The path forward to more efficient combustion in very Large GTanimp.it/prodotti_editoriali/materiali/convegni/pdf/energia_2016_1/Hele... · The path forward to more efficient combustion
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Authors: Gerhard Fruechtel, Alice Pesenti, Paolo Traverso
Speaker: Paolo Traverso
The path forward to more efficient combustion in very Large GT
COMPANY
CONFIDENTIAL 27.09.2016
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High Efficiency and Low Emissions
in Gas Turbines
Why to talk about combustion ?
COMPANY
CONFIDENTIAL
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2016 Combustion Portfolio
1) Hybrid burners for class E & F class
2) EV Alstom technology for 1st stage in F & H class
3) SEV combustion technology for F class
Ansaldo Energia is today owner of following combustion technologies:
4) SEV combustion technology for H class
5) Flamesheet for F & H class owned by PSM
6) G-Top combustor owned by PSM
COMPANY
CONFIDENTIAL
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Ansaldo Energia is today using following combustor architectures:
1) Silo combustors (horizontal & vertical)
3) Double stage dual pressure
Annular combustors
2) Single stage Annular combustors
5) Double stage Cannular combustor
2016 Combustion Portfolio
4) Single stage cannular with Flame sheet options
COMPANY
CONFIDENTIAL
5 COMPANY
CONFIDENTIAL
AE fleet with Hybrid burners
Overview and improvements to F class GT
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Dual Fuel Burner (diffusion/pilot+premix for both fuels)
Parallel Air Paths for diagonal and axial sw.
NG Premix
LFO Premix
NG Diffusion
NG Pilot
LFO Diffusion
NG Igniter
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EMISSIONS AND PERFORMANCE: S.A.S. UPGRADE
Ansaldo Energia s.p.a. reserves all rights on this document that can not be reproduced in any part without its written consent
AIR SAVING ~ 15 kg/s
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VeLoNOx 1A / HR3 + diagonale Low Swirl
HR3 line
4 pipes fed with pilot gas
VeLoNOx 1° lines
4 couples of 3 mm holes
Low Swirl 9 holes (+2°)
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Achievements – CFD + RIGs + Field Validation
• Additional fuel line (gas lance) -> Increased load variation capabilities & stability at B.L. –
Escatron 2014 –Sousse 2015
Fuel gas lance development
Upgrade Design of 50Hz F-class GT AE94.3A
COMPANY
CONFIDENTIAL
10 COMPANY
CONFIDENTIAL
EV & SEV
in the past
for the present
and for the
Large GTs of the future
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EV and SEV technology (Former Alstom)
Single Burner
Silo Combustor
Dry Low NOx Burners
Annular Combustors
1st Generation
Can-annular Combustors
Sequential Combustion
2nd Generation
EV Burners AEV Burners
CPSC Reheat Engine
GT13E GT11N2
GT8C
GT13E2
GT8C2
GT24 / GT26 GT36
SEV Burners
Gas Turbine Burner Development from 500 ppm NOx to 10 ppm NOx and from 20 MW/m3 to > 200 MW/m3
Sequential Burner
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Gas Concentration
Profile
stage 2
stage 1
Lean Premix Mode
• Low NOx emissions • Fuel is evenly distributed
• Almost no sensitivity to
Wobbe index changes • Flame positions shifts slightly
with increasing reactivity of fuel
Rich Premix Mode
• Start-up with high fuel concentration on axis
• Transfer to Lean operation at 5% GT load
stage 2
stage 1
GT26 EV combustor – operational flexibility
EV Burner – fuel injection into swirling air crossflow Premix from idle to full load without switch-points
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GT26 SEV combustor – operational flexibility
Flamefront Mixing zone
Vortex generators
(VGs)
Hot gas from high pressure turbine
Fuel gas, Carrier air
Combustion chamber
No sensitivity to Wobbe Index
• Carrier air is surrounding the fuel jet to enhance penetration > 50% of jet momentum
SEV flame position reacts to C2+/H2 content
• Flame shifts upstream with increasing reactivity
• Flame position controlled by EV/SEV fuel split (C2+ standard operation)
SEV Burner – fuel injection into crossflow with longitudinal vortices
Auto-ignition operation from 10% to 100% relative GT load
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SEV combustor - principle of reheat combustion
SEV flame position is controlled by the variable EV/SEV fuel split
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GT26 Operational Flexibility Improvements
Overview of Extended Load Ranges
A new enhanced operation window without lifetime penalization
Low Load
Operation (Parking)
Low Part Load
Original
Operation window
GT
Lo
ad
(%
)
100%
LLO
Low part load
MEL*
MEL*
0
CO emission limits
exceeded
Baseline Dispatch
Window
Enhanced
Operation window
* MEL : Minimum Environmental Load at 100 mg/Nm3 CO and a natural gas with C2+ 6%
High Fogging
Steam Injection
- 15 %
+ 5 %
+ 6 %
40* - 100 %
10 %
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GT26 Operational Flexibility Improvements
Overview of Extended Load Ranges
The challenge
• At low part load, the SEV Burner
temperature with all burners in
operation is low and causes
incomplete combustion resulting in
increased CO emissions
The solution
• Sequential switch-off of SEV
burners at lower loads
• Reduced power output while
keeping SEV burner temperature
on high level
Optimized low CO emissions
EV
SEV
ca. 15% 25% 40% 100%
GT rel. load
Typical CO limits
GT26 CO emission
SEV Burner temperature
(standard concept)
SEV Burner temperature
(partial burner switch off)
EV – first combustor
SEV – second combustor
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Fuel Gas Flexibility
• Wobbe Index variation tolerance of over +/-15% (31-52 MJ/m3 absolute)
• C2+ variation tolerance up to 18% vol.
• C2+ standard operation covers H2 contents of 5% vol.
• Hydrogen contents of 15% vol. can be handled
Liquid Fuel Flexibility
• Wide experience range within the GT fleet
• Boiling ranges from Naphtha to Kerosene to Oil#2 can be covered
• On GT26 fuel switchover (gas oil) at high loads commercially proven
GT26 Gas Turbine Fuel Flexibility
Superior fuel flexibility proven for GT26
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GT36 Gas Turbine
Evolution of sequential Combustion with CPSC
GT26
GT36
Sequential Combustor Compressor Turbine
Premix
Combustor
Proven benefits of Sequential Combustion:
• Sub 25vppm NOx emissions at plus 1500°C hot gas temperature
• Turn Down to < 25% GT load
• Parking at < 5% GT load
• Fuel Flexibility – Wobbe Range 31-53MJ/m3, ±15%, LHV 29-50MJ/kg
CPSC – additional benefits:
• High pressure cycle removed, eliminating 340 hot gas parts and 1’500 structural parts
− Reduced compressor exit temperature by 90K (160ºF)
• Service orientated GT concept enabling fast hot gas path inspection of 13 days
• Improves rig to engine transferability of combustor behaviour
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Van
e
1st combustor Seq. Burner Seq. Combustor Mixer
GT36 Combustor Constant Pressure Sequential Combustion – Function
• CPSC (SEV) advantage on trade-off between NOx and CO
− Sequential burner technology allows very low residence times, with good CO burnout, without
staging.
− Sequential combustion (with higher secondary burner inlet temperatures and depleted inlet air
O2) permits short residence times for secondary combustor and potential for ultra low NOx.
− NOx emissions at part load are minimal due to the absence of pilot/staging needs.
Temperature
trend
Optimized Residence Times
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Combustor: Design
COMPANY
CONFIDENTIAL
GT36
Premix Combustor
Sequential Combustor
Based on F-class can combustor and proven GT26 sequential combustors
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Reheat burner technology
Multi-Point In-Line Injection with Small-scale mixing devices
• Lowering pressure loss • Enhanced flashback margin • Carrier air reduction • Higher engine performance • Capable of addressing highly reactive fuel • 70/30 H2/N2 demonstrated on HP rig
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HBK5 Test Facility Cologne
Key Parameters
Air mass flow 70 kg/s
Pressure 40 bar
Preheat Temperature 700 °C
Hot Gas Temperature 2000 K
Fuel Types gaseous & liquid
Thermal Power 125 MW
A test facility designed to industry needs
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A new generation is born New products.
New technologies.
New service capabilities.
Ansaldo Energia: a global player in the power generation market.
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