Thermogravimetric study of the oxidation of iron particles

Abstract

Metal fuels, particularly iron, hold great promise as a sustainable source for decarbonating heat or electricity supply. However, a comprehensive understanding of the physics governing the combustion of iron dust flames is currently lacking. In this study, we present the first kinetic investigation on the oxidation of iron micrometer particles. Thermogravimetric analysis experiments were conducted under isothermal conditions and with varying uniform heating rates, with air, and with pure oxygen, as well as with various powders, featuring wide or narrow particle size distribution. Our results indicate that the oxidation of iron particles can achieve completion at relatively low temperatures, even before the appearance of wüstite. The oxidation process is modeled using Wagner's theory; significant discrepancies are observed when a uniform distribution of the particles is assumed for the oxidation of powders featuring a wide particle size distribution. The model, on the other hand, can reasonably capture the particle size dependency for sieved powders. Furthermore, an activation energy of 220 kJ/mol is derived from the Kissinger-Akahira-Sunose method and it is shown that the truncated Sestak and Berggren model can fairly reproduce isothermal and dynamic thermogravimetric analysis experiments.