Thermodynamic equilibrium assessment of the methanation of biomass gasification syngas streams – potential with in situ water removal

Methanation of syngas from biomass gasification is a viable route to substitute natural gas (SNG). This study demonstrates that in situ removal of one reaction product (water) can influence reactor performance by shifting the thermodynamic equilibrium for temperatures and pressures between 200 and 450 °C and 1–30 bar, respectively. In conventional reactor configurations, low temperatures and high pressures enhanced, under equilibrium conditions, both CO x conversion and CH 4 yield. Moreover, no coke formation was observed in these conventional devices under the tested conditions. Multifunctional reactors with water removal (sorption-enhanced or membrane reactors) resulted in modest gains, ca. 3%, in methane yield due to the competition between methanation and coke formation. However, when considering a scenario where coke formation is not considered (e.g., employing selective catalysts), methane yields exceeding 96% for complete water removal across all conditions were achieved, representing a minimum methane yield increase of ca. 15% relative to conventional reactor performance at 450 °C and 1 bar. Water removal also significantly improved compliance for grid injection, widening the operating window that meets regulatory standards. With a scenario of impossibility of coke formation, full compliance was achieved over the entire temperature and pressure ranges studied, emphasizing the potential of such hybrid reactors.