A new cell concept for calciothermic reduction of titanium dioxide and an ongoing test program for its experiments are reported. The thermo-chemical background of this concept and new cell designs are studied. The reduction system consists in a single cell, where both the thermochemical reaction and the electrochemical reaction for recovery of reducing agent coexist in the same molten calcium chloride bath.
A few mol percent Ca dissolves in the melt, which constitutes the media with a strong reducing power. Separated experiments on calciothermic reduction showed that 3.6 ks were enough to reduce titanium dioxide powder at 1173 K, where the oxygen content was lowered below 1000 mass ppm. The optimum concentration of CaO in the molten CaCl2 was lower than 5 mol percent. Combining carbon anode and titanium net cathode, titanium sponge containing 2000 ppm oxygen was produced from TiO2 powder.