Comparative study on the structure characteristics, combustion reactivity, and potential environmental impacts of coal gasification fine slag with different particle size fractions

•The physicochemical properties of CGFS have obvious particle size dependence.•Different model-fitting methods are adopted to confirm the kinetic parameters.•The disparity of combustion reactivity is clarified from carbon and pore structure.•The combustion volatility of heavy metals is related to the residual fraction ratio.•The potential environmental risks of some heavy metals in CGFS should be noticed.