Techno-economic analysis of the biomass gasification and Fischer–Tropsch integrated process with off-gas recirculation

• The techno-economic analysis of BG-FT process of rice straw feedstock is performed.
• Two configurations, once-through and with recirculation concepts, is compared.
• Suitable adjustment of FT off-gas recycle fraction can maximize diesel yield.
• Suitable selection of FT reactor volume offers the high diesel yield.
• Maximizing diesel is not the best choice in economic point of view.

The techno-economic analysis of a BG-FT (biomass gasification and Fischer–Tropsch) integrated process with different configurations, once-through and with recirculation concepts, for green fuel production is presented. Rice straw is considered a feedstock for the gasification process operated under the thermal self-sufficiency condition. Modeling of such an integrated process is performed by using Aspen Custom Modeler program. Regarding one technical aspect, the influence of changing an off-gas recycle fraction at different values of the FT reactor volume on the performance of the syngas processor, the FT synthesis and the energy efficiency is discussed. The production rate of syngas, diesel product and FT off-gas, as well as electricity from the BG-FT process, can be maximized via suitable adjustment of the recycle fraction and selection of the FT reactor volume. The economic analysis using an incremental NPV (net present value) as an economic indicator implies that the use of the recycle concept in the BG-FT process without the installation of any secondary equipment is less feasible than the once-through. Although the maximum diesel production rate is found when the FT reactor volume of 190 m3 and the FT off-gas recycle fraction of 0.4 are chosen, the incremental NPV shows a negative value.