Recovery of metal from metal oxide waste by thermit reaction

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An investigation of the reduction of magnesia and chromia by graphite and aluminum was carried out using a nonisothermal gravimetric technique under an argon atmosphere, in a temperature range from 600 to 1973 K. In the case of MgO-C system, the reduction ratio obtained by using charcoal is larger than that by using graphite. An excess charcoal addition increases the reduction ratio. The activation energy is 192.4〜208.1 kJ/mol. The Boudouard reaction has a large influence on the reaction rate. In the case of MgO-Al system, magnesia is reduced by aluminum to form magnesium and spinel at first, and then the excess aluminum reacts with the spinel slowly. The reaction rate is affected by pellet-forming conditions. The activation energy of the reduction of magnesia by aluminum is 151.2 kJ/mol. In the case of Cr_2O_3-C system, the reduction reaction proceeds through two steps. At first, chromia is reduced by graphite to form chromium carbide, and then the rest of chromia by the chromium carbide. The excess graphite addition increases the reduction ratio, but chromium carbide and not chromium is obtained.