溶融飛灰中重金属の塩化揮発に及ぼす未燃炭素の影響

概要

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The effect of unburned carbon on the chloride-induced volatilization of heavy metals was investigated using model and molten fly ashes, in the temperature range of 873-1173 K under N2 gas flowing condition. As a result, it was found that the volatilization ratio of lead and zinc from the molten fly ash increased with an increase in the temperature. Almost 100% of the lead and zinc were volatilized from the molten fly ash at 1173K. However, the volatilization ratio of lead and zinc from the model ash remained 85% and 25% respectively. It was found that metal oxides in the molten fly ash were converted to metal chlorides of PbCl2, Pb2OCl2, ZnCl2 and reduced metals of Pb, Zn, Cu by parallel reaction of chlorination with CaCl2 and reduction with unburned carbon. Reduction of metal oxides in the molten fly ashes was envisaged in terms of carbon equivalent ratio Rc. Almost 100% of the lead was volatilized at Rc=1.25-13.63 at 1173K. The volatilization ratio of 100% for zinc was also achieved at Rc=13.63. By contrast, the volatilization ratio of copper decreased with an increase in the Rc, resulting in less than 5% of copper volatilization at the Rc greater than 4.0.
一般社団法人廃棄物資源循環学会の論文