Action rules of H₂ and CO in gas-based direct reduction of iron ore pellets

Abstract

The gas-based direct reduction of iron ore pellets was carried out by simulating the typical gas composition in coal gasification process, Midrex and Hyl-III processes. The influences of gas composition and temperature on reduction were studied. Results show that the increasing of H₂ proportion is helpful to improve the reduction rate. However, when φ(H₂):φ(CO)>1.6:1, changes of H₂ content have little influence on it. Appropriate reduction temperature is about 950 °C, and higher temperature (1 000 °C) may unfavorably slow the reduction rate. From the kinetics analysis at 950 °C, the most part of reduction course is likely controlled by interfacial chemical reaction mechanism and in the final stage controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanisms. From the utilizations study of different reducing gases at 950 °C, the key step in reduction course is the 3rd stage (FeO→Fe), and the utilization of reducing gas increases with the rise of H₂ proportion.

Keywords

iron ore pellets / coal gas / gas-based direct reduction / reduction kinetics / gas utilization

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