Novel energy-saving methods to improve the three-column extractive distillation process for separating ethyl acetate and ethanol using furfural

A mixture of ethyl acetate and ethanol is difficult to separate because of a minimum-boiling homogeneous azeotrope. The characteristics of the ethyl acetate/ethanol system are analyzed. The energy-saving potential of a three-column extractive distillation process to separate the system is explored. The effects of the distillate composition of pre-concentrator, the temperature of solvent feed and operating pressures are studied. Energy-saving processes including heat pump distillation, heat integration and partial condensation are proposed. A novel way of partial condensation is proposed and compared with the conventional way. An innovative method of vapor–liquid coupling between the per-concentrator and the extractive column is then proposed. It is more economical and energy-efficient than the above processes. Besides, based on the vapor–liquid coupling process, two further improvements are proposed through heat integration and through compressors. All processes are optimized using the sequential iterative optimization procedure with the minimum total annual cost as the target. Compared with the conventional process operated at 101.3 kPa, the two improved processes can reduce total annual cost by more than 52%, reduce energy consumption by more than 60%, and reduce CO2 emissions by more than 61%.