| In recent years, Chinese airborne fine particulate matter (PM2.5) pollution is serious,which lead to frequent fog and haze and seriously influence people’s health and urbanatmospheric environment. Coal-fired of thermal power industry is an important sourceof PM2.5in atmospheric. Currently, CFB boiler increase in the proportion of China’selectricity production industry, but study of the characteristics of PM2.5from CFB boileris relatively small, five300MW power plant CFB boiler has been field tested in thisparper, by using ELPI after a two-stage dilution system to on-line measurement eachCFB boilers’ number and mass concentration of PM2.5in fuel gas from upstream anddownstream of dust removal device and desulfurization unit; At the same time, usingPM2.5samplers and different membrane collect PM2.5samples for subsequent laboratoryanalysis of physical and chemical characteristics of CFB boiler’s PM2.5; finally calculatethe emission factor of PM2.5for each boiler, this study is meaningful to understandingCFB boiler PM2.5emissions and improving air pollution caused by PM2.5.The mass concentration distribution of CFB boiler’s PM2.5is in a straight upwardtrend and the number concentration is unimodal distribution, CFB boiler withoutexternal bed’s peak is between0.48~0.76μm, external bed CFB boiler’s peak is at0.12μm. the number and mass concentration of PM2.5produced by CFB boiler isdominated by PM0.38~2.5, which indicat that broken-coalesced is the major generatingmechanism of PM2.5of CFB boiler, but after pollution control equipment, the numberconcentration of PM2.5is gradually dominated by PM0.38. The graded removal efficiencyof Electrostatic precipitators and bag filters are in the presence of a minimum in therange of0.1~1μm, but extreme position is slightly different; Electric bag combined dustremover’s electrical characteristics of PM2.5is similar as bag filter. After the wetdesulfurization unit, the total concentration of PM2.5is smaller but some level of particleconcentration of ultrafine particles was increased.The PM2.5of CFB boiler is mostly irregular particles with larger surface area, andmajority of the particles do not have superfine particles attached to their surface. In thelarge representative element of PM2.5from CFB power plant boiler furnace outlet, thehighest content is insoluble oxides and alkali metal oxide content is the minimum, dueto the furnace desulfurization, S element content equally high. Al, Si percentage will berising after baghouse and lowering after electrostatic precipitator, electrostaticprecipitator’s removing effect of Ca is worse than the baghouse; the content of Ca2+andSO42-is much higher than other ions, and after pollution control equipment the contentof this two ions will be further increased; The risk evaluation model calculated throughtoxic elements content, number and mass concertration of PM2.5discharged by CFBboiler shows that the PM2.5after the baghouse have the the lowest risk evaluation, wet desulfurization unit also helps to reduce particle’s risk evaluation; The OC and ECcontent of PM2.5from CFB boiler will increase after dust removing device anddesulfurization.The calculation results of four emission factors including EC, EFWB, EFLB, EFABfor five power plant’s CFB boiler display that the four emission factors show positivecorrelation; external bed CFB boiler’s number emission factor is larger than normalCFB boilers; coal ash content has a great influence on initial emission factors and dustremoval equipment is a key factor for final emission factors. |
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