Since the introduction of ultra-low emissions, the characteristics of particulate matter (PM) emissions from coal-fired power plants have changed. We quantitatively evaluate the emission characteristics of each component in PM and the impact of purification equipment by analyzing three ultra-low emission units of coal-fired power plants (FP1, FP2, and FP3). A DGI was used to sample particles from the wet flue gas desulfurization (WFGD) unit and wet electrostatic precipitator (WESP) inlet and outlet, which were then analyzed by various methods. The results showed that the mass concentrations of PM1, PM2.5, and PM10 discharged from the outlets of the three units were 0.25-0.38, 0.31-0.42, and 0.42-0.57 mg·m-3, respectively, and that the mass concentration of PM10 discharged under the two kinds of units was equivalent. However, there were differences in the particle size distribution and composition of the particles. In comparison to the FP1 and FP2 units, the PM2.5/PM10 ratio of the FP3 unit was the highest. A possible reason for this is that the unit was equipped with a WESP, which can better remove particle sizes of 2.5 μm or more. The total concentrations of water-soluble ions in PM2.5 discharged from the FP2 and FP3 units were 0.20 and 0.06 mg·m-3, respectively. The water-soluble ions emitted from the FP2 unit were mainly Ca2+ and SO42-, whereas those mainly emitted from the FP3 unit were NH4+ and SO42-. Analysis of the PM from the WFGD import and export of the FP2 unit showed that the WFGD process increased the water-soluble ion discharge by entraining the desulfurization slurry containing limestone and gypsum. Addition of a WESP after WFGD can effectively remove PM2.5 and PM10 particles and reduce the influence of water-soluble ions on the atmospheric environment.
Keywords: coal-fired power plant; fine particulate matter; micromorphology analysis; ultra-low emissions; water-soluble ions; wet electrostatic precipitators.