Quantifying the exergetic performance of bio-fuel production process including fast pyrolysis and bio-oil hydrodeoxygenation

Fast pyrolysis of biomass in a dual fluidized bed and bio-oil hydrodeoxygenation are simulated by Aspen plus. The process includes the following unit operations: drying, pyrolysis, char combustion, bio-oil vapor condensation, mild hydrodeoxygenation, and depth hydrodeoxygenation. Based on the simulative results, exergetic analysis of the whole process is performed to optimize the overall exergetic efficiency. The overall exergetic efficiency of the process is 57%. The exergetic efficiencies of the fast pyrolysis process and the bio-oil hydrodeoxygenation process are 68% and 78%, respectively. The results indicate that the exergetic efficiency is improved slightly with a decrement in the system pressure drop. Moreover, the exergetic efficiency of pyrolysis is improved from 69% to 76% when the percentage of the pyrolysis char combusted is reduced from 100% to 65%. Compared to other conversion technologies, biomass to liquid fuel conversion via fast pyrolysis and subsequent hydrodeoxygenation has higher exergetic efficiency.