Preparation of Ferrotitanium from Ilmenite by Electrolysis-Assisted Calciothermic Reduction in CaCl₂-NaCl Molten Salt

Abstract

Electrolysis-assisted calciothermic reduction method is proposed and successfully used to prepare ferrotitanium alloy from ilmenite by using equal-molar CaCl₂-NaCl molten salt as electrolyte, molybdenum rod as cathode, and graphite as anode at 973 K with cell voltages of 3.2–4.4 V under inert atmosphere. Thermodynamics analysis of the process is presented, and the products obtained are examined with x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. It is demonstrated that the calciothermic reduction of ilmenite is a stepwise process since intermediate CaTiO₃ is observed in the products partially reduced. In the calciothermic reduction process, the reduction of FeTiO₃ first gives rise to the formation of Fe and CaTiO₃, which as intermediates will further react with calcium metal to form ferrotitanium alloys. This is in good agreement with the prediction of thermodynamics. Experimental results also show that increasing cell voltage can accelerate the formation of calcium metal through electrolysis of CaO and CaCl₂ and, hence, promote the calciothermic reduction of ilmenite. As the electrolytic zone and reduction zone are combined in the same bath, the theoretical energy requirement for the production of FeTi in the calciothermic process is lower than that in the aluminothermic process.