Dynamic Optimization of HIPS Open-Loop Unstable Polymerization Reactors

We consider dynamic optimization strategies for grade transitions for high-impact polystyrene reactors. Because our desired operating conditions are at unstable points, we apply a simultaneous dynamic optimization (SDO) approach, where state and control variables in the optimal control problem are discretized and a large-scale nonlinear programming solver is applied. For this purpose, we consider Radau collocation on finite elements and the IPOPT NLP solver. In addition, we describe the stability of the SDO strategy through the presentation of dichotomy properties for boundary-value problems. The resulting SDO approach is then demonstrated on a wide variety of operating scenarios for the high-impact polystyrene (HIPS) reactor, with highly reliable and efficient performance results.