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Problem Statement: The control panel does not show all the run messages, it cuts off some important sections, for example the calculation sequence in the beginning of the messages. | Solution: The control panel buffer is limited to 200000 characters and 5000 characters when simulation is running. This was done for performance reasons. It is NOT to configurable since increasing the buffer size has drastic effects on the performance when the control panel is open during run or when it is opening.
This behavior is documented in the help on the Viewing Simulation Status Using the Control Panel Status Messages page. As suggested by that help topic, clicking on History on the Home ribbon will bring up the history file which contains all the simulation messages along with the calculation sequence. This file can be searched to easily find a particular section or keyword.
Keywords: None
References: : CQ00581647, CQ00494445 |
Problem Statement: When setting a Rupture Disc under the Safety Analysis Environment, when you use the Relieving Phase Method as Flow Resistance method and check the Sizing case results, the results are no generated, they appear as <empty>. | Solution: In order to avoid this, the following procedure must be followed:
1. Having created a Rupture Disc on any stream, create a scenario under the new rupture disc:
2. Set the pressure under PRD Data | PRD specifics | Set Pressure:
3. Under Scenario tab, click on Sizing Case:
4. Add some data under Line Sizing tab:
5.  Under Scenario Setup, you can see that the results are <empty> using Flow resistance as Relieving Phase – Method:
6. Â If you change the method to any and come back to this one again the results will be shown.
The above explained is because the Flow Resistance (L/D) Method is very different from the other calculation methods. When it is chosen, the user must specify the rupture disk diameter and it calculates the actual flow. With the other methods, the user specifies the flow and we calculate the rupture disk diameter. So, if this method is used, the Calculated RD Diameter and Calculated RD Area on the Scenario/Setup form will always be <empty>.
Keywords: Safety Analysis, PSV, Rupture Disc, Relieving Phase Method
References: None |
Problem Statement: I've two fluids with viscosity of 1 cP (WATER) and another at 100 cP (COMP2) 0C, I wish to use a mass average mixing law:
           ln (mumx) = x1 ln(MU1) + x2 ln(MU2)
With
           x = mass fraction
           MU =Viscosity
With an excel calculation I should get approx 10 cP but with the Aspen Plus file it is defaulting to 2 cP. | Solution: There is the MUASPEN model to calculate mixture viscosity by mole or mass fraction. The option code determines the mole or mass fraction.
Aspen Liquid Mixture Viscosity Model (MUASPEN) is a correlative model and it is essentially a new mixing rule for calculating the mixture viscosity from the pure component viscosities. It requires the pure component liquid viscosities being calculated by another model before the mixture liquid viscosity can be calculated. To ensure this prerequisite, the route MULMX14 was created particularly for this model. To use this model in a property method you create, you should specify or change the route for MULMX to MULMX14 rather than changing the mixture liquid viscosity model to MUASPEN directly.
The option codes determine if the viscosity is weighted by mole or mass fraction.
Model
Option Code
MUASPEN
0
Mixture viscosity weighted by mole fraction (default)
1
Mixture viscosity weighted by mass fraction
The steps to modify the viscosity calculation are as follows:
1. On the Properties | Property Methods | Routes sheet, the MULMX route is changed to MULMX14.
2. On the Properties | Property Methods | Routes sheet, select the MULMX model and click on the Option Codes button. Change the option code to 1 for mass fraction averaging.
An example file that can run in V7.3 and higher is attached.
Keywords: MULMX
References: None |
Problem Statement: Murphree efficiency cannot be used with the true species approach with Gibbs free energy, but vaporization efficiency can be used. Why is this? | Solution: Murphree efficiency is not valid for a reactive system. You may get a reasonable result but it is only by chance.
The Murphree efficiency is used to account for departure from phase equilibrium stage only. It really should not be used for reactive systems (kinetic or equilibrium reactions) at all as the amount of mass transfer/conversion due to the fact that reactions are un-related to the phase equilibrium driving force (y(eq)-y(in)). This argument does not apply to the apparent component approach where all reactions are handled in the properties and the column only deals with the phase equilibrium problem in apparent compositions.
There are no restrictions on vaporization efficiency at all since this method is basically just modifying the k-value.
Keywords: None
References: : CQ00575710 |
Problem Statement: I looked at | Solution: 131011 and I wasn't able to find my combination of fortran compiler and visio studio. Is it possible to add it manually?
Solution
You can try adding your own configuration to the compilers.cfg file fromSolution 131011. You can open the compilers.cfg file using notepad, and you will notice that there are multiple blocks of statements of the same form:
In order to add your own setup, you will have to create a new entry, and make sure that the variables IFDIR, VSDIR, and SDKDIR are pointing to the right location. In order to do this, you will need administrator rights as you will need to access the registry editor.
Steps:
1. Run the select compiler utility for aspen plus found under Start | All Programs | AspenTech | Process Modeling VX.X | Aspen Plus | Select Compiler for Aspen Plus.
2. You'll notice that there is a path at the very top of the command prompt. Copy this path into windows explorer to be led to the directory with the compilers.cfg file being accessed.
Stop at xeq so that the compilers.cfg file does not open automatically
Note the AprSystem version it is accessing. It should be the latest version, but sometimes it is not.
3. Open the compilers.cfg file and copy and paste one of the blocks of text to the bottom of the list. Make sure you copy from “Begin,” to “End.” Name it something unique so that it is easy to tell apart from the prebuilt files.
4. The procedure will be the same for IFDIR, VSDIR, and SDKDIR. As an example, we will look at editing the SDKDIR path.
5. Open the registry editor by going to the start menu and typing in regedit. Click on the icon that says regedit next to it to access the registry.
6. Following the path on SDKDIR line, we see that path is for HKEY_LOCAL_MACHINE. Open the HKEY_LOCAL_MACHINE folder, and then navigate to SOFTWARE|Microsoft | Microsoft SDKs |Windows
7. On this machine, however, we notice that the SDKDIR installation path is under Windows | v7.0A | InstallationFolder. This means that we have to overwrite this path in our block of custom text.
8. We repeat steps 6 and 7 for VSDIR and IFDIR, and end up with the following block, edited to match the machine specifications.
9. After saving, you can run the select compiler utility and your custom set up will show up.
10. Type the number into the prompt at the bottom of the screen, and you should be able to run fortran no problem.
Keywords: Fortran, aspcomp, regedit, custom
References: None |
Problem Statement: How to plot Consistency Test results from NIST TDE experimental data. | Solution: The NIST TDE has the capability to perform consistency test over VLE data. This test tells the user how well the calculated data fits the experimental data. The easiest way to review the results is by plotting the consistency test results together with the experimental points.
The following procedure shows how to perform the consistency test and how to plot the results.
1. Open the NIST TDE. Select a??Binary mixturea??, choose the components and click a??Retrieve dataa??. Wait while the NIST TDE retrieves the binary data.
2. Select the experimental data group desired and click a??Consistencya?? in order to perform the consistency test.A Wait while the NIST TDE performs the consistency test.
3. Once the consistency test was performed the a??Consistencya?? button will change to a??Resulta??. Click a??Resulta?? and the consistency test results window will pop out with information for the four different consistency tests.
4. Click any of the four tests at the top to see the results of that test and click Plot.
The four consistency tests available are: Herington Test, Van Ness Test, Point Test, and Infinite Dilution Test.A Each of the four tests TDE determines the consistency of the data on a pass-fail basis.A For more information about each consistency test and to review the calculation details please refer to the NIST TDE user guide which can be found in the following link.
NIST TDE 103B - Pour Compounds, Binary Mixtures, and Chemical Reactions User Guide
http://trc.nist.gov/TDE/Help/TDE103b/
Keywords: NIST TDE, Consistency Test, Binary Mixture, VLE
References: None |
Problem Statement: How do you model a Fired Heater? | Solution: An industrial furnace or direct fired heater is used to provide heat for a process. They are used in boiler applications in chemical industries or for providing heat to chemical reactions for processes like cracking. The heat energy to fuel a direct fired heat is supplied directly by fuel combustion. In Aspen Plus, a fired heater for steam generation can use an RSTOIC to model the combustion reactions with a heat stream to a HEATER to model the steam generation.
Attached is an example of a fired heater used for steam generation that will run V7.3 and higher.
Components:
Water (H2O), methane (CH4), CO2, N2, O2,
Physical Properties:
The ASME 1967 Steam Table correlation is used to compute the properties of steam and water passing through the heater.
Parameters for all the components exist in the Aspen Plus pure component databases.
Unit Operation Models:
An RSTOIC block is used to model the combustion of the fuel.
The duty from the combustion is transferred to a HEATER block in which the steam generated.
Keywords: Fired heater
References: None |
Problem Statement: What does it mean when you receive a warning like this on the control panel?
Flowsheet Analysis :
* WARNING DURING FLOWSHEET ANALYSIS
BECAUSE TEAR-VAR=NO IN CONV-OPTIONS, AN INFORMATION TEAR:
STREAM $WRV34 FROM PCAFL TO FST$3PCA
WILL NOT BE CONVERGED BY A CONVERGENCE BLOCK. THIS MAY CAUSE
CONVERGENCE PROBLEMS OR MISLEADING RESULTS. IF THIS STREAM IS
A TEAR, SET TEAR-VAR=YES IN CONV-OPTIONS TO CAUSE IT TO BE
CONVERGED. OTHERWISE, PLEASE CHECK THE LOCATION OF FORTRAN
BLOCK PCAFL IN THE SEQUENCE AND CONSIDER MOVING
IT BY USING THE 'EXECUTE' KEYWORD OR OTHER METHODS. | Solution: This result is a warning that the variables are not being reconciled after they exit the calculator block. Since the calculator blocks modify the results of some streams, this causes the results to be wrong. You should tear these variables.
Calculator blocks were originally designed as a feed forward controller for an Aspen Plus simulation. However, you are not prohibited from using a Calculator block in feedback mode instead of feed forward mode. The Calculator variables that are used in feedback mode are the INFORMATION TEAR variables. One example of a variable used in this way would be when a Calculator block is used to set the Make-up flow for a recycle.
To tear a variable of a calculator:
1. Within the data browser, navigate to: Convergence | Conv Options | Defaults
2. Select the Sequencing, Tab
3. Check the Tear Calculator export variables, option
Despite removing the error, you might find that those errors and warnings are the total accumulation over the course of all the iterations; as long as the final iteration does not return any errors or warnings, it is fine. If Results Available, is displayed at the bottom right hand of the simulation window, then you are good to go.
As a check, one can track the progress of a variable that does not converge within the set number of turns in a $OLVER loop. By the end of the control panel messages, you will notice that it converges within the set number of times in the $OLVER loop, allowing the simulation to go on solving other blocks.
Solution 102299 has an example that needs to tear a Calculator write variable.
Keywords: v7.3.2, v8.0, calculator block, tear, convergence, flowsheet analysis
References: None |
Problem Statement: How to check the energy balance of a simulation using a Mixer?
Sometimes there are different units in a simulation that consume energy as compressors or pumps, and some others that produce energy, as turbines. One way to check the total energy balance of the simulation is by adding a Mixer.
Applicable versions
All versions. | Solution: When there are different units in a simulation that can produce energy (turbines) or consume energy (pumps, compressors, etc), in order to check the global energy balance, a MIXER unit can be used.
Streams used in this case are WORK streams and all of them must be fed to the mixer. An example is shown below:
As the outlet stream of the Mixer, one work stream is specified and results will indicate the global value of the energy balance.
As the energy is produced by the system is negative by convention, remember that the energy consumed by the system is always positive.
Keywords: Energy balance, Compressor, Turbine, Pump.
References: None |
Problem Statement: The definition of property sets for liquid-liquid equilibrium properties require careful definition by the user. In particular, the parameter KLL2 (Liquid-liquid K-value), and the mixture molar volumes are considered, as they are required for the calculation of the commonly reported ‘partition coefficient’ (check | Solution: s 142057 and 142955).Solution
The variation of these properties as a function of temperature or pressure, for example, can be done by defining an Analysis. This has several advantages:
-parametric studies as a function of system variables (p and T) can be calculated and plotted
-thermodynamic method for the analysis can be defined to a different one than that used in the main flowsheet, and can be easily changed.
We can either use the Properties or the Simulation environment (find detailed procedures below). In both cases, please note the most critical steps:
-Defining the type of Analysis appropriately (it has to be Stream Analysis in the Simulation environment).
-Setting correctly the parameters in the Qualifiers tab of property sets.
-Defining correctly the type of flash calculations performed.
Accessing parameters in the Properties environment
The parameters mentioned above can be accessed in Aspen Plus in the following manner:
1) Create a property set (e.g. PS-1), Property Sets folder in the navigation pane.
2) Include the parameter KLL2 in the Properties menu. Add the parameter VMX. In the ‘Qualifiers’ tab, select ‘Liquid 1’ as Phase, and add a new column for ‘Liquid 2’ as second phase. Other fields can be left at default/empty status, and we will accept the default second liquid phase definition (densest phase).
3) Add a new analysis: click the Mixture button in the Analysis section of the Home ribbon, and create e.g. MIX-1.
4) Define this analysis by specifying the component flows in the stream being analyzed. Make sure that flash calculations are performed (check the respective box), and the valid phases are Vapor-Liquid-Liquid. In the Variable tab, specify Temperature as fixed and pressure as variable, for example (other combinations are possible depending on the user). Also, select the previously defined Property sets to report and the thermodynamic method you wish to use.
5) After running the analysis, check Results under PT-1. KLL2 and VMX are listed for all components present in the selected stream.
6) Perform the additional calculation as shown in the example given inSolution 142955 to obtain the value of the partition coefficient.
Accessing parameters in the Simulation environment
1. Create a property set (e.g. PS-1), Property Sets folder in the navigation pane.
2. Include the parameter KLL2 in the Properties menu. Add the parameter VMX. In the ‘Qualifiers’ tab, select ‘Liquid 1’ as Phase, and add a new column for ‘Liquid 2’ as second phase. Other fields can be left at default/empty status, and we will accept the default second liquid phase definition (densest phase).
3. In the Simulation environment, add new analysis click Stream Analysis in the Analysis section of Home ribbon and select Stream Properties. A new case in the Analysis folder of the navigation pane is created (e.g. SPROP-1).
4. Define this analysis by including the previously created property set (e.g. PS-1) and refer it to the stream which is going to be analyzed. The following information/options can be set up: thermodynamic method used for the analysis; manipulated variables over a defined range (such as temperature), and parametric variables (such as pressure). Make sure that flash calculations are performed (check the respective box), and the valid phases are Vapor-Liquid-Liquid.
5. After running the simulation, check Results under SPROP-1 for tabulating data as a function of manipulating and parametric variables. KLL2 and VMX are listed for all components present in the selected stream.
6. Perform the additional calculation as shown in the example given inSolution 142955 to obtain the value of the partition coefficient.
Keywords: Analysis, KLL2, Partition Coefficient, Liquid-Liquid equilibrium, Properties, Thermodynamics, Solubility
References: None |
Problem Statement: I have noticed that when I save the Aspen Plus simulation in V8.4 in BKP format another file is leftover when the problem is closed called Runid.ads. Is this a new file done on purpose or should it be deleted when Aspen Plus exits? | Solution: The .ads file is an “Aspen Data Share” file. This is an XML data store used to transfer data between Aspen Plus and adjacent applications (Economics, Energy Analyzer, etc.). As part of the process to improve the speed and robustness of the activated applications we are moving away from using automation to extract data from Aspen Plus; instead, Aspen Plus stores the required information as it is calculated during simulation. For V8.4, this is used in the new activated economics workflow (for example, displaying costs on the flowsheet).
When you use compound files the ADS file is automatically saved in the compound file (like APPDF and other required files). When using the (APWZ) all of the other files used in the simulation become transparent to the user since they are automatically included.
Keywords: associated files
References: None |
Problem Statement: How to hide and reveal a design specification and other objects through Automation Server in Aspen Plus. | Solution: A design specification sets the value of a variable that Aspen Plus would otherwise calculate. For example, you may want to specify product stream purity or the permissible amount of an impurity in a recycle stream.
When using Automation code, you might want to activate or deactivate design specification or other unit operations such as calculators or sensitivity analysis to name a few. This allows you to compare results and adapt your workflow to different scenarios.
The following code will let you accomplish this
Dim mySim As Happ.IHapp
Dim myNode As Happ.IHNode
Set myNode = mySim.Tree.FindNode(\Data\Flowsheeting Options\Design-Spec\H2RATE)
'-- activate the node --
myNode.AttributeValue(HAP_ACTIVATESTATE) = 0 'or HAPP_ENABLE_DEACTIVATE
'-- activate the node --
myNode.AttributeValue(HAP_ACTIVATESTATE) = 1 'or HAPP_ENABLE_ACTIVATE
ThisSolution includes an attached simulation file and an Excel file with VBA code that provides a practical example. The code will allow to:
· Interactively open a bkp file.
· Load the simulation and show progress
· Activate and deactivate the design specification
· Close the simulation
Keywords: ActiveX, VB, VBA, Visual Basic, Automation Server, getting started, activate, example.
References: None |
Problem Statement: When the user specifies the Number of stages in a RadFrac model under the Configuration (Tab):
And then, under Streams (Tab) | Feed streams | Stage, if the user hovers the mouse over the feed definition’s box the message that appears is: ‘'Enter a Feed stage number between 1 and n+1', being “n” the number of stages of the RadFrac:
Why does the RadFrac model show a message of 'Enter a Feed stage number between 1 and n+1' rather than showing the maximum number of stages “n”?: | Solution: According to the convention that determines how the feed stream is introduced into a column stage. The feed stream convention related to ‘Above-stage’ states that this will be introduced between stages, above the designated stage:
Hence, when the user tries to introduce a stage higher than the latest one “n” using another convention, such as: ‘On-Stage’, ‘Decanter’, ‘Vapor’ or ‘Liquid’; the ‘Override Consistency Check?’ Message will appear preventing inconsistencies on the RadFrac feed stream specification:
Therefore, the user can define a feed stream stage “n+1” only when the ‘Above-Stage’ convention has been set.
Keywords: RadFrac, Feed Stage, Convention, ‘Override Consistency Check?’ Message.
References: None |
Problem Statement: Why is the number of trays reported in the activated APEA different from the number of stages specified in Aspen Plus column Block specification? | Solution: In Aspen Plus, if the Murphree Efficiencies are not specified for the Aspen Plus column stages, Activated APEA will apply a default tray efficiency of 0.7 which is a design criteria whilst sizing and evaluating the column. Hence the number of tray section reported in APEA = Number of Aspen Plus Column stages / 0.7.
To change this default efficiency of 0.7, user can create a new APEA template with the required tray efficiency and choose to use this template in the Activated Economics of Aspen Plus.
However if users specify Murphree Efficiencies for the Aspen Plus column stages, APEA will consider these stages as Ideal stages during sizing and evaluation and report the same number of stages in the Activated APEA result.
Keywords: Murphree Efficiencies, tray efficiency, column stages, Aspen Plus, Activated Economics, APEA, number of trays
References: None |
Problem Statement: What is the relationship between holdup and residence time? | Solution: If you specify residence time, the liquid holdup used in the rate law is calculated on a mole basis as liquid mole flow from stage times liquid residence time.
Aspen Plus calculates the liquid holdup as follows:
HOLDUPL(N) = TIMEL(N)*L(N)
where N is the stage number
HOLDUPL is the molar holdup in kmol
TIMEL is the residence time in sec
L(N) is the liquid flow out of stage N in kmol/s
RadFrac defines the stage flow as the flow of the stream coming out of the stage, not in to the stage.
If the liquid flow on a stage is zero, a small number is assigned to avoid numerical problems.
Keywords: holdup, residence time
References: None |
Problem Statement: The following questions on using the Pressure Relief block may arise:
1. Is it possible to run several pressure relief modules in parallel in one Aspen file, or is it recommended to only run one in a simulation.
2. There is the option to have up to two inlet and two tail pipe sections. Does this means two sections in series, and if so, what are the method and essential tips for modeling, say, an inlet pipe with first section of 6 and second section of 3 on the inlet to a 3 bursting disc?
3. It is intended to size pressure relief devices and inlet/tail pipe on several process vessels. The discharge from these vessels connects into a common emergency vent header. It is also needed to model coincident relief in adjacent vessels and determine whether the vent header is large enough (e.g. 3 vessels relieving concurrently, 1 with two-phase flow, 2 with vapour phase only relief flow). Is it possible to carry out such simulation? | Solution: Answers to the above questions are as follows:
1. Multiple pressure relief blocks can be run in parallel. They are treated like separate runs. The only issue could be with the run times. Some pressure relief cases are very lengthy, especially those with difficult flash convergence.
2. When two tail pipes are specified, the outlet vent performs like the pipeline block with two pipe segments (see the screen shot). The user can check this on RESULTS form (either Dynamic or Steady state), in the property profile folder.
3. Pressure relief in Aspen Plus is really intended for one, standalone vessel. If it is intended to model several vessels in series then the pressure relief model in Aspen Plus Dynamics should be used.
Keywords: Â Pressure relief, multi pipe segments
References: None |
Problem Statement: In Aspen Plus I am unable to export my simulation into Aspen Energy Analyzer | Solution: Before exporting the simulation to Aspen Energy Analyzer the user will need to make sure that the simulation is not on the 'Auto-Run' mode. Inside the Run Settings, on the home ribbon, the user can confirm that the Auto-Run mode is deselected. It is recommended to have the Aspen Plus simulation saved in a folder location which has full read and write access.
To export the simulation to Aspen Energy Analyzer the user can utilize the energy analysis feature.
Inside the Energy Analysis Environment the user is able to 'Analyze' their case. At a later stage they can export their simulation into Aspen Energy Analyzer through the 'details' feature on the ribbon.
Keywords: Aspen Energy Analyzer, Details, Export
References: None |
Problem Statement: How to get access to property values in the Plex using the offset utility DMS_IFCMNC and parameter name. | Solution: DMS_ALIPOFF3 function allows users to get the offset of a property in the Plex such as GAMMA and GAMUS. Using this method, 29 is the property index for ln(GAMUS) and 24 for ln(GAMMA). However, there is an easier way to get access to physical properties in the common dms_plex. The integer function DMS_IFCMNC or DMS_IFCMN returns the offset of the property by entering the parameter name:
INTEGER DMS_IFCMNC, IOFF
CHARACTER*8 CNAME
IOFF = DMS_IFCMNC(CNAME)
C
C where CNAME is the parameter name as is called in Aspen Plus
C
The IPOFF method was the method used before the IFCMNC function was created. With this method, DMS_IFCMNC('GAMMAL') and FN(DMS_ALIPOFF3(24)) with FN(J) = J + LCLIST_LBLCLIST will return the same offset value.
For instance if you want to access the gamma value for the component ‘water’:
#include “dms_plex.cmn”
#include dms_ncomp.cmn
#include dms_lclist.cmn”
DIMENSION B(1)
EQUIVALENCE (B(1), IB(1))
INTEGER DMS_IFCMNC, DMS_KFORMC, IWATER, LGAM, LGAMI
REAL*8 GAM
C
C Locate the offset for GAMUS in the plex
C
LGAM = DMS_IFCMNC('GAMUS')
C
C Locate offsets for the water component in ncomp
C
IWATER=DMS_KFORMC('H2O')
C
C Locate the offset of gamus for the component ‘water’ in the plex.
C
LGAMI = LGAM + IWATER
C
C Access gamus property from the plex
C
GAM = B(LGAMI)
Keywords: Plex Offset Utilities. Fortran subroutines, IFCMNC, ALIPOFF3, GAMMA, GAMUS.
References: None |
Problem Statement: What is the reference for the Equations for Tube Rupture? | Solution: The
Keywords: None
References: Stream for the tube rupture case should be the high pressure side stream (whichever side of the heat exchanger operates at the higher pressure).
Generally speaking, for tube rupture to be applicable you want the high pressure side to operate at at least 1.5 times the design pressure of the low pressure side. So there should always be a quite significant pressure difference between the exchanger tube and shell side for the scenario to even be considered.
The tube rupture calculation should be using the high pressure side condition in the equation. For details see the figures below which explains which number is used at each place in the F1 help.
Vapor flowing through tube rupture break without phase change:
Liquid flowing through tube rupture break without phase change: |
Problem Statement: When using the Aspen Properties Enterprise Database (APED) Manager on Citrix and logged on as a Restricted User, we cannot find the menu Create a new database in the Action menu.
When using a local install, everything works fine. Why would this happen on Citrix? | Solution: When using the Aspen Properties Database Manager to create a new custom database or modify an existing custom database, the customer has to login Citrix with an account having Windows Administrative privilege. The account also must be in the “sysadmin” group of the SQL server instance that was used to restore Aspen system databases, APV88, NISTV88, FACTV88, and APEOSV88.
When using a restricted user account to login, the restricted user account can register databases only.
Keywords: APED
Citrix
Restricted User
References: None |
Problem Statement: How do you write Fortran expressions? | Solution: We are adding a new help topic with some simple instructions on how to use Fortran since so many new engineers have no experience with it. It is important to note that Fortran expressions are used not only in the Calculator block, but on other forms such as Design specification and Sensitivity. Also, basic Fortran is no more complicated than writing an equation in Excel.
How to Write Fortran Expressions
Not sure how to use Fortran? This topic explains the basics of writing code to perform simple calculations in Fortran.
Fortran used in Aspen Plus is limited to Fortran 77 syntax, which the following sections describe. Fortran variable names and function names are not case sensitive; PRES, Pres, and pres all refer to the same variable.
All of the syntax described on this page can be interpreted, which means that you do not need to have a Fortran compiler installed to use it. Some other Fortran statements can also be interpreted; for a full list, see About the Interpreter.
Assignments and Arithmetic Operators
The most commonly used Fortran statements are assignment statements, which have the form
variable = Fortran expression
The variable can be one you have defined as a variable in a Calculator block, or one defined in a declaration statement. The Fortran expression can be a number, another variable, a function call, or an arithmetic operation combining two or more expressions of these types. The value resulting from evaluating the Fortran expression is assigned to the variable when this statement is executed. In some cases in Aspen Plus, such as the Spec, Target, and Tolerance of a Design-Spec and the limits on manipulated variables, you will enter only a Fortran expression. In this case, there is an implicit assignment to the indicated attribute (in the same way that you would simply enter a number in most fields), but the expression is evaluated each time the value of the attribute is required.
The basic arithmetic operators are:
Addition
The + sign is used for addition. The following statement adds 1 to the value of B and assigns the result to A:
A = B + 1
Subtraction
The - sign (ASCII hyphen, not an em dash or en dash character) is used for subtraction. The following statement subtracts 1 from the value of B and assigns the result to A:
A = B - 1
Multiplication
The * character (asterisk) is used to represent multiplication. The following statement multiplies the value of B by 2 and assigns the result to A:
A = B * 2
Division
The / character (slash) is used to represent division. The following statement divides the value of B by 2 and assigns the result to A.
A = B / 2
Note: Division of one integer-type variable by another is integer division: the numbers are divided, the whole part of the result is kept (as an integer-type value), and the remainder is ignored.
Exponentiation
Two asterisks ( ** ) are used to represent exponentiation. Keep in mind the standard mathematical restrictions on exponentiation. The following statement squares the value of B and assigns the result to A:
A = B ** 2
Order of Operations
You can combine multiple arithmetic operations into a single expression. When you do so, Fortran has a specific order in which it performs the operations:
· Exponentiations are performed first, right to left.
· Multiplications and divisions are performed next, left to right.
· Addition and subtraction is performed last, left to right.
For example, 2+5*3 evaluates to 17 because the product 5*3 is calculated first, and then 2 is added to it.
You can group expressions in parentheses to specify a different order of calculations. Everything in parentheses is evaluated before anything outside the parentheses. If parentheses are nested, operations inside the inner parentheses are performed before those in the outer parentheses. For example, (2+5)*3 evaluates to 21.
Comments, Line Numbers, Continuation, and Indentation
You may notice how the examples in this topic are all indented. In Fortran statements, the first 6 columns are special.
· A comment line, which is ignored during calculations, can be indicated by placing a C or c in the first column.
· Line numbers can be indicated by writing the numbers into the third, fourth, and/or fifth columns. These can be used in certain kinds of statements to refer to another line. In lines which are neither comments nor numbered, you should leave the first five columns blank (spaces).
· The sixth column is used only for the continuation character, to indicate that the line is a continuation of the previous line when expressions are very long. Fortran lines must not be longer than 72 characters, including the initial 6 spaces. Any character other than a space in the sixth column will make the line a continuation, but it is traditional to use a plus sign or to use digits (2 for the second line, 3 for the third line, and so forth).
The built-in editor in the Calculator | Input | Calculate sheet automatically leaves 6 blank spaces at the start of each line. If you need to make comments, line numbers, or continuations, you can delete these spaces.
Variable Types and Declarations
Fortran variables have explicit types indicating the kind of data they can hold. The most common variable types found in Fortran used within Aspen Plus are:
· Integer: A variable that holds a whole number such as 0, 1, or -2. Integers are stored in 4 bytes or 32 bits, one of which is used to store the sign, so they can hold values between 231 and -(231), or about 2,000,000,000 and -2,000,000,000. Note, though, that you cannot enter commas when writing large numbers into your Fortran program; just write 10000 instead of 10,000.
· Real*8: A real variable which can hold a whole or fractional (decimal) value. The *8 indicates that the variable uses 8 bytes or 64 bits. This kind of variable (also called double precision) can store about 14 digits of accuracy and can store numbers up to about 10308 or as small as 10-308, as well as the negatives of this range. When you enter decimal numbers directly into your Fortran program, be sure to use a period or full-stop ( . ) as the decimal separator, even if Aspen Plus is configured to use a comma for the decimal separator elsewhere. For example, 1.5 is the correct way to write the number one-and-a-half.
Two less commonly used types are:
· Character*n: A character variable can store a string of text. The n indicates the maximum length of the string which the variable can hold.
· Logical: A variable which can store a true or false value. If you want to write literal true and false values in your Fortran program, they have to be enclosed in period or full-stop characters (.TRUE. or .FALSE.). You can also generate Logical data as the result of using comparison operators.
When you perform arithmetic operations on two numbers, the result is the same type as the numbers you are operating on. If one number is real*8 and the other is integer, the result will be real*8.
Variables you define with a reference to an Aspen Plus variable are automatically declared with the type appropriate to the Aspen Plus variable. This is usually Real*8, but countable items such as stage numbers are of type Integer. If you want to make intermediate variables used during calculations, enter declarations for these variables in the Fortran Declarations dialog box of a Calculator block, or at the start of an external Fortran subroutine. Declarations consist of the variable type followed by the variable, separated by a space. You can declare multiple variables of the same type by separating them with commas. To declare an array variable, enter the dimensions in parentheses, with multiple dimensions separated by commas, after the variable name in a declaration. Example declarations:
INTEGER I, J(2)
REAL*8 TIME,VOLUME,PRES(7,10)
LOGICAL C
CHARACTER*10 NAME
A Fortran variable name must:
Be eight characters or less
Start with an alphabetic character (A – Z)
Have subsequent alphanumeric characters (A – Z, 0 – 9)
Not begin with IZ or ZZ
Conditions and Branching
You can write IF statements to perform certain operations only in certain conditions. The format of an IF statement is:
IF (logical expression) THEN
conditional code
END IF
The logical expression can be a logical variable or the result of a comparison or logical operator. The parentheses around the logical expression are required. If the logical expression evaluates to true, then the conditional code is executed, and otherwise it is skipped.
Comparison Operators
Comparison operators can be used in decision statements, or to store a value in a logical variable which may be used in a decision statement later. The comparison operators in Fortran are:
Operator
Meaning
.LT.
Less than
.GT.
Greater than
.EQ.
Equal
.LE.
Less than or equal
.GE.
Greater than or equal
.NE.
Not equal
For example, the expression B .LT. 3 is true if B is less than 3.
Logical Operators
For complicated logical expressions you can use logical operators to combine multiple logical expressions. The logical operators in Fortran are:
Operator
Meaning
.AND.
And (true only if both expressions are true)
.OR.
Or (true if either or both expressions are true)
.NOT.
Not (reverses result of following logical expression)
For example, the expression A.EQ.3 .OR. B.LT.2 is true whenever A equals 3, B is less than 2, or both.
You can use parentheses to group parts of expressions involving comparison and logical operators. All arithmetic operations are performed first, then comparisons, and logical operators are last, with .NOT. evaluated before .AND., then .OR. is evaluated last.
Function Calls
You can call functions by typing the function name followed by its arguments in parentheses. If the function takes more than one argument, separate the arguments with commas ( , ).
Most commonly you will call the following built-in Fortran functions (the ones beginning with D return a double precision or real*8 result, while the others return an integer result):
Function
Meaning
DABS(X), IABS(J)
Absolute value
DSIN(X), DCOS(X), DTAN(X)
Sine, cosine, and tangent functions of X in radians.
DASIN(X), DACOS(X), DATAN(X)
Inverse sine, cosine, and tangent functions, with the result returned in radians.
DEXP(X)
Exponential function (ex)
DLOG(X)
Natural logarithm of X
DLOG10(X)
Base 10 logarithm of X
DSQRT(X)
Square root of X
DMIN1(X1,X2,...), DMAX1(...)
Minimum and maximum of the arguments (two or more real*8 arguments)
MIN0(J1,J2,...), MAX0(...)
Minimum and maximum of the arguments (two or more integer arguments)
DFLOAT(J)
Converts an integer value to a real*8 value
IDINT(X)
Converts a real value to an integer, truncating the fractional part. IDINT(1.3)=1; IDINT(-2.7)=-2.
Keywords: None
References: None |
Problem Statement: How can I check the results of the downcomer geometry of a RadFrac column? | Solution: When the user does not specify any information about the downcomer geometry (widths/weir lengths), it is possible to check the dimensions considered by Aspen Plus in the Report of the RadFrac column. To do so, the user needs to run the model, then click on the Report option in the Home ribbon:
Then, select the column block and the report will be opened using the Notepad application. Once the text file is opened, scroll down until locating the title DOWNCOMER DIMENSIONS as it is shown in the screenshot below:
Keywords: Downcomer results, downcomer clearance results, weir height results
References: None |
Problem Statement: When modelling a process in Aspen Plus, is it possible to transfer the flowsheet (streams, unit operations) to a PDF file format.
I am using PDF-XChange 4.0 writer, but sometimes some unit operation symbols are not displayed in the PDF file. | Solution: There is another software which is called XPS Document Writer, that allows the user to create a file with the flowsheet drawing. This software belongs to Microsoft, so it is installed by default when using this operating system.
To “print” the flowsheet as a document, go to File | Print and select from the drop list: Microsoft XPS Document Writer. The XPS file will be created.
The last step will be to convert the XPS file to a PDF file, but this requires another part of the software (obtainable from the link below)
XPS to pdf
The file obtained in PDF from a XPS file is attached to theSolution.
Keywords: Flowsheet, XPS, pdf format
References: None |
Problem Statement: How to obtain results for user defined compounds VLE binary interaction properties using UNIF-DMD property method? | Solution: In order to obtain results for user defined compounds VLE properties using UNIF-DMD property method:
1) Run the attached example .aprbkp simulation file and some errors will be shown in the Control Panel:
2) Go to Components | Molecular Structure | B and C | Functional Group (tab), change the Method to UNIFAC and under the Structure (tab) click on Calculate Bonds:
3) Reinitialize the simulation to purge the previous results and re-run it.
4) Now the binary results plots for those components, as well as the table results are shown:
5) If you want now calculate the properties using UNIF-DMD, now you can select this property package from the Methods | Specifications | Global (Tab) under ‘Method name’, reinitialize and re-run the simulation once again.
Keywords: UNIF-DMD Method, VLE, User Defined Compounds.
References: None |
Problem Statement: How to export simulation from Aspen HYSYS or Aspen Plus to Aspen Process Economic Analyzer? | Solution: A converged simulation could be easily exported to Aspen Process Economic Analyzer using the Send to APEA option under the Economics ribbon tab as shown in the screenshot. Please note that you need to uncheck the Economics Active option in order to activate the Send to APEA option. Both cannot be active at the same time.
Keywords: Activated Economics, APEA
References: None |
Problem Statement: What is method by which the relief load is calculated for two-phase flow using the Flow Resistance (Kr) method? Is the Kr method appropriate for two-phase flow?
What is the relieving temperature is used for two-phase flow with the Flow Resistance (Kr) method? | Solution: The Flow Resistance method determines the calculated size of a pressure relief system by analyzing the total system resistance to flow.
This analysis takes into consideration the flow resistance of the following:
· the rupture disk device
· piping and other piping components
· entrance and exit losses
· elbows
· tees
· reducers
· valves
You should use the Flow Resistance method if:
· The 8 & 5 Rule does not apply.
· The rupture disk is not installed in combination with a PSV.
The Kr method calls the Aspen Plus Pressure Relief system to do the calculations. The Kr method is appropriate for two-phase flow.
It uses the operating temperature prior to relief.
Keywords: flow resistance method, relieving temperature
References: None |
Problem Statement: What should I do if I get a message about missing NRTL binary parameters or NRTL parameters for all components pairs are zero?
WARNING IN PHYSICAL PROPERTY SYSTEM
NRTL BINARY PARAMETERS FOR ALL COMPONENT PAIRS ARE ZERO, YOUR RESULTS MAY NOT BE ACCURATE. PLEASE REVIEW AND PROVIDE BINARY PARAMETERS AS APPROPRIATE. | Solution: When all of the NRTL binary pair parameters are zero, the liquid mixture is calculated as ideal. For non-ideal mixtures, this is generally not what is desired. It is essential to have binary pair parameters to accurately model nonideal mixtures. Aspen Plus has a number of binary databanks that can be selected on the Properties | Methods | Parameters | Binary Interaction | NRTL | Databanks sheet. Parameters will show on the form if they are in the databank. Alternatively, binary parameters can be estimated using UNIFAC.
Example:
Please follow below procedure in Properties Environment to estimate missing binary parameters
Define components MEK and Hexene.
Select property method as “NRTL” & click on “Next” then you will see above warning message in the control panel.
If you look at “Analysis” from Home tab the click on “Binary” then select “Txy” and “Run Analysis” it display ideal behaviour plot which is actually wrong for this system.
Go to the Properties | Methods | Parameters | Binary Interaction | NRTL form, on the Databanks sheet, make sure that all of the applicable databanks are selected. If no parameters are available on the Input sheet, please check Estimate missing parameters by UNIFAC at the bottom, or select “Estimation” from Home Tab & click on “Run” then check binary parameters are estimated based on default UNIFAC method which can be seen in below path.
Methods/Parameters/Binary Interaction/NRTL-1
Now again switch to “Analysis” under Home Tab then go to “Binary” then select “TXY” and “Run Analysis”.
Keywords: missing NRTL binary parameters, binary parameters etc;
References: None |
Problem Statement: AspenSplash.exe show up in task manager and Aspen Plus never opens.
Cause
This can occur when you install an Emergency Patch (EP) but not the Cumulative Patch (CP). | Solution: Always install the most recent Cumulative Patch (CP) for a version before installing an Emergency Patch (EP). The notes in the Emergency Patch should indicate the Cumulative Patch that needs to be installed.
Keywords: CP; AspenSplash;
References: None |
Problem Statement: I keep a detailed running log (in Microsoft Word) of my ongoing development work in Aspen Plus. However, I would like to add simulation-specific information/documentation to each run.
Can I put this information into the Setup|Description? It seems that I cannot use any formatting there. Is there another way to save this information with my simulation? | Solution: The description is just simple text with no formatting. It is possible to to use an Excel Calculator to log the information in a spreadsheet.
You can also try saving as a compound (.apwz) file. This is really a zip file that is opened by Aspen Plus. Associated files such as .apmbd or .edr files should be embedded automatically. You can also embed other files in the .apwz and they will be saved with the .bkp or .apw file. You can embed any kind of file.
It is a good idea to save the .apwz file with a .bkp rather than an .apw file. You can set this in File Options on the Files sheet.
To embed files, go to File Edit Compound file.
When you open the .apwz, a directory with the filename with the embedded files will be created in the working directory. You can edit these files such as the Excel and Word files in the example, BUT you MUST remove and re-embed them to preserve the changes.
Linked files are a link and are not saved in the .apwz.
Keywords: .apwz
compound file
References: None |
Problem Statement: How to add a reference to the Aspen Plus type library in VBA | Solution: Before you can perform early binding (https://msdn.microsoft.com/en-us/library/0tcf61s1.aspx) with Aspen Plus Automation Server, you need to add the type definitions contained in the type library for the compiler.
In VBA, from the “Tools” menu, click “
Keywords: ActiveX, VB, VBA, Visual Basic, Automation Server, getting started, libraries, object browser.
References: s”
Browse the drop-down menu and check “Aspen Plus GUI 32.0 Type Library”. Aspen Plus 32.0 corresponds to v8.6, depending on the version installed you may find a library with different number.
Now if you open “Object Browser” from the “View” menu, you will find the class “Happ” which contains all the property and methods of Aspen Plus objects.
Now Visual Basic is configured to work with Aspen Plus Automation Server. |
Problem Statement: If I have a machine with two different Microsoft Office versions installed, which version of Microsoft Excel would be used by the Calculator block in Aspen Plus?
Is there a way to select which version to use? | Solution: The version of Excel used by Aspen Plus via automation is limited by Microsoft.
The rule is that the last version that was installed on your computer is the version that Aspen Plus loads. The recommendation is to either have only one Microsoft Office version installed. If this cannot be done, you would need to uninstall the desired version and then reinstall it again or register and unregister Excel COM components.
To set the Excel default version to be used with Aspen Plus:
Unregister the current version:
1. Open a command prompt as administrator (this can be done by searching for cmd in the Start Menu, right clicking the cmd.exe, and selecting Run as Administrator
2. Run the command: <Excel installation path>\Excel /unregserver
Reregister the desired version:
1. Open a command prompt as administrator
2. Run command: <Excel installation path>\Excel /regserver
You can check what is the current version on the following registry key:
HKEY_CLASSES_ROOT\Excel.Application\CurVer
This way Aspen Plus will recognize this version as the last installed and is the one that will be opened by the calculator block.
Keywords: Calculator block, Microsoft Excel
References: None |
Problem Statement: Is there a way to prioritize one Design Spec above others? | Solution: In order to nest, you can create a convergence block for each esign specification and nest the convergence blocks.
You need to create a Convergence for each Design Spec in the Convergence | Convergence folder. The Secant method is the default method used for single design specifications. The other methods available are Broyden and Newton. Broyden and Newton can also be used to solve multiple design specifications simultaneously. Then, on the Convergence | Nesting Order | Specification sheet, these can be ordered.
Keywords: Design spec, nest, convergence block
References: None |
Problem Statement: What does a Murphree efficiency on a bottom stage with a reboiler mean?
Radfrac allows a user to enter a Murphree stage efficiency for the reboiler stage; however, from the definition of Murphree efficiencies, it does not make sense. | Solution: Murphree efficiencies are only meaningful on the last stage if there is an on-stage feed containing vapor entering that stage, as is typical of absorber columns. The vapor can come from a feed stream or an internal stream such as a pumparound. If Murphree efficiency is defined to be other than 1 on the last stage and there is no vapor feed, a warning will be issued:
-----EFFICIENCY FOR THE LAST STAGE IS IGNORED
Keywords: None
References: : CQ00159975 |
Problem Statement: In V7.1 the Refrigeration Utilities for exchangers did not have any crossover temperatures. In V7.3 the exchangers report errors because of crossover temperatures.
A file created in V7.1 runs and converges; however, when you run the simulation in V7.3, the following error is displayed:
** ERROR
TEMPERATURES CROSS WITH UTILITY REF
IN HEATER BLOCK B1
BLOCK TEMPERATURES 3.109278D+02 K AND 2.748167D+02 K
UTILITY TEMPERATURES 2.674456D+02 K AND 2.801066D+02 K
Attached are two files that demonstrate the problem.
RefrigV71.bkp: created in V7.1 runs without errors in V7,1 but in V7.3 it gives temperature crossover errors.
RefrigV73.bkp: built in v7.3 with the same specifications as RefrigV71. It has temperature crossover errors. | Solution: The error message is correct. The problem was that temperature crossovers were not checked or reported in V7.1 or earlier. Knowing that there is a temperature crossover is important to know in design.
Three modifications to consider:
1. If the exchanger is countercurrent there is a crossover. When it operates in concurrent there is not.
2. The direction of the utility can be changed to avoid the temperature cross over. Utilities | REF | Input | Specifications. Modify the Flow direction.
3. The error message can be changed to a warning message in the consistency check. Utilities | REF | Input | Specifications. Modify the Consistency check.
Keywords: Refrigeration Utilities
Temperature Crossover
Heat exchanger
References: None |
Problem Statement: In the RadFrac | Packing Rating | Results, the max liquid superficial velocity cannot be reported in a unit which is commonly used to report this property in industry. How can this property be reported in units of GPM/sqft? | Solution: The user can add a custom unit to the simulation. SeeSolution 106558 about creating custom units in Aspen Plus.
In the Simulation environment, go to Setup | Custom Units. Select velocity as the physical quantity, and select ft/sec as the base unit. The conversion factor from ft/sec to GPM/sqft is as follows:
1 foot/second = 448.831169 (US gallons per minute) per (square foot)
The max liquid supercritical velocity can now be reported in units of GPM/sqft.
An example file, MeOH-GPMsqft.bkp, has been attached which shows this workflow performed on a methanol/water distillation column with a Packing Rating calculation. The modified unit set ENG-2 has GPM/sqft set as the default unit for velocity.
Keywords: Aspen Plus, custom units, RadFrac, packing rating, liquid superficial velocity, GPM/sqft, gallons per minute per square foot
References: None |
Problem Statement: How are cloud point temperature and pressure computed in Aspen Plus? (TCLOUD, PCLOUD, TCLOUDL, PCLOUDL, TCLOUDU PCLOUDU) | Solution: TCLOUD and PCLOUD are the cloud point temperature and pressure, the temperature (at a given pressure) and pressure (at a given temperature) of the boundary between regions of one and two liquid phases, considering only the liquid phase. The TCLOUD calculation searches rigorously for the formation of a second liquid phase. The system needs water or some other species that would cause the formation of a second liquid phase.
For some systems, such as nicotine-water, the two-phase region may be enclosed, with one-phase regions at both higher and lower temperatures and/or pressures. In these cases, TCLOUD and PCLOUD are ambiguous and may return either of the two points. Use TCLOUDL or PCLOUDL to get the lower temperature or pressure and TCLOUDU or PCLOUDU to get the upper temperature or pressure in this case.
The search executed by these properties can be time-consuming, especially if no two-liquid-phase region is found. If the stream conditions are not in a two-phase region, the search proceeds from the stream temperature or pressure, first downward until a two-phase region is found or a certain limit is reached, and if noSolution is found, then upward from the starting point until a two-phase region is found or another limit is reached. These limits are wide, but they will never be wider than the global temperature and pressure limits on the Setup | Calculation Options | Flash Convergence sheet. You can constrain the search by changing these values, but be aware that they apply to all calculations for the entire simulation, not just cloud point. Furthermore, be aware that TCLOUDU and PCLOUDU only search downward, for a two-phase region below the stream temperature or pressure, and TCLOUDL and PCLOUDL only search upward.
The CLOUD-R1 calculation is an API correlation for petroleum mixtures, to predict the formation of precipitating solids such as wax formation in the liquid hydrocarbon phase.
Keywords: Cloud Point, TCLOUD, PCLOUD, TCLOUDL, PCLOUDL, TCLOUDU PCLOUDU
References: None |
Problem Statement: I cannot see stream IDs unless I zoom in very much. The stream/block IDs don't appear until only four blocks are on the screen even though there is clearly enough room to display these IDs even when all the blocks can be seen on the screen. It is rather inconvenient having to zoom in and out many times to see these IDs. | Solution: There is a label visibility threshold setting that can be set to a level that was far different than the default level.
To reset the threshold, zoom out to the furthest level where you want labels to be visible, then right click in empty space to get the default pop-up menu and uncheck Hide Labels. This zoom level now becomes the new threshold.
Block and Stream IDs can be hidden because of any of the following:
1. Explicitly hiding the ID on a specific block or stream.
2. Clearing the Display Block Name and Display Stream Name options in the Flowsheet tab of Aspen Plus Options sets hide method (1) for newly created blocks and streams.
3. In the Flowsheet Modify tab of the ribbon, Display Options | ID hides all labels when unchecked, regardless of any other options.
4. Right-clicking the flowsheet and checking or unchecking Hide Labels also hides all labels, regardless of any other options, but independently from (3).
5. Hiding the labels as in (4) [ONLY!] and then unhiding at a zoom size of less than 60% sets the zoom threshold to that size, and unhiding at a larger size sets the zoom threshold to 60%. When the zoom level is below the zoom threshold, the labels are always hidden.
6. On very short streams, if there isn't a certain amount of room, the stream label doesn't show. There's no option at all for this, as far as I can tell.
Mechanisms 4 and 5 cause the Q and W indicators on heat and work streams to disappear. The other label hiding mechanisms do not.
Mechanisms 2 and 3 have the opposite sense from all the other ones - these are options to display IDs, rather than to hide them.
Keywords: None
References: : CQ00580375 |
Problem Statement: What method use to create new nodes in Aspen Plus through ActiveX Automation | Solution: Depending on the type of node you want to create the offspring for, you will need to use a different method:
For stream nodes (\Data\Streams) and block nodes (\Data\Blocks) you should use the add function of an IHNodeCol object.
The function Label works with offsets of nodes which their offsprings are generated automatically by A+, for example with component specification (Data\Components\Specifications\Input\Type) or with the multidimensional node that defines component efficiencies in a RadFrac column (…\Input\COMP_EFF). For those nodes there is always an offset location in the memory reserved for that object, so you can address to it using the label function and create new subnodes. SeeSolution 141856 for further details.
Keywords: Automation, methods, add new nodes,
References: None |
Problem Statement: Â During calculations, the sequence stops and I get an error message sayingÂ
*****SYSTEM ERROR
     HISTORY FILE REACHED SIZE LIMIT. EXECUTION TERMINATED
! Calculations terminated because of ASPEN PLUS internal errors | Solution: This error message appears because the history file created during the simulation is much bigger than the upper limit defined in Aspen Plus.
In Aspen Plus V8.6 a new option was added on the Setup | Calculation Options | Limits sheet to limit the size of the history file. This is a rough limit, checked about once a minute, intended to avoid letting the history file get so large on out-of-control simulations that it fills the disk. The default is 500 MB. In most simulation this limit will not cause any warnings; however, if the simulation is large or the diagnostic level has been increased to request a lot of messages, it can cause that above error message to appear.
To avoid this error user has two options:
1. Increase upper limit history file size from default 500 MB to a higher value in the Simulation environment, on the Setup | Calculation options folder | Limits tab.
2. Decrease diagnostic level for history file in Setup | Specification folder | Diagnostic tab. The default level of 4 will show all error and warnings. Note that diagnostic level for History File and Control Panel can be different.
Â
Keywords: History file, system error, limits
References: None |
Problem Statement: What is the OOMF scripting syntax to use for the QUERYVARS function to select which variables will be updated with the restore command? | Solution: The QUERYVARS function returns list of variables using the specified query string.
These query function can be used to return lists of variables or other objects.
You may use the QUERYVARS function to enter a query. For example, to get
a list of variables whose names begin with CVAP and whose values are less
than zero, you may enter:
SET VARLIST = QUERYVARS(NAME=CIN* AND VALUE<0)
For example, to get a list of variables in block C2S, enter:
SET VARLIST = BLOCKVARS( C2S )
See Aspen OOMF Scripting language reference manual for the list of functions.
The following EBS script may be used to see how this can be used with the restore function.
// find matching variables which are *TEMP and calculated
set VARS = queryvars(name=*TEMP and spec=calc)
echo before restore
print var [value,lower,upper,spec,units], &VARS
restore variables [VAL], &VARS from .\Solution.x
echo after restore
print var [value], &VARS
See the attached example script.zip for an example (see the readme.txt file included for instructions to run the example).
Keywords: script, OOMF, EBS, restore, x-file
References: None |
Problem Statement: In Aspen Plus when some parameters are not used within the models, those can be accessed by user or in-house models. For example, the values of the coefficients for the DIPPR second-virial coefficient equation (SVRDIP). | Solution: These values can be accessed form Aspen Properties Database Manager:
· From the desktop click Start | All Programs | AspenTech | Process Modelling VX.X | Aspen Properties and launch Aspen Properties Database Manager.
· Click on the database APVX.X | Select compounds.
· Click on Find Compounds and perform a search by CAS number, component name or alias, molecular weight, boiling point or molecular formula.
· After having selected the compound you can see in which databases the compound is included:
· If you click in Properties and Parameters | Pure you could see which parameters are included in the databanks.
· Click on the SVRDIP parameter (+) under ‘Value’ column, and all the values of the DIPPR second-virial coefficient equation for that component will be shown.
· Those values of the DIPPR second-virial coefficient equation can be used for reference.
Keywords: DIPPR, second-virial coefficient equation, SVRDIP.
References: None |
Problem Statement: Can you calculate the cricondenbar and cricondentherm in Aspen Plus? | Solution: The cricondenbar and cricondentherm are defined as follows:
Cricondenbar refers to the highest pressure at which liquid and vapor phases can exist at equilibrium in a multicomponent system.
Cricondentherm refers to the highest temperature at which liquid and vapor phases can exist at equilibrium in a multicomponent system.
Above the cricondentherm you are sure there will be no condensation when you depressurize the mixture (if you maintain your system at a constant temperature). For example, for a gas well, if the temperature of the reservoir is above the cricondentherm, there will be only gas (dry gas reservoir). If the temperature is lower, then you may get some liquid. If the reservoir temperature is lower, during isothermal depletion, liquid condenses when pressure falls below dewpoint. This is called retrograde condensate (condensation typically occurs when you increase the pressure on a vapor, but in this case it happens when you decrease the pressure, hence the name retrograde condensation). The heavier fractions may be left behind in the reservoir.
To find the cricondenbar and cricondentherm, create a PT-envelope and read the values from the plot. There are no prop-set properties to explicitly calculate the cricondenbar or cricondentherm in Aspen Plus.
To create a PT-envelope in V7.3.2 and higher, click on PT-envelope from the Analysis section of the Home toolbar in the Properties environment. Then, enter the composition of the mixture.
In V7.3 and earlier, specify a stream with the desired composition. Then, right click on the stream and select Analysis then PT-Envelope...
Keywords: cricondenbar, cricondentherm
References: None |
Problem Statement: How can I create and report a .log file generated from a COFE run simulation? | Solution: The .log file from a COFE simulation file shows the information about the thermodynamic systems, as well as property package used during the calculations. The procedure shown below provides the steps to create and report a .log file generated from a COFE run simulation:
1) Open the .fsd file using the COFE program:
2) Open the ‘COLTT 2.1 Controller’ from Windows Start | CAPE-OPEN | COLTT 2.1 | COLTT 2.1 Controller.
3) Select from All Systems | Unit Operations’ drop down list, the unit (s) involve in the simulation process:
4) Click on ‘Log Files’ tab and double click on the .log file created from the run simulation:
5) This is the .log file appearance:
6) Or you can open it ‘COLTT 2.1 Viewer’ from Start | CAPE-OPEN | COLTT 2.1 | COLTT 2.1 Viewer. Click on File and search for the .log in the directory: X:\Users\’PC’\AppData\Local\CAPE-OPEN\COLTT Logs\.
Keywords: COFE, .log file, .fsd file.
References: None |
Problem Statement: How do we match assay boiling points with ASTM D86 curve data entered? | Solution: In order to verify the input values in D86 curve and the results you can add the prop-set property D86CRV to a material stream to see if the system can reasonable reproduce the input D86 distillation curve.
The bubble point (TBUB) and dew point (TDEW) temperatures of the streams are dependent on the property method used and will not necessarily match the D86 data. The bubble point might be close, but the dew point will never match the 100% boil off temperature since the distillation curve is obtained by a distillation process, and the 100% point is not the same as the dew point of the crude.
Keywords: D86CRV, ASTM, assay
References: : CQ00582013 |
Problem Statement: How to use Excel in Calculator Block | Solution: Using calculator with Excel can be as easy as using fortran or even easier and flexible.
As Excel give more flexibility to do customize calculation, most user prefer to use Excel with Calculator block.
Use Excel with Calculator Block
First, User has to define all the variable need to import from simulation flowsheet and the variable that need to export to flowsheet.
Next, go to “Calculate” and choose calculation method as Excel and choose Open Excel Spreadsheet. (Excel spreadsheet that used in Calculator will not save as separate file but embedded inside Aspen Plus file automatically. )
Once the Excel spreadsheet opened, go to the tab “Add-ins” and user will found the following add-ins function.
The drop down list at the left hand side is to list down all the variables that user has defined in calculator block. The remaining buttons serve as function to modify the calculator block directly without need to go back to Aspen Plus.
In Excel spreadsheet, user need to link the defined variables with any cell inside the spreadsheet.
For example, C3 in this spreadsheet has been chose and in drop down list, choose FLWCH4, then this cell will be linked with the variable FLWCH4. (As shown below)
User can leave the cell blank as if this linked variable is import variable, the value will be imported here later after run the simulation.
The cell that linked with variables that going to export to simulation later can be used to enter formulas or reference to any other cell in Excel. The final value in this cell will then export into simulation according to user setting in Calculator block.
(As per screenshot above, the cell C4 is linked with exported variable FLWH2O and the formula is entered in the same cell as well)
The imported Variable is in Green color when linked with cell and exported Variable will be in Blue.
After done with cell linking and formula input in excel, user just need to close the excel and automatically will return to Aspen Plus calculator section.
Once returned to Aspen Plus Calculator section and does not see any update in calculator block for the excel spreadsheet image, user can navigate to another section or tab in calculator or anywhere else and then come back to Calculator | Calculate tab and will see the updated Excel screenshot similar to below:
Result will be shown after the simulation is run.
Keywords: Microsoft Excel, Excel, Calculator, user input, customize, equations, Aspen Plus, Add-ins, Import, Export, Automation
References: None |
Problem Statement: An orifice plate can be modeled in Aspen Plus with the pipe model. How can I check for choked flow in an orifice plate? | Solution: The resistance from the orifice is converted to some L/D, which is added to the length of the pipe to calculate pressure drop. However, if I am interested in checking for choked flow in the orifice plate, it is important to specify the location of the orifice plate.
The way to model this would be to add a pipe model with length = 0, specify the diameter and include only the orifice plate from the Fittings 2 form. This way, the orifice plate can be added at the beginning or at the end of the pipe, and check for choked flow in the orifice plate.
Keywords: Choked flow
Orifice
L/D
References: None |
Problem Statement: In Aspen Plus software there is the possibility to click on recent cases, when opening the program. This feature may not be suitable for the users who would like to restrict access to the previously run simulation files.
This may be problematic in situations that computers are shared amongst many users such as in a university and the different groups of students are not allowed to open files from another group.
How do we clear the files which are visible in the recent cases list? | Solution: The list of recent files is not new to Aspen Plus, it was available in previous versions from the start page or the file menu. The list of recent files is stored on a per user basis.
The list of files is stored in file called application settings which can be found in 'DRIVE:\Users\USERNAME\AppData\Local\AspenTech\Aspen Plus V8.2\application.settings'.
If required this file could be manually edited using notepad editor to remove the recently used files or it can be deleted entirely after one group of students finished their work. If deleted other settings such as windows size and state are lost, too.
Keywords: recent files
References: None |
Problem Statement: How the parameter 'a' is calculated in the flash point estimation methods FLPT-PM and FLPT-TAG? For which components is it available? | Solution: The parameter 'a' in these two methods is available for all components since its value only depends on the MW and an experimental parameter 'k' that takes only two different values, one for FLPT-PM and other for FLPT-TAG (it is not component dependent).
In this two methods, the flash point is calculated as a modified bubble point. This modification is performed by recalculating the equilibrium constant for each component in the mixture using the MW and k:
Ki' = Ki * MWi / k
Where Ki is the k-value computed from the property method and Ki' is the modified k-value at the temperature that satisfies ∑(Zi*Ki') = 1, which is the modified bubble point.
For this estimation the real bubble point temperature won't satisfy ∑(Zi*Ki) = 1, but it will yield a value <1 that we call “a”:
∑(Zi*Ki) = a
Keywords: None
References: None |
Problem Statement: When a user specifies Design Specifications in a column (RadFrac), one can see this in the Components Tab that for some variables there is also an option to specify Base Components. When is this option made active and when will they be used?. We would also like to know how Aspen Plus uses this selection during the calculation run?. The illustration below show the typical setup. | Solution: For Mass/Mole/StdVol purity and Mass/Mole/StdVol Ratio calculations which one can select in Column| Design Specification| <name> folder| Specification tab, Aspen Plus can use different basis for calculations.
For example Stream purity is calculated by:
Where:
x - is a component fraction, on a mole, mass, or standard liquid volume basis
i - is a component from the Components list
j - is a component from the base components list
The default for Base components is all components . Hence, if one does not select anything then as a default Aspen Plus take into account all available components.
However, the user can decide which components will be taken into account during calculations.
The user has a similar option to select for a stream in Column| Design Specification| <name> folder| Feed/Product Streams tab. As one can see the feed streams as a Base streams option is available for Mole/mass/StdVol recovery, Mole/Mass/StdVol ratio, Property difference and Property Ratio.
For these properties the user can select the stream which will be taken into account as a base stream during calculations.
Keywords: Base components, RadFrac, purity, ratio.
References: None |
Problem Statement: How do you use the Custom Stream Summary to remove zero flow components or add phase results? | Solution: If you want to exclude components in the report in the graphical user interface, you can use the Custom Stream Summary or a TFF file; however, you will need to explicitly exclude specific components. Currently, there is no way to do it automatically for all components with zero flow. This means that rows for undesired components in the Custom Stream Summary can be selected and hidden manually, but you cannot do it automatically for all zero flow components .
The work flow to modify the Custom Stream Summary is outlined below.
1. Open a simulation. Make sure that there are some components that are not used. (I used one of our example files testprob.bkp and added some components)
2. Run the simulation.
3. Go to Results Summary | Streams (Custom)
4. Right mouse click on the Default tab and select Add New. Give the new sheet a name if you like. You can add multiple tabs for different properties or for properties for different phases.
5. Right mouse click on the new tab and select Edit View. This is where you get the wizard.
6. On the Property selection tab, select the properties that you want on the tab. There is a search at the bottom. I just selected Component mole flow.
7. On the Calculation Options tab, you can select the components using the drop down arrow. You can also select phases if you want.
8. You can change units of measure or precision on the Display Options tab.
9. Click OK to close the wizard.
10. Click on the new tab again and select Change Type. If you select Global to all records, this will be shown for all streams and block results.
The Custom Stream Summary is shown below:
Keywords: Custom Stream Summary
Stream Report
customize
References: None |
Problem Statement: Ideally when you install Fortran there is an option to allow the installation wizard to update the environment variables automatically and if this option is not selected then you need to set these path addresses manually. Visual studio is also needed to be installed on your computer to link the files into the DLL file. | Solution: It would perhaps be easier if Fortran compiler could be re-installed and to select the option for environment variables to be updated automatically. But you can also fix this manually by checking and changing, if necessary, the following SYSTEM environment variable for your computer (from Windows start menu right-mouse button click on My Computer | Properties | Advanced tab | 'Environment Variables' button) (see screen shots):
1) The environment variable named IFORT_COMPILER90 (or IFORT_COMPILER91 depending on the compiler version that is being installed) should be equal to C:\Program Files\Intel\Compiler\Fortran\9.0. If you don't have it, you should manually add it.
2) The INCLUDE environment variable should contain the following:
C:\Program Files\Microsoft Visual Studio .NET 2003\SDK\v1.1\Lib\;%IFORT_COMPILER90%\IA32\Lib
3) The LIB environment variable should contain:
C:\Program Files\Microsoft Visual Studio.NET2003\SDK\v1.1\include\;IFORT_COMPILER90%\INCLUDE
4) The PATH environment variable should contain the following:
C:\Program Files\Microsoft Visual Studio\Common\Tools; %IFORT_COMPILER90%\IA32\Bin
In all of the above points, IFORT_COMPILER90 might be actually IFORT_COMPILER91, if for examples you have installed version 9.1 of the Intel compiler. To modify SYSTEM environment variables administrative rights must be exercised.
Keywords: Fortran compiler, Environment variables
References: None |
Problem Statement: How to specify Heat Capacity of non-conventional component to a fixed specific value for entire simulation model? | Solution: Sometimes user need to fix the heat capacity of non-conventional component throughout the simulation model. For this user need to specify manually the heat capacity fixed value in to the correlation equations available for non-conventional component in Aspen Plus properties environment.
Follow the steps below.
1) Go to the Properties environment then select Methods | Parameters | Pure Components then create new NC-1 for non-conventional component.
2) In NC-1 select CP1C in parameters. As CP1C uses Kirov correlation for finding the heat capacity of non-conventional component.
3) Kirov correlation (1965) considered coal to be mixture of moisture, ash, fixed carbon, and primary and secondary volatile matter. Secondary volatile matter is any volatile matter up to 10% on a dry ash-free basis; the remaining volatile matter is primary. The correlation developed by Kirov treats the heat capacity as a weighted sum of the heat capacities of the constituents.
4) This correlation calculates heat capacities in Cal/gm-C using temperature in C. See the following parameters and their default values for your reference.
5) In order to make your fixed constant heat capacity value in above correlation user need to make sure that the temperature independent i.e. a (i, j1) value as your fixed value & rest i.e. temperature dependent to 0.
6) Let’s say you have to fix heat capacity value to 0.5 Cal/gm-K in your entire simulation then you have to put manually as below in your correlation.
For further reference, please see the example file attached.
Keywords: Non-conventional, heat capacity, Kirov correlation
References: None |
Problem Statement: How do I implement a simple customized kinetics for considering a reaction rate in a CSTR? | Solution: There are various options to consider: you could use the user subroutine kinetics in a RCSTR or use Aspen Custom Modeler to create a USERACM reaction type. The first approach (user subroutine) requires you install the appropriate fortran compiler. Refer to the documentation for more information.
Nevertheless, another option, that could be suitable for simple cases, is to use a RSTOIC block and implement the reaction kinetics in a design specification. Complex calculations can be specified in the fortran sheet of the design-specifications. The fortran compiler will not be required as long as you use instructions which are supported by the fortran interpreter of Aspen Plus.
The example attached illustrates the idea: the reactor block B2 is the RSTOIC where the simple kinetics is applied; the specified conversion in B2 is used as initial value in the design-spec DS-1 for performing the reaction rate calculations. The design-spec DS-1 evaluates the reaction rate using the kinetic expression specified in the DS-1 | Input | Fortran sheet: as an example, a power-law (you could use any expression) is specified in this sheet. The design spec manipulates the RSTOIC conversion specification to make the rate from the simple kinetic expression equal to the one evaluated from the material balance (rate1 = in - out).
The RCSTR block B1, with the same reaction kinetics specified in the DS-1, is used for demonstrating the consistency of the proposed method.
If you want to implement the calculations with Excel, you would also have to use a calculator block. Convergence with the tear variable option is not good, so the example uses a parameter to pass the value of the imbalance, and the design spec is used to converge. Excel cannot be used directly in design-specifications. For the case of multiple reactions, you would have to create several design-specifications (one for each reaction). Using a calculator block will allow to put all calculations in the same place.
Keywords:
References: None |
Problem Statement: I want to access and modify the FORTRAN subroutine files for an example provided in C:\Program Files (x86)\AspenTech\Aspen Plus Vx.x\GUI\App folder. How can we get the FORTRAN source code for any of these examples? | Solution: AspenTech provides majority of the FORTRAN source codes for the example files under \\GUI\App for the Users (except for source codes on urea and ammonia case studies). To obtain the FORTRAN codes, User needs to double-click the .apwz file (a compound file) provided for many of the examples. A folder with the same file name is generated that will contain all the files used by the simulation, including the user FORTRAN subroutines.
Keywords: FORTRAN subroutine files, Examples
References: None |
Problem Statement: Chemistry packing column diverges in an electrolyte system, with equilibrium reactions and some components present in trace level. The column uses the Rate-Based calculation method. | Solution: ThisSolution provides a recommended configuration aiming to improve convergence in the aforementioned scenarios. The method comprises the change of three parameters; one relative to general block convergence and other two concerning specifically RateSep calculations. Note that equilibrium-based iterations are performed in the initialization of rate-based calculations.
First step: changes in general convergence settings.
If trace components are present in a chemistry column, convergence problems may arise due to changing compositions of those compounds. In these cases, the column would fail to converge while showing relatively small Err/Tol values:
To solve this, go to column sheet form (left panel) / Convergence / Advanced / Eqrxn-form and change the default setting “standard” to “logarithmic”.
Eqrxn-form defines the type of equation in equilibrium reactions, the expression used may be either in a logarithmic or product form. By default, equations are written in the linear form for true-species problems. Choosing a logarithmic scale contributes to soften the effect of severe changes in composition that may take place during iterations for trace components. Small changes in variables driven by convergence methods could mean very important variations for trace components, causing oscillations and finally failure to converge. Generally, product form leads to more robust calculations, therefore, this change is only recommended when columns with chemistry diverge.
Running the simulation again we should get an improvement in convergence:
Note in the screenshot above that the column does not converge despite Err/Tol becoming less than 1. This can occur in columns with chemistry when changes in the column mole-fraction variables are still too large, mainly due to the presence of trace components. Note that the number of iterations of the inside loop (IL), which accounts for theSolution of temperature and composition profiles thorough the column, reaches almost constantly the limit by default (10), therefore despite the Err/Tol of the outside loop, the column continues iterating without converging.
Second Step: changes in the rate-based model.
In Rate-Based columns with very fast kinetic film reactions, or where trace components are present, the extent of the reactions along the interface can be overestimated during calculations, leading to major oscillations in compositions throughout iterations, especially when these components form part of subsequent reactions, and thus propagating the fluctuation to other species. In those cases the Err/Tol for the rate-based calculations reaches a fixed value and stays there. Reefer to below:
If “filmrxn” (see Sizing and Reating / Rate-based form) parameter is selected, the method will consider diffusion resistance and reactions in the film. When either trace components or fast film reactions are present, the changing compositions along the interface could cause once again severe fluctuations during iterations. To soften this effect and help convergence in the rate-based method, we will select again a logarithmic scale for the equilibrium equations.
Go to column sheet form (left panel) / Rate-based Modeling / Rate-Based Setup / Advanced Convergence / Equilibrium reaction formulation, and choose “logarithmic”.
We will also choose “Dogleg” as stabilization method instead of the one selected by default. Both changes are indicated in the following screenshot:
Now, if we run the simulation again, the column should converge:
For further reference, please see the example file attachment.
Keywords: Rate-based column, equilibrium reactions, trace components, convergence, diverge, Eqrxn-form, dopleg, advanced convergence, electrolytes, RadFrac.
References: None |
Problem Statement: How to change the property method in a block using Aspen Plus Automation Server. | Solution: With ActiveX Automation Server, users can use external Windows application to interact with Aspen Plus through a programming interface using a language such as Microsoft's Visual Basic.
With the Automation interface, users can:
· Connect both the inputs and the results of Aspen Plus simulations to other applications such as design programs or databases.
· Write your own user interface to an Aspen Plus plant model. You can use this interface to distribute your plant model to others who can run the Aspen Plus model without learning to use the Aspen Plus user interface.
The following code provides an example of how to change a property method within a block through Visual Basic and how to add new blocks to the simulation:
Sub PropMethod_Example()
' This example changes the property method in a block and let you add a new block.
Dim nStages As Variant
Dim strPrompt As String
Dim PropMethod As Variant
On Error GoTo ErrorHandler
lv_FilePathName = xlGetFilePathName
Set ihAPsim = GetObject(lv_FilePathName)
ihAPsim.Visible = False
Response = MsgBox(Prompt:=Do you want to add a new block'., Buttons:=vbYesNo)
' If statement to check if the yes button was selected.
If Response = vbYes Then
BlockName = InputBox(Introduce the block name)
BlockType = InputBox(Introduce the type in capital letters)
ihAPsim.Tree.Data.Blocks.Elements.Add (BlockName & ! & BlockType)
MsgBox The new block has been created
End If
Response = MsgBox(Prompt:=Do you want to change the property method in a block'., Buttons:=vbYesNo)
If Response = vbYes Then
strOut = ListBlocks(ihAPsim)
BlockName = InputBox(Introduce the name of the block you want to modify & Chr(13) & These are list of blocks in your simulation: & Chr(13) & strOut)
PropMethod = ihAPsim.Tree.Data.Blocks.Elements(BlockName).Input.Elements(OPSETNAME).Value
strPrompt = Existing property method for & BlockName & is: & PropMethod _
& Chr(13) & Enter new Property Method.
PropMethod = InputBox(strPrompt)
If (PropMethod = ) Then GoTo Finish
' edit the simulation
ihAPsim.Tree.Data.Blocks.Elements(BlockName).Input.Elements(OPSETNAME).Value = PropMethod
MsgBox The property method has changed
End If
* Functions “xlGetFilePathName”, “ListBlocks”, “Status” are included in the attached example.
In addition thisSolution includes an attached Excel file with VBA code that will allow to:
· Open any Aspen Plus simulation.
· Change the property method in a block
· Add a new block.
· Save and close the simulation
The example file enclosed is based inSolution 107014.
Keywords: ActiveX, VB, VBA, Visual Basic, Automation Server, getting started, examples, add block, change property methods.
References: None |
Problem Statement: How to check stage wise hydraulic parameters in Radfrac column? | Solution: RadFrac profiles hydraulics sheet gives the option to view profiles of column parameters used for tray and packing hydraulic calculations.
Open above attached file
Then activate check box as “Include hydraulic parameters” under Blocks/Column/Analysis/Report
Results can be viewed under Profiles/Hydraulics
Keywords: stage properties, hydraulic parameters, hydraulic properties, column stage properties etc;
References: None |
Problem Statement: The Aspen Plus user interface is a COM Automation Server. The Automation technology enables an external Windows application to interact with Aspen Plus through a programming interface using a language such as Microsoft's Visual Basic or C#. This | Solution: s shows how to do the connection from Matlab.Solution
Linking Aspen Plus is not officially supported or tested; however, it should be possible. The code below illustrates how to do the linking between Aspen Plus and Matlab:
function aspenlink
AspenVersion = 'apwn.document'; % Progid of Aspen Plus document class.
% Also 'apwn.document.34' to specify V8.8 as the version to be used.
AspenPath = 'C:\myFolder\mySim.bkp'; % Replace with the simulation path
AspenVisible = 1; % 0 for not visible
AspenDialogs = 1;
% Get pointer and load Aspen Plus comserver:
Aspen = actxserver(AspenVersion);
% Open the Aspen-Simulation
invoke(Aspen,'InitFromFile2',AspenPath);
Aspen.visible = AspenVisible; % Make it visible
Aspen.SuppressDialogs = AspenDialogs;
%Reinit and run simulation
Aspen.Reinit();
Aspen.Run2();
% Wait to update GUI
Pause(1);
%Release COM object
Aspen.Quit();
Delete(Aspen)
end
The following are links to the MathWorks KB section that deals with COM Automation including a getting started guide:
http://www.mathworks.com/help/matlab/matlab_external/getting-started-with-com.html
http://www.mathworks.com/help/matlab/using-com-objects-in-matlab.html
You can find more information on Aspen Plus interfaces in our online help, in the following section:
Keywords: Matlab, Linking, Aspen Plus, Automation.
References: None |
Problem Statement: Simulation with RadFrac column (Scrubber) diverges when using true component electrolyte approach with the following error message:
*** SEVERE ERRORCMBAL CALCULATIONS FAILURE: RERUN WITH CHANGES SUGGESTED IF THERE ARE ANY.
The above error is produced for different reasons, however in this case it is because the user is using a true component electrolyte approach which generates an imbalance in terms of the electrolytes involved. This is an electrolytes component mass balance error flag. | Solution: ThisSolution provides a recommended workaround by changing the electrolyte simulation approach to apparent component under the Electrolyte Wizard (Properties Environment):
Having set this modification, go to the Simulation environment and restart/re-run the simulation. The error message will be gone and the simulation converges without issues.
Keywords: Error message: CMBAL CALCULATIONS FAILURE, Component Electrolyte Approach, Convergence.
References: None |
Problem Statement: A user will often need to create Ternary diagrams using the distillation synthesis button in the Simulation Environment in Aspen Plus and they would like to know how Aspen Plus calculates distillation boundaries that are drawn within this diagram. | Solution: In order to have a background about ternary map and distillation boundaries, the user can find this under the Aspen Plus Online Help in the chapter: Locating Azeotropes and Distillation Region Boundaries. In this description the user can find general information about residue curves, azeotropes and how distillation boundaries can be defined.
Aspen Plus uses following steps to calculate distillation boundaries:
1. Search for all the azeotropes formed by the three key components
2. Determine the type of each azeotrope (stable, saddle or unstable)
3. Calculate the path from one azeotrope to the adjacent azeotrope, which defines one distillation boundary.
4. Calculate the path from one azeotrope to the adjacent key component, which defines one distillation boundary.
Using the example file ICPEbegin.bkp (which can be obtained from the following directory: C:\Program Files (x86)\AspenTech\Aspen Plus V8.0\GUI\Examples\Distillation Synthesis), the user can create a following Ternary diagram, if the key components are Methanol, Acetone and Chloroform (CHFL):
There are 4 azeotropes found for this system, marked as A1, A2, A3 and A4. The distillation boundaries are the arrowed lines. The arrow always goes from the lower boiling point to the higher boiling point.
The distillation boundary is calculated by integrating the differential equations that describe the residual curves. The distillation boundary starts from ternary saddle azeotropes if any exist in the mixture. For each azeotrope, the eigenvalues and eigenvectors are calculated. A small step is taken in the direction of each eigenvector. The residual curves are calculated by integrating the differential equations until a singular point is reached. The boundary points of the residual curves are used to create the distillation boundary.
Keywords: Distillation boundaries, Distillation Synthesis, Ternary Plot
References: None |
Problem Statement: When using RBatch the batch reactor at a certain time, one of the reactants goes to zero, therefore no more reaction should take place. However, the total mass keeps on increasing. Why would this happen? | Solution: This can happen when the rate expression is not dependent on the concentration of the feeds, i.e. no exponents are added under Driving Force on the Kinetic sheet of a General type reaction. When the rate is not dependent on concentration, the rate is not zero even if a reactant is zero. This means that the products can still be created. The way to work around this problem is to have a rate that is dependent on the reactant concentrations. If you really want a zero order reaction, make the exponent a very low number.
Keywords: None
References: None |
Problem Statement: New Feature in Aspen Plus V7.2 - Unit Operation Models | Solution: The following enhancements were made to unit operation models in Aspen Plus V7.2.
Columns
Fair72 jet flood method provides a much closer fit to Fair's original graphical correlation than the Fair method previously available in Aspen Plus. Fair72 usually predicts higher flood points (lower percent of flooding) and higher downcomer backup than the earlier Fair method. Also added is the SDO72 jet flood correlation, based on the well-known model by Smith, Dresser, and Ohlswager.
New packings available for rating and sizing calculations: Durapack, Flexisaddle LPD #3, VSP25, VSP40, 1 Tri-Packs, 1.25 Tri-packs, 2 Tri-Packs, 3.5 Tri-Packs.
Information messages are now printed to the Control Panel and history file when jet flooding or excess downcomer backup conditions exist, in both cases when the capacity exceeds 80%.
A new Arithmetic option exists for film discretization in Aspen Rate-Based Distillation. This option divides the film into regions whose thicknesses have a common difference, rather than a common ratio. This can be selected on the RadFrac | Rate-based Distillation Setup | Specifications sheet. When you select it, you must specify the increment. This option enables better model accuracy with fewer discretization points compared to previously available methods.
Reactors
New EO Option for RPlug and RCSTR only, Flash when calling user routine, allows you to choose whether to perform a flash before a user routine is called. Calling this flash reduces the number of variables that must be perturbed, but in some cases may take more time than is saved by the reduction in number of variables. Not calling the flash is generally more stable. Past versions always called this flash, but now the default is not to call it.
RGibbs now checks for the possibility that multiple hydrates, including the anhydrous form, are possible as salt precipitation reactions for any salt, and selects the one which minimizes Gibbs energy.
Reaction sets of the Powerlaw, LHHW, and General types can now use fugacity as the concentration basis for kinetic reactions.
RYield has an option to check the atom balance on the Block Options | Simulation Options sheet. This check is performed by default except when there component with ATOMNO & NOATOM missing, when it cannot be checked. When there are non-conventional component flows the check is performed only for ULTANAL elements (and not for oxygen if there is a change in ASH content), and it is skipped entirely if ULTANAL is missing.
RCSTR, RPlug, and Valve now support the equation-oriented option Remove missing phases and its associated Phase tolerance.
HeatX using Shell&Tube
Aspen Plus now supports the Colburn-Hougen mass transfer condensation model in HeatX blocks using Shell&Tube. You must specify this in your Shell&Tube input file, or in the EDR Browser of the HeatX block, click the Input | Program Options | Methods/Correlations form, then the Condensation sheet, and select HTFS - mass transfer for the Condensation heat transfer model. This model generally gives better results for heat transfer in condensing vapors than the default Silver-Bell model (which uses overall stream properties rather than individual component properties). However, this model is limited to 50 components. Aspen Plus will reduce the component slate given to Shell&Tube for the hot stream down to just the components with non-zero flows, but if this is still more than 50 components, a warning will be issued and it will revert to the Silver-Bell model.
In HeatX blocks using Shell&Tube, the Calculation Method (on the Options | Convergence sheet when Shell&Tube is selected) has a new option Decided by EDR which is the default for new runs. This option lets Shell&Tube determine which calculation method is better for the particular exchanger.
HeatX now allows the exchanger to be specified as co-current when an E shell with multiple tube passes is specified. This does not change the results for this type of exchanger, but it may be useful when the data is passed to other programs (for instance, to correctly locate the nozzles).
HeatX using Shell&Tube, AirCooled, or Plate
Property curve generation is improved. The default curve type (now called System) now generates isobaric curves at inlet and estimated outlet pressures, and when phase change is expected or for all-vapor flow under 50 psi, one to three intermediate pressures. The multi-isobaric curve type was renamed to User-specified, and still generates curves at one to four pressures you specify. However, for improved accuracy, when there is a pressure drop calculated from EDR available for the last run or last iteration of a recycle loop, this pressure drop is used as the estimate.
Pipe
The Pipe model now handles integration failure under choked flow more gracefully, which may allow Design-Specs to find non-choked conditions and converge. See Choked Flow in Pipes for details.
Compr
Regression results for Compr performance curves entered as tabular data are now shown with units on the Results | Regression sheet, and are now accessible in operations such as Calculator blocks as variables REG1-COEF and REG2-COEF.
Dryer
Dryer now reports evaporation rates of moisture components.
Keywords: None
References: None |
Problem Statement: In the BatchFrac model the option of specifying a reflux ratio, etc. on a STDVOL basis can be confusing. | Solution: Only use STDVOL basis when modeling petroleum/hydrocarbon components.
STDVOL is the Standard liquid volume at 60 F and 1 Atm, and is commonly used in the petroleum industry.
Note that the standard liquid volume flow (STDVOL) can be very different from the volumetric flow rate of a stream. The standard liquid
volume is defined at 60 F and 1 atm. The difference increases as the
conditions diverge from 60 F and 1 atm. The volumetric flow rate of a stream may be very different from the standard liquid volume flow if the stream is vapor or has a significant amount of vapor.
Keywords: Concentrate, Distill, BatchFrac
References: None |
Problem Statement: Is it possible to recycle materials between batches? | Solution: Yes. Materials can be recycled from a vessel between batches. The recycle input form is provided as an option in the Charge operation. On the Required tab, click on the 'Details' button next to the Material field to be loaded and then click on Recycle to specify the recycle stream and policy. One can recycle either a single component or the mixture from a vessel.
It is only when running a production plan, consisting of several batches, that the recycled material will be available. The recycle policy and how the amount recycled should be calculated can be specified for each recycle stream. See Batch Plus online help under 'Recycles' for further details.
In the attached example X100 is extracted from Solvent B using Solvent A. Solvent A and X100 are separated in column C102. Solvent A is then recycled.
Run the step once. In Operation 1.1, 1000 kg of Solvent A are loaded from inventory location 'Solvent A Storage'.
Run a production plan with 5 batches of the previous step. In the first Operation 1.1, Solvent A is loaded from inventory location 'Solvent A Storage'. In the following batches, 700 kg of Solvent A are recycled from the recycle tank and only 300 kg are loaded from 'Solvent A Storage'. This can be seen by checking the Schedule view for the production plan (Results -> Schedule).
To import the attached example in a Batch Plus project, go to the File menu, select Import and then Step File.
Keywords: Recycle, recycling
References: None |
Problem Statement: If you want to be able to fit a boundary layer thickness of the flow in an RPlug block as a function of the distance from the inlet, you need the current point along the RPlug axis where the solvers are integrating so you can take this distance and calculate the boundary layer thickness in external Fortran. | Solution: Look for the argument list for the Kinetic Subroutine in the Aspen Plus User Models documentation (e.g. AspenPlusUserModelsV7_1-Ref.pdf) which is available on the Documentation DVD or from the Documentation link on the support website.
In the section Kinetics Subroutine for USER Reaction Type, the variable XCURR is the current location along the reactor. This variable is also used as the current time or iteration number for other reactors.
XCURR (REAL*8)
RPlug: Current reactor location(m)
RBatch, Pres-Relief: Current time(s)
RCSTR: Current iteration number
RadFrac: Current stage number
Keywords: None
References: None |
Problem Statement: Why does the calculated density for NACL (dissolved in water) from different databanks vary markedly? | Solution: In Batch Plus, when a solid is dissolved in the liquid phase, the mixture properties will be calculated using the liquid state parameters. Depending on the availability of parameters, the liquid density is calculated using different methods in this order:
Pure Liquuid:
If the DIPPR parameters (DNLDIP) are available, pure component liquid density is calculated by DIPPR equation.
If the Critical Property Parameters (Tc, Pc, RKTZRA) are available, pure component liquid density is calculated by the Rackett equation.
If no parameters are available, water density is used instead.
Liquid Mixure:
IDEAL (weighted average of pure liquid molar densities)
Rackett Model (requires Tc, Pc, Vc, RKTZRA, RKTZIJ)
In Batch Plus, there are three material databanks:
Property Plus Pure Components
Property Plus Inorganics
Property Plus Solids
The Pure Components databank contains both DNLDIP density parameters and Critical Property Parameters for NACL and water. Depending on the liquid mixture density model selection (IDEAL or Rachett), the calculated liquid mixture density may differ slightly.
The Solids databank contains the Critical Properties Parameters for NACl and water, but no DNLDIP parameters. So the Rachett model will be used.
The Inorganic databank doesn't contain either parameters above, so the density of water is used as default.
Keywords: Density, Properties, Solid, Dissolved, Databank
References: None |
Problem Statement: Can you create a .PDF file of the Process Flow Diagram or of the report (.rep) file? | Solution: Aspen Plus cannot be used to create a PDF file; however, many other programs such as Microsoft Office have this capability. For the flowsheet drawing, simply select all and copy [CTRL+A, CTRL+C], go to PowerPoint, paste [CTR+V], and save as PDF or just use a screen grabber. You can make the report file into a PDF by opening it with Word and using Save as.
It is also possible to use various one of the free PDF printers such as cutepdf and doPDF7. With these, you just print and choose the PDF maker as the printer. It then pops up and asks for a file name and location to write the PDF.
Keywords: None
References: None |
Problem Statement: I have a block that does not properly initialize when I switch from the sequential modular (SM) strategy to the equation oriented (EO) strategy. How can I configure the EO model to solve in this case? | Solution: The Perturbation layer can be applied to a block to allow it to solve within EO when it is not properly initialized. By default, any unit operation model that is not supported by EO is solved in the Perturbation layer. However, you can tell Aspen Plus to solve supported unit operation models in the Perturbation layer using the following procedure:
1. Access the Data Browser folder for the unit operation block in question.
2. Select the Block Options form.
3. Select the EO Options tab.
4. Click the Additional Options button.
5. In theSolution Method field (top left-hand corner) select Closed; use Perturbation layer around closed model.
This will create EO variables around the inlet and outlet of the block allowing it to interface with the other unit operation models in the simulation that are solved using the EO strategy.
Keywords: equation oriented, perturbation
References: None |
Problem Statement: If comparing Radfrac vs Petrofrac and using subcooling in the condenser, the stage 1 temperature will not be the same in the Profile results> TPFQ tab and Profile results> Hydraulics tab.
The profiles section is Found in the Radfrac or Petrofrac folder at the bottom. There you can find 4 main tabs: TPFQ, Compositions, K-Values and Hydraulics. | Solution: Since RadFrac has the subcooling option inside the Total Condenser type, the profile results convention is different from the Petrofrac that has the two type of condenser, Total and Subcooled.
This is only a difference in convention and does not affect the overall performance of the column, for example:
For RadFrac:
1) The TPFQ section show for stage 1 the bubble point temperature. You can look for the subcooled liquid temperature in the hydraulic section of the profiles (see below)
Results of Radfrac showing both temperatures, bubble point and subcooled.
Bubble point for stage 1 in the TPFQ tab. Subcooled temperature in the Hydraulics tab
For PetroFrac:
1) The TPFQ section shows for stage 1 the temperature of the subcooled liquid.You can look for the bubble point temperature in the hydraulic section of the profiles.
Results of the Petrofrac showing only the subcooled temperature.
Subcooled temperature in TPFQ tab. Bubble point in Hydraulics tab.
Keywords: Profile results, Condenser, total, subcooled, temperature, duty, radfrac, petrofrac.
References: None |
Problem Statement: How does Aspen Plus calculates the venting requirements for storage tanks? | Solution: Concerning the required capacity, we do not calculate the required capacity from the API 2000 equation. For the fire scenarios we run a dynamic simulation with the vessel and relief system specified by the user and calculate the flow through the relief device based on the conditions in the vessel and the relief system specifications. If you change the diameter of the emergency relief vent you should see different flows during the relief event. Clearly the equations in API 2000 are not affected by the relief vent diameter. But the Aspen Plus simulation is affected because we calculate the actual flow leaving the vessel during the dynamic run.
Unlike most programs used for vent sizing, the Aspen Plus program actually finds theSolution of the integral equation for vent flow. The equation is described in the DIERS Project Manual, equation II-16 [1]. As the dynamic simulation of the vessel proceeds, we calculate the flow rate through the vent at each time step using that equation.
In order to save time, the default method to solve that equation uses Simpson's shortcut method. Simpson's method gives us a relationship between volume and pressure so we were able to find an analyticalSolution to equation II-16. This speeds up the calculations dramatically without losing any accuracy. There is also the option to not use Simpson's method and instead to do a rigorous integration to solve the valve model at each time step. The user can do this by changing the convergence method for the pressure relief model. These parameters are on the Convergence / Methods form. Simpson's method is described in [2].
Keywords: PSV, vent sizing
References: s:
[1] Emergency Relief System Design Using DIERS Technology: The Design Institute for Emergency Relief Systems (DIERS) Project Manual. H. G. Fisher, H. S. Forrest, Stanley S. Grossel, J. E. Huff, A. R. Muller, J. A. Noronha, D. A. Shaw, B. J. Tilley. ISBN: 978-0-8169-0568-3
[2] Simpson, L. L., “Estimate Two-Phase Flow in Safety Devices,” Chem. Eng., 98 (8), pp. 98–102 (Aug. 1991) |
Problem Statement: When I run the simulation file, the results for convergence and calculator blocks are not shown. How do I display these results? | Solution: It is possible to turn off some of the items included in the report file for a simulation on the Setup | Report Options form. This will also cause the results to not appear in the User Interface (See .bkp example file attached). If some results are not showing even though the simulation has executed, check the Setup | Report Options | Flowsheet tab. If Interactive load results is turned on under Run Settings | Options, then the results may appear immediately after a run, but will disappear when saving.
In order to modify the items with results, one has to follow the steps below:
1) Go to Setup | Report Options, at the Flowsheet Tab, check that all the boxes are active. Specially the “Convergence block” and “Calculator block” if those are missing:
2) Run.
3) Check the different folders for the results. The results should be shown now.
Keywords: Hierarchy, Convergence and Calculator Results.
References: None |
Problem Statement: When using a RBATCH reactor and you try to export an input file with a continuous feed input from a previous Aspen Plus version, for example V7.3 the following error message is shown in the control panel: | Solution: The issue when you try to export an input file with a continuous feed input from a previous A+ version is related to an invalid set of units in that previous version, located under RBATCH (model name) | Setup | Continuous Feeds | ‘Specify flow vs time profile’. On the new GUI (Graphical User Interface), there are no units input for continuous feed time. Therefore, changing the Unit Sets to ENG for example in the new version GUI and redefined the values of time and flow again, it may help to make the simulation converge without problems (see screenshots below):
- Previous Unit Sets (User defined):
- Changing to ENG unit sets:
(Reset the original values of Time vs Flow):
Keywords: RBATCH, Error Message, Unit Sets.
References: None |
Problem Statement: My HEATX heat exchanger is bypassed. The error is
Block: BOILER Model: HEATX
** ERROR WHILE GENERATING RESULTS FOR UNIT OPERATIONS BLOCK: BOILER
(MODEL: HEATX)
COLD STREAM IS HOTTER THAN HOT STREAM
BLOCK BYPASSED | Solution: The problem in this file is that the cold stream was connected to the hot stream port of the HEATX rather than the cold stream port.
To solve this problem, the connections need to be reversed by disconnecting and reconnecting them to the correct port. If you hover over the port on the block, a pop-up help box with the name of the port type will appear.
Note that the reverse case is also a problem:
** ERROR WHILE GENERATING RESULTS FOR UNIT OPERATIONS BLOCK: HEATX
(MODEL: HEATX)
HOT STREAM IS COLDER THAN COLD STREAM
BLOCK BYPASSED
The procedure explained above also applies for this case.
Keywords: Heatx, hot port, cold port, block bypassed
References: None |
Problem Statement: When I open the data filter on the Equation Oriented (EO) variables, the pull down list has ALL and all individual variables listed. What can I do if I want it to list only temperature variables? | Solution: There are a number of simple ways to filter the EO Variables list.
For example, using the EOGSG2.bkp example from the Examples\GSG_EO directory, the EO Variables from Block CONDUA initially has:
If you select a Physical Type of Temperature, you will get all of the variables with a type of temperature:
If you right mouse and click on the column headers and select Show Filter Record. Then, change the = to Contains and type TEMP:
Keywords: None
References: None |
Problem Statement: How is the power requirement for a CRUSHER block calculated? | Solution: The power requirement for a CRUSHER is calculated using the following equation and based in a wet crushing operation.
Where:
The BWI is a semi-empirical parameter that depends on the properties of the material processed and it defines the work consumed in size reduction. These indices have been measured experimentally for a wide range of materials, and are available in the literature.
There are two considerations in the calculation of the power requirements for a CRUSHER:
1. If the Inlet stream contains no liquids, then the CRUSHER will be operated under dry conditions. The power requirements for a dry crushing operation increase by 34%.
2. If is less than 70 micrometers, then the power required is adjusted by:
For example, the attached file compares the work requirement of two CRUSHER blocks that work with the same operating parameters and grindability. The difference is that the inlet stream of CRUSHER 2 mixes with a stream of water before entering the block. Please notice that the power calculated for CRUSHER 1 is 34% higher than the power calculated for CRUSHER 2 which operates under wet conditions.
Keywords: Crusher, Solids, Power, Wet Crushing, Dry crushing
References: None |
Problem Statement: I have a Hierarchy block in my simulation. Is there a way that I can move everything inside into the main flowsheet? | Solution: You can right-click on the Hierarchy block select Move selection.
You can use the Extract hierarchy contents and delete option. Clicking on OK will prompt you to resolve ID conflicts if there any. Ater you resolve conflicts, all the objects will be transferred into the main flowsheet.
Keywords: Hierarchy
Flowsheet
References: None |
Problem Statement: Mass concentration unit <<weight/volume>> is not included on the Design-Spec and Sensitivity Analysis variable define form, however this unit is extensively used in biochemical processes, e.g. bioprocessing, biofuel industries.
How can this unit be handled on Design-Specs and Sensitivity Analysis? | Solution: Mass concentration [weight/volume] can be included on a Prop-Set and then used in Design-Specs, Calculator blocks and Sensitivity Analysis.
Any property set property can be accessed using the Stream-Prop type of data available on the Define sheet. It is important to note that only one property value can be accessed in each prop-set. If a property for multiple components needs to be accessed, a prop-set for each component must be created.
Colligative properties of electrolyticSolutions such as osmotic pressure, boiling point, freezing point, vapor pressure, and the thermal properties ofSolutions containing electrolytes govern a number of living and non-living/ chemical processes.
The attached model Simu gmL-1.bkp uses a Sensitivity block to study the effect of salt concentration (gm/L) in a brine on its boiling point and the duty of a heater used to raise brine?s temperature (Figure 1).
Figure 1. Effect of Salt concentration (NaCl) on brine?s boiling point (?C) and heater duty (BTU/h).
The attached model Simu gmL-2.bkp uses a Design Spec block to adjust the salt concentration in a brine stream to increase the brine?s boiling point to 102 ?C. Figure 2 shows that salt concentration needed is 205.9 gm/L.
Figure 2. Design Spec block results.
Keywords: Concentration unit gm/L, Design Spec, Sensitivity Analysis, Variable definer
References: None |
Problem Statement: What could prevent me from connecting to the remote Aspen Properties Enterprise Database (APED) server?
Cause
This may happen as Server is not configured for remote access and/or Windows Firewall is blocking access. This can happen with either SQL Server Express or Enterprise. | Solution: Please follow the following steps to configure a SQL Server to be used by remote users.
1. Enable protocols.
2. Configure Windows Firewall (different procedures for Windows Server 2008 and 2012).
3. Restart the service and verify they are set to start automatically.
Please see the attached pdf file for the details of the steps.
Key Words
Configuration, SQL Server, Remote Access
Keywords: None
References: None |
Problem Statement: How to define a solid when it is dissolved in a solvent?
Applicable versions
All versions. | Solution: A solid can be defined in Aspen Plus as a Conventional Inert Solid (CI Solid) or Nonconventional Solids (NC Solids). In some processes there are solids in aSolution and at the end of the process they can precipitate coming back to the solid phase. In these cases, the solid must be defined as a Conventional Inert Solid but also as Conventional in order to represent the fluid phase of the solid present in a solvent.
There is an example file attached in which a solid, AlCl3 is mixed with Toluene to create a new dissolvent. In components specification, the AlCl3 component is defined as a solid and as conventional component.
After that, we need to define the reaction that takes place: in this case the AlCl3 is dissolved in Toluene, so the type of reaction selected must be SALT (the procedure will be the same for dissociation reactions), and the equilibrium reaction specified is the following:
AlCl3 (s) == AlCl3 (l)
Once it is defined, in the simulation environment a mixer has been introduced to mix both components: initially the AlCl3 will be only solid as it’s been explained before. (It is defined in a mixed stream because this stream can include Conventional Inert Solids for simple simulations).
Then, a heater has been introduced to check the variation on the composition of the compounds involve in the process and results obtained after the heater show that the flow of the fluid phase, AlCl3 (l), has increased.
Keywords: Solids, solvent, dissolved, dissociated.
References: None |
Problem Statement: How is IONSMÂ (Ionic strength in molality scale) property set calculated in Aspen Plus? | Solution: Ionic strength in molality scale is defined as follows:
Where
m -the ionic concentration in units of molality
mo - 1 mol kg-1
zi - charge number of component i
Keywords: Ionic strength, IONSM
References: Atkins, P. W. Physical Chemistry, 3rd ed.; Oxford University Press: New York, 1986. |
Problem Statement: What do green xs around a flowsheet mean? | Solution: When the flowsheet is locked, a green cross-hatched border appears on the flowsheet.
XXXXXXXXXXXXXXXXXXXX
You can use Lock Flowsheet from the Section section of the Modify tab of the ribbon to lock the flowsheet to prevent unintended changes. This prevents you from adding, deleting, or renaming blocks and streams, changing stream connections, and moving elements around on the flowsheet. You can still make changes to data on forms except on the Flowsheet form. To unlock the flowsheet, select Lock Flowsheet again.
Keywords: None
References: None |
Problem Statement: Is it possible to make a Ternary Phase plot for a Cellulose/ Solvent/ Water (polymer-liquid-liquid) system?
According to the literature cellulose gets dissolved in the solvent/water system only at certain compositions. They are trying to incorporate this dis | Solution: in Aspen Plus.
Solution
The ternary plot does not apply to systems containing polymer or oligomer components. However, you can still setup a Flash3 block to perform liquid-liquid equilibrium (LLE) for a system containing Cellulose and Water.Attached is an example file, LLE-Cellulose-V84.bkp, for such a calculation.
1. Cellulose is defined as an oligomer with 10 Cellulose segments.
2. Benzene and Ethanol are arbitrarily selected as solvents. Water with Benzene and Ethanol show LLE.
3. POLYNRTL is the property method.
4. The NRTL parameter for Water/Benzene is copied to the NRTL parameter for Water/Cellulose Segment. The user can do a data regression if they have LLE data for Water/Cellulose system.
The flash results clearly show LLE for a Cellulose/Solvent/Water system.
Keywords: None
References: None |
Problem Statement: How do you get the Flowsheet window back in Aspen Plus V7.3.2 after closing it? | Solution: Go to the View tab and select Flowsheet from the Show section of the ribbon. This is also the place where you can re-open the Start Page.
Keywords: None
References: None |
Problem Statement: Where is the help menu in Aspen Plus V7.3.2? What is the best way to get to Help? | Solution: There are a few ways to get Help in Aspen Plus.
1. To launch Help, select the small Show Help button from the far right of the ribbon.
Contents: Browse through the documentation, including User Guides and
Keywords: None
References: Manuals
Index: Search for help on a specific topic using the index entries
Search: Search for a help on a topic that includes any word or words
2. With the cursor in the desired field, press the <F1> function key to bring up help for field and/or sheet
3. To get help troubleshooting a specific error or warning message, go to the Troubleshooting button in the Help section of the Get Started ribbon. This help is based on a description of the problem using diagnostic messages and results of failed runs.
4. Users who have Premier Plus support can go to the Online Training button on the Help section of the Get Started ribbon to get video tutorials.
5. If there is no information in the help, users can try the using the technical support Knowledge Base available on our website by clicking on the Support button on the Help section of the Get Started ribbon.
6. Finally, users can always call, email, or chat with the technical support team. Either click on the Live Chat or Send To Support buttons on the Help section of the Get Started ribbon or call one of our toll free numbers. |
Problem Statement: When creating a new property method NRTL-GLR based on WILS-GLR where the liquid gamma is changed to GMRENON, the heat duty with WILS-GLR and NRTL-GLR are different.
NRTL-GLR takes account heat of mixing (though heat of mixing is unchecked on Properties | Specifications form), while WILS-GLR does not takes account it.
Is there any way to change route to let NRTL-GLR not take account heat of mixing? | Solution: When you modify the model from GMWILSON to GMRENON, the GMRENON model will be used in all calculations that require an activity coefficient gamma model. This includes the heat of mixing effect. That's why you get a different heat duty.
To not include the heat of mixing effect, you must change routes for liquid fugacity coefficients (and Gibbs free energy). On the routes form, select PHILMX86 and GLMX86.
This is now documented in V7.2 along with an update that disables this checkbox when users have modified the liquid gamma model. This is documented on the Modifying Property Models topic, which is linked, among other places, from the field help for the Heat of Mixing checkbox.
Note: Turning off Heat of Mixing sets a route to use activity coefficient model GMIDL
for property DHLMX. If you change the Liquid gamma model or its Data set number,
this specifies the activity coefficient model directly, which overrides the route
selection. As a result, the Heat of Mixing option is disabled when you have changed
Liquid gamma or its Data set. For more information on the interaction between models
and routes, see Models in the Physical Property Methods help.
Keywords: None
References: None |
Problem Statement: Increasing number of significant figures shows only zeros. Is it possible to increase precision of the results? | Solution: Internally, all calculations in Aspen Plus are done in double precision using SI units. The results are reported in user units with eight significant figures. The significant figures can not surpass 8 since this is how many are saved for the report data. However, customers can change the unit of the wanted property to a larger one to effectively increase the accuracy for the same significant numbers.
Alternatively, customers can use a Calculator block to write the variable to history or report file. Since values are in double decision, they can be written as any format desired.
Keywords: significant figures
References: : CQ00699383 |
Problem Statement: I am using the NRTL-HOC property method in my simulation. When I run my simulation it converges fine but I get the following error message when trying to view the stream results form for any block:
Can you tell me why this is happening?
Application Version(s)
V7.3, V7.3.2, V8.0, V8.2, V8.4, V8.6 | Solution: This error is displayed because Aspen Plus was not able to determine the mixture viscosity MUMX listed in the property sets HXDESIGN and TXPORT and display it in the stream results when this property set was selected to be included in the stream report under Setup | Report Options | Stream Tab.
The reason for this is because a component(s) in your components list requires the the following parameters (LJPAR-1 and STKPAR-1) to be available:
To make these parameters available, a new temperature dependant parameter sheet can be created and the values for LJPAR-1 and STKPAR-1 can be inputted if the user has these parameters available.
If the user does not have these parameters available then the next option would be to use a different model to calculate the low pressure vapour mixer viscosity MUVMXLP.
From the Properties | Property Methods | NRTL-HOC | Models Tab | Property MUVMXLP. Finally, from the Model Name field click to select MUV2CLSL that corresponds to Chung, Lee, and Starling model.
Re-initialise the simulation and run. Go to the Stream Results form for the block and the results will be displayed.
Keywords: NRTL-HOC, Stream Results, Viscosity, Error Displaying Results
References: None |
Problem Statement: In a HeatX model using rigorous design method with EDR, the outlet temperatures in the EDR environment don't match the temperatures reported in Aspen Plus.Why is this? | Solution: The differences between the results in EDR and A+ are caused by the hot or/and cold stream properties having inappropriate temperature points. If you look in the EDR browser after accepting the design, you will see that the Hot/Cold Stream Properties has most points located in the two-phase region:
There aren't many property points that cover the one-phase-only region, and if the hot/cold side is only in the one-phase region, EDR will have trouble calculating properties. For the same heat load, EDR will calculate a different outlet temperature than Aspen Plus does. The reason being is a default option in Aspen Plus. In 'EDR Options | Property Curves' there is the 'Curve distribution (total 24 pts)' input. The default value is 'Equal-distribution in two-phase', this option will put most of the property points in the two phase region. After changing this to ‘equal distribution’ the outlet T will match:
Keywords: EDR, HeatX, outlet temperatures, property points.
References: None |
Problem Statement: Control objects' labels wrap around, making them unreadable (See Figure 1).
Figure 1. Aspen Plus V7.3. GUI. | Solution: This problem occurs when your computer?s screen is set to use large fonts and can be fixed by
changing the Windows display settings.
Steps to fix this issue:
For Windows 7.
1.Right-click on your desktop, and select Screen ReSolution
2.Select ?Make text and other items larger or smaller?
3.Select the radio button ?Smaller- 100% (default)?
4.Press ?Apply? button and close the dialog box.
Keywords: GUI, Windows screen re
References: None |
Problem Statement: The shortcut to find which use to be Ctrl+F9 in V7.3 and earlier is missing in the new user interface. | Solution: The find dialog is now tied to CTRL+F shortcut keys (to be consistent with HYSYS and other products).
Once you are on find dialog, click the move to check box then click the find button to brings you right to the selected block or stream.
Keywords: None
References: None |
Problem Statement: How do I use the NIST/TDE database such as TDE5n.mdb with Microsoft Access? | Solution: The NIST TDE database can only be accessed through the NIST Thermo Data Engine button on the tool bar or from the Tools menu. All experimental data available can be access in this manner and the data can be saved to the Aspen Plus .bkp file and used in data regression if needed. The access database cannot be directly accessed using query. We do not support this workflow, and our contract with NIST does not allow us to implement this feature.
Keywords: None
References: None |
Problem Statement: When using a conversion reaction inside a RadFrac block, how is the conversion considered in the calculations? | Solution: If conversion reactions are used inside a RadFrac block, the reaction rate is calculated for each reactive stage using the specified conversion, the key component, and the total flow rate of the key component (including vapor and liquid streams entering the stage and the feed streams to that stage).
In the attached example of a RadFrac with 3 stages, the following conversion reaction has been specified for stage 2:
ETOH + AA --> WATER + ETAC
The feed is in stage 2 and the conversion is 50% of AA (Key component)
For stage 2, the conversion is calculated in the following way.
For the key component AA, the total flow of AA in the stage is calculated based on the flows coming from the top and down stages and the feed.
With this total flow, the conversion reaction is calculated.
Reaction rate of AA on stage 2 = conversion * total flow of AA
0.5*113.422kmol/hr = 56.711 kmol/hr
The stoichiometry of the reaction is used to calculate the rates of the other components.
Keywords: Aspen Plus, RadFrac, conversion reactor, reactive distillation
References: None |
Problem Statement: When I run the simulation in Customize Aspen Plus then how to review an error summary report? | Solution: When you run your simulation model in Customize Aspen Plus by using input file then it is difficult to trace errors. If you want to check the errors while running the file in customize option you have to go through following procedure.
1) If you go to Start | All programs | Aspen Teach | Process Modelling V8.8 | Aspen Plus | open Customize Aspen Plus V8.x you will see following window.
2) Then you have to give working directory of your input file location as below.
3) In order to trace errors in your simulation model you have to give following command to customize option.
“Working directory > Aspen File Name.inp test”
4) Hit enter you will see following window. Kindly note that your Runid is Test.
5) When Run is finished then you will see Aspen Plus History file and Aspen Plus Report file in the same working directory.
6) You will get results detailed information in Aspen Plus Report file.
7) In order to trace errors you have to follow Aspen Plus History file. This is separate file which provides detailed information about convergence summary. It will help you to trace out your errors which are associated with your simulation model.
Keywords: Input file, Customize Aspen Plus, Error summary, .inp, history file, report file, command prompt
References: None |
Problem Statement: After Install of V7.3.2 of Aspen Plus The Start Page Shows the following error:
HTTP Error 407 Proxy authentication required. | Solution: Some background info:
The Web server (running the Web site) thinks that the HTTP data stream sent from the client (e.g. your Web browser) was correct, but access to the URL resource requires the prior use of a proxy server that needs some authentication which has not been provided. This typically means you must log in (enter user ID and password) with the proxy server first.
Any client (e.g. your Web browser) goes through the following cycle:
Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
Open an IP socket connection to that IP address.
Write an HTTP data stream through that socket.
Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.
This error occurs in the final step above when the client receives an HTTP status code that it recognizes as '407'.
To resolve:
A 407 error detected via a Web browser can often be resolved by navigating to the URL in a slightly different way (e.g. accessing another URL) for the proxy server first. Your IT Specialist should be able to explain the role of the proxy server in their security setup and how you should use it.
The URL for the start page in Aspen Plus is: http://www.aspentech.com/rss/aspenplus.xml. This URL will have to 'allowed' on the proxy server.
You can set this from the Aspen Plus user interface once you open any Aspen Plus file.
Once an Aspen Plus file is opened, you need to go to File | Options | Start up | and paste this path in the start Page news channel box.
Keywords: Proxy authentication
error 407
HTTP Error 407 Proxy authentication required
References: None |
Problem Statement: In RCSTR, when you have multiple phases, you can specify RES-TIME (overall residence time) or phase residence time. | Solution: When you specify residence time, the reactor assumes no-slip conditions between the phases. This implies the vapor fraction in the reactor is the same as in the mixed outlet stream. Since the molar volume of vapor is >> molar volume of liquid, this makes the liquid residence time very small. This assumption is valid in things like pipe fittings or inline mixers simulated as CSTRs, but it is not appropriate for real reactors with level control
For a real reactor use the condensed phase residence time to specify the reactor.
Keywords: RCSTR, phase residence time
References: None |
Problem Statement: The default node values are in mass basis, how can I retrieve the enthalpy and entropy in molar basis? | Solution: There are different ways to retrieve the enthalpy and entropy in the molar basis:
1. Use the ValueForUnit function of that node to read in the desired basis,
enthMolar = mySim.Tree.FindNode(Data\Streams\S1\Output\HMX\MIXED).ValueForUnit(39, 2)
2. Change the HAP_UNITROW attribute for that node so that it is set to molar enthalpy as physical quantity as follows,
myNode = mySim.Tree.FindNode(\Data\Streams\S1)
myNode.Output.HMX.MIXED.AttributeValue(Happ.HAPAttributeNumber.HAP_UNITROW) = 39
Then you can directly read the value of that node.
3. If you have run the simulation, you can even read the results from the results table in the following node in molar basis,
mySim.Tree.FindNode(\Data\Streams\S1\Stream Results\Table\Enthalpy Btu/lbmol S1)
Solution 140956 provides a detailed explanation about the unit table and how to set and retrieve values specifying basis and units:
Keywords: Unit table, molar basis.
References: None |
Problem Statement: How to generate ASTM curves from a particular stream. | Solution: 1. Right click on a particular stream
2. Select Analysis
3. Select Dist-curve
4. Click in Go
The ASTM curves will be generated as a table
Keywords: ASTM, curve, Distillation curve
References: None |
Problem Statement: This Knowledge Base article provides steps to resolve the issue of Aspen InfoPlus.21 not starting accompanied by the following error:
h21_arcck_local failed with ret = -2120
Also, when trying to update any task in Aspen InfoPlus.21 Manager, such as trying to add NOHIS to TSK_DBCLOCK, user may receive the following error message:
Error updating task to registry. | Solution: Make sure that Aspen Infoplus.21 Task Service is running under a user account that has WRITE access to the Windows Registry.
If in doubt, change the account and restart the service.
Keywords: None
References: None |
Problem Statement: I'm creating a new simulation for H2O with HCl using the Elec Wizard. When I select the default property model ENRTL-RK, I am not getting the same set of pair interaction parameters as with ELECNRTL. Why? | Solution: ELECNRTL model has been available in Aspen Plus for many versions. ENRTL-RK is a new version of the electrolyte NRTL activity coefficient model which addresses some issues found with ELECNRTL - essentially to ensure ENRTL-RK becomes exactly consistent with NRTL-RK when there are no electrolytes. SeeSolution 129664 for more details of the advantages on the new electrolyte models.
We have only verified the water/ion pair interaction parameters (single electrolyteSolutions at low/medium concentrations). The other pair interaction parameters available in ELECNRTL have not yet been integrated in the databank used with ENRTL-RK.
The user has to make a decision whether to use the old ELECNRTL model (this can be selected in the electrolyte wizard) and make use of the larger, more complete set of pair interaction parameters or use ENRTL-RK and get a more limited set of pair interaction parameters. The best choice for the user would be to actually use experimental data and do the regression (using the supplied parameters as a start) to actually assess the quality of the fit.
Keywords: None
References: None |
Problem Statement: When a flowsheet is created in Aspen Plus, the most commonly required physical property parameters are automatically retrieved by the simulation engine from the property data banks.
Quite often user may need to access other physical property parameters such AIT, RON, MON, FLML, FLMU
Related | Solution: s : 3008Â and 113840Solution
Provided that the values for the required parameters are available in the databank, then the first step is to type in the name of the parameters in customize | user parameters (in properties environment) eg FLML (see screen shot)
Next by clicking the retrieve parameters tab in the tool bar ribbon the new parameter should also be included in the Pure Component Form in the Results Folder (see the screen shot)
Keywords: AIT, RON, MON, FLML, FLMU
References: None |
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