ABSTRACT

Additives play an important role in the recycling of complex refractory iron ore by coal-based reduction to improve the self-sufficiency rate of the ore. In this work, the influence mechanisms of CaF₂, Na₂CO₃, and MgCO₃ additives on the coal-based reduction of complex refractory iron ore were studied by x-ray diffraction, thermogravimetry and differential scanning calorimetry, scanning electron microscopy, and energy dispersive spectrometry. The results indicate the three additives could greatly improve the quality of reduction and magnetic separation products. A reduction product metallization degree 93.42%, iron grade 91.23%, and iron recovery 95.48% were obtained under conditions of CaF₂ dosage 6%, reduction temperature 1225 °C, and reduction time 50 min. These results were 3.38%, 8.09%, and 0.39% higher, respectively, than could be obtained without additives. The CaF₂, and the Na₂O and MgO produced by the decomposition of Na₂CO₃ and MgCO₃, could not only replace the FeO from (Mg,Fe)SiO₄ and FeAl₂O₄, but also react with SiO₂ and Al₂O₃ in ore to form their corresponding complex compounds. Moreover, all compounds were benefitted by the increase of the FeO content. The F⁻ ion could replace the O^2- ion in the silicon oxygen tetrahedron to reduce the viscosity and surface tension of reduced ore, thus reducing the resistance of iron particle aggregation and growth. In addition, the formation of a local micro melting phase under the action of additives could promote the diffusion of crystalline particles, which is more conducive to the reduction of iron minerals and the formation and growth of iron particles.

摘要

添加剂在煤基还原回收复杂难选铁矿石，提高矿石自给率方面发挥着重要作用。本工作采用 X_射线衍射、_热重和差_示扫描量热法、扫描电镜和能量色散光谱法。结果表明，三种添加剂可以大大提高还原和磁选产品的质量。_{在CaF 2}条件下得到还原产物金属化度93.42%，铁品位91.23%，铁回收率95.48%用量6%，还原温度1225℃，还原时间50分钟。这些结果分别比没有添加剂的情况下高 3.38%、8.09% 和 0.39%。CaF _{2以及Na 2} CO ₃和MgCO ₃分解生成的Na ₂ O和MgO不仅可以代替(Mg,Fe)SiO ₄和FeAl ₂ O ₄中的FeO ，而且可以与SiO ₂反应。与矿石中的Al ₂ O ₃形成相应的络合物。此外，所有化合物都受益于 FeO 含量的增加。F ^-离子可以取代 O ^2-硅氧四面体中的离子降低还原矿的粘度和表面张力，从而降低铁颗粒聚集和生长的阻力。此外，在添加剂作用下形成局部微熔相，可促进结晶颗粒的扩散，更有利于铁矿物的还原和铁颗粒的形成和生长。