BOILER WATER

CHEMISTRY

Boiler Types1 Coil2 Fire Tube3 Water Tube

Waste recovery Heat Recovery Steam Generators CPP CCPP IPP

Boiler Coil type1 Capacity < 1000 kg/hr2 Pressure

Boiler Fire Tube1 Capacity < 10 TPH2 Pressure

Boiler Water Tube1 Capacity > 5 TPH2 Pressure > 20 kg/cm23 Usage Chemicals & Process

Industry, Oil Extraction Mills, Power Plant, Sugar Industry, etc

4 Plant Accessories Air Pre-heater Economiser De-aerator Super Heater Spray attemperators DM Plant

Boiler - Water Tube1 Water Quality - Feed Water DM water

pH 6.8 7.2 Conductivity 100 0C D.O. < 10 ppb Silica

Goals of Boiler Operations Produce steam for the lowest

possible overall cost Minimize Water Use / Wastage Minimize Chemical Use / Wastage Minimize Operating and

Maintenance Costs

Our goal is to provide value when we address customer

needs.

Resourcefulness Quality Performance Cost-Effectiveness

Objectives of Boiler WaterTreatment

Prevent Scaling and Deposits Prevent Corrosion Failure and

Damage to System Equipment Avoid Carryover of water & solids

into the Steam

CondensateReceiver

BoilerBoilerBoiler

Blowdown flash Blowdown flash tanktank

ProcessProcess

ProcessProcess

ProcessProcess

Flash Flash tanktank

Low pressure Low pressure steamsteam

PrePre--TreatmentTreatmentTurbines

PROBLEMS ASSOCIATED WITH WATER

Corrosion of Boiler or piping - almost always due to oxygen Basic ingredient in respirationAlso, a

great menace to many situations !!! Scale - usually due to hardness,

sometimes silica Corrosion of steam / Condensate piping

or equipment

The success of every boiler water treatment program relies on a primary mechanical means for reducing the potential and deposition, followed by a secondary chemical means

Treatment of Boiler Systems

Is a science Uncontrolled factors or variables

are few Mechanical procedures can solve

many problems Keys are Energy Efficiency &

Equipment Reliability

MAXIMUM RELIABILITY

is Provided by

CONTROL OF OXYGEN CORROSION

Oxygen Corrosion Control

Remove as much oxygen as possible by mechanical methods higher temperature water / feed water de-aeration

Polish with chemical scavenger

Types of Deaerator

Spray Type

Tray Type

Steam

HeatHeat

HeatHeat

HeatHeat

SPRAY TYPE

TRAY TYPE

Chemical Removal of Oxygen

O2 + X Scavenger = XO saltO2 + 2SO3- = 2SO4=

O2 + N2H4 = N2 + H20

O2 + (N2H3)2CO = N2 +H20

BOILER WATER TREATMENT

OXYGEN SCAVENGERS

SCALE AND SLUDGE CONTROL

DISPERSANTS

ANTIFOAM

CONDENSATE LINE CORROSION INHIBITORS

OXYGEN SCAVENGERS

Sulphite, (Catalyzed & USDA Approved)

Hydrazine,(Catalysed)

Carbohydrazide

Other non-sulfite, non-hydrazine compounds, TanninTannin -- LigninLignin

SLUDGE CONTROL

PHOSPHATESPrecipitation of scale forming salts

PHOSPHONATESPrevent deposition of precipitated salts

DISPERSANTSDispersion of sludge for easy removal through blow down

DISPERSANTS & ANTIFOAM

Dispersants based on Polyacrylates, Polymethacrylates & Polymaleates

Specific for high suspended solids

Stable at high temp.

CONDENSATE LINE CORROSION INHIBITOR

CYCLOHEXYL AMINE

DIETHYL AMINO ETHANOL

MORPHOLINE

WHY TO SCAVANGE OXYGEN

MAIN WATER RELATED PROBLEMS Corrosion of Boiler or steam,

condensate lines- almost always due to OXYGEN

Scale usually due to hardness, sometimes silica

Corrosion of steam / condensate piping or equipment

Scale Deposit Formation Heat and Pressure cause natural

reactions Calcium & Magnesium react, form

scales, inverse solubility. Excess Silica can cause hard scale Cu, Fe, galvanic corrosion Iron oxides, corrosion product

increases deposits

Thermal conductivities of various scales and other materials

M a te r ia lsT h e rm a l c o n d u c tiv ity

(B T U /f t2h r . o F in )A n a lc ite 8 .8

C a lc iu m p h o sp h a te 2 5

C a lc iu m su lfa te 1 6

M a g n e s iu m p h o sp h a te 1 5

M a g n e tic iro n o x id e 2 0

S il ic a te sc a le (p o ro u s ) 0 .6

B o ile r s te e l 3 1 0F ire b r ic k 7

In su la tin g b r ic k 0 .7

Methods for Boiler Deposit Control

Remove as much scale potential as possible mechanically

Maximize solubility (Silica + Hardness)

Change reactions to not form scale Condition sludge to not stick, be

removed via blowdown

HIGHEST ENERGY EFFICIENCYis Provided by

MINIMUM BLOWDOWN &

MAXIMUM DEPOSIT PREVENTION

Internal BWT Treatment History

Alkaline Phosphate TreatmentIntroduced in 1920SWidely Used TodayPrecipitates Calcium,

Magnesium and Silica As Sludge Rather Than Scales

Alkaline Phosphate Treatment

Calcium Hardness Forms Calcium Hydroxyapatite(3 Ca3(PO4)2 . Ca(OH)2)

Magnesium Hardness Forms Serpentine(2 MgSiO3 . Mg(OH)2 . H2O)

These Non-Adherent Sludge Are Removed Through Bottom Blowdown

Silica controlled as Serpentine or via Hydrate Alkalinity & Maximum Concentration Control

PHOSPHATE TREATMENTProgram Operation

Phosphate Residual: 30-50 ppm PO4 in the Boiler

Hydrate Alkalinity: 100-600 ppm as CaCO3 in the Boiler

Co-Ordinated Phosphate 4 -10 ppm PO4 in HP Boiler

Co-Ordinated Phosphate treatment - 4 to + 0 ppm Hydrate Alkalinity (2p-m)

AWC PRODUCTS OXYGEN SCAVENGERSAWC A-410: Liquid catalyzed oxygen scavenger for low

and medium pressure boilers (up to 900 psig).AWC A-413: Powdered catalyzed oxygen scavenger for

low and medium pressure boilers (up to 900 psig).AWC A-415: Powdered oxygen scavenger for high

pressure boilers (900 - 1500 psig).AWC A-417: Liquid oxygen scavenger for very high

pressure boilers (> 2500 psig).

AWC PRODUCTS PHOSPHATE TREATMENTS AND SCALE

CONTROLAWC A-430: Powdered polyphosphate blend.AWC A-434: Liquid polymer based sludge conditioner

and metal oxide dispersant.

AWC A-451: Liquid polyphosphate / polymer blend for optimal scale control.

AWC PRODUCTS CORROSION INHIBITORS FOR STEAM

CONDENSATE

AWC A-480: Blend of neutralizing amines for long and short steam distribution lines.

AWC A-485: Blend of neutralizing amines for short steam distribution lines, such as turbines and steam hot water heaters.

AWC PRODUCTS MULTI-FUNCTIONAL BLENDS

AWC A-460: Polyphosphate/sludge conditioner/scale inhibitor/oxygen scavenger.

AWC A-465: Polyphosphate/sludge conditioner/scale inhibitor/oxygen scavenger/neutralizing amines.

Organic Adjuncts Iron Sequestering Agents

Sludge Conditioners

Synthetic Polymers

Synthetic PolymersLong Chain of Repeating

Monomer Units, Typically of Anionic Charge

Distort Scale Crystal Structure

Inhibit Scale Growth

Disperse Scale Particles

Combination Treatment Approaches

Incorporate Proprietary Blends of Sequestrates, Dispersants (Natural and Synthetic), Reducing Agents, Etc. to Minimize Deposition

Blends Can Be Customized to Address Feed water Quality, System Pressure, Testing Requirements, Governmental Regulations

Internal Boiler TreatmentSelection Methodology

Feed water quality

Feed system constraints

Boiler pressure Steam uses Performance, Chemistry Testing needsQuantity requirements , Costs FDA needs

Summary Operating conditions dictate

treatment programs All program options have

advantages and disadvantages Pretreatment equipment and

processes cannot be ignored Proper control is necessary

After BoilerTreatment

After Boiler Section Super heaters Turbines Process equipment Steam-handling equipment Condensate lines

Condensate CorrosionAcidic attack due to acid gasesCarbon Dioxide naturally forms

in boilerCarries over in steam, enters

condensate & forms carbonic acid

After Boiler Corrosion Low pH attack caused by CO2

H2O + CO2 = H2CO3Fe + H2CO3 = FeCO3 + H2

Oxygen attackFe + O2 + H2O = Fe(OH)2 Fe(OH)2 + Heat = Fe2O3

Possible Causes of Low pH Presence and/or formation of carbon

dioxide (CO2) Breakdown of bicarbonate and carbonate

alkalinity in the boiler Free CO2 in raw water (e.g. well water) / air

leakage Internal treatment chemicals (e.g. soda ash) Decomposition of some organic compounds

Breakdown of sulfite above 900 psig to SO2 and H2S

Results in Thinning of metal

Threaded pipe

Grooving

Equipment and piping failure in the steam and Condensate system

Metallic oxides returned to boiler

Corrosion caused leaks

Grooving and Thinning

CO2 Attack

Thinning below water line

Oxygen and Carbonic Acid Attack

Effects of Corrosion on Plant Efficiency

Iron-bound deposits in boilers Destruction of capital equipment Repair and labour costs Steam leaks, wastage Unscheduled outages Lost or damaged production

Treatment OptionsNeutralizing amines React with CO2 to neutralize acid attackSeveral specific amines can be used to tailor the protection to a specific system

Filming aminesForm impermeable barrier to liquid Blended amine Blended amine and metal passivator programs

Conditions Affecting Selection of Chemicals

Complexity of after boiler section Operating pressures of de-aerators Percent boiler blow down Metallurgy of system Direct steam usage FDA regulations

Neutralizing Amines

Neutralizing Amines Ammonia Cyclohexylamine Morpholine Diethylaminoethanol (DEAE) Methoxypropylamine (MOPA) Ethylene diamine Diethyl Tetra amine Amino methyl butanol Monoethanolamine (MEA) Aminomethylpropanol (AMP)

Corrosion Inhibitors

Neutralizing amine blend

Provides control of condensate low pH corrosion

Reaction MechanismNeutralizing amines combine with carbonic acid to raise the condensate pH

OC4H9N + H2CO3 OC4H9NH2CO3

NH

Advantages of Neutralizing Amines

Easy to feedBlends provide good distributionWont slough off iron oxideDont release ammoniacal N2Wont degradeRecycled

Control Condensate pH 8.5 to 9.5 Copper MOC, pH 8.8 - 9.2 Iron Monitoring,

Film-Forming Amines Octadecylamine

CH3- (CH2)16 - CH2- N - (CH3)2 Ethoxylated Soya Amine Ethoxylated Fatty Amines

CH3 - (CH2)16 - CH2- N+ - (OC2H5)3

MECHANISMMECHANISM

METAL

CONDENSATE

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

C

H

H

CH3+N - CH3

CH3

2

Advantages

Theoretically the least expensive

Prevents O2 attackPrevents CO2 attack

Limitations Poor control over recycling No meaningful chemical test Wont film over deposits Wont film over pits Sloughs off iron oxide Degrades Susceptible to contamination Difficult to feed

Solutions are More Than JustChemicals

Mechanical efficiency of boiler systemSteam trap efficiencyProper pretreatment equipment, process and chemistry to optimize the entire system

Monitoring and control issuesHandling and disposal safety

BWT PRODUCTS PHILOSOPHY

- Broad range of deposit control programs Best fit approach for individual

customer needs Able to provide the Total System

Management programs needed

CONDENSATE

POLISHEDD.M.WATER

BFW STORAGETANK

STEAM DRUM

MUD DRUM

T/HR DE-AERATOR

Oxy-ScavAminesScale In

ECONOMISER

Schematic Of Chemical Dosing

Steam toDe-aeration

MONITORING

Drum Operating 0 - 20 21 - 40 61 - 80 100 -120Pressure Kg/cm2Dissolved O2 ppm < 0.007 < 0.007 < 0.007 < 0.007TDS 2500 1500 200 50pH 9.0-10.5 9.8-10.5 9.50-10.0 9.2-9.8 OH -Alk 250 150 10-20 5M-Alkalinity 500 300 20 10 Total Hardness 0.1 0.1 NIL NILPhosphate (PO4) 30-70 30-50 10-20 4 -10Silica -- --

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