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Overview of Tutorial 1

In this tutorial you will:

Use Aspen Plus to modify an existing steady-state example

Add the equipment data and heat transfer information necessary to simulate the processdynamically in Aspen Plus Dynamics

Generate and export the dynamic simulation files from Aspen Plus for using in Aspen PlusDynamics

Allow about 20 minutes for this tutorial.

Experienced Aspen Plus users:

You will be opening the file MCHSPEC in the directory Program Files\AspenTech\Aspen Plus

xx.x\GUI\xmp. If you already know how to do this, open the file then clickhere to jump to the nextstep.

Opening an Existing Aspen Plus Simulation

To open an existing Aspen Plus simulation:

1. On the Aspen Plus File menu, click Open.

2. In the Open dialog box, click the Look in Favorites toolbar button.

3. On the Examples link, click Open.

4. Click the file MCHSPEC to select it; then click Open.

A dialog box appears, asking if you want to close the current run before opening a new run.

5. Click Yes to close the current run and open the MCHSPEC example backup file.

The MCHSPEC example file opens and the process flowsheet appears.

If you cannot see the Dynamic toolbar as shown above, follow these steps to add the toolbar:

1. Ensure the flowsheet window is active, by clicking in it.

2. On the View menu, click Toolbar.

3. In the Toolbars dialog box, ensure the Dynamic check box is selected.

Page 1 of 20Overview of Tutorial 1

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4. Click OK.

The Dynamic toolbar is added to your toolbars.

About the MCH Steady-State Simulation

The MCH example describes a simulation in which 98% pure methylcyclohexane (MCH) is recoveredfrom a mixture of MCH and toluene. Because these components form a close-boiling system that isdifficult to separate by simple binary distillation, phenol is used as an extractant to enhance the relativevolatility of MCH over toluene.

Aspen Plus uses a design specification to determine the phenol flow rate required to achieve the 98%purity in the distillate. You can view the results of stream 2 to see that the required phenol flow rate is

approximately 1515 lbmol/hr.

Aspen Plus design specifications are often used for design purposes and generally do not corresponddirectly to plant control strategies. For this reason, Aspen Plus Dynamics does not automatically convertsteady-state design specifications to dynamic controllers. In tutorial 3, you will create a controller tomaintain the product purity.

Entering Dynamic Data in Aspen PlusBefore entering any dynamic data in Aspen Plus, you would usually run a steady-state simulation toensure it completes normally. For this tutorial you need not do this, because the example file has alreadycompleted normally and has been saved with results.

Before you can enter dynamic data, you have to click the Dynamic button on the Dynamic toolbar. Thisenables you to access the dynamic input data sheets for each block.

1. To access the dynamic data for the MCH column, click the Dynamic button so that it is pressed in.

The RadFrac block (B1) contains forms that require dynamic data, so the status indicator on the statusbar changes toRequired Input Incomplete.

You can now use the Next button to guide you through the required input data forms.




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2. On the Data Browser toolbar, click the Next button .

The Flowsheet Complete dialog box appears.

3. In the Flowsheet Complete dialog box, click OK to display the first required input form.

The Data Browser opens with the Block B1 (RADFRAC) Dynamic form displayed.

Note: At this stage, no data is required on this form.

Entering Condenser and Reboiler Geometry andHeat Transfer Data

In this section, you will enter geometry and heat transfer data for the condenser and reboiler. Geometrydata is used to calculate the vessel holdups. The required data are the:

vessel orientation

head type

length

diameter

For heat transfer purposes, you will use log-mean temperature difference (LMTD) assumptions for thecondenser. Heat duty is dependent on the log mean temperature differential between the process fluidand the heating/cooling medium. The reboiler heat duty is assumed constant.

1. Click the Condenser sheet.

2. In the Heat transfer option box, click the down arrow to see more options and from the listdisplayed, click LMTD.

Do not change the other default values. The Condenser sheet is now complete.

3. Click Next to go to the Reflux Drum sheet.

4. In the Vessel Type field, click Horizontal from the list box.

5. In the Length field, type 6 ft and in the Diameter field, type 3 ft.

Do not change the other values. The Reflux Drum sheet is now complete.




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6. Click Next to continue and the Sump sheet appears.

7. In the Height field, type 5 ft and in the Diameter field, type 3 ft.

Do not change the other values.

8. Press Enter to accept the input.

The Sump sheet is now complete and you have finished entering data for the condenser and reboiler.

Entering Tray Geometry

The tray geometry data is used to calculate the holdups on the trays. Column B1 has 22 theoretical

stagesStage1 being the condenser and Stage22 the reboiler. Stages 2 through 21 are the theoreticaltrays.

In the previous section, you specified the necessary information for the condenser (stage 1) and thereboiler (stage 22). In this section, you will enter the tray diameter geometry for stages 2 through 21.The default values of the other parameters will be used.

1. Click Next to go to the Hydraulics sheet.

2. In the Stage1 column, type 2 and in the Stage2 column, type 21.

3. In the Diameter column, delete 6.56168 and type 5.

4. Press enter to accept the input and leave the remaining values at their defaults.

The Tray geometry specifications are now complete and the sheet looks like this .

You have entered the additional data needed for the RadFrac column, and you are now ready to run thesteady-state simulation. You do this to ensure that all the results required to export the dynamicsimulation are calculated.

5. Click Next to continue.

The Required Input Complete dialog box appears.

Running the Steady-State Simulation




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Having entered the dynamic specifications, you run the steady-state simulation.

To do this:

1. On the Required Input Complete dialog box, click OK.

Aspen Plus displays the Control Panel where you can view the simulation messages during the run.

2. Wait for the message Simulation Calculations Completed to appear and Results Available toappear in the status bar. This indicates that the run is complete.

3. Click the Close button to close the Control Panel window.

Exporting the Dynamic SimulationYou are now ready to export the files necessary to run this simulation dynamically.

To export the dynamic simulation:

1. On the Dynamic Toolbar, click the Export Dynamics (Flow Driven) button.

The dialog box prompts for the name of the dynamic simulation file.

2. Choose a folder other than the xmp folder from which you selected the MCHSPEC example

because this folder is for system files only.

3. In the File name box, type Mchdyn; then click Save.

These files are created:

Mchdyn.dynf, the Aspen Plus Dynamics input file

Mchdyndyn.appdf, which contains physical property data for use by Properties Plus during thedynamic simulation

Saving the Backup File

To save your changes to the Aspen Plus backup file:

1. From the File menu, click Save As.




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2. Go to the folder where you saved your exported dynamic simulation files.

3. In the Save As field, select Aspen Plus Backup files (*.bkp).

4. In the File name field, type Mchdyn then click Save.

A dialog box appears requesting if you want to save the file in Aspen Plus Document (quick restart)format.

5. There is no need to save it as an Aspen Plus Document file, so click No.

Your simulation is saved as a backup file called Mchdyn.bkp.

Quitting Aspen PlusNow that you have generated the files necessary for a dynamic run, you are ready to run Aspen Plus

Dynamics.

To quit Aspen Plus:

On the File menu, click Exit.

Tutorial ReviewIn this basic tutorial, you have learnt how to use Aspen Plus to:

Modify an existing steady-state example

Add the equipment data and heat transfer information necessary to simulate the processdynamically in Aspen Plus Dynamics

Generate and export the dynamic simulation files for use in Aspen Plus Dynamics

To start the next tutorial, clickhere.


To use this tutorial, you must have successfully completed tutorial 1 - Entering Dynamic Data, which




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you do in Aspen Plus.

In this tutorial, you will use Aspen Plus Dynamics to:

Modify the control scheme associated with the column in the MCHDYN simulation by adding acomposition controller to maintain the purity of the distillate stream (stream 3).

The controller will measure the MCH composition in the distillate stream and manipulate the phenolsolvent stream (stream 2).

Modify the controller tuning parameters (gain and integral time) for better control performance.


About Aspen Plus Dynamics Control FeaturesIn Aspen Plus Dynamics you can easily:

Add, change and remove control elements

Select measured and manipulated variables from selection lists

Configure cascade control loops

Import control structures from other Aspen Plus Dynamics generated input files

When an Aspen Plus Dynamics simulation is created, level, pressure and temperature controllers areautomatically included where appropriate. For flow-driven dynamic simulations, these controllers areconfigured as shown in this table:

Adding a New Controller

You will now add a fourth controller, the MCHCOMP PID controller. This controller will maintain thepurity of MCH in the liquid distillate product by manipulating the phenol solvent feed flow rate ofstream 2.

For this type of control This type of controller is used To directly manipulate

Liquid level Proportional only Liquid flow rate

Pressure Proportional integral Vapor flow rate or duty, as appropriate

Temperature Proportional integral Duty




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To add the controller block:

1. In the All Items pane of the Simulation Explorer, click the Expand (+) button next to Libraries;then click the Expand (+) button next to Dynamics (the Dynamics library).

An expanded view of the Dynamics library is displayed.

2. Click the Expand (+) button next to the ControlModels icon.

3. On the ControlModels list, click the PIDIncr object to select it.

4. Drag PIDIncr onto the Process Flowsheet window and drop it in a suitable position above stream2.

5. Click this newly-positioned block to select it.

6. Right-click the block, and on the menu that appears, click Rename Block.

7. In the Input dialog box, type the new controller name MCHCOMP.

8. Click OK.

Adding a Dead Time Block

In this section, you will modify the control scheme to simulate a 5-minute sensor dead time. Thisrepresents a delay in the composition analysis.

To add the dead time block:

1. In the All Items pane of the Simulation Explorer, ensure that the Dynamics library is in expandedview and the ControlModels list is displayed.

2. Click Dead_time and drag it to the Process Flowsheet window. Drop it to the left of theMCHCOMP PID block.

3. Click the newly-positioned block to select it.

4. Right-click the block, and on the menu that appears, click Rename Block.

5. In the dialog box that appears, type the name MCHCOMPDT for the Dead_time block; then click




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OK.

Connecting the Measured Variable

Now you will specify the measured variable as the mole fraction of MCH in the liquid distillate ofcolumn block B1.

1. If the ControlModels list is still expanded, in the All Items pane of the Simulation Explorer, clickthe collapse (-) button by ControlModels to collapse it.

2. In the Dynamics library, click Stream Types to display the stream types in the Contents pane of

the Simulation Explorer.

3. In the Contents pane of the Simulation Explorer, click and hold down the mouse button on theControlSignal icon and drag it to the Process Flowsheet window. Continue holding down themouse button.

The ports that can be connected to this ControlSignal stream type become highlighted with arrows. Asyou move the mouse pointer over a port, the name of the port appears and an arrow is highlighted toguide your selection.

4. Move the mouse pointer over stream 3 and release the mouse button on the port markedOutputSignal.

The Select the Control Variable dialog box for stream 3, the liquid distillate stream, appears.

5. Click STREAMS("3").Zn("MCH") to select the liquid mole fraction of MCH in the liquiddistillate; then click OK.

In the Process Flowsheet window, the cursor becomes an arrow connected to a solid black line.

6. On the MCHCOMPDT dead-time block, click the port marked InputSignal.

Because there is only one input variable to connect to, the control signal is automatically connected tothe dead-time block.

7. In the Contents pane of the Simulation Explorer, click and hold down the mouse button on theControl Signal icon again and drag it to the Process Flowsheet window.

8. Release the mouse button on the port marked OutputSignal of the MCHCOMPDT dead-timeblock.




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A control signal is automatically created and is ready to be connected to a port.

9. On the MCHCOMP block, click the port marked InputSignal to connect the control signal.

10. In the Select the Control Variable dialog box that appears, click MCHCOMP.PV; then click OKto connect the control signal.

Your Process Flowsheet now contains a controller and a dead time block with the measured variableconnected.

Specifying the Manipulated Variable

To specify the manipulated variable:

1. Ensure Stream Types is still selected in the Simulation Explorer.

2. In the Contents pane of the Simulation Explorer, click and hold down the mouse button on theControlSignal icon.

3. Drag it onto the Process Flowsheet to the port marked OutputSignal on the MCHCOMP block.

4. In the Select the Control Variable dialog box that appears, click MCHCOMP.OP; then click OKto connect the control signal.

A control signal (black line with a cursor) is automatically created and is ready to be connected to a port.

5. Move the pointer to stream 2 and click the InputSignal port.

6. To select the phenol component mole flow of stream 2, in the Select the Control Variable dialogbox,click the variable STREAMS("2").FcR ("PHENOL").

7. Click OK to connect the controller output signal to the manipulated variable.

You have finished connecting the MCHCOMP PID controller and the MCHCOMPDT dead-time block.

Now you can modify the tuning properties for the controller blocks.

Modifying Controller Tuning Properties




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When you create new controllers, it is important to specify the correct direction for the action. It is alsoimportant to check other main properties such as gain, integral time, derivative time, bias, and so on.

The following table shows the effects of direct or reverse action:

Initializing Controller Values

To modify properties for the newly-created controller block MCHCOMP:

1. In the Process Flowsheet window, click MCHCOMP to select it.

2. Right-click the block.

3. On the menu that appears, point to Forms then Configure.

4. The Configure dialog box appears.

5.

Aspen Plus Dynamics has set default values for the:

controller gain

integral time

derivative time

Aspen Plus Dynamics can also automatically initialize the values for the:

operator set point

bias

process variable range

controller output range

You can also manually change any of these parameter default values.

When theaction is

And the measured variable Then the manipulated variable is

Direct Increases Increased

Direct Decreases Decreased

Reverse Increases Decreased

Reverse Decreases Increased




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You will now initialize the values of the controller properties:

On the Configure form, the Initialize Values button sets

the value for the operator set point to the current value of the process variable (PV) connected tothe controller (currently the output from the deadtime element)

the value for the bias to the current value of the output (OP) variable (the phenol solvent streamflow)

Because the dead time element has just been created, its output does not yet correspond to the processvariable (the MCH mole composition in the distillate stream).

1. When more than one control elements are connected together, click on the "Initialize ControlScheme" command from the Tools menu.

This initializes each element starting from the process variable stepping through the control scheme tothe manipulated variable. These values are also used to determine default values for the process variable

and output ranges, so that the current value is at 50% of range.

2. The MCHCOMP controller should be reverse acting, so change the controller action.

Specifying Tuning ValuesIn this section, to improve the performance of this controller, you will specify values for the:

operator set point

gain

integral time

You will also modify the controller process variable and output ranges on the Ranges tab.

1. On the Tuning tab, in the Operator set point dialog box, type 0.98.

2. In the Gain field, type a gain of 6.

3. In the Integral time field, type an integral time of 30 minutes.




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Modifying Ranges for Variables

To modify the ranges for the process variable (measured variable) and controller output (manipulatedvariable):

1. Click the Ranges tab.

2. Under Process variable and set point, in the Range minimum box, type 0.0.

3. Under Process variable and set point, in the Range maximum box, type 1.

4. Leave the Output Range values unchanged.

You have now completed the controller specifications.

5. Click Close to close the Configure dialog box.

Modifying Dead Time Block Properties

To incorporate a dead time for the measured variable:

1. In the Process Flowsheet window, click the MCHCOMPDT block.

2. Right-click the block, and on the menu that appears, point to Forms, then Configure.

3. In the Configure table that appears, click the Value cell and type 5 to simulate a sensor dead timeof 5 minutes.

The MCHCOMPDT PID control block configure table looks like this:

You have now completed the specification for the dead time block.

4. Close the Configure table.




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Saving the Aspen Plus Dynamics File

To save your changes to the Aspen Plus Dynamics file

On the File menu, click Save.

The Simulation Messages window shows the file name and the directory in which it has been saved.

Continuing with the Next Tutorial

You have now entered all the necessary information for the newly created MCHCOMP controller block.

To start t next tutorial:

Clickhere.

or

To quit Aspen Plus Dynamics:

On the File menu, click Exit.


To use this tutorial, you must have successfully completed Aspen Plus Dynamics tutorial 1 (EnteringDynamic Data) and tutorial 2 (Modifying the Control Scheme).

In this tutorial, you will:

Start, pause and implement a step disturbance in the feed flowrates of both MCH and toluene

Plot the dynamic responses caused by the disturbance


If you already have the Mchdyn example file open in Aspen Plus Dynamics, clickhere to jump to thenext step.

Opening an Existing Simulation

To open an existing simulation:




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1. On the File menu, click Open.

2. Locate the drive or folder that contains the Mchdyn files from the previous tutorial.

3. From the Files of type list, click Aspen Plus Dynamics Files (*.dynd, *.dynf).

4. Click Mchdyn, then click Open to load the Mchdyn simulation.

Monitoring the Simulation

In this section, you will:

Use a predefined plot to:

Monitor the progress of the dynamic simulation

Disturb and plot selected variables

See how well the column and its controller maintain the desired MCH purity after a feed flowdisturbance, by observing the column response from both the predefined controller plot andfaceplate

Opening the MCHCOMP Controller PlotTo open the predefined plot for the MCHCOMP controller:

1. In the flowsheet, click the MCHCOMP block to select it, then right-click.

2. On the menu that appears, point to Forms; then click ResultsPlot.

The MCHCOMP controller plot appears.

3. Arrange your windows so you can see the plot and the flowsheet.

Opening the MCHCOMP Controller Faceplate




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A faceplate shows the actual values of the controller variables Set Point, Process Variable and Outputduring a simulation. You can also use the faceplate to change controller settings.

To open the faceplate for the MCHCOMP controller:

1. In the flowsheet, double-click the MCHCOMP block.

The MCHCOMP controller faceplate appears:

2. Arrange your windows so you can see the plot and the faceplate.

Formatting the Plot

You will now modify the plot by:

Adding a title

Adjusting the scale

Adding a Title for the Plot

You will now add a title to your plot.

To do this:

1. Click an empty area within the plot; then right-click.

2. From the menu that appears, click Properties.

The Plot Control Properties dialog box appears.

3. Click the Labels tab.

4. In the Title Text field, type in the name for your plot: MCH Purity Control.




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Tip: To rename your plot, double-click the title.

Adjusting the Scale

To adjust the Y-axis MCH composition and controller set point range:

1. On the plot, double-click the numbers on the axis for Process Variable and Set Point to bring upthe Plot Text Setting dialog box.

2. In the Axis Range boxes, enter a range of 0.975 to 0.985.

3. Click OK to accept the changes.

To change the Controller Output axis scale:

1. On the plot, double-click the axis for Controller Output to bring up the Plot Text Setting dialogbox.

2. Change the Grid Interval to 200, then in the Axis Range fields, enter a range of 1200 to 1800.

3. Click OK to accept the changes and close the Plot Text Setting dialog box.

You have now finished formatting the plot.

Opening the Manipulate Table

The Manipulate table displays the variables that you can change manually during the dynamicsimulation. In this example, you will disturb the molar feed flow rates of both the MCH and Toluene.

To open the Manipulate table for the process feed stream:

1. In the flowsheet, click Stream 1 to select it; then right-click.

2. From the menu that appears, point to Forms and click Manipulate.

The Stream 1 Manipulate Table appears.

You are now ready to run the simulation ,and you will need to be able to view the faceplate, plot, and theManipulate table for Stream 1.




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Tip: Maximize Aspen Plus Dynamics, and then arrange the windows yourself or using the Windowmenu.

Starting the Run

In this section, you will program the run to stop at a simulation time of 0.1 hours.

To set the stop point:

1. On the Run menu, click Pause At, which displays the Pause Time dialog box.

2. In the Pause Time dialog box, select Pause at Time and type 0.1 in the box.

3. Click OK to accept the change.

4. On the Run Control toolbar, click the Run button to start the simulation.

Observe the behavior of your plot as the run executes.

The run stops at a simulation time of 0.1 hours and the Run Complete dialog box appears:

5. Click OK to continue.

Because the simulation started with a steady-state result from Aspen Plus, and you have not yetsimulated a disturbance, the plot shows that the variables remain at steady-state.

In the Faceplate window, you can see that the steady-state phenol flowrate (Controller Output) is still

1515 lbmol/hr, which is consistent with the Aspen Plus results, and the PV value is stable at 0.98.

Simulating a Disturbance

Now that you have used Aspen Plus Dynamics to reproduce the steady-state results from Aspen Plus,you can simulate a disturbance by changing the composition of the feed to the column.

To do this:

1. Click the Stream 1 Manipulate Table to make it the active window.

2. Click the value cell for MCH component flow (FcR("MCH"), and replace 200 with 220.




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3. Click the value cell for Toluene component mole flow (FcR("TOLUENE") and replace 200 with180.

4. Press Enter to confirm the changes.

5. Close the Stream 1 Manipulate table.

To set a new stop point, and continue the run:

1. On the Run menu, click Pause At.

The Pause Time dialog box appears.

2. In the Pause At Time field, type 2.5; then click OK.

3. On the Run Control toolbar, click the Run button to continue the simulation.

4. In the MCH Purity Control plot, view the progression of the run.

The run stops at a simulation time of 2.5 hours. The controller response restores a steady-state condition.

After the run stops, you can view the full response.

Viewing the Full Response

When the run has finished, you can view the full response.

To do this:

1. Click an empty area on the plot; then right-click.

2. On the menu that appears, clickZoom Full.

The plot shows how the change in feed composition affects the distillate purity. You also see how thesolvent flow is manipulated by the controller, to maintain the purity set point of 0.98. With the specified

controller parameters, the controller returns the purity to the set point within 2 hours.

Quitting Aspen Plus Dynamics




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Congratulations! You have now completed the last Aspen Plus Dynamics tutorial.

To save your simulation and quit Aspen Plus Dynamics:

1. On the File menu, click Save.

2. On the File menu, click Exit.
