FORMATION OF PRECURSORS TO CHLORINATED DIOXIN FURANS UNDER HETEROGENEOUS CONDITIONS

In our laboratory, we have attempted to simulate MSW-incineration with a spouted bed combustion system. Our studies show that the combustion of simple chlorinated compounds can lead to some potentially important precursors to PCDD/F. This paper presents results from the lean combustion of 1,2-dichlorobenzene. The effect of equivalence ratio and the chlorine to carbon ratio in the fuel are investigated. Maxima in CE, DRE and PICs are observed as a function of equivalence ratio. The carbon to chlorine ratio influences the chlorobenzene (CB) to chlorophenols (CP) ratio in the products. Measurements in MSW (municipal solid waste) incinerators have shown that polychlorinated dioxins/furans (hereafter PCDD/F) can form heterogeneously in the colder (<450-degrees-C) portion of the post combustion regions. However, controversies continue to exist about the rates of these processes and the precursors involved. Quantitative knowledge of potential precursor concentrations as well as their rates of formation and reaction is relatively scarce, but several reports have presented evidence that chlorobenzenes and chlorophenols are major compounds in both gas and solid phases. The results from our laboratory investigations agree with some available incinerator data.