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Control of NOx and other emissions in micro gas turbine combustors fuelled with mixtures of methane and ammonia.

Control of NOx and other emissions in micro gas turbine combustors fuelled with mixtures of methane and ammonia.

Authors :
Okafor, Ekenechukwu C.
Somarathne, K.D. Kunkuma A.
Ratthanan, Rattanasupapornsak
Hayakawa, Akihiro
Kudo, Taku
Kurata, Osamu
Iki, Norihiko
Tsujimura, Taku
Furutani, Hirohide
Kobayashi, Hideaki
Source :
Combustion & Flame. Jan2020, Vol. 211, p406-416. 11p.
Publication Year :
2020

Abstract

Methane–ammonia mixtures have potentials as low-carbon fuels for gas turbines, however significantly high fuel NOx production in their flames present challenges to their application. This study aims to provide deep insight into the physical and chemical processes involved in the formation and control of emissions from the combustion of CH 4 NH 3 –air with up to 30% ammonia by heat fraction in gas turbine combustors. Hence, laser diagnostics techniques such as Particle Image Velocimetry (PIV), and Planar Laser Induced Fluorescence (PLIF) imaging, in addition to Fourier Transform Infrared (FTIR) gas analysis were employed to study the flow field, flame structure and emissions characteristics of a micro gas turbine swirl combustor fuelled with CH 4 NH 3 –air mixtures. The control of emissions from the flames was further studied using Large Eddy Simulation (LES) of a model swirl combustor. The results show that NOx emissions from premixed CH 4 NH 3 –air in single-stage combustion were more than 5000 ppmv at equivalence ratios, Φ = 0.8–1.1, which is about twice more than the values already reported for NH 3 –air. Trends in NOx emissions correspond with the trends in OH radicals concentration in the combustor owing to the relevance of OH radicals in fuel NOx production. Emissions control leading to significantly low emissions such as 49 ppmv of NOx, 2 ppmv of CO and approximately zero N 2 O, HCN and NH 3 emissions with a 99.8% combustion efficiency was achieved using rich-lean combustion. An optimum Φ of the primary combustion zone for low NOx emission was identified, which varied from 1.30 to 1.35 depending on the ammonia fraction. For Φ richer (leaner) than the optimum Φ, NOx emission increased due to an increase in NOx production in the secondary (primary) combustion zone. Rich-lean combustion of CH 4 NH 3 –air emitted less NOx than that of NH 3 -air because the higher flame speed of CH 4 NH 3 –air mixtures ensured lower NOx production in the secondary combustion zone. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00102180
Volume :
211
Database :
Academic Search Index
Journal :
Combustion & Flame
Publication Type :
Academic Journal
Accession number :
141609223
Full Text :
https://doi.org/10.1016/j.combustflame.2019.10.012