(81a) Simulation and Optimization of Tubular Fixed-Bed Fischer-Tropsch Synthesis Reactor with Recycle

The increasing demand of world’s energy and the fast depletion of liquid fossil fuel reserves have made natural gas, coal and biomass increasingly attractive as feedstocks for synthetic liquid fuels. For the last two decades, Fischer–Tropsch synthesis (FTS) has gained renewed interest for the conversion of syngas to liquid hydrocarbons.

In industrial FT reactors, tubular fixed-bed reactor with recycle is widely used. Although many fixed-bed models for FT process have been reported in literature, research on concentration/temperature distributions in fixed-bed reactor with recycle is very limited. In this work, a 2D heterogeneous fixed-bed reactor model with recycle is developed and the simulation results are validated by using the industrial data. The effects of operating conditions on concentration/temperature distributions in FT reactor, such as inlet temperature, pressure, recycle ratio and feed syngas composition, are investigated. The results show that inert content in feed syngas and recycle gas, such as CH₄, N₂, etc., have significant effect on the conversion of CO and temperature distributions in fixed-bed FT reactor. The increase in recycle ratio results in the decrease in the CO conversion for inert gas rich syngas, and the inert gas content in syngas plays an important role to determine the hotspot location and temperature, which can be easily applied to biomass conversion process. Finally, the model is used for multiobjective optimization to maximize CO conversion and minimize the operation cost for fixed-bed FT process with recycle.