Behavior of trace chlorine in sintering bed and its effect on dioxins concentration in exhaust gas of iron ore sintering

Suppression of dioxins emission for iron ore sintering is one of the most important and urgent needs. To the purpose, the basic research for the title is necessary. Sinter pot tests of sinter mixture adding Cl content were carried out, and the results obtained are as followed. (1) 20-40 mass% of Cl content in sinter mixture stays in sintercake. 20-40 mass% of volatile Cl content traps on raw material in sinter bed, while 60-80 mass% of that discharges to exhaust gas without trapping raw material. Trapped Cl content in raw material of sintering bed partly vaporizes again and partly stays at the sintering reaction. The volatile Cl content is mainly composed of metal-chloride such as NaCl, KCl and etc. (2) Dioxins concentration in exhaust gas is proportional to Cl content added to sinter mix by under 500 mg/kg. Source of Cl content in term of kinds of chemical compound also affects on dioxins concentration in exhaust gas. KCl, poly-vinyl-chloride, NaCl, CaCl₂, high Cl ore are rank in order of much concentration of dioxins. Volatile Cl content and organic content are effective factors of dioxins occurrence. The dioxins concentration in the experimental case of high Cl content at upper layer is more than those in the case of uniform Cl content, but in the case of high Cl content at lower layer the dioxins are as same as those.