RELIABLE AND EFFICIENT STEAM GENERATION SYSTEMS FOR MODERN UTILITY SERVICE

The safe, reliable and efficient generation of steam has challenged

boiler designers since steam was first harnessed for power. As market

conditions and customer demands have changed through the years,

The Babcock & Wilcox Company (B&W) has met those challenges with

constant innovation and engineering know-how.

Todays demand for highly efficient, variable pressure steam conditions

has brought out the best in B&Ws engineers. Both our proven supercritical

designs and natural circulation boilers offer the flexibility to meet the

most demanding needs of our customers. We have designed boilers to

burn nearly every fossil fuel imaginable.

Since 1867, when George Babcock and Stephen Wilcox patented the

first water tube boiler, B&W has drawn from its wealth of engineering

experience and incorporates the best available technology into each

new design. We are well prepared to continue our leadership role

in the design, engineering and construction of the most reliable and

efficient steam generating systems available.

3B&Ws proven boiler designsoffer the flexibility to meetthe most demanding needsof our customers. Shown aretwo B&W 420 MW variablepressure, supercritical (spiralwound universal pressure,SWUP) units with boiler terminal conditions of 3596 psi,1054 F/1105 F (248 bar, 568 C/596 C).

Supercritical for todays power demands

Many factors continue todrive improvement in pul-verized coal-fired systemperformance. Key trendsinclude increased thermalefficiency, improved envi-ronmental performance,increased availability andthe overall reduction of the cost of electricity.Deregulation of the world-wide power industry, thedesire for energy supplydiversity plus the high costof imported fuels make highefficiency systems moreattractive.

Higher plant efficiencywith reduced emissions

At supercritical pressures,steam turbine efficiencyimproves significantly compared to the typicalsubcritical cycle. This effi-ciency improvement leadsto reductions in both fuelinput and emissions outputs.The cycle efficiencyimprovement of approxi-mately 2.5% is associatedwith a pressure increasefrom the typical 2400 psi(167 bar) throttle to the typical supercritical throttle pressure of 3600 psi (250 bar).

The combination of theincrease to supercriticalthrottle pressure and anincrease in throttle tempera-ture to 1110 F/1110 F (600 C/600 C) provides an overall 5.5% increase inplant efficiency comparedto the 2400 psi, 1000 F/1000 F (167 bar, 538 C/ 538 C) cycle common inNorth America. Theseimprovements result inoverall cost reductions infuel handling and usage,flue gas treatment, and ash disposal.

B&Ws supercritical boilerhas been designed to takefull advantage of variable pressure turbine operation.Specific advantagesinclude:

The load change rate capa-bility of the system is notrestricted by the turbine

Steam temperature at theinlet and outlet of thereheater is nearly constantover a wide load range

The boiler feedwater pumppower is significantlyreduced at lower loads

Short startup times Higher plant efficiencyover the entire load range

4An optimized multi-lead ribbed tube design providesthe necessary combination of heat transfer and pres-sure drop for a low mass flux once-through boilerdesign to function properly.

Figure 1: The spiral furnace design permits true vari-able pressure operation.

Efficiency and flexibility are key to B&Ws supercritical designs

SPIRAL WOUND DESIGNHIGH MASS FLUX

VERTICAL TUBE DESIGN

Several technologies are cur-rently available for once-through supercritical boilerdesigns. The UniversalPressure (UP) boiler withvertical, multi-pass furnacewas developed by B&W tomeet the base load and loadcycling needs of U.S. utilitiesfor supercritical boiler appli-cations from the 1950s tothe 1980s. When variablepressure and on/off cyclingare required modes of opera-tion, the B&W Spiral WoundUniversal Pressure (SWUP)boiler is the appropriatedesign choice. The VerticalTube Universal Pressure(VTUP) boiler with theSiemens optimized multi-lead ribbed (OMLR) tubingis also being developed forvariable pressure and on/offcycling applications. B&Wssupercritical experience,coupled with the Bensontechnology, gives us a uniqueexperience base for meetingthe customers variousrequirements.

Vertical tube multi-pass furnace (B&W UP) boilerThe high mass flux verticaltube furnace supercriticaldesign features a furnacedesign that operates abovethe critical pressure. Thehigh mass flux in the highabsorption areas of the furnace is achieved byarranging the enclosure tubing in multiple passes. A throttling valve locatedbetween the primary andsecondary superheaterenables the boiler to maintain supercritical operation in the furnace

throughout the operatingload range while operating inthe variable pressure mode atfull steam temperature at thesuperheater outlet. Thisarrangement has proven tobe ideal for base load andload cycling operations.

Spiral wound furnace(B&W SWUP) boilerThe two keys to once-through boiler furnacewater side design are main-taining uniform tube-to-tubetemperatures and maintain-ing adequate heat transferon the inside of the tubes in high heat flux areas. Thespiral wound furnace has aproven record of achievingboth of these goals. Asshown in Figure 1, the spiralfurnace design allows thefluid in the tubes to passthrough the various heatflux zones around the furnace providing a moreuniform outlet enthalpy. Thelayout of the spiral tubesprovides for fewer parallelflow paths than verticaltube arrangements. Thisarrangement produces ahigh mass flux to maintain

adequate heat transfer onthe inside tube wall. B&Wsspiral furnaces utilize multi-lead ribbed tubing to allowonce-through operation atlower minimum loads. Thisdesign is ideal for on/offcycling requirements and,unlike the vertical tube highmass flux designs, permitsvariable pressure operationin the furnace.

Vertical tube universalpressure (B&W VTUP)boilerWhile the spiral furnace iswell suited for daily on/offand variable pressure opera-

Reduced Rib Lead AngleIncreased Rib Height

OptimizedMulti-leadRib Design

Multi-leadRib Design

tion, it is somewhat morecostly to fabricate and erect.The low mass flux verticaltube variable pressure furnace with OMLR tubingcombines the advantages ofvariable pressure operationwith the fabrication anderection simplicity of a vertical tube furnace.

While the multi-pass andspiral furnaces are designedto operate in a high massflux, forced circulationmode, the vertical tube fur-nace design takes advantageof natural circulation char-acteristics similar to a drumboiler. The OMLR tubingmakes this design possible.Through years of laboratorytesting, an optimized ribbedtube has been designed toprovide the combination ofheat transfer and pressuredrop required for a lowmass flux once-throughboiler design to functionproperly. B&W continues todevelop this promisingdesign for application infuture power plants.

Typical B&W spiral wound universal pressure (SWUP) boiler.

Low NOXBurners

OverfireAir Ports

Primary AirFan

TrisectorAir Heaters

Steam CoilAir Heater

Axial ForcedDraft Fan

B&W Roll WheelPulverizers

AmmoniaInjection

Grid

Steam Separators

Water Collection Tank

Primary Superheater

CirculationPump

Primary Reheater

Catalyst

IntermediateSuperheater

SpiralTransitionHeaders

Furnace

SCR

C LowerFurnaceHeaders

Flue GasOutlet

Economizer

PlatenSuperheater

FinalSuperheater

FinalReheater

Primary AirDuct

TemperingAir Duct

Roof InletHeader

PlatenSuperheaterInlet Header

ReheaterOutlet

Header

SuperheaterAttemperator

Baffle WallOutlet Header

Roof Outlet Header

Convection PassRear Wall Outlet Header

Primary Superheater Inlet Header

Circulation Pump Recirculation Line

Reheater Inlet Header

Economizer Inlet Header

Convection Pass Downcomers

FurnaceRear Wall

Outlet Header

Primary Superheater Downcomers

Circulation Pump Subcooling Line

GasBiasing

Dampers

Furnace Downcomer

PlatenSuperheaterOutlet Header

IntermediateSuperheaterInlet Headers

FinalSuperheater

Outlet Header

Convection PassFront Wall

Outlet Header

PrimarySuperheater

Outlet Header

EconomizerOutlet Headers

FurnaceRoof

Figure 2: B&Ws once-through boiler startup systemallows for rapid startups with the least amount ofthermal stress on the components.

From the first supercritical boiler inthe U.S. to units up to 1300 MW,B&W has the proven experience toprovide the worlds most efficientsteam generating systems.

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Rapid startup systems

During startup of a once-through boiler, the water-side components must havea minimum water flowmaintained to ensure ade-quate cooling. B&W startupsystems are well proven toprovide reliable flow to thewaterside components toproduce short startup timesand low thermal stresses.

The typical variable pres-sure boiler startup system is shown in Figure 2. Themain components of thesystem are the verticalsteam separators, water collecting tank and boilerrecirculation pump. Thesteam separator acts similarto a drum in a natural circu-lation boiler. The fluid fromthis separator is recycled tothe economizer inlet whereit mixes with feedwater tomaintain the minimum flowthrough the boiler furnace.

Once minimum load isachieved, the startup systemis put in warm standby forquick use when required.The steam from the separa-tor passes through to thesuperheater and then on tothe turbine. The startupoperation parallels that of adrum boiler. This systemprovides the maximumamount of heat recoveryback to the boiler duringstartup allowing for rapidstartups with the leastamount of thermal stress onthe components.

The continued advancement of ultrasupercritical technology

Current designs are forsteam cycles of 3500 psi(241 bar), with overpres-sure, and temperatures inthe range of 1110 F/1110 F(600 C/600 C). B&W con-tinues the quest for higher

plant efficiencies throughthe development of advancedmaterials. Under sponsor-ship from the U.S. Depart-ment of Energy and theOhio Coal DevelopmentOffice, we have been conducting field testing ofadvanced materials for sev-eral years and are a majorparticipant in the ongoingultra supercritical materialsdevelopment program.

The goal of this program isto develop boiler materialswhich will allow plant effi-ciencies to be boosted tonearly 50%. Attainment ofthese high efficienciesrequires turbine throttletemperatures near 1400 F(760 C). These conditionsrequire materials with sig-nificant improvements infatigue and creep strength,as well as fireside andsteamside corrosion resis-tance. B&Ws involvement

in this program underscoresour dedication to improvingcoal-fired boiler technology.

The experience of B&W

Having supplied more than140 once-through boilers,including 91 supercriticalunits ranging in size up to1300 MW capacity, B&Whas the expertise to designthe worlds highest qualityboilers. B&W designed thefirst supercritical boiler inthe United States whichwent into operation in 1957.From this initial 125 MWunit, B&Ws proven once-through boiler size capabilityincreased to 1300 MW injust 15 years. Today, nineB&W 1300 MW steam generating units have com-bined for more than 200years of operation, includ-ing one unit that, at thetime, set a world record of607 consecutive days with-out shutting down.

The B&W natural circula-tion drum boiler design, orradiant boiler (RB), providesthe advantages of low initialcapital cost, wide flexibility(including multiple fuels),forgiving operation andvery high reliability andavailability.

The basic design featuresinclude a completely water-cooled furnace, balanceddraft design, and horizontaland vertical convectionpasses to minimize initialcapital cost and dry ashremoval. B&W has suppliedmore than 700 RB boilersworldwide up to a capacityof 900 MW.

Recent design improvementshave been incorporated in anumber of areas, includingpulverizers, low NOx com-bustion systems, startup/lowload systems, superheaterheader stress reduction andmaterial upgrades, post-combustion environmentalsystems, and advanced con-trol systems to optimizeoverall performance.

The workhorse baseloaded boiler, for manyyears, has been theB&W natural circulationdrum boiler.

Auxiliary equipment playsan important role in apower plants long-termavailability and reliability.The same high quality stan-dards that are built intoB&W boilers go into all ofour auxiliary and relatedequipment.

B&W Roll Wheelpulverizers

B&W has designed, constructed and placed in operation more than 1,100roll wheel pulverizersgrinding a wide range ofworldwide coals. Featuressuch as a rotating throat,Auto-Spring loading system,DSVS rotating classifier, andWEARESISTOR roll wheeltires offer improved boilerload-following capability,optimal pulverizer perfor-mance, and reduced operat-ing and maintenance costs.These benefits contribute to stable steam generatorperformance regardless ofstation duty. The B&W RollWheel pulverizer has set the standard in the industryfor value.

As a one-stop source fortotal boiler island supply,construction services, envi-ronmental equipment andaftermarket services, B&Whelps minimize your projectand performance risks.

Manufacturing and procurement

B&W has put in place aworldwide procurementprocess for world sourcingand has prequalified equip-ment suppliers. In addition,we operate manufacturingfacilities to serve the powergeneration and industrialboiler market with uniquecapabilities. From special-ized plant components tothe largest steam systems,B&W is your most reliablesource of equipment foryour boiler. We provide our customers with the bestvalue quality productsdelivered on schedule.

Environmental equipment

When it comes to cleansteam generation from fossil-fueled boilers, no othercompany has the experienceof B&W. We have been atthe technological forefrontin providing cost-effectivesolutions to tough emission-control standards. Our continued research andcommercial applications ofNOx, SO2, particulate andmercury reduction have ledto many advancements in airpollution control technology.

A variety of emission-control technologies, bothcombustion and post-combustion, are available tomeet our customers specificenvironmental strategies: Low NOx burners andstaged combustion systems

Selective catalytic reduc-tion (SCR) systems

Wet and dry flue gasdesulfurization (FGD) systems

Fabric filter baghouses Electrostatic precipitators

Services

B&Ws involvement withyour new power plant doesntend when the power isdelivered to the grid. We are recognized as a highlyreliable and responsive ser-vice organization. Whetherthrough our many regionalfield engineering serviceoffices, or our customer service organization, B&Wcan help ensure the safe,reliable and efficient operation of your steamgeneration assets.

Some of the many servicesthat we provide include:

On-site training Startup, testing and commissioning

Replacement parts andinventory management programs

Field engineering services Condition assessment Equipment or plantmaintenance services

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Auxiliaryequipment

Total-scopecapability

Radiant boilers

B&W DRB-4Z low NOxburners, along withstaged combustion sys-tems, offer the plantowner the ultimate incombustion NOx control.

The latest environmentaltechnologies were incor-porated into this powerplant, including ultra-lowNOx burners, SCR system,dry FGD and fabric filterbaghouse.

B&W has supplied morethan 700 radiant boilersworldwide.

The B&W Roll Wheelpulverizer has demon-strated both reliable anddurable operation. B&Wcontinues to improveupon the original designto provide additionalperformance and costbenefits.

1BWCCs experience andknowledge of the latestconstruction technologywill help ensure the safeand successful executionof your project.

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B&Ws family ofbusinesses

Babcock & WilcoxConstruction Co., Inc

Babcock & WilcoxConstruction Co., Inc(BWCC), a subsidiary ofB&W, provides a full-rangeof field construction, con-struction management,advanced construction tech-nology, and maintenanceservices. An experiencedmanagement team com-bined with skilled craftsmenwill help ensure the safeand successful execution ofyour construction project.BWCC continually looks formethods to reduce the over-all construction span of aproject. One such method ismodularization. Modular-ization is an integratedapproach to power plant

construction and must beincorporated at the earliestpossible stages of a projectsplanning phase.

To take full advantage ofnew construction tech-niques, BWCC conductsconstructability reviewsthroughout the project. Thedesign for constructabilityprocess optimizes the integration of constructionknowledge and experienceinto project planning,design, procurement andfield operations to achieveoverall project objectives.

Diamond PowerInternational, Inc.(DPII)Seven out of ten powerplants feature sootblowers

from Diamond PowerInternational, Inc., a B&Wsubsidiary. Using superheatedsteam, saturated steam, compressed air or water,Diamond Power soot-blowers remove deposits, prevent plugging of gas passes and maintain boilerefficiency. From the G9B tothe HYDROJET to theindustry standard the IK Diamond Powers specializedsootblower designs and configurations meet customerneeds for precision, reliabilityand efficiency.

Allen-Sherman-Hoff(A-S-H)Allen-Sherman-Hoff, a division of DPII, is theindustry pioneer in providingash-handling systems, parts

and service. Structural,mechanical and electricalexpertise is incorporated into every design, such asthe ASHVAC segregatingvalve, the HYDROBINdewatering bin and theHYDRO-EJECTOR jetpump. Leading A-S-H products include pneumatic,hydraulic and mechanicaldrag chain conveying systems.

From boiler to stack, B&W and its family of businesses provide products and services for the entire power plant.

Diamond Power, a B&Wsubsidiary, is a leader inproviding boiler cleaningand furnace monitoringdevices.

Babcock & Wilcox Power Generaon Group, Inc.20 S. Van Buren AvenueBarberton, Ohio 44203 USAPhone: 330.753.4511Fax: 330.860.1886The informaon contained herein is provided for general informaon purposes only and is not intended nor to be construed as a warranty, an oer, or any representaon of contractual or other legal responsibility.

B&W, UP, SWUP, VTUP, DRB-4Z, B&W Roll Wheel, Auto-Spring, DSVS and WEARESISTOR are trademarks of Babcock & Wilcox Power Generaon Group, Inc.

HYDROJET, ASHVAC, HYDROBIN and HYDRO-EJECTOR are trademarks of Diamond Power International, Inc.

Benson is a trademark of Siemens AG and is used under license.

2004 Babcock & Wilcox Power Generation Group, Inc. All rights reserved.

E101-3185 1KA0G

Babcock & Wilcox Power Generaon Group, Inc. is a subsidiary of The Babcock & Wilcox Company (B&W). Established in 1867, B&W is a world leader in providing steam generang and emissions control equipment, nuclear operaons and components, and defense program management services.

For more informaon, or a complete lisng of our sales and service oces, call 1-800-BABCOCK (222-2625), send an e-mail to info@babcock.com, or access our Web site.

www.babcock.com

The Babcock & Wilcox Company

is recognized and respected

worldwide for its dependable

and efficient steam generation

systems. We are experts in

converting the energy in fuels

to energy in steam.

Our total-scope capability

includes boiler and boiler island

supply, environmental systems,

auxiliary equipment and

complete construction and

startup services. As a one-stop

source, we minimize your

project and performance risks.

No other boiler company can

duplicate the engineering

excellence and advanced

technologies developed by The

Babcock & Wilcox Company.

B&Ws commitment to our

customers and employees

continues full steam ahead.