(203f) Mitigation of Iron and Aluminum Dust Deflagrations Via Active Explosion Suppression in 1-m3 Sphere Vessel

Explosions induced by ignition of combustible metal powders continue to present a significant threat to metal handling and refining industries. 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. Metal dusts demonstrate an extremely reactive explosion risk due to amplified heat of combustion, burning temperature, flame speed, explosibility parameters (K_St and P_max), and ignition sensitivity. Inhibition efficiency of suppressant agents utilized for active mitigation is shown to be reliant on fuel explosibility, discrete burning mechanism, and combustion temperature range, and thus may be increasingly variable depending on the fuel in question. For this reason, mitigation of metal powder deflagrations at moderate suppression pressures (compared to the strength of the enclosure) and at low agent concentrations remains challenging. This paper reviews recent metal dust suppression testing in Fike Corporation’s 1-m³ sphere combustion chamber, and evaluates the efficacy of multiple suppression agents (sodium bicarbonate [SBC], monoammonium phosphate [MAP], and sodium chloride [Met-L-X]) for the mitigation of iron and aluminum powder deflagrations at suspended fuel concentrations of 2,250 g/m³ and 250 g/m³, respectively.