Numerical study on a single char particle gasification considering Stefan flow effects in a hot CO2/O2/H2O atmosphere

•A particle-scale numerical model for char gasification in CO2/O2/H2O was developed.•The reaction properties of the different positions of the particle were discussed.•Stefan flow has a significant effect on the gas components around the particle.•The particle surface temperature increases when particle diameter decreases.•The effects of the ash layer is mainly reflected in the convective heat transfer.