Use of Hopcalite-Derived Cu-Mn Mixed Oxide as Oxygen Carrier for Chemical Looping with Oxygen Uncoupling Process

An alternative to the chemical looping combustion process using solid fuels with CO2 capture is chemical looping with oxygen uncoupling (CLOU). The CLOU process requires an oxygen carrier with the capability to give gaseous O-2 to burn solid fuels at the appropriate temperature, e.g., manganese oxide and copper oxide. In this work, treated commercial Carulite 300 was evaluated as oxygen carrier for CLOU. Carulite 300 is a hopcalite material composed of 29.2 wt % CuO and 67.4 wt % Mn2O3. The oxygen release rate and the fluidization behavior, with careful attention given to attrition rate and the behavior against agglomeration, were analyzed in a thermogravimetric analyzer and in batch fluidized bed reactors. Experiments in batch fluidized bed reactors were carried out at temperatures ranging from 800 to 930 degrees C with a medium volatile bituminous coal from South Africa and its char as fuels. The hopcalite-derived oxygen carrier showed high O-2 release rate, no unburned products at low oxygen carrier fuel mass ratios, and very high oxygen transference rate by gas-solid reaction. This material has the capacity to generate gaseous oxygen at lower temperatures than Cu-based oxygen carriers, which suggests this material is suitable to work at lower temperatures in the fuel reactor without the presence of unburned products; however, its low mechanical resistance after redox cycles makes necessary an improvement of its physical properties for use as an oxygen carrier.