Moreover, it can be seen from the Figs. 5a and 6 that the particle number concentration decreases with increasing the temperature of inlet flue gas (TG). There are simultaneous heat and mass transfer between the hot gas and cold desulfurization liquid in the WFGD system. The desulfurization liquid evaporates into the gas stream, thus causing the gas moisture content to increase and the gas temperature to decrease, which depends significantly on the temperature difference between the hot gas and cold desulfurization liquid. Hence, the effect of heat and mass transfer improves with the temperature difference, namely the temperature of hot flue gas at the inlet of spray scrubber while the temperature of desulfurization liquid keeping constantly in this experiment. Then the removal of particles due to thermophoresis and diffusiophoresis enhances with the improvement of heat and mass transfer.