Simulation of the downstream processing in the ethanol production from lignocellulosic biomass with ASPEN Plus® and IPSEpro

Background: One of the most promising alternatives to gasoline as fuel in the transport industry is bioethanol, whether if it is conventional (based on raw materials containing sugar and starch) or produced from lignocellulosic biomass. Unfortunately, the energy intensive downstream process in lignocellulosic bioethanol production still limits the ability to compete with conventional bioethanol or petroleum. A process setup that provides possibilities for heat integration would consequently result in a more efficient overall process and increase its competitiveness. Methods: In this work, two different distillation concepts, with an annual production of 100,000 tons of ethanol from straw, are simulated with the modeling tool ASPEN Plus®. To round out the downstream process, simulations of an evaporation system and an anaerobic digester to produce biogas provide results for these two possibilities of subsequent stillage treatment. Furthermore, the simulations done with IPSEpro provide data for pinch analysis of the overall bioethanol process. By applying pinch analysis, the concepts are compared from an energy point of view, to find the optimal distillation concept in context with the background process for the respective subsequent stillage treatment. Results: The results from pinch analysis show that the three-column distillation setup is in favor for both stillage treatment methods. For the concept including five-stage evaporation, the minimum energy consumption per kilogram of ethanol accounts for 17.2 MJ/kgEtOH. When anaerobic digestion is used to treat the distillation stillage, only 10 MJ/kgEtOH has to be provided. Conclusions: An important criteria to specify a process is the overall process efficiency. The overall process efficiency can be improved by reducing the downstream energy consumption, especially in the distillation section. With the best fitting configuration of distillation and stillage treatment concepts the efficiency is improved and by-products as heat, electricity, and pellets allocated. © 2014, Lassmann et al.; licensee Springer.