Study On Spatial And Temporal Evolution Law Of Respiratory Dust Distribution In Fully Mechanized Face With Large Mining Height

In recent years,the technology of fully mechanized mining with large mining height is an important development direction in the field of coal mining,which is mainly used in the western mining areas of China.Fully mechanized mining face with large mining height has prominent advantages such as high production efficiency,high recovery rate,simple process and economic benefit.Meanwhile,the dust problem caused by fully mechanized mining face with large mining height has not been solved effectively.At present,the dust prevention methods of mechanized mining face are all developed on the basis of common mining height,which can not achieve satisfied effect due to unclear airflow distribution on large mining height.Therefore,it is a great significance to study the spatial and temporal evolution law of respiratory dust distribution in such mining faces,which can make a start for follow dust prevention technology,also provide references for complete set of equipment research and development on dust control in fully mechanized mining faces with large mining height.Based on the 8m fully mechanized mining face with large mining height of Bulianta Coal Mine,this paper studied the dust production of coal sample by experiment,compared the effects of different energy and water content on dust promotion.The distribution law of air velocity and respiratory dust was obtained by numerical simulation.And the distribution characteristic of air velocity and respiratory dust in different inlet air velocity and different mining height was discussed.The results of simulation was verified by field measuring.The main research results are as follows:(1)Through the coal dust production experiment,it is found that the dust production is positively correlated with energy in the range of 90J external work.For every 10J energy increase,dust production increases by 0.1g.When the water content exceeds the limit of 3.0%,the average dust production rate of total dust decreases by 0.6%,and the proportion of respiratory dust to total dust is basically about 2%.(2)In the position of shearer and its upwind and downwind sides,the air velocity shows the distribution law of the initial zone-the changing zone-the stable zone,the offset of the high air velocity distribution area is larger when cutting coal downwind.Under different inlet air velocity conditions,the average air velocity of the sidewalk is 1.26-1.31 times of the inlet air velocity,which increases with the increase of the inlet air velocity.Under different mining height,the air velocity of the back drum position of the shearer is the largest,which is 1.8-2.2 times of the inlet air velocity,which decreases with the increase of mining height.(3)When cutting coal,the respiratory dust pollutes the sidewalk less,and the transverse diffusion in the position of shearer is not obvious.When moving the frame,the respiratory dust pollutes the sidewalk more seriously,and it is not easy to settle down along the airflow.With the increase of the inlet air velocity,the maximum respiratory dust concentration on the sidewalk decreases to 0.7-0.9 times of the original;with the increase of mining height,the high respiratory dust concentration on the sidewalk is mostly distributed in the middle and top space;with the apply of dust shield,the respiratory dust concentration in the respiratory belt decreases over 50%;with the increase of water content,the respiratory dust on the middle is first diluted.(4)Through filed measurement,the similarities and differences are analyzed by compared with simulation results.For air velocity,the change trend of the two is the same along the airflow.The changing zone of air velocity has a long distance by simulation,which ranges to 30m downwind the shearer when cutting coal downwind.The distance by measuring is only 20m.In the changing zone of air velocity,the simulated air velocity is larger than the measured value,and the maximum air velocity is about 30%higher.For the concentration of respiratory dust,the results obtained by the two methods are in good agreement.The center of shearer and its downwind side within 10m is a highly polluted area.Along the airflow,the concentration of respiratory dust tends to decrease,and the dust concentration at bottom is at the level of 50mg/m~3,which is fewer than the middle.