Panzhihua Ilmenite Research Articles

Carbothermic reduction of Panzhihua ilmenite in vacuum

The carbothermic reduction of Panzhihua ilmenite with activated carbon in vacuum was investigated by isothermal experiments over the temperature range of 1473–1773 K. The reaction mechanism of the impurity elements in vacuum was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermodynamic calculation. It was found that when the reaction temperature was higher than 1673 K and the reaction time was longer than 4 h, the main phases of the final products obtained at 10 Pa were Fe and TiC, without the presence of MgO and MgAl2O4 which existed when roasting at 1 atm in argon atmosphere. The contents of Mg and Mn in the products decreased with increasing the reaction temperature or lowering the pressure. After the carbothermic reduction process, the main impurity elements of Si and Al were dissolved in the iron.

The application of a new type of hydraulic classification equipment: swirl continuous centrifugal separator

Swirl Continuous centrifugal concentrator was based on principle of hydro cyclone and fluidized bed separation, which is new hydraulic grading equipment. The effect of new equipment on the classification of Panzhihua ilmenite was studied under different operating conditions. The results show that the underflow pressure, the overflow rate, the feed pressure and the recoil pressure have a significant effect on the grading effect of the cyclone centrifugal continuous concentrator. At the same time, the classification effect on the Titanium magnetite of this concentrator is significant. The new equipment is hopeful to be generalized and gradually used in practice of hydraulic classification.

Vacuum Carbothermic Reduction of Panzhihua Ilmenite Concentrate: A Thermodynamic Study

ABSTRACTElectric arc furnace is mainly used in the production of high titania slag; however, since impurities cannot be eliminated, this causes difficulty in the production of titania pigment with chlorination process. Consequently, removing impurities is the crucial way to deal with low-grade ilmenite, especially for the Panzhihua ilmenite concentrate in China. This article studied the theoretical calculation of vacuum carbothermic reduction of Panzhihua ilmenite concentrate. Thus, when the temperature was higher than 1600°C and the carbon amount was greater than 12%, all of the Fe almost entered into the gas phase. When the temperature was higher than 1300°C and the carbon amount was greater than 14%, magnesium also entered the gas phase. When the temperature was higher than 1100°C, most of the element manganese was volatilized in the gas phase. The TiO2 grade increased with the increase in carbon amount (14%). When the temperature was higher than 1600°C and the carbon amount was less than 14%, the TiO2 grade in the slag phase could reach the maximum value, which can be used for the chlorination process to prepare titanium dioxide.

Reductive kinetics of Panzhihua ilmenite with hydrogen

The hydrogen reduction of Panzhihua ilmenite concentrate in the temperature range of 900–1050 °C was systematically investigated by thermogravimetric analysis (TG), X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. It was shown that the products of the Panzhihua ilmenite reduced at 900 °C were metallic iron and rutile. Above 1000 °C, ferrous pseudobrookite solid solution was generated. During the reduction process, element Mg gradually concentrated to form Mg-rich zone which can influence the metallization process. The reduction reaction proceeded topochemically and its related reduction kinetics were also discussed. The kinetics of the reduction indicated that the rate-controlling step was the diffusion process. The apparent activation energy of the hydrogen reduction of Panzhihua ilmenite was calculated to be 117.56 kJ/mol, which was larger than that of synthetic ilmenite under the same reduction condition.

Comprehensive utilization of Panzhihua ilmenite concentrate by vacuum carbothermic reduction

An electric arc furnace is mainly employed to produce high titania slag, although impurities could not be removed through this process, making the production of titania pigment through chlorination difficult. Removal of impurities is crucial to fully utilize low-grade ilmenite, especially the Panzhihua ilmenite concentrate obtained in China. This work proposes a new process to maximize Panzhihua titanium resources. Panzhihua ilmenite concentrate was reduced in a vacuum furnace, and residual slag and condensations were subsequently obtained. When the temperature exceeded 1500 °C and the carbon content exceeded 12%, Mg and Si impurities were removed, entered the gas phase, and formed ferrosilicon alloy. Finally, high-grade titania slag was obtained.

Preparation of nano-titanium dioxide from ilmenite using sulfuric acid-decomposition by liquid phase method

In this study, high purity nano-TiO2 was prepared from Panzhihua ilmenite using sulfuric acid-decomposition by liquid phase method. The effects of H2SO4 molar volume, reaction time, initial pre-heating temperature and H2SO4 concentration on the decomposition rate of ilmenite were investigated in detail. The results showed that the decomposition rate reached 95.21% under the optimal conditions. The resulting titanium solution was qualified with 121g/L Ti4+. Since the initial pH value of hydrolysis system was below 3, the precipitation of metatitanic acid was obtained by direct hydrolysis of the titanium solution. On the other hand, the well-crystallized anatase and rutile were achieved at different calcination temperatures. The purity of the as-prepared TiO2 was above 99% with an average particle size of about 40–100nm. The ilmenite ore, intermediates and final products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray fluorescence spectrometer (EDS), X-ray fluorescence spectroscopy (XRF), thermal gravimetric analysis (TG), inductive coupled plasma emission spectrometer (ICP) and spectrophotometer. The results demonstrated that the process was suitable for industrial production because it was inexpensive, environment-friendly and promising in the preparation of high purity nano-TiO2.

Influence of redox pretreatment on the pulverization of panzhihua ilmenite during hydrochloric acid leaching

The influence of oxidation-reduction (redox) pretreatment on the pulverization of Panzhihua ilmenite during hydrochloric acid leaching to obtain synthetic rutile was investigated in detail. We observed the dissociation of incompact TiO2 products formed via the dissolution-hydrolysis of Ti ions, which was caused by the fast dissolution of FeTiO3 during the leaching process and was the fundamental reason for pulverization for the raw Panzhihua ilmenite. A stirring operation during the acid leaching aggravated the pulverization phenomenon. The formation and consumption of insoluble rutile grains during the redox pretreatment played a key role in preventing the pulverization of pre-treated ilmenites. The rutile network formed during the pre-oxidation was retained and served as a nucleus for the hydrolyzed product during the successive leaching process, providing the leaching products of the pre-oxidized ilmenite with less hydrolyzed TiO2, higher mechanical strength, and thus an excellent resistance to pulverization, even with stirred leaching. Because the following weak reduction process (reduction of ferric iron to ferrous state) at relatively low temperatures (e.g., 873K) did not destroy the rutile network that was formed by the pre-oxidation, it did not change the ability of the pre-oxidation to prevent the pulverization of ilmenite. However, the weak reduction process at high temperatures (e.g. 1023K) weakened the effect of pre-oxidation because most of the rutile grains that were formed by the pre-oxidation were consumed and formed FeTiO3.

Influence of Pre-oxidation on Carbothermic Reduction Process of Ilmenite Concentrate

The pre-oxidation of Panzhihua ilmenite concentrate was investigated at 1073 K and 1273 K under air atmosphere. The products of the pre-oxidation at 1073 K were Fe2O3, TiO2 and Fe2Ti3O9, while Fe2O3, TiO2 and Fe2TiO5 at 1273 K. The influences of pre-oxidation on the carbothermic reduction were studied at 1473 K, 1573 K, 1673 K and 1773 K under argon atmosphere. It was found that the main phases during the reduction process were Ti3O5, Fe, Fe3C, Ti2O3 and TiCxOy. The pre-oxidation was beneficial to the formation of TiCxOy phase compared to the direct carbothermic reduction without pre-oxidation. And the pre-oxidation at 1273 K was better for the carbothermic reduction than pre-oxidation at 1073 K. The rate controlling steps for the carbothermic reduction obeyed the diffusion model. After being reduced for 2 h at 1773 K, the product was changed to TiC with only little O content.

Mineral surface modification induced by low energy ion irradiation: Implications for solar-wind exposure effects in lunar soil

We performed ion irradiation on olivine and ilmenite to simulate solar-wind exposure effects in lunar soil. The surface morphology and microstructure after ion irradiation were characterized by field emission scanning electron microscopy. Sputtering erosion significantly modified the surface of irradiated Luobusha olivine grains. All irradiated grains show smooth surface and round shape. The cleavage fractures on the unirradiated olivine surface were widened and deeply etched after He+ irradiation. Both of these are the consequence of ion sputtering erosion. There are no bubbles or voids foundin the irradiated olivine grains, because He+ dose in this study is lower than saturated fluence. Irradiated Panzhihua ilmenite grains are all covered with smooth flakes with the thickness of about 400 nm. The formation of the flakes should be related with helium bubbles and their growth during He+ implantation. Some columnar-shaped particles are found at the surface of irradiated Panzhihua ilmenite. We speculate that these particles should be sulfide because of significantly high sulfur contents.

Beneficiation of titania by sulfuric acid pressure leaching of Panzhihua ilmenite

The beneficiation of titania (TiO2) by sulfuric acid (H2SO4) pressure leaching of Panzhihua ilmenite was investigated. The reaction temperature, H2SO4 concentration, and concentration of ferrous ions (Fe2+) had significant effects on the enrichment of TiO2. With increasing reaction temperatures, the dissolution of iron from ilmenite was enhanced, while the titanium loss was reduced. Increasing the concentration of Fe2+ had an adverse effect on the beneficiation of TiO2. In contrast, the dissolution of iron from ilmenite was accelerated by increasing concentrations of H2SO4, up to 40wt.% H2SO4. SEM analyses of the leach residues under different leaching conditions indicated that severe agglomeration occurred among the primary hydrolysate particles at high concentrations of H2SO4 or with the addition of ferrous sulfate (FeSO4). Furthermore, a compact layer was formed on the surface of unreacted ilmenite particles, thus retarding the ilmenite leaching. The agglomeration might have resulted from the adsorption of H2SO4 on the primary particle surfaces, as revealed by energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA). The optimal conditions for the beneficiation process were as follows: H2SO4 concentration 40wt.%, acid/ore mass ratio 2:1, reaction temperature 150°C, and reaction time 3h. Thus, a Ti-rich material with a TiO2 content of ~85wt.% was obtained. Moreover, the results demonstrated the technical feasibility of upgrading Panzhihua ilmenite in 40wt.% sulfuric acid obtained by concentrating the diluted acid waste discharged from the sulfate TiO2 process.

Kinetics and mechanism of hydrogen reduction of ilmenite powders

Both isothermal and non-isothermal reduction experiments of Panzhihua ilmenite powders by pure hydrogen were carried out using a thermo-gravimetric (TG) analyzer. Results of X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopic (EDS) analyses showed that in the temperature range of 1146–1201K, the main products were metallic iron, TiO2 and MgTiO3 with the iron being embedded in TiO2 matrix. It was found that the reduction reaction was controlled by the chemical reaction at the reaction interface and the apparent activation energy was extracted to be 98.35–99.02kJ/mol by using a new kinetic model. However, under the non-isothermal condition, as gradually increasing the temperature to 1493K, TiO2 and MgTiO3 could be reduced, and the final products were metallic iron and MgxTi3−xO5 (x was in the range of 0.45–1).

Phase Evolution During the Carbothermic Reduction Process of Ilmenite Concentrate

The phase evolution during the carbothermic reduction process of Panzhihua ilmenite concentrate was investigated under argon atmosphere. The Panzhihua ilmenite concentrate briquette with graphite powder was reduced at 1473 K, 1573 K, 1673 K, and 1773 K (1200 °C, 1300 °C, 1400 °C, and 1500 °C) respectively, with the molar ratios of C to FeTiO3 being 4:1 and 5:1. The phase transformation of the briquette reduced at different temperatures was investigated by X-ray diffraction and scanning electron microscope. During the carbothermic reduction process from 1473 K to 1773 K (1200 °C to 1500 °C), it was found that main phases were Fe, Ti3O5, Ti2O3, and TiC x O y . The lowest temperature for the generation of TiC x O y was 1573 K (1300 °C) for both kinds of briquettes with different C contents. The rate controlling step for the carbothermic reduction above 1573 K (1300 °C) obeyed the diffusion model. The reduction degree of the ilmenite was increased by increasing the temperature. With the increase of reaction temperature and reaction time, TiC x O y phase would be reduced to TiC phase.

Effect of microwave irradiation on selective heating behavior and magnetic separation characteristics of Panzhihua ilmenite

The influences of microwave irradiation on the surface characteristics of Panzhihua ilmenite were systematically investigated. The crystal structures, surface morphology and surface chemical functional groups of ilmenite were characterized before and after microwave irradiation and magnetic separation for different microwave treatment times by using various methods, such as XRD, SEM, and FT-IR, respectively. XRD analysis showed that the microwave treated ilmenite has the strongest peaks of phase more than that of raw samples, indicates that the crystalline compound of ilmenite increased with the microwave irradiation time. SEM analysis showed the micro-cracking appeared at many grain boundaries of ilmenite after being pretreated by microwave treatment. The separations of ilmenite from gangue minerals were completed and the micro-fissure within ilmenite minerals were also formed, which could be attributed to the microwave selective heating characteristics of the different minerals and compounds, and the thermal stresses were caused by the uniform heat rate disturbed under microwave irradiation. The mineral processing results showed that the magnetic separation characteristics and properties of microwave treated ilmenite samples were better than that of microwave untreated ilmenite samples. It was concluded that microwave irradiation can be applied effectively and efficiently to the irradiation processes of Panzhihua ilmenite.

Morphological Changes and Reduction Mechanism for the Weak Reduction of the Preoxidized Panzhihua Ilmenite

Morphological changes and phase transition behaviors were investigated for the weak reduction (reduction of ferric iron-to-ferrous state) of preoxidized Panzhihua ilmenite by hydrogen at 873 K to 1073 K (600 °C to 800 °C). Ilmenite was preoxidized for 4 hours at 1023 K and 1173 K (750 °C and 900 °C), respectively, before the reduction. The results revealed that there were two competing reduction routes. At high reduction temperatures, e.g., 1023 K and 1073 K (750 °C and 800 °C), ferric irons from both hematite and pseudobrookite would combine with rutile grains as formed in the preoxidation to form homogeneous ilmenite phase with pores immingled. However, at lower reduction temperatures, e.g., 873 K (600 °C), hematite and pseudobrookite are reduced mainly through direct reduction without the participation of rutile. As a result, the as-reduced ilmenites show great differences in their phase components and microstructure, especially for the Ti species. For ilmenites preoxidized at 1023 K (750 °C), most of the Ti ions present in the needlelike rutile network, but for ilmenites preoxidized at 1173 K (900 °C), Ti distributed in both irregular rutile grains and ilmenite matrix.

Effect of temperature on dielectric property and microwave heating behavior of low grade Panzhihua ilmenite ore

The permittivity of low grade Panzhuhua ilmenite ore at 2.45 GHz in the temperatures from 20 °C up to 100 °C was measured using the technology of open-ended coaxial sensor combined with theoretical computation. The results show that both the real (ε′ and imaginary (ε″ part of complex permittivity (ε′jε″ of the ilmenite significantly increase with temperature. The loss tangent (tan δ) is a quadratic function of temperature, and the penetration depth of ilmenite decreases with temperature increase from 20 °C to 100 °C. The increase of the sample temperature under microwave radiation displays a nonlinear relationship between the temperature (T) and microwave heating time (t). The positive feedback interaction between complex permittivity and sample temperature amplifies the interaction between ilmenite and the microwave radiation. The optimum dimensions for uniform heat deposition vary from 10 cm to 5 cm (about two power penetration depths) in a sample being irradiated from both sides in a 2.45 GHz microwave field when temperature increases from room temperature to 100 °C.

Influence of phase and microstructure on the rate of hydrochloric acid leaching in pretreated Panzhihua ilmenite

The present study investigated the influence of high temperature oxidation and reduction pretreatments on the leaching rate of Panzhihua ilmenite. The as-pretreated ilmenite was leached with 20% HCl at 105°C. The leaching process was controlled by the phases and microstructures that evolved during the pretreatment processes. The leaching kinetics of pure hematite, ilmenite and pseudobrookite were characterized to clarify the phase effect on the iron-leaching rate; the rate of iron leaching occurs in the following order in the HCl solution: hematite (ferric iron)>ilmenite (ferrous iron)≫pseudobrookite (ferric iron). Therefore, the often-cited notion that ferrous iron dissolves faster in HCl solutions than ferric iron when explaining the pretreatment effects is inaccurate. Moreover, the oxidation pretreatment (at 600–1000°C for 4h) cannot destroy the dense structure of the Panzhihua ilmenite. Therefore, the influence exerted by the oxidation on the leaching process is primarily determined by the phase change; oxidation at 600 and 700°C slightly increased the rate of iron leaching because the ilmenite was transformed into hematite, while the oxidation at 900–1000°C significantly reduced the rate of iron leaching because a pseudobrookite phase formed. The reduction effect was subsequently investigated; the as-oxidized ilmenite was reduced under H2 at 750°C for 30min. The reduction significantly accelerated the rate of subsequent iron leaching such that nearly all of the iron had dissolved after leaching for 2h in 20% HCl at 105°C. This enhanced iron-leaching rate is mainly attributed to the cracks and holes that formed during the reduction process.

Morphological Changes of Panzhihua Ilmenite During Oxidation Treatment

Morphological changes with the phase transitions were investigated in detail for the oxidation roasting of Panzhihua ilmenite in air from 873 K to 1173 K (600 °C to 900 °C). It was found that a thin hematite layer of 1 to 2 μm formed rapidly at the initial stage of the oxidation process, independent of the oxidation temperature, on the surface of ilmenite particles, and the thickness of the hematite layer kept nearly constant with increasing time of oxidation. The morphology inside an ilmenite particle, however, changed with the oxidation temperature. Needlelike rutile network enwrapped by hematite grains was observed after oxidation below 1073 K (800 °C), and the structure can be well preserved during the oxidation process, although grain growth of rutile and hematite did occur with the extension of the oxidation time. The morphological changes at 1073 K (800 °C) and higher showed two distinct stages, where in the first stage ilmenite was oxidized to form rutile and hematite with morphology similar to that of oxidation below 1073 K (800 °C). The as-formed rutile and hematite were not stable and recombined to form pseudobrookite in the second stage, which caused significant morphology change; i.e., the needlelike rutile network gradually “dissolved” to form the final morphology of irregular rutile grains dispersed in the pseudobrookite matrix with some isolated hematite grains. Moreover, the oxidation temperature also has a great effect on the rate of morphological changes, i.e., the increased evolution rate with increasing the oxidation temperature.

Enhancement Reduction of Panzhihua Ilmenite Concentrate with Coke and Conglomeration of Metal with Ferrosilicon

AbstractThe particle size and metallization ratio of iron in reduced ilmenite have an important function in separating the metal from TiO2‐rich slag in the electric arc furnace process. In this study, an ilmenite concentrate supplied by Panzhihua Iron and Steel (Group) Co. was reduced at 1380°C in an electric resistance furnace. The effects of Fe–Si addition and reduction time on the particle size and metallization ratio of iron in the reduced sample were analyzed. The metallization ratio of iron significantly increased with increasing Fe–Si amount and reduction time, and reached ≈90% after 40 min. However, the metallization ratio of iron was about 85% without Fe–Si addition. Meanwhile, the iron particle size increased with increasing Fe–Si amount; the growth was obvious with the addition of 1% Fe–Si. Moreover, the growth rate of the iron particle size also increased with increasing reduction time. The TG‐DTG curves indicated that the mass loss with Fe–Si addition was less than that without Fe–Si addition, and the temperature at which the maximum rate of mass loss rate was achieved was lower than that without Fe–Si addition.

Solid state and smelting reduction of Panzhihua ilmenite concentrate with coke

Solid state and smelting reduction of ilmenite is an important process of upgrading ilmenite to high titania feedstock. In this study, an ilmenite concentrate supplied by Panzhihua Iron and Steel (Group) Co. was first reduced at solid state in an electric resistance furnace, followed by smelting reduction in an induction furnace. The effects of reducing agent (carbon) amount on the chemical composition of the solid state reduction sample and the titania slag reduced from them, were analysed. It was found that the metallisation of iron in the solid reduction samples and the grade of titania slag generally increased with increasing carbon amount from 8 to 12%, and then remained constant when the carbon amount was increased above 12%. The content of metallic iron in the titania slag increased with increasing carbon amount, because the slag viscosity and liquidus temperature increased with decreasing FeO content. It was also known that the content of Ti2O3 increased with decreasing the content of FeO in the slag. Some metallic iron particles were found in the high titania slag samples. The liquidus lines and viscosity of the slag were calculated using FactSage to explain the experimental results.La réduction à l’état solide et par fusion de l’ilménite est un procédé important de valorisation de l’ilménite pour charge d’alimentation à haute teneur en dioxyde de titane. Dans cette étude, un concentré d’ilménite fourni par le groupe Panzhihua Iron and Steel Co. a d’abord été réduit à l’état solide dans un four électrique à résistances, suivi par la réduction par fusion dans un four à induction. On a analysé les effets de la quantité d’agent réducteur (carbone) sur la composition chimique de l’échantillon de réduction à l’état solide et de la scorie de dioxyde de titane réduit à partir de lui. On a trouvé que la métallisation du fer dans les échantillons de réduction solide et la qualité de la scorie de dioxyde de titane augmentaient généralement avec une augmentation de la quantité de carbone de 8 à 12%, et ensuite restaient constantes lorsqu’on augmentait la quantité de carbone au-delà de 12%. La teneur en fer métallique dans la scorie de dioxyde de titane augmentait avec l’augmentation de la quantité de carbone, parce que la viscosité de la scorie et la température du liquidus augmentaient avec une diminution de la teneur en FeO. On sait également que la teneur en Ti2O3 augmentait avec une diminution de la teneur en FeO dans la scorie. On a trouvé quelques particules de fer métallique dans les échantillons de scorie à haute teneur en dioxyde de titane. On a calculé les lignes de liquidus et la viscosité de la scorie en utilisant FactSage pour expliquer les résultats expérimentaux.

Effects of space weathering on diagnostic spectral features: Results from He+ irradiation experiments

We performed ion irradiation of mineral samples with 50keV He+, aimed to investigate ion irradiation effects on diagnostic spectral features. Reflectance spectra of samples in 0.375–2.5μm are measured before and after ion irradiation. Silicates, including Luobusha olivine, plagioclase and basaltic glass, have shown reddening and darkening of reflectance spectra at the VIS–NIR range. Olivine is more sensitive to ion irradiation than plagioclase and basaltic glass. Irradiated Panzhihua ilmenite exhibits higher reflectance and stronger absorption features, which is totally different from lunar soil and analog silicate materials in other experiments. Using continuum removal and MGM fit, we extracted and compared absorption features of olivine spectra before and after irradiation. Ion irradiation can induce band strength decrease of olivine but negligible band centers shift. We estimate band centers shift caused by ion irradiation are quite limited, even less than variations due to chemical composition in silicates. It provides one possible explanation for no systematic shift in band positions in lunar soil. Irradiated Luobusha olivine spectrum matches spectra of olivine-dominated asteroids. Our results suggest space weathering should be new clues to explain the subtle difference between A-type asteroid spectra and laboratory spectra of olivine.