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<p>This study investigated the isothermal reduction behavior of the unoxidized roasting, binder-free magnetite pellets in a pure hydrogen atmosphere at 900&#xa0;°C to 1100&#xa0;°C, which revealed the coupled effects of temperature on reduction degree, microstructure, and pore evolution. An innovative kinetic analysis method based on the model rate constant (<i>dk</i>/<i>dt</i>)/<i>k</i> was proposed, which accurately captured the dynamic evolution path of nucleation, interfacial reaction, and diffusion control during reduction. The results showed that at low temperatures (900&#xa0;°C and 1000&#xa0;°C), the reaction stagnated prematurely due to the formation of whisker-like iron crystals and subsequent sintering in the pellet outer layer. In contrast, at 1100&#xa0;°C, the reaction proceeded thoroughly (achieving a metallization ratio of 98.4&#xa0;pct and a reduction degree of 0.97), forming an interconnected pore network characterized by low total porosity and a high proportion of open pores that effectively maintained gas diffusion channels. Increasing the temperature significantly delayed the dominance of diffusion control and promoted the transition of the reaction pathway to higher-order mechanisms. Furthermore, this study demonstrated that the evolution of pore structure was primarily driven by the reduction reaction itself and speculated a synergistic mechanism between reaction kinetics and gas transport: the high-flux gaseous products generated by the rapid reaction at high temperature effectively suppressed iron-phase densification and dynamically optimized the pore structure by scouring pore channels and occupying surface active sites, thus ensuring the continuous reduction. It is noted that the use of a simplified magnetite pellets system limits direct quantitative extrapolation to industrial practice.</p>

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Coupling Between Interfacial Reaction and Pore Evolution: Mechanism of Hydrogen-Based Reduction of Magnetite Pellets at High Temperature

  • 期刊论文

  • 发表日期：

    2026年5月14日

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  • Shuai Tong,
  • Ying Xu,
  • Lukuo Hong,
  • Caijiao Sun,
  • Liqun Ai,
  • Meijie Zhou

摘要

This study investigated the isothermal reduction behavior of the unoxidized roasting, binder-free magnetite pellets in a pure hydrogen atmosphere at 900 °C to 1100 °C, which revealed the coupled effects of temperature on reduction degree, microstructure, and pore evolution. An innovative kinetic analysis method based on the model rate constant (dk/dt)/k was proposed, which accurately captured the dynamic evolution path of nucleation, interfacial reaction, and diffusion control during reduction. The results showed that at low temperatures (900 °C and 1000 °C), the reaction stagnated prematurely due to the formation of whisker-like iron crystals and subsequent sintering in the pellet outer layer. In contrast, at 1100 °C, the reaction proceeded thoroughly (achieving a metallization ratio of 98.4 pct and a reduction degree of 0.97), forming an interconnected pore network characterized by low total porosity and a high proportion of open pores that effectively maintained gas diffusion channels. Increasing the temperature significantly delayed the dominance of diffusion control and promoted the transition of the reaction pathway to higher-order mechanisms. Furthermore, this study demonstrated that the evolution of pore structure was primarily driven by the reduction reaction itself and speculated a synergistic mechanism between reaction kinetics and gas transport: the high-flux gaseous products generated by the rapid reaction at high temperature effectively suppressed iron-phase densification and dynamically optimized the pore structure by scouring pore channels and occupying surface active sites, thus ensuring the continuous reduction. It is noted that the use of a simplified magnetite pellets system limits direct quantitative extrapolation to industrial practice.