Reduction and Nitridation Behaviors of Ilmenite with Clean Ammonia Energy

Abstract

Ilmenite ore is an important Ti-bearing raw material for titania pigment and titanium metal production. Traditional fluidizing chlorination is not suitable to ilmenite containing high contents of MgO and CaO. In this study, a new process for reduction and nitridation of ilmenite using NH3 gas was proposed to prepare titanium oxynitride, which can be used for low-temperature selective chlorination. The thermodynamic calculation indicated that reduction and nitridation of FeTiO3 by NH3 was feasible at a relatively low temperature. Metallic iron and titanium nitride were the ultimate products. The experimental results showed that titanium oxynitride Ti(N,O) can be formed at 900–1000 ℃. After reacting at 1000 ℃ for 8 h, the main phases were Fe and Ti(N,O). Increasing the reduction temperature and prolonging the duration time were beneficial to the reduction and nitridation process. Density functional theory study was also conducted to reveal the reaction mechanism. Theoretical and experimental results indicated that the reaction process can be divided into two stages: the initial deoxidation to form Fe and TiO2, deep deoxidation and nitridation of TiO2 to generate Ti(N,O). Graphical Abstract: [Figure not available: see fulltext.]