岩浆侵入型煤体孔隙结构突变特征及其对瓦斯吸附解吸动力学影响

The coal-forming process was influenced by the Mesozoic and Cenozoic igneous intrusions activity in many Chinese coal mining areas. The superposition of plutonic metamorphism and regional hydrothermal metamorphism has dramatically changed the pore structure of coal, gas adsorption-desorption characteristics, and methane desorption index of drill-cuttings of coal. The coal seam of igneous thermal evolution zone is high risk area of coal and gas outburst, however, there lated fundamental study has been rarely done in this area. Therefore, we choose igneous intruded coal as the object of study. Firstly, we carry out the research of pore structure change regularity, and determine the mutation characteristics of pore structure according to the parameter increment mutation of pore structure and the corresponding three-dimensional images of atomic force microscope. Then we establish the integrated testing apparatus of methane adsorption-desorption kinetics test and heat determination of methane adsorption to carry out the research of adsorption-desorption kinetics process test and the change law of adsorption heat under different conditions of temperature and pressure. By using the theories of adsorption thermodynamics, adsorption kinetics and surface chemistry, etc., we build the adsorption-desorption kinetics model of igneous intruded coal, and then analyze the relationship between the pore structure characteristic parameter and the methane adsorption and desorption kinetics parameter. This study will reveal the effects mechanism of the pore structure mutation on methane adsorption and desorption kinetics of the magma intrude coal. Finally, we illuminate the internal relations among pore structure changes, adsorption-desorption kinetics characteristic and gas outburst indexes, which could provide theoretical basis for the gas outburst prevention for the igneous intruded coal mine.

我国诸多矿区成煤过程受中、新生代岩浆侵入活动影响，深成变质作用叠加区域岩浆热变质作用，致使煤体孔隙结构、瓦斯吸附解吸特性及钻屑解吸指标显著改变，而岩浆侵入热演化区为煤与瓦斯突出高发区，相关基础研究不足。据此，以岩浆侵入型煤体为研究对象，首先基于孔隙结构参数增量突变与对应原子力显微镜三维图像，确定孔隙结构突变特征；而后运用瓦斯吸附解特性和吸附热测试一体化试验平台，开展不同温压条件下吸附解吸动力学过程和吸附热变化规律研究；进而结合吸附热力学、吸附动力学和表面化学等理论，建立岩浆侵入型煤体吸附解吸动力学模型，分析孔隙结构特征参数与吸附解吸动力学特征参数之间的关系。本研究对于揭示岩浆侵入型煤体孔隙结构变化对瓦斯吸附解吸动力学影响机制，阐明孔隙结构变化、吸附解吸动力学特性与突出指标的内在联系具有重要意义，有望为岩浆侵入型矿井突出防治提供理论支持。

我国众多矿区成煤过程受中、新生代岩浆侵入活动影响，深成变质作用叠加区域岩浆热变质作用，致使煤体孔隙结构、瓦斯吸附解吸特性及瓦斯突出指标显著改变，而岩浆接触变质带煤体为煤与瓦斯突出高发区，相关基础研究不足。据此，以辽宁铁法大兴矿和大隆矿岩浆侵入型煤体为研究对象，采用压汞和液氮吸附法结合扫描电镜定量分析了煤体微观孔隙结构特征，表明岩浆侵入型煤体基质赋存大量有微孔和热解气孔。靠近岩浆岩体煤体的变质程度提高，煤中水分含量降低。采用光谱分析技术定量表征岩浆热演化煤的化学结构，结果表明岩浆侵入热应力改变了接触变质煤芳香层片直径，拉曼光谱表明接触变质煤的结构组成和分子有序化程度更加完善和各项异性；瓦斯吸附解吸试验表明岩浆接触变质带煤具有初始瓦斯（吸附）解吸速度快，前10s的瓦斯解吸量占120分钟累计瓦斯解吸量的50%以上，主要原因是岩浆的热演化作用提高了煤体＜2nm的微孔孔容和BET比表面积；基于瓦斯解吸数据，采用球型煤粒扩散模型计算出岩浆侵入型煤体的扩散系数明显高于正常煤体和相邻矿区煤体的扩散系数。基于靠近岩浆岩体煤水分含量变小的特点，开展了不同外加水分条件下煤体解吸特征和钻屑解吸指标（突出指标）实验研究，表明随着水分的降低，甲烷解吸量增大，瓦斯突出指标变大，煤体突出危险性增强。此外，现场实测接触变质带煤层气体组分变化规律表明，岩浆热演化煤体中含有的CH4和CO2含量均高于相邻正常煤体，暗示岩浆接触变质带煤体具有CH4和CO2双重突出的风险。