Opportunities to Improve
the Efficiency of Existing
Coal-Fired Power Plants
Scott Smouse
Senior Management & Technical Advisor
Strategic Center for Coal
[email protected]
412-386-5725
Clean Energy Ministerial Global Superior Energy Partnership Workshop
28-30 October 2014, Ulaanbaatar, Mongolia
Ecofys 2014 Study
Coal-Fired Power Generation Efficiency
• Coal-fired power generation efficiency around world ranges from low of
26% in India to high of 43% in France (net LHV basis, 2010 data)
• Since 1990, U.S. coal-fired power plant efficiency has been flat while China
has dramatically improved its efficiency by closing many small, old
inefficient units while building new, large, more efficient units
International Comparison of Fossil Power Efficiency and CO2 Intensity, Ecofys, Sep 2014
Ecofys 2014 Study using 2010 Data
• High absolute CO2 emissions reduction potential for fossil power
generation (coal + natural gas) in China, USA, and India owing to large
installed generation base
• CO2 emissions can be reduced by 23% on average around the world
with state-of-the-art technology
Absolute and relative absolute CO2 emission reduction potential for fossil power generation
improvement by replacing all fossil public power production by Best Available Technology
International Comparison of Fossil Power Efficiency and CO2 Intensity, Ecofys, Sep 2014
NETL Studies of Coal-Fired Power Plant Efficiency
• Previous work:
DOE /NETL-2010/1411: “Improving the Efficiency of Coal-Fired Power
Plants for Near Term Greenhouse Gas Emissions Reduction,” NETL,
16-Apr-2010
− examined GHG emission reductions through efficiency improvements to
existing U.S. fleet of coal-fired power plants
− identified retrofits or operational improvements having reduction
potential of up to 2.5% of domestic CO2 emissions
• Current work:
DOE/NETL-2013/1611: “Options for Improving the Efficiency of
Existing Coal-Fired Power Plants,” NETL, 1-Apr-2014
− examined economic case for implementing common retrofits on two
hypothetical subcritical power plants:
› Plant A is representative of existing 400-600 MW U.S. power plants
› Plant B is representative of newer U.S. plants in same capacity range
I
Basis for NETL Study
• Existing U.S. coal-fired power generation fleet
− over 300 GW
− over 1,500 units ranging from few MWs to 1,300 MW
− generates more electricity than any other fuel type
› 37-50% of total kWh annually during last decade
• Total coal power generation projected to increase slightly
over next 2 decades
Technology Options Analyzed by NETL
Improvements achievable by retrofitting four plant
components:
1.
2.
3.
4.
Coal pulverizers
“Off-the-Shelf” technologies
Condenser
Steam turbine
Solar-assisted feed water heaters
Case Studies of Existing Typical
U.S. Subcritical Coal-Fired Power Plants
Year
Built
Net Output,
MWe
Heat Rate,
BTU/kWh
Efficiency,
HHV
Plant A
1968
550
10,559
32.3%
Plant B
1995
550
9,680
35.2%
“Off-the-Shelf”
Technology Improvements
Coal Pulverizer
• Upgrading increases coal particle fineness, which
improves combustion and plant efficiency
• Relatively long payback period
− attractive option for select plants
• Options include:
− latest-generation pulverizers
− advanced classifier
− combustion optimization system
Pulverizer Improvement Examples
Plant
Information
Heat Rate
Improvement
Annual Fuel
Savings
Decrease fuel rejects due to
pulverizer clearance and settings
Decrease fly and bottom ash
unburned carbon by 50%
Decrease primary air flow by 50%
400 MW
10,500 BTU/kWh
75 BTU/kWh
$204,750
Performance enhancements
(classifier reconfiguration,
improved air flow distribution and
accuracy, adjusting grinding spring
tensions, etc.)
Not available
100 – 400
BTU/kWh
Not available
ATRITA pulverizer system upgrade
to reduce LOI and increase fineness
450,000 lb/hr
steam
25 – 50
BTU/kWh*
Not available
200 MW
22 BTU/kWh**
Not available
Corrections
Combustion Optimization System
retrofit
*Based on estimations
**Calculated based on 0.22% efficiency gain
Steam Surface Condenser
• Reducing condenser leakage rate
− potential high-efficiency gains
− available technology
− relatively short-payback period
• Options include:
− tube replacement
− reducing leaks
− condenser reconfiguring
− other upgrades described in study
Condenser Improvement Examples
Corrections
Plant
Heat Rate
Information Improvement
Air InLeakage
Reduction
Condenser
Pressure
Improvement
Replaced Admiralty brass and
copper tubing with stainless steel
Not Available
1 – 2%
75 SCFM
0.7” Hg
Repaired holes in condenser and
added leak detection equipment
445 MW
oil-fired plant
Not Available
35 SCFM
0.539” HgA
Reconfigured condenser shell
side arrangement to reduce air
binding
Not Available
Not Available
Not
Available
1.0” HgA and
0.6” HgA
850-MW
coal-fired
plant
200 BTU/kWh
Not
Available
Not Available
Correcting air in leakage,
fouling, and changing air removal
equipment
Not Available
2%
Not
Available
Not Available
Condenser tube maintenance
plan
Not Available
30 – 70
BTU/kWh
Not
available
Not available
8 leaks were identified and
repaired based in sensor
information
Steam Turbine
• Most attractive of four technology options studied
• Dense-pack turbine retrofit
– steam path redesign upgrades high pressure (HP) or
intermediate pressure (IP) sections including new rotor and
stationary components inside existing turbine shell.
Steam Turbine Improvement Examples
Corrections
Plant
Information
Increase in
Efficiency %
(HP section)
Increase in
Efficiency %
(IP section)
Increase in
Efficiency %
(LP section)
Total
Efficiency
Gain
Abradable Coating Seals
Siemens 2005
0.1–0.2%
3D Blading Technology
Siemens 2005
2%
Advanced Blading
Siemens
600–700 MW
Built <1990
4%
Brush Seals
Siemens 2006
Guardian Packing & Vortex Shedder Seals
(operates with labyrinth seals and Vortex
Shedder Seals)
Hitachi 2008
2–5%
Vortex Shedder Seal
Turbo Parts
2011
1.5– .5%
Full Arc Admission Inlet, Improved Flow
Technology
Eliminate Separate Nozzle Chambers & Nozzle
Blocks
Eliminate 180o steam turn around to HP Blade
Path
Eliminate Impulse Control Stage
3D Blading Technology
Fully Integral Inner Casing
Advanced Sealing Technology (Spring Back and
Retractable seals)
Siemens
365 MW
Built in 1979
Retrofit in
2004
MW
Added
5%
0.5
8–10%
2–4%
4.1–5.5%
15 – 20
Steam Turbine Improvement Examples
Corrections
Eliminate riveted shrouds on front-end
blading
Eliminate riveted shrouds and lashing wires
on large LP blading
Single inner casing with moisture removal
features
Increase resistance to stress corrosion
cracking (SCC)
Increase resistance to high-cycle fatigue
8.7 inches of HgA exhaust pressure limit at
high loads
10-year inspection interval
Torsional compatibility with existing
generator rotor
HP/IP Turbine replaced
2 Double flow LP Turbines replaced (from
30" to 34")
Steam seal package
Standard labyrinth packing rings
Retractable packing rings
Brush Seals
Conventional blade and brush-tip seals
Dense Pack
Dense Pack and LP Turbine
Plant Information
Increase in
Efficiency %
(HP section)
Increase in
Efficiency %
(IP section)
Increase in
Efficiency %
(LP section)
Siemens 365 MW
Built in 1979
Retrofit in 2004
TurboCare, 580 MW
Built in 1974
Retrofit in 2002
7% (HP & IP)
Total
Efficiency
Gain
MW
Added
1.9 – 2.2%
7–8
5%
27
375 MW, Built in
1970s, Retrofit in
2004
GE 2000
1.5 – 3.0%
GE, 365 MW,
Retrofit in 2005
5%
4%
2.5%
1.4%
1.4%
1.5%
11
Cumulative CO2 Emission Reduction Summary
for 3 Technologies Analyzed by NETL
Heat Rate,
BTU/kWh
Pre-retrofit CO2
Emissions,
Million tonnes/yr
Post-retrofit CO2
Emissions,
Million tonnes/yr
CO2 Emissions
Reduction,
Million tonnes/yr
Lower
Bound
10,012
(547↓)
3.93
3.73
0.20
(5.1%)
Upper
Bound
9,828
(731 ↓)
3.93
3.66
0.27
(6.9%)
Lower
Bound
9,510
(170 ↓)
3.60
3.54
0.06
(1.7%)
Upper
Bound
9,340
(340 ↓)
3.60
3.48
0.12
(3.3%)
9,277
(n/a)
3.45
-
-
Plant
Plant A
Plant B
New
Subcritical
PC
$70
Cumulative Efficiency Improvement
First-Year Cost of Electricity
Total
Fuel
$60
Variable O&M
Cost of Electricity ($/MWh)
New Subcritical PC: $59.40/MWh (9,277 BTU/kWh)
$50
Fixed O&M
Capital
$46.33
$45.81
$44.90
$44.42
$27.83
$27.31
$26.41
$25.94
$7.16
$7.16
$7.16
$7.16
$10.42
$10.42
$10.42
$10.42
$0.91
$0.91
$0.91
$0.91
$40
$30
$20
$10
$0
Plant A, Moderate HR
Improvement (10,012 Btu/kWh)
Plant A, High HR Improvement
(9,828 Btu/kWh)
Plant B, Moderate HR
Improvement (9,510 Btu/kWh)
Plant B, High HR Improvement
(9,340 Btu/kWh)
Solar-Assisted Feedwater Heater
Improvements
Solar-Assisted Feedwater Heater (SAFWH)
• Uses solar energy to heat
boiler feedwater
• Not improvement to
existing equipment, but
addition of solar power to
Rankine cycle
• Considered to be less
mature
– may require further
research, development, and
demonstration
SAFWH Installation Cost Examples
Capital Cost
US$ million
(2012)
660-MW Supercritical plant with indirect SAFWH
$103
350-MW Supercritical plant with indirect SAFWH
$34.78
125-MW plant with 7 indirect SAFWH
$17.8
750-MW plant with indirect SAFWH
$98.8
498-MW plant with seven (7) indirect SAFWH
90-MW plant with SAFWH to add to 7.5 MW of power
90*MW plant with SAFWH to increase efficiency and decrease coal usage
$15
$48 – 112
$120 – 280
SAFWH
CO2 Emissions Reduction Summary
Heat Rate,
BTU/kWh
Pre-retrofit
CO2
Emissions,
Million
tonnes/yr
Post-retrofit
CO2
Emissions,
Million
tonnes/yr
CO2
Emissions
Reduction,
Million
tonnes/yr
Plant A
9,820
(739 reduction)
3.93
3.65
0.28
(7.1%)
Plant B
9,332
(348 reduction)
3.60
3.47
0.13
(3.6%)
9,277
(n/a)
3.45
-
-
Plant
New Subcritical PC
SAFWH
First-Year Cost of Electricity
$70
Total
$60
Fuel
New Subcritical PC: $59.40/MWh (9,277 Btu/kWh)
Variable O&M
Cost of Electricity ($/MWh)
Fixed O&M
$50
$45.76
Capital
$47.40
$44.37
$46.02
$40
$30
$27.28
$27.28
$25.91
$25.91
$20
$7.16
$7.16
$7.16
$7.16
$10
$10.42
$0
$0.89
Plant A, 9,820 Btu/kWh ($35
Million Retrofit)
$10.42
$2.53
Plant A, 9,820 Btu/kWh ($100
Million Retrofit)
$10.42
$0.89
Plant B, 9,332 Btu/kWh ($35
Million Retrofit)
$10.42
$2.53
Plant B, 9,332 Btu/kWh ($100
Million Retrofit)
USEPA’s Latest Rules Affecting Coal-Fired Power Plants
Cross-State Air
Pollution Rule
(CSAPR)
Mercury and Air
Toxics Standards
(MATS)
Carbon Pollution
Standard for New
Power Plants
Carbon Pollution
Standard for
Existing Plants
• To reduce SO2 and
NOX emissions from
power plants in
eastern U.S.
• Vacated in federal
court in August 2012
• Clean Air Interstate
Rule (CAIR)
reinstated pending
development of
valid replacement
• Finalized version
April 2013
• No sources required
to comply until April
2015
• To limit mercury,
acid gas, and other
toxic pollution from
power plants
• Replaces Clean Air
Mercury Rule
(CAMR)
• Finalized on January
8, 2014
• Uniform national
limits on amount of
carbon pollution
that future power
plants allowed to
emit (500 g/kWh)
• Proposed on June 4,
2014
• Final standards and
guidelines by June 1,
2015
• Uniform national
limits on amount of
carbon pollution
that existing power
plants allowed to
emit
Conclusions
• Older, less efficient plants – benefit more from technology upgrades
− payback ranged from 1 to 7 years depending on level of efficiency achieved
• Newer plants – certain retrofits might not be economically viable based on
limited efficiency improvement at high capital cost
• Significant efficiency improvements can be achieved at existing plants
− newer existing plants can achieve performance of new subcritical power plant
− older plants achieve 2 or 3 percentage points increase in efficiency
• Significant emissions reductions are possible
− ranging from 1% for retrofits, such as coal pulverizer upgrades on newer plants, to
almost 9% for older plants when cumulative retrofits applied in synergistic ways
• Steam turbine upgrade provided greatest impact at lowest cost ($15/kW)
• Condenser retrofit had similar cost ($17/kW) with slightly lower impact on
performance
• Coal pulverizer and ancillary equipment had highest cost and lowest
performance impact
• SAFWH hold promise for significant reductions in efficiency, but require
additional development and demonstration
Summary
• Current study:
− examined only 3 of many “off-the-shelf” technologies and 1 new
technology at hypothetical typical existing U.S power plants
− significant efficiency improvements can be achieved at existing plants
− significant emissions reductions are possible
− payback ranged from 1 to 7 years depending on level of efficiency
achieved
• Possible additional studies:
− improve veracity of cost estimates
− evaluate other technologies
• Desire to work with utilities and stakeholders
− assess improvements made to real-world assets
Visit Our Websites
Office of Fossil Energy
www.energy.gov/fe/office-fossil-energy
NETL
www.netl.doe.gov