Study On Numerical Simulation Of The Process Of Removing Dust By Cloud Fog

The dust particles in the coal mining process are small(?<100 ?m)and respirable,which harms to workers‘health and brings great potential safety hazard for underground work.At present,the removing dust of coal mine lacks the mature and credible theoretical system to describe,and don't have the completely systematic experimental study.However,in the many theories and technologies of removing dust,removing dust of cloud fog technology has the advantages of high efficiency and small effect on the quality of coal.It is based on the theory of gas-liquid two phase flow,squeezing the air and water into the cloud fog generator according to certain proportion and generating aggregated structure of a larger quality by collision of jetting droplets and dust particles in space,and which can speed up the settling velocity of dust particles to realize the purpose of removing dust.At present,the cognition of this theoretical technology is poorly and the results of the experimental tests are unstable,so there are still many problems need to be solved in the popularization and application of this technology.These obstacles are existing because people are lack of cognition to the migration dust particles and the interaction between dust particles and droplets.Dust particles of coal mine tunnel belong to discrete particle system,so this program tries to base on the thought of DEM(discrete element method).Dynamics model of dust particles collision is built in the improvement of the hard sphere model of DEM,and gets the moving law of the dust particles in the coal mine tunnel;Then,this model builds the interaction between dust particles and droplets by continuing to consider the colliding regular between the dust particles and droplets.The influence of the initial velocity of dust particles,the mass concentration of dust particles,the surface energy of dust particles,the size of dust particles,the spraying flow,the windy speed of coal mine tunnel,the turbulence intensity and so on removing dust efficiency is studied by quantitative.This work shows that the prabability of forming clusters structure by collision(i.e.,cohesive collision)of dust particles and settlement with the increase of the relative impact velocity(dust particle initial velocity of 0.0?10.0 m/s)of two dust particles,the dust particle size(5.0?25.0 ?m)and the wind speed(0.5?2.0 m/s)is decreasing.When the relative speed is greater than the critical collision speed,the clusters structure can't form,which is unfavorable to removing dust of cloud fog.When the surface can continue to increase in the range of 0.04?2.0 J/m2 and dust mass concentration at 94.5?420.0 mg/m3,the probability of cohesive collision increases.According to the above factors affecting the cohesive collision probability and adjusting and controlling the collision regulation of dust particles and cloud droplets,the removing dust efficiency decreases with the increase of wind speed of the coal mine tunnel by calculating;When the droplet diameter is constant,the removing dust efficiency increases with the spray flow rate less than 3.12×106 N/s and reaches the maximum value at that value,then it decreases;With the increase of turbulence intensity in the spray zone,the removing dust efficiency increases firstly,and then it reaches a balance state at the range of 0.15?0.5 m/s of the random fluctuation velocity in the spray zone.According to the above factors,the removing dust efficiency is the best when the wind speed of 0.5 m/s in the coal mine tunnel and spraying flow of 3.12 × 106 N/s.The experimental test results verify the reliability of the theory of removing dust by cloud fog based on DEM.