Characterization of PM, PAHs and Gaseous Pollutants Emitted from Sintering Process and Electric Arc Furnace

Abstract

Iron and steel industry is crucial for economic development. However, large exhaust volume and complex feeding of the steel-making process results in enormous emissions of air pollutants such as particulate matter (PM), sulfur oxides (SO_x), nitrogen oxides (NO_x), polycyclic aromatic hydrocarbon (PAHs) and carbon monoxide (CO). This study sampled and analyzed the concentrations of PM, PAHs, SO_x, NO_x and CO at the inlet and outlet of the air pollution control devices (APCDs) adopted in sintering process (SP) and electric arc furnaces (EAF), respectively, to evaluate the performance of APCDs and emission characteristics of these air pollutants. The results show that filterable PM (FPM) concentrations measured at stacks of SP and EAF are 8.2 ± 1.3 and 13.6 ± 2.2 mg Nm^–3, respectively. The FPM_2.5 concentrations emitted from SP and EAF are 1.8 ± 0.5 and 3.2 ± 1.1 mg Nm^–3, respectively, while the condensable PM (CPM) concentrations emitted from SP and EAF are measured as 37.7 ± 1.3 and 3.4 ± 0.8 mg Nm^–3, respectively. Moreover, the flue gas desulfurization (FGD) and selective catalytic reduction (SCR) equipped in SP removed 82% and 58% of SO_x and NO_x, respectively, whereas SO_x and NO_x emitted from EAF are relatively low (< 1 ppm). The overall PAH removal efficiencies achieved with the APCDs adopted by SP and EAF are 72% and 26%, respectively. For total toxicity equivalency quantity (TEQ) PAH concentrations, similar results for SP (5.45 µg-BaP_eq Nm^–3) and EAF (4.74 µg-BaP_eq Nm^–3) are obtained. Moreover, the diagnosis ratios of FL/CHR, FL/(BaA + CHR), Pyr/5-MC and Pyr/(BaA + CHR) are suggested as the indicators for EAF. The emission factors calculated indicate that operating conditions of the APCDs in the SP investigated are well controlled. The concentrations of air pollutants emitted from SP investigated are lower than other studies. On the other hand, the concentrations of FPM and PM_2.5 emitted from EAF are higher than other studies. However, NO_x, SO_x and PAHs are well controlled. Moreover, the CO emission factors calculated from these two steel-making processes are higher than most reports. Overall, the operation of APCDs should be improved to reduce air pollutants emitted from these two steel-making processes.