A Closed-Loop Control Strategy for Producing Nitrile Rubber of Uniform Chemical Composition in a Semibatch Reactor: A Simulation Study

Abstract

To improve the quality of industrial nitrile rubbers, the copolymer chemical composition, pA(t), should ideally be kept constant along the reaction. This work proposes a closed-loop control strategy for the semibatch operation of the reactor with the aim of regulating pA(t) within a reduced range of variability. The proposed strategy is evaluated by simulating a mathematical model of the process. To this effect, a simplified mathematical model of the reaction is first derived and then utilized to obtain a suboptimal control law and a soft-sensor that estimates the polymerization rates. The suboptimal control law is compensated by adding a term proportional to errors in pA(t). The simulated example considers the production of the low-composition AJLT grade, with the copolymerization reaction represented by a detailed mathematical model adjusted to an industrial plant. Due to the high performance of the soft-sensor, the simulation results suggest that the proposed closed-loop strategy is efficient to adequately regulate pA(t) in spite of structural and parametric uncertainties, while other quality variables remained practically unaffected.