nox-modeling in cfd for coal/biomassacerc.byu.edu/news/conference/2009/presentations/jesper...
TRANSCRIPT
NOX-modeling in CFD for coal/biomass
Jesper Møller Pedersen1, Larry Baxter2, Søren Knudsen Kær3, Peter Glarborg4, Søren Lovmand Hvid1, Helle Junker1
1DONG Energy, Denmark2BYU, USA3AAU, Denmark4DTU, Denmark
Contents
MotivationNOx-modelH, O and OH radical modelsCFD solutions for low NOX swirl-burnerConclusion
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Motivation
The best NOX-models are too large to be used in combination with CFD
SKG03: 510 reactions, 74 speciesGRI-Mech 3.0: 325 reactions, 52 speciesKILPINEN97: 353 reactions, 57 species
Simple models exist based on global reaction ratesDe Soete: 4 reactions, 3 species
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Fuel-NHCN
NH3
NO
N2
+O2
+NO
Contents
MotivationNOx-modelH, O and OH radical modelsCFD solutions for low NOX swirl-burnerConclusion
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NOx-model
NOx-model by Lars Storm Pedersen (LSP)• 3 active species, 8 steady state species, 36 reactions
• Reaction rates for NO, HCN and NH3 become complex algebraic functionso R = f(NO, HCN, NH3, H, O, OH, H2O, O2, H2, CO, CO2, N2)
• Difficult to include in CFD • Obtainable from CFD
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Fuel-NHCN
NH3
NO
N2
+O2
+NO
NO and O2 from plug flow reactor (PFR) simulation with SKG03
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H2 = CO = 4 vol%, H2O = CO2 = 6 vol%, Temperature 1800 K
NH3 = 200 ppm, HCN = 300 ppm, NO = 0 ppm
NO from PFR with SKG03, LSP and De Soete
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H2 = CO = 4 vol%, H2O = CO2 = 6 vol%, Temperature 1800 K
NH3 = 200 ppm, HCN = 300 ppm, NO = 0 ppm
Advantages/Disadvantages with the LSP
Advantages:Reacts as fast as the complex model. De Soete reacts slower.NO levels comparable to complex model. De Soete is off especially at fuel-rich conditions.
Disadvantages:Knowledge of H2O, O2, H2, CO and CO2 required. De Soete requires only O2.
The LSP model requires knowledge of H, O and OH radicals.
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Contents
MotivationNOx-modelH, O and OH radical modelsCFD solutions for low NOX swirl-burnerConclusion
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H-radical models
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8 reactions3 major species O2, H2 and H2O3 radical species H, O and OH
4 solution methods:
• Partial: H, O and OH from partial equilibrium of reaction 1, 4 & 5
• H-steady: H in steady state, O and OH from partial equilibrium of 4 & 5
• H&O-steady: H and O in steady state, OH from partial equilibrium of 5
• H&O&OH-steady: H, O and OH in steady state.
H and O from PFR with SKG03 and the 4 radical models
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H2 = CO = 4 vol%, H2O = CO2 = 6 vol%,
Temperature 1800 K
LSP in combination with radical models compared to SKG03 and De Soete
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H2 = CO = 4 vol%, H2O = CO2 = 6 vol%, Temperature 1800 K
NH3 = 200 ppm, HCN = 300 ppm, NO = 0 ppm
Contents
MotivationNOx-modelH, O and OH radical modelsCFD solutions for low NOX swirl-burnerConclusion
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Two fuel low-Nox swirl-burner reactor
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Fuel line 1: Center
Fuel line 2: Annulus
Swirled secondary air
Stochiometry: ɸ = 0.81Thermal load: 137 kWFuels straw and Coal 50/50 on energy basis
CFD setup:standard k-εDO for radiationEDC for chem-turb. interaction
Ø = 75 cm
NO in the near burner field
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NO [ppm]Measured
NO [ppm]De Soete
NO [ppm]LSP
Main species
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CO [%]Measured
O2 [%]Measured
CO [%]CFD
O2 [%]CFD
Conclusion
PFR simulations with LSP captures the trends of SKG03.
Radical models greatly influence the LSP. The H,O & OH steady state model is best in PFR simulations.
Solutions for temperature, major species, velocity, turbulence etc. need to be good for complex NOX-modeling to make sense.
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