Dynamic simulation and quadratic dynamic matrix control of an industrial low density polyethylene reactor

In this study, a reliable rigorous dynamic model of an industrial low density polyethylene (LDPE) reactor, one of the two 250 litre reactors at an LDPE plant in a petrochemical complex, is developed. The model predicts temperature profile, conversion and some of the polymer properties such as weight average molecular weight, and initiator composition. The predictions are in quite satisfactory agreement with actual plant data. Considering the multi-input, multi-output characteristics of the plant and interaction between control loops, dynamic matrix control algorithm with a quadratic programming routine is applied to the system through simulation. Simulation results showing the performance of the quadratic dynamic matrix control are presented, and are compared to the PI control employed in the plant. The results obtained from this algorithm show promise for a better control of the system, particularly for set point tacking, compared to the conventional control currently employed.