1000MW近零排放燃煤机组重金属排放及分布特征

Emissions and distribution characteristics of heavy metal in 1000MW near-zero emission coal-fired units

采用EPA 29方法对国华寿光电厂2号1000MW超超临界燃煤机组污染物控制单元进行采样,开展了重金属污染物(As、Pb、Se、Cd)全流程监测.建立了包括气体/固体/液体中重金属的燃煤过程中质量平衡,并考察了重金属在机组中的富集与分布特征.结果表明:该机组烟气排放的重金属含量相对较低,100%负荷时As、Se、Pb、Cd排放浓度分别为1.11,0.59,0.33和0.01μg/m^(3),45%负荷时相关重金属排放和100%负荷接近.给出了不同负荷下各种重金属在燃煤机组的分布,燃烧后Pb、Se、Cd主要富集到飞灰中,但低负荷时底渣中Se和Cd的比例明显升高.APCDs中,ESP对烟气中As、Pb、Se、Cd四种元素的脱除率均达到了97%以上,不同负荷下WFGD和WESP对这些重金属具有深度脱除的效果.

The EPA Method 29 was used to sample the 1000 MW unit in Shouguang ultra-supercritical coal-fired power plant,the whole process monitoring of heavy metal pollutants(As,Pb,Se,Cd)at multiple points can be realized.The mass balance of heavy metals in the coal combustion process was established,and the enrichment and distribution characteristics of heavy metals in flue gas in coal-fired power plants were studied.The results showed that the heavy metal content of the flue gas was relatively low,the flue gas emission concentrations of As,Se,Pb and Cd were 1.11μg/m^(3),0.59μg/m^(3),0.33μg/m^(3) and 0.01μg/m^(3) at 100%load,respectively,and the heavy metal content at 45%load was close to that at 100%load.The distribution of various heavy metals in coal-fired units under different loads was presented.Pb,Se,and Cd are all enriched in fly ash,but the proportion of Se and Cd in the bottom slag increased significantly at low load.The removal rates of ESP for As,Pb,Se and Cd all reached more than 97%in the APCDs,and WFGD and WESP can deeply remove heavy metals under different loads.