Upgrading Titanium Ore Through Selective Chlorination Using Calcium Chloride

To develop a simple and effective process for upgrading low-grade titanium ore (ilmenite, mainly FeTiO₃), a new selective chlorination process based on the use of calcium chloride (CaCl₂) as the chlorine source was investigated in this study. Titanium ore and a titanium ore/CaCl₂ mixture were placed in two separate crucibles inside a gas-tight quartz tube that was then positioned in a horizontal furnace. In the experiments, the titanium ore in the two crucibles reacted with either HCl produced from CaCl₂ or CaCl₂ itself at 1100 K (827 °C), leading to the selective removal of the iron present in the titanium ore as iron chlorides [FeCl _x (l,g) (x = 2, 3)]. Various kinds of titanium ores produced in different countries were used as feedstock, and the influence of the particle size and atmosphere on the selective chlorination was investigated. Under certain conditions, titanium dioxide (TiO₂) with purity of about 97 pct was directly obtained in a single step from titanium ore containing 51 pct TiO₂. Thus, selective chlorination is a feasible method for producing high purity titanium dioxide from low-grade titanium ore.     

Studies on the Kinetics of Carbon Tetrachloride Chlorination of Refractory Metal Oxides

Abstract

Studies on the kinetics of chlorination of the oxides of titanium, zirconium, niobium and tantalum by carbon tetrachloride gas in dilution with nitrogen, at low and moderate temperatures, have been carried out. In each case, the effect of time, temperature, partial pressure of carbon tetrachloride and the particle size, on the chlorination of the oxide, has been studied. The influence of some physico-chemical properties of the oxides and their halides on the kinetics process, has been discussed. The chlorination results below and above the dissociation temperature of carbon tetrachloride ( ～ 773 K.) have been examined to find out the difference in the kinetics by CC1₄ and those by elemental carbon and chlorine. From these kinetics results, the mechanism of the chlorination of each of the oxides, has been established and compared. The optimum experimental conditions for preparing the metal chlorides, keeping in view of the maximum utilisation of the carbon tetrachloride, have been established. The merits of carbon tetrachloride as a chlorinating agent, have been highlighted. From these kinetics results, the scope for chlorinating the refractory metal oxides, as well as their mixed oxides, at lower temperatures and lower partial pressures of carbon tetrachloride, with the scope for recycling the reagent, has been briefly discussed. Some preliminary results on the preferential chlorination of these oxides by carbon tetrachloride present in a typical tin slag, have been presented, to further substantiate the merits of carbon tetrachloride as a low temperature chlorinating agent.     

Studies on the Kinetics of Carbon Tetrachloride Chlorination of Refractory Metal Oxides

Studies on the kinetics of chlorination of the oxides of titanium, zirconium, niobium and tantalum by carbon tetrachloride gas in dilution with nitrogen, at low and moderate temperatures, have been carried out. In each case, the effect of time, temperature, partial pressure of carbon tetrachloride and the particle size, on the chlorination of the oxide, has been studied. The influence of some physico-chemical properties of the oxides and their halides on the kinetics process, has been discussed. The chlorination results below and above the dissociation temperature of carbon tetrachloride (～ 773 K) have been examined to find out the difference in the kinetics by CCl₄ and those by elemental carbon and chlorine. From these kinetics results, the mechanism of the chlorination of each of the oxides, has been established and compared. The optimum experimental conditions for preparing the metal chlorides, keeping in view of the maximum utilisation of the carbon tetrachloride, have been established. The merits of carbon tetrachloride as a chlorinating agent, have been highlighted. From these kinetics results, the scope for chlorinating the refractory metal oxides, as well as their mixed oxides, at lower temperatures and lower partial pressures of carbon tetrachloride, with the scope for recycling the reagent, has been briefly discussed. Some preliminary results on the preferential chlorination of these oxides by carbon tetrachloride present in a typical tin slag, have been presented, to further substantiate the merits of carbon tetrachloride as a low temperature chlorinating agent.     

Ti_2O_3与AlCl_3共沉积方法熔盐电解制备Ti-Al合金

在NaCl-KCl熔盐体系中,以AlCl_3作为氯化剂,通过液相反应将钛的氧化物氯化为TiCl_3。对比TiO、Ti_2O_3、TiO_2的氯化效果,并综合AlCl_3与TiO、Ti_2O_3、TiO_2反应热力学分析,较好的结果是Ti_2O_3氯化为TiCl_3。采用不同的电化学测试手段研究了Al(Ⅲ)与Ti(Ⅲ)在Mo电极上的合金化过程,采用共沉积法制备TiAl_2、TiAl_3合金。同时借助于XRD和SEM手段对合金进行了分析,说明通过熔盐电解可以直接制备Ti-Al合金。     

The selective carbochlorination of iron from titanlferous magnetite ore in a fluidized bed

The selective chlorination of iron from titaniferous magnetite ore using solid carbon as a reducing agent was studied in a fluidized bed. The effects of chlorination temperature, chlorine gas partial pressure, ratio of ore to carbon particle sizes, and the amount of added carbon were determined. Experimental results indicate that temperatures between 900 and 1000 K were favorable for the selective chlorination of iron. The rate was found to be first order with respect to chlorine concentration, and the observed effects of particle size, temperature, and the amount of carbon added were expressed quantitatively by using a mixed-control model. Formerly Graduate Student with the Department of Metallurgical Engineering, University of Utah     

Process Optimization and Reaction Mechanism of Removing Copper From an Fe-Rich Pyrite Cinder Using Chlorination Roasting

The aim is to remove copper from a pyrite cinder by optimizing the chlorination roasting process using response surface methodology (RSM) and the reaction mechanism of chlorination roasting based on thermodynamic calculation was discussed. A quadratic model was suggested by RSM to correlate the key parameters, namely, dosage of chlorinating agent, roasting temperature and roasting time to the copper volatilization ratio. The results indicate that the model is well consistent with the experimental data at a correlation coefficient (R²) of 0.95, and the dosage of chlorinating agent and roasting temperature both have significant effects on the copper volatilization ratio. However, a roasting temperature exceeding 1170°C decreases the volatilization ratio. The optimum conditions for removing copper from the cinder were identified as chlorinating agent dosage at 5%, roasting temperature at 1155.10 °C and roasting time of 10 min; under such a condition, a copper volatilization ratio of 95. 16% was achieved from the cinder. Thermodynamic calculation shows that SiO₂ in the pellet plays a key role in the chlorine release from calcium chloride, and the chlorine release reactions cannot occur without it.     

Photolytic effects in alumina chlorination

The temperature dependence of the rate of chlorination of α-alumina with CO/Cl₂ gas mixtures exhibits an anomaly, a departure from the normal Arrhenius behavior, in the range 650 to 850°C; it is manifested as a local maximum in the Arrhenius plot at 670°C followed by a local minimum in the range 770 to 850°C. By carefully studying the effect of irradiation of the CO/Cl₂ gas mixtures on the rate of chlorination of α-alumina, it is shown that such an anomaly, which has been observed in the chlorination of various metallic oxides, is most likely due to the photochemical formation of phosgene (COCl₂) by ambient light incident on the reactant gas mixture during its transport to the main reactor. Phosgene is a better chlorinating agent than a CO/Cl₂ mixture. The mechanism of chlorination of α-Al₂O₃ by CO/Cl₂ mixtures subjected to the light emitted by a high-pressure Hg-vapor lamp is elucidated.     

Kinetics of Iron Chlorination of Roasted Illmenite Ore,Fe2TiO5 in a Fluidized-Bed Reactor

The preferential chlorination reaction of iron constituents in roasted ilmenite ore was studied in an experimental fluidized bed reactor. The influence of the roasting temperature on the selectivity of chlorination reactions was also examined. It was found that preferential iron chlorination is dependent on roasted product morphology. Effects of chemical and process variables in the fluidized bed reactor, such as chlorination temperature, chlorine gas partial pressure, gas-solid contact time and the quantity of coke added, were investigated in order to study the kinetics of the preferential chlorination reaction. A modified bubble assemblage model was applied to analyze behavior of gases and solids in the reactor. The chlorination reaction rate constant was found to be a function of temperature and coke quantity present.     

微粒嵌布难选金红石矿煤基深度还原热力学

关键词：金红石矿;深度还原;配碳比;KOH;K2CO3     

The selective chlorination of iron from llmenite ore by CO-Cl2 mixtures: Part I. intrinsic kinetics

The intrinsic kinetics of the selective chlorination of iron from ilmenite ore using carbon monoxide as the reducing agent were studied in a shallow fluidized bed. Experiments on the effects of chlorination temperature, carbon monoxide and chlorine gas partial pressures, and particle size were conducted in the absence of mass- and heat-transfer influences. Results indicate that the kinetics in the temperature range 923 to 1123 K are represented by the following pore-blocking rate law: λ[ exp (X_Fe/λ) − 1 ] = 33.7 exp (− E/RT)p _co ^0.52 ₂ ^0.32 t where E is 37.2 kJ/mol and p and t are in atm (=101.3 kPa) and minutes, respectively. The partial pressure of carbon monoxide was found to affect the chlorination rate more strongly than that of chlorine. A reaction mechanism in which iron in ilmenite reacts with chlorine before the liberated oxygen is removed by carbon monoxide is proposed. Formerly Graduate Student at the Department of Metallurgical Engineering, University of Utah     

Phase equilibria in the metal-sulfur-oxygen system and selective reduction of metal oxides and sulfides: Part I. The carbothermic reduction and calcination of complex mineral sulfides

The difference in the standard Gibbs free energy for the formation of any two oxides or sulfides is the chemical potential for selective reduction of metals from complex minerals. The magnitude of the Gibbs free energy difference is shown by plotting the univariant relationships for relevant sulfides and oxides. In this investigation, three examples of mineral sulfides are considered, and the experimental results are compared with the predicted thermodynamic calculations. These examples include the reduction conditions for nickel and iron sulfides and pentlandite (Fe,Ni)₉S₈ and chalcopyrite (CuFeS₂) minerals. The reduction behavior of mineral sulfides, such as those of nickel, cobalt, iron, and copper, is illustrated by referring to both the sulfide and alloy phase equilibria. In particular, the solution thermodynamic properties of the metallic phase equilibria are featured for determining the physical chemistry of preferential or selective reduction of the metal oxides and sulfides. The mechanism for the reduction of the aforementioned sulfide minerals is explained with the aid of the governing phase equilibria for the calcination process. The results from the carbothermic reduction of sulfide minerals are also compared. The important roles of lime and calcium sulfate in controlling the emission of sulfurous gases during the reduction reaction are explained. A qualitative analysis of reduction reactions of nickel and iron sulfides is reviewed to provide a comparison of the mechanism for complex nickel-bearing minerals. The importance of these results in producing alloy and pure metallic phases is also examined.     

Flotation of Iron Oxides and Quartz—A Review

Froth flotation of iron oxides and quartz is reviewed over the broad range of particle sizes. The review, which embraces laboratory-, pilot plant- and industrial operations, encompasses (i) surface chemistry of iron oxides and quartz flotation (ii) relevant collectors and their adsorption mechanism and (iii) activation/depression in selective flotation, in this system. The diverse effect of temperature on iron oxides and calcium-activated quartz flotation is also indicated; the flocculation-flotation process of upgrading fine-grained iron ores is highlighted; and the economic advantage of reverse flotation in high grade, coarse- or medium grained iron ore flotation circuits is noted.     

The Thermodynamics of Some Transition Metals in Molten Slags

In the present paper, the thermodynamic behaviour of transition metals, such as Cr, Ti, Nb and V in molten slags is systematically analysed based on a literature survey. These metals exist in molten slags with multi valences. Oxygen partial pressure, slag basicity, total content of each transition metal, content of each component in slag, and temperature are the influential factors on their thermodynamic properties in molten slags. Higher basicity and strong oxidative atmosphere are generally favourable for the stable existence of transition‐metal ions with higher oxidation states. Temperature is a factor that is less influential than the above‐mentioned ones. For a transition metal in molten slag, the concentration ratio of ions of different valences depends on the activity coefficient ratio of their oxides. The present paper summarizes the activity studies regarding the transition metal oxides in various molten slags. For chromium and titanium oxides, information on CaO? SiO₂ based systems is involved. For titanium oxides, its thermodynamic behaviour in MnO? SiO₂ based slags is introduced. For niobium and vanadium, the information in Na₂O? SiO₂, CaO? CaF₂? SiO₂ systems is provided. Thermodynamic studies are described for Nb₂O₅? MnO? SiO₂ molten slag equilibrated with liquid iron at 1828 K.     

Phase equilibria in the Fe-Ti-Cl-H-O system

Conclusions In the Fe-Ti-O system at 1373°K only Ti₂O₃ is stable, and iron is reduced from oxides and passes into solution. At practically all compositions of the solid solution preferential chlorination of titanium takes place, together with its transport to iron. During the chlorination of an iron-titanium alloy only gaseous chlorides are formed (T = 1373°K) because under these conditions equilibrium between the solid solution and liquid chlorides is not attained. Chlorination of titania in the presence of hydrogen as a reducing agent is impractical owing to difficulties in ensuring the required composition of the gaseous phase. The results obtained can be utilized for developing technological processes for the surface alloying of iron parts through a chloride phase and producing iron-titanium alloy powders.Translated from Poroshkovaya Metallurgiya, No. 1(265), pp. 52–55, January, 1985.     

酒石酸盐为释放剂选择性螯合滴定法测定钛

提出一个用酒石酸盐作释放剂，选择性的螯合滴定法测定钛的方法，研究了各种阳离子的干扰，实验表明，各种金属离子都不干扰测定钛的含量。此法已用于测定钛铁合金、钛镍合金和钛铁矿中钛的含量，结果满意。     

Hydrogen Plasma Processing of Iron Ore

Iron is currently produced by carbothermic reduction of oxide ores. This is a multiple-stage process that requires large-scale equipment and high capital investment, and produces large amounts of CO₂. An alternative to carbothermic reduction is reduction using a hydrogen plasma, which comprises vibrationally excited molecular, atomic, and ionic states of hydrogen, all of which can reduce iron oxides, even at low temperatures. Besides the thermodynamic and kinetic advantages of a hydrogen plasma, the byproduct of the reaction is water, which does not pose any environmental problems. A review of the theory and practice of iron ore reduction using a hydrogen plasma is presented. The thermodynamic and kinetic aspects are considered, with molecular, atomic and ionic hydrogen considered separately. The importance of vibrationally excited hydrogen molecules in overcoming the activation energy barriers, and in transferring energy to the iron oxide, is emphasized. Both thermal and nonthermal plasmas are considered. The thermophysical properties of hydrogen and argon–hydrogen plasmas are discussed, and their influence on the constriction and flow in the of arc plasmas is considered. The published R&D on hydrogen plasma reduction of iron oxide is reviewed, with both the reduction of molten iron ore and in-flight reduction of iron ore particles being considered. Finally, the technical and economic feasibility of the process are discussed. It is shown that hydrogen plasma processing requires less energy than carbothermic reduction, mainly because pelletization, sintering, and cokemaking are not required. Moreover, the formation of the greenhouse gas CO₂ as a byproduct is avoided. In-flight reduction has the potential for a throughput at least equivalent to the blast furnace process. It is concluded that hydrogen plasma reduction of iron ore is a potentially attractive alternative to standard methods.     

Effect of TiO2‐content on Reduction of Iron Ore Agglomerates

The effect of titanium oxide on iron ore agglomerates is studied by the use of test sinter, test pellets and synthetic briquettes under laboratory conditions. Titanium favours secondary hematite rather than magnetite, which is the main phase in the sinter of Rautaruukki's Raahe plant. Additionally, the effects of sinter RDI and pellet LTD on the blast furnace process are evaluated using the test results of basket trials in LKAB's Experimental Blast Furnace. The effect of titanium in synthetic hematite is studied as hematite is reduced to magnetite in the RDI test. This occurrence causes deterioration in burden permeability. Synthetic titanium‐bearing iron oxides under controlled conditions are investigated at the University of Oulu. The effect of TiO₂, in solid solution in magnetite, on the magnetite to hematite oxidation is studied separately in order to simulate the final stage of the sintering process. In other experiments, hematite samples doped with various contents of TiO₂ are studied using thermogravimetry under a controlled gas atmosphere (CO/CO₂/H₂/N₂). The TiO₂ content of hematite has a clear effect on reduction degradation. Also increasing content of TiO₂ in solid solution in magnetite radically accelerates the oxidation rate. In the pilot tests, TiO₂ content has a similar negative effect on the reduction strength of both sinter and pellets     

Influences of non-stoichiometry on thermodynamics and kinetics of iron oxides reduction processes

Abstract

Non-stoichiometry influences both the thermodynamic and kinetic analyses of the iron oxide redox processes. The thermochemical data of iron oxide redox reactions in various textbooks are not consistent, and the kinetic characteristics are not well understood because of the non-stoichiometry. To clarify such confusions, some famous thermodynamic data are compared, and highly precise experimental work conducted for verification. It is shown that the thermodynamic data for the pure iron oxide reduction reactions from JANAF agree well with the experimental results; the eutectoid temperature of iron oxides was proven to be 576°C; Dieckmann’s defect model of magnetite was proven in good agreement with the experimental results only at high oxygen activities but not low oxygen activities; and the dependences of iron deficiency on Δwt-% (weight loss ratio) and Fe²⁺% (ferrous ratio) were calculated and experimentally verified in pure iron oxides reduction processes.     

Thermal Analysis on the Pyrolysis of Tetrabromobisphenol A and Electric Arc Furnace Dust Mixtures

The pyrolysis of Tetrabromobisphenol A (TBBPA) mixed with electric arc furnace dust (EAFD) was studied using thermogravimetric analysis (TGA) and theoretically analyzed using thermodynamic equilibrium calculations. Mixtures of both materials with varying TBBPA loads (1:1 and 1:3) were prepared and pyrolyzed in a nitrogen atmosphere under dynamic heating conditions at heating rates of 5 and 10 °C/min. The mixtures degraded through several steps, including decomposition of TBBPA yielding mainly HBr, bromination of metal oxides, followed by their evaporation in the sequence of CuBr₃, ZnBr₂, PbBr₂, FeBr₂, MnBr₂, KBr, NaBr, CaBr₂, and MgBr₂, and finally reduction of the remaining metal oxides by the char formed from decomposition of TBBPA. Thermodynamic calculations suggest the possibility of selective bromination of zinc and lead followed by their evaporation, leaving iron in its oxide form, while the char formed may serve as a reduction agent for iron oxides into metallic iron. However, at higher TBBPA volumes, iron bromide forms, which can also be evaporated at a temperature higher than those of ZnBr₂ and PbBr₂. Results from this work provide practical insight into selective recovery of valuable metals from EAFD while at the same time recycling the hazardous bromine content in TBBPA.