Search Results (22)

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 (T_Br) 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. Full article

Titanium-bearing blast furnace slag is rich in high-melting-point titanium-containing minerals including perovskite, melilite and spinel, which result in the loss of titanium resources and hinder the comprehensive utilization of such slag. On this basis, combined with process mineralogy theories, this study adopted multiple characterization methods, including a polarized light microscope with transmitted and reflected light, XRD and EPMA. These simulations reveal that the bulk SiO₂ content dictates titanium distribution among the mineral phases, thereby laying a solid foundation for the subsequent experiments. Meanwhile, quantitative analyses were performed on the microstructure, mineral composition and perovskite grain size of the slag. The occurrence state and migration law of titanium in the slag were systematically investigated. The results show that the microstructure of titanium-bearing blast furnace slag presents a porphyritic structure at different SiO₂ levels. Its main mineral phases include perovskite, pyroxene, spinel and glass. Titanium is predominantly hosted in perovskite, with small amounts distributed in the pyroxene, spinel and glass phases. Reducing the SiO₂ content facilitates the formation and grain coarsening of perovskite and promotes the migration of titanium from pyroxene and glass into perovskite. When the SiO₂ content is 20%, the perovskite content reaches 44.3%. Among them, the proportion of grains larger than 40 μm is 59.94%, and the distribution ratio of titanium in perovskite is 86.78%. Under the experimental conditions of this study, 20% SiO₂ is the optimal level. These findings can provide a theoretical reference for the efficient separation and recovery of titanium from titanium-bearing blast furnace slag. Full article

Titanium-extracted tailing is a by-product generated during titanium-bearing blast furnace slag treatment process. The crystallization behavior of the titanium-extracted tailing during the cooling process is significant to its utilization for glass ceramics preparation. In this work, the CaO-SiO₂-Al₂O₃-MgO-TiO₂-FeO slag was used to explore the effect of CaO/SiO₂ ratios on titanium-extracted tailing crystallization. FactSage 8.2 calculation and mineralogical characterizations were conducted to investigate the phase and microstructure evolution during the slag cooling process. Single hot thermocouple technique (SHTT) was employed for in situ observation of the crystallization process of the slag during the cooling process. The obtained results indicated that the perovskite, melilite, spinel, diopside and anorthite phases would be crystallized during the cooling process when the CaO/SiO₂ ratios of the slag were 0.7–1.1. Increasing the CaO/SiO₂ ratio to 1.3 and 1.5 promoted the crystallization of olivine and merwinite phases, however, inhibited the crystallization of diopside and anorthite phases. The initial crystallization temperature and the liquid phase disappeared temperature of the slag enhanced with improving CaO/SiO₂ ratios. The initial crystallization temperature was controlled by perovskite phase precipitation when the CaO/SiO₂ ratios of slag reached 0.7–1.3. Whereas the initial crystallization temperature was controlled by the crystallization of spinel phase when the CaO/SiO₂ ratio of slag was 1.5. The incubation time for crystal nucleation reduced with increasing CaO/SiO₂ ratios that promoted slag crystallization. Moreover, increasing the CaO/SiO₂ ratio from 0.7 to 1.5 enhanced the critical cooling rate from 4 °C s⁻¹ to 11 °C s⁻¹. Full article

The present study explores the production of metallized titanomagnetite briquettes, with a view to addressing two key issues. Firstly, it seeks to address the growing shortage of high-quality iron-bearing raw materials. Secondly, it looks at how to meet the increasingly stringent environmental constraints. The conventional blast-furnace treatment of titanomagnetite is hindered by the formation of refractory Ti-rich slags. It is hereby proposed that a single-cycle briquetting process in conjunction with a thermal reduction route should be utilized. This approach enables precise regulation of the Fe/flux ratio. Experiments were conducted on a low-grade titanomagnetite concentrate (68.5% Fe) from the Pervouralsk deposit (Russia). Cylindrical briquettes (D 15–20 mm, h 8–10 mm) were subjected to a pressure of 300 MPa during the pressing process, with the utilization of diverse binders comprising rubber cement, CaO, graphite + water, and basic oxygen-furnace (BOF) slag + sodium silicate. Following an oxidative pre-heating process at 1300 °C for two hours, followed by a gas-based reduction process at 1050 °C for three hours, with a CO/N₂ ratio of 90/10, the products demonstrated an oxidation rate of 85–95% and a cold compression strength of 16–80 MPa. The highest observed strength (80 MPa) was obtained with a binder comprising CaO·MgO·2SiO₂ (diopside/merwinite), which forms a low-viscosity melt, fills 90% of pores and crystallizes as acicular Mg-SFCA-I during cooling. Conversely, the CaO·TiO₂ and FeO·TiO₂ + Fe₃C associations yield brittle structures and a maximum strength of 16 MPa. The optimum briquette (0.55% CaO, D/H = 20/10 mm) exhibited a 95.7% metallization degree, a compressive strength of 48.9 MPa, and dimensional changes within acceptable limits, thus fulfilling the requirements for electric arc furnace feedstock. Further research is required in the form of a full Life Cycle Assessment and pilot-scale testing. However, the results obtained thus far confirm that titanomagnetite briquettes with a binder consisting of CaO, MgO and SiO₂ are a promising alternative to pellets for low-carbon steelmaking. Full article

Ti-bearing blast furnace slag (TBS), a byproduct of vanadium–titanium magnetite smelting, serves as an important secondary resource for titanium recovery. However, the complex mineralogical composition and finely dispersed nature of titanium in TBS present significant challenges for efficient extraction. This review systematically examines four major titanium extraction routes: hydrometallurgical leaching, pyrometallurgical smelting, molten salt electrolysis, and selective precipitation, focusing on their limitations and recent improvements. For instance, conventional acid leaching suffers from acid mist release, a colloidal formation that hinders titanium recovery, and waste acid pollution. The adoption of concentrated sulfuric acid roasting activation effectively suppresses acid mist emission and prevents colloidal generation. Pyrometallurgical approaches are hampered by high energy consumption and substantial carbon emissions, which can be alleviated through the use of gaseous reductants to enhance reaction efficiency and reduce environmental impact. Molten electrolysis faces issues such as polarization and undesirable dendritic deposition; these are mitigated by employing liquid metal cathodes integrated with vacuum distillation to achieve high-purity titanium products. Selective precipitation struggles with strict crystallization conditions and low separation efficiency, though advanced techniques like supergravity separation show improved extraction performance. We propose an integrated technical strategy termed “Online conditioning driven by waste heat-mineral phase reconstruction-directional crystallization-optimized liberation.” This approach utilizes the inherent waste heat of slag combined with electromagnetic stirring to enhance homogeneity and promote efficient titanium recovery, offering a sustainable and scalable solution for industrial TBS treatment. Full article

TiC-bearing slag is an intermediate product in the titanium extraction process following the “high-temperature carbonization and low-temperature chlorination” method. It exhibits complex grinding characteristics, and traditional grinding methods often yield issues such as broad particle size distribution (PSD) and overgrinding, adversely affecting process efficiency. In this study, TiC-bearing slag was investigated as the raw material. Through methods such as SEM-EDS, MLA, and scientific experiments, we established quantitative relationships between mechanical inputs and product granulometry. The results indicate that the coexistence of TiC and pyroxene-group minerals leads to poor grinding selectivity, causing TiC to resist fracturing while pyroxene minerals are prone to overgrinding. Furthermore, the experiments demonstrated that high circulating-load grinding combined with staged sieving is most effective for producing narrow PSD products. This research explores the methods and paths for achieving controlled narrow PSD of TiC-containing slag in the crushing process, and providing data support for the selection of industrial-scale grinding processes. Full article

This study developed a hydrothermal-crystallization coupling strategy for selective titanium extraction from low-grade titanium-bearing blast furnace slag. Systematic parametric optimization revealed that an optimum titanium extraction efficiency of 92.3% was achieved under mild hydrothermal conditions. Phase evolution analysis demonstrated that the leaching residues comprised commercially valuable calcium oxalate hydrate and amorphous silica aggregates, while titanium primarily existed as stable Ti(OH)₂(C₂O₄)₂²⁻ complexes in the leachate. Subsequently, 99.4% of titanium in the leachate was precipitated through the hydrothermal decomposition method, and mixed-phase titanium oxides with a grade of 90.5% were obtained through alkaline washing. Comparative analysis highlights three notable advantages over conventional metallurgical processes: (1) selective extraction specificity for low-concentration titanium minerals, (2) process intensification through integrated hydrothermal-crystallization operations, and (3) environmental benignancy via reagent recyclability. Full article

Ti-bearing blast furnace slag (TBFS) can be converted to impurity bearing TiOSO₄ solution for TiO₂ pigment production. However, the H₂TiO₃ (MTA) hydrolyzed from the solution has too high Fe/V impurity to meet the standard for TiO₂ pigment. In this study, we found that Fe³⁺ and V³⁺ were easily hydrolyzed and entered the MTA lattice, and hence could not be removed by washing. Furthermore, Fe/V was hard to co-remove by the traditional reduction method. Therefore, the Fe/V non-hydrolysis condition (Ti³⁺ = 0.01 M, F = 3.0, T = 130 °C; Ti³⁺ = 0.01 M, F = 3.5, T = 150 °C) was determined by thermodynamic calculations. However, at these conditions, the Ti hydrolysis ratio was low or the reaction time was long. Therefore, a new two-step hydrothermal hydrolysis process was proposed. Step 1 (130 °C, 2 h) ensured the non-hydrolysis of V³⁺, and Ti was partially hydrolyzed to increase the H₂SO₄ concentration. Step 2 (150 °C, 2 h) ensured a high Ti hydrolysis ratio (>0.95) and short total reaction time (4–6 h). Finally, a high-purity MTA was obtained (Fe = 21 ppm, V = 145 ppm). These results provide new insights into the control of the hydrolysis of impurity ions in solutions and help to optimize the process of TiO₂ pigment preparation from TBFS. Full article

A porous geopolymer with adsorption and photocatalytic degradation functions was successfully developed by utilizing Ti-bearing blast furnace slag (TBBFS) as the raw material. The prepared porous geopolymers were characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectrometer, and Fourier transform infrared spectrum. Selective crystallization, water quenching, and natural cooling methods were employed to investigate the influences of these modifications on the applicability of TBBFS as a precursor for geopolymer synthesis. Water-quenched slag with amorphous content was prone to alkali dissolution, and the resulting geopolymer exhibited the highest adsorption capacity (97.18 mg/g) for methylene blue (MB) removal. Selective crystallization at 1400 °C generated a hybrid microstructure consisting of a non-cementitious CaTiO₃ crystallization phase and a cementitious amorphous fraction. The retention of CaTiO₃ in the final geopolymer enables a bifunctionality in adsorption–photodegradation. Particularly, the adsorption and photodegradation processes under various conditions were investigated. The superior removal efficiency for MB could be attributed to the synergistic effects between the geopolymer matrix and CaTiO₃, leading to an enhancement in the formation of hydroxyl radicals. The conversion of TBBFS into porous geopolymer offers an efficient and straightforward solution for slag utilization and dye removal. Full article

The extraction of titanium-bearing components in the form of CaTiO₃ is an efficient utilization of blast furnace slag. The photocatalytic performance of this obtained CaTiO₃ (MM-CaTiO₃) as a catalyst for methylene blue (MB) degradation was evaluated in this study. The analyses indicated that the MM-CaTiO₃ had a completed structure with a special length–diameter ratio. Furthermore, the oxygen vacancy was easier to generate on a MM-CaTiO₃(110) plane during the photocatalytic process, contributing to improving photocatalytic activity. Compared with traditional catalysts, MM-CaTiO₃ has a narrower optical band gap and visible-light responsive performance. The degradation experiments further confirmed that the photocatalytic degradation efficiency of pollutants by using MM-CaTiO₃ was 3.2 times that of pristine CaTiO₃ in optimized conditions. Combined with molecular simulation, the degradation mechanism clarified that acridine of MB molecular was stepwise destroyed by using MM-CaTiO₃ in short times, which is different from demethylation and methylenedioxy ring degradation by using TiO₂. This study provided a promising routine for using solid waste to obtain catalysts with excellent photocatalytic activity and was found to be in keeping with sustainable environmental development. Full article

As the byproduct in the smelting process of vanadium titano-magnetite, titanium-bearing blast furnace slag (TBFS) can be converted to a titanyl sulfate (TiOSO₄) solution containing MgSO₄ and Al₂(SO₄)₃ impurities via dissociation by concentrated H₂SO₄ (80–95%) at 80–200 °C, followed by leaching with H₂O at 60–85 °C. In this study, hydrated TiO₂ was prepared by hydrothermal hydrolysis of a Mg/Al-bearing TiOSO₄ solution at 120 °C and the hydrolysis law was investigated. The experimental results indicate that MgSO₄ and Al₂(SO₄)₃ accelerated the hydrolysis and significantly affected the particle size (increasing the primary agglomerate size from 40 to 140 nm) and dispersion (reducing the aggregate size from 12.4 to 1.5 μm) of hydrated TiO₂. A thermodynamic equilibrium calculation showed TiOSO₄ existed as TiO²⁺ and SO₄²⁻ in the solution, and MgSO₄ and Al₂(SO₄)₃ led to little change of [TiO²⁺], but an obvious decrease of [H⁺], which favored the hydrolysis process. At the same time, the coordination–dissociation mechanism of SO₄²⁻ and Al(SO₄)₂⁻ facilitated the lap bonding of Ti-O-Ti, promoting the growth of hydrated TiO₂ synergistically. Full article

The viscosity of high-titanium blast furnace slag with different TiO₂ content, Al₂O₃ content, and basicity was measured at 1653–1773 K using the rotational cylinder method. The phase composition of the slag is measured by XRD. Phase diagram of the slags is calculated by FactSage software. Ionic network structure of the slags is analyzed by FT–IR. Results show that TiO₂ depolymerizes the silicate network structure, reducing viscosity at high temperature, while increasing Al₂O₃ content generates a more complicated silicate, increasing viscosity. Basicity affects viscosity, with higher basicity resulting in lower viscosity above 1733 K. Perovskite significantly affects the viscosity of slag. This study provides an in-depth understanding of the relationship between the composition and viscosity of high-titanium blast furnace slag, which is very important for improving production efficiency. Full article

Slag compositions are significant for the viscosity of blast furnace slag. An improved Urbain model (IUM) was proposed by introducing R₅ ((X(CaO) + X(MgO) + 2X(TiO₂))/(2X(SiO₂) + 3X(Al₂O₃))) and N (X(MgO)/3X(Al₂O₃)) as the model parameters. By comparing IUM with other models, the model parameters of R₅ and N are more reasonable and suitable for TiO₂-bearing blast furnace slag, and IUM for predicting viscosity has a higher precision, and its relative error is only 10%. The viscosity isolines of the CaO–SiO₂–15%Al₂O₃–MgO–2.5% TiO₂ system were plotted, and the results show that the viscosity center of the slag is between R_w2 (w(CaO)/w(SiO₂)) = 0.77–1.39 and N_w (w(MgO)/w(Al₂O₃)) = 0–1.37, the value of the viscosity center is 0.3 Pa·s, the viscosity increases gradually from the center to the outside, and the viscosity of the slag gradually decreases with the increase in N_w and R_w2. Furthermore, FTIR (Fourier Transform Infrared Spectroscopy) analysis was carried out in order to understand the mechanism between the slag structure and viscosity. With the increase in N_w and R_w2, the peak values of the symmetrical stretching vibration of non-bridging oxygen in the Si–O tetrahedral structure of slag decrease, and the slag structures depolymerize, which leads to the decrease in the viscosity of the slag. Full article

Blast furnace–basic oxygen furnace (BF–BOF) process is the predominant method for smelting vanadium titano-magnetite (VTM) in China. Hydrogen-rich (H₂-rich) gas injection in BF is considered as an important way to reduce CO₂ emission under the background of low carbon metallurgy. In this paper, the softening–melting behaviors of VTM sinter in H₂–rich gases were investigated by the method of determination of its reduction softening drippinger performance under load. The experimental results indicated that the permeability of VTM sinter during the softening–melting process was improved by increasing the H₂ content of the reducing gases. The maximum pressure drop of the burden decreased gradually from 29.76 kPa to 19.97 kPa, and the total characteristic value (representing the comprehensive softening–melting property) also decreased obviously from 2357.52 kPa·°C to 630.94 kPa·°C with the increase in H₂ content. The softening interval of the samples was widened, while the melting–dripping interval increased firstly and then decreased. In that case, the position of the melting–dripping zone in BF would move downwards, which was beneficial to smelting smoothly. The thermodynamic analysis indicated that Ti- and Fe-bearing phases were more difficult to be reduced than iron oxides, and H₂-rich gas is beneficial to the reduction of that kind of oxides. Titano-magnetite will be reduced stepwise to form Fe₂TiO₄, and then in the order of FeTiO₃→TiO₂→Ti(C,N). Wustite (FeO) was an important component during the slag-forming process, whose content increased firstly and then decreased. Perovskite and silicate were the main phases in the dripping slag samples. Full article

Preparing ceramic materials is a meaningful way to treat and utilize industrial slags. In this work, high-performance and low-deformation industrial slag ceramics were prepared from Ti-extraction blast furnace slag and illitic clay. The phase composition and contents, microstructure, physical properties, and pyroplastic deformation of ceramic samples were investigated. With the increasing proportion of illitic clay, the main crystalline phase of ceramic samples changed from akermanite to Fe-bearing diopside. Moreover, the minor crystalline phases changed from perovskite and spinel to anorthite and titanite. The proportion of illitic clay was linearly related to the amorphous phase content. The dense microstructure comprised concentrated short-columnar and granular grains with a few isolated pores, whereas plate-like grains destroyed their denseness. An appropriate proportion of illitic clay helped to improve the physical properties, increase the high-temperature viscosity and reduce the deformation of the ceramics. The optimal proportion of illitic clay was 30%, and the prepared ceramic sample had a dense microstructure and excellent physical properties. Its bulk density was 2.82 g/cm³, bending strength was 62.17 MPa, and water absorption was 0.21%. Full article