Process simulation for bio-ethanol dehydration by azeotropic distillation and extractive distillation

Abstract

Bio-ethanol dehydration has drawn a major attention in the process industry all over the world, due to the emerging requirement of substituting fossil fuels with biofuels in order to prevent the harmful environmental impacts of fossil fuels. Bio-ethanol is generally produced via fermentation and fermented bio-ethanol must be further separated from water to yield anhydrous ethanol above 99.5 mol% purity, before using it as a fuel for the specific applications. There is an obstacle for the conventional separation using simple distillation columns at atmospheric conditions due to the azeotrope in the ethanol/water system, approximately at 89 mol% of ethanol composition. The azeotropic distillation using cyclohexane as the entrainer and extractive distillation using ethylene glycol as the solvent can be considered as the commonly applied bio-ethanol dehydration techniques in order to get rid of the azeotrope barrier. The steady state process simulations were carried out for the two distillation techniques using the Aspen Plus simulator at equal operating conditions and at same final bio-ethanol product concentration of 99.9 mol%, for an unbalanced comparative analysis. The results showed that, the extractive distillation technique has many advantages than the azeotropic distillation technique in terms of different economical aspects. The impact of column sizing towards the capital investment as well as the effects of energy consumption and mass flow conditions to the operating cost of each bio-ethanol dehydration technique were discussed