Combined Cu/Mn oxides as oxygen carrier in chemical-looping with oxygen uncoupling (CLOU)

摘要

Chemical-looping with oxygen uncoupling (CLOU) is an emerging method to capture CO_2 during oxidation of fuels. It utilizes a solid oxygen carrier, normally particles consisting of a metal oxide, to provide O_2 for fuel oxidation. The most common realization of the concept involves circulating oxygen-carrier particles between two fluidized bed reactors. This study investigates O_2 uncoupling properties of five different CuO/Mn_3O_4 combined oxides produced by freeze granulation and calcined at 950°C for 6 hours. Oxygen carriers with 5, 10, 20, 31 and 61 wt % CuO were examined in both inert (pure N_2) atmosphere and in presence of solid fuel (wood char) at 600-800°C. All investigated materials released oxygen in the gas phase in this temperature interval. Based on XRD analysis of the oxygen carriers, the major phase transitions were Mn-2O_3 (⇔) Mn_3O_4 and spinel (Cu,Mn)_3O_4(⇔)CuMnO_2. These transitions provided a considerable amount of O_2 that shows the great potential of this Cu-Mn-O system to be used as oxygen carrier in chemical-looping applications at lower temperatures, perhaps interesting for biofuel combustion.