Effect of impurities on continuous solution methyl methacrylate polymerization reactors: open-loop process identification and closed-loop real-time control results

An automated pilot-scale experimental reactor system with facilities for on-line measurement of process variables has been set up for closed-loop control studies on methyl methacrylate (MMA) polymerization in the presence of impurities. The desirable conversion level is maintained using initiator flow rate as the manipulated variable. Open-loop runs were carried out first to identify process transfer function models. Subsequently, control algorithms were developed and implemented on the reactor system considering variations of the reactive impurities introduced in the feed streams as process uncertainties. Conventional proportional-integral-derivative (PID) control algorithms (e.g., PID, Smith Predictor, Dahlin´s control) and stochastic control strategies (e.g, unconstrained minimum variance control (MVC), constrained MVC (CMVC), and one-step optimal control) were developed and evaluated first at the simulation level to identify promising control runs. Then, closed-loop experimental runs followed in a series of six two- to three-day continuous runs to verify the simulation results. This study not only verifies theoretical control designs with closed-loop experimental runs, but also triggers many interesting control issues for practical polymer reactor control