1996 Volume 36 Issue 6 Pages 624-630
The rate constant of CO2 dissociation on the surfaes of CaO-SiO2, CaO-Al2O3, CaO-SiO2-CaF2 and CaO-SiO2-FexO slags was measured by means of a 13CO2-CO isotope exchange technique as functions of slag basicity, iron content, temprature and imposed equilibrium CO2/CO ratio. It was shown that CaO-SiO2-FexO slags with low iron content and those with high iron content had different rate determining steps. According to those rate determining steps, the apparent rate constant, ka, was calculated for each slag. Consequently, we obtained the equations: ka=k(1-Σiθi) and ka=k(1-Σiθi)(aFeO2)2(PCO2/PCO)–1 for the former slag and the latter, respectively, where k is the rate constant, θi is the fractional coverage of absorbed species i. From the view point of dependence of the rate constant on oxygen partial pressure, these equations well represented the experimental results. For 35mass%CaO-65SiO2 and 50mass%CaO-50Al2O3 slags, activation energies were estimated to be 203 [kJ/mol] and 120 [kJ/mol], respectively. Addition of CaF2 up to 30mass% does not affect ka for CaO-SiO2 melts.