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Problem Statement: The error saying there are missing engine file(s) appears when trying to run a simulation in Aspen Plus | Solution: This often happens when the user, or when the template file the user used to build the model, contains a reference to a user databank that does not exist.
The remedy is fairly easy:
1. Click on the DATA pull-down menu in Aspen Plus and then click on COMPONENTS
2. Click on the DATABANKS tab at the top right side of the component form.
3. Highlight all of the selected User databanks (USRPP1A, USRPP1B, USRPP2A, USRPP2B, USRPP2C), click the left arrow and move these databanks to the left side Available list.
Keywords: missing engine file, user data banks, usrpp1a.dat, usrpp2a, usrpp2b, usrpp2c
References: None |
Problem Statement: It is possible to specify different properties for the two sides of a HeatX block? | Solution: Indeed, it is possible to specify different property methods for the hot and cold sides of a HeatX block. One case where this is needed is if you want to model water or steam properties accurately using steam tables (STEAM-TA, STEAMNBS, or STMNBS2) and model the process stream using some other property method.
To specify the property methods for the HeatX block, go to the HeatX | Block Options | Properties sheet, and choose different Property methods for the hot and cold sides. The following picture shows the form.
Keywords: Heatx, heat exchanger, different property method, two sides, fluid package
References: None |
Problem Statement: What are the flash types available in Aspen Plus CAPE OPEN? | Solution: PVF which requires properties Pressure and PhaseFraction for phase vapor and basis mole to be set in the material object
TVF which requires properties Temperature and PhaseFraction for phase vapor and basis mole
PLF which requires properties Pressure and PhaseFraction for phase liquid and basis mole
TLF which requires properties Temperature and PhaseFraction for phase liquid and basis mole
TP which requires properties Temperature and Pressure
PH which requires properties Pressure and Enthalpy for phase Overall and basis mole
TH which requires properties Temperature and Enthalpy for phase Overall and basis mole
For any of these we expect the material object to contain:
Pressure for the overall phase with calctype mixture
Temperature for the overall phase with calctype mixture
Fraction for the overall phase with mole basis, calctype undefined and compids specified.
Note that Aspen does not yet do mole to mass conversions for values stored in material objects so a Unit Operation of Property Package client must use mole basis where it matters.
Keywords: CAPE-OPEN
References: None |
Problem Statement: How is a partial condenser handled in the shortcut distillation block Distl? | Solution: Distl performs shortcut distillation rating calculations using the Edminster approach for a single-feed, two-product distillation column. Distl assumes constant mole overflow and constant relative volatilities. The column can have either a partial or total condenser.
However, as opposed to a RadFrac block, a partial condenser in Distl results in a vapor only distillate. A total condenser results in a liquid distillate. There is no option to specify the vapor fraction of the distillate. Hence, a single outlet stream is used for the distillate.
Keywords: short-cut
tower
column
References: None |
Problem Statement: Often times, there is no measurement of a column's product flow rates, or the measurement devices are unreliable/rarely calibrated. If accurate Gas Chromatograph (GC) analysis data is available for each product, can Aspen Plus determine the flow rate of each product? | Solution: Aspen Plus' DATA-Fit feature is capable of regressing the product rates from know compositions. In the attached example the spreadsheet lists the GC composition data, highlighted in Yellow. The GC data is entered on the DATA | Model Analysis Tools | Data Fit | Data Set forms.
The attached Aspen Plus model assumes a 5% standard deviation on all GC measurements. Your GC chemist may be able to give you better values for his lab measurements for each component. In this example, one DATA set was created for each measured product stream (4 total) on the MODEL ANALYSIS TOOLS | DATA FIT | REGRESSION | DATA SET form.
Next either supply an accurate feed rate or a best guess. This example uses 100 moles of mixed alcohol feed but varies three of the four product rates:
the distillate product rate
the C3 product draw rate
the C4-C5 product draw rate
This allows the C6 product flowrate to be calculated by difference. Each of these variables requires a starting guess on the appropriate Radfrac input on the RADFRAC | SETUP form's CONFIGURATION and STREAMS sheets. The flowrate for these flow products are defined as variables on the MODEL ANALYSIS TOOLS | DATA FIT | REGRESSION | INPUT form's VARY sheet. A lower and upper bound for acceptable flowrates on must also be supplied for each variable. On the same form, this example also specifies that all four GC composition data sets are to be used on the SPECIFICATIONS sheet.
It takes many regression iterations to solve the model, but eventually, the compositions matched very closely (see the spreadsheet). The flows have a little scatter, but they are acceptable.
The last step is to scale up the feed rate so it matches some plant data for the column. Data you can try to match could be a reboiler duty, or perhaps you know the total tonnage of the combined products or other column measurements.
Keywords: Data-Fit, calculate flow rates, GC
References: None |
Problem Statement: Is it possible to color the streams in a flowsheet to make it easier to trace streams in a large model? | Solution: Starting in version 12 and later, the material streams have a Color & Style attribute as seen in the screenshot below.
To change a stream color, do the following:
1. Go to the flowsheet view in Aspen Plus
2. Left click on the stream or stream label to highlight the stream
3. Right click on the stream and choose COLOR & STYLE from the pop-up box.
4. In the STREAM STYLE dialogue, choose the stream color and line style (thick, thin, dashed, solid, etc).
Keywords: None
References: None |
Problem Statement: When comparing the liquid enthalpy with the solid enthalpy of a component in some simulations, the enthalpy difference between the phases does not equal the heat of fusion (crystalization). Why would this discrepancy occur? | Solution: There are two ways commonly used in Aspen Plus to calculate the solid component enthalpy: the Barin equations (CPSXPn) and the solid heat capacity method (CPSDIP).
The Barin method uses one set of parameters (the CPxXPn parameters) to calculate all of the thermodynamic properties. There are parameters for each phase (CPIXPn for ideal gas, CPLXPn for liquid and CPSXPn for solid). In addition, each phase can have a number of different sets of parameters for different temperature ranges. These sets of parameters are used to calculate Gibbs Energy, Enthalpy, Entropy, and Heat Capacity. These properties are interrelated by basic thermodynamic relationships. The Barin equations are documented in the Help under Aspen Pus
Keywords: fusion, crystalization, Barin, Solid, sublimation, SVLE
References: | Physical Property Methods and Models | Chapter 3 Property models | Thermodynamic Properties | Other Thermodynamic Property Models | Barin Equations for Gibbs Energy, Enthalpy, Entropy, and Heat Capacity.
When using the Aspen (CPSPO1), DIPPR (CPSDIP), or IK-CAPE (CPSPO) solid heat capacity model, enthalpy is calculated from the solid heat of formation (DHSFRM) and the heat capacity. These equations are documented in the Help under Aspen Pus Reference | Physical Property Methods and Models | Chapter 3 Property models | Thermodynamic Properties | Heat Capacity Models | Aspen/DIPPR/Barin/IK-CAPE Solid Heat Capacity.
Normally, Aspen Plus defaults to the Barin equations if the Barin parameters are available. The Barin parameters are located in the INORGANIC databank, and one can use Tools/Retrieve Parameter results to check their availability. The advantage of the Barin equations are that they have a solid heat of formation built into the equation (and do not use DHSFRM) which is consistent with the conventional component enthalpy calculation. That means that when the Barin equations are used HL-HS = heat of fusion.
Unfortunately, sometimes the Barin parameters are not available. If the Barin parameters are not available, Aspen Plus will default to one of the other solid heat capacity models mentioned above (Aspen (CPSPO1), DIPPR (CPSDIP), or IK-CAPE (CPSPO) solid heat capacity model). Often this causes a discrepancy between the solid enthalpy (HS) and the liquid enthalpy (HL). In Aspen Plus, enthalpy is calculated from the ideal gas heat of formation (DHFORM) for the component in the ideal vapor phase. If the component data in the databanks are complete and correct, then typically
DHFORM - DHSFRM = DHVL (latent heat) + Heat of fusion
However, the solid heat of formation (DHSFRM) data is often missing or not accurate. If DHSFRM is missing, it defaults to zero which means that the solid enthalpy will not be inline with the other phases. This is also an issue with Gibbs Free Energies when the Solid Gibbs Free Energy of Formation (DGSFRM) defaults to zero.
In many solid applications where the component is only present as a solid, this discrepancy is not important; however, unfortunately it is an issue when there are solid reactions and phase changes. In order to correct the Aspen Plus simulation, one would have to supply a better value for DHSFRM to Aspen Plus (Enter it under Properties | Parameter | Pure as a Scalar parameter) or perhaps supply Aspen Plus with a set of parameters for the Barin equation (Enter this under Properties | Parameter | Pure as a Temperature dependent parameter). Values for DHSFRM can be obtained from a simple calculation (e.g. DHSFRM = DHFORM - DHVL - Hfusion). CPSXPn would require a property regression run with component enthalpy data in order to obtain the parameters. |
Problem Statement: The electrolyte template and the electrolyte wizard sets the databank search order as follows:
ASPENPCD
AQUEOUS
SOLIDS
INORGANIC
PURE1x
Is this the way that the search order should be for electrolyte application? | Solution: Yes, this is the order because all of the parameters in our electrolyte databanks were regressed using this order. If there is a problem, the parameter from a more recent version can be entered manually on the forms. Since the other parameters used are regressed with the order mentioned, care should be used.
The INORGANIC Barin databank can be moved ahead of the SOLIDS databank in order to have the enthalpy of the solid salts calculated using the Barin heat capacity polynomical parameters. It will not affect the liquid enthalpy calculations since the electrolyte model always calculates enthalpy from the ideal gas enthalpy and the heat of vaporization and not from liquid heat capacity.
Keywords: electrolytes
databank
order
References: None |
Problem Statement: If you watch the control panel in an Aspen Plus run that was launched from an Excel spreadsheet using Visual Basic (for applications, VBA), the control panel results are not updated until the simulation engine finishes the run. Why? | Solution: Starting with version 11.1, the control panel updates were shut off until the run completes for automated runs from VBA. This step was taken to speed the execution.
Please try the following items:
Instead of using the run method, try the Run2 method, i.e. go_simulation.engine.run2 instead of go_simulation.engine.run
If item 1) is not successful, then you will have to switch to Asynchronous run mode (synchronous is the default). The one caveat, is that after you launch an asynchronous run, you do not want to execute any VBA code that refers to the Aspen Plus results until the Aspen Plus run is complete. Here is a code fragment that will do this:
Dim AsynchRun As Boolean
AsynchRun = True
go_Simulation.Engine.Run2 (AsynchRun)
Exit Sub
Keywords:
References: None |
Problem Statement: Aspen Plus customer gets the following error during System Boot
trctrl.exe encounters problem on boot up | Solution: This is the startup service program to be used with Dais and it is not needed to run Aspen Plus.
Please Note: To disable this service, user needs to have system administrative privileges on that system.
To disable this service do as follows:
Right click mouse on My Computer Icon on your desk top and select Manage
Click on the Services and Applications
Then Click on the Services
Double click on Dias Service and select disable under startup type.
Click Ok and exit the Computer Management screen.
Keywords: trctrl.exe
trctrl
Dias
References: None |
Problem Statement: What is the source for the Kij's that are in the binary databanks? | Solution: Kij?s for Peng-Robinson, RKS, Lee-Kesler Plocker came from
Vapor-Liquid Equilibria for Mixtures of Low Boiling Substances, H. Knapp, R. Doring, L. Oellrich, U. Plocker and J. M. Prausnitz, Dechema Chemistry data Series, Vol. VI.
Pure component and Kij?s for BWR-Lee-Starling came from
M.R. Brule, C.T. Lin, L.L. Lee, and K.E. Starling, AIChE J., Vol. 28, (1982) p. 616.
Watanasiri et al., AIChE J., Vol. 28, (1982) p. 626.
Keywords: PENG-ROB
LK-PLOCK
RK-SOAVE
References: None |
Problem Statement: If I use year as a flow unit, how many days does Aspen Plus consider in a year? | Solution: Aspen Plus will consider a year to have 365.25 days. This takes into account leap year. So if you have a flow of mass/day you would multiply it by 365.25 to get the mass/year.
Keywords: year, day, flow, units
References: None |
Problem Statement: During the calculation of a dynamic pressure relief scenario, Aspen Plus issues the following message:
* WARNING
DISENGAGEMENT CALCULATIONS DID NOT CONVERGE AT 2.828389D+03 SEC
What is the meaning of this message? | Solution: When the user chooses bubbly or churn-turbulent disengagement, there is an iterative
calculation to calculate the vapor fraction leaving the vessel at each time point. The warning
message is saying that this calculation failed to converge. If you make a plot of vent flow vs.
time, you can see it happens right when there is a sharp change in the flowrate, so the
derivative is changing very quickly with time and this is probably what is causing the problem.
The calculations proceed fine after the warning and the numbers make sense, so it's
probably OK to ignore the warning.
If you want to, you can loosen the tolerance for this iterative calculation. Go to the Pres Relief
/ ... / Convergence / Parameters form and set Bubbly/Churn loop error tolerance to .01
and the problem will go away. The results are virtually identical.
Another option is to leave the Bubbly/Churn loop error tolerance at its default value and
tighten the Flow loop error tolerance to 1E-05. When you do this the routine that does the
iterative calculations to find the vapor fraction gets better derivatives and is able to converge.
Either way seems to work.
Keywords:
References: None |
Problem Statement: Why are the Aspen Plus NRTL model equations different than the equations in the original Renon paper (Renon, H. and J.M. Prausitz, Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures, AIChE Journal, 14 (1) 135 (1968) ). | Solution: See page 3-73 of the Physical Properties Methods and Models referece manual for the NRTL equation for activity coefficient. This is an extension of the original model presented in the above paper.
In the Aspen Plus implementation of NRTL:
tau,ij = aij + bij/T + eij lnT + fij/T
Gij = exp(-alpha,ij Sij)
alpha,ij = cij + dij (T - 273.15K)
In the original form of the equations as derived by Renon, the quantity tau,ij is related to differences in the intermolecular Gibbs free energies of interaction, delta gij, by the expression:
tau,ij = delta gij / RT
This is equivalent to the expression used in Aspen Plus if the parameters are related as follows:
aij, dij, eij, and fig = 0
bij = delta gij / R
Keywords: gamma
References: None |
Problem Statement: What is the foaming index and what is a reasonable value? | Solution: Foaming or Marangoni index represents the tendency of a liquid mixture to expand due to foaming effects. The values are reported on the RadFrac\Profiles\Hydraulics sheet when the Include Hydraulic Parameters is checked on the RadFrac\Report\Property Options.
The Foaming index is defined as:
Foam-Index = Sigma - Sigmato
Where:
Sigma = Surface tension of liquid from the stage
Sigmato = Surface tension of liquid to the stage
Note that the surface tension for the liquid to means the liquid entering the stage, not the surface tension on the stage above (for example if there is a feed stream).
Because of this definition, the foaming index can be positive or negative. If the foaming index is negative, then no foaming should be expected. Typically a value greater than 0.5 to 1 dyne/cm roughly indicates tendency to foam. The magnitude does not provide additional information relating to extent or criticality of foaming.
Keywords:
References: None |
Problem Statement: What does it mean when variable names are not found and phases are being dropped in EO Reinitialization? How do you suppress these warning messages? | Solution: All warning messages are reported according to the diagnostic level on the Data | Setup | Diagnostics page. It is not recommended to reduce the below the default level as any indications that problems have been encountered may be overlooked causing erroneous results.
When doing an Equation-Oriented (EO) simulation, the following warning messages can be a nuisance as they are reported to the control panel numerous times.
1. Starting EO Synchronization ...
INFORMATION WHILE INSTANTIATING THE EQUATION-ORIENTED STREAM BLOCK:
1FEED
BLOCK VAPOR PHASE DROPPED.
2. * WARNING
ERROR INITIALIZING VARIABLES IN TOP LEVEL HIERARCHY:
There is no variable named FEED_MONETH_X
* WARNING
ERROR CREATING ALIASES IN TOP LEVEL HIERARCHY
EO-ALIAS RAISED THE FOLLOWING ERROR:
There is no variable named 1FEED.BLK.MONETH_MASS_FRAC
These are due to new enhancements (2004.1) in the flash options for Equation-Oriented (EO) simulations.
Phase Dropping
This option allows Aspen Plus to automatically adjust the phases allowed for any flash in a block at the instance the block is created. This option is very effective for reducing the size of a problem and avoiding difficulties associated with highly superheated or subcooled flashes. This feature checks each flash associated with a block (outlet flash, mixed inlet flash, dew or bubble point flash) and checks whether any phase is missing.
There are two ways to prevent these messages from being reported to the control panel.
1. Set the appropriate valid phases as Liquid for the inlet stream.
2. Set the Remove missing phases drop-down list to No on the EO configuration | EO Options | Global | Additional Options button | Flash Options sheet. This is not a recommended way to suppress the messages unless EOSolutions are driven into superheated or subcooled regions.
For more information on limitations to this option and on superheated/subcooled regions, see the online help (Aspen Plus
Keywords: None
References: | EO Reference Manual | Unit Operation Models in EO | Features Common to EO Models | EO Flashes | Automatic Phase Removal for EO Flashes).
Variable Names Not Found
The warnings about no variable names found are due to using non-zero components in the feed stream (e.g. for the message above, component flow is 0 for Moneth).
This feature uses the Component tolerance on the same sheet. If a component's combined inlet mass fraction (in the sum of all inlet streams) is less than this tolerance and missing component removal is enabled for that block, then the component is removed. In this case, the component is dropped when EO is synchronized and therefore the alias names are not found. You could also remove the component or provide a flow larger than the tolerance.
Additional Notes from the Help:
Non-Zero components is an important feature in EO that can be used to reduce the size and improve the robustness of the EO model. Non-zero components reduce the number of components to be created by an EO object. Non-zero components may be specified using the following procedure:
1. Create a Component Group holding the list of non-zero components from the Data Browser, select Components | Comp-Groups and click New. The Create New ID dialog box appears. Enter the name of the component group. Click OK. Select the desired components from the Available Components list and click the appropriate arrow keys.
2. Assign the component group to a block, model, flowsheet section or globally. To assign the group within a block, from the Data Browser, select the block in the Blocks list. From the Block Options form, select the EO Options tab.In the Model Components field, select the component group.
Non-zero components may also be assigned globally, via flowsheet section or for a specific model type:
1. From the Data Browser, select EO Configuration | EO Options.
2. Use the Global tab to select the component group to use globally; Use the Flowsheet Section tab to select the appropriate section and component group. Use the Model Types tab to select the model and component group.
For more information on Using Non-Zero components, refer to the online help (Aspen Plus Reference | EO Reference Manual | Using Non-Zero Components). |
Problem Statement: When using the COMPLEX method to converge an optimization problem, what is the definition of STEP-SIZE? How is STEP-SIZE used in generating the initial simplex? | Solution: STEP-SIZE specifies the fraction of the range (for VARY variables) that is used to generate the points in the initial simplex. Note that a different STEP-SIZE can be specified for each VARY variable. New points in the simplex are determined according to the following equation:
S(I) = LB(I) + RANDOM STEP-SIZE(I) [ UB(I) - LB(I) ]
where
S(I) = new coordinate in the simplex for VARY variable I
LB(I) = lower bound for VARY variable I
UB(I) = upper bound for VARY variable I
RANDOM = a random number
The diagram below illustrates how the three points of the simplex might be determined for an optimization problem with two VARY variables, X1 and X2, assuming the STEP-SIZE for X1=0.7 and the STEP-SIZE for X2=0.2.
IC refers to the initial conditions defined by the input file without the OPTIMIZATION. S refers to points generated in the initial simplex. All of points in the initial simplex must fall within the small rectangle at the lower left except for point IC.
Upper bound of X2 |-------------------|
| |
| |
| |
| IC |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
| |
|++++++++++++++ |
| S + |
| S + |
| + |
Lower bound of X2 |-------------------|
LB UB
X1 X1
NOTE: Because reducing the STEP-SIZE clusters the simplex around the lower bounds instead of around the initial conditions, the use of STEP-SIZE is not recommended. It is best to set realistic bounds and to let the algorithm generate a simplex over the whole range. If you restrict the range (using STEP-SIZE), the initial points may be too close together and the algorithm may fail if the simplex collapses.
Keywords: None
References: None |
Problem Statement: What is the definition of the flash tolerance? | Solution: The flash calculation in Aspen Plus is a modified inside-out algorithm (by Boston and Britt). The algorithm linearizes the equations and these linear parameters are used in the error check. The parameters replace the primitive variables of temperature, pressure, vapor and liquid compositions, phase ratio, and enthalpy.
The error (which needs to be less than the tolerance) is square root of the sum of the squares of the differences in these parameters from one iteration to the next.
In plain English, it means that the convergence is tested on these mathematical parameters which have no direct physical interpretation. However, one can assume that the accuracy of the primitive variables (temperature, pressure, vapor and liquid compositions, phase ratio and enthalpy) will be of the same relative accuracy. Tightening the flash tolerance helps avoiding numerical noise with convergence of tear streams. A value of 1e-7 instead of 1e-4 is suggested in these cases. When you decrease the flash tolerance you may need to increase the number of iterations.
Keywords:
References: None |
Problem Statement: What are the units of measurement for GMELCD?
On the input forms, there is a temperature field; so one can switch between C, F, K and R.
However, looking at the databank values, if I switch from C to K, the values stay the same. If I switch from C to F the values will change. Does it make sense to switch from C to K or is always K used ? | Solution: When GMELCD is available, absolute temperature units are used (K or R). This is the case whenever we have a term with 1/T or ln(T) -- because units conversion cannot be done if it is C or F. In this case, we have D/T.
Fixed in Version
The 2006 online help for GMELCD, GMELCE, NRTL, and CPDIEC will be updated to note that absolute units are used. It is not feasible to limit the units of measure in the drop-down list.
Keywords: electrolyte
References: : CQ00220414 |
Problem Statement: Three equations are available for pure component liquid molar volume (VL): the Rackett equation, the DIPPR equation, and the IK-CAPE equation. The DIPPR equation is used if the parameter DNLDIP is available for a given component. The Rackett equation is used if the parameter RKTZRA is available. The IKCAPE equation is used if the parameter VLPO is available.
What happens if more than one set of parameters are available - how does Aspen Plus choose the equation to use, and can the user control which set is being used if there is more that one? | Solution: What is called the Rackett model for pure component liquid molar volume (VL=VL01 on the Property Method\Routes sheet or
VL=VL0RKT on the Property Method\Models sheet)
is really the RackettDIPPRIKCape model, but
that name is too long so we shorten it to Rackett.
The default order is as follows if multiple parameters are added: VLPO
DNLDIP
RKTZRA
Note that user entered parameters are used over databank values. E.g. if RKTZRA is entered by the user and DNLDIP is in the databank, RKTZRA is used. However, if both RKTZRA and DNLDIP are in the databanks or if both are entered then DNLDIP is used.
There are messages in the Control Panel to note the method used when multiple parameters for a model are entered:
WARNING IN PHYSICAL PROPERTY SYSTEM MULTIPLE PARAMETERS FOR LIQUID DENSITY OR VOLUME HAVE BEEN ENTERED FOR COMPONENT C-DI. THE PARAMETER VLPO WILL BE USED. THE PARAMETER DNLDIP WILL BE IGNORED.
WARNING IN PHYSICAL PROPERTY SYSTEM MULTIPLE PARAMETERS FOR LIQUID DENSITY OR VOLUME HAVE BEEN ENTERED FOR COMPONENT C-DRI. THE PARAMETER VLPO WILL BE USED. THE PARAMETER DNLDIP WILL BE IGNORED.
WARNING IN PHYSICAL PROPERTY SYSTEM MULTIPLE PARAMETERS FOR LIQUID DENSITY OR VOLUME HAVE BEEN ENTERED FOR COMPONENT C-RI. THE PARAMETER VLPO WILL BE USED. THE PARAMETER RKTZRA WILL BE IGNORED.
WARNING IN PHYSICAL PROPERTY SYSTEM MULTIPLE PARAMETERS FOR LIQUID DENSITY OR VOLUME HAVE BEEN ENTERED FOR COMPONENT C-DR. THE PARAMETER DNLDIP WILL BE USED. THE PARAMETER RKTZRA WILL BE IGNORED.
WARNING IN PHYSICAL PROPERTY SYSTEM MULTIPLE PARAMETERS FOR LIQUID DENSITY OR VOLUME HAVE BEEN ENTERED FOR COMPONENT C-DRI. THE PARAMETER VLPO WILL BE USED. THE PARAMETER RKTZRA WILL BE IGNORED.
i.e. If all three are entered, then VLPO will be used.
If VLPO and DNLDIP are entered, VLPO will be used.
If DNLDIP and RKTZRA are entered, DNLDIP will be used.
An example file is attached that has components with all of the combinations of parameters entered to make sure that the Aspen Plus calculations are correct.
Components:
C-DIP = only DNLDIP entered
C-RKT = only RKTZRA entered
C-IKC = only VLPO entered
C-DI = DNLDIP and VLPO entered
C-DR = DNLDIP and RKTZRA entered
C-RI = RKTZRA and VLPO entered
C-DRI = all three entered
To override this defaulting, it is possible to use thermoswitches to select the model. SeeSolution 3026 for more information on thermoswitches.
The above logic is similar for other properties such as pure component liquid viscosity.
Keywords:
References: None |
Problem Statement: What mixing rule is used for molar volume (VL) when components are specified with Tabpoly? | Solution: If Tabpoly is used for VL then the mixing rule for VL (and indirectly density) will be ideal.
The equation is
VL(mixture) = Sum ((VLi) * (xi)
where xi is the molefraction.
This will be used for all components. The built in mixing rules for Rackett will not be used.
For more information about Tabpoly seeSolution 3333.
Keywords: density
References: None |
Problem Statement: How do I access stream properties via ActiveX for a simulation with multiple substreams or that have stream classes other than CONVEN? For example how to I get the total density for a stream of class MXCISOLID? | Solution: Using the variable explorer in Aspen Plus the path to density property for a stream named IN-DRIER is
Application.Tree.Data.Streams.IN-DRIER.Output.STRM_UPP.RHOMX.$TOTAL.TOTAL
An example function in VBA that would return a requested stream property might look as follows:
Function CalcProperty (strStreamName,strProperty) as variant '=> You might also use real, string etc depending on the type of property
CalcProperty = go_Simulation.Tree.Data.Streams.Elements(strStreamName).Output.Elements (STRM_UPP). _
Elements(strProperty).Elements($TOTAL).Elements(TOTAL).Value
End Function
The part of the function that could give problems is the .Elements($TOTAL).Elements (TOTAL).Value section since $TOTAL and TOTAL could change to say MIXED and LIQUID for a different property. In other words, $TOTAL would correspond to the substream and TOTAL would correspond to the a specific phase in the substream.
Keywords: VBA, visual basic, activex, Excel, function
References: None |
Problem Statement: How do you report the reaction rates calculated by a user kinetic reaction? | Solution: The existing user variables feature available in RPLUG or RBATCH can be used to print the reaction rates calculated internally by user kinetics subroutines. This feature is used extensively in Polymers Plus to store and report reaction rates and other intermediate calculations (radical concentrations, etc) in several Polymers Plus models.
A quick summary of how to use this feature is attached. The results are just like any other profile results in RPLUG/RBATCH.
The user variable profiles are not passed to pressure drop or heat transfer routines. As a work-around, turn up your simulation level above 6 to get lots of details in the history file.
Keywords:
References: None |
Problem Statement: Are the RON and MON stored in the Aspen Plus Pure Component databanks for conventional components? If so, how do I retrieve the information into the Graphical User Interface ? | Solution: For the PURExx Databanks, the Research Octane Number (RON) and Motor Octane Number (MON) are stored in the pure component databanks; however, they are not retrieved automatically when using Tools/Retrieve Parameter Results...
For Release 9.3 and 10, add the parameters by going to Properties/Advanced/User-Parameters then type in MOCTNO and ROCTNO in the parameter field. Now the values will be retrieved into the User Interface when using the Tools/Retrieve Parameter Results...
For Release 11 and higher the parameter name has changed. Add the parameter names MOC-NO and ROC-NO in the parameter field under Properties/Advanced/User-Parameters to have the values retrieved when using Tools/Retrieve Parameter Results...
Keywords: Additional parameters
References: None |
Problem Statement: Where are the input fields for the driving force coefficients A B C D under General reaction LHHW or GLHHW?
With Reactions/LHHW you can enter parameters A, B, C, D (coefficients for driving force constant) for terms 1 and 2 of the driving force expression.
With Reactions/General/LHHW or Reactions/General/GLHHW, there is no provision for parameters A, B, C, D, therefore how is the driving force constant calculated?
Does Reaction type GENERAL use a different expression for the driving force than the Reaction type LHHW? The documentation suggests that it does not. | Solution: LHHW and GLHHW in the GENERAL reaction type is assuming k1 (for forward reaction) is 1 and k2 (for backward reaction) is 0. Therefore, the user does not have to enter the coefficients A, B, C and D for driving force. The link to General LHHW Kinetic Sheet from General Kinetic Sheet is misleading, because the expressions for driving force are different.
For 2006, we will improve the GENERAL reaction type. It will allow the user to select either legacy LHHW or the generalized expression of LHHW. The generalized expression of LHHW does not have to assume k1=1 and k2=0. Then, the coefficients for driving force will be available to specify.
Assuming the simple reaction: A + B --> C + D
The documented driving force expression, for the legacy LHHW is:
driving force = k1([A].[B]) - k2([C].[D])
The driving force expression for General/LHHW or GLHHW would be:
driving force = [A].[B] (as k1 = 1, and k2 = 0)
The key for General/LHHW or GLHHW is that k1 is lumped into k in the Kinetic Factor.
Keywords: Langmuir-Hinshelwood-Hougen-Watson
LHHW
References: None |
Problem Statement: Is it possible to handle dilute | Solution: s in the Aspen Plus/FactSage/Chemapp interface?
Solution
Using the diluteSolution capability in FactSage 5.3 with the Aspen Plus/FactSage/Chemapp interface is described below and an example is attached.
Background
FactSage 5.3 has the capability to add components to an existing FactSageSolution. The added components are treated as an ideal, diluteSolution. This example is designed to illustrate proper component mapping to these added diluteSolution components. It is not intended to be a realistic example of any process.
Simulation calculations using the Aspen Plus/FactSage/Chemapp interface rely on proper component mapping between the Aspen Plus component names and the phase/constituent information encoded in a chemsage file (*.cst). Because AspenTech cannot anticipate which components might be added to which FactSageSolutions, the FACTPCD in Aspen Plus does not contain any components present as an idealSolution in anySolution phases. Use of the diluteSolution capability in a simulation requires the user to create a databank with the dilute components. AspenTech recommends that the dilute components be added to a USRPP1A or USRPP1B databank.
This example demonstrates adding HfO2(s), Tl2O(l), Se(l), Se2Cl2(l), NaBr(l), KBr(l), CaBr2(l), Se2Br2(l), Cd(l), CdCl2(l), CdBr2(l), Pb(l), PbS(l), PbCl2(l) and PbBr2(l) to the FACT-SLAG?Solution phase in a USRPP1A databank, and running a simulation that uses the USRPP1A databank. This document assumes that the user is already familiar with the following topics:
Use of Equilib inside FactSage, including creation of a .cst file
Use of Aspen Plus with the Aspen Plus/FactSage/Chemapp interface
Procedures to modify Aspen Plus databanks (GUI and engine)
This example was designed to run in Aspen Plus 12.1 with cumulative hot fix 13 and higher, or in Aspen Plus 2004 with cumulative hot fix 1 or higher. The files were developed in Aspen Plus 12.1.
This document is designed to be used with the following attachments:
FactSage-Dilute-Solution-Example.doc
Documentation
USRFACT1.inp
DFMS input file for USRPP1A.DAT
USRPP1A.DAT
Databank file created by USRFACT1.inp
Usrfact1GUI.dat
MMTBS customization file for USRPP1A
Oxygen.bkp
Example file
Slag.bkp
Example file
Dil-slag.cst
Chemsage file for the example
EquiDilute-slag-example.dat
Equilib file to create Dil-slag.cst
Note that Dil-slag.cst is encoded to a specific FactSage dongle ID. Only AspenTech employees will be able to run the interface with this file. AspenTech customers will need to generate their own version of Dil-slag.cst.
Creating the .cst file in Equilib
Open Equilib to the Reactants window screen. Add 1 mole of each of the following components: Al2O3, CaO, K2O, Na2O, PbO, SiO2. These are all standard components in the FACT-SLAG?Solution.
Add the following new components to the Reactants window screen.: HfO2, Tl2O, Se2Cl2, NaBr, CdCl2, PbS. FactSage will be able to form the other new components from these components in the Reactants window.
Some compounds are present in multiple databases in FactSage. In this example, only the FACT database will be used.
In the Products frame, check the box for suppress duplicates.
In the Duplicate Compounds dialog box, remove all databases, except FACT.
In the Compound Species section of the Products frame on the Menu screen in FactSage, check the checkboxes for gas (ideal), pure liquids and pure solids.
Right click on gas.
Clear all species.
Select O2(g) from the FACT database and click OK. (All .cst files used by the interface must contain a gas phase.)
Right click on pure liquids.
Clear all species.
Execute the following steps for each of the following components: i. Right click on the species, and select IdealSolution#1. ii. Accept the default values of A=0 and B=0 (meaning gamma will equal 1). iii. Enter P,the number of particles inSolution for each species according to the table below. (Note: AspenTech is not an expert in slag chemistry. The numbers below were selected to test the interface at multiple values of P. In real life, these components may or may not dissolve into this many particles.) iv. Accept the defaultSolution name, Ideal-1.
Component
Number of Particles inSolution (P)
HfO2(s)
1
Tl2O(l)
2
Se(l)
1
Se2Cl2(l)
2
NaBr(l)
1
KBr(l)
1
CaBr2(l)
2
Se2Br2(l)
4
Cd(l)
1
CdCl2(l)
1
dBr2(l)
3
Pb(l)
1
PbS(l)
1
PbCl2(l)
1
PbBr2(l)
3
Right click on pure solids.
Clear all species.
Right click on HfO2(s2) and select IdealSolution #1.
Using the values in the FactSage documentation, enter A=1214.9, B=0, and P=1.
At this point, there should be 16 species selected, 1 gas, 14 pure liquids, and 1 pure solid.
In theSolution Species section of the Products frame, select the FACT-SLAG?Solution phase. This selects an additional 18 species in the FACT-SLAG?Solution..
Right click on the + column of FACT-SLAG?
Select merge diluteSolution from DiluteSolution#1 - Ideal-1
A dialog box appears indicating that PbS and PbCL2 are common to both the dilute and originalSolutions. Click OK. How this apparent conflict is resolved will be explained later.
Create the chemsage file, using the name Dil-Slag.cst. The Equilib File can be saved as dilute-slag-example.dat.
Figuring out the proper component names for Aspen Plus
The .cst file has been created using a new set of component names and a newSolution name. Since AspenTech cannot know what components orSolutions the user community will use, the user must be able to determine the appropriateSolution name and component name from the .cst file. Unfortunately, learning about the details of the chemsage file may be an iterative procedure.
Open Oxygen.bkp in Aspen Plus. This is a simple, one block flowsheet that uses dil-slag.cst. The feed stream contains only oxygen, as the mapping of oxygen should be unaffected by the merge of SLAG? With the idealSolution. The other components in the simulation are not used. Some, such as CAO-SL are databank components. Others, such as HFO2-SL are nondatabank components. Physical properties will need to be specified at some point for the nondatabank components.
Run the simulation. The Control Panel includes the following echo of the contents of Dil-Slag.cst. Note that FactSage has included the pure component phases for all of the components that are present in the ?Slag-liquid_Ideal-1Solution phase.
CHEMSAGE FILE has 29 phases
CHEMSAGE Phase 1 is gas_ideal using model IDMX
It contains:
O2
CHEMSAGE Phase 2 is ?Slag-liquid+Ideal-1 using model QSOL
It contains:
(Na2O):2.000
SiO2
CaO
(Al2O3):2.000
(K2O):2.000
CaS
(Na2S):2.000
(K2S):2.000
PbO
PbS
(Na2SO4):2.000
(K2SO4):2.000
CaSO4
NaCl
KCl
CaCl2
PbCl2
PbSO4
Se_Ideal-1
(Se2Cl2_Ideal-1):2.000
NaBr_Ideal-1
KBr_Ideal-1
(CaBr2_Ideal-1):2.000
(Se2Br2_Ideal-1):4.000
Cd_Ideal-1
CdCl2_Ideal-1
(CdBr2_Ideal-1):3.000
(Tl2O_Ideal-1):2.000
Pb_Ideal-1
PbS_Ideal-1
PbCl2_Ideal-1
(PbBr2_Ideal-1):3.000
HfO2(s2)_Ideal-1
CHEMSAGE Phase 3 is Se(liq) using model PURE
CHEMSAGE Phase 4 is Se2Cl2(liq) using model PURE
CHEMSAGE Phase 5 is NaBr(liq) using model PURE
CHEMSAGE Phase 6 is KBr(liq) using model PURE
CHEMSAGE Phase 7 is CaBr2(liq) using model PURE
CHEMSAGE Phase 8 is Se2Br2(liq) using model PURE
CHEMSAGE Phase 9 is Cd(liq) using model PURE
CHEMSAGE Phase 10 is CdCl2(liq) using model PURE
CHEMSAGE Phase 11 is CdBr2(liq) using model PURE
CHEMSAGE Phase 12 is Tl2O(liq) using model PURE
CHEMSAGE Phase 13 is Pb(liq) using model PURE
CHEMSAGE Phase 14 is PbS(liq) using model PURE
CHEMSAGE Phase 15 is PbCl2(liq) using model PURE
CHEMSAGE Phase 16 is PbBr2(liq) using model PURE
CHEMSAGE Phase 17 is HfO2(s2) using model PURE
CHEMSAGE Phase 18 is Al2O3_gamma(s) using model PURE
CHEMSAGE Phase 19 is CaO_lime(s) using model PURE
CHEMSAGE Phase 20 is K2O(s) using model PURE
CHEMSAGE Phase 21 is Na2O(s) using model PURE
CHEMSAGE Phase 22 is PbO_litharge_(red)(s) using model PURE
CHEMSAGE Phase 23 is SiO2_quartz(l)(s) using model PURE
CHEMSAGE Phase 24 is HfO2(s) using model PURE
CHEMSAGE Phase 25 is Tl2O(s) using model PURE
CHEMSAGE Phase 26 is SeCl2(g) using model PURE
CHEMSAGE Phase 27 is NaBr(s) using model PURE
CHEMSAGE Phase 28 is CdCl2(s) using model PURE
CHEMSAGE Phase 29 is PbS(s) using model PURE
Only one component name was mapped, O2:G1. Even the databank components names such as CAO:SLAG were not mapped. The information message indicates the cause of this.
INFORMATION WHILE PERFORMING INITIAL ENTHALPY CALCULATIONS FOR STREAM:
1
CHEMSAGE PHASE ?Slag-liquid+Ideal-1 NOT FOUND IN THE
Solution DICTIONARY - USE THE FIRST FOUR
CHARACTERS OF THE CHEMSAGE PHASE NAME AS
THE ASPEN PLUS PHASE NAME
3 Merging the idealSolution into ?Slag-liquid created a newSolution name, ?Slag-liquid+Ideal-1. ThisSolution needs to be added to APRSYS\ENGINE\xeq\FACTSOLN.TXT. Find the line with SLAG in FACTSOLN.TXT, and replace it with the following line:
2 SLAG ?Slag-liquid+Ideal-1
SLAG will be the four character string that must be included at the end of all of the component names for the components in this phase. Note that no twoSolution phases are allowed to share the same four character identification string. Note also that this will break any other simulations that use the ?Slag-liquid phase without any ideal components.
Alternatively, a newSolution name could be created (e.g. DSLG for dilute slag). This would require additional components to be added to Aspen Plus, such as CAO:DSLG and SIO2:DSLG.
Reinitialize the simulation and run it again. Now all of the databank components map correctly.
COMPONENT MAPPING COMPLETE:
Comp ID Component Name AP Index CHEMAPP CHEMAPP CHEMAPP MWFAC
Const # Phase # Ph. Type
O2 O2:G1 1 1 1 1 1.000
CAO-SL CAO:SLAG 2 3 2 2 1.000
AL2O3-SL AL2O3:SLAG 3 4 2 3 2.000
SIO2-SL SIO2:SLAG 4 2 2 3 1.000
K2O-SL K2O:SLAG 5 5 2 3 2.000
NA2O-SL NA2O:SLAG 6 1 2 3 2.000
PBO-SL PBO:SLAG 7 9 2 3 1.000
PBCL2-SL PBCL2:SLAG 21 31 2 3 1.000
Since the Aspen Plus/FactSage/Chemapp interface relies on the databank name for component mapping, a databank must be created to hold information for the nondatabank components. This will be done in a USRPP1A type of databank. This is preferable instead of modifying FACTPCD itself. Acceptable component names must be determined for all of the new components. Use the following procedure, as illustrated for HFO2 and TL2O.
Go to the Components\Specifications sheet.
In the Component name field for HFO2-SL, enter HFO2: (be sure to enter the colon). Three component aliases appear in the Find dialog box: HFO2-1, HFO2-2 and HFO2-3. Therefore, the alias for the new component can be HFO2-4. (Any number higher than 4 would also be acceptable.) Close the Find dialog box without selecting any of the components.
In the Component name field for TL2O-SL, enter TL2O: (again, be sure to enter the colon). Two components appear in the Find dialog box. Therefore, the alias for the new component can be TLO2-3. Close the Find dialog box without selecting any of the components.
Exit all sessions of Aspen Plus and Aspen Properties.
Create a DFMS input file for the engine with the new components. The DFMS input file for this example has been created in file USRFACT1.inp. Create a GUI customization file with the new components. The GUI customization file for this example has been created as usrfact1GUI.dat.
Issue the command DFMS USRFACT1 to create the engine databank file, usrpp1a.dat.
Edit the report file from the DFMS run, USRFACT1.rep to confirm that the databank was built without errors.
Copy usrfact1gui.dat to your AprSystem\GUI\custom subdirectory, with the name usrpp1a.dat
In the AspenTech\AprSystem 12.1\GUI\custom subdirectory, issue the command MMCUSTOM ALL
In the AprSystem\APrSystem 12.1\GUI\custom subdirectory, issue the command CUSTINST.
Open Slag.bkp. Note that this file looks for component information in USRPP1A and FACTPCD. The databank search order does not matter. The component name for all components has been specified. Run the simulation. The component mapping summary now shows that all components have been mapped.
COMPONENT MAPPING COMPLETE:
Comp ID Component Name AP Index CHEMAPP CHEMAPP CHEMAPP MWFAC
Const # Phase # Ph. Type
O2 O2:G1 1 1 1 1 1.000
CAO-SL CAO:SLAG 2 3 2 2 1.000
AL2O3-SL AL2O3:SLAG 3 4 2 3 2.000
SIO2-SL SIO2:SLAG 4 2 2 3 1.000
K2O-SL K2O:SLAG 5 5 2 3 2.000
NA2O-SL NA2O:SLAG 6 1 2 3 2.000
PBO-SL PBO:SLAG 7 9 2 3 1.000
HFO2-SL HFO2:SLAG 8 33 2 3 1.000
TL2O-SL TL2O:SLAG 9 28 2 3 2.000
SE-SL SE:SLAG 10 19 2 3 1.000
SE2CL2 SE2CL2:SLAG 11 20 2 3 2.000
NABR-SL NABR:SLAG 12 21 2 3 1.000
KBR-SL KBR:SLAG 13 22 2 3 1.000
CABR2-SL CABR2:SLAG 14 23 2 3 2.000
SE2BR2 SE2BR2:SLAG 15 24 2 3 4.000
CD-SL CD:SLAG 16 25 2 3 1.000
CDCL2-SL CDCL2:SLAG 17 26 2 3 1.000
CDBR2-SL CDBR2:SLAG 18 27 2 3 3.000
PB-SL PB:SLAG 19 29 2 3 1.000
PBS-SL PBS:SLAG 20 30 2 3 1.000
PBCL2-SL PBCL2:SLAG 21 31 2 3 1.000
PBBR2-SL PBBR2:SLAG 22 32 2 3 3.000
Solution
of duplicate components in a chemsage phase
As indicated by the echo of the chemsage file, there are two occurrences of PbS (PbS and PbS_Ideal-1) and two occurrences of PbCl2 (PbCl2 and PbCl2_Ideal-1) in the .cst file. However, Aspen Plus only has one component name for each: PBS:SLAG and PBCL2:SLAG.
The component mapping summary indicates that PBS:SLAG is mapped to constituent 30 in phase 2. It further indicates that PBCL2:SLAG is mapped to constituent 31. Both of these constituents are the idealSolution constituents, not the standardSolution constituents.
The Aspen Plus/FactSage/Chemapp interface does not have any mechanism for the user to specify which of duplicate components gets mapped. Aspen Plus just retains the map for the last component that it finds. Since the idealSolution components are located below the standard components, Aspen Plus maps the idealSolution components. It is the user's responsibility to modify the chemsage file if the mapping of duplicate components is incorrect.
Keywords: chemapp
factsage
gtt
References: None |
Problem Statement: Service Pack installation disappears after package install is initiated | Solution: Service Pack installation starts by registry cleanup and it takes a long time for this task. The cleanup process goes on in the background and has installation has not been terminated. Customer should leave the installation and come back to it after a while. After Registry cleanup, Service Pack installation will prompt the user for continuation after which it will complete.
Keywords: SP5
Service Pack
Aspen Service Pack
PATCH
patch
service pack
AspenOne 2004.1 Service Pack
References: None |
Problem Statement: How does Aspen Plus calculates the THYDRATE and PHYDRATE properties used to predict the temperature and pressure of hydrate formation? | Solution: The ability to predict hydrate formation is vital in the design and operations in gas processing plants. The value is in defining how much inhibitors must be added to avoid hydrate formation of a system of a given composition, temperature and pressure. The goal is to prevent the hydrates from clogging equipment and lines.
There are two Prop-Set properties THYDRATE and PHYDRATE, which return the temperature and pressure of Hydration if the other is fixed.
PHYDRATE indicates the lowest pressure at which the hydrate is formed.
THYDRATE indicates the highest temperature at which the hydrate is formed.
For both, the phase qualifier must be V (for vapor).
A property set can be used in physical property tables and analysis. These prop-set properties can also be reported in the stream summary or report (seeSolution 3005 for details) or accessed within a Sensitivity, Design Spec, or Calculator block (seeSolution 3295).
The attached example file has a simple property analysis tabulating PHYDRATE and THYDRATE versus temperature along with a simple flowsheet with these properties reported in the streams.
Method
API Charts are used in determining either the temperature or the pressure at which the hydrate forms from a multicomponent gaseous mixture. These calculations involve an iterativeSolution.
The iterativeSolution is satisfied when the sum of the Xs=1, where Xs=y/K.
Notation:
Xs = mole fraction of a component in the solid gas hydrate on a water-free basis.
y = mole fraction of a component in the vapour on a water-free basis.
K = vapour-solid equilibrium ratio (y/Xs)
TheSolutions converge very slowly when the pressure is greater than 4000 psia or when the mixture is predominantly methane.
Limitations
These properties (THYDRATE and PHYDRATE) are only accurate for systems containing only the following 9 hydrocarbons:
methane
ethane
ethylene
propane
propylene
isobutane
hydrogen sulfide
carbon dioxide
nitrogen
The model does not predict the hydrate composition. The API correlations used were based on some composition; however, Aspen Plus cannot predict those compositions, only that the hydrate forms at certain a Temperature and Pressue.
The model does not handle the presence of inhibitors. There are plans implement a more comprehensive hydrate prediction model including inhibitors for a future release.
Freeze out temperature of a gas such as CO2 can also be calculated for a stream using the TFREEZ property. For TFREEZ, we use the heat of fusion (HFUS) for the solid fugacity and the liquid fugacity is calculated based on the selected property method. SeeSolution 102343 for more details and a comparison to data.
Reliability
The average error in predicting formation pressures (temperature held constant) for natural gases is approximately 7%, and the maximum error is approximately 20%. The average difference between experimental and predicted formation temperatures (pressure held constant) is approximately 1F, with a maximum of approximately 4F. Larger errors may be expected when the gas is rich in propane (>30%) or isobutane. Greater error will be expected if components other than the 9 hydrocarbons are present.
Note that Water is not required in determining hydrate formation pressure or temperature for a petroleum mixture, unless BASIS=DRY is specified in the Prop-Sets Qualifiers. The hydrate formation pressure or temperature are determined based on hydrate formation equilibrium constants which are calculated internally.
Keywords: hydrate
prop-set
References: s
API Techinical Databook, June 1981. |
Problem Statement: How is Ergun's equation used in RPlug? More specifically, how does Aspen Plus evaluate the following with respect to Ergun's equation?
1. What are the value of the Ergun A and B parameters used?
2. How is the pressure drop scale factor used?
3. Please explain exactly how particle diameter is used.
4. How is Sphericity used?
5. How does particle density play into Ergun's equation?
6. Is the particle density the density of the particle material or the bulk density of the catalyst in the reactor?
7. How is residence time defined in RPlug with Ergun's equation? | Solution: Ergun's equation is suitable for computing the pressure drop across packed bed reactors, and as such can be applied within the RPlug unit operation model.
1) The Ergun A and B parameters are the turbulent term and laminar term respectively. In Aspen Plus the turbulent term is set to 150, and the laminar term to 1.75. These are fitted parameters for Ergun's equation. These terms are also visible in the Aspen Plus Help Menu under Ergun's Equation.
2) The pressure drop scale factor is used when a frictional correlation, such as Ergun, is employed within RPlug. Such a correlation is activated from the Data Browser menu location Setup | Pressure for the RPlug model. This figure is simply a multiplier for the pressure drop calculated by the chosen frictional correlation.
3) The particle diameter used by RPlug is a nominal diameter based on screen size or similar measurement. The sphericity is then used to provide the rough shape of the catalyst particles. So if sphericity is equal to one, the particles are considered perfect spheres. As the sphericity value decreases, then the particles become less sphere-like impacting the void faction of the bed. So both the particle diameter and sphericity are used within the Ergun equation. Both are required as sphericity is defined as S = (6*particle volume) / (diameter * surf. area).
4) The original version of Ergun's equation did not take into account non-spherical particles. To account for these, the particle diameter (Dp) in Ergun's equation was replaced by the product of sphericity and equivalent particle diameter.
5) Particle density is one of three bed parameters that can be entered on the RPlug Setp | Catalyst Data Browser sheet (along with Catalyst loading and Bed voidage). If one wishes to include the catalyst bed in the RPlug calculations, then two of those three parameters must be specified. These quantities are required when the species generation rate is dependent upon the catalyst weight in the bed. The particle density plays into Ergun's equation since one of the Ergun parameters is the bed voidage, which can be determined via the particle density given the total catalyst load.
6) The particle density is the mass density of the actual catalyst particle.
7) The presence of catalyst is specified on the Setup | Catalyst sheet for the RPlug model. In an RPlug model, if catalyst is present, the computed catalyst volume is subtracted from the reactor volume when computing residence time. So Aspen Plus calculates a true residence time taking into account the catalyst volume - though you have the option of ignoring the catalyst volume in any rate/residence time calculations (separate checkbox on Setup | Catalyst sheet).
Note also that the porosity of the pellets themselves is accounted for in the sphericity term. As defined, sphericity takes into account surface area, volume, and diameter (see equation in item #3). Given these values, pellet porosity could be inferred based on how un-sphere like the pellet is.
Keywords: None
References: None |
Problem Statement: Is there an option to secure property parameters used in a simulation? | Solution: Aspen Plus V7.0 includes a new feature to allow the property parameters (constants such as critical parameters - TC, correlation coefficients such as PLXANT, binary parameters such as NRTL, pair parameters such as GMELCC) used in the simulation to be secured in the following manners through the use of restricted, secured enterprise databases:
1. The property parameters will be used in the simulation but cannot be reported, viewed or accessed.
2. The property parameters cannot be reported in the report file through the use of Property-report options: params, param-plus and project or through the User Interface settings on the Setup | Report Options | Property tab:
a. All physical property parameters (in SI units)
b. Property parameters' descriptions, equations and source
c. Project data file
The specification will be ignored and a warning message will be issued.
3. The property parameters cannot be shown in the User Interface through the use of the Review button on the Components | Specifications | Selection tab and Tools/Retrieve Parameter Results menu option.
4. The binary and pair parameters from the restricted, secured database will not be displayed in the User Interface (more on restricted, secured database in the section that follows).
The property parameters cannot be used in the Define or Vary form for Design Specification and Sensitivity Analysis. The variable category, Physical Property Parameters cannot be used. Note that the graphical user interface will not prevent you from making the selection, but if these parameters are accessed or varied, input translation errors will be issued when you run the simulation and the simulation will terminate.
The security is achieved through the use of the restricted, secured Aspen Properties Enterprise Database. The property parameters that you want to protect must be included in a restricted, secured database and the database must be used in the simulation (i.e., selected on the Components | Specifications | Enterprise Database tab. The instruction on how to create this type of database is given in the Aspen Properties Database Manager Help and inSolution 125495.
It is important to emphasize that this feature is not available when the legacy databanks are used.
The following behaviors are expected:
? The property parameters used in the simulation are secured automatically when one or more restricted, secured Enterprise databases are used. There is no setting or keyword required.
When the security is in effect, parameters from all the databanks selected, including those that are not restricted, will not be reported (see 2 and 3 above) in the report file and on Properties | Parameters | Results, and Properties | Parameters | Pure Component forms.
When the security is in effect, binary and pair parameters from databases that are not restricted will be displayed on the Properties | Parameters | Binary Interaction and Properties | Parameters | Electrolyte Pair forms. However, parameters from the restricted, secured databases will not be displayed. You can use the Display parameters on forms check box on the Components | Specifications | Enterprise Database tab to enable or disable display of these parameters from the un-restricted databases.
Keywords: None
References: None |
Problem Statement: Is it possible to show the Joule Thompson effect in Aspen Plus ? | Solution: The property routines in Aspen Plus automatically take account of the Joule Thompson effect. For example, if you use an equation of state it is reflected in the enthalpy departure term.
The Joule-Thompson (JT) effect is the inversion of the JT coefficent:
(dT/dP) at constant H
For example (Perry 6th edition page 3-110) the inversion curve locus for Hydrogen at 75 bar is:
Upper Inversion Temperature = 171 K
Lower Inversion Temperature = 44 K
In practice, the effect can be shown with a Heater block and a Sensitivity Analysis. The Sensitivity Analysis varies the inlet temperature, and the HEATER block performs the iso-enthalpic flash (you can use a VALVE model as well) with a pressure drop from 75 to 70 bar. The outlet temperature from the heater is lower or higher, depending on the sign of the JT coefficient. The plot of the results of the last two columns of the sensitivity analysis S-1 is particularly clear (see screenshots).
Keywords:
References: None |
Problem Statement: When using ActiveX automation with Aspen Plus, how to activate and de-activate a node (e.g. a design-specifications or a calculator block)? How is it possible to hide and reveal a node? | Solution: To activate a node, use the attribute value HAP_ACTIVATE STATE and set it to HAPP_ENABLE_ACTIVATE. For example, assuming one wants to deactivate calculator block C-1:
mySim.Tree.FindNode(\Data\Flowsheeting Options\Calculator\C-1).AttributeValue(HAP_ACTIVATESTATE) = HAPP_ENABLE_DEACTIVATE
To activate the same calculator block, set the Attriuute Value HAP_ACTIVATE STATE to HAPP_ENABLE_DEACTIVATE, e.g. :
mySim.Tree.FindNode(\Data\Flowsheeting Options\Calculator\C-1).AttributeValue(HAP_ACTIVATESTATE) = HAPP_ENABLE_DEACTIVATE
This is illustrated in the attached Excel spreadsheet as procedure DeActivate_And_Activate in VBA Module 1.
To hide a node , use the Hide method for the node that is the parent node for the node to be hidden. For example, assuming one wants to hide Caclator block C-1 :
mySim.Tree.FindNode(\Data\Flowsheeting Options\Calculator).Hide (C-1)
To get the names of the ndoes hidden in a specifc location, use AttributeValue(HAP_REVEALLIST). This will return a node that contains the list of hidden nodes at that location:
Dim oBlockList As IHNode
Set oBlockList = mySim.Tree.FindNode(\Data\Flowsheeting Options\Calculator).AttributeValue(HAP_REVEALLIST)
To reveal a node, use the Reveal method. For example, to reveal all blocks listed by the above command, use the following code :
Dim oBlock as IHNode
For Each oBlock In oBlockList.Elements
sBlockName = oBlock.Value
mySim.Tree.FindNode(\Data\Flowsheeting Options\Calculator).Reveal (sBlockName)
Next oBlock
This is illustrated in the attached Excel spreadsheet as procedure Hide_And_Reveal in VBA Module 1.
Keywords: VBA
Visual Basic for Applications
ActiveX
COM
activate
reveal
hide
References: None |
Problem Statement: Is it possible to use pressure relief in Aspen Plus with a stream that includes an assay? | Solution: You cannot specify a stream composition on the Flowsheeting Options | Pres Relief | Setup | Stream tab or the vessel composition on the Setup | Vessel Contents tab. However, you can reference a stream with an assay.
An example file is attached.
Keywords: None
References: None |
Problem Statement: When using the Cyclone model the message LIQUID EXISTS IN MIXED SUBSTREAM appears and the model does not calculate correctly. | Solution: This happens when the the cyclone is fed a liquid fraction in a stream, the Cyclone model needs to only be fed an all vapor stream(vapor fraction =1) in order for the model to function correctly. This error can be remedied by making sure the feed to the cyclone is adjusted to an all vapor stream.
Keywords: Liquid, substream, mixed, vapor fraction, cyclone
References: None |
Problem Statement: Why aren't Fortran variables in Design-Specs updated from one iteration to the next? | Solution: All the DEFINED variables in DESIGN-SPEC are READ-ONLY variables and the values printed in result form are values before executing any Fortran code . They are NOT updated even if it get changed in the Fortran code. In a design-spec convergence loop, the VARY variable is the only variable that is being manipulated to meet the SPEC.
The initial and final value refers to the value of DEFINED variable at the 1st and last spec calculation of the last spec loop (if nested inside other convergence loop). They are all values before executing Fortran code.
In V7.2, the help has been modified:
Design Spec Input sheet:
Added All these variables are read-only, and will not be changed by the Design-Spec itself after You can sample any number of flowsheet variables.
Design Spec Fortran sheet:
Note: All defined variables in Design-Specs are read only. If you change the value of one of these variables, that change lasts only to the end of execution of the Fortran code on this sheet, and does not change the Aspen Plus variable it is associated with.
Keywords: None
References: None |
Problem Statement: There is a security dongle puts a ppmon.dll into the windows\system32 directory. This causes a loading error, because the OS finds the dongles ppmon.dll rather than ours. The error is Unable to load simulation engine. Probable cause: Insufficient disk space or memory message.
Information about the dongle can be found http://www.keylok.com/KB/File%20Descriptions.htm. | Solution: Aspen Properties Plus uses a dll called PPMON.DLL which is located in the properties plus folder. In this dll, PP stands for Properties Plus SLEEK Dongle also uses a dll called PPMON.DLL which is located in the System32 folder. In this dll, PP stands for Parallel Port.
This program provides a security-related function to add greater protection to your application. It is activated by the first call to KEYBD() with an argument value of zero. This call is optional from within your 32-bit program, and may be left out to permit debugging your application while under development.
Aspen Plus gets confused about which dll to use. It tries to use PPMON.DLL belonging to SLEEK instead of the one belonging to Properties Plus. Therefore you get the problem.
TheSolution for this problem is simple. Please follow the steps below:
Re-install Aspen Plus and SLEEK on you computer
First make sure that SLEEK is running properly on your computer
Then go to the C:\WINNT\System32 folder (for NT/2000) or C:\Windows\System32 folder(98/Me/XP) and locate PPMON.DLL
Delete this dll
Now run Aspen Plus. You should not have any problems.
In the future CDs of SLEEK this dll with be renamed this
dll so that Aspen Plus does not get confused.
Keywords:
References: None |
Problem Statement: What units of measure should be used for parameters in DFMS files used to create a user or inhouse databank? | Solution: The parameters should have SI units. You must enter all data in SI units, because DFMS does not perform units conversion.
Parameter Name
Description
Units
AIT
Auto ignition temperature
K
ANILPT
Aniline point
K
API
Standard API gravity at 60?F
Dimensionless
AROMATIC
Aromatic content (1=aromatic, 0=non-aromatic)
Fraction
ATOMNO
Vector containing the atom types (atomic numbers) for a given molecule (e.g., H=1, C=6, O=8). Must use the vector NOATOM to define the number of occurrences of each atom.
Dimensionless
CPDIEC
Dielectric constant
Dimensionless
CPIG
Ideal gas heat capacity coefficients
J/kmol-K
T in K
CPIGDP
DIPPR ideal gas heat capacity coefficients
J/kmol-K
T in K
CPLDIP
DIPPR liquid heat capacity coefficients
J/kmol-K
T in K
CPSDIP
DIPPR solid heat capacity coefficients
J/kmol-K
T in K
DCPLS
Difference between liquid and solid heat capacity at the Triple point
J/kmol-K
DELTA
Solubility parameter at 298.2 K
(J/cum)**.5
DGFORM
Standard Gibbs free energy of formation; ideal gas at 298.2 K
J/kmol
DHFORM
Standard heat of formation; ideal gas at 298.2 K
J/kmol
DHLCVT
Cavett enthalpy departure parameter
Dimensionless
DHVLB
Heat of vaporization at TB
J/kmol
DHVLDP
DIPPR heat of vaporization coefficients
J/kmol
T in K
DHVLWT
Watson heat of vaporization parameters
J/kmol
T in K
DNLDIP
DIPPR liquid density coefficients
kmol/cum
T in K
DNSDIP
DIPPR solid density coefficients
kmol/cum
T in K
ENT
Absolute entropy of formation at 298.2 K
J/kmol-K
FLML
Lower flammability limit
% by volume in air
FLMU
Upper flammability limit
% by volume in air
FP
Flash point
K
FREEZEPT
Normal freezing point (see also TFP)
K
GMUQQ
UNIQUAC area parameter
Dimensionless
GMUQR
UNIQUAC volume parameter
Dimensionless
HCOM
Standard enthalpy of combustion at 298.2 K
J/kmol
HFUS
Enthalpy of fusion at melting point
J/kmol
HYDROGEN
Hydrogen content (weight fraction)
Weight fraction
KLDIP
DIPPR liquid thermal conductivity coefficients
Watt/m-K
T in K
KVDIP
DIPPR vapor thermal conductivity coefficients
Watt/m-K
T in K
MOC-NO
Motor octane number
Dimensionless
MOCTNO
Motor octane number
Dimensionless
MULAND
Andrade liquid viscosity coefficients
N-sec/sqm
T in K
MULDIP
DIPPR liquid viscosity coefficients
N-sec/sqm
T in K
MUP
Dipole moment
(J*cum)**.5
MUVDIP
DIPPR vapor viscosity coefficients
N-sec/sqm
T in K
MW
Molecular weight
kg/kmol
NAPHTHEN
Naphthene content (1=naphthenic, 0=non-naphthenic)
Fraction
NATOM
Vector containing numbers of C, H, O, N, S, F, Cl, Br, I, Ar, and He atoms
Dimensionless
NOATOM
Vector containing the number of occurrences of each atom defined in ATOMNO for a given molecule. ATOMNO and NOATOM define the chemical formula of the molecule.
Dimensionless
NTHA
Nothnagel parameters
cum/kmol
OLEFIN
Olefin content (1=olefin, 0=non-olefin)
Fraction
OMEGA
Pitzer acentric factor
Dimensionless
OMGCTD
Acentric factor for the COSTALD model
Dimensionless
OXYGEN
Oxygen content (weight fraction)
Weight fraction
PARAFFIN
Paraffin content (1=paraffin, 0=non-paraffin)
Fraction
PC
Critical pressure
N/sqm
PLCAVT
Cavett vapor pressure coefficients
N/sqm
T in K
PLXANT
Extended Antoine vapor pressure coefficients
N/sqm
T in K
PRMCP
Mathias-Copeman parameters for PR equation of state
Dimensionless
PRSRP
Schwartzentruber-Renon parameters for PR equation of state
Dimensionless
RGYR
Radius of gyration
meter
RI
Refractive index at 298.2 K
Dimensionless
RKSMCP
Mathias-Copeman parameters for RKS equation of state
Dimensionless
RKSSRP
Schwartzentruber-Renon parameters for RKS equation of state
Dimensionless
RKTZRA
Rackett liquid density parameter
Dimensionless
ROC-NO
Research octane number
Dimensionless
ROCTNO
Research octane number
Dimensionless
SG
Standard specific gravity at 60?F
Dimensionless
SIGDIP
DIPPR surface tension coefficients
N/m
T in K
SULFUR
Sulfur content (weight fraction)
Weight fraction
SVRDIP
Second virial coefficient
cum/kmol
T in K
TB
Normal boiling point
K
TC
Critical temperature
K
TFP
Normal freezing point (see also FREEZEPT)
K
TOTAL-N2
Total nitrogen content (weight fraction)
Weight fraction
TPP
Triple point pressure
N/sqm
TPT
Triple point temperature
K
UFGRP
Functional group information for the UNIFAC model
Dimensionless
UFGRPD
Functional group information for the Dortmund modified UNIFAC model
Dimensionless
UFGRPL
Functional group information for the Lyngby modified UNIFAC model
Dimensionless
VB
Liquid molar volume at TB
cum/kmol
VC
Critical volume
cum/kmol
VLCVT1
Scatchard-Hildebrand characteristic volume parameter
cum/kmol
VLSTD
Standard liquid volume at 60?F
cum/kmol
VSTCTD
Characteristic volume for the COSTALD model
cum/kmol
WATSOL
Water solubility correlation coefficients
Dimensionless
T in K
ZC
Critical compressibility factor
Dimensionless
See the Physical Properties Data
Keywords: inhspcd
user databank
References: Manual for more information.
In version 2004 and later the Physical Properties Data Reference Manual is in the Aspen Physical Property System help. |
Problem Statement: UOSSTAT2 is available in the xml file. What values can UOSSTAT2 have? | Solution: UOSSTAT2 has the following definitions:
UOSSTAT2
Definition
2
Simulation was completed normally
3
Simulation was not completed normally
4
Data regression was completed normally
5
Data regression was completed with errors
6
Assay data analysis was completed normally
7
Assay data analysis was completed with errors
8
Calculations were completed normally
9
Calculations were completed with errors
10
Calculations were completed with warnings
Keywords: .sum
.xml
References: : CQ00221491 |
Problem Statement: Can additional properties be printed in the stream summary or report? | Solution: Yes, additional properties can be printed in the stream summary or report file.
In Aspen Plus 10 and higher,
1. From the Data Browser, go to Setup / Report Options / Streams and click on the Property Sets button.
2. Use the arrows to select any number of Property Sets from those in the Available list. If the Property Set you want to use is not available, you can right mouse click in the Available Property Sets list and select New, and enter a new ID for that set.
3. By pressing the Next button, you advance to the Properties / Prop-Sets form.
4. Enter any property that is available. Use the prompt messages to find the properties of interest. You can click on the Search button to search for all Prop-Sets with a given keyword.
5. Specify the qualifiers that define how the Aspen Physical Property System will calculate the properties selected on the Properties sheet. These include such things as Phase and Components.
All of the property sets listed are calculated and printed for every stream in the flowsheet. These results can be seen in the Results Summary / Streams form and in the Stream section of the report (*.rep) file.
The defalut units for the properties and qualifiers are the units specified in the unit-set such as ENG or METCBAR specified for the form. The units for each property can be changed by selecting the desired units. The units for the qualifiers can only be modified by changing the unit-set for the entire prop-set.
All unit specifications apply to all properties in the property set for which those units are allowed. If you select more than one property and specify more than one set of units, the user interface will calculate and report for the stream each property in the first specified units that are allowed for the property. To see the properties in all allowed units, you must export a report file. Multiple units of measure for each property will be possible on the custom stream form available in 2006 and higher.
Keywords: Properties
Print
Stream
Prop-Set
References: None |
Problem Statement: What are some typical U values for various types of heat exchanger services? | Solution: For most cases, the default value used in the HeatX block (150 Btu/(F-ft2 - hr)) is far too high. It is best to rate the heat exchanger after specifying it's bundle/shell geometry in the HeatX block's input forms. If you need to make a short-cut approximation, here are some general rules:
Sensible heating/cooling of liquids:
Naphtha range hydrocarbon - water 25 - 80 Btu/(F-ft2 - hr)
Fuel oil - water 10 - 40 Btu/(F-ft2 - hr)
Forced air draft cooling:
Condensing vapor < 10 Btu/(F-ft2 - hr) --> 4-5 is more typical
Condensing vapor - Sensible liquid heat transfer:
Steam - water 200 - 400 Btu/(F-ft2 - hr)
Organic Solvents - water 100 - 200 Btu/(F-ft2 - hr)
For more details, please reference Table 10-10 in Perry's Chemical Engineers' Handbook or visit the ChE Resources website at:
http://www.cheresources.com/uexchangers.shtml
Keywords: heatx, u-value, uvalue, u value, heat transfer coefficient.
References: None |
Problem Statement: What is the PC-SAFT EOS model and its applicability? | Solution: The SAFT (Statistical Associating Fluid Theory) EOS is a rigorous thermodynamic model based on perturbation theory. It evaluates the properties of fluids based on interactions at the molecular level. It is able to separate and quantify the effects of molecular structure and interactions on bulk properties and phase behavior. Examples of such effects are: molecular size and shape (e.g. chain length), association energy (e.g., hydrogen bonding), and attractive (e.g., dispersion) energy. The advantage of SAFT is that the model parameter values are well-behaved, which provides predictable trends upon increasing the molar mass of components in the same homologous series in the absence of experimental data.
PC-SAFT (Perturbed-Chain Statistical Association Fluid Theory) EOS is an improved version of the very successful SAFT EOS, with some modifications on the expressions for dispersion forces. Its applicability includes fluid systems of small and/or large molecules over a wide range of temperature and pressure conditions. The big advantage of PC-SAFT EOS method is that it can represent the thermodynamic properties of polymer systems very well. In addition, its accuracy is comparable to, and often better than, the Peng-Robinson EOS or other similar cubic equations of state for small molecules.
The form of the PC-SAFT EOS is shown in equation (1), where Zseg is the segment contribution term, Zchain is chain contribution term, and Zassociation is present when the fluid exhibits hydrogen bonding interactions.
The table below lists the unary and binary parameters for PC-SAFT model. Each component must have FCSFTM, PCSFTV, and PCSFTU specified. PCSFAU and PCSFAV need to be specified for association species. PCSFMU and PCSFXP need to be specified for polar species. The binary parameters PCSKIJ/1~6 are the corresponding coefficients of the temperature dependence expressions (equations (2), (3) and (4)) related to the calculation of the cross energy parameter uij. Even though PC-SAFT property method has been available since version 2006.5, the databank PC-SAFT (containing both unary and binary PC-SAFT parameters available from literature) was not added until V7.0.
Detailed description of the PC-SAFT EOS model can be found in Aspen Polymers User Guide Volume 2: Physical Property Methods and Models. Examples and documentations of using PC-SAFT method are available in folder C:\Program Files\AspenTech\Aspen Plus V7.0\GUI\App\Physical solvents.
(1)
(2)
(3)
(4)
Unary and binary parameters of PC-SAFT model.
Parameter Name/Element
Comment
Description
PCSFTM
Unary
Characteristic segment number parameter
PCSFTV
Unary
Characteristic segment size parameter
PCSFTU
Unary
Characteristic segment energy parameter
PCSFTR
Unary
Characteristic segment ratio parameter
PCSFAU
Unary
Characteristic association energy parameter
PCSFAV
Unary
Characteristic association volume parameter
PCSFMU
Unary
Characteristic polar dipole moment parameter
PCSFXP
Unary
Characteristic dipolar fraction parameter
PCSKIJ/1
Binary
PCSKIJ/2
Binary
PCSKIJ/3
Binary
PCSKIJ/4
Binary
PCSKIJ/5
Binary
PCSKIJ/6
Binary
Keywords: PC-SAFT
References: None |
Problem Statement: Is there an easy way to load Pro/II models into Aspen Plus? | Solution: To convert a Pro/II input keyword file for use with Aspen Plus, there are two primary steps:
1) Open a blank simulation in Aspen Plus and click on TOOLS | OPTIONS and then select the GENERAL tab. Check the box at very bottom of the form to retain the Pro/II block information as in Figure 1, below:
Figure 1- Seting the block mapping for the Pro/II input
2) Select the Pro/II Input file option for File type in the Aspen Plus Open File dialog box. Select the appropriate Pro/II input file and click Open as in Figure 2, below:
Figure 2 - Change the File Type in the Open Dialogue
Aspen Plus converts and saves the information to a backup file, which in turn is opened in Aspen Plus. A dialog box appears, displaying the converted and unconverted input keyword specifications, to help with the conversion process.
The Pro/II conversion capability is provided to assist users in the migration of simulation specifications from Pro/II models. Before attempting to use the conversion tool, a detailed understanding of the Pro/II and Aspen Plus syntax is desirable, especially of the use of Pro/II qualifiers and the Pro/II and Aspen Plus input conventions. A wide range of Pro/II input specifications are converted directly by the tool, covering all the required Pro/II input categories at varying degrees of detail:
? General Data
? Component Data
? Thermodynamic Data
? Stream Data
? Unit Operations Data
The Pro/II conversion capabilities in Aspen Plus have been designed to preserve the information specified in the Pro/II input file even for currently unsupported input keywords by retaining the information as an unconverted Aspen Plus comment in the result file. The optional Reaction Data (RXDATA) category is also supported, but the converted data are linked only to reactions referenced in a Pro/II COLUMN, not to reactor blocks present in the flowsheet model and converted by Aspen Plus. The remaining optional Pro/II input categories (Procedure, Recycle Data, and Case Study) are not currently supported.
The table listed below gives a high level overview of the Pro/II keywords currently supported by the Pro/II Converter capability of Aspen Plus.
The next page lists the features that can and cannot be mapped into Aspen Plus:
Keywords: Pro/II, Proii, PROII, PRO2, interface,
References: None |
Problem Statement: Why Equation-Oriented (EO) script statements in Global and Local Scripts forms in Aspen plus GUI are not run by Aspen Plus? | Solution: In Aspen plus GUI's Global and Local Scripts forms, scripts statements will not run if they are not formatted properly. When you write EO scripts in these 2 places, do not indent lines by more than 3 initial spaces or else they will be ignored. Also, do not write more than 64 characters per line.
Note that the above limitations do not apply to script in text files issued from command line, where indentation is not restricted and line length could be as long as well over 1000 characters.
Keywords: Indentation, indent, script, EO, equation oriented, OOMF, global EO scripts, local EO scripts
References: None |
Problem Statement: What is the syntax for a legacy DFMS input file for binary parameters for an Equation of State model to be used in the customization of the Aspen Properties Enterprise Database (APED)? | Solution: There are two types of parameters, symmetric and unsymmetric ones.
1. Symmetric Parameters kij = kji
Examples of symmetric parameters include SR-POLAR parameters RKUKA0, RKUKA1, and RKUKA2. Symmetric parameter value should appear twice. For example:
PROP-DATA
PROP-LIST RKUKA0 1
BPVAL C2H6O-2 CO2 0.3 0.3
2. Unsymmetric Parameters lij = -lji
Examples of unsymmetric parameters include SR-POLAR parameters RKULA0, RKULA1, and RKULA2. Unsymmetric parameter values should be put in an order with opposite sign. For example:
NEW-PROP RKULA0 1
PROP-DATA
PROP-LIST RKULA0 1
BPVAL C2H6O-2 CO2 -0.02 0.02
Note: The values for the examples in thisSolution are ficticious.
Examples for binary parameters for Activity Coefficient models are delivered with the installation. They can be found under ...\Documents and Settings\All Users\AspenTech\APED xxxx.x (version number of Aspen Properties /Aspen Plus used).
Further documentation can be found in the online help under Aspen Plus
Keywords: eos, dfms, binary parameter, user databank, apdbmgv70, aped
References: -> Physical Property Data Reference Manual -> Using DFMS to Manage Databanks. |
Problem Statement: Cannot run flowsheet because an outlet or intermediate stream is incomplete. Shouldn't the file be able to run and determine the outlet conditions?
Cause
If any piece of input is entered on the Stream form, the form needs to be completed. This is part of the completeness and consistency checking that is part of the Aspen Plus Graphical User Interface. | Solution: Data for intermediate streams is used as an initial guess only if the stream is a tear stream.
If the data is not needed, go to the stream name in the Stream folder of the left hand pane of the Data Browser, right mouse click, and select Clear to remove all data. If the data is needed, complete the form. Use the Next button for help about what input is needed. All open windows containing the stream input form should then be closed.
Keywords: consistency check
completeness
cc check
References: None |
Problem Statement: Is it possible to change the vapor phase equation of state model when using electrolyte models? For example, how do I model a system with electrolytes and organic acids such as acetic acid? Is there a way to use electrolytes with Hayden O'Connell (HOC)? | Solution: It is possible to change the vapor phase equation of state model for phase equilibria and enthalpy calculations. Before 12.1, it was possible to change the vapor phase equation for phase equilibria calculations, but the enthalpy model did not consistently calculate the correct vapor-phase departure.
The vapor-phase enthalpy departure occurs in two places: in the vapor-phase enthalpy model, but also in the liquid-phase enthalpy model. It is the inconsistency in the latter vapor-phase enthalpy departure contribution that has been fixed in Release 12.1.
The liquid enthalpy departure represents the difference between the ideal-gas enthalpy and the liquid enthalpy, and is calculated as follows:
DHL = DHV + DHVL + DHLPC
DHV is the vapor enthalpy departure evaluated at the system temperature and the component's vapor pressure
DHVL is the heat of vaporization. This term is calculated by the DIPPR or Watson Heal of vaporization model; it is the largest contribution to liquid enthalpy departure.
DHLPC is a correction between the component's vapor pressure and the system pressure. DHLPC will be small for incompressible fluids or if the density model is not dependent on pressure.
For additional information, see Technical Tip 3100.
In 12.1, the electrolyte liquid enthalpy was improved so that enthalpy departure term for other non-water solvents can be calculated using the equation of state (EOS). This is controlled using option code 5.
Option Code 5
Method
0
Do not calculate
1
Calculate by ESRK (Redlich-Kwong EOS model)
2
Calculate by ESHOC (Hayden-O'Connell EOS model)
Instructions to use Hayden-O'Connell EOS for the vapor phase:
Go to the Properties \ Property Methods \ ElecNRTL \ Models sheet and make the following changes:
1. Change the Model for vapor phase mixture fugacity (PHIVMX) to the Hayden-O'Connell model (ESHOC).
2. Change the Model for vapor phase pure component fugacity (PHIV) to the Hayden-O'Connell model (ESHOC0).
3. Select the liquid mixture enthalpy model (HMXENRTL) and click on the Option codes button. Change the 5th option code to 2.
Note: In version 2004.1 and earlier, the unmodified ElecNRTL property method must be referenced in the flowsheet on the Properties\Specifications\
Keywords: HOC
References: d sheet so that all required parameters are retrieved. In 2006 and later, these parameters will be retrieved for all property methods that use ElecNRTL in any way. |
Problem Statement: I've always assumed that when a binary parameter is missing for NRTL, the mixture would behave as ideal. However, in this ternary mixture A, B, C where binary parameters have been specified only for A with B, the activity coefficient for C is not one. Why not?
See the attached file nrtl.bkp. | Solution: In the file nrtl.bkp, set the mole flow of A to zero in the property analysis. You will see that the activity coefficient for B and C are 1, indicating that that the binary mixture behaves as an ideal mixture.
The assumption that when binary parameters are missing (or set to 0), the mixture behaves as ideal is correct only for binary mixtures (and this is true only for NRTL, not for UNIQUAC which still has some deviation from ideality even when binary parameters are set to zero).
The results are calculated correctly by Aspen Plus, but the results may not match reality and experiments.
Another way of looking at this is that since the NRTL model is able to represent multicomponent mixtures using binary interaction parameters, it implies that binary parameters have an effect not just on the activity coefficient of the pair of components, but also on the activity coefficient of the other components present in the mixture. If you look at the formula of gamma given in the on-line help for NRTL, you can see that it is a function of the tau and alphas for all components, not just the ones refering to the one specific component (see for example the second term which uses taumj and Gmj).
A simple spreadsheet nrtl.xls is attached with a macro to do the (simplified) NRTL calculations (the code is not written in the most CPU efficient way, but how it's described in the reference manuals and papers about NRTL). You can see that activity coefficients are equal to one only when all binary interaction parameters are set to 0. (These results match the results displayed in Aspen Plus).
Some people explain this using an analogy with soap, which typically has one end that likes water and one that likes oil. A component in a mixture for which you have no binary interaction parameters for NRTL will cause a similar effect, e.g. it will distord the multicomponent equilibrium in a way that is not what would be observed in experiments, acting a bit like a soap in the mixture.
The recommendation is to ensure binary parameters are available for all binaries, using experimental data or estimation. In practice, for liquid-vapor equilibrium, the saturation pressure of the components is typically what drives the equilibrium so this effect may not be important to consider, but for liquid-liquid equilibrium this kind of effect may be responsible for getting wrong results.
An instructive example is attached in the file water-hc.bkp. The mixture contains water, n-butane and n-pentane. No interaction parameters are available for water/n-butane, but you would think this will behave in a similar way to water/n-pentane, e.g. very little mutual miscibility of water and hydrocarbon. The binary parameters delivered in Aspen Plus databanks contain parameters regressed from experimental data; most likely no experimental data were published for the water/n-butane mixture which is why no binary parameters are available for this pair. A Flash3 block predicts that indeed there is a single liquid phase for water/n-butane, while it predicts two liquid phases for water/n-pentane. For a mixture with 34%mol of water, 33%mol of n-butane and 33%mol of n-pentane, you will observe that the aqueous phase contains a lot of n-pentane, e.g. the missing interaction parameter for n-butane/water causes n-butane to drive more n-pentane in the aqueous phase (which is not what would be observed in reality). If you activate the estimation of missing interaction parameters on the NRTL parameter sheet, you will see that the results are closer to the expected result.
Beware of missing binary parameters!
Keywords: nC4
nC5
References: None |
Problem Statement: How to correct error 'Failed to create and load form control: MMComp_Spec.MMComp_Spec_Input'. | Solution: Go to Command prompt and type:
regsvr32 c:\windows\system32\msvbvm60.dll
then all of the form control errors should be solved.
Keywords: Properties
Forms
References: None |
Problem Statement: What is best value of System foaming factor? | Solution: The clear liquid height is the height to which the aerated mass would
collapse in the absence of vapor flow. The clear liquid height gives a measure of the liquid level on the tray and is used in efficiency, flooding, pressure drop calculations. The froth (foam) factor is related to the froth height and the clear liquid height as follows:
hc = F * hf
where
hf is the froth height on the tray
hc is the clear liquid height
F is the froth (or foam) factor
Typical values for foam factors are available in the Help under 'Foaming Calculation for Trays', or in appendix A of Unit Operation Models, p1. A-11.
Suggested values for Ballast trays are:
Service
System Foaming Factor
Non-foaming systems
1.00
Fluorine systems
0.90
Moderate foamers, such as oil absorbers, amine, and glycol regenerators
0.85
Heavy foamers, such as amine and glycol absorbers
0.73
Severe foamers, such as MEK units
0.60
Foam stable systems, such as caustic regenerators
0.30
Suggested values for Flexitrays are:
Service
System Foaming Factor
Depropanizers
0.85 - 0.95
Absorbers
0.85
Vacuum towers
0.85
Amine regenerators
0.85
Amine contactors
0.70 - 0.80
High pressure deethanizers
0.75 - 0.80
Glycol contactors
0.70 - 0.75
Suggested values for Float valve trays are:
Service
System Foaming Factor
Non foaming
1.00
Low foaming
0.90
Moderate foaming
0.75
High foaming
0.60
Keywords: radfrac
tpsar
tray rating
References: None |
Problem Statement: What convergence algorithm should be used in RadFrac? | Solution: No single algorithm works all the distillation problems. Aspen Plus offers a group of algorithms and initializaion methods. We recommend the use of the Standard convergence method first for most two- and three-phase columns. It can be used to perform free-water calculations in the condenser or the entire column. This algorithm is the most efficient, and works for 80% of the problems. If the standard convergence fails, then choose the Convergence Algorthim on the Setup\Configuration sheet based on the process type.
The Azeotropic method is recommended for highly nonideal azeotropic separations, for example, ethanol dehydration using benzene as an entrainer. The Azeotropic method uses the Newton algorithm with Azeotropic initialization. Like all applications of Newton's method, it converges very rapidly if it starts at a point near theSolution.
The Petroleum/wide-boiling method is recommended for petroleum/petrochemical applications involving wide-boiling mixtures and many components/design specifications. RadFrac can perform free-water calculations only in the condenser. The Petroleum/wide-boiling method used Sum-Rates algorithm with Standard initialization. Sum-Rates is slower than Newton is when starting with a good approximation to theSolution. The advantage of Sum-Rates is that it is more stable at finding aSolution without good estimates.
The Strongly nonideal liquid method is recommended for highly nonideal systems when RadFrac encounters slow or difficult convergence using the standard algorithm. The Strongly non-ideal liquid method uses the Nonideal algorithm with Standard initialization. Nonideal is quicker than the Standard method when dealing with columns such as this, because it recalculates activity coefficients every iteration.
The Cryogenic method is recommended for cryogenic applications, such as air separation. Cryogenic method uses the Standard algorithm with Cryogenic initialization.
The Custom method is used to choose the convergence method and initialization method independently on the Convergence \ Basic sheet.
The convergence methods for RadFrac are:
Convergence Algorithm
Descripion
Standard
The standard inside-out method of Boston and Britt. Recommended for
common two- and three-phase distillation calculations.
Sum-Rates
A variation of the inside-out method. Recommended for
petroleum/petrochemical applications involving wide-boiling mixtures
with many components or design specifications. Use only for two-phase
distillation calculations. Can also handle free-water in condenser.
Nonideal
A variation of the inside-out method of Boston and Britt.
Recommended for highly nonideal two- and three-phase distillation
calculations which result in slow or nonconvergence using the standard
inside-out method.
Newton
Recommended for highly nonideal two-phase distillation calculations,
such as azeotropic distillation. Slower than all other inside-out
algorithms.
Each algorithm has a set of convergence parameters which can be adjusted to fine tune convergence.
The initialization methods for RadFrac are:
Initialization Method
Description
Standard
Standard initialization of column profiles recommended for most
common applications.
Crude
Special initialization of column profiles recommended for wide boiling
and multidraw columns.
Chemical
Special initialization of column profiles recommended for
narrow-boiling and highly nonideal chemical systems.
Azeotropic
Special initialization of column profiles recommended for azeotropic
systems (for example, dehydration of ethanol using benzene as an
entrainer).
Cryogenic
Special initialization of column profiles recommended for cryogenic
applications (for example, air separation).
Keywords: column
convergence
algorithm
References: None |
Problem Statement: How is it possible to get a better fit of CO2 partial pressure? How does Aspen Calculate new Total Pressure of CO2 since we specify partial press equal to Total Pressure? | Solution: It is better to just fit the CO2 partial pressure since the water partial pressure typically works reasonably well without fitting and inclusion of it in the fit seems to cause DRS convergence difficulties.
The way to accomplish fitting just the CO2 partial pressure is to:
Provide the liquid-phase composition as in the data.
Make the vapor phase pure CO2. It is possible to give a tiny water composition; however, zero is fine. The water concentration is small enough that it will not affect the results.
Make y(CO2)=1 and set all the y standard deviations to zero.
Only include CO2 in the Constraint form; no water.
The only assumption in this approach is that the fugacity coefficient of pure CO2 at its partial pressure is equal to the fugacity coefficient of CO2 in the water-CO2 vapor at the correct composition. This is a quite reasonable assumption since if y(CO2) is small, total pressure is also small, hence the fugacity coefficient is near unity; if y(CO2) is close to unity, the pressure may be large, but the pure assumption is close to reality.
We have used this approach for several systems and found it to be quite effective. SeeSolution 113347 for an example using CO2 hot potassium carbonate.
Keywords: HOTCA
drs
References: None |
Problem Statement: What is the Vredeveld power law mixing rules for liquid thermal conductivity? | Solution: The Vredeveld power law mixing rule for liquid thermal conductivity (KLMX) is as follows:
KLMX**expt = SUM [ wi * KLi**expt ]
where wi is weight fraction of component i
and KLi is the pure component thermal conductivity of i
The exponent (expt) can be set using the model option code. The most appropriate value of expt is dependent on the ratio of KLj/KLi, where KLj > KLi. (KLj is the maximum value of pure component liquid thermal conductivity in the mixture. KLi is the minimum value of pure component liquid thermal conductivity in the mixture)
For most systems, 1 <= KLj/KLi <= 2, a value of expt = -2 is recommended (and is the default value used).
Option code
Value
Description
1
0 (default)
Do not check ratio of KLj/KLi
1
Check ratio of KLj/KLi. If the ratio is > 2, set expt = 1.
2
0 (default)
expt = -2
1
expt = 0.4
2
expt = 1.0 (weight-fraction average)
Aspen B-JAC products use linear weighting; hence, the values from B-JAC for KLMX may be different.
Keywords: KL
References: None |
Problem Statement: Is it possible to view a subset of streams in a specified order on the ResultsSummary\Streams form? | Solution: 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. For more information on TFF files refer to the Aspen Plus User Guide.
The steps are as follows:
Copy one of the existing .TFF files in the Aspen Plus\GUI\xeq directory to the working directory where the simulation is locate.
Rename the file to whatever name desired for the Format.
Add the line: streams=streamids
Select the streams and the desired order of the streams.
For example,
streams=out in
The ampersand (&) is used to continue a line.
Open the simulation and run. On the ResultsSummary\Streams form, select the new Format from the drop-down list. The streams should appear in the order desired.
Keywords: tff
table file format
stream summary
References: None |
Problem Statement: How are the values calculated in the Regression / Input / Parameters input form for initial value and upper and lower bound after I run a regression case? Can I turn off the automatic filling in of these values? | Solution: The values of the initial value and upper and lower bounds are filled in depending on the option specified in Run / Settings / Options tab Copy Regression and Estimation results onto Parameters form. We recommend turning this option off initially.
The initial value is the regressed value of the parameter and the bounds are determined as follows:
lower bound = initial value - 10 * initial value
upper bound = initial value + 10 * initial value
Keywords: DRS
References: None |
Problem Statement: Is it possible to specify the number of exchangers in series and parellel in a HEATX block? | Solution: In 11.1, it is possible to specify the number of exchangers in series using the Shortcut method only. To model exchangers in parallel, a MULT block should be put before and after the HEATX block.
In 12.1, it is possible to specify heat exchangers in series and parallel also for the rigorous method.
The HEATX model in 12.1 will also
allow rating for shortcut method
add constant UA as additional u-option method. Area will be is optional if UA is specified.
display UA, number of shells in series and in parallel on the output forms.
In addition, there are some minor fixes:
corrected NTU calculation method in hxre.f. Previous version was using calculated area instead of actual area to determine NTU which can be incorrect for over or under surfaced exchangers. the corrected method is to use terminal temperature to determine P_ref and ntu is the ration of p_ref/thetaref which neither p_ref or thetaref is estimated.
use a more robust bisection method to find NTU. for the unconverged NTU, the estimated fmtd may be more close to the actual fmtd.
corrected xi calculation for multiple shells in series. fmtd seems to match B-JAC Hetran fmtd now after this correction.
corrected input value NTU which is used to calculate xi for single E shells in series. The correct NTU should be the fraction of NTU if multiple shells in series is involved.
Keywords:
References: None |
Problem Statement: Is it possible to have a reactive distillation and have the product show up in a solid stream? The React-dist does not allow a reaction product in a solid substream. Is there any other way? | Solution: CISOLIDS and NCSOLIDS do not participate in reactions in RadFrac. The reaction needs to be completed using a reactor before or after the RadFrac column.
Keywords: cisolid
ncsolid
References: None |
Problem Statement: Analyzer EO Variables | Solution: Analyzer EO Variables
A change introduced in V7.0 had compatibility effects not reported until now. Adding support for solids to the EO formulation of Analyzer required reformulating the model slightly to make it more like other models. Specifically, the DELTA_ENTH variable was removed, and a new DUTY variable was added. This is not exactly the same, since the DELTA_ENTH was on a molar basis (J/kmol) while DUTY is on a time basis (J/s).
This has consequences for users who have saved X or VAR files from version 2006.5 or earlier which they intend to load into newer versions, and for anybody who directly manipulated or accessed this EO variable from scripts, etc. In most cases, the variable can be converted by multiplying its value by the molar flow rate in kmol/s and assigning the result to the DUTY variable. Another way of handling it is to swap specs after loading a VAR file so that DUTY is calculated, and once the new DUTY value is calculated, swap back.
Keywords: DELTA_ENTH, DUTY. Analyzer
References: None |
Problem Statement: How does the RStoic conversion specification treat electrolytes? | Solution: When using the True species approach, the conversion will only apply to the true species concentration. For example if you have HCL and H2O completely dissociating into H3O+ and CL-, then a reaction in RStoic using key component HCL will not occur.
When using the Apparent composition approach, the conversion will apply to the apparent species concentration. In the above example, if HCL is the key component, then the reaction will occur, as long as there is HCL as an apparent component.
Keywords: RStoic, electrolytes, reaction
References: None |
Problem Statement: After entering Txy data and regressing the NRTL 2 (Bij and Bji) parameters, the sum of square error is very high (over 1 million), and when reviewing the Regression profile results, the estimated temperature in the first row is much higher than the experimental temperature. | Solution: Normally, the temperature data should have good agreement between the experimental and estimated columnar data. However, a common user error, reversing the composition data (entering component A's composition in the component B column) will cause a temperature error, especially if there is a large difference in boiling point between the 2 components you are regressing.
When you see a large difference in estimated versus experimental temperature, focus on data entry errors for the TPXY, TXY or TXXY data.
Keywords: Regression, DRS, TPXY, TXY, profile, residual, sum of squares error, EST, estimated, EXP, experimental
References: None |
Problem Statement: Why do my design-specs, and sensitivity analyses require a Fortran compiler when they do not have any Fortran or arithmetic expressions? Also, I have reviewed | Solution: document 104149, and my Calculator block does not contain any arithmetic expressions that require a compiler, yet Aspen Plus produces errors about the missing Fortran compiler?
Solution
When Aspen Plus keeps searching for a Fortran compiler, even though one is not needed, it is because there is a setting that has been accidentally set to force the use of a compiler with Design-Specs, Calculator Blocks, Sensitivity Analysis, and Optimization.
Navigate to the Setup | Simulation Option | System sheet, and be sure the Interpret all inline Fortran statements at execution time option for the Fortran compilation is selected. The Write inline Fortran to a subroutine to be compiled and dynamically linked should NOT be selected. To compile Fortran requires you have a supported compiler installed and Aspen Plus configured to use it. Please see below:
Keywords: Design-Spec, Design-Specification, Sensitivity Analysis, Calculator, FORTRAN, Interpret, compile
References: None |
Problem Statement: The unit of measure for HENRY's component data input into Aspen Plus is pressure. However, typically HENRY's component data found in literature are expressed in pressure/concentration such as Atm/(mol/liter). How do you get HENRY's component data calculated in Aspen Plus in the pressure/concentration units found in literature? | Solution: Ideally, HENRY constants could be calculated with a PROP-SET.
In 2006.5, two new Property Sets were added:
1. GAMUSAQ: Unsymmetic activity coefficient based on the aqueous reference state
This property is calculated from gamma(i in the mixture)/gamma infinity of i in water. GAMUSAQ is different from GAMUS in that GAMUS is calculated from gamma(i in the mixture)/gamma infinity of i in the mixed solvent. Here i refers to Henry's components.
2. HNRYMX: Henry's constant of component i in the mixture, where i is the Henry's component
In the interim, Aspen Plus will calculate the HENRY constant using a FLASH2 and SENSITIVITY block. The attached example BKP file reproduces the Acetylene (C2H2)/WATER HENRY's data from Perry's Handbook (6th edition, p.3-101) that used in the regression inSolution ID106047.
The example file contains a single FLASH2 block with a single feed containing the solute and solvent components at an arbitrary flowrate. A PROP-SET is created to retrieve the partial pressure of the solute in the FLASH2 block vapor outlet. The FLASH2 block specification is Temperature and Pressure, again arbitrary. In the SENSITIVITY block, the partial pressure of the solute in the vapor and the mole fraction of the solute in the liquid from the FLASH2 block is accessed through DEFINE variables. Then, the SENSITIVITY varies the FLASH2 block Temperature and calculates the HENRY's constant at the various temperatures by dividing the partial pressure by the mole fraction.
Row/Case
VARY 1
FLASH
PARAM
TEMP
C
C2H2
PARTIAL
PRESSURE
ATM
C2H2
LIQUID
MOLE
FRACTION
HENRY
ATM/MOLF
HENRY
X 10-3
ATM/MOLF
HENRY
ATM/CONC
HENRY
X 10-3
(Perry's)
ATM/MOLF
1
0
4.99402027
0.00692004
721.674291
0.72167429
12.8907763
0.72
2
5
4.99144944
0.00596095
837.357925
0.83735792
15.0095681
0.84
3
10
4.98794942
0.00520475
958.344015
0.95834401
17.2433478
0.96
4
15
4.98324714
0.0046022
1082.79495
1.08279495
19.5609012
1.08
5
20
4.97700813
0.00411752
1208.73718
1.20873718
21.9279834
1.21
6
25
4.96882726
0.00372438
1334.1342
1.3341342
24.3085629
1.33
7
30
4.95821904
0.00340313
1456.95844
1.45695844
26.6660771
1.46
Keywords: HENRY
HENRY's data
HENRY's constant
References: None |
Problem Statement: Which property method is best for steam and water properties for pure water streams or for free-water calculations? | Solution: Three methods are available in Aspen Plus:
STEAM-TA (ASME 1967 steam table correlations)
STEAMNBS (NBS/NCR steam tables)
STMNBS2 (NBS/NCR steam tables with a different root search method)
For process calculation purposes, the accuracy of all three methods is adequate.
STEAM-TA method is made up of different correlations each covering different regions of the PT space. These correlations do not provide continuity at the boundaries which can cause spurious convergence problems. It can also predict wrong trends. For example, the vapor phase enthalpy decreases at pressure of 119 bar and temperature around 320-330C. This abnormal behavior will cause a flash convergence failure. STMNBS2 can also have this problem.
Since STEAMNBS does not have this problem and it also extrapolates better, it may be wise to use it instead of STEAM-TA for pure water streams and for free-water calculations, unless there are other considerations to be taken in account. For similar reasons, it is usually best to use STEAMNBS for Property Methods such as SRK that calculate water properties from the Free-Water Prooperty Method.
Keywords: free water
steam network
References: None |
Problem Statement: Is the percent distilled under Stream Analysis | Dist-Curve in mass or volume percentage? | Solution: The percent distilled is on a liquid volume basis.
Keywords: Stream Analysis, Dist-Curve, %DIST, CQ00570745
References: None |
Problem Statement: What does the SOLID component type do? | Solution: If a component is specified as component type SOLID on the Components | Specifications | Selection sheet
It can be defined as a SALT on the CHEMISTRY block.
The Electrolyte Wizard will create components with the SOLID component type for salts.
A component with the SOLID component type can be entered in the CISOLID or MIXED substream on the Stream form.
Components with the CONV or Conventional component type can only be entered on the Mixed substream on the Stream form.
Specifying a component as SOLID does not change the properties accessed in the databanks. The same databank search order is used if the component type is CONV or SOLID.
Keywords: None
References: None |
Problem Statement: I want to refine my ELECNRTL model by including some heat of mixing (HLXS) data in my regressions. The trouble is, ELECNRTL consistently calculates HLXS to be zero. Is this the right way to set up the problem? Should I be using HLXS? Should I be using some other formulation for the excess enthalpy data? | Solution: The ELECNRTL property method is somewhat different from other activity coefficient methods in the sense that heat of mixing (HLXS) is included in liquid mixture enthalpy calculations. For this reason, ELECNRTL is unable to predict the property HLXS. For the same reason, a regression case which uses ELECNRTL is unable to process the data type HLXS. Liquid mixture enthalpy data (data type: HLMX), however, can be processed.
HLXS is actually just the difference between the liquid mixture enthalpy predicted by ELECNRTL and the ideal liquid mixture enthalpy of the same mixture.
Hence, theSolution can be to predict IDEAL liquid mixture enthalpies for the conditions (temperature, pressure, compositons) at which you have the heat of mixing data, and to add both properties (ideal HLMX + HLXS) together. This composite property is the real liquid mixture enthalpy which can be specified in Aspen Plus (data type: HLMX).
This way, the regression can benefit from the correct data type.
Keywords:
References: None |
Problem Statement: When using the ENTRL-RK databank for binary components, there is a binary parameter pair for CO2-H20. Where does this parameters come from since CO2 would usually be modeled as a Henry's component? | Solution: Although CO2 is usually supercritical and modeled as a Henry's component when using activity based property methods, there are times when the concentration of CO2 in the liquid phase is too large for only the Henry's method to be applicable.
When a component is declared as a Henry component, the concentrations are a function of both the Henry's constant computed from the HENRY parameters and the unsymmetrically normalized activity coefficient (GAMMUS) computed from the NRTL parameters. At very low component concentrations where GAMMUS is equal to 1, the solubility will be represented by the Henry's model. At higher concentrations, GAMMUS will deviate from 1 due to the nonidealities intrinsic to the activity coefficient model. Thus at higher concentrations, the solubility is modeled by a combination of Henry's and activity coefficient (NRTL) models.
In cases where the concentration in the liquid phase can get large, it is necessary to regress the NRTL parameters in addition to the Henry's constants to get a good fit of the VLE data. In the case of CO2/H2O, the NRTL parameters are required to model the CO2/H2O interaction when the concentration of CO2 in liquid can get quite large.
Do note that for most cases the CO2/H2O interaction can simply be modelled with CO2 as a Henry's component.
Keywords: carbon dioxide, water, gamma, modelled
References: None |
Problem Statement: Why are the valve tray types not updated with more recent designs? | Solution: The design procedures for specific vendor tray types have not been updated for some time. This is primarily due to the fact that it is extremely difficult to get competing vendors to share their tray design procedures with a third party who will have access to not only their design procedure but the procedures of other vendors. This clearly leads to concern that proprietary design methods might be compromised.
In Aspen Plus, there are dated design procedures for Koch Flexitrays, Glitsch Ballast Trays, and certain Nutter valve trays. In the intervening years since these design equations were implemented in Aspen Plus, Koch has acquired Glitsch and the packing and tray business of St. Gobain/Norpro. Sulzer has acquired Nutter and Jaeger is now a subsidiary of Raschig. It is a certainty that the design equations for the acquired companies have either been completely abandoned or significantly modified by the purchasing companies. Unfortunately, Aspen Technology does not have agreements in place with the consolidated vendors for their design methods.
It is worthwhile noting that in almost all cases the specific valve type has very little influence on the tray's jet flood capacity. The valve style does affect pressure drop but oftentimes not strongly. The most important thing to keep in mind is that the Koch and Glitsch procedures in Aspen Plus are no longer even used by the combined entitiy Koch-Glitsch. Th same is probably true for Nutter trays after their acquisition by Sulzer. This is readily apparent if the same design information entered into Aspen Plus is entered into one of the vendor's standalone design programs like KGTower or Sulcol. The Aspen Plus results will be quite different from those calculated within the vendor design programs.
Keywords: None
References: None |
Problem Statement: The TEMA sheet gives the weight of shell, weight filled with water and bundle weight. What is the total weight of the shell channel plus the bundle? | Solution: Here are how the three weight results are calculated at the bottom of the TEMA sheet:
Weight per shell:
The weight of the entire heat exchanger. This includes all of the heat exchanger components attached to the shell channel plus the weight of the bundle.
Weight of the bundle:
This is a sub-set of the weight of the entire heat exchanger. It is the weight of all components that make-up the bundle (tubes, tie-rods, spacers, baffles, etc).
Weight filled with water:
The weight of the heat exchanger when both the shell and tube sides are filled with water.
Keywords: B-JAC, HETRAN, TASC+, HTFS+, TEMA, shell and tube
References: None |
Problem Statement: Is there an alkylation example for Aspen Plus? | Solution: Chapter 15 of Gerald Kaes' Refinery Process Modeling - A Practical Guide to Steady State Modeling of Petroleum Processes, reference deals with process simulation of alkylation production units.
Mr. Kaes has authorized Aspen Tech to publish, on our support website, the companion workshops for his reference in Aspen Plus format. These models were originally published for sale in HYSYS (and another simulator) format. An Aspen Tech customer converted some of Mr. Kaes' companion models to Aspen Plus format and donated these converted models to the support website.
Attached, please find 2 alkylation models. A generic alkylation model, and an HF alkylation model.
NOTE: The attached model is provided as-is, but does offer an excellent starting point for modeling alkylation processes. The simulation file will run in Aspen Plus 2004.1 and higher.
The Refinery Process Modeling reference was published in 2000 by:
Kaes Enterprises
522 Kingston Road
Colbert, GA 30628
phone/fax: 706 788 3366
email: [email protected]
Copies of this reference are also available on Amazon and other online book sites.
Keywords: aspen plus, refinery, refining, alkylation, hf alkylation, h2so4 alkylation, petroleum
References: None |
Problem Statement: With Aspen Plus version 12.1 and higher, the import (read-vars) and export (write-vars) are interpreted more strictly. If import (read-vars) are entered, all other accessed variables are assumed to be export (write-vars), and vice versa. This strictness will uncover inconsistencies in existing Calculator blocks.
For example, any calculator block that used to write to an IMPORT variable will not work as it did previously. The write statements will now be ignored.
It is possible to specify both Import/Export variables and EXECUTE; EXECUTE will take precedence. | Solution: Review calculator blocks to ensure they are correctly specified.
Keywords: calculator
fortran block
References: None |
Problem Statement: I am getting FORTRAN errors in my equation-oriented run and I have user code. It is possible that these errors ome either from my own code or from a defect in Aspen Plus. How do I go about debugging my own code to make sure it is in order? | Solution: Please follow attached Word document.
Keywords: EO
References: None |
Problem Statement: How do you recommend modeling multiple interlinked columns? | Solution: We recommend using RadFrac with the Equation-Oriented (EO) paradigm to model such problems. We think that this approach is more flexible and robust than using MultiFrac. In addition, we are focusing more development resources on RadFrac's algorithms than any other column.
Keywords: column, tower
References: None |
Problem Statement: What is the recommended upper temperature range of the various pseudocomponent property methods built into Aspen Plus (e.g. API-METH, API, COAL-LIQ, ASPEN) for heavy petroleum applications in terms of the atmospheric equivalent boiling point of the pseudocomponents? | Solution: There are no documented upper limits for these methods from the authors. Our studies showed that the limits vary depend on the property [molecular weight (MW), boiling point (Tb), critical temperatue (Tc), critical pressure (Pc), etc], but most of them would behave properly up to a normal boiling point of about 800 - 1000 F for the fraction.
In Aspen Plus 12.1, we included a new set of correlations (EXTTWU) that extend the range of application to about 1500 F when the correlations are used to estimate Tc, Pc, MW and acentric factor.
Keywords: equation of state, critical temperature, pressure, molecular weight, boiling point, assay, blend, oil
References: None |
Problem Statement: Is there a way to tabulate internal energy (U) on the stream summary? | Solution: In 2004.1 and higher, there are new Prop-Set properties U (for a pure component) and UMX (for a mixture) that can be used to report the internal energy.
Keywords: U
References: None |
Problem Statement: How to retrieve pure component parameters such as molecular weight, Tc, etc in Aspen Plus? | Solution: The parameters are stored in databanks specified in the Components Specifications Databanks sheet. By default, Aspen Plus do not display all the pure component parameters on the parameter input forms. The data will be retrieved automatically from the databanks during simulation.
To view the parameters for the components specified in the simulation:
From the Tools menu, click Retrieve Parameters Results.
On the Retrieve Parameters Results dialog box, click Ok to generate a report.
On the next Retrieve Parameters Results dialog box, click Ok to view the results.
The results are found in the Properties Parameters Results Pure Component folder.
There are two types of pure component data: the scalar parameters and the T-dependent parameters which are located on different sheets. On each sheet, choose to view the actual parameter values or the status. Three status are possible: available, default or missing.
The retrieved results are temporary loaded and can be lost. Generate a detailed parameter report and save as a text file.
From the View menu, click Report.
On the Report dialog box, choose to Display report for Simulation and click Ok
Save the text file.
From version 11.1 onwards, the parameters can be retrieved directly by clicking onto the Review button located in the Components Specifications Selection sheet. The results will be automatically written into the Properties Parameters Pure Component input forms by default. The Results forms are purge when the simulation is reinitialized, but the input forms will need to be deleted manually.
The auto-filling of input forms can be suppressed in version 11.1 but not 12.1. Before retrieving the parameters, from the Run menu, click Settings. Under Options Physical Properties tab, untick Copy regression and estimation results onto Parameters form. In release 2004, go to menu Tools Options Components Data tab, under Copy results onto Parameters forms, untick Retrieved parameters.
In addition, Version 2004 has a new Clean Property Parameters function under Tools menu. User can choose to i) clean property parameters placed on selected input forms, ii) purge incomplete and empty records or iii) to clear all property parameters. Option (ii) is useful when a component or property method is deleted.
Keywords: Pure component
parameter
References: None |
Problem Statement: How are prompts added for a user databank? | Solution: To add a two-line prompt for a databank, modify the tbmsg.txt file by adding a
section in the following format at the end of all similar sections in the file:
DBANK HELP mmdbname
one or two line prompt.
>
>
$
$
To create databank hypertext Help:
1. Open the file userdata.rtf using Microsoft Word.
2. In place of the Databank1 heading, type the text you want as the heading for your topic.
3. In place of the current text on the page, type the text you want the Help system to display. You may want to modify the current contents of the document footnotes with a topic ID of your choice.
4. Compile the Help source files using the userdata.hpj file with the Microsoft Help Workshop.
For instructions on how to change the Help in the Aspen Plus user interface, see the Aspen Plus System Management
Keywords: user databank
References: Manual, Appendix A. |
Problem Statement: When using the NRTL activity coefficient model, I checked the box on the Properties | Binary interaction | NRTL form to use UNIFAC to estimate all missing parameters. After running the model, I decided to uncheck the box for using UNIFAC to estimate the missing parameters and deleted all of the interaction coefficients that were added when I initially checked the box. The interaction coefficients entered now look like they did prior to checking the above mentioned box; however, I am getting the following errors:
STRUCTURE FOR COMPONENT xxxx HAS NOT BEEN DEFINED.
PCES CANNOT USE GROUP-CONTRIBUTION METHODS TO ESTIMATE MISSING PROPERTIES.
USE THE STRUCTURES PARAGRAPH TO DEFINE STRUCTURES OF THIS COMPONENT.
How do I eliminate these errors? | Solution: When the Estimate all missing parameters by UNIFAC button is checked, Estimate all missing parameters is selected on the Properties | Estimation | Setup sheet and all binary parameters are selected on the Binary sheet. When the box is unchecked, the binary parameter estimation information is deleted, but the Estimate all missing parameters selection remains. Go to the Properties | Estimation | Setup sheet and select Do not estimate any parameters if no estimation is desired.
Keywords: NRTL, WILSON, UNIQUAC
NTRL, WILS, UNIQ
References: None |
Problem Statement: What are the governing equations for the NRTL-SAC model used in Aspen Plus? | Solution: NRTL-SAC is a segment contribution activity coefficient model, derived from Polymer NRTL model. NRTL-SAC can be used for fast, qualitative estimation of the solubility of complex organic compounds in common solvents. Conceptually, the model treats the liquid non-ideality of mixtures containing complex organic molecules (solute) and small molecules (solvent) in terms of interactions between three pairwise interacting conceptual segments: hydrophobic segment, hydrophilic segment, and polar segment. In practice, these conceptual segments become the molecular descriptors used to represent the molecular surface characteristics of each solute or solvent molecule. Hexane, water, and acetonitrile are selected as the reference molecules for the hydrophobic, hydrophilic, and polar segments, respectively. The molecular parameters for all other solvents can be determined by regression of available VLE or LLE data for binary systems of solvent and the reference molecules or their substitutes. The treatment results in four component-specific molecular parameters: hydrophobicity X, hydrophilicity Z, and polarity Y- and Y+; two types of polar segments, Y- and Y+, are used to reflect the wide variations of interactions between polar molecules and water.
The conceptual segment contribution approach in NRTL-SAC represents a practical alternative to the UNIFAC functional group contribution approach. This approach is suitable for use in the industrial practice of carrying out measurements for a few selected solvents and then using NRTL-SAC to quickly predict other solvents or solvent mixtures and to generate a list of suitable solvent systems.
The NRTL-SAC model calculates liquid activity coefficients. The equation for the NRTL-SAC model is:
with
Where:
=
Component index
=
Conceptual segment index
=
Activity coefficient of component I
=
Flory-Huggins term for combinatorial contribution to
=
NRTL term for local composition interaction contribution to
=
Segment mole fraction of component I
=
Effective component size parameter
and
=
Empirical parameters for
=
Total segment number of component I
=
Mole fraction of component I
=
Number of conceptual segment containing in component I
=
Segment mole fraction of conceptual segment in mixtures
=
NRTL binary non-randomness factor parameter for conceptual segments
=
NRTL binary interaction energy parameter for conceptual segments
NRTL binary parameters for conceptual segments.
The NRTL binary parameters between conceptual segments in NRTL-SAC are determined by available VLE and LLE data between reference molecules defined above.
Segment 1
X
X
Y-
Y+
X
Segment 2
Y-
Z
Z
Z
Y+
1.643
6.547
-2.000
2.000
1.643
1.834
10.949
1.787
1.787
1.834
0.2
0.2
0.3
0.3
0.2
Parameters used in NRTL-SAC.
Each component has four molecular parameters,,,, and although only one or two of these molecular parameters are needed for most solvents in practice. Since conceptual segments apply to all molecules, these four molecular parameters are implemented together as a binary parameter, NRTLXY(I, m) where I represents a component (molecule) index and m represents a conceptual segment index.
In addition, the Flory-Huggins size parameter, FHSIZE , is used in NRTL-SAC to calculate the effective component size parameter, . The Flory-Huggins combinatorial term can be turned off by setting for each component in mixtures.
Parameter Name/Element
Symbol
Default
MDS
Lower Limit
Upper Limit
Units
Comment
NRTLXY
-
-
-
-
-
Binary, symmetric
FHSIZE/1
1.0
-
1E-15
1E15
-
Unary
FHSIZE/2
1.0
-
-1E10
1E10
-
Unary
Option codes.
There are no option code in NRTL-SAC.
NRTL-SAC molecular parameters for common solvents.
The molecular parameters are identified for 62 solvents and published.
Solvent name
ACETIC-ACID
0.045
0.164
0.157
0.217
ACETONE
0.131
0.109
0.513
ACETONITRILE
0.018
0.131
0.883
ANISOLE
0.722
BENZENE
0.607
0.190
1-BUTANOL
0.414
0.007
0.485
2-BUTANOL
0.335
0.082
0.355
N-BUTYL-ACETATE
0.317
0.030
0.330
METHYL-TERT-BUTYL-ETHER
1.040
0.219
0.172
CARBON-TETRACHLORIDE
0.718
0.141
CHLOROBENZENE
0.710
0.424
CHLOROFORM
0.278
0.039
CUMENE
1.208
0.541
CYCLOHEXANE
0.892
1,2-DICHLOROETHANE
0.394
0.691
1,1-DICHLOROETHYLENE
0.529
0.208
1,2-DICHLOROETHYLENE
0.188
0.832
DICHLOROMETHANE
0.321
1.262
1,2-DIMETHOXYETHANE
0.081
0.194
0.858
N,N-DIMETHYLACETAMIDE
0.067
0.030
0.157
N,N-DIMETHYLFORMAMIDE
0.073
0.564
0.372
DIMETHYL-SULFOXIDE
0.532
2.890
1,4-DIOXANE
0.154
0.086
0.401
ETHANOL
0.256
0.081
0.507
2-ETHOXYETHANOL
0.071
0.318
0.237
ETHYL-ACETATE
0.322
0.049
0.421
ETHYLENE-GLYCOL
0.141
0.338
DIETHYL-ETHER
0.448
0.041
0.165
ETHYL-FORMATE
0.257
0.280
FORMAMIDE
0.089
0.341
0.252
FORMIC-ACID
0.707
2.470
N-HEPTANE
1.340
N-HEXANE
1.000
ISOBUTYL-ACETATE
1.660
0.108
ISOPROPYL-ACETATE
0.552
0.154
0.498
METHANOL
0.088
0.149
0.027
0.562
2-METHOXYETHANOL
0.052
0.043
0.251
0.560
METHYL-ACETATE
0.236
0.337
3-METHYL-1-BUTANOL
0.419
0.538
0.314
METHYL-BUTYL-KETONE
0.673
0.224
0.469
METHYLCYCLOHEXANE
1.162
0.251
METHYL-ETHYL-KETONE
0.247
0.036
0.480
METHYL-ISOBUTYL-KETONE
0.673
0.224
0.469
ISOBUTANOL
0.566
0.067
0.485
N-METHYL-2-PYRROLIDONE
0.197
0.322
0.305
NITROMETHANE
0.025
1.216
N-PENTANE
0.898
1-PENTANOL
0.474
0.223
0.426
0.248
1-PROPANOL
0.375
0.030
0.511
ISOPROPYL-ALCOHOL
0.351
0.070
0.003
0.353
N-PROPYL-ACETATE
0.514
0.134
0.587
PYRIDINE
0.205
0.135
0.174
SULFOLANE
0.210
0.457
TETRAHYDROFURAN
0.235
0.040
0.320
1,2,3,4-TETRAHYDRONAPHTHALENE
0.443
0.555
TOLUENE
0.604
0.304
1,1,1-TRICHLOROETHANE
0.548
0.287
TRICHLOROETHYLENE
0.426
0.285
M-XYLENE
0.758
0.021
0.316
WATER
1.000
TRIETHYLAMINE
0.557
0.105
1-OCTANOL
0.766
0.032
0.624
0.335
Keywords: NRTL-SAC
References: s
C.-C. Chen and Y. Song, Solubility Modeling with a Nonrandom Two-Liquid Segment Activity Coefficient Model, Ind. Eng. Chem. Res. 43, 8354 (2004). |
Problem Statement: What is the difference between DSTWU, Distl and RadFrac column capabilities? | Solution: DSTWU is used for shortcut distillation design
Distl is used for shortcut distillation rating
RadFrac is used for Rigorous rating and design for single columns
Brief description with different capabilities are explained below for your reference
The DSTWU unit operation is designed for single feed, two product distillation processes.
This column completes calculations using Gilliland?s, Winn?s, and Underwood?s methods for calculations of stages and reflux ratios as indicated below Table.
DSTWU
Calculates For
Winn
Minimum number of stages
Underwood
Minimum reflux ratio
Gilliland
Required reflux ratio for a specified number of stages
or required number of stages for a specified reflux ratio
These calculations are completed based on two assumptions:
constant molar overflow and
constant relative volatilities.
For a specified product recovery (both light and heavy), the DSTWU column first estimates the minimum number of stages and the minimum reflux ratio, and then it calculates the either the required reflux ratio or the required number of theoretical stages based on the user input. During these calculations, Aspen will also estimate the optimum feed stage location and the condenser and reboiler duties.
Distl simulates multistage multicomponent columns with a feed stream and two product streams.
Distl performs shortcut distillation rating calculations for a single-feed, two-product distillation column. The column can have either a partial or total condenser. Distl calculates product composition using the Edmister approach.
Distl assumes constant mole overflow and constant relative volatilities.
The user is required to input a number of the column specifications with this unit operation, including the number of stages, the reflux ratio, and the distillate to feed ratio.
RadFrac is a rigorous model for simulating all types of multistage vapor-liquid fractionation operations. These operations include:
Ordinary distillation
Absorption
Reboiled absorption
Stripping
Reboiled stripping
Extractive and azeotropic distillation
RadFrac is suitable for:
Two-phase systems
Three-phase systems (only in equilibrium mode)
Narrow and wide-boiling systems
Systems exhibiting strong liquid phase nonideality
RadFrac can detect and handle a free-water phase or other second liquid phase anywhere in the column. RadFrac can handle solids on every stage.
RadFrac can handle pumparounds leaving any stage and returning to the same stage or to a different stage.
RadFrac can model columns in which chemical reactions are occurring. Reactions can have fixed conversions, or they can be:
Equilibrium
Rate-controlled
Electrolytic
RadFrac (in equilibrium mode) can also model columns in which two liquid phases and chemical reactions occur simultaneously, using different reaction kinetics for the two liquid phases. In addition, RadFrac (in equilibrium mode) can model salt precipitation.
In equilibrium mode, RadFrac assumes equilibrium stages, but you can specify either Murphree or vaporization efficiencies. You can manipulate Murphree efficiencies to match plant performance. In rate-based mode, RadFrac uses rate-based non-equilibrium calculations to model actual tray and packed columns, based on the underlying mass and heat transfer processes, and does not use empirical factors such as efficiencies and the Height Equivalent to a Theoretical Plate (HETP).
You can use RadFrac to size and rate columns consisting of trays and/or packings. RadFrac can model both random and structured packings.
Keywords: Shortcut distillation, DSTWU, Distil, RadFrac etc;
References: None |
Problem Statement: How is it possible to implement a kinetic model that is based on activities rather than on concentrations? How is the Activity sheet on the Reaction form used? | Solution: The Activity on the Activity sheet of a Reaction form is used to to define reaction activity classes and associate them with reactions. Reaction activity classes are scalar multipliers to the reaction rate. The net reaction rate for a reaction is calculated as the product of the reaction's intrinsic rate and all reaction activity classes associated with the reaction. This has NOTHING to do with activity coefficients used in property models.
It is possible to use activity of a component rather than a concentration in equilibrium reactions; however, for kinetic reactions, a user routine needs to be used (seeSolution 104993). For equilibrium reactions, specify Mole Gamma or Molal Gamma on Power-Law, LHHW, Reac-Dist, or General Reactions forms. In 2006.5 and higher, it will be possible to specify LHHW kinetic reactions based on activity.
Keywords: MOLE-GAMMA, MOLAL-GAMMA
References: None |
Problem Statement: Aspen Properties Enterprise Database on V7.0, V7.1 failed to load on HYSYS or Aspen Plus. | Solution: To install SQL Management tool from the link below:
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=c243a5ae-4bd1-4e3d-94b8-5a0f62bf7796
Download the documentation to troubleshoot random APED issues. (See attached)
Manually re-register APED databases from Aspen Properties Database Manager.
In this example, computer name is followed by \SQLEXPRESS
Users and password for Aspen Properties database
V7.1
V7.0
V2006.5
Login:
Password:
apeduser
Aprop100
apeduser
Aprop100
aped065
Aprop100
Restart SQL Server from SQL Server Management Tool
Lastly, test application again.
Keywords: APED, Aspen Properties Enterprise Database, SQL Server, Aspen Properties V7.1, V7.0, SQL Server Management Tool, Aspen Hysys, Aspen Plus, Databank
References: None |
Problem Statement: Is there any documentation concerning how the steam table methods are extrapolated in Aspen Plus? Are there different extrapolation methods for the different methods? | Solution: The extrapolation methods are different for the three different steam table methods in Aspen Plus: STEAM-TA, STEAMNBS, and STMNBS2.
STEAM-TA
The STEAM-TA method is based on the ASME 1967 steam correlation, which is a piece-wise correlation. In this method, different functions are used to represent different regions of the Pressure-Temperature (P-T) surface of water. This means that there are discontinuities when crossing these boundaries. When the property is extrapolated, it is done linearly with respect to absolute temperature using the slope at the temperature boundary where it is valid. The derivative is computed numerically.
STEAMNBS and STMNBS2
The STEAMNBS and STMNBS2 methods are based on the NBS/NRC 1984 equation of state (EOS). This is a complex EOS with many terms, so the EOS root has to be solved numerically. When theSolution is feasible, i.e., the phase actually exists in nature at the temperature and pressure specified, then there is no problem. In this case, both STEAMNBS and STMNBS2 will give the same answers. The only differences are the result of some numerical noise because the numerical root finding code was written differently. When the phase does not exist, then the EOS root cannot be found and must be extrapolated. There are many ways this can be done, but the basic idea is to obtain a value that is either liquid-like or vapor-like. STEAMNBS uses one extapolation method AspenTech developed which is used in all other EOS methods, such as Peng-Robinson, SR-POLAR, etc. This method tries to locate the extremum of the isotherm and uses it to get the estimate. The extrapolation method used for STMNBS2 uses the extremum of the isotherm directly.
Keywords: steam tables
References: None |
Problem Statement: Why does the pump issue an error saying the feed has more than 0.01% vapor?
FEED HAS MORE THAN 0.01 % VAPOR. OUTLET CONDITIONS | Solution: The pump unit operation in Aspen Plus was designed to handle liquid phases. Those liquid phases can be a single, homogeneous liquid phase, or a two-phase liquid such as water - hydrocarbon(s). In actual plant operations, pumps with unwanted vapor in their feed will experience cavitation and possible mechanical failure. For these two reasons, Aspen Plus issues an error message when the vapor content of a liquid feed stream exceeds 0.01% vapor.
To diagnose the underlying cause of this problem, analyze the upstream unit operations and their attached streams. Check for unwanted or unexpected phase change upstream of the pump.
Keywords: pump, vapor, error
References: None |
Problem Statement: From when are most recent UNIFAC-DMD parameters? Do they date from end of 1990s or are they more recent (via UNIFAC consortium)?
In the 2004.1 help I find the following:
J. Gmehling, J. Li, and M. Schiller, Ind. Eng. Chem. Res. 32, (1993), pp. 178-193.
Are these the ones used in 2004 and 2004.1? Will there be a newer edition in Aspen Plus 2006 ? | Solution: There were some changes to UNIF-DMD made for 12.1. I have pasted the information from the What's New in Aspen Engineering Suite (AES) 12.1. We included all the published parameters at that time (until 2002). We have not updated it since; therefore, 2006 will not have any updates.
A UNIFAC consortium member is not allowed to use any parameters obtained by the consortium in commercial software until they are published in the open literature.
For Aspen Plus and Aspen Properties 12.1:
The modified UNIFAC Dortmund model has been upgraded to include the latest published groups and group interaction parameters. The following new groups have been added:
Group number
Main group # in literature
Sub group
Main group
3450
46
Nmp
cy-con-c
3455
Nep
3460
Nipp
3465
Ntbp
3555
47
AmHCH3
CON(Am)
3560
AmHCH2
3565
48
Am(CH3)2
CONR2
3570
AmCH3CH2
3575
Am(CH2)2
3750
52
AC2H2S
ACS
3755
AC2HS
3760
ACS
3900
53
H2COCH
Epoxy
3910
HCOCH
3925
55
(CH3)2cb
CARBONAT
3930
(CH2)2cb
3935
CH2CH3cb
In addition, the Pyridine group has been changed from C5H4N to AC2H2N, AC2HN and AC2N.
A total of 142 revised and new group interaction parameters have also been added using the following references:
Gmehling, J., J. Lohmann, A. Jakob, J. Li, and R. Joh, ?A Modified UNIFAC (Dortmund) Model. 3. Revision and Extension,? Ind. Eng. Chem. Res. 37, 4876-4882 (1998)
Lohmann, J., R. Joh, and J. Gmehling, ?From UNIFAC to Modified UNIFAC (Dortmund),? Ind. Eng. Chem. Res. 40, 957-964 (2001)
Wittig, R., J. Lohmann, R. Joh, S. Horstmann, and J. Gmehling, ?Vapor-Liquid Equilibria and Enthalpies of Mixing in a Temperature Range from 298.15 to 413.15 K for the Further Development of Modified UNIFAC (Dortmund),? Ind. Eng. Chem. Res. 40, 5831-5838 (2001)
Lohmann, J., and J. Gmehling, ?Modified UNIFAC (Dortmund): Reliable Model for the Development of Thermal Separation Processes,? J. Chem. Eng. Japan, 34(1), 43-54 (2001).
Gmehlig, J., R. Wittig, J. Lohmann, and R. Joh, ?A Modified UNIFAC (Dortmund) Model. 4. Revision and Extension,? Ind. Eng. Chem. Res. 41, 1678-1688 (2002)
The UNIFAC group count (UFGRPD) for 39 components have been changed to make use of the new and revised groups. These changes were made in the PURE12 databank. To maintain upward compatibility, the UFGRPD parameters in PURE856, PURE93, PURE10, and PURE11 databanks were not changed, except to account for the revised pyridine groups. Therefore, to take full advantage of this major upgrade of the UNIFAC Dortmund model, the PURE12 databank should be used.
Component Name
Component Alias
2-METHYLPYRIDINE
C6H7N-D1
2,6-DIMETHYLPYRIDINE
C7H9N-D2
3-METHYLPYRIDINE
C6H7N-D2
4-METHYLPYRIDINE
C6H7N-2
PYRIDINE
C5H5N
QUINOLINE
C9H7N-D2
ISOQUINOLINE
C9H7N-D1
QUINALDINE
C10H9N
3,4-DIMETHYLPYRIDINE
C7H9N-3
2,4,6-TRIMETHYLPYRIDINE
C8H11N-D1
3,5-DIMETHYLPYRIDINE
C7H9N-4
DIBENZOPYRROLE
C12H9N
PYRROLE
C4H5N-2
2,3-DIMETHYLPYRIDINE
C7H9N-1
2,5-DIMETHYLPYRIDINE
C7H9N-2
INDOLE
C8H7N
ACRIDINE
C13H9N
NIACIN
C6H5NO2-D1
8-HYDROXYQUINOLINE
C9H7NO
N-METHYL-2-PYRROLIDONE
C5H9NO-D2
N-METHYLACETAMIDE
C3H7NO-D1
ACETANILIDE
C8H9NO
N,N-DIMETHYLACETAMIDE
C4H9NO-D0
THIOPHENE
C4H4S
BENZOTHIOPHENE
C8H6S
2-METHYLTHIOPHENE
C5H6S-E1
3-METHYLTHIOPHENE
C5H6S-E2
DIBENZOTHIOPHENE
C12H8S
ETHYLENE-OXIDE
C2H4O-2
PROPYLENE-OXIDE
C3H6O-4
2,3-EPOXY-1-PROPANOL
C3H6O2-D2
ALPHA-EPICHLOROHYDRIN
C3H5CLO
1,2-EPOXYBUTANE
C4H8O
1,2-EPOXY-2-METHYLPROPANE
C4H8O-D1
DIMETHYL-CARBONATE
C3H6O3-D3
PROPYLENE-CARBONATE
C4H6O3-D1
DIETHYL-CARBONATE
C5H10O3-D1
ETHYLENE-CARBONATE
C3H4O3
ACETAMIDE
C2H5NO-
Keywords: UNIF-DMD
UNIFAC
References: None |
Problem Statement: When modeling electrolytes with ELECNRTL, pure component heat capacity (Cp) for some ions is negative. Why should it be negative? Does it mean anything? Does it make any sense to report Cp for an ion? When dealing with electrolytes and true component, shouldn't we just focus on mixture heat capacity (CPMX)? | Solution: Ions always exist inSolution together with their counterions to achieve electroneutrality. Consequently, the physically meaningful Cp's are the Cp's for the ion pairs. Cp's for ion pairs should be positive. (Note that we are dealing with Cp's at infinite dilution.)
In order to compute Cp's for ion pairs, the thermodynamics convention has been to assign Cp for proton ion to zero. For example, if Cp for Hydrogen Chloride (H+ Cl-) is 100 unit. The convention is to assign Cp for H+ to 0 and assign Cp for Cl- to 100. If Cp for Sodium Chloride (Na+ Cl-) is 80, given that Cp for Cl- has been assigned to 100, Cp for Na+ will be assigned to -20. This is a convention adopted and accepted by researchers in the field of electrolyte thermodynamics.
It is more important to focus on CPMX, but Cp of the ions are important in that they contribute to the CPMX of the mixture, so we need to have good values for them as well.
Keywords: electrolyte
ions
References: None |
Problem Statement: For a conventional inert solid in a liquid stream, what is the definition of MASSCONC? | Solution: The MASSCONC for a conventional inert solid in a liquid stream is calculated based on the total volume of the liquid and the solid components:
Solid concentration = [mass of solid / volume of (solid + liquid)].
This can be verified by the following steps in the attached example:
1. Define a property set including MASSRHOM and MASSCONC with ?liquid? selected as the qualifier.
2. Run the simulation and the values in the stream report show the following relationship:
.
where
MASSRHOM is the mass density for the mixture of the liquid and the conversional inert solid
MASSCONC is the mass concentration of a component in the above mixture.
For example, for stream WET, you can confirm the calculation of MASSRHOM from the MASSCONC values for solid and liquid:
MASSRHOM = 1.1403 lb/cuft = 0.0223(solid) + 1.1180(liquid)
This conforms that solid concentration is calculated based on the total volume of the liquid and conventional solid.
Keywords: Solid concentration
References: None |
Problem Statement: Service Pack installation disappears after package install is initiated | Solution: Service Pack installation starts by registry cleanup and it takes a long time for this task. The cleanup process goes on in the background and has installation has not been terminated. Customer should leave the installation and come back to it after a while. After Registry cleanup, Service Pack installation will prompt the user for continuation after which it will complete.
Keywords: SP5
Service Pack
Aspen Service Pack
PATCH
patch
service pack
AspenOne 2004.1 Service Pack
References: None |
Problem Statement: How does Aspen Plus calculates the THYDRATE and PHYDRATE properties used to predict the temperature and pressure of hydrate formation? | Solution: The ability to predict hydrate formation is vital in the design and operations in gas processing plants. The value is in defining how much inhibitors must be added to avoid hydrate formation of a system of a given composition, temperature and pressure. The goal is to prevent the hydrates from clogging equipment and lines.
There are two Prop-Set properties THYDRATE and PHYDRATE, which return the temperature and pressure of Hydration if the other is fixed.
PHYDRATE indicates the lowest pressure at which the hydrate is formed.
THYDRATE indicates the highest temperature at which the hydrate is formed.
For both, the phase qualifier must be V (for vapor).
A property set can be used in physical property tables and analysis. These prop-set properties can also be reported in the stream summary or report (seeSolution 3005 for details) or accessed within a Sensitivity, Design Spec, or Calculator block (seeSolution 3295).
The attached example file has a simple property analysis tabulating PHYDRATE and THYDRATE versus temperature along with a simple flowsheet with these properties reported in the streams.
Method
API Charts are used in determining either the temperature or the pressure at which the hydrate forms from a multicomponent gaseous mixture. These calculations involve an iterativeSolution.
The iterativeSolution is satisfied when the sum of the Xs=1, where Xs=y/K.
Notation:
Xs = mole fraction of a component in the solid gas hydrate on a water-free basis.
y = mole fraction of a component in the vapour on a water-free basis.
K = vapour-solid equilibrium ratio (y/Xs)
TheSolutions converge very slowly when the pressure is greater than 4000 psia or when the mixture is predominantly methane.
Limitations
These properties (THYDRATE and PHYDRATE) are only accurate for systems containing only the following 9 hydrocarbons:
methane
ethane
ethylene
propane
propylene
isobutane
hydrogen sulfide
carbon dioxide
nitrogen
The model does not predict the hydrate composition. The API correlations used were based on some composition; however, Aspen Plus cannot predict those compositions, only that the hydrate forms at certain a Temperature and Pressue.
The model does not handle the presence of inhibitors. There are plans implement a more comprehensive hydrate prediction model including inhibitors for a future release.
Freeze out temperature of a gas such as CO2 can also be calculated for a stream using the TFREEZ property. For TFREEZ, we use the heat of fusion (HFUS) for the solid fugacity and the liquid fugacity is calculated based on the selected property method. SeeSolution 102343 for more details and a comparison to data.
Reliability
The average error in predicting formation pressures (temperature held constant) for natural gases is approximately 7%, and the maximum error is approximately 20%. The average difference between experimental and predicted formation temperatures (pressure held constant) is approximately 1F, with a maximum of approximately 4F. Larger errors may be expected when the gas is rich in propane (>30%) or isobutane. Greater error will be expected if components other than the 9 hydrocarbons are present.
Note that Water is not required in determining hydrate formation pressure or temperature for a petroleum mixture, unless BASIS=DRY is specified in the Prop-Sets Qualifiers. The hydrate formation pressure or temperature are determined based on hydrate formation equilibrium constants which are calculated internally.
Keywords: hydrate
prop-set
References: s
API Techinical Databook, June 1981. |
Problem Statement: How is Ergun's equation used in RPlug? More specifically, how does Aspen Plus evaluate the following with respect to Ergun's equation?
1. What are the value of the Ergun A and B parameters used?
2. How is the pressure drop scale factor used?
3. Please explain exactly how particle diameter is used.
4. How is Sphericity used?
5. How does particle density play into Ergun's equation?
6. Is the particle density the density of the particle material or the bulk density of the catalyst in the reactor?
7. How is residence time defined in RPlug with Ergun's equation? | Solution: Ergun's equation is suitable for computing the pressure drop across packed bed reactors, and as such can be applied within the RPlug unit operation model.
1) The Ergun A and B parameters are the turbulent term and laminar term respectively. In Aspen Plus the turbulent term is set to 150, and the laminar term to 1.75. These are fitted parameters for Ergun's equation. These terms are also visible in the Aspen Plus Help Menu under Ergun's Equation.
2) The pressure drop scale factor is used when a frictional correlation, such as Ergun, is employed within RPlug. Such a correlation is activated from the Data Browser menu location Setup | Pressure for the RPlug model. This figure is simply a multiplier for the pressure drop calculated by the chosen frictional correlation.
3) The particle diameter used by RPlug is a nominal diameter based on screen size or similar measurement. The sphericity is then used to provide the rough shape of the catalyst particles. So if sphericity is equal to one, the particles are considered perfect spheres. As the sphericity value decreases, then the particles become less sphere-like impacting the void faction of the bed. So both the particle diameter and sphericity are used within the Ergun equation. Both are required as sphericity is defined as S = (6*particle volume) / (diameter * surf. area).
4) The original version of Ergun's equation did not take into account non-spherical particles. To account for these, the particle diameter (Dp) in Ergun's equation was replaced by the product of sphericity and equivalent particle diameter.
5) Particle density is one of three bed parameters that can be entered on the RPlug Setp | Catalyst Data Browser sheet (along with Catalyst loading and Bed voidage). If one wishes to include the catalyst bed in the RPlug calculations, then two of those three parameters must be specified. These quantities are required when the species generation rate is dependent upon the catalyst weight in the bed. The particle density plays into Ergun's equation since one of the Ergun parameters is the bed voidage, which can be determined via the particle density given the total catalyst load.
6) The particle density is the mass density of the actual catalyst particle.
7) The presence of catalyst is specified on the Setup | Catalyst sheet for the RPlug model. In an RPlug model, if catalyst is present, the computed catalyst volume is subtracted from the reactor volume when computing residence time. So Aspen Plus calculates a true residence time taking into account the catalyst volume - though you have the option of ignoring the catalyst volume in any rate/residence time calculations (separate checkbox on Setup | Catalyst sheet).
Note also that the porosity of the pellets themselves is accounted for in the sphericity term. As defined, sphericity takes into account surface area, volume, and diameter (see equation in item #3). Given these values, pellet porosity could be inferred based on how un-sphere like the pellet is.
Keywords: None
References: None |
Problem Statement: Is there an option to secure property parameters used in a simulation? | Solution: Aspen Plus V7.0 includes a new feature to allow the property parameters (constants such as critical parameters - TC, correlation coefficients such as PLXANT, binary parameters such as NRTL, pair parameters such as GMELCC) used in the simulation to be secured in the following manners through the use of restricted, secured enterprise databases:
1. The property parameters will be used in the simulation but cannot be reported, viewed or accessed.
2. The property parameters cannot be reported in the report file through the use of Property-report options: params, param-plus and project or through the User Interface settings on the Setup | Report Options | Property tab:
a. All physical property parameters (in SI units)
b. Property parameters' descriptions, equations and source
c. Project data file
The specification will be ignored and a warning message will be issued.
3. The property parameters cannot be shown in the User Interface through the use of the Review button on the Components | Specifications | Selection tab and Tools/Retrieve Parameter Results menu option.
4. The binary and pair parameters from the restricted, secured database will not be displayed in the User Interface (more on restricted, secured database in the section that follows).
The property parameters cannot be used in the Define or Vary form for Design Specification and Sensitivity Analysis. The variable category, Physical Property Parameters cannot be used. Note that the graphical user interface will not prevent you from making the selection, but if these parameters are accessed or varied, input translation errors will be issued when you run the simulation and the simulation will terminate.
The security is achieved through the use of the restricted, secured Aspen Properties Enterprise Database. The property parameters that you want to protect must be included in a restricted, secured database and the database must be used in the simulation (i.e., selected on the Components | Specifications | Enterprise Database tab. The instruction on how to create this type of database is given in the Aspen Properties Database Manager Help and inSolution 125495.
It is important to emphasize that this feature is not available when the legacy databanks are used.
The following behaviors are expected:
? The property parameters used in the simulation are secured automatically when one or more restricted, secured Enterprise databases are used. There is no setting or keyword required.
When the security is in effect, parameters from all the databanks selected, including those that are not restricted, will not be reported (see 2 and 3 above) in the report file and on Properties | Parameters | Results, and Properties | Parameters | Pure Component forms.
When the security is in effect, binary and pair parameters from databases that are not restricted will be displayed on the Properties | Parameters | Binary Interaction and Properties | Parameters | Electrolyte Pair forms. However, parameters from the restricted, secured databases will not be displayed. You can use the Display parameters on forms check box on the Components | Specifications | Enterprise Database tab to enable or disable display of these parameters from the un-restricted databases.
Keywords: None
References: None |
Problem Statement: How can I stop my simulation at specific blocks or upon error/warning messages? | Solution: In sequential modular mode, stop points can be used for an interactive simulation. They can be set up through Stop Points from the Run menu or by right clicking on the blocks in the left hand pane of the Control Panel. Users can choose to temporarily halt the simulation either before or after a step, which can be a unit operation block or other features such as Convergence, Sensitivity, Transfer, Calculator, Balance, or Pressure Relief. Users can also choose to specify that the simulation should be temporarily halted when an error with specific severity is encountered. The simulation can be resumed by clicking on the Run button again. If users want to review the simulation results that are available while the simulation is temporary halted, make sure that the option of interactively load results is selected under Run | Settings | Options.
Keywords: Interactive run
References: None |
Problem Statement: Does the Aspen Plus input file (*.inp) contain any of the dynamic keywords used to create Aspen Dynamic models? | Solution: The only link between Aspen Plus and Aspen Dynamics is via the Aspen Plus Graphical User Interface. Since the Aspen Plus Simulation Engine has no links to Aspen Dynamics, none of the dynamic input entered in the Aspen Plus Graphical User Interface is written to the Aspen Plus Input file.
Keywords: Aspen Dynamics, Aspen Plus, dynamic input
References: None |
Problem Statement: Why is the vapor from my flash that has a nonvolatile salt in it not at the dew point? | Solution: The vapor in the flash is in equilibrium with the liquid and salt. However, the vapor, taken aside, is superheated. This is a consequence of the presence of the salt causing a boiling point elevation of the whole mixture. If you boil water and salt, there is a boiling point elevation so it will boil at a temperature above 100C, say 102C. If you separate the vapor, it will be pure water, and it will be superheated at 102C since the boiling point of pure water is 100C. If the vapor is sent to a condenser, it does need to reduce the superheat in addition to condensing the vapor.
In more thermodynamics terms, re-flashing the vapor separated from the liquid it was in equilibrium with will no longer be affected by that liquid phase. In turn, the liquid fugacities are impacted by the presence of the non-volatile species the vapor does not know about. So, detaching the vapor from that vapor-liquid equilibrium will give you different results. Thus, the vapor, taken aside, is superheated as a consequence of the presence of the salt causing a boiling point elevation of the whole mixture.
Keywords: electrolyte, non-volatile component
References: None |
Problem Statement: Is there a way to get a HeatX block running in shortcut mode to calculate the required area? | Solution: Yes, it is possible for HeatX to calculate the required area in the shortcut mode.
Set the HeatX block to have a Calculation type of Rating. Then, enter a guess for the area (see Figure 1) and an outlet process condition as a specification (in this case, the hot outlet stream temperature was set to 140 F). Click on the SETUP form's U METHOD sheet and enter a good guess for a U value. For suggestions on U values for different processes, please seeSolution 119348.
Figure 1:
Run the simulation and when the simulation completes, please review the results to see both the specified area and required area (see Figure 2). The area you originally specified on the input form (see Figure 1) will show up as the Actual Exchanger Area.
Note that had you entered the actual bundle geometry, the actual area field would be populated with the calculated outside tube surface area or the bundle area.
The required area is calculated from equation 2, below
1) Q = UA * LMTD
2) A = Q/(U * LMTD)
The temperature you specified on the HeatX's input form (see Figure 1) is used inside the Log Mean Temperature Difference (LMTD) calculation.
When the required area is less than the actual area, then the heat exchanger is over-surfaced. When the required area is greater than the actual area, then the heat exchanger is under-surfaced. For under-surfaced exchangers, consider using the either detailed mode of HeatX or the HETRAN / TASC or TASC+ option inside HeatX to find more optimal mechanical configurations (better heat transfer coefficients) of the heat exchanger.
Figure 2:
Keywords: heatx, shortcut, detailed, u-value, heat transfer coefficient, area, required area, actual area
References: None |
Problem Statement: Why do mixed mode runs, where part of the flowsheet is solved with Equation Oriented (EO) and part is solved with Sequential Modular (SM), take as long as SM-only runs? | Solution: The problem is that EO needs to have good estimates for every stream and unit operation in the flowsheet. The attached .bkp file is a mixed mode flowsheet. The entire simulation runs in SM except for the one Hierarchy block that runs in EO. The hierarchy block needs to be solved via SM first, and then it can begin the EO calculations.
The Aspen Plus Control Panel below contains the results of the mixed run mode for the attached .bkp file. Except for the very end of the run-time messages (EO), the entire flowsheet was executed using SM first. You can verify that EO calculations took place by viewing any of the EO Variables forms in the DIST Hierarchy block and its associated unit operations.
> EO Convergence Block $EOSVR01 Hierarchy: DIST
Block: COLUMN Model: RADFRAC Hierarchy: DIST
Convergence iterations:
OL ML IL Err/Tol
1 1 3 121.06
2 7 26 393.37
3 9 21 357.54
4 7 18 442.08
5 2 6 258.94
6 2 5 97.522
7 2 5 11.530
8 2 4 2.3652
9 2 4 0.28045
Block: ABSORBER Model: RADFRAC Hierarchy: DIST
Convergence iterations:
OL ML IL Err/Tol
1 1 8 119.01
2 1 5 44.180
3 1 3 12.142
4 1 3 2.8259
5 1 2 0.43322
Block: VV Model: VALVE Hierarchy: DIST
Block: P1 Model: PUMP Hierarchy: DIST
Block: V1 Model: VALVE Hierarchy: DIST
> EO Convergence Block $EOSVR01 Hierarchy: DIST
INFORMATION WHILE INSTANTIATING THE EQUATION-ORIENTED STREAM BLOCK: BZ
IN DIST
BLOCK VAPOR PHASE DROPPED.
All unit operation blocks placed successfully in hierarchy DIST
All feed streams placed successfully in hierarchy DIST
Residual Objective Objective Overall Model
Convergence Convergence Function Nonlinearity Nonlinearity Worst
Iteration Function Function Value Ratio Ratio Model
--------- ----------- ----------- ---------- ------------ ------------ --------
0 4.775D-07 0.000D+00 0.000D+00
SuccessfulSolution.
Optimization Timing Statistics Time Percent
================================ ======== =======
MODEL computations 0.02 secs 66.67 %
DMO computations 0.00 secs 0.00 %
Miscellaneous 0.01 secs 33.33 %
Keywords: None
References: None |
Problem Statement: The physical properties models and methods reference guide says Aspen Plus has a polynomial activity coefficient model used for metallurgical applications. How do I use it? | Solution: This model is very infrequently used, so it does not come in a pre-packaged standard property method. The purpose of this note is to clarify some items explained in the documentation, which you should read first.
To use this model:
1. On the Properties | Specifications sheet, specify an activity coefficient model, such as NRTL or SOLIDS
2. Click the Properties | Property Methods folder.
3. In the Object Manager, click New.
4. In the Create New ID dialog box, enter a name for the new method.
5. In the Base Property Method field of the new method, select NRTL or SOLIDS
6. Click the Models tab.
7. Change the Model Name for GAMMA from GMRENON to GMPOLY.
8. Select this new property method on Properties Specifications sheet or in Block Options of blocks
The model evaluates the activity of each component using two parameters: GMPLYP, a Pure Component T-dependent parameter (which is found under Miscellaneous category) and GMPLY0, a Pure Component Scalar parameter. The model has no binary parameters.
Note that due to a limitation of the graphical interface, only the first 12 elements of GMPLYP can be specified directly on the parameter form (A, B, C, D but not E). If you need to specify all 15 elements, you have to use the input language, under Flowsheeting Options | Add Input | Add After. You should then specify all 15 elements in input language only (e.g. NOT under Properties | Parameters).
The syntax is:
PROP-DATA GMPLYP-1
IN-UNITS SI
PROP-LIST GMPLYP
PVAL WATER 0.0 1.5 0.0 &
0.0 0.0 0.0 &
0.0 0.0 0.0 &
0.0 0.0 0.0 &
0.0 16. 0.0
This would set ln gamma = 1.5 + 16 * x^4 (where x is the mole fraction of water).
The model can be used for liquid and solid phases.
We plan to include these clarifications and allow the 15 parameters to be specified directly in the GUI in a future version.
Keywords: None
References: None |
Problem Statement: How can I generate the list of units available in Aspen Plus, for example to verify units introduced in a new version? | Solution: You can use the SDFRPT utility program (System Definition File Report).
Steps:
1. Open a command window using the Aspen Plus Simulation Engine option
2. At the command prompt, type SDFRPT, then press the enter key
3. At the prompt, type UNIT, then press the enter key
4. At the prompt, type N, then press the enter key
Example:
D:\New Folder (2)>sdfrpt
C:\PROGRA~1\ASPENT~1\APRSYS~1.5\Engine\xeq\sdftab.exe
The following options are available for SDFRPT:
o Type in the name of a table. You can enter
a ? before the name for partial matching.
o Type HELP or <CR> to get a list of tables.
Enter in a name or <CR> to get a list:
UNIT
generating report for: UNITS CONVERSION TABLE
Do you want another table? (Y/N)
N
sdfrpt.rep created.
D:\New Folder (2)>
The file sdfrpt.rep created in the folder can be opened with Notepad or any other word processing program and will show you the list of units with offsets and conversion factors. The SDFRPT utility can also be used to generate list of other system options and parameters available. Use the help to see a list of the tables available.
Keywords: None
References: None |
Problem Statement: My Radfrac electrolyte simulation converges quickly and without problem when using the apparent component approach. If the true component option is enabled the simulation fails. | Solution: When one switches to the true approach, Aspen Plus has to account for the starting concentrations of the ionic and salt species listed in the component list for all the trays . Since these components did not previously exist while running the apparent mode, it is tries to estimate these concentrations. This will often lead to convergence problems in particular with systems with salts since the estimated salt concentrations will often be not feasible for the tower. But even in systems without salts, numerical instability can occur.
In some cases where users had provided compositional estimates for the apparent components, the estimation of the true species concentrations will fail. Deleting the composition estimates and reinitializing the tower should fix this problem and lead to a convergedSolution as most likely what is happening is a mismatch between the estimated concentrations of the ionic species and that provided by the user.
Keywords: electrolytes, convergence, radfrac, Fortran, errors, estimation, composition
References: None |
Problem Statement: How do you access a stream property within a Sensitivity, Design Spec, or Calculator block? | Solution: To use a stream property in a Sensitivity, Design Spec or Calculator block, you will need to first define a property set within the Prop-Sets folder and then reference it in desired Object manager. The procedure is outlined below:
1. Navigate to the Properties Prop-Sets folder within the Data browser. Click the New? button and provide a name, i.e., PS-1.
2. From the Physical properties drop-down list, choose the parameter you want to report in the column profiles, i.e., MUMX for viscosity of a mixture. For easier searching, click on the Search button at the bottom of this form.
If Units are not selected, Aspen Plus will report the property in the default system units.
Define the qualifiers, such phase = Liquid, on the Qualifiers tab.
Either specify values for temperature and pressure or use the system defaults which are stream conditions.
3. In the Define sheet of a Sensitivity, Design Spec, or Calculator block, type in a new variable name and click Edit.
Within the Variable Definition dialog box, choose Stream-Prop from the
Keywords: Prop-sets, properties, parameters, Sensitivity, Design Specs, Calculator, Define
References: Type list.
Choose the Stream name and from the Prop-Set drop-down list, choose PS-1.
Note: Only one property and qualifier (phase or component) is accessible for each variable. To access multiple properties, create additional individual Prop-Sets. If multiple properties or qualifiers are defined in a given Prop-Set, only the first parameter is retrieved.
4. Complete the data entry and run the file. |
Problem Statement: When using the Cyclone model the message LIQUID EXISTS IN MIXED SUBSTREAM appears and the model does not calculate correctly. | Solution: This happens when the the cyclone is fed a liquid fraction in a stream, the Cyclone model needs to only be fed an all vapor stream(vapor fraction =1) in order for the model to function correctly. This error can be remedied by making sure the feed to the cyclone is adjusted to an all vapor stream.
Keywords: Liquid, substream, mixed, vapor fraction, cyclone
References: None |
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