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Aiming at the effective utilization of the abundant high-alumina iron ores with low iron grade, the influence of alumina concentration and type on high-temperature characteristics was clarified based on the analyses of eight typical iron ores. The results indicate that high-temperature characteristics of iron ores in various alumina types are different. Higher Al2O3 concentration is deleterious to assimilability and liquid phase fluidity, but the influence extent of each alumina type is substantially different. Kaolinite (Al2O3·2SiO2·2H2O) contributes to correspondingly better assimilability, followed by hercynite (Fe(Fe, Al)2O4), gibbsite (Al(OH)3), diaspore (AlO(OH)), and free state alumina (Al2O3) in turn. Diaspore promotes relatively higher liquid phase fluidity, followed by kaolinite, free state alumina, and hercynite, while gibbsite possesses the maximum adverse impact. Kaolinite and hercynite are more beneficial to form dendritic or acicular silico-ferrite of calcium and alumina (SFCA) with high strength due to the better reactivity, and gibbsite and diaspore lead to more formation of relatively lower strength lamellar or tabular SFCA, while free state alumina is preferable to form disseminated SCFA with rather poorer strength. Kaolinite and hercynite are the most desirable alumina types for sintering rather than free state alumina. [ABSTRACT FROM AUTHOR]

Silico-ferrite of calcium and aluminum (SFCA) is one of the most commonly-produced phases in fluxed iron-ore sintering, and has long been regarded as an important bonding phase in industrial sinters. It is thus considered to have a significant effect on sinter quality. In this study, a solid solution model and database has been developed for the SFCA phase, and has been incorporated into the thermodynamic software, Multi-Phase Equilibrium (MPE). MPE calculations were compared with the in situ X-ray powder diffraction (XRD) observations of the formation of SFCA phase during sintering. The effects of the raw material composition, temperature and the oxygen partial pressure on the formation of mineral phases in the sinter, as well as the viscosity of the melt formed during sintering under equilibrium conditions, were modelled using MPE. The results show that the formation of SFCA phase can be promoted by increasing oxygen partial pressure and basicity of the raw material. Increases of Al2O3 and MgO content have no significant effect on the SFCA formation under equilibrium condition. The increase of oxygen partial pressure (10−3 atm or above) and basicity also leads to a decrease in melt viscosity, which enhances the fluidity of the melt, and hence, the assimilation of the sinter. However, increases of Al2O3 and MgO result in the increase of melt viscosity. [ABSTRACT FROM AUTHOR]