The Austpac ERMS and EARS Processes for the Manufacture of High-Grade Synthetic Rutile by the Hydrochloric Acid Leaching of Ilmenite1

Austpac Resources ’ proprietary ‘Enhanced Roasting and Magnetic Separation ’ (ERMS) and ‘Enhanced Acid Regeneration ’ (EARS) processes have been developed for the production of very high-grade synthetic rutile for the feedstock market for the chloride TiO2 pigment process. Ilmenite ore is roasted at temperatures in the range of 800°C to 1,000°C to selectively magnetise the ilmenite fraction so that gangue minerals may be easily removed. Roasting also enhances the subsequent leaching operation by activation of the iron component of the ilmenite whilst at the same time rendering the titania fraction insoluble. Iron and other impurities are removed by leaching at atmospheric pressure with near boiling, 25 mass %, hydrochloric acid. The leached solids are filtered, washed and calcined to yield a synthetic rutile of 97 % (or higher) TiO2 grade. Hydrochloric acid is recovered from spent leachate by evaporation and pyrohydrolysis, to yield a super-azeotropic acid. The fuel used can be gas, oil or coal, depending on local economics. A pilot plant has been successfully operated for several years, using many types of fuel and ilmenite feedstock. A new coal-fuelled demonstration plant is now in the final design stage, to utilise ilmenite sourced from India and some of the emerging heavy mineral producers in Australia’s Murray-Darling Basin