Increase in low-temperature reduction degradation of iron ore sinter due to hematite-alumina solid solution and columnar calcium ferrite.

Shigaki, Ichiro; Sawada, Mineo; Gennai, Norio

doi:10.2355/isijinternational1966.26.503

Cited by 51 publications

(34 citation statements)

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“…8(1-C). A number of other authors [30][31][32] have reported that volume expansion will occur during the reduction of this kind of SH, which would adversely affect the low-temperature reduction disintegration of sinter. This volume expansion is mainly due to the rapid cooling of the surface of the sinter cake making the transition of the Fe 2 O 3 phase incomplete.…”

Section: Microstructure Observationmentioning

confidence: 99%

Characteristics of combustion zone and evolution of mineral phases along bed height in ore sintering

Wang

Zhang

Liu

et al. 2017

Int J Miner Metall Mater

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Quantitative parameters of bed combustion, including the thickness of the combustion zone (TCZ), the maximum temperature of the combustion zone (MTCZ), and the bed shrinkage, were characterized through a series of sinter pot tests in transparent quartz pots. The results showed that TCZ first ascended and then descended as the sintering process proceeded. The sintering process was divided into four stages according to the variation rate of the TCZ. A "relative-coordinate" method was developed to obtain the actual reaction temperature of sinter along the height direction. With increasing the sintering temperature, the reactants transformed and entered into liquid phases. The mineral composition and microstructure of the sinter were characterized through X-ray diffraction and scanning electron microscopy-energy-dispersive X-ray spectroscopy. Liquid phases with greater Fe and Al contents were more likely to form acicular-like silico-ferrite of calcium and aluminum after crystallization because of the outward spread of Al, which led to a better fluidity of the liquid. An evolution mechanism of "solid-state reaction-liquid phases formation-crystallization" of the mineral phases is proposed.

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Section: Microstructure Observationmentioning

confidence: 99%

Characteristics of combustion zone and evolution of mineral phases along bed height in ore sintering

Wang

Zhang

Liu

et al. 2017

Int J Miner Metall Mater

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“…5) Other ferrite phases observed in industrial sinters include monocalcium ferrite, CaO. 6) SFCA phases are believed to be the most desirable bonding phases in iron ore sinter because of their high reducibility, 7) high mechanical strength and low reduction degradation, 8,9) all of which are significant factors in determining the productivity and efficiency of the blast furnace.…”

Section: Introductionmentioning

confidence: 99%

Effect of Oxygen Partial Pressure on the Formation Mechanisms of Complex Ca-rich Ferrites

et al. 2013

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The formation mechanisms of the complex Ca-rich ferrite iron ore sinter bonding phases SFCA and SFCA-I, during heating of a synthetic sinter mixture in the range 298-1 623 K and at pO2 = 0.21, 5 × 10 -3 and 1 × 10 -4 atm, were determined using in situ X-ray diffraction. SFCA and, in particular, SFCA-I are desirable bonding phases in iron ore sinter, and improved understanding of the effect of parameters such as pO2 on their formation may lead to improved ability to maximise their formation in industrial sintering processes. SFCA-I and SFCA were both observed to form at pO2 = 0.21 and 5 × 10 -3 atm, with the formation of SFCA-I preceding SFCA formation in each case, but via distinctly different mechanisms at each pO2. No SFCA-I was observed at pO2 = 1 × 10 -4 atm; instead, a Ca-rich phase designated CFAlSi, formed at 1 420 K. By 1 456 K, CFAlSi had decomposed to form melt and a small amount of SFCA. Such a low pO2 during heating of industrial sinter mixtures is, therefore, undesirable, since it would not result in the formation of an abundance of SFCA and SFCA-I bonding phases. In addition, CFA phase, which was determined by Webster et al. (Metall. Mater. Trans. B, 43(2012), 1344) to be a key precursor phase in the formation of SFCA at pO2 = 5 × 10 -3 atm, was also observed to form at pO2 = 0.21 and 1 × 10 -4 atm, with the amount decreasing with increasing pO2.KEY WORDS: iron ore sinter; complex Ca-rich ferrite sinter bonding phases; SFCA and SFCA-I; in situ X-ray diffraction; oxygen partial pressure; phase formation mechanisms; synchrotron X-ray diffraction.

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“…Historically, particularly in Japan, it is strongly believed that the secondary hematite, also known as skeletal rhombohedral hematite, is the major cause of poor reduction degradation resistance of sinter. 15,38) This is based on frequent observations of cracks around the narrow neck regions of such hematite. However, low to intermediate levels of alumina have been reported to reduce the amount of secondary hematite and increase SFCA in the sinter structure, both of which should be advantageous to RDI.…”

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confidence: 99%

Effects of Alumina on Sintering Performance of Hematite Iron Ores

2007

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The integrated blast furnace and oxygen steelmaking (BF-OSM) route is still a dominant process for worldwide steel production, currently producing more than 60 % of the world's total output of crude steel. The counter-current principle on which the blast furnace operates makes it reliant heavily on the quality of its burden to maintain a sufficient level of gas permeability in its upper shaft and of liquid and gas permeability in its lower part. Iron ore sinter, constituting a major proportion of blast furnace burden in most countries, particularly in the Asia-Pacific region, is therefore expected to have a significant impact on blast furnace performance.The chemical composition of iron ore fines, together with the thermal conditions that sinter blends are subjected to, plays an important role in forming the primary melt during the sintering process and consequently determines the sinter structure and quality. Considerable emphasis has therefore been placed on the chemical composition and consistency of iron ore fines, particularly in terms of alumina content. However, due to the limited reserves and increasing depletion of high-grade iron ore resources, the alumina content of iron ores is expected to increase gradually. While the increase in such constituents is relatively slow over a long period, it has still caused problems for blast furnace operators.This paper attempts to clarify the role of different types of alumina present in iron ore fines and their effects on melt formation, sinter structure and sinter quality, as well as the sintering process itself. Mechanisms responsible for the deterioration of the low temperature reduction degradation characteristics (RDI) of sinter due to the increasing alumina content are also reviewed. In addition, potential measures to counter the adverse impacts of alumina on sintering performance of hematite iron ore fines are also discussed.KEY WORDS: High alumina iron ores; kaolinite; gibbsite; melt formation; sinter structure; sintering performance, sinter quality.ISIJ International, Vol. 47 (2007), No. 3, pp. 349-358 Review 349 © 2007 ISIJ alumino-silicates like kaolinite (Al 2 O 3 · 2SiO 2 · 2H 2 O), while the A type ores contain gibbsite (Al(OH) 3 ). 9) Extensive work has been conducted on the effects of alumina on sinter structure, quality and productivity. 1,2,[4][5][6][9][10][11][12][13][14] While the results are not conclusive and sometimes contradict each other, it is generally believed that too much alumina impairs the sinter quality, particularly the low temperature reduction degradation characteristics. However, much of the previous work showing the strong adverse effects of alumina on sinter quality and the sintering process has been focused mainly on Indian ores, 1,[4][5][6]9) which often belong to A type iron ores. Only limited work has been conducted on the majority of iron ores that contain alumina in the form of kaolinite. 2,10,12) From high temperature X-ray diffraction studies on Fe 2 O 3 -SiO 2 -CaO-Al 2 O 3 ores, it has been found that kaolinite ty...

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Increase in low-temperature reduction degradation of iron ore sinter due to hematite-alumina solid solution and columnar calcium ferrite.

Cited by 51 publications

References 0 publications

Characteristics of combustion zone and evolution of mineral phases along bed height in ore sintering

Characteristics of combustion zone and evolution of mineral phases along bed height in ore sintering

Effect of Oxygen Partial Pressure on the Formation Mechanisms of Complex Ca-rich Ferrites

Effects of Alumina on Sintering Performance of Hematite Iron Ores

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