China Nonferrous Metallurgy

Secondary Zn is mainly concentrated in smelting dust and slag, featuring a low grade of Zn and other complex composition. Utilization of secondary Zn refers to recovering valuable metals from it as much as possible. The process of secondary Zn recovery comprises phase restructuring of raw materials and slag and comprehensive hydrometallurgical recovery. The former includes rotary kiln process and fuming furnace process while the latter includes conventional processes, F and Cl removal process, extraction process in chloride salt system and process in alkaline system. This paper elaborates on all relevant processes, analyzes their pros and cons, and points out that phase restructuring only provides favorable conditions for valuable metal recovery and should be coupled with the hydrometallurgical recovery process to realize valuable metal recovery. F and Cl are still main factors affecting hydrometallurgical recovery process of secondary Zn. One single method cannot achieve economical and complete removal of F and Cl, and thus various methods should be integrated and reasonably designed for process optimization.