Comprehensive Evaluation of Distillation Methods for Water-Ethanol Separation: Energy, Exergy, and CO₂ Emission Analysis with Process Enhancement

Azeotropic distillation (AD) and extractive distillation (ED) are two conventional methods for separating azeotropic mixtures. However, these processes consume a high amount of energy like other distillation columns. As an entrainer may significantly affect energy consumption, selecting a proper entrainer is considered a key parameter in designing AD and ED processes. In this study, three different entrainers were used to separate the azeotropic water-ethanol mixture. Two entrainers, benzene and cyclohexane, were used in the AD process, and ethylene glycol was used as an entrainer in the ED process. According to the results, the ED process with ethylene glycol entrainer outperformed the AD process with benzene and cyclohexane entrainer in terms of separation and energy consumption. Therefore, in order to reduce the energy consumption of the ED process with ethylene glycol entrainer, feed splitting (FS) method was used. In addition, to further investigation on these two processes, exergy loss, CO2 emission and TAC were calculated. Results showed that the ED process with heat integration reduced hot and cold utilities, respectively, by 94.33% and 60.56% relative to the AD process. Also, exergy loss, CO2 emission and TAC in the proposed ED process decreased compared to the basic ED process to the extent of 32%, 7% and 80.1%.