On the interfacial rate of reaction of CO2 with a calcium ferrite melt

Abstract

Measurements of the rate of dissociation of CO2 have been made by the14CO2-CO isotope exchange technique on calcium ferrite melts with Ca/Fe = 0.30 at 1300 °C. Studies have also been made of the interfacial rates of oxidation of calcium ferrite melts with an average CaO content of 19.45 wt pct (CaJFe ≃0.33) in CO2-CO atmospheres at 1362 °C. It is shown that the rates of oxidation are consistent with the rates of isotope exchange, indicating a common rate determining step. Measurements of the equilibrium Fe3+/Fe2+ ratio as a function of the CO2/CO ratio for 19.3 wt pct CaO melts at 1360 °C and for 28.7 and 18.6 wt pct CaO melts at 1300 °C are found to be in close agreement with the deductions of Takeda, Nakazawa, and Yazawa. Combination of the equilibrium data with the results of the isotope exchange studies indicate that the apparent first order rate constant for the dissociation of CO2 is inversely proportional to the square of the Fe3+JFe2+ ratio of the melt, as has been previously found for liquid iron oxide, lime-saturated calcium ferrites, silicasaturated iron silicates, and an equimolar “FeO”-CaO-SiO2 melt.