2016 Volume 56 Issue 2 Pages 220-225
To investigate the relation between Al2O3 and the gas permeability resistance in a blast furnace, the effect of Al2O3 on the increment in the slag melt volume and the decrement in the temperature of the slag melt formation has been elucidated by comparing the reactions between liquid olivine and solid 2CaO∙SiO2 and between liquid olivine and solid 2CaO∙Al2O3∙SiO2 at the constant temperature of 1240°C, and eutectic reactions between FeO and 2CaO∙SiO2 and between FeO and 2CaO∙Al2O3∙SiO2 at the constant heating rate of 10°C/min. The reaction temperature of 1240°C has been chosen because the effect of Al2O3 on the gas permeability is markedly observed at that temperature. The heating rate has been set to be 10°C/min as it is considered to be the approximate heating rate of burden in a blast furnace. The fraction of the liquid phase decreases from 38.3% to 30% for olivine-2CaO∙SiO2 system, while it increases from 23.5% to 27.4% for olivine-2CaO∙Al2O3∙SiO2 system in 10 min after the onset of heating. It is considered that the increment in the Al2O3 content of iron ores raises the amount of olivine-like slag melts around 1240°C. The onset temperature of eutectic reaction for mixed FeO and C2AS powders is almost equal to that for mixed FeO and C2S powders when the temperatures are compared for powders with the average particle size smaller than around 40 µm. This implies that a negative effect of Al2O3, that is, lowering the temperatures of slag melt formation could be eliminated when the microstructures of sinters are fine enough.