Yao Zhuangzhuang
China Coal Research Institute, Beijing 100013, China.
State Key Laboratory of Gas Disaster Monitoring and Emergency Technology, Chongqing 400037, China.
ACS Omega. 2023 Mar 28;8(14):12992-13003. doi: 10.1021/acsomega.3c00177. eCollection 2023 Apr 11.
In order to further clarify the transport mechanism of coalbed methane and to study the gas diffusion law in coal, this paper conducted an experimental study on the desorption law of coal particle gas. On the basis of experiment, the time-varying characteristics of the diffusion coefficient in the process of coal particle gas desorption were analyzed, and the gas diffusion calculation model considering the time-varying diffusion coefficient was obtained by experimental fitting. On this basis, the influence of coal particles with different shapes on the gas desorption law is studied, and the gas diffusion equations of flat and cylindrical coal particles based on time-varying diffusion coefficients are established. The corresponding analytical solutions are obtained by using mathematical and physical methods, and the results are verified. The results show that the larger the adsorption equilibrium pressure is, the larger the gas desorption capacity is. At the initial stage of desorption, the larger the particle size is, the smaller the desorption capacity and desorption speed are. However, after reaching the "limit particle size", the particle size has little influence on the desorption capacity and desorption speed. Under different temperature conditions, the gas desorption amount monotonously increases with time. The higher the temperature is, the greater the desorption amount is. The adsorption constant value slightly increases with the increase of temperature and then decreases. The adsorption constant value has a trend of decreasing with the increase of temperature. The research results have very important practical significance for the optimization of the testing method of underground coalbed methane content and the prediction of coal and gas outburst risk.
为了进一步阐明煤层气的运移机制并研究瓦斯在煤中的扩散规律，本文对煤颗粒瓦斯解吸规律进行了实验研究。在实验的基础上，分析了煤颗粒瓦斯解吸过程中扩散系数的时变特征，通过实验拟合得到了考虑时变扩散系数的瓦斯扩散计算模型。在此基础上，研究了不同形状煤颗粒对瓦斯解吸规律的影响，建立了基于时变扩散系数的扁平状和圆柱状煤颗粒的瓦斯扩散方程。利用数学和物理方法得到了相应的解析解，并对结果进行了验证。结果表明，吸附平衡压力越大，瓦斯解吸量越大。在解吸初期，粒径越大，解吸量和解吸速度越小。然而，达到“极限粒径”后，粒径对解吸量和解吸速度的影响很小。在不同温度条件下，瓦斯解吸量随时间单调增加。温度越高，解吸量越大。吸附常数随温度升高先略有增大后减小。吸附常数有随温度升高而减小的趋势。研究成果对优化井下煤层气含量测试方法及预测煤与瓦斯突出危险性具有十分重要的实际意义。
