CuO-Based Oxygen-Carrier Particles for Chemical-Looping with Oxygen Uncoupling – Experiments in Batch Reactor and in Continuous Operation

Abstract

Chemical-looping with oxygen uncoupling (CLOU) is an innovative method to oxidize fuels with inherent CO2 sequestration, which utilizes a solid oxygen-carrier material to provide O-2 for fuel combustion. In this study, a range of CuO-based oxygen-carrier particles have been manufactured and examined. Out of 24 samples prepared, 10 were examined in a batch fluidized-bed reactor, of which three were selected for further examination by continuous operation in a small circulating fluidized-bed reactor system. Composite particles consisting of CuO as active phase and support material such as ZrO2, YSZ, CeO2, and MgAl2O4 were capable of providing full conversion of CH4 at 900 and 925 degrees C, and were also found to release gas phase O-2 into inert atmosphere when fluidized with N-2. Particles using semiactive support such as Fe2O3, Mn2O3, and Al2O3 formed combined spinel phases with CuO. Such materials were still capable of releasing gas phase O-2 but at different concentrations as compared to particles with inert support. Materials with semiactive support had less good reactivity with CH4. No formation of unexpected phases could be detected by X-ray diffractometry, and all chemical reactions were completely reversible. The three materials that were examined in continuous operation were readily capable of providing more or less full conversion of natural gas under the chosen conditions. However, they also suffered from quick attrition and turned into a flour-like substance after a few hours of continuous operation with fuel. Crushing strength analysis showed that particles used in continuous operation were physically much weaker than fresh. In total, 23 h of continuous operation with fuel addition was recorded.