Oxygen Exchange Reaction between CO₂–CO Gas and Molten Oxide Containing Iron Oxide

Abstract

Oxygen exchange reaction rates between CO₂–CO gas and molten oxides containing iron oxide have been measured by isotope exchange technique with ¹⁸O at 1 773 K with P_CO2/P_CO=1. Measured results represent that the oxygen exchange reaction rates show the maximum values at the beginning of the reaction and sharply decrease within approximately 20 s, and then gradually decrease with the reaction time proceeds. These changes indicate that the rate-limiting step would change from the dissociative adsorption of oxygen on the surface of molten oxide in the initial stage of reaction to the mass transfer of oxide ion from the surface to the inside of molten oxide in the following stage. Based on the kinetic analysis of the oxygen exchange process, CO₂ dissociation rate constant, CO₂ re-formation rate constant and the mass transfer coefficient of oxide ion in molten oxides were calculated for the FeO_x–CaO and FeO_x–SiO₂ systems. Addition of CaO and SiO₂ to molten oxide increases and decreases the oxygen exchange reaction rate, respectively.