boiler water chemistry

Boiler Water Management

Water Characteristics and Quality

Fundamental Mission of BoilerPower House Management

Reliable production of steam• continuous & quality steam (no unplanned outages)

Safe production of steam• no injuries. no loss of capital equipment• Food safety: FDA. Kosher

Protect the capital investment• minimize corrosion and scaling

Environmental/Regulatory ComplianceCost effective operation• efficient as possible

Water characteristics and qualityCharacteristics

pH important parameter (acidity. alkalinity)

Hardness combination of Ca and Mg

Conductivity uS/cm (relationship with dissolved solids)

Total Dissolved Solids amount of dissolved ions (mg/l)

Alkalinity amount of buffering

p-alkalinity titration until pH=8.3

m-alkalinity total alkalinity (pH=4.3)

Total Suspended Solids everything that is not dissolved and can be filtered out

Water characteristics and qualityImpurities

MINERALS AIR EARTH

CationsAnions

OxygenCarbon MonoxideCarbon Dioxide

ClaySiltSand

a. Dissolved solids b. Dissolved gases c. Suspended matter

Anions

Bicarbonate HCO3-

Chloride Cl-

Sulphate SO42-

Nitrate NO3-

Silicate HSiO3-

Cations

Sodium Na+

Potassium K+

Calcium Ca2+

Magnesium Mg2+

Ammonium NH4+

Iron Fe2+

Manganese Mn2+

Water characteristics and qualitypH Scale

ACIDIC BASIC

Hydrogen Ions (H+) decrease pH; Hydroxyl (OH-) increase pH

1 2 4 5 6 7 8 9 10 11 12 13 143

pH

Water Characteristics and qualityThree battles

Presence of troublesome water components requires• Deposition Control

– Preventing overheat failures resulting from waterside deposition

• Corrosion Control– Maintaining materials of construction. dealing with

general and localized corrosion mechanisms• Steam Purity

– Preventing carryover of boiler water salts into steam phase

Deposition

DepositionWhat is

• Result of insolubility of inorganic scale formers– Hardness Based Deposits – Metal Oxide Based Deposits

• Can occur as a result of contaminated condensate or feedwater components

– Unlikely with demineralized makeup water– Good pretreatment may limit deposition potential

• Develops at areas of highest heat input• Issue becomes more critical as boiler pressure goes up

Deposition Problems caused

Loss of Boiler Efficiency• Scale reduces heat transfer• Increased fuel/energy consumption

Boiler Tube Failure• Scale elevates tube temperature - causing tube

overheating• Partial destroyed boiler sections and even boiler

explosion due to overheating of tube metal over critical temperature for steel

Under-deposit Corrosion• Caused by high localized concentration of corrosive

molecules

DepositionEfficiency reduction

Water tube boiler, 95 % of Scale CaCO3. No heat recovery20 bar [290 psi], 11.3 ton/h

Deposit in mm

0

2

4

6

8

10

12

14

16

18

20

0

0.4

0.8

1.2

1.6 2

2.4

2.8

3.2

3.6 4

4.4

4.8

Effi

cie

ncy L

oss in

%

DepositionIncreased tube temperature

BScaled surface

resulting in lower T0

while needed T1

Deposit

Wal T2

Resulting boilerwater T0

Boiler water T1

needed

Boiler tubemetal wall

Wall T2

AClean internal heat transfer surface.

T1 for neededsteam production

Boiler tubemetal wall

Boiler water T1

Increasedwall T4

T3

Boiler water T1

CScaled surface

Fire side T2 is increasedto T4 to reach water T1

T3 is critical for metal structure

DepositBoiler tubemetal wall

DepositionEffect of scale on heat transfer

0

40

80

120

160

200

240

0 0.002 0.004 0.006 0.008 0.01

Deposit thickness [mm]

Tem

pera

ture

[°F

]

Ana

lcite

(sod

ium

alu

min

um s

ilica

te)

Magnesium p

hosphate

Magnetic iron oxide

Calcium phosphate

115

95

70

50

25

5

Tem

pera

ture

[°C]

120

100

80

60

40

20

0

Tu

be m

eta

l te

mp

era

ture

in

cre

ase

DepositionFactors

Factors that contribute in waterside deposition:• Presence of ionic scale formers in feedwater (calcium,

magnesium, barium, strontium, silica, iron)• Presence of scale formers treatment derived

(phosphate, alkalinity)• Presence of particulate contaminants• Interactions with existing deposition• Heat input• Flow parameters• “Microclimates” • Location in riser circuit

DepositionSolubilities

Compound ppm as CaCO3

0 °C [32 °F] 100 °C [212 °F]

Calcium Bicarbonate 1620 Decomposes

Carbonate 15 13

Sulfate 1290 1250

Magnesium Bicarbonate 37.000 Decomposes

Carbonate 101 75

Sulfate 170.000 356.000

Sodium Bicarbonate 30.700 Decomposes

Carbonate 61.400 290.000

Chloride 225.000 243.000

Hydroxide 370.000 970.000

Sulfate 33.600 210.000

DepositionHardness precipitation

• Precipitation of insoluble hardness

– 2 HCO3- CO3

2- + CO2+ H2O 100%

– CO32- + H2O CO2 + 2OH- 60 -

80%

– Ca2+ + CO32- CaCO3 boiler scale

– Mg+2 + OH- MgOH+

– H2SiO3 H+ + HSiO3-

– MgOH+ + HSiO3- MgSiO3 + H2O

• Exceeding saturation through evaporation, resulting in crystallization

– eg. CaSO4.SiO2

Scaling & DepositsHeat transfer limitation

Boiler tube failure

DepositionWhy Hardness is Such an Issue

Temperature

Soluble Amount

Most materials are more soluble

at increasing temperature

Ca. Mg. Ba. Sr solubility decreases at increasing

temperature

DepositionBoiler deposits

Name Formula

Acmite Na2O·Fe2O3·4SiO2

Analcite Na2O·Al2O3·4SiO2·2H2O

Anhydrite CaSO4

Aragonite CaCO3 (gamma form)

Basic magnesium phosphate Mg3(PO4)2·Mg(OH)2

Brucite Mg(OH)2

Calcium hydroxide Ca(OH)2

Calcite CaCO3 (beta form)

Copper Cu

Cuprite Cu2O

Ferrous oxide FeO

Goetnite Fe2O3 · H2O (alpha form)

Gypsum CaSO4·2 H2O

Hematite Fe2O3

Hydroxyapatite Ca10(PO4)6(OH)2

Magnetite Fe3O4

Serpentine (magnesium silicate) 3MgO·SiO2·2 H2O

Sodium ferrous phosphate NaFePO4

Tenorite CuO

Thenardite Na2SO4

Xonotlite 5 CaO·5 SiO2 ·H2O

DepositionSilica

• Forms deposits in boilers • Occurs as magnesium silicate or silicic acid

• Selective silica carryover– Silica is selectively dissolved into the steam– Controlled by limiting the silica concentration in the

boiler water– Controlled by limiting boiler pressure– Controlled by maintaining high pH– Cannot be controlled mechanically by steam

separators• Not usually a problem with boilers with less than 40

bar (600 psig) pressure

Deposition Iron scale

Iron is usually found in a boiler as one or more of the following:• A complex with calcium• A complex with phosphate• Hematite - Fe2O3• Magnetite - Fe3O4

Corrosion

CorrosionWhat is

Definition• The deterioration of a material by the interaction with

it’s environment

Impact• Feedwater piping• Feedwater heaters• Economizer• Boiler• Condensate system• …

Oxygen corrosion in flame pipe (6 bar boiler)

CorrosionProblems caused

Impact corrosion on boiler reliability• Premature replacement need of boiler

– boilers should last very long upon correct use– Water side corrosion should be nihil and not a factor

contributing to the life time of the boiler• Unscheduled maintenance to boiler or feed water lines• Unscheduled maintenance to the condensate system• Filthy steam and condensate traps can cause leaking

of steam into condensate system due to malfunctioning valves

Oxygen corrosion in flame pipe (6 bar boiler)

CorrosionBoiler metal passivation

Natural passivation:• Formation of a protective barrier on metal surface by

reaction with waterFe + 2 H2O Fe(OH)2 + H23Fe(OH)2 Fe3O4 + H2 + 2H2O

• Black magnetite film - Fe3O4• Rate of Magnetite formation is

– Temperature dependent– Spontaneous above 180 °C (360 °F)

• Reduces general corrosion• Difficult to quantify results

Oxygen scavengingMetal passivation

SHIKORR REACTION

T < 180 °C• 3 Fe + 6 H2O 3 Fe(OH)2 + 3 H2

• 2 Fe(OH)2 + 2 H2O 2 Fe(OH)3 + H2

• Fe(OH)2 + 2 Fe(OH)3 Fe3O4 + 4 H2O

T > 180 °C• 3 Fe + 4 H2O Fe3O4 + 4 H2

CorrosionSolubility of magnetite in water

CorrosionEffect of pH

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CorrosionTypes

Types of Corrosion• Oxygen corrosion• Alkalinity concentration• Caustic corrosion• Acid corrosion• Chelant corrosion• Erosion/Corrosion

Condensate return pipe with deep attack due to the combined effect of CO2 and O2

CorrosionOxygen Corrosion

ANODE: Fe0 Fe+2 + 2e-

Natural Metal Metal ion Metal electrons

CATHODE: 2e- + 1/2 O2 + H2O 2(OH-)

Electrons Oxygen Water Charged Ion

ANODECATHODE Electron transport

Corrosion productsOxygen.O2

HydroxideOH-

Metal ions dissolve

CorrosionFactors Oxygen corrosion

• Can be found throughout the system• Mechanism same as other oxygen corrosion cells• Corrosion mechanisms affected by:

– pH• Minimize corrosion: pH >9.0

– Temperature• Higher temperatures reduce O2 solubility, but

significantly increase corrosivity

– Dissolved oxygen concentration• Higher O2 concentrations increase corrosivity

– Fluid velocity• Enhances effect of other corrodents• More diffusion - better mass transport


Dissolved oxygen as function of temperature at atmospherical pressure

5.5 ppm O2

2.5 ppm O2

85°C (185 °F)

50°C (122 °F)


Problems associated with oxygen:

• Crack formation in degassers - deaerator cracking• Corrosion pits that require immediate remedy to

obtain approval after periodic inspections by authorities

• Corrosion damage to gray cast iron in feed water pumps

• Leaking feed water pipes, leaking economisers, pits and craters in boiler tubes (low pressure boilers)

Oxygen corrosion in feed water line


Economical impact of oxygen corrosion• Increased energy consumption

– Oxygen corrosion introduces additional iron and copper oxides in the water

• Deposition on heated surfaces (limiting heat transfer)

– Increased blowdown due to turbidity water – Increased conductivity due to addition of oxygen

scavengers (e.g. sulfite) requires increased blowdown

Oxygen corrosion in feed water line (pH

7.5. 50 °C)

CorrosionCaustic Damage

There are two forms of damage caused by caustic soda to high pressure boilers, namely:

– Caustic corrosion– Caustic embrittlementDo we have a

picture Steef??

CorrosionCaustic Corrosion

• Two conditions are necessary for caustic corrosion to occur:

– Presence of a corrosive material in the boiler water (caustic soda)

– Mechanism for concentrating this material, usually due to deposits

• Usually found only in high pressure boilers

Fe3O4 Fe2O3 + FeO (Magnetite dissolution)Fe2O3 + 2 NaOH 2 NaFeO2 + H2O (soluble)FeO + 2 NaOH Na2FeO2 + H2O (soluble)

• Localized in boiler• Also called crater attack or caustic gouging• No embrittlement of metal

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CorrosionCaustic Embrittlement

Embrittlement is a special form of stress corrosion cracking• Should not be confused with caustic corrosion

• Three conditions must be present– Concentrating mechanism present– Metal under high stress– Must contain silica

• Inhibited by improved fabrication techniques and by organic and nitrate-based inhibitors

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nee, do we have a picture Steef?

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Nitrate??!?

CorrosionConcentration mechanism

Steam blanketing

Under deposit / concentration to dryness• Excessive heat input• Insufficient coolant flow• Deposits

Elongated gouge caused by steam blanketing

NaOH

NaOH

NaOH

Fe3O4 porous deposit

Water In

Steam Out

NaOH

NaOH

Magnetite

CorrosionConcentrating Mechanisms

The following conditions can result in dangerously high localized caustic soda concentrations

• (Porous) metal oxide deposits• Operation above rated capacity• Excessive rate of load increase • Excessive localized heat input• Localized pressure differentials• Restrictions in generating tube(s)

CorrosionAcid corrosion

Causes of acidity• Feedwater acid contamination• Acid leaks from demineralizer, e.g. acid regenerant • Breakdown of organic materials• Condenser leaks

– MgCl2 + 2 H2O Mg(OH)2 + 2 HCl• Organic chlorides

– R-X + 2 H2O R-OH + HCl

CorrosionAcid corrosion

Special form of acid corrosion can be found in condensate system:

Alkalinity of BFW breaks down in Boiler • 2 NaHCO3 Na2CO3 + CO2 + H2O

Na2CO3 + H2O 2 NaOH + CO2

CO2 leaves with steam and reacts with condensed water droplets to Carbonic Acid • CO2 + H2O H2CO3

The H2CO3 acid attacks metals by reducing pH

% C

on

vers

ion

Pressue (bar)

Steam purity

Steam PurityWhat is

Defined as the amount of non-water components of the steam• Priming• Foaming• Misting• Selective carry-over

Normally measured in terms of ppb sodium ion and ppb silica.• Sodium Limits to turbines

– Old industrial turbines - max. of 20 ppb– New industrial turbines - max. 5 ppb

• Silica Limits to Turbines - 20 ppb

Steam PurityProblems caused

Effects of low steam purity• Process Contamination • Loss of Turbine Efficiency• Turbine Imbalance• Operational Problems• Plant Shut-down

Water Quality guidelines

Water quality guidelines

Boiler Water component [ppm]

Drum Pressure. psig (bar)

150 (10) 300 (20) 600 (40) 900 (60) 1200 (80) 1500 (100)

TDS (max) 4000 3500 3000 2000 500 300

Phosphate (as PO4)

30-60 30-60 20-40 15-20 10-15 5-10

Hydroxide (as CaCO3)

300-400 250-300 150-200 120-150 100-120 80-100

Sulfite 30-60 30-40 20-30 15-20 Not recommended

Not recommended

Silica (as SiO2. max)

100 50 30 10 5 3

Total Iron (as Fe. max)

10 5 3 2 2 1

Organics 70-100 70-100 50-70 50-70 50-70

Drum-type boilers using softened (not deionized) feedwaters

Different for all boiler types. feed water quality and region

•ASME: USA

•Krachtwerktuigen: Holland

•TUV: Germany

•British Standard: UK

Check Etienne – source???

Water quality guidelinesHigh purity Feed water

Boiler Water Component

Drum pressure psig (bar)

Upto 600 (40)

900 (60) 120 (80) 1500 (100) 1800 (120) 2400 (160)

TDS (max) 500 500 300 200 100 50

Phosphate (as PO4)

15-25 15-25 15-25 5-10 5-10 5-10

pH 9.8-10.2 9.8-10.2 9.8-10.2 9.4-9.7 9.4-9.7 9.4-9.7

Silica (as SiO2. max)

10 10 5 2 1 0.25

Total iron (as Fe. max)

2 2 2 1 0.5 0.25

Hydrazine Idem soft water

0.04-0.06 0.04-0.06 0.04-0.06 0.04-0.06 0.04-0.06

Drum-type boilers using high purity (deionized) feedwaters

Different for all boiler types. feed water quality and region

•ASME: USA

•Krachtwerktuigen: Holland

•TUV: Germany

•British Standard: UK

Check Etienne – source???

Water quality guidelinesgeneral remarks

• Limits on TDS will vary with the design of the boiler and with the needs of the system

• Despite TDS maximums. industrial type boilers (as opposed to utility type) should not be operated above 100 cycles of concentration

• Silica may be carried at higher levels if there are no condensing turbines in the cycle. In any case. maintain an "O"/SiOratio of at least 3/1 to inhibit silica deposition.

• Iron levels shown are theoretical levels based on feedwater iron multiplied by cycles of feed water concentration

ASME Guidelines for Feedwater Quality

Boiler Pressure [bar]

Boiler Pressure [psi]

Hardness [ppm]

I ron [ppm]

Copper [ppm]

0 - 20 0 – 300 0.300 0.100 0.050

21 - 31 301 – 450 0.300 0.050 0.025

32 - 41 451 – 600 0.200 0.030 0.020

42 – 51 601 – 750 0.200 0.025 0.020

52 – 62 751 – 900 0.100 0.020 0.015

63 - 103 901 – 1500 N/D 0.010 0.010

Fire tube

0 - 20 0 – 300 1.0 0.100 0.050

Water tube

Make again in PPT format

Feedwater Quality requirementsFrance - Softened Feedwater

Operating pressure

bar < 15 15 - 25 25 - 35 35 – 45

Feedwater

pH ≥ 8.5 ≥ 8.5 ≥ 8.5 ≥ 8.5

Total Hardness [°F] < 0.5 < 0.2 < 0.2 < 0.1

Oxygen remove remove Remove Remove

Huil absent absent absent Absent

Boiler water

TAC [°F] ≤ 100 ≤ 80 ≤ 60 ≤ 40

TA [°F] 0.7 TAC 0.7 TAC 0.7 TAC 0.7 TAC

Silica [Mg/L] ≤ 200 ≤ 150 ≤ 90 ≤ 40

SiO2 / TAC ≤ 2.5 ≤ 2 ≤ 1.5 ≤ 1

Total dissoloved solids

[Mg/L] < 4000 < 3000 < 2000 < 1500

Chlorine [Mg/L] ≤ 800 ≤ 600 ≤ 400 ≤ 300

Phosphate [Mg/L] 30 - 100 30 - 100 20 - 80 20 – 80

pH 10.5 - 12 10.5 - 12 10.5 - 12 10.5 - 12

Feedwater Quality requirementsFrance - Demineralized Feedwater

Operating pressure

bar 40 - 60 60 - 75 75 - 100

Feedwater

pH ≥ 8.5 ≥ 8.5 ≥ 8.5

Total Hardness [°F] < 0.05 < 0.05 < 0.05

Oxygen remove remove Remove

Huil Mg/l < 0.05 < 0.05 < 0.05

Iron Mg/l < 0.05 < 0.05 < 0.03

Copper Mg/L < 0.03 < 0.03 < 0.01

Boiler water

TAC [°F] ≤ 25 ≤ 10 ≤ 5

TA [°F] ≥ 0.5 TAC ≥ 0.5 TAC ≥ 0.5 TAC

Silica [Mg/L] ≤ 15 ≤ 10 ≤ 5

SiO2 / TAC < 1 < 1 < 1


[Mg/L] < 500 < 300 < 100

Free NaOH [Mg/L] < 20 < 300 < 100

Phosphate [Mg/L] 10 - 60 10 - 40 5 – 20

pH 10 - 11 10 - 11 9.5 – 10.5

Feedwater Quality requirementsFrance – Fire tube boilers

Operating pressure

bar ≤ 10 10 - 15 15 – 25

Feedwater

pH ≥ 8.5 ≥ 8.5 ≥ 8.5

Total Hardness [°F] < 0.5 < 0.5 < 0.2

Oxygen remove remove Remove

Huil Mg/l absent absent Absent

Boiler water

TAC [°F] ≤ 120 ≤ 100 ≤ 80

TA [°F] 0.7 TAC 0.7 TAC 0.7 TAC

Silica [Mg/L] ≤ 200 ≤ 200 ≤ 150

SiO2 / TAC ≤ 2.5 ≤ 2.5 ≤ 2


[Mg/L] ≤ 5000 ≤ 4000 ≤ 3000

Free NaOH [Mg/L] < 20 < 300 < 100

Phosphate [Mg/L] 30 - 100 30 - 100 30 - 100

pH 10.5 - 12 10.5 - 12 10.5 - 12

Feedwater Quality requirementsGermany - VGB

Scope Continuous operation

Continuous operation

Continuous operation

Continuous operation Continuous operation

Fully demineralized feedwater

Demineralized feedwater



Steam for condensing turbines

Alkalized boiler water – Na3PO4 recommended

Alkalized boiler water – Na3PO4 recommended

Volatile agents

Pressure area [bar] > 68 68 - 136 > 136

PH (25 °C)Neutral operationCombined operationAlkaline operation

7-88-99-10

9.8 – 10.2 9.3 – 9.7 Alkaline

Conductivity (25 °C) [uS/cm] < 0.25 < 50 < 50 < 5 (for < 250 kW/m2)< 3 (for > 250 kW/m2)

< 0.2

Oxygen

Neutral operation

Combined operation

Alkaline operation

[mg/l]

0.050 - 0.2500.030 – 0.150< 0.100

Iron [mg/l]

Copper [mg/l] < 0.02< 0.03

< 0.020< 0.030

Na [mg/l] < 0.01 < 0.010

Silica [mg/l] < 0.02 < 0.020

If Na3PO4 is dosed PO4 [mg/L] <6 <3 NA

Boiler water Quality requirementsGermany - TÜV

Scope Softened feedwater

Boiler water on softened feedwater Demin. feedwater

Boiler water based on demin. feedwater

Pressure area [bar] 1 <> 68 1 <> 22 22 <> 44 44 <> 68 < 68 < 68 < 68

Appearance Colourless, free from suspended matter

Conductivity (25 °C) [µS/cm] < 10,000 < 5,000 < 2,500 < 0.2 < 150 < 3

Hardness [ppm CaCO3] < 1.0

Oxygen ppm < 0.02 < 0.1

Phosphate [mg/l ] 10 – 20 5 - 15 5 - 15 < 6

PH (25 °C) 10.5 – 12 10 – 11.8 10 – 11 > 9 9.5 – 10.5 > 7

p-alkalinity [ppm CaCO3] 50 – 600 25 - 300 5 – 50

CO2 fixed [mg/l ] < 25

Iron ppm < 0.03 < 0.03

Copper Ppm < 0.005 < 0.005

Silica [mg/l] NR Graph Graph < 10 < 0.02 < 4 < 4

Organic carbon [ppm as KMnO4] < 10 < 3

Oil ppm < 1 < 1

Boiler water Quality requirementsItaly

Scope

Pressure area [bar]

Appearance

Conductivity (25 °C) [µS/cm]

Hardness [ppm CaCO3]

Oxygen ppm

Phosphate [mg/l ]

PH (25 °C)

p-alkalinity [ppm CaCO3]

CO2 fixed [mg/l ]

Iron ppm

Copper Ppm

Silica [mg/l]

Organic carbon [ppm as KMnO4]

Oil ppm

Boiler water Quality requirementsSpain – Firetube: UNE 9-075-92

Feedwater Feedwater Boiler water Boiler water Boiler water

≤ 0.5 bar > 0.5 bar ≤ 0.5 bar 0.5 <≥ 13 bar > 13 bar

Appearance Colourless and without suspended solids

Hardness [ppm CaCO3] ≤ 10 ≤ 5

Oxygen [mg/L] - ≤ 0.2

PH (20 °C) 8-9 8-9 10.5 – 12.5 10 - 12 10 – 12

CO2 fixed [mg/l ] ≤ 25 ≤ 25

Organic carbon [ppm as KMnO4] ≤ 10 ≤ 10

Oil ppm ≤ 3 ≤ 1

Conductivity (≤ 40 kg/m2) [mg/L] ≤ 6,000 ≤ 6,000 ≤ 4,000

Conductivity (> 40 kg/m2 [mg/L] ≤ 5,000 ≤ 5,000 ≤ 3,000

p-alkalinity [ppm CaCO3] ≤ 1,000 ≤ 800 ≤ 600

Phosphate [mg/l P2O5 ] ≤ 30 ≤ 25 ≤ 20

Silica [mg/l SiO2] ≤ 250 ≤ 200 ≤ 150

Boiler water Quality requirementsSpain - water tube: UNE 9-075-92

Maximum allowed values

Hardness Alkalinity TSS pH (20 °C) Phosphate Silica

[mg/L] [mg/L] [mg/L] [Mg/L P2O5] [mg/l]

< 20 Natural circulation 3,500 700 150 9.5 - 11 25 140

21- 32 Natural circulation 3,000 600 100 9.5 - 11 25 50

33 – 40 Natural circulation 2,500 500 80 9.5 - 11 10 50




71 – 126 Natural circulation 100 100 10 9.5 – 10.5 3 4

127 – 165 Natural circulation 50 40 9.5 – 10.5 3 4



> 98 Forced circulation 0.05 9.5 – 10.5 3 4

< 20 Forced circulation with continuous steam formation

2,000 400 100 - - 140

20 - 40 Forced circulation with continuous steam formation

1,000 200 50 - - 50

Boiler water Quality requirementsNetherlands

Parameters

Krachtwerktuigen KEMA

Waterpijp Low pressure boilers

Pressure area [bar] 0.5-20 <80

Phosphate [mg/l ] 30-80 <15

PH (25 °C) 9.8-10.2

p-alkalinity [ppm CaCO3] 250-750

Chloride [mg/l] <2

Silica [mg/l] <5

TDS

Conductivity [µS/cm] < 6000 (pH=8.3) <2500 (after cation filter)

Organic carbon [ppm CZV] <150

Iso ascorbic acid [mg/l]

CHECK

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Boiler water Quality requirementsUK – Shell tube upto 30 bar

Parameter Unit Feedwater Boiler water Boiler water


Heat flux ≤ 300 > 300

Appearance Clear, no foam

pH (25 °C) 8.5 – 9.5 10.5 – 12.0 9.5 – 10.5

Total Hardness Mg/kg CaCO3 ≤ 2

Oxygen Mg/kg

Total M-alkalinity Mg/kg CaCO3 ≤ 1000 ≤ 100

O- and P-alkalinity Mg/kg CaCO3 ≥ 350 ≥ 20

Oil and grease Mg/kg ≤ 1

Oxygen scavengerSulfite, orHydrazine, orTannin, orIso ascorbic acid, orDEHA

Mg/kg30 – 700.1 – 1.0120 – 16015 – 300.1 – 1.0 (FW)

Assess0.1 – 1.0AssessAssess0.1 –1.0 (FW)

Phosphate Mg/kg 30 – 60 10 – 30

Silica Mg/kg ≤ 150 ≤ 5

Suspended solids Mg/kg ≤ 200 ≤ 20

Dissolved solids Mg/kg ≤ 3500 ≤ 1000

Conductivity (25 °C) uS/cm ≤ 7000 ≤ 2000

CHECK

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Boiler water Quality requirementsUK – Fired Water tube

Parameter Unit 0 - 20 21 – 40 41 - 60 61 - 80 81 - 100 101 - 120 ≥ 121

Feedwater

pH (25 °C) 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5

Total Hardness Mg/kg CaCO3 2 1 ND ND ND ND ND

Oxygen Mg/kg ≤ 0.02 ≤ 0.02 ≤ 0.01 ≤ 0.005 ≤ 0.005 ≤ 0.005 ≤ 0.005

Fe, Cu, and Ni Mg/kg ≤ 0.05 ≤ 0.05 ≤ 0.03 ≤ 0.02 ≤ 0.02 ≤ 0.02 ≤ 0.02

Boiler water

O- and P-alkalinity Mg/kg CaCO3 50 - 300 50 - 150 25 – 50 10 – 20 5 - 10 2 - 5 1 - 5

Oxygen scavengerSulfite, orHydrazine, orTannin, orIso ascorbic acid, orDEHA in FW

Mg/kg30 – 500.1 –10120 – 16015 – 300.1 – 0.25

20 – 400.1 –0.5NR15 – 300.1 – 0.25

15 - 200.1 –0.2NR15 – 300.1 – 0.25

NR0.05 –0.1NRNR0.1 – 0.25

NR0.05 –0.1NRNR0.1 – 0.25

NR0.05 –0.1NRNR0.1 – 0.25

NR0.05 –0.1NRNR0.1 – 0.25

Chloride Assess Assess Assess Assess

Phosphate Mg/kg 30 – 70 20 – 50 20 – 40 15 – 30 10 – 20 3 – 10 3 – 5

Silica Mg/kg ≤ 0.4 x O & P alkalinity

≤ 0.4 x O & P alkalinity

≤ 20 ≤ 5 ≤ 2 ≤ 1.5 ≤ 0.5

Dissolved solids Mg/kg ≤ 3000 ≤ 2500 ≤ 1000 ≤ 200 ≤ 50 ≤ 20 ≤ 10

Conductivity (25 °C) uS/cm ≤ 6000 ≤ 5000 ≤ 2000 ≤ 450 ≤ 150 ≤ 60 ≤ 35

CHECK - Is there an update, have seen the draft!

Boiler water Quality requirementsUK – Other boilers

Non-fired Water Tube



Once through

Coil boiler Coil boiler Electrode boiler

Parameter Unit 0 - 40 41 - 80 > 80 < 40 > 41 101 – 120

Feedwater

pH (25 °C) 9.3 – 9.8 9.3 – 9.8 9.3 – 9.8 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 7.5 – 9.5

Total Hardness Mg/kg CaCO3 ND ND ND ≤ 1 ND ≤ 1

Oxygen Mg/kg ≤ 0.02 ≤ 0.01 ≤ 0.005 ≤ 0.005 Nil

Fe, Cu, and Ni Mg/kg ≤ 0.05 ≤ 0.03 ≤ 0.02 ≤ 0.005 ≤ 0.02 ≤ 0.2

Cond ≤ 400

Boiler water

O- and P-alkalinityTotal

Mg/kg CaCO3 25 - 50 10 - 50 2 – 5 ≥ 300 ≥ 150 ≥ 300≤ 600

Oxygen scavengerSulfite, orHydrazine, orTannin, orIso ascorbic acid, orDEHA in FW

Mg/kg15 - 200.1 –0.5120 – 16015 – 300.1 – 0.25

-0.05 –0.1NR15 – 300.1 – 0.25

-0.05 –0.1NR15 – 300.1 – 0.25

10 - 200.05 –0.1NRNR0.1 – 0.25

NR0.02 –0.05NRNR0.02 – 0.05

50 – 100

pH > 9.5Hardness 0 - 10

Phosphate Mg/kg 20 - 40 15 – 30 3 – 10 Assess 3 - 5

Silica Mg/kg ≤ 20 ≤ 5 1 - 5 ≤ 0.02 < 0.4 X O&P alk < 0.4 X O&P alk

Dissolved solids Mg/kg ≤ 1000 ≤ 200 ≤ 50 ≤ 200 ≤ 8000 ≤ 5000

Conductivity (25 °C) uS/cm ≤ 2000 ≤ 400 ≤ 100 ≤ 0.2 400 – 2000

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Boiler water Quality requirementsUK – Fired Water tube

Parameter Unit 0 - 20 21 – 40 41 - 60 61 - 80 81 - 100 101 - 120 ≥ 121

Pressure bar ≤ 300

Appearance Clear, no foam

pH (25 °C) 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5 8.5 – 9.5

Total Hardness Mg/kg CaCO3 2 1 ND ND ND ND ND

Oxygen Mg/kg ≤ 0.02 ≤ 0.02 ≤ 0.01 ≤ 0.005 ≤ 0.005 ≤ 0.005 ≤ 0.005

Fe, Cu, and Ni Mg/kg ≤ 0.05 ≤ 0.05 ≤ 0.03 ≤ 0.02 ≤ 0.02 ≤ 0.02 ≤ 0.02

Feedwater

boiler water chemistry

Documents

boiler pressure

tube metal

boiler sections

boiler explosion

water t1t3

tube overheatingpartial

co32 caco3 boiler scalemg

scale caco3