CAPÍTULO IV: RESULTADOS
4. Resultados
4.2. Discusión de los resultados
The Nozzles page (from the Rating Tab) in most of the
operations property view enables you to specify the elevation and diameter of the nozzles connected to the operation.
Depending on the type of operation, the options in the Nozzles page varies. The following table lists and describes the common options available in the page:
The Nozzles page is only available if the UniSim Design Fidelity license is activated.
Figure 1.23
Object Description Base Elevation
Relative to Ground Level field
Enables you to specify the height/elevation between the bottom of the operation and the ground.
Diameter row Enables you to specify the diameter of the nozzle for each material stream flowing into and out of the operation.
Elevation (Base) row Enables you to specify the height/elevation between the nozzle and the base of the operation.
Elevation (Ground)
row Enables you to specify the height/elevation between the nozzle and the ground.
Refer to Section 1.6 - UniSim Design
Dynamics in the UniSim Design Dynamic Modeling guide for more information.
Refer to Section 1.6.2 - Nozzles in the UniSim Design Dynamic Modeling guide for more information.
2 Sub-Flowsheet Operations
2.1 Introduction... 2 2.2 Sub-Flowsheet Property View ... 3 2.2.1 Connections Tab... 4 2.2.2 Parameters Tab... 6 2.2.3 Transfer Basis Tab ... 7 2.2.4 Transition Tab ... 8 2.2.5 Variables Tab ... 10 2.2.6 Notes Tab... 11 2.2.7 Lock Tab ... 11 2.3 Adding a Sub-Flowsheet ... 12 2.3.1 Read an Existing Template... 13 2.3.2 Start with a Blank Flowsheet... 13 2.3.3 Paste Exported Objects ... 14 2.4 MASSBAL Sub-Flowsheet ... 14 2.5 Adding a MASSBAL Sub-Flowsheet... 15 2.5.1 Connections Tab... 17 2.5.2 Parameters Tab... 21 2.5.3 Transfer Basis Tab ... 25 2.5.4 Mapping Tab ... 26 2.5.5 Notes Tab... 27 2.5.6 Results Tab... 27
2-2 Introduction
2.1 Introduction
The sub-flowsheet operation uses the multi-level flowsheet architecture and provides a flexible, intuitive method for building the simulation. Suppose you are simulating a large processing facility with a number of individual process units and instead of installing all process streams and unit operations into a single flowsheet, you can simulate each process unit inside its own compact sub-flowsheet.
Once a sub-flowsheet operation is installed in a flowsheet, its property view becomes available just like any other flowsheet object. Think of this view as the “outside” view of the “black box” that represents the sub-flowsheet. Some of the information contained on this view is the same as that used to construct a Template type of Main flowsheet. Naturally this is due to the fact that once a Template is installed into another flowsheet, it becomes a sub-flowsheet in that simulation.
Whether the flowsheet is the Main flowsheet of a simulation case, or it is contained in a sub-flowsheet operation, it possesses the following components:
• Fluid Package. An independent fluid package,
consisting of a Property Package, Components, and so forth. It is not necessary that every flowsheet in the simulation have its own separate fluid package. More than one flowsheet can share the same fluid package.
• Flowsheet Objects. The inter-connected topology of the flowsheet. Unit operations, material and energy streams, utilities, and so forth.
• A Dedicated PFD. A UniSim Design view presenting a graphical representation of the flowsheet, showing the inter-connections between flowsheet objects.
• A Dedicated Workbook. A UniSim Design view of tabular information describing the various types of flowsheet objects.
• A Dedicated Desktop. The PFD and Workbook are home views for this Desktop, but also included are a menu bar and a tool bar specific to either regular or Column Sub-flowsheets.
2.2 Sub-Flowsheet Property View
The Sub-flowsheet property view consists of the following tabs:
• Connections
• Parameters
• Transfer Basis
• Transition
• Variables
• Notes
• Lock
Figure 2.1
Click this button to delete the sub-flowsheet.
Click this button to enter the sub-flowsheet environment.
2-4 Sub-Flowsheet Property View
2.2.1 Connections Tab
You can enter the name of the sub-flowsheet, as well as its Tag name, on the Connections tab. All feed and product connections appear on the Connections tab.
Flowsheet Tags
These short names are used by UniSim Design to identify the flowsheet associated with a stream or operation when that flowsheet object is being viewed outside of its native flowsheet scope. The default Tag name for a sub-flowsheet operation is TPL1 (for Template).
When more than one sub-flowsheet operation is installed, UniSim Design ensures unique tag names by incrementing the numerical suffix; the sub-flowsheets are numbered sequentially in the order they were installed. For example, if the first sub-flowsheet added to a simulation contained a stream called Comp Duty, it would appear as Comp Duty@TPL1 when viewed from the Main flowsheet of the simulation.
Figure 2.2
Feed and Product Connections
Internal streams are the boundary streams within the sub-flowsheet that can be connected to external streams in the Parent flowsheet. Internal streams cannot be specified on this tab, they are automatically determined by UniSim Design.
Basically, any streams in the sub-flowsheet that are not
completely connected (in other words,”open ended”) can serve as a feed or product.
To connect the sub-flowsheet, specify the appropriate name of the external streams, which are in the Parent flowsheet, in the matrix opposite the corresponding internal streams, which are in the sub-flowsheet. The stream conditions are passed across the flowsheet boundary via these connections.
Sub-flowsheet streams that are not connected to any unit operations in the sub-flowsheet appear in the view as well (and are termed “dangling streams”).
Figure 2.3
It is not necessary to specify an external stream for each internal stream.
2-6 Sub-Flowsheet Property View
2.2.2 Parameters Tab
You can view the exported sub-flowsheet variables on the Parameters tab, which allows you to keep track of several key variables without entering the sub-flowsheet environment or adding the variables to the global DataBook. It is also useful when dealing with a sub-flowsheet as a “black box”. The user who created the sub-flowsheet can set up an appropriate Parameters tab, and another user of the sub-flowsheet can be unaware of the complexities within the sub-flowsheet.
These variables display values, which have been calculated or specified by the user. If changes to the specified values are made here, the sub-flowsheet is updated accordingly. For each variable, the description, value, and units are shown.
• The Ignore checkbox is used to bypass the sub-flowsheet during calculations, just as with all UniSim Design unit operations.
• The Update Outlets checkbox enables you to toggle between transferring or not transferring updated values
Figure 2.4
These variables are actually added on the Variables Tab of the property view, but are viewed in full detail on the Parameters tab.
2.2.3 Transfer Basis Tab
The transfer basis for each Feed and Product Stream is listed on the Transfer Basis tab.
The transfer basis only becomes significant when the sub-flowsheet and Parent sub-flowsheet's fluid packages consist of different property methods. The transfer basis is used to provide a consistent means of switching between the different basis of the various property methods. The table below list all the possible transfer basis provided by UniSim Design:
Figure 2.5
The Transfer Basis is also useful in controlling VF, T, or P calculations in column sub-flowsheet boundary streams with close boiling or nearly pure compositions.
Transfer Basis Description
T-P Flash The Pressure and Temperature of the Material stream are passed between flowsheets. A new Vapour Fraction is calculated.
VF-T Flash The Vapour Fraction and Temperature of the Material stream are passed between flowsheets. A new Pressure is calculated.
VF-P Flash The Vapour Fraction and Pressure of the Material stream are passed between flowsheets. A new Temperature is calculated.
2-8 Sub-Flowsheet Property View
2.2.4 Transition Tab
The transition tab allows you to specify the desired type of transition across the fluid package boundaries. UniSim Design supports three types of transitions: FluidPkg, Basic and Black Oil. FluidPkg transition can handle any non-black oil fluid
package transitions and is the default transition for non-black oil streams. Basic transition can be selected only when both the internal and external streams across the sub-flowsheet boundary use the same non-black oil fluid package. Black Oil transition must be selectedif at least one of the streams is a black oil stream.
To change the transition type, click the Transition dropdown list for the desired inlet or outlet stream. To view the selected transition, click the view Transition button in the Inlets or the Outlets group. In the FluidPkg transition, you may select and edit the component maps. Mapping is especially useful when dealing with hypothetical oil components where like components from one fluid package can be mapped cross the sub-flowsheet boundary to another fluid package.
P-H Flash The Pressure and Enthalpy of the Material stream are passed between flowsheets.
User Specs You define the properties passed between flowsheets for a Material stream.
None Required No calculation is required for an Energy stream. The heat flow is simply passed between flowsheets.
<None Set> No transfer basis has been selected.
Transfer Basis Description
Refer to Section 6.2 - Component Maps Tab in the UniSim Design Simulation Basis guide for more information.
When all the internal streams share the same fluid package and all the external sterams also share a fluid package, the two overall material imbalance buttons are available. Click the Overall Imbalance Into Sub-Flowsheet button or Overall Imbalance Out of Sub-Flowsheet button to open the Untransferred Component Info view. The Untransferred component Info view allows you to confirm that all of the components have been transferred into or out of the sub-flowsheet.
Figure 2.6
2-10 Sub-Flowsheet Property View
2.2.5 Variables Tab
The Variables tab of the Main flowsheet property view allows you to create and maintain the list of externally accessible variables.
Although you can access any information inside the sub-flowsheet using the Variable Navigator, the features on the Variables tab allow you to target key process variables inside the sub-flowsheet and display their values on the property view.
Then, you can conveniently view this whole group of information directly on the sub-flowsheet property view in the Parent flowsheet.
To add variables:
1. Click the Add button. The Variable Navigator view appears.
2. On the Variable Navigator view, select the flowsheet object and variable you want.
You can also over-ride the default variable description displayed in the Variable Description field of the Variable Navigator view.
Figure 2.7
Any sub-flowsheet variables added in the Variables tab will appear on the Parameters tab.
Refer to Section 11.18 - Variable Navigator in the UniSim Design User Guide for details on the Variable Navigator.
2.2.6 Notes Tab
The Notes tab provides a text editor where you can record any comments or information regarding the material stream or to your simulation case in general.
2.2.7 Lock Tab
The Lock tab enables you to lock or unlock the subflowsheet and displays the lock status of the subflowsheet.
When the flowsheet is locked, you cannot create or delete objects, or change the topology. You can add Set, Adjust, and Spreadsheet operations; manipulate variable values; or copy the contents of the flowsheet and create your own modifiable version.
• To lock a subflowsheet, enter a password in the Lock Status field and press ENTER.
• To unlock a subflowsheet, enter the correct password in the Lock Status field and press ENTER.
Figure 2.8
Subflowsheets inside a locked subflowsheet have to be specifically locked.
For more information, refer to Section 1.3.2 - Notes Page/Tab.
2-12 Adding a Sub-Flowsheet
2.3 Adding a Sub-Flowsheet
There are two ways you can add a sub-flowsheet to your simulation.
1. From the Flowsheet menu, select the Add Operation command. The UnitOps view appears.
2. Click the Sub-Flowsheets radio button.
3. From the list of available unit operations, select Standard Sub-Flowsheet.
4. Click the Add button. The Sub-Flowsheet Option view appears.
OR
1. In the Flowsheet menu, select the Palette command. The Object Palette appears.
2. Double-click on the Sub-Flowsheet icon on the Object Palette.
3. The Sub-Flowsheet Option view appears.
The Sub-Flowsheet Option view contains the following options:
• Read an Existing Template
• Start with a Blank Flowsheet
• Paste exported objects
• Cancel
Figure 2.9 You can also access the
UnitOps view by pressing the F12 hot key.
You can also open the Object Palette by pressing the F4 hot key.
Sub-Flowsheet icon
2.3.1 Read an Existing Template
If you want to use a previously constructed Template that has been saved on disk, click the Read an Existing Template button on the Sub-Flowsheet Option view. For more information, refer to Section 3.5.2 - Creating a Template Style Flowsheet in the UniSim Design User Guide.
2.3.2 Start with a Blank Flowsheet
If you want to start with a blank subflowsheet, click the Start with a Blank Flowsheet button on the Sub-Flowsheet Option view, UniSim Design will install a sub-flowsheet operation containing no unit operations or streams.
On the Connections tab of the property view of the blank sub-flowsheet, there will be no feed or product connections
(boundary streams) to the sub-flowsheet. You can connect feed streams in the External Stream column by either typing in the name of the stream to create a new stream or selecting a pre-defined stream from a drop-down list. When an external feed connection is made by selecting a pre-defined stream from the drop-down list, a stream similar to the pre-defined stream is created inside the sub-flowsheet environment.
In order to fully define the flowsheet, you have to enter the sub-flowsheet environment. Click the Sub-Flowsheet
Environment button on the property view to transition to the flowsheet environment and its dedicated Desktop. The sub-flowsheet is constructed using the same methods as the main flowsheet. When you return to the Parent environment, you can connect the sub-flowsheet boundary streams to streams in the Parent flowsheet.
2-14 MASSBAL Sub-Flowsheet
2.3.3 Paste Exported Objects
If you want to import previously exported objects into a new sub-flowsheet, click the Paste Exported Objects button on the Sub-Flowsheet Option view.
You copy and paste selected objects inside the same
subflowsheet or another sub-flowsheet. You can also copy and paste sub-flowsheets and column sub-flowsheets. Objects can also be moved into or out of a sub-flowsheet.
2.4 MASSBAL Sub-Flowsheet
UniSim Design solves as a sequential modular solver. Unit operations must have specific degrees of freedom in order for the unit operation to solve. MASSBAL is a simultaneous solver.
In MASSBAL, a completely specified problem requires that there be no degrees of freedom remaining for the flowsheet, however, the specifications are restricted on a unit by unit basis and can be specified anywhere in the flowsheet.
The task is to allow you to use MASSBAL within a UniSim Design interface. The design has two modes of operation:
• Generating Cases via the MASSBAL flowsheet.
Within the MASSBAL flowsheets in UniSim Design, you can create UniSim Design unit operations that can either be solved sequentially or simultaneously. You can select unit operations and streams from the Object Palette and create the PFD in the MASSBAL flowsheet. You can also make a list of specifications within the MASSBAL
flowsheet. Upon calculating simultaneously, MASSBAL uses the specifications to create results files.
The objects that are selected and exported via the PFD can be imported back into a flowsheet without creating a new sub-flowsheet first.
the option of reading in previously created cases into UniSim Design. You can run previously created cases but cannot modify the cases through the UniSim Design interface. You have to modify the *.dat files directly.
2.5 Adding a MASSBAL Sub-Flowsheet
There are two ways you can add a MASSBAL sub-flowsheet to your simulation.
1. From the Flowsheet menu, select the Add Operation command. The UnitOps view appears.
2. Click the Sub-Flowsheets radio button.
3. From the list of available unit operations, select MassBal SubFlowsheet.
4. Click the Add button. The MASSBAL property view appears.
OR
1. In the Flowsheet menu, select the Palette command. The Object Palette appears.
2. Double-click on the MassBal icon on the Object Palette.
Other important information:
• Solving Backwards. All source streams in the MASSBAL flowsheet have to be fully specified (Phase Rule has to be satisfied for each stream).
Specifications can be made elsewhere in the flowsheet.
• Thermo Interfaces. MASSBAL has many different possible stream definitions (for example, Chemical, VLE, Fluid, Food, and Pulp). The only one used in UniSim Design, however, is the VLE stream type.
Thus, in order for MASSBAL to use UniSim Design to perform its thermodynamic calculations, callback functions have been set up to deal with flashes and property calculations of individual components and streams.
You can also access the UnitOps view by pressing the F12 hot key.
You can also open the Object Palette by pressing the F4 hot key.
MassBal icon
2-16 Adding a MASSBAL Sub-Flowsheet
3. The MASSBAL property view appears.
The MASSBAL property view consists of the following tabs:
• Connections
• Parameters
• Transfer Basis
• Mapping
• Notes
• Results
Figure 2.10
You can delete the MASSBAL operation by clicking this button.
You can enter the MASSBAL sub-flowsheet environment by clicking this button.
2.5.1 Connections Tab
The Connections tab allows you to choose between opening a previously created case or generating a case in the MASSBAL flowsheet.
You can change the name of the MASSBAL operation or the Tag name by typing the new name in the Name field or Tab field respectively.
The table below briefly describes the four groups on the Connections tab.
Group Description
Mode Click on one of the radio buttons to select the mode you want to use. There are two radio buttons:
• Read from File. Select this radio button if you want to use an existing case. For more information, refer to the section on Reading in Previously Created Cases.
• Read from Flowsheet. Select this radio button if you want to generate a case in the MASSBAL flowsheet. For more information refer to the section on Generating Cases via the MASSBAL Flowsheet.
Solving Mode Select one of the radio buttons to choose the mode you want to use:
• MASSBAL
• Sequential Modular
The Solving Mode group is only available if you select the Read from Flowsheet radio button in the Mode group.
Feed Connections
to Sub-Flowsheet Allows you to select the external stream you want to enter the MASSBAL sub-flowsheet. In the External Stream column, you can either type in the name of the stream or you can select a pre-defined stream from the drop-down list.
Product Connections to Sub-Flowsheet
Allows you to select the external stream you want to exit the MASSBAL sub-flowsheet. In the External Stream column, you can either type in the name of the stream or you can select a pre-defined stream from the drop-down list.
2-18 Adding a MASSBAL Sub-Flowsheet
Reading in Previously Created Cases
To read a previously created case in the MASSBAL flowsheet, a
*.dat file must be provided containing information of a case.
1. On the Connections tab of the MASSBAL property view,
1. On the Connections tab of the MASSBAL property view,