China Nonferrous Metallurgy

Low-grade oxidized lead‐zinc ores are characterized by complex ore structure， low lead and zinc grades， high oxidation rate， high mud content， and fine particle size. The separation and enrichment of valuable metals via mineral processing technologies face challenges including high processing costs and low separation efficiency. Current literature on the processing of such ores still exhibits limitations such as small processing capacity and difficulty in meeting environmental protection requirements. This paper studied the comprehensive utilisation of a complex， low-grade， oxidized lead-zinc ore in Yunnan Province. The rotary kiln reduction process was used to investigate the impact of important smelting parameters， such as reaction temperature， coal ratio and reaction time， on the behaviour of volatile metals， such as lead， zinc， germanium and silver， during recovery. Combining FactSage thermodynamic calculations with XRD， SEM-EDS， ICP， and other analytical methods， the study revealed the phase evolution rules during the reduction process and the key mechanisms affecting metal volatilisation efficiency. Under the optimised conditions of 1 200℃ and a coal ratio of 20%， the zinc volatilisation rate reached 97. 40%， whereas the lead volatilisation rate was only 47. 87%. Germanium in the raw ore enters smoke dust via the reduction volatilisation process， whereas silver is primarily present in slag. Phase analysis indicates that， at high temperatures， the iron and lead sulfide phases are closely combined due to good wettability， which significantly inhibits the further volatilization of lead. Further exploration of the preoxidation-reduction volatilisation combined process could improve the recovery efficiency of lead and enhance the comprehensive utilisation level of such difficult-to-process resources.