Abstract: Considering the reaction of SO2 and surface CuO，a mathematical model based on the grain model was developed to simulate the SO2 removal process over a NH3-regenerated CuO/Al2O3 pellet. SO2 removal from flue gas over CuO/Al2O3 pallets of various sizes was carried out in a thermogravimetric analyzer to study the effects of reaction temperature, particle diameter and porosity, and to validate the single particle model developed. The reaction of CuO with SO2 and O2 yields CuSO4 that is larger in molecular size than CuO and results in a decrease in particle porosity and gas diffusivity. The effective SO2 diffusivity can be correlated with CuO conversion by De=α(1-x)b, which allows the model to fit the experimental data better. Mathematical analysis using this particle model indicates that the pore diffusion is important for the SO2 removal over CuO/Al2O3 pallets and the activation energy of pore diffusivity increases with the reaction going on.