Laboratory measurements of methane desorption on coal during acoustic stimulation

• Acoustic wave has promoted desorption of methane on coals.
• Desorption amount increases linearly as acoustic intensities increase.
• Desorption model under the effect of acoustic waves was established.
• Mechanical vibration, thermal effect and cavitation effect can promote capacity of desorption.

An apparatus considering the impacts of acoustic waves (mechanical vibration effect, thermal effect, and the cavitation effect) was designed to study the characteristics of gas adsorption and desorption on coals. Experiments of methane desorption on coals were performed under the effects of different acoustic frequencies and different acoustic intensities. The results showed that acoustic wave has promoted desorption of methane on coals. It was found that the initial desorption rate is relatively high, and then desorption rate decreases slowly with time, and finally achieves equilibrium. The desorption amount of methane on coals under the effect of acoustic waves is higher than that obtained without acoustic waves, and we found that desorption amount of methane on coals increases as acoustic intensities increase. It was also found that desorption rate of methane on coals is promoted under the effect of acoustic waves. Since the existing desorption models cannot describe the desorption characteristics of methane on coals under the effect of the acoustic intensity, a correction term was introduced into the existing models in this study, and thus a new model that is able to describe methane desorption under the effect of acoustic waves was established. The promotion mechanism of methane desorption on coals by the acoustic waves was also studied, it was found that the thermal effect of acoustic waves on methane desorption can be clearly seen.