Influence of three suppressants on the propagation of polyethylene flame in vertical pipelines
[Objective]Polyethylene is a widely used thermoplastic resin.However,there is a risk of dust explosion during its production and transport,which can lead to production safety accidents,resulting in casualties,property losses,and considerable environmental damage.Currently,there exists sufficient research on the application of powder explosion suppressants in suppressing organic dust,metal dust,and other explosions.Therefore,investigating the flame propagation characteristics of powder explosion suppressants in inhibiting polyethylene dust explosions is vital for industrial dust explosion prevention and control.[Methods]In this study,an explosion flame suppression pipeline experimental system similar to the Hartmann tube was constructed to investigate explosions involving polyethylene dust at a mass concentration of 1 000 g/m3,both alone and in mixtures with ABC powder,MPP powder,and MCA powder at various ratios.Flame propagation patterns and dust diffusion characteristics were comprehensively investigated.Additionally,a synchronous thermal analyzer was employed to explore the effects of ABC powder,MPP powder,and MCA powder on the pyrolysis process of polyethylene dust.[Results]The results showed that during the propagation of polyethylene dust explosion flames in the pipeline,uneven distribution of dust particles caused discontinuous flame phenomena owing to forces acting on the particles.Outside the pipeline,high-temperature flames,hot airflow,and pressure differences between the inside and outside of the pipe induced a volumetric suction effect.This led to flame"tumbling"and the formation of a"canopy flame."ABC powder exhibited the best suppression effect among the three suppressants.The flame propagation ceased when ABC powder constituted 10％and MCA and MPP powder constituted 15％.Further addition of suppressant powder prevented further explosions.Simultaneous thermal analysis experiments revealed that in the mixed system with 20％ABC,20％MCA,and 20％MPP powder,the initial decomposition temperature of polyethylene dust decreased from 286 ℃ to approximately 267 ℃,271 ℃,and 270 ℃,respectively.The decomposition temperature of ABC powder was approximately 208 ℃.During decomposition,ABC powder formed groups that underwent exothermic reactions with oxygen,resulting in a small exothermic peak around 256 ℃.Additionally,interactions between ABC powder and PE produced similar small exothermic peaks.The macromolecules or groups generated by ABC powder and PE further absorbed heat during decomposition.Consequently,the ABC-containing mixture samples exhibited an overall higher decomposition temperature than standalone PE samples and a reduced maximum heat flux of 110 mW.[Conclusions]In summary,powder explosion suppressants competed with the heat from the polyethylene system for their own decomposition,thereby exerting an suppression effect through physicochemical interactions.This study offers insights for constructing similar explosion experimental equipment and defining experimental conditions and provides a theoretical foundation for preventing and controlling polyethylene dust explosion disasters.
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