New Generation Strategy

1
New Generation Strategy Ultra-Supercritical Techno
logy
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
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/705F
• 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
Supercritical
Subcritical Reheat
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 1050F

9
Generating Technology Ultra-Supercritical (USC)
Pulverized Coal Plants

• What is USC Technology?
• Defined by EPRI as Rankin Cycle steam
  temperatures above 1100F
• 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 1000-1050 oF
  (538-566 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-213-347 HFG Stainless Steel
• RH Outlet Bank SA-213-347 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
Emission 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 0.15 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 1100F
• Equipment Suppliers Can Guarantee Performance and
  Reliability