Simulation And Optimization Control Of The Acetic Acid Azeotropic Distillation Process

Acetic acid dehydration is an important operation in the production of aromatic acid, such as in the manufacture of pure terephthalic aced(PTA). Although acetic acid and water does not form azeotrope, but using simple distillation to sepatate these two components is not practical. The reason is because the system has tangent pinch on the pure water end, thus it is more customary in industry to use an entrainer via a heterogeneous azeotropic distillation column system for the separation, In this study, a selected entrainer is n-butyl acetate. Optimum process design and operating condition are determined to keep high-purity bottom acetic acid composition and also keep a small acetic acid loss through top aqueous draw. Furthermore, the overall control strategy of this column system is proposed to hold both bottom and top product specifications in spite of feed rate and feed composition change.In this paper, through the steady simulation of the azeotropic distillation process of acetic acid dehydration, the generality rule between the feed and reflux has been summarized. Then a expert controller has been designed to control the reflux when the feed changes.