Behavior of magnesium in saprolite nickel laterite by carbothermic reduction in vacuum

The thermodynamic of vacuum carbothermic reduction of Yuanjiang saprolite nickel laterite and the mineral phases transformation and the volatilization and condensation mechanisms of Mg were researched, and the vacuum carbothermic reduction behavior of Mg in saprolite nickel laterite was also researched by means of XRD, SEM-EDS and chemical composition analysis. The results show that the reaction between MgO and C is solid-state reduction in vacuum and the critical temperature is 1467 K. The reduction Mg will extremely volatilized, and desublimated in condensing system. The SiC, Fe-Si alloy, Mg2SiO4, Mg and SiO are found during the reduction processes, and then the SiO disproportionates into Si and SiO2 in the condensing system. With the increases of temperature, carbon content and reaction time, the reduction ratio of Mg increases significantly; The catalytic effect are different from the kinds of additives, especially, CaO and CaF2 have better catalytic effect than other additives. Mg reacted with CO, O2 and Si transforms into MgO or Mg2Si in condensing system at low temperature, in which the purity of Mg metal decreases.