Study On Extraction Technology Of Nickel From Laterite Ores

This paper mainly examines nickel extraction from nickel laterite ores by reduction roasting-magnetic separation process and atmospheric acid leaching process. Technological mineralogy research for these ores was conducted. The scheme of producing nickel sulfate and ferric oxide by leaching and separation was investigated. And the kinetics and mechanism of atmospheric acid leaching of nickel were also discussed.Technological mineralogy research indicates that these ores mainly consist of ferric oxide minerals, occupying63%, such as limonite. Nickel and iron are two kinds of valuable metals which could be extracted, with grades of1.27%and39.93%. No nickel has been discovered in independent nickel mineral and nickel is dispersed in various minerals of the ores.Reduction roasting-magnetic separation test were carried out. The optimum conditions for reduction roasting are as follows:20%coal addition of the ores (g/g), temperature1100℃, roasting time2h. After roasting and milling, the products were separated by magnetic field with intensity of1000e and75.73%recovery of the magnetic concentrates could be obtained with grades of1.62%Ni and47.98%Fe. The recoveries of nickel and iron are87.99%and80.02%, respectively.The research which put emphasis on atmospheric sulfuric acid leaching of the ores was carried out. And the results show that91.95%Ni leaching recovery,99.04%Ni extracting rate,97.52%Ni stripping rate and86.34%Ni total recovery could be obtained by the process of "atmospheric sulfuric acid leaching-Fe precipitated by sodium jarosite-solvent extraction". In this process, Fe leaching recovery is67.96%and after Fe being precipitated by sodium jarosite and roasted, iron oxide products containing55%Fe have been obtained with the total recovery of58.42%.Widely adopted shrinking core model was used to simulate the kinetics equations for nickel atmospheric acid leaching, while Avrami equation could be more satisfactorily fitted. This process is controlled by both interface chemical reaction and solid membrane diffusion, with the activation energy of Ni leaching reaction of29.00kJ/mol.