Study On Coal Dust Wetting Characteristic And Dust-proof Technology In Driving Face Of Outburst Coal Seam

In order to prevent and control occupational hazards caused by dust in fully mechanized driving face of coal roadway in high gas outburst coal seam and eliminate the risk of coal dust explosion,the sampling test and analysis of different coal seams in seven high gas outburst mines in Huaibei mining area were carried out.At the same time,referring to the field situation of 3₂38 machine roadway fully mechanized driving face in Xutuan Coal Mine,the dust migration law of the working face was numerically simulated and studied.The experimental analysis and simulation results analysis objectively analyzed the characteristics of the dust produced on the working face.In addition,the results of coal seam water injection and foam dust falling test on the 3₂38 roadway working face showed that the effect of the single seam water injection was not obvious,and the foam dust reduction technology significantly improved the dust removal efficiency.The main contents of this paper are as follows:1)Sampling test and analysis of outburst coal in seven coal seams,using laboratory measurement and analysis method to analyze the multi-basic characteristics of outburst coal;at the same time,the regional outburst risk prediction index of each coal seam was investigated,measured and analyzed,and different coal bodies were studied from the perspective of multi-characteristics of outburst coal gas;and then the coal dust wettability of outburst coal body was studied.Finally,combining the results of the multivariate test parameters,the comprehensive analysis shows that the multivariate parameters of coal samples have a certain correlation with the wettability characteristics of coal dust.2)Through the methods of single linear regression,multiple linear regression and principal component analysis,the correlation coefficients,multiple linear regression equation and correlation degree results of the influence factors of coal dust wetting characteristics are obtained.The main conclusions are as follows:The optimum regression equation for the influence of coal composition on coal dust contact angle is?=120.042-2.218?ash?,indicating that the mineral content has the greatest influence on the wettability of coal dust;the optimum regression equation for the influence of coal micro-structure parameters on coal dust contact angle is?=111.866-18.044?SSA?indicating that the specific surface area is of the greatest relationship among the coal micro-structure parameters.The correlation degree of each correlation factor and contact angle was ranked by principal component analysis,and the order of correlation was Ash A_d>moisture M_ad>pore volume>specific surface area>firmness coefficient f>hydroxyl?-OH?content>fixed carbon F_cad>volatile matter V_daf>adsorption constant b>maximum gas pressure in coal seam P>initial velocity of gas emission?p>adsorption constant a>the most probable pore size.3)Combining with the site layout of 3₂38 machine roadway,the distribution of airflow in the roadway within 140 seconds after the start of the air supply from the air cylinder in the fully mechanized face of coal roadway is simulated,and it is found that the airflow field is basically stable after 80 seconds,which indicates that the release of dust source after 80 seconds is close to the situation of the dust release in the field excavation;furthermore,the regularity of the dust transport and distribution in the general situation is simulated,and the results show that the airflow dust fills the roadway rapidly within 60 seconds after excavation.Analyzing the distribution of dust concentration in the roadway at 60s after excavation,it is found that the concentration at the location of dust source is the highest and there is a high dust concentration at the return side.There is a high concentration dust accumulation at the intake side where the local roadway air flow is disordered or the wind speed is low.High concentration dust mass is quickly accumulated near the roadway roof and the wall of the air duct.Dust is quickly captured by the roadway wall,and a large amount of dust is deposited on the roadway floor.In addition,combined with the different working conditions on the site,the law of dust migration under different dispersion conditions is simulated.The results show that the dust concentration of 60s under different dispersion conditions is still the highest on the return side.With the decrease of dust dispersion,the ability of dust escaping in the air decreases.The overall dust concentration decreases,and the dust concentration of large particles attached to the floor increases.When the tunneling starts at 60s under the condition of MD=50um,most of the dust is difficult to reach 50m away from the tunneling face,that is,the key area of dust fall tend to move forward gradually.4)Based on the results of numerical simulation,it is concluded that the dust control in the fully mechanized excavation face should be focused on the return air side within 50 meters of the excavation face,and the dust accumulation in the roadway should be regularly cleaned up.At the same time,it is suggested to strengthen the dust control work at the dust source.The analysis of the coal sample properties in the outburst coal seam shows that the content of free silica in the coal sample is high,the wettability is poor,the harm to human body is worse,and the dust reduction is difficult.In addition,a simple coal seam water injection test is carried out in the field working face and the result is not ideal,while the results of foam dust reduction test showed that the dust removal effect was significantly higher than that of the original spray.