Mathematical analysis of reactions in metal oxide/carbon mixtures

Tien, R. H.; Turkdogan, E. T.

doi:10.1007/bf02657661

Cited by 23 publications

(26 citation statements)

References 6 publications

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“…19). The activa- These values are also close to the low limit of the range of activation energy reported in the literature 15,20,24) for wustite reduction by CO.…”

Section: Activation Energy Of Scale Reduction By Carbonsupporting

confidence: 88%

“…Reduction of iron oxides by solid reductants has also been studied, especially when developing the self reducing iron oxide and carbon composite briquettes. [20][21][22][23][24][25][26][27][28] These studies, with different iron oxides and carbon bearing materials, have shown that the self reduction mechanism and kinetics are more complicated because beside the reaction of reduction it includes sensibly endothermic carbon gasification reaction which very often is found to control the overall rate of self reduction. Moreover, other phenomena could influence 28) (like a devolatilization of the reducing agent) or even control 24) (like a heat transfer) the rate of self reduction.…”

Section: Introductionmentioning

confidence: 99%

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Characterization and Reduction Behavior of Mill Scale

et al. 2011

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This paper presents an initial part of a project devoted to the recycling of mill scale in the form of selfreducing briquettes. First chemical and morphological characteristics of mill scale were investigated and next its gaseous reduction behavior was studied by thermogravimetry. The chemical characterization showed that wustite is the major constituent of this waste matter, with small amounts of magnetite, hematite and metallic iron. The microscopic examination of the scale revealed its complex and layered microstructure with three distinct zones. The outer layer is relatively thin and porous. It is mainly composed of hematite and magnetite. The intermediate layer is made of the dense, columnar grains of wustite. The inner layer is a very porous wustite. The gaseous reduction by carbon monoxide has a topochemical character regardless of initial morphology of scale and, depending on temperature and reducing gas composition it produces a porous iron or the iron whiskers. The unreacted shrinking core model with one interface fits quite well the kinetic data and the activation energy of reduction is about 80 kJ/mol.

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“…19). The activa- These values are also close to the low limit of the range of activation energy reported in the literature 15,20,24) for wustite reduction by CO.…”

Section: Activation Energy Of Scale Reduction By Carbonsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Characterization and Reduction Behavior of Mill Scale

et al. 2011

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“…The dilution effect caused by the back-diffusion of the inert gas into the sample may be another reason behind the significant differences between the experimental and computed reaction rates observed at lower temperatures, as was seen in the work of Tien and Turkdogan. [24] The validation experiments indicate the obtained reaction rate constants are reasonable. The reaction rate constants for carbon oxidation for coal-char and wu¨stite reduction for wu¨stite obtained from PAH have been tabulated in Table III for different temperatures.…”

Section: Figures 4 Andmentioning

confidence: 81%

Reduction of Iron-Oxide-Carbon Composites: Part I. Estimation of the Rate Constants

Halder

Fruehan

2008

Metall Mater Trans B

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A new ironmaking concept using iron-oxide-carbon composite pellets has been proposed, which involves the combination of a rotary hearth furnace (RHF) and an iron bath smelter. This part of the research focuses on studying the two primary chemical kinetic steps. Efforts have been made to experimentally measure the kinetics of the carbon gasification by CO 2 and wu¨stite reduction by CO by isolating them from the influence of heat-and mass-transport steps. A combined reaction model was used to interpret the experimental data and determine the rate constants. Results showed that the reduction is likely to be influenced by the chemical kinetics of both carbon oxidation and wu¨stite reduction at the temperatures of interest. Devolatilized wood-charcoal was observed to be a far more reactive form of carbon in comparison to coalchar. Sintering of the iron-oxide at the high temperatures of interest was found to exert a considerable influence on the reactivity of wu¨stite by virtue of altering the internal pore surface area available for the reaction. Sintering was found to be predominant for highly porous oxides and less of an influence on the denser ores. It was found using an indirect measurement technique that the rate constants for wu¨stite reduction were higher for the porous iron-oxide than dense hematite ore at higher temperatures (>1423 K). Such an indirect mode of measurement was used to minimize the influence of sintering of the porous oxide at these temperatures.

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“…One such mechanism is the transfer of H 2 , CO, H 2 O, and CO 2 to and from the reacting interface through a porous reduced layer or through a bulk gas-boundary layer. [9][10][11] Another is the reaction of the reducing gases at the receding interface [12] or the bulk of the particle. [13] The final mechanism is a heattransfer-controlled reaction, [14] which is relatively fast for small samples.…”

Section: A Mechanisms Controlling Volatile Reductionmentioning

confidence: 99%

The reduction of iron oxides by volatiles in a rotary hearth furnace process: Part I. The role and kinetics of volatile reduction

Sohn

Fruehan

2005

Metall Mater Trans B

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With iron ore reduction processes using coal-ore pellets or mixtures, it is possible that volatiles can contribute to reduction. By simulating the constituents of the individual reducing species in the volatiles, the rates for H 2 and CO were investigated in the temperature and reduction range of interest; hydrogen is the major reductant and was studied in detail. The kinetics of the reduction by H 2 has been found to be a complex mechanism with, initially, nucleation and growth controlling the rate. There is a catalytic effect by the existing iron nuclei, followed by a mixed control of chemical kinetics and pore diffusion. This results in a topochemical reduction of these iron oxide particles. Up to 1173 K, reduction by H 2 is considerably faster than by carbon in the pellet/mixture or by CO. It was also found that H 2 S, which is involved with the volatiles, does not affect the rate at the reduction range of interest.

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Mathematical analysis of reactions in metal oxide/carbon mixtures

Cited by 23 publications

References 6 publications

Characterization and Reduction Behavior of Mill Scale

Characterization and Reduction Behavior of Mill Scale

Reduction of Iron-Oxide-Carbon Composites: Part I. Estimation of the Rate Constants

The reduction of iron oxides by volatiles in a rotary hearth furnace process: Part I. The role and kinetics of volatile reduction

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