Quantification of Formation Rate of Dioxins from Unburned Carbon Particles and the Suppression of their Formation

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This study aims to propose the principle to suppress the dioxin emission, by means of clarifying the mechanisms concerning the formation reaction of dioxins in the oxidation (combustion) process of organic materials like solid wastes. The detailed formation mechanisms of dioxins and the reaction rates from carbonaceous residue"soot"condensed/precipitated in the cooling process of exhaust gas have been demanded because its role to the dioxin formation is regarded as major part through various fundamental researches and the studies on the actual combustion processes.First, several series of experiments were conducted on the formation of dioxin formation from carbonaceous residue having macro structure of carbon by using model carbon particles prepared by composing of various metallic compounds and chlorides. Further, formation rate of dioxins and other relating reaction rates such as carbon oxidation and chlorinated organic compounds were measured. Using these data, the effects of experi … More mental parameters on the reaction rates were attempted to quantitatively understand. On the other hand, composing (existing) states of carbon, metallic compounds and chlorinated organic compounds was evaluated by analyzing trace elements in the samples before and after experiments and fly ash samples from actual process. In addition, it was found that the addition of urea leaded to the reduction of dioxin emission through exhaust gas by lea than one tenth. Detailed analysis on the various organic compounds formed by the addition of urea gives the fact that several hydrocarbons having the amino or cyano groups and organic compounds containing nitrogen Like pyridine. Based on the obtained results, it was considered as that such compounds forms by the displacement reaction of the functional groups with active nitrogen and nitrogen compounds generated through thermal reactions concerning urea and intercalation reaction of nitrogen into macro carbon structure and their effects on the dioxin formation was verified. Less