Kinetics of low temperature reduction of hematite to magnetite

The kinetics of low temperature (450 degrees C) reduction of hematite to magnetite in a CO-CO2 gas mixture has been studied using the continuous gravimetric method. The results have been analysed in terms of both 'crackling' and shrinking core models. It has been found that the crackling core model not only fits the kinetic data better, but also is in agreement with the morphology of hematite grains under reduction. It should be emphasised, however, that this model may be used successfully only when the initial grain radius is high enough for fragmentation of the initial grains into subgrains of smaller size.