Intrapore water–gas shift reaction inhibits coal gasification in supercritical water

Abstract

Water-gas shift reaction (WGSR) is key to the supercritical water gasification (SCWG) of coal in hydrogen production, but it has not been considered in studies inside pores where coal conversion occurs. Here, to investigate the impact of intrapore WGSR on the SCWG of single irregular-shaped coal particle, a three-dimensional multi-species reaction–diffusion model is proposed and validated through experiments. We observe that the intrapore WGSR inhibits the SCWG of coal by slowing down the fluid diffusion and retarding the fixed-carbon steam reforming heterogeneous reaction (FSRR). Increasing gasification temperature enhances the inhibition by WGSR while increasing mole fraction of H2O weakens the inhibition. The area and volume of pores have little effect on the inhibition because increasing area enhances the FSRR but retards the diffusion while increasing volume facilitates the WGSR but promotes the diffusion. An analytical model is thereby proposed to quantify the inhibition, and to characterize the prolonged gasification time.