Abstract: A method separating magnesium and boron from ascharite by vacuum thermal reduction using calcium carbide as redutant was studied experimentally. The reason that led to low reduction ratio of MgO in the vacuum thermal reduction process was researched by phase analysis of calcined ascharite and the influencing factors were analyzed. The results show that magnesium in the calcined ascharite is mainly involved in magnesium borate and magnesium silicate, reduction of which is difficult and only small amount is free state of MgO, which is the main cause of low reduction ratio. The addition of CaO during calcination of ascharite can promote formation of more free state MgO and reduction of more MgO. As long as enough CaO is added, magnesium and boron can be effectively separated and reduction rate can be over 85%. The main phases in reduction slag are CaO and 3CaO·B₂O₃. The reduction slag can be used as raw material for production of alkali free glass fiber. So the comprehensive utilization of ascharite ore can be realized.

Key words: separation, ascharite ore, reduction, magnesium, phase change

摘要： 对以硼镁石为原料，以碳化钙为还原剂的真空热还原炼镁以实现硼镁分离进行了研究，通过对煅烧后的物料进行物相分析，对碳化钙还原硼镁石过程中氧化镁还原率较低的原因进行了分析，并对还原过程中影响氧化镁还原率的因素进行了探讨。研究结果表明：以硼镁石为原料进行煅烧后获得的煅后硼镁石的氧化镁主要以硼酸镁和硅酸镁化合物的形式存在，游离的氧化镁较少是导致还原过程中氧化镁还原率较低的主要原因。在煅烧过程中添加氧化钙可使以化合物形式存在的氧化镁游离出来大幅增加氧化镁的还原率。在煅烧过程中配入氧化钙后进行真空热还原炼镁可有效实现硼镁石中的硼镁分离，其还原过程中的氧化镁还原率可达85%以上，还原后获得的还原渣主要物相为CaO和3CaO·B₂O₃，可作为生产无碱玻璃纤维的原料，能够实现硼镁石的综合利用。

关键词: 分离, 硼镁石, 还原, 镁, 相变