Performances and emission characteristics of NH3–air and NH3CH4–air combustion gas-turbine power generations

Kurata, Osamu; Iki, Norihiko; Matsunuma, Takayuki; Inoue, Takahiro; Tsujimura, Taku; Furutani, Hirohide; Kobayashi, Haruo; Hayakawa, Akihiro

doi:10.1016/j.proci.2016.07.088

Cited by 309 publications

(134 citation statements)

References 14 publications

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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%

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

confidence: 99%

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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“…Xiao et al 22 numerically investigated the premixed combustion of ammonia/methane in terms of various flame properties. Kurata et al 28 performed successful NH 3 /CH 4 /air operation tests in gas turbine. However, it was found that the NO emission of the gas turbine increases significantly with increase of ammonia concentration.…”

Section: Introductionmentioning

confidence: 99%

Experimental and modeling study on ignition delay of ammonia/methane fuels

et al. 2020

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Summary Ammonia mixed with methane is a potential clean fuel for engine applications toward a low carbon economy. Studies are scarce on ignition phenomenon for ammonia/methane fuels in literature. In the present study, the ignition characteristics for ammonia–methane–air mixtures have been investigated by both experimental measurements and numerical simulations. Ignition processes of a 60%ammonia/40%methane (mol%) fuel blend were investigated with shock‐tube experiments. Measurements of the ignition delay times were performed behind reflected shock waves for such fuel/air mixtures with different equivalence ratios of 0.5, 1, and 2, at pressures around 2 and 5 atm within the temperature range of 1369 to 1804 K. Experimental results were then compared with numerical prediction results employing detailed kinetic mechanism, which showed satisfactory agreement within most of the range of the temperatures, equivalence ratios, and pressures investigated. Within the temperature range of 1300 to 1900 K, pressure range of 1 to 10 atm, equivalence ratio range of 0.5 to 2, and methane proportion range of 0% to 50% in fuel blends, the impacts of temperature, pressure, equivalence ratio, and methane additive were simulated on the ignition delay times of the fuel blends based upon the numerical model. It was found that the improvement of ammonia/methane ignition is significant with the increase of temperature, pressure, and methane additive while it is relatively not sensitive to equivalence ratio within the studied conditions. This suggests a promising potential of such fuel blends in real engine application. In addition to the calculations, reaction sensitivity analyses were also performed to have a deep insight into the observed differences between ammonia/methane/air ignition delay times with variation of conditions.

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“…In recent years, various tests and numerical analysis have been conducted to develop low-emission combustors for NH 3 Iki et al, 2015, Okafor et al, 2019b, Kurata et al, 2017, Valera-Medina et al, 2015. carried out laminar NH 3 /air flame tests and 1D, numerical studies; they showed that low NO x and unburnt NH 3 are produced by rich combustion, with an equivalence ratio of 1.1.…”

Section: Introductionmentioning

confidence: 99%

Emission characteristics of a lean-premixed ammonia/natural-gas gas-turbine combustor and effect of secondary ammonia injection

Ito

Uchida

Katō

et al. 2019

Mechanical Engineering Journal

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To develop an NH 3 /natural gas-fired gas-turbine combustor with minimal modifications to a natural gas-fired combustor, the effect of co-firing NH 3 with natural gas on emission characteristics and combustion efficiency is investigated experimentally under atmospheric pressure. In this experiment, a lean premixed combustor that has basically the same structure and same size as those of an actual 2 MW-class gas-turbine combustor is used and the effects of equivalence ratio, NH 3 mixing ratio, and NH 3 injection method were evaluated. The results of NH 3 /natural gas/air premixed combustion show that NO emission shows a local maximum at a certain NH 3 mixing ratio, when equivalence ratio is fixed. The NH 3 mixing ratio where this maximal NO emission occurs shifts to higher ratios, when equivalence ratio is increased towards stoichiometric condition. At the same time, the maximal NO emission increases. The variation of NO x concentration can be explained by the change in the selective non-catalytic reduction (SNCR) effect, which depends on temperature and NH 3 concentration in the flame. In particular, the influence of NH 3 concentration on the SNCR effect appears to be stronger than that of temperature. On the other hand, concentrations of N 2 O and unburnt NH 3 increase with increasing NH 3 mixing ratio in the very lean case, when decreasing flame temperature approaches the lean flame blow-off limit. When NH 3 is directly injected into the lean premixed flame of natural gas, NO and N 2 O concentrations are simultaneously reduced; this is attributed to the local increase of NH 3 concentration and flame temperature. Finally, it is proposed to consider NO x as unburnt component in the calculation of combustion efficiency. When NH 3 is fired, the enthalpy content of NO x is very high, and its influence on combustion efficiency cannot be ignored. It is also found that NH 3 direct injection is effective in increasing combustion efficiency, achieving more than 99.6% of the combustion efficiency even if the enthalpy of NO x is considered.

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Performances and emission characteristics of NH3–air and NH3CH4–air combustion gas-turbine power generations

Cited by 309 publications

References 14 publications

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

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

Experimental and modeling study on ignition delay of ammonia/methane fuels

Emission characteristics of a lean-premixed ammonia/natural-gas gas-turbine combustor and effect of secondary ammonia injection

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