Magnesium Production by Vacuum Aluminothermic Reduction of a Mixture of Calcined Dolomite and Calcined Magnesite

A new method of magnesium production was proposed that using a mixture of calcined dolomite and calcined magnesite as raw materials with the molar ratio of MgO to CaO was 6:1 by vacuum aluminothermic reduction. The reduction process was studied by thermodynamic analysis and X-ray diffraction analysis of reduction residue. The reaction of reduction process was CaO+6MgO+4Al=CaO•2Al₂O₃+6Mg. The effect of briquetting pressure, reduction temperature, time and CaF₂ (MgF₂) on reduction ratio of MgO was investigated. And the reduction residue that the main phase of CaO•2Al₂O₃ was leached in alkaline solution for producing sodium aluminateme raw material for special alumina. The results show that the reduction ratio is increased with increasing of the temperature, time, briquetting pressure in range from 40 to 100 MPa and addition of CaF₂ or MgF₂ in range from 0 to 3%. The alumina leaching ratio of reduction residue reached 88% at the conditions of leaching temperature 95 °C and the concentration ratio of Na₂CO₃ to NaOH was 100:75 in leaching solution.