New Generation StrategyUltra-Supercritical

Technology

New Generation StrategyUltra-Supercritical

Technology

Presented by:

Tim Riordan, Manager

New Generation Design & Eng.

APP Site Visit

October 30 – November 4, 2006

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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

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Typical Heat Balance

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SCR NOx control added to meet NOx SIP Call. Additional NOx control greater than 85%

FGDS to reduce SO2 by greater than 90%

Low NOx Burners. NOx reduction greater than 50 %

Bag filter to remove Particulate

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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)

The Basic Heat Cycle

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Gaining Efficiency Higher Pressure and Temperature

Power Plant CycleImprovement from Higher Steam Temperature

Entropy

Tem

per

atu

re

1'

Increase in Heat input: b'-3'-2'-2-3-b-b'Increase in Work: 3'-2'-2-3

Net increase in cycle efficiency

a

1

2

3

b

2'

3'

b'

Critical Point

•

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The Evolution Continues

Comparison

Entropy

Tem

per

atu

re

Ultra Supercritical

1940 Vintage Subcritical Non-Reheat

Early 20th Century Vintage Subcritical Non-Reheat

1960 Vintage Subcritical Reheat Supercritical

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History of Supercritical Units

First Supercritical Unit: AEP Philo Unit 6 Initial Operation Date: 1957 (49 years ago)125 MWSteam 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

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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

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

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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.

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Steam Generator Cross Section

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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

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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

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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

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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

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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

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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

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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

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Efficiency and CO2 Emissions Comparison

CO2 Emissions varywith Heat Rate & Coal Rank

0.85

0.90

0.95

1.00

1.05

1.10

8500 9000 9500 10000 10500

Net Unit Heat Rate (Full Load), Btu/kwh

CO

2 E

mis

sio

ns,

To

ns/

MW

H

Bituminous

Sub Bituminous

Lignite

Figures for Supercritical and Subcritical are for existing units w /environmental control retrofits.

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Emission Ultra SC3800psi/1100F/1100F

Supercritical3500psi/1000F/1000F

IGCC2X1 7FB GT – Dry Feed

Subcritical2400psi/1000F/1000F

SO20.91 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

CO20.97 T/MWh 1.03 T/MWh 0.99 T/MWh 1.06 T/MWh

Emission Comparison Sub-Bituminous Coal

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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