Study On Dust Dispersion Characteristics Of Fully Mechanized Face And Optimization Methods On Dust Control

The problem of dust pollution is becoming more and more serious with the development of mechanization technology.Dust harms the physical and mental health of the miners,impairs the life of the underground equipments,which may induce the dust explosions.The local design of the dust removal system and the layout plan can't achieve the best effects due to the lack of systematic understanding on the temporal and spatial distribution of dust in the coal roadway.Therefore,it is urgent to investigate the temporal and spatial movement of dust in a coal roadway and the optimization method on dust control.The present work studied dust generation and movement in a typical coal roadway with a fully mechanized heading face based on the gas–solid two-phase flow.According to the actual situation of the coal production,the distribution characteristics of different-sized dust and its temporal and spatial evolution changes under different working conditions were analyzed.The optimization method on dust conctrol was proposed purposefully.The main results and conclusions are as followsThe spatiotemporal distribution of dust in the coal roadway was studied with the air curtain system via CFD–DPM method,and the spatiotemporal concentration of dust and the main influence factors were considered.The dust movement was simulated via the Euler-Lagrange method.Meanwhile,dust was treated as a discrete phase under a Lagrangian frame,and the air flow was modelled as the continuous phase.Selected simulation results were verified by relative field measurements with some field test data.The results show that the spatiotemporal concentration of dust clearly reduces after the air curtain when compared with that of the system without the air curtain,the PM_2.5 concentration around the driver is reduced approximately23.3%according to the fitting function.The PM_2.5concentration around the driver can be further reduced by using the optimized air curtain generator.In addition,the PM_2.5concentration and its proporation in the breathing zone are also reduced by using the optimized air curtain generator.The initial supply air velocity,the initial air curtain velocity,and the angle of the jet flow from the air curtain have significant effects on dust diffusion in the coal roadway.The increase of the initial supply air velocity can reduce the dust concentration in the roadway,and the magtitude of the reduction in dust concentration decreases with the increase of the initial supply air velocity.The proper increase of the initial air curtain velocity can reduce the dust concentration in the working area.However,the entrainment effect of air curtain increases with the excessive initial air curtain velocity,which is not conducive to the reduction of dust concentration in the working area.The angle of the jet flow is adjusted to improve the sealing effect of the air curtain,which is conducive to reducing the dust concentration in the working area.To study dust distribution in detail,the dust dispersion and its distribution disciplinarians under the ventilationwith the supply airflow and the air curtain system were studied based on the CFD-DEM method.Based on CFD-DEM simulation,the existence of the solid phase of dust particles and its effect on the air phase were considered.Then the two-phase flow was considered with the Euler-Lagrangian method,and the coupled two-phase flow was obtained.Meanwhile,each dust particle was traced,and the particle collisions were considered via the hard-sphere model and the direct simulation Monte Carlo method.The influence of the initial supply air velocity and the initial air curtain velocity on the dust dispersion in the coal roadway was studied.The results showed that different dust distribute with different layers.The finer and the fine dust particles can be easily separated from the mainstream of dust particles,and disperse in the upper region in the coal roadway.There are few big particles(>40?m)around the driver.The quantity concentration of the small particle size dust around driver is relatively higher,including the finer particles(2.5?m?10?m),the fine particles(10?m?20?m)and the coarse particles(20?m?40?m).The quantity concentration of the small particle size dust around driver decreases with the increase of initial supply velocity.Based on the ventilationwith the supply airflow,the effect of water spray on dust deposition in the roadway was studied.The VOF model was used to calculate the continuous gas-liquid phase.The DPM model was used to simulate the discrete phase.The process of dust deposition and its dispersion under the three-phase field in the coal roadway was studied.The research showed that the water spray can promote dust deposition and reduce the quantity concentration of PM_2.5 suspended in the roadway.Water spray reduce the PM_2.5 concentration around the driver by approximately 30%.The research results provide a theoretical basis for multi-stage dust removal of fully mechanized face,which provide theoretical guidance and analysis method for optimization of dust control technology.