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The extractive distillation of ethanol using glycerol as entrainer is studied in order to find its optimal design and operating conditions. The optimization is formulated as a mixed integer nonlinear programming (MINLP) problem. The discrete variables determine the number of stages of the columns and their feed stage locations. The continuous variables include the variables of the equilibrium model and operating variables. The solution of the optimization problem is achieved through a two-level strategy that combines stochastic and deterministic algorithms. The result obtained establishes the process that maximizes an economic criterion for the industrial production of bioethanol satisfying the problem constraints.

The acetone-methanol extractive distillation using water as an entrainer was simulated on Aspen Plus software package using rigorous methods. Calculation of the vapor-liquid equilibrium for the ternary system was done by the UNIQUAC model according to the experimental results obtained in a previous work. The effects of the solvent to feed molar ratio, reflux ratio, feed stage, feed solvent stage, and solvent feed temperature were studied to obtain the best design of the extractive distillation column with minimal energy requirements. The most appropriate configuration is 52 theoretical stages. The best binary mixture and entrainer feeding stages were obtained at 48 and 22 respectively with a solvent to feed molar and reflux ratio of 2.0 and 5.0, respectively. The simulation results show the effect of the main variables on the extractive distillation process.

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-The aim of this work is to simulate and analyze an extractive distillation process for azeotropic ethanol dehydration with ethylene glycol and calcium chloride mixture as entrainer. The work was developed with Aspen Plus® simulator version 11.1. Calculation of the activity coefficients employed to describe vapor liquid equilibrium of ethanol -water -ethylene glycol -calcium chloride system was done with the NRTL-E equation and they were validated with experimental data. The dehydration process used two columns: the main extractive column and the recovery column. The solvent to feed molar ratio S/F=0.3, molar reflux ratio RR=0.35, number of theoretical stages Ns=18, feed stage Sf=12, feed solvent stage SS=3, and feed solvent temperature TS=80 ºC, were determined to obtain a distillate with at least 99.5 % mole of ethanol. A substantial reduction in the energy consumption, compared with the conventional processes, was predicted by using ethylene glycol and calcium chloride as entrainer.