Determination of the rate of CO2 dissociation on the surface of CaO-SiO2, CaO-Al2O3, CaO-SiO2-CaF2 and CaO-SiO2-FexO melts

The rate constant of CO2 dissociation on the surfaces of CaO-SiO2, CaO-Al2O3, CaO-SiO2-CaF2 and CaO-SiO2-FexO slags was measured by means of a (CO2)-C-13-CO isotope exchange technique as functions of slag basicity, iron content, temperature 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, k(a), was calculated for each slag. Consequently, we obtained the equations: k(a) = K(1 - Sigma(i) theta(i)) and k(a) = k(1 - Sigma(i) theta(i))(aFeO(2)(-))(2)(P-CO2/P-CO)(-1) for the former slag and the latter, respectively, where k is the rate constant, theta(i) 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-65SiO(2) and 50mass%CaO-50Al(2)O(3) slags, activation energies were estimated to be 203[kJ/mol] and 120[kJ/mol], respectively. Addition of CaF2 up to 30 mass% does not affect k(a) for CaO-SiO2 melts.