Effect of CaO on the reduction behaviour of iron ore-coal composite pellets in multi-layer bed rotary hearth furnace

The effect of CaO on the reduction behaviour of iron ore-coal composite pellets has been studied in a laboratory scale multi-layer bed rotary hearth furnace at 1250 degrees C for 20 min. Reduced pellets have been characterised through weight loss, porosity measurement, phase analysis by XRD, and morphology study by SEM. The addition of CaO to the composite pellets showed different effects at different carbon levels. For higher carbon-containing pellets (C/Fe2O3 molar ratio at the upper stoichiometric level of 3), the addition of CaO increased the extent of reduction for all three layers significantly up to a certain limit (4 wt-%); and thereafter the degree of reduction is decreased with a further increase in CaO percentage in the pellets. For low carbon-containing pellets (C/Fe2O3 molar ratio of 1.66), the addition of CaO to the pellets did not show any beneficial effect.