| The fully mechanized coal face is one of the areas with the most serious dust pollution,and the coal dust in fully mechanized face mainly comes from shearer cutting coal and support moving.Large power and fast cutting speed of fully mechanized mining equipment lead to a large amount of coal dust in the process of coal crushing.,which seriously threatens the health of workers.Although the state attaches increasing importance to coal dust control,there are still many coal mines which have a series of problems in coal dust management,such as weak theoretical knowledge,strong artificial subjective experience and backward dust removal technology.Therefore,in order to effectively control coal dust pollution of fully mechanized coal face,this paper adopts the method combining theoretical analysis,field test,numerical simulation and experimental research.theoretical analysis,field test,numerical simulation and experimental research,meso scale studies the coal dust migration rule of fully mechanized coal face,parallel coupling of mixed pneumatic spray and cyclone coupling technology of controlling coal dust.Based on the stress model of coal dust in the air,the stress and micro-movement characteristics of coal dust under wind disturbance were analyzed.Through the measurement of coal dust concentration on 22205 working face of Hanjiawa coal mine,the distribution rule of coal dust concentration and the particle size distribution characteristics of coal dust was obtained under the condition of cutting coal with the wind or against the wind.By Fluent numerical simulation software,on the basis of working face site and dynamic grid technology,a geometric model was established,the dynamic model of gas-particle two-phase turbulence was constructed,the diffusion law of coal dust was studied under the conditions of multi dust source coupling in different roadway wind speed,different scraper running speed,different wall conditions and different coal dust moisture content in the coal mining process on fully mechanized coal face.In the case of cutting coal with(against)the wind,the coal dust mass concentration reached the maximum at about 5m(15m)downwind direction of the second drum in the wind direction.Based on the theory of hydrodynamics and aerodynamics,the atomization mechanism of nozzle jet is expounded,the macro characteristics and droplet size distribution of the pneumatic spray nozzle under different water supply pressure and air supply pressure are studied by experimental meso,it is concluded that the air supply pressure is the main influencing factor of droplet size,range and atomization angle.And the swirl coupling mode of the pneumatic spray was proposed,the mist curtain formed by swirl coupling of pneumatic nozzle was studied experimentally and the atomization characteristics under the influence of air supply pressure,water supply pressure,working angle of the nozzle and the length of the air guide baffle were studied experimentally,and the empirical formula of working angle of the pneumatic nozzle and baffle length was fitted.Based on gas-liquid two-phase flow theory and fog drop collision model,fragmentation model and evaporation model,the fragmentation,collision and condensation of droplets in the process of parallel coupling atomization of single and multiple nozzles were simulated,and the influence factors of fog drop movement trajectory,fog drop velocity and particle size distribution were studied.In order to optimize the atomization characteristics of multi pneumatic spray nozzles,a meso simulation was carried out for the mixed use of several pneumatic nozzles with different air supply pressure and water supply pressure,and the influence of the particle size distribution characteristics of fog drops on changing nozzle spacing,the water supply pressure and air supply pressure with parallel coupling was studied.The best condition for parallel coupling of multi mixture spray is that the coupling volume accounts for about 1/3 of the total volume.On this basis,a mathematical model of multi swirl spray coupling was established,and the influence rule of the atomization characteristics was studied when the water supply pressure and air supply pressure were changed.It was concluded that the best operating angle of the nozzle is about 60° after swirl coupling of the pneumatic spray.The dust removal efficiency of different particle size of fogs for different particle size of coal dust was studied experimentally,on this basis,the effects of the relative velocity of droplet and coal dust,the ratio of droplet concentration to coal dust concentration on the dust reduction efficiency are obtained.According to this theory,a reasonable coupling mode of pneumatic nozzle,nozzle spacing,air supply pressure and water supply pressure were designed,and the parameters needed for the optimal efficiency of dust reduction are obtained through experiments.Under the condition of similar simulation of coal face in laboratory,and the dust removal efficiency of the spray system reached above 91.51%.The results show that this dust removal system can effectively reduce coal dust pollution and control coal dust diffusion,it is important reference significance for controlling coal dust for other fully mechanized coal face.In this paper there are 90 figures,41 tables and 152 references. |
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