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<p>Revealing the gasification kinetics of coke under simultaneously varying temperature and CO<sub>2</sub> concentration is crucial for accurately understanding its degradation behavior in a blast furnace. However, traditional approaches are limited as non-isothermal experiments cannot decouple the synergistic effects of temperature and atmosphere, while isothermal tests lack the capability to replicate the actual continuous heating process. To overcome these limitations, this study introduces an integrated methodology that couples non‑isothermal experiments of coke particles with isothermal carbon‑matrix kinetics by employing the Damköhler number <i>Da</i> and the efficiency factor <i>η</i>, revealing a complete kinetic transition behavior of coke gasification under simulated blast furnace conditions. The results show that the apparent gasification rate of coke particles peaks with a modest rate of 0.21 pct·min<sup>−1</sup> at a low conversion of 13.5 pct under the variable atmosphere, in sharp contrast to the delayed, high-intensity peak under pure CO<sub>2</sub>. The intrinsic kinetics of the coke matrix under low CO<sub>2</sub> partial pressure followed an <i>n</i>‑order Volumetric Model with an essentially constant reaction order <i>n</i> of approximately 0.9 and an apparent activation energy of 233 kJ&#xa0;mol<sup>−1</sup> to 241 kJ&#xa0;mol<sup>−1</sup>. Crucially, the rate‑limiting step of coke gasification under simulated blast furnace conditions transitions quantitatively from chemical‑reaction control below 1233 K, through a mixed regime, to complete external‑diffusion control above 1383 K, indicating that coke weight loss converges under the fixed external mass‑transfer conditions in the lower blast furnace, thereby highlighting the importance of coke high‑temperature strength after gasification rather than its intrinsic reactivity. Based on these findings, this study proposes that coke evaluation should shift from static, universal indices toward a zonal framework aligned with distinct kinetic regimes, providing a new perspective for the future optimization of coke utilization and blast furnace operation.</p>

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Coke Gasification Kinetics Under Variable Conditions of Increasing Temperature and Decreasing CO2 Concentration from 1173 K to 1573 K

  • 期刊论文

  • 发表日期：

    2026年5月8日

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  • Jingbo Chen,
  • Shengfu Zhang,
  • Jianguo Ji,
  • Xi Zhang,
  • Zhifang Wei,
  • Chenguang Bai

摘要

Revealing the gasification kinetics of coke under simultaneously varying temperature and CO2 concentration is crucial for accurately understanding its degradation behavior in a blast furnace. However, traditional approaches are limited as non-isothermal experiments cannot decouple the synergistic effects of temperature and atmosphere, while isothermal tests lack the capability to replicate the actual continuous heating process. To overcome these limitations, this study introduces an integrated methodology that couples non‑isothermal experiments of coke particles with isothermal carbon‑matrix kinetics by employing the Damköhler number Da and the efficiency factor η, revealing a complete kinetic transition behavior of coke gasification under simulated blast furnace conditions. The results show that the apparent gasification rate of coke particles peaks with a modest rate of 0.21 pct·min−1 at a low conversion of 13.5 pct under the variable atmosphere, in sharp contrast to the delayed, high-intensity peak under pure CO2. The intrinsic kinetics of the coke matrix under low CO2 partial pressure followed an n‑order Volumetric Model with an essentially constant reaction order n of approximately 0.9 and an apparent activation energy of 233 kJ mol−1 to 241 kJ mol−1. Crucially, the rate‑limiting step of coke gasification under simulated blast furnace conditions transitions quantitatively from chemical‑reaction control below 1233 K, through a mixed regime, to complete external‑diffusion control above 1383 K, indicating that coke weight loss converges under the fixed external mass‑transfer conditions in the lower blast furnace, thereby highlighting the importance of coke high‑temperature strength after gasification rather than its intrinsic reactivity. Based on these findings, this study proposes that coke evaluation should shift from static, universal indices toward a zonal framework aligned with distinct kinetic regimes, providing a new perspective for the future optimization of coke utilization and blast furnace operation.