Low carbon liquid fuels are needed for maritime shipping and long-haul trucking which are difficult to decarbonize by use of battery energy storage or hydrogen. Thermochemical conversion of biomass to liquid fuel (BTL) is a promising option to produce carbon-neutral liquid fuel. However, no commercial BTL plants are yet operating and one of the main reasons is the cost of produced fuel. Here we propose two processes in order to improve the economic appeal of BTL process for producing methanol. These processes employ natural gas as a swing fuel and utilize the synergy between natural gas reforming and biomass gasification. Through this integration, we can use the synergistic effects of adding H2-rich syngas (H2/CO mixture) from natural gas to carbon-rich syngas from biomass to produce the right H2/CO ratio for methanol synthesis while maintaining a high carbon utilization. The biomass syngas generation step in both designs is the same and utilize the illustrative example of an entrained flow gasifier (EFG) with subsequent cleaning of the generated syngas to remove H2S, dust, soot, etc. The differentiating feature of these processes is the syngas generation step from natural gas. In the first design, an autothermal reformer (ATR) is used to generate syngas, while the O2 required for both biomass gasification and natural gas reforming is provided by a solid oxide electrolysis cell (SOEC). The H2 stream from the SOEC is used to adjust the stoichiometry of the methanol synthesis reactor. In the second design, natural gas is sent to a gas-heated-reformer (GHR) followed by an ATR. The heat required in the GHR is provided by the exhaust stream from the ATR, which is the best method to utilize the high temperature exergy of the exhaust stream. The reformed gas has high hydrogen content, but not enough to have the correct stoichiometric number prior to the methanol synthesis. Therefore, a fraction of the reformed gas is sent to a water gas shift (WGS) reactor followed by a CO2 capture unit. The produced stream is used to adjust the stoichiometric number prior to the methanol synthesis reactor. The flexibility and economics of the two processes are compared to a stand-alone BTL process. While the produced methanol includes some fossil carbon, the synergy of this integration and added flexibility would increase the economic viability of deployment of biomass-based fuel production.
Keywords renewable fuel, methanol, biomass gasification, natural gas reforming