Effect of CaO Component on Strength of Pre-granulated Pellets in Composite Sinter Products

Abstract

Depletion trend of high-grade iron ore resources have become significant due to the recent increase in world steel production. Therefore, effective utilization of low-grade and low-quality ores has been and will be strongly required. Since iron ore concentrates obtained by beneficiation processes are usually fine, e.g., less than 100 µm in particles size, it is difficult to directly use a large amount of them to the sintering process. To cope with such a problem, the composite sintering process, namely MEBIOS (Mosaic EmBedding Iron Ore Sintering), has been proposed, which pre-granulates fine ores to be green pellets. The present study deals with the effects of limestone size and substituting ratio with burnt lime on the compression strength of the sintered pellets. The green pellets were prepared using fine hematite ores, limestone and burnt lime and sintered at up to 1300°C. The compression strength of the sintered pellet increased with a decrease in particles size of limestone when it was less than 500 µm, although relatively higher strength was obtained for the case using limestone having 500-1000 µm in size. The porosity of the pellets prepared by the partial substitution of limestone with burnt lime decreased and their compression strength increased with an increase in the substitution ratio. It seems due to the dispersion effect of extremely fine slacked lime particles formed by the hydration reaction of burnt lime.