Research On The Pore Structure Of The Middle And High Rank Coal And Its Controlling Factors

Coalbed methane resource is abundance in China, while, compared with USA, Australia and Canada and so on China’s coalbed methane production is too low, Foreign made breakthrough progress at low and middle rank coal, but our country is at middle and high rank coal, so, this paper study on pore structure characteristics of middle and high rank coal has a very important significance development and utilization of coalbed methane in our country.In this paper, the coal samples collected from Pingdingshan NO.13 mine, the part of the mine area is intrusived by magma, the coal samples in this paper is collected near the magma, control coal degree of metamorphism according to control the distance from sampling to intrusive make the continuous change of metamorphic degree of coal.Industrial analysis experiment of coal samples obtain the moisture, ash and volatile of the coal samples, observation the microstructure of coal by microscope, and then determination the maceral content of coal macerals and the maximum reflectance of vitrinite.Determination of coal pore combine mercury injection experiment and low tempreture nitrogen adsorption analysis, we get the result the higher the porosity the total intrusion volume and total pore area is larger by mercury injection experiment,then calculated pore volume and area of the proportion of each aperture section, we know that the pore distribution shows the shape of Shuangfeng, the main contribution of the surface area is micro pore, then the coal samples are divided into three categories, we got different pore pore morphology by low tempreture nitrogen adsorption analysis, and the pore existence "ink bottle" shaped, we got the fractal dimension of pore surface of coal samples through fractal of coal samples.Analysis of influence factors of the coal pore distribution of the middle and high rank, the volatile and the vitrinite reflectance of coal are the main influence factors, there is a negative correlation between the volatile content and the total pore volume and pore specific surface area of the coal samples, the fractal dimension decreases with the increase of reflectivity of the coal samples, that is to say, with the vitrinite reflectance increases the pore surface complexity gradually reduce of the coal samples and the pore surface become more uniform and smooth, the total pore volume of coal sample reaches a minimum value at the reflectivity is 1.6%, the coal samples its reflectivity more than 6%, the total pore volume with the reflectivity decreases first and then increases, while the total pore surface area showed increasing trend.