Application of chemical looping air separation for MILD oxy-combustion: Identifying a suitable operational region

Abstract

In this study, chemical looping air separation (CLAS) is integrated with moderate or intense low-oxygen dilution (MILD) oxy-combustion. CO2-rich flue gas is used as a purging agent for oxygen decoupling in a reduction reactor. This work identifies the suitable operational region of different oxygen carriers for CLAS based on heat balance. The oxygen fraction in air determines the maximum temperature in the oxidization reactor. The maximum oxygen fraction produced for CuO-Cu2O, Co3O4-CoO, Mn2O3-Mn3O4, and MnO2-Mn2O3 are 16.8%, 13.2%, 14.4%, and 12.0%, respectively, with a reduction temperature 10 °C less than that of the maximum oxidization temperature. The inert solid flow is determined by the temperature difference between the two reactors and the reaction enthalpy change. The inert solid flow increases with decreasing temperature difference between the two reactors. With a drop in temperature difference between the two reactors, the inert solid flow increases. A higher change in reaction enthalpy of oxides also increases the inert solid flow. A higher reduction temperature generates a higher oxygen fraction level of the product mixture stream.