Fundamental Aspects of Dioxin (PCDD) and Furan (PCDF) Formation from Combustion

摘要

Formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinateddibenzofurans (PCDF) was investigated in a spouted bed combustor and in a low temperature fly ash reactor using plausible precursors. Combustion of chlorinated benzenes and chlorinated phenols yielded measureable quantities comparable in some instances to those observed in incinerators of PCDD/F as well as of many chlorinated benzene (CB) and chlorinated phenol (CP) isomers. In the absence of flay ash, the dominant PCDD appears to be OCDD (octa-chlorodibenzo-p-dioxin) favoring a gas phase mechanism. However, there is also evidence that the tetra-through-octa congeners of PCDD and PCDF were formed from the combustion of 1,2-dichlorobenzene. A few experiments with a solid fuel, RDF (refuse-derived fuel) showed that PCDD/F could be readily formed; 1,2-dichlorobenzene and RDF produced similar distribution of chlorobenzene isomers. Separate studies in a fly ash reactor indicated that such diverse reactants as carbon and 1,2-dichlorobenzene can be (approximately 300 deg C) PCDD, and PCDF's were also found. Modeling studies showed that drastic adjustments in model parameters were required to reconcile laboratory and incinerator findings.