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

摘要：

研究了转炉渣中钴氧压硫酸体系选择性浸出过程的行为及其动力学。通过改变搅拌速度、反应温度、硫酸浓度、氧分压、物料粒度以及反应时间等浸出条件,考察钴浸出率的变化及影响,获得转炉渣中钴的浸出动力学规律。结果表明,钴的浸出率随着温度、酸度、氧分压的增加而增加;硫酸质量浓度大于0.4 mol·L^-1会导致铁大量溶出;浸出过程符合未反应芯收缩核模型,前期受化学反应控制,然后转变为混合控制,后期受固体产物层扩散控制。化学反应控制和固体产物层扩散控制过程的活化能分别为43.19 kJ·mol^-1 和10.49 kJ·mol^-1。化学反应控制过程对硫酸浓度、氧分压及粒度的反应级数分别为0.79、0.85和 -0.95。

关键词: 浸取, 转炉渣, 氧压浸出, 动力学, 多相反应