CuO supported on manganese ore as an oxygen carrier for chemical looping with oxygen uncoupling (CLOU)

The chemical-looping with oxygen uncoupling (CLOU) is a promising technology that could be used for combustion of solid fuels with inherent separation of carbon dioxide. In this work, manganese ore supported CuO (CMO) oxygen carrier was synthesized. The oxygen transport capacity (Ro) and the reaction reactivity of CMO were investigated in TGA. The CLOU tests with biochar as fuel were performed. The reaction reactivity with biochar was enhanced due to the synergistic effect between manganese ore and CuO, and a value of Ro, 3.31%, was observed in TGA at 950 °C after 15 redox cycles. In fluidized bed tests, CMO shows excellent cycle performance; full conversions of biochar and the values closed to 100% carbon capture efficiency were obtained in the temperature range of 850-950 °C. However, obvious sintering of CMO was observed when the operating temperature reached 1,000 °C, which was further verified by the SEM, BET and PSD results. From XRD patterns, CuMn2O4, CuO, Fe2O3, and SiO2 were detected in the fresh CMO sample. The presence of CuMn2O4 in fresh CMO sample indicated that manganese ore reacted with CuO during calcination. The CuMnO2, Cu2O and Mn3O4 observed in reduced CMO sample indicated that the gaseous oxygen was derived from CuO/Cu2O and CuMn2O4/CuMnO2 systems. The CMO was fully regenerated in air reactor after 10 cycles at 950 °C. In addition, CMO sample showed a higher crushing strength and magnetic property. These results indicated that CMO can be used as a good oxygen carrier candidate for CLOU below 950 °C.