In this paper

a two-stage dilution sampling method was applied to collect PM2.5 in flue gas before and after the WFGDs in a utility pulverized coal boiler

a utility CFB boiler and an industrial grate-fired boiler

respectively. PSDs (particle size distributions) of PM2.5 number and mass concentrations were analyzed by ELPI (electrical low pressure impactor)

microstructures of PM2.5 were analyzed by SEM (scanning electron microscopy)

and the contents of minor and tract elements and water-soluble ions in PM2.5 were analyzed by XRF (X-ray fluorescence)

ICP-OES (inductively coupled plasma optical emission spectroscopy) and IC (ion chromatography)

respectively. The results showed that the mass concentrations of PM2.5 generated from the pulverized coal boiler and the CFB boiler after desulfurization were higher than those before desulfurization

but the mass concentrations of PM2.5 generated from the pulverized coal boiler and the CFB boiler after desulfurization were lower than those before desulfurization. There existed blocky

layered and finely columnar microstructures on the surfaces of PM2.5 after the WFGDs

and several particles belonging to PM2.5 were the agglomerates consisting of fine spherical particles. The attachment of the slurry composition and the desulfurization product will cause a significant change in the appearance of the PM2.5. After desulfurization

the contents of Ca

S and Ca2+ and SO42- in PM2.5 were significantly increased due to the participation of desulfurization slurry

while the contents of Si and Al decreased. The As

Se and Hg in the flue gas will also undergo different chemical changes to enter PM2.5. During the wet desulfurization process the slurry can trap particles in the flue gas

but the desulfurization slurry composition and desulfurization products will be dried to form particles or be collocated with the original particles to form new ones.