(380e) Metal Dust Explosion Risks: A Hazard Analysis and Review of Contemporary Industry Objectives

Throughout recent years, metal dust deflagrations continue to pose a critical threat toward safety in the metal processing and refining industry. Following ignition of a metal dust cloud within a contained volume, deflagration can quickly transition to detonation if the process enclosure operates unprotected. Such extreme pressure generation is capable of producing devastating loss of life and property. Metal dusts demonstrate an exceedingly reactive explosion risk due to amplified heats of combustion, burning temperatures, flame speeds, explosibility parameters (K_St and P_max), and ignition sensitivities. In comparison to fuel types of organic composition, the spontaneous nature of metal powder oxidation mechanisms exhibits capacity for characteristically intensified explosion severity. These conceptions will be exemplified through both examination of several case studies involving metal dust explosion incidents and single-particle fuel combustion modeling. Addition of non-combustible inert material to combustible dust mixtures, either through pre-mixing or high-rate injection as the incipient flame front begins to develop, is common practice for preventative inhibition or explosion protection via active suppression, respectively. However, proper mitigation techniques for enclosures conveying metal powders have posed challenging; commonly, design calls for saturation of the protected volume with exceedingly high concentrations of suppressant agent to achieve moderate maximum observable pressures. Thus, this review additionally outlines the application of new materials toward a more efficient metal dust explosion suppression design, with computational fluid dynamic (CFD) simulation as an effective supplement.