民用燃煤烟气中甲基多环芳烃的排放特征

摘要

利用全流稀释烟气采样系统,对20个煤/炉组合方式(涉及4种烟煤和1种无烟煤、块煤和蜂窝煤2种燃烧方式、3种北方地区常用的炉灶类型)的燃烧烟气进行了采样和分析,获取了多环芳烃的排放因子数据.针对具有更强“三致”作用的甲基多环芳烃(A-PAHs)的排放特征进行讨论,并与原煤的有机溶剂抽提物进行对比.结果表明,不同煤种和燃烧方式的8种A-PAHs排放因子(EFA PAHs)差别显著,其中,烟煤在块煤与蜂窝煤两种燃烧方式下的变化范围分别为0.5～1.6mg/kg和63.9～100.1mg/kg,无烟煤以块煤与蜂窝煤燃烧的EFA PAHs分别为0.1 mg/kg和67.3mg/kg;蜂窝煤的平均EFA PAHs比块煤高约2个数量级,说明作为洁净煤技术被推广使用的蜂窝煤燃烧方式存在“不洁净”的方面,应引起重视.对比原煤抽提物中A-PAHs的变化特征,可知燃煤烟气中的A-PAHs部分来自于煤的受热挥发,具有原煤的一些特征,但是更多的A-PAHs来自于燃烧过程中的高温裂解反应.%A large-size,full-flow dilution and fractional sampling system was employed to collect samples of emissions from 20 different coal/stove combinations,involving four bituminous coals and one anthracite in two combustion forms (Raw-coal-chunk/Honeycomb-coal-briquette),and three types of stoves widely used in northem area.Then,the emission factors of PAHs were obtained through chemical analysis and calculation.Furthermore,the emission characteristics of Alkyl-PAHs (A-PAHs),which were known for the stronger mutagenesis,carcinogenesis and deformation,were discussed and compared with the extraction rates from the raw coal.Notable difference existedin the emission factors of 8 A-PAHs (EFA-PAHs) ofdifferent coal/combustion formcombinations.The total EFA-PAHs of bituminous coal ranged from 0.5 to 1.6mg/kg for RCC and 63.9 to 100.1mg/kg for HCB,while the anthracite EFA-PAHs ranged from 0.1mg/kg for RCC and 67.3mg/kg for HCB.The averaged EFA-PAHs of HCB were higher by two orders of magnitude than those of RCC.HCB had some negative effect although it was widely used in clean coal technology.Comparing with the variation characteristics of A-PAHs in extracts of five raw coals,we found that some of A-PAHs came from the thermal volatilation of coal,inheriting some characteristics of raw coal.However,more A-PAHs came from the high-temperature pyrolysis reaction in the combustion process of coal.