Towards the development of an efficient low-NOx ammonia combustor for a micro gas turbine

Okafor, Ekenechukwu C.; Somarathne, Kapuruge Don Kunkuma Amila; Hayakawa, Akihiro; Kudo, Taku; Kurata, Osamu; Iki, Norihiko; Kobayashi, Haruo

doi:10.1016/j.proci.2018.07.083

Cited by 273 publications

(115 citation statements)

References 20 publications

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“…NH 3 can be directly oxidized in the bulk liquid by means of electrochemical fuel cells (Rees and Compton, 2011) or burned together to methane to (Valera-Medina et al, 2017). This last option would have two drawbacks: (1) the increase of NO x during combustion which can be avoid by using suitable burners designs (Okafor et al, 2018) or catalyzers (Hinokuma et al, 2018); (2) the energy required for gas stripping which is generally higher than that energy recovered (van Eekert et al, 2012). Moreover, costs associated to pH fitting made no economically viable these processes to valorize ammonia from the liquid fraction of digestates.…”

Section: Ammonia Combustionmentioning

confidence: 99%

Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review

Campos

Crutchik

Franchi

et al. 2019

Front. Sustain. Food Syst.

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Anaerobic digestion (AD) is commonly used for the stabilization of agro-food wastes and recovery of energy as methane. Since AD removes organic C but not nutrients (N and P), additional processes to remove them are usually applied to meet the stringent effluent criteria. However, in the past years, there was a shift from the removal to the recovery of nutrients as a result of increasing concerns regarding limited natural resources and the importance given to the sustainable treatment technologies. Recovering N and P from anaerobically pretreated agro-food wastes as easily transportable and marketable products has gained increasing importance to meet both regulatory requirements and increase revenue. For this reason, this review paper gives a critical comparison of the available and emerging technologies for N and P recovery from AD residues.

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Section: Ammonia Combustionmentioning

confidence: 99%

Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review

Campos

Crutchik

Franchi

et al. 2019

Front. Sustain. Food Syst.

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“…3 More recent investigations [48][49][50] have achieved some success in stabilizing ammonia-air flames in simplified laboratory models of gas-turbine combustors while, at the same time, reducing NO x and N 2 O emissions to values closer to the regulatory limits. Early studies have illustrated, already several decades ago, some of the challenges emerging by substitution of ammonia to hydrocarbon fuels in gas turbines, due to the low reactivity and poor combustion characteristics of ammonia.…”

Section: Combustion Behavior Of Ammonia-derived Fuels and Comparison mentioning

confidence: 99%

“…Early studies have illustrated, already several decades ago, some of the challenges emerging by substitution of ammonia to hydrocarbon fuels in gas turbines, due to the low reactivity and poor combustion characteristics of ammonia. 3 More recent investigations [48][49][50] have achieved some success in stabilizing ammonia-air flames in simplified laboratory models of gas-turbine combustors while, at the same time, reducing NO x and N 2 O emissions to values closer to the regulatory limits. These advances have, however, been attained at the cost of a considerable increase of the fuel-air equivalence ratio (beyond stoichiometry) and of the residence time inside the combustion chamber, thereby raising possible issues with ammonia slip and reducing the fuel flexibility (fuel-switching capabilities) of the combustion system, respectively.…”

Section: Combustion Behavior Of Ammonia-derived Fuels and Comparison mentioning

confidence: 99%

An updated short chemical‐kinetic nitrogen mechanism for carbon‐free combustion applications

et al. 2019

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Chemical-kinetic combustion mechanisms for hydrogen-oxygen-nitrogen systems, motivated originally by concerns about NO x emissions during hydrogen burning, have recently acquired renewed interest as a result of the possibility of employing ammonia-hydrogen mixtures in gas turbines and reciprocating engines as drop-in fuel to replace the use of natural gas. Specifically, this is of relevance to the implementation of engineering approaches for economical power generation with carbon sequestration or to large-scale energy-storage schemes, based on hydrogen or efficient hydrogen carriers such as ammonia. Because computational investigations are facilitated by short mechanisms (since the use of large mechanisms is often prohibitively expensive in reactive flow simulations), in response to the original concerns, a short nitrogen mechanism was developed in San Diego in the 1990s (not updated since 2004), without consideration of ammonia combustion. In view of the renewed interest in this topic, that mechanism has now been expanded to encompass 60 elementary steps among 19 reactive chemical species, including ammonia burning and NO x production, as reported herein, greatly improving predictions. With particular attention to high reactant temperatures and high-pressure conditions, relevant to industrial applications, it is shown that the present short mechanism retains satisfactory accuracy, exhibiting deviations that in most cases are within acceptable bounds (±20%). The revisions maintain the shortness of the original mechanism, adding only one more reactive species and six more elementary steps (while updating values of rate parameters of nine other steps, on the basis of newly available information). In addition, the short mechanism is applied herein to the analysis of fundamental combustion properties of ammonia/hydrogen/nitrogen-air laminar premixed flames, at unstrained and strained conditions, for comparison with methane-air flames as a reference gas-turbine fuel. It is found by comparing carbon-free and hydrocarbon laminar flames that these reactive mixtures, even if characterized by nearly identical adiabatic flame temperature and laminar flame speeds, nevertheless exhibit substantially different resistance to strain, with the ammonia/hydrogen flames exceeding the strain limit of methane flames by a factor of 5.

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“…These unsurprising results provided clues to improve the combustion of this fuel using modern stabilization techniques (i.e., swirling flows, better atomization, doping, etc.). Kobayashi et al [30] set a new trend in the development of new combustion concepts, eventually leading to the recognition of fluid mechanic stabilized systems with enough residence time, recirculation, and mixing to efficiently burn ammonia [31]. Simultaneously, works performed by Valera-Medina et al [32] and Hewlett et al [33] have also demonstrated the efficient use of various ammonia blends (i.e., methane, hydrogen, coke oven gas) under a great diversity of conditions (i.e., humidified, highly oxygenated, etc.)…”

Section: Introductionmentioning

confidence: 99%

Numerical Predictions of a Swirl Combustor Using Complex Chemistry Fueled with Ammonia/Hydrogen Blends

et al. 2020

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Ammonia, a chemical that contains high hydrogen quantities, has been presented as a candidate for the production of clean power generation and aerospace propulsion. Although ammonia can deliver more hydrogen per unit volume than liquid hydrogen itself, the use of ammonia in combustion systems comes with the detrimental production of nitrogen oxides, which are emissions that have up to 300 times the greenhouse potential of carbon dioxide. This factor, combined with the lower energy density of ammonia, makes new studies crucial to enable the use of the molecule through methods that reduce emissions whilst ensuring that enough power is produced to support high-energy intensive applications. Thus, this paper presents a numerical study based on the use of novel reaction models employed to characterize ammonia combustion systems. The models are used to obtain Reynolds Averaged Navier-Stokes (RANS) simulations via Star-CCM+ with complex chemistry of a 70%–30% (mol) ammonia–hydrogen blend that is currently under investigations elsewhere. A fixed equivalence ratio (1.2), medium swirl (0.8), and confined conditions are employed to determine the flame and species propagation at various operating atmospheres and temperature inlet values. The study is then expanded to high inlet temperatures, high pressures, and high flowrates at different confinement boundary conditions. The results denote how the production of NOx emissions remains stable and under 400 ppm, whilst higher concentrations of both hydrogen and unreacted ammonia are found in the flue gases under high power conditions. The reduction of heat losses (thus higher temperature boundary conditions) has a crucial impact on further destruction of ammonia post-flame, with a raise in hydrogen, water, and nitrogen through the system, thus presenting an opportunity of combustion efficiency improvement of this blend by reducing heat losses. Final discussions are presented as a method to raise power whilst employing ammonia for gas turbine systems.

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Towards the development of an efficient low-NOx ammonia combustor for a micro gas turbine

Cited by 273 publications

References 20 publications

Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review

Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review

An updated short chemical‐kinetic nitrogen mechanism for carbon‐free combustion applications

Numerical Predictions of a Swirl Combustor Using Complex Chemistry Fueled with Ammonia/Hydrogen Blends

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