Study On The Emission Characteristics Of Fine Particles In Coal-fired Power Plants

Coal-fired power plants are an important contributor to PM_2.5 emissions,especially due to the popularization of ultra-low emissions in recent years.The emission conditions of the flue gas have undergone profound changes so that it is very important to study the characteristics of flue gas emission in coal-fired power plants and take practical control measures for the comprehensive treatment of air pollution.This subject has studied the system error of particulate matter sampling at high humidity and low temperature.The system error is mainly derived from the effect of pipe adhesion,weighing error and filter membrane filtration efficiency.There are three conditions to influence the adhesion of the pipe,which are the humidity(X_SW),the temperature of the smoke（T_S）and the flow rate of smoke（V_S）.The differential operation of X_SW,T_S and V_S is carried out,and the contribution value of each factor to the adhesion error is calculated,and the adhesion error is obtained.Finally,the calculation model of the sampling system error is obtained by combining the system error,the weighing error and filter membrane filtration efficiency.The emission concentration,particle size distribution and physicochemical characteristics of PM_2.5 before and after desulfurization of 3 coal-fired units were tested and analyzed.The emission concentration of PM_2.5 at the desulfurization outlet is 1.87².99 mg/Nm³,and that of TSP was 9.11¹7.84 mg/Nm³.Before desulfurization,the proportion of PM_2.5 is between 7.33%and 11.79%,and the proportion of desulphurization is between 21.50%and 18.33%.The minor elements of PM_2.5 are mainly Si and Al before and after desulphurization and they accounted for 66.46%and 50.84%.As for trace elements,the contents of Cr,Zn and As in PM_2.5were relatively high before and after desulphurization.As for the establishment of an estimation model for particulate matter emission,firstly,the empirical method or element method is used to calculate the amount of flue gas in a coal-fired power plant,and then the pollution factor and the emission factor of the particles are estimated.The relative deviations of TSP,PM10 and PM_2.5 from the estimated to the tested were 46.93%,47.84%and 50.07%respectively.