Dehydration of Bioethanol by Hybrid Process Liquid–Liquid Extraction/Extractive Distillation

Abstract

Bioethanol is among the most promising of biofuels because it has an energy content similar to gasoline while generating lower pollutant emissions than gasoline. But, in order to be used as an automotive fuel mixed with gasoline, ethanol must have less than 0.5 wt % of water. To achieve required ethanol purity, in light of the fact that the ethanolÀwater mixture forms an azeotrope, unconventional separation techniques such as extractive distillation or azeotropic distillation are necessary. However, the purification of ethanol using conventional distillation followed by extractive distillation has the disadvantage of high cost of services. Thus, this study proposes alternative hybrid systems using liquidÀliquid extraction and extractive distillation. The use of n-dodecane as entrainer for liquidÀliquid extraction and glycerol as entrainer for extractive distillation has been considered. The proposed systems are analyzed and a comparison is done on their performance in terms of energy and total annual cost. It has been found that the hybrid scheme presents both lower total energy consumption and lower total annual cost as compared to the traditional purification scheme with conventional distillation and extractive distillation.

Purification of 2,3-butanediol from fermentation broth: process development and techno-economic analysis

“…The organic phase is then inserted into a distillation column where the solvent is recycled back to the extractor and 2,3-BDO is recovered from the top. HED has been effectively proven and widely used for the separation of liquid mixtures [ 38 ], particularly for the recovery of products such as butanol [ 39 ], bioethanol [ 40 ], furfural [ 41 ], pyridine [ 42 ], acetic acid [ 43 , 44 ], n -propanol [ 45 ], and ester [ 43 ].…”

Design of non-equilibrium stage separation systems by a stochastic optimization approach for a class of mixtures

“…2a and b, respectively) using water as solvent to obtain purities higher than the azeotropic ones. The second azeotropic mixture consists on ethanol (ETOH) and water (H 2 O), where a maximum boiling azeotrope exists between ethanol and water for purities higher than 90 mol% of ethanol (about 96 wt%) [23,24]. This mixture is also purified in an extractive direct sequence, using ethylene glycol as solvent.…”

“…The presence of an azeotropic point can be observed for the binary system acetone/ethanol at a temperature of 328.39 K. For mixture M4F2, a feed molar flow rate of 100 kmol/h has been considered. Thermodynamic model NRTL-RK has been used to analyze this mixture [23,24]. In Fig.…”

Optimal Economic Design of an Extractive Distillation Process for Bioethanol Dehydration

“…The composition of the distillate from the PDC unit is a key optimization variable that has so far been neglected in the optimal design of extractive distillation systems for ethanol dehydration. For example, Ryan and Doherty [6] assumed a composition of 94.9 wt % (88 mol %) ethanol, which is rather close to the azeotropic composition, and other authors [7][8][9][10] selected more practical compositions of approximately 93.5 wt % (85 mol %).…”