Extended Kalman Filter-Based Nonlinear Model Predictive Control for a Continuous MMA Polymerization Reactor

Abstract

A mathematical model was developed for a continuous reactor in which free radical polymerization of methyl methacrylate (MMA) occurred. Elementary reactions considered in this study were initiation, propagation, termination, and chain transfers to monomer and solvent. The reactor model took into account the density change of the reactor content and the gel effect. To measure the conversion and weight-average molecular weight on line, the on-line densitometer and viscometer were installed in such a way that the measured values of density were used to calculate the conversion and the viscosity measurement along with conversion data was used to determine the weight-average molecular weight. A control system was designed for a continuous reactor using an extended Kalman filter (EKF)-based nonlinear model predictive controller (NLMPC) to control both the conversion and the weight-average molecular weight of the polymer product. The control input variables were the jacket inlet temperature and the feed flow rate. For the purpose of validating the control strategy, an on-line digital control experiment was conducted with an on-line densitometer and viscometer installed. Despite the complex and nonlinear features of the polymerization reaction system, the EKF-based NLMPC performed quite satisfactorily for the property control of the continuous polymerization reactor.

Model Predictive Control of Nonlinear Processes

“…Sequential quadratic programming (SQP) is widely used classical optimization algorithm to solve nonlinear optimization problems. However, for the solution of large problems, it has been reported that gradient based methods like SQP requires more computational efforts (Ahn et al, 1999). More over, classical optimization methods are more sensitive to the initialization of the algorithm and usually leads to unacceptable solutions due to convergence to local optima.…”

Free‐Radical Polymerization: Homogeneous

“…However, simple models can often be combined with limited on-line measurements (for example, in Refs. [109][110][111][112] to improve control performance. Fundamental models can also be used to test empirical models developed for control purposes [113].…”

An experimental study on on-line optimizing control of free radical bulk polymerization in a rheometer–reactor assembly under conditions of power failure

“…Ali et al (2007) studied the modelbased control of propylene polymerization, with the monomer conversion and melt flow index controlled using the flow rate of the cooling water and the inlet concentration of hydrogen. Several workers (Park and Rhee, 2003;Ahn et al, 1999;Catalgil-Giz et al, 2002) have used the intrinsic viscosity to control and monitor the polymerization reactor. However, not much work has been reported in the open literature on the on-line optimizing control of bulk polymerizations of methyl methacrylate (MMA).…”