AN OPTIMIZATION STUDY ON ENHANCING THE VACUUM DISTILLATION UNIT USING MPC IN COMARISON WITH PID CONTROLLER

Abstract

This research examines the process of choosing between the reliable proportional-integral-derivative (PID) controller and the recommended model predictive control (MPC) controller for the vacuum distillation unit (VDU) by analyzing dynamic behavior. Aspen HYSYS V12.1 and MATLAB Simulink environment (2021 A) programs were used in this study to compare the performance of the PID and MPC controller to analyze the overhead temperature response and the temperature response in the middle of the tower (stage No.15), both of them are basic factors to improve product quality and quantity, through a set point (SP) step change in the mass flowrate of feed stream, feeding temperature and flow rate of stripping steam, in addition to study the effect of disturbance step change to the feed pump efficiency, as well as making a  change in the overhead temperature and the temperature of (Stage No.15) to clarify the performance difference between the (PID) and (MPC). The study result showed that (MPC) is better than (PID) in reaching the desired value, overcome turbulence effect, in response time it is found that the response time in MPC is shorter than the PID controller by 50%, In the overshot and raising time the MPC is better, and temperature Response time of overhead in MPC shorter than PID with step change in feed flow, feed temperature and stripping steam flow is respectively: 18.2min ,258min and 33.4 min. while (stage No.15) temperature is respectively 207.6min ,161.6 min and 22 min.

 This study showing that how is the efficiency of the distillation separation process can be increased through the prediction disturbance, overcoming it and high response time to reach the desired value, which increases the production quality, quantity and reduces the energy associated with the production process (steam, fuel, electricity, etc.).