LAUSR

The investigations on direct reduced iron (DRI) have commonly been made at two different scales: the pellet scale and the macroscopic or reactor scale. The reduction of a single pellet is typically investigated for developing kinetics of chemical reactions accompanied by heat and mass transport, whereas in the macroscopic view, the reduction process is investigated in the reactor scale. However, these two aspects are not independent of each other and usually the kinetic parameters that are used in the reactor modeling come from the single pellet study. This article reviews the most relevant models in the literature with regard to direct reduction reactions in the pellet scale together with more recently developed new approaches. This review also presents a critical assessment of the previously proposed models in terms of which models are applicable under what conditions and to what types of the solid structure. The flaws and pitfalls in some of these models are also pointed out with cautions. The present article is broadly divided into experimental and mathematical sections.