Microwave reduction of oxidised ilmenite concentrates

Abstract

This paper covers preliminary investigations into the novel use of microwave energy as a heat source for the partial reduction of oxidised ilmenite (FeTiO 3) concentrates. Microwave energy has potential for the speedy and efficient heating of minerals and in a commerical context may provide savings in both time and energy. The oxidation and reduction of iron in ilmenite concentrates between the ferrous and ferric states has been found to greatly enhance its chemical activity. When reduced to the correct extent, iron can be preferentially extracted to yield a titanium rich beneficiate suitable for use as a feed for the production of titanium dioxide (TiO 2) pigments via the Chloride Process. Two ilmenite concentrates were first oxidised in a conventional muffle furnace at 1000°C. The ferric iron was then reduced back to ferrous iron by heating with a fine carbon powder under an inert nitrogen atmosphere. The reduction process was carried out in a variable power (0 to 1500 kW), 2.45 GHz microwave oven. Duplicate control samples were reduced at temperatures over the range 700 to 1000°C in a conventional muffle furnace. The mineral phase changes occurring during the oxidation and reduction stages were detected by X-ray diffraction techniques. Changes in the surface morphology of the concentrate particles were detected by scanning electron microscopy and quantitatively described through changes in the specific surface area. Samples were leached with 25% hydrochloric acid to detect changes in the activity of both iron and titanium components.