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<p>Maintaining a high pore diffusivity of iron ore pellets during gas-based reduction is important for improving reaction efficiency. To investigate the possibility that adding a small amount of lignocellulosic biomass (woody biomass, pine sawdust) to vanadium-titanium magnetite pellets (biomass-added pellets) could create pores and improve gas diffusion, the thermal decomposition characteristics of biomass, biomass-added pellets roasting at 1250&#xa0;℃ for 20&#xa0;minutes, and their reduction with hydrogen (60 pct H<sub>2</sub> to 40 pct Ar, 1&#xa0;atm) at 1100&#xa0;°C for 40&#xa0;minutes were carried out. The biomass addition corresponded to a fixed carbon-to-iron molar ratio of 0.08 (≈ 7 wt pct of the concentrate). The results showed that, compared to biomass-free pellets (raw ore pellets), adding biomass could increase the porosity of roasted pellets from 6.37 to 13.8 pct, but the compressive strength slightly decreased, from 2078.1 to 1895.6&#xa0;N. The reduction process of the biomass-added pellets had better kinetic characteristics, which was mainly controlled by the chemical reaction. The reduction degree increased from 0.84 to 0.94, and the metallization rate increased from 86.16 to 94.58 pct. On this basis, the original biomass-added pellets were optimized to design a novel graded-porous-structure biomass-added pellets (GPS biomass-added pellets). These GPS biomass-added pellets incorporated biochar in the core, while incorporating natural biomass in the outer layer, forming a layered structure with tight outside and loose inside. This structure enabled GPS biomass-added pellets to maximize gas-solid reactions by harnessing the reduction characteristics of hydrogen during the initial reduction stage. As the reaction continued, the increased diffusion resistance resulting from dense iron phase formation in the outer layer and solid-phase sintering, and the internal loose structure provided an effective diffusion channel for H<sub>2</sub>, thereby facilitating the continuation of gas-solid reactions. It realized the regulation of gas-solid reaction and solid-phase sintering in gas-based reduction processes.</p>

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Reduction Kinetics and Structural Regulation of Graded-Porous-Biomass-Added Pellets with Hydrogen Atmosphere

  • 期刊论文

  • 发表日期：

    2026年5月29日

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

摘要

Maintaining a high pore diffusivity of iron ore pellets during gas-based reduction is important for improving reaction efficiency. To investigate the possibility that adding a small amount of lignocellulosic biomass (woody biomass, pine sawdust) to vanadium-titanium magnetite pellets (biomass-added pellets) could create pores and improve gas diffusion, the thermal decomposition characteristics of biomass, biomass-added pellets roasting at 1250 ℃ for 20 minutes, and their reduction with hydrogen (60 pct H2 to 40 pct Ar, 1 atm) at 1100 °C for 40 minutes were carried out. The biomass addition corresponded to a fixed carbon-to-iron molar ratio of 0.08 (≈ 7 wt pct of the concentrate). The results showed that, compared to biomass-free pellets (raw ore pellets), adding biomass could increase the porosity of roasted pellets from 6.37 to 13.8 pct, but the compressive strength slightly decreased, from 2078.1 to 1895.6 N. The reduction process of the biomass-added pellets had better kinetic characteristics, which was mainly controlled by the chemical reaction. The reduction degree increased from 0.84 to 0.94, and the metallization rate increased from 86.16 to 94.58 pct. On this basis, the original biomass-added pellets were optimized to design a novel graded-porous-structure biomass-added pellets (GPS biomass-added pellets). These GPS biomass-added pellets incorporated biochar in the core, while incorporating natural biomass in the outer layer, forming a layered structure with tight outside and loose inside. This structure enabled GPS biomass-added pellets to maximize gas-solid reactions by harnessing the reduction characteristics of hydrogen during the initial reduction stage. As the reaction continued, the increased diffusion resistance resulting from dense iron phase formation in the outer layer and solid-phase sintering, and the internal loose structure provided an effective diffusion channel for H2, thereby facilitating the continuation of gas-solid reactions. It realized the regulation of gas-solid reaction and solid-phase sintering in gas-based reduction processes.