Rongrong Wang

The oxygen blast furnace (OBF) represents a key pathway toward deep decarbonization in ironmaking. The main difference between it and the traditional blast furnace is that the atmosphere in the furnace has high reduction potential and little nitrogen content. However, the burden metallurgical performance under CO-H₂-rich, N₂-lean atmospheres remains unclear. This study investigated the isothermal and non-isothermal reduction and softening–melting behavior of sinter and pellets. As CO increased from 59.2 to 79.2 vol%, the reduction degree rose from ~27% to ~90% within 180 min, with a rate index of 0.72–0.75%·min⁻¹. The apparent activation energies of sinter and pellets were 113.0 kJ·mol⁻¹ and 57.9 kJ·mol⁻¹, respectively, indicating that the gas–solid interfacial chemical reaction is the rate-controlling step. Under non-isothermal conditions, the reduction start temperatures of both sinter and pellets decreased, and complete reduction was achieved at 1200 °C. Microstructural analysis revealed a four-stage structural evolution pathway. The softening–melting behavior indicated that oxygen-enriched conditions decrease the softening start temperature, whereas the melting start temperature increases due to the thickening of the metallic iron shell. The maximum pressure difference of the cohesive zone was reduced by 32.9%, and the air permeability was significantly improved. This study reveals the mechanism of charge reaction and structure evolution under OBF conditions and provides a theoretical basis for charge optimization and OBF operation control.

Ferro-coke is a material that not only enables the efficient utilization of iron-containing resources and coal but also significantly enhances the energy efficiency and emission-reduction potential of blast furnaces, making it a major focus of current research. However, the performance and mechanism of ferro-coke prepared by iron-carbon containing dust and weakly caking coal are still unclear. This paper investigated the effects of addition type and addition amount of iron-carbon containing dust on the properties of ferro-coke. Based on multi-scale joint characterization methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and industrial computed tomography (CT), the correlation between the macroscopic properties and microstructural evolution of ferro-coke was elucidated. Results show that: Compared to electric furnace dust, refining dust has a more significant deteriorating effect on the mechanical strength of ferro-coke. At the same time, with the increase of electric furnace dust addition, reactivity increases and post-reaction strength decreases. Microstructural analysis showed that dust promoted the development of pores and the formation of microcracks at the coal particle interface. As the amount of electric furnace dust added increases, the total porosity increases significantly, the size of graphite microcrystals decreases, and the structural order decreases. The synergistic effect of pore structure deterioration and carbon structure disorder ultimately leads to a decrease in the strength of ferro-coke. This study elucidates the structure-property relationship of ferro-coke prepared from dust, providing a theoretical basis for the efficient utilization of metallurgical solid waste in ferro-coke preparation.

This study evaluated how raw-material compounding strategies affect the high-temperature compressive strength of ferro-coke. Ferro-coke was prepared using varying additions of iron-carbon-containing dust (ICD) and different gasification temperatures. High-temperature experiments were conducted to study the reactivity (CRI) and hot strength of ferro-coke, and fracture morphologies were examined by microscopy and Micro-CT. The results show that both the increase in ICD addition amount and gasification temperature would increase the reactivity and decrease the high temperature of ferro-coke. As ICD addition increased from 5% to 20%, the reactivity of the ferro-coke rose from 58.70% to 76.32%, and high-temperature strength decreased from 3260 N to 1954 N at 800 °C. This trend is attributed to catalytic components in ICD (e.g., Fe, Zn), which would accelerate gasification, increase porosity, and reduce high-temperature strength. Similarly, increasing the gasification temperature from 1000 °C to 1200 °C enhanced reactivity from 51.95% to 65.51%, but the hot strength was reduced. The higher carbon gasification rate at elevated temperature increases porosity and weakens the coke matrix, lowering compressive strength.

Biomass and H ₂ are characterized as environment‐friendly, and can be used as reductant in the reduction process of iron oxides, therefore to achieve carbon neutrality of the shaft furnace direct reduction ironmaking process, and meanwhile produce carbon‐containing direct reduced iron (DRI). For the synergistic utilization of biomass and H ₂ , this study used H ₂ to reduce biomass embedded self‐reducing pellets (SRP) to produce DRI. The relative mass loss ratio, reduction degree and metallization degree, and microstructure of pellets reduced under different conditions (750–950 °C, CO involved, H ₂ involved and N ₂ atmosphere) are analyzed to clarify the reduction behavior of torrefied biomass‐ and charcoal‐embedded pellets. Results indicate that higher temperature, H ₂ involved atmosphere, and higher embedded biomass content favors the hybrid reduction of iron oxides; addition of biomass affects the reduction efficiency of pellets from two aspects, porosity and solid carbon reduction. Under the optimal reducing condition (950 °C and 40% H ₂ %–60% N ₂ atmosphere), reduction degree of 87% can be achieved by reducing torrefied biomass embedded SRP, and DRI with acceptable carbon content is expected be produced.