Combustion performance, flame structure and EINO scaling of an industrial burner with high excess air fired with natural gas, hydrogen and blends: a numerical study
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Date
2026
Authors
Chishty, M.A.
Katoch, A.
Saw, W.
Evans, M.J.
Medwell, P.R.
Nathan, G.J.
Chinnici, A.
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Applications in Energy and Combustion Science, 2026; 26:100475-1-100475-13
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M.A. Chishty, A. Katoch, Woei Saw, Michael J. Evans, Paul R. Medwell, G.J. Nathan, A. Chinnici
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Abstract
We report on a method to scale NOₓ emissions from a numerical study of a 7.5 MWth industrial-scale, non-premixed, swirl burner (register-type) used as a hot gas generator (HGG) for an iron ore pelletisation plant firing a range of blends containing hydrogen. The method considers pure natural gas (NG), hydrogen or their blends. A detailed 3D CFD model of the burner and HGG was developed in Ansys Fluent 2024 (version R1) incorporating a realisable k-ε turbulence model, detailed GRI 3.0 chemistry, a non-adiabatic steady diffusion flamelet model, and the Discrete Ordinates radiation model. NOₓ formation was modeled via both thermal and prompt pathways. The blend ratios were varied with both a constant thermal input, whilst also keeping one of the following two additional parameters constant relative to the NG baseline, namely: (i) constant inlet air mass flow rate, and (ii) constant equivalence ratio. The model was verified against plant-scale NG operation data, and laboratory-scale NG, H₂ and NG/H₂ flame experiments, demonstrating good agreement. Results show that while flame shape remains relatively insensitive to fuel type, H₂ addition significantly increases peak flame temperature and Emission Index of NOₓ (EINO) values. Local extinction zones near to the base of the burner were found to more likely as the fraction of NG is increased, leading to a reduction in NOₓ emissions. It was also found that blending with a constant air mass flow rate maintains the flue gas enthalpy and temperature near to the baseline levels, ensuring minimal disruption to downstream pelletising operations - unlike the constant equivalence ratio approach. A method of scaling NOₓ emissions was proposed, based on local strain rate, with all calculated data following a linear trend regardless of fuel type and firing strategy. Two linear NOₓ emissions regimes were also observed, namely high NOₓ and low NOₓ regimes. It also shows that retrofitting the current industrial burner for H₂ co-firing (up to 90% H₂ by volume) is technically feasible with minimal process impact, provided that the air flow rate is appropriately managed. However, full H₂ conversion will necessitate burner redesign and refined firing strategies to meet NOₓ emission constraints.
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© 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).