Prereduction and melting of domestic titaniferous materials
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INTRODUCTION
W I T H the dwindling supply and high cost of futile and high-grade ilmenites, it becomes more important for the United States to devise lower cost and more efficient technology for processing lower grade domestic titaniferous materials. With proper treatment, these resources can provide viable alternative sources of TiOz pigment. Effective use of domestic resources also would decrease the reliance of the United States on imports. The objectives of this investigation are (1) to evaluate the feasibility of prereducing a variety of domestic titaniferous materials with low-grade domestic reductants, and (2) to compare the melting characteristics and products derived from the prereduced materials with those made from the same unreduced ores and concentrates. These objectives are part of two goals of the Bureau of Mines: (1) to devise methods for wider use of abundant materials as substitutes for scarce materials, and (2) to devise techniques for recovering minerals and metals that improve efficiency and recovery rates. The advantages of prereduction have been enumerated in the literature. 7 Of particular interest to this work is that prereduction can use relatively inexpensive and more readily available reductants. More expensive electrical energy, which otherwise must be used during reduction to melt the entire charge, is conserved. Prereduction of the charge materials provides a more easily controlled melting operation, with inherent increased productivity, higher recoveries, and better slag and metal quality. Previous work involving the solid-state prereduction of titaniferous materials has been limited. Early work included the prereduction of Wyoming ores with coal in a rotary kiln by the Strategic-Udy Process. Metallizations of 68 pct were achieved. H Another process, developed by New Zealand Steel, Ltd., involves the concentration of titaniferous ironbearing sands from the Waikato North Head deposit. The concentrate is mixed with recycled char and fed into an inclined rotary kiln for reduction with a subbituminous coal or lignite. 1 Later developments involved the reduction of the ilmenite at 1200 ~ (2192 ~ in a kiln using coal char. 8 Iron and anosovite (Ti305) were the reduction products. Up to R.H. NAFZIGER, Research Supervisor, and R . R . JORDAN, Metallurgist, are both with Albany Research Center, Bureau of Mines, United States Department of the Interior, P.O. Box 70, Albany, OR 97321. Manuscript submitted May 11, 1982. METALLURGICAL TRANSACTIONS B
87 pct metallization is realized in this process. Highveld Steel and Vanadium Corporation operates a plant at Witbank, South Africa, in which vanadium-bearing titaniferous magnetite ore is prereduced at 1000 ~ in rotary kilns with coal. 4 Western Titanium has operated a semicommercial facility at Capel in Western Australia in which ilmenite is oxidized to form constituents that increase reduction efficiency and then reduced in a fluidized bed at 949 ~ (1650 ~ with hydrogen for 0.5 hour. In 1975, a commercial plant with a capacity of 30,000 tons
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