Prevention and mitigation of dust and hybrid mixture explosions

The results presented in this article focus on the importance of the prevention and mitigation of dust and hybrid mixture explosions. The main objective is to demonstrate the use of the inherent safety principle of moderation to achieve a significant reduction of the fisk of explosions. Experiments and a companion modeling study were conducted with a test matrix composed of various size fractions of polyethylene powder together with concentrations of hydrocarbon gas (ethylene, hexane, and propane). The results quantitatively show the increased hazard posed by fine particle sizes of dust and the addition of flammable gases. There are clear implications for industry in terms of moderating the risk of an explosion. Gas concentrations used in this work were all less than the lower flammability limit (M) of the particular chemical species and the ratio of gas concentration to LFL concentration was at least 75%. The enhancement of mixture reactivity brought about by a flammable gas admixture could therefore be correlated with the burning velocity of the gas. This article describes bow to predict K(St) for hybrid mixtures and includes the concept of using propane as a surrogate for hexane. Additionally, it shows that the avoidance of both fine dust sizes and hybrid mixtures is a beneficial approach in the process industries to reduce the risk arising from the hazards posed by combustible dusts and their mixture with flammable gases. (C) 2009 American Institute of Chemical Engineers Process Saf Prog 29: 17-21, 2010