Pressure Control in a Distillation Column

The transfer function relating the signal from the pressure sensor at the top of a distillation to the signal to the control valve throttling the cooling water to the condenser is

Kp equals 0.0178 radians per second. A proportional controller closes the control loop.

a) Determine the values of the controller gain, which stabilize the control

system.

PI Control of a Second order systemA proportional + integral (PI) controller is used to control a process with transfer function

s has units of radians per minute.

a) Determine the values of the controller gain which stabilize the system

when the integral time is 0.5 minutes.

b) Determine the minimum value of the integral time which guarantees

that the control system is stable for all positive values of the controller

gainFrequency response of an Adsorption column

The open loop transfer function of a packed column gas adsorber is

s has a units of radian per minute and K = 1.67 ( 103 (rad/min)3A proportional controller with unity gain close the loop

a) Determine the value of the loops gain cross over frequency, (1b) Determine the value of the loop phase cross over frequency, ((c) Determine the loop gain margin and phase marginDistillation Column Control

A PI controller regulates the boil up rate in a small packed distillation column by throttling the steam flow to the boiler. The vapor flow rate is determined by measuring the pressure drop across the packing. The transfer function relating y the measurement signal to u the signal to the steam valve is

where the time constant have the units of seconds. The controller setting are to be determine by the procedure of table below.

(i) Set the controller time constants by using straight line approximations to phase behaviour on a Bode plot

(ii) Set the controller gain by using the loops gain margin as the relative stability criterion.

a) Estimate the phase cross over frequency of Gpb) Find the minimum value of the integral time for which the controller

contributes no phase lag at the crossover frequency of Gp

c) Using the integral time found in part b, determine the controller gain

which gives a gain margin of two for the control loop.8.3 A liquid level control system can be configured in either of two ways: with control valve manipulating flow of liquid into the holding tank (as in the left figure), or with a control valve manipulating the flow of liquid from the tank (right figure).Assuming the liquid level transmitter always is direct acting.

a) For each configuration what control action should a proportional

pneumatic controller have if the control valve is air to open

b) Repeat part a) for an air to close control valve_1121958685.unknown

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