Behaviour of Silicon in Nickel Laterite by Carbothermic Reduction in Vacuum

The carbonthermal reduction of high Mg-Si nickel laterite was studied under vacuum. The effects of adding calcium oxide and the reducing agent on the reduction of silicon in residue were studied at pressures of 10-200 Pa and different temperatures, with varying proportions of carbon and CaO. The analysis of the residue was performed using X-ray diffraction and chemical composition analysis. The results show the following: At 1350 degrees C with a C/O ratio of 1.5:1, the recovery of Si reached a maximum 71.09%. Under these conditions, Si exists mainly in the forms of Fe3Si, Fe2Si, FeSi and SiC. The recovery of Si was above 80% when the temperature was 1450 degrees C, the C/O ratio 1:1, and 15% addition of CaO. When CaO addition was 22.61%, all of the solid phase was Ca2SiO4.