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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.
2. On the Advanced form, you can search by component name or formula, Component class, ranges of Molecular weight and normal Boiling point, or CAS number.
A useful selection is to check the box next to 'Match alternate names' to use the broadest of search criteria to find the component you desire.
3. Double-click on the component to add it to your list.
Keywords: Find, components, databank, component class, CAS number
References: None |
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 goes through a Heater, the flash results will be slightly different.
You can force RadFrac to reflash its streams by going to the RadFrac block Convergence | Advance sheet and setting Eff-Flash = Yes. This will force a flash of the product streams when efficiencies are specified. Once this is changed, the column profile results and stream results may NOT agree.
Keywords: RadFrac, flash, Murphree, efficiency, enthalpy
References: None |
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 variables and the tear stream variables. Constraints are a function of the independent variables.
Consider OBJ = OBJ of x1, x2, x3
c1 = c1 of x1, x2
c2 = c2 of x2, x3
We start by solving the flowsheet at a base point - x1b, x2b, x3b and calculate OBJb, c1b and c2b Then, variable one is perturbed to x1p and the flowsheet is solved again yield OBJpx1, c1px1 and c2px1 dOBJ/dx1 = (OBJb - OBJpx1) / (x1b-x1p)
dc1/dx1 = (c1b - c1px1) /
(x1b-x1p)
dc2/dx1 = (c2b - c2px1) /
(x1b-x1p) = 0 in our case since c2 is not a function of x1
Then x1 is set back to its base value and x2 is perturbed to x2p and the flowsheet is solved again. dOBJ/dx2 = (OBJb - OBJpx2) / (x2b - x2p)
dc1/dx2 = (c1b - c1px2) / (x2b - x2p)
dc2/dx2 = (c2b - c2px2) / (x2b - x2p)
Then x2 is set back to its base value and x3 is perturned to x3p and the flowsheet is solved again. dOBJ/dx3 = (OBJb - OBJpx3) / (x3b - x3p)
dc1/dx3 = (c1b - c1px3) / (x3b - x3p) = 0 in our case since c1 is not a function of x3
dc2/dx3 = (c2b - c2px3) / (x3b - x3p)
Things to look for in the derivatives:
Verify that some variables have an effect on objective function and constraints.
For inequality constraints, a positive base value indicates that the constraint is satisfied.
Objective function derivatives should be small at an unconstrained minimum
Keywords:
References: None |
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 unequal to 1. | 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 warning.
* WARNING
EFFICIENCY FOR SOME STAGES IS IGNORED BECAUSE PACKING SIZING/RATING
CALCULATIONS ARE REQUESTED WITH P-UPDATE=YES
If you go to the RadFrac | Profiles | Efficiency sheet, if Update pressure profile is checked, all of the efficiencies will be 1 even if efficiencies are entered.
The reason is that even if you enter an overall efficiency, these models assume 100% efficiency. An overall efficiency is expressed through the ratio of actual trays to theoretical plates. Hence, the overall efficiency is not a direct input to the model; instead overall efficiency sets the number of stages in the RadFrac block.
Example:
For a column with condenser, reboiler and 30 trays:
At 70% efficiency, 30 trays = 21 theoretical stages.
Add stages for condenser and reboiler => 23 total
This only applies to pack sizing/rating calculations. The tray sizing/rating correlations can make use of the efficiencies specified on the RadFrac Efficiencies Vapor-Liquid Sheet. For tray rating calculations, you can specify efficiencies on either the Efficiencies form or on the Tray Rating form but not both.
Keywords: RadFrac
Efficiency
Sizing and Rating for Trays and Packings
References: None |
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.
TheSolution is to force RadFrac to perform flash calculations to determine the equilibrium temperature of column products. The option to flash all non-equilibrium streams from RadFrac is located on the Convergence/Advanced sheet. For the parameter Eff-flash, specify YES to perfom flash calculation (the default is NO).
An alternativeSolution would be to send the stream from RadFrac to a heater block with Pressure drop=0 and duty=0 before connecting it to MHeatX.
Keywords: RadFrac, Efficiency, Equilibrium, MHeatX
References: None |
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 liquid phase, as well as the vapor phase. Using a chemistry block, this property package represents the complex formation in the liquid phase. The Hayden-O'Connell model represents the dimers formed in the vapor phase.
The UNIFAC liquid activity coefficient model describes the liquid-phase nonideality; UNIFAC group binary parameters have been determined from experimental data.
To better represent liquid mixture enthalpy and heat capacity, the property package calculates the liquid enthalpy of pure components using the integration of liquid heat capacity polynomials (property route DHL09 is used).
This package uses the Apparent chemistry approach and is suitable for RadFrac or other Aspen Plus blocks.
The property package is applicable for the following range of conditions:
Temperature:
0 to 100 C
Pressure:
0 to 3 Bar
Mole fraction of formaldehyde:
0.0 to 0.60
The insert was regressed with the apparent approach, but apparent approach really should not be used because volatile species are formed by chemistry.
Unfortunately, it can't really be used with true species either because the apparent regressions fictitiously forced all of the oligomers out of the vapor phase.
The insert has been used successfully by customers, but these inconsistencies exist. In fact, we no longer provide the formaldehyde insert because of the these issues.
Keywords: CH2O
CH4O
References: s
1. Vapor-Liquid Equilibrium of Formaldehyde-and Water- Containing Multicomponent Mixtures. G. Maurer, AIChE J., Vol.32, No.6,p932-948,June 1986.
2. Enthalpy Change on Vaporization of Aqueous and Methanoic Formaldehyde |
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 set of regression codes, one for each element.
The LCD files (e.g. PLXANT.LCD) document the regression codes as well as other information about parameters. These files are part of the Aspen Plus Table Building System or TBS. There is a utility EXTR_TBS.EXE in the \Program Files\AspenTech\APrSystem xxxx\Engine\Utl that can be used to extract all of the TBS files.
Here is the summary of the regression codes:
Code
Meaning
0
Not regressable. (You cannot regress these parameters.)
1
Regressable. By default, Aspen Plus does not use in the
regression. (By default, the term does not show up on the regression form. You can add the term to the regression.)
2
By default, Aspen Plus uses the term in the regression (that
it appears on the form). (You can remove the term from the
regression.)
>5
Delta-T switch. If delta-T of the data is greater than the code, the parameter appears by default on the regression form. (You can easily add it to regression if delta-T is less than the code, or remove from the regression if delta-T is greater than the code.)
<0
Number of data points switch.
If the number of data points exceeds the absolute value of the code, by default, Aspen Plus uses this parameter in the regression. (You can add to regression if the number of data points is less than the code, or remove from the regression if the number of data points is more than the code.)
Using Aspen Plus's extended Antoine equation for liquid vapor pressure as an example:
The equation is:
ln(p) = C1 + C2/(T+C3) + C4*T + C5*Ln(T) + C6*T**C7 for C8 < T < C9
where C1 is PLXANT/1, C2 is PLXANT/2, etc.
The following codes are assigned: (Values can be fixed as part of the regression, even for unconditional coefficients)
Parameter
Value
Meaning
C1
2
Used in regression by default
C2
2
Used in regression by default
C3
1
Regressable, but not defaulted
C4
60
Default is to use if delta T more than 60 degrees
Default is to not use if delta T less than 60 degrees
(User can override)
C5
100
Default is to use if delta T more than 100 degrees.
Default is to not use if delta T less than 100 degrees.
(User can override)
C6
1
Default is to not use (User can override)
C7
1
Default is to not use (User can override)
C8
0
Unconditionally not Regressable
C9
0
Unconditionally not Regressable
See the Aspen Plus System Management Guide for information about how to modify the TBS.
Keywords: None
References: None |
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 use Aspen Plus except within Aspen Dynamics
If you need an updated license, Call AspenTech Product Manager.
Keywords:
References: None |
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 wrong too. The vapor pressure trend is to decrease with temperature!
Checking further shows that the databank is actually MISSING the Antoine Vapor Pressure coefficients (PLXANTs) for WF6. No warning/error is produced, and Aspen actually grabs some information and generates a curve. | 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 its liquid Gibbs free energy larger than its vapor Gibbs free energy by a very large amount (artificially). This is a common practice in metallurgy. As a result, Gibbs Free Energy of the liquid (GL) is greater than the Gibbs Free Energy of the vapor (GV); therefore, the vapor state is more stable. For data from the INORGANIC databank, vapor pressure can be calculated from (GL-GV)/RT; not from PLXANT. With an artificial value of GL, PL is artificially large. This is in a way good. We know that this component will always be a gas. As to the trend, we did not want to change the Temperature dependency because it may cause GL to cross with GV. PL is very very large anyway. Ignore the vapor pressure values and any liquid properties. Only gas properties for WF6 can be calculated by Aspen Plus with the parameters available in the databanks.
Keywords: PL
References: None |
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 box.
Keywords: None
References: None |
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 system wide. The system wide change would have to be done at the source code level in the routine PRRSMP.F. This routine processes the PROPERTY-REPORT primary keyword (PKW).
Within the routine the 1st value of a given keyword (ITABLE) is the default.
For example,
DATA ITABLE /
1 4HNORE, 4HPORT, 4HREPO, 4HRT ,
2 4HNONE, 4H , 4HALL , 4H ,
3 4HNOCO, 4HMPS , 4HCOMP, 4HS ,
4 4HNOOP, 4H-SET, 4HOP-S, 4HETS ,
5 4HNORO, 4HUTES, 4HROUT, 4HES ,
6 4HNOSO, 4HURCE, 4HSOUR, 4HCES ,
7 4HNOPA, 4HRAMS, 4HPARA, 4HMS ,
8 4HNONC, 4H-PRO, 4HNC-P, 4HROPS,
9 4HNOPC, 4HES , 4HPCES, 4H ,
1 4HNOPR, 4HOP-D, 4HPROP, 4H-DAT,
2 4HNODF, 4HMS , 4HDFMS, 4H ,
3 4HNOPR, 4HOJEC, 4HPROJ, 4HECT ,
4 4HNOPA, 4HRAM-, 4HPARA, 4HM-PL,
5 4HNONE, 4HUTRA, 4HNEUT, 4HRAL /
In this DATA statement for ITABLE, the REPORT NOPARAMS is the default as shown by
7 4HNOPA, 4HRAMS, 4HPARA, 4HMS ,
To make PARAMS the default you will need to switch the order of the words as follows:
X 4HPARA,4HMS ,4HNOPA,4HRAMS,4H ,4H ,4H ,4H ,
To eliminate PARAMS as being an option, you will replace the word PARAMS with the word NOPARAMS as follows:
X 4HNOPA,4HRAMS,4HNOPA,4HRAMS,4H ,4H ,4H ,4H ,
In the event that the user does specify PROPERTY-REPORT PARAMS an IT error message will be generated stating:
INVALID PROPERTY-REPORT OPTION :PARAMS, OPTION IGNORED
Upon making these changes, the routine should be compiled and the Aspen Plus executable will need to be rebuilt.
For Aspen Plus 10.x the routine PPRSMP.F is located in the node ZESEM2.
Keywords: PROPERTY-REPORT
PARAMS
NOPARAMS
PRRSMP
ZESEM2
References: None |
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 Plus 11.1\\Gui\\Xmp\\pfdtut.bkp);
HRESULT hr;
Happ::IHappPtr spHapp; // the ASPEN Simulation Case
hr = spHapp.CreateInstance( Happ::CLSID_HappLS );
spHapp->InitFromArchive2(&bstrFileName);
// TODO: Your stuff here
spHapp = NULL;
retval = 0;
}
catch (...)
{
retval = 1;
}
CoUninitialize();
return retval;
}
Please note that AspenTech does not officially support the use of this language and user is solely responsible for writing his own code.
Keywords: Interface, C++, Code
References: None |
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:
Temp: 147 C
RHO:
45.9 lb/cuft or 735.0 kg/cum
RHOMX:
45.9 lb/cuft or 736.4 kg/cum
Temp: 25 C
RHO:
54.5 lb/cuft or 872.9 kg/cum
RHOMX:
54.6 lb/cuft or 874.2 kg/cum
In this case the values are nearly the same. For other components, such as methanol, the differences may be larger. Even in the case of methanol, the differences are still less than 3.5%.
All Aspen Plus calculations for stream flows or block calculation use the mixture molar volume (or density). The pure component molar volume, like all pure component properties, is a separate calculation. The pure component density is not used in most calculations in your flowsheet. For many components, the difference will be very small.
When can this difference occur?
This can occur when using a physical property method that uses the property route VL01 for the pure component liquid molar volume **AND** uses the property route VLMX01 or VLMX20. Property Methods that use these property routes include IDEAL, NRTL, UNIQUAC, WILSON, VAN-LAAR and their variances, RK-SOAVE, PENG-ROB, UNIFAC, and CHAO-SEA. Property Methods that do not use this combination include RKS-BM, PR-BM, PSRK, PRWS, RKSWS. Go to the Properties / Property Method / Routes sheet to view the routes used for VL and VLMX. If some other method such as an equation of state or COSTALD is used to calculate molar volume, then the pure component and mixture values will be the same.
Components will use a different equation for pure and mixture molar volume if the above Property Method is used AND:
The DIPPR pure component liquid molar volume parameter, DNLDIP, is used from the PURExx (PURECOMP in Aspen Plus 9) physical property databank. You can select Retrieve Parameter Results from the Tools menu to determine if a component has a DNLDIP parameter in the databank. The DIPPR equation only calculates pure component molar volume and is not used for the mixture molar volume calculations.
If the component does not have a DNLDIP parameter, the component then uses the parameter RKTZRA if available for the Rackett equation to calculate BOTH pure component and mixture molar volumes. See Aspen Plus Physical Properties Methods and Models
Keywords: density
rho
molar volume
References: Manual, Chapter 3 for more information on the Rackett/DIPPR Pure component Liquid Volume equations.
The property route VLMX01 or VLMX20, uses the Rackett mixture molar volume equation for components. However VLMX20 will calculate molar volume using the API method for pseudocomponents.
If the Rackett equation is used for pure component or if mixture molar volume is calculated from pure component molar volume and mole fraction only (VLMX26), then there will be no difference in the two properties.
How can I change this calculation?
If you wish to use a mixing rule or mole fraction averaging to ensure that the pure and mixture properties use the same equation you can change the proprerty route for VLMX by:
1. Select the Property Method you want to change from the Properties / Property Method folder in the Data Browser.
2. On the Routes sheet, in the first column on the left, scroll down to the property VLMX. Change the name VLMX01 or VLMX20 to VLXM26.
This property method will now calculate mixture molar volume from a mole-fraction average of the pure component molar volume.
An alternative approach is to request using a Thermoswitch that for individual components, the Rackett equation be used even if the DNLDIP parameter would normally be used. For more information regarding this approach see |
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 Plus
References: None |
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 later), neither of these code fragments will prevent the confirmation dialog box from being displayed. The better way to handle this is to use the suppress dialog method:
go_Simulation.SuppressDialogs = 1 ' disable the confirmation dialog
Call go_Simulation.Engine.Reinit(IAP_REINIT_SIMULATION)
go_Simulation.SuppressDialogs = 0 ' restore display confirmation dialogs
Note: This code will suppress all of Aspen Plus' confirmation dialogues such as those that pop-up after property estimation, reconciliation, etc.
In the attached example, open the spreadsheet, and then open the Aspen Plus PFDTUT.bkp model (included in the attached zip file). Somewhat minimize both the Aspen Plus and Excel sessions so that you can view both programs side-by-side. In the spreadsheet's checkbox for the Control Panel, enable viewing the Control Panel.
Run the simulation. Try both REINIT command buttons and verify the suppression or display of the reinitialization confirmation dialog.
Keywords: ActiveX, Automation, VBA,Visual Basic, reinitialization, suppress dialogues
References: None |
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 RPlug / Results form; you find the residence profile on the RPlug / Profile form. Unless the volumetric flowrate changes dramatically, a plot of the residence time will be linear.
If a no-slip condition is assumed when two phases exist; both the vapor and liquid phases are assumed to travel together at the same velocity through the reactor. No liquid holdup is considered. The phase volumes cannot be specified independently. The no-slip assumption is valid for situations where one phase is dispersed as droplets or bubbles in a second, continuous phase, such as dew in a vapor phase or small gas bubbles in a liquid phase. This assumption is not valid for multiphase plug flow reactors with controlled levels. In earlier versions, to avoid this assumption, users had to write their own user kinetic subroutine that calls the flash model directly. In 2004 and higher, it is possible to use a two-phase correlation or explicitly specify the liquid holdup.
If no slip, the volume available to the reacting phase is determined using the weighted molar volume for the vapor and liquid at each integration interval. For example, the volume available for a liquid reaction would be:
V= Vt * (xl*Vl)/(xl*Vl + xv*Vv)
where Vt = Total volume,
xl = Mole fraction of liquid,
Vl = Molar liquid volume,
xv = Mole fraction of vapor,
Vv = Molar vapor volume.
The length, diameter, and number of tubes are specified to calculate the total volume of the reactor. Note that the total reactor volume cannot be specified; however, the aspect ratio (length/diameter) has no influence on the model predictions. Thus, the diameter can be set to 1.12838 units, which corresponds to an area of 1.0000 units-squared. With this area, the length in units and volume in units-cubed have the same numerical value, thus the specified length is equal to the volume.
Keywords: None
References: None |
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 successfully but DCOM to fail to make a connection.
When DCOM fails a dialog will appear saying something like:
Aspen.DCOM
Error retrieving IASCSimulation object.
System returns - Access is denied. (0x80070005)
Security credentials may not be sufficient to use DCOM method calls on the server machine.
OK
The consequences of this is that EO functionality will not work at all. If it is attempted to be used after this warning, then there is some potential for either the GUI or the Engine to lock up. (Obviously, that is not desired but does seem to happen on some machines.)
The scenario where this occurs most frequently is when you have a local account on the client and are using that account to connect to a server with another account. The error will occur if the server machine cannot figure out who the client is.
An example would be if Alice has an account Alice on AlicesMachine and Bob has an account Bob on BobsMachine. Alice logs into AlicesMachine and starts up the GUI then connects to BobsMachine and uses the Bob account for the server then this error will occur when BobsMachine tries to figure out who Alice is on AlicesMachine and decides it does not trust the account.
Normally at AspenTech we do not use this approach but instead use a trust authority called ASPENTECH and create accounts with that authority. If Alice and Bob used FOO as their authority, then Alice would probably login as FOO\Alice to both AlicesMachine and BobsMachine. When BobsMachine tries to figure who Alice is, it goes to FOO and usually determines that it can trust Alice and lets DCOM calls through. | 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 application security. With an Administrator account run the utility dcomcnfg. Locate the Aspen Plus Document in the list of application. There may be several so open the properties and check that the path is the correct path to apwn.exe. Change the Authentication Level from Connect to (none) on the General sheet. This has known side-effects of causing paste links from Excel into the Aspen Plus GUI to sometimes not work properly. Only experts and administrators should do this because, like the registry, users can create problems for themselves if they toy around with the utility.
Disable DCOM on the GUI. This can be done by editing the mmg.ini file in Aspen Plus 11.1\GUI\xeq and changing the dcomconnect value to 0. This is known to break EO completely and XML file exports when in client/server mode.
Keywords:
References: None |
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 method that calculates it directly or by a different method. But the difference from one temperture to another or one pressure to another should be comparable.
For almost all property methods (except electrolyte property methods) the Entropy can be calculated based on the following relationship:
S = (H-G)/T
and will be true for vapor, ideal gas, liquid and solid.
The reference points are DHFORM (Standard enthalpy of formation for ideal gas at 25 C) and DGFORM (Standard free energy of formation for ideal gas at 25 C) and the parameters CPIG (Ideal gas heat capacity), DHVLWT (Watson heat of vaporization) or DHVLDP (DIPPR heat of vaporization) are some of the parameters needed to calculate H and G. The Benson method is used to calculate DHFORM and DGFORM.
The difference between the Absolute entropy values (S0 at 298) reported in Reid, Sherwood and Prausnitz and the numbers reported by Aspen Plus is the Entropy of formation (delta Sf). The conversion is
S = S0 - delta Sf (at 298 K)
Delta Sf is calculated from the elements in the molecule.
Keywords: None
References: None |
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 uses the MS sans serif font by default. You should verify that the font definition file for the default font is present under \Windows\Fonts or \Winnt\Fonts and that you can display that font within the Font control panel. Reinstall this font definition file if it is missing or damaged.
Keywords: Font, Data browser.
References: None |
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 Names? | 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: None |
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/Systems/DAO/Disk1. Run the setup.exe in that folder. Take all the defaults to make a complete install.
Run the file mdac_typ.exe. This is also found on the Aspen CD under i386/Systems. Take all the defaults to make a complete install.
Reboot
Try running Aspen. If you still get the same problems, then reinstall Aspen Plus, when prompted for Upgrade, say NO (You want to reinstall), select the same path and select CUSTOM install (instead of FULL), select all the components. Then try Aspen again.
Download and run Regclean.exe from Microsoft. This has been known to solve this problem in the past.
For Aspen Plus version 10.2, the process is a little different:
Run ApwnSetup.exe, found in the folder \program files\AspenTech\Aspen Plus 10.2\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, found under \core\DAO. Run the setup.exe in that folder and accept all the defaults.
Re-install MDAC from the CD, found in \core\Mdac. Again run the setup.exe and accept any defaults.
Reboot
Try running Aspen. If you still get the same problems, then reinstall Aspen Plus and select. Then try Aspen again.
Download and run Regclean.exe from Microsoft. This has been known to solve this problems.
Keywords: graphical user interface gui forms mmscrollarea from control
References: None |
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 and then add QVALGRS and QVALNET to the property set. You may want to visit the QUALIFIERS sheet for the new Property-Set and in the very bottom text box, WATER BASIS, select either WET and/or DRY.
Note: If you select WET and DRY, both values will print in the stream results, but neither will have the WET OR DRY qualifier. They will print in the order requested. For example, if the user enter WET in the first column and DRY on the second column of the QUALIFIER sheet, and both the QVALGRS and QVALNET properties, the data would be printed in the following sequence:
QVALGRS (WET - although the wet qualifier will not be displayed)
QVALNET (WET - although the wet qualifier will not be displayed)
QVALGRS (DRY - althought the dry qualifier will not be displayed)
QVALNET (DRY - althought the dry qualifier will not be displayed)
QVALGRS and QVALNET will calculate the heating values for pure components or pseudo components (from petroleum fractions). In the case of pseudo components, the heating value is caluculated using API Procedure 14A1.3, 4th Edition (1983). The heating value is a function of API gravity corrected for impurity concentrations of H2O, S and other inert.
The calculation method for heating values of petroleum fractions (pseudo components) is documented inSolution Document 102280 (60 Commonly Asked Petroleum Application Questions About Aspen Plus):
Heating value is also called heat of combustion. The heat of combustion of a substance is the change in enthalpy when that substance is converted to its final oxidation products by means of molecular oxygen. The beginning and ending state :
standard heat of combustion: 77 F and 1 atm
gross heat of combustion: 60 F and 1 atm
The normal state for the water formed by the reaction is liquid in both cases. Since the sensible heat of water from 60 to 77 F is usually negligible in comparison with the heat of combustion, the gross and standard heats of combustion are approximately equal.
The net heat of combustion is the heat evolved in combustion beginning and ending at 60 F with product water in gaseous phase. Therefore, the net heat of combustion is less than the gross heat of combustion by the heat of vaporization of the water product.
Net/Gross heating value can be reported in Dry/Wet basis for a stream:
Dry basis - excludes water already present in the stream before combustion,
Wet basis - includes water already present in the stream before combustion.
The methods for calculating pure component and petroleum fractions heating value are different. (The method for calculating pure component heating values is documented in the attachedSolution document #3179)
Keywords: API, heating values, lower heating value, upper heating value.
References: None |
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 in enthalpies (which include heat of formation plus departure terms) between the components entering and the components leaving the reactor.
Heat of Reaction = Enthalpy Leaving block - Enthalpy Entering block - Heating or Cooling Duty
In Aspen Plus 10:
To report the calculated Heat of Reaction for a reaction at a given temperature and pressure, simply use the RStoic / Setup / Heats of Reaction sheet to calculate or specify the heats of reaction. The default is to not calculate or specify heat of reaction.
You must provide specifications for ALL reactions using the same reaction number as given on Setup / Reactions sheet and a reference component that must be a reactant for that reaction.
Heat of reaction are calculated at the specified reference conditions based on consumption of a unit mole of the reference reactant selected for each reaction.
Different reference states can be given; the default is 25 C and 1 atm.
For the same effect, you could adjust the heats of formation (DHFORM) of one or more components to make the heat of reaction match data.
If the specified heat of reaction differs from the heat of reaction that Aspen Plus computes from the differences of the enthalpies between products and reactants, RStoic adjusts the calculated reactor heat duty to reflect the differences. Outlet stream enthalpy will not be consistent with reactor duty except if the Heat duty set to zero where the outlet temperature will include the specified heat of reaction.
In Aspen Plus 9:
To report the calculated Heat of Reaction for a reaction at a given temperature and pressure, create an Aspen Plus Flowsheet run using a single RStoic block. Specify the reaction stoichiometry and a complete conversion of the reaction. Specify the reactor temperature and pressure to be the same as those of the inlet stream so that no additional duty is added to the system. The heat duty reported in the reactor Block Results form is the Heat of Reaction in units of enthalpy/time. Divide this value by the extent of a reactant or product. Molar extent is calculated by dividing the molar flowrate by the stoichiometric coefficient of that component.
The simplest case is a reaction of stoichiometric coefficients of 1. If you specify inlet flowrates of 1 g-mol/hr for each reactant, then the duty reported for the reactor would be the Heat of Reaction per g-mol.
Keywords:
References: None |
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 parameters RACKET/1..5.
RACKET/1 = R*TCI/PCI
RACKET/2 = RKTZRA
RACKET/3 = di = CAMPBELL-THODOS PARAMETER RACKET/4 = LOWER TEMPERATURE LIMIT
RACKET/5 = UPPER TEMPERATURE LIMIT
The third RACKET parameter is a flag which determines whether the Campbell-Thodos or Rackett model is used, i.e.:
If RACKET/3 < 0.11, Campbell-Thodos is used
If RACKET/3 = 2/7, Rackett is used
The Rackett model is documented in Chapter 3 of the Physical Property Methods and Models Manual. For the model to work correctly, the value should less than 0.11 to use Campbell-Thodos or equal to 2/7 for all components to use Rackett (default). Other values are not valid. If the user inadvertently specifies a different value for any of the components, a warning is issued, e.g.:
WARNING IN PHYSICAL PROPERTY SYSTEM
EXPONENT IN RACKETT EQN. FOR X IS NOT 2/7.
DENSITIES OF MIXTURE INCLUDING X MAY BE WRONG.
where X is the component ID.
Note that in the graphical user interface, it is not possible to only enter RACKET/3 in the parameter form, RACKET/1 and /2 must be entered explicitly to complete the form. If using an input file in the Simulation Engine, RACKET/3 can be entered alone and the default for RACKET/1 and /2 are used in the simulation.
Keywords: Campbell-Thodos
Rackett
RACKET
RKTZRA
References: None |
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 is not specifically limited, any component found in the Component | Specifications form may be produced by the RGibbs reactor.
3. If a possible product slate is already specified, remove it. It may be impossible to form the products asked for under the specified operating conditions.
4. Ensure that the maximum number of fluid phases (NPHASE) on the Setup | Specifications sheet correctly indicates the number of fluid phases expected in the reactor.
Keywords: None
References: None |
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 fatal error has been encountered. You must exit and start Aspen Plus again.
Finally, in the Control Panel, you may see the error message:
Entering CAPE-OPEN (version 1.0.0) Unit Adapter DLL initialization Adding factor CAPEOPENUNIT 03487C50 | 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 registering a type library but we have one, which is attached. Just extract it and run it via the command line:
To register: Regtypelib <type library>
To unregister: RegTypelib .<type library> /u
Steps:
Open the folder c:\program files\common files\CAPE-OPEN\
Copy the program Regtypelib in this folder (or any folder in your PATH)
Open a command window in c:\program files\common files\CAPE-OPEN\
Type: regtypelib capeopenv1-0-0.tlb
Note:
Please note the error message above is very generic, and may have other causes.
Keywords: CAPE OPEN
MixNSplit
tlb
crash
References: None |
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 overall number of transfer units in that tray.
When requesting the tray efficiency to be calculated, the user must specify the base-components on the RateSep Report | Efficiency / HETP Comp. sheet. The base components are those which are being transferred significantly between phases. The NTU will be the average value (Geometric mean) for the base-components if multiple base components are selected.
Keywords: column rate-based distillation
References: None |
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
Aspen Plus plots are a useful way of viewing the date from a run. You can use plots to display:
?Input and results profiles for unit operation blocks
?The results of flowsheeting options and model analysis tools such as Sensitivity, Optimization, and Pres-Relief.
There are three steps involved in generating a plot:
1. Displaying the sheet containing the data you want to plot. The sheet may contain either input or results data.
2. Generating the plot either by:
Using the Plot Wizard
OR
Selecting the X-Axis, Y-Axis, and parametric variables
Multiple Y-Axis variables may be selected.
3. Customizing the plot appearance.
Keywords: None
References: None |
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 Zyqad
The full installation media (without the Patch DVD) will be needed in the following cases:
If you are updating AspenTech products from a version prior to aspenONE 2004
If you want to run both 2004 and 2004.1
If you are using one of the products listed above not available as a patch
Keywords: aspenONE
2004 Update 1
References: None |
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 the Properties/Parameters/Results/Binary Interaction/T-dependent form to display the matrix of the parameter status.
Status Abbr. Indicates the parameter is
------ -----
Keywords: None
References: None |
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 temperature.
In releases before Aspen Plus11.1, you could have set the inlet stream at 25C and use a Heater block to bring the feed to the desired temperature for the process.
Keywords:
References: None |
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 execution.
When compiling user fortran subroutines, this DLOPT file also needs to be referenced. For example, use the command:
aspcomp usrsub dlopt=create.opt
Subroutines can also be manually linked using the DLOPT file:
asplink mydll dlopt=create.opt
SeeSolution 102368 for more information on using the Dynamic Linking Options (DLOPT) files.
To always include these libraries, the asplink.prl needs to be modified. SeeSolution 103455 for directions about how to accomplish this modification.
Keywords:
References: None |
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 temperature.
If your system has 2 liquid phases for some compositions, you must remember to change the valid phase setting to liquid-liquid-vapor. If you leave the valid phase setting to liquid-vapor, the diagram will be incorrect, and it may look very strange, such as the bubble temperature curve becoming higher than the dew temperature curve.
The interactive Analysis tool also allows you to do a Gibbs energy of mixing calculation, which can be used to show if 2 liquid phases will form. It is usually difficult to detect this from visual inspection.
The interactive binary analysis tool can therefore give you a quick idea on whether the system will form two liquid phases. Sometimes however, you want to know the composition of the two liquid phases or have more control over the points tabulated. In these cases, you can use the generic analysis. ThisSolution describes how to proceed.
The liquid-liquid equlibrium at various temperatures can be calculated by using a proper Analysis table.
To do this with the run mode Property Analysis:
in properties, create in Analysis a table of type Generic
make sure you select Valid phases as Vapor-liquid-liquid
enter a composition that you know it will show 2 liquid phases
in Variable sheet:- enter the pressure (a value large enough to keep everything in the liquid phase) - select a range of temperature
in Tabulate sheet, create a Prop-Set to report the composition MOLEFRAC (or MASSFRAC) for the components in Liquid1 and Liquid2
This will then let you analyse the liquid-liquid equilibrium. An example is attached to illustrate this.
Some comments specific to the example (water/2-butanol):
we have selected the NRTL model
we use LLE-ASPEN NRTL binary parameters (press F1 on the parameters, to show the range of composition and temperatures)
the Analysis table evaluates the LLE from 0 C to 107 C (which is very close to the upper limit of the experimental range)
the global composition of water/2-butanol is 85%mol water, 15%mol 2-butanol, so that we always stay in the 2 liquid phases region (50%/50% will not work)
the maximum number of iterations for the flash calculation had to be increased to 100, to ensure convergence at every temperature
to plot the results, you can select the composition as the x axis, and T as the y axis
if you do a Txy analysis (using the interactive analysis tool), you can even plot these solubilities over the Txy diagram to have the full picture.
This method can be extended to a mixture with any number of components.
Keywords:
References: None |
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 MESSAGES.
*** SEVERE ERROR
COULD NOT RESOLVE USER OR IN-LINE FORTRAN SUBROUTINE(S):
SUBROUTINE ZZSPCS IS MISSING
*** SEVERE ERROR
PROGRAM TERMINATED DUE TO UNRESOLVED ROUTINES
! Errors while processing input specifications
The purpose of the missing Fortran subroutine ZZSPCS is to calculate values of design-spec residuals such as the manipulated variable range and expressions for specifications, target, and tolerance. | 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 subroutine contains all the design-spec Fortran statements and is compiled and linked dynamically (during the run) by the external Fortran compiler installed on the user's machine.
The most commonSolutions to the ZZSPCS is missing error message are:
Verify that you are using a supported Fortran compiler version and that this compiler is properly installed. The Aspen Engineering Suite Installation Guide gives detailed instructions on how to verify the installation of the FORTRAN Compiler .
If no Fortran compiler is available to you, avoid Fortran commands that require compilation. In other words, rewrite your Fortran code to make sure that all the statements are interpretable. SeeSolution 104149 for a list of Fortran statements that can be interpreted.
Tip: Further possible causes of error messages about missing Fortran subroutines and theirSolutions are reported in Document 4351.
Keywords: ZZSPCS
design specification
subroutine
compiler
Fortran
References: None |
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 menu select Run, then type Regedit
2 - Navigate to location HKEY_LOCAL_MACHINE\SOFTWARE\AspenTech
3 - Delete the Setup entry
Now it should be possible to install AES 10.2 components on any drive.
Keywords:
References: None |
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 structure for both components in the binary system can be described by means of UNIFAC groups (i.e., all required groups are available). As the method is used to predict the required activity coefficients at infinite dilution, it is recommended to use UNIFAC-Dortmund (UNIF-DMD) whenever possible as this method has a database that includes these coefficients. Original UNIFAC has a well-known deficiency in the reliable prediction of activity coefficients at infinite dilution.
No matter which data type is used, the procedure behind the estimation is the following:
Wilson, NRTL and UNIQUAC predict activity coefficients as a function of composition, temperature and binary interaction parameters. The estimation assumes constant temperature and infinite dilution. At these conditions, the activity coefficient model equations simplify such that the infinite dilution activity coefficient is only a function of the binary interaction parameters:
LN (GAMINF,component_1) = f (tau12, tau21)
LN (GAMINF,component_2) = f (tau12, tau21)
where
LN (GAMINF,component_1): natural logarithm of the infinite dilution activity coefficient of component 1 tau12, tau21: binary interaction parameters of WILSON, NRTL or UNIQUAC
That means at infinite dilution and at a given temperature, the activity coefficients in a binary system only depend on the two binary parameters tau12 and tau21 (for NRTL there is a 3rd non-randomness parameter which is, however, not subject to estimation i.e., it is fixed). As (GAMINF,component_1) and (GAMINF,component_2) are either predicted by UNIFAC or given as experimental data, the problem consists of two equations with two unknowns (tau12 and tau21) - a rather simple algebraic problem for Aspen Plus to solve.
In summary: We can use experimental infinite dilution activity coefficients (GAMINF) or UNIFAC to estimate (not regress!) binary interaction parameters for Wilson, Renon (NRTL) and UNIQUAC activity coefficient models.
Due to its predictive nature and the simplifying assumptions (e.g., no isomer distinction), a method like UNIFAC can never be as accurate as a correlation based on regressed parameters such as NRTL. By using UNIFAC to estimate binary parameters for NRTL, you will certainly get more authentic results than from an NRTL-calculation without any binary parameters (= ideal). Yet, the inaccuracy of one method (UNIFAC) is populated into another (NRTL).
Keywords: PCES
property estimation
binary interaction parameters
UNIFAC
GAMINF
activity coefficient at infinite dilution
References: None |
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 theoretical stages can be simulated by specifying 10 stages (excluding the reboiler and condenser for the sake of discussion) on the RadFrac / Setup / Configuration sheet in the Number of stages field. This is usually sufficient if you are only interested in the reflux, heat duty, and other column operating conditions.
For rating calculations, a Tray Rating object needs to be created. Since the number of theoretical stages is specified on the RadFrac / Setup sheet, it is necessary to specify an Overall Section Efficiency on the Design/Pdrop sheet to let RadFrac know that the actual number of trays is 20. With this information, the tray pressure drop, tray loading, flooding factor can be computed correctly. Note that this efficiency does not affect the main part of the RadFrac calculation where reflux, reboiler duty etc. are calculated based on the specified number of total stages (which in this case is 10, excluding the condenser and reboiler), which is independent of the tray rating calculations.
The only time that the tray rating calculations can have an effect on the RadFrac separation part is by checking the box Update section pressure profile on the same sheet (Design/Pdrop sheet).
Another question is What happens if user specified a Murphree efficiency on the RadFrac / Efficiencies form?
As soon as the Murphree efficiency is specified, you basically implicitly tell RadFrac that the total number of stages you specified on the RadFrac / Setup sheet is the actual number of trays. In this case, the Overall Section Efficiency under Tray Rating should not be specified (by leaving it at the default (=1)). Otherwise, there will be erroneous results.
The Murphree efficiency entered will affect the separation. If you have 20 actual trays each with a Murphree efficiency of 50%, you need to enter the actual number of trays (20) on the RadFrac / Setup / Configuration sheet and then enter the Murphree efficiency on the RadFrac / Efficiencies / Vapor-Liquid sheet. In the Tray Rating section, you leave the Overall Section Efficiency at 1. Then the Tray Rating section will treat the number of stages you entered on the RadFrac / Setup / Configuration as the actual number of trays (excluding the condenser and reboiler).
Note that Murphree efficiency is not the same as overall tray efficiency. In the above example, a Murphree efficiency of 50% does not mean that the column has 10 theoretical stages. Many tray manufacturers use the overall tray efficiency defined as the number of theoretical stages divided by the actual number of stages. This tray efficiency is different from the Murphree efficiency.
Confusion can arise when you do not have Murphree efficiency, but rather have the overall tray efficiency as defined above. In this case, on the RadFrac / Setup / Configuration sheet, you need to use the theoretical stages. Therefore, if the tray efficiency is 50%, the total number of theoretical stages would be 10. When you want to do a Tray Rating, you then need to specify the Overall Section Efficiency as 0.5 on the Tray Rating form.
When you have different types or sizes of trays in a column, you need to divide the column into different sections.
Keywords: Radfrac
Tray Efficiency
Section Efficiency
Murphree efficiency
Tray Rating
References: None |
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 in future versions of AspenPlus.
The Fortran code is:
LBproc = dms_locati(2)
NBtitle = ib(LBproc + 18)
LBtitle = DMS_LOCATI(NBtitle)
WRITE(*,10) (IB(LBtitle + i),i=0,15)
10 FORMAT(32A4)
and the necessary Fortran Declarations are:
#include dms_plex.cmn
REAL*8 B(1)
EQUIVALENCE (B(1), IB(1))
See the attached AspenPlus 10.1 BKP file for an example.
Keywords: Fortran Calculator hollerith strings plex
References: None |
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 hydrogen in the mixture? | 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 specified to take place in the liquid phase; then, the concentrations of the components would all be the liquid phase concentration. I.e. the H2 concentration would be the amount of H2 dissolved in the liquid phase. Partial pressure is not allowed for a reaction in the liquid phase. However, if the above reaction is specified to take place in the vapor phase, the concentrations of A and B will be close to zero.
There are two ways around this problem:
1. Write your own user kinetic subroutine.
2. Rewrite the rate expression in terms of the concentration of species in only one phase. For example, specify the liquid phase, and use the amount of H2 dissolved in the liquid phase in the rate expression. It should be possible to use a Henry's law type expression.
Keywords: reactor
kinetic
lhhw
References: None |
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 Aspen Engineering Suite 10.2 Service Pack 1 for Aspen Plus. Click this link to go to the Aspen Engineering Suite 10.2 Service Pack 1 download page:
http://support.aspentech.com/webteamcgi/ | 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 aniline/H2O system as an example:
BINARY PARAMETERS
-----------------
WILSON WILSON BINARY PARAMETERS
LN(TAUIJ) = AIJ + BIJ/T + CIJ LN(T) + DIJ T
UNITS: F
SET: 1
COMP I COMP J VALUE I-J VALUE J-I
H2O ANILINE Aij = 2.46610 Aji = -14.5794
Bij = -2289.53 Bji = -12782.2
Cij = 0.000000E+00 Cji = 0.000000E+00
Dij = 0.000000E+00 Dji = 0.000000E+00
T RANGE = 210.20 TO 334.40 F
SOURCE = INPUT
The above parameters are from the default databank (VLE-IG).
For this system at 100F, ln(tau_ij) = -20.4292 and ln(tau_ji) = -142.4014. For comparison, the ln(tau) values for an ethanol-water system are both less than ten.
Other Property Methods such as NRTL or UNIQUAC can predict two liquid phases for binary systems with large activity coefficients. However, because of thermodynamic assumptions, Wilson cannot ever predict the formation of two liquid phases. Aspen Plus gives the warning for Wilson parameters so that users can separately evaluate if there will be two liquid phases for the system.
Using NRTL for the temperature ranges of 46.4 F to 328.1 F, it is predicted that the system will form two liquid phases at some compositions. Hence, there is a possibility that the derivative calculation of heat of mixing or flash calculation would fail if Wilson method is used for such a system.
To resolve this problem, you have three options:
Use a different Property Method if two liquid phases are expected
Ignore the warning if you are confident that two liquid phases will never be present in your simulation.
Regress new parameters to fit the conditions of your system.
Keywords: Wilson, tau
References: None |
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 Plus.
Keywords: ActiveX, COM, reference, type library, GUI type library, VB, VBA, Visual Basic, Visual Basic Editor, VBE, migration, migrating
References: None |
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 run button to make the simulation start again.
Keywords: Control Panel
References: None |
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 is installed with incorrect paths. These index files (.gid, .fts, and *.ftg) are generated when you run a help file for the first time, or use the Search function for the first time. These files contain file paths including the drive letter. If users access the help from file shares assigned to different drive letters, these paths can be incorrect for some users. | 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 reinstallation of applications if they were installed to use different drive letters on different computers.Solution 2: Delete all .gid, .fts, and .ftg from the help directories as above. Ensure that all users have read-only access to the file server. In this case, Windows Help will write the index files to a directory on the local computer, such as \WinNT\Help under Windows NT 4.0.
Keywords: Lite Client
Help
References: None |
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 use an intercooler between each compression stage and an aftercooler following the last compression stage. No cooling is performed before the first compression stage. Enter one of the following for each cooler:
Outlet temperature of the cooler
Cooler heat duty
Ratio of the outlet to the inlet temperature of the cooler
You may use inlet heat streams in place of duty specifications.
Keywords:
References: None |
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 / NamingOption sheet, select the User-defined list option and list names of all pseudocomponents. These pseudocomponents can then be accessed in Reactions, Design-Spec and Sensitivity paragraphs.
Alternatively, it is possible to manually take the results and enter them on the Components / Specifications form as user-created pseudocomponents.
Automatic convertion of generated pseudocomponent property results to input forms for new user-defined pseudocomponents will be considered for a future release.
Keywords: ADA
PCS
pseudocomponent
petroleum
assay data analysis
References: None |
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 reference reactant selected for each
reaction.
Keywords: rstoic
References: Phase for heat of reaction calculation in RStoic block? How is the Heat of Reaction
defined? |
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 varied to meet this specification. Another example is when the flow of a utility stream needs to be determined.
This is a difficult specification because if the water flowrate is too low, you have super heated steam, which also has a vapor fraction of 1. So the design specification may fail. | 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, these methods will only work around the issue that the specification of temperature or vapor fraction are not univocal definition of the state.
OneSolution is to specify the enthalpy of the stream. As it is difficult to know the exact value for different temperatures and pressures, it is best to let Aspen Plus do this calculation. In the attached example, a Heater block is used to evaluate the saturation enthalpy, and the design specification STEAMX accesses this variable to vary the feed water flowrate.
However, probably the best approach is:
Put a Flash2 block downstream of the steam raising heater cold side (i.e. the steam drum) SAT
Set the Pressure and Vapor Fraction in the Flash2. The Pressure is the steam raising pressure and Vapor Fraction can be 1.0 for saturation or 0.995 for 0.5% blowdown (or similar).
Set the design specification to adjust the water flow such that the calculated duty on the Flash2 (drum) is driven to 0.0.
This gives a robust and monotonicSolution plus adds a blowdown feature. See the attached file (blocks on the right hand side).
Just to be complete: if you want to specify a feed stream at saturation, you simply need to select the vapor fraction instead of the temperature or pressure. This option is not available for single phase calculations.
Keywords:
References: None |
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 pipe.
The elevation term depends upon only the density, gravitational constant, and height. All three of these should be the same for both pipes. BUT, when you use a correlation such as Beggs & Brill that calculates the liquid HOLDUP in the pipe, the density is the density of the material in the pipe and this is NOT the same as the material coming in. Below is the equation we use to calculate the density of material in the pipe. DENL is liquid density, DENG is vapor density, HL is liquid holdup, DENTP is the density of the mixture:
DENTP = DENL*HL + DENG*(1.-HL)
If you use a correlation that ignores holdup, such as DARCY, the elevational terms are the same. Change the frictional methods to DARCY if you want to ignore holdup.
Keywords: pipe
friction
References: None |
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 does not pass the data when the subroutine is compiled and linked as a link library (.dll). The User2 common gets zero for all the values in the Common block.
(Note: when using this technique to initialize a Common block, the Calculator block should execute first to guarantee that the Common block is intialized prior to executing the User2 block.) | 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 dll for the Calculator code), each DLL has its own private /USRRI1/ and hence the problem of not sharing data.
To enable the same /USRRI1/ to be used by both codes, you have to
Make usr2.f export the /USRRI1/ common
Make the calculator to import the /USRRI1/ common
The safest way to accomplish the task is to perform following the following steps
Step 1. Create an include file, say usrri1.cmn, with the following content
REAL*8 PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
#ifdef EXPORT_USRRI1
COMMON /USRRI1 [DLLEXPORT]/
+ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
#else
COMMON /USRRI1 [DLLIMPORT]/
+ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
#endif
What this file does is it will specify [DLLEXPORT] attribute when EXPORT_USRRI1 is specified and it would specify [DLLIMPORT] attribute otherwise.
Step 2. Modify usr2.f by replacing
REAL*8 PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
COMMON
+ /USRRI1/ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
with
#define EXPORT_USRRI1
#include usrri1.cmn
so that usr2.f (and the DLL file created from it) would export /USRRI1/.
Step 3. Modify the calculator block input by replacing
F
with
COMMON /USRRI1/ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
F
#include usrri1.cmn
so that the code would import /USRRI1/. Note that we leave EXPORT_USRRI1 undefined.
Note that:
The symbol EXPORT_USRRI1 is arbitrary. You can use whatever symbol that is appropriate.
The new setup should also work with .obj file - you would be just importing from the same DLL.
Pay attention to the strange #include syntax in Calculator FORTRAN. Most other variations would not work. The statements with the # at the beginning are precompiler directives that are turned into code prior to compiling.
It is possible to explicitly place the export/import directives and COMMON block in the Calculator block and usr2.f without using the check for the symbol described above - the risk is that the COMMON blocks could get out of synch.
(See attached files: test1.bkp, test1.inp, usr2.f, usrri1.cmn)
Keywords:
References: None |
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
usrxls.f
References: Manual and in the Aspen Plus Getting Started Customizing Unit Operation Models.
By default, Aspen Plus passes only material streams to the Excel stream table. It is possible to also pass inlet heat and work streams to the Excel spreadsheet by resizing the table ROWNAMES and INSTREAMS such that heat and work streams are passed to Excel.
In the attached Fortran code, INSTREAMS has been resized to include the heat and work streams. Number of heat of work streams is passed to the USRXLS routine by the argument NINFI. SINFI is the array containing the heat and work stream data. SINFI is then used to set the vectors in table INSTREAMS corresponding to the heat/work streams.
LABELS contains the variable description, stored on two integers (one string of eight ASCII characteers = two integers). See the DATA LABELS statement at the beginning of the code. LABELS are then stored in ROWNAMES before ROWNAMES is transferred to the Excel spreadsheet.
Visual Fortran is required to run this example. You should include it in the Setup form for the USER2 block, entering the name USRXLS in the 'User2 Subroutines Model' text box. USRXLS.F should be compiled as any other user model routine, using aspcomp, and asplink if required.
To run this example:
1. Create a working directory (e.g. C:\work)
2. Copy the Excel file, the Fortran code and the BKP file in this directory.
3. Open the Aspen Plus xxxx Simulation Engine window ( Start -> Programs -> AspenTech -> Process Modeling xxxx -> Aspen Plus xxxx -> Aspen Plus Simulation Engine Window)
4. Go to your working folder (e.g. cd c:\work)
5. type: aspcomp usrxls-hw.f
6. Open the BKP file. Go to block USER2-XL . In the Setup form , in the 'Excel File Name', type C:\WORK\TESTXL.XLS
7. Make sure that in the Setup form for the USER2-XL model, the text box User2 subroutines - Model' contains the name of the Fortran routine used to pass the parameters to Excel, i.e. USRXLS.
No DLOPT file is needed as Aspen Plus will just link the USRXLS-hw.OBJ file to the simulation at run-time.
Files for this example are in the attached ZIP file. |
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 stage (stage 10) and the vapor is fed back to stage above the reboiler (stage 9). Hence, no thermal or phase equilibrium is enforced on the bottom stage (stage 10) and the liquid is drawn from this stage. In other words, the bottom stream is not an equilibrium stream. Results can be seen in Blocks | B1 | Profiles.
This particular feature was designed in consultation with customers who uses thermsyphon reboiler on a regular basis, who confirmed the fact that the bottom stream is not an equilibrium stream when the vapor is not fed back to the sump.
See the attached bkp file, which compares the thermosyphon as handled by RadFrac, and the approach using external blocks.
Thermosyphon as handled by RadFrac:
Approach using external blocks:
Keywords: radfrac
reboiler
thermosyphin
thermosiphon
References: None |
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 molecular structure. Click on Input.
The Molec-Struct Input Menu appears.
Select General. The Properties Molec-Struct.General Form appears.
Enter the molecular strcuture, one pair of atoms at a time.
Field
What to Enter
No.
Atom number that you assigned
Type
Atom type (for example, carbon or oxygen)
Bond
Type of bond that connects a pair of atoms (for example single or double)
ASPEN PLUS has additional bond types, which can be used as shortcuts for entering saturated hydrocarbon chains and rings.
For more information about entering structures, see the ASPEN PLUS User Guide Volume 1, Chapter 10.
From the Forms pulldown menu, select Properties, then Estimation. The Estimation Input Menu appears.
Select Main.
The Estimation.Main form appears. Select the ALL option. This option requests the estimation of all missing parameters that PCES can estimate.
For more information about property estimation see the ASPEN PLUS User Guide Volume 1, chapter 10.
Use the Property Parameters for Data forms to enter the component property parameters you know to get better results. If you use the DATA form for:
CPIG
PLXANT
DHVLWT
RKTZRA
MULAND
MUVDIP
KLDIP
SIGDIP
Use the DATA estimation method on the Estimation.T-Dependent form. See ASPEN PLUS User Guide, Volume 1, page 10-14 and 10-3 for more information about the DATA method.
Note for all cases: It is highly recommended that you provide the boiling point (TB) if known.
For an example about how to estimate physical property parameters, refer to the ASPEN PLUS Getting Started Building and Running a Process Model, Chapter 6.
Keywords: None
References: None |
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 NOT RUN AFTER 12/31/99 due to limitations in the calculation engines internal security routines. This is completely independent of the license key.
Keywords: Y2K
Year 2000
References: None |
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 the pressure correction of Stiel-Thodos. At low pressures, there should not be any significant differences; however, at higher pressures, there may be discrepancies and the route should be changed. At higher pressures, it is appropriate to include the pressure correction and use the Stiel-Thodos route for both the pure component and the mixture calculations.
Wordaround:
Change the Thermal Conductivity Mixture (KVMX) Route to use KVMX02, which uses the Stiel-Thodos model to make the results consistent.
To change the route:
1 - Select RK-SOAVE as the Property Method.
2 - Go to Property Methods, RK-SOAVE using the Data Browser.
3 - On the Routes tab change Property to Mixture Transport.
4 - The third property down the list shown should be KVMX. CHange the Route ID to KVMX02.
Fixed in Version:
Undetermined Release
Keywords:
References: None |
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 equation-of-state option set. Components included in the package are EG, DEG, TEG, WATER, METHANOL, CO2, N2, H2S, METHANE, ETHANE, PROPANE, N-BUTANE, N-PENTANE, N-HEXANE, N-HEPTANE, N-OCTANE, N-NONANE, N-DECANE, BENZENE, TOLUENE, O-XYLENE, ISO-BUTANE, ISO-PENTANE, ETHYLENE, and PROPYLENE.
The data used in these package covers a very wide range of temperatures and pressures.
To use this data package:
1. From the File pulldown menu, select Import or Open.
2. Click on the Look in Favorites button on the toolbar. (It looks like a folder with an asterisk in it.)
3. Open the Data Package folder A list of available data packages appears.
4. Select Glycols.bkp, and click on the Open button.
This file is located in the Aspen Plus xxxx\GUI\Datapkg folder.
Keywords: None
References: None |
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 and data regression in the Data File Management System format (DFMS). This can be used to make a Inhspcd or User databank. In V7.2, this file will also include user and databank parameters to make it easier to use it to import properties into new Aspen Properties Enterprise Databanks (APED).
Property data format file (.PRD) - This file contains property parameter results of PCES and data regression in the the form of Prop-Data paragraphs. Prop-Data paragraphs can be used to add property data to an Aspen Plus input file.
Project data file (.APPRJ, previously .PRJ) - This file contains all parameters (pure component, binary, electrolyte pair) used in the simulation run in the form of Prop-Data paragraphs. This includes all parameters retrieved from pure component and binary databanks, not just the parameters that appear in the GUI. The project file can be renamed to an input file (.INP) and opened in the Graphical User Interface.
IK-CAPE PPDX Neutral File (.IKC) - The IK-CAPE neutral file as a way to transfer select physical property parameters and data between different applications.
All of these files are created in the working directory during a run as temporary files after a report file is exported, e.g. _1234abc.DFM or _1234abc.PRD. Before reinitializing or exiting, these files can be renamed and saved.
The .DFM and .PRD files are generated automatically when you export a Report file (Select Export from the File menu). In 12.1 and higher, the .APPRJ and .IKC files are also saved when you export a Report file.
Keywords: None
References: None |
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-fraction averaged together to obtain the mixture surface tension.
Keywords: SIGMA
SIGMAMX
References: None |
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 installation. | 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 platforms and different versions of Aspen Plus. ***Starting in Aspen Plus 2004, a .bkp file is embedded in the .apw file. This means that if a user tries to open an .apw file created with 2004 in a higher release, it will automatically open the .bkp file which is stored inside the .apw file.***
The document or quick restart files are more easily corruptable.
There is also a difference in the way in which the results are accessed. When a file is saved in the document or quick restart format, the process definition file (.pdf in Aspen Plus 9 and .appdf in Aspen Plus 10) and dynamic link files are saved on the engine. The process definition file contains all the results, as well as the entire plex array, and the dynamic link file contains pointers to objects that are dynamically link to the simulation. If these two files were to be deleted, the subsequent run would behave much like a run using a backup file.
One way to combine the advantages of both file types is to reconcile tear streams and save as a backup file. Simulation results for a stream can be copied onto the its input form in Aspen Plus 10.1 to provide tear stream estimates. Even if the flowsheet is re-initialized, the next simulation solves much quicker because excellent starting data has been provided for the tear stream via its stream input form. This process is called Reconcile a stream. See document 102354 for more information about reconciling streams.
Keywords:
References: None |
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 features which can now use UNC paths are compile, link and getridof.
The changes will allow Working Directory specifications with UNC
path names as commonly encountered when using a remote server.
To apply the Aspen Engineering Suite 10.2 Service Pack 1 for Aspen Plus. Click this link to go to the Aspen Engineering Suite 10.2 Service Pack 1 download page:
http://support.aspentech.com/webteamcgi/ | 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 close to the azeotropic point and the bottom product is close to the pure component.
For a maximum azeotrope system, the top product is close to the pure component and the bottom product is close to the azeotropic point.
Keywords: Distillation
Column
Azeotrope
Azeotropic point
References: None |
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 file type window: Select His, Aspen plus History File
Now modify the association of this file with what ever application you like
Select Change, A new window with a list of all installed applications will appear Scroll down and select Winword or any other application
Key Words
Aspen Plus File Type
History files
Output files
Keywords: None
References: None |
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 the calculated temperature on block B2, the code would be:
CalcDuty = go_simulation.Tree.Data.Blocks.B2.Output.QCALC.value
To retrieve the dimensional units for CalcDuty, the code is:
DutyUnits = go_simulation.Tree.Data.Blocks.B2.Output.QCALC.unitstring
The value of both variables, above, can be changed to reflect other dimensional units. Aspen Plus uses a two dimensional table to calculate unit conversions - the type of measure (pressure, heat, temperature, etc.) is stored in the rows. The dimensional units for a given type of measure are stored in the columns. For example, pressure would have N/sqm, psi, & atm stored in its first 3 columns.
To change the dimensional units for a retrieved value, there are 3 steps:
1. find out the unit-row & unit-column of the currently retrieved value
2. obtain the column number for the new dimension units, in this case column 3 is metric
3. use the ValueForUnit method to issue a command to recalculate the retrieved value in the new dimensional units(metric).
Using the TestProb.bkp model, the retrieved value for duty for block B2 was in MMBTU/Hr (ENGlish). If you want to report the duty in Calories/second (metric), here is the code:
Public Sub SimpleChangeUnits()
Dim CalcDuty As Variant, DutyUnits As String, NewDutyUnits As String Dim nROW As Integer, nCOL As Integer
Dim MetricDuty As Double
nCOL = go_Simulation.Tree.Data.Blocks.B2.Output.QCALC.AttributeValue(HAP_UNITCOL)
nROW= go_Simulation.Tree.Data.Blocks.B2.Output.QCALC.AttributeValue(HAP_UNITROW)
REM Note: in this case nCol = 8 (MMBTU/Hr) and nRow = 13 (pressure)
REM use the AspenPlus Unit Table to retrieve the name of the new dimensional units
REM NOTE: the column number for metric units is always '3'
NewDutyUnits = go_Simulation.Tree.Elements(Unit Table).Elements(nROW -1). _
.Elements.Label(0, 2)
REM convert the currently retrieved duty value to metric units (Row number 3)
MetricDuty = go_Simulation.Tree.Data.Blocks.B2.Output.QCALC.ValueForUnit(nROW, 3)
End Sub
Keywords: VBA, Automation, ActiveX
References: None |
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, there is a check to see whether the stream contains only light ends.
There are three checks. The curve is not calculated if the stream meets one of the following conditions: 1 - Too Many Light Ends
In Aspen Plus 11.1, the curve is not calculated if more than 80% of the stream by mole has a boiling point less than 100F. In 11.1 SP1 and 12.1, the limit is 99% and in RT-Opt 10.0, the limit is 85%.
2 - Not Enough Components
The curve is not calculated if fewer than 4 components have non-trivial compositions.
3 - Too Hydrogen-Rich
The curve is not calculated if the stream has more than 1% by mole Hydrogen. In 12.1, the curve is not calculated if the stream has more than 10% by mole Hydrogen.
You should get an information message if the Simulation diagnostics are 5 or higher.
Keywords: Petroleum, assay, distillation curves, D86CRV, TBPCRV, D2887CRV, D1160CRV, Radfrac, Petrofrac.
References: None |
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 tables are not appropriate to use because they only apply to pure water systems.
Keywords:
References: None |
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. However, the stream display order cannot be saved in the system or with the file.
In order to save the order permanently, a customized stream summary file (.TFF) can be created. Files with the TFF extension (filename.tff) are used by Aspen Plus to format the Stream Summary result form. SeeSolution 115879. For more information on TFF files refer to the Aspen Plus User Guide.
Another option is to name the streams using a numerical prefix. For example:
03FEED
02LIQUID
01VAPOR
In the display, they will be in the order of 01VAPOR, 02LIQUID, 03FEED. If there are more than 9 streams, use 2-digit prefix. If there are more than 99 streams, use 3-digit prefix. Streams 1 through 10 will be reported as 1, 10, 2, 3, ..., 9. Realizing that the stream name is limited to the maximum of 8 alphanumerical characters without space and underscore, this workaround does have its disadvantage.
Stream Report View - text file opened from View\Report\Stream from the Menu
The streams reported in the Stream Report View are in alphanumerical order, same as in the GUI case. The user can choose to display one or all streams, but cannot set the display order. Naming the streams using a numerical prefix as descibed above is the only option.
Report File (.rep) - text file exported from File\Export
The streams reported in the Report File are in alphanumerical order, by default. However, the order can be specified by the user. The following procedures are to be followed:
Go to Setup\Report Options\Stream sheet.
Click on the Include Streams button.
Select the streams to be included in the left windows and move them to the right window.
Arrange the sequence of the streams by selecting a stream and using the Up or Down button to move.
The above specification controls only the Report File only, not the other two.
Keywords: stream
report
sequence
order
view
summary
rep
gui
References: None |
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 model from http://www.aspentech.com/tspsd/example/example.htm but get a page expired message or unauthorized Access. | 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 to match specified reactor duty
Mass Balance Loop
Solve conservation equations for component mass
Flash Loop
Solve system of equations for phase equilibrium
Finalization
Calculate and store results
Conservation Equations:
Conservation equations have the form:
Residual = Input - Output + Generation
for each component, i, and enthalpy.
RCSTR iterates to minimize the error in Ri/Si, where Si is a scaling factor for component i.
Broyden is the default algorithm; it solves problems based on the maximum error, Max(Ri/Si).
You can also use the Newton method; it tests the root mean square error, SQRT(Sum((Ri/Si)**2)).
Block converges when the error falls below the specified mass-balance tolerance (Convergence Parameter sheet Mass balance error tolerance).
Two scaling factors are available:
Components method
Substream method.
The component scaling method uses a different scaling factor for each component mole-flow, while the substream method uses a single mole-flow for all residuals. The scale factors are estimated flows.
Component-based scaling generally provides more accurate results than Substream-based, especially for trace components. You can increase Trace accuracy by lowering Trace Scaling factor in the Advanced Parameters dialog box on the Convergence Parameters sheet.
Initial estimates for both algorithms can be are obtained by integrating the conservation equations from t=0 to the residence time.
Solver Algorithms:
Information about the solver algorithms:
Broyden (Default):
The Broyden method (default) achieves fast convergence of reaction networks involving relatively few components and slow reaction rates. You can increase stability by decreasing the value of the parameter Damping factor on mass balance variables on the Advanced Parameters dialog box on the Convergence Parameters sheet. Damping factor on mass balance variables decreases step-size; therefore, additional iterations may be required.
Fast but unstable. Performance can be bad when rates are very fast and/or reaction kinetics are highly non-linear.
Increase stability by decreasing the value of the parameter DAMP-FAC. Because this factor decreases the step-size; additional iterations may be required to reach theSolution.
Performance is a strong function of the quality of the initial guess.
Newton:
The Newton algorithm is recommended for systems in which simultaneous kinetic and equilibrium reactions occur. This method is slower but stable
It explicitly calculates the full Jacobian Performance is good for fast and non-linear kinetics. This method is recommended for systems in which simultaneous kinetic and equilibrium reactions occur.
Slow but stable. Performance is good for fast and non-linear kinetics.
Use Newton's method when equilibrium reactions are specified in powerlaw or LHHW kinetics.
Increase the parameter TERM-LEVEL to 7 on the Setup.Diagnostics or the Rcstr.Blockops form to increase the control panel messages.
Here are some tips for convergence:
Problem 1:
Outer Loop Fails (The Outer Loop solves T when Duty is specified)
Solutions:
Verify that the reactor converges with a Temperature specification.
Decrease MAX-TSTEP on the Rcstr.Convergence form.
Problem 2: The Inner Loop fails, but the error/tolerance (MAX-ERR/TOL on control
panel) decreases.
Solution
Increase MB-MAXIT parameter on the Rcstr.Convergence form.
Problem 3: The Inner Loop fails maximum error/tolerance and varies erratically.
Solutions:
Supply estimated values on the Rcstr.Flow-Est form
Decrease DAMP-FAC on the Rcstr.Convergence form by logarithmic increments (0.5, 0.3, 0.1, 0.05, etc) until converges. If it does not converge with a value of 0.0001 then try anotherSolution (1, 3 or 4)
Specify the Newton algorithm by choosing NEWTON in the Solver field on the Rcstr.Convergence form.
Use Integration initialization by specifying INTEGRATOR in the Algorithm field on the Initialize form.
Problem 4: Diagnostic messages read X-CUT or T-CUT loop failure.
Solution
Increase FLASH-MAXIT or loosen FLASH-TOL on the Rcstr.Convergence form.
Keywords: None
References: None |
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-called Barin equations are in fact three heat capacity models (one for solids, one for liquid, and one for ideal gas) in which the only state variable is temperature. The three equations are different depending on the phase being Solids, Liquids, or Ideal Gas.
Each of the three Barin equations has a set of parameters, which, if available, are stored in the Aspen Plus INORGANIC databank. For solids, the name of the parameters starts with CPSX..., for liquids, CPLX...., for Ideal Gas, CPIX....
As a rule of thumb, if the Barin parameters exist, the Barin equation will be used.
If the INORGANIC databank is the first databank listed on the sheet Components/Specifications/Databanks sheet, and the databank contains Barin parameters, Barin equation is used.
If the INORGANIC databank is not lised as the first databank, but the databank before it contains no parameter necessary for H, G, or S calculation, then the Barin parameters in the INORGANIC databank will be used.
If user enters any parameter value on the Properties/Parameters/Pure Component, such as CPIXP1 (Barin ideal gas heat capacity coefficients), Barin equation is used. This is true even if user has entered some other parameters such as CPIGDP (DIPPR ideal gas heat capacity parameter). For example, if user select IDEAL as the physicla property method, and then goes to the Properties.Parameters form and enters both CPIGDP and CPIXP1, the CPIGDP would have no impact on the enthalpy calculated since CPIXP1 will be used for the enthalpy calculation. If CPIXP1 is removed, then the enthalpy will be calculated based on the standard IDEAL method, i.e., CPIGDP would be used.
For those users who are familiar with Thermo Switch (THRSWT) inside AspenPlus, one can specify the value for THRSWT to explicitly specify what equations are being used. Refer toSolution 3026 for more info on THRSWT. You can also find the information in the Aspen Plus on line help by searching the key word THRSWT. A value of 200 or greater for any element of THRSWT means that property is calculated using the BARIN equations.
Three example bkp files are attached. The first example, barin-inorganic.bkp shows that once you put INORGANIC databank first, the 7th element of THRSWT is 200 (user can find this by viewing the report file), indicating that Barin equation is being used for the ideal gas heat capacity calculation (which subsequently means that H, S, and G are calculated from the BARIN as well). If one puts INORGANIC behind PURE10, then THRSWT element 7 is 107. This example verifies 1).
The second attached example, Barin-CPIXP1.bkp shows that once you enter CPIXP1 under Properties.Parameters.Pure Component, Barin equation is used. This verifies 3).
The third example, Barin-thermoswitch, shows how user can use thermoswithc to specify Barin as the default model for the ideal gas heat capacity.
Keywords: Barin
Thrswt
thermoswitch
.
References: None |
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
References: 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 state, you need to add 15970312.47 J/kg to the enthalpy value to account for the heat of formation of water. | 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 attached. The reference state used in this example is liquid water at 60F and 1 ATM.
Please compile the file, called USRENT.FOR, on your working directory.
The name of this subroutine must be declared on the Properties | Advanced | User Property form.
The name that is assigned to the object used to store this property becomes the name for the user property.
This name is assigned before the User-Property form is entered. The user property must also be specified in a
property set to be included in a stream report.
Create three new USER-PROPERTYs
1.- call the first one ENTHMOLE (use this one to report the molar enthalpy). On the ADVANCED.USER-PROPERTY form fill in the following:
SUBROUTINE usrent
FLASH yes
UNITS TYPE mole-enthalp
2.- call the second one ENTHMASS (use this one to report the mass enthalpy). On the ADVANCED.USER-PROPERTY form fill in the following:
SUBROUTINE usrent
FLASH yes
UNITS TYPE mass-enthalp
3.- call the third one ENTHFLOW (use this one to report the enthalpy flow). On the ADVANCED.USER-PROPERTY form fill in the following:
SUBROUTINE usrent
FLASH yes
UNITS TYPE enthalpy-flo
Once the three user properties have been created, create a property set that will report ENTHMOLE, ENTHMASS and ENTHFLO. Make sure you have entered the propset name on the Report Options | Streams form using the Property Sets button, in order to have the enthalpies reported for the streams.
Keywords: user prop-set property
References: None |
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 request thermodynamic consistency tests is checked for any data set on the Regression Input Setup Sheet, the case will test the thermodynamic consistency for binary VLE data and report just that (i.e., whether the data-set has passed the test, or not). No other results will be reported.
Evaluation runs to evaluate the accuracy of known model parameters.
Uncheck all of the checkboxes for consistency tests, and the evaluation run will now evaluate the accuracy of existing model parameters with the data groups specified. Results will be reported on three different sheets: Residuals, Profiles, and Evaluation. Plots can be created to compare model predictions to experimental data.
Note that you can only do one of these types of runs at a time.
Keywords: data regression
evaluation
thermodynamic consistency
References: None |
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 any input variables accessible within Aspen Plus. It allows users to reconcile measurements while fitting Aspen Plus variables.
Some typical reactor parameters that can be fitted using Data-Fit:
Pre-exponential factor
Activation energy
Temperature exponent
Power law exponent
Volume of the reacting phase
and many more...
Note: It was very difficult to fit both the Pre-exponential factor and the Activation energy at the same time using Aspen Plus 9. A reference Temperature was added to the power-law expression in Aspen Plus 10, and this expression can be used to fit both the Pre-exponential factor and the Activation energy more easily. SeeSolution 103041 for more details about the reference temperature for the power-law expression.
How to define Data-Fit with Aspen Plus:
Define the measured data.
Define the data to be fitted.
Define the parameter(s) to be fitted.
An example of using Data Fit to regress the Pre-exponential Factor for a power-law rate expression used in a RCSTR is attached.
Please see the Aspen Plus 10 User Guide, Chapter 23, Fitting a Simulation Model to Data (Aspen Plus 9 User Guide Volume 2 Chapter 19) for more details.
Keywords:
References: None |
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/application name for Aspen Plus in MODULE1:
Public go_Simulation As IHapp
In version 11 or later, this will sometimes cause an error when your code tries to open the simulation. The way to remedy this is easy - change the Class name from IHapp to HappLS (the local server class type):
Public go_Simulation As HappLS
Generally speaking, all of the other features should be forward compatible, unless the syntax in Aspen Plus was changed. Should you encounter a node spcific error (streams, unit blocks, sensitivity analysis, design-spec, calculator block, etc), you may have to look up that path-to-node dot notation in the Aspen Plus Variable Explorer and paste the new path-to-node name into your VBA code. There are some nice pointers for navigating the Aspen Plus Variable Explorer inSolution document #106094.
Note: Between version 10.0 and later versions, there were syntax changes made to the Calculator block (called a FORTRAN block in v10.0 and earlier) and the Design-Spec expression fields.
Sometimes it is also helpful to change the reference library specified in the VBA editor. In the VBA editor, click on TOOLS |
Keywords: VBA, migration, multiple versions, activex, compatibility
References: s, remove the check box on the current Aspen Plus GUI TYPE LIBRARY, and click on the new Aspen Plus GUI TYPE LIBRARY.
Another source of errors is opening a spreadsheet with VBA code designed for a newer version of Aspen Plus than the default version on the current PC. You can either add VBA code to trap for the version number of Aspen Plus (see |
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 VLE data contain only temperature, pressure, and liquid mole fractions. Vapor mole fractions are not reported. For this type of system, the vapor phase generally contains mainly the Henry's component. It is not problem to leave the vapor phase composition column blank for the data set.
Henry Coefficient vs. Temperature data is entered using a data type of Henry.
The units for Henry constant values are the same as the pressure units in the user selected Unit-sets. If the pressure units are changed in the Data set, the new pressure units are used for the Henry constant. Typically Henry's constant data is reported in atm or bar units. When entering Henry's constant parameters, you can check the units for each parameter using on-line help. The first parameter is not temperature depended but all others are.
The units (gm/L-atm) is the inverse of Henry's constant, and need to be multiplied with mole fraction or concentration of the related species involved.
One problem when entering Henry data is that Temperature, Pressure, Mole Fraction and Henry Coefficient are all needed on the form. The question is what to enter for the mole fraction and the pressure. These values are needed because in Aspen Plus Henry's constant is part of the liquid fugacity coefficient calculation and is a function of T, P, and x.
The temperature term is from the basic expression for the Henry's constant, ln H = a + b/T etc.
The pressure term is a pressure correction term similar to the Poynting correction term (integral from vapor pressure to system pressure of partial molar volume). At low pressures, this term will be negligible. Also, the Poynting correction is not used in a number of Property Methods such as Ideal. There is a check box to turn the Poynting correction on and off on the Properties/Specifications/Global sheet if you need to modify the Property Method.
The concentration term is from the mixing rules for mixed solvent and for the computation of assymmetric gamma (=gamma/gamma infinitity). If the Ideal property method is used, interactions are Ideal so the value of the concentration should not matter. Alternatively, it is reasonable to enter a very small value for the composition.
Instread of using Data Regression in Aspen Plus, you can simply use Excel to fit Ln(Hij) to the T function (assume the pressure is at saturation) and transfer the results.
Two example files are attached. The data in the example files is from Perry's Chemical Engineering Handbook, 4th edition, p. 14-3.
These examples illustrate how to determine Henry's constants for a Henry's component in a solvent, using Henry Constant data. Henry's constants are required when an asymmetric-convention activity coefficient property method is used to model a system containing non-condensable components with solvents. Examples of propery methods requiring Henry's constants are UNIFAC, NRTL, WILSON and UNIQUAC. Examples of the solvents are water and alcohol. The non-condensable components (e.g. oxygen and carbon dioxide) are called Henry's components in Aspen Plus. The Henry's law approach is generally used for sparingly-solutble gases, so that the mole fractions of the gases in the liquid phase are very small. Because there is not sufficient variation in liquid mole fractions to accurately determine the activity coefficient parameters, only the Henry's law constants are usually determined for these systems.
One example uses the Henry Constant data for acetylene and water to determine the Henry's parameters for the Henry's component acetylene in the solvent water. The IDEAL property method is used so that the value of the concentration should not matter as described above. Acetylene is defined
as a Henry's component. The other example uses TPXY data to regress the Henry's Constant parameters for the Henry's component CO2 in the solvent water. This example uses the NRTL property method though any Activity Coefficient model should give similar results
Since the Henry's constants for these components with water
are available in the Aspen Plus BINARY databank, the Property data is used to set the elements that are not regressed to zero.
In the acetylene example, a data type of HENRY is used.
The pressure can be entered as an ambient pressure of 1 atm. The units of the pressure are the same as the units of pressure in the Henry Constant (HNRYMX). Since the concentration does not matter, it is reasonable to enter a very small value of 1e-9 for the composition of the gas (X) in the liquid phase.
In the CO2 example, a data type of TPXY is used.
The temperature and pressure are the system temperature and pressure. The compositions can be given in Mole or Mass fractions or percents. The column for vapor composition is left blank since it was not provided.
For the regression, the Binary Parameter called HENRY
is regressed. It is possible to regress up to 4 elements. These elements correspond to the Aij, Bij, Cij and Dij for the HENRY parameter on the
Property / Parameters / Binary Interaction / HENRY-1 form.
Keywords:
References: None |
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 volume when PSRK property method is used? | 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 with the API/Rackett model for some of the simple EOS property methods (RK-SOAVE, PENG-ROB, and LK-PLOCK) to provide a more accurate representation. This method calculates liquid density using the API correlation for pseudocomponents and the Rackett model for real components. Activity Coefficient models use Rackett for the liquid volume calculations. The problem with using Rackett model is that it is not consistent with the EOS. For example, if you have a supercritical fluid where vapor and liquid properties should match, they will not match if you are using Rackett for liquid molar volume. This will lead to discontinuities. All other equation-of-state methods use the equation of state to calculate liquid density, except that SRK and some of the methods based on it correct this density with a volume translation term based on the Peneloux-Rauzy method.
To check if a Property Method uses some other model such as the API/Rackett model for liquid volume.
1. Go to the Properties | Property Methods | Models sheet.
2. Go to the VLMX Property and check if the Model Name is the equation of state (ESxxx) and matches the route for VVMX or if it is the API/Rackett Model (VL2API or VL2RKT).
To get better match with the standard volume, it is possible to modify the liquid molar volume calculation to use the Rackett method. To make this change, the route needs to be changed for liquid molar volume (we recommend changing the route rather than the model because it is easier to understand what properties will be affected).
1. Go to the Properties | Property Methods | Routes sheet for PSRK
2. Change the VLMX route to VLMX20 (Liquid Molar volume using the API method) instead of the default VLMX45 (PSRK method).
3. For the pure component liquid volume VL, change the route to VL01 (Rackett Method) rather than the default (VL25).
In the attached file fixed.bkp, the routes have been modified as described above. In this file, the outlet stream has a flow rate of 11878 bbl/day and the standard volume flow rate is 11865 bbl/day. This result is comparable to the original results from the PSRK method in the original.bkp file (14174 bbl/day).
Keywords: EOS, PSRK, VOLUMES, STANDARD VOLUMES.
References: None |
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 of continuous feeds. The Continuous feeds can remain constant or follow a specified time profile.
The Feed profile is specified on the RBatch / Setup / Continuous Feeds sheet. This allows users to to simulate a fed-batch configuration using multiple
feeds and vary time and flow rate (mass only).
The values entered on the Continuous Feeds sheet should use the Unit Set for the block. RBatch interpolates between the values you enter. If you need to enter a step change, enter the two flow values for the same time as two separate entries. If you do not enter flow at time zero, RBatch uses the value entered for the first time point for time zero. If RBatch integrates beyond the last time point entered, a constant flow corresponding to the value entered for the last time point is assumed for that stream.
To specify a continuous feed of x for 1 hour and then continue without a feed for the rest of the time, the time profile could be entered as:
time
flow
1
x
1
0
Keywords:
References: None |
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 example, one desires to set the flow rate of stream 2 to the absorber. Since a small portion of the solvent in the recycle stream is typically lost in the absorber vent (stream 3) and the stripper product (stream 6), a small makeup stream of solvent (7) is required. To keep the flow rate of stream 7 constant, a BALANCE block is used to control the makeup flow rate. The steps to build the model to control stream 2 flow rate are...
1. Build the flowsheet as shown in the diagram. Provide all necessary input so the model can be run.
2. Select stream 2 (the stream flow rate to be set) as the TEAR stream by selecting stream 2 in the Data Browser under Convergence | Tear.
3. Enter a starting stream composition, flow and remaining operating conditions for stream 2 making sure to enter the desired total flow rate.
4. Create a BALANCE block by going to Flowsheeting Options | Balance in the Data Browser.
5. Under Setup in the Mass Balance tab of the Balance block, create Mass balance number 1. For Enter blocks or streams to define mass balance envelope select Blocks and enter the block MUSOLV.
6. In the Calculate tab of the Balance block, select stream 7 as the stream to calculate for the Balance block.
7. In this example, the Convergence tolerance had to be reduced to 1E-5 in order to more closely reach the desired recycle flow. The tolerance is set in the Balance block under the Advanced | Parameters tab.
Details on how to use the Balance block can be found in the Help Topics in Aspen Plus. A BKP file of this example (for release 12.1 and newer) is included for reference.
Keywords: None
References: None |
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 phase or the organic phase). Can I draw the LLE curve on the same plot to have a complete picture of the VLLE? | 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 the data browser in Properties > Analysis > VLE. These are the results of a VLE (T-xy) calculation saved while doing a Tools > Analysis > Property > Binary > TXY type analysis.
3. Use the Plot Wizard from the Plot pull-down menu and create a standard T-xy plot, by selecting TXY and following the prompts.
4. Keep the plot window open. This is very important because once you close the plot, it is gone forever.
5. Go back to the data browser and open the Properties > Analysis > LLE. This is a Generic Property Analysis defined by flashing an unstable composition (e.g. the heterogeneous azeotrope) at various temperatures. The mole fraction in the 2 coexisting liquid phases was calculated as a function of temperature. Temperature range and increments for the calculations should be fine-tuned to ensure a smooth transition. The data entered is as follows:
o Points along a flash curve
o Valid phases: Vapor-Liquid-Liquid
o Component flows: 0.15 moles of N-BUOH and 0.85 moles of WATER.
o Fixed state variable: Pressure: 1.01325 bar
o Adjusted variable: Temperature, lower bound: 75C, upper bound: 95.9C, increments: 0.5C
o Plotted properties have been defined in Prop-Set PS-2 and they are the mole fraction for each component in each liquid phase.
6. Go to Results of Property Analysis LLE. If you don't have results please re-run the Analysis. Select the liquid1 mole fraction of the component which represents the independent mole fraction in the T-xy plot (e.g., N-BUOH) by clicking on the column header. Go to Plot menu and choose X-axis variable. This assigns Liquid 1 mole fraction of N-BUOH to be in the X-axis variable.
7. Select the temperature and assign it to be the Y-axis variable, again by going to the Plot menu and selecting Y-axis variable.
8. Go back to the Plot menu and select Add a new curve. A list of currently available (open) plots will come up. Select the T- xy plot that you had created with the VLE data. Click OK. A line will appear over the T- xy plot.
9. Go back to Results of Property Analysis LLE. Select the liquid2 mole fraction of the component which represents the independent mole fraction in the T-xy plot (e.g., N-BUOH) by clicking on the column header. Go to Plot menu and choose X-axis variable. This assigns Liquid 2 mole fraction of N-BUOH to be in the X-axis variable.
10. Select the temperature again and assign it to be the Y-axis variable, again by going to the Plot menu and selecting Y-axis variable.
11. Go back to the Plot menu and select Add a new curve. A list of currently available (open) plots will come up. Select the T- xy plot that you had created with the VLE data. Click OK. A line will appear over the T- xy plot.
12. Return to the plot window. You should see 4 curves now, i.e., T-x, T-y, and the 2 branches of the binodal (LLE) curve. There currently are three independent T axis (y axis) and the plot does not look very tidy. We need to reduce the temperatures to one single y axis.
13. Right-click on the plot and select Properties. On Axis Map, select All in one. If necessary, change the color of lines and other properties as appropriate.
Keywords: VLLE
plot
plot wizard
References: None |
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 Aspen Plus Analysis features to create a ternary diagram without an Aspen Split license. To use this feature, go to Tools --> Analysis --> Property --> Ternary. Select the ternary mixture and the pressure and then click the Go button. Some options from the Split Conceptual design tool such as using a mass fraction basis are not available.
3 - In the Aspen Plus 2006 and earlier GUI, It is not straightforward to plot a ternary diagram since is only possible to plot it using Data Regression (step by step procedure described below). It is also possible to generate the data using Analysis and then use some other graphing program to plot the ternary diagram.
As an example, let's consider the mixture Water, Acetic Acid (ACETI-01) and DIISOPROPYL-ETHER (DIISO-01) .
Below are the steps to follow:
1 - Use Flowsheet or Data Analysis as Run Type
2 - Create a Property Analysis module - You can use PT-1 as a default name and Select Type to be Generic
3 - For the Input tick Points along a flash curve
4 - Valid phases as Vapor-Liquid-Liquid
5 - System: Specify component flow and enter 50 kg/hr for DIISO-01 and 50 kg/hr for Water.
6 - In Variable enter Temperature and Pressure and in Adjusted Variables, enter Mass flow as Variable and ACETI-01 as Component
7 - In Range/List Enter Range as a choice for Variable range or list and 0 as Lower and 81.1 (this latter value could be amended depending on the system and on available data) as Upper and an increment of 1.
8 - In Tabulate Go to Selected Prop-Sets and with a Right Mouse Click select new - You can choose PS-1 as the default name (Note that you can create a Prop-Set before hand and Select it from Available Prop-Sets).
9 - You now have to go into the Prop-Set you have just created and Select MASSFRAC in Physical Properties and Select 1st liquid and 2nd liquid in Qualifiers.
10 - Run the simulation and go to Analysis and copy the results to Excel for example.
11 - At that stage you can generate the plot in Excel but the chart won't be a triangular one.
12 - To plot it in Aspen Plus, here are the steps:
13 - You need to change the run type to Data Regression and create a data ID Type Mixture. Select the 3 components and Data type as TXX, Composition basis as Mass fraction. In the Data sheet, copy the values you had copied earlier into Excel. In the temperature column use 20C in all the rows.
14 - Under Data regression Select Evaluation in the Calculation type. In Parameters, delete all the columns
15 - Run the simulation and go to Results then Profiles
16 - Under Plot select Plot wizard and choose Triangular.
Enclosed is an example - Data from: Treybal - Mass Transfer Operations (3rd ed.)
Keywords: Physical properties, Mixture, ternary, Triangular diagram, analysis, regression, VLLE, LLE, Liquid-Liquid, Aspen Split
References: None |
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 AllVariables table of the block B1
Launch the dynamic run
Change the value of K on B1 table to 0.1
Observe the discrete action of the level controller
There are some issues with a discrete controller to consider:
how do you want to handle rewind/restart
how to force the integration to step at specific times
The example is a simple proportional level controller, which sets the input flowrate to (3 - volume). The volume is measured every 0.1 hr, to update the flowrate.
This is implemented in the procedure pControl, which is coded in the file control.f.
The rewind/restarts are handled automatically by the fact that the workspace of the procedure is rewound/restarted.
The integration steps are forced by calling the SAX function to schedule event with the option code -1. Note that this works only for Variable Step Implicit Euler integration method, not Gear.
This example also shows how to call a C function from a FORTRAN subroutine.
INTERFACE TO INTEGER*4 FUNCTION ACM_ScheduleTimeEvent
* [C,ALIAS:'_ACM_ScheduleTimeEvent'] (time)
double precision time [VALUE]
END
If you don't have a C compiler, you can comment out the line that tries to compile ACM_ScheduleTimeEvent.c (see comments in makefile.txt).
ACM_ScheduleTimeEvent.c:
#include sax_support.h
#include ATDLL.h
/*
This function can be used to schedule an event, ie force ACM to do a step at
the specified time.
Note that currently this is working correctly only with VSIE.
*/
int ACM_ScheduleTimeEvent(double time)
{
int RqstOption = 31;
int iinfo;
double SimTime;
char *sinfo;
ACMProblemHandle pProblemHandle;
int i;
/* Get simulation time */
i = SputRqst(&RqstOption, &iinfo, &SimTime, &sinfo);
/* Get handle for use in calling SAX utilities */
pProblemHandle = ACM_GetProblemHandle();
/* if time is not passed, schedule event */
if (time > SimTime) SAX_ScheduleTimeEvent(pProblemHandle, -1, time);
return 0;
} | 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 Components\) are available in the Stream Input form. This is the default.
If Generation is specified, only assays and blends specified there are available in the Stream Input form.
If an assay does not show up in the stream input form list, add it to the Generation form.
Keywords: petroleum
ada
assay
generation
stream
References: None |
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 specifications can also be changed. When changing input, Aspen Plus will enforce the same data entry rules as it does if the change is made manually. This means that it may be necessary to delete one specification before another can be made.
For example, Radfrac only permits the specification of two operating conditions. If the distillate to feed ratio and reflux ratio have been specified, one of these specifications must be deleted before another specification can be made. In Visual Basic or Excel/VBA, Aspen Plus data can be deleted by setting the value to Nothing. The following two lines will delete the reflux ratio and set the distillate rate to 150 for a Radfrac column:
'' Clear the reflux ratio specification first
go_Simulation.Tree.Data.Blocks.B1.Input.BASIS_RR.Value = Nothing
'' Add a specification for the distillate rate
go_Simulation.Tree.Data.Blocks.B1.Input.BASIS_D.Value = 150
The variable go_Simulation is a global object variable that represents the Aspen Plus simulation. It is defined by a Dim statement as an IHapp type.
Keywords: VBA, ActiveX
References: None |
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 editor besides Notepad in the Aspen Plus graphical user interface? | 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
Microsoft Word:
C:\Program Files\Microsoft Office\OFFICE11\WINWORD.EXE
The advantage of using Word is that it does respect the hard coded formating characters such as page breaks and it has excellent memory management. Both Wordpad and Word also have more detailed print dialogues to allow you to change your printer's attributes, such as double sided printing, multiple pages per sheet of paper, etc.
This default text editor is used on the VIEW pull-down menu for viewing history, report, input summary and also from the RUN pull-down menu's SETTING | OPTIONS sheet's Edit keyword input before starting calculations option.
Keywords: printing,
References: None |
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 box lists a remedy in Excel, but the Add-In option under Excel''s TOOLS pull-down menu does not seem to be available.
This error occurs in the Windows 95, 98 and 2000 operating systems. There are no reports of this error occuring in Windows NT.
Wordaround:
The Add-In menu option is not always available in Excel, when Excel has been spawned by Aspen Plus. If you do not see the Add-In option under the Tools menu in Excel, close Excel, and start a fresh, stand-alone Excel session.
In the stand-alone Excel session, go to the Tools menu and select Add-Ins. On the Add-Ins dialogue, click on the Browse button and navigate to the directory where the Aspen Plus Graphical User Interface is installed:
typically: C:\Program Files\Aspen Tech\Aspen Plus 10.2\gui\xeq
Find the file called: CalcExcelAddIn.xla (typically the only file that will show up when you have navigated to the correct directory).
Shut down Excel, restart Aspen Plus and go back to the Calculator block. Try to open the Excel spreadsheet from inside the Calculator block.
In some rare cases, this fix will not provide a remedy. In those cases, please load the attached Aspen Plus model (or any Aspen Plus model that has a fully functional Calculator block from another machine). Download the attached Aspen Plus model, CumeneXL.BKP and its companion .APMBD file and as the Calculator block executes, the problem with the Add-In reference is remedied.
Fixed in Version:
Aspen Plus 10.2 Service Pack 1
To apply the Aspen Engineering Suite 10.2 Service Pack 1 for Aspen Plus. Click this link to go to the Aspen Engineering Suite 10.2 Service Pack 1 download page:
http://support.aspentech.com/webteamcgi/ | 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 exceptionally large and what exactly do we mean by Computational difficulties? | 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 equilibrium (LLE) if the components are of similar volatility. However, the Wilson property method cannot predict LLE based its thermodynamic assumptions. When this message occurs, it is advisable to check if LLE could be occurring. If no data is available, Check if there are binary parameters in the LLE-ASPEN databank for NRTL or UNIQUAC and use on of those methods to see if LLE is predicted. If not check if UNIFAC or UNIF-LL predict LLE. The computational difficulties lie in taking derivatives (for heat of mixing) and probably doing routine flash calculations (like a PQ flash).
Keywords: LLE
References: None |
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 to enter a list of vapor pressures and have the corresponding temperatures calculated.
2. For components, select the desired component and any other component.
3. For the compositions basis, select the desired component.
4. Choose to list compositions, and enter 1.
5. Select the number of points as 1.
6. Enter a range or a list of temperatures or pressures.
7. Click Go.
8. There will be no plot, close plot window and use the Plot menu to plot Pressure vs Temperature from the Table.
Results for Methane:
TEMP TOTAL
PRES
F atm
-161.5 0.96464616
-152.3 1.96858614
-138.3 4.79188609
-124.8 9.60220447
-108.5 19.1296128
-96.3 29.600914
-86.3 40.7094588
This plot can also be created using Generic Analysis. SeeSolution 103646 for more details.
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. However, PL tabulates vapor pressure as calculated from the Antoine coefficients for the component not from the equation of state used.
Keywords: EOS, Vapor Pressure
References: None |
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 using a generic Property Analysis by filling out forms in the Data Browser.
1. In the Properties folder, go to Analysis and create a New Analysis with a Type of GENERIC.
2. Define the component you want to use by putting a value of 1 in the component flow field.
3. Move to the next sheet by clicking the Variable tab.
o For one of the two thermodynamic specifications, make Vapor Fraction a fixed variable. A value of 0.5 works well.
o Choose temperature as an adjusted variable. With Temperature selected, hit the Range/List button and enter the temperatures you wish to get vapor pressure.
4. Move to the Tabulate sheet by clicking on the tab.
None of our built-in Prop-Sets has pressure as a property, so it is necessary to create a new Prop-Set. You create a Prop-Set here by clicking the right mouse button in the Selected Prop-Sets field and picking New. After naming the Prop-Set, the analysis is complete.
5. You can click on the Next button to go to the Properties/Prop-Sets form for your new Prop-Set.
On the Properties sheet, add PRES (and any other properties you wish) to the list.
The analysis is now ready to run. If the run type is set to Property Analysis (on the Setup/Specifications form) the property table can be generated immediately without needing to run a flowsheet.
Results:
Below are the results of the Analysis in the attached example file for Methane, Ethane and Propane.
The data in the tables is from Perry's Chemical Engineers' Handbook, 6th edition.
The Aspen Plus Analysis was done using the RK-SOAVE property method.
Methane:
Vapor
Vapor
Temp.
Pres.
Pres.
data
predicted
[C]
[atm]
[atm]
-161.5
1
0.9646459
-152.3
2
1.968586
-138.3
5
4.791886
-124.8
10
9.602206
-108.5
20
19.12961
-96.3
30
29.60091
-86.3
40
40.70945
Ethane:
Vapor
Vapor
Temp.
Pres.
Pres.
data
predicted
[C]
[atm]
[atm]
-88.6
1
0.9757294
-75
2
1.943413
-52.8
5
4.914951
-32
10
9.959587
-6.4
20
20.37753
10
30
30.15209
23.6
40
40.45313
Propane:
Vapor
Vapor
Temp.
Pres.
Pres.
data
predicted
[C]
[atm]
[atm]
-42.1
1
0.9872828
-25.6
2
1.950454
1.4
5
4.903547
26.9
10
9.962344
58.1
20
20.37973
78.7
30
30.52821
94.8
40
40.59472
Keywords: None
References: None |
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 does not pass the data when the subroutine is compiled and linked as a link library (.dll). The User2 common gets zero for all the values in the Common block.
(Note: when using this technique to initialize a Common block, the Calculator block should execute first to guarantee that the Common block is intialized prior to executing the User2 block.) | 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 dll for the Calculator code), each DLL has its own private /USRRI1/ and hence the problem of not sharing data.
To enable the same /USRRI1/ to be used by both codes, you have to
Make usr2.f export the /USRRI1/ common
Make the calculator to import the /USRRI1/ common
The safest way to accomplish the task is to perform following the following steps
Step 1. Create an include file, say usrri1.cmn, with the following content
REAL*8 PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
#ifdef EXPORT_USRRI1
COMMON /USRRI1 [DLLEXPORT]/
+ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
#else
COMMON /USRRI1 [DLLIMPORT]/
+ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
#endif
What this file does is it will specify [DLLEXPORT] attribute when EXPORT_USRRI1 is specified and it would specify [DLLIMPORT] attribute otherwise.
Step 2. Modify usr2.f by replacing
REAL*8 PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
COMMON
+ /USRRI1/ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
with
#define EXPORT_USRRI1
#include usrri1.cmn
so that usr2.f (and the DLL file created from it) would export /USRRI1/.
Step 3. Modify the calculator block input by replacing
F
with
COMMON /USRRI1/ PARM1, PARM2, PARM3, PARM4, PARM5, PARM6
F
#include usrri1.cmn
so that the code would import /USRRI1/. Note that we leave EXPORT_USRRI1 undefined.
Note that:
The symbol EXPORT_USRRI1 is arbitrary. You can use whatever symbol that is appropriate.
The new setup should also work with .obj file - you would be just importing from the same DLL.
Pay attention to the strange #include syntax in Calculator FORTRAN. Most other variations would not work. The statements with the # at the beginning are precompiler directives that are turned into code prior to compiling.
It is possible to explicitly place the export/import directives and COMMON block in the Calculator block and usr2.f without using the check for the symbol described above - the risk is that the COMMON blocks could get out of synch.
(See attached files: test1.bkp, test1.inp, usr2.f, usrri1.cmn)
Keywords:
References: None |
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 enter the relevant connection name in the block field.
For Aspen Plus 10.2 Update 1, the connection names for the Hierarchy block can be read off the Input file. (Select Input Summary from the View menu, and then search for CONNECT in the file.)
For Aspen Plus 11.1, the connection names can be seen on the Hierarchy block''s Input/Connections sheet.
An example file is attached..
Keywords: Hierarchy
hierarchy
sequence
sequencing
connections
user sequence
References: None |
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 extract it. Win95_**.cab, is number, the number which containing ftsrch.dll is different for each version. Copy ftsrch.dll under system directory. (c:\Windows\system).
Note:
Windows NT 4.0 also has ftsrch.dll, but do not use it under Windows 95/98 since it is not compatible.
Keywords: Online
Help
Find
Search
Windows 95
Windows 98
References: None |
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 absorption (delta_h_abs) is the amount of heat exchanged for the absorption of 1 mole gas. Taking a simple approach for the temperature dependence of Henry's constant, e.g.:
ln(H) = a + b/T
we can conclude that
delta_h_abs = b * R
(where R is the universal gas constant).
The first attachment (file: example1.bkp) is intended to demonstrate that Aspen Plus indeed performs its calculations this way. It is a gas solubility example at 25 C and the modified HENRY coefficients make sure that the gas solubilty is sufficiently high. There is no gas phase (i.e., no latent heat effect etc.), so the calculated flash heat duty should be equal to the enthalpy of absorption of 1 kmol O2. The Fortran block RESIDUAL calculates the heat of absorption and the residual of [delta_h_abs/R = b]. This is true for any model combination activity coefficient model/Henry's law, except for the electrolyte activity coefficient models.
Absorption accompanied by chemical reaction, e.g. CO2 in water
Next to the physical absorption step,
CO2 (g) ---> CO2 (aq)
another contribution to the heat of absorption should arise from the subsequent chemical reaction(s):
CO2 + 2 H2O
<-->
H3O+
+
HCO3-
HCO3- + H2O
<-->
H3O+
+
CO3-2
where the enthalpy due to chemical reaction can be obtained according to
d ln (K)/dT = delta_h_rxn/R*T^2
The overall heat of absorption should then be made up from both contributions, i.e. physical plus chemical contribution.
delta_h_abs + delta_h_rxn
Using another example (file: example2.bkp) which is based on the KEMDEA insert, those two contributions to the overall enthalpy are calculated. Three flash blocks are used: B1 with a complete setup, and a series of B2 and B3 with B2 operating without chemistry to exclude the assumed effect of the heat of reaction [delta_h_rxn]. Again, the process is tuned to avoid any latent heat effects, such as enthalpy of vaporization etc. Finally, a Fortran block is used to calculate the residual of the enthalpy balance. The actual value for the residual is printed in the Control Panel and indicates that these contributions are balanced.
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