都市垃圾焚化飛灰因含有戴奧辛（PCDD/Fs）、重金屬及高濃度氯鹽，具有高度環境風險，且傳統固化掩埋方式難以達到污染物減量與資源化目的。本研究以鈣系飛灰（CaFA）與鈉系飛灰（NaFA）為研究對象，探討水洗與低溫熱裂解處理順序對焚化飛灰中 PCDD/Fs 及氯鹽去除效率之影響。實驗分別設計先水洗後低溫熱裂解（WP）及先低溫熱裂解後水洗（PW）兩種處理程序，並以 350°C、375°C 及 400°C 作為熱裂解操作溫度，分析處理前後飛灰之基本特性、氯含量、PCDD/Fs 質量濃度、毒性當量濃度及去除與破壞效率。結果顯示，水洗可有效降低飛灰中氯含量，CaFA 及 NaFA 經水洗後氯含量分別由 20.0± 0.131% 及 22.2 ± 0.393% 降至 6.88 ± 0.302% 及 5.63 ± 0.515%，去除率分別為 65.60 ± 0.361% 及 74.64 ± 0.264%。然而，水洗對 PCDD/Fs 並無直接破壞作用，且因可溶性鹽類溶出造成固體質量降低，使水洗後飛灰中 PCDD/Fs 單位重量濃度呈現上升。低溫熱裂解則可有效降低 PCDD/Fs 濃度，且處理效果隨溫度升高而提升。水洗後飛灰經 375°C 以上熱裂解後，WCaFA 與 WNaFA 之毒性當量濃度皆可降至 0.020 ng I-TEQ/g 以下，符合歐盟再利用參考標準。於 375°C、15 分鐘條件下，CaFA 與 NaFA 之質量濃度破壞效率分別為 99.54% 及 99.70%，毒性當量破壞效率則分別為 98.42% 及 98.68%，顯示低溫熱裂解過程中 PCDD/Fs 主要以分解破壞為主，氣相逸散比例有限。進一步比較兩種處理順序可知，先熱裂解後水洗程序於最終除氯效果上優於先水洗後熱裂解程序，尤其在 400°C 條件下最為明顯。PW400CaFA 與 PW400NaFA 之氯含量分別降至 5.21 ± 0.365% 及 4.02 ± 0.120%，顯示熱裂解可能改變飛灰中氯鹽存在型態，使後續水洗更易將氯由固相移除。能耗估算結果顯示，CaFA、WCaFA、NaFA 及 WNaFA 由 25°C 升溫至 400°C 所需理論升溫能耗分別為 42.72、60.41、41.70 及 55.24 kWh/ton，其中水洗後飛灰因表觀比熱較高，其理論升溫能耗高於原始飛灰。此結果顯示，水洗處理雖有助於降低飛灰中氯鹽含量，但水洗後樣品於後續升溫過程中具有較高之理論熱需求。綜合 PCDD/Fs 去除、氯鹽去除及操作風險評估，先熱裂解後水洗具有較佳最終除氯效果，而先水洗後熱裂解則可先降低熱處理前之氯鹽負荷，有助於減少設備腐蝕風險並提升程序穩定性。;Municipal waste incineration fly ash contains polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)， heavy metals， and high concentrations of chloride salts， posing significant environmental risks. This study investigated the effects of treatment sequence on PCDD/Fs and chloride removal using calcium-based fly ash (CaFA) and sodium-based fly ash (NaFA). Two processes were evaluated: water washing followed by low-temperature pyrolysis (WP) and low-temperature pyrolysis followed by water washing (PW)， with pyrolysis conducted at 350°C， 375°C， and 400°C. Physicochemical properties， chlorine content， PCDD/Fs mass and toxic equivalent concentrations， removal and destruction efficiencies， and theoretical heating energy consumption were assessed. Water washing reduced the chlorine contents of CaFA and NaFA from 20.0 ± 0.131% and 22.2 ± 0.393% to 6.88 ± 0.302% and 5.63 ± 0.515%， corresponding to removal efficiencies of 65.6 ± 0.361% and 74.64 ± 0.264%， respectively. However， washing did not directly destroy PCDD/Fs， and salt dissolution increased their concentrations per unit mass. Low-temperature pyrolysis effectively reduced PCDD/Fs concentration， with greater removal at higher temperatures. At 375°C or above， the toxic equivalent concentrations of both fly ashes decreased below 0.020 ng I-TEQ/g， meeting the European Union reference standard for reuse. At 375°C for 15 min， the mass-based destruction efficiencies of CaFA and NaFA were 99.54% and 99.70%， while the toxic equivalent destruction efficiencies were 98.42% and 98.68%， indicating that PCDD/Fs were mainly destroyed with limited gas-phase release. PW achieved better final chlorine removal than WP， particularly at 400°C， with chlorine contents of PW400CaFA and PW400NaFA decreasing to 5.21 ± 0.365% and 4.02 ± 0.120%， respectively. The theoretical heating energy consumption from 25°C to 400°C was 42.72， 60.41， 41.70， and 55.24 kWh/ton for CaFA， WCaFA， NaFA， and WNaFA， respectively， indicating that washed fly ashes required higher theoretical heating energy due to their higher apparent specific heat. Overall， PW provides better final chlorine removal and lower theoretical heating energy demand during the thermal treatment stage， whereas WP reduces chloride loading before thermal treatment， thereby lowering corrosion risks and improving process stability. Therefore， PW is preferable when chlorine removal and theoretical heating energy demand are prioritized， while WP may be more suitable when operational stability and equipment safety are emphasized.
