Gas–Solid Reduction Behavior of In‐flight Fine Hematite Ore Particles by Hydrogen

Abstract

The ironmaking processes that directly use the raw materials of iron ore fines have more advantages on the aspects of environmental protection and energy conservation. In this work, the gas–solid reduction behavior and kinetic mechanism of the in‐flight fine hematite particles in hydrogen atmosphere are studied with a High‐temperature Drop Tube Furnace (HDTF). The experiments are carried out at 1450–1550 K. The particle size is 53–64 µm and the reaction time is 0.65–1.93 s. With the morphological observation, it is found that the unreacted shrinking core model can describe the in‐flight reduction process of the fine hematite particles in hydrogen atmosphere. According to the analysis based on micro‐kinetics, the rate‐controlling step of the gas–solid reduction process is the solid‐state diffusion of oxygen ions through a dense product layer. This is attributed to the blocking of the tiny pores at high temperature or the generation of dense‐iron layer that nucleate and spread over the oxide. The blocking or the dense‐iron layer region prevent the reducing gas from direct contact with the reaction interface. The activation energies of the gas–solid reaction calculated by model‐fitting and model‐free approaches are 338 and 310 kJ mol−1, respectively.