不同煤阶煤中芳香晶格条纹特征研究

    Study on characteristics of aromatic lattice fringes in different rank coals

    • 摘要: 系统了解煤化过程中芳香晶格条纹特征及演化规律有利于煤炭资源的安全回采及高值化利用。为了了解煤化过程中微晶结构的演化规律,通过Digital Micrograph软件和Image J软件对高分辨率透射电镜(HRTEM)的原始图像进行降噪、二值化和骨架化处理,并利用ArcGIS软件提取图像中的芳香晶格条纹,分别对低、中、高阶煤中芳香晶格条纹的形态、长度、角度及堆垛进行定量分析。结果表明:不同煤阶煤样中芳香晶格条纹边缘基本为弯曲形态且具有短程有序、长程无序的特点;随着煤阶的提高,煤结构中芳香晶格条纹数量减少,条纹排列有序程度和紧密程度增加;3种煤样中短条纹最多,长条纹最少,芳香晶格条纹数量随条纹长度的增加而减少,由1~3个芳环组成碳原子数在13以内的多环芳香烃层片比重最大;芳香晶格条纹数量随其长度的增加而减少,长条纹比重与煤阶呈正相关关系,短条纹比重与煤阶呈负相关关系,芳香晶格条纹的平均长度随煤阶的增加而增加;条纹取向度在高阶煤中最高,中阶煤中的脂肪烃结构可能导致其条纹取向度小于低阶煤;芳香晶格条纹总体有序度随煤阶的增加而增加;芳香晶格条纹堆垛的数量随其堆垛层数的增加而减少,形成条纹堆垛的数量随煤阶的增加而增加;小分子化合物的脱除及芳环缩合作用的变化导致煤微晶结构从低阶至高阶的不断变化。

       

      Abstract: A systematic understanding of the characteristics and evolution of aromatic lattice fringes during coalification is beneficial to the safe mining and high-value utilization of coal resources. To elucidate the evolution of microcrystalline structures during coalification, we employed Digital Micrograph and ImageJ softwares for noise reduction, binarization, and skeletonization of the original high-resolution transmission electron microscopy (HRTEM) images. Subsequently, ArcGIS software was utilized to extract the aromatic lattice fringes from these images. We conducted a quantitative analysis of the morphology, length, angle, and stacking characteristics of aromatic lattice fringes in low-rank, mid-rank, and high-rank coals. The results show that the edges of aromatic lattice stripes in different rank coals are curved and characterized by short-range order and long-range disorder. With the increase of coal rank, the number of aromatic lattice fringes within the coal structure diminishes, while the orderliness and compactness of these fringes augment. Among the three coal samples analyzed, short fringes are most prevalent, long fringes are least abundant, and the quantity of aromatic lattice fringes exhibits a decreasing trend as fringe length increases. The specific gravity of polycyclic aromatic hydrocarbon sheets composed of 1-3 aromatic rings with carbon atoms less than 13 is the largest. The number of aromatic lattice fringes decreases with their length, the specific gravity of long fringes is positively correlated with the coal rank, the specific gravity of short fringes is negatively correlated with the coal rank, and the average length of aromatic lattice fringes increases with the coal rank. The orientation is the highest in high-rank coal, and the aliphatic hydrocarbon structure in middle-rank coal may cause the orientation to be less than that in low-rank coal. The overall order degree of aromatic lattice fringes increases with the coal rank. The number of aromatic lattice fringes stacks decreases with the increase of the number of stacking layers, and the number of fringes stacks increases with the coal rank. The removal of small molecular compounds and the change of aromatic ring condensation result in a constant change of microcrystalline structure from low to high rank coals.

       

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