High concentrations of CO and CO₂ inhibit lignite gasification in supercritical water

Supercritical water gasification (SCWG) technology enables the efficient utilisation of lignite to produce H₂, CO, and CO₂. Coal gasification differs under different atmospheres and H₂ promotes the pyrolysis of carbon structures. While simultaneous increases in H₂, CO, and CO₂ are observed, their combined effect on the SCWG of coal remains unknown. Formic acid (FA) was used to produce H₂, CO, and CO₂ in the supercritical water, and the impact of the gaseous product generated from high-concentration (>30 wt%) FA decomposition on the SCWG of lignite was experimentally investigated. In comparison to lignite gasification in pure supercritical water, the carbon efficiency of lignite gasification in 30 wt% FA solution decreased by 7.66 %, and the mass conversion of lignite decreased by 4.0 %. Higher concentrations of CO and CO₂ yielded stronger inhibition of lignite SCWG.