Formation and distribution of dioxins in agglomerated products and emitted dust during iron ore sintering

This study investigated the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in sintered products and emitted dust samples. Four types of iron ores were used in this study and tested in a sinter pot grate. The PCDD/F analysis showed that the PCDD concentrations (0.175-1.415, pg/g, 0.028-0.087 pg WHO-TEQ/g) were higher than the PCDFs (0.105-0.327 pg/ g, 0.006-0.032 pg WHO-TEQ/g) in sinter. In dust samples, three of the four test experiments showed PCDDs < PCDFs in their measured concentrations. Although PCDD/F concentrations were different in sinter and dust samples, the PCBs presented similar behavior in both solid samples. The PCB analysis (pg WHO-TEQ/g) showed that non-ortho PCBs were higher in concentration than the mono-ortho PCBs. The statistical analysis showed significant correlations between low chlorinated PCDD/F congeners and high chlorinated PCDD/F congeners, as well as strong correlations between non-ortho PCBs and mono-ortho PCBs in both sinter and dust samples. However, the dust samples presented stronger and more positive correlations among the PCDD/F and PCB congeners in comparison to corresponding data in sinter samples. The differences in PCDD/F profiles and correlation matrix in sinter and dust samples suggest the dioxin formation during sintering undergos different mechanisms in the sinter and dust samples.