Transcript Slide 1
ULTRA SUPERCRITICAL
Pulverized Coal-Fired Steam Generators
August 13, 2009
Introduction
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
Economic Pressures – Fuel Prices
Environmental Pressures
Clean Air Act
Clear Skies
Local BACT
Future CO2
Social/Political Pressures
Quest for Permit
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Introduction
CYCLE HEAT RATE IMPROVEMENT
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Operating Results
Supercritical: Evolution
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
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Operating Results
Availability of Subcritical versus Supercritical Units – N. America
(Data from NERC 1982-1997)
Equivalent Forced Outage Factor (EFOF),%
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12
10
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Plant - Supercr.
Plant - Subcr.
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SG - Supercr.
SG - Subcr.
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2
0
1982-1984
1985-1987
1988-1990
1991-1999
1994-1996
1997
Years
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Operating Results
Availability Data for Supercritical verses Subcritical Units (Europe)
Equivalent Forced Outage Factor
(EFOF), %
VGB Statistics, 1988-1997
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5
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2
1
0
Subcritical
Supercritical
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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
Recent Activities Assessing Ultra Supercritical 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
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Advanced Designs and Materials
Ultra Supercritical: Current State-of-the-Art
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.
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Advanced Designs and Materials
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Advanced Design and Materials
Significant Issues with Ultra Supercritical Project Implementation
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
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
AD700 Program
UltraGen II
UltraGen III
1150°F (630°C)
1295°F (700°C)
1400°F (760°C)
Ferritic Steels
Austenetic alloys
and nickel based
superalloys
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
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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.
August 13, 2009
Future Generation USC
Beyond Advanced Steam Conditions
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
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