Variation in Iron Ore Sinter Mineralogy with Changes in Basicity

Abstract

The target basicity of iron ore sinter is set by blast furnace slag composition requirements, and therefore varies with the proportion of acid burden such as lump iron ore and pellets. Increasing the lump proportion of the burden will increase the target sinter basicity. The mineralogy of sinter produced with a range of basicity between 1.0 and 3.0 was analysed using optical point counting under reflected light microscopy. Sinter from BlueScope Steel’s industrial sinter strand was analysed over a 30-year period, during which time a wide range of iron ore fines blends were utilised and several significant process modifications made. These data were compared with the mineralogy of sinters produced in a pilot-scale sinter pot, a laboratory-scale milli-pot, and small-scale sinter analogues. The mineralogy of the sinters from all scales followed a predictable trend with basicity, generally following the diagram proposed by Bagnall. At a basicity of 1.0, high temperatures were required to produce sinter with adequate strength, resulting in bonding phases dominated by magnetite and glass. Increasing basicity to 2.0 decreased the required sintering temperature and changed the mineralogy to a majority of hematite and SFCA. Further increases in basicity to 3.0 further decreased the required sintering temperature and increased the SFCA and dicalcium silicate content.