The kinetics on selective chlorination of iron from ilmenite ore by CO-Cl₂ gas mixtures

Titanium metal or high purity titanium dioxide are obtained by reduction of titanium tetrachloride which is produced by chlorination of rutile, mainly. However, as the demand for titanium and titanium product increase and the resource of rutile is diminish, ilmenite ore has become an alternative resource in the production of titanium tetrachloride by removing iron. Due to the high content of iron in ilmenite, the process of removing iron is not only necessary to obtain synthetic rutile, but also preferred because it results in increased porosity and surface area which brings the reactivity higher. In the present study, the selective chlorination of iron from ilmenite ore was carried out by CO-Cl₂ gas mixture and the effects of temperature, CO/Cl₂ ratio, and the particle size of ilmenite were investigated. The ilmenite ore used in this study contained 53.6 wt.% TiO₂, 27.0 wt.% Fe and around 1.0 wt.% each of silica, manganese, alumina, magnesium, etc. The chlorination was conducted in fixed bed reactor under isothermal condition and the temperature, CO/Cl₂ ratio, and particle size was varied in each experiment. After chlorination, the sample was analyzed by XRD, SEM and ICP. Also, the weight of the chlorinated sample was measured and the removal ratio of iron was calculated according to the analysis results. It was found that the pores were formed on the surface of ilmenite particles after chlorination, which make Cl₂ gas diffuse easily into the inner part of ilmenite particle. Also, the experimental results indicate that the removal rate of iron increased with increasing CO/Cl₂ ratio and temperature and the removal ratio of iron reached an extremely high value of 98 % at 1173 K, when the CO/Cl₂ ratio was 1. The kinetics was investigated based on the shrinking core model and the chlorination was controlled by chemical reaction controls.