Simultaneous reduction and carburization of ilmenite
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I.
INTRODUCTION
TRADITIONALLY, titania pigment has been produced from ilmenite or high titania slags by the sulphate process. The advent of the "new" chloride process, for which neither high titania slag or ilmenite is suitable, has resulted in an increasing requirement for mineral rutile. The increasing demand for mineral rutile and the consequent rising price has created an impetus for development of a process to convert ilmenite to a mineral rutile substitute. Several processes have been proposed, tl,2J of which only the Associated Mineral Consolidatedt3,*,5,6j process operates at present, and all of these have the common feature that the iron values are lost. The present work was aimed at carrying out reduction using coal at a relatively high temperature to produce titanium carbide and carbon saturated iron. This process was expected to have the following advantages: (a) titanium carbide chlorinates more readily than titanium oxides; (b) manganese impurities that are detrimental to pigment will be confined to the iron phase; and (c) the iron will be liquid and, if it can be encouraged to agglomerate, can be separated and sold as a byproduct.
24.0 pct FeO, 0.9 pct AI203, 0.13 pct V205, 0.16 pct MgO, 1.6 pct MnO, 0.15 pct Nb205, 0.4 pct SiO2, and Collie coal 59.5 pct total carbon (48.4 pct fixed carbon), 3.6 pct hydrogen, 0.34 pct sulphur, 2.65 pct ash, and 23.3 pct volatiles at 105 ~ Reduction was carried out in a vertical tube furnace under an atmosphere of flowing argon (250 cc/min). One gram pellets were placed in an alumina crucible, which was placed in an outer graphite crucible and introduced into the hot zone of the furnace under flowing gas. After reduction, samples were lowered to the cold end of the furnace and cooled under argon. The reaction was monitored by weighing the pellets before and after reduction, and X-ray diffraction and metallography were used to provide mechanistic information.
III.
RESULTS
Reaction kinetics were investigated by following the change in the fraction reacted, F, with time. F is defined by F-
(W0 - W)
(W 0 - WTiC)
II.
EXPERIMENTAL
Samples of Western Mineral Sands (WMS) ilmenite and 1.77 times the stoichiometric requirement of "Collie" coal*, calculated relative to the total carbon content of *Collie coal is a Western Australian coal of medium to high reactivity.
the coal, were mixed overnight and pressed in a pellet die at a pressure of 690 MPa, producing a cylindrical pellet of 6.35-mm diameter and approximately 15 mm in length. The compositions of the reactants were as follows: WMS ilmenite 54.2 pct TiO2, 18.0 pct Fe203, K.S. COLEY, formerly with Imperial College, London, is Lecturer, Metallurgy and Engineering Materials Group, Department of Mechanical Engineering, University of Strathclyde, Glasgow, GI 1XN United Kingdom. B.S. TERRY, Lecturer, is with the Department of Materials, Imperial College, London. P. GRIEVESON, Retired, is formerly with the Department of Materials, Imperial College, London. Manuscript submitted January 18, 1994. METALLURGICALAND MATER
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