In this study, a semi-analytical model was developed to illustrate the relationship between filtration performance (filtration efficiency and pressure drop) and dust loading under two different particle deposit stru...In this study, a semi-analytical model was developed to illustrate the relationship between filtration performance (filtration efficiency and pressure drop) and dust loading under two different particle deposit structures based on theoretical analysis and computational fluid dynamic (CFD) technology. Under the compact deposit structure, within the practical parameter ranges (fiber diameter, air velocity, dust loading mass), a slight efficiency enhancement (∽10%) occurred at the most penetration particle size (MPPS) and pressure drop increased significantly (∽100%) in response to the solidity increase from 5% to 15%. However, under the dendritic particle deposit structure, both filtration efficiency (∽40%) and pressure drop (4600%) increased significantly with the same solidity increase due to the larger air velocity and swerve change between fibers.展开更多
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
Particles of dust washed off streets by stormwater are an important pathway of polyaromatic hydrocarbons (PAHs) into urban streams. This article presented a comprehensive assessment of the size distribution of PAHs ...Particles of dust washed off streets by stormwater are an important pathway of polyaromatic hydrocarbons (PAHs) into urban streams. This article presented a comprehensive assessment of the size distribution of PAHs in street dust particles, the potential risks of the particles in urban streams, and the sources and sinks of PAHs in the stream network. This assessment was based on measurements of 16 PAHs from the USEPA priority list in street dust particles and river sediments in Xincheng, China. The content of total PAHs ranged from 1629 to 8986 Dg/kg in street dust particles, where smaller particles have a higher concentrations. Approximately 55% of the total PAHs were associated with particles less than 250 μm which accounted for 40% of the total mass of street dust. The PAH quantities increased from 2.41 to 46.86 μg/m2 in the sequence of new residential, rising through main roads, old town residential, commercial and industrial areas. The sediments in stream reaches in town were found to be sinks for street dust particle PAHs. The research findings suggested that particle size, land use and the hydrological conditions in the stream network were the factors which most influenced the total loads of PAH in the receiving water bodies.展开更多
Dispersion of volcanic ash and dust is traditionally modeled as advection and Gaussian diffusion. This is the tradition in treating smoke stack plumes. About 100 meters above earth the velocity profile may disintegrat...Dispersion of volcanic ash and dust is traditionally modeled as advection and Gaussian diffusion. This is the tradition in treating smoke stack plumes. About 100 meters above earth the velocity profile may disintegrate, diffusion coefficients become rather unpredictable and stratified flow occur. It is suggested that gravitational flattening may be the main cause of dispersion in dust plumes above the turbulent boundary layer. A dust plume in between two layers of small temperature difference has a certain carrying capacity of dust. The corresponding mass loading can be estimated from the temperature difference between the layers above and beneath the plume. Such dust plumes will be forced to jettison a load they may have in excess of this carrying capacity;this may be seen as streak fallout from the plume. In the same time, the plume will be subjected to gravitational flattening to the sides, in addition to any diffusion if there is any. The plume width resulting from the flattening may be estimated from the temperature difference. This can explain the behavior of plumes like the plume from the Eyjafjallaj<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">?</span></span></span></span></span>kull 2010 in absence of diffusion. In the long run diffusion and gravitational flattening will cause different developments of the plume width. Gravitational flattening and streak fallouts are important elements from plume physics not included in most plume models. It is concluded that modelling dust plumes with diffusion and ordinary fallout only;can cause serious errors in the model, the simulated plumes will become too big. <span style="font-family:;" "="">To avoid them, the new model should be included in dust models in the same manner as the turbulent diffusion, <i>i.e.</i> as a sub grid model. Then, the plume model only needs to include horizontal turbulent diffusion of the same order of magnitude as the vertical one.</span>展开更多
基金supported by National Nature Science Foundation of China(Grant no.51208372)the State Key Laboratory of Pollution Control and Resource Reuse Foundation(Grant no. PCRRY11011)
文摘In this study, a semi-analytical model was developed to illustrate the relationship between filtration performance (filtration efficiency and pressure drop) and dust loading under two different particle deposit structures based on theoretical analysis and computational fluid dynamic (CFD) technology. Under the compact deposit structure, within the practical parameter ranges (fiber diameter, air velocity, dust loading mass), a slight efficiency enhancement (∽10%) occurred at the most penetration particle size (MPPS) and pressure drop increased significantly (∽100%) in response to the solidity increase from 5% to 15%. However, under the dendritic particle deposit structure, both filtration efficiency (∽40%) and pressure drop (4600%) increased significantly with the same solidity increase due to the larger air velocity and swerve change between fibers.
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 Key Project of Zhe-jiang Province (No. 2006C13057)the CAS Program(No. KZCX1-YW-06-02)the Jiaxing City Project(No. 2005AZ3040).
文摘Particles of dust washed off streets by stormwater are an important pathway of polyaromatic hydrocarbons (PAHs) into urban streams. This article presented a comprehensive assessment of the size distribution of PAHs in street dust particles, the potential risks of the particles in urban streams, and the sources and sinks of PAHs in the stream network. This assessment was based on measurements of 16 PAHs from the USEPA priority list in street dust particles and river sediments in Xincheng, China. The content of total PAHs ranged from 1629 to 8986 Dg/kg in street dust particles, where smaller particles have a higher concentrations. Approximately 55% of the total PAHs were associated with particles less than 250 μm which accounted for 40% of the total mass of street dust. The PAH quantities increased from 2.41 to 46.86 μg/m2 in the sequence of new residential, rising through main roads, old town residential, commercial and industrial areas. The sediments in stream reaches in town were found to be sinks for street dust particle PAHs. The research findings suggested that particle size, land use and the hydrological conditions in the stream network were the factors which most influenced the total loads of PAH in the receiving water bodies.
文摘Dispersion of volcanic ash and dust is traditionally modeled as advection and Gaussian diffusion. This is the tradition in treating smoke stack plumes. About 100 meters above earth the velocity profile may disintegrate, diffusion coefficients become rather unpredictable and stratified flow occur. It is suggested that gravitational flattening may be the main cause of dispersion in dust plumes above the turbulent boundary layer. A dust plume in between two layers of small temperature difference has a certain carrying capacity of dust. The corresponding mass loading can be estimated from the temperature difference between the layers above and beneath the plume. Such dust plumes will be forced to jettison a load they may have in excess of this carrying capacity;this may be seen as streak fallout from the plume. In the same time, the plume will be subjected to gravitational flattening to the sides, in addition to any diffusion if there is any. The plume width resulting from the flattening may be estimated from the temperature difference. This can explain the behavior of plumes like the plume from the Eyjafjallaj<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">?</span></span></span></span></span>kull 2010 in absence of diffusion. In the long run diffusion and gravitational flattening will cause different developments of the plume width. Gravitational flattening and streak fallouts are important elements from plume physics not included in most plume models. It is concluded that modelling dust plumes with diffusion and ordinary fallout only;can cause serious errors in the model, the simulated plumes will become too big. <span style="font-family:;" "="">To avoid them, the new model should be included in dust models in the same manner as the turbulent diffusion, <i>i.e.</i> as a sub grid model. Then, the plume model only needs to include horizontal turbulent diffusion of the same order of magnitude as the vertical one.</span>