Reduction Of Ilmenite Research Articles

Agave Bagasse Biomass as Reducing Agent for the Reduction of Ilmenite

Agave Bagasse Biomass as Reducing Agent for the Reduction of Ilmenite

Constitutive Model and Experimental Verification of Kinetics of Non-isothermal Hydrogen Reduction of Ilmenite: A Case Study on Kahnuj Ilmenite

Constitutive Model and Experimental Verification of Kinetics of Non-isothermal Hydrogen Reduction of Ilmenite: A Case Study on Kahnuj Ilmenite

Location-dependent flight cost difference from the lunar surface to an orbital fuel depot and its influence on in situ resource utilisation location selection

Given the increasing relevance of lunar activities, the location selection for in situ resource utilisation (ISRU) facilities is necessary for identifying the most suitable configuration during mission planning. To gather information about the dominant location dependencies, a scenario is established wherein an ISRU product is exported to an orbital depot and its mass costs are used for classification. In the selected scenario, oxygen is produced in an ilmenite reduction plant and subsequently exported to the lunar gateway via an oxygen–hydrogen fuelled launcher operated in a round-trip to refuel oxygen at the lunar surface and hydrogen at the lunar gateway. This showed that the transport cost variations could be avoided entirely or have a recessive influence on the mission’s total costs over an extended period of time, such as 20 years. The identification of the top-10 most optimal locations for various resolutions was altered only slightly upon consideration of flight costs as compared to considering only the ISRU factors; this indicates the insignificance of flight cost dependencies for the analysed case.

Possibility of Lunar Crustal Magmatism Producing Strong Crustal Magnetism

AbstractThe Moon generated a long‐lived core dynamo magnetic field, with intensities at least episodically reaching ∼10–100 μT during the period prior to ∼3.56 Ga. While magnetic anomalies observed within impact basins are likely attributable to the presence of impactor‐added metal, other anomalies such as those associated with lunar swirls are not as conclusively linked to exogenic materials. This has led to the hypothesis that some anomalies may be related to magmatic features such as dikes, sills, and laccoliths. However, basalts returned from the Apollo missions are magnetized too weakly to produce the required magnetization intensities (>0.5 A/m). Here, we test the hypothesis that subsolidus reduction of ilmenite within or adjacent to slowly cooled mafic intrusive bodies could locally enhance metallic FeNi contents within the lunar crust. We find that reduction within hypabyssal dikes with high‐Ti or low‐Ti mare basalt compositions can produce sufficient FeNi grains to carry the minimum >0.5 A/m magnetization intensity inferred for swirls, especially if ambient fields are >10 μT or if fine‐grained Fe‐Ni metals in the pseudo‐single domain grain size range are formed. Therefore, there exists a possibility that certain magnetic anomalies exhibiting various shapes such as linear, swarms, and elliptical patterns may be magmatic in origin. Our study highlights that the domain state of the magnetic carriers is an under‐appreciated factor in controlling a rock's magnetization intensity. The results of this study will help guide interpretations of lunar crustal field data acquired by future rovers that will traverse lunar magnetic anomalies.

Chemical looping of synthetic ilmenite, Part I: Addressing challenges of kinetic TGA measurements with H[formula omitted]

Reliable experimental data and models are required to better understand and design chemical looping processes with oxygen carrier materials like ilmenite. A dubious variability of suggested kinetics for similar oxygen carrier materials has been presented in the literature. Part I of this work focuses on thermogravimetric analysis (TGA) of gas–solid kinetics and addresses several of its challenges, which are possible reasons behind such deviations. The reduction of synthetic ilmenite (60 mass% Fe2O3＋40 mass% TiO2) powder with H2 in a TGA system was investigated for this purpose.Multiple steps were necessary to overcome mass transfer limitations during the measurements: (i) small sample masses down to 1.6mg, (ii) high gas flow rates, (iii) a suitable sample carrier and (iv) proper sample dispersion on the sample carrier. Three types of sample carriers (crucible, basket and plate) were tested; the plate showed the best performance overall. It was alarming that an exemplary increase in sample mass from 1.6 to 3mg, which was still significantly lower than all other studies reviewed, already introduced a noticeable influence of diffusion. Isothermal (650–950°C, 17–50vol% H2) and nonisothermal parameter studies were conducted and yielded vastly different isoconversional activation energies. A computational fluid dynamics (CFD) study of the TGA system suggested considerable axial dispersion of H2 influencing the initial conversion period.These findings help to assess the reliability of kinetic studies and guide towards diffusion-free, kinetic measurements. The results will be used for model development in part II.

Mechano-thermic reduction of low-grade titanium ore for high-grade TiO2 synthesis

A systematic study on the mechano-thermic reduction of low-grade ilmenite concentrate for the production of high-grade TiO2 powder used in the production of non-oxide ceramics for cutting tool applications has been successfully carried out. Samples were prepared via planetary ball milling and carbothermic reduction processes, and the as-reduced product was subsequently leached in order to improve the synthesized TiO2 by removing the metallic iron in it and other minor soluble impurities dissolved in the iron. The mechano-thermic reduction was achieved by milling a representative mixture of ilmenite and carbon in a molar ratio of 1:1, followed by carbothermic reduction at 1000 °C in a laboratory high-temperature furnace for 60 min. The as-reduced product was subsequently leached at 80 °C for 6 h in a hydrochloric acid solution. It was found that there was a complete reduction of ilmenite to metallic iron and TiO2 at 1000 °C. The results of the FESEM showed there were only two distinct regions of metallic iron (bright region) and titanium dioxide (grey region) with minor traces of unreacted carbon (dark spots), although there was clear regional demarcation between these regions. However, the iron dissolution during the acid treatment was almost 100% as there were no peaks of iron in the as-leached powder. The results of these analyses confirmed the synthesis of high-grade TiO2, which finds application in cutting tool applications and other areas such as in reflective pigment production.

Effects of Na2CO3 on the carbothermic reduction and magnetic separation of ilmenite concentrate

Ilmenite concentrates are the raw material used for the production of titania pigment and metallic titanium. This work studies the effect of the addition of Na2CO3 in direct carbothermic reduction of ilmenite concentrate to enhance the separation of metallic iron from titanium components. The effects of temperature, Na2CO3 content and C/O molar ratio on the mineral phases, metallization degree of iron, and iron grain size of the reduced product are evaluated. The optimal conditions for the direct reduction of ilmenite concentrate are 1300 °C, a C/O molar ratio of 1.1, and 5 wt% Na2CO3. Under these optimal reduction conditions, the metallization of iron reaches the maximum of 96.8%, and the average iron grain size is 20.1 μm. After grinding and magnetic separation, the direct reduced iron product (magnetic component) contains 93.9 wt% of iron and 4.66 wt% of TiO2, with an iron recovery of 93.9%, while the non-magnetic product contains 69.9 wt% of TiO2 and 7.61 wt% of iron, with a TiO2 recovery of 93.5%. The results show that an appropriate amount of Na2CO3 effectively promotes the reduction of ilmenite. However, excessive Na2CO3 adversely affects ilmenite reduction. The phase transition patterns of Na2CO3 in the direct reduction of ilmenite is investigated.

Isothermal reduction and nitridation kinetics of ilmenite concentrate in ammonia gas

Low-temperature chlorination is considered a suitable process for ilmenite containing high contents of MgO and CaO. However, reduction carbonization or nitridation is essential to convert titanium oxide to carbide or nitride, which can be enriched by magnetic separation. In this paper, the isothermal reduction–nitridation kinetics of Panzhihua ilmenite concentrate in an ammonia atmosphere was investigated. Both model–free and model–fitting methods were used to compare the isothermal kinetics. The reaction process can be divided into two successive stages: the reduction reaction and the nitridation reaction. The average apparent activation energy for the reduction reaction was 139.63 kJ/mol, obtained by the model–free method. The reduction process can also be subdivided into two stages by the model–fitting method. The chemical reaction (G(α) = 1–(1–α)1/3 = kt) and three–dimensional diffusion (G(α) = [1–(1–α)1/3]2 = kt) were identified as the mechanism function for the reduction process. The activation energies of these two stages were 121.73 kJ/mol and 141.40 kJ/mol, respectively. The function G(α) = 1–(1–α)1/3 = kt, which also corresponds to the chemical reaction mechanism (R3), exhibited the best fit for the nitridation stage. The corresponding activation energy was 32.10 kJ/mol. Metallic iron and Ti3O5 were formed in the reduction stage, while Ti3O5 was then transformed to Ti(N,O) in the nitridation stage.

Novel Ti2O3–Al2O3 raw materials with controllable Ti2O3 content from the aluminothermic reduction of ilmenite

Titanium-containing refractories have excellent performance, but the high cost limits their application. A series of Ti2O3–Al2O3 raw materials with different Ti2O3 contents were prepared by aluminothermic reduction of ilmenite, while the generated ferrotitanium alloy can be used as raw materials for special steels. Regulating the amount of aluminum added in the system regulates the degree of titanium reduction, and the formed ferrotitanium alloy can achieve separation from the oxides. With decreasing aluminum content of, the Ti2O3 content increased, and the continuous distribution of the corundum area decreased, resulting in a continuously distributed Ti2O3 area. Our results indicated that the molar ratio of aluminum to ilmenite should be higher than 1.4 to achieve slag iron separation. The reaction model for the aluminothermic reduction was established, and the formation mechanism of Al2O3 and Ti2O3 in the system was discussed.

Effect of different carbon sources on the conversion of ilmenite into synthetic rutile via ball milling induced carbothermic reduction

Carbothermic reduction reduces ilmenite into TiO2 or acid-soluble intermediates. This method gained more attention due to several industrial applications of TiO2 and metal Ti. However, the efficiency of carbothermic reduction of ilmenite into synthetic rutile is poorly investigated for different carbon sources. In this study, several advanced characterization techniques were used to examine the effect of carbon on the carbothermic reduction of ilmenite via ball milling and isothermal annealing. Fourier transform infrared spectroscopic (FTIR) analysis showed new broad bands appearing in ball milled mixtures (ranging from ∼650 cm−1 to 1200 cm−1), due to temporary bonding of Ti–O–C overlapped with Ti–O–Ti bonding. Scanning electron microscopic (SEM) analysis also suggested that carbon was incorporated in the crystal lattice of ilmenite during ball milling. However, no new phases were observed in the X-ray diffraction (XRD) patterns of ball milled ilmenite-carbon mixtures. Therefore, the energy transferred during ball milling is not sufficient to overcome the activation energy of carbothermic reduction of ilmenite. Phase transformation of ilmenite occurred after annealing at 1000 °C by forming new phases such as rutile, pseudorutile, and pseudobrookite. Intermediate phases such as pseudorutile and pseudobrookite decreased with the use of carbon. Consequently, the efficiency of carbothermic reduction decreased in the order of coconut shells (amorphous)> activated carbon> vein graphite (crystalline). The absence of temporary bonding of Ti–O–C in annealed samples further confirmed the phase transformation of ilmenite. This study also showed that ball milled, and annealed samples resulted in highly crystalline rutile. Thermodynamic behavior of carbothermic reduction was finally simulated using the calculated enthalpy, entropy, and the Gibb’s free energy for each reaction.

Effects of pre-oxidation on the hydrogen-rich reduction of Panzhihua ilmenite concentrate powder: Reduction kinetics and mechanism

The objective of this study was to investigate the effect of pre-oxidation treatment on the hydrogen-rich reduction of Panzhihua ilmenite concentrate powder on the reduction kinetics and mechanisms. In this study, reduction processes of raw and pre-oxidized ilmenite concentrates reduced by H2/CO mixtures (H2/CO = 0.4 and H2/CO = 2.5) at 950, 1000, and 1050 °C were systematically investigated using a thermal analyzer. The hydrogen-rich reduction rate was accelerated by the pre-oxidation treatment of raw ilmenite concentrate and an increase in H2 in H2/CO mixtures. The hydrogen-rich reduction of raw and pre-oxidized ilmenite concentrates can be divided into two stages according to the first derivatives of the reduction process: Fe3+ to Fe2+ and Fe2+ to Fe. The results of the research on the model function demonstrated that the reaction mechanism of raw and pre-oxidized ilmenite concentrates were three-dimensional diffusion models in the first stage. In the second stage, the reaction mechanism of the raw ilmenite concentrate was a phase boundary reaction model, and for the pre-oxidized ilmenite concentrate, it was a chemical reaction model. Furthermore, the apparent activation energies of both raw and pre-oxidized ilmenite concentrates under different reducing atmospheres were determined and compared. It was demonstrated that pre-oxidation treatment could effectively reduce the apparent activation energies of the reduction reaction. It is feasible to combine the advantages of the pre-oxidation treatment and hydrogen-rich reduction with a higher hydrogen ratio for the efficient reduction of Panzhihua ilmenite concentrate.

Reclamation of Red Mud for the TiO2 Production by Ilmenite Smelting at Lower Temperature

ABSTRACT Red mud produced from the Bayer process was used for the high temperature metallurgical processing of ilmenite. The major components of the red mud were Fe2O3, Al2O3, Na2O, and TiO2, which play important roles in the flux material. The process temperature of ilmenite slag was lowered from 1794 K (1521°C) to 1687 K (1414°C), as a preliminary study by a high-temperature microscope. Thermochemical calculations using FactSageTM 7.0 confirmed the effect of red mud on the lowered melting temperature of ilmenite slag. The discrepancy between the observed results of the microscope and the calculated phase diagram was due to the slag viscosity, which was significantly affected by Al2O3 in red mud. The reduction of ilmenite at lower temperatures by the addition of red mud was investigated at 1723 K (1450°C). Ilmenite, pseudobrookite, and associated clay minerals were the major phases in the reduced ilmenites which was confirmed by X-ray diffraction (×RD) analysis. Microscopic images obtained by scanning electron microscopy (SEM) showed variations in the pseudobrookite phases according to the amount of fluxed red mud. The benefits of red mud utilization are discussed with regard to the lower energy consumption and recovery of resources.

Effects of Na2CO3 on reduction mechanism and kinetics of iron during deep reduction of ilmenite concentrate

Effects of Na2CO3 on reduction mechanism and kinetics of iron during deep reduction of ilmenite concentrate

Reduction and Nitridation Behaviors of Ilmenite with Clean Ammonia Energy

Reduction and Nitridation Behaviors of Ilmenite with Clean Ammonia Energy

Novel approach to prepare Fe-TiN cermets from ilmenite concentrate using clean NH3 gas

Fe-based cermets are of considerable research interest owing to their excellent physical and mechanical properties. In this study, a new process for the reduction and nitridation of Panzhihua ilmenite using NH3 was proposed to prepare Fe-TiN composites, and the process was deemed feasible by thermodynamic calculations. The final products, Fe and TiN, could be formed based on the reaction conditions. The experimental results validated that metallic Fe could be easily formed, while MgTiO3 was more difficult to reduce than FeTiO3. The final products of Fe/TiN/MgO obtained at 1373–1473 K were consistent with those from the thermodynamic analysis. By increasing the reduction temperature or duration, the Fe particles increased in size and mixed with the TiN particles. The elemental content of Mg, Al, and Ca in the magnetic product was 5.85 wt% after magnetic separation. A Fe-TiN cermet was prepared from the magnetic product by hot-pressing (HP) sintering. Fe and TiN were uniformly distributed in the cermet, and the hardness of the obtained cermet reached 18.2 GPa. This work could offer a new approach to the preparation of Fe-based cermets from low-grade ilmenite.

Using Na2CO3 as an additive to enhance the growth kinetics of iron grains during carbo-thermic reduction of ilmenite concentrate

The deep reduction of ilmenite concentrates through carbothermic way with the addition of Na2CO3 to produce high-quality titanium slag and iron powder is a novel energy-efficient process to utilise the low-grade ilmenite concentrate effectively. The growth behaviour of iron grain in this process is of great significance for the subsequent separation between iron and slag. Thus, the growth behaviour and kinetics of iron grain in this process under different Na2CO3 concentrations were investigated. The results show that the increase of reduction temperature, time, and Na2CO3 addition promoted the growth of iron grains. Particularly, the influence of additives was more significant when the reduction temperature was over 1300 °C. The growth of iron grain gradually changed from being controlled by surface diffusion to being controlled by grain boundary diffusion with increasing Na2CO3 addition. Growth models of iron grain under different Na2CO3 concentrations were also established in this study.

Carbothermic Reduction of Ilmenite Concentrate with Sodium Carbonate Additive to Produce Iron Granules and High Titania Containing Slag

The influences of heating pattern and sodium carbonate addition on the carbothermic reduction of ilmenite concentrate have been experimentally studied. The experiments were carried out using isothermal–gradient temperature technique between 1000 °C and 1500 °C with different temperature profiles for a total reduction time between 110 and 160 min. The sodium carbonate was varied between 0 to 60 wt%. It was found that the temperature profile and sodium carbonate addition play an important role on the separation between metallic iron granule and titania rich slag. The optimum condition was achieved at initial and final reduction temperatures of 1300 °C and 1500 °C, respectively, with sodium carbonate addition of 30 wt%. At the optimum condition, the iron recovery was 97.1% and the solidified slag contained titanium pentoxide (Ti3O5), anatase (TiO2), and sodium titanium dioxide.

Enhanced reduction of ilmenite ore by pre-oxidation in the view of pore formation

The promotion effect of pre-oxidation on reduction of ilmenite was revealed from the view of pore formation. The result shows that the enhancement of pre-oxidation on reduction of ilmenite ore is attributed to the formation of porous structure during the reduction process. Reduction of ilmenite is inhibited by iron-rutile topology structure formed on the particle surface. By contrast, porous structure ilmenite is regenerated during the ferric-to-ferrous reduction stage of the pre-oxidized ilmenite with dominant reduction rate over diffusion rate of produced ferrous ω ≥ 33.2 mol/m4. The newly formed porous structure ilmenite enlarges particle surface area with facilitated gas-solid contact, thus it is responsible for the enhancement of the reduction of pre-oxidized ilmenite. A novel formation mechanism of porous structure is also proposed based on the competition and coordination between the reduction rate and diffusion rate determined by reduction potential and temperature.

Characterisation of titania slag produced by a novel process: acidolysis performance

ABSTRACT The sulfuric acid leaching of titania slag produced by semi-molten state reduction of Panzhihua ilmenite concentrate followed by magnetic separation is studied. The titanium-bearing phase of the slag is mainly composed of anosovite (MxTi3-xO5, 0 ≤ x≤2, M represents: Ti, Fe, Mg, Mn, and Al) and M2O3 solid solutions. The titania slag was leached in two stages using sulfuric acid, with the second stage using a stronger acid, a higher acid to solid ratio, and smaller particles to further leach the titanium. The results showed that the overall acidolysis ratio of titanium in the titania slag with additive-free, addition of sodium carbonate, and addition of sodium sulfate is 0.90, 0.81, and 0.89 respectively. It was found that fine grinding of the titania slag is beneficial to the leaching of titanium. The overall recoveries of titanium in the novel process after sulfuric acid leaching for the additive-free, Na2CO3-added, and Na2SO4-added slags are 0.61, 0.76, and 0.79, respectively. The phase and morphology of the raw titania slag and leaching residue related to the leaching behaviour were also characterised.

Effect of sodium carbonate addition on carbothermic reduction of ilmenite concentrate

The enhanced reduction mechanism and kinetics of different Na2CO3 additions in the carbothermic reduction of ilmenite concentrate were investigated. The reduction process was carried out at different heating rates in a thermogravimetry facility, and the kinetics was studied using the Starink method. The results indicate that Na2CO3 addition enhanced the reduction effect as well as reduced the initial temperature of the reaction and the activation energy by increasing reactant activity in reactant form; however, it deteriorated the late-stage kinetic conditions by generating a molten phase, thereby reducing the reaction rate in the late stages of reduction. The average apparent activation energies of ilmenite concentrate with 0%, 3%, and 6% Na2CO3 are 447, 289, and 430 kJ/mol, respectively. The results from kinetics parameters confirm that Na2CO3 addition accelerated the reduction kinetics; however, excessive addition worsened the reduction kinetics.