Abstract Metal magnesium is mainly produced from the calcined dolomite by the silicothermic production. However, in this process, the reduction temperature is higher while the reaction speed is slow, which results in higher energy consumption and serious environmental problems. In this paper, adding aluminum into the ferrosilicon reducing agent is expected to lower the reaction temperature so as to solve the problems above. The phase transition involved in the whole reduction process including with and without aluminum addition were investigated in details by theoretical calculation and experimental research. The influence of aluminum on the magnesium oxide reduction path was analysis to clarify the internal mechanism. The results show that aluminum added into the ferrosilicon would first react with magnesium oxide to form magnesium vapor and alumina under vacuum pressure of 10 Pa when the temperature rises to 720°C. Then, calcium aluminate would be formed by the reaction of aluminum oxide and calcium oxide. Once the temperature reaches 1150°C, silicon begins to reduce the magnesium oxide to create the silicon oxide that will finally react with calcium oxide to form calcium silicate. When the temperature rises above 1150°C, both the aluminum and silicon will participate in the reduction of magnesium oxide. In the process of heating up, the mixture of aluminum, ferrosilicon and calcined dolomite forms Mg2Al4Si5O18 and Ca3Al2(OH)12 phase with the components in calcined dolomite. Mg2Al4Si5O18 and Ca3Al2(OH)12 phase finally form Ca12Al14O33 phase. The interaction between aluminum and ferrosilicon in the mixture is less; the mixture of aluminum and ferrosilicon first forms Al3FeSi2 phase, and finally has the trend of forming Al4.5FeSi phase. There is a great difference between the phase transformation of aluminum in the mixture of aluminum, ferrosilicon and calcined dolomite and that of aluminum in the mixture of aluminum and ferrosilicon.

中文翻译：

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硅铁与铝添加剂还原煅烧白云石中氧化镁过程中的相变

摘要 金属镁主要以煅烧白云石为原料，采用硅热法生产。但该工艺还原温度较高，反应速度较慢，能耗较高，环境问题严重。本文希望通过在硅铁还原剂中加入铝来降低反应温度来解决上述问题。通过理论计算和实验研究，详细研究了包括加铝和不加铝在内的整个还原过程所涉及的相变。分析铝对氧化镁还原路径的影响，阐明其内在机理。结果表明，在10Pa的真空压力下，当温度升至720℃时，加入硅铁中的铝首先与氧化镁反应生成镁蒸气和氧化铝。然后，氧化铝和氧化钙反应生成铝酸钙。一旦温度达到 1150°C，硅开始还原氧化镁，生成氧化硅，最终与氧化钙反应形成硅酸钙。当温度升高到1150℃以上时，铝和硅都会参与氧化镁的还原。在升温过程中，铝、硅铁和煅烧白云石的混合物与煅烧白云石中的成分形成Mg2Al4Si5O18和Ca3Al2(OH)12相。Mg2Al4Si5O18 和 Ca3Al2(OH)12 相最终形成 Ca12Al14O33 相。混合物中铝和硅铁之间的相互作用较小；铝和硅铁的混合物先形成Al3FeSi2相，最后有形成Al4.5FeSi相的趋势。铝、硅铁和煅烧白云石混合物中铝的相变与铝和硅铁混合物中铝的相变有很大差异。