Selective Removal of Iron from Low-Grade Ti Ore by Reacting with Calcium Chloride
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INTRODUCTION
THE Kroll process is the current commercial process for the production of Ti metal. However, the productivity of this process is low, owing to its slow production speed and batch-type processing. The FFC (Fray– Farthing–Chen),[1] the OS (Ono-Suzuki),[2] and the electronically mediated reaction/molten salt electrolysis (EMR/MSE)[3] processes have been proposed as alternatives to overcome the limitations of the Kroll process. The FFC and OS processes have been found to be promising among the new processes, because these are simple and semi-continuous processes. In the FFC or the OS process, Ti metal can be obtained directly from TiO2 in a molten CaCl2 by an electrochemical method or metallothermic method using calcium (Ca) as a reducing agent. During the electrochemical reductions in the FFC process, CaTiO3 is generated as an intermediate.[4,5] This CaTiO3 is eventually reduced to Ti metal, as reported by Jiang et al.[4] and Vishnu et al.[6] Recently, Metalysis Ltd, U.K., reported an interesting result that rutile (94 to 96 pct TiO2) can be used as a feedstock in the FFC process.[7] This indicates that the removal of Fe from ilmenite, which is the most
JUNGSHIN KANG, formerly Graduate Student with the Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan, and with Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505 Japan, is now Senior Researcher with Korea Institute of Geoscience and Mineral Resources, 124 Gwahang-no, Yuseong-gu, Daejeon, 305-350, Korea, and also Assistant Professor with the University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 305-350, Korea. Contact e-mails: [email protected], [email protected], [email protected] TORU H. OKABE, Professor, is with the Institute of Industrial Science, The University of Tokyo. Manuscript submitted November 3, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
important Ti mineral resource, is indispensable when a low-grade Ti ore (mainly FeTiO3) is used in the FFC process. In the current Ti ore upgrading industry, synthetic rutile is prepared by the Becher,[8] Benilite,[9–11] or slag and UGS (Upgraded Slag)[12] process. The Becher, Benilite, and UGS processes use concentrated acid for the removal of Fe and other impurities from a low-grade Ti ore or Ti slag. As a result, acid waste solution is generated, and the treatment of this waste solution is costly in countries with stringent environmental regulations. In 2007, Zheng[13] developed a novel method for the selective chlorination of Ti ore using CaCl2 as a chlorinating agent reacting with Fe and forming CaTiO3. However, the Fe in the ore was only partially removed: the mass percent of Fe decreased from 51 to 17 pct at 1293 K (1020 C). The authors also reported that the mass percent of Fe decreased from 50 to 18 pct at 1100 K (827 C) through the selective removal of Fe by CaCl2.[14] The authors analyzed that Fe was only partially removed b
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