Sintering of blends containing magnetite concentrate and hematite or/and goethite ores

Many sinter plants in China use magnetite concentrate and imported sintering fines in their blends. It has been found that sintering performance is improved with the addition of the sintering fines. This work studies sintering behaviour of a hematite ore (Ore B) and a geothite ore (Ore C) in blends containing 50-70 mass% concentrate. With addition of 3 mass%,burnt lime, sintering performance improves with increasing Ore B or Ore C level in the blend. Partial substitution of Ore C for Ore B in the blends did not cause significant changes in major sintering parameters. Granulation was identified as the key issue in sintering of such blends. A method to improve granulation efficiency was proposed, which involves pre-granulating the sintering fines and a part of the concentrate, and then granulating the pre-granulated materials with the rest of mix. It has been found that by using the pre-granulation technique, the productivity for blend composed of 50 mass% magnetite concentrate and 50 mass% Ore C increased from below 30 t/m(2) d to around 40 t/m(2) d at unchanged mix moisture levels. The technique also led to rises of various extent in productivity in sintering of blends containing magnetite concentrate, Ores B or/and C. The chief reason for this is that the improved granulation efficiency improves bed permeability and shortens sintering time. The sintering results for blends containing 50 mass% magnetite concentrate and 50 mass% Ore B or 50 mass% Ore C by adding 3 mass% burnt lime and using the pre-granulation technique are comparable to a blend composed of 100 mass% fines (no concentrate). The sinter RDI is generally low and the sinter reducibility is improved by adopting the pre-granulation technique.