| 摘要: | 本研究針對北部某一有害事業廢棄物焚化廠進行煙道氣三點同步及四種固體物採樣，焚化對象分別為醫療廢棄物及含PCB絕緣油，探討各空氣污染防制設備對戴奧辛類化合物之去除效率。煙道氣分別於超音波溼式洗滌塔出口、袋式集塵器入口及煙囪排氣；固體物則分為底渣、污泥、熱交換器灰及袋式集塵灰進行同步採樣。分析結果顯示焚化醫療廢棄物時PCDD/Fs及dl-PCBs排放總濃度高達6.30 ng WHO-TEQ/Nm3，推測是因整體燃燒效率較差及廢氣通過防制設備時有明顯之de novo反應生成所致；焚化含PCB絕緣油時PCDD/Fs及dl-PCBs排放總濃度則為0.48 ng WHO-TEQ/Nm3，原因推測有三，一為液態廢棄物性質均勻且燃燒穩定，二為爐體燃燒狀態穩定，三為煙道氣之氯化氫濃度低，氯化潛勢相對較低，故排放濃度比焚化醫療廢棄物時為低。煙道氣三點濃度以袋式集塵器入口最高，推測廢氣流經熱交換器發生de novo反應且管道內累積大量含鐵鏽粉塵所致。煙道氣毒性當量物種分布方面，不論是焚化醫療廢棄物或是含PCB絕緣油，PCDD/Fs皆以1,2,3,7,8-PeCDD、2,3,4,7,8-PeCDF及2,3,4,6,7,8-HxCDF為優勢物種；dl-PCBs則以PeCB-126為優勢物種，主要原因為這些物種之TEF係數較高所致。就固體物而言，袋式集塵灰及污泥具有較高的PCDD/Fs及dl-PCBs濃度，乃因袋式集塵器可有效去除粒狀物及超音波聚塵效應所致。就活性碳噴入+袋式集塵器對PCDD/Fs及dl-PCBs之去除效率而言，焚化醫療廢棄物時分別達65.4 %及67.1 %；焚化含PCB絕緣油時則為63.8 %及66.1 %。數據顯示氣固相去除效率皆偏低，固相濃度去除效率低是因袋式集塵器對粒狀物去除效率未達預期所致；氣相濃度去除效率低則是因活性碳噴注系統有架橋及堵塞影響所致。焚化醫療廢棄物之PCDD/Fs及dl-PCBs排放係數分別為63.3及3.71 μg WHO-TEQ/ton；焚化含PCB絕緣油之PCDD/Fs及dl-PCBs排放係數則分別為1.05及0.08 ng WHO-TEQ/L。分析結果顯示含PCB絕緣油之PCDD/Fs及dl-PCBs原始濃度分別為32.5 ng/g和1.47 μg/g，經焚化處理總PCDD/Fs破壞效率達99.92 %；總dl-PCBs破壞效率更高達99.9999 %，顯示焚化是處理含PCB絕緣油之有效手段。;In this study, PCDD/Fs and dl-PCBs emissions from burning medical waste and PCB-containing oil of a hazardous waste incinerator were characterized individually. Flue gas samples were simultaneously taken at three different points. The first was taken at the ultrasonic wet scrubber outlet. The second was in baghouse inlet and the last was in stack. Solid matter samples were divided into four kinds, including bottom ash, sludge, heat exchanger ash and baghouse ash. The results showed that the concentration of PCDD/Fs and dl-PCBs in combustion of medical waste was as high as 6.30 ng WHO-TEQ/Nm3 in stack, which was due to poor combustion efficiency and de novo reaction in APCDs. On the other hand, concentrations of PCDD/Fs and dl-PCBs was 0.48 ng WHO-TEQ/Nm3 from combusting PCB-containing oil, because combustion condition was stable and concentration of hydrogen chloride in flue gas was lower than that of incinerating medical waste. As a result, the concentrations of PCDD/Fs and dl-PCBs measured at the baghouse inlet was the highest due to significant de novo formation in heat exchanger and the accumulation of particles on the pipe. Major PCDD/Fs and dl-PCBs congeners contributing to TEQ in flue gas include1,2,3,7,8-PeCDD, 2,3,4,7,8-PeCDF, 2,3,4,6,7,8-HxCDF and PeCB-126, due to their high TEFs. As for the solid matter, baghouse ash and sludge were of high PCDD/F and dl-PCB concentrations, because baghouse removed most particles and ultrasonic machine gathered dust. The PCDD/Fs and dl-PCBs removal efficiencies achieved with activated carbon injection and baghouse were 65.4 % and 67.1 %, respectively when medical waste was incinerated. On the other hand, the removal efficiencies of PCDD/Fs and dl-PCBs were 63.8 % and 66.1%, respectively when PCB-containing oil was incinerated. It was found that removal efficiencies of PCDD/Fs and dl-PCBs in both gas and solid phases were relatively low due to relatively low particle removal efficiencies achieved with baghouse and the inappropriate operating condition of activated carbon injection system. The emission factors of PCDD/Fs and dl-PCBs for incinerating medical waste were 63.3 and 3.71 μg WHO-TEQ/ton while 1.05 and 0.08 ng WHO-TEQ/L were recorded, respectively, for the incineration of PCB-containing oil. Original PCDD/Fs and dl-PCBs concentrations in PCB-containing oil were also measured and the results indicated that PCDD/Fs and dl-PCBs concentration were 32.5 ng/g and 1.47 μg/g, respectively. Analysis of the mass balance for incinerating PCB-containing oil indicated that overall PCDD/Fs destruction efficiency reached 99.92% while 99.9999% destruction efficiency was achieved for dl-PCBs. The results demonstrated that incineration with good engineering practice is an effective approach for treating PCB-containing oil. |
