碱度对白云鄂博铁精矿球团矿还原膨胀性能的调控机制

The ironmaking process in Baotou Iron and Steel Co., Ltd. takes Baiyun Obo iron concentrate as the main iron-containing raw material, and its harmful elements such as potassium, sodium and fluorine cause abnormal reduction swelling of pellets, which limits the high proportion of the Baiyun Obo iron concentrate in production process of pellets. Based on the study of the effect of basicity on the reduction swellability of the pellets prepared from the concentrates containing potassium, sodium and fluoride, the influencing factors of the reduction swelling behavior of pellets are classified into two types according to the theory of reduction of iron oxides in pellets. That is, crystal structure change of iron oxide and growth behavior of iron whisker in reduction process(internal factors), the high temperature characteristics of the slag phase and the reduction kinetic behavior of the pellets(external factors). The in-depth study on the influence mechanism of basicity on the two factors will be carried out to clarify the regulation mechanism of basicity on the reduction swellability of the pellets prepared from the Baiyun Obo iron concentrates. The research results will enrich and improve the theory of reduction swellability of special ore pellets in China, and can be directly used in smelting practice of complex symbiotic ore to provide theoretical support for the preparation of flux pellets by Bayan Obo iron concentrate.

包钢炼铁生产以白云鄂博铁精矿为主要含铁原料，其含有的钾、钠、氟等有害元素引起球团矿异常还原膨胀，限制了包钢球团矿生产工艺高比例应用自产白云鄂博铁精矿。本项目在对碱度影响含钾、钠、氟球团矿还原膨胀性能的规律研究基础上，根据球团矿铁氧化物还原理论，将球团矿还原膨胀行为的影响因素归类为两种，即还原过程铁氧化物晶体结构变化及铁晶须生长行为（内部因素）、球团矿渣相高温特性及球团矿还原动力学行为（外部因素），分别从碱度对两种因素的影响机理入手深入研究，从而阐明碱度对白云鄂博铁精矿球团矿还原膨胀性能的调控机制，研究成果将丰富和完善我国特殊矿球团还原膨胀理论，并可直接用于复杂共生矿冶炼实践，为白云鄂博铁精矿制备熔剂性球团矿提供理论支撑。

高比例球团矿冶炼技术是实现钢铁生产绿色化的重要手段之一。本文基于铁氧化物还原理论，研究了球团矿还原过程体积膨胀行为、铁氧化物晶体结构变化、液相高温特性、动力学行为、还原产物微观形貌，并探究了碱度对白云鄂博铁精矿球团矿还原膨胀性能的调控机制。结果表明，在碱度为0.8时球团矿的膨胀率最大，为75.743%。综合球团矿的含铁品位和还原膨胀特性，得到制备球团矿的最优碱度为1.4。碱度为0.8的球团矿结晶度低，晶粒尺寸小、晶粒间距大、晶体平均堆垛层数少，使得晶体结合能小、活动空间大，为还原第三阶段铁晶须从边、角、棱进入球团矿内部奠定基础。碱度为0.8的球团矿液相开始生成温度值最高，为1091℃，液相生成量最少，仅为10.042g。同时进入液相中的含K、Na的成分最多。液相中的K、Na元素更易进入铁氧化物的晶格中，造成铁氧化物因晶格畸变而结晶度降低，晶粒尺寸减小，残余应力增大。碱度为0.8的球团矿有最大的反应率，为35.695%。因为其发生还原反应所需要的反应活化能最少，仅需94.731kJ/mol。碱度为0.8的球团矿，其焙烧产物表现为Fe2O3晶体的连晶程度差且晶粒的分布分散，还原第一阶段产物发生了从板状晶型向粒状晶型的转变，还原第二阶段产物中出现了硅酸盐液相，还原第三阶段产物有粗大的铁晶须生成。此外，在同一个还原阶段，碱度为0.8的球团矿中K、Na元素进入铁氧化物晶格中的量要远大于其他碱度的球团矿。