Scalable preparation of Ca2AlMnO5+δ-based spherical pellets for efficient thermochemical energy storage and air separation

The redox metal oxide Ca 2 AlMnO 5+δ (CAMO) has excellent oxygen storage and thermal storage properties. However, its widespread application is limited by the high cost of raw materials and the complexity of preparation techniques. This study reports an economical preparation route for CAMO via a solid-state reaction method, utilizing low-cost CaCO 3 , Al(OH) 3 , and MnCO 3 as raw materials. Furthermore, a continuous pelleting technique is developed and optimized to facilitate future industrial production. The CAMO spherical pellets with a diameter of 3 mm demonstrate good redox activity within the temperature range of 723.15-923.15 K, specifically achieving an oxygen storage capacity of 1653.6 μmol-O/g and a gravimetric heat storage density of 318.48 J/g. In addition, the spherical pellets possess good compressive strength, with a compressive load of 214.3 N for the 3 mm pellets used in the subsequent kinetic and cycling studies. The oxidation reaction process is governed by the Jander equation model and the Exponential law model, and the corresponding mechanism-related activation energy determined by the Phadnis method is 196.22 kJ/mol. Even after hundreds of cycles, the spherical pellets exhibit minimal performance degradation, with structural integrity and dimensional stability remaining well preserved. These findings demonstrate that the CAMO thermochemical spherical pellets, prepared via the continuously developed and optimized pelleting technique in this study, possess strong reactivity and high compressive strength, and can be directly applied to CSP reactors. This process achieves air separation while storing heat, thereby improving overall energy utilization efficiency and contributing to the development of carbon neutrality technologies.