Laboratory Study On Optimisation Of Sampling Conditions For Fine Particulate Matter In High Humidity Flue Gas From Coal-fired Power Plants And The Impact On Emission Inventories

With the implementation of the "Ultra-Low Emission Standards" in China,all coal-fired power plants(CFPPs)employed Wet Flue Gas Desulfuration(WFGD)technology to further reduce emissions in order to meet the emission standards.The extensive installation of the WFGD increased the humidity of the flue gas significantly,even achieving nearly 100%relative humidity(saturation state).The filter for PM2.5 collection suffers reliability problems,and even filter damage when the sample humidity is too high.The condensed water on the inside wall of the probe might result in serious particle loss.However,The MEP standard method for particulate matter sampling from stationary sources,GB/T 16157-1996 and HJ 836-2017 cannot avoid the impact of the high humidity of the flue gas on the determination of the low-concentration particulate matter.Therefore,it is necessary to establish a particulate matter sampling method for high-humidity flue gas from CFPPs to eliminate the measurement bias of the fine particles in high-humidity flue gas,and further improve the accuracy of the PM2.5 emission inventories for CFPPs.In this study,a wet desulfurization high-humidity flue gas generator was used.The diffusion dryers were used to control the flue gas humidity,and the particle size distribution,transmission loss,and PM2.5 mass concentration were measured under different relative humidity conditions to understand the influence of relative humidity on the sampling accuracy of particulate matter.Based on the experimental data,the PM2.5 emission inventory of CFPPs was established.The results showed that:(1)With increasing flue gas humidity,the concentration of particulate matter increases for all size ranges.At 40%relative humidity,the mass concentration of PM2.5 in the flue gas is 22.77 mg/m3,and the total particle concentration is 1.16×106 particles/cm3.As the flue gas humidity increases to 50%,60%,and 80%,the mass concentration of PM2.5 increased by 1.06,4.35,and 4.69 times,respectively,and the particle number concentration increased by 1.31,1.70,and 1.76 times,respectively.(2)After the dehumidification of the flue gas with diffusion dryers,the particulate matter penetration rate increased significantly compared to that without humidity control.The peak concentrations of particulate matter mass distribution were 2.08,2.50,and 2.14 times that of the control group,respectively;with the increase in dehumidification rate,the decrease in the moisture content of particulate matter leads to a decrease in the mass concentration of particulate matter.The maximum mass concentration of PM2.5 is 27.17 mg/Nm3 at the highest RH of 94.9%,as the RH decreased to 81.4%,68.5%,48.7%and 30.4%,the mass concentration decreased by 14.5%,28.8%,43.0%and 45.7%,respectively.(3)The flue gas humidity control by Using a diffusion dryer could reduce the particle loss in the sampling tube and the PM2.5 cyclone.The mass concentrations of PM2.5 were collected at 94.9%,81.4%,and 68.5%relative humidity,and were 3.02,2.73,and 2.57 times higher than that in the control group.(4)After the correction of the amounts of PM2.5 emissions from CFPPs with the WFGD,the improvement in the amounts of PM2.5 emissions differed from regions in China.Higher amounts of CFPPs equipped with WFGD were found in Hebei and Henan provinces,and the total amount of PM2.5 emission increased by 2.60 and 2.66 times,respectively.