The condition of high-SiO2 dolomite unfavorable for the magnesium production at the silicothermic process by thermodynamic was investigated. The thermodynamics analysis was used to study the processes of the dolomite calcination and the magnesium production by reduction, and ArGe - T relations of the chemical reactions involving SiO2 were obtained. The results show that the effect of SiO2 is the formation of 2CaOSiO2 in the final calcined dolomite, which reduce the CaO. The reactions involving SiO2 in the calcination process are complex and several intermediate product, such as 2MgOSi02, 2CaOSiO2 and 3CaOMgO-2SiO2 form. With the increase of SiO2 in dolomite, the magnesium output sharply decreases, and the decrease is about 4 times of the SiO2 content when SiO2 is less than 4%.%采用热力学方法针对西南地区的白云石SiO2含量偏高不利于硅热法炼镁的情况进行研究.对硅热法炼镁工艺的白云石煅烧过程和真空还原过程的物料体系进行热力学分析,得到各体系中有SiO2参与化学反应的ΔrGθ -T关系.结果表明:SiO2对炼镁结果的影响在于其在白云石煅烧过程的最后阶段会消耗CaO生成2CaO·SiO2;然而该过程中SiO2参与的反应很复杂,并可能生成多种硅化合物(2MgO·SiO2、2CaO·SiO2和3CaO·MgO·2SiO2).计算表明:随着白云石中SiO2的增多,单罐镁产量急剧减少；当SiO2含量小于4％时,减少量约为SiO2含量的4倍.
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