The investigations of hematite-CuO oxygen carrier in chemical looping combustion

Cu-Fe bimetallic oxygen carrier is a promising candidate for chemical looping combustion, but the cost of manufacture is a significant limit for its application. In this study, the bimetallic oxygen carrier was prepared using hematite and CuO simply through direct mixing method with low cost. The cyclic combustion performance and effects of temperature were investigated in a batch fluidized bed. Cycle experiments with gas fuel indicated that the bimetallic oxygen carrier possessed increasing reactivity with cycle, which could be ascribed to improved porous structure. However, some agglomeration occurred when the content of Cu reached 20% in weight. Besides, the cyclic operation with coal showed that the bimetallic oxygen carriers with Cu ratios of 5% and 10% possessed good long term operation characteristics and the oxygen carrier with 10% Cu performed better. The conversion of coal increased with the reaction temperature and higher temperature, above 900 °C, was needed for fast conversion of coal. Additionally, the manufactured oxygen carriers were characterized. In the bimetallic oxygen carriers, Cu distributed uniformly on the surface of particle but the content of Cu decreased with cycles caused by attrition. Besides, the bimetallic oxygen carrier possessed a stable chemical composition. Overall, the Cu-Fe bimetallic oxygen carrier prepared by direct mixing method is a competitive oxygen carrier, which deserves more attention.