Determining the kinetic of the oxidation of metallic solid particles

The use of non-nano iron particles is currently under investigation for several industrial applications, including carbon-free power production. Nevertheless, poor understanding from the fundamental point of view has been reached on the phenomena ruling the oxidation, with detrimental effects on the performance and safety of reactive systems. In this perspective, this work presents an experimental campaign investigating the oxidation of iron particles in a quiescent regime, exposed to external heat fluxes. Different boundary conditions were explored to this scope, monitoring the sample mass and heat release rate along with the tests. The acquired measurements were integrated with Scanning Electron Microscopy analyses. A mechanicistic model identifying the production of FeO, Fe3O4, and Fe2O3 was proposed and corroborated by the comparison of the collected data, showing excellent agreement between the enthalpy of reactions deriving from experiments and literature. The variations in oxidized structures lead to a regime ruled by intraparticle diffusion of oxygen, once large diameters are explored. The investigation of the kinetic and ignitability of iron powder allows for a technical-based approach for a proper, optimized, and safe design of reactive and storing systems involving iron and iron oxide particles, debottlenecking their use at industrial scales.