Experimental Study On Adsorption/Desorption Law Of Coal Body Under Far-Infrared

Coalbed methane,as an associated mineral resource of coal,is a clean,high-quality energy and chemical raw material,and is an unconventional natural gas.Chinese coalbed methane reserves are abundant,but due to poor storage conditions,reservoir characteristics are characterized by low pressure,low permeability,low saturation,coalbed methane desorption and migration difficulties,resulting in low gas output of most CBM wells during mining.The yield decays quickly.In order to improve the mining efficiency of coalbed methane and increase the output of coalbed methane,the research team based on the current theory and technology,proposed a new technology for the production of coalbed methane-the use of far infrared to extract low permeability coalbed methane.In this paper,the experimental research on the influence of coal adsorption/desorption law under far-infrared action is carried out.The research contents of this paper mainly include the following aspects.Firstly,qualitative and quantitative analysis of pore fracture development and microscopic impurities was carried out by performing SEM electron microscopy and EDS spectrum analysis of granular coal samples under different far-infrared conditions.Secondly,combined with the microscopic characteristics of the sample under the different far-infrared conditions,the macroscopic far-infrared effect is applied to the experimental study of the gas adsorption/desorption law in coal.The experimental data are fitted by LangmuirEXT1 mathematical model.And the characterization is quantitatively analyzed about various parameters of adsorption performance;Finally,the thermodynamic characteristics of the adsorption/desorption process under far-infrared reaction are analyzed in combination with the relevant theory.The surface free energy change,?-? adsorption characteristics and the equivalent adsorption heat of the adsorption/desorption process are quantitatively calculated and the variation law is obtained.Summarize the above experimental results and analyze them.The following conclusions were obtained:(1)The effects of far-infrared radiation on the micro-state of the coal body and the promotion of pore development can affect the change of specific surface area of coal and rock,and thus affect the macroscopic adsorption performance.(2)The adsorption/desorption process of coal body under far-infrared radiation accords with the quantitative expression of LangmuirEXT1 mathematical model,and there is obvious hysteresis in desorption and adsorption.During the adsorption/desorption process,as the far-infrared power increases,the value of the adsorption constant a decreases synchronously,and the Langmuir synthesis parameter b changes inversely with respect to the far-infrared power.(3)The ultimate adsorption capacity of coal and the residual amount of desorption are affected by the changes of far infrared radiation power,water content and pressure.The ultimate adsorption amount and the desorption residual amount and the far-infrared radiation power and water content change inversely,and the pressure changes in the same direction.(4)In the adsorption process,when the far-infrared radiation power is the same,the change gradient of the gas content relative pressure is higher than the change gradient of the gas content relative to the water content;in the desorption process,when the far-infrared radiation power is the same,the change gradient of the gas content relative pressure and the change in gas volume relative to water is basically the same.(5)The power variation of far-infrared radiation affects the adsorption capacity of the coal surface by affecting the change of free energy on the surface of the coal.The greater the far-infrared power,the slower the process,the enhanced desorption capacity of the coal,and the results are consistent with the results of the macroscopic adsorption experiments.(6)The adsorption characteristics of coal under different power far infrared radiation accord with the basic properties of the Polanyi adsorption potential theory on the adsorption curve prediction model.The result is the basis for establishing the basic model of coal adsorption/desorption evaluation and prediction under far infrared radiation.(7)The coal body is a heat release process for the gas pressure-adsorption process,and the pressure-reduction process is an endothermic process.During this process,the adsorption amount and the heat of adsorption are linearly increasing.In this paper,the experimental study on the adsorption/desorption of coal under far-infrared radiation by the combination of microscopic analysis,macroscopic adsorption/desorption experiments and thermodynamic calculations has further enriched the study of gas adsorption in reservoirs under far-infrared radiation.The related processes of desorption and migration can provide a theoretical reference for further in-depth study of low-infrared coalbed methane.