Study On The Relationship Between Adsorption Time And Adsorption Saturation Of Gas In Granular Coal

When carry out gas diffusion and seepage experiment of methane adsorption in laboratory,due to limited precision equipment,adsorption time have not prescribed value,high methane adsorption saturation is an important guarantee to obtain accurate diffusion and seepage experiment parameters,and different particle size of coal-initial boundary conditions at different adsorption pressure there is a big difference between the time required for saturation.Therefore,mastering the relationship between adsorption saturation and adsorption time with particle sizes under different pressure conditions,which is very important to effective and accurate methanogenic adsorption time.In order to obtain the commonly used laboratory adsorption saturation and adsorption time mathematical model of radial pressure conditions,carried out the following works:(1)Different particle sizes coal and initial equilibrium pressure gas diffusion experiments;(2)The methane concentration was determined by using MATLAB software in the calculation of coal particles with the internal boundary to the center of distribution;(3)To investigate the fit effect of LangmuirEXT1,LangmuirEXT2,FreundlichEXT,BET 4 adsorption models and ExpGro1 index model of adsorption saturation data,optimization model and obtain the characteristic parameters.The study found:(1)The classical diffusion model in various experimental conditions before 10 min diffusion rate fitting effect best,fitting effect with the coal particle sizes decreases the error expansion after 30 min;diffusion coefficient D decreases with the increase of experimental time;the diffusion coefficient D value with the increase of the initial pressure of adsorption equilibrium,first decreases and then increases,and the inflection point was 3 MPa.(2)The center of the methane concentration of methane with boundary pressure increased,the smaller the particle size,the growth trend is more obvious;the same boundary methane pressure conditions,the center of methane concentration with the increase of particle size decreased;large size coal particles 24 h adsorption saturation in the condition of 4 MPa maximum was only 30.60%,for large particles of coal,according to the required adsorption saturation to extended adsorption time.(3)With the particle sizes of coal and the boundary pressure increase,to achieve the same adsorption saturation,the adsorption time increased;adsorption saturation higher accuracy,the time was longer;if not high precision experiment,experiments could be started when the adsorption saturation is 0.9;the best fitting effect model between coal particle adsorption time and adsorption saturation is LangmuirEXT2,BET model is the worst;The LangmuirEXT2 model fit effect for all experitents the data were well,Adj.R-Square values were above 0.96409,LangmuirEXT2 model could be used to describe the adsorption time and adsorption saturation relationship;the relationship between time and adsorption saturation adsorption couled be calculated,according to the characteristics parameters of different test conditions and LangmuirEXT2 model.Combined with the requirements of experimental adsorption saturation,formulating reasonable adsorption time,providing the basis for the rational selection of the time of adsorption.