Aqueous Carbonation of Steel Slag: A Kinetics Study

In this study, the kinetics of aqueous carbonation of steel slag in an atmospheric three-phase system containing steel slag, water, and CO2 gas was studied. Also, some factors likely affecting this process were investigated, such as reaction time and temperature, steel slag particle size (d(0.5)), CO2 flow rate, and the mass ratio of liquid to solid (L/S). The particle size of steel slag and the reaction temperature were found to be the major factors affecting the carbonation degree. The carbonation degree was determined to be 26.4% under the following conditions: reaction time of 3 h, temperature of 60 degrees C, CO2 flow rate of 600 ml/min, d(0.5) = 12.8 mu m, L/S=10, corresponding to a capacity of 0.264 kg CO2/kg steel slag. The experimental results were employed to study the reaction mechanism using the shrinking core model. The aqueous carbonation process of steel slag was found to be limited by the diffusion of calcium carbonate through the product layer. The apparent activation energy of the aqueous carbonation of steel slag was found to be 4.8 kJ/mol. It was confirmed that aqueous carbonation of steel slag is an effective approach for enhancing the CO2-sequestration capacity and reducing the environmental impacts of steel slag.