Vanadium–titanium magnetite is a critical strategic polymetallic mineral resource in China, and blast furnace smelting represents the dominant large-scale industrial process for its utilization. The melting and fluidity properties of titanium-bearing blast furnace slags (TBFS) directly govern stable blast furnace operation and the recovery efficiency of vanadium–titanium resources. This paper systematically reviews research progress on the melting and flow characteristics of TBFS. The influences of main components (TiO2, CaO/SiO2, MgO, Al2O3), trace oxides, and strongly reduced products TiC and TiN on slag mineral phases, break point temperature (TBr) and viscosity are summarized. Combined with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman characterizations and FactSage thermodynamic calculations, the inherent mechanisms are revealed from the perspectives of microstructural network polymerization and crystalline phase precipitation. TiO2 exerts dual effects: it depolymerizes the silicate network to reduce slag viscosity while promoting the precipitation of high-melting-point perovskite. Al2O3 intensifies network polymerization and impairs slag fluidity. MgO, basicity, MnO and BaO can decrease slag viscosity. Solid particles of TiC and TiN generated under the strong reducing atmosphere inside blast furnaces drastically increase slag viscosity and Tbr. This paper proposes that future research should focus on slag systems with higher TiO2 contents, so as to provide theoretical support for the high-efficiency blast furnace smelting of VTM and resource utilization of titanium-bearing slags.

To improve the poor and unstable dephosphorization of 65Mn high-carbon steel in a single-slag basic oxygen furnace (BOF) process with a high-carbon end point, a multi-constraint slag design strategy was established by combining FactSage calculations, industrial trials, and slag microstructural characterization. In the CaO-SiO2-FeO-MgO-Al2O3 system, feasible slag compositions were screened by jointly considering liquidus temperature, apparent viscosity, and dephosphorization potential. With MgO and Al2O3 fixed at 8 wt% and 3 wt %, respectively, the optimal slag window was determined as 34-38 wt% CaO, 17-20 wt% SiO2, and 20-24 wt% FeO, corresponding to a basicity (R--CaO/SiO2) of 1.8-2.2, under the constraints of liquidus temperature below 1350 degrees C and apparent viscosity at 1400 degrees C below 0.5 Pa s. Industrial trials in a 120 t BOF demonstrated that controlling FeO at 20-24 wt% and basicity at 2.0-2.6 reduced the average end-point phosphorus from 0.026 wt% to 0.015 wt% and markedly improved process stability. The dephosphorization rate(eta P) increased from 70.5% to 85.2%, while the phosphorus partition ratio (LP) increased from 62.0 to 78.0. Microstructural analyses revealed that efficient dephosphorization was associated with the preferential formation and continuous distribution of P-enriched 2CaO center dot SiO2-3CaO center dot P2O5(C2S-C3P) solid solutions, whereas the enrichment of FeO-MnO-MgO divalent-oxide solid-solution phases (RO phases) and Fe-rich phases reduced the effective basicity and hindered mass transfer. Finally, a slag prediction model coupling thermodynamic calculations with mass and energy balances was established to output recommended basicity and FeO control windows, a target end-point temperature, and the predicted end-point phosphorus, offering practical guidance for the stable production of high-carbon low-phosphorus steel.

Lump ore reduction generates fines that can induce furnace hanging or slipping. Reducing this degradation is key to maintaining stable operation. To address the degradation problem of lump ores during direct reduction in hydrogen-based shaft furnaces, this study systematically investigated the effects of reduction temperature and reduction time on the degradation behavior of three lump ores with distinct crystal structures under HYL atmosphere. The phase evolution, thermal decomposition characteristics and microstructural damage mechanisms during reduction were elucidated. The results showed that all three lump ores exhibited the most severe degradation after 60 min of reduction at 700 °C, with reduction degradation index values below 3.15 mm (RDI−3.15mm) of 32.50%, 15.17%, and 22.42% for Lump Ore 1, Lump Ore 2, and Lump Ore 3, respectively. During isothermal reduction at 500 °C, pronounced degradation occurred in all three ores at around 20 min (RDI−3.15mm: 33.09%, 18.09%, and 8.85% for Lump Ore 1, Lump Ore 2, and Lump Ore 3, respectively). Microscopic mechanism analysis revealed that dehydration of lump ores with high crystal water content caused structural damage, which was coupled with phase transformation stresses during reduction and led to severe degradation. In porous lump ore, stress was more readily dissipated and crack propagation was effectively buffered. In contrast, dense lump ore was prone to stress accumulation caused by locally nonuniform reduction, ultimately resulting in penetrating cracks. This study clarifies the degradation behavior of the three lump ores under different reduction regimes and reveals the evolution of phases and microstructures during reduction, providing a theoretical basis for stable operation of hydrogen-based shaft furnaces.

High-alumina slags in chromium-bearing pyrometallurgical processes require reliable control of melting behavior and fluidity. In this work, the effects of Cr2O3 and MnO on the melting temperature and viscosity of CaO-SiO2-MgO-Al2O3 slags were investigated using in situ hot-thermocouple measurements and rotating-cylinder viscometry, with FactSage 8.1 calculations as thermodynamic support. Experimentally, the melting temperature increased by similar to 60 degrees C for each 5 wt.% Cr2O3 added (5-15 wt.%), and rose from 1500 degrees C to 1545 degrees C as MnO increased from 3 wt.% to 9 wt.%. Cr2O3 significantly increased viscosity (2.39 Pa s at 1600 degrees C for 5 wt.% Cr2O3 vs 0.37 Pa s without Cr2O3) and the apparent viscous-flow activation energy, suggesting enhanced network polymerization and/or increased solid-phase tendency. In contrast, MnO addition reduced viscosity (0.99 to 0.64 Pa s at 1450 degrees C for 0-6 wt.% MnO), consistent with depolymerization of aluminate/silicate structural units. The quantified trends provide guidance for balancing slag fluidity and operating temperature windows in high-alumina industrial slags containing Cr and Mn.

Municipal solidMunicipal solid waste incineration fly ash waste incinerationElectric arc furnace melting fly ash (MSWI-FA) has the prominent issues of high content of heavy metals and chlorides, significant environmental hazards, and the substantial challenges in achieving large-scale and harmless treatmentHarmless treatment. This study employs a 50 kVA pilot-scale DC electric arc furnace (EAF) melting experiment to investigate the impact of water-washingWater washing and Na2CO3 additionNaCO addition on the vitrified product (VP) generated during the harmless treatmentHarmless treatment of MSWI-FA via EAF melting. The results demonstrate that water-washingWater washing significantly reduces the chloride content in MSWI-FA, achieving removal efficiencies of 95.2

Chromite pellets have become the mainstream burden for electric furnace smelting of ferrochrome. However, raw chromite powder generally exhibits poor pelletizing performance, resulting in insufficient green pellet strength and inadequate consolidation strength.To tackle these issues, high-pressure grinding rolls (HPGR) were adopted for chromite pretreatment. The effects of HPGR and conventional ball milling on the physical properties, particle size distribution, green pellet performance, and thermal consolidation strength of chromite were systematically compared. Experimental results indicated that compared with ball milling pretreatment, HPGR pretreatment could broaden the particle size distribution and refine fine fractions of chromite,forming a denser particle packing structure. HPGR pretreatment alleviated bentonite aggregation, promoted uniform dispersion of bentonite and mineral fines, and strengthened capillary force as well as interparticle bonding. Moreover, the optimized packing structure enhances interfacial reaction activity and promotes crystal bridge formation, further elevating the comprehensive strength of chromite pellets. Under identical thermal conditions, pellets prepared with HPGR pretreatment exhibited a preheating strength 100 N/P higher than those with ball milling pretreatment, while their roasting strength was elevated by over 400 N/P.

The phase composition at the slag-iron interface and the distribution behavior of titanium, vanadium, chromium and silicon between hot metal and Ti-bearing electric furnace slag were thoroughly explored. The basicity range for the anosovite phase region was defined by using a phase diagram and a minimum smelting temperature was set at 1540 degrees C. Thermodynamic calculations demonstrate that the activities of TiO2 and SiO2 in the slag decrease with increasing basicity, while those of V2O3 and Cr2O3 increase. Similarly, the activities of [Ti] and [Si] in the molten metal decrease, while those of [V] and [Cr] rise with increasing basicity. As basicity increases, the distribution ratios, LTi and LSi decrease, whereas LV and LCr increase. Significantly, the recovery efficiencies of vanadium and titanium are improved with higher basicity. The primary phases identified in the slag include anosovite, diopside, and titanium spinel. However, when the basicity exceeds 0.8, the formation of the perovskite phase becomes less favorable, suggesting that basicity should be maintained at or below 0.8.

The low-carbon transition of the iron and steel industry may intensify competition for regional water resources. While carbon emissions are well-studied, systematic assessments of the industry's life cycle water footprint (LCWF) remain limited. To address this knowledge gap, four representative steel production routes: conventional blast furnace-basic oxygen furnace route (BF-BOF based Route 1) and three EAF-based routes (DRI+scrap-based Route 2, full scrap-based Route 3 and China-style HM+scrap-based Route 4) are selected. The LCWFs based on 1 t of steel tubes of four routes are systematically quantified by integrated life cycle assessment and water flow network analysis. The results reveal that EAF-based routes achieve water-saving potentials of 1.350-2.363 t H2O compared to BF-BOF based routes considering the LCWFs of 17.028, 15.678, 14.664, and 14.818 t of Routes 1-4 respectively. Route 3 exhibits the lowest LCWF, followed by Route 4 and Route 2, indicating that HM outperforms DRI in water conservation efficacy under equivalent scrap ratio (70 %). From process and material-energy based perspectives, steelmaking sub-processes (3.067-9.079 t) and full-process electricity (6.071-11.534 t) emerge as the predominant contributor to LCWF. Among eight electricity structures, under wind power mode, the system achieves the most substantial WF mitigation, particularly for Routes 2-4. These routes exhibit approximately 50 % reduction in LCWFs, with the LCWF ranging from 5.845 t (minimum) to 8.150 t (maximum). When integrated wind or solar-based electricity, EAF-based route offers synergistic water conservation and decarbonization benefits.

The addition of MgO is widely used to improve the high-temperature metallurgical performance of iron ore pellets, including vanadium–titanium magnetite pellets. However, the effects of MgO addition on the oxidation consolidation and low-temperature reduction disintegration behavior of vanadium–titanium magnetite pellets remain unclear. Therefore, magnesium-containing vanadium–titanium magnetite pellets were prepared to systematically investigate their oxidation and reduction behaviors, especially on the reduction disintegration mechanism. The pellets strength initially increased and then decreased as the addition of MgO increased. When the MgO addition increased from 0 to 2.0 wt.

The calcification roasting-sulfuric acid leaching process is an effective technique for the extraction of vanadium from vanadium-titanium magnetite (VTM). This method surpasses the sodium roasting-water leaching technique in the total utilization of iron, vanadium, and titanium. Current studies on the calcification roasting-acid leaching process has primarily concentrated on improving efficiency. At the same time, limited attention has been given to the underlying mechanisms of vanadium migration behavior and the transition of the vanadiumbearing phase during the roasting process. This study methodically examines the impact of calcific agent on leaching efficacy, phase transformation, and the migration behavior of vanadium and iron. The experimental results reveal that adding calcific agents increases the basicity of the pellets, promoting the migration of vanadium and iron into the silicate phase. Compared with vanadium primarily exists in haplotypite and pseudobrookite phases. These phases exhibit weak reactivity with sulfuric acid, resulting in minimal dissolution of both vanadium and iron during acid leaching. Upon the addition of the calcific agent, the basicity of the pellet increases, which promotes the formation of calcium-containing silicates. This phase transformation facilitates the migration of vanadium and iron into the calcium-containing silicate. Calcium-containing silicates possess significantly higher reactivity with sulfuric acid compared to titaniferous phases. Consequently, the acid dissolution of the silicate phase enables vanadium and iron to transfer into the leachate, thereby markedly enhancing the vanadium leaching efficiency. The silicate phases exhibit greater reactivity with sulfuric acid, thereby enhancing the leachability of vanadium and iron. When the dosage of calcific agent reaches 2.0 %, the basicity of the pellets increases to 1.15, and the vanadium leaching efficiency rises to 74.89 %. There is still some vanadium remaining in the haplotypite and pseudobrookite phases that is difficult to leach out. A secondary calcification roasting process further drives the remaining vanadium into the silicate phase, and subsequent acid leaching yields an additional vanadium recovery of 51.73 %. Overall, the two-step calcification roasting-leaching process achieves a cumulative vanadium leaching efficiency of 87.88 %, offering new insights into the role of calcific agents in enhancing vanadium extraction from VTM.

Accurate prediction of endpoint temperature in electric furnace steelmaking is crucial for reducing energy consumption in steel industry. This study proposes an innovative hybrid framework integrating data processing, balanced weighted gaussian mixture model (BWGMM) clustering, residual enhanced wasserstein generative adversarial network (RWGAN), and particle swarm optimization (PSO) based ensemble learning. The BWGMM method categorizes data by grouping samples with similar high-dimensional characteristics. A RWGAN model processes the clustered data and trained a regression generator for endpoint temperature prediction. The PSO algorithm is employed to optimize an ensemble model, improving both generalization capability and predictive accuracy. The proposed model outperformed all reference models, achieving MAE, MAPE, and MSE values of 8.47, 0.52 %, and 322.92, respectively. Hit rates (HR) reached 68.91 %, 79.89 %, 84.79 %, 87.89 %, and 90.31 % at error margins of +5 degrees C, +10 degrees C, +15 degrees C, +20 degrees C, and +25 degrees C, respectively. Compared to other models, the proposed framework reduced MAE, MAPE, and MSE by an average of 61.43 %, 61.59 %, and 63.47 %, while improving hit rates at +5 degrees C, +10 degrees C, and +15 degrees C by an average of 51.22 %, 45.52 %, and 36.97 %, respectively. Results demonstrate that the proposed framework provides a reliable and effective solution for accurate endpoint temperature prediction in complex electric furnace steelmaking process.

Fluoride leaching is a promising and clean route for extracting titanium from Ti-bearing furnace slag (TBFS). This study systematically investigated the phase-controlled selective separation of Ti, with particular focus on the effect of the [NH4+]/[F-] molar ratio on Ti dissolution and impurity behavior. The results reveal two main controlling factors. First, the acidity (H+ concentration) governs the overall dissolution efficiency of TBFS, and higher acidity promotes complete slag decomposition. Second, the [NH4+]/[F-] molar ratio (0-0.5) controls the phase transformation of the products. Titanium selectively dissolves as stable TiF62-complexes, while Ca, Al, and Mg precipitate as distinct fluoride phases (MgAlF5 & sdot;1.5H2O, MgF2, AlF3, and CaMg2Al2F12). The presence of NH4+ promotes the formation of additional coordination compounds (NH4MgAlF6 and (NH4)3AlF6), further enhancing phase separation of impurities. Reactivity analysis indicates that FeTi2O5 is the most readily leached phase within the MxTi3-xO5 system. Under optimized [NH4+]/[F-] conditions, the Ti-rich leachate can be directly converted to TiO2 precursors ((NH4)3TiOF5 and (NH4)2TiOF4) through controlled ammonia hydrolysis. These findings provide mechanistic insights into selective Ti recovery from TBFS and demonstrate the potential of fluoride leaching for clean titanium resource utilization.

The molten salt chlorination process for producing TiCl4 inevitably generates molten salt chlorination residue (MSCR) that poses a serious environmental threat. Meanwhile, MSCR is rich in metal chlorides and rare earth chlorides, making it highly valuable for utilization. The industrial application of traditional hydrometallurgical processes has been impeded by the substantial generation of chlorination wastewater. Herein, a novel approach for thorough detoxification, complete desalination and efficient pre-enrichment of metal elements of MSCR by perovskite structure driven phase transformation-separation method was proposed. The elements migration mechanism revealed that, introducing sodium carbonate, metal chlorides were transformed to corresponding metal oxides, spinel, and calcium manganate under an air atmosphere at 900 °C. The formation of Can+1MnnO3n+1 perovskite structure in calcium manganate effectively immobilized heavy metal elements while enhancing the capture of rare earth elements. Through water leaching-filtration separation, high-purity NaCl was collected, and recovery efficiencies of 99.49% for scandium, 99.26% for yttrium, and 99.07% for cerium were achieved. Finally, the ions concentrations presented in toxic extraction solution of phase transformation products are all meeting the standards for Class IV groundwater quality (GB/T 14,848-2017). This innovative method holds promising commercial application prospects and can be extended to the comprehensive utilization of other salt-based solid waste.

High-alumina slags in chromium-bearing pyrometallurgical processes require reliable control of melting behavior and fluidity. In this work, the effects of Cr2O3 and MnO on the melting temperature and viscosity of CaO–SiO2–MgO–Al2O3 slags were investigated using in situ hot-thermocouple measurements and rotating-cylinder viscometry, with FactSage 8.1 calculations as thermodynamic support. Experimentally, the melting temperature increased by 60°C for each 5 wt.

Direct extraction of vanadium from vanadium titanomagnetite (VTM) by calcification roasting-sulfuric acid leaching can achieve the clean and efficient vanadium extraction. However, a large amount of vanadium extracted pellets (VEP) are generated after sulfuric acid leaching. Roasting VEP directly to prepare blast furnace charge offers a potential method for the economic recovery of valuable iron and titanium resources. However, VEP are porous, low strength and high sulfur content. There is a lack of systematic research on the preparation of blast furnace charge by VEP. This article thoroughly studied the VEP desulfurization and consolidation behavior during the direct roasting process and the reduction characteristic of roasted pellets. The results reveal that an appropriate amount of silicate phase connection bridges is key to maintaining high cold compressive strength and large porosity in roasted pellets. Additionally, these silicate phase connection bridges and large porosity are crucial factors for achieving roasted pellets with satisfactory physical and metallurgical properties. Roasted pellets with a cold compressive strength of 2593.8 N/pre and a sulfur content of 0.0033 % were prepared at 1250 degrees C for 25 min. The Reduction Swelling Index, Reducibility Index, and Reduction Degradation Index were 9.07 %, 81.13 %, and 96.89 %, respectively. Finally, a pilot-scale rotary kiln was successfully used to prepare roasted pellets with a cold compressive strength of 2649.0 N/pre and a sulfur content of 0.008 % at 1230 degrees C for 20 min.

Molten salt chlorination process in the titanium industry is difficult to apply on a large scale because of producing a large amount of environmentally polluting molten salt chloride slag. The phase transition method is an effective novel method to achieve the separation of the impurity components and recovery of NaCl from the molten salt chloride slag, which is mainly composed of ternary mixed molten salt NaCl-MgCl2-CaCl2. This study investigated how the physical properties of the liquid phase influence the separation behavior of NaCl during the phase transition of chloride salt slag. Molecular dynamics simulations were used to study the physical properties of the liquid phase of molten salt chloride slag with Na2SiO3 additive, including radial distribution function, ion self-diffusion coefficient, density and viscosity. The ternary mixed molten salt NaCl-MgCl2-CaCl2 system with oppositely charged ion pairs exhibits a more stable coordination structure, with the interaction strengths following the order Mg-Cl > Ca-Cl > Na-Cl. The recovery of NaCl at different temperatures was investigated by phase transition method using Na2SiO3 additive. The additive of Na2SiO3 leads to a decrease in the ionic self-diffusion coefficients, density and viscosity of the mixed molten salt. The determination coefficients R2 for the fitted models of density/viscosity (mixed molten salt with Na2SiO3) and NaCl recovery during the phase transition of molten salt chloride slag were 0.9626 and 0.9073, respectively. The regression equation describing the relationship between density and NaCl recovery showed better agreement. The experimental results provide a reliable validation of the calculated results. These research results provide important insights to solve the pollution problem of molten salt chloride slag.

Reducing raw materials consumption (RMC) in electric arc furnace (EAF) steelmaking process is beneficial to the reduction in resource and energy consumption. The conventional indicator of evaluating RMC only focuses on EAF inputs and outputs, neglecting the associations between smelting operations and RMC. Traditional methods of reducing RMC rely on manual experience and lack a standard operation guidance. A method based on association rules mining and metallurgical mechanism (ARM-MM) was proposed. ARM-MM proposed an improved evaluation indicator of RMC and the indicator independently showed the associations between smelting operations and RMC. On the basis, 1265 heats of real EAF data were used to obtain the operation guidance for RMC reduction. According to the ratio of hot metal (HM) in charge metals, data were divided into all dataset, low HM ratio dataset, medium HM ratio dataset, and high HM ratio dataset. ARM algorithm was used in each dataset to obtain specific operation guidance. The real average RMC under all dataset, medium HM ratio dataset, and high HM ratio dataset was reduced by 279, 486, and 252 kg/heat, respectively, when obtained operation guidance was applied.

The efficient recovery of iron, nickel and chromium from laterite nickel ore by the pyrometallurgy process is important for the stainless steel industry. In general, the increasing Al2O3 content of the low-grade laterite nickel caused the high melting temperature of slag and affected the recovery rates of valuable elements. The study on the element distribution behavior between slag and iron in the smelting process of high Al2O3-type low-grade laterite nickel ore has important guiding significance for efficient recovery of Cr and other alloying elements. In this study, the influences of slag composition on the distribution of elements between the high Al2O3 slag and molten iron were studied by thermodynamic calculations and high-temperature equilibrium experiments. The results indicated that for the CaO-SiO2-MgO-Al2O3-Cr2O3 slag system, with the increase of Al2O3 content, the sulfur distribution ratio between slag and iron decreased and the recovery of valuable elements decreased with the higher Al2O3 content. The distribution of Cr between iron and slag increased with the increase of MgO content but decreased with the increase of MnO content. Moreover, the S distribution ratio between slag and iron increased with the increase of MgO and MnO contents.

The existing blast furnace burden structure in China is mainly dominated by high-alkalinity sinter and acid pellets, with a relatively small proportion of lump ore blended in. Against the backdrop of the “dual-carbon” goals, iron and steel plants are under enormous pressure to save energy and reduce carbon emissions. Lump ore is directly extracted from mines and belongs to zero-carbon-emission blast furnace burden. Therefore, adjusting and optimizing the blast furnace burden structure by partially replacing sinter and pellets with lump ore is an important approach for iron and steel plants to reduce carbon emissions. Based on the metallurgical properties and decrepitation index of different types of lump ore as well as the proportion of lump ore charged into the blast furnace, and with full consideration of the interaction of the comprehensive metallurgical properties of the blended burden charged into the furnace, the metallurgical properties of sinter are adjusted to ensure good comprehensive metallurgical properties of the blended burden. By adjusting the blast furnace operation to an appropriate regime, the proportion of comprehensive lump ore in the charged burden has been achieved to be ≥28%, and the blast furnace fuel ratio to be ≤515 kg per ton of iron.

Currently, the grinding performance of porous metal-bonded diamond tools under liquid-cooled conditions has been extensively studied, but their grinding performance and wear mechanisms under dry conditions remain insufficiently explored. In this work, porous Cu-Sn-Ti diamond tools were used to grinding YSZ ceramics under dry conditions. And the effects of grinding parameters including grinding load, grinding speed, and grinding time on the tool's surface morphology, material removal rate (MRR), grinding ratio (G), and YSZ surface roughness (SR) were systematically investigated. The results indicated that during the dry grinding process, as the grinding loads increase, the attrition degree of diamond grits in the porous Cu-Sn-Ti tools gradually increase. With the increase of grinding loads, the inhibitory effect of pores on the adhesion of YSZ debris to the tool surface significantly decreased, and the adhesion degree of YSZ debris first increased and then decreased. Increasing grinding loads and grinding speeds were correspondingly elevated the proportion of severe fracture and detachment of diamond grits. When the grinding load and grinding speed were 15 N and 1000 rpm respectively, the detachment proportion of diamond grits reached the highest. At this time, the proportion of micro-fracture, severe fracture and detachment of diamond grits was 35:37:28. The most critical factors influencing the material removal rate, grinding ratio, and YSZ surface roughness of porous Cu-Sn-Ti diamond tools were grinding speed, grinding load and grinding time, respectively. The porous Cu-Sn-Ti diamond tool was suitable for use under low load (3 N) and high speed (1000 rpm), achieving MRR, grinding ratio, and YSZ roughness of 26.44 x 10(-3 )mm(3)/ s, 42.30, and 3.34 mu m, respectively. This work provides insights into the application of porous metal-based diamond tools under dry conditions.