Improved regulatory control of industrial gas phase ethylene polymerization reactors

Abstract

This paper investigates the application of two techniques to improve the PI control performance when implemented to stabilize the operation of gas phase polyethylene reactors around optimal operating point which is open-loop unstable. The first technique deals with improving the performance of SISO control loop through employing on-line adaptive tuning strategy. The purpose of the tuning strategy is to force the closed-loop response to fit inside desired time-domain specification envelope by automatically adapting the PI setting values. The second technique deals with improving the MIMO control performance by simple selection of proper control structure design. The objective of the proposed control design is to avoid the procedure of screening various control structure candidates. Moreover, since there are more inputs than outputs, split-range configuration is used to utilize all available manipulated variables. This configuration allow for tight control. Simulation results demonstrated the success of the proposed methods to provide better regulatory control performance when compared to what have been reported in earlier work.