Question

How does a PID controller work in a adsorption column, clasifier and tank in a waste water treatment plant? Justify why did you put controller there.

Its a dyeing waste water treatment plant

Answer 1

PID CINTROLLER.

PID - Proportional Integral Derivative controller is a type of controller used in industrial applications. It uses a closed loop feed back mechanism to process control variables and are most accurate stable controller.

Now consider PV = Process variable

SP = Set point

Error of the system is e= Set point- process variable.

The controller installed in the system works to minimize the error.

In PID controller it consists three terms .

1. Proportional: it regulate the out put proportional to the error produced

2. Integral : here the controller work on the system on integral if time until the errror minimized.

3. Derivative : here the controller predict the future error may happens to the system based on the history data and work on this to minimize error.

Q) A controller is provided in the system to reduce steady state errors and imprive the efficiency and hence stability can be achieved. In PID controller, as it give fast response helps in reducing unwanted offfset.

Here given it is a dyeing watste water treatment plant.

So objective of the process system is to make zero spillage of dye to surrounding. For this it uses an adsorption column , clarrufier and a tank.

Our objective is zero spillage of dye.

Error of the system is concentration of dye in output.

Here volume of clarrifier & tank are cinstant. Variable in the system is the flow of adsorbent in the adsorption tank & inlet flow of waste water to the system.

So if a PID Controller is installed in this system, it reduce the error by adjusting flow rate of either adsorbent or waste water.

Consider the controller works on adsorbent flow rate.

If error in system observed, controller act on flow on adsorbent and proportional to the error it regulate the flow.

Now since it is a PID controller, before analyzing the next sample, the integral action of the controller comes in action. Controller makes changes to input of the process based in the error accumulated over a period of time.

Derivate action of controller analyze the previous error happens to the system with reference to process variables and make some future prediction of error that comes to the sytem. Based on this the controller take some advance precaution on flow change,( regulate the flow rate of adsorbent) to save the system from making deviation. All these three controlling action act on the error ( spillage of dye in out let flow) to minimize the deviation and make it stable.