| 摘要: | PCDD/FS可經由燃燒過程產生，國內外的研究指出都市垃圾焚化爐及燃燒製程為PCDD/FS 的重要排放源，國內的數據顯示除了垃圾焚化廠排放量較大外，電弧爐在熔煉過程中所產生的戴奧辛排放亦相當可觀，再加上「煉鋼爐戴奧辛空氣汙染物排放標準」已公佈實施，因此如何降低戴奧辛生成排放，尋找可行之控制技術與方法，乃成為重要的課題。 針對國內採用合流式煙道及百葉窗式排氣系統之電弧爐煉鋼廠進行煙道氣採樣，以探討戴奧辛濃度分佈及各物種之去除效率，此外也對電弧爐煉鋼廠含高濃度戴奧辛灰份及爐渣之濃度及分佈特性進行分析研究。 以煙道式及百葉窗式排氣系統之電弧爐進行袋式集塵器前與煙囪處之採樣，結果顯示在電弧爐EAF-A袋式集塵器前戴奧辛總濃度為 29.12 ng/Nm3，粒狀物上戴奧辛濃度高於氣相，戴奧辛總毒性當量濃度為3.43 ng I-TEQ/Nm3 ，煙囪處煙道氣戴奧辛的總濃度為 22.50 ng/Nm3 ，戴奧辛的總毒性當量濃度為1.72 ng I-TEQ/Nm3 ，其中粒狀物上戴奧辛毒性當量濃度去除效率(86 %)高於氣相(50 %)，EAF-A電弧爐煉鋼廠戴奧辛灰份之濃度為37.78 ng/g，毒性當量濃度為2.05 ng I-TEQ/g ，EAF-A電弧爐煉鋼廠戴奧辛爐渣之濃度為0.11 ng/g，毒性當量濃度為0.003 ng I-TEQ/g，EAF-A的排放係數為11.62 ng-I-TEQ/kg-鋼胚。 而電弧爐EAF-B百葉窗處煙道氣總戴奧辛的濃度為2.19 ng/Nm3，總戴奧辛的毒性當量濃度為0.14 ng I-TEQ/Nm3 ，在EAF-B一次集塵處煙道氣總戴奧辛的濃度高達2559.67 ng/Nm3 ，其中粒狀物上戴奧辛濃度遠高於氣相(佔99 %)，總戴奧辛的毒性當量濃度96.80 ng I-TEQ/Nm3，電弧爐煉鋼廠戴奧辛灰份之濃度為5.54 ng/g，毒性當量濃度為0.23 ng I-TEQ/g，EAF-B電弧爐煉鋼廠戴奧辛爐渣之濃度為0.09 ng/g，毒性當量濃度為0.002 ng I-TEQ/g，EAF-B的排放係數為7.36 ng-I-TEQ/kg-鋼胚。 EAF-A廠及EAF-B廠不論PCDD或是PCDF其固相百分比均隨著氯數增加而逐漸上升，1,2,3,4,6,7,8-HpCDF，OCDD和OCDF為各氣固相中共同的優勢物種，而2,3,4,7,8-PeCDF其毒性當量濃度百分比在各氣固相中均超過50%。 Many studies indicate that both municipal waste incinerators (MWIs) and the industrial activities containing combustion processes are important sources of PCDD/F emissions. Local studies indicate that dioxin in ambient air originates mainly from electric arc furnaces. Electric arc furnaces (EAFs) have been identified as the major sources of PCDD/F emissions in Taiwan. Two kinds of EAFs including the direct evacuation system and the building evacuation system are selected for measuring the dioxin emission. Results indicate that the PCDD/F concentration of stack gas in EAF-A was 22.50 ng/Nm3, and the total Toxic Equivalent Quantity (TEQ) concentration was 1.72 ng I-TEQ/Nm3. The PCDD/F concentration of stack gas in EAF-B was 2.19 ng/Nm3, and the TEQ concentration was 0.14 ng I-TEQ/Nm3. This result showed that the direct evacuation system emitted more dioxin than the building evacuation system. The other results obtained on gas/particulate partitioning of PCDD/Fs in EAFs indicate that more than 90% in the particulate-phase before the flue gas passed through APCD. The emission factor of EAF-A is 11.62 ng-I-TEQ/kg-product, while 7.36 ng-I-TEQ/kg-product is found for EAF-B. 1,2,3,4,6,7,8-HpCDF, OCDD and OCDF were the major contributors of the dioxin concentrations in each phase and the percentage of PCDD/F in particulate phase increases with the chlorination level of the PCDD/F congeners. The distributions of total Toxic Equivalent Quantity (TEQ) concentrations on 2,3,4,7,8-PeCDF at each sampling site were about 50%. |
