High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal min...High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5 collector,controllable PM2.5 generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working condition,this study investigated the effects of dust loading,wearing time,and dust concentration on the filtration efficiency,breathing resistance,and quality factor of N95 elastomeric respirators.With the increase of dust loading,the respirator filtration efficiency firstly decreased,then increased(minimum value 97.5%).The breathing resistance increased exponentially from 120 to 180 to 1020-1530 Pa,and the quality factor decreased logarithmically from 0.051 to 0.076 to 0.0058-0.0085 Pa^(-1).As the PM2.5 coal dust concentration increased from 5 to 50 mg/m^(3),the wearing time for the respirator breathing resistance to exceed 300 Pa reduced from 7 h to less than 1 h.One N95 elastomeric respirator is not able to perform an 8-h work shift.To avoid the excessive breathing resistance caused by dust loading,more filter cartridges are needed for coal miners.展开更多
The permeability is a key factor to determine the efficiency of coalbed methane(CBM)production.The borehole enlargement technology using hydraulic and mechanical measures to cut coal is an effective method to increase...The permeability is a key factor to determine the efficiency of coalbed methane(CBM)production.The borehole enlargement technology using hydraulic and mechanical measures to cut coal is an effective method to increase the coal seam permeability and improve the efficiency of gas drainage.Reasonable design of the layout of boreholes is the prerequisite for efficient and economical gas drainage.In this paper,based on the strain-softening model,the stress and permeability model of the coal seam around the enlarged borehole was built,and based on the dual-medium model,the gas migration model in the coal seam was established.Then the borehole enlargement gas drainage engineering of E9/10 coal seam in Pingdingshan No.8 coal mine was simulated by using COMSOL Multiphysics software.The distribution of stress and permeability in the coal seam around a borehole was analyzed,and the reasonable borehole radius of 0.25 m and reasonable borehole spacing of 6 m were determined.Finally,in Pingdingshan No.8 coal mine,field application was carried out in E9/10 coal seam-21070 working face from the high-level gas drainage roadway.The results show that the actual average coal slag discharge rate is 77.82%,which achieved borehole enlargement.The natural gas flow rate from an enlarged borehole is 2.3–7.3 times that of a normal borehole,and the influence range of enlarged boreholes is more than 6 m.The average gas drainage concentration of a group of enlarged boreholes is about 42%,and the average gas drainage amount is about 0.53 m3/min.After two months of gas extraction,the outburst risk in this area was eliminated,which provides a guarantee for safe coal mining.展开更多
基金supported by the National Natural Science Foundation of China(No.51904291)the Basic Research Program of Jiangsu Province(No.BK20190638)+2 种基金the Fundamental Research Funds for the Central Universities(No.2020XGYJ08)the Project funded by China Postdoctoral Science Foundation(No.2020 M681781),the Jiangsu Planned Projects for Postdoctoral Research Funds(No.2020Z076)the State Key Laboratory of Strata Intelligent Control and Green Mining Co-founded by Shandong Province and the Ministry of Science and Technology(No.SICGM202105).
文摘High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5 collector,controllable PM2.5 generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working condition,this study investigated the effects of dust loading,wearing time,and dust concentration on the filtration efficiency,breathing resistance,and quality factor of N95 elastomeric respirators.With the increase of dust loading,the respirator filtration efficiency firstly decreased,then increased(minimum value 97.5%).The breathing resistance increased exponentially from 120 to 180 to 1020-1530 Pa,and the quality factor decreased logarithmically from 0.051 to 0.076 to 0.0058-0.0085 Pa^(-1).As the PM2.5 coal dust concentration increased from 5 to 50 mg/m^(3),the wearing time for the respirator breathing resistance to exceed 300 Pa reduced from 7 h to less than 1 h.One N95 elastomeric respirator is not able to perform an 8-h work shift.To avoid the excessive breathing resistance caused by dust loading,more filter cartridges are needed for coal miners.
基金supported by the Assistance Program for Future Outstanding Talents of China University of Mining and Technology(No.2020WLJCRCZL041)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX20_0816).
文摘The permeability is a key factor to determine the efficiency of coalbed methane(CBM)production.The borehole enlargement technology using hydraulic and mechanical measures to cut coal is an effective method to increase the coal seam permeability and improve the efficiency of gas drainage.Reasonable design of the layout of boreholes is the prerequisite for efficient and economical gas drainage.In this paper,based on the strain-softening model,the stress and permeability model of the coal seam around the enlarged borehole was built,and based on the dual-medium model,the gas migration model in the coal seam was established.Then the borehole enlargement gas drainage engineering of E9/10 coal seam in Pingdingshan No.8 coal mine was simulated by using COMSOL Multiphysics software.The distribution of stress and permeability in the coal seam around a borehole was analyzed,and the reasonable borehole radius of 0.25 m and reasonable borehole spacing of 6 m were determined.Finally,in Pingdingshan No.8 coal mine,field application was carried out in E9/10 coal seam-21070 working face from the high-level gas drainage roadway.The results show that the actual average coal slag discharge rate is 77.82%,which achieved borehole enlargement.The natural gas flow rate from an enlarged borehole is 2.3–7.3 times that of a normal borehole,and the influence range of enlarged boreholes is more than 6 m.The average gas drainage concentration of a group of enlarged boreholes is about 42%,and the average gas drainage amount is about 0.53 m3/min.After two months of gas extraction,the outburst risk in this area was eliminated,which provides a guarantee for safe coal mining.
