| Polishing dust is one of the important sources of dust in the surface treatment process of metal products,and the health and safety problems brought by it are getting more and more attention.The dust concentration in the polishing workshop is high and the environment is harsh,and there is little research on the mechanism and characteristics of polishing dust at both domestic and foreign scholars,and even less research on the control technology of polishing dust.Polishing dust has a wide particle size distribution,complex physical structure(including extruded strips and molten spheres),complex generation mechanism and transport law,and single dust removal technology is no longer suitable for large scale polishing dust removal,which makes dust collection and reduction more difficult.In this paper,we use theoretical analysis,numerical simulation,experimental research and field application to analyze the dust collection mechanism of dust hood,cyclone separation mechanism and cartridge filtration mechanism,and propose a comprehensive and precise dust collection and reduction technology of dust collection by dust hood,separation of large-size dust by cyclone separator and filtration of small-size dust by pleated cartridge.Based on the experimental results,a small composite dust collector prototype is made,tested in the laboratory for dust removal effect and applied in the polishing workshop on site.To address the problem of high dust concentration in the polishing workshop,theoretical analysis and numerical simulation were used to analyze the process of polishing dust generation and reveal the diffusion mechanism of polishing dust.The physical and chemical characteristics of polishing dust were analyzed by scanning electron microscopy,and it was found that the larger polishing dust showed stripes and the smaller polishing dust showed spherical shape.The particle size of the polishing dust ranged from 0.1-656 ?m and showed an obvious bimodal distribution.The polishing process was analyzed,and the relationship between polishing volume and polishing times,workpiece density,polishing thickness and edge length was deduced.To address the problem of wide particle size distribution and difficult collection of polishing dust,a small composite dust collector hood is designed according to the collection mechanism of spherical and non-spherical polishing dust.Based on the dust collection mechanism of the dust hood,numerical simulation is applied to study the effects of five factors on the performance of the dust hood:air flowrate,grinding wheel speed,dust hood diameter,suction pipe diameter and installation angle,and to narrow down the range of influencing factors.In the range of simulation results,the response surface method is applied to design the dust collection hood structure optimization experiment and obtain the optimal structure parameters of the dust collection hood.The cyclone separator is used to initially separate the polishing dust collected by the dust collection hood,but the conventional cyclone separator has the disadvantage of high pressure drop and low efficiency when separating dust below 5.0 ?m.Based on the cyclone separation mechanism and the Lapple cyclone separator model,a new two-stage cyclone separator was designed and developed.Combining with the actual situation of the polishing workshop,the numerical simulation method is applied to study the influence of four factors on the performance of the dust collector:air flowrate,the diameter of the 1st-stage cyclone,the area of the 1st-stage cyclone inlet and the number of 2nd-stage cyclone inlets,to narrow the range of influencing factors.According to the simulation results,the response surface method is applied to design the two-stage cyclone structure optimization experiment and obtain the best structure parameters of the two-stage cyclone.Compared with the conventional Lapple cyclone,the optimized two-stage cyclone has 49.1%lower pressure drop and 12.3%higher efficiency.The small particle size dust not separated by the two-stage cyclone will be filtered by the pleated cartridge.Using numerical simulation method,the pressure drop of clean pleated cartridge is analyzed from the qualitative analysis of pressure field and flow field,and the variation law of pressure drop with pleat density and pleat rate is quantified along the static pressure distribution.The simulation results show that the pressure drop of clean pleated cartridge decreases and then increases with the increase of pleat density for the same inner diameter and outer diameter,and the pressure drop of clean pleated cartridge decreases and then increases with the increase of pleat rate for different inner diameter and outer diameter.Based on the gas-solid two-phase flow theory and fiber filtration theory,a pleated cartridge dust loading experiment was built to study the dynamic evolution of pleated cartridge performance with dust loading.The optimum pleat density and pleat ratio of the pleated cartridge after dust loading were determined,which improved the dust capacity of the pleated cartridge,reduced the number of dust cleaning and extended the life time.Based on the optimal parameters of each part of the small composite dust collector obtained from numerical simulation and experimental optimization results,a prototype small composite dust collector was made.The laboratory dust removal effect analysis of the small composite dust collector shows that the dust reduction efficiency of all dusts at the experimental site exceeds 91.3%and the dust reduction efficiency of respiratory dusts exceeds 92.3%.The results show that the dust reduction efficiency of the polishing workshop is more than 83.6%and the respirable dust reduction efficiency is more than 90.0%for both fixed and mobile polishing sites,and for both single and multi-group operations. |
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