Estimation of Sintering Kinetics of Magnetite Pellet Using Optical Dilatometer
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IN the prospects of ores getting leaner and finer, pelletization is increasing globally as the most widely practiced agglomeration technique for the ore fines. The major ores being the iron bearing minerals—hematite and magnetite whose fines are being pelletized at large scale across the world. Magnetite ore fines, in particular, have the advantage because of its exothermic oxidation reaction making it more suitable and efficient for T.K. SANDEEP KUMAR, Doctorate Student, is with the Department of Civil, Environmental and Natural Resources (SBN), Lulea University of Technology (LTU), Lulea, 97187 Sweden Contact e-mail: [email protected] NEELAKANTAN NURNI VISWANATHAN, Visiting Professor, is with the Department of Civil, Environmental and Natural Resources (SBN), Lulea University of Technology (LTU), and also Professor, with the Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology Bombay (IITB), Mumbai 400076, India. HESHAM M. AHMED, Assistant Professor, is with the Department of Civil, Environmental and Natural Resources (SBN), Lulea University of Technology (LTU), and also with the Central Metallurgical Research & Development Institute (CMRDI), Cairo, Egypt. CHARLOTTE ANDERSSON, Specialist/Senior Researcher - Oxidation Metallurgy Research & Development, is with the Luossavaara-Kiirunavara Aktiebolag (LKAB), Malmberget, Ga¨llivare, 98381 Sweden. B. BJO¨RKMAN, Emeritus Professor, is with the Department of Civil, Environmental and Natural Resources (SBN), Lulea University of Technology (LTU). Manuscript submitted June 3, 2015 Article published online November 16, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
induration subsequent to pelletization. In Sweden, where major source of iron ore is magnetite has developed the expertise in pelletization over the years, as it is the largely practiced agglomeration technique. The blast furnaces in Sweden operate primarily with pellets except for a small proportion of briquettes made out of steel plant solid waste materials. In pelletization process, magnetite ore is ground and mixed with bentonite as binder then balled in pelletizer to produce green pellets. These green pellets are then heat hardened during induration. Thus, induration is a vital process in pelletization to attain desired pellet quality parameters of strength and reducibility. Induration is carried out either in a straight grate furnace or in a grate kiln furnace. The hot gases are allowed to flow upward as well as downward through the packed bed and in counter-current direction across the furnace for efficient heat transfer. During induration, magnetite pellet undergoes drying, oxidation, and sintering.[1] During induration of magnetite pellets, both oxidation and sintering occur. Ideally, it is desirable to have sintering after the complete oxidation of magnetite pellet.[1,2] In reality, sintering and oxidation may proceed simultaneously. Magnetite sintering will start at a lower temperature than hematite sintering, and remaining magnetite in the core can therefore sh
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