焚化系統中抑制戴奧辛生成之初步研究; Investigation of PCDD/PCDF Formation by Inhibitors in Laboratory-scale Experimental System

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Title:	焚化系統中抑制戴奧辛生成之初步研究;Investigation of PCDD/PCDF Formation by Inhibitors in Laboratory-scale Experimental System
Authors:	鄭銚強;Yao-Chiang Cheng
Contributors:	環境工程研究所
Keywords:	戴奧辛;抑制;硫;焚化;inhibitor;reduce;MSWI;PCDD/Fs
Date:	2003-12-22
Issue Date:	2009-09-21 12:15:41 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	焚化系統中戴奧辛排放控制技術主要採用噴入活性碳吸附及觸媒破壞兩種類型，兩者都能有效去除煙道排氣中之戴奧辛，但這兩項技術皆屬管末處理技術，基於永續發展及源頭減量之考量，有效減少戴奧辛於焚化過程之生成才是治本之道。國外研究指出於廢棄物焚化過程中如添加抑制劑，如含硫、胺、氮及鹼性物質，可有效抑制戴奧辛的生成。本研究結果顯示各項抑制劑對戴奧辛之抑制生成率並非與抑制劑的添加量成一正相關，而是有一最佳添加比例。研究顯示添加硫粉可有效抑制戴奧辛之生成，其中又以S/Cl mole比為2時，其抑制效率最好（54.2﹪），硫粉對於戴奧辛的抑制效果並非隨著硫粉的添加量增加而上升，而是與焚化過程中之氯源含量存有最適的添加量。SO2/HCl濃度比為0.55時，可達50.6﹪的抑制效果，SO2對於PCDF生成的抑制效果較佳，約40~70﹪，而對PCDD則較差，並且在SO2/HCl過低或過高時對戴奧辛之抑制效果皆明顯下降。以氫氧化鈣做為抑制劑時，無論Ca/Cl mole比為0.5、1或2時，其抑制效果皆可高於90﹪以上。氫氧化鈣會與氣流中之HCl反應，形成氯化鈣減少戴奧辛之生成以及氯化能力。尿素在N/Cl mole比為0.1時，抑制率最佳為86.9﹪，尿素易與催化金屬銅形成Cu+-urea錯合物，降低催化金屬之催化能力，尿素遇高溫會自行分解而產生NH3，與氣流中之HCl反應生成NH4Cl，降低氯化反應之進行。抑制劑之抑制效果皆有其最佳之比例，因此於焚化系統中添加抑制劑時，需先了解廢棄物組成中之氯含量並作適度之調整，以達到最佳之抑制效果。成本效益分析結果顯示添加抑制劑技術之成本低於活性碳吸附以及觸媒破壞技術，且國內外研究顯示抑制劑之抑制率可達85~95%，應用抑制劑減少戴奧辛之生成可作為另一項控制戴奧辛排放之源頭控制技術。 Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) are very toxic compounds mainly emitted from municipal solid waste incinerators(MSWI). These compounds will affect human health when inhaled. Activated carbon injection (ACI) and SCR decompostition are two major end-of-pipe pollution control technologies currently used. It is proved that addition of inhibitors (such as sulfur, SO2, urea, alkaline materials) could decrease formation of dioxins. Experimental results indicate that addition of sulfur in incineration process can reduce PCDD/F formation. PCDD/F formation can be effectively reduced when S/Cl molar ratio is about 2. Dioxins decrease dramatically at SO2/HCl ratio as 0.55. The sulfur component will react with Cl2 and convent it into HCl. In addition, S or SO2 affect dioxin formation by vulcanizating phenolic precursors and catalysis metal, thus inhibiting chlorination reaction. Calcium hydroxide can reduce dioxin formation by more than 90﹪when Ca/Cl molar ratio is over 0.5. Addition of urea can also reduce PCDD/F formation about 50~87﹪when N/Cl mole ratio is about 0.1. The role of urea is to block catalysis metal and to form complex compounds with Cu and to prevent Ullmann reaction. Inhibition of dioxins formation will be the best way to reduce dioxin emissions. The cost of applying inhibitors for reducing dioxin formation is considerably lower than that of using activated carbon injection (ACI) and SCR decompostition. Adding inhibitors technology has a good potential for controling dioxins formation and emission in the future.
Appears in Collections:	[Graduate Institute of Environmental Engineering ] Electronic Thesis & Dissertation

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