摘要
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。
Currently, the mineral component and anisotropic microstructure of the low-rank coal are lack of systematically quantitative research. The scanning electron microscope（SEM） test and mercury test were carried out to analyze the anisotropic characteristics of the morphology and distribution of microcracks. The microscopic images were processed into the binary digital images of minerals and micro-cracks with the appropriate gray threshold. The mineral percentage in coal, the volumetric percentage of microcracks in parallel directions and perpendicular directions oft,he beddingswere calculated. The box fractal dimension of micro-cracks that parallel to and perpendicular to bedding seam scanned by SEM were calculated based on the fractal theory, according to which the micro cracks perpendicular to bedding microstructure is relatively smooth and irregular. According to the mercury test to coal samples, the total volume of injected mercury changes with pressure, the apertures of coal samples were mostly distributed in 10- 100 nm or 15- 95 ktm, and the largest specific surface area for microcrack is around 10 - 100 nm. The pore distribution of coal explant lamellar structure and mineral floc structure by SEM also arotmd 10 - 100 nm, It indicates that the explant lamellar structure and minerals flocculent structure of coal could provide a larger specific surface area and the coal explant could have very strong adsorption capacity of coal bed methane（CBM）.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2016年第9期1805-1814,共10页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金杰出青年基金项目(51225902)
国家重点基础研究发展计划(973)项目(2013CB036006
2015CB057906)~~
关键词
岩石力学
长焰煤
扫描电镜试验
数字图像
分形理论
孔径分布
rock mechanics
low-rank coal
the SEM test
digital image
the fractal theory
pore size distribution
