Experiment Study Of Impact Of The External Pressure Solution On Desorption Characteristic About Coal With Gas

Coal seam water infusion is one of the important technical measures in prevention and controlling of coal and gas outburst,but the mechanism of it has not been revealed deeply yet,one of the main performance is that there is a divergence about the impact of water injection on desorption characteristic.For the problem,the impact of the external solution and pressure water on desorption characteristic about coal with gas is studied by means of experimental research and theoretical analysis in this thesis.Based on the coal samples preparation,basic parameters test of coal samples and surfactant selection,through the homemade experimental device,gas desorption process of different water injection pressure,different adsorption equilibrium pressure,different injection solution and different metamorphic grade of coal were tested.Then the moisture content,residual gas content and pore structure characteristic of coal samples were tested,and the impact mechanism was discussed and analyzed combining the macroscopic experimental phenomena and theoretical analysis under the micro scale.The results show that:(1)Cumulative desorption quantity and desorption rate were reduced after the water injection,and the larger the water injection pressure is,the greater the decreased degree is,the moisture content and residual gas content is.Except that the micropore volume does not change significantly before and after water injection,the pore volume of the macropore,mesopore and small pore are increased after water injection,and the total pore volume,the average pore diameter and the porosity are also increased in different degrees.After the comprehensive analysis,the reducing effect of capillary force generated by pressure water which expands pore is less than increasing effect from the decrease of pore size,the capillary force increases as a whole,and the obstruction of the gas desorption process is enhanced,which causes that the inhibitory effect on gas desorption is more obvious.(2)The greater adsorption equilibrium pressure,the greater adsorption quantity,the stronger obstruction effect of water injection process,the greater the pore scale that the pressure water can enter,the smaller the capillary force and the weaker inhibitory effect on gas desorption,the greater the cumulative desorption quantity and desorption rate.(3)Compared with the injection of pure water,the capillary force increases after the injection of compound solution,which causes that the pore size is deeper and the resistance of desorption process is greater.The stronger the inhibitory effect on gas desorption,the smaller the cumulative desorption quantity and desorption rate.(4)The higher the metamorphic grade of coal,the stronger the ability to adsorb gas and the greater the adsorption quantity.The high pressure gas are more likely to form,and the stronger the ability to overcome capillary force,the greater the cumulative desorption quantity and desorption rate.