scholarly journals The story of NCN as a key species in prompt-NO formation

2021 ◽  
Vol 87 ◽  
pp. 100940
Author(s):  
Nathalie Lamoureux ◽  
Pascale Desgroux ◽  
Matthias Olzmann ◽  
Gernot Friedrichs
Keyword(s):  
No Formation ◽  
Key Species

A Model for the Prediction of Thermal, Prompt, and Fuel NOx Emissions From Combustion Turbines

1986 ◽  
Vol 108 (2) ◽  
pp. 340-347 ◽  
Author(s):  
J. L. Toof
Keyword(s):  
Alternative Fuels ◽  
Water Injection ◽  
Flame Temperature ◽  
Equilibrium Concentration ◽  
Flame Length ◽  
Nox Emissions ◽  
No Formation ◽  
Finite Concentration ◽  
Key Species ◽  
Hydrocarbon Chemistry

A model has been developed for the prediction of NOx emissions from combustion turbines. Thermal, prompt, and fuel NO are all treated and are all assumed to be formed at a stoichiometric equivalence ratio. Prompt and fuel NO are assumed to be fast with respect to thermal NO and establish a finite concentration of NO at the beginning of the thermal NO formation process. Thermal NO is calculated via the extended Zeldovich mechanism; a thermal NO formation time is determined from the ratio of flame length to convective velocity within the combustor. Prompt NO is assumed to be formed from the hydrocarbon chemistry and is related to the equilibrium concentration of NO rather than to O-atom overshoot. Fuel NO is calculated assuming an indispensible intermediate in the formation mechanism and a constant Fenimore α parameter for combustion turbine flames. The model employs equilibrium hydrocarbon chemistry; the flame temperature and concentrations of key species are determined in an equilibrium subroutine. The effects of water or steam injection and ambient humidity are included through their impact on the flame temperature and species concentrations. The model has been applied to can-type combustors and its accuracy has been verified by data on high and low nitrogen fuels with and without water injection, and on combustors of different geometry. The treatment of all three mechanisms of NO formation is unique to this model and permits prediction of emissions for the range of conventional and alternative fuels encountered in industrial combustion turbines.

WET BURNING – THE MODERN TREND IN ENVIRONMENTAL BENIGN FUEL COMBUSTION AND IN SOLUTION TO THE PROBLEM OF SUSTAINABLE DEVELOPMENT OF THE POWER GENERATION

2018 ◽  
pp. 96-117 ◽  
Author(s):  
B. S. Soroka
Keyword(s):  
Numerical Simulation ◽  
Nitrogen Oxides ◽  
Chemical Kinetics ◽  
Fuel Combustion ◽  
Transport Processes ◽  
Cfd Modeling ◽  
Furnace Chamber ◽  
Modern Trend ◽  
Atmospheric Air ◽  
No Formation

The article considers the role and place of water and water vapor in combustion processes with the purpose of reduction the effluents of nitrogen oxides and carbon oxide. We have carried out the complex of theoretical and computational researches on reduction of harmful nitrogen and carbon oxides by gas fuel combustion in dependence on humidity of atmospheric air by two approaches: CFD modeling with attraction of DRM 19 chemical kinetics mechanism of combustion for 19 components along with Bowman’s mechanism used as “postprocessor” to determine the [NO] concentration; different thermodynamic models of predicting the nitrogen oxides NO formation. The numerical simulation of the transport processes for momentum, mass and heat being solved simultaneously in the united equations’ system with the chemical kinetics equations in frame of GRI methane combustion mechanism and NO formation calculated afterwards as “postprocessor” allow calculating the absolute actual [CO] and [NO] concentrations in dependence on combustion operative conditions and on design of furnace facilities. Prediction in frame of thermodynamic equilibrium state for combustion products ensures only evaluation of the relative value of [NO] concentration by wet combustion the gas with humid air regarding that in case of dry air – oxidant. We have developed the methodology and have revealed the results of numerical simulation of impact of the relative humidity of atmospheric air on harmful gases formation. Range of relative air humidity under calculations of atmospheric air under impact on [NO] and [CO] concentrations at the furnace chamber exit makes φ = 0 – 100%. The results of CFD modeling have been verified both by author’s experimental data and due comparing with the trends stated in world literature. We have carried out the complex of the experimental investigations regarding atmospheric air humidification impact on flame structure and environmental characteristics at natural gas combustion with premixed flame formation in open air. The article also proposes the methodology for evaluation of the nitrogen oxides formation in dependence on moisture content of burning mixture. The results of measurements have been used for verification the calculation data. Coincidence of relative change the NO (NOx) yield due humidification the combustion air revealed by means of CFD prediction has confirmed the qualitative and the quantitative correspondence of physical and chemical kinetics mechanisms and the CFD modeling procedures with the processes to be studied. A sharp, more than an order of reduction in NO emissions and simultaneously approximately a two-fold decrease in the CO concentration during combustion of the methane-air mixture under conditions of humidification of the combustion air to a saturation state at a temperature of 325 K.

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

2019 ◽  
Author(s):  
Hassan Harb ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Valence Electron ◽  
Density Functional Theory Calculations ◽  
Electron Configuration ◽  
Functional Theory ◽  
Key Species ◽  
Pi Orbitals ◽  
Lanthanide Hydroxide ◽  
Linear Geometry

Lanthanide hydroxides are key species in a variety of catalytic processes and in the preparation of corresponding oxides. This work explores the fundamental structure and bonding of the simplest lanthanide hydroxide, LnOH (Ln=La-Lu), using density functional theory calculations. Interestingly, the calculations predict that all structures of this series will be linear. Furthermore, these results indicate a valence electron configuration featuring an occupied sigma orbital and two occupied pi orbitals for all LnOH compounds, suggesting that the lanthanide-hydroxide bond is best characterized as a covalent triple bond.

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

2019 ◽  
Author(s):  
Hassan Harb ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Valence Electron ◽  
Density Functional Theory Calculations ◽  
Electron Configuration ◽  
Functional Theory ◽  
Key Species ◽  
Pi Orbitals ◽  
Lanthanide Hydroxide ◽  
Linear Geometry

Lanthanide hydroxides are key species in a variety of catalytic processes and in the preparation of corresponding oxides. This work explores the fundamental structure and bonding of the simplest lanthanide hydroxide, LnOH (Ln=La-Lu), using density functional theory calculations. Interestingly, the calculations predict that all structures of this series will be linear. Furthermore, these results indicate a valence electron configuration featuring an occupied sigma orbital and two occupied pi orbitals for all LnOH compounds, suggesting that the lanthanide-hydroxide bond is best characterized as a covalent triple bond.

Nω-Hydroxy-L-arginine and Its Homologues. Chemical and Biological Properties. A Review

2004 ◽  
Vol 69 (3) ◽  
pp. 499-510 ◽  
Author(s):  
Petra Beranová ◽  
Karel Chalupský ◽  
Gustav Entlicher
Keyword(s):  
Inhibitory Activity ◽  
Biological Activities ◽  
Biological Effects ◽  
Biological Properties ◽  
No Synthase ◽  
Point Of View ◽  
No Donor ◽  
Good Substrate ◽  
No Formation ◽  
Vasorelaxant Activity

Nω-Hydroxy-L-arginine (NOHA) is a stable intermediate in NO formation from L-arginine catalyzed by NO synthase (NOS). Apparently, NOHA can be released and serve as a stable reserve NO donor (as a substrate of NOS) or transported and exert its own biological effects. It shows endothelium-dependent as well as endothelium-independent vasorelaxant activity. The latter case indicates that NOHA can be metabolized by pathways independent of NOS. These possibilities are discussed in detail. Of the available NOHA homologues homo-NOHA is a good substrate of NOS while nor-NOHA seems to be a very poor substrate of this enzyme. On the contrary, nor-NOHA exerts arginase inhibitory activity 20 times higher than NOHA whereas homo-NOHA is inactive. Detailed investigation of biological activities of NOHA and its homologues seems to be promising from the pharmacological point of view. A review with 43 references.

scholarly journals Sensitivity of the Norwegian and Barents Sea Atlantis end-to-end ecosystem model to parameter perturbations of key species

PLoS ONE ◽  
2019 ◽  
Vol 14 (2) ◽  
pp. e0210419 ◽  
Author(s):  
Cecilie Hansen ◽  
Kenneth F. Drinkwater ◽  
Anne Jähkel ◽  
Elizabeth A. Fulton ◽  
Rebecca Gorton ◽  
...  
Keyword(s):  
Barents Sea ◽  
Ecosystem Model ◽  
Key Species ◽  
Parameter Perturbations ◽  
End To End

Enzyme and osmotic adjustment compounds of key species can help explain shrub encroachment in a semiarid sandy grassland

2019 ◽  
Vol 101 ◽  
pp. 541-551 ◽  
Author(s):  
Liu Yang ◽  
Liming Lai ◽  
Jihua Zhou ◽  
Sangui Yi ◽  
Qinglin Sun ◽  
...  
Keyword(s):  
Osmotic Adjustment ◽  
Shrub Encroachment ◽  
Key Species ◽  
Sandy Grassland

Numerical Analysis on the CO-NO Formation Production near Burner Throat in Swirling Flow Combustion System

2014 ◽  
Vol 69 (2) ◽  
Author(s):  
Mohamad Shaiful Ashrul Ishak ◽  
Mohammad Nazri Mohd Jaafar
Keyword(s):  
Swirling Flow ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Recirculation Region ◽  
Mixing Enhancement ◽  
Ansys Fluent ◽  
Pressure Losses ◽  
No Formation ◽  
Swirl Angle ◽  
Air Mixing

The main purpose of this paper is to study the Computational Fluid Dynamics (CFD) prediction on CO-NO formation production inside the combustor close to burner throat while varying the swirl angle of the radial swirler. Air swirler adds sufficient swirling to the inlet flow to generate central recirculation region (CRZ) which is necessary for flame stability and fuel air mixing enhancement. Therefore, designing an appropriate air swirler is a challenge to produce stable, efficient and low emission combustion with low pressure losses. A liquid fuel burner system with different radial air swirler with 280 mm inside diameter combustor of 1000 mm length has been investigated. Analysis were carried out using four different radial air swirlers having 30°, 40°, 50° and 60° vane angles. The flow behavior was investigated numerically using CFD solver Ansys Fluent. This study has provided characteristic insight into the formation and production of CO and pollutant NO inside the combustion chamber. Results show that the swirling action is augmented with the increase in the swirl angle, which leads to increase in the center core reverse flow, therefore reducing the CO and pollutant NO formation. The outcome of this work will help in finding out the optimum swirling angle which will lead to less emission.  

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