韩城矿区构造煤纳米级孔隙结构的分形特征Fractal characteristics of nano-pore structure in tectonically deformed coals in Hancheng mining area
张晓辉,要惠芳,李伟,王秀娟,阎纪伟
ZHANG Xiaohui,YAO Huifang,LI Wei,WANG Xiujuan,YAN Jiwei
摘要(Abstract):
构造变形可以引起煤纳米级孔隙结构的变化,变形机制的不同对孔隙结构的影响程度也不同。煤的孔隙非均质性极强,传统实验方法难以准确地描述孔隙结构的复杂性,而分形理论提供了描述这一复杂性的量化方法。基于渭北煤田韩城矿区不同类型构造煤的低温氮吸附实验,采用分形FHH方法,定量表征了构造变形对煤纳米级孔隙结构的影响程度。结果表明:韧性变形煤比脆性变形煤的孔隙分形维数高,孔隙结构复杂,非均质性增强,导致毛细凝聚效应增强,吸附滞后突出;构造煤分形维数随着平均孔径的降低和中孔含量的升高而增大,说明构造变形程度越大,平均孔径越小,孔隙结构越复杂。研究认为,分形维数定量反映了煤构造变形的强弱,可以指示煤中纳米级孔隙结构的变形程度。
The nano-pore structure can be changed under tectonic deformation, and the different deformation mechanisms influence also the pore structure in various degrees. Pore structure of coals is very inhomogeneous, and is exactly described difficultly by the conventional experimental methods, but the fractal theory provides a quantitative method for describing the complexity of the pore structure. The influence of tectonic deformation on nano-pore structure of different deformed coals collected from Hancheng mining area in Weibei coalfield was quantitatively analyzed by nitrogen gas adsorption experiment based upon the fractal Frenkel-Halsey-Hill(FHH) theory. The results show that ductile deformed coals with higher pore fractal dimensions have higher heterogeneity and more complicated pore structure compared to brittle deformed coals, resulting in higher capillary condensation and prominent adsorption hysteresis. Fractal dimensions of tectonic coal increase with reduction of the average pore diameter and the increase of meso-pore content, indicating the stronger the tectonic deformation, the smaller the average pore size, the more complicated the pore structure. With the stress strengthening, fractal dimension shows an increasing trend. Thus, the fractal dimension can be used as an indicator of the deformation degree of the nano-pore structure.
关键词(KeyWords):
韩城矿区;构造煤;孔隙结构;分形维数
Hancheng mining area;deformed coals;pore structure;fractal dimension
基金项目(Foundation): 国家科技重大专项课题(2009ZX05062-009;2011ZX05062-009)
作者(Author):
张晓辉,要惠芳,李伟,王秀娟,阎纪伟
ZHANG Xiaohui,YAO Huifang,LI Wei,WANG Xiujuan,YAN Jiwei
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