Effect of granulation condition and property of raw material on strength of granulated particle by tumbling granulation

In order to clarify the factors on strength of granules for iron ore sinter, especially made of limonite iron ore, the effects of porosity, moisture and revolution speed of pelletizer on the strength of granules were examined with using reagent hematite. Moreover, using three kinds of commercial iron ores, the relationship between granule size and strength was examined. The strength measurement was undertaken before and after drying with a compression taster. The results obtained are follows: (1) In case of reagent hematite sample, the strength after drying became very low compared with that before drying. The compressive strength of sample just after granulation is determined by the adhesion force between hematite particles by liquid bridge of added water, but the strength after drying is maintained by the adhesion force by intertwined particles. (2) In case of commercial iron ores, the compressive strength after drying was very high compared with that in wet condition. (3) The cause for the different effect of drying on compressive strength between the commercial iron ore and reagent hematite seems to be the difference of gangue minerals that exist only in the iron ore and/or that of surface properties because the particle size distribution of reagent hematite and iron ores used is the same.