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Laboratory investigation on pore characteristics of coals with consideration of various tectonic deformations
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2021-04-08 , DOI: 10.1016/j.jngse.2021.103960
Kun Zhang , Zhaoping Meng , Shimin Liu , Haijin Hao , Tao Chen

Coal structure is highly related to paleo-stress variation and the pore structure of coals can be modified through tectonic activities. This study characterizes the pore structure variations for various coal samples with different tectonic deformation intensities. The low temperature N2 and pressure CO2 adsorption analyses were conducted to quantify the pore structures, and high pressure CH4 adsorption measurements were carried out for the sorption analysis. The pores were classified into ultramicropores (<2 nm), micropores (2–10 nm), mesopores (10–100 nm) and macropores (>100 nm). The results show that with the increase of coal deformation intensity, the proportion of pore size of 50–300 nm decreased, showing that more macropores and mesopores were deformed to the smaller pores (<50 nm). Micropores (2–10 nm) in granulated and mylonitic coals obviously increased. The predominant ultramicropore in four kinds of coal structures were distributed at the range of 0.45–0.6 nm and 0.80–1.0 nm. Tectonic coals formed more ultramicropores lower than 0.65 nm. The adsorption of CH4, N2 and CO2 increased as the coal deformation degree increased, following the order: mylonitic coal > granulated coal > cataclastic coal > intact coal. Fractal dimensions show that tectonic coals characterized the rougher pore surface (higher D1) and more homogeneous pore structures (lower D2), which led to the higher adsorption capacity. The development of micropores was positive with Langmuir VL, but the ultramicropore SSAs were significantly larger than the contribution to SSAs of micropores and mesopores. Thus, ultramicropore provided the main adsorption sites for CH4. The variations of adsorption potential increased with the coal deformation intensity increased, and the smaller the adsorption space volume was, the larger adsorption potential would be, illustrating that adsorption in micropores was higher than mesopores and macropores. Tectonic coals have the higher reduced rate of cumulative surface free energy, which shows that tectonic damages promote the adsorption potential and surface free energy in coals.



中文翻译:

考虑各种构造变形的煤孔隙特征室内研究

煤的结构与古应力的变化高度相关,煤的孔隙结构可以通过构造活动来改变。这项研究表征了具有不同构造变形强度的各种煤样的孔隙结构变化。进行了低温N 2和高压CO 2吸附分析以定量孔结构,高压CH 4进行吸附测量以进行吸附分析。毛孔分为超微孔(<2 nm),微孔(2-10 nm),中孔(10-100 nm)和大孔(> 100 nm)。结果表明,随着煤变形强度的增加,孔径在50-300 nm的比例减小,表明更多的大孔和中孔变形为较小的孔(<50 nm)。粒状煤和淀粉质煤中的微孔(2-10 nm)明显增加。四种煤结构中主要的超微孔分布在0.45–0.6 nm和0.80–1.0 nm范围内。构造煤形成了更多的低于0.65 nm的超微孔。CH 4,N 2和CO 2的吸附随煤变形程度的增加而增加,依次为:my煤>粒煤>碎裂煤>完整煤。分形维数表明,构造煤具有较粗糙的孔隙表面(较高的D 1)和较均匀的孔隙结构(较低的D 2),这导致较高的吸附能力。Langmuir V L的微孔发展为阳性,但超微孔SSA明显大于微孔和中孔对SSA的贡献。因此,超微孔提供了CH 4的主要吸附位点。吸附势的变化随煤变形强度的增加而增大,吸附空间体积越小,吸附势就越大,说明微孔中的吸附高于中孔和大孔。构造煤具有较高的累积表面自由能降低率,这表明构造破坏促进了煤的吸附势和表面自由能。

更新日期:2021-04-14
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