Studies on the redox reaction kinetics of Fe2O3-CuO/Al2O3 and Fe2O3/TiO2 oxygen carriers

This paper contains the results of research work on chemical looping combustion (CLC). CLC is one of the most promising combustion technologies and has the main advantage of the production of a concentrated CO2 stream, which is obtained after water condensation without any energy penalty for CO2 separation. The objective of this work was to study the kinetics of both the reduction and oxidation reactions for the selected bi-metallic Fe2O3-CuO/Al2O3 and mono-metallic Fe2O3/TiO2 oxygen carriers. Based on our previous CLC research results, the most promising oxygen carriers were selected for the analysis. Tests were performed at isothermal conditions (600-950 °C) in multiple redox cycles using a thermo-gravimetric analyzer (Netzsch STA 409 PG Luxx). For the reduction, 3% H2 in Ar was used, and for the oxidation cycle, air was used. The activation energy and the pre-exponential factor were determined, and the reaction model was selected. The F1 (volumetric model) and R3 (shrinking core model) were suitable models for Fe2O3/TiO2, with Ea equal to 33.8 kJ/mole where F1 and D3 (3-dimensional diffusion model), were suitable for Fe2O3-CuO/Al2O3 reduction reaction kinetics decryption with Ea = 42.6 kJ/mole (F1 model). The best fits for oxidation reaction was obtained for R3 model, and F1 was also good for Fe2O3/TiO2 oxygen carrier. The chemical looping oxygen uncoupling (CLOU) effect of Fe2O3-CuO/Al2O3 material is the best described by the F1 or D3 models. The CLOU effect activation energy is equal to 22.2 kJ/mole.