Influence of Cu, Fe, Pb, and Zn Chlorides and Oxides on Formation of Chlorinated Aromatic Compounds in MSWI Fly Ash

摘要

Model fly ashes containing admixed Cu, Fe, Pb, and Zn chlorides and oxides were heated at a temperature corresponding to the postcombustion zone of a municipal solid waste incinerator (MSWI), resulting in the formation of chlorinated aromatic compounds, including polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs), polychlorinated biphenyls (PCBsl, and chlorobenzenes (CBzs). The concentrations of these compounds were measured and compared with those occurring in real fly ash. The orderwith respect generative capacity of each metal additive was calculated from principal component analysis of the concentrations of the different chlorinated aromatic compounds as CuCl_2-2H_2O > Cu_2(OH)_3Cl > FeCl_3·6H_2O > FeCl_2FeCI24H_2O > CuO > Fe_2O_3 > PbCl_2 > blank (no metal added) > ZnCl_2 > PbO > ZnO. From hierarchical cluster analysis of the concentrations and congener distribution patterns of the PCDDs, PCDFs, PCBs, and CBzs, the metallic compounds were divided into five groups: Group A (CuCl_2·2H_2O and Cu_2(OH)_3CII, B (FeCl_3·6H_2O and FeCl_2·4H_2O), C (CuO and PbCl_2), D (Fe_2O_3, blank, and ZnCl_2), and E (PbO and ZnO). Cluster analysis showed the congener distribution patterns of model fly ashes to be similar to the pattern of real MSWI fly ash. The formation of PCDDs was influenced mainly by group B, blank, and PbO; PCDFs, mainly by CuO, Fe_2O_3 and ZnCl_2; PCBs, mainly by groups B and C; and CBzs, mainly by groups A and B. Thus, the multiple promotion of chlorinated aromatic compound formation by metallic chlorides and oxides in the fly ashes of MSWIs and other thermal processes has considerable importance for the environment.