Developmen of Cu-based oxygen carriers for chemical-looping with oxygen uncoupling (CLOU) process

Abstract

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 for CO2 separation 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 uses oxygen carriers based on some metal oxides that have the capability to evolve gaseous oxygen at high temperatures. 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 a suitable oxygen carrier is a key factor for the CLOU technology development. The aim of this work was to produce and characterize oxygen carrier materials based on CuO with high oxygen transfer capability, high oxygen generation rates and good fluidization properties. Several oxygen carriers were prepared with different CuO contents, inert supports and preparation methods (incipient wet impregnation, mechanical mixing following by pelletizing by extrusion, or pelletizing by pressure). The reaction rates for oxygen generation (reduction) 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 oxygen carriers were tested by redox 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. Oxygen carriers with 60 wt% of CuO on MgAl2O4 and with 40 wt% CuO on ZrO2 prepared by mechanical mixing following by pelletizing by pressure were identified as suitable materials for CLOU process.