A study of reduction and magnetic separation of iron from high iron bauxite ore

The removal of iron as magnetite from a high iron bauxite ore was investigated by carbothermal reduction and magnetic separation. Thermodynamic calculations using HSC Chemistry 6.1 were utilised to determine the equilibrium compositions of the reaction products as a function of temperature and carbon additions. Under equilibrium conditions, the formation of hercynite (FeAl2O4) restricted the conversion of haematite to magnetite and the equilibrium calculations were adjusted so that the amount of hercynite was limited. Also, thermogravometric analysis and differential thermal analysis with evolved gas analysis tests were performed in order to elucidate the reduction reactions. Furthermore, high temperature reduction experiments were carried out in order to quantify the effects of processing time, temperature and carbon additions on the amount of the magnetic fraction. The degree of removal of the iron and the alumina recovery were determined. For a given set of conditions, the maximum iron removal as magnetite could only be achieved by quenching the reacted samples. The results demonstrated that at a reduction temperature of similar to 1073 K, similar to 58% of the iron could be removed in the magnetic fraction with an alumina recovery of similar to 85% in the non-magnetic fraction.