Physicochemical evolution of a Cu/Mn/Fe oxygen carrier in a 50 kWth chemical looping with oxygen uncoupling unit with solid fuels

• First evaluation of physicochemical properties of CLOU Cu-based carrier in combustion. • Cu migrated to particle surface increasing porosity and reducing crushing strength. • Chipping was primary attrition mechanism during operation. • Formation of stable Cu-Mn-Fe spinel phase maintained reactivity. • Used oxygen carrier maintained magnetic properties. Chemical looping combustion with oxygen uncoupling (CLOU) is a promising technology for efficient CO 2 capture. Identification of a suitable oxygen carrier is a key issue for the scale-up of the CLOU process. This study investigates the performance of a CuMnFe-based oxygen carrier (Cu30MnFe) after 40 h of operation in a 50 kW th CLOU unit using various solid fuels, including biomass and coal. Key physicochemical properties such as porosity, magnetic permeability, mechanical strength, particle size distribution, and phase composition were monitored throughout the campaign. Results revealed increased porosity and reduced mechanical strength, with chipping identified as the dominant attrition mechanism. Despite particle degradation, magnetic separation remained highly effective (99.5 %) for separation of fine particles from ash. SEM-EDX and ICP-OES analyses confirmed the chemical stability of Cu, Mn, and Fe, although a transformation from CuO to a spinel-type Cu-Mn-Fe oxide phase was observed, maintaining oxygen release capacity. Surface accumulation of ash elements like Si was detected, but no operational issues such as agglomeration or defluidization occurred. This work represents a step forward in the knowledge of Cu-based materials and will be useful for the future development of durable oxygen carriers with oxygen uncoupling and magnetic properties.