Volatilisation behaviour of iron, silicon and magnesium during vacuum carbothermal reduction of ilmenite concentrate

The non-isothermal reduction kinetics and volatilisation behaviour of iron (Fe), silicon (Si), and magnesium (Mg) during the vacuum carbothermal reduction of ilmenite concentrate were investigated from 1350 degrees C to 1550 degrees C. Mg species was reduced to metallic Mg before volatilisation. Some Si elements were reduced to Si, which entered into the Fe phase to form ferrosilicon alloy, and others were reduced to SiO before volatilisation. The volatilisation of Fe came from the metallic Fe phase. For the comprehensive consideration of Satava-Sestak and Coats-Redfern methods, the rate-limiting factors of Fe, Mg, and Si were diffusion control. The integral mechanism functions of Fe, Mg, and Si were G(alpha) = [1-(1-alpha)(1/3)](2), G(alpha) = 1-2 alpha/3-(1-alpha)(2/3), and G(alpha) = (1-alpha)ln(1-alpha) + alpha, respectively. The apparent activation energy for volatilisation processes of Fe, Mg, and Si were 1043.02 +/- 12.29, 253.15 +/- 7.63, and 314.46 +/- 6.04 kJ mol(-1), respectively.