Sintering behavior of raw material bed placing large particles

The pot tests, under the condition that large particles were placed in the sintering bed, were carried out for improvement of permeability. The large particles include green balls made from Marra Mamba ore, fired pellets, dense alumina balls and pisolite lump ore. In the course of pot tests, permeability before ignition and during sintering, bulk density and yield were measured. Also the cross sections of sinter cakes were observed. As a result, the permeability before ignition and during sintering was both increased regardless of the increase in the bulk density of sintering bed. When the large particles were placed, the calculated bulk density of sinter mixture (the rest part of bed excluding the large particles) decreased in inverse proportion to the surface area of large particles. Therefore, the effect of placing large particles was concluded to cause the permeability increase. Placing large particles occasionally decreased yield owing to void formation under the alumina balls in the sinter cake, which was confirmed the visual observation. It is proposed that the increase of coke and/or CaO contents in fine layer and adding carbon in the green balls are effective for yield recovery.