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

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 (1000 °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.