吸附平衡时间对瓦斯吸附常数测值的影响

Effect of adsorption equilibrium time on determination of gas adsorption constants

煤的瓦斯吸附常数是煤矿瓦斯防治的重要基础参数,它的准确测定对煤矿瓦斯预测、瓦斯抽采和瓦斯突出防治均有重要的意义.煤炭行业标准MT/T 752—1997《煤的甲烷吸附量测定方法(高压容量法)》要求测定过程中煤对瓦斯吸附的平衡时间为7 h,但研究发现大部分煤样在7 h内并不能达到吸附平衡.选用无烟煤、贫煤和气肥煤3类不同煤阶的煤样,进行了不同吸附时间下的瓦斯吸附常数的对比测试.结果表明,吸附时间对瓦斯吸附常数影响非常明显;对固定煤阶煤样,吸附时间越长,吸附常数a值有增大的趋势;煤阶越高,瓦斯吸附常数a值受吸附时间的影响程度越大,煤对瓦斯的饱和吸附平衡时间越长.因此,对于高阶煤样,吸附时间应适当延长,从而提高测值可信度和工程应用价值.

Gas adsorption constants of coal samples are fundamental parameters for gas control and drainage in coal mines.The accuracy of these values plays an important role in gas content measurement and gas extraction.Even though the adsorption equilibrium time is defined in 7 hours by the standard of MT/T 752—1997,it is found that the most of coal samples cannot reach the state of adsorption equilibrium in 7 hours during the experimental work conducted.In order to understand the effect of adsorption time upon the value of gas adsorption constants,two gas adsorption constants,a and b were measured under different adsorption time for three different coal ranks.The result shows that the higher the coal rank,the higher the adsorption capacity and higher the value of gas adsorption constant a.The value of gas adsorption constant b presents the trend of decreasing with the increase of coal ranks under identical experimental conditions.In addition,with the increase of coal ranks,the gas adsorption constant a is more sensitive to adsorption time,which has prolonged adsorption equilibrium time.Therefore,when conducting the tests for gas adsorption constants,reasonable adsorption equilibrium time should be adjusted on the basis of a coal rank,particularly to these coal samples with a higher degree of metamorphism.For such coal samples,adsorption equilibrium time should be extended so as to enhance the reliability and accuracy of adsorption constant values measured