PCM Distillation Tutorial

8/10/2019 PCM Distillation Tutorial

http://slidepdf.com/reader/full/pcm-distillation-tutorial 1/6

1

Rev.: 3-14-11

PCM Distillation Module Tutorial©

for

Process Dynamics and Control, 3/e

by Seborg, Edgar, Mellichamp and Doyle (2010)

1. Download PCM Distillation tutorial files

The PCM Distillation tutorial files can be downloaded from the book website

(http://www.wiley.com/WileyCDA/WileyTitle/productCd-EHEP001620.html).

Double-click on the PCM file and follow the instructions to install the software.

Note that you need to have MATLAB on your computer in order to use these

modules. During the installation, you will be asked if you would like to create ashortcut icon to the software on your desktop (recommended).

2. Running the Software

There are two ways to execute the software; the first is to double-click the PCM

icon on the desktop to launch MATLAB and the PCM. The second way is to

manually open MATLAB and to start the PCM software by selecting the PCM

installation folder and typing PCM followed by <enter>.

3. Open and initialize the Distillation Column simulation

Type 0.04 into the text box that initially has a value of 0. The new value reduces

the speed at which the real-time plots are generated. (See Fig. 1.)

Next, select “Distillation Column” in the drop down “Module” menu.

Click the “Introduction” button and read the information about the “Binary

Distillation Column” file.

Figure 1. The PCM Distillation Module.



2

4.

Organize MATLAB windows

Click on the “Operator Interface” button. The “Column” and “COLUMN

PROCESS MONITOR” windows should open, although one window may be

hidden behind the other.

In the “COLUMN PROCESS MONITOR” window, click the drop down menu

for the Desktop and select “dock COLUMN PROCESS MONITOR”.

Important: Resize the docked window and the Column window so that they do

not overlap and you can see both windows clearly at the same time. (See Fig. 2.)

Figure 2. Computer display showing the COLUMN PROCESS MONITOR (left), theOperator Interface, or “Column” display (right).

5. Simulate the column response to step changes in the reflux ratio and the vapor flow

rate

Some useful tips:

For any data point on a plot in the COLUMN PROCESS MONITOR, the

numerical values of the time and process variable can be displayed. In order to do

so, click on the Pointer box for that variable and drag its crosshairs to the selected

data point. If the crosshairs do not appear, click on the Data Curser item in the

Tools menu.

Be sure to note the time when you press “Pause”, you may need it in your

simulation. The current time is located below the Column diagram, as shown in

Fig. 3.

3000 s is sufficient for this simulation. Do not run one step of the simulation too

long, because some data may be lost when you save it to the local file.



3

It is much better to run a new simulation for the step changes in vapor flow rate

in order to make sure that all the data is successfully saved. Before you run a new

simulation, first press “Stop” in the “Column” window and close both windows,

and do not save the changes. Then type “clear all” in the Command Window in

MATLAB, and restart a new simulation and save the useful data.

Procedure Press the “Play” button (i.e., the black triangular in the top row) in the “Column”

window in Fig. 3 to start the simulation. Let the simulation proceed for

approximately 3000 s in the “COLUMN PROCESS MONITOR” window and

then click the “Pause” button (the adjacent button with two vertical lines.). You

can determine the exact time from the bottom of the “Column” window in Fig. 3.

Figure 3. The Operator Interface (“Column”) display showing the current time and the Play

and Stop buttons.

Next, double click on the “reflux ratio” block in the “Column” window and multiply

the current entry in the “Current Value” tab by a factor of 1.1.

Begin the simulation again press “Play”. Let the simulation run for approximately

3000 additional seconds and then pause the simulation.

Play Stop

Current time



4

Reset the reflux ratio to the original value and run it for approximately 3000

additional seconds and then press the “Pause” and change the reflux ratio to another

value (1.75*1.2, 1.75*1.3), then run for 3000 s.

After you have finished three step responses for the reflux ratio, press “Stop” in the

“Column” window.

Save your data by creating a data file. Enter the name of the data file (e.g., Reflux

Ratio) in the Column box, as shown in Fig. 4.

Press “Save”. Your data file (e.g., “Reflux_Ratio.mat”) is generated in the current

dictionary.

Then repeat for three step changes in the vapor flow rate input. Multiply the original

value by 1.05, 1.1 and 1.15 to generate the three step responses.

Figure 4. Save your data by typing your file name in the “Column” box at the lower right

side of this display.

Rename the file in this box.

Save



5

Figure 5. Column response to step changes in reflux ratio.

6. Stop the simulation and prepare the data for export to an Excel file

Click the “Stop” button (i.e., the black square in the top row of the Furnace window)

to terminate the simulation. (Typical simulation results are shown in Fig. 5.)

Now you have your own data file (i.e., Reflux_Ratio.mat) in the current dictionary.

Double click on the file name in the “Current dictionary” window and all the data

will be transferred to the “Workspace” window.

Figure. 6. List of variables for the column simulation.

Open the “Workspace” window and select the useful data. N



6

The time variables ‘d1t’, ‘d2t’, ‘d3t’, and ‘d4t’ are the same and represent the time in

the simulation, in seconds.

‘d1y’ means the “overhead flow rate” (mol/s).

‘d2y’ means the “overhead composition” (fraction).

‘d3y’ means the “bottoms flow rate” (mol/s).

‘d4y’ means the “bottoms composition” (fraction).

You can copy these data to Excel and then analyze them.

If these data are row vectors, which are not so convenient to be copied, you can type

the following script in the command window of MATLAB to change them into

column vectors.

d1t=d1t ' ;d1y=d1y' ;d2y=d2y' ;d3y=d3y' ;d4y=d4y' ;

Documents

PCM Distillation Tutorial