Dioxins from thermal and metallurgical processes: recent studies for the iron and steel industry

• Published in: Chemosphere (Oxford) Vol. 42; no. 5; pp. 729 - 735
• Main Authors: Buekens, A., Stieglitz, L., Hell, K., Huang, H., Segers, P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2001; Elsevier
• Subjects: Applied sciences; Atmospheric pollution; De novo synthesis; Exact sciences and technology; Inhibition; Iron ore sintering; Other pollution sources in industry; PCB; PCBz; PCDD; PCDF; PCPh; Pollution; Pollution control; Pollution sources. Measurement results; Thermal metallurgical processes; PCDF; Iron ore sintering; Thermal metallurgical processes; PCDD; Pollution control; De novo synthesis; Inhibition; PCBz; PCPh; PCB; Chlorine Organic compounds; Pollution prevention; Pollutant formation; Metallurgical industry; Air pollution; Steelmaking plant; Polychlorobiphenyl; Pollutant emission
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/S0045-6535(00)00247-2

In thermal metallurgical processes such as iron ore sintering and metal smelting operations, large flows of off-gases are generated. Mainly due to residue recycling in such processes, chlorine and volatile organics are always present in the feed. As a consequence of “de novo” formation, the off-gases from such processes typically contain dioxins in the range 0.3–30 ng I-TEQ/Nm 3. So far there are only very few studies about the mechanisms of dioxin formation and destruction in these metallurgical processes. In an European Union (EU) research project “Minimization of dioxins in thermal industrial processes: mechanisms, monitoring and abatement (MINIDIP)”, integrated iron and steel plant has been selected as one of the industrial sectors for further investigation. A large number of particulate samples (feed, belt siftings, electrofilter) were collected from the iron ore sintering installations from various steel plants and analyzed for their organochlorocompound contents. Measurable amounts of PCDD/F, PCBz, PCB were found for all samples. The various parameters influencing their de novo synthesis activity were also evaluated in laboratory experiments, and such activity was found to be moderate for samples from the ore sinter belt, but extremely high for some ESP dusts. Fine dust is active in a wide range of temperatures starting at 200°C and declining above 450°C; the optimal temperature for de novo synthesis was found to be around 350°C; some inhibitors, such as triethanolamine, may reduce de novo activity by 50 %, and lowering the O 2 concentration in the gas stream leads to a much lower amount of PCDD/F formation. On the basis of their relative mass, typical operating conditions and specific activity of the different samples, the regions in the sintering plant where de novo synthesis may take place were tentatively established.