As an initial step of collaborative studies carried out by the SDD project, some series of sinter-pot tests were carried out to examine formation/decomposition behavior of dioxins in the sintering bed. Test method was first assessed from a view of accurate determination of dioxins discharged in the outlet gas. It was confirmed that the pot test is an effective way to measure dioxins emissions from the sintering process.Then, the effect of additives, i.e., PVC, NaCl, oil, mill scale, anthracite and dusts form steel works, was evaluated by the pot tests. They were chosen in terms of organic/inorganic chlorine sources, volatile matters convertible to "soot" during combustion and so forth. Based on the results, possibility of de novo synthesis of dioxins from the electrostatic precipitator (EP) dust and soot formed/trapped in the sintering bed was discussed. Further, accumulation behavior of dioxins in the raw materials due to the recycle use of dusts formed in the waste gas treatment process was examined using raw materials initially containing the dust from an electrostatic precipitator of a sintering process and 13 C-labeled reagents of O8CDF, 2378-T4CDF and 246-CP.
The emissions of dioxins to the environmental air from iron ore sintering plants become to be regulated by the new Japanese law against dioxins. The emissions from Japanese sintering plants have been already fairly low levels by large efforts made so far for their reduction. However, substantial and systematic countermeasures are not yet developed and, further, detailed information has not been available on the formation/decomposition of dioxins in the sintering plant.In the present investigation, two different plants were chosen and samplings were made for gaseous, liquid and solid materials at various positions of the processes. Concentrations of dioxins and other compounds of the samples were analyzed. Understanding of the characteristics of the dioxins formation in the sintering process has been attempted on the basis of the analytical results. Macroscopic behavior of dioxins in the sintering and waste gas treatment processes is discussed. Further, the results of the plant test obtained with and without use of recycling materials are reported.
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