Kinetic Studies on Gas-Based Reduction of Vanadium Titano-Magnetite Pellet

Vanadium titano-magnetite is a significant resource in China, and in this study, we characterize its isothermal reduction mechanisms in the mixture of H2, CO, and N2 where the variables considered here include reduction time, reduction temperature, gas composition, and pellet size. The kinetics of the reduction process are mainly studied, which follows a shrinking core model. The results indicate that the reduction degree of oxidized VTM pellets increases with the increase of reduction time, reduction temperature but decreases with the increase of pellet size. Moreover, we found that an increase of H2/(H2+CO) ratio induces an increase of the reduction degree. Then the transformation of main Ti-bearing mineral phases is discussed, and the most probable reaction mechanism is revealed. In the whole reduction process, the kinetic results confirm the existence of an early stage and a latter stage, which are controlled by interface chemical reaction and diffusion, respectively. Furthermore, the results show that the diffusion-control step can be observably shortened with the decrease of pellet size because a thinner product layer is formed during the reduction process. Our study thus provides a valuable technical basis on the VTM industrial application.

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Kinetic Studies on Gas-Based Reduction of Vanadium Titano-Magnetite Pellet

Metals ◽

10.3390/met9010095 ◽

2019 ◽

Vol 9 (1) ◽

pp. 95 ◽

Cited By ~ 3

Author(s):

Junwei Chen ◽

Weibin Chen ◽

Liang Mi ◽

Yang Jiao ◽

Xidong Wang

Keyword(s):

Reduction Process ◽

Kinetic Studies ◽

Industrial Applications ◽

Product Layer ◽

Diffusion Control ◽

Reduction Degree ◽

Reduction Temperature ◽

Pellet Size ◽

Reduction Time ◽

Shrinking Core

Vanadium titano-magnetite (VTM) is a significant resource in China—analysis shows that China possesses approximately 10 billion tons of VTM. In this study, we characterize VTM’s isothermal reduction mechanisms in the mixture of H2, CO, and N2 where the variables considered include reduction time, reduction temperature, gas composition, and pellet size. The kinetics of the reduction process were studied following a shrinking core model. The results indicate that the reduction degree of oxidized VTM pellets increases with increases of reduction time and reduction temperature but decreases with increasing pellet size. Moreover, we found that an increase of H2/(H2 + CO) ratio induced an increase of the reduction degree. We discuss the transformation of main Ti-bearing mineral phases, and we consider the most probable reaction mechanism. For the entire reduction process, the kinetic results confirm the existence of an early and later stages that are controlled by interface chemical reaction and diffusion, respectively. Furthermore, the results show that the diffusion-control step can be observably shortened via decreased pellet size because a thinner product layer is formed during the reduction process. Our study thus provides a valuable technical basis for industrial applications of VTM.

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Effect of Different Additives on Reaction Characteristics of Fluorapatite During Coal-Based Reduction of Iron Ore

Metals ◽

10.3390/met9090923 ◽

2019 ◽

Vol 9 (9) ◽

pp. 923 ◽

Cited By ~ 5

Author(s):

Yongsheng Sun ◽

Wentao Zhou ◽

Yuexin Han ◽

Yanjun Li

Keyword(s):

Iron Ore ◽

Contact Point ◽

Energy Dispersive Spectrometer ◽

Structural Evolution ◽

Reduction Process ◽

Reduction Degree ◽

Reduction Temperature ◽

Exponential Factor ◽

Reduction Time ◽

Effect Mechanism

In the coal-based reduction of high phosphorus oolitic hematite, it is particularly important to study the mechanism of phosphorus regulation during the formation of iron metals for the efficient development and utilization of iron ore. In this study, the thermodynamics of the coal-based reduction process of fluorapatite in different mineral systems, effect mechanism of the reduction degree, kinetics, mineral composition, and morphology of structural evolution samples were systematically investigated using FactSage software, single factor analysis, the isothermal method, X-ray diffraction (XRD), scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). Thermodynamic analysis indicates that the effect of the SiO2–Fe2O3–C system on reducing the initial reduction temperature of fluorapatite was stronger than that of the Al2O3–Fe2O3–C system. The effect mechanism of the reduction degree demonstrates that increasing the dosage of silica, iron oxide, carbon, reduction time, and reduction temperature could promote the reduction reaction of fluorapatite under certain conditions. Dynamics analysis shows that the best kinetic mechanism functions of the SiO2–Fe2O3–C system and the Al2O3–Fe2O3–C system were A1/3 = 1/3(1 − α)[−ln(1 − α)]−2 and A1/2 = 1/2(1 − α)[−ln(1 − α)]−1, respectively. The activation energy and pre-exponential factor of the reduction kinetics equation in the system containing silica were significantly lower than that in the system containing alumina, which explained that the catalytic effect of silica on the reduction of calcium fluorophosphate was far greater than that of alumina. XRD and SEM/EDS analysis indicate that the solid–solid reaction of alumina, silica, iron, and fluorapatite occurred during the reduction process, while calcium aluminate, calcium silicate, and calcium oxide were formed at the contact point. Among them, iron could absorb P2 gas so that it played a greater role in promoting the reduction of fluorapatite. Increasing the reduction temperature and prolonging the reduction time were beneficial to the reduction of fluorapatite.

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Recovery of Iron, Chromium, and Nickel from Pickling Sludge Using Smelting Reduction

Metals ◽

10.3390/met8110936 ◽

2018 ◽

Vol 8 (11) ◽

pp. 936 ◽

Cited By ~ 4

Author(s):

Zhaohui Tang ◽

Xueyong Ding ◽

Xinlin Yan ◽

Yue Dong ◽

Chenghong Liu

Keyword(s):

Reduction Process ◽

Slag Basicity ◽

Experimental Results ◽

Iron Ores ◽

Reduction Temperature ◽

Smelting Reduction ◽

Reduction Time ◽

Temperature Reduction ◽

Pickling Sludge ◽

Iron Chromium

This paper reports the recoveries of iron, chromium, and nickel from pickling sludge using coal-based smelting reduction. The influences of slag basicity (CaO/SiO2, which is controlled by high phosphorus oolitic hematite iron ores), reduction temperature, reduction time, and the C/O mole ratio on the recoveries of Fe, Cr, and Ni are investigated systematically. The experimental results show that high recoveries of Fe (98.91%), Cr (98.46%), and Ni (99.44%) are produced from pickling sludge with optimized parameters for the smelting reduction process. The optimized parameters are a slag basicity of 1.5; a reduction temperature of 1550 °C, a reduction time of 90 min, and a C/O mole ratio of 2.0. These parameters can be used as technical support for the recycling of pickling sludge with pyrometallurgy.

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A Kinetic Study on the Reduction of Single Magnetite Particle with Melting Products at High Temperature Based on Visual and Surface Analytical Techniques

Metals ◽

10.3390/met11081268 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1268

Author(s):

Zhongjie Shen ◽

Shuang Sun ◽

Yulong Zhu ◽

Dong Han ◽

Zhan Du ◽

...

Keyword(s):

Particle Size ◽

High Temperature ◽

Reduction Process ◽

Analytical Techniques ◽

Gas Diffusion ◽

Reduction Degree ◽

Reduction Temperature ◽

Magnetite Particle ◽

Exponential Factor ◽

Magnetite Particles

In this study, the reduction characteristics of single magnetite particles with melting products at high temperature were investigated by using visualization and surface analytical techniques. The morphology evolution, product type, reduction degree, and reduction rate of single magnetite particles during the reduction process were analyzed and compared at different reduction temperatures. The results showed that the morphology of the product formed at the reduction temperature of 1300 °C was a mainly nodular structure. When the reduction temperature was above 1400 °C, the products were melted to liquid and flowed out of the particle to form a layered structure. The morphology of the melted products finally transformed to be root-like in structure on the plate around the unmelted core. Raman spectroscopy was used to determine the product types during the reduction process. Experiments studying the effects of gas flowrate and particle size on the reduction degree were carried out, and the results showed that both increasing the temperature and gas flowrate can increase the reduction degree. The internal/external diffusion influence can be ignored with a particle size smaller than 100 μm and a gas flowrate more than 200 mL/min. However, owing to the resistance of the melted products to gas diffusion, the reduction rates at 1400 and 1500 °C were reduced significantly when the reduction degree increased from 0.5 to 1.0. Conversely, the formation of the liquid enlarged the contact area of the reducing gas and solid–liquid and further increased the reduction degree. The kinetics parameters, including average activation energy and pre-exponential factor, were calculated from the experimental data. The reduction kinetics equation of the single magnetite particle, considering the effect of melted products is also given in this study.

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Impact of Iron on the Fe–Co–Ni Ternary Nanocomposites Structural and Magnetic Features Obtained via Chemical Precipitation Followed by Reduction Process for Various Magnetically Coupled Devices Applications

Nanomaterials ◽

10.3390/nano11020341 ◽

2021 ◽

Vol 11 (2) ◽

pp. 341

Author(s):

Tien Hiep Nguyen ◽

Gopalu Karunakaran ◽

Yu.V. Konyukhov ◽

Nguyen Van Minh ◽

D.Yu. Karpenkov ◽

...

Keyword(s):

Particle Size ◽

Magnetic Properties ◽

Reduction Process ◽

Chemical Precipitation ◽

Precipitation Method ◽

Magnetic Characteristics ◽

Reduction Temperature ◽

Fe Content ◽

Magnetic Features ◽

Co Precipitation

This paper presents the synthesis of Fe–Co–Ni nanocomposites by chemical precipitation, followed by a reduction process. It was found that the influence of the chemical composition and reduction temperature greatly alters the phase formation, its structures, particle size distribution, and magnetic properties of Fe–Co–Ni nanocomposites. The initial hydroxides of Fe–Co–Ni combinations were prepared by the co-precipitation method from nitrate precursors and precipitated using alkali. The reduction process was carried out by hydrogen in the temperature range of 300–500 °C under isothermal conditions. The nanocomposites had metallic and intermetallic phases with different lattice parameter values due to the increase in Fe content. In this paper, we showed that the values of the magnetic parameters of nanocomposites can be controlled in the ranges of MS = 7.6–192.5 Am2/kg, Mr = 0.4–39.7 Am2/kg, Mr/Ms = 0.02–0.32, and HcM = 4.72–60.68 kA/m by regulating the composition and reduction temperature of the Fe–Co–Ni composites. Due to the reduction process, drastic variations in the magnetic features result from the intermetallic and metallic face formation. The variation in magnetic characteristics is guided by the reduction degree, particle size growth, and crystallinity enhancement. Moreover, the reduction of the surface spins fraction of the nanocomposites under their growth induced an increase in the saturation magnetization. This is the first report where the influence of Fe content on the Fe–Co–Ni ternary system phase content and magnetic properties was evaluated. The Fe–Co–Ni ternary nanocomposites obtained by co-precipitation, followed by the hydrogen reduction led to the formation of better magnetic materials for various magnetically coupled device applications.

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A Kinetic Model for the Modification of Al2O3 Inclusions during Calcium Treatment in High-Carbon Hard Wire Steel

Materials ◽

10.3390/ma14051305 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1305

Author(s):

Zuobing Xi ◽

Changrong Li ◽

Linzhu Wang

Keyword(s):

Kinetic Model ◽

Early Stage ◽

Morphological Evolution ◽

Product Layer ◽

Melting Time ◽

Calcium Treatment ◽

High Carbon ◽

Inclusion Modification ◽

Shrinking Core ◽

Wire Steel

Laboratory-scale experiments for the modification of Al2O3 inclusions by calcium treatment in high-carbon hard wire steel were performed and the compositions and morphological evolution of inclusions were studied. The kinetics of the modification of Al2O3 inclusions by calcium treatment were studied in high-carbon hard wire steel based on the unreacted shrinking core model, considering the transfer of Ca and Al through the boundary layer and within the product layer, coupled with thermodynamic equilibrium at the interfaces. The diffusion of Al in the inclusion layer was the limiting link in the inclusion modification process. The Ca concentration in molten steel had the greatest influence on the inclusion modification time. The modification time for inclusions tended to be longer in the transformation of higher CaO-containing calcium aluminate. The modification of Al2O3 into CA6 was fastest, while the most time was needed to modify CA into C12A7. It took about six times time longer at the later stage of inclusion modification than at the early stage. The complete modification time for inclusions increased with the square of their radii. The changes of CaO contents with melting time were estimated based on a kinetic model and was consistent with experimental results.

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Effect of Coated Cow Dung on Fluidization Reduction of Fine Iron Ore particles

Processes ◽

10.3390/pr9071175 ◽

2021 ◽

Vol 9 (7) ◽

pp. 1175

Author(s):

Qiyan Xu ◽

Zhanghan Gu ◽

Ziwei Wan ◽

Mingzhu Huangfu ◽

Qingmin Meng ◽

...

Keyword(s):

Iron Ore ◽

Linear Velocity ◽

Operating Conditions ◽

Inhibition Mechanism ◽

Cow Dung ◽

Reduction Temperature ◽

Reduction Time ◽

Reducing Gas ◽

Fine Iron ◽

Ironmaking Process

The effects of reduction temperature, gas linear velocity, reduction pressure, reduction time, and reducing gas on the fluidized ironmaking process were studied for the fine iron Newman ore particles (0.154–0.178 mm) and the optimal experimental operating conditions were obtained. Under the optimal conditions, the effects of the coated cow dung on the reduction of fine iron ore particles were studied, and the inhibition mechanism of cow dung on particle adhesion in the fluidized ironmaking process was elucidated. The experimental results show that the optimal operating parameters are linear velocity of 0.6 m/s, reduction pressure of 0.2 MPa, reduction temperature of 1023 K, H2 as the reducing gas, and reduction time of 60 min. Cow dung can react with oxide in the ore powder to form a high melting point substance that can form a certain isolation layer, inhibit the growth of iron whiskers, and improve the fluidization.

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Reduction Kinetics of Mill Scale Briquettes by Using A3 Fine Coal as a Reductant

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.19101 ◽

2021 ◽

Vol 21 (4) ◽

pp. 2563-2567

Author(s):

Nguyen Hoang Viet ◽

Pham Ngoc Dieu Quynh ◽

Nguyen Thi Hoang Oanh

Keyword(s):

Reaction Rate ◽

Reduction Process ◽

Reduction Reaction ◽

Reaction Rate Constant ◽

Reduction Degree ◽

Furnace Temperature ◽

Time Duration ◽

Mill Scale ◽

Fine Coal ◽

Kinetics Of

In this work, a mixture of mill scale with 5 wt% molasses as binder was pressed under pressure of 200 MPa to prepare briquettes. The reduction process was performed at the temperature of 1000, 1050, 1100, 1150 and 1200 °C in the bed of A3 fine coal as the reductant. The degree of reduction was evaluated at time duration of 15, 30, 45, 60, 90 and 150 minutes, after the furnace temperature reached the predetermined reduction temperature. The highest reduction degree is 94.7% at the reduction process temperature of 1200 °C. Reaction rate constant (k) increased from 4.63×10-4 to 5.03×10-3 min-1 when the temperature increased from 1000 to 1200 °C. The apparent activation energy of the reduction reaction (Ea) is about 95.6 kJ/mole.

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Influence of SiO2 on the Compressive Strength and Reduction-Melting of Pellets

Metals ◽

10.3390/met9080852 ◽

2019 ◽

Vol 9 (8) ◽

pp. 852 ◽

Cited By ~ 3

Author(s):

He Guo ◽

Xin Jiang ◽

Fengman Shen ◽

Haiyan Zheng ◽

Qiangjian Gao ◽

...

Keyword(s):

Compressive Strength ◽

Reduction Process ◽

Melting Behavior ◽

Sio2 Content ◽

Reduction Degree ◽

Negative Effects ◽

Experimental Conditions ◽

Compact Structure ◽

Reduction Behavior ◽

Effective Utilization

The effects of SiO2 content on the compressive strength, reduction behavior and melting-dripping properties of the pellets were investigated under experimental conditions. The experimental results indicated that the compressive strength of pellets gradually decreased with increasing SiO2 content, mainly because the pellets with high SiO2 had poor crystallization capacity, a more liquid phase and more pores. With increasing SiO2 content from 2.19 wt% to 8.13 wt%, the reduction degree of pellets descreased due to the generation of 2FeO·SiO2. Based on the morphology analysis, inside of the pellets, 2FeO·SiO2 caused the compact structure and fewer microspores with increasing SiO2 content, which was unfavorable for the reduction process and resulted in the decrease of the reduction degree. Also, increasing the SiO2 content had negative effects on the melting-dripping properties of pellets. The melting-dripping properties can be improved by adding some sinter with high basicity in the mixed burden. The current work established the relation between SiO2 content and reduction-melting behavior of pellets, which can provide theoretical and technical support for the effective utilization of pellets with different SiO2 content in blast furnace process.

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Effect of BaSO4 on the compressive strength and reduction behavior of pellets

Metallurgical Research & Technology ◽

10.1051/metal/2020022 ◽

2020 ◽

Vol 117 (2) ◽

pp. 207

Author(s):

Jiantao Ju ◽

Chenmei Tang ◽

Xiangdong Xing ◽

Shan Ren ◽

Guangheng Ji

Keyword(s):

Compressive Strength ◽

Theoretical Basis ◽

Energy Dispersive Spectrometer ◽

Reduction Process ◽

Reduction Degree ◽

Experimental Conditions ◽

Reduction Behavior ◽

Influence Mechanism ◽

Scanning Electron ◽

Peak Value

To provide theoretical basis for the production of pellets, the effect of BaSO4 in the range of 0 to 5.0% on properties of pellets was studied under experimental conditions. The influence mechanism of BaSO4 on the compressive strength of preheated pellets as well as roasted pellets and reduction behavior of roasted pellets was investigated by means of scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). From the results, it can be observed that the compressive strength of preheated pellets varies slightly whereas roasted pellets has a great change when BaSO4 content increases from 0 to 5%. The compressive strength of roasted pellets initially increases then decreases, which reaches the peak value of 3411 N with BaSO4 content of 1.5%. The reduction degree enhances from 80.7 to 97.9% and FeO content reduces from 2.33 to 1.57% with increasing BaSO4 content from 0 to 5.0%. The degree of polycrystalline of hematite improves and the hole size increases obviously when BaSO4 content varies from 0 to 1.5%. The crystallization of hematite decreases and the holes whose distribution is uneven increases when BaSO4 content is more than 1.5%. In reduction process, the wustite reduces and metallic iron increases with increasing BaSO4 content from 0 to 5.0%.

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