Plasma assisted NH3 combustion and NOx reduction technologies: Principles, challenges and prospective

Combustion is the cornerstone for generating energy in various sectors and applications. The predominance of hydrocarbons combustion causes several environmental and human health issues. The ever-increasing demand for decarbonization of combustion technologies in order to reduce or eliminate undesirable emissions has created a major challenge, putting tremendous pressure on the international research community to develop alternative fuels. Ammonia has recently been explored as a promising carbon-free fuel and a great alternative to hydrocarbon fuels to achieve zero-carbon emissions. However, despite its advantages over hydrogen, ammonia combustion has some drawbacks including low burning velocity, flame stability, and high NOx emissions. This review begins with energy and environmental issues before moving on to hydrogen and ammonia as promising potential solutions, their advantages and drawbacks, and ammonia combustion kinetics. It summarises the principles of chemical kinetics of both ammonia combustion and NOx reduction coupled with the chemistry, kinetic mechanisms and impact of plasma on ammonia combustion. The effects of plasma on ammonia combustion and NOx reduction are also discussed, with a comparison of NOx reduction mechanisms and plasma approach. Finally, the review discusses the perspectives and challenges of using plasma in ammonia combustion.