摘要
In this study,the formation mechanism and removal efficiency of polychlorinated dibenzo-p-dioxins, dibenzofurans（PCDD/Fs） achieved with bag filter（BF） in an electric arc furnace（EAF） in Taiwan is evaluated via intensive stack sampling and analysis.The results indicate that the PCDD/F concentration measured in the stack gas of the EAF investigated was 0.16 ng I-TEQ/m1,which was significantly lower than the PCDD/F emission limit（0.5 ng I-TEQ/m;） set for existing EAFs in Taiwan.Due to the low operating temperature（<60℃） of the BF adopted by the EAF investigated,76%of total toxicity PCDD/Fs could be removed from the flue gas stream. In addition,the partitioning of PCDD/Fs between vapor and solid phase at different locations in EAF did not change significantly,while a reduction of solid-phase PCDD/Fs was observed at the outlet of BF.As the chlorination level of PCDD/Fs congener increases,the vapor pressure of PCDD/F congener decreases,resulting in the increase of PCDD/Fs existing in solid phase.Hence,the removal efficiencies of highly chlorinated congeners were significantly higher than that of lowly chlorinated congeners.PCDFs accounted for more than 85%of the TEQ in flue gas of the EAF investigated,among them 2,3,4,7,8-PeCDF（> 43%） was of the highest contribution.Overall,2,3,7,8-TCDD,2,3,7,8-TCDF and 2,3,4,7,8-PeCDF can serve as the unique congeners in the flue gas of the stainless steel EAF process.
In this study,the formation mechanism and removal efficiency of polychlorinated dibenzo-p-dioxins, dibenzofurans(PCDD/Fs) achieved with bag filter(BF) in an electric arc furnace(EAF) in Taiwan is evaluated via intensive stack sampling and analysis.The results indicate that the PCDD/F concentration measured in the stack gas of the EAF investigated was 0.16 ng I-TEQ/m1,which was significantly lower than the PCDD/F emission limit(0.5 ng I-TEQ/m^3) set for existing EAFs in Taiwan.Due to the low operating temperature(<60℃) of the BF adopted by the EAF investigated,76%of total toxicity PCDD/Fs could be removed from the flue gas stream. In addition,the partitioning of PCDD/Fs between vapor and solid phase at different locations in EAF did not change significantly,while a reduction of solid-phase PCDD/Fs was observed at the outlet of BF.As the chlorination level of PCDD/Fs congener increases,the vapor pressure of PCDD/F congener decreases,resulting in the increase of PCDD/Fs existing in solid phase.Hence,the removal efficiencies of highly chlorinated congeners were significantly higher than that of lowly chlorinated congeners.PCDFs accounted for more than 85%of the TEQ in flue gas of the EAF investigated,among them 2,3,4,7,8-PeCDF(> 43%) was of the highest contribution.Overall,2,3,7,8-TCDD,2,3,7,8-TCDF and 2,3,4,7,8-PeCDF can serve as the unique congeners in the flue gas of the stainless steel EAF process.
