Dynamics and Control of a Heterogeneous Azeotropic Distillation Column: Conventional Control Approach

Abstract

In this work, bifurcation analysis and dynamic simulation were used to investigate the optimum conventional control strategy of an isopropyl alcohol (IPA), cyclohexane (CyH), and water (H2O) heterogeneous azeotropic column. Steady-state process analysis shows that the optimal operation point should be located at a critical reflux, a transition point at which the distillation path switches from a route that passes through the IPA + H2O azeotrope to one that passes through the IPA + CyH azeotrope. A good control strategy must be able to maintain a steady column temperature profile that shows a plateau near 70 °C to ensure passage around the IPA + CyH azeotrope. An inverse double-loop control strategy is proposed based on principal component analysis. This scheme is capable of maintaining the desired column temperature profile given all kinds of feed disturbances, thus keeping the product IPA purity at the desired level.