| The greenhouse effect and energy crisis are serious problems facing the current national society.CO2 storage and displacement of coal seam CH4 are effective means to solve this problem and this method is usually used in deep formations under high temperature and high pressure.Therefore,in order to study the characteristics of coal adsorption of CH4 and CO2 under high temperature and high pressure,this paper uses the German Rubotherm magnetic suspension balance,using a gravimetric method,at a constant temperature of 313.15K to conduct a unit of No.3 anthracite with a diameter of0.18-0.25mm Adsorption experiment of gas and mixed gas 0-15MPa.The following conclusions are obtained:Regardless of the pure gas or the mixed gas,because the experimental instrument can not measure the volume of the adsorption phase,the buoyancy of the adsorption phase is ignored,resulting in the appearance of the inflection point of the adsorption curve.The excess adsorption capacity of coal for CH4 and CO2 single component and mixed gas appears a maximum value with increasing pressure,and then the excess adsorption capacity gradually decreases;the absolute adsorption capacity of CH4 increases continuously with the increase of adsorption pressure,which is close to the critical pressure of CH4 4.59 At MPa,the increase in absolute adsorption capacity slows down and tends to stabilize.At low pressure,the coal particles adsorbed CH4 molecules in a monolayer,and the surface of the coal sample was calculated to be 190.76m2/g using the coal surface.Calculate the number of high-pressure point adsorption layers.In the near supercritical state,CH4 is partially adsorbed on the surface of coal particles.The adsorption of CO2 single component is 1-4MPa.At low pressure,it is mainly composed of two-layer adsorption.The adsorption layer can be up to 3 layers,and the coal particles have a greater adsorption capacity for CO2.At the same time,the calculation and analysis from the energy angle-surface free energy proves this conclusion.Coal particles have a scale effect on the adsorption of binary components of CH4 and CO2.When the volume concentration of CO2 component is close to medium concentration,it shows obvious competitive advantage and has a good effect of displacing CH4.Finally,the diffusion coefficient and adsorption rate of the pure and mixed gas are analyzed.The diffusion coefficients are different under different pressures and gas ratios.Related factors need to be considered in the process of CO2 storage and CH4 displacement. |
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