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Problem Statement: What are the assumptions for the heat of combustion parameter HCOM, which is used for reporting the net and gross heating values of streams (QVALNET and QVALGRS property sets)? | Solution: HCOM assumes that the products are CO2(g), H2O(g), F2(g), Cl2(g), Br2(g), I2(g), SO2(g), N2(g), P4O10(Cr), SiO2(crystobalite) and Al2O3(crystal, alpha). This cannot be changed.
Note that HCOM is a parameter and is not calculated from DHFORM and the chemical formula of the component by Aspen Plus. When the p... |
Problem Statement: Can polymer reactors run in equation oriented (EO) mode? | Solution: One can easily see if the polymers feature is supported in Equation Oriented (EO) by running the simulation in Aspen Plus and then switch to EO mode. If you get an error message or a message saying the perturbation layer is used, it means there is no full support of EO. The perturbation layer can be used for ... |
Problem Statement: Is it possible to make Binary Analysis plots for electrolyte systems? The binary plots for the binary TXY analysis look proper, but the True component plots do not. | Solution: Binary Analysis plots can be completed using the Apparent electrolyte approach. The results are not valid using the True approach since the vapor and liquid compositions are on different bases and involve the concentrations of more (i.e., true) components.
The valid composition range for the electrolyte param... |
Problem Statement: Is it possible to hide and reveal design specs via the VBA automation tool? | Solution: To hide a design spec:
Dim spec As IHNode
Set go_Simulation = GetObject(~:\.............bkp)
Set spec = go_Simulation.Application.Tree.Data.Elements(Flowsheeting Options).Elements(Design-Spec)
spec.hide (DS-1)
and to reveal the design spec:
spec.reveal (DS-1)
Keywords: Design-spec
hide
re... |
Problem Statement: How can I write volume flow to a feed stream from a Calculator block? | Solution: The calculator block only allows standard volume flow (STDVOL_FLOW) as the volumetric flow variable reference for the stream even though stream inputs accept actual flow. A workaround for this would be to calculate the required volumetric flowrate, multiply the volumetric flow with the mass density of the str... |
Problem Statement: The AES 12.1 products worked fine until installing products from the aspenONE discs. Products that were running now suddenly return license errors. | Solution: SLM supports license grouped into buckets. For 12.1, the SLM would automatically search the SLM Server for all buckets, but for 2004, the SLM must be configured to look for other buckets than the default bucket. This was done in order to add support for checking out a license from specific buckets instead of ... |
Problem Statement: How do you write messages to the Control Panel in Aspen Plus from a Presolve script in an exported Aspen Custom Modeler model? | Solution: Use Application.Msg in the script code as in the example below to see message printed in the Control Panel when running the model in Aspen Plus:
if SMStatus = Not solved then
Application.msg Running Presolve script
...
end if
This will print the message
Running Presolve script
in the Aspen Plus... |
Problem Statement: How does the design-spec (and other in-line Fortran objects) handle the division of integer quotients? | Solution: Sometimes it is easier for users to specify an integer quotient, say 111/ 555 instead of 0.2 for a spec value. Both Fortran and C++ interpret an integer quotient (integer numerator divided an integer denominator) as an integer division. When integer division is performed for 111/555, the result is 0.
To ensur... |
Problem Statement: What is the pressure-drop correlation parameter that can be specified for a Heater? | Solution: In Aspen Plus 11.1 and higher, there is an option of Pressure-drop correlation parameter for a Heater specification. If this option is selected, users must enter a pressure-drop correlation parameter (k) that is then used to calculate the pressure drop (DP) using a flow-dependent correlation.
The correlation ... |
Problem Statement: When should I use the Pipe or Pipeline unit operation in Aspen Plus? | Solution: Pipe or Pipeline calculates the pressure drop in a pipe.
Pipeline
When you use Pipeline Operation, you can add one or more segments in the same block.
In order to add one or more segments, you have to go to Setup - Connectivity; when you click on button New, a window about a new segment opens. You have to... |
Problem Statement: What are the units of measurement on the estimation forms?
On the Properties/Estimation/Input/Binary sheet, temperature at which to estimate the binary parameters can be specified. Are the units in SI or are they the Global units-set? | Solution: Temperatures are in units from the units set selected in the tool bar of this form. The Estimation form has its own unit setting; however in version V7.1 and earlier, the unit set does not show in the tool bar. It is set as global unit when the node is created. If global unit is changed after the simulation i... |
Problem Statement: How can I enter a component viscosity in Aspen Plus that is not temperature dependant? | Solution: For Property methods using the Andrade viscosity model, the second and third Andrade elements/terms can be omitted to specify a non-temperature dependant liquid viscosity. The equation then reduces to ln (visc) = A where A is the first term to be specified on the Andrade form.
Keywords: viscosity, mu, T-depen... |
Problem Statement: What is the Plex? | Solution: Plex comes from the Greek word Plexus (plek'sus) meaning an interwoven combination of parts or elements in a structure or system. The term Plex actually refers to the linked list data structure but we use it to mean the data area that is used to hold this plex data structure.
Plex in Aspen Plus is a large mem... |
Problem Statement: If you select in the property set VOLFLMX you are not allowed to specify a pressure and temperature on the Qualifiers tab. If you select VMX you are allowed to. However, it is not obvious where this difference comes from and it is not documented in the on-line help why you can not specify a temperatu... | Solution: VMX is the molar volume of a mixture; it is based on a stream, but if temperature & pressure are specified, it only uses the stream as a source for composition data.
VOLFLMX is volumetric flow rate of a stream, because there is no flow rate without using the stream itself. These stream properties are alwa... |
Problem Statement: The CAPE OPEN unit model MixNSplit example delivered in version 11.1 of Aspen Plus does not work with Aspen Plus 12.1. | Solution: The problem is that the Material Object was improved in version 12.1 so that it properly respected the use of the basis qualifier in GetProp and SetProp calls. This was done to resolve the problem that values of Enthalpy returned from getProp were the same whether basis was specified as mass or mole.
The MixN... |
Problem Statement: When using Unifac-HOC to handle carboxylic acid (acetic acid, acrylic acid, etc), how does HOC calculate the density of vapor phase. Is the dimer Molecular Weighgt (MW) used or just the component MW? | Solution: Hayden-OConnell (HOC) calculates the vapor volume using the true number of species (i.e., after dimerization). Thus the true molar volume is V/Nt, where V is the vapor volume and Nt is the true or actual number of moles.
However, Aspen Plus does not report this true molar volume. It reports the apparent molar... |
Problem Statement: When I click on the Blocks folder, why is the Reconcile option not available to reconcile all blocks? | Solution: It is possible to right mouse click on the Blocks folder in the Data Browser, and choose Reconcile to reconcile all block input similar to the way that all stream input can be reconciled by right mouse clicking on the streams folder.
There are a number of possible reasons that the option is not available:
Res... |
Problem Statement: Is is possible to retrieve the completion status for the simulation or individual nodes inside the Aspen Plus simulation? | Solution: Basically, the completion status is retrieved by adding the AttributeType property to the path-to-node variable with the (HAP_COMPSTATUS) constant specified as its qualifier.
For the overall simulation status:
SimStatus = go_Simulation.Tree.Data.AttributeValue(HAP_COMPSTATUS)
For an individual unit/block:
Sim... |
Problem Statement: What hydraulic correlation methods are available in the Pipe and Pipeline blocks? | Solution: The following correlations are available in the Pipe and Pipeline blocks:
Pipe orientation
Inclination
Friction factor correlations
Liquid holdup correlations
Horizontal
-2 deg to
+2 deg
Beggs and Brill (BEGGS-BRILL)
Dukler (DUKLER)
Lockhart-Martinelli (LOCK-MART)
Darcy (DARCY)
User subroutine (USER-SUBR)
Beg... |
Problem Statement: * WARNING BLOCK: HEATX CALCULATED FEED TEMPERATURE FOR THE HOT (or cold) SIDE IS INCONSISTENT WITH ITS INLET STREAM VALUE PROBABLE CAUSE: UPSTREAM BLOCK WITH DIFFERENT NPHASE OR PROP SET THE CALCULATED VALUE WILL BE USED IN BLOCK . | Solution: 1. Check valid phases at the Heatx or Heater block, the block after it and all relevant blocks. If you have two liquid phases, for example, but the valid phase is vapor-liquid, you may get this warning.
2. Tighten flash tolerance in HeatX or heater block
3. It it is withing a recycle look, tighten tear tolera... |
Problem Statement: Some utility routines are available to users writing USER2 model. Those routines are documented in the attached Word document and in the 11.1 USer Model Guide, page 5-31 | Solution: The first set of routines documented in the attached Word ddocument give the user access to INT, REAL, and CHAR arrays, the EXCEL file name, and the user subroutines named on the USER-MODELS sentence.
The second group of functions allows the user to set and get the values from the INT, REAL and CHAR arrays by... |
Problem Statement: Does Aspen Plus have built-in binary interaction parameters for vapor-liquid (VLE) and vapor-liquid-liquid equilibrium? | Solution: Aspen Plus 9.1-3 and higher have databanks with binary interaction parameters for both activity coefficient based and equation of state based property methods. After selecting the components and the property method, Aspen Plus shows the available binary parameters on the forms.
There are parameters for over 3... |
Problem Statement: The Henry's constants for HCl/Water stored in the HENRY databank give poor results when modeling an electrolyte system. | Solution: The Henry's constants for HCl/Water stored in the HENRY databank should not be used. This set of parameters is not appropriate for use in modeling this electrolyte system. The values of HCL/WATER from the HENRY databank were kept for upward compatibility.
Use ELECNRTL with chemistry to model the dissociation ... |
Problem Statement: Is it possible to fit the U value of a heat exchanger from online data? | Solution: Here is an example of using Data-Fit to determine the U value of a condenser.
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.
A few points about Data-Fit:
It uses the maximum likelihood approach.
It permits users to f... |
Problem Statement: Is it possible to install AspenTech Cumulative Hot Fixes Silently? | Solution: Download the .msp file or .exe file for the Cumulative Hot Fix from the Cumulative Hot Fix
document. For a .exe file use an extraction tool such as WinZip to extract the .msp file
from the self extracting executable.
Open a Command Prompt and type the following command line:
msiexec.exe /q /p {Full Path to ... |
Problem Statement: How to do you format the VBA code when Aspen Plus' path-to-node name contains one or more '#' symbols followed by a number? For example, what is the VBA code needed to write to a Property Analysis table's manipulated variable fields? | Solution: The path-to-node names often contain '#' symbols when the object it references is a two dimensional table. In the attached example, for Aspen Plus' Variable Explorer reveals the following dot notations for the Property Analysis table's second list value for the pressure variable:
Path-to-Node notation:
Appli... |
Problem Statement: While doing an Aspen Plus customization for Aspen Plus 11.1, I noticed that the option codes for the Hayden-O'Connell model (ESHOC and ESHOC0) for the vapor phase calculations in NRTL-HOC are now two numbers in 11.1 whereas before (i.e., in 10.2) there was only one.
What is the second number for? I h... | Solution: The 2nd option code for this model is used to control the check for the specified pressure being too high. It applies to the case without Chemical Theory (i.e., for case with Chemical Theory, this option code is not used).
The pressure limit is imposed because the model is valid at low to moderate pressures o... |
Problem Statement: How can I easily get the Stream Table results from a simulation into Excel using VBA? | Solution: The Data/Results Summary/Streams/Material sheet Stream Table can be accessed in Excel using the following simple VB code. This prints the entire stream table in Excel exactly as it would appear in Aspen Plus including the table headings.
Private Sub cmdStreamData_Click()
Dim Table As IHNode
Dim NDim As Intege... |
Problem Statement: The density as calculated by the property RHOMX (density of a mixture) for a process at 60F and atmospheric pressure, does not give the same result as the property RHOLSTD (standard liquid density for a mixture at 60F and atmospheric pressure) for the same mixture.
Both densities are calculated at th... | Solution: The property RHOMX is calculated by the property method specified on the Data/Properties/Specification/Global sheet. However, the standard density RHOLSTD is calculated from the standard mixture volume (VLSTDMX) which is simply a molar average of the pure component standard liquid volume as given by the param... |
Problem Statement: CAPE-OPEN Unit Operations implementing v1.0 of the standard are displayed for use in Aspen Plus 11.1 but will not work. | Solution: You cannot use CAPE-OPEN version 1.0 Unit Operations in Aspen Plus 11.1 because Aspen Plus 11.1 supports only versions 0.9 and 0.9.3 of the CAPE-OPEN standard.
If a CAPE-OPEN Unit Operation implementing version 1.0 of the standard is installed on your machine (for example MixNSplit 12 which is supplied with A... |
Problem Statement: Is there a way to reinitialize and re-run just one unit operation in a large flowsheet? | Solution: Yes - follow this procedure:
1) Make sure the control panel is open and in the current view. If it is not open, click on the VIEW menu and then click on CONTROL PANEL.
2) The control panel will show 2 windows, a large gray window with run time messages, and narrow white window with the calculation sequence.... |
Problem Statement: In the restricted equilibrium sheet of RGibbs, I can choose Entire System by T approach. If I do this I can then enter a value for temperature approach and select the units. However the units are confusing. Why do I have:
K
F
C
R
Delta K
Delta F
Delta C
Delta R | Solution: The units are indeed confusing. The first four units are equivalent to the following four, i.e. choosing K is the same as choosing Delta K and so forth.
Fixed in Version
Currently, there are no plans to fix this problem.
Keywords:
References: None |
Problem Statement: When accessing a property parameter such as TC or HCOM in a Calculator block, the value was different from that retrieved from the databank. The simulation is using English units. | Solution: Accessed property parameters are always in SI units even when the input and output units of the simulation are different.
Keywords: calculator
design specification, desiign spec, design-spec
sensitivity
References: None |
Problem Statement: When entering vapor pressure (PL) or ideal gas heat capacity (CPIG) data for user defined component wizard, data is not used. Only the data form is populated. What needs to be done to have this data used? | Solution: This data can be used for a simple regression of the PL or CPIG parameters using the Estimation capabilities. The data regression function can be used for a more advanced regression.
Steps:
1. Go to the Properties \ Estimation \ Input \ Setup sheet and select Estimate all missing parameters.
2. Go to the Prop... |
Problem Statement: Derivatives of properties can be calculated on molefraction basis (dx) or moleflow basis (dn). When using ELECNRTL, the values of dHMX/dx are equal to dHMX/dn. Why? | Solution: Property derivatives with ELECNRTL are calculated using numerical perturbations. The molefraction derivatives (dQ/dx) are made equal to the mole derivatives and should not be used. The mole derivatives (dQ/dn) are correct.
Keywords:
References: None |
Problem Statement: How to 'close' a recycle loop once in EO mode in Aspen Plus. | Solution: The purpose of this example is to show how to avoid a convergence loop in Sequential Modular (SM) mode, by simply leaving the recycle loop open , and then close it once in Equation-Oriented (EO) mode and eventually get the flowsheet to converge using the EO solver. It is based on the cumene.bkp simulation ava... |
Problem Statement: CAPE-OPEN blocks do not restore properly when saved to .bkp format. .apw is OK. The reason is that private CAPE-OPEN block data is only saved to .appdf files and is therefore lost when saving to .bkp. There is no warning. | Solution: When you save simulations containing CAPE-OPEN unit operation models, you must save them in .apw format to preserve the private data of the block. The .bkp format does not preserve this information. Users should save in .apw format instead. Note that when upgrading to new versions of Aspen Plus all the CAPE-O... |
Problem Statement: We are in the midst of implementing our in-house equation of state (EOS) in AspenPlus. Looking at the argument list for ESU and ESU0, I could not find anything for pressure and composition derivatives. We will be testing the new EOS model in Equation Oriented (EO) mode. Is there any reason why ESU ro... | Solution: User models cannot return pressure and composition derivatives. These derivatives will be determined automatically by numerical perturbations. Some of the built-in models (including EOS models) work this way. The analytical derivatives are obtained by using ADIFOR (automatic code generation program); they wer... |
Problem Statement: MCompr gives the following warning message in the control panel:
WARNING TWO PHASES ENTERING STAGE = 2 AND NO LIQUID SEPARATION IS SPECIFIED
How do I specify the liquid separation at a given stage of the compressor? | Solution: Each compression stage in MCompr contains a compressor operation and a cooler operation, known as an interstage cooler. The interstage coolers can perform a one, two or three phase flash calculation - valid phases are specified on the Data\Blocks\ MCompr\Setup\Convergence sheet. They are effectively a flash b... |
Problem Statement: Is it possible to enter a second set of Wilson parameters for the same binary pair in a Userpp2 databank? | Solution: You need to use two separate databanks. Then when defining your flowsheet for WILSON-1, you select one databank first and in WILSON-2, you select the other one first. You can also mix and match. It would be similar to how we have different binary databanks.
Documentation on how to create a user binary databan... |
Problem Statement: When I use the interactive binary property analysis tool, the predicted bubble point curve compares well to my reference data. The dew point curve, however, looks like it has been interpolated rather than rigorously calculated by a model. When compared to experimental dew point data, there are signif... | Solution: With [Tools/Analysis/Property/Binary... TXY] you are actually performing a bubble point calculation. In other words, the temperatures you see are bubble point temperatures.
Since phase equilibrium also includes the assumption of thermal equilibrium, these temperatures will be assigned to the predicted vapor c... |
Problem Statement: When using an Aspen Plus file with links to multiple Excel spreadsheets, is it possible to have a new identical Aspen Plus file with no links to any other Excel files? When using File/Save as in Aspen Plus, all the links go with the new Aspen Plus file. | Solution: If the linked Excel file is saved after changes are made, then the link goes with new file. If the linked file is closed, then the source file is saved under a new name, the link will remain with the original file.
In order to get a clean file without any link outside of Aspen Plus, save the current file with... |
Problem Statement: Previous versions the component Sodium Acetate as NACH3CO2. Why is it not included in the Solids databank for 2004? | Solution: In 12.2, the name of component NACH3CO2 in the Solids databank was changed to C2H3NAO2 (Sodium-Acetate) so that the same alias is used across all databanks.
Old Name New Name Alias Databank
NACH3CO2 SODIUM-ACETATE C2H3NAO2 SOLIDS
Input files that contain the old alias will be converted to use the new alia... |
Problem Statement: How do I create a custom icon? | Solution: To create a custom icon, you first need to create a model library. Then,
you can change or add new icons to better represent the equipment that the proprietary model represents.
Creating a model library allows work groups to create Model Menu tabs within the Aspen Plus User Interface for proprietary or third ... |
Problem Statement: How do you model liquid CO2? | Solution: SR-POLAR is probably the best property method to use. The RKUC0, 1, and 2 terms can be used to fit density better. The second and third volume-shifting terms can cause inconsistencies in enthalpy (isotherms may have enthalpy crosses, etc.). Just fitting the first parameter is safe, however and should give goo... |
Problem Statement: How does one create inhouse binary databanks for 12.1? | Solution: There are two types of binary databanks; the first is created through the Aspen Plus User Interface Customization DOS prompt and then accessed through the GUI at simulation time, and the second is created through DFMS and accessed through the simulation engine at simulation time. ThisSolution Document covers ... |
Problem Statement: What are the hardware and software requirements for the Aspen Plus 12.1? | Solution: Hardware and Software Systems Requirements for Aspen Plus 12.1 (and associated add-in products) are as follows:
Hardware requirements
Resource
Recommended Requirements
CPU
A PC with an Intel Pentium III 750 MHz processor.
Note: If you are purchasing a new PC, select the fastest CPU
available.
Monitor
A sup... |
Problem Statement: Is it possible to have VBA (or VB) construct an Aspen Plus flowsheet? | Solution: Yes. Please see the example files attached. The example works by opening a General With English Units template file (.APT). The VBA code then adds the component list, property method, streams and stream data, units and unit specification. Lastly, the code launches a run in the fresly created flowsheet.
Sugges... |
Problem Statement: How do I access a Block-Vec variable on the Tabulate Sheet in a sensitivity block? | Solution: If you have the variable TEMP defined as:
VECTOR-DEF TEMP PROFILE BLOCK=Block VARIABLE=TEMP SENTENCE=PROFILE
Then in the Sensitivity Tabulate sheet, the tabulated variables would be:
Column No.
Tabulated Variable or Expression
1
TEMP(1)
2
TEMP(2)
3
TEMP(3)
.
.
.
.
.
.
10
TEMP(10)
Keywords: vector
Sensitivity
... |
Problem Statement: Is it possible to set the tabulated value to missing in a sensitivity analysis block for some rows, e.g. when the result is meaningless and should not be displayed, so that plotting can be used more easily? | Solution: TheSolution is to use and tabulate a local fortran variable, which will be set to -1e35 when the value of the accessed variable should not be displayed. The value -1e35 is detected by Aspen Plus as a flag for a missing value.
See the attached example to see how this can be accomplished. The sensitivity analys... |
Problem Statement: Is it possible to define an inequality specification? For example, for centrifugal compressors it is common to have a recycle loop from the exhaust of the compressor back to the suction line, with a valve that is manipulated to control the flowrate in a way that the suction flowrate is larger than th... | Solution: One approach is to use an optimization solver. It will be necessary to define both a constraint (i.e. approach to surge > 10%) and an optimization case (i.e. to minimize the power requirement in the compressor, and satisfy the inequality constraint). See the attached file compressor-sensitivity-surge-opt.bkp.... |
Problem Statement: How does the Maximum-Likelihood algorithm for data regression work? | Solution: The Maximum-Likelihood (ML) method is a generalization of the least squares (LS) method. In LS, the measurements of independent variables are assumed to be error free. Errors in the dependent variables are minimized by adjusting one or more model parameters. While the concept of independent and dependent vari... |
Problem Statement: Is it possible to report the mass or mole flowrate of a subset of components? How about the mass or mole fractions? | Solution: One approach is to use a user property set. See the reference manual User Models for details.
Attached you will find a file groups.f which contains 3 user property subroutines and the file example.bkp which shows how this can be used.
To report the mass flowrate of a group of components, you need to:
- cr... |
Problem Statement: Is it possible to access the ambient pressure in a Fortran user subroutine or in a Calculator block? | Solution: Atmospheric pressure is not available in any of the Common block; however,
in Aspen Plus 12.1, there is a new utility subroutine to obtain the ambient pressure.
The syntax is
CALL UU_GETP_AMB (PAMB)
The return value of PAMB is in SI unit. An example of using this utility in a Calculator block is attach... |
Problem Statement: Can Aspen Plus handle the pressure relief of a liquid-only fluid?
There is an error when the fillage is above a value of 0.994:
** ERROR
INTEGRATION IS BEING DISCONTINUED BECAUSE LIQUID VOLUME IN REACTOR
IS GREATER THAN 99.5% OF REACTOR VOLUME. LIQUID VOLUME = 2.4703
REACTOR VOLUME = 2.4820 . CHECK I... | Solution: No, Aspen Plus' pressure relief feature was designed to handle either vapor-liquid or vapor only pressure relief. our pressure relief model is not designed to handle liquid-filled vessels, so we limit the liquid volume fraction to 0.995. If the vessel is liquid-filled, the pressure in the vessel is determined... |
Problem Statement: The Flexible and Predictive Equation-of-State (EOS) Property Methods can be used for mixtures of polar and non-polar components and light gases. The property methods can deal with high pressures and temperatures, mixtures close to their critical point, and liquid-liquid separation at high pressure. E... | Solution: This modification has been used successfully by existing customers. It is possible to change the GAMMA model on the Properties | Property Methods | Models sheet from PSRK UNIFAC (GMUFPSRK) method to NRTL (GMRENON) or UNIQUAC (GMUQUAC). Given the framework of these methods, any activity coefficient model can b... |
Problem Statement: The XMLSchema for Exported Aspen Plus XML Results is documented in | Solution: 114419; however, it does not give details about the definition of the variables.
What is the difference between the attributes PRES_OUT and RES_PRES etc ?
What is the difference between the attributes MOLEFLMX and RES_MOLEFLOW? The data for MOLEFLMX is written to RES_VOLFLOW and vice versa.
Most of the attr... |
Problem Statement: How does RadFrac handle inert solids? | Solution: In addition to salts which are handled using Chemistry, RadFrac can handle inert conventional (CI) and/or non-conventional (NC) solids. RadFrac handles solids only in equilibrium mode. In rate-based mode RadFrac cannot handle solids.
There are two Solids handling methods which can be specified on the RadFra... |
Problem Statement: RadFrac pack rating does not include the pressure drop for the last stage in the bottom product pressure. The update pressure profile option has been enabled. | Solution: Radfrac assumes each stage is in equilibrium - both temperature and pressure equilibrium are maintaned. Even though we know the bottom of a theoretical packed stage has to be at a higher pressure than the top of the stage, pressure equilbrium is maintained and the bottom pressure is assumed to equal the top p... |
Problem Statement: After the UNIFAC-customization (see | Solution: 102863) is completed, I can no longer calculate systems which contain light gases such as CO2. The control panel message reads:
*** SEVERE ERROR IN PHYSICAL PROPERTY SYSTEM
DORTMUND MODIFIED UNIFAC MODEL: GMUFDMD HAS MISSING PARAMETERS: GMUFDQ (DATA SET 1) MISSING FOR GROUP 3850
GMUFDR (DATA SET 1) MISSING FO... |
Problem Statement: How is the property COMB-O2 calculated?
Is it possible that Aspen Plus assumes that CO3 is an oxygen donor i.e.
CO3 ==> CO2 + O
even though this reaction does not happen in reality? | Solution: COMB-O2 is the amount of added O2 needed to combust all the C, H, S, and N (except N2) in a given material to CO2, H2O, SO2, and NO2.
Any hydrogen present in the stream is converted to water (H2O).
Any carbon present in the stream is converted to carbon-dioxide (CO2).
Any sulfur present in the stream is con... |
Problem Statement: Is it possible to handle a solid that partially dissolves in a solvent using salt formation in CHEMISTRY? | Solution: A solid partially dissolves in the aqueous phase can be modeled using CHEMISTRY.
This method was tested using some data for sucrose solubility in water found in CRC.Solution 102340 includes the sucrose example file.
1. The component is defined as two component IDs: one in the aqueous phase (type=conv) a... |
Problem Statement: The simulation results report gives a vapor fraction, but does not indicate if the basis is molar, mass or volume fraction. | Solution: The vapor fraction on the form is the MOLAR vapor fraction. In Aspen Plus, all vapor fractions are on a molar basis unless otherwise stated.
Keywords: vapour fraction
vfrac
References: None |
Problem Statement: What parameters are loaded automatically when the ElecNRTL property method is used? | Solution: The following parameters are loaded automatically from the system definition file (SDF) when the ElecNRTL property method is used. There is currently no way to change this behavior in 2006 and earlier. In 2006.5, you can uncheck the Require Engine to load parameters from databank for electrolyte method option... |
Problem Statement: Can Convergence block parameters be accessed by the DEFINE statement? User would like to be able to access the values for MAXIT, TOL, the current iteration number, and the current ERR/TOL. | Solution: This is not possible in Aspen Plus. Convergence parameters are not accessible. The semantic processing that happens during input translation evaluates inline Fortran in Calculator blocks and Design-specs before Convergence blocks are constructed; hence, there is no destination to assign the Fortran variable t... |
Problem Statement: How can electrical conductivity be calculated for stream properties? | Solution: Electrical conductivity can be entered in Properties/Prop-Sets/Properties sheet as ELECCOND. However, ELECCOND can only be used if the OLI Property Method is specified when using the OLI Interface. It is NOT part of the basic Aspen Plus. When using the OLI Property Method, a license is required along with the... |
Problem Statement: How do you make cells on user defined Visual Basic input forms disappear or reappear, depending on values in other cells? | Solution: Add in code setting MMVisible = True or False.
For example, assume there are two MMLBUText boxes MMLBUText1 and MMLBUText2 on form. Following code will make the first one appear and the second dissappear, or vice versa, dependent on whether value for Var1 = Option1 or Option2
If (Var1 = Option1) Then
... |
Problem Statement: PSANT parameters used to calculate the vapor pressure of a solid can be entered on the Properties | Parameters | T-dependent form. Are PSANT parameters used in any calculations within Aspen Plus? | Solution: PSANT is used to calculate the reference state fugacity coeff (PHIS) for a component in a solidSolution in the equilibrum reactor model RGIBBS. It is also available for use in a USER model.
Keywords: None
References: None |
Problem Statement: How do I get rid of the retrieved parameters on the input forms? | Solution: In 2004, the Clean Property Parameters feature can be accessed from the Tools menu.
This dialog box can be used to perform three functions:
1 - Clean property parameters that have been placed on input forms: Remove property parameters which have been added to input forms as a result of running regressions, es... |
Problem Statement: One of the | Solution: documents notes that it is necessary to change the code to write to the History and Report files. How is this done?
Solution
There is a new utility (DMS_WRTALN) for writing to the History or Report file using any compiler. This utility MUST be used when the compiler used internally to compile Aspen Plus (Comp... |
Problem Statement: When running simulation that use SRK, you will get the warning message:
WARNING IN THE PROPERTIES PARAGRAPH WHICH BEGINS ON LINE 375
FREE-WATER METHOD SHOULD BE STEAMNBS WHEN THE MAIN PROPERTY METHOD IS SRK. DEFAULT FREE-WATER METHOD IS STEAM-TA PLEASE SPECIFY THE RECOMMENDED FREE-WATER METHOD AND RU... | Solution: For the SRK property method, by default, water is treated in a special way. The following properties of water: enthalpy, entropy, Gibbs free energy, and molar volume, are calculated using steam tables. That is the contribution of water to these properties for a mixture is calculated using an appropriate steam... |
Problem Statement: How do you access electrolyte pair parameters (GMELCC, GMELCD, GMELCE, GMELCN) in a user subroutine?
The User Model | Solution: The GMELC* are electrolyte pair - electrolyte pair, or electrolyte pair - molecule interaction parameters.
You need to know the number of cations, anions, and molecular species. From this, the gmelc* space is indexed by the following:
MI - molecule index, from 1 to the number of molecules
IPI - ion pair index... |
Problem Statement: How can you create a Property Set (Prop-Set) to sum selected component fractions? | Solution: In the attached file (built in Aspen Plus version 12.1), the total light gas composition is calculated by summing the molar compositions of hydrogen, nitrogen, and methane and reporting it as a single value in the stream summary results.
To report a summation of component fractions:
1. Navigate to the P... |
Problem Statement: How do you add drop down menu items to user defined Visual Basic input forms, and take action dependent on the option selected? | Solution: Using the VB tookbox, add an MMAdvCombo box to the form.
Right click on the new box, and select properties.
On the General tab, select the Fancy Combo Box radio button.
In the options list, use the Add button to add in the menu options that will appear when the drop down menu is selected - for example, add... |
Problem Statement: Customer gets the following error while running Aspen Plus 11.1 on a Windows 2000 system.
Failed to create script engine Class Factory cannot supply requested class | Solution: One of the GUI components namely pfsicon.ocx produces this error message.
The following could cause the problem:
VBScript is not installed properly in the system or the registry entry has been corrupted. VB script is used when drawing graphics on the flowsheet.
The customer or their company may somehow have... |
Problem Statement: How do I print out forms from Aspen Plus? | Solution: Some forms such as the Streams Results form CAN be printed from the graphical user interface using Print from the File menu. Unfortunately, this does not work from Column Profiles or other tabular forms, just Stream Results.
Other input and resuls forms can be printed using the Windows print screen functional... |
Problem Statement: How should the equilibrium of the hydrogen chloride-water system, including vapor-liquid equilibrium as well as liquid-liquid equilibrium be modeled | Solution: This report provides a brief description of preliminary work to represent the phase equilibrium of the hydrogen chloride-water system, including vapor-liquid equilibrium as well as liquid-liquid equilibrium.
Model Description
The ElectrolyteNRTL model of Chen and co-workers (1982, 1986) has been used as the ... |
Problem Statement: In the Aspen Plus User Interface Customization Window, when entering the command mmcustom mmtbs to customize the GUI of Aspen Plus or Properties, you get the following message:
F:\Program Files\aspentech\APRSYSTEM 11.1\GUI\Custom>mmcustom mmtbs
Unable to retrieve value of MMTOP from Registry
Unab... | Solution: Use mmcustap instead of mmcustom for Aspen Plus if Aspen Properties is not installed.
Use mmcustpr instead of mmcustom for Aspen Properties if Aspen Plus is not installed.
If both Aspen Plus and Aspen Properties are installed, use mmcustom to do the customization.
Keywords: user databank inhouse
Reference... |
Problem Statement: What is the basis of the Reynolds number? | Solution: The Reynolds number in the Pipe unit operation model output on the Pipe\Results\Stream is the traditional dimensionless Reynolds number. However, the Property Set property RE is a dimensional Reynolds number for a mixture which has units of length.
Re = (mass flow) / (pi/4) / viscosity
The dimensionless Reyn... |
Problem Statement: Are UNC paths allowed in DLOPT and DEF files? | Solution: UNC paths (\\servername\sharename\...) are accepted in DLOPT, DEF and command line qualifiers.
This means that customizations can be placed on a central file server for access by everyone. Previously, references to files on servers had to use a mapped drive letter (e.g., x:\AspenFiles\...). The problem was ev... |
Problem Statement: How can you model a heat exchanger (HEATX) where the inlets could be either hot or cold? | Solution: 106498
Creation Date: 11-Aug-2003 04:50AM
Applicable Version(s)
11.1
Keywords: HEATX
References: None |
Problem Statement: How do I model ethylene flowsheet properties? | Solution: In general it is best to use the Ethylene property databank. The ETHYLENE databank contains pure component and binary interaction parameters required to model the typical ethylene process. The parameters are for the SRK property method which include the critical temperature, critical pressure, acentric factor... |
Problem Statement: How can the heat on mixing of a property method be eliminated? | Solution: It is possible to eliminate the heat of mixing of an activity coefficient property method on the Properties \ Specification \ Global sheet.
The steps are as follows:
1. Go to the Properties \ Specification \ Global sheet.
2. Select an activity coefficient based property method such as NRTL or UNIQ... |
Problem Statement: How do you enter the boiling point temperature for a component? The boiling point predicted is way too low. | Solution: Boiling point is entered as the scalar property parameter TB on the Properties | Parameters | Pure Component | Scalar form. This value is used in Property Methods and in estimation.
If a parameter is estimated and written back to the forms, it will not be re-estimated. This means that if TB is entered after a... |
Problem Statement: It is possible to specify that a component is a Hypothetical liquid on the Components \ Specifications sheet. What does this mean? | Solution: A Hypothetical Liquid component type is used when solid properties should be used for a component in the liquid phase. The liquid properties are extrapolated from the solid parameters. It should only be used for small concentrations of the component in the liquid.
This type of component is used for pyrometall... |
Problem Statement: While compiling user FORTRAN code in the Aspen Plus Engine Window the following error may pop up:
gcpp.exe has encountered a problem and needs to close. We are sorry for the inconvenience.
In the Engine window you may also see a FORTRAN error:
f90: Severe: The input stream is empty | Solution: Please check the user code for #include lines such as:
#include ppexec_user.cmn !Passes USER_NHSTRY. (1)
#include dms_plex.cmn !Passes arrays containing component data
The #include lines cannot have comments at the end starting with !. These lines are processed by the pre-c... |
Problem Statement: In the Sensitivity Results, why is there an extra point at the end that is out of order from the others? | Solution: This is the base case originally specified in the flowsheet. By default, the base case is executed last after the Sensitivity points.
The Execution options are specified on the Optional sheet of a Sensitivity. These options effect when the base case is executed, not just the order the results are printed in t... |
Problem Statement: Where can I see the atomic mass of the elements as used by Aspen Plus? | Solution: The atomic mass of the atoms are available in the System Definition File (SDF) of Aspen Plus. The values for each atom are listed below and included in the attached excel spreadsheet.
The values are extracted from the SDF by opening an Aspen Plus Simulation Engine window, typing SDFRPT, then entering type 5... |
Problem Statement: In EO, how do you specify a block result variable for a block that is solved by the perturbation layer? For example, how do you specifying UA in an MHEATX in EO? | Solution: In Aspen Plus 12.1, when blocks are solved by the perturbation layer in EO, EO variables are only created for the streams in and out of the perturbed block. To create EO variables for a block result, the block result must be accessed, either in a Calculator block or a Design-Spec. For example, the following D... |
Problem Statement: Is it possible to transfer heating/cooling curves property data from Aspen Plus to HTFS or HTRI? | Solution: This can be done using the program HTXINT.
First you need to create heat/cooling curves in Aspen Plus and select the property set HXDESIGN in the properties to be reported. (This prop-set is available in most Aspen Plus templates). It's a good idea to generate these curves at different pressures (and this is ... |
Problem Statement: There is a slight difference between the mass flow rate of the hot water, when using a heater block versus a hot water utility. How is the heating / cooling value calculated for the UTILITIES ? | Solution: Based on the inlet and outlet conditions, the utility determines the heating value (heat capacity) of the fluid. When a block uses a utility, the duty of the block divided by the heating value determines the flow rate of the utility needed.
To mimic what the utility is doing, you need to reverse the directio... |
Problem Statement: How does the Pipe model calculate entrance and exit effects?
The Pipe model should be able to have the the following fittings:
Pipe entry diameter
Pipe exit diameter
Sudden enlargements
Sudden contractions | Solution: These fittings have been added for Aspen Plus 12.2 and higher. They are added on the Pipe | Setup | Fittings2 sheet.
The K values in this document are taken from Flow of fluids through valves, fittings, and pipes, Technical Paper No. 410, published by the Crane Company (1988).
1. Pipe Entrance
a. ... |
Problem Statement: Is there a data package (or electrolyte insert) for the system of H2SO4 + SO3? | Solution: AspenTech has developed an Insert for this type of system, but it is not included with the general Aspen Plus release. This package should be treated as AspenTech confidential.
Oleum Package Contents:
The Aspen Inorganics Oleum package contains a report and four Aspen Plus bkp files.
The report file is in p... |
Problem Statement: What is the clearance factor used in the compressor block COMPR when type is positive displacement (reciprocating)? | Solution: The clearance fraction (also called clearance factor) measures the amount of extra spacing (clearance) that is available for vapor to expand to during compression stroke.
The clearance fraction is equal to clearance volume (minimum volume between cylinder head and piston) over the piston stroke volume.
The cl... |
Problem Statement: The Hcurve input form (available for Radfrac, Flash2 & Flash3, Heater, Heatx, etc.) has a pressure drop field. How can the user generate isobaric hcurve data at pressures other than the inlet or outlet pressures? | Solution: In version 12.1 and earlier, the Hcurve has the following Pressure Profile Options:
Option
Profile
Constant
Isobaric using the unit's outlet pressure
Linear2
Interpolated linearly between [Pin and (Pin-DP)]
Linear3
Interpolated linearly between [(Pout + DP) and Pout]
Outlet
Isobaric using the unit's outlet pr... |
Problem Statement: Can you compare using a rate-based distillation model vs. using an equilibrium stage model with efficiencies? | Solution: The RadFrac distillation model in Aspen Plus offers both equilibrium and rate-based modeling options. There are a number of factors to consider in determining when it is appropriate to use the equilibrium approach or the rate-based option.
Equilibrium-stage approach with efficiencies
Equilibrium-stage distill... |
Problem Statement: What can be done when an electrolyte column fails to converge? | Solution: Following is a list of things to try:
Check if the column specifications are feasible. The things to check include flow rate, concentration, non-condensible gases, heavy component, etc.
Remove any design specifications.
If using the apparent approach, switch to the true-component approach. In the true-comps... |
Problem Statement: What is the purpose of MAWP temperature in Pressure Relief? It does not seem to have an effect on my simulation | Solution: The maximum allowed temperature in the vessel is the HIGHER value of 3000 Kelvin or MAWP Temperature specified by the user.
So if MAWP specified < 3000K, then you will not see it have an effect on the simulation.
Keywords:
References: None |
Problem Statement: The critical temperature of SO2 and SO3 are much higher than room temperature, however SO2 is handled by the electrolyte wizard as a Henry component but not SO3. Moreover there's no reaction generated for SO3 (e.g H2SO4 <==> SO3 + H2O.)
I have seen also that H3PO4 is handled as a Henry component by... | Solution: The choice is arbitrary and depends on what data is available or regressed. It is often simpler to use Henry's law to model the solubility of a component when the solubility is small. The Henry's law formulation does not preclude its usage when the component is not supercritical; however, it is not generally ... |
Problem Statement: How do you change the default version of Aspen Plus? | Solution: The last version installed is the default version by default.
To change the default version (12.1 only),
Go to the Start -> Programs -> AspenTech -> Aspen Engineering Suite -> Aspen Plus 12.1 -> Aspen Plus Registry Fix Utility.
This will run apregfix.exe that is located in Program Files\Common Files\AspenTech... |
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