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Overview of Factors Affecting Fouling in Recovery Boilerswhitty/blackliquor/... · • Sootblower...
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Overview of Factors Affecting Fouling in Recovery Boilers
Honghi TranUniversity of Toronto
Colloquium on Black Liquor combustion and Gasification, Park City, May 12-16, 2003
Fouling
Plugging
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Three Principal Parameters Determining the Rate of Fouling
ParticleConcentration
ParticleStickiness
Sootblowing Efficiency
ParticleConcentration
ParticleStickiness
Deposition
Less StickyLow Conc.
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ParticleConcentration
ParticleStickiness
Deposition
Less StickyLow Conc.
SootblowingEfficiency
Fouling/Plugging
High Efficiency
Types of Particles
Carryover500 µm
(100 µm - 3 mm)
ISP20 µm
(1 - 100 µm)
Fume0.5 µm
(0.1 - 1 µm)
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Carryover Fume
ISP
ISP Covered with Fume
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Economizer
Superheater
Boiler Bank
Fume ISP
Carryover
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Three Principal Parameters Determining the Rate of Fouling
ParticleConcentration
ParticleStickiness
Sootblowing Efficiency
Factors Affecting CarryoverConcentration
• Firing load• Air flow rate and distribution• Black liquor properties• Black liquor sprays
• Nozzle design• Liquor temperature and pressure• Liquor properties
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Liquor Spray Study at Domtar Espanola
May 2, 2003
Three Principal Parameters Determining the Rate of Fouling
ParticleConcentration
ParticleStickiness
Sootblowing Efficiency
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Factors Affecting Carryover Stickiness (Liquid Content)
• Particle composition• Black liquor composition (Cl, K)• Black liquor droplet size
• Particle temperature• Flue gas temperature• Retention time• All burning particles are sticky!
U of T Entrained Flow Reactor
Gas burner
Sample
Probe
Furnace9 m
Particles
Camera
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0 mole% Cl/(Na+K)
5
10
20
1
420 - 850 µm
300 - 420 µm
150 - 300 µm
Effect of Particle Size on Deposition
Mill “A” Black Liquor EFR Temp. = 800oC
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Sticky Temperature540
560580
600
780
660640
620
800760
820
740720
700680
0
5
10
15
20
25
30
0 1 2 3 4 5Cl/(Na+K) mole%
K/(N
a+K
) mol
e%20 mole% CO3/(Na2+K2)
717oC
587oC
Prediction of Sticky Temperature
Black Liquor Composition
Particle Composition
Sticky Temperature
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Carryover
Na2CO3(65)
Na2SO4(30)
NaCl (2)K-salts (2.5) Carbon/
impurities (1)
Composition (Wt%)
(50)
(45)
(2)(2.5) (1)
Oxidized Smelt
Carryover Particle Composition Continuously Changes
• Cl, K and carbonate contents are lower than previous thought
• S (sulphate and sulphide) content is higher • Changes depend strongly on particle size,
temperature and excess O2
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Boiler 2
100 µm
20 sec5 sec
Boiler 2
100 µm
20 sec5 sec 20 sec5 sec
Factors Affecting SootblowingEfficiency
• Sootblower nozzle design• Blowing sequence and frequency• Deposit adhesion strength
• Composition• Tube temperature
• Tube arrangement
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Three Principal Parameters Determining the Rate of Fouling
ParticleConcentration
ParticleStickiness
Sootblowing Efficiency
Deposit Removal Studies• Laboratory studies
• Composition• Tube surface temperature• Particle size
• Numerical simulation• Free jet• Jet-deposit interaction
• Field studies• Sootblowing efficiency
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1.81.61.4
1.00.80.60.40.20.0
1.2
2 10 12 14 164 6 8mole% Cl/(Na+K)
PIP
(MPa
)Probe temp.=400oC0% K% CO3
Effect of Chloride on RemovalM
inim
um P
IP (M
Pa)
1.4
1.2
0.80.60.40.20.0
1.0
mole% K/(Na+K)0 5 10 15 20 25
5 mole%Cl/(Na+K)
2 mole% Cl/(Na+K)
Effect of Potassium on Removal
Probe temp.=400oC0% CO3
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Nozzle
Pitot tube
Air Jet ImpingementApparatus
TubeArrays
Sootblowing Efficiency Studies at Domtar Espanola
May 2, 2003
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Conclusions
ParticleConcentration
ParticleStickiness
Deposition
Less Sticky
Low Conc.
SootblowingEfficiency
Fouling/Plugging
High Efficiency
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ParticleConcentration
ParticleStickiness
Deposition
Less Sticky
Low Conc.
SootblowingEfficiency
Fouling
High Efficiency
Alstom PowerAndritzAracruz CeluloseBabcock & WilcoxBoise Paper SolutionsBowaterCanforClyde-BergemannDaishowa-Marubeni
DomtarGeorgia Pacific International PaperIrving Pulp & PaperKvaerner PulpingMeadWestvacoStora-Enso ResearchVotorantim Celulose E PapelWeyerhaeuser Paper
NSERC
AcknowledgementsResearch Consortium on “Increasing Recovery Boiler Throughput and
Reliability of Recovery Boilers and Lime Kilns”