Thermodynamic behaviour of carbonate in CaO based slag

Carbonate solubility was measured for CaO bearing slag systems at 1600 °C under different thermodynamic conditions by using equilibration techniques. Carbonate solubility increased with activity of (CaO). The reaction mechanism of the carbonate dissolution in slag can be expressed as a reaction between CO₂ gaseous phase and oxygen ion to form carbonate (CO₃^2-). Carbonate capacities of various slags depended not only on oxygen ion but also activity coefficient of carbonate ion. The activity coefficient of carbonate ion in CaO-SiO₂ slag changed with CaO content, but that of CaO-Al₂O₃ slag did not change remarkably. Substitution of MgO by CaO for solubility of carbonate had a similar effect as in the case of carbide in CaO-SiO₂-MgO slag. The critical oxygen potential for carbide and carbonate stability was found to be 10^-10 bar.