Evaluation of chlorination of nitrided ilmenite by statistical analysis

Abstract

A novel low-temperature chlorination process of nitrided ilmenite (TiOxCyNz) for efficient and economical production of titanium is investigated. Knowledge and understanding of the mechanism and influential factors affecting chlorination are required to establish an effective low-chlorination process with higher production of Fe-free TiCl4. In this study, the chlorination of nitrided ilmenite using statistical design of experiments was investigated. Malaysian ilmenite was carbothermally reduced at 1250°C for 180 minutes in the presence of a 50-50 vol.% mixture of H2-N2 gas. The three carbon sources used for carbothermal reduction (CTR) process are graphite, activated carbon (AC) and carbon nanotubes (CNT). Nitrided ilmenite obtained from the CTR process were chlorinated based on the factorial design (2k) for a temperature range of 400-500°C, chlorination duration of 1-3 hours and different carbon reactants. Ilmenite was reduced to titanium oxycarbonitride (TiOxCyNz) through simultaneous carbothermal reduction and nitridation process for further chlorination into titanium tetrachloride. Microstructural characterization and phase analysis of raw materials and reduced samples were conducted. DOE analysis suggested that the type of carbon reactant was the most influential factor in the chlorination of nitrided ilmenite. The highest extent of chlorination i.e., 72 % was obtained for a chlorination temperature of 500°C, chlorination time of 3 hours and carbon nanotube as a carbon reactant in the CTR process.