Low- and high-temperature reoxidation of direct reduced iron: a relative assessment

Bandopadhyay, Amitava; Ganguly, Anindita; Prasad, K. Krishna; Sarkar, S. B.; Ray, H. S.

doi:10.1016/0168-7336(90)80010-h

Cited by 8 publications

(8 citation statements)

References 1 publication

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“…Reoxidation at low temperatures was aided by the development of cracks and fissures resulting from physicochemical phenomena. [2] They also found that the rate of corrosion was initially high, followed by a very slow second stage that obeys a logarithmic rate law. This transition was attributed to the decrease in surface area available for oxidation, as well as changes in local void fraction of the particle; pores are blocked by the theoretical volume difference between iron and its oxides.…”

Section: Introductionmentioning

confidence: 96%

“…Parabolic and logarithmic models have been fitted to experimental data by various other authors. [1,2,3] Bandopadhyay et al [1] found that at low temperatures (35°C), the reoxidation behavior of moistened DRI in a pure oxygen environment for 1 hour indicated that the reaction was diffusion controlled, and resistance offered by the oxide surface layer played a vital role. Reoxidation at low temperatures was aided by the development of cracks and fissures resulting from physicochemical phenomena.…”

Section: Introductionmentioning

confidence: 99%

“…There are several possible cathodic processes, which may take place in nearly neutral solutions depending on the acidity and aeration of the solution. In aerated solutions, the cathodic reactions involve dissolved oxygen: [2] [3]…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and mechanism of corrosion of laboratory hot briquetted iron

Gray

Sahajwalla

Paramguru

2005

Metall Mater Trans B

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While considerable work has been reported in the literature on the corrosion behavior and products of direct reduced iron and sponge iron, very little has been published on hot briquetted iron (HBI). The present article reports the kinetics and mechanism of HBI corrosion. As corrosion is an electrochemical process, measurements using electrochemical techniques have been made and these are compared to data gained by measuring mass changes in the briquettes over time. Similar trends were seen in data from both techniques, and the corrosion extent predicted by electrochemical measurements in saline solution was very close to the mass gain result obtained. Kinetic analysis of the data from mass gain over time trials was conducted. The activation energy for corrosion at temperatures between 25 °C and 80 °C has been calculated. The values of activation energy obtained indicate that corrosion was predominantly controlled by diffusion of oxygen in the liquid state. The internal structure of the briquettes was observed by microscopy both before and after corrosion in distilled water.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Kinetics and mechanism of corrosion of laboratory hot briquetted iron

Gray

Sahajwalla

Paramguru

2005

Metall Mater Trans B

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“…(4), (5), (9), and (13) as, ..... (14) where F is the fractional oxygen content relative to Fe2O3, R is the gas constant in J/(mol·K), is partial pressure of oxygen in kPa, and t is time in seconds.…”

Section: Complete Rate Equationmentioning

confidence: 99%

“…And the rate-controlling step at the last stage of re-oxidation was solid-state diffusion in which voids formed at the interfaces between the oxide films and unreacted iron grains, with the rate following a logarithmic expression indicative of the formation of protective oxide layer. Bandopadhyay et al [7][8][9][10] performed thermogravimetric studies on the isothermal re-oxidation of direct reduced iron in dry air at 720 -870 K. Sponge iron samples in small pieces of about 500 mg each were produced by coal reduction in a rotary kiln. Passivation was observed at the later stages of re-oxidation and was believed to be caused by the pore blockage resulting from the formation of iron oxide.…”

Section: Introductionmentioning

confidence: 99%

Re-Oxidation Kinetics of Flash Reduced Iron Particles in O2–N2 Gas Mixtures Relevant to a Novel Flash Ironmaking Process

Yuan

Sohn

2014

ISIJ Int.

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A novel flash ironmaking process based on hydrogen-containing reduction gases is under development at the University of Utah. This process will directly reduce fine iron oxide concentrate particles in suspension in a flash reactor. During handling and transportation, product iron particles may come into contact with air. Since direct reduced iron is usually prone to oxidation, re-oxidation kinetics is of concern. The goal of this work was to determine the re-oxidation kinetics of flash reduced iron particles in O2-N2 gas mixtures. The effects of temperature (673 -873 K) and O2 partial pressure (4 -18 kPa) were studied and the nucleation and growth model was found to describe the initial period of oxidation before the rate decreased precipitously at certain conversion. The pressure dependence of the rate was first order with respect to oxygen partial pressure, and the activation energy was 14.4 kJ/mol. A complete rate equation that adequately represents the experimental data was developed.

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Long‐Term Reoxidation of Hot Briquetted Iron in Various Prepared Climatic Conditions

Daghagheleh

Schenk

Zheng

et al. 2022

steel research int.

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The application of hot briquetted iron (HBI) in the electric arc furnace (EAF) is a promising method to obtain high‐quality steel products with a guaranteed purity level. However, during the long‐term transportation and storage, the HBI will be partially reoxidized, resulting in a loss of metallization degree. Herein, long‐term reoxidation behaviors of commercial HBI under various prepared climatic conditions are investigated. The results show that HBI exposed to ambient air conditions develops nearly no reoxidation. However, interval and cyclic wetting and drying of HBI lead to the worst metallization loss problem, which must be avoided. Based on morphological analysis, the reoxidation is supposed to occur at the surface and then spread into the center area through cracks or pellet boundaries. The reoxidation gradually decreases the porosity of HBI by the closure of cracks and pores with rust but shows little influence on its physical strength.

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Low- and high-temperature reoxidation of direct reduced iron: a relative assessment

Cited by 8 publications

References 1 publication

Kinetics and mechanism of corrosion of laboratory hot briquetted iron

Kinetics and mechanism of corrosion of laboratory hot briquetted iron

Re-Oxidation Kinetics of Flash Reduced Iron Particles in O2–N2 Gas Mixtures Relevant to a Novel Flash Ironmaking Process

Long‐Term Reoxidation of Hot Briquetted Iron in Various Prepared Climatic Conditions

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