Burning Natural Gas / Hydrogen Mixtures in DLN Gas … · Burning Natural Gas / Hydrogen Mixtures in DLN Gas Turbines ... Jet-Stabilized FLOX ... Confidential Slide 19 > Final Report

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


Ignition delay time



Wobbe-Index



Conclusions

Outline


Ignition delay time



Wobbe-Index



Conclusions



Ignition delay time



Wobbe-Index



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


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


Hydrogen (100%vol H2)

Density0.082kg/Nm³

LHV119.494MJ/kg

9.831MJ/Nm³


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

]


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)

*


*


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


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


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

*


*


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:


-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



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



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




Conclusions






Conclusions


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)


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


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


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


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


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




Conclusions





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


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


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


Documents

Burning Natural Gas / Hydrogen Mixtures in DLN Gas … · Burning Natural Gas / Hydrogen Mixtures in DLN Gas Turbines ... Jet-Stabilized FLOX ... Confidential Slide 19 > Final Report