Production practice of zinc powder replacement Ga and Ge slag by pressure oxidation leaching

The paper introduces production practice of gallium, germanium and copper leaching from zinc powder replacement residue for comprehensive recovery of valuable metals in Danxia Smelter. The leaching process was designed with pretreatment of replacement residue with oxidation roasting, two stage countercurrent oxygen pressure leaching, single stage conventional leaching and separate mixed acid leaching. The design of leaching rates of gallium, germanium and copper were 94%, 94% and 95%, respectively. During trial production in 2017, their leaching rates were 94.06%, 59.37% and 98.90%, respectively. After analyzing the composition and leaching mechanism of replacement residue, the design process was optimized and improved based on the principle of minimum chemical reactivity by cancelling oxidation roasting, strengthening the second oxygen pressure reaction condition and inhibiting the formation of silica gel in solution. The annual average leaching rate of germanium increased from 59.37% in 2017 to 75.35% in 2019 and the leaching rates of gallium and copper increased by 0.75% and 0.12% respectively. After optimization, it was expected to save 3.55 million yuan in production costs in a year, with the process streamlined, and the production site safer and greener.