Tc3

Figure 10.2 Control structure for liquid sidestream column.

Figure 10.2 Control structure for liquid sidestream column.

Figure 10.3 Controller faceplates.

Now the remaining issue is how to manipulate the sidestream flowrate. One effective method is to ratio the sidestream flowrate to the reflux flowrate. This lets the sidestream flowrate move as disturbances occur. For example, suppose that too much methanol starts to move down the column. This will decrease the temperature on stage 51, and the TC51 temperature controller will increase the reboiler heat input. This sends more vapor up the column, which increases the reflux drum level. The level controller increases reflux flow, and the S1/R1 ratio causes the sidestream flowrate to increase, which pulls more methanol out of the column.

460 440 — 420 a 400 J 380 360 340 320

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