Über den Verlauf der Reduktion von Wüstit mit Zusätzen an Fremdoxiden

Piepenbrock, Robert; Koch, Klaus; Trömel, Gerhard; Fix, Wolfdietrich

doi:10.1002/srin.197603794

Cited by 14 publications

(2 citation statements)

References 7 publications

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“…9. The decreasing tendency of kЈ in Al 2 O 3 -containing wustite was in accordance with the result by Piepenbrock et al 15) Therefore, coexisting Al 2 O 3 in CaO-SiO 2 -wustite leads to a decrease in the dissolved content of CaO and in the reduction rate. The obtained D is almost the same as that of CaO-SiO 2 -wustite as shown in Fig.…”

Section: Effect Of Al 2 O 3 In Cao-sio 2 -Wustite On Ksupporting

confidence: 91%

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

Inami

Suzuki

2003

ISIJ International

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The effects of SiO 2 and Al 2 O 3 on the lattice parameter and the initial reduction rate of CaO-containing wustite were studied at 1 273 K. Wustite plates containing 0.5-2 mass% CaO, 0.2-2 mass% SiO 2 and 1 mass% Al 2 O 3 were prepared at the mass fractions of CaO/SiO 2 ϭ0.5-5. The lattice parameter of CaO-SiO 2 -containing wustite decreased with decreasing CaO/SiO 2 ratio at a constant CaO content. This corresponded to a decrease of the dissolved content of CaO in the wustite due to a formation of CaO-FeO-SiO 2 compounds. Similarly, the dissolved content of CaO decreased in CaO-SiO 2 -Al 2 O 3 -containing wustite. The process of CO gas reduction within the wustite phase field was traced with the lattice parameter measurement of the partially reduced samples and was analyzed with a mixed-control model of chemical reaction at the surface and the solid state diffusion in the wustite. The chemical reaction rate constant, kЈ, decreased with increasing the amount of SiO 2 addition at a constant CaO content. The dependence of kЈ on SiO 2 (and Al 2 O 3 ) addition was in good accordance with the change in the dissolved content of CaO in the wustite owing to the formation of the compounds containing CaO. The inter-diffusion coefficient, D , tended to decrease slightly with increasing the amount of compound.KEY WORDS: wustite; CO gas reduction; chemical reaction rate constant; inter-diffusion constant; mixedcontrol model; lattice parameter; iron making. brated wustite samples was about 5.4ϫ10 3 kg/m 3 and slightly less than that of pure wustite summarized by Onoda and Sasaki. 4) The reduction experiments were conducted at 1 273 K by using a thermo-balance. CO-CO 2 -Ar gas mixtures (P CO 2 / P CO ϭ0.04 and 0.16, hereafter a), flowing at a rate of 2.5ϫ10 Ϫ5 m 3 /s, were used as reducing gas in order to avoid carbon-deposition from the gas mixtures. Under these conditions, the effect of gas-side resistance on the over all rate of reduction is negligibly small as demonstrated previously. 1) X-ray diffraction analysis was performed for the partially reduced sample and the change in lattice parameter in the depth direction of the samples was measured by stepwise polishing of the samples. As the lattice parameter has been reported to be a parameter corresponding to wustite composition, 5) the concentration profile of iron ion in the samples partially reduced was estimated from the lattice parameter profile measured. Moreover, morphological observation and analysis of elements on the section of samples were carried out with EPMA. Thereafter, prepared wustite samples were distinguished as follows: The SiO 2 -and CaO-SiO 2 -wustite denoted the wustite containing only SiO 2 and both CaO and SiO 2 , respectively. Experimental Results Lattice Parameter and Morphology of CaO-SiO 2 -Wustite before Reduction The dependences of lattice parameter on oxide content in 5) SiO 2 -, and Al 2 O 3 -wustite equilibrated with the CO-CO 2 gas mixture (Ksϭ50/50) at 1 273 K are shown in Fig. 1(a). The lattice parameter a increased linearly with an in...

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Section: Effect Of Al 2 O 3 In Cao-sio 2 -Wustite On Ksupporting

confidence: 91%

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

Inami

Suzuki

2003

ISIJ International

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“…32,33 It has also been reported that the presence of extraneous cations, such as Mg 2z , in such low contents, reduces the activity of wu ¨stite and consequently lowers its reduction rate because of deteriorating thermodynamic conditions. 34,35 Figure 3 shows a photomicrograph of MgO doped Fe 2 O 3 and reduced at 500uC in H 2 which indicates the development of metallic iron (light grey) which entrapped magnesioferrite phase (dark grey). This magnesioferrite patches are also characterised by the presence of central macropores which favour the formation of this phase in the vicinity of large pores.…”

Section: Methodsmentioning

confidence: 99%

Effect of additives on the reduction behaviour and CO₂catalytic decomposition of nanocrystallite Fe₂O₃

Khedr¹,

Bahgat²,

Nasr³

et al. 2008

Mineral Processing and Extractive Metallurgy

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Compacts of pure Fe 2 O 3 mixed with 5 wt-%MgO, CuO, SiO 2 or TiO 2 separately, were sintered at 500uC for 1 h and then isothermally reduced with H 2 at 500uC to metallic iron. The oxygen weight loss resulting from Fe 2 O 3 -Fe reduction steps were continuously recorded as a function of time. Xray analyses, reflected light microscope and scanning electron microscope were used to characterise the fired and reduced compacts. The influence of MgO, CuO, SiO 2 and TiO 2 on the reduction and CO 2 catalytic decomposition behaviour of Fe 2 O 3 was intensively studied. The reduction was correlated to the microstructure of the reduced samples. The results obtained showed that doping of Fe 2 O 3 with these fluxing oxides decreases the reduction of Fe 2 O 3 at 500uC. This was attributed to formation of entrapped lower oxide relics, which hindered gaseous diffusion. On the other hand, for the CO 2 catalytic decomposition process, it was found that the rate of reoxidation of samples reduced from pure Fe 2 O 3 is higher than those samples obtained from Fe 2 O 3 doped with CuO, MgO, TiO 2 and SiO 2 at the initial stage, whereas at the final stages, the rate of reoxidation of reduced pure Fe 2 O 3 is less than that for reduced Fe 2 O 3 doped with CuO, MgO, TiO 2 and SiO 2 .

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An investigation of the critical influence of potassium on the reduction of wustite

1986

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Über den Verlauf der Reduktion von Wüstit mit Zusätzen an Fremdoxiden

Cited by 14 publications

References 7 publications

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

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

Effect of additives on the reduction behaviour and CO₂catalytic decomposition of nanocrystallite Fe₂O₃

An investigation of the critical influence of potassium on the reduction of wustite

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Über den Verlauf der Reduktion von Wüstit mit Zusätzen an Fremdoxiden

Cited by 14 publications

References 7 publications

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

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

Effect of additives on the reduction behaviour and CO2catalytic decomposition of nanocrystallite Fe2O3

An investigation of the critical influence of potassium on the reduction of wustite

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Effect of additives on the reduction behaviour and CO₂catalytic decomposition of nanocrystallite Fe₂O₃