The reduction of metallic oxides with the reducing gas and recyclic use of the metallic oxides were investigated as an elemental study of looping combustion process newly developed for efficient utilization of thermal energy(i.e., the three stages of combustion: steam-reforming of fuel at low temperature, reduction of metallic oxides at low temperature by the reformed product, and oxidization of metal or partially reduced metallic oxides at high temperature).
αhematite(Fe₂O₃) was chosen as a metallic oxide. The reduction and oxidization rates were measured at various temperatures. Hydrogen-water vapor mixtures and air were used in the reduction and oxidization processes, respectively.
In the case of Fe₂O₃_??_Fe cycle, the oxidization rate remarkably decreased with the number of reduction and oxidization repetitions at 1 173K, while the reduction rate was unchanged.
In the case of Fe₂O₃_??_Fe_1-yO cycle, both reduction and oxidization rates were unchanged under repetitions of reduction at low temperature(973K) and oxidization at high temperature(1 253K) as well as at the same temperature as that for Fe₂O₃_??_Fe cycle(1 173K).
It was found that αhematite has a bright prospect as a reaction medium at reduction and oxidization stages in the looping combustion process.