AIChE 2010 Annual Meeting, November 7-12, Salt Lake City, UT. Bioethanol Dehydration in Thermally Integrated Extractive Distillation Columns Nghi Nguyen, Jiwon Sim, Yaşar Demirel* Department of Chemical and Biomolecular Engineering, University of Nebraska Lincoln, Lincoln, NE 68588 ABSTRACT Bioethanol plants produce dilute mixture of around 10-wt% of ethanol in water. Ethanol is distillated to 96%, and most commonly, sent to a molecular sieve, which absorbs water. The molecular sieve is regenerated by heating to remove water. As the capacity of ethanol production increases molecular sieve becomes thermally inefficient. Beside that the distillation of ethanol could consume up to 50% of the overall energy used in a typical grain alcohol plant. Ethanol purification by distillation requires extractive distillation with an entrainer, such as pentane, benzene, diethyl ether, ethylene glycol, toluene, cyclohexane, methoxy-ethanol, ethyl tert-butyl ether, and bioglycerol. Entrainer breaks the azeotrope which forms between ethanol and water at 95.6 wt% ethanol (at atmospheric pressure). The study analyzes the potential of using thermally integrated columns to save energy for the purification of ethanol from water using ethylene glycol as entrainer. Keyword: Ethanol, azeotrope, thermally integrated column, ethylene glycol *Corresponding Author. Tel: 402 472 2745, fax:402 472 6989. E-mail address: ydemirel2@unl.edu 1. Introduction A reasonable blend of anhydrous ethanol into gasoline can be used as fuels without any modification of engine necessary [1,2]. Usually, dilute ethanol-water mixture (around 10-wt% or less ethanol) is obtained from the fermentation process of a bioethanol plant [3]. However, separation of ethanol-water is a major drawback due high energy requirement because of the formation of azeotrope around 96-wt% of ethanol at atmospheric pressure. Several methods have been introduced to produce fuel grade ethanol, such as using molecular sieves, pressure-swing distillation, and homogeneous and heterogeneous azeotropic distillations using suitable entrainers. Molecular sieve is most frequently used but becomes thermally inefficient as the capacity of ethanol production increases. Pressure-swing distillation requires two distillation columns operate under a different pressure to cross the azeotrope. Hence, this research will focus on the possibility of using thermally integrated distillation columns to separate ethanol from water by homogeneous azeotropic distillation columns [4-6]. Conventional extractive distillation of ethanol-water mixture with an entrainer requires at least two distillation columns, extractive column and entrainer recovery column. The first column uses