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/bf02670879

Cited by 40 publications

(13 citation statements)

References 9 publications

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“…This finding could be attributed to the 'rate minimum' phenomenon, which is often reported in the literature and is associated with hydrogen reduction. 12) The phenomenon is reported by many researchers 10,12) in the literature; It is reported to occur as the reduction rate slows down when the temperature rises to between 600 and 900°C, and then increases at temperatures above 900°C. This phenomenon is attributed to the formation of an impermeable iron layer on the wüstite surface, which slows down gas diffusion through the formed metallic layer to reduce wüstite.…”

Section: Reduction Rate and Curvesmentioning

confidence: 93%

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Influence of H2–H2O Content on the Reduction of Acid Iron Ore Pellets in a CO–CO2–N2 Reducing Atmosphere

et al. 2020

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Using hydrogen as a reducing agent for iron production has been the focus of several studies due to its environmental potential. The aim of this work is to study the influence of H 2-H 2 O content in the gas phase on the reduction of acid iron ore pellets under simulated blast furnace conditions. Temperature and gas compositions for the experiments were determined with multi-point vertical probes in an industrial blast furnace. The results of the reduction tests show that higher temperatures and H 2 content increase the rate and extent of reduction. For all the gas and temperature combinations, morphological, mineralogical, and microstructure changes were observed using different characterization techniques. Microscopy images reveal that H 2-H 2 O, in the gas phase, has a positive influence on reduction, with metallic iron forming at the pellet's periphery and core at lower temperatures compared to CO-CO 2-N 2 reducing gas. Porosity and surface area changes were determined using a gas pycnometer and the BET method. The results indicate that increasing the reduction temperatures and H 2 content results in greater porosity and a larger surface area. Moreover, carbon deposition did not take place, even at lower temperatures. A rate minimum was detected for pellets reduced at 800°C, probably due to metallic iron formation, hindering the diffusion of reducing gases through the product iron layer.

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Section: Reduction Rate and Curvesmentioning

confidence: 93%

“…This is likely to be due to sintering as dense iron was formed, which contains isolated, large pores. 10) The effect of sintering was more pronounced in pellets reduced at 1 100°C in a CO-CO 2 -H 2 -H 2 O-N 2 atmosphere. These observations are in agreement with the literature.…”

Section: Porosity and Surface Areamentioning

confidence: 95%

Influence of H2–H2O Content on the Reduction of Acid Iron Ore Pellets in a CO–CO2–N2 Reducing Atmosphere

et al. 2020

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“…According to Yu et al [27], this phenomenon is due to the reaction rate governed by gas diffusion through the sample. In addition, the iron layer formed around the unreacted core can hamper the diffusion for both the reducing gas into the pellet and the products formed outward pellet [28,29].…”

Section: Kinetic Investigationmentioning

confidence: 99%

Synthetic zinc ferrite reduction by means of mixtures containing hydrogen and carbon monoxide

Junca

Oliveira

Restivo

et al. 2015

J Therm Anal Calorim

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Solid waste generation is one of the main problems in the steelmaking process. One of the most problematic waste products is the electric arc furnace dust, which is a by-product rich in iron and zinc and is present as zincite (zinc oxide) or franklinite (zinc ferrite). This work focuses on the reduction kinetics of synthetic zinc ferrite by gases containing hydrogen and carbon monoxide. This process was examined via forced stepwise isothermal analysis. The test was conducted at temperatures ranging from 500 to 950°C. Reduction of zinc was accomplished using a mixture of hydrogen and carbon monoxide in order to simulate reformed natural gas. The results indicated that reduction of zinc ferrite occurred in two stages (550-750°C and 800-900°C). The first stage was characterized by iron oxide reduction, where a mix control between nucleation and diffusion was determined. The apparent activation energy obtained was 71.5 kJ mol -1 . The second stage was characterized by zinc oxide reduction, where the controlling mechanism was identified as a mixed control between diffusion and phase boundary reaction. The apparent activation energy was 135.5 kJ mol -1 . The formation of a dense layer of metallic iron around the unreacted core may have caused the apparent activation energy to increase.

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“…In developing Eq. [7], it is assumed that only one reaction takes place. However, as seen in Figure 11(a), there are two distinct peaks followed by a significant drop.…”

Section: Heating Under Hydrogen Gasmentioning

confidence: 99%

“…This has subsequently been explained by the fact that a dense iron layer was formed, hindering gas diffusion. [7] It has further been shown that for iron oxide powders less than 350 m, the reduction by hydrogen follows the uniform internal reduction model. [4,5,6] This suggests that the calcines, which are typically less than 50 m, also are reduced uniformly.…”

Section: Introductionmentioning

confidence: 98%

Hydrogen reduction of oxidized nickel concentrates

Crowe¹,

Utigard

2003

Metall Mater Trans B

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Thermal gravimetric analysis was used to investigate the weight change of Ni/Cu/Co calcines upon heating in an inert as well as hydrogen atmosphere. The two calcines investigated contained approximately 50 wt pct combined of hematite and magnetite in addition to sulfides of Ni, Cu, Co, and Fe. Mass spectrometry was used to analyze the gas species evolved during heating and reduction.The calcine samples are 100 pct less than 100 m with hematite/magnetite rims around a central sulfide core. When heating the calcines at 10°C/min in hydrogen, reduction starts at around 400°C and is nearly complete at about 700°C with all the reducible oxygen removed. Isothermal reduction tests show that at temperatures from 650°C to 800°C, half the oxygen is removed in less than 4 min. The TGA results combined with microscopic analysis show that the reduction followed a uniform internal reduction model. The reduced calcines will quickly get re-oxidized if they are allowed to contact air while they remain hot.

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

Cited by 40 publications

References 9 publications

Influence of H<sub>2</sub>–H<sub>2</sub>O Content on the Reduction of Acid Iron Ore Pellets in a CO–CO<sub>2</sub>–N<sub>2</sub> Reducing Atmosphere

Influence of H<sub>2</sub>–H<sub>2</sub>O Content on the Reduction of Acid Iron Ore Pellets in a CO–CO<sub>2</sub>–N<sub>2</sub> Reducing Atmosphere

Synthetic zinc ferrite reduction by means of mixtures containing hydrogen and carbon monoxide

Hydrogen reduction of oxidized nickel concentrates

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