AspenTech Incorporations
Aspen Hysys V8.8
Cases Solved in Hysys Version 8.0 are same as Version 8.8
Chemical Process Principles
Matbal-001H
Revised: Nov 7, 2012
Cyclohexane Production with Aspen HYSYS® V8.0
1. Lesson Objectives


Construct an Aspen HYSYS flowsheet simulation of the production of cyclohexane via benzene
hydrogenation
Become familiar with user interface and tools associated with Aspen HYSYS
2. Prerequisites


Aspen HYSYS V8.0
Knowledge of chemical process operations
3. Background/Problem
Construct an Aspen HYSYS simulation to model the production of cyclohexane via benzene hydrogenation. The
simplified flowsheet for this process is shown below. Fresh benzene and hydrogen feed streams are first fed
through a heater to bring the streams up to reactor feed temperature and pressure conditions. This feed
mixture is then sent to a fixed-bed catalytic reactor where 3 hydrogen molecules react with 1 benzene molecule
to form cyclohexane. This simulation will use a conversion reactor block to model this reaction. The reactor
effluent stream is then sent to a flash tank to separate the light and heavy components of the mixture. The
vapor stream coming off the flash tank is recycled back to the feed mixture after a small purge stream is
removed to prevent impurities from building up in the system. The majority of the liquid stream leaving the flash
tank goes to a distillation column to purify the cyclohexane product, while a small portion of the liquid stream is
recycled back to the feed mixture to minimize losses of benzene. Process operating specifications are listed on
the following page.
1
Matbal-001H
Revised: Nov 7, 2012
Feed Streams
Benzene Feed (BZFEED)
Hydrogen
Nitrogen
Methane
Benzene
Total Flow (lbmol/hr)
Temperature (°F)
Pressure (psia)
Composition (mole fraction)
1
100
100
15
Hydrogen Feed (H2FEED)
Hydrogen
Nitrogen
Methane
Benzene
Total Flow (lbmol/hr)
Temperature (°F)
Pressure (psia)
97.5
0.5
2.0
310
120
335
Feed Preheater
Outlet Temperature
Outlet Pressure
300 °F
330 psia
Reactor
Stoichiometry
Conversion
Outlet temperature
Pressure drop
Benzene + 3H2  Cyclohexane
99.8% of benzene
400°F
15psi
Flash Tank
Temperature
Pressure drop
120°F
5psi
Purge Stream
Distillation Column
Number of stages
Feed stage
Reflux Ratio
Cyclohexane recovery
Condenser Pressure
Reboiler Pressure
15
8
1.2
99.99 mole % in bottoms
200 psia
210 psia
Purge rate is 8% of vapor recycle stream
Liquid Split
70% of liquid stream goes to distillation column
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
2
Matbal-001H
Revised: Nov 7, 2012
4. Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0, select New on the Start Page to start a new simulation.
4.02.
Create a component list. In the Component Lists folder, select the Add button to create a new HYSYS
component list.
4.03.
Define components. Use the Find button to select the following components: Hydrogen, Nitrogen,
Methane, Benzene, and Cyclohexane.
4.04.
Select a property package. In the Fluid Packages folder in the navigation pane click Add. Select SRK as
the property package.
3
Matbal-001H
Revised: Nov 7, 2012
4.05.
We must now specify the reaction involved in this process. Go to Reactions folder in the navigation
pane and click Add to add a reaction set.
4.06.
In Reactions | Set-1 select Add Reaction. Select the Hysys radio button and select Conversion. Then
click Add Reaction. Once a new reaction (Rxn-1) can be seen on the reaction set page, close the
Reactions window shown below.
4.07.
Double click on Rxn-1 to define the reaction. In the reaction property window, add components
Benzene, Hydrogen, and Cyclohexane to the Stoichiometry Info grid. Enter -1, -3, and 1, respectively,
for stoichiometry coefficients. In the Basis grid select Benzene as Base Component, Overall for Rxn
Phase, 99.8 for Co, and 0 for both C1 and C2. This indicates that the reaction will convert 99.8% of
benzene regardless of temperature. Close this window when complete.
4
Matbal-001H
Revised: Nov 7, 2012
4.08.
Attach this reaction set to a fluid package by clicking the Add to FP button. Select Basis-1 and click Add
Set to Fluid Package. The reaction set should now be ready.
4.09.
We are now ready to enter the simulation environment. Click the Simulation button in the bottom left
of the screen.
5
Matbal-001H
Revised: Nov 7, 2012
4.10.
First we will place a Mixer and a Heater block onto the flowsheet.
4.11.
Double click on the mixer (MIX-100) to open the mixer property window. Create 2 inlet streams:
H2FEED, BZFEED; and 1 outlet stream: ToPreHeat.
6
Matbal-001H
4.12.
Revised: Nov 7, 2012
Go to the Worksheet tab to define streams H2FEED and BZFEED. First we will define the Conditions of
each stream. For H2FEED, enter a Temperature of 120°F, a Pressure of 335 psia, and a Molar Flow of
310 lbmole/hr. For BZFEED, enter a Temperature of 100°F, a Pressure of 15 psia, and a Molar Flow of
100 lbmole/hr. Note that you can change the global unit set to Field if the units are different than those
displayed below.
7
Matbal-001H
Revised: Nov 7, 2012
4.13.
Next we will define the Composition of the two feed streams. In the Worksheet tab go to the
Composition form. Enter the compositions shown below. You will notice that after inputting the
composition, the mixer will successfully solve for all properties.
4.14.
Double click on the heater block (E-100) to configure the heater. Select stream ToPreHeat as the inlet
and create an outlet stream called R-IN. Add an energy stream called PreHeatQ.
8
Matbal-001H
4.15.
Revised: Nov 7, 2012
Go to the Worksheet tab and specify the outlet stream R-IN temperature and pressure. Enter 300°F for
Temperature and 330 psia for Pressure.
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Matbal-001H
Revised: Nov 7, 2012
4.16.
The flowsheet should look like the following at this point.
4.17.
We will now add a Conversion Reactor to the flowsheet. Press F12 on the keyboard to open the
UnitOps window. Select the Reactors radio button and select Conversion Reactor. Press Add.
4.18.
In the Conversion Reactor property window, select the inlet stream to be R-IN, and create a Liquid
Outlet called LIQ and a Vapour Outlet called VAP. In the Parameters form, enter a Delta P of 15 psi.
10
Matbal-001H
Revised: Nov 7, 2012
11
Matbal-001H
4.19.
Revised: Nov 7, 2012
In the Reactions tab, select Set-1 for Reaction Set. Notice that when the reactor solves, the contents of
the reactor are entirely in the vapor phase, therefore there is no liquid flow leaving the bottom of the
reactor.
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Matbal-001H
Revised: Nov 7, 2012
4.20.
Next we will add a Cooler to the main flowsheet to cool down the vapor stream leaving the reactor.
4.21.
Double click on the cooler block (E-101) to open the cooler property window. Select VAP as the inlet
stream and create an outlet stream called COOL. Also add an energy stream called COOLQ. In the
Parameters form enter a Delta P of 5 psi.
13
Matbal-001H
4.22.
Revised: Nov 7, 2012
Go to the Worksheet tab to specify the outlet stream temperature. Enter 120°F for the Temperature of
stream COOL. The cooler will solve.
14
Matbal-001H
Revised: Nov 7, 2012
4.23.
We will now add a Separator block to separate the vapor and liquid phases of stream COOL. From the
model palette add a Separator to the flowsheet.
4.24.
Double click on the separator block (V-100). Select COOL as the inlet stream and create liquid and vapor
outlet streams called LIQ1 and VAP1. The separator should solve.
15
Matbal-001H
Revised: Nov 7, 2012
4.25.
The flowsheet should now look like the following.
4.26.
We will now add 2 Tee blocks, 1 for each of the separator outlet streams. One tee will be used to purge
a portion of the vapor stream to prevent impurities from building up in the system. The other tee will
be used to recycle a portion of the liquid back to the mixer and the rest of the liquid will be fed to a
distillation column.
16
Matbal-001H
4.27.
Revised: Nov 7, 2012
Double click on the first Tee block (TEE-100). Select stream VAP1 as the inlet, and create 2 outlet
streams VAPREC, and PURGE.
17
Matbal-001H
Revised: Nov 7, 2012
4.28.
Go to the Parameters page and enter 0.08 for the Flow Ratio for stream PURGE.
4.29.
You can rotate the icon for a block by selecting the icon and clicking the Rotate button in the
Flowsheet/Modify tab in the ribbon.
18
Matbal-001H
4.30.
Revised: Nov 7, 2012
Double click the second Tee block (TEE-101). Select LIQ1 for the inlet stream and create 2 outlet
streams LIQREC, and ToColumn.
4.31. In the Parameters tab enter a Flow Ratio of 0.7 for stream ToColumn.
19
Matbal-001H
Revised: Nov 7, 2012
(FAQ) Useful Option To Know: Saving Checkpoints
Save “checkpoints” as you go. Once you have a working section of the flowsheet, save as a new
file name, so you can revert to an earlier checkpoint if the current one becomes too complex to
troubleshoot or convergence errors become persistent.
4.32.
The flowsheet should now look like the following.
20
Matbal-001H
4.33.
Revised: Nov 7, 2012
We are now ready to connect the recycle streams back to the mixer. On the main flowsheet, add 2
Recycle blocks.
21
Matbal-001H
Revised: Nov 7, 2012
4.34.
Double click on the first recycle block (RCY-1). Select stream VAPREC as the inlet stream and create an
outlet stream called VAPToMixer.
4.35.
Double click the second recycle block (RCY-2). Select LIQREC as the inlet stream and create an outlet
stream called LIQToMixer.
22
Matbal-001H
Revised: Nov 7, 2012
4.36.
Connect the recycle streams back to the mixer. Double click the mixer block ( MX-100). On the Design |
Connections sheet add LIQToMixer and VAPToMixer as inlet streams. The flowsheet should converge.
4.37.
The flowsheet should now look like the following.
23
Matbal-001H
Revised: Nov 7, 2012
4.38.
We are now ready to add the distillation column to the flowsheet. From the Model Palette add a
Distillation Column Sub-Flowsheet.
4.39.
Double click on the Distillation Column Sub-flowsheet. This will launch the Distillation Column Input
Expert. Enter 15 for # Stages and specify ToColumn as inlet stream on stage 8_Main TS. Select Full
Reflux for Condenser, create an Ovhd Vapour Outlet stream called Off Gas, create Bottoms Liquid
Outlet stream called Bot, and add a Condenser Energy Stream called Cond Q. When finished click Next.
24
Matbal-001H
4.40.
Revised: Nov 7, 2012
On page 2 of the Distillation Column Input Expert keep the default selections for Reboiler Configuration
and click Next.
25
Matbal-001H
Revised: Nov 7, 2012
4.41.
On page 3 of the Distillation Column Input Expert enter a condenser pressure of 200 psia and a reboiler
pressure of 210 psia. Click Next.
4.42.
On page 4 of the Distillation Column Input Expert leave fields for temperature estimates blank and click
Next. On the final page of the column expert enter a molar Reflux Ratio of 1.2 and click Done to
configure the column.
26
Matbal-001H
4.43.
Revised: Nov 7, 2012
After completing the input for the column expert the Column property window will open. We want to
create a design specification in order to ensure that 99.99% of the cyclohexane is recovered in the
bottoms stream. Go to the Design | Specs sheet. Click Add and select Column Component Recovery.
In the Comp Recovery window specify Stream for Target Type, Bot@COL1 for Draw, 0.9999 for Spec
Value, and Cyclohexane for Components. Close this window when finished.
27
Matbal-001H
Revised: Nov 7, 2012
4.44.
Go to the Specs Summary sheet and make sure that the only active specs are Reflux Ratio and Comp
Recovery. The column should converge.
4.45.
The flowsheet is now complete and should look like the following.
28
Matbal-001H
Revised: Nov 7, 2012
This flowsheet is now complete.
5. Conclusion
This is a simplified process simulation, however you should now have learned the basic skills to create and
manipulate a steady state chemical process simulation in Aspen HYSYS V8.0.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
29
Matbal-002H
Revised: Nov 7, 2012
Calculation of Gasoline Additives with Aspen HYSYS® V8.0
1. Lesson Objectives


Learn how to specify a mixer
Learn how to use the spreadsheet in Aspen HYSYS to perform customized calculations
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Ethyl tert-butyl ether (ETBE) is an oxygenate that is added to gasoline to improve Research Octane Number
(RON) and to increase oxygen content. The goal is to have 2.7% oxygen by weight in the final product. The legal
limit is that ETBE cannot exceed more than 17% by volume. For simplicity, we use 2,2,4-trimethylpentane to
represent gasoline. Since ETBE's molecular weight is 102.18 g/mol, the ETBE in the product stream can be
calculated as following:
This yields 17.243% of ETBE by weight in the product stream. Given this, the spreadsheet tool can be utilized to
target the ETBE feed to achieve the desired oxygen content.
In this tutorial we will calculate:


For a certain flow rate of gasoline (e.g., 100 kg/hr), how much ETBE should be added to achieve the
oxygen content of 2.7% by weight in the blended gasoline.
Check whether or not the legal limit of ETBE content is satisfied.
A HYSYS spreadsheet is used to perform calculations on each criterion. Both targets should be met in the
simulation.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
Matbal-002H
Revised: Nov 7, 2012
4. Aspen HYSYS Solution
4.01.
Start a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add 2,2,4-trimethylpentane and
ETBE to the component list.
4.03.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
4.04.
Enter the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
Add a Mixer to the flowsheet from the Model Palette.
2
Matbal-002H
4.06.
Revised: Nov 7, 2012
Double click on the mixer (MIX-100). Create two Inlets called ETBE and Gasoline. Create an Outlet
called Blend.
3
Matbal-002H
Revised: Nov 7, 2012
4.07.
Define feed streams. Go to the Worksheet tab. For stream ETBE enter a Temperature of 25°C and a
Pressure of 1 bar. Leave Mass Flow empty as we will solve for it later.
4.08.
In the Composition form under the Worksheet tab, enter a Mole Fraction of 1 for ETBE in the ETBE feed
stream.
4
Matbal-002H
Revised: Nov 7, 2012
4.09.
Define gasoline feed stream. In the Conditions form in the Worksheet tab, enter a Temperature of
25°C, a Pressure of 1 bar, and a Mass Flow of 82.76 kg/h.
4.10.
In the Composition form enter a Mole Fraction of 1 for 224-Mpentane in the Gasoline stream. The
gasoline stream should solve. However. the mixer will not solve because the flow rate of ETBE is still
unknown.
5
Matbal-002H
4.11.
Revised: Nov 7, 2012
We will now create a spreadsheet to calculate the target mass flowrate of stream ETBE. Add a
Spreadsheet to the flowsheet from the Model Palette.
6
Matbal-002H
4.12.
Revised: Nov 7, 2012
Double click on the spreadsheet (SPRDSHT-1). Go to the Spreadsheet tab and enter the following text in
cells A1 and A2.
7
Matbal-002H
Revised: Nov 7, 2012
4.13.
Right click on cell B1 and select Import Variable. Select the following to import the Mass Flow of stream
Gasoline to cell B1. Press OK when complete.
4.14.
Click cell B2 and enter the following formula: = (B1*0.17243) / (1-0.17243). This will calculate the mass
flow rate for stream ETBE. From the background section, we know that in order to reach the oxygen
content goal of 2.7%, we will need the gasoline stream to contain 17.243% ETBE by weight.
8
Matbal-002H
4.15.
Revised: Nov 7, 2012
We now wish to export the calculated flow rate in cell B2 to stream ETBE. Right click cell B2 and select
Export Formula Result. Make the following selections and click OK when complete. The mixer should
now solve.
9
Matbal-002H
Revised: Nov 7, 2012
4.16.
We will now calculate the volume percent of ETBE in the blended stream to make sure that the ETBE
content is below the legal limit of 17 volume percent. This can easily be observed in the spreadsheet. In
the spreadsheet, enter the following text in cell A4.
4.17.
Right click on cell B4 and select Import Variable. Make the following selections to import Master Comp
Volume Frac of ETBE in the blended stream. Click OK when complete.
10
Matbal-002H
4.18.
Revised: Nov 7, 2012
The volume fraction of ETBE in the blended stream is 0.1596, which is below the legal limit of 0.17. It is
determined that the target flow rate of ETBE to be mixed with this gasoline stream is 17.24 kg/h.
11
Matbal-002H
Revised: Nov 7, 2012
5. Conclusions
For a specified gasoline mass flow rate of 82.76 kg/hr, 17.24 kg/hr of ETBE is needed to achieve 2.7% oxygen
content by weight in the final product. Furthermore, after blending, the product does not exceed the legal limit
for ETBE of 17% by volume. If gasoline contains a single component, manual calculation should be easy without
a simulator. However, real gasoline contains many unknown components and gasoline’s contents vary as
feedstock or plant operation conditions change. Therefore, manual calculation becomes very difficult and the
use of a simulator such as Aspen HYSYS can be helpful to carry out the calculation.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their re spective companies.
12
Thermodynamics for Chemical Engineers
Prop-001H
Revised: Nov 16, 2012
Generate Ethylene Vapor Pressure Curves with Aspen HYSYS® V8.0
1. Lesson Objectives

Generate vapor pressure curves for Ethylene
2. Prerequisites


Aspen HYSYS V8.0
Introduction to vapor-liquid equilibrium
3. Background
Separation processes involving vapor-liquid equilibrium exploit volatility differences which are indicated by the
components’ vapor pressure. Higher vapor pressure means a component is more volatile.
Ethylene is an important monomer for polymers and there are many ethylene plants around the world. A vital
step in ethylene production is separating it from other compounds and as a result the vapor pressure of
ethylene is an important physical property for ethylene production.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Determine the vapor pressure of ethylene at 5 °C, and its normal boiling point. Also create a plot of vapour
pressure versus temperature.
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component List folder select Add. Add Ethylene to the component list.
1
Prop-001H
4.03.
Revised: Nov 16, 2012
Double click on Ethylene to view the pure component properties. Go to the Critical tab. Make a note
that the Critical Temperature is 9.2°C and the Normal Boiling Point is -103.8°C.
2
Prop-001H
Revised: Nov 16, 2012
4.04.
Define property methods. Go to the Fluid Packages folder and click Add. Select Peng-Robinson as the
property package.
4.05.
Move to the simulation environment. Click the Simulation button in the bottom left of the screen.
4.06.
Add a Material Stream to the flowsheet.
3
Prop-001H
Revised: Nov 16, 2012
4.07.
Double click on material stream (1). The vapor pressure of liquid is the atmospheric pressure at which a
pure liquid boils at a given temperature. The point at which the first drop of liquid begins to boil is
called the bubble point, which is found in HYSYS by specifying a vapour fraction of 0. Therefore, we can
find the vapor pressure of pure liquid by specifying a temperature and vapour fraction of 0.
4.08.
In material stream 1, enter a Vapour Fraction of 0, a Temperature of 5°C, and a Molar Flow of 1
kgmole/h. In the Composition form under the Worksheet tab enter a Mole Fraction of 1 for Ethylene.
4.09.
You can see that the Pressure is 45.93 bar. This is equivalent to the vapour pressure of ethylene at this
temperature. Next we would like to determine the normal boiling point of ethylene. Instead of
specifying temperature, we will specify pressure. Empty the field for temperature and enter a value of 1
bar for Pressure.
4
Prop-001H
Revised: Nov 16, 2012
4.10.
The newly calculated temperature is -104.3°C. This is the boiling temperature of ethylene at a pressure
of 1 bar.
4.11.
Next we would like to create a plot of vapour pressure versus temperature. First, in the Material
Stream 1 window, empty the field for Pressure and enter any Temperature (below critical temperature).
This will allow us to vary temperature when we perform a case study. Go to the Case Studies folder in
the Navigation Pane and click Add.
5
Prop-001H
4.12.
Revised: Nov 16, 2012
In Case Study 1, click Add to select the variables. Select the Temperature and Pressure of stream 1. In
the Independent Variable field enter a Low Bound of -150°C, a High Bound of 0°C, and a Step Size of
10°C. Click Run.
6
Prop-001H
4.13.
Revised: Nov 16, 2012
After running the case study, go to the Plots tab. Here you will see a plot of Pressure vs Temperature.
7
Prop-001H
4.14.
Revised: Nov 16, 2012
Note that by looking at the plot you can verify that at around -104°C the vapour pressure if
approximately 1 bar, indicating the normal boiling point.
5. Conclusions
As we can see from the generated plot, ethylene is a very volatile component. At 5°C, its vapor pressure is
about 45.93 bar. From this analysis, we also see that ethylene’s normal boiling point temperature is about –104
°C.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent o f
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
8
Prop-003H
Revised: Nov 5, 2012
Retrieve Pure Component Property Data with Aspen HYSYS® V8.0
1. Lesson Objectives

Learn how to retrieve property data for pure components in Aspen HYSYS.
2. Prerequisites

Aspen HYSYS V8.0
3. Background
There are many reasons that we need physical properties of pure components.
When we look for a solvent for extractive distillation (a technology that uses a third component, the solvent, to
separate two components in a mixture that are difficult to separate directly via distillation), we look for
components with normal boiling point temperatures that are higher (but not too much higher) than the
components to be separated. For such a case, we need to know the normal boiling point temperatures of
candidate solvents during the search.
When we look for a solvent for extraction, we need to check the densities of candidate solvent s to ensure the
two liquid phases formed during extraction have enough differences in density. For the selected solvent, we
also need to check its density against the existing liquid phase so that we know which liquid phase is heavier.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
The pre-condition of this example is that 3-methylhexane is now considered a promising candidate solvent for
separation of acetone and water. The task is to determine whether the density of 3-methylhexane is different
enough from the density of water. We also need to determine which of the two liquid phases formed mainly by
these two components is heavier.
1
Prop-003H
Revised: Nov 5, 2012
Aspen HYSYS Solution
4.01.
Create a new case in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select the Add button to add a new component
list.
2
Prop-003H
4.03.
Revised: Nov 5, 2012
Enter 3-methylhexane in the Search for box. Aspen HYSYS should display the relevant search results. If
the component you are looking for does not appear, you can also use the Filter or Search by drop-down
list for different search criteria. Click the < Add button to add the component to the component list.
3
Prop-003H
Revised: Nov 5, 2012
4.04.
To retrieve and view the pure component property data and, double-click the component 3-Mhexane. A
new window should appear.
4.05.
Go to the Critical tab in the new window. You will see a list of property data in the Base Properties and
Critical Properties frames. Note that the Ideal Liquid Density for 3-methylhexane is 690.2 kg/m3.
4
Prop-003H
4.06.
Revised: Nov 5, 2012
In the navigation pane, go to the Components | Component List -1 sheet. Enter water in the Search for
box and add the component to the component list.
5
Prop-003H
4.07.
Revised: Nov 5, 2012
Double-click on the component H2O. A new window should appear.
6
Prop-003H
4.08.
Revised: Nov 5, 2012
Go to the Critical tab in the new window. You will see a list of property data in the Base Properties and
Critical Properties frames. Note that the Ideal Liquid Density for Water is 998.0 kg/m3.
5. Conclusions
The density of 3-methylhexane is around 690.2 kg/m3, which is clearly less than the density of water (998.0
kg/m3). The liquid phase formed mainly by 3-methylhexane should be lighter than the phase formed mainly by
water and, thus, the aqueous phase should be at the bottom and the other liquid phase should be at the top.
7
Prop-003H
Revised: Nov 5, 2012
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
8
Prop-005H
Revised: Nov 7, 2012
Hypothetical Components and Petroleum Assays
with Aspen HYSYS® V8.0
1. Lesson Objectives


Create hypothetical components in Aspen HYSYS
Characterize a petroleum assay
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Aspen HYSYS allows you to create non-library or Hypothetical components. These hypothetical components can
be pure components, defined mixtures, undefined mixtures, or solids. A wide selection of estimation methods
are provided for various Hypo groups to ensure the best representation of behavior for the Hypothetical
component in the simulation.
In order to accurately model a process containing a crude oil, such as a refinery operation, the oil properties
must be defined. It is nearly impossible to determine the exact composition of an oil assay, as there are far too
many components in the mixture. This is a situation where hypothetical components are useful. Boiling point
measurements of distillate fractions of an assay can be used to characterize the oil properties.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Create a hypothetical component group in Aspen HYSYS and characteri ze a petroleum assay to be used in a
refinery simulation.
Aspen HYSYS Solution
4.01.
Start a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Change the Select field to
Hypothetical and enter the Initial and Final Boiling Points for the hypothetical group shown below.
Click Generate Hypos when complete. This will generate a group of hypothetical components with
estimated properties based on the specified boiling point of each cut.
1
Prop-005H
4.03.
Revised: Nov 7, 2012
Click Add All to add the entire hypothetical group to the component list.
2
Prop-005H
Revised: Nov 7, 2012
4.04.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
4.05.
Enter the simulation environment by clicking the Simulation button in the bottom left of the screen.
3
Prop-005H
Revised: Nov 7, 2012
4.06.
Add a Material Stream to the flowsheet from the Model Palette. Double click the stream and go to the
Composition form under the Worksheet tab.
4.07.
You will notice that the mole fractions of all the components are empty. If you would like to assign an
oil assay to this stream go to the Petroleum Assay form under the Worksheet tab. Select the option
Create New Assay On Stream.
4
Prop-005H
4.08.
Revised: Nov 7, 2012
Click the Petroleum Assay Specifications button. This page allows you to enter assay distillation data or
import data from a known oil assay.
5
Prop-005H
Revised: Nov 7, 2012
4.09.
Click the Import From button and select Assay Library to import data from a known assay in the HYSYS
assay library.
4.10.
Say, for example, that we want to model a refinery process using Bachaquero heavy crude from
Venezuela. Scroll down the list of assays and select Bachaquero, Venezuela. Click Import Selected
Assay.
6
Prop-005H
Revised: Nov 7, 2012
4.11.
After a few moments the MacroCut Data window will be filled with distillation cut data for Bachaquero
heavy crude.
4.12.
Click the Calculate Assay button to assign mole fractions to the hypothetical components defined for
the stream. Exit the MacroCut Data window and view the Components form of the material stream.
7
Prop-005H
4.13.
Revised: Nov 7, 2012
The composition for the stream is now defined and will model the properties of the selected petroleum
assay through the use of hypothetical components.
5. Conclusions
This example demonstrates how to create hypothetical components and how to assign a petroleum assay to a
stream in order to model the assay properties in a simulation.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
8
Thermo-002H
Revised: Nov 6, 2012
Flash Calculation in Aspen HYSYS® V8.0
1. Lesson Objective


Learn how to model a Flash separator and examine different thermodynamic models to see how
they compare.
Flash blocks in Aspen HYSYS
2. Prerequisites

Aspen HYSYS V8.0
3. Problem
We want to investigate Vapor-Liquid separation at different pressures, temperatures and compositions. Assume
you have a feed with an equimolar binary mixture of ethanol and benzene at 1 bar and 25°C. Examine the
following flash conditions using the heater block in Aspen HYSYS. Use Vapor-Liquid as the Valid Phase in the
computation.





Condition #1 (P-V Flash): At 1 bar and a vapor fraction of 0.5, find the equilibrium temperature and
the heat duty.
Condition #2 (T-P Flash): At the temperature determined from Condition #1 and a pressure of 1 bar,
verify that the flash model results in a vapor fraction of 0.5 at equilibrium.
Condition #3 (T-V Flash): At the temperature of Condition #1, and a vapor fraction of 0.5, verify that
the flash model results in an equilibrium pressure of 1 bar.
Condition #4 (P-Q Flash): At 1 bar and with the heat duty determined from Condition #1, verify that
the temperature and vapor fraction are consistent with previous conditions.
Condition #5 (T-Q Flash): At the temperature and heat duty determined from Condition #1, verify
that the pressure and vapor fraction are consistent with previous conditions.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Aspen HYSYS Solution:
4.01.
Start Aspen HYSYS V8.0. Select New to start a new simulation.
4.02.
Create a component list. In the Component Lists folder select Add. Select Ethanol and Benzene.
1
Thermo-002H
Revised: Nov 6, 2012
4.03.
Create a fluid package. In the Fluid Packages folder select Add, and select NRTL as the property package.
4.04.
Go to the simulation environment. Click the Simulation button in the bottom left of the screen.
4.05.
Place a Heater block onto the flowsheet from the Model Palette.
2
Thermo-002H
Revised: Nov 6, 2012
4.06.
Double click the Heater to open the property window. Create an Inlet stream called FEED, an Outlet
stream called OUT, and an Energy stream called Q.
4.07.
Specify conditions of FEED stream. Go to the Worksheet tab and enter a Temperature of 25°C, a
Pressure of 1 bar (100 kPa), and a Molar flow of 1 kgmole/h. Also enter Mole Fractions of 0.5 for each
component on the Composition form.
3
Thermo-002H
Revised: Nov 6, 2012
4.08.
Condition #1 Compute the temperature to get 0.5 vapor fraction at 1 bar. In the Conditions form under
Worksheet, enter a Vapour Fraction of 0.5 and a Pressure of 1 bar (100 kPa) for stream OUT. The
heater will automatically solve and you will see that the calculated temperature is 67.03°C.
4.09.
Condition #2 Compute vapor fraction at 1 bar and at the temperature obtained in Condition #1. Clear
the field for Vapour Fraction for stream OUT, then enter a Pressure of 1 bar (100 kPa) and a
Temperature of 67.03°C. In order to be able to enter a temperature, you must first empty the entry
field for Vapour Fraction. This is done by clicking the entry field and pressing delete on the keyboard.
Once a Temperature is entered, the Vapour Fraction will solve.
4
Thermo-002H
4.10.
Revised: Nov 6, 2012
Condition #3 Compute pressure at the temperature obtained in Condition #1 with 0.5 vapor fraction.
Delete the value in the Pressure field and enter a Vapour Fraction of 0.5. The pressure should solve.
5
Thermo-002H
Revised: Nov 6, 2012
4.11.
Condition #4 Compute temperature and vapor fraction at 1 bar and using the heat duty obtained in
Condition #1. Empty the fields for Temperature and Vapour Fraction in stream OUT. In stream OUT
enter a Pressure of 1 bar. In stream Q, enter a Heat Flow of 2.363e004 kJ/h. The Temperature of
67.03°C and Vapour Fraction of .500 are consistent with Condition #1.
4.12.
Condition #5 Compute pressure and vapor fraction at the temperature and heat duty obtained in
Condition #1. In stream OUT, empty the field for Pressure. Enter a Temperature of 67.03°C. The
Pressure and Vapor Fraction should be the same as Condition #1.
6
Thermo-002H
Revised: Nov 6, 2012
5. Conclusion
You have gone through the five flash methods which are most common in Aspen HYSYS. Here is a brief
summary.
Flash Method
T (C)
P (bar)
V (-)
Q (MJ/hr)
P-V Flash
67.03
1
0.5
23.63
T-P Flash
67.03
1
0.5099
23.98
T-V Flash
67.03
1
0.5
23.63
P-Q Flash (or P-H)
67.03
1
0.5
23.63
T-Q Flash (or T-H)
67.03
1
0.5
23.63
Specified
Computed
Feed Condition: ETHANOL/BEZENE (Equimolar mixture) at 1 bar and 25 Celsius.
7
Thermo-002H
Revised: Nov 6, 2012
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
8
Thermo-003H
Revised: Nov 6, 2012
Steam Tables in Aspen HYSYS® V8.0
1. Objective
Learn how to access Steam Tables in Aspen HYSYS, and how to interpret the Steam Table data.
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Aspen HYSYS offers 2 types of Steam Tables Properties Methods:
Property Method Name
Models (Steam
Tables)
Note
The ASME Steam property method uses the:
 1967 International Association for
Properties of Water and Steam (IAPWS,
http://www.iapws.org) correlations for
thermodynamic properties
ASME Steam
NBS Steam
ASME 1967
NBS 1984
STEAM-TA method is made up of different
correlations covering different regions of the P-T
space. These correlations do not provide
continuity at the boundaries, which can lead to
convergence problems and predict wrong trends.
The NBS Steam property methods uses the:
 1984 International Association for
Properties of Water and Steam (IAPWS,
http://www.iapws.org) correlations for
thermodynamic properties
Use the NBS Steam property method for pure
water and steam with temperature ranges of
273.15 K to 2000 K. The maximum pressure is
over 10000 bar.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
Thermo-003H
Revised: Nov 6, 2012
4. Problem
Using Aspen HYSYS, we want to calculate saturated steam properties from 100°C to 300°C. We would like to
create a table that displays mass enthalpy, mass entropy, pressure, and density.
Aspen HYSYS Solution:
4.01.
Start Aspen HYSYS V8.0. Select New to start a new simulation.
4.02.
Create a component list. In the Component Lists folder, select Add. Add Water to the component list.
4.03.
Create a fluid package. In the Fluid Packages folder, select Add. Select NBS Steam as the property
package.
4.04.
Go to the simulation environment.
2
Thermo-003H
Revised: Nov 6, 2012
4.05.
Add a material stream to the flowsheet from the Model Palette. Double click on the stream to open the
property window. Rename this stream STEAM and enter a Mole Fraction of 1 for water.
4.06.
In the navigation pane, go to Stream Analysis and click on the dropdown arrow next to Add and select
Property Table. In the Select Process Stream window that appears, select STEAM and press OK.
4.07.
Next, double click on Property Table-1 to open the property window. Under Independent Variables
select Temperature as Variable 1. Enter a Lower Bound of 100°C and an Upper Bound of 300°C. Enter
100 for # of Increments. Select Vapour Fraction for Variable 2 and select State for Mode. Enter a value
of 1 for State Values. We are going to be varying the temperature while holding the vapour fraction
constant at 1.
3
Thermo-003H
4.08.
Revised: Nov 6, 2012
We must now define the dependent properties that we are interested in viewing results for. Go to the
Dep. Prop form under the Design tab. Select Add. Here we will add Mass Enthalpy, Mass Entropy,
Pressure, and Mass Density.
4
Thermo-003H
4.09.
Revised: Nov 6, 2012
Click Calculate to generate the property table. Results can be viewed in the Performance tab of the
property table window.
5
Thermo-003H
Revised: Nov 6, 2012
5. Conclusion
After completing this exercise you should now be familiar with how to access and interpret thermodynamic
properties for steam using Aspen HYSYS.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use wit h,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
6
Thermo-004H
Revised: Nov 6, 2012
Heat of Vaporization with Aspen HYSYS® V8.0
1. Lesson Objectives


Learn how to calculate heat of vaporization using the heater block in Aspen HYSYS
Understand the impact of heat of vaporization on distillation
2. Prerequisites

Aspen HYSYS V8.0
3. Background
The driving force for distillation is energy. The most energy consuming part of a distillation column is the
vaporization of material in the reboiler to cause vapor to flow from the bottom of the column to the top of the
column. Heat of vaporization determines the amount of energy required. Therefore, it is important to know the
heat of vaporization of various species during solvent selection. With everything else equal, we should select a
component with lower heat of vaporization so that we can achieve the same degree of separation with less
energy. This example contains three isolated heater blocks. Each heater block is used to calculate the heat of
vaporization for a pure component.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
Thermo-004H
Revised: Nov 6, 2012
4. Aspen HYSYS Solution:
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder, select Add. Select Water, 3-methylhexane,
and 1,1,2-trichloroethane.
4.03.
Create a fluid package. In the Fluid Packages folder, select Add. Select UNIQUAC as the property
package and select RK as the Vapour Model.
4.04.
Enter the simulation environment.
2
Thermo-004H
Revised: Nov 6, 2012
4.05.
Add three separate Heater blocks to the flowsheet.
4.06.
Double click on E-100 to open the property window. This first heater will vaporize a stream of pure
water. Create an Inlet stream called Feed-Water, an Outlet stream called Water-Out, and an Energy
stream called Q-Water.
3
Thermo-004H
Revised: Nov 6, 2012
4.07.
Go to the Worksheet tab. Specify the feed stream to be at a Pressure of 100 kPa, a Vapour Fraction of
0, and with a Molar Flow of 1 kgmole/h. In the Composition form under the Worksheet tab, enter a
Mole Fraction of 1 for Water in the feed stream. Lastly, we must specify the outlet pressure and the
outlet vapour fraction. Enter 100 kPa for Pressure, and 1 for Vapour Fraction of the Water-Out stream.
The heater should solve. Make note of the Heat Flow of the energy stream Q-Water.
4.08.
We will now repeat this process for heaters E-101 and E-102. E-101 will vaporize 3-methylhexane and E102 will vaporize 1,1,2-trichloroethane.
4.09.
Double click on E-101. Create an Inlet stream called Feed-3MH, an Outlet stream called 3MH-Out, and
an Energy stream called Q-3MH.
4
Thermo-004H
4.10.
Revised: Nov 6, 2012
In the Worksheet tab, for the feed stream enter a Vapour Fraction of 0, a Molar Flow of 1 kgmole/h,
and a Pressure of 100 kPa. In the Composition form, enter a Mole Fraction of 1 for 3-methylhexane in
the feed stream. Lastly specify the outlet conditions of 100 kPa for Pressure and a Vapour Fraction of 1.
Make note of the Heat Flow for the energy stream.
5
Thermo-004H
Revised: Nov 6, 2012
4.11.
Double click E-102. Create an Inlet stream called Feed-1,1,2, an Outlet stream called 1,1,2-Out, and an
Energy stream called Q-1,1,2.
4.12.
In the Worksheet tab, for the feed stream enter a Vapour Fraction of 0, a Molar Flow of 1 kgmole/h,
and a Pressure of 100 kPa. In the Composition form, enter a Mole Fraction of 1 for 1,1,2trichloroethane in the feed stream. Lastly specify the outlet conditions of 100 kPa for Pressure and a
Vapour Fraction of 1. Note the Heat Flow of the energy stream.
6
Thermo-004H
Revised: Nov 6, 2012
5. Conclusions
Although water has small molecular weight, its heat of vaporization is large. Heat of vaporization for water is
about 18% higher than that of 1,1,2-trichloroethane and about 30% higher than that of 3-methylhexane. Of the
three options, 3-methylhexane has to lowest heat of vaporization and would require the least amount of energy
as a solvent in a distillation.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
7
Therm-005H
Revised: Nov 6, 2012
Simulation of Steam Engine with Aspen HYSYS® V8.0
1. Lesson Objectives


Learn how to simulate a steam engine with Aspen HYSYS
Learn how to specify pumps, heaters, coolers, expanders
2. Prerequisites


Aspen HYSYS V8.0
Introductory thermodynamics
3. Background
A steam engine consists of the following steps:




Water is pumped into a boiler using a pump.
Water is vaporized in a boiler and becomes high temperature and pressure steam.
Steam flows through a turbine and does work. The pressure and temperature go down during t his
step. The steam is also partially condensed.
The steam is further cooled to be condensed completely. Then, it is fed to the pump mentioned in
the first step to be re-used.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder, select Add. Add Water to the component list.
1
Therm-005H
Revised: Nov 6, 2012
4.03.
Create a fluid package. In the Fluid Packages folder, select Add. Select NBS Steam as the property
package.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen. In
the Home ribbon, select EuroSI as the Unit Set.
4.05.
Enter the simulation environment. Add a Heater, a Cooler, a Pump and an Expander as shown in the
flowsheet.
2
Therm-005H
Revised: Nov 6, 2012
4.06.
Double click the pump (P-100) to open the pump specification window. Create an Inlet stream called
Liq-Water, an Outlet stream called ToBoiler, and an Energy stream called Q-Pump.
4.07.
In the Worksheet tab, specify an outlet Pressure of 1.2 bar.
3
Therm-005H
Revised: Nov 6, 2012
4.08.
Double click the heater (E-100). Select ToBoiler as the Inlet stream, create an Outlet stream called
HPSteam (high pressure steam), and create an Energy stream called Q-Heat.
4.09.
In the Worksheet tab, specify an outlet Pressure of 40 bar, and a Temperature of 460°C.
4
Therm-005H
4.10.
Revised: Nov 6, 2012
Double click the expander (K-100). Select HPSteam as the Inlet stream, create an Outlet stream called
LPSteam, and create an Energy stream called Q-Expand.
5
Therm-005H
4.11.
Revised: Nov 6, 2012
In the Worksheet tab, specify an outlet Pressure of 1 bar.
6
Therm-005H
4.12.
Revised: Nov 6, 2012
Double click the cooler (E-101). Select an Inlet stream of LPSteam, an Outlet stream of Liq-Water, and
create an Energy stream called Q-Cool.
7
Therm-005H
Revised: Nov 6, 2012
4.13.
In the Worksheet tab, specify an outlet Vapour Fraction of 0 and a Pressure of 1 bar.
4.14.
The flowsheet is now ready to solve. All that is left to do is to specify the composition and flowrate of a
stream within the loop. Double click on stream Liq-Water and specify a Mole Fraction of 1 for Water
and a Mass Flow if 10,000 kg/h.
8
Therm-005H
Revised: Nov 6, 2012
9
Therm-005H
4.15.
Revised: Nov 6, 2012
The flowsheet should now solve.
5. Conclusions
The steam engine system can be simulated using Aspen HYSYS. This flowsheet clearly shows where energy is
being input to the system and where energy is being released.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
10
Thermo-006H
Revised: Nov 6, 2012
Illustration of Refrigeration with Aspen HYSYS® V8.0
1. Lesson Objectives


Learn how to specify compressors, heaters, and valves in Aspen HYSYS
Understand a refrigeration loop
2. Prerequisites


Aspen HYSYS V8.0
Introductory thermodynamics
3. Background
In a typical refrigeration system, the refrigerant starts at room temperature and ambient pressure. It is
compressed, which increases the refrigerant’s temperature and pressure so it i s a superheated vapor. The
refrigerant is cooled by air with a fan so that it is close to room temperature. At this point, its pressure remains
high and the refrigerant has been condensed to a liquid. Then, the refrigerant is allowed to expand through an
expansion valve. Its pressure decreases abruptly, causing flash evaporation, which reduces the refrigerant’s
temperature significantly. The very cold refrigerant can then cool a fluid passed across a heat exchanger (e.g.,
air in an air conditioner). Of course, for an AC unit to work, the air that is used to cool down the super-heated
refrigerant must be air outside of the room; the air that is cooled by the cold refrigerant is the air inside the
room.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Aspen HYSYS Solution
Problem Statement
Determine the cooling capacity of 300 kgmole/h of CFH2-CF3 when allowed to expand from 10 bar to 1 bar.
1
Thermo-006H
Revised: Nov 6, 2012
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add 1,1,1,2-tetrafluoroethane to
the component list.
4.03.
Create a fluid package. In the Fluid Packages folder, select Add. Select NRTL as the property package.
4.04.
Move to the simulation environment. Click the Simulation button in the bottom left of the screen. In
the Home ribbon, select EuroSi as the Unit Set.
4.05.
Add a Compressor, a Cooler, a Heater, and a Valve to the main flowsheet.
2
Thermo-006H
4.06.
Revised: Nov 6, 2012
Double click on the compressor (K-100). Create an Inlet stream called Vapor, an Outlet stream called
SuperHeat-Vapor, and an Energy stream called Q-Comp.
3
Thermo-006H
4.07.
Revised: Nov 6, 2012
In the Worksheet tab, specify an outlet Pressure of 10 bar.
4
Thermo-006H
Revised: Nov 6, 2012
4.08.
Double click the Cooler (E-100). Select SuperHeat-Vapor as the Inlet stream, create an Outlet stream
called Liquid, and create an Energy stream called Q-Cool.
4.09.
In the Worksheet tab, specify an outlet Temperature of 30°C. In the Parameters form under the Design
tab, enter a Delta P of 0.
5
Thermo-006H
4.10.
Revised: Nov 6, 2012
Double click the valve (VLV-100). Select stream Liquid as the Inlet stream and create an Outlet stream
called LowP.
6
Thermo-006H
4.11.
Revised: Nov 6, 2012
In the Worksheet tab specify an outlet Pressure of 1 bar.
7
Thermo-006H
Revised: Nov 6, 2012
4.12.
Double click on the heater (E-101). Select stream LowP as the Inlet stream, select stream Vapor as the
Outlet stream, and create an Energy stream called Q-Heat.
4.13.
In the Worksheet tab, specify an outlet Temperature of 25°C. In the Parameters form under the Design
tab, specify a Delta P of 0.
8
Thermo-006H
Revised: Nov 6, 2012
We must now specify the molar flowrate and composition of the refrigerant. Double click any stream,
for example stream Liquid. Enter a Molar Flow of 300 kgmole/h. In the Composition form specify a
Mole Fraction of 1 for the refrigerant.
9
Thermo-006H
4.14.
Revised: Nov 6, 2012
The flowsheet will now solve.
10
Thermo-006H
4.15.
Revised: Nov 6, 2012
Check results. To view the cooling capacity of this refrigeration loop, double click energy stream Q-Heat.
The stream is removing 1.26e006 kcal/h, or approximately 350 kcal/sec.
5. Conclusions
Refrigeration is a process where heat moves from a colder location to a hotter one using external work (e.g., a
compressor). We know that vaporization of a liquid takes heat. If there is no external heat available, the heat
will come from the liquid itself by reducing its own temperature.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
11
Thermo-007H
Revised: Nov 6, 2012
Maximum Fill up in Propane Tanks with Aspen HYSYS® V8.0
Using a Spreadsheet
1. Lesson Objectives




How to calculate the maximum liquid level in propane tanks
How to access stream variables in Aspen HYSYS
How to configure a heater block
How to use the Spreadsheet tool to perform customized calculations
2. Prerequisites

Aspen HYSYS V8.0
3. Background
When a propane tank is filled at 25°C, we need to leave enough volume for liquid propane expansion due to an
increase in temperature. The hottest weather ever recorded is about 58°C. In real life practices, propane tanks
are only filled up to 80-85% of the tank volume. Why? We know that propane expands when it is heated up.
However, why 80-85%?
We can answer this question by using a simple flash calculation i n Aspen HYSYS.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Propane tanks are filled at 25°C with liquefied propane. These tanks will be stored and used in an environment
at 1 bar and ambient temperature. How much, in terms of volume %, can each tank be filled up to?
1
Thermo-007H
Revised: Nov 6, 2012
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add Propane to the component list.
4.03.
Create a fluid package. In the Fluid Packagers folder, select Add. Select Peng-Robinson as the property
package.
4.04.
Go to the simulation environment. Click the Simulation button in the bottom left of the screen.
4.05.
Add a Heater to the flowsheet.
2
Thermo-007H
4.06.
Revised: Nov 6, 2012
Double click on the heater (E-100). Create an Inlet stream, an Outlet stream, and an Energy stream,
named 1, 2, and Q, respectively.
3
Thermo-007H
4.07.
Revised: Nov 6, 2012
Define feed stream. Go to the Worksheet tab. For the feed stream, enter a Vapour Fraction of 1, a
Temperature of 25°C, and a Molar Flow of 1 kgmole/h. In the Composition form, enter 1 for Mole
Fraction of propane.
4
Thermo-007H
Revised: Nov 6, 2012
4.08.
Specify outlet conditions. For the outlet stream, enter a Vapour Fraction of 0, and a Temperature of
58°C. The heater should solve.
4.09.
Add a Spreadsheet to the flowsheet to calculate the maximum percent to fill the propane tank to allow
for expansion when heated.
5
Thermo-007H
4.10.
Revised: Nov 6, 2012
Double click the spreadsheet (SPRDSHT-1). Go to the Spreadsheet tab and enter the following in cells
A1, A2, and A3.
6
Thermo-007H
Revised: Nov 6, 2012
4.11.
Now we will link flowsheet variables to the spreadsheet. Right click on cell B1 and select Import
Variable. Make the following selections to import the Molar Density of stream 1. Click OK when
complete.
4.12.
Right click on cell B2 and select Import Variable to import the Molar Density of stream 2. Make the
following selections and click OK.
7
Thermo-007H
Revised: Nov 6, 2012
4.13.
The spreadsheet should now look like the following.
4.14.
Next, click cell B3 and enter “=(B2/B1)*100”. This divides the molar density at 58°C by the molar density
at 25°C. The resulting number is the percentage that a propane tank should be filled at 25°C to allow for
thermal expansion up to a temperature of 58°C.
4.15.
The maximum fill % of propane at 25°C is 87.86%, as seen in the spreadsheet.
8
Thermo-007H
Revised: Nov 6, 2012
5. Conclusions
The calculation shows that the maximum fill up is 87.8% if the ambient temperature doesn’t exceed 58 °C. To
accommodate special cases, typically, propane tanks are filled up to 80-85%. After completing this exercise you
should be familiar with how to create a spreadsheet to perform custom calculations.
It is important to note that, in real life, the content in a filled propane tank is typically a mixture instead of pure
propane. In addition to propane, the mixture also has a few other light components such as methane and
ethane. Therefore, to carry out calculations for a real project, we need to know the compositions of the mixture
we are dealing with.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
9
Thermo-013H
Revised: Nov 7, 2012
Generate PT Envelope with Aspen HYSYS® V8.0
1. Lesson Objectives

Learn how to generate PT envelopes in Aspen HYSYS
2. Prerequisites

Aspen HSYSY V8.0
3. Background
It is very important to know the phase conditions of a mixture at a given temperature and pressure. For
example, the phase conditions of a fluid in a heat exchanger have an impact on the heat transfer rate.
Formation of bubbles (vapor phase) in inlet streams can also be very damaging to pumps. The phase conditions
of a fluid in a pipe can impact pipeline calculations.
The PT envelope for a given mixture provides a complete picture of phase conditions for a given mixture.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0 and start a new simulation.
4.02.
Create a component list. In the Component Lists folder select Add. Add Ethane and n-Pentane to the
component list.
1
Thermo-013H
Revised: Nov 7, 2012
4.03.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
Add a Material Stream to the flowsheet. To create a PT Envelope we must perform a Stream Analysis,
and in order to perform a Stream Analysis we need a material stream.
2
Thermo-013H
Revised: Nov 7, 2012
4.06.
Double click the material stream (1). Enter a Molar Flow of 100 kg/h. In the Composition form enter
Mass Fractions of 0.5 for each component.
4.07.
Right click on the stream and select Create Stream Analysis | Envelope.
3
Thermo-013H
4.08.
Revised: Nov 7, 2012
In the Envelope window, go to the Performance tab. Here you will see a PT Envelope. Note that you
can change the Envelope type using the radio buttons in the bottom right corner of the window. On the
graph, the blue line represents the dew point and the red line represents the bubble point. The area
between the lines represents the 2-phase region.
4
Thermo-013H
Revised: Nov 7, 2012
5. Conclusions
With the PT envelope of a mixture, we can determine its phase conditions for a given temperature and pressure.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
5
Thermo-014H
Revised: Nov 7, 2012
Retrograde Behavior Illustrated with Aspen HYSYS® V8.0
1. Lesson Objectives

Observe retrograde behavior
2. Prerequisites


Aspen HYSYS V8.0
Completion of teaching module Thermo-013
3. Background
For a mixture, the amount of liquid (liquid fraction) increases as pressure increases at constant temperature.
However, in the retrograde region near the critical region, we may see some interesting behavior—vapor
fraction increases as pressure increases (at constant temperature).
Many mixtures have retrograde behavior near the critical region. In this example, we will examine the
retrograde behavior using a binary mixture of ethane and pentane.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Retrograde behavior can be observed in the mixture of ethane and pentane. In Aspen HYSYS, use PT Envelope to
determine the critical region of the mixture. Then, use a Property Table to examine the retrograde behavior near
the critical region.
1
Thermo-014H
Revised: Nov 7, 2012
Aspen HYSYS Solution
4.01.
Open the file titled Thermo-14H_Retrograde_Behavrior_Start.hsc. This is identical to the file that was
created in lesson Thermo-013H_PT_Envelope.
4.02.
In the PT Envelope that appears in the Performance tab of the Envelope window, notice that there is a
region near the critical point where the vapor fraction will increase as pressure increases while
temperature is held constant.
2
Thermo-014H
4.03.
Revised: Nov 7, 2012
We can demonstrate this behavior by creating a property table in HYSYS. In the Stream Analysis folder
in the Navigation Pane, click the dropdown arrow next to Add and select Property Table. Select stream
1 and click OK.
3
Thermo-014H
Revised: Nov 7, 2012
4.04.
Double click Property Table-1. Select Temperature for Variable 1 and select State for Mode. Enter a
State value of 115°C. Select Pressure for Variable 2 and Incremental for Mode. Enter a Lower Bound
of 60 bar, an Upper Bound of 69 bar, and a # of Increments of 20.
4.05.
In the Dep. Prop form under the Design tab click Add. Select Vapour Fraction and click OK.
4
Thermo-014H
Revised: Nov 7, 2012
4.06.
Click Calculate. Once complete, go to the Performance tab. Here you can view the results in either table
or plot form. Go to Plots and select View Plot.
4.07.
From the plot you can clearly see the region where increasing the pressure will cause the vapour
fraction to increase.
5. Conclusions
For the binary mixture of ethane and pentane (50% each on mass basis), we observed that vapor fraction
increases from 0.701457 to 1 as pressure increases from 65.22 bar to 66.78 bar, which is a retrograde behavior.
This retrograde behavior can be a source of multiple solutions to process simulation.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
5
Thermo-014H
Revised: Nov 7, 2012
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied w ith or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
6
Thermo-019H
Revised: Nov 7, 2012
Remove Hydrogen from Methane, Ethylene and Ethane
with Aspen HYSYS® V8.0
1. Lesson Objectives


Learn how to remove bulk of hydrogen using a cooler and a vapor liquid separator
Learn how to use adjust block and spreadsheets
2. Prerequisites


Aspen HYSYS V8.0
Introduction to vapor-liquid equilibrium
3. Background
In an ethylene plant, we have a feed stream containing hydrogen, methane, ethylene, and ethane . Before this
stream can be fed to the demethanizer, hydrogen must be removed so the volumetric flow is less, which
decreases the required size for the demethanizer column. Because hydrogen has a much higher vapor pressure
than the other components, one or more flash drums can be used for hydrogen removal.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
The feed stream is a combination of 6,306 lb/hr of hydrogen, 29,458 lb/hr of methane, 26,049 lb/hr of ethylene,
and 5,671 lb/hr of ethane. The mole fraction of hydrogen in the feed stream is greater than 0.51, indicating a
large volume of hydrogen in the feed stream. There are two goals for this section of the process:


After bulk of hydrogen is removed, the stream contains less than 0.02 mole fraction of hydrogen
Loss of ethylene to the hydrogen stream should be less than 1%
1
Thermo-019H
Revised: Nov 7, 2012
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add Hydrogen, Methane, Ethylene,
and Ethane to the component list.
4.03.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
4.04.
Go to the simulation environment. Click the Simulation button in the bottom left corner of the screen.
4.05.
Add a Cooler block to the flowsheet from the Model Palette.
2
Thermo-019H
4.06.
Revised: Nov 7, 2012
Double click the cooler (E-100). Create an Inlet stream called Feed, an Outlet stream called ToSep, and
an Energy stream called Q-Cool.
3
Thermo-019H
4.07.
Revised: Nov 7, 2012
In the Parameters form, enter a Delta P of 0, and a Duty of 0 kcal/h. We will create an adjust block to
vary the duty to reach the desired specifications.
4
Thermo-019H
Revised: Nov 7, 2012
4.08.
Define feed stream. Go to the Worksheet tab. Enter a Temperature of -90°F (-67.78°C), and a Pressure
of 475 psia (32.75 bar).
4.09.
Define composition. Go to the Composition form and enter the following Mass Flow rates in kg/h.
5
Thermo-019H
Revised: Nov 7, 2012
4.10.
Add a Separator to the flowsheet from the Model Palette.
4.11.
Double click the separator (V-100). Select stream ToSep as the Inlet stream, and create Outlet streams
called Vap and Liq.
6
Thermo-019H
4.12.
Revised: Nov 7, 2012
Go to the Worksheet tab to view the separation results. You can see that the liquid stream has a
flowrate of 0. We must now add an adjust block and a spreadsheet to find the cooler duty required to
limit the loss of ethylene to the vapor stream to less than 1%.
7
Thermo-019H
Revised: Nov 7, 2012
4.13.
Add a Spreadsheet to the flowsheet from the Model Palette.
4.14.
Double click on the spreadsheet (SPRDSHT-1). In the Spreadsheet tab enter “Ethylene flow in Feed” in
cell A1, and “Ethylene flow in Liq stream” in cell A2. Right click on cell B1 and select Import Variable.
Select the Master Comp Molar Flow (Ethylene) in the Feed stream. Right click cell B2 and select Import
Variable. Select the Master Comp Molar Flow (Ethylene) in the Liq stream.
8
Thermo-019H
Revised: Nov 7, 2012
4.15.
Enter the text “Fraction Ethylene Lost” in cell A3. In cell B3 enter the following formula: = (B1-B2)/B1.
4.16.
You can see that right now we are losing 100% of the Ethylene to the vapor stream. We will now add an
adjust block to vary the cooler duty in order to limit the fraction lost to under 0.01. Add an Adjust block
to the flowsheet from the Model Palette.
9
Thermo-019H
4.17.
Revised: Nov 7, 2012
Double click on the adjust block (ADJ-1). Specify the Adjusted Variable to be the Duty of cooler block E100. Specify the Target Variable to be cell B3 of SPRDSHT-1. Enter a Specified Target Value of 0.01.
10
Thermo-019H
4.18.
Revised: Nov 7, 2012
In the Parameters tab enter a Step Size of 1e+005 kcal/h and change the Maximum Iterations to 100.
Click Start to begin calculations.
11
Thermo-019H
Revised: Nov 7, 2012
4.19.
The fraction of ethylene lost in the vapor stream will now be less than 1%. We must also make sure that
the Mole Fraction of Hydrogen in the liquid stream is less than 0.02. Double click the Liq stream and go
to the Composition form under the Worksheet tab.
4.20.
The Mole Fraction of hydrogen in the liquid stream is 0.0172, which is less than the specified value of
0.02.
12
Thermo-019H
Revised: Nov 7, 2012
5. Conclusions
The vapor pressure of hydrogen is much higher (6,600 times higher than methane at -150 °C) than the vapor
pressures of the other components in the feed stream. We used the adjust block and a spreadsheet to
determine a good value for the heat duty of the cooler block to remove the bulk of hydrogen from the feed
stream through a separator block.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior w ritten consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
13
Thermo-020H
Revised: Nov 7, 2012
Use of a Decanter to Recover Solvent and Cross Distillation
Boundaries with Aspen HYSYS® V8.0
1. Lesson Objectives

Use a 3 phase separator to recover solvent
2. Prerequisites


Aspen HYSYS V8.0
Introduction to liquid-liquid equilibrium
3. Background
In an anhydrous ethanol production plant, cyclohexane is used as an entrainer during separation to break the
ethanol-water azeotrope. The stream from the top of the first distillation column is typically a mixture with a
composition that is very close to the ternary azeotrope. Since cyclohexane and water are not miscible, a
decanter can be used to separate cyclohexane from the ethanol and water. The second role of this liquid-liquid
separation is to cross distillation boundaries. One of the two outlet streams from the decanter is recovered
solvent. The other stream has a composition in the ethanol-rich distillation region and is fed to the second
column.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Use of a Decanter for solvent recovery
Problem Statement
A 100 kmol/hr feed stream that is 35 mol-% ethanol, 6 mol-% water, and 59 mol-% cyclohexane is fed to a
decanter. Determine the compositions of the two outlet streams from the decanter and their flowrates.
1
Thermo-020H
Revised: Nov 7, 2012
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0 and create a new simulation.
4.02.
Create a component list. In the Component Lists folder select Add. Add Ethanol, Water, and
Cyclohexane to the component list.
4.03.
Define property package. In the Fluid Packages folder select Add. Select UNIQUAC as the property
package. In the Activity Model Specifications grid, select RK for Vapour Model.
4.04.
Go to the simulation environment. Click the Simulation button in the bottom left of the screen.
4.05.
Add a 3-Phase Separator to the flowsheet from the Model Palette.
2
Thermo-020H
4.06.
Revised: Nov 7, 2012
Double click the 3 phase separator vessel (V-100). Create an Inlet stream called Feed, and three Outlets
called Vapor, Liquid1, and Liquid2.
3
Thermo-020H
Revised: Nov 7, 2012
4.07.
Define feed stream. Go to the Worksheet tab. Enter a Temperature of 25°C, a Pressure of 1 bar, and a
Molar Flow of 100 kgmole/h.
4.08.
In the Composition form enter Mole Fractions of 0.35 for ethanol, 0.06 for water, and 0.59 for
cyclohexane. The separator should solve when compositions are complete.
4
Thermo-020H
4.09.
Revised: Nov 7, 2012
Check results. You can see that the feed stream was separated into two separate liquid streams
because of a difference in density between the two liquid phases. Stream Liquid1 has flowrate of 54.6
kgmole/h, while the heavier stream Liquid2 has a flowrate of 45.4 kgmole/h.
5
Thermo-020H
4.10.
Revised: Nov 7, 2012
Check stream composition. Stream Liquid1 is enriched in cyclohexane while stream Liquid2 is enriched
in ethanol.
6
Thermo-020H
Revised: Nov 7, 2012
5. Conclusions
A Decanter can be used to concentrate cyclohexane from 59% to 78% so it can be recycled or repurposed. The
other outlet (Liquid2) has a composition in a different distillation region from the Feed stream, providing a
product that crosses distillation boundaries. This serves as the decanter’s second role mentioned in the
background section.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
7
Mass Transfer Operations
Dist-001H
Revised: Nov 7, 2012
Distillation of Close Boiling Components with Aspen HYSYS® V8.0
1. Lesson Objectives




Distillation column modeling
Column profiles
Custom stream results
Material balance across distillation column
2. Prerequisites



Aspen HYSYS V8.0
Experience inserting blocks and connecting streams in HYSYS
Introduction to vapor liquid equilibrium
3. Background
Ethylene is an important monomer, and is made from ethane. The conversion of the reaction is not perfect, so
the ethylene must be separated from the system. Ethane and ethylene are molecularly similar, and so are
difficult to separate. The difficulty of the separation is compounded by the fact that polymer production
requires extremely pure feedstocks.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem: A stream containing 68.5wt% ethylene with a total flowrate of 7.3 million lb/day is fed into a
distillation column consisting of 125 stages. It is desired to produce a distillate product stream containing a
minimum of 99.96 wt% ethylene with a total flowrate of 5 million lb/day. It is also desired that the bottoms
product contains no more than 0.10wt% ethylene. Determine if this separation is feasible.
1
Dist-001H
Revised: Nov 7, 2012
Assumptions:
-
100% tray efficiency
Total condenser
300 psig column operating pressure
A refrigerant utility stream capable of condensing the ethylene mixture (not included in model)
Feed mixture is at 350 psig and is a vapor
125 stages
Feed enters the column at stage 90
Peng-Robinson equation of state
Aspen HYSYS Solution:
4.01.
Start Aspen HYSYS V8. Select New to start a new simulation.
4.02.
Create a Component List. In the Properties environment, select the Component Lists folder in the
navigation pane and click Add to add a new HYSYS component list. In Component List – 1 add Ethane
and Ethylene to the selected components list. You may need to use the search function by typing in
ethene and pressing enter to find the component ethylene.
2
Dist-001H
Revised: Nov 7, 2012
4.03.
Create a Fluid Package. Click on the Fluid Packages folder in the navigation pane and select Add to add a
new HYSYS fluid package. Select Peng-Robinson as the property package. The Peng-Robinson equation
of state is typically used to model systems containing hydrocarbons at high pressures.
4.04.
You are now ready to enter the simulation environment and construct the flowsheet. Go to the
simulation environment by clicking the Simulation button at the bottom left of the screen. On the main
flowsheet insert a Distillation Column Sub-Flowsheet from the Model Palette under the Columns tab.
3
Dist-001H
4.05.
Revised: Nov 7, 2012
Double click on the Distillation unit on the main flowsheet, or go to UnitOps | T-100 in the navigation
pane. The Distillation Column Input Expert window will appear. Here we will create the feed and
product streams, as well as define the operating conditions of the column. On the first page, enter 125
for # Stages and define the feed and product streams as shown below.
4
Dist-001H
Revised: Nov 7, 2012
4.06.
Click Next and page 2 will appear. This page allows you to configure the reboiler. Select Regular Hysys
reboiler for Reboiler Type Selection, and select the Once-through radio button. Click Next.
4.07.
This next page allows you to input the pressure and pressure drop in the condenser and reboiler. Enter
a Condenser Pressure and Reboiler Pressure of 300 psig (2170 kPa). This indicates that there is no
pressure drop through the column, which is acceptable for this simplified example.
4.08.
Click Next. This page (page 4 of 5) allows you to enter optional temperature estimates for the
condenser, top stage, and reboiler. In this case we will leave these fields blank. Click Next. The final
page allows you enter a liquid distillate rate or a reflux ratio. From our problem statement, we know
that distillate rate will be 5 million lb/day of ethylene. Select Mass for Flow Basis and enter 5000000
lb/day (94498.4 kg/h) for Liquid Rate. Select Done to enter the column property window.
4.09.
We must first define the feed stream going into the column. In the Column property window, go to the
Worksheet tab. On the Conditions form, enter a pressure of 350 psig (2514 kPa), a Vapour fraction of
1, and a Mass Flow of 7.3e+06 lb/day (1.380e+005 kg/h) for the Feed@COL1 stream. Go to the
Compositions sheet in the Worksheet tab. Here we will define the composition of the feed stream.
Type a number into the Feed composition grid for Ethane to open the Input Composition for Stream
window. Select the Mass Fractions radio button, enter 0.315 for Ethane and 0.685 for Ethylene. Click
OK. The feed stream on the main flowsheet should turn blue, indicating that all required input has been
5
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Revised: Nov 7, 2012
entered and that it has solved for all properties. If you open the Feed stream property window you will
see a green status bar saying OK at the bottom.
6
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Revised: Nov 7, 2012
4.10.
Now we must enter design specs to reach the desired product compositions as provided in the problem
statement. In the Column property window, go to Design | Specs. Our two design specifications for this
simulation will be distillate rate and mass fraction of ethylene in the bottoms stream. In the column
specifications form there should already be a Distillate Rate spec that was created from the column
input expert. Make sure that the distillate specification value is correct (9.450e+004 kg/h) and that the
spec is checked as active.
4.11.
In the Column Specifications form, click Add and select a Column Component Fraction specification. In
the Comp Frac Spec window select the Stream radio button for Target Type. Enter Ethane@COL1 for
Draw, Mass Fraction for Basis, and 9.0e-004 for Spec Value. Select Ethylene for Components. Close
this form when all information is entered.
7
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4.12.
Revised: Nov 7, 2012
Make sure that this spec (Comp Fraction) is checked as Active in the Specification Details area. You will
notice that after activating the Comp Fraction spec, the Degrees of Freedom changes to -1. This means
that the problem is over specified. To fix this, simply deactivate one of the column specifications, in this
case the Reflux Ratio. Once the reflux ratio design spec is deactivated, the column should solve. You will
notice that the status bar at the bottom of the sheet will turn green and say Converged.
8
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4.13.
Revised: Nov 7, 2012
Check results. In the Column property window, go to the Performance tab. On the Summary sheet you
can see the flowrates and compositions of the feed and product streams. You can see that both
specifications described in the problem statement are met.
9
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Revised: Nov 7, 2012
4.14.
In the Column Profiles sheet you can view the calculated reflux ratio, boilup ratio, as well as material
and energy profiles through the column.
4.15.
On the Plots sheet you can create plots such as temperature and composition along the column, as
shown below.
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Revised: Nov 7, 2012
11
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4.16.
Revised: Nov 7, 2012
Finally, on the Cond./Reboiler sheet you can view the calculated operating conditions for both the
condenser and reboiler.
5. Conclusions
The 125 stage column was able to exceed the specification of 99.96wt% ethylene at 5 million lb/day, as well as
the bottoms having less than 0.10wt% ethylene. It could then be concluded that this column is capable of
completing the desired separation. Aspen HYSYS allows engineers to model existing equipment and see if it is
possible to repurpose it or, otherwise, design new equipment that would meet very specific criteria.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or othe r incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
12
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Revised: Nov 5, 2012
Pressure Swing Distillation with Aspen HYSYS® V8.0
1. Lesson Objectives


Configure distillation columns in Aspen HYSYS
Learn to use pressure swing to overcome azeotropic mixture
2. Prerequisites


Aspen HYSYS V8.0
Working knowledge of vapor-liquid equilibrium and distillation
3. Background
Basics on Azeotropic Distillation
An azeotrope occurs when the liquid and vapor mole fractions of each component are the same. On a y -x plot,
an azeotrope is shown by a line which passes through the x = y line. Azeotropes present challenges to
separation processes and need to be accounted for in process design and operation.
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Revised: Nov 5, 2012
No further enrichment can occur in either phase when the system reaches the azeotrope constraint because the
driving force is eliminated. A mixture will separate towards a pure component and the azeotropic mixture. The
component which is purified depends on which side of the crossover the initial mixture is. To purify the minority
component, you must first cross the azeotrope. This can be done by adding an entrainer, another chemical
which breaks the azeotrope. This creates the need for additional separation and usually material recycle with a
purge stream. Alternatively, the composition of the azeotrope is dependent on pressure, which can be
exploited to get the mixture across the azeotrope. This is called pressure swing distillation.
Ethanol and water form an azeotrope at approximately 95.5mol-% ethanol at 1 atm. This is a low-boiling point
(or positive) azeotrope. The boiling point of the mixture is lower than either of the pure components, so the
azeotropic mixture exit from the top of the column regardless of which compound is being enriched in the
bottoms.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement
A feed of 24,000 kg/h of 20mol-% ethanol and 80 mol-% water must be separated. The required product stream
is 99 mol-% ethanol at a flowrate of at least 7,500 kg/h. This separation will be achieved by using pressure swing
distillation.
We begin by creating a technically feasible design for a two-column separation train. We will report for each
column: operating pressure, number of stages, reflux ratio, and the purity and recovery specifications. Also
report a stream table with the flowrates and compositions of relevant streams. Material recycle will be
necessary to achieve these results. We will use an operating pressure of 0.1 bar for the first column, and an
operating pressure of 20 bar for the second column.
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add ethanol and water to the
component list.
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Revised: Nov 5, 2012
4.03.
Define property package. In the Fluid Packages folder select Add. Select NRTL as the property package.
Select RK as the Vapour Model. The non-random, two liquid (NRTL) model works well for very non ideal
liquid systems which is important because of the hydrogen bonding present. The Redlich-Kwong
equation model works much better at high pressures than the ideal gas assumption in the vapour phase.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
Add a Distillation Column Sub-Flowsheet to the flowsheet from the Model Palette.
3
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4.06.
Revised: Nov 5, 2012
Double click the column (T-100). This will open the Distillation Column Input Expert window. Enter the
following information and click Next when complete.
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Revised: Nov 5, 2012
4.07.
On the second page of the input expert leave the default selections for a Once-through, Regular Hysys
reboiler and click Next.
4.08.
On page 3 of the input expert enter Condenser and Reboiler Pressures of 0.1 bar. Click Next when
complete.
4.09.
On page 4, leave all fields for temperature estimates blank. Click Next to continue. On page 5 of the
input expert, again leave all fields blank and click Done to configure the column.
4.10.
We will now define the feed stream. Double click on the Feed stream. In the Worksheet tab enter a
Temperature of 65°C, a Pressure of 1.2 bar, and a Mass Flow of 24,000 kg/h.
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Revised: Nov 5, 2012
4.11.
Go to the Composition form under the Worksheet tab to define the composition of the feed stream.
Enter Mole Fractions of 0.2 for ethanol and 0.8 for water. When complete, the feed stream should be
fully defined and will solve.
4.12.
Double click the column (T-100) to finish specifying the operating conditions. Go to the Specs form
under the Design tab. First, we would like to recover 99% of ethanol from the feed stream. To do this
we will click the Add button and select Column Component Recovery. Select stream D1 as the Draw,
enter a Spec Value of 0.99, and select Ethanol as the Component.
6
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4.13.
Revised: Nov 5, 2012
Second, we would like the distillate stream (D1) to have a mole fraction of 0.90 for ethanol. The
azeotrope prevents us from the reaching the desired product purity of 99% with a single column, but we
would still want the distillate from the first column to be very pure while losing as little product to the
bottoms stream as possible. Click Add and select Column Comp Fraction. Select Stream for Target
Type, D1 for Draw, 0.90 for Spec Value, and Ethanol for Component.
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Revised: Nov 5, 2012
4.14.
Go to the Specs Summary form under the Design tab. Make sure that the only specifications marked as
active are Comp Recovery and Comp Fraction. The column will attempt to solve once these specs are
active.
4.15.
If the solver fails to converge, we may have to add some parameter estimates. For example, we can
provide an estimate for the distillate stream flow rate based on a simple mass balance. We know that
the feed contains approximately 200 kgmole/h of ethanol. We also know that we want to recover 99%
of ethanol with an ethanol mole fraction of 0.9 in the distillate. We can then provide an estimate of 220
kgmole/hr for the distillate stream. In the Specs Summary grid, enter 220 kgmole/h for Distillate Rate
which will serve as an estimate as long as it is not an active specification. Click Run when complete. The
column should now converge. Also note that the bottoms stream is over 99% water, which means that
we are throwing away very little ethanol. A pure water stream is also desirable because we can now
repurpose or dispose of this stream with minimal further processing.
8
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4.16.
Revised: Nov 5, 2012
We are now ready to construct the second column, which will operate on the other side of the
azeotrope at a pressure of 20 bar. We first need to insert a pump to increase the pressure of the
distillate stream leaving the first column. Add a pump to the flowsheet from the Model Palette.
9
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Revised: Nov 5, 2012
4.17.
Double click the pump (P-100). Select stream D1 as the Inlet, create an Outlet stream called Feed2, and
create an Energy stream called Q-Pump.
4.18.
In the Worksheet tab, enter a Pressure of 20 bar (operating pressure of the second column) for stream
Feed2. The pump should solve.
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Revised: Nov 5, 2012
4.19.
Next we will insert the second Distillation Column Sub-Flowsheet to the flowsheet, after the pump.
4.20.
Double click the second column (T-101). This will open the Distillation Column Input Expert. On the
first page, enter the following information and click Next when complete.
4.21.
On page 2 of the input expert, leave the default selections for a Once-through, Regular Hysys reboiler.
Click Next.
4.22.
On page 3 of the input expert, enter Condenser and Reboiler Pressures of 20 bar. Click Next when
complete.
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Revised: Nov 5, 2012
4.23.
On page 4 leave all fields for temperature estimates blank. Click Next. On the final page, also leave all
fields blank. Click Done to configure the column.
4.24.
We must now enter the operating specifications for the column. In the column window for T-101 go to
the Specs form under the Design tab. Add a column specification for the mole fraction of ethanol in the
bottoms stream. Click Add and select Column Component Fraction. Select Stream for Target Type,
Ethanol for Draw, 0.99 for Spec Value, and Ethanol for Component.
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Revised: Nov 5, 2012
4.25.
We will now add a specification for the mole recovery of ethanol in the bottoms stream. In the Specs
Summary form under the Design tab, double click the specification for Btms Prod Rate. We know that
approximately 203 kgmole/h of ethanol are entering the process in the original feed stream. Since we
are recovering 99% of the ethanol in the first column, we expect the final product stream to have a
flowrate of approximately 200 kgmole/h.
4.26.
In the Specs Summary form, make sure that the only active specifications are Btms Prod Rate and Comp
Fraction. The column will attempt to solve, but you should find that it will not be able to converge. This
is because we need to add a recycle stream to the flowsheet.
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Revised: Nov 5, 2012
4.27.
Double click on the first column (T-100) and add a second Inlet Stream called Recycle. This stream will
enter on the same stage as the Feed stream (stage 25).
4.28.
We will define the recycle stream with a guess of what the actual recycle stream will consist of. We will
use this “dummy” recycle stream to allow both columns to converge, and then we will add a recycle
block to find the actual recycle stream conditions. Double click the Recycle stream on the flowsheet. In
the Worksheet tab enter a Vapour Fraction of 0, a Pressure of 1.2 bar, and a Molar Flow of 400
kgmole/h. In the Composition form enter Mole Fractions of 0.9 for ethanol, and 0.1 for water. Again,
these values are just guesses that will be used to converge both columns. The actual value s for the
recycle stream will be determined later through the use of a recycle block. Make sure that you specify
Recycle in its own window, rather than in the Worksheet tab of Column T-100, as this will cause a
consistency error due to overspecification when you try to complete the recycle loop.
14
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Revised: Nov 5, 2012
4.29.
Once the recycle stream is fully specified, double click on each column and click Run to converge the
columns. Both columns should now successfully converge.
4.30.
Now we can close the recycle loop to determine the actual values for the Recycle stream. First we must
lower the pressure of stream D2 through the use of a valve. Add a Valve to the flowsheet from the
Model Palette.
15
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Revised: Nov 5, 2012
4.31.
Double click on the valve (VLV-100). Select stream D2 as the Inlet and create an Outlet called Rec.
4.32.
Go to the Worksheet tab and specify an outlet Pressure of 1.2 bar. The valve should solve.
16
Dist-002H
4.33.
Revised: Nov 5, 2012
We will now add a Recycle block to the flowsheet from the Model Palette.
17
Dist-002H
4.34.
Revised: Nov 5, 2012
Double click on the recycle block (RCY-1). Select stream Rec as the Inlet and stream Recycle as the
Outlet. The recycle block should automatically solve.
18
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Revised: Nov 5, 2012
4.35.
Go to the Worksheet tab to view recycle convergence results. The two streams should be equal to each
other within a certain tolerance.
4.36.
If you are not satisfied with the recycle convergence, go to the Parameters tab and lower the
sensitivities. For example if we change the sensitivity value to 1 for Flow and Composition we get the
following results.
19
Dist-002H
4.37.
Revised: Nov 5, 2012
The flowsheet is now complete. Further analysis can be performed to optimize the column size, feed
location, and energy requirements, but that analysis is not covere d in this lesson.
20
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Revised: Nov 5, 2012
5. Conclusions
The azeotrope in the ethanol-water system presents a barrier to separation, but pressure swing distillation can
be used to purify ethanol. A technically feasible design for purifying ethanol to 99mol-% with pressure swing
distillation can be constructed using Aspen HYSYS. A column with 30 equilibrium stages and operating at 0.1 bar
with a reflux ratio of 6.9 increases the ethanol composition to 90mol-%. A second column with 75 equilibrium
stages and operating at 20 bar with a reflux ratio of 10.8 increases the purity to 99mol-%.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
21
Dist-003H
Revised: Nov 7, 2012
First-Pass Distillation Estimates with Aspen HYSYS® V8.0
1. Lesson Objectives


Short cut distillation modeling
Initial column sizing
2. Prerequisites


Aspen HYSYS V8.0
Introduction to vapor liquid equilibrium
3. Background
Short Cut Distillation Block
The Short Cut Column performs Fenske-Underwood short cut calculations for simple refluxed towers. The
Fenske minimum number of trays and the Underwood minimum reflux are calculated. A specified ref lux ratio
can then be used to calculate the vapor and liquid traffic rates in the enriching and stripping sections, the
condenser duty and reboiler duty, the number of ideal trays, and the optimal feed location. The Short Cut
Column is only an estimate of the Column performance and is restricted to simple refluxed Columns. For more
realistic results the rigorous Column operation should be used. This operation can provide initial estimates for
most simple Columns
Heavy and Light Keys
In two-component distillation, the column splits the feed so a single component is enriched in each exit stream.
In multi-component distillation, there are more components than effluent streams, so there are multiple
components enriched in at least one of the exit streams. The key components are the components that are split
by the column. The light key is the least volatile component enriched in the distillate stream; the heavy key is
the most volatile component enriched in the bottoms stream. If there are components A, B, C, and D with
decreasing volatility, a column can create the following separations:
1
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Revised: Nov 7, 2012
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem
A stream containing 68.5 wt% ethylene and 31.5 wt% ethane with a total flowrate of 7.3 million lb/day must be
separated. Report a reasonable starting point for a more detailed design including an estimate of the number of
theoretical stages and reflux ratio required to achieve a separation of 99.9% recovery of ethylene and 99.0%
recovery of ethane.
Aspen HYSYS Solution
Initial estimation for distillation of relatively ideal components like ethane and ethylene can be done using
graphical methods and semi-empirical equations like the equations described in the background section. In
Aspen HYSYS, the Short Cut Column uses these equations. The user must input which components are the light
and heavy keys and the recovery of each of these components, the pressure in the condenser and reboiler, and
the reflux ratio. These equations are good starting points, but the Shortcut Column is not a rigorous calculation
block; it does not directly use thermodynamics to solve for the reflux ratio or required number of stages. A
more rigorous look at this separation problem is available in Dist-001_C2Splitter.
4.01.
Create a new case in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add Ethane and Ethylene to the
component list. You may need to type “ethene” in the Search for field to find ethylene.
2
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Revised: Nov 7, 2012
4.03.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
4.04.
Go to the simulation environment by clicking on the Simulation button below the navigation pane.
4.05.
Add a Short Cut Distillation model to the flowsheet from the Model Palette.
4.06.
Double click on the column (T-100). Create an Inlet called Feed, a Condenser Duty called Q-Cond, a
Distillate called Dist, a Reboiler Duty called Q-Reb, and a Bottoms called Bot. Check the Liquid radio
button under Top Product Phase, which specifies a total condenser.
3
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Revised: Nov 7, 2012
4.07.
Define feed stream. Go to the Worksheet tab. Enter a Vapour Fraction of 1, a Pressure of 350 psig
(25.14 bar), and a Mass Flow of 7,300,000 lb/day (1.38e+005 kg/h).
4.08.
In the Composition form enter Mass Fractions of 0.315 for Ethane and 0.685 for Ethylene. The feed
stream should solve.
4
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Revised: Nov 7, 2012
4.09.
Go to the Parameters form under the Design tab in the Shortcut Column window. Using the recovery
percentages specified in the problem statement along with a simple mass balance, it can be determined
that the mole fraction of ethane in the distillate stream will be approximately 0.004, and the mole
fraction of ethylene in the bottoms will be approximately 0.002. Enter these values into the
Components grid in the Parameters form.
4.10.
Specify the Condenser and Reboiler Pressures to both be 300 psig (21.698 bar). You can see that HYSYS
has now calculated the Minimum Reflux Ratio required to complete the specified separation with an
infinite number of stages.
4.11.
You may now enter a Reflux Ratio and the Shortcut Column will calculate the number of stages, feed
stage location, condenser and reboiler temperatures, and material and energy flows. For example,
enter 4.5 as the External Reflux Ratio.
5
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4.12.
Revised: Nov 7, 2012
In the Performance tab you will see the following results.
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Revised: Nov 7, 2012
5. Conclusions
Estimation using the Short Cut Column can be done very quickly, even for complex distillation systems. The
results can then be used as a starting point for more complex analysis, such as a with a rigorous distillation
model.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, I nc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
7
Dist-004H
Revised: Nov 7, 2012
Gibbs Phase Rule in a Distillation Column with Aspen HYSYS® V8.0
1. Lesson Objectives

Use Aspen HYSYS to observe one-to-one relation between stage temperatures and compositions in a
distillation column for a binary system with fixed pressure.
2. Prerequisites

Aspen HYSYS V8.0
3. Background
According to the Gibbs phase rule, the degrees of freedom ( ) is equal to the number of components (C) minus
number of phases ( , plus 2.
For a binary mixture involving vapor-liquid equilibrium, there are no degrees of freedom left once temperature
and pressure are fixed. All state variables are fixed, including vapor and liquid compositions. This is useful for
distillation column control. In distillation column simulations, the product compositions are typically the most
important results. Therefore, compositions are typically measured and controlled. However, measuring
compositions is a slower, more costly process than measuring temperatures. When pressure is fixed,
temperature and composition have a one-to-one correspondence (except for cases with azeotropes).
Therefore, measuring and controlling top/bottom stage temperatures is the same as measuring and controlling
top/bottom stage composition.
In this example, we will carry out several case studies to show that compositions for top and bottom stages are
constant when top and bottom stage temperatures are fixed regardless of changes in other operating conditions
and column configurations.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
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Revised: Nov 7, 2012
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
For a distillation column consisting of a binary mixture of ethane and ethylene, when the pressure and
temperature for an equilibrium stage have been fixed, will the vapor and liquid compositions leaving this stage
change with other conditions of the column?
Aspen HYSYS Solution
4.01.
Create a new case in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add Ethane and Ethylene to the
component list. Ethylene can be found by entering “ethene” in the Search for field.
4.03.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
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Revised: Nov 7, 2012
4.05.
Add a Distillation Column Sub-Flowsheet to the flowsheet from the Model Palette.
4.06.
Double click on the distillation column (T-100). The Distillation Column Input Expert window will open.
On the first page of the expert enter the following information. Click Next when complete.
3
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Revised: Nov 7, 2012
4.07.
On the second page of the input expert leave the default selections for a Once –through, Regular HYSYS
reboiler and click Next.
4.08.
On the third page of the input expert enter Condenser and Reboiler Pressures of 100 kPa. Click Next.
4.09.
On the fourth page of the input expert leave all fields for temperature estimates blank and click Next.
Also leave all fields blank on the fifth page and click Done to configure the column.
4.10.
We will first define the feed stream. Double click on the Feed stream. Enter a Vapour Fraction of 0.5, a
Pressure of 100 kPa, and Molar Flow of 100 kgmole/h.
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Revised: Nov 7, 2012
4.11.
In the Composition form enter Mole Fractions of 0.5 for both Ethylene and Ethane. The stream should
solve.
4.12.
Double click the column (T-100) to complete the specifications for the column. Go to the Specs form
under the Design tab. We would like to specify the temperatures of the top and bottom stages. Click
the Add button and select a Column Temperature specification type. Select Stage 1 and enter a Spec
Value of -104.193°C. This temperature corresponds to a mole fraction of 0.99 ethylene in the distillate.
4.13.
Add a second Temperature specification and select Stage 50 and enter a Spec Value of -88.971°C. This
temperature corresponds to a mole fraction of 0.99 ethane in the bottoms.
5
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4.14.
Revised: Nov 7, 2012
In the Specs Summary form, make sure that the only active specifications are the two temperature
specs that were just created. After both temperature specs are made active the column should solve.
6
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4.15.
Revised: Nov 7, 2012
Check product composition results. In the column property window, go to the Performance tab. In the
Summary form you can see that the mole fraction of ethylene in the distillate is 0.9934 and the mole
fraction of ethane in the bottoms is 1.
7
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Revised: Nov 7, 2012
4.16.
To view the Reflux and Boilup Ratios go to the Column Profiles form under the Performance tab.
4.17.
We will now change the feed location to the column while holding the top and bottom stage
temperature specifications constant. The product compositions should not change because we are
holding temperature and pressure constant. Go to the Design tab in the column window and change
the Feed stream Inlet Stage to 29. Click Run to begin calculations. The column should converge.
8
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Revised: Nov 7, 2012
4.18.
Go to the Performance tab to view results. Note that the product compositions have not changed. You
will notice however that the Reflux and Boilup Ratios have changed.
4.19.
We will now change the composition of the feed stream. Double click the Feed stream and go to the
Composition form under the Worksheet tab. Change the Mole Fractions to 0.6 for Ethylene and 0.4 for
Ethane. When finished the column should automatically update and converge. Again, the product
compositions should not change because we are still holding the temperature and pressure of the top
and bottom stage constant.
9
Dist-004H
Revised: Nov 7, 2012
4.20.
Go to the Performance tab in the column window to view the composition results.
4.21.
Lastly, we will add 10 stages to the column and observe the effect on product purity. Go to the Design
tab of the column window and enter 60 for Num of Stages. Press Run when complete. The column
should converge.
10
Dist-004H
4.22.
Revised: Nov 7, 2012
Go to the Performance tab to view results. Once again you will see that the product compositions
remain unchanged.
5. Conclusions
This example shows that for a binary distillation column, fixing top/bottom stage temperatures holds
top/bottom compositions constant regardless of changes to other things (e.g., feed conditions and locations or
the number of stages in the column). This behavior can be leveraged for control. For binary mixtures with
azeotrope(s), this still holds true assuming that a composite feed stays within a certain region divided by
azeotropes.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
11
Dist-009H
Revised: Nov 19, 2012
Separation of Acetone-Water with Aspen HYSYS® V8.0
Liquid-Liquid Extraction with 3-Methylhexane as the Solvent
1. Lesson Objectives


Learn how to build an extraction and solvent recovery flowsheet.
Learn how to configure a liquid-liquid extractor and a distillation column.
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Water has a high latent heat (heat of vaporization) compared to many other components. For the separation of
a water-acetone mixture (50 wt-% each), it may be more energy efficient to use extraction instead of direct
distillation. In this example, we utilize 3-methylhexane as a solvent to remove water via liquid-liquid extraction,
followed by distillation to remove the solvent from acetone.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Determine how much energy is required to separate a 50 wt-% acetone 50 wt-% water stream using 3methylhexane as a solvent.
Aspen HYSYS Solution
4.01.
Start a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add Acetone, Water, and 3methylhexane to the component list.
1
Dist-009H
Revised: Nov 19, 2012
4.03.
Select property package. In the Fluid Packages folder select Add. Select PRSV as the property package.
For information about the PRSV property package see Aspen HYSYS help.
4.04.
Move to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
First we will add a Mixer to the flowsheet from the Model Palette. This mixer will serve to mix together
the recycled solvent stream and the solvent make up stream.
2
Dist-009H
4.06.
Revised: Nov 19, 2012
Double click the mixer (MIX-100). Create two Inlet streams called Make Up and Solvent-Recycle.
Create an Outlet stream called Solvent.
3
Dist-009H
Revised: Nov 19, 2012
4.07.
Double click on the Make Up stream. Specify a Temperature of 25°C, a Pressure of 1 bar, and a Molar
Flow of 0. We will later assign this stream a flowrate, but for now it will have zero flow. In the
Composition form enter a Mole Fraction of 1 for 3-methylhexane.
4.08.
Double click on the Solvent-Recycle stream. Enter a Temperature of 30°C, a Pressure of 1 bar, and a
Mass Flow of 150 kg/h. In the Composition form enter a Mole Fraction of 1 for 3-methylhexane. These
specifications will serve as an initial guess as to what the actual recycle stream will be.
4
Dist-009H
Revised: Nov 19, 2012
4.09.
Add a Liquid-Liquid Extractor to the flowsheet from the Model Palette.
4.10.
Double click on the extractor (T-100) to open the Liquid-Liquid Extractor Input Expert window. On the
first page enter a Top Stage Inlet called Feed and select Solvent for the Bottom Stage Inlet. Change the
number of stages to 8. Enter an Ovhd Light Liquid stream called Rich-Sol and a Bottoms Heavy Liquid
stream called Water. Click Next when complete.
5
Dist-009H
Revised: Nov 19, 2012
4.11.
On Page 2 of the Input Expert enter Top and Bottom Stage Pressures of 1 bar. Click Next when
complete.
4.12.
On the final page of the Input Expert enter a Top Stage Temperature Estimate of 25°C. Click Done
when complete to configure the column.
6
Dist-009H
Revised: Nov 19, 2012
4.13.
We must now define the feed stream. Go to the Worksheet tab in the Column: T-100 window. For the
Feed stream enter a Temperature of 25°C, a Pressure of 1 bar, and a Mass Flow of 100 kg/h.
4.14.
In the Compositions form under the Worksheet tab enter Mass Fractions of 0.5 for acetone and water
in the Feed stream.
7
Dist-009H
Revised: Nov 19, 2012
4.15.
Click the Run button at the bottom of the Column: T-100 window to begin column calculations. The
column should converge.
4.16.
Check the composition of the Water stream exiting the bottom of the column. You will see that the
mole fraction for water is 1.
8
Dist-009H
Revised: Nov 19, 2012
4.17.
We will now insert a Distillation Column Sub-Flowsheet from the Model Palette.
4.18.
Double click the column (T-101) to open the Distillation Column Input Expert. On Page 1 enter the
following information and click Next when complete.
9
Dist-009H
Revised: Nov 19, 2012
4.19.
On Page 2 of the Input Expert leave the default selections for a Once-through, Regular Hysys Reboiler.
Click Next.
4.20.
On Page 3 of the Input Expert enter Condenser and Reboiler Pressures of 1 bar. Click Next when
complete.
10
Dist-009H
Revised: Nov 19, 2012
4.21.
On Page 4 and 5 leave all fields blank. Click Done on the final page to configure the column.
4.22.
We must define the design specifications for this column. Go to the Specs Summary form under the
Design tab. Enter 1.2 for Reflux Ratio and make sure that the reflux ratio specification is the only active
design specification.
4.23.
We will now add a specification for the mole fraction of acetone in the distillate stream. Go to the Specs
form under the Design tab. Click Add and select Column Component Fraction. Select Stream for Target
Type, Acetone for Draw, enter 0.99 for Spec Value, and select Acetone for Component.
4.24.
The Degrees of Freedom for the column should now be 0. Click the Run button to begin column
calculations. The column should solve.
11
Dist-009H
4.25.
Revised: Nov 19, 2012
We now need to add a cooler to cool the bottoms stream in order to recycle it back to the mixer. Add a
Cooler to the flowsheet from the Model Palette.
12
Dist-009H
Revised: Nov 19, 2012
4.26.
Double click on the cooler (E-100). Select stream Sol-Rec as the Inlet, and create an Outlet called LeanSol and an Energy stream called Q-Cool.
4.27.
In the Worksheet tab enter an outlet Temperature of 30°C and a Pressure of 1 bar. The block should
solve.
13
Dist-009H
Revised: Nov 19, 2012
4.28.
Now we will add a Spreadsheet to control to flowrate of solvent in the Make Up stream.
4.29.
Double click on the spreadsheet (SPRDSHT-1). Go to the Spreadsheet tab and enter the following text in
cells A1 and A2.
14
Dist-009H
Revised: Nov 19, 2012
4.30.
Right click on cell B1 and select Import Variable. Select Master Comp Molar Flow of 3-methylhexane in
the acetone product stream.
4.31.
Click on cell B2 and enter “=B1”. Right click on cell B2 and select Export Formula Result. Select the
Molar Flow of stream Make Up. This will set the Make Up stream flowrate equal to the flowrate of
solvent being lost in the product stream.
15
Dist-009H
4.32.
Revised: Nov 19, 2012
We will now recycle the bottoms streams from the second column in order to prevent throwing away
acetone product. Add a Recycle block to the flowsheet from the Model Palette.
16
Dist-009H
Revised: Nov 19, 2012
4.33.
Double click on the recycle block (RCY-1). Select stream Sol-Rec as the Inlet and stream Solvent-Recycle
as the Outlet. The flowsheet should solve.
4.34.
We can now try to minimize the amount of solvent that we are recycling. It is possible that there are
many solutions for the amount of solvent recycle, and we wish to find the optimum solution. We can
vary the mass flow of the recycle stream and find where the reboiler duty is at the lowest.
4.35.
Go to Case Studies in the navigation pane and click Add. In Case Study 1 click Add and select the Mass
Flow of stream Solvent-Recycle and the Reboiler Duty of column T-101. Enter a Low Bound of 75 kg/h,
a High Bound of 200 kg/h, and a Step Size of 5 kg/h. Click Run.
17
Dist-009H
4.36.
Revised: Nov 19, 2012
Check results. Go to the Plots tab and you will see that the reboiler duty is the lowest when the solvent
recycle flow is around 75 kg/h. You may try setting the flowrate of Solvent-Recycle even lower, but you
will find that the flowsheet will not converge.
18
Dist-009H
Revised: Nov 19, 2012
4.37.
Double click on stream Solvent-Recycle and enter a Mass Flow of 75 kg/h. The flowsheet should
converge after a few moments.
4.38.
Check results. Double click on column T-101 and go to the Cond./Reboiler form under the Performance
tab. Make note of the Condenser and Reboiler Duty.
4.39.
Double click on energy stream Q-Cool and make note of the cooling duty.
19
Dist-009H
Revised: Nov 19, 2012
4.40.
The total heating duty for this design is 16,270 kcal/h and the total cooling duty is 9,218 kcal/h.
4.41.
Save this the HYSYS file as Dist-009H_Extraction.hsc.
5. Conclusions
Based on the simulation results, it would require 16,270 kcal/h of heating and 9,218 kcal/h of cooling to
separate the water –acetone mixture via liquid-liquid extraction. This design is proven to be feasible, however it
may or may not be the optimal design. Another option would be dire ct distillation of water and acetone. Direct
distillation of water and acetone would require less equipment, but it may require more energy.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use wit h,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
20
Dist-010H
Revised: Nov 20, 2012
Pressure Swing to Overcome Azeotropes with Aspen HYSYS® V8.0
Separation of Ethanol and Benzene
1. Lesson Objectives

Learn how to use pressure swing to separate a binary mixture that forms an azeotrope into two
pure components
2. Prerequisites



Aspen HYSYS V8.0
Introduction to azeotropic mixtures
Introduction to distillation
3. Background
Ethanol and benzene form an azeotrope and the azeotropic composition is sensitive to pressure. Therefore, it is
possible to use pressure swing to separate this binary mixture into pure components.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
The first column operates under a pressure of 3 bars and the second one at 0.1 bar. A compressor is used to
pressurize the recycle stream from 0.1 bar to 3 bars before it is recycled back to the first column.
Since the relative volatility is large except for the azeotrope point, there is no need to add a third component (as
a solvent).
Aspen HYSYS Solution
4.01.
Start a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add Ethanol and Benzene to the
component list.
1
Dist-010H
Revised: Nov 20, 2012
4.03.
Define property package. In the Fluid Packages folder select Add. Select PRSV as the property package.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
We will first add two Material Streams to the flowsheet. Name one of the streams Feed and the other
Recycle.
2
Dist-010H
Revised: Nov 20, 2012
4.06.
Double click on the Feed stream. This will be the ethanol-benzene feed to the process. In the
Worksheet tab enter a Vapour Fraction of 0.5, a Pressure of 3 bar, and a Molar Flow of 100 kgmole/h.
In the Composition form enter Mole Fractions of 0.5 for both ethanol and benzene.
4.07.
We will now define the stream Recycle. This stream will consist of ethanol and benzene vapors that
come off the top of the second column, which we will recycle so we don’t throw away any product.
Double click on the Recycle stream. In the Worksheet tab enter a Vapour Fraction of 1, a Pressure of 3
bar, and a Molar Flow of 200 kgmole/h. In the Composition tab enter Mole Fractions of 0.5 for both
ethanol and benzene. These values are initial estimates. They will eventually be replaced by the actual
recycled product.
3
Dist-010H
4.08.
Revised: Nov 20, 2012
We are now ready to add a Distillation Column Sub-Flowsheet to the flowsheet from the Model
Palette.
4
Dist-010H
Revised: Nov 20, 2012
4.09.
Double click the distillation column (T-100). This will launch the Distillation Column Input Expert. On
Page 1 specify the following information. Change the # Stages to 30 and select streams Feed and
Recycle to enter on stage 10. Select Full Reflux for Condenser, create an Ovhd Vapour Outlet stream
called Vap, a Bottoms Liquid Outlet called Benzene, and a Condenser Energy Stream called Q-Cond1.
When complete click Next.
4.10.
On Page 2 of the Distillation Column Input Expert select a Once-through, Regular Hysys reboiler. Click
Next.
4.11.
On Page 3 of the Distillation Column Input Expert enter Condenser and Reboiler Pressures of 3 bar.
For this simulation we will assume no pressure drop through the column. In real life this wouldn’t be
the case. Click Next.
5
Dist-010H
Revised: Nov 20, 2012
4.12.
Page 4 asks for Temperature estimates. These are optional values that will help the column solver
converge. For this column we will leave all estimates blank. Click Next.
4.13.
On the final page of the expert enter a Reflux Ratio of 3. Click Done.
6
Dist-010H
4.14.
Revised: Nov 20, 2012
The Column: T-100 window will now appear. We must define the design specifications for the column.
We have already specified the reflux ratio, but we still need to specify the mole fraction of benzene in
the bottoms stream. First go to the Specs Summary form and make sure that only the Reflux Ratio
specification is checked as active.
7
Dist-010H
Revised: Nov 20, 2012
4.15.
Now we will create a specification for the mole fraction of benzene in the bottoms stream. Go to the
Specs form under the Design tab. Click Add and select Column Component Fraction. Select Stream for
Target Type, Benzene for Draw, enter 0.999 for Spec Value, and select Benzene for Component.
4.16.
The Degrees of Freedom for the column should now be 0. Click the Run button to begin calculations.
The column should quickly converge.
8
Dist-010H
Revised: Nov 20, 2012
4.17.
We will now insert a second Distillation Column Sub-Flowsheet.
4.18.
Double click on the second column (T-101) to open the Distillation Column Input Expert. On the first
page change the # Stages to 30 and select the stream Vap to enter on stage 10. Select Full Reflux for
the Condenser, create an Ovhd Vapour Outlet called Rec, a Bottoms Liquid Outlet called Ethanol, and a
Condenser Energy Stream called Q-Cond2. Click Next when complete.
9
Dist-010H
4.19.
Revised: Nov 20, 2012
On Page 2 of the Distillation Column Input Expert leave the default selections for a Once-through,
Regular Hysys reboiler. Click Next.
10
Dist-010H
Revised: Nov 20, 2012
4.20.
On Page 3 of the Distillation Column Input Expert enter Condenser and Reboiler Pressures of 0.1 bar.
Click Next when complete.
4.21.
On Page 4 of the Distillation Column Input Expert leave all fields for temperature estimates blank. Click
Next.
11
Dist-010H
Revised: Nov 20, 2012
4.22.
On the final page of the Distillation Column Input Expert enter a Reflux Ratio of 1. Click Done when
complete to configure the column.
4.23.
Go to the Specs Summary form under the Design tab. We wish to specify the reflux ratio and the mole
fraction of ethanol in the bottoms stream. We have already specified the reflux ratio, but we still need
to create a specification for the mole fraction of ethanol in the bottoms. First, make sure that the only
current active specification is the Reflux Ratio.
4.24.
Now we will create a specification for the mole fraction of ethanol in the bottoms stream. Go to the
Specs form under the Design tab. Click Add and select Column Component Fraction. Select Stream for
Target Type, Ethanol for Draw, enter 0.999 for Spec Value, and select Ethanol for Component.
12
Dist-010H
4.25.
Revised: Nov 20, 2012
The Degrees of Freedom for the column should now be 0. Click the Run button to begin calculations.
The column should converge.
13
Dist-010H
4.26.
Revised: Nov 20, 2012
Before we connect the recycle loop we must first add a compressor to raise the pressure of stream Rec.
Add a Compressor to the flowsheet from the Model Palette.
14
Dist-010H
Revised: Nov 20, 2012
4.27.
Double click on the compressor (K-100). Select stream Rec as the Inlet. Create an Outlet called RecHighP and an Energy stream called Q-Comp.
4.28.
In the Worksheet tab enter an outlet Pressure of 3 bar. The compressor should solve.
15
Dist-010H
Revised: Nov 20, 2012
4.29.
We are now ready to connect the recycle loop. Add a Recycle block to the flowsheet from the Model
Palette.
4.30.
Double click on the recycle block (RCY-1). Select stream Rec-HighP as the Inlet and select stream
Recycle as the Outlet. The flowsheet should solve after a few moments.
16
Dist-010H
4.31.
Revised: Nov 20, 2012
The flowsheet is now complete. Check results. Double click on stream Benzene and stream Ethanol.
You will find that the flowrate of each stream is roughly 50 kgmole/h with a mole fraction of 0.999 of
each respective product.
17
Dist-010H
Revised: Nov 20, 2012
5. Conclusions
Pressure swing distillation can be a good method for separating a binary mixture that forms an azeotrope when:


The azeotropic composition is sensitive to a pressure change
The relative volatility of the two components is large except at the azeotropic point
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights re served. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital file s supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
18
Dist-011H
Revised: Nov 20, 2012
Azeotropic Distillation with Aspen HYSYS® V8.0
Production of Anhydrous Ethanol Using an Entrainer
1. Lesson Objectives




Design a separation train for anhydrous ethanol production using cyclohexane as an entrainer
Include recycle of cyclohexane and the azeotropic mixture so that the recovery of ethanol is >99.5%
and the recovery of cyclohexane is nearly 100 %
Successfully converge a flowsheet with multiple recycle streams
Configure a three phase distillation column
2. Prerequisites


Aspen HYSYS V8.0
Understanding of azeotropes
3. Background
Ethanol production via fermentation occurs in water, which must later be separated to make anhydrous ethanol
(99.95% ethanol). There is an azeotrope in the ethanol-water system at approximately 95 mol-% ethanol, which
is a barrier to separation. Cyclohexane is one of the solvents used for the production of anhydrous ethanol for
food and pharmaceutical usage. It is used as an entrainer: the ternary mixture forms a ternary azeotrope with a
different ethanol concentration, which allows ethanol to enrich in the other stream. The azeotropic liquid is
separated to recover the entrainer and the ethanol that exits the column in the azeotropic mixture.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
The feed to the separation train is a stream at 100 kgmole/h with 87 mol-% ethanol and 13 mol-% water.
Cyclohexane is added to the column, and > 99.95 mol-% ethanol exits the bottom of the column. The distillate is
then separated in three phase condenser. The cyclohexane-rich stream is recycled directly to the first column,
while the water- and ethanol-rich stream is sent to a second column from which almost-pure water exits in the
bottoms. The distillate of the second column is recycled to the first column.
Design the separation train so that the ethanol product stream meets the purity specification and the water
effluent stream has a purity of 99mol-%.
1
Dist-011H
Revised: Nov 20, 2012
Aspen HYSYS Solution
This model is built using a specific path. The order in which things are done is important for successful
convergence of the model. Do not reinitialize the run unless asked to, and if steps are skip ped or done out of
order you may need to be start at the beginning or from a previously saved version.
4.01.
Start a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder click Add. Add Ethanol, Water, and
Cyclohexane to the component list.
4.03.
Select property package. In the Fluid Packages folder click Add. Select PRSV as the property package.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
We will begin by adding the feed and recycle streams to the flowsheet. Add four Material Streams and
a Mixer to the flowsheet. Name them as shown below.
2
Dist-011H
4.06.
Revised: Nov 20, 2012
Double click on the mixer (MIX-100). Select streams Make Up and Solvent Recycle as Inlets and create
an Outlet called Solvent.
3
Dist-011H
Revised: Nov 20, 2012
4.07.
In order for the mixer to solve, we must define the inlet streams. Double click on stream Make Up. This
stream will add a small amount of solvent to the system to account for any solvent losses to product
streams. We will later implement an adjust block to solve for the correct flow rate of solvent, but for
now we will enter a small number as a guess. In the Worksheet tab enter a Temperature of 25°C, a
Pressure of 1 bar, and a Molar Flow of 0.01 kgmole/h. In the Composition form enter a Mole Fraction
of 1 for cyclohexane.
4.08.
Double click on the Solvent Recycle stream. This stream will be the solvent that exits the condenser of
the first column and will be recycled and fed back into the column. We will add a recycle block that will
calculate the correct flowrate and composition, but for now we will enter an initial guess. In the
Worksheet tab enter a Temperature of 25°C, a Pressure of 1 bar, and a Molar Flow of 400 kgmole/h. In
the Composition form enter Mole Fractions of 0.5 for cyclohexane and ethanol.
4
Dist-011H
4.09.
Revised: Nov 20, 2012
The mixer should now solve.
5
Dist-011H
Revised: Nov 20, 2012
4.10.
We will now define the Feed and Feed Recycle streams. Double click on the Feed stream. This is the
stream that pumps the ethanol-water mixture into the process. Enter a Vapour Fraction of 0.3, a
Pressure of 1 bar, and a Molar Flow of 100 kgmole/h. In the Composition form enter Mole Fractions of
0.87 for Ethanol and 0.13 for Water.
4.11.
Lastly we will define the Feed Recycle stream. This stream will be the ethanol-water mixture that exits
the condenser of the second column. This stream will be fed back to the first column to prevent losses
of ethanol. Later on we will implement a recycle block to calculate the actual specifications for this
stream, but for now we will enter an initial guess. Double click on the Feed Recycle stream. In the
Worksheet tab enter a Vapour Fraction of 0, a Pressure of 1 bar, and a Molar Flow of 25 kgmole/hr. In
the Composition form enter Mole Fractions of 0.7 for Ethanol, and 0.3 for Water.
6
Dist-011H
Revised: Nov 20, 2012
4.12.
Remember to frequently save your progress as you are creating this simulation. Save this file as Dist011_Azeotropic_Distillation.hsc.
4.13.
We are now ready to insert a Three Phase Distillation Column to the flowsheet.
7
Dist-011H
Revised: Nov 20, 2012
4.14.
Double click on the column (T-100) to open the Three Phase Column Input Expert window. In the first
window that appears select the Distillation radio button. Click Next.
4.15.
In the next window, change the Number of Stages to 62. Make sure that the Condenser is selected to
check for two liquid phases. Click Next when complete.
8
Dist-011H
Revised: Nov 20, 2012
4.16.
In the third window, select the Total radio button for Condenser Type. Create a Light Outlet stream
called Sol-Rec, a Heavy Outlet stream called C2-Feed, and an Energy stream called Q-Cond. Click Next
when complete.
4.17.
In the fourth window, leave all fields blank and click Next.
9
Dist-011H
Revised: Nov 20, 2012
4.18.
The Distillation Column Input Expert window will now appear. Select streams Feed, Feed Recycle, and
Solvent as Inlet Streams. Specify streams Feed and Feed Recycle to enter on stage 20, and stream
Solvent to enter on stage 1. Create a Bottoms Liquid Outlet stream called ETOH. Click Next when
complete.
4.19.
On Page 2 of the Distillation Column Input Expert click Next.
10
Dist-011H
Revised: Nov 20, 2012
4.20.
On Page 3 of the Distillation Column Input Expert enter Condenser and Reboiler Pressures of 1 bar.
Click Next when complete.
4.21.
On Page 4 of the Distillation Column Input Expert leave all fields for temperature estimates blank. Click
Next.
11
Dist-011H
4.22.
4.23.
Revised: Nov 20, 2012
On the final page of the Distillation Column Input Expert click Done to configure the column.
The Column: T-100 window should automatically open. We must define the design specifications for
this column. Go to the Specs Summary form under the Design tab. For this column we will specify the
Heavy Reflux Ratio, the Light Reflux Ratio, and the Mole Fraction of Ethanol in the bottoms. Enter a
value of 3.5 for the Heavy Reflux Ratio and a value of 1 for the Light Reflux Ratio. First uncheck the
active box for Bot Product Rate and check the active boxes for Light Reflux Ratio and Heavy Reflux
Ratio.
12
Dist-011H
4.24.
Revised: Nov 20, 2012
We must create a specification for the mole fraction of ethanol in the bottoms stream. Go to the Specs
form under the Design tab. Click Add and select Column Component Fraction. Select Stream for Target
Type, ETOH for Draw, enter 0.9995 for Spec Value, and Ethanol for Component. The column should
automatically solve.
13
Dist-011H
4.25.
Revised: Nov 20, 2012
Again, be sure to periodically save your simulation as you make progress.
4.26.
Before we construct the second column, we will add an Adjust block and a Spreadsheet to find the
correct flowrate for the Make Up stream.
4.27.
Double click on the spreadsheet (SPRDSHT-1). Go to the Spreadsheet tab. Enter the following text in
cells A1 and A2.
14
Dist-011H
Revised: Nov 20, 2012
4.28.
Right click on cell B1 and select Import Variable. Select the Master Comp Molar Flow of Cyclohexane in
stream ETOH.
4.29.
Right click on cell B2 and select Import Variable. Select the Molar Flow of the Make Up stream. Having
these two flow rates side by side will easily allow you to check that the amount of solvent leaving the
system is equal to the amount of solvent entering the system.
15
Dist-011H
4.30.
Revised: Nov 20, 2012
As you can see from the spreadsheet there is more solvent leaving the system than is entering. This will
cause convergence issues when we attempt to close the recycle streams. This is where we will use the
adjust block. Double click on the adjust block (ADJ-1). Select the Adjusted Variable to be the Molar
Flow of the Make Up stream, select the Target Variable to be the Master Comp Molar Flow
(Cyclohexane) of stream ETOH, and set the Target Value to cell B2 in the spreadsheet.
16
Dist-011H
Revised: Nov 20, 2012
4.31.
The adjust block will vary the Make Up stream flowrate until the amount of solvent leaving the system
equals the amount entering the system. Go to the Parameters tab. Change the Tolerance to 0.001
kgmole/h and change the Step Size to 0.01 kgmole/h. Click the Start button to begin calculations. After
a few moments the flowsheet will converge.
4.32.
Open the spreadsheet and you will see that the solvent leaving the system is now equal to the solvent
entering the system.
4.33.
Save the simulation.
17
Dist-011H
Revised: Nov 20, 2012
4.34.
We will now add a Recycle block to close the recycle loop for the solvent.
4.35.
Double click on the recycle block (RCY-1). Select the Inlet stream to be Sol-Rec and select the Outlet
stream to be Solvent Recycle. The flowsheet should converge after a few moments.
18
Dist-011H
Revised: Nov 20, 2012
4.36.
We are now ready to add the second column. Add a Distillation Column Sub-Flowsheet from the Model
Palette.
4.37.
Double click on the column (T-101) to open the Distillation Column Input Expert window. Change #
Stages to 50 and select stream C2 Feed as the Inlet stream entering on stage 35. Select Total for
Condenser and create an Ovhd Liquid Outlet called Feed Rec, a Bottoms Liquid Outlet called Water,
and a Condenser Energy Stream called Q-Cond2. Click Next when complete.
19
Dist-011H
4.38.
Revised: Nov 20, 2012
On Page 2 of the Distillation Column Input Expert leave the default selections for a Once-through,
Regular Hysys reboiler. Click Next.
20
Dist-011H
Revised: Nov 20, 2012
4.39.
On Page 3 of the Distillation Column Input Expert enter Condenser and Reboiler Pressures of 1 bar.
Click Next when complete.
4.40.
On Page 4 of the Distillation Column Input Expert leave all fields blank for temperature estimates. Click
Next.
21
Dist-011H
Revised: Nov 20, 2012
4.41.
On the final page of the Distillation Column Input Expert enter a Reflux Ratio of 0.5. Click Done when
complete to configure the column.
4.42.
The Column: T-101 window should automatically open. We need to define another design specification
in order for the column to solve. Go to the Specs Summary form under the Design tab and make sure
that the Reflux Ratio is the only active specification.
4.43.
We must now create a specification for the mole fraction of water in the bottoms stream. Go to the
Specs form under the Design tab. Click Add and select Column Component Fraction. Select Stream for
Target Type, Water for Draw, enter 0.99 for Spec Value, and select H2O for Component.
22
Dist-011H
4.44.
Revised: Nov 20, 2012
The Degrees of Freedom for the column should now be 0. Click Run to begin calculations. The column
should solve.
23
Dist-011H
Revised: Nov 20, 2012
4.45.
Save the simulation.
4.46.
The last step is to connect the Feed Recycle loop. Add a Recycle block to the flowsheet.
4.47.
Double click on the recycle block (RCY-2). Select stream Feed Rec as the Inlet and stream Feed Recycle
as the Outlet. The flowsheet will begin to solve. After a minute or two the flowsheet will solve. Be
patient as there are many variables attempting to converge. At each iteration both recycle loops must
converge, both columns must converge, and the adjust block must converge.
24
Dist-011H
4.48.
Revised: Nov 20, 2012
The flowsheet is now complete and should look similar to the following.
25
Dist-011H
Revised: Nov 20, 2012
5. Conclusions
In this example, cyclohexane is used as the entrainer to separate water and ethanol to produce anhydrous
ethanol. By using the proper amount of solvent, we obtain pure ethanol from the bottom of the first column.
The stream from the top of the first column is separated into two streams using a three phase condenser: One
stream is solvent rich and is recycled back to the first column as solvent; the other stream is well within another
distillation region so that we can use the second column to obtain pure water. The top stream of the second
column is recycled back to the first column as feed.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written conse nt of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
26
Dist-012H
Revised: Nov 19, 2012
Extractive Distillation for Heptane-Toluene Separation using
Aspen HYSYS® V8.0
1. Lesson Objectives


Essentials of extractive distillation
How to compare design alternatives
2. Prerequisites


Aspen HYSYS V8.0
Introduction to distillation
3. Background
When the two components in a binary mixture have very close normal boiling points, their relative volatility is
likely to be small if they do not form an azeotrope. For such cases, it may be more efficient to use extractive
distillation with a solvent than normal distillation. In extractive distillation, a less volatile solvent is used to
increase the relative volatilities of the original mixtures, allowing for easier separation. In this example, phenol
is used as the solvent for the separation of n-heptane and toluene.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Determine whether conventional distillation or extractive distillation with phenol as a solvent is a more efficient
method to separate n-heptane and toluene.
Aspen HYSYS Solution
4.01.
We will build models to simulate the separation of n-heptane and toluene. One model has a single
distillation column and the other uses the extractive distillation approach with two columns. First we
will build a simulation for a single distillation column. Start a new simulation using in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add n-Heptane and Toluene to the
component list.
1
Dist-012H
Revised: Nov 19, 2012
4.03.
Select property package. In the Fluid Packages folder select Add. Select NRTL as the property package
and select RK as the Vapour Model.
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
2
Dist-012H
Revised: Nov 19, 2012
4.05.
Place a Distillation Column Sub-Flowsheet on the main flowsheet from the Model Palette.
4.06.
Double click on the column (T-100) to open the Distillation Column Input Expert. On Page 1 enter the
following information and click Next when complete.
3
Dist-012H
Revised: Nov 19, 2012
4.07.
On Page 2 of the Input Expert leave the default selections for a Once-through, Regular Hysys reboiler.
Click Next.
4.08.
On Page 3 of the Input Expert enter Condenser and Reboiler Pressures of 1 bar. Click Next when
complete.
4
Dist-012H
Revised: Nov 19, 2012
4.09.
On Page 4 and 5 of the Input Expert leave all fields empty. Click Done on the final page to configure the
column.
4.10.
In the Column: T-100 window go to the Worksheet tab to specify the feed stream. For the Feed stream
enter a Vapour Fraction of 0.5, a Pressure of 1 bar, and a Molar Flow of 100 kgmole/h.
4.11.
In the Composition form under the Worksheet tab enter Mole Fractions of 0.5 for both components.
This stream should solve.
4.12.
Now we must define the column design specifications. Go to the Specs Summary form under the
Design tab. Uncheck the Active boxes so that there are no active specifications.
5
Dist-012H
Revised: Nov 19, 2012
4.13.
Go to the Specs form under the Design tab. We want to add a specification for the mole purity of both
product streams. Click Add and select Column Component Fraction. Select Stream for Target Type,
Heptane for Draw, enter 0.99 for Spec Value, and select n-Heptane for Component.
4.14.
Add a similar specification for the mole fraction of toluene in the bottoms product stream.
6
Dist-012H
Revised: Nov 19, 2012
4.15.
After entering both design specifications the Degrees of Freedom should now be 0. Click Run to begin
calculations. The column should converge.
4.16.
Go to the Cond./Reboiler form under the Performance tab. Make a note of both the Condenser and
Reboiler duties. The Condenser Duty is 5.390e+006 kcal/h and the Reboiler Duty is 5.388e+006 kcal/h.
7
Dist-012H
Revised: Nov 19, 2012
4.17.
Save this file as Dist-012H-Single_Column.hsc.
4.18.
We will now create a second simulation, this time using extractive distillation. Create a new file in
Aspen HYSYS V8.0.
4.19.
Create a component list. In the Component Lists folder select Add. Add n-Heptane, Toluene, and
Phenol to the component list.
4.20.
Select property package. In the Fluid Packages folder select Add. Select NRTL as the property package
and select RK as the Vapour Model.
8
Dist-012H
Revised: Nov 19, 2012
4.21.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.22.
Add a Distillation Column Sub-Flowsheet to the main flowsheet from the Model Palette.
9
Dist-012H
4.23.
Revised: Nov 19, 2012
Double click on the column (T-100) to open the Distillation Column Input Expert. Enter the following
information on Page 1 and click Next when complete.
10
Dist-012H
Revised: Nov 19, 2012
4.24.
On Page 2 of the Input Expert leave the default selections for a Once-through, Regular Hysys reboiler.
Click Next when complete.
4.25.
On Page 3 of the Input Expert enter Condenser and Reboiler Pressures of 1 bar. Click Next when
complete.
4.26.
On Page 4 and 5 leave all fields empty. Click Done on the final page to configure the column.
4.27.
First we must define the feed streams. In the Column: T-100 window go to the Worksheet tab. For the
Feed stream enter a Vapour Fraction of 0.5, a Pressure of 1 bar, and a Molar Flow of 100 kgmole/h.
For the Solvent stream enter a Temperature of 181°C, a Pressure of 1 bar, and a Molar Flow of 60
kgmole/h.
11
Dist-012H
Revised: Nov 19, 2012
4.28.
In the Composition form under the Worksheet tab enter Mole Fractions of 0.5 for n-Heptane and
Toluene in the Feed stream, and a Mole Fraction of 1 for Phenol in the Solvent stream. Both streams
should solve.
4.29.
We must now define our design specifications for the column. Go to the Specs Summary sheet under
the Design tab. We want to specify a distillate product rate of 50 kgmole/h with a mole fraction of 0.99
n-Heptane. Enter 50 kgmole/h in the field for Vent Rate and uncheck the active box for Reflux Ratio.
12
Dist-012H
Revised: Nov 19, 2012
4.30.
Go to the Specs form under the Design tab. Here we will add a specification for the mole fraction of
heptane in the distillate stream. Click Add and select Column Component Fraction. Select Stream for
Target Type, Heptane for Draw, enter 0.99 for Spec Value, and select n-Heptane for Component.
4.31.
The Degrees of Freedom for the column should now be 0. Click Run to begin calculations. The column
should solve.
4.32.
We must now add a second column to separate the solvent from the toluene in the Rich-Solvent
stream. Insert a second Distillation Column Sub-Flowsheet from the Model Palette.
13
Dist-012H
Revised: Nov 19, 2012
4.33.
Double click on the second column (T-101) to open the Distillation Column Input Expert. On Page 1
enter the following information and click Next when complete.
4.34.
On Page 2 of the Input Expert leave the default selections for Once-through, Regular Hysys reboiler.
Click Next.
4.35.
On Page 3 of the Input Expert enter Condenser and Reboiler Pressures of 1 bar. Click Next when
complete.
14
Dist-012H
Revised: Nov 19, 2012
4.36.
On Page 4 and 5 of the Input Expert leave all fields blank and click Done on the final page to configure
the column.
4.37.
We must define the design specifications for this second column. Go to the Spec Summary form under
the Design tab. Uncheck the active boxes so that there are no active specifications.
4.38.
Go to the Specs form under the Design tab. Here we will create two specifications for the mole
fractions of toluene and phenol in the product streams. Click Add and select Column Component
Fraction. Select Stream for Target Type, Toluene for Draw, enter 0.99 for Spec Value, and select
Toluene for Component.
15
Dist-012H
Revised: Nov 19, 2012
4.39.
Add a similar specification for the mole fraction of phenol in the bottoms product stream. Enter .99999
for Spec Value.
4.40.
The Degrees of Freedom for the column should now be 0. Click Run to begin calculations. The column
should converge.
16
Dist-012H
4.41.
Revised: Nov 19, 2012
We will now recycle the Lean-Solvent stream back to the first column. Add a Recycle block to the
flowsheet from the Model Palette.
17
Dist-012H
Revised: Nov 19, 2012
4.42.
Double click on the recycle block (RCY-1). Select stream Lean-Solvent as the Inlet and stream Solvent as
the Outlet. The recycle block should solve.
4.43.
Check results. Double click on the first column (T-100) and go to the Cond./Reboiler form under the
Performance tab. Make note of the Condenser and Reboiler Duties.
18
Dist-012H
Revised: Nov 19, 2012
4.44.
Double click the second column (T-101) and go to the Cond./Reboiler form under the Performance tab.
Make a note of the Condenser and Reboiler Duties.
4.45.
The following table will summarize the energy requirements from the case with 1 column versus the
case using extractive distillation.
Total Heating Duty (kcal/h)
Total Cooling Duty (kcal/h)
Single Column Distillation
5,388,000
5,390,000
Extractive Distillation
1,803,000
1,410,000
5. Conclusions
For the separation of n-heptane and toluene, extractive distillation has a significant advantage in total energy
requirements. Adding phenol as a solvent increased the relative volatilities of n-heptane and toluene in the
mixture and allowed for a much easier separation. However, extractive distillation required more equipment in
this case. Therefore a further analysis on capital versus operational costs would have to be performed in order
to make a decision as to which design is the better option.
19
Dist-012H
Revised: Nov 19, 2012
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
20
Dist-017H
Revised: November 6, 2012
Sour Water Stripper with Aspen HYSYS® V8.0
1. Lesson Objectives



Configure distillation column
Configure heat exchanger
Optimize column feed temperature
2. Prerequisites


Aspen HYSYS V8.0
Introduction to distillation
3. Background
Many refinery operations produce what is called sour water. Any refinery process water that contains sulfides is
considered to be sour water. Sour water typically contains ammonia and hydrogen sulfide, which must be
removed before the water can be repurposed or sent to a wastewater system. In this lesson we will simulate
this process as well as analyzing the effect that feed temperature has on the column.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Construct a simulation of a sour water stripper using Aspen HYSYS. A sour water stream containing mass
fractions of 0.988 water, 0.005 ammonia, and 0.007 hydrogen sulfide is produced from a crude tower. This
stream is at 37.78°C, 2.758 bar, and has a mass flow of 328,900 kg/h. The goal is to produce a pure water
stream with a maximum of 0.00005 mole % ammonia while recovering 99% of the water in the feed stream.
1
Dist-017H
Revised: November 6, 2012
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component List folder select Add. Add Water, Ammonia, and
Hydrogen Sulfide to the component list.
4.03.
Define property package. In the Fluid Packages folder select Add. Select Sour PR as the property
package. The Sour PR model combines the Peng-Robinson equation of state and Wilson’s API-Sour
Model for handling sour water systems.
4.04.
Enter the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
Add a Material Stream to the flowsheet from the Model Palette. This stream will serve as our sour
water feed.
2
Dist-017H
4.06.
Revised: November 6, 2012
Double click on the material stream (1). In the Worksheet tab, rename this stream Sour Water. Enter a
Temperature of 37.78°C, a Pressure of 2.758 bar, and a Mass Flow of 328,900 kg/h.
3
Dist-017H
Revised: November 6, 2012
4.07.
In the Composition form under the Worksheet tab, enter Mass Fractions of 0.988 for H2O, 0.007 for
H2S, and 0.005 for Ammonia. The stream should now be fully defined and will solve.
4.08.
Add a Heater to the flowsheet from the Model Palette. This heater will serve to heat the sour water
stream before it enters the column.
4.09.
Double click on the heater (E-100). Select stream Sour Water as the Inlet, create an Outlet stream
called StripperFeed, and create an Energy stream called Q-Heat.
4
Dist-017H
Revised: November 6, 2012
4.10.
In the Parameters form under the Design tab, specify a Delta P of 0.6895 bar.
4.11.
In the Worksheet tab enter an outlet Temperature of 100°C. The heater should solve.
5
Dist-017H
Revised: November 6, 2012
4.12.
Add a Distillation Column Sub-Flowsheet from the Model Palette.
4.13.
Double click on the column (T-100). The Distillation Column Input Expert will open. On page 1 of the
input expert enter the following information and click Next when complete.
6
Dist-017H
Revised: November 6, 2012
4.14.
On Page 2 of the Input Expert, leave the default settings for a Once-through, Regular Hysys reboiler.
Click Next.
4.15.
On Page 3 of the Input Expert, enter a Condenser Pressure of 1.979 bar and a Reboiler Pressure of
2.255 bar. Click Next when complete.
7
Dist-017H
Revised: November 6, 2012
4.16.
On Page 4 of the Input Expert leave all fields for temperature estimates blank. Click Next. On the final
page of the Input Expert leave all fields blank and click Done to configure the column.
4.17.
The Column: T-100 window will automatically appear. Go to the Specs form under the Design tab to
complete the column specifications. First we will create a specification for the mole fraction of
ammonia in the reboiler. Click Add and select Column Component Fraction. Select Reboiler for Stage,
enter 0.00005 for Spec Value, and select Ammonia for Component.
4.18.
We also would like to recover 99% of the water from the feed stream. Create this specification by
clicking Add and selecting Column Component Recovery. Select Water for Draw, enter 0.99 for Spec
Value, and select H2O for Component.
8
Dist-017H
Revised: November 6, 2012
4.19.
Go to the Specs Summary form and make sure that the only active specifications are Comp Fraction and
Comp Recovery. Once these two specifications are made active the column will attempt to solve. If the
solver fails to converge you may need to take a look at the Damping Factor.
4.20.
Go to the Solver form under the Parameters tab. You will notice a default Damping Factor of 1. The
damping factor serves to reduce the amplitude of oscillations that occur in the solver. Often times
convergence can become cyclic, which can prevent the solver from finding a solution. This is where a
damping factor becomes useful. If you click the Troubleshooting icon on the ribbon under Get Started
and search for ‘damping factor’ you will see the following guidelines.
4.21.
We are working with a sour water stripper, therefore the recommended damping factor is between 0.25
and 0.5. In the Solver form under the Parameters tab, enter a Fixed Damping Factor of 0.4. After
clicking Run, the column should solve.
9
Dist-017H
Revised: November 6, 2012
4.22.
Save this file before continuing.
4.23.
If you look at the Water stream leaving the reboiler, you will notice that this stream contains
superheated water. We can potentially use the energy of this stream to heat the column feed stream,
thus lowering the energy input required for this process. Delete the heater block ( E-100) and place a
Heat Exchanger block onto the flowsheet. Note that you can right click on the Heat Exchanger block
and select Change Icon to select a different icon to display.
10
Dist-017H
Revised: November 6, 2012
4.24.
Double click on the heat exchanger (E-100). Select stream Sour Water as the Tube Side Inlet,
StripperFeed as the Tube Side Outlet, Water as the Shell Side Inlet, and create a stream called WaterCool for the Shell Side Outlet.
4.25.
In the Parameters form under the Design tab enter a Pressure Drop of 0.6895 bar for both the Shell and
Tube side. Also change the number of Tube Passes to 1. The heat exchanger should solve.
11
Dist-017H
Revised: November 6, 2012
4.26.
We will now perform a case study to determine the optimal column feed temperature. In the
Navigation Pane click the Case Studies folder and select Add. In Case Study 1, add the StripperFeed
Temperature and the Heat Flows of energy streams Q-Cond and Q-Reb.
4.27.
For the Independent Variable (StripperFeed Temperature), enter a Low Bound of 80°C, a High Bound of
115°C, and a Step Size of 2°C.
4.28.
Click Run to begin the calculations. To view results go to the Results or the Plots tab.
12
Dist-017H
4.29.
Revised: November 6, 2012
From the case study, you can see that at higher feed temperatures we have a lower reboiler duty but a
higher condenser duty. Since the cost of steam is generally higher than the cost of cooling water, we
should increase the temperature of the column feed stream to 115°C.
5. Conclusions
In this lesson we learned how to simulate a sour water stripping process. We configured a distillation column as
well as a heat exchanger. It was determined through the use of a case study that a higher column feed
temperature will lead to lower energy costs for this separati on.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
13
Dist-018H
Revised: December 3, 2012
Atmospheric Crude Tower with Aspen HYSYS® V8.0
1. Lesson Objectives



Assign petroleum assay to stream
Configure column pre-heater
Configure crude tower
2. Prerequisites


Aspen HYSYS V8.0
Introduction to distillation
3. Background
Oil refineries take crude oil and separate it into more useful/valuable products such as naphtha, diesel,
kerosene, and gas oil. An atmospheric distillation column is one of the many unit operations that can be found
in an oil refinery. Crude oil is fed into the atmospheric distillation column and several fractions are produced
which are then fed to other process units such as hydrotreaters, hydrocrackers, reformers, and vacuum
distillation columns. In this lesson we will be focusing solely on the atmospheric crude unit.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
In this simulation we wish to simulate an atmospheric crude fractionator. 100,000 barrel/day of Arabian Light
crude is fed to a furnace that will vaporize a portion of the crude. This crude stream is then fed to an
atmospheric crude column. The column will operate with three coupled side strippers and three pump around
circuits.
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component List folder, select Add. Add Water, Methane, Ethane,
Propane, i-Butane, and n-Butane to the component list.
1
Dist-018H
4.03.
Revised: December 3, 2012
Add hypotheticals to the component list. In the Component List – 1 form, change the Select option to
Hypothetical. Enter an Initial Boiling Point of 30°C, a Final Boiling Point of 900°C, and an Interval of
10°C. Click Generate Hypos to generate a hypothetical group.
2
Dist-018H
Revised: December 3, 2012
4.04.
After generating the hypothetical group, click Add All to add all generated hypotheticals to the
component list.
4.05.
Define property package. In the Fluid Packages folder select Add. Select Peng-Robinson as the
property package.
3
Dist-018H
Revised: December 3, 2012
4.06.
We will now characterize our crude oil. Go to the Petroleum Assays folder. Click Add. Enter Arabian
Light for Name, select Specified for Assay Source, and select Basis-1 for Fluid Package.
4.07.
In the Arabian Light form, select Import From. A window will appear, select Assay Library.
4.08.
The Assay Library window will appear. Since we wish to model the Arabian Light crude, we will select
Middle East for Region Name, and Saudi Arabia for Country Name. We can then select Arabian Light
and click Import Selected Assay.
4
Dist-018H
4.09.
Revised: December 3, 2012
After a few moments the distillation cut data for the Arabian Light crude will populate the Assay
Property form.
5
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Revised: December 3, 2012
4.10.
Go to the Light Ends form to enter data for the light components to be included in the crude. Enter the
following Volume % for each component. Check the box for Input and enter a Total Percentage of 1.4.
This means that the specified light ends will comprise 1.4 percent of the total crude.
4.11.
Move back to the Assay Property form and click Calculate Assay. After a few moments the status bar
should turn green and say OK. You can go to the Results tab to view a true boiling point (TBP) curve,
composition data, and bulk properties of the crude, among other results.
6
Dist-018H
Revised: December 3, 2012
4.12.
We are now ready to move to the simulation environment to begin creating our flowsheet. Click the
Simulation button in the bottom left of the screen.
4.13.
In the Home ribbon, change the units to Field units.
4.14.
Add a material stream to the flowsheet. This will be our crude feed which will be heated by a furnace
and then fed to the distillation column.
7
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Revised: December 3, 2012
4.15.
Double click the material stream and rename it Raw Crude. Enter a Temperature of 77°F, a Pressure of
58.02 psia (4 bar), and a Std Ideal Liq Vol Flow of 100,000 barrels/day.
4.16.
We must now attach the petroleum assay to this stream. Go to the Petroleum Assay form and select
Petroleum Assay From Library. Next, select Arabian Light. You will notice that the stream compositions
will populate and the stream will solve.
8
Dist-018H
4.17.
Revised: December 3, 2012
If you go to the Composition form you will see that the composition for all hypothetical components
and light ends are complete.
9
Dist-018H
4.18.
Revised: December 3, 2012
We will now add a Heater block to the flowsheet. This will serve to pre-heat the crude stream and
prepare it to enter the distillation column.
10
Dist-018H
4.19.
Revised: December 3, 2012
Double click the heater block (E-100). Select Raw Crude as the Inlet stream, create an Outlet stream
called ColumnFeed, and create an Energy stream called Q-Heat.
11
Dist-018H
Revised: December 3, 2012
4.20.
In the Parameters form, enter a Delta P of 7.252 psi (0.5 bar).
4.21.
In the Worksheet tab enter an outlet Temperature of 626°F. The heater should solve.
12
Dist-018H
4.22.
Revised: December 3, 2012
Before adding the column to the flowsheet, we must first define the steam and energy streams that will
be used by the column. Add 3 Material Streams to the flowsheet. Name them Main Steam, Diesel
Steam, and AGO Steam.
13
Dist-018H
4.23.
Revised: December 3, 2012
Double click on each steam stream and enter the following information. Enter a Mole Fraction of 1 for
Water for each stream as well.
Stream Name
Main Steam
Ago Steam
Diesel Steam
4.24.
Vapor Fraction
1
1
1
Pressure (psia)
145
145
145
Mass Flow (lb/hr)
6614
2205
2205
Add an Energy stream called Q-Trim. This stream does not require any specifications; it will be
calculated by the column.
14
Dist-018H
4.25.
Add a Blank Column Sub-Flowsheet from the Model Palette.
4.26.
A window will appear, select Read an Existing Column Template.
4.27.
Select template 3sscrude.col and click Open.
Revised: December 3, 2012
15
Dist-018H
4.28.
Revised: December 3, 2012
The column property window will appear. On the Design | Connections form, you can view all the
internal streams within the column sub-flowsheet. The first thing we must do is connect the Internal
and External Streams as shown below. Also enter a top stage pressure of 14.5 psia and a bottom
pressure of 20.31 psia.
16
Dist-018H
Revised: December 3, 2012
4.29.
We must now modify the stage locations for the side strippers and pump arounds. Go to the Side Ops
tab. In the Side Strippers form select the following Liq Draw and Vap Return Stages.
4.30.
In the Pump Arounds form select the following Draw and Return Stages.
4.31.
We must now define the column operating specifications. Go to the Specs form under the Design tab.
You will notice that in order to run this column you must define 13 specifications. The table below
summarizes the design specifications chosen for this column.
Specification
Reflux Ratio
Condenser Temp
Kerosene D86 95% Temperature
Diesel D86 95% Temperature
AGO TBP 95% Temperature
Pump Around 1 Return Temp
Pump Around 2 Return Temp
Pump Around 3 Return Temp
Vapour Flow off condenser
Kerosene SS Duty
Pump Around 1 Draw Rate
Pump Around 2 Draw Rate
Pump Around 3 Draw Rate
4.32.
Spec Value
1
110°F
520°F
665°F
885°F
175°F
310°F
450°F
0 kgmole/h
3.966 MMBtu/hr
15,100 barrel/day
15,100 barrel/day
15,100 barrel/day
In the Specs form it may be easiest to initially delete all of the default specifications for the column.
17
Dist-018H
4.33.
Revised: December 3, 2012
Click Add to add each design specification one by one. The following pages will include a screenshot of
each individual specification window.
Reflux Ratio
Condenser Temperature
18
Dist-018H
Revised: December 3, 2012
Kerosene D86 95% Temperature
The D86 95% stream property is found under the Petroleum branch after clicking Select Property.
19
Dist-018H
Revised: December 3, 2012
Diesel D86 95% Temperature
AGO TBP 95% Temperature
The TBP 95% stream property is found under the Petroleum branch after clicking Select Property.
20
Dist-018H
Revised: December 3, 2012
Pump Around 1 Return Temperature
Pump Around 2 Return Temperature
21
Dist-018H
Revised: December 3, 2012
Pump Around 3 Return Temperature
Vapour Flow off condenser
22
Dist-018H
Revised: December 3, 2012
Kerosene SS Duty
Pump Around 1 Draw Rate
23
Dist-018H
Revised: December 3, 2012
Pump Around 2 Draw Rate
Pump Around 3 Draw Rate
4.34.
Once all 13 specifications are entered you should notice that the Degrees of Freedom is now 0. This
means that the column is ready to begin calculations.
24
Dist-018H
4.35.
Revised: December 3, 2012
Before we run the column, we will enter top and bottom stage temperature estimates to help the
column to converge. Go to the Profiles form under the Parameters tab. Enter a Condenser
temperature of 110°F and a Stage 29 temperature of 630°F. The bottom stage temperature estimate
was chosen because we know the column feed stream is being fed into stage 29, therefore the stage 29
temperature should be around the same temperature.
25
Dist-018H
4.36.
Revised: December 3, 2012
Click the Run button and the column will begin calculations. After a few moments the column should
converge.
26
Dist-018H
4.37.
Revised: December 3, 2012
Check results. Go to the Summary form under the Performance tab. Here you can view the flowrates
and compositions for each product stream. Note that Arabian Light is a light crude, therefore there is a
large flowrate for the light products in the naptha stream, and lower flowrates for kerosene, diesel, and
gas oil.
27
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Revised: December 3, 2012
5. Conclusions
In this lesson we learned how to model a petroleum assay and assign a stream to an assay. We also learned how
to insert and configure an atmospheric crude tower to produce petroleum products. A light crude, such as
Arabian Light, will produce a high quantity of light products such as gasoline and naptha, while a heavier crude
will produce a higher quantity of heavier products such as kerosene, diesel, and fuel oil.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
28
Dist-019H
Revised: Nov 8, 2012
Propylene Glycol Production with Aspen HYSYS® V8.0
1. Lesson Objectives

Use Aspen HYSYS to simulate the production process for propylene glycol
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Propylene glycol (C3H8 O2) is a very common organic compound that is used in many applications. It is used as an
oil dispersant, a solvent in pharmaceuticals, an antifreeze, and as a moisturizer, and many other applications. It
is produced via the hydrolysis of propylene oxide which is usually accelerated by acid or base catalysis. Reaction
products typically contain around 20% of propylene glycol, and therefore further separation (distillation) is
required in order to yield a product stream with 99.5% propylene glycol.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Simulate the propylene glycol production process, including the reaction and separation processes. Assume a
propylene oxide feed stream of 3952 kg/h and a water feed stream of 4990 kg/h. Our goal is to produce a final
product containing 99.5% propylene glycol. Assume a CSTR reactor with a volume of 8,000 L. The simplified
reaction kinetics are shown below.
1
Dist-019H
Revised: Nov 8, 2012
(
)
(
)
Design a distillation column that is capable of producing a product with 99.5% purity while recovering 100% of
the product fed to the column.
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add water, propylene oxide, and
propylene glycol to the component list.
4.03.
Define property methods. In the Fluid Packages folder select Add. Select UNIQUAC as the property
package.
4.04.
Define reaction. Go to the Reactions folder and select Add to create a new reaction set. In Set-1 click
Add Reaction and select Kinetic to add a new kinetic reaction.
2
Dist-019H
Revised: Nov 8, 2012
4.05.
Double click Rxn-1 to specify the kinetic reaction. Select the reactants and product components and
enter the stoichiometric coefficients (-1 for water and propylene oxide, and 1 for propylene glycol).
Change the Fwd Order for water to 0. Select 12C3Oxide for Base Component and CombinedLiquid for
Rxn Phase. Change the Basis Units to kgmole/m3 and the Rate Units to kgmole/m3-h. Enter 1.7e+13
for A, and 75362 kJ/kgmole (18012 kcal/kgmole) for E.
4.06.
Close the reaction definition window when complete. Click the Add to FP button and select Basis-1 to
attach the reaction set to a fluid package.
3
Dist-019H
Revised: Nov 8, 2012
4.07.
Enter the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.08.
Add a Material Stream to the flowsheet. This stream will be the propylene oxide feed stream. Double
click on the stream once you successfully place it onto the flowsheet.
4.09.
Change the name of this stream to Prop Oxide. Enter a Temperature of 25°C, a Pressure of 1 bar, and a
Mass Flow of 3952 kg/h. In the Composition form enter a Mole Fraction of 1 for propylene oxide.
4
Dist-019H
4.10.
Revised: Nov 8, 2012
Add a second Material Stream to the flowsheet. This stream will be the water feed stream. Change the
name of this stream to Water Feed. Enter a Temperature of 25°C, a Pressure of 1 bar, and a Mass Flow
of 4990 kg/h. In the Composition form enter a Mole Fraction of 1 for water.
5
Dist-019H
Revised: Nov 8, 2012
4.11.
Add a Mixer to the flowsheet in order to mix the two feed streams together.
4.12.
Double click on the mixer (MIX-100). Select both feed streams as Inlet streams and create an Outlet
called Mixer Out. The mixer should solve.
6
Dist-019H
Revised: Nov 8, 2012
4.13.
We will now add the reactor to the flowsheet. Add a Continuous Stirred Tank Reactor to the flowsheet
from the Model Palette.
4.14.
Double click the reactor (CSTR-100). Select stream Mixer Out as the Inlet, create a Vapour Outlet called
Reactor Vent, create a Liquid Outlet called Reactor Products, and create an Energy stream called QCool.
7
Dist-019H
Revised: Nov 8, 2012
4.15.
In the Parameters form enter a reactor Volume of 8000 L and a Liquid Volume % of 85.
4.16.
In the Reactions tab select Set-1 as the Reaction Set.
8
Dist-019H
4.17.
Revised: Nov 8, 2012
Since we added an energy stream to the reactor, we must either specify the duty or the outlet
temperature. In the Worksheet tab enter an outlet Temperature of 60°C. The reactor should solve.
9
Dist-019H
Revised: Nov 8, 2012
4.18.
Add a Distillation Column Sub-Flowsheet from the Model Palette.
4.19.
Double click on the column (T-100). This will launch the Distillation Column Input Expert. On the first
page of the input expert enter the following information. Enter 10 for # Stages, select Reactor Products
as the Inlet Stream on Stage 5, create Condenser Energy Stream called Q-Cond, an Ovhd Liquid Outlet
stream Recycle, and a Bottoms Liquid Outlet called Product. Click Next when complete.
10
Dist-019H
Revised: Nov 8, 2012
4.20.
On Page 2 of the input expert leave the default selections for a Once-through, Regular Hysys reboiler.
Click Next.
4.21.
On Page 3 of the input expert enter Condenser and Reboiler Pressures of 1 bar. Click Next.
11
Dist-019H
Revised: Nov 8, 2012
4.22.
On Page 4 of the input expert leave all fields blank for temperature estimates. Click Next. On Page 5
leave all fields blank and click Done to configure the column.
4.23.
The column property window will open. We must define the desired operating specifications of the
column. Go to the Specs form under the Design tab. We will first add a specification to have a mole
fraction of 0.995 of propylene glycol in the product stream. Click Add and select Column Component
Fraction. Select Stream for Target Type, Product for Draw, 12-C3diol for Component, and enter a Spec
Value of 0.995.
4.24.
Go to the Specs Summary form under the Design tab. Enter a value of 1 for Reflux Ratio. Make sure
that the only active specifications are Comp Fraction and Reflux Ratio. Once these are checked as
active the column will begin to solve.
12
Dist-019H
4.25.
Revised: Nov 8, 2012
Check results. Go to the Composition form under the Worksheet tab. Here you will see that the
product purity specification has been reached, and you can also see that the distillate stream contains
no propylene glycol.
13
Dist-019H
Revised: Nov 8, 2012
5. Conclusions
This simulation models the production of propylene glycol. A continuous stirred tank reactor was used to create
a product stream containing roughly 20% propylene glycol, and then a distillation column was designed in order
to produce a product stream with a purity of 99.5% propylene glycol. The column also recovers all of the
propylene glycol fed to the column.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
14
Dist-020H
Revised: Nov 9, 2012
Amine Scrubbing with Aspen HYSYS® V8.0
1. Lesson Objectives

Use Aspen HYSYS to simulate a CO2 absorber column
2. Prerequisites

Aspen HYSYS V8.0
3. Background
In recent times there has been much interest in the recovery of carbon dioxide from flue gasses. Recovering
carbon dioxide will lead to lower greenhouse gas emissions, and the captured carbon dioxide can be sold for
profit. Carbon dioxide capture is also gaining interest from enhanced oil capture processes where CO2 is
injected underground into oil wells, which reduces the viscosity and surface tension of the oil and leads to
higher oil recovery rates. Gas-liquid absorption, also known as gas stream scrubbing, can be used to remove
CO2 from a flue gas stream using MEA (monoethanolamine) as a solvent. MEA acts as a weak base and
neutralizes acidic compounds such as CO 2 . This will cause CO2 to ionize into HCO3- which will prevent CO2 from
leaving the solvent, resulting in a gas stream largely free of carbon dioxide.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
Dist-020H
Revised: Nov 9, 2012
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
It is known that amine solvents have a theoretical loading of 0.5 moles of CO 2 for every mole of amine.
Calculate the amount of MEA required to successfully remove the CO 2 from a flue gas stream containing 10
mol% carbon dioxide with a total flow rate of 1,000 tons/day. Use Aspen HYSYS to simulate this process and
confirm the results. Assume an aqueous solvent stream with a mass fraction of 0.25 MEA and a 20 stage
absorber column.
Aspen HYSYS Solution
4.01.
Create a new simulation in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add water, carbon dioxide,
nitrogen, monoethanolamine, and oxygen to the component list.
4.03.
Define property methods. In the Fluid Packages folder select Add. Select the Amine Pkg as the
property package.
2
Dist-020H
Revised: Nov 9, 2012
4.04.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
4.05.
Add a material stream to the flowsheet. This will be the flue gas stream. Double click the stream and
rename it Flue Gas. Enter a Temperature of 65°C, a Pressure of 1.2 bar, and a Mass Flow of 1000
tonne/day (4.167E+004 kg/h). In the Composition form enter Mole Fractions of 0.10 for CO2, 0.70 for
Nitrogen, 0.15 for Water, and 0.05 for Oxygen. The stream should solve.
4.06.
By looking at the Flue Gas stream, we can see that it contains ~150 kgmole/h of carbon dioxide. This
means that we would need a minimum of ~300 kgmole/h of MEA to remove all of the carbon dioxide. In
our simulation we will create a feed with slightly more MEA than the calculated minimum to ensure
3
Dist-020H
Revised: Nov 9, 2012
successful removal of carbon dioxide. Since our solvent feed has a MEA mass fraction of 0.25 this means
that our solvent stream will need a total mass flow of approximately 80,000 kg/h.
4.07.
Add a second material stream to the flowsheet. This will be the solvent stream. Double cl ick the stream
and rename it Solvent. Enter a Temperature of 25°C, a Pressure of 1 bar, and a Mass Flow of 80,000
kg/h. In the Composition form enter Mass Fractions of 0.25 for MEA and 0.75 for water. The stream
should solve.
4.08.
Add an Absorber Column Sub-Flowsheet from the Model Palette.
4
Dist-020H
4.09.
Revised: Nov 9, 2012
Double click the column (T-100). This will open the Absorber Column Input Expert. On the first page of
the input expert select stream Solvent as the Top Stage Inlet and stream Flue Gas as the Bottom Stage
Inlet. Create an Ovhd Vapour Outlet called Clean Air and a Bottoms Liquid Outlet called Solution.
Enter 20 for # Stages. Click Next when complete.
5
Dist-020H
Revised: Nov 9, 2012
4.10.
On the second page of the input expert enter a Top Stage Pressure of 1 bar and a Bottom Stage
Pressure of 1.2 bar. Click Next when complete.
4.11.
On the final page of the input expert enter Top and Bottom Stage Temperature estimates of 50°C. This
estimate does not have to be extremely accurate, but will help the solver converge on a solution. Click
Done to configure the column.
6
Dist-020H
4.12.
Revised: Nov 9, 2012
The column property window will now appear. Click Run to begin calculations. The absorber column
should converge.
7
Dist-020H
4.13.
Revised: Nov 9, 2012
Check results. Double click on stream Clean Air. Go to the Composition form under the Worksheet tab.
You will see that there is essentially no carbon dioxide remaining in the stream.
5. Conclusions
This simulation has confirmed the calculated amount of MEA that is required to remove carbon dioxide from the
flue gas stream. It was found that a solvent flow of 80,000 kg/h is sufficient to remove the carbon dioxide from
a 1000 tonne/day flue gas stream. The clean air stream can now be released to the atmosphere and the
captured carbon dioxide can be removed from the solvent and sold or used for variou s applications.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
8
Dist-020H
Revised: Nov 9, 2012
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
9
Chemical Reaction Engineering
RX-003H
Revised: Nov 6, 2012
Isomerization in a CSTR with Aspen HYSYS® V8.0
1. Lesson Objectives


Use component mass balances to calculate the time required to reach a desired conversion in a
continuous stirred tank reactor.
Use Aspen HYSYS to confirm the analytical solution
2. Prerequisites


Aspen HYSYS V8.0
Basic knowledge of reaction rate laws and mass balances
3. Background
2-Butene is a four carbon alkene that exists as two geometric isomers: cis-2-butene and trans-2-butene. The
irreversible liquid phase isomerization reaction with 1st order reaction kinetics is shown below. It is desired to
determine the residence time required to reach 90% reaction conversion in a continuous stirred tank reactor.
Assume steady state.
Homogeneous reaction
1st order reaction kinetics
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
RX-003H
Revised: Nov 6, 2012
4. Solution
Analytic Solution:
Component A Mole Balance
Conversion (Χ)
Residence Time (τ)
Aspen HYSYS Solution:
∴
4.01.
Start Aspen HYSYS V8.0. Select New to create a new simulation.
4.02.
Begin by creating a Component List. In the properties navigation pane, go to Component Lists and
select Add. Change the Search by criteria to Formula and search for C4H8. Select cis2-Butene and tr2Butene and add them to the component list.
2
RX-003H
4.03.
Revised: Nov 6, 2012
Add a Fluid Package. Go to Fluid Packages in the navigation pane and select Add. Select NRTL as the
property package.
3
RX-003H
Revised: Nov 6, 2012
4.04.
Define reaction. Go to Reactions in the navigation pane and click Add to add a new reaction set. In
Reaction Set 1, click Add Reaction and select a HYSYS, Kinetic reaction.
4.05.
Double click on Rxn-1 to define kinetic reaction. In the Kinetic Reaction: Rxn-1 window, Add cis2Butene and tr2-Butene to the component column, and assign Stoich Coeffs of -1 and 1, respectively. In
the Forward Reaction section, set A to be .23000 and both E and B to 0.00000. Make sure that the Base
Units and Rate Units are lbmole/ft3 and lbmole/ft3-min, respectively.
4
RX-003H
Revised: Nov 6, 2012
4.06.
Attach the reaction to a fluid package. In the Set-1 (Reaction Set) form, click Add to FP and select Basis1.
4.07.
Move to the simulation environment by clicking the Simulation button on the bottom left of the screen.
5
RX-003H
Revised: Nov 6, 2012
4.08.
Press F-12 to open the UnitOps window. Select the Reactors radio button and add a Cont. Stirred Tank
Reactor to the flowsheet.
4.09.
Upon clicking Add, the Cont. Stirred Tank Reactor: CSTR-100 window will appear. Enter an Inlet stream
called Feed, a Vapour Outlet stream called VAP-Product, and a Liquid Outlet stream called LIQ-Product.
6
RX-003H
4.10.
Revised: Nov 6, 2012
Go to the Reactions tab and select Set-1 for Reaction Set.
7
RX-003H
Revised: Nov 6, 2012
4.11.
Specify the feed stream. Go to the Worksheet tab. For the Feed stream enter a Temperature of 25°C, a
Pressure of 10 bar (1000 kPa), and a Molar Flow of 1 kgmole/h.
4.12.
Go to the Composition form and enter a Mole Fraction of 1 for cis2-Butene.
8
RX-003H
Revised: Nov 6, 2012
4.13.
In the Design | Parameters form, enter a volume of 0.005 m3 and specify a Liquid Volume of 100%. This
is just a random volume, we will soon add an adjust block to determine the volume required to achieve
90% reaction conversion.
4.14.
Add an Adjust block to the flowsheet from the Model Palette.
9
RX-003H
Revised: Nov 6, 2012
4.15.
Double click the adjust block (ADJ-1). We would like adjust the reactor volume in order to achieve a
reaction conversion of 90%. For the Adjusted Variable select the Tank Volume of CSTR-100. For the
Targeted Variable select Act. % Cvn. of CSTR-100. Enter a Specified Target Value of 90.
4.16.
In the Parameters tab, change the Maximum Iterations to 1000. Press Start to begin calculations. The
block should solve.
10
RX-003H
Revised: Nov 6, 2012
4.17.
Create a spreadsheet to calculate the residence time. Add a Spreadsheet to the flowsheet from the
Model Palette.
4.18.
Double click the spreadsheet (SPRDSHT-1). In the Spreadsheet tab, enter the following text in cells A1,
A2, and A3.
11
RX-003H
Revised: Nov 6, 2012
4.19.
Right click on cell B1 and select Import Variable. Select the Tank Volume of CSTR-100. Right click on
cell B2 and select Import Variable. Select the Actual Volume Flow of stream LIQ-Product.
4.20.
In cell B3 enter the following formula: = (B1/B2)*60. This will display the residence time in minutes.
4.21.
The residence time is 39.13 minutes, identical to the analytical solution.
5. Conclusion
Both the analytical solution and design spec in Aspen HYSYS produced the same required residence time of
39.13 min. to achieve 90% reaction conversion in a CSTR. The residence time for a CSTR is longer than for a
12
RX-003H
Revised: Nov 6, 2012
batch reactor or PFR because of the back-mixing: product is mixed in with the feed, slowing the reaction. Using
reactor models in Aspen HYSYS will allow you to model complex reaction systems including parallel and series
reactions which lead to coupled systems of ODEs which would be difficult to calculate by hand.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or cons equential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
13
RX-004H
Revised: Nov 6, 2012
Isomerization in CSTRs in Series with Aspen HYSYS® V8.0
1. Lesson Objectives


Use component mass balances to calculate the reaction conversion achieved with two continuous
stirred tank reactors in series.
Use Aspen HYSYS to confirm the analytical solution
2. Prerequisites


Aspen HYSYS V8.0
Basic knowledge of reaction rate laws and mass balances
3. Background
2-Butene is a four carbon alkene that exists as two geometric isomers: cis-2-butene and trans-2-butene. The
irreversible liquid phase isomerization reaction with 1st order reaction kinetics is shown below.
Homogeneous reaction
1st order reaction kinetics
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Solutions
Problem #1
Determine the conversion achieved if two CSTRs are used in series. Each CSTR has a residence time of 20 min.
Assume steady state.
1
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Revised: Nov 6, 2012
Analytic Solution:
First Reactor Component A Balance
Second Reactor Component A Balance
Conversion
Aspen HYSYS Solution:
(
)
4.01.
Start Aspen HYSYS V8.0. Create a new simulation.
4.02.
Create a component list. In the Component Lists folder select Add. Change the Search by criteria to
Formula and search for C4H8. Select cis2-Butene and tr2-Butene and add them to the component list.
2
RX-004H
Revised: Nov 6, 2012
4.03.
Define property package. In the Fluid Packages folder select Add. Select NRTL as the property package.
4.04.
Define reaction. In the Reactions folder select Add to create a new reaction set. In the newly created
reaction set select Add Reaction and select Kinetic. Close the Reactions window.
3
RX-004H
Revised: Nov 6, 2012
4.05.
Rxn-1 will be created. Double click on Rxn-1 to define the kinetic reaction. Add cis2-Butene and tr2Butene to the component column, and assign Stoich Coeffs of -1 and 1, respectively. In the Forward
Reaction section, set A to be .23000 and both E and B to 0.00000. Make sure that the Base Units and
Rate Units are lbmole/ft3 and lbmole/ft3-min, respectively.
4.06.
Attach reaction to a fluid package. Click Add to FP and select Basis-1.
4.07.
Go to the simulation environment. Select the Simulation button in the bottom left of the screen.
4
RX-004H
4.08.
Revised: Nov 6, 2012
Add two CSTR blocks to the flowsheet. Press F12 to open the UnitOps window. Select the Reactors
radio button and add 2 Cont. Stirred Tank Reactors to the flowsheet.
5
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Revised: Nov 6, 2012
4.09.
Double click on the first reactor (CSTR-100). Create an Inlet stream called Feed, a Vapour Outlet called
Vap1, and a Liquid Outlet called Liq1.
4.10.
In the Reactions tab select Set-1 for Reaction Set.
6
RX-004H
Revised: Nov 6, 2012
4.11.
Specify the feed stream. Go to the Worksheet tab and enter a Temperature of 25°C, a Pressure of 10
bar, and a Molar Flow of 1 kgmole/h.
4.12.
In the Composition form under the Worksheet tab, enter a Mole Fraction of 1 for cis-2-butene in the
feed stream.
7
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Revised: Nov 6, 2012
4.13.
In the Design | Parameters form, enter a Volume of 0.005 m3 and a Liquid Volume % of 100%. We will
soon create an Adjust block and a Spreadsheet to find the volume required for the desired residence
time of 20 minutes.
4.14.
Add a Spreadsheet to the flowsheet from the Model Palette.
8
RX-004H
4.15.
Revised: Nov 6, 2012
Double click the spreadsheet (SPRDSHT-1). In the Spreadsheet tab enter the following text in cells A1,
A2, and A3.
9
RX-004H
Revised: Nov 6, 2012
4.16.
Right click on cell B1 and select Import Variable. Select the Tank Volume of CSTR-100. Right click on
cell B2 and select Import Variable. Select the Actual Volume Flow of stream Liq1. Click on cell B3 and
enter the following: = (B1/B2)*60. This will display the residence time in minutes of CSTR-100.
4.17.
We will now create an adjust block to vary the tank volume of CSTR-100 to achieve a residence time of
20 minutes. Add an Adjust block to the flowsheet from the Model Palette.
10
RX-004H
4.18.
Revised: Nov 6, 2012
Double click on the adjust block (ADJ-1). Specify the Adjusted Variable to be the Tank Volume of CSTR100. Specify the Target Variable to be cell B3 of SPRDSHT-1. Enter a Target Value of 20.
11
RX-004H
Revised: Nov 6, 2012
4.19.
In the Parameters tab, change the Maximum Iterations to 1000. Click Start to begin calculations. The
block should solve.
4.20.
The first CSTR is now fully specified and has residence time of 20 minutes. Note that the vapor outlet
stream has a flowrate of zero.
12
RX-004H
4.21.
Revised: Nov 6, 2012
Double click the second reactor (CSTR-101). Select Liq1 as the Inlet stream and create Outlet streams
called Vap2 and Liq2.
13
RX-004H
4.22.
Revised: Nov 6, 2012
In the Reactions tab select Set-1 as the Reaction Set.
14
RX-004H
Revised: Nov 6, 2012
4.23.
Repeat steps 4.13 to 4.20 for the second reactor. When finished the second reactor should solve and
have a residence time of 20 minutes.
4.24.
Check the results of stream Liq2. Double click stream Liq2 and go to the Composition form under the
Worksheet tab.
15
RX-004H
4.25.
Revised: Nov 6, 2012
You can see that the mole fraction of trans-2-butene in the outlet stream is 0.9681. You can add the
reaction extents of each reaction to achieve the total reaction conversion. To find the reaction extent,
double click a reactor and go to the Reactions | Results page. In this case the reaction extent of the first
CSTR is 0.8214 and 0.1467 for the second CSTR. This totals to 0.9681, identical to the analytic solution.
16
RX-004H
Revised: Nov 6, 2012
Problem #2
Consider the same 1st order reaction, except this time using two CSTRs of different sizes. Calculate the
conversion achieved if the first reactor has a residence time of 30 min and the second reactor has a residence
time of 10 min. Assume steady state.
Analytic Solution:
First Reactor Component A Balance
Second Reactor Component A Balance
Conversion
(
)(
)
Aspen HYSYS Solution:
4.26.
The same procedure described in the case of two equal volume CSTRs in series should be followed. The
only difference being the first CSTR has a residence time of 30 min and the second CSTR has a residence
time of 10 min.
17
RX-004H
4.27.
Revised: Nov 6, 2012
Open the file you created for the previous problem. In the Adjust blocks change the Target Value to 30
for the first reactor and 10 for the second reactor.
18
RX-004H
4.28.
Revised: Nov 6, 2012
Check results. Add up the reaction extent for both reactors. The first reactor has a reaction extent of
0.8734, and the second reactor has an extent of 0.08822. This totals to 0.9616, which is identical to the
analytic solution.
5. Conclusion
The conversion is slightly higher when the residence times are the same. When both are 20 min., the conversion
is 96.81%, and it is only 96.16% when they are 30 and 10 min. respectively. This is a result of the decreasing
dependence of conversion on residence time: the second derivative of conversion with respect to residence
time is negative.
Total residence time is not sufficient to describe a series system of CSTRs. Multiple CSTRs in series yield higher
conversion than a single CSTR that has a residence time equal to the sum of the series arrangement.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
19
RX-005H
Revised: Oct 15, 2012
Esterification in CSTRs in Series with Aspen HYSYS® V8.0
1. Lesson Objectives

Use Aspen HYSYS to determine whether a given reaction is technically feasible using three
continuous stirred tank reactors in series.
2. Prerequisites


Aspen HYSYS V8.0
Basic knowledge of reaction rate laws
3. Background
Consider the reversible liquid phase esterification of acetic acid shown below.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
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Revised: Oct 15, 2012
4. Problem Statement and Aspen HYSYS Solution
It is desired to produce 375 kg/h of ethyl acetate product from a feed stream consisting of 13 mole % acetic acid,
35 mole % ethanol, and 52 mole % water. This feed stream is available at 100,000 kg/day. Three 2,600 L CSTRs
are available to use for this process. Determine if it is possibl e to achieve the desired production rate of ethyl
acetate by operating these three reactors in series.
4.01.
Start Aspen HYSYS V8.0. Create a new simulation.
4.02.
Create a component list. In the Component Lists folder select Add. Add Acetic-Acid, Ethanol, EthylAcetate, and Water to the component list.
4.03.
Define property package. In the Fluid Packages folder select Add. Select NRTL as the property package.
4.04.
Define reaction. In the Reactions folder select Add to create a new reaction set. In Set-1 select Add
Reaction and select Kinetic.
2
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Revised: Oct 15, 2012
4.05.
Double click Rxn-1 to define the kinetic reaction. Enter the following information and close the window
when complete. Be sure to specify the Rxn Phase as AqueousPhase.
4.06.
Attach reaction to fluid package. Click Add to FP and select Basis-1.
3
RX-005H
Revised: Oct 15, 2012
4.07.
Go to the simulation environment by clicking the Simulation button in the bottom left corner of the
screen.
4.08.
Place three CSTR blocks onto the flowsheet. Press F12 to open the UnitOps window. Select the
Reactors radio button and add three Continuous Stirred Tank Reactors to the flowsheet.
4
RX-005H
4.09.
Revised: Oct 15, 2012
Double click on the first reactor (CSTR-100). Create an Inlet stream called Feed and Outlet streams
called Vap1 and Liq1.
5
RX-005H
4.10.
Revised: Oct 15, 2012
In the Parameters form under the Design tab enter a Volume of 2.6 m3 (2600L), and enter a Liquid
Volume % of 100%.
6
RX-005H
Revised: Oct 15, 2012
4.11.
In the Reactions tab select Set-1 for Reaction Set.
4.12.
In the Worksheet tab, for the Feed stream, enter a Temperature of 25°C, a Pressure of 1 bar, and a
Mass Flow of 100,000 kg/day.
7
RX-005H
Revised: Oct 15, 2012
4.13.
In the Composition form enter Mole Fractions of 0.13 for Acetic Acid, 0.35 for Ethanol, 0 for Ethyl
Acetate, and 0.52 for water. When complete, the reactor should solve. You should note that the vapor
outlet has a mass flow of zero because the entire contents of the reactor are liquid.
4.14.
Double click the second reactor (CSTR-101). Select Liq1 as the Inlet stream. Create Outlet streams
called Vap2 and Liq2.
8
RX-005H
4.15.
In the Parameters tab enter a Volume of 2.6 m3 and a Liquid Volume % of 100%.
4.16.
In the Reactions tab, select Set-1 as the Reaction Set. The reactor should solve.
Revised: Oct 15, 2012
9
RX-005H
Revised: Oct 15, 2012
4.17.
Double click the third reactor (CSTR-102). Select Liq2 as the Inlet stream, and create Outlets called
Vap3 and Liq3.
4.18.
In the Parameters form enter a Volume of 2.6 m3 and a Liquid Volume % of 100%.
10
RX-005H
Revised: Oct 15, 2012
4.19.
In the Reactions tab select Set-1 as the Reaction Set. The reactor should solve.
4.20.
The flowsheet is now complete.
4.21.
To check results right click on stream Liq3 and select Show Table. A table will appear on the flowsheet
showing Temperature, Pressure, and Molar Flow. Double click on the table and select Add Variable.
11
RX-005H
Revised: Oct 15, 2012
4.22.
Select the Master Comp Mass Flow and select E-Acetate. Click OK. The component mass flow of ethyl
acetate will be added to the table.
4.23.
The mass flow of ethyl acetate in the final liquid stream is 672.55 kg/h, which is greater than the desired
flow rate specified in the problem statement. This shows that this reactor setup is capable of producing
the desired rate of product.
12
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Revised: Oct 15, 2012
5. Conclusion
The CSTRs can be used in series to make the target amount of product. Aspen HYSYS can be used to model
existing equipment in addition to designing new equipment. Modeling existing equipment lets engineers decide
if they can repurpose equipment and improve performance by changing state variables.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other i ncidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
13
RX-006H
Revised: Nov 6, 2012
Isomerization in a PFR with Aspen HYSYS® V8.0
1. Lesson Objectives

Use chemical reaction kinetics to calculate the reactor length required to reach a desired conversion
in a plug flow reactor
2. Prerequisites


Aspen HYSYS V8.0
Basic knowledge of reaction rate laws and plug flow reactors
3. Background/Problem
2-Butene is a four carbon alkene that exists as two geometric isomers: cis-2-butene and trans-2-butene. The
irreversible isomerization reaction with 1st order reaction kinetics is shown below.
Homogeneous reaction
1st order reaction kinetics
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Calculate the reactor length required to achieve 90% reactor conversion. Assume steady state operation, a
single tube reactor with a diameter of 2 inches, and a feed stream of 100% cis-2-butune with a flow rate 1
kgmole/h at 10 bar and 25°C.
Aspen HYSYS Solution:
4.01.
Start Aspen HYSYS V8.0. Create a new simulation.
4.02.
Create a component list. In the Component Lists folder select Add. Change the Search by criteria to
Formula and search for C4H8. Select cis2-Butene and tr2-Butene and add them to the component list.
1
RX-006H
Revised: Nov 6, 2012
4.03.
Define property package. In the Fluid Packages folder select Add. Select NRTL as the property package.
4.04.
Define reaction. In the Reactions folder select Add to create a new reaction set. In Set-1 select Add
Reaction and click Kinetic.
4.05.
Double click Rxn-1 to define the kinetic reaction. Add cis2-Butene and tr2-Butene to the component
column, and assign Stoich Coeffs of -1 and 1, respectively. In the Forward Reaction section, set A to be
.23000 and both E and B to 0.00000. Make sure that the Base Units and Rate Units are lbmole/ft3 and
lbmole/ft3-min, respectively.
2
RX-006H
Revised: Nov 6, 2012
4.06.
Attach reaction to fluid package. Click the Add to PF button and select Basis-1.
4.07.
Go to the simulation environment by clicking the Simulation button in the bottom left of the screen.
3
RX-006H
Revised: Nov 6, 2012
4.08.
Add a plug flow reactor to the flowsheet. Press F12 to open the UnitOps window. Select the Reactors
radio button and add a Plug Flow Reactor to the flowsheet.
4.09.
Double click the reactor (PFR-100). Create an Inlet stream called Feed and an Outlet stream called
Product.
4
RX-006H
4.10.
Revised: Nov 6, 2012
In the Reactions tab select Set-1 for Reaction Set.
5
RX-006H
Revised: Nov 6, 2012
4.11.
In the Rating tab enter a Length of 1 m and a Diameter of 2 in (5.080e-002 m). This tube length is an
initial guess; an adjust block will be used to determine the length required to reach the desired reactor
conversion.
4.12.
In the Parameters form under the Design tab enter a Delta P of 0.
6
RX-006H
Revised: Nov 6, 2012
4.13.
Specify the feed Stream. Go to the Worksheet tab and enter a Temperature of 25°C, a Pressure of 10
bar, and a Molar Flow of 1 kgmole/h.
4.14.
In the Composition form enter a Mole Fraction of 1 for cis-2-butene. When complete the reactor
should solve.
4.15.
Use an adjust block to determine the length required to achieve 90% conversion. Add an Adjust block to
the flowsheet from the Model Palette.
7
RX-006H
4.16.
Revised: Nov 6, 2012
Double click the adjust block (ADJ-1). Specify the Adjusted Variable to be the Tube Length of PFR-100.
Specify the Target Variable to be the Act. % Cnv. of PFR-100. Enter a Target Value of 90.
8
RX-006H
4.17.
Revised: Nov 6, 2012
In the Parameters tab, change the Step Size to 0.1 m and change the Maximum Iterations to 1000.
Click Start to begin calculations, the block should solve after several iterations..
9
RX-006H
4.18.
Revised: Nov 6, 2012
To view the reactor length, double click the reactor and go to the Rating tab. Here you will see that the
required reactor length is 8.348 meters.
5. Conclusion
Aspen HYSYS can be used to calculate the required reactor length to achieve a desired reaction conversion in a
plug flow reactor. The required reactor length was determined to be 8.348 meters in order to achieve 90%
reactor conversion. This same strategy can be applied for much more complex reactions and multi -tube
reactors, which would be much more difficult to attempt to solve using hand calculations.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
10
RX-006H
Revised: Nov 6, 2012
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
11
RX-007H
Revised: Nov 5, 2012
Esterification in a PFR with Aspen HYSYS® V8.0
1. Lesson Objectives

Use Aspen HYSYS to determine whether a given reaction is technically feasible using a plug flow
reactor.
2. Prerequisites


Aspen HYSYS V8.0
Basic knowledge of reaction rate laws
3. Background
Consider the reversible liquid phase esterification of acetic acid shown below.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
It is desired to produce 375 kg/h of ethyl acetate product from a feed stream consisting of 13 mole % acetic acid,
35 mole % ethanol, and 52 mole % water. This feed stream is available at 100,000 kg/day. A single tube plug
flow reactor with a length of 10 meters and a diameter of 1 m is available for use in an existing chemical plant.
Determine if it is feasible to achieve the desired product using this reactor.
1
RX-007H
Revised: Nov 5, 2012
Aspen HYSYS Solution:
4.01.
Start a new case in Aspen HYSYS V8.0.
4.02.
Create a component list. In the Component Lists folder select Add. Add acetic acid, ethanol, ethyl
acetate, and water to the component list.
4.03.
Define the property package. In the Fluid Packages folder select Add. Select NRTL as the property
package.
4.04.
Define reaction. In the Reactions folder select Add to add a new Reaction Set. In Set-1 click Add
Reaction and select Kinetic to add a new kinetic reaction.
2
RX-007H
Revised: Nov 5, 2012
4.05.
Double click Rxn-1 to define the kinetic reaction. Enter the following information and close the window
when complete. Be sure to select Aqueous Phase as the Rxn Phase.
4.06.
Attach reaction set to fluid package. Click the Add to FP button and select Basis-1.
4.07.
Create the flowsheet. Enter the simulation environment by clicking the Simulation button in the bottom
left of the screen.
3
RX-007H
Revised: Nov 5, 2012
4.08.
Place a Plug Flow Reactor block onto the flowsheet from the Model Palette.
4.09.
Double click the reactor (PFR-100). Create an Inlet stream called Feed and an Outlet stream called
Product.
4
RX-007H
4.10.
Revised: Nov 5, 2012
In the Reactions tab select Set-1 as the Reaction Set.
5
RX-007H
4.11.
In the Rating tab, specify a Length of 10 meters and a Diameter of 1 meter.
4.12.
In the Parameters form under the Design tab, enter a Delta P of 0.
Revised: Nov 5, 2012
6
RX-007H
Revised: Nov 5, 2012
4.13.
We must now define the Feed stream. Go to the Worksheet tab. For the Feed stream, enter a
Temperature of 25°C, a Pressure of 1 bar, and a Mass flow of 100,000 kg/day (4167 kg/h).
4.14.
In the Composition form enter Mole Fractions of 0.13 for acetic acid, 0.35 for ethanol, 0 for ethyl
acetate, and 0.52 for water. The feed stream should now be fully defined and the reactor should solve.
7
RX-007H
Revised: Nov 5, 2012
4.15.
Check results. Right click on the Product stream and select Show Table. A table will appear on the
flowsheet. Double click the table and select Add Variable.
4.16.
Select the Master Comp Mass Flow and select component E-Acetate.
8
RX-007H
4.17.
The mass flow rate of ethyl acetate will now be added to the table.
4.18.
The mass flow rate of ethyl acetate in the product stream is 453.4 kg/h.
Revised: Nov 5, 2012
5. Conclusion
The use of the 10 meter reactor and provided feed stock to produce 375 kg/h is feasible. Aspen HYSYS can be
used to model existing equipment in addition to designing new equipment. Modeling existing equipment lets
engineers decide if they can repurpose equipment and improve performance by changing state variables.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
9
RX-008H
Revised: Nov 6, 2012
Simple Combustion Reactor with Aspen HYSYS® V8.0
1. Lesson Objectives



Use conversion reactor block
Determine air flow rate needed for a clean burn
Determine heat available from a fuel stream
2. Prerequisites


Aspen HYSYS V8.0
Understanding of enthalpy of combustion
3. Background
Natural gas, which is primarily methane, is distributed in underground pipes. The pressure in these pipes varies
depending on where in the pipe it is: the closer to the pumping station, the higher the pressure. An industrial
customer can expect to get natural gas at around 60 psig, and is typically charged per cubic foot of natural gas
used. Methane burns in the following reaction:
CH4 + 2 O2  CO2 + 2 H2O
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem
Determine how much energy is available from a 5 ft 3/h (0.472 kg/h) fuel stream that consists of only methane at
60 psig. The air feed should be approximated with 80 mol-% nitrogen and 20 mol-% oxygen. There should be
10% excess oxygen in the air stream so the fuel-air mixture is not too rich. Assume the exhaust is 182 °C. Report
the air flow rate in mol/h and ft 3 /h (at 1 atm) in addition to the available heat in kW.
Mole Balance
Two moles of oxygen are required to combust each mole of methane. Oxygen is one fifth of the moles in air.
Therefore there will need to be ten moles of air for each mole of methane for a stoichiome tric mixture. A 10%
excess requires a 10% increase in the relative amount of air, or 11 moles of air for each mole of methane.
1
RX-008H
Revised: Nov 6, 2012
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0. Select New to create a new simulation.
4.02.
Create a component list. In the navigation pane find Component Lists and select Add to create a new
HYSYS component list. Add Oxygen, Nitrogen, Methane, Carbon Dioxide, and Water to the component
list.
4.03.
Add a fluid package. Go to Fluid Packages and select Add. Select Peng-Robinson as the property
package.
4.04.
Define reaction. Go to Reactions and click New to create a new reaction set. In the form for the newly
created reaction set, click Add Reaction and select Hysys, Conversion.
2
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Revised: Nov 6, 2012
4.05.
Double click Rxn-1 to open the Conversion Reaction: Rnx-1 window. Enter the following information.
Notice that the Reaction Heat is automatically calculated to be -8.0e+05 kJ/kgmole.
4.06.
Attach reaction to fluid package. In the Reaction Set 1 form, click the Add to FP button. Select Basis-1.
3
RX-008H
Revised: Nov 6, 2012
4.07.
At this point, you are ready to move to the simulation environment. To do so, click the Simulation
button at the bottom left of the screen.
4.08.
On the main flowsheet create a material stream using the Model Palette. Select the icon for material
stream and place it onto the flowsheet.
4
RX-008H
Revised: Nov 6, 2012
4.09.
Double click the stream to open the stream property window. Change the stream name to Methane,
and enter a Temperature of 25°C, a Pressure of 515 kPa, and a Mass Flow of 0.472 kg/h.
4.10.
Go to the Composition form and enter a Mole Fraction of 1 for Methane. You will notice that after
entering the stream composition, the status bar will turn green and say OK. This indicates that stream is
fully defined and solved for all parameters.
5
RX-008H
4.11.
Revised: Nov 6, 2012
Create a second material stream to be the air stream that is required for combustion. Double click on
the new material stream and enter the following information. Bold blue font indicates a user-entered
value. From the solved Methane stream, we know there are 0.02942 kgmole/hr of Methane. We
would like there to be 11 moles of air for each mole of methane, therefore we will enter a molar
flowrate of 0.324 kgmole/hr for the air stream. Enter a Mole Fraction of 0.2 for Oxygen and mole
fraction of 0.8 for Nitrogen. The stream should then solve.
6
RX-008H
4.12.
Revised: Nov 6, 2012
The flowsheet should now look like the following.
7
RX-008H
Revised: Nov 6, 2012
4.13.
We will now place a valve in order to reduce the pressure of the methane stream to ambient pressure.
Select a Control Valve from the Model Palette and place it onto the flowsheet.
4.14.
Double click the valve to open the valve property window. In the Connections page select Methane as
the Inlet stream and create an Outlet called Methane-LP.
8
RX-008H
4.15.
Revised: Nov 6, 2012
Specify valve outlet pressure. Go to the Worksheet tab and enter a Pressure of 101.3 kPa for the
Methane-LP stream. The valve should solve.
9
RX-008H
Revised: Nov 6, 2012
4.16.
Insert reactor. Press F12 to open the UnitOps window. Select the Reactors radio button and add a
Conversion Reactor to the flowsheet.
4.17.
In the Conversion Reactor property window select streams Air and Methane-LP as Inlet streams.
Create a Vapour Outlet stream called VAP-Out and a Liquid Outlet called LIQ-Out.
10
RX-008H
4.18.
Revised: Nov 6, 2012
Go to the Reactions tab. Select Set-1 for Reaction Set. The reactor should solve and the status should
turn green and say OK.
11
RX-008H
Revised: Nov 6, 2012
4.19.
The flowsheet should now look like the following.
4.20.
To check results go to Worksheet tab of the Conversion Reactor. You can see that the stream VAP-Out
is leaving the reactor at an extremely high temperature. This is due to the high heat of reaction. To
calculate exactly how much energy is released from this reaction simply take the heat of reaction found
in the Reactions tab and multiply it by the methane molar flowrate. In this case, burning 5 ft 3 /h of
methane releases 6.5 kW.
12
RX-008H
Revised: Nov 6, 2012
5. Conclusions
5 ft3 /h of methane produces 6.5 kW of heat. To run a quality, lean mixture there must be 280 ft 3 /h of air (that is
20 mol-% oxygen) which is 0.324 kgmole/h. The conversion reactor block is useful for quick simulations with
well understood reactions. Reactions with slow kinetics, or complex systems with series or parallel reactions are
outside the scope of this reactor model.
This simulation could also be created using a Gibbs reactor block. The Gibbs reactor is unique in that it can
function without a defined reaction set. This reactor block will minimize the Gibbs free energy of the reacting
system to calculate the product composition. This reactor block is useful when the exact reactions or kinetics
are unknown, and the reaction reaches equilibrium very quickly. It may be a useful exercise to repeat this
module using a Gibbs reactor and compare results.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
13
Instrumentation and Process Control
Dyn-001H
Revised: Nov 13, 2012
Dynamic Analysis of a CSTR with Aspen HYSYS® V8.0
1. Lesson Objective:



Understand the basic workflow to create and run a dynamic simulation using Aspen HYSYS Dynamics
Set up a simple dynamic simulation of a CSTR
Observe the effect of perturbations through changes in the controller settings
2. Prerequisites



Aspen HYSYS V8.0
File Dyn-001_CSTR_Start.hsc
Basic knowledge of controllers
3. Background
Dynamic Simulation in Chemical Engineering
Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into
the models via derivative terms i.e. accumulation of mass and energy. The advent of dynamic simulation means
that the time-dependent description and control of real processes in real or simulated time are possible. This
includes the description of starting up and shutting down a plant, changes of conditions during a reaction,
holdups, thermal changes and more. Dynamic simulations require increased calculation time and are
mathematically more complex than steady-state simulations. They can be seen as repeatedly calculated steadystate simulations (based on a fixed time step) with constantly changing parameters. Dynamic simulation can be
used in both an online and offline fashion. The online case being model predictive control, where the real-time
simulation results are used to predict the changes that would occur for a control input change, and the control
parameters are optimized based on the results. Offline process simulation can be used in the design,
troubleshooting and optimization of process plant as well as the conduction of case studies to assess the
impacts of process modifications.
4. Problem Statement and Aspen HYSYS Solution
Problem: Use the provided Aspen HYSYS file Dyn_001_CSTR_Start.hsc, prepare a dynamic simulation flowsheet
and perform the following studies to investigate how the reactor system behaves dynamically when:


Manipulate the level controller set point
Vary the reactor feed flowrate
1
Dyn-001H
Revised: Nov 13, 2012
Aspen HYSYS Solution:
4.01.
Start Aspen HYSYS V8.0. Open Dyn_001H_CSTR_Start.hsc
4.02.
Observe the flowsheet. This scenario simulates the production of propylene glycol from water and
propylene oxide. The controllers FIC-100, TIC-100, and LIC-100, control the feed flow, reactor
temperature, and reactor liquid level, respectively. Click on the Dynamics tab in the Ribbon. Notice that
the simulation is already in Dynamics Mode.
4.03.
Press SHIFT + P. This will display the pressures of all the streams. Notice that input and output streams
(PreFeed, Reactor Vent, PRODUCT) have stars next to their values. This indicates that there is a
pressure specification on the streams. These specifications are needed for the dynamic simulation to be
Pressure Driven, as the dynamic flowrates are determined by pressure drops. The specifications can be
observed by double clicking on a stream and going to the Dynamics tab. Click SHIFT + N to display the
stream names.
2
Dyn-001H
Revised: Nov 13, 2012
(FAQ) Types of Dynamic Simulations

Flow driven
 Feed flowrate and pressures are specified
 Flowrate is not controlled by pressure differences
 Useful for a first approach of the dynamic behavior of the process
 Good for liquid processes (usually good flow controllability)

Pressure driven
 Feed and product pressures are specified
 Flowrate results from pressure difference
 A bit more complex to specify (because you need to balance the pressures in Aspen
HYSYS with valves, pumps, ...) but more rigorous
4.04.
The PRODUCT stream will be observed to determine the effects on the changing system. Double click
on the PRODUCT, and go to the Dynamics | Stripchart page. In the Variable Set dropdown menu, select
T, P, and F. Click Create Stripchart. This will create a new stripchart called PRODUCT-DL1.
3
Dyn-001H
4.05.
Revised: Nov 13, 2012
We will run following scenario to investigate the reactor dynamics:
 Run the dynamic simulation for 2 hours (Note: this is in simulation time, not in real time)
 Change the Level Controller (LIC-100) set point to 60%
 Run the dynamic simulation for 3 additional hours; find how the product stream results are
being affected
4.06.
In the Navigation Pane, click on the Strip Charts folder and press the Display button.
4.07.
Right click on the chart and select Graph Control. In the Axes tab check Automatic Auto Scale in the
Auto Scale section and Show All in the Axis Display section.
4
Dyn-001H
Revised: Nov 13, 2012
4.08.
In the Time Axis tab, click the Set-up Logger button. This allows you to change the number of samples
the logger will keep on the plot. The full simulation takes 5 hours, which is equal to 900 20-second
intervals. Enter 900 in the Logger Size field.
4.09.
In the Dynamics tab in the Ribbon, click on the Integrator button.
4.10.
In the Integrator menu, enter an end time of 120 minutes. Click the Start button to run the first 2 hours
of the simulation.
5
Dyn-001H
4.11.
Revised: Nov 13, 2012
On the Flowsheet, double click on LIC-100, and change the set point to 60%. This specifies a tank level
that is 60% full.
6
Dyn-001H
Revised: Nov 13, 2012
4.12.
Change the End Time of the Integrator to 300 minutes, and press Continue to finish the remaining 3
hours of the simulation.
4.13.
When the simulation finishes, right click on the strip chart PRODUCT-DL1 and select Graph Control. In
the Time Axis tab, change Low Time to 0 minutes.
4.14.
Resize PRODUCT-DL1 by dragging the corner. Observe the effect that changing the tank height had on
the product stream.
7
Dyn-001H
Revised: Nov 13, 2012
4.15.
Change in feed rate. We will now experiment with another scenario to investigate the reactor dynamics.
(1) Run simulation for 2 hours
(2) Linear ramp up the feed rate from 2.064e+4 lb/hr to 2.8e+4 lb/hr in 2 hours
(3) Linear ramp down the feed rate from 2.8e+4 lb/hr to 0 lb/hr in 1 hour
4.16.
Click the Integrator button in the Dynamics tab on the Ribbon. Clear the value for End Time so that it
reads <Non-stop> and press the Reset button. Click Yes on the subsequent window that appears.
8
Dyn-001H
Revised: Nov 13, 2012
4.17.
Change the SP of LIC-100 back to 87.22 and run the simulation until the PRODUCT stream stabilizes. This
will return the simulation to its original state. Reset the Integrator again.
4.18.
Under Modeling Options in the Dynamics tab of the Ribbon, click on Event Scheduler.
4.19.
The Event Scheduler allows us to set up a series of events that can take place at different times or due
to specific triggers. Click Add under Schedule Options to create a new schedule. Click Add on the righthand side of the window to create a new Sequence within the schedule.
9
Dyn-001H
Revised: Nov 13, 2012
4.20.
Click View to open Sequence A. This sequence will consist of three events. Ramping up the controller
set point, ramping down the set point, and terminating the sequence. Click the Add button three times
to create three events.
4.21.
Double click on Event 1 to specify the first event. In the Condition tab, click the A Specific Simulation
Time radio button and enter 2 hours for Wait Until.
10
Dyn-001H
Revised: Nov 13, 2012
4.22.
In the Action List tab, click Add to create a new Action. In the Type dropdown menu, select Ramp
Controller. Click Select Target and choose FIC-100 for Controller. Enter 28000 lb/hr for the Target SP,
and 2 hours for Ramp Duration. Close the window.
4.23.
In the window titled Sequence A of Schedule 1, double click on Event 2. This is the step where the
controller ramps down, and it occurs 4 hours into the simulation. Once again, click the A Specific
Simulation Time radio button, and this time enter 4 hours in the Wait Until field. Add a new Action in
the Action List tab, and select Ramp Controller for Type. Select FIC-100 for Controller, 0 for Target SP,
and 1 hour for Ramp Duration.
4.24.
Double click on Event 3 in the Sequence A of Schedule 1 to specify the final event. Select the A Specific
Simulation Time radio button and enter 5 hours in the Wait Until Field in the Condition tab. In the
Action tab, Add a new Action, and select Stop Integrator for Type.
4.25.
In the Sequence A of Schedule 1 window, click Start under Sequence Options.
11
Dyn-001H
Revised: Nov 13, 2012
4.26.
The simulation is ready to begin. Click Run in the Dynamics tab of the Ribbon.
4.27.
View strip chart PRODUCT-DL1 to see the effects of changing the flow rate.
5. Conclusion
You should now be familiar with the basic setup of a dynamic simulation in HYSYS. You should also be familiar
with how to initialize a simulation, create custom plots, display results, and make changes in process conditions.
Changes in controller set points or other process conditions can have large effects on the overall process and it
is important to understand these effects when designing or operating a process.
12
Dyn-001H
Revised: Nov 13, 2012
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or conseq uential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
13
Dyn-002H
Revised: Nov 9, 2012
Dynamic Analysis of a PFR with Aspen HYSYS® V8.0
1. Lesson Objective:




To understand basic workflow to create and run dynamic simulation using Aspen HYSYS
To setup a simple dynamic simulation of PFR
To setup a basic controller
To observe the effect of perturbations on the controller settings
2. Prerequisites


Aspen HYSYS V8.0
File Dyn-002_PFR_Start.hsc
3. Background
Dynamic Simulation in Chemical Engineering
Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into
the models via derivative terms i.e. accumulation of mass and energy. The advent of dynamic simulation means
that the time-dependent description and control of real processes in real or simulated time are possible. This
includes the description of starting up and shutting down a plant, changes of conditions during a reaction,
holdups, thermal changes and more. Dynamic simulations require increased calculation time and are
mathematically more complex than steady-state simulations. They can be seen as repeatedly calculated steadystate simulations (based on a fixed time step) with constantly changing parameters. Dynamic simulation can be
used in both an online and offline fashion. The online case being model predictive control, where the real-time
simulation results are used to predict the changes that would occur for a control input change, and the control
parameters are optimized based on the results. Offline process simulation can be used in the design,
troubleshooting and optimization of process plant as well as the conduction of case studies to assess the
impacts of process modifications.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
Dyn-002H
Revised: Nov 9, 2012
4. Problem Statement and Solution
Problem: Using the provided Aspen HYSYS file Dyn-002H_PFR_Start.hsc, prepare a dynamic simulation
flowsheet by adding the required dynamic data. Then perform the following study to investigate how the
reactor system behaves dynamically in response to changes in feed temperature.
Description of the provided Aspen HYSYS file “Dyn-002_PFR_Start.hsc”:
-
PFR reactor
Reaction activation energy E = 5000 cal/mol; which will allow a temperature sensitivity to the reactor
during the course of the dynamic simulation
Reactor type = Adiabatic
Pressure drop = 0.1bar
Aspen HYSYS Solution:
4.01.
Start Aspen HYSYS V8.0. Open Dyn-002_PFR_Start.hsc.
4.02.
The system consists of a PFR with a Heater that preheats the FEED stream.
4.03.
Insert a controller. A controller will be used to control the FEED Temperature. In the Model Palette,
click on the Dynamics tab and double click on PID Controller.
2
Dyn-002H
4.04.
Revised: Nov 9, 2012
A window called IC-100 will appear. Click the Select PV button to specify the Process Variable. This is the
variable that will be controlled. In this case, the PV is FEED Temperature.
3
Dyn-002H
4.05.
Revised: Nov 9, 2012
The output (OP) is the variable that is varied in order to control the PV. Click the Select OP button, and
choose Q for Object and Control Valve for Variable. This is the heat flow to the heater.
4
Dyn-002H
4.06.
Revised: Nov 9, 2012
Click the Control Valve… button to specify the range of values for the OP. In the Direct Q section, enter
1e+04 kcal/h for Min. Available and 1e+07 kcal/h for Max. Available.
5
Dyn-002H
4.07.
Revised: Nov 9, 2012
Back in the TIC-100 window, move to the Parameters tab. In the Range section, set PV Minimum to
10°C and PV Maximum to 80°C. The sets the range of values for the FEED Temperature. In the
Operational Parameters section, make sure that Action: is set to Reverse. A Reverse action controller
means that when the error is positive (i.e. the temperature is higher than the set point), the OP will
decrease (reduce heat flow). Set Mode to Auto, which will vary the OP to reach the SP. Manual Mode
allows you to adjust the OP manually. Finally, under Tuning Parameters, enter 0.1 for Kc and 0.2 for Ti.
The Parameters tab should look like the image shown below.
6
Dyn-002H
Revised: Nov 9, 2012
4.08.
Go to the Dynamics tab, press the Dynamic Mode button.
4.09.
A dialog box will warn you that there are items that need attention. Click Yes to bring up the Dynamics
Assistant.
7
Dyn-002H
4.10.
Revised: Nov 9, 2012
In order for Dynamics to run properly, either the pressure or the flow must be specified in the input and
output streams. Move to the Streams tab, and the Assistant will show which streams need
specifications and which do not.
8
Dyn-002H
4.11.
Revised: Nov 9, 2012
Double click on the stream FEED, and move to the Dynamics tab. Uncheck the Active box under Flow
Specification and Pressure Specification.
9
Dyn-002H
Revised: Nov 9, 2012
4.12.
Close the window. Double click on both PREFEED and PRODUCT streams, and make sure the Pressure
Specifications are Active and the Flow Specifications are not. Click the Analyze Again button in the
Dynamics Assistant window. In the Streams tab, there should now be no streams in either box.
4.13.
In the checklist in the General tab, there are now only two entries. A way to expedite the setup process
is to use the Make Changes button, which will automatically resolve the issues. This button can be
useful, but may make changes that are undesired. In this case, we will click Make Changes. Click Finish
when complete.
10
Dyn-002H
Revised: Nov 9, 2012
4.14.
We are now ready to enter Dynamics mode. Click the Dynamics Mode button in the Dynamics tab, and
click Yes when prompted.
4.15.
Strip charts can be used to monitor the changes that take place. Double click on the Product stream and
move to the Dynamics tab. On the left-hand side of the window, click Stripchart. The dropdown menu
next to Variable Set has many premade strip charts that can be used. Select the T, P, and F chart, which
contains the variables Temperature, Pressure, and Molar Flow.
11
Dyn-002H
4.16.
Revised: Nov 9, 2012
Click on Create Stripchart to create a strip chart called Product-DL1. Click on Display to bring up the
actual plot.
12
Dyn-002H
4.17.
Revised: Nov 9, 2012
Right now, the only label on the Y-axis is Molar Flow. Right click on the plot and select Graph Control.
In the Axes tab, check the Show All box in Axis Display for all three variables to be displayed. Also check
the Automatic Auto Scale box under Auto Scale.
13
Dyn-002H
Revised: Nov 9, 2012
4.18.
We also want to change the timeframe that the chart will observe. In the Time Axis tab of the Strip
Chart Configuration window, click the Set-up Logger button. Change the Logger Size to 900. This means
that the logger will take 900 samples at 20 second intervals, giving a total observation time of 5 hours.
4.19.
Strip charts can also be created from scratch. Click on the Strip Charts folder in the Navigation Pane,
and click the Add button to create a new Strip Chart. Name this chart PRODUCT-COMP.
14
Dyn-002H
4.20.
Revised: Nov 9, 2012
Double click on PRODUCT-COMP. Click on the Add button to add variables to the strip chart. Add the
Master Comp Mole Flow for Acetic Acid and E-Acetate in the Product stream.
15
Dyn-002H
Revised: Nov 9, 2012
4.21.
In the PRODUCT-COMP window, click on Display to bring up the plot. Once again, right click on the
graph and open up Graph Control to display all variables on the Y-Axis. Also check the Automatic Auto
Scale box and set the Logger Size to 900.
4.22.
We will create the following scenario to investigate the reactor dynamics.






4.23.
Run the dynamic simulation for 1 hour at 10°C (Note: this is in simulated time, not in actual time)
Ramp up the feed temperature from 10 to 60°C over the course of 1 hour
Continue the dynamic run for another hour
Ramp the feed temperature down from 60 to 10°C over 1 hour.
Continue the dynamic run for an additional hour
Look at the impact on the product stream results (component flows, temperature, etc.)
In the Dynamics tab of the Ribbon, click on Event Scheduler in Modeling Options.
16
Dyn-002H
Revised: Nov 9, 2012
4.24.
Click Add under Schedule Options to create a new schedule. Click Add on the right-hand side of the
window to create a new Sequence in the schedule.
4.25.
Double click on Sequence A to bring up the Sequence A of Schedule 1 window. Click Add 3 times to
create 3 Events. Double click on Event 1 to configure the conditions for the first event in the scenario.
17
Dyn-002H
4.26.
Revised: Nov 9, 2012
The first step in the scenario is to run the simulation for 1 hour. Select the A Specific Simulation Time
radio button under Wait For…, and enter 1 hour in the Wait Until field.
18
Dyn-002H
4.27.
Revised: Nov 9, 2012
Move to the Action List tab. Click Add in List of Actions For This Event to create Action 1. Make sure
that the Type is Ramp Controller. In Configuration, click Select Target, and select the TIC-100 as the
variable. Enter 60°C in the Target SP box and 1 hour in the Ramp Duration box.
19
Dyn-002H
4.28.
Revised: Nov 9, 2012
Close the window. Back in the Sequence A window, double click on Event 2. After the temperature is
elevated to 60°C, the simulation is to run for an additional hour before the temperature is reduced to
10°C. Therefore, the event should occur at the 3 hour mark. Select the radio button for A Specific
Simulation Time and enter a Wait Until value of 3 hours. In the Action List tab, add a new action.
Select Ramp Controller for Type and TIC-100 for Target, and enter 10°C for Target SP and 1 hour for
Ramp Duration.
20
Dyn-002H
Revised: Nov 9, 2012
4.29.
Finally, double click on Event 3. The simulation is to run for another hour before ending, meaning the
total process will run for 5 hours. Select the radio button for A Specific Simulation Time and enter 5
hours for the Wait Until value. In the Action List tab add a new action and select Stop Integrator for
Type.
4.30.
The Scenario is ready to start. In the Sequence A of Schedule 1 window, click Start under Sequence
Options.
21
Dyn-002H
Revised: Nov 9, 2012
4.31.
Both strip charts can be viewed by going to their respective folders in the Navigation Pane and clicking
Display.
4.32.
In the Dynamics Tab in the Ribbon, click Run.
4.33.
The changes in product flow and stream conditions can be monitored in the strip charts as the
simulation takes place. When it is finished, right click on the charts and select Graph Control. The Axes
and Time Axis tabs can be used to change the axis size and observe the entire simulation. The charts
should look like those presented below.
22
Dyn-002H
Revised: Nov 9, 2012
23
Dyn-002H
4.34.
Revised: Nov 9, 2012
If you wish to rerun the simulation or run a difference sequence, you must reset the integrator and
restart the sequence.
5. Conclusion
You should now be familiar with how to take a simple Aspen HYSYS simulation and convert it to a HYSYS
Dynamics simulation, as well as how to set up controllers and use the Dynamics Assistant utility. Changes in
controller set points or other process conditions can have large effects on the overall process and it is important
to understand these effects when designing or operating a process.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
24
Dyn-003H
Revised: Nov 20, 2012
Dynamic Analysis of Cyclohexane Production
with Aspen HYSYS® V8.0
1. Objectives



Convert previously created Aspen HYSYS process simulation to Aspen HYSYS Dynamics simulation
Become familiar with Aspen HYSYS Dynamics V8.0 user interface
Investigate the effects of a sudden changes in hydrogen feed rate on product composition and
flowrate
2. Prerequisites


Aspen HYSYS V8.0
File Dyn_003H_Cyclohexane_Start.hsc
3. Background
Aspen HYSYS is used to design new plants or model existing ones at what is considered to be the nominal
process operating conditions at steady-state. However, real processes operate at steady-states that may be very
different from the nominal one assumed by the static simulator. In particular, HYSYS Dynamics allows users to
observe how the system switches from one steady-state condition to another one, or how the process responds
to all sort of disturbances—reactant stream flowrate or purity changes, pressure or temperature variations at
different locations—and finally, the prediction of worst case scenarios in case of power loss, fires, deactivated
catalyst bed in reactors or reactors in runaway conditions, etc.
Aspen HYSYS Dynamics is also used to design the right control scheme that would minimize or better “reject”
the effect of severe disturbances on the plant performance and, as you may expect, process dynamics and
process control can hardly be conceived without one another.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
1
Dyn-003H
Revised: Nov 20, 2012
4. Aspen HYSYS Solution
In this example we will investigate the dynamic response of a small section of a cyclohexane plant to changes in
feed rate to the reactor.
4.01.
Open the Aspen HYSYS file called Dyn_003H_Cyclohexane_Start.hsc.
4.02.
Modify the simulation in order to enable dynamics mode in Aspen HYSYS. In the Dynamics tab of the
Ribbon, click on the Dynamics Assistant button. This will bring up the Dynamics Assistant window.
4.03.
The window shows information that needs to be specified in order for the simulation to be converted to
a dynamic case. Double click on the first entry, Enable stream pressure specifications.
2
Dyn-003H
4.04.
Revised: Nov 20, 2012
The Pressure Specs form under the Streams tab will appear. There are three streams that are listed
under Set pressure specifications in these streams. These are the input and output streams. If you
double click on a stream, it will bring up the corresponding window. Move to the Dynamics tab of the
window, and check the Pressure Specification box. Activate the pressure specifications for each listed
stream.
3
Dyn-003H
Revised: Nov 20, 2012
4.05.
In the General tab of the Dynamics Assistant window, click on Analyze Again. Notice that the first item
on the list is removed.
4.06.
The next item on the list is Valves not sized. Close the window, and double click on VLV-101 on the flow
sheet. In the Rating tab of the VLV-101 window, click the Size Valve button, and HYSYS will
automatically size VLV-101. The parameters that HYSYS determines are a good starting point, but they
may need to be modified once the simulation is actually run. If the tuner indicates that the valve is
completely open, but the flow is not reaching the setpoint, then Cv, the conductance, may need to be
increased. Conductance is a measure of how much flow can pass through the valve. Repeat this step
with valve VLV-100.
4
Dyn-003H
4.07.
Revised: Nov 20, 2012
If you try to click the Size Valve button for VLV-102, you will be given a message that HYSYS is unable to
size the valve because there is no flow across it. In the Sizing Methods block of the Sizing tab, make
sure the Cv radio button is selected. This valve controls the flow out the bottom of the reactor.
However, the reaction takes place almost entirely in the vapor phase, so only a negligible amount of
liquid flow is expected. Therefore, a small conductance, such as 5, is acceptable. Enter 5 in the Cv entry
of the table.
5
Dyn-003H
4.08.
Revised: Nov 20, 2012
Click on the Dynamic Assistant button again. If you click on Miscellaneous specification changes, you
will be brought to the Other tab. The Dynamics Assistant recommends that the pressure drop over
CRV-100 be set to 0. However, we are setting up a pressure driven simulation, where flow is
determined from pressure differences. In order to avoid reverse flows, we will not remove the pressure
drop from the reactor.
6
Dyn-003H
4.09.
Revised: Nov 20, 2012
The final entry on the in the General tab of the Dynamics Assistant indicates that a volume needs to be
specified. This is referring to the conversion reactor, CRV-100. Double click on the reactor in the flow
sheet, and move to the Rating tab. The Vertical and Cylinder radio buttons should be selected.
Heuristics exist that can determine what volume is necessary for a reaction to take place. We will use
1080 ft3.
7
Dyn-003H
Revised: Nov 20, 2012
4.10.
The Dynamics Assistant should now only display the Miscellaneous change. We are now ready to move
to Dynamics mode. Click the Dynamics Mode button in the Dynamics tab of the Ribbon, and click No
when asked whether you would like to resolve identified items in need of attention.
4.11.
The controllers are currently set to manual. Double click on H2-TUNE and move to the Parameters
window. Select Auto for Mode, and make sure that SP is set to 310 lbmole/hr. Do the same for BZTUNE, but make sure SP is set to 100.
8
Dyn-003H
4.12.
Revised: Nov 20, 2012
Click on the flowsheet and type Shift+F on the keyboard. This will display the molar flow of every
stream. Click the Run button in the Dynamics tab on the Ribbon, and again choose not to resolve the
items the Dynamics Assistant identified. Allow the simulation to run until the flows have stabilized, then
click the Stop button next to the Run button. The flow sheet should look as displayed below.
9
Dyn-003H
4.13.
Revised: Nov 20, 2012
The goal of this simulation is to observe the effect that a sudden changes in the hydrogen feed will have
on the reaction. We will now construct a strip chart for that purpose. Click on the Strip Charts folder in
the Navigation Pane, and click Add to create a strip chart named DataLogger1.
10
Dyn-003H
Revised: Nov 20, 2012
4.14.
Double click on DataLogger1, and then click Add to select the variables that will be displayed on the
chart. Add the Molar Flow and Master Comp Mole Frac (Cyclohexane) for the FLASH-IN stream. Click
the Display button to create the plot.
4.15.
Right click on the black plot area of DataLogger1 and select Graph Control. In the Axes window, check
the Automatic Auto Scale and Show All boxes.
4.16.
Move to the Time Axis tab. Click the Set-up Logger button, and enter 900 in the Logger Size field. This
will cause the logger to keep 900 points, taken at 20 second intervals, which translates to 5 hours of
runtime.
11
Dyn-003H
4.17.
Revised: Nov 20, 2012
We will be running the following sequence:





Run the simulation for 1 hour.
Over the course of 1 hour, ramp the hydrogen feed from 310 lbmole/hr to 300 lbmole/hour.
Run the simulation for 1 hour.
Over the course of 1 hour, ramp the hydrogen feed up to 320 lbmole/hr.
Run the simulation of an additional hour.
4.18.
Click on the Integrator button in the Dynamics tab of the Ribbon.
4.19.
The first step in the sequence is to run the simulation for 1 hour. In the End Time field, enter 1 hour (60
minutes). First hit the Reset button in the Dynamics ribbon to reset the integrator, then click Run to run
the simulation.
12
Dyn-003H
Revised: Nov 20, 2012
4.20.
DataLogger1 should show constant flow and mole fraction, as shown as shown below. The scale of the
time axis can be changed by dragging the red arrow at the bottom of the window.
4.21.
The next step is to ramp the hydrogen feed down to 300 lbmole/hr over an hour. Double click on H2TUNE and move to the Parameters | Advanced page. In the Set Point Ramping section, click Enable to
enable ramping of the tuner. Change the Target SP to 300 lbmole/hr and Ramp Duration to 1 hour (60
minutes).
13
Dyn-003H
Revised: Nov 20, 2012
4.22.
Open the Integrator window again, and change the End Time to 2 hours. Run the simulation. Right
click on DataLogger1 and select Graph Control. In the Axes tab, uncheck the Automatic Auto Scale box.
Axis2-Mole Fraction should be selected in the list on to the left. Under Scaling, enter .9 for Low Range
Value and .95 for High Range value. To the left, select Axis1-Molar Flow, and enter 94 for the Low
Range and 103 for the High. DataLogger1 should now be easier to read.
4.23.
The simulation must now be run for 1 hour. Open the Integrator, and change End Time to 3 hours. Run
the simulation.
14
Dyn-003H
4.24.
Revised: Nov 20, 2012
Next, we will Ramp up the hydrogen feed to 320 lbmole/hr over an hour. Set the SP of H2-TUNER to
Ramp up to 320 lbmole/hr in 1 hour. Open the Integrator window, and change End Time to 4 hours,
then Run the simulation. Resize the axes on DataLogger1 so that you can observe the full range of
values.
15
Dyn-003H
4.25.
Revised: Nov 20, 2012
The simluation needs to run for 1 hour. Set the Integrator to end after 5 hours. Run the simulation and
resize DataLogger1.
16
Dyn-003H
Revised: Nov 20, 2012
5. Conclusion
You can see that when the hydrogen flowrate decreases, the mole fraction of cyclohexane in the product stream
significantly decreases. This is because there is not enough hydrogen in the feed to convert all the benzene,
which results in unreacted benzene in the product stream. From a business standpoint, this is not good for
several reasons. There is money being lost by throwing away benzene in the product stream, and the product
stream may not even meet composition specifications anymore. This means you will be forced to recycle and
process the product stream which leads to extra costs, or you may be forced to sell the product at a much lower
price than desired. When the flowrate of hydrogen was increased, all the benzene was reacted and excess
hydrogen was being fed into the system. This is the reason for the increased product flowrate and decreased
fraction of cyclohexane when the hydrogen feed increased. The excess hydrogen represents another cost, as
larger equipment will be needed to transport and separate the stream.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
17
Dyn-003H
Revised: Nov 20, 2012
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
18
Dyn-004H
Revised: Nov 14, 2012
Tank Filling and Draining with Aspen HYSYS® V8.0
1. Lesson Objective:


To observe the interaction between set points and process variables in a dynamic system
To understand basics of a dynamic simulation in Aspen HYSYS
2. Prerequisites


Aspen HYSYS V8.0
File Dyn-004H_Tank_Start.hsc
3. Background
Dynamic Simulation in Chemical Engineering
Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into
the models via derivative terms i.e. accumulation of mass and energy. The advent of dynamic simulation means
that the time-dependent description and control of real processes in real or simulated time are possible. This
includes the description of starting up and shutting down a plant, changes of conditions during a reaction,
holdups, thermal changes, and more. Dynamic simulations require increased calculation time and are
mathematically more complex than steady-state simulations. They can be seen as repeatedly calculated steadystate simulations (based on a fixed time step) with constantly changing parameters. Dynamic simulation can be
used in both an online and offline fashion. The online case utilizes model predictive control, where the real-time
simulation results are used to predict the changes that would occur for a control input change, and the control
parameters are optimized based on the results. Offline process simulation can be used in the design,
troubleshooting and optimization of process plant as well as the conduction of case studies to assess the
impacts of process modifications.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Solution
Problem Statement
An inlet stream with the following specifications is fed to a 3 m 3 tank:



Pressure: 3 bar
Temperature: 25 °C
Mass flow rate: 4000 kg/hr
1
Dyn-004H

Revised: Nov 14, 2012
Composition: 80% water and 20% air
The outlet streams are discharged at 1 bar. Using the provided Aspen HYSYS file Dyn-004H_Tank_Start.hsc,
prepare a dynamic simulation flowsheet and observe the dynamic response of changing the liquid level set point
for the tank.
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0. Open Dyn-004H_Tank_Start.hsc.
4.02.
Before a transition from steady state to dynamic occurs, the simulation flowsheet should be set up so
that a high-to-low pressure gradient exists across the flowsheet. The pressure gradient is necessary as
no pressure gradient means no flow. Add three valves to the flowsheet and connect and rename the
streams as shown in the screenshot below.
4.03.
Open the material stream Feed and go to the Worksheet | Conditions page. Enter 25°C for
Temperature, 3 bar_g for Pressure, and 4000 kg/h for Mass Flow.
2
Dyn-004H
Revised: Nov 14, 2012
4.04.
Go to the Worksheet | Composition page. Click the Edit button and enter 0.8, 0.04, and 0.16 for H2O,
Oxygen, and Nitrogen, respectively. Click the OK button when finished.
4.05.
Go to the Dynamics tab. Confirm that only the Pressure Specification is Active in the Dynamic
Specifications frame.
3
Dyn-004H
Revised: Nov 14, 2012
4.06.
Open the material stream Air and go to the Dynamics tab. Enter 1 bar_g for Pressure and check the
Active checkbox in the Pressure Specification frame.
4.07.
Open the material stream Water and go to the Dynamics tab. Enter 1 bar_g for Pressure and check the
Active checkbox in the Pressure Specification frame.
4.08.
Open the material stream 3 and go to the Dynamics tab. Enter 2 bar_g for Pressure and uncheck the
Active checkbox in the Pressure Specification frame. This will solve the steady state solution and aid the
transition to dynamics.
4
Dyn-004H
Revised: Nov 14, 2012
4.09.
Open the valve VLV-100 and go to the Dynamics | Specs page. Enter 70 for Conductance (Cv) and check
the checkbox for Pressure Flow Relation.
4.10.
Open the valve VLV-101 and go to the Dynamics | Specs page. Enter 50 for Conductance (Cv) and check
the checkbox for Pressure Flow Relation.
4.11.
Open the valve VLV-102 and go to the Dynamics | Specs page. Enter 50 for Conductance (Cv) and check
the checkbox for Pressure Flow Relation.
4.12.
Open the tank V-100 and go to the Dynamics | Specs page. Enter the Vessel Volume of 3 m3 and 0 % for
Liquid Volume Percent. Click the Add/Configure Level Controller button.
5
Dyn-004H
4.13.
Revised: Nov 14, 2012
Open the added controller LIC-100 and go to the Connections tab. Confirm the process variable and
controller output are selected as shown in the screenshot below.
6
Dyn-004H
4.14.
Revised: Nov 14, 2012
Go to the Parameters | Configuration page. Select Auto for Mode and enter 50% for SP in the
Operational Parameters frame. Change the Kc and Ti to 0.5 and 5 minutes respectively. Click the Face
Plate button to view the face plate for the controller.
7
Dyn-004H
Revised: Nov 14, 2012
4.15.
Add a new PID Controller to the flowsheet from the Dynamics tab in the Model Palette. Go to the
Connections tab of this controller. Click the Select PV button and select Feed and Mass Flow for the
Object and Variable.
4.16.
Click the Select OP button and select VLV-100 and Actuator Desired Position for the Object and
Variable. The Connections tab should appear as the screenshot below.
8
Dyn-004H
4.17.
Revised: Nov 14, 2012
Go to Parameters | Configuration page. Enter 0 kg/hr and 5000 kg/hr for PV Minimum and PV
Maximum, respectively. Select Reverse for Action, Auto for Mode, and enter 4000 kg/hr for SP. Change
the Kc and Ti to 0.5 and 1.0 minute, respectively. Click the Face Plate button to display the face plate of
this controller.
9
Dyn-004H
4.18.
Revised: Nov 14, 2012
Now the flowsheet should appear as the following screenshot. FIC-100 will allow a constant flow rate
into the tank and we will use LIC-100 to control the draining of the tank.
10
Dyn-004H
Revised: Nov 14, 2012
4.19.
Go to the Dynamics tab of the ribbon. Click the Dynamics Mode button and click Yes to the dialogue.
4.20.
From the Dynamics tab of the ribbon, click the Integrator button.
4.21.
Change the Acceleration to 0.50. This will allow a slower integration in order to observe the changes in
the system. Enter an End Time of 90 minutes to pause the integration after 1.5 hours.
11
Dyn-004H
Revised: Nov 14, 2012
4.22.
From the Dynamics tab of the ribbon, click the Strip Charts button. In the new window, click Add button.
Then, highlight the DataLogger1 and click the Edit button.
4.23.
Click the Add button in the DataLogger1 window. Add the following variables to the strip chart:


4.24.
V-100 | Liquid Percent Level
LIC-100 | SP
The DataLogger1 window should appear as the screenshot below. Click the Display button to display the
chart.
12
Dyn-004H
Revised: Nov 14, 2012
4.25.
The bottom of the strip chart has the log controller bar which controls the time axis. Click and drag the
red marker to the left to expand the range of display.
4.26.
From the Dynamics tab of the ribbon, click the Run button to initialize the dynamic system.
4.27.
When the run is complete, the strip chart DataLogger1 should look like the following screenshot. The
controller LIC-100 reached the set point with some overshoot and oscillation.
13
Dyn-004H
Revised: Nov 14, 2012
4.28.
Open the integrator from the Dynamics tab of the ribbon. Change the End time to 180 minutes.
4.29.
From the face plate, change the set point for LIC-100 to 75 %. The set point indicator will be moved.
14
Dyn-004H
Revised: Nov 14, 2012
4.30.
Click the Run button from the Dynamics tab of the ribbon. When the run is complete, the strip chart
should look like the following screenshot. Some overshoot and oscillations are observed and the offset is
minimal.
4.31.
Open the Integrator from the Dynamics tab of the ribbon. Change the End time to 270 minutes.
4.32.
From the face plate, change the set point for LIC-100 to 25 %.
4.33.
Click the Run button from the Dynamics tab of the ribbon. When the run is complete, the strip chart
should look like the following screenshot. Some overshoot and oscillations are observed and the offset
is minimal.
15
Dyn-004H
Revised: Nov 14, 2012
5. Conclusion
With the tuning parameters used in this process, the level controller produced some overshoot and oscillation
with minimal offset. We observed the effect of changing the set points on the process variables. In order to
eliminate the overshoot or oscillation in the controller, one can tune the controller parameters further via
several different methods. We will investigate the tuning methods in Dyn-005H_Controller Tuning. You should
now be familiar with how to take a simple Aspen HYSYS simulation and convert it to a HYSYS Dynamics
simulation. In HYSYS Dynamics, you should be familiar with how to initialize a simulation, create custom plots,
display results, and make changes in process conditions. Changes in controller set points or other process
conditions can have large effects on the overall process and it is important to understand these effects when
designing or operating a process.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
16
Dyn-004H
Revised: Nov 14, 2012
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
17
Dyn-005H
Revised: Nov 16, 2012
Controller Parameter Tuning with Aspen HYSYS® V8.0
1. Lesson Objective:


Use Ziegler-Nichols, Cohen-Coon, and time integral tuning methods to determine the optimal
controller tuning parameters
To understand basics of dynamic simulation in Aspen HYSYS
2. Prerequisites


Aspen HYSYS V8.0
File Dyn-005H_Controller_Tuning_Start.hsc
3. Background
There are several methods for tuning a controller, including Ziegler-Nichols, Cohen-Coon, and the ITAE tuning
method. In this tutorial, we will utilize these methods to determine the tuning parameters for a second order
system. Most processes can be well approximated by a first order response with time delay. Analysis of this
response can then be used to determine tuning parameters for the process.
A process reaction curve can be obtained from the controlled process with the controller disconnected. From
the process reaction curve, one can acquire values of K, τ, and α, which allows approximation of the process
reaction curve via a first-order system with time delay:
( )
Given this, several tuning methods can be used to obtain approximate tuning parameters. In this tutorial, we will
use a PID controller, which has the following tuning rules:
Tuning Method
Ziegler-Nichols
Cohen-Coon
ITAE
( )
( )(
( ))
( )
[
[
( )
( )
]
( )]
[
( )
]
( )
1
Dyn-005H
Revised: Nov 16, 2012
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Solution
Problem Statement
There are two tanks in series with water flowing into and out of each tank. There are two water streams being
fed into the first tank, a hot water stream and a cold water stream. We would like to control the temperature of
the second tank by varying the flowrate of the hot and cold streams flowing into the first tank. This setup is
shown below.
In this flowsheet we have several controllers. Each tank has a controller to keep its liquid level constant. The
cold water stream has a controller that maintains a constant combined water stream flowrate. So, if the hot
water valve opens, the cold water valve will close accordingly. We have installed a controller attached to the
hot water valve that we wish to use to control the temperature of the second tank. In this lesson we will
determine the tuning parameters for this controller.
In order to determine the tuning parameters for the temperature controller, we must first obtain a process
reaction curve. We have disconnected the controller from the valve and implemented a 15% increase in the
valve opening. We have recorded the resulting response in the temperature of the second tank. This plot is
shown below.
2
Dyn-005H
Revised: Nov 16, 2012
16
Vessel Temperature % Change
14
12
10
8
6
4
2
0
0
100
200
300
400
500
600
Time (seconds)
A tangent line can be drawn at the inflextion point on the curve and the values for the key paramters can be
estimated from the graph:



α =20 seconds = 0.33 minutes
τ = 200 seconds = 3.33 minutes
16
Vessel Temperature % Change
14
12
10
8
6
4
2
0
0
100
200
300
400
500
600
Time (seconds)
3
Dyn-005H
Revised: Nov 16, 2012
Using the Zieglar-Nichols PID tuning rules we can obtain the following tuning parameters:
(
(
(
)
)
)
Using the Cohen-Coon PID tuning rules we can obtain the following tuning parameters:
(
)(
(
))
(
(
)
]
)
(
]
)
[
[
Using the Minimum ITAE PID tuning rules we can obtain the following tuning parameters:
(
[
(
)
(
)(
)]
)
We can then use a simulator such as Aspen HYSYS to model the process and determine the optimal tuning
parameters for this system.
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0. Open Dyn-005_Controller_Tuning_Start.hsc.
4.02.
On the face plate for the temperature controller (TIC-100), select Auto to activate the controller.
4
Dyn-005H
Revised: Nov 16, 2012
4.03.
In the Dynamics tab in the ribbon, click the Strip Charts button. This will open the StripChart window.
Click Display.
4.04.
The DataLogger1 window will appear. Close the StripChart window.
5
Dyn-005H
Revised: Nov 16, 2012
4.05.
Click the Run button from the Dynamic tab of the ribbon.
4.06.
You will see two lines on the strip chart. The blue line is the controller set point and the purple line is
the vessel temperature. You should notice immediately that there is an offset between the set point
and the actual value. This is because the controller is currently only acting as a proportional controller.
If you click the Tuning button on the temperature controller you will see the tuning parameters.
6
Dyn-005H
4.07.
Revised: Nov 16, 2012
Change the set point (SP) for the temperature controller to 60°C.
7
Dyn-005H
4.08.
Revised: Nov 16, 2012
You should see the following response on the strip chart. Notice that there are oscillations and a
significant steady state offset.
8
Dyn-005H
4.09.
Revised: Nov 16, 2012
Change the set point (SP) to 75°C. The response should look like the following.
9
Dyn-005H
Revised: Nov 16, 2012
4.10.
Click the Stop button in the Dynamics tab of the ribbon.
4.11.
We will now enter the tuning parameters that we calculated using the Ziegler-Nichols tuning rules. Click
the Tuning button on the temperature control face plate. Enter the new tuning parameters as shown
below.
10
Dyn-005H
Revised: Nov 16, 2012
4.12.
Change the set point (SP) to 65°C and click the Run button in the ribbon. The response should look like
the strip chart shown below. You can see that the new tuning parameters have eliminated the steady
state offset, however we still have significant oscillations. The Ziegler-Nichols tuning method often leads
to very aggressive parameters, which would explain the large overshoot seen in the response.
4.13.
Change the tuning parameters to the values calculated using the Cohen-Coon tuning method.
11
Dyn-005H
4.14.
Revised: Nov 16, 2012
Run the dynamic simulation again. Starting from 75°C, change the set point to 65°C. The response
should look like the strip chart below. These tuning parameters are also quite aggressive and lead to a
large overshoot of the set point.
12
Dyn-005H
4.15.
Revised: Nov 16, 2012
Lastly, change the tuning parameters to the values calculated using the ITAE method. Note that these
particular correlations for the tuning parameters are designed for a set-point response and are meant to
be less aggressive than other methods.
13
Dyn-005H
4.16.
Revised: Nov 16, 2012
Run the simulation in dynamic mode and make a set point change to 65°C starting from a temperature
of 75°C. The response should look like the strip chart below. You can see that with these parameters
the tank reaches the set point very quickly with little overshoot and oscillations.
14
Dyn-005H
Revised: Nov 16, 2012
5. Conclusion
In this lesson we learned how to determine tuning parameters using three different methods. Using Aspen
HYSYS we could observe how the system responds to different tuning parameters and controller step changes.
Tuning parameters found from the methods used in this lesson are often a starting point which is followed by
manual tuning. Manual tuning allows the operator to modify the tuning parameters as is needed, but often
requires experience to know how to manipulate the controller correctly. Aspen HYSYS allows users to
manipulate tuning parameters to observe how the system responds to changes.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
15
Dyn-005H
Revised: Nov 16, 2012
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
16
Dyn-006H
Revised: Nov 28, 2012
Depressuring with Aspen HYSYS® V8.0
1. Lesson Objective:

To construct a simple case using the Depressuring Analysis in Aspen HYSYS.
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Any process dealing with gasses has the potential for unsafe pressure buildup. This can happen because of
instrument failure, loss of power, or an unforeseen heat source such as a fire. If pressure does build up, there
must be a depressuring system in place to depressurize in a safe manner. The pressure is bled through a valve
until it reaches a safe level. The excess gas can also be sent to a pressure vessel, but these vessels are also
equipped with valves to prevent overpressure. Gas blowdown valves are common in oil wells. When the wells
are not in use, the pressure can build up. A blowdown valve vents the excess gas to a flare, where the
hydrocarbons can be burned before being released into the atmosphere.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Solution
Problem Statement
A nitrogen stream that has built up an excess pressure



Pressure: 2161 psia
Temperature: 62.6 °F
Molar flow rate: 2.205 lbmole/hr
Use the Aspen HYSYS Depressuring Utility to determine the behavior of the gas in a depressuring process that
takes 100 seconds. Assume an adiabatic case with no external heat source.
1
Dyn-006H
Revised: Nov 28, 2012
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0. Open a New case.
4.02.
The Component Lists window will be displayed. Click Add to create Component List-1 and add Nitrogen
to the list.
4.03.
Click the Fluid Packages folder in the Navigation Pane, then click Add to create Basis-1. Select the
Peng-Robinson property package.
2
Dyn-006H
Revised: Nov 28, 2012
4.04.
Move to the simulation environment by clicking on the Simulation button in the bottom right corner of
the screen.
4.05.
Insert a Material Stream from the Model Palette.
4.06.
Double click on the stream. In the Worksheet tab, enter a Temperature of 62.6° F, a Pressure of 2161
psia, and a Molar Flow of 2.205 lbmole/hr. If necessary, change the Unit Set to Field in order to match
the units being used. In the Worksheet | Composition frame, enter a Mole Frac of 1 for Nitrogen.
4.07.
In the Home tab of the Ribbon, click on Analysis | Depressuring.
3
Dyn-006H
Revised: Nov 28, 2012
4.08.
Click Add to create Depressuring-Dynamics-1, then click Edit to enter in values for the Depressuring
utility.
4.09.
Select stream 1 for Inlets. HYSYS will automatically size the vessel. However, we will choose different
values. Make sure the Vertical radio button is selected under Vessel Parameters, then delete the entry
for Flat End Vessel Volume. Enter a Height of 5 ft and a Diameter of 0.8957 ft, and the rest of the
values should be calculated. The page should resemble the image below.
4
Dyn-006H
4.10.
Revised: Nov 28, 2012
Click Heat Flux in the left side of the window, and change the Ambient Temperature to 62.33° F under
Heat Loss Parameters.
5
Dyn-006H
4.11.
Revised: Nov 28, 2012
Notice that Unknown Vessel Metal Thickness is displayed in the status bar at the bottom of the window.
To address this, select the Conduction radio button. In the table under Metal, enter a Thickness of
0.9843 inches. Also, under insulation enter a Thickness of 0 inches.
6
Dyn-006H
Revised: Nov 28, 2012
4.12.
Click on Valve Parameters on the left side of the window. Change the Vapour Flow Equation to General,
then ender a Cd of 0.7 and an Area of 4.907e-2 in2. A Cd that is less than 1 signifies that the effective
orifice flow area is less than the physical area, which is a common occurrence.
4.13.
Click on Operating Conditions in the left side of the window. Under Operating Parameters, change the
Time Step Size to 0.05 seconds and the Depressuring Time to 100 seconds.
7
Dyn-006H
Revised: Nov 28, 2012
4.14.
The Depressuring utility should be ready to calculate. Move to the Performance tab and select Strip
Charts on the left side of the window. There is a premade chart named Depressuring-Dynamics-1-DL.
However, this chart has over 20 variables, and will be difficult to read. We will create a new plot that
only contains the most relevant information. Click on the Create Plot button to create DataLogger1,
then click Add Variable… to select the variables for the plot.
4.15.
We are only concerned with the vapour flow, as we down not anticipate any liquid. DepressuringDynamics-1 should be selected under Flowsheet. Under the Object column, select Vapour@TPL1 and
Mass Flow under Variable. Also add Vapour@TPL1, Pressure and Vapour@TPL1, Temperature.
8
Dyn-006H
4.16.
Revised: Nov 28, 2012
In the Performance tab, change the Sampling Interval of DataLogger1 to 0.05 seconds, then click View
Strip Chart….
9
Dyn-006H
Revised: Nov 28, 2012
4.17.
Click Display in the DataLogger1 window to display the plot. Right click on the plot and select Graph
Control. In the Axes tab, check the boxes marked Automatic Auto Scale in the Auto Scale section and
Show All in the Axis Display section.
4.18.
Move to the Time Axis tab, and click on Set-up Logger. Change the Logger Size to 2003, and make sure
the Sample Interval is 0.05 seconds.
4.19.
We are now ready to run the simulation. Close the Strip Chart Configuration window and return to the
Depressuring-Dynamics-1 window. The sub-flowsheet will run in dynamics until the depressuring time
is complete, and then the system will return to steady state. Click the Run button at the bottom of the
Depressuring-Dynamics-1 window, and wait for the simulation to complete.
10
Dyn-006H
Revised: Nov 28, 2012
4.20.
View DataLogger1 to see how the Vapour Mass Flow, Pressure, and Temperature behaved. The Time
Axis can be adjusted by using the red triangle at the bottom of the chart.
4.21.
Additional information can be found in the Summary page of the Performance tab.
4.22.
In the Main Flowsheet, double click on Depressuring-Dynamics-1 (Flowsheet), and click the SubFlowsheet Environment… button. This will enter the depressuring sub-flowsheet.
11
Dyn-006H
4.23.
Revised: Nov 28, 2012
The sub-flowsheet contains information for the vessel, as well as spreadsheets that can export data.
12
Dyn-006H
Revised: Nov 28, 2012
5. Conclusion
In this lesson we examined a basic case of an adiabatic depressuring. The adiabatic case describes a system such
as an oil well where excess pressure has built up but there is no external heat. Pressure buildup can also be the
result of an accident such as a fire. In this case, the Operating Mode can be changed to Fire Mode, which allows
you to specify a heat flux. The Use Spreadsheet option is also available, which allows a user to edit the duty
spreadsheet without the values being overwritten when the utility runs. Depressuring is important in assuring
the safety of a process.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
13
Dyn-006H
Revised: Nov 28, 2012
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
14
Chemical Engineering Plant Design
Design-001H
Revised: Nov 7, 2012
Ammonia Synthesis with Aspen HYSYS® V8.0
Part 1 Open Loop Simulation of Ammonia Synthesis
1. Lesson Objectives



Become comfortable and familiar with the Aspen HYSYS graphical user interface
 Explore Aspen HYSYS flowsheet handling techniques
 Understand the basic input required to run an Aspen HYSYS simulation
Determination of Physical Properties method for Ammonia Synthesis
Apply acquired skill to build an open loop Ammonia Synthesis process simulation
 Enter the minimum input required for an simplified Ammonia Synthesis model
 Examine the open loop simulation results
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Ammonia is one of the most highly produced chemicals in the world and is mostly used in fertilizers. In 1913
Fritz Haber and Carl Bosch developed a process for the manufacture of ammonia on an industrial scale (HaberBosch process). This process is known for extremely high pressures which are required to maintain a reasonable
equilibrium constant. Today, this process produces 500 million tons of nitrogen fertilizer per year and is
responsible for sustaining one-third of the Earth’s population.
Ammonia is produced by reacting nitrogen from air with hydrogen. Hydrogen is usually obtained from steam
reformation of methane, and nitrogen is obtained from deoxygenated air. The chemical reaction is shown
below:
Our goal is to produce a simulation for the production of ammonia using Aspen HYSYS. We will create a very
simplified version of this process in order to learn the basics of how to create a flowsheet in the Aspen HYSYS
V8.0 user interface. A diagram for this process is shown below.
1
Design-001H
Revised: Nov 7, 2012
Knowledge Base: Physical Properties for Ammonia Process
Equation-of-state models provide an accurate description of the thermodynamic properties of the hightemperature, high-pressure conditions encountered in ammonia plants. The Peng-Robinson equation of state
was chosen for this application.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
2
Design-001H
Revised: Nov 7, 2012
4. Aspen HYSYS Solution
Build a Process Simulation for Ammonia Synthesis
4.01.
Start Aspen HYSYS V8.0. Select New on the Start Page to create a new simulation.
4.02.
Create a component list. In the Component Lists folder, select Add. Add the following components to
the component list.
4.03.
Create a fluid package. In the Fluid Packages folder, select Add. Select the Peng-Robinson property
package.
4.04.
Define reactions. Go to the Reactions folder, and click Add. This will create a new reaction set called
Set-1. In Set-1, select Add Reaction and select Hysys, Conversion. This will create a new reaction called
Rxn-1.
3
Design-001H
Revised: Nov 7, 2012
4.05.
Double click on Rxn-1 to open the Rxn-1 window. Enter the following information. Close this window
when complete.
4.06.
In Set-1, we must now attach the reaction set to a fluid package. Click the Add to FP button and select
Basis-1. The reaction set should now be ready.
4
Design-001H
Revised: Nov 7, 2012
4.07.
Go to the simulation environment. Click on the Simulation button in the bottom left of the screen. Then
find the Flowsheet Main tab. The Flowsheet Main is the main simulation flowsheet where you will
create a simulation.
4.08.
From the Model Palette, add a Compressor to the main flowsheet.
5
Design-001H
4.09.
Revised: Nov 7, 2012
Double click the compressor (K-100) to open the property window. Create an Inlet stream called
SynGas, an Outlet stream called S2, and an Energy stream called Q-Comp1.
6
Design-001H
Revised: Nov 7, 2012
4.10.
We must define our SynGas feed stream. In K-100, go to the Worksheet tab. For the stream SynGas,
enter a Temperature of 280°C, a Pressure of 25.5 bar_g, and a Molar Flow of 7000 kgmole/h. In the
Composition form enter the following mole fractions. Stream SynGas should now solve.
4.11.
Specify the compressor outlet pressure. In the Worksheet tab of K-100, enter a Pressure of 274 bar_g
for stream S2. The compressor should now solve.
7
Design-001H
4.12.
The flowsheet should look like the following.
4.13.
Next, we will add a mixer. Add a Mixer to the flowsheet from the Model Palette.
Revised: Nov 7, 2012
8
Design-001H
4.14.
Revised: Nov 7, 2012
Double click on the mixer (MIX-100) to open the mixer window. Select stream S2 as the Inlet and create
an Outlet stream called S3. The mixer should solve. We will eventually use this mixer to connect a
recycle stream to the process.
9
Design-001H
Revised: Nov 7, 2012
4.15.
Next, add a heater to the flowsheet.
4.16.
Double click on the heater (E-100) to open the heater window. Select S3 as the Inlet stream, create an
Outlet stream called S4, and create an Energy stream called Q-Heater. In the Parameters form in the
Design tab, enter a Delta P of 0. In the Worksheet tab, specify an outlet Temperature of 775 K
(481.9°C). Note that this heater is currently acting as a cooler, but once we connect the recycle stream
this block will in fact add heat and raise the temperature of the stream.
10
Design-001H
4.17.
Revised: Nov 7, 2012
Next, we will add a reactor to the flowsheet. This process uses plug flow reactors to accomplish
synthesis reaction, but for this simplified simulation we will use a conversion reactor. To use a plug flow
reactor, we would need to have detailed kinetics describing the reaction. Press F12 to open the UnitOps
window. Select the Reactors radio button and select Conversion Reactor. Click Add.
11
Design-001H
Revised: Nov 7, 2012
4.18.
After clicking Add, the conversion reactor window will open. Select an Inlet stream of S4 and create a
Vapour Outlet stream of S5V, a Liquid Outlet stream of S5L, and an Energy stream called Q-Reac.
4.19.
In the conversion reactor window (CRV-100), go to the Reactions tab. Select Set-1 for Reaction Set. In
the Worksheet tab enter an outlet Temperature of 481.9°C for stream S5L. This value will copy over to
S5V. The reactor should then solve. Notice that the contents of the reactor are entirely vapor;
therefore the liquid outlet stream has a flowrate of zero.
12
Design-001H
4.20.
The flowsheet should now look like the following.
4.21.
We will now add a cooler to cool the vapor stream leaving the reactor.
Revised: Nov 7, 2012
13
Design-001H
4.22.
Revised: Nov 7, 2012
Double click the cooler (E-101) to open the cooler window. Select stream S5V as the Inlet stream,
create an Outlet stream called S6, and create an Energy stream called Q-Cooler.
14
Design-001H
4.23.
Revised: Nov 7, 2012
In the Parameters form under the Design tab, enter a Delta P of 100 bar. We want to lower the
pressure in order to allow an easier separation of ammonia. In the Worksheet tab, specify an outlet
stream Temperature of 300 K (26.85°C). The cooler should solve.
15
Design-001H
Revised: Nov 7, 2012
4.24.
Add a separator block to the flowsheet.
4.25.
Double click on the separator (V-100). Select an Inlet stream of S6, create a Vapour Outlet called S7,
and create a Liquid Outlet called NH3. The separator should solve.
16
Design-001H
Revised: Nov 7, 2012
4.26.
The flowsheet should now look like the following.
4.27.
Review simulation results. Double click stream NH3. In the Conditions form under the Worksheet tab
you can view the stream flowrate and conditions. In the Composition form you can view the stream
composition. Here you can see that the mole fraction of ammonia is equal to 0.9754.
17
Design-001H
4.28.
Revised: Nov 7, 2012
After completing this simulation, you should save the file as a .hsc file. It is also good practice to save
periodically as you create a simulation so you do not risk losing any work. The open loop simulation is
now ready to add a recycle stream, which we will then call a closed loop simulation. See module Design002H for the closed loop design.
5. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
18
Design-002H
Revised: Nov 7, 2012
Ammonia Synthesis with Aspen HYSYS® V8.0
Part 2 Closed Loop Simulation of Ammonia Synthesis
1. Lesson Objectives


Build upon the open loop Ammonia Synthesis process simulation
 Insert a purge stream
 Learn how to close recycle loops
 Explore closed loop convergence methods
Optimize process operating conditions to maximize product composition and flowrate
 Learn how to utilize the model analysis tools built into Aspen HYSYS
 Find the optimal purge fraction to meet desired product specifications
 Determine the effect on product composition of a decrease in cooling efficiency of the pre -flash
cooling unit
2. Prerequisites


Aspen HYSYS V8.0
Design-001 Module (Part 1 of this series)
3. Background; Recap of Ammonia Process
1
Design-002H
Revised: Nov 7, 2012
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Aspen HYSYS Solution:
In Part 1 of this series (Design-001H), the following flowsheet was developed for an open loop Ammonia
Synthesis process.
This process produces two outlet streams; a liquid stream containing the ammonia product and a vapor stream
containing mostly unreacted hydrogen and nitrogen. It is desired to capture and recycle these unreacted
materials to minimize costs and maximize product yield.
Add Recycle Loop to Ammonia Synthesis Process
Beginning with the open loop flowsheet constructed in Part 1 of this series, a recycle loop will be constructed to
recover unreacted hydrogen and nitrogen contained in the vapor stream named S7, shown below.
4.01.
The first step will be to add a tee to separate the vapor stream S7 into two streams; a purge stream and
a recycle stream. As a rule of thumb, whenever a recycle stream exists, there must be an associated
purge stream to create an exit route for impurities or byproducts contained in the process. Often times
if an exit route does not exist, impurities will build up in the process and the simulation will fail to
converge due to a mass balance error.
2
Design-002H
Revised: Nov 7, 2012
4.02.
On the main flowsheet add a Tee block from the Model Palette. The tee block will fractionally split a
stream into several streams according to user specifications. Note that you can rotate the tee using the
Rotate button on the Flowsheet/Modify tab of the ribbon.
4.03.
Double click the tee (TEE-100) to open the property window. Select S7 as the Inlet stream and create
two Outlet streams called Rec1 and Purge.
3
Design-002H
4.04.
Revised: Nov 7, 2012
In the Parameters form under the Design tab, enter a value of 0.01 for the Flow Ratio of the purge
stream. This means that 1% of the S7 stream will be diverged to the purge stream. The tee should solve.
4
Design-002H
Revised: Nov 7, 2012
4.05.
In order to recycle stream Rec1 back to the mixer, we must add a Recycle block to the flowsheet. The
recycle block is a theoretical block which acts to compare and modify the values of the outlet stream
until the inlet and outlet streams are equal to a specified tolerance.
4.06.
Double click the recycle block (RCY-1). Select Rec1 as the Inlet stream and create an Outlet stream
called Rec2. The flowsheet should now look like the following.
5
Design-002H
Revised: Nov 7, 2012
4.07.
We need to add a compressor to raise the pressure of the recycle stream before we can connect it back
to the mixer. Add a Compressor to the flowsheet. Select Rec2 as the Inlet stream, create an Oulet
stream called Rec3, and create an Energy stream called Q-Comp2. Specify an outlet stream Pressure of
274 bar_g in the Worksheet tab. The compressor should solve and the flowsheet should look like the
following.
4.08.
The recycle stream is now ready to be connected back to the mixer block to close the loop. Double click
on the mixer (MIX-100) to open the property window. Add stream Rec3 to the Inlet streams. The
flowsheet should solve.
6
Design-002H
4.09.
Revised: Nov 7, 2012
Check results. Double click on stream NH3. In the Composition form under the Worksheet tab you can
see that the mole fraction of ammonia is now 0.9581. This is below our desired mole fraction of 0.96.
Optimize the Purge Rate to Deliver Desired Product
4.10.
We now wish determine the purge rate required to deliver a product with a mole fraction of 0.96
ammonia. Add an adjust block to the flowsheet.
7
Design-002H
4.11.
Revised: Nov 7, 2012
Double click the adjust block (ADJ-1) to open the adjust window. We must define our adjusted and
targeted variables. For the Adjusted Variable select Flow Ratio_2 of object TEE-100. To do this, click
the Select Var… button and select the following options. When finished select OK.
8
Design-002H
4.12.
Revised: Nov 7, 2012
Next, select the targeted variable. Choose Master Comp Mole Frac of Ammonia in stream NH3. This is
shown below. When finished click OK.
9
Design-002H
Revised: Nov 7, 2012
4.13.
Next, we will specify the target of 0.96 for the Mole Fraction of Ammonia in the product stream. The
adjust window should now look like the following.
4.14.
Go to the Parameters tab and enter a Step Size of 0.001, and a Maximum Iterations of 1000. Click Start
to begin calculations. The adjust block should solve. Go to the Monitor tab to view results. You can see
that the mole fraction of ammonia in the product stream reached 0.96 at a purge fraction of 0.019.
10
Design-002H
Revised: Nov 7, 2012
11
Design-002H
4.15.
Revised: Nov 7, 2012
The flowsheet should now look like the following.
Investigate the Effect of Flash Feed Temperature on Product Composition
4.16.
We would now like to determine how fluctuations in flash feed temperature will affect the product
composition. Changes in cooling efficiency or utility fluid temperature can change the temperature of
the flash feed stream. This change in temperature will change the vapor fraction of the stream, thus
changing the composition of the product and recycle streams. First, we need to deactivate the adjust
block. Double click the adjust block and check Ignored.
4.17.
In the navigation pane go to Case Studies and click Add.
4.18.
A new case study called Case Study 1 will be created. In Case Study 1 click Add to add variables to the
study. First we will select the Mole Fraction of Ammonia in the product stream NH3.
12
Design-002H
4.19.
Revised: Nov 7, 2012
Next, we will add the Temperature of stream S6.
13
Design-002H
Revised: Nov 7, 2012
4.20.
We will vary the Temperature of stream S6 from 25°C to 100°C with a Step Size of 5°C.
4.21.
Click the Run button, and then go to the Plots tab to view the results.
4.22.
You will see that as temperature increases, the ammonia mole fraction decreases which means that
when operating this process it will be very important to monitor the flash feed temperature in order to
deliver high quality product.
14
Design-002H
Revised: Nov 7, 2012
5. Conclusion
This simulation has proved the feasibility of this design by solving the mass and energy balances. It is now ready
to begin to analyze this process for its economic feasibility. See module Design-003H to being the economic
analysis.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
15
Design-003H
Revised: Nov 7, 2012
Ammonia Synthesis with Aspen HYSYS® V8.0
Part 3 Process Economic Analysis
1. Lesson Objectives



Acquire basic knowledge on the evaluation of the economics of a chemical process
Build upon the closed loop Ammonia Synthesis process simulation
 Add process stream prices in feed and products
 Add utility costs in the equipment
Learn how to perform economic evaluation within Aspen HYSYS.
 Transform simplified process into a more realistic design
 Economic Analysis of followings:
 Capital Cost
 Operating Cost
 Raw Materials Cost
 Product Sales and Utilities Cost
 Estimation of ‘Pay Off’ period
2. Prerequisites



Aspen HYSYS V8.0
Microsoft Excel
Completed design modules Design-001H and Design-002H
1
Design-003H
Revised: Nov 7, 2012
3. Background, Recap of Ammonia Process
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Brief Introduction to Process Economic Analysis
During the conceptual design phase 80% of capital costs are determined and 95% of your operating costs are
determined at this phase. Operating costs are typically 2-3 times the amount of capital costs. Decisions made
during the conceptual design process have a major impact on the final project – so it is important to make the
right decisions based on rigorous cost estimates instead of guesswork. The typical workflow of the cost
estimation process is shown below.
2
Design-003H
Revised: Nov 7, 2012
Typical Workflow of Cost Estimation
5. Aspen HYSYS Solution
The following flowsheet was developed for a closed loop Ammonia Synthesis process.
5.01.
Open the solution .hsc file for the closed loop Ammonia Synthesis.
(Design_002_AmmoniaSynthesis_ClosedLoop.hsc)
3
Design-003H
Revised: Nov 7, 2012
5.02.
The final step of Design_002 was to run a Case Study. This altered the Temperature of stream S6, and
thus changed the purity of stream NH3. Double click on stream S6. In the Worksheet | Conditions page,
change the Temperature back to 26.85°C.
5.03.
Next, double click on TEE-100 and set the Flow Ratio of Purge to .019. We are now ready to evaluate
cost.
5.04.
First we will enter the buying and selling prices of our feed and product streams in order to determine if
our process is capable of making money. Double click the SynGas feed stream and go to the Cost
Parameters form under the Worksheet tab. Select Mass Flow for Flow Basis and enter 0.26 Cost/kg for
Cost Factor.
4
Design-003H
5.05.
Revised: Nov 7, 2012
Next, double click the product stream NH3. In the Cost Parameters form, select Mass Flow for Flow
Basis and enter 500 Cost/ton for Cost Factor.
5
Design-003H
Revised: Nov 7, 2012
5.06.
To view the total stream costs, go to the Economics tab in the ribbon and select Stream Price.
5.07.
This will open up the Model Summary Grid. Here you can view the total cost for each material stream.
SynGas has a total cost of $15,941/hr, while the product stream NH3 has a value of $28,794.7/hr. In
this case the product stream is roughly twice as valuable as the feed stream. This is a good sign and
indicates that this process may be profitable.
6
Design-003H
5.08.
Revised: Nov 7, 2012
Next we will estimate costs for utilities. Double click on energy stream Q-Comp1. Select Power for
Utility Type.
7
Design-003H
Revised: Nov 7, 2012
5.09.
Double click on energy stream Q-Comp2 and select Power for Utility Type.
5.10.
Double click on energy stream Q-Heater and select Fired Heat (1000) for Utility Type.
8
Design-003H
5.11.
Double click energy stream Q-Cooler and select Cooling Water for Utility Type.
5.12.
Double click Q-Reac and select Cooling Water for Utility Type.
Revised: Nov 7, 2012
9
Design-003H
Revised: Nov 7, 2012
5.13.
To view the utility summary, click Flowsheet Summary in the Home tab of the ribbon.
5.14.
The Flowsheet Summary window will appear. Go to the Utility Summary tab. Here you can view the
cost of each utility and the total costs of utilities. The Total Costs of Hot Utilities are $2792/hr, and the
Total Costs of Cold Utilities are $25.47/hr.
5.15.
The operating profit of this process is equal to:
10
Design-003H
Revised: Nov 7, 2012
The operating profit of this process is $10,036.23 per hour. The next step is to evaluate the capital costs
of the process.
5.16.
This simulation has so far taken into account the mass and energy balances but it has yet to consider
realistic equipment design constraints. This simulation is highly simplified and has served to prove this
process has potential to be profitable. The next step is to transform this highly simplified design into a
‘real-life’ design which will provide more accurate estimations for capi tal and operating costs. This is
done using the built in economics in Aspen HYSYS.
Transform simplified design using built in Economic Analyzer
5.17.
Go to the Economics tab, and select Activate Economics. This will enable the Economic Analysis
functionality in Aspen HYSYS.
5.18.
When the economic analysis is Activated, the Integrated Economics buttons are enabled and ready to
apply economic calculations. Next, click the Map button.
5.19.
The map function is a key step in determining project scope and cost. This function enables unit
operations from the simulation model to be mapped to “real-world” equipment so that preliminary
equipment sizing can be performed. This mapping process is analogous to equipment selection and
sizing and will serve as the basis in determining costs. When the Map button is clicked, the following
window will appear. Press OK to continue.
11
Design-003H
5.20.
Revised: Nov 7, 2012
The following window titled Map Preview will allow you to change the mapping for certain unit
operations. The Economic Analysis has pre-defined default mappings for unit operations. However,
these may be changed to create a more realistic cost evaluation. For example, the default mapping for
heaters are floating head shell and tube exchangers, but heater block E-100 is a furnace which burns
natural gas.
Select E-100 and click the drop down menu under Equipment Type.
12
Design-003H
5.21.
A new window will appear, select Heat exchangers, heaters and press OK.
5.22.
Next, choose Furnace and click OK.
Revised: Nov 7, 2012
13
Design-003H
5.23.
Revised: Nov 7, 2012
Lastly, select Vertical cylindrical process furnace and click OK.
14
Design-003H
Revised: Nov 7, 2012
5.24.
You have now successfully changed the mapping of E-100 and its cost will be evaluated accordingly. We
must also change the mapping of the reactor from an agitated tank to a plug flow reactor. For this
process it is sufficient to model the reactor as a shell and tube heat exchanger, because the reactor will
be a vessel containing tubes. Select the CRV-100 and click the drop down menu to change equipment
type. Select Heat exchangers, heaters | Heat Exchanger | Fixed tube sheet shell and tube exchanger.
Click OK in the mapping window to complete the mapping process.
5.25.
Next, click on Size. The sizing process will complete.
5.26.
Select View Equipment to view the results of the sizing.
15
Design-003H
Revised: Nov 7, 2012
5.27.
The Economic Evaluation Equipment Summary Grid will open. Go to the Equipment tab. You may
encounter an error for CRV-10 involving both the shell and tube streams being heated. This can be
addressed by changing the outlet temperature (stream S5V) from CRV-10 to 481.8 °C, which assures
that the shell stream will decrease in temperature.
5.28.
We are ready to evaluate. Click the Evaluate button in the ribbon. The economic engine will perform
the analysis, it may take a few moments.
16
Design-003H
Revised: Nov 7, 2012
5.29.
Click View Equipment, and go to the Equipment tab to view any errors that occurred during evaluation.
These errors will tell you what inputs or changes are required in order to cost the simulation more
realistically.
5.30.
The evaluation error for compressor E-100 states that the material specified is inadequate for design
conditions. To fix this, go to the EFU VERTICAL tab and select a suitable material for construction.
Select 304S (stainless steel) for Material.
17
Design-003H
Revised: Nov 7, 2012
5.31.
The error for K-100 is that the inlet temperature is too high. To fix this we will had a cooler before the
compressor to cool down the inlet stream.
5.32.
Double click K-100 and remove stream SynGas as an Inlet stream. Create an Inlet stream called
SynGas2. Add a Cooler block to the flowsheet and select SynGas as the Inlet stream, SynGas2 as the
Outlet stream, and create an Energy stream called Q-Cooler2. Specify a Delta P of 0 and an outlet
Temperature of 300 K. Double click stream Q-Cooler2 and specify Cooling Water as the Utility Type.
The flowsheet should now look like the following.
5.33.
The errors for both E-101 and CRV-100 are that there are no materials in the database that are suited
for such a high temperature and pressure combination. These materials will likely have to be custom
made for this specific process and priced accordingly. However for this simplified simulation, we can try
lowering the operating pressure in order to get a cost estimate. In real life it may not be plausable to
18
Design-003H
Revised: Nov 7, 2012
change the operating conditions, as the reaction kinetics may be very dependent on temperature and
pressure. However, for this simulation we are not using kinetics. Therefore the reaction will not be
affected.
5.34.
Double click each compressor and change the outlet pressure to 190 bar_g. The process will now
operate at lower pressures, allowing economic evaluation to produce a cost estimate.
5.35.
Repeat the mapping and sizing process since a new piece of equipment now exists on the flowsheet.
When ready, click Evaluate. The equipment results will now look like the following in the Economic
Evaluation Equipment Equipment Grid. There should not be any errors.
5.36.
Go the Summary tab to view results.
5.37.
This table displays the different costs associated with constructing and operating this process as well as
the total product sales per year. This process appears to have the potential of being a highly profitable
investment, with a payoff period of only 3.64 years.
5.38.
Click on the Investment Analysis button.
19
Design-003H
Revised: Nov 7, 2012
5.39.
This will open up a Microsoft Excel spreadsheet that summarizes the results. In the Excel spreadsheet
there will be the following sheets: Run Summary, Executive Summary, Cash Flow, Project Summary,
Equipment, Utility Summary, Utility Resource Summary, Raw Material Summary, and Product
Summary.
5.40.
The Executive Summary sheet is a very useful sheet which displays the project name, capacity, plant
location, description, scheduling, and investment information. This is shown below.
5.41.
The Cash Flow sheet is also useful and displays various costs and assumptions that went into making the
economic estimations.
20
Design-003H
Revised: Nov 7, 2012
6. Conclusion
Aspen HYSYS along with the economic analyzer tool can quickly create first approximations of process sizing and
costs. This is very useful when attempting to compare several process designs to decide which design will have
the best potential to be profitable. If a process has proven to be profitable at this level of analysis, costing
engineers will then take this preliminary design and fine tune it in a more detailed costing application such as
Aspen Capital Cost Estimator. Taking a conceptual design from a process simulator and being able to accurately
estimate the associated costs is extremely valuable and can be the difference between a successful investment
and a company going out of business.
21
Design-003H
Revised: Nov 7, 2012
7. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
22
Petroleum Refinery Engineering
PET-001H
Revised: Nov 6, 2012
Gas Oil Separation Process with Aspen HYSYS® V8.0
1. Lesson Objectives


Understand the gas oil separation process (GOSP)
Understand how to utilize Conceptual Design Builder in Aspen HYSYS
2. Prerequisites

Aspen HYSYS V8.0
3. Background
An oil well commonly produces the crude consisting of gas, oil, water, and contaminants. A gas oil separation
process (GOSP) handles the crude from the well and separates oil, gas, water, and contaminants. The processed
oil and gas can then be sent to oil refineries and gas processing plants, respectively.
For field development research and assessment, a number of process scenarios must be quickly generated and
assigned with different probabilities. Aspen HYSYS and the Conceptual Design Builder allow you to quickly
generate the necessary iterated, individual scenarios necessary for field development research and assessment.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
An oil field produces crude oil with the following specifications that is processed in a gas oil separation plant:



Gas/oil ratio (GOR): 200
Water/oil ratio (WOR): 0.02
Production rate: 2000 barrels/day
Using Aspen HYSYS and the Conceptual Design Builder, determine the oil, gas, and water production rate from
this process.
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0. Click the Conceptual Design Builder button from the Get Started tab of the
ribbon to initialize Conceptual Design Builder (CDB).
1
PET-001H
Revised: Nov 6, 2012
4.02.
From the Project Setup tab of the CDB window, select Oil Field for Field Type, High for both
Environmental Sensitivity and Political Risk Sensitivity, and Low for Population Density. The latter
three specifications are for reporting purposes.
4.03.
Go to the Project Specification tab. Enter a Production Rate of 2000 barrels/day, GOR of 200, and WOR
of 0.02 vol/vol.
2
PET-001H
4.04.
Revised: Nov 6, 2012
Go to the Design Preferences tab. In the Separation frame, select 3 Stages for the Number of Stages.
This will provide a three-stage separation train for the process. Click the Run Design Case button from
the Home tab of the ribbon.
3
PET-001H
Revised: Nov 6, 2012
4.05.
The Conceptual Design Builder will now automatically construct the flowsheet in HYSYS according the
specifications and preferences. Navigate back to Aspen HYSYS, and a flowsheet should be constructed
like the screenshot below. The generated process consists of GOSP (Gas-oil separation), gas
compression, gas sweetening, and dehydration sections.
4.06.
Open the stream WellFluid2 and go to the Worksheet | Conditions page. Confirm the Temperature and
Pressure is 40 °C and 48.99 bar_g, respectively.
4
PET-001H
4.07.
Revised: Nov 6, 2012
Go to the Worksheet | Oil & Gas Feed page. Confirm that the Total GOR and Total WOR is 200 and
0.02, respectively, as specified in the CDB.
5
PET-001H
Revised: Nov 6, 2012
4.08.
The GOSP unit utilizes a three-stage separation process to separate the oil, gas, and water. Open the
GOSP_1 and click the Sub-Flowsheet Environment button to enter the sub-flowsheet environment.
4.09.
From the sub-flowsheet, three stages of 3 Phase Separators are included in GOSP_1. The gas, oil, and
water exit the separators as vapor, light liquid, and heavy liquid, respectively.
4.10.
In order to return to the main flowsheet, click the View Parent button from the Flowsheet/Modify tab
of the ribbon.
6
PET-001H
Revised: Nov 6, 2012
4.11.
Open the stream Produced_Water. The water production rate from the process is 297.9 kg/hr.
4.12.
Open the stream Export_Oil. The oil production rate from the process is 11152 kg/hr.
7
PET-001H
4.13.
Revised: Nov 6, 2012
Open the stream ExportGas. The gas production rate from the process is 1987 kg/hr.
5. Conclusions
An oil field produces 13510 kg/hr of crude from the well and is processed via a gas oil separation process
(GOSP). The GOSP produced 11152 kg/hr, 1987 kg/hr, and 297.9 kg/hr of oil, gas, and water, respectively. The
detailed Aspen HYSYS simulation case was generated from the preliminary field data, reducing the financial risk
when developing a suitable engineering design.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
8
PET-002H
Revised: Nov 30, 2012
Hydrate Formation in Gas Pipelines
with Aspen HYSYS® V8.0
1. Lesson Objectives

Understand the hydrate formation calculation within a pipeline model in Aspen HYSYS
2. Prerequisites

Aspen HYSYS V8.0
3. Background
Hydrates are commonly formed in natural gas pipelines when water is condensed in the presence of methane at
high pressures. Natural gas hydrates are basically modified ice structures that enclose methane and other
hydrocarbons. The issue with hydrates is that at high pressures they have higher melting points than ice and can
cause blockages in pipelines and other processing equipment.
There are several methods used to prevent hydrate formation in pipelines such as heating or reducing the
pressure. A common method used is to add a hydrate inhibitor (anti-freeze) such as ethylene glycol which will
decrease the temperature that hydrates will form. In this demo we will be simulating the piping network that
mixes streams from 3 gas wells before they are sent to a gas-oil separator. The ambient temperature is 0°C, and
as the gas streams cool due to heat loss in the pipeline, the risk of hyrdate formation increases.
The examples presented are solely intended to illustrate specific concepts and principles. They may not
reflect an industrial application or real situation.
4. Problem Statement and Aspen HYSYS Solution
Problem Statement
Using the pre-built Aspen HYSYS flowsheet PET-002H_Hydrate_Formation_Start.hsc, determine the flowrate of
ethylene glycol that is required to prevent any hydrates from being formed in the gas pipeline.
Aspen HYSYS Solution
4.01.
Start Aspen HYSYS V8.0. Open the file named PET-002H_Hydrate_Formation_Start.hsc.
4.02.
Once the case file loads and solves, you will see that there are three gas well streams and an ethylene
glycol inhibitor stream being fed into an Aspen Hydraulics Sub-Flowsheet (AH-100).
1
PET-002H
4.03.
Revised: Nov 30, 2012
The Aspen Hydraulics Sub-Flowsheet allows for simulation of pipes, junctions, mixers, swages, and
valves. Pipeline and hydraulic network simulations can be solved in Steady State mode or Dynamic
mode. Right click on AH-100 and select Open Flowsheet as New Tab.
2
PET-002H
Revised: Nov 30, 2012
4.04.
Flowsheet TPL1 will appear. Here you will see the piping network used to mix the gas well streams and
the ethylene glycol inhibitor.
4.05.
If you place the mouse over the EG Inhibitor stream, a tool tip will appear showing you the temperature,
pressure, and flow of the stream. The ethylene glycol stream currently has a flow rate of 0.1 kg/h.
4.06.
We would now like to check if any hydrates are being formed with the current flow rate of inhibitor.
Double click on the pipe segment Pipe-104. Go to the Flow Assurance tab and select the Hydrates form.
In the plot you will see a blue line and a red line. The red line represents the temperature at each point
along the pipe and the blue line represents the temperature at which hydrates will begin to form. With
the current flow of ethylene glycol you can see that hydrates will begin to form at approximately 40
meters into the pipe. This suggests that in order to prevent hydrate formation we will need to add more
inhibitor to the pipeline.
3
PET-002H
4.07.
Revised: Nov 30, 2012
Move back to the main flowsheet (Flowsheet Main). Double click on the EG Inhibitor stream and
change the flowrate to 50 kg/h. The flowsheet will solve after a few moments.
4
PET-002H
4.08.
Revised: Nov 30, 2012
Now if you go back to the Aspen Hydraulics Sub-Flowsheet and view the Hydrates form for Pipe-104
you will see the following. The hydrate formation temperature is now lower but hydrates still begin to
form in the pipe.
5
PET-002H
4.09.
Revised: Nov 30, 2012
We will now increase the ethylene glycol flow again. Go to the main flowsheet and change the mass
flow of stream EG Inhibitor to 100 kg/h. The flowsheet will solve after a few moments.
6
PET-002H
4.10.
Revised: Nov 30, 2012
The hydrate formation plot now looks like the following.
7
PET-002H
4.11.
Revised: Nov 30, 2012
The blue line (hydrate formation temperature) is now completely below the red line (temperature
profile). This indicates that hydrate formation is unlikely for this pipeline with an inhibitor flowrate of
100 kg/h.
5. Conclusions
Using Aspen HYSYS V8.0 we were able to determine the amount of ethylene glycol is required to prevent
hydrate formation in a pipeline network. It was determined that an ethylene glycol flowrate of 100 kg/h is
sufficient for this gas pipeline.
6. Copyright
Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be
reproduced or distributed in any form or by any means without the prior written consent of
AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH
RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be
liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential
damages arising out of the use of the information contained in, or the digital files supplied with or for use with,
this work. This work and its contents are provided for educational purposes only.
8
PET-002H
Revised: Nov 30, 2012
AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and
product names mentioned in this documentation are trademarks or service marks of their respective companies.
9