Performance study of a methanation process for a syngas obtained from a sorption enhanced gasification process

Abstract

Synthetic Natural Gas (SNG) produced from renewable sources constitutes a solution for the transition to net-zero emissions for natural gas relying sectors. From the different biomass-to-SNG routes, the gasification of biomass to produce a syngas that is further converted into SNG has a large potential in a near future. In this work, the methanation process under quasi commercial conditions was demonstrated for a syngas generated from biomass gasification. The influence of process variables like pressure, steam/CO ratio and syngas composition (i.e. content of CO2, CH4 and light hydrocarbons) were analyzed to evaluate the maximum CH4 purity achieved in a commonly used two-step methanation process. Moreover, the need of adding green H2 produced from renewable sources was studied to adjust the H2/CO/CO2 ratio for methanation. A product gas with 78 %vol. CH4 was produced using a commercial Ni-based catalyst, being the conversion of CO2 the limiting factor towards the fulfilment of a higher CH4 content (only 37 % of CO2 conversion was reached in the second methanation reactor at 270 °C, 4 bar and 2140 h−1 of gas space velocity). Alternative operating conditions and/or intensified process schemes stand as the most promising alternatives for the conversion of syngas into high purity SNG.