| Gas is produced in the process of coal formation and is consist of different gases,it also is one of the main factors that lead to coal mine accidents,such as coal and gas outburst,gas explosion.And coal seam gas content directly determines the possibility of gas accident in coal mine underground mining process.Therefore,the study of methane adsorption characteristics of coal is of great significance for prevention and control of mine gas disasters.In this article,through laboratory experimental study on the methane adsorption characteristics of coal under different influencing factors,temperature,pressure,particle size and moisture of coal are studied.According to the experimental results,two methods are used to predict the adsorption isotherm of coal,one method is to optimize saturated vapor pressure parameters k of adsorption potential theory,build a new simple adsorption isotherm prediction model and to make a prediction,another method is to predict adsorption isotherm by using the theory of adsorption heat.The main research content and conclusions are as follows:(1)The results of adsorption experiments1)At a given particle size,with the increase of temperature adsorption amount is reduced and adsorption constant a and b are becoming smaller.2)At a given temperature,with the increase of pressure adsorption amount increases gradually and finally tends to a stable value;The relationship between adsorption amount increment rate and pressure can be roughly divided into three stages,namely rapidly decrease phase,slow decrease phase and stable phase.3)At a given temperature,adsorption isotherms of different particle sizes show similar variation tendency;But the relationship between adsorption constant a and b is not obvious,further work is needed.4)At a given temperature,within the scope of the test pressure adsorption amount of dried coal samples is greater than that of wet coal samples;And adsorption constant of dried coal samples is also greater than that of wet coal samples.(2)The prediction results of coal adsorption isotherm1)According to the experimental results and the adsorption potential theory,the adsorption characteristic curves of multiple temperature are got,and then a simple adsorption isotherm prediction model is built(Eq.4.6).The process of optimizing k is conducted and the relationship of optimized k and corresponding fitting accuracy R2 is expressed by the quadratic polynomial.The corresponding optimal k are 4.427,5.997,3.274 and 5.194,for the wet coal samples 60~80,40~60,20~40 and 12~20 mesh,and 6.956,5.620,5.603 and 5.862,corresponding to dried coal samples 60~80,40~60,20~40 and 12~20 mesh.2)Based on the simple adsorption isotherm prediction model,the adsorption isotherm is predicted under 313 K and 323 K.The optimal k is used to predict the adsorption isotherm and the predicted results are compared with the predicted results of using k=2.And the calculated average absolute error results show that the predicted precision of using optimal k is higher than that of using k=2.In order to verify the accuracy of the model,another adsorption experiment of 308 K is carried out and the predicted result of the model by using the optimal k and k=2 is compared with the measured result.And the comparison result show that the result predicted by using the optimal k is obviously better than that of using k=2,which also reflects that the accuracy of the model is verified.3)The adsorption heat theory is used to predict adsorption isotherm of coal under 313 K and 323 K,the result shows that the predicted result is in accordance with the measured result,which demonstrates that it can be used to obtain the adsorption isotherm of coal and has a high prediction precision.4)The prediction error of the optimized adsorption potential theory prediction model is much less than that before optimization prediction model,and the prediction error of the optimized adsorption potential theory prediction model is almost the same as that of the adsorption heat theory. |
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