Multi-rate control of a polymerization reactor: a comparative study

Abstract

A comparative study of multi-rate control of a jacketed styrene polymerization reactor is presented. A multirate nonlinear control system is used to regulate weightaverage molecular weight of the polymer product and temperature in the reactor, by manipulating the flow rate of an initiator feed stream and the rate of heat input to the reactor jacket. The multi-rate control system consists of a multi-rate nonlinear state estimator and a mixed errorand statefeedback controller. The state estimator p r e vides continuous estimates of state variables of the p r e cess from (i) frequent measurements of the reactor temperature, the jacket temperature and the reacting-mixture density, and (ii) infrequent and delayed measurements of the leading moments of the molecular weight distribution of the dead polymer chains. The infrequent and delayed measurements have sampling periods of three hours and measurement delays of one hour. In the presence of processmodel mismatch and measurement noise, by numerical simulations the performance of the multi-rate nonlinear control system is shown and compared with those of a multi-rate, proportional integral (PI), parallel cascade, control system and a multi-rate, PI, completely decentralized, control system.