Optimization of Coke Breeze Segregation in Sintering Bed under High Pisolite Ore Ratio

Increased demand and the diminishing high grade resources have resulted in a shift to using low grade iron ore in Japanese steel mills. Especially, pisolite ore ratio is quite high. Therefore, decrease in sinter productivity became serious problem with increasing the amount of pisolite ore. To improve the sinter productivity, effective method at the charging device in sintering machine was investigated by laboratory experiments. The following results were obtained. 1) It was expected that the holding time over 1200 degrees C at the middle and bottom layer of the sintering bed decreased with high pisolite ore ratio. On the other hand, in order to preserve the sinter strength, it was suggested that the holding time over 1200 degrees C in sintering must be extended under high pisolite ore ratio. 2) There is the optimum coke segregation degree according to the pisolite ore ratio. It was decreased with increase of the pisolite ore ratio. 3) To control the coke segregation in the sintering bed, Magnetic Braking Feeder (MBF) was introduced, and the operating conditions were investigated with the laboratory charging tests and sintering pot test. 4) Based on the fundamental research, MBF has been applied to Keihin No. 1 sinter plant, and the productivity was improved by 4.2% under constant sinter strength.