镜铁矿制备直接还原铁与胶凝材料耦合工艺基础研究

Specularite has characteristics of high grade, abundant reserves and low price. However,its high cost, poor ball-forming and combustibility in complex mineral processing cause severe effect on the qualities of pellet and sinter. Therefore, specularite cannot be used in BF iron making production, resulting in difficulties in the utilization of specularite. In this project, a new process will be proposed to utilize the specularite. In the process, iron in specularite is reduced by carbon. At the same time, gangues react with limestone to form cementing material. Finally, iron and cementing will be separated by magnetic separation. Thermodynamic calculations and experiment will be carried out to study the mechanisms of the reduction of iron followed growth and the formation of cementing material. Simultaneously, the interaction of the reduction and grow of iron and the formation of cementing material will be studied. Besides, the interaction effect between the growing process of iron and generating process of cementing material will be illustrated. Finally, a novel method of specularite comprehensive utilization without solid waste, environmental pollution and without metallurgical coke will be established. This process will provide an effective method of specularite utilization for our country.

镜铁矿品位高、储量丰富，但因其选矿工艺复杂、成球性差、难烧结等问题制约了其在钢铁工业中的大规模应用。本课题在系统文献综述和前期研究基础上提出了镜铁矿制备直接还原铁和胶凝材料耦合新工艺，即适量配比的镜铁矿粉、与煤粉与石灰石在固态反应条件下，先后实现铁的还原与长大，和脉石成分的改性处理，进而通过磁选分离分别获得高品位直接还原铁粉与胶凝材料。课题通过理论计算与实验验证相结合阐明镜铁矿固态还原长大与胶凝材料制备的热力学及动力学耦合条件，明晰镜铁矿还原过程铁元素还原长大机制与脉石成分的改性路径，掌握磁选分离工艺对于产物物相、化学成分和元素回收率的影响规律，确定耦合新工艺的能量及物料平衡及分布关系。最终实现清洁高效的镜铁矿制备直接还原铁和胶凝材料的新工艺。

本项目针对镜铁矿应用中存在的制粒性和高温反应性较差等问题，将直接还原炼铁技术与回转窑水泥熟料生产技术相结合，提出镜铁矿煤基直接还原与胶凝材料制备耦合技术。通过合理的过程控制，在实现铁氧化物还原的同时将剩余的脉石组分转化为胶凝材料，并经过理论和实验研究证明了其可行性。结果表明：使用高挥发分的低阶煤作为还原剂，煤的热解过程与还原过程产生耦合。煤热解产生的还原性气体使还原反应迅速启动，而高活性的固体炭能够促进还原过程中的气化反应，从而加快还原进程，避免低熔点物相对生成胶凝组元的不利影响。采用两段法升温制度，分别进行铁氧化物的还原和胶凝材料的生成。设定体系合适的碳氧比，即可使铁氧化物可完全还原为金属铁，产物不粘结且易分离，有利于后续磨选过程。根据胶凝材料生成热力学，精准控制温度和碱度条件可以使金属铁与硅酸三钙等胶凝材料在高温下共存。镜铁矿还原与胶凝组元生成存在耦合作用，未还原的FeO会导致体系内液相增多，使胶凝组元无法生成，铁矿的还原度对胶凝材料的生成状态具有重要的影响。样品焙烧后迅速冷却，避免胶凝组元分解。磁选分离后的脉石组分表现出较好的胶凝特性，符合水泥熟料的使用要求。研究成果将为镜铁矿和低阶煤资源实现高效、环保、经济的综合利用提供理论支撑。