[Conversion Characterizations of Sulfate Ion and Nitrate Ion in Particulate Matter from Coal-fired Power Plants]

The particulate matter emitted from coal-fired power plants includes condensable particulate matter(CPM) and filterable particulate matter(FPM). By analyzing the concentration of SO₄^2-and NO₃^- components of CPM and FPM in the inlet/outlet of wet flue gas desulfurization(WFGD) and the outlet of wet electrostatic precipitator(WESP) from 7 ultra-low emission coal-fired power plants, the variation laws and transformation characteristics were investigated. The results showed that the concentration of SO₄^2- and NO₃^- of CPM decreased after WFGD, with reduction rates of 43.12%-86.84% and 17.99%-91.58%, respectively, which were different from the conversion trend of FPM. The concentrations of SO₄^2- and NO₃^- of CPM increased after WESP, with reduction rates of 21.05%-424.65% and 13.51%-298.37%, respectively, which were also different from that of FPM. In the WFGD system, CPM could be transformed into FPM due via condensation and aggregation under the decreasing temperature and increasing of humidity of the flue gas. In the WESP system, SO₂ and NO₂ in the flue gas combine with water vapor in a redox reaction, which promotes the generation of SO₄^2- and NO₃^- in CPM through synergistic action.