Optimal-grade transition strategies for multistage polyolefin reactors

Polymer producing companies normally produce many polymer grades in each po lymerization reactor train according to customer demands; therefore, many g rade-transition operations are necessary. However, the determination of the se optimal strategies is difficult. To solve this problem, several sample s imulations showing the optimal solutions of grade-transition strategies for multistage olefin polymerization reactors with bimodal products were perfo rmed. The methodology utilized a dynamic process simulator, POLYRED, couple d to a sequential quadratic programming, nonlinear optimization algorithm, by using two different objective functions with and without state constrain ts. Ir is shown that the most beneficial case of using the optimization tec hnology is the grade transition where the hydrogen content in a reactor mus t be decreased and/or constraints are imposed on state variables.