A study of the mechanism of reduction with hydrogen of pure wustite single crystals

Moukassi, M.; Stein, Nicolas; Dupré, Bernard; Gleitzer, C.

doi:10.1007/bf02654061

Cited by 6 publications

(8 citation statements)

References 8 publications

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“…Several macroscopic studies exist on the reduction of iron oxide exposed to different gas mixtures (in part including hydrogen) in the temperature range of 500-900 °C [21][22][23][24] . However, key aspects that influence the reduction kinetics in terms of the microstructure, nano-chemistry, porosity, and mechanics of the ores and partially reduced products are not well understood.…”

Section: Approaches To Hydrogen-based Reduction Of Iron Oxide and Thementioning

confidence: 99%

Influence of Microstructure and Atomic-Scale Chemistry on Iron Ore Reduction with Hydrogen at 700°C

et al. 2020

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With 1.85 billion tons produced per year, steel is the most important material class in terms of volume and environmental impact. While steel is a sustainability enabler, for instance through lightweight design, magnetic devices, and efficient turbines, its primary production is not. For 3000 years, iron has been reduced from ores using carbon. Today 2.1 tons CO2 are produced per ton of steel, causing 30% of the global CO2 emissions in the manufacturing sector, which translates to 6.5% of the global CO2 emissions. These numbers qualify iron-and steel-making as the largest single industrial greenhouse gas emission source. The envisaged future industrial route to mitigate these CO2 emissions targets green hydrogen as a reductant. Although this reaction has been studied for decades, its kinetics is not well understood, particularly during the wüstite reduction step which is dramatically slower than the hematite reduction. Many rate-limiting factors of this reaction are set by the micro-and nanostructure as well as the local chemistry of the ores. Their quantification allows knowledge-driven ore preparation and process optimization to make the hydrogen-based reduction of iron ores commercially viable, enabling the required massive CO2 mitigation to ease global warming. Here, we report on a multi-scale structure and composition analysis of iron reduced from hematite with pure H2, reaching down to near-atomic scale. The microstructure after reduction is an aggregate of nearly pure iron crystals, containing inherited and acquired pores and cracks. Crucial to the reduction kinetics, we observe the formation of several types of lattice defects that accelerate mass transport inbound (hydrogen) and outbound (oxygen) as well as several chemical impurities within the Fe in the form of oxide islands that were not reduced. With this study, we aim to open the perspective in the field of carbon-neutral iron production from macroscopic processing towards a better understanding of the underlying microscopic reduction mechanisms and kinetics.

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Section: Approaches To Hydrogen-based Reduction Of Iron Oxide and Thementioning

confidence: 99%

Influence of Microstructure and Atomic-Scale Chemistry on Iron Ore Reduction with Hydrogen at 700°C

et al. 2020

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“…The summary given here is based upon four studies (23)(24)(25)(26) employing rate measurements, microscopy, and X-ray diffraction as the experimental techniques on both single crystals and powder briquets.…”

Section: The Mechanism Of the Reduction Of Magnetitementioning

confidence: 99%

Preparation and Activation of the Technical Ammonia Synthesis Catalyst

Schlögl

1991

Catalytic Ammonia Synthesis

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“…A desaceleração da reação de redução causada pela formação de uma camada reagida é uma situação corriqueira nos estudos de redução de óxidos de ferro. Esta barreira dificulta a difusão, tanto dos reagentes como dos produtos gasosos, tornando assim, a difusão a etapa limitante da reação (148,149,150) .…”

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“…De acordo com o autor, esta desaceleração é devido à mudança alotrópica que ocorre na redução de FeO para ferro. Em adição, (95) , realizou observações no microscópio eletrônico de varredura durante a redução de wustita. Foi observado que com o andamento da redução, a estrutura se torna cada vez mais densa, assim, atuando como uma barreira para a difusão de gás nos poros.…”

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Reciclagem de poeira de aciaria: estudo da redução da poeira de aciaria LD, elétrica e ferrita de zinco.

Junca¹

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Resumo Uma grande quantidade de poeiras e fumos contendo óxidos de ferro, zinco, alumínio, cálcio, chumbo, magnésio e cádmio são habitualmente gerados durante a produção do aço em usinas siderúrgicas semiintegradas. Processos hidrometalúrgicos e pirometalúrgicos têm sido desenvolvidos para o tratamento da poeira de aciaria elétrica (PAE). O processo Waelz, que recupera parte destes resíduos por meio de reações metalúrgicas de redução e oxidação em um forno rotativo, é uma tecnologia de destaque empregada para a recuperação dos metais voláteis, e tem sido a mais usada nos últimos 40 anos. Neste trabalho, foi realizado um estudo termodinâmico do processo Waelz, visando à otimização das condições metalúrgicas necessárias para garantir a recuperação dos metais voláteis (em especial zinco), de forma a assegurar a minimização de impactos ambientais e maximização de opções de processamento para a recuperação do zinco contido. As variáveis cinéticas foram estudadas por meio da execução de uma serie de 6 experimentos, englobando os principais fatores do processamento, tais como: tipo de redutor e tempo/temperatura de processamento. Também foi avaliado o comportamento mecânico das pelotas para cada formulação. Caracterizações por meio de microscopia eletrônica com microanálise via EDS, difração de raios X, fluorescência de raios X, análise granulométrica a laser, resistência à compressão, porcentagem de matéria volátil, carbono fixo e cinzas foram empregados. Palavras-chave: Pelotas autorredutoras; Recuperação do zinco; Tratamento de resíduo de aciaria; Processo Waelz. Abstract A high amount of residues such as dust and fumes containing iron oxides, zinc, aluminum, calcium, lead, magnesium and cadmium are usually generated during the steel production in steel mills, which produce it from scrap melting. Hydrometallurgical and pyrometallurgical processes have been developed to the treatment of electric arc furnace dust (EAF). The Waelz process, that recovers part of these residues through metallurgical reactions of oxidation and reduction in a rotary kiln, is a leading technology used for the recovery of volatile metals, and has been widely used over the past 40 years. In this work, an initial thermodynamic and kinetic study of the Waelz reduction process was conducted, aiming to optimize the metallurgical conditions needed to ensure the recovery of volatile metals (especially zinc) and therefore assure the minimization of environmental impacts and maximization of more sustainable processing options and with higher added value due to the increase of zinc recovery from the dust and metallurgical residues. Kinetic variables were studied by running a series of six experiments, covering the main processing variables such as content and type of the binder, content and type of the reducer and processing time/temperature. The behavior and thermomechanical properties will also be assessed. There were used characterizations by electron microscopy, X-ray diffraction, X-ray fluorescence, particle size analysis with laser, compressive ...

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A study of the mechanism of reduction with hydrogen of pure wustite single crystals

Cited by 6 publications

References 8 publications

Influence of Microstructure and Atomic-Scale Chemistry on Iron Ore Reduction with Hydrogen at 700°C

Influence of Microstructure and Atomic-Scale Chemistry on Iron Ore Reduction with Hydrogen at 700°C

Preparation and Activation of the Technical Ammonia Synthesis Catalyst

Reciclagem de poeira de aciaria: estudo da redução da poeira de aciaria LD, elétrica e ferrita de zinco.

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