Reactivity of Coke Ash on Alumina-Carbon Blast Furnace Hearth Refractories

Abstract

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 1450° to 1550°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.