Study On Vacuum Carbothermal Reduction Of Magnesium With High Magnesium Silicon Laterite Nickel Ore

With the increasing depletion of nickel sulfide resources available for development and utilization in recent years,the development and utilization of laterite nickel ore has gradually become a focus of attention,and the garnierite has become a top priority due to the higher nickel content.Garnierite is suitable for treatment by the pyrometallurgical process,but there are problems such as large slag production,the high content of magnesium in the slag,and difficulty in secondary utilization.In view of the above problems,the carbothermal reduction in vacuum was used to treat garnierite to remove magnesium,and then recycle it,providing theoretical support for the comprehensive development and utilization of garnierite.The main research results of this article are as follows:（1）The X-ray diffraction analysis,scanning electron microscopy,TG-DSC and other analytical testing methods were used to analyze the thermodynamic properties of garnierite.The thermodynamics of forsterite（Mg₂SiO₄）and refractory（Mg SiO₃）during carbothermal reduction at normal pressure and in vacuum were calculated,and the results showed that under normal pressure conditions,the initial reaction temperature of the two substances was as high as 1700°C or higher;the initial reaction temperature was reduced to 1100-1300°C in vacuum.The results indicated that it is theoretically feasible to treat garnierite by carbothermal reduction in vacuum to remove and collect magnesium from it.（2）An experimental study on carbothermal reduction reaction of garnierite in vacuum showed that:at a mass ratio of mineral/reductant,100:28.3;a reduction temperature,1550°C;a reduction time,120 min;and a system pressure,10-50 Pa.The removal rate of magnesium could reach 93.23%.At the same time,X-ray diffraction analysis showed that the product collected in the condensation system was mainly metal magnesium,and Ni and Fe in the reduction residuum were enriched and could be further used.When CaO was used as an additive,the results of the experiments showed that:when the amount of CaO added was 25 wt%,the removal rate of magnesium increased to 99.45%under the above conditions.The reason is CaO can react with forsterite,and a new phase with a lower melting point is formed,and the appearance of the melt is favorable for the escape of magnesium vapor generated by the carbothermal reduction,thereby promoting the removal of magnesium.（3）The kinetic mechanism of the carbothermal reduction in vacuum is analyzed.The results show that the carbothermal reduction in vacuum of garnierite is controlled by the interface chemical reaction,which is in line with the two-dimensional interface chemical reaction control model,whose kinetic equation is:1-（1-a）^1/2=(-20682.988^1/7+1.702)t,the apparent activation energy is E_a=1.720×10⁵ J/mol,the pre-finger factor is K₀=5.484 s^-1.