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Currently, the typical charge structure for blast furnace smelting of vanadium–titanium magnetite (VTM) is the addition of acidic pellets, high‐basicity sinters, and lumps. To increase the percentage of pellets entering the blast furnace, it is necessary to transfer the basicity burden to the pellets. In this study, the effect of basicity on the phase transition and oxidation hardening mechanism of VTM pellets is investigated. In the results, it is indicated that when the preheating temperature is 950 °C, the preheating time is 15 min, the roasting temperature is 1260 °C, and the roasting time is 15 min, with the basicity (CaO/SiO2) increasing from 0.08 to 1.3, the compressive strength of pellets shows a trend of "increasing first and then decreasing," with the highest value reaching 3159 N pellet−1 at basicity of 0.5. As the basicity increases, calcium ferrate can be generated by CaO in the liquid phase with Fe2O3 in addition to silicate with SiO2, which will increase the amount of the liquid phase. With the increase of basicity, the oxide‐bonded induration is gradually weakened, and the slag‐bonded induration is gradually enhanced. A moderate amount of liquid phase can play the role of bonding and filling, thereby improving compressive strength. [ABSTRACT FROM AUTHOR]

The elucidation of the deadman's behavior and the interaction between slag–iron–coke within the blast furnace hearth are essential for the realization of low‐carbon and safe production. In this review, the macrostate of the deadman, the interactions between slag–iron–coke, carburizing behaviors, and renewal mechanisms are comprehensively examined. First, the formation and state of the deadman, voidage, and the distribution of coke sizes within the blast furnace hearth are characterized. The average coke particle size ranges from 20 to 30 mm, and the deadman void fraction of 30–50%. Second, the interaction between slag–iron–coke as well as the occurrence state of the mineral layer at the interface within the deadman is elucidated. The ash composition and content of coke are the key factors affecting the slag–iron–coke interaction and interface phase composition. Third, the influence exerted by critical factors such as the physical properties of the carbon source, molten iron, and temperature on the carburizing behavior are analyzed, with the renewal mechanisms of the deadman also being disclosed. Finally, three future focal areas are proposed: characterization and intelligent monitoring of deadman permeability, analysis of slag–iron–coke properties and interface mineral layers control, and in‐depth analysis of deadman renewal and carbon carburization in molten iron. It is anticipated that the studies will enhance the comprehension of deadman behavior and the interactions between slag–iron–coke, thereby fostering the blast furnace's sustainable development. [ABSTRACT FROM AUTHOR]

Analyzing the wetting behavior between carbon brick and molten iron in a blast furnace is crucial for understanding prolonging the furnace's lifespan. This study investigates the wetting behavior between microporous carbon brick and molten iron. The contact angle between the carbon brick and molten iron is measured at various temperatures and carbon saturation conditions, while the microscopic morphology of the reacted interface is examined. Furthermore, the wetting mechanism of molten iron on the carbon brick surface is elucidated. The findings reveal that both the microporous carbon brick and molten iron remain in a never‐wetting state within the furnace. As the temperature rises from 1150 to 1450 °C, the contact angle decreases from 138° to 128°, whereas the initial carbon content in the molten iron increases from 2.6 wt% to 4.1 wt%. Additionally, the initial contact angles gradually increase from 128.3° to 133.6°, with final equilibrium contact angles of 119.2° to 127.0°, indicating a nonwetting state. The carbon dissolution reaction occurs within the carbon matrix region of the microporous carbon brick prior to carbon saturation in the molten iron. Conversely, the presence of a ceramic phase in the ceramic area hampers both chemical erosion and physical penetration of the molten iron. [ABSTRACT FROM AUTHOR]

Investigating the presence of a Ti(C,N) protective layer in molten iron is of great significance for achieving low carbon and safe production in blast furnaces. This study focuses on analyzing the high temperature dissolution experiment of TiC0.3N0.7 in molten iron to elucidate the kinetics and mechanisms involved, as well as strategies for regulating its dissolution. The results reveal that the dissolution reaction of TiC0.3N0.7 is predominantly influenced by the temperature and flow speed of the molten iron. The dissolution process can be categorized into two stages: dissolution reaction and physical penetration. Diffusion mass transfer is the dominant factor controlling the dissolution of TiC0.3N0.7, with an apparent activation energy of 60.15 kJ/mol. Upon contact with molten iron, dendritic penetration of TiC0.3N0.7 particles occurs, starting from the edges. To enhance the stable presence of TiC0.3N0.7, recommendations include reinforcing furnace cylinder cooling, reducing the heat transfer coefficient of the blast furnace hearth's resistant material, increasing the carbon content of the molten iron, and decreasing the sulfur content of the molten iron. [ABSTRACT FROM AUTHOR]

Blast furnace smelting is a traditional iron-making process. Its product, hot metal, is an important raw material for the production of steel. Steelmaking efficiency can be improved and steel product quality can be stabilized by using proper hot metal. Sulfur is an important indicator reflecting the quality of hot metal, it is necessary to establish an accurate prediction model to predict the sulfur content of hot metal, to effectively guide the production process. There is a non-linear relationship among the factors influencing the desulfurization effect during the blast furnace smelting process, and the back propagation neural network (BPNN) model has a strong ability to solve nonlinear problems. However, BPNN has the disadvantages of slow convergence speed and easy to fall into local minima. To improve the prediction accuracy, an improved algorithm combining Kmeans and BPNN is proposed in this paper. The study showed that compared with the BPNN model and case-based reasoning (CBR) model, the Kmeans-BPNN model has the lowest RMSE and MAPE values, which indicates a high degree of fit and a low degree of dispersion. The Kmeans-BPNN model has the largest HR value, which indicates the highest prediction accuracy. The proposed Kmeans-BPNN prediction model achieves a hit rate of 96%, which is 4.5% higher than before the improvement. It can effectively improve the prediction accuracy of hot metal sulfur content. [ABSTRACT FROM AUTHOR]

As essential materials, iron and steel, which form the core of many national economies, guarantee the survival and development of the country. However, the iron and steel industry is also a typical example of an industry with high energy consumption and high pollution levels. Against the backdrop of a double carbon and green environment, the steel industry still needs to achieve high‐quality development. The sintering and pelletizing processes are one of the limiting links that need to be broken through. This article focuses on the source, change process, and emission modes of sulfur in the sintering and pelletizing processes, and also systematically introduces the migration behavior and law of sulfur, along with several typical desulfurization processes. Finally, the future green development of the iron and steel industry is considered. [ABSTRACT FROM AUTHOR]

The shape of shaft furnace is a crucial feature of direct reduction processes, as it affects both particle and gas flow during production. However, current knowledge on the impact of furnace shape on particle flow is limited. Herein, the discrete element method is employed for numerical simulations, in which two different methods of varying the wall angle (i.e., changing the radius or the height) are utilized to investigate the effect of wall angle on the flow behavior of particles in a shaft furnace. The effect of wall angle under different combinations of radius and height on the transformation of the particle flow pattern is innovatively examined, compared to previous studies on charging particles and internal furnace conditions. It is demonstrated in the results that the wall angle of the shaft furnace has a significant influence on the transformation of particle flow mode, with a reduction in the wall angle facilitating the transformation of particle flow mode to mass flow. Furthermore, it is shown in the study that different methods of changing the wall angle have varying effects on the transformation of particle flow mode. [ABSTRACT FROM AUTHOR]

This study simulated the corrosion reaction of S-carbon bricks in a hearth at different carbon contents, flow velocities and temperatures, and their macroscopic and microscopic morphologies were observed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that the dissolution of elemental carbon from carbon bricks into molten iron was a rate-controlled reaction. Increasing the temperature to around 1500 °C and decreasing the carbon content to around 4.5% reduced the saturated solubility of carbon in molten iron, and the erosion degree and dissolution rate of the carbon bricks increased correspondingly. For the flow velocity, its increase promoted mechanical flushing and led to an increase in the convective heat transfer coefficient of molten iron, which would increase the hot-side temperature of the hearth sidewall, promoting carbon unsaturation in hot metal and the dissolution reaction. [ABSTRACT FROM AUTHOR]

A new tuyere small sleeve coating structure that balances the high thermal conductivity of the copper substrate with the high wear resistance of the protective layer was developed in this paper. This structure can achieve a low-carbon blast furnace by reducing the heat loss from the tuyere. The 3D model was established via Solidworks for modeling and Ansys for numerical simulation, the temperature field of the annular wear-resistant layer structure tuyere small sleeve with different widths of the wear-resistant layer was analyzed and compared with the temperature and stress field of traditional tuyere small sleeve. The results show that the design of the annular wear-resistant layer structure of the tuyere small sleeve is more effective. The new annular wear-resistant layer structure for the tuyere small sleeve results in a decrease of 24 K in the average temperature of the wear-resistant coating. The comparison of this structure with tuyere sleeves without wear-resistant coatings shows a 16.7% reduction in heat loss, improves the wear resistance of the tuyere, providing new technological ideas for low-carbon blast furnace production. Compared with the tuyere sleeve completely covered with a wear-resistant coating, the maximum thermal stress of this structure decreased from 624.98 Mpa to 427.99 Mpa, resulting in a reduction of 31.5%, which is beneficial for the service life of the tuyere sleeve. The copper surface temperature of the new tuyere small sleeve is in a safe range when the temperature is below 2273 K. [ABSTRACT FROM AUTHOR]

Understanding the heat transfer properties of the slag crust is critical to the safe operation of copper staves. The distribution of metallic iron and bubbles in the slag crust is detected by X‐ray computed tomography. The thermal conductivity of the slag crust is modified based on an effective thermal conductivity model and laser thermal conductivity measurements to predict the effect of metallic iron and bubbles on the heat transfer in the slag crust. The results show that the average volume fractions of metallic iron and air bubbles in the slag crust are 3% and 4.5%, respectively. The measured value is consistent with the trend of the effective thermal conductivity calculation model, and the calculation result of the Maxwell–Eucken effective thermal conductivity model is very accurate. Variations in the volume fraction of metallic iron in the slag crust have a greater effect on the thickness of the slag crust, while variations in the volume fraction of bubbles have a smaller effect on the thickness of the slag crust. It is recommended to keep it between 10 and 30 mm in blast furnace production to help improve the operational life of the copper stave. [ABSTRACT FROM AUTHOR]

The sulfur content of hot metal in a blast furnace is an important index that reflects the production effects and quality of the hot metal. Establishing an accurate prediction model for hot metal sulfur content can guide the production process. In the present study, the blast furnace production data were collected and then preprocessed using box plotting. Cross-validation was used in the training process of the model to improve the generalization performance and robustness of the model. Two models for predicting the sulfur content in hot metal were established based on extreme gradient boosting (XGBoost) and multilayer perceptron (MLP) algorithms. The results show that coal consumption (CC), coal ratio (CLR), and sinter consumption (SC) are all positively correlated with hot metal sulfur content. The oxygen enrichment rate (OER) was negatively related to hot metal sulfur content. Both the extreme gradient boosting (XGBoost) and multilayer perceptron (MLP) models predicted hot metal sulfur content effectively; however, the extreme gradient boosting (XGBoost) model had a higher hit rate, accuracy, and stability, with the hit rate achieving 95.07%. [ABSTRACT FROM AUTHOR]

In recent years, with the attention given to hydrogen reduction‐related technologies, the parameter indicators of direct reduction in the shaft furnace have gained importance. Herein, the numerical simulation of the particle flow field in the shaft furnace is investigated with the help of discrete element method (DEM) model. In contrast to the subregional modeling and the single particle shape study of the previous studies, this study innovatively uses the real shape of the particles and the overall structure of the vertical furnace for modeling. The transient characteristics of solid particle flow under ten lump ore ratios and three shapes are considered. The results show that the mass fraction and the shape of lump ore have little effect on the particle falling speed, but have a significant effect on the particle segregation behavior. In addition, the void ratio responds to the permeability condition in the furnace, which is also influenced by the lump ore proportion and shape. [ABSTRACT FROM AUTHOR]

Precisely predicting the hopper discharge rate and trajectory is of great significance for industrial processing of granular materials. This study uses the DEM (Discrete Element Method)-based open-source software LIGGGHTS to analyze the flow behavior of spherical particles in six cone-shaped hoppers with different outlet shapes (circle, triangle, square, rectangle, pentagon and hexagon) with the various opening area. It was found that the particle flow velocity and mass flow rates are mainly determined by the outlet areas, while the outlet shape have an obvious influence on the particle trajectory which determines the stagnation area in the hopper. The results of the present study can provide meaningful guidance for the optimization of industrial hopper structure design and control. [ABSTRACT FROM AUTHOR]

HIsmelt is well suited for smelting vanadium–titanium magnetite due to its flexibility in feedstock selection and tolerance to high viscosity slag, compared with the blast furnace. In this work, the effect of smelting time on the distribution behavior and recovery rates of vanadium and titanium in HIsmelt smelting of vanadium–titanium magnetite was investigated by experiment for the first time. The relationship between slag viscosity and temperature at different smelting times was further revealed by thermodynamic calculations. The experimental results show that extending the smelting time increases the FeO content in the slag, the LV rose from 0.66 to 5.02, the LTi declined from 206.90 to 114.86, the shorter smelting time is favorable for increasing the recovery ratio of vanadium and titanium in metal and slag. In addition, slag viscosity decreases with increasing smelting time. The precipitation of high melting point titania spinel and CaTiO3 phases is responsible for the significant increase in slag viscosity at 1300 °C. [ABSTRACT FROM AUTHOR]

The thickness of the carbon bricks is one of the important factors of the longevity of the blast furnace. Herein, a large number of brittle carbon bricks in the hearth sidewall and the continuous rectangle‐shape floating refractory in residual iron are found during the blast furnace hearth dissection. The occurrence state of the carbon brick is characterized through chemical analysis, X‐ray diffraction (XRD), and scanning electron microscope (SEM)–energy‐dispersive X‐ray spectroscopy (EDS). The contents of K, Na, Cl, Zn, and Fe in brittle carbon bricks are relatively high, and a large number of large‐scale Al2O3 phases and nepheline appear in the floating carbon brick. It indicates that K, Na, Cl, Zn, and Fe are major causes for the serious erosion of the carbon brick, and the floating carbon brick may come from brittle carbon bricks on the sidewall. In addition, the source of Al2O3 and the consumption pathway of SiO2 and ZnO in floating refractory in residual iron are analyzed. Finally, the disappearing mechanism of carbon brick is proposed, which is that the carbon bricks floated up to the tuyere and burnt. [ABSTRACT FROM AUTHOR]

High-alumina fly ash microbeads and steel slag were used as main raw materials to synthesize feldspar porous ceramics via high-temperature solid phase sintering by adding pulverized coal as a pore-forming agent. The effects of the steel slag and pore-forming agent on the apparent porosity and flexural strength of porous ceramics were investigated. The phase composition and microstructure of porous ceramics were characterized using X-ray diffraction and scanning electron microscopy, and the results indicated that the added amount of steel slag was only related to the amount of liquid phase formed in porous ceramics. The higher the amount of steel slag added, the more the liquid phase formed. At the same sintering temperature, the higher the pore former content, the higher the porosity of the porous ceramics and the lower the bending strength. When porous ceramics were sintered at 1160 °C steel slag melted and fly ash microsphere structures were formed. When the porous ceramics were sintered at 1190 °C, the fly ash microsphere structure disappeared. After the internal liquid phase of the ceramic was formed, the lower the sintering temperature, the larger the porous ceramic structure factor, the more sensitive the flexural strength to changes in porosity and the higher the theoretical strength of ceramic densification. Moreover, as the sintering temperature decreased, the network structure formed during the reaction of fly ash microbeads with CaO greatly increased the flexural strength of fly ash ceramics. When the sintering temperature, sintering time and pore former content were 1170 °C, 120 min, and 10%, respectively, the obtained porous ceramics presented superior apparent porosity and flexural strength (49.21% and 12.88 MPa, respectively), and the main crystalline phase of porous ceramics was anorthite featuring pore size ranging from 5 to 50 μm. [ABSTRACT FROM AUTHOR]

Steel slag, clay, quartz, feldspar, and talc were mixed to prepare steel slag ceramics. Crystalline phase transitions, microstructures, and the main physical-mechanical properties (water absorption, linear shrinkage, and flexural strength) of steel slag ceramics for various MgO/Al2O3 ratios were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mechanical testing. The results indicated the significant effect of the MgO/Al2O3 ratio on these properties. A decrease in the MgO/Al2O3 ratio resulted in a major crystalline phase transformation from quartz and pyroxene phases to quartz and anorthite phases. High MgO content facilitated production of pyroxene phases. High Al2O3 content favored production of anorthite phases. The water absorption of all the samples (below 0.5%) met the Chinese national standard requirements. Samples with an MgO/Al2O3 ratio of 0.6 exhibited excellent flexural strength, reaching 62.20 MPa. FactSage software was used to predict batch viscosity, which increased with decreasing MgO/Al2O3 ratios. [ABSTRACT FROM AUTHOR]

In this study, SiO2–Al2O3–CaO–MgO steel slag ceramics containing 5 wt % MgO were used for the preparation of ceramic bodies, with the replacement of 5–20 wt % quartz and feldspar by fly ash. The effect of the addition of fly ash on the sintering shrinkage, water absorption, sintering range, and flexural strength of the steel slag ceramic was studied. Furthermore, the crystalline phase transitions and microstructures of the sintered samples were investigated by XRD, Fourier transform infrared (FTIR), and SEM. The results showed that the addition of fly ash affected the crystalline phases of the sintered ceramic samples. The main crystal phases of the base steel slag ceramic sample without fly ash were quartz, diopside, and augite. With increasing fly ash content, the quartz diffraction peak decreased gradually, while the diffraction peak intensity of anorthite became stronger. The mechanical properties of the samples decreased with the increasing amount of fly ash. The addition of fly ash (0–20 wt %) affected the optimum sintering temperature (1130–1160 °C) and widened the sintering range. The maximum addition amount of fly ash should be 15 wt %, for which the optimum sintering temperature was 1145 °C, water absorption was 0.03%, and flexural strength was 43.37 MPa higher than the Chinese national standard GBT 4100-2015 requirements. [ABSTRACT FROM AUTHOR]

Red mud is a kind of by-product generated in alumina production and typically contains some rare metals like Sc and Ga. In this study, Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) and Electron Probe Micro-Analysis (EPMA) were used to investigate the affinities of Sc and Ga with the major elements including Fe, Al, Si, Ti and Ca existed in red mud. Combined the mapping analyses of high mass resolution of ToF-SIMS with individual spot and mapping analyses of EPMA, the substitution of scandium and gallium for these major elements should follow the order of Ti > Fe > Al > Si and Fe > Al > Ti > Ca > Si, respectively. Scandium has an apparent enrichment in the mineral phases of anatase, hematite and goethite. The hetero-valent isomorphism of 4Sc 3+  → 3Ti 4+ plays a critical role in substitution of Sc 3+ into the anatase structure and is different from that of Sc 3+  → Fe 3+ occurred in hematite or goethite. Part of scandium is also found to be existed in silicon-rich minerals of quartz or zeolite. Gallium is closely coordinated with ferrum and aluminum, suggesting that it can proxy for these elements in the crystal lattices of hematite, goethite and gibbsite. All the observations are fundamental clues to the extraction technology of scandium and gallium from red mud. [ABSTRACT FROM AUTHOR]

Red mud, fly ash and oil shale residue are all industrial solid wastes with a huge discharging throughout the world, causing serious environmental problems. In this paper, the microstructure of red mud-fly ash blended cement during hydration process was observed by NMR, IR and SEM in an attempt to understand the reaction mechanism of the hydrates mixed with oil shale calcined at 400°C and 700°C. As the reaction progress, the coordination of Al (IV, V, and VI) mostly transfers to IV when the paste mixed with oil shale calcined at 700°C. However, a number of 6-coordinated Al still occur in the hydrated paste mixed with oil shale calcined at 400°C. Under the effect of alkaline, generated from the hydration of clinker, a certain amount of Si and Al atoms are dissolved or hydrolyzed from aluminosilicate to generate geomonomers in solutions and then polycondense to form networks. It is indicated that the distortion degree of [SiO4] and [AlO4] tetrahedra play a significant role during hydration process. [ABSTRACT FROM AUTHOR]

The slag, iron and coke in the deadman are extremely difficult to obtain in regular production. In this study, a commercial blast furnace was shut down and the samples were adopted systematically through a dissection study. The image processing method was also involved to clarify the macroscopic morphology of the deadman coke and the coke size distribution as well as the variation of the deadman voidage. It was found that the average size of coke was distributed in "M-shape" and voidage of deadman decreased with the increase of distance to the hearth wall in the horizontal direction. The voidage in the middle and lower of the vertical deadman was the largest and the average size of coke decreased with the increase of the distance to the taphole centerline in the height direction. In addition, the formation mechanism was analyzed, including carburization with hot metal, coke graphitization, the erosion of slag, hot metal, gas flow, etc., which provided an important reference for the high efficiency and low carbon smelting of the blast furnace. • Coke size decreased gradually and the deadman voidage increased in the height direction of the hearth. • Coke size distributes in "M-shape" while voidage in "V-shape" in the horizontal direction. • Main ways of coke consumption are carburization reaction and consumption in the raceway zone, followed by graphitization and the washing of hot metal. • The consumed coke was replaced by the "new" coke falling from the upper loose coke zone to update the deadman. [ABSTRACT FROM AUTHOR]