Stability limits and NO emissions of technically-premixed ammonia-hydrogen-nitrogen-air swirl flames

Khateeb, Abdulrahman A.; Guiberti, Thibault F.; Zhu, Xuren; Younes, Mourad; Jamal, Aqil; Roberts, William L.

doi:10.1016/j.ijhydene.2020.05.236

Cited by 105 publications

(49 citation statements)

References 43 publications

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“…Here, ammonia must be partially dissociated (the process is also referred as cracking) resulting in a blend including nitrogen in addition to hydrogen, with a 3:1 nitrogen to hydrogen volume ratio. The stability limits of this blend show similar trends of ammoniahydrogen blends [25].…”

Section: Ammoniasupporting

confidence: 61%

“…The issue related to the low reactivity of ammonia can be mitigated by blending with a more reactive fuel such as hydrogen. Recent studies [24,25] showed that ammoniahydrogen flames can be stabilized and that broader stable range compared to pure hydrogen or ammonia can be achieved. Furthermore, due to the high reactivity of hydrogen, ammonia-hydrogen-air combustion can be operated at lean conditions with competitive NO emissions (few hundreds of ppm or less).…”

Section: Ammoniamentioning

confidence: 99%

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Recent Combustion Strategies in Gas Turbines for Propulsion and Power Generation toward a Zero-Emissions Future: Fuels, Burners, and Combustion Techniques

et al. 2021

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The effects of climate change and global warming are arising a new awareness on the impact of our daily life. Power generation for transportation and mobility as well as in industry is the main responsible for the greenhouse gas emissions. Indeed, currently, 80% of the energy is still produced by combustion of fossil fuels; thus, great efforts need to be spent to make combustion greener and safer than in the past. For this reason, a review of the most recent gas turbines combustion strategy with a focus on fuels, combustion techniques, and burners is presented here. A new generation of fuels for gas turbines are currently under investigation by the academic community, with a specific concern about production and storage. Among them, biofuels represent a trustworthy and valuable solution in the next decades during the transition to zero carbon fuels (e.g., hydrogen and ammonia). Promising combustion techniques explored in the past, and then abandoned due to their technological complexity, are now receiving renewed attention (e.g., MILD, PVC), thanks to their effectiveness in improving the efficiency and reducing emissions of standard gas turbine cycles. Finally, many advances are illustrated in terms of new burners, developed for both aviation and power generation. This overview points out promising solutions for the next generation combustion and opens the way to a fast transition toward zero emissions power generation.

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Section: Ammoniasupporting

confidence: 61%

Section: Ammoniamentioning

confidence: 99%

Recent Combustion Strategies in Gas Turbines for Propulsion and Power Generation toward a Zero-Emissions Future: Fuels, Burners, and Combustion Techniques

et al. 2021

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“…Several methods have been proved effective when it comes to enhance ammonia combustion stability, such as cracking part of the NH3 to produce H2, generating swirling flows inside the combustor, increasing the combustor inlet temperature, and working under a suitable Equivalence Ratio (ER) to avoid lean or rich blowouts, as well as flashback risks [3,20]. According to the literature reviewed, it is predicted that cracking between 15% and 35% of the NH3 would result in a good trade-off between combustion properties, flame stability, and NOx emissions: with a large H2 fraction the resulting mixture shows similar combustion properties to CH4, whereas a low H2 fraction favours low NOx and easier cracking.…”

Section: Ammonia In Gas Turbinesmentioning

confidence: 99%

Simulation of the HiPowAR power generation system for steam-nitrogen expansion after ammonia oxidation in a high-pressure oxygen membrane reactor

2021

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The EU project HiPowAR studies a novel power generation system based on ammonia flameless oxidation with pure oxygen in a high-pressure membrane reactor and expansion of the resulting high-temperature H2O-N2 stream. The system combines the advantages of high temperature at expander inlet, typical of gas turbines, and small compression demand, typical of steam cycles. Water is injected into the reactor to control the very high adiabatic temperature, at the limited energy expenditure of liquid pumping. This work assesses the performance potential of the HiPowAR system under different design conditions, through simulations with a model developed in Aspen Plus®. The system shows a high efficiency (up to 55%) when operating at high temperature (e.g., 1350°C at expander inlet); hence, O2 membranes capable of working at very high temperature are required. The cycle features an optimal sub-atmospheric expansion pressure (in the range 0.1-0.2 bar), which requires the re-pressurization of the off-gas (steam-saturated nitrogen). The system also produces liquid water as a net output. A reduction of the expander inlet temperature to values acceptable by typical steam cycles (600°C) significantly limits the efficiency, despite allowing to demonstrate the process using conventional steam expanders.

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“…Results denoted the intrinsic instability of using two fuels with different reaction characteristics. Furthermore, research advanced towards the use of various blends at various equivalence ratios have shown a reduced operability range at low Reynolds numbers with a unitary swirl number, a dynamic process that at higher ammonia concentrations would improve through a sudden change of combustion dynamics [25]. Simultaneously, other studies with ammonia/methane showed that the region of 1.05-1.20 equivalence ratio would be the best for operation of these blends, as the production of NO decreases due to the excess in ammonia and amidogen radicals (which recombine with NO produced downstream).…”

Section: Introductionmentioning

confidence: 99%

Methane/Ammonia Radical Formation during High Temperature Reactions in Swirl Burners

et al. 2021

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Recent studies have demonstrated that ammonia is an emerging energy vector for the distribution of hydrogen from stranded sources. However, there are still many unknown parameters that need to be understood before ammonia can be a substantial substitute in fuelling current power generation systems. Therefore, current attempts have mainly utilised ammonia as a substitute for natural gas (mainly composed of methane) to mitigate the carbon footprint of the latter. Co-firing of ammonia/methane is likely to occur in the transition of replacing carbonaceous fuels with zero-carbo options. Hence, a better understanding of the combustion performance, flame features, and radical formation of ammonia/methane blends is required to address the challenges that these fuel combinations will bring. This study involves an experimental approach in combination with numerical modelling to elucidate the changes in radical formation across ammonia/methane flames at various concentrations. Radicals such as OH*, CH*, NH*, and NH2* are characterised via chemiluminescence whilst OH, CH, NH, and NH2 are described via RANS κ-ω SST complex chemistry modelling. The results show a clear progression of radicals across flames, with higher ammonia fraction blends showing flames with more retreated shape distribution of CH* and NH* radicals in combination with more spread distribution of OH*. Simultaneously, equivalence ratio is a key parameter in defining the flame features, especially for production of NH2*. Since NH2* distribution is dependent on the equivalence ratio, CFD modelling was conducted at a constant equivalence ratio to enable the comparison between different blends. The results denote the good qualitative resemblance between models and chemiluminescence experiments, whilst it was recognised that for ammonia/methane blends the combined use of OH, CH, and NH2 radicals is essential for defining the heat release rate of these flames.

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Stability limits and NO emissions of technically-premixed ammonia-hydrogen-nitrogen-air swirl flames

Cited by 105 publications

References 43 publications

Recent Combustion Strategies in Gas Turbines for Propulsion and Power Generation toward a Zero-Emissions Future: Fuels, Burners, and Combustion Techniques

Recent Combustion Strategies in Gas Turbines for Propulsion and Power Generation toward a Zero-Emissions Future: Fuels, Burners, and Combustion Techniques

Simulation of the HiPowAR power generation system for steam-nitrogen expansion after ammonia oxidation in a high-pressure oxygen membrane reactor

Methane/Ammonia Radical Formation during High Temperature Reactions in Swirl Burners

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