Thermal reduction of iron–manganese oxide particles in a high-temperature packed-bed solar thermochemical reactor

The reduction of iron–manganese oxide particles in a high-temperature packed-bed solar thermochemical reactor is investigated using an advanced transient three-dimensional heat and mass transfer model. The model couples the reaction kinetics and fluid flow to conductive, convective, and radiative heat transfer. A reactor prototype that features a reaction tube confining the packed particles and a surrounding diffuse reflective cavity is tested under simulated high-flux solar irradiation to validate the model. The numerically predicted temperature profiles and oxygen generation rates are in good agreement with the experimental data. The validated model is applied to evaluate the thermochemical performance of the reactor. The calculated temperature profiles indicate that uniform temperature distribution in the reactive packed particles is achieved from the onset of the reaction. An energy rate balance analysis shows the instantaneous peak solar-to-chemical energy efficiency reaches 9.3%.