Carbothermal Reduction of a Primary Ilmenite Concentrate in Different Gas Atmospheres

The carbothermal reduction of a primary ilmenite concentrate was studied in hydrogen, argon, and helium. Ilmenite and graphite were uniformly mixed and pressed into pellets. Reduction was studied in isothermal and temperature-programmed reduction experiments in a tube reactor with continuously flowing gas. CO, CO2, and CH4 contents in the off-gas were measured online using infrared sensors. The phase composition of reduced samples was characterized by X-ray diffraction (XRD). Oxygen and carbon contents in reduced samples were determined by LECO analyzers (LECO Corporation, St. Joseph, MI). The main phases in the ilmenite concentrate were ilmenite and pseudorutile. The reaction started with the reduction of pseudorutile to ilmenite and titania, followed by the reduction of ilmenite to metallic iron and titania. Titania was reduced to Ti3O5 and even more to Ti2O3, which was converted to titanium oxycarbide. Reduction was faster in hydrogen than in helium and argon, which was attributed to involvement of hydrogen in the reduction reactions. The formation of titanium oxycarbide in hydrogen started at 1000 °C and was completed in 300 minutes at 1200 °C, and 30 minutes at 1500 °C. The formation of titanium oxycarbide in argon and helium started at 1200 °C and was not completed after 300 minutes at 1300 °C.