11

Black Liquor SpraysBlack Liquor Sprays

Rick Wessel, Ph.D.Rick Wessel, Ph.D.

Advisory EngineerAdvisory Engineer

The Babcock & Wilcox CompanyThe Babcock & Wilcox Company

Slide 2OutlineOutline

•• Objectives and key variablesObjectives and key variables

•• Black liquor spray nozzlesBlack liquor spray nozzles

•• Droplet size distributionDroplet size distribution

•• Spray distributionSpray distribution

•• Implications for recovery boilersImplications for recovery boilers

22

Slide 3Black Liquor GunsBlack Liquor Guns

Flexible hoseFlexible hose

ShutShut--offoffvalvevalve

RingRingheaderheader

SteamSteam--outoutlineslines

LiquorLiquorgungunsupportsupport

LP LP steamsteamlineline

LiquorLiquorgungunLiquorLiquorgungunportport

Slide 4Key Parameters for BL SprayKey Parameters for BL Spray

Operating ParametersOperating Parameters•• Number and Number and

arrangement of gunsarrangement of guns•• Tilt or oscillation of Tilt or oscillation of

gun barrelsgun barrels•• Nozzle type and sizeNozzle type and size•• Firing temperatureFiring temperature•• Liquor flow rate and Liquor flow rate and

pressurepressure

Process VariablesProcess Variables•• Liquor dry solids Liquor dry solids •• Liquor elevated Liquor elevated

boiling pointboiling point•• Physical properties Physical properties

(density, viscosity, etc)(density, viscosity, etc)•• Liquor burning Liquor burning

characteristics characteristics (swelling)(swelling)

33

Slide 5Spray CharacteristicsSpray Characteristics

•• Median droplet diameterMedian droplet diameter

•• Droplet size distributionDroplet size distribution

•• Spray velocitySpray velocity

•• Flow distributionFlow distribution

Slide 6Impact of Droplet Size on TrajectoryImpact of Droplet Size on Trajectory

Smeltcoalescence

Swollen char

Walldeposits

Combustionair

Smelt

Black liquor

Char Bed

Initial Droplet Diameter

Small (< 1mm)Medium (1 to 2 mm)Large (> 2 mm)

44

Slide 7Objectives for Effective SprayingObjectives for Effective Spraying

•• Control droplet size (2 to 4 mm)Control droplet size (2 to 4 mm)

–– Minimize particle carryoverMinimize particle carryover

–– Deliver mostly dry liquor to bedDeliver mostly dry liquor to bed

–– Control height of char bedControl height of char bed

•• Distribute liquor sprayDistribute liquor spray

–– Minimize liquor on furnace wallsMinimize liquor on furnace walls

–– Create a uniform symmetrical bed shapeCreate a uniform symmetrical bed shape

Slide 8

Splash PlateNozzle

Nozzle TypesNozzle Types

V-TypeNozzle

Typical NozzleGun Assembly

SwirlconeNozzle

55

Slide 9Splash Plate Nozzle GeometrySplash Plate Nozzle Geometry

Looking downLooking downon a splashon a splashplate nozzleplate nozzle 3535°°

plateplateangleangle

4545°°plateplateangleangle

Barrel TiltBarrel Tilt

Coupling AngleCoupling Angle

Splash PlateSplash PlateAngleAngle Black LiquorBlack Liquor

CouplingCouplingBarrelBarrel

Slide 10Swirlcone and VSwirlcone and V--Type NozzlesType Nozzles

Nozzle capNozzle cap

Swirl plateSwirl plate

Black liquorBlack liquor Black liquorBlack liquor

Swirlcone Swirlcone VV--Type Type

66

Slide 11BL Nozzle Operating ConditionsBL Nozzle Operating Conditions

2 - 42 – 4Median droplet size, mm

20 – 4025 – 75Flow, GPM

12 – 1815 – 45Pressure, psi

0.4 – 0.750.7 – 1.25Orifice size, in.

Swirlcone & V-typeSplash Plate

Slide 12Black Liquor Spray BreakupBlack Liquor Spray Breakup

Splash plate Splash plate tiptip

Direction of sprayDirection of spray

77

Slide 13Spray Size Distribution for BL NozzlesSpray Size Distribution for BL Nozzles

00

2020

4040

6060

8080

100100

0.10.1 11 1010

♦

♦ ♦ ♦♦ ♦♦♦♦♦♦♦

♦

♦♦

♦♦♦♦♦♦♦

♦♦♦♦♦♦♦♦

♦♦♦♦♦♦

♦

♦

⊕⊕

⊕⊕

⊕⊕⊕⊕

⊕⊕

⊕⊕

⊕⊕

⊕⊕

⊕⊕⊕⊕

⊕⊕⊕⊕

⊕⊕⊕⊕⊕⊕

Mas

s Les

s Tha

n D

, %M

ass L

ess T

han

D, %

Diameter/Median DiameterDiameter/Median Diameter

Splash plate and swirlcone nozzles with hot, concentrated black liquor

♣♣♣♣

♣♣♣♣

♣♣

♣♣

♣♣♣♣

♣♣♣♣

♣♣ ♣♣♣♣ ♣♣

♣♣

♣♣ ♣♣♥♥

♥♥

♥♥ ♥♥

♥♥

♥♥

♥♥

♥♥

♥♥

♥♥

♥♥

♥♥ ♥♥♥♥

Slide 14Median Droplet SizeMedian Droplet Size

•• Splash plate, Splash plate, swirlconeswirlcone, and V, and V--type nozzlestype nozzles•• DDmedianmedian = median droplet diameter= median droplet diameter•• KKNN, K, KLL = nozzle and liquor constants= nozzle and liquor constants•• SS = liquor dry solids (weight fraction)= liquor dry solids (weight fraction)•• TT = liquor temperature, = liquor temperature, °°C (nonC (non--flashing)flashing)•• DDnn = nozzle diameter, m= nozzle diameter, m•• QQ = volume flow rate, m= volume flow rate, m33/s/s

1.23 0.62

0.23 0.140.290 nmedian L N

D SD K KQ T

=

88

Slide 15

Solids Content (%)

Ele

vate

dB

oilin

gP

oint

(o F)

(o C)

50 60 70 80 90210

220

230

240

250

260

270

280

290

300

100

110

120

130

140

150

Liqu

orTe

mpe

ratu

reor

Elevated Boiling PointElevated Boiling Point

Non-Flashing

9°F

Transitional

FlashingT – TBP > 9°F (5°C)

5°CTypical

Range ofOperation

Elevated Boiling PointFlashing Temperature

Slide 16Three Temperature RegimesThree Temperature Regimes

Non-Flashing FlashingTransitional

Solids = 69%, EBP = 115°CExcess Temperature, ΔTe = T - TEBP

99

Slide 17Black Liquor FlashingBlack Liquor Flashing

FlashingFlashing

Higher nozzle velocityHigher nozzle velocitydue to expansion ofdue to expansion ofsteam bubblessteam bubbles

NonNon--flashingflashing

Slide 18Example Nozzle Spray ConditionsExample Nozzle Spray Conditions

•• Splash plate nozzleSplash plate nozzle•• Nozzle diameter Nozzle diameter –– 30/32 in (24 mm)30/32 in (24 mm)•• Solids content Solids content –– 70 %70 %•• Temperature Temperature –– 245245°°F (118F (118°°C), transitionalC), transitional•• Volume flow rate Volume flow rate –– 74.5 74.5 gpmgpm (4.7 (4.7 l/sl/s))•• Liquor pressure Liquor pressure –– 16.4 psig (1.13 bar)16.4 psig (1.13 bar)

•• Median droplet diameter Median droplet diameter –– 3.3 mm3.3 mm•• Spray velocity Spray velocity –– 30 ft/s (9.1 30 ft/s (9.1 m/sm/s))

1010

Slide 19Effect of Nozzle Diameter on Drop SizeEffect of Nozzle Diameter on Drop Size

∝ 1.23median nD D

Non-Flashing

Note: liquor mass flow rate, temperature and solids are fixed

Slide 20Effect of Nozzle Diameter on VelocityEffect of Nozzle Diameter on Velocity

Non-Flashing

Note: liquor mass flow rate, temperature and solids are fixed

∝ 2n1 DV

1111

Slide 21Effect of Temperature on Drop SizeEffect of Temperature on Drop Size

Dmedian ∝ 1/T0.14

Note: liquor mass flow rate, solids, and nozzle diameter are fixed

Slide 22Effect of Temperature on VelocityEffect of Temperature on Velocity

Note: liquor mass flow rate, solids, and nozzle diameter are fixed

1212

Slide 23Liquor Spray DistributionLiquor Spray Distribution

Wall FiringWall Firing•• Small boilersSmall boilers•• 1 or 2 oscillating1 or 2 oscillating

gunsguns

Stationary FiringStationary Firing•• Large boilersLarge boilers•• 4 to 12 fixed guns4 to 12 fixed guns

Slide 24Predicting Spray Distribution and DepositsPredicting Spray Distribution and Deposits

•• Based on computational analysis of the Based on computational analysis of the

trajectories of large dropstrajectories of large drops

•• Useful for sensitivity studiesUseful for sensitivity studies

•• Useful for initial optimizationUseful for initial optimization

•• Examples for one particular boilerExamples for one particular boiler

–– Demonstrates sensitivity to operating parametersDemonstrates sensitivity to operating parameters

–– Can show interactions between parametersCan show interactions between parameters

1313

Slide 25Recovery Boiler Used in ExamplesRecovery Boiler Used in Examples

Stationary firingFiring method

220°F (104.4°C) non-flashingLiquor temperature

65.8%Liquor dry solids

49° (median)Splash plate angle

#38 (38/32 inches or 1 3/16”)Nozzle size

- 20° (median)Barrel tilt

4, one at center of each wallNumber of guns

31.5 x 28.4 ft (9.6 x 8.7 m)Floor dimensions

Slide 26Impact of Barrel Tilt on Bed ShapeImpact of Barrel Tilt on Bed Shape

- 10° - 20° - 30°

1414

Slide 27Impact of Nozzle SizeImpact of Nozzle Size

#34 nozzle#34 nozzle #40 nozzle#40 nozzle

Front Wall

Left

Wal

lBL

SA

PA

TA

Front WallLeft Wall

25002300210019001700150013001100900700500300100

DepositionRate

(kg/hr-m2)

Front Wall

Left

Wal

l

BL

SA

PA

TA

Front WallLeft Wall

Slide 28Impact of Splash Plate AngleImpact of Splash Plate Angle

3535°° 4949°°

Front Wall

Left

Wal

l

25002300210019001700150013001100900700500300100

DepositionRate

(kg/hr-m2)BL

SA

PA

TA

Front WallLeft Wall

Front Wall

Left

Wal

l

BL

SA

PA

TA

Front WallLeft Wall

1515

Slide 29Impact of FlashingImpact of Flashing

NonNon--FlashingFlashing FlashingFlashing

Front Wall

Left

Wal

l

25002300210019001700150013001100900700500300100

DepositionRate

(kg/hr-m2)BL

SA

PA

TA

Front WallLeft Wall

Front Wall

Left

Wal

l

BL

SA

PA

TA

Front WallLeft Wall

Slide 30Implications for Recovery BoilersImplications for Recovery Boilers

•• Select nozzle type, number, arrangement, Select nozzle type, number, arrangement, and barrel tilt for liquor spray distributionand barrel tilt for liquor spray distribution

•• Select nozzle size for required flow, liquor Select nozzle size for required flow, liquor pressure and median droplet sizepressure and median droplet size

•• Recognize and control flashingRecognize and control flashing

–– Flashing impacts spray velocity and droplet sizeFlashing impacts spray velocity and droplet size

–– Stay above or below flashing temperatureStay above or below flashing temperature

–– If above, use temperature to control droplet sizeIf above, use temperature to control droplet size