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Nox formation in GT-Combustors: A case study
Mohsen D. Emami
Associate professor, Mechanical Engineering Department
Isfahan University of Technology
Isfahan-IRAN
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities
Outline
• Some facts about Isfahan
• Air pollution in Isfahan
• Industrial Plants around Isfahan
• Description of the studied case
• A brief Literature Review
• Nox Models
• Results of the Numerical simulation
• Conclusions
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 2
Some facts about Isfahan
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 3
Air Pollution in Isfahan
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 4
Industrial Plants around Isfahan
• North: Refinery
• South: Chemical Plants (Polyacryl, DMT), power plant (~700 MW)
• East: Industrial Zone (Small & Medium size factories/workshops)
• West: cement plant, power plant (~1300 MW)
• NW: Petrochemical plant, power plant(~1600 MW)
• SW: Iron- and steel-making complex
• NE: Airport , Industrial Zone (Small & Medium size factories/workshops)
stationary 24
mobile 76 Source:IEPA(2009)
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 5
Description of the studied case
• 5 transportation lines of NG from south to north (3 passing from Isfahan)
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 6
A brief Literature Review
• Barths et al. in 1998: ULFM pollutant formation in an aircraft gas-turbine combustor
• Sharma and Som in 2004: fuel volatility and spray parameters on combustion characteristics and NOx emission in a gas turbine combustor (less volatility increases Nox)
• Fichet and Kannichen 2010: NOx emissions in gas turbines via a reactor network model.
• Gobbato et al in 2012 : computational fluid dynamics model for calculation of flow field and NOx emissions of a gas turbine combustor.
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 7
Nox Models
• Thermal Nox:
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NOx Models (Continued)
• Prompt Nox model
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Nox Models (Continued)
• N2O intermediate
• Assumptions: [H]0 ; [O] & [OH] partial equilibrium
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Source term of transport eq. for NO
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Problem Details for Numerical Simulations
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 12
Results(Combustion results)
-0.5
0
0.5
1
1.5
2
2.5
Y
0.511.522.533.5Z
1
23
2
4
3 5
7
8
7
10 0.9091
9 0.8182
8 0.7273
7 0.6364
6 0.5455
5 0.4545
4 0.3636
3 0.2727
2 0.1818
1 0.0909
Mixture fraction
-0.5
0
0.5
1
1.5
2
2.5
Y
0.511.522.533.5Z
8
6
76
8
6
9
10
12
10
8
10
8
9
6
12 2186
11 2166
10 2097
9 2075
8 1898
7 1752
6 1605
5 1313
4 1020
3 727
2 581
1 434
Temperature (K)
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 13
Results (NOx results)
Y
-0.5
0
0.5
1
1.5
2
2.5
Z
0.511.522.533.5
8.
8.
8.6.
7.
6.
6.5.
6.
2.4.
3. 1.
8. 4.500x10-04
7. 3.288x10-04
6. 2.402x10-04
5. 1.755x10-04
4. 1.282x10-04
3. 9.367x10-05
2. 6.844x10-05
1. 5.000x10-05
Mass Fraction of Thermal NOx
Y
-0.5
0
0.5
1
1.5
2
2.5
Z
0.511.522.533.5
8
8
8
75
6
4
32
7
6
7
6
5
4
4
8 6.859x10-05
7 6.001x10-05
6 5.144x10-05
5 4.287x10-05
4 3.429x10-05
3 2.572x10-05
2 1.715x10-05
1 8.573x10-06
Mass Fraction of Prompt NOx
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 14
Y
-0.5
0
0.5
1
1.5
2
2.5
Z
0.511.522.533.5
8
8
8
8
6
8
7
762
4
11
7
6
8 5.181x10-07
7 4.533x10-07
6 3.886x10-07
5 3.238x10-07
4 2.591x10-07
3 1.943x10-07
2 1.295x10-07
1 6.476x10-08
Mass Fraction on N2O-intermediate NOx
Results (NOx results….continued)
Y
-0.5
0
0.5
1
1.5
2
2.5
Z
0.511.522.533.5
8
8
8
7
6
5
5
4
33
2
7
6
6
8 4.790x10-04
7 4.191x10-04
6 3.592x10-04
5 2.994x10-04
4 2.395x10-04
3 1.796x10-04
2 1.197x10-04
1 5.987x10-05
Mass Fraction of Thermal & Prompt NOx
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 15
Results (Influence of air to fuel ratio)
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Results (Influence of combustion air temperature)
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Results (Influence of swirl angle)
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Results (Influence of fuel temperature)
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Results (summary of Effects of combustion parameters on Temperature and Nox)
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Conclusions
• Thermal Nox and Prompt Nox are the dominant mechanisms in Nox formation in GT combustors. The Nox generation of the former mechanism is an order-of-magnitude higher than the latter.
• Increasing air temperature is more effective in generating Nox than increasing the fuel stream temperature.
• Increasing AFR above the stoichiometric value decreases the outlet Nox due to dilution effect, as well as temperature reduction.
• There exists an optimum swirl angle that enhances the combustion and yields acceptable Nox at the outlet.
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 21
Thanks to: National Iranian Gas Company (NIGC) Sharif University of Technology World Learning American Association for Advancement of Science (AAAS) National Academy of Science International Visitors Program UC Irvine USC
3-5 Sep. 2013 US-Iran Symposium on Air Pollution in Megacities 22