Two Stage Ammonia Combustion in a Gas Turbine like Combustor for Simultaneous NO and Unburnt Ammonia Reductions

Akihiro Hayakawa*, K.D. Kunkuma A. Somarathne, Masaaki Tsukamoto, Taku Kudo, Hideaki Kobayashi, Tohoku University, Japan

15th Annual NH3 Fuel Conference, Pittsburgh, PA, October 31, 2018
NH3 Energy+ Topical Conference at the AIChE Annual Meeting

ABSTRACT

Ammonia is expected not only as a hydrogen energy carrier but also as a carbon free fuel. Recently, ammonia fueled gas turbine combustor was successfully demonstrated. However, large amount of NOx was produced when ammonia burns because ammonia includes nitrogen atom in the ammonia molecule. In addition, unburnt ammonia concentration in exhaust gas also needs to be reduced. In this study, we proposed a combustion concept in order to reduce NO and unburnt ammonia concentrations in the exhaust gas simultaneously in a gas turbine like model swirl combustor. In this concept, two stage (rich – lean) combustion was employed. Two stage (rich – lean) combustion has been already employed in hydrocarbon fueled gas turbine combustors in order to reduce thermal NOx. However, the two stage combustion for ammonia fuel is different from that of hydrocarbon because production path of NO is different each other, i.e., NOx is generated via fuel NOx path in the ammonia flame.

In two stage combustion for ammonia, rich flame is generated in the primary zone, and our previous study showed that NO concentration decreases with an increase in the equivalence ratio in rich flame region. Therefore, the exhaust gas from the primary zone has very low amount of NO, nevertheless, considerable amount of unburnt ammonia and hydrogen are contained. Then, the secondary air is injected at the downstream of the primary zone, and then injected air and the exhaust gas from the primary zone mix and burn in the secondary combustion zone. Consequently, over-all NO emission can be reduced if the ammonia concentration in the exhaust gas from the primary zone is low. Secondary air does not reduce NO and ammonia simultaneously if unburnt ammonia concentration in the exhaust gas from the primary zone is high, i.e., equivalence ratio is too high. Therefore, it was clarified that the equivalence ratio control is important in order to achieve simultaneous NO and ammonia reduction.

Read the abstract at the AIChE website.

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RELATED NH3 FUEL CONFERENCE PAPERS

2018: Development of Low-NOx Combustor of Micro Gas Turbine Firing Ammonia Gas
2017: Combustion Emissions from NH3 Fuel Gas Turbine Power Generation Demonstrated
2016: Power Generation and Flame Visualization of Micro Gas Turbine Firing Ammonia or Ammonia-Methane Mixture
2016: Combustion characteristics of ammonia/air flames for a model swirl burner and an actual gas turbine combustor
2015: Enhancement of reaction and stability of ammonia flames using hydrogen addition and swirling flow [PDF]
2015: Micro Gas Turbine Firing Ammonia [PDF]
2014: Micro Gas Turbine Operation with Kerosene and Ammonia

LINKS

Institute of Fluid Science, Tohoku University
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One response to “Two Stage Ammonia Combustion in a Gas Turbine like Combustor for Simultaneous NO and Unburnt Ammonia Reductions

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