Overview of Factors Affecting Overview of Factors Affecting Fouling in Recovery Boilers Fouling in Recovery Boilers

Honghi TranHonghi TranUniversity of TorontoUniversity of Toronto

Colloquium on Black Liquor combustion and Gasification, Colloquium on Black Liquor combustion and Gasification, Park City, May 12Park City, May 12--16, 16, 2003

Fouling

Plugging

Three Principal Parameters Determining the Rate of Fouling

ParticleConcentration

ParticleStickiness

Sootblowing Efficiency

ParticleConcentration

ParticleStickiness

Deposition

Less StickyLow Conc.

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)

Carryover Fume

ISP

ISP Covered with Fume

Economizer

Superheater

Boiler Bank

Fume ISP

Carryover

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

Liquor Spray Study at Domtar Espanola

May 2, 2003

Three Principal Parameters Determining the Rate of Fouling

ParticleConcentration

ParticleStickiness

Sootblowing Efficiency

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

0 mole% Cl/(Na+K)0 mole% Cl/(Na+K)

55

1010

2020

11

420 - 850 µm

300 - 420 µm

150 - 300 µm

Effect of Particle Size on Deposition

Mill “A” Black Liquor EFR Temp. = 800oC

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

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

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

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

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 Removal

Min

imum

PIP

(MPa

)

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

Nozzle

Pitot tube

Air Jet ImpingementApparatus

TubeArrays

Sootblowing Efficiency Studies at Domtar Espanola

May 2, 2003

Conclusions

ParticleConcentration

ParticleStickiness

Deposition

Less Sticky

Low Conc.

SootblowingEfficiency

Fouling/Plugging

High Efficiency

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”