Study on the reaction mechanism of multi-source metallurgical dust for zinc extraction and iron enrichment

Abstract

Multi-source metallurgical dust can realize the purpose of zinc extraction and iron enrichment by high-temperature reduction. In this paper, based on the zinc extraction and iron enrichment from multi-source metallurgical dust in rotary kiln process, thermodynamic calculations and reduction kinetic experiments were carried out to clarify the thermodynamic conditions and kinetic limiting factors of the reduction of Fe-Zn-C-O system of metallurgical dust, and to obtain the suitable parameters of reduction temperature and reaction time, etc. The results showed that Fe mainly existed in the form of Fe₂O₃ and Fe₃O₄ in metallurgical dust. Zn mainly existed in the form of ZnO and ZnFe₂O₄, with a small amount existed in ZnS. The starting temperatures of the reduction of ZnO, ZnFe₂O₄, ZnS with C were 951.09 °C, 581.55 °C and 1862.44 °C, respectively. Combined with the temperature of the smelting condition of rotary kiln, it was known that the presence of ZnS was the key factor leading to the limitation of zinc removal rate. ZnO and ZnFe₂O₄ showed higher reduction difficulty compared to iron oxides, so the metallization rate of rotary kiln slag could be improved by controlling the smelting atmosphere. The weight loss rate, metallization rate and dezincification rate of multi-source metallurgical dust showed an increasing trend with the change of temperature and time, and the more desirable effect of weight loss rate, metallization rate and dezincification rate were 46.7%, 87.1%, and 92.5% under laboratory conditions at reduction temperature 1100 °C and reaction time 50 min.