Effect of the oxygen carrier ilmenite on NOx formation in chemical-looping combustion

The formation of NOx from fuel-bound nitrogen is important for the design of chemical-looping combustion (CLC) power plants. This work studied to what extent NO and NH3 reacts with the perovskite-like oxygen carrier ilmenite under conditions relevant to CLC. Based on mass balance calculations, N-2 was the major outlet N-species in all experiments. More NO was measured at lower temperatures and at a higher oxidation level of the oxygen carrier. The presence of syngas hindered the reduction of NO by ilmenite. There were significant differences between the two ilmenites studied with respect to N-species selectivity. Norwegian (rock) ilmenite reduced NO efficiently and showed a stable reaction behavior compared to Australian (sand) ilmenite. This could be attributed to the higher titanium content of Norwegian ilmenite.