Reaction of a Particle Suspension in a Rapidly‐Heated Oxidizing Gas

Abstract

AbstractThe reaction of a suspension of solid particles in a rapidly‐heated oxidizing gas is relevant to metalized explosives and propellants, as well as to combustion of solid fuel‐particle suspensions in premixed‐gaseous‐fuel clouds encountered in accidents within the mining and process industries. A simplified model is considered, using a constant‐volume approximation, which assumes that non‐volatile particles react heterogeneously via a one‐step surface reaction. The resulting unified particle reaction rate includes both kinetic and diffusive reaction resistances. It is shown that the onset of the chemical reaction in a rapidly heated particulate suspension may occur by two different physical mechanisms. The first mechanism, realized in a dilute suspension of particles, is defined by the ignition of a single particle, i.e., by the critical phenomenon associated with the rapid transition from a kinetically‐ to diffusively‐limited reaction regime. The second mechanism dominates the reaction onset in a dense particulate suspension and occurs in a similar manner to the reaction onset in a rapidly‐heated homogeneous gas mixture, where the highly‐activated reaction occurs in an explosion‐like manner after some time delay and preheating. Unlike the single particle ignition phenomenon, the second mechanism lacks criticality and is not limited to particles above a certain size. The interplay between these two reaction‐onset mechanisms leads to a nontrivial dependence of the total reaction time on the particle size and solid‐fuel concentration within the suspension.