Process Design and Economic Evaluation of an Ethanol Production Process by Biomass Gasification

Abstract

A large number of studies are being conducted on finding eco-friendly substitutes for petroleum-based fuels. Utilizing biomass as an energy source can significantly reduce dependency on petroleum, and the emission of greenhouse gases. Ethanol can be produced by gasification of biomass and then subsequent fermentation of the syngas. The objective of this research is to develop full scale steady-state process models for ethanol production from syngas using a computer aided simulation (ASPEN(TM) Plus software). Simulation results were compared with experimental data obtained from an earlier research project conducted at Oklahoma State University. Sensitivity analyses were performed on major units in the process model to determine the minimum ethanol production cost. An economic comparison was also carried out on two commonly used chemical separation processes (Azeotropic distillation and molecular sieve). The two processes were successfully modeled. These process models show that 99.5 wt% ethanol can be produced using either azeotropic or molecular sieve separation. The simulation results indicate that there is a potential to increase the experimental H2 and CO2 production in the gasifier and higher experimental conversion to ethanol is possible in the syngas fermentation process. The production of high purity ethanol using molecular sieves requires less energy than the azeotropic separation process. This can reduce the operating cost of the process significantly which results in a lower price of the final ethanol product.