5-2 Recovery Boiler Water Treatment - TAPPI · Boiler Minor 0 or Minor Feedwater System -- Minor...
Transcript of 5-2 Recovery Boiler Water Treatment - TAPPI · Boiler Minor 0 or Minor Feedwater System -- Minor...
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Kraft Recovery CourseKraft Recovery Course
Recovery BoilerRecovery BoilerWater TreatmentWater Treatment
JanuaryJanuary20082008
Presented ByPresented By
Sheppard T. PowellAssociates, LLC
Baltimore Marylandwww.stpa.com
Presentation FormatPresentation Format
Objectives Of Treatment ProgramSteam/Water Cycle: Basic ComponentsTop Routine Chemistry ParametersSummary
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Objectives Of Treatment ProgramObjectives Of Treatment Program
00Turbines
00Superheaters
0 or MinorMinorBoiler
Minor--Feedwater System
Minor--Condensate System
CorrosionDepositComponent
Boiler Deposit ExampleBoiler Deposit Example
Thick Nose Tube Deposits of Copper and Copper Oxides Over Mixed Iron Oxide, Hardness Phosphate and Carbon
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Boiler Blistering ExampleBoiler Blistering Example
Boiler Corrosion ExampleBoiler Corrosion Example
Deposits After Brushing
Under-Deposit Corrosion
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Turbine Deposits ExampleTurbine Deposits Example
Superheater Corrosion ExampleSuperheater Corrosion Example
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Steam/Water Cycle DiagramSteam/Water Cycle Diagram
S
S
FeedwaterHeater(s)
DeaeratorAnd Storage
Steam
Steam
Vent
Desuper-heatingWater
MakeupStorage
Blowdown/MakeupHeat Exchanger
CondensateStorage
Mill Condensate(s)
TreatedMakeup
S
S
SS
S
S
S
S
S
S
S
Usually Operated As A Grab Sample Point
CondensateFilter/Polisher
System
NaCCNaCC
pHSC
pHSCNaDOSiO2
NaCC
SC
SC
SCSiO2Na
(For Each)
Desup.Water
SweetwaterCondenser
FW OutFW In
TUBoiler
QuestionsQuestions
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Specific ConductivitySpecific Conductivity
Total Conductive Solids (Salts, Acids, Alkalis)High Levels Can Cause Foaming and/or CorrosionUnits: Usually µS/cmMicromho (µmho/cm) = Microsiemen (µS/cm)Millimho (mmho/cm) = Millisiemen (mS/cm)1 mS/cm = 1000 µS/cm (Beware of auto-switching ranges on meter!)
Specific ConductivitySpecific Conductivity
(a) Much Higher For Low Pressure Boilers On Softened Makeup
3 to 5 × PO420 – 150 (a)Boiler Water
Amine Feed2.0 – 6.0Condensate & Feedwater
NaOH Leakage0.05 – 5.0Demineralized Water
Main SourceNormal Values, µS/cmSample
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Example of Amine Blend Effect on ConductivityExample of Amine Blend Effect on Conductivity
0 1 2 3 4 5 6 7 8 9 10Volume of Amine Blend, ppm
Spec
ific C
ondu
ct ivit
y,µS
/cm
12
10
8
6
4
2
0
Trial A - Change in SC(33.9 - 35.7°C)Trial B - Change in SC(34.0 - 36.3°C)
pH (Relative Acidity and Alkalinity)pH (Relative Acidity and Alkalinity)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Neutral
106 105 104 103 102 10 1 1 10 102 103 104 105 106
Acid Units Base Units
pHpH
5% Sulfuric AcidLemon Juice
Vinegar
DemineralizedWater
Condensate/FeedwaterBoiler WaterHousehold Ammonia
4% Caustic Soda
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Example of Amine Blend Effect on pHExample of Amine Blend Effect on pH
Volume of Amine Blend, ppm1 2 3 4 5 6 7 8 9 10
pH9.4
9.2
9.0
8.8
8.6
8.4
8.2
Trial A - pH (33.9 - 35.7°C)Trial B - pH (34.0 - 36.3°C)
Effect of pH on Copper TransportEffect of pH on Copper Transport
1.0
10.0
50.0
0.27.0 8.0 9.0 10.0
pH
70Cu/30Ni90Cu/10NiCo
pper
C or ro
sion
Pro d
uctR
elea
se, g
/ mY e
ar2
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Dissolved OxygenDissolved Oxygen
Oxygen as O2 (from air) dissolved in water. Corrodes copper and steel (economizer shown).1 ppm O2 = 1 mg/L = 1000 ppb = 1000 µg/L
Dissolved Oxygen Effect on Copper CorrosionDissolved Oxygen Effect on Copper Corrosion
0
2
4
6
8
10
12
14
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0 50 100 150 200 250 300 350 400 450Temperature °F
Corro
sion
Rate
,mp y
70Cu/30Ni (Alloy 715) 3 ppb O2 100-200 ppb H70Cu/30Ni (Alloy 715) 200 ppb O2 25 ppb H90Cu/10Ni (Alloy 706) 3 ppb O2 100-200 ppb H90Cu/10Ni (Alloy 706) 200 ppb O2 25 ppb H
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Dissolved OxygenDissolved Oxygen
Normal ValuesMill Water or Demineralized Water
Saturated (8,000 - 14,000 ppb)Condensate: 10 - 100 ppb O2
Feedwater: <5 - 10 ppb O2
SourcesAir Leaks
Where Water Leaks Out, Air Leaks InMill Water In-leakage
0.1% Raw Water = 8 - 14 ppb O2
Dissolved Oxygen Control: DeaeratorDissolved Oxygen Control: Deaerator
SteamInlet
Trays
Distributor NozzlesVentWater Inlet
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Deaerator Spray Nozzles And TraysDeaerator Spray Nozzles And Trays
Oxygen Scavengers Oxygen Scavengers –– Carbohydrazide ExampleCarbohydrazide Example
Oxygen Scavenging (Reduces Oxygen) Oxygen + Carbohydrazide → Inerts + Carbonic Acid
PassivationRed Rust + Scavenger → Black Rust + Carbonic Acid
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Oxygen Scavenger FeedOxygen Scavenger Feed
UnderfeedCopper Corrosion in Steam/Condensate SystemPitting of Economizer
OverfeedFAC: Flow Accelerated Corrosion and Rupture of Steel Pipe Lines (e.g., Feedwater Line)Decomposition Products
QuestionsQuestions
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Hardness In Generation Bank TubeHardness In Generation Bank Tube
Hardness Scale In Generation Bank Tube, Dispersant TreatmentWithout Dispersants, Gray Mayonnaise Deposits Are In Drums
Hardness Hardness –– DefinitionDefinition
Mainly the Calcium (Ca) and Magnesium (Mg)Precipitates and Forms Hardness Scale In BoilerPrecipitation Can Result in Decreased Boiler pH
H2SO4+2Na2SO4+Ca3(PO4)2→2Na2HPO4+3CaSO4
Sulfuric Acid+Sodium
Sulfate+Calcium Phosphate→Sodium
Phosphate+Calcium Sulfate
Acid+Salt+Sludge→Phosphate+Hardness
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Hardness Hardness -- LimitsLimits
Expected Values (ppm CaCO3)Feedwater and Turbine Condensate: 0.0Process Condensate 0.0 – Trace
SourcesMill Water In Condensate/FeedwaterProblem In Makeup Demineralization System
Control of Hardness: Prevent IntrusionControl of Hardness: Prevent Intrusion
Condensate/Feedwater
CoolingWater Drain
Two Isolation ValvesFor HP Service
ThrottlingValve
Drain
Condensate/FeedwaterPump Discharge
Pump Seals
Seal Water
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Phosphate (POPhosphate (PO44))
Amount of Sodium Phosphate Dissolved in Boiler WaterUnits: ppm PO4 = mg/L PO4
Purpose: Stabilizes pHPrecipitates Hardness as Softer DepositsBackup Indication of Hardness Contamination
Phosphate/pH Control CurvesPhosphate/pH Control Curves
10.5
10.0
9.5
8.5
9.0
8.0 6 10 14 18 22 26 30
pH
Phosphate, mg/L
3.0
2.4
Na:P
OM o
larR
a tio4
Equilibrium Line (1 ppm NaOH)
1500 psig
(10.3 MPa)
1200 psig(8.3 MPa)
800 psig(5.5 MPa)
2.7
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Phosphate Effect on Boiler Water pHPhosphate Effect on Boiler Water pH
Sodium-To-PhosphateMolar Ratio
Blowdown
Phosphate, mg/L
pH
NaOH
TSP
DSP(MSP)
3.0
2.62.4
2.2
2.1
2.0
Summary: What Should You Know?Summary: What Should You Know?
Top Chemistry Parameters in Steam/Water CycleConductivity µS/cmpHDissolved Oxygen, ppb O2 (and Oxygen Scavengers)Hardness, ppm CaCO3
Phosphate, ppm PO4
Steam/Water Cycle, Basic ComponentsOther (See Appendices)
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AppendicesAppendices
A: Makeup Water TreatmentB: Condensate Collection and TreatmentC: Feedwater Treatment SystemD: Boiler Water TreatmentE: Steam Purity ConsiderationsF: Additional Chemistry TestingG: Preventive MaintenanceH: Personnel TrainingI: Chemical Cleaning
For More InformationFor More Information
TAPPI Technical Information PapersTIP 0416-03 – Water Quality and Monitoring Requirements for Paper Mill Boilers Operating on High Purity Water, 1999TIP 0416-04 – Design Engineer Decision Tree: Paper Mill Boiler Feedwater, 1999TIP 0416-05 – Response to Contamination of High Purity Boiler Feedwater, 2000TIP 0416-06 – Keys to Successful Chemical Cleaning of Boilers, 2000