1. New Generation Strategy
Ultra-Supercritical
Technology
Presented by:
Tim Riordan, Manager
New Generation Design & Eng.
APP Site Visit
October 30 – November 4, 2006

2. AGENDA Power Plant Steam Cycle – (Rankin Cycle)
History of Supercritical Units
Ultra-supercritical (USC) Overview
AEP Ultra-supercritical Design
Steam Generator Design
Turbine/Generator Design
Efficiency and Emissions Comparison

3. Typical Heat Balance

4. Bag filter to remove Particulate
SCR NOx control added
to meet NOx SIP Call.
Additional NOx control
Low NOx Burners.
greater than 85%
NOx reduction
greater than 50 %
FGDS to reduce SO2 by
greater than 90%
Bag filter to remove Particulate

5. The Basic Heat Cycle Critical Point – 3208psi/705°F
Sub-Critical Steam Cycles : Water boiling to steam with pressures below ‘critical point’
Super-Critical Steam Cycles: Water to steam without boiling. Pressure above ‘critical point’
Ultra-Supercritical Steam Cycles: Steam temperatures above 1100 °F as defined by Electric Power Research Institute (EPRI)

6. Gaining Efficiency Higher Pressure and Temperature
Critical Point

7. The Evolution Continues
Comparison
Ultra Supercritical
1960 Vintage
Subcritical Reheat
Supercritical
Temperature
Early 20th Century Vintage
Subcritical Non-Reheat
1940 Vintage Subcritical
Non-Reheat
Entropy

8. History of Supercritical Units
First Supercritical Unit: AEP Philo Unit 6
Initial Operation Date: 1957 (49 years ago)
125 MW
Steam Conditions: 4500psi/1150F/1050F/1000F (double-reheat)
World-wide – Over 200 units
Typical steam pressures: 3350 to 4200 psi
Typical steam temperatures: 1000 to 1050°F

9. Generating Technology: Ultra-Supercritical (USC) Pulverized Coal Plants
What is USC Technology?
Defined by EPRI as Rankin Cycle steam temperatures above 1100°F
Limited to ASME code approved metallurgy for pressure part design
Higher temperatures increase cycle efficiency
USC technology is most efficient cycle available for selected fuels (sub-bituminous coal)
Higher efficiency = Less emissions
IGCC is limited for sub-bituminous coal applications

10. Generating Technology: Ultra-Supercritical (USC) Pulverized Coal Plants
An ultra-supercritical (USC) steam generation unit operates at supercritical pressure (typically 3500 psi or higher) and at steam temperatures above 1100 oF (593 oC).
For comparison, a conventional supercritical unit operates at steam temperatures of oF ( oC).
Modern chrome and nickel-based super alloys in the steam generator, steam turbine, and piping systems can withstand prolonged exposure to this high temperature steam.
By operating at elevated steam temperatures, the turbine cycle is more efficient. This reduces fuel (coal) consumption, and thereby reduces emissions.
USC technology is compatible with all types of coal.

11. Steam Generator Cross Section

12. AEP USC Steam Generator Design Conditions
Pulverized Coal-fired Benson Cycle, Spiral-wound Boiler
PRB Coal
Main Steam: 3675 psi/1115 F
Reheat Steam: 1130 F

13. USC Impact on Steam Generator
High Temperature Oxidation
Internal oxidation of boiler tubing above 1050 oF
Exfoliation of oxide layers leads to tube pluggage and could damage turbine blading.
SA-213-T91 material not used in heat transfer zone
Approaching limits of dissimilar metal weld (DMW) designs
DMW Design Limit = 1150 oF

14. Steam Generator Materials of Construction
SSH Outlet Bank: SA HFG Stainless Steel
RH Outlet Bank: SA HFG Stainless Steel
Superheater Headers : SA-335 –P92
Other alloys typical of previous supercritical designs

15. Steam Turbine/Generator
Current Turbine Design for AEP USC Unit:
Four-casing, 3600 RPM, Tandem Compound, Single Reheat
Single-flow High-pressure (HP) turbine section
Double-flow Intermediate-pressure (IP) turbine section
Two (2) Double-flow Low-pressure (LP) turbine sections
Designed for full arc, sliding pressure operation
Improved Efficiency
Minimize Component Thermal Fatigue Damage

16. Steam Turbine/Generator
Generator Design for AEP USC Unit:
Two-Pole, Three-Phase Synchronous Machine
840 MVA Rating
Direct Hydrogen cooled field and stator core
Direct water cooled stator windings

17. USC Impact on Turbine
Higher operating temperatures call for improved materials of construction:
Most important components:
Forgings (rotors)
Castings (casings)
Piping
Material Requirements to handle USC operating conditions:
High creep rupture strength
Resistance against embrittlement
Low oxidation growth and no loosening of oxidation layer
Ease in manufacturing and availability

18. Turbine Materials of Construction
Main Steam and Reheat Steam Piping: SA-335-P92
Main Steam Valve Casing: 9Cr (CB2)
HP Inner Shell: 9Cr (CB2)
HP Rotor: 9Cr (FB2)
HP Rotating Blading – Inlet Stages: Nimonic (Ni80TiAl)
Nickel-based alloy
Superior to steel alloys at temperatures above 1050 oF

19. Efficiency and CO2 Emissions Comparison

20. Emission Comparison Sub-Bituminous Coal
Ultra SC
3800psi/1100F/1100F
Supercritical
3500psi/1000F/1000F
IGCC
2X1 7FB GT – Dry Feed
Subcritical
2400psi/1000F/1000F
SO2
0.91 lb/MWh
0.97 lb/MWh
0.55 lb/MWh
0.99 lb/MWh
NOx
0.64 lb/MWh
0.68 lb/MWh
0.65 lb/MWh
0.70 lb/MWh
PM-10
0.14 lb/MWh
0.15 lb/MWh
0.09 lb/MWh
CO2
0.97 T/MWh
1.03 T/MWh
0.99 T/MWh
1.06 T/MWh

21. Conclusion Ultra-supercritical Pulverized Coal Technology
Higher Temperatures = Better Efficiency
Better Efficiency = Less Emissions and Less Carbon Dioxide
Metallurgy Currently Available for Temperatures above 1100°F
Equipment Suppliers Can Guarantee Performance and Reliability