Oxygen Uncoupling of Cu-Based Oxygen Carrier with the Presence of Coal Ash in Chemical Looping Process

Chemical looping with oxygen uncoupling (CLOU) represents a potentially high-efficiency approach to capture CO, in the utilization of solid fuels. With the presence of complex mineral matters in solid fuels, the interaction between oxygen carrier and coal-derived ash in CLOU was necessary to be well understood. In this work, three typical coal ashes were selected and mixed with a Cu-based oxygen carrier (OC), and their impacts on the chemical and physical behavior of the oxygen carrier were studied comprehensively. The factor including coal ash types, ash content, CLOU cycle number, and reaction kinetics was evaluated. The results suggest that the presence of ash could lead to an obvious decrease of solid conversion during oxygen uncoupling. The most probable reason was attributed to the consumption of dissociate CuO with the formation of CuAl2O4. With the mass ratio of ash increased, the oxygen-releasing ability of samples was seen to become worse. Both of these effects tended to be a bit more serious after cyclic operation. Not only that, with the presence of ash, the reaction activation energy became higher and the reaction type changed from shrinking-core model to the nucleation and nuclei growth model.