Characteristic of zinc ferrite decomposition by calcium and magnesium oxides

Abstract

Electric arc furnace (EAF) dust generated in steelmaking is a valuable waste material with high content of zinc, lead and iron. Recovery of zinc by current industrial hydrometallurgical methods at zinc plants is difficult due to the presence of zinc in the hardly soluble ferrite form and high contents of chlorine and fluorine that are harmful impurities for further electrolysis. To decompose zinc ferrite and remove halogens from EAF dust there is a promising approach that promote zinc ferrite decomposition to highly soluble zinc oxide and volatilization of halogens in one pyrometallurgical stage, where EAF dust are calcined with lime at 900-1100°C. This paper aims to investigatekinetics of the reaction between pure ZnFe2O4 and CaO to determine its controlling step and evaluate its characteristics. The reaction between pure ZnFe2O4 and MgO is also considered. The investigation of the EAF dust sample has confirmed that majority of zinc is in the form of hardly soluble ferrite. The results of experiments have shown that the reaction of zinc ferrite with calcium oxide at 900-1000°C is kinetic controlled, so temperature has a significant effect of on the reaction rate. The degree of conversion of the reaction between zinc ferrite and magnesium oxide is negligible, so the application of MgO during the EAF dust processing is inexpedientat the studied temperatures.