The concentrate obtained from the wet concentrator plants contains a mix of valuable heavy minerals in different assemblages, as well as clays and other non-valuable heavy mineral components and trash.
The heavy minerals, being ilmenite, rutile, leucoxene, zircon and monazite are separated out in a dry processing circuit using the heavy minerals’ electrostatic, magnetic and density characteristics.
Iluka purifies its zircon for use in the ceramics industry by an additional acid wash to remove iron oxide coatings.
Ilmenite, which is an iron/titanium oxide mineral, is upgraded to synthetic rutile (or upgraded ilmenite [UGI]) containing between 88 and 95 per cent highly valued titanium dioxide (TiO2).
The synthetic rutile plant involves a two stage process. The first stage is a pyrometallurgical process in which the ilmenite is heated in a large rotary kiln in the presence of a reductant. The result is iron oxide impurities within the ilmenite crystal lattice are converted to metallic iron. The second stage involves the removal of iron by oxidation and leaching in a hydrometallurgical process leaving upgraded ilmenite.
Three basic grades of synthetic rutile are produced – standard, premium and SREP. These reflect the removal of different portions of the residual non-titanium elements from the original ilmenite. This is done by adding specific additives such as sulphur and hydroboracite during the pyrometallurgical stage and then modifying the leaching conditions in the hydrometallurgical stage.
Iluka is working at optimising the efficiency of its synthetic rutile plants and has installed a waste heat recovery plant at one of its two synthetic rutile kilns at its North Capel operations in Western Australia. The waste heat recovered is used for the cogeneration of steam which in turn is used to produce approximately 6MW of electrical energy for use on the plant and for direct export into the electricity supply grid.
Please refer to the diagram Mineral Sands Production Process.