The Research Of Vacuum Carbonthermal Reduction-Magnetic Separation Technology For Garnierite

As the main alloying element of stainless steel, nickel hans become one of the most important metal nowaday. With decreasing of sulfide nickel resources, we must develop a new technology to treat the laterite, which accounted for 70% of total nickel reserves. For dealing with the pollution caused by magnesium, we have developed a new technology as vacuum carbonthermal reduction-magnetic separation process of garnierite, and get the following conclusion:The research of properties of nickel laterite ore showed that the adsorption, crystallization and structural water are removaled at 103.4℃,581.7℃ and 794.2℃ respectively. When the pretreatment temperature was higher than 800℃, the product of forsterite (Mg2SiO4) gradually increased, and the activity of magnesium is decreased. The reduction rate of magnesium was 96.06% at 1200℃ pretreatment.In the process of vacuum carbothermal reduction of laterite, we could get magnesium bulk in condensate. But in the condensation process, the metal magnesium vapor and CO reverse reaction occurs, but also with the volatile SiO the disproportionation product Si reacts Mg2Si.In the process of vacuum distillation of crude magnesium, in the temperature range, the removal rate of silicon was greater than 99%. But as the temperature rised, the removal rate of calcium decreased, decreased from 97.84% to 93.87%. Therefore, the best temperature of the vacuum distillation was 823K.The research of effect of carbon ratio on carbonthermal reduction of nickel laterite at vacuum showed that the direct recovery of silicon were the obvious rise with the carbon ratio, and the direct recovery of iron and nickel was also corresponding rised. The maximum direct recovery of Fe and Ni was 97.82% and 98.18% respectively when the carbon ratio was 1.5 under 1350℃.The research of additive CaO reinforced carbonthermal reduction of nickel laterite under vacuum shows that with the increase of CaO addition amount, the recovery of Si, Fe, Ni were also will increased. when added amount of CaO was larger than 20%, the recovery of Si was higher than 80%, and the recovery of Fe and Ni were higher than 96%. With the increase of CaO, slag phase appeared Ca2SiO4 and metal Fe phase, the FeSi alloy phase diffraction intensity gradually weakened, it can make better separation of iron-nickel and silicon via magnetic separation.The research of magnetic separation of slag experimental showed that with the increase of CaO addition amount, the content of silicon and calcium were gradually reduce, and the content of iron and nickel enrichment ratio gradually increases. When the amount of CaO was 22.64%, the enrichment ratio of iron and nickel were maximum, reached 6.32 times and 6.72 times respectively. The recovery of iron and nickel was 90% or more at the magnetic separation process.For the whole process of carbon thermal reduction-magnetic separation for nickel laterite, the recovery of iron was greater than 84%, the maximum recovery was 92.54% when the amount of CaO was 20%; the recovery of nickel was greater than 90%, the maximum recovery was 97.27% when the amount of CaO was 14.16%The process of multipurpose utilization of valuable metals from garnierite solved the pollution caused by magnesium.And this process had good value for industrialization.