Hydrogen reduction of ilmenite: effects of oxidation

Abstract

The effects of oxidation on H2 reduction were studied on two different ilmenite ores, Ilmenite A from Senegal and Ilmenite B from South Africa. Both ores were oxidised at 700, 800, and 1000◦C for 1 hour. Both ores were reduced at 800◦C, while Ilmenite A was also reduced at 900, and 1000◦C. Varying reduction times, 5, 15, 35, and 60 minutes, were chosen to examine the reduction path. It was found that the oxidation extent and rate were dependant on temperature. The rate of oxidation increased with increasing temperature. At 1000◦C, complete oxidation was found. The samples mainly consisted of pseudobrookite. Ilmenite B underwent greater changes during oxidation due to a lower degree of weathering prior. The different degrees of weathering was one of the reasons why as-received Ilmenite B did not reach complete reduction at 800◦C, while Ilmenite A did. Oxidation was seen to increase the reduction rates. The final reduction degree decreased for the more oxidised samples, at reduction temperatures of 1000◦C. The extent of reduction was measured by determining the O:Fe ratio. The zero point of the ratio is set to complete metellisation of the iron, giving O:Fe=0. If this ratio is 1, then O bonded to Ti was also removed. As-received Ilmenite A reduced at 1000◦C had a O:Fe ratio of −0.25, whereas 1000◦C oxidised Ilmenite A had a ratio of −0.16. This suggest that, in both cases, some higher Ti-oxides were reduces to lower oxides.