Flammability limits of dusts: Minimum inerting concentrations

A new flammability limit parameter has been defined as the Minimum Inerting Concentration (MIC). This is the concentration of inertant required to pre vent a dust explosion regardless of fuel concentration. Previous experiment al work at Fike in a 1-m(3) spherical chamber has shown this flammability l imit to exists for pulverized coal dust and cornstarch. In the current work , inerting experiments with aluminium, anthraquinone and polyethylene dusts as fuels were performed, using monoammonium phosphate and sodium bicarbona te as inertants. The results show that an MIC exists only for anthraquinone inerted with sodium bicarbonate. The other combustible dust and inertant m ixtures did not show a definitive MIC, although they did show a strong depe ndence between inerting level and suspended fuel concentration. As the fuel concentration increased, the amount of inertant required to prevent an exp losion decreased. Even though a definitive MIC was not found for most of the dusts an effecti ve MIC can be estimated from the data. The use of MIC data can aid in the d esign of explosion suppression schemes.