Ethanol Dehydration in Packed Distillation Column Using Glycerol as Entrainer: Experiments and Hetp Evaluation

Abstract

-The ethanol-water separation is very important because ethanol is widely applied in the chemical industry and its use as a fuel can reduce the pollution emitted to the air. However, anhydrous ethanol production using conventional distillation is impossible, at atmospheric pressure, due to the presence of an azeotrope. In the present work, experimental tests were carried out in order to evaluate the use of glycerol as an entrainer, in substitution of ethylene glycol in an extractive distillation. The use of glycerol is motivated by the biodiesel production units, due to the fact that it is the main byproduct and a new market is necessary to consume its overproduction. The experiments were carried out in a distillation column packed with Raschig rings, varying the glycerol/feed (ethanol and water) ratio, S/F, from 0.5 to 0.9. The samples were analyzed using a digital densimeter. The results showed that glycerol was effective to promote ethanol dehydration and the presence of an azeotrope was not observed using a solvent to feed ratio (S/F) equal to 0.9. Some empirical correlations were investigated to evaluate the HETP (Height Equivalent to a Theoretical Plate), and the results provided a useful tool for designing a packed bed column for ethanol-water separation.

Pool Boiling Heat Transfer Coefficients in Mixtures of Water and Glycerin

“…Extractive distillation is the most widely used method for the production of anhydrous ethanol [10] and glycerin is able to increase the purity of the produced ethanol [9]. The product is free of glycerin and might be used in chemical industry or as a clean-burning fuel [1]. Similar entraining capabilities of glycerin were also reported for 1-propanol-water and 2-propanol-water mixtures [11,12].…”

“…Nowadays, there is a surplus of glycerin on the market as glycerin is the main byproduct of biodiesel production. Biodiesel is commonly produced by transesterification of vegetable oils or animal fats and approximately 1 kg of crude glycerin to 10 kg of biofuel is produced this way [1,2]. This is the reason behind ongoing research and growing interest towards suitable utilization of glycerin.…”

“…Glycerin is one of the most effective substances which are able to completely suppress the azeotropic behavior of ethanol-water mixtures [1,8]. Glycerin mass fraction of about 10% is needed for complete suppression of the azeotrope [3].…”

“…It is, therefore, employed as an entrainer for extractive distillation of ethanol-water mixtures. Glycerin is more effective and cheaper than commonly used entrainers such as ionic liquids or ethylene glycol, which is also toxic and harmful [1,9]. Extractive distillation is the most widely used method for the production of anhydrous ethanol [10] and glycerin is able to increase the purity of the produced ethanol [9].…”

Glycerol waste to value added products and its potential applications

“…It is the prominent alcohol formed in the fermentation process. It is used as a solvent, aerosols, paints, detergents, and thermometers [ 88 ].…”