Study On Dust Prevention Technology Of Dynamic And Static Pressure Combined Water Injection In Low Permeability Coal Seam

In recent years,with the progress of coal mining technology,the mechanization level of underground production has been greatly improved.However,with the improvement of mechanization level,the degree of fragmentation of coal mining increases,and the amount of dust produced also increases significantly.The dust prevention and control through coal seam water injection technology is of great significance to the construction of green mines.Taking Wangzhuang Coal Mine as an experimental mine,combined with the previous practical experience of coal seam water injection,this paper puts forward a combined water injection and dust prevention technology using gas extraction hole as water injection hole and alternating dynamic pressure water injection and static pressure water injection.The water injection process and parameters are studied and optimized through theoretical research,laboratory experiments and field tests,and the following research results are obtained:(1)The mechanism of dynamic and static pressure combined water injection is studied.By analyzing the wetting process of coal seam water injection and the permeability law of water in the coal seam,the dynamic and static pressure combined water injection mode using dynamic pressure water injection and static pressure water injection alternately is proposed.Through the transformation of fracture network system by dynamic pressure water injection and the filling of fracture pores by static pressure water injection,the coal seam can be wetted in the threedimensional directions of length,width and height,and the dust reduction effect can be improved.(2)On site sampling was used to measure the basic parameters of 3#coal seam in Wangzhuang coal mine.Through the measurement of pore fracture characteristics,water absorption,porosity,firmness coefficient,water permeability coefficient and other permeability related parameters,it is concluded that it is a weakly permeable coal seam;Through the measurement of wettability related parameters such as contact angle,infiltration rate and surface functional groups of coal samples,it is concluded that it is difficult to wet coal seams.(3)In view of the weak permeability of coal seams,the key technical parameters of dynamic and static pressure water injection pressure,conversion time,water injection area and hole sealing method are determined through mathematical model calculation and field test;In view of the poor wettability of coal seams,a composite water inj ection wetting agent based on synergistic effect was developed,and the wetting effect of the composite dust inhibitor was enhanced with the help of inorganic salts.The pore structure difference of the coal before and after the wetting agent was analyzed in an all-round "macro micro" way,and it was concluded that the ratio of the new composite wetting agent was 0.1wt%Rapid Permeability t+0.1wt%OA-12+0.1wt%NaCl.(4)It has been applied in 9102 working face of Wangzhuang coal mine.The field monitoring data show that after water injection,the average increment of coal moisture is 2.33%,the wetting radius is about 2.5m,the total dust concentration of the working face is reduced by 82.9%,and the respiratory dust concentration is reduced by 80.3%.The dust reduction and wetting effect of the dynamic and static pressure combined water injection dust prevention technology is remarkable.