Intensified Separation Processes for the Recovery and Dehydration of Bioethanol from an Actual Lignocellulosic Fermentation Broth

摘要

Bioethanol from fermentation of lignocellulosic feedstock is a potential gasoline-substitute or partial substitute due to its fuel similarities. Regarding the whole bioethanol production process, separation and purification represent a technical challenge because of the dilute stream obtained, besides the presence of an ethanol-water azeotrope. In the real production situation, the actual lignocellulosic fermentation broth consisted of a set of representative components involved in every production step. Thus, the mixture consisted of gas, liquid, and both soluble and insoluble solids. This was separated in four sub-streams of interest destination: CO2 for algae growing, bioethanol as transportation biofuel, stillage for water recovery, and insoluble solids for energy recovery. The process simulator Aspen Plus V8.0 was used to simulate two starting configurations consisting of one single bioethanol recovery and two types of dehydration sections. Due to the nature of the mixture, the separation train consisted of different types of units, making the intensification a non-trivial task. Therefore, alternatives were proposed consisting of intermediate condensers, thermal couplings, side-column sections and divided wall column (DWC) to reduce the number of equipment and evaluate their total annual cost (TAC). It was found that some alternatives achieved moderate TAC savings (～20 %) with respect to the starting cases besides reducing the number of equipment. The novelty of this work was the synthesis and design of intensified alternatives for the separation process of an actual lignocellulosic fermentation broth.