【作者】 陈向军；

【导师】 袁亮； 程远平；

【作者基本信息】 中国矿业大学 ， 安全技术及工程， 2013， 博士

【摘要】 煤层注水后将增加煤体内外加水分，煤的瓦斯解吸特性随之也发生变化。为研究外加水分增加后煤的瓦斯解吸特性变化规律，在分析水分对瓦斯解吸影响研究现状的基础上，研制了一套高压吸附状态下注水解吸测试装置，实验装置能够对吸附高压瓦斯煤注水时进行搅拌，较好地改善了注水后煤样水分含量分布均匀程度。CH4和H2O分子在煤表面吸附模拟及其之间的作用力估算结果表明：煤对H2O的吸附能力大于对CH4的吸附能力。煤解吸瓦斯类型分为升温解吸、降压解吸、置换解吸和混合解吸四种类型，注入外加水分实验过程中主要发生了置换解吸和降压解吸。在考察确定1-3mm煤样为注水实验用合理粒径的基础上，利用自制的高压吸附-注水-解吸测试装置，在实验温度30℃、吸附平衡压力0.5MPa、0.84MPa、1.5MPa和2.5MPa条件下，采用先对干燥煤样吸附平衡，再对其进行边注水边搅拌的实验方法分别对高变质的永红煤（YH煤）和高家庄煤（GJZ煤）、中等变质程度的祁南煤（QN煤）和低变质程度的大隆煤（DL煤）注入不同外加水分后的瓦斯解吸过程进行了测试。实验结果表明，外加水分能够置换吸附的瓦斯，外加水分越大，水分对吸附瓦斯的置换量和置换率越大。外加水分对YH煤的置换量和置换率最大，对DL煤和QN煤的置换量和置换率居中，对GJZ煤的置换量和置换率最小。外加水分对卸压后煤的瓦斯解吸量、解吸速度、钻屑瓦斯解吸指标、扩散系数、解吸率和瓦斯放散初速度均有影响，它们总体上随着外加水分的增加逐渐减小。外加水分对卸压后煤的前40min内瓦斯解吸速度影响较大，对40min后的瓦斯解吸速度影响较小。外加水分对不同变质程度煤的瓦斯解吸量和钻屑瓦斯解吸指标影响程度存在差异，对DL煤极限解吸量影响最大，对QN煤和YH煤影响次之，对GJZ煤极限解吸量影响最小，造成这种差异性与煤样大孔、中孔和小孔总比表面积有关；对YH煤钻屑瓦斯解吸指标影响最大，对QN煤和DL煤影响次之，对GJZ煤钻屑瓦斯解吸指标影响最小，对钻屑瓦斯解吸指标影响差异性与小孔孔容占总孔容的比例有关。实验数据表明，外加水分对不同煤种解吸瓦斯的综合影响效果不同，它总体上对中、高变质程度煤的瓦斯解吸起到促进作用，对低变质程度煤的瓦斯解吸起到抑制作用。数值模拟和工程实践表明，外加水分对煤解吸瓦斯既有促进作用，又有抑制作用。煤层注水对瓦斯解吸的综合影响效应与注水后煤层渗透率变化和水对吸附瓦斯的置换强度有关，若注水后煤层渗透性降低程度较小，水对煤层吸附的瓦斯置换强度较大时，注水将促进煤层瓦斯解吸，反之，注水将抑制煤层瓦斯解吸。更多还原

【Abstract】 Injecting water into coal seam can increase the additional moisture of coal, and then themethane desorption characteristics of the coal will change. To research the change rule of coalmethane desorption properties after injecting water, based on the analysis of moisture effecton methane desorption, a device was developed for injecting water and the measurement ofdesorption under the high-pressure adsorption state. The device could stir the coal sampleswhen injecting water into coal, and it improved the wet effect of the coal sample.Through simulation for CH4and H2O molecules adsorption on the surface of coal andestimation for forces of CH4and H2O molecules on coal, the paper obtained the results whichthe adsorption ability of H2O on coal was bigger than the adsorption ability of CH4on coal.Coal desorption methane types were divided into cooling desorption, step-down desorption,replacement desorption and mixed desorption, and replacement desorption and step-downdesorption occured in the process of injecting water.Based on study the reasonable size of1-3mm for injecting water experiment, throughthe homemade device of high-pressure adsorption-injecting water-desorption,the methanedesorption of Yonghong coal (YH coal) and Gaojiazhuang coal (GJZ coal), which exhibited ahigh metamorphic degree, and Qinan coal (QN coal) and Dalong coal (DL coal), whichexhibited a moderate and a low metamorphic degree, were tested after the injection of water.The experimental temperature was30℃, and the experimental adsorption pressures were0.5MPa,0.84MPa,1.5MPa, and2.5MPa.The results show that injected water can displaceadsorbed methane, and the replacement amount and replacement ratio increase with theamount of injected water. the maximum replacement amount and replacement ratio areobtained from the YH coal, moderate replacement amount and replacement ratio are obtainedfrom the DL and the QN coal, and the lowest replacement amount and replacement ratio isobtained from the GJZ coal. Injected waters have the impacts on methane desorption quantity,desorption velocity, gas desorption index of drill cuttings, methane diffusion coefficient,desorption rate and methane initial diffusion velocity after the pressure relief,and the methanedesorption quantity,desorption velocity, gas desorption index of drill cuttings, methanediffusion coefficient, desorption rate and methane initial diffusion velocity are graduallydecreased with the increase of injected water. In the first40minutes, the impact of theinjected water on the methane desorption velocity is obvious; however, after40minutes, thiseffect can be ignored.The influence of the injected water on the methane desorption quantityand gas desorption index of drill cuttings are different for coal samples with differentmetamorphic degrees.The maximum effect is obtained from the DL coal methane desorption quantity, moderate effects are obtained from the QN and the YH coal methane desorptionquantity, and the lowest effect is obtained from the GJZ coal methane desorption quantity.The main reason of the difference is the total surface area of the macropores, mesopores, andpores in the different coal samples. The influence of the injected water on the gas desorptionindex of drill cuttings is maximal from YH coal. In contrast, the influences of the injectedwater on the gas desorption index of drill cuttings are moderate from the QN and the DL coals,and the influence of the injected water on the gas desorption index of drill cuttings is lowestfrom the GJZ coal. These differences are due to the ratio of the pore volume to the totalvolume.The comprehensive effects of injected water on methane desorption for different coalsare inconsistent from the experimental datas, and injected waters have promoting effect onmethane desorption for the high and moderate metamorphic degree coal, but injected watershave inhibition effect on methane desorption for the low metamorphic degree coal.Injected water can promote and inhibit methane desorption of coal seam from thenumerical simulation and engineering practice. The combined effects of injecting water intocoal seam on methane desorption have something to do with the changes of coal seampermeability and replacement adsorbed methane effect of water. When the decrease degree ofcoal seam permeability is smaller and replacement adsorbed methane effect of water is largerafter injecting water, the injected water will promote the coalbed methane desorption,conversely, it will inhibit coal seam methane desorption.更多还原