Design and control of extractive distillation process for separation of the minimum-boiling azeotrope ethyl-acetate and ethanol

Design and control of extractive distillation process is explored by taking the separation of minimum-boiling azeotrope ethyl-acetate and ethanol as an example. The two evaluation indicators of second-law efficiency and CO2 emissions are employed to evaluate different alternatives, which consist of conventional case, F-E process (hot solvent stream to preheat fresh feed of extractive column), B-1-E process (hot solvent stream to preheat feed of recovery column), and F-B-1-E process (hot solvent stream to preheat feed of extractive and recovery column). The conventional case can reduce 32.23% in total annual cost (TAC), 28.81% in energy-saving comparing to economically optimum fully heat-integrated pressure-swing distillation process. Besides, it can further cut 4.38% in TAC and 9.79% in steam cost by heat integration B-1-E configuration while others are 1.11% (1.30%) in TAC and 10.45% (12.11%) in steam cost, where, data in the brackets are for F-B-1-E process. Furthermore, the control of extractive distillation process is explored since the interaction of parameters is complicated. For conventional process, the effectiveness of single-end control strategy is determined by the method of feed composition sensitive analysis. The appropriate control scheme (CS3) is screened by the indicator of integral absolute error (IAE) since its deviations of product purities to specifications are the least. A new control scheme of bypassing portion of hot stream around economizer with dual-point temperature control strategy is proposed for the efficient economics thermal integration alternative, and it can still achieve robust control performance at facing feed flowrate and composition disturbances. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.