Influence of original structure on the kinetics and mechanisms of carbon monoxide reduction of hematite compacts.

Green, porous and dense Fe203compactshaving 54, 35 and 8 •/• porosity respectively were obtained at different tem- peratures.Thestructure of these compacts was examinedand correlated to their thermal history.Thesecompacts were isothermally reduced with carbon monoxide at 500-1 100'C using weight-loss technique.The structural changes accompanyingthe reduction process were examinedwith mercury pressure porosimeter and with optical and scanning electron microscopes while the different phasesformed during reduction was identified by X-ray ditfraction technique.At the initial stages of reduction, the rate was increased with temperature and with increase in original porosity of compacts.With progress of reduction, a reduction rate minimum was observed at 950-975'C and was attributed to sintering and densification of Y-iron.The retardation in the rate was not detected during the reduction of dense compactsdue to the disintegration of iron grains resulting from carbon deposition and subsequent reactions.The values of apparent activa- tion energy were calculated and correlated with both the original structure of compacts and the reduction mechanisms.