摘要
長久以來，燃燒為最終處理固態和有害廢棄物之共同處理方案，在台灣已發展19座區域性焚化廠以處理超過90% 之都市固體廢棄物。此外，尚有超過4千個小型焚化爐被設置在商業或工業的單元中，用來處理各種不同種類之工業廢棄物或有機廢溶劑。廢棄物焚化雖可解決垃圾減量問題，但焚化廠之煙道排氣也衍生了空氣污染問題。其中尤以戴奧辛號稱世紀之毒，特別為民眾所關切。 自煙道排氣中移除PCDD/Fs之控制技術，包括活性碳吸附及催化分解等兩大系統，均能達成0.1 ng-TEQ/Nm3之排放標準。但是依據經驗焚化廠產生之PCDD/Fs有20%由氣相排放，80%是附著在飛灰固相和吸附於活性碳吸附劑。由此可見，採用活性碳吸附方式，只是將空氣中的戴奧辛污染物質再轉嫁到不同的介面而已，並未真正的解決問題。 本研究之主要企圖係在發展出一種可被環境接受並兼具成本效益之技術，以減少小型焚化爐排放戴奧辛之風險。研究內容包括：先將原擬廢棄之含鐵污泥再生製成類似氧化鐵之觸媒材料；次於實際焚化燃燒過程中探討氯苯不同含氯濃度與戴奧辛形成之關係，並評估此再生觸媒添加後之最佳破壞溫度；最後再以戴奧辛標準品來實驗測試該氧化鐵觸媒之破壞去除效率，以及說明其可能之催化氧化機制。 污泥再生實驗結果顯示：含鐵污泥在經過脫水、高溫加熱後研磨之粉末狀觸媒（環境觸媒），屬於α-Fe2O3之氧化鐵型態。將之投入焚化爐與含氯化合物反應，能產生催化及破壞氯化結構之作用。 觸媒催化活性評估實驗發現：在未添加觸媒，且定溫燃燒的情況下(一次爐450 oC，二次爐 780oC)，戴奧辛形成濃度與氯苯之含氯量呈線性正比關係，其回歸方程式為 (PCDD/Fs)Cl = 0.261(Cl)+0.052。此外， 在添加一定劑量觸媒(100g/hr)之實驗條件下，當燃燒溫度大於750 oC 時，戴奧辛濃度即從0.78 降至0.1 ng-TEQ/Nm3。 戴奧辛焚化破壞實驗之結果顯示：在添加300g/hr 觸媒之幫助下，戴奧辛標準品之破壞效率高達95% (TEQ)，並接近於96% ( TEQ)之去除效率。此二值之所以如此接近，顯見此氧化鐵觸媒破壞戴奧辛之機制係藉由催化氧化效果而非吸附作用，意即戴奧辛污染物鮮少殘留在觸媒上，較無二次污染必須處理之問題。同時實驗也發現，在不同戴奧辛同屬物種中，氧化鐵觸媒對於最具毒性之2,3,7,8-TeCDD之破壞效果最佳。此外，在觸媒加入反應之環境下進行實驗發現，氯苯產生一氧化碳之燃燒效率超過98%（850℃）；五種含氯化合物之破壞去除效率亦超過99.9到99.999%。並且以實際含氯廢溶劑測試結果，平均戴奧辛檢測值為0.038 ng-TEQ/Nm3皆低於排放標準。如未添加環境觸媒，或僅添加活性碳吸附劑，實驗結果皆超出排放標準。
並列摘要
Combustion has long been a common alternative for the ultimate disposal of solid and hazardous wastes. In Taiwan, there are 21 regional incinerators developed to manage more than 90% of municipal solid wastes (MSWs). In addition, there are more than four thousands small size incinerators in commercial and industrial sectors for disposal of various industrial wastes and organic solvent. Unfortunately, the dioxin-like compounds emitted in flue gas and present in the solid residues generated after combustion process have become a very sensitive environmental problem. Owing to catalytic destruction of chlorinated compounds is one of the key methods in reducing pollutant emissions. Therefore, the aims of this project were focus on the development of novel catalyst, furthermore, for the purpose of utilizing waste materials to suppress chlorinated compounds formation. If feasible, this would achieve waste reuse and enhance combustion efficiency in general, and reduce dioxin emission in particular. Consequently, this study was undertaken to evaluate the performance of the regenerated iron oxide for oxidizing carbon monoxide and suppressing PCDD/F formation in a pilot-scale incinerator. Ferric iron sludge is commonly generated in metal removal facilities, after the preparation of dewatered, heated (800 oC for 4 hrs), and ground into smaller particles. The regenerated ferric oxide particles were then used as the oxidation catalyst to destroy CO formation during the combustion of three chlorinated solvents and to suppress dioxin formation in flue gas in a real waste solvent. In the presence of catalyst, the combustion efficiency (ratio of CO2 to the sum of CO2 and CO) for chlorobenzene was more than 98% at 850 oC in a pilot scale incinerator. The destruction and removal efficiencies of chlorobenzene, 2,4-dichlorophenol and trichlorofluoroethane were more than six nines. In the absence of catalysts, the flue gas emission from a real waste could not meet the regulatory dioxin standard of 0.1 ng-TEQ/Nm3 even with the powdered activated carbon injection. The use of catalyst at either 100 or 300 g/hr, however, was able to meet the emission standard.
參考文獻
延伸閱讀
- 金育德（2011）。微量環境污染物：戴奧辛之流佈與相性轉化研究〔博士論文，國立屏東科技大學〕。華藝線上圖書館。https://doi.org/10.6346/NPUST.2011.00229
- 邱虹梓、蔡冠男（2022）。商業化媒裂觸媒配方調整及微活性測試之實際應用及成果。石油季刊，58(4)，55-70。https://www.airitilibrary.com/Article/Detail?DocID=10229671-202212-202212280003-202212280003-55-70
- 林明樞（2006）。利用線性轉殖與特定點重組製備戴奧辛之生物吸附劑〔碩士論文，國立臺北科技大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0006-1408200616270200
- 謝俊弘（2008）。以螢光共振能量轉移技術作為戴奧辛生物檢測模式之研究〔碩士論文，國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2008.03076
- 林紀佑、謝俊弘、李偉山、張簡國平、潘建源、李心予（2007）。以螢光共振能量轉移技術作為戴奧辛生物檢測模式之研究。生物科學，50(1)，12-25。https://doi.org/10.29981/CB.200712.0002