Exergetic optimisation of a production process of Fischer-Tropsch fuels from biomass

An exergy analysis of Biomass Integrated Gasification-Fischer–Tropsch process is presented. The process combines an air-blown, atmospheric gasifier, using sawdust as feedstock, with a Fischer–Tropsch reactor and a steam-Rankine cycle for electricity generation from the Fischer–Tropsch tail gas. Results show that the rational (exergetic) efficiency is 36.4%, consisting of 34.5% efficiency to Fischer–Tropsch diesel and wax, and 1.9% efficiency to electricity. The largest exergy losses take place in biomass gasification and in generation of electricity from the Fischer–Tropsch tail gas. Recommendations are given for process improvements, which increase the rational efficiency to 46.2%.