Review on nucleation and growth behavior of iron grain during deep reduction

At present, a large quantity of iron resource could not be utilized effectively, such as iron oxides (e.g., oolitic hematite, limonite and cyanide residue) and smelting slags in the form of fayalite (e.g., iron slag, copper slag and nickel slag). This kind of iron resources, containing 30%–40% iron, is still very difficult to be recycled or utilized. Currently, deep reduction technology, which has been put forward to improve the grade of iron ore, is developing rapidly and is expected to solve the resource problem. But the research on the mechanism of iron grain nucleation and growth behavior in the deep reduction process is not systematic and thorough. We summarize the thermodynamic theory of iron grain nucleation, combined with Turnbull linear model and Dubey-Ramachandrarao theoretical model. Based on Hillert-type 3D grain growth rate model and Avrami-Erofeyev model, the total free energy in the reaction process is analyzed, critical nucleation radius of iron grain is calculated, the mechanism of iron grain nucleation and growth behavior of iron grain is clarified. This paper provides a systematic theory and experimental validation for nucleation mechanism and iron grain growth behavior in deep reduction of Fe-based oxygen carrier.