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Ignition Reliability in SGT-750 for Gas Blends at Arctic Conditions
Magnus Persson Combustion Expert / Distributed Generation / Sweden
siemens.com/power-gas © Siemens AG 2017 All rights reserved.
June 2017 Page 2 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Table of content
• Objectives of the Project
• SGT-750 Combustion System
• Test Scope
• Atmospheric Combustion Rig
• High Pressure Combustion Rig
• Engine Validation Test
• Rig Operation on Cold Air
• Results
• Summary
June 2017 Page 3 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Objectives of the Project
Growing needs of ability to operate medium size gas turbines on the broad range of gaseous fuels at extremely low ambient (arctic) conditions was a main driver for this project The overall goals were realized by three-step test approach • Simulation of ignition and startup reliability on natural gas blends with CO2/N2 inert content and the
process air temperature at minus 60˚C ⇒ Full-scale, single-burner system in Atm Comb Rig • Screening of system performance and operation on natural gas blends at pressurized conditions.
Pressure and temperature of the process air were adjusted to the operation line at true arctic conditions ⇒ Full-scale, single-burner system in HP Combustion Rig
• Effect of the inert gas content on operation ability and combustion performance during start and loading ⇒ Standard SGT-750 engine in test bed
All test were performed with original standard engine hardware
June 2017 Page 4 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
SGT-750 Combustion system
SGT-750 • Twin-shaft, rated at 41 MW with 41.6% simple cycle
efficiency • Pressure ratio of 24 • Compressor discharge temperature 490ºC
Burner Can
Transition duct
SGT-750 Combustion System • Eight can annular type combustors • Dry Low Emission burners • Compressor air fed to the burner through serially cooled
can and to impingement cooled double-skin transition duct
• Three premixed fuel stages – pilot Main1 and Main 2 • Rich Pilot Lean (RPL) burner in the center • Radial swirl generator to maintain fuel mixing and flame
stability by central recirculation zone
June 2017 Page 5 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Test Setup Atmospheric Combustion Test Facility
For the test purposes the test rig facility was completed by adding • Fuel mixing station • Air supply unit (cold air)
H-NG
N2
CO2Q,f
FD
1
2
3
4
5
67 8
9
10 11 1211
13 14 15 1622 19
20O2
18
34
Liquid air23wt%O277wt%N2-220°C/5 bar
Dies
el
1- Liquid air storage2- Flexible hose3- Evaporator4- Steam generator5- Diesel fuel tank6- Air flow governing valves7- Safety overpressure valve8- Orifice plate process air9- Compensator10- Flowmeters
10
TIgn
Toxy
17
Air supply unit
Fuel mixing station Test rig
10- Flow meters11- Governing valves12- Gas mixer13- Burner14- RPL igniter15- Combustor16- T-duct17- Air temp sensor18- O2 probe19- Exhaust casing20- Dilution compressor21- stack22- optical flame detector
Objective: Screening of start settings at true arctic conditions and diluted natural gas for reliable ignition Test hardware: Original single-burner combustor with original auxiliaries (exciter, flame sensing)
Test vessel
Air inlet
Burner
RPL
CanTransition
DuctEmission
Probe
ViewPort
ExhaustChannel
RPLFD/TC
MainFD
June 2017 Page 6 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Test Setup High Pressure Test Rig
• Air pressure and preheat temperature set to arctic conditions across the engine operating line • Test with natural gas with up to 40 vol% CO2 and 53 vol% of N2
Objective: Stress test of combustion performance at authentic arctic compressor discharge data and natural gas diluted with inert gases Test hardware: Single burner complete combustion system
Burner CameraAir inlet
Emission probes
Guide vanes
Burner CameraAir inlet
Emission probes
Guide vanes
June 2017 Page 7 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Test Setup Engine in Test Bed
• No modification of the fuel nozzles needed • No gas chromatograph for Wobbe index required • Max content of inert gases tested: N2 > 45 CO2 > 35 vol%
Objective: Validation of engine operation with N2/CO2 diluted natural gas at near ISO conditions Test unit: Standard SGT-750 with governing software adapted to automatic sensing of fuel Wobbe Test bed: A temporary fuel mixing station and storage for N2/CO2 for test purposes was assembled
Flowmeter for test
Atomatic fuelcharacteristicadaptation algoritm for fuel limiters
No gas chromatograph
June 2017 Page 8 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Atmospheric Ignition Test on Cold Air Air Supply Station
The air supply station was specially assembled for the ignition test purposes Main components: - Liquid air storage (~20 tons) - Liquid air evaporator with steam driven heat exchanger - Diesel fired boiler, providing steam to the evaporator - Air flow and temperature control unit
Test constraints & requirements: - Air flow rate: 400 ÷ 600 g/s ± 20 g/s - Air temperature: -60 ÷ -15 ºC ± 5 ºC - Oxygen content in process air : 20 ÷ 22 vol%
Risks: - Oxygen/nitrogen separation in storage – oxygen
content outside permissible range - Temperature in exhaust below design limit
Air storage
Steam generator
Evaporator
Control valves
Safety valve
Displayfor
process data
Insulated air hoseand valves
Steam hose
Liquid air hose
Flow control unit
Process air plumbing
June 2017 Page 9 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Fuel mixing station
Ice deposits
Orifice plate
Burner flange
Atmospheric Ignition Test on Cold Air Test Rig
Three main components were deployed: • Fuel gas mixing station − Mass flow meters on each gas component
• Pressure vessel − Thick thermal insulation needed to keep the
process air temperature at required level − New orifice plate at insulated pipe
• Exhaust passage − Stream of fresh ambient air to be mixed with
cold process air – design requirement
The oxygen content in the process air was monitored by a sampling probe in the exhaust
Governingvalves
Flowmeters
Mixing device
NG line
N2 line
CO2 line
Test rig in operation on cold air
June 2017 Page 10 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Results Ignition Window of Main Flame for N2 gas blends – ISO vs. Arctic Conditions
Reliable ignition was validated as a function of equivalence ratio at burner outlet. Flame light was indicated by the optical flame detector installed in the burner
NG20vol%
30vol%40vol%55vol%
-1
0
1
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65
-1 -
N/A
; 0-fa
iled;
1-f
lam
e on
Equivalence Ratio [-]
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65NG -1 -1 1 1 1 1 1 -120vol% -1 -1 1 -1 -1 -1 -1 -130vol% -1 -1 1 -1 -1 -1 -1 -140vol% -1 -1 -1 1 1 -1 -1 -155vol% 1 1 -1 -1 -1 -1 -1 -1
Main flame ignition window for N2 gas blends -60˚C
NG20vol%
30vol%40vol%55vol%
-1
0
1
0.35 0.4 0.45 0.5 0.55 0.6 0.65
-1 -
N/A
; 0-fa
iled;
1-f
lam
e on
Equivalence Ratio [-]
0.35 0.4 0.45 0.5 0.55 0.6 0.65NG -1 1 1 1 1 1 -120vol% -1 1 1 -1 -1 -1 -130vol% -1 1 1 -1 -1 -1 -140vol% -1 1 1 -1 -1 -1 -155vol% -1 1 1 -1 -1 -1 -1
Main flame ignition window for N2 gas blends - ISO
June 2017 Page 11 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Results Ignition Window of Main Flame for CO2 gas blends – ISO vs. Arctic Conditions
Reliable ignition was validated as a function of equivalence ratio at burner outlet. Flame light was indicated by the optical flame detector installed in the burner
NG20vol%
30vol%40vol%48vol%
-1
0
1
0.35 0.4 0.45 0.5 0.55 0.6 0.65
-1 -
N/A
; 0-fa
iled;
1-f
lam
e on
Equivalence Ratio [-]
0.35 0.4 0.45 0.5 0.55 0.6 0.65NG -1 1 1 1 1 1 -120vol% -1 1 1 -1 -1 -1 -130vol% -1 1 1 -1 -1 -1 -140vol% -1 1 1 -1 -1 -1 -148vol% -1 0 0 -1 -1 -1 -1
Main flame ignition window for CO2 gas blends - ISO
NG20vol%
30vol%40vol%48vol%
-1
0
1
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65
-1 -
N/A
; 0-fa
iled;
1-f
lam
e on
Equivalence Ratio [-]
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65NG -1 -1 1 1 1 1 1 -120vol% -1 -1 0 1 1 1 -1 -130vol% -1 -1 1 1 1 0 -1 -140vol% -1 -1 0 0 0 0 -1 -148vol% -1 -1 0 0 0 0 -1 -1
Main flame ignition window for CO2 gas blends -60˚C
June 2017 Page 12 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Results Summary of Ignition Test at Arctic Conditions
The test outcome of ignition reliability in SGT-750 combustion system at artic conditions give satisfactory results and fulfilled the project requirements
• Reliable ignition of the central RPL-burner was obtained at:
• Reliable ignition of the main flame was obtained at:
June 2017 Page 13 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Results Summary of HP Combustion Test on N2/CO2 Blends in Single Burner Rig
Part load operating points with high concentrations of N2 and CO2 in the fuel were tested • Stress test of operability and stability • Pressure and preheat temperature adjusted to arctic conditions (-60°C)
June 2017 Page 14 M. Persson / Siemens AG
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Results Summary of Engine Test on N2/CO2 Blends
Final verification of SGT-750 fuel flexibility. The test was performed at near ISO ambient conditions
NOX in stack vs Engine Load on Inert Gas Blends CO in stack vs Engine Load on Inert Gas Blends
June 2017 Page 15 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Summary
• The fuel flexibility test campaigns extensively performed in 2016 have proven the SGT-750 and its combustion system to be very tolerant to variation of fuel quality at various ambient conditions
• Three-step approach starting with ignition testing in atmospheric rig through testing in high pressure rig and finally engine test was satisfactory from testing methodology point of view
• The tests at the combustion rigs both atmospheric and high pressure were carried out with the original setup of the SGT-750 single burner combustor and the flame monitoring devices
• It was proven that the ignition capability and reliability at artic conditions is satisfactory for natural gas blends containing up to 55 vol% of N2 and 30 vol% of CO2
• Stress test in the high pressure combustion rig of a single burner combustor has proven operability and combustion stability on the inert gas blends
• Engine operation of the SGT-750, including ignition, start and transient load changes was successfully performed using gaseous fuels containing up to 50 vol% of nitrogen and 40 vol% of carbon dioxide
• Start settings and the algorithm for governing software can be directly applied in the engine’s control system
June 2017 Page 16 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
Thank you for your attention
Dr. Magnus Persson Combustion Expert Gas Turbine Research & Development
612 83 Finspang Sweden
Phone: +46 122 87703 Mobile: +46 702 36 63 28
E-mail: [email protected]
siemens.com/power-gas
June 2017 Page 17 M. Persson / Siemens AG
© Siemens AG 2017 All rights reserved. AL: N ECCN: N
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