The Flow Law And Deposition Characteristic Of The High Concentration Dust In Transportation Pipeline Of The Dust Removal System

Quarry crushing, screening and grinding process will produce lots of high concentration dust, pose a significant threat to the environment and the health of workers. Due to a large number of the dust producing points in the quarry, the centralized dust removal system is generally used to transport and process the dust.Because of the complexity of the system structure, the pipe network pressure is easy to unbalance, if the air velocity in the pipe is low, dust will be deposited into the pipe wall, even plug the pipe, the dust removal system will be affected. Different from the air conditioning ventilation system, the concentration of aerosol particles is low, the settlement is small, the quarry dust concentration is higher, and the settlement is big,and the dust deposition in the dust removal pipeline is intensified. Increasing the ventilation rate can effectively reduce the dust deposition in the pipe, but the increase of air velocity not only increases the energy consumption of the dust removal system,but also increases the wear of the dust particles to the pipe of the dust removal system.Therefore, the flow and deposition of dust particles in the dust removal pipeline is needed to be studied, looking for the most suitable air velocity that most of the dust can be taken away, easy deposited parts and suitable local pipe fittings, which will provide guidance for air velocity optimization, local component optimization and key point clearing of the dust removal system.Through theoretical research and experimental study, this paper explores the flow and deposition of dust in different structural parts of the dust removal pipeline.The three pipe systems which are composed of straight pipe, elbow and T-pipe are designed in this paper, the dust used in the deposition experiment in different air velocity is a specific calcium carbonate dust, which sizes are 10μm, 50μm and100μm.In the theoretical analysis, the law of motion of dust in the dust removal pipeline,the way of settling and the main factors affecting the dust deposition in the pipeline are analyzed; The re-suspension of dust particles in the laminar boundary layer of the near wall region of the dust removal pipeline is discussed, and the formula for calculating the diameter of suspended particles is derived.Through the experiment, for the three kinds of particle size(10μm, 50μm and100μm), the most suitable ventilation velocity of the dust removal pipeline are 18m/s,20m/s and not less than 20m/s. The 10μm particle size dust is mainly affected by theturbulent diffusion, the gravity sedimentation is weak, and the difference between the wall of the pipeline is small; the 50μm particle size dust is influenced by gravity sedimentation, and the turbulent diffusion effect is weakened, and the deposition rate of the bottom of the pipe is much larger than that of the side wall and the top; The particle size of 100μm dust is mainly affected by gravitational sedimentation,deposition concentrated in the bottom of the tube, the deposition of the side wall and the top is almost never produced.The elbow will increase the sediment of outside and bottom of the upstream pipe,The deposition amount of the downstream was significantly lower than straight pipe section of the system I. 10μm particle size dust is mainly deposited on the inside of elbow, 50μm and 10μm particle size dust is mainly deposited on the inside of elbow.Increase the curvature radius of elbow, the deposition amount inside and upstream of the elbow is decreased, the outside is increased, and the amount of deposition in the downstream of the elbow is still low. Therefore, it is suggested that the elbow structure of the dust removal pipeline should be chosen with larger curvature radius(R=1.5D).The deposition of T-pipe is mainly distributed in G and H. Increase the branch angle and branch flow velocity, the deposition amount of the three kinds of dust is increased in G and H. Therefore, it is suggested that the dust removal pipeline should choose the small angle of T-pipe(30°), the air velocity of the branch pipe shouldn’t higher than main pipe.