The Elements of Gas—Solid Reaction Systems Involving Single Particles

Szekely, J.

doi:10.1016/b978-0-12-680850-6.50007-x

Cited by 11 publications

(4 citation statements)

References 59 publications

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“…In order to confirm the validity of the reduction mechanism predicted from activation energy values, mathematical formulations (2)–(4) were derived from gas–solid mathematical models [15–18] as follows: for gaseous diffusion mechanism: for chemical reaction mechanism: for mixed control mechanism: where X = fractional reduction degree, t * = dimensionless time, σ = gas–solid reaction modulus.…”

Section: Resultsmentioning

confidence: 99%

Comparative studies on isothermal and non-isothermal reduction of haematite in carbon monoxide atmosphere

El-Geassy

Nasr

El‐Raghy

et al. 2019

Ironmaking & Steelmaking

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Iron ore fines was isothermally and non-isothermally reduced with CO and the total mass loss was continuously recorded. The different phases developed during the reduction process were identified by X-ray diffraction analysis. The structural changes accompanying the reduction reactions were microscopically examined. During the isothermal reduction tests, temperature has a significant effect on the reduction reaction. At a given temperature, the highest rate was obtained at initial stages whereas the minimum rate was observed at the later stages due to the formation of dense iron layer. The activation energy values (Ea) at the early stages was 39.23kJ mol -1 revealed that the reduction is most likely controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanism. At later stages, the Ea values were 54.19 kJ mol-1 indicated that the interfacial chemical reaction is the rate controlling mechanism. Testing of the mathematical formulations derived from the gas-solid reaction model confirmed these controlling mechanisms. The non-isothermal reduction experiments were carried out using different heating rates which showed a considerable effect on the degree of reduction. The reduction conversion continuously increased with rise in temperature. The reduction mechanism was predicted from model free and model fitting. The activation energy values were ranging from 135-40 kJ.mol-1 indicating that gas diffusion is the rate controlling step.

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Section: Resultsmentioning

confidence: 99%

Comparative studies on isothermal and non-isothermal reduction of haematite in carbon monoxide atmosphere

El-Geassy

Nasr

El‐Raghy

et al. 2019

Ironmaking & Steelmaking

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“…In order to confirm the validity of the rate controlling mechanism, the experimental reduction results were tested against the mathematical equations of the gas solid reaction models derived by Szekely as given in equations ( 3)-( 5). 16 For gaseous diffusion mechanism…”

Section: Reduction Kinetics and Mechanismsmentioning

confidence: 99%

Reduction of iron oxide compacts with simulated blast furnace top and shaft gases to mitigate CO₂emissions

Mousa

Bahgat

El-Geassy

2013

Ironmaking & Steelmaking

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The mitigation of CO 2 emissions has become a global priority in the iron and steel industry. One promising solution to decrease CO 2 emissions is recycling of the blast furnace top gas to be reused in the reduction of iron oxide. In this study, iron oxide compacts were reduced isothermally with simulated conventional blast furnace top gas (BFTG: 20%CO, 20%CO 2 , 5%H 2 , 55%N 2 ) at 700-900uC using a thermogravimetric technique. The reduction reached 30-34% depending on the applied temperature. The compacts were reduced completely to wü stite (Fe 0?925 O or Fe 0?971 O) with a few grains of metallic iron, which appeared only at 900uC. To investigate the reduction behaviour at the later stages, the compacts reduced with BFTG at 900uC were followed by isothermal reduction with simulated blast furnace shaft gas (BFSG: 30%CO, 5%CO 2 , 10%H 2 , 55%N 2 ) at 950-1100uC. The total reduction extents were increased to 66-90% at 950-1100uC respectively. The remaining unreduced wü stite (Fe 0?974 O) has a higher Fe/O ratio compared with that formed by reduction with BFTG. At the initial stages of reduction, the rate controlling mechanism was interfacial chemical reaction, while at the later stages, solid state diffusion was the rate controlling mechanism. Reflected light microscope, scanning electron microscope, X-ray diffraction and Poresizer techniques are used to estimate the reduction kinetic and mechanisms.

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“…A Figura 5a mostra que na temperatura de 900°C ocorreu a formação de uma camada reagida em volta do núcleo da pelota. Este núcleo, conforme por ser observado na Figura 5b, apresenta uma estrutura sinterizada e densa, o que pode limitar a passagem do gás redutor em direção ao núcleo da pelota [28].…”

Section: Análise Cinéticaunclassified

Estudo Cinéticos Da Redução De Pelotas De Poeira De Aciaria Ld Por Hidrogênio

Junca

Restivo

Espinosa

et al. 2015

TMM

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A geração de poeira de aciaria LD é um dos problemas encontrados por empresas do setor siderúrgico. Desta forma, torna-se importante o desenvolvimento de estudos que possam viabilizar, ou pelo menos indicar um caminho para a reutilização deste resíduo. A técnica de redução direta pode ser uma alternativa, uma vez que, produtos ricos em ferro metálicos são obtidos. Assim, este trabalho tem por objetivo estudar a cinética de redução de pelotas feitas com poeira de aciaria LD através de uma mistura contendo hidrogênio e argônio, obtendo assim os mecanismos que estão envolvidos na redução das pelotas e a energia de ativação aparente envolvida em cada etapa. Aplicou-se a técnica conhecida como Forced Stepwise Isothermal Analysis na investigação cinética entre as temperaturas de 500°C a 1.100°C. Os resultados mostraram que a reação de redução ocorreu em três etapas. Na primeira etapa, o mecanismo controlador foi por nucleação com uma energia de ativação de 24 kJ/mol. Na segunda e terceira etapa, o mecanismo controlar foi por difusão, porém, na segunda etapa, a energia de ativação aparente obtida foi de 54,9kJ/mol enquanto que na terceira etapa foi de 80,7 kJ/mol. Palavras-chave: Cinética química; Poeira de aciaria LD; Redução direta.

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The Elements of Gas—Solid Reaction Systems Involving Single Particles

Cited by 11 publications

References 59 publications

Comparative studies on isothermal and non-isothermal reduction of haematite in carbon monoxide atmosphere

Comparative studies on isothermal and non-isothermal reduction of haematite in carbon monoxide atmosphere

Reduction of iron oxide compacts with simulated blast furnace top and shaft gases to mitigate CO₂emissions

Estudo Cinéticos Da Redução De Pelotas De Poeira De Aciaria Ld Por Hidrogênio

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The Elements of Gas—Solid Reaction Systems Involving Single Particles

Cited by 11 publications

References 59 publications

Comparative studies on isothermal and non-isothermal reduction of haematite in carbon monoxide atmosphere

Comparative studies on isothermal and non-isothermal reduction of haematite in carbon monoxide atmosphere

Reduction of iron oxide compacts with simulated blast furnace top and shaft gases to mitigate CO2emissions

Estudo Cinéticos Da Redução De Pelotas De Poeira De Aciaria Ld Por Hidrogênio

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Product

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Reduction of iron oxide compacts with simulated blast furnace top and shaft gases to mitigate CO₂emissions