Cyclic Oxygen Release Characteristics of Bifunctional Copper Oxide/Calcium Oxide Composites

Integrated Ca-Cu looping is a novel carbon capture technology which uses CuO to transport oxygen and CaO to capture CO2 in the same process. Investigation on the oxygen release behaviour of the bi-functional CuO/CaO composite is critical to assess the potential of applying this technology to solid fuels like coal. In this study, three different CuO/CaO composites having different relative percentages (CuO75CaO25, CuO50CaO50 and CuO25CaO75) were manufactured in a commercial granulator and then tested in a bubbling fluidised bed reactor to examine their oxygen release characteristics at temperatures in the 880–920oC range. All the composites exhibited clear oxygen release properties during the testing, indicating that the solid fuel can be directly oxidised rather than being gasified first in the Ca-Cu looping process, even though the equilibrium oxygen concentration is much lower than the theoretical value. At the same temperature, the oxygen release rate of CuO25CaO75 is the quickest and its final oxygen yield is the largest, followed by CuO75CuO25 and CuO50CaO50. XRD results show that there is Ca2CuO3 formed in the used samples of CuO75CuO25 and CuO50CaO50, but not in the case of CuO25CaO75, which may explain the performance difference observed. Further examination of the attrition and agglomeration behaviour shows that all the composites are very stable and strong, among which CuO25CaO75 is the most stable and strongest.