Effects of Coke Ash on Erosion of Carbon Composite Brick

Abstract

Carbon composite brick has attracted increased attention because it is widely used on the hot face of blast furnace hearth. In order to reduce the erosion rate of carbon composite brick and investigate effects of coke ash on the erosion of carbon composite brick, the minerals CaO·Al₂O₃, CaO·2Al₂O₃, and CaO·6Al₂O₃ (CA, CA2, and CA6), which were considered to be the main components of coke ash in hearth, were prepared by heating a mixture of CaCO₃ and Al₂O₃. Experiments of the minerals coupled with carbon composite brick were carried out at different temperatures in a high temperature tube furnace. The mass change fraction of the experimental assembly was calculated using mass measurements before and after the experiment. The reaction products at different temperatures were predicted on the basis of ternary phase diagrams, and the thickness of the reaction layer was measured using scanning electron microscopy (SEM). The results show that the reaction rate of carbon composite brick with the minerals increased with an increase of the Ca content in the minerals. The results of reaction interface analysis show that the diffusion of Ca²⁺ was the dominant process during reaction. Cation diffusion was considered to be the rate determining step, and this was in agreement with experimental results. Therefore, reducing the ash content of coke, especially the CaO in ash, is the key to reduce the erosion rate of carbon composite bricks below the centerline of taphole.