Energy performance of Power-to-Liquid applications integrating biogas upgrading, reverse water gas shift, solid oxide electrolysis and Fischer-Tropsch technologies

Power-to-liquid (P2L) pathways represent a possible solution for the conversion of carbon dioxide into synthetic value-added products. The present work analyses different power-to-liquid options for the synthesis of Fischer-Tropsch (FT) fuels and chemicals. The FT section is integrated into a complete carbon capture and utilization route. The involved processes are a biogas upgrading unit for CO2 recovery, a reverse water gas shift, a solid oxide electrolyser and a Fischer-Tropsch reactor. The upgrading plant produces about 1 ton/h of carbon dioxide. The recovered CO2 is fed to either a reverse water gas shift reactor or a solid oxide electrolysis unit operating in co-electrolysis mode for the generation of syngas. The produced syngas is fed to a Fischer-Tropsch reactor at 501 K and 25 bar for the synthesis of the Fischer-Tropsch products, which are further separated into different classes based on their boiling point to yield light gas, naphtha, middle distillates, light waxes and heavy waxes. The developed process model uses a detailed carbide kinetic model to describe the formation of paraffins and olefins based on real experimental data. The effect of Fischer-Tropsch off-gas recirculation has been studied against a one-through option. Finally, energy integration of each configuration plant is provided. Results from process simulations show that the best model configurations reach a plant efficiency of 81.1% in the case of solid oxide electrolyser as syngas generator, and 71.8% in the case of reverse water gas shift option, with a global carbon reduction potential of 79.4% and 81.7%, respectively.