Analysis of emissions reduction, spatial distribution, and reaction pathways of NOx during MILD combustion of biomass gasification gas
(2025) In International Journal of Hydrogen Energy 188.- Abstract
Biomass gasification gas (BGG), a carbon-neutral renewable fuel and important hydrogen carrier, holds significant promise for sustainable energy systems. However, its practical implementation is challenged by combustion instability and elevated NOx emissions, primarily due to localized high-temperature zones induced by the hydrogen content. MILD (Moderate or Intense Low-oxygen Dilution) combustion applied to BGG in a jet-in-hot-coflow (JHC) effectively stabilizes combustion while achieving substantial reductions in NOx emissions. This study presents a comprehensive analysis of NOx emission reduction pathways under MILD combustion, combining experimental investigations, computational fluid dynamics (CFD),... (More)
Biomass gasification gas (BGG), a carbon-neutral renewable fuel and important hydrogen carrier, holds significant promise for sustainable energy systems. However, its practical implementation is challenged by combustion instability and elevated NOx emissions, primarily due to localized high-temperature zones induced by the hydrogen content. MILD (Moderate or Intense Low-oxygen Dilution) combustion applied to BGG in a jet-in-hot-coflow (JHC) effectively stabilizes combustion while achieving substantial reductions in NOx emissions. This study presents a comprehensive analysis of NOx emission reduction pathways under MILD combustion, combining experimental investigations, computational fluid dynamics (CFD), and detailed chemical kinetics. The results demonstrate that MILD combustion reduces NOx emissions by 26%–51%, with the greatest reduction observed at lower oxygen concentrations. BGG contributes NOx minimally (<16%) under MILD conditions. While the hot coflow introduces nitrogen that could promote NOx formation, the MILD regime suppresses thermal-NO pathways through temperature homogenization and oxygen dilution. Additionally, the inherently high dilution of BGG further limits NOx production. This effect is quantitatively supported by ROP analysis, which reveals that the normalized NO-reburning rate exceeds the total formation rate by factors of 1.1, 1.3, and 0.7 at 3%, 6%, and 9% O2 concentrations, respectively, further demonstrating that NO reburning is the dominant mitigation mechanism in MILD combustion. This reburning primarily occurs on the inner side of the flame zone. Furthermore, NO is mainly formed in regions with high concentrations of OH radicals and reduced in areas where CH3 radicals are prevalent.
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- author
- Zhou, Shengquan ; Liu, Xiaoyun ; Wu, Zhaoting ; Bai, Xue song LU ; Yan, Beibei LU ; Mansour, Mohy ; Cheng, Zhanjun and Chen, Guanyi
- organization
- publishing date
- 2025-11-13
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Biomass gasification gas, CFD simulation, Chemical kinetics analysis, MILD combustion, NO emissions
- in
- International Journal of Hydrogen Energy
- volume
- 188
- article number
- 152111
- publisher
- Elsevier
- external identifiers
-
- scopus:105019087966
- ISSN
- 0360-3199
- DOI
- 10.1016/j.ijhydene.2025.152111
- language
- English
- LU publication?
- yes
- additional info
- Publisher Copyright: © 2025 Hydrogen Energy Publications LLC
- id
- 15589ffe-7fd9-4fd9-9029-567d2ca651cc
- date added to LUP
- 2025-12-11 10:20:27
- date last changed
- 2025-12-11 10:20:47
@article{15589ffe-7fd9-4fd9-9029-567d2ca651cc,
abstract = {{<p>Biomass gasification gas (BGG), a carbon-neutral renewable fuel and important hydrogen carrier, holds significant promise for sustainable energy systems. However, its practical implementation is challenged by combustion instability and elevated NO<sub>x</sub> emissions, primarily due to localized high-temperature zones induced by the hydrogen content. MILD (Moderate or Intense Low-oxygen Dilution) combustion applied to BGG in a jet-in-hot-coflow (JHC) effectively stabilizes combustion while achieving substantial reductions in NO<sub>x</sub> emissions. This study presents a comprehensive analysis of NO<sub>x</sub> emission reduction pathways under MILD combustion, combining experimental investigations, computational fluid dynamics (CFD), and detailed chemical kinetics. The results demonstrate that MILD combustion reduces NO<sub>x</sub> emissions by 26%–51%, with the greatest reduction observed at lower oxygen concentrations. BGG contributes NO<sub>x</sub> minimally (<16%) under MILD conditions. While the hot coflow introduces nitrogen that could promote NO<sub>x</sub> formation, the MILD regime suppresses thermal-NO pathways through temperature homogenization and oxygen dilution. Additionally, the inherently high dilution of BGG further limits NO<sub>x</sub> production. This effect is quantitatively supported by ROP analysis, which reveals that the normalized NO-reburning rate exceeds the total formation rate by factors of 1.1, 1.3, and 0.7 at 3%, 6%, and 9% O<sub>2</sub> concentrations, respectively, further demonstrating that NO reburning is the dominant mitigation mechanism in MILD combustion. This reburning primarily occurs on the inner side of the flame zone. Furthermore, NO is mainly formed in regions with high concentrations of OH radicals and reduced in areas where CH<sub>3</sub> radicals are prevalent.</p>}},
author = {{Zhou, Shengquan and Liu, Xiaoyun and Wu, Zhaoting and Bai, Xue song and Yan, Beibei and Mansour, Mohy and Cheng, Zhanjun and Chen, Guanyi}},
issn = {{0360-3199}},
keywords = {{Biomass gasification gas; CFD simulation; Chemical kinetics analysis; MILD combustion; NO emissions}},
language = {{eng}},
month = {{11}},
publisher = {{Elsevier}},
series = {{International Journal of Hydrogen Energy}},
title = {{Analysis of emissions reduction, spatial distribution, and reaction pathways of NO<sub>x</sub> during MILD combustion of biomass gasification gas}},
url = {{http://dx.doi.org/10.1016/j.ijhydene.2025.152111}},
doi = {{10.1016/j.ijhydene.2025.152111}},
volume = {{188}},
year = {{2025}},
}