Studies in modeling and design of controllers for a nonideal continuous stirred tank reactor

Abstract

A Continuous Stirred Tank Reactor (CSTR) is one of the most important unit operations in chemical industries which exhibits a highly nonlinear behaviour and usually has wide operating ranges. Unfortunately, in the real world, the behaviour of the CSTR is very different from that expected from the ideal CSTR. From the literature review, it is observed that the modeling and control of an ideal reactor has been extensively studied. Hence the objective of the present work is to derive a mathematical model for a nonideal CSTR and investigate a suitable control strategy for the reactor system. In the present work, the mathematical modeling and closed loop studies are carried out for a CSTR under ideal and nonideal mixing conditions. In the present work, the performance of the ideal CSTR with decoupling control scheme is found to be better than that of decentralized control scheme. The objective function for tuning the controller is to minimize the Integral Square Error. Both servo and regulatory responses are studied for all the control schemes using MATLAB. The quantitative error measures ISE and IAE associated with the responses have been determined. From the simulation studies, it is seen that the decoupling control scheme provides better results than the decentralized control scheme for the ideal CSTR. Accordingly, the thesis consists of six chapters. The major findings of the present work include Formulation of mathematical model of a nonideal CSTR from the modeling equations of an ideal CSTR; Fuzzy gain scheduled GA based multivariable control scheme of the CSTR provides better set point tracking and load disturbance rejection than the conventional control scheme; The closed loop performance of the real CSTR is improved by incorporating the effects due to nonideal mixing in the CSTR model and implementing the fuzzy gain scheduled GA based multivariable PID control schemes on the real CSTR. newline