Study On Explosion Characteristics And Inertion Of Low-density Polyethylene Dust/Ethylene Gas Hybrid Mixture

In the production process of Low-density polyethylene（LDPE）powder,the pneumatic conveying pipes and silos usually have the risk of dust explosion.A small amount of ethylene gas is often left and may form a powder/gas mixture with LDPE powder,aggravating the complexity of the original explosion risk,simultaneously adding to the difficulty of risk assessment and accident prevention and control.Therefore,the experiments were based on the self-designed minimum ignition energy test device for combustible dust/combustible gas mixture and the object of a mixture of typical industrial-grade LDPE powder and ethylene gas with a concentration lower than the lower explosive limit.The distribution of minimum ignition energy of such mixtures,flame propagation characteristics in long tubes and the inerting effect of typical inerting gas on the mixture were systematically studied by means of experiments.First,with standards of the minimum ignition energy test method for dust clouds,a self-designed minimum ignition energy test device for combustible dust/combustible gas mixture was developed,which improved the mixing method of combustible gas,dust and air in the powder spraying state.It also solved the problem that the premixed gas and the air in the tube are too late to mix at the moment of ignition,making the explosive environment closer to reality.Secondly,by means of the above-mentioned self-designed device,the minimum ignition energy of the mixture of LDPE powder and a small amount of ethylene gas below the lower explosion limit was experimentally studied.The distribution characteristics of the minimum ignition energy of the mixture with the dust weight,particle size and ethylene concentration were revealed,and a multi-factor correlation model of the minimum ignition energy was established to provide a basis for the LDPE dust explosion risk assessment and effective prevention.Thirdly,the experimental study of the explosion development process of the LDPE dust/ethylene mixture in the long tube revealed the flame propagation law and morphological evolution characteristics in the long tube,summarized the effects of ethylene concentration and dust quality and particle size on the explosion pressure during the flame development.The law provided a reference for the identification of flame characteristics in the early stage of explosion and the suppression of flame propagation.Finally,N₂ was selected as a typical inerting medium to conduct inerting studies of LDPE dust/ethylene gas mixture,and revealed the effect of N₂ on the explosion pressure of the powder/gas mixture under different ethylene concentration.Furthermore,the correlation between the limit oxygen content of the mixture and the ethylene concentration was obtained,which laid the foundation for the further optimization of the inerting technology parameters.