Nox formation in GT- Combustors: A case study - AAAS · Nox formation in GT-Combustors: A case...

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


Air Pollution in Isfahan


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)


Description of the studied case

• 5 transportation lines of NG from south to north (3 passing from Isfahan)


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.


Nox Models

• Thermal Nox:


NOx Models (Continued)

• Prompt Nox model


Nox Models (Continued)

• N2O intermediate

• Assumptions: [H]0 ; [O] & [OH] partial equilibrium


Source term of transport eq. for NO


Problem Details for Numerical Simulations


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)


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


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


Results (Influence of air to fuel ratio)


Results (Influence of combustion air temperature)


Results (Influence of swirl angle)


Results (Influence of fuel temperature)


Results (summary of Effects of combustion parameters on Temperature and Nox)


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.


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


Questions?

[email protected]


Nox formation in GT- Combustors: A case study - AAAS · Nox formation in GT-Combustors: A case...

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