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不同变形机制下构造煤大分子结构演化机理

Macromolecular structure evolution mechanism of tectonically deformed coal under different deformation mechanisms

  • 摘要: 构造煤是一期或多期构造应力作用的产物,其物理和化学性质均发生了深刻的变化,并显著制约了煤层瓦斯突出和煤层气产出。为了探讨构造应力对煤中有机大分子结构的影响,应用傅里叶变换红外光谱(FTIR)对淮北矿区不同类型构造煤的大分子结构及演化进行了对比分析。结果表明:煤中有机大分子结构对构造应力十分敏感,随着构造煤变形程度增加,煤中脂烃减少13.28%、芳烃增加25.45%、脂肪侧链长度减小1.29、芳环缩聚程度增加4.9。不同应力-应变环境对构造煤结构影响迥异,与原生结构煤相比,脆性变形序列构造煤(片状煤和碎粒煤)脂烃降低了9.24%,芳烃增加了18.89%;而韧性变形序列构造煤(揉皱煤和糜棱煤)中的脂烃减少量比脆性变形煤高6.36%、芳烃增加量高4.02%,说明构造应力对韧性变形序列构造煤的改造作用尤为明显,韧性变形过程更易促使脂肪链发生裂解重组,并促使脱落的小分子物质缩聚成稳定的芳香结构。

     

    Abstract: Tectonically deformed coal (TDC) is product of tectonic stress in one stage or multiple stages. The physical and chemical properties of tectonic coal have changed greatly during its formation, which significantly influence the coal and gas outburst and coalbed methane exploitation. To investigate the organic macromolecular structure evolution of TDC under different stress and strain, the Fourier transform infrared spectroscopy (FTIR) was used to compare the macromolecular structure and evolution of different types of TDCs in Huaibei mining area. The results show that the organic macromolecular structure of TDC is sensitive to tectonic stress. As the deformation degree of TDCs increases, the aliphatic hydrocarbons and the long aliphatic chains decrease by 13.28% and 1.29 respectively, while the aromatics and the polycondensation of aromatic rings increase by 25.45% and 4.9 respectively. Different stress-strain environments have different effects on the TDCs. Compared with the undeformed coal, the brittle-deformation sequence of coal (include flake and granulated coal) of aliphatic hydrocarbons is reduced by 9.24% and aromatics increase by 18.89%. The ductile deformation sequence (winkle and mylonitic coal) of aliphatic hydrocarbons is 6.36% higher than that of brittle deformed coal and 4.02% higher than that of aromatic hydrocarbons, indicating that tectonic stress is particularly effective in the TDC in ductile deformation series. The ductile deformation process is more likely to cause cracking and recombination of the fat chain, and promote the condensation of the detached small molecules into a stable aromatic structure.

     

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