Dispersion Mechanism Of Dust Falling And Dust Suppression Method Based On Industrial Production Process

In the manufacturing process,raw materials usually need to undergo various processing and handling.The processing and handling of industrial raw materials often bring a variety of environmental pollution problems.For example,in the production process of heavy industry or non-ferrous metal products,some powdered industrial raw materials,such as coal powder,magnesium powder,aluminum powder,carbon powder,cement,etc.,are frequently and widely used in industrial production.A series of processes in industrial production,such as transfer,transportation and unloading,are often accompanied by the“falling and dispersing”of industrial dust--accompanied by the“primary dusting”and“secondary dusting”movement processes.There are many kinds of particles with different particle sizes in industrial dust.The large particles have a greater influence on the air induction during the movement,while the fine inhalable particles are more difficult to deposit in the air and escape to the surroundings.Mastering the mechanism of dust falling dispersion in industrial production processes is one of the key factors in formulating dust suppression strategies.Through theoretical derivation,PIV experiments and numerical calculations,the authors studied the induced entrainment characteristics caused by the industrial dust falling process and proposed a dust suppression strategy for dust baffle.The dissertation mainly includes the following aspects:(1)The calculation formula of the entrained air volume in the industrial dust free-fall process was derived through theoretical derivation,which takes into account factors such as the dust initial velocity and the void fraction of the material flow core area.Drawing on the comparison between the theory of air free jets and adherent jets,it is obtained the formula for calculating the entrained air volume during the industrial dust adheres wall fall process.(2)The experimental study found that for the industrial dust free fall process,the entrained air velocity gradually increases as the dust falls,and the distribution of the entrained air velocity at different height sections show a Gaussian distribution.For the industrial dust adheres wall fall process,when the distance between the hopper outlet and the wall surface is s/d≤5,the entrained air can better adhere to the vertical wall;When s/d>5,the characteristics of entrained air flow field tend to approach the free fall process.(3)Numerical studies show that the change of dust particles velocity during the dust free fall process is divided into three stages:In stage Ⅰ(Re_p≤53.3),the dust particles are similar to falling in a vacuum,and the dust particle acceleration is slightly smaller than the gravitational acceleration g;In stage Ⅱ(53.3<Re_p<85.2),the dust particles continue to accelerate in a state where the acceleration is significantly less than g.In stage Ⅲ(Re_p≥85.2),the dust particles drops at a constant velocity.In addition,dust initial velocity increased from 0.1 m/s to 10 m/s,which has little effect on the entrained air volume flow rate during the dust fall process.When the dust source outlet angle is between 30°and 45°,the volume of the entrained air volume at the different height sections is at the peak state.The influence of the horizontal airflow on the entrained air flow field in the industrial dust horizontal projectile fall process is significantly greater than that in the vertical fall process.Numerical simulations show that the industrial dust falling along the vertical wall(the dust source is at different distances from the wall surface)correspondingly reduces the entrained air flow rate,and thus reduces the dust escape.When s/d=0(adheres wall),the entrained air volume in the adheres wall fall process was 22%lower than during the free fall process.(4)Numerical calculations are employed to analyze the effects of three different types of baffles and baffle positions on dust escape.Studies have shown that under the same working conditions,for different shapes baffles,semi-circular baffle are better,followed by V-baffle,and the straight panel baffle is poor.It is analyzed the effect of different baffle arrangements on dust control.