声场作用下煤中甲烷解吸扩散的特性

为了深入研究超声波的机械振动效应、热效应、空化效应提高煤层气抽采率的机理，研制了可控声场作用下甲烷吸附、解吸试验系统。实验研究了不同频率的超声波、不同声强的声波作用下煤中甲烷的解吸特性，得出：不加声场与声场作用下煤中甲烷的解吸动力学特性一致，甲烷解吸全过程中，初始解吸速度较快，随时间的增加，解吸速度越来越慢，最终趋于0；声场作用下甲烷的解吸量增加了20%～90%，且解吸量随声强的增大而增大；煤中甲烷的扩散规律可用单一扩散模型描述，声场作用下传质毕欧准数减小，扩散系数增大，表明声场作用使煤体内部扩散阻力减小，传质速度加快，扩散能力增强，有利于煤中甲烷的解吸、扩散。

Characteristics of methane desorption and diffusion on coal under acoustic wave

In order to study the mechanism of acoustic wave’s mechanical vibration effect，thermal effect and cavitation effect on improving coal bed methane extraction rate，the desorption tests under different acoustic frequencies and different intensities were conducted.The results show that the desorption dynamic characteristic of methane on coal under the effect of acoustic wave is in accordance with that of no acoustic wave.In the whole process of desorption，the initial desorption rate is relatively high，and as time goes on，decreases slowly and eventually reaches 0；the amount of desorption under acoustic wave increases by 20% to 90% under acoustic wave，and increases with the increase of sound intensity.The diffusion regularity of methane on coal can be described by single diffusion model，and mass transfer biot criterion decreases as diffusion coefficient increases under the effect of acoustic wave.It shows that acoustic wave effect reduces coal internal diffusion resistance，mass transfer speed，diffusion ability enhancement，which are advantageous to the coal methane desorption and diffusion.