Grundlagen

Bogdandy, Ludwig von; Engell, Hans Jürgen

doi:10.1007/978-3-642-92935-9_2

Cited by 4 publications

(3 citation statements)

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“…For the design and optimisation of direct reduction processes, detailed knowledge of kinetics of iron ore fines reduction is necessary, to be able to model heterogeneous reactions. Numerous models were developed by several authors, [1][2][3][4][5][6][7][8][9][10][11][12] including structural parameters such as porosity, specific surface area and mean pore diameter. Investigations regarding the changes of particle structure including also sintering effects during reaction were done.…”

Section: Structural Changes During Heterogeneous Reactionsmentioning

confidence: 99%

“…Investigations regarding the changes of particle structure including also sintering effects during reaction were done. [11][12][13][14][15][16][17][18][19] During heterogeneous reactions, chemical and physical effects are competing for the changes of porosity, specific surface area and pore size distribution. Chemical reaction can result in an increase and decrease in porosity and specific surface area.…”

Section: Structural Changes During Heterogeneous Reactionsmentioning

confidence: 99%

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Structural and morphological changes during reduction of hematite to magnetite and wustite in hydrogen rich reduction gases under fluidised bed conditions

Weiss

Sturn

Voglsam

et al. 2011

Ironmaking & Steelmaking

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During the reduction of iron ore fines structural changes in particles have a significant influence on the rate of reduction. Investigations regarding porosity, specific surface area and mean pore diameters in the reduction of hematite with hydrogen rich reducing gases were performed by mercury porosimetry. Morphological changes were examined by metallographic analyses of polished sections in reflected light. In the magnetite equilibrium phase, significant influence of temperature on structural parameters and sintering effects were found. For wustite phases, the influence of temperature was less pronounced. For the reduction of hematite to magnetite and magnetite to wustite topochemical phase growth and microporous product layers were observed. In the single step, reduction of hematite to wustite progressive conversion and significant increase in the mean pore diameter were found. The results presented in this work are of high importance for understanding the reaction kinetics of iron ore fines and essential for modelling heterogeneous reactions.List of symbols a 1 constant for increase in specific surface area, g 22 min 21 a 2 constant for decrease in specific surface area, g 22 min 21/2 A Sp specific surface area, m 2 g 21 A Sp,0 initial specific surface area, m 2 g 21 A Sp,de term for decrease in specific surface area, m 2 g 21 A Sp,in term for increase in specific surface area, m 2 g 21 p i partial pressure p tot total pressure, bar t time, min T temperature, K c parameter for decrease in specific surface area 14 h temperature, uC Structural changes during heterogeneous reactionsDirect reduction of iron ore fines receives increasing attention in the area of alternative iron making. For the design and optimisation of direct reduction processes, detailed knowledge of kinetics of iron ore fines reduction is necessary, to be able to model heterogeneous reactions. Numerous models were developed by several authors, 1-12 including structural parameters such as porosity, specific surface area and mean pore diameter. Investigations regarding the changes of particle structure including also sintering effects during reaction were done. [11][12][13][14][15][16][17][18][19] During heterogeneous reactions, chemical and physical effects are competing for the changes of porosity, specific surface area and pore size distribution. Chemical reaction can result in an increase and decrease in porosity and specific surface area. Decisive therefore are the molar volume of solid reaction products, 9,20-22 the stoichiometry of the reaction and the initial porosity of the reactant.Furthermore, decrease in porosity and specific surface area during heterogeneous reactions is caused by sintering effects, recrystallisation and reordering of solid species. Sintering effects during iron ore fines reduction were investigated by several authors. [22][23][24][25][26][27] Decrease in specific surface area observed by Heizmann et al. 25 was interpreted as reorganisation effects of solid reaction products.

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Section: Structural Changes During Heterogeneous Reactionsmentioning

confidence: 99%

Section: Structural Changes During Heterogeneous Reactionsmentioning

confidence: 99%

Structural and morphological changes during reduction of hematite to magnetite and wustite in hydrogen rich reduction gases under fluidised bed conditions

Weiss

Sturn

Voglsam

et al. 2011

Ironmaking & Steelmaking

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“…However, when the arc was run between the iron ore and graphite electrode, at high temperatures, it was possible to produce magnetite. This is because, corresponding to the Fe3O4−Fe2O3 line in the Ellingham diagram and extending the line to high temperatures, the Gibbs energy will be positive [40]. Furthermore, the composition of 1 mol haematite at equilibrium at temperatures between 1500 and 2000 °C was calculated using FactSage TM 7.2 (Database: FactPS and FToxide (2018)) and the results are shown in Figure 9.…”

Section: Results and Discussion Of The Experimentsmentioning

confidence: 99%

Reduction of Haematite Using Hydrogen Thermal Plasma

2019

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The development of hydrogen plasma smelting reduction as a CO2 emission-free steel-making process is a promising approach. This study presents a concept of the reduction of haematite using hydrogen thermal plasma. A laboratory scale and pilot scale hydrogen plasma smelting reduction (HPSR) process are introduced. To assess the reduction behaviour of haematite, a series of experiments have been conducted and the main parameters of the reduction behaviour, namely the degree of hydrogen utilization, degree of reduction and the reduction rate are discussed. The thermodynamic aspect of the hematite reduction is considered, and the pertinent calculations were carried out using FactSageTM 7.2. The degree of hydrogen utilization and the degree of reduction were calculated using the off-gas chemical composition. The contribution of carbon, introduced from the graphite electrode, ignition pin and steel crucible, to the reduction reactions was studied. The degree of reduction of haematite, regarding H2O, CO and CO2 as the gaseous reduction products, was determined. It is shown that the degree of hydrogen utilization and the reduction rate were high at the beginning of the experiments, then decreased during the reduction process owing to the diminishing of iron oxide. Conducting experiments with the high basicity of slag B2 = 2 led to a decrease of the phosphorus concentration in the produced iron.

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Punktfehlstellen in Metalloxiden

Ilschner¹

1970

Advances in Solid State Physics

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Grundlagen

Cited by 4 publications

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Structural and morphological changes during reduction of hematite to magnetite and wustite in hydrogen rich reduction gases under fluidised bed conditions

Structural and morphological changes during reduction of hematite to magnetite and wustite in hydrogen rich reduction gases under fluidised bed conditions

Reduction of Haematite Using Hydrogen Thermal Plasma

Punktfehlstellen in Metalloxiden

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