高炉焦炭在渣铁催化体系下碳结构有序化及性能演变机制

The contradiction between the increasing coke quality requirement for blast furnace (BF) ironmaking and the degradation of coke quality is sharpening, and this has become a common problem for current and future BF ironmaking industry. An in-depth understanding about the coke degradation behavior inside BF is essentially important to solve this problem. The ordering of coke carbon structure is the most fundamental structural evolution in the BF high temperature zone, while the mechanism of coke carbon structure evolution is still unclear, lacking of scientific evaluation. Firstly, experiment and molecular dynamic (MD) simulation will be adopted in this project to uncover the coke carbon transformation mechanism in full scale and construct the evolution model of spatial aggregated coke carbon structure, while the effective catalytic component and catalytic mechanism of coke ash on coke carbon transformation will be studied by experiment with coke analogue. Secondly, the independent and coupled catalytic mechanisms of BF slag and metal on the coke carbon ordering process will be investigated by annealing coke with slag and metal, while the interface characteristics and interaction effect between slag-coke-metal will be uncovered. Finally, the relationship between various coke structural factors and coke properties will be obtained by physical and chemical method as well as mathematical model, and the index model of coke carbon ordering will be proposed. The evaluation system and detection method to characterize the effect of coke carbon ordering in BF will be proposed to improve the coke quality evaluation system, which will provide theoretical and technical foundation of the reduction of carbon consumption in the ironmaking system.

高炉对焦炭质量要求的提高与焦炭品质劣化之间的矛盾日益突出，这已成为当前及未来高炉炼铁行业必须面对的共性问题，深入理解焦炭在高炉内的劣化行为是解决此问题的基础，碳结构有序化是焦炭在高炉高温条件下最基本的结构转变，但目前对焦炭在高炉内的碳结构演变机制尚不清楚，缺乏科学评价。本项目首先采用实验与分子模拟相结合的手段，从全尺度范围揭示焦炭中碳结构在高炉高温区的演变机制，构建焦炭基体空间聚合碳结构的演变模型，同时通过焦炭类似物实验揭示焦炭灰分催化碳结构演变的有效组元及其催化机理；其次，通过共同热处理的方法研究熔渣和铁液单独以及耦合催化碳结构有序化的机理，揭示熔渣-焦炭-铁液三相的界面特征和交互作用过程；最后，采用物化法及数学模型构建各种结构因子与焦炭性能之间关系，建立焦炭碳结构有序化指数模型，提出高炉内焦炭有序化影响的评价体系和检测方法，为完善焦炭质量评价，降低炼铁系统碳素消耗奠定理论和技术基础。

焦炭作为料柱骨架在高炉炼铁过程中起到了不可替代的作用，焦炭的碳结构决定焦炭的冶金性能。高炉内焦炭石墨化过程影响焦炭与气体的反应，铁对焦炭石墨化具有明显的催化作用。本项目通过实验和分子动力学模拟研究了焦炭碳结构演变机制及其铁催化焦炭石墨化机理，发现Lc值及La值随着退火温度升高而增加，相应的石墨烯层数也增加。退火温度1500℃时，无定形碳结构可以在热退火过程中转变为石墨层。与垂直方向（Lc）相比，在石墨烯平面（La）方向上不易形成好的有序结构。温度高于1200℃时，铁催化焦炭石墨化的作用很强，碳结构阶数明显增加。1200℃时碳大量溶解到铁中导致铁颗粒的熔点降低。铁催化石墨化后，微晶石墨的晶格条纹长度和堆积数明显增加，而晶体取向没有明显变化，表明微晶石墨的生长是沿着它原来的方向生长的。DFT模拟分析水分子在各种缺陷石墨烯表面的吸附和反应机理，确定了最佳稳定的物理吸附构型。同时对原始石墨烯（Pr）和单空位（MV）石墨烯与O2氧化过程进行分子动力学模拟，在氧化反应开始时，氧化石墨烯反应观察到异常的热行为，两种石墨烯氧化区域的成核和生长机制存在显着差异。原始石墨烯在4350-4450 K，单空位石墨烯在4300-4450 K的热区，整体反应动力学明显变慢。