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Problem Statement: Why is the molar flow of the 'pseudo stream' not reported properly in a calculator block when selecting P-Mole-Flow? | Solution: P-Mole-Flow as can be observed in the screenshot below. It is described as the molar flow rate of a pseudo product stream. It could be understood as a block result, however, P-Mole-Flow is the input molar flow rate of a pseudo product stream which can be found in the calculator block specification as Block-Var for a RadFrac column.
This is specified as a block variable, because in the RadFrac Block under RadFrac | Specification | Setup folder | Streams tab, there is an option to enter molar flow rate manually as an input specification:
Using the Block Variable: P-Mole-Flow in a calculator block the value shown above can be manipulated.
To access the mole flow of pseudo streams, it needs to be selected as a normal stream, specifying it in the calculator block as Stream Variable as shown in the screenshot below:
Keywords: Calculator block, mole flow, pseudo stream
References: None |
Problem Statement: When I copy the MULDIP viscosity parameters for a databank component of a user defined component, the viscosity reported for the components is very different. | Solution: If you specify components and then retrieve parameters for them then Aspen Plus/ Aspen Properties will show the parameters including the method parameters for the thermodynamic (THRSWT) and transport (TRNSWT) models which tell which equation will be used to calculate properties.
Based on this information, users can see that for some databank components liquid viscosity is calculated using equation 100 (TRNSWT/1 = 100) which is a simple polynomial equation, mu = a + bT, etc.
If you do a pure component analysis and check how Aspen calculates Viscosity, for retrieved parameters one can observe that all results were calculated using the same simple polynomial equation. However, if you manually specify the MULDIP parameter value and run the simulation, then, one can notice that results are different even if the specified value is the same as was retrieved from databanks. This is because Aspen Plus is not using simple polynomial equation (eq. 100) any more, it is using the default. Once you enter the MULDIP parameter manually, the system sets the equation to be the default equation associated with the model, which is the log form (ln mu = a + bT, etc) equation 101.
We can notice that if source of data in MULDIP folder and TRNSWT folder are the same then Aspen Plus will use equation selected in TRNSWT. If the source of data are different, like in our example when MULDIP parameter was entered by user and TRNSWT/1 parameter was retrieved from databanks, then Aspen is not taking into account this specification, but a defalt equation number is used. The list of Default equation can be found below or in online-help see Pure-Component Temperature-Dependent Properties.
To make sure that Aspen Plus is using equation which was shown in TRNSWT folder, when specifying temperature-dependent property parameters for DIPPR equations on the Methods | Parameters | Pure Component form, it is best to set the THRSWT or TRNSWT element corresponding to that parameter on the same form, even if the correct value is already set in databanks. Because each DIPPR parameter can be used with more than one equation, when a DIPPR parameter is selected, only the THRSWT or TRNSWT element found in the same source is used, to ensure a correct interpretation of the parameter. If you do not, the default value from the table above is used.
Keywords: None
References: None |
Problem Statement: In RadFrac itself a user has two different ways to select a property method. One is in the Specification| Block option folder. The second place where the user can select the property method for segments, reboiler and condenser is Specification| Properties folder. Given the various methods, which method selection has a higher priority during the calculations in an Aspen Plus run?
An  example of is when the user chooses the SRK property method in the properties sheet for all stages and the Peng Robinson method in the Block option sheet. How does the program decide which property method has priority when the run is initiated for the phase equilibrium calculations on each column stage? | Solution: If the user specified the property method for a section of the column in the Specification | Properties folder, that method will override the default property method for this section of the column. For example, if the user specified SRK for stages 2 to 5 in the Specification | Properties folder, then SRK will be used to calculate the properties for stages 2 to 5 regardless of the property method specified in the Specification | Block Options folder.
This is what the online help says about Specification| Properties folder:
Keywords: None
References: None |
Problem Statement: What's New in Aspen Plus V7.3 - Start page with news feed | Solution: Aspen Plus V7.3 makes it easier than ever to stay informed with news about upcoming webinars, training events, how-to knowledgebase articles, and short animated tutorials. The new Start Page features quick links to help topics, including a summary of new features of Aspen Plus V7.3 and previous versions. There are quick links to the customer support pages for Aspen Plus and Aspen Polymers, and links to the training site so you can find a training course in your area.
The Support Live Chat link opens an interactive chat window where you can receive help directly from AspenTech's staff of professional Customer Support Engineers. This option for getting immediate help is also available directly from the customer support web site.
The right hand side of the new start page includes a set of live news feeds. The Product News tab shows news items related to Aspen Plus and closely related products that interoperate with Aspen Plus. These news items will include training opportunities, 'how-to' knowledgebase items, short animated tutorials, webinar announcements, and important information about future service packs or software patches.
Most news articles link to more detailed information - just click the blue headers to read the full text , to get access to attached sample files, and to view animated tutorials.
The second tab is customizable. You can populate this sheet with a news feed related to your organization, a professional organization, or to any other RSS feed. The second tab can also be customized through scripted installations - allowing your organization to use this tab to send messages to your internal user base, so you can keep your staff informed about internal training programs, or maybe just to share best practices with each other.
Go to Tools| Options | Start Page to customize the start page options, including the update frequency and the ?My News? URL.
Keywords: None
References: None |
Problem Statement: Are Options/Preferences being saved in Template file? | Solution: Batch Plus users can create a new Project based on a saved Template. Options are being saved in Template file along with other data (equipment, materials, mixtures, utilities, reactions, cells, packaging materials, equipment pools, and preferences) of the Project on which the template is saved. Many users implemented templates for their companies or departments to speed up the creation of recipe in Batch Plus (common equipment, components, utilities) and to comply with company/department standards.
Keywords: Template, options, preference, customize, save
References: None |
Problem Statement: How to customize the language used in the Batch Plus Recipe Text? | Solution: Language templates are stored in Access database. Go to Preferences\Language\Setup User Templates. Select or specify a directory to store the new template files. Click Copy to create the templates. They will begin with the name User (for example UserEnglish.lng).
Use MS Access to open and edit these files when modifying the language of the text recipe.
To modify the text for a given operation:
Open the Language template for the appropriate language (e.g. UserEnglish.lng)
Open the table called TblOperationGroupLibrary. Sort the Operation by Ascending or Descending. Note the OperationGroupId's for the operation you want to modify. For example, Age uses 1-3, 482, 543, 606, 607 623 and 682.
Open the table TblOpeartionGroupRecipe. Find the any corresponding OperationGroupID's from step 2. In the case of Age it is only the first value. Modify the text in the Head and/or Tail fields. Do not modify any other fields.
Save this database. It is a good idea to keep a backup of the last version so you can always go back to a validated version.
Select this database by going to File\Preferences\Language and clicking on the ... button. Select the new database file. The existing Recipe text will be converted. This may take a while. Now the current Project will use this language template by default.
Keywords: None
References: None |
Problem Statement: After a 'Load Column' operation, the final volume of the column is greater than the capacity of the column. Why is that? | Solution: The column fill factor defines the amount of 'free space' in the column. If the fill factor is equal to one (default), all the column capacity is available to the liquid material. The material which is retained in the resin will be considered as additional volume. Hence, if some material is retained in the column, it will appear as 'additional' volume.
If the user wants the column capacity to account for the resin presence, it should specify a capacity that will account for the presence of resins and a fill factor lower than one.
The fill factor is defined as follows:
Fill factor = (Total Column Capacity - Resin Volume)/(Total Column Capacity)
During a 'Load column' operation, the retained material will hence be 'included' in the resin volume, and the final column volume will be equal to the column capacity.
Keywords:
References: None |
Problem Statement: Currently any custom Fortran shared libraries that support User Models, User Properties, User Physical Property models etc. require a DLOPT file that points to the location of the supporting dll's. Sometimes this is confusing to new users and is often overlooked. A more efficient way of including established custom dll's would be to use a default folder that is always linked against that would not require any DLOPT specification. For example, create a folder under the C:\Program Files\Aspen Plus xxx\Engine\inhouse\Dll that system managers can put the Standard dll's that are needed to support the simulations. These dll's can be installed as part of customization procedures that install databanks and custom option sets. You need to maintain the current DLOPT method for specifying dll's, obj's etc. for new models as they are developed. Any model specified by the DLOPT specification would superceed any model of the same name in the above default folder. | Solution: The user/administrator can specify a default DLOPT file by adding a line like
DLOPT: ${ASPTOP}\xeq\InhDlopt.opt
(the name specified is arbitrary) into the %asptop%\xeq\aspfiles.def. The specified DLOPT file will be used by Aspen Plus runs unless the user explicitly specified a DLOPT file.
This mechanism does not impose a certain directory structure and allows for Aspen Plus version independent libraries, or libraries from multiple directories to be specified. If the user want to use additional libraries, he also has to copy over the content of the common DLOPT file.
Keywords: user fortran subroutine
dlopt
References: None |
Problem Statement: Is it possible to specify multiple feed compositions within a production plan? The production plan includes several batches with varying recycle stream composition or feeds compostion (ie the feed compositions change with each new batch). | Solution: It is possible to do this by using the Start Or ..Series ...End Or
Keywords: within the recipe.
To do this:
Highlight the text recipe you want the OR keyword to be inserted before or after .
Note:
The Keyword can be inserted before or after the text. The deafult is to insert after. To change the default, click on the Edit menu and then select either Insert After or Insert Before.
Click on Edit\Insert Keyword\Or - the OR keyword will be inserted before or after the highlighted text.
The example below demonstrates how a single production plan uses the three different starting feed compositions. Specifically the output intermediates from three different steps are used as the. When the plan is simulated, the first operation in the Start Or ..End Or series is used for the first batch, then the second operation in the Start Or ..End Or series for the second batch.
The charges are outputs from different plants and have different compositions.
Note:
If there are more batches than operations in the Start Or ..End Or series, the subsequent batch uses the first operation again, and so on.
Step: Purification with Recycle (Example)
Unit Procedure: Multiple Feed Composition
Start Or
Series
1.1. Charge RE-500 with 1000 gal of Production PlantA - Output.
Series
1.2. Charge RE-500 with 1000 gal of Production PlantB - Output.
Series
1.3. Charge RE-500 with 1000 gal of Production PlantC - Output.
End Or
1.4. Continuously react the mixture from unit RE-500 in unit
CSTR-1 via reaction DummyReaction. The mixture feed rate is
7.5 gal/min. Continuously add NaOH,23% at a rate of 2.6
gal/min. Continuously add WATER at a rate of 5 gal/min.
Continuously add METHANOL at a rate of 2 gal/min.
Comments: This operation models a buffer tank. There is no reaction
actually happening.
1.x. ..........
1.8. .........
1.9. Transfer ...........................
Keywords
Start
Series
Or
Multiple
Composition
Variable
Variability
Plan
Production
References: None |
Problem Statement: Why are there inconsistent results between PC-SAFT and POLYPCSF?
PC-SAFT is a new and the better option, so we are migrating from POLYPCSF; however, PC-SAFT is giving different, wrong answers. | Solution: A possible causes for the inconsistent results between PC-SAFT and POLYPCSF is that both PC-SAFT and CPIG parameters for the polymer are entered (instead of its segment) when using PC-SAFT.
In the Online Help for PC-SAFT, there is the following description regarding the parameter input for PC-SAFT:
Since the copolymer PC-SAFT is built based on the segment concept, the unary (pure) parameters must be specified for a solvent or a segment. Specifying a unary parameter for a polymer component (homopolymer or copolymer) will be ignored by the simulation...
For POLYPCSF, either enter the parameters either for a polymer/oligomer or its segments. If entering the parameters for both, only the parameters for the polymer will be used.
Keywords: None
References: None |
Problem Statement: How does Aspen Polymer Plus handles solubility as function of polymer molecule weights? | Solution: Polymers Plus provides two types of property models: segment-based and component-based. The segment-based models such as POLYNRTL and PC-SAFT have already taken into account the changes due to the polymer molecular weight. The model parameters are defined for segments that can be used to construct a polymer and then the polymer parameters or properties are calculated using its segment parameters and its molecular weight.
While the segment parameters for a defined polymer are not changed during the polymerization, the polymer molecular weight can certainly change and therefore the polymer properties also change, so do the non-polymer properties in the mixture.
Sometimes users have external data or other correlations between solubility and molecule weights. To capture this information into the model, one can convert the solubility as a function of the polymer molecular weight to a set of vapor-liquid equilibrium (TPXY) data where each set corresponds to a specific polymer molecular weight. One can then use these data sets to determine the interaction parameters between the monomer and the polymer-segment.
Using POLYNRTL as an example:
1. Define a monomer and a polymer-segment.
2. Define as many oligomers as needed based on the same polymer segment defined above; each oligomer corresponds to a polymer molecular weight from the solubility as a function of the polymer molecular weight.
3. For each oligomer, convert the solubility at the oligomer molecular weight into a set of TPXY data
4. Select POLYNRTL as the polymer property method
5. Setup a data regression case to determine NRTL parameters between the monomer and the polymer-segment; all data sets should be used in the data regression.
If the user then uses POLYNRTL with NRTL parameters just determined using the above steps, the polymer model should reflect solubility as a function of the polymer molecular weight as that from the source data.
Keywords: Solubility, polymer, POLYNRTL, MW, molecule weight, segment, PC-SAFT
References: None |
Problem Statement: Aspen Plus V7.3.2 will not start after applying Emergency Patch 1 (EP1) | Solution: Here is how you can resolve the problem.
Log off the system and login with a privileged account
Try to run Aspen Plus V7.3.2, if you are able to run the application then do as follows:
Rename the profile of the user who is not able to run the program. Here is how you can rename the profile:
Open windows browser and browse to C:\Documents and Settings
Each system user has a folder (the same as login name) under C:\Documents and Settings. Rename the folder (add org to the end of the folder name) of the user who is not able to start Aspen Plus V7.3.2
Log of the system and login again with the account that is not able to run the program
System recreates user profile so the login will be slower than normal. You should be able to run Aspen Plus V7.3.2 at this time
Keywords: Aspen Plus V7.3.2
Aspen Plus
AspenPlus V7.3.2
AspenPlus
References: None |
Problem Statement: Simulation that ran without problem in a previous release now fails during the report generation. | Solution: The errors occur in the report pass, not during the simulation. Turn off Aspen Dynamics. From Tools | Options | Startup, uncheck Aspen Plus Dynamics under enable forms for layered products. Aspen Dynamics requires some additional calculations, and these are triggering the errors.
Keywords: None
References: : CQ00432113 |
Problem Statement: Is it possible to have the files that are imported and exported use a different working folder than files that are saved and/or opened? | Solution: It is not possible to set this in Aspen Plus. However, one can add a shortcut to a folder in the Favorites folder. Then, this folder can be reached easily by clicking on the Favorites button when importing or exporting. The user needs to be an Administrator to add the new shortcut.
Keywords: None
References: None |
Problem Statement: When two different polymers are formed in one reactor at the same time, it is not possible to look at the Molecular weight distribution of each polymer separately. I need to get the molecular weight distribution (MWD) of each polymer not the sum of both. | Solution: Polymers need to be separated in order to get separate MWD for each polymer. For this purpose, a separator (Sep) block can be used. Attached file which uses the library example ldpe.bkp demonstrates the above methodology.
Keywords: Polymers, Molecular weight distribution.
References: None |
Problem Statement: If you go in Aspen Plus v7.2 under Components |Specifications on the Enterprise Database tab, only pure component data bank selection is available.
In V7.1 you could select pure component databanks and binary parameter databanks separately.
From Tools, Options, the Component Data tab allows both pure components and binary default bank search order to be nominated. So this is not adhering to the V7.2 Components | Specifications form where only pure components bank selection is possible.
Please clarify. | Solution: If you uncheck the option Retrieve binary and pair parameters automatically in the GUI, then you can select the binary parameter databanks under Components, Specifications, Entreprise database. This option prevents duplicating the parameters in the GUI (e.g. if the databank is updated, the simulation will use the latest values, which is cleaner). You can see that when this option is unchecked, the Databanks tab in binary parameters becomes disabled (because it's not used anymore).
If the option is checked (default), then the databanks for binary parameters are selected under Properties, Parameters, Binary Interaction. That's how it was in V7.1. However in V7.1, the binary databank selection was still shown under pure components, those settings were simply ignored. V7.2 hides that selection when it is not relevant to prevent any confusion. The databanks can also be selected from Tools, Options, Component Data (again, this applies only if you retrieve the parameters in GUI - the old style of Aspen Plus).
So the user has now two options:
old style - databanks are selected under Tools, Options, Component Data and under Properties, Parameters, Binary interaction (and pair). Parameters are loaded into the user interface.
new style - databanks are selected on the Components | Specifications form. Parameters are not loaded up into the user interface by default when Retrieve binary and pair parameters automatically in the GUI is checked.
Let's now look at how does the default binary parameter bank get selected (this is property method dependent).
The discussion below refers to the default case where binary parameters are retrieved in GUI. The selection is based on databanks selected under Tools, Options, Component Data. For activity coefficient models (NRTL, UNIQUAC, etc), Aspen Plus tries to assist the user in the selection of the databank for binary parameters. When you select NRTL, the GUI will put VLE-IG first. If you had selected NRTL-HOC, then the GUI would have put VLE-HOC first. If you select NRTL, then change your mind and select NRTL-HOC, the GUI will leave the databank VLE-IG instead of VLE-HOC, so you'll end up with inconsistent binary parameters with respect to the vapor model (which may or may not have a dramatic impact). (This is the same for NRTL-RK, and for other activity coefficient models, such as UNIQUAC, UNIQ-RK, etc).
It's also an issue for Henry binary parameters. If you select ELECNRTL, the databank ENRTL-RK will be put first in the binary Henry parameters, instead of BINARY or HENRY. For some components (those which dissociate in ions), the parameters are very different (e.g. CO2 - in BINARY/HENRY, CO2 in liquid represents CO2 and CO3-, while in ENRTL-RK, the Henry parameter is assuming CO2, and CO3- is just not volatile since it is an ion, so the numerical value of the parameter has to be different).
This is not an issue for Equation of State (EOS) models since they have their own binary parameters though you do need to make sure that the databank is selected. If the databank is not selected in the default list, then no parameters will be retrieved.
The bottom line is that binary databank selection must be carefully checked by the user, either to ensure the selected databanks are correct (based on what's explained above) or that the binary interaction parameters are available and valid in the range of temperature and compositions (this requires carefully validation, and sometimes regression work is required).
Keywords: None
References: None |
Problem Statement: Presence of Double quotes ('') in the Setup | Specifications | Description will give the following error message:
** ERROR IN A DESCRIPTION PARAGRAPH
SKW: DESCRIPTION
INVALID USE OF POSITIONAL NOTATION.
THE SENTENCE AS ENTERED WOULD ASSIGN THE VALUE:
QUOTES TO TERTIARY KEYWORD NUMBER 2.
HOWEVER, THERE ARE ONLY 1 VALID TERTIARY | Solution: Double quote () have not been allowed in the description since 2006.5. Single quote (') are allowed. If the file is saved using 2006.5 or earlier, delete the double quote () from the description. You will not be able to re-enter it.
Keywords: FOR THIS SENTENCE. SENTENCE IGNORED.
References: : CQ00432897 |
Problem Statement: What's New in Aspen Plus V7.3? | Solution: Aspen Plus V7.3 includes many new and improved features to help you save time and effort developing new conceptual designs, evaluate relative capital and operating costs for alternative process schemes, improve the energy efficiency of your processes, and examine the carbon footprint of proposed designs.
There are many reasons to upgrade to Aspen Plus V7.3, including the following:
1. Save weeks of effort collecting physical property data to validate or fine tune the thermodynamics in your process models. With Aspen Plus V7.3, the NIST ThermoData Engine provides access to over 3 million mixture property and phase equilibrium data points for over 30000 pairs of components, as well as pure component data for over 24000 species.
See knowledgebase article 131612 for more details and to view a short demonstration of this feature.
2. Many nations and states now require manufacturing companies in the continuous process industries to report greenhouse gas emissions. Aspen Plus V7.3 includes new features to calculate and report greenhouse gas emissions and evaluate the annual carbon tax for your process.
See knowledgebase article 131613 for a detailed explanation and to view a short demonstration.
3. Integrated economic analysis makes it easy for Process Engineers to us AspenTech's rigorous and proven cost modeling technology from inside Aspen Plus. Use estimated capital and operating costs to make better engineering design decisions. Compare alternatives on a consistent basis using relative costing early in the conceptual design process, then send the preliminary cost files to your cost estimation department for detailed estimates using Aspen Capital Cost Estimator. With Aspen Plus V7.3 you can even customize the costing and sizing algorithms using your own MS Excel worksheets and Aspen Process Economic Analyzer templates.
See knowledgebase article 131614 to learn more about these and other costing improvements and to view a short demonstration.
4. With Aspen Plus V7.3 you can export heat exchanger data from your process model directly to Aspen's Exchanger Design and Rating tool. The new exchanger sizing feature exports exchanger and property data for heater blocks, heat exchanger (HEATX) blocks, and for the condensers and reboilers in distillation column models.
See knowledgebase article 131615 to learn about this feature and to view a short demonstration.
5. Check the energy efficiency of your process in minutes by sending the case file to Aspen Energy Analyzer. With Aspen Plus V7.3, you can do this with one mouse click. You can use the Energy Analyzer to identify and compare different heat recovery schemes against the thermodynamic limits determined by heat pinch theory.
See knowledgebase article 131616 to learn more about this feature and to view a short demonstration.
6. Make rigorous physical property calculations and data available to your entire technical staff using Aspen Properties Mobile V7.3. The Aspen Properties Mobile client runs on Apple iPhones, iPod touch, and the iPad. With Aspen Properties Mobile Chemists, Engineers, and Scientists can all have easy access to a consistent set of property data, including your in-house databases.
See knowledgebase article 130636 to learn more.
7. Stay informed with news about upcoming webinars, training events, how-to knowledgebase articles, and animated tutorials. The new Start Page features quick links to help topics, on-line customer support, and training resources to help you get up to speed quickly.
See knowledgebase article 131617 to learn more.
8. Modeling processes with solids is easier with Aspen Plus V7.3. You no longer need to define CISOLID sub-streams to carry the solids (unless you need to track particle size distributions). See ?What's New? in the Aspen Plus help for more details.
9. Aspen Plus V73 includes a new biodiesel databank containing 461 common triglycerides, diglycerides, and monoglycerides. The new PURE25 databank, based on the January 2010 DIPPR database, includes 42 additional components and updated parameters for a wide range of components. The newest NIST-TRC databank, based on the June 2010 NIST SOURCE database, includes data for over 24000 pure components. Many other improvements have been made to the physical property data and models. See ?What's New? in the Aspen Plus help for more details.
10. Aspen's Rate-Based distillation model is more accurate than ever before for packed columns. The new Hanley correlations, developed by AspenTech, apply to Pall rings, b-ETA rings, IMTP rings, CMR rings, and sheet metal structured packings. See ?What's New? in the Aspen Plus help for more details.
11. Aspen's DRYER model can be used to simulate drying of non-conventional solids, which track moisture content through component attributes. This feature is useful for simulating biomass or coal drying operations.
12. Several usability enhancements are included in Aspen Plus V7.3. The new Analysis toolbar makes it easier to create sensitivity studies, set up data regression cases, and launch residue curve and ternary analysis tools. The Analysis toolbar can also be used to send simulation data to Aspen Exchanger Design and Rating, Aspen Energy Analyzer, and Aspen Flare Analyzer.
13. There are many other enhancements in Aspen Plus V7.3. To learn more, install Aspen Plus 7.3 and click ?What's New? on the new start page. You can see all the new features of V7.3, and many previous releases.
14. Click the link below to see a summary of all the new features in Aspen Plus V7.2
What's New in Aspen Plus V7.2 - Overview
Keywords: None
References: None |
Problem Statement: Unable to get results message when trying to issue Excel reports.
The Excel templates shipped with Batch Plus 2.1 are compatible with Microsoft Excel 95, 97 and 2000. The problem is that the three different versions of Excel have conflicting references to DAO (Data Access Object).
The templates shipped with Batch Plus 2.1 handle the references properly in most cases. In some circumstances, users have difficulty when they install other applications that also have DAO references. | Solution: The patch contains new Batch Plus 2.1 templates which explicitly reference the version of DAO compatible with Microsoft Excel 97 and 2000 only.
The enclosed self-extractable file contains 53 new templates. The new templates replace the existing templates present in C:\Program Files\AspenTech\Batch Plus 2.1\Templates\Excel (the exact location may vary depending in your installation.)
1/ Download the attached file : BP_XL.exe (1.5 MB)
2/ Quit any Batch Plus and Excel applications.
3/ Keep a copy of the old *.bpr files from the folder C:\Program Files\AspenTech\Batch Plus 2.1\Templates\Excel in a new subfolder, such as C:\Program Files\AspenTech\Batch Plus 2.1\Templates\Excel\Bpr_old folder
4/ Extract the patched .bpr files from the BP_XL.exe in the folder C:\Program Files\AspenTech\Batch Plus 2.1\Templates\Excel, overriding the old ones.
5/ Re-run Batch Plus.
Keywords: DAO, reports, template, Excel, Results
References: None |
Problem Statement: Is it possible to embed an Aspen Plus *.bkp file in a Microsoft Word document? | Solution: To embed a bkp file in word document (or any Microsoft Office application) do the following:
1. In Microsoft Word click on the Insert | Object then you will get the following Object Window:
2. Click on the Browse button and locate the bkp file as shown below:
3. Click OK and then bkp file will appear on the word file
Keywords: Word, Embed, bkp
References: None |
Problem Statement: How does one take a second liquid from RadFrac? | Solution: RadFrac can handle two liquid phases along with a vapor phase in the column. There is an example file called 3phase.bkp in the Favorites | Applications directory of Aspen Plus that has an example that uses a side stream attached to a decanter in a column. SeeSolution 115269.
To remove one or a mixture of the two liquid phases from the column, one needs to use a Column Decanter.
To specify the decanter,
1. Go to the RadFrac Decanter Object Manger.
2. Click on the New button to create a new decanter.
3. Specify the stage of the decanter. This should be the same as that specified for the side product on the Setup form. For the 3phase example, the decanter stage is 10.
4. Specify the fraction of the liquid flows returned to the column for both of the liquid phases. For the 3phase example, both the 1st and 2nd liquid return fractions is 0.3.
This is a rather unusual specification; typically the water phase is decanted. For example, one would take 95% (a fraction of 0.95) of the water phase usually the 2nd liquid phase and 5% (a fraction of 0.05) of the hydrocarbon phase usually the 1st liquid phase to realistically model incomplete phase separation in the decanter.
To specify the side stream,
1. Connect a stream to the Side Product port on the Process Flow Diagram.
2. On the RadFrac Setup | Streams sheet specify the side product stage and a phase of Liquid. For the 3phase example, the side product is called SIDE and it is takes from stage 10. For a Liquid product, a Decanter unit operation block could then be used to separate the single side product stream into two streams, one for the 1st liquid and the other for the 2nd liquid. Alternatively, two side product streams could be defined for stream 10. One would have a phase of 1st Liquid and the other would have a phase of 2nd Liquid.
Note: If the side product stream is created before the decanter is specified, the Flow specification will be empty and the form will be incomplete. Once the decanter is created for that stage, the Setup form will be completed and the Flow specification will be grayed out.
Keywords: None
References: None |
Problem Statement: I cannot perform a regression because I am getting an error of a required parameter is missing, what can I do? | Solution: If you are conducting some property analysis together with your regression run, calculations will stop at input specifications if the routes involved in the calculation of the properties are incomplete, that is, all the required parameters for the routes are not available. When performing analysis, in order to progress with the run, you need to have at least all those parameters included either in regressions, estimations or already available for all components involved.
Keywords: Regression, analysis, error, required parameters
References: None |
Problem Statement: What is the meaning of the abbreviations that appear in the zone profiles tab of MHeatX block? | Solution: In the context of a pinch point you can have either a local or global pinch point and this are the abbreviations
GBL = GLOBAL
LOC = LOCAL
The Streams/Phases column is used to indicate whether a stream is at its dew or bubble point, or whether it enters or leaves the exchanger at that location. The abbreviations meanings are the following.
DP = DEW POINT,
BP = BUBBLE POINT
Keywords: MHeatX, Zone profiles, Pinch Point
References: None |
Problem Statement: Is it possible to use CALUPP in a user property set subroutine? Sometimes it works ok, but sometimes there are strange results. | Solution: CALUPP should not be called from user property subroutines. Doing so may result in recursive function calls which may overwrite variables (such as those in Common blocks) used in the first call, which that call may still need. This will lead to unpredictable results.
Extensive use of Common blocks in Aspen Plus makes it impossible to safely call subroutines recursively. One execution of the subroutine may alter memory occupied by variables used in the first call, leading to unpredictable results.
Keywords: None
References: : CQ00482225 |
Problem Statement: Aspen Plus Compound file folder user defined contents are removed when the Aspen Plus file is closed. | Solution: Aspen Plus Compound file format apwz includes the Heat Exchangers, ads and apw file. Any files manually placed inside the folder would not be stored once the apwz file is closed.
User defined files can be stored in apwz file format from the Aspen Plus -> File -> Edit Compound File -> Embed new files. The embedded files would be available when the Aspen Plus file (apwz) is opened.
Keywords: Compound file, apwz, EDR.
References: None |
Problem Statement: How to make the OLI database available to Aspen Plus when working with compound files (apwz). | Solution: The apwz is a compress file type that puts together all the input data, simulation results, and any other external files that the simulation may require. When you open the compound file (apwz), a temporary folder is created in the working directory with the unpacked contents and other temporary files. If you put the dbs file in that location, in a similar way you would do with a bkp file (seeSolution 139980), when you close the simulation, that temporary folder will be deleted and so will be the OLI database.
There is an easy way to solve this, you can modify the contents of an apwz package. Please go to File | Edit Compound File and attach the dbs as follows:
Now the dbs will be always available with the compound file.
Keywords: OLI, dbs, apwz.
References: None |
Problem Statement: I would like to have a table with stream results in Excel which does update automatically when the simulation is complete. This can be done with Aspen Simulation Workbook but the selection of the streams is very tedious. | Solution: There is now a Model Summary feature in Aspen Plus V8.6 which can be used to complete this task. The attached document highlight the steps you can follow to generate such a table (the instructions look long, but it's really only a few mouse clicks).
Steps to export the stream results to Excel with ASW links
Step 1: Run the simulation
Step 2: Select the stream results from the Results Summary | Stream sheet (Streams (Custom) result sheet does not work. The copy all button does not work, you must select the values.)
Step 3: Navigate to the Results Summary | Models form or click the Model Summary button on the Ribbon. Click Paste button
Step 4: After the Paste operation, there is now a MATERIAL tab with the stream results.
Step 5: To make the new tab permanent, click Save, possibly change the template name, then click OK
Step 6: Click Close
Step 7: Click Export to Excel button. Select only the MATERIAL table, leave the option Export variable link... checked and click Export Tables to Excel
The Excel spreadsheet will contain a table with link to the selected stream variables.
Keywords: ASW, Aspen Simulation Workbook, Excel, stream, results
References: None |
Problem Statement: Selecting edit/insert/time stamp from Aspen Plus flow sheet menu and clicking anywhere on the flow sheet produces garbage. Which registry is used to fetch the pertinent information from? | Solution: Selecting Tools/options will open the following window:
The information within the Time Stamp.. gets displayed when you Select edit/insert/time stamp. If these information are not correct or you want to change them then Clicking on the Time Stamp.. option will display the following window:
Remove all the information within the box and click on either or all of the following options: Time, Date, Username, Runid, or Version.
Keywords: Aspen
Time Stamp
Runid
References: None |
Problem Statement: New Feature in Aspen Plus V7.2 - Molecular Structure Editor | Solution: Aspen Plus V7.2 includes a new tool to draw molecular structure
You can open the molecule editor:
Within the User-Defined Component Wizard
From the Properties | Molecular Structure | Structure sheet
From the Tools menu or the toolbar button
This tool allows you to draw the structure of a molecule in order to estimate parameters for that molecule. This new workflow eliminates the need to enter molecular structure symbolically in the molecular structure form.
You can copy the molecule image and place it on your process flowsheet drawing or copy it as an image to other applications such as MS Word. You can also save a .mol file for later use in Aspen Plus and Aspen Properties or other programs which can read .mol files.
The placements of atoms, lengths of bonds, and stereochemistry drawn using this tool are ignored in Aspen Plus and Aspen Properties; only the connectivity information is used in estimation by the Aspen Physical Property System or by TDE.
If you opened the editor from the User-Defined Component Wizard or the Molecular Structure form, then the drawing is automatically saved inside the simulation for this molecule when you close the editor, but you cannot reload it in the molecule editor from Aspen Plus. Save a .mol file from the editor if you want to edit it later.
Keywords: None
References: None |
Problem Statement: Is it possible to display the version, file name, date and time created in the flowsheet? | Solution: It is possible to display the version, file name, date and time created in the flowsheet. To add this information in the flowsheet, execute the following steps:
1. Click on the A button for adding a text box to the flowsheet. The A button is on the far left of the Draw toolbar in the Process Flowsheet Window.
2. Click on the Process Flowsheet Window in the location desired to add the text box.
3. In the text box, use the following strings to get the desired information.
To Print
Type
Version
&[VERSION]
File name
&[RUNID]
Time
&[TIME]
Date
&[DATE]
User name
& [USER]
4. You can write each one in a single line or enter multiple in the same line separated by comma.
5. Once you finish adding the text, click elsewhere on the flowsheet to finish. The text box should then display the appropriate information.
Similar steps can be followed in a plot to mark the date and time that the plot was created.
Keywords: Date, user name, plot
References: None |
Problem Statement: Is there a comparative list available for incorporated features in Aspen Plus versions of V7.2, V7.3, V7.3.2, V8.0, V8.2 and V8.4? | Solution: There had been updates in terms of Operating systems, Databank components and Additional tools among various versions of Aspen Plus.
Here are the major segments updated:
Operating Systems: Supported Operating Systems and Supported MS Office Versions
Databank: Pure components and Mixture Systems
Additional Tools: New MS Office Style User Environment, Green House Gas Emissions Reporting, Integrated Economic Analysis, Activated Economic Analysis, Integrated Energy Analysis, Activated Energy Analysis, Integrated Heat Exchanger Sizing and Rating, Activated Heat Exchanger Sizing and Rating, Intelligent Search, Online Training, Improved Solid Equipment Models and Characterization, View Plant Data and Model Results Together, Access to Models and Applications with aspenONE Exchange and Custom Tables.
Here is a table detailing the features available in various versions of Aspen Plus.
Aspen Plus® – New Feature Availability
Newly Introduced Features
V7.2
Jul. 2010
V7.3
May 2011
V7.3.2
Feb. 2012
V8.0
Dec. 2012
V8.2
May 2013
V8.4
Nov. 2013
Supported Operating Systems
XP, VISTA
XP, VISTA,
WIN 7x32,
WIN 7x64
XP, VISTA,
WIN 7x32,
WIN7x64
XP, WIN 7x32,
WIN 7x64
XP, WIN 7x32,
WIN 7x64
WIN 7x32,
WIN 7x64,
WIN 8x64
Supported MS Office Versions
2003, 2007
2003, 2007,
2010
2003, 2007,
2010
2007, 2010
2007, 2010
2010, 2013
Pure Components
>19,500
>24,000
>24,000
>24,000
>24,000
>24,000
Mixture Systems
>3,000
>3,000
>3,000
>3,000
>12,000
>12,000
New MS Office Style User Environment
√
√
√
Greenhouse Gas Emission Reporting
√
√
√+
√+
√+
Integrated Economic Analysis
√
√
√
√
√
√
Activated Economic Analysis*
√
√
√+
Integrated Energy Analysis
√
√
√
√
√+
Activated Energy Analysis
√
√
√+
Integrated Heat Exchanger Sizing and Rating
√
√
√
√
√
Activated Heat Exchanger Sizing and Rating*
√
Intelligent Search
√
√
√
√
√
Online Training
√
√
√
√
√
Improved Solid Equipment Models and Characterization
√
√+
√++
View Plant Data and Model Results Together
√
√
√
Access to Models and Applications with aspenONE Exchange
√
√
Custom Tables
√
√
√+
*Activation simplifies analysis by displaying key cost, energy, and operability metrics on a dashboard.
Please find a .pdf version of the table as attached file.
Key Words
Aspen Plus, Operating Systems, Databank, Economic Analysis, Energy Analysis, Greenhouse Gas Emissions.
Keywords: None
References: None |
Problem Statement: Aspen plus로3개 이상 성분들의 공비점을 계산할 수 있는가? | Solution: 계산할 수 있다. Aspen plus는 Aspen Distillation Synthesis 라고 하는 기능으로 3개 이상의 성분들의 공비점을 계산할 수 있다. 조성성분들을 모두 입력한 후, 물성방법을 NRTL로 선정한다.
그리고, Tools | Conceptual Design | Azeotrope Search를 선택한다.
Azeptrope Analysis 입력창에서 원하는 성분들을 임의로 선택한 후, Report를 클릭하면 공비점 결과들을 볼 수 있다.
참고로, Aspen split이라고 하는 라이센스가 있어야 한다.
Please find theSolution 133389 for the original English version.
Keywords: Components, azeotropes
References: None |
Problem Statement: Where are the Run Settings in Aspen Plus V7.3.2? They used to be found on the Run menu. | Solution: To enter Run Settings, go to the small arrow at the lower right corner of the Run section of the Home ribbon.
They are also found from the Options button on the Developer ribbon.
Keywords: None
References: None |
Problem Statement: Why doesn't Aspen Plus predict the correct adiabatic flame temperature for methane or propane in pure oxygen? | Solution: An RGibbs block can be used to predict the adiabatic flame temperature; however, this value may not be correct if trace components are not specified on the Components | Specification form so that they are available as possible products. If the combustion products are restricted to complete combustion, the adiabatic flame temperature is much too high. If some of the other possible products are allowed, the flame temperature is much closer to that which is reported.
In Flame and Combustion by J.F. Griffiths and J.A. Barnard, pp.16-17, In an adiabatic methane flame, in addition to carbon dioxide and water as the final products of combustion, there may be traces of residual reactants (CH4 and O2), other molecular products (e.g. CO and H2) and free radical intermediates (e.g. H, O, OH and CH3). In general, when any reaction has reached equilibrium there will be varying amounts of chemical species other than the expected final products. This is relatively unimportant in most combustion processes at low final temperatures, but the presence of the temperature multiplier in the TdS term means that the trace materials become more important at elevated temperatures. The effect is fairly small up to about 2000 K but is very marked at 3000 K.
In the attached example file, there are RGIBBS blocks to combust either a stoichiometric mix of methane and oxygen or propane and oxygen adiabatically with ether the components restricted to the feed plus CO2 and H2O or with a wider list of possible products. The resulting flame temperatures are in the following table:
Combustion with Oxygen
Fuel Gas
literature*
Aspen Plus restricted components
Aspen Plus additional components
(oC)
(oC)
(oC)
Methane
2,810
4921
2783
Propane
2,820
5187
2824
* http://www.engineeringtoolbox.com/flame-temperatures-gases-d_422.html
Keywords: None
References: None |
Problem Statement: What are the differences between HappLS, IHapp, HappAprop, HappIP, HappAPropIP types? | Solution: HappLS represents the COM class component (coclass name), or in other words, it contains the executable implementation of a COM object (dll or exe) and its instantiation constitutes the server. HappLS implements IHapp along with some other interfaces. HappAprop is the coclass name for Aspen Properties standalone application. HappIP and HappAPropIP are the legacy in-process server implementation and are no longer supported.For those the client program runs in the same process space as the server (dll implementation).
Keywords: COM Server, types, interfaces.
References: None |
Problem Statement: After opening the Aspen Plus Simulation Engine Window there is a message, The system cannot find the path specified. None of the Aspen Plus commands such as aspen, aspcomp, makeins, or strlib work.
The Simulation Engine Window is shown below:
Cause
The paths are not set properly most likely due to installing without full administrator privileges. | Solution: To correct this problem you need to go to C:\Program Files\AspenTech\Aspen Plus Vx.x\Engine\Xeq\ or C:\Program Files (x86)\AspenTech\Aspen Plus Vx.x\Engine\Xeq\ if it is a 64bit system, make a copy of the aspsetup.bat file and edit it, it will be like this where asptop, aprsys, and oomftop are blank:
You need to define3 paths:
set asptop=C:\Program Files\Aspentech\Aspen Plus Vx.x\Engine\
set aprsys=C:\Program Files\Aspentech\APrSystem Vx.x\Engine\
set oomftop=C:\Program Files\Aspentech\OOMF Vx.x\
The file will look like this:
Save this file to your Desktop and then replace the one on C:\Program Files\AspenTech\Aspen Plus Vx.x\Engine\Xeq\ , you will need Admin privileges to replace it.
Re-open the Aspen Plus Simulation Engine window, and it will be without errors.
Keywords: Insert Library, simulation engine error, simulation engine
References: None |
Problem Statement: How do you turn off the automatic block or stream naming so that you do not start with default names for blocks and streams? | Solution: In Aspen Plus, when a new block/stream is inserted, it is automatically assigned a prefix B/S. If however, it is intended to provide a logical name to the block/stream without having it initially named with BXX/SXX, the user can uncheck the naming option as shown in the screenshot. The flowsheet Display Options can be accessed by going to File --> Options --> Flowsheet
Keywords: Block, stream, display name, prefix
References: None |
Problem Statement: FAQs for Issues and scope of modeling Inverse emulsion Polymerization in Aspen Polymer | Solution: 1) Is there an appropriate way to model inverse emulsion polymerizations, where a water-soluble monomer is emulsified in an oil phase? Or does model only work when continuous phase is water and monomer is immiscible with water?
The system allows you to specify a dispersant component. Usually this is water. In this case I tried modeling reverse emulsion using heptane as the dispersant phase. I specified partition coefficients to make the initiator and monomer soluble in the water phase. It appears to work.
2) What area exactly is being asked for when describing micellar nucleation?
Emulsion polymerization is sensitive to the critical micelle concentration (CMC) and the surfactant coverage (area). These parameters are widely available from many sources including the surfactant manufacturer and common handbooks. NIST also publishes CMC data which you can find online (google ?surfactant CMC?).
3) How does the redox couple specification work with emulsion polymerization? Does the
reducing agent have to be a ferrous salt? Also, is there a place to specify redox kinetics?
You can specify any pair of components for the salt and reductant. You can add the reduction and oxidation reactions from the ?Reactions? tab. Click the ?New? button at the bottom of the form and then select reaction type as ?Reduction? or ?Oxidation? as shown below. After you do this the system will let you enter the rate constants as shown in the 2nd screen
4) For redox couple: Does emulsion polymerization model account for situation where one of the species is soluble in the droplet and the other species is soluble in the continuous phase? If so, how is that done?
Solubility of the species in each phase is determined by the partition coefficients you enter. There is always some solubility in both phases. As you can see above, you can enter rate constants for the redox reactions in both phases (or either phase) to cover any situation.
5) Radical exchange kinetics: is there a database to help find typical values, or are these values usually optimized to give a best fit to data? (Or should values be measured in fundamental studies?)
We don?t have a built-in database of radical exchange rates. You can find some information for well-known polymers in the open literature. Otherwise you need to fit some of these parameters against available data. For example, propagation rate drives the overall conversion of monomer to polymer. Chain transfer to monomer influences the average chain length.
6) When specifying cmc and area for particle data for emulsion polymerization, what is the best source of information ? literature, some default rule of thumb, data?
Surfactant vendor first, literature if the vendor does not provide the data.
Keywords:
References: None |
Problem Statement: Where is the blue Next button in Aspen Plus V7.3.2? Did AspenTech get rid of this very useful feature? | Solution: The Next button functionality is still available, however, the button looks a bit different. The Next button is now green . It is located in the Run section of the Home ribbon plus it is on the Quick Access tool bar at the very top of the Aspen Plus User Interface window.
Keywords: navigation, user interface, buttons, menus
References: None |
Problem Statement: In RadFrac, a user can specify distillate flowrate or bottom flowrate. When there is a need to access the specification in a Calculator block or sensitivity analysis, what is the internal variable to select? | Solution: A user opens the Variable Definition dialog, or the Vary datasheet (in sensitivity analysis).
The Type field should be Block-Var. The Variable field should be MOLE-D for distillate mole flowrate, MASS-D for distillate mass flowrate, STDVOL-D for distillate standard liquid volume flowrate, and MOLE-B for bottom mole flowrate, MASS-B for bottom mass flowrate, STDVOL-B for bottom standard liquid volume flowrate.
The Sentence field should show COL-SPECS.
Keywords: operating specification, column spec, spec, sensitivity analysis, calculator.
References: None |
Problem Statement: 여러 버전의 Aspen Hysys가 설치되어 있을 경우, default버전을 어떻게 설정하는가? | Solution: Aspen Hysys는 Excel automation work을 연동하여 모사할 수 있다. 만약 한 컴퓨터에 여러버전의 Aspen Hysys가 설치되어 있을 경우엔 default Aspen Hysys버전설정이 필요하다. Aspen Hysys는 별첨한 스크립트파일을 이용하여 간단하게 원하는 버전을 등록 혹은 해제할 수 있다.
1. RegHYSYS72.txt파일을 다운로드한다.
2. RegHYSYS72.txt확장자명을 RegHYSYS72.bat로 바꾼다.
3. 더블클릭하면 모든 Aspen Hysys버전들이 해제됨과 동시에 v7.2로 재등록된다.
이 스크립트파일은 오른쪽 마우스 클릭으로 편집이 가능하다. 만약 v7.1버전이 필요하면 스크립트에서 ?gREM?h 해당 명령어를 V7.1로만 편집하면 된다.
Excel VBA에 관련된 Aspen Hysys type library는Solution ID 129694를 참조하기 바란다.
Please find theSolution 131162 for the original English version.
Keywords: Automation, Excel, Register, KR-
References: None |
Problem Statement: Scrubbers cannot be selected in batch operations, such as Utilize and Custom. They do not appear in the dropdown list. | Solution: Scrubber is a continuous equipment type, so it cannot be selected for batch operations. In fact, any equipment of a continuous type cannot be selected for batch operations; it can be selected for continuous operations only.
Keywords:
References: None |
Problem Statement: What is the syntax if I need to split a format string (or any string) in a OOMF (equation oriented) script?
I've tried this:
SET FMT = %-15s \
%-15.3f \n
PRINT FORMATTED &FMT, hello, 123
but it does not work. | Solution: The correct syntax is as follows:
SET FMT = %-15s \
. %-15.3f \n
PRINT FORMATTED &FMT, hello, 123
The reason is that when you don't close a string, the syntax is ambiguous and Aspen Plus does not use the backslash (continuation character) as such, it just sees it as part of the string, which causes a syntax error. So the trick is to close the string (hence the double quote just before the backslash on the first line), then concatenate the rest of the string on the next line with the dot operator (string concatenation operator).
Do not enter more than 64 characters per line, and do not begin lines with more than 3 spaces within the Aspen Plus user interface. See the OOMF Script Language documentation page 180 for the syntax in input language. Scripts in EBS files or the command line may start in any column and go to column 256.
The example attached illustrates the method for Aspen Plus v7.1. To run the example:
1. Open the simulation file
2. Run the simulation (SM then EO)
3. At the command prompt in the control panel, type INVOKEGLOBAL DEMO
Keywords: None
References: None |
Problem Statement: Simulation with RadFrac column (Scrubber) diverges when using true component electrolyte approach with the following error message:
*** SEVERE ERRORCMBAL CALCULATIONS FAILURE: RERUN WITH CHANGES SUGGESTED IF THERE ARE ANY.
The above error is produced for different reasons, however in this case it is because the user is using a true component electrolyte approach which generates an imbalance in terms of the electrolytes involved. This is an electrolytes component mass balance error flag. | Solution: ThisSolution provides a recommended workaround by changing the electrolyte simulation approach to apparent component under the Electrolyte Wizard (Properties Environment):
Having set this modification, go to the Simulation environment and restart/re-run the simulation. The error message will be gone and the simulation converges without issues.
Keywords: Error message: CMBAL CALCULATIONS FAILURE, Component Electrolyte Approach, Convergence.
References: None |
Problem Statement: A user will often need to create Ternary diagrams using the distillation synthesis button in the Simulation Environment in Aspen Plus and they would like to know how Aspen Plus calculates distillation boundaries that are drawn within this diagram. | Solution: In order to have a background about ternary map and distillation boundaries, the user can find this under the Aspen Plus Online Help in the chapter: Locating Azeotropes and Distillation Region Boundaries. In this description the user can find general information about residue curves, azeotropes and how distillation boundaries can be defined.
Aspen Plus uses following steps to calculate distillation boundaries:
1. Search for all the azeotropes formed by the three key components
2. Determine the type of each azeotrope (stable, saddle or unstable)
3. Calculate the path from one azeotrope to the adjacent azeotrope, which defines one distillation boundary.
4. Calculate the path from one azeotrope to the adjacent key component, which defines one distillation boundary.
Using the example file ICPEbegin.bkp (which can be obtained from the following directory: C:\Program Files (x86)\AspenTech\Aspen Plus V8.0\GUI\Examples\Distillation Synthesis), the user can create a following Ternary diagram, if the key components are Methanol, Acetone and Chloroform (CHFL):
There are 4 azeotropes found for this system, marked as A1, A2, A3 and A4. The distillation boundaries are the arrowed lines. The arrow always goes from the lower boiling point to the higher boiling point.
The distillation boundary is calculated by integrating the differential equations that describe the residual curves. The distillation boundary starts from ternary saddle azeotropes if any exist in the mixture. For each azeotrope, the eigenvalues and eigenvectors are calculated. A small step is taken in the direction of each eigenvector. The residual curves are calculated by integrating the differential equations until a singular point is reached. The boundary points of the residual curves are used to create the distillation boundary.
Keywords: Distillation boundaries, Distillation Synthesis, Ternary Plot
References: None |
Problem Statement: How can the Fill Volume reported in Emission Details be different from the volume reported in Equipment Contents? | Solution: Fill Volume reported in Emission Details is the total volume of liquids and solids that enter an equipment unit in an operation. This will be equal to the total volume of all the streams going to this vessel for the operation. Emission calculations use the total amount of material that enters an equipment unit in each operation.
The volumes reported in the Equipment Contents are the initial and final contents of an equipment unit at the beginning and end of each operation. These will be equal to the difference between the inlet stream and the outlet stream volumes. The Equipment Contents reports the accumulation within the unit. For example, if 150 liters of materials are charged into a previously empty vessel V-1 and 90 liters are transferred out, the Fill Volume in Emission Details will be 150 liters. In Equipment Contents, the initial volume will be 0 liters and the final volume will be 60 liters.
Keywords:
References: None |
Problem Statement: 用Aspen plus可以计算三个以上混合物的共沸点吗？ | Solution: 可以的。Aspen plus里有个功能叫做Aspen Distillation Synthesis.用它来可以轻松地计算三个以上混合物的共沸点。首先，输入混合物组分。
接着选NRTL为物性方法和激活 Tools | Conceptual Design | Azeotrope Search.
然后，在Azeotrope Analysis 输入栏里指定要测试的组分。点Report 会看见被Aspen Plus计算出来的共沸点结果值。
要是运行此功能必须有Aspen Split license.
Please find theSolution 133389 for the original English version.
Keywords: Components, azeotropes
References: None |
Problem Statement: Why can't I see the predefined cells from the cell pulldown in an operation? In the CELL-DISRUPT/Optional/Cell Disruption form, the newly predefined cells do not show up. | Solution: The reason is that the defined cells are not selected for the step yet. The cells will appear in the dropdown list after they are selected for the step in the Step/(Information/) Optional/Cells form. Batch Plus allows up to 2 kinds of cells in each step.
Keywords: cell-disrupt
predefined cells
step
batch plus
pulldown
protein
References: None |
Problem Statement: Is it possible to specify percentage of the equilibrium conversion at a given temperature do this kind of specification for a reactor? | Solution: There is not a direct way to specify a percentage of equilibrium conversion in any type of reactor. The issue is that the conversion at equilibrium for a given temperature is unknown.
With the help of a REquil block it is possible to obtain the conversion at equilibrium and a Calculator block it is used to set the percentage of the equilibrium conversion in an RStoic block.
The attached example (Percentage of the equilibrium conversion.pdf) explains how to obtain the equilibrium conversion using a REquil block and how to set the operation conditions of a second RStoic reactor using percentage of the equilibrium conversion with the support of a Calculator block.
Keywords: Conversion
Equilibrium
Percentage of Equilibrium
References: None |
Problem Statement: Is it possible to specify that a certain percentage of QC Tests fail and that the recipe takes a different course with the product from failed QC tests? | Solution: To specify that a certain percentage of Quality Control (QC) tests fail and that recipes with failures take a different course, one could use the Start Or/End Or structure in a Batch Plus recipe. The Start Or function is used as a step within a plan to specify parallel operations or unit procedures that happen out of phase. Each time this batch is run within the plan or campaign, Batch Plus executes a single branch of operations or unit procedures within the Start Or/End Or structure.
Groups of operations or unit procedures that happen in series within the Start Or structure are preceded by a Series keyword. Between a Start Or/End Or structure, there must be at least two Series structures. Each batch simulation of the Recipe may potentially have a different cycle-time since the sequence of Operations depends on the batch number. For instance, the second batch will run the second Series listed in the Start Or structure.
To specify that 33% of QC tests fail and that when they fail, the product must be dumped and remade through a reaction operation, one would use a Start Or structure with three Series keywords. One out of the three QC tests will fail (33%) and the recipe will take a different path when that happens. This step must be simulated at least 3 times in a production plan. Every third time, the QC test will fail.
This is illustrated in the following example:
Reaction 1.1. Charge V201 with 120 kg of Int-I. 1.2. Charge V201 with 140 lb of DCM-Liquid. 1.3. React in unit V201 via Reaction-R1-R2. The final temperature of the batch is 30 C. Start Or
Series
1.4.
QC-Test the material in unit V201.
Series
1.5.
QC-Test the material in unit V201.
Series
1.6.
QC-Test the material in unit V201. If
the specification is not met, then: QC-Test failed!
1.7.
Transfer contents of unit V201 to Waste Treatment.
1.8.
Charge V201 with 120 kg of Int-I.
1.9.
Charge V201 with 140 lb of DCM-Liquid.
1.10.
React in unit V201 via Reaction-R1-R2. The final temperature
of the batch is 30 C.
1.11.
End Or
QC-Test the material in unit V201.
After the End-Or statement, any remaining operations in the recipe will function normally.
Keywords: QC-Test, Start-Or, End-Or, Or, Series
Quality Control
References: None |
Problem Statement: What does it mean when I uncheck Components with zero flow or fraction on the Setup | Report Options | Stream sheet? I do not see a difference in the graphical user interface. | Solution: If you uncheck Components with zero flow or fraction, when you export or view the text stream report, it will be generated with no streams with zero flow or fraction.This only applies to the .REP report file and not to the stream report in the graphical user interface.
If you want to exclude components in the report in the graphical user interface, you can use the Custom Stream Summary or a TFF file; however, you will need to explicitly exclude specific components. Currently, there is no way to do it automatically for all components with zero flow.
Keywords: Component with zero flow, report file
References: None |
Problem Statement: On Windows 7 and Windows Server 2008, you may encounter difficulties and failures with aspenONE deployment:
1. When installing/uninstalling aspenONE engineering products.
2. When using certain features. | Solution: The problem in most cases has something to do with the fact that you did not run your task as ?administrator?. Windows 7 and Windows Server 2008 enforce a stricter policy regarding user privileges than we were used to under XP. In Win 7, only tasks running with Administrative privileges are permitted to change Registry, modify or create files, among other restrictions. This means being an administrator or with administrative privilege is not enough, you must run the task as administrator. As a rule of thumb, if you think your task is going to affect the registry (particularly under HKEY_LOCAL_MACHINE) or will change or create a file on your PC, you should run your task as administrator.
To run as administrator, use the right-mouse option menu on the program or short-cut and select Run as administrator. An example for the Command Prompt Window is shown below:
You must run these tasks as administrator:
1. Install Microsoft SQL Server Express 2005 SP3 or later as a pre-requisite.
2. Install aspenOne. Installation always requires administrator privileges. You need to execute aspenONE installation using a user account with administrator privileges AND run it as administrator.
3. Uninstall aspenONE.
4. Setup or a license though the SLM Configuration Wizard.
5. Change SQL authentication mode through ?Aspen Properties Database Configuration Tester?.
6. Restore Aspen Properties databases with through ?Aspen Properties Database Configuration Tester? and LocalDB.
7. Manually restore Aspen Properties databases under a Command Prompt Window.
8. Manually delete LocalDB instance under a Command Prompt Window.
You don?t need to run these tasks as administrator:
1. Launch an Aspen product user interface, Aspen Plus, Aspen Properties, Aspen HYSYS, EDR, Aspen Custom Modeler, Aspen Batch Process Development, etc.
2. Launch an Aspen product simulation engine window for Aspen Plus and Aspen Properties.
Keywords: APED
References: None |
Problem Statement: In RPlug model I see that 'Heat duty' reported in the Results | Summary is different from the summation of duties reported in Profiles | Summary | Duty. Why is there a difference in the duties obtained? | Solution: The difference in heat duty values in the RPlug Profiles page and in the RPlug Results page can be explained based on the stream conditions and the reactor operating conditions. Thus, if the feed stream temperature and the Rplug temperature is same, then the last value of the 'Duty' in the Profiles | Summary page will match with the 'Heat duty' in Results page. If it is not, then the difference in duties occur because, the Profile reports only the heat generated or absorbed in the RPlug block whereas the Results sheet reports heat duty based on heat generated/absorbed plus the heat duty arising out of the temperature difference between the feed stream and reactor temperature.
In the attached example file (rplug-dutyv73.bkp), both the scenarios are simulated. Both RPlugs (RPLUG200 and RPLUGI) are operating at 200 C. However, RPLUG200 has the feed at lower temperature (150 C) while RPLUGI has feed at 200 C (same temperature as the reactor). It can be seen that both the reactors has the same profile duty. However, the duty reported in Results | Summary is different in both the reactors because the feeds need to be brought to the reactor temperature (for RPLUG200) and that amount is added to the net duty for the block.
Keywords: None
References: None |
Problem Statement: When you save a compound file (.bpz) in Aspen Batch Process Developer, files with extension .prj (project), .eqm (equipment), .mtl (material), .stp (step) are also saved in the project working directory. How can I save the file such that ONLY a compound file (.bpz) is saved? | Solution: By modifying the Aspen Batch Process Developer registry settings one can save file only as compound file (.bpz).
Navigate to the registry location: HKEY_CURRENT_USER\Software\AspenTech\Batch Plus\version number\Batch Plus\Options. Create a new DWORD type registry entry called SaveOnlyAsCompoundFile and set this value to 1.
Once this registry entry is set then when you select File/Save as Compound File, Aspen Batch Process Developer will selectively delete the .prj, .mtl, .eqm and .stp files from the project working directory. All other files will remain intact, e.g. Excel reports, Notepad results, Aspen Properties files etc, and not be deleted.
Keywords: compound files, compound, save as compound file
References: None |
Problem Statement: In reactions such as Step-Growth, it is necessary to add end elements with one active group and nonactive group, to stop chain from growing. How is it possible to specify this element? | Solution: The steps are as follows:
Categorize the chain stopper as Segment in Components/Specifications form.
Define the chain stopper segment as END type on the Components/Polymers/Characterization form.
If the chain stopper segment is not a databank component, define the van Krevelen functional group on the Properties/Estimation/Molecular Structure/Functional Group, choose VANKREV. Refer to the User Guide Volume 2, Appendix B for the van Krevelen functional group definitions. Other functional group methods or the general structure form cannot be used for segment property estimation.
Keywords: end element
chain stopper
polymer
step growth
step-growth
References: None |
Problem Statement: Can a user add new equipment to the Equipment Catalog? | Solution: No. Users can't add equipment to the Equipment Catalog.
KeyWaords:
Keywords: None
References: None |
Problem Statement: Often liquid mixture and pure component densities may be different, even though the mixture is 100% pure. This occurs when a different equation is used to calculate pure component and mixture liquid molar volume. Refer to | Solution: 3261 Why are the Mixture and Pure Property liquid densities different?
The workaround provided inSolution 3261 is to change the model for property VLMX from VLMX01 or VLMX20 to VLMX26, so that the mixture molar volume is calculated from a mole-fraction average of the pure component molar volume.
However, if you are using a Polymer Plus property method, such as POLYNRTL, then this workaround is not valid. Polymers Plus does not have an available model combining the Van Krevelan model with mole-averaging mixing.Solution
For non-polymer components, typically the DIPPR equation is used for pure component liquid molar volume if the parameters are available and thermal switch THRSWT/2 is not specified. However, the Rackett model is used for the mixture molar volume. You can use the following method to make the mixture molar volume model (Rackett) consistent with the pure component model (DIPPR).
Use Aspen Property Analysis to make a table of PURE liquid density over a wide range of temperatures (freeze point to boil point)
use the generic type and include property sets for RHO and RHOMX so you can compare.
Take the data into a spreadsheet for safe keeping - optional.
Change run type to Property Regression.
Create a Data Set for mixture density (VLMX)
use two-component system where one component is just a dummy.
specify composition as 0.9999999 of the component of interest (don't use 1 - it will cause divide by zero errors).
Regress the data using RKTZRA and RACKET(3) as regression parameters.
Copy RKTZRA and RACKET(3) parameters back to your other models.
If the regression fit is good, the Property Anayalis table should show very close results for mixture and pure component molar volume. In essence, you have used DIPPR model to re-fit the RACKETT model to make the two consistent.
The attached example uses ethylene glycol with the property method POLYNRTL. The Property Analysis before the regression, clearly shows the difference in density for the pure component and mixture. The regression runs well and as a result, the mixture and pure density are nearly equal. This procedure should work equally well for polymer and non-polymer applications.
Keywords: POLYNRTL
liquid density
Van Krevelen
References: None |
Problem Statement: How do I simulate polyurethane processes using Aspen Polymers? | Solution: Polyurethanes are a family of polymers produced by pseudocondensation reactions involving diisocyanates. They are characterized by the presence of urethane (~NHCOO~) groups in the polymer backbone. These materials are used to produce adhesives, engineering plastics, and foam sheets.
Segmentation
Aspen PolymersTM represents polymeric components using a patented segment-based approach. Each polymer component is composed of one or more ?segments? which represent characteristic repeat units, end groups, and branch points in the polymer chain. The physical property and reaction kinetics models track the flow rates of segments and the moments of the polymer molecular weight distribution. Using this technique, it is possible to characterize the average size and composition of the polymer molecules in the distribution.
Polymer molecules can be segmented (divided into segments) in several different ways. The manner in which the polymers are segmented can have a major influence on model development, including:
The number of physical property parameters required to predict final product properties and phase equilibrium;
The accuracy of physical property estimations;
The number of reactions which must be defined to fully represent the polymerization kinetics, especially for copolymers; and,
The level of detail of the model (for example, the ability to distinguish different types of similar reactions).
In general, the polymer should be segmented in a way that minimizes the total number of segments required to thoroughly define the reaction kinetics. This task is especially difficult for polyurethanes because these processes can involve a number of side reactions that lead to the formation of additional functional groups including amine groups and several types of branch points including biuret groups, allophanate groups, and acylurea groups (see figures below).
Linear Polyurethanes with Simultaneous Formation of Urea Links
Consider the reaction of diethylene glycol (DEG) with diphenyl methane diisocyanate (MDI):
The resulting polymer molecule can be defined as a repeat unit with two end groups:
As two repeat units with two end groups:
As two end groups:
And so on. If we consider only the main pseudocondensation reaction between DEG and MDI, the latter approach would result in the smallest number of segments (note that the location where the two groups are divided is somewhat arbitrary).
However, small amounts of water are present in the raw materials used in this process. The isocyanate groups can react with this water to produce an amine end group and carbon dioxide:
The resulting amine groups react with isocyanate groups to produce urea bonds:
The resulting polymer contains a mixture of urethane and urea bonds. This could make the segmentation very complicated. For example, using the later approach above, you would need to define four types of MDI end group:
MDI ends with an isocyanate end and a urethane bond;
MDI ends with an amine end and a urethane bond;
MDI ends with an isocyanate end and a urea bond; and
MDI ends with an amine end and a urethane bond.
The situation becomes even more complicated when branching reactions are included; resulting in even more combinations of functional groups and thus more segments.
Based on these observations, we suggest treating urea and urethane bonds as segments. For example, we can write the first addition reaction as:
This methodology can be extended to the urea group and to the various types of branching points that are formed by secondary reactions. Further, this methodology makes it very easy to represent polymerization products involving several different comonomers.
The group of components and segments shown below are sufficient to completely characterize the reaction network between DEG and DMI, including aminization reactions and the formation of urea bonds. Further, this methodology is easy to extend to branching reactions and other side reactions. For example, consider the formation of an allophanate links by the following reaction:
This reaction can be represented in terms of segments as shown below:
Similarly, we can characterize biuret formation by defining an additional biuret segment:
This approach can be easily extended to cover side reactions involving other side reactions that occur when polyurethanes are reacted with polyamides, polyols, cyclic ethers, and other materials.
Components and Segments to Represent Polymerization of MDI and DEG
Model ID
Common Name
Database ID
Component Structure
DEG
Diethylene Glycol
C4H10O3
HO(CH2)2O(CH2)2OH
MDI
Diphenyl Methyl Diisocyanate
not in DB
H2O
Water
H2O
H2O
CO2
Carbon dioxide
CO2
CO2
PU
Polyurethane
PU
variable
DEG-E
DEG end segment
not in DB
~(CH2)2O(CH2)2OH
DEG-R
DEG repeat segment
not in DB
~(CH2)2O(CH2)2~
MDI-E
MDI end segment
not in DB
MDI-R
MDI repeat segment
not in DB
URETHANE
Urethane linkage (repeat)
not in DB
MDA-E
Diphenyl Methyl Diamine end segment
not in DB
UREA
Urea segment (repeat)
not in DB
ALLOPHAN
Allophane segment (branch3)
not in DB
BIURET
Biuret segment (branch3)
not in DB
Reaction Network
The reaction network involves the following types of reactions:
1. Urethane formation (urethane link formed by addition of isocyanate and alcohol)
2. Amine formation (water and isocyanate react to form an amine group and CO2)
3. Urea formation (formation of urea link by addition of isocyanate and amine)
4. Allophane formation (isocyanate groups react with urethane groups, creating a branch point).
5. Biuret formation (isocyanate groups react with urea groups, creating a branch point)
Each reaction can involve various species (monomers or segments) that contain the reacting functional groups. For simplicity in this example, we have dropped some of the side reactions (for example, reactions between water and MDI monomer to generate a monomer with one isocyanate end and one amine end).
The resulting reaction network is shown in the figure below.
Reaction Network for the MDI reacting with DEG and Water
As a first approximation, we have assumed that the reaction rate is independent of the chain length, e.g., the reactivities of the functional groups are the same in the monomers and the corresponding polymer end groups. Further, we have assumed that the reactions are first order with respect to each reactant. The resulting rate expressions can be written as shown below.
Rate Expressions
Reaction
Type
Rate Expression
1
Urethane formation
group/group rate constant = k1
4 [ DEG ][ MDI ] k1
2
2 [ DEG ][ MDI-E ] k1
3
2 [ DEG-E ][ MDI ] k1
4
[ DEG-E ][ MDI-E ] k1
5
Amine formation, k2
[ MDI-E ][ H2O ] k2
6
Urea formation, k3
2[ MDA-E ][ MDI ] k3
7
[ MDA-E ][ MDI-E ] k3
8
Allophanate formation, k4
2 [ MDI ][ URETHANE ] k4
9
[ MDI-E ][ URETHANE ] k4
10
Biuret formation, k5
2 [ MDI ][ UREA ] k5
11
[ MDI-E ][ UREA ] k5
Note 1: the pre-factor 4 in reaction (1) and the factor of 2 in reactions (2), (3), (6), (8), and (10) account for the number of like functional groups in the reactants
The rate constants used in this example are for illustrative purposes only - they have not been tuned against process data.
Keywords: None
References: None |
Problem Statement: It is sometimes required to carry out a detailed design of the re-boiler or the condenser of the Radfrac distillation column.
Based on KB #130085, it is possible to create a pseudo stream in the Radfrac block to represent the mixture properties present in the re-boiler or the condenser. This pseudo stream can now be connected to a HX block for the detailed design of the re-boiler /condenser.
The input specification required for the HX block thus created, could be selected from the variety of options available for the HX block. One such option is the duty for the HX block.
The following query has been raised by a user:
I've applied KB #130085, but, in addition, I need to connect the re-boiler duty to the external heat exchanger. My intention is to update the duty of the external re-boiler as soon as the internal duty of the Radfrac changes.
Could you explain how I can transfer calculated duty values from Radfrac into the HX block? | Solution: The calculated duty values from the Radfrac block re-boiler can be transferred to the input of the HX block by using a transfer block.
The transfer blocks can be found in the flowsheet option folder. In the attached example file, in the “From� tab the Block-Var variable REB-Duty has been selected (see the screen shot).
In the “To� tab of the transfer block the HX block variables duty has been selected (see the screen shot).
Keywords: Transfer block, Radfrac, HX block
References: None |
Problem Statement: What is the meaning of color code status in the fields in Aspen Plus V7.3.2? | Solution:
Keywords: color code, color status
References: None |
Problem Statement: When copying to Excel, how do you get everything expanded in the Stream Summary? | Solution: If you click the upper left cell in the table, you will copy what is shown. If the flows are not expanded, they will not be copied. If you click Export to Excel in the Report section of the stream summary ribbon, you will export a table with everything expanded.
Keywords: V9 new stream summary
References: : CQ00703614 |
Problem Statement: What is the difference between expansion through a VALVE and expansion through a COMPR? | Solution: In summary, a VALVE performs an isenthalpic expansion whereas a COMPR performs an isentropic expansion. Both processes are assumed to be adiabatic. By definition, an isenthalpic process is a special case of an adiabatic process that does no work and is irreversible, and an isentropic process is a special case of an adiabatic process that is reversible.
VALVE
The change in internal energy (or enthalpy) of a gas can be expressed in terms of heat duty and work done by the gas during the expansion:
Eqn. 1
The sign convention used in Aspen Plus implies that positive duty is equivalent to heat being added to the gas. Thus, if Q > 0, the enthalpy of the gas increases. Also, work done by the gas on the surroundings is considered negative work. Thus, if W < 0, the gas is doing work on the surroundings, and the enthalpy of the gas decreases.
The VALVE and all blocks except COMPR and MCOMPR assume that the gas does no work on the surroundings during an expansion, so W = 0. The valve is also adiabatic since no external heating or cooling is supplied, so Q = 0. Thus, according to Eqn. 1, the enthalpy of the inlet and outlet streams are equal, and the valve performs an isenthalpic flash to determine the outlet conditions.
COMPR
When a gas expands through a COMPR block, it performs work on its surroundings in the form of shaft work. so W < 0. COMPR is also adiabatic since there is no external heating or cooling. Thus, according to Eqn. 1, the enthalpy of a gas decreases when it expands through a COMPR. The process is assumed to be reversible, and a reversible adiabatic process is also isentropic.
When selecting an isentropic turbine, the user has an option to input the isentropic efficiency. By default, it is at 1. The isentropic efficiency is defined as the ratio of actual work to isentropic work:
Eqn. 2
Since Q = 0, work is the only term that changes the enthalpy of the gas according to Eqn. 1. Thus, Eqn. 2 reduces to:
Eqn. 3
Eqn. 4
The isentropic efficiency is loosely related to the reversibility of the process. When the isentropic efficiency is 1, the process is reversible, and the actual work is equal to the isentropic work. When the isentropic efficiency is 0, no work is done by the gas (actual work = 0), the process is irreversible, and the expansion reduces to an isenthalpic process.
Keywords: VALVE COMPR expansion efficiency isenthalpic isentropic adiabatic
References: None |
Problem Statement: In V8.0, there is no longer a Block Options form for RadFrac in order to change the property method or to select if results from the previous pass are used. | Solution: The Block Options form exists for all blocks. For RadFrac, the form still exists only it has been moved into the RadFrac | Specifications folder. The forms for RadFrac were re-organized into folders since there were so many of them it was getting unwieldy. Only the results forms are now at the top level.
Keywords: None
References: None |
Problem Statement: In the Aspen Plus built-in example (Biodiesel Production from Vegetable Oil), why do I see NaOH, H3PO4 and Na3PO4 are all defined as H2O in the component list? | Solution: In this special example, Sodium hydroxide is used as the catalyst, and is removed by adding H3PO4 to precipitate Na3PO4. Because electrolyte chemistry is not modeled in detail, these electrolytes are modeled using physical property data for water, but with their correct molecular weights.
User can find the correct molecular weights from Parameters | Pure.
Due to this modification, the user should take extra care when exporting and applying this component list to other simulation cases.
Keywords: Biodiesel Production from Vegetable Oil, Components.
References: None |
Problem Statement: The parameter KLL2 is listed as one of the thermodynamic properties available in Aspen Plus for components in mixtures. It is described as the Liquid-liquid K-value for a component in a mixture. While it gives the user information concerning the equilibrium between two liquid phases, it should not be confused with the commonly reported ‘partition coefficient’ (check | Solution: 142955 for information on the latter).Solution
Parameter definition
The KLL2 parameter corresponds to the distribution coefficient and is available directly from Aspen Plus for components in a given system under certain conditions. For an activity coefficient-based model, it is defined as:
where and are the activity coefficients (on a molar basis) of component in liquid phase (1) and (2), respectively. Liquid 2 is defined by default as the phase with higher density.
Accessing parameters in Streams
The parameters mentioned above can be accessed in streams in Aspen Plus Simulation environment in the following manner:
1) Create a property set (e.g. PS-1), Property Sets folder in the navigation pane.
2) Include the parameter KLL2 in the Properties menu.
3) Go to Setup in the navigation pane. Choose Report Options. In the Stream tab, click in Property Sets, and move the desired set PS-1, from ‘Available Property Sets’ to ‘Selected Property Sets’.
4) Create desired stream(s), define conditions and composition in the Mixed tab. In the Flash Options tab, choose ‘Vapor-Liquid-Liquid’ as ‘Valid Phases’.
5) Run the simulation, and access the Results or Stream Results (Custom) menu for the desired stream (this can be found in the left hand-side menu). Scroll down the table to find the above-mentioned properties.
The calculation is performed at streams conditions and composition, using the thermodynamic method selected for the simulation. More importantly, the default setting for Valid phases in the flash calculation needs to be changed to account for liquid-liquid equilibrium.
Keywords: KLL2, Partition Coefficient, Liquid-Liquid equilibrium, Properties, Thermodynamics, Solubility
References: None |
Problem Statement: In Aspen Plus when one is creating a default utility from the ‘Utilities’ folder in the Simulation Environment, there is not enough information about the different utilities available and their specifications to be used in the simulation’s models. Hence, one wonders what are the physical properties, default values used and cost index (Cost/kcal) of using a specific utility in the model? | Solution: In order to illustrate comprehensively these characteristics of the different utilities available in Aspen Plus, the table below provides comprehensive and useful information about the specifications and conditions of these utilities:
Table No. 1: Utilities specifications and conditions templates used by Aspen Plus and Aspen HYSYS
The above table also contains the different values of inlet and outlet temperature, heat transfer coefficient, minimum delta of temperature, viscosity, conductivity; among others physical properties used by Aspen Plus as default inlet and outlet values.
NOTE: The table No. 1 shown above is available in Aspen HYSYS and has been used for reference purposes, since these are the same values available utilities in Aspen Plus.
Keywords: Utilities, Cost Index.
References: None |
Problem Statement: When retrieving data from Aspen Plus using Excel VBA to following error might be displayed.
Microsoft Office Excel is waiting for another application to complete and OLE action. | Solution: This problem could happen when a simulation takes a long time to converge. Excel may think that Aspen Plus is not responding and hence issue the message.
Please add the following code to avoid Excel doing this:
Application.DisplayAlerts = False
Keywords: VBA
Excel
Visula Basic
OLE action
References: None |
Problem Statement: What method is being used in the Flash2 block? The help mentions the Inside-Out algorithm.
Do you have the literature reference? | Solution: Flash2 uses the flash convergence algorithm specified on the Setup | Calculation Options | Flash Convergence sheet, or on the the block's Block Options | Simulation Options sheet.
Setup | Calculation Options | Flash Convergence sheet:
Block options | Simulation Options:
The available methods are Inside-Out and Gibbs. These methods are used for all flash calculations, not just Flash2.
The Inside-out method is the method of Boston and Britt. Inside-out is the traditional flash algorithm used in Aspen Plus. This algorithm calculates K-values and other such properties in the outer loop, true-species chemistry (if applicable) in the middle loop, and mass and energy balances in the inner loop. This algorithm is used by default for all flash calculations except three-phase true-species electrolyte calculations.
Boston, J. F. and H. I. Britt, A radically different formulation for solving phase equilibrium problems, Comp. and Chem. Engr., 2, p. 109 (1978) Gautam, R. and Seider, W.D., Computation of Phase and Chemical Equilibrium, Parts I, II, and III, AIChE J. 25, 6, November, 1979, pp. 991-1015.
The Gibbs method is the method of Gautam, Seider, and White. The Gibbs algorithm is based on Gibbs energy minimization, as in the RGibbs unit operation model. It calculates mass and energy balances, true-species chemistry (if applicable), and properties simultaneously. Aspen Plus will use this algorithm automatically when solving for three-phase true-species chemistry calculations. Select this algorithm if the default inside-out algorithm exhibits convergence difficulties, especially when solving three-phase problems, and almost all vapor electrolyte chemistry with salts.
White, C.W. and Seider, W.D., Computation of Phase and Chemical Equilibrium: Approach to Chemical Equilibrium, AIChE J., 27, 3, May, 1981, pp.446-471.
Keywords: Flash2
Flash
Algorithm
Convergence
References: None |
Problem Statement: The following warning appears while using Aspen Rate-Based Distillation:
UNUSUAL (type) PROFILE FOR COMP (component id).
PLEASE DOUBLE CHECK THE | Solution: AND/OR ADJUST FLOW MODEL,
TRANSFER/REACTION CONDITION NUMBERS, PACKING HEIGHT/NSTAGE, ...
Type may be LIQUID MOLEFRAC, LIQUID INTERFACE MOLEFRAC, COMPONENT GENERATION, INTERFACE MASS TRANSFER, or INTERFACE HEAT TRANSFER, the last of these without a component ID.
Solution
This can be caused by poor choices for column specifications or configuration options.
Try changing the Flow model condition factor (top) or Flow model condition factor (bottom) closer to or equal to 1, depending on which part of the column the convergence difficulty occurs in. These parameters are entered on the Rate-based Setup | Specifications sheet. Setting the bottom factor to 1 is a good choice for absorber columns.
To adjust the flow model, change it on the Rate-based | Rate Based sheet of a Tray Rating or Packing Rating section. The Countercurrent model is reasonable for packed columns if the section height is not too large. If the Countercurrent model fails, try the Vplug model. For more information about flow models, see Flow Models.
The packed height per stage is closely related to the flow model. You can change this to model a packed section as more stages with less packing in each by changing the packed height per stage on the Packing Rating | Setup | Specifications sheet, the number of stages on the Setup | Configuration sheet, and stage numbers on other forms. The Stage wizard available on the Setup | Configuration sheet can help you adjust the other stage number specifications.
Transfer condition number and Reaction condition number can be specified on the Rate-based Setup | Specifications sheet. For fast kinetic reactions, change Transfer condition number and Reaction condition number from the default 0.5 toward 1.0. For very fast kinetic reactions, use 1.0.
Keywords: None
References: None |
Problem Statement: How do I select and specify the convergence method in Aspen Plus? | Solution: In Aspen Plus, we have the ability to use different convergence methods. The available methods are as follows:
Wegstein Method: Wegstein method is used for tear streams and it is the default method for Aspen Plus tear stream convergence.It has different, adjustable, parameters such as acceleration parameter ,maximum flow sheet evaluations etc. It does not count variable interaction thus this approach works well on flow sheet where the components do not interact strongly.
Direct substitution: This is simplest method. We are not using any parameter and thus it converge slowly . Direct substitution is equivalent to Wegstein when lower bound is equal to upper bound =0. It is used for tear stream convergence.
Scant Method: It is a polynomial fit for a function based on previous evaluation. In Aspen Plus it is used for convergence of single design specifications. Secant is default method for design specification convergence.
Newton Method: It is derivative based method and calculates the Jacobian matrix at each iteration .The beauty of Newton?s method is that it exhibits quadratic convergence which is characterized by doubling of the exponent of error. It's drawback is the computation of derivative as well as it is very sensitive to initial the guess. It is used for tear streams as well as design specs convergence. It is useful when you have recycle loops and/or design specifications that are highly interrelated.
Broyden Method: Broyden method also known as quasi-Newton method because it doesn't require the calculation of Jacobian (J(x) .In fact it constructs its own approximation (B) of the jacobian matrix and updates it in each iteration. Rank one Broyden method converges superlinearly. It is used for tear streams ,two or more design specifications ,or tear streams and design specs convergence simultaneously ,
We can specify the convergence method as follows.
Go to the Convergence folder .Click on Conv Options and select default method tab. Here you can get list of default convergence method used. You can change and select a different method as per the requirement.
We can click on Methods in the Conv Options and here we have parameters associated with each method. Thus we can change the parameters associated with convergence method for faster convergence.
Keywords: Convergence ,Broyden ,Newton
References: None |
Problem Statement: Why are there no message prompts at the bottom of forms in V7.3.2? | Solution: The message prompts were replaced by the pop-up tool tips. If you prefer the prompts, go to the View tab and select Message Panel from the Show section of the ribbon.
Keywords: user interface, tool tips, notifications, menus, message prompts
References: None |
Problem Statement: What is the property method for steam and cooling water utilities? | Solution: Physical properties are needed to determine the heating value for utilities when you select the Specify inlet/outlet conditions option on the Specifications sheet. The answer to this question is on the Properties sheet of the Utility block. Steam and Water utilities use the global free-water property method for this calculation. Other utilities use the main property method shown in the Property method field. This sheet is also used to override global values of physical properties for Refrigeration and General utilities. For other utility types, the sheet is gray and you can only view the global values.
Keywords: None
References: None |
Problem Statement: How to retrieve and use the attribute completion status of a node | Solution: In order to retrieve the attribute completion status of a node, you should use the AttributeValue(attrnumber) method of an IHNode, where the argument is an enumerated value from the HAPAttributeNumber, in this case HAP_COMPSTATUS.
The value of the completion status attribute can be used for bitwise comparison with the bitmasks contained in Happ.HAPCompStatusCode.HAP_INPUT_COMPLETE enumeration to retrieve a set of multiple status of the node. You can check the status of any required node, including blocks, streams and also for the global simulation found under (“\Data”). So for instance:
myNode = mySim.Tree.FindNode(\Data)
CompStat = myNode.AttributeValue(Happ.HAPAttributeNumber.HAP_COMPSTATUS)
If ((CompStat And Happ.HAPCompStatusCode.HAP_INPUT_COMPLETE) = _
Happ.HAPCompStatusCode.HAP_INPUT_COMPLETE) Then
status = Input complete
ElseIf ((CompStat And Happ.HAPCompStatusCode.HAP_RESULTS_SUCCESS) = _
Happ.HAPCompStatusCode.HAP_RESULTS_SUCCESS) Then
status = Results available
End If
The code above retrieves the status attribute of the Data node and checks both if the input data for the simulation is complete and results are available. The attribute value is a hexadecimal number that should be converted into binary. The bitwise comparison performed is illustrated below:
Keywords: ActiveX interfaces, VBA, Automation
References: None |
Problem Statement: How can I use in Aspen Plus the property method Peng Robinson with enthalpies calculated by Lee-Kesler method? | Solution: There are no property methods in Aspen Plus/Aspen Properties that include this option by default. To use this combination, the calculation route has to be modified. In order to use the Peng-Robinson equation for the fugacity calculations but the Lee-Kesler model for enthalpy and additionally for Gibbs free energy and entropy, please follow these steps:
1) Create the component list.
2) Create a new property method in Methods | Specifications | Method name. Type a name and select PENG-ROB as base method
3) Go to Methods | Selected Methods and click on the method that was just created
4) In routes change the following routes
Property
Route ID
HVMX
HVMX13
HLMX
HLMX13
GVMX
GVMX13
GLMX
GLMX13
SVMX
SVMX13
SLMX
SLMX13
Keywords: Lee-Kesler, Peng-Robinson, fugacity, enthalpy, Gibbs free energy, entropy
References: None |
Problem Statement: I am using supplementary stream report with a user written routine. In the user interface, the report is not generated, however, when I run an input file in the simulation engine, it does generate the user report file. In V7.3, the report file is generated when the results are written. | Solution: The supplementary stream report is generated when you export a report (.rep) file since the report is only in the text report file and not on the user interface forms. In earlier versions, it was generated during the user interface report calculations.
Keywords: None
References: None |
Problem Statement: How can I create a dump file? | Solution: To create a dump file please follow the steps:
Step 1
Open your Aspen Plus and run your simulation
Step 2
Load the task manager in your machine
Step 3
Right click on the process (Aspen Plus) and then select Create dump file.
A dialogue box will tell you in which folder the dump file will be saved.
Keywords: Dump file
References: None |
Problem Statement: In a DSTWU block, why is the user not allowed to specify a heavy key component recovery that is higher than the light key component recovery? | Solution: In a DSTWU block, recovery always refers to distillate recovery. It is equal to the mole flow of the component in the distillate divided by the mole flow of the component in the feed. This convention applies to both light and heavy key recoveries. Thus, the recovery of the heavy key component cannot be greater than the recovery of the light key component in the distillate.
If the user attempts to enter a heavy key recovery greater than the light key recovery, the following pop-up warning will appear:
If the user is supplied a high number of heavy key recovery such as 0.99, it most likely refers to heavy key recovery in the bottoms. In this case, the user should enter 0.01 into the input field for heavy key recovery. \
Keywords: DSTWU heavy key light key recovery
References: None |
Problem Statement: I want to include mass transfer in my RPLUG model, how can I do it? | Solution: In the RPLUG block model you can specify user subroutine parameters for kinetics, heat transfer, pressure drop, but there is no direct way to specify a subroutine for the mass transfer.
What you can do is to define a subroutine for reaction kinetics that consider the mass transfer in its parameters if these fitted parameters represent both the kinetics and the mass transfer mechanisms.
For more information on user-defined kinetic subroutines, see the Aspen Plus User Models Guide, Chapter 11: User Kinetics Subroutines and theSolutions attached.
Keywords: RPLUG, mass transfer, kinetics, user subroutine.
References: None |
Problem Statement: How do I find application simulation examples delivered with Aspen Plus V7.3.2? | Solution: Click on the Examples icon on the Get Started ribbon to go to the directory of simple and complex examples shipped with Aspen Plus.
There are a wide range of examples from rate-based amine columns to ammonia to biodiesel to coal to polymers along with the files associated with the Getting Started manuals.
You can also access these examples from File | Open by clicking on the favorites button and selecting the Examples folder.
Keywords: None
References: None |
Problem Statement: I want to add an NQ Curve to my column. However, the button to add it isn't enabled. Why is this and how can I enable it? | Solution: To add NQ Curves, there must be a design specification related to each of the product streams of the column. So if for example, you have a column with a bottoms product, liquid and vapor distillate products, you will need three design specifications in order to enable the NQ Curves. Before adding these, the NQ Curves summary will look like this:
Once you add the design specs, the New....buttton will be enabled:
And you will be able to add the NQ Curve.
Keywords: curve, NQ, RadFrac
References: None |
Problem Statement: The file name is shown on the screen in an almost invisible color combination (dark gray on black?). Is it possible to change the color so the file name is readily visible, e.g. White on black. | Solution: The color of the top bar, which contains the file name, depends on the background (desktop or any other app) where its placed. For example, if your desktop is blue, the file name would appear darker. If the desktop is light background, the colors are better visible.
Font size and color used for the window title bar is controlled by operating system.
Users can change the font color (and size if desired) using the Windows Control Panel. For example, in Windows 7, go to Personalization and click the Windows Color icon in the bottom row to open the Window Color and Appearance dialog. If the Windows 7 Aero theme is selected, the Window Color and Appearance control panel will open first and Advanced appearance settings needs to be clicked. In the Window Color and Appearance dialog, select the Item Active Title Bar and set the Font Size and Color as desired.
Keywords: change display color, font
References: None |
Problem Statement: Automation in Aspen Plus: How to change the value of a variable in the units specified by the user with the Unit Table. | Solution: The unit table consists of rows representing physical quantities and columns representing the units of measurement in which the quantities can be expressed. It can be found in the variable explorer immediately under the root node (see picture below).
The following code will let you change the value of a variable in the units that you specify. It will also check if the variable can be manipulated by the user:
Dim mySim As Happ.IHapp
Dim myNode As Happ.IHNode
'If you have a block called “B1”. Accessing the variable temperature in the block.
Set myNode = mySim.Tree.Data.Blocks.B1.Input.Elements(TEMP)
'If statement to check if the variable can be manipulated by the user. Then change the variable in the specified units (30 C).
If myNode.AttributeValue(Happ.HAP_ENTERABLE) = 1 Then
myNode.SetValueAndUnit 30, 4
End If
The method, SetValueAndUnit of an IHNode object, requires as arguments Value and unitcol as integer:
SetValueAndUnit(ByVal Value, ByVal unitcol As Integer, [ByVal force])
Where unitcol represents the columns in the Unit Table as shown below:
In other example, if the user requires the temperature in F, they should type:
myNode.SetValueAndUnit 250, 2
To get the variable in the tree structure, please refer to theSolution 140584
To configure VBA to work with Aspen Plus, you need to add firstly the reference of the corresponding object type library. Please, check the followingSolution 140585
Keywords: ActiveX, VB, VBA, Visual Basic, Automation Server, getting started, Unit Table, Set value and unit.
References: None |
Problem Statement: In an electrolyte system I am getting densities for streams significantly lower than experimental data, what could be the problem? | Solution: If you selected H+ as hydrogen ion type, the inconsistency in the density results you are noticing are probably caused by this selection indeed. When you use H+, the mass density is computed from the MW of the apparent H+ instead from the real hydronium ion. Hence the difference. Please use the H3O+ approach to obtain a more accurate representation of real conditions.
Keywords: Density, H+, HO3+, Electrolytes
References: None |
Problem Statement: For piping calculations I need to get a stream with the flow coming out of the condenser of a RadFrac block. The pseudo stream to return the liquid flow on stage 1 actually gives the liquid flow going to stage 2, which is excluding the distillate. How can I define a stream with the flow of both distillate and reflux? | Solution: This information is not available in the pseudo stream of RadFrac, but you can easily work around this limitation using a calculator block. The attached file illustrates for Aspen Plus V7.3 how this can be done.
The calculator block C-1 imports the liquid flowrate (molar) from the RadFrac block for stage 1. Pseudo stream LIQTOT1 is specified that it is a copy of liquid from stage 1. In the Sequence tab of the calculator, the import and export variables are specified to ensure that the sequence is correct. Note that in general it is not good practice to overwrite the flowrate of the outlet stream of a block. This is why Aspen Plus prints a warning:
* WARNING DURING FLOWSHEET ANALYSIS
FORTRAN WRITE-VAR PSEUDO IN FORTRAN BLOCK C-1
IS WRITING TO AN OUTLET STREAM VARIABLE.
This warning can be safely ignored, and in fact it is not reported as a warning in the simulation status. Since pseudo streams are not accounted for in the material balance of a block, their flowrate can be set to any value.
This approach is correct if there's no subcooling or if both reflux and distillate are subcooled. See the file radfrac-liq-from-condenser.bkp.
If the option only reflux is subcooled is selected, you need to modify the calculator block to set the temperature of the pseudo stream to the temperature of the distillate. See file radfrac-liq-from-condenser-subcool.bkp.
Keywords: None
References: None |
Problem Statement: What is the Aspen Remote Simulation Service? | Solution: Aspen Remote Simulation Service (ARSS) is a component that provides a remote execution environment for other AspenTech tools including Aspen Simulation Workbook and Aspen Model Deployment.
ARSS allows model developers to deploy models onto a server accessible to several client computers.
AspenTech simulation software must be installed on the server, but it is not required on the client computers. This significantly reduces the installation requirements for the client computers.
Keywords: Remote
Simulation
Service
Deployment
References: None |
Problem Statement: When adding pure water in a stream at 1 atm and 25 C using H2O dissociation chemistry, why doesn´t the dissociation composition correspond to the 1e-7 constants value? The dissociation shows concentrations of 1e-10 kmol/hr. | Solution: The dissociation displayed for the stream results are molar flows and not molar concentrations (mol/l). If you add a property set to report the dissociation concentrations, you will see the correct values.
The property that needs to be added to a property set is MOLECONC with units in mol/l.
This property set can be used to show the molar concentrations for water dissociation and the 1e-7 mol/L per H3O+ and OH-
Keywords: Water dissociation, Aspen Plus, Chemistry, Molar concentration
References: None |
Problem Statement: Is it possible to use polymers in the solid unit operation models? | Solution: Before V8.8, Component Type “Polymer” was not supported in Solid handling models. Polymer pellets could be defined under “Solid” type. If you use MIXCISLD streams and put the polymer in the CISOLID substream, Aspen Plus will ignore phase equilibrium involving the polymer. CISOLID polymers are treated as crystalline solids.
In V8.8, Polymer Modeling in Aspen Plus was extended so that polymers and oligomers can be recognized as particulate solids, enabling optimization of many more common processes. Aspen Polymers has always calculated properties for polymers below their melting point properly, but now the solid-handling unit operations can also treat them as solids.
Aspen Plus originally treated solid polymers as liquid-phase components in order to address phase equilibrium. Small molecules (solvents and monomers) dissolve inside the solid polymers even when the polymer is below the melt transition temperature. By including the solid polymers in the liquid phase, the Aspen Plus flash algorithms are able to calculate the equilibrium concentration of dissolved monomers in the polymer phase. For solid-liquid systems, like emulsion polymerization, the system will treat the polymer as a second liquid phase (you need to have appropriate binary parameters between segments and monomer/solvent components to force the phase split).
The polymer property models calculate the glass and melt transition points of the polymer and compare these with the phase temperature. If the polymer is below the melting point, the system will switch the pure component property models to use the appropriate method for solids. You can specify degree of crystallinity using the polymer property POLCRY (mass fraction crystallinity) between 0 (no crystal) and 1 (pure crystal). The polymer property models will call appropriate routes for amorphous, glassy, or crystalline solid to calculate properties such as density, enthalpy, heat capacity, and so on.
In V8.8, It is possible for Aspen Plus's solid-handling unit operations to treat polymer components as solids. To enable this the Treat polymers below the polymer melting point and catalysts as solids box on the Components | Polymers | Characterization | Options sheet in the Properties environment needs to be checked. For more details see the Polymers in Solid Handling Models topic in the Help.
Keywords: None
References: None |
Problem Statement: How to hide and reveal a design specification and other objects through Automation Server in Aspen Plus. | Solution: A design specification sets the value of a variable that Aspen Plus would otherwise calculate. For example, you may want to specify a product stream purity or the permissible amount of an impurity in a recycle stream.
When using Automation code, you might want to activate or deactivate design specification or other unit operations such as calculators or sensitivity analysis to name a few. This allows you to compare results and adapt your workflow to different scenarios.
The methods Hide and Reveal of an IHNode object let you accomplish this. They require the name of the object as a string:
Sub Hide(ByVal Name As String)
Sub Reveal([ByVal Name As String])
The following code will hide a node that you specify. It will also check if the node can be hidden.
Dim mySim As Happ.IHapp
Dim myNode As Happ.IHNode
myNode = mySim.Tree.Data.Elements(Flowsheeting Options).Elements(Design-Spec)
'-- check if the node can be hidden.In this case a design-spec (DS-1) --
If myNode.Elements(DS-1).AttributeValue(Happ.HAPAttributeNumber.HAP_CANHIDE) = 1 Then
myNode.hide (DS-1)
End If
ThisSolution includes a simulation file and an Excel file with VBA code that provides a practical example. The code will allow to:
· Interactively open a bkp file.
· Detect the example provided and inform the user if a different file has selected
· Load the simulation and show progress
· Hide and unhide the design specification
· Close the simulation
Keywords: ActiveX, VB, VBA, Visual Basic, Automation Server, getting started, activate, hide, reveal, example.
References: None |
Problem Statement: My question is related to the selection of the mass transfer correlation that can yield results with some confidence to go forward to vendors for final design. The Stichlmair constants for the Super Raschig Rings are not defaulted and when trying to compare correlations some significant differences occur. Also, when selecting Billet and Schultes there are two additional parameters not filled in and it seems to be sensitive to these CL and CV values.
Currently I am evaluating the performance of packed columns designed to evaporate water from an effluent stream using ambient air (attached is the .bkp file). Comparing the performance of packing hydraulics and HETP can give a basic understanding of the future direction (as well as understanding potential fouling characteristics). | Solution: This is a very difficult topic to discuss. There are a many mass transfer correlations available for packings. Aspen Plus includes a selection of the more popular and successful ones. However, one cannot depend on any given mass transfer correlation to give quantitative design results for a specific packing type, size, and material of construction for every specific type of situation (absorption versus distillation, for example) and for any selection of chemical species. In other words, one usually has to verify that a specific mass transfer correlation “works” for your specific situation or for one very similar to it.
In addition, Aspen Rate Based Distillation requires the user to select certain options for the mathematicalSolution of the column. These include, for example, the mixing model (“mixed”, “countercurrent”, or “vplug”, for example), the number ofSolution nodes for the packed height, and a value to adjust the predicted interfacial area (defaulted to unity). These selections can also greatly influence theSolution even for the same packing and mass transfer coefficient correlation.
Finally, some type of meaningful summary output from the columnSolution which can be easily compared to experiment can depend on the type of mass transfer problem. The HETP, for example, is a common measure of packing performance in binary or pseudo-binary distillation scenarios. The HETP is rarely used for gas absorption or stripping where the HTU – either overall gas or overall liquid- is more commonly used as a measure of performance … more about this below.
In other words, it is very dangerous to blindly use any mass transfer coefficient correlation coupled with any set of Aspen PlusSolution parameters, to design or rate a column without first doing a very thorough investigation, usually through experimentation, about its predictive accuracy for a given packing and a given chemical system.
There are a few rules of thumb that one can use to get started with rate based column simulations. In the case of packings, it is probably most appropriate to select the “countercurrent” flow model. Unfortunately, this selection often causes convergence difficulties. A very good second choice is the “vplug” mixing model. This selection usually gives results that are close to those one would see with the “countercurrent” flow model selection but it is usually much more stable and forgiving with respect to solving the column.
In addition, the user should play with the number ofSolution nodes employed with the problem. The columnSolution will depend on the number ofSolution nodes up to a point and then become independent of that number. Therefore, the number ofSolution nodes should be set to a value large enough to guarantee that theSolution is independent of this number but small enough to guarantee that the column solves in a reasonable amount of computation time.
In the attached simulation PackingRating.bkp, the column is being used to humidify air. Water is the major component in the liquid phase, but there are several minor chemical species also. The performance of a packing for air humidification with a stream of water alone (a good approximation in this case) is usually reported using the overall gas phase Height of Transfer Unit – HTUOg – rather than via the HETP. The reasons for this can be found in any good book on mass transfer. In short, the HETP is appropriate for use in situations where there is equimolal counterdiffusion or something very close to that. The use of the overall gas phase HTU is more appropriate for situations where one species is diffusing through a non-diffusing second species. In the case of the simulation here, water vapor is diffusing through non-diffusing air (very little of the air is absorbed by the water). Further, the approximation that the liquid phase is essentially pure water means that there are no concentration gradients on the liquid side – all that is happening is that water is evaporating from the liquid and then diffusing and mixing with the gas phase – primarily composed of air. In addition, the humidification operation usually results in some heat transfer – that is, the water temperature changes with packed height (as does the gas temperature to some degree).
Unfortunately, Aspen Plus is not set up to automatically calculate and report the overall gas phase height of a transfer unit – HTUOg. Aspen does report an “HETP” for such systems, but one must treat this number with a great deal of suspicion. Without going into the details, the HETP is simply not appropriate here. Books like Treybal’s Mass Transfer Operations offer a pretty good explanation.
The correct calculation of the number of transfer units – NTUOg – and the height of a transfer unit – HTUOg – proceeds from this identity:
Here “Z” is the packed height. The number of transfer units - NTUOg – can be approximated from the following expression:
where yt and yb are the mole fractions of water in the vapor phase at the top and bottom of the packed bed. The quantity reported in the literature for the performance of a given packing, HTUOg, can then be determined thusly:
The expression above for NTUOg must be evaluated numerically from the results of the rate based simulation in Aspen Plus. I have adjusted the supplied simulation (it is attached) and then used it to get results. Below is an example of how the procedure described above would proceed using Koch-Glitsch plastic CMR 3A and the Onda mass transfer correlation:
Node
Bulk yH2O in vapor phase
yH2O at interface
1
0.08458103
0.118046008
2
0.08169304
0.114246487
3
0.078912146
0.110650847
4
0.076206989
0.10723604
5
0.073568044
0.103982468
6
0.070986756
0.10087318
7
0.068455381
0.097893421
8
0.065966853
0.095030276
9
0.063514665
0.092272385
10
0.061092784
0.08960971
11
0.058695564
0.087033344
12
0.056317679
0.084535349
13
0.053954066
0.082108631
14
0.051599867
0.079746828
15
0.049250389
0.077444219
16
0.046901055
0.075195645
17
0.044547369
0.072996447
18
0.042184877
0.070842411
19
0.039809139
0.068729717
20
0.037415686
0.066654906
And below is a plot of (y – yi)-1
Using these results I calculate that NTUOg for this choice of packing and mass transfer correlation is 1.57628. Therefore, HTUOg = (4’/1.57628) = 2.5376 feet.
The same procedure can be carried out for the various mass transfer coefficient selection options:
Correlation
Packed height (ft)
NTUOg
HTUOg (ft)
Onda
4
1.57628
2.5376
Bravo and Fair (1982)
4
6.13744
0.65174
Hanley (2010)
4
1.65674
2.4144
Billet and Schultes
(CL = 0.3; CV = 0.9)
4
13.3032
0.30068
As you can see there is a large spread in the values of HTUOg for the different correlations. The only way to validate the appropriateness of one choice over another is to compare the HTUOg results with experimental data taken for the same system/packing or one that is very close to it. Unfortunately, finding such data in the open literature is often difficult.
Below are some humidification data taken for2” slotted rings as a function of liquid and vapor velocities:
For low liquid rates HTUOg is on the order of 2 feet; for high liquid rates it is on the order 0.75 to 1 foot. In the simulation supplied the liquid rate is about 10 gpm/ft2. So we would expect the HTUOg to be about 1.1 feet.
These data do not apply to the packings the user is concerned about. The only way to judge which correlation is appropriate and which Aspen Plus parameters are good is to have data available for each packing. That being said, the following statements are probably true here – plastic packings have higher HTU values than do metals or ceramic packings, and the Onda correlation usually works well in for these types of columns and packings.
Keywords: None
References: None |
Problem Statement: What are typical friction parameters for solid particles for materials to specify within the Aspen Plus Pipe dilute solid conveying option? | Solution: The following chart shows typical sliding friction factors (Fluid friction parameters) and particle size for various solid materials in the dilute phase.
Solid Material
Particle Size
[μm]
Coefficient of sliding friction f
Against aluminum
Against stainless steel
Against steel
ABS Powder (Butadiene)
30. . .50
0.51
0.44
0.57
Adipic Acid
100
0.53
0.46
0.59
Bisphenol Powder
50
0.55
0.51
0.64
Silicic acid
Micron Range
0.67
0.67
0.84
Sodium perborate
150
0.44
0.42
0.54
PA granulate (Polyamide)
3000. . .4000 cubes
0.42
0.34
0.45
PE granulate (Polyethylene)
3,000 Lenticular pellets
0.23
0.19
0.28
Soot pellets
500. . .1,000 granulate pellets
0.78
0.72
0.90
PP granulate (Polypropylene)
3000
0.27
0.23
0.32
PP powder (Polypropylene)
300
0.36
0.44
0.56
PS granulate (Polystyrol)
3000. . .4000 cubes
0.3
0.27
0.36
Soot powder
5…50
0.75
0.75
0.93
PVC powder
150
0.40
0.36
0.47
Alumina
40…100
0.58
0.53
0.66
Titanium Dioxide pigment
1…20
0.90
0.90
1.11
TPA powder
100
0.34
0.40
0.52
Wheat flour
20…120
0.36
0.34
0.44
These parameters are specified on the Pipe Setup | Solids Conveying sheet as the Solid-wall sliding friction parameters.
Keywords: Fluid friction
Particle size
Solids Processing
Muschelknautz
Dilute Phase
References: s:
Ulrich Muschelknautz, Druckabfall im Druckluft Fördertechnik, VDI e.V. VDI-Wärmeatlas , DOI 10.1007/978-3-642-19981-3_12, Springer-Verlag Berlin Heidelberg 2013 |
Problem Statement: What are typical Conveyance values in Dilute phase for pipes in Solids Conveying? | Solution: The chart below proposes several operating values in different suspended flows (Dilute Phase).
Solid / Fluid velocity ratio is the average particle velocity divided by the average divided by the average axial velocity of a gas. Furthermore you will find values for Load Ratio, Mean particle size of feed, average axial velocity of a gas, and pressure drop.
Conveyance State
μ
Load Ratio
d50
[mm]
Mean particle size of feed
ν
[m/s]
Average axial velocity of gas
c/ ν
Average particle velocity/ average axial velocity of gas
Δp/100 m
[Bar]
Diagram
Fully suspended flow
1-10
0.1
20
0.8
0.15-0.5
1
30
0.65
0.15-0.5
10
40
0.5
0.15-0.5
Strand type conveying
10-50
0.01
20
1
0.75-2
0.1
25
0.3
0.75-2
0.5
30
0.4
0.75-2
Strand type conveying and
plug flow
20-50
0.01
15
1
0.4-0.8
0.1
20
0.3
0.4-0.8
1
25
0.5
0.4-0.8
These parameters can be entered on the Pipe Setup | Solids Conveying sheet:
Keywords: Solid / Fluid velocity ratio
Load Ratio
Mean particle size of feed
Average axial velocity of a gas
Pressure drop
References: s:
Muschelknautz E (1959) Theoretische und experimentelle Untersuchungen über die Druckverluste pneumatischer Forderleitungen unter besonderer Berucksichtigung des Einflusses von Gutreibung und Gutgewicht. VDI- Forschungsheft 476
Barth W (1958) Strömungsvorgänge beim Transport von Festteilchen und Flüssigkeitsteilchen in Gasen. Chem- Ing- Techn 30:171–181 |
Problem Statement: In Aspen Plus and Aspen HYSYS from version V8.0, the user has the option to use aspenONE Exchange to search for examples from the knowledge base. These files may be downloaded and accessed from within the application as shown below:
After the file has been downloaded, a window prompts to open the file in the application:
When you click OK, the file will be downloaded and opened automatically.
If the simulation is closed, how do I open it again? | Solution: All files downloaded using aspenONE Exchange are available when you open the Exchange window in Aspen Plus and there you can find in the 'My Downloads' section where Aspenplus has saved the history for all downloaded items. The screenshot below illustrates this.
Here you can just click on the title, download and open the example file again or you can select OPEN a file from temporary directory using the dropdown list next to each item in My Downloads section. You can also find an option to remove items from the temporary directory.
Another way of opening this is to enter a key word in the Exchange search window. Use the search button to find the file which will be the most accurate for your issue and open it in the same way as you opened it first time.
Keywords: Exchange, All Content
References: None |
Problem Statement: What is the difference between “RES-TIME (overall residence time)” and “phase residence time” when specifying a RCSTR? | Solution: In RCSTR, when you have multiple phases, you can specify RES-TIME (overall residence time) or phase residence time.
When you specify residence time, the reactor assumes no-slip conditions between the phases. This implies the vapor fraction in the reactor is the same as in the mixed outlet stream. Since the molar volume of vapor is larger than the molar volume of liquid, this makes the liquid residence time very small. This assumption is valid in unit operations like pipe fittings or inline mixers simulated as CSTR's, but it is not appropriate for real reactors with level control.
For a real reactor use the condensed phase residence time to specify the reactor.
Keywords: RCSTR, residence time
References: None |
Problem Statement: Why are the global data not showing anymore on my PFD? | Solution: There are actually three places controlling the display of Global Data:
Settings on Tools | Options | Results View where
Setting for View | Global Data where the display of the selected stream variables can be activated or de-activated globally
Setting for the background context menu | Hide Labels where if a user right click on the background in PFD window, and check Hide Labels, the global data will all be hidden
Keywords: Global data, label
References: None |
Problem Statement: When using the option of size independent growth described by McCabe’s law of growth in a Crystallizer model in Aspen Plus and this is not providing similar results to the PSD seeds added plus a size independent increase, as the below formula states:
Where:
R: ratio of final and initial weight of crystal
wi: fraction of crystal of size Li
L0i: initial dimension of crystal i
Li: final dimension of crystal i
You can ask how does Aspen Plus distribute the increase in the crystal mass on the various size classes when size independent growth described by McCabe’s law is specified? | Solution: According to the McCabe’s law above, the w_i is the fraction in the number distribution. That is how we obtain one delta_L valid for all particles. The picture below shows how we then redistribute the particles on the existing size bins. The wider the size bins (low number of intervals) the bigger the numerical error will be:
We do consider a change in particle density, in case it occurs. Then the equation should look like:
Keywords: McCabe’s law, Crystallizer, PSD, Various Size Classes.
References: None |
Problem Statement: How to get heat curve data from a Thermal and phase state changer model (For example: Heater). The data will include vapor and liquid phase properties like Density, viscosity, heat capacity, surface tension etc. | Solution: Please follow the steps:
1. Complete the input section of the model
2. Create a new HCurve file (H Curves > New)
3. In the SetuP form, chose number of data points (Set Up > Number of data points)
4. Select desired property sets (Additional Properties > select and transfer from Available to Selected Property sets)
5. Reinitialize and Run
6. Please See the Results (HCurves > File > Results)
Please also see the attached file as an example.
Key Words
Heat Curve, data, Liquid Phase, Vapor Phase
Keywords: None
References: None |
Problem Statement: In rate-based MEA model to simulate a CO2 absorber/stripper combination, how are MEA chemistry block Keq's calculated? | Solution: Aspen Plus has the ability to calculate the equilibrium of ions / apparent components using Gibbs free energy. If there are parameters for the equation for the equilibrium constant for a particular reaction on the Equilibrium sheet on the REACTIONS | CHEMISTRY | GLOBAL form, it will have a higher priority. But in the absence of input for these equilibrium constants, the equilibrium constants are calculated from the reference state Gibbs free energies of the participating components.
Keywords: Electrolytes, MEA, Keq, Gibbs Free Energy, Chemistry
References: None |
Problem Statement: Converged RadFrac distillation column simulation appears to be out of Enthalpy Balance. | Solution: The Aspen Plus RadFrac distillation column block report summarizes the heat and material balance. The mass and enegy balance results are shown on the RadFrac | Results | Balance sheet.
These Converged RadFrac results often have a very small (less than 1E-10) relative mass/mole difference between inlet and outlet streams. However RadFrac will often have a very large (.01 or .001) relative difference in the enthalpy balance between inlet and outlet streams. This would seem to imply the RadFrac block was out of enthalpy balance. The following RadFrac mass and energy balance from the testprob.bkp example in the Aspen Plus Favorites directory illustrates this point:
Total
Units
In
Out
Rel. diff
Mole-flow
lbmol/hr
103.6608
103.6608
0
Mass-flow
lb/hr
8465.402
8465.402
4.75E-14
Enthalpy
Btu/hr
-6629725
-5330314
-0.196
There are Results | Balance sheets for all unit operation blocks. These results are based on the inlet and outlet stream results only and do not account for duties. It is easier to see that for the Heater in the same file that the enthalpy difference is simply the heat duty for the block. In RadFrac, it is more complex since there can be reboilers, condensers, and stage heaters. The RadFrac calculation do take into account all necessary duties and are consistent.
In the case of the RadFrac column.
The Condenser duty is -110585.998 Btu/hr and the Reboiler duty is 1409996.63 Btu/hr.
Enthalpy balance = Enthalpy In - Enthalpy Out + Condenser Duty + Reboiler Duty
= -6629725 - (-5330314) + (-110586) + 1409997 Btu/hr
= 0
This indicates the relative difference in the RadFrac enthalpy balance was 0.0 and the RadFrac block is in enthalpy balance.
Keywords: None
References: None |
Problem Statement: I am using an equation of state method, but I have been able to report the activity coefficient (gamma) for the stream using a property set. There is no activity coefficient model used in the simulation. What is being calculated? | Solution: We calculate the activity coefficient (gamma) from fugacity coefficients. For activity coefficient (gamma) models such as NRTL, the property gamma simply came from the model itself. For equation of state (EOS) models such as PR, we would calculate gamma from fugacity coefficients. Note that for the equation of state models with mixing rules that use the activity coefficient such PSRK, there is an activity coefficient calculated from the gamma model specified in the mixing rules. This activity coefficient is not the same as that computed from the equation of state itself.
Keywords: None
References: None |
Problem Statement: How to solve the following error:
SEVERE ERROR
ERROR DURING DYNAMIC LINK OF USER ROUTINE(S) OR IN-LINE FORTRAN
PLEASE CHECK FILE _3347vfr.ld FOR LINKER MESSAGES.
*** SEVERE ERROR
COULD NOT RESOLVE USER OR IN-LINE FORTRAN SUBROUTINE(S):
SUBROUTINE USRSTR IS MISSING | Solution: This is a linker error that indicates that a user subroutine is active in your simulation and the binary file with the subroutine couldn't be found by the linker during symbol reSolution. By the subroutine's name we can infer that it is a stream report subroutine in this case. In order to solve this, we have two options: deactivate the customized stream report subroutine or provide the compiled file to the linker.
Deactivate the subroutine:
Please go to Setup | Report Options | Stream sheet. Click on the Supplementary Stream button, click on Subroutine and then remove the field contents for the subroutine name.
Use the subroutine:
We need to provide the compiled files that contain the subroutine, this can be an object file .obj, a static library .lib or a dynamic shared library .dll. For the first two the simplest method of supplying Fortran user models to Aspen Plus is by putting the user model’s object files (the results of the aspcomp command) in the run directory. Alternatively, you can write a Dynamic Linking Options (DLOPT) file that specifies the path where to find a dynamic shared library (dll).
The screenshot below shows where to supply the name of the stream report subroutine you want to use:
Keywords: Severe error, USRSTR missing.
References: None |
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