Effect of wet flue gas desulfurization (WFGD) on fine particle (PM_2.5) emission from coal-fired boilers

In this study, the characteristics of fine particles before and after wet flue gas desulfurization (WFGD) in three coal-fired heating boilers in northern China were investigated by using a dilution-based emission sampling experimental system. The influences of the WFGD process on the mass and number concentrations as well as the chemical composition of fine particles were analyzed. The removal efficiency of desulfurization processes on particulate matter mass was 30.06%-56.25% for the three study units. The WFGD had a great influence on the size distributions of particle mass concentration and number concentration. A significant increase in the number and mass concentration of particles in the size range of 0.094-0.946 μm was observed. The water-soluble ion content accounted for a very large proportion of PM_2.5 mass, and its proportion in PM_2.5 increased from 28.39%-41.08% to 48.96%-61.21% after the WFGD process for the three units. The desulfurizing process also drastically increased the proportion of cation component (Ca²⁺ for unit A, Mg²⁺ for unit B, and Na⁺ for unit C) and the proportion of SO₄^2- in PM_2.5, and it increased the CE/AE values of PM_2.5 from 0.82-0.98 to 0.93-1.27 for the three study units.