| This paper was aimed to study the following two aspects:the ratio change of displacement and replacement of the injected N2 and O2 in the air process of injection displacement and replacement experiment of methane in coal,and the transformation relations of N2 and O2 air in the process of air injection displacement and replacement methane in coal,the simulation device of air injection displacement and replacement the methane in coal was established,with constant vertical load 150KN,ensured the gas injection pressure of started time in coal methane was 0.1MPa,respectively,the effect of methane replacement in coal in air pressure of 0.6MPa、0.8MPa、1.0MPa and1.4MPa was studied,the conclusions was draw as follows:（1）Four groups of experiment time were respective 1865min,1230min,886min and 388min,the breakthrough time of N2 was respective in the between 15-18min,8-12min,6-8min and 0-2min,the breakthrough time of O2 was respective in the between 29-35min,8-12min,6-8min and 0-2min.The ratio of concentration in the gas mixture of N2 and O2 was reduced from more than 3.76（the original air concentration ratio is 79%:21%=3.76）to below 3.76,then gradually rose to 3.76 eventually,the phenomenon confirmed the movement of gas in coal was comprehensively resulted by the adsorption properties of the them in the coal、the friction resistance of the coal and interaction of all the gas in coal seam.（2）With the gas injection pressure was constant,the flowed rate of methane and the efficiency of displacement and replacement methane increased rapidly firstly,and then decreased after reaching the peak value.With the injection pressure higher,the larger flowed rate of the methane was,the lower the displacement efficiency was.（3）After four groups experiment of injection gas was stared,before the N2 and O2was both breakthrough the coal,N2 and O2 were all stuck in the coal,this part of the gas retention could be understood as the main function of displacement and weak function,of replacement,with N2 and O2 gradually breakthrough the coal,the retention ratio decreases gradually,the replacement ratio increased gradually,indicating that the function of displacement was decreased gradually and the function of replacement N2and O2 was increased gradually,which indicated that the function of displacement was transformed to replacement gradually.In the early stage,the displacement ratio of O2was higher than that of N2,and then the displacement ratio of N2 was higher than that of O2,and the turning points were respectively 394-544min,279-293min,182-192min,128-138min.（4）Under the injection air press of 0.6MPa,0.8MPa,1.0MPa and 1.4MPa pressure during the whole experiment,the cumulative displacement ratio were 20%,16%,25%and 35.6%,the cumulative replacement ratio were 80%,84%,75%and 64.4%,the function of replacement was made leading roal in the whole four groups experiment... |
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