煤的表面自由能随瓦斯抽采的变化规律
Surface free energy of coal and its variation law with gas extraction
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摘要: 为了提高瓦斯抽采效果，防治煤与瓦斯突出，探讨了煤孔隙内表面的结构特点，从表面自由能的角度揭示了煤-瓦斯之间的界面作用，构建了煤的表面自由能与瓦斯吸附量之间的表达式；利用OCG方法，测定沙曲煤矿煤样的表面自由能在实验室条件下为43.33 mJ/m2；利用瓦斯抽采流-固-热耦合控制方程，对沙曲煤矿的瓦斯抽采过程进行了数值模拟。研究表明：煤的孔隙内表面处于不均匀的力场之中，煤孔隙内表面相比煤体相内部具有附加的表面自由能，煤孔隙内表面的表面自由能愈大，其吸附能力愈强；煤的表面自由能随瓦斯抽采作业不断增加，且在抽采钻孔附近区域的表面自由能最高；在瓦斯抽采作业之前，通过有效的技术措施降低煤的表面自由能，有利于提高瓦斯抽采效果。Abstract: In order to improve the effect of gas extraction and prevent coal and gas outburst, the structural characteristic of coal pore inner surface was discussed, the interface interaction between coal and gas was revealed from the perspective of surface free energy, and the expression between the coal surface free energy and the amount of gas adsorption was constructed. Using the OCG method, the surface free energy of the coal sample in Shaqu Coal Mine was determined to be 43.33 mJ/m2 under laboratory conditions. Through the hydraulic-mechanical-thermal coupled governing equations for gas extraction, the gas extraction process in Shaqu Coal Mine was numerically simulated. The results show that the inner surface of coal pore is in an asymmetrical force field, and the inner surface of coal pore has additional surface free energy compared to the inside of the coal phase, the greater the surface free energy of the coal pore inner surface, the stronger its adsorption capacity; the coal surface free energy continues to increase with the gas extraction operation, and the surface free energy is the highest in the area near the extraction borehole; before the gas extraction operation, effective technical measures to reduce the surface free energy of coal are helpful to improve the gas extraction effect.
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