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本文对煅白真空碳热还原法制取镁反应过程进行了热力学分析,在系统压力30~100 Pa,还原温度1573 K条件下,C与MgO反应生成镁蒸气;温度达到1667 K时,C与CaO反应生成CaC2,在此温度条件下,CaC2也可与MgO反应生成镁蒸气。因此,煅白真空碳热还原法制取镁的过程,除了C直接还原MgO,还有C还原CaO生成CaC2参与还原反应制取镁。另外,通过热力学计算,真空条件下,碳热还原过程中3CaO·SiO2,2CaO·SiO2,SiC和CaS是可以产生的,而煤中的硫酸钙和单质硫主要参与了生成CaS的反应。实验结果分析表明:3CaO·SiO2,2CaO·SiO2,SiC和CaS产物的生成与剩余物的X射线衍射(XRD)分析相吻合,验证了热力学计算的正确性。通过对冷凝物的XRD分析,冷凝物中大部分为Mg,有少部分的MgO是由于金属Mg和CO蒸气发生逆反应所得。
In this paper, the thermodynamics of Mg reaction in calcined white vacuum carbothermal reduction was investigated. Under the conditions of system pressure 30 ~ 100 Pa and reduction temperature 1573 K, C reacts with MgO to form magnesium vapor. When the temperature reaches 1667 K, C and CaO The reaction generates CaC2, at this temperature, CaC2 also reacts with MgO to form magnesium vapor. Therefore, calcined white vacuum carbothermal reduction of magnesium preparation process, in addition to C direct reduction of MgO, and C reduction CaO CaC2 involved in the reduction reaction of magnesium. In addition, through the thermodynamic calculation, 3CaO · SiO2, 2CaO · SiO2, SiC and CaS can be produced during the carbothermal reduction process under vacuum, and the calcium sulfate and elemental sulfur in the coal are mainly involved in the reaction for CaS generation. The experimental results show that the formation of 3CaO · SiO2, 2CaO · SiO2, SiC and CaS products are consistent with the XRD analysis of the residue, which verifies the correctness of the thermodynamic calculation. By XRD analysis of the condensate, the majority of the condensate is Mg, and a small portion of the MgO is due to the reverse reaction of the metal Mg and CO vapors.