Test and analysis of coal adsorption volume of CH₄

CH₄ in coal seams mainly occurs in free state and adsorbed state. The performance of coal adsorption of CH₄ is often affected by various factors such as coal rank, temperature, pressure, particle size and moisture content. In order to study the influence of multi-factor coupling on the Langmuir volume of coal adsorbing CH₄ According to the law, coal samples from changcun and zhaozhuang Coal mines in Changzhi area of Shanxi are selected, and the HCA–1 high-pressure adsorption device is used to determine the volume of CH₄ adsorbed by coal samples with different ambient temperature, coal sample size and water content, and then the test results of Zhaozhuang Coal mine Based on the design of the Box Behnken test using Design Expert software, a quadratic regression response surface model of coal adsorption CH₄ volume was constructed to analyze the influence of temperature, particle size, and moisture content on the volume of coal adsorption CH₄ when the three factors are coupled. The volume of coal adsorbed CH₄ was predicted and verified, and the engineering application enlightenment of the test results was discussed. The results show that the amount of CH₄ adsorption decreases with the increase of temperature, particle size and moisture content; when the ambient temperature increases from 15 ℃ to 40 ℃, the amount of CH₄ adsorption of Changcun and Zhaozhuang Coals decreases by 37.09% and 37.5%, respectively; coal samples When the particle size increases from 0.15 mm to 0.3 mm, the CH₄ adsorption capacity decreases by 14.87% and 15.52%, respectively; the water content of the Changcun coal sample increases from 0.08% to 4.21%, the CH₄ adsorption capacity decreases by 10.61%, and the water content of the Zhaozhuang coal sample decreases from Increased from 0.04% to 3.62%, the amount of CH₄ adsorption decreased by 16.31%; the single factors of temperature, particle size, and water content all had a very significant impact on the amount of CH₄ adsorption (P<0.000 1), and the degree of influence of the three factors on the amount of CH₄ adsorption It is: temperature (F=2 307.95)> coal sample particle size (F=346.64)> water content (F=133.32); the degree of influence of each interaction item on the amount of CH₄ adsorption is: particle size and water content (F=21.31)> temperature And particle size (F=6.33)>temperature and water content (F=3.65), the interaction between particle size and water content is extremely significant (P=0.002 4), and the interaction between temperature and coal sample particle size is significant (P=0.040 1). The interaction with water cut is not significant (P=0.097 8); the maximum deviation between the test value and the model prediction value outside the coding interval is 3.98%, the minimum is 2.01%, and the average error rate is 3.315%; during downhole recovery, temperature and water cut when the coal sample particle size and other factors change, firstly monitor the temperature change in real time to prevent the sudden change in temperature from causing a large amount of gas desorption, leading to excessive gas limit and even coal and gas outburst accidents.