Mineralogical Study on Degradation of Sinter Structure at Low Temperature Reduction

Sakamoto, Noboru; Fukuyo, Hiroshi; Iwata, Yoshihito; Miyashita, Tsuneo

doi:10.2355/tetsutohagane1955.70.6_512

Cited by 20 publications

(17 citation statements)

References 3 publications

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“…Many researchers have investigated the mechanism of disintegration and the methods to prevent it. It is well known that disintegration under CO gas occurs in a significant amount at around 800 K. 2,3) The main cause for disintegration is the volumetric expansion of the iron oxide phase, due to its reduction from hematite to magnetite.…”

Section: Reduction and Disintegration Behavior Of Sinter Under N 2 -Cmentioning

confidence: 99%

Reduction and Disintegration Behavior of Sinter under N2–CO–CO2–H2–H2O Gas at 773 K

2015

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Section: Reduction and Disintegration Behavior Of Sinter Under N 2 -Cmentioning

confidence: 99%

Reduction and Disintegration Behavior of Sinter under N2–CO–CO2–H2–H2O Gas at 773 K

2015

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“…Therefore, the mechanism and suppression method of disintegration of sinter have been the focus of research for a long time. 4,5) It is well known that the disintegration under CO gas reduction occurs significantly at around 800 K. The main factor of the disintegration is volumetric expansion of the iron oxide phase due to the reduction from hematite to magnetite. 4) In addition, sinter is composed of hematite with various phases, which have different effects on disintegration.…”

Section: Introductionmentioning

confidence: 99%

Reduction Disintegration Behavior of Iron Ore Sinter under High H2 and H2O Conditions

et al. 2012

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Reduction of CO2 emissions is an important object for the iron and steel industry. One feasible method may be the utilization of H2 gas as a reducing agent in the blast furnace (BF). However, for stable BF operation, it is first necessary to understand the effects of high H2, and therefore high H2O, concentrations in the reducing gas on the disintegration behavior of iron ore sinter, because it significantly affects the gas permeability of the upper part of the BF. In the present study, disintegration behavior of a sinter sample at 773 K for 3.6 ks under gas flow of N2-CO-CO2-H2-H2O system was examined. The results showed a remarkable increase in the reduction degree and reduction-disintegration index (RDI) upon the addition of a small amount of H2. However, further increase in the H2 concentration caused these values to decrease gradually. Reduction by CO gas led to the formation of magnetite phases with not only thick and long but also fine cracks near the surface. In contrast, H2 reduction did not lead to formation of a significant number of fine cracks. Image analysis of samples revealed that the crack length density showed the similar trend to RDI value. CO gas reduction mainly proceeds near the surface of sinter particles, while H2 gas reduction tends to proceed inside the particles. Accordingly, reduction of H2 gas gave lower RDI than CO gas to the sinter with same reduction degree.

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“…It has a possibility that the crack density and the amount of ACF-A loss decreases because increasing the reduction temperature leads to decreasing the stress caused by the reduction of hematite. 13) …”

Section: Effect Of Calcium Ferritementioning

confidence: 99%

Effect of the Reduction of Calcium Ferrite on Disintegration Behavior of Sinter under High Hydrogen Atmosphere

2015

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The utilization of H 2 gas as a reducing agent in blast furnaces is one potential method to reduce CO 2 emissions from the iron and steel industry. In order to maintain stable operation of the blast furnace under a high H 2 concentration, it is necessary to understand the effects of H 2 and H 2 O gases on the disintegration of the iron ore sinter by reduction under various conditions. In this study, the effect of the reduction of calcium ferrite on the disintegration of sinter was examined.Reduction experiments were carried out under N 2 -20% CO -20% CO 2 (CO reduction) and N 2 -12% CO -x% CO 2 -8% H 2 -(20-x)% H 2 O (CO-H 2 reduction) at temperatures from 773 to 973 K. The reduction of hematite to magnetite mainly proceeds at 773 K. However, longer reduction time is necessary for acicular calcium ferrite as 5.4 ks by CO reduction and 3.6 ks for CO-H 2 reduction, while columnar calcium ferrite is not reduced at such temperature. The reduction of acicular calcium ferrite begins after 1.8 ks at 873 K and accelerates disintegration of sinter. At 973 K, on the other hand, disintegration is inhibited because the volume expansion of skeletal hematite becomes small and the cracks formed in the sinter seem to be mended.

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Mineralogical Study on Degradation of Sinter Structure at Low Temperature Reduction

Cited by 20 publications

References 3 publications

Reduction and Disintegration Behavior of Sinter under N<sub>2</sub>–CO–CO<sub>2</sub>–H<sub>2</sub>–H<sub>2</sub>O Gas at 773 K

Reduction and Disintegration Behavior of Sinter under N<sub>2</sub>–CO–CO<sub>2</sub>–H<sub>2</sub>–H<sub>2</sub>O Gas at 773 K

Reduction Disintegration Behavior of Iron Ore Sinter under High H2 and H2O Conditions

Effect of the Reduction of Calcium Ferrite on Disintegration Behavior of Sinter under High Hydrogen Atmosphere

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