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Pore structure evolution during the coke graphitization process in a blast furnace
International Journal of Minerals, Metallurgy and Materials ( IF 4.8 ) Pub Date : 2020-06-15 , DOI: 10.1007/s12613-019-1927-1
Hao-bin Zhu , Wen-long Zhan , Zhi-jun He , Ying-chang Yu , Qing-hai Pang , Jun-hong Zhang

Pore structure is an important factor influencing coke strength, while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace. Therefore, an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace. Coke graphitization was simulated at different heating temperatures from 1100 to 1600°C at intervals of 100°C. The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method. Results show that the adsorption and desorption curves of graphitized coke have intersection points, and the two curves did not coincide, instead forming a “hysteresis loop.” Based on the hysteresis loop analysis, the porous structure of the graphitized coke mostly appeared in the shape of a “hair follicle.” Furthermore, with an increase in heating temperature, the apparent porosity, specific surface area, total pore volume, and amount of micropores showed good correlation and can divided into three stages: 1100–1200, 1200–1400, and 1400–1600°C. When the temperature was less than 1400°C, ash migration from the inner part mainly led to changes in the coke pore structure. When the temperature was greater than 1400°C, the pore structure evolution was mainly affected by the coke graphitization degree. The results of scanning electron microscopy, energy dispersive spectrometry, and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400°C contributed to these changes.



中文翻译:

高炉焦炭石墨化过程中的孔结构演变

孔结构是影响焦炭强度的重要因素,而焦炭的性质对于维持高炉中的气体和液体渗透性是必不可少的。因此,对石墨化过程中孔结构演变的深入了解可以揭示焦炭尺寸在高炉下降过程中的降解行为。在1100至1600°C的不同加热温度下以100°C的间隔模拟了焦炭石墨化。采用真空排水法和氮气吸附法对不同石墨化程度的焦炭孔隙结构进行定量评价。结果表明,石墨化焦炭的吸附和解吸曲线具有交点,并且两条曲线不重合,而是形成“磁滞回线”。根据磁滞回线分析,石墨化焦炭的多孔结构主要以“毛囊”的形式出现。此外,随着加热温度的升高,表观孔隙率,比表面积,总孔体积和微孔数量显示出良好的相关性,可以分为三个阶段:1100–1200、1200–1400和1400–1600°C。当温度低于1400℃时,灰分从内部的迁移主要导致焦炭孔结构的变化。当温度高于1400℃时,孔结构的演变主要受焦炭石墨化程度的影响。扫描电子显微镜,能量分散光谱法和灰分含量分析的结果还证实,在高达1400°C的石墨化过程中,内部灰分向基质表面的迁移是造成这些变化的原因。

更新日期:2020-06-15
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