Ni/BAC觸媒結合熱裂解技術去除焚化飛灰中PCDD/Fs之效率探討

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Title:	Ni/BAC觸媒結合熱裂解技術去除焚化飛灰中PCDD/Fs之效率探討
Authors:	吳彥慶;Wu, Yen-Ching
Contributors:	環境工程研究所
Keywords:	焚化飛灰;戴奧辛/呋喃;觸媒裂解;球狀活性碳;預處理;毒性溶出程序;Fly ash;PCDD/Fs;Catalytic pyrolysis;BAC;Pretreatment;TCLP
Date:	2025-08-16
Issue Date:	2025-10-17 13:07:16 (UTC+8)
Publisher:	國立中央大學
Abstract:	作為我國主要之廢棄物處理方式，焚化雖可以有效減量，但也衍生含有多氯二聯苯戴奧辛與多氯二聯苯呋喃（PCDD/Fs）的焚化飛灰（以下簡稱飛灰），已成為當前廢棄物管理與環境保護的重要課題。本研究製備鎳負載於球狀活性碳之觸媒（Ni/BAC），並應用於熱裂解系統以降低飛灰中PCDD/Fs濃度至歐盟End of Waste（EoW）標準（≦ 0.02 ng TEQ/g），系統性探討觸媒裂解對飛灰組成、預處理方式與反應時間之影響。研究結果顯示，水洗預處理可顯著去除飛灰中的氯鹽含量並減少其重量，且相較於酸洗預處理更能提升熱裂解與觸媒裂解之效能。添加Ni/BAC進行觸媒裂解鈣系及鈉系飛灰之PCDD/Fs質量與毒性當量去除效率均超過99%。於350°C反應10分鐘並添加10 wt.% 觸媒條件下，鈣系與鈉系飛灰之PCDD/Fs毒性當量濃度分別降至0.012 ng I-TEQ/g及0.013 ng I-TEQ/g，符合EoW標準。處理後之觸媒可實現全回收，且經三次循環測試後，Ni/BAC觸媒仍維持優異之去除效能，且皆符合EoW標準，顯示其穩定性與重複使用潛力。此外，Ni/BAC的穩定性及可全回收性也未導致處理後飛灰中Ni之毒性溶出濃度增加，顯示該觸媒的環境友善性。本研究亦針對固相及氣相PCDD/Fs分布進行分析，以全面掌握PCDD/Fs的遷移與轉化行為。鈣系飛灰之尾氣及觸媒殘留之PCDD/Fs總質量濃度分別佔原始PCDD/Fs總質量濃度的0.0043%與0.0140%，鈉系飛灰則分別佔原始PCDD/Fs總質量濃度的0.0009%與0.0025%，不論鈣系或鈉系皆僅有極少量PCDD/Fs經尾氣排放或殘留於觸媒。針對不同氧氣濃度的實驗結果顯示，熱裂解系統於1 %氧氣濃度仍然保有良好的去除效率，且處理後飛灰中的PCDD/Fs濃度仍符合EoW標準。最後，研究依據水洗預處理順序研擬兩套具實場應用潛力之熱裂解處理流程，提供飛灰資源化處理策略之參考。本研究對不同組成分飛灰之處理提供新見解，顯示觸媒裂解技術在國內未來飛灰循環再利用領域深具發展潛力。;Incineration remains the primary method for municipal solid waste treatment in Taiwan. While effective in reducing waste volume, it generates significant amount of fly ash (FA) which contains polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), posing challenges to waste management and environmental protection. This study prepared a nickel-supported bead-shaped activated carbon catalyst (Ni/BAC) and applied it in catalytic pyrolysis to reduce PCDD/Fs in FA, aiming to meet the EU End-of-Waste (EoW) criteria (≤ 0.02 ng TEQ/g). The effects of FA composition, pretreatment method, and reaction time on the performance of catalytic pyrolysis system are systematically investigated. Water washing significantly reduced chloride content and FA mass, outperforming acid washing in enhancing both thermal and catalytic efficiency. With Ni/BAC addition, PCDD/Fs mass and TEQ removal efficiencies achieved for both Ca-based (CaFA) and Na-based (NaFA) FA exceeded 99%. Under optimized conditions (350 °C, 10 min, 10 wt.% catalyst), TEQ concentrations were reduced to 0.012 ng I-TEQ/g (CaFA) and 0.013 ng I-TEQ/g (NaFA), respectively, meeting EoW criteria. Ni/BAC maintained excellent removal performance after three reuse cycles, exhibiting high stability and reusability. No increase in nickel leachability was observed, confirming its environmental compatibility. PCDD/Fs distribution in solid and gas phases was analyzed to assess the possible migration behavior. For CaFA, PCDD/Fs in flue gas and residual catalyst were 0.0043% and 0.0140% of the original mass; for NaFA, 0.0009% and 0.0025%, respectively, indicating negligible emissions. Results under varying oxygen concentrations confirmed sustained removal efficiency under low-oxygen conditions (≤ 1%), with treated FA still meeting EoW criteria. Finally, based on the water-washing pretreatment, two practical pyrolysis process flows were proposed, offering strategies for FA resource recovery and management. This study provides new insights into FA treatment and highlights low-temperature catalytic pyrolysis as a promising sustainable approach.
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