CaF2在真空铝热还原炼镁过程中的行为研究

对CaF2在以白云石和菱镁石为原料的铝热还原过程中的行为进行了研究,通过X射线衍射对还原渣和结晶产物的物相进行了分析,对CaF2在铝热还原过程的反应过程以及加速还原反应的机理进行了探讨。实验研究结果表明,在还原过程中加入CaF2可降低还原反应的活化能,加快还原反应速率,可使还原过程中的氧化镁还原率提高3%以上,但添加CaF2的效果随还原温度的升高而降低。加入CaF2后一部分CaF2参与还原反应生成了11CaO.7Al2O3.CaF2,另外一部分CaF2被铝还原在结晶器上生成了一种主要成分为MgF2和Al的结晶物。CaF2对铝热还原反应的促进作用是化学反应促进和提高煅白表面活性共同作用的结果。

Influence of CaF2 Addition on Vacuum Aluminothermic Reduction

Here,we addressed the aluminothermic reduction of dolomite and magnesite in vacuum.The impacts of the vacuum reduction conditions,such as the pressure,addition of CaF2,and reduction temperature and time,on extraction of Mg were experimentally studied,and the reactions were analytically evaluated.The condensate and reduction slag were characterized with X-ray diffraction.The results show that the CaF2 addition significantly improves the MgO reduction ratio(by 3%),possibly because the CaF2 addition reduced the activation energy in the reduction,and speeds up the reduction rate.However,the CaF2 addition slightly lowered the MgO reduction ratio because of an increase of reduction temperature.Some CaF2 was found in the 11CaO·7Al2O3·CaF2 phase;whereas the rest of CaF2 was reduced by Al,forming the MgF2 and Al crystalline composites in the condensate.Possible mechanisms responsible for the enhancement of the MgO reduction ratio were also tentatively discussed.