Titanium-bearing Blast Furnace Slag Research Articles

Thermodynamic and Experimental Studies of Selective Decomposition of Diopside in Ti-Bearing Blast Furnace Slag.

Titanium-bearing blast furnace slag (TBFS) is formed during the smelting of vanadium-titanium magnetite ore, containing more than 10 wt % Ti. The metal resource in TBFS has not yet been utilized because of the difficulty of extracting the objective phase from the complex eutectic. In this work, thermodynamic and experimental studies of selective leaching of diopside phase in TBFS in 20 wt % H2SO4 were conducted. The Gibbs free energy of reaction with H2SO4 calculated by applying a mechanical mixture model was in the order of Ti-bearing diopside < MgAl2O4 < Ti-rich diopside < CaTO3. The extraction rate of Ti ions was controlled by the leaching temperature and leaching time in 20 wt % H2SO4. The extraction rate of Ti reached as high as 0.50 under optimal conditions. The diopside phases in TBFS were completely decomposed, while the perovskite (CaTiO3) was almost unaffected by 20 wt % H2SO4. The experimental results agreed with the trend of thermodynamic calculations, supporting their validity. The hydrolysis of TiOSO4 showed the possibility of obtaining high-purity TiO2. This work shows the selective leaching of the diopside phase in TBFS and suggests an environmentally friendly method for utilizing Ti-bearing blast furnace slag and waste acid.

Preparation of ferrotitanium alloy by aluminothermic reduction of perovskite

Titanium-bearing blast-furnace slag is an important secondary resource. Artificial perovskite, with CaTiO3 as the main crystal phase, can be obtained after settling of the slag. Preparation of ferrotitanium alloy using perovskite as the titanium-containing material and aluminum as the reducing agent was studied. X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and elemental chemical analysis were used to determine the composition and microstructure of the products. The results show that FeTi50 alloy can be prepared by aluminothermic reduction of perovskite. Reduction temperature has a strong influence on the separation of alloy and slag: when the reduction temperature increased from 1500 ℃ to 1600 ℃, the ferrotitanium alloy and slag effectively separated and Ti recovery exceeded 80%. The Al and O contents in the alloy decreased with decreasing aluminum addition, but also reduced Ti recovery. An alloy conforming to the industrial standard for FeTi50-A was obtained when the aluminum addition was 90 mass% of the stoichiometric value regarding reduction of perovskite.

Extraction of Valuable Metals from Titanium-bearing Blast Furnace Slag by Acid Leaching

Extraction of Valuable Metals from Titanium-bearing Blast Furnace Slag by Acid Leaching

Expanded titanium-bearing blast furnace slag phase change aggregate: Preparation, performance and phase change energy storage mortar application

Expanded titanium-bearing blast furnace slag (ETS), containing rich connected pores, largely accumulated, due to low hydration activity and particle strength. In this study, the pore system of ETS was fully utilized to load paraffin for fabrication of phase change aggregate (PCA), and then the PCA was used to prepare phase change energy storage mortar (PCEM) and mechanical properties, thermal performances and energy-saving efficiency were subsequently evaluated. The results indicated that the 28-day and 56-day compressive strength of mortar containing 100 % PCA reached to 7.8 MPa and 8.6 MPa. The energy saving efficiency of building reached to 8.1 %, the peak indoor temperature of building decreased by 1.2 °C and 2.3 °C in spring and summer, respectively. These facts give confidence of ETS consumption in building energy-saving materials.

Selective enrichment and extraction of well-catalyzed perovskites on melting-microwave heating process from blast furnace slag

Titanium-bearing blast furnace slag (TBFS) is an important secondary resource, accounting for half of the world's titanium resource reserves, but its utilization ratio is less than 3%. Making full use of the difference in microwave absorption ability, density and melting point of titanium-bearing components with others in TBFS, this research pioneered a new technology of melt pretreatment-microwave selective heating process to extraction of well-catalyzed CaTiO3 derived from low-grade titanium-bearing resource. It is found that melt pretreatment (1300 °C for 1 h) promoted the transition of titanium from low-valent to high-valent, which is beneficial to enhance the difference of microwave absorption ability among components in TBFS. Furthermore, microwave heating induced the extrication of CaTiO3 from silicate to form crystal-branched structures with special aspect ratio. Meanwhile, microwave effect arose the silicate melt dripping to realize directional migration of CaTiO3. CaTiO3 product (content of 82 wt%) obtained by gravity separation performed well-catalyzed characterization with band gap of 2.25 eV. This study provided the key guidance and feasible route for component extraction derived from titanium-bearing slag.

Preparation, microstructure, performance and mortar application of paraffin/titanium-bearing blast furnace slag phase change aggregate

The application of phase change materials (PCM) in building energy saving is limited by the cost and performance of PCM carriers. Using solid waste as a PCM carrier can reduce cost and environmental impacts. In this study, lightweight and porous titanium-bearing blast furnace slag (Ti-BFS) was innovatively used as PCM carrier to prepare paraffin/Ti-BFS phase change aggregate (PTA) by vacuum impregnation, and then PTA was used to develop thermal energy storage cement mortar by replacing sand. The microstructure and performance of aggregate and mortar were also investigated. The results indicated that PTA has a paraffin loading rate of 21.9%, latent heat of 65.7 J/g for melting and 65.0 J/g for freezing, and good chemical compatibility. The microstructure reveals that PTA has good compatibility with cement matrix. Compared with ordinary cement mortar, a reduction percentage of 28-day compressive strength, dry density and thermal conductivity at 100% PTA substitution rate are respectively 39.8%, 29.1% and 52.5%. However, a significant capacity to weaken temperature fluctuation was observed.

Ce-doped perovskite-type catalyst derived from Ti-bearing blast furnace slag for photocatalytic removal of gaseous toluene under visible light

Since the yield of titanium-bearing blast furnace slag (TF) during the smelting of vanadium titanium magnetite is large, it is urgent to find ways to recycle it and implement its value-added utilization. In this study, a perovskite-rich photocatalyst was prepared by acid-washing of TF, and then Ce was doped to modify it for photocatalytic removal of gaseous toluene under the irradiation of visible light. XRD, XRF and XPS analyses demonstrated that the perovskite phase was enriched after the acid-washing, and the content of CaTiO3 in the acid-washed slag (AS) also increased after Ce doping. The combined N2 adsorption-desorption, UVVis DRS, EIS, PL, and ESR analysis results indicated that the photocatalytic performance of the mentioned photocatalyst was related to the Ce dopant content. The AS doped with 20% Ce (20% Ce-AS) had a lower band gap and larger specific surface area than the others catalysts. Under visible light radiation, more active radicals were produced, and the removal efficiency of toluene reached 92.08% for 20% Ce-AS. In addition, the results of the in situ DRIFTS tests indicated that toluene was gradually degraded by the Ce-doped perovskite-type photocatalyst to alcohols and aldehydes and mineralized to H2O and CO2. This study is expected to provide a new approach for the technical development of the value-added utilization of TF coupled with the efficient removal of toluene.

A novel approach for pre-concentrating titanium from Ti-bearing blast furnace slag

ABSTRACT Titanium-bearing blast furnace slag (Ti-bearing BF slag) is an important Ti-bearing resource as it contains almost 8–25% TiO2. Over 80 million tons of Ti-bearing BF slag have been accumulated in China. Therefore, recovering the Ti resource from Ti-bearing BF slag is of significance for the sustainable supply of titanium in China as well as in the world. In this paper, based on the chemical composition characteristic of Ti-bearing BF slag, a magnetic Ulvöspinel (Fe2TiO4) phase was formed by the addition of Fe2O3 in Ti-bearing slag. The effects of roasting temperature, roasting time, molar ratio of Fe2O3 to carbon powder and mass ratio of Fe2O3 to Ti-bearing BF slag on the fromation of Fe2TiO4 phase were investigated. The formation mechanism of the Fe2TiO4 grains was revealed by XRD, SEM-EDS, VSM and dissolution experiments. The result show that when 25% mass of Fe2O3 relative to the Ti-bearing BF slag was added, without adding carbon powder, and roasted at 1400°C for 6 h, a titanium concentrate with 22.5% of TiO2 was obtained, and more than 92% of the total titanium in the Ti-bearing BF slag was recovered.

Preparation of Hydrated TiO2 Particles by Hydrothermal Hydrolysis of Mg/Al-Bearing TiOSO4 Solution.

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.

Influence of TiO2, Al2O3, and Basicity on Viscosity and Structure of High Titanium-Bearing Blast Furnace Slag

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.

Preparation and characterization of the glass-ceramics by co-utilization of ferrochromium slag and titanium-bearing blast furnace slag

Ferrochromium slag (FCS) and titanium-bearing blast furnace (TBFS) were used as the main raw materials to prepare glass-ceramics by the conventional melting method in this study. The DTA tests and crystallization kinetics analysis were conducted to determine the optimum heat-treatment temperatures. The effects of FCS and TBFS addition on the glass-ceramics crystalline phase, microstructure evolution, and physical properties were investigated systematically. The results show that the dominant crystalline phases are Cr-containing augite and wollastonite in the glass-ceramics prepared from single FCS. With the increasing addition of FCS, though the crystallization ability enhanced continuously, a large amount of Cr-containing spinel precipitated, resulting in serious shrinkage cavities. When the TBFS was introduced into FCS glass-ceramics, the original silicon-oxygen was destroyed and the titanium-oxygen-silicon composite glass network formed. The ability of crystallization is further enhanced and the size of the grain is significantly refined. Simultaneously, the Cr-containing spinel is decreased obviously, which alleviates the shrinkage cavities and improves the mechanical properties of glass-ceramics. The final obtained glass-ceramics exhibits a flexural strength of 86.7 MPa, a Vickers hardness of 741.1 HV, a bulk density of 2.96 g/cm3, a water absorption rate of 0.36%, and a Cr ion leaching concentration of 0.66 mg/L. This study clarifies the mechanism of Cr2O3 and TiO2 in glass ceramics, which has important reference significance for the value-added utilization of FCS and TBFS.

Kinetics of isothermal growth of Ulvöspinel (Fe3-xTixO4) in Ti-bearing blast furnace slag with Fe2O3 powder additive

Based on chemical composition and mineral composition of Ti-bearing BF slag, Fe2O3 is introduced to the Ti-bearing BF slag, a magnetic Ulvöspinel phase is formed after roasting, then enriched by magnetic separation. The effects of Fe2O3 dosage, holding temperature and holding time on the grain size and crystal area of Ulvöspinel in titanium bearing blast furnace slag were investigated by SEM-EDS analyses. The occurrence of Ca, Si, Fe, Ti and other elements in roasted slag were studied by EDS. The grain size and crystallization area of Ulvöspinel (&gt;30 µm) in roasted slag under different conditions were counted by image plus pro 6.0 software. The growth kinetics of Ulvöspinel in isothermal process was described by Johnson-Mehl-Avrami-Kologoromov (JMAK) model, the apparent activation energy of Ulvöspinel growth was obtained. The results show that the mixed roasted slag of Ti-bearing BF slag and Fe2O3 is mainly composed of Ulvöspinel phase and calcium-silicon phase; Titanium mainly occurs in Ulvöspinel Fe3-xTixO4 (0 &lt; x &lt; 1), and only trace titanium exists in the calcium silicate phase; The growth of Ulvöspinel phase mainly includes two processes: crystal nucleus growth and Ostwald coarsening; The temperature of about 1073 K is favorable for the growth of Ulvöspinel. If the temperature is too high, low undercooling (ΔT = 1693–Tk) may lead to the slow the nucleation rate, and when the temperature is below 1073 K, the high viscosity slag leads to the slow dissolution of molten Ulvöspinel grains; when mass ratio 25% Fe2O3 to Ti-bearing BF slag, as holding time prolonging, the size and crystal area of Ulvöspinel (&gt;30 µm) gradually increases, and the average size and area fraction of Ulvöspinel (&gt;30 µm) is 56.67 µm and 78.79% after 120 min. After that, the growth of Ulvöspinel almost stopped. The growth process of Ulvöspinel can be described by JMAK equation, and its apparent activation energy is 550.39 kJ. mol−1.

Process Optimization and Kinetics of Titanium Leaching from Mechanically Activated Titanium-Bearing Blast Furnace Slag

Process Optimization and Kinetics of Titanium Leaching from Mechanically Activated Titanium-Bearing Blast Furnace Slag

A Sustainable Method for Ti, Al and Mg Recovery from Titanium-Bearing Blast Furnace Slag Coupled with CO2 Sequestration by Leaching Residue

A Sustainable Method for Ti, Al and Mg Recovery from Titanium-Bearing Blast Furnace Slag Coupled with CO2 Sequestration by Leaching Residue

Recovery of Residual Carbon from Ti-Extraction Blast Furnace Slag by Flotation with Simultaneous Dechlorination

Ti-extraction blast furnace slag (EBFS) is a secondary slag produced by titanium extraction of titanium-bearing blast furnace slag (TBBFS), which is challenging to be used directly because of its residual carbon and chlorine. This study was performed to recover the residual carbon and remove chlorine from EBFS by froth flotation. The finely ground EBFS (FEBFS) contained graphitized carbon and khamrabaevite and had a 10.19% loss on ignition (LOI) and 5.52% Cl. The graphitized carbon was mainly recovered by flotation rather than khamrabaevite. Graphitized carbon appeared as flakes embedded in or stacked on the surface of the concentrate grains. The irregular-shaped particles were amorphous aluminosilicate glasses, whose presence adversely affected the quality and performance of the flotation concentrate. The Cl contents of the flotation concentrate and tailings obtained under the optimized flotation conditions were significantly reduced to 1.17% and 0.4%, respectively. The dechlorination efficiency reached 71.56%. Meanwhile, the LOI of flotation tailing was reduced to 1.32% and the carbon recovery was 84.79%. Froth flotation could recover residual carbon and remove chlorine from EBFS simultaneously, a novel way to deal with EBFS as a resource and harmless process.

Recovery of titanium, aluminum, magnesium and separating silicon from titanium-bearing blast furnace slag by sulfuric acid curing—leaching

Recovery of titanium, aluminum, magnesium and separating silicon from titanium-bearing blast furnace slag by sulfuric acid curing—leaching

Si/TiSi2/G@void@C composite with good electrochemical performance as anode of lithium ion batteries

Silicon anode has been vigorously developed as an up-and-coming candidate for anode materials of lithium ion batteries, as it is featured by the sizeable theoretical capacity and resource superiority. However, it cannot be unrestrictedly adopted in practice because of the enormous volumetric change during the process of lithiation–delithiation again and again, as well as the low electrical conductivity. Herein, we expect to solve its intrinsic weakness through a synergy strategy that combines metal alloying, cavity structure, and carbon compositing. Si/TiSi2/G@void@C (STGvC) composites were designed and synthesized by induction melting and mechanical ball milling methods, adopting silicon waste produced in the photovoltaic industry and titanium-bearing blast furnace slag produced in the steel industry as raw materials. Meanwhile, the synthesis employs NaCl as a pore-forming agent, and polyvinyl pyrrolidon and waste graphite as carbon sources. As a result, the optimized STGvC sample with adding appropriate amount of NaCl harvests favorable cycling performance. It still records a discharge capacity of 886.6 mAh g−1 after 300 cycles during the circulating process at 1600 mA g−1. This investigation presents a unique strategy to prepare Si-based anodes with bright future and makes the effective utilization of industrial solid waste in the battery industry possible.

Study on optimization and mechanism of mechanical activation process of titanium-bearing blast furnace slag

In the present work, the specific surface area (BET), X-ray diffraction analyses (XRD), scanning electron microscopy (SEM) energy-dispersive X-ray analysis (EDS), and laser particle size analysis were employed in the investigation of mechanical activation mechanism of titanium-bearing blast furnace slag. The results indicated that the specific surface area of the activated slag was significantly larger than that of the unactivated slag. The reduced intensity of the (121), (202), (123) and (242) diffraction peaks, which belong to the perovskite (CaTiO3), stems mainly from the increase in the lattice distortion and the decrease in the unit-cell volume. Compared with the unactivated slag, the cumulative volume of medium particles (1 μm ≤ PS ≤ 100 μm) in the activated titanium-bearing blast furnace slag was significantly higher, which was suitable for the subsequent leaching process. With the increase of ball-to-material mass ratio, mechanical activation time, mechanical activation rotation rate, the activated titanium-bearing blast furnace slag were extensively bonded and agglomerated. According to the results obtained by XRD, BET, SEM and laser particle size analysis, we concluded that the optimum mechanical activation process parameters are ball-to-material mass ratio of 20:1, activation time of 170 min, and activation rotation rate of 400 min/r, respectively. We also concluded that mechanical activation mechanism of titanium-bearing blast furnace slag can be attributed to the increase of specific surface area, amorphization of mineral particles, enhanced strain, preferential dissolution of select crystal faces, structural disorder, change of microtopography, leading to more amenable to leaching process.

In-situ DRIFTS study on the k-poisoning resistance mechanism of titanium bearing blast furnace slag catalyst by Sm/La doping

Benefiting from the construction of lamellar framework Sm-CeZrTiAl amorphous mixed oxides synthesized by the hydrothermal method, enhanced NH3-SCR performance over a wide temperature window for K poisoning resistance was observed. The Sm-CeZrTiAl catalyst preserved higher catalytic performance after K was introduced than the catalysts without added Sm, as it maintained > 90% NO conversion between 300 and 420 °C. The outstanding K poisoning-resistance of the Sm-CeZrTiAl catalyst could benefit from its good nano-Al2O3 flake skeleton structure, high specific surface area, and rich pore channels. In addition, Sm doping can effectively increase the number of surface acid sites, especially strong acid sites, which promote the formation of NOx adsorption species such as nitrite, bidentate nitrate and bridging nitrate intermediates and facilitate the conversion of NO to N2 by following the Langmuir-Hinshelwood mechanism. In addition, the synergy between Sm/La and Ce leads to more Ce3+ and Brønsted acid sites. Through the redox cycle of Ce4++Sm2+→Ce3++Sm3+ or Ce4++La2+→Ce3++La3+, catalytic reduction can be realized with good performance. Moreover, a significant portion of K on the catalyst surface preferentially interacted with strong acidic sites provided by Sm/La doping, thereby preventing Ce species from poisoning and leaving them available for the catalytic cycle.

Enhanced Strength and Electrical Conductivity in Graphite-Cement Mortars with Carbonized Titanium-Bearing Blast Furnace Slag as an Aggregate

Titanium-containing carbide slag (TCS) is the product obtained by high-temperature carbothermal reduction in Titanium-bearing blast furnace slag (TBFS), which contains a large amount of TiC phase with excellent electrical conductivity. In this paper, conductive cement mortar was prepared with TCS as an aggregate and graphite as a conductive phase. The content of graphite on the compressive strength and electrical resistivity of the prepared cement mortar was investigated. The results showed that the replacement of standard sand with TCS as an aggregate not only significantly reduced the electrical resistivity of the cement mortar, but also improved its compressive strength. When the graphite content was 10 wt%, the cement mortar with TCS as the aggregate exhibited excellent comprehensive performance with the 28d compressive strength of 34.0 MPa and the electrical resistivity of 2.9 Ω m in dry condition, respectively. The results of this paper provided a new way both for the utilization of TBFS and the preparation of conductive cement mortars.