Key Takeaways & Executive Findings
- •• CO at 20% volume proportion in H2/CO mixed gas promotes Fe2O3 reduction at 850°C, enhancing overall reduction efficiency. • ReaxFF MD simulations reveal that H2 reduces Fe2O3 faster initially than CO, but CO-induced cementite formation creates active carbon sites that facilitate further reduction. • Internal CO generation from cementite can disrupt the dense surface layer, influencing reduction swelling and surface morphology. • CO-reduced surfaces exhibit larger surface area, which accelerates subsequent H2 reduction, highlighting a synergistic effect in mixed gas reduction.
Abstract
The experiment explored the Fe2O3 reduction process with H2/CO mixed gas and confirmed a promoting effect from CO when its volume proportion in mixed gas is 20% at 850°C. The ReaxFF molecular dynamics (MD) simulation method was used to observe the reduction process and provide an atomic-level explanation. The accuracy of the parameters used in the simulation was verified by the density functional theory (DFT) calculation. The simulation shows that the initial reduction rate of H2 is much faster than that of CO (from 800 to 950°C). As the reduction proceeds, cementite, obtained after CO participates in the reduction at 850°C, will appear on the iron surface. Due to the active properties of C atoms in cementite, they are easy to further react with the O atoms in Fe2O3. The generation of internal CO may destroy the dense structure of the surface layer, thereby affecting the overall reduction swelling of Fe2O3. However, excess CO is detrimental to the reaction rate, mainly because of the poor thermodynamic conditions of CO in the temperature range and the molecular diffusion capacity is not as good as that of H2. Furthermore, the surface structures obtained after H2 and CO reduction have been compared, and it was found that the structure obtained by CO reduction has a larger surface area, thus promoting the subsequent reaction of H2.
1. Introduction
In iron production, direct reduction refers to a process that does not involve melting the ore. Iron ore is reduced in its solid state, frequently utilizing reduction gases or coal as a reducing agent [1–5]. The resulting product is designated as direct reduced iron (DRI) or sponge iron, which can subsequently be employed in the steelmaking process [6–7]. Reduction gases typically contain H2 and CO in direct reduction processes. Based on the requirement of low carbon environment, the development of hydrogen-based reduction technologies is a viable path [8–9]. Therefore, it is of research value to analyze the influence of temperature, gas composition, and other factors on the reduction process [10–11]. The effect of H2/CO gas composition on the reduction of hematite was further investigated [12–13]. The selection of CO and H2 as reducing agents is discussed, with CO identified as the more effective reducing agent at a lower temperature from a thermodynamic perspective while it will produce more CO2 [14].
Phase transitions are defined as the changes in the physical and chemical states of iron ore that occur as a result of reduction, which is a crucial process for controlling the quality of DRI. The interplay between the aforementioned factors results in the formation of intricate microstructures, which are characterized by a diverse range of defects spanning multiple orders of magnitude in length. These include but are not limited to, vacancies, dislocations, internal interfaces, and free surfaces in the form of cracks and pores [15]. Among these, the formation of cementite has a more significant effect on the structure change during the reduction process. Zhang et al. [16] revealed that cementite may be generated in the middle and late stages of reduction due to the involvement of CO and the C/Fe mass ratio on the surface has a significant influence on the stickiness and also the fluidization behavior of DRI particles.
Loading authentic research manuscript (Pages 1–5)...
Qiang Cheng, Alberto N. Conejo, Jianliang Zhang, Daniel Sopu, Yaozu Wang, Zhengjian Liu (2025). Mechanisms and interactions in the reduction of Fe2O3 by H2/CO mixed gas: Atomic insights from ReaxFF molecular dynamics simulations and experiments. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-3061-y
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the optimal CO proportion in H2/CO mixed gas for Fe2O3 reduction?
The study found that a CO volume proportion of 20% at 850°C promotes the reduction of Fe2O3, enhancing the overall reduction process.
How does ReaxFF molecular dynamics simulation help understand Fe2O3 reduction?
ReaxFF MD simulations provide atomic-level insights into the reduction mechanisms, revealing the roles of H2 and CO, the formation of cementite, and the effects on surface structure and swelling.
Why is excess CO detrimental to the reduction rate?
Excess CO is detrimental because of its poor thermodynamic conditions in the temperature range and its lower molecular diffusion capacity compared to H2, which slows down the reduction kinetics.
What role does cementite play in the reduction process?
Cementite, formed when CO participates in reduction, contains active carbon atoms that react with oxygen in Fe2O3, generating internal CO that can disrupt the dense surface layer and influence reduction swelling.
How does CO reduction affect subsequent H2 reduction?
CO reduction produces a surface with a larger surface area compared to H2 reduction, which promotes the subsequent reaction of H2, indicating a synergistic effect in mixed gas reduction.
Related Technical Papers & Translations
Direct Repair of the Crystal Structure and Coating Surface of Spent LiFePO4 Materials Enables Superfast Li-Ion Migration
The rapid accumulation of spent LiFePO4 (LFP) cathodes from retired lithium-ion batteries necessitates the development of effective and environmental-friendly recycling strategies. In this context, direct regeneration has emerged as a promising approach for reclaiming LFP cathode materials, offering a streamlined pathway to restore their electrochemical functionality. We report an integrated regeneration protocol that simultaneously repairs the degraded crystal structure and reconstructs the damaged carbon coating in spent LFP. The regenerated cathode material had superfast lithium-ion diffusion kinetics and a stable cathode–electrolyte interface, giving a remarkable rate capability with specific capacities of 122 mAh g−1 at 5C and 106 mAh g−1 at 10C (1C = 170 mA g−1). It also maintained capacities of 110.7 mAh g−1 (5C) and 84.1 mAh g−1 (10C) after 400 cycles. It could be used in harsh environments and could be stably cycled at subzero temperatures (−10 and −20 °C) and in solid-state electrolyte batteries. Life cycle assessment combined with economic evaluation using the EverBatt model reveals that this direct regeneration approach has high economic and environmental benefits.
Oxide Semiconductor for Advanced Memory Architectures: Atomic Layer Deposition, Key Requirement and Challenges
Oxide semiconductors (OSs), introduced by the Hosono group in the early 2000s, have evolved from display backplane materials to promising candidates for advanced memory and logic devices. The exceptionally low leakage current of OSs and compatibility with three-dimensional (3D) architectures have recently sparked renewed interest in their use in semiconductor applications. This review begins by exploring the unique material properties of OSs, which fundamentally originate from their distinct electronic band structure. Subsequently, we focus on atomic layer deposition (ALD), a core technique for growing excellent OS films, covering both basic and advanced processes compatible with 3D scaling. The basic surface reaction mechanisms—adsorption and reaction—and their roles in film growth are introduced. Furthermore, material design strategies, such as cation selection, crystallinity control, anion doping, and heterostructure engineering, are discussed. We also highlight challenges in memory applications, including contact resistance, hydrogen instability, and lack of p-type materials, and discuss the feasibility of ALD-grown OSs as potential solutions. Lastly, we provide an outlook on the role of ALD-grown OSs in memory technologies. This review bridges material fundamentals and device-level requirements, offering a comprehensive perspective on the potential of ALD-driven OSs for next-generation semiconductor memory devices.
Laser powder bed fusion of biodegradable Zn-4Cu alloy: Processing, microstructure and properties
Zn's natural degradability and biocompatibility make it a promising candidate for implants, however, its mechanical properties remain insufficient for bone applications. In this study, the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion (LPBF). Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed. Under optimized conditions of 100 W and 100 mm/s, high-density (99.58%) Zn-Cu alloys with improved hardness (68.2HV) and yield strength (160 MPa) were achieved. These improvements are attributed to solid solution strengthening, segregation strengthening, and grain refinement. The Zn-Cu alloys also demonstrated favorable degradation behavior, with a rate of 0.16 mm/year. This degradation is primarily driven by micro-galvanic corrosion between the CuZn5 phase and Zn matrix, along with refined grains and increased grain boundary density. This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.