In a thermodynamic analysis of oxygen carriers for CLC, the oxide pairs CuO-Cu2O, Mn2O3-Mn3O4 and Co3O4-CoO were not possible to use as oxygen carriers for normal chemical-looping combustion at higher temperatures due to decomposition of the most oxidized phase. Later, this “problem” was identified as a possible advantage, and these systems were suggested as possible candidates for a new concept, or chemical-looping with oxygen uncoupling (CLOU). The mono-metallic oxides of Cu, Mn and Co release oxygen in the fuel reactor, e.g.: 4CuO « 2Cu2O + O2(g) DH850=263.2 kJ/mol O2 In the following step, the released oxygen reacts directly with the fuel through combustion. In the third and final step the oxygen carriers need to be oxidized back to the fully oxidized state, i.e. reverse of the reaction above. CLOU particles need to fulfill many of the same criteria as normal CLC oxygen carriers: The particles need to have high resistance towards attrition and fragmentation in a fluidized bed system, Be produced at low-cost for an economical carbon capture process and Be non-toxic for environment and human health. In addition, CLOU oxygen carriers need to have special thermodynamic and kinetic requirements in comparison to oxygen carriers used in normal CLC. More specifically: The metal oxide needs to have a sufficient equilibrium partial pressure of O2 as to create a significant driving force for reaction in the fuel reactor, The oxide system needs to have an equilibrium partial pressure low enough for oxidation to be possible at the oxygen concentration level in the outlet of the air reactor, The reactions in the fuel reactor, including O2 release by the carrier and combustion of the fuel, should be overall exothermic. This will result in a temperature increase in an adiabatic fuel reactor, which will promote the release rate of gas-phase oxygen from the particle to the bulk gas. Since the technology was proposed in 2009, there has been significant research around CLOU, with a significant number of materials tested, both pure and mixed oxides. Aspects related to oxygen carrier development and testing, kinetic modeling as well as process simulations have been studied. This presentation will be on work related to oxygen carrier development, with emphasis on the research conducted in the last few years with gas, liquid and solid fuels.

Materials for chemical-looping with oxygen uncoupling (CLOU) for gas, liquid and solid fuels: Status of development

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.