Ammonia combustion in furnaces: A review

Ammonia is a formidable chemical that has been investigated over 150 years for its use in the chemical processing field. The potential of the molecule to be used in farming applications has enabled a demographic explosion whilst its implementation in refrigeration technologies ensure continuous operation of cooling systems at high efficiencies. Other areas have also benefited from ammonia, whilst the use of the molecule in fuelling applications was scarce until the 2010s. A combination of factors that include climate change and energy dependency have reignited the interest of using ammonia as an energy vector that can potentially support applications that range from small devices to large power applications, thus supporting the transition to a net zero economy. Therefore, ammonia appears as a tangible option towards the reduction of emissions that can support a truly carbon-free energy transition in the coming years. As the recognition of the molecule increases, research areas based on combustion processes have also expanded towards the utilization of ammonia. The research around the topic has considerably augmented not only in the academic community, but also across governmental institutions and industrial consortia willing to demonstrate the potential of such a chemical. Therefore, this review approaches the latest findings and state-of-the-art research on the use of ammonia as a combustion fuel for furnaces. Different to other reviews, the present work attempts to gather the latest fundamental research, the most critical technologies evaluating ammonia for system operation, and novel approaches that suggest various breakthrough concepts that will ensure the reliable, cleaner consumption of the molecule as furnace fuel. Further, the present manuscript includes the latest research from all corners of the world, in an attempt to summarise the extensive work that dozens of groups are currently conducting. Finally, future trends and requirements are also addressed, providing guidance to those interested in doing research and development in ammonia-fuelling systems.