Iron and steel industry is the pillar industry of the national economy, but it is also the source of highest carbon emission in manufacturing industry. With the proposal of China’s goal of peaking carbon emissions and achieving carbon neutrality, the steel industry urgently requires substantial technological breakthroughs in carbon reduction. About 90% of China’s crude steel production is produced through the blast furnace-basic oxygen furnace process, and blast furnace carbon consumption accounts for more than 70% of steel process carbon consumption. Therefore, blast furnace carbon reduction is the focal point of China’s steel industry’s efforts to mitigate carbon emissions. The hydrogen-rich gas injection to blast furnace and blast furnace with top gas recycling process are effective ways to reduce carbon emissions. However, these approaches still rely heavily on the fossil fuel coal-dominated energy structure. With the rapid development of renewable energy hydrogen production in China, hydrogen-rich oxygen blast furnace technology, which replaces carbon with hydrogen, can significantly reduce carbon emissions from ironmaking at the source. This article establishes a multizone constrained mathematical model for hydrogen-rich oxygen blast furnaces, calculates energy balance based on the constraint conditions of each zone, and systematically studies the influence of hydrogen injection, burden metallization rate on the coke ratio, top gas recycling injection volume, reducing gas composition, and CO ₂ emission reduction of hydrogen-rich oxygen blast furnaces. The research results show that at maximum hydrogen injection rate of about 600 N·m ³ H ₂ ·t ⁻¹ -HM (ton-hot metal), a replacement ratio of about 0.4 kg-coke·(N·m) ⁻³ -H ₂ was achieved with about 27% CO in the reduced gas of the shaft, 68% H ₂ , 90% burden metallization rate. Coke ratio of the hydrogen-rich oxygen blast furnace is reduced to 203 kg and the CO ₂ emission is reduced to 501 kg·t ⁻¹ -HM, 55% lower than that without hydrogen injection with a very significant CO ₂ reduction at the source.

MgO addition plays an essential role in the blast furnace smelting process, including softening-melting characteristics and metallurgical properties of slag. In the present study, the effect of MgO distribution on the softening-melting characteristics and slag system of vanadium-titanium magnetite burden were explored by simulating BF conditions. The results show that the MgO flux addition significantly affects the crystallization temperature of slag-phase, the precipitated phase components, and slag viscosity. This indicates that appropriate MgO addition can improve the metallurgical properties of blast furnace slag effectively, thereby improving the softening-melting-dripping performance of the mixed burden. The V-Ti pellets with a MgO content higher than 2.40 wt% exhibit optimum metallurgical properties. With a constant MgO content in mixed burden, the softening-melting properties of composite burden could be improved effectively as the MgO partitioning scheme includes 1.90 wt% MgO in sinter and 3.02 wt% MgO in pellet.

Hydrogen-based direct reduction (H-DR) represents an environmentally benign and energy-efficient alternative in ironmaking that has significant industrial potential. This study reviews the current status of H-DR shaft furnaces and accompanying hydrogen-rich reforming technologies (steam and autothermal reforming), assessing the three dominant numerical frameworks used to analyze these processes: (i) porous medium continuum models, (ii) the Eulerian two-fluid model (TFMs), and (iii) coupled computational fluid dynamics (CFD)–discrete element method (DEM) models. The respective trade-offs in terms of computational cost and model accuracy are critically compared. Recent progress is evaluated from an engineering standpoint in four key areas: optimization of the pellet bed structure and gas distribution, thermal control of the reduction zone, sensitivity analysis of operating parameters, and industrial-scale model validation. Current limitations in predictive accuracy, computational efficiency, and plant-level transferability are identified, and possible mitigation strategies are discussed. Looking forward, high-fidelity multi-physics coupling, advanced mesoscale descriptions, AI-accelerated surrogate models, and rigorous uncertainty quantification can facilitate effective scalable and intelligent application of hydrogen-based shaft furnace simulations.

Hydrogen-rich shaft furnaces operated with coke oven gas (COG) represent an important low-carbon ironmaking route. Conventional porous-medium CFD models, however, do not explicitly resolve geometry-dependent burden descent or downward advection of solid sensible heat in variable-cross-section moving beds. To address this gap, a user-defined-scalar (UDS)-based pseudo-fluid moving-bed dual-temperature CFD framework is developed in this study. The framework couples geometry-dependent pseudo-solid kinematics, UDS-based transport of pseudo-solid species and sensible enthalpy, and a 12-step reduction-reforming-carbon reaction network on a fixed Eulerian mesh. It is applied to a 0.5 Mt·a⁻¹ industrial reactor through one reference case and three parametric groups covering solid descent velocity, cooling-side back pressure, and CH₄ content. Mesh-independence and mass-conservation checks indicate that the medium mesh is adequate for the intended trend-level assessment; the fine-to-medium deviations are 0.54% for DRI metallization, 0.23% for DRI outlet temperature, and 0.20% for top-gas temperature, with a net global mass residual of 1.53 × 10⁻⁶ kg·s⁻¹; the baseline DRI metallization (96.3%), carbon content (1.1%), and combined H₂ + CO utilization (29.45%) all fall within the reported ranges of the HBIS demonstration line and Energiron-ZR projects. As the descent velocity increases from 2.88 to 6.72 × 10⁻⁴ m·s⁻¹, DRI metallization drops from 98.0% to 79.4% and the outlet temperature rises from 313.3 to 719.4 K. Increasing the cooling-gas outlet back pressure from 60 to 100 kPa reduces the cooling-outlet excess flow from 1.49 to 0.11 kg·s⁻¹, indicating a dynamic gas-seal control between the two gas circuits, whereas raising the inlet CH₄ fraction from 10 to 23 vol% lowers the apparent CH₄ conversion from 29.5% to 18.5% and broadens the carbon-deposition zone. The framework offers a continuum basis for proof-of-concept and trend-level analysis of variable-cross-section hydrogen-rich moving-bed shaft furnaces.

Vanadium–titanium magnetite (VTM) is an iron ore abundantly available in China. The dominant utilization route is blast furnace smelting; however, Ti in the ore deteriorates sinter strength, making it urgent to clarify Fe-Ti-Ca interactions during sintering. In this work, single-phase FeTiO₃ and Fe₂TiO₄ were synthesized and each paired with CaO to fabricate diffusion couples. The couples were heated at 1200 °C for 30, 60, 90, and 120 min to investigate their interdiffusion behaviors and microstructure recombination mechanisms. The results show that, at 1200 °C, solid-state diffusion—not interfacial reaction—controls mass transfer in both FeTiO₃-CaO and Fe₂TiO₄-CaO systems. Distinct Fe-rich and Ti-rich sublayers appear within the reaction zone, and banded CaTiO₃ forms adjacent to the FeTiO₃/Fe₂TiO₄ matrices. The interdiffusion coefficients were determined to be 4.08 × 10⁻¹⁰ cm²·s⁻¹ and 7.81 × 10⁻¹⁰ cm²·s⁻¹, and the growth of the reaction layer follows a parabolic law, which can be expressed as x² = 2 × 1.562 × 10⁻⁹ t and x² = 2 × 0.8159 × 10⁻⁹ t, respectively. The coefficients of determination exceed 0.90, indicating reliable regression fits.

High-phosphorus iron ore is an abundant yet refractory resource whose industrial exploitation is severely constrained by its elevated phosphorus content. Guided by the ore’s reduction characteristics, two process routes were designed and compared: carbon-composite pellet direct reduction followed by melting separation (CCP-DR–MS) and direct reduction–magnetic separation–melting separation (DR–MS–MS). Systematic experiments under simulated industrial conditions evaluated the metallization degree, dephosphorization efficiency, and smelting performance while clarifying the key factors that govern the differences in phosphorus removal between the two processes. The results show that both routes raised the ore’s metallization degree to above 95% during direct reduction, but the DR–MS–MS route delivered markedly better dephosphorization, achieving a maximum phosphorus removal rate of 89.20%. Although the slags produced by the two processes showed comparable phosphorus capacities, the difference in overall dephosphorization efficiency stemmed from their distinct reduction mechanisms: in DR–MS–MS, metallic iron is generated mainly via CO-mediated reduction, which suppresses phosphorus reduction, whereas in CCP-DR–MS, phosphorus and iron are simultaneously reduced by carbon. Consequently, DR–MS–MS attains superior phosphorus removal.