ASPEN Tutorial _ Chemical Engineering & Materials Science (CHEMS)

8/16/2019 ASPEN Tutorial _ Chemical Engineering & Materials Science (CHEMS)

1/16

2/29/2016 ASPEN Tutor ial | Chemi cal Engi neer ing & Mater ial s Science ( CHEM S)

http://www.chems.msu.edu/resources/tutorials/ASPEN

CHEMS Home | EGR Home | MSU Home | Contact Us

Prospective Students Current Students Friends & Alumni

ASPEN TutorialHome / ASPEN Tutorial

1. Aspen Introduction

ASPEN is a process simulation software package widely used in industry today. Given a process design and an appropriateselection of thermodynamic models, ASPEN uses mathematical models to predict the performance of the process. Thisinformation can then be used in an iterative fashion to optimize the design. This accurate modeling of thermodynamicproperties is particularly important in the separation of non‐ideal mixtures, and ASPEN has a large data bases of regressedparameters. ASPEN can handle very complex processes, including multiple‐column separation systems, chemical reactors,distillation of chemically reactive compounds, and even electrolyte solutions like mineral acids and sodium hydroxidesolutions.

ASPEN does not design the process. It takes a design that the user supplies and simulates the performance of the processspecified in that design. Therefore, a solid understanding of the underlying chemical engineering principles is required tosupply reasonable values of input parameters and to evaluate the suitability of the results obtained. For instance, a usershould have some idea of the column behavior before attempting to use ASPEN. This information could come from anapproximate method, such as the McCabe‐Thiele approach, general modeling of the T‐x‐y behavior, or residue curve maps.

ASPEN cannot tell you how many stages to use for a g iven separation. You must set the number of stages and see what typeof separation results. Some preliminary or 'back of the envelope' calculations are generally recommended.

MSU has a variety of Aspen packages for different simulations. Briefly, here are the programs and capabilities:

Aspen Adsim ‐ Fixed bed adsorption for pressure swing adsorption, etc.Aspen Chromatography ‐ Fixed bed adsorption, simulated moving bed chromatography. Runs independent of Aspen Plus.Aspen Custom Modeler ‐ A utility to permit the creation of user unit operations.Aspen Distil ‐ Aspen's 'Conceptual Engineering Product' for planning for processing schemes. Runs independent of Aspen Plus.Aspen Dynamics ‐ Unsteady‐state simulator.Aspen Plus ‐ Steady‐state process simulator.Aspen Properties ‐ Modeling of properties and phase equilibria. Incorporated into most other components, though it can berun as a stand‐alone subset. All of the phase equilibria and mixture property methods discussed on this site are accessible ineither Aspen Plus or Aspen Properties.Aspen Polymers ‐ Modeling of polymerization reactors and polymer thermodynamics. This package is available within AspenPlus or Aspen Properties rather than via an external menu.BatchSep ‐ Batch distillations. Runs independently of Aspen Plus.

Normally undergraduate student projects will involve Aspen Plus or Aspen Properties . To start either of these packages,be sure to look for the corresponding User Interface on the start menu.

1.1 Getting more help

This document is intended to be an overview. ASPEN has extensive online help. Do not try to contact ASPEN directly. They donot respond to student requests. Work through your instructor and TA for getting answers to your questions. If your questionsare not answered with online help, see the pdf documents available from the ASPEN documentation folder available on theSTART menu. Most common tasks are covered.

To find descriptions/equations for the thermodynamic models and parameter variables, are in online Properties Help,Chapter 3.

2. Getting Started with Aspen Plus or Aspen Properties

Normally undergraduate student projects will i nvolveAspen Plus or Aspen Properties . To start either of thesepackages, be sure to look for the corresponding UserInterface on the start menu. When you are prompted toconnect to the engine (license) configure the window as

shown, and click OK.

Figure 2.1 ‐ Connection dialog

About CHEMS

Undergraduate Program

Graduate Program

Friends and Alumni

Research

People

Resources

http://www.chems.msu.edu/alumnihttp://www.chems.msu.edu/alumnihttp://www.msu.edu/http://www.msu.edu/http://www.chems.msu.edu/resourceshttp://www.chems.msu.edu/peoplehttp://www.chems.msu.edu/researchhttp://www.chems.msu.edu/alumnihttp://www.chems.msu.edu/academics/graduatehttp://www.chems.msu.edu/undergraduatehttp://www.chems.msu.edu/abouthttp://www.chems.msu.edu/resources/tutorials/ASPENhttp://www.chems.msu.edu/http://www.facebook.com/pages/East-Lansing-MI/MSU-Department-of-Chemical-Engineering-Materials-Science/127939713925601http://www.abet.org/http://www.chems.msu.edu/alumnihttp://www.chems.msu.edu/contacthttp://www.msu.edu/http://www.egr.msu.edu/http://www.chems.msu.edu/http://www.msu.edu/http://www.chems.msu.edu/


2/16


http://www.chems.msu.edu/resources/tutorials/ASPEN 2

3. Specification of Flowsheet in Aspen Plus

If you are work ing with Aspen Properties, you may skip to section 4 of this document.

To demonstrate how to build a process simulation using ASPEN, we will develop a distillation column for separation of ethanol and water.

The first step in developing a simulation is to develop the process flow diagram (PFD), which consists of the unit operations(blocks) and streams that feed and connect the blocks. The blocks are listed by category at the bottom of the main window(columns, reactors, etc.) in a toolbar known as the 'Model Library', a portion is shown in Figure 3.1. There are a widevariety of block available. Documentation for the algorithm for each block is provided in the ASPEN documentation.

The first step is to choose the column type for the ethanol‐waterseparation. Click on columns to view the different columnsimulations available. The two types of common interest are'DSTWU', which is the multicomponent shortcut distillationmethod, and 'RadFrac', which is the rigorous simulation of asingle column.

Figure 3.1 ‐ Column and Stream menu

For the ethanol + water system, the short‐cut will not be appropriate since the system has an azeotrope. Choose 'RadFrac'.Click on the small arrow on the right side of 'RadFrac' to select the column icon that you want to use on the PFD. The menuwill disappear; move the crosshairs to the desired location on the main f lowsheet window and click the mouse button.

Next you have to add streams to the block. Click on the small arrow to theright of the STREAMS button at the lower left corner of your screen (as shownin Figure 3.1), and choose the stream icon you want from the menu(material, energy or work). For this example, set up the feed stream: choosethe Material stream by clicking on it. The column will now show arrowswhere the stream can be connected; red arrows indicate required streams asshown in Figure 3.2

Figure 3.2 ‐ Required and optional streamconnection points

To set up the feed stream to the column, move the crosshair on top of thered feed position and left click once. Now, move the mouse to the left andclick again. You should now have a defined feed stream (Stream 1). For theoutlet streams click the column outlet fi rst to connect the bottoms (Stream2) and liquid distillate (Stream 3).

If you make a mistake and want to delete a stream or block, click on the

arrow (select) button at the upper left of the Model Library toolbar, thenclick on the stream or block you want to delete and hit the DELETE key.

Figure 3.3 ‐ Column after connection of material streams

Now that you have defined the unit operations to be simulated and set up the streams into and out of the process, you mustenter the rest of the information required to complete the simulation. Within Aspen Plus, the easiest way to find the nextstep is to use one of the following equivalent commands: (1) click the Next icon (blue N ‐>); (2) find 'Next' in the Toolsmenu; or (3) use keyboard shortcut F4. Any option will open the Data Browser.

4. Configuring Units and Settings

In the Data Browser, you are required to enter information at locations where there are red semicircles. When you havefinished a section, a blue checkmark will appear. However, providing some 'Setup' settings is often desirable.

http://www.chems.msu.edu/sites/default/files/content/columnmenu-ASPEN.jpg


3/16


4/16



5. Specifying Components

Here you have to enter all the components you are using in the simulation. The opening screen is shown below.

5.1 Entering compound information

The easiest way to enter component information is to click on the 'Find' button and enter the name of the component. Startby typing 'ethanol', and then select ETHANOL from the list of components that appears. Click the 'Add' button to add it tothe components list. Repeat to add water to the components list. The ‘Component ID’ is an arbitrary name of your choicethat will be used to label the component in your calculations. The ‘Type’ is a specification of how ASPEN wi ll calculatethermodynamic properties. For fluid processing of organic chemicals, it i s usually appropriate to use ‘Conventional’. If youmake a mistake adding a component, right click on the row to specify deletion.


5/16



6. Specification of Thermodynamic Methods

Aspen furnishes a "Property Method Selection Assistant" to assist in selection of a reasonable thermodynamic model,

Tools>Property Method Selection Assistant. Also, Appendix D of the "Introductory Chemical Engineering Thermodynamicsby Elliott and Lira furnishes a flowchart to assist with model selection.

You need to be aware of the manner in which Aspen implements parameter values because Aspen offers temperature‐dependent functions in place of parameters, and sometimes uses different signs on parameters than the same models in theliterature.

To find information on the property models, access the online help file, and on the page "Accessing other Help", use the linkfor "Aspen Properties Help". Then browse to "Aspen Properties Reference". Then, to find the model description andparameters implementation click in the help window, click on "Physical Property Methods and Models". Look in Chapter 3 fordescriptions of the EOS and activity models. If you have trouble finding "Physical Property Methods and Models" via the onlinehelp links, load the correct help file C:\Program Files\AspenTech\APrSystem V7.1\GUI\Xeq\aprsystem.chm. You mayalso find a pdf file by browsing from the Start menu to C:\Program Files\AspenTech\Documentation\Aspen EngineeringV7_1\Aspen Properties\AspenPhysPropModelsV7_1‐Ref.pdf.

The screen to select the property method is shown below.

The ‘Process Type’ will narrow down the choices for thermodynamic methods. Often for undergraduate design, ‘Chemical’will provide a wide range of methods. However to access the van Laar model, you must select 'all'. The ‘Base method’ willspecify the default calculation method for all blocks though you can control which method is used in individual blocks by


6/16



editing the setup for the individual blocks. You wi ll generally not use ‘Henry Components’ or ‘Free water’. For the examplehere, select UNIQUAC, a well‐accepted model for non‐ideal multicomponent liquid mixtures at low pressure.

By clicking the ‘N‐>’ button, you wi ll be shown the binary parameters as shown in the screenshot below. When you close thewindow or click 'Next', you have provided approval of the values, and you wi ll receive no further prompting for parametervalues. If parameters are blank, zeros will be used. This does not imply that the ideal mixture assumption will be usedbecause many models predict non‐ideal behavior with parameter values of zero.

Understanding Aspen Binary Parameters

The form of the thermodynamic model parameters usually differs from the form in the published literature because ASPEN


7/16



often replaces parameters with functions of temperature. To find the form of equation used in Aspen, open the Help file,and from the 'index' tab, search for the index for the model name (e.g. UNIQUAC), click on the resulting model name in theindex pane, select the entry with the 'model' name (e.g. 'UNIQUAC activity coefficient Model'). You should then seeequations very similar to the published literature. To understand where you are within the help file system, switch back tothe Contents tab of the help folder and you will see links to the other activity coefficient methods. You will be in Chapter 3of the Physical Properties Methods and Models Manual.

For UNIQUAC the typical published form of the parameters is

tau.ij = exp(‐a.ij/T)

In ASPEN, this is implemented as

tau.ij = exp(a.ij + b.ij/T + c.ij*lnT + d.ij * T + e.ij/T^2)

So the published parameters are related to the aspen parameters:

b.ij (aspen) = ‐a.ij (published)

WHEN THE ASPEN UNITS ARE SET TO K (See the dialog box above, note the temperature units are specified in the top row of the table).

To verify the pure component values (e.g. UNIQUAC R and Q), in the data browser, click the 'Components' folder. Then inthe right pane on the 'selection' tab, click the 'Review' button at the bottom right. The listing will include constants pulledfrom the Aspen databases, including GMUQR and GMUQQ and GMUQQ1. For our purposes GMUQQ and GMUQQ1 are the same.These should match the values from the textbook.

7. Specifying Stream and Block Information

This section applies to Aspen Plus; if you are working with Aspen Properties, skip to the Section 8.

Click on 'Next'. Stream specifications will appear. You must choose the stream composition, flow rate, and state for feedstreams. The state is specified by pressure, temperature, and vapor fraction. For this example, for the feed stream (1)

choose a pressure of 1 atm and a temperature of 25 oC. Now enter the component molar flow rates as 20 kmol/hr for EtOHand 980 kmol/hr for water. (If you enter feed composition as mole fractions, you also have to specify the total flow rate.)

Click on Next. The block (RadFrac) setup will appear. For this rigorous simulation, you must specify the columnconfiguration. Enter the number of stages as 33 and specify total condenser. In the 'Operating Specifications' section, set thedistillate flow rate to 23 kmol/hr, and set the boilup rate at 1500 kmol/hr as shown below.


8/16


9/16



You can plot the column profiles using "Plot>Plot Wizard...". For compositions, choose the composition tool, specify liquidmole fractions. The analysis below shows that there may be more stripping stages than necessary for the given column 33stages, flowrates, reflux and boilup. Naturally, compositions at the top of the column are limited by the azeotrope.

7.4 Printing your work

See the note about the ASPEN print bug workaround at the top of this web page.

You can print the process flowchart and include the stream table if you have pasted it onto the PDF. Go to the 'Setup' page,and click on 'Use Specified Font Size' in order to get a readable printout. Then select 'Print'. To print 'Input Summary','History', or results ('Report'), go to the 'View' menu and select your choice. Save the information as a Notepad (.txt text)file, which you can then import into Word or Excel and print much more efficiently. The default reports have moreinformation than you typically need. Avoid printing reports without reviewing them or pasting them in a Word

document or you will use up print quota quickly!

7.5 Saving your Work

As you work with Aspen plus and Aspen Properties, saving files in the 'backup' format will assure that they can be opened inthe next version of Aspen. Currently it is not possible to open 'standard' files when upgrading Aspen. The backup format endswith an 'bkp' as the last part of the file extension.

7.6 Running the simulation again, and reinitializing

You will want to modify your process parameters to run the case again. After modifying, you can click the 'Next' button, orthe 'Run' button. The 'Run' button is blue '>' triang le in the main toolbar.

Aspen will 'reuse' the last state to start the next simulation. When a case crashes, this is usually not desirable. Toreinitialize, use the '|


10/16



For example, after setting up a acetic acid + water system to use the Hayden‐O’Connell method for vapor fugacities and theUNIQUAC method for liquid properties, a T‐x‐y diagram can be quickly generated using ‘Tools ‐> Analysis ‐> Binary…’. Besure to edit the ‘Valid phases’ box if you expect there may be ‘VLL’ equilibria. (Do not use ‘Free Water’ unless you cansafely assume that an aqueous liquid phase is pure water. This assumption can sometimes be used in petroleum processingof hydrocarbons, but is not valid for most functional organics).

The diagram is displayed:


11/16



When you close the diagram you will fi nd the table with some intermediate calculations. If you would like to get the valuesinto Excel, drag the mouse over the columns, and copy. Then paste into Excel.

Here is another example for methanol + benzene.


12/16



8.4 Calculating Mixture Properties

It is also possible to plot fugacity coefficients, activity coefficients, or other properties as a function of composition ortemperature, etc. Mixture properties typically require that you specify a property set and then 'run' the case.

First, specify the components as shown in Section 5. To get properties as a function of composition at a fixed T and P, youwill have to set up a property set and then request execution of the set.

8.4.1 Establishing the property set

Open the folder for 'Properties>Prop‐Sets'.

Click 'New...'

Give the 'Property Set' a name that will help you remember the calculated properties. In this example the property set iscalled 'PHIMIX'. On the 'Properties' tab, select the APSEN name for the property that you want to tabulate. You will probablyneed to consult the documentation to find the ASPEN name for the property. In this case, I will select 'PHIMX', the ASPENname for the component fugacity coefficient in a mixture. Enter the units if appropriate for your property.


13/16



On the 'Qualifiers' tab, set the other details for the calculation. In the case of fugacity coefficients, I chose to calculate

them for the vapor phase.

To instruct ASPEN how to use the property set, you next specify the analysis to be performed.

8.4.2 Specifying the Analysis to run for the property set.

Select the folder for 'Properties>Analysis'. The screen will look much like the 'Property Set' page in Section 8.4.1'Establishing the Property Set'. Click 'New' and name the analysis set. I w ill call mine 'PhiCalc'. Also for most properties youwill want to select 'Generic' unless it is clearly an envelope or residue curve. T‐x‐y, P‐x‐y and residue curves are accessiblemore easily as shown in Section 8.3 'Calculating Pure Properties, Binary Phase Behavior or Ternary Residue Curves'.


14/16


15/16



On the variable tab of the 'Property Analysis' set, you will specify the fixed state variables and the adjusted variables asshown below. Note that the upper section of the form is for the Fixed state variables, in this case set to be 120C and 1 atm.The lower table has been edited to vary the mole fraction of acetic acid. Before leaving the form, the values or range forthe adjusted variables must be specified. To provide this information, first put the cursor in the variable field (e.g. thevariable 'Mole fraction' is selected below), and then click the form button named 'Range/List' to specify the range/list forthat variable.

Specify the the Range or List of Values to be varied as shown below. Here the range will be from 0 to 1 at intervals of 0.05.

8.4.3 Generating the calculated values

At this point, ASPEN has enough information to calculate the desired information. C lick the 'Run' button on the toolbar. The'Run' button is the blue triangle in the top tool bar (it is 'g rayed out' on all screen shots on this web page). You can tell thatresults are available when the 'Analysis' folder changes to blue as shown below. Note that the blue 'PHICALC' folder has'Results' available. The columns of calculations as shown below can be copied to the Windows clipboard by dragging themouse over the column titles, using the Edit menu (or Ctrl‐C). The clipboard contents can be pasted into Excel.


16/16


CHEMS Links

CHEMS Home

About CHEMS

Undergraduate Program

Graduate Program

Friends And Alumni

Research

People

Resources

Department Links

College Of Engineering

Applied Engineering Sciences

Biosystems & Agricultural Engineering

Chemical Engineering & Materials Science

Civil & Environmental Engineering

Computer Science & Engineering

Electrical & Computer Engineering

Mechanical Engineering

Help

How Tos And FAQs

Report Broken Link

DECS Help & Support

W e b S t a n d a r d s : X H T M L 1 . 0 S t r i c t | C S S | W C A G A A | D e v e l o p e d B y D E C S

© M i c h i g a n S t a t e U n i v e r s i t y . A l l R i g h t s R e s e r v e d

8.5 Sharing parameter values between simulation files

When a significant number of user parameters have been entered, it is convenient to transfer them to another file in a moreefficient method than a copy/paste method. This section discusses a method to export parameters and import them into anew simulation.

As an overview, Aspen Properties files hold all the pure component and binary parameter information, but none of theprocess schematic information. They also include information about the property 'methods' including customization of howthe vapor phase fugacity is calculated, etc., and all reaction chemistry, etc. Plus they hold user parameters that have beenused to specify property information and binary interaction parameters.

So it is possible to export an Aspen Properties file from one aspen simulation using File>Export, and then import it into theother simulation. When you export, choose the Aspen Properties backup format, *.aprbkp for greatest compatibility. I alsostrongly suggest that you open the exported file using the Aspen Properties interface and enter a good description of theproperties file in the description window (Setup>Description). This description is viewable when using the Fi le>Open dialogbox which is helpful. Resave the properties file after documenting the file.

When you import to a new simulation using File>Import, you must select from a list the properties that you wish to import,and there are two options: merge or replace. I have not studied these closely, but it in my trials, I had to use 'replace' tooverwrite the binary parameters. Also, I did not have the patience to figure out which row in the property list imports thebinary interaction parameters. I just used shift‐click to select all rows and used the 'replace' button.

*If you notice any errors or outdated information on this page, please contact Professor Lira who maintains this content.
http://www.msu.edu/http://www.egr.msu.edu/decs/http://www.w3.org/WAI/WCAG1AA-Conformancehttp://www.w3.org/TR/REC-CSS2/http://www.w3.org/TR/xhtml1/http://www.msu.edu/about.htmlhttp://www.egr.msu.edu/decs/supporthttp://www.egr.msu.edu/decs/contacthttp://www.egr.msu.edu/decs/how-tohttp://www.egr.msu.edu/me/http://www.egr.msu.edu/ecehttp://www.cse.msu.edu/http://www.egr.msu.edu/cee/http://www.chems.msu.edu/http://www.egr.msu.edu/age/http://www.egr.msu.edu/aes/http://www.egr.msu.edu/egr/http://www.chems.msu.edu/resourceshttp://www.chems.msu.edu/peoplehttp://www.chems.msu.edu/researchhttp://www.chems.msu.edu/alumnihttp://www.chems.msu.edu/academics/graduatehttp://www.chems.msu.edu/undergraduatehttp://www.chems.msu.edu/abouthttp://www.chems.msu.edu/

Documents

ASPEN Tutorial _ Chemical Engineering & Materials Science (CHEMS)