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Problem Statement: How do you search for components not automatically found in the Aspen Plus databanks? | Solution: On occasion, Aspen Plus may use alternate names for components: for example, isopropanol is called isopropyl-alcohol in the PURE13 databank. There are several options you can employ when searching databanks for specific components.
1. First, from the Components Specifications form, click the Find button... |
Problem Statement: RadFrac overhead flash results differ from heater flash results. When the column overhead stream is sent through a Heater with Pressure drop = 0 and Heat Duty = 0, the outlet temperature should not change. But it does. | Solution: The results of a vapor stream coming out of RadFrac are reported directly from column calculations, NOT from a separate flash calculation. When Murphree efficiency is specified, the stream coming out of RadFrac may not be in equilibrium with liquid. In other words, it may not be saturated. When this stream go... |
Problem Statement: When the convergence diagnostic level is set to 7 (CONV-LEVEL=7), the SQP optimization convergence derivatives are printed in the history file. What do those derivatives mean and what is their relationship to one another? | Solution: Derivatives with respect to all independent variables are perturbed by the base case. This is done for each independent variable for each constraint. All others are kept fixed at the base case value.
The objective function (OBJ) is a function of the independent variables - these include both the VARY variable... |
Problem Statement: When a pack sizing/rating calculation is specified, RadFrac reports the efficiencies of the stages involved to be equal to 1, no matter what has actually been entered for the efficiencies of these stages. This will affect the overall column results, if they are based e.g., on Murphree efficiencies un... | Solution: Pressure Profile Update (As checked on the RadFrac | Pack Sizing | PDrop sheet or on the RadFrac | Pack Rating | Design / Pdrop sheet) cannot be used in PackSizing or PackRating sections while also using efficiency specifications. Efficiency specifications on stages in such sections will be ignored with a war... |
Problem Statement: MHeatX zone analysis might encounter convergence problem when the inlet stream comes from RadFrac with efficiency specified. | Solution: If efficiency is specified in RadFrac, then the streams are by nature not in equilibrium. If these streams are fed to a MHeatX block donwstream, convergence problem might occur when MHeatX tries to do an iteration on the zonal temperatures because MHeatX assumes that the streams are in equilibrium.
TheSolutio... |
Problem Statement: How do I model a system with Formaldehyde/Methanol/Water? | Solution: Aspen Plus 9.2-1 introduced a property data package for systems containing Formaldehyde, Methanol and Water.
You can use this property package to model formaldehyde, methanol and water systems. This system is highly nonideal, and in fact, reactive, because formaldehyde and methanol form complexes in the liqui... |
Problem Statement: How does Aspen Plus determine the parameters that appear on the Regression form? | Solution: Aspen Plus determines the most likely parameters to be regressed from the combination of option set and Data group.
In addition, Aspen Plus determines the combination of parameter elements that can be regressed and that will appear on the Regression form by default for a given parameter. Each parameter has a ... |
Problem Statement: User cannot run Aspen Plus independently, it can only be run through Aspen Custom Modeler / Aspen Dynamics.
The following Error message is given:
*****TERMINAL ERROR
USE OF ASPEN SIMULATION CAPABILITIES NOT PERMITTED AT THIS INSTALLATION
CALL ASPEN TECHNOLOGY, INC. AT 888-996-7001 FOR ASSISTANCE. | Solution: License key is enabled for use of Aspen Plus with other products but not stand alone.
For Aspen Plus 10.x
Check Product License Key Certificate for line stating:
Properties Plus Only: Yes
For AES 11.1
Check Vendor line in Flexlm License Key file. Look for SIMOK Parameter. If SIMOK=0; This means you can not u... |
Problem Statement: When simulating a Tungsten Hexafluoride (WF6) process, the normal boiling point is about 62 F which is reasonable. However, the vapor pressure (PL) range predicted by Aspen Plus between 0 and 150 F ranges from 2.05 E 16 to 1.5 E 16 psia. Not only are these numbers way off, but the trend produced is w... | Solution: There are some gaseous components such as WF6 in the databanks that only have limited data available for them.
The only data available are Gibbs Free Energy (G), Enthalpy (H), Entropy (S), and Heat Capacity (CP) for ideal gas. In Aspen Plus, we want to make sure that this component stays as vapor, so we make ... |
Problem Statement: How do I make a plot update automatically when a new run is made? | Solution: When any plot is the active window, from the Edit menu choose Live plot. The plot will then be redrawn when new results are available.
For plots that are created with the Plot Wizard, you can turn this on at creation by going all the way through the Wizard to the last form and checking the Live plot option bo... |
Problem Statement: How can the Aspen Plus system administrator suppress the echoing of the physical property paramaters used in a simulation despite the PROPERY-REPORT PARAMS being invoked by the user? | Solution: PROPERY-REPORT PARAMS sentence is used at user level to report all physical property parameters used in a simulation. At times, the Aspen Plus administrators would like to disable this feature to prevent the end-users from accessing proprietary property parameters.
There is no SDF table to make this change sy... |
Problem Statement: User wants to use C++ to control his Aspen Plus simulations | Solution: The sample code below can be used as a starting point for users.
C++ Sample:
#include <atlbase.h>
#import C:\Program Files\AspenTech\APRSYSTEM 11.1\GUI\xeq\happ.tlb named_guids
int main(int argc, char* argv[] )
{
CoInitialize( NULL );
try
{
CComBSTR bstrFileName(C:\\Program Files\\AspenTech\\Aspen... |
Problem Statement: Why are the Mixture and Pure component property liquid densities different? | Solution: It is possible that for some components, a different equation will be used to calculate pure component and mixture liquid molar volume.
For example, if you reported the liquid mass densities, RHO and RHOMX, for a stream of pure benzene using the NRTL-HOC property method, the values would be slightly different... |
Problem Statement: How will the Aspen Plus / Icarus interface change now that Aspen Technology has acquired Icarus? | Solution: From a user''s perspective, the interface will continue to operate as it currently does throughout AES 10.x and AES 11.1.
Beyond AES version 11.1, there are very preliminary planning sessions occuring now. It is too soon to speculate on what the interface will evolve to.
Keywords: ICARUS, interface, Aspen Plu... |
Problem Statement: VBA code written for version 10.2 that suppressed the dialog box when reinitializing the model no longer suppresses the confirmation dialog in version 11.1 and later. Is there a way to suppress these dialogs in version 11.1 and later? | Solution: Aspen Plus 11.1 has a new method to suppress dialogues. In version 10.2, the common way to reinitialize and suppress the confirmation dialog was:
Call go_Simulation.Engine.Reinit(IAP_REINIT_SIMULATION)
OR
SendKeys {ENTER}
Call go_Simulation.Engine.Reinit(IAP_REINIT_SIMULATION)
In version 11.1 (and... |
Problem Statement: How does Aspen Plus calculate the residence time in the RPlug unit operation model? | Solution: Because the volumetric flowrate can change in the reactor, the total residence time is calculated by integration.
If the volumetric flowrate does not change in the reactor, then the residence time equals:
(volume of the reactor)/(volumetric flowrate)
Note that the cumulative residence time is reported on the ... |
Problem Statement: When starting up the GUI, a connection to the engine the GUI goes through sockets (TCP is a common example). We usually refer to this internally as the XC (cross communication) connection. After the connection is made the GUI the proceeds to make a DCOM connection. It is possible for XC to connect su... | Solution: There are a coupleSolutions to this problem:
Use accounts belonging to a common trust authority, like the ASPENTECH domain here. Most large companies will probably have one. (I.e. use a domain account).
Create an account with the same username and password on both client and server machines.
Lower the appli... |
Problem Statement: The calculated value of Entropy is negative. Why is this the case ? How does Aspen Plus calculate the entropy ? According to data from Benson group contribution (taken from Prausnitz) the delta S is a positive number eg: group 104 = 115.6 J/kmole-K? | Solution: First of all, Enthalpy (H), Gibbs Free Energy (G) and Entropy (S) are by definition interrelated. See any Thermodynamic text for the basic relationships. In Aspen Plus, entropy S is calculated as a function of H and G. This will lead to variation on the values at a given reference state when compared to a met... |
Problem Statement: Abnormal fonts used in the Aspen Plus data browser. | Solution: The data browser makes usage of the default font(s) configured in the windows control panel.
If no customizaiton is made on the font setting in Control Panel - Display - Appearance tab, then the problem is probably related to the font substitution because of a missing/damaged font definition file. The Windows... |
Problem Statement: When using the Assay Library on the Component specification form, the assay names are rather cryptic. There are some help screens available, but they assume the user knows the crude''s source continent or region. Is there a single list cross referencing Assay Library file names & the formal Assay Nam... | Solution: Not yet. Below is an alphabetical list of the cryptic crude assay ID''s in Aspen Plus and a formal description of the crude and its source continent/region. Also, please see the attached spreadsheet for a sorting by Assay ID name and by fomal Assay name.
File Names Assay Names
Keywords: None
References: ... |
Problem Statement: Opening the Data Browser causes the error Unable to load form control. None of the forms are able to be displayed. | Solution: For Aspen Plus versions 10.0 and 10.1:
Run regfix.bat and then run ApwnSetup.exe. They are found in the folder \program files\AspenTech\Aspen Plus 10.1-0\gui\xeq. Accept all the defaults. Then try Aspen again. If it doesn''t work, go to step 2.
Install the DAO from the Aspen Plus CD. This is under i386/Syste... |
Problem Statement: How does a user add the API Upper and Lower Heating values to the stream results? | Solution: These properties are available as the Property-Set parameters:
QVALGRS (Gross Heating Value) - API High Heating Value
QVALNET (Net Heating Value) - API Low Heating Value
To add these parameters to the stream report, use the Data Browser to visit the Prop-Set sub-folder under Properties. Add a new property set... |
Problem Statement: How is the Heat of Reaction calculated in Aspen Plus? How can I see the value? | Solution: Enthalpy calculation is based on the Heat of Formation of the reaction components at reference state (DHFORM). Because Aspen Plus can calculate the enthalpy of a compound at the given conditions, the Heat of Reaction is implicitly included in the enthalpy calculations. The Heat of Reaction is the difference i... |
Problem Statement: What is the Campbell-Thodos model for liquid density and how is it used? | Solution: The Campbell-Thodos model is essentially the same as the Rackett equation for liquid mixture molar volumes except that it contains an additional term which permits varying the RKTZRA pararameter as a linear function of (1-Tr).
ZRA,mixture = sumi ( xi RKTZRA ( 1 + di (1 - Tr) )
The model uses T-dependent param... |
Problem Statement: What can be done to solve problems converging a RGibbs reactor model? | Solution: There are several different approaches to try:
1. Increase the maximum iterations (MAXIT) on the Advanced | Convergence sheet from the default of 50 to 100.
2. Limit possible product slate by specifying possible products from the RGibbs reactor on the Setup | Products sheet. If the product slate i... |
Problem Statement: When trying to place any CAPE OPEN unit operation, including the example MixNSplit, on the flowsheet, Aspen Plus crashes.
The following messages may be seen:
Aspen.DCOM
The Aspen Plus Server object could not be accessed.
Please check that the DCOM service is started and working properly.
Then:
!!!A f... | Solution: This problem has been observed on one machine. For some unknown reason, CAPE-OPEN type libraries were not properly registered during the installation of the softwares. This can be fixed by re-registering program files\common files\CAPE-OPEN\capeopenv1-0-0.tlb.
Microsoft does not provide a utility for register... |
Problem Statement: How is tray efficiency calculated in RateSep? | Solution: RateSep does not use tray efficiency in calculating separations or outlet stream compositions, but they will report tray efficiency if requested on the RateSep Report | Efficiency Options sheet.
The tray efficiency is calculated from the following expression:
tray-eff = 1 - exp ( - NTU )
where NTU is the... |
Problem Statement: How can I plot results in Aspen Plus? | Solution: Aspen Plus has an easy-to-use plotting capability. On any results form containing columns of results (profiles), the commands listed on the Plot menu are active. The Using Aspen Plus Help contains a more detailed description of the plotting features in the Working with Plots section under Using Aspen Plus
Asp... |
Problem Statement: Icon problem - How do you import icons? | Solution: Existing AutoCAD DXF files can also be imported into the Icon Editor. When the Icon Editor is active, a main Icon menu becomes available on the menu bar for the main window. Select Import DXF from the Icon menu.
Keywords:
References: None |
Problem Statement: What''s the default property method for petroleum charaterization? | Solution: There are five property methods for petroleum characterization.
API-METH
COAL-LIQ
ASPEN
LK
API-WU
The default is ASPEN.
Note: If running the input from command line, the default is API-METH. When in doubt, explicitly select a method.
Keywords:
References: None |
Problem Statement: The following error occurs during AES 11.1 or AES 11.0 Core Component installation.
Failed to set special folder location 25 during AES 11.1 installation or
The Installation of Core Component MS Common Failed. setup can not continue | Solution: Run the attached executable on the problem computer and click the Fix button.
Keywords: AES 11.1
Core
Component
Common
References: None |
Problem Statement: To install 2004.1, do I need the 2004.1 product update Patch DVD at all?
To get the 2004.1 version for one of the products on the Patch DVD working, must I install 2004.0 then use Patch DVD to upgrade to Update 1? | Solution: The Patch DVD is ONLY needed to upgrade select products from 2004.0 to 2004.1.
Only 2004.1 will be installed after using the Patch DVD.
These products that can be upgraded from 2004 to 2004.1 are
Aspen HTFS (ACOL, APLE, FRAN, FIHR, MUSE, PIPE, TASC, TICP)
Aspen OnLine
Aspen Process Tools
Aspen Utilities
Aspen... |
Problem Statement: Is it possible to print out a matrix of NRTL parameters, showing which binaries have data, which are estimated, etc.? | Solution: Yes. It is possible to view the status of any pure or binary parameter. This is a very handy way to visualize the data that is available for the components.
After doing a Tools/Retrieve Parameter Results,
toggle to Status from Parameters View on one of the Properties/Parameters/Results forms. For NRTL go to t... |
Problem Statement: You have all the feed stream information in conc-mass at 25 C, as this is what is measured in the laboratories, but is of course not the actual stream inlet temperature.
To give the flowsheet on to normal users, you need to define a new feed stream input form. | Solution: On the Stream Input Specifications form, Click the Ref Temperature button to set a different reference temperature for volume flows and/or volume-based composition specifications.
By default Standard liquid volume is defined at 1 atmosphere and defaults to 60°F and the concentrations are at the stream temper... |
Problem Statement: Is it possible to link a personal library file with Aspen Plus? These can be commercial libraries such as Microsoft Access or IMSL or personal libraries. | Solution: To do this for an individual run, the key is to specify the user libraries in the Dynamic Linking Options (DLOPT) files.
To do this, place the object files and the library files in a specific directory and specify that directory in the DLOPT file so Aspen Plus uses those files when it does the linking upon ex... |
Problem Statement: The binary analysis procedure allows to generate all the diagrams for a VLE from an existing model. How can I execute similar calculations for the liquid-liquid equilibrium? | Solution: The binary analysis tool can also generate the VLLE equilibrium diagram. The horizontal line on the the bubble curve is a clear sign that the system forms two liquid phases. Compositions for which the buble curve is horizontal will form 2 liquid phases when the system temperature is lower than the bubble temp... |
Problem Statement: In Aspen Plus 10, one sometimes encounters the following problem when running a simulation with a flowsheet-level design specification that uses Fortran code:
*** SEVERE ERROR
ERROR DURING DYNAMIC LINK OF USER ROUTINE(S) OR IN-LINE FORTRAN
PLEASE CHECK FILE _0556adg.LD FOR LINKER MESSAG... | Solution: The cause of this error message is a non-interpretable Fortran command on the Design Spec Fortran Sheet. When Aspen Plus encounters a design specification which uses a Fortran statement that can not be interpreted, it creates a temporary Fortran file that contains a subroutine with the name ZZSPCS. This subro... |
Problem Statement: When upgrading some Aspen Engineering Suite clients to AES 11.1, is it necessary to keep a previous versions of the License Manager or will the latest version will be able to provide keys to all versions of Aspen Engineering Suite. | Solution: Yes, if you are going to used Aspen Engineering Suite 11.1 and earlier versions at the same time, you need to have the new FLEXlm License Manager running along with the earlier version of License Manager.
Keywords: FlexLM,
LM3
LM2.2
AES 11.1
References: None |
Problem Statement: System does not allow the user to Install/Reinstall AES 10.2 on a drive other than C: or D: | Solution: This problem occurs after an incomplete install or an improper uninstall of AES elements. To solve this problem, modify the registry and remove the Setup entry.
Remove the setup entry from the following location
HKEY_LOCAL_MACHINE\SOFTWARE\AspenTech\Setup
To modify the registry:
1 - From the Windows Start men... |
Problem Statement: What does Aspen Plus do to estimate the binary interaction parameters for Wilson, Renon (NRTL) and UNIQUAC activity coefficient models? Which estimation methods are recommended? | Solution: Aspen Plus can estimate binary interaction parameters for Wilson, Renon (NRTL) and UNIQUAC activity coefficient models based on
experimental data for activity coefficients at infinite dilution (data type: GAMINF)
activity coefficients at infinite dilution estimated from UNIFAC.
Using UNIFAC means that the str... |
Problem Statement: What is the Overall Section Efficiency that has to be specified in a tray rating calculation on the RadFrac / Tray Rating / Design/Pdrop sheet and how is it used? | Solution: The Overall Section Efficiency in the rating section of a RadFrac column on the Design/Pdrop sheet does not have anything to do with the separation calculation of RadFrac. This efficiency value is used solely for the rating calculation. For example, a column of 20 trays where the 20 trays are equivalent to 10... |
Problem Statement: How I can I access the Title of the simulation inside a Fortran block? | Solution: The Title of the simulation as specified on the Setup / Specifications / Global sheet is not accessible using standard, publicly documented calls to AspenPlus internals. It is possible to access this information only by using undocumented AspenPlus features; this means that this workaround may be unsupported ... |
Problem Statement: How do I address a situation where one of the reactants is in the vapor phase? For example:
A + H2 <-> B where H2 is hydrogen
Keq = [B]/[A][H2]
where [H2] is the partial pressure of H2 over the mixture.
Aspen does not allow a reaction in both liquid and vapor phase, how does one address the hydroge... | Solution: The way that Aspen Plus defines a reaction, it can only be in one phase. For a reaction such as A + H2 <-> B, it must be defined as either in the liquid phase OR the vapor phase. The concentrations used in the rate expression are the concentrations in that specified phase. For example, if the reaction is spec... |
Problem Statement: Flowsheet as Wallpaper option does not persist when opening a new flowsheet.
Wordaround:
With the AES 10.2 Service Pack 1, the setting of Flowsheet as Wallpaper has been made persistent. Thus, if users change this setting - it will come up as desired on the next launch of the program.
To apply the A... | Solution: Display_view.cgi?key=104681
Alternatively install Aspen Engineering Suite 10.2 Update1 for Aspen Plus. Update1 is available on CD from the end of February 2001.
Fixed in Version:
Aspen Plus 10.2 Service Pack 1
Keywords:
References: None |
Problem Statement: Aspen Plus gives the following warning during the input translation:
WARNING IN PHYSICAL PROPERTY SYSTEM ABSOLUTE VALUE OF LN(TAU) IS EXCEPTIONALLY LARGE FOR DATASET 1 COMPONENTS ANILINE AND H2O IN THE WILSON MODEL. THIS MAY CAUSE COMPUTATIONAL DIFFICULTIES. | Solution: This message warned the user that the value of ln(tau) might affect the convergence. When ln(tau) is large, the activity coefficient value will also be large, and large activity coefficients can indicate that two liquid phases are present.
The following is a part of a report file that had been generated for a... |
Problem Statement: An Excel VBA interface written for older versions of Aspen Plus may not function correctly (including crashes), when used with newer Aspen Plus versions. | Solution: On the TOOLS | REFERENCES menu in the Visual Basic editor (VBE), the referenced type library will be for the older version of Aspen Plus. It is a good idea to check the referenced type library in the VBE and search for an Aspen Plus GUI Type library that is consistent with the currently used version of Aspen ... |
Problem Statement: Is there a way that I can tell the simulation to stop when the a block fails to converge? | Solution: Use Stop Points (select Stop Points from the Run menu).
In this dialog box, you can set a stop point after a particular block, but you can also say to stop after an error or warning. You can have any number of Stop Points. When you run, the simulation stops when it hits the stop point. You can click on the ru... |
Problem Statement: Lite Client users cannot access online help or cannot access the search tab of the online help. Errors occur such as the file apwn.cnt could not be opened when opening help or when opening the Search tab of the help.
Cause:
This occurs when Windows Help finds index files in the directory where help ... | Solution: Solution 1: Delete all .gid, .fts, and .ftg files from the file server directories where help is installed in the affected programs (such as gui\xeq in an Aspen Plus installation). Ensure that all users use the same drive letter for the share. This may require lite-client-side reconfiguration or reinstallatio... |
Problem Statement: The Outlet Temperature is same as first stage cooler on a multistage compressor (MCompr). How are intercoolers specified? | Solution: Cooler specifications are made on the MCompr / Setup / Cooler sheet.
If you do not specify coolers for all stages, the missing specifications default to the values for the previous stage cooler. A specification for stage 1 is required.
If no aftercooler is present, enter Duty=0 for the final stage.
You can us... |
Problem Statement: How do I access pseudocomponents in reactions, Des-Specs, Sensitivities, etc.? | Solution: An easy way to access properties of pseudocomponents generated from ADA is by doing the following:
Create a PC-CALC paragraph. In the Aspen Plus Graphical User Interface create an item under the Components / PetroCharacterization / Generation folder.
On the Components / PetroCharacterization / Generation / N... |
Problem Statement: What's the default | Solution: RStoic calculates the heat of reaction from the heats of formation in the databanks when you select the Calculate
Heat of Reaction option on the Setup | Heat of Reaction sheet. The heats of reaction are calculated at the specified
reference conditions based on consumption of a unit mole or mass of the referen... |
Problem Statement: How is it possible to specify the flowrate so that a stream is at saturation?
One example where this is needed is a system with steam generators, where there is a heater which receives a duty from the furnace, and the vapor fraction of the outlet is 1. The water flowrate is unknown and needs to be va... | Solution: One approach is to specify a vapor fraction with a value of 0.999 instead of 1, and use the bracket option (yes or Check bounds) in the Secant options (under Convergence, Conv Options, Methods, Secant).
Another approach is to specify the temperature, to a value larger than the saturation temperature.
However,... |
Problem Statement: 2 phase pipe output -- 6 pipe giving larger pressure drop than a 4 pipe | Solution: The results show the reason that the 6 pipe has a greater pressure drop. It is because the dominant component of the pressure drop is the elevational component. The frictional component for the 4 pipe is actually larger than for the 6 pipe. The elevational component for the 4 pipe is much less than for the 6 ... |
Problem Statement: It is possible to create a simulation that uses a Calculator (or FORTRAN) block with FORTRAN to populate a Common block, and then have this Common block accessed in a User2 block. This simulation passes the data as expected when the User2 subroutine is compiled as an object file(*.obj); however, it d... | Solution: The reason sharing COMMON /USRRI1/ works with *.obj is because the FORTRAN code from the calculator and usr2.f are linked together in the default problem DLL so they use the same COMMON.
However, when the Calculator and USR2.F are linked into separate DLLs (the user defined dll for USR2 and the default probid... |
Problem Statement: How to have Heat and Work input streams connected to a USER2 Excel model? The example provided in the Getting Started Guide 'Customizing Unit Operation Models', only material streams are passed to the Excel stream table. | Solution: Modify the USRXLS.F routine such that heat and work streams are passed in the stream table created in Excel. The USRXLS.F routine should be modified such that information streams are also transferred to Excel.
This routine is described in the Aspen Plus User Models
Keywords: USER2
Excel
Heat Work stream
usrxl... |
Problem Statement: The temperature of the liquid leaving the column if the thermosyphon is selected with above-stage return convention is higher than the bubble temperature of the stream. How is it possible that a liquid is at a temperature above its bubble point? | Solution: When the above-stage option is used, the liquid from stage above the reboiler (in this case stage 9) is not flashed at the bottom stage or sump (stage 10). It is taken through a pumparound where it is flashed at a specified vapor fraction (VFRAC). The liquid from the pumparound flash is fed back to bottom sta... |
Problem Statement: How do I enter the component structure into ASPEN PLUS so that property estimation (PCES) will estimate the missing properties parameters? | Solution: The procedure is as follows:
Sketch the structure of the molecule on paper.
Assign a number to each atom, omitting hydrogen. The numbers must be consecutive, starting from 1.
From the Forms pulldown menu, select Properties, then Molec-Struct.
Select a component ID for which you want to specify the molecula... |
Problem Statement: Will older Aspen Plus versions operate in the new millenium (beyond year 2000)? | Solution: Aspen Plus 10.x was certified Y2K compliant.
Aspen Plus 9.3x, is not Y2K certified; however, we do not anticipate problems that would prevent operation after 12/31/99. Since we have not tested the 9.3x version, we can not make commitments as to it not encountering Y2K problems.
Aspen Plus 9.2 and earlier WILL... |
Problem Statement: When using the RK-SOAVE Property method, different results can be obtained when tabulating Thermal Conductivity for a stream that contains only one component using the K (pure component) and KMX (mixture) Properties. | Solution: The difference found is due to the routes used to calculate KVMX and KV by RK-SOAVE. The default route for KVMX is the Wasiljewa-Mason-Saxena model instead of Stiel-Thodos, which is used for the pure component KV calculation.
The Wasiljewa-Mason-Saxena model is designed for low pressures and does not include ... |
Problem Statement: What properties should be used for Glycol dehydration? | Solution: AspenTech introduced a new data package for Glycol Dehydration in Aspen Plus 9.3. This data package can be used to model natural gas dehydration processes using glycols (Ethylene glycol (EG): C2H6O2, Diethylene glycol (DEG): C4H10O3 or Tri-ethylene glycol (TEG): C6H14O4).
The data package uses the SR-Polar eq... |
Problem Statement: What is the difference between the different property files that can be select on the Report Options form? | Solution: On the Setup / Report Options / Property sheet, there are four additional files that can be generated during a simulation. These are all text files that are generated during report writing.
The four types are listed below:
DFMS format input file (.DFM) - This file contains property parameter results of PCES a... |
Problem Statement: How is surface tension for a supercritical component calculated? | Solution: The reduced Temperature (Tr) is set to 0.999 is for the pure supercritical (Henry) components. Aspen Plus calculates and uses the pure component surface tension of the supercritical species at Tr=0.999 even if Tr(pure component) is actually greater than 1. Then, the pure component surface tensions are mole-fr... |
Problem Statement: On Windows NT 4.0 (with SP5), users may be prompted with a Wrong Volume error while installing AES 11.1 applications on AES 11.1 CD2. If the user puts back the AES 11.1 CD1 into the CDROM, then the system will ask for CD2. This cycle can continue for a few times and eventually crashes the AES 11.1 in... | Solution: The currentSolution is to upgrade to Windows NT 4.0 Service Pack 6 before installing AES 11.1.
Keywords: AES 11.1 applications,
Windows NT 4.0 w/ SP5
References: None |
Problem Statement: What is the difference between backup and document (.apw) files in Aspen Plus 10 or quick restart (.iwb and .iwd) files in Aspen Plus 9? The backup file evidently contains results, so why are they not used to initialise the subsequent run? | Solution: There are several important differences between the two file types:
The document or quick restart files are much larger.
The document or quick restart files are binary files, whereas backup files are ASCII files. This means that the document or quick restart files are not compatible between different platfor... |
Problem Statement: MHeatX won''t solve in Equation-Oriented (EO) mode | Solution: For Equation-Oriented mode, MHeatX only works in perturbation mode for version 2004.1 and earlier. An EO version of MHeatX will be added for version 2006.
Keywords: mheatx
References: None |
Problem Statement: Are UNC (Universal naming Convention) Paths supported?
Wordaround:
With the AES 10.2 Service Pack 1, several of the Aspen Plus utilities have been modified to accept UNC path names of the type \\servername\sharename rather than requiring mapping the foreign drive to a local drive. Among those featur... | Solution: Display_view.cgi?key=104681
Alternatively install Aspen Engineering Suite 10.2 Update1 for Aspen Plus. Update1 is available on CD from the end of February 2001.
Fixed in Version:
Aspen Plus 10.2 Service Pack 1
Keywords:
References: None |
Problem Statement: What is the composition of the column products for binary distillation with an azeotropic point? | Solution: An azeotropic point restricts the separation in distillation. For a binary system, it is not possible use a single column to obtain a composition of the product if it is separated from feed composition by the azeotropic point.
There are two possible outcomes:
For a minimum azeotrope system, the top product is... |
Problem Statement: When a user double clicks on Aspen Plus Output Files, Notepad is executed and the file is opened for examination and editing. Is it possible to change the default for opening Aspen Plus files from Notepad to Winword. | Solution: There are two possible approaches.
In Windows XP or 2000 you can click on the Right Mouse Button (RMB) on the file name and select Open With. This will provide the option to open the output file with what ever application you wish.
Open any folder. Select Tools/Folder Option/File Types . Under Registered fil... |
Problem Statement: When VBA/ActiveX retrieves a value from Aspen Plus, how do you know which dimensional units are being used?
Is it possible to convert that value to another dimensional unit with VBA Code? | Solution: Yes - VBA can both retrieve a value with its current dimensional units AND it can change that value to reflect a different set of dimensional units.
The code to check the dimensional units for the currently retrieved value is very similar in syntax to the code to retrieve the value. For example, to retrieve t... |
Problem Statement: What do the numerical values for Flow regime in Sensitivity for a Pipe block mean?
Flow regime in and out of the Pipe can be tabulated in a Sensitivity, but the results are numerical values instead of the descriptive words that are in the Pipe block Results / Streams sheet. | Solution: The values correspond to the regimes in the following list:
Value
Regime
1
SEGREGATED
2
DISTRIBUTED
3
STRATIFIED
4
SLUG
5
MIST
6
BUBBLE
7
INTERMITTENT
8
TRANSITION
9
ANNULAR
10
ALL LIQUID
11
ALL VAPOR
12
UNDEFINED
13
HEADING
14
WAVE
15
DISP. BUBBLY
16
MISSING
Keywords: PIPE
References: None |
Problem Statement: Why won't D86, TBP and other curves print in the stream results for certain streams such as column overhead liquid streams? | Solution: Aspen Plus automatically suppresses the distillation curves for streams that are too light. In particular,the distillation curve generation for a stream depends on the composition and requires 4 components with significant molefraction (>1e-2) in the stream. Otherwise the values are set to missing. Also, ther... |
Problem Statement: Which Physical Property method best predicts the process of quenching hot air with water? | Solution: We recommend that you use the Ideal physical property method for low pressures (less than 5 bar), and treat Nitrogen and Oxygen as Henry's components.
For higher temperatures and pressure that approach the critical temperature of water, use an equation of state option set, such as SR-POLAR or PSRK.
The steam ... |
Problem Statement: Can the reporting order of streams be specified by the user? | Solution: The stream summary can be viewed in three ways:
Graphical User Interface (GUI) - window display under Results Summary\Streams in the data browser
The streams reported in the Graphical User Interface are in alphanumerical order, by default. The user can rearrange the order after the summary is generated. Howev... |
Problem Statement: A recent article, An Industrial design/control Study for the Vinyl Acetate Monomer Process by M. Luyben and B. Tyreus in Computers in Chemical Engineering (Vol. 22, No. 7-8, pp. 867-877, 1998) provides a web address for a complete model for vinyl acetate on our website. Users try to down load the mod... | Solution: This dynamic model is not available from AspenTech. Â Unfortunately, Aspen Technology could not get the information to the magazine in time to remove it from the article and the website information before it was printed. Â
We apologize for the inconvenience.
Â
Keywords:
References: None |
Problem Statement: How is RCSTR (CSTR reactor block) converged and how can convergence be improved? | Solution: RCSTR uses a trial-and-error algorithm to solve conservation equations for energy, component mole flows, and some component attributes.
Basic Algorithm:
Initialization
Set initial values and scaling factors
Residence Time Loop
Vary volume to match specified residence time
Energy Balance Loop
Vary temperature... |
Problem Statement: Aspen Plus stores Barin parameters for pure components in the pure component INORGANIC databank. But when does Aspen Plus use BARIN equations since BARIN method is not one of the physical property methods that user can explicitly select? | Solution: Barin equations are documented in the Aspen Plus Physical Property Methods and Models manual. One can also use the on-line help in Aspen Plus to find it. Basically, the method treats H, G, and S simple functions of heat capacity and calculates them from the Barin heat capacity (Cp) model. Therefore, the so-ca... |
Problem Statement: I have a pipeline with several turns feeding into a pump. We need to determine the pressure drop across each section of pipe and determine where cavitation is prone to start. Can I just use one pipe and input all the 90 deg. elbows, or should I use a separate pipe for each of them? | Solution: When modeling a pipe with elbows we calculate the total L/D for the elbows and add that to increase the length of the pipe. There’s no way to know the position of the elbows. It is more accurate to model it as individual lengths of pipe with other pipe models of 0 length to model the elbows.
Keywords: None
... |
Problem Statement: How is the holdup for the rate-controlled reactions in the RadFrac model defined ? If we specify it on a segment base, the number to enter is the total segment holdup or the holdup in each stage within that segment? | Solution: The holdup specification is per stage even if you specify on a segment base. The segment is just a group of stages each with the same holdups. Instead of entering the same number for each stage, you can enter it just for the segment.
Keywords: reactive distillation residence time
References: None |
Problem Statement: Aspen Plus uses 298 K and 1 atm for the constituent elements as an ideal gas as the reference state. This is why most reported enthalpies are negative. Other sources may use a reference state of 60F and 1 atm, and typically report positive enthalpies.
To get the enthalpy in the steam tables reference... | Solution: You cannot change the way that Aspen Plus does its calculations; however, it is possible to add a new way of reporting enthalpy of a mixture using a User Property.
Included in this document is a way to report enthalpy of a mixture using a User Property set. The Fortran subroutine and an example input file are... |
Problem Statement: How are Evaluation runs used in Data Regression? | Solution: Using the data regression tool in Aspen Plus/Aspen Properties, evaluation runs can produce different results depending on what you defined to be the goal of the evaluation.
There are two types of evaluation runs:
Evaluation runs to test the thermodynamic consistency of binary VLE data.
If the checkbox to requ... |
Problem Statement: Using Data-Fit Capabilities in Conjunction with Reactors | Solution: Data Fit was one of the new features in Aspen Plus 9. Users can use this feature to fit Aspen Plus models to plant and/or laboratory data. This capability extends to ALL of the reactors available within Aspen Plus.
A few points about Data-Fit :
It uses the maximum likelihood approach.
It permits users to fit ... |
Problem Statement: Is the VBA code written to automate Aspen Plus runs from MS Excel compatible with future version of Aspen Plus and MS Excel? | Solution: For version 11.1 and later, few compatibility issues have been reported. The most common issue is the class HAPP library class used to globally and publicly define the Aspen Plus object in MODULE1. Many of our old examples have the following line of code to globaly define go_Simulation as the object/applicati... |
Problem Statement: How do I regress the coefficients for the Henry's constant correlation? | Solution: Either solubility data or Henry Coefficient vs. Temperature data can be used.
Solubility data is entered as a data type of TPXY. This data can be used to regress the Henry's constants, or it can be used to regress binary interaction parameters.
For data sets with Henry components, typically, the experimental ... |
Problem Statement: I have a question in relation to the PSRK method and why are the results obtained with this method so different from the results obtained with the SRK or UNIFAC methods, even at low pressures.
Why is there a big difference in the actual volume (calculated at 60 F and 1 atm) and the standard liquid vo... | Solution: Equation of State (EOS) model generally do a poor job of predicting liquid density. The result is that the actual liquid volume may have a large error when calculated using a standard cubic EOS such as RK-SOAVE, PENG-ROB, or PSRK. In Aspen Plus, the route for calculating liquid molar volume has been replaced ... |
Problem Statement: User wants to model a fed batch operation where he feeds continuously for a time of 1 hout but then lets the reaction continue without a feed.
Can this be done playing with Batch Feed Time and Total Cycle Time? | Solution: Batch Feed Time or Total Cycle Time (only one can be specified) is used to determine the amount of material transferred to the reactor at the start of the reactor cycle.
Amount of charge = Charge stream flowrate * Batch Feed Time or Total Cycle Time
Multilpe feeds are allowed - one batch charge and any number... |
Problem Statement: How does one set the flow rate of a recirculation loop between different unit operation blocks, for example, the absorption fluid rate in an absorber-stripper process? | Solution: Often in a simulation model, one needs to set the recirculation flow between different unit operation blocks. A typical example is an absorber-stripper process where the recycle absorption fluid to the absorber needs to be maintained at a specified value. A simple flowheet of this situation is...
In this exa... |
Problem Statement: For a vapor-liquid-liquid phase equilibrium (VLLE) of a organic/aqueous mixture I wish to generate a complete T-xxy phase diagram. The binary analysis plot only displays the vapor-liquid equilibrium (VLE) and does not depict the liquid-liquid phase equilibrium (LLE) curves on either side (aqueous pha... | Solution: The plot wizard currently provides templates for T- xy and T- xx figures but not for a combined plot. However, to combine both plot types, you can simply add the T- xx curves to an existing T- xy plot. Here is how to add the T- xx curves to a standard T- xy plot:
1. Open the attached file.
2. Open... |
Problem Statement: How to plot a ternary diagram in Aspen Plus ? | Solution: 1 - One possibility is to use Aspen Split through the Aspen Plus GUI by going to Tools --> Conceptual Design --> Ternary Maps. Select the ternary mixture and the pressure and then go to Ternary Plot. (In order to use Aspen Split, you need a valid license.)
2 - In Aspen Plus 2006.5 and higher, you can use the ... |
Problem Statement: This example shows how to implement a discrete controller with a procedure.
Extract the files from the archive (zip) file
Copy the control.dll in a folder listed in your PATH (alternatively, enter the path in the procedure definition)
Open the file ext.acmf
Open the flowsheet plot vars
Open the AllVa... | Solution: See the attached zip file
Keywords: SAX
References: None |
Problem Statement: Assays entered are not shown in the stream input form. Is this a bug? How to fix it? | Solution: This is not a bug. In Aspen Plus, an assay may or may not show on the stream input form, depending on whether the pseudocomponent Generation is specified manually by the user.
If Generation (under Components\Petro Characterization\) is not specified, all assays entered in the Assay/Blend form (under Component... |
Problem Statement: Can an Aspen Plus block specification be deleted by a Visual Basic Application? | Solution: Visual Basic applications or Visual Basic for Applications with Excel (Excel/VBA) can change Aspen Plus block specifications using the Happ ActiveX interface. This interface is documented in Chapter 38 of the Aspen Plus User Guide.
Normally, these applications are used to retrieve block results. Input specifi... |
Problem Statement: Sometimes the Aspen Plus reports are too large to display in the graphical user interface's default text editor (Notepad). When printing the reports from Notepad, the hard coded page breaks are ignored resulting in improperly paginated printed reports. Is thIs there a way to use a different text edit... | Solution: Yes, this attribute can be changed by clicking on the TOOLS pull-down menu, click on OPTIONS, then click on the STARTUP tab or sheet:
Here it is possible to alternate text editors (you are not limited to just WordPad or Microsoft Word).
For example,
WordPad:
C:\Program Files\Windows NT\Accessories\wordpad.exe... |
Problem Statement: When trying to create a Calculator block, using an Excel Spreadsheet (instead of Fortran), an error occurs after clicking on the OPEN EXCEL SPREADSHEET button. The error states The CalcExcelAddin Addin is not installed. [A copy of the exact error message is available in the attached files]. The error... | Solution: Display_view.cgi?key=104681
Alternatively install Aspen Engineering Suite 10.2 Update1 for Aspen Plus. Update1 is available on CD from the end of February 2001.
Keywords: Calculator Block, Excel, Addin, Add-Ins,
References: None |
Problem Statement: When using the Wilson Property Method, there is a warning:
Warning in Physical Property system during Calculations Absolute Value of LN (TAU) is exceptionally large for Dataset 1 Components Aniline and Water in the Wilson Model . This may cause computational difficulties.
What is meant by exceptional... | Solution: This message occurs with the default Wilson parameters. When ln(Tau) (aij + bij/T + cij lnT +dij T + eij/T^2) is large, the activity coefficient can be large (but not necessarily). In other property methods such as NRTL or UNIQUAC, large values for the activity coefficient, gamma, can cause liquid-liquid equi... |
Problem Statement: Is there a way to quickly generate and plot vapor pressure (PL) curve for a pure component when an Equation of State (EOS) property method is used? When you choose analysis from the tools menu, it does not allow plotting of PL if an EOS property method is selected. | Solution: It is possible to generate vapor pressure curve using Binary analysis from the Tools menu (Tools -> Analysis -> Property -> Binary) as described below:
1. Choose either Txy or Pxy. Select Pxy if you wish to enter a list of temperature where you want the vapor pressure calculated. Select Txy if you wish ... |
Problem Statement: How can I tabulate or plot vapor pressure (PL) for a pure component using an equation of state (EOS)? When I choose analysis from the tools menu, it does not allow plotting PL if I am using an EOS. | Solution: In version 2006 and higher, it is possible to choose PL in the Tools -> Analysis -> Property -> Pure dialog for an EOS property method; however, this option was not allowed in earlier versions. One work around was to use Binary analysis as described inSolution 106281.
Another method is to make these tables us... |
Problem Statement: It is possible to create a simulation that uses a Calculator (or FORTRAN) block with FORTRAN to populate a Common block, and then have this Common block accessed in a User2 block. This simulation passes the data as expected when the User2 subroutine is compiled as an object file(*.obj); however, it d... | Solution: The reason sharing COMMON /USRRI1/ works with *.obj is because the FORTRAN code from the calculator and usr2.f are linked together in the default problem DLL so they use the same COMMON.
However, when the Calculator and USR2.F are linked into separate DLLs (the user defined dll for USR2 and the default probid... |
Problem Statement: How to User Sequence blocks within a Hierarchy in a flowsheet. | Solution: To User Sequence the blocks within a Hierarchy in a flowsheet requires the CONNECTIONS that are created IN and OUT of the Hierarchy block to be sequenced along with each individual block within the Hierarchy itself. In the Data/Convergence/Sequence/Specification sheet, select Connection as the block type and ... |
Problem Statement: Under Windows 95/98, there is no Find tab on the on-line help. Text find function for on-line help is very useful. | Solution: To use the Find function under Windows 95/98, you need to install ftsrch.dll in your system directory.
The ftsrch.dll is located on the Windows 95 install CD (There is no ftsrch.dll in the Windows 98 install CD) inside win95_**.cab. Win95_**.cab is an archive file; therefore, some unzip program is needed to e... |
Problem Statement: How is the heat of absorption calculated in Aspen Plus? | Solution: Looking at absorption processes, we have to distinguish two processes: Physical and chemical absorption.
Physical absorption, e.g. oxygen in water:
O2 (g) ---> O2 (aq)
The heat of absorption can be obtained from the derivative of the Henry's constant:
d ln(H)/d(1/T) = delta_h_abs/R
where the enthalpy of absor... |
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