Behavior of calcium chloride in reduction process of titanium dioxide by calcium vapor

CaCl2 has played an indispensible role in many extraction processes for metallic titanium from titanium dioxide. In this paper, behavior of CaCl2 in reduction process of titanium dioxide by calcium vapor was investigated and analyzed by means of XRD (X-ray diffraction), SEM (Scanning electron microscope), EDS (Energy Dispersive Spectrometer), DSC-TG (Differential Scanning Calorimetry-Thermogravimetry) and thermodynamic calculation. The results show CaCl2 has a strong moisture absorption behavior and easily transforms CaCl2·nH2O (n = 6, 4 and 2). Then CaCl2·nH2O would dehydrate to be CaCl2·H2O step by step and CaCl2·H2O as an unstable compound would further dehydrate to be CaCl2 or decompose to be CaClOH and CaO with temperature increasing. Additionally, CaCl2 could volatilize on the experimental condition as well. When CaCl2 was added in TiO2 as raw materials, these above behaviors of CaCl2 and CaCl2·nH2O could not only discharge some gas or vapor to make raw material of TiO2 porous, but also would conduct TiO2 to form CaTiO3 phase in raw material. The above facts would help the calciothermic reduction process of TiO2 more easily proceed.