Experimental Study Of Pore Structure Characteristics Of Full-Aperture Section Of Middle And Low Rank Coal In Xinjiang Mining Area

The mining area in Xinjiang Province is rich in coal resources,which is mainly composed of medium and low rank coal.Coal gas is mainly stored in coal pores,the adsorption and desorption characteristics of coal are affected by pore structure.The paper selects 8 typical coal samples in Xinjiang mining area.Through experimental test and theoretical analysis,the pore characteristics of low-order coal in the Xinjiang mining area are studied.The pore type and characteristic parameters of medium and low rank coal were tested by low temperature nitrogen adsorption experiment and high pressure mercury intrusion test.The low rank coal micropores are relatively large,and contains a large number of semi-open holes such as bottle-shaped holes and wedge-shaped holes The proportion of transitional pores of step coal is larger than that of low rank coal.The pore types are mostly open pores such as cylindrical pores and slit-shaped pores.Compared with medium-rank coal,open pores of low-rank coal are more developed,and connectivity between pores is more.it is good.According to the experimental results of the low-temperature nitrogen adsorption and the high-pressure mercury-mercury method,and the difference of the two methods in the test of the characteristic parameters of the pore,the principle of pore size and full aperture of medium and low rank coal samples is proposed,obtain the joint hole parameters of two coal samples.Pore parameter test by nitrogen adsorption method when the pore diameter is smaller than the joint hole diameter,and when the pore diameter is larger than the joint hole diameter,the pore parameters are tested by mercury intrusion method.The distribution of pore specific surface area in the full pore section of low rank coal is dominated by micropores,while the middle rank coal is affected by both micropores and transitional pores.The pore volume of the full-bore section of medium and low-rank coal are dominated by mesopores and macropores.Applying fractal theory to optimize the pore fractal model of medium and low rank coal for experimental use in Xinjiang mining area,and obtain the full fractal comprehensive fractal dimension of medium and low rank coal.Compared with medium-rank coal,the pores of low-rank coal are more developed and have stronger heterogeneity.The relationship between the composite fractal dimension and the composition,microscopic composition and pore structure of coal is discussed.The degree of influence of various factors was ranked by principal component analysis,The pore structure has a significant effect on the comprehensive fractal dimension of the experimental coal sample,and the effects of the macerals and coal quality components on the macerals are relatively small.