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目前利用扫描电镜(SEM)数字图像对低阶煤的矿物质成分含量、微裂隙发育及微观结构的各向异性特征缺乏系统的研究。结合扫描电镜试验和压汞试验,对珲春煤田低阶煤微观形态及微裂隙发育的各向异性特征进行研究。通过选择合适的灰度阈值,将扫描电镜中观察的平行和垂直层理的微观图像处理成矿物质成分二值数字图像和微裂隙二值数字图像,计算得到矿物质成分的百分含量以及平行层理面和垂直层理面中微裂隙体积百分比。分别研究平行和垂直层理方向微裂隙发育的分形特征,计算得到微裂隙的分形盒维数,结果显示,与平行层理相比,垂直层理方向微裂隙表面光滑性、规则性较差,空间充填能力较强,比表面积较大,而且具有更强的吸附能力。压汞试验结果表明,煤样的孔径多分布在10~100 nm及15~95μm范围,在10~100 nm附近比表面积变化量最大,扫描电镜观测得到的煤植体层片状结构和矿物质絮状结构形成的孔隙结构近似分布于此范围,说明煤植体层片状结构和矿物质絮状结构确实能够提供较大的比表面积,层片状煤植体结构能够贡献较强的煤层气储存吸附能力。
At present, scanning electron microscopy (SEM) digital images of the low-rank coal mineral composition, micro-fracture development and anisotropy of the microstructure of the lack of systematic research. Combined with scanning electron microscopy and mercury intrusion test, the anisotropy of microstructure and micro-fracture development of low rank coal in Hunchun coal field was studied. By selecting the appropriate grayscale threshold, the parallel and vertical bedding microscopic images observed in the SEM were processed into binary digital images of the mineral composition and binary digital images of the microcracks to calculate the percentage content of the mineral components and the parallel Microfluid volume percentages in bedding planes and vertical bedding planes. The fractal characteristics of microcracks development in parallel and vertical bedding directions were studied respectively. The fractal box dimension of microcracks was calculated. The results showed that compared with parallel bedding, the micro-cracks in vertical bedding plane have poor smoothness and regularity, Strong space filling capacity, larger specific surface area, but also has a stronger adsorption capacity. The results of mercury intrusion test showed that the pore sizes of coal samples were distributed in the range of 10-100 nm and 15-95 μm, and the change of specific surface area was the largest at 10-100 nm. The lamellar structures and minerals The pore structure formed by the floc structure is approximately distributed in this range, which shows that the flake structure and the mineral floc structure of the coal implant layer can indeed provide a large specific surface area, and the flaky coal implant structure can contribute to the strong CBM Storage adsorption capacity.