Copyright Notice Documentation Credits Contacting AEA

Copyright Notice Documentation Credits Contacting AEA
Copyright Notice
The copyright in this manual and its associated computer program are the property of
AEA Technology - Hyprotech Ltd. All rights reserved. Both this manual and the computer
program have been provided pursuant to a License Agreement containing restrictions on
use.
Hyprotech reserves the right to make changes to this manual or its associated computer
program without obligation to notify any person or organization. Companies, names and
data used in examples herein are fictitious unless otherwise stated.
No part of this manual may be reproduced, transmitted, transcribed, stored in a retrieval
system, or translated into any other language, in any form or by any means, electronic,
mechanical, magnetic, optical, chemical manual or otherwise, or disclosed to third
parties without the prior written consent of AEA Technology Engineering Software,
Hyprotech Ltd., Suite 800, 707 - 8th Avenue SW, Calgary AB, T2P 1H5, Canada.
© 2000 AEA Technology - Hyprotech Ltd. All rights reserved.
HYSYS, HYSYS.Plant, HYSYS.Process, HYSYS.Refinery, HYSYS.Concept, HYSYS.OTS,
HYSYS.RTO and HYSIM are registered trademarks of AEA Technology Engineering
Software - Hyprotech Ltd.
Microsoft® Windows®, Windows® 95/98, Windows® NT and Windows® 2000 are
registered trademarks of the Microsoft Corporation.
This product uses WinWrap® Basic, Copyright 1993-1998, Polar Engineering and
Consulting.
Documentation Credits
Authors of the current release, listed in order of historical start on project:
Sarah-Jane Brenner, BASc; Conrad, Gierer, BASc; Chris Strashok, BSc; Lisa Hugo, BSc, BA;
Muhammad Sachedina, BASc; Allan Chau, BSc; Adeel Jamil, BSc; Nana Nguyen, BSc;
Yannick Sternon, BIng;Kevin Hanson, PEng; Chris Lowe, PEng
Since software is always a work in progress, any version, while representing a milestone,
is nevertheless but a point in a continuum. Those individuals whose contributions
created the foundation upon which this work is built have not been forgotten. The
current authors would like to thank the previous contributors.
A special thanks is also extended by the authors to everyone who contributed through
countless hours of proof-reading and testing.
Contacting AEA Technology - Hyprotech
AEA Technology - Hyprotech can be conveniently accessed via the following:
Website:
Technical Support:
Information and Sales:
www.software.aeat.com
[email protected]
[email protected]
Detailed information on accessing Hyprotech Technical Support can be found in the
Technical Support section in the preface to this manual.
Table of Contents
Welcome to HYSYS ........................................... vii
Hyprotech Software Solutions .............................................vii
Use of the Manuals ..............................................................xi
Technical Support ............................................................. xvii
1
2
3
4
5
Steady State Modeling ..................................... 1-1
1.1
Engineering ....................................................................... 1-3
1.2
Operations......................................................................... 1-6
Streams ............................................................ 2-1
2.1
Material Stream Property View.......................................... 2-3
2.2
Energy Stream Property View ......................................... 2-11
Heat Transfer Equipment ................................. 3-1
3.1
Air Cooler .......................................................................... 3-3
3.2
Cooler/Heater .................................................................. 3-11
3.3
Heat Exchanger............................................................... 3-18
3.4
LNG ................................................................................. 3-49
Piping Equipment ............................................. 4-1
4.1
Mixer.................................................................................. 4-3
4.2
Pipe Segment.................................................................... 4-7
4.3
Tee .................................................................................. 4-34
4.4
Valve ............................................................................... 4-38
4.5
Relief Valve ..................................................................... 4-41
4.6
References ...................................................................... 4-46
Rotating Equipment.......................................... 5-1
5.1
Compressor/Expander ...................................................... 5-3
5.2
Pump ............................................................................... 5-16
iii
6
7
8
9
Separation Operations ..................................... 6-1
6.1
Separator / 3-Phase Separator / Tank .............................. 6-3
6.2
Shortcut Column.............................................................. 6-11
6.3
Component Splitter.......................................................... 6-16
Column.............................................................. 7-1
7.1
Column Subflowsheet ....................................................... 7-3
7.2
Column Theory.................................................................. 7-8
7.3
Column Installation.......................................................... 7-13
7.4
Column Property View..................................................... 7-21
7.5
Column-Specific Operations............................................ 7-82
7.6
Running the Column........................................................ 7-96
7.7
Column Troubleshooting ................................................. 7-98
7.8
References .................................................................... 7-103
Solid Separation Operations ............................ 8-1
8.1
Simple Solid Separator (Simple Filter) .............................. 8-3
8.2
Cyclone ............................................................................. 8-5
8.3
Hydrocyclone..................................................................... 8-9
8.4
Rotary Vacuum Filter....................................................... 8-12
8.5
Baghouse Filter ............................................................... 8-15
Reactors ........................................................... 9-1
9.1
The Reactor Operation...................................................... 9-3
9.2
CSTR / General Reactor Design Tab................................ 9-4
9.3
CSTR / General Reactor Reactions Tab ........................... 9-8
9.4
CSTR / General Reactor Rating Tab............................... 9-25
9.5
CSTR / General Reactor Work Sheet Tab ...................... 9-29
9.6
CSTR / General Reactor Dynamics Tab ......................... 9-29
9.7
Plug Flow Reactor (PFR) Property View ......................... 9-29
10 Logical Operations ......................................... 10-1
10.1 Adjust .............................................................................. 10-3
10.2 Balance ......................................................................... 10-15
10.3 Parametric Unit Operation............................................. 10-32
10.4 Recycle.......................................................................... 10-40
10.5 Set ................................................................................. 10-62
10.6 Spreadsheet .................................................................. 10-67
iv
11 Optimizer ........................................................ 11-1
11.1 Optimizer ......................................................................... 11-3
11.2 Optimizer View ................................................................ 11-4
11.3 Optimization Schemes .................................................... 11-9
11.4 Optimizer Tips ............................................................... 11-12
11.5 Optimizer Examples ...................................................... 11-13
11.6 References .................................................................... 11-21
Index ..................................................................I-1
v
vi
Welcome to HYSYS
vii
Welcome to HYSYS
We are pleased to present you with the latest version of HYSYS — the
product that continually extends the bounds of process engineering
software. With HYSYS you can create rigorous steady-state and
dynamic models for plant design and trouble shooting. Through the
completely interactive HYSYS interface, you have the ability to easily
manipulate process variables and unit operation topology, as well as
the ability to fully customize your simulation using its OLE extensibility
capability.
Hyprotech Software Solutions
HYSYS has been developed with Hyprotech’s overall vision of the
ultimate process simulation solution in mind. The vision has led us to
create a product that is:
• Integrated
• Intuitive and interactive
• Open and extensible
Integrated Simulation Environment
In order to meet the ever-increasing demand of the process industries
for rigorous, streamlined software solutions, Hyprotech developed the
HYSYS Integrated Simulation Environment. The philosophy underlying
our truly integrated simulation environment is conceptualized in the
diagram below:
Figure 1
vii
Hyprotech Software Solutions
The central wedge represents the common parameters at the core of
the various modelling tools:
• model topology
• interface
• thermodynamics
The outer ring represents the modelling application needs over the
entire plant lifecycle. The arrows depict each Hyprotech product using
the common core, allowing for universal data sharing amongst the
tools, while providing a complete simulation solution.
As an engineer you undoubtedly have process modelling requirements
that are not all handled within a single package. The typical solution is
to generate results in one package, then transfer the necessary
information into a second package where you can determine the
additional information. At best, there is a mechanism for exchanging
information through file transfer. At worst, you must enter the
information manually, consuming valuable time and risking the
introduction of data transfer errors. Often the knowledge you gain in
the second application has an impact on the first model, so you must
repeat the whole process a number of times in an iterative way.
In a truly integrated simulation environment all of the necessary
applications work is performed within a common framework,
eliminating the tedious trial-and-error process described previously.
Such a system has a number of advantages:
• Information is shared, rather than transferred, among
applications.
• All applications use common thermodynamic models.
• All applications use common flowsheet topology.
• You only need to learn one interface.
• You can switch between modelling applications at any time,
gaining the most complete understanding of the process.
The plant lifecycle might begin with building a conceptual model to
determine the basic equipment requirements for your process. Based
on the conceptual design, you could build a steady-state model and
perform an optimization to determine the most desirable operating
conditions. Next, you could carry out some sizing and costing
calculations for the required equipment, then do some dynamic
modelling to determine appropriate control strategies. Once the design
has become a reality, you might perform some on-line modelling using
actual plant data for "what-if" studies, troubleshooting or even on-line
optimization. If a change at any stage in the design process affects the
common data, the new information is available immediately to all the
other applications — no manual data transfer is ever required.
viii
Welcome to HYSYS
ix
While this concept is easy to appreciate, delivering it in a useable
manner is difficult. Developing this multi-application, informationsharing software environment is realistically only possible using Object
Oriented Design methodologies, implemented with an Object Oriented
Programming Language. Throughout the design and development
process, we have adhered to these requirements in order to deliver a
truly integrated simulation environment as the HYSYS family of
products:
For information on any of
these products, contact your
local Hyprotech
representative.
HYSYS Product
Description
HYSYS.Process
Process Design - HYSYS.Process provides the
accuracy, speed and efficiency required for process
design activities. The level of detail and the
integrated utilities available in HYSYS.Process
allows for skillful evaluation of design alternatives.
HYSYS.Plant
Plant Design - HYSYS.Plant provides an integrated
steady-state and dynamic simulation capability,
offers rigorous and high-fidelity results with a very
fine level of equipment geometry and performance
detail. HYSYS.Plant+ provides additional detailed
equipment configurations, such as actuator
dynamics.
HYSYS.Refinery
Refinery Modeling - HYSYS.Refinery provides
truly scalable refinery-wide modeling. Detailed
models of reaction processes can be combined with
detailed representations of separation and heat
integration systems. Each hydrocarbon stream is
capable of predicting a full range of refinery
properties based on a Refinery Assay matrix.
HYSYS.OTS
Operations Training System - HYSYS.OTS
provides real-time simulated training exercises that
train operations personnel and help further develop
their skills performing critical process operations.
Increased process understanding and procedural
familiarity for operations personnel can lead to an
increase in plant safety and improvements in
process performance.
HYSYS.RTO
Real-Time Optimization - HYSYS.RTO is a realtime optimization package that enables the
optimization of plant efficiency and the management
of production rate changes and upsets in order to
handle process constraints and maximize operating
profits.
HYSYS.Concept
Conceptual Design Application - HYSYS.Concept
includes DISTIL which integrates the distillation
synthesis and residue curve map technology of
Mayflower with data regression and thermodynamic
database access. HYSYS.Concept also includes
HX-Net, which provides the ability to use pinch
technology in the design of heat exchanger
networks. Conceptual design helps enhance process
understanding and can assist in the development of
new and economical process schemes.
ix
Hyprotech Software Solutions
Intuitive and Interactive Process Modelling
We believe that the role of process simulation is to improve your
process understanding so that you can make the best process
decisions. Our solution has been, and continues to be, interactive
simulation. This solution has not only proven to make the most
efficient use of your simulation time, but by building the model
interactively – with immediate access to results – you gain the most
complete understanding of your simulation.
HYSYS uses the power of Object Oriented Design, together with an
Event-Driven Graphical Environment, to deliver a completely
interactive simulation environment where:
• calculations begin automatically whenever you supply new
information, and
• access to the information you need is in no way restricted.
At any time, even as calculations are proceeding, you can access
information from any location in HYSYS. As new information becomes
available, each location is always instantly updated with the most
current information, whether specified by you or calculated by HYSYS.
Open and Extensible HYSYS Architecture
HYSYS is the only
commercially available
simulation platform designed
for complete User
Customization.
The Integrated Simulation Environment and our fully Object Oriented
software design has paved the way for HYSYS to be fully OLE
compliant, allowing for complete user customization. Through a
completely transparent interface, OLE Extensibility lets you:
• develop custom steady-state and dynamic unit operations
• specify proprietary reaction kinetic expressions
• create specialized property packages.
With seamless integration, new modules appear and perform like
standard operations, reaction expressions or property packages within
HYSYS. The Automation features within HYSYS expose many of the
internal Objects to other OLE compliant software like Microsoft Excel,
Microsoft Visual Basic and Visio Corporation’s Visio. This functionality
enables you to use HYSYS applications as calculation engines for your
own custom applications.
By using industry standard OLE Automation and Extension the custom
simulation functionality is portable across Hyprotech software
updates. The open architecture allows you to extend your simulation
functionality in response to your changing needs.
x
Welcome to HYSYS
xi
Use of the Manuals
HYSYS Electronic Documentation
The HYSYS Documentation
Suite includes all available
documentation for the HYSYS
family of products.
All HYSYS documentation is available in electronic format as part of the
HYSYS Documentation Suite. The HYSYS Documentation CD-ROM is
included with your package and may be found the Get Started box. The
content of each manual is described in the following table:
Manual
Description
Get Started
Contains the information needed to install HYSYS,
plus a Quick Start example to get you up and
running, ensure that HYSYS was installed correctly
and is operating properly.
User’s Guide
Provides in depth information on the HYSYS
interface and architecture. HYSYS Utilities are also
covered in this manual.
Simulation Basis
Contains all information relating to the available
HYSYS fluid packages and components. This
includes information on the Oil Manager,
Hypotheticals, Reactions as well as a
thermodynamics reference section.
Steady State
Modeling
Steady state operation of HYSYS unit operations is
covered in depth in this manual.
Dynamic Modeling
This manual contains information on building and
running HYSYS simulations in Dynamic mode.
Dynamic theory, tools, dynamic functioning of the
unit operations as well as controls theory are
covered.
This manual is only included with the HYSYS.Plant
document set.
Customization
Guide
Details the many customization tools available in
HYSYS. Information on enhancing the functionality
of HYSYS by either using third-party tools to
programmatically run HYSYS (Automation), or by
the addition of user-defined Extensions is covered.
Other topics include the current internally extensible
tools available in HYSYS: the User Unit Operation
and User Variables as well as comprehensive
instruction on using the HYSYS View Editor.
Tutorials
Provides step-by-step instructions for building some
industry-specific simulation examples.
Applications
Contains a more advanced set of example problems.
Note that before you use this manual, you should
have a good working knowledge of HYSYS. The
Applications examples do not provide many of the
basic instructions at the level of detail given in the
Tutorials manual.
Quick Reference
Provides quick access to basic information regarding
all common HYSYS features and commands.
xi
Use of the Manuals
Contact Hyprotech for
information on HYSYS
training courses.
If you are new to HYSYS, you may want to begin by completing one or
more of the HYSYS tutorials, which give the step-by-step instructions
needed to build a simulation case. If you have some HYSYS experience,
but would still like to work through some more advanced sample
problems, refer to the HYSYS Applications.
Since HYSYS is totally interactive, it provides virtually unlimited
flexibility in solving any simulation problem. Keep in mind that the
approach used in solving each example problem presented in the
HYSYS documentation may only be one of the many possible methods.
You should feel free to explore other alternatives.
Viewing the On-Line Documentation
HYSYS On-Line Documentation is viewed using the Adobe Acrobat
Reader®, which is included on the Documentation CD-ROM. Install
Acrobat Reader on your computer following the instructions on the
CD-ROM insert card. Once installed, you can view the electronic
documentation either directly from the CD-ROM, or you can copy the
Doc folder (containing all the electronic documentation files) and the
file named main.pdf to your hard drive before viewing the files.
Manoeuvre through the on-line documentation using the bookmarks
on the left of the screen, the navigation buttons in the button bar or
using the scroll bars on the side of the view. Blue text indicates an active
link to the referenced section or view. Click on that text and Acrobat will
jump to that particular section.
Attaching the On-line CD Index
One of the advantages in using the HYSYS Documentation CD is the
ability to do power searching using the Adobe Acrobat® Query tool. By
selecting the Query button or selecting Query from the Search
submenu of the Tools menu, you can search simultaneously through all
the manuals for keywords.
For more information on the
search tools available in
Adobe Acrobat Reader®,
consult the Help files provided
with the Reader.
In order to make use of this powerful searching tool, you must attach
the index file to Acrobat using the following procedure:
1.
2.
xii
To open the Index Selection view you must do one of the following:
• Select Indexes from the Search submenu in the Tools menu.
• Press CTRL SHIFT X
Press the Add button. This should open the Add Index view.
Welcome to HYSYS
3.
xiii
Ensure that the Look in field is currently set to your CD-ROM drive
label. There should be two directories visible from the root
directory: Acrobat and Doc.
Figure 2
4.
Open the Doc directory. Inside it you should find the Index.pdx
file. Select it and press the Open button.
Figure 3
5.
The Index Selection view should display the HYSYS
Documentation Index to be attached. Press the OK button and you
may begin making use of the Query tool.
Other Acrobat features include a zoom-in tool in the button bar, which
allows you to magnify the text you are reading. If you wish, you may
print pages or chapters of the online documentation using the FilePrint command under the menu.
xiii
Use of the Manuals
Conventions used in the Manuals
The following section lists a number of conventions used throughout
the documentation.
Keywords for Mouse Actions
As you work through various procedures in the manuals, you will be
given instructions on performing specific functions or commands.
Instead of repeating certain phrases for mouse instructions, keywords
are used to imply a longer instructional phrase:
These are the normal (default)
settings for the mouse, but you
can change the positions of the
left- and right-buttons.
Keywords
Action
Point
Move the mouse pointer to position it over an item.
For example, point to an item to see its Tool Tip.
Click
Position the mouse pointer over the item, and rapidly
press and release the left mouse button. For
example, click Close button to close the current
window.
Right-Click
As for click, but use the right mouse button. For
example, right-click an object to display the Object
Inspection menu.
Double-Click
Position the mouse pointer over the item, then
rapidly press and release the left mouse button
twice. For example, double-click the HYSYS icon to
launch the program.
Drag
Position the mouse pointer over the item, press and
hold the left mouse button, move the mouse while
the mouse button is down, and then release the
mouse button. For example, you drag items in the
current window, to move them.
Tool Tip
Whenever you pass the mouse pointer over certain
objects, such as tool bar icons and flowsheet
objects, a Tool Tip will be displayed. It will contain a
brief description of the action that will occur if you
click on that button or details relating to the object.
A number of text formatting conventions are also used throughout the
manuals:
xiv
Format
Example
When you are asked to invoke a HYSYS menu
command, the command is identified by bold
lettering.
File-Save indicates
opening the File menu and
choosing the Save
command.
When you are asked to select a HYSYS button,
the button is identified by bold, italicized
lettering.
Cancel identifies the
Cancel button on a
particular view.
Welcome to HYSYS
Note that blank spaces are
acceptable in the names of
streams and unit operations.
Format
Example
When you are asked to select a key or keys to
perform a certain function, keyboard
commands are identified by words in bold and
small capitals (small caps).
"Select the F1 key."
The name of a HYSYS View (or window) is
indicated by bold lettering.
Session Preferences
The name of a Group within a view is identified
by bold lettering.
Initial Build Home View.
The name of Radio Buttons and Check Boxes
are identified by bold lettering.
Ignored
Material and energy stream names are
identified by bold lettering.
Column Feed,
CondenserDuty
Unit operation names are identified by bold
lettering.
Inlet Separator,
Atmospheric Tower
HYSYS unit operation types are identified by
bold, uppercase lettering.
HEAT EXCHANGER,
SEPARATOR,
When you are asked to provide keyboard input,
it will be indicated by bold lettering.
"Type 100 for the stream
temperature."
xv
Bullets and Numbering
Bulleted and numbered lists will be used extensively throughout the
manuals. Numbered lists are used to break down a procedure into
steps, for example:
1.
Select the Name cell.
2.
Type a name for the operation.
3.
Press ENTER to accept the name.
Bulleted lists are used to identify alternative steps within a procedure,
or for simply listing like objects. A sample procedure that utilizes
bullets is:
1.
Move to the Name cell by doing one of the following:
• Select the Name cell
• Press ALT N
2.
Type a name for the operation.
• Press ENTER to accept the name.
Notice the two alternatives for completing Step 1 are indented to
indicate their sequence in the overall procedure.
xv
Use of the Manuals
A bulleted list of like objects might describe the various groups on a
particular view. For example, the Options page of the Simulation tab on
the Session Preferences view has three groups, namely:
• General Options
• Errors
• Column Options
Callouts
A callout is a label and arrow that describes or identifies an object. An
example callout describing a graphic is shown below.
Figure 4
HYSYS Icon
Annotations
Annotation text appears in the
outside page margin.
Text appearing in the outside margin of the page supplies you with
additional or summary information about the adjacent graphic or
paragraph. An example is shown to the left.
Shaded Text Boxes
A shaded text box provides you with important information regarding
HYSYS’ behaviour, or general messages applying to the manual.
Examples include:
The resultant temperature of the mixed streams may be quite
different than those of the feed streams, due to mixing effects.
Before proceeding, you should have read the introductory
section which precedes the example problems in this manual.
The use of many of these conventions will become more apparent as
you progress through the manuals.
xvi
Welcome to HYSYS
xvii
Technical Support
There are several ways in which you can contact Technical Support. If
you cannot find the answer to your question in the manuals, we
encourage you to visit our Website at www.software.aeat.com, where a
variety of information is available to you, including:
•
•
•
•
•
answers to frequently asked questions
example cases and product information
technical papers
news bulletins
hyperlink to support email.
You can also access Support directly via email. A listing of Technical
Support Centres including the Support email address is at the end of
this chapter. When contacting us via email, please include in your
message:
• Your full name, company, phone and fax numbers.
• The version of HYSYS you are using (shown in the Help, About
HYSYS view).
• The serial number of your HYSYS security key.
• A detailed description of the problem (attach a simulation case
if possible).
We also have toll free lines that you may use. When you call, please have
the same information available.
xvii
Technical Support
Technical Support Centres
Calgary, Canada
AEA Technology Engineering Software
[email protected] (email)
Hyprotech Ltd.
(403) 520-6181 (local - technical support)
Suite 800, 707 - 8th Avenue SW
1-888-757-7836 (toll free - technical support)
Calgary, Alberta
(403) 520-6601 (fax - technical support)
T2P 1H5
1-800-661-8696 (information and sales)
Barcelona, Spain (Rest of Europe)
AEA Technology Engineering Software
[email protected] (email)
Hyprotech Europe S.L.
+34 93 215 68 84 (technical support)
Pg. de Gràcia 56, 4th floor
900 161 900 (toll free - technical support - Spain only)
E-08007 Barcelona, Spain
+34 93 215 42 56 (fax - technical support)
+34 93 215 68 84 (information and sales)
Oxford, UK (UK clients only)
AEA Technology Engineering Software
[email protected] (email)
Hyprotech
0800 7317643 (freephone technical support)
404 Harwell, Didcot
+44 1235 434351 (fax - technical support)
Oxfordshire, OX11 0RA
+44 1235 435555 (information and
United Kingdom
sales)
Kuala Lumpur, Malaysia
AEA Technology Engineering Software
Hyprotech Ltd., Malaysia
Lot E-3-3a, Dataran Palma
[email protected] (email)
Jalan Selaman ½, Jalan Ampang
+60 3 470 3880 (technical support)
68000 Ampang, Selangor
+60 3 471 3811 (fax - technical support)
Malaysia
+60 3 470 3880 (information and sales)
Yokohama, Japan
AEA Technology Engineering Software
AEA Hyprotech KK
Plus Taria Bldg. 6F.
3-1-4, Shin-Yokohama
xviii
Kohoku-ku
[email protected] (email)
Yokohama, Japan
81 45 476 5051 (technical support)
222-0033
81 45 476 5051 (information and sales)
Welcome to HYSYS
xix
Offices
Calgary, Canada
Yokohama, Japan
Tel: (403) 520-6000
Tel: 81 45 476 5051
Fax: (403) 520-6040/60
Fax: 81 45 476 3055
Toll Free: 1-800-661-8696
Newark, DE, USA
Houston, TX, USA
Tel: (302) 369-0773
Tel: (713) 339-9600
Fax: (302) 369-0877
Fax: (713) 339-9601
Toll Free: 1-800-688-3430
Toll Free: 1-800-475-0011
Oxford, UK
Barcelona, Spain
Tel: +44 1235 435555
Tel: +34 93 215 68 84
Fax: +44 1235 434294
Fax: +34 93 215 42 56
Oudenaarde, Belgium
Düsseldorf, Germany
Tel: +32 55 310 299
Tel: +49 211 577933 0
Fax: +32 55 302 030
Fax: +49 211 577933 11
Hovik, Norway
Cairo, Egypt
Tel: +47 67 10 6464
Tel: +20 2 702 0824
Fax: +47 67 10 6465
Fax: +20 2 702 0289
Kuala Lumpur, Malaysia
Seoul, Korea
Tel: +60 3 470 3880
Tel: 82 2 3453 3144 5
Fax: +60 3 470 3811
Fax: 82 2 3453 9772
xix
Technical Support
Agents
International Innotech, Inc.
Katy, USA
Tel: (281) 492-2774
Fax: (281) 492-8144
International Innotech, Inc.
Beijing, China
Tel: 86 10 6499 3956
Fax: 86 10 6499 3957
International Innotech
Taipei, Taiwan
Tel: 886 2 809 6704
Fax: 886 2 809 3095
KBTECH Ltda.
Bogota, Colombia
Tel: 57 1 258 44 50
Fax: 57 1 258 44 50
KLG Systel
New Delhi, India
Tel: 91 124 346962
Fax: 91 124 346355
Logichem Process
Johannesburg, South Africa
Tel: 27 11 465 3800
Fax: 27 11 465 4548
Process Solutions Pty. Ltd.
Peregian, Australia
Tel: 61 7 544 81 355
Fax: 61 7 544 81 644
Protech Engineering
Bratislava, Slovak Republic
Tel: +421 7 4488 8286
Fax: +421 7 4488 8286
PT. Danan Wingus Sakti
Jakarta, Indonesia
Tel: 62 21 567 4573 75/62 21 567 4508
10
Fax: 62 21 567 4507/62 21 568 3081
Ranchero Services (Thailand)
Co. Ltd.
Bangkok, Thailand
Tel: 66 2 381 1020
Fax: 66 2 381 1209
S.C. Chempetrol Service srl
Bucharest, Romania
Tel: +401 330 0125
Fax: +401 311 3463
Soteica De Mexico
Mexico D.F., Mexico
Tel: 52 5 546 5440
Fax: 52 5 535 6610
Soteica Do Brasil
Sao Paulo, Brazil
Tel: 55 11 533 2381
Fax: 55 11 556 10746
Soteica S.R.L.
Buenos Aires, Argentina
Tel: 54 11 4555 5703
Fax: 54 11 4551 0751
Soteiven C.A.
Caracas, Venezuela
Tel: 58 2 264 1873
Fax: 58 2 265 9509
ZAO Techneftechim
Moscow, Russia
Tel: +7 095 202 4370
Fax: +7 095 202 4370
Internet
Website: www.software.aeat.com
Email: [email protected]
xx
xxi
HYSYS Hot Keys
File
Create New Case
Open Case
Save Current Case
Save As...
Close Current Case
Exit HYSYS
CTRL+N
CTRL+O
CTRL+S
CTRL+SHIFT+S
CTRL+Z
ALT+F4
Simulation
Go to Basis Manager
Leave Current Environment
(Return to Previous)
Main Properties
Access Optimizer
Toggle Steady-State/Dynamic
Modes
Toggle Hold/Go Calculations
Access Integrator
Start/Stop Integrator
Stop Calculations
CTRL+B
CTRL+L
CTRL+M
F5
F7
F8
CTRL+I
F9
CTRL+BREAK
Flowsheet
Add Material Stream
Add Operation
Access Object Navigator
Show/Hide Object Palette
Composition View (from
Workbook)
F11
F12
F3
F4
CTRL+K
Tools
Access Workbooks
Access PFDs
Toggle Move/Attach (PFD)
Access Utilities
Access Reports
Access DataBook
Access Controller FacePlates
Access Help
CTRL+W
CTRL+P
CTRL
CTRL+U
CTRL+R
CTRL+D
CTRL+F
F1
Column
Go to Column Runner
(SubFlowsheet)
Stop Column Solver
CTRL+T
CTRL+BREAK
Window
Close Active Window
Tile Windows
Go to Next Window
Go to Previous Window
Editing/General
Access Edit Bar
Access Pull-Down Menus
Go to Next Page Tab
Go to Previous Page Tab
Cut
Copy
Paste
CTRL+F4
SHIFT+F4
CTRL+F6 or CTRL+TAB
CTRL+SHIFT+F6 or
CTRL+SHIFT+TAB
F2
F10 or ALT
CTRL+SHIFT+N
CTRL+SHIFT+P
CTRL+X
CTRL+C
CTRL+V
xxi
xxii
xxii
Steady State Modeling
1-1
1 Steady State
Modeling
1.1 Engineering................................................................................................... 3
1.2 Operations .................................................................................................... 6
1.2.1 Installing Operations ................................................................................ 6
1.2.2 The Unit Operation Property View ........................................................... 7
1-1
1-2
1-2
Steady State Modeling
1.1
1-3
Engineering
As you have seen in the User’s Guide and Simulation Basis manual,
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, represents a
significant advancement in the industry.
The various components that make up HYSYS have produced 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 last fact 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 - including as calculations are
being performed - you gain the greatest understanding of each
individual aspect of your process.
The multi-flowsheet architecture of HYSYS is vitally important to this
overall approach to modeling. Although HYSYS has been designed to
allow the use of multiple property packages and the creation of prebuilt templates, the greatest advantage of multi-flowsheeting is that it
provides 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.
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
1-3
1-4
Engineering
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 will be 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 Dynamics mode.
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 SubFlowsheet, 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
1-4
Steady State Modeling
1-5
five available solution algorithms for both unconstrained and
constrained optimization problems, with an automatic backup
mechanism when the Flowsheet moves into a region of nonconvergence.
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 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. As there is not the same wealth of
process modeling experience in this area as there is for steady state
modeling, information regarding the dynamic response of a model has
been included in the Dynamic Modelling guide to ensure that you will
realize the greatest benefit of this revolutionary product
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.
For more information on
Dynamic Modelling unit
operations, consult the
Dynamic Modelling guide.
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.
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 will calculate 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 will immediately pass the
composition and flow to the outlet. If you then provide a percent
efficiency and pressure rise, the outlet and energy streams will be fully
defined. If, on the other hand, the flowrate of the inlet stream is
1-5
1-6
Operations
undefined, HYSYS will not be able to 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.
1.2
1.2.1
Operations
Installing Operations
There are a number of ways to install unit operations into your
Flowsheet. The operations which are available will depend on where
you are currently working (Main Flowsheet, Template Sub-Flowsheet or
Column Sub-Flowsheet). If you are in the Main or Template
environments, all operations will be 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.
For detailed information on installing unit operations, refer to Section
1.3.3 - Object Palette or Section 1.3.5 - Installing Operations in the
User’s Guide.
The two primary areas from which you can install operations are the
UnitOps view and the Object Palette.
1-6
Operation Category
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
Steady State Modeling
Operation Category
Types
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)
Prebuilt Columns
3 Stripper Crude, 4 Stripper Crude, Absorber,
Distillation, FCCU Main Fractionator, LiquidLiquid 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
1-7
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.
Prior to describing each of the unit operations, a quick overview of the
material and energy streams will be provided, as they are the means of
transferring process information between operations.
1.2.2
The Unit Operation Property
View
Although each Unit Operation differ in funcionality and operation, in
general, the Unit Operation property view remains fairly consistent in
its overall appearance. Figure 1.1 show a generic property view for a
Unit Operation. The Operation property view may 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 fairly similar functionality.
1-7
1-8
Operations
Figure 1.1
The Name of
the Unit
Operation
The various
pages of the
active tab.
The active tab
of the
property view.
Deletes this Unit
Operation from the
Flowsheet.
1-8
Displays the calculation
status of this Unit
Operation. It may also
display what specifications
are required.
Ignores this Unit
Operation.
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.
Dynamics
Sets the dynamic parameters associated with this Unit
Operation such valve sizing and pressure flow relations.
Not relevant to Steady State modeling. For information on
Dynamic Modelling implications of this tab, consult the
Dynamic Modelling guide.
Streams
2-1
2 Streams
2.1 Material Stream Property View.................................................................... 3
2.1.1
2.1.2
2.1.3
2.1.4
Worksheet Tab ......................................................................................... 4
Attachments Tab .................................................................................... 10
Dynamics Tab ........................................................................................ 10
User Variables Tab ................................................................................. 10
2.2 Energy Stream Property View ................................................................... 11
2.2.1
2.2.2
2.2.3
2.2.4
Stream Tab..............................................................................................11
Unit Ops Tab .......................................................................................... 12
Dynamics Tab ........................................................................................ 12
User Variables Tab ................................................................................. 12
2-1
2-2
2-2
Streams
2.1
Material Stream Button
(Blue Arrow)
2-3
Material Stream
Property View
Material Streams are added to a simulation in the Main Simulation
Environment, where you can define their properties and composition.
There are several ways to add a Material Stream, represented on the
Object Palette by a blue arrow, to your simulation. One of the simplest
ways to install a Material Stream is by pressing the F11 key. For
information on other available methods, refer to Section 3.3 - Installing
Streams and Operations in the User’s Guide.
The Material Stream property view contains several tabs and associated
pages that allow you to define parameters, view properties, add utilities
and specify dynamic information. Figure 2.1 shows the initial view of a
new Material Stream after it has been added to a simulation.
Figure 2.1
View Upstream Operation
Button
View Downstream Operation
Button
The buttons and Status Bar at the bottom of the view are always visible
when the Material Stream view is open. If you want to copy properties
or compositions from existing streams from your flowsheet, you can do
so by pressing the Define from Other Stream button. This button opens
a window from which you can choose the stream properties and/or
compositions you want to copy to your stream.
The buttons with the green arrows to the left of the Status Bar are the
View Upstream Operation and View Downstream Operation buttons.
2-3
2-4
Material Stream Property View
The left-pointing arrow indicates the downstream position and the
right-pointing arrow the upstream position. If the stream you are
looking at is attached to an operation, selecting these buttons will open
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 buttons will open a Feeder Block or a
Product Block.
2.1.1
Worksheet Tab
The Worksheet tab has three associated pages that display information
relating to the stream properties. These pages are: Conditions,
Properties and Compositions.
Figure 2.2 shows the Worksheet tab view of a solved Material Stream
within a simulation.
Figure 2.2
The green status bar
containing OK indicates a
completely solved stream
Conditions Page
The Conditions page displays all of the default stream information as it
is shown on the Material Streams Workbook page. The names and
current values for the following parameters are shown:
• Stream Name
• Vapour/Phase Fraction
2-4
Streams
•
•
•
•
•
•
•
•
2-5
Temperature
Pressure
Molar Flow
Mass Flow
LiqVol Flow
Molar Enthalpy
Molar Entropy
Heat Flow
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.
•
•
•
•
•
Temperature
Pressure
Vapour Fraction
Entropy
Enthalpy
Note that 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.
Depending on which of the state variables are known, HYSYS will
automatically perform the correct flash calculation.
Once a stream is flashed, all other properties about the stream are
calculated as well. You can examine these properties through the
additional pages of the property view. Note that a flowrate is required to
calculate the Heat Flow.
The Stream parameters may be specified on the Conditions page or in
the Workbook. Changes in one area will be reflected throughout the
Flowsheet.
Note that while the Workbook displays the bulk conditions of the
stream, the Conditions, Properties and Compositions pages will also
show the values for the individual phase conditions. For instance, if you
expand the width of the default stream view from Figure 2.2, you will
2-5
2-6
Material Stream Property View
see the view shown in Figure 2.3. In this case, the vapour phase and
liquid phase properties are displayed beside the overall stream
properties. If there was another liquid phase, it would be shown as well.
Figure 2.3
Rather than expanding the view, you may use the horizontal Scroll Bar
to view phase properties which are not currently being shown.
Note that when you are viewing a Stream property view in the
Column Sub-Flowsheet, there will be an additional Create
Column Stream Spec button on the Conditions page. For more
information this button’s functionality, see the Specification
Types Section of Chapter 7 - Column of the Steady State
Modelling Guide.
Properties Page
The Properties page shows all the Transport Properties for each stream
phase. These properties include:
•
•
•
•
•
•
2-6
Vapour/Phase Fraction
Temperature
Pressure
Actual Vol. Flow
Mass Enthalpy
Mass Entropy
Streams
•
•
•
•
•
•
•
•
•
•
•
2-7
Molecular Weight
Molar Density
Mass Density
Std. Liquid Mass Density
Molar Heat Capacity
Mass Heat Capacity
Thermal Conductivity
Viscosity
Surface Tension
Specific Heat
Z Factor
Expand the view or use the scroll bar to view the individual phase
parameters, as shown in Figure 2.4. None of the parameters shown on
this page (i.e., the parameters shown in black) can be edited, since they
are dependent on the basic stream conditions (pressure, temperature,
compositions, etc.)
Figure 2.4
Composition Page
You are unable to change the
composition of streams
calculated by HYSYS. The
default colour for specified
stream values is blue and
black for those calculated by
HYSYS.
Select Composition on the Worksheet tab to view the Composition
page for the Material Stream. You can specify or change the stream
composition by either pressing the Edit button or by entering a value in
a worksheet cell and pressing ENTER. Either action will access the Input
Composition view.
For the example shown in Figure 2.5, the mole fractions for each
component in the overall phase, the vapour phase and the aqueous
2-7
2-8
Material Stream Property View
phase are displayed. You may view the composition in a different basis
by selecting the Basis button.
Figure 2.5
Close Button
For fractional bases, selecting
the OK button automatically
normalizes the composition if
all compositions contain a
value. The Cancel button
closes the dialog without
accepting any changes.
After pressing the Basis button, you can select one of the radio buttons
on the Stream dialog to choose a new compositional basis. After
pressing the Close button, the stream compositions will be shown using
the new basis.
Pressing the Edit button in the Material Stream property view opens
the Input Composition dialog. When working in the Input
Composition dialog you can edit the compositions by selecting a radio
button in the Composition Basis group and entering the compositions
into the appropriate cells.
The Composition Controls group has two buttons that can be used to
manipulate the compositions.
You will not be able to edit the compositions for a stream that is
calculated by HYSYS. When you move to the Comp page for
such a stream, the Edit button will be inaccessible.
2-8
Streams
Composition
Control Button
Action
Erase
Clears all compositions.
Normalize
Allows you to enter any value for fractional compositions
and has HYSYS normalize the values such that the total
equals 1. This button is useful when many components
are available, but you wish to supply compositions for only
a few. When you enter the compositions, press the
Normalize button and HYSYS will ensure the Total is 1.0,
while also specifying any <empty> compositions as zero.
If compositions are left as <empty>, HYSYS will not
perform the flash calculation on the stream. Note that the
Normalize button does not apply to flow compositional
bases, since there is no restriction on the total flowrate.
2-9
K Value Page
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: Ki = Distribution Coefficient
yi = mole fraction of component i in the vapour phase
xi = mole fraction of component i in the liquid phase
Figure 2.6
2-9
2-10
Material Stream Property View
Notes Page
You can use this page to add any notes pertinent to the unit operation
or the simulation case in general.
2.1.2
Attachments Tab
Unit Ops Page
On the Unit Ops page, you can view the names and types of unit
operations and logicals to which the stream is attached. The view
shows 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 the specific unit operation or
logical by double clicking on a Name or Type cell.
Utilities Page
The options on the Utilities page allow you to:
• Attach Utilities to the current Stream.
• View existing Utilities that are attached to the Stream.
• Delete existing Utilities that are attached to the Stream.
2.1.3
Dynamics Tab
The options on the Dynamics tab allow you to set the dynamic
specifications for a simulation. Unless you plan to run the case in
Dynamics mode, you are not required to change any of the information
available on the Specs page of this tab.
2.1.4
User Variables Tab
On this tab you can create and implement your own User Variables for
use in a HYSYS simulation. For more information on User Variables see
the User Variables chapter in the Customization Guide.
2-10
Streams
2.2
Energy Stream Button (red)
2-11
Energy Stream
Property View
Energy Streams are represented by the red arrow button on the Tool
Palette. One method of adding an Energy Stream is by pressing this
button and then clicking on the PFD. This method will immediately
access the Energy Stream property view. You can also open the Energy
Stream view from the Energy Streams page of the Workbook by double
clicking in a cell associated with the stream.
The Energy Stream view contains four tabs which allow you to define
stream parameters, view objects to which the stream is attached and
specify dynamic information. These tabs are: Streams, Unit Ops,
Dynamics and User Variables.
View Downstream Operation
Button
View Upstream Operation
Button
When converting an Energy
Stream to a Material Stream,
all Material Stream properties
will be unspecified, except for
the stream name.
As with the Material streams, the Energy Stream view has View
Upstream Operation and View Downstream Operation buttons that
allow you to view the unit operation to which the stream is connected.
However, 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 Energy stream) the associated button will not be active.
2.2.1
Stream Tab
From this tab, you can specify the Stream Name and Heat Flow on the
Stream. In addition, you can convert the current stream to a material
stream by selecting the Convert to Material button. When you convert
to a material stream, you will lose all of the current stream information,
except for the stream name. Figure 2.7 shows the Stream tab of the
Energy Stream property view.
Figure 2.7
2-11
2-12
Energy Stream Property View
2.2.2
Unit Ops Tab
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 will either show 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 2.8
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.
2.2.3
Dynamics Tab
The options on the Dynamics tab allow you to set the dynamic
specifications for a simulation. Unless you plan to run the case in
dynamic mode, you are not required to change any of the information
available on the Specs page of this tab.
2.2.4
User Variables Tab
On this tab you can create and implement User Variables for use in your
HYSYS simulation. For more information on working with User
Variables, see the User Variable chapter in the Customization Guide.
2-12
Heat Transfer Equipment
3-1
3 Heat Transfer
Equipment
3.1 Air Cooler ...................................................................................................... 3
3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3.1.6
3.1.7
Theory ...................................................................................................... 3
Design Tab ............................................................................................... 4
Rating Tab ................................................................................................ 6
Worksheet Tab ......................................................................................... 7
Performance Tab...................................................................................... 7
Dynamics Tab .......................................................................................... 8
Air Cooler Example .................................................................................. 9
3.2 Cooler/Heater.............................................................................................. 11
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.6
3.2.7
Theory .....................................................................................................11
Design Tab ..............................................................................................11
Rating Tab .............................................................................................. 13
Worksheet Tab ....................................................................................... 13
Performance Tab.................................................................................... 14
Dynamics Tab ........................................................................................ 16
Example - Gas Cooler............................................................................ 16
3.3 Heat Exchanger .......................................................................................... 18
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3.6
3.3.7
Theory .................................................................................................... 19
Design Tab ............................................................................................. 20
Rating Tab .............................................................................................. 30
Worksheet Tab ....................................................................................... 43
Performance Tab.................................................................................... 44
Dynamics Tab ........................................................................................ 46
Heat Exchanger Examples..................................................................... 46
3-1
3-2
3.4 LNG.............................................................................................................. 49
3.4.1
3.4.2
3.4.3
3.4.4
3.4.5
3.4.6
3-2
Design Tab ............................................................................................. 50
Rating Tab .............................................................................................. 57
Worksheet Tab ....................................................................................... 58
Performance Tab.................................................................................... 58
Dynamics Tab ....................................................................................... 61‘
LNG Example......................................................................................... 61
Heat Transfer Equipment
3.1
3-3
Air Cooler
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:
Air Cooler Button
• The overall heat transfer coefficient, UA
• The total air flow
• The exit stream temperature
To install the AIR COOLER operation, press F12 and choose Air Cooler
from the UnitOps view or select the Air Cooler button in the Object
Palette.
To ignore the AIR COOLER, select the Ignore check box. HYSYS will
completely disregard the operation (and will not calculate the outlet
stream) until you restore it to an active state by clearing the check box.
3.1.1
Theory
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 shown as follows:
Mair(Hout - Hin)air = Mprocess(Hin - Hout)process
(3.1)
where: Mair = Air stream mass flow rate
Mprocess = Process stream mass flow rate
H = Enthalpy
3-3
3-4
Air Cooler
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 = -UADTLMFt
(3.2)
where: U = Overall heat transfer coefficient
A = Surface area available for heat transfer
DTLM = Log mean temperature difference (LMTD)
Ft = correction factor
The LMTD correction factor, Ft, is calculated from the geometry and
configuration of the air cooler.
3.1.2
Design Tab
The Design tab provides access to four pages: the Connections,
Parameters, User Variables and Notes page.
Connections Page
On the Connections page, provide the names of the Feed and Product
streams attached to the AIR COOLER. You can change the name of the
operation in the Name cell. Figure 3.1 shows the Connections page for
the Air Cooler.
Figure 3.1
3-4
Heat Transfer Equipment
3-5
Parameters Page
On the Parameters page, the following information is displayed:
Air Cooler
Parameters
Description
Delta P
The pressure drops (DP) for the process side of the air
cooler can be specified. The pressure drop can be
calculated if both the inlet and exit pressures of the process
stream are supplied. There is no pressure drop associated
with the air stream. The air pressure through the cooler is
assumed to be atmospheric.
UA
This is 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
may either be specified or calculated by HYSYS.
Configuration
The Configuration drop-down list 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.
Inlet/Exit Air
Temperatures
The inlet and exit air stream temperatures may be specified
or calculated by HYSYS.
Figure 3.2
User Variables Page
The User Variables page allows you to attach code and customize your
HYSYS simulation case by adding User Variables. For more information
on implementing this option, see the User Variables chapter in the
Customization Guide.
3-5
3-6
Air Cooler
Notes Page
The Notes page provides an editor where you can record any remarks
pertaining to the AIR COOLER or to your simulation case in general.
3.1.3
Rating Tab
The Rating tab contains two pages: the Sizing and thr Nozzles page.
Sizing Page
Figure 3.3
In the Sizing page, the following fan rating information is displayed for
the AIR COOLER operation:
3-6
Fan Data
Description
Number of Fans
Specify the number of fans you want in the air cooler.
Speed
This is the actual speed of the fan.
Demanded
Speed
This is the desired speed of the fan. In Steady State
mode, the demanded speed will always equal the speed
of the fan. The desired speed is either calculated from
the fan rating information or user-specified.
Max Acceleration
This parameter is applicable only in Dynamics mode.
Design Speed
This is the reference Air Cooler fan speed. It is used in
the calculation of the actual air flow through the cooler.
Design Flow
This is the reference Air Cooler air flow. It is used in the
calculation of the actual air flow through the cooler.
Current Air Flow
This may be calculated or user-specified. If the air flow
is specified no other fan rating information needs to be
specified.
Heat Transfer Equipment
3-7
The air flow through the fan is calculated using a linear relation:
Speed
Fan Air Flow = ------------------------------------ × Design Flow
Design Speed
(3.3)
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 =
3.1.4
The PF Specs page is relevant
to Dynamics cases only.
∑ Fan Air Flow
(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 AIR
COOLER. The Conditions, Properties, and Composition pages contain
selected information from the corresponding pages of the Worksheet
tab for the stream property view. The PF Specs page contains a
summary of the stream property view Dynamics tab.
3.1.5
Performance Tab
The Performance tab contains pages that display the results of the Air
Cooler calculations.
Results Page
The information from the Results page is shown as follows:
Results
Working Fluid
Duty
Description
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
This is the product of the Overall Heat Transfer
Coefficient and the Total Area available for heat
transfer. The UA may either be specified or calculated
by HYSYS.
3-7
3-8
Air Cooler
Results
Description
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 ) )
LMTD
where:
∆T 1 = T hot, out – T cold, in
∆T 2 = T hot, in – T cold, o ut
Inlet/Exit Process
Temperatures
The inlet and exit process stream temperatures may
be specified or calculated in HYSYS.
Inlet/Exit Air
Temperatures
The inlet and exit air stream temperatures may be
specified or calculated in HYSYS.
Figure 3.4
3.1.6
When working in Steady State
mode, you are not required to
change anything on this page.
3-8
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. For information on running the COOLER and HEATER
operations in Dynamic mode, see the Dynamic Modelling guide for
details.
Heat Transfer Equipment
3.1.7
3-9
Air Cooler Example
An Air Cooler will be used to cool a liquid process stream.
1.
Create the following Fluid Package and add the Material stream
Feed:
Property Package
Components
NRTL
Ethanol, 1-Pentanol
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
2.
Input Area
Entry
Temperature
100.0000 °F
Pressure
16.0000 psi
Molar Flow
2200.0000 lbmole/hr
Ethanol Mole Frac
0.5
1-Pentanol Mole Frac
0.5
Specify the AIR COOLER connections and parameters as shown in
the table below. The Parameters page contains the fan rating and
speed specifications.
AIR COOLER [AC-100]
Tab [Page]
Input Area
Design
[Connections]
Feed
Feed
Product
Product
Design [Parameters]
3.
Entry
Delta P
1.2 psi
Configuration
1 tube row, 1 pass
Air Intake
Temperature
77 °F
Air Outlet
Temperature
86 °F
Using the following specifications, HYSYS is able to calculate the
actual volumetric flow of air:
AIR COOLER [AC-100]
Tab [Page]
Rating [Sizing]
Input Area
Entry
Number of Fans
1
Demanded Speed
42 rpm
Design Speed
60 rpm
Design Flow
5.5x107 barrel/day
3-9
3-10
Air Cooler
4.
At this point, the Air Cooler unit operation is fully specified. The
exit stream conditions are displayed in the Conditions page of the
Worksheet tab.
Figure 3.5
5.
The Air Cooler unit operation parameters are shown in the Results
page of the Performance tab:
Figure 3.6
3-10
Heat Transfer Equipment
3.2
Cooler button
3-11
Cooler/Heater
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
Heater button
3.2.1
The only difference between
the COOLER and HEATER is
the energy balance sign
convention.
Theory
The COOLER and HEATER use the same basic equation; the primary
difference is the sign convention. You specify the absolute energy flow
of the utility stream, and HYSYS will then apply 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
(3.5)
• For a HEATER, the heat flow of the energy stream is
added:
Heat Flowinlet + Dutycooler = Heat Flowoutlet
(3.6)
To install the COOLER operation, press F12 and choose Cooler from the
UnitOps view or select the Cooler button in the Object Palette. You may
install the HEATER in a similar manner.
3.2.2
Design Tab
The Design tab provides access to four pages: the Connections,
Parameters, User Variables and Notes page.
Connections Page
On the Connections page, provide the names of the Inlet, Outlet and
Energy streams attached to the operation. You may change the name of
the Operation in the Name cell. Figure 3.7 shows the Connections Page
for a COOLER operation.
3-11
3-12
Cooler/Heater
Figure 3.7
Parameters Page
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 3.8 shows this page.
Figure 3.8
Remember that HYSYS will use the proper sign convention for
the unit you have chosen, so you may always enter a positive
duty value.
3-12
Heat Transfer Equipment
3-13
You may supply a negative Duty value, however, be aware that:
• 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 attach code and customize your
HYSYS simulation case by adding User Variables. For more information
on implementing this option, see the User Variables chapter in the
Customization Guide.
Notes Page
The Notes page provides an editor where you can record any remarks
pertaining to the COOLER or HEATER or to your simulation case.
3.2.3
Rating Tab
Nozzles Page
You are required to supply
rating information only when
working with a Dynamics
simulation.
On this page you are able to specify nozzle parameters on both the Inlet
and Outlet streams connected to a COOLER or HEATER. Because the
addition of nozzles to HEATERS and COOLERS is relevant when
creating dynamic simulations, detailed information relating to this
page is available in the Dynamics Modelling guide, Chapter 4 - Heat
Transfer Equipment.
Heat Loss Page
Rating information regarding heat loss is relevant only in Dynamics
mode. For information on specifying information on this page, see the
Dynamic Modelling guide.
3.2.4
The PF Specs page is relevant
to Dynamics cases only.
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
3-13
3-14
Cooler/Heater
3.2.5
Performance Tab
The Performance tab contains pages that display calculated stream
information. The performance parameters include the following
stream properties:
•
•
•
•
Pressure
Temperature
Vapour Fraction
Enthalpy
All information displayed on the Performance tab is read-only
Profiles Page
When viewing the Profiles page when working in Steady State,
regardless of the number of zones specified, the Zone Conditions will
be calculated for the Inlet zone only.
Figure 3.9
Plots Page
On the Plots page you can graph any of the performance parameters to
view the changes that occurs across the operation. In Steady State, this
will always be a straight line because the stream calculated stream
properties are taken only from the Inlet and Outlet streams. These
values are not calculated incrementally through the operation. All
performance parameters are listed in the X Variable and Y Variable
3-14
Heat Transfer Equipment
In Steady State, stream
property readings are taken
only from the Inlet and Outlet
streams for the plots. As such,
the resulting graph will
always be a straight line.
3-15
drop down boxes located below the graph. Select the axis and variables
you want to compare and the plot will be displayed. You can also
specify the number of calculation intervals you want calculated across
the graph, in the cell at the bottom of the page. This will simply divide
the plot line up into equally spaced intervals, with the values displayed
as described on the Tables page.
A temperature - pressure graph for a COOLER, with 5 intervals
specified, is shown in Figure 3.10.
Figure 3.10
Tables Page
Information on the Tables
page is read-only.
This page shows the Tabular Plot Results that are used to produce the
graphs on the Plots page. All values for the pressure, temperature,
vapour fraction and enthalpy calculated for each interval is listed here.
You can specify the number of calculation intervals at the bottom of
this page.
Figure 3.11
3-15
3-16
Cooler/Heater
3.2.6
When working in Steady State
mode, you are not required to
change anything on this page.
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. For information on running the COOLER and HEATER
operations in Dynamic mode, see the Dynamic Modelling guide,
Chapter 4 - Heat Transfer Equipment for details.
3.2.7
Example - Gas Cooler
A gas stream needs to be cooled from 60oF to -105oF with a pressure
drop of 15 psi.
1.
Create the following Fluid Package:
Property Package
Components
Peng Robinson
Nitrogen, Carbon Dioxide, C1, C2, C3, i-C4,
n-C4, i-C5, n-C5, n-C6, n-C7, n-C8
2.
Install a material stream with the following specifications.
MATERIAL STREAM [E-1 Inlet]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
3-16
Input Area
Entry
Temperature
60.0000 F
Pressure
600.0000 psi
Molar Flow
100.0000 lbmole/hr
Nitrogen Mole Frac
0.0149
CO2 Mole Frac
0.0020
Methane Mole Frac
0.9122
Ethane Mole Frac
0.0496
Propane Mole Frac
0.0148
i-Butane Mole Frac
0.0026
n-Butane Mole Frac
0.0020
i-Pentane Mole Frac
0.0010
n-Pentane Mole Frac
0.0006
n-Hexane Mole Frac
0.0001
n-Heptane Mole Frac
0.0001
n-Octane Mole Frac
0.0001
Heat Transfer Equipment
3.
3-17
Install a COOLER, and complete the Connections page as shown in
Figure 3.12.
Figure 3.12
Cooler Button
The duty required to cool
stream E-1 Inlet to the
conditions of E-1 Outlet is the
Heat Flow of stream E-1 Duty.
This duty will also be
displayed on the Parameters
page of the Design tab of the
COOLER property view.
4.
Specify a Pressure Drop of 15 psi on the Parameters page.
5.
Move to the Conditions page of the Worksheet tab. At this point,
stream E-1 Outlet is not completely known, nor is the Duty value
known. Use up the one degree of freedom remaining by specifying
the temperature of E-1 Outlet to be -105oF. HYSYS will calculate
the remaining conditions of the outlet stream, as well as the
necessary cooling Duty. The specified values are as follows:
Name
E-1 Inlet
E-1 Outlet
Temperature [F]
60.0000
-105.0000
Pressure [psia]
600.0000
<empty>
Molar Flow [lbmole/hr]
100.0000
<empty>
3-17
3-18
Heat Exchanger
6.
With these specifications, the solution should converge. The
results are shown on the Conditions page of the Worksheet tab.
Figure 3.13
3.3
Additional Heat Exchanger
models, such as TASC and
STX, are also available.
Contact your local Hyprotech
representative for details.
Heat Exchanger
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 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.
To install the HEAT EXCHANGER operation, press F12 and choose Heat
Exchanger from the UnitOps view or select the Heat Exchanger button
in the Object Palette.
Heat Exchanger Button
3-18
To ignore the Heat Exchanger, select the Ignored check box. HYSYS will
completely disregard the operation (and will not calculate the outlet
stream) until you restore it to an active state by clearing the check box.
Heat Transfer Equipment
3.3.1
3-19
Theory
The HEAT EXCHANGER calculations are based on energy balances for
the hot and cold fluids. 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
(3.7)
where: M = Fluid mass flow rate
H = Enthalpy
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.
Qleak = Heat Leak
Qloss = Heat Loss
The Balance Error is a HEAT EXCHANGER Specification that will equal
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 Heat Exchanger duty may also be defined in terms of the overall
heat transfer coefficient, the area available for heat exchange and the
log mean temperature difference:
Q = UADTLMFt
(3.8)
where: U = Overall heat transfer coefficient
A = Surface area available for heat transfer
DTLM = Log mean temperature difference (LMTD)
Ft = LMTD correction factor
Note that 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.
3-19
3-20
Heat Exchanger
3.3.2
Design Tab
The Design tab contains five pages: the Connections, Parameters,
Specs, User Variables and Notes pages.
Connections Page
On the Connections page, you provide the operation name as well as
the names of the shell and tube inlet and outlet streams.
Figure 3.14
Refer to the Heat Exchanger
Example in Chapter 2 Flowsheet Architecture for
information on installing a
HEAT EXCHANGER across
Flowsheet boundaries.
The Main Flowsheet is the default Flowsheet for the Tube and Shell
side. You may select a Sub-Flowsheet on the Tube and/or Shell side
which will allow 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
On the Parameters page, you can select the Heat Exchanger Model and
specify relevant physical data. The Parameters page display depends
3-20
Heat Transfer Equipment
3-21
on the Heat Exchanger Model selected.
This section discusses the
Steady State functioning of the
Dynamic Rating heat
exchanger. See the Dynamic
Modelling guide, Chapter 4 Heat Transfer Equipment for
detailed information on the
Dynamic Rating in Dynamics
mode.
Note that 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 SubFlowsheet, the Heat Exchanger is “Calculated from Column” as
a simple heat and mass balance.
From the drop down list, select the calculation model for the HEAT
EXCHANGER. The following heat exchanger models are available:
•
•
•
•
Exchanger Design (Endpoint)
Exchanger Design (Weighted)
Steady State Rating
Dynamic Rating
All Heat Exchanger models allow the specification of either Counter or
Co-Current tube flow. See Section 3.3.3 - Rating Tab for further details.
End Point Design Model
The End Point exchanger design model is based on the standard heat
exchanger duty equation (Equation (3.8)) defined in terms of overall
heat transfer coefficient, area available for heat exchange and the log
mean temperature difference. The main assumptions of the model are:
1.
Overall heat transfer coefficient, U is constant.
2.
Specific heats of both shell and tube side streams are constant.
In short, this 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.
3-21
3-22
Heat Exchanger
Figure 3.15
The following parameters are available when the End Point model is
selected:
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.
End Point
Parameter
Description
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides
of the exchanger may be specified here. If you do
not specify the Delta P values, HYSYS will calculate
them from the attached stream pressures.
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.
UA
This is 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 may either be
specified, or calculated by HYSYS.
Weighted Design Model
The Weighted Heat Exchanger
Model is available for countercurrent exchangers only.
3-22
The Weighted exchanger design model is an excellent model to deal
with 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.
Heat Transfer Equipment
3-23
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.
When you select the Weighted model, the Parameters page will appear
as shown in Figure 3.16.
Figure 3.16
The following table describes the items available on this page:
Item
Description
You can specify whether or not there is heat loss/
heat leak by choosing one of the radio buttons. By
default, the None radio button is selected. The other
two options incorporate heat loss/heat leak:
Heat Loss/Leak
• 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.
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides
of the exchanger may be specified here. If you do
not specify the DP values, HYSYS will calculate
them from the attached stream pressures.
UA
This is 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 may either be
specified, or calculated by HYSYS.
3-23
3-24
Heat Exchanger
For each side of the HEAT EXCHANGER, the following parameters are
displayed (all but the Pass Names may be modified):
Individual Heat
Curve Details
Description
Pass Name
Identifies the shell and tube side according to the
names you provided on the Connections page.
Intervals
The number of intervals may be specified. For nonlinear temperature profiles, more intervals will be
necessary.
Dew/Bubble Point
Check this box 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 box
should be checked.
There are three choices for the Step Type in the Individual Heat Curve
Details group box:
Step Type
Step Description
Equal Enthalpy
All intervals have an equal enthalpy change.
Equal Temperature
All intervals have an equal temperature change.
Auto Interval
HYSYS will determine where points should be added
to the heat curve. This is designed to minimize the
error, using the least number of intervals.
The Pressure Profile is updated in the outer iteration loop, using one of
the following methods:
Pressure Profile
Calculation Method
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
The 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.
3-24
Heat Transfer Equipment
3-25
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 3.17
The following parameters are available on this page when the Steady
State Rating model is selected:
End Point
Parameter
Description
Tubeside and
Shellside Delta P
The pressure drops (DP) for the tube and shell sides
of the exchanger may be specified here. If you do
not specify the Delta P values, HYSYS will calculate
them from the attached stream pressures.
UA
This is 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 may 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.
Note that the Specs page will no longer appear when Dynamic Rating is
selected.
The Basic model is based on the same assumptions as the End Point
design model which uses the standard heat exchanger duty equation
(Equation (3.8)) defined in terms of overall heat transfer coefficient,
3-25
3-26
Heat Exchanger
area available for heat exchange, and the log mean temperature
difference. The Basic model is actually the counterpart of the End Point
design model for Dynamics and dynamic rating but can also be used
for Steady State heat exchanger rating.
The Detailed model is based on the same assumptions as the Weighted
design 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 design
model for Dynamics and dynamic rating but can also be used for
Steady State heat exchanger rating.
Once Dynamic Rating is selected, no further information is required
from the Parameters page of the Design tab. Choice of Basic or
Detailed model is made on the Parameters page of the Rating tab.
Figure 3.18
Specs Page
If you are working with a
Dynamic Rating model, this
page will not appear on the
Design tab.
3-26
On the Specs page, you will find three group boxes that organize the
various specification and solver information. The information provided
in the Specs page is only valid for the Weighted, Endpoint and Steady
State Rating models. This page will not appear when the Dynamic
Rating model is selected
Heat Transfer Equipment
3-27
Figure 3.19
Solver Group
The following parameters are listed in the Solver group box:
Solver 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 is displayed. In
the outer loop, the heat curve is updated and the
property package calculations are performed. Nonrigorous 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 specified input. Once the unit has solved, the values of these
variables will be displayed.
Specifications Group
Without the Heat Balance
specification, the heat
equation will not balance. For
this reason it is considered a
Heat Exchanger constraint.
Note that 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 box.
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.
3-27
3-28
Heat Exchanger
You can View or Delete highlighted specifications by using the buttons
at the right of the group box. A specification view appears automatically
each time a new spec is created via the Add button. Shown in Figure
3.20 is a typical view of a specification, which is accessed via the View
or Add button.
Each specification view has two tabbed pages: Parameters and
Summary. As an example, defining the Delta Temp spec requires two
stream names, and a value for the specification.
Figure 3.20
The Summary page is used to define whether the specification is Active
or an Estimate. The Spec Value is also shown on this page.
An Active specification is one
that the convergence
algorithm is trying to meet. An
Active specification is on when
both check boxes are selected.
3-28
Note that information supplied on the specification view will also
appear in the Specifications group.
All specifications will be one of the following three types:
Specification Type
Description
Active
An active specification is one that the convergence
algorithm is trying to meet. Note that an active
specification always serves as an initial estimate
(when the Active box is checked, HYSYS
automatically checks the Estimate box). An active
specification exhausts one degree of freedom.
Heat Transfer Equipment
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
may be made Active or an
Estimate at a later time.
Specification Type
Description
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,
clear the Active check box. The value will then serve
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, clear both the Active and
Estimate check boxes. By ignoring rather than
deleting a specification, it will be available if you wish
to use it later.
3-29
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 wish to determine which ones should
be active, which should be estimates and which ones should be ignored
altogether. By manipulating the check boxes among various
specifications, you can test various combinations of the three types to
see their effect on the results.
The available specification types include:
Specification
Description
The Hot Inlet Equilibrium
temperature is the
temperature of the inlet hot
stream minus the heat loss
temperature drop.
Temperature
The temperature of any stream attached to the HEAT
EXCHANGER. The hot or cold inlet equilibrium
temperature may also be defined.
Delta Temp
The Cold Inlet Equilibrium
temperature is the
temperature of the inlet cold
stream plus the heat leak
temperature rise.
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) may 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 will be 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 may be specified between any two of the
following duties: overall, error, heat loss and heat
leak.
3-29
3-30
Heat Exchanger
Specification
Description
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 attach code and customize your
HYSYS simulation case by adding User Variables. For more information
on implementing this option, see the User Variables chapter in the
Customization Guide.
Notes Pages
The Notes page provides a text editor where you can record any
comments or information regarding the HEAT EXCHANGER or
pertaining to your simulation, in general.
3.3.3
Rating Tab
The Rating tab contains four pages: the Sizing, Parameters, Nozzles
and Heat Loss pages. The Parameters page is used exclusively by the
Dynamics Heat Exchanger Model and will only become active either in
Dynamics mode or while using the Dynamic Rating model.
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 organized by three radio buttons: Overall, Shell, and
Tube.
3-30
Heat Transfer Equipment
3-31
Overall
Tube flow direction can be
defined as either Counter or CoCurrent for all Heat Exchanger
calculation models.
If the Overall radio button is selected, the overall Heat Exchanger
geometry is displayed:
Figure 3.21
In the Configuration section, you can specify whether multiple shells
will be used in the heat exchanger design. The following fields are
displayed and can be modified in the Configuration section.
Field
Description
If a multiple number of shells are specified in series,
the configuration is shown as follows:
Number of Shells in
Series
If a multiple number of shells are specified in parallel,
the configuration is shown as follows:
Number of Shells in
Parallel
Note: Currently, multiple shells in parallel are not
supported in HYSYS.
Tube Passes per
Shell
The number of tube passes per shell. Usually equal
to 2n where n is the number of shells.
3-31
3-32
Heat Exchanger
Field
Description
The exchanger orientation defines whether or not the
shell is horizontal or vertical. Used only in dynamic
simulations.
Exchanger
Orientation
When the shell orientation is vertical, you can also
specify whether the shell feed is at the top or bottom
via a checkbox:
First Tube Pass
Flow Direction
Specifies whether or not the tube feed is co-current
or counter-current.
Elevation (base)
The height of the base of the exchanger above the
ground. Used only in dynamic simulations.
You may 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
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 is used in the Dynamics Heat Exchanger Model in
the calculation of liquid level in the shell.
TEMA Type Drop down Lists
The shape of Heat Exchanger may 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. For a more
detailed discussion of TEMA-style shell-and-tube heat exchangers,
refer to page 11-33 of the Perry’s Chemical Engineers’ Handbook (1997
edition).
In the Calculated Information group, the following heat exchanger
parameters are listed:
•
•
•
•
•
•
•
•
•
3-32
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
Heat Transfer Equipment
3-33
Shell
If the Shell radio button is selected, the shell configuration and the
baffle arrangement in each shell can be specified.
Figure 3.22
In the Shell and Tube Bundle Data section, you can specify whether
multiple shells will be used in the heat exchanger design. The following
fields are displayed and can be modified in this section.
Field
Description
Shell Diameter
The diameter of the shell(s) is shown in this field.
Number of Tubes
per Shell
This is the number of tube holes on the tube sheet.
Tube Pitch
This is the shortest distance between the centres of
two adjacent tubes.
In HYSYS, the tubes in the a single shell may be
arranged in four different symmetrical patterns:
• Triangular (30°)
• Triangular Rotated (60°)
Tube Layout Angle
• 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.
3-33
3-34
Heat Exchanger
The following fields are displayed and can be modified in the Shell
Baffles section:
Field
Description
You can choose 4 different baffle types:
Shell Baffle Type
•
•
•
•
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 the baffle occupies
relative to the cross sectional area of the shell.
Baffle Spacing
You can specify the space between each baffle.
Tube
If the Tube radio button is selected, information about the tube
geometry in each shell can be specified:
Figure 3.23
In the Dimensions group, the following tube geometric parameters
may be specified:
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
Tube Length
3-34
This is the heat transfer length of one tube in a single
heat exchanger shell. Note that this value is not the
actual tube length.
Heat Transfer Equipment
3-35
In the Tube Properties group, the following metal tube heat transfer
properties must be specified:
•
•
•
•
Tube Fouling Factor
Thermal Conductivity
Wall Specific Heat Capacity, Cp
Wall Density
Parameters Page
The Parameters page of the Rating tab is used to define rating
parameters for the Dynamic Rating model or the Dynamics Heat
Exchanger 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’s 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
Selecting the Basic model radio button on the Parameters page in
Dynamics mode will bring up the following view:
Figure 3.24
3-35
3-36
Heat Exchanger
The Dimensions section 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 may be specified but does not impact the steady state
solver.
The Parameters section includes the following Heat Exchanger
parameters. All but the correction factor, F, may be modified:
Field
Description
Overall UA
This is 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 may 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 may be specified here. If you do
not specify the DP values, HYSYS will calculate
them from the attached stream pressures.
Detailed Model
The Detailed model option allows you to specify the Zone Information,
Heat Transfer Coefficient, and DeltaP details. Selecting the Detailed
model radio button on the Parameters page will bring up the following
view shown in Figure 3.25.
3-36
Heat Transfer Equipment
3-37
Figure 3.25
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.
In the Zone Information section you can specify:
Field
Zones per Shell
Pass
Zone Fraction
Description
Enter the number of zones you would like for one
shell. The total number of zones in a heat exchanger
shell is calculated as:
Total Zones = Total Shell Passes ⋅ Zones
The zone fraction is the fraction of space the zone
occupies relative to the total shell volume. HYSYS
automatically sets each zone to have the same
volume. You may modify the zone fractions to
occupy a larger or smaller proportion of the total
volume. Press the Normalize Zone Fractions
button in order to adjust the sum of fractions to equal
one.
3-37
3-38
Heat Exchanger
Heat Transfer Coefficients
The Heat Transfer Coefficients section 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 in the Parameters page and the stream
conditions.
• The user 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:
0.023D i D i G i 0.8 C p, i µ i 1 ⁄ 3  µ i  0.14
---------h i = -------------------  ------------  ---------------
 µ i, w
km  µi   km 
(3.9)
where: Gi = Mass velocity of the fluid in the tubes (Velocity* Density)
mi = Viscosity of the fluid in the tube
mi,w = viscosity of the fluid inside tubes, at the tube wall
Cp,i = Specific heat capacity of the fluid inside the tube
The relationship between the local heat transfer coefficients and the
overall heat transfer coefficient is shown in Equation (3.10).
1
U = --------------------------------------------------------------------Do
1
1
----- + r o + r w + ------  r i + ----
Di 
h i
ho
where: 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
3-38
(3.10)
Heat Transfer Equipment
3-39
The following information is provided in the Heat Transfer coefficients
group:
Field
Description
Shell/Tube Heat
Transfer Coefficient
The local Heat Transfer Coefficients, ho and hi, may
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 the user.
Delta P
The Delta P section 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 following information is provided in the Delta P section:
Field
Description
Shell/Tube Delta P
The pressure drops across the Shell/Tube side of
the heat exchanger may be specified or calculated.
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
• 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 the user.
• Non specified - This option is only applicable in
Dynamics mode. Pressure drop across the heat
exchanger is calculated from a pressure flow
relation.
3-39
3-40
Heat Exchanger
Detailed Heat Model Properties
By pressing the Specify Parameters for Individual Zones button, a view
appears detailing heat transfer parameters and holdup conditions for
each zone appears. 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
labelled: Z0, Z1, and Z2.
Holdup
HYSYS represents the holdup within each zone with
the letter “H”. Holdups are numbered starting from 0.
“Holdup 0” will always be the holdup of the shell
within the zone. Holdups 1 through n will represent
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 may 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 3.26
3-40
Heat Transfer Equipment
3-41
Heat Transfer (Individual) Tab
Figure 3.27
Information regarding the heat transfer elements of each tube location
in the heat exchanger is displayed on the Heat Transfer (Individual)
tab. 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 may choose whether Conductive or
Convective elements are to be displayed 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 may
be calculated by HYSYS or modified by the user.
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 are displayed. The conductivity may be
modified by the user.
3-41
3-42
Heat Exchanger
Heat Transfer (Global) Tab
This tab displays the heat transfer elements for the entire Heat
Exchanger. You may choose whether the overall Conductive or
Convective elements are to be displayed by selecting the appropriate
element type in the Heat Transfer Type drop-down list.
Tabular Results Tab
The Tabular Results tab displays the following stream properties for the
shell and tube fluid flow paths. The feed and exit stream conditions are
displayed for each zone.
•
•
•
•
•
•
•
•
Temperature
Pressure
Vapour Fraction
Molar Flow
Enthalpy
Cumulative UA
Cumulative Heat Flow
Length (into heat exchanger)
You may choose whether the flow path is shell or tube side by selecting
the appropriate flow path in the Display which flowpath? drop-down
list.
Specs (Individual) Tab
Figure 3.28
3-42
Heat Transfer Equipment
3-43
This tab displays the pressure drop specifications for each shell and
tube holdup in one spreadsheet. The Pressure Flow K and Use Pressure
Flow K columns are applicable only in Dynamics mode.
You may choose whether the shell or tube side is displayed by selecting
the Display which flowpath? drop-down list.
Specs (Global) Tab
This 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 Dynamics mode.
You may choose whether the shell or tube side is displayed by selecting
the Display which flowpath? drop-down list.
Plots Tab
The information displayed in this tab is a graphical representation of
the parameters provided in 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
3.3.4
To see the stream parameters
broken down per stream
phase, open the Worksheet tab
of the Stream Property View.
Worksheet Tab
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. The Conditions, Properties, and
Composition pages contain selected information from the
corresponding pages of the Worksheet tab for the stream property view.
The PF Specs page contains a summary of the stream property view
Dynamics tab.
3-43
3-44
Heat Exchanger
3.3.5
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.
Details Page
The information from the Details page is shown in Figure 3.29:
Figure 3.29
The appearance of this page is
slightly different for the
Dynamic Rating.
Overall Performance Group
The Overall Performance group box contains the following parameters
that are calculated by HYSYS:
3-44
Overall Performance
Parameter Description
Duty
This is the heat flow from the hot stream to the cold
stream.
Heat Loss
This is the 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
This is the 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
This is the uncorrected LMTD multiplied by the Ft
factor. For the Weighted Rating Method, the
uncorrected LMTD equals the effective LMTD.
Hot Pinch
Temperature
The hot stream temperature at the minimum
approach.
Heat Transfer Equipment
3-45
Overall Performance
Parameter Description
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 Endpoint rating method) - The
LMTD is calculated in terms of the temperature
approaches (terminal temperature differences) in the
exchanger, using the Equation (3.11).
Uncorrected LMTD equation:
∆T 1 – ∆T 2
∆T LM = --------------------------------------ln ( ∆T 1 ⁄ ( ∆T 2 ) )
where:
(3.11)
∆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
Chapter 6 - Output Control in
the User’s Guide for more
information.
You can plot curves for the hot and/or cold fluid. Use the Plot check
boxes to specify which side(s) of the exchanger should be plotted.
The following variables may be plotted along either the x or y-axis:
Temperature, UA, Delta T, Enthalpy, Pressure and Heat Flow. Select the
combination from the Plot Type drop down list.
3-45
3-46
Heat Exchanger
Figure 3.30
Tables Page
On the Tables page, you can view the 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.
3.3.6
For detailed information on
using HEAT EXCHANGERS in
dynamics mode, see Chapter 4
- Heat Transfer Equipment in
the Dynamic Modelling
guide.
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through
this tab. Any information specified in the Rating tab is also displayed in
the Dynamics tab. For more information on running the Heat
Exchanger operations in Dynamics mode, see the Dynamic Modelling
guide for further details.
3.3.7
For Heat Exchanger Examples,
see Chapter 11 - Optimizer in
this manual and Chapter 2 Flowsheet Architecture in the
User’s Guide.
3-46
Dynamics Tab
Heat Exchanger Examples
A simple water-water Heat Exchanger example is outlined in this
section. There is an additional Heat Exchanger example in this manual
and a further example in the User’s Guide, both of which are more
advanced:
Heat Transfer Equipment
3-47
• An example of Multiple Heat Exchangers is shown in the
Chapter 11 - Optimizer.
• Refer to the SubFlowsheet Refrigeration Cycle Example
(Chapter 2 - Flowsheet Architecture in the User’s Guide) to
see how subflowsheets can be used within HEAT
EXCHANGER.
1.
In this example, the inlet streams are fully defined as follows (using
the ASME Steam property method):
MATERIAL STREAM [Tube In]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
120.0000 °F
Pressure
100.0000 psi
Molar Flow
5000.0000 lbmole/hr
H2O Mole Frac
1.0000
MATERIAL STREAM [Shell In]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
2.
Input Area
Entry
Temperature
90.0000 °F
Pressure
100.0000 psi
Molar Flow
4000.0000 lbmole/hr
H2O Mole Frac
1.0000
The HEAT EXCHANGER connections are shown below:
Figure 3.31
3-47
3-48
Heat Exchanger
In order to incorporate Heat
Loss/Leak, the Rating Method
must be Weighted. When Heat
Loss/Leak is set to Extremes,
heat is "lost" on the hot side
where the temperature is
highest. Conversely, heat is
"gained" on the cold side
where temperature is lowest.
Note that the Heat Balance
specification is included by
default.
3.
On the Parameters page, enter Tube Side Delta P and Shell Side
Delta P values of 5 psi.
4.
Note that at this point, there is just one degree of freedom
available. Specifying an outlet temperature on either side of the
exchanger would result in the HEAT EXCHANGER having enough
information to calculate. Select the Weighted rating method from
the Heat Exchanger Model drop down list, and choose the
Extremes radio button in the Heat Loss/Leak group. This increases
the degrees of freedom to three, because specifications have to be
supplied to account for the Heat Leak and Heat Loss.
5.
On the Specs page of the Design tab, you need to add two
specifications to the list. Press the Add button and complete the
forms as follows:
Figure 3.32
6.
Enter the Specification values and supply the required
information:
Specification
Value
UA [Btu/F-hr]
2.50E+06
o
Temperature of Tube Out [ F]
100
Heat Loss [Btu/hr]
1E+6
The solution will now converge. Move to the Conditions page of the
Work Sheet tab:
Figure 3.33
3-48
Heat Transfer Equipment
Keep in mind that this is a
simple problem, and that heat
curves are generally not linear.
3-49
Note that if you increase the number of Intervals on the
Parameters page, the solution does not change significantly. For
instance, increase the number of intervals to 15 for each side.
When you view the Heat Exchanger Plot, the Heat Flow vs.
Temperature curve is linear, very similar in appearance to the case
where the number of intervals is one.
3.4
LNG
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.
LNG Button
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 which attempts to
determine the solution which satisfies not only the energy balance, but
any constraints, such as temperature approach or UA.
To install the LNG operation, press F12 and choose LNG or select the
LNG Exchanger button in the Object Palette.
The LNG allows for multiple streams, while the HEAT
EXCHANGER allows only one hot side stream and one cold side
stream.
3-49
3-50
LNG
3.4.1
Design Tab
There are five pages on the Design tab: Connections, Parameters,
Specs, User Variables and Notes.
Connections Page
Note that any number of Sides
may be added simply by
selecting the Add Side button.
To remove a side, select the
Delete Side button after
positioning the cursor in the
appropriate row.
The Connections page is shown in the Figure 3.34.
For each exchanger side:
• An inlet stream and outlet stream are required.
• The Pressure Drop is optional. Each specified Pressure Drop
reduces the Degrees of Freedom by one, as seen on the
Specs page.
• The Hot/Cold designation can be specified. This will be used
as an estimate for calculations and will also be used for
drawing the PFD. If a designated hot pass is actually cold (or
vice versa), the operation will still solve 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. Refer to the Heat Exchanger Example in Chapter 2 Flowsheet Architecture in the User’s Guide to see how SubFlowsheets can be used in the HEAT EXCHANGER or LNG.
Figure 3.34
3-50
Heat Transfer Equipment
3-51
The LNG status is displayed on the bottom of the property view,
regardless of which page is currently shown. It will display an
appropriate message such as Under Specified, Not Converged or OK.
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 3.35
Exchanger Parameters Group
If there are more than two
LNG sides, then only the
Weighted rating method can
be used.
Exchanger
Parameter
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.
3-51
3-52
LNG
In Steady State mode, you can select either an End Point or Weighted
Rating Method.
Heat Leak/Loss Group
By default, the None radio button is selected. The other two radio
buttons incorporate heat loss/heat leak:
Heat Loss
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 will be applied over each
interval.
Note that Heat Loss/Leak options can be set only when the Rating
Method is Weighted.
Exchange Details Group
The LNG Exchange Details are displayed as follows:
Figure 3.36
For each side, the following parameters may be specified:
3-52
Parameter
Description
Intervals
The number of intervals, applicable only to the
Weighted Rating Method, may be specified. For nonlinear temperature profiles, more intervals will be
necessary.
Dew/Bubble Point
Check this box to add a point to the Heat curve for a
phase change. Figure 3.37 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
Heat Transfer Equipment
Parameter
Description
Equilibrate
All sides that are checked will come 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 will not be
affected. If two or more hot or cold streams are
checked, then the effective driving force will be
reduced. All unchecked streams enter the composite
curve at their respective temperatures.
3-53
There are three choices, described below.
Step Type
• Equal Enthalpy - All intervals have an equal
enthalpy change.
• Equal Temperature - All intervals have an
equal temperature change.
• Auto Interval - HYSYS will determine where
points should be added to the heat curve. This
is designed to minimize the error, using the least
amount of intervals.
The Pressure Profile is updated in the outer iteration
loop, using one of the following methods described
below.
Pressure Profile
• 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 3.37
10 Intervals; Dew Bubble Points
included
3 Intervals; Dew Bubble Points
not included
3-53
3-54
LNG
Specs Page
On the Specs page, you will find four group boxes which organize the
various specification and solver information.
Figure 3.38
Solver Group
The Solver group box includes the solving parameters used for LNG’s:
Solver Parameter
Specification Description
Tolerance
You may set the calculation error tolerance.
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 is displayed. In
the outer loop, the heat curve is updated and the
property package calculations are performed. Nonrigorous property calculations are performed in the
inner loop. Any constraints are also considered in
the inner loop.
Degrees of Freedom Group
To help reach the desired solution, unknown parameters (flows,
temperatures) can be manipulated in the attached streams. Each
parameter specification will reduce the Degrees of Freedom by one.
3-54
Heat Transfer Equipment
3-55
The Degrees of Freedom value for the LNG is shown within the Solver
group.
The number of Constraints (specs) must equal the number of
Unknown Variables. When this is the case, the Degrees of Freedom will
be equal to zero, and a solution will be calculated.
Unknown Variables Group
HYSYS lists all unknown LNG variables according to your specified
input. Once the unit has solved, the values of these variables will be
displayed.
Specifications Group
The Heat Balance
specification is a default LNG
specification that must be
active for the heat equation to
balance.
Note that 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
will not balance. Without the Heat Balance spec, 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 box.
You can View or Delete highlighted specifications by using the buttons
that align the right of the group box. A specification view appears
automatically each time a new spec is created via the Add button.
Shown here is a typical view of a specification, which is accessed via the
View or Add button.
Figure 3.39
Each specification view has two tabbed pages, Parameters and
Summary. As an example, defining the Delta Temp Spec requires two
stream names, and a value for the specification.
3-55
3-56
LNG
The Summary page is used to define whether the specification is Active
or an Estimate. The Spec Value is also shown on this page.
Note that information supplied on the Summary page of the
specification view will also appear in the Specifications group.
All specifications will be one of the following three types:
An Active specification is one
which the convergence
algorithm is trying to meet.
Both check boxes are selected
for this specification.
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 which is
ignored completely by the
convergence algorithm, but
may be made Active or an
Estimate at a later time.
Specification Type
Action
Active
An active specification is one which the convergence
algorithm is trying to meet. Note that an active
specification always serves as an initial estimate
(when the Active box is checked, HYSYS
automatically checks the Estimate box). 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,
clear the Active check box. The value will then serve
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, clear both the Active and
Estimate check boxes. By ignoring rather than
deleting a specification, it will be available if you wish
to use it later or simply view its current value.
The specification list lets you 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 check boxes among various
specifications, you can test various combinations of the three types to
see their effect on the results.
The available specification types are:
3-56
Specification
Description
Temperature
The temperature of any stream attached to the LNG.
The hot or cold inlet equilibrium temperature may
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 may also
be used.
Heat Transfer Equipment
Specification
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.
3-57
Description
Minimum Approach
The minimum temperature difference between the
specified pass and the opposite composite curve.
For example, if you select a cold pass, this will be 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 (3.12) in Section 3.4.4 Performance Tab.
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 will be 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 may 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 attach code and customize your
HYSYS simulation case by adding User Variables. For more information
on implementing this option, see the User Variables chapter in the
Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
information or comments regarding the LNG unit operation, or
pertaining to your simulation, in general.
3.4.2
Rating Tab
When working exclusively in Steady State mode, you are not required
to change any information on the pages accessible through this tab. For
more information on running the LNG unit operations in Dynamic
mode, see the Dynamic Modelling.
3-57
3-58
LNG
3.4.3
Worksheet Tab
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
3.4.4
Performance Tab
This tab details performance results of the LNG exchanger. Only the
first three pages, SS Results, Plots and Tables, are relevant to Steady
State mode simulation.
SS Results Page
Figure 3.40
3-58
Heat Transfer Equipment
3-59
Overall Performance Group
Parameter
Description
Duty
This is the 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
This is the loss of cold side duty to leakage.
Heat Loss
This is the loss of hot side duty to leakage.
UA
This is the 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 (3.12).
∆T 1 – ∆T 2
∆T LM = ---------------------------------ln ( ∆T 1 ⁄ ∆T 2 )
(3.12)
where: ∆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 will be 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.
3-59
3-60
LNG
Parameter
Description
Cold Inlet
Equilibrium
Temperature
The Equilibrium Temperature for the cold streams.
When streams are not equilibrated (see 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 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 are displayed.
Plots Page
You can plot composite curves or individual pass curves for the LNG.
Use the Plot check boxes to specify which curve(s) you want displayed.
Figure 3.41
You can modify the
appearance of the plot via the
Graph Control view. Refer to
Chapter 6 - Output Control of
the User’s Guide for more
information.
3-60
The following variables may be used for either the x or y-axis:
Temperature, UA, Delta T, Enthalpy, Pressure and Heat Flow. Select the
combination from the Plot Type drop down list. To view the plot area
only, select the View Plot button.
Heat Transfer Equipment
3-61
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.
Dynamic and Layers Pages
The Dynamic and Layers pages of the Performance tab display results
from Dynamic mode operation. For more information on these pages,
see the Dynamic Modelling guide.
3.4.5
Dynamics Tab
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through
this tab. For more information on running the LNG unit operations in
Dynamics mode, see the Dynamic Modelling guide for further details.
3.4.6
LNG Example
Consider the following LNG Heat Exchanger:
Figure 3.42
The problem is to determine the flow of an Ethane Refrigerant stream
(Cold C2) necessary to meet the Heat Exchange and Temperature
approach specifications of the Exchanger. Create a case with the
following Fluid Package:
Property Package
Components
Peng Robinson
C1, C2, C3, i-C4, n-C4, i-C5, n-C5
3-61
3-62
LNG
Specify the following for the feed streams are:
MATERIAL STREAM [Plant Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
20.0000 °C
Pressure
500.0000 kPa
Molar Flow
1000.0000 kgmole/hr
Methane Mole Frac
0.5386
Ethane Mole Frac
0.1538
Propane Mole Frac
0.0769
i-Butane Mole Frac
0.0692
n-Butane Mole Frac
0.0615
i-Pentane Mole Frac
0.0538
n-Pentane Mole Frac
0.0462
MATERIAL STREAM [Warm C1]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
30.0000 °C
Pressure
5000.0000 kPa
Molar Flow
50.0000 kgmole/hr
Methane Mole Frac
0.9500
Ethane Mole Frac
0.0500
Propane Mole Frac
0.0000
i-Butane Mole Frac
0.0000
n-Butane Mole Frac
0.0000
i-Pentane Mole Frac
0.0000
n-Pentane Mole Frac
0.0000
MATERIAL STREAM [Cold 1]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
3-62
Input Area
Entry
Vapour Frac
1.0000
Pressure
2000.0000 kPa
Molar Flow
75.0000 kgmole/hr
Methane Mole Frac
0.9500
Ethane Mole Frac
0.0500
Propane Mole Frac
0.0000
i-Butane Mole Frac
0.0000
n-Butane Mole Frac
0.0000
i-Pentane Mole Frac
0.0000
n-Pentane Mole Frac
0.0000
Heat Transfer Equipment
3-63
MATERIAL STREAM [Cold 1]
Tab [Page]
Input Area
Entry
Worksheet
[Conditions]
Vapour Frac
0.0000
Pressure
250.0000 kPa
Methane Mole Frac
0.0200
Worksheet
[Composition]
Ethane Mole Frac
0.9800
Propane Mole Frac
0.0000
i-Butane Mole Frac
0.0000
n-Butane Mole Frac
0.0000
i-Pentane Mole Frac
0.0000
n-Pentane Mole Frac
0.0000
Connections Page
Install the LNG Exchanger as follows.
Figure 3.43
LNG Button
You will have to add two
additional sides by pressing
the Add Side button.
Parameters Page
Select the Extremes radio button in the Heat Loss/Leak group. Note
that this increases the number of unknown variables by two, and thus
the Degrees of Freedom by two.
In the Exchange Details group, set the number of intervals for each of
the four passes to 20.
3-63
3-64
LNG
Specifications Page
In order for the operation to solve, the number of independent
unknowns must be equal to the number of constraints (i.e. Degrees of
Freedom = 0). The LNG considers constraints to be parameters such as
UA, Minimum Temperature Approach, or a temperature difference
between two streams.
In this problem, two types of specs are required. First, add the following
Delta Temp specs:
Name
Cold Feed Cold 1
Warm C1 - Cold
1 Out
Warm C1 - Cool
C1
Type
Delta Temp
Delta Temp
Delta Temp
Stream (+)
Cold Feed
Warm C1
Warm C1
Stream (-)
Cold 1
Cold 1 Out
Cool C1
Spec Value [C]
15.00
2.00
5.00
Then add two Duty Ratio Specs:
Name
Heat Leak Fraction
Heat Loss Fraction
Type
Duty Ratio
Duty Ratio
Pass
Heat Leak
Heat Loss
Pass (/)
Overall
Overall
Spec Value
0.00
0.00
On the Worksheet page, specify the Vapour Fraction of Cold C2 Out to
be 1.
At this point, the Degrees of Freedom will be zero and the LNG will
begin to solve. The status message at the bottom of the LNG property
view will read Temperature Cross. Move to the Plots page to see that
the Composite curves clearly show a temperature cross at the hot side
entrance (see Figure 3.44).
3-64
Heat Transfer Equipment
3-65
Figure 3.44
A different approach that can be used is to remove the Temperature
difference between Cold 1 Out and Warm C1, and instead specify a
Minimum Temperature Approach for the Exchanger at 2oC.
Return to the Specs page and clear the Active check box for the Warm
C1 - Cold 1 Out specification. Add the minimum approach
specification, as described to the below.
When you add the Minimum
Temperature Approach
specification, the LNG
Exchanger quickly solves.
Name
Min. T Approach
Type
Min. Approach
Pass
Overall
Spec Value
2.00 C
3-65
3-66
LNG
Results
Move to the Conditions page of the Worksheet tab of the LNG:
Figure 3.45
On the SS Results page of the Performance tab, you will find the
Performance and the Side Results:
Figure 3.46
3-66
Piping Equipment
4-1
4 Piping Equipment
4.1 Mixer .............................................................................................................. 3
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
Design Tab ............................................................................................... 4
Rating Tab ................................................................................................ 5
Worksheet Tab ......................................................................................... 5
Dynamics Tab .......................................................................................... 6
Example ................................................................................................... 6
4.2 Pipe Segment................................................................................................ 7
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.2.8
Calculation Modes ................................................................................... 8
Design Tab ............................................................................................. 12
Rating Tab .............................................................................................. 18
Worksheet Tab ....................................................................................... 27
Performance Tab.................................................................................... 28
Dynamics Tab ........................................................................................ 30
Pipe Example ......................................................................................... 30
Modifying the Fittings Database............................................................. 32
4.3 Tee ............................................................................................................... 34
4.3.1
4.3.2
4.3.3
4.3.4
Design Tab ............................................................................................. 35
Ratings Tab ............................................................................................ 37
Worksheet Tab ....................................................................................... 37
Dynamics Tab ........................................................................................ 37
4.4 Valve ............................................................................................................ 38
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
Design Tab ............................................................................................. 39
Ratings Tab ............................................................................................ 40
Worksheet Tab ....................................................................................... 40
Dynamics Tab ........................................................................................ 40
Valve Example ....................................................................................... 40
4-1
4-2
4.5 Relief Valve ................................................................................................. 41
4.5.1
4.5.2
4.5.3
4.5.4
4.5.5
Design Tab ............................................................................................. 41
Ratings Tab ............................................................................................ 44
Worksheet Tab ....................................................................................... 44
Dynamics Tab ........................................................................................ 44
Relief Valve Example ............................................................................. 44
4.6 References .................................................................................................. 46
4-2
Piping Equipment
4.1
Mixer Button
4-3
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 will always be 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 will be calculated automatically since the composition, pressure
and enthalpy will be known for that stream.
The mixture pressure and temperature are usually the unknowns to be
determined. However, the MIXER will also calculate 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 will flash the outlet stream using the combined enthalpy.
Note 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.
To ignore the Mixer during calculations, activate the Ignored check
box. HYSYS will disregard the operation until you clear the check box.
To install the MIXER operation, press F12 and choose Mixer or select
the Mixer button in the Object Palette.
4-3
4-4
Mixer
4.1.1
Design Tab
The Design tab provides access to four pages: the Connections,
Parameters, User Variables, and Notes page.
Connections Page
Figure 4.1
On the Connections page, specify any number of inlet streams to the
MIXER; a single outlet stream is also required.
Parameters Page
On the Parameters page, indicate which type of Automatic Pressure
Assignment HYSYS should use for the streams attached to the MIXER.
The default is Set Outlet to Lowest Inlet, in which case all but one
attached stream pressure must be known. HYSYS will assign the lowest
inlet pressure to the outlet stream pressure.
If you specify Equalize All, HYSYS will give all attached streams the
same pressure once one of the attached stream pressures is known. If
you choose Equalize All, and two or more stream pressures are not
equal, you will generate an inconsistency error. 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 will be no automatic pressure assignment since
all the stream pressures are known
4-4
Piping Equipment
4-5
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 may seem to be extraneous, it is of special
importance when the MIXER is being used to simulate the junction of
multiple pipe nodes.
Note that if you select Equalize All and two or more of the
attached streams have different pressures, a pressure
inconsistency message will appear. 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.
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 option, see the User Variables chapter in the
Customization Guide.
Notes Page
The Notes page provides an editor where you can record any remarks
pertaining to the MIXER or to your simulation case in general.
4.1.2
Rating Tab
You are not able to specify any rating information for the TEE operation
in HYSYS.Process.
4.1.3
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
4-5
4-6
Mixer
4.1.4
In Dynamic mode, changes in inlet
streams to the MIXER will be seen
instantaneously in the outlet
stream; the MIXER has no holdup.
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. For more information on running the Mixer operation in
Dynamics mode, see the Dynamic Modeling guide for further details.
4.1.5
Example
In this example, two streams, STREAM 1 and STREAM 2, are mixed to
form stream MIX OUT. Define the feed streams as shown here, using
the Peng Robinson property method. When you install the MIXER,
ensure that the Automatic Pressure Assignment is Set Outlet to Lowest
Inlet on the Parameters page in the Design tab.
MATERIAL STREAMS
Tab [Page]
Input Area
Temperature [C]
Worksheet
[Conditions]
4-6
STREAM 2
10.0000
-20.0000
4100.0000
4000.0000
35.0000
2.0000
Methane Mole Frac
0.1900
0.2500
Ethane Mole Frac
0.1500
0.2100
Mole Frac Propane
0.1000
0.1500
i-Butane Mole Frac
0.1000
0.1100
Pressure [kPa]
Molar Flow [kgmole/hr]
Worksheet
[Composition]
STREAM 1
n-Butane Mole Frac
0.1100
0.1300
i-Pentane Mole Frac
0.0800
0.0500
n-Pentane Mole Frac
0.0900
0.0700
n-Hexane Mole Frac
0.0900
0.0200
Piping Equipment
4-7
The results can be viewed in the Worksheet tab as shown below.
Figure 4.2
4.2
OLGAS is a third-party option
which can be purchased through
Hyprotech or SCANDPOWER.
Pipe Segment Button
Pipe Segment
The PIPE SEGMENT is used to simulate a wide variety of piping
situations ranging from single/multiphase plant piping with rigorous
heat transfer estimation, to large capacity looped pipeline problems. It
offers two pressure drop correlations: one developed by Gregory, Aziz
and Mandhane, and the other by Beggs and Brill. A third 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 three calculation modes: Pressure Drop,
Flow, and Length; the appropriate mode will automatically be selected
depending on the information supplied. In order to solve the pipe, you
must supply enough information to completely define both the
material balance and energy balance.
To ignore the PIPE SEGMENT during calculations, activate the Ignored
check box. HYSYS will disregard the operation until you clear the check
box.
To install the PIPE SEGMENT, press F12 and choose Pipe Segment from
the Unit Ops view or select the Pipe Segment button in the Object
Palette.
4-7
4-8
Pipe Segment
Before the pages of the PIPE SEGMENT property view are described,
the Calculation Modes and Material/Energy Balance calculations are
explained.
4.2.1
Note that HYSYS does not
check for Sonic Flow during
these calculations.
Calculation Modes
There are three calculation modes: Pressure Drop, Length and Flow.
The mode will automatically be 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 supplied 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:
Pressure Drop
Assuming that a feed, product and energy stream are attached to the
pipe, the following information is required:
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.
4-8
•
•
•
•
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:
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.
Piping Equipment
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.
Method 2. If you supply 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.
5. If the calculated outlet pressure is
not equal to the actual pressure, a
new estimate is made for pressure
(Return to 1).
The calculated pressure drop accounts for fittings, frictional and
hydrostatic effects.
Length Calculation:
Length
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).
The Pipe will also solve for the
length if you provide one pressure
and two temperature
specifications, and the duty.
4-9
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 will be
made for the length, and calculations will continue.
A good initial guess and step size will greatly decrease the solving time.
4-9
4-10
Pipe Segment
Flow
Flow Calculation:
Assuming that a feed, product and energy stream are attached to the
pipe, the following information is required:
1. Estimate Flow. At the end where
temperature is specified, solve for
the outlet temperature and pressure
in the first segment.
• 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
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).
Using the flow estimate and known stream conditions (at the end with
the known temperature), HYSYS will calculate 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 will be made for
the flow, and calculations will continue.
Again, a good initial guess will decrease 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:
4-10
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 (Beggs and Brill, Gregory Aziz
Mandhane, or OLGAS)
5.
With the pressure gradient, the outlet pressure can be calculated.
6.
The calculated pressure and estimate pressure are compared. If
their difference exceeds a tolerance (0.01%), a new outlet pressure
is estimated, and steps 3 to 6 are repeated.
7.
Once the inner pressure loop has converged, the outlet
temperature is calculated:
Piping Equipment
4-11
• If U and the ambient temperature are specified, then the outlet
temperature is determined from the following equations:
Q = UADTLM
(4.1)
Q = Qin - Qout
(4.2)
where: Q = Amount of heat transferred
U = Overall heat transfer coefficient
A = Outer heat transfer area
DTLM = 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 a
tolerance (0.01oC), a new outlet temperature is estimated, and new
fluid properties are calculated (return to step 3).
8.
When both the temperature and pressure converge, the outlet
results are passed to the inlet of the next increment, where
calculations continue.
4-11
4-12
Pipe Segment
4.2.2
Design Tab
The Design tab provides access to five pages: the Connections,
Parameters, Calculation, User Variables, and Notes page.
Connections Page
Figure 4.3
On the Connections page, you must specify the Feed and Product
material streams. This can be done by selecting existing streams from
the drop down boxes list associated with the Feed and Product fields.
You can also create new streams by selecting the particular field and
enter the new stream name in the Edit Bar.
In addition to the material stream connections, you also have the
option of attaching an Energy stream to the PIPE SEGMENT. You may
also edit the operation name on this page.
4-12
Piping Equipment
4-13
Parameters Page
In the Pressure Gradient Parameters group, you can select the gradient
method which will be used for Two-Phase (VL) flow calculations.
Figure 4.4
The options are:
OLGAS is a third-party option
which can be purchased through
Hyprotech or SCANDPOWER.
• Beggs and Brill
• Gregory Aziz Mandhane
• OLGAS
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
section. The total heat loss can be calculated using estimated heat
transfer coefficients or specified on the Heat Transfer page of the
Ratings tab.
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 will be calculated by HYSYS, provided all other required
parameters are supplied.
The Gravitational Energy Change displays the change in potential
energy experienced by the fluid across the length of the pipe. It is
4-13
4-14
Pipe Segment
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.
Note that 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.
The overall pressure drop, which may 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.
Beggs and Brill Pressure Gradient
The Beggs and Brill6 method is based on work done with an air-water
mixture at many different conditions, and is applicable for inclined
flow. 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. 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
4-14
Piping Equipment
4-15
friction factor is calculated and the pressure gradient determined.
Figure 4.5
Beggs and Brill Flow Regimes
1000
Distributed
Froude Number
100
10
Segregated
1
Transition
0.0001
0.001
0.01
Input Liquid Content
0.1
1
Gregory Aziz Mandhane Pressure Gradient
For the Gregory Aziz Mandhane correlation, an appropriate model is
used for predicting the overall pressure drop in two-phase flow.
Figure 4.6
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)
4-15
4-16
Pipe Segment
Regime
Model
Slugflow
Mandhane, et. al. modification #1 of Lockhart-Martinelli
Dispersed
Bubble Mandhane, et. al. modification #2 of LockhartMartinelli
Annular Mist
Lockhart-Martinelli
Elongated
Bubble
Mandhane, et. al. modification #1 of Lockhart-Martinelli
Stratified
Lockhart-Martinelli
Wave
Lockhart-Martinelli
OLGAS Pressure Gradient
OLGAS 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 two-phase flow laboratory in
Norway.
It predicts the pressure gradient, liquid holdup and flow regime. It has
been tested in one degree increments for all angles from horizontal to
vertical. OLGAS gives one of the best overall predictions of pressure
drop and liquid holdup of any currently available method. Contact your
Hyprotech agent for more information on OLGAS.
All methods account for static head losses, while only the 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.
4-16
Piping Equipment
4-17
Calculations Page
Figure 4.7
You can supply any of the Calculation Parameters on this page:
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.
Length Initial Guess
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
Default Increments
The increment number which appears for each
segment on the Dimensions page
When calculating Flow or Length, good initial guesses and step
sizes can greatly reduce solution time.
4-17
4-18
Pipe Segment
User Variables Page
The User Variables page allows the user to create and implement
variables in the HYSYS simulation case. For more information on
implementing the User Variables option, see the User Variables chapter
in the Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the Pipe Segment or pertaining to
your simulation, in general.
4.2.3
Rating Tab
The Ratings tab provides access to two pages: the Sizing page and the
Heat Transfer page. On the Sizing page you provide 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 4.8
4-18
Piping Equipment
4-19
For a given length of pipe which is modelled in HYSYS, the parameters
of each segment are entered separately, as they are for each fitting.
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 4.9
Fittings
D
Y2
C
F2
F3
X2
X3
Y1 B
A
X1
Example of Pipe Sections
and Fittings Modelled in the
Pipe Segment Operation
F1
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. Note that horizontal pipe
sections have an Elevation of 0. A positive elevation indicates that the
outlet is higher than the inlet.
Number
1
2
3
4
5
6
7
Represented by
A
F1
B
F2
C
F3
D
Pipe
Fitting/Pipe
Pipe
Fitting
Pipe
Fitting
Pipe
Fitting
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.
4-19
4-20
Pipe Segment
Adding Segments
Figure 4.10
You can add segments to the length-elevation profile by pressing the
Add Segment button.
For each segment that you add, you must supply the following:
Field
Description
Select a pipe section or one of the available fittings
from the Edit Bar 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.
The fittings pressure drop is calculated as:
ρKV 2
∆P = -------------2g c
Fitting/Pipe
where:
(4.3)
ρ = density
K =Pipe Fitting factor (K-factor)
V = Average superficial fluid velocity
gc = Gravitational constant
You may modify the Fittings Database, which is
contained in file FITTING.DB. For more information,
see Section 4.2.8 - Modifying the Fittings
Database.
4-20
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.
Piping Equipment
Pipe fittings increase the pressure
drop in the PIPE SEGMENT. The
pressure drop is proportional to the
K-factor for that fitting.
Field
Description
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 in which the pipe section
is divided for calculation purposes.
4-21
Viewing Segments
Figure 4.11
Once you have selected the segment type (pipe or fitting), you can
supply detailed information concerning the highlighted segment. With
the cursor located on a segment, press the View Segment button.
The Pipe Info dialog will appear for pipe sections. On this view, the
following information is shown:.
Field
Description
Select one of the following:
Pipe Schedule
Nominal Diameter
• Actual - The nominal diameter cannot be
specified. The inner diameter can be specified.
• Schedule 40
• Schedule 80
• Schedule 160
HYSYS contains a pipe database for three pipe
schedules (40, 80, 160). If a schedule is specified, a
popup menu will be displayed indicating the possible
nominal pipe diameters that may be specified.
Provides the nominal diameter for the pipe section.
4-21
4-22
Pipe Segment
Field
Description
Inner Diameter
For Schedule 40, 80, or 160, this will be 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 may be selected from the drop
down list in the Edit Bar.The roughness factor is
automatically supplied for pipe material chosen from
this list. You may also specify the roughness factor
manually. A table of pipe materials and
corresponding Absolute Roughness factors is shown
below.
Roughness
A default value is provided based on the Pipe
Material. You can specify a value if you wish.
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
Removing a Segment
No confirmation is given by
HYSYS before segments are
removed.
4-22
To remove a segment from the Length-Elevation Profile group box,
highlight one of its parameters and press the Delete Segment button.
You can remove all input from the Length-Elevation Profile group box
by pressing the Clear Profile button.
Piping Equipment
4-23
Heat Transfer Page
On the Heat Transfer page, you can select the method that HYSYS will
use for the heat transfer calculations. In the Specify By group box,
select one of the radio buttons:
• By Segment - you specify the Ambient Temperature and HTC
(Heat Transfer Coefficient) for each segment that was created
on the Sizing page.
Figure 4.12
• Overall - one of four heat transfer methods will be applied to
the whole pipe segment based on your input in the Heat
Transfer Summary and Heat Transfer Coefficient
Estimation group boxes. The heat transfer methods are:
Method
Description
Duty Method
If the Overall heat duty of the segment is known, the
energy balance can be calculated immediately. Each
increment is assumed to have the same heat loss.
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.
Stream
Temperatures
If both inlet and outlet temperatures are specified, a
linear profile is assumed and overall heat duty will be
calculated. This method allows fast calculation when
stream conditions are known.
4-23
4-24
Pipe Segment
Method
Description
Overall Heat
Transfer Coefficient
Specified
If the overall heat transfer coefficient and a
representative ambient temperature are known,
rigorous heat transfer calculations are performed on
each increment.
Heat Transfer
Coefficient
Estimation
The overall heat transfer coefficient can be “built”
from its component parts
Inside Film Convection
You may directly specify the inside film heat transfer coefficient or
prompt HYSYS to estimate it using one of the correlations provided.
Figure 4.13
The three 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 )
(4.4)
Dittus and Boelter (1930)
k
h = --- 0.023Re d0.8 Pr n
d
0.4 → for heating
n = 0.3 → for cooling
4-24
(4.5)
Piping Equipment
4-25
Sieder and Tate (1936)
k
h = --- 0.027Re d0.8 Pr 1 ⁄ 3
d
(4.6)
Outside Conduction/Convection
Outside convection to either Air, Water or Ground can be included by
checking the Estimate Outer HTC box. For air and water, the velocity of
the ambient medium is defaulted to 1 m/s and is user-modifiable. 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
(4.7)
Figure 4.14
If Ground is selected as the ambient medium, the Ground type can
then be selected. The thermal conductivity of this medium is displayed
but is also modifiable by typing over the default value.
4-25
4-26
Pipe Segment
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
Most 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
Ground Types and Conductivities
The heat transfer resistance is estimated from:
2
2Z b + 4Z b2 – D ot
1
R surroundings = -------- ln -------------------------------------------D ot
2k s
(4.8)
where: 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/pipe
Conduction through the insulation or any other pipe coating can also
be supplied. Several representative materials are provided, with their
respective thermal conductivities. You must supply a thickness for this
coating. You may specify your own value which could also take into
account conduction through the pipe itself.
4-26
Piping Equipment
4-27
Figure 4.15
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
4.2.4
Worksheet Tab
The Worksheet tab contains a summary of the information contained
in the stream property view for all the streams attached to the unit
operation. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
4-27
4-28
Pipe Segment
4.2.5
Performance Tab
The Performance tab provides access to the Profiles page. The Profiles
page allows the user to access information about the fluid stream
conditions for each specified increment in the pipe segment.
Profiles Page
The Profile page provides a summary table for the segments which
make up the PIPE SEGMENT. The Distance (Length), Elevation and
number of Increments are displayed for each segment. None of the
values can be modified on this view.
Figure 4.16
By pressing the View Profile button, you access the Pipe Profile view,
which consists of a Table page and a Plot page. The Table page displays
the following information for each increment along the pipe segment:
•
•
•
•
•
•
•
•
•
4-28
Length
Elevation
Pressure
Temperature
Heat Transferred
Flow Regime
Liquid Holdup
Friction Gradient
Static Gradient
Piping Equipment
•
•
•
•
•
4-29
Accel Gradient
Liquid Reynolds Number
Vapour Reynolds Number
Liquid Velocity
Vapour Velocity
Figure 4.17
The Plot page 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 4.18
Refer to Section 6.4 - Graph
Control of the User’s Guide for
information regarding the
customization of plots.
You can modify the plot by object inspecting the plot area and selecting
Graph Control from the menu.
4-29
4-30
Pipe Segment
4.2.6
Dynamics Tab
This unit operation is currently not available for dynamic simulation.
4.2.7
Pipe Example
This example will illustrate the use of the PIPE SEGMENT, where the
flowrate is unknown.
1.
Create the Feed stream using the Peng Robinson property method
and the required components.
Property Package
Components
Peng Robinson
Methane, Ethane, Propane, i-Butane,
n-Butane, i-Pentane, CO2, H2O
2.
Create the stream Feed with the following specifications:
MATERIAL STREAM [Feed]
Tab [Page]
Input Area
Entry
Worksheet
[Conditions]
Temperature [C]
50.0000
Pressure [kPa]
3000.00
Methane
0.8800
Ethane
0.0600
Worksheet
[Composition]
3.
Propane
0.0300
i-Butane
0.0050
n-Butane
0.0050
i-Pentane
0.0020
CO2
0.0100
n-Butane
0.0080
Install the PIPE SEGMENT with the following
PIPE SEGMENT [Pipe-100]
Tab [Page]
Design [Connections]
Design [Parameters]
4-30
Input Area
Entry
Feed
Feed
Product
Product
Energy
Duty
Pipe Flow Correlation
Beggs and Brill
Delta P [kPa]
1000.0000
Piping Equipment
4.
4-31
On the Sizing page of the Ratings tab, add one segment to the unit
operation by pressing the Add Segment button. Specify the Fitting/
Pipe, the Length, the Elevation and the Increments as shown
below.
Tab [Page]
Rating [Sizing]
Input Area
Entry
Fitting/Pipe
Pipe
Length
500 m
Elevation Change
0m
Material
Mild Steel
Increments
10
5.
Press the View Segment button to select a 101.6 mm (4-inch)
nominal diameter Schedule 40 pipe. The Outer Diameter and
Inner Diameter will be calculated by HYSYS.
6.
Specify a Heat Loss of 5000 kJ/h in the Heat Transfer page of the
Rating tab. Once you do this, the PIPE SEGMENT begins its
calculations.
Results
Examine the results on the Profile page in the Performance tab by
pressing the View Profile button. The Table page is shown:
Figure 4.19
The calculated flowrate of the fluid through the PIPE SEGMENT can be
seen on the Worksheet page. A molar flow rate of 761.56 kgmole/hr is
calculated for a 1000 kPa pressure drop through 500 m of 4-in. mild
steel, Schedule 40 pipe.
4-31
4-32
Pipe Segment
Figure 4.20
4.2.8
Modifying the Fittings
Database
In the "fittings.db" file you will see something like the following:
FittingType elbow45std
VHFactor 0.35
Desc "Elbow: 45 Std"
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 two members (parameters): a
VH Factor (K-Factor) and a description. Note that the object
name "elbow45std" is only an internal name; it doesn’t appear in
any lists or windows.
4-32
Piping Equipment
2.
4-33
VHFactor 0.35
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.
4.
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. Note 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.
Note that HYSYS will 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.
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 will get
errors that may or may not tell you what is actually wrong.
4-33
4-34
Tee
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!"
end
You have now created a fitting. Note that you don’t have to indent the
VHFactor and Desc lines, it just makes for neater and easier to read
files. Now, the fitting is 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!" will appear in the fittings drop down list,
and if you add a "Loop-de-loop!" to the fittings list, it will come up with
a K-Factor of 10.0.
To take out the fitting, just delete the lines that were previously added.
4.3
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.
Tee Button
4-34
To install the Tee operation, press F12 and choose Tee from the Unit
Ops view or select the Tee button in the Object Palette. To ignore the Tee
operation during calculations, activate the Ignored check box. HYSYS
will disregard the operation until you clear the check box.
Piping Equipment
4.3.1
4-35
Design Tab
The Design tab provides access to four pages: the Connections,
Parameters, User Variables, and Notes page.
Connections Page
On the Connections page, provide the name of the Feed stream as well
as any number of Product streams, all of which will be assigned the
conditions and composition of the Feed. 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 you specify on the Dynamics page (Dynamic mode).
Figure 4.21
Parameters Page
For steady-state calculations, provide the desired flow ratio (the ratio of
the outlet stream flow to the total inlet flow). 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 will have a negative flow ratio
and a negative flow (backflow). For N outlet streams attached to the
TEE, you must provide N-1 flow ratios. HYSYS will then calculate the
unknown stream flow ratio and the outlet flow rates.
4-35
4-36
Tee
Figure 4.22
N
∑ ri
= 1.0
(4.9)
i=1
fi
r i = --F
(4.10)
where: ri = Flow ratio of the ith stream
F
1
f1
fi = Outlet flow of the ith stream
2
f2
F = Feed flow rate
3
f3
N = Number of outlet streams
.....
N
•
•
•
•
4-36
fN
Inlet flow F
N outlet streams
Specify N-1 flow
ratios ri
Outlet stream flows f1
= r1 F
For example, if you have four outlet streams attached to the TEE, you
must give three flow ratios and HYSYS will calculate the fourth. If you
switch to Dynamics mode, the flow ratio values will not change if
they’re between 0 and 1 (they will be equal to the dynamic flow
fractions).
Piping Equipment
4-37
User Variables Page
The User Variables page allows the user to create and implement
variables in the HYSYS simulation case. For more information on
implementing the User Variables option, see the User Variables
chapter in the Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the Tee operation or pertaining to
your simulation, in general.
4.3.2
Ratings Tab
You are unable to specify any rating information for the TEE operation
in HYSYS.Process.
4.3.3
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
4.3.4
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. For more information on running the Tee operation in
Dynamics mode, see the Dynamic Modeling guide for further details.
4-37
4-38
Valve
4.4
Valve Button
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 may be specified by the user in
the Valve operation. A total of three specifications are required before
the valve operation will solve. At least one temperature specification
and one pressure specification are required. HYSYS will calculate the
other two unknowns:
•
•
•
•
•
Inlet temperature
Inlet pressure
Outlet temperature
Outlet pressure
Valve Pressure Drop
To install the Valve operation, press F12 and choose Valve from the Unit
Ops view or select the Valve button in the Object Palette.
To ignore the Valve operation during calculations, activate the Ignored
check box. HYSYS will disregard the operation until you clear the check
box.
4-38
Piping Equipment
4.4.1
4-39
Design Tab
The Design tab provides access to four pages: the Connections,
Parameters, User Variables, and Notes page.
Connections Page
On the Connections page, provide the name of the Valve, as well as the
Feed and Product stream names.
Figure 4.23
Parameters Page
The pressure drop of the Valve operation may be specified on the
Parameters page.
User Variables Page
The User Variables page allows the user to create and implement
variables in the HYSYS simulation case. For more information on
implementing the User Variables option, see the User Variables
chapter in the Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the VALVE operation or pertaining
to your simulation, in general.
4-39
4-40
Valve
4.4.2
Ratings 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. For more information on running the VALVE operation in
Dynamics mode, see the Dynamic Modeling guide for further details.
4.4.3
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the Stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
4.4.4
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. For more information on running the VALVE operation in
Dynamics mode, see the Dynamic Modeling guide for further details.
4.4.5
Valve Example
This example will illustrate the use of the VALVE operation. In this case,
the temperature and pressure of the Feed to the valve is specified.
1.
Create the Feed stream using the Peng Robinson property method
and the required components.
Property Package
Components
Peng Robinson
Propane, Propene
2.
Install the stream Feed with the following
MATERIAL STREAM [Feed]
4-40
Tab [Page]
Input Area
Entry
Worksheet
[Conditions]
Temperature [C]
50.0000
Pressure [kPa]
2000.0000
Worksheet
[Composition]
Propane Mole Frac
0.9500
Propene Mole Frac
0.0500
Piping Equipment
3.
4-41
Install a VALVE operation and specify as follows:
VALVE [VLV-100]
Tab [Page]
Input Area
Entry
Design
[Connections]
Feed
Feed
Product
Letdown
Design [Parameters]
Delta P [kPa]
1500.0000
View the results on the Worksheet tab as shown in Figure 4.24.
Figure 4.24
4.5
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.
The flow through the RELIEF VALVE may be vapour, liquid, liquid with
precipitate or any combination of the three.
4.5.1
Design Tab
The Design tab of the Relief Valve property view consists of four pages:
Connections, Parameters, User Variables and Notes.
4-41
4-42
Relief Valve
Connections Page
Figure 4.25
The Connections page is where the inlet and outlet streams of the
RELIEF VALVE are specified. The page contains three objects:
4-42
Object
Description
Feed
Stream entering RELIEF VALVE. You may 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 entering the stream name in the Edit Bar.
Product
RELIEF VALVE exit stream. Like the Feed field, you may
either select an existing stream from the associated drop
down or you can create a new stream by selecting the
field and entering the stream name in the Edit Bar.
Name
The name of the RELIEF VALVE. HYSYS will provide a
default designation for the unit operation, however, you
may edit this name at any time by entering a new name in
this field.
Piping Equipment
4-43
Parameters Page
Figure 4.26
The Parameters page contains only two fields:
Object
Description
Opening Pressure
The pressure at which the relief valve will begin to
open.
Full Open Pressure
The pressure at which the relief valve is fully open.
User Variables Page
The User Variables page allows the user to create and implement
variables in the HYSYS simulation case. For more information on
implementing the User Variables option, see the User Variables chapter
of the Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the RELIEF VALVE or pertaining to
your simulation, in general.
4-43
4-44
Relief Valve
4.5.2
Ratings 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. For more information on running the RELIEF VALVE operation
in Dynamics mode, see the Dynamic Modeling guide for further
details.
4.5.3
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the Stream property view. The PF Specs page
contains a summary of the Stream property view Dynamics tab.
4.5.4
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. For more information on running the RELIEF VALVE operation
in Dynamics mode, see the Dynamic Modeling guide for further
details.
4.5.5
Relief Valve Example
This example illustrates the use of a RELIEF VALVE with regards to a
simple storage tank in Steady State mode.
1.
4-44
Create a new case using the Peng Robinson Property Package and
add the following components.
Property Package
Components
Peng Robinson
H2O
Piping Equipment
2.
4-45
Create and specify the stream Feed with the following conditions
and composition.
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
3.
Input Area
Entry
Vapour Fraction
0
Pressure [kPa]
2000.0000
Mass Flow [kg/hr]
1
H2O Mole Frac
1.0
Now add a SEPARATOR to the Flowsheet with the following
specifications:
SEPARATOR [Sep]
Tab [Page]
Design [Connections]
Design [Parameters]
Relief Valve Button
Input Area
Entry
Feed
Feed
Liquid Outlet
Relief-In
Pressure Drop
0 psia
Type
Tank
4.
The last unit operation you will require is the RELIEF VALVE. To
add a RELIEF VALVE you can either press F12 and add one from the
Unit Ops dialogue or select the Relief Valve button from the Object
Palette.
5.
Fill out the Design tab of Relief Valve property view as shown in the
following table.
RELIEF VALVE [RV-100]
Tab [Page]
Input Area
Design
[Connections]
Feed
Relief-In
Product
Relief-Out
Design [Parameters]
Entry
Opening Pressure
150 kPa
Full Open Pressure
200 kPa
6.
On the Worksheet tab of the Relief Valve property view, set the
pressure of the Relief-Out stream to 101.325 kPa.
7.
The system is now fully specified.The status bar at the bottom of
the Relief Valve property view should be red and display the
message: Material Flows into closed relief valve. The Relief-Out
stream should remain unsolved.
The valve should be closed as the vessel pressure is not high enough for
the Relief Valve to open.
4-45
4-46
References
8.
Change the pressure of the Feed stream to 160 kPa. This should
open the Relief Valve. Go to the Worksheet tab of the Relief Valve
property view. It should appear as shown in Figure 4.27.
Figure 4.27
4.6
4-46
References
1
Gregory, G.A., Mandhane, J. and Aziz, K., Some Design Considerations
for Two-Phase Flow in Pipes, J. Can. Petrol. Technol., Jan. - Mar.
(1975).
2
Beggs, H.D., and Brill, J.P., A Study of Two-Phase Flow in Inclined
Pipes, J. Petrol. Technol., p. 607, May (1973).
Rotating Equipment
5-1
5 Rotating Equipment
5.1 Compressor/Expander................................................................................. 3
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
5.1.6
5.1.7
Theory ...................................................................................................... 4
Design Tab ............................................................................................... 8
Rating Tab .............................................................................................. 10
Worksheet Tab ....................................................................................... 13
Performance Tab.................................................................................... 13
Dynamics Tab ........................................................................................ 14
Compressor Example............................................................................. 14
5.2 Pump ........................................................................................................... 16
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
5.2.6
5.2.7
Theory .................................................................................................... 17
Design Tab ............................................................................................. 19
Rating Tab .............................................................................................. 21
Worksheet Tab ....................................................................................... 21
Performance Tab.................................................................................... 21
Dynamics Tab ........................................................................................ 22
Pump Example....................................................................................... 22
5-1
5-2
5-2
Rotating Equipment
5.1
5-3
Compressor/Expander
The COMPRESSOR operation is used to increase the pressure of an
inlet gas stream. Depending on the information supplied, the
COMPRESSOR calculates either a stream property (pressure or
temperature) or a compression efficiency.
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 will calculate either a stream property or an expansion
efficiency.
There are several methods for the COMPRESSOR (EXPANDER) to
solve, depending on what information has been supplied and whether
or not you are using curves. In general, the solution is a function of flow,
pressure change, applied energy and efficiency. The COMPRESSOR/
EXPANDER provides a great deal of flexibility with respect to what you
can supply and what it will then calculate. You must ensure that you do
not enable too many of the solution options or inconsistencies may
result.
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 will calculate the required energy, outlet
temperature and other efficiency.
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 will calculate outlet pressure, temperature,
and other efficiency.
Compressor Button
Expander Button
4. HYSYS calculates outlet pressure, temperature,
and applied duty.
3. HYSYS calculates outlet pressure, temperature,
and applied duty.
The thermodynamic principles governing the COMPRESSOR and
EXPANDER operations are the same, but the direction of the energy
stream flow is opposite. Compression requires energy, while expansion
releases energy.
To install the COMPRESSOR operation, press F12 and select
Compressor from the UnitOps view or select the Compressor button in
the Object Palette. The EXPANDER operation is installed similarly.
5-3
5-4
Compressor/Expander
To ignore the COMPRESSOR or EXPANDER during calculations, select
the Ignored check box. HYSYS will completely disregard the operation
until you restore it to an active state by clearing the check box.
5.1.1
Theory
For a 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
(5.1)
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 Producedisentropic
(5.2)
For an adiabatic COMPRESSOR or EXPANDER, HYSYS calculates the
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 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 will be 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 (5.1) and
Equation (5.2).
Note that all intensive quantities are determined thermodynamically,
using the specified Property Package. In general, the work for a
5-4
Rotating Equipment
5-5
mechanically reversible process can be determined from:.
W =
∫ V dP
(5.3)
As with any unit operation, the calculated information depends on the
information which is supplied 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 compressor or expander type. The actual
power is equivalent to the heat flow (enthalpy) difference between the
inlet and outlet streams.
For the COMPRESSOR:
Power Requiredactual = Heat Flowoutlet - Heat Flowinlet
(5.4)
where the efficiency of the 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
(5.5)
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 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
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 will always be lower than the outlet temperature
for a real compression or expansion.
5-5
5-6
Compressor/Expander
Equations Used
If the COMPRESSOR is selected, the compressor equations are used. If
the EXPANDER is selected, the expander equations are used.
Compressor Efficiences
The Adiabatic and Polytropic Efficiences are included in the
compressor calculations. An isentropic flash (Pin and Entropyin) is
performed internally to obtain the ideal (isentropic) properties.
Expander Efficiences
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
Adiabatic
COMPRESSOR
(H
–H )
Work Required ( ideal )
out
in ( ideal )
---------------------------------------------------------- = -------------------------------------------------------(H
–H )
Work Required
out
in ( actual )
( actual )
 P out
 ------------
 P in 
–1
n
------------
 n 
k–1
n
– 1 ×  ---------------- ×  -----------
 ( n – 1 )  k 
EXPANDER
(H
–H )
Work Produced ( actual )
out
in ( actual )
------------------------------------------------------------ = -------------------------------------------------------(H
–H )
Work Produced
out
in ( ideal )
( ideal )
 P out
 ------------
 P in 
– 1
 k--------- k 
–1
------------------------------------------------------------------------------------------------------------ × AdiabaticEff ------------------------------------------------------------------------------------------------------------ × AdiabaticEff
– 1
–1
 k---------n
------------
 k 
 n 
 P out
 P out
k–1
n
–1
– 1 ×  ---------------- ×  -----------
 ------------
 ------------
 ( n – 1 )  k 
 P in 
 P in 
Polytropic
where:
where:
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
H = Mass Enthalpy
ρ = Mass Density
out = Product Discharge
n = Polytropic Exponent
in = Feed Stream
k = Isentropic Exponent
P = Pressure
5-6
Rotating Equipment
5-7
Compressor Heads
The Adiabatic and Polytropic Heads are performed after the
compressor calculations are completed, only when the “Results” page
of the 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 Analysisof
Centrifugal Compressors”, Journal of Engineering for Power, J.M.
Schultz, January 1962, p. 69-82).
Expander Heads
The Adiababitc 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
Adiabatic
COMPRESSOR
EXPANDER
Work Required
1
( actual )
---------------------------------------------------------- × AdiabaticEff × ----------------MassFlowRate
( g ⁄ gc )
P out

  P in
1
n
f ×  ------------ ×  ------------------------------- –  --------- × ---------------- n – 1
(g ⁄ g )
ρ
 out ,actual  ρ in
c
where:
Polytropic
where:
Work Produced
1
1
( actual )
------------------------------------------------------------ × ----------------------------------- × ----------------MassFlowRate
AdiabaticEff ( g ⁄ g c )
n 
– f ×  ----------- ×

n–1
P out

  P in
1
 ------------------------------- –  --------- × ----------------(g ⁄ g )
ρ
 out ,actual  ρ in
c
where:
H
–H
out ,ideal
in
f = ----------------------------------------------------------------------------------P


 P in
k 
out
 ---------- ×  --------------------------- –  ---------
 k – 1
 ρ out ,ideal  ρ in
H
–H
out ,ideal
in
f = ----------------------------------------------------------------------------------P


 P in
k 
out
 ---------- ×  --------------------------- –  ---------
 k – 1
 ρ out ,ideal  ρ in
log ( P
⁄P )
out in
n = ---------------------------------------------------------log ( ρ
⁄ρ )
out, actual in
log ( P
⁄P )
out in
n = ---------------------------------------------------------log ( ρ
⁄ρ )
out, actual in
log ( P out ⁄ P in )
k = -----------------------------------------------------log ( ρ
⁄ρ )
out, ideal in
log ( P out ⁄ P in )
k = -----------------------------------------------------log ( ρ
⁄ρ )
out, ideal in
H = Mass Enthalpy
ρ = Mass Density
out = Product Discharge
f = Polytropic Head Factor
in = Feed Stream
n = Polytropic Exponent
P = Pressure
k = Isentropic Exponent
5-7
5-8
Compressor/Expander
5.1.2
Design Tab
Connections Page
The Connections page, as shown in Figure 5.1, is for the
COMPRESSOR. 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.
Figure 5.1
On the Connections page, supply the operation name, as well as the
names of the Inlet, Outlet and Energy Streams.
Parameters Page
The Parameters pages are identical for both the COMPRESSOR and
EXPANDER. The only difference is that their respective icons are used.
You may specify the duty of the attached energy stream on this page, or
allow HYSYS to calculate it. The adiabatic and polytropic efficiencies
are displayed as well.
5-8
Rotating Equipment
5-9
Figure 5.2
Note that you may specify only one efficiency, either adiabatic or
polytropic. If you specify one efficiency and a solution is obtained,
HYSYS will then back calculate the other efficiency, using the calculated
duty and stream conditions.
User Variables Page
The User Variables page allows the user to create and implement
variables in the HYSYS simulation case. For more information on
implementing the User Variables option, see the User Variables
chapter in the Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the COMPRESSOR or EXPANDER,
or pertaining to your simulation in general.
5-9
5-10
Compressor/Expander
5.1.3
Rating Tab
The Rating tab contains four pages: the Curves, Flow Limits, Nozzles
and Inertia page.
Curves Page
If you do not use curves, supply four of the following variables, and the
fifth will be calculated, along with the duty:
•
•
•
•
•
Inlet Temperature
Inlet Pressure
Outlet Temperature
Outlet Pressure
Efficiency
It is assumed that you have provided the composition and flow.
Figure 5.3
To supply data for a curve, follow this procedure:
5-10
1.
Select the Enable Curves check box.
2.
Choose either an Adiabatic or Polytropic efficiency, using the
corresponding radio button. This determines the basis of your
input efficiency values.
3.
Press the Add Curve button to access a Curve view.
Rotating Equipment
4.
5-11
On the Curve view, you may add Flow, Head and %Efficiency data
points, as well as a Speed value for a single curve.
Figure 5.4
5.
For each additional curve, repeat steps #3 and #4. The efficiency
type must be the same for all input curves.
HYSYS will use the curve(s) to determine the appropriate efficiency for
your operational conditions. If you supply curves, ensure the efficiency
values on the Parameters page are empty or a consistency error will be
generated.
Once a curve has been created, the View Curve, Delete Curve and Plot
Curves buttons will become available. By using these first two buttons
respectively, you can either access the Curve view to edit your input
data or simply delete the highlighted curve from the simulation. Also,
for each curve, an Activate check box will be present. To remove a
specific curve from the calculations, you can deactivate its check box.
The Curve view is accessed via the Add Curve or View Curve button.
You can supply the following data in the Curve view:
Curve Data
Description
Name
Name of this curve.
Speed
The rotational speed of the COMPRESSOR or
EXPANDER. This is optional if you supply only
one curve.
Flow Units/ Head Units
Units for the flow and head.
Flow/ Head/ Efficiency
Enter any number of data points for the curve.
5-11
5-12
Compressor/Expander
When you choose the Erase Selected button, the current row (Flow,
Head or Efficiency) will be deleted. Choose the Erase All button to
delete all Flow, Head and Efficiency data for the curve.
Single Curve
When you have a single curve, the following combinations of input will
allow the operation to completely solve (assuming the feed
composition and temperature are known):
•
•
•
•
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).
Multiple Curves
Each curve is named and has
an associated Activate check
box. You can turn individual
curves on and off.
If multiple curves have been installed and an operating speed is
specified on the Parameters page, then only the curve with the
corresponding speed will be used. Note that you can specify a speed
that is different than the speeds given for the curves. For example, if you
provide curves for two speeds (1000/min and 2000/min), and you
specify a speed of 1500/min, HYSYS will interpolate between the two
curves to obtain the solution. You must also provide an inlet pressure
and one of 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
will be determined, and the other two variables will then be calculated.
Note that a COMPRESSOR may 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 wish to pump a fluid near its critical point (where it
5-12
Rotating Equipment
5-13
becomes compressible), you may do so by representing the PUMP with
a COMPRESSOR. The COMPRESSOR operation takes into account the
compressibility of the liquid, thus performing a more rigorous
calculation.
Flow Limits Page
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through
this page. For more information on running the Compressor or
Expander operations in Dynamic mode, see the Dynamic Modelling
guide for further details.
5.1.4
Worksheet Tab
The Worksheet tab contains a summary of the information contained
in the stream property view for all the streams attached to the unit
operation. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
5.1.5
Performance Tab
Results Page
On the Results page, you can view a table of calculated values for the
COMPRESSOR. The values include:
•
•
•
•
•
•
•
•
Adiabatic Head
Polytropic Head
Adiabatic Efficiency
Polytropic Efficiency
Duty
Polytropic Head Factor
Polytropic Exponent
Isentropic Exponent
5-13
5-14
Compressor/Expander
5.1.6
Dynamics Tab
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through
this tab. For more information on running the COMPRESSOR and
EXPANDER unit operations in Dynamic mode, see the Dynamic
Modelling guide.
5.1.7
Compressor Example
A compressor will be modelled using efficiency curves. Consider the LP
gas from an Oil Production facility as a FEED to a compressor station.
In this problem, we will simply determine the efficiency, based on the
flow rate of the feed stream.
1.
Create a fluid package using the Sour PR property package and add
the following components: H2O, H2S, CO2, C1, C2, C3, i-C4, and nC4.
Property Package
Components
Sour PR
H2O, H2S, CO2, C1, C2, C3, i-C4, nC4
2.
Install the stream FEED and define it as follows:
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
5-14
Input Area
Entry
Temperature
69.0000 °C
Pressure
120.0000 kPa
Molar Flow
500.0000 kgmole/hr
H2O Mole Frac
0.2375
H2S Mole Frac
0.0727
CO2 Mole Frac
0.0607
C1 Mole Frac
0.0430
C2 Mole Frac
0.1072
C3 Mole Frac
0.2522
i-C4 Mole Frac
0.0765
n-C4 Mole Frac
0.1502
Rotating Equipment
3.
5-15
Install a COMPRESSOR unit operation with the following
information:
COMPRESSOR [K-100]
Tab [Page]
Design
[Connections]
Input Area
Entry
Inlet
Feed
Outlet
Out
Energy
Comp Duty
4.
On the Parameters page, delete the default Adiabatic Efficiency
value. Both the Adiabatic and Polytropic efficiencies should read
<empty> to avoid a consistency error or a compressor over
specification.
5.
Switch to the Rating tab, and open the Curves page.
6.
Ensure that the Adiabatic radio button in the Efficiency group is
selected.
7.
Check the Enable Curves box, and press the Add Curve button.
8.
Complete the curve as shown in Figure 5.5.
Figure 5.5
It is not necessary to enter a
Speed since only one curve is
being used.
9.
Close the Curve view and check the Activate box for the curve
which was just created.
5-15
5-16
Pump
The conditions of stream OUT can be viewed on the Performance tab
of the Compressor property view and are shown in the table below.
MATERIAL STREAM [Out]
Tab [Page]
Performance
[Results]
Input Area
Entry
Vapour Fraction
1.0000
Temperature
108.3858 °C
Pressure
203.7000 kPa
Molar Flow
500.0000 kgmole/hr
Mass Flow
18819.3064 kg/hr
Liq Vol Flow
33.4319 m3/hr
Heat Flow
-7.2473e+07 kJ/hr
The Performance tab of the COMPRESSOR property view is displayed
in Figure 5.6.
Figure 5.6
5.2
Pump
The PUMP operation is used to increase the pressure of an inlet liquid
stream. Depending on the information supplied, the PUMP calculates
either an unknown pressure, temperature or pump efficiency.
The On Pump Switch activates and deactivates the PUMP. If this box is
checked, the PUMP is "on", and will work as normal. If this box is not
checked, HYSYS will pass the inlet stream unchanged; that is, the outlet
stream will be exactly the same as the inlet stream. When you use the
5-16
Rotating Equipment
5-17
On Pump Switch option, you should supply a pressure rise rather than
specify the pressures of the inlet and outlet streams. If you supply a
Delta P, this value will simply be ignored when you turn the PUMP off.
On the other hand, if you specify the pressures of the inlet and outlet
streams, you will get a consistency error when you turn the PUMP off,
as HYSYS attempts to pass the inlet stream conditions to the outlet
stream.
Pump Button
To install the PUMP operation, press F12 and choose Pump from the
Unit Ops view or select the Pump button in the Object Palette.
To ignore the PUMP during calculations, select the Ignore check box.
HYSYS will completely disregard the operation (and will not calculate
the outlet stream) until you restore it to an active state by clearing the
check box.
5.2.1
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
(5.6)
where: Pout = Pump outlet pressure
Pin = Pump inlet pressure
Note that the above 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
(5.7)
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 ( % )
(5.8)
5-17
5-18
Pump
Finally, the actual power is equal to the difference in heat flow between
the outlet and inlet streams:
Power Requiredactual = (Heat Flowoutlet - Heat Flowinlet)
(5.9)
If the feed is fully defined, only two of the following variables need to be
supplied for the PUMP to calculate all unknowns:
• Outlet Pressure or Pressure Drop
• Efficiency
• Pump Energy
HYSYS can also back-calculate the inlet Pressure.
Note that 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 wish 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 will always be 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.
5-18
Rotating Equipment
5.2.2
5-19
Design Tab
Connections Page
On the Connections page, provide the names of the inlet, outlet and
energy streams attached to the PUMP.
Figure 5.7
Parameters Page
The applicable PUMP parameters are the Adiabatic Efficiency, Delta P
and Pump Energy (power). Note that you may provide both inlet and
outlet stream pressures, in which case HYSYS will calculate Delta P.
Alternatively, you may supply one stream pressure and a Delta P value;
in this case, the other stream pressure will be calculated by HYSYS.
5-19
5-20
Pump
Figure 5.8
Curves Page
If you wish to supply a pump curve, move to the Curves page and
provide the coefficients for the quadratic pump equation, as well as the
units for pressure and flow. Then select Activate Curves check box, and
HYSYS will determine 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.
Figure 5.9
5-20
Rotating Equipment
5-21
User Variables Page
The User Variables page allows the user to create and implement
variables in the HYSYS simulation case. For more information on
implementing the User Variables option, see User Variables chapter in
the Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the PUMP, or pertaining to your
simulation in general.
5.2.3
Rating Tab
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through
this tab. For more information on running the PUMP unit operation in
Dynamic mode, see the Dynamic Modelling guide.
5.2.4
Worksheet Tab
The Worksheet tab contains a summary of the information contained
in the stream property view for all the streams attached to the unit
operation. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
5.2.5
Performance Tab
Results Page
The Results page contains pump head information. The values for
Pressure Head, Velocity Head and Delta P excluding static head are
calculated values.
The Total Head cell is used only for Dynamic simulation. For more
information regarding this please refer to Chapter 6 - Rotating
Equipment of the Dynamic Modelling guide.
5-21
5-22
Pump
5.2.6
Dynamics Tab
The Dynamics tab is used only for Dynamic simulation. For more
information regarding this tab, please refer to Chapter 6 - Rotating
Equipment of the Dynamic Modelling guide.
5.2.7
Pump Example
To illustrate the use of the PUMP Operation, stream FEED will be
pumped from 455 psia to 800 psia. The pump efficiency is 75 percent.
1.
Create a fluid package using the Peng Robinson EOS and the
following components: C1, C2, C3, i-C4, n-C4, i-C5, n-C5, n-C6, nC7, n-C8.
Property Package
Components
Peng Robinson
C1, C2, C3, i-C4, n-C4, i-C5, n-C5, nC6, n-C7, n-C8
2.
Create a stream named Feed and define it as follows:
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
5-22
Input Area
Entry
Temperature
250.0000 °F
Pressure
455.0000 psi
Molar Flow
300.0000 lbmole/hr
Methane Mole Frac
0.0000
Ethane Mole Frac
0.0001
Propane Mole Frac
0.0200
i-Butane Mole Frac
0.1859
n-Butane Mole Frac
0.1748
i-Pentane Mole Frac
0.1592
n-Pentane Mole Frac
0.1372
n-Hexane Mole Frac
0.1613
n-Heptane Mole Frac
0.0923
n-Octane Mole Frac
0.0692
Rotating Equipment
3.
5-23
Now install the PUMP unit operation and provide the following
information:
PUMP [P-100]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Inlet
Feed
Outlet
Outlet
Energy
P-100 Energy
Adiabatic Efficiency
75 %
Delta P
345 psi
The results are shown in the tables below and can be viewed in the
PUMP property view. The energy stream has a positive enthalpy value.
In the PUMP operation, this signifies the amount of energy which is
supplied to the inlet stream to produce the pump outlet conditions.
MATERIAL STREAM [Outlet]
Tab [Page]
Worksheet [Results]
Input Area
Entry
Vapour Frac
0.0000
Temperature
254.5474 °F
Pressure
800.0000 psi
Molar Flow
300.0000 lbmole/hr
Mass Flow
22287.0308 lb/hr
Liq Vol Flow
2427.8569 barrel/day
Heat Flow
-2.0726e+07
MATERIAL STREAM [P-100 Duty]
Tab [Page]
Worksheet [Results]
Input Area
Entry
Vapour Frac
<empty>
Temperature
<empty>
Pressure
<empty>
Molar Flow
<empty>
Mass Flow
<empty>
Liq Vol Flow
<empty>
Heat Flow
58610.6306
Note that if you clear the On Pump Switch check box, the conditions of
stream FEED are directly passed to OUTLET.
5-23
5-24
5-24
Pump
Separation Operations
6-1
6 Separation
Operations
6.1 Separator / 3-Phase Separator / Tank......................................................... 3
6.1.1
6.1.2
6.1.3
6.1.4
6.1.5
6.1.6
6.1.7
Theory ...................................................................................................... 3
Design Tab ............................................................................................... 5
Reactions Tab .......................................................................................... 7
Rating Tab ................................................................................................ 8
Worksheet Tab ......................................................................................... 9
Dynamics Tab .......................................................................................... 9
3-Phase Separation Example .................................................................. 9
6.2 Shortcut Column ........................................................................................ 11
6.2.1
6.2.2
6.2.3
6.2.4
6.2.5
6.2.6
Design Tab ..............................................................................................11
Rating Tab .............................................................................................. 13
Worksheet Tab ....................................................................................... 13
Performance Tab.................................................................................... 13
Dynamics Tab ........................................................................................ 14
Shortcut Column Example ..................................................................... 14
6.3 Component Splitter .................................................................................... 16
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
Theory .................................................................................................... 17
Design Tab ............................................................................................. 18
Rating Tab .............................................................................................. 20
Worksheet .............................................................................................. 20
Dynamics Tab ........................................................................................ 20
Example ................................................................................................. 20
6-1
6-2
6-2
Separation Operations
6.1
All information in this section
applies to the SEPARATOR,
the 3-PHASE SEPARATOR
and the TANK Operation,
unless indicated otherwise.
Separator / 3-Phase
Separator / Tank
Because the property views for SEPARATOR, 3-PHASE SEPARATOR
and TANK are almost identical, these 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 wish 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.) will be retained. The key differences in
these operations are the stream connections (related to the feed
separation):
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, and one liquid product stream. The
TANK is generally used to simulate liquid surge
vessels.
Separator Button
3-Phase Separator Button
Tank Button
6-3
6.1.1
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).
For a detailed explanation of
Separator Dynamics, see
Chapter 7 - Separation
Operations in the Dynamic
Modelling Guide.
As well as standard forward applications, the SEPARATOR and 3PHASE 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.
6-3
6-4
Separator / 3-Phase Separator / Tank
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
Note that if you are using multiple feed streams, only one feed
stream can have an unknown composition in order for HYSYS
to back-calculate.
To install the SEPARATOR operation, press F12 and choose Separator
from the Unit Ops view or select the Separator button in the object
palette. Add the 3-PHASE SEPARATOR and TANK similarly, using their
appropriate buttons. If you want to use the SEPARATOR as a reactor,
you can either install a SEPARATOR or choose GENERAL REACTOR
from the Unit Ops view.
Figure 6.1
If you toggle from a
SEPARATOR to a TANK
operation, you will
permanently lose the vapour
stream connection. If you
change back to the
SEPARATOR, you will have to
reconnect the vapour stream.
6-4
Operation type
toggle group.
Figure 6.1 shows the Parameters page for the SEPARATOR. The
operation toggle is available on this page. You are able to change
between the SEPARATOR, 3-PHASE SEPARATOR and TANK by
selecting the appropriate radio button.
Separation Operations
6-5
For a TANK operation, the outlet stream will always be a liquid. If the
outlet stream cannot be calculated as a liquid phase due to the stream
specifications and the specified pressure drop across the vessel, the
pressure drop may be adjusted so that the exiting stream is at its bubble
point temperature.
6.1.2
Design Tab
For Steady State simulation, it is necessary to specify information on
the Connections and Parameters pages of the Design tab.
Connections Page
Any of the available separation operations will accept multiple feed
streams, as well as an optional energy stream. You must also provide
the names of the product streams. Figure 6.2 shows the different
connections pages for the three operations:
Figure 6.2
6-5
6-6
Separator / 3-Phase Separator / Tank
Heat Transfer
You may also specify an 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
(6.1)
where: 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. The following Vessel Parameters are displayed:
Vessel Parameter
Description
Vessel Volume
This is 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.
Physical Parameters
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:
Note that Pfeed is assumed to
be the lowest pressure of all the
feed streams.
P = Pv = Pl = Pfeed - DP
(3.1)
where: 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
DP = Pressure drop in vessel (Delta P)
6-6
Separation Operations
6-7
The default pressure drop across the vessel is zero.
The Vessel Volume is necessary
in Steady State when
modelling 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
(6.2)
where: PV(%Full) is the liquid level in the vessel at time t.
The default vessel volume is 2 m3.
User Variables Page
On this page you can write User Variables associated with the operation
to increase its functionality within your simulation case. For more
information on creating and executing User Variables in HYSYS, see the
User Variables chapter in the Customization Guide, available with the
on-line documentation.
Notes Page
A text field is available on this page that lets you to write and store
information and comments regarding the specific unit operation, or
about your case in general.
6.1.3
Reactions Tab
Results Page
Reaction Sets may be attached to the SEPARATOR, 3-PHASE
SEPARATOR, or TANK Operations. You may attach a Reaction Set to the
operation by selecting it from the drop down list. The Set Status field
will display the status (Ready or Not Ready) of the currently selected
Reaction Set.
6-7
6-8
Separator / 3-Phase Separator / Tank
Figure 6.3
Reaction and component information can also be examined in the
Reaction Results group box. Select the Reaction Balance radio button
to view the total inflow, total reaction, and total outflow for all of the
components in the reaction.
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 selecting
the View Global Rxn button.
6.1.4
You are required to supply
rating information only when
working with a Dynamic
simulation.
Rating Tab
The Rating tab includes the Sizing and Heat Loss pages. The
information on the three pages is not relevant when working in
exclusively in Steady State mode. For information on specifying
information on these pages, see the Dynamic Modelling guide, Section
7.1.1 - Rating Tab.
Sizing Page
On the Sizing page, you can define the geometry of the unit operation.
Also, it allows for indication as to whether or not the unit operation has
a Boot associated with it. If it does, then you can specify the Boot
dimensions.
6-8
Separation Operations
6-9
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.
6.1.5
Worksheet Tab
The Worksheet tab contains a summary of the information available in
the stream property view for all the streams attached to the unit
operation. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view Dynamics tab.
6.1.6
Dynamics Tab
Information available on this page is relevant only to cases in Dynamics
mode. For information on Dynamic simulation, see the HYSYS
Dynamic Modelling Guide.
6.1.7
3-Phase Separation
Example
A simple three-phase separation is illustrated in this example. Create a
New HYSYS case with the following properties:
New Case Button
Property Package
Components
Peng Robinson
C1, C2, C3, i-C4, n-C4, i-C5, n-C5, H2O
Create a stream named Feed with the following properties:
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Input Area
Entry
Temperature [C]
20.0000
Pressure [kPa]
200.0000
Molar Flow [kgmole/hr]
100.0000
6-9
6-10
Separator / 3-Phase Separator / Tank
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Composition]
Input Area
Entry
Methane Mole Frac
0.1000
Ethane Mole Frac
0.0300
Propane Mole Frac
0.0400
i-Butane Mole Frac
0.0800
n-Butane Mole Frac
0.1000
i-Pentane Mole Frac
0.1200
n-Pentane Mole Frac
0.1300
H2O Mole Frac
0.4000
Note that this stream has three phases. You can verify this by expanding
the Worksheet tab of the Feed property view.
3-Phase Separator Button
Install the 3-PHASE SEPARATOR. On the Connections page of the
Design tab, input the information in the table below. For the remainder
of the fields, the 3-PHASE SEPARATOR default values will be used.
3-PHASE SEPARATOR [3-Phase Separator]
Tab [Page]
Design
[Connections]
Input Area
Entry
Feeds
Feed
Vapour
Vapour
Light Liquid
Light
Heavy Liquid
Heavy
These are the results that can be found on the Worksheet tab:
Figure 6.4
6-10
Separation Operations
6.2
Shortcut Column Button
6-11
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.
To install the SHORTCUT COLUMN operation, press F12 and choose
Shortcut Column from the Unit Ops view or select the Shortcut
Column button in the Object Palette.
6.2.1
Design Tab
Connections Page
The Connections page of the Design tab of the SHORTCUT COLUMN
is shown in Figure 6.5. A feed stream, overhead product, bottoms
product, condenser and reboiler duty name should all be specified. The
overhead product can either be an Overhead Vapour or a Distillate
stream, depending on the radio button selection in the Top Product
Phase group. The operation name can also be changed on this page.
Figure 6.5
You can specify the top
product to be either liquid or
vapour using the radio
buttons in the Top Product
Phase group.
6-11
6-12
Shortcut Column
Parameters Page
The SHORTCUT COLUMN requires the light and heavy key
components (keys) 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.
The composition of the light key in the bottoms and the heavy key in
the overhead are the only composition specifications required.
Figure 6.6
In the Components group, select a Light Key and Heavy Key from the
drop down list in the Edit Bar and supply their corresponding mole
fraction specifications. 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.
Define the column pressure profile by specifying a Condenser Pressure
and a Reboiler Pressure in the Pressures group.
In the Reflux Ratios group, the calculated Minimum Reflux Ratio will
be displayed once streams are attached on the Connections page and
the required parameters are specified in the Components and
Pressures groups.
6-12
Separation Operations
6-13
You can then input an External Reflux Ratio, which will be used to
calculate the tray traffic, the condenser and reboiler duties, the ideal
number of trays and the optimum tray location. The External Reflux
must be greater than the Minimum Reflux Ratio.
6.2.2
Rating Tab
You are currently unable to supply any rating information for the
SHORTCUT COLUMN.
6.2.3
Worksheet Tab
The Worksheet tab provides the same information as the default
Material Streams page of the Workbook. However, this page only
displays the streams that are currently attached to the SHORTCUT
COLUMN.
6.2.4
Performance Tab
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 6.7
6-13
6-14
Shortcut Column
The following results are available:
Column Result
Description
Minimum Number of Trays
This is the Fenske minimum number
of trays, which is not affected by the
External Reflux Ratio specification.
Actual Number of Trays
This is calculated using a using the
Gilliland method.
Optimal Feed Stage
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
These are the estimated average
flow rates above the feed location.
Stripping Section Vapour and
Liquid traffic flow rates
These are the estimated average
flow rates below the feed location.
Condenser and Reboiler Duties
The duties, as calculated by HYSYS.
6.2.5
Dynamics Tab
The SHORTCUT COLUMN currently runs only in Steady State mode. As
such, there is no information available on the Dynamics tab.
6.2.6
Shortcut Column Example
The following example builds a SHORTCUT COLUMN as a typical
depropanizer, having the stream Feed as the tower feed. Start building
the case with the following properties:
Property Package
Components
Peng Robinson
C2, C3, i-C4, n-C4, i-C5, n-C5, C6
Create the stream Feed with the following properties:.
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
6-14
Input Area
Entry
Temperature [F]
207.37
Pressure [psia]
100.0000
Molar Flow [lbmole/hr]
1271.5190
Separation Operations
6-15
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Composition]
Input Area
Entry
Ethane Mole Frac
0.0148
Propane Mole Frac
0.7315
i-Butane Mole Frac
0.0681
n-Butane Mole Frac
0.1462
i-Pentane Mole Frac
0.0173
n-Pentane Mole Frac
0.0150
n-Hexane Mole Frac
0.0071
Install a SHORTCUT COLUMN to your case. On the Connections page
of the Design tab, complete the fields as follows:
SHORTCUT COLUMN [Depropanizer]
Shortcut Column Button
Tab [Page]
Design
[Connections]
Input Area
Entry
Feed
Feed
Distillate
Distillate
Bottoms
Bottoms
Condenser Duty
Cond Q
Reboiler Duty
Reb Q
Top Product Phase
Liquid
Supply the following information on the Parameters page of the Design
tab:
SHORTCUT COLUMN [Depropanizer]
Tab [Page]
Input Area
Entry
Light Key in Bottom
Component - Propane
Mole Fraction - 0.025
Design [Parameters]
Heavy Key in
Distillate
Component - i-Butane
Condenser Pressure
100 psia
Reboiler Pressure
103 psia
External Reflux Ratio
1.5
Mole Fraction - 0.020
HYSYS will automatically calculate the Minimum Reflux Ratio as 0.979.
6-15
6-16
Component Splitter
Results
For a reflux ratio of 1.5, the following results are displayed on the
Performance tab:
Figure 6.8
6.3
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 supply. You are required to 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.
The COMPONENT SPLITTER is strictly a Steady State operation,
and cannot be run in Dynamic mode.
Component Splitter Button
6-16
To install the COMPONENT SPLITTER operation, press F12 and select
Component Splitter from the UnitOps view or select the Component
Splitter button from the Object Palette.
Separation Operations
6.3.1
6-17
Theory
The Component Splitter satisfies the material balance for each
component:
fi = ai + bi
(6.3)
where: 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:
ai = xi fi
(6.4)
bi = (1-xi ) fi
(6.5)
where: 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
(6.6)
where: hE = Enthalpy of unknown Energy Stream
hF = Enthalpy of Feed Stream
hO = Enthalpy of Overhead Stream
hB = Enthalpy of Bottoms Stream
6-17
6-18
Component Splitter
6.3.2
Design Tab
Connections Page
On the Connections page, you can specify an unlimited number of
Feed streams to the Component Splitter. Overhead and Bottoms
product streams must also be specified, and an unlimited number of
Energy streams may be specified as well.
Figure 6.9
One of the attached energy streams should have an unspecified energy
value to allow the operation to solve the energy balance.
Parameters Tab
This page displays the stream parameters that must be specified.
Included are the vapour fraction and pressure of the Overhead and
Bottoms streams.
Figure 6.10
6-18
Separation Operations
6-19
Splits Page
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 or Bottoms streams. For example, if the
majority of your components are going overhead, simply select 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.
Figure 6.11
User Variables Page
On this page you can attach code to create User Variables associated
with the COMPONENT SPLITTER in order to increase its functionality
within your simulation case. For more information on creating and
executing User Variables in HYSYS, see the User Variables chapter of
the Customization Guide.
Notes Page
A text field is available on this page that lets you to write and store
information and comments regarding the installed COMPONENT
SPLITTER, or about your case in general.
6-19
6-20
Component Splitter
6.3.3
Rating Tab
You are not able to provide any information for the Component Splitter
on the Rating tab.
6.3.4
Worksheet
The Worksheet tab provides the same information as the default
Material Streams page of the Workbook. However, this page only
displays the streams that are currently attached to the COMPONENT
SPLITTER.
6.3.5
Dynamics Tab
The COMPONENT SPLITTER does not run in Dynamic mode.
6.3.6
Example
The following example illustrates the use of the COMPONENT
SPLITTER. Stream 1 is the attached feed stream; stream 2 is the
overhead product stream, and stream 3 is the bottom product stream.
The energy stream is Q-100.
Create a case with the following Fluid Package:
Property Package
Components
Peng-Robinson
Ethane, Propane, i-Butane, n-Butane, i-Pentane, nPentane, n-Hexane
Define the feed stream 1 as follows:
MATERIAL STREAM [1]
Tab [Page]
Worksheet
[Conditions]
6-20
Input Area
Entry
Temperature [F]
200.0000
Pressure [psia]
500.0000
Molar Flow [lbmole/hr]
1000.0000
Separation Operations
6-21
MATERIAL STREAM [1]
Tab [Page]
Worksheet
[Composition]
Input Area
Entry
Ethane Mole Frac
0.0148
Propane Mole Frac
0.7315
i-Butane Mole Frac
0.0681
n-Butane Mole Frac
0.1462
i-Pentane Mole Frac
0.0173
n-Pentane Mole Frac
0.0150
n-Hexane Mole Frac
0.0071
Now install a COMPONENT SPLITTER. Complete the Connections
page is shown in Figure 6.12:
Component Splitter Button
Figure 6.12
Complete the Parameters page with the following information:
Figure 6.13
The splits for the Overhead stream are specified on the Splits page:
Figure 6.14
6-21
6-22
Component Splitter
The attached stream properties can be viewed on the Worksheet tab of
the Component Splitter property view. The Conditions page is as
follows:
Figure 6.15
From the information on the Composition page, the overhead fractions
can be confirmed by comparing the product stream component molar
flows. For instance, the propane overhead fraction is:
Propane Overhead Fraction = 716.87/731.50 = 0.98
6-22
(6.7)
Column
7-1
7 Column
7.1 Column Subflowsheet.................................................................................. 3
7.2 Column Theory ............................................................................................. 8
7.2.1 Three Phase Theory .............................................................................. 10
7.2.2 Detection of Three Phases .................................................................... 10
7.2.3 Initial Estimates ...................................................................................... 10
7.3 Column Installation .................................................................................... 13
7.3.1 Input Experts.......................................................................................... 14
7.3.2 Templates............................................................................................... 14
7.4 Column Property View ............................................................................... 21
7.4.1
7.4.2
7.4.3
7.4.4
7.4.5
7.4.6
7.4.7
7.4.8
7.4.9
Design Tab ............................................................................................. 22
Parameters Tab ...................................................................................... 44
Side Ops Tab.......................................................................................... 58
Rating Tab .............................................................................................. 62
Worksheet Tab ....................................................................................... 63
Performance Tab .................................................................................... 63
Flowsheet Tab ........................................................................................ 72
Reactions Tab ........................................................................................ 75
Dynamics Tab......................................................................................... 82
7.5 Column-Specific Operations ..................................................................... 82
7.5.1
7.5.2
7.5.3
7.5.4
Condenser ............................................................................................. 83
Reboiler.................................................................................................. 88
Tray Section ........................................................................................... 90
Tee ......................................................................................................... 95
7-1
7-2
7.6 Running the Column .................................................................................. 96
7.6.1 Run ........................................................................................................ 97
7.6.2 Reset...................................................................................................... 98
7.7 Column Troubleshooting ........................................................................... 98
7.7.1 Heat and Spec Errors Fail to Converge ................................................. 99
7.7.2 Equilibrium Error Fails to Converge ..................................................... 102
7.7.3 Equilibrium Error Oscillates.................................................................. 102
7.8 References ................................................................................................ 103
7-2
Column
7.1
For detailed information
about subflowsheet
manipulation, see Chapter 2 Flowsheet Architecture in the
User’s Guide.
7-3
Column Subflowsheet
The Column is a special type of subflowsheet 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 subflowsheet. You may wish to 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.
In this chapter, the use of the
Column property view and
Column Templates are
explained. Section 7.5 Column-Specific Operations ,
describes the unit operations
available in the Column build
environment are described.
See Chapter 2 - Flowsheet
Architecture in the User’s
Guide for a column template
example.
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 columns (as will be illustrated in the Column example),
you need to enter the Column build environment. Once inside, you can
access the Column-specific operations (Tray Sections, Heaters/Coolers,
Condensers, Reboilers, etc.) and build the column as you would any
other flowsheet.
If you wish to create a custom column template for use in other
simulations, choose File-New on the menu bar, and then select
Column from the side menu. Since this is a column template, you
access the Column build environment directly from the Basis
environment. Once you have created the template, you can store it to
disk. Before you install the template in another simulation, ensure that
the Use Input Experts check box in the Session Preferences view is
cleared.
Having a Column subflowsheet provides a number of advantages:
•
•
•
•
Isolation of Column Solver
Optional use of different Property Packages
Construction of custom templates
Ability to solve multiple towers simultaneously
7-3
7-4
Column Subflowsheet
Isolation of 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 the
Parent flowsheet by using the
Workbooks or PFDs options
under Tools in the Menu Bar.
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 will not be
recalculated until you return to the parent build environment.
When you are working in the Column build environment, you are
actually working inside the Column subflowsheets. Therefore, when
you activate the Workbook or PFD, you will see the Column workbook
or PFD rather than those of the parent flowsheet.
The subflowsheet environment permits easy access to all streams and
operations associated with your column. If you want to access
information regarding column product streams, view the Column
workbook, which displays the Column information exclusively.
Independent Fluid Package
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
will speed up the column solution.
• In some cases, a different Fluid Package may be better suited
to the column conditions. For example, you may want to
redefine Interaction Parameters such that they are applicable
for the operating range of the column.
• In Dynamic mode, different columns may operate at very
different temperatures and pressures. With each Fluid
Package, you may 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.
7-4
Column
7-5
Ability to construct Custom Column Configurations
Complex custom columns and
multiple columns may 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,
and defining the parameters.
Custom column configurations can be stored as templates, and
recalled into another simulation. To create a custom template, select
New and then Column under File in the Menu Bar. When you store the
template, it will have a.col extension.
There exists a great deal of freedom when defining column
configurations and you may 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 subflowsheet uses a simultaneous solver whereby all
operations within the subflowsheet are solved simultaneously. The
simultaneous solver permits the user to install multiple unit operations
within the subflowsheet (interconnected columns, for example)
without the need for RECYCLE blocks.
The Column Property View
Figure 7.1
7-5
7-6
Column Subflowsheet
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 may enter the Column subflowsheet to add
new pieces of equipment, such as additional Tray Sections or Reboilers
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 subflowsheet. This is
described in Section 7.4 - Column Property View .
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 subflowsheet. Major
changes, such as adding a second tray section, require you to enter the
Column subflowsheet. To access to the Column build environment
select the Column Environment button at the bottom of the Column
property view.
Main/Column Subflowsheet 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 will be
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 input and
output streams, and various adjustable parameters. If changes are
made to any of these basic column parameters, both the Column and
parent flowsheets will be recalculated.
When you install a Column, HYSYS creates a subflowsheet containing
all operations and streams associated with the template you have
chosen. This subflowsheet operates as a unit operation in the main
flowsheet. Figure 7.2 shows this concept of a Column subflowsheet
within a main flowsheet.
7-6
Column
7-7
Main Flowsheet / Subflowsheet Concept
Consider a simple Vapour-Liquid Absorber in which you wish to
remove CO2 from a gas stream using H2O as the solvent. A typical
approach to setting up the problem would be as follows:
1.
Create the gas feed stream, FeedGas, and the water solvent stream,
WaterIn, in the main flowsheet.
2.
Select the Absorber button from the Object Palette and provide the
stream names, number of trays, pressures and estimates. You must
also provide the names of the outlet streams, CleanGas and
WaterOut.
3.
Run the Column from the main flowsheet Column property view.
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 subflowsheet 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 7.2
Note that the connected streams do not necessarily have the same
parameters - all specified values will be identical, but calculated stream
variables may be different depending on the Fluid Packages and
Transfer Basis.
7-7
7-8
Column Theory
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 subflowsheet will
recalculate (just as if you had selected the Run button); the main
flowsheet will also recalculate once a new column solution is reached.
Note that if you delete any
streams connected to the
column in the main flowsheet,
these streams will also be
deleted in the Column
subflowsheet.
However, if you are inside the Column subflowsheet 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 subflowsheet build environment. When you
enter this environment, the main flowsheet is put on "hold" until you
return.
7.2
Column Theory
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 may 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 Figure 7.3:
7-8
Column
7-9
Figure 7.3
Lj-1
Vj
VSDj
Fj
Stage j
Qj
Rj
LSDj
Vj+1
Lj
F = Stage feed stream
L = Liquid stream travelling to stage below
V = Vapour stream travelling to stage above
LSD = Liquid side draw from stage
VSD = Vapour side draw from stage
Q = Energy stream entering stage
More complex towers may 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, may be used
on some towers to help purify side liquid products. With the exception
of Crude distillation towers, very few columns will 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 will depend on your hardware
configuration and the amount of computer memory you have
available.
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7-10
Column Theory
7.2.1
Three Phase Theory
For non-ideal systems with more than two components, boundaries
may exist in the form of azeotropes for 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. The Three Phase
Distillation Template sub-section in Section 7.3.2 - Templates further
details the three phase capabilities in HYSYS.
For non-ideal multi component 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 AEA Technology representative for details.
7.2.2
Look at the Trace Window for
column convergence
messages.
Detection of Three Phases
Whenever your Column converges, HYSYS will automatically perform 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 will be
produced.
If there is a water draw, HYSYS checks the next stage for a second liquid
phase, with the same results as above. This will continue down the
Tower until a stage is found that is two phase only. Note that if there is a
three phase stage below one that was found to be two phase, it will not
be detected because the checking would have ended previously.
HYSYS will always indicate the existence of the second liquid phase.
This will continue until the Column reverts to VLE operation, or all
applicable stages have water draws placed on them.
7.2.3
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 will converge. It is important to remember that specifications
become initial estimates, so if you have replaced one of the original
7-10
Column
7-11
default specifications (overhead vapour flow, side liquid draw or reflux
ratio) with new active specifications, the new values become initial
estimates. For this reason it is recommended you provide reasonable
values initially even if you know you will be replacing them.
Initial estimates may be provided via the Column Runner, either on the
Monitor page, of the Design tab, in the specification list or on the
Estimates page of the Parameters tab. Although HYSYS does not
require any estimates to converge to a solution, reasonable estimates
will help in the convergence process.
Temperatures
Temperature estimates may be given for any stage in the column,
including the condenser and reboiler using the Estimates page in the
Column Runner. Intermediate temperatures will be 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.
Note that if the overhead product is a subcooled liquid, it is best
to supply an estimated bubble-point temperature for the
condenser rather than the subcooled temperature.
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. To place the feed
liquid phase on one stage, and the feed vapour phase on the stage
7-11
7-12
Column Theory
above, the total feed stream are first be fed to a separator. The product
streams (single phase) from the separator are now fed individually to
separate stages of the column.
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.
You may 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 will "back" this value into the column
and use this value for the convergence process. If you do supply a
stream pressure that allows HYSYS to calculate the column pressure
profile, it is not necessary to supply another value within the column
property view. If you later change the pressure of an attached stream,
the COLUMN will be rerun.
Recall that whenever a change is made in a stream, HYSYS
checks all operations attached to that stream and recalculates
as required.
The 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
wish, you may change the numbering scheme to bottom-up by
selecting this scheme in the Column Runner.
7-12
Column
7-13
HYSYS initially treats the stages as being ideal. If you wish your stages
to be treated as real stages, you must specify efficiencies on the Eff page
of the Column Runner. Once you provide efficiencies for the stages,
even if the value you specify is 1, HYSYS treats the stages as being real.
Feed Stream
The Feed stream location, conditions and composition are treated as
Basic Column Parameters during convergence.
7.3
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 may be used for installing a new Column. The
most basic Column types are:
Basic Column Types
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.
There are also more complex Column types:
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 steamstripped 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 two-product-stream
sidestripper, a lower pump around reflux
circuit and product draw, and a quench
pump around circuit at the bottom of the
column.
7-13
7-14
Column Installation
Complex Column Types
Description
Three Phase Distillation
Tray section, three-phase condenser,
reboiler. Condenser can be either
chemical or hydrocarbon specific.
Wet Vacuum Tower
Tray section, 2 side product draws with
pump around reflux circuits and a wash
oil-cooled steam stripping section below
the flash zone.
7.3.1
Input Experts
Input Experts guide you through the installation of a Column. They are
available for the following five standard column templates:
•
•
•
•
•
•
Refer to Section 7.7.5 Preferences in the User’s
Guide for details on how to
access the Session Preferences
view.
Absorber
Liquid-Liquid Extractor
Reboiled Absorber
Refluxed Absorber
Distillation
Three Phase Distillation0
Details related to each column template are outline in Section 7.3.2 Templates . Each Input Expert contains a series of input pages whereby
you must supply the required information for the page before
advancing to the next one. When you have worked through all the
pages, you will have supplied the basic information required to get
build your column. You will then be placed in the Column property
view which gives comprehensive access to most of the column features.
Note that 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 Simulation
page of the Session Preferences view. If you do not use the Input
Experts, you will move directly to the Column property view when you
install a new column.
7.3.2
Templates
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
7-14
Column
7-15
necessary for defining the particular column type, as well as a default
set of specifications.
Figure 7.4
Press F12 to access the above view, which allows you to add a new
column. All Column templates can be viewed by selecting the Prebuilt
Columns radio button.
When you add a new Column, HYSYS will give 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 will install the equipment
and streams for you in a new Column subflowsheet. Stream
connections will already be in place, and HYSYS will provide default
names for all internal streams and equipment. You may then make
modifications by adding, removing or changing the names of any
streams or operations to suit your specific requirements.
Selecting the Side Ops button on the final page of the Column Input
Expert will open the Side Operations Input Expert wizard which will
guide 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 may create custom Templates containing Column
configurations that you commonly use.
7-15
7-16
Column Installation
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.
The following are some of the conventions, definitions and
descriptions of the basic columns:
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.
Column Component
Description
Tray Section
A HYSYS unit operation that represents the series of
equilibrium trays in a Column. The trays are
numbered from 1 to N.
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 may be selected on the Connections
page of the Design tab on the Column property
view.
Overhead Vapour
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.
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 may use the specifications that HYSYS provides, or
replace these specifications with others more suited to your
requirements.
7-16
Column
7-17
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.
•
•
•
•
•
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.
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 appears to
the left.
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, will 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 (see figure).
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.
7-17
7-18
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.
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 may 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:
• 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).
Distillation Template
If you select the Distillation template, HYSYS will create 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
Reflux Ratio
When you add both a REBOILER and a CONDENSER (Distillation), you
must supply three specifications for partial condensers and two
specifications for total condensers. The third default specification (in
addition to Overhead Vapour Flow Rate and Side Liquid Draw) is the
Reflux Ratio.
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 figure). If a
water draw is present, its flow is not included in the ratio.
7-18
Column
7-19
As with the Refluxed Absorber, the Distillation template may 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 in the tower is, in essence, a replaceable specification, in
that you can change the pressure for any stage from the Column
property view. Note that the pressures remain fixed during the Column
calculations.
The following table gives a summary of replaceable column (default)
specifications for the basic column templates.
Templates
Reboiled Absorber
Vapour Draw
Distillate Draw
Reflux Ratio
X
Refluxed Absorber
X
Total Condenser
Partial Condenser
X
X
Distillation
Total Condenser
Partial Condenser
X
X
X
X
X
Three Phase Distillation Template
If you select the Three Phase Distillation template, HYSYS will create a
COLUMN based on a three phase column model. The same standard
column types exist for a three phase system that are available for the
“normal” two phase (binary) systems.
Using the Three Phase Column Input Expert, the initial view allows the
choice of: Distillation, Refluxed Absorber, Reboiled Absorber, and
Absorber. Each choice builds the appropriate column based on their
respective standard (two phase) system templates.
7-19
7-20
Column Installation
Figure 7.5
If the Input Expert is turned off, installing a Three Phase column
template will open 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.
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 AEA Technology
representative for details.
When using the Three Phase Column Input Expert some additional
specifications may be required when compared with the standard
(binary system) column setups. An Azeotropic Input Expert is also
integrated into the setup which can is accessible by selecting the
Azeotropic Initialization button from the final Specifications setup
page of the Input Expert.
Selecting the Side Ops button on the final page of the Three Phase
Column Input Expert will open the Side Operations Input Expert
wizard which will guide you through the process of adding a side
operation to your column.
Three phase distillation columns are notoriously difficult to solve, and
thus the Input Experts are designed to properly initialize temperatures,
flows and compositions to aid in convergence of the tower.
7-20
Column
7.4
Column Runner is another
name for the Column Property
View.
7-21
Column Property View
The Column property view is a book of tabs containing pages with
information pertaining to the Column, which is accessible from the
main flowsheet or Column subflowsheet. In the Column subflowsheet,
the Column property view is also known as the Column Runner, and
can be accessed by selecting the Column Runner button.
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.
Column Runner Button
There are some differences in
the Column property view in
the main flowsheet and in the
Column subflowsheet. These
differences will be noted.
The Column property view is essentially the same when accessed from
the main flowsheet or Column subflowsheet. 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 subflowsheet 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.
It should be noted that in order to make changes or additions to
the Column in the Main Simulation Environment, the Solver
should be Active. Otherwise HYSYS may not 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 (see the Specification Tolerances for Solver section for more
information).
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7-22
Column Property View
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 7.6
A summary of each of the tabs in the COLUMN property view follows.
7.4.1
Design Tab
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 (subflowsheet), unless stated
otherwise.
Connections page (Main Flowsheet)
Note that if you have modified
the Column Template (e.g. added an additional Tray
Section), the Connections
page will appear differently
than what is shown in Figure
7.7.
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. Note that the
streams shown in this view reside in the parent or main flowsheet; they
do not include Column subflowsheet streams, such as the Reflux or
Boilup. In other words, only feed and product streams (material and
energy) are displayed on this page.
The appearance of the Connections page will vary depending
on the template you are using.
7-22
Column
7-23
Figure 7.7
Connections page (Column Runner)
The Connections page displayed in the Column Runner (inside the
Column subflowsheet) appears as shown in the following figure.
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.
You can connect or disconnect
streams from this page, as well
as change the stream location.
Figure 7.8
All Feed and Energy Streams, as well as the associated stage, are
displayed in the left portion of the Connections page. Liquid, Vapour
and Water Product streams and locations are displayed on the righthand side of the page.
7-23
7-24
Column Property View
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 7.9
HYSYS will display 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 are displayed
during convergence.
The Current checkbox
shows the current
specs that are being
used in the column
solution. The user
cannot check this box.
Specification types, the value of each
specification, the current calculated
value and the weighted error are
displayed here.
7-24
Buttons for working with
specifications.
Column
7-25
Optional Checks Group
In the Optional Checks group, you will find the following two buttons:
Button
Refer to Section 5.4 - Object
Status Window/Trace
Window in the User’s Guide
for details concerning the
Trace Window.
Input Summary
View Initial
Estimates
Function
This button will provide 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 press 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 will be displayed.
This button will open the Summary page of the Column
property view and display initial temperature and flow
estimates for the column. You can then use the values
generated by HYSYS to enter estimates on the Est. 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
will be honoured in the displayed estimates.
Profile Group
During the column calculations, a profile of temperature, pressure or
flow will be displayed and updated as the solution progresses. Select
the appropriate radio button to display the desired variable versus tray
number profile.
Specifications Group
New specifications are 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 will be reflected across all locations.
Double clicking on a cell within the row for any listed specification will
open its property view. In this view, you define all the information
associated with a particular specification. Each specification view has
three tabbed pages: Parameters, Summary and Spec Type. This view
can also be accessed from both the Specs and Specs Summary pages.
Further details are outined in following Specification Property View
sub section.
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7-26
Column Property View
Spec Status Check Boxes
The status of listed specifications will be one of the following types:
Spec Status Check Boxes
An Active specification is one
which the convergence algorithm
is trying to meet initially. An
Active specification has the
Estimate check box selected also.
An Estimate is used as an initial
"guess" for the convergence
algorithm, and is considered to be
an Inactive specification.
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 may be made
Active or an Estimate at a later
time.
Status
Description
Active
The active specification is one that the convergence
algorithm is trying to meet. Note that an active
specification always serves as an initial estimate (when
the Active box is checked, HYSYS automatically checks
the Estimate and Current boxes). 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, clear the
Active box by selecting it. The value will then serve only
as an initial estimate for the convergence algorithm. An
estimate does not exhaust an available degree of
freedom.
Current
Completely
Inactive
This check box shows the current specs being used by
the column solution. When the Active box is checked, the
Current box will automatically be checked. The user
cannot alter this check box.
When Alternate specs are used and an existing hard to
solve spec has been replaced with an Alternate spec, this
check box makes it clear to the user the current specs
used to solve the column.
To disregard the value of a specification entirely during
convergence, clear both the Active and Estimate check
boxes. By ignoring a specification rather than deleting it,
you will always be able to use it later if required. The
current value will be displayed 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 is displayed 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.
Note that variables such as the duty of the reboiler stream, which is
specified in the Workbook, or feed streams that are not completely
known will 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.
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Column
7-27
Specification Group Buttons
The four buttons which align the bottom of the Specifications group
allow you to manipulate the list of specs:
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 select the View
button to display its property view. You may then make
any necessary changes to the specification. See the
following Specification Property View sub section for
more details.
To change the value of a specification only, move to the
Specified Value input cell for the specification you wish
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 press the Add
Spec(s) button.
The property view for each new spec will be shown and its
name will be added to the list of existing specifications.
See the following Specification Types sub section for a
description of the available specification types.
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.
Specs Page
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 (see the Default
Replaceable Specifications sub-section in Section 7.3.2 - Templates ).
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7-28
Column Property View
Figure 7.10
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. See the following
Specification Property View sub section for more
details.
Add
Delete
Available Specification Types
7-28
Opens the Column Specifications menu list, from which
you can select one or multiple (by holding the CTRL key
while selecting) specifications and then press the Add
Spec(s) button.
The property view for each new spec will be shown and its
name will be added to the list of existing specifications.
See the following Specification Types sub section for a
description of the available specification types.
Removes the highlighted specification from the list.
Column
7-29
Note that you are only able to add Column Stream
Specifications via the Stream Property View of a draw stream
within the Column subflowsheet.
From the Default Basis drop down list, you can choose the basis of new
specifications to be Molar, Mass or Volume.
The Update Specs from Dynamics button will replace the Specified
Value of each specification with the Current Value (lined out value)
obtained from dynamics mode.
Specification Property View
Shown below is a typical property view of a specification. In this view,
you define all the information associated with a particular
specification. Each specification has three tabbed pages: Parameters,
Summary, and 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.
Note that 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 will
automatically update across all other locations. For example, you may
enter the Spec Value in one location and the change will be reflected
across all other locations.
Figure 7.11
Specify the stage to
which the specification
applies.
Provide the name of
the component(s) to
which the specification
applies.
Specify Liquid or
Vapour phase for this
specification.
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7-30
Column Property View
The Summary tab (shown to the left) is used to supply tolerances and
define whether the specification is Active or simply an Estimate.
The Spec Type tab 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.
Figure 7.12
Specify the interval for
use with a Ranged
Spec Value.
Define as either a Fixed or
Ranged Spec. A Ranged Spec
will allow 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 following section further details the advanced solving options
available in HYSYS.
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 will read
“Converged - Alternate Specs”
highlighted in purple.
7-30
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. See the Advanced Solving
Options Button sub section in Section 7.4.2 - Parameters Tab for
further details.
Column
7-31
Fixed/Ranged Specs
When the solver attempts to
meet a Ranged spec, the Wt.
Error will become zero when
the Current Value is within the
Ranged interval (as shown on
the Monitor page).
A Fixed Spec is one which 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 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), may 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 check box becomes unchecked for the original (not
met) spec and is checked for the
alternate spec.
The number of active Alternate
specs must always equal the
number of inactive Alternate
specs.
A Primary Spec is one which 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), may help solve columns where some
specifications can be ignored (enabling another) to meet the rest of the
specifications and converge the column.
Note that 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 has been provided to allow 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 the Section 7.4.2 - 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
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7-32
Column Property View
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 may be provided for each individual
specification. HYSYS calculates two kinds of errors for each
specification: an absolute error and a weighted error. The absolute
error is simply the absolute value of the difference between the
calculated and specified values:
When the Weighted and
Absolute Errors are less than
their respective tolerances, an
Active specification has
converged.
Errorabsolute = |Calculated Value - Specified Value|
(7.1)
The Weighted Error is a function of the particular specification type.
When a specification is active, the convergence algorithm is trying to
meet both the Weighted and the Absolute Tolerances. 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 may be set tighter (smaller) than
the other specification tolerances. If you delete any tolerances, HYSYS
will not apply the individual specification criteria to that specification,
and Ignore will appear in the tolerance input cell.
The specification tolerance feature is simply an "extra" to permit you to
work with individual specifications and change their tolerances if
desired.
7-32
Column
7-33
Specification Details Group
Figure 7.13
You can edit any specification
values shown in blue.
For a highlighted specification in the Column Specifications group, the
following information will be displayed:
• Spec Name
• Convergence Condition - if the weighted and absolute errors
are within their tolerances, the specification has converged and
Yes will be displayed.
• Status - you can manipulate the Active and Use As Estimate
check boxes. See the Monitor Page for further details
concerning the use of these check boxes.
• Spec Type - you can select between Fixed/Ranged and
Primary/Alternate specs. See the Ranged and Alternate
Specs sub section for more details.
• Specified and Current Calculated Values
• Weighted/Absolute Tolerance and Calculated Error
Specs Summary Page
You can edit any specification
details shown in blue.
You can also double click in a
specfication cell to open its
property view. See the
Specification Property View
sub section for more details
The Specs Summary page lists all Column specifications available
along with relevant information. This specification information is
shared with the Monitor and Specs Summary pages. Altering
information in one location will automatically update across all other
locations.
Figure 7.14
7-33
7-34
Column Property View
Subcooling Page
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
The Notes page provides a text editor where you can record any
comments or information regarding the COLUMN unit operation or
pertaining to your simulation, in general.
Specification Types
This section outlines the various specification types available along
with relevant details.
Cold Property Specifications
Cold Property
Description
Flash Point
This 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
This allows you to specify the ASTM Pour Point
temperature for the liquid or vapour flow on any stage in
the column.
RON
Specify the Research Octane Number for the liquid or
vapour flow on any stage.
Figure 7.15
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
7-34
Column
7-35
selected stage, these will be included with the internal vapour and
liquid flows.
Figure 7.16
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 7.17
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 7.18
7-35
7-36
Column Property View
Component Recovery
This 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 7.19
Cut Point
Note that while initial and
final cutpoints are permitted,
it is often better to use 5 and 95
percent cutpoints to minimize
the errors introduced at the
extreme ends of boiling point
curves
This option allows a cutpoint temperature to be specified for the liquid
or vapour leaving any stage. The types are TBP, ASTM D86, D1160 Vac,
D1160 ATM, ASTM D2887. For D86, you will be given the option to use
ASTM Cracking Factor. For D1160, you will be given an Atmospheric
Pressure option. The cutpoint can be on a mole, mass or volume
fraction basis, and any value from 0 to 100 percent is allowed.
Figure 7.20
Draw Rate
The molar, mass or volume flowrate of any product stream draw may be
specified.
Figure 7.21
7-36
Column
7-37
Delta T (Heater/Cooler)
The temperature difference across a heater or cooler unit operation
may be specified. The heater/cooler unit must be installed in the
Column subflowsheet and the Modified HYSIM Inside-Out Solving
Method must be selected on the Solver page of the Parameters tab.
Delta T (Streams)
The temperature difference between two Column subflowsheet
streams may be specified.
Figure 7.22
Duty
You can specify the duty for an energy stream.
Figure 7.23
Duty Ratio
You may 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 7.24
7-37
7-38
Column Property View
Feed Ratio
This type of specification is
useful for turn down or
overflash of a crude feed.
Selecting this 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 will
be prompted for the stage, flow type (Vapour, Liquid, Draw), and the
external feed stage.
Figure 7.25
Gap Cut Point
The Gap Cut Point is defined as the temperature difference between a
cutpoint (Cut Point A) for the liquid or vapour leaving one stage, and a
cutpoint (Cut Point B) on a different stage.
You have a choice of specifying that the distillation curve used: TBP,
ASTM D86, D1160 Vac, D1160 ATM or ASTM D2887.
You may define Cut Point A and Cut Point B, which together must total
100%. The cutpoints can be on a mole, mass or volume basis.
Figure 7.26
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.
Liquid Flow
The net Molar, Mass or Volume Liquid (Light or Heavy) Flow may be
specified for any stage.
Figure 7.27
7-38
Column
7-39
Physical Property Specifications
The mass density can be specified for the liquid or vapour on any stage.
Figure 7.28
Pump Around Specifications
Note that the Pump Around
Rate as well as the Pump
Around Temperature Drop
are the default specifications
HYSYS will request 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
This option 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
Pump Around return temperature.
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 may specify the duty for any Pump Around.
Return Vapour
Fraction
You may 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 the Duty Ratio specification type for
further details.
Figure 7.29
7-39
7-40
Column Property View
Reboil Ratio
Specifies the molar, mass or volume ratio of the vapour leaving a
specific stage to the liquid leaving that stage.
Figure 7.30
Reflux Ratio
This 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 7.31
The Reflux Ratio specification
is normally used only for top
stage condensers, but it may
be specified for any stage.
Tee Split Fraction
The split fraction for a TEE operation product stream can be specified.
The TEE must be installed within the Column subflowsheet 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 on the Params page.
Refer to Section 4.3 - Tee for
details on the TEE operation.
7-40
Tee split fraction specifications are automatically installed as you install
the tee operation in the Column subflowsheet; however, you can select
which specifications become active on the Monitor or Specs page.
Changes made to the split fraction specification value are updated on
the Splits page of the tee operation.
Column
7-41
Tray Temperature
The temperature of any stage can be specified.
Figure 7.32
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.
Note that the computing time required to satisfy a vapour viscosity
specification may be considerably longer than that needed to meet a
liquid viscosity specification.
Figure 7.33
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 will be
used in the spec calculations.
Figure 7.34
7-41
7-42
Column Property View
Vapour Flow
The net Molar, Mass or Volume Vapour Flow may be specified for any
stage. Feeds and draws to that tray are taken into account.
Figure 7.35
Vapour Fraction
The vapour fraction of a stream exiting a stage can be specified.
Figure 7.36
Vapour Pressure Specifications
Two types of vapour pressure specifications are available: true vapour
pressure (@100°F) and Reid vapour pressure.
Vapour Type
Description
Vapour
Pressure
The true vapour pressure at 100°F can be specified for
the vapour or liquid leaving any stage.
Reid Vapour
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.
Figure 7.37
7-42
Column
7-43
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
may 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 subflowsheet. Clicking on this button will bring up the Stream
Spec view.
Figure 7.38
Creating a new stream
specification for a stage, or
activating a specification will
automatically deactivate 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 may 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 change from Create Column
Stream Spec to View Column Stream Spec and can be selected to view
the Stream Specification view.
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7-44
Column Property View
7.4.2
Select the Molar, Mass or
Volume radio buttons to
display the flow estimates on a
different basis. At least one
iteration must have occurred
for HYSYS to convert between
bases. In this way, values for
the compositions on each tray
will be available.
This Column subflowsheet
shown on the following page
contains two columns, which
results in a break in the
pressure profiles, as shown in
the graph.
Parameters Tab
The contents of the Parameters tab shows column calculation results
and is used to define some basic parameters for the Column solution.
Profiles Page
The Profiles is used to show the column pressure profile and to provide
estimates for the temperature, net liquid and net vapour flow for each
stage of the column. You can input tray estimates in the Temperature,
Net Liquid and Net Vapour or view the values calculated by HYSYS. 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: Molar, Mass
or Volume.
The graph on the right hand side of the view depicts the pressure profile
across the column.
Figure 7.39
The buttons at the bottom of the view are defined as follows:
7-44
Profiles 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) will not be updated.
Clear
Deletes values for selected tray.
Clear All
Deletes values for all trays.
Column
Profiles Button
Function
Lock
Changes all red values (unlocked estimates, current
values, interpolated values) to blue (locked), which means
that they will not be overwritten by current values when
the Update from Solution button is pressed.
Unlock
Changes all blue values (locked) to red (unlocked).
Unlocked values will be overwritten by current values
when the Update from Solutions button is pressed.
Stream
Estimates
Displays the temperature, molar flow and enthalpy of all
streams attached to the column operation.
7-45
Estimates Page
The Estimates page is used to view and provide composition estimates.
Estimates are NOT a requirement for convergence.
To see the initial estimates
generated by HYSYS, press the
View Initial Estimates button
on the Monitor page.
Estimates are NOT required
for column convergence.
When you provide estimates on stages that are not adjacent to each
other, HYSYS will not interpolate values for intermediate stages until
the solution algorithm begins.
On this view, you can provide 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 7.40
HYSYS will interpolate intermediate tray component values when you
input 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.
7-45
7-46
Column Property View
Select either the Vap or Liq radio button in the Phase group box to
display the table for the vapour or liquid phase, respectively.
The Composition Estimates View has several buttons available:
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) will not 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 will be shown as
<empty>. This button essentially reverses the effect of
the Update button. Unlocked estimates (red) that had
been replaced after pressing the Update button will be
restored.
Normalize
Trays
This button will normalize the values on a tray so that the
total of the composition fractions equals 1. HYSYS
ignores <empty> cells and will normalize 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 will not be overwritten by current values when
the Update button is pressed.
Unlock
Estimates
Changes all blue values (locked) to red (unlocked).
Unlocked values will be overwritten by current values
when the Update button is pressed.
Efficiencies Page
Note that fractional
efficiencies may not 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 may easily be specified.
The functionality of this page is slightly different when working
with the Amines Property Package. See the end of this section
for details.
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.
7-46
Column
7-47
Figure 7.41
To specify an efficiency to
multiple cells, highlight the
desired cells, enter a value in
the Eff. Multi-Spec field and
press the Specify button.
The data table on the Efficiency page gives a stage-by-stage efficiency
summary. Note that the efficiencies are fractional, i.e. an efficiency of
1.0 corresponds to 100% efficiency.
Overall stage efficiencies may be supplied by selecting the Overall radio
button in the Efficiency Type group, and entering values in the
appropriate cells.
Component-specific efficiencies may be supplied 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 Runner, HYSYS will calculate 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 will
use its default tray values to determine the efficiency values.
The Reset H2S, CO2 button
and the Transpose check box
are available only if the
Efficiency Type is set to
Component.
If you specify values for the CO2 and H2S efficiencies, these are the
values that HYSYS will use to solve the column. If you would like to
solve the column again using efficiencies generated by HYSYS, select
the Reset H2S, CO2 button, which is available on this page. Run the
column runner again, and HYSYS will calculate and display the new
values for the efficiencies.
7-47
7-48
Column Property View
Activate the Transpose check-box 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 see Appendix
C- Amines Property Package of the Simulation Basis Manual.
Solver Page
Solving Options
Specify your preferences for the column solving behaviour in the
Solving Options group.
Figure 7.42
Maximum Number of Iterations
The Column convergence process will terminate 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
will terminate.
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 will always
converge to the same solution. However, you have the option of
changing these two values if you wish. 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
7-48
Column
7-49
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.
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.
7-49
7-50
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 may be
encountered on one or more stages in the Column. If HYSYS
encounters supercritical phase behaviour, appropriate messages will
be displayed 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 may
specify which method you wish HYSYS to use to model the phase
behaviour. There are three choices for supercritical calculations:
See Section 5.4 - Object Status
Window/Trace Window in
the User’s Guide for details on
the Trace Window.
Model
Description
Simple K
This is 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 the user 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 may be set to Low, Medium or High. The default is
Low.
Initialize from Ideal K's
When this check box is activated, 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 check box is cleared. HYSYS
uses specified composition estimates or generates estimates to
rigorously calculate K-values.
7-50
Column
7-51
Two Liquids Check Based on
This option allows the selection of the Two Liquids Check based on one
of the following criteria:
• No. 2 Liq Check
• Tray Liquid Fluid
• Tray Total Fluid
Solving Method
The Solving Method drop down list allows you to select the column
solution method.
Figure 7.43
The text box, which is displayed 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.
Open the Trace Window at the
bottom of the HYSYS DeskTop
to view messages regarding the
convergence of the column.
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
subflowsheet.
Newton Raphson
Inside-Out
General purpose method which allows liquid-phase
kinetic reactions inside the Column subflowsheet.
Sparse Continuation
Solver
This is 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.
Inside-Out
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.
7-51
7-52
Column Property View
Acceleration
When activated, the Accelerate K value & H Model Parameters check
box displays two input cells which relate to an acceleration program
called the Dominant Eigenvalue Method (DEM).
By default, the Accelerate K
value & H Model Parameters
option is de-activated.
Figure 7.44
The DEM is a numerical solution program which will accelerate
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. Note that the Accelerate K value & H
Model Parameters check box should NOT be activated for
AZEOTROPIC columns, as convergence tends to be impeded.
The listed DEM parameters include:
7-52
Parameter
Description
Acceleration
Mode
Select either Conservative or Aggressive. With the
Conservative approach, smaller steps will be 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 will use to
obtain a solution.
Column
7-53
Damping
Choose the Damping method by selecting either the Fixed or Adaptive
radio button.
Figure 7.45
With the Fixed method, 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.
Note that changing the damping factor will have no effect on
problems where the heat and spec error does not converge.
In addition to the above word of caution, 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.
Type of Column
The Azeotropic check box on
the Solver page of the
Parameters tab of the Column
Runner must be activated for
an azeotropic column to
converge.
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
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*
7-53
7-54
Column Property View
As shown in the above table, an azeotropic column requires that the
azeotrope check be enabled. There are two ways to indicate to HYSYS
that you are simulating an azeotropic column:
1.
Enter a negative damping factor, and HYSYS will automatically
select the Azeotropic check box. Note that the absolute value of the
damping factor is always displayed.
2.
Enter a positive value for the damping factor and select the
Azeotropic check box.
Adaptive Damping
If you select the Adaptive radio button, the Damping matrix will display
three fields. HYSYS will update 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 will look 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.
Update Initial
Damping Factor
If this option is checked, the current damping factor will be used
the next time the column is solved. If it is not checked, the
damping factor before adaptive damping was applied will be
used.
Initial Estimate Generator Parameters
You can enable the initial estimate generator (IEG) by activating the
Dynamic Integration for IEG check box. The IEG will then perform
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 check
box is activated.
Figure 7.46
7-54
Column
7-55
Select the Dynamic Estimates Integrator button and the following
view, which allows you to further define the dynamic estimates
parameters, opens.
Figure 7.47
From this view you can set parameters for the time period over which
the dynamic estimates are calculated, as well as set the calculation
tolerance. A checked Active option 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 pressing the Start button. If
you want to stop calculations before the specified time has elapsed,
select the Stop button. You do not have to manually select the Start
button to generate the estimates; if the Dynamic Integration for IEG
option is active, HYSYS will generate them automatically whenever the
column is run.
The Shortcut Mode check-box allows you to bypass this step once a set
of estimates is generated, that is, once the column has converged. If you
are running simulation with an iterative solving procedure where the
column will have to be calculated several times, it is a good idea to
select this option to save on calculation time.
7-55
7-56
Column Property View
Advanced Solving Options Button
The Advanced Solving Options button accesses the Advanced Solving
Options property view.
Figure 7.48
If the Column converges on an
Alternate or Ranged Spec, the
status bar will read
“Converged - Alternate Specs”
highlighted in purple.
The order in which the
solving options are
executed is based on
the priority.
The “use” check boxes
must be selected in
order to enable a
particular option.
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 will
replaced with an alternative inactive spec with
minimum error.
These check boxes are
only enabled if the
corresponding spec type
exists.
On the Advanced Solving Options property view, each solving option
(i.e. Alternate, Ranged and Autoreset) has a solving priority and also a
check option. To use a particular solving option, the user has to check
the corresponding checkbox. The user 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 will
switch to the original set of
specs after each recycle
iteration or the next time the
column solves.
7-56
Advanced solving options will not be used until the minimum number
of iterations are met. If the column is not solved after the minimum
number of iterations, the solver will switch to an advanced solving
option according to the solving priority. This process will be repeated
until all the solving options have been attempted or the column
converges.
Column
7-57
2/3 Phase Page
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. The Liquid Phase
Detection table (see Figure 7.63) 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,
select the box in the Check column. If a second liquid phase is
calculated, this will be indicated in the Detected column and by a
calculated flowrate value in the L2Rate column. The buttons on the
right side of the view serve as aids in selecting and de-selecting the
trays you want to check.
The group 2nd Liquid Type allows you to specify the type of calculation
HYSYS performs when checking for a second liquid phase. When the
Pure 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 button.
Note that checking for liquid phases in a three phase
distillation tower greatly increases the solution time. Typically,
checking the top few stages only, will provide reasonable
results.
Amines Page
The Amines Property Package
is an optional property
package that must be
purchased in addition to the
base version of HYSYS.
This Amines page is visible 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 will be used to determine the tray
efficiencies. The list includes: Tray Section, Weir Height, Weir Length,
Tray Volume, Tray Diameter.
If tray dimensions are not specified, HYSYS will use the default tray
dimensions to determine the efficiency values.
For more information on the Amines Property Package, see Appendix
C- Amines Property Package in the Simulation Basis Manual.
7-57
7-58
Column Property View
7.4.3
Side Ops Tab
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, press the Side Ops Input Expert button or go to the
appropriate Side Ops page and choose the Add button.
If you are using the Side Ops Input Expert, a wizard will guide 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 select Install. Note that specifications that are created when you
add a side operation are automatically added to the Monitor and Specs
pages. 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
subflowsheet.
You may view or delete any Side Operation simply by positioning the
cursor in the same line as the Operation, and selecting 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 will not register your changes.
Side Strippers Page
You may install a reboiled or steam-stripped Side Stripper from 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
steam-stripped configuration it is necessary to specify the Steam Feed.
The property view of the Side Stripper is shown in Figure 7.49.
7-58
Column
7-59
Figure 7.49
Remember that to change the
Side Stripper Draw and
Return Stages from the
Column Runner view, the
Solver must be Active in the
Main Simulation
Environment.
When you choose the Install button, a side stripper tray section will be
installed, as well as a reboiler if you selected the Reboiled
configuration.
By default, the Tray Section will be named SS1, the Reboiler SS1_Reb
and the reboiler duty stream SS1_Energy. As you add additional Side
strippers, the index will increase (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.
The Vapour and Liquid Product rates, as well as the Reflux Ratio are also
required. These specifications are added to the Monitor and Specs
pages of the Column property view.
7-59
7-60
Column Property View
Figure 7.50
When you install the Side Rectifier, a Side Rectifier Tray Section and
Partial Condenser are added.
By default, the Tray Section will be named SR_1, the Condenser
SR_1_Cond and the condenser duty stream SR_1_Energy.
Pump Arounds Page
When you install the pump around, a cooler will also be installed. The
default pump around specifications are the pump around rate and
temperature drop. These are added on the Monitor and Specs page of
the Column property view.
When installing a
Pumparound, it is necessary
to specify the Draw stage,
Return stage, Molar Flow and
Duty.
7-60
After you select the Install button, the Pumparound property view will
change significantly, as shown in Figure 7.51, allowing you to change
pumparound specifications, and view pump around calculated
information.
Column
7-61
Figure 7.51
Vap Bypasses Page
As with the Pumparound, 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 will
be displayed on the Vapour Bypass view.
The Vapour Bypass flowrate is automatically added as a specification.
Figure 7.52 shows the Vapour Bypass view once the side operation has
been installed.
Figure 7.52
7-61
7-62
Column Property View
Side Draws Page
The Side Draws page allows you to view and edit information regarding
the side draw streams in the column. The information included on this
page are:
•
•
•
•
•
•
Draw Stream
Draw Stage
Type (Vapour, Liquid or Water)
Mole Flow
Mass Flow
Volume Flow
7.4.4
Rating Tab
The Rating tab has three pages: the Tray Sections, Vessels, and
Equipment pages.
Tray Sections Page
This page provides information regarding tray sizing. On this page, you
can specify the following:
•
•
•
•
•
•
Tray Section (Name)
Tray Diameter
Weir Height
Weir Length
Tray Space
Tray Volume
Vessels Page
This page provides information regarding vessel sizing. On this page,
you can specify the following:
•
•
•
•
•
•
•
•
7-62
Vessel (Name)
Diameter
Length
Volume
Orientation
Vessel has a Boot
Boot Diameter
Boot Length
Column
7-63
Equipment Page
The Equipment page contains a list of Other Equipment in the Column
flowsheet.
7.4.5
Note that the Column
Environment also has its own
Workbook.
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the stream property view. The PF Specs page
contains a summary of the stream property view’s Dynamics tab.
7.4.6
Performance Tab
Summary Page
The Summary Page gives a tabular summary of Column stage
temperatures, pressures, flows and duties.
Figure 7.53
Note that the Liquid and
Vapour flows are net flows for
each stage.
You can split a feed stream
into its phase components
either on the Connections
page of the Design tab or on
the Setup page on the
Summary tab.
You may change the basis for which the data is displayed by selecting
the appropriate radio button in the Flow 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 (*) will follow the phase designation. If there is a duty stream on a
stage, a "Q" will appear in the Type column to the right of the Feed
7-63
7-64
Column Property View
Column. Note that the direction of the energy stream is indicated by the
sign of the duty, rather than the column in which the "Q" appears. In
the Type column, an “F” designates a feed stream and a “D” designates
a draw stream.
Profiles Page
On the Profiles page, you can view various column profiles or refinery
assay curves in a graphical or tabular format.
Figure 7.54
Tray by Tray Properties Group
To view a column profile, follow this process:
To make changes to the plot,
object Inspect the plot area
and select Graph Control
from the menu. Refer to
Chapter 6 - Output Control in
the User’s Guide.
7-64
1.
Select a profile from the list in the Tray by Tray Properties group.
The choices include: Temperature, Pressure, Flow, MW, Dens,
Visc., Composition, K Value and Light/Heavy Key.
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
From the drop down list, select a tray section. The
main tray section along with the condenser and
reboiler are considered one section, as is each side
stripper.
From/To
Use the drop-down lists to specify a specific range of
the column. The first cell will contain the tray that is
located at a higher spot in the tower (i.e. for top to
bottom tray numbering, the first cell could be tray 3
and the second tray 6).
Column
3.
7-65
After selecting a tray range, press either the View Graph or View
Table button to display a plot or table respectively.
Figure 7.55
Plots and tables are
expandible views that can
remain open without the
column property view.
4.
Depending on the profile selected, you may have to make further
specifications. Refer to the specific profile description.
Temperature Profile
The temperature profile displays the temperature for the tray range
selected. No further specification is needed.
Pressure Profile
The pressure profile displays the pressure of each tray in the selected
range. No further specification is needed for this profile.
Flow Profile
On both the Flow Profile plot and table, you will find a Properties
button. Pressing this button will access the Properties View, on which
you must specify the parameters for the display. Changes made on the
Properties View will affect both the table and plot.
In the Basis group box, select Molar, Mass or Liquid Volume for the
flow basis. The Molar default is selected in Figure 7.56.
Figure 7.56
7-65
7-66
Column Property View
In the Phase group box, activate the check box for the flow of each
phase that you wish to display. Multiple flows can be shown. If three
phases are not present in the column, the Heavy Liquid check box will
not be available, and thus, the Light Liquid check box will represent the
liquid phase.
MW, Dens., Visc… Profile
On both the plot and table, you will find a Properties button. Upon
selecting this button, you will access the Properties View, on which you
must specify the parameters for the display. Changes made on the
Properties View will affect both the table and plot.
In the Basis group box, select Molar or Mass for the property basis.
Figure 7.57
The Properties Profile table
displays all of the properties
for the phase(s) selected.
In the Phase group box, activate the check box for the flow of each
phase that you wish to display. Multiple flows can be shown. If three
phases are not present in the column, the Heavy Liquid check box will
not be available, as is the case in Figure 7.57.
The radio buttons in the Axis Assignment group box apply to the plot
only. You have the option of displaying one or two properties on the
plot. The property options that can be plotted include:
•
•
•
•
•
•
Molecular Weight
Density
Viscosity
Thermal Conductivity
Surface Tension
Heat Capacity
By selecting a radio button under Left, you will assign the values of the
appropriate property to the left y-axis. To display a second property,
choose a radio button under Right. The right y-axis will then show the
range of the second property. If you wish to display only one property
on the plot, select the None radio button under Right.
7-66
Column
7-67
Composition Profile
There is a Properties button on both the Composition Profile plot and
table. By selecting this button, you will access the Properties View
(Figure 7.58), on which you must specify the parameters for the display.
Changes made on the Properties View will affect both the table and
plot.
Figure 7.58
In the Basis group box, select Molar, Mass or Liquid Volume for the
composition basis.
In the Phase group box, activate the check box for the flow of each
phase that you wish to display. Multiple flows can be shown. If there are
not three phases present in the column, the Heavy Liquid check box
will not be available, and thus, the Light Liquid check box will represent
the liquid phase.
Choose either Fractions or Flows in the Comp Basis group by selecting
the appropriate radio button.
The Components group (Figure 7.58) displays a list of all the
components that enter the tower. You can display the composition
profile of any component by activating the appropriate check box. The
plot will display any combination of component profiles.
K Values Profile
The K Values profile displays the K Values of each tray in the selected
range. There is a Properties button and this will let you access the
Properties View. You can specify which component you want included
in the profile.
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7-68
Column Property View
Figure 7.59
Light/Heavy Key Profile
This profile displays the Fraction Ratio for each stage. There is a
Properties button that allows you to access the Properties View. You
can specify the Basis (Molar, Mass, or Liquid Volume), the Phase
(Vapour, Light Liquid or Heavy Liquid), and Comp Basis (Fractions or
Flows). In the Light Key(s) and Heavy Key(s) groups, you can specify
the key component(s).
Figure 7.60
Refinery Assay Curves Group
You can access the following plots and tables:
•
•
•
•
7-68
Boiling Point Assay
Molecular Weight Assay
Density Assay
User Properties
Column
7-69
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 press either the View Graph or View Table button.
You must now specify the parameters for the display. The Profile Data
Control button, which is located on every plot and table, accesses the
Data Control property view. The Data Control property view is a view
that is common to all plots and tables on the Curves page. For a
selected curve, all changes made on the Data Control property view
will affect the data of both the plot and table. The Data Control
property view consists of five group boxes as shown in Figure 7.61.
Figure 7.61
Style Group
Select either the Multi Tray or Single Tray radio button. The layout of
the Data Control property view will differ slightly for each selection.
For the Single Tray selection, you must open the drop down list and
select one tray.
If you select the Multi Tray radio button, the drop down list is replaced
by a list of all the trays in the column. Each tray has a corresponding
check box, which you activate to display the tray property on the plot or
table.
Properties Group
Refer to Chapter 3 - HYSYS Oil
Manager in the Basis
Manager for details on boiling
point curves.
This group box displays the properties available for the plot or table.
Each Curve option will have its own distinct Properties group. For a
single tray selection, you can choose as many of the boiling point
curves as required. Activate the check box for any of the following
options: TBP, ASTM D86, D86 Crack Reduced, D1160 Vac, D1160 ATM
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7-70
Column Property View
and D2887. When multiple trays have been chosen in the Style group
box, the check box list is replaced by a drop down input cell. You can
only choose one boiling point curve when displaying multiple trays.
Basis Group
In the Basis group box, select Molar, Mass or Liquid Volume for the
composition basis.
Phase Group
In the Phase group box, activate the check box 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 check box
will not be available, and thus, the Light Liquid check box will represent
the liquid phase.
Visible Points Group
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 will appear for each curve.
Pinch Page
Figure 7.62
The Pinch page is for viewing only and it lists the information for the
individual trays of the Tray Section, Condenser and Reboiler. You are
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Column
7-71
allowed to select the Flow Basis, and then HYSYS lists the Flow and
Enthalpy values for each tray, and the condenser and reboiler
according to the chosen Flow Basis.
2/3 Phase Page
Figure 7.63
By default, HYSYS will select 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
can always be changed by the
user.
This 2/3 Phase Page on the Performance tab displays additional liquid
flow rate information associated with three-phase distillation. You can
specify that HYSYS check for and calculate the flowrate of a second
liquid phase on any or all the trays of the column.This information is
then displayed in the L2Rate column. The Summary page displays a
single liquid flowrate for each stage of the column; you must view this
page to see the two-liquid-phase breakdown of the liquid stream.
Note that the 2nd Liquid Type group lists two options: Rigorous and
Pure. The Rigorous method can take substantially longer to solve than
the Pure method. When dealing with hydrocarbons, the Pure method is
the preferred choice. When dealing with chemicals (using activity
models) the Rigorous method may produce better results.
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7-72
Column Property View
7.4.7
Flowsheet Tab
Setup Page
This page defines the connections between the internal (subflowsheet)
and external (Parent) flowsheets.
To split all material inlet
streams into their phase
components before being fed
to the column, select the Split
Feeds check box.
The Labels, as noted previously, attach the external flowsheet streams
to the internal subflowsheet 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.
Figure 7.64
The Transfer Basis is significant only when the subflowsheet and
parent flowsheet Property Packages are different.
7-72
Flash Type
Action
T-P Flash
The Pressure and Temperature of the Material
stream are passed between flowsheets. A new
Vapour Fraction will be calculated.
VF-T Flash
The Vapour Fraction and Temperature of the
Material stream are passed between flowsheets. A
new Pressure will be calculated.
VF-P Flash
The Vapour Fraction and Pressure of the Material
stream are passed between flowsheets. A new
Temperature will be calculated.
P-H Flash
The Pressure and Enthalpy of the Material stream is
passed between flowsheets. This is the default
transfer basis.
Column
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
User Specs
You specify the Transfer Basis for a Material Stream.
None Required
No calculation is required for an Energy stream. The
heat flow will simply be passed between flowsheets.
7-73
When the Split check box for any of the inlet material streams is
selected, that stream is split into its vapour and liquid phase
components when fed to the column. The liquid stream is then fed to
the specified tray and the vapour phase to the tray immediately above
the specified feed tray.
The Flowsheet Topology group provides stage information for each
element in the flow sheet. In Figure 7.64, the Flowsheet Topology group
shows the number of stages involved with the Main TS, Kero_SS,
Diesel_SS, AGO_SS, Condensers, and Reboilers.
Flowsheet Variables Page (Main)
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 boxes
are not checked. The value of
this variable will be displayed
in the Current value column,
and this "pseudospecification" will not affect
the solution.
This page allows you to select and monitor any flowsheet variables
from one location. You can examine subflowsheet variables from the
outside Column property view, without actually having to enter the
Column subflowsheet environment.
You can add, edit or delete variables in the Selected Column flowsheet
Variables group.
Figure 7.65
Adding a Variable
Refer to Section 5.2.2 Variable Navigator in the
User’s Guide for information
on the Variable Navigator.
1.
Press the Add button.
2.
From the Variable Navigator, select each of the parameters for the
variable.
3.
Press the OK button.
4.
The variable is added to the Selected Column Flowsheet Variables
group.
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7-74
Column Property View
Editing a Variable
If you decide that you do not
want to keep the changes
made in the variable
navigator, press the Cancel
button.
You can edit a variable in the Selected Column Flowsheet Variables
group as follows:
1.
Highlight a variable.
2.
Press the Edit button.
3.
Make changes to the selections in the variable navigator.
4.
Press the OK button.
Deleting a Variable
You can remove a variable in any of the following ways:
• Highlight a variable and press the Delete button.
• Highlight a variable, press the Edit button, and then press the
Disconnect button from the Variable Navigator.
Internal Streams Page
On this page, you can create a flowsheet stream that will represent 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 will automatically be transferred to the
stream which you have created.
Figure 7.66
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.
Press the Add button.
2.
Place the cursor in the cell under Stream and enter the name
Liquid7. The name will appear in the edit bar as you type.
3.
With the cursor in the cell under Stage, you can open the drop
down list in the edit bar and choose tray 7 or simply type 7, which
will locate the selection in the list.
Column
7-75
4.
Under Type, you can select the phase that you wish to represent.
The options include Vapour, Liquid or Aqueous. Select Liquid in
this case.
5.
When the cursor is in the cell under Net/Total, you must select
either Net or Total. 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. By selecting Total, the
internal stream will represent all the material leaving the stage (i.e.
includes draws, pumparound streams, etc.). For the stage 7 liquid,
Net was selected.
7.4.8
Reactions Tab
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.
The Reactions tab allows you to attach multiple reactions to the
column. The tab consists of two pages: the Stages page which allows
you select the reaction set and its scope across the column and the
Results page which displays the reaction results stage by stage.
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
Vapour, Liquid
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7-76
Column Property View
Solving Method
Reaction Type
Reaction Phase
Newton Raphson InsideOut
Kinetic Rate, Simple
Rate
Liquid
Simultaneous Correction
Kinetic Rate, Simple
Rate, Equilibrium
Reaction
Vapour, Liquid,
Combined Phase
Note also that 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 matrix and three buttons.
Column Reaction Stages Matrix
The matrix consists of four columns.
Figure 7.67
7-76
Column
Column
Description
Column Reaction
Name
This is the name you have associated with column
reaction. Note that 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 will be occurring.
Last Stage
The lowest stage of the stage range over which the
reaction will be occurring.
Active
Activates the associated reaction thereby enabling it
to occur inside the column.
7-77
The view also contains three buttons that control the addition,
manipulation and deletion of column reactions.
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
see the subsection Column Reaction view,
appearing later in this section.
Edit
Allows you to edit the column reaction set whose
name is currently selected in Column Reaction
Stages matrix. The selected reaction’s Column
Reaction view should open. For more information on
the Column Reaction view, see the following section
Column Reaction View.
Delete
Allows you to delete the column reaction set whose
name is currently selected in the Column Reaction
Stages matrix.
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7-78
Column Property View
Column Reaction View
Figure 7.68
The addition and revision of column reactions is done via the Column
Reaction view. The Column Reaction view shown in Figure 7.68
consists of two group boxes: the Reaction Set Information group which
allows you to select the reaction set and the scope of its application and
the Reaction Information group which contains thermodynamic and
stoichiometric information about the reaction you are applying to the
selected section of the column.
Reaction Set Information Group
The Reaction Set Information group consists of six objects:
7-78
Objects
Description
Name
The name you would like to associate with the
column reaction. This is the name that will appear in
the Column Reaction Name column of the Column
Reaction Stages matrix.
Reaction Set
Allows you to select a reaction set from a list of all
the reactions 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.
Column
Objects
Description
Delete
Deletes this Column Reaction from the column.
Active
Allows you to enable and disable the associated
column reaction.
7-79
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. You can open up the selected reaction’s Reaction
view by selecting the View Reaction button.
This group also contains three subgroups which allow you to view or
specify the selected reactions properties:
Subgroup
Description
Allows you to view and make changes to the
stoichiometric formula of the reaction currently
selected in Reaction drop down field. The group
contains three columns:
Stoichiometry
You may make changes to the
fields in these subgroup boxes.
Note that these changes will
affect all the unit operations
associated with this reaction.
Select the View Reactions
button for more information
about the attached reaction.
• 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 this reaction.
Consists of two fields:
Basis
• Base Component - displays the reactant to
which the reaction extent will be calculated. This
is often the limiting reactant.
• Reaction Phase - displays the phase for which
the kinetic rate equations for different phases can
be modelled in the same reactor. To see the
possible reactions, select the Reaction
Information button in the View Reaction group.
Consists of two fields:
Heat and Balance
Error
• Reaction Heat - displays the reaction heat.
• Balance Error - displays any error in the mass
balance around the reaction.
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7-80
Column Property View
Results Page
Figure 7.69
The Results page displays the results of a converged column. The page
consists a matrix containing four 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.
Note that if you have more than one reaction occurring at any
particular stage, each reaction will appear simultaneously.
Note that the Rxn Extent results will be displayed only if the
Sparse Continuation Solver is chosen as the Solving Method.
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Column
7-81
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 subdivided into three sections: the Rectifying Section,
Reactive Section and the Stripping Section.
Figure 7.70
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.
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.
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7-82
Column-Specific Operations
• 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 may be compromised.
7.4.9
Dynamics Tab
The Dynamics tab has three related pages: Vessels, Equipment and
Holdup. If you are working exclusively in Steady State mode, you are
not required to change any information on the pages accessible
through this tab. For more information on running the COLUMN
operation in Dynamic mode, see the Dynamic Modelling guide for
further details.
7.5
Column-Specific
Operations
The procedure for installing unit operations in a Column subflowsheet
is the same as in the main flowsheet (see Section 1.2.1 - Installing
Operations for details). The UnitOps view for the COLUMN is activated
by selecting Add Operation under Flowsheet in the Menu Bar, or by
pressing F12.
Figure 7.71
Note that only the operations
which are applicable to a
Column operations are
available within the Column
subflowsheet.
The unit operations available within the Column subflowsheet are
listed in the following table. Most operations shown here are identical
to those available in the main flowsheet in terms of supplied and
calculated information, property view structure, etc.
There are also additional unit operations which are not available in the
main flowsheet. They are: the Condenser (Partial, Total, 3-Phase),
Reboiler and Tray Section. The Bypasses and Side Operations (Side
Strippers, Pump Arounds, etc.) are available on the Side Ops page of the
7-82
Column
7-83
Column property view. Available unit operations in the Column
subflowsheet 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
7.5.1
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:
Note that 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. Note that 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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7-84
Column-Specific Operations
The Condenser property view uses a Type drop-down menu, letting
you to switch between condenser types without having to delete and
re-install a new piece of equipment.
Partial Condenser Button
Figure 7.72
Total Condenser Button
Three-Phase Condenser
Button
When you switch between the condenser types, the pages will change
appropriately. For instance, the Connections page for the TOTAL
CONDENSER will not show the Vapour stream. If you switch from the
PARTIAL to TOTAL CONDENSER, the Vapour stream is disconnected.
If you then switch back, you will have to reconnect the stream.
You are not required to modify
information on the
Condenser’s Rating or
Dynamics tabs when working
in Steady State Mode.
For a detailed description of
the Rating and Dynamics tabs
for the Condenser see Chapter
8 of the Dynamics Modelling
guide for further information.
7-84
When you add a Column to the simulation using a pre-defined
template, there may 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 select a Condenser from the Column Palette.
The Condenser property view has the same basic five tabs that are
available on any unit operation: Design, Rating, Worksheet,
Performance and Dynamics.
It is necessary to specify the Connections and the Parameters for the
Condenser. The information on the Rating and Dynamics tabs are not
relevant in Steady State.
Column
7-85
Design Tab
Connections Page
On the Connections page, provide the operation name, as well as the
names of the Feed(s), Vapour, Water, Reflux, Product and Energy
streams. The Total Condenser will not have a vapour stream, as the
entire feed will be liquefied. Neither the Partial nor the Total Condenser
has a Water Stream. The Connections page will show 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.
Parameters Page
Figure 7.73
The condenser parameters that can be specified are:
It is better to use a Duty spec
than specifying the heat flow
of the Duty stream.
• Pressure Drop
• Duty
• Subcooling Data
7-85
7-86
Column-Specific Operations
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
(4.1)
where:
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)
Note that you typically supply a pressure for the condenser during the
column setup, in which case the pressure of the top stage is the
calculated value.
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 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. If the Energy stream was given a name on the
Connections page, that name will be shown here.
The steady-state condenser energy balance is defined as:
Hfeed - Duty = Hvapour + Hliquid
where:
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)
7-86
(7.2)
Column
7-87
SubCooling
In Steady-State, SubCooling
applies only to the TOTAL
CONDENSER. There is no
SubCooling in Dynamics.
In some instances, you may wish to specify Condenser SubCooling. In
this situation, either the Degrees of SubCooling or the SubCooled
Temperature may be specified. If one of these fields is set, the other will
be calculated automatically.
Estimate Page
On this page you can estimate the flows and phase compositions of the
streams exiting the Condenser.
Figure 7.74
Worksheet Tab
The Worksheet page provides the same information as the default
Material Streams page of the Workbook. However, this page displays
only the streams that are currently attached to the Condenser.
Performance Tab
In Steady State, the displayed
plots will all be straight lines.
Only in Dynamic Mode, when
the concept of zones is
applicable, will the plots show
variance across the vessels.
The performance tab has two pages: Plots and Tables. From these
pages you can view the calculated values and plot any combination of
the calculated Temperature, Pressure, Heat Flow, Enthalpy or Vapour
Fraction. At the bottom of either page, specify the interval size over
which the values should be calculated and plotted.
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7-88
Column-Specific Operations
7.5.2
Reboiler
If you choose a Reboiled Absorber or Distillation template, it will
include a REBOILER which is connected to the bottom tray in the TRAY
SECTION with the streams to Reboiler and Boilup.
The Reboiler is a column operation which is used to partially or
completely vapourize liquid feed streams. You must be in a Column
subflowsheet to install the Reboiler.
Reboiler Button
To install the REBOILER operation, press F12 and choose Reboiler.
From the UnitOps view or select the Reboiler button in the Column
Palette.
The Reboiler property view has the same basic five tabs that are
available on any unit operation: Design, Rating, Worksheet,
Performance and Dynamics.
For a detailed description of
the Rating and Dynamics tabs
for the Reboiler see Chapter 8
of the Dynamics Modelling
guide for further information.
It is necessary to specify the Connections and the Parameters for the
Reboiler. The information on the Rating and Dynamics tabs are not
relevant in Steady State.
Design Tab
Connections Page
On the Connections page, you must provide the Reboiler name, as well
as the names of the Feed(s), Boilup, Vapour Draw, Energy and Bottoms
Product. The Vapour Draw Stream is optional.
The Reboiler is typically used with the column, 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.
7-88
Column
7-89
Figure 7.75
Parameters Page
The Pressure Drop across the reboiler (Delta P) is zero by default.
It is better to use a Duty spec
rather than specifying the heat
flow of the Duty stream.
The Duty for the Energy Stream can be specified here. The Duty should
be positive, indicating that energy is being added to the Reboiler
feed(s). If a name was provided for the Energy Stream on the
Connections page, that name will be shown here. Note that if you
specify the duty, a degree of freedom is used. However, it is preferable to
define a duty specification on the Monitor or Specs page of the Column
property view instead of specifying this value here.
Figure 7.76
7-89
7-90
Column-Specific Operations
The steady-state reboiler energy balance is defined as:
Hfeed + Duty = Hvapour + Hbottom + Hboilup
(7.3)
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
Worksheet Tab
The Worksheet tab provides the same information as the default
Material Streams page of the Workbook. However, this page displays
only the streams that are currently attached to the Reboiler.
Performance Tab
The Performance tab has two pages: Plots and Tables. At the bottom of
either page, specify the interval size over which the values should be
calculated and plotted.
7.5.3
Tray Section
At the very minimum, the Column Templates will include 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.
Shown in Figure 7.77 is the property view for the TRAY SECTION of a
Distillation Column template.
7-90
Column
7-91
Figure 7.77
For more information on the
dynamics of the tray section
see Chapter 8 of the Dynamic
Modelling guide.
The tray section property view contains the five tabs that are common
to most unit operations: Design, Rating, Worksheet, Performance and
Dynamics. You are not required to change anything on the Rating and
Dynamics tabs because the information on these pages are not
relevant in Steady State Mode.
Design Tab
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 7.77). 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).
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Column-Specific Operations
The location may be changed by selecting the desired feed tray
from the Edit Bar drop-down list, or by entering the tray number
in the appropriate field.
• Streams entering and leaving the top and bottom trays are
always placed in the Liquid or Vapour Inlet/Outlet cells.
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) will
automatically result 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 will be 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, 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: Vapour, Liquid or Water and then the cells to
name the side draw stream and specify the tray from which it is taken.
Parameters Page
You may 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 modelled using a
modified Murphree Efficiency.
Figure 7.78
By default, the Use Tray
Section Name for Stage Name
check box is selected.
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Column
7-93
You can add or delete trays anywhere in the column by selecting 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. Figure
7.79 shows the dialog box that appears when the Customize button is
selected:
Figure 7.79
You may add and remove trays in the following ways:
• Specify a new number of trays in the Current Number of
Trays cell. This is the same as changing the number of
theoretical trays on the Connections page. All inlet and outlet
streams will move appropriately; for example, if you are
changing the number of trays from 10 to 20, a stream initially
connected to tray 5 will now be at tray 10, and a stream initially
connected at stream 10 will now be at tray 20.
To add trays to the tray section:
1.
Enter the number of trays you wish to add in the Number of Trays
to Add/Delete input cell.
2.
Specify the tray number after which you wish to add the trays in
the Tray to Add After or Delete First input cell.
3.
Select the Add Trays button and HYSYS will insert 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 will be moved down (or up) by the number
of trays that were inserted.
When you are adding or
deleting trays, all FEEDS will
remain connected to their
current trays.
To remove trays from the tray section:
1.
Enter the number of trays you wish to delete in the Number of
Trays to Add/Delete input cell.
2.
Enter the first tray in the section you wish to delete in the Tray to
Add After or Delete First cell.
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Column-Specific Operations
3.
Select the Remove Trays button. All trays in the selected section
will be 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 will be 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 will be removed.
4.
Streams connected to a higher tray (numerically) will not be
affected; for example, if you are deleting 3 trays starting at tray
number 6, a side draw initially at tray 5 will remain there, but a side
draw initially connected to tray 10 will now be at tray 7. Any draw
streams connected to trays 6,7 or 8 will be deleted with your
confirmation to do so.
If you select Side Stripper or Side Rectifier from the radio buttons at
the bottom of the view, this will affect 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
This 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 will calculate the top and bottom tray pressures
based on the Condenser and Reboiler pressure drops. The
intermediate tray pressures will then be calculated by linear
interpolation
Figure 7.80
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Column
7-95
Worksheet Tab
The Work Sheet tab provides the same information as the default
Material Streams page of the Workbook. However, this page displays
only the streams that are currently attached to the Tray Section.
Performance Tab
The Performance tab has two pages: Plots and Tables. At the bottom of
either page, specify the interval size over which the values should be
calculated and plotted.
7.5.4
Refer to Chapter 4 - Piping
Equipment for more details
on the property view of the
TEE.
Tee
The TEE operation is available when using the Modified HYSIM I/O
method only. The property view for the TEE operation in the Column
subflowsheet has all of the pages and inherent functionality contained
by the Tee in the Main Environment with one addition, the Estimates
page.
Figure 7.81
On the Estimates page, you can help the convergence of the Column
subflowsheet's simultaneous solution by supplying flow estimates for
the tee product streams. To supply 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
input cell next to the stream name.
There are four buttons that appear on the Estimates page:
The Modified HYSIM InsideOut Solving Method must be
selected on the Solver page of
the Parameters tab on the
column property view when
the TEE is used in the Column
subflowsheet.
Radio Button
Related Setting
Update
Will replace all estimates except user supplied
estimates (in blue) with values obtained from the
solution.
Clear Selected
Deletes the highlighted estimate.
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7-96
Running the Column
Radio Button
Related Setting
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 will be added to the list of column
specifications for each tee product stream that you supply. As you
specify the split fractions for the product streams, these values will be
transferred to the individual column specifications on the Monitor and
Specs pages of the column property view.
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, please see its
respective chapter (e.g., for information on the Heat
Exchanger, see Section 3.3 - Heat Exchanger ). The only point
that must be stressed is that all operations within the Column
subflowsheet environment are solved simultaneously.
7.6
Running the Column
Once you are satisfied with the configuration of your Column
subflowsheet and you have supplied all necessary input, the next step is
to run the Column solution algorithm.
Run and Reset Buttons in the Column
property view.
Stop Button in the Column property
view
Run Button (green) in the
Button Bar
Stop Button (red) in the
Button Bar
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On the Button Bar, the Run
and Stop buttons are two
separate buttons. Whichever
button is toggled on has light
grey shading.
The iterative procedure will begin when you select Run from the
Column property view. Note that the Run/Reset buttons may be
accessed from any page of the Column property view. When you are
inside the Column build environment, a Run button 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 selected, the
Run/Reset buttons will be replaced by a Stop button which, when
selected, will terminate the convergence procedure. The Run button
may then be selected again to continue from the same location.
Similarly, a Stop button replaces the toolbar Run button after it is
activated.
When you are working inside the Column build environment, the
Column will run only when you select the Run button on the Column
Runner, or the Run button from the Button Bar. When you are working
with the Column property view in the Main build environment, the
Column will automatically Run when:
• you change a specification value after a converged solution has
been reached.
Column
7-97
• you change the Active specifications, such that the Degrees of
Freedom return to zero.
7.6.1
Run
Selecting Run will begin the iterative calculations necessary to simulate
the column described by the input. On the Monitor Page of the Column
Runner, a summary showing the iteration number, equilibrium error,
and the heat and specification errors will appear. Detailed messages
showing the convergence status will be shown in the Trace Window (see
Section 7.4.1 - 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 run, the status line at the bottom of the screen
will first track the calculation of the initial properties used to generate
the simple models. Then the determination of a Jacobian matrix will be
displayed, which is used in the solution of the inner loop. Next, the
status line will report the inner loop errors and the relative size of the
step taken on each of the inner loop iterations. Finally, the rigorous
thermodynamics will again be 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 will not converge and
press Stop to terminate the calculation.
If difficulty is encountered in converging the inner loop, the program
will occasionally recalculate 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 (see Section 7.7 - Column
Troubleshooting ) if trouble is encountered achieving the desired
solution).
Any estimates which are displayed in the Column Runner Profile
Estimates page will be used as initial guesses for the convergence
algorithm. If no estimates are present, HYSYS will begin the
convergence procedure by generating initial estimates (see Section
7.4.2 - Parameters Tab for more information on the Estimates page).
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Column Troubleshooting
7.6.2
Reset
This command will clear the current Column solution and any
estimates appearing on the Estimates page of the Column Runner. If
you make major changes after getting a converged Column, it may be a
good idea to Reset to clear the previous solution. This will allow the
Column solver to start fresh and distance itself from the previous
solution. If you make only minor changes to the Column, try selecting
Run before Resetting.
Once the column calculation is started it will continue 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 will continue indefinitely in an attempt to solve
the column unless the Stop button is selected. Unconverged results can
be analysed, as discussed in Section 7.7 - Column Troubleshooting .
7.7
Column
Troubleshooting
Although HYSYS does not require any initial estimates for convergence,
good estimates of top and bottom temperatures and one product will
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 will provide 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
will not 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 will remain fixed. To achieve the desired
specifications the Column will only adjust variables which have been
supplied 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
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Column
7-99
is your responsibility to ensure that you have entered a reasonable set
of operating conditions (initial estimates) and specifications (Basic
Column Parameters) that will permit solution of the column. There are
obviously many combinations of column configurations and
specifications that may make 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.
7.7.1
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
press 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
will simply cause your tower to converge more slowly. However,
occasionally the effect is more serious. Consider the following:
• 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.
Input Errors
Pressing the Input Summary
button on the Monitor page of
the column property view will
display 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:
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7-100
Column Troubleshooting
• 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 may not be 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 will become single phase. Since they do
not represent any equilibrium mass transfer, they should be
removed or the feed should be moved. The tower will not
converge with this configuration.
• Note the tower will fail immediately if any of the sidestrippers do
not have a stripping feed stream or a reboiler. If this should
occur, a message will be generated stating that a reboiler or
feed stream is missing in one of the sidestrippers.
• 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 may 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
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Column
7-101
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.
• 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.
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 cutpoint specification is similar to a flow rate spec; you
cannot specify all flows and leave one unspecified and then
specify the cutpoint 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.
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7-102
Column Troubleshooting
• 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.
7.7.2
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 200 F.
• If the column almost converges, you may have too many water
draws.
7.7.3
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 (see Section 7.4.2 - Parameters Tab ).
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Column
7.8
1
7-103
References
Sneesby, Martin G., Simulation and Control of Reactive Distillation,
Curtin University of Technology, School of Engineering, March
1998.
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7-104
References
Solid Separation Operations
8-1
8 Solid Separation
Operations
8.1 Simple Solid Separator (Simple Filter) ....................................................... 3
8.1.1
8.1.2
8.1.3
8.1.4
Design Tab ............................................................................................... 3
Rating Tab ................................................................................................ 4
Worksheet Tab ......................................................................................... 5
Dynamics Tab .......................................................................................... 5
8.2 Cyclone ......................................................................................................... 5
8.2.1
8.2.2
8.2.3
8.2.4
8.2.5
Design Tab ............................................................................................... 6
Ratings Tab .............................................................................................. 7
Worksheet Tab ......................................................................................... 8
Performance Tab...................................................................................... 8
Dynamics Tab .......................................................................................... 8
8.3 Hydrocyclone................................................................................................ 9
8.3.1
8.3.2
8.3.3
8.3.4
8.3.5
Design Tab ............................................................................................... 9
Ratings Tab .............................................................................................11
Worksheet Tab ........................................................................................11
Performance Tab.....................................................................................11
Dynamics Tab ........................................................................................ 12
8.4 Rotary Vacuum Filter ................................................................................. 12
8.4.1
8.4.2
8.4.3
8.4.4
Design Tab ............................................................................................. 12
Ratings Tab ............................................................................................ 14
Worksheet Tab ....................................................................................... 15
Dynamics Tab ........................................................................................ 15
8.5 Baghouse Filter .......................................................................................... 15
8.5.1
8.5.2
8.5.3
8.5.4
8.5.5
Design Tab ............................................................................................. 15
Rating Tab .............................................................................................. 17
Worksheet Tab ....................................................................................... 17
Performance Tab.................................................................................... 17
Dynamics Tab ........................................................................................ 17
8-1
8-2
8-2
Solid Separation Operations
8.1
8-3
Simple Solid Separator
(Simple Filter)
The SIMPLE SOLID SEPARATOR performs a non-equilibrium
separation of a stream containing solids. This operation will 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.
Simple Solid Separator Button
To install the SIMPLE SOLID SEPARATOR operation, press F12 and
choose Simple Solid Separator from the Unit Ops view or select the
Simple Solid Separator button in the Object Palette (you must first
press the Solids Handling radio button).
To ignore the SIMPLE SOLID SEPARATOR during calculations, select
the Ignored check box. HYSYS will completely disregard the operation
until you restore it to an active state by clearing the check box.
8.1.1
Design Tab
Connections Page
On the Connections page, you may specify the name of the Operation,
and the Feed and Product streams (Vapour, Liquid, Solids).
Figure 8.1
8-3
8-4
Simple Solid Separator (Simple Filter)
Parameters Page
You may specify the Pressure drop on the Parameters page.
Splits Page
On the Splits page, you must choose the split method by defining a
Type of Fraction:
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 will be calculated by
HYSYS. You must also specify the fraction of liquid in
the bottoms (solid product).
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
Stream Fractions
In the Flowsheet, the streams will not be 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 option, see User Variables chapter in the
Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the unit operation or pertaining to
your simulation, in general.
8.1.2
Rating Tab
This unit operation does not currently have rating features.
8-4
Solid Separation Operations
8.1.3
8-5
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. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab for the Stream property view.
8.1.4
Dynamics Tab
This unit operation is currently not available for dynamic simulation.
8.2
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.
Cyclone Button
To install the CYCLONE operation, press F12 and choose Cyclone from
the Unit Ops view or select the Cyclone button in the Object Palette
(you must first press the Solids Handling radio button).
To ignore the CYCLONE during calculations, select the Ignored check
box. HYSYS will completely disregard the operation until you restore it
to an active state by clearing the check box.
8-5
8-6
Cyclone
8.2.1
Design Tab
Connections Page
On the Connections page, you can provide the name of the operation,
as well as the feed, vapour product and solid product streams.
Figure 8.2
Parameters Page
You may specify the following parameters:
Parameter
Description
Configuration
Select either High Efficiency or High Output.
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 will be recovered. All other solids in the inlet stream
are removed at an efficiency related to these parameters.
8-6
Solid Separation Operations
8-7
Solids Page
On the this 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 (accessed through the Edit Bar),
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.
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 option, see the User Variables chapter in the
Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the unit operation or pertaining to
your simulation, in general.
8.2.2
Ratings Tab
Sizing Page
Specify the following parameters:
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.
8-7
8-8
Cyclone
Parameter
Description
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 will automatically be
calculated, within the provided constraints. If Design
Mode is off, then you may specify this value.
Constraints Page
You may specify the minimum and maximum diameter for the
CYCLONE, applicable only when the Design Mode is on.
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.
8.2.3
Worksheet Tab
The Work Sheet tab provides the same information as the default
Material Streams tab of the Workbook. However, this tab displays only
the streams that are currently attached to the unit operation.
8.2.4
Performance Tab
Results Page
The calculated Pressure Drop, Overall Efficiency and number of
parallel cyclones are displayed.
8.2.5
Dynamics Tab
This unit operation is currently not available for dynamic simulation.
8-8
Solid Separation Operations
8.3
8-9
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.
Hydrocyclone Button
To install the HYDROCYCLONE operation, choose Add Operation from
the Flowsheet Menu, and select HYDROCYCLONE. Alternatively, select
the Hydrocyclone button in the Object Palette (you must first press the
Solids Handling radio button).
To ignore the HYDROCYCLONE during calculations, select the Ignored
check box. HYSYS will completely disregard the operation until you
restore it to an active state by clearing the check box.
8.3.1
Design Tab
Connections Page
On the Connections page, you can provide the name of the operation,
as well as the feed, liquid product and solid product streams.
Figure 8.3
8-9
8-10
Hydrocyclone
Parameters Page
You may 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 will be recovered. All other solids in the inlet stream
are removed at an efficiency related to these parameters.
Solids Page
The following solids information may be specified:
Parameter
Description
Solid Name
You must provide either the name of a solid already
installed in the case (accessed from the drop down
menu in the Edit Bar), 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 option, see the User Variables chapter in the
Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the unit operation, or pertaining
to your simulation in general.
8-10
Solid Separation Operations
8.3.2
8-11
Ratings Tab
Sizing Page
Specify the following parameters:
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 will automatically be
calculated, within the provided constraints. If Design
Mode is off, then you may specify this value.
Constraints Page
You may specify the minimum and maximum diameter for the Cyclone,
applicable only when the Design Mode is on.
The Maximum Pressure Drop and Maximum Number of Cyclones may
also be set on this page.
8.3.3
Worksheet Tab
The Worksheet tab provides the same information as the default
Material Streams tab of the Workbook. However, this tab displays only
the streams that are currently attached to the unit operation.
8.3.4
Performance Tab
Results Page
The calculated Pressure Drop, Overall Efficiency and number of
parallel cyclones are displayed on this page.
8-11
8-12
Rotary Vacuum Filter
8.3.5
Dynamics Tab
This unit operation is currently not available for dynamic simulation.
8.4
Rotary Vacuum Filter
The ROTARY VACUUM FILTER assumes that there is 100% removal of
the solid from the solvent stream. This operation will determine 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.
Rotary Vacuum Filter Button
To install the ROTARY VACUUM FILTER operation, press F12 and
choose Rotary Vacuum Filter from the Unit Ops view or select the
Rotary Vacuum Filter button in the Object Palette (you must first press
the Solids Handling radio button).
To ignore the operation during calculations, select the Ignored check
box. HYSYS will completely disregard the operation until you restore it
to an active state by clearing the check box.
8.4.1
Design Tab
Connections Page
On the Connections page, define the Operation Name, as well as the
Feed, Liquid Product and Solids Product streams.
8-12
Solid Separation Operations
8-13
Figure 8.4
Parameters Page
The Rotary Vacuum Filter parameters are:
Parameter
Description
Pressure Drop
Pressure drop across the filter.
Cycle Time
This is the complete time for a cycle (one complete
revolution of the cylinder).
Dewatering
This is 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.
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 option, see User Variables chapter in the
Customization Guide.
8-13
8-14
Rotary Vacuum Filter
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the Rotary Vacuum Filter, or
pertaining to your simulation in general.
8.4.2
Ratings Tab
Sizing Page
You may specify the following filter 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.
Cake Page
The Cake Properties are defined on this page:
Property
Description
Mass Fraction of
Cake
This is 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 will calculate
this from the sphericity and diameter of the solid.
You may define the resistance or use a resistance equation, allowing
HYSYS to calculate this value.
The Filtration Resistance equation is as follows:
Resistance = a(dP)s
where: a and s are constants
dP is the pressure drop
8-14
(8.1)
Solid Separation Operations
8.4.3
8-15
Worksheet Tab
The Worksheet tab provides the same information as the default
Material Streams tab of the Workbook. However, this tab displays only
the streams that are currently attached to the unit operation.
8.4.4
Dynamics Tab
This unit operation is currently not available for dynamic simulation.
8.5
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 will be determined from this curve. The solids being
separated must be previously specified and installed as components in
the stream attached to this operation.
Baghouse Filter Button
To install the BAGHOUSE FILTER operation, press F12 and choose
Baghouse Filter from the Unit Ops view or select the Baghouse Filter
button in the Object Palette (you must first press the Solids Handling
radio button).
To ignore the BAGHOUSE FILTER during calculations, select the
Ignored check box. HYSYS will completely disregard the operation until
you restore it to an active state by clearing the check box.
8.5.1
Design Tab
Connections Page
On the Connections page, supply the name of the operation, as well as
the feed, vapour product and solid product streams.
8-15
8-16
Baghouse Filter
Figure 8.5
Parameters Page
On the Parameters page, you must supply the following information:
Parameter
Description
Configuration
When you make a change to any of the parameters,
the configuration will change 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 option, see the User Variables chapter in the on-line
Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the unit operation or pertaining to
your simulation, in general.
8-16
Solid Separation Operations
8.5.2
8-17
Rating Tab
Sizing Page
The following parameters may 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.
8.5.3
Worksheet Tab
The Worksheet tab provides the same information as the default
Material Streams tab of the Workbook. However, this tab displays only
the streams that are currently attached to the unit operation.
8.5.4
Performance Tab
Results page
The following Filtration results are displayed on this page:
•
•
•
•
•
Filtration Time
Number of Cells
Area/Cell
Total Cell Area
Particle Diameter
8.5.5
Dynamics Tab
This unit operation is currently not available for dynamic simulation.
8-17
8-18
8-18
Baghouse Filter
Reactors
9-1
9 Reactors
9.1 The Reactor Operation................................................................................. 3
9.2 CSTR / General Reactor Design Tab........................................................... 4
9.2.1 Connections Page.................................................................................... 5
9.2.2 Parameters Page ..................................................................................... 6
9.3 CSTR / General Reactor Reactions Tab ..................................................... 8
9.3.1
9.3.2
9.3.3
9.3.4
Conversion Reactor Reactions Tab.......................................................... 8
CSTR Reactions Tab.............................................................................. 13
Equilibrium Reactor - Reaction Tab........................................................ 17
Gibbs Reactor Reactions Tab ................................................................ 22
9.4 CSTR / General Reactor Rating Tab ......................................................... 25
9.5 CSTR / General Reactor Work Sheet Tab ................................................. 29
9.6 CSTR / General Reactor Dynamics Tab.................................................... 29
9.7 Plug Flow Reactor (PFR) Property View .................................................. 29
9.7.1
9.7.2
9.7.3
9.7.4
9.7.5
9.7.6
9.7.7
PFR Design Tab ..................................................................................... 30
Reactions Tab ........................................................................................ 37
Ratings Tab ............................................................................................ 45
Work Sheet Tab...................................................................................... 46
Performance Tab.................................................................................... 47
Dynamics Tab ........................................................................................ 49
PFR Example Problem........................................................................... 49
9-1
9-2
9-2
Reactors
9.1
9-3
The Reactor Operation
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 may only support
one particular reaction type. For instance, a CONVERSION REACTOR
will only function properly with conversion reactions attached. If you
try to attach an equilibrium or a kinetic reaction to a CONVERSION
REACTOR, an error message will appear. The GIBBS REACTOR is
unique in that it can function with or without a reaction set.
You have great deal flexibility in defining and grouping reactions. You
may:
Refer to Chapter 4 - Reactions of
the Simulation Basis manual or
Section 7.4.1 - Reaction Package of
the User’s Guide for details on
installing reactions and Reaction
Sets.
• 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 will be 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.
The four reactors which share common property views include:
•
•
•
•
CSTR (Continuous-Stirred Tank Reactor)
GIBBS REACTOR
EQUILIBRIUM REACTOR
CONVERSION REACTOR
9-3
9-4
CSTR / General Reactor Design Tab
To remove local changes, move to
the appropriate cell and press the
DELETE key.
The last three reactors are referred to as General Reactors. In order to
avoid redundancy, these operations will be discussed co-currently. In
areas of the property view where there are differences, such as the
Reactions tab, the differences will be clearly noted.
The PLUG FLOW REACTOR, or PFR, has quite a different property
views from the other reactors. As a result it will be discussed on its own
in Section 9.7 - Plug Flow Reactor (PFR) Property View.
General Reactors Button
Conversion Reactors Button
A Reactor operation can be installed by pressing F12 and selecting the
operation from the UnitOps view or by selecting the appropriate button
from the Object Palette. In order to implement a GIBBS, CONVERSION
or EQUILIBRIUM reactor, you must first press the General Reactors
button to access the distinct button for each Reactor type in the Object
Palette.
Equilibrium Reactors Button
9.2
Gibbs Reactor Button
CSTR / General
Reactor Design Tab
The CSTR and GENERAL Reactors property view consists of five tabs
the first of which is the Design tab. It contains four pages:
CSTR (Continuous-Stirred Tank
Reactor) Button
9-4
Page
Description
Connections
Connects the feed, product, and energy streams to
the reactor.
Parameters
Set heat transfer and pressure drop parameters for
the reactor.
User Variables
Allows for the creation and implementation of User
Variables.
Notes
Allows you to add relevant comments which are
exclusively associated with this unit operation.
Reactors
9.2.1
9-5
Connections Page
Figure 9.1
The Connections page, is the same for both the CSTR and the three
General Reactors. The page consists of 5 objects:
At least one product stream is
required.
Object
Input Required
Name
Contains the name of the reactor. You may edit the Name
at any time by simply selecting the field (double click the
cursor inside the field) and inputting a new name.
Inlets
Allows for the connection of a single feed or multiple feed
streams to the reactor. You may either attach the feed
stream(s) by selecting previously created streams from
the drop down in the Edit Bar, or by selecting an empty
cell in the Inlets matrix and entering a new stream name
in the Edit Bar.
Vapour Outlet
Connects the Vapour product stream to the Reactor. As
with the Inlets field, you may select an existing stream
from the drop down or create a new product stream by
selecting the field and typing the new stream name in the
Edit Bar
Liquid Outlet
Connects the Liquid product stream to the Reactor. As
with the Feeds field, you may select an existing stream
from the drop down or create a new product stream by
selecting the field and typing the new stream name in the
Edit Bar
Energy
(Optional)
Allows for the connection or creation of an energy stream
if one is required for this operation.
9-5
9-6
CSTR / General Reactor Design Tab
9.2.2
Parameters Page
Figure 9.2
Note that Pfeed is assumed to be the
lowest pressure of all the feed
streams.
The Parameters page allows you to specify the Pressure Drop, Vessel
Volume, Duty and Solving Behaviour.
Object
Description
This field contains the pressure drop across the vessel.
The pressure drop is defined as:
∆P = P – P v = P – P l
The vessel pressure is used in the
reaction calculations.
where:
Delta P
(9.1)
P = Vessel pressure
Pv = Pressure of vapour product stream
Pl = Pressure of liquid product stream
Pfeed = Pressure of feed stream
∆P = Pressure drop in vessel (Delta P)
The default pressure drop across the vessel is zero.
9-6
Reactors
Object
9-7
Description
If you have attached an energy stream, you can specify
that 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.
Note that 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.
Duty
The Steady-State Reactor energy balance is defined
below
Duty = H vapour + H liquid – H feed
where:
(9.2)
Duty = the 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)
Heating /
Cooling
If you change from Heating to Cooling (or vice versa),
the magnitude of the energy stream does not change.
However, the sign will change in the energy balance. For
Heating, the duty is added. For Cooling, the duty is
subtracted.
User specified, this is the total volume of the vessel. 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 is necessary
when modelling reactors in Steady
State, as it determines the residence
time.
Volume
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
where:
(9.3)
PV(%Full) is the 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 for the specification of a single phase reaction.
Otherwise HYSYS will consider it a vapour-liquid reaction.
Only available for Gibbs reactors, this gives you a choice
regarding the type of reactor you require:
Type
• Separator - applies a two phase Gibbs minimization
to the reactants.
• Three Phase - applies a three phase Gibbs
minimization to the reactants.
9-7
9-8
CSTR / General Reactor Reactions Tab
To ignore the unit operation entirely during calculations, select the
Ignored check box. HYSYS will disregard the operation entirely until
you restore it to an active state.
9.3
9.3.1
Conversion Reactor
Refer to Section 4.4.2 - Conversion
Reaction of the Simulation Basis
guide for details on creating
Conversion Reaction Sets and
Conversion Reactions.
CSTR / General
Reactor Reactions Tab
Conversion Reactor
Reactions Tab
The CONVERSION REACTOR is a vessel in which Conversion reactions
are performed. You may only attach Reaction Sets that contain
Conversion Reactions. Each reaction in the set will proceed until the
specified conversion is attained or until a limiting reactant is depleted.
The Reactions tab, consists of two pages: Details and Results.
Details Page
Figure 9.3
9-8
Reactors
9-9
On this page you can attach the Reaction Set to the operation and
specify the conversion for each reaction in the set. The Reaction Set can
contain only conversion reactions. The page is split into 4 objects:
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
Opens the Reaction property view for the reaction
currently selected in the Reaction drop down. This allows
you to edit the reaction.
[Radio buttons]
These three radio buttons toggles between the
Stoichiometry group box, the Basis group box or the
Conversion group box (each described in the following
subsections).
Stoichiometry Radio Button
Figure 9.4
The Stoichiometry group allows you to examine the components
involved in the selected reaction, their molecular weights as well as
their stoichiometric coefficients. The Balance Error and the Reaction
Heat (Heat of Reaction) are also shown for the current reaction.
9-9
9-10 CSTR / General Reactor Reactions Tab
Basis Radio Button
Figure 9.5
In the Basis group, you can view the Base Component, the Conversion
and the Reaction Phase for each reaction in the Reaction Set. Here, you
may also change the local specified conversion.
Conversion Radio Button
Figure 9.6
Note that in the Fractional
Conversion Equation group box,
spaces showing red or blue colour
indicate that the variable may be
cloned.
9-10
In the Fractional Conversion Equation group allows implementation
of a conversion model based on the Conversion(%) equation listed. The
parameters for the attached conversion reaction(s) can be cloned as
local variables belonging to the Conversion Reactor. Therefore a user
can either use the parameters specified in the reaction(s) from the
attached reaction set by selecting the UseDefault cross box or specify
locally the values within the Fractional Conversion Equation group.
Reactors
9-11
View Reaction Button
Figure 9.7
Pressing this button opens the Conversion Reaction property view of
the reaction currently selected in the Reaction drop down box. Note
that any changes made to the Conversion Reaction property view will
be 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 Figure 9.7, the change will be 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 is
made up of the Reactor Results Summary group box which contains
two radio buttons: Reaction Extents and Reaction Balance. The type of
results displayed depends on which radio button is active.
9-11
9-12 CSTR / General Reactor Reactions Tab
Reaction Extents Radio Button
Figure 9.8
When selected, the Reaction Extents option 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 will occur first.
Specified %
Conversion
This is either the global value or a local value which
applies to the current operation only.
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.
When there are multiple reactions in a Reaction Set, HYSYS
automatically ranks the reactions. A reaction with a lower ranking
value will occur 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 will affect all Reaction Sets
to which the reaction is attached,
provided local changes have not
been made.
9-12
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%.
Reactors
9-13
Reaction Balance Radio Button
When 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 9.9
Values appear after all reactions have been completed. 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.
For more information on Kinetic,
Heterogeneous Catalytic and
Simple Rate reactions see Chapter 4
- Reactions of the Simulation Basis
guide.
CSTR Button
9.3.2
CSTR Reactions Tab
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.
On the Reactions tab, you can select a Reaction Set for the operation.
You may 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
9-13
9-14 CSTR / General Reactor Reactions Tab
where: X represents the actual % conversion
NAin represents the base component flowrate into the reactor
NAout represents the base component flowrate (same basis as
the inlet rate) out of the reactor
The Reactions tab consists of two pages: Details and Results.
Details Page
Figure 9.10
On this page you can attach the appropriate Reaction Set to the
operation and specify the conversion for each reaction in the set. As
mentioned earlier in this section, the selected Reaction Set can contain
only Kinetic, Heterogeneous Catalytic and Simple Rate reactions.
The page is split into 4 objects:
9-14
Object
Description
Reaction Set
Allows you to select the appropriate Reaction Set.
Reaction
From this drop down you can select the one of the
reactions from the selected Reaction Set.
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 box or
the Basis group box. (described in the following
subsection)
Reactors
9-15
Stoichiometry Radio Button
Figure 9.11
The Stoichiometry group allows you to examine the components
involved in the currently selected reaction, their molecular weights as
well as their stoichiometric coefficients.The Balance Error and the
Reaction Heat are also shown for the current reaction.
Basis Radio Button
Figure 9.12
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. To view any these properties for a specific
reaction simply select the reaction in the Reaction drop down and its
data will appear 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
check box. For instance, if you have made a change to the forward
reaction activation energy (E), the Use Default E check box will be
empty. Select this check box to return to the global E value.
9-15
9-16 CSTR / General Reactor Reactions Tab
Results Page
The Results page displays the results of a converged reactor. The page is
made up of the Reaction Results Summary group box which contains
two radio buttons: Reaction Extents and Reaction Balance.
Reaction Extents Radio Button
Figure 9.13
When selected, the Reaction Extents option will display the following
results for a converged reactor:
9-16
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.
Reactors
9-17
Reaction Balance Radio Button
Figure 9.14
When selected the Reaction Balance option provides an overall
component summary for the CSTR. All components which appear in
the Fluid Package are shown here.
Values appear after all reactions have been completed. 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.
9.3.3
Refer to Section 4.4.3 - Equilibrium
Reaction of Simulation Basis guide
for details on creating and
installing Equilibrium Reactions.
Equilibrium Reactor Reaction Tab
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 will be 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.
Equilibrium Reactor Button
Any changes made to the global
reaction will affect all reaction sets
to which the reaction is attached,
provided local changes have not
been made.
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.
9-17
9-18 CSTR / General Reactor Reactions Tab
Details Page
The Details page consists primarily of four radio buttons:
Stoichiometry, Basis, Ln[K] and Table. Selecting one of the radio
buttons makes a specific group box visible.
Stoichiometry Radio Button
Figure 9.15
Note: Changes made to the global
reaction will affect all Reaction Sets
which contain the reaction, and
thus all operations to which the
Reaction Set is attached.
Activating the Stoichiometry radio button makes the Stoichiometric
Info group box visible. This group allows you to view and make local
changes to the stoichiometric formula of the reaction currently selected
in the Reaction drop down list.
The Balance Error and the Reaction Heat are also shown for the current
reaction.
Basis Radio Button
Figure 9.16
Refer to Section 4.4.3 - Equilibrium
Reaction of Simulation Basis guide
for details on Equilibrium
Constant source.
9-18
The Basis radio button makes viewable the Basis group. The group
allows you to view or edit (locally) various information for each
reaction in the Reaction Set including: the Basis for the equilibrium
calculations, the Phase in which the reaction occurs, the temperature
Approach of the equilibrium composition and the temperature range
for the equilibrium constant are shown. The source for the calculation
of the equilibrium constant is also shown.
Reactors
9-19
Keq Radio Button
Selecting the Keq radio button displays the Ln(Keq) relationship which
may vary depending upon the Ln(K) Source value selected for the
reaction (see Basis radio button).
Figure 9.17
For a Ln(K) Source being the Ln(Keq) Equation, the parameters of the
equilibrium constant equation are displayed. These values are either
supplied when the reaction was created or are calculated by HYSYS. If a
fixed equilibrium constant was provided, it will be shown here.
Any of the parameters in the Ln(K) Equation group box can be
modified on this page. Changes made to the parameters will 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
selecting the appropriate Use Default check box.
Approach Radio Button
Figure 9.18
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 will only affect the selected reaction in the current
9-19
9-20 CSTR / General Reactor Reactions Tab
reactor. After a change has been made, you can have HYSYS return the
original calculated value by selecting the appropriate Use Default cross
box.
For more detailed information on
equilibrium reactions, see Chapter
4 - Reactions of Simulation Basis
guide.
You can edit a reaction by pressing the View Reaction button. The
property view for the highlighted reaction appears.
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 is
made up of the Results Summary group box which contains two radio
buttons: Reaction Extents and Reaction Balance.
Reaction Extents
Figure 9.19
When selected the Reaction Extents option will display the following
results for a converged reactor:
Result Field
Description
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
Actual %
Conversion
(9.5)
in
where:
X represents the actual % conversion.
NAin represents the base component flowrate into
the reactor.
NAout represents the base component flowrate (same
basis as the inlet rate) out of the reactor.
9-20
Reactors
Result Field
Description
Base
Component
The reactant to which the conversion is applied.
9-21
The equilibrium constant is calculated at the reactor
temperature by the following:
B
ln K = A + --- + C ln T + DT
T
Eqm Const.
where:
(9.6)
T represents the reactor temperature, in Kelvin
A, B, C, D are equation parameters
The four parameters for each
equilibrium equation are listed on
the Rxn Ln(K) page.
The four parameters in Equation (9.6) will be calculated
by HYSYS if they are not supplied during the installation
of the equilibrium reaction.
Rxn Extent
Lists the molar rate consumption of the base component.
Reaction Balance
Figure 9.20
When selected, the Reaction Balance option provides an overall
component summary for the EQUILIBRIUM REACTOR. All
components which appear in the Fluid Package are shown here.
Values appear after all reactions have been completed. 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.
9-21
9-22 CSTR / General Reactor Reactions Tab
9.3.4
Gibbs Reactor Reactions
Tab
Figure 9.21
Gibbs Reactor Button
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 will be at a minimum at equilibrium is used to calculate the
resultant mixture composition. As with the EQUILIBRIUM REACTOR,
neither pure components nor the reaction mixture are assumed to
behave ideally.
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.
Overall Page
On the Overall page, you must first select the Reactor Type. The objects
that will be visible will depend on which radio button you have selected
in the Reactor Type group box. You can then attach a Reaction Set if
necessary and specify the vessel parameters on the Rating tab.
9-22
Reactors
9-23
Reactor Type Group
In the Reactor Type group, choose a radio button to define the method
which HYSYS will use to solve the GIBBS REACTOR:
Radio Button
Gibbs
Reactions Only
Specify
Equilibrium
Reactions
NO Reactions
(=Separator)
Description
No reaction set is required as HYSYS solves the system
by minimizing the Gibbs free energy while attaining phase
and chemical equilibrium. Users may also customize the
maximum iteration number and equilibrium error tolerance
in the Solving Option group.
Will display 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.
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 box, the Gibbs Reaction Details
group. The group box consists of two radio buttons: Flow Specs and
Atom Matrix. The information that will be viewable on the page
depends on which of the two radio buttons is active.
9-23
9-24 CSTR / General Reactor Reactions Tab
Flow Specs Option
Figure 9.22
Selecting the Flow Specs radio button opens a view similar to the one
seen in Figure 9.22. 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 check box 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 will
equal 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 will be 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 will attempt to meet that flowrate in calculating the
outlet stream’s composition. If the constraint cannot be met, a message
will be displayed alerting you to that effect.
9-24
Reactors
9-25
Atom Matrix Option
Figure 9.23
When the Atom Matrix radio button is active, you can specify the
atomic composition of any species for which the formula is unknown
or unrecognized.
The atomic matrix input form displays all components in the case with
their atomic composition as understood by HYSYS. You have the
opportunity here to enter the composition of an unrecognized
compound or to correct the atomic composition of any compound.
9.4
You are required to supply
rating information only when
working with a Dynamics
simulation.
CSTR / General
Reactor Rating Tab
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 these pages, please see the Dynamics
Modelling guide.
Sizing Page
On the Sizing page, you can define the geometry of the unit operation.
Also, it allows for indication as to whether or not the unit operation has
a Boot associated with it. If it does, then you can specify the Boot
dimensions.
9-25
9-26
CSTR / General Reactor Rating Tab
Figure 9.24
The view consists of three main objects:
9-26
Object
Description
Geometry
Allows for the specification of the vessel geometry.
This Reactor has a
Boot
When activated, makes the Boot Dimensions
group.
Boot Dimensions
Allows you to specify the dimensions of the vessel’s
boot.
Reactors
9-27
Geometry Group
This group contains 5 objects which aid in the specification of the
vessel volume:
Object
Description
Toggles the shape of the vessel between Sphere and
Cylinder. This will affect the number of specifications
required as well as the method of volume calculation.
If Cylinder is selected and a diameter and height have
been specified, the vessel volume will be calculated as:
2
Diameter
V reactor =  ---------------------------π × Height + V boot


4
Cylinder /
Sphere
(9.8)
If Sphere is selected and either the height or diameter
have been specified the vessel volume is calculated as:
3
( Height or Diameter ) π
V reactor = ---------------------------------------------------------- + V boot
6
where:
(9.9)
Vreactor = the Volume of the reactor
Vboot = the volume of the boot
Height, Diameter = the values taken from the
respective fields
You may choose the orientation of the vessel as either:
Orientation
• Horizontal - the ends of the vessels are horizontally
orientated.
• Vertical - the ends of the vessel are vertically
orientated.
Contains the total volume of the vessel.
There are three possibilities for values in this field:
Volume
• If the height and/or diameter have been entered, this
field will display 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 will
back calculate 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 will be
calculated assuming a ratio of 3/2 (i.e. Height:
Diameter).
Diameter
Holds the diameter of the vessel. If the vessel is a Sphere,
then it will be 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 will be the same value as the diameter.
The Geometry group contains three fields: Volume, Diameter and
Height (or Length depending on orientation). If you specify the Volume
9-27
9-28
CSTR / General Reactor Rating Tab
then you are not required to specify the other two parameters as HYSYS
will calculate a Height (or Length) and Diameter assuming a ratio of
Height to Diameter of 3/2. You may however specify one of the two
parameters (either Height or Diameter) and the third will be
automatically calculated using either Equation (9.8) or Equation (9.9).
Boot Dimensions
If the reactor you are rating has a Boot, you may include it’s volume in
the total vessel volume by activating the This Reactor has a Boot check
box. This will make the Boot Dimensions group box visible. The Boot
Dimensions group consists of two fields:
Field
Description
Boot Diameter
This is the diameter of the boot. The default value for
this field is usually 1/3 the reactor diameter.
Boot Height
This value is the height of the boot which is defaulted
at half the reactor diameter.
The volume of the boot is calculated using a simple cylindrical volume
calculation:
2
Boot Diameter
V Boot = π  ----------------------------------- × Boot Height


2
(9.10)
and the default reactor parameters are:
2
Diameter
Diameter
V Boot = π  ------------------------- × ------------------------

6
2
3
(9.11)
π ( Diameter )
= -----------------------------------72
This means that this too can be estimated by just entering the total
Reactor volume.
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, please
see the Dynamics Modelling guide.
9-28
Reactors
9.5
9-29
CSTR / General
Reactor Work Sheet
Tab
The Work Sheet tab contains a summary of the information contained
in the Stream property view of all the streams attached to the unit
operation. The Conditions, Properties, and Composition pages
contain selected information from the corresponding pages of the
Worksheet tab of the stream property view. The PF Specs page contains
a summary of the Stream property view Dynamics tab.
9.6
CSTR / General
Reactor 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. For more information on running the CSTR and General
Reactors in dynamic mode, see the HYSYS Dynamic Modelling guide.
9.7
Plug Flow Reactor
(PFR) Property View
Figure 9.25
The PFR (Plug Flow Reactor, or Tubular Reactor) generally consists of a
bank of cylindrical pipes or tubes. The flow field is modelled as plug
flow, implying that the stream is radially isotropic (without mass or
energy gradients). This also implies that axial mixing is negligible.
As the reactants flow the length of the reactor, they are continually
consumed, hence, there will be an axial variation in concentration.
Since reaction rate is a function of concentration, the reaction rate will
also vary axially (except for zero-order reactions).
9-29
9-30 Plug Flow Reactor (PFR) Property View
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
(9.12)
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 will equal zero, and the equation reduces to:
F j = F j0 + r j V
(9.13)
To install the PFR operation, press F12 and choose Plug Flow Reactor
from the Unit Ops view or select the Plug Flow Reactor button in the
Object Palette.
PFR Button
9.7.1
PFR Design Tab
The Design tab of the PFR consists of five pages:
9-30
Page
Input Required
Connections
Attaches the feed and product streams to the
reactor.
Parameters
Allows for the specification of pressure drops and
energy streams.
Heat Transfer
Allows you to specify the heat transfer parameters.
User Variables
Creates user variables for use in this operation as
well as several others.
Notes
Allows you to add notes to this reactor.
Reactors
9-31
Connections Page
Figure 9.26
On the Connections page, you may provide the Operation name, as
well as the names of the feed(s), product and energy streams. Note that
if you do not provide an energy stream, the operation is considered to
be adiabatic.
Object
Input Required
Inlets
Where the reactor feed streams are selected.
Outlet
Contains the name of the reactor product stream.
Energy
(Optional)
As mentioned in the field name, you are not required to
provide an energy stream however under those
circumstances HYSYS will assume that the operation is
adiabatic.
9-31
9-32 Plug Flow Reactor (PFR) Property View
Parameters Page
Figure 9.27
To ignore the PFR during
calculations, select the Ignore check
box. HYSYS will completely
disregard the operation until you
restore the operation to an active
state by clearing the check box.
9-32
The Parameters page is divided into three sections, from which you
instruct HYSYS on the calculations for pressure drop and heat transfer
and also decide whether the operation will be included in the
calculations.
Reactors
9-33
Delta P
In this group box, you select one of the available radio buttons for the
determination of the total pressure drop across the reactor:
Radio Button
Description
User Specified
You must supply a pressure drop in the Pressure Drop
(Delta P) cell.
HYSYS uses the Ergun equation to calculate the
pressure drop across the PFR. The equation parameters
include values which you supply 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
When the Ergun Equation radio
button is selected, the Pressure
Drop input cell colour switches
from blue to black, indicating a
value calculated by HYSYS.
where:
Ergun Equation
(9.14)
∆P = pressure drop across the reactor
gc = Newton’s-law proportionality factor for the
gravitational force unit
L = the reactor length
ϕs= particle sphericity
Dp = particle (catalyst) diameter
ρ = fluid density
If you select the Ergun Equation
radio button for a PFR with no
catalyst (solid), HYSYS sets ∆P = 0.
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:
Radio Button
Description
Formula
HYSYS will calculate the energy stream duty after you
supply further heat transfer information on the Heat
Transfer page. The two cells 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 supply a duty value for the energy
stream.
You may 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.
9-33
9-34 Plug Flow Reactor (PFR) Property View
Your selection in the SS Duty
Calculation Option group is also
transferred to the Heat Transfer
group on the Parameters page.
Heat Transfer Page
The format of the Heat Transfer page depends on your selection in the
SS Duty Calculation Option group box, either Formula or Direct Q
Value.
Direct Q Value Option
Figure 9.28
When the Direct Q Value radio button is selected, the Heat Transfer
group box is made viewable. It consists of three objects:
Object
Description
Energy Stream
The name of the duty stream.
Duty
The duty value to be supplied in the energy stream.
Heating \ Cooling
Selecting one of these 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.
Formula Option
Figure 9.29
For the Formula option, you must
have an energy stream attached to
the PFR. You cannot use this option
while operating adiabatically.
9-34
With the Formula option, you instruct HYSYS to rigorously calculate
the duty of each PFR subvolume using local heat transfer coefficients
Reactors
9-35
for the inside and the outside of each PFR tube using Equation (9.15)
and Equation (9.16).
Qj = UjA(Tbulkj - Toutj)
Resistance of the tube wall to heat
transfer is neglected.
(9.15)
where: 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
The final term in Equation (9.16),
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.
Toutj = temperature outside of the PFR tube (utility fluid)
1
1 xw
1
---- = --------- + ------ + -----h out h w k m
U
(9.16)
where: 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
km
calculations)
In each subvolume, heat is being transferred radially between the PFR
fluid and the utility fluid. The two group boxes available on the Heat
Transfer page allow you to supply parameters which will be used in the
determination of the duty.
Heat Medium Side Heat Transfer Infos Group
Figure 9.30
If you specify a Heat Flow on the
Energy Stream property view and
select the Formula radio button on
the Heat Transfer page,
inconsistencies will appear in the
solution. You cannot specify a duty
and have HYSYS calculate the same
duty.
9-35
9-36 Plug Flow Reactor (PFR) Property View
In this group, you can modify the parameters which are used to
calculate the duty (Qj) for the outside of each PFR subvolume:
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) will
affect 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
Parameter
Duty calculated for each PFR subvolume.
The equation used to determine the temperature of the utility fluid
entering each subvolume j is:
Qj = mρCp(Tj - Tj+1)
(9.17)
Tube Side Heat Transfer Info Group
In this group box, you can select the method for determining the inside
local heat transfer coefficient (hw) by choosing a radio button and
supplying the required parameters:
Radio Button
Description
Supply a value for the local heat transfer coefficient
in the User Specified input cell.
User
9-36
View
Reactors
Radio Button
Description
9-37
View
Supply coefficients for the empirical equation which
relates the heat transfer coefficient to the flowrate of
the PFR fluid via the following equation:
Empirical
h w = A × Flow
B
(9.18)
You can also choose the basis for the equation as
Molar, Mass or Volume.
Supply coefficients for the calculation of the Nusselt
number, which is then used to calculate the local
heat transfer coefficient:
Standard
N u = A × Re B × Pr C
(9.19)
Nu kg
h w = -----------Dp
(9.20)
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 option, see Chapter 5 - User Variables of the
Customization Guide.
Notes Page
The Notes page provides a text editor where you can record any
comments or information regarding the PFR or pertaining to the
simulation in general.
9.7.2
Reactions Tab
You may add a Reaction Set to the PFR on the Reactions tab. Note that
only Kinetic, Heterogeneous Catalytic and Simple Rate reactions are
allowed in the PFR. The tab consists of three pages: Overall, Details and
Results.
9-37
9-38 Plug Flow Reactor (PFR) Property View
Overall Page
Figure 9.31
On this page, the Reaction Set and calculation information are
specified. The page is split into three groups: Reaction Info, Integration
Information, and Catalyst Data.
Reaction Info Group
Figure 9.32
In this group box you are required to supply two pieces of information:
the Reaction Set to be used and the segment initialization method. The
Reaction Set is selected from the aptly named Reaction Set drop down
list. Note that the Reaction Set you wish 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 will obtain a solution in each segment
of the reactor. The segment reactions may be initialized using the
following methods:
9-38
Reactors
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
Reinitializes the current segment reaction
calculations.
9-39
Integration Information
Figure 9.33
This group consists of three fields:
The length of each segment stays
constant during the calculations.
However, if a solution cannot be
obtained for an individual
segment, it will be divided into
smaller sections until a solution is
reached. This does not affect the
other segments.
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 will
split too.
Minimum Step
Length
The product of the Reactor Length and the Minimum
Step Fraction.
During each segment calculation, HYSYS will attempt to calculate a
solution over the complete segment length. If a solution cannot be
obtained, the current segment will be halved, and HYSYS will attempt
to determine a solution over the first half of the segment. The segment
will continue to be halved until a solution is obtained, at which point
the remaining portion of the segment will be calculated. If the segment
is divided to the point where its length is less than the Minimum Step
Length, calculations will stop.
9-39
9-40 Plug Flow Reactor (PFR) Property View
Catalyst Data
Figure 9.34
If you specified a void fraction less than one on the Ratings tab, the
Catalyst Data group will be displayed. The following information must
be provided:
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 will have 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.
Equal to the Solid Density multiplied by one minus
the void fraction.
ρ b = ρ s ( 1 – ε ma )
Bulk Density
where:
(9.21)
ρb= bulk density
ρs = solid density
εma = macroparticle voidage (void fraction)
Solid Heat Capacity
9-40
This is used to determine the solid enthalpy holdup
in Dynamics.The bulk density is also required in this
calculation.
Reactors
9-41
Details Page
Figure 9.35
On this page you can manipulate the Reactions attached to the selected
Reactions Set. The page is split into 3 objects:
Object
Description
Reaction
From this drop down you must select the appropriate
reaction from the Reaction Set selected on the Overall
page.
View Reaction
Opens the Reaction property view for the selected
Reaction. This allows you to edit the reaction. Editing the
Reaction dialogue will effect all other implementations of
the particular Reaction.
Specifics
These radio buttons allow you to toggle between the
Stoichiometry group box or the Basis group box.
(described in the following subsection)
9-41
9-42 Plug Flow Reactor (PFR) Property View
Stoichiometry Group
Figure 9.36
The Stoichiometry group allows you to examine the components
involved in currently selected reaction, their molecular weights as well
as their stoichiometric coefficients. The Balance Error and the
Reaction Heat are also shown for the current reaction. Note that any
changes made to the Stoich. Coeff. (stoichiometric coefficients) will be
local changes, meaning other implementations of this reaction will not
be affected. To affect change in the reaction over the entire simulation
you must select the View Reaction button and make the changes to the
Reaction’s property view.
Basis Group
Figure 9.37
In the Basis group, you can view the Base Component, the rate
expression parameters. You can make changes to these parameters,
however these changes will only affect the current implementation of
the reaction and will not be affected by other reactors using this
Reaction Set or Reaction.
View Reaction Button
Pressing this button opens the Reaction property view of the reaction
currently selected in the Reaction drop down box. Note that any
9-42
Reactors
9-43
changes made to the Conversion Reaction property view will be 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 is
made up of the Reaction Balance group box which contains two radio
buttons: Reaction Extents and Reaction Balance. The type of results
displayed depend on which radio button is active.
Reaction Extents
Figure 9.38
When selected, 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 consumption of the base
component.
9-43
9-44 Plug Flow Reactor (PFR) Property View
Reaction Balance
Figure 9.39
Any changes made to the global
reaction will affect all reaction sets
to which the reaction is attached,
provided local changes have not
been made.
When selected the Reaction Balance option provides an overall
component summary for the PFR. All components which appear in the
fluid package are shown here.
Values appear after all reactions have been completed. 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.
9-44
Reactors
9.7.3
9-45
Ratings Tab
The Ratings tab contains one page: Sizing.
Sizing Page
Figure 9.40
On the Sizing page, you can specify the Tube Dimensions and the Tube
Packing information in their respective groups.
Tube Dimensions
For the tube dimensions, you will need to specify any three of the
following four parameters:
Tube Dimension
Description
Total Volume
Total volume of the PFR.
Length
The total length of the individual tube.
Diameter
The diameter of an individual tube.
Number of tubes.
The total number of tubes required. This will always
be calculated to the nearest integer value.
When three of these dimensions are specified, the fourth will
automatically be calculated. Note that the Total Volume refers to the
combined volumes of all tubes.
9-45
9-46 Plug Flow Reactor (PFR) Property View
By default, the number of tubes is set to 1. Although the number of
tubes is generally specified, you may set this parameter as a calculated
value by selecting the Number of Tubes field and pressing the DELETE
key. The number of tubes will always be 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 will have to re-specify the tube dimensions.
The Tube Wall Thickness may also be specified.
The Void Volume is used to
calculate the spatial velocity, which
impacts the rate of reaction.
Tube Packing
This group consists of two fields: Void Fraction and 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 will be 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 will also be 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.
9.7.4
Work Sheet Tab
The Worksheet tab contains a summary of the information contained
in the Stream property view for all the streams attached in the unit
operation. The Conditions, Properties, and Compositions pages
contain selected information from the corresponding pages of the
Worksheet tab for the Stream property view. The PF Specs page
contains a summary of the Stream property view Dynamics tab.
9-46
Reactors
9.7.5
9-47
Performance Tab
Figure 9.41
To examine various axial profiles in the PFR, go to the Performance tab.
The tab consists of five pages each containing a general type of profile:
Conditions, Flows, Reaction Rates (Rxn Rates), Transport and
Compositions.
Each page consists of a table containing the relevant performance data
and a Plot button which converts the data to graphical form. Note that
the Reactor Length is always plotted on the x-axis.
The data points are taken in the middle of each reaction segment, and
correspond to the number of reaction segments you specified.
Conditions Page
Physical Parameters
Temperature
Pressure
Enthalpy
Entropy
Duty
Vapour Fraction
On this page you may 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.
If you select the Plot button, a plot similar to the one shown in Figure
9.42 will be displayed. It shows the selected Physical parameter as a
function of the Reactor Length.
9-47
9-48 Plug Flow Reactor (PFR) Property View
Figure 9.42
Flows Page
There are four overall flow types which may be viewed in a table or
plotted as a function of the Reactor Length:
• Material Flow: Molar, Mass or Volume
• Energy: Heat
If you select the Plot button, the table will be displayed in graphical
form.
Reaction Rates Page
Although only one Reaction Set can
be attached to the PFR, it can
contain multiple Reactions.
You may view either Reaction Rate or Component Production Rate data
as a function of the Reactor Length on the Rxn Rates page. You may
toggle between the two data sets by selecting the appropriate radio
button.
You may view the data in graphical form by selecting the Plot button.
Transport Properties
Transport Page
Viscosity
Molar Weight
Mass Density
Heat Capacity
Surface Tension
Z Factor
9-48
The overall Transport properties are displayed in tabular form as a
function of the Reactor Length on the Transport page.
You may view the data in graphical form by selecting the Plot button.
Select the appropriate radio button to display the chosen plot.
Reactors
9-49
Compositions Page
You may 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 may display the data in plot form by choosing the Plot button.
9.7.6
Dynamics Tab
If you are working exclusively in Steady State mode, you are not
required to change any information on the pages accessible through
this tab. For more information on running the PFR in Dynamic mode,
see the Dynamic Modelling guide for further details.
9.7.7
PFR Example Problem
In this example, consider the adiabatic vapour-phase cracking of
acetone to ketene and methane in a PFR:
CH 3 COCH 3 → CH 2 CO + CH 4
For this reaction, Jeffreys gives the following rate equation:
– 34222
k = 8.2 × 10 14 exp  ------------------
 T 
where: k is the specific reaction rate in reciprocal seconds
See Chapter 4 - Reactions for more
details on the Reaction Manager.
T is in Kelvin.
Fluid Package and Reaction Setup
1.
Create a Fluid Package using the PRSV property method.
2.
From the Reaction Manager (Reactions tab of the Simulation Basis
Manager view), press the Add Comps button.
3.
Select the Library radio button in the Add Comps group.
9-49
9-50 Plug Flow Reactor (PFR) Property View
The Reverse Orders are not required
for this reaction, but are
automatically provided when you
enter the stoichiometric coefficient.
Since reverse reaction information
is not supplied, the Reverse Orders
are ignored.
4.
Choose Acetone, Methane and Ketene as the components for the
example.
5.
Close the Reaction Component Selection view.
6.
After returning to the Reaction Manager, press the Add Reaction
button.
7.
Highlight Kinetic in the Reactions view and press the Add Reaction
button. The Kinetic Reaction property view will appear.
8.
Complete the Stoichiometry, Basis and Parameters tabs as shown
below:
Figure 9.43
The value of A was taken
directly from the given rate
equation, but a calculation was
needed to obtain E. It can be
seen that E/R = 34222 (units
K). Therefore, E = 34222R and
R must be chosen such that
temperature units are obtained
for the constant value. Use
R = 8.31 kJ/kmol K, obtaining
E = 2.85 x 105 kJ/kmol.
The general Kinetic expression is:
k = Ae
9-50
E
– ------RT
Since there is only one reaction being used, we can use the Global Rxn
Set. The reaction is automatically attached in this set.
Now you must attach the reaction components to the Fluid Package
and make the reaction set available in the Main Flowsheet. This can be
done from the Reaction Manager view:
1.
Highlight the Global Rxn Set in the Reaction Sets group.
2.
Press the Add to FP button.
Reactors
3.
Highlight the Fluid Package, created previously, in the Add ’Global
Rxn Set’ view.
4.
Press the Add Set to Fluid Package button.
5.
Press the Enter Simulation Environment button.
9-51
Feed Stream and Connections
Install the Acetone feed stream and Plug Flow reactor as follows:
MATERIAL STREAM [Acetone]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
761.8500 °C
Pressure
162.0000 kPa
Molar Flow
137.9000 kgmole/hr
Acetone Mole Frac
1.0000
Ketene Mole Frac
0.0000
Methane Mole Frac
0.0000
Figure 9.44
On the Parameters page of the Design tab, select the User Specified
radio button and specify the Pressure Drop to be 0 kPa.
On the Heat Transfer page of the Design tab, select the Direct Q Value
radio button. In the Heat Transfer group, specify the Duty to be 0 kJ/hr,
as this is an Adiabatic operation.
9-51
9-52 Plug Flow Reactor (PFR) Property View
Rating Tab
Complete the Tube Dimensions and Tube Packing as shown in Figure
9.45. Only specify the Tube Volume, Length, Number of Tubes, Wall
Thickness and Void Fraction (Total Volume will be calculated). The
Diameter of the tubes will be calculated.
Figure 9.45
Consider a reactor consisting of a bank of one thousand 1-in. schedule
40 tubes, 2.28 m in length. The internal diameter of 1-in. schedule pipe
is 1.049" (0.0266 m) and the wall thickness is 0.133" (0.0034 m). Use a
void fraction of 1.
Reactions Tab
On the Overall page of the Reactions tab, attach the Global Rxn Set to
the PFR. It is not necessary to change the Integration Information from
the default values. The Reactor should immediately begin solving.
Because the void fraction is specified as 1, you are not required to input
any catalyst information. In essence, you have indicated that no
catalyst is present.
9-52
Reactors
9-53
Steady State Solution and Profiles
HYSYS will now converge to a Steady State Solution. Watch the Status
Line at the bottom of the property view, and observe the temperature.
The solution will converge when the temperature reaches about 664oC.
The product stream (PFR Product) specs are shown below.
Name
Vapour Frac
1.0000
Temperature [C]
649.0101
Pressure [kPa]
162.0000
Molar Flow [kgmole/hr]
Mass Flow [kg/hr]
Liq Vol Flow [m3/day]
Heat Flow [kJ/hr]
Object inspect the plot area and
select Graph Control to access the
graph editing options. Refer to
Section 6.4 - Graph Control for
more information.
PFR Product
167.9292
8009.2488
11.3991
-1.7157e+07
Comp Mole Frac [Methane]
0.6424
Comp Mole Frac [Acetone]
0.1788
Comp Mole Frac [Ketene]
0.1788
You may view various reactor profiles by going to the Performance tab
and pressing the Plot button. The axial temperature profile will initially
be displayed. You can select other profiles on the Conditions page by
choosing a different radio button in the Type group.
Figure 9.46
Select any of the five pages to view other PFR data, either in graphical
or tabular form.
9-53
9-54 Plug Flow Reactor (PFR) Property View
9-54
Logical Operations
10-1
10 Logical Operations
10.1 Adjust .......................................................................................................... 3
10.1.1
10.1.2
10.1.3
10.1.4
10.1.5
10.1.6
Connections Tab .................................................................................... 4
Parameters Tab...................................................................................... 6
Monitor Tab ............................................................................................ 9
Starting the Adjust................................................................................ 10
Individual ADJUST ................................................................................11
Multiple ADJUST.................................................................................. 14
10.2 Balance...................................................................................................... 15
10.2.1
10.2.2
10.2.3
10.2.4
10.2.5
10.2.6
10.2.7
Connections Tab .................................................................................. 16
Parameters Tab.................................................................................... 17
Mole and Heat Balance........................................................................ 17
Mole Balance ....................................................................................... 21
Mass Balance ...................................................................................... 23
Heat Balance ....................................................................................... 25
General Balance .................................................................................. 27
10.3 Parametric Unit Operation....................................................................... 32
10.3.1 Design Tab ........................................................................................... 32
10.3.2 Parameters Tab.................................................................................... 37
10.3.3 Worksheet Tab ..................................................................................... 39
10.4 Recycle...................................................................................................... 40
10.4.1
10.4.2
10.4.3
10.4.4
10.4.5
10.4.6
10.4.7
Connections Tab .................................................................................. 41
Parameters Tab.................................................................................... 42
Worksheet Tab ..................................................................................... 47
Monitor Tab .......................................................................................... 47
Calculations ......................................................................................... 48
Reducing Convergence Time............................................................... 49
Single Recycle Example ...................................................................... 50
10-1
10-2
10.4.8 Multiple Recycle Example .................................................................... 54
10.4.9 Multiple Recycle Example Revisited .................................................... 59
10.5 Set.............................................................................................................. 62
10.5.1 Connections Tab .................................................................................. 63
10.5.2 Parameters Tab.................................................................................... 64
10.5.3 Set Example......................................................................................... 64
10.6 Spreadsheet.............................................................................................. 67
10.6.1
10.6.2
10.6.3
10.6.4
10-2
Spreadsheet Functions ........................................................................ 68
Spreadsheet Interface.......................................................................... 72
Spreadsheet Tabs ................................................................................ 76
Spreadsheet Example.......................................................................... 82
Logical Operations
10.1
10-3
Adjust
The ADJUST operation will vary 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.
The Independent variable
cannot be a calculated value;
it must be specified.
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 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.
To install the ADJUST operation, choose Add Operation from the
Flowsheet Menu, and select Adjust. Alternatively, select the Adjust
button in the Object Palette.
Adjust Button
10-3
10-4
Adjust
10.1.1
Connections Tab
The first tab of the the ADJUST property view, as well as several other
logicals, is the Connections tab. The tab is mainly comprised of three
groups: Adjusted Variable, Target Variable, and the Target Value.
Figure 10.1
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 may be a
Unit Operation, Stream, or a Utility.
Selecting Variables Using the Variable Navigator
You select the Object and its Variable simultaneously by using the
Variable Navigator, accessed by choosing the Select Var button.
Clicking the button should bring up a view similar to Figure 10.2.
10-4
Logical Operations
10-5
Figure 10.2
The Variable Navigator view consists of 4 list boxes which aid in the
variable selection process by acting as a filter. The list boxes work
sequentially, meaning a list box can only be manipulated if a selection
has been made in the parent list box. The table below lists the 4 list
boxes in hierarchical order:
List Box
Descriptions
Flowsheet
This box will display the flowsheets and
subflowsheets contained in the case. Note that
columns are also considered as subflowsheet and
therefore the column name must be selected in this
box in order to select any internal variables.
Object
Once a flowsheet is selected, the Object list box
should display all the objects contained by the
flowsheet. If the list contains too many objects, it can
be filtered choosing one of the object type radio
buttons in the Object Filter group box.
Variable
Once an object is selected (highlighted), all the
variables contained by the object will become visible.
Variable Specifics
The use of this list box is occaisonally required to
specify some variable details such as unit operation
specifications.
Once the appropriate adjust/target variable is chosen, click OK and the
chosen object and variable should appear in the appropriate fields of
the tab.
10-5
10-6
Adjust
Target Value
Once the Target Object and Variable are defined, there are two choices
for how the Target is to be satisfied:
• If the Target Variable is to meet a certain numerical value,
choose the User Supplied radio button (as shown in Figure
10.1), and enter the appropriate value in the Specified Target
Value cell.
• If the Target Variable is to meet the value (or the value plus an
offset) of the same variable in another stream or operation,
choose the Another Object radio button (as shown below),
and select the stream or operation of interest as the Matching
Value Object. If applicable, enter an offset in the available field.
Figure 10.3
10.1.2
Parameters Tab
Figure 10.4
Once you have chosen the dependent and independent variables, the
10-6
Logical Operations
10-7
convergence criteria must be defined. This is usually done in the
Parameters tab.
Solving Parameter
Description
Simultaneous
Solves multiple ADJUST loops simultaneously.
There is only one simultaneous solving method
available therefore when this option is activated the
Method cell 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.
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 will be solved last
among unknown operations.
You may 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 a multiple-variable Broyden
search algorithm. A single adjust loop can be solved in the
Simultaneous mode, however, this method is usually reserved for
multiple inter-linked loops.
When the Simultaneous check box is activated the Method field is no
longer visible.
Figure 10.5
10-7
10-8
Adjust
Tolerance
For the ADJUST to converge, the error in the dependent variable must
be less than the Tolerance.
Error = Dependent Variable Value – Target Value
(10.1)
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. Note that the tolerance and error
values are absolute (with the same units as the dependent variable)
rather than relative or percentage-type.
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 will be used until the solution has been bracketed, at which
time a different convergence algorithm is applied. The value which is
supplied 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 will initially
increment the independent variable, while a negative value will initially
decrement the independent variable. If the ADJUST steps away from
the solution, the direction of the steps will automatically be reversed.
Before installing the ADJUST module, it is often a good practice
to initialize the independent variable, and perform one adjust
"manually". Solve your Flowsheet once, and note 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.
The Independent variable
must be initialized (have a
starting value) in order for the
ADJUST to work.
10-8
Maximum/Minimum
These two optional criteria are the allowable upper and lower bounds
for the independent variable. If either bound is encountered, the
ADJUST will stop its search at that point.
Logical Operations
10-9
Maximum Iterations
You can also use the Solver
Trace Window to view the
Iteration History (See Section
5.4 - Object Status Window/
Trace Window of the User’s
Guide for more information).
The default maximum number of iterations is 10. Should the ADJUST
reach this many iterations before converging, the calculations will stop,
and you will be asked if you want to continue with more iterations. You
may enter any value for the number of maximum iterations.
10.1.3
Monitor Tab
Tables Page
For each Iteration of the ADJUST, the Number, Adjusted Value and
Target Value are displayed. If necessary, use the scroll bar to view
iterations which are not currently visible.
Figure 10.6
Independent (Adjusted)
Variable
Iteration
number
Dependent (Target)
Variable
10-9
10-10
Adjust
Plots Page
The Plots page displays the Target and Adjusted Variables like on the
Tables page, except the information is presented in graph form.
Refer to Section 6.4 - Graph
Control for information on
customizing plots.
Figure 10.7
10.1.4
With the exception of the
Minimum and Maximum
values of the independent
(adjusted) variable, all
Parameters are required before
the ADJUST will begin
calculations.
Starting the Adjust
There are two ways to start the ADJUST:
1.
If you have provided values for all the fields of the Parameters tab,
the ADJUST will automatically begin its calculations.
2.
If you have omitted one or both value in the Minimum/Maximum
fields (of the Parameters tab) for the independent variable (which
are optional Parameters) and you would like the ADJUST to start
calculating, simply press the Start button.
The Start button will then change to a red box, indicating the progress
of the calculations. The box initially indicates that calculations are "Not
Solved"; when the error is less than the tolerance, the status box will
display a green "OK" message. If the ADJUST reaches the maximum
number of iterations without converging, a red "Reached iteration
Limit without converging" message is displayed.
If you press Start when all of the required Parameters are not defined,
the yellow status box will display the "Incomplete" message, and
calculations will not begin.
10-10
Logical Operations
10-11
Once calculations are underway, you may view the progress of the
convergence process by moving to 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 will automatically trigger the ADJUST
calculation.
To stop or disable the ADJUST activate the Ignored check box.
10.1.5
Individual ADJUST
The Individual ADJUST algorithm, either Secant or Broyden, uses a
step-wise trial-and-error method and displays values for the
dependent and independent variables on each trial. The step size
supplied on the Parameters tab is used to increment or decrement the
independent variable for its initial step. The algorithm will continue to
use steps of this size until the solution is bracketed. At this point, the
algorithm uses either the Secant search (and its own step sizes) or
Broyden search, depending on your choice, to quickly converge to the
desired value. If a solution has not been reached in the maximum
number of iterations, the routine will pause and ask 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.
Example
Note that the feed stream has a
specified temperature of 60 °F.
The independent variable
must be a specified value for
the ADJUST to manipulate it.
The following will illustrate a simple application of the ADJUST using
the Secant algorithm. Stream Feed is fed to a separator (V-100) to
produce streams SepLiq and SepVap. The ADJUST is used to vary the
temperature of stream Feed until the flow of SepLiq is 100 lbmoles/hr.
To begin, open a new case with Peng Robinson as the Property Package
and the following components: Methane, Ethane, Propane, i-Butane,
n-Butane, i-Pentane, n-Pentane, n-Hexane, n-Heptane and n-Octane.
Create the following stream Feed.
10-11
10-12
Adjust
Streams
MATERIAL STREAM (Feed)
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
60.0000 °F
Pressure
600.0000 psi
Molar Flow
144.0000 lbmole/hr
Methane Mole Frac
0.4861
Ethane Mole Frac
0.1389
Propane Mole Frac
0.0694
i-Butane Mole Frac
0.0625
n-Butane Mole Frac
0.0556
i-Pentane Mole Frac
0.0486
n-Pentane Mole Frac
0.0417
n-Hexane Mole Frac
0.0486
n-Heptane Mole Frac
0.0278
n-Octane Mole Frac
0.0208
Install a separator V-100 so that the Connections page of the the Design
tab match Figure 10.8. Ignore the rest of the tabs as they will not be
needed for this example.
Figure 10.8
10-12
Logical Operations
10-13
Now install the ADJUST by selecting Add Operation from the Flowsheet
menu, followed by choosing the ADJUST option. The Specifications for
the Connections and Parameters are given below:
ADJUST [ADJ-1]
Tab [Page]
Design
[Connections]
Design [Parameters]
Use the Variable Navigator to
choose the Adjusted and
Target Variables. For the
Adjust Variable, Select the
Object Feed, and the Variable
Temperature.
Input Area
Entry
Adjusted Variable
Feed Temperature
Target Variable
SepLiq Molar Flow
Spec. Target Value
100 lbmole/h
Method
Secant
Tolerance
1 lbmole/h
Step Size
20 F
Maximum Iterations
10
Note that Maximum or Minimum values for the independent variable
are not set. When you press Start, HYSYS immediately begins the
convergence procedure. The Monitor tab will display the values for the
independent and dependent variables. For this example the iterations
history is shown in Figure 10.9.
Figure 10.9
10-13
10-14
Adjust
The ADJUST converges to the required flow in seven iterations. The
new stream conditions are shown in the following table.
STREAM
Name
Feed
Vapour Frac
0.3064
Temperature [F]
-16.68
Pressure [psia]
600.00
Molar Flow [lbmole/hr]
144.
Mass Flow [lb/hr]
5438
Liq Vol Flow [barrel/
day]
788.6
Heat Flow [Btu/hr]
-7.321e+06
Note that the temperature of Feed shows the converged value of 16.68°F in bold typeface (i.e. as a specified value). Although the value
which had originally been specified was 60°F, the ADJUST causes the
converged solution for the independent variable to become a specified
value. If you delete the ADJUST, the new values remain in the
Flowsheet.
10.1.6
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.
See the Looped Pipeline
Example in the Applications
guide 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 will be up to you to select the variables to adjust to solve
your Flowsheet problem.
HYSYS uses a Broyden type search 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
10-14
Logical Operations
10-15
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 will appear informing you that a
temperature crossover exists (see Section 3.3 - Heat Exchanger), and a
very large UA value will be computed for that heat exchanger. This
value will be 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 (Parameters tab,
Simultaneous), then press Start to begin the calculations.
10.2
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 will
solve in both the forward and backward directions. For instance, it will
back out the flowrate of an unknown feed, given that there are no
degrees of freedom.
There are five BALANCE Types:
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
modelling 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.
10-15
10-16
Balance
Most operations in HYSYS
perform a Heat and Material
Balance as part of their
solution.
Balance Type
Definition
Mole and Heat
An overall balance is performed where the heat and molar
flow is 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.
Note that most of the unit operations in HYSYS perform
the equivalent of a Mole and Heat Balance besides their
other more specialized calculations.
General
HYSYS will solve a set of n unknowns in the n equations
developed from the streams attached to the operation.
Component ratios may be specified on a mole, mass or
liquid volume basis.
To add a BALANCE Operation, choose Add Operation from the
Flowsheet menu and select Balance. Alternatively, you may also select
the Balance button in the Object Palette.
Balance Button
10.2.1
Connections Tab
The Connections tabs is the same for all of the Balance Types.
Figure 10.10
10-16
Logical Operations
10-17
On the Connections tab, you must provide the following information:
To ignore the BALANCE
during calculations, select the
Ignored checkbox at the
bottom of the property view.
HYSYS will completely
disregard the operation until
you restore it to an active state
by clearing the check box.
Whenever new streams or
Ratios are added to the
BALANCE Operation, the
Auto Calculation check box
(found at the bottom of the
property view) becomes
unchecked. Once all of the
streams have been updated,
select the box to instruct the
BALANCE to calculate.
Required Input
Description
Name
Enter 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 may have an unlimited amount of
Inlet and Outlet streams. Use the scroll bar to view
streams that are not visible.
10.2.2
Parameters Tab
The Parameters tab contains two group boxes: Balance Type and Ratio
List. The Balance Type group box contains a series of radio buttons
Figure 10.11
which allow you to choose the type of Balance you wish to use: Mole,
Mass, Heat, Mole and Heat, and General. Note that the Ratio List group
applies only to the General balance. This will be discussed in the
General Balance section.
10.2.3
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.
10-17
10-18
Balance
• The Mole and Heat Balance will independently balance energy
and material.
• The Mole and Heat Balance will 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 will always balance with
regard to material and energy. As such, this constraint will
reduce 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.
Example
An example is shown here to illustrate how the Mole and Heat Balance
can be used to back out the stream flow rate and intermediate
temperature of two coolers in series. The duties of the coolers are
known.
Figure 10.12
10-18
Logical Operations
10-19
The Stream and Cooler specifications are as follows (use PengRobinson):
MATERIAL STREAM [E1 Inlet]
Tab [Pabe]
Input Area
Entry
Worksheet
[Conditions]
Temperature
60.0000 °F
Worksheet
[Composition]
Pressure
600.0000 psi
Nitrogen Mole Frac
0.0149
CO2 Mole Frac
0.0020
Methane Mole Frac
0.9122
Ethane Mole Frac
0.0496
Propane Mole Frac
0.0148
i-Butane Mole Frac
0.0026
n-Butane Mole Frac
0.0020
i-Pentane Mole Frac
0.0010
n-Pentane Mole Frac
0.0006
n-Hexane Mole Frac
0.0001
n-Heptane Mole Frac
0.0001
n-Octane Mole Frac
0.0001
MATERIAL STREAM [E2 Outlet]
Tab [Page]
Input Area
Entry
Worksheet
[Conditions]
Temperature
-60.0000 °F
COOLER [E-100]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Inlet
E1 Inlet
Outlet
E1 Outlet
Energy
E1 Duty
Delta P
5 psi
Duty
1.2e+06 Btu/hr
Input Area
Entry
Inlet
E1 Outlet
COOLER [E-101]
Tab [Page]
Design
[Connections]
Design [Parameters]
Outlet
E2 Outlet
Energy
E2 Duty
Delta P
5 psi
Duty
2.5e+06 Btu/hr
10-19
10-20
Balance
At this stage, there is insufficient information to complete mass and
energy balances. The heat balance can only be completed if the stream
flow rate through the coolers is known. However, this can be backed out
by a heat and material balance around the entire Flowsheet involving
Streams E1 Inlet, E2 Outlet, E1 Duty, and E2 Duty.
Add a BALANCE operation, and complete the Connections and
Parameters tabs as shown here.
Figure 10.13
Activate the Auto Calculate check box at the bottom of the property
view. HYSYS immediately executes an overall heat and material
balance. The results are as follows:
STREAMS
Name
E1 Inlet
E1 Outlet
E2 Outlet
E1 Duty
E2 Duty
Vapour Frac
1.0000
1.0000
0.9795
<empty>
<empty>
Temperature [F]
60.00
16.42
-60.00
<empty>
<empty>
Pressure [psia]
600.0
595.0
590.0
<empty>
<empty>
Molar Flow [lbmole/hr]
2648
2648
2648
<empty>
<empty>
Mass Flow [lb/hr]
46867.5
46867.5
46867.5
<empty>
<empty>
Liq Vol Flow [barrel/
day]
1.010e+04
1.010e+04
1.010e+04
<empty>
<empty>
Heat Flow [Btu/hr]
-8.771e+07
-8.891e+07
-9.141e+07
1.20e+06
2.50e+06
Note that most of the unit operations in HYSYS perform the equivalent
of a Heat and Mass Balance in addition to their other more specialized
calculations.
10-20
Logical Operations
10-21
If this example had been solved without the Mole and Heat
Balance, it would have been necessary to specify the flow rate.
When the Mole and Heat Balance was installed, a degree of
freedom was used and the flows of the streams were calculated.
10.2.4
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 will calculate 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.
Example
An example where the Mole Balance could be used is in the case where
you want to create a stream that has the same molar composition and
flow rate as another stream, but a different pressure and temperature
(e.g. - at dew point conditions). This is possible with the Mole Balance,
because Pressure and Temperature conditions are not passed to other
streams. In this example, the composition and flowrate of stream Sales
Gas is passed to stream HC DewPt (see Mole Balance Connections to
the left).
10-21
10-22
Balance
The initial conditions of the stream Sales Gas is shown in the following
table (use Peng-Robinson).
MATERIAL STREAM [Sales Gas]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
10.0000 °C
Pressure
3930.0000 kPa
Molar Flow
30.0000 kgmole/hr
Methane Mole Frac
0.8237
Ethane Mole Frac
0.1304
Propane Mole Frac
0.0272
i-Butane Mole Frac
0.0101
n-Butane Mole Frac
0.0059
i-Pentane Mole Frac
0.0016
n-Pentane Mole Frac
0.0009
n-Hexane Mole Frac
0.0002
Next, create a material stream called HC DewPt but do not specify any
information for it at this point.
Now add a BALANCE operation, as shown below.
Figure 10.14
Activate the Auto Calculation check box. Notice the Not Solved message
appearing in the status bar. Stream HC Dew Point contains molar
flowrate and composition information because that is all we have asked
it to balance. The stream contains no information to flash the stream
such as temperature, pressure or vapour fraction.
10-22
Logical Operations
10-23
By adding the vapour fraction and pressure of stream, HC Dew Point
can now be set to determine the dew point conditions.
Figure 10.15
While composition and molar flowrates have been transferred
via the Mole Balance, the stream will not flash as none of the
flash terms (vapour fraction, temperature or pressure) have
carried over in to the HC Dew Point stream.
10.2.5
By adding the vapour fraction and pressure (in either the
Workbook or the Workbook tab of the Balance property
view), the HC Dew Point stream will flash.
Mass Balance
This operation performs an overall balance where only the mass flow is
conserved. An application is the modelling 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 will
determine 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 will determine the flow of that stream by a mass
balance.
• Energy, Mole 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.
10-23
10-24
Balance
Example
A simple example of the Mass Balance is presented here; all the
components of gas stream RX Inlet are converted to pure propane in
the outlet stream RX Outlet. Specify stream RX Inlet using the PengRobinson Property Package and respective components (see following
table). Specify the composition of stream RX Outlet as 100% Propane.
Streams RX Inlet and RX Outlet are shown below.
MATERIAL STREAM [RX Inlet]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Vapour Frac
1.0000
Temperature
60.0000 °C
Pressure
4000.000 kPa
Molar Flow
100.0000 kgmole/hr
Methane Mole Frac
0.9271
Ethane Mole Frac
0.0516
Propane Mole Frac
0.0148
i-Butane Mole Frac
0.0026
n-Butane Mole Frac
0.0020
i-Pentane Mole Frac
0.0010
n-Pentane Mole Frac
0.0006
n-Hexane Mole Frac
0.0001
n-Heptane Mole Frac
0.0001
n-Octane Mole Frac
0.0001
MATERIAL STREAM [RX Outlet]
Tab [Page]
Worksheet
[Composition]
Input Area
Entry
Methane Mole Frac
0.0000
Ethane Mole Frac
0.0000
Propane Mole Frac
1.0000
i-Butane Mole Frac
0.0000
n-Butane Mole Frac
0.0000
i-Pentane Mole Frac
0.0000
n-Pentane Mole Frac
0.0000
n-Hexane Mole Frac
0.0000
n-Heptane Mole Frac
0.0000
n-Octane Mole Frac
0.0000
Insert a MASS BALANCE operation. On the Connections tab of the
BALANCE operation property view, Inlet Stream is RX Inlet, and the
Outlet Stream is RX Outlet. Select Mass as the Balance Type on the
10-24
Logical Operations
10-25
Parameters tab. Then the Auto Calculation checkbox found at the
bottom of the property view.
The results should appear as follows:
STREAMS
Name
RX Inlet
RX Outlet
Vapour Frac
1.0000
<empty>
Temperature [C]
60.0000
<empty>
Pressure [kPa]
4000.000
<empty>
Molar Flow [kgmole/hr]
100.0000
39.6637
The mass flowrate of RX Inlet is passed to RX Outlet. The molar and
liquid volume flows are calculated based on the specified composition
of RX Outlet.
10.2.6
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 will not be 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 will calculate 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.
Example
In this example, consider a Multi-Pass Heat Exchanger, with two warm
and two cold feeds. The total heat flow of the feeds into the system
needs to be determined. The stream conditions are shown below using
the Peng Robinson Property Package. Do not enter any values shaded
in grey as they will be calculated by HYSYS.
10-25
10-26
Balance
MATERIAL STREAMS
Name
WARM 1
FEED
COLD 1
COLD 2
Vapour Frac
<empty>
<empty>
1
0
Temperature [C]
30.0000
20.0000
<empty>
<empty>
Pressure [kPa]
5000.000
5000.000
2000.000
250.0000
Molar Flow [kgmole/hr]
50.0000
100.0000
75.0000
100.0000
Comp Mole Frac [Methane]
0.9500
0.5386
0.9500
0.0200
Comp Mole Frac [Ethane]
0.0500
0.1538
0.0500
0.9800
Comp Mole Frac [Propane]
0.0000
0.0769
0.0000
0.0000
Comp Mole Frac [i-Butane]
0.0000
0.0692
0.0000
0.0000
Comp Mole Frac [n-Butane]
0.0000
0.0615
0.0000
0.0000
Comp Mole Frac [i-Pentane]
0.0000
0.0538
0.0000
0.0000
Comp Mole Frac [n-Pentane]
0.0000
0.0462
0.0000
0.0000
Create an Energy stream and call it QTOTAL. Do not provide any
information for this stream.
Set up the Heat Balance as shown in Figure 10.16, where QTOTAL is an
energy stream.
Figure 10.16
Activate the Auto Calculation check box and the calculation should
begin. The Heat Flow for energy stream QTOTAL is -3.034e+07 kJ/h.
10-26
Logical Operations
10.2.7
10-27
General Balance
The General Balance is capable of solving a greater scope of problems.
It will solve 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 will be maintained.
• The GENERAL BALANCE will solve material and energy
balances independently. An Energy Stream is an acceptable
inlet or outlet stream.
• The operation will solve 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.
Setting a Ratio
Figure 10.17
Go to the Parameters tab of the BALANCE operation property view and
select the General Balance radio button. The Ratio List group box
should now be visible. Click the Add Ratio button to specify
component ratios. To view a specific ratio, highlight it and click the
View Ratio button. To delete a ratio, you must first view it, and then
select the Delete button in that Ratio view.
10-27
10-28
Balance
Ratio View
Figure 10.18
The following information must be completed on the Ratio definition
view:
Required Input
Description
Name
Enter the name of the Ratio.
Stream
Provide the name of the stream.
Ratio Type
Specify the Ratio Type: Mole, Mass or Volume.
Component/Ratio
Provide the relative compositions of two or more
components. Other components in the stream will be
calculated accordingly, and it is not necessary nor
advantageous to include these in the table. All ratios
must be positive; non-integer values are acceptable.
Number of Unknowns
The GENERAL BALANCE determines the maximum number of
equations, and hence unknowns, in the following manner (note 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.
10-28
Logical Operations
10-29
Example 1
The feed to a Shift Reformer reactor requires a fixed ratio between two
of the components (Methane and H2O). FEED 1 is a feedstock stream
composed primarily of methane, with traces of other components.
FEED 2 is a stream consisting of pure water. Streams FEED 1 and FEED
2 are combined to create the feedstock stream called REACFEED.
The compositions and conditions are given below (using Peng
Robinson Property Package).
MATERIAL STREAMS
Name
FEED 1
FEED 2
REACFEED
Temperature [C]
40.0000
200.0000
<empty>
Pressure [kPa]
7000.0000
7000.0000
7000.0000
Molar Flow [kgmole/hr]
10000.0000
<empty>
<empty>
Comp Mole Frac [Methane]
0.9500
0.0000
<empty>
Comp Mole Frac [CO]
0.0050
0.0000
<empty>
Comp Mole Frac [CO2]
0.0400
0.0000
<empty>
Comp Mole Frac [H2O]
0.0050
1.0000
<empty>
Add the BALANCE Operation. Set up the Connections tabs as shown
here:
Figure 10.19
Go to the Parameters tab and select the General Balance radio button
from the Balance Type group box. Open up the Ratio view by selecting
the Add Ratio button. Modify the view to appear as shown in Figure
10.20.
10-29
10-30
Balance
Figure 10.20
Once you have completed entering this information, activate the Auto
Calculation check box and the operation will be calculated.
The resulting stream specifications are as follows:
MATERIAL STREAMS
Name
FEED 1
FEED 2
REACFEED
Vapour Frac
0.9964
0.0000
0.5349
Temperature [C]
40.0000
200.0000
128.8739
Pressure [kPa]
7000.0000
7000.0000
7000.0000
Molar Flow [kgmole/hr]
10000.0000
9450.0000
19450.0000
Mass Flow [kg/hr]
172312.73
170242.70
342555.43
Liq Vol Flow [m3/hr]
533.0374
170.5863
703.6237
Heat Flow [kJ/hr]
-8.9457e+08
-2.5630e+09
-3.4575e+09
Comp Mole Frac [Methane]
0.9500
0.0000
0.4884
Comp Mole Frac [CO]
0.0050
0.0000
0.0026
Comp Mole Frac [CO2]
0.0400
0.0000
0.0206
Comp Mole Frac [H2O]
0.0050
1.0000
0.4884
Note that the mole fractions of methane and water in stream
REACFEED are both equal to 0.4884, fulfilling the Ratio specification.
Example 2
Since the General Balance
solves a set of linear equations,
it can be used to back out
necessary feed rates to a
column.
10-30
In the Azeotropic Column example (see Applications Book), a mixture
of Benzene and CycloHexane is separated in the column using Acetone
as the entrainer. Nearly pure Benzene is produced from the bottom of
the column, while an azeotropic mixture of Acetone and Cyclohexane is
produced overhead.
Logical Operations
10-31
The amount of Acetone needed to sufficiently separate the Benzene /
CycloHexane azeotrope will be determined. The required Acetone feed
rate (based on a fixed feed of Benzene and CycloHexane) involves
solving a set of linear equations, which means the General Balance can
be used.
The Mass flow rate and compositions of the Azeo feed are specified.
The overhead composition from the tower is a near azeotropic mixture
of Acetone and CycloHexane, with an Acetone mass fraction of 0.6876.
The known stream flows and compositions are (using UNIQUAC):
MATERIAL STREAMS
Name
Azeo Feed
Acetone
Azeo Liquid
Benzene
Mass Flow [kg/hr]
85.0000
<empty>
<empty>
<empty>
Liq Vol Flow [m3/hr]
0.1023
<empty>
<empty>
<empty>
Comp Mass Frac [Benzene]
0.5180
0.0000
0.0000
1.0000
Comp Mass Frac
[Cyclohexane]
0.4820
0.0000
0.3124
0.0000
Comp Mass Frac [Acetone]
0.0000
1.0000
0.6876
0.0000
A General Balance will do individual component balances, while Mole
or Mass Balances only perform overall flow balances and cannot solve
this problem.
Set up a General Balance with Inlet Streams Azeo Feed and Acetone,
and Outlet Streams Azeo Liquid and Benzene. Activate the Auto
Calculation check box.
This operation will not completely solve, however the mass flowrates
Acetone, Azeo Liquid, and Benzene should now be calculated.
STREAMS
Name
Azeo Feed
Acetone
Azeo Liquid
Benzene
Mass Flow [kg/hr]
85.00
90.18
131.1
44.03
Comp Mass Frac [Benzene]
0.5180
0.0000
0.0000
1.0000
Comp Mass Frac
[Cyclohexane]
0.4820
0.0000
0.3124
0.0000
Comp Mass Frac [Acetone]
0.0000
1.0000
0.6876
0.0000
The mass flow of the Acetone stream will immediately be calculated to
be 90.18 kg/h.
Note that if you are using the General Balance in this manner, you must
delete it prior to running the Column.
10-31
10-32
Parametric Unit Operation
10.3
Parametric Unit
Operation
The PARAMETRIC unit operation allows selected unit operations,
streams and variables to be solved using a Parametric model. The main
function of the Parametric model is to approximates an existing HYSYS
model. To build the Parametric model, the Parametric Utility tool is
required. This utility integrates Neural Network (NN) technology into
its framework. For more information on this utility, refer to Chapter 8 Utilities of the User’s Guide. A data file with the appropriate data may
be used in place of the Parametric Utility.
Using a Parametric model with neural network capability to
approximate a HYSYS model will significantly improve the robustness
of the model, reduce its calculation time, and improve the overall online performance. The accuracy of the model will depend upon the data
available and type of model being approximated.
In the flowsheet, the PARAMETRIC unit operation essentially “pulls
out” a collection of HYSYS unit operations and replaces them.
Therefore, this unit operation may be thought of as a “black box” with
inputs and outputs. When the flowsheet is solved, the Parametric
model is used in place of the individual HYSYS unit operation models.
To install the PARAMETRIC unit operation, choose Flowsheet - Add
Operation from the menu, and select Parametric Unit Operation. To
ignore this unit operation, click the Ignore check box at the bottom its
the property view.
10.3.1
Design Tab
Connections Page
The Connections page allows the PARAMETRIC unit operation to be
connected with the information required for the Parametric model.
This information may be found in either a Parametric Utility or a data
file.
This tab is always comprised of two groups: Name and Input Data. The
rest of the view is unique for the chosen Input Data type.
The Name group lets you define a unique name for the unit operation.
The Input Data group allows you to define where the input data to the
10-32
Logical Operations
10-33
Parametric model is to be found. The rest of the view will be altered
depending on the radio button selected. The options available are: Use
Utility Data and Inputs from a Data File
Figure 10.21
Use Utility Data Radio Button
When this radio button is selected the view appears as the left hand
view in Figure 10.21. This view has one additional group, and two
additional buttons available.
Parametric Utility Selection Group
If any Parametric Utilities exist in the case, one may be selected as the
utility to be used by clicking the Browse button. This button will bring
up the Select Parametric Utility view, as shown in Figure 10.22.
Highlight the Parametric Utility to be used for the unit operation and
click the OK button.
Create Utility Button
If a Parametric Utility does not exist in the HYSYS case, or the user
wishes to create a new Utility, clicking this button will create one for use
in the Parametric unit operation.
10-33
10-34
Parametric Unit Operation
Figure 10.22
View Utility Button
Clicking this button will bring you to the property view for the selected
Parametric Utility.
Inputs from a Data File Radio Button
When using this option, the Parametric unit operation does not have to
obtain the model parameters from a utility. Instead, an external data
file may be used.
Data File Selection Group
The information in the *.dat
file is in the format:
input1, input2, input3, .....,
ouput1, output2,
input1, input2, input3, ....,
ouput1, ouput2,
Clicking the Browse button allows you to navigate and locate the data
file that contains the required information for the Parametric model.
The information in the file is comma delimited, and is stored in a *.dat
file.
Input Units from Data File Group
Using the drop down box, the units used in the data file may be defined.
Modeled Streams for Input and Output
The input and output streams that are being modeled may be selected
from the list of existing streams in the drop down box. A new stream
may be created and used in the Parametric unit operation by entering a
new stream name in the appropriate cell.
10-34
Logical Operations
10-35
Setup Page
The appearance of this page, like the Connections page, is dependant
on the radio button selected in the Input Data group on the
Connections page. When the Use Utility Data radio button is selected,
the view appears as the left hand view in Figure 10.23. When the Inputs
from a data file radio button is selected, the view appears as the right
hand view in Figure 10.23
Figure 10.23
Use Utility Data Radio Button
Available Unit Op Models from Utility
When the Use Utility Data radio button is selected on the Connections
page, only one group is available on the Setup page. In this table, all
unit operations that have a Parametric model in the selected
Parametric Utility are displayed. The name of the unit operation, the
status of the model activity, and the operation status of the unit
operations are all displayed. The Model Activity may be chosen to be
active or inactive by clicking the check box. When the model is inactive,
it is only removed from the Parametric Utility.
Inputs from a data file Radio Button
When the Inputs from a Data File radio button is selected on the
Connections page, two groups become available on the Setup page:
10-35
10-36
Parametric Unit Operation
Data Mapping and Training Pair Status.
Data Mapping Group
Two radio buttons are available in this group: Inputs and Outputs. The
properties displayed and their descriptions follow.
Property
Description
Number of Training
Pairs
the number of data sets read in from the data file.
Data Point
a specific data point within the data file.
Mapped Variable
the variable type of the data point. This may be
selected from the drop down box.
Variable Type
functionality for this column has not been
implemented for this version.
Identifier
allows the user to enter a unique name to identify the
data points.
Low and High Value
the minimum and maximum values in the data set.
Bad Variable Status
if an ‘X’ is displayed, the data is good. If a check
mark is displayed, there is bad data in the data set.
Current Value
the value used in the worksheet after training.
Training Pair Status Group
A training pair is defined as a
set of input data and a pair of
output data. In the data file
this would be:
input1, input2, input3,....
ouput1, output2
10-36
Displays the individual training pairs, and indicates whether the pair
contains bad data. If an ‘X’ is displayed, there is no bad data. If a check
mark is displayed, there is bad data in the data set.
Logical Operations
10-37
Notes Page
You can use this page to add any notes pertinent to the unit operation
or the simulation case in general.
Figure 10.24
10.3.2
Parameters Tab
The Parameters tab displays the training variables of the attached
Parametric Utility. There are four main objects in this view:
Figure 10.25
10-37
10-38
Parametric Unit Operation
Connected Unit Operations
The number of unit operations connected to the Parametric unit
operation is displayed in this box.
Manipulated Variables
By selecting the Manipulated radio button, the manipulated variables
in the Parametric model will be displayed. The manipulated variables
are the variables being modified in the Parametric Utility and obtained
from the HYSYS PFD model simulation. The name of the variable is
displayed, and the selected status is shown. You may select or deselect
the variable for use in the parametric model by clicking the check box.
The lower and upper values used for training are also displayed.
Targeted Variables
By selecting the Targeted radio button, the targeted variables in the
Parametric model will be displayed. The targeted variable is the same
as the Observable variable in the Parametric Utility. Targeted variables
are the HYSYS variables whose values are known and used as training
data when calculating the Parametric model. The name of the variable
is displayed and the selected status is shown. You may select or deselect
the variable for use in the Parametric model calculation by clicking the
check box. The lower and upper values for training are also displayed.
Train Button
Clicking the Train button will initialize the Parametric Utility training
engine to determine the parameters for the Parametric model.
The Parametric model approximates the HYSYS model in the sense
that, given the same values of the training input variables, the values of
the output variables of the Parametric model must be close to the
values from the HYSYS model.
It is important to realize that there are no methods for training neural
networks that can “magically” create information that is not contained
in the training data. The neural network model is only as good as its
training data.
10-38
Logical Operations
10.3.3
10-39
Worksheet Tab
The Worksheet tab displays the various Conditions, Properties and
Compositions of the unit operations, streams, and variables that are
using the Parametric model. From here you can use the neural network
instead of the flowsheet, and where the training pairs have been used
from a file, see how the neural network has modeled the operation from
which your training pairs were generated. These objects are displayed
as different pages on the tab. For more information on the Workbook,
refer to Chapter 4 - Workbook in the User’s Guide.
Figure 10.26
10-39
10-40
Recycle
10.4
Recycle
The capability of any Flowsheet simulator to solve recycles reliably and
efficiently is critical. HYSYS has inherent advantages over other
simulators in this respect. It has the unique ability to back-calculate
through many operations in a non-sequential manner, allowing many
problems with recycle loops to be solved explicitly. For example, most
heat recycles can be solved explicitly (without a RECYCLE operation).
Material recycles, where downstream material mixes with upstream
material, require a RECYCLE operation.
The RECYCLE installs a theoretical block in the process stream. The
feed into the block is termed the calculated recycle stream, and the
product is the assumed recycle stream. The following steps take place
during the convergence process:
Recycle Button
10-40
1.
HYSYS uses the conditions of the assumed stream and solves the
Flowsheet up to the calculated stream.
2.
HYSYS then compares the values of the calculated stream to those
in the assumed stream.
3.
Based on the difference between the values, HYSYS modifies the
values in the calculated stream and passes the modified values to
the assumed stream.
4.
The calculation process repeats until the values in the calculated
stream match those in the assumed stream within specified
tolerances.
To install the RECYCLE operation, choose Add Operation from the
Flowsheet menu, and select Recycle. Alternatively, select the Recycle
button in the Palette.
Logical Operations
10.4.1
10-41
Connections Tab
Figure 10.27
This tab consists of 3 fields:
Field
Description
Name
In this field the Name of the RECYCLE operation
can be specified by selecting it and making changes
to the Edit bar.
Feed
This drop down box holds the inlet stream which is
the latest calculated recycle; it will always be a
product stream from a unit operation.
Product
This drop down box contains the outlet stream
which is the latest assumed recycle; it will always be
a feed stream to a unit operation.
10-41
10-42
Recycle
10.4.2
Parameters Tab
The Parameters tab contains two pages: Tolerance and Numerical.
Tolerance Page
Figure 10.28
HYSYS allows you to set the convergence criteria factor for each of the
variables listed. The tolerance values you input actually serve as a
multiplier for HYSYS’ internal convergence tolerances. The internal
absolute tolerances, except flow which is a relative tolerance, are shown
below.
HYSYS Internal Tolerances
The Internal Vapour Fraction
tolerance, when multiplied by
the recycle tolerance, is 0.1
which appears to be very
loose. However, in most
situations, if the other recycle
variables have converged, the
vapour fraction in the two
streams will be identical. The
loose Vapour Fraction
tolerance is critical for closeboiling mixtures, which can
vary widely in vapour fraction
with minimal difference in
other properties.
10-42
Variable
Internal Tolerance
Vapour Fraction
0.01
Temperature
0.01
Pressure
0.01
Flow
0.001**
Enthalpy
1.00
Composition
0.0001
**Note that flow tolerance is relative rather than absolute
For example, the internal tolerance for Temperature is 0.01 and the
default multiplier is 10, so the absolute tolerance used by the RECYCLE
convergence algorithm is 0.01*10 = 0.1. Therefore, if you are working in
SI units, the temperatures of the assumed and calculated recycle
streams must be within 0.1°C of each other if the RECYCLE is to
converge.
Logical Operations
To ignore the RECYCLE
Operation during
calculations, select the Ignore
checkbox. HYSYS will
completely disregard the
operation until you restore it
to an active state by clearing
the check box.
10-43
A multiplier of 10 (default) is normal and is recommended for most
calculations. Values less than 10 are more stringent; that is, the smaller
the multiplier, the tighter the convergence tolerance.
It is not required that each of the multipliers be identical. For example,
if you are dealing with ppm levels of crucial components, you can set
the Composition tolerance multiplier much tighter (smaller) than the
others.
Numerical Page
Figure 10.29
The Numerical page contains the options related to the Wegstein
Acceleration Method. This method is used by the RECYCLE to modify
the values it passes from the inlet to outlet streams, rather than using
direct substitution.
Numerical Parameters Description
Maximum Iterations
The number of iterations before HYSYS stops (default
is 10). You may continue with the calculations by
selecting the Continue button on the Numerical page.
Wegstein Count
The number of iterations before an acceleration step is
applied to the next iteration (default is 3).
Flash Type
The Flash method to be implemented by the Recycle
unit op.
Q maximum/Q
minimum
Damping factors for the acceleration step (defaults are
0 and 20).
10-43
10-44
Recycle
Numerical Parameters Description
Acceleration Delay
This delays the acceleration until the specified step.
Type
Options are Nested or Simultaneous (default is
Nested).
Acceleration Options
There are two options for the method of acceleration:
Acceleration
Options
Description
Wegstein
Ignores interactions between variables being
accelerated.
Dominant
Eigenvalue
Includes interactions between variables being
accelerated. Further, the Dominant Eigenvalue
option is superior when dealing with non-ideal
systems or systems with strong interactions between
components.
Maximum Number of Iterations
When HYSYS has reached the maximum number of iterations, a
warning message will appear stating that the RECYCLE failed to
converge in the specified number of iterations. You may then choose
whether or not to continue calculations.
If you are starting a new Flowsheet, use a small number of Maximum
Iterations, such as 3. Once it is evident that the calculations are
proceeding well, the count can be increased. The iterations required
will depend not only on the complexity of your Flowsheet, but also on
your initial estimate and the convergence tolerances you use.
Damping Factors - Qmax and Qmin
The Wegstein acceleration method uses the results of previous
iterations in making its guesses for the recycle stream variables.
Assumed values are calculated as follows:
X n + 1 = QX n + ( 1 – Q )Y n
where: X = Assumed value
Y = Calculated value
10-44
(10.2)
Logical Operations
10-45
n = Iteration number
Q = Acceleration factor
If you are finding that your
RECYCLE is still oscillating,
even with the Wegstein Count
set to ensure direct
replacement, you can input a
slightly larger value for Qmax
to damp the direct
replacement.
HYSYS determines the actual acceleration (Q) to apply based on the
amount of change between successive iterations. The values for Qmax
and Qmin set bounds on the amount of acceleration applied. Note from
the equation that when Q = 0, direct replacement is used. When Q is
negative, acceleration is used. When Q is positive and smaller than 1,
damping occurs.
Wegstein Count
The Wegstein Count is the number of RECYCLE iterations before an
acceleration step is applied when calculating the next assumed recycle
value. The default count is 3; after three iterations (assuming the
Acceleration Delay is less than 3), the assumed and calculated recycle
values will be compared and the Wegstein acceleration factor will be
determined and applied to the next assumed value. When the
acceleration factor is not being used (in all iterations up to the Wegstein
Count), the next assumed value is determined by direct replacement.
Note that Acceleration Delay takes precedence over the Wegstein
Count. This means that for a Acceleration Delay value of x, the initial x
iterations will use direct replacement, even if the Wegstein Count is set
to less than x. The x+1 iteration will use the acceleration after which the
Wegstein Count will apply.
Figure 10.30
if W ≤ AD then N = AD+1
else if W > AD then N = W
N
W
W
W
W
iterations
Recycle
Iterations
Begin
AD - Acceleration Delay
W - Wegstein Count
Although acceleration generally works well for most problems, in some
cases it may result in over-correction, oscillation and possibly nonconvergence. Examples of this type of problem include highly-sensitive
recycles and multiple recycle problems with strong interactions among
recycles. In cases such as these, direct replacement may be the best
method for all iterations. To eliminate the use of acceleration, simply
10-45
10-46
Recycle
set the Wegstein Count (or Acceleration Delay) to a very high number
of iterations (for example, 100) which will never be reached. In the rare
instance where even direct replacement causes excessive overcorrections, damping is required. Use the set of parameters discussed
below to control this.
Acceleration Delay
The Acceleration Delay parameter delays the acceleration until the
specified step. This delay applies to the initial set of iterations and once
the specified step is reached the Wegstein Count is applied. That is to
say no acceleration is performed until the delay value is reached and
after that iteration the acceleration is applied according to the Wegstein
count. The default is specified as 2 but now it can be specified to any
value.
For example if the ’delay’ is set to 5 and the Wegstein count is 3 then the
first 5 iterations will use direct replacement and the sixth will use
acceleration then after every third iteration the acceleration step is
applied.
Type of Recycle
The Calculation Level for a
RECYCLE (accessed under
Main Properties) is 3500,
compared to 500 for most
streams and operations. This
means that the RECYCLE will
be solved last among
unknown operations. You
may set the relative solving
order of RECYCLES by
modifying the Calculation
Level.
There are two choices for the type of RECYCLE: Nested and
Simultaneous. The Nested option will result in the RECYCLE being
called whenever it is encountered during the calculations. In contrast,
the Simultaneous option will cause all RECYCLES to be invoked at the
same time once all recycle streams have been calculated. If your
Flowsheet has a single RECYCLE operation, or if you have multiple
recycles which are not connected, use the Nested option (default). If
your Flowsheet has multiple inter-connected recycles, use the
Simultaneous type.
There are several additional points worth noting about the RECYCLE:
The Convergence tab provides
a history of the Recycle
calculations.
10-46
• When the RECYCLE cannot be solved in the number of
iterations you specify, HYSYS will stop. If you decide that the
problem might converge with more iterations, simply select the
Continue button on the Numerical tab. The RECYCLE will
initialize the iteration counter and continue until a solution is
found or it again runs out of iterations.
• If your problem does not converge in a reasonable number of
iterations, there are probably constraints in your Flowsheet
which make it impossible to solve. In particular, if the size of the
recycle stream keeps growing, it is likely that the Flowsheet
does not permit all of the material entering the Flowsheet to
Logical Operations
10-47
leave. An example of this occurs in gas plants when you are
trying to make a liquid product with a low vapour pressure and
a vapour product which must remain free of liquids even at cold
temperatures. Often, this leaves no place for intermediate
components like propane and butane to go, so they accumulate
in the plant recycle streams. It is also possible that the
tolerance is too tight for one or more of the RECYCLE variables
and cannot be satisfied. This can readily be determined by
examining the convergence history and comparing the
unconverged variable deviations with their tolerances.
• The logical operations (such as the RECYCLE, ADJUST and
CONTROLLER) are different from other operations in that they
actually modify the specifications of a stream. As a result, if you
remove any of these operations, the outlet stream
specifications remain. Thus, nothing in the Flowsheet is
"forgotten" for these operations. You may Delete or Ignore a
RECYCLE when you wish to make Flowsheet modifications,
but do not want to invoke the iterative routines.
• Tolerance settings are important to a successful RECYCLE
solution. This is especially true when multiple recycles are
involved. If there is no interaction among the recycles, or if they
are inter-connected and are being solved simultaneously,
tolerance values can be identical for all RECYCLES if desired.
However, if the RECYCLES are nested, tolerances should be
made increasingly tighter as you go from the outermost to the
innermost RECYCLE. Without this precaution, the outside
RECYCLE may not converge.
10.4.3
Worksheet Tab
The Worksheet tab displays the various Conditions, Properties and
Compositions of the Feed and Product streams. For more information
refer to the Workbook.
10.4.4
Monitor Tab
The Setup page allows you to specify which variables you want to view
or monitor. To view a variable, select the View check box corresponding
to the variable of interest.
The Tables and Plots pages display the convergence information as the
calculations are performed in tabular and graphical form respectively.
The inlet value, outlet value, and variable are shown, along with the
iteration number.
10-47
10-48
Recycle
Figure 10.31
Setup page
Tables page
In Dynamic mode, HYSYS
ignores the RECYCLE
operation; the outlet stream is
identical to the inlet stream.
Plots page
10.4.5
Calculations
HYSYS provides a very simple means of solving recycle problems, and
its interactive nature provides a high degree of control and feedback to
the user as to how the solution is proceeding. The RECYCLE can be set
up as a single unit operation to represent a single recycle stream in a
process Flowsheet, or a number of them can be installed to represent
multiple recycles, interconnected or nested, as well as a combination of
interconnected and nested recycle loops. Similar to the multi-ADJUST
operation, the RECYCLE will solve all the recycle loops simultaneously,
if requested to do so.
The step-by-step procedure for setting up a recycle is as follows:
1.
10-48
Make a guess for the assumed recycle stream (temperature,
pressure, flow rate, composition).The flow rate can generally be
Logical Operations
10-49
zero, but, obviously, better estimates will result in faster
convergence. Note that if the recycle is a feed to a tower, a
reasonable estimate is needed to ensure that the column will
converge the first time it is run.
2.
Build your Flowsheet until the calculated recycle stream can be
determined by HYSYS (note that the calculated and assumed
recycle streams must have different names).
3.
Install the RECYCLE block.
10.4.6
Reducing Convergence
Time
Selection of the recycle tear location is vitally important in determining
the computer run time to converge the RECYCLE. Although the
physical recycle stream itself is often selected as the tear stream, the
Flowsheet can be broken at virtually any location. In simulating a
complex system, a number of factors must be considered. Following are
some general guidelines:
Choose a Tear Location to Minimize the
Number of Recycles
Reducing the number of locations where the iterative process is
required will save on total convergence time. Choosing the location of
the Recycle will depend on the Flowsheet topology. Attempt to choose a
point such that specifying the assumed stream will define as many
streams downstream as possible. It generally occurs downstream of
gathering points and upstream of distribution points. Examples
include downstream of mixers (often mixing points where the physical
recycle combines with the main stream), and upstream of tees,
separators and columns.
Choose a Tear Location to Minimize the
Number of Recycle Variables
Avoid choosing tear streams
which have variables
determined by an ADJUST
operation.
Variables include vapour fraction, temperature, pressure, flow,
enthalpy, and composition. Choose the tear stream so that as many
variables as possible are fixed, thus effectively eliminating them as
variables and increasing convergence stability. Good choices for these
locations are at separator inlets, compressor aftercooler outlets, and
trim heater outlets.
10-49
10-50
Recycle
Choose a Stable Tear Location
The tear location can be chosen such that fluctuations in the recycle
stream have a minimal effect. For example, by placing the tear in a
main stream, instead of the physical recycle, the effect of fluctuations
will be reduced. The importance of this factor depends on the
convergence algorithm. It is more significant when successive
substitution is used. Choosing stable tear locations is also important
when using simultaneous solution of multi-recycle problems.
10.4.7
Single Recycle Example
In this example, a two-phase feed stream (FEED) is mixed with a
recycled stream (RECYCLE) and fed to separator V-100. The vapour
from V-100 is expanded in expander E-100 and then reflashed in
separator V-101. Half of the liquid from this separator is fed to pump
P-100 and then recycled back and mixed with the fresh feed..
Figure 10.32
The conditions and composition of stream FEED are shown here (using
the Peng Robinson Property Package).
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
10-50
Input Area
Entry
Temperature
60.0000 °F
Pressure
600.0000 psi
Molar Flow
1 MMSCFH
Logical Operations
10-51
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Composition]
Input Area
Entry
Nitrogen Mole Frac
0.0069
CO2 Mole Frac
0.0138
Methane Mole Frac
0.4827
Ethane Mole Frac
0.1379
Propane Mole Frac
0.0690
i-Butane Mole Frac
0.0621
n-Butane Mole Frac
0.0552
i-Pentane Mole Frac
0.0483
n-Pentane Mole Frac
0.0414
n-Hexane Mole Frac
0.0345
n-Heptane Mole Frac
0.0276
n-Octane Mole Frac
0.0206
Add the following unit operations.
SEPARATOR [V-100]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Inlets
Feed
Vapour Outlet
V-100 Vap
Liquid Outlet
V-100 Liq
Pressure Drop
0 psi
EXPANDER [K-100]
Tab [Page]
Design
[Connections]
Worksheet
[Conditions]
Input Area
Entry
Inlet
V-100 Vap
Outlet
V-101 Feed
Energy
V-101 Duty
V-101 Feed Pressure
300 psi
SEPARATOR [V-101]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Inlets
V-101 Feed
Vapour Outlet
V-101Vap
Liquid Outlet
V-101 Liq
Pressure Drop
1.4500 psi
10-51
10-52
Recycle
TEE [TEE-100]
Tab [Page]
Input Area
Entry
Inlet
V-101 Liq
Design
[Connections]
Outlets
TEE-100 Prod
Design [Parameters]
Flow Ratio
0.5 (set either one)
Input Area
Entry
P-100 Feed
PUMP [P-100]
Tab [Page]
Design
[Connections]
Inlet
P-100 Feed
Product
P-100 Out
Energy
P-100 Duty
Design [Parameters]
Efficiency
75%
Worksheet
[Conditions]
P-100 Out Pressure
600 psi
Stream RECYCLE
Specify the stream RECYCLE using the P-100 OUT specs. First, create
stream RECYCLE; from the bottom of the Stream property view, choose
the Define from other Stream button, and then select stream P-100
OUT from Available Streams list box on the Spec Stream As view. Attach
this stream as an inlet to Separator V-100. The Flowsheet will resolve,
and the RECYCLE operation can now be added.
Recycle RCY-1
RECYCLE [RCY-1]
Tab [Page]
Input Area
Entry
Design
[Connections]
Feed
P-100 Out
Product
RECYCLE
Leave all parameters at their defaults.
The Flowsheet will now solve, and the RECYCLE should quickly
converge.
10-52
Logical Operations
10-53
The assumed and calculated recycles will be almost identical, once a
solution is reached.
STREAMS
Name
RECYCLE
P-100 Out
Temperature [F]
9.9185
9.9184
Pressure [psia]
600.0000
600.0000
Molar Flow [lbmole/hr]
14.5063
14.5064
Comp Mole Frac [Nitrogen]
0.0006
0.0006
Comp Mole Frac [CO2]
0.0081
0.0081
Comp Mole Frac [Methane]
0.1249
0.1249
Comp Mole Frac [Ethane]
0.1490
0.1490
Comp Mole Frac [Propane]
0.1448
0.1448
Comp Mole Frac [i-Butane]
0.1636
0.1636
Comp Mole Frac [n-Butane]
0.1494
0.1494
Comp Mole Frac [i-Pentane]
0.1144
0.1144
Comp Mole Frac [n-Pentane]
0.0888
0.0888
Comp Mole Frac [n-Hexane]
0.0388
0.0388
Comp Mole Frac [n-Heptane]
0.0136
0.0136
Comp Mole Frac [n-Octane]
0.0041
0.0041
Let us now look at a Multiple Recycle Example.
10-53
10-54
Recycle
10.4.8
Multiple Recycle Example
A multi-stage gas compression process will be set up, as shown in the
figure below.
Figure 10.33
Note that the actual physical recycles in this problem have been
selected as tear streams.
Inlet Stream Feed enters at 50°F and 80 psia and is compressed up to
1000 psia through three stages of compression. After each compression
stage, the liquid dropout at the interstage knockout drum is recycled
back to the inlet of the preceding compression stage. The interstage
temperature-pressure conditions are 120°F and 200 psia after
compression stage 1, 120°F and 500 psia after stage 2, and 120°F and
1000 psia after stage 3.
Add Stream Feed shown following (using the Peng Robinson Property
Package).
10-54
Logical Operations
10-55
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
50.0000 °F
Pressure
80.0000 psi
Molar Flow
2500.0000 lbmole/hr
Nitrogen Mole Frac
0.0069
CO2 Mole Frac
0.0138
Methane Mole Frac
0.4827
Ethane Mole Frac
0.1379
Propane Mole Frac
0.0690
i-Butane Mole Frac
0.0621
n-Butane Mole Frac
0.0552
i-Pentane Mole Frac
0.0483
n-Pentane Mole Frac
0.0414
n-Hexane Mole Frac
0.0345
n-Heptane Mole Frac
0.0276
n-Octane Mole Frac
0.0206
To set up this Flowsheet, a series of separators, compressors, coolers
and mixers have to be installed as shown in the figure. The recycle
streams will be added after the operations have been installed. Install
the operations as described on the next few pages.
Leave all parameters at their defaults unless otherwise indicated.
MIXER [MIX-100]
Tab [Page]
Input Area
Design
[Connections]
Inlet
Feed
Outlet
V-100 Feed
Pressure Assignment
Set Outlet to Lowest
Inlet
Design [Parameters]
Entry
10-55
10-56
Recycle
The Recycled Stream Recycle 1 will be added to this mixer after all the
operations have been installed.
SEPARATOR [V-100]
Tab [Page]
Design
[Connections]
Input Area
Entry
Inlets
V-100 Feed
Vapour Outlet
V-100 Vao
Liquid Outlet
V-100 Liq
COMPRESSOR [K-100]
Tab [Page]
Design
[Connections]
Input Area
Entry
Inlet
V-100 Vap
Outlet
K-100 Out
Energy
K-100 Duty
COOLER [E-100]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Feed Stream
K-100 Out
Product Stream
E-100 Out
Energy Stream
E-100 Duty
Pressure Drop
5 psia
Specify the temperature and pressure of stream E-100 Out as 120 °F
and 200 psi.
MIXER [MIX-101]
Tab [Page]
Input Area
Entry
Design
[Connections]
InletE-100
Out
Design [Parameters]
Outlet
V-101 Feed
Pressure Assignment
Set Unknown Outlet
to Lowest Inlet
The Recycled Stream Recycle 2 to this mixer will be added after all the
operations have been installed.
SEPARATOR [V-101]
Tab [Page]
Design
[Connections]
10-56
Input Area
Entry
Feed
V-101 Feed
Vapour Outlet
V-101 Vap
Liquid Outlet
V-101 Liq
Logical Operations
10-57
COMPRESSOR [K-101]
Tab [Page]
Design
[Connections]
Input Area
Entry
Inlet
V-101 Vap
Outlet
K-101 Out
Energy
K-101 Duty
COOLER [E-101]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Feed Stream
K-101 Out
Product Stream
E-101 Out
Energy Stream
E-101 Duty
Pressure Drop
5 psi
Specify the temperature and pressure of stream E-101 Out as 120 °F
and 500 psi.
MIXER [MIX-102]
Tab [Page]
Input Area
Entry
Design
[Connections]
Inlet
E-101 Out
Design [Parameters]
Outlet
V-102 Feed
Pressure Assignment
Set Outlet to Lowest
Inlet
The Recycled Stream Recycle 3 will be added to this mixer after all
operations are installed.
SEPARATOR [V-102]
Tab [Page]
Design
[Connections]
Input Area
Entry
Feed
V-102 Feed
Vapour Outlet
V-102 Vap
Liquid Outlet
V-102 Liq
Input Area
Entry
Inlet
V-102 Vap
COMPRESSOR [K-102]
Tab [Page]
Design
[Connections]
Outlet
K-102 Out
Energy
K-102 Duty
10-57
10-58
Recycle
COOLER [E-102]
Tab [Page]
Design
[Connections]
Design [Parameters]
Input Area
Entry
Feed Stream
K-102 Out
Product Stream
E-102 Out
Energy Stream
E-102 Duty
Pressure Drop
5 psi
Specify the temperature and pressure of stream E-102 Out as 120 °F
and 1000 psi.
SEPARATOR [V-103]
Tab [Page]
Design
[Connections]
Input Area
Entry
Feed
E-102 Out
Vapour Outlet
V-103 Vap
Liquid Outlet
V-103 Liq
Next, add the recycled streams, by selecting the Define from other
Stream button from the bottom of the Material stream property view
and using the Spec Stream As view to define them using another
stream’s properties.
Recycle Streams
By using this sequence, better
starting points for the Recycle
streams will be used.
• Specify Stream Recycle 1 as Stream V-101 Liq and connect
as a feed to MIX-100
• Specify Stream Recycle 2 as Stream V-102 Liq and connect
as a feed to MIX-101
• Specify Stream Recycle 3 as Stream V-103 Liq and connect
as a feed to MIX-102
The properties of Streams V-101 Liq, V-102 Liq and V-103 Liq serve as
the initial estimates for the recycle streams. Before adding the
RECYCLE operations, you may want to put the Flowsheet into hold
mode.
RECYCLE Operations
• RCY-1 - Feed: Stream V-101 Liq; Product: Stream Recycle 1
• RCY-2 - Feed: Stream V-102 Liq; Product: Stream Recycle 2
• RCY-3 - Feed: Stream V-103 Liq; Product: Stream Recycle 3
Solve the Flowsheet, and you will obtain the following converged
material stream conditions as shown in Figure 10.34.
10-58
Logical Operations
10-59
Figure 10.34
10.4.9
Multiple Recycle Example
Revisited
To choose the proper tear streams to reduce convergence time, it is
necessary to examine the Flowsheet topography and the specified
conditions in the process. In the following figures, each of the
individual compression loops has been broken out of the overall
process.
Figure 10.35
10-59
10-60
Recycle
Figure 10.36
Figure 10.37
Note that if the Mixers had
been bypassed to feed directly
to the Separators, the number
of Recycles could not have
been reduced.
By examining each stage of compression, it can be seen that streams V101 Feed and V-102 Feed are part of more than one loop. Instead of
using the physical recycle streams (V-101 Liq, V-102 Liq and V-103 Liq),
choose streams V-101 Feed and V-102 Feed as shown in the following
diagram. Not only does this reduce the number of tear streams from
three to two, but these streams are also more stable.
Using your existing Multiple Recycle Example, configure the Flowsheet
by doing the following:
10-60
1.
Put the Flowsheet into Hold mode.
2.
Delete operations RCY-1, RCY-2 and RCY-3.
3.
Delete streams Recycle 1, Recycle 2, and Recycle 3.
4.
Attach V-101 Liq as a feed to MIX-100.
5.
Attach V-102 Liq as a feed to MIX-101. Detach product stream V101 Feed, and attach the new product stream MIX-101 OUT.
6.
Attach V-103 Liq as a feed to MIX-102. Detach product stream V102 Feed, and attach the new product stream MIX-102 OUT.
Logical Operations
7.
Add RCY-1, with MIX-101 OUT as the feed, and V-101 Feed as the
Product.
8.
Add RCY-2, with MIX-102 OUT as the feed, and V-102 Feed as the
Product.
10-61
In this case, an estimate is required for both recycle streams (V-101
Feed and V-102 Feed) in order to initiate Flowsheet calculations. A
simple and satisfactory method is to specify both of these streams as
Feed, by selecting the Define from other Stream button and accessing
the Spec Stream As view.
These estimates are adequate and the Flowsheet converges in eight
iterations.
The new process PFD and Workbook tab results are shown on below:
Figure 10.38
10-61
10-62
Set
Figure 10.39
10.5
Set
The SET is an operation used to set the value of a specific Process
Variable (PV) in relation to another PV. The relationship is between the
same PV in two like objects; for instance, the temperature of two
streams, or the UA of two exchangers. The operation can be used in
both Dynamic and Steady State mode.
The dependent, or target, variable is defined in terms of the
independent, or source, variable according to the following linear
relation:
Y = MX + B
(10.3)
where: Y = Dependent (target) variable
X = Independent (source) variable
M = Multiplier (slope)
B = Offset (intercept)
To install the SET operation, choose Add Operation from the Flowsheet
menu, and select Set. Alternatively, select the Set button in the Palette.
Set Button
10-62
Logical Operations
10.5.1
10-63
Connections Tab
Figure 10.40
On the Connections tab, specify the following information:
Input Required
Description
Target Object
The stream or operation to which the dependent
variable belongs. This is chosen using the Select
Var button. This will bring up the Variable Navigator
(see Section 5.2.2 - Variable Navigator of the
User’s Guide for more infomation about using the
Variable Navigator)
Target Variable
The type of variable you wish to set, i.e.,
temperature, pressure, flow. The available choices
for Variable are dependent on the Object type
(stream, heat exchanger, etc.) Your choice of
Variable will automatically be assigned to both the
Target and Source object.
Source Object
The stream or operation to which the independent
variable belongs.
Note that when you choose an object for the Target, the available
objects for the Source are restricted to those of the same object type.
For example, if you choose a stream as the Target, only streams will be
available for the Source.
HYSYS will solve for either the Source or Target variable, depending on
which is known first (bi-directional solution capabilities).
10-63
10-64
Set
10.5.2
Parameters Tab
Figure 10.41
On the Parameters tab, provide values for the Slope (Multiplier, or ’M’value) and the Intercept (Offset, or ’B’-value in the set equation). The
default values for the Multiplier and Offset are 1 and 0, respectively.
To ignore the SET during calculations, select the Ignore checkbox.
HYSYS will completely disregard the operation until you restore it to an
active state by clearing the check box.
10.5.3
Set Example
In this example, the feed streams to a reactor will be specified in
stoichiometric proportion using the SET operation.
First, select the Property Package (Peng Robinson), and add the four
components CO, Hydrogen, H2O and Methane.
The following conversion reaction will be modelled:
CO + 3H 2 → CH 4 + H 2 O
(10.4)
Add a Conversion Reaction and complete the Stoichiometry tab of the
Conversion Reaction as shown here. On the Basis tab of the Conversion
Reaction view, set the Base Component to be CO, and the Conversion
to 80%.
10-64
Logical Operations
10-65
Figure 10.42
If you wish, create a Reaction Set, and add the Conversion Reaction to
that Set. This is not necessary, however, as the reaction is automatically
added to the Global Rxn Set. Add the Global Rxn Set to the fluid
package by clicking on the Add to FP button. Once this is done, exit the
Basis Environment.
There will be two feed streams to the reactor (Separator), one being
pure CO, and the other pure H2. The feed streams are displayed below.
The Molar Flowrate of CO Feed is known and equal to 100 kgmole/hr.
STREAMS
Name
CO Feed
H2 Feed
Vapour Frac
1.0000
1.0000
Temperature [C]
550.0000
550.0000
Pressure [kPa]
1000.0000
1000.0000
Molar Flow [kgmole/hr]
100.0000
<empty>
Comp Mole Frac [CO]
1.0000
0.0000
Comp Mole Frac [H2]
0.0000
1.0000
Comp Mole Frac [H2O]
0.0000
0.0000
Comp Mole Frac [Methane]
0.0000
0.0000
Add a SEPARATOR with the following specifications:
SEPARATOR [SEP-100]
Tab [Page]
Design
[Connections]
Input Area
Entry
Inlets
CO Feed, H2 Feed
Vapour Outlet
Product
Liquid Outlet
Liquid
10-65
10-66
Set
SEPARATOR [SEP-100]
Tab [Page]
Input Area
Entry
Design [Parameters]
Delta P
0 kPa
On the Reactions tab of the Separator property view, add the reaction
set which contains the Conversion Reaction you defined earlier.
Now install a SET operation which sets the Molar Flow of H2 Feed in
stoichiometric proportion to CO Feed.
Figure 10.43
The Flowsheet will immediately solve, giving the following results:
Figure 10.44
In situations where non-pure
streams are being fed to a
reactor, particularly when a
RECYCLE is involved, the
General Balance is the
preferred route.
10-66
Although this example is trivial, this type of application can be useful
when applied to larger problems. For instance, in Flowsheets where
feed(s) to the reactor are recycled, the SET can ensure that their relative
flowrates are always in stoichiometric proportion.
Logical Operations
10.6
10-67
Spreadsheet
Figure 10.45
The SPREADSHEET applies the functionality of Spreadsheet programs
to Flowsheet modelling. With essentially complete access to all process
variables, the SPREADSHEET is extremely powerful and has many
applications in HYSYS.
The SPREADSHEET can be used to manipulate or perform custom
calculations on Flowsheet variables. Because it is an operation,
calculations will be performed automatically; Spreadsheet cells are
updated when Flowsheet variables change.
One application of the SPREADSHEET is the calculation of pressure
drop during dynamic operation of a Heat Exchanger. In the HYSYS Heat
Exchanger, the pressure drop remains constant on both sides regardless
of flow. However, using the Spreadsheet, the actual pressure drop on
one or both sides of the exchanger could be calculated as a function of
flow.
The HYSYS SPREADSHEET
has standard row/column
functionality. You can import
a variable, or enter a number
or formula anywhere in the
spreadsheet.
Complex mathematical formulas can be created, using syntax which is
similar to conventional Spreadsheets. Arithmetic, logarithmic and
trigonometric functions are examples of the mathematical
functionality available in the Spreadsheet. The Spreadsheet also
provides logical programming in addition to its comprehensive
mathematical capabilities. Boolean logic is supported, which allows
you to compare the value of two or more variables using logical
operators, and then perform the appropriate action depending on that
result.
10-67
10-68
Spreadsheet
You may import virtually any variable in the simulation into the
Spreadsheet, and you can export a cell’s value to any specifiable field in
your simulation. There are two ways of importing and exporting
variables to and from the Spreadsheet:
Note that when using the
Dragging Variables method,
the views have to be nonmodal.
Method Import/
Export
Description
Using the Variable
Navigator
On the Connections tab, select the Add Import or
Add Export button. Then using the Variable
Navigator, select the variable you wish to import or
export.
Dragging Variables
Using the secondary mouse button, simply click the
variable value you wish to import, and drag it to the
desired location in the Spreadsheet. If you are
exporting the variable, drag it from the Spreadsheet
to an appropriate location.
When you are using the Spreadsheet to return a result back to the
Flowsheet, you must consider its application in terms of the overall
calculation sequence, particularly when Recycles are involved. If the
Spreadsheet performs a calculation and sends the results back
upstream, the potential exists for creating inconsistencies as the full
effect of the previous Recycle loop has not propagated through the
Flowsheet. By using the Calculation Sequencing option (see Section
7.3.1 - Main Properties of the User’s Guide), you can minimize the
potential for problems of this nature.
To install the SPREADSHEET, choose Add Operation from the
Flowsheet menu, and select Spreadsheet. Alternatively, you could
select the Spreadsheet button in the Palette.
Spreadsheet Button
10.6.1
Spreadsheet Functions
The HYSYS Spreadsheet has extensive mathematical and logical
function capability. To view the available Spreadsheet Functions and
Expressions, select the Function Help button. Note that this Help
Window has three tabs, Mathematical Expressions, Logical
Expressions and Mathematical Functions.
All functions must be preceded by "+" (straight math) or "@"
(special functions - logarithmic, trigonometric, logical, etc.)
Examples are "+A4/B5" and "@ABS(A4-B5)".
10-68
Logical Operations
10-69
General Math Functions
The following arithmetic functions are supported:
General Operations
Method of Application
View
Use the "+" symbol.
Addition
Use the "-" symbol.
Subtraction
Use the "*" symbol.
Multiplication
Division
Use the "/" symbol, typically located on the numeric
keypad, or next to the right SHIFT key. (Do not use the
"\" symbol).
"@Abs".
Absolute Value
Several other mathematical functions are also available:
Advanced
Operations
Method of Application
View
Use the "^" symbol.
Example: +3^3 = 27
Power
Example 2: +27^(1/3)=3. Note that the parentheses
are required in this case, since the cube root of 27
(or 27 to the power of one-third) is desired. See
Calculation Hierarchy (following page).
"@SQRT".
Square Root
Example: @sqrt(16) = 4. Note that capitalization is
irrelevant. You may also use "@RT" to calculate a
square root (Example: @rt(16)=4)
Simply enter "+pi" to represent the number 3.1415...
Pi
Use the "!" symbol. Example: +5!-120=0
Factorial
10-69
10-70
Spreadsheet
Calculation Hierarchy
The usual hierarchy of calculation is used (Brackets, Exponents,
Division and Multiplication, Addition and Subtraction). For example:
+6+4/2 = 8 (not 5)
since division is performed before addition. However,
+(6+4)/2 = 5
because any expressions in parentheses are calculated first.
Logarithmic Functions
Log Function
Method of Application
View
"@ln".
Natural Log
Example: @ln(2.73)=1.004
"@log".
Base 10 Log
Example: @log(1000)=3
"@exp".
Exponential
Example: @exp(3)=20.09
“@sinh”, “@cosh”, “@tanh”.
Hyperbolic
Example: @tanh(2) = 0.964
Trigonometric Functions
All of the trigonometric functions are supported, including inverse and
hyperbolic functions:
Trig Function
Method of Application
“@sin”, “@cos”, “@tan”.
Standard
Example: @cos(pi) =-1 (Radian Angles)
Inverse
“@asin”, “@acos”, “@atan”. In this case, the number
to which the function is being applied must be
between -1 and 1.
Example: @asin(1) = 1.571 (Radian Angles)
10-70
Logical Operations
10-71
Trigonometric functions can be calculated using radian, degree or grad
units, by selecting the appropriate type from the Angles in drop down
in the Current Cell group box.
Note that parentheses are required for all logarithmic and
trigonometric functions. The capitalization is irrelevant; HYSYS will
calculate the function regardless of how it is capitalized.
Logical Operators
The Spreadsheet supports Boolean logic. For example, suppose cell A1
had a value of 5 and cell A2 had a value of 10. Then, in cell A3, you
entered the formula (+A1<A2).
The Spreadsheet would return a value of 1 in cell A3, since the
statement is True (A1 is less than A2). If the value of either cell A1 or A2
changes such that the statement is False, cell A3 will become zero.
You may use the following operators:
Boolean
Method of Application
Equal To
"=="
Not Equal To
"!="
Greater Than
">"
Less Than
"<"
Greater Than or Equal to
">="
Less Than or Equal to
"<="
IF/THEN/ELSE Statements
The general format of IF/THEN/ELSE statements is:
“@if (condition) then (if true) else (if false)”
The condition is a logical expression, such as "B1 == 15".
For example, suppose cell A3 contained the number 6. The statement
“@if (A3>10) then (10) else (A3/2)”
would result in the value 3 being displayed in the cell.
10-71
10-72
Spreadsheet
Figure 10.46
You always need to provide an ELSE clause (IF/THEN
statements are not accepted).
Parentheses are mandatory for IF/THEN/ELSE statements.
10.6.2
Spreadsheet Interface
Importing and Exporting Variables by
dragging
A non-Modal view has a
Minimizing and Maximizing
buttons in the upper-right had
corner, and has a double
border. You can drag variables
outside a non-Modal view.
A Modal view has a ‘pin’ in the
upper-right hand corner, and
has a single border. You
cannot drag variables outside
a Modal view.
Select the pin to convert a
Modal property view to a NonModal view.
10-72
You may drag the contents of any cell in the simulation into the
Spreadsheet. Simply position the pointer on that field, click and hold
the secondary mouse button, and drag the value to any cell in the
Spreadsheet. Note that the window from which you are dragging must
be unpinned (non-modal). The Spreadsheet window is modal by
default.
When you drag to a cell in the Spreadsheet, you will see the "bulls-eye"
cursor. Release the secondary mouse button, and the value will be
dropped in that cell. In the Imported From field in the Current Cell
group box (which appears when the cursor is on an imported cell), you
will see the Object for that particular cell. The Object Variable is
displayed in the Variable field. Every time you make a change to (or
HYSYS re-calculates) a variable you have placed in the Spreadsheet,
your data will be updated appropriately.
Logical Operations
10-73
Figure 10.47
Using the secondary mouse button, drag a variable (in
this case, Feed Molar Flow) to a cell in the
Spreadsheet. You will see the bulls-eye cursor,
indicating that you can transfer the variable to that
location. Release the mouse button and the variable will
be transferred. In the Imported From cell, you can view
the variable source.
This menu is accessed by
clicking the secondary mouse
button.
You can remove an attachment at any time by positioning the pointer
in the appropriate cell, clicking the secondary mouse button and
selecting Disconnect Import/Export.
Figure 10.48
Importing Variables by Browsing
You may also import a variable by positioning the cursor in an empty
field of the Spreadsheet and clicking the secondary mouse button. You
will see the menu as shown in Figure 10.49. Choose Import Variable,
and using the Variable Navigator (see Section 5.2 - Navigation of the
User’s Guide) select the Flowsheet variable you wish to import to the
10-73
10-74
Spreadsheet
Spreadsheet. This method of importing variables is similar to the way
variables are imported on the Connections tab (see below).
Figure 10.49
Exporting Formula Results
If you export into a field
containing a calculated value,
you will get a consistency
error, except in the unlikely
case that the calculated and
exported values are exactly the
same. An export value will
replace a specifiable value.
Variables are exported using the Variable Navigator, or by "dragging"
the variable. You can only export Formula Results, i.e. values that are
displayed in red. There are three ways to export:
• Click and hold the secondary mouse button, and drag to the
location where you want to export the formula result. You will
see a bulls-eye cursor indicating that you may export to the
current location. Note that you can only drag to non-modal
views.
• Click the secondary mouse button and select Export Formula
Result. Using the Variable Navigator, choose where you want
to export the Formula Result.
Figure 10.50
• Define an exported variable on the Connections tab by
selecting the Add Export button and selecting the export
object and variable using the Variable Navigator.
Note that you cannot use the same Spreadsheet cell as both the Target
and Source field in calculations. Similarly, the same Spreadsheet cell
cannot act as the Source for more than one field. To work around this,
type the cell name with the variable you want to export into a new
location in the Spreadsheet, and export the new variable.
10-74
Logical Operations
10-75
Figure 10.51
Because the contents of Cell A1 cannot be both an import and
export, the formula +A1 is entered in Cell B1. Cell B1 is then
exported to the RECYCLE 1 pressure.
Note that when you export a variable from a Spreadsheet cell, that
variable is given the same units as the units of the location to which you
exported it.
For this simple example, you
could use the SET Operation.
For more complex situations,
you must use the Spreadsheet.
For example, suppose you wanted to assign the pressure of stream Feed
to another stream. In cell B1, enter the formula +A1, and then export
the contents of the cell to the pressure cell of the appropriate stream,
using one of the methods outlined above.
View Associated Object
You can view an object associated with a specific cell by clicking the
secondary mouse button, and selecting View Associated Object. For
instance, if you dragged the temperature of a stream from the
WorkSheet into the Spreadsheet, the Associated Object would be that
stream. When you select View Associated Object, you will be taken to
the property view for that Stream. Note that you can also view the
associated object of an imported cell, by double-clicking on that cell.
Figure 10.52
If there is no object associated with the current cell, this menu selection
will be disabled.
10-75
10-76
Spreadsheet
10.6.3
Spreadsheet Tabs
Connections Tab
On the Connections tab, you can add, edit and delete Imports and
Exports. As mentioned earlier, you may also import and export
variables by dragging to and from the Spreadsheet.
To add an import, select the Add Import button, and choose the
variable using the Variable Navigator (For more information, see
Section 5.2 - Navigation of the User’s Guide). In the Cell column, type
or select from the drop down list the Spreadsheet cell to be connected
to that variable. When you move to the Spreadsheet tab, that variable
will appear in the cell you specified.
Figure 10.53
You may edit or delete an import by positioning the cursor in the
appropriate row, and selecting the Edit Import or Delete Import
buttons. Adding, editing and deleting Exports is performed in a similar
manner.
Note that you may also edit the Spreadsheet Name on this tab.
10-76
Logical Operations
10-77
Parameters Tab
Figure 10.54
On this tab of the Spreadsheet property view, you can set the
dimensions of the Spreadsheet and choose a Unit Set.
Spreadsheet
Parameters
Description
Number of Columns
and Rows
You may set the dimensions of the Spreadsheet.
Note that if you set the dimensions of the
Spreadsheet smaller than what is already specified,
you will permanently delete the contents of cells
which are removed. For instance, the contents of cell
A4 will be deleted when you set the Number of Rows
to 3.
Units
You may choose a Unit Set for the Spreadsheet. All
values in the Spreadsheet will be displayed using
units from the set you have chosen (see Section
7.7.5 - Preferences)
Exportable Cells
The Visible Name and
Variable Name columns
display variables which can be
exported. The fact that a
variable appears in this list
does not necessarily mean that
the variable has been
exported.
Prior to explaining how the Exportable cells are created, the difference
between exporting from the Spreadsheet (assigning a value from the
Spreadsheet to a Process Variable) or importing from the Spreadsheet
(accessing a Spreadsheet variable from another object) must be
explained. Results that are exported from the Spreadsheet to a
specifiable process variable can only be connected once, i.e., the same
cell cannot be connected to two process variables.
10-77
10-78
Spreadsheet
However, locations in the program which can import from the
Spreadsheet (e.g. PID CONTROLLER Cascade Source, ADJUST Target
Variable or DataBook Variable) can access any cell, including those
which are being exported to a Flowsheet process variable. The
Exportable Cells list has been created to allow objects which use the
Variable Navigator to access variables associated with the Spreadsheet.
When you access the
Spreadsheet as the Object (e.g.
- through the Variable
Navigator), the contents of the
Visible Name cell will appear
in the Variable List.
The Exportable Cells group box will display all cells which can be
exported (including those which have been exported). The Visible
Name, Variable Name and Variable Type will either display the
information you have specified for the associated cell on the
Spreadsheet itself, or will contain the information appropriate to the
process variable that the cell has been exported to. In the former case,
this information is modifiable; you can change it here or on the
Spreadsheet itself. In the latter, you cannot modify the information as it
is set by the process variable the cell has been exported to. For instance,
if you export a Spreadsheet value to the Separator Valve Opening cell,
the Variable Name and Variable Type will be Valve Opening and
Percent, respectively.
You can edit the Variable Name and Variable Type for all non-exported
variables which appear in the list (Note that Spreadsheet variables
attached to the Controller, Adjusts and Databook are not exported, but
are imported from that Object).
10-78
Logical Operations
10-79
Figure 10.55
There are four
variables in the
Variable List for
SPRDSHT-1
corresponding to
cells B1, B4, and
B7 and D1. Note
that the Variable
Names were added
manually.
When you use the
Variable Navigator
and select
SPRDSHT-1 as the
Object you will see
cells B1, B2, B3,
B4, B5, B7 and D1
in the Variable List.
Formulas Tab
The Formulas tab displays a summary of all the formulas included in
your spreadsheet. The table lists the name of the cell the formula is
located in, the formula and the result of the formula.
Figure 10.56
10-79
10-80
Spreadsheet
Spreadsheet Tab
The Spreadsheet tab, with the labelled rows and columns, is similar to
conventional Spreadsheets.
From this tab, you can import and export variables, disconnect
imports/exports, view associated object views, define formula
expressions, and modify variable names.
Spreadsheet
Function
For More Information
Importing and
Exporting
See Subsections: Importing and Exporting
Variables by dragging, and Importing
Variables by Browsing.
Associated Object
Views
See Subsection: View Associated Object.
Formula
Expressions
See Subsection: Spreadsheet Functions.
Variable Names
See Subsection: Exportable Cells.
Current Cell Group Box
The Current Cell group box will display information specific to the
contents of the highlighted cell. For all cases, the Current Cell location
is displayed.
Cell containing a Formula or non-imported specifiable value
Figure 10.57
The Variable Type sets the
units for the Spreadsheet cell.
For example, the SI units for
Variable Type Area are m2.
10-80
The Variable Type and Variable Name are shown. You may choose a
new Variable Type from the drop down list, and you can edit the
Variable name (see example). Cells containing a formula or a nonimported specifiable value will be automatically added to the Variable
list on the Parameters tab; the Exportable box will be checked.
Logical Operations
10-81
Cell containing an Export
Figure 10.58
The object and variable to which the contents of the cell were exported
are shown. The Exportable box is checked in this case. You cannot
change the Variable Name, since it is a HYSYS default.
Cell containing an Import
Figure 10.59
The object and variable from which the contents of the current cell
were imported are shown. You cannot change the Variable name, since
it is a HYSYS default.
Function Help and Spreadsheet Only
buttons
Selecting the Function Help button allows you to view the available
Spreadsheet Functions and Expressions. Note that this Help Window
has three tabs, Mathematical Expressions, Logical Expressions and
Mathematical Functions. See Section 10.6.1 - Spreadsheet Functions
for more information.
Select the Spreadsheet Only button to view just the Spreadsheet cells in
a separate window. This feature is useful when you have completely set
up the Spreadsheet and you only want to view the cell results.
10-81
10-82
Spreadsheet
10.6.4
Spreadsheet Example
In this example, the Spreadsheet will be used to calculate the Reynold’s
Number for a water stream flowing through a pipe.
Specify the stream as shown here, using the Peng Robinson property
package.
MATERIAL STREAM [Feed]
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
Input Area
Entry
Temperature
30.0000 °C
Pressure
101.3250 kPa
Mass Flow
400.0000 kg/hr
H2O Mole Frac
1.0000
The Reynold’s Number is calculated as follows:
duρ
Re = ---------µ
(10.5)
where: d = Characteristic length (diameter)
u = Fluid velocity
ρ = Fluid density
µ = Fluid viscosity
Add a SPREADSHEET and move to the Spreadsheet tab. The steps
involved in setting up the Spreadsheet shown are described below:
Diameter
All of the text in columns A
and C was entered by typing it
in the appropriate cells. You
may wish to enter this text as
you do the example, to
improve the clarity of your
Spreadsheet.
10-82
The diameter of the pipe is assumed to be 2 cm. In cell B1, enter the
number 0.02. Initially, this number will not have any units. Although it
is not necessary for this example, you can add length units by
positioning the cursor in cell B1, and selecting Length from the
Variable Type drop down. HYSYS then gives that number the default
length units which is dependent on the Unit Set defined on the
Parameters tab. In this case, the default length unit is metres.
Logical Operations
10-83
Figure 10.60
Area
In order to calculate the fluid velocity, the pipe area must be known,
which is:
2
πd
--------4
(10.6)
Enter the following formula into cell D1:
+0.25*pi*b1^2
The diameter is displayed
blue, indicating that it is a
specifiable value. The area is
displayed red, indicating that
it is a formula.
The result of the formula (0.000314159 m2) will be displayed in cell D1.
Again, no units will be displayed unless you add length units by
selecting Area from the Variable Type drop down.
Mass Flow
You will have to import this value from stream Feed. Recall that you can
import variables in one of two ways:
The Mass Flow is displayed in
blue, indicating that it is
specifiable. If you change the
value of the Mass Flow in the
Spreadsheet, it will also
change in the stream from
which it was imported.
• Drag it from the Material Stream View to the Spreadsheet.
• Import it using the Variable Navigator. You can do this by
choosing the Add Import button on the Connections tab, or
by clicking the secondary mouse button on cell B2, and
choosing Import Variable.
10-83
10-84
Spreadsheet
When you have successfully imported the Mass Flow, it will be
displayed in the cell. As well, in the Current Cell group box, HYSYS will
show that the variable is Mass Flow, and was imported from stream
Feed.
Density
Import the Mass Density into cell B3 the same way you imported the
Mass Flow. The density is dependent on the basic stream properties
(temperature and pressure) and is therefore not specifiable. It is
displayed black, indicating that it is a calculated value and cannot be
changed.
Velocity
The velocity can now be calculated as follows:
u = m· ⁄ ( ρA )
(10.7)
where: m· = Mass flowrate
ρ = Density
A = Area
Enter this formula into cell B4:
+(B2/3600)/(B3*D1)
It is necessary to divide the mass flow by 3600 to convert the time unit
from hours to seconds.
Viscosity
Import the Viscosity of stream Feed into cell B5. The Viscosity is a
calculated value and cannot be specified.
Reynold’s Number
The Reynold’s Number can now be calculated by entering the following
formula into cell B7:
+(B1*B4*B3)/(B5/1000)
10-84
Logical Operations
10-85
The viscosity needs to be divided by 1000 to maintain consistent units.
Figure 10.61
The Reynold’s number, which is 8873, is now displayed in cell B7. These
calculations show that the flow is turbulent.
10-85
10-86
10-86
Spreadsheet
Optimizer
11-1
11 Optimizer
11.1 Optimizer ..................................................................................................... 3
11.2 Optimizer View............................................................................................ 4
11.2.1
11.2.2
11.2.3
11.2.4
Variables Tab.......................................................................................... 4
Functions Tab ......................................................................................... 5
Parameters Tab ...................................................................................... 6
Monitor Tab............................................................................................. 8
11.3 Optimization Schemes ............................................................................... 9
11.3.1
11.3.2
11.3.3
11.3.4
11.3.5
11.3.6
Function Setup ....................................................................................... 9
BOX Method......................................................................................... 10
SQP Method..........................................................................................11
Mixed Method........................................................................................11
Fletcher Reeves Method .......................................................................11
Quasi-Newton Method.......................................................................... 12
11.4 Optimizer Tips........................................................................................... 12
11.5 Optimizer Examples ................................................................................. 13
11.5.1 Part I: Solving Multiple UA Exchangers................................................ 13
11.5.2 Part II: Optimizing Overall UA .............................................................. 19
11.6 References ................................................................................................ 21
11-1
11-2
11-2
Optimizer
11.1
11-3
Optimizer
HYSYS contains a multi-variable Steady-State Optimizer. Once your
Flowsheet has been built and a converged solution has been obtained,
you can use the Optimizer to find the operating conditions which
minimize (or maximize) an Objective Function. The object-oriented
design of HYSYS makes the Optimizer extremely powerful, since it has
access to a wide range of process variables for your optimization study.
The Optimizer owns its own Spreadsheet for defining the Objective
function, as well as any constraint expressions to be used. The
flexibility of this approach allows you, for example, to construct
Objective Functions which maximize profit, minimize Utilities or
minimize Exchanger UA. The following terminology is used in
describing the Optimizer.
Terms
Definition
Primary Variables
These are the variables imported from the Flowsheet
whose values are manipulated in order to minimize
(or maximize) the objective function. You set the
upper and lower bounds for all of the primary
variables, which are used to set the search range, as
well as for normalization.
Objective Function
This is the function which is to be minimized or
maximized. There is a great deal of flexibility in
describing the Objective Function; primary variables
may be imported and functions defined within the
Optimizer SpreadSheet, which possesses the full
capabilities of the Main Flowsheet SpreadSheet.
Inequality and Equality Constraint functions may be
defined in the Optimizer SpreadSheet. An example
of a constraint is the product of two variables
satisfying an inequality (e.g. -A*B<K).
The Optimizer is available for
Steady-State calculations
only; it will not run in
Dynamics mode.
Constraint Functions
The Box, Mixed and Sequential Quadratic
Programming (SQP) methods are available for
constrained minimization with inequality constraints.
Only the SQP method can handle equality
constraints.
The Fletcher-Reeves and Quasi-Newton methods
are available for unconstrained optimization
problems.
You have the ability to define not only how the Optimizer Function is
set up, but also how the Optimizer reaches a solution. You may set
parameters such as the Optimization Scheme used, the Maximum
Number of Iterations and the Tolerance.
11-3
11-4
Optimizer View
To invoke the Optimizer, select Optimizer under Simulation in the
Menu Bar, or press F5.
11.2
Optimizer View
Figure 11.1
The Optimizer view contains four tabs, each of which will be detailed in
the following sections.
Refer to Section 5.2.2 Variable Navigator in the
User’s Guide for details of the
Variable Navigator.
Only user-specified variables
can be used as Primary
Variables.
11.2.1
Variables Tab
When you invoke the OPTIMIZER for the first time, the Variables tab of
the Optimizer view appears, as shown in Figure 11.1. On the Variables
tab, you import the primary variables which minimize or maximize the
objective function. Any process variable that is modifiable (userspecified) can be used as a primary variable. New variables are added
via the Variable Navigator. All variables must be given upper and lower
bounds, which are used to normalize the Primary Variable:
x – x low
x norm = ---------------------------x high – x low
The upper and lower bound for each Primary Variable should be
chosen such that a reasonable Flowsheet solution is obtained within
the entire range. For example, assume that the Primary Variable is the
Molar Flow of a stream being fed to the tube side of a heat exchanger. If
11-4
Optimizer
11-5
this Molar Flow is too low, a temperature cross may result in the heat
exchanger, which will stop the Optimizer calculations. In this case, the
lower bound should be chosen such that the temperature cross does
not occur.
11.2.2
Functions Tab
Figure 11.2
For information on using the
Spreadsheet, see Chapter 10 Logical Operations.
To open the Optimizer
SpreadSheet, select the
SpreadSheet button.
The BOX, Mixed and SQP
Methods allow for Inequality
Constraints. Only the SQP
Method incorporates Equality
Constraints.
The Functions tab contains two groups, namely, the Objective
Function and Constraints Functions.
Note that the Optimizer possesses a dedicated Spreadsheet which is
used to develop the Objective function, as well as any Constraint
functions to be used. The Optimizer’s SpreadSheet is identical to the
SpreadSheet operation; process variables can be attached by dragging
and dropping, or using the Variable Navigator. Once the necessary
process variables are connected to the SpreadSheet, you can construct
the Objective Function and any constraints using the standard syntax.
In the Objective function group, specify the Objective Function in the
Objective Function Cell field. The current value of the objective
function is provided. Further, the objective function group is the
location where you can specify (via radio buttons) to minimize or
maximize the objective function.
The Constraint Functions group is where you can specify the left and
right sides of the Constraint function (in the LHS Cell and RHS Cell
columns). Specify the relationship between the left hand and right
hand cell (LHS > RHS, LHS < RHS, LHS = RHS) in the Cond column. The
11-5
11-6
Optimizer View
Constraint Function is multiplied by the Penalty Value in the
Optimization calculations. If you find that a constraint is not being met,
increase the Penalty Value; the higher the Penalty Value, the more
weight that is given to that constraint. The Penalty Value is equal to 1 by
default.
The current values of the Objective Function and the left and right sides
of the Constraint Function cells are displayed in their respective fields.
11.2.3
Parameters Tab
Figure 11.3
The Parameters tab is used for selecting the Optimization Scheme and
defining associated parameters.
Parameters
Primary Variables are
normalized:
Scheme
See Section 11.3 - Optimization Schemes.
Maximum Function
Evaluations
This field sets the maximum number of function
evaluations (not to be confused with the
maximum number of iterations). During each
iteration, the relevant portion of the flowsheet is
solved several times, depending on factors
such as the Optimization Scheme, and number
of primary variables.
Tolerance
HYSYS will determine the change in the
objective function between iterations, as well as
the changes in the normalized primary
variables. Using this information, HYSYS will
determine if the specified tolerance is met.
Maximum Iterations
The maximum number of iterations.
Calculations will stop if the maximum number of
iterations is reached.
x – x low
x norm = ---------------------------x high – x low
All of the methods except the
BOX method use derivatives.
11-6
Description
Optimizer
Shift B ensures that the Shift
interval xShift will never be
zero.
Parameters
Description
Maximum Change /
Iteration
The maximum allowable change in the
normalized primary variables between
iterations. For instance, assume the maximum
change per iteration is 0.3 (this is the default
value). If you have specified molar flow as a
primary variable with range 0 to 200 kgmole/hr,
then the maximum change in one iteration
would be (200)(0.3) or 60 kgmole/hr.
11-7
Derivatives of the objective function and/or
constraint functions with respect to the primary
variables are generally required and are
calculated using numerical differentiation.
In general, it should not be
necessary to change Shift A
and Shift B from their
defaults.
The numerical derivative is calculated from the
following relationship:
x shift = ShiftA∗ x + ShiftB
Some Schemes move all
Primary variables
simultaneously, while others
move them sequentially.
where: x = Perturbed variable
(normalized)
xshift = Shift interval (normalized)
Derivatives are calculated using:
To determine each derivative,
a variable evaluation must be
made in addition to the Main
Flowsheet evaluation which is
done after each iteration
(main step change). Therefore,
if there are two primary
variables, there will be three
function evaluations for every
iteration.
Note that if you have selected
the Mixed Optimizer Scheme,
the Box and SQP methods are
used in sequence - this is the
reason why the Function
Evaluations are reset part way
through the calculations.
Shift A / Shift B
y2 – y1
∂y
----- = ---------------x shift
∂x
where: y2 = The value of the affected
variable corresponding to
x+xshift
y1 = The value of the affected
variable corresponding to x
Prior to each step, the Optimizer needs to
determine the gradient of the optimization
surface at the current location. The Optimizer
moves each primary variable by a value of xShift
(which due to the size of Shift A and Shift B will
be a very small step). The derivative is then
evaluated for every function (Objective and
Constraint) using the values for y at the two
locations of x. From this information and the
Optimizer history, the next step direction and
size are chosen.
11-7
11-8
Optimizer View
11.2.4
Monitor Tab
Figure 11.4
The Monitor tab displays the values of the Objective Function, primary
variables and constraint functions during the Optimizer calculations.
New information is updated only when there is an improvement in the
value of the Objective Function. The constraint values are positive if
inequality constraints are satisfied and negative if inequality
constraints are not satisfied.
There are three buttons that can be seen in the Optimizer view, no
matter which page is being viewed. These include:
11-8
Buttons
Description
Delete
Erases all the current information from the
Optimizer and its Spreadsheet.
Spreadsheet
Accesses the Optimizer’s dedicated
Spreadsheet.
Start/Stop
Starts or stops the Optimizer calculations. An
objective function must be defined prior to the
start of the calculations.
Optimizer
11.3
11.3.1
In general, the primary
variables should not be part of
the Objective Function.
Optimization Schemes
Function Setup
The Optimizer manipulates the values of a set of primary variables in
order to minimize (or maximize) a user-defined Objective Function,
constructed from any number of process variables.
min f ( x 1, x 2, x 3, ..., x n )
xi is a process variable used to
define the Objective Function.
x0i is a primary variable
which is manipulated by the
Optimizer.
yi is a variable used to define
the Constraint Function.
11-9
(11.1)
where: x1,x2,...,xn are process variables.
Each primary variable, x0, will be manipulated within a specified range:
0
xi
0
LowerBound
0
< xi < xi
UpperBound
with i = 1, ..., j
(11.2)
The general equality and inequality constraints are:
c i ( y 1, y 2, y 3, ..., y n ) = 0,
c i ( y 1, y 2, y 3, ..., y n ) ≤ 0,
c i ( y 1, y 2, y 3, ..., y n ) ≥ 0,
i = 1, ..., m 1
with
i = m 1 + 1, ..., m 2
(11.3)
i = m 2 + 1, ..., m
The constraint functions should generally not use the primary
variables.
It is a good idea to manually
manipulate the primary
variables to get a feel for the
appropriate boundaries. Use
the Data Recorder or Case
Study tool for this purpose.
Refer to Section 5.3 DataBook in the User’s Guide.
All primary variables are normalized from the lower bound through the
upper bound. Thus, reasonable lower and upper bounds must be
supplied. Exceedingly high or low variable bounds should obviously be
avoided as they may result in numerical problems when scaling. An
initial starting point must be supplied, and it should be within the
feasible region. Constraints are optional and are not supported by all of
the Optimization Schemes.
If HYSYS fails to evaluate the objective function or any of the constraint
functions, the Optimizer will reduce the incremental step of the last
11-9
11-10
Optimization Schemes
primary variable by a half. The Flowsheet is then recalculated. If the
function evaluation is still unsuccessful, the optimization is stopped.
By Default, the Optimizer is set up to minimize the objective function.
A Maximize radio button is provided on the Functions page if you wish
to maximize an objective function. Internally the Optimizer simply
reverses the sign.
11.3.2
The BOX Method only handles
inequality constraints.
BOX Method
The procedure is loosely based on the "Complex" method of Box1; the
Downhill Simplex algorithm of Press et al.2 and the BOX algorithm of
Kuester and Mize.3
This method is a sequential search technique which solves problems
with non-linear objective functions, subject to non-linear inequality
constraints. No derivatives are required. It handles inequality
constraints but not equality constraints. This method is not very
efficient in terms of the required number of function evaluations. It
generally requires a large number of iterations to converge on the
solution. However, if applicable, this method can be very robust.
Procedure:
11-10
1.
Given a feasible starting point, the program generates an original
"complex" of n+1 points around the centre of the feasible region
(where n is the number of variables).
2.
The objective function is evaluated at each point. The point having
the highest function value is replaced by a point obtained by
extrapolating through the face of the complex across from the high
point (reflection).
3.
If the new point is successful in reducing the objective function,
HYSYS tries an additional extrapolation. Otherwise, if the new
point is worse than the second highest point, HYSYS does a onedimensional contraction.
4.
If a point persists in giving high values, all points are contracted
around the lowest point.
5.
The new point must satisfy both the variable bounds and the
inequality constraints. If it violated the bounds, it is brought to the
bound. If it violated the constraints, the point is moved
progressively towards the centroid of the remaining points until
the constraints are satisfied.
6.
Steps 2 through 5 are repeated until convergence.
Optimizer
11.3.3
11-11
SQP Method
The Sequential Quadratic Programming (SQP) Method handles
inequality and equality constraints.
SQP is considered by many to be the most efficient method for
minimization with general linear and non-linear constraints, provided
a reasonable initial point is used and the number of primary variables
is small.
The implemented procedure is based entirely on the Harwell
subroutines VF13 and VE174. The program follows closely the
algorithm of Powell5.
It minimizes a quadratic approximation of the Lagrangian function
subjected to linear approximations of the constraints. The second
derivative matrix of the Lagrangian function is estimated automatically.
A line search procedure utilizing the "watchdog" technique
(Chamberlain and Powell6) is used to force convergence.
11.3.4
The Mixed Method handles
inequality constraints only.
This method attempts to take advantage of the global convergence
characteristics of the BOX method and the efficiency of the SQP
method. It starts the minimization with the BOX method using a very
loose convergence tolerance (50 times the desired tolerance). After
convergence, the SQP method is then used to locate the final solution
using the desired tolerance.
11.3.5
The Fletcher Reeves
(Conjugate Gradient) Method
does not handle constraints.
Mixed Method
Fletcher Reeves Method
The procedure implemented is the Polak-Ribiere modification of the
Fletcher-Reeves conjugate gradient scheme. The approach closely
follows that of Press et al.2, with modifications to allow for lower and
upper variable bounds. This method is efficient for general
minimization with no constraints. The method used for the onedimensional search can be found in reference 2, listed at the end of this
chapter.
Procedure:
1.
Given a starting point evaluate the derivatives of the objective
11-11
11-12
Optimizer Tips
function with respect to the primary variables.
2.
Evaluate the new search direction as the conjugate to the old
gradient.
3.
Perform one-dimensional search along the new direction until the
local minimum has been reached.
4.
If any variable exceeds its bound, bring it back to the bound.
5.
Repeat steps 1 through 4 until convergence.
11.3.6
The Quasi-Newton Method
does not handle constraints.
The Quasi-Newton method of Broyden-Fletcher-Goldfarb-Shanno
(BFGS) according to Press et al.2 has been implemented. In terms of
applicability and limitations, this method is similar to the of FletcherReeves method. It calculates the new search directions from
approximations of the inverse of the Hessian Matrix.
Method
Unconstrained
Problems
Constrained
Problems:
Inequality
Constrained
Problems:
Equality
Calculates
Derivatives
BOX
X
X
Mixed
X
X
SQP
X
X
FletcherReeves
X
X
Quasi-Newton
X
X
11.4
11-12
Quasi-Newton Method
X
X
X
Optimizer Tips
1.
Reasonable upper and lower variable bounds are extremely
important. This is necessary not only to prevent bad Flowsheet
conditions (e.g. temperature crossovers in Heat Exchangers) but
also because variables are scaled between zero and one in the
optimization algorithms using these bounds.
2.
For the BOX and Mixed methods, the Maximum Change/Iteration
of the primary variables (set on the Parameters page) should be
reduced. A value of 0.05 or 0.1 is more appropriate.
3.
The Mixed method generally requires the least number of function
evaluations (i.e., is the most efficient).
4.
If the Box, Mixed or SQP Methods are not honouring your
constraints, try increasing the Penalty Value on the Functions page
by 3 or 6 orders of magnitude (up to a value similar to the expected
Optimizer
11-13
value of the objective function). In other words, it is helpful to
attempt to get the magnitude of the objective function and penalty
as similar as possible (especially when the Box Method is used).
5.
By default the Optimizer minimizes the objective function. You can
maximize the objective function by choosing the Maximize radio
button on the Functions page. Note, that internally, the Optimizer
multiplies the objective function by minus one for maximization.
11.5
11.5.1
Optimizer Examples
Part I: Solving Multiple UA
Exchangers
The first part of this problem consists of performing UA calculations on
three interdependent exchangers. The inlet stream is fed to a prechilling section, where it is split into two streams. Chilling of the split
feed stream is accomplished by exchanging heat with a parallel set of
heat exchangers. One stream is cooled by a demethanizer overhead
return stream (E-100 Cool In) and the other stream is chilled by a trim
propane refrigerant unit (Valve In) and by heat exchange with a side
reboiler (E-102 Cool In) in a demethanizer column.
Solving single or multiple UA exchangers is a common simulation
problem, where existing exchangers are used under slightly different
operating conditions or applications. In these cases, the engineer has to
determine what potential heat exchange is available from the existing
heat exchangers, which are limited in performance by their design UA
values.
11-13
11-14
Optimizer Examples
PFD
Figure 11.5
The inlet process streams, specifications and required operations are
displayed on the next page. The PR property method is used.
Inlet Process Streams
MATERIAL STREAMS
Tab [Page]
Worksheet
[Conditions]
Worksheet
[Composition]
11-14
Input Area
Feed
E-100 Cool
In
Valve In
E-102 Cool
In
Temperature
20 F
-142 F
120 F
<empty>
Pressure
1000 psia
250 psia
350 psia
251 psia
Molar Flow
2745 lbmole/
hr
1542 lbmole/
hr
<empty>
1640 lbmole/
hr
Methane
Mole Frac
0.7515
0.9073
0.0000
0.2828
Ethane
Mole Frac
0.2004
0.0927
0.0000
0.2930
Propane
Mole Frac
0.0401
0.0000
1.0000
0.1414
i-Butane
Mole Frac
0.0040
0.0000
0.0000
0.1313
n-Butane
Mole Frac
0.0040
0.0000
0.0000
0.1515
Optimizer
11-15
Process Operations
A tee, valve, mixer and three heat exchangers are required for this
process. Input the data as shown in the figures.
Figure 11.6
Figure 11.7
11-15
11-16
Optimizer Examples
Figure 11.8
Heat Exchanger E-100
HEAT EXCHANGER [E-100]
Tab [Page]
Design [Parameters]
Figure 11.9
11-16
Input Area
Entry
Tubeside Delta P
10 psia
Shellside Delta P
10 psia
UA
4.00e+04 Btu/F-hr
Heat Loss/Leak
None
Heat Exchange Model
Weighted
Intervals (E-100 Feed)
10
Intervals (E-100 Cool In)
10
Dew/Bubble Pt (E-100
Cool In)
Inactive
Optimizer
11-17
Heat Exchanger E-101
HEAT EXCHANGER [E-101]
Tab [Page]
Design [Parameters]
Input Area
Entry
Tubeside Delta P
5 psia
Shellside Delta P
1 psia
UA
5.00e+04 Btu/F-hr
Heat Loss/Leak
None
Heat Exchange Model
Weighted
Intervals (E-100 Feed)
10
Intervals (E-100 Cool In)
10
Figure 11.10
Heat Exchanger E-102
HEAT EXCHANGER [E-102]
Tab [Page]
Design [Parameters]
Input Area
Entry
Tubeside Delta P
5 psia
Shellside Delta P
5 psia
UA
3.50e+04 Btu/F-hr
Heat Loss/Leak
None
Heat Exchange Model
Weighted
Intervals (E-100 Feed)
10
Intervals (E-100 Cool In)
10
Dew/Bubble Pt (E-102
Cool In)
Inactive
11-17
11-18
Optimizer Examples
Figure 11.11
Stream Specifications
•
•
•
•
•
Temperature of stream E-102 Out g -40°F
Vapour Fraction stream E-101 Cool Out g 1.00
Temperature of stream E-100 Out g -65°F
Pressure of E-101 Cool Out g 20 psia
Do not check the Dew/Bubble pt. box for E-101 Cool In or E102 Cool In.
Results
The calculated streams are shown below:
Figure 11.12
11-18
Optimizer
11.5.2
11-19
Part II: Optimizing Overall
UA
In this part of the example, the Optimizer will be used to determine the
optimum Tee flow ratio such that the Overall UA is minimized.
It is therefore necessary to delete the individual heat exchanger UA
specs, and replace these with three new specifications:
• The temperature of E-102 Cool In: -85°F.
• The flowrate of Valve In: 495 lbmole/hr.
• The flowrate of E-101 Feed - this is the variable we will
optimize. Initially, it is set to the previous flow rate (1670
lbmole/hr).
Once you have made these specifications, the Flowsheet will solve, and
you will obtain calculated UA’s very close to what you specified in the
first part of this example.
Open the Optimizer, and specify the Primary Variable using the Low
and High Bounds as shown:
Figure 11.13
Import the Exchanger UA’s,
either by using drag and drop
or the Variable Navigator.
Place the UA’s for the Heat
Exchangers E-100, E-101, and
E-102 in cells A1, A2, and A3,
respectively. Enter the formula
+A1+A2+A3 in cell A4, and
enter a zero in cell A5.
The search will be constrained to a range of 1450 lbmole/hr - 1800
lbmole/hr to avoid a temperature cross.
Import the three Heat Exchanger UA’s to the Optimizer SpreadSheet. To
do this, press the SpreadSheet button, and select the Spreadsheet tab.
Import the information as shown below. In cell A4, enter the formula
which will sum the UA’s (Enter the formula +A1+A2+A3). In cell A5,
11-19
11-20
Optimizer Examples
enter 0.0. This will be used in the constraints.
Figure 11.14
On the Functions tab in the Optimizer property view, it is necessary to
define the Objective Function, as well as the Constraint Functions. The
Objective Function is the expression we are trying to minimize, which
in this case is the sum of the Heat Exchanger UA’s.
In the Objective Function Cell, enter A4. The value of the cell will be
displayed in the Objective Function value field. Ensure that the
Minimize radio button is selected.
Figure 11.15
11-20
Optimizer
11-21
It is necessary to enter constraint functions to ensure that the solution
is reasonable. Each Heat Exchanger UA must be greater than zero.
Complete the Constraint Function group as shown above.
On the Parameters tab, use the Mixed scheme, leaving the parameters
at their defaults.
Select the Start button. If you wish, move to the Monitor page and
watch the progress of the Optimizer.
An optimum molar flow of 1800 lbmole/hr is obtained for stream E-101
Feed, corresponding to an overall UA of about 1.43e5 Btu/F-hr. This
compares to the specified value of 1.5e5 Btu/F-hr in the first part of this
example.
11.6
References
1
Box, M.J. "A New method of Constrained Optimization and a
Comparison with other Methods," Computer J., 8, 42-45, 1965.
2
Press, W.H., et al., "Numerical Recipes in C," Cambridge university
Press, 1988.
3
Kuester, J.L. and Mize, J.H., "Optimization Techniques with
FORTRAN," McGraw-Hill Book Co., 1973.
4
Harwell Subroutine Library, Release 10, Advanced Computing Dept.,
AEA Industrial Technology, Harwell laboratory, England, 1990.
5
Powell, M.J.D., "A Fast Algorithm for Non-Linearly Constrained
Optimization Calculations," Numerical Analysis, Dundee, 1977,
Lecture Notes in Math. 630, Springer-Verlag, 1978.
6
Chamberlain R.M. and Powell, M.J.D., "The Watchdog Technique for
Forcing Convergence in Algorithms for Constrained
Optimization," Mathematical Programming Study, 16, 1-17, 1982.
11-21
11-22
11-22
References
Index
A
Absorber Template (Column) 7-17
Adiabatic Efficiency 5-10, 5-13
Adjust 10-3
example 10-11
individual 10-11
maximum iterations 10-9
multiple 10-14
solving methods 10-7
start 10-10
step size 10-8
tolerance 10-8
Adjusted Object 10-4
Air Cooler 3-3
duty 3-4
example 3-9
theory 3-3
Annular Mist 4-16
B
Baghouse Filter 8-15
parameters 8-16
sizing 8-17
Balance 10-15
general 10-27
heat 10-25
mass 10-23
mole 10-21
mole and heat 10-17
types 10-15
Beggs and Brill Correlation 4-14
BOX Method (Optimizer Operation) 11-10
Broyden Method (Adjust) 10-7
C
Col Dynamic Estimates 7-56
Cold Property Specifications (Column) 7-34
Column 7-3
3-phase detection 7-10
acceleration 7-53
advanced solving options 7-30
build environment 7-6–7-8
composition estimates 7-46–7-47
conflicting specifications 7-104
conventions 7-16
convergence 7-25
damping 7-54
design tab 7-22
dynamics tab 7-84
equilibrium error 7-49, 7-105
flowsheet tab 7-74
flowsheet variables 7-76
fluid package 7-4
heat and spec error 7-49, 7-50, 7-102, 7-105
impossible specifications 7-104
initial estimates 7-10
inner loop errors 7-100
input errors 7-102
installation 7-13
operations 7-85
parameters tab 7-44
performance tab 7-64
plots 7-66
poor initial estimates 7-102
property view 7-5
rating tab 7-63
reactions tab 7-78
run / reset buttons 7-21
runner 7-21
running 7-99–7-101
side ops tab 7-59
solver 7-4
solver tolerance 7-31
specifications 7-34–7-43
stream specification 7-43
tee 7-97
theory 7-8
I-1
I-2
transfer basis 7-21, 7-75
troubleshooting 7-101
worksheet tab 7-64
Column Sub-Flowsheet 7-3
relationship with main flowsheet 7-6–7-8
Component Flow Rate Specification (Column) 7-35
Component Fractions Specification (Column) 7-35
Component Ratio Specification (Column) 7-36
Component Recovery Specification (Column) 7-36
Component Splitter 6-16
example 6-20
splits page 6-19
theory 6-17
Compressor 5-3
curves 5-10–5-13
example 5-14
isentropic efficiency 5-4
solution methods 5-3
theory 5-4
Condenser (Column) 7-86
duty 7-88
pressure drop 7-88
subcooling 7-89
Conduction through insulation/pipe 4-26
Cooler 3-11
duty 3-13
example 3-16
pressure drop 3-12
theory 3-11
zones 3-14
Create Column Stream Spec Button 2-6
CSTR 9-4
reactions 9-13
Cutpoint Specification (Column) 7-36
Cyclone 8-5
constraints 8-8
parameters 8-6
sizing 8-7
solids information 8-6
D
Damping Factors
recycle 10-44
Delta Temp Specification
column 7-37
heat exchanger 3-29
LNG exchanger 3-56
Distillation Column Template 7-18
Dittus and Boelter Correlation 4-24
I-2
Draw Rate Specification (Column) 7-37
Duty Ratio Specification (Column) 7-38
Duty Specification
column 7-38
heat exchanger 3-29
Dynamic Estimates Integrator 7-56
E
Energy Stream 2-11
convert to material stream 2-11
Equilibrium Reactor 9-17
Ergun Equation 9-33
Examples
3-Phase Separation 6-9
air cooler 3-9
component splitter 6-20
compressor 5-14
gas cooler 3-16
general balance 1 10-29
general balance 2 10-30
heat balance 10-25
heat exchanger 3-46
individual adjust 10-11
LNG exchanger 3-61
mass balance 10-24
mixer 4-6
mole and heat balance 10-18
mole balance 10-21
multiple recycle 10-54
multiple recycle revisited 10-59
optimizer part I 11-13
optimizer part II 11-19
PFR 9-49
pipe segment 4-30
pump 5-22
relief valve 4-44
set 10-64
shortcut column 6-14
single recycle 10-50
spreadsheet 10-82
valve 4-40
Expander 5-3
curves 5-10–5-13
isentropic efficiency 5-4
solution methods 5-3
theory 5-4
F
Feed Ratio Specification (Column) 7-38
Index
Filters
baghouse 8-15
rotary vacuum 8-12
Fittings Database
modifying 4-32
Fletcher Reeves Method (Optimizer Operation) 1111
G
Gap Cut Point Specification (Column) 7-38
General Balance 10-27
example I 10-29
example II 10-30
ratios 10-27
Gibbs Reactor 9-22
Gregory Aziz Mandhane Correlation 4-15
H
Heat Balance 10-25
example 10-25
Heat Exchanger 3-18
basic model (dynamic rating) 3-25, 3-35
delta pressure 3-39
detailed model (dynamic rating) 3-26, 3-36
dynamic rating 3-25
end point design model 3-21, 3-24, 3-25
examples 3-46
heat balance 3-27
models 3-21
plots 3-45
steady state rating model 3-24
theory 3-19
weighted design model 3-22, 3-26
Heat Exchangers
zones 3-37
Heat Transfer
coefficients 3-38
conductive elements 3-42
convective elements 3-42
PFR 9-34
separator 6-6
tank 6-6
three-phase separator 6-6
Heater 3-11
duty 3-13
pressure drop 3-12
theory 3-11
zones 3-14
Heavy Key (Shortcut Column) 6-12
I-3
Hydrocyclone 8-9
constraints 8-11
parameters 8-10
sizing 8-11
solids information 8-10
I
If/Then/Else Statements 10-71
Input Experts 7-14
Inside Film Convection 4-24
L
Lapple Efficiency Method (Cyclone) 8-6
Leith/Licht Efficiency Method (Cyclone) 8-6
Light Key (Shortcut Column) 6-12
Liquid Flow Specification (Column) 7-39
LMTD
air cooler 3-4, 3-7
heat exchanger 3-19
LNG exchanger 3-57, 3-59
LNG Exchanger 3-49
example 3-61
heat balance 3-55
plots 3-60
M
Main Flowsheet
relationship with column sub-flowsheet 7-3
Manipulated Variables 10-38
Mass Balance 10-23
example 10-24
Material Stream 2-3
Mixed Method (Optimizer Operation) 11-11
Mixer 4-3
example 4-6
Mole and Heat Balance 10-17
example 10-18
Mole Balance 10-21
example 10-21
N
Neural Networks
See Parametric Unit Operation
Normalizing Compositions 2-9
O
OLGAS Correlation 4-16
Operation(s)
I-3
I-4
installing 1-6
property view 1-7
Optimizer 11-3
BOX method 11-10
constrant function 11-5
example part I 11-13
example part II 11-19
fletcher reeves method 11-11
function setup 11-9
maximum iterations 11-6, 11-7
mixed method 11-11
quasi-newton method 11-12
schemes 11-9
shift A/shift B 11-7
SQP method 11-11
tips 11-12
Outside Conduction/Convection 4-25
P
Parametric Unit Operation 10-32
connections 10-32
inputs from data file 10-34
manipulated variables 10-38
parameters 10-37
setup 10-35
targeted variables 10-38
training 10-38
training pairs 10-36
utility data 10-33
Petukov Correlation 4-24
PFR. See Plug Flow Reactor
Physical Property Specification (Column) 7-39
Pipe Material Type 4-22
Pipe Segment 4-7
adding 4-20
calculation modes 4-8
example 4-30
flow calculation 4-10
heat transfer 4-23
length calculation 4-9
material and energy balances 4-10
pressure drop calculation 4-8
removing 4-22
roughness factor 4-22
sizing 4-18
Pipe. See Pipe Segment
Plug Flow Reactor 9-29
catalyst data 9-40
duty 9-33
I-4
example problem 9-49
heat transfer 9-34
physical parameters 9-47
pressure drop 9-33
reaction balance 9-44
reaction extents 9-43
reactions 9-37
sizing 9-45
Polytropic Efficiency 5-10, 5-13
Power Requirement
pump 5-17
Pressure Profile
heat exchanger 3-24
LNG exchanger 3-53
Pump 5-16
curves 5-20
example 5-22
pump efficiency 5-17
pump switch 5-16
theory 5-17
Pump Around 7-61
column specifications 7-40
Q
Quasi-Newton Method (Optimizer Operation) 11-12
R
Reactor 9-3
conversion 9-8
CSTR 9-4
equilibrium 9-17
general 9-4
gibbs 9-22
parameters 9-6
PFR 9-29
Reboil Ratio Specification (Column) 7-40
Reboiled Absorber Template (Column) 7-17
Reboiler (Column) 7-90
duty 7-92
pressure drop 7-92
Recycle 10-40
acceleration 10-44
calculations 10-48
damping factors 10-44
maximum iterations 10-44
multiple recycle example 10-54
multiple recycle example revisited 10-59
single recycle example 10-50
types 10-46
Index
Reflux Ratio Specification (Column) 7-41
Refluxed Absorber Template (Column) 7-18
Relief Valve 4-41
example 4-44
Resistance Equation
rotary vacuum filter 8-14
Rotary Vacuum Filter 8-12
cake properties 8-14
parameters 8-13
resistance equation 8-14
sizing 8-14
Roughness Factor (Pipe) 4-22
S
Secant Method (Adjust) 10-7, 10-11
Separator 6-3
physical parameters 6-6
reaction sets 6-7
theory 6-3
Sequential Quadratic Programming (Optimizer
Operation) 11-11
Set 10-62
example 10-64
Shells
baffles 3-34
diameter 3-33
fouling 3-33
in parallel 3-31
in series 3-31
shell and tube bundle data 3-33
Shortcut Column 6-11
example 6-14
Side Operations Input Expert 7-59
Side Rectifier 7-60
Side Stripper 7-59
Sieder and Tate Correlation 4-25
Simple Filter. See Simple Solid Separator
Simple Solid Separator 8-3
splits page 8-4
Solid Operations
baghouse filter 8-15
cyclone 8-5
hydrocyclone 8-9
rotray vacuum filter 8-12
simple solid separator 8-3
Specifications
active 3-28, 7-26
advanced solving options 7-30
alternate 7-26
I-5
completely inactive 3-28
current 7-26
estimate 3-28, 7-26
fixed and ranged 7-31
heat exchanger 3-27–3-30
LNG Exchanger 3-55
primary and alternate 7-31
property view 7-29
types 7-34
Splits
component splitter 6-19
Simple Solid Separator 8-4
Spreadsheet 10-67
example 10-82
exporting variables 10-68, 10-72, 10-74
general math functions 10-69
importing variables 10-68, 10-72, 10-73
logarithmic functions 10-70
logical operations 10-71
trigonometric functions 10-70
SQP Method. See Sequential Quadratic
Programming
Steady State Mode
terminology 1-4
Stopping/Resetting Column Calculations 7-101
Stream
Column Specifications 7-43
Streams
energy (See Energy Stream)
material (See Material Stream)
T
Tank 6-3
physical parameters 6-6
reaction sets 6-7
theory 6-5
Targeted Variables 10-38
Tear Location (Recycle) 10-49
Tee 4-34
splits 4-35
Tee (Column) 7-97
Tee Split Fraction Specification (Column) 7-41
Templates
3 sidestripper crude column 7-13
4 sidestripper crude column 7-13
absorber 7-17
column 7-14–7-21
distillation 7-18
FCCU main fractionator 7-13
I-5
I-6
liquid-liquid extractor 7-13
reboiled absorber 7-17
refluxed absorber 7-18
three phase distillation 7-14
wet vacuum tower 7-14
Three Phase Distillation
detection of three phases 7-10
three phase theory 7-10
Three-Phase Separator 6-3
example 6-9
physical parameters 6-6
reaction sets 6-7
theory 6-3
Training 10-38
Training Pairs 10-36
Transport Property Specifications (Column) 7-41
Tray Section (Column) 7-93
connections page 7-94
parameters page 7-95
performance page 7-97
pressures page 7-96
side draws page 7-94
Tray Temperature Specification (Column) 7-41
Tubes (Heat Exchanger) 3-34
dimensions 3-34
heat transfer length 3-34
U
UA
heat exchanger 3-23
LNG exchanger 3-57, 3-59
User Property Specification (Column) 7-42
Utility Data 10-33
V
Valve 4-38
example 4-40
Vapour Flow Specification (Column) 7-42
Vapour Fraction Specification (Column) 7-43
Vapour Pressure Specifications (Column) 7-43
W
Wave Flow (Pipe Segment) 4-15
Wegstein Count
recycle 10-43, 10-45
Z
Zones
I-6
cooler/heater 3-14
heat exchanger 3-37
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