(178b) Comparative Evaluation of Novel Oxygen Carriers for Chemical Looping Combustion

Chemical looping combustion (CLC) is an emerging technology for clean energy-production from fossil and renewable fuels. In CLC, an oxygen carrier (typically a metal) is first oxidized with air. The hot metal oxide is then reduced in contact with a fuel in a second reactor, thus combusting the fuel. Finally, the reduced metal is transferred back to the oxidizer, closing the materials ?loop?. CLC thus allows for flame-less, NOx-free combustion without requiring expensive air separation. Furthermore, CLC produces sequestration-ready CO2-streams without significant energy penalty. However, CLC is currently suffering from insufficient stability of the oxygen carrier (particularly metal sintering), and slow metal re-oxidation kinetics.

We report on a comparative study in which conventionally prepared bentonite-based oxygen carriers are evaluated and compared to novel nanostructured oxygen carriers. Ni-, Fe-, and Cu-based nanocomposites were synthesized, characterized, and evaluated in TGA and reactor studies using a syngas fuel. In particular, the influence of particle and metal loading were investigated.

Both types of carriers showed stable, reproducible redox kinetics at reaction conditions. Nanostructuring of the oxygen carrier led to a drastic acceleration of the oxidation kinetics in Ni- and Fe- based carriers, but only weakly accelerated kinetics for Cu-based materials. Experimental results and the great potential of these carrier materials for clean energy applications will be discussed in detail in the presentation.