The efficiency of wet flue gas desulfurization (WFGD) used in thermal power plants that burn high-sulfur coal can be improved by adopting dual-loop spray tower (DLST). In this paper, the process of gas-liquid flow, mass transfer and chemical reaction in the DLST were fully investigated through a pilot-scale DLST and the corresponding numerical model. The numerical model was verified based on the experiment and applied to predict a DLST of 200 MW coal-fired unit. Investigation results show that higher the inlet SO2 concentration, more significant advantage on improving the desulfurization efficiency for DLST. The mass transfer resistance of liquid-film is still the main effect of SO2 absorption for the upper and lower loops in DLST. The ratios of the gas-film resistance to liquid-film resistance in the upper and lower loops are 0.65 and 0.35, respectively. The designed size of the bowl separator has a significant effect on the system resistance loss. The minimum ratio between the diameter of the bowl and the diameter of the desulfurization tower to avoid "flooding" phenomenon above the bowl separator is about 0.7. Furtherly, the lowest system operating resistance loss can be obtained when the ratio is about 0.82. The simulation results of the desulfurization efficiency and system resistance loss agree well with the test data. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.