以铁品位70.25%、SiO2含量1.86%的铁精矿为原料，探究添加剂（CaO、Na2CO3、Na2SO4）对铁精矿制备还原铁粉的影响。采用热力学计算对添加剂与硅酸亚铁（Fe2SiO4）的反应进行了分析，其中CaO与Fe2SiO4反应的热力学条件最佳，反应起始温度最低为650 K。随后在1423 K下，研究了添加剂对碳-氢两步法还原铁精矿的影响。添加Na2CO3效果最佳，铁精矿粉经两步法还原、磁选后，所得产物中的T. Fe含量高达98.32%，SiO2含量低至0.93%；而添加CaO的产物中的T. Fe含量为93.27%，SiO2为1.65%。添加CaO可以抑制Fe2SiO4的生成，但由于金属铁将Ca与Si形成的新相（3CaO?SiO2）包裹在中心，使其通过磁选难以去除。
The effect of additives (CaO, Na2CO3, Na2SO4) on the preparation of reduced iron powder from iron concentrate containing 70.25% Fe and 1.86% SiO2 was investigated. The thermodynamics calculation of the reactions between additives and ferrous silicate (Fe2SiO4) was analyzed. The optimum additive is CaO deduced from the thermodynamic analysis for the beginning temperature of reaction is the lowest of 650 K. Then the effects of additives on the preparation of reduced iron powder were investigated by the experiment: two-step carbon-hydrogen reduction of iron concentrate at 1423 K. The results indicated that adding Na2CO3 increased the T. Fe content of the reduced iron powder to 98.32%. Adding CaO dropped the T. Fe content to 93.27%, and the SiO2 content was declined to 1.65%. The additive (CaO) can inhibit the formation of Fe2SiO4, but a new phase (3CaO?SiO2) which was composite of Ca and Si was wrapped in metallic iron. The wrapped structure contributed to the hard removal of Si.
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