1.3 Dynamic Simulation
1.3.1 Modifying the Steady State Flowsheet
It is necessary to add unit operations such as valves, heat exchangers, or pumps, to define pressure flow relations
between unit operations that have no pressure flow relation. In this tutorial, valve operations will be added between Separator, Mixer, and Column operations.
A Heater operation will also be added between the Mixer and Column operation for dynamic simulation purposes. Installing a heater allows you to vary the temperature of the feed entering the column.
This is only one method of preparing a steady state case for Dynamic mode.
A completed dynamic case has been pre-built and is called De-Propanizer - Dynamic Model-2.hsc in the HYSYS\Samples directory.
Valves will be added to the following material streams: • SepLiq
• LTSLiq • TowerFeed • LiquidProd
Set Session Preferences
The first task is to set the session preferences.
1. Open the pre-built case file Sweet Gas Refrigeration
Plant.hsc located in your HYSYS\Samples directory.
2. From the Tools menu, select Preferences. The Session Preferences property view appears. 3. Click the Variables tab, then select the Units page. 4. In the Available Unit Sets group list, select Field.
5. Click the Simulation tab, then select the Dynamics page. 6. In the Assistant group, uncheck both the Set dynamic
stream specifications in the background and the Perform checks when switching to dynamics or starting the integrator checkboxes.
In the Dynamic simulation part of this tutorial you will work with the default Field units.
7. Close the Session Preferences property view along with all the open property views on the HYSYS desktop (except for the PFD property view) by clicking the Close icon in the top right corner of each property view.
Remove Specified Pressures
In the PFD, the stream pressure for Feed 2 will be deleted so that it will be calculated by the MIX-100 in dynamic mode. 1. Double-click the Feed 2 stream icon to open its property
view.
2. On the Conditions page of the Worksheet tab, click in the
Pressure cell, then press DELETE to remove the stream
pressure.
3. Close the stream property view.
Next you will change the pressure setting for the MIX-100 so that the whole PFD can be simulated.
4. Double-click the MIX-100 icon to open its property view. 5. On the Design tab, select the Parameters page.
6. In the Automatic Pressure Assignment group, click the
Equalize All radio button.
7. Close the MIX-100 property view.
Insert Sep Valve
Next you will insert a valve operation between the SepLiq stream and the MIX-101 unit operation.
1. Click the Break Connection icon in the PFD toolbar.
2. Break the SepLiq stream connection by doing the following: • Position the mouse pointer over the connection line
between the SepLiq stream icon and the MIX-101 icon. • When the mouse pointer has a checkmark beside it, left-
click and the SepLiq stream will disconnect from the MIX- 101.
3. Open the Object Palette by pressing F4.
4. On the Object Palette, right-click and hold on the Valve icon. 5. Drag the cursor over the PFD.
The mouse pointer becomes a bullseye.
Break Connection icon
6. Position the bullseye pointer beside the SepLiq stream and release the mouse button.
7. A Valve icon named VLV-100 appears.
8. Double-click the VLV-100 icon on the PFD to open its property view.
9. In the valve property view, specify the following connections:
10. Click the Close icon to close the valve property view. 11. Connect the SepExit stream to the inlet of the MIX-101 unit
operation by doing the following: • Click the PFD Attach Mode icon.
• Position the mouse pointer at the tip of the SepExit stream arrow. A white box appears.
• Click and drag the pointer to the left side of MIX-101. A white box appears, indicating a connection point.
• Release the mouse button to complete the connection. • Click the Attach Mode icon again to exit from the attach
mode.
Insert LTS Valve
Next you will insert a valve operation between the LTSLiq stream and the MIX-101 unit operation.
1. Break the line between the LTSLiq stream and the MIX-101 unit operation.
• Click the Break Connection icon in the tool bar. • Click to the right of the arrow on the LTSLiq stream. 2. Install a second valve operation.
• On the Object Palette, right-click the Valve icon. • Drag the cursor to the right of the LTSLiq stream. • Release the mouse button.
Tab [Page] In this cell... Enter...
Design
[Connections] NameInlet Sep ValveSepLiq
Outlet SepExit
Design [Parameters] Delta P 25 psi
4. Specify the following connections:
5. Close the valve property view.
6. Attach the LTSExit stream to the MIX-101 unit operation. • Click the Attach Mode icon
• Move the cursor over the LTSExit stream icon. A white box appears.
• Click and drag the cursor to the inlet side of the MIX-101 icon. A white box appears, indicating a connection point. • Release the mouse button to complete the connection. • Click the Attach Mode icon again to exit the attach
mode.
Insert Tower Valve
Next you will add a valve operation between the MIX-101 unit operation and the TowerFeed stream.
1. Break the line between the TowerFeed stream and the MIX- 101 unit operation. Be sure to break the line to the left of the TowerFeed stream arrow.
2. Install a third valve operation with the following connections:
3. Close the valve property view.
Tab [Page] In this cell... Enter...
Design
[Connections] NameInlet LTS ValveLTSLiq
Outlet LTSExit
Design [Parameters] Delta P 5 psi
Tab [Page] In this cell... Enter...
Design
[Connections] NameInlet Tower ValveTowerIn
Outlet TowerInlet
4. Click the Attach Mode icon, then connect the TowerIn stream to the exit of the MIX-101 unit operation.
5. Exit the attach mode.
6. Install a Heater operation and position it near the Tower Valve and the DePropanizer.
• In the Object Palette, click once on the Heater icon. • In the PFD, click where you want to insert the heater. 7. Open the heater property view and specify the following
connections:
8. In the heater property view, click the Worksheet tab, then select the Conditions page.
9. In the Temperature cell of the TowerFeed stream, enter
24.73°F.
You can use the scroll bars to navigate around the PFD. You can also use the PAGE UP and PAGE DOWN keys to zoom in and out of the PFD, respectively.
Tab [Page] In this cell... Enter...
Design
[Connections] NameInlet HeaterTowerInlet
Outlet TowerFeed
Energy Heater Q
Design [Parameters] Delta P 9 psi
10. Close the Heater property view.
Insert Reboil Valve
Next you will add a valve to the LiquidProd stream in the Column subflowsheet. The valve operation will be inserted between the LiquidProd stream and the Reboiler unit operation in the Column subflowsheet.
When considering pieces of equipment associated with a column, it may be necessary to enter the Column sub- flowsheet environment.
1. Double-click the DePropanizer column to open its property view.
2. Click the Column Environment button to enter the Column Sub-flowsheet environment.
3. In the PFD of the column sub-flowsheet, break the connection between the LiquidProd stream and the
Reboiler unit operation.
4. Press F4 to open the Object Palette.
5. Install a valve operation between the Reboiler and the LiquidProd stream icon. Move the LiquidProd stream to make room if required.
Figure 1.121
The Object Palette in the Column Environment contains fewer available unit operations than the Object Palette in the Parent Environment.
6. Open the valve property view and specify the following connections:
7. Close the valve property view.
8. Press CTRL to connect the LiquidExit stream to the liquid exit connection point of the Reboiler.
9. Click the Run Column Solver icon in the tool bar.
The column will solve with the existing column specifications and the added valve unit operations.
Tab [Page] In this cell... Enter...
Design
[Connections] NameInlet Reboil ValveLiquidExit
Outlet LiquidProd
Design [Parameters] Delta P 25 psi
Figure 1.122 Run Column Solver icon
Remove Non-Applicable Operations
Next you will delete unit operations that have no impact on the Dynamic solver.
1. Return to the Main Flowsheet environment by clicking the
Enter Parent Simulation Environment icon in the toolbar.
2. Close the DePropanizer column property view.
The ADJ-1 and DewPoint logical operations have calculated the ColdGas stream temperature required to achieve a 10°F dewpoint in the SalesGas stream.
3. In the PFD, double-click the ColdGas icon to open the stream property view.
4. Record the temperature of the ColdGas material stream so that it may be controlled in Dynamic mode:
5. Close the ColdGas property view.
6. On the PFD, click on the ADJ-1 logical operation icon, then press the DELETE key.
Figure 1.123
Variable Value
Cold Gas Stream Temperature 4.444°F Enter Parent Simulation
7. HYSYS prompts you to confirm that you want to delete the object. Click the Yes button.
8. Delete the DewPoint logical operation and the SalesDP material stream from the PFD.
9. Ensure that the Standard Windows file picker radio button is selected on the File tab in the Session Preferences property view.
10. From the File menu, select Save As. Save the file as De-
Propanizer - Dynamic Model-1.hsc.