Analysis of syngas methanation for bio-SNG production from wastes: kinetic model development and pilot scale validation

Bio-substitute natural gas (or bio-SNG) produced from gasification of waste fuels and subsequent methanation of the product gas could play a crucial role in the decarbonisation of heating and transportation, and could be a vital part of the energy mix in the coming decades. Although the methanation of trace quantities of carbon oxides has been practiced commercially for many years, methanation from syngas poses a more severe problem due to the high and unstable concentrations of reactants in the produced gas. In this work, a low-Ni methanation catalyst was tested in a differential reactor to derive a kinetic model that could determine a practical operating scheme for the first methanation step of a typical bio-SNG process. The model, comprising water gas shift and methanation reactions, along with their reverse reactions, was used for realistic modelling of the methanation process using high quality syngas, obtained from steam-oxygen gasification of wastes and gas plasma conversion, and to better determine the operation conditions in the first reactor of a bio-SNG pilot plant in Swindon (UK). The tests undertaken show that the catalyst was performing as expected using the waste-derived syngas at industrially relevant conditions, when compared to predictions of models derived from works using bottled gases. This gives confidence that the same approach can be used for the detailed design and operation of once through methanation reactor elements and process system configuration for bio-SNG production at larger scale.