ASPEN Plus Simulation of Combined Biomass Gasification and Fisher-Tropsch Synthesis of Liquid Fuels

APSEN Plus Simulation of Combined Biomass Gasification and Fisher-Tropsch synthesis of liquid fuels

Mohammad Rafati, Lijun Wang, Abolghasem Shahbazi

Abstract

Combined biomass gasification and subsequent Fischer-Tropsch (FT) synthesis is a promising pathway to replace the fossil-based fuels. In a FT process, a mixture of H₂ and CO (syngas) is converted to dominantly olefins and paraffins with various carbon chain-length in the presence of typically a Fe- or Co-based catalyst. CO₂ is a major constituent of syngas derived from biomass gasification which it typically removed from syngas with expensive and energy intensive separation unit operations prior sending the syngas to the FT reactor. CO₂ could be reactive in presence of Fe-based catalysts as Fe exhibits water-gas shift activity, in contrast to Co-based catalysts.  We have developed and examined several process flow diagrams of combined gasification and FT synthesis for the production of liquid fuels from biomass using the ASPEN PLUS process modeling package. Intrinsic kinetic rate equations and detailed product distribution models of Fe- and Co-based catalysts are implemented into a FT reactor block using FORTRAN subroutines to accurately compare the effect of FT catalysts on process product distribution. The effects of various process parameters including catalyst type and recycling ratio on carbon conversion efficiency, energy conversion efficiency, and CO₂ emissions are examined.