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RIL-Hazira/BWT-Technical TrainingGEWPT- Confidential Material
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Boiler Technical TrainingAt
Reliance Industries LimitedHazira Manufacturing Division
February 26, 2008K S Rajan
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RIL-Hazira/BWT-Technical TrainingGEWPT- Confidential Material
BOILER WATER TREATMENT
• BASIC WATER CHEMISTRY• BOILER DESCRIPTION• OXYGEN PITTING & CONTROL• CONDENSATE TREATMENT• INTERNAL TREATMENT, COORDINATED
pH/PO4• STEAM PURITY• BOILER STORAGE• DISCUSSION, Q&A
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Basics & Interpretation of Water Analysis
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“The Basics”
• Hydrologic Cycle• Properties of Water• pH and Alkalinity• Langelier Saturation Index• Analytical Expressions• Water Analysis/Deposit Analysis• Corrosion and Deposition & Monitoring• Chemical Feed
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Properties of Water
•Density - 1 kg/l @ 4 oC ; 0.998 kg/l @ ambient temperature and varies inversely with temperature•Boiling point = 100 oC and freezing point @ 0 oC•Viscosity ~ 1 cps at ambient temperature and varies inversely with temperature•Specific heat - 1 BTU/lb-deg F or 1 kcal/kg-deg C or 4.2 kJ/kg-deg C•Universal solvent - dissolves most substances to some extent
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Impurities found in Water
• 3 Categories
• SUSPENDED SOLIDS (Silt)
• DISSOLVED SOLIDS (Minerals)
• DISSOLVED GASES
• Where do these things come from?
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Hydrologic Cycle
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Impurities found in Water
• Dissolved solids present as ions
• Cations - Ions that carry net positive charges e.g. Calcium (Ca2+), Magnesium
(Mg2+), Sodium (Na+), Iron (Fe2+), Aluminium (Al3+)
• Anions - Ions that carry net negative charges e.g. Bicarbonates (HCO3-),
Carbonates (CO32-), Sulfate (SO4
2-), Chlorides (Cl-), Oxides (O2-), Hydroxides (OH-)
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Water Impurities
Impurity Concern Removal
Suspended SolidsSilt, Iron,
Microbiogical
FoulingErosion
Underdeposit corrosion
ClarificationFiltration
Dissolved SolidsMinerals,Organics
ScalingCorrosion
Ion ExchangeReverse Osmosis
Evaporation
Dissolved GasesO2, CO2, NH3
PittingGeneral CorrosionCorrosion products
DeaerationSteam Stripping
Dissolved Solids
Cations Anions
Na+K+
NH4+
Organic acids
SiO2, possibly free CO2
HCO3-possibly OH- & CO3--
Cl- F-
SO4--
Ca++ Mg++
NO3- PO4 ---
TotalAlkalinity
MineralAcidity
TemporaryHardness
PermanentHardness
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Dissolved Solids Commonly Found in Water
Calcium
Magnesium
Sodium
Silica
Iron
BicarbonateSulfate
BicarbonateSulfate
BicarbonateSulfateChloride
Oxide
BicarbonateHydroxideSulfate
Ca(HCO3)2CaSO4
Mg(HCO3)2MgSO4
NaHCO3Na2SO4NaCl
SiO2
Fe(HCO3)2Fe(OH)3FeSO4
Chemical NameAnionCation
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Factors Affecting Solubility
•Temperature - Most salts increases except for Ca and Mg Salts
with increasing temperature
•Alkalinity - Most salt solubility increases with decreasing
alkalinity with the exception of Silica
•pH - most salts solubility increases as the pH drops
•Oxidation state - Fe and Mn salt solubility increases with
decreasing oxidation state
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Impurities found in Water
• Turbidity - suspended solids– silt, organic matters, precipitated
salts• Color - suspended solids and
dissolved solids• Dissolved gases e.g. CO2, O2, NH3,
H2S• Organics - humus, vegetation, micro-
organisms
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Typical Water Analysis
pHConductivity μS/cmAlkalinity “P” as CaCO3, ppmAlkalinity “M” as CaCO3, ppmSulfate as SO4, ppmChloride as Cl, ppmHardness, Total, as CaCO3, ppmCalcium Hardness, as CaCO3, ppmMagnesium Hardness, as CaCO3 ppmCopper, Total as Cu, ppmIron, Total as Fe, ppmSodium, as Na, ppmPhosphate, Total, as PO4, ppmSilica (reactive), as SiO2, ppmTurbidity, NTUTSS, ppmColor, HazenTOC, as C, ppm
ValueParameter
7.31500201510201550.051.512<0.054502031
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Special Ions
• pH • Hydrogen, H+
• Hydroxide, OH-
• Alkalinity• Bicarbonate, HCO3
-
• Carbonate, CO3--
• Hydroxide, OH-
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pH
• Hydrogen Ion Concentration• Logarithmic Scale• pH = -log [H+] • Unit change in log scale
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How Does pH Apply to Us?
• pH < 7: Acidic (corrosion)• pH > 7: Alkaline (deposition)
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Alkalinity Relationships •M-Alkalinity = Total
– Titration to pH = 4.3– Sum of: HCO3
- + CO3- + OH-
•P-Alkalinity = OH- + 1/2 CO3-
– Titration to pH 8.3
•OH-Alkalinity = 2P - M or titration– Neutral barium chloride precipitates CO3
-
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Conductivity
• Inverse of Resistance [mho]• Measure of concentration of ions in solution
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Types of Solubility
Normal: Increases with Temperature• Table Salt (NaCl)• Sugar
Retrograde: Decreases with Temperature
• Calcium Carbonate• Calcium Phosphate
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How Do We Quantify What Is in the Water?
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Analytical Expressions
• “Concentration”• units of solute per unit of solvent:
• PPM (parts per million)– parts of solute per million parts of
solvent• mg/l (milligrams per liter)
– 1 gram solute/1,000,000 grams solvent
• PPB (Parts Per Billion)parts of solute per Billion parts of solvent
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Analytical Expressions
•“Mg as CaCO3”Magnesium expressed as its Equivalent weight in Calcium Carbonate
100 (MW CaCO3) = 4.124 (MW Mg)
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Analytical Expressions
• Different Conventions • We use “ppm as CaCO3”• ppm ppm• as substance factors as CaCO3• Ca 50 2.5 125• Mg 20 4.1 82•
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Boiler DescriptionsBoiler Descriptions
FIRETUBE BOILERS
ADVANTAGES DISADVANTAGESHigh load swing capacity Low pressureEase of repair Capacity limitLow space requirement Usually no superheaterSelf contained package Usually no economizerRelatively low cost Usually low efficiencyEase of installation One fuel at a time
FOUR-PASS FIRETUBE BOILER
– Economizer– Steam drum– Mud Drum– Headers– Boiler Bank
• Downcomers - Risers• Waterwalls• Screen tubes• Arches• Floor tubes• Roof tubes
– Superheater– Air Heater
WATERTUBE BOILERS
Typical Parts of a Water Tube
Boiler Includes:
WATERTUBE BOILERS
BOILER DESIGN
WATER WALLS
SUPERHEATER
SCREEN TUBESSTEAMDRUM
MUDDRUM
ECONOMIZER
AIR HEATER
RISERSDOWNCOMERS
140-150 CTo stack
Coal
Lower WaterWalls Header
Fire Tube
Water FlueGases
Water TubeSteam
SteamDrumFeedwater CBD
MudDrum
IBD
FlueGases
Risers
Downcomers
Comparison - Watertube vs. Firetube:
WATERTUBE BOILERS
ADVANTAGESLow to super critical
pressureVirtually unlimited capacityTypically high efficiencySuperheaters
EconomizersMultiple fuelsDrum or once-throughPackage or field-erected
DISADVANTAGESHigh CostRequire Large SpaceUsually require higher quality
feedwater Sensitive to low load operation
WATERTUBE BOILER: A-TYPE
BFW
Steam Exit Drum
Flue GasPath
Sidewall Problem Area
Downcomers
Risers
Burner
Furnace Wall Tubes
Steam Drum
Downcomers
Risers
D-FramePackage Boiler
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Babcock & WilcoxCoal Fired Boiler
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Power Utility BoilerSimplified Flow Diagram
B&W Boiler
BD
Sat SteamHP SH Steam
HP Turbine
Cold Reheat
BFW
LP Heaters
HP Heaters
Cond Polisher
IP Turbine LP Turbine
Condenser
Deaerator
MB MU
Hot Reheat
CAUSE AND EFFECT DIAGRAM FOR BOILER PROBLEMS
BOILERCORROSION
OXYGEN PITTING
STRESS CORROSION CRACKING
DOWNTIMECORROSION
MECHANICALDEAERATOR
PERFORMANCE
SCAVENGERUNDERFEED
OXYGENIN-LEAKAGE
STRESSEDAREA
EMBRITTLING WATERCHARACTERISTICS
CONCENTRATINGMECHANISM
POOR pH CONTROL
DEPOSITION
POOR CHEMICALFEED CONTROL
DOWNTIMECORROSION
INADEQUATEBLOWDOWN
CONTROL
POOR BOILERFEEDWATER
QUALITY
CONDENSATECONTAMINATION
POOREXTERNAL
TREATMENT
CONDENSATECONTAMINATION
POOR EXTERNALTREATMENT
INADEQUATEBLOWDOWN
CONTROL
POOR CHEMICALFEED CONTROL
POOR BOILERFEEDWATER
QUALITY
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Boiler Calculations FeedWater = Steam + Blowdown
% Blowdown = 1 X 100Cycles
FeedWater (kg/hr) = Steam Generation (kg/hr)1 – (%blowdown)
100
FW= STM ( C )C-1
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Determining Cycles of Concentration
•Feedwater vs. Boiler Water analysis
•BFW Cycles = [Boiler Conc.] / [FW Conc.]
• Cycles = Neutralized Boiler Water Cond. (umhos at 25C)___________________________________________
Feedwater Cond. (umhos at 25C)
• Check via Chlorides, Silica
• Do not use compounds that routinely precipitate (phosphate,hardness) or that are part of treatment (sulfite/sulfate)
•Demineralized or RO make-up – Tracer methods• Molybdate
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Steam, Feed Water & Blowdown Relationships
% Blowdown = 100 / FW Cycles• % BD at 20 FW cycles = 100/20 = 5%
Feedwater = Steam X [Cycles / (Cycles –1)]• FW = 100 MM ppy steam X [20 / (20 – 1)] = 105.3
Feedwater = Steam + Blowdown• BD = FW – ST = (105.3 – 100) MM ppy = 5.3 MM
ppy
Feedwater = Make-up + Condensate
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Oxygen Control• Deaeration
• Chemical treatment
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Corrosion of Iron by Oxygen
WATER
Fe(OH)3O2
Fe2+ OH- O2
ANODE CATHODEANODE REACTION
Fe. = Fe++ 2e-CATHODE REACTION
1/2 O2 + H2O + 2e- = 20H-
• Iron Is Oxidized on the Surface (Anode) - Metal Loss• Oxygen Is Reduced (Cathode)
MECHANISM
ELECTRON FLOW
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Oxygen Corrosion
• Corrosion Rate Doubles With Every 10 C Increase in Water Temperature
• Metal Loss is low• Localized attack• Pit Formation • Rapid Failure
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Rapid Perforation ~ Equipment Failure
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Oxygen Guidelines
Organization Dissolved O2 Level, ppb
ASME
TAPPI
ABMA
EPRI
DEAERATORGUARANTEE
TYPICAL DEAERATORO2 LEVELS
< 7
< 7
NO RECOMMENDATION
< 5
7
15 - 40
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Types of Oxygen Scavengers
• Solid
– Sodium Bisulfite
– Sodium Sulfite
• Non-Solids
– Hydrazine
– Hydroquinone
– Diethylhydroxlamine (DEHA)
– CARBOHYDRAZIDE
– ASCORBIC ACID
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Residual (ppm SO3-) Pressure
30 - 60 < 40 bar10 - 20 40 - 60 bar
ATTEMPERATION / DESUPERHEATING: NO
RECOMMENDEDSULFITE CONTROL LIMITS
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HydrazineReaction:
N2H4 + O2 N2 + 2H2ODecomposition Reaction:
2N2H4 + HEAT + 2H2O 4NH3 + O2
Feedrates:3 x (ppm O2 + Residual)
Control Limits:0.1 ppm Residual N2H4 at Economizer Inlet
Attemperation / Desuperheating:Yes
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Hydrazine
• Advantages:– Doesn’t contribute to TDS– True residual test
• Disadvantages:– Poor reactivity with low temperature– Expensive compared to Sulfite– Suspect carcinogen– Requires special handling / feed
equipment– Decomposes to NH3, which can lead to
copper corrosion
Hydrazine
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Organic O2 Scavengers
• Pressure > 900 psig (60 bar)
• BFW used for superheat attemperation
• Condensing turbine present
• High-Purity Makeup (Demin./RO)
• Coordinated PO4 / pH control
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HYDROQUINONE
REACTION:C6H6O2 + 1/2O2 H2O + C6H4O2
CONTROL LIMITS:DISSOLVED OXYGEN TEST
IRON REDUCTION TEST
OH
OH
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OHOH
OHOH
++ OO22 ==
OO
OO
• DOES NOT CONTRIBUTE TO TDS• FASTEST ORGANIC OXYGEN SCAVENGER• REQUIRES NO SPECIAL HANDLING• EXCELLENT FOR WET LAY-UP• AVOIDS SULFUR CATALYST POISON• NOT A LISTED CARCINOGENIC
HYDROQUINONEADVANTAGES
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Carbohydrazide
REACTION:
DECOMPOSITION REACTION:
CORTROL-OS-5613RESIDUAL(0.3-0.5 ppm product)
N4H6CO + O2 2 N2 + 3H2O + CO2
N4H6CO + H2O + HEAT 2N2H4 + CO2
2N2H4 + HEAT + 2H2O 4NH3 + O2
HH 33NN22-- C C -- NN 22HH
33OO
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CarbohydrazideAdvantages
• Low/no cation conductivity contribution– Does not form LMW organic
acids– CO2 contribute to non degassed
cationic conductivity
• Well-accepted in Industry
• Much safer than hydrazine
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Variables Influencing Scavenger Reaction
• Time• Temperature• pH• Catalyst
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pH and Temperature Recommendations
OXYGEN SCAVENGER
SULFITES
HYDRAZINE
HYDROQUINONE (HQ)
HYDROXYLAMINES (HA)
ASCORBIC ACID
CARBOHYDRAZIDE
*FOR EFFICIENT OXYGEN SCAVENGING PERFORMANCE
MINIMUM TEMP*
80 OF (27 C)
190 OF (88 C)
80 OF (27 C)
>200 OF (> 93 C)
180 OF (82 C)
>200 oF(> 93 C)
MINIMUM pH*
>8.5
>8.5
>8.5
>8.5
>8.5
>8.5
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Monitoring
1) Primary sample point for oxygen testing2) Sample point necessary for deaerator studies and for
troubleshooting oxygen intrusion through the pump
ECONOMIZER1
2
Ideal Point
MONITORING • pH• Conductivity• Hardness, silica• Oxygen• Corrosion
– metals analysis– corrosion coupons
Millipore Iron Testing
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Feed Water and Condensate System Treatment
• Ammonia
• Amines
• Condensate polishing
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Condensate TreatmentIn The Condensate:• Carbon Dioxide
H2CO3 H+ + HCO3-
CO2 + H2O H2CO3
pH DECREASES
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Feedwater AlkalinityIs a Source of CO2 in Condensate
IN THE BOILER:
2HCO3- CO3
= + H20 + CO2
CO3= CO2 + 2OH-
STEAMCO2
FEEDWATERHCO3
-
CO3=
OH-
BLOWDOWN
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Relative Corrosion Rate of Copper Alloys and Carbon Steel vs pH
7 8 9 10
CORROSIONRATE
COPPER
CARBONSTEEL
pH
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Fundamental Amine Characteristics
• Distribution Ratio
• Neutralizing Capacity
• Basicity
• Thermal Stability
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NEUTRALIZING AMINES
10
9
8
7
6
5 0 2 4 6 8 10 12 14 16AMINE FEED (ppm)
CO
ND
ENSA
TE,
pH
R - NH2 + H2CO3 R - NH3+ + HCO3
-
R - NH2 + H2O R - NH3+ + OH-
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BASICITY
MorpholineAmmoniaEthanolamineDEAEMOPACyclohexylamine
2183266126440
Neutralizing Basicity Constant
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Concentration in steamConcentration in liquid
DR =
VAPOR
LIQUID
HIGH DISTRIBUTIONRATIO
LOW DISTRIBUTIONRATIO
DISTRIBUTION RATIOS
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DISTRIBUTION RATIOS
DRAMINE 0 PSIG 200 PSIG 1000 PSIGAMMONIA 10 7.1 3.6CYCLOHEXYLAMINE 4.0 16.0 9.3DEAE 1.7 4.5 3.4MOPA 1.0 2.4 2.5MORPHOLINE 0.4 1.6 1.0ETHANOLAMINE 0.07 0.15 0.29DIAMINE 0.45 1.9 2.7CONTAMINANTSCO2 5400 500 100
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Boiler Internal Treatment& Steam Purity
• Coordinated PO4 /pH
• Steam purity
Deposit Formation
• Deposition rate increases with heat flux (Btu/Ft2)• Reduces Heat Transfer• Increases tube wall temperature• Induces corrosion• Ultimately - Tube failure
Effect of Deposition on Heat Transfer
500°F500°FWatersideWaterside
600°F600°FFiresideFireside
800°F800°FFiresideFireside
500°F500°FWatersideWaterside
CombustionCombustionGasesGases
Tube MetalTube Metal
InsulatingInsulatingScaleScale
Scaled Tube Scaled Tube SurfaceSurface
Clean Tube Clean Tube SurfaceSurface
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Cause and Effect Diagram for Boiler Deposition
IntermittentContamination
DepositionFouling
Condensate HardnessContamination
Chemical Underfeed
Poor NaZ Performance
Condensate HydrocarbonContamination
Poor Blowdown Control
IntermittentContamination
Condensate Corrosion
Poor Blowdown Control
Chemical Underfeed
Poor Chemical Feed Control
Poor Storage Practices
Hardness Salts Iron
High Boiler SilicaPoor SeparationEquipment Performance
Hydrocarbon Contamination
Poor Blowdown Control
Rapid Load Swings
Header Pressure Swings
Hydrocarbon Superheater/Turbine Fouling
Monitoring Tools1. On-Line Total Analyzer2. Boiler Feedwater Inspection3. Equipment Inspections
Monitoring Tools1. Steam Purity Monitoring2. Routine Boiler Testing3. On-Line Sodium Analyzer4. Equipment Inspections5. Data Tracking
Monitoring Tools1. Boiler Feedwater/ Condensate
Iron Monitoring2. Turbidity Monitoring3. Equipment Inspections
Monitoring Tools1. Monitor NaZ Performance:2. Monitoring Boiler Feedwater/
Condensate Hardness3. On-Line Hardness Analyzers4. Equipment Inspections5. Routine Blowdown Testing6. Data Tracking
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Coordinated Phosphate/pH Programs
Used Primarily in high pressure boilers to protect against caustic gouging
Applicable for lower pressure boiler systems on demin quality makeup
Sodium (caustic) is primary feedwatercontaminant
Iron may also be a problem polymers used for iron control
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Coordinated PO4/pH Boiler Treatment
• To control boiler water pH......
• ......Create a buffer systembetween PO4 and NaOH
Under-Deposit Corrosion
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High or Low Boiler Water pH Corrodes Boiler Steel
1 2 3 4 5 6 7 8 9 10 11 12 13 14
RELATIVECORROSIVE
ATTACK
pH
8.5 pH 12.7 pH
SAFE RANGE
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Na: PO4 RATIO OUT OF CONTROLEXCESS “SODIUM LEAKAGE”
Na2 HPO4 + 2NaOH Na3PO4 + NaOH + H2O
4Na + 1PO4Na:PO4 = 4:1
Low DSP Fed “Free Caustic”
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PREVENTING CAUSTIC CONCENTRATION
NaOH + Na2HPO4 Na3PO4 + H2OCaustic Disodium
PhosphateTrisodiumPhosphate Water
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2Na2 HPO4 + 2NaOH 2Na3PO4 + 2H2O
6Na + 2PO4Na:PO4 = 3:1
“Exact” DSP Fed
Coordinated Phosphate/pH Control
Under-Deposit Neutralization
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C O O R D IN A T E D p H /P H O S P H A T E C O N T R O L10.8
10 .6
10 .4
10 .2
10 .0
9 .8
9 .6
9 .4
9 .2
9 .0
8 .8
8 .6
8 .4
8 .21 .0 2 3 4 5 6 7 8 10 15 20 30 40 50 60
p p m O rth o p h o s p h a te , a s P O 4
``F ree '' C au sticR eg io n
``C ap tive ''A lka lin ityR eg io n
V ecto rC o ntro lD iag ramC o ntro l Area
>2600 ps i
C o ntro l Are a20 01 -2500 p s i
C o ntro l Area15 01 -2000 p s i
C o ntro l Area90 1 -1500 ps i
C o ntro l Area<9 00 ps i
C O N T R O L A R E A2501 -2600 p s i
M A X IM U M B O U N D A R Y 3 .0 :1 M O L A R R A T IO
2.6 :1 N a /P O 4
2 .7 :1 N a /P O 4
2 .8 :1 N a /P O 4
C O N T R O L B O U N D AR Y2 .2 :1 N a /P O 4
M O L A R R A T IO B L O W D O W N M O N O -S O D IU MP H O S P H A T E
D I-S O D IU MP H O S P H A T E
T R I-S O D IU MP H O S P H A T E
C A U S T IC
p H A T25C
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Di-sodium PO4
Caustic
Blowdown
Tri-sodium PO4
Mono-sodium PO4
Caustic-Phosphate Equilibrium
Reality CheckYour 90 bar boiler has a pH 9.5 and PO4 of 30 ppm.Boiler PO4 control range is 10 - 20 ppm
How should we respond?
[A]
Reality CheckYour readings for this 100 bar boiler are pH 10.2 and PO4 of 6. PO4 control range is 4 - 8 ppm.
What actions will put you back into control?
[A]
Acid Phosphate Corrosion
Acid PO4 corrosion potential exists when boiler water Na/PO4 ratio is less than 2.3
Sodium PO4 (Di or Mono) can react with Magnetite or Iron to form Maricite (NaFePO4) under high temperature (>300 C)
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Steam Purity
Importance of Steam PurityProtect Capital Investments, such as:
– Superheaters– Turbines– Steam lines and valves
Maintain ProductionPrevent Process Contamination
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Definitions • Steam PuritySolid, liquid or vaporous
contamination in the steam
• Steam QualityA measure of the moisture in
the steam
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Steam Purity Guidelines • Turbine manufacturer (ppb
levels)
• Boiler manufacturer (ppm levels)
• Industry professional organizations
• Operations
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Turbine Manufacturers’ Steam Purity Limits
GeneralElectric
Westinghouse
AllisChalmers
PARAMETER NORMAL 100 HR. 24 HR. NORMAL 2 WEEK 24 HR. NORMAL
Cation Cond.uS/cm
0.2 0.5 1 0.3 0.3-0.5 0.5-1.1 0.1
Sodium, ppb 3 6 10 5 5-10 10-20 10
Chloride, ppb A A A 5 5-10 10-20 10
Silica, ppb A A A 10 10-20 20-50 10
Iron, ppb A A A 20 5
Copper, ppb A A A 2 1
Oxygen, ppb A A A 10 10-30 30-100 5
A - Governed by requirements of the steam-generator manufactureer
Steam Turbine - Problems
• Deposition
– Deposit thickness 0.1 mm reduces stage efficiency by 3%
• Surface Roughness
– Affects flow passage width
– Reduce stage efficiency• LP Blade corrosion
– Stress corrosion cracking (NaOH, Cl)
– Pitting
– Erosion
Industrial Steam TurbinesTypical Sources of Impurities
Makeup Water
Demineralizers
Water Treatment Chemicals
Process ChemicalsCorrosion Products
Condenser Leaks
Air In-Leakage
Chemical Cleaning
Waterand
Steam
STEAM PURITY
Steam Purity vs Steam Quality• Steam purity is the solid, liquid, or vaporous contamination
in the steam• Steam quality is the measurement of moisture in steam
Steam Purity Guidelines• Turbine & Boiler Manufacturers• Industry Professional Organizations
– (ASME, ABMA, EPRI, VGB, BS )• Boiler Manufacturers • Operations
Steam Purity GuidelinesNormal Operation
Parameter ABB G E Westinghouse Mitsubishi
Na, ppb < 10 <20 < 10 < 10
SiO2, ppb < 20 < 20 < 20 < 15Total Fe, ppb < 20 < 20 < 5
Cu, ppb < 3 < 2Cl, ppb < 15 < 2
CationicCond. us/cm <0.2 < 0.2 < 0.3 < 0.2
Steam Purity GuidelinesAbnormal Operation (Westinghouse)
* Time refers to continuous time in the range and also to total time in a 12-month period in the range
Parameter 2-week * 24-Hour * ImmediateShut Down
Cation Cond.us/cm
0.3 - 0.5 0.5 - 1.0 > 1.0
Na, ppb 10 - 20 20 - 35 > 35SiO2, ppb 20 - 40 40 - 80 > 80
Cl, ppb 15 -30 30 - 50 > 50
SO4, ppb 15 -30 30 - 50 > 50
CARRYOVER: MECHANICAL CAUSES
• STEAM SEPARATION EQUIPMENT
• STEAM DRUM LEVEL
• STEAM LOAD
• OVERFIRING
CARRYOVER: CHEMICAL CAUSES
• FOAMING
– TDS– Alkalinity– Organics/ Polymer Overfeeding– Antifoam
• SELECTIVE VAPOROUS CARRYOVER (GOVERNED BY DRUM pH, PRESSURE AND TEMPERATURE
– Silica– Others - Cl, SO4, Fe
ATTEMPERATION WATER
• FEEDWATER
–Quality of Feed water–Chemical Treatment
• SWEET WATER CONDENSER
–Source of Coolant–Purity of Steam Source
• CONDENSATE
MONITORING STEAM PURITY
SODIUM• On Line Analyzer• Isokinetic Sampling • Bottle Study (Na free
bottles)
• Saturated Steam
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Boiler Storage• Most oxygen corrosion occurs or is
initiated when boiler is off-line (wet storage)
• Key to Success - Alkaline & oxygen-free during wet storage
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• Dry Storage with a desiccant is recommended for long-term storage
• What constitutes ‘long-term’?– Off-season storage– Rule-of-thumb: Normally recommend
dry storage if lay-up will be >1 month and boiler will not be needed on short notice
Boiler Storage
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• Wet storage is recommended when:– Boiler is required for emergency
stand-by or on short notice– Capacity required to meet peak
demand– Unit will be out-of-service for
< 1 month
Boiler Storage
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Wet Storage Methods1. Volatile Chemicals
2. Sulfite & Caustic
3. Cascade lay-up / Hot standby
4. Dry lay-up with desiccant
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• Add chemicals to fill water as it is pumped into boiler
• Fire boiler moderately after chemical addition to circulate & distribute or utilize external circulation pump– Always follow boiler manufacturers
recommendations for firing the boiler
• Adjust pH/alkalinity with amine or caustic consistent with the lay-up chemical being used.
General guidelines for wet storage with chemicals
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• Weekly testing during wet storage– Measure pH/Alkalinity – Test dissolved oxygen and/or
scavenger residual– Maintain dissolved oxygen level below
10 ppb– Supplement scavenger/amine as
required
• Preventing oxygen ingress during storage:– Connect surge tank (drum) filled with
lay-up solution to upper vent – Alternative - 5 psig (0.34 bar) nitrogen
‘cap’
General guidelines for wet storage of high-pressure boilers with chemicals
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Volatile Chemicals
• Required when: – Above 900 psig (60 bar)– Non-drainable superheaters– Turbines– High-purity make-up
• Sulfite is NOT suitable
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• Acceptable water for preparation of high-pressure boiler lay-up solutions:– Good-quality demineralized H2O– Good quality condensate (no solids)– No softened-quality, RO or raw water
with appreciable TDS
• Add chemicals to fill water as it is pumped into boiler
Volatile Chemicals
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Suitable volatileoxygen scavengers
• Hydroquinone– Fastest reaction with oxygen at
ambient temp– Must use neutralizing amine with HQ– Important - Amine MUST be
compatible with HQ (or will develop sludge):
• Hydroxylamines – Most volatile & compatible with
amines
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Suitable volatile oxygen scavengers
• Hydrazine - 200 ppm as N2H4
– Excellent passivator at > 200 ppm as N2H4, BUT:
– Not recommended - Safety hazard!– Amine is not typically required
• Ascorbic acid - Not recommended:– Poor thermal stability– Acidic decomposition products– Non-volatile
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• Special lay-up product - CorTrol OS7700
• HQ plus special low-volatility amine package
• Avoids low pH excursions on re-start
• Feedrate: 2000 ppm product – 4000 ppm in new systems (non-
passivated)– Maintain pH above 10.5 throughout
Volatile Chemicals
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• Drain boiler
• Hot air/heat to remove all moisture
• Use desiccant (with color indicator)– Silica gel– Quick lime– Activated alumina
Dry LayDry Lay--up with Desiccant up with Desiccant (Long(Long--term term storage)storage)
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PRESENT TREATMENT PROGRAM AT HAZIRA
• CORTROL-5613-OXYGEN SCAVENGER– FEED RATE 0.5-1.0 PPM – RESIDUAL MONITORING.
• STEAMATE-NA8590– CONDENSATE TREATMENT– LOW DR AMINE
• TRI SODIUM PHOSPHATE– FOR pH/PO4 coordination
• AMMONIA– FEED WATER & STEAM pH CONTROL
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Thank You