China Nonferrous Metallurgy

In China, zinc smelting is mainly based on the traditional "roastingleachingpurificationelectrolysiscasting" process. Due to the lack of zinc resources, the raw material for zinc smelting is mainly high iron sphalerite. In the process of smelting, zinc ferrite is inevitably generated. Due to the relatively stable nature of zinc ferrite, the leaching rate of zinc is reduced, which not only wastes zinc and iron resources, but also seriously pollutes the environment. Based on the above, zinc concentrate of a zinc smelter in Guangxi is taken as the research object, and the process of carbon roastingleaching is adopted to reduce ferric ion into ferrous ion, so as to prevent the generation of zinc ferrite and improve the leaching rate of zinc. The characteristics of raw materials were analyzed by determining element content with Xray fluorescence spectrum (XRF). The effects of proportion of carbon, roasting temperature, roasting time, type of carbon and leaching method on the leaching rate were studied in order to determine the optimal process conditions of carbon roastingleaching. The study results show that the best process conditions of zinc concentrate roasting with carbon are as follows: roasting temperature 950℃, roasting time 1.5h, carbon ratio 3%, under the above conditions, the leaching rate of 84.39% can be obtained by using activated carbon, the leaching rate of carbonfree roastingleaching is only 65.32%; the ferric ion can be reduced into ferrous ion by roasting with carbon, which can effectively prevent the formation of zinc ferrite and improve the leaching rate of zinc; by acid reverse leaching, the leaching rate of zinc with reduced coal can reach 78.42%, which is much lower than that of conventional leaching, therefore, the conventional leaching process is more suitable for the carbon roastingleaching process than the acid reverse leaching process.