Removal of zinc from dusts and sludges from basic oxygen furnaces in the process of ammoniacal leaching

Abstract

More than 20kg of dust and sludge per 1ton of produced metal are generated in the basic oxygen furnaces used in steel metallurgy. In this type of waste there may be many non-ferrous metals, including also zinc. The content of this metal in dusts ranges from 1 to 6%. After lowering the zinc content to a level of about 1%, such type of waste may become a full-fledged iron-bearing material used in ferrous metallurgy. There is also a possibility to recover and manage the zinc removed from waste materials. Recycling of these materials also reduces the risk to the natural environment, resulting from e.g. the transition of metal compounds contained in stored waste materials into the groundwater and soil. The article presents the results of ammonia leaching of wastes from basic oxygen furnaces where the zinc content is 2.82%. Ammonia leaching allows the turn zinc into the liquid phase with minimal loss of iron in this process. The examinations apply three compounds of ammonia (NH4Cl, (NH4)2CO3 and NH4OH) to analyze the efficiency of the leaching process at different times, temperatures, concentrations of applied compounds and ratios of liquid phase to the solid phase.