Characteristics of PCDD/F Emissions from Electric Arc Furnaces in Taiwan

摘要

Electric arc furnaces (EAFs) have been identified as major sources of PCDD (polychlorinated dibenzo-p-dioxin) and PCDF (polychlorinated dibenzofuran) emissions in Taiwan. Two typical emission types of EAFs including the stack system (EAF-A) and the shutter system (EAF-B) are selected for measuring PCDD/F emission in this study. Results indicate that PCDD/F concentration of stack gas in EAF-A was 20.51 ng/Nm3, and the total Toxic Equivalent Quantity (TEQ) concentration was 1.47 ng I-TEQ/Nm3. The PCDD/F concentration of stack gas in EAF-B was 2.19 ng/Nm3 while the TEQ concentration was 0.14 ng I-TEQ/Nm3. The results obtained on gas/particalate partitioning of PCDD/Fs in EAFs indicate that more than 90% existing in paniculate phase before the flue gas entering APCD. This results in high removal efficiency (88%) achieved by APCDs for particulate-phase PCDD/Fs, while the average removal efficiency for gas-phase PCDD/Fs is only about 38%. OCDF is the major distributor at all sampling sites in EAE-A and EAF-B. Besides, the percentage of particulate-phase PCDD/Fs decreases sharply as the flue gas passes through the APCDs due to the high removal efficiency (over 95%) achieved with BF for particulate matter.