Работа №8. Исследование динамических свойств технологической схемы и подбор оптимальных контуров регулирования и их оптимальных настроек

3 Tutorial 3 - Running the

Dynamic Simulation

To use this tutorial, you must have successfully completed tutorials

1 and 2.

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

Allow about 40 minutes for this tutorial.

If you already have the Mchdyn example file open in Aspen

Dynamics, go to page 3-2.

3-2  Tutorial 3 - Running the Dynamic Simulation Getting Started Guide

Starting Aspen Dynamics

To open Aspen Dynamics:

➤ Click your desktop Start button, then point to:

Programs | AspenTech | Aspen Engineering Suite | Aspen

Dynamics 11.1

Opening an Existing Simulation

To open an existing simulation:

1. From 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, select Aspen Dynamics Files

(*.dynd, *.dynf)

4. Select 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 flow disturbance, by observing the

column response from both the predefined controller plot and

faceplate

Getting Started Guide Tutorial 3 - Running the Dynamic Simulation  3-3

Opening the MCHCOMP Controller

Plot

To open the predefined plot for the MCHCOMP controller:

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

click the right mouse button.

2. From 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

A faceplate shows the actual values of the controller variables Set

Point, Process Variable and Output during a simulation. You can

also use the faceplate to change controller settings.

3-4  Tutorial 3 - Running the Dynamic Simulation Getting Started Guide

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

You will now add a title to your plot.

To do this:

1. Click an empty area within the plot, then click the right mouse

button.

2. From the menu that appears, click Properties.

The Plot Control Properties dialog box appears.

Adding a Title for the

Plot

Getting Started Guide Tutorial 3 - Running the Dynamic Simulation  3-5

3. Click the Labels tab.

4. In the Title Text box, type in the name for your plot: MCH

Purity Control.

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

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 up the Plot Text Setting dialog

box.

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

The Plot Text Setting dialog box looks like this:

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 dialog box.

2. Change the Grid Interval to 200, then in the Axis Range

boxes, enter a range of 1200 to 1800.

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

Setting dialog box.

Adjusting the Scale

3-6  Tutorial 3 - Running the Dynamic Simulation Getting Started Guide

You have now finished formatting the plot and it looks like this:

Opening the Manipulate Table

The Manipulate table displays the variables that you can change

manually during the dynamic simulation. 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 click the

right mouse button.

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 the Manipulate table for

Stream 1.

Tip Maximize Aspen Dynamics and then arrange the windows

yourself or using the Window menu.

Getting Started Guide Tutorial 3 - Running the Dynamic Simulation  3-7

Starting the Run

In this section, you will program the run to stop at a simulation

time of 0.1 hours.

Tip You can use the Run Control toolbar to control the

simulation run and view the simulation and diagnostic messages. In

addition to these buttons, more commands are available from the

Run menu.

To set the stop point:

1. From 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. From the Run Control toolbar, click the Run button to

start the simulation.

The run begins. Observe the behavior of your plot as the run

executes. Because the simulation started with a steady-state

result from Aspen Plus, and you have not yet simulated a

disturbance, the plot shows that the variables remain at steady-

state.

3-8  Tutorial 3 - Running the Dynamic Simulation Getting Started Guide

The run stops at a simulation time of 0.1 hours and the Run

Complete dialog box appears:

5. Click OK to continue.

The plot that appears is similar to this:

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.

Getting Started Guide Tutorial 3 - Running the Dynamic Simulation  3-9

Simulating a Disturbance

Now that you have used Aspen 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. Select 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.

3. Click the value cell for Toluene component mole flow

(FcR("TOLUENE") and replace 200 with 180.

4. Press Enter to confirm the changes.

The Stream 1 Manipulate Table looks like this:

5. Close the Stream 1 Manipulate table.

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

1. From the Run menu, click Pause At. The Pause Time dialog

box appears.

2. In the Pause At Time box, Type 2.5, and 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.

3-10  Tutorial 3 - Running the Dynamic Simulation Getting Started Guide

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

To do this:

1. Click an empty area on the plot and click the right mouse

button.

2. From the menu that appears, click Zoom Full.

The plot that appears is similar to this:

The plot shows how the change in feed composition affects the

distillate purity. You also see how the solvent 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 Dynamics

Congratulations! You have now completed all the tutorials in this

book. To save your simulation and quit Aspen Dynamics:

1. From the File menu, click Save.

2. From the File menu, click Exit.

You have successfully completed your first dynamic simulation

using Aspen Dynamics.