Experimental Study On The Effect Of Soluble Organic Matter In Coal On The Adsorption And Desorption Of Coal By CO₂

Gas disaster is a major hazard that threatens the safe mining of coal mines.At the same time,coal seam gas is a clean energy with high calorific value.China's coal-bed methane reserves are abundant.Effective utilization of coal seam gas can improve the utilization rate of energy and optimize the energy structure.Carbon dioxide displacement of coal seam gas is an important technology of coal seam gas mining,and also plays an important role in the management of coal seam gas.The adsorption and desorption capacity of coal gas is carbon dioxide flooding based for coal seam gas,the pore structure is an important factor to affect the adsorption capacity of the gas,and the soluble organic matter in coal is have a certain impact on the pore structure of coal,and coal seam gas for impact on efficient carbon dioxide flooding.Therefore,this paper is based on the raw coal and residual coal pore structure,adopting the methods of theory analysis and simulation experiment of combining the difference between coal and residual coal pore structure,adsorption,desorption,influencing mechanism analysis of soluble organic matter adsorption and desorption characteristics of coal carbon dioxide;Study on displacement of temperature and pressure on efficient carbon dioxide flooding effect for gas,and to investigate the effects of soluble organic matter in coal driving mechanism for coal seam gas of carbon dioxide.Microwave assisted extraction of tetrahydrofuran was carried out in the coal samples of Huaibei mining area,and the residual coal?soluble organic matter was dissolved?was obtained.The raw coal and the residual coal pore structure characteristic parameter was tested by liquid nitrogen adsorption method,through comparative analysis,extraction,pore structure of coal has been simplified to a certain extent,the total pore volume of coal increases,the average pore size and porosity of large coal micropore reduced surface area,micropore volume decreased,and big hole ratio increases,produced by reaming hole phenomenon.The isothermal adsorption experiment of coal and residual coal at different temperatures was carried out with the aid of isothermal adsorption experimental system.Based on the Langmuir and BET adsorption model,the characteristics of carbon dioxide adsorption characteristics of raw coal and residual coal were analyzed.The analysis shows that the saturated adsorption capacity of coal a value is larger than the residual coal,adsorption constant b value is less than the residual coal,after extraction,adsorption ability of coal is reduced to some extent,but the relative adsorption rate of coal can be increased;based on the thermodynamics theory,the surface free energy of coal and coal residue value changes the change rule and the isosteric heat of adsorption,analyzed the variation of soluble organic matter in coal on interaction between coal and carbon dioxide from the view of thermodynamics.After extraction,the surface free energy and equivalent adsorption heat of residual coal are all less than those of raw coal.The adsorption temperature is higher than that of raw coal,which reduces the capacity of coal to adsorb carbon dioxide.The residual coal coal and carbon dioxide desorption experiments carried out by desorption experiment system,desorption curve of each coal coal and residual coal were determined,in-depth study of the residual coal coal and carbon dioxide desorption,desorption rate and diffusion coefficient of variation.The results show that:after extraction,the residual coal accumulation of carbon dioxide desorption and desorption limit increased,desorption rate,effective diffusion coefficient and that after extraction,simplifies the pore structure of coal,increasing the effective diffusion channel,reducing the diffusion migration resistance to CO₂ diffusion from the coal matrix,the carbon dioxide desorption more thoroughly.The displacement of carbon dioxide gas to carry out experiment,the soluble organic matter in coal on temperature,pressure and displacement of high carbon dioxide gas through the experiment of coal seam,methane methane desorption rate,replacement ratio and residual gas content of the three indicators of displacement experiment evaluation.The results show that increasing displacement temperature and pressure can improve displacement efficiency and increase displacement cost and increase economic cost.Considering the displacement pressure is 1¹.5 times of the original storage pressure of coal seam,the displacement effect is more efficient.After extraction,the desorption rate of methane is increased,which is beneficial to the diffusion of gas molecules and the decrease of the content of residual gas in coal,which improves the stability of coal.The effect of carbon dioxide displacing the residual coal methane is better than that of the raw coal,and the soluble organic matter in coal is helpful to improve the effect of carbon dioxide displacement of coal seam gas.