Recovery of metal from metal oxide waste by thermit reaction

在600~1973K温度范围内，用非等温热重法研究了石墨和铝在Ar气氛中还原氧化镁和氧化铬的反应。在MgO-C体系中，木炭的还原比大于石墨的还原。过量的木炭添加会增加还原比。活化能为192.4~208.1 kJ/m o l。Boudouard反应对反应速率有很大影响。在镁铝系中，氧化镁首先被铝还原成镁和尖晶石，然后过剩的铝与尖晶石发生缓慢的反应。反应速度受造粒条件的影响。铝还原氧化镁的活化能为151.2 kJ/m o l。在Cr2O3C体系中，还原反应分两步进行。首先，铬被石墨还原成碳化铬，然后剩下的铬被碳化铬还原。过量的石墨增加了还原比，但得到的是碳化铬而不是铬。

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.