Bioethanol dehydration in thermally integrated extractive distillation columns

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.