By:

Boiler – Fundamentals
and Best Practices
 Boiler - Fundamentals

Steam production and steam uses

Steam purity and steam quality
Types of boilers
Basic boiler principles
Basic boiler calculations
Steam Production
and
Steam Uses
Steam Production
When heat is added to water, its
temperature rises at a rate of 0.56°C
(1°F) for each heat input of 2.095
kJ/kg (1 Btu/lb)

If we take water at 0°C (32°F) and we

add 419 kJ/kg (180 Btu/lb) then we
will increase the temperature of the
water by 100°C (180°F)

This rise in temperature can be

detected and is called Sensible Heat
(Specific Enthalpy - Water)
 Steam Tables
Pressure Temperature Sensible Heat Latent Heat Total Heat Volume Dry
psig °F Btu/lb Btu/lb Btu/lb Saturated ft3/lb
0 212 180 971 1151 26.80
15 250 218 946 1164 13.90
31 275 244 929 1173 9.30
51 299 268 912 1180 6.60
100 338 309 882 1190 3.89
150 366 339 858 1997 2.76
200 388 362 838 1200 2.14

Pressure Temperature Water Evaporation Steam Specific Volume

barg °C kJ/kg kJ/kg kJ/kg Steam m3/kg
0 100.00 419.04 2257.00 2676.00 1.673
1 120.42 505.60 2201.10 2706.70 0.881
2 133.69 562.20 2163.30 2725.50 0.603
4 151.96 640.70 2108.10 2748.80 0.374
6 165.04 697.50 2066.00 2763.50 0.272
10 184.13 781.60 2000.10 2781.70 0.177
14 198.35 845.10 1947.10 2792.20 0.132
 Steam Production
At normal atmospheric pressure, any
further addition of heat to water at
Steam 100°C will not increase the
temperature but will convert some of
the water into steam

In order to convert water into steam

2,257 kJ/kg (971Btu/lb) of additional
heat must be added

This cannot be detected as a rise in

temperature and is called the Latent
Heat of Vaporisation (Specific
Enthalpy - Evaporation)
 Steam Production

Steam
Total Heat of Steam = Sensible Heat +
Latent Heat of Vaporisation

Specific Enthalpy :
Steam = Water + Evaporation

Thus the Total Heat of Steam

(Specific Enthalpy - Steam) is 2,676
kJ/kg (1151 Btu/lb)

This data is found in Steam Tables

 Steam Production

Steam From steam tables we can see that the

total heat of steam does not vary a
great deal as the boiler pressure
increase

The boiling point (b.p.) increases as the

pressure increases

Thus the sensible heat increases as the

pressure increases, and the latent
heat decreases

Boiler pressures are expressed in psia,

psig, bar, kg/cm2, kpa
 Steam Uses

Space heating
Drying - paper mill
Process heating
Sterilisation
Humidification
Power generation
Steam Purity
and
Steam Quality
 Steam Purity

Steam purity is an expression of the quantity of

non water components in the steam

Components can be dissolved in the steam,

dissolved in water droplets entrained in the
steam or carried as discrete solid particles in
the steam

Steam impurities are normally expresses as a

quantity in parts per million (ppm) or parts per
billion
 Steam Quality

Steam quality relates to the quantity of

moisture present in the steam
100% quality specifying no moisture
content
0% quality specifying all liquid
Liquid droplets entrained in the steam
leaving a boiler contain dissolved
solids
Types of Boilers
 Types of Boilers

• Fire Tube

• Water Tube

• Waste Heat
 Types of Boilers

Fire Tube Boilers

Low Pressure Systems

Water Tube Boilers

Medium to High Pressure
Systems

Waste Heat Boilers

Process applications
HRSG
 Fire Tube Boilers
Also referred to as smoke tube boilers, shell
boilers, package boilers

Multiple gas paths - 2, 3 and 4 pass

Internal furnace or fire box as the 1st pass

Dry back or wet back design

Single fuel or dual fuel design

Little or no steam separation equipment

Fire Tube Boilers
Fire Tube Boilers
 Fire Tube Boilers
Typical designs are O, D and A type boilers
Steam separation equipment - drum
furniture
Cyclone separators
Demister pads
Baffle plates

Have economisers and superheaters

Large water tube boilers are field erected
and may be unique design
 Fire Tube Boilers
STEAM DRUM
RISERS
DOWNCOMERS SUPERHEATER
SCREEN TUBES

ECONOMISER

WATER WALLS

AIR HEATER

MUD
DRUM
Fire Tube Boilers
Waste Heat Boilers

Various types and designs

Shell and tube exchanger
Linked to process
Ammonia plant
 Waste Heat Boiler

Ammonia
Plant
Heat Recovery Steam
Generators (HRSG)
Various types and designs
Shell and tube exchanger
Water tube boiler
Multiple drum system
low pressure (LP)
medium pressure (MP)
high pressure (HP)
Multi Pressure Boiler System
with Integral Deaerator
 Steam Generators

Coil designs, vertical or horizontal

Bucket types
Steam water separator
Boiler water returned to feed tank
May include economiser and superheater
Steam Generator - Coil
Basic Boiler Principles
 Basic Boiler Principles
SATURATED STEAM
EXTERNAL MAKE UP EVAPORATED WATER
TREATMENT
WATER
AND
SOLIDS
HOT WELL FEEDWATER
DEAERATOR
WATER
AND
RETURNED CONDENSATE SOLIDS
WATER AND HEAT
Continuous
Blowdown - Removes boiler water with blowdown
to remove
a high concentration of solids which is
Intermittent blowdown dissolved
replaced by feedwater containing a low to remove suspended solids in
concentration of solids solids in boiler water boiler water
 Basic Boiler Principles

Water and solids enter the boiler

Water leaves the boiler as steam
Solids concentrate in the boiler
Therefore the boiler water will contain more solids
than the feedwater
This Concentrating effect is called

The Cycles of Concentration or The Cycles

Basic Boiler Principles

A boiler can only tolerate a specific

number of cycles of
concentration
This will vary depending on

Type and pressure of the boiler

Type of external treatment

Percentage condensate return

Basic Boiler Principles

The chemical factors which limit the

boiler water cycles of concentration are

Suspended solids (Total Hardness)

Dissolved solids
Total alkalinity (M Alkalinity)
Silica
Basic Boiler Principles

How do we determine the chemical

control limits that we apply to an
operating boiler ?

• British Standard BS2486:1997

• ASME Guidelines* 1994

Consensus on operating practices for

the control of feedwater and boiler
water chemistry in modern industrial
boilers
Basic Boiler Calculations
Basic Boiler Calculations
Make Up

Feedwater

Condensate
Return
Basic Boiler Calculations

• Feedwater = Make up +
Condensate Return
Basic Boiler Calculations

Steam Make (Flow)

Feedwater
Flow

Blowdown
 Basic Boiler Calculations

• Feedwater = Make up + Condensate

Return

• Feedwater Flow (FWF) = Steam Make

+ Blowdown
 Basic Boiler Calculations

• Feedwater = Make up + Condensate Return

• Feedwater Flow (FWF) = Steam Make +

Blowdown(BD)

• Feedwater Flow (FWF) = Steam Make + Steam Make

• Cycles -
1
 Basic Boiler Calculations
• Feedwater = Make up + Condensate Return

• Feedwater Flow (FWF) = Steam Make +

Blowdown(BD)

• Feedwater Flow (FWF) = Steam Make + Steam

Make
• Cycles -1

• Blowdown = Steam make or = FWF

• Cycles –1 Cycles

• % Blowdown = 1 as a % of FWF
• Cycles
 Basic Boiler Calculations

Condensate Return is also expressed as % of

FWF

If Condensate Return = 60% Make up = 40%

% Condensate + % Make up = 100% = FWF

As the boiler water cycles of concentration

increase then the feedwater flow and the steam
make approach the same number
 Basic Boiler Calculations
Calculate the feedwater composition (impurities)
from make up and condensate analysis below

Make-Up Condensate Feedwater

Total Hardness 2 0
M Alkalinity 200 10
TDS 350 15
Silica 6 0
% Condensate 50
 Basic Boiler Calculations

Calculate the feedwater composition (impurities)

from make up and condensate analysis below

Make up Condensate Feed water

Total Hardness 2 0 1
M Alkalinity 200 10 105
TDS 350 15 182.5
Silica 6 0 3
% Condensate 50
Boiler Water Best Practises
 Boiler Water
Internal Treatment
Technology
Why is Effective Internal Boiler
Water Treatment Necessary ?
Effective Internal Boiler Water
Treatment

Controls

• Deposition

• Corrosion

• Carryover

and
 Enhances System Reliability
and Efficiency

• Avoids unscheduled shutdowns

• Helps ensure uninterrupted production

• Reduces maintenance costs

• Reduces operating costs

What Operating Costs are
Associated with Boiler
Operation ?
 Boiler Operating Costs

• Fuel - Gas, Oil, Coal

• Water - Influent and Effluent

• Regenerants - Salt, Acid,

Caustic

• Water Treatment
 Boiler Operating Costs
• Fuel - Gas, Oil, Coal
• Water - Influent and Effluent
• Regenerants - Salt, Acid, Caustic

• Water Treatment
 Boiler Operating Costs
• Need to minimise all operating costs
Reducing boiler water blowdown gives
water, energy and chemical savings

• Need to maximise efficiency

Maintain clean heat transfer surfaces
Heat recovery systems
Effective Internal Boiler Water
Treatment

Controls
Deposition •
Boiler Water Deposit Control

• Hardness salts
• Calcium
• Magnesium

• Metal oxides
• Iron
• Copper
Comparison of Heat Transfer Surfaces
With and Without Deposits

Metal Metal Scale

Fireside Waterside Fireside Waterside

800°F
and
600°F above
500°F 500°F

Without deposits With deposits

 Energy Loss from Scale Deposits
(from Energy Conservation Programme Guide for Industry & Commerce)
8
e
al

ale
7 c
tS

Sc
n
nte ale

ica
c
6
Co eS
at

S il
n n
Energy Loss %

Iro rbo

n&
5
igh Ca
Iro H
c i um
4 Cal
al "
orm
3 "N

0
1 1 3 1 5 3
64 32 64 16 64 32
0.4 mm 0.8 mm 1.2 mm 1.6 mm 2.0 mm 2.4 mm

Scale Thickness, inches or mm

Long Term Overheating
Boiler Water Deposit Control

• Removal of impurities
• Pretreatment plant

• Chemical treatment
• Controlled blowdown
Effective Internal Boiler
Water Treatment

Controls
• Deposition

• Corrosion
Boiler Water Corrosion Control

• Oxygen pitting

• Caustic corrosion
• Embrittlement or gouging

• Acidic attack
Oxygen Corrosion - Pitting
Caustic Gouging
 Acid Corrosion

Acid Corrosion
Effective Internal Boiler
Water Treatment

Controls
• Deposition

• Corrosion

• Carryover
Control of Boiler Water Carryover

• Effective mechanical steam separation

• Proper control of boiler water chemistry
• Antifoam, as needed
• Avoid major contaminant ingress
• Proper boiler operating practices
 What Types of
Internal Boiler Water

Treatments are
Available ?
 Internal Treatment
Programmes

General Classifications
• Precipitating

• Solubilising

• Combination
 Internal Treatment
Programmes
• Phosphate/Polymer

• Phosphonate/Polymer

• Chelant/Polymer

• Phosphate/Chelant/Polymer

• All Polymer

• Coordinated pH/Phosphate/Polymer

• All Volatile Treatment (AVT)

Boiler Water Polymers

are Crucial to the

Success of any

Internal Treatment
Programme
How do Boiler Water Polymers
Function ?
 Boiler Water
Polymers
The mechanisms by which boiler
water polymers function are

• Complexation / Solubilisation

• Crystal modification

• Dispersion
Calcium phosphate,
magnesium silicate
crystals formed in
boiler water without
dispersant
Calcium phosphate,
magnesium silicate
crystals formed in
boiler water in the
presence of a
sulphonated polymer
Variables Affecting Polymer
Performance

• Functional group
• carboxylated (SCP/SCCP)
• sulfonated (SSP)
• phosphorylated (HTP)

• Polymer backbone

• Molecular weight
 Typical Polymer Structures
CH CH2 CH2 CH CH2 CH

C=O C=O C=O

O- OH NH2
X X

Polyacrylate Acrylate-Acrylamide Copolymer

CH3
CH2 CH CH CH
C CH2
C
= C =
O O
C=O O
SO3-
X Y
O-
X

Polymethacrylate Sulfonated Styrene-Maleic

Anhydride Copolymer
 Typical Polymer Structures
CH2 CH CH2 CH
O-

R P=O C=O CH2

O- O- H+ O [CH2 CH2 O]m H

n

Phosphonate
Polyethylene glycol allyl ether (PEGAE)

CH3 CH3
O O
=

C
=

-O
CH2
P C P O-
O=P OH
-O OH O-
O-
HEDP X
Poly (isopropenyl phosphonic acid)
PIPPA
 Polymer Performance
vs
Molecular Weight
Deposition

Polymer Molecular Weight

 Programme Selection
Considerations
• Boiler pressure, design

• Pre-treatment plant type

• Feedwater quality

• Hot well, deaerator type

• Steam turbine

• Control capabilities
 Chemical Factors

• Total Dissolved Solids (TDS)

• Alkalinity

• Silica

• Suspended Solids
 ASME Boiler Feedwater Quality
Guidelines for Modern Industrial
Water-Tube
Iron
Boilers
Copper Hardness
Drum Pressure •
(kg/cm²) • (ppm Fe) (ppm Cu) (ppm CaCO3)

0 - 21 • 0.10 0.05 0.30

22 - 31 • 0.05 0.025 0.30
32 - 42 • 0.03 0.02 0.20
43 - 52 • 0.025 0.02 0.20
53 - 63 • 0.015 0.10
0.02
64 - 70 • 0.05
0.02 0.015
71 - 105 •
0.01 0.01 0.0
 Internal Treatment
Programmes

• Phosphate/Polymer
 Phosphate/Polymer Treatment

• Reactions:

• Ca + PO4 + OH
Ca(OH)PO4
• Calcium Phosphate Hydroxide
Hydroxyapatite
•

• Mg + SiO3 + OH
Mg(OH)SiO3
• Magnesium Silica Hydroxide Serpentine
 Phosphate/Polymer Treatment

Characteristics
• Hardness controlled by precipitation
• Polymers used to control hardness
sludge and metal oxides
• Phosphate residual used for programme
control
• Hydroxide alkalinity required (pH : 10.5 -
12)
 Phosphate/Polymer
Treatment
Boiler Control Parameters
• Phosphate residual as PO4 depending on
hardness in the feedwater
• usually associated with boiler pressure
• and environmental legislation
• M alkalinity of 700 ppm as CaCO3 (25 % of
TDS)
• Polymer : min 360 ppm as SP8100
• Still the most used method for treating low
pressure boilers
 Phosphate/Polymer
Treatment
Advantages • Disadvantages

• Tolerates a wide range of • Is a precipitation

feedwater hardness programme (some
deposition is normal)
• Non corrosive treatment
• Higher blowdown rates
may be required
• Suitable for low to medium
pressure systems

• Easy operator control

Internal Treatment Programmes

• Phosphate/Polymer

• Phosphonate/Polymer
 Phosphonate/Polymer

Characteristics

• Organic phosphor donors combined

with three synergistic polymers
• Complexes hardness, iron and copper
ions in BFW
• Disperses/solubilises contaminants in
boiler minimising sludge formation
 Phosphonate/Polymer
a) Solubilising
Boiler Control Parameters
– 200 - 300 ppm in blowdown
– (BFW hardness + tot Fe) max 1 ppm for
300 ppm in boiler
– filtered tot. PO4 min 6 ppm in BD
– Other :
• conductivity
• SiO2
• M-alk
 Phosphonate/Polymer
b) Precipitating
Boiler Control Parameters

• Phosphate residual as PO4 depending on

hardness in the feedwater
• M alkalinity of 700 ppm as CaCO3 (25 % of
TDS)
 Internal Treatment
Programmes
• Phosphate/Polymer

• Phosphonate/Polymer

• Chelant/Polymer
 Chelant/Polymer
Treatment
• Common Chelating Agents

• EDTA

• NTA
 Chemical Structure of
EDTA

H H
- OOC - CH2 CH2 - COO -
N-C-C-N
- OOC - CH2 CH2 - COO -
H H
EDTA/Calcium Complex

CO
O CH2
CO CH2

O N
CH2
Ca
O N CH2

CO CH2 O CH2

CO
 Chelant/Polymer Treatment

Characteristics
• Are solubilising treatments
• Chelant complexes hardness and soluble iron /
copper
• Polymers used to enhance metal oxide control
• Must be fed to the feedwater line
 Chelant/Polymer Treatment
Advantages • Disadvantages

• Solubilising treatment • Requires intensive

operator control
• Effective on hardness and
soluble iron • Potentially corrosive if
misapplied
• Allow reduced blowdown

• Increased reliability and

efficiency

• Suitable for low to medium

pressure systems
 Internal Treatment
Programmes
• Phosphate/Polymer

• Phosphonate/Polymer

• Chelant/Polymer

• Phosphate/Chelant/Polymer
 Chelant/Phosphate/Polymer
Treatment
Characteristics
• Utilises EDTA chelant (partial chelation)
• Primarily a solubilising programme
• Phosphate provides back-up upset protection
• Residual phosphate test used as programme control
• Polymers used to control metal oxides and other
precipitates
 Chelant/Phosphate/Polymer
Advantages
Treatment
• Disadvantages
• Primarily a solubilising treatment
• Some precipitation is
• Effective on hardness and iron possible
• May allow reduced blowdown • Potentially corrosive
if misapplied
• Increased reliability and
efficiency

• Easy and accurate control test

• Tolerates a wide range of

feedwater hardness

• Suitable for low to medium

pressure systems
 Internal Treatment
Programmes
• Phosphate/Polymer

• Chelant/Polymer

• Phosphate/Chelant/Polymer

• All Polymer
 All Polymer Treatment
Characteristics
• Certain polymers can be effective
complexing agents
• Principle mechanism is complexation of
soluble impurities
• Secondary mechanism is dispersion of
particulates
• Fed to the boiler feedwater
Limitations of Polyacrylate Based
All Polymer Programmes

• Low tolerance to feedwater quality upsets

• Potential for calcium polyacrylate deposition
• Releases ammonia
• Economiser iron pick-up
• Precise testing for polymers is difficult
 Internal Treatment
Programmes
• Phosphate/Polymer

• Phosphonate/Polymer

• Chelant/Polymer

• Phosphate/Chelant/Polymer

• All Polymer/OptiSperse AP
 What is OptiSperse AP ?

• A new, revolutionary programme using

patented co-polymer technology

• A stand-alone all polymer / all organic boiler

internal treatment programme which
provides superior control over hardness and
iron deposition
 OptiSPerse AP Treatment vs.
Traditional All Polymer
• Traditional All Polymer • OptiSperse AP
Programme Programme
• Generates ammonia • No ammonia generated
• Forms calcium-polymer • No treatment related
deposits with BFW deposition
hardness excursions or
underfeed
• No steam purity
• Overfeed may cause problems
foaming
• Not corrosive to preboiler
• Corrosive to economiser circuit
surfaces
• May be fed ahead of
• Must be fed downstream of copper alloys in BFW
copper alloys
 Research Boiler Studies Under Fouling
Conditions
Test Conditions
900 psig (63 kg/cm2)
All-polymer Programme
Ca/Mg/Fe present

TRADITIONAL
ALL-POLYMER
DWD

OPTISPERSE AP

0 1 2 3 4 5
POLYMER/HARDNESS RATIO
 Research Boiler Studies
Under Potential Fouling Conditions
(Equal Polymer Actives)
Deposit Weight Density

300 psig (21 kg/cm2) 600 psig (42 kg/cm2) 900 psig (63 kg/cm2)

OPTISPERSE AP Traditional All-Polymer

 Internal Treatment
Programmes
• Phosphate/Polymer

• Phosphonate/Polymer

• Chelant/Polymer

• Phosphate/Chelant/Polymer

• All Polymer

• Coordinated
pH/Phosphate/Polymer
 Coordinated pH/Phosphate
Polymer Treatment
Characteristics
• Primarily for high purity/high pressure
systems
• Mainly a corrosion control programme
• Phosphate used to control pH and neutralise
excess caustic
• Polymers used to control deposition
 Corrosion of Mild Steel vs. pH

Relative Corrosive Attack

8.5 pH 12.7 pH

Safe Range
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Caustic Concentration
Mechanism

Magnetite

NaOH

Steam Out

NaOH NaOH
NaOH

NaOH
Boiler Water in

Fe3O4 Porous
Deposit

NaOH
Prevention
magnetite
steam
escapes
porous
deposit
HPO42 - Na+
Na +

HPO42 -
Na+ Na+ HPO42 -
HPO42 -
Na+
HPO42 -
Boiler water in
 Minimising Caustic
Concentration and Corrosion
using Phosphate

NaOH + Na2HPO4 Na3PO4 + H2O

Caustic Disodium Trisodium Water

Soda Phosphate Phosphate
 Co-ordinated Congruent Phosphate/pH
Control Chart
10.8
10.6
"Free" Caustic O4
10.4 tio a/P
Region r Ra 2.8:
1N
Mola
10.2 O
a/P
4
1 N
10.0 3.0:
n dary
9.8 Bo u
O4
a/P
m 1N
i mu 2.7: "Captive"
9.6 Max r Ratio
Alkalinity
pH

ol a
9.4 O4 M Region
O4 Na /P
a/P 1
9.2 2.6:
1N 2.2:
nd ary
9.0 Bou
on trol

p h iu m
C

e
os od
at
8.8

Ph i-S
Vector

Caustic
Tr
Di-Sodium
Control
8.6 Diagram B lo
wd
own
M
o
Phosphate

Ph no-
os So
8.4 ph diu
at m
e

8.2
1 2 3 4 5 6 7 8 10 15 20 30 40 50 60
Ortho-phosphate, as PO4 mg/l
 Internal Treatment
Programmes
• Phosphate/Polymer

• Phosphonate/Polymer

• Chelant/Polymer

• Phosphate/Chelant/Polymer

• All Polymer

• Coordinated pH/Phosphate/Polymer OptiSperse

HTP
 Characteristics of HTP-2

• A unique new phosphorylated boiler polymer

• Particularly effective on iron

• Demonstrated clean-up ability

• Designed for high purity/high cycles systems

• Suitable for use up to 125 kg/cm²

 HTP-2 Polymer Structure

CH3

CH2 C

O=P OH

O-

X
Poly (isopropenyl phosphonic acid) . . . PIPPA
 Internal Treatment
Programmes
• Phosphate/Polymer - OptiSperse PO, OptiGuard MCP

• Phosphonate/Polymer - OptiSperse PQ

• Chelant/Polymer - OptiSperse CL

• Phosphate/Chelant/Polymer - OptiSperse CP

• All Polymer - OptiSperse AP, OptiGuard MCA

• Coordinated pH/Phosphate/Polymer - OptiSperse HTP

• All Volatile Treatment (AVT)