Effects of SiO2 and Al2O3 on the Lattice Parameter and CO Gas Reduction of CaO-containing Dense Wustite.

Inami, Takashi; Suzuki, Kanae

doi:10.2355/isijinternational.43.314

Cited by 12 publications

(10 citation statements)

References 11 publications

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“…The difference between reducibilities of FeO and CW in sintered ores could directly be evaluated using high temperature X-ray diffraction (XRD) analysis because the lattice constant of CW increases with increasing CaO concentration in the solid solution even under a constant oxygen partial pressure, 13,14) and the diffraction peaks of FeO and CW can be distinguished from each other to compare the intensities of these diffraction peaks corresponding to the respective concentrations. Consequently, the aim of this study is to clarify the difference between reducibilities of FeO and CW and the effect of hydrogen on the reducibility using high temperature XRD.…”

Section: Introductionmentioning

confidence: 99%

Reducibilities of Wüstite and Calcio-wüstite in Terms of High Temperature X-ray Diffraction Analysis

et al. 2017

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Reducibilities of wüstite and calcio-wüstite have been examined using high temperature X-ray diffraction analysis including the effect of hydrogen on the reducibility. Fe 2 O 3 reagent powders and hematite ore powders were used for reduction of wüstite (denoted as FeO) and sintered ore powders were used for reduction of FeO and calcio-wüstite (denoted as CW). High-temperature X-ray diffraction was applied to these samples in a flow of CO-CO 2 -He mixtures with and without 3.9 vol% of hydrogen during the heating cycle which simulates a blast furnace condition. The diffraction angle was scanned in the range from 33° to 55°. In experiment on sintered ore powders without hydrogen, the main peak around 48.5° shifted to lower angles with increasing temperature. This shift also continued while temperature was kept at 1 000°C where wüstite was saturated with iron; on the contrary, the peak shift did not take place for hematite ore powders. This main peak is associated with wüstite (200), which is actually composed of peaks due to FeO and CW for sintered ore powders. The peak shift reflects that the peak intensity of CW increases relative to that of FeO, which suggests that the reduction of FeO proceeds faster than that of CW, and the reducibility of FeO is higher. In contrast, the peak shift did not take place in experiment on sintered ore powders with hydrogen additions. This suggests that the reducibility of CW is comparable to that of FeO in the presence of hydrogen.

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Section: Introductionmentioning

confidence: 99%

Reducibilities of Wüstite and Calcio-wüstite in Terms of High Temperature X-ray Diffraction Analysis

et al. 2017

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“…17) The effects of SiO 2 on the lattice parameters, 18) porosity 19) of SiO 2 -containing 'FeO' were elucidated to understand the relation between reduction rate and mechanism. El-Geassy 23) and H 2 -CO 17) showed that the reduction increased with the amount of CaO dissolved.…”

Section: Introductionmentioning

confidence: 99%

Influence of CaO and SiO2 on the Reducibility of W^|^uuml;stite Using H2 and CO Gas

et al. 2012

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CaO-(0-20 mass%) and SiO2-containing (0-30 mass%) wüstite ('FeO') compacts were isothermally reduced at 1 273 K under CO and H2 gas. Prior to reduction, the phase of dicalcium ferrite (Ca2Fe2O5) and fayalite (Fe2SiO4) was equilibrated with 'FeO' at 1 273 K under 50%CO/50%CO2 and identified using X-ray diffraction and scanning electron microscopy. The rate of reduction for CaO-containing 'FeO' compacts under both H2 and CO increased up to the vicinity of 2.5 mass% CaO, and then decreased with higher CaO dependent on the formation of an intermediate phase of dicalcium ferrite. For SiO2-containing 'FeO', the rate decreased with SiO2 additions. When the dense fayalite is present reduction using CO was limited, while considerable reduction was observed using H2. The reduction was affected by three distinct reduction mechanisms of interfacial chemical reaction, gaseous mass transport, solid state diffusion of oxygen or a combination of these individual mechanisms termed the mixed control. The contribution of each mechanism with the content of CaO or SiO2 affecting the reduction behavior was determined. The compact porosity increased when CaO was added to approximately 2.5 mass% and subsequently decreased with higher CaO, but continuously decreased with SiO2 additions. The ratio of the effective diffusivity (De) to molecular interdiffusivity (D) was highest at the vicinity of 2.5 mass% CaO and thus the maximum reduction rate was obtained when the porosity was highest.

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“…Since the actual wustite reduction mechanism comprises many more complex steps, a lot of investigations are still directed to handle the reduction of this non-stoichiometric oxide and factors affecting it and though it has not been fully covered in the previous research work [2,3]. The wtistite stoichiometry varies with impurity content, temperature and gas composition and so the presence of impurities in wtistite has significant effects on its reduction kinetics and mechanism as has been shown in many investigations [4][5][6][7][8][9]. In the steel research int.…”

Section: Introductionmentioning

confidence: 99%

“…78 (2007) No. 6 present study, the effect of MgO on the behaviour of wustite during reduction is thoroughly investigated.…”

Section: Introductionmentioning

confidence: 99%

Reduction Behaviour of Wüstite Doped with MgO

Bahgat

Halim

Nasr

et al. 2007

steel research international

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Compacts made from pure wüstite and compacts doped with 2% MgO were annealed at 1000°C for 3 hrs in 50%CO‐CO2 gas mixtures. The annealed samples were isothermally reduced at 800‐1100°C in H2 gas. Selected samples were isothermally reduced at 1000°C with pure CO and 50%H2‐CO gas mixture to investigate the effect of gas composition on the reduction processes. The oxygen weight loss resulting from the reduction of the samples was recorded as a function of time. X‐ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy and porosity measurements were used to characterize the annealed and reduced samples. Magnesio‐wüstite (MgO·FeO) phase was formed during the annealing of MgO doped wüstite. The MgO·FeO in turn decreased the porosity of the annealed doped samples compared to pure wüstite compacts. The influence of temperature, gas composition and MgO content on the reduction behaviour and the morphology of the annealed samples was investigated. The values of the apparent activation energy were calculated from Arrhenius plots and correlated with the reduction mechanism. The reduction rate increased with reaction temperature. In doped compacts, the MgO·FeO phase was not completely reduced both at lower reduction temperature (800°C) and during reduction with pure CO. From the activation energy values, the initial reaction stage was controlled by the combined effect of chemical reaction and gas diffusion while solid state diffusion controlled the final stage of reduction. Morphologically, metallic iron was formed in different shape structures under the effect of MgO addition and reduction conditions.

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Effects of SiO2 and Al2O3 on the Lattice Parameter and CO Gas Reduction of CaO-containing Dense Wustite.

Cited by 12 publications

References 11 publications

Reducibilities of Wüstite and Calcio-wüstite in Terms of High Temperature X-ray Diffraction Analysis

Reducibilities of Wüstite and Calcio-wüstite in Terms of High Temperature X-ray Diffraction Analysis

Influence of CaO and SiO2 on the Reducibility of W^|^uuml;stite Using H2 and CO Gas

Reduction Behaviour of Wüstite Doped with MgO

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