Reactivity of coke ash on alumina-carbon blast furnace hearth refractories
Understanding the degradation of blast furnace hearth refractories by coke ash products is a crucial component in achieving long furnace life. This study has been conducted to determine the reactivity of calcium aluminates (CaO·Al2O3, CaO·2Al2O3 and CaO·6Al2O3) in contact with an alumina-carbon refractory at representative hearth temperatures of 1 450° to 1 550°C. The rate of reaction between the alumina-carbon refractory and calcium aluminates was observed to increase with CaO content. The largest reaction layer was observed in CaO·Al2O3 followed by CaO·2Al2O3 and CaO·6Al2O3. The calcium aluminate (CaO·Al2O3, CaO·2Al2O3) and alumina-carbon reactions observed in this study were found to be consistent with the logarithmic rate law, with the exception of CaO·6Al2O3 where no reaction was observed. Energy dispersive spectroscopy analysis indicated the formation of CaO·2Al2O3, CaO·6Al2O3, corundum (Al2O3), plagioclase (CaO·Al2O3·2SiO2) and melilite (2CaO·Al2O3·SiO2) at the reaction interface of the reaction couples. The large volume changes due to the formation of these phases may result in spalling at the hot face of the hearth refractory.