| dc.description.abstract | The major fly ash sources in Taiwan include municipal solid waste incinerators (MSWIs), electric arc furnaces (EAFs) and secondary metal smelting processes. Because fly ashes contain high concentration of dioxin and heavy metal, they belong to hazardous waste and have to be treated before its releases. Fly ashes account for 62% of total hazardous industrial waste in Taiwan, and fly ashes are mostly treated with stabilization/solidification in Taiwan, resulting in the increase of fly ash volume. So how to efficiently lower the toxicity in fly ashes, reducing the stabilization/solidification fly ashes volume are the most important issue in Taiwan. This study is motivated to understand the fly ash characteristics and construct a pyrolysis system for degrading dioxins in the fly ashes. The fly ashes investigated in this study include municipal solid waste incinerators fly ashes, electric arc furnaces fly ashes, Waelz process fly ashes and secondary copper smelting fly ashes. The results show that the dioxin removal efficiency is higher as the reaction time gets longer or temperature gets higher. At 3 hour, 400oC, 100% nitrogen flow, the dioxin removal efficiency is 98.1% in MWI fly ashes, 26% in secondary copper smelting fly ashes, 72% in EAF fly ashes; it shows that MWI fly ash has the highest dioxin removal efficiency. The dioxin removal efficiencies do not change significantly whether the system contains the flow or not. Dioxin formation is observed when the flow contains 5% oxygen, and the secondary copper smelting fly ashes is of the highest formation. The dioxin removal efficiency achieved by adding Ca(OH)2 is higher than that of adding CaO.
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