煤粒瓦斯变压吸附数学模型及数值解算

Coal particle gas adsorption mathematical model and numerical solution under variable pressures

  • 摘要: 为了验证达西定律是煤粒瓦斯流动的普适性规律,在之前所做的不同形状煤粒的定压吸附解吸及变压解吸实验基础上,设计了封闭空间内煤粒瓦斯变压吸附实验,分别得到42.976,11.600~13.800,3.350~4.000和1.180~1.400 mm四种不同粒径的煤样在0.5,1,2和4 MPa四种初始压力下瓦斯累积吸附量随时间的变化情况。基于达西和菲克定律,分别建立封闭空间内煤粒瓦斯变压吸附数学模型。运用有限差分法计算模型,并编制Visual Basic计算机程序对方程进行解算,得到两种模型在不同时间不同初始瓦斯压力下的瓦斯累积吸附量。通过对比分析实验和数值模拟得到的ln1-(Q_t/Q_∞)~2与t关系图,发现封闭空间内煤粒瓦斯吸附过程同样遵循达西定律。这与之前所做的一系列研究所得结论一致,即无论是吸附还是解吸过程,煤粒外部压力变化与否,煤粒形状如何,均可得到达西定律是煤粒瓦斯流动基本规律。

     

    Abstract: In order to verify the universality of Darcy law in coal particle gas flow,the coal particle gas adsorption ex- periment in enclosed space under variable pressures was designed on the basis of the constant pressure adsorption and desorption and variable pressure desorption experiments of different coal particles shapes. And the gas accumulative adsorption amount with time variation of 42. 976,11. 600 ~ 13. 800,3. 350 ~ 4. 000 and 1. 180 ~ 1. 400 mm coal parti- cles under 0. 5,1,2 and 4 MPa initial pressures were obtained. Based on Darcy and Fick law,the gas adsorption math- ematical models were proposed separately. The use of finite difference method,combined with the computer program coded in Visual Basic,enabled to solve the equations. And the gas accumulative adsorption amount of two models at different times and different initial gas pressures were obtained. By comparing and analyzing ln1-(Qt / Q∞ )2 vs. t di- agrams from experiment and numerical simulation,it is found that the gas adsorption process of coal particles in the en- closed space also follows Darcy’s law. This conclusion is consistent with a series of previous researches,namely wheth- er the adsorption or desorption process,and the coal particle external pressure and the coal particle shape change or not,it is concluded that Darcy law is the basic rule of coal particle gas flow.

     

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