Bubbling Fluidized-Bed BoilersBurning Biomass and Low-Cost FuelsClean, efficient, reliable and easy to operate

RENEWABLE | ENVIRONMENTAL | THERMAL

Since 1867, industries worldwide have benefited from The Babcock & Wilcox

Company’s engineering expertise, manufacturing technology and operating

experience as a major supplier of steam generating equipment. Babcock & Wilcox

(B&W), continues this tradition as a leader in reliable steam generation with our

bubbling fluidized-bed (BFB) boiler.

B&W’s involvement with fluid-bed technology began in the 1950s with the first

combustor at its state-of-the-art research center in Alliance, Ohio. Now, with an

experience base of more than 30 BFB units, these facilities are helping the world

realize the promise of clean energy from a wide variety of fuels.

Fuel Flexible

The ability to utilize various fuelsources and types provides ownerswith the flexibility to take advantageof changing cost and availability.

B&W’s BFB boiler is designedwith a very large operating windowto allow a wide range of fuels to beburned, separately or in combination.

This is necessary because fuel propertiesvary widely. For example, biomass fuelshave a wide range of moisture andheating values depending upon theirsource and the time of year.

Our BFB boilers are designed with ahigh degree of flexibility to facilitateair movement between the bubblingbed and the overfire air system, to varythe gas recirculation volumes, and toadjust the fuel delivery to the bed. Thisoperational flexibility allows ownersto burn cheaper opportunity fuels andcontrol fuel costs.

B&W’s bubbling fluidized-bedboilers can burn a wide range oflow-cost opportunity fuels.

Viable fuels for a BFB:

• Wood waste

• Bark

• Paper mill sludge

• Recycled paper

facility sludge

• Sewage sludge

• Tire-derived fuels

(in combination)

• Oil

• Natural gas

• Coal (in combination)

• Peat

• Biomass

• Sugar cane waste

• Agricultural waste

Low Emissions

BFB boiler installations are proven to havelower NOx, CO, VOC, SO2 and particulateemissions than stoker-fired boilers withequivalent capacity.

Significant environmental benefits areachieved with BFB technology.

NOX

Due to the low temperaturesub-stoichiometric combustionprocesses that occur in thebubbling bed, the generationof nitrogen oxides (NOX) isinherently lower than that ofa stoker-fired boiler.

Because of good carbon burnout,a selective catalytic reduction(SCR) system can cost-effectivelybe located before dust removalequipment to further reduce NOX.

CO and VOCsDue to the intimate contactbetween the bed material and thefuel, improved fuel burnout occurs.This results in very low carbonmonoxide (CO) and volatile organiccompound (VOC) emissions.

SO2

The intimate contact betweenthe fuel and bed material allowsfor in-bed capture of sulfurdioxide (SO2). When burningbiomass in combination withsulfur fuels, alkali normallypresent in the biomass will resultin reduced SO2. Limestone canalso be added to the bed materialfor greater SO2 capture.

ParticulateDue to improved carbonburnout compared with astoker boiler, the potential forfires in back-end environmentalequipment is significantlyreduced. This allows for the useof a baghouse to meet lowerparticulate requirements.

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0.5

CO Comparison

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0.3

0.4

0.5

CO ( l

b/10

6 Bt

u)

NOx Comparison

Unc

ontr

olle

d N

Ox

( lb/1

06 Bt

u)

BFB Stoker BFB Stoker

Reliable

B&W’s advantage

B&W’s BFB boiler is designed withreliability in mind. Several featurescombine to provide low maintenancecosts, high availability and long-termreliability:

• An open bottom design permits easy removal of oversized or foreign material.

• A water-cooled, gas-tight lower furnace eliminates the potential for gas leaks caused from refractory damage.

• Bottom-supported hoppers remove load from the boiler, reduce capital requirements, and reduce potential mechanical stresses between water- cooled and non-cooled components.

Incorporated in B&W’s design arethese features to reduce maintenancecosts:

• No wear parts

• No moving parts

• No water-cooled screws or beams

• No cinder re-injection system

• Long-lasting bubble caps

B&W was the first inNorth America to offer the open

bottom BFB design. Designedwith no floor, the open

bottom furnace results incomplete debris removal

with lower capital costsand maintenance expenses.

B&W’s underbed ashremoval system consists ofbottom-supported hoppers

which isolate the bubblingbed foundation and steel

from the boiler steel.This design is considered

an advantage, particularlywhen retrofitting

an existing top-supportedunit to a BFB.

B&W’s bubble capis durable and rarely

requires replacement. Inone installation, the original

bubble caps are still inservice 12 years after

commissioning.

The open bottom designand widely spacedbubble caps allow easyremoval of oversized orforeign material, greatlyreducing downtime.

Tramp materialmoves down andcools beforebeing removedthrough thebottom hoppers.Tables ensureeven flow fromthe bed.

Fuel isdeliveredto bed byair-sweptspouts.

Widely spacedbubble capsallow removalof large trampmaterial.

Gas-tight,membranedwater-cooledwalls extend intothe bubbling bed.

Air isintroducedthroughround airducts.

Easy to Operate

Advanced combustion controlsautomatically adjust to changes inoperating conditions.

A B&W BFB boiler respondsrapidly to sudden changes in fueland steam demand. This feature is acritical requirement for easy operationof the steam generator.

Our advanced controls systemautomatically moves air fromthe bed to the overfire air systemand modulates the volume of gasrecirculation to adjust for changesin the fuel or sudden changes insteam demand.

The bubbling fluidized bed carries aninventory of hot bed material that will

rapidly convert the fuel’s energy tosteam. Automatically removingcombustion air and fuel from thebubbling bed will accommodaterapid reductions in steam load.

The ability to adjust the throw distanceof the fuel feed system allows finetuning to accommodate variationsin fuel moisture.

The B&W bubbling fluidized-bedboiler is the ideal biomasscombustion system.

Efficient

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Bottom-Supported Towerpak® BFB Boiler

The thermal mass of thebubbling bed providesstability for fuel variations.

B&W’s BFB boilers provideimproved efficiency. Intimate contactbetween the bed materials in thefluidized bed and the fuel reduces thecarbon remaining from incompletecombustion and greatly reduces theexcess air required. This improvedefficiency means lower fuel costs.

Design features:• Top- or bottom-supported• One- or two-drum designs• New or retrofit boiler

applications• Provides an option to reduce

SO2 and NOX emissions• Reduces paper mill sludge volume

while producing steam• Superior to other technologies for

burning wet wood-based fuels –between approximately 2800 and3500 Btu/lb HHV (6513 and 8141kJ/kg) without support fuels

Capacity:• Bottom-supported: up to

225,000 lb/h (28.4 kg/s)• Top-supported: from 225,000 to

1,000,000 lb/h (28.4 to 126 kg/s)

Steam pressure:To 2600 psig (17.9 MPa) throttlepressure

Superheater/reheater outlettemperatures:As required, up to 1000F (538C)

Fuels:Able to burn a wide range ofconventional fuels and waste fuelswith high moisture, including:• Wood wastes and bark• Paper mill sludges• Recycled paper facility sludges• Sewage sludge• Tire-derived fuel, in combination• Oil and natural gas• Coal, in combination• Peat• Biomass• Sugar cane waste• Agricultural waste

Lower fuel costs from

Efficiency improvement from improved carbon burnout

BFB Stoker

UBC

% o

f Hea

t Inp

ut

Efficiency improvement from lower O2

% E

xces

s A

ir

5

10

15

20

25

30

35

BFB Stoker

~

1% E

ffici

ency

1

2

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4

5

BFB boilerspecificationsfor a variety ofapplications

A comparison

between BFB

and stoker-fired

technologies

Uses a baghouse and will

meet particulate requirements

No furnace size limit

Lower NO, emissions

Lower CO emissions

In-bed so, control

Higher efficiency

from lower o,

Higher efficiency from

low unburned carbon

Low potential for back-end

fires caused by carryover

Stable steam generation

with fuel variations

No moving parts

Burns high-moisture fuels

and sludge

No cyclone dust collectors

required

Small or no tubular air heater

is ideal for recovery boiler retrofits

No submerged scraper conveyor

No high-maintenance cinder

re-injection system

Can burn biomass and

multiple fuels

Ability to remove oversized

or foreign material in ash

No bed make-up material

required

Capital cost

Operating cost

High availability

High percentage coal

High alkali fuels

Refuse derived fuels

*Not required on most BFBs

BFB Stoker

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Whether you’re considering anew BFB boiler, or a conversion ofyour recovery, stoker-fired poweror small utility boiler, fluidized-bedcombustion offers significantoperational advantages:• Fuel flexibility

• High efficiency

• Low environmental emissions

• Reduced capital costs andoperating expenses

Why B&W’s fluidized-bedtechnology?• The completely open

bottom design hasproven advantages

• Extensive research anddevelopment of fluid-bedcombustion

• Operating experience witha wide range of unit sizesand high-moisture fuels

B&W offers quality andcommitment to service• Innovative design and technical

expertise to increase production,optimize equipment andlower costs

• Capability, experience and trackrecord to ensure your projectwill progress on schedule andreach performance targets

• A tradition of excellencesince 1867

© 2020 The Babcock & Wilcox Company. All rights reserved.

The Babcock & Wilcox Company1200 E Market Street, Suite 650Akron, Ohio, U.S.A. 44305Phone: +1 330.753.4511

www.babcock.com

The information contained herein is provided for general information purposes only and is not intended nor to be construed as a warranty, an offer, or any representation of contractual or other legal responsibility.

Towerpak is a trademark of The Babcock & Wilcox Company.

E101-3161A D21E

From engineeringand design throughconstruction andstartup, B&W providestotal support for yourBFB project.

Established in 1867, Babcock & Wilcox is a global leader in renewable, environmental and thermal technologies and services for power and industrial applications.

For more information or to contact us, visit our website at www.babcock.com.

RENEWABLE | ENVIRONMENTAL | THERMAL