Carburization Degree of Iron Nugget Produced by Rapid Heating of Powdery Iron, Iron Oxide in Slag and Carbon Mixture

Ohno, Ko Ichiro; Miki, Tsuneharu; Sasaki, Yasushi; Hino, Mitsutaka

doi:10.2355/isijinternational.48.1368

Cited by 24 publications

(26 citation statements)

References 9 publications

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“…The deviation to lower temperature form the Fe-C liquidus line was also mentioned in previous work. 10) In that work, it was concluded that agglomeration of iron molten do not need to completely melt. In other words, several remaining of solid iron in the sample could not cause prevention to change their shape the same as slag.…”

Section: Discussionmentioning

confidence: 99%

“…3,4) At the same time, it was reported that the slag melting behavior has strong effect on the direct contact carburization reaction by several researchers. [5][6][7][8][9][10] In this study, the slag melting behavior means minerals in iron ore and ash in cokes change from solid phase to liquid phase. Matsui et al 6) reported the effect of minerals of iron ore on carburization behavior.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Slag Melting Behavior on Metal-Slag Separation Temperature in Powdery Iron, Slag and Carbon Mixture

et al. 2011

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Utilization of self reducing pellet in blast furnace is one of the effective technologies to mitigate the CO2 emissions in the steel industry. However, there are not sufficient researches on how the pellet behaves around cohesive zone. Therefore, purpose of this study is to clarify the effect of slag melting behavior on metal-slag separation behavior. In order to simulate the behavior around cohesive zone, electrolytic iron powder, carbon powder, and synthetic slag were prepared as reduced iron, residual carbon and slag components, respectively. They were well mixed as given mass ratios decided from the composition of the self reducing pellet. Different kinds of slag compositions were adopted to change properties, such as melting temperature and viscosity. The mixtures were pressed into tablets and used as experimental samples. "In-situ" observations of metal-slag separation behavior in the mixtures during constant rate heating were done by a laser microscope combined with infra-red furnace and metal-slag separation temperatures were decided. Following results were obtained. The metal-slag separation behavior was dominated largely by agglomeration behavior of liquid phase of iron. The separation surely occurred when both phases of iron and slag change to liquid phases. At the same time, the separation could also occur even if a small amount of solid phases still remained in the mixture. In this experimental condition, the effect of slag melting temperature on the separation was larger than the effect of slag's viscosity.KEY WORDS: slag melting temperature; viscosity of slag; metal-slag separation behavior; agglomeration behavior of Fe-C liquid; laser microscope; "in-situ" observation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Slag Melting Behavior on Metal-Slag Separation Temperature in Powdery Iron, Slag and Carbon Mixture

et al. 2011

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“…Ohno et al 7,9) showed that the iron carburization could occur through the slag even if the iron was separated from the graphite. That is, the existence of liquid slag mediates the transport of molten Fe-C particle from the interface with the graphite to that with the iron.…”

Section: Introductionmentioning

confidence: 99%

“…Several researchers [1][2][3][4][5][6][7] have investigated the carburization and melting of iron in the mixture of powdery carbonaceous materials and iron ores. It has been known that iron melting rate is very high because of the direct contact of the iron with carbonaceous material as well as the small size of reduced iron particles.…”

Section: Introductionmentioning

confidence: 99%

The Role of Molten Slag in Iron Melting Process for the Direct Contact Carburization: Wetting and Separation

Kim

Sasaki

2010

ISIJ Int.

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Rapid iron melting initiation and molten slag separation which take place in carbon composite iron ores are quite interesting phenomena, but their mechanisms have not been established yet. Since the size of carbonaceous material and iron ore particles is tiny in carbon composite iron ores, molten slag can dynamically play a critical role in the iron melting initiation and the slag separation. The behavior of the molten slag was clarified by direct observation of phenomena occurring in a simplified carbon composite agglomerate sample (iron disk-slag particle-graphite or coke particle) via a confocal laser scanning microscope combined with an image furnace. It was found that the molten slag wetting induced the iron melting initiation by attracting graphite or coke to iron and the molten slag separation took place with iron melting propagation. However, the high content of coke ash could suppress the iron melting initiation. In addition, the mechanism of molten slag separation from Fe-C melt was verified by phase field modeling.KEY WORDS: iron melting initiation; slag wetting; slag separation; coke ash; carbon composite iron ore; confocal laser scanning microscope; phase field method. 1099© 2010 ISIJ ExperimentalIron disks (diameter: 1.0 mm, purity: 99.99%) were prepared by polishing sliced iron particles from an iron rod. Thickness of the iron disks was 0.5 mm. Graphite disks (diameter: 1 mm; high purity) were made by punching a graphite plate (thickness: 0.5 mm). Cokes fragments (mesh: Ͻ1.0 mm) were prepared by crushing the original cokes (mesh: Ͻ60 mm), whose composition is given in Table 1. In order to know the ash effect on the wetting behavior, higher ash content containing cokes were made by the reaction of the broken cokes particles with CO 2 gas at 1 273 K for 20 min. Slag was prepared by heating mixture of oxide powders (CaO: 22.2%, Al 2 O 3 : 15.1%, SiO 2 : 62.7%) up to 1 673 K in a platinum crucible by using a muffle furnace. According to a literature, 11) the melting temperature of the slag is around the eutectic temperature, 1 446 K, which was confirmed by direct observation via a confocal laser scanning microscope. A piece of, approximately, 0.8 mg slag was positioned between an iron disk and a graphite disk or a fragment of coke on an alumina plate as shown in Fig. 1(a). The plate was slightly coated with boron nitride by a BN spray in order to prevent the slag from reacting with the alumina crucible. "In-situ" observation of the phenomena within iron, slag and carbonaceous material was conducted. The sample was heated up to 1 523 K at the rate of 200 K/min under the atmosphere of purified Ar. The behavior of the particles and the slag were recorded in a personal computer at a frame rate of 15 frames/s.The present experiment consisted of two sub-experiments. The first one was designed that the wetting behaviors of CaO-Al 2 O 3 -SiO 2 slag would be compared for different types of carbonaceous material: graphite, coke and reacted coke. Since ash in coke plays a critical role in slag wetting at the in...

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“…Therefore the appropriate amount of iron oxides must be required to effectively increase the melting rate of iron in the CCA or DRI reduction processes. 21) It is well known that the solid inclusions can be absorbed into molten slags. Thus, by the addition of slag with appropriate composition into CCA or DRI, the floated particles may possibly be eliminated.…”

Section: Carburizing and Melting Process Of Fe Bymentioning

confidence: 99%

Enhancement of Iron Melting Rate under the Co-existence of Graphite and Wüstite

2010

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Carburization and melting processes of solid Fe under the co-existence of graphite and wüstite has been investigated based on a confocal laser scanning microscope "in-situ" observation of the movement of the interface between Fe-C melt and solid Fe at 1 523 K. In the experiments, strong stirring flow at the surface of the Fe-C melt is observed. This flow is found to be Marangoni flow and is introduced by the surface tension gradient due to the difference of oxygen concentration between the Fe-C melt interface with graphite and solid iron. The velocity of Marangoni flow is measured from the moving velocities of bubbles at the molten Fe-C surface. The melting rate of Fe is analyzed by computational fluid flow simulations of the Fe-C melt. Based on these results, it is confirmed that the carburization and melting rate of solid Fe can be enhanced by allowing Fe-C melt to come into contact with wüstite and graphite simultaneously.

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Carburization Degree of Iron Nugget Produced by Rapid Heating of Powdery Iron, Iron Oxide in Slag and Carbon Mixture

Cited by 24 publications

References 9 publications

Effect of Slag Melting Behavior on Metal-Slag Separation Temperature in Powdery Iron, Slag and Carbon Mixture

Effect of Slag Melting Behavior on Metal-Slag Separation Temperature in Powdery Iron, Slag and Carbon Mixture

The Role of Molten Slag in Iron Melting Process for the Direct Contact Carburization: Wetting and Separation

Enhancement of Iron Melting Rate under the Co-existence of Graphite and Wüstite

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