300 MW CFB锅炉配套半干法烟气脱硫的汞排放试验研究

Experimental Research on Mercury Emission Characteristics of a 300 MW CFB Boiler Equipped with Semi-Dry Flue Gas Desulfurization

某300 MW循环流化床(CFB)锅炉采用炉内脱硫、SNCR、预电除尘器和烟气循环流化床半干法脱硫装置实现了超低排放。对不同工况下不同位置的烟气汞浓度和灰渣等固体副产物中的汞含量进行测试分析,研究结果表明:燃煤在循环流化床锅炉燃烧产生的汞主要以气态汞和颗粒汞形式存在;锅炉负荷提高,烟气中气态汞和颗粒汞浓度均有所提高,炉内脱硫对原始汞排放特性几乎没有影响;烟气循环流化床半干法脱硫装置可脱除71%~77%的气态汞和86%~88%的颗粒汞;采用预电除尘器与烟气循环流化床半干法脱硫结合的超低排放路线,总汞脱除率可达到82%~87%,使烟囱排放的汞浓度不高于1.5μg/m^3。副产物分析结果表明,烟气中脱除的汞主要富集于粉煤灰和半干法脱硫灰中。

Study was conducted on a 300 MW CFB boiler,which was equipped with in-furnace desulfurization,SNCR,pre-ESP,and circulating fluidized bed flue gas desulfurization(CFB-FGD)to fulfill ultra-low emission control.At different operation conditions,mercury concentration in the flue gas was detected at different sampling points,and mercury content in byproducts was analyzed.The results revealed that mercury in coal is mostly emitted into flue gas during combustion,and exists in the form of gaseous and particulate mercury.The concentrations of gaseous and particulate mercury increase with boiler load,but are mostly unaffected by in-furnace desulfurization.71%-77%gaseous mercury and 86%-88%particulate mercury are removed by CFB-FGD.With the synergetic effects of pre-ESP and CFB-FGD,the total mercury removal efficiency reaches 82-87%,and final mercury emission level is reduced to less than 1.5μg/Nm^3.The mercury removed from flue gas is generally concentrated in fly ash and CFB-FGD byproduct.