Coal full-pore-diameter measuring and pore shape semi-quantifying method

Abstract

The invention discloses a coal full-pore-diameter measuring and pore shape semi-quantifying method. A mercury intrusion method and a liquid nitrogen adsorption method are organically combined to analyze the change condition of the coal pore volume along with the grain size change, a mercury intrusion method is selected for measuring the pore diameter section larger than 20 nm, a liquid nitrogen adsorption method is used for measuring the pore diameter section smaller than 20 nm, a theoretical calculation method is adopted for obtaining the number of particles contained in each gram of coal, then the full-pore-diameter pore volume distribution characteristic of single-particle coal is obtained, the pore length distribution data of the single-particle coal are obtained through a theoretical calculation formula, and a semi-quantitative coal pore shape is obtained through the coal pore shape distribution characteristic. A more visual observation method is provided for researching adsorption or desorption in gas in coal.

Description

technical field [0001] The invention relates to a method for measuring the total pore diameter of coal and its semi-quantitative pore shape, belonging to the technical field of coal pore structure measurement. Background technique [0002] Coal is a kind of pore-fissure double porous medium with complex structure. Its pore characteristics directly determine the coal gas adsorption ability, coal permeability and strength and other properties, and the coal pore structure and gas adsorption performance affect the coal seam gas content, Coal and Gas Highlight Hazards and Gas Drainage. For this reason, many scholars at home and abroad have studied the pore structure of coal and its influence on gas adsorption characteristics in coal. The research results show that the pores in coal are distributed in a wide range, and the pore diameter can be as small as 0.5nm of micropores. As large as 1000nm macropores, there are extremely developed <10nm micropores in the coal body. The sp...

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Problems solved by technology

[0004] However, the low-temperature liquid nitrogen adsorption method and mercury porosimetry also have their shortcomings. Theoretically, the liquid nitrogen adsorption method can measure pores from 0.35 to 100 nm, while the mercury porosimetry can measure pores from 7.2 nm to 750 μm, but when the pressure is greater than 35 MPa, When the corresponding pore radius is 20nm, the coal body is compressed, and the pore structure may cause damage

For this reason, the full pore size distribution of coal cannot be obtained by using a single method

In addition, the qualitative pore shape data and quantitative pore structure data obtained by these two methods are not organically combined, and the difficulty of gas migration in coal cannot be intuitively seen through these data.

The indirect method for measuring coal seam gas content needs to measure the real gas pressure of the coal seam underground, and measure the adsorption constant (a, b value), porosity, ash content, water content and other data of a single particle size coal sample in the laboratory, and determine it through calculation. Coal seam gas content, due to different mining areas and different coal seams, the degree of fragmentation of coal samples under the same force is different, and the measurement of coal seam gas content by using a single particle size coal sample cannot reflect the true value of the measured coal seam gas content

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