Boiler Water Training

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InfrastructureWater & Process Technologies

RIL-Hazira/BWT-Technical TrainingGEWPT- Confidential Material


Boiler Technical TrainingAt

Reliance Industries LimitedHazira Manufacturing Division

February 26, 2008K S Rajan




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




Basics & Interpretation of Water Analysis




“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




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




Impurities found in Water

• 3 Categories

• SUSPENDED SOLIDS (Silt)

• DISSOLVED SOLIDS (Minerals)

• DISSOLVED GASES

• Where do these things come from?




Hydrologic Cycle





• 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-)




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




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




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





• 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




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




Special Ions

• pH • Hydrogen, H+

• Hydroxide, OH-

• Alkalinity• Bicarbonate, HCO3

-

• Carbonate, CO3--

• Hydroxide, OH-




pH

• Hydrogen Ion Concentration• Logarithmic Scale• pH = -log [H+] • Unit change in log scale




How Does pH Apply to Us?

• pH < 7: Acidic (corrosion)• pH > 7: Alkaline (deposition)




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

-




Conductivity

• Inverse of Resistance [mho]• Measure of concentration of ions in solution




Types of Solubility

Normal: Increases with Temperature• Table Salt (NaCl)• Sugar

Retrograde: Decreases with Temperature

• Calcium Carbonate• Calcium Phosphate




How Do We Quantify What Is in the Water?




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





•“Mg as CaCO3”Magnesium expressed as its Equivalent weight in Calcium Carbonate

100 (MW CaCO3) = 4.124 (MW Mg)





• Different Conventions • We use “ppm as CaCO3”• ppm ppm• as substance factors as CaCO3• Ca 50 2.5 125• Mg 20 4.1 82•




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




Babcock & WilcoxCoal Fired Boiler




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




Boiler Calculations FeedWater = Steam + Blowdown

% Blowdown = 1 X 100Cycles

FeedWater (kg/hr) = Steam Generation (kg/hr)1 – (%blowdown)

100

FW= STM ( C )C-1




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




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




Oxygen Control• Deaeration

• Chemical treatment




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




Oxygen Corrosion

• Corrosion Rate Doubles With Every 10 C Increase in Water Temperature

• Metal Loss is low• Localized attack• Pit Formation • Rapid Failure




Rapid Perforation ~ Equipment Failure




Oxygen Guidelines

Organization Dissolved O2 Level, ppb

ASME

TAPPI

ABMA

EPRI

DEAERATORGUARANTEE

TYPICAL DEAERATORO2 LEVELS

< 7

< 7

NO RECOMMENDATION

< 5

7

15 - 40




Types of Oxygen Scavengers

• Solid

– Sodium Bisulfite

– Sodium Sulfite

• Non-Solids

– Hydrazine

– Hydroquinone

– Diethylhydroxlamine (DEHA)

– CARBOHYDRAZIDE

– ASCORBIC ACID




Residual (ppm SO3-) Pressure

30 - 60 < 40 bar10 - 20 40 - 60 bar

ATTEMPERATION / DESUPERHEATING: NO

RECOMMENDEDSULFITE CONTROL LIMITS




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




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




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




HYDROQUINONE

REACTION:C6H6O2 + 1/2O2 H2O + C6H4O2

CONTROL LIMITS:DISSOLVED OXYGEN TEST

IRON REDUCTION TEST

OH

OH




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




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




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




Variables Influencing Scavenger Reaction

• Time• Temperature• pH• Catalyst




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




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




Feed Water and Condensate System Treatment

• Ammonia

• Amines

• Condensate polishing




Condensate TreatmentIn The Condensate:• Carbon Dioxide

H2CO3 H+ + HCO3-

CO2 + H2O H2CO3

pH DECREASES




Feedwater AlkalinityIs a Source of CO2 in Condensate

IN THE BOILER:

2HCO3- CO3

= + H20 + CO2

CO3= CO2 + 2OH-

STEAMCO2

FEEDWATERHCO3

-

CO3=

OH-

BLOWDOWN




Relative Corrosion Rate of Copper Alloys and Carbon Steel vs pH

7 8 9 10

CORROSIONRATE

COPPER

CARBONSTEEL

pH




Fundamental Amine Characteristics

• Distribution Ratio

• Neutralizing Capacity

• Basicity

• Thermal Stability




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-




BASICITY

MorpholineAmmoniaEthanolamineDEAEMOPACyclohexylamine

2183266126440

Neutralizing Basicity Constant




Concentration in steamConcentration in liquid

DR =

VAPOR

LIQUID

HIGH DISTRIBUTIONRATIO

LOW DISTRIBUTIONRATIO

DISTRIBUTION RATIOS




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




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




Cause and Effect Diagram for Boiler Deposition

IntermittentContamination

DepositionFouling

Condensate HardnessContamination

Chemical Underfeed

Poor NaZ Performance

Condensate HydrocarbonContamination

Poor Blowdown Control

IntermittentContamination

Condensate Corrosion


Chemical Underfeed

Poor Chemical Feed Control

Poor Storage Practices

Hardness Salts Iron

High Boiler SilicaPoor SeparationEquipment Performance

Hydrocarbon Contamination


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




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




Coordinated PO4/pH Boiler Treatment

• To control boiler water pH......

• ......Create a buffer systembetween PO4 and NaOH

Under-Deposit Corrosion




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




Na: PO4 RATIO OUT OF CONTROLEXCESS “SODIUM LEAKAGE”

Na2 HPO4 + 2NaOH Na3PO4 + NaOH + H2O

4Na + 1PO4Na:PO4 = 4:1

Low DSP Fed “Free Caustic”




PREVENTING CAUSTIC CONCENTRATION

NaOH + Na2HPO4 Na3PO4 + H2OCaustic Disodium

PhosphateTrisodiumPhosphate Water




2Na2 HPO4 + 2NaOH 2Na3PO4 + 2H2O

6Na + 2PO4Na:PO4 = 3:1

“Exact” DSP Fed

Coordinated Phosphate/pH Control

Under-Deposit Neutralization




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




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)




Steam Purity

Importance of Steam PurityProtect Capital Investments, such as:

– Superheaters– Turbines– Steam lines and valves

Maintain ProductionPrevent Process Contamination




Definitions • Steam PuritySolid, liquid or vaporous

contamination in the steam

• Steam QualityA measure of the moisture in

the steam




Steam Purity Guidelines • Turbine manufacturer (ppb

levels)

• Boiler manufacturer (ppm levels)

• Industry professional organizations

• Operations




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




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




• 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




• 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




Wet Storage Methods1. Volatile Chemicals

2. Sulfite & Caustic

3. Cascade lay-up / Hot standby

4. Dry lay-up with desiccant




• 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




• 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




Volatile Chemicals

• Required when: – Above 900 psig (60 bar)– Non-drainable superheaters– Turbines– High-purity make-up

• Sulfite is NOT suitable




• 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




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




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




• 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




• 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)




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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Boiler Water Training

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