Field measurements on the generation and emission characteristics of PM2.5 generated by utility pulverized coal boiler

Abstract

In this work, the concentrations, size distributions, the morphology characteristics, and the elemental composition of PM2.5 from eighteen utility pulverized coal boilers are determined experimentally before and after the dust collectors, and after the wet flue gas desulfurizations (WFGDs). In situ monitoring and sampling concentrations and particle size distributions of PM2.5 were carried out with an electrical low pressure impactor. The morphological characteristics and elemental composition were analyzed by scanning electron microscope and X-Ray Fluorescence, respectively. The results indicate that before and after the dust collectors, the number concentration distributions of PM2.5 display obvious bimodal distributions, with the peaks near 0.12 μm and 0.76 μm, respectively. In addition, the peaks value of fine mode particles tend to be an order of magnitude higher than those of the central mode particles. The mass concentration distributions of PM2.5 at boilers outlet appear a peak value at near 0.2 μm. The number concentration of PM2.5 is dominated by the PM0.38, which are mainly formed by gasification-condensation; the mass concentration of PM2.5 is dominated by the PM0.38–2.5, which are formed by the char fragmentation and coalescence of ash particles on the char surface. For total number and mass removal efficiency of PM2.5, the hybrid electrostatic filter precipitators (EFPs) are superior to the fabric filters (FFs), the FFs are superior to the electrostatic precipitators (ESPs). The WFGDs can capture PM0.38–2.5 effectively, but the WFGDs have relatively weak faculty to capture PM0.38 and even tend to increase the number of PM0.38. The PM2.5 generated by pulverized coal boiler are mainly rough-surfaced spherical. The mass percentages of Si and Al in PM2.5 decrease after the dust collectors and the WFGDs, but S increase; the mass percentages of Na, K, Fe in PM2.5 before and after the dust collectors and the WFGDs are nearly the same; the mass percentages of Ca are nearly the same before and after the dust collectors, but decrease after the WFGDs.