Investigation of Combined Supports for Cu-Based Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)

The chemical-looping with oxygen uncoupling (CLOU) process is a novel solution for efficient combustion with inherent separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor. In the fuel reactor, the metal oxide releases gas phase oxygen, which oxidizes the fuel through normal combustion. In this study, Cu-based oxygen carrier materials that combine different supports of MgAl2O4, TiO2, and SiO2 are prepared and characterized with the objective of obtaining highly reactive and attrition resistant particles. The oxygen carrier particles were produced by spray-drying and were calcined at different temperatures ranging from 950 to 1030 °C for 4 h. The chemical-looping performance of the oxygen carriers was examined in a batch fluidized-bed reactor in the temperature range of 900–950 °C under alternating reducing and oxidizing conditions. The mechanical stability of the oxygen carriers was tested in a jet-cup attrition rig. All of the oxygen carriers showed oxygen uncoupling behavior with oxygen concentrations close to equilibrium. During reactivity tests with methane, oxygen carriers with lower mechanical stability showed higher reactivity, yielding almost complete fuel conversion. Oxygen carrier materials based on support mixtures of MgAl2O4/TiO2, MgAl2O4/SiO2, and TiO2/SiO2 showed a combination of high mechanical stability, low attrition rates, good reactivity with methane, and oxygen uncoupling behavior.