Investigation of the fate of nitrogen in chemical looping combustion of gaseous fuels using two different oxygen carriers

The influence of nitrogenous fuel impurities in a 120 kWth chemical looping combustion pilot unit was investigated. Two oxygen carriers were used. An in industrial scale produced perovskite type CaMn0·775Mg0·1Ti0·125O3-δ, called C28 and a copper based oxygen carrier (Cu15) prepared by impregnation were applied. Natural gas was used as fuel and ammonia (NH3) were added as a model NOX precursor up to a fuel-N content of 1.4 wt%, to investigate the path of nitrogen and emissions of nitrogen oxides. The exhaust gas streams of air and fuel reactor were analyzed against NH3 and NOX. The two oxygen carriers performed differently in the presence of NH3 in the fuel feed. While the general fuel conversion performance of both oxygen carriers were not affected, the NH3 conversion with C28 was only around 72% in the fuel reactor, full NH3 conversion was measured with Cu15. During the experiments with C28, NOX emissions in form of NO occurred in the fuel reactor, opposite to this no NOX have been detected while using Cu15. During all experiments no NOX was observed in the air reactor exhaust gas stream. A regeneration during CLC operation after switching off the ammonia feed was possible. •The fate of fuel nitrogen in Chemical Looping Combustion has been investigated.•Two different materials, a CLOU and a CLC oxygen carrier, were used in the study.•Fuel nitrogen had no negative effect on fuel conversion.•NOx emissions are different for the CLOU and CLC material.