煤体瓦斯放散特性电场响应研究

Investigation on the response of the electric field to the methane diffusion characteristics in the coal body

针对含瓦斯煤放散特性的电场响应,对不同煤阶的煤样施加不同静电压,测试其放散初速度,结果表明,静电场具有提高瓦斯放散初速度的作用,受其影响程度由大到小为烟煤(YM)构造煤、烟煤(YM)非构造煤、无烟煤(WYM)非构造煤、无烟煤(WYM)构造煤。这一现象符合不同煤级自由基浓度的分布规律,利用灰色关联分析法验证了静电场是通过影响煤岩组分中固定碳来宏观改变瓦斯放散速度,分析其影响机理,静电场下煤与瓦斯分子发生极化,增加了吸附势阱深度,计算静电压下煤表面能的变化,即电压升高,煤表面能降低值增大,两者都使得煤表面吸附更多瓦斯,提高了瓦斯放散时的瞬时瓦斯压力梯度,从而促使瓦斯放散初速度加快。

This paper is inclined to introduce our exploration of the coal polarization under the electrostatic field and the change of the surface energy of the coal impacts on the methane diffusion from the variation characteristics of value b. We have finished the research based on the electric field response of diffusion characteristics of the coal containing methane, whose initial speed can be tested via the different electrostatic voltages of the coal samples made of different coal ranks. The results of our study show that it is possible to improve the initial speed of the methane diffusion under the electrostatic field. The regularity that accounts for the improvement lies in a descending order of the aforementioned coal ranks, that is： YM tectonic coal 〉 YM non-tectonic coal 〉 WYM non-tectonic coal 〉 WYM tectonic coal. The regularity we have found is well in accord with the distribu- tion regularity of the free radical concentration of different coal ranks. What is more, the electrostatic field has a great impact on value b in Langmuir equation, which tends to have an increasing effect trend. From the research, it can also be concluded that the coal and gas molecules tend to be polarized, which may increase the adsorption po- tential with the increase of the well depth. What is more, it can be discovered from the physical meaning of value that value b and the depth of the potential well may well be positively correlated in that, as b increases, the methane adsorption capacity increases too at a certain temperature. As to the change of coal surface energy, it can be worked out under the static voltage. Namely, with the increase of the voltage value, the value of the coal surface energy would in- crease, too. And, in turn, the more the surface energy decreases, the more gas the coal surface can absorb, and, consequently, the greater the methane diffusion will be. Therefore, with the current ex- perimental methods, the instantaneous methane diffusion pressure will be gradually heightened as the value of methane adsorption increases, which tends to contribute to the initial speed of methaiae diffusion.