Review on NOx Mitigation Techniques for Ammonia Combustion

Ammonia is gaining attention for decarburizing the energy sectors with high volumetric energy density and stable industry as favorable features compared to hydrogen. The low reactivity of ammonia is successfully addressed to approve ammonia as fuel. However, higher fuel NOx emissions are a major concern that limits ammonia utilization in practical combustion systems as NOx is a highly reactive and poisonous atmospheric pollutant. This suggests the need for NOx reduction techniques for commercializing ammonia as fuel. This review work is aimed at presenting different NOx reduction strategies for ammonia combustion with favorable results. Initially, the chemical kinetics of ammonia oxidation is understood to emphasize the crucial NOx and De-NOx pathways. Later, the majorly explored NOx reduction strategies for ammonia combustion such as different fuel injection techniques, raising combustor pressure, humidification, air staging, fuel staging, and mild combustion are discussed in detail at various operating conditions. This work systematically elaborates the underlying De-NOx chemistry for each NOx reduction strategy. The mitigation of NOx emissions during ammonia combustion is of utmost importance in order to preserve the environment, ensure the well-being of the public, adhere to regulatory requirements, contribute to global sustainability objectives, and exhibit corporate accountability. The implementation of this initiative yields extensive advantages for both the natural environment and the broader societal framework.