CH₄ and CO₂ Desorption Characteristics of Low-Gas Mine Coals

Mastering coal gas desorption characteristic is the key to improve coalbed gas recovery and prevent coal mine gas outburst. However, relevant research targets frequently tend to the high-gas coal mines rather than low-gas mines, even though huge potential coalbed gas resource deposit and not a few gas outburst accidents exist in the low-gas mines. To further address the research gap on low-gas coal mines and clarify the gas desorption patterns of CH₄ and CO₂ within these mines, we selected four low-gas coal samples and investigated the effects of temperature, adsorption equilibrium pressure, and particle size on the desorption of CH₄ and CO₂. Pore structure characteristics were also analyzed to explain the gas desorption patterns. The findings indicated that the effects of these three factors on the desorption amount of low-gas coal were similar to those of high-gas coal. Nonetheless, the desorption curves more closely aligned with the Qin Yueping model, based on Darcy’s law. Additionally, the initial process of desorption could be described by the Fick’s law-based exponent model, and the effective diffusion coefficients of the low-gas coals were larger than those of high-gas coals. These findings shed light on figuring out gas release characteristics of low-gas coal mines.