红土镍矿真空碳热还原过程中镁的行为

摘要

以云南元江红土镍矿为研究对象,采用XRD,EM-EDS和化学成分分析等手段,研究红土镍矿真空碳热还原反应的热力学、还原产物的物相转变和金属镁的挥发冷凝机理,探讨红土镍矿真空碳热还原过程中镁的行为.实验结果表明:真空中氧化镁的还原是固体碳直接还原的固-固反应,临界反应温度为1 476 K,生成的金属镁极易挥发,在冷凝系统凝华收集;还原产物主要有SiC,Fe-Si合金,Mg2SiO4,Mg和SiO气体;SiO在冷凝系统生成Si和SiO2;反应温度的升高、还原煤用量的增加和反应时间的延长,镁的还原率都显著增大;不同种类的添加剂催化效果不同,CaO和CaF2的催化效果较好:在温度较低的冷凝系统,Mg容易与CO,O2和Si发生反应生成MgO和Mg2Si,影响金属镁的纯度.%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 1 467 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.