2017 Volume 57 Issue 1 Pages 41-47
The relative effects of gibbsite, kaolinite and aluminous goethite as alumina sources on the thermal stability, concentrations and formation mechanisms of silico-ferrite of calcium and aluminium (SFCA and SFCA-I) iron ore sinter bonding phases, was investigated using in situ X-ray diffraction. Iron ore containing gibbsite as the primary source of alumina is less likely to form high quality sinter due to the lower reactivity of the alumina leading to low amounts of SFCA-I and SFCA bonding phases being generated. Sintering of this ore is likely to require higher fuel as higher temperatures are required to generate the bonding phases. Alumina in the form of kaolinite or aluminous goethite, however, produced larger amounts of both SFCA-I and SFCA and at lower temperatures. Use of kaolinite resulted in the formation of a highly reactive gehlenite intermediate phase that maximised the formation of SFCA-I, the matrix phase that imparts high strength and good reducibility characteristics to sinter. Iron ore containing aluminous goethite also generated SFCA bonding phases however the difference in the reaction mechanism between kaolinite and aluminous goethite containing ore led to less SFCA-I being formed overall. These findings give some insight into why sintering investigations using Australian ores with kaolinite tend to show less impact on sinter quality than the more widely reported alumina studies involving gibbsite-rich ores.