Numerical simulation on high-temperature supercritical CO2/gaseous H2O mixture flowing over a single reactive spherical char particle

•Non-uniform distributed Stefan flow leads obvious variations on Cdp and Cp under different reaction temperatures.•Strong endothermic effect of heterogeneous reactions enhances the heat transfer of the sphere surface.•Increasing the relative content of gaseous H2O leads the higher heterogeneous reaction rate.•Ash layer leads larger drag, while inhibits the heat transfer and heterogeneous reaction rate.