(UniSim\256 Design Tutorials and Applications)

(UniSim\256 Design Tutorials and Applications)
Refining Tutorial
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flowsheet appears below.
Figure 2.2
The following pages guide you through building a UniSim Design case
for modeling this process. This tutorial illustrates the complete
construction of the simulation, from selecting a property package and
components, characterizing the crude oil, to installing streams and unit
operations, through to examining the final results. The tools available in
UniSim Design are utilized to illustrate the flexibility available to you.
Before proceeding, you should have read Chapter A - UniSim
Design Tutorials which precedes the Tutorials in this guide.
2.2 Steady State Simulation
2.2.1 Process Description
This example models a crude oil processing facility consisting of a prefractionation train used to heat the crude liquids, and an atmospheric
crude column to fractionate the crude into its straight run products. The
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Steady State Simulation
Main Flowsheet for this process appears in the following figure.
Figure 2.3
Preheated crude (from a preheat train) is fed to the pre-flash drum,
modeled as a Separator, where vapours are separated from the crude
liquids. The liquids are then heated to 650°F in the crude furnace,
modeled as a Heater. The pre-flash vapours bypass the furnace and are
re-combined, using a Mixer, with the hot crude stream. The combined
stream is then fed to the atmospheric crude column for separation.
The crude column is modeled as a Refluxed Absorber, equipped with
three pump-around and three side stripper operations. The Column
sub-flowsheet appears in the figure below.
Figure 2.4
The main column consists of 29 trays plus a partial condenser. The
TowerFeed enters on stage 28, while superheated steam is fed to the
bottom stage. In addition, the trim duty is represented by an energy
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stream feeding onto stage 28. The Naphtha product, as well as the
water stream WasteH2O, are produced from the three-phase
condenser. Crude atmospheric Residue is yielded from the bottom of
the tower.
Each of the three-stage side strippers yields a straight run product.
Kerosene is produced from the reboiled KeroSS side stripper, while
Diesel and AGO (atmospheric gas oil) are produced from the steamstripped DieselSS and AGOSS side strippers, respectively.
The Workbook displays
information about
streams and unit
operations in a tabular
format, while the PFD is
a graphical
representation of the
flowsheet.
The two primary building tools, Workbook and PFD, are used to install
the streams and operations and to examine the results while
progressing through the simulation. Both of these tools provide you
with a large amount of flexibility in building your simulation, and in
quickly accessing the information you need.
The Workbook is used to build the first part of the flowsheet, from
specifying the feed conditions through to installing the pre-flash
separator. The PFD is then used to install the remaining operations,
from the crude furnace through to the column.
2.2.2 Setting Your Session
Preferences
1. Start UniSim Design and create a new case. The Simulation Basis
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Steady State Simulation
Manager view appears.
Figure 2.5
The default Preference
file is named UniSim
Design.prf. When you
modify any of the
preferences, you can
save the changes in a
new Preference file by
clicking the Save
Preference Set button.
UniSim Design prompts
you to provide a name
for the new Preference
file, which you can later
use in any simulation
case by clicking the
Load Preference Set
button.
Your first task is to set your Session Preferences.
2. From the Tools menu, select Preferences.
The Session Preferences view appears.
The most important preference you will set is the unit set. UniSim
Design does not allow you to change any of the default unit sets
listed, however, you can create a new unit set by cloning an existing
one. In this tutorial you will create a new unit set based on the
UniSim Design Field set and customize it.
3. Click the Variables tab, then select the Units page.
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4. In the Available Unit Sets group, select Field.
Figure 2.6
5. Click the Clone button.
A new unit set named NewUser appears and is automatically
selected as the current unit set.
6. In the Unit Set Name field, rename the new unit set to Fielddensity.
You can now change the units for any variable associated with this
new unit set.
7. In the Display Units group, use the vertical scroll bar to find the
Standard Density cell.
The current default unit for Standard Density is lb/ft3. A more
appropriate unit for this example is API_60.
8. Click in the Standard Density cell on lb/ft3.
9. Press the SPACEBAR or the DOWN arrow to open the drop-down
list of available units.
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Steady State Simulation
10. In the unit list, select API_60.
Figure 2.7
11. Repeat steps #8-#10 to change the Mass Density units to API.
Figure 2.8
All commands accessed
via the toolbar are also
available as Menu items.
12. Your new unit set is now defined. Close the Session Preference view
to return to the Simulation Basis Manager view.
2.2.3 Building the Simulation
Selecting Components
Before defining a fluid package in UniSim Design, you will create a
component list for the fluid package. In this example, the component
list contains non-oil components, Light Ends, and hypocomponents. You
must first add the non-oil components and Light Ends from UniSim
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Design pure component library into the component list.
1. Click the Components tab, then click the Add button. The
Component List View view appears.
Figure 2.9
There are a number of ways to select components for your
simulation. One method is to use the matching feature.
Notice that each component is listed in three ways on the Selected
tab:
The Component List View
view contains two tabs. In
this example, the
Selected tab is the only
tab used, because it
contains all the functions
you need to add
components to the list.
Matching Method
Description
SimName
The name appearing within the simulation.
FullName/
Synonym
IUPAC name (or similar), and synonyms for many
components.
Formula
The chemical formula of the component. This is useful
when you are unsure of the library name of a
component, but know its formula.
At the top of each of these three columns is a corresponding radio
button. Based on the selected radio button, UniSim Design will
locate the component(s) that best matches the input you type in
the Match cell.
2. Optional: To rename the component list, click in the Name field at
the bottom of the view and type a new name.
For this tutorial example, you will add the following non-oil
components: H2O, C3, i-C4, n-C4, i-C5 and n-C5.
First, you will add H2O using the match feature.
3. Ensure the Sim Name radio button is selected, and the Show
Synonyms checkbox is checked.
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You can also move to the
Match field by pressing
ALT M.
4. Click in the Match field.
5. Begin typing ‘water’. UniSim Design filters through its library as you
type, displaying only those components that match your input.
Figure 2.10
6. With Water selected, add it to the Current Component List by doing
one of the following:
• Press the ENTER key.
• Click the Add Pure button.
• Double-click on Water.
You can also use the Family Filter to display only those components
belonging to certain families. Next, you will add Propane to the
component list using a Family Filter:
7. Ensure the Match field is empty, and click the View Filter button.
The Filters view appears as shown on the left.
8. On the Filters view, check the Use Filter checkbox to activate the
Family Filter.
Filters view
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9. Check the Hydrocarbons checkbox. The remaining components
are known to be hydrocarbons.
Figure 2.11
On the
Component
View view,
Propane
appears
near the top
of the
filtered list.
The Match feature
remains active when you
are using a family filter,
so you could have also
typed C3 in the Match
field and then added it
to the component list.
10. Double-click Propane to add it to the component list.
Next you will add the remaining Light Ends components i-C4
through n-C5. The following procedure shows you quick way to add
components that appear consecutively in the library list.
11. Click on the first component to be added (in this case, i-C4).
12. Do one of the following:
To select consecutive
components, use the
SHIFT key.
•
To select nonconsecutive components,
use the CTRL key.
•
Hold down the SHIFT key and click on the last component, in
this case n-C5. All components i-C4 through n-C5 are now
selected. Release the SHIFT key.
Click and drag from i-C4 to n-C5. Components i-C4 through to
n-C5 are selected.
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13. Click the Add Pure button. The selected components are
transferred to the Selected Component group.
Figure 2.12
To remove a
component from the
Current Components
List, select it and
click the Remove
button or press the
DELETE key.
The complete list of non-oil components appears in the figure
above.
14. Close the Component List View and Filters views to return to the
Simulation Basis Manager view.
On the Components tab, the Component Lists group now contains
the name of the new component list that you created.
Defining a Fluid Package
In the Simulation Basis Manager view, your next task is to define a fluid
package.
UniSim Design displays the current Environment and Mode in
the upper right corner of the view. Whenever you begin a
new case, you are automatically placed in the Basis
environment, where you can choose the property package
and non-oil components.
The Simulation Basis
Manager allows you to
create, modify, and
otherwise manipulate
fluid
packages
your
UniSim
Design in
has
simulation
case.
Most of
created a fluid
package
the
as withname
this
withtime,
the default
example,
youcan
require
Basis-1. You
only
onethe
fluid
package
change
name
of
for
thisyour
fluidentire
package by
simulation.
typing a new name in
the Name field at the
bottom of the view.
A fluid package contains the components and property methods that
UniSim Design will use in its calculations for a particular flowsheet.
Depending on what is required, a fluid package can also contain other
information, such as a petroleum fluid characterization.
The fluid package for this example will contain the property package
(Peng Robinson), the pure components H2O, C3, i-C4, n-C4, i-C5, n-C5,
and the hypothetical components which are generated in the Oil
characterization.
1. Click the Fluid Pkgs tab, then click the Add button. The Fluid
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Package: Basis-1 view appears.
Figure 2.13
This view is divided into a number of tabs that allow you to supply
all the information necessary to completely define the fluid
package. For this tutorial, however, only the Set Up tab is used.
On the Set Up tab, the currently selected Property Package is
<none>. Before you begin characterizing your petroleum fluid, you
must choose a property package that can handle hypothetical
components.
2. Select the Peng Robinson property package by doing one of the
following:
•
•
•
Type Peng Robinson. UniSim Design finds the match to your
input.
Use the up and down arrow keys to scroll through the list of
available property packages until Peng Robinson is selected.
Use the vertical scroll bar to scroll through the list until Peng
Robinson becomes visible, then click on it.
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The Fluid Package: Basis - 1 view appears as shown below.
Figure 2.14
The Property Pkg indicator now indicates Peng Robinson
is the current property package for this fluid package.
Alternatively, you could have selected the EOSs radio button in the
Property Pkg Filter group. The list would then display only those
property packages that are Equations of State. Peng Robinson
would appear in this filtered list.
If you have multiple fluid
packages and components
lists in a case, you can
use the drop-down list in
the Component List
Selection group to attache
a component list to a
particular property
package.
In the Component List Selection group, you could use the dropdown list to find the name of any component lists you had created
(currently empty).
The View button opens the Component List View view of the
selected component list.
If the selected component list contains components not
appropriate for the selected property package, UniSim
Design opens the Components Incompatible with Property
Package view. On this view, you have the options of UniSim
Design removing the incompatible components from the
component list or changing to a different property package
using the drop-down list or the Cancel button.
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3. Close the Fluid Package: Basis - 1 view to return to the Simulation
Basis Manager view.
Figure 2.15
The list in the Current Fluid Packages group displays the new fluid
package, Basis-1, showing the number of components (NC) and
property package (PP). The new fluid package is assigned by default
to the main flowsheet, as shown in the Flowsheet-Fluid Pkg
Associations group.
Creating Hypocomponents
Your next task is to create and add the hypocomponents to the
component list. In this example, you will characterize the oil (Petroleum
Fluid) using the given Assay data to create the hypocomponents.
Characterizing the Oil
In this section, you will use the following laboratory Assay data:
Bulk Crude Properties
MW
300.00
API Gravity
48.75
Light Ends Liquid Volume Percent
i-Butane
0.19
n-Butane
0.11
i-Pentane
0.37
n-Pentane
0.46
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Steady State Simulation
TBP Distillation Assay
Liquid Volume
Percent Distilled
Temperature (°F)
Molecular Weight
0.0
80.0
68.0
10.0
255.0
119.0
20.0
349.0
150.0
30.0
430.0
182.0
40.0
527.0
225.0
50.0
635.0
282.0
60.0
751.0
350.0
70.0
915.0
456.0
80.0
1095.0
585.0
90.0
1277.0
713.0
98.0
1410.0
838.0
API Gravity Assay
Liq Vol% Distilled
API Gravity
13.0
63.28
33.0
54.86
57.0
45.91
74.0
38.21
91.0
26.01
Viscosity Assay
Liquid Volume
Percent Distilled
Viscosity (cP) 100°F
Viscosity (cP) 210°F
10.0
0.20
0.10
30.0
0.75
0.30
50.0
4.20
0.80
70.0
39.00
7.50
90.0
600.00
122.30
Accessing the Oil Environment
The UniSim Design Oil Characterization procedure is used to convert
the laboratory data into petroleum hypocomponents.
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The Associated Fluid
Package drop-down list
indicates which fluid
package is used for the
oil characterization.
Since there is only one
fluid package, UniSim
Design has made
Basis-1 the Associated
Fluid Package.
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1. On the Simulation Basis Manager view, click the Oil Manager tab.
Figure 2.16
The text on the right side of the view indicates that before entering
the Oil Environment, two criteria must be met:
•
•
at least one fluid package must be present. In this case, only
one fluid package, Basis-1, is selected.
the property package must be able to handle Hypothetical
Components. In our case, the property package is Peng
Robinson, which is capable of handling Hypothetical
components.
Since both criteria are satisfied, the oil is characterized in the Oil
Environment.
2. To enter the Oil Characterization environment, do one of the
following:
Oil Environment icon
The Oil Characterization
view allows you to
create, modify, and
otherwise manipulate
the Assays and Blends
in your simulation case.
For this example, the oil
is characterized using a
single Assay.
•
•
click the Enter Oil Environment button on the Oil Manager
tab.
click the Oil Environment icon on the toolbar.
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Steady State Simulation
The Oil Characterization view appears.
Figure 2.17
In general, three steps must be completed when you are characterizing
a petroleum fluid:
1. Supply data to define the Assay.
2. Cut the Assay into hypothetical components by creating a Blend.
3. Install the hypothetical components into the fluid package.
Defining the Assay
UniSim Design has
given the new Assay
the default name of
Assay-1. You can
change this by typing a
new name in the Name
field.
1. On the Assay tab, click the Add button to create and view a new
Assay. The Assay view appears.
Figure 2.18
When the property view for a new Assay is opened for the first time,
the view contains minimal information. Depending on the Assay
Data Type you choose, the view is modified appropriately. For this
example, the Assay is defined based on TBP data.
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2. From the Assay Data Type drop-down list, select TBP. The view is
customized for TBP data.
Figure 2.19
The next task is to enter the composition of the Light Ends in the
Assay.
3. From the Light Ends drop-down list, select Input Composition.
4. In the Input Data group, select the Light Ends radio button.
5. Ensure that Liquid Volume% is selected in the Light Ends Basis
drop-down list.
6. Click in the Composition cell for i-Butane.
7. Type 0.19, then press the ENTER key. You are automatically
advanced down one cell to n-Butane.
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Steady State Simulation
8. Type the remaining compositions as shown. The total Percent of
Light Ends in Assay is calculated and displayed at the bottom of the
table.
Figure 2.20
Before entering any of the assay data, you must activate the
molecular weight, density, and viscosity curves by choosing
appropriate curve types in the Assay Definition group. Currently,
these three curves are not used.
9. From the Bulk Properties drop-down list, select Used. A new radio
button labeled Bulk Props appears in the Input Data group.
10. From Molecular Wt. Curve drop-down list, select Dependent. A new
radio button labeled Molecular Wt appears in the Input Data
group.
11. From the Density Curve and Viscosity Curves drop-down lists, select
Independent as the curve type. For Viscosity, two radio buttons
appear as UniSim Design allows you to input viscosity assay data at
two temperatures.
Your view now contains a total of seven radio buttons in the Input
Data group. The laboratory data are input in the same order as the
radio buttons appear.
In the next few sections, you will enter the following laboratory assay
data:
•
•
•
•
•
bulk molecular weight and density
TBP Distillation assay data
dependent molecular weight assay data
independent density assay data
independent viscosity assay data (at two temperatures)
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Entering Bulk Property Data
1. Select the Bulk Props radio button, and the bulk property table
appears to the right of the radio buttons.
2. Click in the Molecular Weight cell in the table. Type 300 and press
ENTER. You are automatically advanced down one cell to the
Standard Density cell.
3. In the Standard Density cell, enter 48.75 and press SPACE BAR.
To the right of the cell, a field containing the current default unit
associated with the cell appears. When you defined the new unit
set, you specified the default unit for standard density as API_60,
which appears in the field.
Figure 2.21
4. Since this is the correct unit, press ENTER, and UniSim Design
accepts the density value.
No bulk Watson UOPK or Viscosity data is available for this assay.
UniSim Design provides two default temperatures (100°F and
210°F) for entering bulk viscosity, but these temperature values are
ignored unless corresponding viscosities are provided. Since the
value for bulk viscosity is not supplied, there is no need to delete or
change the temperature values.
Entering Boiling Temperature (TBP) Data
The next task is to enter the TBP distillation data.
1. Click the Calculation Defaults tab.
2. In the Extrapolation Methods group, select Lagrange for each
method using the drop-down lists.
3. Return to the Input Data tab.
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4. Select the Distillation radio button. The corresponding TBP data
matrix appears. UniSim Design displays a message under the
matrix, stating that ‘At least 5 points are required’ before the assay
can be calculated.
5. From the Assay Basis drop-down list, select Liquid Volume.
6. Click the Edit Assay button. The Assay Input Table view appears.
7. Click in the top cell of the Assay Percent column.
8. Type 0 then press ENTER. You are automatically advanced to the
corresponding empty Temperature cell.
9. Type 80 then press ENTER. You are automatically advanced down
to the next empty Assay Percent cell.
10. Repeat steps #8 and #9 to enter the remaining Assay Percent and
Temperature values as shown.
Figure 2.22
11. Click the OK button to return to the Assay property view.
Entering Molecular Weight Data
1. Select the Molecular Wt radio button. The corresponding assay
matrix appears. Since the Molecular Weight assay is Dependent, the
Assay Percent column displays the same values as those you
entered for the Boiling Temperature assay. Therefore, you need only
enter the Molecular Weight value for each assay percent.
2. Click the Edit Assay button and the Assay Input Table view
appears.
3. Click on the first empty cell in the Mole Wt column.
4. Type 68, then press the down arrow key.
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5. Type the remaining Molecular Weight values as shown.
Figure 2.23
6. Click the OK button when you are finished.
Entering Density Data
1. Select the Density radio button. The corresponding assay matrix
appears. Since the Density assay is Independent, you must input
values in both the Assay Percent and Density cells.
2. Using the same method as for the previous assays, enter the API
gravity curve data as shown here.
Figure 2.24
Entering Viscosity Data
1. Select the Viscosity 1 radio button. The corresponding assay
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Steady State Simulation
matrix appears.
2. In the Viscosity Type drop-down list above the assay matrix, ensure
Dynamic is selected.
3. In the Viscosity Curves group, select the Use Both radio button.
The Temperature field is for each of the two viscosity curves.
Click the Edit Assay
button to access the
Assay Input Table.
4. Input the Viscosity 1 assay data as shown here. This viscosity curve
corresponds to Temperature 1, 100°F.
Figure 2.25
5. Select the Viscosity 2 radio button.
6. Enter the assay data corresponding to Temperature 2, 210°F, as
shown.
Figure 2.26
The Assay is now completely defined based on our available data.
7. Click the Calculate button at the bottom of the Assay view. UniSim
Design calculates the Assay, and the status message at the bottom
of the view changes to Assay Was Calculated.
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8. Click the Working Curves tab of the Assay property view to view
the calculated results.
Figure 2.27
UniSim Design has calculated 50 points for each of the Assay
Working Curves.
The plot view can be resized to make the plot
more readable. To re-size
the view, do one of the
following:
• Click and drag the
outside border to the
new size.
• Click the Maximize
icon.
9. To view the Assay data you input in a graphical format, click the
Plots tab. The input curve that appears is dependent on the current
variable in the Property drop-down list. By default, UniSim Design
plots the Distillation (TBP) data. This plot appears below.
Figure 2.28
Maximize icon
The independent (x-axis) variable is the Assay percent, while the
dependent variable is the TBP in °F. You can view any of the other
input curves by selecting the appropriate variable in the Property
drop-down list.
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The remaining tabs in the Assay property view provide access to
information which is not required for this tutorial.
10. Close the Assay view to return to the Oil Characterization view.
Cutting the Assay (Creating the Blend)
Now that the assay has been calculated, the next task is to cut the
assay into individual petroleum hypocomponents.
1. Click the Cut/Blend tab of the Oil Characterization view.
2. Click the Add button. UniSim Design creates a new Blend and
displays its property view.
Figure 2.29
3. In the list of Available Assays, select Assay-1.
4. Click the Add button. There are two results:
•
The Assay is transferred to the Oil Flow Information table.
(When you have only one Assay, there is no need to enter a Flow
Rate in this table.)
• A Blend (Cut) is automatically calculated based on the current
Cut Option.
In this case, the Blend was calculated based on Auto Cut, the
default Cut Option. UniSim Design calculated the Blend based on
the following default values for the boiling point ranges and number
of cuts per range:
•
IBP to 800°F: 25°F per cut, generating [(800-IBP)/25]
hypocomponents
• 800 to 1200°F: 50°F per cut, generating 8 hypocomponents
• 1200 to 1400°F: 100°F per cut, generating 2 hypocomponents
The IBP, or initial boiling point, is the starting point for the first
temperature range. The IBP is the normal boiling point (NBP) of the
heaviest component in the Light Ends, in this case n-Pentane at
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96.9°F. The first range results in the generation of (800-96.9)/25 =
28 hypocomponents. All the cut ranges together result in a total of
28+8+2 = 38 hypocomponents.
5. Click the Tables tab to view the calculated properties of these
hypocomponents.
Figure 2.30
These components could be used in the simulation. Suppose,
however, that you do not want to use the IBP as the starting point
for the first temperature range. You could specify another starting
point by changing the Cut Option to User Ranges. For illustration
purposes, 100°F is used as the initial cut point.
6. Return to the Data tab.
Since the NBP of the
heaviest Light Ends
component is the
starting point for the cut
ranges, these
hypocomponents were
generated on a “lightends-free” basis. That is,
the Light Ends are
calculated separately
and are not included in
these hypocomponents.
7. From the Cut Option Selection drop-down list, select User Ranges.
The Ranges Selection group appears.
8. In the Starting Cut Point field, enter 100°F. This is the starting
point for the first range. The same values as the UniSim Design
defaults are used for the other temperature ranges.
9. In the Cut End point T column in the table, click on the top cell
labeled <empty>. The value you will enter in this cell is the upper
cut point temperature for the first range (and the lower cut point for
the second range).
10. Type 800 then press ENTER.
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11. Enter the remaining cut point temperatures and the number of cuts
values as shown in the figure below.
Figure 2.31
12. Once you have entered the data, click the Submit button to
calculate the Blend based on the current initial cut point and range
values. The message Blend Was Calculated appears in the status
bar.
UniSim Design has
provided the Initial
Boiling Point (IBP) and
Final Boiling Point (FBP).
The IBP is the normal
boiling point (NBP) of
the heaviest component
in the Light Ends (in this
case, n-Pentane). The
FBP is calculated by
extrapolating the TBP
Assay data to 100%
distilled.
13. Click the Tables tab to view the properties of the petroleum
hypocomponents.
Figure 2.32
Use the vertical scroll bar to view the components which are not
currently visible in the Component Physical Properties table.
Viewing the Oil Distributions
1. To view the distribution data, select Oil Distributions from the Table
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Type drop-down list. The Tables tab is modified as shown below.
Figure 2.33
At the bottom of the Cut Input Information group, the Straight Run
radio button is selected, and UniSim Design provides default TBP
cut point temperatures for each Straight Run product. The Cut
Distributions table shows the Fraction of each product in the Blend.
Since Liquid Vol is the current Basis in the Table Control group, the
products are listed according to liquid volume fraction.
These fractions can be used to estimate the product flow rates for
the fractionation column. For example, the Kerosene liquid volume
fraction is 0.129. With 100,000 bbl/day of crude feeding the tower,
the Kerosene production is expected at 100,000 * 0.129=12,900
or roughly 13,000 bbl/day.
If you want, you can investigate other reporting and plotting
options by selecting another Table Type or by viewing information
on the other tabs in the Blend property view.
2. When you are finished, close the Blend view to return to the Oil
Characterization view. Now that the Blend has been calculated,
the next task is to install the oil.
Installing the Oil
The last step in the oil characterization procedure is to install the oil,
which accomplishes the following:
•
•
The petroleum hypocomponents are added to the fluid package.
The calculated Light Ends and Oil composition are transferred to
a material stream for use in the simulation.
1. On the Oil Characterization view, click the Install Oil tab.
2. In the Stream Name column, click in the top blank cell.
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3. Type the name Preheat Crude, then press the ENTER key. UniSim
Design creates a new stream named Preheat Crude in the flowsheet
associated with the fluid package associated with this oil.
Figure 2.34
In this case, there is only one fluid package (Basis-1) and one
flowsheet (the main flowsheet), so the stream is created in the main
flowsheet. UniSim Design assigns the composition of the calculated
oil and light ends to stream Preheat Crude. The properties of the
new stream can be viewed from the Simulation environment.
The characterization procedure is now complete.
4. Return to the Basis environment by clicking the Return to Basis
Environment icon.
5. Click the Components tab of the Simulation Basis Manager view.
Leave Oil Environment
icon
6. Select Component List - 1 from the list in the Component Lists
group. Click the View button to open the component list property
view.
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7. The hypocomponents generated during the oil characterization
procedure now appear in the Selected Components group.
Figure 2.35
Hypothetical
components
are indicated
by a * after
the component
name.
Viewing Component Properties
To view the properties of one or more components, select the
component(s) and click the View Component button. UniSim Design
opens the property view(s) for the component(s) you selected.
Press and hold the CTRL
key to select more than
one component.
1. In the Selected Components list, select H2O and NBP[0]113*.
2. Click the View Component button. The property views for these
two components appear.
Figure 2.36
See Chapter 4 Hypotheticals in the
UniSim Design
Simulation Basis guide
for more information on
cloning library
components.
The Component property view provides you with complete access to
the component information. For pure components like H2O, the
information is provided for viewing only. You cannot modify any
parameters for a library (pure) component, however, UniSim Design
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allows you to clone a library component into a Hypothetical
component, which you can then modify as required.
The petroleum hypocomponent shown here is an example of a
hypothetical component. You can modify any of the parameters
listed for this component. For this example, the properties of the
hypothetical components generated during the oil characterization
are not changed.
3. Close each of these two component property views.
Basis Manager icon
4. The fluid package is now completely defined, so close the
Component List view. The Simulation Basis Manager view should
again be visible; if not, click the Basis Manager icon to access it.
5. Click the Fluid Pkgs tab to view a summary of the new fluid
package.
Figure 2.37
The list of Current Fluid Packages displays the new fluid package,
Basis-1, showing the number of components (NC) and property
package (PP). The fluid package contains a total of 44 components:
•
6 library (pure) components (H2O plus five Light Ends
components)
• 38 petroleum hypocomponents
The new fluid package is assigned by default to the Main Flowsheet,
as shown in the Flowsheet-Fluid Pkg Associations group. Next
you will install streams and operations in the Main Simulation
environment.
2.2.4 Entering the Simulation
Environment
Enter Simulation
Environment icon
1. To leave the Basis environment and enter the Simulation
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environment, do one of the following:
• Click the Enter Simulation Environment button on the
Simulation Basis Manager view.
• Click the Enter Simulation Environment icon.
When you enter the Simulation Environment, the initial view that
appears depends on your current preference setting for the Initial
Build Home View.
Three initial views are available: PFD, Workbook, and Summary.
Any or all of these can be displayed at any time, however, when you
first enter the Simulation Environment, only one appears. For this
example, open the Workbook under the Tools menu or by
pressing CTRL W.
Figure 2.38
There are several things to note about the Main Simulation
Environment. In the upper right corner, the Environment has
changed from Basis to Case (Main). A number of new items are
now available on the menu and toolbar, and the Workbook and
Object Palette are open on the Desktop. These latter two objects
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are described below.
You can toggle the
palette open or closed
by pressing F4, or by
selecting Open/Close
Object Palette from the
Flowsheet menu.
Objects
Description
Workbook
A multiple-tab view containing information regarding the
objects (streams and unit operations) in the simulation
case. By default, the Workbook has four tabs, namely
Material Streams, Compositions, Energy Streams and Unit
Ops. You can edit the Workbook by adding or deleting tabs,
and changing the information displayed on any tab.
Object
Palette
A floating palette of buttons which can be used to add
streams and unit operations.
Also notice that the name of the stream (Preheat Crude) you
created during the Oil characterization procedure appears in the
Workbook, and the white Object Status window at the very bottom
of the environment view shows that the stream has an unknown
pressure. As you specify the conditions of Preheat Crude, the
message displayed in the Object Status window is updated
appropriately. Before specifying the feed conditions, you can view
the stream composition, which was calculated by the Oil
characterization.
Viewing the Feed Composition
1. In the Workbook, click the Compositions tab to view the
composition of the streams.
Figure 2.39
The Light Ends and petroleum hypocomponents are listed by Mole
Fraction. To view the components which are not currently visible,
use the up and down arrow keys or the vertical scroll bar to advance
down the component list.
Before proceeding any further to install streams or unit operations,
save your case.
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2. Do one of the following:
Save icon
If you enter a name that
already exists in the
current directory, UniSim
Design ask you for
confirmation before
over-writing the existing
file.
• Click the Save icon on the toolbar.
• Select Save from the File menu.
• Press CTRL S.
If this is the first time you have saved your case, the Save
Simulation Case As view appears. By default, the File Path is the
cases sub-directory in your UniSim Design directory.
3. In the File Name field, type a name for the case, for example
REFINING. You do not have to enter the *.usc extension; UniSim
Design adds it automatically.
4. Once you have entered a file name, press the ENTER key and
UniSim Design saves the case under the name you gave it. The
Save As view does not appear again unless you choose to give it a
new name using the Save As command.
2.2.5 Using the Workbook
Click the Workbook icon on the toolbar to ensure the Workbook view
is active.
Workbook icon
Specifying the Feed Conditions
In general, the first task in the Simulation environment is to install one
or more feed streams, however, the stream Preheat Crude was already
installed during the oil characterization procedure. At this point, your
current location should be the Compositions tab of the Workbook
view.
1. Click the Material Streams tab. The preheated crude enters the
pre-fractionation train at 450°F and 75 psia.
2. In the Preheat Crude stream, click in the Temperature cell and
type 450. UniSim Design displays the default units for temperature,
in this case °F.
Figure 2.40
When you press ENTER
after entering a stream
property, you are
advanced down one cell
in the Workbook only if
the cell below is
<empty>. Otherwise,
the active cell remains
in its current location.
3. Since this is the correct unit, press the ENTER key. UniSim Design
accepts the temperature. UniSim Design advances to the Pressure
cell.
If you know the stream pressure in another unit besides the default
of psia, UniSim Design will accept your input in any one of a number
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of different units and automatically convert the value to the default.
For example, the pressure of Preheat Crude is 5.171 bar, but the
default units are psia.
4. In the Pressure cell, type 5.171.
5. Press SPACE BAR. The field containing the active cell units
becomes active.
6. Begin typing ‘bar’. The field opens a drop-down list and scrolls to the
unit(s) most closely matching your input.
Figure 2.41
Alternately, you can
specify the unit simply
by selecting the unit in
the drop-down list.
7. Once ‘bar’ is selected, press the ENTER key. UniSim Design accepts
the pressure and automatically converts to the default unit, psia.
8. Click in the Liquid Volume Flow cell, then type 1e5. The stream
flow is entered on a volumetric basis, in this case 100,000 barrel/
day.
9. Press the ENTER key.
If UniSim Design does not
flash the stream, ensure
that the Solver Active
icon in the tool bar is
selected.
The stream is now completely defined, so UniSim Design flashes it
at the conditions given to determine the remaining properties. The
properties of Preheat Crude are shown below. The values you
specified are a different colour (blue) than the calculated values
(black).
Figure 2.42
Solver Active icon
The next task is to install and define the utility steam streams that
will be attached to the fractionation tower later.
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Installing the Utility Steam Streams
1. On the Material Streams tab, click in the header cell labeled
**New**.
UniSim Design accepts
blank spaces within a
stream or operation
name.
2. Type the new stream name Bottom Steam, then press ENTER.
UniSim Design creates the new stream.
3. In the Temperature cell, enter 375°F.
4. In the Pressure cell, enter 150 psia.
Figure 2.43
5. In the Mass Flow cell, enter 7500 lb/hr.
6. Create a new utility stream called Diesel Steam.
7. Define the conditions of this stream as follows:
• Temperature 300°F
• Pressure 50 psia
• Mass Flow 3000 lb/hr.
The Workbook view appears as shown below.
Figure 2.44
Providing Compositional Input
Now that the utility stream conditions have been specified, the next
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Steady State Simulation
task is to input the compositions.
1. Click the Compositions tab in the Workbook. The components are
listed by Mole Fraction by default.
2. In the Bottom Steam column, click in the input cell for the first
component, H2O.
3. Since the stream is all water, type 1 for the H2O mole fraction, then
press ENTER.
The Input Composition for Stream view appears, allowing you to
complete the compositional input.
The Input Composition for Stream view is Modal, indicated by the
absence of the Minimize/Maximize icons in the upper right corner.
Figure 2.45
When a Modal view is visible, you are unable to move outside the
view until you are finish with it, by clicking either the Cancel or OK
button.
The Input Composition for Stream view allows you to specify a
stream composition quickly and easily. The following table lists and
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describes the features available on this view:
Features
Description
Compositional
Basis Radio
Buttons
You can input the stream composition in some
fractional basis other than Mole Fraction, or by
component flows, by selecting the appropriate radio
button before providing your input.
Normalizing
The Normalizing feature is useful when you know the
relative ratios of components (2 parts N2, 2 parts CO2,
etc.) Rather than manually converting these ratios to
fractions summing to one, enter the numbers of parts
for each component and click the Normalize button.
UniSim Design computes the individual fractions to
total 1.0.
Normalizing is also useful when you have a stream
consisting of only a few components. Instead of
specifying zero fractions (or flows) for the other
components, enter the fractions (or the actual flows)
for the non-zero components, leaving the others
<empty>. Click the Normalize button, and UniSim
Design forces the other component fractions to zero.
These are the default
colours; yours can
appear differently
depending on your
settings on the Colours
page of the Session
Preferences view.
Calculation
status/colour
As you input the composition, the component fractions
(or flows) initially appear in red, indicating the final
composition is unknown. These values become blue
when the composition has been calculated. Three
scenarios result in the stream composition being
calculated:
• Input the fractions of all components, including
any zero components, such that their total is
exactly 1.0000, then click the OK button.
• Input the fractions (totalling 1.000), flows or
relative number of parts of all non-zero
components, then click the Normalize button then
the OK button.
• Input the flows or relative number of parts of all
components, including any zero components,
then click the OK button.
This stream is pure water, therefore, there is no need to enter
fractions for any other components.
4. Click the Normalize button and all other component fractions are
forced to zero.
5. Click the OK button. UniSim Design accepts the composition and
you are returned to the Workbook view.
The stream is now completely defined, so UniSim Design flashes it
at the conditions given to determine the remaining properties.
6. Repeat steps #2 to #5 for the other utility stream, Diesel Steam.
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Steady State Simulation
If you want to delete a
stream, move to the
Name cell for the
stream, then press
DELETE. UniSim Design
ask for confirmation of
your action.
7. Click the Material Streams tab. The calculated properties of the
two utility streams appear here.
Figure 2.46
Next, you will learn alternative methods for creating a new stream.
8. To add the third utility stream, do any one of the following:
Material Stream icon
Add Object icon
•
•
•
•
Press F11.
From the Flowsheet menu, select Add Stream.
Double-click the Material Stream icon on the Object Palette.
Click the Material Stream icon on the Object Palette, then click
on the Palette's Add Object icon.
Each of these four methods displays the property view for the new
stream, which is named according to the Auto Naming setting in
your Preferences. The default setting names new material streams
with numbers, starting at 1, and energy streams starting at Q-100.
9. In the stream property view, click in the Stream Name cell and
rename the stream AGO Steam.
10. Press enter.
Both of the temperature
and pressure
parameters are in the
default units, so you do
not need to change the
unit with the values.
11. In the Temperature cell, enter 300.
Do not enter a flow, it is
entered through the
Composition page.
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12. In the Pressure cell, enter 50.
Figure 2.47
13. Select the Composition page to begin the compositional input for
the new stream.
Figure 2.48
14. Click the Edit button. The Input Composition for Stream view
appears.
The current
Composition Basis
setting is set to the
Preferences Default of
Mole Fractions. The
stream composition is
entered on a mass
basis.
15. In the Composition Basis group, select the Mass Flows radio
button.
16. Click in the compositional cell for H2O.
17. Type 2500 for the steam mass flow, then press ENTER. As there
are no other components in this stream, the compositional input is
complete.
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Steady State Simulation
Since only H2O contain
any significant value,
UniSim Design
automatically forces all
other components’ value
to be zero.
18. Click the OK button to close the view and return to the stream
property view.
Figure 2.49
UniSim Design performs a flash calculation to determine the
unknown properties of AGO Steam, as shown by the status indicator
displaying ‘OK’. You can view the properties of each phase using the
horizontal scroll bar in the matrix or by re-sizing the property view.
In this case, the stream is superheated vapour, so no Liquid phase
exists and the Vapour phase is identical to the overall phase. To
view the vapour compositions for AGO Steam, scroll to the right by
clicking the right scroll arrow, or by click and dragging the scroll
button.
The compositions are currently displayed by Mass Flows. You
can change this by clicking the Basis button and choosing
another Composition Basis radio button.
19. Close the AGO Steam property view.
2.2.6 Installing Unit Operations
Now that the feed and utility streams are known, the next task is to
install the necessary unit operations for processing the crude oil.
Installing the Separator
The first operation is a Separator, used to split the feed stream into its
liquid and vapour phases. As with most commands in UniSim Design,
installing an operation can be accomplished in a number of ways. One
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method is through the Unit Ops tab of the Workbook.
1. Click the Workbook icon to ensure the Workbook is the active
view.
Workbook icon
2. Move to the Unit Ops tab.
3. Click the Add UnitOp button. The UnitOps view appears, listing all
available unit operations.
4. In the Categories group, select the Vessels radio button. UniSim
Design produces a filtered list of unit operations, showing only
those in the current category.
Figure 2.50
5. Add the separator by doing one of the following:
•
Select Separator in the list of Available Unit Operations, and
click the Add button or the ENTER key.
• Double-click on Separator.
The property view for the separator appears in the figure below.
Figure 2.51
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Steady State Simulation
UniSim Design provides
the default name V-100
for the separator. The
default naming scheme
for unit operations can be
changed in your Session
Preferences.
A unit operation property view contains all the information defining
the operation, organized into tabs and pages. The Design, Rating,
and Worksheet tabs appear for most operations. Property views for
more complex operations contain more tabs.
Many operations, like the separator, accept multiple feed streams.
Whenever you see a matrix like the one in the Inlets group, the
operation accepts multiple stream connections at that location.
When the matrix is active, you can access a drop-down list of
available streams.
6. Click in the Name field, type PreFlash, then press enter. The status
indicator at the bottom of the view shows that the operation
requires a feed stream.
7. In the Inlets matrix, click in the <<Stream>> cell.
8. Click the down arrow
streams.
Alternatively, you could
have made the
connection by typing the
exact stream name in
the cell, and pressing
ENTER.
to open the drop-down list of available
9. Select Preheat Crude from the list. Preheat Crude appears in the
Inlets matrix, and the <<Stream>> label is automatically moved
down to a new empty cell. The status indicator now displays
‘Requires a product stream’.
Figure 2.52
10. Click in the Vapour Outlet field, or press tab to move to the field.
11. Type PreFlashVap in the field, then press enter. This stream does
not yet exist, so UniSim Design creates this new stream.
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12. Click in the Liquid Outlet field and type PreFlashLiq. UniSim
Design creates another new stream.
Figure 2.53
An Energy stream
could be attached to
heat or cool the vessel
contents, however, for
the purposes of this
example, the energy
stream is not required.
The status indicator displays a green OK message, showing that
the operation and attached streams are completely calculated.
13. Select the Parameters page. The default Delta P (pressure drop)
of zero is acceptable for this example. The Liquid Level is also
acceptable at its default value.
Figure 2.54
Since there is no energy
stream attached to the
separator, no Optional
Heat Transfer
information is required.
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Steady State Simulation
14. To view the calculated outlet streams, click the Worksheet tab.
This is a condensed Workbook displaying only those streams
attached to the operation.
Figure 2.55
15. Now that the separator is completely known, close the PreFlash
view and the UnitOps view, and return to the Workbook view. The
new separator appears on the Unit Ops tab.
Figure 2.56
The matrix shows the operation Name, its Object Type, the
attached streams (Inlet and Outlet), whether it is Ignored, and
its Calculation Level.
Optional Methods for Accessing Property Views
When you click the View UnitOp button, the property view for the
operation occupying the active row in the matrix opens. Alternatively,
by double-clicking on any cell (except Inlet and Outlet) associated
with the operation, you also open its property view.
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You can also open the property view for a stream directly from the Unit
Ops tab of the Workbook. When any of the Name, Object Type,
Ignored or Calc. Level cells are active, the display field at the bottom
of the view displays all streams attached to the current operation.
Currently, the Name cell for PreFlash is active, and the display field
displays the three streams attached to this operation. To open the
property view for one of the streams attached to the separator (such
as Preheat Crude), do one of the following:
•
•
Double-click on Preheat Crude in the display field at the bottom
of the view.
Double-click on the Inlet cell for PreFlash. The property view for
the first listed feed stream opens. In this case, Preheat Crude is
the only feed stream, so its property view also opens.
2.2.7 Using Workbook Features
Before you install the remaining operations, you will examine a number
of Workbook features that allow you to access information quickly and
change how information appears.
Accessing Unit Operations from the Workbook
Return to the Material
Streams tab of the
Workbook.
Any utilities attached to
the stream with the
Workbook active are also
displayed in (and are
accessible through) this
display field.
There are a number of ways to open the property view for an operation
directly from the Workbook besides using the Unit Ops tab.
When your current location is a Workbook streams tab (Material
Streams, Compositions, and Energy Streams tabs), the field at the
bottom of the Workbook view displays the operations to which the
current stream is attached. In this display field, you can click on any
cell associated with the stream.
For example, if you click in any cell for Preheat Crude, the field displays
the name of the operation, PreFlash, to which this stream is attached.
The display field also displays FeederBlock_Preheat Crude, because the
Preheat Crude stream is a boundary stream. To access the property
view for the PreFlash operation, double-click on PreFlash. The operation
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Steady State Simulation
property view appears.
Figure 2.57
Stream Preheat Crude is the current
Workbook location.
The operation to which Preheat Crude is attached appears in this
display field. Double-click the operation name to access its
property view.
Adding a Tab to the Workbook
When the Workbook is active, the Workbook item appears in the UniSim
Design menu bar. This item allows you to customize the Workbook.
In this section, you will create a new Workbook tab that displays only
stream pressure, temperature, and flow.
The four existing tabs are
listed in the Workbook
Tabs area. When you add
a new tab, it is inserted
before the selected tab
(currently Material
Streams). You will insert
the new tab before the
Compositions tab.
1. Do one of the following:
• From the Workbook menu, select Setup.
• Object inspect (right-click) the Material Streams tab in the
Workbook, then select Setup from the menu that appears.
The Workbook Setup view appears.
Figure 2.58
Currently, all
variables appear
with four
significant
figures. You can
change the
display format or
precision of any
Workbook
variables by
clicking the
Format button.
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2. In the Workbook Tabs group list, select Compositions.
3. Click the Add button. The New Object Type view appears.
Figure 2.59
4. Click the + beside Stream, select Material Stream from the
branch, then click the OK button. You return to the Setup view, and
the new tab appears after the existing Material Streams tab.
5. In the Tab Contents Object group, click in the Name field.
6. Change the name of the new tab to P,T,Flow to better describe the
tab contents.
Figure 2.60
The next task is to customize the tab by removing the variables that
are not required.
7. In the Variables group, click on the first variable, Vapour Fraction.
8. Press and hold the CTRL key.
9. Click on the other variables, Molar Flow, Mass Flow, Heat Flow,
and Molar Enthalpy. These four variables are now highlighted.
10. Release the ctrl key.
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Steady State Simulation
If you want to remove
variables from another
tab, you must edit each
tab individually.
11. Click the Delete button to remove them from this Workbook tab.
The finished Setup view appears below.
Figure 2.61
The new tab
now appears
in the list of
Workbook
Tabs in the
same order as
it appears in
the Workbook.
The new tab
displays only
these three
Variables.
12. Click the Close icon to return to the Workbook view and see the
new tab.
Figure 2.62
13. Save your case by doing one of the following:
Save icon
•
•
•
Click the Save icon on the tool bar.
Select Save from the File menu.
Press CTRL S.
2.2.8 Using the PFD
The PFD is the other main view used in UniSim Design. The PFD item
appears in the UniSim Design menu bar whenever the PFD is active.
PFD icon
1. To open the PFD, click the PFD icon on the tool bar. The PFD view
should appear similar to the one shown below, except some stream
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icons may overlap each other.
Figure 2.63
PFD toolbar
Stream/Operation labels
Material
Stream icon
Unit
Operation
icon for a
Separator
As a graphical representation of your flowsheet, the PFD shows the
connections among all streams and operations, also known as ‘objects’.
Each object is represented by a symbol, also known as an ‘icon’. A
stream icon is an arrow pointing in the direction of the flow, while an
operation icon is a graphic representing the actual physical operation.
The object name, also known as a ‘label’, appears near each icon.
The PFD shown above has been rearranged by moving the three utility
stream icons below and to the left of the Separator. To move an icon,
click and drag it to the new location.
You can click and drag either the icon (arrow) itself, or the
label (stream name), as these two items are grouped
together.
Like any other non-modal view, the PFD view can be re-sized by
clicking and dragging anywhere on the outside border.
Size Mode icon
Other things you can do while the PFD is active include the following:
•
•
Zoom Out 25% icon
Display Entire PFD icon
•
•
•
•
Zoom In 25% icon
Access commands and features through the PFD toolbar.
Open the property view for an object by double-clicking on its
icon.
Move an object by click and dragging it to the new location.
Access “pop-up” summary information for an object simply by
placing the cursor over it.
Change an icon's size by clicking the Size Mode icon, clicking on
the icon, and click and dragging the sizing handles that appear
around the icon.
Display the Object Inspection menu for an object by placing the
cursor over it, and right-clicking. This menu provides access to a
number of commands associated with the particular object.
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•
Zoom in and out, or display the entire flowsheet in the PFD
window by clicking the zoom buttons at the bottom left corner of
the PFD view.
Some of these functions are illustrated here; for more information, see
Section 7.24 - PFD in the UniSim Design User Guide.
Calculation Status
Before proceeding, you will examine a feature of the PFD that allows
you to trace the calculation status of the objects in your flowsheet. If
you recall, the status indicator at the bottom of the property view for a
stream or operation displays one of three possible states for the object:
Status
Keep in mind that these
are the UniSim Design
default colours; you can
change the colours in
the Session Preferences.
Description
Red Status
A major piece of defining information is missing from
the object. For example, a feed or product stream is
not attached to a separator. The status indicator is red,
and an appropriate warning message appears.
Yellow Status
All major defining information is present, but the
stream or operation has not been solved because one
or more degrees of freedom is present, for example, a
cooler where the outlet stream temperature is
unknown. The status indicator is yellow, and an
appropriate warning message appears.
Green Status
The stream or operation is completely defined and
solved. The status indicator is green, and an OK
message appears.
When you are in the PFD, the streams and operations are colour-coded
to indicate their calculation status. The inlet separator is completely
calculated, so its normal colours appear. While installing the remaining
operations through the PFD, their colours (and status) changes
appropriately as information is supplied.
The icons for all streams
installed to this point are
dark blue, indicating
they have been flashed.
Heater icon (Red)
A similar colour scheme is used to indicate the status of streams. For
material streams, a dark blue icon indicates the stream has been
flashed and is entirely known. A light blue icon indicates the stream
cannot be flashed until some additional information is supplied.
Similarly, a dark red icon is for an energy stream with a known duty,
while a purple icon indicates an unknown duty.
Installing the Crude Furnace
In this section, you will install a crude furnace. The furnace is modeled
as a Heater.
Cooler icon (Blue)
1. Ensure the Object Palette is visible (if it is not, press F4).
You will add the furnace to the right of the PreFlash Separator, so
make some empty space available by scrolling to the right using the
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horizontal scroll bar.
2. In the Object Palette, click the Heater icon. The cursor changes to
a special cursor, with a black frame and plus (+) symbol attached to
it. The frame indicates the size and location of the operation icon.
3. Position the cursor over the PFD to the right of the separator.
Figure 2.64
Notice the heater has
red status (colour),
indicating that it
requires feed and
product streams.
4. Click to ‘drop’ the heater onto the PFD. UniSim Design creates a
new heater with a default name, E-100.
Next you will change the heater icon from its default to one more
closely resembling a furnace.
5. Right-click the heater icon. The Object Inspect menu appears.
6. Select Change Icon from the menu. The Select Icon view
appears.
Figure 2.65
7. Click the WireFrameHeater5 icon (scroll to the right), then click
the OK button. The new icon appears in the PFD.
Furnace icon
Attach Mode icon
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Steady State Simulation
Attaching Streams to the Furnace
When you are in Attach
mode, you are not able
to move objects in the
PFD. To return to Move
mode, click the Attach
button again. You can
temporarily toggle
between Attach and
Move mode by holding
down the ctrl key.
1. Click the Attach icon on the PFD tool bar to enter Attach mode.
2. Position the cursor over the right end of the PreFlashLiq stream
icon. A small box appears at the cursor tip.
Figure 2.66
At the square connection
point, a pop-up description
appears attached to the
cursor. The pop-up “Out”
indicates which part of the
stream is available for
connection, in this case, the
stream outlet.
3. With the pop-up ‘Out’ visible, click and hold the mouse button. The
white box becomes black, indicating that you are beginning a
connection.
4. Drag the cursor toward the left (inlet) side of the heater. A trailing
line appears between the PreFlashLiq stream icon and the cursor,
and a connection point appears at the Heater inlet.
5. Place the cursor near the connection point of the heater, and the
trailing line snaps to that point. As well, a white box appears at the
cursor tip, indicating an acceptable end point for the connection.
Figure 2.67
6. Release the mouse button, and the connection is made to the
heater inlet.
Break Connection icon
If you make an incorrect
connection:
1. Click the Break
Connection icon on
the PFD toolbar.
2. Move the cursor over
the stream line
connecting the two
icons. A checkmark
attached to the cursor
appears, indicating an
acceptable connection
to break.
7. Position the cursor over the right end of the heater icon. The
connection point and pop-up ‘Product’ appears.
8. With the pop-up visible, click and hold the mouse button. The white
box again becomes black.
9. Move the cursor to the right of the heater. A stream icon appears
with a trailing line attached to the heater outlet. The stream icon
indicates that a new stream is being created.
Figure 2.68
3. Click once to break the
connection.
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10. With the stream icon visible, release the mouse button. UniSim
Design creates a new stream with the default name 1.
11. Create the Heater energy stream, starting the connection from the
bottom left connection point on the Heater icon labeled ‘Energy
Stream’. The new stream is automatically named Q-100, and the
heater now has yellow (warning) status. This status indicates that
all necessary connections have been made, but the attached
streams are not entirely known.
Figure 2.69
12. Click the Attach icon again to return to Move mode.
The heater outlet and energy streams are unknown at this point,
so they appear light blue and purple, respectively.
Modifying Furnace Properties
1. Double-click the Heater icon to open its property view.
2. Click the Design tab, then select the Connections page. The
names of the Inlet, Outlet, and Energy streams appear in the
appropriate fields.
Figure 2.70
3. In the Name field, change the operation name to Furnace.
4. Select the Parameters page.
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Steady State Simulation
5. In the Delta P field, enter 10 psi, then close the view.
Figure 2.71
The Furnace has one available degree of freedom. Either the outlet
stream temperature or the amount of duty in the energy stream can
be specified. In this case, you will specify the outlet temperature.
6. Double-click the outlet stream icon (1) to open its property view.
7. In the Stream Name field, change the name to Hot Crude.
8. In the Temperature field, specify a temperature of 650°F.
Figure 2.72
The remaining degree of freedom in the Furnace has now been
used, so UniSim Design can flash Hot Crude and determine its
remaining properties.
9. Close the view to return to the PFD view. The Furnace now has
green status, and all attached streams are known.
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10. Double-click on the energy stream icon (Q-100) to open its
property view. The required heating duty calculated by UniSim
Design appears in the Heat Flow cell.
11. In the Stream Name cell, rename this energy stream Crude Duty,
then close the property view.
Figure 2.73
Installing the Mixer
In this section, you will install a Mixer operation. The Mixer is used to
combine the hot crude stream with the vapours bypassing the furnace.
The resulting stream is the feed for the crude column.
1. Make some empty space available to the right of the Furnace using
the horizontal scroll bar. Move other objects if necessary.
2. Click the Mixer icon on the Object Palette.
Mixer icon
3. Position the cursor over the PFD to the right of the Hot Crude
stream icon.
4. Click to ‘drop’ the mixer onto the PFD. UniSim Design creates a
new mixer with the default name MIX-100.
5. Press and hold the CTRL key to temporarily enable the Attach mode
while you make the mixer connections (you will not release it until
step #13).
6. Position the cursor over the right end of the PreFlashVap stream
icon. The connection point and pop-up ‘Out’ appears.
Multiple connection
points appear because
the Mixer accepts
multiple feed streams.
7. With the pop-up visible, click and hold the mouse button, then drag
the cursor toward the left (inlet) side of the mixer. Multiple
connection points appear at the mixer inlet.
8. Place the cursor near the inlet area of the mixer, and when the
white box appears at the cursor tip, release the mouse button to
make the connection.
9. Repeat steps #6 to #8 to connect the Hot Crude stream to the
Mixer.
10. Position the cursor over the right end of the mixer icon. The
connection point and pop-up ‘Product’ appears.
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Steady State Simulation
11. With the pop-up visible, click and drag to the right of the mixer. A
white stream icon appears, with a trailing line attached to the mixer
outlet.
12. With the white stream icon visible, release the mouse button.
UniSim Design creates a new stream with the default name 1.
13. Release the ctrl key to leave Attach mode.
14. Double-click on the outlet stream icon 1 to access its property view.
When you created the mixer outlet stream, UniSim Design
automatically combined the two inlet streams and flashed the
mixture to determine the outlet conditions.
15. In the Stream Name cell, rename the stream Tower Feed, then
close the view.
Figure 2.74
16. Double-click the mixer icon, MIX-100. Change the name to Mixer,
then close the view.
Resizing Icons in the PFD
Resize icons in the PFD to make it easier to read.
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1. Resize the PFD view by clicking and dragging the outside border.
Zoom All icon
2. Click the Zoom All icon to fill the PFD window, including any
objects that were not visible previously. A possible view of the
resized PFD appears in the figure below.
Figure 2.75
3. Click the Size Mode icon on the PFD toolbar.
Size Mode icon
4. Click the Furnace icon in the PFD. A frame with sizing handles
appears around the icon.
5. Place the cursor over one of the sizing handles. The cursor changes
to a double-ended sizing arrow.
Figure 2.76
Doubleended sizing
arrow
6. With the sizing arrow visible, click and drag to resize the icon.
7. Click the Size Mode icon again to return to Move mode.
Adding an Energy Stream
In this section, you will add an energy stream. Prior to installing the
column, an energy stream must be created to represent the trim duty
on stage 28 of the main tower.
Energy Stream icon
1. Double-click on the Energy Stream icon on the Object Palette.
UniSim Design creates a new energy stream with the default name
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Steady State Simulation
Q-100 and display its property view.
2. In the Stream Name field, change the name to Trim Duty.
3. Close the view.
4. Save your case by doing one of the following:
•
•
•
Refluxed
Save
iconAbsorber icon
If you choose to use the
pre-built crude column
template you still have
to customize the column
by modifying the various
draw and return stages
and default
specifications. Although
using the template
eliminates the majority
of the work over the
next few pages, it is
recommended that you
work through these
pages the first time you
build a crude column in
UniSim Design. Once
To
this column
youinstall
are comfortable
using
thewith
pre-built
crude
working
the side
column
template:
equipment,
try using the
template.
Instructions
1. Double-click
on the
on Custom
using theColumn
crude icon
column
template
are
on the
Object Palette.
given in an annotation
2. On
view
that
on
thethe
next
page.
appears, click the
Read an Existing
Column Template
button. The Available
Column Templates
view appears, listing
the template files
*.col that are
provided in your
UniSim
Design\template
directory. Both 3- and
4-side stripper crude
column templates are
provided.
3. Select 3sscrude.col
and click the OK
button. The property
view for the new
column appears. You
can now customize the
new column.
press CTRL S.
from the File menu, select Save.
click the Save icon.
Installing the Column
UniSim Design has a number of pre-built column templates that you
can install and customize by changing attached stream names, number
of stages and default specifications, and adding side equipment. One of
these templates is going to be used for this example (a crude column
with three side strippers), however, a basic Refluxed Absorber
column with a total condenser is installed and customized in order to
illustrate the installation of the necessary side equipment.
1. Before installing the column, select Preferences from the UniSim
Design Tools menu. Click the Simulation tab.
2. On the Options page, ensure the Use Input Experts checkbox is
checked, then close the view.
3. Double-click the Refluxed Absorber icon on the Object Palette.
The first page of the Input Expert appears.
Figure 2.77
The Input Expert is a Modal view, indicated by the absence of the
Maximize/Minimize icons. You cannot exit or move outside the
Expert view until you supply the necessary information or click the
Cancel button.
When you install a column using a pre-built template, UniSim Design
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supplies certain default information, such as the number of stages. The
current active field is # Stages (Number of Stages), indicated by the
thick border inside this field. There are some other points worth noting:
•
•
These are theoretical stages, as the UniSim Design default stage
efficiency is one.
If present, the Condenser and Reboiler are considered separate
from the other stages, and are not included in the # Stages
field.
Entering Inlet Streams and Number of Trays
For this example, the main column has 29 theoretical stages.
1. Enter 29 in the # Stages field.
2. Advance to the Optional Inlet Streams table by clicking on the
<<Stream>> cell, or by pressing tab.
3. Click the down arrow
feeds.
to open the drop-down list of available
Figure 2.78
4. Select Tower Feed as the feed stream to the column. UniSim
Design supplies a default feed location in the middle of the Tray
Section (TS), in this case stage 15 (indicated by 15_Main TS).
However, the feed stream needs to enter stage 28.
5. In the Optional Inlet Streams group, click in the Inlet Stage cell for
TowerFeed.
6. Type 28 and press enter, or select 28_Main TS from the dropdown list of stages.
7. Click on <<Stream>> in the same table, which was automatically
advanced down one cell when you attached the Tower Feed stream.
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Steady State Simulation
8. From the Stream drop-down list, select the Trim Duty stream,
which is also fed to stage 28.
Figure 2.79
9. Advance to the Bottom Stage Inlet field by clicking on it or by
pressing tab.
10. In the Bottom Stage Inlet field, click the down arrow
the drop-down list of available feeds.
to open
11. From the list, select Bottom Steam as the bottom feed for the
column.
Entering Outlet Streams
In the Condenser group of the Input Expert view, the default
condenser type is Partial. To the right of this group, there are two
Overhead Outlets, vapour and liquid. In this case, the overhead
vapour stream has no flow, and two liquid phases (hydrocarbon and
water) are present in the condenser. The hydrocarbon liquid product is
attached in the liquid Overhead Outlets field, while the water draw is
attached using the Optional Side Draws table.
Figure 2.80
The water
draw is
attached
using this
table.
Overhead
vapour
product field.
Overhead
liquid
product field.
Although the overhead vapour product has zero flow, do not change the
condenser to Total. At this time, only the Partial radio button allows
you to specify a three-phase condenser.
1. Click in the top Ovhd Outlets field.
2. Enter Off Gas as the name of the overhead vapour product stream.
UniSim Design creates and attaches a new stream with this name.
3. Press tab again to move to the bottom Ovhd Outlets field, and
enter the new stream name Naphtha.
The next task is to attach the water draw stream to the condenser.
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4. In the Optional Side Draws table, click in the <<Stream>> cell.
5. Enter the name of the draw stream, WasteH2O. UniSim Design
automatically places a hydrocarbon liquid (indicated by the L in the
Type column) draw on stage 15. You will change this to a
condenser water draw.
6. Click on the Type cell (the L) for the WasteH2O stream.
7. Specify a water draw by typing W then pressing enter, or by
selecting W from the drop-down list.
8. Click on the Draw Stage cell (15_Main TS) for the WasteH2O
stream.
9. Select Condenser from the drop-down list. The condenser is now
three-phase.
Figure 2.81
10. In the Column Name field, enter Atmos Tower.
11. In the Bottoms Liquid Outlet field, type Residue to create a new
stream.
12. In the Condenser Energy Stream field, type Cond Duty to define
a new stream. Press ENTER.
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Steady State Simulation
All stream attachments
made on this page
result in the creation of
Column sub-flowsheet
streams with the same
names. For example,
when the Main
Flowsheet stream
BottomSteam was
attached as a feed,
UniSim Design
automatically created
an identical stream
named BottomSteam to
be used in the Column
sub-flowsheet.
The first page of the Input Expert should appear as shown below.
Figure 2.82
The Next button now becomes available, indicating sufficient
information has been supplied to advance to the next page of the
Input Expert.
13. Click the Next button to advance to the Pressure Profile page.
Entering the Initial Estimate Values
1. On
•
•
•
the Pressure Profile page, specify the following:
Condenser Pressure 19.7 psia
Condenser Pressure Drop 9 psi
Bottom Stage Pressure 32.7 psia
Figure 2.83
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2-65
2. Click the Next button to advance to the Optional Estimates page.
Although UniSim Design does not usually require estimates to
produce a converged column, good estimates result in a faster
solution.
3. Specify the following:
•
•
•
Condenser 100°F
Top Stage 250°F
Bottom Stage 700°F
Figure 2.84
4. Click the Next button to advance to the fourth and final page of the
Input Expert. This page allows you to supply values for the default
column specifications that UniSim Design has created.
In general, a refluxed absorber with a partial condenser has two
degrees of freedom for which UniSim Design provides two default
specifications. For the two specifications given, overhead Vapour
Rate is used as an active specification, and Reflux Ratio as an
estimate only.
5. From the Flow Basis drop-down list, select Volume. All flow
specifications are provided in barrels per day.
6. Specify the following:
•
Vapour Rate 0
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Steady State Simulation
•
Reflux Ratio 1.0.
Figure 2.85
7. Click the Done button. The Column property view appears.
Figure 2.86
Adding Specification Values
1. On the Design tab, select the Monitor page.
The main feature of this page is that it displays the status of your
column as it is being calculated, updating information with each
iteration. You can also change specification values, and activate or
de-activate specifications used by the Column solver, directly from
this page.
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The basic column has
three available degrees
of freedom. Currently,
two Specifications are
Active, so the overall
Degrees of Freedom is
one. The number of
available degrees of
freedom increases with
the addition of side
equipment.
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The current Degrees of Freedom is one, indicating that only two
specifications are active. As noted earlier, a Refluxed Absorber with
a partial condenser has two degrees of freedom and, therefore,
requires two active specifications. In this case, however, a third
degree of freedom was created when the Trim Duty stream was
attached as a feed, for which the heat flow is unknown. UniSim
Design has not made a specification for the third degree of
freedom, therefore you need to add a water draw spec called
WasteH2O Rate to be the third active specification.
2. Select the Specs page. Here you will remove two specifications and
add one new specification.
3. In the Column Specifications group, select Reflux Rate and then
click the Delete button.
4. Delete the Btms Prod Rate specification also.
5. Next you will add the WasteH2O Rate specification. Click the Add
button. The Add Specs view appears.
6. Select Column Draw Rate and click the Add Spec(s) button. The
Draw Spec property view appears.
The Draw Spec is
entered so that the
degrees of freedom is
kept at zero throughout
this tutorial. It is good
practice to keep the
degrees of freedom at
zero as you modify your
column so that you can
solve the column after
every modification.
7. In the Name cell, type WasteH2O Rate. No further information is
required as this specification is de-activated and only estimated
when you run the column.
Figure 2.87
8. Close the view. The new specification appears in the Column
Specifications group. The Degrees of Freedom is now zero.
9. Select the Connections page. See Figure 2.86.
The Connections page is similar to the first page of the Input
Expert. Currently, the column is a standard type, so this page
shows a column schematic with the names of the attached streams.
When the side equipment is added to the column, the page
becomes non-standard. There are a large number of possible nonstandard columns based on the types and numbers of side
operations that are added. Therefore, UniSim Design modifies the
Connections page into a tabular format, rather than a schematic
format, whenever a column becomes non-standard. In the next
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Steady State Simulation
section you will add the side equipment and observe how the
Connections page is modified.
Installing the Side Strippers
1. Click the Side Ops tab of the Column property view.
Figure 2.88
When you install side
equipment, it resides in
the Column subflowsheet. You can build
a complex column in the
sub-flowsheet while in
the Main Flowsheet, the
column appears as a
single operation. You
can then transfer any
needed stream
information from the
sub-flowsheet by simply
attaching the stream to
the Main Flowsheet.
On this tab, you can Install, View, Edit, or Delete all types of Side
Equipment. The table displays summary information for a given
type of side operation, depending on the page you are currently on.
2. Ensure that you are on the Side Strippers page.
3. Click the Add button. The Side Stripper view appears.
Figure 2.89
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Refining Tutorial
This is a reboiled 3stage stripper with a
0.75 boil up ratio, so
leave the
Configuration radio
button at Reboiled, and
the k = and Boil Up
Ratio fields at their
defaults.
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4. In the Name field, change the name to KeroSS.
5. In the Return Stage drop-down list, select stage 8 (8_Main TS).
6. In the Draw Stage drop-down list, select stage 9 (9_Main TS).
7. In the Flow Basis group, select the Std Ideal Vol radio button.
8. In the Product Stream field, enter Kerosene.
The straight run product distribution data calculated during the Oil
Characterization appears in the figure below.
Figure 2.90
Kerosene
Liquid
Volume
Fraction
The Kerosene liquid volume fraction is 0.129. For 100,000 bbl/day
of crude fed to the tower, Kerosene production can be expected at
100,000 * 0.129 = 12,900 or approximately 13,000 bbl/day.
9. In the Draw Spec field, enter 13000. The completed Side
Stripper view appears below.
Figure 2.91
10. Click the Install button, and a view summarizing your input
appears.
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Steady State Simulation
11. Click the Close icon to return to the Column property view.
Summary information for the new side operation appears in the
table on the Side Ops tab.
Close icon
Figure 2.92
12. Use the previous steps to install the two remaining side strippers
DieselSS and AGOSS. These are both Steam Stripped, so choose
the appropriate Configuration radio button and create the Steam
Feed and Product streams as shown in the following figures. The
@COL1 suffix is added automatically.
The completed DieselSS and AGOSS side stripper views appear
in the following figure.
Figure 2.93
Although not a requirement, the names of the Steam Feed
streams created for these side strippers are identical to the
names of the utility steam streams that were created
previously in the Main Flowsheet. The conditions of these
Steam Feed streams, which reside in the Column subflowsheet, are unknown at this point. The conditions of the
Main Flowsheet streams are duplicated into these subflowsheet streams when the stream attachments are
performed.
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The completed Side Stripper Summary table appears below.
Figure 2.94
13. Click the Design tab and select the Monitor page.
The Specifications table on this page has a vertical scroll bar,
indicating that new specifications have been created below the
default ones. Resize the view to examine the entire table.
14. Click and drag the bottom border of the view down until the scroll
bar disappears, making the entire matrix visible.
Figure 2.95
The addition of the side
strippers has created
four more degrees of
freedom above the basic
column, resulting in a
total of seven available
degrees of freedom.
Currently, however,
seven Specifications are
Active, so the overall
Degrees of Freedom is
zero.
The installation of the side strippers created four additional degrees
of freedom, so UniSim Design created a Prod Flow (product flow)
specification for each side stripper, plus a BoilUp Ratio
specification for the Kerosene side stripper. The new specifications
were automatically made Active to exhaust the four degrees of
freedom, returning the overall Degrees of Freedom to 0.
Installing the Pump Arounds
1. Click the Side Ops tab and select the Pump Arounds page.
2. Click the Add button. The initial Pump Around view appears.
3. In the Return Stage drop-down list, select stage 1 (1_Main TS).
4. In the Draw Stage drop-down list, select stage 2 (2_Main TS).
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Steady State Simulation
5. Click the Install button, and a more detailed Pump Around view
appears.
Figure 2.96
Each cooled pump around circuit has two specifications associated
with it. The default Pump Around Specifications are circulation
rate and temperature drop (Dt) between the liquid draw and liquid
return. For this example, the Dt specification is changed to a Duty
specification for the pump around cooler. The pump around rate is
50,000 bbl/day.
6. In the empty cell under the PA_1_Rate(Pa) specification, enter
5e4.
7. Double-click in the blank space under the PA_1_Dt(Pa)
specification, and the Spec view appears.
8. In the Spec Type drop-down list, select Duty.
Notice the negative sign
convention indicates
cooling.
9. in the Spec Value cell, enter -55e6.
Figure 2.97
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2-73
10. Click the Close icon to return to the Pump Around view.
Figure 2.98
The remainder of the information on the above view is calculated by
the Column solver.
11. Click the Close icon on the main Pump Around view to return to
the Column property view.
1. Click the Add
button.
2. Specify the Return
Stage and Draw
Stage.
3. Click the Install
button. The second
view appears.
12. Repeat the previous steps to install the two remaining pump
arounds. Enter Rate specifications of 3e4 barrel/day and Duty
specifications of -3.5e7 Btu/hr for both of these pump arounds.
The completed Pump Around views and Liquid Pump Around
Summary table appear in the following figures.
Figure 2.99
4. Specify the 1st
Active spec.
5. Double-click the
empty cell in the 2nd
Active spec.
6. Select Duty from the
Spec Type dropdown list.
7. Enter the Spec
Value.
8. Close the view.
Figure 2.100
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Steady State Simulation
13. Click the Design tab and select the Monitor page. Re-size the
property view again so the entire Specifications table is visible.
Figure 2.101
The addition of the
pump arounds has
created six more
degrees of freedom,
resulting in a total of
13 available degrees of
freedom. Currently, 13
Specifications are
active, so the overall
Degrees of Freedom is
zero.
The addition of each pump around created two additional degrees of
freedom. As with the side strippers, the specifications for the pump
arounds have been added to the list and were automatically
activated.
14. Select the Connections page.
Figure 2.102
The Connections page of a standard refluxed absorber property
view is essentially identical to the first page of the refluxed absorber
Input Expert, with a column schematic showing the feed and
product streams. Side equipment have been added to the standard
refluxed absorber, however, making the column non-standard. The
Connections page has therefore been modified to show tabular
summaries of the Column Flowsheet Topology (i.e., all
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equipment), Feed Streams, and Product Streams.
The column has 40 Total Theoretical Stages:
• 29 in the main tray section
• 1 condenser for the main column
• 9 in the side strippers (3 side strippers with 3 stages each)
• 1 reboiler for the Kerosene side stripper
This topology results in 4 Total Tray Sections—one for the main
column and one for each of the three side strippers.
Completing the Column Connections
When the stream attachments were made on the initial page of the
Input Expert, UniSim Design automatically created Column subflowsheet streams with the same names. For example, when Bottom
Steam was attached as a column feed stream, UniSim Design created
an identical sub-flowsheet stream named Bottom Steam. In the Inlet
Streams table on the Connections page, the Main Flowsheet stream
is the External Stream, while the sub-flowsheet stream is the
Internal Stream.
Figure 2.103
If you scroll down the list of Inlet Streams, notice that the two side
stripper steam streams, DieselSteam and AGOSteam, are Internal
and External, meaning that these streams are attached to the Main
Flowsheet streams that were created earlier.
For the purposes of this tutorial, it is not required to export the pump
around duty streams PA_1_Q, PA_2_Q, and PA_3_Q to the Main
Flowsheet, so their External Stream cells remain undefined.
Adding Column Specifications
Select the Monitor page of the Column property view.
The current Degrees of Freedom is zero, indicating the column is
ready to be solved. Before you run the column, however, you will have
to replace two of the active specifications, Waste H2O Rate and
KeroSS BoilUp Ratio, with the following new ones:
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•
•
Overflash specification for the feed stage (Tray Net Liquid Flow
specification)
Kerosene side stripper reboiler duty specification
Adding the Overflash Specification
1. On the Design tab, move to the Specs page.
Figure 2.104
2. In the Column Specifications group, click the Add button. The
Add Specs view appears.
3. Select Column Liquid Flow as the Column Specification Type.
4. Click the Add Spec(s) button, and the Liq Flow Spec view
appears.
5. Change the name from its default to Overflash.
6. In the Stage cell, select 27_Main TS from the drop-down list of
available stages.
A typical range for the Overflash rate is 3-5% of the total feed to the
column. In this case, the total feed rate is 100,000 barrels/day. For
the Overflash specification 3.5%, or 3,500 barrels/day is used.
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7. In the Spec Value cell, enter 3500.
Figure 2.105
8. Close the view to return to the Column property view. The new
specification appears in the list of Column Specifications group on
the Specs page.
Adding the Duty Specification
1. Click the Add button again to add the second new specification.
2. Select Column Duty as the Column Specification Type, then click
the Add Spec(s) button. The Duty Spec view appears.
3. In the Name cell, change the name to Kero Reb Duty.
4. In the Energy Stream cell, select KeroSS_Energy @COL1 from
the drop-down list.
5. In the Spec Value cell, enter 7.5e6 (Btu/hr).
Figure 2.106
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6. Close the view to return to the Specs page of the Column property
view. The completed list of Column Specifications is shown in the
figure below
Figure 2.107
Running the Column
1. Select the Monitor page to view the Specifications matrix.
The Degrees of Freedom is again zero, so the column is ready to
be calculated, however, a value for the distillate (Naphtha) rate
specification must be supplied initially. In addition, there are some
specifications which are currently Active that you want to use as
Estimates only, and vice versa.
Make the following final changes to the specifications:
2. In the Specified Value cell for the Distillate Rate specification,
enter 2e4 (barrel/day).
3. Activate the Overflash specification by clicking its Active
checkbox.
4. Activate the Kero Reb Duty specification.
5. Activate the Vap Prod Rate specification.
6. Deactivate the Reflux Ratio specification.
7. Deactivate the Waste H2O Rate specification.
If the column begins to
run on its own before you
click the Run button, click
the Stop button and
continue activating or
deactivating
specifications.
8. Deactivate the KeroSS BoilUp Ratio specification.
UniSim Design begins calculations and the information displayed on
the page is updated with each iteration. The column converges as
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shown in the figure below.
Figure 2.108
This matrix displays the
Iteration number, Step size,
Equilibrium error and Heat/
Spec error.
The column temperature profile is shown
here. You can view the pressure or flow
profiles by picking the appropriate radio
button.
The status indicator has changed from Unconverged to Converged.
The converged temperature profile is currently displayed in the
upper right corner of the view. To view the pressure or flow profiles,
select the appropriate radio button.
9. Click on the Performance tab, then select the Column Profiles or
Feed/Products page to see a more detailed stage summary.
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The Column Profiles page appears below.
Figure 2.109
In the Basis group near the top of the view, select the Liq Vol radio
button to examine the tray vapour and liquid flows on a volumetric
basis.
Viewing Boiling Point Profiles for the
Product Stream
You can view boiling point curves for all the product streams on a single
graph:
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1. On the Performance tab, click on the Plots page.
Figure 2.110
2. In the Assay Curves group, select Boiling Point Assay.
3. Click the View Graph button, and the Boiling Point Properties
view appears.
Figure 2.111
No data is plotted
on the graph,
since there is
currently No Tray
Attached, as
shown in the title
bar.
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4. Click the Profile Data Control button, and the Data Control view
appears as shown below.
Figure 2.112
You can view boiling
point properties of a
single tray or multiple
trays. The boiling point
properties of all stages,
from which products are
drawn, are important for
this Tutorial.
5. Select the Multi Tray radio button in the Style group. The Data
Control view is modified, showing a matrix of column stages with a
checkbox for each stage.
6. Activate the following stages by clicking on the corresponding
checkboxes:
• Condenser (Naphtha product stage)
• 29_Main TS (Residue)
• KeroSS_Reb (Kerosene)
• 3_DieselSS (Diesel)
• 3_AGOSS (AGO)
The TBP profile for the light liquid phase on each stage can be
viewed, on a liquid volume basis.
7. Select TBP in the drop-down list under the tray matrix in the Style
group.
8. In the Basis group, select the Liquid Vol radio button.
9. Activate the Light Liquid checkbox in the Phase group to activate
it.
10. Leave the Visible Points at its default setting of 15 Points. You
can display more data points for the curves by selecting the 31
Points radio button.
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The independent (xaxis) variable is the
Assay Volume Percent,
while the dependent (yaxis) variable is the TBP
in °C.
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The completed Data Control view is shown below.
Figure 2.113
11. Click on the Close icon
to close the Data Control view. You return
to the Boiling Point Properties view, which now displays the TBP
curves.
12. Make the Boiling Point Properties view more readable by clicking
the Maximize icon in the upper right corner of the view, or by
clicking and dragging its border to a new view size.
Move the graph legend
by double-clicking inside
the plot area, then click
and drag the legend to
its new location.
The Boiling Point Properties view is shown below.
Figure 2.114
PFD icon
13. When you are finished viewing the profiles, click the Close icon.
Workbook icon
Column Runner icon
Moving to the Column Sub-Flowsheet
When considering the column, you might want to focus only on the
column sub-flowsheet. You can do this by entering the column
environment.
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1. Click the Column Environment button at the bottom of the column
property view.
2. While inside the column environment, you might want to:
•
•
view the Column sub-flowsheet PFD by clicking the PFD icon.
view a Workbook of the Column sub-flowsheet objects by
clicking the Workbook icon.
• access the “inside” column property view by clicking the
Column Runner icon. This property view is essentially the
same as the “outside”, or Main Flowsheet, property view of the
column.
The Column sub-flowsheet PFD is shown below.
Figure 2.115
Maximize icon
Zoom All icon
Customizing the Column PFD
You can customize the PFD shown above by re-sizing the column and
“hiding” some of the column trays to improve the overall readability of
the PFD. To hide some of the trays in the main column:
1. Click the PFD icon to ensure the column PFD is active.
2. Click the Maximize icon in the upper right corner of the PFD view
to make it full-screen.
3. Click the Zoom All icon at the bottom left of the PFD view to fill the
re-sized PFD view.
4. Object inspect (right-click) the main column tray section and the
object inspection menu appears.
Object Inspect menu
5. Select Show Trays from the object inspection menu. The Stage
Visibility view appears.
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6. Select the Selected Expansion radio button.
7. Click the Check All button.
8. Hide stages 4, 5, 6, 11, 12, 13, 14, 24, 25, and 26 by deactivating
their Shown checkboxes.
Figure 2.116
9. Click the Close icon on the Stage Visibility view to return to the
PFD. The routing of some streams in the PFD can be undesirable.
You can improve the stream routing by completing the next step.
10. From the PFD menu item, select Auto Position All, and UniSim
Design rearranges the PFD in a logical manner.
Size icon
Enlarge Icon
The next task in customizing the PFD is to enlarge the icon for the main
column:
1. Click on the icon for the main tray section (Main TS).
2. Click the Size icon on the PFD button bar, and a frame with eight
sizing handles appears around the tray section icon.
3. Place the cursor over the handle at the middle right of the icon, and
the cursor changes to a double-ended sizing arrow.
4. With the sizing cursor visible, click and drag to the right. An outline
appears, showing what the new icon size is when you complete the
next step.
5. When the outline indicates a new icon size of about 1.5 to 2 times
the width of the original size, release the button. The tray section
icon is now re-sized.
6. Click the Size icon again to return to Move mode.
The final task is to customize the PFD by moving some of the
streams and operation labels (names) so they do not overlap. To
move a label:
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7. Click on the label you want to move.
8. Right-click and select Move/Size Label.
9. Move the label to its new position by clicking and dragging it, or by
pressing the arrow keys.
You can also move the icon on its own simply by clicking and
dragging it to the new location.
10. When you are finished working with the maximized Column PFD,
click the Restore icon
for the PFD (not for the UniSim Design
Application view) in the upper right corner of the view of the PFD.
The PFD returns to its previous size.
11. You can manually resize the view, and expand the PFD to fill the
new size by again clicking the Zoom All icon in the lower left corner
of the PFD view.
For more information on customizing the PFD, refer to Section
7.24 - PFD in the UniSim Design User Guide.
The customized PFD appears below.
Figure 2.117
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12. To view the workbook for the column, click the Workbook icon.
Figure 2.118
13. When you are finished working in the Column environment, return
to the Main Flowsheet by clicking the Enter Parent Simulation
Environment icon.
Enter Parent Simulation
Environment icon
The PFD shown in the
Figure 2.119 has been
manually rearranged by
moving some of the
stream icons, and by
enlarging the furnace
icon.
14. Open the PFD for the Main Flowsheet, then select Auto Position
All from the PFD menu item. UniSim Design arranges the Main
Flowsheet PFD in a logical manner according to the layout of the
flowsheet.
Figure 2.119
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2.2.9 Viewing and Analyzing
Results
1. Open the Workbook to access the calculated results for the Main
Flowsheet. The Material Streams tab of the Workbook appears
below.
Figure 2.120
Using the Object Navigator
Now that results have been obtained, you can view the calculated
properties of a particular stream or operation. The Object Navigator
allows you to quickly access the property view for any stream or unit
operation at any time during the simulation.
Object Navigator icon
1. Open the Navigator by doing one of the following:
• Press F3.
• From the Flowsheet menu, select Find Object.
• Double-click on any blank space on the UniSim Design Desktop.
• Click the Object Navigator icon.
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The Object Navigator view appears:
Figure 2.121
The UnitOps radio button in the Filter group is currently selected, so
only Unit Operations appear in the list of objects. To open a property
view, select the operation in the list and click the View button, or
double-click on the operation. You can change which objects appear by
selecting a different Filter radio button. For example, to list all the
streams and unit operations, select the All radio button.
You can start or end the
search string with an
asterisk (*), which acts
as a wildcard character.
This lets you find
multiple objects with
one search. For
example, searching for
VLV* will open the
property view for all
objects with VLV at the
beginning of their name.
You can also search for an object by clicking the Find button. When the
Find Object view appears, enter the Object Name and click the OK
button. UniSim Design opens the property view for the object whose
name you entered.
2.2.10 Installing a Boiling Point
Curves Utility
Previously, the boiling point profiles for the product streams was viewed
using the Plots page in the column property view. You can also view
boiling point curves for a product stream using UniSim Design' BP
Curves Utility. To create a Boiling Point Curves utility for the Kerosene
product:
1. Open the Navigator using one of the methods described above.
2. Select the Streams radio button.
3. Scroll down the list of Streams and select Kerosene.
4. Click the View button, and the property view for stream Kerosene
appears.
5. On the Attachments tab, move to the Utilities page of the stream
property view.
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6. Click the Create button. The Available Utilities view appears,
presenting you with a list of UniSim Design utilities.
Figure 2.122
7. Find BP Curves and do one of the following:
• Select BP Curves, then click the Add Utility button.
• Double-click on BP Curves.
8. UniSim Design creates the utility and opens the Boiling Point Curves
view.
9. On the Design tab, go to the Connections page. Change the name
of the utility from the default Boiling Point Curves-1 to Kerosene
BP Curves.
A Utility is a separate
entity from the stream it
is attached to; if you
delete it, the stream is
not affected. Likewise, if
you delete the stream,
the Utility remains but
cannot display any
information until you
attach another stream
using the Select Object
button.
10. Change the curve basis to Liquid Volume by selecting it from the
Basis drop-down list.
Figure 2.123
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11. You can scroll through the matrix of data to see that the TBP
ranges from 267°F to 502°F by going to the Performance tab and
selecting the Results page.
Figure 2.124
This boiling range predicted by the utility is slightly wider than the
ideal range calculated during the Oil characterization procedure for
Kerosene, 356°F to 464°F.
Figure 2.125
Ideal boiling
range calculated
during Oil
Characterization.
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12. Select the Plots page on the Parameters tab of the utility property
view to view the data in graphical format.
Figure 2.126
To make the envelope
more readable,
maximize or resize the
view.
13. When you move to the Plots view, the graph legend can overlap the
plotted data. To move the legend, double-click anywhere in the plot
area then click and drag the legend to its new location.
14. When you are finished viewing the Boiling Point Curves, click the
Close icon.
Installing a Second Boiling Point Curves
Utility
Alternative to using the Utilities page of a stream property view, you
can also install a utility using the Available Utilities view. Another BP
Curves utility is installed for stream Residue. This utility is used for the
case study in the next section. To install the utility:
1. Do one of the following:
• press CTRL U.
• from the Tools menu, select Utilities.
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The Available Utilities view appears.
Notice the name of the
utility created
previously, Kerosene BP
Curves, appears in the
Available Utilities view.
Figure 2.127
2. Select Boiling Point Curves and click the Add Utility button. The
Boiling Point Curves view appears, opened to the Design tab.
Figure 2.128
3. Change the name from its default Boiling Point Curves-1 to Residue
BP Curves.
4. Change the Basis to Liquid Volume by selecting it in the dropdown list. The next task is to attach the utility to a material stream.
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5. Click the Select Object button, and the Select Process Stream view
appears.
Figure 2.129
6. Select Residue in the Object list, then click the OK button. UniSim
Design calculates the boiling point curves. The completed
Performance tab appears below.
Figure 2.130
Notice that the stream
name Residue now
appears in the Stream
cell.
7. Click the Close icon on the Residue BP Curves view, and then on the
Available Utilities view.
2.2.11 Using the Databook
The UniSim Design Databook provides you with a convenient way to
examine your flowsheet in more detail. You can use the Databook to
monitor key variables under a variety of process scenarios, and view
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the results in a tabular or graphical format.
1. To open the Databook, do one of the following:
• press CTRL D.
• from the Tools menu, select Databook.
The Databook appears below.
Figure 2.131
Adding Variables to Databook
The first step is to add the key variables to the Databook using the
Variables tab. For this example, the Overflash specification is varied
and examined to investigate its effect on the following variables:
•
D1160 Boiling Temperature for 5% volume cut point of stream
Residue
• heat flow of energy stream Trim Duty
• column reflux ratio
1. Click the Insert button and the Variable Navigator view appears.
2. Select the UnitOps radio button in the Object Filter group. The
Object list is filtered to show unit operations only.
3. Select Atmos Tower in the Object list, and the Variable list available
for the column appears to the right of the Object list.
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The Variable Navigator
is used extensively in
UniSim Design for
locating and selecting
variables. The Navigator
operates in a left-toright manner—the
selected Flowsheet
determines the Object
list, the chosen Object
dictates the Variable list,
and the selected
Variable determines
whether any Variable
Specifics are available.
4. Select Reflux Ratio in the Variable list.
Figure 2.132
5. Click the Add button. The variable appears in the Databook and the
Variable Navigator view remains open.
6. To add the next variable, select the Streams radio button in the
Object Filter group. The Object list is filtered to show streams
only.
7. Scroll down and click on Trim Duty in the Object list, and the
Variable list available for energy streams appears to the right of
the Object list.
8. Select Heat Flow in the Variable list.
The variable name is duplicated in the Variable Description field. If
you want, you can edit the default description. To edit the default
description:
9. Click inside the Variable Description field and delete the default
name.
10. Type a new description, such as Trim Duty, and click the Add
button. The variable now appears in the Databook.
Figure 2.133
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11. To add the third variable, the ASTM D1160 cut point from the
Residue BP Curves utility, select the Utility radio button in the
Navigator Scope group.
12. Select Residue BP Curves in the Object list.
13. Select ASTM D1160 - Vac in the Variable list.
14. Select Cut PT-5.00% in the Variable Specifics column. This
corresponds to the 5% volume cut point.
15. In the Variable Description field, change the variable name to
ASTM 1160 - Vac 5% Residue, and click the Close button.
Figure 2.134
16. The completed Variables tab of the Databook appears below.
Figure 2.135
Create a Data Table
Now that the key variables to the Databook have been added, the next
task is to create a data table to display those variables:
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1. Click on the Process Data Tables tab.
2. Click the Add button in the Available Process Data Tables group.
UniSim Design creates a new table with the default name
ProcData1.
Figure 2.136
3. Change the default name from ProcData1 to Key Variables by
editing the Process Data Table field.
Notice that the three variables added to the Databook appear in
the matrix on this tab.
4. Activate each variable by clicking on the corresponding Show
checkbox.
Figure 2.137
5. Click the View button to view the new data table, which is shown
below.
Figure 2.138
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This table is accessed later to demonstrate how its results are
updated whenever a flowsheet change is made.
6. For now, click the Minimize icon in the upper right corner of the
Key Variables Data view. UniSim Design reduces the view to an
icon and place it at the bottom of the Desktop.
Recording Data
Suppose you now want to make changes to the flowsheet, but you
would like to record the current values of the key variables before
making any changes. Instead of manually recording the variables, you
can use the Data Recorder to automatically record them for you.
To record the current values:
1. Click on the Data Recorder tab.
Figure 2.139
When using the Data Recorder, you first create a Scenario
containing one or more of the key variables, then record the
variables in their current state.
2. Click the Add button in the Available Scenarios group, and
UniSim Design creates a new scenario with the default name
Scenario 1. It is required to include all three key variables in this
scenario.
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3. Activate each variable by clicking on the corresponding Include
checkbox.
Figure 2.140
4. Click the Record button to record the variables in their current
state. The New Solved State view appears, prompting you for the
name of the new state.
5. Change the Name for New State from the default State 1 to 3500
O.F. (denoting 3500 bbl/day Overflash). Click the OK button and
you return to the Databook.
6. In the Available Display group, select the Table radio button.
7. Click the View button and the Data Recorder appears showing the
values of the key variables in their current state.
Figure 2.141
Now you can make the necessary flowsheet changes and these
current values remain as a permanent record in the Data Recorder
unless you choose to erase them.
8. Click the Minimize icon to reduce the Data Recorder to an icon.
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Changing the Overflash Specification
The value of the Overflash specification is going to be changed in the
column and the changes is viewed in the process data table:
1. Click the Object Navigator icon on the toolbar.
2. Select the UnitOps radio button in the Filter group.
Object Navigator icon
3. Select Atmos Tower and click the View button. The Atmos
Tower property view appears.
4. Go to the Design tab and select the Monitor page.
5. Scroll down to the bottom of the Specifications table so the
Overflash specification is visible.
A typical range for the Overflash rate is 3-5% of the tower feed. A
slightly wider range is examined: 1.5-7.5%, which translates to
1500-7500 bbl/d.
6. Change the Specified Value for the Overflash specification from
its current value of 3500 barrel/day to 1500 barrel/day. UniSim
Design automatically recalculates the flowsheet.
7. Double-click on the Key Variables Data icon to restore the view to
its full size. The updated key variables are shown below.
Figure 2.142
As a result of the change:
•
•
the Trim Duty has decreased
the Residue D1160 Vacuum Temperature 5% cut point has
decreased
• the column reflux ratio has decreased
8. Press CTRL D to make the Databook active again. You can now
record the key variables in their new state.
9. Move to the Data Recorder tab in the Databook.
10. Click the Record button, and UniSim Design provides you with the
default name State 2 for the new state.
11. Change the name to 1500 O.F. and click the OK button to accept
the new name.
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12. Click the View button and the Data Recorder appears, displaying
the new values of the variables.
Figure 2.143
13. Record the process variables for Overflash rates of 5500 and
7500 barrels/day. Enter names for these variable states of 5500
O.F. and 7500 O.F., respectively. The final Data Recorder appears
below.
Figure 2.144
14. Save your case by doing one of the following:
•
•
•
Save icon
This complete dynamic
case has been pre-built
and is located in the file
DynTUT2.usc in your
UniSim Design\Samples
directory.
press CTRL S.
from the File menu, select Save.
click the Save icon.
2.3 Dynamic Simulation
In this tutorial, the dynamic capabilities of UniSim Design are
incorporated into a basic steady state oil refining model. A simple
fractionation facility produces naphtha, kerosene, diesel, atmospheric
gas oil, and atmospheric residue products from a heavy crude feed. In
the steady state refining tutorial, preheated crude was fed into a preflash drum which separated the liquid crude from the vapour. The liquid
crude was heated in a furnace and recombined with the vapour. The
combined stream was then fed to the atmospheric crude column for
fractionation. The dynamic refining tutorial only considers the crude
column. That is, the crude preheat train is deleted from the flowsheet
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