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August 13, 2009August 13, 2009
ULTRA SUPERCRITICALPulverized Coal-Fired Steam Generators
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August 13, 2009
Introduction
Economic Pressures – Fuel Prices Environmental Pressures
Clean Air Act Clear Skies Local BACT Future CO2
Social/Political Pressures Quest for Permit
Q: What is Ultra Supercritical (USC)?A: Not universally defined, but generally can be considered to be >3800 psig and >1100 F final steam conditions
Q: Why Consider Ultra Supercritical?
A: Dramatic Improvement in Plant Efficiency
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Introduction
1000 1050 11000
1
2
3
4
5
6
7
2400
3625
4350
HE
AT
RA
TE
IM
PR
OV
EM
EN
T (
%)
STEAM TEMPERATURE (F)
CYCLE HEAT RATE IMPROVEMENT
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Operating Results
Early Supercritical Units had problems Lengthy start-ups Poor load following flexibility Poor availability Slagging/fouling/corrosion
Some of those problems not related to supercritical but other boiler evolution issues
Most early design issues have been effectively addressed and availability has improved, though maintenance costs are relatively high
Current supercritical designs in Europe and Japan have availability and maintenance commensurate with subcritical units
Supercritical: Evolution
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Operating Results
0
2
4
6
8
10
12
14
Equi
vale
nt F
orce
d O
utag
e Fa
ctor
(EFO
F),%
1982-1984 1985-1987 1988-1990 1991-1999 1994-1996 1997
Years
Plant - Supercr.Plant - Subcr.SG - Supercr.SG - Subcr.
Availability of Subcritical versus Supercritical Units – N. America(Data from NERC 1982-1997)
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Operating Results
0
1
2
3
4
5
6
Eq
uiv
ale
nt
Fo
rce
d O
uta
ge
Fa
cto
r (E
FO
F),
%
Subcritical Supercritical
VGB Statistics, 1988-1997
Availability Data for Supercritical verses Subcritical Units (Europe)
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Design Criteria
Size Current commercial range from 300-1100 MW
Steam Conditions Trade off efficiency gains (fuel savings) vs. capital cost
Example: Change from 1000/1000 to 1100/1100 results in 3-5% overall increase in plant cost
Fuel More difficult fuels (often less expensive) require designs higher in capital costs
Feedwater Temperature Affected by cycle design
Operating Requirements Base load, load following, cycling, on-off peaking
Emissions Limits Current and future, including CO2
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Advanced Designs and Materials
DOE/NETL - Cost and Performance Baseline for Fossil Energy Plants – 2007
EPRI – CoalFleet Guideline for Advanced Pulverized Coal Power Plants – 2008
EPRI - Engineering and Economic Assessment of Ultra-Supercritical Pulverized Coal Power Plants for Near Term Development – Ongoing
Thermie (Europe)
Japanese Program
U.S. - DOE and State of Ohio
Shandong Technical Exchange – Henan Design Institute – Henan Province, PRC
Recent Activities Assessing Ultra Supercritical Designs and Materials
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Advanced Designs and Materials
Latest Units in Europe 4000 psig, 1105/1110 F China moving up to 3800 psig, 1120/1135 F Most aggressive unit in Japan 3950 psig, 1121/1153 F U.S. Market generally around 3700 psig, 1080/1080 F Most advanced U.S. plant in Engineering Phase at
3800 psig, 1112/1135 F
With advanced materials and careful design, Ultra Supercritical units have maintenance and availability similar to more recent standard supercritical units.
Ultra Supercritical: Current State-of-the-Art
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Advanced Designs and Materials
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Advanced Design and Materials
Long term validation of materials ASME/ASTM Re-rating of materials: Grade 91, 92, 122, 23, etc. Creep-Rupture, exfoliation, corrosion resistance
Fabrication Welding procedures, heat treatment, bending, etc.
Construction Qualified crafts, qualification of procedures, tight Q/A
Compatibility of valves, fittings and appurtenances Many shapes, valves, etc. not available in advanced materials
Significant Issues with Ultra Supercritical Project Implementation
Above issues present risks to project costs, schedule, and performance which are significant in comparison to standard
subcritical or supercritical cycles.
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Future Generation USC
Increase steam conditions to further improve efficiency: For typical US facility, efficiencies up to 48% (HHV) achievable Benefits include:
− Reduced emissions (including CO2)
− Lower CO2 capture costs per MWh
Materials for advanced boilers:
Current
1150°F (630°C)
Ferritic Steels
AD700 ProgramUltraGen II
1295°F (700°C)
Austenetic alloys and nickel based
superalloys
UltraGen III
1400°F (760°C)
Nickel based super alloys
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Future Generation USC
100,000 Creep-Rupture Stress for USC Boiler Materials
P.J. Maiasz, I.G. Wright, J.P Shingeldecker, T.B. Gibbons, and R.R. Romanosky, “Defining the Materials Issues and Research for Ultra-Supercritical Steam Turbines,” Proceedings to the Fourth International Conference on Advances in Materials Technology for Fossil Power Plants (Hilton Head, SC, Oct. 25-28, 2004). ASM-International, Materials Park, OH, 2005.
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Future Generation USC
Double Reheat Reduction of Boiler Exit Gas Temperature Low Level Exit Gas Heat Recovery Coal Drying Combustion Air Preheating Feedwater Heater External Desuperheater Multi-Pressure Condenser Maximizing Cooling Tower Performance Optimized Turbine Cycle for Ambient Conditions Variable Speed Drives
Beyond Advanced Steam Conditions
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