The blast furnace（BF） remains the dominant reactor for global hot metal production, yet its internal high-temperature, high-pressure, multiphase-coupled "black box" nature renders direct measurement extremely difficult. Computational fluid dynamics （CFD） full-scale blast furnace models have therefore become an indispensable tool for revealing in-furnace phenomena details and supporting operational decision-making. This paper systematically reviews the development history of CFD blast furnace mathematical models based on the transient/steady multi-fluid model framework, categorising their evolution into three generations. The first generation comprised steady-state models, which underwent continuous expansion from one-dimensional gas-solid systems to three-dimensional gas-solid-liquid-powder multiphase systems, incorporating dozens of chemical reactions and phase transformation processes. A key milestone of this generation was the introduction of a layered reacting structure across the entire furnace, assigning independent chemical reaction systems to ore layers and coke layers, respectively, which significantly improved the descriptive accuracy of cohesive zone morphology and gas flow distribution. The second generation was the transient model capable of simulating the dynamic response of the BF internal state following changes in operating parameters, such as sudden blast temperature drops, wet burden charging and hydrogen injection. This generation achieved simultaneous advancement in spatial dimensionality and physical fidelity. The third generation comprised intelligent models integrating machine learning, which used high-fidelity CFD simulation data as training sources to construct surrogate models capable of near-real-time prediction of full in-furnace state distributions, laying the foundation for the next version and real blast furnace digital twins. In practical applications, the selection of blast furnace models should be guided by specific industrial requirements. It should also be noted that the development of high-fidelity blast furnace models typically represents years of dedicated research efforts by academic institutions and is associated with a high barrier to reproduction, relying on long-term systematic accumulation of knowledge. As such, collaboration between industry and universities provides an effective pathway for the development and application of blast furnace mathematical models. This paper also identifies key challenges facing model development, including the balance between fidelity and computational efficiency, insufficient validation methods, model sustainability, and the construction of physics-constrained AI（artificial intelligence） integration frameworks, and provides an outlook on the development direction of intelligent blast furnace simulation platforms oriented towards industrial deployment.

Scrap-based electric arc furnace （EAF） steelmaking is an important route for the low-carbon transition of the iron and steel industry. However, owing to the complex origins of scrap steel, impurities such as oil residues, plastics, rubber, coatings, and halogen-containing additives are often introduced into EAFs. During scrap preheating, melting-oxidation, and flue gas cooling, these impurities can release chlorine sources, organic carbon sources, and aromatic precursors, thereby increasing the formation risk of polychlorinated dibenzo-p-dioxins and dibenzofurans （PCDD/Fs）. The emission characteristics, formation pathways, and full-process control technologies of PCDD/Fs during scrap-based EAF steelmaking are reviewed. Existing studies show that primary flue gas, the scrap-preheating section, and high-load zones upstream of bag filtration are important nodes for PCDD/Fs formation and migration, with typical concentrations ranging from 0.35 to 17 ng-TEQ/m³. The mass concentrations of PCDFs are generally higher than those of PCDDs, and 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD are the major contributors to toxic equivalency （TEQ）. In terms of formation pathways, PCDD/Fs in scrap-based EAFs are mainly formed through precursor reactions and de novo synthesis. De novo synthesis dominates in dust-laden flue gas cooling sections and is affected by heterogeneous catalysis involving unburned carbon, chlorine sources, and Cu/Fe-containing metal species on fly ash surfaces. Current control technologies include scrap cleaning, secondary combustion, rapid quenching, inhibitor injection, activated carbon adsorption, and catalytic oxidation. Among them, activated carbon injection coupled with bag filtration is a relatively mature end-of-pipe safeguard technology. However, it essentially transfers PCDD/Fs between phases and increases the disposal pressure of PCDD/Fs-containing fly ash. Future control of PCDD/Fs in scrap-based EAF steelmaking should shift from single end-of-pipe treatment toward coordinated control integrating source reduction, in-process inhibition, and end-of-pipe purification, with emphasis on deep mitigation technologies that combine in-process inhibition with end-of-pipe catalytic degradation. This strategy can provide support for the coordinated development of low-carbon EAF steelmaking and the control of characteristic organic pollutants.

The maximum temperature of sintering exhaust gas reflects the advancement of the combustion zone within the material bed and the intensity of gas-solid heat transfer. It serves as an external quantitative indicator of terminal thermal stability, correlating with but not equating to the precise location of the sintering endpoint. Based on industrial monitoring data and mechanistic studies, the temperature distribution of sintering exhaust gas along the machine length exhibits a spatial pattern of initially low temperatures, followed by a rise and subsequent decline. The wet material zone at the machine head exhibits lower temperatures due to evaporation heat absorption and heat exchange limitations. Temperatures gradually increase as drying and preheating are completed and the combustion zone descends, reaching a maximum when the combustion zone advances to the bottom of the material bed and approaches the burn-through point. Temperatures then gradually decrease in the rear section of the machine tail and are relatively sensitive to operating condition disturbances. The peak sintering exhaust gas temperature is influenced by the coupled effects of fuel, process parameters, and raw materials. Finer fuel particle size and increased mixture moisture content reduce peak temperature. Higher carbon content, ignition intensity, and bed thickness elevate peak temperature. Alkalinity and its regulation methods alter thermal intensity in high-temperature zones by affecting liquid phase formation and thermal equilibrium. Excessively low temperatures may lead to insufficient liquid phase formation, restricted development of the sintered phase, and reduced strength. Conversely, excessively high temperatures or prolonged exposure to high temperatures may induce over-sintering and promote the formation of thin-walled, large-pore structures, adversely affecting sinter quality. Future research should focus on the synergistic objectives of "quality-energy consumption-emissions", combining mechanistic and data-driven approaches to investigate the online characterization and regulation of the maximum sintering exhaust gas temperature, thereby supporting the development of low-carbon sintering processes.

Hydrogen-based direct reduction （HyDR）, in which green hydrogen replaces fossil reductants, is one of the core technological routes for deep decarbonization of the steel industry. The process spans multiple scales, from atomic interfacial reactions to multiphysics coupling in the shaft furnace reactor, while the correlation between its dynamically evolving multiscale behavior and the macroscopic reaction behavior remains insufficiently understood, constituting a key scientific problem that must be resolved to refine the theoretical framework of hydrogen metallurgy. Following an "electron/atom-micro/meso-macro reactor" framework, this review systematically summarizes the full-chain, multiscale advances in the HyDR of iron oxides. At the atomic/electronic scale, density functional theory （DFT） reveals the facet-dependent dissociative adsorption and interfacial reaction of H₂ and CO on iron-oxide surfaces and the corresponding rate-determining steps, while large-scale molecular dynamics driven by deep-learning potentials reproduce at DFT-level accuracy the defect evolution of wüstite and the nucleation-crystallization pathway from an "amorphous iron intermediate" to crystalline iron. At the micro/meso scale, X-ray computed tomography and environmental transmission electron microscopy combined with deep learning quantitatively decouple the dynamic evolution of the pore-crack network and confirm a vacancy-mediated,fluid-like aggregation mechanism of amorphous iron, on which basis the applicability limits of the unreacted shrinking-core, grain and random-pore models are clarified. At the macro scale, three numerical frameworks for the shaft furnace, namely the porous-media continuum model, the Eulerian two-fluid model, and computational fluid dynamics-discrete element method （CFD-DEM） coupled approach, are systematically analyzed. In view of the strongly endothermic nature of pure hydrogen reduction, thermal-management and process-optimization strategies based on coordinated thermal parameters are proposed. Finally, future directions are outlined for cross-scale coupling, general-purpose machine-learning potentials, in situ quantitative characterization, and industrial data validation to refine the theoretical framework of hydrogen metallurgy and provide theoretical support for advancing HyDR from mechanistic understanding to engineering practice.

Metallurgical oil-containing solid wastes have both pollution potential and resource value, and their efficient disposal and resource utilization represent an important direction for promoting green and low-carbon development in the metallurgical industry. This paper focuses on typical metallurgical oil-containing solid wastes including rolling oil bearing sludge, oily copper scraps, and oily aluminum scraps. It systematically reviews their sources, compositional characteristics, generation scales, and management requirements. The review emphasizes the research progress in collaborative utilization pathways through return to metallurgical processes such as sintering, coke making, blast furnace injection, rotary hearth furnace treatment, and smelting, as well as on deoiling pretreatment technologies including chemical hot washing, solvent extraction, oxidation, pyrolysis, centrifugal separation, and distillation. Existing studies show that co-utilization in metallurgical processes offers advantages such as large treatment capacity, high metal recovery rates, and easy integration with existing production processes. However, due to factors such as the presence of oil in raw materials and environmental pollution caused by heat treatment, oily solid wastes are usually difficult to be directly utilized in large proportions. Deoiling pretreatment facilitates oil solid separation and improves material properties, serving as a key prerequisite for enhancing compatibility with these processes, yet it still faces bottlenecks including high cost, energy consumption, secondary pollution, and insufficient deoiling depth. Based on analysis of the applicability and limitations of various technologies, this paper points out that the resource utilization of metallurgical oil-containing solid wastes require the construction of differentiated technical routes according to parameters such as oil mass fraction, viscosity, and metal value. Finally, it discusses future research directions including graded utilization tailored to different wastes characteristics, demand oriented deoiling and conditioning technologies, and synergistic recovery of oil and metals. This paper aims to organize the technical framework for the disposal and resource utilization of such solid wastes, clarify the application characteristics and development directions of various technologies, and provide a reference for research on multi component synergistic recovery and utilization.

Renewable energy is a critical energy foundation for promoting deep decarbonization of the steel industry,and its supply stability and coupling adaptability directly determine the decarbonization efficiency. This paper systematically reviews the application history, major difficulties,and developing trends of solar energy, biomass energy, and wind energy in the steel industry. It shows that photovoltaic power generation has achieved large-scale application in distributed settings within the steel industry, however, the fundamental contradiction between its intermittency and the continuity of smelting processes has yet to be resolved.As a substitute for coke, biochar as a reducing agent faces several metallurgical bottlenecks, including high reactivity, alkali metal enrichment, and insufficient mechanical strength, which significantly limit its industrial injection ratio. Wind power can replace part of the energy demand in coastal or northwestern steel plants through self-developed wind farms, but its deployment is constrained by regional resource availability and limited construction space.Based on these findings, two core contradictions in coupling renewable energy with steelmaking processes are identified in this paper. First, the spatiotemporal mismatch between the intermittent nature of renewable energy supply and the continuous requirements of smelting, second, the conflict between the regionally differentiated characteristics of renewable resources and the stringent demands of metallurgical raw material quality. Looking forward, relying on a single energy source as a substitute cannot fundamentally solve the problem. The deep integration of multi-energy complementary systems with the hydrogen-based direct reduction short process represents the leading pathway toward establishing a zero-carbon closed loop of green electricity, green hydrogen, and green steel. Accordingly, this paper recommends differentiated, region-specific strategies, coastal steel plants should develop offshore wind power and hydrogen metallurgy, inland resource-rich areas should pursue wind-solar power generation coupled with energy storage, and biomass-rich regions should advance biochar injection into blast furnaces.

The burn-through point （BTP） is a key thermal parameter reflecting the arrival of combustion zone at the material layer bottom and the burning through status of layer. Its stability directly affects sinter quality, fuel consumption, and sintering production stability. Due to factors such as raw material fluctuation, changes in bed permeability, distribution uniformity, delayed characterization of thermal state, and multivariable coupling, the BTP is difficult to accurately determine and stably control using a single signal. For BTP online identification, advance prediction, and optimal control, related research has gradually developed a trajectory from multi-source sensing including wind box temperature fields, flue gas components, machine tail images, and infrared thermography, to predictive modeling using shallow neural networks, ensemble learning, and deep learning, and further to single objective stable BTP control, coordinated control of BTP and bin material level, and intelligent optimal control under complex operating conditions. This paper systematically reviews the research progress in BTP sensing and identification methods, prediction models, and control strategies, with a focus on analyzing the applicable scenarios and engineering limitations of different technical approaches. Existing studies show that BTP control is evolving from empirical judgment and local feedback regulation towards multi-source sensing, feedforward prediction, and collaborative optimization. However, further breakthroughs are still needed in multi-source heterogeneous data fusion, cross condition generalization, model interpretability, and long term online application. The analysis results presented in this paper can support the development of intelligent BTP control systems and the optimization of the sintering process.

For the casting residual slag generated during the steelmaking and continuous casting processes, this paper systematically reviews the relevant research progress and industrial practices of its recycling into the production processes for resource utilization, and summarizes the source, compositional characteristics of casting residual slag as well as its recycling methods and application effects in different steelmaking procedures. Comprehensive analysis shows that casting residual slag is dominated by the CaO-Al₂O₃-SiO₂ system, featuring high basicity and certain metallurgical activity, thus being applicable as a secondary resource in steelmaking slag formation and refining processes. Among them, hot casting residual slag, by virtue of its sensible heat and molten state, is more suitable for direct recycling to converters and refining processes. This contributes to shortening the slag formation time, reducing the consumption of fluxes such as lime and dolomite, and improving the final slag structure. After undergoing crushing, magnetic separation and composition homogenization treatment, cold tailing slag can be stably applied in converters, ladle furnace, Ruhrstahl-Heraeus degasser and tundishes, replacing part of the slag-forming agents or covering agents and extending its metallurgical functions. In general, the recycling of casting residual slag into production processes can achieve comprehensive benefits such as flux saving, metal recovery and indirect carbon reduction without a significant increase in energy consumption. However, its further promotion and application are still confronted with challenges including large composition fluctuation, complex pretreatment processes for cold tailing slag and insufficient cross-process adaptability. In the future, it is necessary to improve the technical system consisting of source classification, on-line composition detection and graded recycling, so as to promote the large-scale and high-efficiency resource utilization of casting residual slag in iron and steel production.

Under the global carbon neutrality background, the steel industry, as one of the most concentrated industrial sectors in greenhouse gas emissions, is accelerating its transformation toward low carbon and green development. Australia is considered an important future development region for the global green iron and steel due to its unique advantages in resources and energy. This paper takes the major research and development projects and industrial practices in Australia's green steel field in recent years as the research object, systematically reviews the latest progress in iron ore upgrading and pretreatment, green steel technology development, and industrial layout, and focuses on the analysis of representative projects supported by the Australian Renewable Energy Agency. Research shows that in response to the difficulty of directly applying medium and low grade iron ores from the Pilbara region to traditional hydrogen based direct reduction processes, Australia is forming a pattern of coordinated development across multiple technology routes, including low temperature agglomeration, ore upgrading, hydrogen based direct reduction combined with electric arc furnaces, hydrogen based direct reduction combined with electric smelting furnaces, flash green ironmaking, direct electrochemical reduction, and traditional blast furnace carbon reduction retrofitting. In terms of industrialisation, Australia is gradually forming a development model with Western Australia as the core and intermediate product export as the orientation, and multiple green steel projects have entered the demonstration, planning, or construction stages. Overall, Australia has preliminarily built an industrial system covering resource development, ore upgrading, product export, and policy support, but still faces challenges such as green hydrogen cost, renewable electricity and transmission infrastructure, water resource security, green product certification, and international market competition. With the decline in green hydrogen cost, the maturation of key technologies, and the advancement of industrial coordination, Australia is expected to gradually transform from a traditional iron ore exporter to a global green iron and steel supply center, providing an important reference for deep decarbonisation of the steel industry.

Sintering machine head dust is one of the major solid wastes generated during iron and steel metallurgical processes. Its composition is dominated by iron, while also containing various impurity elements such as potassium, sodium, lead, and chlorine. These impurities originate from diverse sources and predominantly exist in the form of chloride salts agglomerated on or adhered to the surface of iron oxide particles. Currently, the treatment of sintering machine head dust has evolved into an integrated recovery process system centered on a combined flowsheet of "water leaching for alkali metal removal-returning iron-rich residue to sintering" and "leachate purification for impurity removal-evaporative crystallization for alkali metal salt recovery", supplemented by physical beneficiation and other methods to improve the quality of iron-rich residue. This comprehensive recovery process has been applied in some iron and steel enterprises. With the deepening of supply-side structural reform in the steel industry, enterprises have raised higher demands for the thorough removal of alkali metals, process simplification, and benefit enhancement. This paper starts with the source tracing of sintering machine head dust, followed by analysis of its physicochemical characteristics, elucidation of the formation, migration and conversion mechanisms of iron and key impurity components, and accordingly summarizes the existing recovery processes and innovative improvement directions. In response to the bottleneck issues commonly encountered in current treatment processes, such as poor universality, lengthy process, and valuable-component loss, a comprehensive strategy of "targeted regulation-quality-based treatment-refined recycling" is proposed. It is expected to offer a theoretical basis and technical references for efficient and high-value resource-oriented utilization of similar ferrous metallurgical dusts.

Low-energy NO_x abatement in the sintering process of the iron and steel industry is a key step toward achieving the synergy between pollution reduction and carbon reduction. In the conventional selective catalytic reduction denitrification process, the flue gas, which drops to 100-150 ℃ after desulfurization, must be reheated to 280-320 ℃ to meet the catalyst activity requirements. This reheating process consumes a large amount of blast furnace gas and results in significant carbon emissions. To address this challenge, significant progress has been made in recent years in low-energy denitrification technologies, following two main pathways, "lowering the selective catalytic reduction（SCR） reaction temperature" and "replacing external heating with internal heat sources from the flue gas itself". Based on a review of domestic and international literature and analyses of industrial engineering cases, four technical routes, i.e., low-temperature SCR catalyst development, activated carbon high-efficiency purification coupled with low-temperature SCR, precious metal CO catalytic-SCR coupling, and transition metal CO catalytic-SCR coupling, are systematically reviewed in terms of their principles, application status, and economic performance. The results indicate that low-temperature SCR catalysts can achieve high denitrification efficiency at 150-200 ℃, and when combined with upstream activated carbon desulfurization and dust removal, the reheating energy consumption can be substantially reduced or even eliminated. The CO catalytic-SCR coupling technology utilizes the strong exothermic effect of catalytic oxidation of CO, which exists at high mass concentrations （6 000-10 000 mg/m³） in sintering flue gas, to provide heat compensation for denitrification, achieving CO removal efficiencies exceeding 70% and gas savings of 63%-100%. However, the long-term stability of low-temperature SCR catalysts under SO₂ and H₂O containing complex flue gas conditions remains a core bottleneck, and the poison resistance of non-precious metal CO catalysts has not yet reached the requirements for industrial application. Future development should focus on improving the sulfur and water resistance and service life of low-temperature SCR catalysts, advancing CO catalytic-SCR coupling from single-function catalysts toward bifunctional integrated catalysts that enable synergistic CO oxidation and SCR denitrification within a single catalyst bed, and gradually replacing precious metals with non-precious metal catalysts to further reduce costs and promote the large-scale application of low-energy denitrification technologies in the steel industry.

Binders play critical role in determining the quality and performance of iron ore agglomerates. To develop a low-dosage and highly efficient binder suitable for the agglomeration of Bayan Obo iron ore, a novel coal-based colloidal composite binder （3Co-binder） independently developed by Central South University was investigated. The binder was prepared using high-humic-acid weathered coal from Xinjiang as the main raw material, and its preparation process and application performance in the agglomeration of Bayan Obo iron ore were systematically studied. The results indicate that the optimal preparation conditions are water-to-coal ratio of 5.5-6.0, alkali-to-humic-acid ratio of 27%-30%（mass fraction）, and alkali pre-activation time of 4-24 h. Under these conditions, 3Co-binder exhibits stable rheological behavior and maintains good flowability and stability for up to 6-10 d. 3Co-binder shows excellent compatibility with Bayan Obo iron ore. When used as replacement for bentonite in pelletizing, a dosage of only 1.5% （corresponding to 0.21% on a dry basis,mass fraction） is sufficient to achieve superior green pellet quality compared with that obtained using 2.0%（mass fraction） bentonite under comparable conditions. Scale-up simulation tests of the grate-rotary kiln process demonstrated that, under conditions of preheating temperature of 950 ℃, preheating time of 12 min, roasting temperature of 1 200-1 225 ℃, and roasting time of 20 min, the compressive strength of preheated pellets exceeds 440 N per pellet, while that of roasted pellets exceeds 2 600 N per pellet. Compared with oxidized pellets produced with 2.5% bentonite, pellets prepared with 0.21% （dry basis,mass fraction） 3Co-binder exhibit an increase in iron grade by 1.39 percentage points and an improvement in reducibility index by 4.1 percentage points. In sintering applications with high proportions of Bayan Obo iron ore, the addition of 3Co-binder significantly improves granulation behavior and enhances product quality and productivity. During secondary mixing, adding 0.3% binder （0.04% on dry basis,mass fraction） in place of part of the granulation water increases the proportion of more than 3 mm granules and optimizes the particle size distribution. As a result, the sintering productivity increases by 0.19 t/（m²·h）, and the tumbler index increased by 1.73 percentage points. Overall, 3Co-binder enables significant dosage reduction through enhanced interparticle interaction among iron ore particles, thereby strengthening granulation and bonding processes, ultimately achieving coordinated enhancement of agglomeration product quality and productivity.

To address the potential issue of low-temperature reduction disintegration （LTD） caused by the use of lump ore in hydrogen rich gas-based reduction processes, this study systematically investigated the effects of reduction temperature （450-600 ℃） and reducing atmosphere [φ（H₂）/φ（H₂+CO） is 0.6-1.0] on the low temperature reduction disintegration behavior of a typical iron ore lump. The disintegration mechanism was revealed by combining weight loss rate, reduction degree, X-ray diffraction （XRD）, and microstructural characterization. The results show that the reduction temperature is the dominant factor controlling the low temperature reduction disintegration behavior of lump ore. Within the range of 450-600 ℃, as the reduction temperature increases, the weight loss rate and reduction degree of lump ore gradually increase, but the low temperature reduction disintegration performance significantly deteriorates. Taking the atmosphere with φ（H₂）/φ（H₂+CO）=0.6 as an example, when the temperature increases from 450 ℃ to 600 ℃, the L_TD>6.3 index （the mass fraction of particles larger than 6.30 mm after the low temperature reduction disintegration test） decreases from 75.56% to 20.16%, while the severe disintegration index L_TD<0.5 （the mass fraction of particles smaller than 0.50 mm after the test） sharply increases from 5.08% to 23.05%. Increasing the H₂ proportion in the reducing gas promotes the reduction reaction and may shorten the stress accumulation stage caused by the prolonged coexistence of hematite and magnetite, thereby improving the disintegration performance of lump ore to a certain extent. Microstructural analysis indicates that the lump ore has a dense structure and low porosity, so the volumetric stress generated during the transformation from hematite to magnetite is difficult to release in time, leading to crack propagation along grain boundaries, pores, and pre existing defects. Dynamic evolution results at 550 ℃ further reveal that the low temperature reduction disintegration process of the lump ore can be divided into three stages, preferential reduction at the edge, inward advancement of the phase transformation interface, and crack penetration. The essence of low temperature reduction disintegration of lump ore lies in the dense matrix limiting the uniform penetration of reducing gas into the deep part, forming a non uniformly advancing phase transformation front. The stress concentration induced by phase transformation and the inward penetration of cracks constitute the fundamental causal mechanism leading to overall aligned cracking and structural instability of the lump ore. This study provides a theoretical basis for the rational use of lump ore and the optimization of burden structure under hydrogen rich reduction conditions.

Thick-bed sintering is an important approach for reducing energy consumption and carbon emissions in the sintering process because it enhances heat accumulation within the bed and improves productivity under existing operating conditions. However, increasing bed height promotes heat accumulation in the lower bed region, resulting in excessive liquid phase formation and local over-melting, which deteriorates bed permeability and limits the effectiveness of segregated addition of return fines. To clarify the matching relationship between segregated addition of return fines and thermal regime under thick-bed sintering conditions, a series of 950 mm sintering pot tests were conducted, combined with cold-state permeability measurements, infrared thermal imaging, and flue gas analysis. The effects of the synergistic regulation of return fines segregation and fuel ratio on the sintering process were systematically investigated. The results show that the segregated addition of return fines alone exhibits limited improvement in sintering performance under 950 mm bed height. Reducing the fuel ratio appropriately alleviates heat accumulation and excessive liquid phase formation in the thick bed, thereby enabling the permeability-enhancing effect of the return-fines skeleton structure to be fully realized. Under a total return fines ratio of 20%, the optimum performance is achieved at a critical particle size of 1 mm, segregated addition ratio of 62%, and fuel ratio of 4.0%, yielding sinter yield of 83.17%, tumble strength of 74.64%, and solid fuel consumption of 48.09 kg/t. The enhancement effect of segregated addition of return fines is found to depend not only on the particle size and segregation ratio of return fines, but also on the fuel ratio. The return-fines skeleton structure improves gas flow distribution and moisture migration, while a reduced fuel ratio suppresses excessive liquid phase formation. The synergistic effect of these factors enhances bed permeability, combustion efficiency, and sintering performance simultaneously, providing theoretical guidance for quality improvement and energy conservation in thick-bed sintering.

Ammonia, as a hydrogen carrier, has well-established trade routes and relatively low liquefaction costs, and can be directly used as a clean reducing agent for iron ore. Existing studies have provided thermodynamic parameters and reaction activation energy of ammonia reduction through thermodynamic calculations, basic experiments, and kinetic fitting, but the mechanism of ammonia reduction remains unclear. In this study, the reaction behavior, mineral composition and micro-structure of ammonia reduction of pellets at different temperatures and times was investigated, and further combined the changes in reduction expansion rate, thermodynamics analysis, and kinetic analysis, the mechanism of ammonia reduction of pellets were obtained. The results showed that the time for the reduction degree to reach 0.95 decreased from 93.5 min to 43.2 min as the temperature increased from 700 ℃ to 900 ℃. In addition, the mass fraction of nitrogen in the reduced pellet decreased from 0.029% to 0.019%. The results of kinetic fitting indicate that the mechanisms of ammonia reduction of pellets at various temperatures are diverse. The reduction is controlled by diffusion, chemical reaction, and nucleation respectively as the reduction proceeded at 700 ℃. However, the whole reduction duration is controlled by diffusion at 900 ℃. Overall, The reduction between ammonia and hematite mainly occurred on the outside of pellet, and the reduction of hematite to magnetite led to a first swelling of the pellets. The decomposition of ammonia is promoted by the catalysis of metallic iron as the reaction progresses, which led to the second swelling of pellets and the formation of a large number of cracks, and the interior of pellets are further reduced by hydrogen produced from ammonia decomposition. The research results have certain significance for understanding the ammonia reduction mechanism of pellets, promoting the application of ammonia in the iron-making process and the development of low-carbon technologies.

To investigate the hydrogen-rich reduction behavior of high-purity iron concentrate pellets with different basicities and to reveal the influence mechanism of liquid phase properties on reduction swelling, this study combined microstructural characterization with quantitative analysis to systematically examine the microstructure evolution and hydrogen-rich reduction behavior of high-purity iron concentrate pellets at different basicities （R=0.07-1.0）. The mechanism by which liquid phase properties affect the reduction swelling performance of pellets with different basicities was emphatically revealed. The results show that as the pellet basicity increases, the amount of liquid phase within the pellets gradually increases, and the contents of Ca and Fe components in the liquid phase rise. Under simulated HYL（Hojalata Y Lamina） hydrogen-rich gas conditions, the reducibility index of different pellets first decreases and then increases, while the reduction swelling index shows the opposite trend. Abnormal swelling occurs during the reduction of roasted pellets in the basicity range of 0.4-0.8. At low basicity （R=0.07）, the amount of liquid phase formed in the roasted pellets is small, and under reducing conditions, metallic iron primarily grows in a dense layered manner. At medium basicity （R=0.60）, the dynamic "dissolution-precipitation" behavior occurred between the glass phase and iron oxides during reduction induces the formation of a porous structure and mound-like iron morphology, leading to abnormal swelling. At high basicity （R=1.00）, the amount of liquid phase in the pellets increases significantly, forming a continuous glass phase skeleton after cooling, which effectively suppresses the reduction swelling of pellets. Under the condition of basicity of 0.6, by appropriately increasing the SiO₂ and CaO contents in the pellets, the reduction swelling index significantly decreases from 48.92% to 7.38%. By controlling the composition and content of the liquid phase in iron ore pellets with different basicities, the reduction swelling performance of pellets can be significantly improved, providing a theoretical and technical basis for the preparation of high-performance iron oxide pellets.

Conventional sintering methods are characterized by elevated energy consumption and significant environmental pollution, particularly when processing complex low-grade iron ores, such as vanadium titano-magnetite. In contrast, pelletizing represents a more environmentally friendly technique for producing agglomerated iron ore products. Consequently, the increased utilization of pellet burden of vanadium titano-magnetite in blast furnace low-carbon ironmaking process has emerged as a critical advancement in the field. To overcome challenges associated with vanadium titano-magnetite pellets such as poor oxidation behavior, the propensity to develop core-shell structures, and low mechanical strength, a calcium ferrite flux was synthesized via sintering and pelletizing techniques and introduced as an innovative additive to improve pellet consolidation characteristics. Experimental findings indicate that the calcium ferrite flux produced by sintering predominantly comprises acicular or tabular silico-ferrite of calcium and aluminum （SFCA）, achieving an effective content of SFCA exceeding 78.54%（area fraction） in particles larger than 5 mm. In contrast, the flux prepared through pelletizing mainly consists of monocalcium ferrite and dicalcium ferrite, with an effective content of SFCA of 97.30% （area fraction）. The addition of 2.0%（mass fraction） pelletized calcium ferrite flux to vanadium titano-magnetite pellets facilitates the formation of liquid phase, such as calcic iron olivine, which acts as effective bridging agents promoting intergranular consolidation. This results in a marked increase in titanium hematite grain size, enhances recrystallization bonding and decreases pellet porosity. 26.2% improvement in pellet compressive strength under consistent preheating and calcination conditions is achieved.

To increase the proportion of vanadium-titanium pellets in blast furnace burden and alleviate the deterioration of high-temperature performance caused by matching high pellet ratios with high-basicity sinter, a burden design strategy based on basicity matching was proposed. Fluxed vanadium-titanium pellets with different basicities were prepared under the boundary conditions of maintaining the iron grade, slag basicity, w（MgO）/w（Al₂O₃） ratio, and thermal regime. Their cold strength, reduction disintegration, reducibility, and softening-melting behavior were systematically evaluated. The results show that, with increasing pellet basicity （from 0.13 to 0.62）, the mass fraction of CaO in the pellet increases from 0.32% to 2.13%, and the compressive strength reaches 2 714.6 N per pellet. At a pellet basicity of 0.62, the reduction degradation index （I_{RD<3.15 mm}） decreases to 1.60%, indicating good low- and medium-temperature the reduction degradation resistance. However, the reduction swelling index （I_RS） reaches 17.84%. For a single pellet bed, the softening-melting behavior deteriorates with increasing basicity, and the gas permeability index （S value） increases from 340.60 to 2 000.27 kPa·℃. In the composite burden composed of basic sinter, acid sinter, Baima pellets, and vanadium-titanium pellets, however, a clear synergistic slagging effect occurs between sinter and pellets. At a total pellet ratio of 59% and a vanadium-titanium pellet basicity of 0.47, the composite burden exhibits the best high-temperature performance, with a softening interval of 75 ℃, a melting-dripping interval of 130 ℃, and the lowest S value of 1 372.91 kPa·℃. Ore-blending calculations indicate that, while maintaining the slagging regime, the pellet ratio can be increased from 55% to 61%, the vanadium-titanium ore proportion increases by 3.44 percentage points, the mass fraction of TiO₂ in the slag is increased to 23.15%, and the ore-blending cost decreases by 38.10 yuan/t（hot metal）. These results provide a basis for optimizing high-proportion vanadium-titanium pellet burden and for the low-cost and efficient utilization of vanadium-titanium magnetite.

To elucidate the influence of the complementary characteristics of different types of low-grade lateritic nickel ore on the hydrogen-rich reduction behavior of composite pellets, oxidized pellets of limonite （HT）, germination （GD）, and humicite （FZ） lateritic nickel ore were selected as research objects. Reduction tests were conducted on single-ore pellets and composite pellets under different reducing atmospheres and temperatures. X-ray diffraction and scanning electron microscopy-energy dispersive spectroscopy （SEM-EDS） analyses were used to reveal their phase transformation and microstructure evolution. The results show that the reduction behaviors of the three types of single-ore pellets differed significantly. HT-type pellets, due to their higher iron oxide content and lower content of stable silica-magnesium phases, exhibit the fastest reduction rate, reaching reduction degree of 86% in 30 min and near-complete reduction in 120 min. GD-type pellets, limited by high SiO₂ and MgO content and magnesium silicate and spinel phases, have a reduction rate of only 72% in 120 min. The reduction degree of FZ-type pellets fall between the two. Composite ore blending can improve the pellet reduction process. With a fixed FZ-type ore mass fraction of 30%, B2 pellets （HT-type, GD-type, FZ-type mass fraction ratio of 20%∶50%∶30%） exhibit both a faster initial reduction rate and a higher degree of reduction in the middle and later stages, reaching a reduction degree of 87% after 60 minutes. Increasing the H₂ volume fraction and reduction temperature can promote the reduction of Fe and Ni oxides, resulting in enhanced diffraction peaks of metallic iron, an increase in the iron-nickel metallic phase, and a shift of the reduction interface inwards. The hydrogen-rich reduction process is characterized by preferential reduction at the surface, inward shift of the reaction interface, and enhanced diffusion resistance in the later stages. Residual magnesium silicate and spinel phases encapsulating the unreduced matrix are important factors limiting the depth of reduction in the internal regions.

To clarify the synergistic effect of externally added biomass on the reduction behavior of carbon-containing pellets under rotary kiln conditions, magnetite-biochar pellets were taken as the research object. In combination with the thermal characteristics of an industrial rotary kiln, the effects of preparation method, heat-treatment schedule, C/O molar ratio, and atmosphere on the metallization rate, cold compressive strength （CCS）, and microstructural evolution of the pellets were systematically investigated. The results show that the disc pelletizing method is more favorable than extrusion forming for developing a graded pore structure that balances gas transport and carbon-iron contact, and thus significantly improves both the deep reduction behavior and mechanical properties of the pellets. Under a reducing atmosphere, after being treated at 1 050 ℃ for 30 min, the pellets achieved a metallization rate of 97.52% and a CCS of 942 N, while the shatter strength met the requirement for industrial application. An increase in temperature accelerated the stepwise reduction from Fe₃O₄ to FeO and then to Fe, and promoted the formation of a metallic iron framework. However, when the temperature is too high or the holding time is too long, local liquid-phase formation and structural densification increased the risk of ring formation. The C/O molar ratio plays a decisive role in both reduction efficiency and structural stability. When the C/O molar ratio increases from 0.2 to 0.4, the metallization rate rose markedly, and a continuous intergrown metallic iron skeleton forms. When the C/O molar ratio further exceeded 0.6, excessive carbon gasification led to the formation of more large internal pores and aggravated residual carbon inclusion, resulting in a clear decrease in pellet strength. The comparison of atmospheres further indicates that the C/O molar ratio generated by external biomass gasification not only directly participates in the reduction of iron oxides, but also suppresses the overly rapid consumption of internal carbon and maintains the reducing potential inside the pellets at the later stage, thereby strengthening the synergistic effect between the external atmosphere and the internal carbon source. Considering metallization rate, strength, and ring formation risk together, disc pelletizing, a C/O molar ratio of 0.4, 1 050 ℃, and 30 min are the more suitable process conditions. This study provides an experimental basis for the application of biomass as a substitute for fossil carbon in the rotary kiln direct reduction process.

To meet the requirements of energy conservation, carbon reduction, and ultra-low emissions in the iron and steel industry, ϕ6.858 m×45.72 m pellet rotary kiln was investigated. A co-combustion model of pulverized coal and natural gas/hydrogen was established based on computational fluid dynamics （CFD） and the finite-rate/eddy-dissipation （FR/ED） mechanism. Flow field, temperature field, and pollutant formation characteristics in the kiln were systematically investigated under pure pulverized coal combustion and under different substitution ratios of natural gas and hydrogen.Results show that, after hydrogen-rich gaseous fuel is introduced, typical recirculation zone is formed near the burner nozzle, which is favorable for more complete fuel combustion. With the addition of natural gas or hydrogen, the flame gradually changes from the slender cylindrical shape under the pure pulverized coal condition to compact spindle-like shape at high natural gas substitution ratios, effectively alleviating the ignition delay of pulverized coal and making the temperature distribution more uniform. In particular, the front-end combustion enhancement effect is more pronounced under hydrogen-blending conditions than under natural gas-blending conditions. However, at high substitution ratios, a new local high-temperature zone appears near the kiln head, especially under hydrogen-blending conditions, which is more likely to increase the thermal load on the burner nozzle and the front-end refractory materials. Fuel substitution can significantly suppress NO_x formation. At a substitution ratio of 60%, the outlet NO_x mass fraction decreases from 0.034 2% under the pure coal condition to 0.013 5% for natural gas and 0.013 2% for hydrogen, respectively, corresponding to reductions of more than 60%. Natural gas and hydrogen exhibit significant differences in the mechanism of CO₂ reduction. At a substitution ratio of 60%, the peak CO₂ mass fraction only decreases from 0.17 to about 0.13 under natural gas substitution, whereas it drops to below 0.08 under hydrogen substitution, with a reduction of more than 50%, indicating a much stronger decarbonization effect. Considering the thermal stability of the rotary kiln, equipment safety, and emission reduction requirements, 40% is recommended as the optimal substitution ratio for both natural gas and hydrogen. This study provides an important theoretical basis and engineering guidance for fuel structure optimization and low-carbon clean combustion in rotary kilns.

The Bayan Obo ore contains relatively high contents of fluorine, potassium, and sodium, which cause K₂O, Na₂O, and CaF₂ to exert significant influences on the metallurgical properties of primary slag formed during the blast furnace smelting of this ore. However, the influence mechanisms of these components on the primary slag properties remain insufficiently understood. This work systematically investigated the effects of w（K₂O）/w（Na₂O） and w（CaF₂） on the viscosity and structure of CaO-SiO₂-MgO-Al₂O₃-FeO based blast furnace primary slags. The viscosity of the blast furnace primary slag was determined by the rotating cylinder method, and the microstructural characteristics of the slag were investigated using Raman spectra. The viscosity experimental results indicate that the addition of Na₂O alone decreases the viscosity of the primary slag, whereas an equivalent mass substitution of K₂O for Na₂O increases the viscosity. Moreover, the viscosity of the primary slag gradually decreases with increasing w（CaF₂）. Raman spectra analyses reveal that the equivalent mass substitution of K₂O for Na₂O reduces the number of O^2- ions and inhibits the conversion of O⁰ to O^-, thereby promoting the polymerization of the slag network. The Al—O bonds in AlO₄ tetrahedra charge-compensated by K⁺ ions are stronger than those charge-compensated by Na⁺ or Ca²⁺ ions, leading to the formation of more stable aluminate structural units, which ultimately results in the viscosity increase of the primary slag upon the equivalent mass substitution of K₂O for Na₂O. With increasing CaF₂ contents in slags, the F^- ions provided by CaF₂ promotes the depolymerization of the silicate network structural units, thereby simplifying the slag structure and reducing the viscosity. Furthermore, as a flux, CaF₂ significantly reduces the liquidus temperature of the slag and therefore enhancing its flowability under the experimental conditions. As a result, the viscosity of the primary slag decreases with w（CaF₂） increasing. The findings of this study provide a theoretical foundation for optimizing the performance of primary slag in the blast furnace smelting of Bayan Obo ore.

The steel industry faces an extremely urgent task of decarbonization. Biochar, as a renewable fuel with carbon neutral properties, can promote deep decarbonization in blast furnace ironmaking. To investigate the effectiveness and economic benefits of biochar injection in blast furnaces, this study developed a full furnace energy and mass balance model that considered the physicochemical properties of different fuels and the distribution of reactions within the furnace. The model compared and analyzed the changes in smelting parameters, carbon emission reduction, and economic performance when injecting wood chip biochar （Biochar A） and corn stalk biochar （Biochar B） at injection ratios ranging from 0 to 40%. Industrial trials were also conducted at injection ratios of 0 to 20%. The model results indicate that the physicochemical properties of biochar affect the thermal state of the blast furnace and fuel performance. As the injection ratio increases to 40%, injecting Biochar A reduces the fuel rate from 509 kg/t to 504 kg/t, increases the theoretical combustion temperature from 2 172 ℃ to 2 208 ℃, decreases the proportion of total furnace heat loss from 5.92% to 4.79%, and improves the gas utilization rate. Injecting Biochar B raises the theoretical combustion temperature to 2 186 ℃ but increases the fuel rate to 516 kg/t and causes a slight decrease in the gas utilization rate. The industrial trial results show that under short term operation with a injection of 10% to 20%, the blast furnace operating parameters remain within an acceptable range. The fuel rate is maintained between 509 kg/t and 511 kg/t, and parameters such as top temperature, permeability index, hot metal temperature, and the gas flow distribution in furnace （W）, furnace condition stability （Z）, and gas flow uniformity （K） values all fluctuate within normal ranges. In terms of carbon emission reduction and economic performance, based on the model boundaries and the carbon neutral assumption for biochar, at the injection ratio of 40%, fossil derived CO₂ emissions are reduced from 1 318 kg/t to 1 252 kg/t, achieving a net reduction of 66 kg/t. The fuel cost （excluding carbon tax） increases from 839.11 yuan/t to 881.26 yuan/t. A scenario analysis incorporating a carbon tax reveals that when the price of biochar is 1.5 yuan/kg, a minimum carbon tax of 173.31 yuan/t （CO₂） can ensure economic viability. When the carbon tax is 0 yuan/t （CO₂）, a maximum biochar purchase price of 1.326 yuan/kg can ensure economic viability.

The steel industry is fundamental sector of the national economy and also the largest carbon emitting industry in the manufacturing sector. Under the background of China's carbon peak and carbon neutrality goals, the steel industry faces urgent need for large scale deep carbon reduction. Hydrogen metallurgy, through replacing carbon with hydrogen, has become the most effective pathway to achieve deep decarbonization in the steel industry. Domestic trials of technologies such as hydrogen-based shaft furnace direct reduction and hydrogen rich blast furnace ironmaking have been conducted and have achieved significant carbon reduction effects. However, the current development of hydrogen metallurgy technology still faces the bottleneck of high cost of hydrogen rich reducing gas and the difficulty of coordinating carbon reduction with cost reduction. To address this challenge, this paper proposed a synergistic carbon reduction process coupling hydrogen-based shaft furnace and blast furnace production, taking into account China's energy structure and resource characteristics. This process fully utilized the respective smelting advantages of the hydrogen-based shaft furnace and the blast furnace while avoiding the economic disadvantage of the electric furnace melting separation step for direct reduced iron, thereby reducing production costs while achieving carbon reduction. A multi zone constrained mathematical model of the coupled hydrogen-based shaft furnace and blast furnace process was developed to systematically analyze the effects of three different reducing gas sources, namely natural gas, coke oven gas, and pure hydrogen, on the shaft furnace direct reduction process and the subsequent blast furnace smelting of direct reduced iron. The calculation results indicate that under current technical and market conditions, the coke oven gas shaft furnace and blast furnace coupled process is the most suitable technical route for promoting large scale low carbon metallurgy in Chinese steel enterprises. In this process, the optimal metallization rate of direct reduced iron in the shaft furnace direct reduction stage is approximately 90%, the coke oven gas consumption per ton of hot metal is 400 m³（normal state）, and the blast furnace fuel rate is 285 kg/t （including a coke rate of 165 kg/t）. The CO₂ emission per ton of hot metal in the coupled process is 1 090 kg, which is 30% lower than that of the conventional blast furnace process. The fuel cost per ton of hot metal is 601 yuan, which is 21% lower than that of the conventional blast furnace process.

To address the challenges of carbon emission reduction and iron ore resource constraints, the influence of direct reduced iron （DRI） on the key smelting indexes such as theoretical combustion temperature, bosh gas index and productivity coefficient of blast furnace was studied by establishing the energy and mass balance model of adding DRI to blast furnace. The results indicate that adding a significant amount of DRI easily leads to insufficient heat of blast furnace. Constraining the total heat loss of the blast furnace to no less than 80% of the base case, the maximum DRI addition is 2.6%. A further decrease in the metallization rate of the DRI would exacerbate the total heat expenditure of the blast furnace. Under the premise of maintaining the heat loss consistent with the base case, the suitable amount of DRI that could be added is almost the same after either increasing the blast temperature or the oxygen enrichment ratio. Although increasing the pulverized coal significantly increases the suitable DRI amount, the theoretical combustion temperature and bosh gas volume index of blast furnace are seriously deteriorated. Increasing the blast temperature or oxygen enrichment ratio on thermal compensation is basically the same and can be replaced by each other, and problems such as the decrease in theoretical combustion temperature caused by pulverized coal injection are alleviated. Under comprehensive thermal compensation measures, the maximum DRI addition reaches 12.12%, and the carbon consumption per ton of hot metal decreases by 56 kg.

To address the prominent problems of low titanium recovery, high energy consumption, and high carbon emissions in the traditional blast furnace basic oxygen furnace process for smelting vanadium-titanium magnetite, this paper proposed a process route of hydrogen metallurgy coupled with electric furnace melting separation for vanadium titanomagnetite, and conducted fundamental research and industrial trials. First, oxidized pellets were prepared using vanadium-titanium magnetite as raw material. Then these pellets were then used to produce metallized pellets via hydrogen based shaft furnace. Finally, electric furnace melting separation was applied to achieve the separation and enrichment of iron, vanadium, and titanium. Based on this approach, this study systematically investigated the optimal control conditions for each process step including oxidized pellet production, hydrogen based reduction, and electric furnace melting separation. Experimental results show that oxidized pellets meeting the requirements for hydrogen based shaft furnace can be obtained under preheating temperature of 930 ℃ and preheating time of 18 min. Increasing the reduction temperature and the H₂ volume fraction significantly improves the reducibility index, while high temperature and low H₂ volume concentration exacerbate pellet reduction swelling and sticking behavior. The low temperature reduction disintegration index first increases and then decreases with rising H₂ volume fraction. The optimal slag metal separation for electric furnace melting separation is achieved at 1 600 ℃ with a C/O mole ratio [n（C）/n（O）] of 1∶1. Industrial trial results demonstrate that the average recovery rates of iron and vanadium in vanadium bearing hot metal exceed 95% and 90% respectively, and the average recovery rate of titanium in titanium slag reaches over 92%. This process achieves efficient recovery of the three valuable components of iron, vanadium, and titanium from vanadium-titanium magnetite, providing a new technical solution and theoretical support for the high value and green utilization of vanadium-titanium magnetite.

To evaluate the service stability of refractory linings in the high-hydrogen zone of hydrogen-based shaft furnace under strong reducing atmosphere, and clarify the response laws of phase, microstructure and properties of different materials under high H₂ partial pressure, Fluent simulation was first used to calculate the furnace-wall temperature, pressure, and gas-composition distributions. The middle-lower part of the reduction section and the region near reducing-gas inlet were identified as key locations with high temperature and high H₂ partial pressure, and were taken as the basis for the 930 ℃ H₂ reduction experiment. Grade I high-alumina brick, Grade Ⅱ high-alumina brick, corundum-SiC microporous brick, Sialon-corundum brick, and Si₃N₄-SiC brick were selected as the research objects. The samples were held in H₂ at 930 ℃ for 5, 10, 15, 20, 25 h. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, mass change, bulk density, apparent porosity, and cold compressive strength tests were used to investigate the evolution of phase structure and macroscopic properties. The results show that the Al₂O₃ skeleton phase remains stable under the experimental conditions, whereas sensitive components such as SiO₂, Fe₂O₃, and TiO₂ are more likely to participate in reduction reactions or structural rearrangement. After 25 h, the mass change rates of the five materials are -0.318%, -0.477%, +0.063%, -0.044%, and -0.262%, respectively. Among them, Grade II high-alumina brick exhibits the largest mass loss, indicating that higher contents of SiO₂ and Fe₂O₃ weaken its stability in a high-H₂ atmosphere. The corundum-SiC microporous brick shows the smallest mass change, together with increased bulk density and decreased apparent porosity, indicating good structural retention and resistance to H₂ penetration. Comprehensive analysis indicates that corrosion of lining materials in the high-H₂ zone can be described as a coupled process involving H₂ penetration into the material through open pores and microcracks, reduction or reconstruction of active components, pore-network evolution, and mechanical-property response. The corrosion resistance is mainly controlled by the thermodynamic stability of components, pore connectivity, and bonding-phase evolution. This study provides a reference for the selection and optimized design of refractory linings in the high-H₂ zone of hydrogen-based shaft furnaces.

Blast furnace gas （BFG） is the core carrier of CO₂ emissions in the long steel production. To solve the carbon reduction problem under the "dual carbon" goals, this paper proposed a new process of biomass co-reforming BFG, which realized deep carbon fixation in the system and significant increase in the calorific value of syngas by directed the reduction of CO₂ to CO. This paper used HSC Chemistry software to build a thermodynamic equilibrium model of the reforming process and systematically investigated the effects of gasification temperature, n（C）/n（CO₂）（molar ratio）, and system pressure on gasification performance. Based on the process parameters obtained from calculation and energy balance, the optimal efficiency of the reforming process was determined. The results show that moderately increasing the gasification temperature and n（C）/n（CO₂） ratio can significantly improve the quality of syngas, but excessively elevating these operating parameters will lead to a sharp increase in heat loss and limited conversion efficiency, while increasing the system pressure has inhibitory effect on the syngas yield. Comprehensive evaluation shows that under the optimal conditions of 1 000 ℃, n（C）/n（CO₂）= 10∶3, and 0.1 MPa, the carbon conversion rate and syngas yield of the system are both as high as 99%, and the higher heating value （HHV） of the produced syngas reaches 209.80 MJ/kmol, which is 2.41 times higher than that of the original blast furnace gas. Further economic benefit analysis shows that for every ton of biomass co-reformed with 1 767.36 m³ of blast furnace gas, 3 314.55 m³ of high-calorific value syngas can be produced, creating a value of 5 668.59 yuan, demonstrating significant industrial application potential and economic feasibility. The biomass and blast furnace gas co-reforming technology developed in this study provides important theoretical support and engineering reference for the efficient and high-value utilization of by-product gases in steel enterprises and for pollution reduction and carbon emission reduction.

Electric arc furnace dust （EAFD） is typical hazardous solid waste generated during the steelmaking process in electric arc furnaces. Because it is rich in valuable metals such as lead, zinc, and iron, it holds high potential for resource utilization. This study aims for the efficient recovery of lead from EAFD. It focused on the interaction within the PbO-Fe₂O₃ system, specifically investigating the lead reduction and volatilization behavior during vacuum carbon thermal reduction at molar ratio of PbO and Fe₂O₃ was 1∶1. The FactSage 8.0 thermodynamic software was used to calculate the system's saturated vapor pressure, equilibrium phase composition, and Gibbs free energy changes. Combined with characterization methods such as X-ray diffraction analysis （XRD） and scanning electron microscope energy dispersive spectrometer （SEM-EDS）, the study systematically analyzed the effects of carbon addition, reduction temperature, and holding time on phase evolution, microstructure, and the lead volatilization rate. Thermodynamic results show that vacuum conditions significantly lower the initial reaction temperature of the system, favoring the reduction of PbO and the volatilization of metallic lead. The reduction of iron oxides mainly follows the stepwise transformation path of Fe₂O₃→Fe₃O₄→FeO→Fe, while lead primarily undergoes the reduction and volatilization process of PbO（s）→Pb（l）→Pb（g）. Experimental results demonstrate that under the conditions of reduction temperature of 1 150 ℃, carbon addition （mass fraction） of 16%, and holding time of 60 min, the system achieves the best lead volatilization effect, with a lead volatilization rate exceeding 99%, realizing efficient separation of lead from the iron phase. Kinetic analysis further reveals that the vacuum carbon thermal reduction process of PbO can be divided into different controlling stages. The early stage of the reaction is mainly controlled by interfacial chemical reactions, with the apparent activation energy increasing from 123.60 kJ/mol to 152.17 kJ/mol. The later stage gradually transitions to gas diffusion control, with the apparent activation energy stabilizing within the range of 150.33 to 155.49 kJ/mol. The findings elucidate the phase transformation regularities and lead volatilization mechanism in the PbO-Fe₂O₃ system during vacuum carbon thermal reduction, providing a theoretical basis and process reference for the selective separation and efficient recovery of lead from electric arc furnace dust.

The rotary hearth furnace is currently the mainstream technology for treating iron and steel metallurgical dust, yet its practical operation still faces challenges such as poor reduction homogeneity of pellets, difficulty in deep dezincification, and challenges in the synergistic optimization of key performance indicators. This study first systematically analyzed the raw material properties of typical metallurgical dust for rotary hearth furnace processing and investigates its effectiveness during microwave reduction roasting. Subsequently, Maps statistical analysis was employed to visualize and quantify the reduction homogeneity and pore structure characteristics of the pellets. Finally, a stepwise EDS（energy dispersive spectroscopy） analysis method was adopted to conduct a systematic investigation into the zinc phase evolution and dezincification mechanism, from the macroscopic to the microscopic scale. The results indicate that the iron phases in the metallurgical dust primarily include Fe_xO, Fe, Fe₂O₃, and Fe₃O₄, while the zinc phases consist of ZnS, ZnFe₂O₄, and ZnO. All raw materials exhibit excellent heating characteristics within the microwave field. Compared to conventional roasting, microwave roasting can increase the metallization rate of metallized pellets by approximately 15 percentage points, raise the dezincification rate by about 20 percentage points, and enhance the compressive strength by roughly 1 kN. Microwave roasting synchronously improves the reduction degree, structural compactness, and dezincification effectiveness across different internal zones of the metallized pellets, while also enhancing the uniformity of radial reduction and longitudinal dezincification, demonstrating advantages in low carbon emissions and high efficiency. Furthermore, a typical negative correlation exists between the distribution characteristics of the metallization rate and the residual Zn content within the pellets, providing an effective basis for indirectly inferring the distribution features of residual zinc and facilitating simple, intuitive analysis of its distribution patterns. Concurrently, sulfur present in the metallurgical dust is difficult to remove effectively during the reduction roasting process and tends to capture zinc as ZnS or （Zn,Fe）S solid solutions, leading to suboptimal dezincification. Microwave roasting can mitigate this capture and fixation of zinc. Through the characterization of typical metallurgical dust for rotary hearth furnaces, combined with Maps statistical analysis and stepwise EDS analysis, this study systematically elucidates the mechanism of microwave roasting, reveals its significant effects and operative mechanisms, and provides theoretical foundation and technical guidance for the low-carbon and high-efficiency resource utilization of metallurgical dust.

Converter dust is a metallurgical secondary resource rich in iron oxides. It is prepared as a coolant and returned to the converter for recycling,which can efficiently recover the iron resources. However,the content of alkali metals such as potassium and sodium in converter dust is high. In the process of preparing coolant by grate-kiln process,alkali metals are prone to volatilize in the preheating section of the grate,causing equipment bonding and affecting stable operation. To address this issue,converter dust and iron concentrate powder were used as raw materials. The raw material ratio of converter coolant produced on site was taken as the benchmark, and a single-factor variable method was adopted to design the control and experimental groups. By adjusting the proportions of limestone and bentonite in the raw materials,the solidification mechanism of K and Na was investigated through briquetting. The drying-preheating process of the coolant briquette samples was strictly simulated according to the thermal regime of the on-site grate. A BFD-1200 blast-exhaust drying high-temperature box furnace was used to simulate the drying section of the grate,and a CVD three-stage high-temperature tube furnace was employed to simulate the working conditions of the first and second preheating sections of the on-site grate. The phase composition,microstructure and chemical composition of the coolant briquettes were systematically characterized by means of X-ray diffraction,FactSage thermodynamic calculation, SEM-EDS and chemical analysis. The optimum raw material ratio was determined, and the alkali metal solidification mechanism was clarified. The results show that the main components SiO₂ and Al₂O₃ in bentonite can react with K₂O and Na₂O to form KAlSiO₄ and NaAlSiO₄,which can effectively solidify K and Na elements,inhibit their high temperature volatilization,and reduce the adverse effects on field production. With the increase of bentonite addition,the K and Na elements in the system were significantly solidified. When the bentonite addition reached 4%,the curing of K and Na basically tended to be stable, and the curing rates of K and Na elements were 85.8% and 74.6%,respectively. The high temperature curing law of alkali metal revealed in this study also provides an important theoretical reference for the harmless disposal and resource utilization of other alkali-rich metal metallurgical secondary resources.

To integrate biomass valorisation, waste heat recovery from hot steel slag, and CO₂ mineralisation for carbon sequestration, a vertical high-temperature injection gasification system was established using bamboo chips and hot basic oxygen furnace steel slag as feed stocks. The effects of the CO₂ volume fraction in the carrier gas, steel slag particle size, and reaction temperature on syngas production and coupled carbon sequestration were systematically examined. Kinetic analysis and multiple characterisation techniques were combined to clarify the mechanisms of gas release and solid-phase evolution. The results show that temperature is the dominant factor governing CO formation and carbon sequestration behaviour. When the temperature increases from 700 ℃ to 1 100 ℃, the CO yield increases from 81.5 mL/g to 207.8 mL/g. At 1 000 ℃, the peak CO volume fraction reaches 10.48%, with the shortest reaction completion time. Kinetic analysis shows that the apparent activation energy during the high-temperature gasification stage is 222.50-268.69 kJ/mol. Increasing the CO₂ volume fraction in the carrier gas promotes bamboo char gasification, dry reforming, and CO₂ mineralisation by steel slag. The effect of steel slag particle size shows clear temperature dependence. Within the range of 900-1 100 ℃, fine steel slag is more effective in increasing the peak CO volume fraction and CO yield, and the peak CO volume fraction is reaching 12.16% at 1 100 ℃, bigger than 9.79% for coarse steel slag. In contrast, coarse steel slag better maintains gas-flow channels within the particle bed, thereby improving carbon sequestration. The carbon sequestration rate generally increases with temperature and reaches its maximum value of 16.60% at 1 000 ℃. After the reaction, carbonation, iron oxide reduction-reoxidation, and calcium silicate structural reconstruction occurs simultaneously in the steel slag. Considering both gas production and carbon sequestration, 1 000 ℃, a higher CO₂ partial pressure, and an appropriate steel slag particle size can be regarded as preferred process conditions for balancing CO release and CO₂ mineralisation. If maximising CO yield is the primary objective, 1 100 ℃ and fine steel slag are more favourable. This study provides experimental support for the synergistic resource utilization of biomass solid waste and metallurgical steel slag.

To address the problems of lagging thermal state assessment, delayed laboratory assay feedback, and insufficient feature representation under complex operating conditions in blast furnace thermal regulation, a furnace thermal state prediction method based on mechanism-enhanced features and a hybrid LSTM-TCN model is proposed. Using nearly one year of production data from No.6 blast furnace at TISCO, abnormal samples were removed through a combined Z-score and boxplot approach, followed by multi-source heterogeneous data preprocessing, time alignment, and sample construction. A burden mechanism model was established to derive the slag-iron heat index, thermal loss in the high-temperature zone, and multi-scale temporal features. Meanwhile, the maximum relevance minimum redundancy method was introduced to optimize high-dimensional features through dimensionality reduction and to identify key variables strongly correlated with hot metal temperature and silicon content, thereby enhancing the model’s ability to characterize the nonlinear, time-varying, and multivariable coupling relationships in the blast furnace process. A hybrid LSTM-TCN network architecture was then constructed to achieve collaborative modeling of temporal dependencies and local sequential features. Experimental results show that, for hot metal temperature prediction, the proposed model achieved an E_MA of 4.74 ℃, an E_RMS of 6.01 ℃, and a prediction accuracy of 92.5%; for silicon content prediction, the E_MA and E_RMS were 0.016 7% and 0.022 8%, respectively, with an accuracy of 93.5%. Compared with conventional single models and comparative models without mechanism-based features, the proposed method exhibited superior prediction accuracy, stability, and generalization capability. Industrial application results further demonstrate that the model can effectively support early identification of blast furnace thermal states and operational regulation, and thus has significant engineering value for improving the stability of hot metal quality, assisting operators in precise intervention, and promoting stable blast furnace operation.

The blast furnace tuyere raceway is the dynamic core of ironmaking process, and real time changes in coke particle size directly reflect the thermal strength degradation of coke and the activity of hearth. However, traditional monitoring methods relying on furnace stoppage sampling have disadvantages such as strong sampling intermittence, large human random errors, and significant disruption to normal production, making it difficult to meet the intelligent and continuous monitoring demands of modern blast furnaces. To address this issue, this paper developed an online monitoring system for coke particle size at the blast furnace tuyere, aiming to achieve real time and accurate perception of coke geometric dimensions in closed high temperature environment using computer vision technology. The study proposed a lightweight detection model named ESG-YOLO （EffectiveSE GhostConv-YOLO）. This model introduced a GhostConv module in the backbone network for lightweight feature extraction, utilized an EffectiveSE mechanism to enhance edge perception, designed a weighted feature fusion （WFF） module to capture spatial correlations of cross scale features, and adopted the Focal-PIoU2 loss function to optimize localization regression. Experimental results show that the improved ESG-YOLO model reduces computational cost by 33.33% while increasing the mean average precision P_mA50 and P_mA50：95 to 98.10% and 90.90% respectively, and raising the F₁ score to 96.40%. These improvements significantly enhancing the model's robustness in low signal to noise ratio environments with high temperature, high brightness, and pulverized coal injection interference. Industrial field validation demonstrates that the system achieves an average inference speed of 106.8 F/s, enabling real time capture of coke particle size evolution during unsteady processes such as furnace stoppage and restart. By analyzing the dynamic correlation between circumferential particle size standard deviation and the permeability index, the result indicates that particle size fluctuation can serve as a quantitative prior indicator for characterizing circumferential inhomogeneity in the hearth. The application of this system effectively reduces manual sampling intensity and provides scientific basis and engineering support for online evaluation of tuyere raceway activity using machine vision.

Carbon footprint accounting for steel products relies on Life Cycle Assessment （LCA）. In practice, LCA applications in the steel industry have diverged into two functionally distinct forms. Analysis-LCA is anchored in physical material flows and serves compliance verification and process evaluation, whereas Message-LCA targets the transfer of carbon assets and low-carbon signalling, with considerable accounting flexibility. The concurrent use of these two forms has led to inconsistent accounting practices and undermined the credibility of low-carbon claims, a problem that has not received sufficient attention in existing literature.This paper focused on the operational mechanisms and potential risks of Message-LCA, with Analysis-LCA serving as a benchmark throughout the discussion as its well-established institutional framework and accounting principles provided a reference point for identifying the deviations inherent in Message-LCA. World Steel Association's mass balance approach and the Rocky Mountain Institute's Book & Claim system as the primary objects of analysis, the paper examined how these two tools amplified risks in the absence of adequate regulation. The former reallocated emission reduction attributes among different products through internal credit transfers, while the latter achieved a complete decoupling of emission reduction credits from physical steel products via certificate transactions. The findings indicate that these tools can incentivise process improvements through carbon premiums when properly regulated, but in the absence of institutional constraints, they tend to become vehicles for greenwashing and may discourage genuine low-carbon investment. Based on a comparative analysis of domestic and international regulatory frameworks and typical case studies, this paper proposes several optimisation pathways, i.e. drawing clear application boundaries between Analysis-LCA and Message-LCA, strengthening disclosure requirements for Message-LCA calculations, establishing a triple-ledger management system for steel enterprises, and setting a transition period with a gradual phase-out of virtual accounting tools. The core argument is that the conflict between the two LCA forms does not lie in technical details, but in their fundamentally different functional orientations. The solution is not to deny the market value of Message-LCA, but to design institutional rules that keep it operating within its proper boundaries.

To support enterprises in achieving low-cost carbon compliance during the 2024—2026 expansion and transition period of the iron and steel industry in China's carbon market,an optimal compliance cost model incorporating carbon emission intensity coefficient, carbon quota surplus and deficit volume as well as carbon price is established in accordance with the latest carbon quota allocation rules issued by the Ministry of Ecology and Environment. Three typical types of iron and steel enterprises including low-emission enterprises （S₁）, medium-emission enterprises （S₂） and high-emission enterprises （S₃） are selected for simulation analysis. The results indicate that S₁ enterprises obtain carbon quota surpluses due to their superior emission performance against industrial benchmarks with the carbon emission intensity deviation degree higher than 20%. S₂ enterprises with a deviation degree ranging from -10% to 15% face minor carbon quota deficits, while S₃ enterprises with the deviation degree lower than -10% bear prominent pressure for quota supplementation. Compared with three carbon trading strategies of annual supplementary purchase, one-time supplementary purchase and over-purchase strategy, the one-time supplementary purchase strategy locks the low carbon price of 85 yuan per ton in 2025. It effectively reduces capital occupation and total compliance costs of S₂ and S₃ enterprises, with cost savings of 1.393 5 million yuan and 4.455 million yuan respectively, which presents the optimal economic efficiency. Based on the research findings, differentiated compliance schemes are proposed at the enterprise level,a collaborative trading platform is suggested to be constructed at the industrial level, and improvements on quota allocation systems and supporting carbon financial mechanisms are advocated at the policy level. This study provides practical approaches and decision-making references for the efficient low-carbon transformation of the iron and steel industry.