Abstract To enhance desorption of coalbed methane and increase extraction efficiency, a technique using microwave irradiation is proposed. Methane desorption experiments without and with microwave irradiation were carried out in the laboratory using an experimental system developed to study methane desorption. The experimental results show that microwave irradiation causes the total quantity of methane desorbed to increase from 1.91 to 3.92 times larger than the quantity desorbed without MI. Two hour trials were performed, applying microwaves for 4, 8 or 16 min, equivalent to output energies of 192, 384 and 768 kJ. These results show that 1 kJ of microwave energy can cause methane desorption to increase by 0.0088 ml per gram of coal. Under successive microwave irradiations of 40 s, the desorption rate increases by a factor of 10.2. Kinetic analysis also found that microwave irradiation enhances the methane diffusion coefficient and decreases the attenuation coefficient. Regardless of which diffusion model is used to determine the diffusion coefficient, the quantity of gas desorbed increases as the microwave irradiation time increases. The pore and surface features of coal samples exposed to microwaves were determined by using mercury intrusion porosimetry and nitrogen adsorption and specimens were examined by scanning electron microscopy. Methane desorption evidently results from both the microwave thermal effect and structural damage to the coal. The results reported herein reveal the mechanisms that promote methane desorption by microwave irradiation and suggest a new field technique for extracting coalbed methane.

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微波辐照促进煤层气解吸的作用及解吸动力学分析

摘要 为了提高煤层气的解吸效率，提高提取效率，提出了一种利用微波辐射的技术。没有和有微波辐射的甲烷解吸实验是在实验室中使用为研究甲烷解吸而开发的实验系统进行的。实验结果表明，微波照射引起的甲烷解吸总量比没有MI的解吸量增加1.91倍至3.92倍。进行了两个小时的试验，应用微波 4、8 或 16 分钟，相当于 192、384 和 768 kJ 的输出能量。这些结果表明，1 kJ 的微波能量可使每克煤的甲烷解吸量增加 0.0088 ml。在 40 秒的连续微波照射下，解吸速率增加了 10.2 倍。动力学分析还发现，微波辐照提高了甲烷扩散系数并降低了衰减系数。无论采用哪种扩散模型来确定扩散系数，随着微波照射时间的增加，解吸的气体量也增加。用压汞法和氮吸附法测定微波作用下煤样的孔隙和表面特征，并用扫描电子显微镜检查样品。甲烷解吸显然是由微波热效应和煤的结构破坏造成的。本文报告的结果揭示了微波辐射促进甲烷解吸的机制，并提出了一种新的煤层气提取现场技术。