operations
11-15
Solver Page
On the Solver page, you can specify the upper and lower bounds of the
manipulated variable, the tolerance of specified variable, and the
maximum iterations/steps of calculations the solver performs before
stopping.
Figure 11.9
Currently, the flow rate of the Reagent stream is the manipulated
variable used by the precipitator solver to search for a solution.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
11-15
11-16
Precipitator Operation
11.3.2 Rating Tab
Precipitator operation currently does not support any rating
calculations.
11.3.3 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Precipitator.
Refer to Section 1.2.3 - Worksheet Tab for more information.
11.3.4 Dynamic Tab
Precipitator operation currently does not support dynamic mode.
11-16
Electrolyte Operations
11-17
11.4 Crystalizer Operation
The Crystallizer operation models the crystallization of a fully defined
inlet stream to attain a specified amount of selected solids
concentration that is present in the effluent. The Crystalizer operation
contains four tabs: Design, Rating, Worksheet, and Dynamics.
Theory
The figure below represents the crystallizer model. A Crystallizer has a
product stream that contains liquid and solid. By adjusting the
operation condition like Crystallizer temperature and pressure or heat
duty, the amount of solid or solid component product in the liquid
stream can be controlled or estimated.
Figure 11.10
The Crystallizer vessel is modeled as a perfect mixing in HYSYS. Heat
can be added or removed from the Crystallizer, and a simple constant
duty model is assumed.
11-17
11-18
Crystalizer Operation
Boundary Condition
Since the electrolyte flow sheet implements a forward calculation only,
the Crystallizer does not solve until the Inlet Stream is defined. If the
energy stream is not specified, the crystallizer is treated as an adiabatic
one. You must specify two of the following to define the boundary
condition for crystallizer solver to proceed:
•
•
•
•
•
T. Crystallizer temperature
P or DeltP. Crystallizer’s pressure or pressure drop
E. Heat Duty
Fcry. Crystal product flow rate (total or a specific component)
Fvap. Vapor flow
Equations
The crystallizer solves under the constraint of mass and energy balance
equations:
E product stream + E vapour stream = E inlet stream + E duty
(11.9)
M product stream + M vapour stream = M inlet stream
(11.10)
with the target solid equation:
F solid ( product stream ) – F solid ( specified ) = 0
where:
(11.11)
Fsolid(product stream) = solid flow rate in the outlet liquid stream
Fsolid(specified) = desired solid flow rate in the outlet liquid stream
E = energy/heat transfer rate
M = mass flow rate
11-18
Electrolyte Operations
11-19
11.4.1 Design Tab
The Design tab contains five pages:
•
•
•
•
•
Connections
Parameters
Solver
User Variables
Notes
Connections Page
You can specify the inlet stream, outlet stream, and energy stream on the
Connections page.
Figure 11.11
To ignore the electrolyte
operations during
calculations, activate the
Ignored checkbox. HYSYS
completely disregards the
operation until you restore it
to an active state by
deactivating the checkbox.
Object
Description
Name
You can change the name of the operation by typing a new
name in the field.
Inlet
You can enter one or more inlet streams in this table, or use the
drop-down list to select the streams you want.
Vapour Outlet
You can enter the name of the vapour product stream or use
the drop-down list to select a pre-defined stream.
Liquid Outlet
You can enter the name of the product stream in this field or
use the drop-down list to select a pre-defined stream.
11-19
11-20
Crystalizer Operation
Object
Description
Energy (Optional)
You can add an energy stream to the operation by selecting an
energy stream from the drop-down list or typing the name for a
new energy stream.
Fluid Package
Displays the fluid package currently being used by the
operation. You can select a different fluid package from the
drop-down list.
Parameters Page
The flow rate of crystal
product depends on the
solubility of the product at
the crystallizer’s operation
condition.
On the Parameters page, you can specify the pressure drop and solid
output flow rate.
Figure 11.12
The four radio buttons allow you to control the specified solid output in
the liquid stream by crystallization operation:
•
•
•
•
Mole Flow. Select this radio button to specify the flow rate value
in mole basis.
Mass Flow. Select this radio button to specify the flow rate value
in mass basis.
Component. Select this radio button to control a specified solid
component in the operation.
Total. Select this radio button to control the total solid flow rate in
the liquid stream.
This page also displays the degrees of freedom for the operation at the
current setting.
11-20
Electrolyte Operations
11-21
Solver Page
On the Solver page, you can specify the upper and lower bounds of the
manipulated variable, the tolerance of specified variable, and the
maximum iterations/steps of calculations the solver performs before
stopping.
Figure 11.13
Crystallizer operates on various boundary conditions. The following
table lists all the possible options. As soon as the operation condition (as
listed in the Specified Variables column) is known, the crystallizer will
start to solve. The Crystallizer Calculates column lists some of the
calculation variables for the operation.
Specified Variables
Crystallizer Calculates
Temperature & Pressure
Heat Duty, Crystal product flow rate, Vapour flow rate
Temperature & Heat Duty
Pressure, Crystal product flow rate, Vapor flow rate
Temperature & Crystal
product flow rate
Pressure, Heat Duty, Vapor flow rate
Temperature & Vapour flow
rate
Pressure, Crystal product flow rate, Heat Duty
Pressure & Heat Duty
Temperature, Crystal product flow rate, Vapor flow
rate
Pressure & Crystal product
flow rate
Temperature, Heat Duty, Vapor flow rate
Pressure & Vapour flow rate
Temperature, Crystal product flow rate, Heat Duty
11-21
11-22
Crystalizer Operation
The bounds for the Manipulated Variables and tolerances for the Target
Variables are shown on the Solver tab and are user-modifiable. As well,
the Active status for the Manipulated Variable used by the solver is
shown. However, this flag is meant for displaying information only thus
cannot be changed.
User Variables Page
The User Variables page allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
Notes Page
For more information, refer
to Section 7.20 - Notes
Manager in the User Guide.
The Notes page provides a text editor where you can record any
comments or information regarding the specific unit operation, or your
simulation case in general.
11.4.2 Rating Tab
Crystalizer operation currently does not support any rating calculations.
11-22
Electrolyte Operations
11-23
11.4.3 Worksheet Tab
The PF Specs page is
relevant to dynamics cases
only.
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Crystallizer.
Refer to Section 1.2.3 - Worksheet Tab for more information.
The Crystallizer Worksheet tab also has one extra page called the Solids
page. On the Solids page, you can view the precipitate molar and mass
flow rates.
Figure 11.14
11.4.4 Dynamic Tab
Crystalizer operation currently does not support dynamic mode.
11-23
11-24
11-24
Crystalizer Operation
Logical Operations
12-1
12 Logical Operations
12.1 Adjust..............................................................................................4
12.1.1
12.1.2
12.1.3
12.1.4
12.1.5
12.1.6
12.1.7
12.1.8
Adjust Property View............................................................4
Connections Tab ..................................................................5
Parameters Tab....................................................................9
Monitor Tab ........................................................................15
User Variables Tab .............................................................16
Starting the Adjust..............................................................16
Individual Adjust .................................................................17
Multiple Adjust....................................................................18
12.2 Balance .........................................................................................19
12.2.1
12.2.2
12.2.3
12.2.4
12.2.5
12.2.6
Balance Property View.......................................................20
Connections Tab ................................................................21
Parameters Tab..................................................................22
Worksheet Tab ...................................................................27
Stripchart Tab .....................................................................27
User Variables Tab .............................................................27
12.3 Boolean Operations.....................................................................28
12.3.1 Boolean Logic Blocks Property View .................................29
12.3.2 And Gate ............................................................................34
12.3.3 Or Gate ..............................................................................35
12.3.4 Not Gate.............................................................................36
12.3.5 Xor Gate.............................................................................37
12.3.6 On Delay Gate ...................................................................38
12.3.7 Off Delay Gate ...................................................................39
12.3.8 Latch Gate..........................................................................40
12.3.9 Counter Up Gate ................................................................41
12.3.10 Counter Down Gate .........................................................42
12.3.11 Cause and Effect Matrix ...................................................43
12-1
12-2
Logical
12.4 Control Ops.................................................................................. 54
12.4.1
12.4.2
12.4.3
12.4.4
12.4.5
12.4.6
12.4.7
Adding Control Operations................................................. 54
Split Range Controller........................................................ 56
Ratio Controller .................................................................. 77
PID Controller .................................................................... 97
MPC Controller ................................................................ 126
DMC Controller ................................................................ 147
Control Valve.................................................................... 160
12.5 Digital Point ............................................................................... 164
12.5.1
12.5.2
12.5.3
12.5.4
12.5.5
12.5.6
Digital Point Property View .............................................. 164
Connections Tab .............................................................. 165
Parameters Tab................................................................ 166
Stripchart Tab................................................................... 169
User Variables Tab........................................................... 169
Alarm Levels Tab ............................................................. 170
12.6 Parametric Unit Operation ........................................................ 171
12.6.1
12.6.2
12.6.3
12.6.4
Parametric Unit Operation Property View ........................ 171
Design Tab ....................................................................... 172
Parameters Tab................................................................ 180
Worksheet Tab ................................................................. 181
12.7 Recycle ....................................................................................... 182
12.7.1
12.7.2
12.7.3
12.7.4
12.7.5
12.7.7
12.7.8
Recycle Property View..................................................... 183
Connections Tab .............................................................. 184
Parameters Tab................................................................ 185
Worksheet Tab ................................................................. 192
Monitor Tab ...................................................................... 192
Calculations ..................................................................... 193
Reducing Convergence Time .......................................... 194
12.8 Selector Block ........................................................................... 195
12.8.1
12.8.2
12.8.3
12.8.4
12.8.5
12.8.6
12-2
Selector Block Property View........................................... 196
Connections Tab .............................................................. 197
Parameters Tab................................................................ 198
Monitor Tab ...................................................................... 201
Stripchart Tab................................................................... 202
User Variables Tab........................................................... 202
12-3
Logical
12.9 Set ............................................................................................... 203
12.9.1
12.9.2
12.9.3
12.9.4
Set Property View ............................................................ 203
Connections Tab .............................................................. 204
Parameters Tab................................................................ 205
User Variables Tab........................................................... 206
12.10 Spreadsheet............................................................................. 206
12.10.1
12.10.2
12.10.3
12.10.4
Spreadsheet Property View ........................................... 207
Spreadsheet Functions .................................................. 208
Spreadsheet Interface.................................................... 213
Spreadsheet Tabs .......................................................... 219
12.11 Stream Cutter ........................................................................... 226
12.11.1
12.11.2
12.11.3
12.11.4
Stream Cutter Property View ......................................... 226
Design Tab ..................................................................... 234
Transitions Tab ............................................................... 235
Worksheet Tab ............................................................... 241
12.12 Transfer Function .................................................................... 242
12.12.1
12.12.2
12.12.3
12.12.4
12.12.5
Transfer Function Property View.................................... 243
Connections Tab ............................................................ 244
Parameters Tab.............................................................. 245
Stripchart Tab................................................................. 257
User Variables Tab......................................................... 257
12.13 Controller Face Plate .............................................................. 257
12.14 ATV Tuning Technique ............................................................ 262
12-3
12-4
Adjust
12.1 Adjust
The Adjust operation varies the value of one stream variable (the
independent variable) to meet a required value or specification (the
dependent variable) in another stream or operation.
The Adjust is a steady state
operation; HYSYS ignores it
in dynamic mode.
In a flowsheet, a certain combination of specifications may be required,
which cannot be solved directly. These types of problems must be solved
using trial-and-error techniques. To quickly solve flowsheet problems
that fall into this category, the Adjust operation can be used to
automatically conduct the trial-and-error iterations for you.
The Independent variable
cannot be a calculated value;
it must be specified.
The Adjust is extremely flexible. It allows you to link stream variables in
the flowsheet in ways that are not possible using ordinary “physical”
unit operations. It can be used to solve for the desired value of just a
single dependent variable, or multiple Adjusts can be installed to solve
for the desired values of several variables simultaneously.
The Adjust can perform the following functions:
•
•
Adjust the independent variable until the dependent variable
meets the target value.
Adjust the independent variable until the dependent variable
equals the value of the same variable for another object, plus an
optional offset.
12.1.1 Adjust Property View
You can also add an adjust
by clicking the F12 hot key.
You can also open the
Object Palette by clicking
the F4 hot key.
There are two ways that you can add an Adjust to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Logicals radio button.
3.
From the list of available unit operations, select Adjust.
4.
Click the Add button. The Adjust property view appears.
OR
5.
12-4
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
Logical Operations
6.
12-5
Double-click the Adjust icon. The Adjust property view appears.
Figure 12.1
Adjust icon
You can also delete an
Adjust by clicking on the
Adjust icon on the PFD and
pressing the DELETE key.
To delete the Adjust operation, click the Delete button. HYSYS will ask
you to confirm the deletion.
To ignore the Adjust during calculations, activate the Ignored checkbox
at the bottom of the property view. HYSYS completely disregards the
operation until you restore it to an active state by deactivating the
checkbox.
12.1.2 Connections Tab
The first tab of the Adjust property view, as well as several other logicals,
is the Connections tab. The tab contains two pages:
•
•
Connections
Notes
12-5
12-6
Adjust
Connections Page
The Connections page comprises of three groups:
•
•
•
Adjusted Variable
Target Variable
Target Value
Figure 12.2
Adjusted/Target Variable Groups
The Adjusted and Target Variable groups are very similar in appearance,
each containing an Object field, Variable field, and a Select Var button.
The Adjusted Object is the owner of the independent variable which is
manipulated in order to meet the specified value of the “Target”
variable. The Target Object is the owner of the dependent variable
whose value you are trying to meet. A Target Object can be a unit
operation, stream, or a utility.
12-6
Logical Operations
12-7
Selecting Variables Using the Variable Navigator
You select the object and its variable simultaneously by using the
Variable Navigator view, accessed by clicking the Select Var button.
Figure 12.3
The Variable Navigator view consists of four lists, which aid in the
variable selection process by acting as a filter. The lists work
sequentially, meaning a list can only be manipulated if a selection has
been made in the parent list. The table below lists the four lists in
hierarchical order:
List
Descriptions
Flowsheet
Displays the flowsheets and sub-flowsheets contained in the
case.
Note: Columns are also considered as a sub-flowsheet, and
therefore the column name must be selected in this list in order
to select any internal variables.
Object
Once a flowsheet is selected, the Object list displays all the
objects contained by the flowsheet. If the list contains too many
objects, it can be filtered by selecting one of the object type
radio buttons in the Object Filter group.
Variable
Once an object is selected, all the variables contained by the
object become visible.
Variable Specifics
The use of this list is occasionally required to specify some
variable details such as unit operation specifications.
Once the appropriate adjust/target variable is chosen, click the OK
button, and the chosen object and variable appears in the appropriate
fields on the Connections tab.
12-7
12-8
Adjust
Target Value Group
Once the target object and variable are defined, there are three choices
for how the target is to be satisfied:
•
If the target variable is to meet a certain numerical value, select
the User Supplied radio button (as shown in the figure below),
and enter the appropriate value in the Specified Target Value
field.
Figure 12.4
•
If the target variable is to meet the value (or the value plus an
offset) of the same variable in another stream or operation, select
the Another Object radio button (as shown in the figure below),
and select the stream or operation of interest from the Matching
Value Object drop-down list. If applicable, enter an offset in the
available field.
Figure 12.5
•
If the target variable is to meet the value (or the value plus an
offset) of the same variable specified in the spreadsheet, select
the SpreadSheetCell Object radio button (as shown in the figure
below), and select the cell that you want from the Matching Value
Object drop-down list. This allows the SpreadSheetCell to be
attached as an adjusted variable, and source to the target
variable. You can also specify the offset in the available field.
Figure 12.6
12-8
Logical Operations
For more information, refer to
Section 7.20 - Notes
Manager in the User Guide.
12-9
The Notes page provides a text editor, where you can record any
comments or information regarding the operation or to your simulation
case in general.
12.1.3 Parameters Tab
Once you have chosen the dependent and independent variables, the
convergence criteria must be defined. This is usually done on the
Parameters tab.
Figure 12.7
Solving Parameter
Description
Simultaneous Solution
Solves multiple Adjust loops simultaneously. There is only
one simultaneous solving method available therefore when
this checkbox is activated the Method field is no longer
visible.
Method
Sets the (non-simultaneous) solving method: Secant or
Broyden.
Tolerance
Sets the absolute error. In other words, the maximum
difference between the Target Variable and the Target
Value.
Step Size
The initial step size employed until the solution is
bracketed.
Maximum / Minimum
The upper and lower bounds for the independent variable
(optional) are set in this field.
Maximum Iterations
The number of iterations before HYSYS quits calculations,
assuming a solution has not been obtained.
12-9
12-10
Adjust
Solving Parameter
Description
Sim Adj Manager
Opens the Simultaneous Adjust Manager allowing you to
monitor and modify all Adjusts that are selected as
simultaneous.
Optimizer Controlled
Passes a variable and a constant to the optimizer. When
activated the efficiency of the simultaneous Adjust is
increased. This option requires RTO.
Choosing the Solving Methods
The Calculation Level for an
Adjust (accessed under Main
Properties) is 3500,
compared to 500 for most
streams and operations. This
means that the Adjust is
solved last among unknown
operations. You can set the
relative solving order of the
Adjusts by modifying the
Calculation Level.
Adjust loops can be solved either individually or simultaneously. If the
loop is solved individually, you have the choice of either a Secant (slow
and sure) or Broyden (fast but not as reliable) search algorithm. The
Simultaneous solution method uses modified Levenberg-Marquardt
method search algorithm. A single Adjust loop cannot be solved in the
Simultaneous mode. In Simultaneous mode, the adjust variable is
adjusted after the last operation in the flowsheet has solved. The
calculation level has no effect on the Adjust operation in the
Simultaneous mode.
When the Simultaneous Solution checkbox is activated, the Method
field is no longer visible.
Figure 12.8
12-10
Logical Operations
12-11
Simultaneous Adjust Manager
All adjusts from old cases in
Simultaneous mode are
automatically added to the
SAM.
The Simultaneous Adjust Manager (SAM) allows you to monitor, and
modify all Adjusts that are selected as simultaneous. This gives you
access to a more efficient method of calculation, and more control over
the calculations.
The SAM requires two or
more active (i.e., not ignored)
adjusts to solve. If you are
using only one adjust, you
cannot use the SAM.
The SAM is launched by clicking the Sim Adj Manager button on the
Parameters tab, or by selecting Simultaneous Adjust Manager from the
Simulation menu.
The SAM consists of three tabs:
•
•
•
Configuration
Parameters
History
The SAM also consists of the Stop and Start buttons. The ignored
checkbox when activated switches the SAM off, as well as, all of the
Adjusts selected as simultaneous.
Figure 12.9
12-11
12-12
Adjust
Configuration Tab
The Configuration tab displays information regarding Adjusts that have
been selected as simultaneous. You can view the individual Adjusts by
double-clicking on the Adjust name. You can also modify the target
value or matching value object, value, and offset. This tab also allows
you to ignore individual Adjusts.
Parameters Tab
The Parameters tab allows you to modify the tolerance, step size, max,
and min values for each Adjust, as well as, displays the residual, number
of iterations the SAM has taken, and the iteration status. This tab also
allows you to specify some of the calculation parameters as described in
the table below.
Parameter
Description
Type of Jacobian Calculation
Allows you to select one of three Jacobian
calculations:
• ResetJac. Jacobian is fully calculated and
values reset to initial values after each jacobian
calculation step. Most time consuming but most
accurate.
• Continuous. Values are not recalculated
between Jacobian calculation steps. Quickest,
but allows for “drift” in the Jacobian therefore not
as accurate.
• Hybrid. Hybrid of the above two methods.
Type of Convergence
Allows you to select one of three convergence types:
• Specified. SAM is converged when all Adjusts
are within the specified tolerances.
• Norm. SAM is converged when the norm of the
residuals (sums of squares) is less then a user
specified value.
• Either. SAM is converged with which ever of the
above types occurs first.
12-12
Max Step Fraction
The number x step size is the maximum that the
solver is allowed to move during a solve step.
Perturbation Factor
The number x range (Max - Min) or the number x 100
x step size (if no valid range). This is the maximum
that the solver is allowed to move during a Jacobian
step.
Max # of Iterations
Maximum number of iterations for the SAM.
Logical Operations
12-13
History Tab
The History tab only displays
the values from a solve step.
The values calculated during
a Jacobian step can be seen
on the Monitor tab of the
adjust for the individual
results.
The History tab displays the target value, adjusted value, and residual
value for each iteration of the selected Adjust(s). One or more Adjusts
can be displayed by clicking on the checkbox beside the Adjust name.
The Adjusts are always viewed in order from left to right across the page.
For example, if you are viewing Adjust 2 and add Adjust 1 to the view,
Adjust 1 becomes the first set of numbers, and Adjust 2 is shifted to the
right.
Tolerance
For the Adjust to converge, the error in the dependent variable must be
less than the Tolerance.
Error = Dependent Variable Value – Target Value
(12.1)
It is sometimes a good idea to use a relatively loose (large) tolerance
when initially attempting to solve an Adjust loop. Once you determine
that everything is working properly, you can reset the tolerance to the
final design value.
The tolerance and error values are absolute (with the same units as the
dependent variable) rather than relative or percentage-type.
12-13
12-14
Adjust
Step Size
A negative initial step size
causes the first step to
decrement the independent
variable.
The step size you enter is used by the search algorithm to establish the
maximum step size adjustment applied to the independent variable.
This value is used until the solution has been bracketed, at which time a
different convergence algorithm is applied. The value which is specified
should be large enough to permit the solution area to be reached
rapidly, but not so large as to result in an unreasonable overshoot into
an infeasible region. A positive step size initially increments the
independent variable, while a negative value initially decrements the
independent variable. If the Adjust steps away from the solution, the
direction of the steps are automatically reversed.
Before installing the Adjust module, it is often good practice to initialize
the independent variable, and perform one adjust “manually”. Solve
your flowsheet once, and notice the value for the dependent variable,
then self-adjust the independent variable and re-solve the flowsheet.
This assures you that one variable actually affects the other, and also
gives you a feel for the step size you need to specify.
Maximum/Minimum
The Independent variable
must be initialized (have a
starting value) in order for
the Adjust to work.
These two optional criteria are the allowable upper and lower bounds
for the independent variable. If either bound is encountered, the Adjust
stops its search at that point.
Maximum Iterations
The default maximum number of iterations is 10. Should the Adjust
reach this many iterations before converging, the calculations stop, and
you are asked if you want to continue with more iterations. You can
enter any value for the number of maximum iterations.
12-14
Logical Operations
12-15
12.1.4 Monitor Tab
The Monitor tab consists of two pages:
•
•
Tables
Plots
Tables Page
You can also use the Solver
Trace Window to view the
Iteration History (Refer to
Section 1.3 - Object Status
Window/Trace Window in
the User Guide for more
information).
For each Iteration of the Adjust, the number, adjusted value, target
value, and residual appear. If necessary, use the scroll bar to view
iterations which are not currently visible.
Figure 12.10
Dependent
(Target)
Variable
Residual
(Error)
Independent
(Adjusted)
Variable
Iteration
Number
12-15
12-16
Adjust
Plots Page
Refer to Section 10.4 Graph Control in the User
Guide for information on
customizing plots.
The Plots page displays the target and adjusted variables like on the
Tables page, except the information is presented in graph form.
Figure 12.11
12.1.5 User Variables Tab
The User Variables tab allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
12.1.6 Starting the Adjust
With the exception of the
minimum and maximum
values of the independent
(adjusted) variable, all
parameters are required
before the Adjust begins its
calculations.
12-16
There are two ways to start the Adjust:
•
•
If you have provided values for all the fields on the Parameters
tab, the Adjust automatically begins its calculations.
If you have omitted one or both values in the Minimum/Maximum
fields (on the Parameters tab) for the independent variable
(which are optional parameters), and you would like the Adjust to
start calculating, simply click the Start button.
Logical Operations
12-17
The Start button then disappears, indicating the progress of the
calculations. When the error is less than the tolerance, the status bar
displays in green the “OK” message. If the Adjust reaches the maximum
number of iterations without converging, the “Reached iteration Limit
without converging” message appears in red on the status bar.
If you click the Start button when all of the required parameters are not
defined, the status bar displays in yellow the “Incomplete” message, and
calculations cannot begin.
Once calculations are underway, you can view the progress of the
convergence process on the Iterations tab.
The Start button only appears in the initialization stage of the Adjust
operation. It disappears from the property view as soon as it is pressed.
Any changes made to the Adjust or other parts the flowsheet
automatically triggers the Adjust calculation.
To stop or disable the Adjust activate the Ignored checkbox.
12.1.7 Individual Adjust
The Individual Adjust algorithm, either Secant or Broyden, uses a stepwise trial-and-error method, and displays values for the dependent and
independent variables on each trial. The step size specified on the
Parameters tab is used to increment, or decrement the independent
variable for its initial step. The algorithm continues to use steps of this
size until the solution is bracketed. At this point, depending on your
choice, the algorithm uses either the Secant search (and its own step
sizes) or Broyden search to quickly converge to the desired value. If a
solution has not been reached in the maximum number of iterations,
the routine pauses, and asks you whether another series of trials should
be attempted. This is repeated until either a solution is reached, or you
abandon the search. The Secant search algorithm generally results in
good convergence once the solution has been bracketed.
12-17
12-18
Adjust
12.1.8 Multiple Adjust
The term Multiple Adjust typically applies to the situation where all of
the Adjusts are to be solved simultaneously. In this case, where the
results of one Adjust directly affect the other(s), you can use the
Simultaneous option to minimize the number of flowsheet iterations.
Refer to Chapter C2 Synthesis Gas
Production in the Tutorials
& Applications manual for
an example using Multiple
Adjusts.
Examples where this feature is very valuable include calculating the flow
distribution of pipeline looping networks, or in solving a complex
network of UA-constrained heat exchangers. In these examples, you
must select the stream parameters which HYSYS is to manipulate to
meet the desired specifications. For a pipeline looping problem, the
solution may be found by adjusting the flows in the branched streams
until the correct pressures are achieved in the pipelines downstream. In
any event, it is up to you to select the variables to adjust to solve your
flowsheet problem.
HYSYS uses the modified Levenberg-Marquardt algorithm to
simultaneously vary all of the adjustable parameters defined in the
Adjusts until the desired specifications are met. The role of step size with
this method is quite different. With the single Adjust algorithm, step size
is a fixed value used to successively adjust the independent variable
until the solution has been bracketed. With the simultaneous algorithm,
the step size for each variable serves as an upper limit for the
adjustment of that variable.
One requirement in
implementing the Multiple
Adjust feature is that you
must start from a feasible
solution.
In solving multiple UA exchangers, the starting point should not be one
that contains a temperature crossover for one of the heat exchangers. If
this occurs, a warning message appears informing you that a
temperature crossover exists (refer to Section 4.3 - Heat Exchanger),
and a very large UA value is computed for that heat exchanger. This
value is insensitive to any initial change in the value of the adjustable
variable, and therefore the matrix cannot be solved.
Install all Adjusts using the simultaneous option on the Parameters tab,
then click the Start button to begin the calculations.
12-18
Logical Operations
12-19
12.2 Balance
The Balance operation provides a general-purpose heat and material
balance facility. The only information required by the Balance is the
names of the streams entering and leaving the operation. For the
General Balance, component ratios can also be specified.
The Balance overrides the
filtering of streams that
HYSYS typically performs.
Since HYSYS permits streams to enter or leave more than one operation,
the Balance can be used in parallel with other units for overall material
and energy balances. The Balance Operation solves in both the forward
and backward directions. For instance, it backs out the flowrate of an
unknown feed, given that there are no degrees of freedom.
There are six Balance types which are defined in the table below.
Most of the unit operations in
HYSYS perform the
equivalent of a Mole and
Heat Balance besides their
other more specialized
calculations.
Balance Type
Definition
Mole
An overall balance is performed where only the molar flow of each
component is conserved. It can be used to provide material balance
envelopes in the flowsheet, or to transfer the flow and composition
of a process stream into a second stream.
Mass
An overall balance is performed where only the mass flow is
conserved. A common application would be for modeling reactors
with no known stoichiometry, but for which analyses of all feeds and
products are known.
Heat
An overall balance is performed where only the heat flow is
conserved. An application would be to provide the pure energy
difference in a heat balance envelope.
Mole and Heat
An overall balance is performed where the heat and molar flow are
conserved. The most common application for this unit operation
would be to perform overall material (molar basis) and energy
balance calculations of selected process streams to either check for
balances, or force HYSYS to calculate an unknown variable, such
as flow.
Mass and Heat
An overall balance is performed where the overall mass flow and
heat flow are conserved.
General
HYSYS solves a set of n unknowns in the n equations developed
from the streams attached to the operation. Component ratios can
be specified on a mole, mass or liquid volume basis.
12-19
12-20
Balance
12.2.1 Balance Property View
You can also add a balance
by clicking the F12 hot key.
You can also open the
Object Palette by clicking
the F4 hot key.
There are two ways that you can add a Balance to your simulation:
1.
In the Flowsheet menu, click the Add Operation command. The
UnitOps view appears.
2.
Click the Logicals radio button.
3.
From the list of available unit operations, select Balance.
4.
Click the Add button. The Balance property view appears.
OR
5.
In the Flowsheet menu, click the Palette command. The Object
Palette appears.
6.
Double-click the Balance icon. The Balance property view appears.
Figure 12.12
Balance icon
To ignore the Balance during calculations, activate the Ignored
checkbox at the bottom of the property view. HYSYS completely
disregards the operation until you restore it to an active state by
deactivating the checkbox.
12-20
Logical Operations
12-21
12.2.2 Connections Tab
The Connections tab is the same for all of the Balance Types.
Figure 12.13
On the Connections tab, you must specify the following information:
•
•
•
Name. The name of the balance operation.
Inlet Streams. Attach the inlet streams to the balance.
Outlet Streams. Enter the outlet streams to the balance
operation. You can have an unlimited number of inlet and outlet
streams. Use the scroll bar to view streams that are not visible.
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12-22
Balance
12.2.3 Parameters Tab
The Parameters tab contains two groups:
•
•
Balance Type
Ratio List
Figure 12.14
The Balance Type group contains a series of radio buttons, which allow
you to choose the type of Balance you want to use. The radio buttons
are:
•
•
•
•
•
•
Mole
Mass
Heat
Mole and Heat
Mass and Heat
General
The Ratio List group applies only to the General balance. This is
discussed in the General Balance section.
12-22
Logical Operations
12-23
Mole Balance
This operation performs an overall mole balance on selected streams;
no energy balance is made. It can be used to provide material balance
envelopes in the flowsheet or to transfer the flow and composition of a
process stream into a second stream.
•
•
•
The composition does not need to be specified for all streams.
The direction of flow of the unknown is of no consequence.
HYSYS calculates the molar flow of a feed to the operation based
on the known products, or vice versa.
This operation does not pass pressure or temperature.
Mass Balance
This operation performs an overall balance where only the mass flow is
conserved. An application is the modeling of reactors with no known
stoichiometry, but for which analyses of all feeds and products are
available. If you specify the composition of all streams, and the flowrate
for all but one of the attached streams, the Mass Balance operation
determines the flowrate of the unknown stream. This is a common
application in alkylation units, hydrotreaters, and other nonstoichiometric reactors.
•
•
•
•
The composition must be specified for all streams.
The flowrate must be specified for all but one of the streams.
HYSYS determines the flow of that stream by a mass balance.
Energy, moles, and chemical species are not conserved. The
Mass Balance operation determines the equivalent masses of the
components you have defined for the inlet and outlet streams of
the operation.
This operation does not pass pressure or temperature.
12-23
12-24
Balance
Heat Balance
This operation performs an overall heat balance on selected streams. It
can be used to provide heat balance envelopes in the flowsheet or to
transfer the enthalpy of a process stream into a second energy stream.
•
•
•
•
The composition and material flowrate must be specified for all
material streams. The heat flow is not passed to streams which
do not have the composition and material flowrate specified, even
if there is only one unknown heat flow.
The direction of flow for the unknown stream is of no
consequence. HYSYS calculates the heat flow of a feed to the
operation based on the known products, or vice versa.
This operation does not pass the pressure or temperature.
You cannot balance the heat into a Material Stream.
Mole and Heat Balance
The most common application for this balance is to perform overall
material (molar basis), and energy balance calculations of selected
process streams to either check for balances or force HYSYS to calculate
an unknown variable, such as a flowrate.
•
•
•
•
•
12-24
The Mole and Heat Balance independently balance energy and
material.
The Mole and Heat Balance calculate ONE unknown based on a
total energy balance, and ONE unknown based on a total
material balance.
The operation is not directionally dependent for its calculations.
Information can be determined about either a feed or product
stream.
The balance remains a part of your flowsheet and as such
defines a constraint; whenever any change is made, the streams
attached to the balance always balances with regard to material
and energy. As such, this constraint reduces by one the number
of variables available for specification.
Since the Mole and Heat Balance work on a molar basis, it should
not be used in conjunction with a reactor where chemical species
are changing.
Logical Operations
12-25
Mass and Heat Balance
Similar to the Mass balance mode, this balance mode performs a
balance on the overall mass flow. In addition, however, energy is also
conserved.
•
•
•
•
The composition must be specified for all streams.
Flow rate must be specified for all but one of the streams. HYSYS
determines the flow of that stream by a mass balance.
Enthalpy must be specified for all but one of the streams. HYSYS
determines the enthalpy of that stream by a heat balance.
Moles and chemical species are not conserved.
General Balance
The General Balance is capable of solving a greater scope of problems. It
solves a set of n unknowns in the n equations developed from the
streams attached to the operation. This operation, because of the
method of solution, is extremely powerful in the types of problems that
it can solve. Not only can it solve unknown flows and compositions in
the attached streams (either inlet or outlet can have unknowns), but
ratios can be established between components in streams. When the
operation determines the solution, the prescribed ratio between
components are maintained.
•
•
•
The General balance solves material and energy balances
independently. An Energy Stream is an acceptable inlet or outlet
stream.
The operation solves unknown flows or compositions, and can
have ratios specified between components in one of the streams.
Ratios can be specified on a mole, mass or liquid volume basis.
Ratios
A Ratio, which is unique to the general Balance, is defined between two
components in one of the attached streams. Multiple ratios within a
stream (e.g. 1: 2: 1: 1.5) can be set with a single Ratio on a mole, mass or
liquid volume basis. Each individual ratio, however (1: 2, 1: 1, 1: 1.5) uses
a degree of freedom.
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12-26
Balance
Setting a Ratio
Figure 12.15
1.
On the Parameters tab of the Balance operation property view,
select the General Balance radio button.
2.
The Ratio List group should now be visible. Click the Add Ratio
button to specify component ratios.
3.
To view a specific ratio, highlight it and click the View Ratio button.
To delete a ratio, you must first view it, and then click the Delete
button in that Ratio view.
Ratio View
Figure 12.16
The following information must be completed on the Ratio definition
view:
•
•
•
•
12-26
Name. The name of the Ratio.
Stream. The name of the stream.
Ratio Type. Allows you to specify the Ratio Type: Mole, Mass or
Volume.
Component/Ratio. Provides the relative compositions of two or
more components. Other components in the stream are
calculated accordingly, and it is not necessary nor advantageous
to include these in the table. All ratios must be positive; noninteger values are acceptable.
Logical Operations
12-27
Number of Unknowns
The general Balance determines the maximum number of equations,
and hence unknowns, in the following manner (notice that the material
and energy balances are solved independently):
•
•
•
One equation performing an overall molar flow balance.
{Number of Components (nc)} equations performing an individual
molar balance.
{Number of Streams (ns)} equations, each performing a
summation of individual component fractions on a stream by
stream basis.
This is the maximum number of equations (1 + nc + ns), and hence
unknowns, which can be solved for a system. When ratios are specified,
they reduce the available number of unknowns. For each ratio, the
number of unknowns used is one less than the number of components
in the ratio. For example, for a three-component ratio, two unknowns
are used.
12.2.4 Worksheet Tab
The Worksheet tab contains a summary of the information contained in
the stream property view for all the streams attached to the Air Cooler.
Refer to Section 1.2.3 - Worksheet Tab for more information.
12.2.5 Stripchart Tab
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The Stripchart tab allows you to setup the strip chart for various variable
sets. You can select the variable set by clicking the Variable Set dropdown list, and then clicking the Create Stripchart button to display the
strip chart.
12.2.6 User Variables Tab
The User Variables tab allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
12-27
12-28
Boolean Operations
12.3 Boolean Operations
The Boolean Logic block is a logical operation, which takes in a specified
number of boolean inputs and then applies the boolean operation to
calculate an output. A typical use of the Boolean Logic is to apply
emergency shutdown of an exothermic reactor, such as closing the
valves on the fuel and air line to the reactor when the reactor core
temperature exceeds its setpoint. It is also used to simulate the ladder
diagrams, which are found in most of the electrical applications.
The following Boolean Logic blocks are available in HYSYS:
•
•
•
•
•
•
•
•
•
•
And Gate
Or Gate
Not Gate
Xor Gate
On Delay Gate
Off Delay Gate
Latch Gate
Counter Up Gate
Counter Down Gate
Cause And Effect Matrix
To evaluate the Boolean Logic blocks at each time step, open the
Integrator view and go to the Options tab. In the Calculation Execution
Rates group, change the Control and Logical Ops field value to 1.
This change ensures that your time sensitive Boolean Logic blocks like
On Delay and Off Delay are executed at the required time instead of a
one time step delay. This change also slows down the HYSYS
calculation rate and is noticeable for large cases.
For more information about the Integrator view, refer to Section 7.7 Integrator in the User Guide.
12-28
Logical Operations
12-29
12.3.1 Boolean Logic Blocks Property View
You can also add the
boolean logical operations
by clicking the F12 hot key.
You can also open the
Object Palette by clicking
the F4 hot key.
There are two ways that you can add Boolean Logic Blocks to your
simulation:
1.
From the Flowsheet menu, click Add Operation. The UnitOps view
appears.
2.
Click the Logicals radio button.
3.
From the list of available unit operations, select the Boolean Logic
that you want.
4.
Click the Add button. The selected Boolean Logic property view
appears.
OR
1.
From the Flowsheet menu, click Palette. The Object Palette appears.
2.
Click on the Boolean Ops icon. The Boolean Palette appears.
3.
Double-click the icon of the Boolean Logic that you want.
Boolean Logic
Boolean
Ops icon
Icon
Not Gate
And Gate
Or Gate
Xor Gate
Off Delay Gate
12-29
12-30
Boolean Operations
Boolean Logic
Icon
On Delay Gate
Latch Gate
Counter Up Gate
Counter Down Gate
Cause And Effect
Matrix
4.
The selected Boolean Logic property view appears.
Figure 12.17
12-30
Logical Operations
12-31
The property view for all the Boolean Logic blocks in HYSYS contains
four tabs (Connections, Monitor, Stripchart, and User Variables), a
Delete button and a Face Plate button. Click the Delete button to delete
the Boolean Logic block from the flowsheet. HYSYS will ask you to
confirm the deletion.
Click the Face Plate button to open the Face Plate view. The Face Plate
view allows you to see the Boolean type and output value at a glance.
Figure 12.18
This field displays the
Boolean Logic type.
Click on the Setup
button to open the
Boolean Logic view.
This field displays the
output value.
On the PDF view, the digital/boolean and boolean/boolean logical
connections have the capability to display the change of logical state by
changing the line colour to either green (1) or red (0).
Figure 12.19
OP = 0
OP = 1
The output is set up to have a default initial value of 1 for all the Boolean
Logic blocks.
Connections Tab
The Connections tab is where you connect operations to the Boolean
Logic block. Boolean unit operations can make logical connections with
Digital Point, as well as, among themselves. The connections can either
be made from the Connections tab, or through the PFD.
If the Boolean type supports multiple process variable sources, the
Process Variable Sources group contains a table with three buttons with
the same functions as the buttons in the Output Target group.
12-31
12-32
Boolean Operations
The figure below displays the Connections tab of a Boolean Not Gate
operation.
Figure 12.20
The type of Boolean
Logic block is shown in
this display field.
Edit OP button allows you
to change the selected
output connection.
Add OP button allows
you to add an output
connection.
Delete OP button allows
you to delete the selected
output connection.
Adding/Editing Process Variable Source
The Select Input PV view is
similar to the Variable
Navigator view. Refer to
Section 11.21 - Variable
Navigator in the User
Guide for information on
how to use the view.
12-32
Depending on the Boolean type, you have to click the Select PV button,
the Edit PV button or the Add PV button to open the Select Input PV
view.
Figure 12.21
Logical Operations
12-33
Adding/Editing Output Target
Click the Edit OP button or Add OP button to open the Select Output PV
view.
Figure 12.22
Select the operation to
receive the output value
from the list, then click the
OK button.
Click the Disconnect button
to disconnect the connection
in the view.
Click the Cancel button to
exit the view without
changing anything.
Use the radio button in the Object Filter group to filter the Object list to
the operations you want.
Monitor Tab
The Monitor tab allows you to monitor the input and output values of
the Boolean Logic block. The contents of this tab varies from one
Boolean Logic type to another. For example, the Monitor tab of an On
Delay Gate boolean also contains a field where you can specify the time
delay.
Stripchart Tab
Refer to Section 11.7.3 Strip Charts in the User
Guide for more information
about strip charts.
The Stripchart tab allows you to setup the strip chart for various variable
sets. You can select the variable set by clicking the Variable Set dropdown list, and then clicking the Create Stripchart button to display the
strip chart.
12-33
12-34
Boolean Operations
User Variables Tab
The User Variables tab allows you to create and implement variables in
the HYSYS simulation case. For more information on implementing the
User Variables, refer to Chapter 5 - User Variables in the Customization
Guide.
12.3.2 And Gate
This unit operation performs a logical AND function on a set of inputs.
The output is always low as long as any one of the input is low and it is
high when all of the inputs are high. The table below displays the
function logic for the And Gate.
Input 1
Input 2
Input 3
Output
1
1
1
1
1
0
0
0
0
1
0
0
0
0
1
0
0
0
0
0
The Monitor tab of the And Gate displays the following information:
The And Boolean Logic
block can have any number
of inputs and a single output,
which can be fanned out.
The input and output values
can only be 1 or 0.
•
•
•
•
Input. Contains the name and number used to designate the
input connection.
Object. Displays the operation name of the input connection.
Initial State. Displays the input value received by the Boolean
Logic block.
Output Value. Displays the output value of the Boolean Logic
block, based on the Boolean type and the input values from the
input connections.
Figure 12.23
12-34
Logical Operations
12-35
12.3.3 Or Gate
This unit operation performs a logical OR function on a set of inputs.
The output is always high as long as any one of the input is high and