Gas–Liquid Reduction Behavior of Hematite Ore Fines in a Flash Reduction Process

Abstract

Novel ironmaking technologies that directly use the raw materials of iron ore fines without preprocessing have greater benefits in environmental protection and energy conservation. In this work, the gas–liquid reduction behavior and kinetic mechanism of hematite ore fines in the flash reduction processes are investigated using a high-temperature drop tube furnace. Morphological observations show the hematite ores to be completely molten at 1700 K and above. The metallic iron is enwrapped in the liquid wustite and the aggregation state of metallic iron inside the wustite is highly dependent on the reaction temperature. Many small irregularly shaped iron particles are found to be scattered in the liquid wustite at 1650 K to 1700 K, while only one big spherical iron particle is observed at 1700 K to 1800 K. The gas–liquid reduction reaction always occurs at the surface of the liquid wustite particle, and the kinetic analysis reveals that the interfacial chemical reaction at the liquid wustite surface is the rate-controlling step during the reduction process. The chemical kinetics limiting rate equation of gas–liquid reduction is determined. The activation energies of the gas–liquid reaction calculated by the model-fitting and the model-free approaches are 148 and 143 kJ/mol, respectively.