Desired Development Aspects for Spray Roasted Iron Oxides Predominantly for the Production of Ferrites

Abstract

Different grades of spray roasted iron oxides are produced in form of chemical by-products at steel mills. Originating from the thermal decomposition of up-graded iron chloride solutions, these synthetic iron oxides became a strategic raw material source for the production of soft and hard ferrites, and a series of chemical, ceramic and metallurgical products. Manganese contents in the order of 0.25 up to 1.0 per cent limit their usage for some applications, which presently being serviced by iron oxides based on other precursors. Another fast growing market concerns olivine structured LiFePO4 cathode battery materials, which contain about 50 wt.% Fe2O3. Spray roasters have been designed to yield iron oxides exhibiting specific surface area data in the range of 0.5 up to 25.0 m2/g. Preferred BET-data are: 0.5 up to 4.0 m2/g for hard ferrites, 3.0 up to 5.5 m2/g for soft ferrites and 8.0 up to 12.0 m2/g for pigments. Washed iron oxides exhibiting total chloride levels in the order of 600 ppm Cl− are available. Further washing results in Cl− levels of 300 ppm and an additional thermal treatment, by means of a short treatment within a vertical un-obstructed furnace, yields iron oxides with <20 ppm Cl−.