Study On Dust-producing Mechanism Of Dumping Material And Dust-controlling Mode Of Negative Pressure

In the process of intermittently unloading bulk materials,along with a large amount of dust escaping,the operators have been in the dust-dispersed space for a long time,and their health is seriously threatened.However,the existing dust removal methods mostly use the induced draft fan to actively form a negative pressure zone,resulting in excessive energy consumption of the induced draft fan.In view of the difficulty of dust control,this thesis takes the transient dust generation of dumped materials as the research object,explores its dust generation mechanism and the influence of different factors on the dust generation rate,dust concentration,and particle diffusion characteristics of time and space.Insufficient,a"passive"negative pressure dust suppression system was proposed and experimental research was carried out to provide new ideas for suppressing dust diffusion.Through theoretical analysis of the force status and dust generation mechanism of the particles in the falling process,the main factors affecting the transient dust generation of dumped materials are revealed;the similarity criterion number is derived according to the similarity principle;the similarity criterion number is established on the basis of meeting the similarity criterion number Scaled test bench,to conduct experimental research on the influence of different unloading conditions on the temporal and spatial distribution characteristics of dust concentration with or without negative pressure dust suppression;use high-speed camera to capture the dynamic diffusion phenomenon of particles,and use PCC3.4 software to analyze and process the pictures.Experimental research results show that the negative pressure dust suppression system uses elastic airbags to instantly deflate to create a negative pressure zone,so that the dust-laden airflow generated during unloading intermittently migrates to the negative pressure zone in an organized and"passive"manner,so that the dust concentration in this area is higher than the natural sedimentation.Dust concentration at time.When the discharge volume is less than 1500g,the PM2.5 and PM10 concentrations in the negative pressure zone increase with the increase of the discharge volume.When the discharge volume is greater than 1500g,the induced PM2.5 and PM10 concentrations decrease.The induction force of the airbag in the negative pressure dust suppression system should match the discharge volume.The greater the discharge angle,the greater the peak dust concentration in the negative pressure zone.At 60°,the peak PM2.5 concentration increases by 300.22μg/m~3 compared to the natural settlement,and PM2.5 accounts for about 43%of PM10.The greater the discharge height,the greater the peak dust concentration in the negative pressure zone.At 1.6m,the peak concentrations of PM2.5and PM10 in the negative pressure zone are 1.35 times and 1.66 times that of the non-negative pressure dust suppression mode.The peak concentration of PM2.5 and PM10 in the negative pressure zone when the underlying surface is a stock pile is 2.8 times and3.52 times that when the underlying surface is a blanket.Due to the existence of the superimposed flow field in the two airbags,the maximum PM2.5 is 1.18 times and 1.15times that of the single lower airbag and single upper airbag,respectively,and the peak PM10 concentration has increased by 1.45 times and 1.19 times.Through the analysis of the dynamic dust diffusion phenomenon,it can be known that with the generation of vortex in the initial stage of unloading,the particle outflow direction is more obvious when the particle collides.In summary,it can be seen that the"passive"negative pressure dust suppression system can effectively induce dust to the negative pressure area to facilitate subsequent dust removal,to a large extent,to reduce the pollution area of the dust-containing airflow and reduce the consumption of the induced draft fan.The research results will provide an effective theoretical basis for the treatment of transient dust generation and dust generation during intermittent discharge.