超临界条件下煤中瓦斯吸附孔径特征

Pore Size Characteristics of Gas Adsorption in Coal at Supercritical State

采用高低温瓦斯吸附解吸试验测试系统,在超临界温度下测试了煤的瓦斯吸附等温线,并基于DRK吸附理论,从低压到高压以分段拟合的方法得到瓦斯吸附参量,并计算分析瓦斯吸附的孔径变化规律。研究结果表明:随着温度降低,煤对瓦斯的吸附能力增强。在低压条件下,甲烷分子优先吸附在孔径较小的孔中,而在高压时气体分子开始吸附在孔径较大的孔中。在相同吸附温度下,从低压到高压吸附瓦斯在煤孔隙中的覆盖面积增大,吸附瓦斯的平均孔径也逐渐增大。吸附覆盖面积和平均孔径均随温度的降低而增大,即降低温度,煤表面能量均匀性增大,吸附能力增强。

The gas adsorption and desorption test system in high and low temperature was used to test the gas adsorption isotherm of coal at supercritical temperature. Based on the DRK adsorption theory, gas adsorption parameters were obtained by using the method of segmentation fitting from low to high pressure, and the pore size variation of gas adsorption was calculated and analyzed in the same time. The research shows that the adsorption capacity of coal to gas is enhanced with the decreasing of temperature.At the low pressure conditions, gas molecules are preferentially adsorbed in pores with the smaller pore size. Gas molecules are preferentially adsorbed in pores with the larger pore size at high pressure conditions. At the same adsorption temperature, the coverage area of the adsorbing gas in the coal pores increases from low to high pressure and the average pore size of the adsorbing gas also gradually increases. Both the adsorption coverage area and the average pore size increase with the decreasing of temperature, which is that the uniformity of the coal surface energy increases and the adsorption capacity enhances with the temperature decreasing.