Electrifying with High-Temperature Water Electrolysis to Produce Syngas from Wood via Oxy-Gasification, Leading to Superior Carbon Conversion Yield for Methanol Synthesis

Due to concerns regarding fossil greenhouse gas emissions, biogenic material such as forest residues is viewed nowadays as a valuable source of carbon atoms to produce syngas that can be used to synthesise biofuels such as methanol. A great challenge in using gasified biomass for methanol production is the large excess of carbon in the syngas, as compared to the H-2 content. The water-gas shift (WGS) reaction is often used to add H-2 and balance the syngas. CO2 is also produced by this reaction. Some of the CO2 has to be removed from the gaseous mixture, thus decreasing the process carbon yield and maintaining CO2 emissions. The WGS reaction also decreases the overall process heat output. This paper demonstrates the usefulness of using an extra source of renewable H-2 from steam electrolysis instead of relying on the WGS reaction, for a much higher performance of syngas production from gasification of wood in a simple system with a fixed-bed gasifier. A commercial process simulation software is employed to predict that this approach will be more efficient (overall energy efficiency of about 67%) and productive (carbon conversion yield of about 75%) than relying on the WGS reaction. The outlook for this process that includes the use of the solid oxide electrolyser technology appears to be very promising because the electrolyser has the dual function of providing all of the supplemental H-2 required for syngas balancing and all the O-2 required for the production of a suitable hot raw syngas. This process is conducive to biomethanol production in dispersed, small plants using local biomass for end-users from the same geographical area, thus contributing to regional sustainability.

Automated summary

This paper discusses the feasibility of using steam electrolysis as an additional source of renewable H-2 to increase the production efficiency of gasified wood syngas. Compared to relying on the water-gas shift reaction, this method is more efficient and promising in increasing carbon conversion yield in biomethanol production.