Purification of Bioethanol from a Fermentation Process: Alternatives for Dehydration

In this work, a process for the production of bioethanol from lignocellulosic materials is proposed and analyzed using the process simulator Aspen Plus. The stream leaving the reactive section, which has a bioethanol composition of around 5.7 wt%, enters to a stripping column where water and by-products are separated from ethanol. From that column, a side stream is withdrawn, containing mainly ethanol and water in an approximately equimolar mixture, with traces of by-products. For that stream, three alternatives of separation trains are studied, aiming to obtain anhydrous bioethanol: a distillation column to reach the azeotropic composition, followed by vapour permeation membranes; a distillation column followed by an extractive distillation column; and a liquid-liquid extraction column followed by an extractive distillation columns. All the alternatives are compared in terms of energy consumption and total annual cost.