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Mitigation of Iron and Aluminum Powder Deflagrations via Active Explosion Suppression in a 1 m3 Sphere Vessel

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journal contribution
posted on 12.09.2019 by Nicholas S. Reding, Thomas M. Farrell, Robert Jackson, Jérôme Taveau, Mark B. Shiflett
Combustible metal dust explosions continue to present a significant threat to metal handling and refining industries. Addition of noncombustible inert material to combustible dust mixtures, through either premixing 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 (KSt and Pmax), and ignition sensitivity. Inhibition efficiency of suppressant agents used 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 total suppressed pressures (relative to the overall strength of the enclosure) and at low agent concentrations remains challenging. This paper reviews recent metal dust suppression testing in a Fike Corporation’s 1 m3 sphere combustion chamber and evaluates the efficacy of multiple suppression agents (sodium bicarbonate [SBC], sodium chloride [Met-L-X], and monoammonium phosphate [MAP]) for the mitigation of iron and aluminum powder deflagrations at suspended fuel concentrations of 2250 and 500 g/m3, respectively.