| The tectonics conditions of coalfields in China are complex,and tectonic coal is widely distributed.Structural coal has the characteristics of low permeability and easy protrusion,making it a key and difficult point in the prevention and control of mine gas disasters.Moisture can affect the gas adsorption of coal,and the moisture content of coal seams varies among different coal mines.Studying the influence of different water contents on the pore structure and gas adsorption of structural coal is of great significance for gas control in structural coal regions.This article uses laboratory testing methods to conduct research,collecting primary structural coal and structural coal from the Panzhihua coal mine site,and preparing samples for testing.Conduct industrial analysis and determination of solidity coefficient to obtain the physical parameters of primary structural coal and structural coal.Control the different moisture content of coal by spraying distilled water.By conducting low-temperature nitrogen adsorption and carbon dioxide adsorption experiments,the pore parameter data of micropores,mesopores,and macropores of each coal sample were obtained.The pore volume,average pore diameter,and specific surface area of each coal sample were compared,and it was found that the micropores,mesopores,and macropores of structured coal were more developed compared to the original structural coal,with larger pore volume and specific surface area.Moisture can reduce the pore volume and specific surface area of coal,and as the moisture continues to increase,the pore volume of some large pores increases.The micropore volume and quantity of primary structural coal and structural coal decrease with the increase of water content.The average pore diameter of structural coal increases with the increase of water content.Moisture can cause changes in the type and quantity of pores in coal.According to the experimental data of nitrogen and carbon dioxide adsorption at low temperature,the fractal dimension of each coal sample was calculated.Obtaining water can make the pore walls of mesopores and macropores in coal tend to be smooth,reduce the complexity of pores,and make the pore walls of micropores in coal tend to be smooth first and then rough.The structural action makes the pore structure of micropores approach simplicity.Study the gas adsorption characteristics of primary structured coal and structured coal with different moisture contents through methane isothermal adsorption experiments.By using the Langmuir equation to fit experimental data,it was found that as the water content increased,the methane adsorption rate and methane adsorption amount of the constructed coal decreased,and the magnitude of the decrease in a value decreased.The influence of water content on a value was greater when the water content was smaller.The value of b increases with the increase of water content,and the magnitude of the increase in b value increases with the increase of water content.Based on the methane isotherm adsorption test data,the thermodynamic parameters of methane adsorption in coal samples were calculated,and it was found that as the water content increased,the Gibbs free energy of the constructed coal increased.Moisture has a certain promoting effect on the increase of Gibbs free energy when pressure increases.As the water content increases,the gas adsorption entropy of the structural coal decreases.The structural coal with a moisture content of 1.29% has the highest gas adsorption entropy,the most chaotic adsorption system,and the worst adsorption performance.Calculate the adsorption potential of structured coal with different moisture contents and conclude that as the moisture content increases,the adsorption of structured coal is generally inhibited.The pore parameters and gas adsorption test data were fitted,and it was found that the correlation coefficient between micropore volume,Langmuir volume,and Langmuir pressure was high,showing a positive correlation.The correlation coefficient between total pore specific surface area and Langmuir volume is relatively high.The fractal dimension of low-temperature nitrogen experiment is highly correlated with Langmuir volume and Langmuir pressure.The relationship between pressure,pore volume,specific surface area and fractal dimension and methane adsorption parameters of coal was studied,Moisture has an inhibitory effect on the gas adsorption of structural coal.The Langmuir pressure of structural coal decreases almost linearly with the increase of water content,and there is no significant difference in the effect of water gradually increasing in micropores and mesopores compared to the effect of water gradually blocking large pores on gas adsorption rate.When the moisture content of structural coal increases,both the microporous specific surface area and Langmuir pressure decrease linearly,and there is a correlation between the microporous specific surface area and Langmuir pressure.With the increase of water content,the fractal dimension,Langmuir pressure and volume of low temperature nitrogen experiment of tectonic coal decrease.This article compares and studies the pore structure and gas adsorption characteristics of primary structured coal and structured coal with different water contents,and obtains the influence of water content on the pore structure and gas adsorption characteristics of structured coal.This has certain reference significance for the on-site treatment of Watts in the area of structured coal. |
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