Research and Development of Continuous Production of Titanium from the Oxide by means of Combination of Calciothermic Reduction and Electrolysis in Molten Calcium Chloride

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A new process is established to produce metallic titanium from its oxide directly. This does not use any transient, compound such as TiCl_4 in the conventional Kroll process. This process consists of (A) calciothermic reduction by calcium dissolved in molten salt, and of (B) electrolysis of the by-product CaO. Combination of these two elemental steps into a single bath was confirmed experimentally as an industrial applicable process.Two fundamental experiments, (A) calciothermic reduction in large scale molten calcium chloride and (B) molten salt electrolysis of CaO to produce Ca for recycling, were conducted separately in order to find the yield, impurities, ionic transfer thermal convection, suitable crucible materials, and space arrangement of electrodes. Successively the combination of (A) and (B) was planed for continuous production in large scale, and constructed for confirmation.Titanium containing only 500 ppm oxygen could be formed in (A), which arrived at the equilibrium. In so-called OS process, (A)+(B), the obtained titanium was contaminated with carbon which was introduced from the evolved gas, CO/CO_2,at the anode. This contamination was, however, removed by using the membrane of ZrO_2 solid electrolyte. OS process could be applied for production of Nb, Ta, V, Zr and Cr directly from their oxides, and this was proposed as a new production method applicable in the industry for energy-saving.