A kinetic study on the carbonation of steelmaking slags

Carbonation of a synthesized CaO-Al₂O₃-MgO-SiO₂ ladle refining slag has been kinetically studied using a thermo-gravimetric analyzer (TGA). The effects of extended basicity (CaO/Al₂O₃), temperature, and the crystal phase ratio were considered. The carbonation ratio and the initial reaction rate increased with basicity. However, for the same basicity of the slag, a decreasing crystal phase ratio seemed to accelerate the carbonation reaction due to the higher reactivity of the O^2- ions within the slag. The carbonation ratio and the initial reaction rate were also found to increase with temperature in the range between 973 K and 1073 K, where the temperature effect was clearly observed at the onset of the reaction. Parameters were set to identify the carbonation mechanism and their values were calculated via regression analysis. The activation energy for carbonation was calculated to be 129.9 kJ/mol at C/A=1.0 and 109.0 kJ/mol at C/A=1.2.