Effects of reduction conditions on the cycling performance of hydrogen storage by iron oxides: Storage stage

In the present work, reduction of iron oxides as a hydrogen storage material by the reaction of Fe 3 O 4 + 4 H 2 → 3 Fe + 4 H 2 O was conducted at 673 K under different hydrogen partial pressures. A shrinking-core model with reaction control was well fitted to the experimental data obtained by thermogravimetric analysis. Since the oxidation state of iron showed a very steep reaction front along the length of the tube reactor during the reduction, metallic iron was exposed to hydrogen until all the iron oxides in the reactor were sufficiently reduced. A simulated moving bed-type reactor was proposed to solve this problem, and the calculation was made using the reaction model based on the assumption of irreversible reaction, isothermality, and plug flow. The calculation results indicate that the simulated moving bed-type reactor can achieve high hydrogen storage efficiency without over-exposure of metallic iron to hydrogen.