The Effect of Calcium Carbonate on the Reducibility of Iron-Oxide Agglomerates

Abstract

The work described is a continuation of that previously carried out at the University of Toronto (1, 2). The object was to gain a better understanding of the effect of lime and calcium carbonate on the reducibility of iron oxides and to remove discrepancies arising out of earlier experiments.Briquettes, consisting of pure ferric oxide and ferric oxide with 1, 2, 5, and 10 per cent calcium carbonate, were sintered at 1200°C. Then they were reduced by hydrogen in a loss-in-weight furnace at temperatures ranging from 600 to 1000°C. It was found that calcium carbonate increased the, reducibility in all instances. At low reduction temperatures, the effect was more pronounced as the calcium carbonate content increased. This, in turn, corresponded to a greater, initial porosity which was developed during sintering. At higher reduction temperatures, however, this effect was more pronounced for briquettes with small calcium carbonate additions. In this instance, the porosity which was developed during reduction became more important than that which was developed during sintering.