burning natural gas / hydrogen mixtures in dln gas turbines
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Vortrag: EU-Turbines workshop_final, 06.10.2011Institute of CombustionTechnology
Burning Natural Gas / Hydrogen Mixtures inDLN Gas Turbines
M. Aigner, EU-Turbines & GERG Workshop, Brussels 12. October 2011
Outline
Combustion Fundamentals Natural Gas (NG)Hydrogen
Ignition delay time
Laminar flame speed (flashback risk)
Flame temperature (emissions)
Wobbe-Index
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 2 Institute of Combustion Technology
Combustion Fundamentals Natural Gas (NG)Hydrogen
Ignition delay time
Laminar flame speed (flashback risk)
Flame temperature (emissions)
Wobbe-Index
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
Outline
Combustion Fundamentals Natural Gas (NG)Hydrogen
Ignition delay time
Laminar flame speed (flashback risk)
Flame temperature (emissions)
Wobbe-Index
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 3 Institute of Combustion Technology
Combustion Fundamentals Natural Gas (NG)Hydrogen
Ignition delay time
Laminar flame speed (flashback risk)
Flame temperature (emissions)
Wobbe-Index
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
Combustion Fundamentals - Physical Properties
Natural gas (92%vol CH4, 8%vol C2H6)
Density0.699kg/Nm³
LHV49.564MJ/kg
34.657MJ/Nm³
Specific heat capacity2.134kJ/kg∙K @ 288.15K4.062kJ/kg∙K @ 723.15K4.230kJ/kg∙K @ 923.15K
Hydrogen (100%vol H2)
Density0.082kg/Nm³
LHV119.494MJ/kg
9.831MJ/Nm³
Specific heat capacity14.224kJ/kg∙K @ 288.15K14.480kJ/kg∙K @ 723.15K14.838kJ/kg∙K @ 923.15K
Evaluation of Combustor Concepts for H2 Combustion > 08.02.2011
Slide 4 > Final Report
Natural gas (92%vol CH4, 8%vol C2H6)
Density0.699kg/Nm³
LHV49.564MJ/kg
34.657MJ/Nm³
Specific heat capacity2.134kJ/kg∙K @ 288.15K4.062kJ/kg∙K @ 723.15K4.230kJ/kg∙K @ 923.15K
Hydrogen (100%vol H2)
Density0.082kg/Nm³
LHV119.494MJ/kg
9.831MJ/Nm³
Specific heat capacity14.224kJ/kg∙K @ 288.15K14.480kJ/kg∙K @ 723.15K14.838kJ/kg∙K @ 923.15K
Combustion Fundamentals - Ignition Delay TimeNG/H2 Blends
Boundary conditions:p = 16 barΦ = 0.5Oxidizer: Air
Effects:Strong decrease infor increasing T0
Strong decrease infor higher H2 content
Inflection in (T0) for100% H2, typical forH2-System
*
Igni
tion
dela
y tim
e[s
]
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 5 Institute of Combustion Technology
Boundary conditions:p = 16 barΦ = 0.5Oxidizer: Air
Effects:Strong decrease infor increasing T0
Strong decrease infor higher H2 content
Inflection in (T0) for100% H2, typical forH2-System
*
*rest: NG
**
Igni
tion
dela
y tim
e[s
]
Combustion Fundamentals - Laminar Flame SpeedNG/H2 Blends
Boundary conditions:p = 16 barT0 = 723 KOxidizer: Air
Effects:Increase in sL for:
higher Tad (i.e. Φ) atconstant H2 content
higher H2 content atconstant Tad (i.e. Φ)
*
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 6 Institute of Combustion Technology
*
Boundary conditions:p = 16 barT0 = 723 KOxidizer: Air
Effects:Increase in sL for:
higher Tad (i.e. Φ) atconstant H2 content
higher H2 content atconstant Tad (i.e. Φ)
*rest: NG
***
Laminar Flame Speed –H2 Mixture & Dilution
Numerical & experimental datareported by Mu et al. [3]
Fuel50%vol H2; 50%vol CODiluent: H2O, N2 or CO2
Boundary conditionsp = p∞, T = T∞
EffectsDecrease in sL for increasingdilutionDecrease in sL depending ondilution medium
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 7 Institute of Combustion Technology
no dilution H2O dilution N2 dilution CO2 dilution
Numerical & experimental datareported by Mu et al. [3]
Fuel50%vol H2; 50%vol CODiluent: H2O, N2 or CO2
Boundary conditionsp = p∞, T = T∞
EffectsDecrease in sL for increasingdilutionDecrease in sL depending ondilution medium
Dilution amount:Xd = Vdiluent / Vfuel
Combustion Fundamentals - Adiabatic Flame TemperatureNG/H2 Blends
Boundary conditions:p = 16 barT0 = 723 KOxidizer: Air
Effects:Increase in Tad for higherΦ at constant H2 content
Higher Tad for increasingH2 content at constant Φ
Same slope for allconsidered NG/H2 blends
*
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 8 Institute of Combustion Technology
*
Boundary conditions:p = 16 barT0 = 723 KOxidizer: Air
Effects:Increase in Tad for higherΦ at constant H2 content
Higher Tad for increasingH2 content at constant Φ
Same slope for allconsidered NG/H2 blends
*rest: NG
***
Combustion Fundamentals - Wobbe IndexNG/H2 Blends
FuelNG / H2
Wobbe Index(Hu)
Volume/Volume NG
Density /Density NG
[Vol.%] [MJ/mN3] [-] [-]
100 / 0 48.1 1.0 1.00
80 / 20 45.5 1.2 0.82
60 / 40 42.9 1.5 0.65
40 / 60 40.4 2.1 0.47
20 / 80 38.5 3.4 0.29
0 / 100 40.9 8.4 0.12
pure NG:
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 9 Institute of Combustion Technology
-Natural Gas (NG): approx. 95 vol. % methane
-Definition Wobbe Index: )/( ,, AirNormGasNorm
uu
HWI
FuelNG / H2
Wobbe Index(Hu)
Volume/Volume NG
Density /Density NG
[Vol.%] [MJ/mN3] [-] [-]
100 / 0 48.1 1.0 1.00
80 / 20 45.5 1.2 0.82
60 / 40 42.9 1.5 0.65
40 / 60 40.4 2.1 0.47
20 / 80 38.5 3.4 0.29
0 / 100 40.9 8.4 0.12pure H2:
Combustion Fundamentals - Summary
Physical propertiesLHVmass for H2 higher than for natural gasLHVvol for H2 lower than for natural gasSmaller mass flow & larger volume flux for H2 at constant thermal power inputcompared to natural gas Changes in fuel supply and fuel injection system required comparedto NG combustor
Ignition Delay TimeNG/H2-blends: shortage ignition delay time for increasing H2 contentDilution with CO; CO2; H2O: significant effect only for very high diluentcontentShortage in ignition delay time Flame stabilization closer to burner Increasing risk of auto-ignition in mixing section
Evaluation of Combustor Concepts for H2 Combustion > 08.02.2011
Slide 10 > Final Report
Physical propertiesLHVmass for H2 higher than for natural gasLHVvol for H2 lower than for natural gasSmaller mass flow & larger volume flux for H2 at constant thermal power inputcompared to natural gas Changes in fuel supply and fuel injection system required comparedto NG combustor
Ignition Delay TimeNG/H2-blends: shortage ignition delay time for increasing H2 contentDilution with CO; CO2; H2O: significant effect only for very high diluentcontentShortage in ignition delay time Flame stabilization closer to burner Increasing risk of auto-ignition in mixing section
Combustion Fundamentals - Summary
Adiabatic flame temperatureNG/H2-blends: increasing adiabatic flame temperature for increasing H2 contentDilution with CO; CO2; H2O: reduction in adiabatic flame temperatureIncreasing adiabatic flame temperature Operating point for constant turbine inlet temperature shifts towardsleaner conditions
Laminar flame speedNG/H2-blends: increase in laminar flame speed for increasing H2 contentDilution with CO; CO2; H2O: reduction in laminar flame speedIncrease in laminar flame speedTurbulent flame speed also depending on properties of turbulent flow field
Increasing risk of flash-back
Evaluation of Combustor Concepts for H2 Combustion > 08.02.2011
Slide 11 > Final Report
Adiabatic flame temperatureNG/H2-blends: increasing adiabatic flame temperature for increasing H2 contentDilution with CO; CO2; H2O: reduction in adiabatic flame temperatureIncreasing adiabatic flame temperature Operating point for constant turbine inlet temperature shifts towardsleaner conditions
Laminar flame speedNG/H2-blends: increase in laminar flame speed for increasing H2 contentDilution with CO; CO2; H2O: reduction in laminar flame speedIncrease in laminar flame speedTurbulent flame speed also depending on properties of turbulent flow field
Increasing risk of flash-back
Outline
Combustion Fundamentals Natural Gas (NG)Hydrogen
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
Evaluation of Combustor Concepts for H2 Combustion > 08.02.2011
Slide 12 > Final Report
Combustion Fundamentals Natural Gas (NG)Hydrogen
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
H2 capability of state-of-the-art GTs with DLN combustors
Nowadays GT Characteristics:lean premixed combustion system for burning natural gashigh efficiencylow emissions
Gas
Gasinjection
Vortexbreakdown
Swirler
Gas injection
Burner exit plane
Combustionair
Premixing(Gas Combustion air)
Flame front
Vortex breakdown
EV-Burner (Premix Combustion)
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 13 Institute of Combustion Technology
Source: Siemens SGT5-8000H press release
combustionsystem
Source: ALSTOM GT 26
Gas
Gasinjection
Vortexbreakdown
Swirler
Gas injection
Burner exit plane
Combustionair
Premixing(Gas Combustion air)
Flame front
Vortex breakdown
State-of-the-Art Combustion SystemsCurrent Combustor Concepts – Swirl-Stabilized
General descriptionSwirling flow generated via radial, axial or diagonal swirler Formation of inner & outer recirculation zone due to vortex breakdown Flame stabilization in shear layer between incoming fluid andrecirculated exhaust gasNon-premixed combustion Mixing of oxidizer & fuel within combustion chamber High local peak temperature due to combustion at/close to Φ = 1.0Premixed combustion Mixing of oxidizer & fuel prior combustion chamber In gas turbines often only technically premixed Local peak temperature depending on premixing quality
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 14 Institute of Combustion Technology
General descriptionSwirling flow generated via radial, axial or diagonal swirler Formation of inner & outer recirculation zone due to vortex breakdown Flame stabilization in shear layer between incoming fluid andrecirculated exhaust gasNon-premixed combustion Mixing of oxidizer & fuel within combustion chamber High local peak temperature due to combustion at/close to Φ = 1.0Premixed combustion Mixing of oxidizer & fuel prior combustion chamber In gas turbines often only technically premixed Local peak temperature depending on premixing quality
Typical Features GT Burners (swirl-stabilzed flame)Example Fuel Effects in “VESKO Burner”
Temperature [K]
FUEL COMPOSITION (Vol.-%):
H2 CO CH4 N2
fuel 1: 42.5 2,4 - 55
fuel 2: 46 - 3.7 50CFD results: 15 bar, =0.6, 23 kW
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 15 Institute of Combustion Technology
Temperature [K]
fuel 2: H2/CH4/N2
fuel 1: H2/CO/N2
1. Shorter ignition delay time-> flame stabilises closer to combustor head
-> less time for premixing -> higher unmixedness -> higher NOx
-> higher risk of combustor head overheating
2. Increase of flame speed
-> higher flashback risk in premixing zone
3. Changes in thermo acoustics
-> H2-rich fuels more susceptible for thermo acoustic pulsations
-> pulsations shifted to higher frequencies
Consequences of H2 fuel enrichment 1/2
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 16 Institute of Combustion Technology
1. Shorter ignition delay time-> flame stabilises closer to combustor head
-> less time for premixing -> higher unmixedness -> higher NOx
-> higher risk of combustor head overheating
2. Increase of flame speed
-> higher flashback risk in premixing zone
3. Changes in thermo acoustics
-> H2-rich fuels more susceptible for thermo acoustic pulsations
-> pulsations shifted to higher frequencies
4. Wobbe Index & Flow Rate Changes-> lower WI and much higher volumetric flow rate (higher pressure lossacross fuel injection system)
5. Dilution of the fuel (H2) by N2, steam or CO2
-> reduces especially the flame speed
-> increases the fuel volume flow even more
-> decreases efficiency and increases cost strongly, if not available forother reasons
Consequences of H2 fuel enrichment 2/2
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 17 Institute of Combustion Technology
4. Wobbe Index & Flow Rate Changes-> lower WI and much higher volumetric flow rate (higher pressure lossacross fuel injection system)
5. Dilution of the fuel (H2) by N2, steam or CO2
-> reduces especially the flame speed
-> increases the fuel volume flow even more
-> decreases efficiency and increases cost strongly, if not available forother reasons
Today’s DLN combustors are not capable of burning fuels with high H2 contents
-> New or adapted GT Combustion Concepts are necessary
Outline
Combustion Fundamentals Natural Gas (NG)Hydrogen
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 18 Institute of Combustion Technology
Combustion Fundamentals Natural Gas (NG)Hydrogen
H2 capability of state-of-the-art GTs with DLN combustors
Combustion Concepts optimized for NG/H2 Combustion
Conclusions
New or Adopted Combustion ConceptsExample: Jet-Stabilized FLOX®
General description of a research burnerAxial injection of oxidizer at high velocityCoaxial fuel injection within air nozzleFormation of recirculation zone due to shear layers of incoming oxidizer/fuel jetVolumetric heat release at/close to adiabatic flame temperature of global mixture Homogeneous temperature distribution within combustion chamber Avoidance of high peak temperature low thermal NOx emissions
Evaluation of Combustor Concepts for H2 Combustion > 08.02.2011Confidential Slide 19 > Final Report
General description of a research burnerAxial injection of oxidizer at high velocityCoaxial fuel injection within air nozzleFormation of recirculation zone due to shear layers of incoming oxidizer/fuel jetVolumetric heat release at/close to adiabatic flame temperature of global mixture Homogeneous temperature distribution within combustion chamber Avoidance of high peak temperature low thermal NOx emissions
DLR FLOX® combustor
New or Adopted Combustion ConceptsJet-Stabilized FLOX®
Exemplary results: FLOX® combustorCombustor: DLR FLOX® combustorFuel: NG/C3H8/H2-blend up to 100%vol H2
Combustor inlet conditions: T0 = 673K, p0 = 7bar
ResultsStable operation for NG, NG/C3H8-blends up to20%vol C3H8 (limited by test rig) & NG/H2-blendsup to 100%vol H2
High fuel flexibilityNo flashback into mixing section detectedNo auto-ignition within mixing section detectedShortage in reaction zone for increasing H2 content
Evaluation of Combustor Concepts for H2 Combustion > 08.02.2011Confidential Slide 20 > Final Report
Exemplary results: FLOX® combustorCombustor: DLR FLOX® combustorFuel: NG/C3H8/H2-blend up to 100%vol H2
Combustor inlet conditions: T0 = 673K, p0 = 7bar
ResultsStable operation for NG, NG/C3H8-blends up to20%vol C3H8 (limited by test rig) & NG/H2-blendsup to 100%vol H2
High fuel flexibilityNo flashback into mixing section detectedNo auto-ignition within mixing section detectedShortage in reaction zone for increasing H2 content
NG
50%vol NG/50%vol H2
Flame position for NG & H2 combustion
Enhanced FLOX® Burner Development 6/6Fuel flexibility
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 21 Institute of Combustion Technology
modern large gas turbines
next generation
Technically relevanttest conditions
Identical burnerfor all fuelsLow NOx operationcould be achievedin all cases
Conclusions
Adding higher H2 amounts to natural gas, significantly changes combustioncharacteristics (ignition delay & flame speed) and volumetric fuel flow rate
Todays GTs (DLN combustors) are optimised for burning natural gas
Extremely low NOx, CO emissions are achieved
However, fuel flexibility (e.g. with respect to H2-enrichment) is weak;only moderate H2 amounts can be tolerated
However!
Future, adapted GTs in principal can deal with higher H2 amounts
Research work (e.g. FLOX®, Reheat) has shown this potential
There is still more research as well as demonstration of combustiontechnologies adopted for H2 to be done
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 22 Institute of Combustion Technology
Adding higher H2 amounts to natural gas, significantly changes combustioncharacteristics (ignition delay & flame speed) and volumetric fuel flow rate
Todays GTs (DLN combustors) are optimised for burning natural gas
Extremely low NOx, CO emissions are achieved
However, fuel flexibility (e.g. with respect to H2-enrichment) is weak;only moderate H2 amounts can be tolerated
However!
Future, adapted GTs in principal can deal with higher H2 amounts
Research work (e.g. FLOX®, Reheat) has shown this potential
There is still more research as well as demonstration of combustiontechnologies adopted for H2 to be done
Reserve
Vortrag: EU-Turbines workshop_final, 06.10.2011Folie 23 Institute of Combustion Technology
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