Optimization of Extractive Distillation Process with a Single Column for Anhydrous Ethanol Production

Distillation is one of the oldest and most used separation processes that exist in chemical industries worldwide. In cases of azeotropic mixtures, simple distillation is unable to perform separation at a certain composition, so they are separated using azeotropic distillation. Traditionally, there are two different configurations used to produce anhydrous ethanol by azeotropic distillation. One of them is the heterogeneous azeotropic distillation and the other one is the homogeneous azeotropic distillation. In both configurations, it is necessary to add a third component (solvent) to promote separation and it is also necessary to use a second distillation column in order to recover the solvent. This paper deals with homogeneous azeotropic distillation (also called extractive distillation) and the process of obtaining anhydrous ethanol was chosen as a case study. For this case, the solvent used to break the azeotrope was ethylene glycol. The purpose of this work is to determine the optimal conditions of a new configuration of extractive distillation process for producing anhydrous ethanol using only one column with a sidestream withdrawal, using the process simulator Aspen Plus®. After optimization, it was possible to achieve a reduction of 18.53 % in the reboiler heat duty. A comparison, in terms of energy consumption of the reboilers, between the traditional extractive configuration and the new configuration, was also assessed.