Sorption time is a key parameter for calculating the gas mass exchange between the matrix and the fracture system of coal, and which is generally defined as the time taken for coals to desorbed 63.2% of the total adsorbed CH₄. It's usually measured through CH₄ isothermal adsorption-desorption experiments with coal particles or blocks. However, the conventional method has many problems in determining the sorption time, including (1) over the experiments, due to the presence of adsorption-desorption hysteresis, the residual gas may be >36.8% of the adsorbed volume, which makes it impossible to determine the sorption time, and (2) the sorption time test results for granular coals have a significant particle-size effect, while for coal blocks they’re affected by the seepage behavior because all measured desorption parameters undergo the coupled “diffusion-seepage” motion. Therefore, this study conducted a series of experiments in coal columns with pre-fabricated holes to decouple the “diffusion-seepage” behavior and calculate sorption time by a new method. Coal columns with pre-fabricated holes modified the seepage channels while hardly altering the diffusion pore system, which achieves the quantification of the seepage behavior. As observed, the equilibrium time of CH₄ was found to be much longer than of He. It suggests that the diffusion process is the master factor for the CH₄ adsorption equilibrium in coal. Comparing the gas desorption rates of the coal columns, in the first 62.5–67.5 min the differences among desorption rates were large, while afterward the differences disappeared. It is inferred that the desorption process in the earlier stage is controlled by seepage behavior, while dominated by diffusion in the later stage of the gas transport. The key point of the new method is to acquire the diffusion-dominated CH₄ desorption volume by eliminating the effect of seepage behavior. The sorption time in this study was calculated directly by the interporosity flow function, which ranged from 266.4 min to 276.4 min. The new method can avoid many problems of a conventional method and is highly scalable.

吸附时间是计算煤的基质与裂缝系统之间气体质量交换的关键参数，一般定义为煤解吸63.2%的总吸附CH ₄所需的时间。通常通过 CH _4测量煤颗粒或块的等温吸附-解吸实验。然而，常规方法在确定吸附时间方面存在许多问题，包括（1）在实验过程中，由于存在吸附-解吸滞后，残留气体可能> 36.8％的吸附体积，这使得不可能确定吸附时间，以及（2）颗粒煤的吸附时间测试结果具有显着的粒度效应，而对于煤块，它们受到渗流行为的影响，因为所有测量的解吸参数都经历了耦合的“扩散-渗流”运动。因此，本研究在预制孔煤柱中进行了一系列实验，以解耦“扩散-渗流”行为并通过新方法计算吸附时间。预制孔煤柱在改变渗流通道的同时几乎不改变扩散孔系统，实现了渗流行为的量化。正如所观察到的，CH 的平衡时间₄被发现比He长得多。这表明扩散过程是煤中CH ₄吸附平衡的主要因素。比较煤柱的瓦斯解吸速率，前62.5~67.5 min解吸速率差异较大，之后差异消失。推测前期解吸过程受渗流行为控制，而后期气体输运主要受扩散控制。新方法的关键是获得以扩散为主的CH ₄通过消除渗流行为的影响来解吸体积。本研究中的吸附时间由孔隙间流动函数直接计算得出，范围为 266.4 至 276.4 分钟。新方法可以避免传统方法的许多问题，并且具有高度的可扩展性。