Wet Flue Gas Desulfurization (WFGD) unit based upon spray scrubber has been widely employed to control SO2 emissions from flue gas in coal-fired power plant.To clarify the dependence of desulfurization performance on inter-phase transfer behaviors with non-ideal contacting patterns of flue gas and slurry droplets,three regions in spray scrubber are distinguished in terms of gas-slurry flow structures using CFD method in the Eulerian-Lagrangian framework.A comprehensive model is established by involving the transfer process between two phases and chemical reactions in aqueous phase,which is validated with the measured data from a WFGD scrubber of 330 MW coal-fired power unit.Numerical results show that the overall uniformity degree of flue gas in whole scrubber is largely determined by the force-balanced droplets in the middle part of scrubber,which is dominated by counter-current mode.Both momentum transfer behavior and SO2 chemical absorption process present the synchronicity with the evolution of gas-slurry flow pattern,whilst the heat transfer together with H2O evaporation has little effect on overall absorption process.Three regions are firstly defined as Gas Inlet Region (GIR),Dominant Absorption Region (DAR) and Slurry Dispersed Region (SDR) from the bottom to top of scrubber.SO2 is mainly scrubbed in DAR,which provides much more intensive interaction between two phases compared to GIR or SDR.A better understanding of the desulfurization process is obtained from the fundamental relationship between transport phenomena and chemical reactions based upon the complicated hydrodynamics of gas-slurry two-phase flow,which should be useful for designing and optimizing the scrubber in coal-fired power unit.