Process Simulation Of Ethylene Glycol-Assisted Extractive Distillation For High-Purity Bioethanol

Abstract

The practice of ethanol purification has obtained considerable intellectual interest in current discussions owing to its extensive set of applications, including its use as a renewable energy source, an industrial solvent, and in medicinal formulations. Separating ethanol from water is challenging due to the formation of an azeotrope. Extractive distillation is regarded as one of the most advantageous techniques for the separation of ethanol from aqueous solutions, attributable to its favorable energy efficiency and reduced capital expenditure prerequisites. Glycols, particularly ethylene glycol and glycerol, have exhibited considerable effectiveness as solvents in the extractive distillation processes that involve mixtures of ethanol and water. In this study, an extractive distillation simulation of the dehydration of bioethanol process using ethylene glycol as the solvent was conducted. The sensitivity analysis was carried out using the Aspen Plus Simulation to determine the optimal operating conditions. The Non-Random Two Liquid Model (NRTL) thermodynamic model was used in this study. An extensive simulation of the extractive distillation column was ultimately performed, integrating a secondary recovery column for the solvent mixture along with a recycling loop. In the sensitivity analysis, the impact of the number of stages, binary feed stage, entrainer feed stage, reflux ratio (RR) on the purity of ethanol with minimum reboiler and condenser heat duties were studied. The optimal configurations for attaining elevated ethanol concentrations while minimizing energy expenditure in the extractive distillation apparatus consist of 25 stages, a binary feed introduced at stage 22, a solvent feed introduced at stage 3, and a reflux ratio maintained at 1. In the recovery of solvent column, the optimum conditions were found as the number of stages 10, solvent rich feed entry at stage 5 and reflux ratio of 1. Finally, an ethanol purity of 99.7 mole% was achieved with the inclusion of solvent recycling.