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为了解红土镍矿在真空碳热还原过程中SiO2的还原特性和还原过程的主要影响因素,在系统压力2～200 Pa下,以分析纯的SiO2、Fe2O3以及煤炭为原料,在热力学分析的基础上,采用X射线衍射、扫描电子显微镜-能量散射谱和化学成分分析等手段,研究了Fe/Si摩尔比、配碳量对SiO2还原过程、硅的挥发率和还原反应速率的影响。通过热力学计算,得出Fe,Si氧化物被碳还原的化学反应自由能和还原反应临界温度,表明在100 Pa条件下SiO2的临界反应温度降低了477～584 K。实验结果表明:Fe/Si摩尔比的增大和配碳量的增加,均降低了Si的挥发率,提高了SiO2还原反应速率;SiO2发生了气化反应生成了SiO气体并在石墨冷凝系统歧化生成Si和SiO2,且有部分SiO气体与石墨或者CO反应生成SiC;反应残渣中的石英颗粒被Fe-Si合金和SiC包围,结合紧密。
In order to understand the reduction characteristics of SiO2 and the main influencing factors of the reduction process of laterite nickel ore in vacuum carbothermal reduction process, under the condition of system pressure of 2 ~ 200Pa, using analytically pure SiO2, Fe2O3 and coal as raw materials, based on the basis of thermodynamic analysis , The effect of Fe / Si molar ratio and carbon content on the reduction of SiO2, the volatilization rate of silicon and the reduction reaction rate were investigated by X-ray diffraction, scanning electron microscopy-energy dispersive spectroscopy and chemical composition analysis. Through the thermodynamic calculation, the free energy of chemical reaction of reduction of Fe and Si by carbon and the critical temperature of reduction reaction are obtained, which shows that the critical reaction temperature of SiO2 decreases by 477-584 K at 100 Pa. The experimental results show that the increase of molar ratio of Fe / Si and the increase of carbon content all decrease the volatilization rate of Si, and increase the reduction rate of SiO2. SiO2 gasification reaction produces SiO gas and disproportionation of graphite condensation system Si and SiO2, and part of the SiO gas reacts with graphite or CO to form SiC. The quartz particles in the reaction residue are surrounded by Fe-Si alloy and SiC and are tightly bonded.