铝与硅铁混合物还原煅烧白云石中氧化镁

皮江法炼镁是金属镁生产的主流工艺，该工艺的还原温度较高，导致镁还原过程能耗高，改进还原剂是降低原镁生产能耗的途径之一。本研究以铝和硅铁的混合物作为还原剂进行了煅烧白云石中氧化镁还原的理论和实验研究，探讨了铝配入量、还原时间、还原温度对镁还原率的影响，并对铝与硅铁共同还原氧化镁过程及铝与硅铁在不同温度时的物相转变进行了研究。研究结果表明，铝的加入可以使硅热法还原氧化镁的起始反应温度降低至700℃以下，并且在低温阶段对提高氧化镁的还原率效果明显，铝还原氧化镁的过程包括两方面，一方面是直接参与还原氧化镁而转变为MgO?Al2O3，随温度升高，MgO?Al2O3进一步被铝还原；另一方面铝与硅铁形成Al3FeSi2相，降低了硅参与氧化镁还原反应的温度。硅还原氧化镁的过程为：温度在700~950℃之间时，硅以Al3FeSi2的形式参与氧化镁还原，在1200℃时，以Si和FeSi2的形式进行氧化镁还原。在实验条件下，铝参与硅铁还原镁时，随着铝配入量的增加，氧化镁的还原率在逐渐升高，铝粉添加量为12%、1000℃时，氧化镁的还原率可达到90%以上。铝参与氧化镁的还原可提高镁的还原速率。

Reduction of magnesium oxide in calcined dolomite with a mixture of aluminum and ferrosilicon

The Pidgeon process is the main process of magnesium production. The higher reduction temperature of the silicothermic process results in high energy consumption in the magnesium reduction process. Improving the reducing performance of reducing agents was one of the ways to reduce the energy consumption of metallic magnesium production. The theoretical and experimental research on the reduction of MgO in calcined dolomite was studied by the mixture of aluminum and ferrosilicon as reducing agents. The effects of aluminum dosage, reduction time and temperature on the reduction rate of magnesium were discussed. The reduction process of magnesium oxide and the phase transformation of aluminum and ferrosilicon at different temperatures were studied. The results showed that when aluminum was involved in the reduction of magnesium oxide by silicothermic method, the initial reaction temperature of reduction of MgO by silicothermic method was reduced to below 700℃, and the effect of improving the reduction rate of MgO was obvious in the low-temperature stage. The reduction process of magnesium oxide by aluminum included two aspects. On the one hand, it was directly involved in the reduction of magnesium oxide to MgO?Al2O3. With the increase of temperature, MgO?Al2O3 was further reduced by aluminum. On the other hand, aluminum and ferrosilicon from the Al3FeSi2 phase, which promoted the reduction of silicon and reduced the temperature of silicon participating in the reduction of magnesium oxide. In the presence of aluminum, the reduction process of magnesium oxide by ferrosilicon was as follows: at 700~950℃, silicon participated in a reduction in the form of Al3FeSi2, and at 1200℃, the magnesium oxide was reduced in the form of Si and FeSi2. Under the experimental conditions, when aluminum participated in the reduction of magnesium by ferrosilicon, the reduction rate of magnesium oxide increased gradually with the increase of aluminum dosage. When the aluminum dosage was 12% and 1000℃, the reduction rate of magnesium oxide can reach more than 90%. Aluminum participated in the reduction of MgO to produce alumina, which reactd with CaO and SiO2 in calcined dolomite to produce CaAl2O4, CaAl2Si2O8.