Study On Electrolytic Reduction Of Ilmenite From Chloride Molten Salt System

Ferrotitanium alloy is not only the significant materials in steel smelting which can improve the quality of steel, but also the important magnetic materials and one of the most promising hydrogen storage materials. It is used widely in industries. Now the ferrotitanium alloy is mainly produced by aluminothermic reduction method and remelting process. But the ferrotitanium alloy is high content of oxygen with the former method and its raw materials are limited and energy consumption is high by the remelting process.In the research, based on FFC method, electrolysis experiments were performed with a two-electrode system consists of ilmenite cathode and graphite anode in LiCl-KCl and LiCl-KCl-CaCl2 molten salts. The thermodynamics of the possible reactions are calculated by HSC6.0.According to the thermodynamics, the theoretical decomposition potential for the reduction of Fe(â…¡) in ilmenite to metallic Fe is the lowest. In the electro-reduction of the ilmenite, the possible intermediate products are CaTiO3 and Li2TiO3, etc. The electro-reduction potential of CaTiO3 is lower than that of Li2TiO3, which indicates that CaTiO3 is more easily to be reduced. According to the theoretical electrochemical potentials, it reveals that Fe2Ti rather than FeTi would be preferentially formed. From thermodynamics, the reduction potentials can be lowered with producing CO/CO2 at anode.The electrolytic experimental results show that Fe and Li2TiO3 are obtained after electrolysis for 36h in LiCl-KCl molten salt with a cell voltage of 3.2V at 673K, no ferrotitanium phase was detected in the products. Fe2Ti can be prepared from ilmenite in LiCl-KCl molten salt with the same cell voltage for 20h at 1073K. Ilmenite can be electrochemically reduced to FeTi after electrolysis for 20h in LiCl-KCl-CaCl2 molten salt. With a cell voltage of 2.8V, ilmenite was reduced to Fe and Fe2Ti in LiCl-KCl-CaCl2 molten salt. High cell voltage was in favor of the eletro-reduction of ilmenite.According to the compositions of the products from the interrupted experiments both in LiCl-KCl and LiCl-KCl-CaCl2 molten salts, the electro-reduction of ilmenite could be divided into the following steps:Fe(â…¡)in ilmenite is firstly reduced to metallic Fe. Secondly, the oxygen removed from FeTiO3 pellet dissolves in the molten salt. Titanium oxides existed in the products as Li2TiO3 or CaTiO3. In the further electrolysis process, Li2TiO3 or CaTiO3 will be deoxidized to form titanium sub-oxide. Finally, metallic titanium is reduced from titanium sub-oxide and combines with metallic Fe to form ferrotitanium alloy.Besides, the gas produced at anode and cathode were analysized by gas chromatography. It suggested that the gas produce at anode was composed of carbon dioxide and carbon monoxide and the gas produced at cathode was carbon monoxide.From the phases of redced samples obtained from LiCl-KCl and LiCl-KCl-CaCl2 respectively, it indicates that Ca2+in molten salt is beneficial to the electro-reduction of ilmenite. The electro-reduction of ilmenite can be accelerated by the addition of CaCl2 into LiCl-KCl molten salt.