Behavior of New Zealand Ironsand During Iron Ore Sintering
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TRODUCTION
IRONSAND deposits along the western coast of the North Island of New Zealand are currently mined as iron ores for steel production.[1] The composition of the New Zealand ironsands approximates that of titanomagnetite (Fe3-xTixO4) containing about 60 wt pct iron, 8 wt pct titania (TiO2), and a small amount of other impurities such as silica, phosphorus, and lime.[1–3] Recently, BlueScope’s Port Kembla sinter plant has begun incorporating 2 to 3 wt pct ironsand as a component of its iron ore sinter blend. The ironsand provides a cheaper, alternative source of iron, and its incorporation into sinter provides an appropriate method of its utilization in ironmaking as its small particle size precludes direct charging into a blast ZHE WANG, Ph.D. Student, HAROLD ROGERS, Senior Research Fellow, BRIAN J. MONAGHAN, Professor, and GUANGQING ZHANG, Lecturer, are with the School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia. Contact e-mail: gzhang@ uow.edu.au. DAVID PINSON, Senior Research Engineer, and SHENG CHEW, Principal Research Engineer, are with the Steelmaking Technology and Planning, BlueScope, PO Box 202, Port Kembla, NSW 2505, Australia. MARK I. POWNCEBY, Principal Research Scientist, and NATHAN A. S. WEBSTER, Research Scientist, are with CSIRO Mineral Resources Flagship, Private Bag 10, Clayton South, VIC 3169, Australia. Manuscript submitted June 16, 2015. Article published online November 23, 2015. 330—VOLUME 47B, FEBRUARY 2016
furnace.[4] The introduction of a minor amount of titanium-bearing burden into blast furnaces has previously been demonstrated to be beneficial through the formation of titanium carbonitride precipitates that can deposit on the hearth lining and, consequently, extend operating campaigns.[5,6] Limited work[4,7,8] on the addition of titanium-bearing minerals via a sinter plant indicates that a high level of Ti in the sinter mix may reduce productivity, lower sinter strength, and result in deterioration of sinter reducibility. In the most comprehensive study, Bristow and Loo[4] examined the effect of addition of an ironsand from New Zealand into two iron ore blends containing 10 and 20 pct pisolitic limonite, respectively, on the properties of sinter prepared using a pilot-scale sintering facility. It was found that the addition of up to 2 pct titanomagnetite did not significantly affect the sinter quality; however, increasing the titanomagnetite levels to greater than 3 pct caused a significant increase in the reduction degradation index (RDI) of the sinters. It was postulated that the addition of titanium decreased the fracture toughness of glass phase which is the weakest phase in a sinter and would increase the vulnerability of the sinter to crack propagation, thereby resulting in deterioration in sinter RDI. While the previous studies have provided useful information on how the addition of titanomagnetite potentially affects sinter quality, no satisfactory conclusion has been forthcoming as to how the titanomagnetite
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