Isothermal reduction behavior and kinetics of Russian high-chromium vanadium-titanium magnetite pellets under gas atmospheres of CO–CO₂–N₂ and CO–N₂ at 873 K–1173 K

ABSTRACT

In this paper, detailed investigations on the reduction characteristics and kinetics mechanism of Russian high-chromium vanadium–titanium magnetite pellets under gas atmospheres of CO–CO₂–N₂ and CO–N₂ at 873 K–1173 K were made, and comparisons of the atmospheres were researched. It was found that the reduction temperature and gas atmosphere have great effects on pellet reduction at this temperature range, and the reverse reduction appeared uniquely for some time after 2 h reduction in the CO₂-bearing gas atmosphere. The reduction was further researched with crushing strength tests, X-ray diffraction (XRD) patterns, and SEM microscopic examination, and results showed that the cause of the change in crushing strength, the phase transformation patterns, and microstructures were consistent across both atmospheres. For the CO–CO₂–N₂ gas atmosphere, the controlling step was predominantly the interfacial chemical reaction with the reaction activation value of 38.01 kJ/mol at the initial stage. This gradually became mixed control of the interfacial chemical reaction and gas internal diffusion through the solid product layer, with the reduction proceeding with 23.55 kJ/mol before 120 min. However, the controlling step became irregular after 120 min. For the CO–N₂ gas atmosphere, the rate controlling step was predominantly the interfacial chemical reaction with 31.41–38.27 kJ/mol at the initial stage, after which the rate controlling mechanism was the mixed control with 17.97–19.33 kJ/mol until 180 min mark.

KEYWORDS:

• Russian high-chromium vanadium–titanium magnetite
• pellet
• isothermal reduction mechanism
• CO–CO₂–N₂
• CO–N₂

Nomenclature

Table

Acknowledgments

The authors are especially thankful to the National Natural Science Foundation of China (Grant No. 51674084 and No. 21908020) and Fundamental Research Funds for the Central Universities (Grant No. N182503035).

Additional information

Funding

This work was supported by the Fundamental Research Funds for the Central Universities [N182503035]; the National Natural Science Foundation of China [21908020].

Notes on contributors

Gongjin Cheng

Gongjin Cheng, PhD, Lecturer in Northeastern University in China, is majoring in resource comprehensive utilization of vanadium-titanium magnetite.

Xuefei Zhang

Xuefei Zhang, PhD student in Northeastern University in China, is majoring in resource comprehensive utilization of vanadium-bearing slag.

Zixian Gao

Zixian Gao, PhD student in Northeastern University in China, is majoring in resource comprehensive utilization of ilmenite.

He Yang

He Yang, Professor in Northeastern University in China, is majoring in environmental science.

Xiangxin Xue

Xiangxin Xue, Professor in Northeastern University in China, is majoring in resource comprehensive utilization of multi-metal associated ores including vanadium-titanium magnetite and ludwigite.