Experimental Study On Desorption Characteristics Of Different Particle Sizes And Gas Pressures Under Coal Steam

The pace of economic development is accelerating,and the need for resources is also greater.The availability of stable and sustainable energy supply has become a key factor constraining the stable and rapid economic growth.The highly polluted and extensive resources such as petroleum and coal have gradually become inconsistent with China's national conditions.China's coal mines and other extensive high-polluting resources have increasingly limited resources for resource constraints,and new energy sources such as solar energy and wind power are still in the research stage.There are many constraints to their use.The clean energy CBM associated with coal mining should receive sufficient attention.Therefore,how to efficiently develop CBM resources becomes extremely important.Coalbed methane is a mineral asset that is accompanied by coal and most of it coexists with coal and rock in the form of sorption.It is also known as gas,and its constituents are in the form of methane.In the past,production did not pay attention to the exploitation and utilization of coalbed methane,and the low utilization rate of coalbed methane was generally directly discharged into the atmosphere.This not only wastes resources but also pollutes the environment.The chemical nature of methane is flammable in the presence of open flames,and mixed with air and coal powder.Explosion is a major cause of accidents in coal mines and an important indicator that coal mines need to monitor in real time.The problem of poor coal permeability in CBM extraction is not satisfactory,so solving the problem of poor permeability is a key issue.Many experts and scholars have done relevant research.Nowadays,hydraulic fracturing technology is widely accepted in the industry to improve the permeability of coal seams.In the hydraulic fracturing technology,water will enter the pores of the coal seam during the implementation of the fracturing technology,thereby suppressing the development of the coalbed methane extraction.Based on this,this paper proposes an experimental study on the desorption characteristics of coalbed methane steam injection at different particle sizes and gas pressures.The particle size,adsorption pressure,water injection,hot water injection steam and other factors were studied.And get the following conclusions:?1?Effect of particle size on adsorption and desorption rate The experimental analysis shows that the rate increases with decreasing particle size,which is mainly due to the decrease in particle size and the shorter distance required for adsorption and desorption,making it possible to achieve faster balance.However,the effect of particle size on the adsorption and desorption capacity is smaller at the experimental scale in this paper.The reason for this is that the change of particle size at this scale does not essentially change the surface area of pores and crevices but only affects the pore volume.Therefore,the impact of particle size in this experiment is mainly reflected in the time needed to reach equilibrium.?2?Water Injection Inhibition Mechanism:Since the adsorption of coal on water molecules,gas,CO₂ and other adsorbents is physical adsorption,after water injection,the coal adsorbs water molecules into the pores,and it will compete for adsorption sites;The entry of water molecules makes the seepage channel blocked and the adsorbed adsorbate closed.Moreover,due to the high pressure and strong water injection,the pressure in the pores and the gap become larger,so that the free gas in the pores and gaps appears as an adsorption state due to the influence of water,and the inhibition effect is essentially generated.?3?Intensification by heat injection:For enhanced desorption of uninjected water,the surface activity of the adsorbent decreases with the increase of temperature,and a large amount of adsorption sites desorb the adsorbates from the adsorption sites,and the adsorbed substances are obtained as the temperature increases.The large energy facilitates the breakthrough of capillary forces.The reason for the analysis of the enhanced steam injection after the water injection suppression is that the high temperature steam causes the water in the pores to accelerate due to the injection of water and part of the water will be discharged together with the adsorbate gas during the process,due to the water phase state.The changes made coal permeability increased.In addition,because the injection of heat makes the gas in the adsorbed state obtain greater energy and also facilitates desorption,the heat-injection enhanced desorption after injection suppression is still higher than natural desorption,which illustrates the feasibility of steam extraction by hot water injection.?4?The desorption time effect reflected by the t₀ value is obtained by fitting the experimental results.According to the value of the t₀ value,compared with the case of non-injected hot water steam,the coal bed methane recovery rate after hot water steam injection is obtained.It has been greatly improved and the time has been greatly shortened.The fitted t₀ value is in good agreement with the experimental law.At the same time,the feasibility of hot water injection to improve the efficiency of CBM extraction has also been obtained.