supercritical boiler technology
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LEADING THE INDUSTRYIN SUPERCRITICAL
BOILER TECHNOLOGY
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Alstom is a global leader in the world of power generation, setting the
benchmark for clean, innovative technologies to create customer value.
We supply major equipment in 25% of the installed base worldwide.
And weve developed an unmatched level of expertise in steam
generation and fuel combustion technology, having supplied more
than 400 GWe of boilers around the world.
Our boilers convert fuel into steam for the generation of electricity
cleanly, cost-effectively, reliably. As the No 1 supplier of boilers
worldwide, we can meet your project requirements today and in the
future with the design, manufacture and supply of state-of-the-art
systems and equipment.
HIGH-EFFICIENCY
SUPERCRITICAL TECHNOLOGY
Alstom pioneered supercritical steam generation and today leads
the industry in supercritical boiler technology. We have directly
supplied more than 80,000 MWe of supercritical boilers world-
wide. In addition weve trained and licensed other companies to
install an additional 72,000 MWe of Alstom supercritical boilertechnology. Globally, we have unmatched experience in tailoring
boiler designs to fuel properties.
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FOR CLEAN POWER TODAY!
Leading Through Technology
Today, our advanced high-efficiency pulverized coal supercritical
boilers offer plant owners many benefits. The technologys higher
steam temperature and pressure parameters deliver the most
economical way to improve plant efficiency and operatingflexibility, achieve fuel cost savings, and reduce emissions for each
kWh of electricity generated. Alstoms Advanced Supercritical
technology reduces allemissions, including CO2.
In fact, an efficiency improvement of 1 percentage point equals
2%-3% less CO2 emitted.
Alstom is also driving the development and deployment of the
next generation ofclean coal combustion technologies. We are
investing in the future of clean power across 22 development
centers and 13 laboratories around the world with the express
goal of minimizing environmental impact. One Alstom combustion
technology currently in the pilot plant demonstration phase
enables the capture
of CO2 emissions
from fossil fuels,
including pulverized
coal boilers. Known
as oxy-fuel firing,
this technology is
being tested in a 30
MWth pilot at the
Schwarze Pumpe
Power Station in Germany. Oxy-fuel firing is especially promising
for CO2 -free supercritical generation in the near term.
In addition to our own R&D activities, we participate in a
number of public development projects and partnerships,
including those sponsored by the European Union and the US
Department of Energy, as well as nearly all joint boiler materialsdevelopment programs.
Why Alstom Advanced
Supercritical?
Superior environmental
performance
Highest unit efficiency
Operating flexibility
Design tailored to fuel choice
Fuel cost savings
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Once-through supercritical technology offers important benefits
to plant owners, including:
Increased efficiency
Lower emissions levels
Lower operating costs
Greater operating flexibility
These benefits are possible because of the higher steam pressures
and temperatures which are a hallmark of the technology.
Understanding Supercritical Technology
Water/steam circulation systems are divided into two main
classifications: once-through, in which the water and steam
generated in the furnace waterwalls passes through only once;
and drum-type boilers, in which water/steam separation occurs,and water is recycled back to the waterwalls.
Supercritical conditions occur when the boiler pressure increases
above the critical pressure of 3,208 psi / 221.2 bar. Above this
point, two phase mixtures of water and steam cease to exist, and
are replaced by a single supercritical fluid. This eliminates the need
for water/steam separation in drums during operation, and allows
a simpler separator to be employed during start-up conditions.
Increased Efficiency and Lower Emission Levels
Plants that employ todays generation of Alstom supercritical
boilers can operate at cycle efficiencies in excess of 42-45% HHV
(44-47% LHV). As efficiency is increased, less fuel is consumed per
kilowatt-hour (kWh) with a corresponding decrease in emissions
per kWh. Because these units do not have thick-walled steam
drums, their start-up times are quicker, further enhancing
efficiency and plant economics. We continue to develop increasingly
efficient supercritical cycles for improved efficiency. Alstoms current
technology development will lead to our prototype ultra-supercritical
plant, operating at 1290 F (700 C) / 5075 psi (350 bar).
Lower Operating Costs
Lower fuel consumption is a direct consequence of higher
efficiencies. Fuel costs are a power plants largest operating costitem. Because the capital cost of supercritical plants is close to
those of subcritical plants, overall life cycle costs are often reduced.
THE SUPERCRITICAL
DIFFERENCE
Heat Rate Improvement vs.
Steam Conditions (Single Reheat)
Faster Start-up Time with Once-Through Design
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Greater Operational Flexibility
Todays market realities demand that units are not only designed
for baseload operation, but are capable of cycling and/or two-shiftoperation. Units must be designed for rapid response times.
Alstom once-through supercritical boilers have the ability to
respond and adjust to changes in load demand while maintaining
tight control of steam temperatures.
Alstoms supercritical boilers operate in the sliding pressure
mode, where pressure is reduced with load. This allows the
maintenance of relatively constant first-stage turbine temperature,
reducing the thermal stress on components as the unit is cycled.
Less stress translates into less maintenance and higher availability.
Todays generation of supercritical boilers boast high availabilities,
comparable to those of subcritical units, as well as improved plant
efficiency at lower loads.
Unlike drum boilers, once-
through units do not have a
fixed evaporative point: the
final evaporation occurs in the
furnace wall systems with steam
that is leaving the furnace
walls being superheated to a
certain degree. Since the
evaporation point is not fixed,
heat duties can be shifted
between the furnace and the
superheaters, allowing for
adjustment to changing
slagging and fouling
conditions caused by
changing fuel properties.
Sliding Pressure Operation
for Once-Through Boilers
1. Constant pressure operation
2. Modified sliding pressure operation3. Pure sliding pressure operation
Efficiency Improvement with Increasing Steam Conditions
Today
psi/OF/OF(bar/OC/OC)
SUBCRITICAL
Material Improvement Milestones
1960 1980 2000 2010 2020
Efficiency
Increase
5075/1350/1400350/730/760
SUPERCRITICAL
Mature technology
CONTINUED ADVANCEMENTS
Steam Conditions
2400/1000/1000167/540/540
3500/1000/1050240/540/565
3900/1075/1110270/580/600
4050/1110/1150
280/600/620
5075/1290/1330350/700/720
R&D ongoing USAUSC MaterialsConsortium & EC
AD 700 project(Ni-base)
R&D ongoing
Marketintro. by
JapanandEurope
DOE USC Matl.
DOE Steam Turbine Matl.AD 700 projectCOMTES 700
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Alstom technologies deliver realistic solutions for reliable clean
coal generation now. Our advanced supercritical boiler designs are
at the heart of todays state-of-the art plants, meeting the diverse
requirements of projects all over the globe and firing the full
range of international coals.
With Alstoms supercritical boiler design advantages, coal is
clean, economical and secure.
ADVANCED
BOILER DESIGNS
1 x 750 MWe, US
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Spiral Configuration
Benefits from averaging of lateral heat absorption variation
(each tube forms a part of each furnace wall)
Simplified inlet header arrangement
Large number of operating units
Use of smooth bore tubing throughout
entire furnace wall system
No individual tube orifices
Vertical Configuration
Simpler windbox openings
Simpler furnace water wall support system
Elimination of intermediate furnace wall transition header
Less costly to construct
Easier to identify and repair
tubes leaks
Lower water wall system pressure
drop thereby reducing required feed
pump power
Furnace Wall Designs
In todays market, two designs dominate for once-through units:
the spiral furnace tube arrangement and thevertical tube arrangement.
Design choice is governed by furnace size and customer preference
there are advantages to both, depending on project drivers.
The furnace walls are exposed to the greatest heat flux of all
heat-absorbing surfaces. This is because of the intense radiant
heat from the fireball.
For any given furnace size, the spiral wall unit in which the tube is
wrapped around the unit has fewer tubes than the vertical wall unit.
The vertical waterwall design uses internal ribbing in the tubes to
improve heat transfer. The vertical wall option is available for larger
units where lower perimeter-to-furnace plan area ratios result in
higher fluid flow per tube. The vertically oriented tubes are
self-supporting within the wall, allowing a simpler
support system. In fact, the relative simplicity of a
vertical wall furnace can result in significant
construction cost savings.
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Two-Pass, Pendant ArrangementTower Boiler Arrangement
Tower and Two-Pass Designs
Alstom provides tower and two-pass boiler designs, both of
which are widespread in power generation applications. In a tower
design, all heating surfaces are horizontal and drainable, and
generally in a single vertical configuration within the furnace
bounding walls.
Niederaussem Unit K, Germany
1 x 1000 MWe
Tower Design
Houshi Units 5-7, China
3 x 600 MWe
Two-Pass Design
Two-pass is a shorter design which incorporates vertical heating
surface in the radiant section of the furnace, and horizontal
surface in a parallel backpass. The selection of boiler configuration
is project specific, with consideration given to fuel ash
characteristics, site restrictions, and customer preference.
ADVANCED
BOILER DESIGNS
Nominal 900 MWe
2 x 800 MWe, South Korea
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Advanced Materials
High temperature materials enable the steam conditions and
corresponding thermal efficiency of advanced supercritical
steam cycles. Ideally, materials used in steam generator pressure
parts combine high temperature strength with reasonable
resistance to oxidation. In addition, the workability of the
materials and corrosion behavior are important attributes.
The increase of steam conditions primarily affects the waterwalls,
final superheater and reheater tubing, and the thick-walled
components, mainly the high pressure outlet headers and piping
to the turbine. Classes of materials include conventional and
advanced ferritic steel, austenitic steel, and nickel alloys.
Several boiler materials with improved mechanical properties
have been developed recently, and new materials still in the R&D
stages will enable higher ultra-supercritical steam cycles than are
today commercially available. Most materials development is
being conducted under national or internationally coordinated
programs. Alstom participates in nearly all cooperative materials
development programs, including the AD 700 / COMTES 700
program funded by the European Commission, and the US
Ultra-Supercritical Materials Consortiumsponsored by the
US Department of Energy.
Material Development Stages and Related Steam Parameter Limits
Membrane Wall
FutureOptions
Current
Past
Tubes SH Outlet Header
T92Nickel Alloy
Nickel Alloy Nickel Alloy
Austenitic NF 12,SAVE 12, VM12
7 CrMo VTiB 10 10HCM 2S
Austenitic E 911, P 92, P 122
Bar SHO0C - SH Temp0C - RH Temp
Austenitic P 9113 CrMo 4 4
260550570
270580600
290600620
300630650
350700720
260550570
270580600
290600620
300630650
350700720
260550570
270580600
290600620
300630650
350700720
9-12%Cr-Steels
X 20CrMoV 121
X 20CrMoV 121
Waterwall Tubes SH Outlet Header
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BEIJIANG CHINA
2 x 1000 MWe
Chinese Bituminous
Owner: Tianjian Guotou Jinning
Power Generation Ltd.
Commercial operation: 2010
Most advanced steam
conditions for China
COMANCHE 3 US
1 x 814 MWe
Powder River Basin coal
Owner: Xcel Energy
Commercial operation: 2009
Will achieve one of the
lowest NOx levels in US
Recent ReferencesAlstom Advanced Supercritical Boiler Technology
A WORLD OF
SUCCESS STORIES
BELCHATOW POLAND
1 x 833 MWe
Lignite
Owner: BOT Elektrownia
Belchatow SACommercial operation: 2010
Highest efficiency level of
any brown coal-fired plant
in the country
IATAN 2 US
1 x 920 MWePowder River Basin coal
Owner: Kansas City Power
& Light
Commercial operation: 2010
Features advanced vertical
wall construction
NEURATH F & G GERMANY
2 x 1100 MWe
Lignite
Owner: RWE Power AG
Commercial operation: 2010
CO2, SO2, NOx and dust
emissions reduced by 31%
compared to existing
lignite-fired plants
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PEE DEE US
1 x 640 MWe
Eastern Bituminous
Owner: Santee Cooper
Commercial operation: 2011
Designed to fire up to
30% petcoke
YONGHUNG SOUTH KOREA
2 x 800 MWe
International coal
Owner: KEPCO
Commercial operation: 2004
First units based on the new
800 MWe Korean Standard
Thermal Power Plant
NING HAI CHINA
2 x 1000 MWe
Range of Chinese coals
Owner: Zhejiang Guohua Zheneng
Power Generation Co.
Commercial operation: 2009
Another addition to Chinas
highest-efficiency fleet
WAI GAO QIAO PHASE II CHINA
2 x 900 MWe
Range of Chinese coals
Owner: Shanghai Municipal
Electric Company
Commercial operation:
2003-2004
Design replicated in Wai Gao
Qiao Phase III 2 x 1000 MWe,
scheduled to enter commercial
operation in 2008
1954: Earliest Extant Supercritical Generating Unit in the World
Alstom laid the foundation for todays Advanced Supercritical fleet at
Philadelphia Electric Companys Eddystone Unit 1 (US). Eddystone
pushed the technology for steam generating electric plants, pioneering
substantial increases in steam pressure, steam temperature and unit
size. At the time of start up, the 394 MWe Eddystone 1 was
the most efficient plant in the United States. It is still operating
at advanced steam conditions.
Initial steam cycle: 5293 psig, 1200/1050/1050 F
365 bar, 649/566/566 C
Current steam cycle: 5200 psig, 1130/1030/1030 F
359 bar, 610/554/554 C
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Alstom is a global leader in supplying firing systems for utility
boilers. Our firing systems burn a wide range of fuels, reduce
emissions levels and retain excellent levels of availability
and reliability.
Primary classes of utility-scale firing systems include suspension
firing and fluidized bed combustion.
In suspension firing, the fuel is either finely ground (for solid
fuels), atomized (for liquid fuels), or fired as a gas that quickly
burns as it mixes with combustion air and passes through the
furnace. Fuel is not recirculated in suspension firing as it is in
fluidized bed combustion.
FIRING SYSTEMS
Taean, one of the 20 x 500 MWe sliding pressure supercritical units using Alstom
technology in Korea. Since 1995, this unit has operated in daily two-shift operation
with high reliability.
State of the Art. Proven. Innovative.
2 x 800 MWe efficient and highly reliable supercritical steam generation since
1996 at the Schwarze Pumpe Station in Germany.
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TangentialFiring
Alstoms preeminent
suspension firing
system is tangential
(corner) firing,
with a track record of reliable performance, efficient combustion,
and very low nitrogen oxide emissions.
With tangential firing, a stable fireball is formed in the center of
the furnace over the entire operating range. Heat absorption
profiles are more predictable. As boiler load changes, corresponding
fuel elevations are deployed. Tangential firing has the additional
advantage of a stable flame pattern with any combination of
fuel elevations in service. Unbalances are minimized, and the
predictable lateral heat absorption profiles allow a more
conservative design of furnace wall circuits.
Alstoms family of TFS
2000 firing systems
employs both horizontal
and vertical staging of combustion air to produce ultra-low NOx
emissions. The latest addition to this product line is the TFS-XP
system, delivering enhanced performance to owners of new
pulverized coal units. Vortex control improvements to this design
result in better gas mixing, lower combustible gaseous emissions,
and uniform furnace outlet energy.
Circulating Fluidized Bed
Alstoms most popular fluidized bed combustion system is the
Circulating Fluid Bed (CFB). Used especially for more difficult to
burn fuels, CFBs also reduce NOx emissions because of their
lower combustion temperatures. Longer residence time of fuel in
the boiler is key unburned fuel is captured and recirculated for
further combustion. The addition of a sorbent (generally limestone)
also allows SO2 capture within the boiler for reduced SO2emissions without post-combustion capture.
Supercritical CFB For Maximum Fuel Flexibilityand Efficiency
Alstom has led the power industry in scaling-up utility-class CFB
boilers from 50 MWe to 600 MWe. Now customers can benefit
from our expertise in both supercritical and CFB technology
with Alstoms commercial designs for 400-600 MWe supercritical
CFB units. This premier technology application combines the
improved efficiency of advanced supercritical steam cycles with
the unparalleled fuel flexibility of CFBs. Based on rational design
innovations in larger size boilers, including 6 cyclones and higher
steam parameters, Alstoms supercritical CFB technology is
another step in bringing our customers added value, improving
the overall environmental performance of coal-fired plants, and
reducing global CO2 emissions.
Alstom An Industry Leader
Alstom introduced tangential firing
systems to the power generation
industry. Today, Alstoms family of
advanced low NOx tangential firing
systems leads the industry in
reduced emissions.
Supercritical CFB Boiler Design
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Alstom has the expertise and experience to make todays energy
production as clean and efficient as it can be. We are a world-
leading provider ofintegrated environmental solutions for power,
petrochemical and industrial plants including ways to improve
the performance and lifespan of your existing units.
In addition to high-efficiency boilers, Alstom's supercritical plant
offering includes supercritical turbines, mills, air heaters and post-
combustion equipment. Alstoms in-furnace and post-combustion
technologies can help meet todays strictest requirements for NOx,
SOx, VOCs, mercury, CO and particulates. And our integrated
boiler/backend designs will optimize your units sizing and
performance criteria, all with the lowest installed and operating costs.
Renewable targets? Alstoms experts in biomass co-firing can
reduce your carbon footprint and help your bottom-line.
Alstoms unparalleled breadth of product offering in Air Quality
Control (AQS) systems and Energy Recovery systems means we
can meet your toughest project requirements. With the largest
installed base in the world for air preheaters and coal pulverizers,
our customers benefit from superior performance, increased
efficiencies, and reliable service. And with more than 70 years
of experience in customizing AQS systems for new and existing
plants, you can depend on Alstom to deliver sustainable,
high-quality solutions at a competitive cost and performance ratio.
MORE SOLUTIONS
FOR CLEAN POWER
1 x 1000 MWe, Germany
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For further information,
please contact one of our
Regional Offices or e-mail
Western Europe/South America/
Africa/Middle East
Sales Region
Tel: +33 (0)1 46 29 16 32
Fax: +33 (0)1 46 29 16 70
Central and Eastern Europe/India
Sales Region
Tel: +49 711 917 1269
Fax: +49 711 917 1222
Tel: +91 124 4221 100
Fax: +91 124 4221 660
Asia Pacific
Sales Region
Tel: +33 (0)1 46 29 15 85
Fax: +33 (0)1 46 29 16 70
North America/Mexico/
Central America/CaribbeanSales Region
Tel: +1 860 285 2348
Fax: +1 860 285 4172
Ref: PWER/BPROB/BOILERTECHNO/eng/BUBB/12.07/US/3329 ALSTOM 2007. Alstom, the
Alstom logo and any alternative version thereofare trademarks and service marks of Alstom.The other names mentioned, registered or not,are the property of their respective companies.Please note: The information in this brochure isof a general nature, and may not be applicable foruse in any specific application. Reprinted 2007.
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