This document discusses the importance of monitoring steam-water cycle chemistry parameters and water treatment in thermal power plants. It outlines the key parameters that should be continuously monitored, including cation conductivity, pH, dissolved oxygen, sodium and others. It also describes diagnostic parameters that are monitored periodically. Maintaining proper monitoring and treatment is necessary to prevent corrosion, scale deposition and deposition in turbines for high availability and efficiency.

1. Sudhanshu Dash
Chemistry
Department, HEL
SIGNIFICANCE OF
STEAM-WATER CYCLE
PARAMETERS AND SWAS
RELIABILTY

2. Thermal Power Cycle water And Steam
Flow

3. To maintain boilers & turbines at a
high level of availability and
efficiency, we need to prevent
• Corrosion in feed, boiler and
steam path.
• Scale & Deposit formation on
heat transfer surfaces
• Deposition & Corrosion in
turbines.
• And finally proper feed water
treatment
Why Chemistry Parameter Monitoring
Requirements ?

4. Types of Feed Water Treatment
As per current guidelines there are 3 types of feed water treatment and
four types of boiler water treatment and Effective cycle chemistry
programs require proper selection of treatments consistent with unit
Characteristics.
Feed water Treatment:-
1. Reducing all-volatile treatment, AVT(R), in which the feed water
must be dosed with reducing agent to minimize corrosion of
copper alloy components (HEL using this treatment)
2. Oxidizing all-volatile treatment, AVT(O), in which no reducing
agent is added or needed since there are no copper alloys in the feed
water system
3. Oxygenated treatment, OT, in which the feed water is dosed with
oxygen; OT can only be used in cycles where the feed water meets
necessary purity criteria, employs condensate polishing and no copper
alloys are present following the condensate pump discharge.

5. Types of Boiler Water treatment.
 Boiler Water Treatment:-
 All-volatile treatment-AVT, in which the feed water treatment is
either AVT(R) or AVT(O) as appropriate and no further chemical
treatment is applied within the boiler.
 Phosphate Continuum Treatment - PC, in which a drum boiler is
dosed principally with trisodium phosphate (TSP); dosing of the
boiler water with sodium hydroxide is also allowed as a
supplement to TSP when needed for pH control. Low and high level
TSP dosage variants of PC, termed PC(L) and PC(H), respectively
may be considered depending on the characteristics and needs of
the unit.
 Caustic Treatment [2], CT, in which a drum boiler is dosed with
sodium hydroxide.
 Oxygenated Treatment [3], OT, in which the feed water dosed with
oxygen as needed for OT is used in the boiler without further
treatment; OT may be used in cycles with once-through or drum
type boilers, however, with the latter feed water oxygen dosing
must be more carefully controlled so as to avoid possible
corrosion in the boiler.

6. Types of Parameter Monitoring in Cycle Chemistry
In thermal power plant we are monitoring the
significance chemistry parameter in two ways one is
offline and another is online analysers.
i:e-
1.Those parameters which all thermal plants should have
for optimum chemistry control –Core parameters.
2. Those parameters which are regarded as diagnostic
parameters that may be monitored as needed for
troubleshooting or during
Commissioning-Diagnostic parameter.

7. Core Monitoring Parameter
Parameter Monitoring Points
After Cation Conductivity Condensate Pump Discharge,
Economizer Inlet, Reheat , Main Steam,
Saturated Steam & Boiler Water
Specific Conductivity Condensate Pump Discharge,
Economizer Inlet, Reheat , Main Steam,
Saturated Steam & Boiler Water
pH Condensate Pump Discharge,
Economizer Inlet, Reheat , Main Steam,
Saturated Steam &Boiler Water
Dissolved Oxygen Condensate Pump Discharge,
Economizer Inlet,Deartor Out let
Sodium Condensate Pump Discharge,
Saturated Steam ,Main Steam

8. Diagnostic Parameter
In customizing the cycle chemistry programs, the organization may elect
to monitor one or more of the diagnostic parameters with on-line
analysers
The Diagnostic Parameters are
1.Ammonia-Check in main steam and Feed water
2.Chloride-Check in MS , Feed , CEP , Boiler water ,SS and RH
3.Hydrazine- Feed Water, Online also check
4.Phosphate- Boiler water ,
5.Silica-Check in MS , Feed , CEP , Boiler water ,SS and RH (Online
Monitoring Required )
6.Iron & Copper-BD ,Feed,CEP
7.Total Organic Carbon-Steam Condensate water/Make up Water
8.Alaknity -BD

9. SIGNIFICANCE OF pH
 To maintain pH levels within acceptable limits.
 Corrosion of metals and alloys is a function of pH.
 Alkaline pH values increase the stability of the oxide
film and reduce oxide solubility in water.
 To facilitate the correlation between two or more
water chemistry parameter (e.g., pH, conductivity,
ammonia correlation).
 To provide a feedback signal for automated chemical
dosing and process control.
 To indicate leakage of contaminants.
 To indicate of condensate polisher malfunction

10. pH Graph with ammonia
Relationship Between Ammonia, Sp. Conductivity and pH in the Absence of
carbon Dioxide.

11. SPECIFIC OR DIRECT CONDUCTIVITY
 To maintain conductivity levels within
acceptable limits.
 To facilitate the correlation of a water chemistry
parameter (e.g., pH, conductivity, ammonia
correlation).
 To check the accuracy of water chemistry
control (such as ammonia or pH).
 To indicate of condenser tube leakage/ seepage
 To indicate of condensate polisher malfunction.
 To monitor for the intrusion of volatile
contaminates (e.g., CO2 or volatile organics).

12. AFTER CATION
CONDUCTIVITY(ACC)
The measurement was adopted
for monitoring the power plant
steam / water cycle as it can
detect low levels of anion
contaminants such as chlorides,
sulphates, and organic
acids (parts per billion) on a
continuous basis, while at the
same time the measurement is
very simple and easy to
maintain.

13. Chloride concentration Vs Cation Conductivity
ACC GRAPH WITH CHLORIDE

14. SODIUM
 Sodium is a Core Monitoring Parameter. It
should be monitored continuously on-line to
check the acceptability of water chemistry,
thereby ensuring that corrosion rates are
kept at low levels.
 To maintain sodium levels within acceptable
limits.
 To indicate of in-leakage of contaminants.
 To indicate of boiler water carryover.
 To identify cooling water in-leakage at the
main steam condenser.
 To indicate of condensate polisher
malfunction. (Not Applicable for HEL)

15. DISSOLVE OXYGEN
 To maintain dissolved oxygen levels within
acceptable limits.
 To check the accuracy of water chemistry
control, so ensuring that corrosion rates are
kept at acceptable low levels.
 To facilitate the correlation of a water chemistry
parameter with plant operating variables, with
an aim to optimizing operations (e.g.,
condenser air removal or de-aerator
operations).

16. DISSOLVE OXYGEN
 To provide feedback stimulus for automated
process control, e.g., for oxygen control on
oxygenated treatment (OT). Not applicable for
HEL)
 To monitor for condensate pump seal leakage.
 During and following changes in feed water
treatment.

17. REACTIVE SILICA
 To maintain silica levels within
acceptable limits.
 To indicate of in-leakage of
contaminants.
 To facilitate the correlation of a water
chemistry parameter with plant
operating variables, with an aim to
optimizing operations.
 To check the accuracy of water
chemistry control (for silica), so
ensuring that carry-over and deposit
rates are kept at acceptable low levels.
 To indicate of condensate polisher
malfunction.

18. AMMONIA
 Ammonia is monitored to:
 Check the accuracy of water
chemistry control, so
ensuring that corrosion rates
are kept at acceptable low
levels.
 Facilitate the correlation of
ammonia with other chemistry
parameters (i.e., pH and
specific conductivity).

19. HYDRAZINE
Hydrazine is monitored in mixed
metallurgy feed water cycles using
reducing All Volatile Treatment -AVT(R).
It is monitored in the plant for the
following reasons:
 To maintain hydrazine levels within
acceptable limits.
 To evaluation of other chemistry
parameters (i.e., ORP and dissolved
oxygen).
 Hydrazine is also instrumental in
promoting magnetite (Fe3O4)
formation which provides an iron
oxide surface that consumes
dissolved oxygen

20. CHLORIDE
Elevated chloride concentrations in the boiler can lead to corrosive
conditions which can damage the water wall tubes.
 To indicate of in-leakage of contaminants
(primarily condenser cooling water ingress).
 To facilitate the correlation with other
chemistry parameters (i.e., cation
conductivity).
 To check the accuracy of water chemistry
control (for chloride), so ensuring that
carryover and deposit rates are kept at
acceptable low levels.
 To indicate of condensate polisher
malfunction.
 To indicate of make-up demineralizer
malfunction.

21. SODIUM
 Sodium is a Core Monitoring Parameter. It
should be monitored continuously on-line to
check the acceptability of water chemistry,
thereby ensuring that corrosion rates are kept at
low levels.
 To maintain sodium levels within acceptable
limits.
 To indicate of in-leakage of contaminants.
 To indicate of boiler water carryover.
 To identify cooling water in-leakage at the main
steam condenser.
 To indicate of condensate polisher malfunction.

22. IRON AND COPPER
Iron and copper are analyzed periodically to measure corrosion
product levels in the steam-water cycle. Corrosion product monitoring
in the plant is conducted primarily for the following reasons:
 To facilitate the correlation of a water
chemistry parameter with plant operating
variables.
 To check the accuracy of water chemistry
control (such as reducing agent, oxygen,
ammonia or pH), so ensuring that
corrosion rates are kept at acceptable low
levels.

23. OXIDATION REDUCTION POTENTIAL
Oxidation-reduction potential (ORP) is
monitored in units on ATV(R) and OT. The
purpose for monitoring ORP is to ensure
that feed water is in a reducing condition
as needed to minimize copper transport
when operating with AVT(R) chemistry
and in oxidizing condition as needed to
minimize iron transport and FAC when
operating with OT in all ferrous feed water
units and supercritical units

24. Total Organic Carbon
Organic contaminants may be introduced to the steam cycle through
contaminated source water, condenser leaks, or via deliberate
introduction as a form of chemical treatment. These compounds
decompose in the boiler environment to form carbon dioxide and
organic acids. Both of these species increase conductivity after
cation exchange (ACE) measurements, confounding the utility of this
measurement for monitoring sulfate and chloride. Organic acids can
also lead to corrosion in the steam cycle. As a result, monitoring low
levels of organic contamination via TOC analysis is an important
aspect of maintaining high quality boiler water and minimizing
corrosion.
Limit < 100 ppb in Steam Condensate and make up water from DM
Plant

25. Alkanity (BD)
 Alkalinity is a key control parameter for boilers
(outside of the prescribed operating range, it
can lead to corrosion, caustic metal
embrittlement, carryover and Scale)
 Depending upon the pH of the water, alkalinity
can exist in water in three basic forms:
carbonate (CO3), bicarbonate (HCO3), or
hydroxide (OH). Total alkalinity is the sum of
these three forms
 Higher value of alkalinity leads to scale
formation and overheating of the inside of the
boiler causing internal damage
 Lower value of alkalinity leads to corrosion of
the boiler causing internal damage

26. THANK YOU