Particle Size Influence on the Transport Classification Labels and Other Flammability Characteristics of Powders

Dust explosions and fires pose an industrial safety problem, due to the human and material losses caused by them. As many fuel processes and material transport generate powder particles, the effect of granulometry in different flammability properties has been studied to define the relationship between both. Deep knowledge of this relationship reduces the self-ignition and self-combustion processes, and the accidents associated with these processes. In this study, six different samples, including biomass, charcoal, and dog food, are tested in three different particle sizes, so differences in their flammability behavior could be appreciated (not only considering fine particles, but also coarse samples). The transport classification test was carried out, obtaining significant results in two samples, where the same material did not self-ignite when tested at its coarse size, but it did when tested at fine particle size. Similar results were obtained when analyzing initial temperature for related-combustion gasses emission: the finer the particle size, the lower the initial temperature. To understand the heat mechanisms, thermal analyses were performed, such as thermogravimetric analysis and differential scanning calorimetry. Finally, a self-ignition risk was assessed for all samples according to their activation energy and characteristic temperature. All the test results lead to conclude that biomasses easily start self-heating process, but its composition difficult the heat transmission to reach self-ignition, while charcoals are more susceptible to self-ignition.