Low temperature reduction of hematite in red-mud to magnetite

Abstract

Red-mud, the residue generated from the Bayers processing of bauxite ore in Jamaica was subjected to a low temperature reduction process. Hematite (~60 m%) was reduced to magnetite employing a gas based mixture of CO, CO2 and N2 as a diluent. Extensive thermodynamic study was conducted to identify the stability region for magnetite. ‘Optimal conditions’ for the gas-phase reduction were determined to be: a processing temperature of 540 °C ± 10 °C, partial pressures CO(g) and CO2(g) each of 0.070 atm (bar) ± 0.001 atm (bar)/inert diluent-gas: N2(g), for a conversion-time of 30 min. Mathematical model for reduction based on unidirectional diffusion is also formulated in this paper.