The larger part of the molten fly ash which is generated when municipal solid waste (MSW) is treated using gasifying and melting furnaces is handled as a specially-controlled waste in the same manner as incineration fly ash (fly ash from stoker-type incinerators), and is disposed of by landfill burial after stabilization treatment by methods designated by the national government, such as chelate treatment or cement fixation. Basically, however, these are not methods which separate out harmful substances. On the other hand, a shortage of landfill disposal sites has also become a major social problem. Therefore, the establishment of a technology which separates harmful substances such as lead, cadmium, etc. in fly ash as completely as possible, stabilizes the residual trace amounts of heavy metals, and enables recycling of the residue has been desired. In research on a process of this type, the authors constructed a pilot plant (45kg/h) for treatment of molten fly ash and conducted tests of detoxification and conversion to aggregate using several kinds of molten fly ash as raw materials, and carried out technical development of a new roasting treatment technology which enables advanced detoxification of molten fly ash and effective utilization of the residue. The results confirmed that this roasting process possesses sufficient potential for practical application as a treatment for molten fly ash. In the course of this research, (1) the mechanism of chlorination-volatilization of lead (Pb) was clarified, (2) a 99.5% Pb volatilization rate was achieved, and (3) 99.5% volatilization was possible with lead oxide-containing glass (lead glass from end-of-life televisions and computer monitors) by adequately crushing the lead glass and performing mixed roasting treatment with fly ash.
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