Synergistic behavior of flammable dust mixtures: A novel classification

In this work the flammable/explosive behavior of mixtures of flammable dusts is investigated. In particular, minimum ignition temperature, minimum ignition energy, maximum pressure and deflagration index have been measured at varying the relative content of dusts in the mixtures. The thermal behavior of these mixtures has been also studied by means of DSC analysis coupled to chemical analysis performed by HPLC and ATR-FTIR. Depending on the mixtures, a synergistic behavior has been found due to physical and/or chemical reactions. For some mixtures, the more severe behavior has been attributed to the presence of a eutectic point (niacin/anthraquinone, ascorbic acid/niacin), in other cases, to chemical reactions with the formation of volatiles (ascorbic acid/irganox 1222, ascorbic acid/glucose). On this basis, we propose a new classification of dusts mixtures in three mixtures safety classes (MSC): MSC 0 (no synergistic effect, ideal behavior); MSC 1 (deviation from ideality, safety parameters included between those of the pure dusts) and MSC 2 (at least 1 parameter with more sever value than those of pure dusts).