(763a) Reducing Costs In Bioethanol Purification Using a Hybrid Process Liquid-Liquid Extraction - Extractive Distillation

Nowadays, an important concern for human kind is to ensure the supply of energy for incoming years. Such energy is used in transportation, industrial processes, heating devices and other tasks. Traditionally, the energy requirements have been satisfied using fossil fuels such as petroleum derivates. Nevertheless, on the last years a reduction on the petroleum production has been observed, and it has been predicted that this tendency will continue on the next decades. By the other hand, fossil fuels are responsible for the increase on the concentration of greenhouse gases on the atmosphere, leading to a constant increase on the temperature of the planet. Considering this perspective, different efforts have been made to found alternative sources of energy, which must be renewable, clean and cheap. Among those fuels, bioethanol is considered as a promissory biofuel, since it possesses energy contents similar to those of the gasoline and lower pollutant emissions. On the last years, research has been developed to find appropriate, non-edible biomass sources to produce bioethanol. Such biomass sources usually contain lignocelluloses. Examples of non-edible raw materials considered to produce bioethanol are crop residues, sawdust, sludges and livestock manures. Purification of ethanol represents one of the most challenging stages when producing bioethanol, because of the azeotrope existent between ethanol and water. In order to be used as an automotive fuel, ethanol must have less than 0.5wt% of water. Considering this constraint, unconventional separation techniques, such as extractive distillation or azeotropic distillation, are necessary to avoid the azeotrope and achieve the required purity for ethanol. The traditional method to purify ethanol consists on using conventional distillation followed by extractive distillation. Nevertheless, such method has the disadvantage of high energy requirements at the conventional distillation column. Thus, in this work alternative hybrid systems using liquid-liquid extraction and extractive distillation are proposed. To pre-concentrate the ethanol, n-dodecane is considered to be used as entrainer for a liquid-liquid extraction system and, to achieve the desired purity for ethanol, glycerol is considered as entrainer for extractive distillation. An analysis is performed for the proposed systems in terms of energy and total annual cost. It has been found that the hybrid scheme presents savings of around 30% in total energy consumption and of around 47% in total annual costs in comparison with the traditional purification scheme.