Molecular Weight Control in Semi Batch Copolymerization Reactor through Temperature Tracking: Evaluation of Control Strategies

Molecular weight is one of the influential attributes in a polymerization process and its control in semi-batch operation poses considerable difficulty due to complexities of the process. The present study focuses on the development of different control strategies for controlling the molecular weight by tracking reactor temperature and composition control using jacket temperature and feed flow rate as manipulated variables. The copolymerization of styrene acrylonitrile with xylene as solvent and AIBN as initiator is considered for the present study. The control strategies evaluated are Multi-loop-proportional integral (PI) control, multivariable-PI control and nonlinear generic model control (GMC). The present study showed that control of temperature and composition has resulted in achieving the desired molecular weight. Nonlinear GMC control is able achieve targeted molecular weight closely even in the presence of unmeasured load disturbances in the monomer feed concentration and initial initiator concentration, whereas multi-loop and multivariable PI controllers resulted in some offset.