Study On The Effect Of Water On Displacement Methane In Coal By Isobaric Diffusion

In order to improve the gas extraction rate of low permeability coal seam,many strengthening anti-reflection methods,including water-based anti-reflection measures,are adopted at present.In the implementation of the anti-reflection method,moisture migration of coal adsorption and desorption of anti-reflection and displacement,inhibiting effect,but they are the influence of mutual coupling has greatly increased the difficulty of the study of its mechanism,find a separate variable in all kinds of effect of coal adsorption desorption,the impact of measures will contribute to improving irrigation of anti-reflection effect of coal seam,the current study,Most experiments are carried out on coal samples after drying treatment,but the actual production of coal itself contains moisture,and research shows that moisture not only affects part of the physical and chemical characteristics of coal,but also significantly affects the adsorption and desorption of coal to gas.In order to study the effect of methane in CO₂replacement coal under water equivalence pressure diffusion,the author carried out isothermal adsorption experiment of CH₄and CO₂and systematic study of CH₄in CO₂replacement coal in Yangquan Shangshe No.2 well anthracite.Firstly,the influence of moisture on the adsorption and desorption characteristics of coal is studied theoretically,including the law of moisture and gas migration in coal,the influence of moisture on coal gas migration,and the influence of moisture on the adsorption and desorption of gas in coal.Secondly,the team built a set of multi-gas replacement experiment platform for gas-bearing coal and conducted isothermal adsorption experiment for CH₄/CO₂single component gas.Finally,the adsorption capacity of CO₂/CH₄by coal with different moisture content（0%,0.75%,1.5%,2.25%,3%）was measured under the same pre-adsorption equilibrium pressure at a constant temperature of 25℃,and the influence of moisture on the adsorption of CO₂/CH₄by coal sample was studied.Since the replacement effect of CO₂on CH₄in coal is better than that of high-pressure injection under the condition of isobaric diffusion,finally,under the experimental method of isobaric diffusion,the experiment of replacing CH₄in coal with CO₂injection was carried out on coals with different moisture content to analyze the influence of moisture content on the replacement experiment and explore the reasons for the influence.The results show that the isothermal adsorption of CH₄/CO₂by coal with different moisture content conforms to the Langmuir equation,and the adsorption capacity is CO₂>.CH₄,with the increase of moisture in coal samples,the adsorption capacity of CH₄/CO₂decreases,and the A and B values of CO₂and CH₄also decrease,indicating that moisture has a inhibitory effect on the ultimate adsorption capacity and adsorption speed of CH₄/CO₂of coal,and the inhibitory effect on CO₂adsorption is stronger than that on CH₄.In the experiment of CO₂isobaric replacement of CH₄,the total adsorption capacity of mixed gas,CO₂adsorption capacity and CH₄adsorption capacity are negatively correlated with the change of water content under the same adsorption equilibrium pressure and constant temperature at 25℃.With the increase of water content in coal,the replacement capacity of CH₄decreases,and the desorption rate of CH₄and CO₂injection ratio also decrease.The results showed that CO₂replacement of CH₄had an inhibitory effect under the condition of water equivalence diffusion,and the inhibitory effect was stronger with the increase of water content.Water displacement effect of CO₂causes inhibition of functional groups,adsorption heat,capillary force,pore structure,adsorption heat and hydrogen bond Angle,mainly divided into three types:one is water plugging in and out of the coal gas channel,the second is block into the coal gas adsorption,three water molecules adsorption heat is big,preferential adsorption fast stable coal sample.There are 25 figures,10 tables and 88 references.