Reduction of hematite pellets with carbonized coal in a static bed.

The reduction of individual iron ore pellets immersed in coal char was measured at 900°-1200°C for times up to 3h. The results were compared with published data for other iron oxide/carbon systems to evaluate the kinetics of reduction in static beds, rotary and shaft kilns, and in composite pellets. Reaction rates and activation energies measured in these studies were similar to published values obtained with intimate mixtures of iron oxides and comparable types of carbon at temperatures up to 1000°C, where carbon gasification was rate controlling. However, reduction rates for pellets surrounded by char fell significantly at higher temperatures due to the influence of gas diffusion. Reduction rates, for pellets were similar, for both static bed and rotary kiln conditions at 1000°-1150°C, and were decreased by internal slag forma&ion above 1075°C. Reduction was further inhibited above 1150°C by the formation of dense shells of metallic iron around partly-reduced, slag-rich regions, especially towards the centres of the pellets.