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Deposits in Gas-fired Rotary Kiln for Limonite Magnetization-Reduction Roasting: Characteristics and Formation Mechanism

1
School of Metallurgy and Environment, Central South University, Changsha 410083, China
2
Changsha Research Institute of Mining and Metallurgy Co. Ltd., Changsha 410012, China
3
School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China
*
Authors to whom correspondence should be addressed.
Metals 2019, 9(7), 764; https://doi.org/10.3390/met9070764
Received: 4 June 2019 / Revised: 28 June 2019 / Accepted: 5 July 2019 / Published: 8 July 2019
(This article belongs to the Special Issue Advances in Pyrometallurgy)
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Abstract

The formation mechanism of deposits in commercial gas-fired magnetization-reduction roasting rotary kiln was studied. The deposits ring adhered on the kiln wall based on the bonding of low melting point eutectic liquid phase, and the deposit adhered on the air duct head by impact deposition. The chemical composition and microstructure of the deposits sampled at different locations varied slightly. Besides a small amount of quartz and limonite, main phases in the deposits are fayalite, glass phase and magnetite. The formation of the deposits can be attributed to the derivation of low melting point eutectic of fine limonite and coal ash, and the solid state reaction between them. Coal ash, originated from the reduction coal, combining together with fine limonite particles, results in the accumulation of deposits on the kiln wall and air duct. Fayalite, the binder phase, was a key factor for deposit formation. The residual carbon in limonite may cause an over-reduction of limonite and produce FeO. Amid the roasting process, SiO2, originated from limonite and coal ash, may combine with FeO and reduce the liquefaction temperature, therewith liquid phase generates at high temperature zone, which can significantly promote the growth of deposits. View Full-Text
Keywords: limonite; magnetization reduction roasting; rotary kiln; deposit; fayalite; FeO; liquid phase limonite; magnetization reduction roasting; rotary kiln; deposit; fayalite; FeO; liquid phase
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Fu, X.; Chen, Z.; Xu, X.; He, L.; Song, Y. Deposits in Gas-fired Rotary Kiln for Limonite Magnetization-Reduction Roasting: Characteristics and Formation Mechanism. Metals 2019, 9, 764.

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