| It is of great significance to choose the best test method of coal seam gas content,predict the gas emission accurately and effectively prevent coal and gas outburst by gas desorption characteristics.In this paper,the columnnar coal and granular coal with different metamorphic degree in four mining areas are studied,by using the method of combining theory analysis with laboratory test,this paper compares and analyses the gas desorption rate and desorption speed of columnar coal and granular coal,and finds out their similarities and differences,and studies the pore fissure of the method of mercury and NMR.Reveal the cause of the difference.In this experiment,the influence of the metamorphic degree,the adsorption equilibrium pressure and the grain level factors on the experimental results are considered,and the characteristic laws are analyzed and summarized.The study found that no matter how bad the coal sample was,under the same adsorption equilibrium pressure,the cumulative gas desorption and desorption rate are inversely proportional to the particle level,the smaller the particle size,the larger the unit time desorption capacity,the faster the desorption rate,the desorption rate and desorption speed show a significant particle-level effect,and the coal samples with two 0.5-1mm and 1-3mm can reach the limit grain size quickly.Under the same adsorption equilibrium pressure,the coal samples with different metamorphic degree of equal granularity,except low rank coal,the cumulative gas desorption and desorption rate of the remaining three kinds of metamorphic degree are positively correlated with the degree of deterioration.The decay rate of low rank coal is faster than that of other metamorphic coal samples,the first desorption is complete;by using two empirical formulas to fit the data of 96 sets of measured desorption,we know that the law of gas desorption in WYM,PSM,JM columnar coal and granular coal and CYM coal is more accurate by power function.The CYM column coal is more accurate to describe the law of gas desorption by logarithmic function.Under the same conditions,the main reason for the same metamorphic degree of granular coal is that the cumulative gas desorption capacity and the fast desorption rate are mainly due to the more development of granular coal than columnar coal,the larger pore and fissure,and the smaller particle size.The solution of the gas in the adsorption state of the matrix is short,the channel is smooth.Under the same conditions,the main factors affecting the cumulative gas desorption rate and desorption velocity are the ratio of small hole in coal sample,the higher the proportion of the coal samples with different metamorphic degree,and the larger the two characteristic quantities.The CYM columnar coal sample and granular coal sample in the initial stage of desorption,cumulative gas desorption,desorption speed is greater than other metamorphic degree,such as particle grade coal samples are: CYM of which large pores and fissures are relatively developed,and open pores,the connectivity between the pores than other metamorphic coal better. |
PDF Full Text Request