Simulation study of the production of high purity ethanol using extractive distillation: Revisiting the use of inorganic salts

Abstract

High purity ethanol can be obtained using extractive distillation with several entrainers; for instance, organic solvents, ethylene-glycol, glycerol, and ionic liquids. However, some of these entrainers are considered toxic; for that reason, in this paper, pilot conventional and dividing wall distillation columns are simulated to test the separation of the ethanol-water mixture using inorganic salts as entrainers for an experimental afterwards evaluation, considering the operational requirements.First, the electrolyte-NRTL model was selected, and the binary interaction parameters were obtained by using reported experimental vapor-liquid equilibrium data. With the selected thermodynamic model, the best operating conditions, of an existing distillation column, are determined by simulation considering several inorganic salts, resulting the calcium chloride as the best option for obtaining high purity ethanol with the lowest energy requirement in the reboiler.Finally, a pilot dividing wall distillation column was simulated for the dehydration process using a mixture of ethanol-water-calcium chloride as entrainer. The results show that it is possible to obtain high purity ethanol (mass purity around 0.99) using the pilot dividing wall distillation column. Also, calcium chloride, with 16% wt in a mixture of ethanol-water, can be reconsidered in extractive distillation processes for the production of high purity ethanol.