燃煤电厂排放PAHs的气粒分配机制和排放通量

对循环流化床锅炉(CFB)布袋除尘器进口和出口的多环芳烃(PAHs)进行了分析,研究了PAHs在气相和颗粒相中的分配机理.结果表明, 除尘过程气相和颗粒相PAHs对应的去除率分别为45.59%与70.67%~89.06%.气相中主要为低分子量PAHs,颗粒相中主要为高分子量PAHs.随着粒径的增加,低分子量PAHs比例呈上升趋势.除尘过程PAHs主要以吸附状态附着在颗粒物上. “开尔文效应”导致挥发性相对低的高分子量PAHs更易凝结在细颗粒上.PAHs的气粒分配主要受有机碳吸收作用控制,其吸收作用强弱与烟气颗粒物颗粒大小有明显的相关性.PAHs排放因子为3.55mg/kg,其中气相和颗粒相PAHs的排放因子分别为0.55和3.0mg/kg.通过计算得出安徽省CFB燃煤电厂PAHs排放量从2010年的29000kg逐年增加至2014年的34200kg,随后保持稳定的趋势,并于2017年又明显增加到35900kg.

Studies on the gas-particle partitioning mechanism of polycyclic aromatic hydrocarbons (PAHs) and emission amount from coal-fired power plants

16US EPA priority PAHs at the inlet and outlet of fabric filter in a circulating fluidized bed boiler of CFPPs were analyzed. The partitioning mechanism of PAHs in the gas- and particle-phases with different particle sizes was studied. The results showed that the removal rates of gas phase and particulate PAHs by the fabric filter were 45.6% and 70.7%~89.1%, respectively. The gas phase mainly contained low molecular weight PAHs, while medium and high molecular weight PAHs were predominant in particle phases. The fractions of low molecular weight PAHs showed a declining trend with the decrease of particle size. The gas-particle partitioning of PAHs was primarily controlled by organic carbon absorption, and it had an apparent dependence on particle sizes. Most of PAHs species in the particles of different particle sizes in flue gas exhibited bi-model structures, with one mode peaking in the accumulation size range (1.1~2.1μm) and another peaking in the coarse size range (4.7~5.8μm). The emission factor of PAHs was 3.55mg/kg of coal burned, with 0.55mg/kg in gas phase and 3.0mg/kg in particle phase, respectively. Emissions of PAHs increased gradually from 29000kg in 2010 to 34200kg in 2014, then remained constant from 2014 to 2016, and finally significantly increased to 35900kg in 2017.