Topochemical approach of kinetics of the reduction of hematite to wüstite

Piotrowski, Krzysztof; Mondal, Kanchan; Wiltowski, Tomasz; Dydo, Piotr; Rizeg, G.

doi:10.1016/j.cej.2006.12.024

Cited by 134 publications

(87 citation statements)

References 50 publications

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“…The Ea of each step from both macrokinetics and microkinetics have been calculated by many investigators. [21][22][23][24][25] The typical ranges of Ea of different rate controlling steps have been summarized by Strangway.…”

Section: Reduction Mechanismmentioning

confidence: 99%

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Reduction Kinetics of Fine Hematite Ore Particles with a High Temperature Drop Tube Furnace

et al. 2015

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HIsarna is a new coal based smelting reduction process, which has the excellent features of using coal and fine hematite ore directly as raw materials instead of coke and pellet. In this context, the reduction kinetics of hematite ore fines in the smelting cyclone was studied in the laboratory scale. The gas-solid and gas-molten particle reduction behaviour were studied with a High-temperature Drop Tube Furnace (HDTF) and a combination of various characterization methods was used to track the kinetic behaviour such as chemical titration, optical microscope and Scanning Electron Microscope (SEM). A series of experiments with different reaction time (210-2 020 ms) has been conducted at different temperatures from 1 550 K to 1 750 K, thus enabling the kinetic study of the partially reduced hematite ore particles. It was found that a quantity of micro pores was formed during the reduction process mainly due to the loss of oxygen. The un-reacted shrinking core model could be used to describe both gas-solid particle reaction and gas-molten particle reaction.

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Section: Reduction Mechanismmentioning

confidence: 99%

“…13. The correlation coefficients were used elsewhere, 18,25) which was helpful in judging the linear relationship of lines. It was found that the kinetic plots of chemical control at the three temperatures have the best linear relationship compared to gaseous diffusion control and mixed control.…”

Section: Kinetic Datamentioning

confidence: 99%

Reduction Kinetics of Fine Hematite Ore Particles with a High Temperature Drop Tube Furnace

et al. 2015

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“…It is clearly visible that the experimental data do not exactly coincide with the theoretical predicted values. This is because this kinetic model only applies to the surface reaction of the hematite particles, without considering the influence of mass or heat transfer resistances during the reaction process [15]. However, the mass and heating transfer resistances occur, induced by the gradually thicker magnetite layer during the fluidized reduction process of hematite, and lead to a deviationbetween the experimental data and the theoretical predicted values.…”

Section: Determination Of the Kinetic Modelmentioning

confidence: 82%

“…Eventually, the original hematite particles were completely transformed into magnetite particles with a porous structure (Figure 10c). As mentioned above, the reduction process of hematite to magnetite may be theoretically divided into three periods, namely, an induction period (0 < α < 0.15), an acceleratory period (0.15 < α < 0.50), and a deceleratory period (0.5 < α < 1) [15,28]. In the initial induction period, the fresh microcracks were formed as a result of normal swelling due to the crystal structure difference between the starting hematite (hexagonal closed-packed) and the newly formed magnetite (cubic spinal).…”

Section: Microstructure Changes After Reduction Roastingmentioning

confidence: 99%

Mechanism and Kinetics of the Reduction of Hematite to Magnetite with CO–CO2 in a Micro-Fluidized Bed

Han

et al. 2017

Minerals

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Abstract:The mechanism and kinetics of the reduction of hematite to magnetite in a laboratory-scale, micro-fluidized bed reactor were isothermally investigated. The procedure consisted of the isothermal heating in a flow of a 20%CO-80%CO 2 mixture at temperatures from 500 • C to 600 • C. It was found that the Avrami-Erofe'ev model of nucleation and 1D growth (n = 1.58) successfully described the phase transition of hematite to magnetite, and the value of activation energy ∆E a of the reaction was estimated to be 48.70 kJ/mol. The microstructure properties for specimens with different conversion degrees were analyzed using the Brunauer, Emmett and Teller (BET) method and scanning electron microscopy (SEM). The results showed that the magnetite nuclei were needle-like, and the hematite specimens became thoroughly porous after complete reduction to magnetite. The physical and chemical processes of the reaction were also discussed.

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“…When iron oxide is reduced by acetylene gas, the reduced iron contains many transient vacancies and defects after losing oxygen atoms through topochemical reactions. 24,31 At that time, excess carbon can penetrate into the vacancies and defects in the reduced iron. Carbon then precipitates from inside the iron, causing it to break as time progresses.…”

Section: -9mentioning

confidence: 99%

Growth of bridging carbon nanofibers in cracks formed by heat-treating iron oxide thin sheets in acetylene gas

et al. 2013

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We produced novel carbon nanofibers (CNFs) by oxidizing high-purity iron foil and then carburizing it in acetylene gas flow. This formed cracks in the heat-treated iron foil with CNFs bridging the two walls of each crack. The CNFs were drawn out from the walls as the crack opened during heat treatment. This will be a new method to grow and arrange carbon nanotubes and nanosheets without using metal nanoparticles or template substrates

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Topochemical approach of kinetics of the reduction of hematite to wüstite

Cited by 134 publications

References 50 publications

Reduction Kinetics of Fine Hematite Ore Particles with a High Temperature Drop Tube Furnace

Reduction Kinetics of Fine Hematite Ore Particles with a High Temperature Drop Tube Furnace

Mechanism and Kinetics of the Reduction of Hematite to Magnetite with CO–CO2 in a Micro-Fluidized Bed

Growth of bridging carbon nanofibers in cracks formed by heat-treating iron oxide thin sheets in acetylene gas

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