Waterside Cleaning of Recovery Boilers….. Pay Now or Pay Later€¦ · Waterside Cleaning of...

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Waterside Cleaning of Recovery Boilers…..Pay Now or Pay Later

Norris N. JohnstonApplication Team Manager – Water Management Technology

Lacey’s Spring, AlabamaUSA


Waterside Cleaning of Recovery BoilersIntroduction

• Recovery Boiler Emphasis

• The true topic of discussion

• Pay Now or Pay Later!– The Price of Deposition– Evaluating your Boiler’s Health– The Decision to Clean– Options

• Summary


The Price of Deposition


The Price of Deposition - Reliability

• Surprises!

• Unscheduled Downtime

• Budget Variances


RELIABILITY


The Price of Deposition - Safety

• Threat to Personnel!

• Threat to Equipment


SAFETY


The Price of Deposition - Economy

• Fuel to Energy Conversion

• Heat transfer efficiency



% Loss of Heat Transfer

Dep

osit

Thic

knes

s, in

ches

1 2 3 4 5 6 7 8 9

1/64

1/32

3/64

1/16

5/64

3/32Normal phosphate sludge

Sludge with 4% Fe

Sludge with 8% Fe

Sludge with 8% Fe & SiO2



0.6Porous silicate scale0.7Insulating Brick7Fire Brick

8.8Analcite (NaO . Al2O3 . 4SiO2 . 2H2O)15Magnesium Phosphate

15.6Calcium Carbonate16Calcium Sulfate20Magnetic Iron Oxide25Calcium Phosphate

310Boiler SteelBtu / hr-ft2-ºF/ inchMaterial

Selected Thermal Conductivity Values


ECONOMY


Evaluating your Boiler’s Health


The Decision to Clean

Elapsed Time Since Chemical Cleaning

Risk

$$

Che

mic

al C

lean

ing

Cost

$$


• Convenience

• After Failure

• Company Policy -- Time and/or Data Based

• Engineering approach– History: Failures, Excursions, Inspections– System: Mechanical Treatment– Data: Deposit data, BFW Quality– Control: Duration and Severity of Excursions– Internal boiler water treatment

Evaluating your Boiler’s Health – The Decision to Clean


Evaluating your Boiler’s Health

Independent Consultant Used?

Yes84%

No16%

Yes

No

Cleaning Policy Enforced

Yes70%

No30%

Yes

No


Evaluating your Boiler’s HealthCleaning Time Required

24 h6%

36 h22%

48 h28%

> 48 h44%

24 h

36 h

48 h

> 48 h


• Time Based– Alstom (ABB/CE) = 7 years for Recovery Boilers– Survey says = 30% time based

• Data Based– B&W = 20 to 40 g/ft2 @ < 1000 psig

12 – 20 g/ft2 @ > 1000 psig and ALL BLRBs– Survey says = 52% data based

• Both Time and Data Based– Survey says = 18%

Evaluating your Boiler’s Health – When to Clean?


Evaluating your Boiler’s Health – When to Clean?

2 feet

2 feet

2 feet

Tube portion to be removed

Year 0 Year 1 Year 2 Year 3 Year 4

2 feet

0

0

0

0

1 1

1

1

2

3

4

Tube Sample Protocol


The Cleaning Process

• Safety

• Pre-engineering / Consultation

• Preparation and Execution

• Post cleaning evaluation


Alternatives to Cleaning“Options?”


Mechanical Options

• Feedwater Makeup

– Demineralized water or better

– Redundant protection against contaminant intrusion

• Condensate

– Resin and/or Electromagnetic Filtration Polishers

– Redundant protection against contamination


Chemical Options

• Condensate Treatment Chemistry

– Appropriate treatment for existing metallurgy

– Passivating agent to maximize condensate return

• Internal Treatment Chemistry

– Congruent Phosphate with high purity feedwater

– Boiler water dispersant


Chemical Options – Boiler Water Dispersant

0

100

200

300

400

500

600

700

800

900

1000

23-A

ug-9

4

21-D

ec-9

4

23-M

ar-9

5

19-J

ul-9

5

12-O

ct-9

5

9-Ja

n-96

3-Ap

r-96

20-A

pr-9

6

23-A

pr-9

6

29-A

pr-9

6

10-J

un-9

6

10-J

ul-9

6

12-A

ug-9

6

29-A

ug-9

6

30-S

ep-9

6

21-O

ct-9

6

18-N

ov-9

6

16-D

ec-9

6

13-J

an-9

7

26-F

eb-9

7

17-M

ar-9

7

7-Ap

r-97

9-Ju

l-97

17-S

ep-9

7

6-N

ov-9

7

14-J

an-9

8

12-M

ar-9

8

12-M

ay-9

8

24-M

ar-9

9

16-J

un-9

9

21-S

ep-9

9

20-J

an-0

0

ppb

Start of Dispersant Trial

Boiler comingon-line

Canadian Kraft MillRecovery Boiler - Iron Transport


Blowdown Iron

0

50

100

150

200

250

300

350

400

450

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73

Sample Day

Tota

l Iro

n, p

pb

1500 psig75 - 100 cycles5 ppb FW Iron

Start DispersantHere

Chemical Options – Boiler Water DispersantMidwest Paper Mill


Southern U.S. Paper MillDeposit Loading History

05

101520253035404550

1989 1990 1991 1992 1993 1994 1995

DW

D -

g / f

t2

Started HTP-2

Acid Cleaned

Acid Cleaned


Monitoring – Decision Making Data


STG

Superheater

Deaerator

FeedwaterStorage

BlowdownHeat Exchanger

FeedwaterMakeup

To Waste

BlowdownFlash Tank

Cooling Water

Pulp MillDigester Paper Mill

Cooling Water

Fresh SteamMultiple Effect

EvaporatorDirtyCondensate

Weak Black Liquor from Washers

StrongBlack Liquor

Condenser

Clean Condensateto Utilities

Process Steam UsersLow Pressure Steam

High Pressure Steam

HP CondensateFlash Tank

LP Condensate

CondensateCollection

Tank

Condensate Polisher (Resin and/or Magnetic )

HP Condensate

Sweet Water Condenser

Economizer

FeedwaterRegulator

Valve

PRV

SP

SP

Typical Sample Point

SP

SP

SP

SP

SP

SP

SPSP

SPSP

SP

SP

SP

SP

Best Practices – Monitoring and Control


SummaryPay Now or Pay Later

• Operating Costs

• Treatment Costs

• Cleaning Costs


Postpone, maybe?…….Do it sometime, for sure!


Questions?

Waterside Cleaning of Recovery Boilers….. Pay Now or Pay Later€¦ · Waterside Cleaning of...

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