熱裂解降解飛灰中戴奧辛之研究; Degradation of Dioxin in Fly Ashes via Pyrolysis

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Title:	熱裂解降解飛灰中戴奧辛之研究;Degradation of Dioxin in Fly Ashes via Pyrolysis
Authors:	廖振淵;Chen-yuan Liao
Contributors:	環境工程研究所
Keywords:	戴奧辛;飛灰;熱裂解;鹼劑;Dioxin;Fly Ashes;Pyrolysis;Alkali Additive
Date:	2010-07-28
Issue Date:	2010-12-08 13:50:21 (UTC+8)
Publisher:	國立中央大學
Abstract:	國內飛灰主要來源為垃圾焚化爐、電弧爐煉鋼廠及二次金屬冶煉產業，由於含高濃度之戴奧辛及重金屬，屬有害事業廢棄物。每年產生之飛灰量佔有害事業廢棄物總量的62 %，且穩定化後之體積明顯增加，該如何有效降低飛灰毒性、減少固化體積及提升飛灰再利用之可行性已成為國內迫在眉捷亟需解決之環境議題。本研究擬針對都市垃圾焚化爐飛灰、二次銅冶煉飛灰、電弧爐集塵灰及電弧爐集塵灰處理廠飛灰進行特性分析，並透過熱解方式分解飛灰中之戴奧辛，為我國飛灰處理問題尋求完善且可行之處理技術。其結果指出，溫度越高、反應時間越長，飛灰有較高之PCDD/Fs去除率，在3小時、400oC、有氣流及無氧的環境下，都市垃圾焚化爐飛灰之PCDD/Fs去除率為98.1%，二次銅冶煉飛灰之PCDD/Fs去除率為26%，電弧爐集塵灰處理廠飛灰之PCDD/Fs去除率為72%，顯示此操作條件下，都市垃圾焚化爐飛灰之PCDD/Fs去除率為最高。而氣流之有無對不同產業飛灰而言，PCDD/Fs去除效率差異不大。若飛灰操作於3小時、400oC及含5%氧之氣流中，四種飛灰皆有顯著PCDD/Fs生成，其中以二次銅冶煉之PCDD/Fs生成毒性濃度值最高，為304.5 ng-TEQ/g。添加氧化鈣與氫氧化鈣於四種飛灰上，大體而言氫氧化鈣對飛灰中PCDD/Fs之去除效率較氧化鈣好，在各種添加量下，氫氧化鈣之毒性去除效率大多高於氧化鈣。 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.
Appears in Collections:	[Graduate Institute of Environmental Engineering ] Electronic Thesis & Dissertation

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