关键词: 浸取, 转炉渣, 氧压浸出, 动力学, 多相反应

Abstract:

The dissolution kinetics and behavior of cobalt extraction from low nickel matte converter slag by pressure oxidative leaching with sulfuric acid were investigated. The effects of stirring speed, temperature, sulfuric acid concentration, oxygen partial pressure and particle size on extraction rate of cobalt were studied for exploring the kinetics law of cobalt dissolution from the slag. The experimental results showed that the extraction efficiency of cobalt increased with the increases of temperature, sulfuric acid concentration and oxygen partial pressure, but the sulfuric acid concentration above 40 g·L^-1 can cause an increase of iron extensive dissolving in the solution. The stirring speeding above 700 r·min^-1, oxygen partial pressure beyond 650 kPa and particle size of less than 74 mm were found to have no effect on the extraction of cobalt. The dissolution kinetics analysis of the experimental data based on the shrinking core model for various conditions indicated that the reaction rate of leaching was mainly controlled by the chemical reaction during its early stages, then switched to be controlled by mixed chemical-reaction and product-layer diffusion, and finally was controlled solely by diffusion through a surface product layer in the later stage. The activation energy was calculated to be 43.19 kJ·mol^{-1 in the early surface chemical reaction controlled stage and 10.49} kJ·mol^{-1 in the later diffusion controlled stage, respectively. In the chemical reaction controlled stage, the reaction orders with respect to sulfuric acid concentration, oxygen partial pressure and particle size are 0.79, 0.85} and -0.95, respectively.

Key words: leaching, converter slag, pressure oxidative leaching, kinetics, multiphase reaction