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Problem Statement: What are the assumptions for the heat of combustion parameter HCOM, which is used for reporting the net and gross heating values of streams (QVALNET and QVALGRS property sets)? | Solution: HCOM assumes that the products are CO2(g), H2O(g), F2(g), Cl2(g), Br2(g), I2(g), SO2(g), N2(g), P4O10(Cr), SiO2(crystobalite) and Al2O3(crystal, alpha). This cannot be changed.
Note that HCOM is a parameter and is not calculated from DHFORM and the chemical formula of the component by Aspen Plus. When the parameter is not specified, the default value of 0 is taken, which could lead to errors in the calculated heat of combustion. If you know the value of the heat of formation (DHFORM) of a component, you may want to try using a RSTOIC block to evaluate the appropriate value of HCOM to be specified.
Keywords: heating values
heat of combustion
properties
References: None |
Problem Statement: Can polymer reactors run in equation oriented (EO) mode? | Solution: One can easily see if the polymers feature is supported in Equation Oriented (EO) by running the simulation in Aspen Plus and then switch to EO mode. If you get an error message or a message saying the perturbation layer is used, it means there is no full support of EO. The perturbation layer can be used for EO, but is typically much slower. You can only know how well this perturbation layer performs by testing it with the type of problem you want to solve. It's quite likely some polymers attributes may be difficult to access in EO.
Keywords: Polymer, EO, Aspen Plus, Perturbation layer
References: None |
Problem Statement: Is it possible to make Binary Analysis plots for electrolyte systems? The binary plots for the binary TXY analysis look proper, but the True component plots do not. | Solution: Binary Analysis plots can be completed using the Apparent electrolyte approach. The results are not valid using the True approach since the vapor and liquid compositions are on different bases and involve the concentrations of more (i.e., true) components.
The valid composition range for the electrolyte parameters may not include all compositions which can lead to anomalous result as the parameters are extrapolated.
When doing binary analysis plots for electrolyte, one should always start with water and then add the electrolyte (just like in the Chemistry Lab!). The flash and property algorithms have a hard time with concentrated electrolyteSolutions. The flash restart then leads to differentSolutions as x is changed.
Keywords: flashcurve
elec
txy
pxy
References: None |
Problem Statement: Is it possible to hide and reveal design specs via the VBA automation tool? | Solution: To hide a design spec:
Dim spec As IHNode
Set go_Simulation = GetObject(~:\.............bkp)
Set spec = go_Simulation.Application.Tree.Data.Elements(Flowsheeting Options).Elements(Design-Spec)
spec.hide (DS-1)
and to reveal the design spec:
spec.reveal (DS-1)
Keywords: Design-spec
hide
reveal
activate
deactivate
VBA
References: None |
Problem Statement: How can I write volume flow to a feed stream from a Calculator block? | Solution: The calculator block only allows standard volume flow (STDVOL_FLOW) as the volumetric flow variable reference for the stream even though stream inputs accept actual flow. A workaround for this would be to calculate the required volumetric flowrate, multiply the volumetric flow with the mass density of the stream and write the mass flow rate back to the stream.
This is done in the attached example (12.1 bkp file). Note that in the example the feed volume of stream 2 is calculated on stream 1. Since stream 2 is a feed stream, its properties are not known until the block it is connected to has been calculated. As such, the calculator will fail since there is no mass or mole density available for this stream at the start of the simulation. In order to circumvent this problem, a dummy MIXER block is placed in stream 2 and the density is measured from the exit of this dummy block. Furthermore, this particular example introduces a informational tear variable which is converged iteratively with a Wegstein convergence block.
Keywords: Fortran tear, write, volume flow
References: None |
Problem Statement: The AES 12.1 products worked fine until installing products from the aspenONE discs. Products that were running now suddenly return license errors. | Solution: SLM supports license grouped into buckets. For 12.1, the SLM would automatically search the SLM Server for all buckets, but for 2004, the SLM must be configured to look for other buckets than the default bucket. This was done in order to add support for checking out a license from specific buckets instead of all buckets. To configure SLM:
Open the SLM Configuration Wizard ( Start | Programs | Aspentech | Common Utilities )
When Prompted for Connecting to a Server, make sure Yes is selected. Click Next.
In the Add servers window, in the Configured Server frame, highlight the server, then click the Buckets button.
If you know which buckets you need to add, type the number in the Add Bucket field, then click the Add Bucket button. If you don't know which bucket to add, type in the number 1, then click on Add Bucket. Then type in 2, and then click on Add Bucket. Continue to do so until you add the number 7. Click OK
Keep clicking Next until you can click the Finish button. Click Finish and then test the products.
If you still have problems, repeat the process but add 8 and 9 to the buckets list. If it still doesn't work, you should contact Aspen Tech support and send the support specialist a copy of your license file.
Keywords:
References: None |
Problem Statement: How do you write messages to the Control Panel in Aspen Plus from a Presolve script in an exported Aspen Custom Modeler model? | Solution: Use Application.Msg in the script code as in the example below to see message printed in the Control Panel when running the model in Aspen Plus:
if SMStatus = Not solved then
Application.msg Running Presolve script
...
end if
This will print the message
Running Presolve script
in the Aspen Plus Control Panel when the script executes.
Keywords: ACM
References: None |
Problem Statement: How does the design-spec (and other in-line Fortran objects) handle the division of integer quotients? | Solution: Sometimes it is easier for users to specify an integer quotient, say 111/ 555 instead of 0.2 for a spec value. Both Fortran and C++ interpret an integer quotient (integer numerator divided an integer denominator) as an integer division. When integer division is performed for 111/555, the result is 0.
To ensure that a real value is returned for the quotient, be sure to specify a decimal point on one or both of the numbers in the quotient expression:
a) 111.0 / 555.0
OR
b) 111.0 / 555
In both of cases a or b, the result value will be 0.2.
Keywords:
References: None |
Problem Statement: What is the pressure-drop correlation parameter that can be specified for a Heater? | Solution: In Aspen Plus 11.1 and higher, there is an option of Pressure-drop correlation parameter for a Heater specification. If this option is selected, users must enter a pressure-drop correlation parameter (k) that is then used to calculate the pressure drop (DP) using a flow-dependent correlation.
The correlation used is:
DP = k W^2 (1/rhoin + 1/rhoout)/2
Where:
DP = Pressure drop (Pa)
W = Mass flow rate (kg/s)
rhoin = Inlet density (kg/m3)
rhoout = Outlet density (kg/m3)
If mole flow does not change, this is equivalent to:
DP = k F^2 M (Vin+Vout)/2
Where:
F = Mole flow rate (kg-mol/m3)
M = Molecular weight
Vin = Inlet molar volume (m3/kg-mol)
Vout = Outlet molar volume (m3/kg-mol)
Note that there is an iterative loop to evaluate the outlet density, which is a function of the pressure drop being calculated.
The pressure drop correlation parameter is expressed in SI units in the result sheet of the heater block.
Keywords:
References: None |
Problem Statement: When should I use the Pipe or Pipeline unit operation in Aspen Plus? | Solution: Pipe or Pipeline calculates the pressure drop in a pipe.
Pipeline
When you use Pipeline Operation, you can add one or more segments in the same block.
In order to add one or more segments, you have to go to Setup - Connectivity; when you click on button New, a window about a new segment opens. You have to give a number to the segment and numbers for inlet and outlet nodes.
One limitation for Pipeline is that fittings are not taken into consideration.
Pipe
When you use Pipe Operation, you can only add one segment, however fittings can be considered.
If you go to Setup, you have two tabs: Fittings1 and Fittings2.
Fittings1 is used for:
- valves (gate or butterfly)
- elbows (large 90 deg.)
- tees (straight or branched)
- you can also include your own K factor or L/D
Note that it is possible to include any number of each type of fitting.
Fittings2 is used for:
- consider entrance/exit effects
- enlargement/contraction
- orifices
Note you can only include one of each type above.
Pipe X Pipeline?
If you have more than one segment and if you have to consider fittings effects, you need to use many Pipe blocks in series. In this way, you can consider fittings and more than one segment.
Fittings are considered as an equivalent length, so it doesn't matter if you include a fitting in a segment or in the following one. It only matters if the diameter of the segments are different or if there are entrance/exit effects.
Keywords: pipe, pipeline, pressure changers, fittings, segment, limitation, pressure drop
References: None |
Problem Statement: What are the units of measurement on the estimation forms?
On the Properties/Estimation/Input/Binary sheet, temperature at which to estimate the binary parameters can be specified. Are the units in SI or are they the Global units-set? | Solution: Temperatures are in units from the units set selected in the tool bar of this form. The Estimation form has its own unit setting; however in version V7.1 and earlier, the unit set does not show in the tool bar. It is set as global unit when the node is created. If global unit is changed after the simulation is created, the Estimation will keep the original unit. In V7.2, the units are shown in the tool bar so that users now can tell the unit that estimation uses, and change it as well.
When temperatures are used for the infinite-dilution activity coefficients estimation, these temperatures define the limit over which the estimated binary parameters are valid. By default the estimation is calculated at the default temperature of 25 deg. C If only one temperature is specified, the Aspen Physical Property System estimates only the second binary parameter (for example, WILSON/2 for the Wilson model). If more than one temperature point is specified, the Aspen Physical Property System estimates both binary parameters (for example, WILSON/1 and WILSON/2).
Keywords: unit set
binary estimation
pces
nrtl, uniquac, uniq, wilson
References: : CQ00186491 |
Problem Statement: How can I enter a component viscosity in Aspen Plus that is not temperature dependant? | Solution: For Property methods using the Andrade viscosity model, the second and third Andrade elements/terms can be omitted to specify a non-temperature dependant liquid viscosity. The equation then reduces to ln (visc) = A where A is the first term to be specified on the Andrade form.
Keywords: viscosity, mu, T-dependant, Andrade
References: None |
Problem Statement: What is the Plex? | Solution: Plex comes from the Greek word Plexus (plek'sus) meaning an interwoven combination of parts or elements in a structure or system. The term Plex actually refers to the linked list data structure but we use it to mean the data area that is used to hold this plex data structure.
Plex in Aspen Plus is a large memory area where all the data for your simulation is stored in a flexible way in order to allow maximum use of the memory space. So for instance, instead of having a maximum size array to handle the information for a maximum number of blocks, streams, property data, etc., where not all of them may be used in a particular simulation (and therefore be partially empty), the Plex system will allocate the actual size required in the memory, therefore freeing up space and allocating it according to particular requirement. For instance between systems that have a lot of property data requirement but only a few blocks, or vice-versa. This eliminates restrictions in the number of blocks, Streams, Components, etc. that a simulation can have.
So to summarise the above, the Plex is a pool of storage in computer memory.
Keywords:
References: None |
Problem Statement: If you select in the property set VOLFLMX you are not allowed to specify a pressure and temperature on the Qualifiers tab. If you select VMX you are allowed to. However, it is not obvious where this difference comes from and it is not documented in the on-line help why you can not specify a temperature and presure for VOLFLMX. What is the reason for this ? | Solution: VMX is the molar volume of a mixture; it is based on a stream, but if temperature & pressure are specified, it only uses the stream as a source for composition data.
VOLFLMX is volumetric flow rate of a stream, because there is no flow rate without using the stream itself. These stream properties are always based on the temperature and pressure of the specified stream. Thus this property and LFRAC, MASSFLMX, MASSSFRAC, MASSVFRAC, MOLEFLMX, SFRAC, VFRAC are defined to always use the temperature and pressure of the stream.
Keywords: prop-set
References: None |
Problem Statement: The CAPE OPEN unit model MixNSplit example delivered in version 11.1 of Aspen Plus does not work with Aspen Plus 12.1. | Solution: The problem is that the Material Object was improved in version 12.1 so that it properly respected the use of the basis qualifier in GetProp and SetProp calls. This was done to resolve the problem that values of Enthalpy returned from getProp were the same whether basis was specified as mass or mole.
The MixNSplit example delivered with Aspen Plus 11.1 tries to get the value of the TotalFlow property without specifying mole as the basis hence a value of 0 is returned. Subsequently, the flash calculation fails. If the code is modifed to add mole as the basis qualifer for this call then it works in Aspen Plus 12.1.
Since the source code for MixNsplit 11 is provided, it is possible to fix this problem.
In the ICapeUnit_Calculate method in Program Files\Aspentech\Aspen Plus 11.1\Engine\CapeOpen Example Models\MixNSplit.cls change the line
v = CapeMO.GetProp(totalFlow, Overall, Empty, vbNullString, vbNullString)
to
v = CapeMO.GetProp(totalFlow, Overall, Empty, vbNullString, mole)
Then rebuild the DLL in VB and re-register it using
Program Files\Aspentech\Aspen Plus 11.1\Engine\CapeOpen Example Models\capedescription.reg
Keywords:
References: None |
Problem Statement: When using Unifac-HOC to handle carboxylic acid (acetic acid, acrylic acid, etc), how does HOC calculate the density of vapor phase. Is the dimer Molecular Weighgt (MW) used or just the component MW? | Solution: Hayden-OConnell (HOC) calculates the vapor volume using the true number of species (i.e., after dimerization). Thus the true molar volume is V/Nt, where V is the vapor volume and Nt is the true or actual number of moles.
However, Aspen Plus does not report this true molar volume. It reports the apparent molar volume using the moles based on the components listed on the Component form. Thus, the reported molar volume is V/Na, where V is still the true vapor volume calculated considering dimer formation, whereas Na is the number of moles of the apparent species, i.e., the number of moles without considering dimer formation.
Therefore, user does not need to find out the real molecular weight in order to calculate density. The apparent molecular weight for the mixture can be used. RHOMX in a Property-set will report a correct density value.
The effect of dimer formation can be calculated by the ratio of the Z's. User can first use a Prop-set to report the Z for the vapor phase. For high pressure system, user can first use Unifac-RK to calculate the Z (which would be the Z without considering any dimer formation) and then use Unifact-HOC to calculate the true Z (with dimer formation) Since RK (Redlich-Kwong) calculates the other non-ideality withoutc onsidering the effect of dimer and HOC calculates the overall non-ideality (dimer formation as well as other non-ideality), the ratio of the two Z's is the effect of dimer formation. For low pressures, the Z calculated using RK will be essentially 1.
Keywords: Molecular Weight
dimer
carboxylic acid
References: None |
Problem Statement: When I click on the Blocks folder, why is the Reconcile option not available to reconcile all blocks? | Solution: It is possible to right mouse click on the Blocks folder in the Data Browser, and choose Reconcile to reconcile all block input similar to the way that all stream input can be reconciled by right mouse clicking on the streams folder.
There are a number of possible reasons that the option is not available:
Results are not loaded. Go to Run\Load Results and try again. When the full results are not loaded, only individual blocks can be reconciled.
The input did not change very much. There is a check that the input varied by a certain amount.
The block does not support input reconciliation. See the help orSolution 108012 for a list of limitations.
The Design Specifications or Calculator blocks do not manipulate any block variables.
Keywords:
References: None |
Problem Statement: Is is possible to retrieve the completion status for the simulation or individual nodes inside the Aspen Plus simulation? | Solution: Basically, the completion status is retrieved by adding the AttributeType property to the path-to-node variable with the (HAP_COMPSTATUS) constant specified as its qualifier.
For the overall simulation status:
SimStatus = go_Simulation.Tree.Data.AttributeValue(HAP_COMPSTATUS)
For an individual unit/block:
SimStatus = go_simulation.Tree.Data.Blocks.B1.AttributeValue(HAP_COMPSTATUS)
In either case, the returned value is an integer (the SimStatus variable would have to be declared as an integer variable). For the sake of simplicity, let's work with the first word of the integer (highlighted in pale yellow in the attached spreadsheet). If you look at the binary value of the returned completion status, it will be a value between:
00000000
and
11111111
If a bit is enabled (one of the digits equals 1), then that particular error/warning/or event occured. Since it is possible for multiple events to occur for each node in the flowsheet, this integer can keep track of multiple parallel events with its bit structure.
For example, if the completion status' returned value is 66 (decimal), this translates to 01000010 binary. If the right most bit is bit #0, and the left most bit is bit #7, in this case, bits 1 and 6 are set. To Translate this to the actual error message, please see the attached spreadsheet. When bit #1 is set (2**1), this translates to No Results. When bit #6 is set (2**6 or 64), this translates to Input incomplete. In this case, someone tried to run with incomplete input and there are no results. Both conditions are trapped.
In the below code, the corresponding constant for bit #1, is HAP_INPUT_INCOMPLETE, and the corresponding constant for bit #6 is, HAP_NO_RESULTS. Each of these constants can be viewed in the Visual Basic editor's OBJECT BROWSER under the VIEW pull-down menu (see the screen capture in the attached MS WORD document). Each of these named constants represents a specific bit in the completion status result integer. In your code, you could use the integer value or the contstant name (i.e, 64 or HAP_INPUT_INCOMPLETE).
=============== Completion Status Function ===========================
Function GetStatus(node As iHNode) As String
On Error Resume Next
Dim lStatus As Long
Dim strStatus As String
'Dim iColor As Integer 'Future support ?
GetStatus =
Const HAP_OUTPUT = HAP_RESULTS_SUCCESS Or HAP_NORESULTS Or
HAP_RESULTS_WARNINGS Or HAP_RESULTS_INACCESS Or
HAP_RESULTS_INCOMPAT Or HAP_RESULTS_ERRORS
Const HAP_INPUT = HAP_INPUT_INCOMPLETE Or HAP_INPUT_COMPLETE Or
HAP_INPUT_INACCESS Or HAP_INPUT_NEUTRAL
If (Not IsEmpty(node)) And (node.AttributeType(HAP_COMPSTATUS) <> 0) Then
lStatus = node.AttributeValue(HAP_COMPSTATUS)
If (lStatus) Then
If (lStatus And HAP_INPUT_INCOMPLETE) Then
strStatus = Required Input Incomplete
'iColor = 4
ElseIf (lStatus And HAP_RESULTS_INCOMPAT) Then
strStatus = Input Changed
'iColor = 3
ElseIf (lStatus And HAP_RESULTS_ERRORS) Then
strStatus = Results Available with Errors
'iColor = 1
ElseIf (lStatus And HAP_RESULTS_WARNINGS) Then
strStatus = Results Available with Warnings
'iColor = 0
ElseIf (lStatus And HAP_RESULTS_SUCCESS) Then
strStatus = Results Available
'iColor = 2
ElseIf (lStatus And HAP_INPUT_COMPLETE) Then
strStatus = Input Complete
'iColor = 5
ElseIf (lStatus And HAP_NORESULTS) Then
strStatus = Results Not Available
'iColor = 5
ElseIf (lStatus And HAP_INPUT_NEUTRAL) Then
strStatus = No User specified data
'iColor = 5
End If
If ((lStatus And HAP_OUTPUT) And (CStr(strStatus) <> )) Then
If (lStatus And HAP_UNRECONCILED) Then
strStatus = strStatus + . Unreconciled.
ElseIf (lStatus And HAP_UNRECONCILED) Then
' Dummy stub for future support
End If
End If
'Const HAP_INACTIVE = 4096
'If (((lStatus And HAP_INACTIVE)) And (CStr(GetStatus) <> )) Then
' strStatus = strStatus + (Inactive)
'End If
' EO status variables
If (lStatus And HAP_EOERROR) Then
strStatus = strStatus + . EO error.
ElseIf (lStatus And HAP_EOFAIL) Then
strStatus = strStatus + . EO synchronization failed.
ElseIf (lStatus And HAP_EODISABLE) Then
strStatus = strStatus + . EO disabled.
ElseIf (lStatus And HAP_EOSYNC) Then
strStatus = strStatus + . EO synchronized.
End If
GetStatus = strStatus
End If
End If
End Function
Keywords: ActiveX
Automation
Visual Basic
VBA
Completion status
References: None |
Problem Statement: What hydraulic correlation methods are available in the Pipe and Pipeline blocks? | Solution: The following correlations are available in the Pipe and Pipeline blocks:
Pipe orientation
Inclination
Friction factor correlations
Liquid holdup correlations
Horizontal
-2 deg to
+2 deg
Beggs and Brill (BEGGS-BRILL)
Dukler (DUKLER)
Lockhart-Martinelli (LOCK-MART)
Darcy (DARCY)
User subroutine (USER-SUBR)
Beggs and Brill (BEGGS-BRILL)
Eaton (EATON)
Lockhart-Martinelli (LOCK-MART)
Hoogendorn (HOOG)
Hughmark (HUGH)
User subroutine (USER-SUBR)
Vertical
+45 deg to +90 deg
Beggs and Brill (BEGGS-BRILL)
Orkiszewski (ORKI)
Angel-Welchon-Ros (AWR)
Hagedorn-Brown (H-BROWN)
Darcy (DARCY)
User subroutine (USER-SUBR)
Beggs and Brill (BEGGS-BRILL)
Orkiszewski (ORKI)
Angel-Welchon-Ros (AWR)
Hagedorn-Brown (H-BROWN)
User subroutine (USER-SUBR)
Downhill
-2 deg to
-90 deg
Beggs and Brill (BEGGS-BRILL)
Slack (SLACK)
Darcy (DARCY)
User subroutine (USER-SUBR)
Beggs and Brill (BEGGS-BRILL)
Slack (SLACK)
User subroutine (USER-SUBR)
Inclined
+2 deg to
+45 deg
Beggs and Brill (BEGGS-BRILL)
Dukler (DUKLER)
Orkiszewski (ORKI)
Angel-Welchon-Ros (AWR)
Hagedorn-Brown (H-BROWN)
Darcy (DARCY)
User subroutine (USER-SUBR)
Beggs and Brill (BEGGS-BRILL)
Flanigan (FLANIGAN)
Orkiszewski (ORKI)
Angel-Welchon-Ros (AWR)
Hagedorn-Brown (H-BROWN)
User subroutine (USER-SUBR)
The following closed-form methods are also available:
Smith
Weymouth
AGA
Oliphant
Panhandle A
Panhandle B
Hazen-Williams
Refer to the online help within Aspen Plus for further details.
Keywords: Pipe, pipeline, two-phase flow, flow correlations, hydraulic, horizontal, vertical, downhill, inclined
References: None |
Problem Statement: * WARNING BLOCK: HEATX CALCULATED FEED TEMPERATURE FOR THE HOT (or cold) SIDE IS INCONSISTENT WITH ITS INLET STREAM VALUE PROBABLE CAUSE: UPSTREAM BLOCK WITH DIFFERENT NPHASE OR PROP SET THE CALCULATED VALUE WILL BE USED IN BLOCK . | Solution: 1. Check valid phases at the Heatx or Heater block, the block after it and all relevant blocks. If you have two liquid phases, for example, but the valid phase is vapor-liquid, you may get this warning.
2. Tighten flash tolerance in HeatX or heater block
3. It it is withing a recycle look, tighten tear tolerance and/or try a different method for tear convergence- such as Broyden.
4.
Keywords:
References: None |
Problem Statement: Some utility routines are available to users writing USER2 model. Those routines are documented in the attached Word document and in the 11.1 USer Model Guide, page 5-31 | Solution: The first set of routines documented in the attached Word ddocument give the user access to INT, REAL, and CHAR arrays, the EXCEL file name, and the user subroutines named on the USER-MODELS sentence.
The second group of functions allows the user to set and get the values from the INT, REAL and CHAR arrays by name.
Keywords: utility routine
USER2
USRUTL
USRUTL_NUMSTR
USRUTL_GETHSTR
USRUTL_GETCSTR
USRUTL_SETHSTR
USRUTL_SETCSTR
USRUTL_GETSUB
USRUTL_NUMINTS
USRUTL_GETINT
USRUTL_SETINT
USRUTL_NUMREALS
USRUTL_GETREAL
USRUTL_SETREAL
USRUTL_GETEXCEL
USRUTL_GETVAR
USRUTL_GET_REAL_PARAM
USRUTL_GET_INT_PARAM
USRUTL_GET_CHAR_PARAM
USRUTL_GET_HCHAR_PARAM
USRUTL_HTOCHAR
USRUTL_CHARTOH
USRUTL_SET_REAL_PARAM
USRUTL_SET_INT_PARAM
USRUTL_SET_CHAR_PARAM
USRUTL_SET_HCHAR_PARAM
References: None |
Problem Statement: Does Aspen Plus have built-in binary interaction parameters for vapor-liquid (VLE) and vapor-liquid-liquid equilibrium? | Solution: Aspen Plus 9.1-3 and higher have databanks with binary interaction parameters for both activity coefficient based and equation of state based property methods. After selecting the components and the property method, Aspen Plus shows the available binary parameters on the forms.
There are parameters for over 3600 component pairs for the following activity coefficient based property methods:
NRTL
UNIQUAC
WILSON
NRTL-RK
UNIQ-RK
WILS-RK
NRTL-HOC
UNIQ-HOC
WILS-HOC
In addition, there are 700 component pairs from LLE data for teh NRTL and UNIQUAC property methods, and 3500 component pairs for VLE parameters reported in DECHEMA.
In addition, Aspen Plus has built-in binary interaction parameters for the following equation of state based property methods:
RK-SOAVE (Redlich-Kwong-Soave)
PENG-ROB (Peng-Robinson)
BWR-LS (BWR-Lee-Starling)
LK-PLOCK (Lee-Kesler-Plocker)
The built-in databanks available are listed below:
Databank
Description
Property Methods
ASPEN-BM
Modified PR and RKS equations of state
(Boston-Mathias modifications).
PR-BM and RKS-BM
EOS-LIT
Standard RKS, standard PR, Lee-Kesler-Plocker,
BWR-Lee-Starling, and Hayden-O'Connell
equation-of-state models.
Obtained from the literature.
RK-SOAVE, PENG-ROB,
LK-PLOCK, BWR-LS and
*-HOC
BINARY
Henry's constants of about 60 solutes in water.
All property methods that allow Henry's law
ENRTL-RK
Binary and pair parameters for the
electrolyte NRTL model
ELECNRTL
HENRY
Henry's law constants for about 1600 sets
of solute-solvent pairs.
The solvents are water and other organic components.
Developed by AspenTech using Dortmund Data Bank.
All property methods
that allow Henry's law
LLE-ASPEN
NRTL and UNIQUAC models.
Developed by AspenTech for LLE applications
using Dortmund Data Bank.
All methods based on
NRTL and UNIQUAC models
LLE-LIT
UNIQUAC model obtained from the literature.
For LLE applications.
All methods based on
UNIQUAC model
SRK-ASPEN
SRK and modified SRK equations of state.
SRK and SRK-*
VLE-HOC
Wilson, NRTL and UNIQUAC models
with Hayden-O'Connell vapor EOS.
Developed by AspenTech for VLE applications
using Dortmund Data Bank.
WILS-HOC, NRTL-HOC,
UNIQ-HOC
VLE-IG
Wilson, NRTL and UNIQUAC models
with ideal gas vapor EOS.
Developed by AspenTech for VLE applications
using Dortmund Data Bank.
WILSON, NRTL, UNIQUAC
VLE-LIT
Wilson, NRTL and UNIQUAC models
with ideal gas vapor EOS,
obtained from the literature.
For VLE applications using Dortmund Data Bank.
WILSON, NRTL, UNIQUAC
VLE-RK
Wilson, NRTL and UNIQUAC models
with Redlich-Kwong EOS.
Developed by AspenTech for VLE applications
using Dortmund Data Bank.
WILS-RK, NRTL-RK, UNIQ-RK
For more information about built-in binary interaction parameters see the Aspen Property System help.
Key Words
opset
option set
option-set
Keywords: None
References: None |
Problem Statement: The Henry's constants for HCl/Water stored in the HENRY databank give poor results when modeling an electrolyte system. | Solution: The Henry's constants for HCl/Water stored in the HENRY databank should not be used. This set of parameters is not appropriate for use in modeling this electrolyte system. The values of HCL/WATER from the HENRY databank were kept for upward compatibility.
Use ELECNRTL with chemistry to model the dissociation of HCl in water, and use the binary parameters from the ENRTL-RK databank for the HENRY parameter for HCl in water.
Please note that the Henry's constants for this pair of components in the ENRTL-RK databank will not be changed and are recommended for use with the ElecNRTL property method when modeling HCl/Water system.
For upward compatibility reasons, if you need to use the Henry's constants that have been removed, you will need to go into the Properties/Parameters/Binary Interaction/Henry-1 form and enter the following values (in SI units):
Component i = HCL
Component j = H2O
Aij = -36.022701
Bij = 1215.0, 8.3707
Cij = -0.009593
Tlower = 253.15
Tupper = 293.15
Eij = 0
The screen should look as follows:
Input language parameters:
PROP-DATA HENRY-1
IN-UNITS SI
PROP-LIST HENRY
BPVAL HCL H2O -36.02270100 1215.000000 8.370700000 & -9.5930000E-3 &
253.1500000 293.1500000
Keywords: HENRY
HCL
ELECNRTL
ENRTL-RK
solubility
supercritical
solvent
solute
regression
CQ00123229
References: None |
Problem Statement: Is it possible to fit the U value of a heat exchanger from online data? | Solution: Here is an example of using Data-Fit to determine the U value of a condenser.
Data Fit was one of the new features in Aspen Plus 9. Users can use this feature to fit Aspen Plus models to plant and/or laboratory data.
A few points about Data-Fit:
It uses the maximum likelihood approach.
It permits users to fit any input variables accessible within Aspen Plus.
It allows users to reconcile measurements while fitting Aspen Plus variables.
How to define Data-Fit with Aspen Plus:
1. Define the measured data.
2. Define the data to be fitted.
3. Define the parameter(s) to be fitted.
Please see the Aspen Plus Help under Using Aspen Plus, Flowsheeting Options and Model Analysis Tools, Fitting a Simulation Model to Data for more details.
Keywords: datafit, heatx
References: None |
Problem Statement: Is it possible to install AspenTech Cumulative Hot Fixes Silently? | Solution: Download the .msp file or .exe file for the Cumulative Hot Fix from the Cumulative Hot Fix
document. For a .exe file use an extraction tool such as WinZip to extract the .msp file
from the self extracting executable.
Open a Command Prompt and type the following command line:
msiexec.exe /q /p {Full Path to newly extracted HotFix.msp\HotFix.msp filename} REINSTALL=ALL REINSTALL=omus e.g.
msiexec.exe /q /p C:\HotFixFolder\ACMHotFix12.1.1.msp REINSTALL=ALL REINSTALLMODE=omus
Should you wish to create a BAT file to perform this for you, provided the .msp file is in the same location as the BAT file, you may use the filename only,
e.g.
msiexec.exe /q /p ACMHotFix12.1.1.msp REINSTALL=ALL REINSTALLMODE=omus
A log file can be generated to monitor the success of the HotFix, to do this, append the following switch to the end of the command line.
/l {Desired Location\Desired filename}
e.g.
msiexec.exe /q /p C:\HotFixFolder\ACMHotFix12.1.1.msp REINSTALL=ALL REINSTALLMODE=omus /l %TEMP%\ACMHotFix12.1.1.log
At the bottom of the log file there will be a message stating either
Configuration failed. or
Configuration completed successfully.
Keywords:
References: None |
Problem Statement: How to do you format the VBA code when Aspen Plus' path-to-node name contains one or more '#' symbols followed by a number? For example, what is the VBA code needed to write to a Property Analysis table's manipulated variable fields? | Solution: The path-to-node names often contain '#' symbols when the object it references is a two dimensional table. In the attached example, for Aspen Plus' Variable Explorer reveals the following dot notations for the Property Analysis table's second list value for the pressure variable:
Path-to-Node notation:
Application.Tree.Data.Properties.Analysis.PROP-TBL.Input.LIST.#0.#0
-OR-
FindNode notation:
Application.Tree.FindNode(\Data\Properties\Analysis\PROP-TBL\Input\LIST\#0\#0)
As you can see from the last two nodes in the above dot notations, the variable is clearly a 2-dimensional array. In this case, the first element number (#0) refers to the item number of the manipulated variable (since the property analyis table can have multiple manipulated variables. The second #0 refers to each list value for a given manipulated variable. In the attached example, the first element is always going to have a value of 0 because there is only one manipulated variable in this property analysis table, and the list of manipulated variables is zero-indexed (i.e. the first item is refered to as item #0). The second element is going to vary between 1 and the number of values in the list (this element is not zero-indexed)
It is best if you can obtain the FindNode syntax, append it with the .Value property and test it in the immediate window (seeSolution 105470). For example, you could open the VBA immediate window by typing <Ctrl-G> in the VBA editor and then test the code by typing the following into the immediate window:
? go_simulation.Tree.Data.Properties.Analysis.elements(PROP-TBL).Input.elements(LIST).elements(0,2).value
-OR-
? go_simulation.Tree.Data.Properties.Analysis.elements(PROP-TBL).Input.elements(LIST).elements(0,2).value
where: go_simulation is the name of the Aspen Plus application in the VBA
code
While in the immediate window, you can increment the element values to see which parameters refer to the table's rows and columns:
? go_simulation.Tree.Data.Properties.Analysis.elements(PROP-TBL).Input.elements(LIST).elements(0,1).value
20 [ value calculated by VBA]
? go_simulation.Tree.Data.Properties.Analysis.elements(PROP-TBL).Input.elements(LIST).elements(0,2).value
25 [ value calculated by VBA]
Also, there are some potential problems in trying to copy and paste from an element in an Aspen Plus table (as inSolution document 106094):
1. The copy/paste from the input or result form may not reveal anything when pasted into the Variable Explorer (in which case you have to manually navigate the Variable Explorer
2. Sometimes the path-to-node field will be populated but not the FINDNODE field after pasting into the Variable Explorer (in which case you will have to use and properly format the path-to-node notation).
3. Sometimes the FindNode reported in the Variable Explorer for tables is either incorrect or incomplete (in which case you will have to experiment in the Immediate Window).
Keywords: VBA, Tables, path-to-node notation, findnode notation, find node,2 dimensional variables.
References: None |
Problem Statement: While doing an Aspen Plus customization for Aspen Plus 11.1, I noticed that the option codes for the Hayden-O'Connell model (ESHOC and ESHOC0) for the vapor phase calculations in NRTL-HOC are now two numbers in 11.1 whereas before (i.e., in 10.2) there was only one.
What is the second number for? I have checked the on-line help and the Physical Property Methods and Models manual, but they only describe the first option code. | Solution: The 2nd option code for this model is used to control the check for the specified pressure being too high. It applies to the case without Chemical Theory (i.e., for case with Chemical Theory, this option code is not used).
The pressure limit is imposed because the model is valid at low to moderate pressures only. The rule we used was to limit pressure to a value corresponding to density which is 1/2 of the critical density. The molar volume is calculated at this cut-off pressure. A warning is issued.
Some customers do not like this limit and prefer to use the specified pressure and let the model return the molar volume. So this option code is used.
When the second option code equals 0 (DEFAULT), the high pressure limit is checked. Volume calculated at cut-off pressure.
When the second option code equals 1, the high pressure limit is not checked. Volume is calculated directly by the model at T and P.
Below is a summary of the possible option codes for the Hayden-O'Connell model (ESHOC, ESHOC0, PHV0HOC):
Option Code
Value
Description
1
0
Hayden-O'Connell model.
Use chemical theory only if one
component has HOCETA=4.5. (default)
1
1
Always use the chemical theory
regardless of HOCETA values.
1
2
Never use the chemical theory
regardless of HOCETA values.
2
0
Check high-pressure limit.
If exceeded, calculate volume at
cut-off pressure. (default)
2
1
Ignore high-pressure limit.
Calculate volume model T and P.
The second option code is now documented in the help.
Keywords: Hayden-O'Connell
Option Codes
kop
References: None |
Problem Statement: How can I easily get the Stream Table results from a simulation into Excel using VBA? | Solution: The Data/Results Summary/Streams/Material sheet Stream Table can be accessed in Excel using the following simple VB code. This prints the entire stream table in Excel exactly as it would appear in Aspen Plus including the table headings.
Private Sub cmdStreamData_Click()
Dim Table As IHNode
Dim NDim As Integer
Dim NPoints As Integer
Dim k As Integer
Dim h As Integer
' set the stream table object
On Error GoTo NoStreamResultsLoaded
Set Table = go_Simulation.Tree.Data.Elements(Results Summary).Elements (Stream-Sum).Elements(Stream-Sum).Table On Error GoTo 0 ' end error checking
' Determine number of rows and columns to print in the spreadsheet
NDim = Table.Elements.RowCount(0) 'count the dimensions (variables listed in stream table) NPoints = Table.Elements.RowCount(1) 'count the no of points per dimension (number of streams in stream table)
'
' Populated the spreadsheet
For k = 0 To NPoints - 1 'for each point....
For h = 0 To NDim - 1 'in each dimension
Range(StreamTable).Offset(h, -1).Value = Table.Elements.Label(0, h) Range(StreamTable).Offset(-1, k).Value = Table.Elements.Label(1, k) Range(StreamTable).Offset(h, k).Value = Table.Elements.Item(h, k).Value Next h
Next k
Set Table = Nothing ' release memory for the table variable Exit Sub
NoStreamResultsLoaded: ' handle the possibility of no stream results in the model
MsgBox The Aspen Plus Run does not contain any stream results, vbCritical, ERROR LOADING STREAM RESULTS On Error GoTo 0 ' turn off error checking
Set Table = Nothing ' release memory for the table variable
End Sub
See the attached files for a working example.
Keywords: VB
VBA
Stream Table
References: None |
Problem Statement: The density as calculated by the property RHOMX (density of a mixture) for a process at 60F and atmospheric pressure, does not give the same result as the property RHOLSTD (standard liquid density for a mixture at 60F and atmospheric pressure) for the same mixture.
Both densities are calculated at the same process conditions (and same units) but give different results. Why is that? | Solution: The property RHOMX is calculated by the property method specified on the Data/Properties/Specification/Global sheet. However, the standard density RHOLSTD is calculated from the standard mixture volume (VLSTDMX) which is simply a molar average of the pure component standard liquid volume as given by the parameter VLSTD. This parameter is constant for each pure component.
RHOLSTD = 1/VLSTDMX where
VLSTDMX = [ (MOLESa*VLSTDa + MOLESb*VLSTDb + ...
+ MOLESj*VLSTDj) / ( MOLESa + MOLESb + ... + MOLESj) ]
In the attached simulation, the properties RHOMX, RHOLSTD and VMXSTD are calculated for a process stream at 60 F and 1 atm via property sets. The value of RHOMX is different from RHOLSTD.
A calculator block calculates VLSTDMX and RHOLSTD as per the above equations. The results of the calculator block compare with the values of VMXSTD and RHOLSTD from the prop-set.
Keywords: mixture density
density
RHOMX
RHOLSTD
VMXSTD
References: None |
Problem Statement: CAPE-OPEN Unit Operations implementing v1.0 of the standard are displayed for use in Aspen Plus 11.1 but will not work. | Solution: You cannot use CAPE-OPEN version 1.0 Unit Operations in Aspen Plus 11.1 because Aspen Plus 11.1 supports only versions 0.9 and 0.9.3 of the CAPE-OPEN standard.
If a CAPE-OPEN Unit Operation implementing version 1.0 of the standard is installed on your machine (for example MixNSplit 12 which is supplied with Aspen Plus 12.1) Aspen Plus 11.1 will display it in the CAPE-OPEN tab of the Model Palette but it will not work properly.
When you place such a block on the flowsheet, the Aspen Plus engine will run and the block will appear to have been created, but when you double-click the block its GUI will not be displayed. Instead, the Aspen Plus Data Browser will open at the block and the Ports and Parameters grids will be empty. If you check history file using the View menu (or Ctrl-Alt-H) you will see the following error message:
Entering CAPE-OPEN (version 0.9.3) Unit Adapter DLL intialization.
Adding factory CAPEOPENUNIT 01A1C0E0
CocreateInstance failed with error: -2147221164
****TERMINAL ERROR WHILE CHECKING INPUT SPECIFICATIONS
FIRST ID: B1 SECOND ID: USER3 (ZECOADAPTER.1)
BLOCK B1 WAS NOT CREATED SUCCESSFULLY - CODE -2147219710.
You can use CAPE-OPEN version 1.0 Unit Operations in Aspen Plus 12.1
Keywords:
References: None |
Problem Statement: Is there a way to reinitialize and re-run just one unit operation in a large flowsheet? | Solution: Yes - follow this procedure:
1) Make sure the control panel is open and in the current view. If it is not open, click on the VIEW menu and then click on CONTROL PANEL.
2) The control panel will show 2 windows, a large gray window with run time messages, and narrow white window with the calculation sequence. Examine the calculation sequence and find the unit operation you wish to reinitialize.
3) Right click on the desired unit operation or block in the calculation sequence (white) window, and choose the REINITIALIZE option. Note: When successful, you will see a reinitialization message in the message (grey) window.
4) Right click on the unit again, and choose MOVE TO option. Again you should see a confirmation message in the message (gray) window.
5) Go to the top left corner of the control panel, and find the button that looks like an outline triangle (when you hover your mouse cursor on top of this button, you should see a pop-up text box that says STEP). Click on this step button and watch the run-time messages in the gray mesage window.
Keywords: re-initialize, reinit block
References: None |
Problem Statement: In the restricted equilibrium sheet of RGibbs, I can choose Entire System by T approach. If I do this I can then enter a value for temperature approach and select the units. However the units are confusing. Why do I have:
K
F
C
R
Delta K
Delta F
Delta C
Delta R | Solution: The units are indeed confusing. The first four units are equivalent to the following four, i.e. choosing K is the same as choosing Delta K and so forth.
Fixed in Version
Currently, there are no plans to fix this problem.
Keywords:
References: None |
Problem Statement: When accessing a property parameter such as TC or HCOM in a Calculator block, the value was different from that retrieved from the databank. The simulation is using English units. | Solution: Accessed property parameters are always in SI units even when the input and output units of the simulation are different.
Keywords: calculator
design specification, desiign spec, design-spec
sensitivity
References: None |
Problem Statement: When entering vapor pressure (PL) or ideal gas heat capacity (CPIG) data for user defined component wizard, data is not used. Only the data form is populated. What needs to be done to have this data used? | Solution: This data can be used for a simple regression of the PL or CPIG parameters using the Estimation capabilities. The data regression function can be used for a more advanced regression.
Steps:
1. Go to the Properties \ Estimation \ Input \ Setup sheet and select Estimate all missing parameters.
2. Go to the Properties \ Estimation \ Input \ T-Dependent sheet and select the Data method for PL or CPIG for the new component.
Fixed in Version
Deferred
Keywords: estimation, pces
References: : CQ00204113 |
Problem Statement: Derivatives of properties can be calculated on molefraction basis (dx) or moleflow basis (dn). When using ELECNRTL, the values of dHMX/dx are equal to dHMX/dn. Why? | Solution: Property derivatives with ELECNRTL are calculated using numerical perturbations. The molefraction derivatives (dQ/dx) are made equal to the mole derivatives and should not be used. The mole derivatives (dQ/dn) are correct.
Keywords:
References: None |
Problem Statement: How to 'close' a recycle loop once in EO mode in Aspen Plus. | Solution: The purpose of this example is to show how to avoid a convergence loop in Sequential Modular (SM) mode, by simply leaving the recycle loop open , and then close it once in Equation-Oriented (EO) mode and eventually get the flowsheet to converge using the EO solver. It is based on the cumene.bkp simulation available in the introduction to Aspen Plus course.
The attached simulation file has already the recycle loop opened, with streams RECYCLE and RECY2.
1 - For the RECY2 stream, go to the Input form, EO Options tab, click on the 'Additional Options' button and set 'Pass-through' to Yes. Click on Close button.
2 - Run the simulation in SM then in EO mode.
3- In order to 'close' the loop in EO mode, we will now establish a Port connection between the stream RECYCLE and the stream RECY2. The problem is to know which port to use. From the Control Panel;, type in the following command:
PRINT BLOCK PORTS
All the available ports available will then be shown.
Block: REACTOR
Port Type Direction Phase Attached stream
======== ================== ========= ============ ===============
FEED MATERIAL_MOLE_FRAC INPUT UNKNOWN FEED
RECY2 MATERIAL_MOLE_FRAC INPUT UNKNOWN RECY2
REAC-OUT MATERIAL_MOLE_FRAC OUTPUT UNKNOWN REAC-OUT
1 MATERIAL_MOLE_FRAC INPUT UNKNOWN FEED
2 MATERIAL_MOLE_FRAC INPUT UNKNOWN RECY2
3 UNDEFINED UNSPECIFIED
4 UNDEFINED UNSPECIFIED
5 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN REAC-OUT
12 UNDEFINED UNSPECIFIED
13 UNDEFINED UNSPECIFIED
14 UNDEFINED UNSPECIFIED
Block: COOL
Port Type Direction Phase Attached stream
======== ================== ========= ============ ===============
REAC-OUT MATERIAL_MOLE_FRAC INPUT UNKNOWN REAC-OUT
COOL-OUT MATERIAL_MOLE_FRAC OUTPUT UNKNOWN COOL-OUT
6 MATERIAL_MOLE_FRAC INPUT UNKNOWN REAC-OUT
7 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN COOL-OUT
8 UNDEFINED UNSPECIFIED
9 UNDEFINED UNSPECIFIED
11 UNDEFINED UNSPECIFIED
Block: SEP
Port Type Direction Phase Attached stream
======== ================== ========= ============ ===============
COOL-OUT MATERIAL_MOLE_FRAC INPUT UNKNOWN COOL-OUT
RECYCLE MATERIAL_MOLE_FRAC OUTPUT UNKNOWN RECYCLE
PRODUCT MATERIAL_MOLE_FRAC OUTPUT UNKNOWN PRODUCT
1 MATERIAL_MOLE_FRAC INPUT UNKNOWN COOL-OUT
2 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN
3 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN RECYCLE
4 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN PRODUCT
11 INFORMATION INPUT
Block: FEED
Port Type Direction Phase Attached stream
======== ================== ========= ============ ===============
1 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN FEED
2 UNDEFINED UNSPECIFIED
3 UNDEFINED UNSPECIFIED
4 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN FEED
5 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN FEED
Block: RECY2
Port Type Direction Phase Attached stream
======== ================== ========= ============ ===============
1 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN RECY2
2 UNDEFINED UNSPECIFIED
3 UNDEFINED UNSPECIFIED
4 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN RECY2
5 MATERIAL_MOLE_FRAC OUTPUT UNKNOWN RECY2
31 MATERIAL_MOLE_FRAC INPUT UNKNOWN
We want to connect port 31 from feed block RECY2:
31 MATERIAL_MOLE_FRAC INPUT UNKNOWN
And the RECYCLE PORT from block SEP:
RECYCLE MATERIAL_MOLE_FRAC OUTPUT UNKNOWN RECYCLE
4 - Under EO Configuration -> Connection create a connection with;
Destination = RECY2.31 and Source = SEP.RECYCLE (you have to type in manually the text RECY2.31 and SEP.RECYCLE)
Make sure that you check the option 'Port connection' when defining the connection.
5 - Run the simulation in EO mode. The flowsheet converges with the recycle loop 'closed'. See cumene-completed.bkp for the final result.
6 - Note the port type MOLE FRACTION may be misleading, as the port contains not only the mole fraction of the components, but also the temperature, pressure, total molar flowrate, molar enthalpy and molar volume. You can print more details of the ports with the following commands.
PRINT BLOCKS PORT DETAILED
and
PRINT BLOCKS PORT DETAILED name
For example:
PORT NAME: 31
Internal type: MATERIAL
Basis: MOLE FRACTION
Phase: UNKNOWN
Direction: INPUT
Connected stream:
Number of variables: 8
Number of components: 3
Port elem Var index Variable name
========= ========= ==========================================================
1 162 RECY2.BLK.INLET_MOLES
2 163 RECY2.BLK.INLET_TEMP
3 164 RECY2.BLK.INLET_PRES
4 165 RECY2.BLK.INLET_ENTH
5 166 RECY2.BLK.INLET_MVOL
6 167 RECY2.BLK.INLET_BENZENE
7 168 RECY2.BLK.INLET_PROPYLEN
8 169 RECY2.BLK.INLET_CUMENE
7 - Note that you can also use the option Single Pass or Single Pass (once) which tells the sequential modular (SM) mode to execute the blocks only once, not attempting to converge any solver block. This option was not available in earlier versions of Aspen Plus.
Keywords: port
References: None |
Problem Statement: CAPE-OPEN blocks do not restore properly when saved to .bkp format. .apw is OK. The reason is that private CAPE-OPEN block data is only saved to .appdf files and is therefore lost when saving to .bkp. There is no warning. | Solution: When you save simulations containing CAPE-OPEN unit operation models, you must save them in .apw format to preserve the private data of the block. The .bkp format does not preserve this information. Users should save in .apw format instead. Note that when upgrading to new versions of Aspen Plus all the CAPE-OPEN data will have to be re-entered anyway since .apw format is version specific.
This problem cannot be fixed since private data is not allowed to be saved to .bkp.
Keywords: cape-open htri
References: : CQ00218097 |
Problem Statement: We are in the midst of implementing our in-house equation of state (EOS) in AspenPlus. Looking at the argument list for ESU and ESU0, I could not find anything for pressure and composition derivatives. We will be testing the new EOS model in Equation Oriented (EO) mode. Is there any reason why ESU routine still cannot return pressure and composition derivatives? | Solution: User models cannot return pressure and composition derivatives. These derivatives will be determined automatically by numerical perturbations. Some of the built-in models (including EOS models) work this way. The analytical derivatives are obtained by using ADIFOR (automatic code generation program); they were not coded by hand. Therefore, the code that deals with composition and pressure derivatives is designed to work with the ADIFOR generated code and cannot be readily adapted to work with user models.
Fixed in Version
In version 2006.5, it will be possible for users to calculate all of the derivatives themselves using an analytical method using two new user model interfaces ESU2 and ESU20.
Keywords: user subroutine properties
References: : CQ00256507 |
Problem Statement: MCompr gives the following warning message in the control panel:
WARNING TWO PHASES ENTERING STAGE = 2 AND NO LIQUID SEPARATION IS SPECIFIED
How do I specify the liquid separation at a given stage of the compressor? | Solution: Each compression stage in MCompr contains a compressor operation and a cooler operation, known as an interstage cooler. The interstage coolers can perform a one, two or three phase flash calculation - valid phases are specified on the Data\Blocks\ MCompr\Setup\Convergence sheet. They are effectively a flash block, where the user can specify either an outlet temperature, heat duty or ratio of outlet to inlet temperature, and a pressure drop.
A warning message of two phases entering a stage is due to:
The user specifications of the interstage cooler(s) produces a 2 phase mixture in the flash calculation.
A liquid knockout material stream has not been connected to the MCompr block, thus the liquid from the interstage cooler is carried over into the next stage of compression.
To specify this liquid separation in the intercoolers, the user must connect a knockout material stream to the MCompr block on the process flowsheet. The MCompr block has an optional outlet port for any number of liquid knockout and water decant (for free-water only) streams.
There are two ways of specifying the liquid knockout material stream:
One knockout material stream for each interstage cooler. Note that for this option, if you use a knockout stream from one stage, then you must use them for all stages (except the last stage). Define the outlet stream to a specified MCompr stage on the Data\Blocks\MCompr\Setup\Material sheet - Product Streams (leave Global at default value of No).
A single global knockout stream for the liquid formed in ALL interstage coolers i.e this is a collective stream. On the Data\Blocks\MCompr\Setup\Material sheet - Product Steams, set the Global field to Yes.
Specifying liquid knockout material stream(s) will ensure that 2 phases do not enter any stage of compression in the MCompr block.
Keywords: MCompr
Knockout
compression
compressor
References: None |
Problem Statement: Is it possible to enter a second set of Wilson parameters for the same binary pair in a Userpp2 databank? | Solution: You need to use two separate databanks. Then when defining your flowsheet for WILSON-1, you select one databank first and in WILSON-2, you select the other one first. You can also mix and match. It would be similar to how we have different binary databanks.
Documentation on how to create a user binary databank is in the Aspen Plus 11.1 System Management
Keywords:
References: Manual, p.4-10. Page 4-15 has an example of the input for Wilson. This example is also in the
..AspenTech\APRSYSTEM 11.1\GUI\custom\Examples directory. |
Problem Statement: When I use the interactive binary property analysis tool, the predicted bubble point curve compares well to my reference data. The dew point curve, however, looks like it has been interpolated rather than rigorously calculated by a model. When compared to experimental dew point data, there are significant deviations. What is the reason for this? Did something go wrong during the analysis? | Solution: With [Tools/Analysis/Property/Binary... TXY] you are actually performing a bubble point calculation. In other words, the temperatures you see are bubble point temperatures.
Since phase equilibrium also includes the assumption of thermal equilibrium, these temperatures will be assigned to the predicted vapor compositions, too.
There is nothing wrong with this approach for a binary system with both constituents being of comparable volatility. In other words, a system in which the compositions of the coexisting phases (vapor and liquid) do not differ dramatically from each other.
Figure 1 shows the T-xy diagram of the binary system methanol - water. The two components are of comparable volatility. In figure 1 the green (T-y) curve is the result of the interactive (bubble point) analysis, while the red curve is a dew point curve that was calculated separately. As can be seen from figure 1, the explicitly predicted dew point curve agrees well with the one from the interactive analysis.
For wide-boiling systems, the method of re-using the bubble temperatures to construct a dew point curve is not accurate enough.
In such a system, the compositions of the coexisting phases differ significantly from each other. While the liquid phase composition is an input to the calculation (and can therefore be provided with the desired reSolution, e.g., a 0.05 increment), most of the corresponding vapor phase composition values will be close to unity for the low boiling component.
When constructing the dew point curve from this data, Aspen Plus linearly interpolates between a small concentration of the low-boiler in the vapor phase, and - effectively - the mole fraction of the pure component.
This is shown in figure 2 for the binary system diethyl-ether - n-heptyl-benzene. The green T-y curve is the result of such an interpolation for diethyl-ether. Compared to an explicitly calculated dew point curve (in red), the deviations and the inaccuracy of the interpolated T-y curve are revealed.
Conclusion: Increase the accuracy of the results by decreasing the increment of the manipulated mole fraction (e.g., from 0.1 to 0.05 or smaller). If this does not help, an explicit calculation of the dew point curve is recommended in addition to an interactive T-xy analysis.
Keywords:
References: None |
Problem Statement: When using an Aspen Plus file with links to multiple Excel spreadsheets, is it possible to have a new identical Aspen Plus file with no links to any other Excel files? When using File/Save as in Aspen Plus, all the links go with the new Aspen Plus file. | Solution: If the linked Excel file is saved after changes are made, then the link goes with new file. If the linked file is closed, then the source file is saved under a new name, the link will remain with the original file.
In order to get a clean file without any link outside of Aspen Plus, save the current file with links to a new file name, then save the linked files. The original Aspen File will be left without any links (or broken links). Alternatively, have all the linked files closed and save the Aspen Plus file as a new name, the new file will have no links to other files.
Here are some possible workflows.
Workflow 1:
Break all links. (i.e. Menu Edit|Links... Select Link in list. Select Break Link. )
Save as new file name.
Close any external linked documents without saving.
Workflow 2:
Export as new file name.
Open new file name. Decline to establish links.
Break all links from Edit Links... menu.
Save.
Keywords:
References: None |
Problem Statement: Previous versions the component Sodium Acetate as NACH3CO2. Why is it not included in the Solids databank for 2004? | Solution: In 12.2, the name of component NACH3CO2 in the Solids databank was changed to C2H3NAO2 (Sodium-Acetate) so that the same alias is used across all databanks.
Old Name New Name Alias Databank
NACH3CO2 SODIUM-ACETATE C2H3NAO2 SOLIDS
Input files that contain the old alias will be converted to use the new alias automatically in 2006. Users will have to manually choose the new alias for .bkp files prior to version 12.2.
Keywords: sodium-acetate
References: None |
Problem Statement: How do I create a custom icon? | Solution: To create a custom icon, you first need to create a model library. Then,
you can change or add new icons to better represent the equipment that the proprietary model represents.
Creating a model library allows work groups to create Model Menu tabs within the Aspen Plus User Interface for proprietary or third party Unit Operation Models. You can insert these models into an Aspen Plus simulation by dragging a user-designed graphical representation of that model from a user-defined Model Menu tab. You can create and display model variables such as Channel Hydraulic Diameter on the Input form and Permeate Protein Concentration on the Results form. Default input values for these variables can be stored in the library with the model.
You can configure a single user model differently, for example, by specifying different combinations of input and making each configuration available as separate icons. You can also insert each configuration into a simulation by dragging the appropriate icon into the simulation diagram.
To create a custom model library:
Open the Aspen Plus User Interface.
Select New from the Library menu to create a new user-defined model library.
Name the library something such as MyLibrary by entering the name into the Display Name field.
Specify a filename with full path to store the library definitions. Select the Create button.
From the Library menu, select the new library then Edit.
From the Categories menu, select New. Enter a new name such as MyModels as the category name. A MyModels tab will be automatically inserted into the library.
Select the MyModels tab. Click any model in the simulation diagram, right click and select Add to Model Library from the pop-up menu.
Enter a new model name such as the Model name and select Copy/create user model configuration. Select OK.
Note: Any Aspen Plus model from the Model Menu can be moved into
the new library by selecting the icon and dragging the icon by
holding down the left mouse button. Once the left mouse button
is released over the new library, the Add to Library form is
displayed. It is possible to select Copy all icons to insert all the
icons associated with that model. You can modify these icons
later.
Update the library file by selecting the new library from the Library menu then Save. Aspen Plus now creates the new category tab in the Model Library Menu along with the other Aspen Plus models.
To change the Model icon:
Open the Model Library Editor for the new model by selecting the new library from the Library menu then Edit.
Select the new model. Click the right mouse button, then select Edit Current Icon.
Once in the editor, edit the icon using the buttons. Note The small enclosed cross indicates the position where the block id will be placed.
Exit the Icon Editor by closing the window. Select Yes to save new icon.
Save the icon as part of the library by selecting the new library from the Library menu then Save.
Tip: Existing AutoCAD DXF files can also be imported into the Icon
Editor. When the Icon Editor is active, a main Icon menu
becomes available on the menu bar for the main window. Select
Import DXF from the Icon menu.
Keywords:
References: None |
Problem Statement: How do you model liquid CO2? | Solution: SR-POLAR is probably the best property method to use. The RKUC0, 1, and 2 terms can be used to fit density better. The second and third volume-shifting terms can cause inconsistencies in enthalpy (isotherms may have enthalpy crosses, etc.). Just fitting the first parameter is safe, however and should give good results.
Another alternative is to use one of the corresponding-states methods (BWR-LS or LK-PLOCK). These should do a reasonable job near and beyond critical. Their big limitation is that they have no component-specific parameters and nothing adjustable -- they are pure corresponding-states models. Version 11 and higher has a new variation of BWR (BWRS) that does have component-specific parameters, and that might be the best bet when available. See the help for more specifics.
Keywords: supercritical fluid
References: None |
Problem Statement: How does one create inhouse binary databanks for 12.1? | Solution: There are two types of binary databanks; the first is created through the Aspen Plus User Interface Customization DOS prompt and then accessed through the GUI at simulation time, and the second is created through DFMS and accessed through the simulation engine at simulation time. ThisSolution Document covers the first type (accessed through the GUI), which tends to be the more typical approach.
Instructions for creating a user binary databank and adding binary components in the GUI are described below. The example files are attached.
Procedure
The following procedure should be run from the command prompts in the Aspen Plus User Interface CustomizationDOS prompt.
Create a binary databank input file (name should have an extension of .dat such as Wilson.dat). This is a plain text file, and its format can be found in Section 4-10 of the System Management Documentation.
Modify the MMTBS Driver file (tbprop.dat) to include the binary databank input file name created in Step 1.
Update the User Interface record definition and help files to add your binary databank by running the command in the Aspen Plus User Interface Customization window: Mmcustom mmtbs
Verify that the databank is correctly installed, by opening the file custom.bkp located in the directory \ProgramFiles\AspenTech\APRSystem 12.1\GUI\custom. This uses the modified RecDef file locally. Include your added binary components in the COMPONENT statement, choose your physical property method under PROPERTIES specifications form, then go the binary form and look for your method. Click on the method, and your components should be available from your newly entered binary databank.
If Step 4 is OK, install the modified files by entering custinst at the DOS prompt.
Example
This example shows how to create a new user binary databank called USER1 and add Renon NRTL parameters for the HCLO-WATER and CCL4-WATER. First a text file is created with the data. This text file is called NRTL-USE.DAT.
The NRTL-USE.DAT text is as follows:
DBANK REPLACE GAMKIJ
1
1
1 NRTL 0 0 2 2 0 0 2 2
3
4 aij aji bij bji
4 cij dij eij eji
4 fij fji Tlower Tupper
1
ESRK GMRENON USER1
2
HCLO H2O -7.175849 11.25094 0.0000 0.0000
0.3000 0.0000 0.0000 0.0000
0.0000 0.0000 273.15 373.15
CCL4 H2O -2.297253 97.28083 0.0000 0.0000
0.3000 0.0000 0.0000 0.0000
0.0000 0.0000 298.15 383.15
More pairs can be added to the file using the same syntax.
Next the tbprop.dat file needs to be modified to include the new binary databank. To do this add the line: INCLUDE NRTL-USE
The new tbprop.dat file is as follows:
/*********************************************************************
/* !!! Change tbcustom.dat for non-properties stuff
/* Copied from tbcustom.dat - removed non-properties stuff
/*********************************************************************
/* $Log: tbcustom.dat,v $
/* Revision 1.5 1996/04/30 19:34:23 apbuild
/* Dutta Add AQU92.DAT
/*
/* Revision 1.4 1996/02/27 22:03:03 rampy
/* Add Pack database table pkinfo1
/*
/* Revision 1.3 1996/01/31 22:57:17 duvedi
/* Duvedi: add new table VALDAT
/*
/* Revision 1.2 1996/01/10 18:50:53 mmunix
/* jezak - add logging messages
/*
/* ==========================cvs revision history========================
/** #13 4-SEP-2002 PING LI: Add databank pure12 */
/** #12 17-MAY-2000 SUPHAT: Add databank ethylene */
/** #11 20-MAY-1999 PING LI: Add databank dmo */
/** #10 14-APR-1999 PING LI: Add databank pure11 */
/** #9 6-SEP-1995 MOSIAS: Change databank order for P+ */
/** #8 5-JUL-1995 DUTTA: add lcd_cust and mdl_cust */
/** #7 17-MAR-1995 LODGE: Release USER3 */
/** #6 13-FEB-1995 DURRANI: add table for fortran execute */
/** #5 20-JAN-1995 VEGEAIS: ADD REACPROF TABLE */
/** #4 7-JAN-1995 MOSIAS: Add POLYMERS PLUS Files */
/** #3 28-DEC-1994 CHU: Include bps.dat */
/** #2 28-JUL-1994 YEUNG: add tbmsg.txt */
/** #1 21-JUN-1994 YEUNG: Add databank input files(except binary) */
/* */
/** dummy files for customization of lcd and ppcnvpmd */
/* */
INCLUDE lcd_cust.dat
INCLUDE mdl_cust.dat
/* */
/* DATABANK INPUT FILES */
/* */
INCLUDE polymer.dat
INCLUDE segment.dat
INCLUDE pure12.dat
INCLUDE pure11.dat
INCLUDE pure10.dat
INCLUDE pure93.dat
INCLUDE pure856.dat
INCLUDE ethylene.dat
INCLUDE aqueous.dat
INCLUDE aqu92.dat
INCLUDE inorgani.dat
INCLUDE aspenpcd.dat
INCLUDE solids.dat
INCLUDE combust.dat
INCLUDE usrpp1a.dat
INCLUDE usrpp1b.dat
INCLUDE usrpp2a.dat
INCLUDE usrpp2b.dat
INCLUDE usrpp2c.dat
INCLUDE bps.dat
INCLUDE factpcd.dat
INCLUDE ppdsgui.dat
INCLUDE synonyms.dat
INCLUDE syn_cust.dat
INCLUDE nrtl-use.dat
/* INCLUDE polypcd.dat */
/* INCLUDE segpcd.dat */
/* */
/* Reactions table */
/* */
INCLUDE reactns.dat
/* */
/* TABLE SORT FILES */
/* */
INCLUDE ppcmattr.srt
INCLUDE ppstoptn.srt
INCLUDE packprop.srt
/* */
/* PHYSICAL PROPERTY TABLE INPUT FILES */
/* */
INCLUDE ppcmattr.dat
INCLUDE ppcnvdum.dat
INCLUDE ppncnpmd.dat
INCLUDE ppenmprt.dat
INCLUDE ppensprt.dat
INCLUDE ppstoptn.dat
INCLUDE pproctyp.dat
INCLUDE ppeosbip.dat
INCLUDE pcprops.dat
INCLUDE pcpopset.dat
INCLUDE packprop.dat
INCLUDE ppgroup.dat
INCLUDE ppcesprp.dat
INCLUDE ppcestr.dat
/* */
/* DRS STATE VARIABLE INPUT FILES */
/* */
INCLUDE propsptb.dat
INCLUDE drsprops.dat
INCLUDE drspure.dat
/* */
/* BUILT-IN STREAM CLASS TABLE INPUT FILES */
/* */
INCLUDE biphattr.dat
INCLUDE bistattr.dat
INCLUDE biphclas.dat
INCLUDE bistclas.dat
INCLUDE comtype.dat
INCLUDE mfud.dat
INCLUDE tbmsg.txt
Next, run the command mmcustom from the the Aspen Plus User Interface Customization window: Mmcustom mmtbs
When the customization is finished running, open the Custom.Bkp file in the directory \ProgramFiles\AspenTech\APRSystem 12.1\GUI\custom to test if the databank is indeed present. First, add water, hclo, and ccl4 in the Components form. In the Properties form, choose nrtl. Next, go to the binary databank form, go to the Databank tab, and move USER1 from the available databanks to the selected databanks. Use the arrows on the right to move USER1 to the top of the choices for databanks. This will make USER1 the first databank searched. Then, click on the input tab to see that the binary data entered has been chosen. Exit Aspen Plus.
Finally run custinst from Aspen Plus User Interface Customization window. This will allow the added binary parameters to be available for any simulation file.
Keywords: customize
customise
user databank
References: None |
Problem Statement: What are the hardware and software requirements for the Aspen Plus 12.1? | Solution: Hardware and Software Systems Requirements for Aspen Plus 12.1 (and associated add-in products) are as follows:
Hardware requirements
Resource
Recommended Requirements
CPU
A PC with an Intel Pentium III 750 MHz processor.
Note: If you are purchasing a new PC, select the fastest CPU
available.
Monitor
A super VGA color monitor with 1024 x 768 reSolution or higher.
Physical Memory
256 MB for typical sequential-modular models.
512 MB - 1 GB or higher for large plant or equation-oriented models.
Hard Disk Space
Aspen Plus Only installation requires approximately 500 MB of
total disk space, broken down as follows:
- Aspen Plus GUI requires 175 MB
- Aspen Plus Engine requires 50 MB
- AES shared GUI components require 70 MB
- AES shared Engine components require 170 MB
- AES setup components require 5 MB on system disk
- Aspen Plus documentation requires 30 MB
When Aspen Plus is installed as part of a larger AES installation,
240 MB of the above requirements are shared with other AES
products, causing the addition of other AES products to use
less space than if installed standalone. For example,
the AES property system GUI and engine components, APrSystem
folder, utilizes 170 MB of disk space and is shared between
Aspen Plus, Aspen Properties, Aspen Custom Modeler, etc.
As a general rule, for a full AES installation, up to
2.0 GB of free disk space is needed for software and typical usage,
depending upon which AES products are installed.
Note 1: The Installer displays and validates space requirements
for the selected products.
Note 2: The Installation requires 240Meg of disk space on the system
drive even if AES products are installed on other drives.
Virtual memory
512 MB - 1 GB consisting of physical memory and swap file.
Large plant models or multiple open applications may require
additional virtual memory.
For very large equation-oriented models, such as a plant-wide
online, real-time optimizer, which might exceed a 2 GB memory
requirement, the 3GB option is available in Windows NT Server
and Windows 2000 Server allows an additional 1 GB of memory.
Pointing device
A mouse or other pointing device
CD-ROM drive
Available on the local PC or through the network during the
installation.
Licensing
License Manager requires a network adapter.
Software Requirements
The following software requirements apply to all AES products:
Operating System
Notes
WindowsA? 2000 Professional
Service
Pack 3 or higher required.
WindowsA? 2000 Server,
WindowsA? 2000 Advanced Server
Service Pack 3 or higher required.
Windows XPA? Professional
Service
Pack 1 or higher required.
Aspen Products:
Component
Notes
License Manager
None
Additional software:
Software
Notes
Adobe Acrobat Reader
Version 4.0 or higher
Internet Explorer
Version 5.0 or higher
Required for BPE component
(Plantelligence & Enterprise Optimization installations)
Microsoft Office
Office 2000 for Windows 2000
Office XP for Windows XP
BR&E ProMax Interface
PROSIM or TSWEET Version 98.3
Required for access to Bryan Research & Engineering PROMAX
property system
HTRI IST Interface
Xist 2.0
Required for communication to HTRI Xchanger Suite's
shell & tube exchanger software
GTT Technologies ChemApp
ChemApp 4.1 or 5.0
Required for interface between ChemApp and F*A*C*T
thermophysical property data
DECHEMA DETHERM Interface
Required for access of DECHEMA properties over the internet
Compaq Visual Fortran
Version 6.6
Required for custom model development
Keywords:
References: None |
Problem Statement: Is it possible to have VBA (or VB) construct an Aspen Plus flowsheet? | Solution: Yes. Please see the example files attached. The example works by opening a General With English Units template file (.APT). The VBA code then adds the component list, property method, streams and stream data, units and unit specification. Lastly, the code launches a run in the fresly created flowsheet.
Suggestion: Insert a breakpoint in the Build & Run code. Then, split your Windows session so the VBA editor is on the left side of your display and the newly created Aspen Plus session is on the right side of your display. [The Aspen Plus is created after you hit the OPEN button and check the Make Visible checkbox.] With the two sessions side-by-side, single step through the VBA code and watch either the flowsheet view or data browser view inside Aspen Plus.
Note that the example files are created with Aspen Plus 11.0 and will not work for previous versions.
Keywords: VBA, VB, ActiveX, automation, flowsheet, add objects
References: None |
Problem Statement: How do I access a Block-Vec variable on the Tabulate Sheet in a sensitivity block? | Solution: If you have the variable TEMP defined as:
VECTOR-DEF TEMP PROFILE BLOCK=Block VARIABLE=TEMP SENTENCE=PROFILE
Then in the Sensitivity Tabulate sheet, the tabulated variables would be:
Column No.
Tabulated Variable or Expression
1
TEMP(1)
2
TEMP(2)
3
TEMP(3)
.
.
.
.
.
.
10
TEMP(10)
Keywords: vector
Sensitivity
Fortran
References: None |
Problem Statement: Is it possible to set the tabulated value to missing in a sensitivity analysis block for some rows, e.g. when the result is meaningless and should not be displayed, so that plotting can be used more easily? | Solution: TheSolution is to use and tabulate a local fortran variable, which will be set to -1e35 when the value of the accessed variable should not be displayed. The value -1e35 is detected by Aspen Plus as a flag for a missing value.
See the attached example to see how this can be accomplished. The sensitivity analysis block varies both the feed flowrate and the speed of a compressor. It is desired to plot the outlet pressure (POUT) as a function of the suction mass flowrate and the compressor speed. When the compressor is below surge or above stonewall, the value should be set to missing.
The define sheet accesses the approach to surge (SURGE) and to stonewall (SWALL). On the tabulate sheet, we specify that we want to tabulate a variable POUTC, instead of POUT which has been defined as the outlet pressure. On the fortran sheet we have defined the following code:
if(surge.lt.0.or.swall.lt.0)then
poutc = -1e35
else
poutc = pout
endif
The plot can then easily be generated by looking at the sensitivity analysis results. Click the MASSFLOW column heading, then press ctrl-alt-X (Plot, X axis variable), then click the column SPEED, press ctrl-alt-Z (Plot, Z axis variable), click the column POUTC, press ctrl-alt-Y (Plot, Y axis variable), and finally press ctrl-alt-P to display the plot.
Keywords: sensitivity
missing
rmiss
References: None |
Problem Statement: Is it possible to define an inequality specification? For example, for centrifugal compressors it is common to have a recycle loop from the exhaust of the compressor back to the suction line, with a valve that is manipulated to control the flowrate in a way that the suction flowrate is larger than the surge flowrate. In the context of flow driven simulations as in Aspen Plus, this is done by manipulating the split fraction of a FSplit block.
The difficulty is that this is not an equality constraint, which could be done easily with a design specification. Actually, when the suction flowrate is large enough, we want the split fraction to be set to zero or close. | Solution: One approach is to use an optimization solver. It will be necessary to define both a constraint (i.e. approach to surge > 10%) and an optimization case (i.e. to minimize the power requirement in the compressor, and satisfy the inequality constraint). See the attached file compressor-sensitivity-surge-opt.bkp.
Another approach is to use a calculator block with a torn variable. The calculator block accesses the approach to surge (SURGE) and the split fraction (SPLIT). See the file compressor-sensitivity-surge.bkp. For this approach to work, the tearing of fortran write variables needs to be enabled on the Convergence, Conv Options, Defaults, Sequencing for by check the option Tear Calculator write variables.
The Fortran code for this example is as follows:
c surge limit
surgel = 10
c if we are below surge limit, increase recycle
if(surge.lt.surgel)then
split = split+0.1
endif
c if we are above surge limit, decrease recycle
if(surge.ge.surgel+0.01)then
split = split/(1+(surge-surgel)/100)
endif
c if we are ok, no change
if(split.gt.0.9999) split = 0.9999
if(split.lt.1e-4) split = 1e-4
Essentially, the calculator block tries to move the split fraction to a value as low as possible, but increment it when the constraint is not satisfied. This approach will also work for multiple compressors. See file two-stages-Solution.bkp for an example with 2 compressors.
Keywords: design-spec
optimization
fortran calculator
References: None |
Problem Statement: How does the Maximum-Likelihood algorithm for data regression work? | Solution: The Maximum-Likelihood (ML) method is a generalization of the least squares (LS) method. In LS, the measurements of independent variables are assumed to be error free. Errors in the dependent variables are minimized by adjusting one or more model parameters. While the concept of independent and dependent variables makes for a nice mathematical construct, real life phase equilibrium problems are not as neat. The governing equation for phase equilibrium (when using an activity coefficient based option set) is:
phivi yi P = gammai xi fl*i
where phivi is the fugacity coefficient in the vapor phase of component i
yi is the mole fraction in the vapor phase of component i
P is the system pressure
gammai is the activity coefficient in the liquid of component i
xi is the mole fraction in the liquid of component i
fl*i is the fugacity in the liquid of pure component i
T, P, x and y are neither truly independent nor truly dependent. They are interdependent. When measuring T, P, x and y in a laboratory experiment, there can be measurement errors in all variables. The ML method was developed to take this into account. The general formulation of the problem is as follows. (Note: although this document defines the algorithm for TPXY data, it is equally valid for other data types.)
NDG NP
Q = Sum wn Sum {[ (Test,i - Tmeas,i) / sT,i ]^2 +
n=1 i=1
[ (Pest,i - Pmeas,i) / sP,i ]^2 + NC-1
Sum [ (xest,i,j - xmeas,i,j) / sx,i,j ]^2 +
j=1 NC-1
Sum [ (yest,i,j - ymeas,i,j) / sy,i,j ]^2 }
where Q is an objective function to be minimized by the data regression
NDG is the number of Data-Groups in the Regression case
wn is the weight of Data-Group n
NP is the number of data points in Data-Group n
NC is the number of components present in the Data-Group
Test,i is the estimated Temperature of data point i
Tmeas,i is the measured Temperature of data point I
Pest,i is the estimated Pressure of data point i
Pmeas,i is the measured Pressure of data point i
xest,i,j is the estimated liquid mole fraction of component j of data point i
xmeas,i,j is the measured liquid mole fraction of component j of data point i
yest,i,j is the estimated vapor mole fraction of component j of data point i
ymeas,i,j is the measured vapor mole fraction of component j in data point i
si is the standard deviation of measurement i. Note that if si= 0,
this point is not included in the objective function, and the
estimated value is set equal to the measured value.
Different data points can have a different standard deviation.
The objective function is minimized by manipulating the physical property parameters identified in the regression case, and manipulating the estimated value corresponding to each measurement. Minimization of Q is subject to the constraints of phase equilibrium:
phivi yi P - gammai xi fl*i = 0 (Actual constraint, one for each component)
gammai = gammai (T,P and x) (Implicit constraint - will never be violated)
phivi = phivi (T, P and y) (Implicit constraint - will never be violated)
fl*i = fl*i (T and P) (Implicit constraint - will never be violated)
Liquid mole fractions must sum to 1.0 (Implicit constraint - will never be violated)
Vapor mole fractions must sum to 1.0 (Implicit constraint - will never be violated)
Occasionally data regression will converge, but will report that the phase equilibrium constraints are not tightly converged. [Note that the convergence tolerance can be adjusted on the Algorithm sheet of the Regression Case.] Actual Constraint values for each component can be reported to the history file by setting the simulation diagnostic level to 6 or higher on the Diagnostics sheet of the Regression Case or on the /Setup/Specifications/Diagnostics form. If the constraint values are in the order of 1d-5(absolute) or smaller, the results should be acceptable. Higher constraint values indicate that the regression results should not be trusted. Taking one or more of the following actions may lead to a better regression result:
Set different initial guesses and limits for the regressed parameters.
Evaluate the data for inconsistencies in the data points with high constraint values
Confirm that the standard deviations are appropriate for the data points with high constraint values
Add additional parameters to be regressed
Keywords:
References: None |
Problem Statement: Is it possible to report the mass or mole flowrate of a subset of components? How about the mass or mole fractions? | Solution: One approach is to use a user property set. See the reference manual User Models for details.
Attached you will find a file groups.f which contains 3 user property subroutines and the file example.bkp which shows how this can be used.
To report the mass flowrate of a group of components, you need to:
- create in Components, Component Groups, a component group with the components you want to select (e.g. C5FLOW)
- create in Properties, Advanced, User Properties a new user property
- the name of the property must be the same as the component group (e.g. C5FLOW)
- select the type standar property
- enter the subroutine name UMASFL
- use the option do not flash
- use the Mixture property type
- on the Units sheet, select the option unit conversion performed by Aspen Plus
- select the unit type MASS-FLOW
- in Properties, Prop-sets, create a new property set (e.g. GROUPS)
- select the property C5FLOW
- add the property set in the stream report options, block profile options, etc
To report the mole flowrate of a group of components:
- create in Components, Component Groups, a component group with the components you want to select (e.g. C5FLOWM)
- create in Properties, Advanced, User Properties a new user property
- the name of the property must be the same as the component group (e.g. C5FLOWM)
- select the type standar property
- enter the subroutine name UMOLFL
- use the option do not flash
- use the Mixture property type
- on the Units sheet, select the option unit conversion performed by Aspen Plus
- select the unit type MOLE-FLOW
To report the sum of mass or mole fraction of a group of components, you can use the standard properties SUM-MLFR (sum of mole fractions of components selected in a group) and SUM-MSFR (sumo of mass fractions of components selected in a group). See in the example file the property set SUM-MLFR.
It is also possible to use the subroutines included in the fortran code attached with the example.
To report the sum of mass fractions of a group of components:
- create in Components, Component Groups, a component group with the components you want to select (e.g. C5MASS)
- create in properties, Advanced, User Properties a new user property
- the name of the property must be the same as the component group (e.g. C5MASS)
- select the type standar property
- enter the subroutine name USRGRP
- use the option do not flash
- use the Mixture property type
- on the Units sheet, select the option Units conversion performed by user subroutine
- enter the unit label MASSFRAC
To report the sum of mole fractions of a group of components:
- create in Components, Component Groups, a component group with the components you want to select (e.g. C5MOLE)
- create in properties, Advanced, User Properties a new user property
- the name of the property must be the same as the component group (e.g. C5MOLE)
- select the type standar property
- enter the subroutine name USRGRP
- use the option do not flash
- use the Mixture property type
- on the Units sheet, select the option Units conversion performed by user subroutine
- enter the unit label MOLEFRAC
Keywords: None
References: None |
Problem Statement: Is it possible to access the ambient pressure in a Fortran user subroutine or in a Calculator block? | Solution: Atmospheric pressure is not available in any of the Common block; however,
in Aspen Plus 12.1, there is a new utility subroutine to obtain the ambient pressure.
The syntax is
CALL UU_GETP_AMB (PAMB)
The return value of PAMB is in SI unit. An example of using this utility in a Calculator block is attached (p_amb.inp).
Keywords: user routine
References: None |
Problem Statement: Can Aspen Plus handle the pressure relief of a liquid-only fluid?
There is an error when the fillage is above a value of 0.994:
** ERROR
INTEGRATION IS BEING DISCONTINUED BECAUSE LIQUID VOLUME IN REACTOR
IS GREATER THAN 99.5% OF REACTOR VOLUME. LIQUID VOLUME = 2.4703
REACTOR VOLUME = 2.4820 . CHECK INITIAL CONDITIONS, INITIAL
VAPOR FRACTION MAY BE TOO SMALL. | Solution: No, Aspen Plus' pressure relief feature was designed to handle either vapor-liquid or vapor only pressure relief. our pressure relief model is not designed to handle liquid-filled vessels, so we limit the liquid volume fraction to 0.995. If the vessel is liquid-filled, the pressure in the vessel is determined by the elasticity of the walls of the vessel. We cannot model that.
One workaround, especially if it is a full vessel exposed to a heat scenario, is to specify a small amount of vapor with a large fillage fraction (0.9 or greater) and also specify a pad gas.
Keywords:
References: None |
Problem Statement: The Flexible and Predictive Equation-of-State (EOS) Property Methods can be used for mixtures of polar and non-polar components and light gases. The property methods can deal with high pressures and temperatures, mixtures close to their critical point, and liquid-liquid separation at high pressure. Examples of applications are gas drying with glycols, gas sweetening with methanol, and supercritical extraction.
In these methods pure component thermodynamic behavior is modeled using the Peng-Robinson or Redlich-Kwong-Soave equations of state. Then mixing rules are used to capture the non-idealities that are not typically captured well in a standard EOS. Modified Huron-Vidal mixing rules can predict non-ideality at high pressure from low-pressure (group-contribution) activity coefficient models (e.g., Wong-Sandler, MHV2, PSRK) . The predictive capabilities of modified Huron-Vidal mixing rules are superior to the predictive capabilities of SR-POLAR.
How appropriate is it to substitute a different activity model (gamma) route in one of these property methods to improve Aspen predictions to actual data. For example, how reasonable it is to use NRTL rather than the UNIFAC property route in the PSRK property method? Have others been successful in achieving results that are better than without modifying the activity route? | Solution: This modification has been used successfully by existing customers. It is possible to change the GAMMA model on the Properties | Property Methods | Models sheet from PSRK UNIFAC (GMUFPSRK) method to NRTL (GMRENON) or UNIQUAC (GMUQUAC). Given the framework of these methods, any activity coefficient model can be used; however, the models were designed and were fit using the default method. For example when using PSRK, UNIFAC can be replaced with NRTL; however, it somewhat defeats the purpose of using this as this is a predictive model. Aspen Plus does not allow the mixing of two gamma models for a given property method. One must be chosen.
For the gamma models, the light gases are handled using the Henry's law approximation. There are many Henry's law parameters available in the Aspen Plus built-in binary data banks. These parameters are determined from the gas solubility data. The gamma parameters are normally set to zero for gas-solvent pairs.
PSRK has some different custom UNIFAC groups and values (UNIFPS groups). The UNIFPS parameters have been tuned for this purpose especially for the light gas groups that are not part of the traditional UNIFAC groups. These custom values help PSRK be more accurate than if only the standard UNIFAC groups were used.
Simply changing the GMUFPSRK method to GMRENON in the PSRK method will work for solvent-solvent pairs as the NRTL parameters are available for them and are valid for the PSRK approach. For the gas-solvent pairs, additional work will be required to transform the information of the Henry's parameters to NRTL parameters. This can be achieved by generating the solubility data in the range of interest using the valid models (either Henry-Gamma or PSRK ) and regressing the PSRK-NRTL parameters.
In summary, if NRTL or UNIQUAC is used in PSRK, the databank values will not always be accurate and should be ideally regressed. Using NRTL turns PSRK into a normal fitted model. If you need to regress data, one can always use NRTL (unless at high pressures) or use other available methods such as SRK-ML or SRK.
Keywords: PRMHV2
PRWS
PSRK
RK-ASPEN
RKSMHV2
RKSWS
References: None |
Problem Statement: The XMLSchema for Exported Aspen Plus XML Results is documented in | Solution: 114419; however, it does not give details about the definition of the variables.
What is the difference between the attributes PRES_OUT and RES_PRES etc ?
What is the difference between the attributes MOLEFLMX and RES_MOLEFLOW? The data for MOLEFLMX is written to RES_VOLFLOW and vice versa.
Most of the attributes coming from the prop-sets have the suffix _PS but not the MOLEFLOW (_CPS); MOLEFRAC, MASSFLOW, MASSFRAC, HMX, RHOMX (2); VFRAC (_OUT2); why?
The units written for the data coming from the prop-sets are the same as for the main stream data. However in the prop-sets different units are used and the numbers written to the file correspond with the units specified in the input.
Solution
The .XML file contains all the results that are written to the summary file. It rarely does any reformatting of the results. For all intents and purposes it is the summary file written in XML format.
Here are the answers to the questions listed above:
The information written to the summary file is contained in packages called DSETs. The XML file contains the same information but with the DSETs stripped out. The summary file is used to transfer results from the AspenPlus engine to the GUI. Various parts of the GUI look for specific DSETs to display results. PRES_OUT is written to a DSET named STR_MAIN, and is displayed on the Stream Results form. RES_PRES is written to DSET RES_STR, and is displayed on the PDF (Process Flowsheet Window) if the user has checked any of the boxes under Tools/Options/Results View/Stream results. The values of PRES_OUT and RES_PRES should be the same, but PRES_OUT contains units information, whereas RES_PRES does not.
MOLEFLMX and RES_MOLEFLOW should have the same value. There is a bug in the summary file writer in 2004; however, they are the same in 2004.1 and higher. Also, the values RES_MOLEFLOW and RES_VOLFLOW were switched, but are now correct. In the summary file, MOLEFLMX is written to DSET STR_MAIN and RES_MOLEFLOW is written to RES_STR. As with PRES_OUT and RES_PRES, MOLEFLMX is written with units information, RES_MOLEFLOW is not.
The names of the variables written to the XML file are based on the object to which they belong. For instance, we know ahead of time that variable MOLEFLMX is calculated for every stream. The information about these variables is stored in data files and we can retrieve it when we write the XML file. An exception is PROP-SET property variables. We have to create the variable names while generating the XML file. The variable names have to be unique or we run the risk of overwriting another variable's data. In order to create unique names, we append two underscores to the name of a PROP-SET property and then add a single character for each qualifier. For instance, MOLEFLOW has qualifiers COMPONENTS, PHASE, and SUBSTREAM. When it is written to the XML file, it gets the name MOLEFLOW__CPS. If you see two underscores in a variable name you can bet it is a PROP-SET property. Some variables, for instance VFRAC_OUT, have been given names with underscores by the developers and there is no significance to the fact that it has an underscore. This table shows the character appended for each of the possible qualifiers in a PROP-SET:
Qualifier
Appended Character
BASIS
B
COMPONENTS
C
PHASE
P
TREF
T
PREF
R
PCLV
D
SUBSTREAM
S
In 12.1, we assumed that all data written to the XML file had units specified by the user's Output Results units set. The bug was that the user could specify units for a PROP-SET property. If the units specification on the PROP-SET form was different from his Output Results unit set, the variable was converted to the PROP-SET units but the units attached to the variable was from his Output Results units set. This bug has been fixed for release 2004.
Keywords: xml
References: None |
Problem Statement: How does RadFrac handle inert solids? | Solution: In addition to salts which are handled using Chemistry, RadFrac can handle inert conventional (CI) and/or non-conventional (NC) solids. RadFrac handles solids only in equilibrium mode. In rate-based mode RadFrac cannot handle solids.
There are two Solids handling methods which can be specified on the RadFrac block's Convergence | Basic sheet:
Overall - By default, solids are dumped into the bottom stream directly.
In the calculations the solids are temporarily removed from the input stream before column calculations are completed. Then, the solids are adiabatically mixed with liquid product from the bottom stage. The overall-balance method maintains an overall mass and energy balance around the column. But it does not satisfy individual stage balances.
? Stage - The solids participate in tray by tray energy balance.
The stage-by-stage method treats solids rigorously in all stage mass and energy balances. The ratio of liquids to solids on a stage is maintained in the product streams withdrawn from that stage. The specified product flow is the total flow rate of the stream, including the solids. If a nonconventional (NC) solids substream is present in the column feeds, you must give all column flow and flow ratio specifications on a mass basis.
The two methods differ in how they treat solids in the mass and energy balances. Neither method considers inert solids in the phase equilibrium calculations. However, salts formed by salt precipitation reactions are considered in phase equilibrium calculations. Handling solids by the Overall method is quicker, but it can result in errors in bottom temperatures and duties.
When you specify a decanter, RadFrac can decant the solids partially or totally. By default, RadFrac decants the solids partially along with the second liquid phase. RadFrac uses the return fraction you specify for the second liquid phase (Fraction of 2nd Liquid Returned on the Decanters Specifications sheet) to decant the solids. If there is no second liquid phase in the decanter, RadFrac decants the solids partially along with the first liquid phase. RadFrac uses the return fraction you specify for the first liquid phase (Fraction of 2nd Liquid Returned on the Decanters | Specifications sheet) in this case. You can request complete decanting of the solids by selecting Decant Solids Totally on the Decanters | Options sheet.
Keywords: CISOLID NCSOLID
References: None |
Problem Statement: RadFrac pack rating does not include the pressure drop for the last stage in the bottom product pressure. The update pressure profile option has been enabled. | Solution: Radfrac assumes each stage is in equilibrium - both temperature and pressure equilibrium are maintaned. Even though we know the bottom of a theoretical packed stage has to be at a higher pressure than the top of the stage, pressure equilbrium is maintained and the bottom pressure is assumed to equal the top pressure for a given equilibrium stage.
For example, using a 3 stage packed absorber, the pressure at the top of the 3rd packed stage, would be reported as the bottom product's stream pressure. In other words, the bottom product stream pressure would equal to the column's top pressure plus the pressure drop on stage 1 and stage 2.
One possible workaround is to add some additional height the HETP height. In this example, let's assume we have 3 stages, with an HETP equal to 10 feet of packing for each stage. To get the correct pressure we could scale the HETP height by 50% to make up for the 3rd stage (which will not be used to calculate the bottom product stream pressure). In this case 2 stages with 15 feet of packing would be equivalent to 3 stages with 10 feet of packing.
Keywords: TPSAR
References: None |
Problem Statement: After the UNIFAC-customization (see | Solution: 102863) is completed, I can no longer calculate systems which contain light gases such as CO2. The control panel message reads:
*** SEVERE ERROR IN PHYSICAL PROPERTY SYSTEM
DORTMUND MODIFIED UNIFAC MODEL: GMUFDMD HAS MISSING PARAMETERS: GMUFDQ (DATA SET 1) MISSING FOR GROUP 3850
GMUFDR (DATA SET 1) MISSING FOR GROUP 3850
****PROPERTY PARAMETER ERROR
ERRORS ENCOUNTERED IN CALCULATION OF LIQUID MIXTURE PROPS USING OPTION SET UNIF-DMD FOR PHIMX
Solution
In uncustomized Aspen Plus or Aspen Properties, you can use UNIFAC or any flavor of the UNIFAC method (UNIF-DMD, UNIF-LBY, ...) to calculate systems which contain light gases such as N2, O2, CO, CO2, H2S, etc. As with any activity coefficient model, the solubility of these components should be modelled using Henry's law. Yet, UNIFAC group parameters for the gases are required to calculate activity coefficients and related properties.
The view of the UNIFAC consortium is that functional groups for the light gases (e.g., group no. 3850 for CO2) have been defined for PSRK and MHV2 equations of state only. Modified UNIFAC (Dortmund) does not define a CO2-group or groups for other gases. Hence, an error message makes sense, if someone attempts to calculate CO2-systems with the UNIF-DMD property method.
Originally in Aspen Plus, we have decided to follow a more lenient approach and allow light gases to work. This explains the change of behavior before and after the customization. For consortium members, if they trust the consortium recommendations, then the above error message is the expected behavior. If they want more lenient treatment, then they have to add these groups to the consortium files before running the customization.
Keywords: UNIFAC
UNIF-DMD
customisation
light gases
group parameter
References: None |
Problem Statement: How is the property COMB-O2 calculated?
Is it possible that Aspen Plus assumes that CO3 is an oxygen donor i.e.
CO3 ==> CO2 + O
even though this reaction does not happen in reality? | Solution: COMB-O2 is the amount of added O2 needed to combust all the C, H, S, and N (except N2) in a given material to CO2, H2O, SO2, and NO2.
Any hydrogen present in the stream is converted to water (H2O).
Any carbon present in the stream is converted to carbon-dioxide (CO2).
Any sulfur present in the stream is converted to sulfur-dioxide (SO2).
Any nitrogen present as part of a compound other than N2 is converted to nitrous-oxide (NO2).
The calculations will not be correct if other oxidizable atoms are
present in the stream.
Keywords: O2-COMB
References: None |
Problem Statement: Is it possible to handle a solid that partially dissolves in a solvent using salt formation in CHEMISTRY? | Solution: A solid partially dissolves in the aqueous phase can be modeled using CHEMISTRY.
This method was tested using some data for sucrose solubility in water found in CRC.Solution 102340 includes the sucrose example file.
1. The component is defined as two component IDs: one in the aqueous phase (type=conv) and one in the solid phase (type=solid). The component type is assigned on the Components | Specifications form.
2. The solid component is treated as a precipitating salt using CHEMISTRY form.
3. The equilibrium constant for the precipitation (K-SALT) can be regressed from solubility data.
4. With the true component approach, the amount of solid in the aqueous and in the solid phase is reported.
5. Most option sets can be used using the true component approach. (The KSALT parameters for sucrose are regressed using NRTL, RK-SOAVE and IDEAL option sets, and all gave the same results for the regression and in the prop-table.)
6. It is possible to use solvents other than water such as methanol. (The solubility of sucrose in pure methanol was predicted to be higher than sucrose in water. Solubility in a mixed solvent was predicted to be in between these two values.)
Note:
Only activity coefficient models with true approach for other property methods are recommended. It is necessary to use the true approach with volatile components and to see salts automatically in the stream report. In addition, property methods, other than ElecNRTL do not have a built in route to convert apparent species to true species.
Keywords: electrolyte
solid solubility
solid precipitation
References: None |
Problem Statement: The simulation results report gives a vapor fraction, but does not indicate if the basis is molar, mass or volume fraction. | Solution: The vapor fraction on the form is the MOLAR vapor fraction. In Aspen Plus, all vapor fractions are on a molar basis unless otherwise stated.
Keywords: vapour fraction
vfrac
References: None |
Problem Statement: What parameters are loaded automatically when the ElecNRTL property method is used? | Solution: The following parameters are loaded automatically from the system definition file (SDF) when the ElecNRTL property method is used. There is currently no way to change this behavior in 2006 and earlier. In 2006.5, you can uncheck the Require Engine to load parameters from databank for electrolyte method option on the Setup | Simulation Options | Calculation sheet to have Aspen Plus NOT use these parameters.
There are 11 parameters retrieved for 11 components and 28 parameters retrieved for 9 components.
11 parameters
for 11 components
OMEGA
H2O
DHFORM
CO2
DGFORM
H2S
VLBROC
H3N
CPDIEC
H2SO4
DHVLWT
HCL
CPAQ0
C5H13NO2
PLXANT
C2H7NO
CPIG
NO3-
DGAQFM
HSO4-
THRSWT
SO4-2
28 parameters
for 9 components
TC
H2SO4
PC
C2H7NO
VC
C5H13NO2
ZC
C4H11NO-1
MW
HCLO
VB
C4H11NO2-1
TB
C4H11NO2-2
OMEGA
HNO3
DHFORM
H3PO4
DGFORM
DGAQFM
DHVLB
DHAQFM
RKTZRA
VLBROC
CPDIEC
DHVLWT
MULAND
TRNSWT
MUVDIP
KLDIP
SIGDIP
DHVLWT or DHVLDP
CPIGDP
CPAQ0
THRSWT
PLXANT
CPIG or CPIGDP
Note that some components will have CPIG while others will have CPIGDP; similarly for DHVLWT and DHVLDP.
Keywords: elecnrtl
References: None |
Problem Statement: Can Convergence block parameters be accessed by the DEFINE statement? User would like to be able to access the values for MAXIT, TOL, the current iteration number, and the current ERR/TOL. | Solution: This is not possible in Aspen Plus. Convergence parameters are not accessible. The semantic processing that happens during input translation evaluates inline Fortran in Calculator blocks and Design-specs before Convergence blocks are constructed; hence, there is no destination to assign the Fortran variable to when the Fortran is evaluated. Because Fortran can be used to adjust block variables, this is a requirement of the algorithm.
It is possible to count the iterations in the Calculator block. To get the convergence block current iteration number use a Parameter variable in a Calculator, and increment it by 1 every time it is executed. In the beginning of a loop. initialize the parameter to zero with another Calculator outside the loop in case the convergence is nested.
A dummy variable that accesses a flowsheet variable may need to be defined in order that the Calculator blocks execute properly every time. By default, Aspen Plus has affected block logic that will not execute a block that has no changes to it.
See the attached example file. It can be opened in Aspen Plus 2004.1 and higher.
Keywords: Convergence, Fortran, Calculator
References: None |
Problem Statement: How can electrical conductivity be calculated for stream properties? | Solution: Electrical conductivity can be entered in Properties/Prop-Sets/Properties sheet as ELECCOND. However, ELECCOND can only be used if the OLI Property Method is specified when using the OLI Interface. It is NOT part of the basic Aspen Plus. When using the OLI Property Method, a license is required along with the OLI software and interface.
The OLI Databank contains model parameters for the prediction of thermodynamic, transport, and physical properties for 79 inorganic elements of the periodic table, and their associated aqueous species, as well as over 3000 organics. Thus, most mixtures of chemicals in water can be accurately and reliably modeled.
Keywords: electrical conductivity, OLI, stream,
References: None |
Problem Statement: How do you make cells on user defined Visual Basic input forms disappear or reappear, depending on values in other cells? | Solution: Add in code setting MMVisible = True or False.
For example, assume there are two MMLBUText boxes MMLBUText1 and MMLBUText2 on form. Following code will make the first one appear and the second dissappear, or vice versa, dependent on whether value for Var1 = Option1 or Option2
If (Var1 = Option1) Then
MMLBUText1.MMVisible = True
MMLBUText1.MMVisible = False
ElseIf (Var1 = Option2) Then
MMLBUText1.MMVisible = False
MMLBUText1.MMVisible = True
End If
Keywords: user routine
user input form
Visual Basic
References: None |
Problem Statement: PSANT parameters used to calculate the vapor pressure of a solid can be entered on the Properties | Parameters | T-dependent form. Are PSANT parameters used in any calculations within Aspen Plus? | Solution: PSANT is used to calculate the reference state fugacity coeff (PHIS) for a component in a solidSolution in the equilibrum reactor model RGIBBS. It is also available for use in a USER model.
Keywords: None
References: None |
Problem Statement: How do I get rid of the retrieved parameters on the input forms? | Solution: In 2004, the Clean Property Parameters feature can be accessed from the Tools menu.
This dialog box can be used to perform three functions:
1 - Clean property parameters that have been placed on input forms: Remove property parameters which have been added to input forms as a result of running regressions, estimations, and/or retrieving property parameters from the databanks for review.
2 - Purge incomplete property parameters and empty records: Such parameters can exist because the forms were incompletely filled out, or because a component with property parameter data was removed, or because a property method was removed and there were parameters specified which only exist for that property method.
3 - Clean all parameters: This restores these forms under Properties | Parameters to their initial state in a new simulation.
To enable or disable the automatic copying of estimation, regression and retrieved parameter results to Parameters forms, you can deselect this option on the Options sheet of the Run Settings window. To open the Run Settings window, choose Settings from the Run menu.
Keywords: retrieve parameters
delete component
deleting
References: None |
Problem Statement: One of the | Solution: documents notes that it is necessary to change the code to write to the History and Report files. How is this done?
Solution
There is a new utility (DMS_WRTALN) for writing to the History or Report file using any compiler. This utility MUST be used when the compiler used internally to compile Aspen Plus (Compaq for 2004.1 and Intel for 2006 and higher) is different from the user's installed compiler. If the compilers match, then either this way OR the old way of writing to the history or report file can be used.
If you want to write to the history file, follow these steps:
1. Include the following (beginning in column 1):
#include ppexec_user.cmn
2. Define character string for the buffer. For example, to write a two-line message:
CHARACTER*256 BUFFER(2)
3. Write the two-line message to the buffer:
WRITE (BUFFER, 2000)
4. Call DMS_WRTALN to write to the history file one line at a time:
CALL DMS_WRTALN(USER_NHSTRY,BUFFER(1))
CALL DMS_WRTALN(USER_NHSTRY,BUFFER(2))
Note: Use USER_NRPT to write to the report file.
Example: Writing to history file using different compilers
SUBROUTINE USR002
.
.
.
IMPLICIT REAL*8 (A‑H, O‑Z)
#include ppexec_user.cmn
DIMENSION ID(2)
CHARACTER*256 BUFFER(3)
.
.
.
C
C WRITE MULTIPLE LINES TO HISTORY FILE
C
2000 FORMAT ('FLASH OF STREAM', 2A4, 'FAILED',/,
+ 'CHECK INPUT SPECIFICATIONS')
WRITE (BUFFER, 2000) ID(1), ID(2)
CALL DMS_WRTALN(USER_NHSTRY, BUFFER(1))
CALL DMS_WRTALN(USER_NHSTRY, BUFFER(2))
.
.
.
RETURN
END
Keywords: Intel Visual Fortran
Compaq Visual Fortran
HP Visual Fortran
CVF
compiler
References: None |
Problem Statement: When running simulation that use SRK, you will get the warning message:
WARNING IN THE PROPERTIES PARAGRAPH WHICH BEGINS ON LINE 375
FREE-WATER METHOD SHOULD BE STEAMNBS WHEN THE MAIN PROPERTY METHOD IS SRK. DEFAULT FREE-WATER METHOD IS STEAM-TA PLEASE SPECIFY THE RECOMMENDED FREE-WATER METHOD AND RUN AGAIN.
Why does STEAMNBS need to be selected? By using a steam table, does this force SRK to use a free water? | Solution: For the SRK property method, by default, water is treated in a special way. The following properties of water: enthalpy, entropy, Gibbs free energy, and molar volume, are calculated using steam tables. That is the contribution of water to these properties for a mixture is calculated using an appropriate steam tables, then mixed (molar averaged) with the contributions from the remaining components, which are calculated from the SRK model. Note that fugacity coefficient of water in the mixture is NOT affected. This special treatment of water applies to all property calculations, not just for the free-water phase.
The steam tables used is that specified in the Free-Water Property Method. STEAMNBS is the recommended choice rather than STEAM-TA or STMNBS2 because it extrapolates better and does not exhibit any discontinuity. This is especially relevant because properties of water are frequently requested out of the range of the steam tables.
Option Code 3 of the SRK model defines whether or not water is explicitly identified and treated differently at all times. It does not mean that free water is used.
0 - Water is not explicity identified.
It is treated as any other component.
Do not calculate water properties from steam tables. (default for Redlich-Kwong-Soave models)
1 - Water is explicitly identified.
Calculate properties (H, S, G, V) of water from steam tables as specified in the Free-water method.
This does NOT affect fugacity coefficient of water.
(default for SRK models)
Note that the above warning occurs even when all the correct property methods are specified. This is a warning, so it does not stop the simulation.
Keywords: srk
References: None |
Problem Statement: How do you access electrolyte pair parameters (GMELCC, GMELCD, GMELCE, GMELCN) in a user subroutine?
The User Model | Solution: The GMELC* are electrolyte pair - electrolyte pair, or electrolyte pair - molecule interaction parameters.
You need to know the number of cations, anions, and molecular species. From this, the gmelc* space is indexed by the following:
MI - molecule index, from 1 to the number of molecules
IPI - ion pair index, from 1 to the number of ion pairs
IPIP - ion pair-ion pair index, from 1 to the unique ion pairs
MI + IPI are indexed twice to give all of the left and right pairings.
IPIP are index after the MI and IPI twice for all of the left and right pairings.
Example
With the following component list:
H2O
HNO3
NO3-
H3O+
Na+
NaNO3
They would be indexed internally as:
Index
Pair
lgmlecc + 1
H2O (H3O+ NO3-)
lgmlecc + 2
H2O (Na+ NO3-)
lgmlecc + 3
HNO3 (H3O+ NO3-)
lgmlecc + 4
HNO3 (Na+ NO3-)
lgmlecc + 5
NaNO3 (H3O+ NO3-)
lgmlecc + 6
NaNO3 (Na+ NO3-)
lgmlecc + 7
(H3O+ NO3-) H2O
lgmlecc + 8
(Na+ NO3-) H2O
lgmlecc + 9
(H3O+ NO3-) HNO3
lgmlecc + 10
(Na+ NO3-) HNO3
lgmlecc + 11
(H3O+ NO3-) NaNO3
lgmlecc + 12
(Na+ NO3-) NaNO3
lgmlecc + 13
(H3O+ NO3-)(Na+ NO3-)
lgmlecc + 14
(Na+ NO3-)(H3O+ NO3-)
Keywords: user subroutine accessing parameters plex gmelcc gmelcd gmelce gmelcn
References: Manual, chapter 6, describes how to access parameters, but how would the GMELC* parameters be indexed? |
Problem Statement: How can you create a Property Set (Prop-Set) to sum selected component fractions? | Solution: In the attached file (built in Aspen Plus version 12.1), the total light gas composition is calculated by summing the molar compositions of hydrogen, nitrogen, and methane and reporting it as a single value in the stream summary results.
To report a summation of component fractions:
1. Navigate to the Properties Prop-Sets folder within the Data browser. Click the New... button and provide a unique name, i.e., PS-1.
2. From the Physical properties drop-down list, choose the property SUM-MLFR to sum mole fractions, SUM-MSFR to sum mass fractions, or SUM-VLFR to sum liquid volume fractions.
3. On the Qualifiers tab, choose the components you want included in the summation. After you add the first component, Aspen Plus will add a column to the right from which you can choose the second component, and so on.
4. To report this parameter in the Streams report, navigate to the Setup Report Options form and click the Property Sets button on the Streams sheet. Move PS-1 to the Selected property sets area. The value is reported at the very bottom of the Results Summary Streams form.
You can also use this Prop-set in a Sensitivity analysis, Design Spec, or Calculator block.
Keywords: Properties, Prop-Set, parameters
References: None |
Problem Statement: How do you add drop down menu items to user defined Visual Basic input forms, and take action dependent on the option selected? | Solution: Using the VB tookbox, add an MMAdvCombo box to the form.
Right click on the new box, and select properties.
On the General tab, select the Fancy Combo Box radio button.
In the options list, use the Add button to add in the menu options that will appear when the drop down menu is selected - for example, add two items Option1 and Option2
Click on the variable tab, and add in a new variable, say Var1.
Make the Datatype String, and add in a name for the path - say Select1 (anything will do).
Check name of new box by clicking on box in VB, and pressing F4 key. Let's assume box is named advSubstr1.
Add in code as follows, to check for variable Var1, and take action based on value
Private Sub Subadv()
Dim StrVal as String
StrVal = advSubstr1.GetVar(Var1).Value
If (strVal = Option1) Then
'enter code for option 1
ElseIf (strVal = Option2) Then
'enter code for option 2
'ElseIf......
'further code for other conditions
End If
End Sub
Keywords: user routine
user input form
Visual Basic
References: None |
Problem Statement: Customer gets the following error while running Aspen Plus 11.1 on a Windows 2000 system.
Failed to create script engine Class Factory cannot supply requested class | Solution: One of the GUI components namely pfsicon.ocx produces this error message.
The following could cause the problem:
VBScript is not installed properly in the system or the registry entry has been corrupted. VB script is used when drawing graphics on the flowsheet.
The customer or their company may somehow have restricted use of VBScript (email viruses typically deploy themselves as vbs files) but that would only be a guess.
It is likely that this system probably has trouble with other applications that might use vbscript.
How to test vbscript:
Create a file with the .VBS extension like test.vbs and placing the following line inside.
MsgBox Hello, world!
Save the file and double click on the file from explorer. You should get a dialog with the caption VBScript and the text Hello, world!
If you do not get the caption VBScript and the text Hello, world! then your VBScript needs to be reinstalled.
Keywords: Script
Engine
Class
Factory
AES 11.1
Windoes 2000
Aspen 11.1
References: None |
Problem Statement: How do I print out forms from Aspen Plus? | Solution: Some forms such as the Streams Results form CAN be printed from the graphical user interface using Print from the File menu. Unfortunately, this does not work from Column Profiles or other tabular forms, just Stream Results.
Other input and resuls forms can be printed using the Windows print screen functionality:
In Aspen Plus, have whatever you want printed visible.
Click on the Prnt Scrn (print screen) key. This captures whatever is on the screen.
Go to Start -> Programs -> Accessories -> Paint
Select Paste from the Edit menu. This pastes whatever was captured with the Prnt Scrn key.
You can edit or crop or whatever from this drawing program.
Select Print from the file menu.
Tables can also be copied to Excel and printed from there.
Keywords: print form
References: None |
Problem Statement: How should the equilibrium of the hydrogen chloride-water system, including vapor-liquid equilibrium as well as liquid-liquid equilibrium be modeled | Solution: This report provides a brief description of preliminary work to represent the phase equilibrium of the hydrogen chloride-water system, including vapor-liquid equilibrium as well as liquid-liquid equilibrium.
Model Description
The ElectrolyteNRTL model of Chen and co-workers (1982, 1986) has been used as the basis of the correlation. This model has been described in the literature and in AspenTech documents and thus a detailed description is not provided here.
The only point that is discussed here is the representation of the pure-component fugacity, which is given by:
where,
The fugacity expression in the above equation is based upon a pure-component reference state for component i, i.e., the symmetric convention. This may pose a problem for hydrogen chloride since its critical temperature (51.45?C) lies in the temperature range of interest for the phase equilibrium calculations considered here. It is usual to treat such a component in the unsymmetric convention, where the reference state is at infinite dilution in the solvent (water). However, we wish to describe liquid-liquid equilibrium where the HCl phase is highly concentrated in HCL, and thus the symmetric convention is necessary.
Two features are required to effectively apply the symmetric convention for a supercritical component. First, the vapor pressure expression must extrapolate reasonably beyond the critical temperature. It is assumed that this condition will be satisfied since the reduced temperature of HCl will, at most, only be slightly above unity. Second, the exponential term in the above equation must be well behaved in the Poynting correction. Aspen Properties typically uses the Rackett equation for molar volume of i, which is invalid above the critical temperature and varies strongly with temperature in the vicinity of the critical temperature. We have overcome this problem by using a constant value for molar volume of i. The constant value is assumed to be the saturated liquid molar volume of component i at its normal boiling point. This provides a compromise between using a theoretically justified method to represent the fugacity and ensuring a reasonable and smooth variation of the thermodynamic properties.
Data Fitting and Results
The various data collected for fitting the parameters of the HCl-water model are shown in Table 1. As far as possible, the model parameters (e.g., reference-state properties, vapor pressure) were taken from the literature. The key parameters that were regressed were the pair parameters between the H3O+ ion pair and the molecular species HCl and water. The data sets used in the regression were G0, G0A, G10A, G20, G20A, G30A, G40, G40A, G50A, G60, G80, G100, BORNS, RUPERT and KAO. The data sets provide good coverage of the VLE data from about 0?C to 100?C. Only a single data point is available for LLE data, which is the data of Rupert (1909) at 0?C. A good fit of the available data has been obtained by the model.
Table 1. Phase Equilibrium Data Used in data Regression
Dataset Name
Source
Type of Data
Range of Data
BORNS
Landolt-Bornstein
VLE
0.04<x(HCl)<0.11, 1 atm
G0
Perry
VLE
0.04<x(HCl)<0.11, 0?C
G0A
Fritz and Fuget
VLE
0<x(HCl)<0.22, 0?C
G10A
Fritz and Fuget
VLE
0<x(HCl)<0.22, 10C
G20
Perry
VLE
0.03<x(HCl)<0.26, 20?C
G20A
Fritz and Fuget
VLE
0<x(HCl)<0.22, 20?C
G25
Perry
VLE
0.03<x(HCl)<0.26, 25?C
G30A
Fritz and Fuget
VLE
0<x(HCl)<0.22, 30?C
G40
Perry
VLE
0.03<x(HCl)<0.23, 40?C
G40A
Fritz and Fuget
VLE
0<x(HCl)<0.22, 40?C
G50A
Fritz and Fuget
VLE
0<x(HCl)<0.21, 50?C
G60
Perry
VLE
0.03<x(HCl)<0.22, 60?C
G80
Perry
VLE
0.03<x(HCl)<0.19, 80?C
G100
Perry
VLE
0.03<x(HCl)<0.17, 100?C
HASSE
Haase et al.
VLE
0.08<x(HCl)<0.22, 25?C
LUTUGINA
Lutugina and Kokovkina
VLE
0.01<x(HCl)<0.11, 25?C
RUPERT
Rupert
LLE
0?C
VEGA
Vega
VLE
0.05<x(HCl)<0.24, 25?C
Figure 1 presents Txy calculations of the model at 1 atmosphere and 25 atmosphere and comparisons to the Tx data at 1 atmosphere.
Model Calculations and Conclusions
The ElectrolyteNRTL model has been applied to the HCl-water mixture. The model is expected to provide accurate results for the temperature range from 0?C to about 100?C. Above 100?C, the model is expected to provide reasonable extrapolations, but this has not been tested with data. Good results are expected for VLE; the results for LLE are expected to be reasonable, but only limited comparisons with experimental data have been made.
The model is available in Aspen Plus. Calculations for VLE are robust and reliable. Convergence difficulty has been experienced with LLE calculations; for calculations where only two liquids (i.e., no vapor phase) are encountered, the DECANT block seems to be more reliable than FLASH3.
Keywords: hcl
hydrogen chloride
h2o
regression
drs
References: s
Chen, C-C. and L.B. Evans, A Local Composition Model for the Excess Gibbs Energy of Aqueous Electrolyte Systems, AIChE J., 32, 444 (1986).
Chen, C-C., H.I. Britt, J.F. Boston, and L.B. Evans, Local Composition Model for Excess Gibbs Energy of Electrolyte Systems, AIChE J., 28, 588 (1982).
Fritz, J.J, and C.R. Fuget, Vapor Pressure of Aqueous Hydrogen Chloride |
Problem Statement: In the Aspen Plus User Interface Customization Window, when entering the command mmcustom mmtbs to customize the GUI of Aspen Plus or Properties, you get the following message:
F:\Program Files\aspentech\APRSYSTEM 11.1\GUI\Custom>mmcustom mmtbs
Unable to retrieve value of MMTOP from Registry
Unable to retrieve value of MMCOMMONTOP from Registry
\xeq does not contain Aspen Plus user interface files
Aspen Plus customization skipped
Unable to retrieve value of MMTOP from Aspen Properties Registry
Unable to retrieve value of MMCOMMONTOP from Registry
\xeq does not contain Aspen Properties user interface files
Aspen Properties customization skipped | Solution: Use mmcustap instead of mmcustom for Aspen Plus if Aspen Properties is not installed.
Use mmcustpr instead of mmcustom for Aspen Properties if Aspen Plus is not installed.
If both Aspen Plus and Aspen Properties are installed, use mmcustom to do the customization.
Keywords: user databank inhouse
References: : CQ00057586 |
Problem Statement: What is the basis of the Reynolds number? | Solution: The Reynolds number in the Pipe unit operation model output on the Pipe\Results\Stream is the traditional dimensionless Reynolds number. However, the Property Set property RE is a dimensional Reynolds number for a mixture which has units of length.
Re = (mass flow) / (pi/4) / viscosity
The dimensionless Reynolds number may be computer from the property RE by dividing by the pipe diameter.
Reynolds Number = RE / Diameter
The stream does not have diameter information; therefore, it is not possible for Aspen Plus to calculate the traditional dimensionless Reynolds number.
Keywords:
References: None |
Problem Statement: Are UNC paths allowed in DLOPT and DEF files? | Solution: UNC paths (\\servername\sharename\...) are accepted in DLOPT, DEF and command line qualifiers.
This means that customizations can be placed on a central file server for access by everyone. Previously, references to files on servers had to use a mapped drive letter (e.g., x:\AspenFiles\...). The problem was every used had to ensure that they mapped to the fileserver with the identical. Using UNC convention allows you to place items in a central location and reference them from DLOPT or DEF files or from the Run/Settings dialog using a more general path convention.
This also means that packaged User Routines (in DLLs) can be used in WebModels, as long as the published BKP file has the appropriate references to DEF or DLOPT files located in a central file server that is accessible to the WebModels application server.
Here is an example of the contents of the DLOPT file (InhouseDLL.dlopt): ! You can even use a UNC path to reference routines to be dynamically linked \\MyComputer\MyShare\Plug\*.dll
If you have a local version of one of the routines that you are using (for testing, etc), it can still be used in preference to the default system version referenced in the aprsysfiles.def.
Keywords:
References: None |
Problem Statement: How can you model a heat exchanger (HEATX) where the inlets could be either hot or cold? | Solution: 106498
Creation Date: 11-Aug-2003 04:50AM
Applicable Version(s)
11.1
Keywords: HEATX
References: None |
Problem Statement: How do I model ethylene flowsheet properties? | Solution: In general it is best to use the Ethylene property databank. The ETHYLENE databank contains pure component and binary interaction parameters required to model the typical ethylene process. The parameters are for the SRK property method which include the critical temperature, critical pressure, acentric factor and binary interaction parameters. The parameters are available for 85 components commonly encountered in the ethylene process. The ETHYLENE databank should be used with the most recent PURExx databank and the SRK property method.
The data for the Ethylene databank is from Dechema-VLE Data for Low Boiling Mixtures volume 6. All available data for ethylene plant mixtures was used which amounts to a total of over 4900 VLE data points. Pure component vapor pressure data was correlated with the pure component acentric factor. VLE dat was correlated with SRK using the binary interaction parameters.
The ETHYLENE component databank contains data for these parameters:
Property
Description
SRKKIJ
Binary interaction parameter for the SRK equation of state model
(called SRKAIJ and SRKBIJ in 11.1)
SRKOMG
Acentric factor for the SRK equation of state
SRKPC
Critical pressure for the SRK equation of state
SRKTC
Critical temperature for the SRK equation of state
The table below lists the components present in the ETHYLENE component databank:
Alias
Name
AR
ARGON
CCL2F2
DICHLORODIFLUOROMETHANE
CH4
METHANE
CO
CARBON-MONOXIDE
CO2
CARBON-DIOXIDE
C2H2
ACETYLENE
C2H4
ETHYLENE
C2H6
ETHANE
C3H4-1
PROPADIENE
C3H4-2
METHYL-ACETYLENE
C3H6-2
PROPYLENE
C3H7NO
N,N-DIMETHYLFORMAMIDE
C3H8
PROPANE
C4H10-1
N-BUTANE
C4H10-2
ISOBUTANE
C4H4
VINYLACETYLENE
C4H6-4
1,3-BUTADIENE
C4H8-1
1-BUTENE
C4H8-2
CIS-2-BUTENE
C4H8-3
TRANS-2-BUTENE
C4H8-5
ISOBUTYLENE
C5H10-1
CYCLOPENTANE
C5H10-2
1-PENTENE
C5H12-1
N-PENTANE
C5H12-2
2-METHYL-BUTANE
C5H6
CYCLOPENTADIENE
C5H8
CIS-1,3-PENTADIENE
C5H8-1
CYCLOPENTENE
C5H8-3
1-TRANS-3-PENTADIENE
C5H8-4
1,4-PENTADIENE
C5H8-6
2-METHYL-1,3-BUTADIENE
C6H10-2
CYCLOHEXENE
C6H12-1
YCLOHEXANE
C6H12-3
1-HEXENE
C6H14-1
N-HEXANE
C6H14-5
2,3-DIMETHYL-BUTANE
C6H6
BENZENE
C7H14-6
METHYLCYCLOHEXANE
C7H14-7
1-HEPTENE
C7H16-1
N-HEPTANE
C7H16-2
2-METHYLHEXANE
C7H8
TOLUENE
C8H10-2
M-XYLENE
C8H10-4
ETHYLBENZENE
C8H16-1
1,1-DIMETHYLCYCLOHEXANE
C8H16-16
1-OCTENE
C8H18-1
N-OCTANE
C8H18-2
2-METHYLHEPTANE
C8H8
STYRENE
C9H10
ALPHA-METHYL-STYRENE
C9H12-5
1-METHYL-4-ETHYLBENZENE
C9H18-1
N-PROPYLCYCLOHEXANE
C9H18-3
1-NONENE
C9H20-1
N-NONANE
C9H20-D1
2-METHYLOCTANE
C9H8
INDENE
C10H14-9
1,2,4,5-TETRAMETHYLBENZENE
C10H20-1
N-BUTYLCYCLOHEXANE
C10H20-5
1-DECENE
C10H22-1
N-DECANE
C10H8
NAPHTHALENE
C11H10-1
1-METHYLNAPHTHALENE
C11H22-2
1-UNDECENE
C11H24
N-UNDECANE
C12H18-D2
P-DIISOPROPYLBENZENE
C12H24-2
1-DODECENE
C12H26
N-DODECANE
C13H10
FLUORENE
C13H26-2
1-TRIDECENE
C13H28
N-TRIDECANE
C14H10-1
ANTHRACENE
C14H28-2
1-TETRADECENE
C14H30
N-TETRADECANE
C15H24
N-NONYLBENZENE
C15H32
N-PENTADECANE
C16H12
1-PHENYLNAPHTHALENE
C18H12
CHRYSENE
C20H16
TRIPHENYLETHYLENE
C26H20
TETRAPHENYLETHYLENE
H2
HYDROGEN
H2O
WATER
H2S
HYDROGEN-SULFIDE
N2
NITROGEN
O2
OXYGEN
O2S
SULFUR-DIOXIDE
The table below lists the binary pairs present in the ETHYLENE component databank.
Note: In version 12.1, the binary interaction parameter for the SRK model (SRKKIJ) for propane/propylene were been changed from 0.0109753 to 0.003 to improve results in C3 splitter simulation. The Ethylene databank has been changed. If using 11.1, the new value of 0.003 should be entered on the SRKAIJ binary parameter form.
Steps:
Select the PURExx and the ETHYLENE databanks on the Components\Specifications\Databank sheet.
Select SRK as the global property method on the Properties\Specifications\Global sheet.
Other options include PR-BM, RKS-BM, but there are some problems matching temperatures in cold sections.
Note that where water is present, use Vapor-Liquid-FreeWater calculations. Specify SteamNBS or SteamNBS2 for the water property method. Specify water solubility method option 0 - Water solubility in HC phase from solubility data, vapor fugacity of water using free water phase properties (e.g. SteamNBS). This is especially important for water quench towers and CGC sections.
The benefits of using the Ethylene databank with the SRK property method is that we have seen a better temperature match in cold (methane-rich) sections and improved accuracy for tight separations (e.g. C2 and C3 splitters) due to improved binary interaction parameters.
Keywords: ethylene
References: None |
Problem Statement: How can the heat on mixing of a property method be eliminated? | Solution: It is possible to eliminate the heat of mixing of an activity coefficient property method on the Properties \ Specification \ Global sheet.
The steps are as follows:
1. Go to the Properties \ Specification \ Global sheet.
2. Select an activity coefficient based property method such as NRTL or UNIQUAC.
3. Check the Modify property models box.
4. Enter a new name for the property method.
5. Uncheck the Heat of mixing box.
Keywords: heat of mixing
hlxs
References: None |
Problem Statement: How do you enter the boiling point temperature for a component? The boiling point predicted is way too low. | Solution: Boiling point is entered as the scalar property parameter TB on the Properties | Parameters | Pure Component | Scalar form. This value is used in Property Methods and in estimation.
If a parameter is estimated and written back to the forms, it will not be re-estimated. This means that if TB is entered after a parameter such as the Antoine Vapor pressure, PLXANT, has been estimated and written to the forms, the parameter values must be deleted for the newly entered TB to be used in the regression.
To remove estimated parameters from the forms, go to Tools \ Clean Property Parameters and select Clean property parameters placed on input forms. This will remove all of the estimated parameters and will leave only the values that have been entered such as TB.
When the simulation is re-run, the value of TB will be used in the estimation of vapor pressure which will make the normal boiling point calculated match the entered value of TB.
Keywords: None
References: None |
Problem Statement: It is possible to specify that a component is a Hypothetical liquid on the Components \ Specifications sheet. What does this mean? | Solution: A Hypothetical Liquid component type is used when solid properties should be used for a component in the liquid phase. The liquid properties are extrapolated from the solid parameters. It should only be used for small concentrations of the component in the liquid.
This type of component is used for pyrometallurgical applications such as Carbon in steel. Carbon properties only exist for the solid, but carbon can be contained in the molten steel.
Attached is an example where Carbon is used as a hypothetical liquid.
Keywords: hypo-liq
References: None |
Problem Statement: While compiling user FORTRAN code in the Aspen Plus Engine Window the following error may pop up:
gcpp.exe has encountered a problem and needs to close. We are sorry for the inconvenience.
In the Engine window you may also see a FORTRAN error:
f90: Severe: The input stream is empty | Solution: Please check the user code for #include lines such as:
#include ppexec_user.cmn !Passes USER_NHSTRY. (1)
#include dms_plex.cmn !Passes arrays containing component data
The #include lines cannot have comments at the end starting with !. These lines are processed by the pre-compiler and comments are not allowed. The comments must be removed as follows:
#include ppexec_user.cmn
#include dms_plex.cmn
We actually use this currently as an example both in version 12.1 and Aspen One 2004 in the HFUM subroutine in the Aspen Plus Getting Started Customizing Unit Operation Models, Chapter 4, but we will update the documentation accordingly.
If the above does not apply to your particular problem, please report it to our Technical Support team so we can investigate.
Keywords: Getting Started Customizing
References: None |
Problem Statement: In the Sensitivity Results, why is there an extra point at the end that is out of order from the others? | Solution: This is the base case originally specified in the flowsheet. By default, the base case is executed last after the Sensitivity points.
The Execution options are specified on the Optional sheet of a Sensitivity. These options effect when the base case is executed, not just the order the results are printed in the report. Execute base case last is the default. In this case, blocks and streams will be left with the values on the input forms. For the other options, Execute base case first and Do not execute base case, blocks and streams will be left with values from the last row of the sensitivity.
Keywords: sensivitity
References: None |
Problem Statement: Where can I see the atomic mass of the elements as used by Aspen Plus? | Solution: The atomic mass of the atoms are available in the System Definition File (SDF) of Aspen Plus. The values for each atom are listed below and included in the attached excel spreadsheet.
The values are extracted from the SDF by opening an Aspen Plus Simulation Engine window, typing SDFRPT, then entering type 58 (which is the table number that contains the atomic mass). The results are in a text file called sdfrpt.rep.
Atomic Number
Symbol
Atomic Mass
1
H
1.00794
2
HE
4.0026
3
LI
6.941
4
BE
9.01218
5
B
10.811
6
C
12.011
7
N
14.00674
8
O
15.9994
9
F
18.9984
10
NE
20.1797
11
NA
22.98977
12
MG
24.305
13
AL
26.98154
14
SI
28.0855
15
P
30.97376
16
S
32.066
17
CL
35.4527
18
AR
39.948
19
K
39.0983
20
CA
40.078
21
SC
44.95591
22
TI
47.88
23
V
50.9415
24
CR
51.9961
25
MN
54.93805
26
FE
55.847
27
CO
58.9332
28
NI
58.69
29
CU
63.546
30
ZN
65.39
31
GA
69.723
32
GE
72.61
33
AS
74.92159
34
SE
78.96
35
BR
79.904
36
KR
83.8
37
RB
85.4678
38
SR
87.62
39
Y
88.90585
40
ZR
91.224
41
NB
92.90638
42
MO
95.94
43
TC
98.9063
44
RU
101.07
45
RH
102.9055
46
PD
106.42
47
AG
107.8682
48
CD
112.411
49
IN
114.82
50
SN
118.71
51
SB
121.75
52
TE
127.6
53
I
126.90447
54
XE
131.29
55
CS
132.90543
56
BA
137.327
57
LA
138.9055
58
CE
140.115
59
PR
140.90765
60
ND
144.24
61
PM
146.9151
62
SM
150.36
63
EU
151.965
64
GD
157.25
65
TB
158.92534
66
DY
162.5
67
HO
164.93032
68
ER
167.26
69
TM
168.93421
70
YB
173.04
71
LU
174.967
72
HF
178.49
73
TA
180.9479
74
W
183.85
75
RE
186.207
76
OS
190.2
77
IR
192.22
78
PT
195.08
79
AU
196.96654
80
HG
200.59
81
TL
204.3833
82
PB
207.2
83
BI
208.98037
84
PO
208.9824
85
AT
209.9871
86
RN
222.0176
87
FR
223.0197
88
RA
226.0254
89
AC
227.0278
90
TH
232.0381
91
PA
231.0359
92
U
238.0289
93
NP
237.0482
94
PU
244.0642
95
AM
243.0614
96
CM
247.0703
97
BK
247.0703
98
CF
251.0796
99
ES
252.0829
100
FM
257.0951
101
MD
258.0986
102
NO
259.1009
103
LR
260.1053
104
RF
261.1087
105
HA
262.1138
106
D
2.014
107
E-
0.00055
108
T
3.02006
Keywords: molecular weight
MW
atomic number
atomic mass
periodic table
References: None |
Problem Statement: In EO, how do you specify a block result variable for a block that is solved by the perturbation layer? For example, how do you specifying UA in an MHEATX in EO? | Solution: In Aspen Plus 12.1, when blocks are solved by the perturbation layer in EO, EO variables are only created for the streams in and out of the perturbed block. To create EO variables for a block result, the block result must be accessed, either in a Calculator block or a Design-Spec. For example, the following Design-Spec in SM could be be used to specify the UA of an MHEATX block named MHX by varying the outlet temperature of one of its hot-side streams(LP).
DESIGN-SPEC UASPEC
DEFINE UA BLOCK-VAR BLOCK=MHX VARIABLE=UA SENTENCE=RESULTS
DEFINE MITA BLOCK-VAR BLOCK=MHX VARIABLE=MITA SENTENCE=RESULTS
SPEC UA TO 25000
TOL-SPEC 1
VARY BLOCK-VAR BLOCK=MHX VARIABLE=TEMP SENTENCE=HOT-SIDE ID1=LP
LIMITS -200 -180
When this is translated into EO, the following EO variables are created for Design-Spec UASPEC. Note that all are created as Calculated variables.
BLK.$MHXHTR_RESULTS_UA
25000
J/SEC-K
Calculated
BLK.$MHXHTR_RESULTS_MIT
1.71917
DELTA-K
Calculated
VARY.$MHXH01_PARM_TEMP
181.852
C
Calculated
BLK.SPECLH
25000
*
Calculated
BLK.SPECRH
25000
*
Calculated
Instead of making BLK.$MHXHTR_RESULTS_UA Const with value 25,000, the EO implementation writes an additional equation (shown below). This is done because the SPEC fields in the Design-Spec are actually FORTRAN expressions. Although they are individual variables in this case, that is not the general case.
BLK.$SSRHTR_RESULTS_UA - 25000 = 0.
So far, an EO variable has been created, but as a Calc variable. The variable could be switched from Calc to Const, but the problem would no longer be square. Some other variable in the simulation could also be switched from Const to Calc, but it is not always readily apparent what that variable should be, if you want the EO formulation to be similar to the SM formulation.
If you want the Design-Spec to have a variable that is Const, define a Local Parameter with that value and use it in the second Spec field. Here is the Design-Spec with the Parameter for the MHEATX example.
DESIGN-SPEC UASPEC
DEFINE UA BLOCK-VAR BLOCK=MHX VARIABLE=UA SENTENCE=RESULTS
DEFINE MITA BLOCK-VAR BLOCK=MHX VARIABLE=MITA SENTENCE=RESULTS
DEFINE P1 LOCAL-PARAM PHYS-QTY=UA UOM=J/sec-K INIT-VAL=25000.
SPEC UA TO P1
TOL-SPEC 1
VARY BLOCK-VAR BLOCK=MHX VARIABLE=TEMP SENTENCE=HOT-SIDE ID1=LP
LIMITS -200 -180
In EO, the local parameter gets created as a new Const variable. For the MHEATX example, this creates the following EO variables for Design-Spec UASPEC, making it easier to modify the spec value from 25000 to something else in EO.
BLK.$MHXHTR_RESULTS_UA
25000
J/SEC-K
Calculated
BLK.$MHXHTR_RESULTS_MIT
1.71917
DELTA-K
Calculated
BLK.LOCAL_PARAM_P1
25000
J/SEC-K
Constant
VARY.$MHXH01_PARM_TEMP
181.852
C
Calculated
BLK.SPECLH
25000
*
Calculated
BLK.SPECRH
25000
*
Calculated
Keywords:
References: None |
Problem Statement: Is it possible to transfer heating/cooling curves property data from Aspen Plus to HTFS or HTRI? | Solution: This can be done using the program HTXINT.
First you need to create heat/cooling curves in Aspen Plus and select the property set HXDESIGN in the properties to be reported. (This prop-set is available in most Aspen Plus templates). It's a good idea to generate these curves at different pressures (and this is possible).
Then you need to save the simulation as a bkp with the results (.bkp) or export the so-called summary file, from File, Export menu, select summary file (.sum).
To run the interface program HTXINT, you need to open a Customize Aspen Plus Vx.x command window from the Start menu and change to the directory where the bkp or sum file has been saved.
At the prompt, type:
HTXINT name of the bkp without the extension or
HTXINT name of the summary file without the extension
Then this is how this looks like:
D:\New Folder>htxint heatx-water-nc10
+
+ + +
+ + +
+ + + + +
+ + + + + + + + +
+ + + + + + + + + + +
+ + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + + + +
+ + + + + + + + + + + + + + +
+ + + + + + +
+ + +
+ + + ASPEN PLUS Release 10.0
+ + + HTXINT Heat Exchanger Program Interface
+ + + Copyright (c) 1996 Aspen Technology, Inc.
+ + + All rights reserved.
+
Enter ? at any prompt for help.
Please enter the required interface. (B-JAC, HTFS, M-HTFS or HTRI) > M-HTFS
Please select the units to display the data. (SI, ENG or MET) > SI
Please enter the output file name. (Default is heatx-water-nc10.psf)
> test
File D:\New Folder\test.psf opened for output.
The following blocks have Hcurves.
+
Keywords: None
References: None |
Problem Statement: There is a slight difference between the mass flow rate of the hot water, when using a heater block versus a hot water utility. How is the heating / cooling value calculated for the UTILITIES ? | Solution: Based on the inlet and outlet conditions, the utility determines the heating value (heat capacity) of the fluid. When a block uses a utility, the duty of the block divided by the heating value determines the flow rate of the utility needed.
To mimic what the utility is doing, you need to reverse the direction of the heat stream. Then you need a design spec around HEATERH to vary the flowrate to match the outlet temperature. See the attached file Utility_new.bkp.
Keywords: utility
References: None |
Problem Statement: How does the Pipe model calculate entrance and exit effects?
The Pipe model should be able to have the the following fittings:
Pipe entry diameter
Pipe exit diameter
Sudden enlargements
Sudden contractions | Solution: These fittings have been added for Aspen Plus 12.2 and higher. They are added on the Pipe | Setup | Fittings2 sheet.
The K values in this document are taken from Flow of fluids through valves, fittings, and pipes, Technical Paper No. 410, published by the Crane Company (1988).
1. Pipe Entrance
a. Inward Projecting
K=0.78
b. Flush
K depends on the ratio of the radius to the diameter (r/d).
r/d
K
0.0
0.5
0.02
0.28
0.04
0.24
0.06
0.15
0.10
0.09
0.15 & up
0.04
2. Pipe Exit
K=1.0
3. Sudden and Gradual Enlargement: (d1 < d2; Pipe Diameter is d1; beta = d1 / d2)
a. theta <= 45?
K1 = 2.6 x sin(theta/2) x (1 - beta2)2
b. 45? < theta <= 180?
K1 = (1 - beta2)2
4. Sudden and Gradual Enlargement: (d1 < d2; Pipe Diameter is d2; beta = d1 / d2)
a. theta <= 45?
K2 = K1 / beta4 ; K1 = 2.6 x sin(theta/2) x (1 - beta2)2
b. 45? < theta <= 180?
K2 = K1 / beta4 ; K1 = (1 - beta2)2
5. Sudden and Gradual Contraction: (d1 < d2; Pipe Diameter is d1; beta = d1 / d2)
a. theta <= 45?
K1 = 0.8 x sin(theta/2) x (1 - beta2)
b. 45? < theta <= 180?
K1 = 0.5 x sqrt(sin(theta/2)) x (1 - beta2)
6. Sudden and Gradual Contraction: (d1 < d2; Pipe Diameter is d2; beta = d1 / d2)
a. theta <= 45?
K2 = K1 / beta4 ; K1 = 0.8 x sin(theta/2) x (1 - beta2)
b. 45? < theta <= 180?
K2 = K1 / beta4 ; K1 = 0.5 x sqrt(sin(theta/2)) x (1 - beta2)
Keywords: None
References: None |
Problem Statement: Is there a data package (or electrolyte insert) for the system of H2SO4 + SO3? | Solution: AspenTech has developed an Insert for this type of system, but it is not included with the general Aspen Plus release. This package should be treated as AspenTech confidential.
Oleum Package Contents:
The Aspen Inorganics Oleum package contains a report and four Aspen Plus bkp files.
The report file is in pdf format and describes the approach to sulfuric acid modeling and provides selected results.
The Aspen Plus bkp files are as follows:
OLEUMDRS.BKP SO3 partial pressure data regression file RHODRS.BKP Oleum density data regression file HMIXSEN.BKP Heat ofSolution sensitivity study file OLEUMINS.BKP Oleum data package insert file
The four bkp files provide details on the basis of the Oleum package and facilitate the development of simulation models using the Oleum package.
OLEUMDRS.BKP deals with the representation of the vapor-liquid equilibrium of the oleum system, in particular the partial pressure of SO3.
RHODRS.BKP deals with the representation of the density of oleum mixtures.
HMIXSEN.BKP uses Aspen Plus to display the heat of mixing of water SO3 mixtures. It has been used to ensure that the Oleum package provides an accurate representation of the heat of mixing of oleum mixtures.
OLEUMDRS.BKP, RHODRS.BKP and HMIXSEN.BKP provide background information and are not necessary to use the Oleum data package to develop plant simulations.
The oleum data package has been prepared as an Aspen Plus bkp file called OLEUMINS. The insert file contains all necessary paragraphs for identifying COMPONENTS, DATABANKS, PROPERTIES, and PROP-DATA. To invoke the insert file, simply open it and add the flowsheet, or import this file into an existing simulation using standard Aspen Plus procedures.
Overview
Scope of Data Package
The data package includes physical property parameters for vapor-liquid equilibrium calculations, enthalpy and heat capacity calculations and density calculations. The data package is to be used within Aspen Plus for the purpose of simulating the oleum absorption towers in sulfuric acid plants.
Three apparent components have been included in the data package:
1. H2O water
2. H2SO4 sulfuric acid
3. SO3 sulfur trioxide
There are three ionic species present in the oleum system:
1. H3O+ - hydronium ion
2. HSO4- bisulfate ion
3. SO4-2 sulfate ion
In addition, it is known that a sulfuric acid-sulfur trioxide complex, pyro-sulfuric acid, is formed:
H2S2O7 pyro-sulfuric acid
The data package covers a concentration range from 0 to 100% sulfuric acid and to 100% oleum (or 100% SO3). The temperature range for the data package is ambient to 300?F. The pressure range is vacuum to 30 psia. The data package and related files are delivered as Aspen Plus bkp files.
Data Used
Literature data were searched, compiled, evaluated, and fitted to determine the necessary physical property parameters for the pure components and the binary pairs of the oleum system. The literature data include pure component data, vapor-liquid equilibrium data, density data, heat capacity data and heat of mixing data.
Validation
The performance of the data package is judged to be accurate and reliable based on the successful regression of available binary and ternary system data. In addition, the package was found to give good results for a number of operating oleum absorption towers.
Documentation
This report describes the thermodynamic basis of physical property representation, the pertinent references and data sources used, the data regression runs, and the oleum physical property bkp file itself.
Deliverables
The deliverables include electronic media containing the data package documentation, the oleum physical property parameters (in the form of an Aspen Plus bkp file), and the Aspen Plus data regression input files.
Technical Discussion
Technical Basis for the Physical Property Representation The fundamental strategies in developing the data package were to properly account for theSolution chemistry of the oleum system and to use the ElecNRTL equation as the activity coefficient model to capture the nonideal behavior of the oleum system. All existing phase equilibrium data and other pertinent thermodynamic data related to the oleum system were compiled and regressed to determine theSolution chemistry and the ElecNRTL interaction parameters.
TheSolution Chemistry
As stated earlier, there are three apparent components in the oleum system
Water
Sulfuric acid
Sulfur trioxide
Sulfuric acid is solvated by water to form ionic species: hydronium ion, bisulfate ion and sulfate ion. In addition, a sulfuric acid-sulfur trioxide complex, pyro-sulfuric acid, is formed. ThisSolution chemistry represents the majorSolution nonideality for the oleum system. ThisSolution chemistry can be summarized as follows:
H2O + H2SO4 --> H3O+ + HSO4-
H2O + HSO4- --> H3O+ + SO4-2
SO3 + H2O --> H2SO4
SO3 + H2SO4 --> H2SO7
The chemical equilibrium constants for the first three reactions are known since the Gibbs energies of formation for the participating reactants and the products are well established in the literature. However, the chemical equilibrium constant for the fourth reaction must be regressed from the available SO3 partial pressure data in the oleum system because the thermodynamic properties of pyro-sulfuric acid are not known.
The Electrolyte NRTL Model
The Electrolyte Non-random Two Liquid (ElecNRTL) model has been used to represent the activity coefficients of the various true species in the oleum system. The model was originally proposed by Chen et al. (1982) and Chen and Evans (1986) as an excess Gibbs energy expression for aqueous electrolytes and mixed-solvent electrolytes (Mock et al, 1986). The model has proved to be very successful in representing thermodynamic properties of various aqueous and mixed-solvent electrolyte systems (Chen et al., 1999), and systems containing zwitterions (Chen et al., 1989).
The model assumes that there are two contributions to the excess Gibbs energy of electrolyte systems. The first contribution accounts for the local interactions between ion and ion, between molecule and molecule, and between ion and molecule. The second contribution accounts for the long-range ion-ion interactions. The local interaction contribution is represented by a modified form of the Non-random Two Liquid (NRTL) equation. The long-range interaction contribution is represented by the combination of the Pitzer-Debye-Huckel equation and the Born equation.
Note that the Born term is used to account for the Gibbs energy of transferring charged species (ions and zwitterions) from the infinite dilution state in pure water to the infinite dilution state in a mixed solvent. In the absence of nonaqueous solvents, the Born term reduces to zero.
The main adjustable parameters with the Electrolyte NRTL model are the binary interaction energy parameters, t, associated with binary molecule-molecule pairs, binary molecule-electrolyte pairs, and binary electrolyte-electrolyte pairs. There are two binary interaction energy parameters per binary pair since the binary parameters are asymmetric. Being neutral molecular solvent species and zwitterionic species are considered as molecules, while cation-anion pairs are treated as electrolytes in the context of the Electrolyte NRTL model.
For further details of the Electrolyte NRTL model, please refer to the work of Chen et al. (1982, 1986).
The Clarke ElectrolyteSolution Density Model The Clarke model is used to calculate the densities of aqueous electrolyteSolutions. It can be used for single or multiple electrolyte systems and is capable of handling molecular components. The model is designed to provide a high degree of accuracy for most electrolyte systems from a minimum of data.
Pure Component Properties
The Aspen Plus Pure Component databank provides the pure component physical property parameters for all components except pyro-sulfuric acid. The physical property parameters of pyro-sulfuric acid were assumed to be same as those of sulfuric acid, except molecular weight and ideal gas heat of formation. These two properties are critical to mass and enthalpy balance calculations.
Data Compilation
A literature search was carried out for the oleum system. The data sources are summarized below:
Specific Heat and Enthalpy
Specific heat at 20?C, up to 100% sulfuric acid: Perry, R.H. and C.H. Chilton, Chemical Engineers' Handbook, 5th Ed., p 3-135, McGraw-Hill, New York, 1973.
Heat capacity of oleum at 20?C: Kirk-Othmer Encyclopedia of Chemical Technology, 3rd. Ed., Vol. 22, pp. 190-232, John Wiley & Sons, New York (1983).
Enthalpy - concentration chart for the system H2O-SO3: Ross, W.D., Chemical Engineering Progress, pp. 314-315, June, 1952.
Heat ofSolution of the system sulfur trioxide - water: Morgen, R.A., Industrial and Engineering Chemistry, pp. 571-574, May, (1942).
Heat of formation of oleums from sulfur trioxide and water: Herrmann, C.V., Industrial and Engineering Chemistry, pp. 898-899, July, (1941).
Vapor-Liquid Equilibrium
Partial pressures of H2SO4 and H2O over sulfuric acidSolutions: Perry, R.H. and C.H. Chilton, Chemical Engineers' Handbook, 5th Ed., Page 3-65, McGraw-Hill, New York, 1973.
Partial pressures of SO3 over fuming sulfuric acid (up to 115% H2SO4): Perry, R.H. and C.H. Chilton, Chemical Engineers' Handbook, 5th Ed., Page 3-65, McGraw-Hill, New York, 1973.
Physical - chemical analysis of the H2O-SO3 system. 1. vapor-liquid phase equilibrium in the H2O-SO3 system: Lutchinsky, G.P., Zh. Fiz. Khim., 30(6), pp. 1207-1222 (1956).
The vapor pressure of oleum: Miles, F.D., H. Niblock and G.L. Wilson, Transactions of the Faraday Society, No. 226, pp. 345-356 (1940).
The vapor pressure of the system sulfuric acid-disulfuric acid: Brand, J.C.D. and A. Rutherford, Journal of the Chemical Society, pp. 3916-3922 (1952).
Vapor pressure studies of sulfur trioxide and the water-sulfur trioxide system: Colwell, J.H. and G.D. Halsey, Jr., J. of Phys. Chem., Vol. 66, pp. 2179-2182 (1962).
Dampfdruckmessungen an dem system H2SO4/SO3: Remy, H. and W. Meins, Berichte der Deutschen Chemischen Gesellschaft, Jahrg. 75, Nr. 12, pp. 1901-1911 (1942).
Density
Critical temperatures and densities of the H2O-SO3 system: Stuckey, J.E. and C.H. Secoy, Journal of Chemical and Engineering Data, Vol. 8, No. 3, pp. 386-386 (1963).
Density of oleums vs temperature: Kirk-Othmer Encyclopedia of Chemical Technology, 3rd. Ed., Vol. 22, pp. 190-232, John Wiley & Sons, New York (1983).
Data Regression
Two Aspen Plus input files have been prepared to perform data regression for the available literature data. These two files are included in this package as bkp files, and are demonstrated as input files in Appendix A.
Note that AspenTech had already developed the necessary parameters for the H2O-H2SO4 binary system. The input files prepared in this study are concerned with the addition of SO3 to the system.
The first data regression input file deals with the determination of the chemical equilibrium constant for reaction (2d). The SO3 partial pressure data of Perry and Chilton (1973) were used in the regression. It should be noted that the vapor-liquid equilibrium data of Lutchinsky (1956) were included in the input file. However, these SO3 partial pressure data were found to be too low and they were excluded from the data regression.
The second data regression input file deals with the determination of the compressibility factors of the Rackett equation for SO3, H2SO4 and H2S2O7. The oleum density data of Kirk-Othmer (1983) were used. It was interesting to find that it was possible to regress the density data only after we have identified the correct chemical equilibrium constant for reaction (2d). The reaction (2d) has a dramatic impact to the density of oleum systems. The overall consistency of the results increase confidence in the consistency of the results.
The standard deviations of the data have been assigned with the following values:
Isothermal VLE Data
Standard Deviation
Temperature
Error free
Pressure
10%
Composition
0.01 wt% for liquid phase compositions
error free for vapor phase compositions
Density Data
Standard Deviation
Temperature
Error free
Composition
Error free
Specific gravity
0.01
The Aspen Plus data regression system does not allow regression of heat ofSolution data. Therefore, a special Aspen Plus sensitivity study input file has been created to allow manual adjustment to the ideal gas heat of formation of H2S2O7 to match the heat ofSolution data of Morgan (1942). The sensitivity study input file (HMIXSEN) is also included in Appendix A.
The Oleum Data Package Insert
The oleum data package has been prepared as an Aspen Plus bkp file called OLEUMINS. An Aspen Plus input file demonstrating the parameters of OLEUMINS.BKP id presented in Appendix B.
The insert file contains all necessary paragraphs for identifying COMPONENTS, DATABANKS, PROPERTIES, and PROP-DATA. To invoke the insert file, simply open it and add the flowsheet, or import this file into an existing simulation using standard Aspen Plus procedures.
Note that the delivered data package has been expanded to include N2, O2, CO2 and SO2. However, the parameters associated with these additional components have not been reviewed or validated. These additional parameters are mainly indicative of the parameters necessary to properly handle these components.
Keywords: sulfuric
sulfur trioxide
electrolyte
H2SO4
SO3
insert
package
oleum
References: s
Chen, C.-C., H.I. Britt, J.F. Boston, and L.B. Evans, AIChE J., 25, 820 (1982).
Chen, C.-C. and L.B. Evans, AIChE J., 32, 444 (1986).
Chen, C.-C., Y. Zhu, and L.B. Evans, Biotechnology Progress, 5, (3), 111-118 (1989).
Chen, C.-C., P. M. Mathias and H. Orbey, AIChE J., 45, 1576 (1999).
Clarke, M., private communications (1984).
Mock, B., L.B. Evans, and C.-C. Chen, AIChE J., 32, 1655 (1986). |
Problem Statement: What is the clearance factor used in the compressor block COMPR when type is positive displacement (reciprocating)? | Solution: The clearance fraction (also called clearance factor) measures the amount of extra spacing (clearance) that is available for vapor to expand to during compression stroke.
The clearance fraction is equal to clearance volume (minimum volume between cylinder head and piston) over the piston stroke volume.
The clearance fraction is used to calculate the volumetric efficiency. SeeSolution http://support.aspentech.com/webteamcgi/SolutionDisplay_view.cgi?key=108625 for further details.
Keywords: Compr
pressure change
References: None |
Problem Statement: The Hcurve input form (available for Radfrac, Flash2 & Flash3, Heater, Heatx, etc.) has a pressure drop field. How can the user generate isobaric hcurve data at pressures other than the inlet or outlet pressures? | Solution: In version 12.1 and earlier, the Hcurve has the following Pressure Profile Options:
Option
Profile
Constant
Isobaric using the unit's outlet pressure
Linear2
Interpolated linearly between [Pin and (Pin-DP)]
Linear3
Interpolated linearly between [(Pout + DP) and Pout]
Outlet
Isobaric using the unit's outlet pressure (same as the CONSTANT spec).
Inlet
Isobaric using the unit's inlet pressure
MidPoint
Isobaric using [(Pin + Pout) / 2]
So, to get an isobaric hcurve, use one of the isobaric pressure profiles: Constat, Outlet, Inlet or MidPoint.
In version 2004 and later, 2 more isobaric options were added:
Option
Profile
Constant2
Isobaric using Pin - DP
Constant3
Isobaric using Pin + DP
If you are not sure which of the above pressure profile options best suits your needs, enter multiple HCurves, one using each pressure profile type of interest.
Keywords: Hcurves, heating curves, cooling curves, isobaric, linear
References: None |
Problem Statement: Can you compare using a rate-based distillation model vs. using an equilibrium stage model with efficiencies? | Solution: The RadFrac distillation model in Aspen Plus offers both equilibrium and rate-based modeling options. There are a number of factors to consider in determining when it is appropriate to use the equilibrium approach or the rate-based option.
Equilibrium-stage approach with efficiencies
Equilibrium-stage distillation models are among the most commonly used models in process simulators. Process engineers are familiar with specifying distillation problems using the equilibrium-stage approach, andSolution algorithms in models such as RadFrac are well-established and robust for a wide range of systems. Because of the ubiquity of equilibrium-based models, it is convenient for users to specify efficiency factors to introduce non-equilibrium behavior into equilibrium-stage models.
For equilibrium-stage models, you can specify Vaporization or Murphree efficiencies. Aspen Plus provides the flexibility of entering Vaporization or Murphree efficiencies for stages or for column sections. Component efficiencies can also be entered for specific components on a given stage or column section.
Although convenient, the use of equilibrium stage models with Vaporization and Murphree efficiencies has certain limitations. Efficiency factors will vary with column conditions (flow, temperature, pressure). This means that they are not predictive and generally do not extrapolate well to other conditions. Also, efficiencies will not work well in reactive systems because the mass transfer due to kinetic or equilibrium reactions is not related to the phase equilibrium driving force, and should not be used in such systems.
If Murphree component efficiencies are used, the maximum number of component efficiencies (if liquid phase saturation is assumed) is the number of stages times the number of independent component efficiencies per stage (c-1, where c is the number of components). This is a large a number of adjustable parameters to try to fit to a limited set of operating data. The typical practice is to specify or adjust only one or two component efficiencies per column or column section to try to match operating data and let the other component efficiencies default to unity. This approach allows users some ability to conveniently match operating data, but may result in the condition that the liquid phase may not be at saturation.
Using Vaporization efficiency effectively changes the K-values for vapor-liquid equilibrium which are calculated by property models, altering the volatility of components. This changes the equilibrium condition so that the calculated vapor and liquid phases may not be at saturation.
Efficiency approaches should be used with care, as non-judicious specification of efficiency values can lead to unrealistic column results. Whenever possible, efficiency values should be calibrated against plant data. Extrapolation to other conditions is not recommended.
Rate-based approach
As an alternative to using Vaporization and Murphree efficiencies with the equilibrium modeling approach, RadFrac also provides a rigorous rate-based modeling option that avoids some of the shortcomings associated with the efficiency approach.
The rate-based distillation model uses mass and heat transfer correlations based on transfer properties and tray/packing geometry to predict column performance, without the need of efficiency factors. The rate-based model balances gas and liquid phase separately and considers mass and heat transfer resistances according to the film theory by explicit calculation of interfacial fluxes and film discretization. The film model equations are combined with relevant diffusion and reaction kinetics and include the specific features of electrolyteSolution chemistry, electrolyte thermodynamics, and electroneutrality where appropriate. The hydrodynamics of the column is accounted for via correlations for interfacial area, hold-up, pressure drop, and mass transfer coefficients.
Users of the rate-based model will need to provide more input parameters, including tray geometry data and information for heat and mass transfer correlations and calculation of interfacial areas. However, the RadFrac rate-based option has default values for many of these parameters. The rate-based approach also require accurate properties, kinetic and equilibrium constants. With reasonable values for these parameters, the rate-based approach can be predictive for a wide range of conditions.
The rate-based model also has adjustable parameters such as the interfacial area factor and the heat transfer factor that can be used to calibrate the model more accurately to actual operating data. Once the column is calibrated to one set of conditions, it does generally extrapolate to other conditions. This added degree of rigor is especially critical for modeling gas scrubbers, sour water strippers, azeotropic systems, reactive distillations, nitric acid absorption columns, narrow-boiling separations, and other highly non-ideal separation processes.Â
Note: Users of the RadFrac model can easily switch between the equilibrium mode and the rate-based mode.
Keywords: RADFRAC
column
tower
efficiencies
rate-based distillation
RateSep
References: None |
Problem Statement: What can be done when an electrolyte column fails to converge? | Solution: Following is a list of things to try:
Check if the column specifications are feasible. The things to check include flow rate, concentration, non-condensible gases, heavy component, etc.
Remove any design specifications.
If using the apparent approach, switch to the true-component approach. In the true-comps approach, the K-values are less composition dependent which may improve column convergence. The exception is with HCL systems, some HCL columns work better with the apparent component approach.
When switiching between true and apparant approach, it is best to reinitialize the tower to get rid of potential compositional mismatches. For example, when one switches to the true approach, Aspen Plus has to account for the starting concentration on the various trays of the ionic and salt species listed in the component list. If these components did not previously exist while running the apparent mode, these compositions are estimated which can lead to convergence problems. In systems with salts, the estimated salt concentrations will often be not feasible for the tower. Even in systems without salts, numerical instability can occur.
Provide good composition profiles on the Estimates form. Please note the following regarding composition estimates:
It is important that the appoach matches the the composition estimates, i.e. if running using true approach and the estimates were given for the apparant components only, a mismatch for the calculated compositions of the ionic species will occur.
Consider switching from the Standard Convergence method on the Setup\Configuration sheet to the Strongly non-ideal liquid method which uses the Nonideal algorithm which has been very successful in some cases.
Adjust Kmodel. Try setting Kmodel to Y or X on the Convergence\Advanced sheet. Kmodel defines the temperature dependency of K values in a local property model.
Increase the value of RMSOL1 on the Convergence\Advanced sheet. The default is 0.1. Increasing the value will make the Broyden method used earlier in the outside loop.
Quite often electrolytic towers may need some convergence damping (Convergence\Dampening = Mild). It is usually a good idea to increase the maximum iterations to at least 100 when dampening is turned on.
For electrolytic absorbers or strippers, set the Absorber-Stripper field to Yes on the Convergence\Advanced sheet when using the Standard convergence method. This quite often improves convergence.
Keywords: radfrac
electrolyte
References: None |
Problem Statement: What is the purpose of MAWP temperature in Pressure Relief? It does not seem to have an effect on my simulation | Solution: The maximum allowed temperature in the vessel is the HIGHER value of 3000 Kelvin or MAWP Temperature specified by the user.
So if MAWP specified < 3000K, then you will not see it have an effect on the simulation.
Keywords:
References: None |
Problem Statement: The critical temperature of SO2 and SO3 are much higher than room temperature, however SO2 is handled by the electrolyte wizard as a Henry component but not SO3. Moreover there's no reaction generated for SO3 (e.g H2SO4 <==> SO3 + H2O.)
I have seen also that H3PO4 is handled as a Henry component by the electrolyte wizard while its critical temperature is around 756C.
Why? | Solution: The choice is arbitrary and depends on what data is available or regressed. It is often simpler to use Henry's law to model the solubility of a component when the solubility is small. The Henry's law formulation does not preclude its usage when the component is not supercritical; however, it is not generally done.
No reaction for SO3 is supplied by the electrolyte wizard because we did not have data for the system. See theSolution 104108 for some data specific to SO3/H2SO4 system.
Keywords: elecnrtl
elec wizard
References: None |
Problem Statement: How do you change the default version of Aspen Plus? | Solution: The last version installed is the default version by default.
To change the default version (12.1 only),
Go to the Start -> Programs -> AspenTech -> Aspen Engineering Suite -> Aspen Plus 12.1 -> Aspen Plus Registry Fix Utility.
This will run apregfix.exe that is located in Program Files\Common Files\AspenTech Shared.
Select the desired default version from Aspen Plus 10.2, 11.1 and 12.1.
The registry will be reset for the selected version.
This utility can also be used to repair installations that have become corrupt.
Keywords: apregfix
regfix
References: None |
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