Study On Diffusion Regularity And Control Methods Of Ultrafine Dust In Thermal Spraying Workshop

Thermal spraying is one of the important processes of surface treatment techniques,widely used in aerospace,metallurgy,defense industry,petrochemical equipment and machinery manufacturing.But at the same time,lots of dust particles will be generated in the thermal spraying process inevitably,including ultrafine dust,which will not only endanger the health of workers,but also cause serious environmental problems.Therefore,this paper studied the regularity of dust diffusion and analyzed the influence of external factors on the distribution of ultrafine dust concentration in thermal spraying workshop which is of great significance to control dust pollution and reduce dust hazards.The ultrafine dust generation mechanism in thermal spray process and was analyzed in this paper.In order to obtain the control measures of ultrafine particles in the process of thermal spraying,based on the actual thermal spraying workshop,the similar model of thermal spraying workshop was established by combining the similarity principle and the gas-solid two-phase flow theory.The diffusion regulation of ultrafine particles was studied experimentally under different ventilation conditions.The results show that mechanical ventilation has a significant effect on reducing the concentration of ultrafine particles in thermal spraying workshop.Both the concentration of ultrafine particles and the time of dust removed entirely decrease with the increase of the ventilation flow per unit time in the workshop.The ventilation combing the bottom and the side is suitable to achieve the removal and sedimentation of ultrafine particles compared with the strong ventilation over a single side udder the same ventilation rate.The ultrafine dust generation mechanism in thermal spray process was analyzed in this paper.And the motion equation of ultrafine particle is established by analyzing the force on it.Then based on the computational fluid dynamics theory and the gas-solid twophase flow theory,the numerical simulation method was used to analyze the characteristics of flow field and temperature field and the dust ultrafine diffusion process of thermal spraying workshop in Fluent.Results showed that the distribution of airflow in the workshop was nonuniform,the distribution of airflow was shifted to the right integrally under the ventilation parameters of the enterprise.The temperature decreased rapidly along the radial direction from the heat source and high temperature area is small relatively.The dust concentration is approximately symmetrical in the respiratory layer of the workshop.The area of high concentration mainly concentrates near the source,and decreases gradually along the radial direction.The ultrafine dust concentration of the right is significantly higher than the left affected by the right ventilation airflow.Comparing experimental data with simulation data,both of them proved that results are basically identical.Finally,the main method of dust post treatment was excluded.And the general steps to select dust cleaning device were summarized.Combined with cases,it is analyzed how to choose the suitable type of dust collector considering the actual situation of the enterprises.