Low Temperature Roasting (LTR)
The LTR process was developed by Austpac to upgrade contaminated ilmenite concentrates. The process uses controlled fluid bed roasting at less than 700°C to enhance the magnetic susceptibility of the ilmenite so it can be easily separated from less magnetic, deleterious gangue minerals, such as chromite. LTR-roasted ilmenite is still soluble in sulfuric acid, and can therefore be used to produce TiO2 pigment via the “sulfate” process. If ilmenite is roasted at high temperature, as is the normal procedure, the titania component is insoluble in acid and it is unsuitable for making TiO2 pigment.
In 2004, the LTR process was demonstrated in a 2.5 tonnes per hour roasting and magnetic separation plant designed by Austpac. The LTR plant was built by New Zealand Steel at their facilities at Glenbrook near Auckland, New Zealand, and successfully operated for six months. Iron minerals previously rejected as waste were recovered and conditioned for use in the steel making process, together with an ilmenite concentrate as a separate stream.
Test work conducted in 2008 at Austpac’s Newcastle facilities demonstrated that the LTR process is able to produce a clean, sulfateable ilmenite from highly chrome-contaminated ilmenite concentrates such as the Corridor Sands deposit in Mozambique.