Research On Numerical Simulation And Venting Of Dust Explosion In Cyclone Dust Collector

Dust explosion seriously restricts the development of my country’s powder industry.In the actual powder production and processing,the inside of the dust collector can easily reach the explosive limit concentration,which is the initial explosion source of most dust explosion accidents.Dust explosion release technology,as one of the simplest and most effective methods,can effectively weaken the intensity of the explosion and reduce the possibility of secondary explosions.For this reason,the study of the dust explosion pressure relief law for cyclone dust collectors has been carried out to provide theoretical guidance and experimental basis for the explosion-proof design of industrial dust collector systems.Based on the industrial cyclone dust collector of 0.25 m3 and FLACS explosion simulation software,the dust explosion release experiment and numerical simulation research are carried out in this paper.Using corn starch as the experimental medium,the influence of various influencing factors on the discharge effect of the dust collector was discussed,and the influence of different discharge positions and different discharge areas on the entire discharge process of the dust collector was studied.At the same time,the measured values were compared.It was compared with the predicted value in the GB/T15605 standard,and the internal and external pressure development and external flame propagation and temperature changes were analyzed.The experimental results show that the peak value of internal overpressure is significantly reduced after the discharge of dust collector.The installation position of the relief device has an effect on both the internal overpressure peak value and the external flame propagation distance of the dust collector.Under the same dust mass concentration,the overpressure peak value generated by the pressure relief at the side and top of the cylinder of the dust collector is small,so it is recommended to use the side and top pressure relief.However,the flame propagation distance outside the two-position discharge orifice is long,so the safety distance should be fully considered in the discharge design.The larger the discharge area is,the smaller the peak value of the internal overpressure of the dust collector will be.However,in the condition of joint discharge of multiple discharge positions,the discharge devices are not all opened,so the installation of multiple discharge devices should be at the same horizontal position as far as possible to increase the discharge efficiency.The greater the dust mass concentration is,the greater the distance between the peak overpressure inside the dust collector and the external flame propagation is.The maximum peak overpressure measured in the experiment is 34.5KPa,and the maximum propagation distance of the external flame can reach 2.5m.In addition,when the dust mass concentration is large,the external uncombustible dust cloud ejected by the shock wave is more likely to be ignited by the subsequent flame,resulting in the lengthened flame length and increased flame width.Within the effective discharge range,the measured pressure values are all below the standard prediction line.In the standard,the maximum horizontal flame length is predicted to be about 6.3m,but the maximum flame length measured by the experiment is only 2.5m,far below the predicted value.Therefore,the prediction of internal pressure and external flame length of the dust collector in the discharge standard is conservative,and the prediction formula needs to be refined.The numerical simulation results are in good agreement with the experimental results.The results show that the discharge process of dust collector can be divided into three stages.In the first stage,the discharge device is opened and the pressure is earlier than the flame discharge.In the second stage,the flame spreads to the discharge position,and the pressure and flame are discharged together.The third stage is pressure relief to end the short discharge of the flame.The higher the opening pressure is,the greater the peak value of the internal overpressure of the dust collector is,and the peak value of the external overpressure at each measuring point decreases first and then increases and then decreases.However,the external flame propagation distance and the internal temperature of the dust collector are less affected by the opening pressure.The distribution state of the initial dust cloud and the ignition position both have an influence on the explosive discharge of the dust collector.When the dust cloud fills the whole dust collector and the ignition position occurs at the bottom of the dust collector,the internal pressure of the dust collector can reach 55KPa,and the explosion risk of the dust cloud evenly distributed at the bottom is higher than that of the dust cloud distributed at the top.