Key Takeaways & Executive Findings
- •• Iron ore addition enhances iron coke gasification by increasing micropores and specific surface area, providing more CO2 adsorption sites and lowering initial gasification temperature. • Metallic iron from ore reduction disrupts carbon structure order, boosting carbon atom reactivity and overall gasification kinetics. • The random pore model accurately describes iron coke gasification, with activation energy decreasing from 246.2 kJ/mol (coke) to 192.5 kJ/mol (15wt% iron coke). • Accelerating heating rate in non-isothermal gasification improves iron coke reactivity, offering process optimization for low-carbon ironmaking.
Abstract
The utilization of iron coke provides a green pathway for low-carbon ironmaking. To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification, the effect of iron ore on the microstructure of iron coke was investigated. Furthermore, a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method. The findings indicate that compared to coke, iron coke exhibits an augmentation in micropores and specific surface area, and the micropores further extend and interconnect. This provides more adsorption sites for CO2 molecules during the gasification process, resulting in a reduction in the initial gasification temperature of iron coke. Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke. The metallic iron reduced from iron ore is embedded in the carbon matrix, reducing the orderliness of the carbon structure, which is primarily responsible for the heightened reactivity of the carbon atoms. The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure. Moreover, as the proportion of iron ore increases, the activation energy for the carbon gasification gradually decreases, from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.
1. Introduction
The low-carbon ironmaking in blast furnaces (BF) is a crucial step towards achieving green steel production and serves as a significant strategy to support the national goal of “double carbon” [1–3]. Using iron coke is widely concerned as a potential energy-saving and carbon-reducing technology in low-carbon ironmaking [4]. Iron coke serves a dual role: it lowers the temperature in the thermal reserve zone of BF to achieve low-carbon production [5], and expands the utilization of weakly caking coal, thereby decreasing ironmaking costs [6]. The iron coke exhibits a heightened gasification reaction activity, attributable to the catalytic effect of metallic iron or iron oxide, which makes its gasification behavior different from that of conventional coke. This characteristic significantly influences the location of the indirect and direct reduction zones in BF [7]. Consequently, it directly affects the energy utilization of BF gas and the efficiency of the furnace shaft. However, a higher reactivity often implies a diminished post-reaction strength [8], which can potentially undermine its role as a BF skeleton. The dual roles frequently present conflicting demands for iron coke reactivity, making the performance regulation of iron coke challenging. Therefore, it is crucial to clarify the impact of iron coke structure on its reactivity and to unravel the mechanism of iron coke gasification for a comprehensive understanding of the gasification behavior and practical application of iron coke.
A series of studies examining the gasification behavior of iron coke and its influencing factors have been conducted by researchers. Nomura et al. [9] and Shi et al. [10] reported a reduction of approximately 120°C in the initial gasification temperature of iron coke when added with 30wt% iron ore. Qiu et al. [11] demonstrated that iron coke gasification was promoted by iron-containing substances, with the effectiveness descending in the order of Fe2O3, Fe3O4, and FeC2O4. Bao et al. [12] further revealed that the post-reaction strength significantly declined as the reactivity increased, particularly when the iron ore addition exceeded 25wt%. Additionally, they noted a gradual decrease in gasification reactivity as the carbonization time increased [13]. Afterwards, Wang et al. [14–15] studied the isothermal gasification behavior of iron coke, concluding that the oxidation of iron was accompanied by iron coke gasification. Recently, Zhu et al. [16] examined the co-gasification behavior of iron coke-coke under hydrogen-rich conditions. Their findings revealed that the lower gasification temperature of iron coke exerted a protective effect on coke. To efficiently utilize resources, some scholars used metallurgical dust, steel slag, and low-caking coal to prepare iron coke and investigate its gasificat
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Jie Wang, Wei Wang, Xuheng Chen, Junfang Bao, Qiuyue Hao, Heng Zheng, Runsheng Xu (2025). Role of iron ore in enhancing gasification of iron coke: Structural evolution, influence mechanism and kinetic analysis. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-2873-0
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Frequently Asked Questions
What is iron coke and why is it important?
Iron coke is a composite material made by blending iron ore with coal before carbonization. It is important because it lowers the thermal reserve zone temperature in blast furnaces, reducing CO2 emissions and enabling the use of cheaper, weakly caking coals, thus contributing to low-carbon ironmaking.
How does iron ore affect the gasification of iron coke?
Iron ore enhances gasification by increasing micropores and specific surface area, providing more active sites for CO2 adsorption. The metallic iron produced during reduction disrupts the carbon structure, increasing carbon atom reactivity, which lowers the initial gasification temperature and activation energy.
What kinetic model best describes iron coke gasification?
The random pore model (RPM) effectively represents iron coke gasification due to its rich pore structure. It accounts for the evolution of pore surface area during reaction, providing accurate predictions of conversion rates.
What are the activation energy values for coke and iron coke gasification?
The activation energy for coke gasification is 246.2 kJ/mol, while for iron coke with 15wt% iron ore it decreases to 192.5 kJ/mol, indicating that iron ore addition significantly reduces the energy barrier for gasification.
How does heating rate influence iron coke gasification?
Accelerating the heating rate in non-isothermal gasification enhances the reactivity of iron coke, likely due to faster devolatilization and more rapid formation of active sites, improving overall gasification performance.
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