Reactivity assessment and oxidation kinetic model for CO2 splitting on Fe-based oxygen carrier

In this paper presents the experimental investigation of the oxidation reactivity and kinetics of Fe-based oxygen carrier (OC) by CO2 and applies a classical method for the selection of the best-fitting kinetic model for the reaction. The CO production has been explored for the CO2 concentration range of 20-40% and temperatures range of 700-1000oC. It is observed that the CO production rates increase with CO2 concentration and temperature until 900oC. The material shows a gradual deactivation at 1000oC with a lower CO yield. The deactivation is attributed to surface sintering which results in slower kinetics and formation of Fe3C at high temperature due to the thermodynamic equilibrium of the CO/CO2 atmosphere. Therefore, to have a good CO yield the temperature of the present oxygen carrier has to be in the range of 800-900oC. The kinetic study is performed in the temperature range of 700-900oC with a CO2 concentration between 20-40 vol% in the feed. The results of the study suggest that the CO2 oxidation of iron oxide occurs through a two-step reaction in which CO2 interacts with the surface of each oxygen carrier particle particles and then migrate through oxygen vacancy diffusion to the cores of each grain of the particle.