Emissions of PCDD/Fs from Steel and Secondary Nonferrous Productions

Abstract

Abstract Emissions of polychlorinated debenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the stack gas, fly ashes of steel and nonferrous productions, including iron ore sintering process (Sinter), electric arc furnace (EAF), secondary copper production (SCu), secondary aluminum production (SAl) and secondary lead production (SPb) were investigated. The concentrations of PCDD/Fs in stack gases of various sources ranging form high to low were as follow: SCu> SAl> EAF> Sinter> SPb, while those in fly ashes were: SCu> SAl> SPb> EAF> Sinter. It is worth noting that the toxic equivalency quantity (TEQ) in fly ash from SCu rotary kiln, at 40352ng TEQ/kg, was relatively higher than the value of municipal waste incinerator fly ashes. Due to the ratio of PCDF/PCDD>1 both in stack gases and fly ashes of this study, the de novo synthesis may be the dominant mechanism of formation of PCDD/Fs in those processes. For PCDD/Fs congeners profiles, 2,3,7,8-TCDF was the most abundant congener in stack gases from Sintering, SCu and SAl, while the major congeners in EAF and SPb were 1,2,3,4,6,7,8-HpCDD and 1,2,3,4,6,7,8- HpCDF, respectively. The emission factors and total emission amounts of PCDD/Fs released to air from these industries were calculated. Noteworthily, the average PCDD/Fs emission factors of secondary copper and aluminum production were 2.94 and 0.291 mg TEQ/ton production, higher than those from other industries. The emission factors of Sinter, EAF, SPb were 800.1, 3160 and 4297 ng TEQ/t, respectively. For the two iron ore sintering machines, the total emission amounts of PCDD/Fs reached 100.49 g TEQ/year. Due to the high emission factors or total emission amounts, eliminating the releases of PCDD/Fs from steel and secondary nonferrous productions should attract more attentions.