Softening behaviors of acid and olivine fluxed iron ore pellets in the cohesive zone of a blast furnace

Antti Kemppainen, Ko-Ichiro Ohno, Mikko Iljana, Olli Mattila, Timo Paananen, Eetu Pekka Heikkinen, Takayuki Maeda, Kazuya Kunitomo, Timo Fabritius

Research output: Contribution to journalArticle

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Abstract

A ferrous burden loses its permeability in the cohesive zone of a Blast Furnace (BF) which has an effect on the flow of reducing gases. Iron ore pellets with various chemical compositions have different softening properties. Due to the occurrence of numerous simultaneous phenomena the clarification of different variables is difficult. In this study the effect of Reduction Degree (RD) on the softening behavior of individual acid and olivine fluxed iron ore pellets was experimentally tested under inert conditions. The acid pellet softened rapidly at 1 150°C and reached about 40% contraction at 1 200°C. The olivine fluxed pellet softened gradually in the range of 1 150 and 1 350°C and reached 30-35% contraction. The RDs of 50-70% for acid and 50-65% for olivine fluxed pellet had no significant effect on the softening behavior. However, the highest contraction-% was reached with the lowest RD. The results indicate that softening of the pellets is caused by the softening of the pellet core. The early softening of the acid pellet was attributed to high SiO2 content and formation of fayalite slag with high wüstite solubility. The superior properties of the olivine fluxed pellet were attributed to the low SiO2 content and favorable effects of fluxes to prevent wüstite dissolution. FactSage V6.4 -software and its FToxid-database was used to compute the phase equilibrium of a pre-reduced pellet with a quaternary FeO-SiO2-CaO-MgO system in the core region. The computed phase equilibrium provided additional information about the effects of different components in the phase equilibrium.

Original languageEnglish
Pages (from-to)2039-2046
Number of pages8
JournalISIJ International
Volume55
Issue number10
DOIs
Publication statusPublished - Jan 1 2015

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Iron ore pellets
Olivine
Blast furnaces
Phase equilibria
Acids
Slags
Dissolution
Solubility
Gases
Fluxes
olivine
Chemical analysis

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

Softening behaviors of acid and olivine fluxed iron ore pellets in the cohesive zone of a blast furnace. / Kemppainen, Antti; Ohno, Ko-Ichiro; Iljana, Mikko; Mattila, Olli; Paananen, Timo; Heikkinen, Eetu Pekka; Maeda, Takayuki; Kunitomo, Kazuya; Fabritius, Timo.

In: ISIJ International, Vol. 55, No. 10, 01.01.2015, p. 2039-2046.

Research output: Contribution to journalArticle

Kemppainen, Antti ; Ohno, Ko-Ichiro ; Iljana, Mikko ; Mattila, Olli ; Paananen, Timo ; Heikkinen, Eetu Pekka ; Maeda, Takayuki ; Kunitomo, Kazuya ; Fabritius, Timo. / Softening behaviors of acid and olivine fluxed iron ore pellets in the cohesive zone of a blast furnace. In: ISIJ International. 2015 ; Vol. 55, No. 10. pp. 2039-2046.
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abstract = "A ferrous burden loses its permeability in the cohesive zone of a Blast Furnace (BF) which has an effect on the flow of reducing gases. Iron ore pellets with various chemical compositions have different softening properties. Due to the occurrence of numerous simultaneous phenomena the clarification of different variables is difficult. In this study the effect of Reduction Degree (RD) on the softening behavior of individual acid and olivine fluxed iron ore pellets was experimentally tested under inert conditions. The acid pellet softened rapidly at 1 150°C and reached about 40{\%} contraction at 1 200°C. The olivine fluxed pellet softened gradually in the range of 1 150 and 1 350°C and reached 30-35{\%} contraction. The RDs of 50-70{\%} for acid and 50-65{\%} for olivine fluxed pellet had no significant effect on the softening behavior. However, the highest contraction-{\%} was reached with the lowest RD. The results indicate that softening of the pellets is caused by the softening of the pellet core. The early softening of the acid pellet was attributed to high SiO2 content and formation of fayalite slag with high w{\"u}stite solubility. The superior properties of the olivine fluxed pellet were attributed to the low SiO2 content and favorable effects of fluxes to prevent w{\"u}stite dissolution. FactSage V6.4 -software and its FToxid-database was used to compute the phase equilibrium of a pre-reduced pellet with a quaternary FeO-SiO2-CaO-MgO system in the core region. The computed phase equilibrium provided additional information about the effects of different components in the phase equilibrium.",
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AU - Kemppainen, Antti

AU - Ohno, Ko-Ichiro

AU - Iljana, Mikko

AU - Mattila, Olli

AU - Paananen, Timo

AU - Heikkinen, Eetu Pekka

AU - Maeda, Takayuki

AU - Kunitomo, Kazuya

AU - Fabritius, Timo

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