Evaluation of control strategies for a semi batch copolymerization reactor

Polymerization processes are characterized by exothermic reactions with complicated nonlinear dynamics, especially in batch / semi-batch mode. The complexities of the polymerization kinetics and reactor behaviour pose difficult quality control problems. Therefore a control strategy that ensures an optimal as well as robust operation of polymerization reactors, under the influence of various disturbances control, is required to achieve the desired product specifications. It is extremely important to develop efficient methods for the synthesis of polymerization control strategies. In this work, the optimal target values of molecular weight and copolymer composition for a semi-batch styrene-acrylonitrile (SAN) copolymerization reactor are set as set point trajectories and are tracked by PI controllers. Two versions of PI control, namely two independent SISO controllers and multivariable PI controller are attempted in this study for control of molecular weight and copolymer composition using coolant temperature and inlet feeding flow rate as manipulated inputs. This approach overcomes the drawbacks of open loop optimal control implementation though handling of the effects of load disturbances as well as set point changes. The simulation results demonstrate the usability of this approach for online optimization and control.