Info

Figure 7.10 Controller placed on flowsheet.
Figure 7.11 Selecting control signal.

To place a control signal on the flowsheet, we place the cursor over the ControlSignal icon, click and hold the left mouse button, and move the cursor to the flowsheet. A number of blue arrows show up that indicate where a control signal can be placed. Placing the cursor on the arrow coming out of the reboiler and releasing the mouse button opens the window shown in Figure 7.12, on which we can scroll down to stage 32 and select Level.

Clicking OK connects the control signal line to the reboiler and lets us connect the other end to the controller (see Fig. 7.13a). Clicking on the blue arrow on the left side of the controller opens the window shown in Figure 7.13b, where we select LC11.PV. Clicking OK completes the control signal connection between the reboiler and the level controller.

The next step is to connect a control signal from the controller to the valve V11 on the bottoms stream. Dragging and dropping another control signal at the arrow exiting the controller opens the window shown in Figure 7.14a. We select the LC11.OP and click OK. Then the line is connected to the valve. The final LC11 loop is shown in Figure 7.14b.

To set up the controller, double-click on the "LC11" icon on the flowsheet. The controller faceplate shown in Figure 7.15a opens. Controller faceplates are where we keep track of what is going on in the dynamic simulation, set controller parameters, switch from manual to automatic control, change setpoints, and perform other tasks. The very first thing to do is to click the Configure button. This opens the window shown in Figure 7.15b. Then we click on the Initialize Values button at the bottom of this window. This provides the steady-state values of the base level (6.35 m) and the control valve opening (Bias = 50%).

Name

Description

BL0CKS("C1 ").Stage(31).Q BLOCKS("C1 ").Stage(31).T

Actual duty Temperature

BL0CKS("C1 ").Stage(31).Q BLOCKS("C1 ").Stage(31).T

BL0CKS("C1 ").Stage(32).P BL0CKS("C1 ").Stage(32).Q BL0CKS("C1 ").Stage(32).T

B LO CKS (" C1 "). Stag e (31 ) ,x(" 031 ') B LO CKS ('101 "). Stag e (31 ) ,x('11C4") B LO CKS ('101 "). Stag e (31 ) ,y('1031 ') BLOCKS ("01 "). Stage (31 ).y("IC4")

Liquid mole fraction Liquid mole fraction Vapor mole fraction Vapor mole fraction

Liquid level on model stage.

Used

BL0CKS("C1 ").Stage(32).P BL0CKS("C1 ").Stage(32).Q BL0CKS("C1 ").Stage(32).T

Pressure Actual duty Temperature

Was this article helpful?

0 0

Post a comment