Development of CuO-based oxygen-carrier materials suitable for Chemical-Looping with Oxygen Uncoupling (CLOU) process

The Chemical Looping with Oxygen Uncoupling (CLOU) process is a Chemical Looping Combustion (CLC) technology that allows the combustion of solid fuels with inherent CO2 separation using oxygen-carriers. This technology has low energy penalty and thus low CO2 capture costs. The CLOU process is a new option, when the direct use of a solid fuel in a CLC technology is considered. The CLOU process takes advantage of the capability of some metal oxides to evolve gaseous oxygen at high temperatures. The oxygen-carrier particles for CLOU process are based on those metal oxides. The oxygen generated by the metal oxide reacts directly with the solid fuel, which is mixed with the oxygen-carrier in the fuel-reactor. The selection of suitable oxygen-carriers is a key factor for the CLOU technology development. The aim of this work was to produce and characterize oxygen-carrier materials based in CuO with high oxygen transfer capability, reactivity and good fluidization properties. Several oxygen-carriers were prepared with different CuO contents, using different inert supports and using different preparation methods (incipient wetness impregnation, mechanical mixing + extrusion, and mechanical mixing + pelletizing by pressure). The reaction rate for oxygen generation (decomposition) and regeneration were determined carrying out successive cycles in a TGA system. In this way it was determined the chemical suitability of the materials. Selected materials were tested by redox decomposition-regeneration cycles in a batch fluidized bed reactor working at different temperatures and reacting atmospheres. The fluidization behaviour against agglomeration and attrition during a high number of cycles was determined. A window of suitable operating conditions for the CLOU process using CuO oxygen-carriers was found.