| Abstract: | 本研究針對電弧爐煉鋼廠及中小型焚化爐之戴奧辛排放特性進行探討，針對電弧爐廠煉鋼過程之氧化期與還原期進行煙道採樣分析，並同時針對爐渣及集塵灰進行採樣與分析工作;另一方面，亦針對國內中小型焚化爐戴奧辛物種濃度分佈與空氣污染防制設備關聯性進行探討。就煉鋼製程之氧化期濃度顯示，CO轉化槽後氧化期PCDD/Fs濃度（862.3 ng/Nm3 ; 48.48 ng I-TEQ/Nm3），袋濾式集塵器前氧化期PCDD/Fs濃度（711.7 ng/Nm3 ; 32.52 ng I -TEQ/Nm3）;而在煉鋼製程之還原期濃度，CO轉化槽後還原期PCDD/Fs濃度（817.3 ng/Nm3 ; 33.43 ng I -TEQ/Nm3），袋濾式集塵器前還原期PCDD/Fs濃度（546.7 ng/Nm3 ; 25.49 ng I -TEQ/Nm3），由此可知，煉鋼製程氧化期濃度略高於還原期濃度，且各採樣點皆以固相PCDD/Fs為主。電弧爐煉鋼廠所分析飛灰中以BF ash之PCDD/Fs濃度(31.2 ng/g)為最高，推測係由於BF捕集較多微細粒狀物，導致BF ash之PCDD/Fs濃度較高。中小型事業廢棄物焚化爐分別探討濕式靜電集塵器與活性碳吸附塔對於PCDD/Fs之去除效率與特性，濕式靜電集塵器對於固相戴奧辛去除效率（90.5 %）優於氣相（28.8 %）。活性碳吸附塔對於氣相戴奧辛去除效率（84.5 %）優於固相（-13.4 %），固相戴奧辛經過活性碳吸附塔後不減反增，推測與活性碳吸附塔之碳微粒剝落有關。所分析之灰份以EP washing sludge之濃度值(5,313 ng/g)最高，由於洗滌水為一再循環回收再利用，因此戴奧辛一直在其中累積導致濃度值較高。電弧爐煉鋼廠之煙道氣PCDD/Fs濃度分佈百分比與中小型事業廢棄物焚化爐相似，以PCDF為主，且以1,2,3,4,6,7,8-HpCDF、OCDF及OCDD為主要優勢物種;而PCDD/Fs之TEQ濃度百分比亦以PCDF為主，且以2,3,4,7,8-PeCDF為最主要優勢物種(佔40~50 %)。 Electric arc furnaces (EAFs) and industrial waste incinerators (IWIs) are major emission sources of dioxins in Taiwan. For EAFs, the flue gases were sampled after CO converter, prior to baghouse and stack to measure dioxin concentrations and to investigate the characteristics of PCDD/F congener distribution. Dioxin emissions at stages of oxidation and reduction at an EAF were also characterized. Besides, slag, BF ash, and cyclone ash were sampled and analyzed. In EAF, the PCDD/F concentration emitted at oxidation stage is higher than that during reduction stage for all sampling points, including the points of CO converter outlet, prior to baghouse and stack. The removal efficiency (86.2 %) of particulate-phase PCDD/Fs was higher than that in gas phase (35.6 %) with fabric filtration. BF ash has the highest PCDD/F concentration (31.2 ng/g) of all ashes sampled. As for IWI, WET-EP applied achieves a higher removal efficiency for particulate-phase PCDD/Fs (90.5 %) than that in gas-phase. The removal efficiency (84.5 %) of gas-phase PCDD/Fs was significantly higher than that in particulate-phase with fixed carbon bed. PCDD/F concentration of EP washing sludge is the highest (5,313 ng/g) in IWI. It is important to note that the washing water is circulated for reuse, therefore, PCDD/Fs accumulate in that, resulting in its high PCDD/F concentration. Major contributors to the dioxin concentrations at each sampling point of EAF and IWI include 1,2,3,4,6,7,8-HpCDF, OCDD and OCDF. 2,3,4,7,8-PeCDF contributes about 50 % Toxic Equivalent Quantity (TEQ) concentrations at each sampling point. |
