Study On Dust Explosion Characteristics And Inertion Of LDPE

As one of the main types of polyethylene products,low-density polyethylene（LDPE）powders are flammable and tend to mixing with air to form dust clouds in pneumatic conveying pipes,silos and other related processes and devices,resulting in the dust explosion accident.The lack of both characteristic parameters of LDPE dust explosion and inerting safety parameters has limited the meticulous safety design as well as the accident prevention and control of such production processes.For this reason,typically industrial LDPE powders are investigated.The quantitative distribution rules of LDPE dust explosion parameters are studied.Simultaneously,the inerting effects of typical inert gases on LDPE dust explosion are compared,and the characterstics of flame propagation of LDPE dust cloud in the pipeline is further explored.First,from the point of view for the sensitivity and severity of explosion,the distribution characteristics of explosion parameters are comprehensively studied,such as the maximum explosion pressure,maximum pressure rise rate,explosion index,minimum explosive concentration,minimum ignition energy,and minimum ignition temperature of dust clouds,with the aid of device to test the minimum ignition energy,device to test the minimum ignition temperature of dust cloud and other standard test devices.The quantitative effect of the size distribution and concentration of dust clouds on characteristic parameters,is also discussed.Moreover,a quantitative prodiction model,based on the characteristic parameters of the size distribution among median particles,is established,in terms of the perspective of engineering applications such as safety assessment and risk assessment.Secondly,the inertion of LDPE dust is disclosed through selecting N₂ and CO₂ as inerting medium and the inerting effects of N₂ and CO₂ on LDPE dust explosion with different particle sizes under the most dangerous explosive concentration,is analysed by controling the ratios of selected inerting medium and air.As a result,the changes of maximum explosion pressure of dust cloud and the maximum pressure rising rate,along with both the O₂ content in the air and the particle size of the dust,are concluded.In consideration of the corresponding minimum oxygen content and inerting effect on LDPE with different particle sizes in two inerting medium,it is demonstrated that the minimum oxygen content of CO₂ corresponding to LDPE is higher than that of N₂ when the particle size is same,suggesting that CO₂ possesses more effective inerting effects on the LDPE dust explosion,which is confirmed by analysis of reversible reaction,ternary collision theory,chain reaction,and TG-DSC.Thirdly,the flame propagation characteristics of the local dust clouds in the pipeline is studied,depending on design-independent long-tube experimental device with a high-speed camera.Accordingly,the relationships between maximum or instantaneous flame propagation speed and concentration,particle size and distribution ranges of the LDPE dust,are demonstrated.In addition,the distribution charateristic of the flame microstructure,along with the forementioned factors,is analyzed.