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.

MICROWAVE-ASSISTED CARBOTHERMIC REDUCTION OF ILMENITE

The microwave-assisted carbothermic reduction of ilmenite was investigated by thermogravimetric analysis under argon atmosphere. A comparison between microwave assisted reduction and the conventional one was made. It was demonstrated that the instantaneously volumetric heating of microwaves could significantly enhance the overall reduction process. By microwave application, the reduction could take place at much lower temperatures and the activation energy for the process could be lowered.The mechanism of the reduction was discussed according to the experimental data.

Carbothermic reduction of vanadium titanomagnetite with the assistance of sodium carbonate

The carbothermic reduction of vanadium titanomagnetite concentrate(VTC)with the assistance of Na_(2)CO_(3)was conducted in an argon atmosphere between 1073 and 1473 K.X-ray diffraction and scanning electron microscopy were used to investigate the phase transformations during the reaction.By investigating the reaction between VTC and Na_(2)CO_(3),it was concluded that molten Na_(2)CO_(3)broke the structure of titanomagnetite by combining with the acidic oxides(Fe_(2)O_(3),TiO_(2),Al_(2)O_(3),and SiO_(2))to form a Na-rich melt and release FeO and MgO.Therefore,Na_(2)CO_(3)accelerated the reduction rate.In addition,adding Na_(2)CO_(3)also benefited the agglomeration of iron particles and the slag–metal separation by decreasing the viscosity of the slag.Thus,Na_(2)CO_(3)assisted carbothermic reduction is a promising method for treating VTC at low temperatures.

Effect of Temperature on Carbothermic Reduction of Ilmenite

The reduction of ilmenite (FeTiO_3) has been studied extensively. Temperature for the carbothermic reduction of ilmenite ranges from 900 ℃ to 1 400 ℃, and the reduction degree of Panzhihua ilmenite increases with increasing temperature. X-ray diffraction analysis and SEM analysis were used to identify the phase before and after reduction, and to identify the morphology of reduced samples respectively. It is found that the reaction initiates at about 860 ℃. The reaction rate varies with temperature simultaneously. Impurities in Panzhihua ilmenite decrease the reduction degree. Magnesium and calcium oxide-rich zone is formed preventing complete reduction of Fe 2+. In general, the reaction products are iron, Ti_3O_5 and carbon.

Analysis of the behavior of magnesium and CO vapor in the carbothermic reduction of magnesia in a vacuum

The aim of this paper is to experimentally investigate the behavior of magnesium and carbon monoxide vapor in the carbothermic reduction of magnesia at condensing zone temperatures ranging from 923 K to 1223 K.The phase,surface morphology,and composition of the condensates obtained were examined by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy.The main findings of this paper include:the reverse reaction products,carbon and magnesium oxide,were formed following the process of magnesium vapor condensation,preventing two metal clusters from mutually combining.Moreover,the nearer the temperature of the condensation zone approached the liquid transformation temperature(810-910 K),the lower the rate of the reverse reaction between carbon monoxide and magnesium vapor.Decrease in the rate of the reverse reaction of magnesium was possible by controlling the condensation temperature.

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 Ca CO3 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 18 wt%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 50μm.Hence,the separation of calcium titanate and metallic iron will be the focus in the future study.

Magnesium production by carbothermic reduction in vacuum

In present work,we investigate production of magnesium by carbothermic reduction under vacuum conditions.The process was divided into two parts,one is reduction process,and the other one is condensation process.The experimental results revealed that during reduction process,the gas-solid reaction between MgO and CO was not occurred at a temperature and pressure of 1723 K and 30-100 Pa respectively.So the main reduction reaction was MgO(_(s))+C(_(s))=Mg(_(g))+CO(_(g))(under vacuum)and reaction type belonged to solid-solid reaction.In Condensation Process,according to a contrast and analysis,the condensation quality of magnesium is associated with CO concentration.The resultant product C was formed and it followed magnesium vapor condensation which prevents mutual combination of two metal droplets to forms the compact condensation produces.Therefore,in order to compact morphological forms of magnesium crystal whiskers,we must control the technical conditions and find the method to separate the magnesium vapor and carbon monoxide.That's the key factor to get better crystalline structure.

Preparation of Mg and Ca metal by carbothermic reduction method–A thermodynamics approach

The Gibbs free energy and critical reaction conditions of preparing Mg and Ca metal by carbothermic reducing calcined dolomite were calculated and analyzed.New thermodynamic criterion for reduction reaction,including the critical temperature and vacuum degree,was studied.The results show that:when T/P^(0.0449)<1199.2,neither MgO nor CaO can be reduced by carbon;when T/P^(0.0449)≥1199.2 and T/P^(0.0462)<1350.9,MgO can be reduced while CaO can not be;when T/P^(0.0462)≥1350.9,both MgO and CaO can be reduced.According to the requirements,we can obtain only Mg,Mg first then Ca,Mg and Ca simultaneously by controlling temperature,vacuum degree or both of them properly,by carbothermic reducing calcined dolomite.

Catalytic Mechanism of KCl during Carbothermic Reduction of Pre-Oxidized Ilmenite

As alkali additive,KC1 catalyzes effectively the carbothermic reduction of pre-oxidized ilmenite,and the catalytic effect becomes more remarkable as the amount of KC1 increases.During the carbothermic reduction,the gaseous product consists mainly of CO,and the partial pressure of which increases with reaction temperature.The EPMA and XPS of the partially reduced ilmenite ore and that of the used graphite as reductant showed that the potassium ions enter both ilmenite particles and graphite powders during reduction.The above-mentioned phenomena result in the distortion of ilmenite and carbon structure by potassium ions and reaction activity of carbon and ilmenite was enhanced.As a result,the overall carbothermic reduction was catalyzed by KC1.

Mineral sulphide-lime reactions and effect of CaO/C mole ratio during carbothermic reduction of complex mineral sulphides

Mineral sulphide （MS）-lime （CaO） ion exchange reactions （MS ＋ CaO = MO ＋ CaS） and the effect of CaO/C mole ratio during carbothermic reduction （MS ＋ CaO ＋ C = M ＋ CaS ＋ CO（g）） were investigated for complex froth flotation mineral sulphide concentrates. Phases in the partially and fully reacted samples were characterised by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The primary phases during mineral sulphide-lime ion exchange reactions are Fe304, CaSO4 Cu2S, and CaS. A complex liquid phase of Ca2CuFeO3S forms during mineral sulphide-lime exchange reactions above 1173 K. The formation mechanisms of Ca2CuFeO3S liquid phase are determined by characterising the partially reacted samples. The reduction rate and extent of mineral sulphides in the presence of CaO and C increase with the increase in CaO/C ratio. The metallic phases are surrounded by the CaS rich phase at CaO/C 〉 1, but the metallic phases and CaS are found as separate phases at CaO/C 〈 1. Experimental results show that the stoichiometric ratio of carbon should be slightly higher than that of CaO. The reactions between CaO and gangue minerals （SiO2 and A1203） are only observed at CaO/C 〉 1 and the reacted samples are excessively sintered.

Use of Solid State Carbothermic Reduction in Production of Transition Metals and Their Carbides

The use of solid state carbothermic reduction as a precursor to the smelting of transition metal ores was examined . The advantages of the introduction of a prereduction stage include enabling the more efficient use of fines and the achievement of higher energy efficiencies. A solid state reduction using carbon as the reductant offers a simpler alternative for their treatment. Subsequent treatment of the reduced material could include intensive bath smelting to produce ferroalloys or, in some case, solid state separation of the transition metal carbide where this has commercial significance.

Phase transformation behavior of titanium during carbothermic reduction of titanomagnetite ironsand

The reduction of titanomagnetite（TTM） ironsand, which contains 11.41wt% TiO_2 and 55.63wt% total Fe, by graphite was performed using a thermogravimetric analysis system under an argon gas atmosphere at 1423–1623 K. The behavior and effects of titanium in TTM ironsand during the reduction process were investigated by means of thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. During the reduction procedure, the titanium concentrated in the slag phase, where the phase transformation followed this sequence： Fe O ＋ FeTiO_3 → Fe_2 TiO_4 → FeTiO_3 → FeTi_2O_5 → TiO_2. The calculated results for the reduction kinetics showed that the carbothermic reduction was controlled by the diffusion of ions through the product layer. Furthermore, the apparent activation energy was 170.35 k J·mol^（-1）.

Catalytic effect of alkali chlorides on carbothermic reduction of pre oxidized ilmenite

A computer monitoring thermogravimetric system was used to study the effect of alkali chlorides(MCl, M=Li, Na, K and Cs) on the carbothermic reduction of pre oxidized ilmenite in the course of a linear rise in temperature from 600 ℃ to 1 000 ℃. The experimental results indicate that all the alkali chlorides can speed up the reduction process of pre oxidized ilmenite, moreover, KCl is the most effective catalyst of the chlorides, while the catalytic effects of LiCl and CsCl are relatively weaker. It seems that the catalytic mechanism of LiCl is different from those of the other alkali chlorides. The cross sectional morphology of the partially reduced pre oxidized ilmenite particles and the distribution of potassium ions within them were examined by means of scanning electronic microscopy and electronic probe microanalysis, respectively, which shows that the reduction proceeds topochemically and the alkali ion enriches at the periphery of the particles.[

Carbothermic reduction behaviors of Ti–Nb-bearing Fe concentrate from Bayan Obo ore in China

To support the development of technology to utilize low-grade Ti-Nb-bearing Fe concentrate, the reduction of the concentrate by coal was systematically investigated in the present paper. A liquid phase formed when the Ti Nb-bearing Fe concentrate/coal composite pel- let was reduced at temperatures greater than 1100℃. The addition of CaCO3 improved the reduction rate when the slag basicity was less than 1.0 and inhibited the formation of the liquid phase. Mechanical milling obviously increased the metallization degree compared with that of the standard pellet when reduced under the same conditions. Evolution of the mineral phase composition and microstructure of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet at 1100~C were analyzed by X-ray diffraction and scanning electron microsco- py-energy-dispersive spectroscopy. The volume shrinkage value of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet with a basicity of 1.0 was approximately 35.2% when the pellet was reduced at 1100℃ for 20 min, which enhanced the external heat transfer to the lower layers when reduced in a practical rotary hearth furnace. The present work provides key parameters and mechanism understanding for the development of carbothermic reduction technology of a Ti-Nb-bearing Fe concentrate incorporated in a pyrometallurgical utilization flow sheet.

Kinetics of Carbothermic Reduction of MnO_2 and Catalytic Effect of La_2O_3

Kinetics of carbothermic reduction of manganese oxide and the catalyticeffect of La_2O_3 on the reduction have been studied by the measurement of mass loss in N_2atmosphere at different temperatures and followed by SEM analysis. It is concluded that the kineticsof carbothermic reduction of manganese oxide is divided into three stages: gas diffusioncontrolling stage, carbon gasification con-trolling stage and solid state diffusion controllingstage. La_2O_3 has catalytic effect on the reduction. The catalytic effect of La_2O_3 increases withthe added amount of La_2O_3. SEM analysis shows that the catalytic mechanism is that La_2O_3promotes the transfer of oxygen ions so that carbon gasifying is catalyzed and thus carbothermicreduction of MnO_2 is catalyzed.

Thermodynamic analysis of the carbothermic reduction of a high-phosphorus oolitic iron ore by FactSage

A thermodynamic analysis of the carbothermic reduction of high-phosphorus oolitic iron ore（HPOIO） was conducted by the Fact Sage thermochemical software. The effects of temperature, C/O ratio, additive types, and dosages both on the reduction of fluorapatite and the formation of liquid slag were studied. The results show that the minimum thermodynamic reduction temperature of fluorapatite by carbon decreases to about 850°C, which is mainly ascribed to the presence of SiO_2, Al_2O_3, and Fe. The reduction rate of fluorapatite increases and the amount of liquid slag decreases with the rise of C/O ratio. The reduction of fluorapatite is hindered by the addition of CaO and Na_2CO_3, thereby allowing the selective reduction of iron oxides upon controlled C/O ratio. The thermodynamic results obtain in the present work are in good agreement with the experimental results available in the literatures.

Enhanced leaching of metals from spent lithium-ion batteries by catalytic carbothermic reduction

Spent Li-ion battery(LIB)recycling has become a challenge with the rapidly developing electric vehicle(EV)industry.To address the problems of high cost and low recovery of Li in the recycling of spent LIBs using traditional hydrometallurgical processes,we developed an alkali metal catalytic carbothermic reduction method to recover spent LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM).Using alkali metal catalysts,such as NaOH,significantly reduced the temperature required for carbothermic NCM material reduction and realized targeted control of the phase of the reduction product,where Li was first separated by prior water leaching,followed by Ni,Co,and Mn recycling by acid leaching.The optimized carbothermic reduction conditions were a reaction time of 3 h,temperature of 550℃,NaOH dosage of 15 wt%,and graphite dosage of 15 wt%.The Li leaching efficiency reached 78.5 wt%during water leaching.And during acid leaching,the Ni,Co and Mn leaching efficiencies were 99.8 wt%,99.7 wt%,and 99.5wt%,respectively.This study provides strong technical support for the development of LIB industry.

Synthesis of Al_(4)SiC_(4) powders via carbothermic reduction: Reaction and grain growth mechanisms

Highly pure Al_(4)SiC_(4) powders were prepared by carbothermic reduction at 2173 K using Al_(2)O_(3),SiO_(2),and graphite as raw materials.The obtained Al_(4)SiC_(4) powders owned hexagonal plate-like grains with a diameter of about 200-300μm and a thickness of about 2-6μm.Based on the experimental results,the reaction of Al_(4)SiC_(4) formation and grain evolution mechanisms were determined from thermodynamic and first-principles calculations.The results indicated that the synthesis of Al_(4)SiC_(4) by the carbothermic reduction consisted of two parts,i.e.,solid-solid reactions initially followed by complex gas-solid and gas-gas reactions.The grain growth mechanism of Al_(4)SiC_(4) featured a two-dimensional nucleation and growth mechanism.The gas phases formed during the sintering process favored the preferential grain growth of(0010)and(110)planes resulting in formation of hexagonal plate-like Al_(4)SiC_(4) grains.

Carbothermic Reduction Mechanism of Vanadium-titanium Magnetite

To achieve the high-efficiency utilization of vanadium-titanium magnetite（ VTM）,reduction experiments were conducted to determine the carbothermic reduction mechanism of VTM. Effects of volatile matter,temperature,time,and carbon ratio（ molar ratio of fixed carbon in coal to oxygen in iron oxides of VTM） on reduction degree were investigated.Results show that reduction degree increases with increasing volatile matter in coal,temperature,time,and carbon ratio.Phase transformation,microstructure,and reduction path were analyzed by X-ray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,and Fact Sage 6. 0. The thermoravimetry-differential scanning calorimetry-quadrupole mass spectrometer method was used for kinetic analysis of the main reduction process. Results indicate that the kinetic mechanism follows the principle of random nucleation and growth（ n = 4）,and the activation energy values at 600-900 and 900-1 350 ℃ are 88. 7 and 295. 5 kJ / mol,respectively.

Carbothermic Reduction of MoO_3 for Direct Alloying Process

The thermodynamics of Mo-O- C and Ca-Mc-O-C systems was studied in order to understand the carbothermic reduction of molybdenum trioxide, and kinetic studies were also carried out by means of thermogravimetrie analysis under argon atmosphere with a heating rate of 10 ℃/min. Subsequently, reaction products at various temperatures were identified by X-ray diffraction （XRD） and the results confirmed the previous thermodynamics analysis. Mean- while, it was found that intermediate products MoO2 and CaMoO4 appeared in the process of carbothermic reduction of MoO3 with or without CaO, which were subsequently reduced to Mo or molybdenum carbide. An experimentally determined reaction mechanism was proposed and discussed. The reduction reaction of MoO3 with carbon could be divided into two stages. The first stage includes the direct reaction between MoO3 and carbon and the carbon gasifica- tion reaction. The second stage is the gas-solid reaction between CO and MoO2, and the diffusion of gases through the surface of MoO2 determines the overall reaction rate. The activation energies of the mixtures with or without CaO were estimated to be 56.6 and 52.9 kJ/mol, respectively.