Vanadium Titanomagnetite Research Articles

Effect of Al2O3 on the gas-based direct reduction behavior of Hongge vanadium titanomagnetite pellet under simulated shaft furnace atmosphere

As a successive work to develop a novel and clean smelting process for the comprehensive utilization of Hongge vanadium titanomagnetite (HVTM), the effect of Al2O3 on the gas-based direct reduction behavior of HVTM pellet (HVTMP) under simulated shaft furnace atmosphere was systemically investigated in this study. It was found that the reduction rate was accelerated by Al2O3 at the initial stage due to the increase of original porosity of HVTMP; however, as the reduction proceeded, the reduction degree significantly decreased with the increase of Al2O3 due to the formation of FeAl2O4, which was difficult to reduce. With the increase of Al2O3, the amount and size of metallic iron grains decreased, and the grains visibly separated from each other. In addition, FeAl2O4 was entrapped with metallic iron grains and remained in the Ti-rich phase, which retarded further reduction. The increased Al2O3 changed the distribution of metallic iron whiskers from close to dispersed clusters and decreased their hardness, leading to the increase of reduction swelling. The findings of this study not only establish a relationship between Al2O3 and its reduction behavior, but also greatly contribute to the effective utilization of HVTM either in blast furnace or shaft furnace.

Behavior of vanadium during reduction and smelting of vanadium titanomagnetite metallized pellets

Abstract The effects of CaO content, MgO content and smelting temperature on the vanadium behavior during the smelting of vanadium titanomagnetite metallized pellets were investigated. The thermodynamics of reduction and distribution of vanadium was analyzed and the high-temperature smelting experiments were carried out. The thermodynamic calculations show that the distribution ratio of vanadium between the slag and the hot metal decreases with the increments of CaO and MgO content in the slag as well as the increase of the smelting temperature. The smelting experiments demonstrate that the vanadium content in iron and the recovery rate of vanadium in pig iron increase as the CaO content, MgO content and smelting temperature increase, whereas the vanadium distribution ratio between the slag and iron tends to decrease. Moreover, the recovery rate of vanadium in pig iron has a rising trend with increasing the optical basicity of the slag. The addition of MgO in the slag to increase the slag optical basicity can not only improve the vanadium reduction but also promote the formation of magnesium-containing anosovite, which is beneficial to following titanium extraction.

Formation of calcium titanate in the carbothermic reduction of vanadium titanomagnetite concentrate by adding CaCO3

The formation of calcium titanate in the carbothermic reduction of vanadium titanomagnetite concentrate (VTC) by adding CaCO3 was investigated. Thermodynamic analysis was employed to show the feasibility of calcium titanate formation by the reaction of ilmenite and CaCO3 in a reductive atmosphere, where ilmenite is more easily reduced by CO or carbon in the presence of CaCO3. The effects of CaCO3 dosage and reduction temperature on the phase transformation and metallization degree were also investigated in an actual roasting test. Appropriate increase of CaCO3 dosages and reduction temperatures were found to be conducive to the formation of calcium titanate, and the optimum conditions were a CaCO3 dosage of 18wt% and a reduction temperature of 1400°C. Additionally, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) analysis shows that calcium titanate produced via the carbothermic reduction of VTC by CaCO3 addition was of higher purity with particle size approximately 50 µm. Hence, the separation of calcium titanate and metallic iron will be the focus in the future study.

Recovery of TiO2-enriched material from vanadium titano-magnetite concentrates by partial carbon reduction and mild acid leaching

Vanadium-titano magnetite (VTM) is a typical resource in China. The typical method used to recover valuable elements from VTM concentrates is by the blast furnace smelting method. However, titanium is nearly all wasted in the form of blast furnace slag. A new pathway towards obtaining TiO2-enriched material for titanium extraction was designed in this study. The main means is the combination of partial carbon reduction and mild acid leaching. After reduction and leaching, most of the iron and other elements are transferred into solution, leaving a TiO2-enriched residue. Iron and vanadium are reclaimed from the leaching liquid later. In this study, the reduction and leaching parameters were optimized, which included reducing at 1000 °C for 3 h with a carbon addition of 6% by mass of VTM and leaching at 80 °C for 3–4 h by using a 0.2 mol/L H2SO4 solution with a liquid-to-solid ratio of 100:1. The dehydrated residue was mainly rutile containing 72.2 wt% TiO2, which is a satisfactory material for Ti extraction. In addition, upon determining the phase composition and the mass loss after reduction with different dosages of carbon, the reduction route for iron in the magnetite phase and the main gas byproduct during reduction were analyzed. This study provides a new idea for extracting titanium from VTM concentrates.

Optimization of Basicity of High Ti Slag for Efficient Smelting of Vanadium Titanomagnetite Metallized Pellets

Slag basicity (mass ratio of CaO to SiO2) is an important index to ensure smooth operation and efficient separation between the metal and slag within the metallurgical industry. Effects of basicity of the high titanium slag on the recovery of iron and vanadium, the separation behaviors between iron and slag, as well as the slag foaming behavior during the smelting process with the operating temperature of 1550 °C have been experimentally investigated. The results show that the recovery ratios of iron and vanadium increase with higher slag basicity. The amount of dispersed metallic iron droplets in the slag decreases sharply when the basicity increases from 0.5 to 0.8, then decreases slowly when the basicity is from 0.8 to 1.1. Furthermore, the perovskite (CaTiO3) phase appears when the basicity is above 0.8. The foaming height is at a high level when the basicity is from 0.5 to 0.6, then it decreases when the basicity is increased from 0.6 to 0.7, whereas it slowly increases with higher slag basicity. Finally, the optimum basicity range of titanium slag for efficient smelting of vanadium titanomagnetite is proposed to be 0.8 to 1.1 by considering the combined effects on the recovery, foaming, and minimization on the retention of the metal droplets within the slag.

Mechanism of vanadium(IV) resistance of the strains isolated from a vanadium titanomagnetite mining region.

Microbial treatment for vanadium contamination of soils is a favorable and environment-friendly method. However, information of the resistant mechanism of the strains in soils to vanadium, especially to tetravalent vanadium [vanadium(IV)], is still limited. Herein, potential of the vanadium(IV) biosorption and biotransformation of the strains (4K1, 4K2, 4K3 and 4K4) which were capable of tolerating vanadium(IV) was determined. For biosorption, the bioadsorption and the bioabsorption of vanadium(IV) occur on the bacterial cell wall and within the cell, respectively, were taken into consideration. Comparison of the vanadium(IV) adsorbed on the bacterial cell walls and remained in the cells after sorption indicated the major bacterial vanadium(IV) sorption role of the bioadsorption which was at least one order of magnitude higher than the bioabsorption amount. Isotherm study using various isotherm models revealed a monolayer and a multilayer vanadium(IV) biosorption by 4K2 and the others (4K1, 4K3 and 4K4), respectively. Higher biosorption was observed in acidic conditions than in alkaline conditions, and the maximum biosorption was 2.41, 9.35, 7.76 and 8.44mgg-1 observed at pH 6 for 4K1, at pH 3 for 4K2, and at pH 4 for 4K3 and 4K4, respectively. At the present experimental range of the initial vanadium(IV) concentration, optimal biosorption capacity of the bacteria was observed at the vanadium(IV) level of 100-250mgL-1. Different biotransformation level of vanadium(IV) in soils by the stains was observed during a 28-d pot incubation of the soils mixed with the strains, which can be attributed to the discrepancy of both soil properties and bacterial species. Present study can help to fill up the gaps of the insufficient knowledge of the vanadium(IV) resistant mechanism of the strains in soils.

Influence of different comminution flowsheets on the separation of vanadium titano-magnetite

Comparative separation tests of vanadium titano-magnetite (VTM) were conducted in this study by employing a high-pressure grinding roller (HPGR) and a jaw crusher (JC); these were followed by a parallel and stage separation, respectively. The results revealed that the products generated with the HPGR are finer with a wider size distribution than those obtained with the conventional JC. The newly formed ore grains after grinding were similar to those of the JC products with a grinding fineness of 65% passing 74 μm. The HPGR product is more beneficial for iron oxide mineral liberation at a coarse grinding fineness. Owing to the preferential liberation of iron-bearing minerals in the primary grinding, a marketable titanium magnetite concentrate can be obtained by magnetic separation via the parallel separation of Fe–Ti. The argillation of iron oxides is more severe during the grinding stage of ilmenite with the JC than with the HPGR. Once the particle size decreased, particularly to less than 19 μm, the difficulty of capturing ilmenite using a magnetic field increased sharply and led to poor floatability.

An effective and cleaner process to recovery iron, titanium, vanadium, and chromium from Hongge vanadium titanomagnetite with hydrogen-rich gases

ABSTRACT This study presents an effective and cleaner process with hydrogen-rich gases that uses oxidation roasting followed by gas-based direct reduction and melting separation to recovery iron, titanium, vanadium, and chromium from Hongge vanadium titanomagnetite (HVTM). The process parameters were systematically investigated and determined to be roasting temperature at 1200°C, roasting time of 15 min, reduction temperature at 1050°C, volume ratio of H2 to CO of 2.5, melting temperature at 1580°C, melting time of 30 min. Under optimized conditions, after melting separation, the recovery rates of iron, titanium, vanadium, and chromium were 97.9, 89.8, 96.7, and 97.8%, respectively. Furthermore, the melting separation mechanism was determined. The separated iron is a clean raw material for steelmaking and the Ti-rich slag can send for further processing to recover titanium. This study aims to provide a theoretical and technical basis for the comprehensive utilization of HVTM.

Effects of calcium compounds on the carbothermic reduction of vanadium titanomagnetite concentrate

Effects of calcium compounds on the carbothermic reduction of vanadium titanomagnetite concentrate (VTC) were investigated. It was found that calcium compounds had great effects on the metallization rate of the reduction product, the order of the metallization rate of reduction product being CaCO3 > no additive > CaSO4 > CaCl2, which indicated that the addition of CaCO3 was more conducive to promoting the reduction of iron than other calcium compounds. Gas analysis showed that there were mainly two processes in the carbothermic reduction of VTC, a solid-solid and a solid-gas reaction. The concentrations of CO and CO2 were highest when CaCO3 was added, while that in a roasting system decreased the most when CaCl2 was added. X-ray diffraction (XRD) analysis showed that calcium compounds could change the reduction process of ilmenite in VTC. The phase compositions of the reduction products were changed from metallic iron (Fe) and anosovite (FeTi2O5) to metallic iron (Fe) and perovekite (CaTiO3) when calcium compounds were added. Additionally, CaSO4 and CaCl2 could significantly promote the growth of metallic iron particles, though the existence of Fe-bearing Mg2TiO4 in reduction products was not conducive to the reduction of iron. The formation of FeS would further hinder the reduction of iron after adding CaSO4.

Coextraction of vanadium and manganese from high-manganese containing vanadium wastewater by a solvent extraction-precipitation process

High-manganese containing vanadium wastewater (HMVW) is commonly produced during the vanadium extraction process from vanadium titano-magnetite. HMVW cannot be reused and discharged directly, and is harmful to the environment and affect product quality due to heavy metals in the wastewater. The wastewater is usually treated by lime neutralization, but valuable metals (especially V and Mn) cannot be recovered. In this study, an efficient and environmentally friendly method was developed to recover valuable metals by using a solvent extraction-precipitation process. In the solvent extraction process, 98.15% of vanadium was recovered, and the V2O5 product, with a purity of 98.60%, was obtained under optimal conditions. For the precipitation process, 91.05% of manganese was recovered as MnCO3 which meets the III grade standard of HG/T 2836-2011. Thermodynamic simulation analysis indicated that MnCO3 was selectively precipitated at pH 6.5 while Mg and Ca could hardly be precipitated. The results of X-ray diffraction and scanning electron microscopy demonstrated that the obtained V2O5 and MnCO3 displayed a good degree of crystallinity. The treated wastewater can be returned for leaching, and resources (V and Mn) in the wastewater were utilized efficiently in an environmentally friendly way. Therefore, this study provides a novel method for the coextraction of V and Mn from HMVW.

Leaching Behaviors of Impurities in Titanium-Bearing Electric Furnace Slag in Sulfuric Acid

Titanium-bearing electric furnace slag (TEFS) was prepared from vanadium titanomagnetite and leached with sulfuric acid. The Ti leaching rate of vanadium titanomagnetite TEFS is significantly lower than that of ilmenite TEFS. The impurity content in vanadium titanomagnetite TEFS is higher than that in ilmenite TEFS. This might be one of the main factors resulting in the low leaching rate of Ti, so the leaching behaviors of various impurities under different conditions (temperature, acid/solid weight ratio, particle size, and initial sulfuric acid concentration) were investigated. The following trends were observed under different leaching conditions: The leaching rate of Fe increased rapidly and reached equilibrium quickly, that of Si increased quickly in the early stage and then decreased in the later stage, that of Ca increased initially and reached equilibrium later, and the leaching rates of Mg and Al increased gradually until the equilibrium was reached. The leaching rate of Fe was too rapid to be able to investigate its leaching kinetics, and the insoluble leached products of Si and Ca interfered with their leaching. The effects of leaching parameters on the leaching of impurities were further analyzed by X-ray diffraction (XRD) and scanning electron microscopy analysis. XRD data indicated that spinel is the major Mg- and Al-bearing mineral in TEFS. Mg and Al showed similar leaching behaviors, and their leaching conformed to a new model based on interface transfer and diffusion across the product layer, both of which affect the leaching rate.

Blast Furnace Ironmaking Process with Super-High TiO2 in the Slag: Viscosity and Melting Properties of the Slag

To increase the utilization fraction of vanadium titano-magnetite in the blast furnace burden to > 80 pct, a new slag zone with high MgO was found. The effect of the TiO2 content and MgO/CaO mass ratio on the viscosity and liquidus temperature of the high TiO2-bearing blast furnace slag was investigated in the present work. The results indicated that at a fixed CaO/SiO2 ratio of 1.1, the viscosity decreases with increasing TiO2 content at a range of 20 to 34 mass pct. Conversely, increasing the MgO/CaO ratio from 0.32 to 0.65 causes a slight increase in the slag viscosity. The activation energy may show a concomitant variation corresponding to the viscosity of slag. The liquidus temperature first increases and then slightly decreases with TiO2 content. However, the liquidus temperature first decreases and then increases with the MgO/CaO ratio, similar to the variation of the thermodynamic calculation using FactSage software. Various viscosity models were employed to predict the viscosity, and Yan’s model was found to be the most reliable in predicting the viscosity in the present study. In addition, the iso-viscosity distribution diagram was obtained using Yan’s model calculation. It may have potential for application in the blast furnace ironmaking process with super-high (> 80 pct) vanadium titano-magnetite. A suitable slag composition was found to satisfy the smelting process in a blast furnace with super-high TiO2 content at low temperature by using more MgO and less CaO content.

Coal and Coke Based Reduction of Vanadium Titanomagenetite Concentrate by the Addition of Calcium Carbonate

ABSTRACT Effects of different coals and coke on the direct reduction of vanadium titanomagnetite concentrate (VTC) added with calcium carbonate were investigated. Lignite was found to provide a better reduction effect than bituminous coal, coke or anthracite, mainly because the gasification reactivity of lignite was obviously better than that of other three reductants, and the metallization degree could reach 95.11 wt% when used lignite. Coals and coke showed little influence on the existence form of Ti in the reduction product, where Ti existed mainly as calcium titanate. Additionally, lignite, coke or anthracite all promoted the growth of metallic iron and calcium titanate particles batter than bituminous coal, which were conducive to subsequent magnetic separation. However, the use of coke or anthracite gave lower purity calcium titanate because of the existence of unreduced iron. Furthermore, these reductants caused large amounts of FeS around metallic iron particles, which hindered the further reduction of iron.

Influence Mechanism of SiO2 on the Oxidation Behavior and Induration Process of Hongge Vanadium Titanomagnetite Pellets

As part of ongoing work to develop a low fuel consumption smelting process for comprehensive utilization of Hongge vanadium titanomagnetite (HVTM), the influence mechanism of SiO2 on the oxidation behavior and induration process of HVTM pellets (HVTMP) was investigated in this study. Results showed that as the amount of added SiO2 increased, the oxidation degree and compressive strength of HVTMP decreased rapidly while porosity increased. SiO2 had little effect on phase composition; however, it greatly influenced the microstructural evolution of HVTMP. Moreover, the Si-rich phases that precipitated at the grain boundary reduced grain migration, eventually suppressed grain growth, and affected the induration process. A schematic based on the experimental results was proposed to discuss the induration mechanism of HVTMP with different SiO2 additions. The results could provide theoretical and technical foundations for the comprehensive utilization of HVTM.

Research on mining filling material prepared by high titanium metallurgy waste residue

Using the vanadium titano-magnetite for iron-making, the steel enterprises have discharged water-quenched Ti-bearing slag. Due to the high titanium content, low activity and difficult-to-use characteristic, there are vast amount of high titanium slags, which not only occupies the land, but also causes resources wasting and environment polluted. This paper analyzed the chemical component, microstructure, grindability, activity index and other factors of high titanium slag and studied the mining filling material prepared by high titanium slag. The results show that the main chemical components of high titanium slag are similar with the ordinary slag. Both of them consist of CaO, SiO2 and Al2O3, all of which account for about 80% of the total weight. However, the content of TiO2 accounts for 8.4%, which is much higher than that of ordinary slag. Therefore, the grindability of TiO2 is poor. The solid waste cementitious material was prepared by slag, flue gas desulfurization gypsum and high titanium slag, whose specific surface area was 530 m2/kg. After the maintenance for 28 hours, the compressive strength of this material reaches 3MPa.

Investigation of the oxidation induration mechanism of Hongge vanadium titanomagnetite pellets with different Al2O3 additions

As part of an ongoing research on the development of a novel clean smelting process for the comprehensive utilization of Hongge vanadium titanomagnetite (HVTM), this study examined in detail the oxidation induration mechanism of HVTM pellets (HVTMP) with different Al2O3 additions. The results indicated that the addition of Al2O3 significantly lowered the oxidation degree and compressive strength of HVTMP mainly because of the markedly increased porosity and decreased grain size. However, Al2O3 exerted only a marginal effect on the phase composition. With an increase in the amount of Al2O3 added, grain growth was suppressed, the pore size significantly increased, and porous microstructures that formed by the non-homogenous distribution of grains were also obtained. Moreover, Al-rich phases distributed homogeneously in the grains and along the grain boundaries, resulting in the low oxidation induration of HVTMP. A schematic of the oxidation induration mechanism is also presented based on the experimental results, providing a reference for the production of HVTMP and other Al-bearing Fe–Ti oxide minerals.

Effect of Cr2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets (CVTP) with Cr2O3 addition were studied, and the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP with simulated coke oven gas (COG) injection were investigated. The results showed that the CS of the CVTP decreases and the porosity of the CVTP increases with increasing amount of Cr2O3 added. The Cr2O3 mainly exists in the form of (Cr, Fe)2O3 solid solution in the CVTP and as Fe-Cr in the reduced CVTP. The CS of the reduced CVTP increases and the RSI of the reduced CVTP decreases with increasing amount of Cr2O3 added. The limited aggregation and diffusion of metallic iron contribute to the formation of dense lamellar crystals, which leads to the slight decrease for reduction swelling behavior of reduced CVTP. This work provides a theoretical and technical basis for the utilization of CVTP and other Cr-bearing ores such as chromite with COG recycling technology.

Thermodynamic studies on gas-based reduction of vanadium titano-magnetite pellets

Numerous studies have focused on the reduction thermodynamics of ordinary iron ore; by contrast, the literature contains few thermodynamic studies on the gas-based reduction of vanadium titano-magnetite (VTM) in mixed atmospheres of H2, CO, H2O, CO2, and N2. In this paper, thermodynamic studies on the reduction of oxidized VTM pellets were systematically conducted in an atmosphere of a C–H–O system as a reducing agent. The results indicate that VTM of an equivalent valence state is more difficult to reduce than ordinary iron ore. A reduction equilibrium diagram using the C–H–O system as a reducing agent was obtained; it clearly describes the reduction process. Experiments were performed to investigate the effects of the reduction temperature, the gas composition, and two types of iron ores on the reduction of oxidized VTM pellets. The results show that the final reduction degree increases with increasing reduction temperature, increasing molar ratio of H2/(H2 + CO), and decreasing H2O, CO2, and N2 contents. In addition, the reduction processes under various conditions are discussed. All of the results of the reduction experiments are consistent with those of theoretical thermodynamic analysis. This study is expected to provide valuable thermodynamic theory on the industrial applications of VTM.

Effect of B2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

Abstract The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.

Effect of V<sub>2</sub>O<sub>5</sub> Addition on Oxidation Induration and Swelling Behavior of Chromium-Bearing Vanadium Titanomagnetite Pellets with Simulated Coke Oven Gas Injection into Blast Furnace

Effect of V<sub>2</sub>O<sub>5</sub> Addition on Oxidation Induration and Swelling Behavior of Chromium-Bearing Vanadium Titanomagnetite Pellets with Simulated Coke Oven Gas Injection into Blast Furnace