scholarly journals Kinetics of the Volume Shrinkage of a Magnetite/Carbon Composite Pellet during Solid-State Carbothermic Reduction

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1050 ◽  
Author(s):  
Guang Wang ◽  
Jingsong Wang ◽  
Qingguo Xue
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Apparent Activation Energy ◽  
Carbothermic Reduction ◽  
Iron Ore ◽  
Carbon Composite ◽  
Volume Shrinkage ◽  
Reduction Temperature ◽  
Iron Particles ◽  
Composite Pellet

The volume shrinkage evolution of a magnetite iron ore/carbon composite pellet during solid-state isothermal reduction was investigated. For the shrinkage, the apparent activation energy and mechanism were obtained based on the experimental results. It was found that the volume shrinkage highly depended on the reduction temperature and on dwell time. The volume shrinkage of the pellet increased with the increasing reduction temperature, and the rate of increment was fast during the first 20 min of reduction. The shrinkage of the composite pellet was mainly due to the weight loss of carbon and oxygen, the sintering growth of gangue oxides and metallic iron particles, and the partial melting of the gangue phase at high temperature. The shrinkage apparent activation energy was different depending on the time range. During the first 20 min, the shrinkage apparent activation energy was 51,313 J/mol. After the first 20 min, the apparent activation energy for the volume shrinkage was only 19,697 J/mol. The change of the reduction rate-controlling step and the automatic sintering and reconstruction of the metallic iron particles and gangue oxides in the later reduction stage were the main reasons for the aforementioned time-dependent phenomena. The present work could provide a unique scientific index for the illustration of iron ore/carbon composite pellet behavior during solid-state carbothermic reduction.

Structure evolution of a magnetite iron ore/carbon composite pellet during solid-state reduction under microwave heating

2021 ◽  
Vol 98 ◽  
Author(s):  
Cuong Phung Kien ◽  
◽  
Dung Ngo Quoc ◽  
Anh Do Thi ◽  
Hieu Nguyen Sy ◽  
...  
Keyword(s):  
Solid State ◽  
Microwave Heating ◽  
Metallic Iron ◽  
Iron Ore ◽  
Reference Sample ◽  
Carbon Composite ◽  
Structure Evolution ◽  
Firing Time ◽  
State Reduction ◽  
Composite Pellet

In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron ore/carbon composite pellets in a microwave-heating kiln under different microwave wattage of 60 and 90 % (with the firing time from 15 to 120 min.) was investigated. The microstructure of the pellets was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction (XRD). The phase formation was indexed using MDI Jade from the peaks matching the reference sample. At the microwave’s wattage of 60 %: the wustite (FeO) has appeared after firing time of 60 min., the metallic iron and fayalite have appeared in the reduced samples after firing time of 90 min. to 120 min. with retained phases of Fe203, Fe304, FeO and Si02– While at the microwave’s wattage of 90 %, the metallic iron has appeared in the reduced samples after firing time of 30 min. to 120 min and fayalite has appeared in the reduced samples after firing time of 60 min. to 120 min. The final reduced pellet, under microwave’s wattage of 90 % and firing time of 120 min., shows the only phases of metallic iron and fayalite according to the XRD resolution. The present work could provide a scientific understanding to illustrate iron ore/carbon composite pellet behavior during solid-state carbothermic reduction under a microwave-heating.

scholarly journals Solid-State Kinetic Investigations of Nonisothermal Reduction of Iron Species Supported on SBA-15

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
N. S. Genz ◽  
D. Baabe ◽  
T. Ressler
Keyword(s):  
Activation Energy ◽  
Iron Oxide ◽  
Solid State ◽  
Apparent Activation Energy ◽  
Reduction Process ◽  
Kissinger Method ◽  
Iron Loading ◽  
Iron Species ◽  
Vis Spectroscopy ◽  
Model Independent

Iron oxide catalysts supported on nanostructured silica SBA-15 were synthesized with various iron loadings using two different precursors. Structural characterization of the as-prepared FexOy/SBA-15 samples was performed by nitrogen physisorption, X-ray diffraction, DR-UV-Vis spectroscopy, and Mössbauer spectroscopy. An increasing size of the resulting iron species correlated with an increasing iron loading. Significantly smaller iron species were obtained from (Fe(III), NH4)-citrate precursors compared to Fe(III)-nitrate precursors. Moreover, smaller iron species resulted in a smoother surface of the support material. Temperature-programmed reduction (TPR) of the FexOy/SBA-15 samples with H2 revealed better reducibility of the samples originating from Fe(III)-nitrate precursors. Varying the iron loading led to a change in reduction mechanism. TPR traces were analyzed by model-independent Kissinger method, Ozawa, Flynn, and Wall (OFW) method, and model-dependent Coats-Redfern method. JMAK kinetic analysis afforded a one-dimensional reduction process for the FexOy/SBA-15 samples. The Kissinger method yielded the lowest apparent activation energy for the lowest loaded citrate sample (Ea ≈ 39 kJ/mol). Conversely, the lowest loaded nitrate sample possessed the highest apparent activation energy (Ea ≈ 88 kJ/mol). For samples obtained from Fe(III)-nitrate precursors, Ea decreased with increasing iron loading. Apparent activation energies from model-independent analysis methods agreed well with those from model-dependent methods. Nucleation as rate-determining step in the reduction of the iron oxide species was consistent with the Mampel solid-state reaction model.

scholarly journals Effect of the Particle Size of Iron Ore on the Pyrolysis Kinetic Behaviour of Coal-Iron Ore Briquettes

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2595 ◽  
Author(s):  
Heng Zheng ◽  
Wei Wang ◽  
Runsheng Xu ◽  
Rian Zan ◽  
Johannes Schenk ◽  
...  
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Synergistic Effect ◽  
Apparent Activation Energy ◽  
Conversion Rate ◽  
Iron Ore ◽  
High Reactivity ◽  
Particle Sizes ◽  
Low Carbon ◽  
Pyrolysis Behaviour

High reactivity coke is beneficial for achieving low carbon emission blast furnace ironmaking. Therefore, the preparation of highly reactive ferro-coke has aroused widespread attention. However, the effects of the particle size of iron ore on the pyrolysis behaviour of a coal-iron ore briquette are still unclear. In this study, the effect of three particle sizes (0.50–1.00 mm, 0.25–0.50 mm and <0.74 mm) of iron ore on the thermal and kinetic behaviours of coal-iron ore briquettes were investigated by non-isothermal kinetic analysis. The results showed that the synergistic effect of iron ore and coal during coking mainly occurred during the later reaction stage (850–1100 °C) and smaller particle sizes of iron ore have a stronger synergistic effect. The addition of iron ore had little effect on T0 (the initial temperature) and Tp (the temperature at the maximum conversion rate) of briquette pyrolysis, however itgreatly affected the conversion rate and Tf (the final temperature) of the briquettes. T0 decreased with the decrease of iron ore particle sizes, while Tp and Tf showed opposite trends. After adding iron ore into the coal briquette, the reaction kinetics at all stages of the coal-iron ore briquettes changed. The weighted apparent activation energy of the caking coal (JM) briquette was 35.532 kJ/mol, which is lower than that of the coal-iron ore briquettes (38.703–55.627 kJ/mol). In addition, the weighted apparent activation energy gradually increased with decreasing iron ore particle sizes.

scholarly journals Carbothermic Reduction of the Composite Pellet of Iron Ore and Coal in the Packed Bed with Air Flow

2006 ◽  
Vol 92 (12) ◽  
pp. 809-814 ◽  
Author(s):  
Takaho OTOMO ◽  
Yasushi TAKASAKI ◽  
Atsushi SHIBAYAMA ◽  
Takazo KAWAGUCHI ◽  
Eiki KASAI
Keyword(s):  
Carbothermic Reduction ◽  
Iron Ore ◽  
Air Flow ◽  
Packed Bed ◽  
Composite Pellet

scholarly journals Lowering Reduction Temperature of Iron Ore and Carbon Composite by Using Ores with High Combined Water Content

2009 ◽  
Vol 49 (11) ◽  
pp. 1686-1693 ◽  
Author(s):  
Taichi Murakami ◽  
Takeshi Nishimura ◽  
Eiki Kasai
Keyword(s):  
Water Content ◽  
Iron Ore ◽  
Carbon Composite ◽  
Reduction Temperature

Kinetics of the Solid State Reaction between MoO3 and SrCO3

1972 ◽  
Vol 27 (6) ◽  
pp. 1020-1022 ◽  
Author(s):  
G. Flor ◽  
V. Massarotti ◽  
R. Riccardi
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Apparent Activation Energy ◽  
Solid State Reaction ◽  
Diffusion Mechanism ◽  
Optical Observations ◽  
Kcal Mole ◽  
Temperature Range ◽  
Kinetics Of

AbstractThe solid state reaction MoO3 + SrCO3 → SrMoO4+ CO2 has been studied on mixtures of powdered reagents. Thermogravimetric measurements in the temperature range 412° -498 °C have been made on different mixtures and under different atmospheres. Moreover, optical observations and conductometric measurements have been carried out. The results show that the reaction is governed by a diffusion mechanism with an apparent activation energy of (60 ± 1) kcal/mole and that the main diffusing species is the Mo6+ ion.

scholarly journals The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Guanghao Cheng ◽  
Gurong Shen ◽  
Jun Wang ◽  
Yunhao Wang ◽  
Weibo Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Aging Time ◽  
Reaction Path ◽  
Aging Treatment ◽  
Hydrothermal Stability ◽  
Hydrothermal Aging ◽  
Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

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