| 摘要: | 伴隨人類活動與文明發展，焚燒廢棄物將產生具有高毒性的焚化飛灰，礙於台灣地狹人稠，以往的水泥固化法掩埋，已無法支撐逐年累積的飛灰產量，其去化途徑儼然成為人們無法逃避的難題，達成飛灰再利用之目標蔚為新的趨勢。近年來，國內空污控制技術的革新搭配鹼劑的替換，使焚化飛灰成分大幅改變。本研究期以低熱裂解技術，作為焚化飛灰處理的方法，降低飛灰中戴奧辛/呋喃的濃度至歐盟最終廢棄物再利用標準（≤ 20 pg TEQ/g），計算各樣品的氯化程度與物種反應速率，同時探討兩種飛灰之物化性質差異及降解機制。結果顯示，所有樣品經實驗後，氯化程度都有所降低，物種濃度有往低氯數物種集中之趨勢，代表整體去的反應式以脫氯為主。鈉系飛灰在350°C實驗條件下，PCDD/Fs質量濃度去除效率均超過99%。反應時間為5、15和30分鐘時，毒性當量濃度分別降至0.0059、0.0013和0.0011 ng I-TEQ/g，達到歐盟最終廢棄物再利用標準。後續結合水洗技術能進一步提升PCDD/Fs的去除效率，300°C下，特別是鈣系飛灰之毒性當量濃度明顯降低，證實氯含量的對去除效率的影響力。綜上所述，鈉系飛灰較鈣系飛灰普遍具有更良好的戴奧辛去除效率，主要原因推測為飛灰中氯含量與金屬化合物的成分的差異導致。此外，裂解實驗後之氣相與固相戴奧辛分佈，經檢測尾氣排放濃度為0.44 ng I-TEQ/Nm3，發現有0.19%的質量濃度被脫附出來，以毒性當量濃度計算則佔1.91%。本研究對國內廢棄物去化處理提供見解，飛灰熱裂解技術在本國未來廢棄物處理領域深具發展潛力。;Incineration of waste generates highly toxic fly ash. Given Taiwan′s limited land and dense population, traditional cement solidification and landfill methods can no longer accommodate the increasing fly ash production. Finding effective treatment and disposal methods has become an unavoidable challenge, and achieving the goal of fly ash reuse has emerged as a new trend. In recent years, development of innovative air pollution control technologies coupled with the replacement of alkaline sorbents, have significantly altered the composition of incineration fly ash. This study aims to apply low-temperature pyrolysis as a method for treating incineration fly ash, reducing the concentration of PCDD/Fs in the fly ash to meet the EU-EoW criteria (≤ 20 pg TEQ/g). The study calculates the chlorination degree of PCDD/Fs in the samples while examining the differences in the physicochemical properties and degradation mechanisms of the two types of fly ash. The results show that all samples experienced a reduction in chlorination degree after pyrolysis, with the concentration of species trending towards lower-chlorinated compounds, indicating that dechlorination was the primary reaction mechanism. Sodium-based fly ash achieved over 99% removal efficiency of PCDD/Fs based on mass concentration when operated at 350°C. The toxic equivalency concentration decreased to 0.0059, 0.0013, and 0.0011 ng I-TEQ/g after reaction of 5, 15, and 30 minutes, respectively, meeting the EU-EoW criteria. Subsequent combination with water washing techniques further improved PCDD/Fs removal efficiency, especially for calcium-based fly ash at 300°C, confirming the influence of chloride content on removal efficiency. In summary, sodium-based fly ash generally exhibited better dioxin removal efficiency compared to calcium-based fly ash. This is likely due to the differences in chloride content and the composition of metal compounds in the fly ash. Additionally, the distribution of gaseous and solid-phase dioxins in pyrolysis revealed that 0.19% of the mass concentration was desorbed, accounting for 1.91% of the toxic equivalency concentration, translating to an exhaust emission concentration of 0.44 ng I-TEQ/Nm3. This study provides insights into domestic waste disposal methods, demonstrating that fly ash pyrolysis technology holds significant potential for future waste management in Taiwan. |
