Particulate matter(PM)samplings were performed on a 660 MW coal-fired unit

at the inlet and outlet of electrostatic precipitator(ESP)

and the outlet of limestone-gypsum wet flue gas desulfurization(WFGD)tower

to study the formation characteristics of PM_(2.5) when firing different types of coal.The influences of the ESP and WFGD on emission characteristics of PM_(2.5) were investigated.A low pressure impactor(LPI)was applied to collect the PMs with different sizes

and the particle size distribution(PSD)and concentration of PMs were obtained via calculation.The results show that

the PMs produced from the combustion of the two tested coals are of bimodal size distribution.However

the PM yield differs from each other due to the different ash contents in coal.The ESP has a removal efficiency of 99.812%

99.711% and 99.402% for PM_(10)

PM_(2.5)and PM_(1.0)

respectively

with the lowest removal efficiency for PMs in the size range from 0.1μm to 1μm.When the flue gas passes through the WFGD tower and gasgas heater(GGH)

the concentration of PMs with size below 1.0μm increases by about 35%

but the concentration of PMs with size larger than 1.0μm reduces by 40%.Captured by the sprayed desulfurizationslurry helps the concentration of PMs with size larger than 1.0μm be reduced

while the coagulation of ultrafine PMs and the gypsum slurry entrainment will cause an increase in concentration of the PMs with size less than 1.0μm.