高炉散料层铁焦气化过程中三维结构与热态强度演变机制研究

Blast furnace ironmaking is currently faced with the huge pressure of energy conservation and emissions reduction. The development and utilization of high reactivity-high strength iron coke is one of the most important research to optimize blast furnace ironmaking process and reduce fuel consumption. The gasification characters and thermal compressive strength features of iron coke will directly affect the smelting efficiency and operation smoothly of blast furnace, and then determine the maximum usage of iron coke in the blast furnace. At present, however, the evolution mechanism of gasification behavior and thermal compressive strength of iron coke in the lumpy zone of blast furnace is not yet clear, and the corresponding theoretical needs to be deeply studied. This study will investigate the influence of intrinsic characteristics of iron coke, CO2-CO-water vapor, alkali metals and zinc on the gasification character, and then reveal the evolution and influencing factors system of the reaction rate and kinetic parameters of iron coke in lumpy zone of blast furnace under the complex environment. The serial sectioning and 3D-reconstruction technology will be introduced to this study to obtain the 3D microstructure information, then the 3D evolution mechanism of pore structure and maceral component of iron coke will be revealed. Based on the testing results of thermal compressive strength of iron coke during the gasification process, the relationship between thermal compressive strength of iron coke and the internal working atmosphere in blast furnace as well as the intrinsic characteristics of iron coke will be explored, then the synergetic evolution mechanism of 3D microstructure and thermal compressive strength of iron coke during the gasification process will be revealed. This study can provide theoretical basis for the prediction and control of metallurgical performance of iron coke in the blast furnace.

当前高炉炼铁面临着节能减排的巨大压力，研发和使用高反应性高强度铁焦是优化高炉炼铁工艺、降低燃料消耗的重要研究方向之一。铁焦在高炉内部的气化特性和热态强度不仅影响高炉的冶炼效率和顺行程度，也决定了铁焦在高炉内部最大的使用量。然而，目前对高炉散料层内铁焦的气化反应行为和热态强度演变机制尚不明晰，需要进一步探索。本项目拟通过研究铁焦自身特性、CO2-CO-水蒸气、碱金属和锌对铁焦气化反应的影响，揭示铁焦在高炉散料层复杂环境中的反应速率和动力学参数的演变及其影响因素体系；采用序列切片-三维重建技术获取铁焦三维微观结构信息，阐明不同气化过程中的铁焦气孔结构和显微组分的三维演变机制；基于铁焦气化反应进程中的在线抗压强度检测结果，研究铁焦热态强度与高炉内部环境、铁焦本征特性的相关性，揭示铁焦气化反应进程中三维微观结构与热态强度的协同演变机制，为高炉内铁焦反应行为和热态强度的预测和调控提供理论基础。

本项目针对新型炼铁炉料铁焦在高炉内的气化反应行为及高温热态强度演变过程展开研究，揭示了铁焦自身结构特性、高炉内部环境对铁焦消耗、侵蚀的影响规律，探明了铁焦反应速率和热态强度的调控方向，主要结论如下：.（1）铁焦制备过程中主要发生煤热解与铁矿粉还原耦合反应，铁矿粉在炭化过程被逐步还原为金属铁。铁矿粉种类、粒度、添加量对炭化过程中煤-矿压块的脱气行为和焦饼的体积演变具有较大的影响。随着铁矿粉添加量的增加，铁焦气化反应性逐渐增大，但转鼓强度逐渐降低。综合考虑铁焦的反应性与转鼓强度，宜采用10%的鄂西铁矿粉与气煤混合炭化制备性能较好的铁焦。.（2）自身特性、反应温度、反应气氛和有害元素对铁焦在高炉散料层内的气化反应行为具有较大的影响。随着铁矿粉的粒度由1.00mm减小到0.074mm，铁焦的气化反应性逐渐增加，但强度先增加后降低，铁矿粉粒度在0.2-0.5mm范围铁焦综合性能最佳。随着反应温度增加，铁焦的反应性大幅提高；CO2-水蒸气混合气氛下，铁焦的气化反应性要好于纯CO2气氛下；在碱金属富集条件下，铁焦的气化反应受到碱金属的催化作用而提高。反应温度对铁焦气化反应影响最大、其次为自身特性、气氛和有害元素。铁焦气化反应机制满足未反应核模型，受界面化学反应控速。.（3）建立了铁焦序列切片-三维重构的方法，实现了铁焦三维结构的表征与分析。气化反应后铁焦整体结构主要由疏松多孔的活性碳基质、致密少孔的惰性碳基质和小颗粒金属铁和灰渣组成。从三维结构可知金属铁和灰渣主要以实心结构存在，而碳基质大多数观察不到完整的颗粒，主要以多孔的局部基质形貌呈现。.（4）随着反应时间的增长，铁焦的热态抗压强度逐渐降低，但不同种类铁焦变化规律不同。铁焦的气孔结构与矿粉还原产物分布均匀度是决定铁焦热态抗压强度的主要因素。在30%铁矿粉配比条件下，添加10%的沥青能够显著提高铁焦的冷态强度，但对其改善效果有限，仅能提高100N。因此，铁焦热态强度的提升需要后续深入研究。