The process control of the triple-column pressure-swing extractive distillation with partial heat integration

Abstract

Recently, increasing researches have focused on the intensified heat-integrated triple-column pressure-swing extractive distillation (HITPED) owing to its superiority in economic and environmental benefits than the conventional extractive distillation. However, the dynamic controllability investigation for HITPED was lacking, resulting in the difficulties for industrial application. Therefore, separating the ternary azeotropic mixture tetrahydrofuran (THF)-methanol-water by HITPED is taken as an example to fully investigate the dynamic controllability. On the basis of the open-loop analysis a basic control structure CS1 is firstly proposed. To deal with the 20% disturbance in feed composition more effectively, the CS2 with a low selector and composition controllers is then developed. Nevertheless, composition controllers are less applied in chemical industry than temperature controllers owing to the long delay and high cost. As such, two different control structures (CS3 and CS4) without any composition controllers are then put forward. Integral absolute error (IAE) is applied to compare the dynamic performance. Under the 20% disturbances of the feed flowrate and composition, the robust control strategy CS4 with temperature controllers and a high selector exhibits the gratifying dynamic performance. The application of the selector further enlarges the dynamic researches in the distillation process.