ETHYL ALCOHOL - WATER SEPARATION BY EXTRACTIVE DISTILLATION: SIMULATION USING ASPEN PLUS™ AND EXPERIMENTAL VALIDATION

Abstract

Dilute ethyl alcohol (ethanol, EtOH) is produced using fermentation (< 20 mass%), but it needs to be further purified because it contains large water content. EtOH forms an azeotrope with water and to separate this azeotrope, advanced separation processes like pressure swing distillation (PSD), azeotropic distillation (AD), and extractive distillation (ED) are employed. In this work, ethylene glycol (EG) was used as an entrainer in extractive distillation. Vapour liquid equilibrium (VLE) data was used to validate the chosen rigorous thermodynamic model. To find a workable range of operating parameters, sensitivity analysis was performed to find out the number of stages (N), feed stage (NF), distillate rate (DR), and reflux ratio (RR). Simulation shows that use of accurate operating parameters and correct entrainer can help to obtain almost pure EtOH (99.89 mole %, 99.92 mass %). In order to validate the theoretical findings from the simulation, experimental investigations in the form of batch and semi - batch distillation runs were conducted. It was seen from these runs that it is indeed possible to obtain EtOH with high purity. It was also verified that EG can be separated and recycled back with high purity with a very high recovery.