两种典型生活垃圾焚烧炉烟气中二 相态分布特征

采集了机械炉排焚烧炉和循环流化床焚烧炉两种典型生活垃圾焚烧炉排放烟气样品,应用高分辨气相色谱/高分辨质谱(HRGC/HRMS)同位素内标稀释法分别测定了烟气不同相样品中17种2,3,7,8-位氯取代的PCDDs/PCDFs同类物的含量.结果表明,两种炉型中PCDDs/PCDFs同类物及毒性当量贡献率在冷凝水相中所占的比例均在85%以上,远远高于在滤筒相和XAD-2树脂相中所占的比例,机械炉排炉焚烧排放烟气中∑PCDFs与∑PCDDs的比值为0.77;而循环流化床焚烧排放烟气∑PCDFs与∑PCDDs的比值为5.28.机械炉排炉焚烧烟气三相中OCDD为优势分布,尤其是滤筒相中OCDD的百分比含量高达51.1%.流化床焚烧炉焚烧烟气滤筒、树脂、冷凝水相中没有出现某个单体对总浓度具有绝对优势的贡献.机械炉排焚烧炉和循环流化床焚烧炉排放的烟气中PCDFs的毒性当量贡献最大,尤其是单体2,3,4,7,8-PeCDF对总毒性当量的贡献均在30%以上.

Multiphase distribution characteristics of PCDDs/PCDFs from two typical municipal waste incinerators

Samples of stack gas were collected from two typical municipal waste incinerators, i.e., mechanical stoker incinerator and fluidized-bed incinerator, and the concentrations of PCDDs/PCDFs in these samples were determined with internal standard-calibrated isotope dilution method in combination with high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). Average percentages of PCDDs/PCDFs and their toxicity equivalents were both above 85% in condensate water phase, which were much higher than that in filter thimble phase and in XAD-2 resin phase for the two incinerators; the ratio of ∑PCDFs to ∑PCDDs was as low as 0.77 in stack gas from mechanical stoker incinerator, but turned out to be as high as 5.28 in stack gas from fluidized bed incinerator. Among the three phases of stack gas from the mechanical stoker incinerator, the PCDDs/PCDFs were found to be dominated by OCDD, with the concentration of OCDD being up to 51.1% particularly in the filter thimble phase. However, among the three phases of stack gas from the fluidized-bed incinerator, the PCDDs/PCDFs were found to be not dominated by a single congener. In stack gas from both incinerator types, PCDFs showed the highest contribution to toxicity equivalent (I-TEQ), and particularly, 2,3,4,7,8-PeCDF made higher than 30% contribution to the total toxicity equivalent.