电场对煤表面结构及瓦斯吸附性的影响

采用直流电场作为物理场,利用已研制的电场作用下煤的瓦斯吸附试验装置,对电压作用下煤的瓦斯吸附性进行了试验研究,对电压作用前后试验煤样表面结构进行了XPS能谱测试,对煤样表面结构C元素含氧官能团的种类及其相对含量进行了分析,目的是基于煤表面结构揭示电场作用对煤的瓦斯吸附性影响机理。试验结果表明:电压作用可以弱化煤的瓦斯吸附性,在80 k Hz/1 k V,80 k Hz/3 k V和80 k Hz/5 k V电场作用下,煤表面结构C元素含氧官能团发生改性,C—C/C—H键相对含量从47.22%减少到24.95%,生成C—O键、C=O羰基官能团、COO—羧基或醌官能团,使得这3种含氧官能团相对含量增加,其最大值分别为54.44%,13.89%和7.39%;随着煤表面结构C元素C—C/C—H键相对含量的减少,煤的瓦斯饱和吸附量a呈线性规律减小,吸附常数b呈指数规律减小;与电场作用前相比,作用后煤总孔面积、中值孔径(体积)、中值孔径(面积)和平均孔径等孔隙结构参数均增加。

Coal surface structure and gas adsorption under direct current electric field treatment

The direct current electric field was used as a physical field.An experimental apparatus affecting the gas adsorption in coal with voltage weakening was utilized.The experiment on the gas adsorption in coal under the voltage treatment had been conducted.The coal surface structures of the experimental samples were measured by XPS.The species and the relative contents of the C element with oxygen functional groups in the coal surface structure were analyzed.The law between the coal gas adsorption under the voltage and the C element with oxygen functional groups was studied.The experimental results were as follows：the gas adsorption in coal could be weakened under the voltage treatment.Under the electric field of 80 kHz/1 kV,80 kHz/3 kV and 80 kHz/5 kV,the oxygen functional group of the C element on the coal surface structure was modified,the relative content of C—C/C—H reduced from 47.22% to 24.95%,and the new oxygen functional groups were C—O,C〖CDS1〗O and COO—.The relative contents of the third oxygen functional groups increased and the maximum contents were 54.44%,13.89% and 7.39%,respectively.With the decrease of the relative content of C—C/C—H,the saturated adsorption capacity reduced with a linear law and the adsorption constant reduced with an exponential law.The coal pore structure parameters including the total pore area,the median pore size (volume),the median pore size (area) and the mean pore size were increased under the electric field.