black liquor sprays - tappi.org · 3 slide 5 spray characteristics • median droplet diameter •...
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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
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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