Reduction Kinetics of Fe2O3/Al2O3 by Ultralow Concentration Methane under Conditions Pertinent to Chemical Looping Combustion

Abstract

Fe2O3/Al2O3 is found to be a suitable oxygen carrier candidate for the chemical looping combustion with ultralow methane concentration in a previous study by our team. In order to facilitate the fundamental reactor design and understand the energy consumption, the reduction kinetics mechanism of Fe2O3 (hematite) with 0.5 vol % CH4 was determined and the kinetic parameters were estimated based on the thermogravimetric analysis. Two oxygen carriers (i.e., Fe25Al and Fe45Al) were prepared and used in the TGA experiment. It was observed that the reduction of Fe2O3 was a two-steps process. Initially, Fe2O3 is transformed into Fe3O4 (magnetite) at a fast reaction rate and followed by a slow step corresponding to the reduction from Fe3O4 to FeAl2O4. A topochemical approach associated with Hancock and Sharp’s method was therefore applied to determine the most suitable kinetic model for the reduction process. It was found that the initial fast step can be described by the Avrami-Erofe’ev phase change model, the A2...