Separation of ethanol and water by extractive distillation with salt and solvent as entrainer: process simulation

Abstract

-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.

Otimização De Uma Coluna De Destilação Azeotrópica Homogênea Aplicada À Obtenção De Etanol Anidro

“…A simulação da obtenção de etanol anidro através da destilação extrativa foi baseada em trabalhos já publicados (Junqueira et al, 2012;Meirelles et al, 1992;Oliveira, 2009;Gil et al, 2008). Foi realizada a construção do fluxograma do processo de desidratação do etanol no Aspen Plus Para a simulação da coluna foi usada a rotina RadFrac, a qual realiza cálculos rigorosos de operações multi-estágios de fracionamento líquido-vapor.…”

Simulation of ethanol extractive distillation with mixed glycols as separating agent

“…Among the most popular processes used in ethanol dehydration, heterogeneous azeotropic distillation uses solvents such as benzene, pentane, isooctane and cyclohexane, among others; extractive distillation with solvents and salts as separating agents; adsorption with molecular sieves; and, processes that use pervaporation membranes (Black et al, 1980;Gomis et al, 2007;Hanson et al, 1988;Jacques et al, 1999;Pinto et al, 2000;Ulrich et al, 1988;Uyazán et al, 2006;Gil et al, 2008;Ravagnani M.A.S.S., et al, 2009). All these processes have had industrial applications and some of them have actually disappeared, due to their inherent high costs of operation, operational problems, and increased energy consumption levels.…”

“…In certain occasions, azeotropic alcohol may come from the rectification column in the liquid or vapor phase; also, it is possible to establish heat recovery schemes within the process, in order to adjust the thermal condition of the feed. Most studies included in the literature (Meirelles et al, 1992;Lee and Pahl, 1985;Chianese and Zinnamosca, 1990;Uyazán et al, 2006;Gil et al, 2008) use azeotropic feed at the bubble point as the starting point. Although preheating the mixture could increase the cost of the process, it is feasible to consider an integrated heat exchanger network in the system.…”

Review of Retrofitting Distillation Columns Using Thermally Coupled Distillation Sequences and Dividing Wall Columns to Improve Energy Efficiency

“…Extractive distillation (Figure 12) is used widely in many processes (Arifin and Chien, 2008;Gil et al, 2008;Hernán-dez, 2008;Gil et al, 2009;Gutiérrez-Guerra et al, 2009), but its high energy consumption is a major disadvantage that should be overcome. To reduce the energy requirements, TCDS can be utilized through the implementation of interconnecting streams to achieve thermally coupled extractive distillation sequences (TCEDS-SR) (Gutiérrez-Guerra et al, 2009;Ibarra-Sánchez and Segovia-Hernández, 2010).…”