Nitrogen Oxides as a by-product of Ammonia/Hydrogen combustion regimes

Abstract

Alternative fuels are under scrutiny for mitigating carbon dioxide emissions. One of these alternatives is 
\nammonia, which can be produced from waste sources, renewable energy and even nuclear power with 
\npotentially zero carbon emissions over most of its life cycle. The difficulties of pure ammonia combustion, 
\npartially due to its low flame speed and flammability, can be addressed by doping ammonia mixtures with
\nhydrogen, which increases the reactivity of these blends and allows combustion features similar to those of 
\nsome fossil fuels. However, NOx emissions are still a problem when burning ammonia, with some circumstances 
\nwhere emissions are even worse than with fossil-based systems. This is a consequence of the considerable 
\nformation of N2O, a greenhouse gas that is known to possess up to 300 times the Global Warming Potential 
\n(GWP) of carbon dioxide, making these regimes unsuitable for the purpose of fuel replacement to combat 
\nclimate change. Therefore, this work shows bespoke results for unburned NH3 and NOx emissions, specifically 
\nNO, NO2 and N2O, at various conditions of operation whilst employing ammonia-hydrogen blends in a tangential 
\nswirl burner representative of industrial gas turbines. The results show a good compromise of NOx emissions at 
\nthe near 1.05 - 1.2 equivalence ratio, with further understanding behind the chemistry that precludes the 
\nformation/consumption of these unwanted emissions for full deployment of ammonia-based energy systems.

Topics & Concepts