Melt Absorbability of Iron Ore Nuclei and Its Influence on Suitable Liquid Content of Sintered Body
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HIGH basicity sinter is one of the major raw materials used in blast furnace ironmaking because its high reducibility and good mechanical strength are significant factors in determining the productivity and efficiency of the blast furnace. However, with the depletion of high-grade iron ores, steel enterprises have to increase the use of low-grade iron ores with high LOI (the loss on ignition) or high gangue content iron ores in the sintering process for economic reasons, which affects the sintering indexes to some extent. With the intention of overcoming the declining quality of iron ore resources, the concept of quasi-particles has been introduced to utilize low-quality iron ore in the sintering process.[1,2]
SHENG-LI WU, MING-YIN KOU, YUAN LI, and WEI-LI ZHANG are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Room 503, Yejin Building, No. 30 Xueyuan Road, Haidian District, Beijing 100083, China. BO SU is with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing and also with State Key Laboratory of Advanced Steel Processing and Products, Central Iron and Steel Research Institute, Beijing 100081, China. Contact e-mail: [email protected] YUAN-HONG QI is with the State Key Laboratory of Advanced Steel Processing and Products, Central Iron and Steel Research Institute. Manuscript submitted May 19, 2017. Article published online July 31, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
The quasi-particle consists of coarse ores in the center as nuclei particles and adhering fines of fine ores, flux, and fuel. In the sintering process, the initial melt generates within adhering fines by forming calcium ferrites and silicates with low melting temperatures. Then, the initial melt spreads out and continues to react with the surrounding particles to form the primary melt. Finally, the primary melt reacts with the nucleus, and assimilation occurs to form secondary melts.[3] Therefore, the nuclei ore property plays an important role in affecting the assimilation behavior and sinter qualities of quasi-particles. Liquid phase formation, wetting and penetration behaviors of different composition adhering fines have been widely investigated,[4–13] but the high-temperature reaction characteristic of iron ore nuclei has rarely been reported. Okazaki et al.[14] previously studied the melt evolution process within the adhering layer in quasi-particles using paired tablets consisting of an ore tablet and an initial melt tablet. The morphology of the ore surface before and after dehydration and the chemical composition of ores were found to determine the penetration behavior of the melt, and the product yield and the strength of sinter were reflected by the penetration length of the blended ores. Wu et al.[15–17] proposed the new concept of the ‘‘melt absorbability characteristic’’ to estimate the reaction degree between primary melts and nuclei ores, and found that high melt absorbability had an adverse effect on bonding strength. However,
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