Thermodynamic Consideration of the Removal of Iron from Titanium Ore by Selective Chlorination

Thermodynamic study of the chlorination reactions of oxides such as titanium oxides and iron oxides at elevated temperatures was carried out in order to consider the removal of iron from titanium ore using selective chlorination method. In particular, various chlorination reactions were analyzed by utilizing chemical potential diagrams, and the applicability and usefulness of this thermodynamic study for analyzing the selective chlorination of titanium ore were demonstrated. Furthermore, chlorination reactions using various types of chlorinating agents were discussed from different viewpoints. It was shown that the selective chlorination of iron from titanium ore by HCl gas is thermodynamically feasible and efficient for upgrading titanium ore. Further, thermodynamic analysis showed that under certain conditions, TiCl₄ can be used as a chlorinating agent for the iron in the ore, and iron can be removed by evaporation directly from the ore as chloride gas. The results presented in this study provide useful information for developing a process for upgrading low-grade titanium ore for use as a titanium smelting feed through a dry method.     

Preparation of High-Grade Titania Slag from Ilmenite-Bearing High Ca and Mg by Vacuum Smelting Method

Ilmenite produced from the Panxi area in China has high impurities such as Ca and Mg. High-grade titanium (Ti) slag can be obtained by the electric arc furnace process, a traditional method of treating ilmenite. Thus, Ti slag prepared from the Panxi ilmenite contains high CaO and MgO, exceeding 5 pct of the slag content. This high CaO and MgO content confers considerable difficulty in producing titania (TiO₂) white using fluidizing chlorination. In this study, a new process named vacuum separation was found to produce high-grade TiO₂ materials. The effects of separation temperature and time on the TiO₂ grade were studied. The high-grade TiO₂ slag, which has 93 pct TiO₂, <0.1 pct MgO, <1.2 pct SiO₂, and <0.5 pct CaO, can be produced at 1823 K (1550 °C) in 45 minutes through the proposed method.     

Production of Titanium Powder by Sodiothermic Reduction in CaCl2 Molten Salts

A new sodiothermic reduction process of TiO₂ in CaCl₂ melt was proposed aimed at fine Ti powder preparation. The chemical analysis and direct potentiometric methods were used to investigate the reaction pathway of sodiothermic reduction in CaCl₂ melt. The as-prepared samples were characterized by X-ray diffraction and scanning electron microscopy. It was found that when reductant of Na was added into the CaCl₂ melt, Ca²⁺ was reduced to Ca by Na and Ca dissolved in the CaCl₂ melt. The whole melt would have the reducing power with dissolved Ca. Using this melt as a reaction medium, fine and uniform Ti powder with a purity of around 99 mass pct was successfully produced at 1173 K (900 °C). In addition, as the CaCl₂ melt could dissolve about 20 mol pct CaO, it was found that the molar ratio of TiO₂ and CaCl₂ should be 1:20 to eliminate the by-product CaO from the reaction interface within the experimental period to continue the reduction.     

Microbial Beneficiation of Salem Iron Ore Using Penicillium purpurogenum

High alumina and silica content in the iron ore affects coke rate, reducibility, and productivity in a blast furnace. Iron ore is being beneficiated all around the world to meet the quality requirement of iron and steel industries. Choosing a beneficiation treatment depends on the nature of the gangue present and its association with the ore structure. The advanced physicochemical methods used for the beneficiation of iron ore are generally unfriendly to the environment. Biobeneficiation is considered to be ecofriendly, promising, and revolutionary solutions to these problems. A characterization study of Salem iron ore indicates that the major iron-bearing minerals are hematite, magnetite, and goethite. Samples on average contains (pct) Fe₂O₃-84.40, Fe (total)-59.02, Al₂O₃-7.18, and SiO₂-7.53. Penicillium purpurogenum (MTCC 7356) was used for the experiment. It removed 35.22 pct alumina and 39.41 pct silica in 30 days in a shake flask at 10 pct pulp density, 308 K (35 °C), and 150 rpm. In a bioreactor experiment at 2 kg scale using the same organism, it removed 23.33 pct alumina and 30.54 pct silica in 30 days at 300 rpm agitation and 2 to 3 l/min aeration. Alumina and silica dissolution follow the shrinking core model for both shake flask and bioreactor experiments.     

Thermodynamics of TiO x in blast furnace-type slags

Equilibrium studies between CaO-SiO₂-10 pct MgO-Al₂O₃-TiO_1.5-TiO₂ slags, carbon-saturated iron, and a carbon monoxide atmosphere were performed at 1773 K to determine the activities of TiO_1.5 and TiO₂ in the slag. These thermodynamic parameters are required to predict the formation of titanium carbonitride in the blast furnace. In order to calculate the activity of titanium oxide, the activity coefficient of titanium in carbon-saturated iron-carbon-titanium alloys was determined by measuring the solubility of titanium in carbon-saturated iron in equilibrium with titanium carbide. The solubility and the activity coefficient of titanium obtained were 1.3 pct and 0.023 relative to 1 wt pct titanium in liquid iron or 0.0013 relative to pure solid titanium at 1773 K, respectively. Over the concentration range studied, the effect of the TiO _x content on its activity coefficient is small. In the slag system studied containing 35 to 50 pct CaO, 25 to 45 pct SiO₂, 7 to 22 pct Al₂O₃, and 10 pct MgO, the activity coefficients of TiO_1.5 and TiO₂ relative to pure solid standard states range from 2.3 to 8.8 and from 0.1 to 0.3, respectively. Using thermodynamic data obtained, the prediction of the formation of titanium carbonitride was made. Assuming hypothetical ‘TiO₂,’ i.e., total titanium in the slag expressed as TiO₂, and using the values of the activity coefficients of TiO_1.5 and TiO₂ determined, the equilibrium distribution of titanium between blast furnace-type slags and carbon-saturated iron was computed. The value of [pct Ti]/(pct ‘TiO₂’) ranges from 0.1 to 0.2.     

Evaluation of Isothermal Separating Perovskite Phase from CaO-TiO2-SiO2-Al2O3-MgO Melt by Super Gravity

Perovskite phase was successfully separated from CaO-TiO₂-SiO₂-Al₂O₃-MgO melt by super gravity. Under the hypothesis that the titanium exists in the slag in terms of TiO_2, with the gravity coefficient G = 600, time t = 5 minutes, and temperature T = 1563 K (1290 °C), the mass fraction of TiO₂ in the concentrate is up to 52.94 pct, while that of the tailing is just 5.88 pct. The recovery ratio of Ti in the concentrate is up to 81.28 pct by centrifugal separation.     

Chlorination Kinetics of Titanium Nitride for Production of Titanium Tetrachloride from Nitrided Ilmenite

The kinetics of chlorination of titanium nitride (TiN) was investigated in the temperature range of 523 K to 673 K (250 °C to 400 °C). The results showed that the extent of chlorination slightly increased with increasing temperature and decreasing particle size of titanium nitride at constant flow rate of N₂-Cl₂ gas mixture. At 523 K (250 °C), the extent of chlorination was 85.6 pct in 60 minutes whereas at 673 K (400 °C), it was 97.7 pct investigated by weight loss measurement and confirmed by ICP analyses. The experimental results indicated that a shrinking unreacted core model with mixed-control mechanism governed the chlorination rate. It was observed that the surface chemical reaction of chlorine gas on the surface of TiN particles was rate controlling in the initial stage and, during later stage, internal (pore) diffusion through the intermediate product layer was rate controlling step. Overall the process follows the mixed-control model incorporating both chemical reaction and internal diffusion control. The activation energy for the chlorination of TiN was found to be about 10.97 kJ mol^?1. In processing TiCl₄ from TiN and TiO_0.02C_0.13N_0.85, the solids involved in the chlorination process were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectrometer (EDX). The SEM/EDX results demonstrated the consumption of TiN particles with extent of chlorination that showed shrinking core behavior.     

Reduction of Sn-Bearing Iron Concentrate with Mixed H<Subscript>2</Subscript>/CO Gas for Preparation of Sn-Enriched Direct Reduced Iron

The development of manufacturing technology of Sn-bearing stainless steel inspires a novel concept for using Sn-bearing complex iron ore via reduction with mixed H₂/CO gas to prepare Sn-enriched direct reduced iron (DRI). The thermodynamic analysis of the reduction process confirms the easy reduction of stannic oxide to metallic tin and the rigorous conditions for volatilizing SnO. Although the removal of tin is feasible by reduction of the pellet at 1223 K (950 °C) with mixed gas of 5 vol pct H₂, 28.5 vol pct CO, and 66.5 vol pct CO₂ (CO/(CO + CO₂) = 30 pct), it is necessary that the pellet be further reduced for preparing DRI. In contrast, maintaining Sn in the metallic pellet is demonstrated to be a promising way to effectively use the ore. It is indicated that only 5.5 pct of Sn is volatilized when the pellet is reduced at 1223 K (950 °C) for 30 minutes with the mixed gas of 50 vol pct H₂, 50 vol pct CO (CO/(CO + CO₂) = 100 pct). A metallic pellet (Sn-bearing DRI) with Sn content of 0.293 pct, Fe metallization of 93.5 pct, and total iron content of 88.2 pct is prepared as a raw material for producing Sn-bearing stainless steel. The reduced tin in the Sn-bearing DRI either combines with metallic iron to form Sn-Fe alloy or it remains intact.     

Calciothermic reduction of titanium oxide and <Emphasis Type="Italic">in-situ</Emphasis> electrolysis in molten CaCl<Subscript>2</Subscript>

A concept for calciothermic direct reduction of titanium dioxide in molten CaCl₂ is proposed and experimentally tested. This production process consists of a single cell, where both the thermochemical reaction of the calciothermic reduction and the electrochemical reaction for recovery of the reducing agent, Ca, coexist in the same molten CaCl₂ bath. A few molar percentages of Ca dissolve in the melt, which gives the media a strong reducing power. Using a carbon anode and a Ti basket-type cathode in which anatase-type TiO₂ powder was filled, a metallic titanium sponge containing 2000 ppm oxygen was produced after 10.8 ks at 1173 K in the CaCl₂ bath. The optimum concentration of CaO in the molten CaCl₂ was 0.5 to 1 mol pct, to shorten the operating time and to achieve a lower oxygen content in Ti.     

Solid-State Metalized Reduction of Magnesium-Rich Low-Nickel Oxide Ores Using Coal as the Reductant Based on Thermodynamic Analysis

The solid-state metalized reduction of magnesium-rich low-nickel oxide ore using coal as a reductant was studied based on thermodynamic analysis. The major constituent minerals of the ore were silicates and goethite. The former was the main nickel-bearing mineral, and the latter was the main iron-bearing mineral. Single factor tests were conducted to investigate the effects of reduction temperature, duration, and coal dosage on the beneficiation of nickel and iron such that optimal conditions were achieved. Considering the low recoveries of nickel and iron (Ni, 13.9 pct; Fe, 30.3 pct) under the obtained optimal conditions, an improved process, adding CaF₂ before the reaction, was proposed to modify the solid-state metalized process. The results showed that the recoveries of nickel and iron reached to 96.5 and 73.4 pct, respectively, and that the grades of nickel and iron in the concentrate increased from 2.5 and 62.6 wt pct to 6.9 and 71.4 wt pct, respectively. Nickel and iron in the absence of CaF₂ were metalized; nevertheless, the size of ferronickel particles was only 1 μm. Furthermore, alloys in the presence of CaF₂ aggregated and exhibited bands with a length greater than 200 µm. These observations suggested that CaF₂ could effectively reduce the surface tension of the newly generated alloy interface and promote the migration and polymerization of the alloy particles, which improves the beneficiation of nickel and iron by magnetic separation.     

Recovery of Iron from Pyrite Cinder Containing Non-ferrous Metals Using High-Temperature Chloridizing-Reduction-Magnetic Separation

This study presents a new technique that uses high-temperature chloridizing -reduction-magnetic separation to recover iron from pyrite cinder containing non-ferrous metals. The effects of the reduction temperature, reduction time, and chlorinating agent dosage were investigated. The optimized process parameters were proposed as the following: CaCl₂ dosage of 2 pct, chloridizing at 1398 K (1125 °C) for 10 minutes, reducing at 1323 K (1050 °C) for 80 minutes, grinding to a particle size of 78.8 pct less than 45 μm, and magnetic field intensity of 73 mT. Under the optimized conditions, the Cu, Pb, and Zn removal rates were 45.2, 99.2, and 89.1 pct, respectively. The iron content of the magnetic concentrate was 90.6 pct, and the iron recovery rate was 94.8 pct. Furthermore, the reduction behavior and separation mechanism were determined based on microstructure and phase change analyses using X-ray powder diffraction, scanning electron microscope, and optical microscopy.     

Calciothermic reduction of titanium oxide in molten CaCl<Subscript>2</Subscript>

Titanium oxides were reduced to metallic titanium using the liquid calcium floating on the molten CaCl₂. A part of Ca dissolved into CaCl₂ and reacted with TiO₂ settled below CaCl₂. The by-product CaO also dissolved by about 20 mol pct into CaCl₂, which was effective in reducing the oxygen concentration in the obtained Ti particles. The compositional region in the Ca-CaCl₂-CaO system was examined for the less oxygen contamination in Ti and the better handling in leaching. A large amount of the residual calcium oxidized the titanium powder in leaching. The metallic Ti powder less than 1000 mass ppm oxygen could be obtained only for 3.6 ks using 5 to 7 mol pct Ca-CaCl₂ at 1173 K. The powder was slightly sintered like sponge, and contained approximately 1500 ppm Ca. The anatase phae, the intermediate product in the refining process of TiO₂, could be also supplied as raw material as well as rutile.     

Microstructural Evolution of the Interface Between Pure Titanium and Low Melting Point Zr-Ti-Ni(Cu) Filler Metals

Low melting point Zr-based filler metals with melting point depressants (MPDs) such as Cu and Ni elements are used for titanium brazing. However, the phase transition of the filler metals in the titanium joint needs to be explained, since the main element of Zr in the filler metals differs from that of the parent titanium alloys. In addition, since the MPDs easily form brittle intermetallics, that deteriorate joint properties, the phase evolution they cause needs to be studied. Zr-based filler metals having Cu content from 0 to 12 at. pct and Ni content from 12 to 24 at. pct with a melting temperature range of 1062 K to 1082 K (789 °C to 809 °C) were wetting-tested on a titanium plate to investigate the phase transformation and evolution at the interface between the titanium plate and the filler metals. In the interface, the alloys system with Zr, Zr₂Ni, and (Ti,Zr)₂Ni phases was easily changed to a Ti-based alloy system with Ti, Ti₂Ni, and (Ti,Zr)₂Ni phases, by the local melting of parent titanium. The dissolution depths of the parent metal were increased with increasing Ni content in the filler metals because Ni has a faster diffusion rate than Cu. Instead, slow diffusion of Cu into titanium substrate leads to the accumulation of Cu at the molten zone of the interface, which could form undesirable Ti _x Cu _y intermetallics. This study confirmed that Zr-based filler metals are compatible with the parent titanium metal with the minimum content of MPDs.     

Formation of Hydroxyapatite Coating on Anodic Titanium Dioxide Nanotubes via an Efficient Dipping Treatment

Hydroxyapatite (HA) depositions on metallic biomedical implants have been widely applied to generate bioactive surfaces in simulated biological environments. Meanwhile, highly ordered TiO₂ nanotubes obtained via anodization have attracted increasing interest for biomedical applications. However, the capability to grow HA coating on TiO₂ nanotubes at room temperature remains problematic. In this study, we applied a dipping treatment for biomimetic formation of an adhesive HA coating on titanium dioxide nanotubes. The coatings formed using this procedure did not require high-temperature annealing or high supersaturation of the simulated biological condition. The as-formed TiO₂ nanotubes on titanium were treated using several dip-and-dry steps, through which the TiO₂ nanotubes were filled and covered with calcium phosphate nucleation sites. The specimens readily grew HA once immersed in the original simulated biological fluid (SBF) after little more than 12 hours. The carbonated HA coating was formed with 10-??m thickness after 4 days of immersion, while only a few calcium phosphate particles were observed on annealing TiO₂ nanotubes immersed in the same solution for the same duration. Tensile testing showed that the bonding strength between HA coating and substrate was 27.2 ± 1.6 MPa. This treatment dramatically improved efficiency for promoting HA formation on anodic TiO₂ nanotubes at room temperature.     

Microstructure and Magnetic Properties of Ni2(Mn,Fe)Ga Heusler Alloys Rapidly Solidified by Melt Spinning

The microstructure and magnetic properties of Ni₂MnGa base alloys with “Fe” substitution in place of “Mn” are studied. The processing technique used is melt spinning at wheel speeds of 20 m/s and 30 m/s followed by annealing at 1273 K (1000 °C) for 1 hour. Fe content is varied from 2 at. pct to 11 at. pct for alloys of Ni₅₀Mn_(25?x)Fe _x Ga₂₅ with Heusler stoichiometry. Austenite with B2 partial atomic ordering and premartensitic tweed structures were found at room temperature for all the alloys at different wheel speeds. After annealing at 1273 K (1000 °C) for 1 hour, austenite phase with L2₁ Heusler atomic ordering is stabilized in samples of all the processing conditions. Saturation magnetization, martensitic transformation temperature, and Curie temperature are measured. Martensite temperature and Curie temperature increase in proportion to iron content in the alloy. Saturation magnetization is sensitive to the phase content and compositional inhomogeneities.     

Thermodynamics of iron alumino-chromite spinel inclusions in steel

The effect of chromium on the oxygen concentration of iron melts in equilibrium with various spinel reaction products has been determined. Alumina crucibles were used and experiments were performed at 1550, 1600, and 1650°C. Thermodynamic relationships between the equilibrium concentrations of chromium and oxygen in the iron melts have been established for chromium concentrations ranging up to 20 wt pct. Results from X-ray and electron microprobe analyses for the composition of the deoxidation products, together with solute activity relationships, indicate that the composition of the equilibrium spinel phase changes progressively from iron aluminate in the absence of chromium, through a series of aluminate-chromite solid solutions, FeO (Al _x Cr_1−x )₂O₃, (<0.5 pct chromium), to a complex chromite spinel, Fe₂Cr₇O₁₂, (0.5 to 3 pct chromium), and finally chromium oxide, Cr₃O₄ (>3 pct chromium). Deoxidation diagrams have been constructed and the effects of small amounts of alloying elements on the deoxidation behavior of aluminum interpreted in terms of buffered reactions which maintain oxygen concentrations in the melt at levels in excess of those normally associated with aluminum killed steel in equilibrium with alumina alone.     

Fluidized Bed Selective Oxidation-Sulfation Roasting of Nickel Sulfide Concentrate: Part II. Sulfation Roasting

The fluidized bed sulfation roasting process followed by water leaching was investigated as an alternative process to treat nickel sulfide concentrate for nickel production. The effects of several roasting parameters, such as the sulfation gas flow rate, roasting temperature, the addition of Na₂SO₄, and the roasting time, were studied. 79 pct Ni, 91 pct Cu, and 95 pct Co could be recovered with minimal dissolution of Fe of 4 pct by water leaching after two-stage oxidation-sulfation roasting under optimized conditions. The sulfation roasting mechanism was investigated, showing that the outermost layer of sulfate melt and the porous iron oxide layer create a favorable sulfation environment with high partial pressure of SO₃. Sulfation of the sulfide core was accompanied by the conversion of the sulfide from Ni_1?x S to Ni₇S₆ as well as inward diffusion of the sulfation gas.     

Vacuum Carbothermic Reduction of Panzhihua Ilmenite Concentrate: A Thermodynamic Study

Electric 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.     

Reduction Behavior of Panzhihua Titanomagnetite Concentrates with Coal

The reduction behavior of the Panzhihua titanomagnetite concentrates (PTC) briquette with coal was investigated by temperature-programmed heating under argon atmosphere in a vertical tube electric furnace. The mass loss behavior of the PTC-coal mixture was checked by thermogravimetric analysis method in argon with a heating rate of 5 K (5 °C)/ min. It was found that there are five stages during the carbothermic reduction process of the PTC. The devolatilization of coal occurred in the first stage, and reductions of iron oxides mainly occurred in the second and third stages. The reduction rate of iron oxide in the third stage was much higher than that in the second stage because of the significant rate of carbon gasification reaction. The iron in the ilmenite was reduced in the fourth stage. In the final stage, the rutile was partially reduced to lower valence oxides. The phase transformation of the briquette reduced at different temperatures was investigated by X-ray diffraction (XRD). The main phases of sample reduced at 1173 K (900 °C) are metallic iron, ilmenite (FeTiO₃), and titanomagnetite (Fe_3–x Ti _x O₄). The traces of rutile (TiO₂) were observed at 1273 K (1000 °C). The iron carbide (Fe₃C) and ferrous-pseudobrookite (FeTi₂O₅) appeared at 1473 K (1200 °C). The titanium carbide was found in the sample reduced at 1623 K (1350 °C). The shrinkages of reduced briquettes, which increased with increase in the temperature, were found to depend greatly on the temperature. With increasing the reduction temperature to 1573 K (1300 °C), the iron nuggets were observed outside of the samples reduced. The nugget formation can indicate a new process of ironmaking with titanomagnetite similar to ITmk3 (Ironmaking Technology Mark 3).     

Characterization of Cu-SiO2 Composite Synthesized by Hydrogen Reduction of Chalcopyrite Concentrate Followed by Acid Leaching

A Ghatshila chalcopyrite concentrate (average particle size, 50 μm) containing primarily CuFeS₂ and SiO₂ (Cu 16 pct, Fe 26 pct, S 14 pct, Si 5 pct, and O 33 pct) was reduced by a stream of hydrogen in a horizontal tube furnace at 1323 K (1050 °C), producing a mixture of Cu (26 pct), SiO₂, Fe₂O₃, Fe₃O₄, Cu₂O, and Fe. Subsequent acid leaching with 1 M HCl solution of the reduction product removed all iron oxides and iron, and other impurities too, leaving a Cu (53.3 pct) + SiO₂ mixture, with a small percentage of Cu₂O in it. This result compares well with the predicted final mixture of Cu (59 pct)-SiO₂ based on a mass balance on the starting concentrate. Elemental chemical analyses were done by energy-dispersive X-ray spectroscopy, which were crosschecked by atomic absorption spectroscopy in the majority of cases. The phase identification and microstructural characterization of Cu-SiO₂ mixtures were done by X-ray diffraction, Fourier transform infrared spectroscopy, Rietveld analysis, scanning electron microscopy, and high-resolution transmission electron microscopy (HRTEM). It was found that Cu-SiO₂ composites were formed in the final product, with a copper grain size of 385 nm.