(654b) Effect of Nitrogen Oxide on the Reactivity of Cu-Mn Oxygen Carrier for Chemical Looping with Oxygen Uncoupling

Chemical looping with oxygen uncoupling (CLOU) is a variant of chemical looping combustion (CLC), which is one of the promising carbon capture and storage technologies. In CLOU, the fuel reacts with gaseous O₂ released by a metal oxide (oxygen carrier) at suitable temperatures and oxygen partial pressures, unlike the CLC, where only the lattice oxygen reacts with the fuel. The kinetically favored gas-solid reaction makes CLOU more effective than CLC for solid fuels like coal and biomass. As a CLOU oxygen carrier, bi-metallic Cu-Mn oxide demonstrates high combustion efficiency for solid and gaseous fuels. However, the effects of pollutant species, such as nitrogen oxide (NO), on its performance are not well-understood.

The purpose of this study is to investigate the interaction of NO with a mixed Cu-Mn oxide and how it affects the performance of the oxygen carrier for CH₄ combustion under CLOU conditions. The oxygen carrier was reduced via CH₄-N₂ gas mixture with and without NO. A parametric study was conducted with various NO concentrations (500, 2500, 5000 ppm), and reducing gas compositions (3, 6, 9% CH₄) at different temperatures (850, 900, 950°C). Oxygen carrier particles were characterized using XRD and XPS before and after NO exposure under CLOU conditions. The presence of NO negatively impacts CO₂ formation as seen from increased CO and unreacted CH₄ amount in the combustion products. The parametric study indicates that the change in NO or feed CH₄ concentration has a negligible effect, but decreasing the temperature to 850°C increases the adverse effects of NO on CO₂ formation.