Control of emissions from cracked ammonia swirling flames by heat loss management

Davies, Jordan, Sato, Daisuke, Mashruk, Syed, Pugh, Daniel ORCID: https://orcid.org/0000-0002-6721-2265 and Valera Medina, Agustin ORCID: https://orcid.org/0000-0003-1580-7133 2025. Control of emissions from cracked ammonia swirling flames by heat loss management. International Journal of Hydrogen Energy 168 , 151061. 10.1016/j.ijhydene.2025.151061

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Abstract

Implementation of renewably produced ammonia as a zero-carbon fuel faces challenges relating to emissions of NOx and unburned NH3. This study employs a premixed atmospheric swirl burner with integrated cooling channels to examine the effects on emissions of NO, NO2, N2O, NH3 and H2 by managing heat loss from the flame. A blend of 0.67/0.25/0.08 (mol.) NH3/H2/N2, representing 20 % (vol.) cracked ammonia was used with a constant net thermal power of 10 kW. For the range of equivalence ratios 0.7 < Φ < 1.3, two heat loss cases were assessed. A comparison was made between a conventional baseline configuration, and a secondary case with additional heat loss added by flowing 16 g/s of water through the burner face. A previously developed chemical reactor network (CRN) was utilised to investigate the main reactions responsible for emissions differences. Due to a reduction in availability of free H atoms caused by lower temperatures from additional heat loss, N2O emissions at lean conditions were increased. Therefore, focus was shifted to slightly rich conditions instead. NO emissions at Φ = 1.1 were found to be 67 % lower with additional heat loss when compared to the base case. One reason for this was a reduction in NO production via the HNO pathway, also stemming from lower temperatures. More interestingly, the increased heat loss moved flame temperatures nearer to the optimal temperature window for consumption of NO by NH2, further reducing NO emissions with a reduced penalty in unburned NH3, as found when targeting solely a reduction in HNO production. This resulted in unburned NH3 emissions increasing by only 12 % at Φ = 1.1 – a reasonable trade-off for the NO reduction found. It is also suggested that lower post-flame zone temperatures from the additional heat loss case decomposed less unburned NH3 into H2, resulting in similar mass-based combustion efficiencies calculated for both cases.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Engineering
Publisher:	Elsevier
ISSN:	0360-3199
Date of First Compliant Deposit:	1 September 2025
Date of Acceptance:	18 August 2025
Last Modified:	01 Sep 2025 14:09
URI:	https://orca.cardiff.ac.uk/id/eprint/180790

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