Diffusion And Adsorption Study Of CO₂ In Mined-out Areas Of Coal Mines Filled With Coal Gangue Materials

Coal mine filling mining is an important way to green mining,combine CO₂sequestration and coal mine goaf filling,damage reduction in filling the strata movement and surface subsidence on the basis of the realization of mine waste rock and other solid waste disposal and the dual role of CO₂ sequestration in mining residual space,which is of great significance for the use of coal mining space.Research and calculation of coal gangue adsorption of CO₂ process,as well as different particle size gangue for CO₂ adsorption capacity difference,can better develop and improve coal gangue gas adsorption theory,for CO₂ storage,coal mine goaf utilization is of great significance.By adding graphite to gangue and other aggregates to form suitable filling materials,improve the adsorption performance of gangue composite materials,and reveal the diffusion and adsorption rules of CO₂ in gangue filling materials is a key scientific problem to be solved.The characteristics of CO₂ diffusion with time in coal gangue samples are simulated,and the experimental results are fitted Based on the Langmuir isothermal adsorption model,the adsorption capacity formula of gangue filling body in goaf is deduced The main achievements are as follows.Sample based on this the paper in different size groups of coal gangue as the research object,using laboratory isothermal adsorption experiment,fitting equation and software simulation method,the system of the coal gangue samples were studied,the pore development characteristics of coal gangue samples were analyzed and studied under the different size of CO₂ adsorption amount of experimental data,and the experimental data obtained by the fitting of the equation,simulated the CO₂ in the porous medium samples over time and diffusion characteristics,and based on the Langmuir isotherm adsorption model,on the adsorption quantity of coal mine goaf coal gangue filling body formula derivation.The main research results are as follows:(1)Through the pretreatment,grinding,ultrasonic cleaning,scanning electron microscopy and other experimental means of gangue sample,the internal pore structure characteristics of gangue are comprehensively analyzed from the perspective of image.The gangue is a porous medium solid with rough surface and well-developed cracks,which is good for adsorption.(2)Using Flow Prep 060 sample degassing treatment system and Tristar?surface and pore test system,indoor experiments were carried out on the adsorption of gangue samples with different particle sizes under isothermal conditions,and the distribution characteristics of internal pores of gangue samples with different particle sizes were analyzed.The gas adsorption capacity of gangue samples with particle size of 5mm was the largest.At the same time,graphite with mass fraction of 2%was added to form the composite material.The study found that the coal gangue composite material with graphite could not improve the adsorption performance of the pair.By comparing the adsorption results,it can be seen that the adsorption performance of gangue is better than that of graphite for the same mass fraction of coal gangue and graphite.(3)With the help of many physical field simulation software COMSOL Multiphysics,we constructed the adsorption model in the coal gangue and so on diffusion in porous media,change of gas diffusion coefficient,with the result of simulation analysis found that the diffusion coefficient changed from 10⁹ to 10-7,almost no impact on the rate of diffusion in porous media,spread the finished time no change;When the diffusion coefficient is 10-1,the diffusion rate in porous media such as coal gangue increases significantly,and the diffusion time is shortened by one tenth.(4)Based on the Langmuir isothermal adsorption model,the theoretical adsorption capacity formula of gangue backfill in the goaf of coal mine was deduced,and combined with the actual engineering geological conditions,a simple theoretical calculation was carried out to provide a reference for engineering practice.