Titanium-bearing Blast Furnace Slag Research Articles

Simultaneous CO2 mineral sequestration and rutile beneficiation by using titanium-bearing blast furnace slag: Process description and optimization

CO2 mineral sequestration is a promising method for abating global warming. Mineral carbonation with titanium-bearing blast furnace slag (TBFS) can offer a sustainable option for simultaneous CO2 emission reduction and comprehensive utilization of solid waste. In this study, a novel process combining CO2 mineral sequestration and rutile beneficiation was proposed by using TBFS and copperas as feedstocks. TBFS and copperas were roasted at 550–750 °C to convert the calcium and magnesium into the corresponding sulfates, while titanium in the TBFS was beneficiated to rutile. The roasted slag was then subjected to carbonation followed by recovery of rutile and hematite through flotation and magnetic separation, respectively. The effects of process parameters were studied systematically. It was found that addition of Na2SO4 significantly enhanced the conversion efficiency of Ti (from 53% to 98%). The mechanism revealed that the addition of Na2SO4 promoted the formation of molten Na3Fe(SO4)3, and gas-liquid-solid reactions proceeded much faster and efficiently. The carbonation of sulfated TBFS results indicated that the optimal CO2 storage capacity can reach 187 kg t−1 TBFS. In this process, two solid wastes were utilized for CO2 mineralization, realizing the multiple benefits of CO2 emission reduction, solid waste disposal as well as valuable byproducts recovery.

Novel process for deep removal of chlorine and recycling of chlorinated tailings from titanium-bearing blast-furnace slag

Given the high chloride ion content in chlorinated tailings that harm the surrounding environment cannot be directly utilized, a new process for the deep removal of chloride ions from chlorinated tailings with additives was proposed. The products obtained included tailing slag, which can be used as a building material, and salt, which can be used in industry. Theoretical calculations and experiments were performed to determine the feasibility of the new process. The results showed that the chloride ions from the chlorinated tailings and sodium ions from the additives formed NaCl, which could be removed during water leaching. NaOH served as a better additive than sodium sulfate. An increase in the molar ratio and the prolongation of ball-milling was beneficial for the dechlorination of the water leaching residue. An increase in the roasting temperature leads to an increase in particle size, which worsens the kinetics of subsequent leaching and reduces the leaching rate. The developed process can obtain tailings with chloride ion content of less than 0.1%, which meets the standard for building materials applications. Meanwhile, NaCl with a purity greater than 99% could be obtained, preventing chloride ion pollution of water resources and the comprehensive utilization of chlorinated tailing.

Gas-based reduction and carbonization of titanium minerals in titanium-bearing blast furnace slag: A combined thermodynamic, experimental and DFT study

The utilization of titanium-bearing blast furnace slag (TBFS) has been widely concerned, which is mainly related to the recovery of titanium resources. In order to realize the efficient and clean recovery of titanium resource, the main titanium-bearing phases (CaTiO3, MgTiO3 and Mg2TiO4) in TBFS with high content of MgO were investigated in CH4–H2 system in this work. Thermodynamic calculation indicated that CaTiO3, MgTiO3 and MgTi2O4 could be ultimately reduced to TiCxOy at 1300 °C, 1200 °C and 1200 °C respectively. The reduction experiments were carried out in flowing CH4–H2, which considered the influences of time, temperature and addition, the results of which showed that the optimal reduction temperatures of CaTiO3 and MgTiO3 were 1400 °C and 1200 °C respectively. DFT calculation results also confirmed that MgTiO3 had stronger CH4 adsorption capacity than CaTiO3 and Mg2TiO4. However, Mg2TiO4 could not be reduced completely even at 1450 °C, because excessive MgO in the reduced products prevented further reaction in kinetics. Both increasing temperature and adding iron oxides contributed to the reduction kinetics. The results suggested that the appropriate increase of the proportion of MgO in TBFS was beneficial to titanium extraction. This work provides a way to develop new process to extract titanium from TBFS, especially the slag with high MgO.

A novel slag-based Ce/TiO2@LDH catalyst for visible light driven degradation of tetracycline: performance and mechanism

As a kind of bulk solid waste in iron and steel industry, titanium-bearing blast furnace slag (Ti-BFS) poses a serious threat to the environment, its disposal and reuse has been a hot and difficult spot. In this study, a new and high efficient hydrotalcite-like photocatalytic material (denoted CeTL) was prepared from Ti-BFS, and applied to the visible light catalytic degradation of antibiotics in water environment. The results showed that the degradation rate of tetracycline (TC) by the optimized CeTL reached 92.8% after 90 min of illumination. Dissolved organic matter with molecular weight 1–3 kDa was the most inhibiting to degradation rate. The introduction of Ce contributed to the nanopore structure and increased the specific surface area (302.58 m²/g), and effectively promoted the development of active surface oxygen and oxygen vacancies in the lattice, thus reducing the excited energy of photoelectron and expanding the spectral response range. Moreover, Ce acted as a medium to transfer photoelectrons, which successfully separates the reducing photoelectron in conduction band (CB) and the oxidized hole in valence band (VB), and generated·O2− and·OH with O2 and OH−, respectively. These active species attacked TC molecules adsorbed on CeTL surface, degraded them into small molecules, and improved the antibacterial activity of CeTL. The good adsorption capacity and the enhanced visible light catalysis of CeTL synergistic realized the efficient removal of TC. This work enriched the research system of comprehensive utilization of Ti-BFS, and provided a new strategy for the preparation of efficient applied photocatalysts and the recycling of resources.

Formation Mechanism of Titanium Carbide in Titanium-bearing Blast Furnace Slag

The formation of titanium carbide (TiC) may result in slag thickening, slag foaming and difficulty in separation between hot metal and slag etc during the blast furnace smelting process with Vanadic Titanomagnetite. Therefore, it is very important to understand and manage the formation of titanium carbide. The formation mechanism of titanium carbide during the reduction process of blast furnace slag - bearing titanium was studied with theoretical calculations and experiments. In the experiment, blast furnace slag - bearing titanium was subjected to 6 hours’ isothermal treatment at temperature range of I300°C-I550°Cin graphite crucible with Ar flow rate of 2L/min (1 atm). The reduced slag was characterized by mineralogical microscope and SEM-EDS detection methods. As a result, the formation of titanium carbide started at a temperature higher than I400°C.

Preparation of high-purity TiSi2 and eutectic Si–Ti alloy by separation of Si–Ti alloy for clean utilization of Ti-bearing blast furnace slag

Titanium-bearing (Ti-bearing) blast furnace slag is not only industrial waste but also an important Ti resource. However, the cleaning of Ti-bearing blast furnace slag for utilization is a difficult problem. In this study, a new process is proposed to prepare Titanium disilicide (TiSi2) and eutectic Si–Ti alloy (Si/TiSi2), using Ti-bearing blast furnace slag and low-purity Si as raw materials. Firstly, Titanium oxide (TiO2) in the Ti-bearing blast furnace slag was reduced by Si and an Si–Ti alloy was obtained. The obtained Si–Ti alloy was then separated into TiSi2 and eutectic Si–Ti alloy by directional crystallization. In addition, MgO, Al2O3 and graphite crucibles were used and their influences on the results were investigated to obtain the optimal reaction container to prepare high-purity TiSi2 and eutectic Si–Ti alloy. The results show that the separation of Si–Ti alloy using an MgO crucible as a reaction container has little influence on the purity of the TiSi2 (>98%) and eutectic Si–Ti alloy (>97%) and that most of the impurities could be eliminated from the bulk TiSi2 crystal and eutectic Si–Ti alloy. The results of this study provide a theoretical and experimental basis for the simultaneous preparation of TiSi2 and eutectic Si–Ti alloy materials and proposes a new approach for the comprehensive utilization of Ti-bearing blast furnace slag.

Slag-foaming phenomenon originating from reaction of titanium-bearing blast furnace slag: Continuous monitoring of foaming height and calibration

The present study monitored the foaming phenomenon originating from the reaction of titanium-bearing blast furnace slag by using the relationship between the current change in a circuit and the foaming height. A series of experiments at room temperature and high temperature were designed to check the feasibility and reproducibility of the experimental apparatus. Experiments at different levels of basicity and TiO2 content at high temperature were designed to determine the effect of these parameters on the relationship between the foaming height and current. It was proved that the electric current method used in this study to monitor the real-time foaming process is feasible and reliable. The relationship between the foaming height and current change was also established.

Estimation of Reaction Heat in Ti-Bearing Blast Furnace Slag—Sulfuric Acid System Based on Mechanical Mixture Model

This paper reported the calculation of the reaction heat in titanium-bearing blast furnace slag (abbreviated as TBFS)-H2SO4 system based on estimation of thermodynamic data of CaTiAl2O6 by mechanical mixture model. The thermodynamic analysis indicated that CaTiAl2O6 was more stable than the corresponding ternary oxides as CaO·TiO2, CaO·Al2O3, and Al2O3·TiO2. TBFS-H2SO4 system was highly exothermic since all of the reactions involved in the system were exothermic. For example, the increase of temperature from 25 to 200°C led to the increase of the release of the reaction heat in TBFS (100.0g)-H2SO4 system from 181.28 to 189.73kJ. Eighty-five to 90% of the reaction heat in TBFS-H2SO4 system was contributed by the reactions among CaTiAl2O6, CaTiO3, CaMgSi2O6, and H2SO4.

Simultaneous Co2 Mineral Sequestration and Rutile Beneficiation by Using Titanium-Bearing Blast Furnace Slag: Process Description and Optimization

Simultaneous Co2 Mineral Sequestration and Rutile Beneficiation by Using Titanium-Bearing Blast Furnace Slag: Process Description and Optimization

A novel recycling approach for efficient extraction of titanium from high-titanium-bearing blast furnace slag

The recycling of high-titanium-bearing blast furnace slag (TiO2 > 23 wt.%) is an urgent problem that has attracted global research attention. To achieve high-efficiency, low-consumption, clean, and high value-added recycling utilization, a new process is proposed herein, which entails reacting a CH4-H2-N2 gas mixture with the titanium-bearing blast furnace slag to initially produce Ti(C, N, O) at a low temperature, whereafter the product is purified and chlorinated. The effects of Fe2O3, urea, and sawdust on the reduction and carbonitriding characteristics are also investigated. The results indicate that the Fe2O3 additive can promote the formation of Ti(C, N, O), while urea and sawdust are instrumental for enhancing gas diffusion in solid powders. The proposed novel recycling process was assessed and it evinced many advantages and great feasibility.

Simultaneous preparation of TiO2 and ammonium alum, and microporous SiO2 during the mineral carbonation of titanium-bearing blast furnace slag

Abstract In this study, a route for simultaneous mineralization of CO2 and production of titanium dioxide and ammonium alum, and microporous silicon dioxide from titanium-bearing blast furnace slag (TBBF slag) was proposed, which is comprised of (NH4)2SO4 roasting, acid leaching, ammonium alum crystallization, silicic acid flocculation and Ti hydrolysis. The effects of relevant process parameters were systematically investigated. The results showed that under the optimal roasting and leaching conditions about 85% of titanium and 84.6% of aluminum could be extracted while only 30% of silicon entered the leachate. 84% of Al3+ was crystallized from the leachate in the form of ammonium aluminum sulfate dodecahydrate with a purity up to 99.5 wt%. About 85% of the soluble silicic acid was flocculated with the aid of secondary alcohol polyoxyethylene ether 9 (AEO-9) to yield a microporous SiO2 material (97.4 wt%) from the crystallized mother liquor. The Al- and Si-depleted solution was then hydrolyzed to generate a titanium dioxide (99.1 wt%) with uniform particle size distribution. It was figured out that approximately 146 kg TiO2 could be produced from 1000 kg of TBBF slag. Therefore, the improved process is a promising method for industrial application.

Slag-foaming phenomenon originating from reaction of titanium-bearing blast furnace slag: effects of TiO2 content and basicity

ABSTRACTThe foaming behaviour originating from the reduction of iron oxide in molten CaO–SiO2–MgO–Al2O3–TiO2 slag was studied at 1500°C with the aid of a real-time foaming process monitoring system. The effect of TiO2 content and binary basicity on the slag foaming were investigated. It was found that the TiO2 content has a significant influence on the foaming degree, while the basicity of the slag has a smaller influence. The foam-generation time, foam duration, and foam-elimination time greatly increased with increasing TiO2 content, while they slightly increased with increasing basicity. Furthermore, the source of gas and the effect of physical properties of the slag on the foaming behaviour were also discussed. This study can provide a guideline for the utilisation of high-ratio titanium-bearing magnetite ore in the blast-furnace iron-making process, which is seriously affected by the slag-foaming problem.

A novel method for preparing Ti5Si3 from Ti-bearing blast furnace slag

Effective recovery of titanium resources from titanium-bearing blast furnace slag had always been a difficult problem. In the present study, Ti5Si3 was synthesized via silicothermic reduction of titanium-bearing blast furnace slag. The effects of reduction temperature and reaction time on the formation of Ti5Si3 were studied by X-ray diffraction and scanning electron microscope. The results indicated that Ti5Si3 was the only silicide in the finally obtained products. Ti5Si3 will gradually sinter to form a porous skeleton, and a small amount of slag will be trapped in the porous skeleton of Ti5Si3. It provided a feasible route for the treatment of titanium-bearing blast furnace slag and the recovery of titanium resources. It was also found that the longer the reaction time and the higher the reaction temperature (1823 K), the less the slag trapped in the alloy will be.

Particle size controllable jet milling technology for efficiently recycling titanium-bearing blast furnace slag: Numerical simulation and industrial test

Abstract Large amounts of titanium-bearing blast furnace slag have been dumped in China, resulting in serious environmental contamination and a waste of precious titanium resource. At present, a process for recovering titanium from titanium-bearing blast furnace slag has been developed. Unfortunately, current size reduction techniques fail to meet the material size requirements. In this paper, a particle size controllable jet milling technology was proposed based on the idea of one-time collision between the particle and the target. To better control the breakage size, computational fluid dynamics was used to model the new jet mill giving a detailed understanding of the mechanisms. Simulated results showed that the acceleration region of the low velocity fluid was located inside the ejected stream. The velocity at which the fluid hits the target was relatively uniform. It indicated that the new jet mill was advantageous for obtaining a pulverized product having a narrower particle size distribution. Experimental results showed that the excessive size reduction was effectively reduced. The average mass fraction of the particles with the particle size of 150 μm was 8.2%, meeting the requirement for titanium recycling from titanium-bearing blast furnace slag in industry. This study provides a feasible method for reducing particle size to a desired distribution to promote resource sustainable utilization and pollution reduction in an environmentally friendly way.

Reduction of perovskite-geikielite by methane–hydrogen gas mixture: Thermodynamic analysis and experimental results

The present study investigated the reduction and carbonization behavior of perovskite-geikielite by using CH4–H2 gas mixture, which aimed to recycle the titanium resource in titanium-bearing blast furnace slag. Thermodynamic phase equilibrium analysis in the CaTiO3–CH4–H2, MgTiO3–CH4–H2 and CaTiO3–MgTiO3–CH4–H2 systems was performed by FactSage. The analysis indicated that CaTiO3 could be ultimately reduced and carbonized to TiCxOy by CH4–H2 gas mixture at temperature above 1300 °C, while the temperature for reduction of MgTiO3 was above 1200 °C. MgTiO3 is found to be reduced prior to CaTiO3 in the CaTiO3–MgTiO3–CH4–H2 systems. The reduction experiments of perovskite-geikielite were carried out in a temperature range of 1300 °C to 1450 °C in a flowing CH4–H2 atmosphere. Experimental results showed that perovskite-geikielite could be reduced completely to TiCxOy at 1400 °C and above after 8 h reduction, while geikielite was reduced prior to perovskite. The reduction and carbonization extent of samples increased with increasing time and temperature when in a low temperature range (below 1400 °C). However, a much higher temperature (above 1400 °C) would hinder further carbonization of TiCxOy for the production of deposited carbon. Addition of iron oxides to sample strongly facilitated the reduction reaction, and even promoted the reduction of titanium to be completed at only 1300 °C after 8 h reduction. The gas-solid reaction provided a low temperature method to reduce and carbonize perovskite and geikielite, and thus it provided a possible way to use titanium-bearing blast furnace slag.

New integrated method to recover the TiO2 component and prepare glass-ceramics from molten titanium-bearing blast furnace slag

Titanium-bearing blast furnace slag (TBBFS), which contains 15–30 wt% TiO2, is a by-product of the iron-making process and is discharged at approximately 1500 °C. To efficiently utilize molten TBBFS, we propose a new integrated method that the slag was cooled to a certain temperature at which the perovskite precipitated as solid crystals and the supernatant remained in liquid form. The solid component containing perovskite was thereby enriched with TiO2 and separated from the residual liquid by using super-gravity. Simultaneously, the residual liquid was prepared into glass-ceramics by the petrurgic method. Samples were analyzed by XRF, XRD, SEM, and by conducting flexural strength and density tests. The results showed that, during the process of cooling in TBBFS, TiO2 in the form of perovskite precipitated at a temperature approximately 100 °C higher than the precipitation temperature at which pyroxene and melilite precipitated. The optimal temperature for separating perovskite is at 1250 °C and at this temperature, the separated TiO2-rich component had a TiO2 content of 24.44 wt% and a recovery rate of 75.98%. In addition, the glass-ceramics from the residual molten slag had a compact structure and flexural strength of 40.54 MPa and low TiO2 content of 9.46%. The crystals in the glass-ceramics were those of augite and melilite. However, the glass-ceramics contained no perovskite because of the poor TiO2 content, which plays the role of a nucleating agent, and which contributed to the favorable properties of the glass-ceramics.

An approach to employ titanium-bearing blast-furnace slag to prepare Ti and Al–Si alloys

Ti-bearing blast-furnace slag is a metallurgical waste but a promising Ti resource. In this study, Ti and Al–Si alloys can be prepared directly by separating a Ti–Si–Al alloy that was prepared by reducing Ti and Si from Ti-bearing blast-furnace slag with Al. The technology of directional solidification with electromagnetic force was employed to carry out the separation of the Ti–Si–Al alloy. When additions of CaO and Al were 24 wt% and 40 wt%, respectively, the composition of the obtained Ti–Si–Al alloy was 31.8 wt% Ti, 22.7 wt% Si, 28.5 wt% Al, and 10.2 wt% Fe. Ti5Si4, TiSi, Al–Si–Ti (τ2), Al–Si–Fe (τ4), and Al–Si alloys were prepared in sequence after separating the Ti–Si–Al alloy using directional solidification with electromagnetic force. However, when the composition of the Ti–Si–Al alloy was changed to 21.2 wt% Ti, 48.5 wt% Si, 19 wt% Al, and 6.8 wt% Fe, the TiSi2, Si, Al–Si–Fe and Al–Si alloys were prepared in sequence. This study will propose an approach to employ the metallurgical waste, titanium-bearing blast-furnace slag, to prepare Ti and Al–Si alloys.

Optimisation study and affecting mechanism of CaO/SiO2 and MgO on viscous behaviours of titanium-bearing blast furnace slag

ABSTRACTTo improve the metallurgical properties of titanium-bearing blast furnace slag, the orthogonal test was carried out and analysed by the multi-index synthetic weighted scoring method. The optimal slag compositions of titanium-bearing BF slag were CaO/SiO2 1.25, MgO 12.00 wt-%, Al2O3 11.00 wt-% and TiO2 10.00 wt-%. In addition, the CaO/SiO2 and MgO content had important effects on the break-point temperature, viscosity and activation energy of viscous flow. With an increasing CaO/SiO2 from 1.10 to 1.30, the break-point temperature increased, the slag viscosity and the activation energy of viscous flow decreased. As the MgO content grew from 6.00 to 12.00 wt-%, the viscosity decreased, while the break-point temperature and the activation energy of viscous flow first reduced and then increased. Besides, the deeply relevant mechanism was researched by Factsage 7.0, Fourier transform infrared spectroscopy and X-ray diffraction.

Nonisothermal Carbothermal Reduction Kinetics of Titanium-Bearing Blast Furnace Slag

The kinetics of carbothermal reduction of titanium-bearing blast furnace (BF) slag has been studied by thermogravimetric analysis and quadrupole mass spectrometry. The kinetic parameters (activation energy, preexponential factor, and reaction model function) were determined using the Flynn–Wall–Ozawa and Satava–Sestak methods. The results indicated that reduction of titanium-bearing BF slag can be divided into two stages, namely reduction of phases containing iron and gasification of carbon ( 1095°C). CO2 was the main off-gas in the temperature range of 530–700°C, whereas CO became the main off-gas when the temperature was greater than 900°C. The activation energy calculated using the Flynn–Wall–Ozawa method was 221.2 kJ/mol. D4 is the mechanism function for carbothermal reduction of titanium-bearing BF slag. Meanwhile, a nonisothermal reduction model is proposed based on the obtained kinetic parameters.

Effect of the Basicity on the Crystallization Behavior of Titanium Bearing Blast Furnace Slag

AbstractBasicity of titanium bearing blast furnace (BF) slag is critical for its crystallization behavior. Thermodynamics calculation indicates that rutile is the main phase after crystallization (or at room temperature). It precipitates during the cooling when the basicity of the slag is lower than 0.7. With increasing basicity, perovskite appears and becomes the main phase instead which contains titanium. Crystallization temperature of perovskite is higher than that of rutile and the other phases. Namely, perovskite crystallizes firstly from the molten slag during decreasing temperature. XRD analysis shows that CaTi21O38 is the main phase with a basicity of 0.6. CaMg0.39Al0.87Ti0.48Si1.26O6, CaTiSiO5 and CaMgSi2O6 are the main crystallization phases with a basicity of 0.8. The difference between experimental and thermodynamics calculation is due to the complicate crystallization behavior of the multiple slag under super cooling rate. When the slag basicity increases to 1.1, the main precipitatied phase is perovskite, which agrees well with theory calculation. In addition, the crystal structure of the synthesized titanium bearing slag is basically similar regardless of the basicity.