1. TREATMENT OF WATER FOR HIGH PRESSURE BOILERS
& STEAM-WATER QUALITY PARAMETERS
BY
DILIP KUMAR
simdilip@yahoo.com
POWER PLANT CHEMISTRY

2. PRETREATMENT PLANT
AERETOR
BY GANGA MAKEUP
PUMPS
RIVER GANGA
•Suspended particles
•Dissolved inorganic salts
•Dissolved organic compounds
•Micro organisms &
•Dissolved gasses
IMPURITIES IN RAW WATER
AERATION
Exposing Water to Atmospheric air thereby
oxidizing some of the dissolved salts.
During aeration, two impurities viz. Ferrous
Bicarbonate and Manganous Bicarbonate are
oxidized as follows;
Fe(HCO3) + O2 -- FeO(OH) + CO2 + H2O
Mn(HCO3) + O2 -- MnO2(OH) + CO2 + H2O

3. AERATION
Exposing Water to Atmospheric air thereby
oxidizing some of the dissolved salts.
During aeration, two impurities viz. Ferrous
Bicarbonate and Manganous Bicarbonate are
oxidized as follows;
Fe(HCO3) + O2 -- FeO(OH) + CO2 + H2O
Mn(HCO3) + O2 -- MnO2(OH) + CO2 + H2O
•Alum Al2 (SO4)3, 18H2O : For coagulation.
•Lime Ca (OH)2 : To maintain the pH.
•Chlorine Cl2 : As a disinfectant.
DOSING OF CHEMICALS
Al2(SO4)3.18 H2O + 3 Ca(HCO3)2 =2AI(OH)3 + 3CaSO4 + 18H2O + 6CO2
Al2(SO4)3.18 H2O + 3 Ca(OH)2 = 2AI(OH)3 + 3CaSO4 + 18H2O
Cl2 + H2O HOCL + HCl
CLARIFIER
CASCADE AERATOR
Clarifier outlet turbidity < 20NTU
Clarifier outlet residual Cl2: 0.2-0.5 ppm

4. RAW WATER INLET
CLARIFIED WATER OUTLET
SLUDGE OUTLET

5. Clarified water turbidity < 20NTU
Clarified water residual Cl2: 0.2-0.5 ppm
CLARIFIER
Turbidity reduced
Micro-organisms are killed
GRAVITY SAND FILTER (GSF)
Sand
Gravel
Rapid rate gravity filtration is the most widely
used technology for removing turbidity and
microbial contaminants from pretreated
surface water and groundwater.
FILTERATION
Filtered water turbidity < 5 NTU
Clarified water residual Cl2: 0.2-0.5 ppm

6. FOR DRINKING
FOR DEMINERALIZATION
TO DM PLANT
FILTERED WATER SUMP
Filtered water turbidity < 5 NTU
Clarified water residual Cl2: 0.2-0.5 ppm
REMAINING IMPURITIES
Dissolved inorganic salts
Dissolved gasses
Dissolved organic compounds

7. Degasser
FW water
ACF WAC SAC
WBA
SBA MB
CST
Processes …..
DEMINERALISATION STREAM

8. Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
ACF
Acts on principle of adsorption which is a surface active phenomenon
It removes residual turbidity (<2 NTU) of water to its 1/10 level.
It removes organic molecules to control colour and odour.
It removes free residual chlorine present in filtered water(0.5 ppm Nil)
Processes …..

9. Degasser
FW water
ACF WAC SAC
WBA SBA
MB
CST
WAC resin is capable to exchange cations of alkalinity producing salts only
i.e., for carbonate hardness removal purpose.
2 R-COOH + Ca(HCO3)2  (RCOO)2Ca2+ 2 H2CO3
WAC resin can exchange ions only in neutral to alkaline pH range.
WAC results efficient TDS reduction in high carbonate hardness water.
Efficient regeneration takes place even with very dilute acid solution.
Processes …..

10. Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
SAC resin works over wide pH range & is capable to
exchange any type of cations present in salts as sulphonic
acid group is strongly acidic.
2 R-SO3-H+ + CaCl2  (RSO3)2Ca2+ 2 (H+ + Cl- )
Processes …..

11. Degasser
FW water
ACF WAC SAC
WBA SBA
MB
CST
Water from the ex-cation contains carbonic acid which is very weak acid and
difficult to be removed by strongly basic anion resin and causing hindrance
to remove silicate ions from the bed.
The ex-cation water is trickled in fine streams from top of a tall tower
packed with rasching rings, and compressed air is passed from the bottom
Carbonic acid break into CO^ and water. carbon dioxide escapes into the
atmosphere. Water is pumped back to anion exchanger bed
Processes …..

12. Degasser
FW water
ACF WAC SAC
WBA SBA
MB
CST
Weak anion resins derive their functionality from primary
(RNH2),secondary(R-NHR’)& tertiary amine (R3N)groups. The weak
weak-base anion resins remove free minerals acidity(FMA) such as
HCl & H2SO4 but doesn’t remove weakly ionized acids such silicic
acid and bicarbonates
Processes …..

13. Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
The Strong base anion resins derived their
functionality from quaternary ammonium exchange
sites.These are capable of exchanging anions like Cl-
,HCO3-,Silica.
Processes …..

14. Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
ex-anion water is fed to the mixed bed exchanger containing both cationic
resin and anionic resin.
This bed not only takes care of sodium slip from cation but also silica slip
from anion exchanger very effectively
The final output from the mixed bed is an extra-ordinarily pure water having
less than 0.2/Mho conductivity, H 7.0 and silica content less than 0.02 ppm.
Processes …..

15. CATIONS
Ca2+,Mg2+
Na+,Fe3+,
K+
ANIONS
Cl-,SO4
2-,
NO3
-,CO3
2-
HCO3,SiO2
2
WATER
SAC
R-H+R-H+
R-H+
R-H+
R-H+
R-H+
R-H+
CATIONS
H+
ANIONS
Cl-,SO4
2-,
NO3,CO3
2-
HCO3,SiO2
2-
AIR
DG
CATIONS
H+
ANIONS
Cl-,SO4
2-,
NO3
-,SiO2
2-
WATER
WATER
R-OH-
R-OH- R-OH-
R-OH-
R-OH- R-OH-
CATIONS
H+
ANIONS
OH-
WBA+SBA
CO2
ION EXCHANGE - PROCESS CHEMISTRY
WAC +

16. REGENERATION PROCESS
R2-Ca2+ R2Mg2+
R-Na+ R-K+
R3-Fe+3 R3-Al+3
HCl
R-H+ R-H+
R-H+ R-H+
R-H+ R-H+
NaCl,CaCl2 etc.
TO
DRAIN
SAC SAC
R-Cl
R2-SO4
R-NO3
R-Cl
NaOH
TO
DRAIN
R-OH-
R-OH- R-OH-
R-OH-
R-OH- R-OH-
SBA SBA+ WBA
R2-SiO2
R2-SiO2
R2-SiO2
WBA

17. Parameters pH Conductivity Turbidity Residual
Chlorine
Silica
ACF 6.5 – 7.5 -- <2.0 NTU Nil --
Anion 6.5 – 8.0 <10 Nil Nil <200 ppb
Mixed Bed 6.5-7.0 <0.2 Nil Nil < 20 ppb

18. Why DM water can’t be used directly in boiler?
• - Principle says if water is acidic – Corrosive.
- Principle say if water is alkaline – Scale forming.
As DM water (also called as hungry water) is having no
salt, when it comes in contact with metal surface attacks
the metal.

19. CONDENSER
CEP
LPH
DEAERATOR
H
P
H
ECONOMISER
WATER WALLS
BOILER DRUM
TURBOGENERATOR GT SWITCHYARD
BOTTOM RING HEADER
UPPER RING HEADER
D
O
W
N
C
O
M
M
E
R
S
SH
TO STACK TO ESP BFP
CT

20. BFP
DOSING OF CHEMICALS TO PROTECT THE BOILER AND PREBOILER SYSTEM FROM CORROSION

21. BFP
AMMONIA IS USED TO INCREASE THE pH OF THE SYSTEM &
NH3+ CO2 = (NH4)2CO3
N2H4 + O2 =N2 + H2O
3N2H4 =4NH3 + N2 ( this reaction takes place in the boiler
drum
AMMONIA DOSING

22. BFP
Tri-sodium phosphate hydrolyses & gives
Na3PO4+H2O= Na2HPO4 + NaOH
Na2HPO4+H2O= NaH2PO4 + NaOH
NaOH + HCl (As Impurity)= NaCl + H2O
TRISODIUM PHOSPHATE DOSING IN BOILER DRUM

23. BFP
SAMPLING POINTS AND PARAMETERS
CONDENSATE SAMPLE COLLECTED FROM
CEP DISCHARGE
PH 9.0-9.2
K 3.0-4.0 µs/cm
SILICA 10 ppb
DO <40 ppb
NH3 1.0 ppm
Fe <10 ppb
Cu <3.0 ppb

24. BFP
SAMPLING POINTS AND PARAMETERS
FEED SAMPLE COLLECTED FROM
ECONOMIZER INLET
PH 9.0-9.2
K 3.0-5.0 µs/cm
ACC 0.2 µs/cm
SILICA 10 ppb
DO <5 ppb
Fe <10 ppb
Cu <3.0 ppb

25. BFP
SAMPLING POINTS AND PARAMETERS
BOILER DRUM(BD) SAMPLE COLLECTED
FROM BOILER DRUM
PH 9.1-9.4
K <20 µs/cm
SILICA 0.1 ppm
PHOSPHATE 1.0-2.0 ppm
CHLORIDE 0.5 ppm
TDS 10 ppb

26. BFP
SAMPLING POINTS AND PARAMETERS
SATURATED STEAM SAMPLE COLLECTED
FROM BOILER DRUM OUTLET
PH 9.0-9.2
K 3.0-5.0 µs/cm
ACC 0.2 ppm
SILICA 10 ppb
Na <5.0 ppb
NH3 <1.0 ppm
Fe <10 ppb

27. BFP
SAMPLING POINTS AND PARAMETERS
MAIN STEAM SAMPLE COLLECTED FROM
SUPER HEATER OUTLET
PH 9.0-9.2
K 3.0-5.0 µs/cm
SILICA 10 ppb
Na <5.0 ppb
NH3 1.0 ppm
Fe <10 ppb
Cu <3.0 ppb

28. BFP
SAMPLING POINTS AND PARAMETERS
DEAERATOR OUTLET SAMPLE
DO <5 ppb

29. GENERAL LAYOUT OF MAIN PLANT

30. FUEL SYSTEM
COAL UNLOADING
CRUSHER
HOUSE
CONVEYOR BELT
COAL BUNKERS
COAL FEEDERS
COAL MILLS

31. FUEL SYSTEM
COAL HANDLING
PLANT
CRUSHER
HOUSE
CONVEYOR BELT
COAL BUNKERS
COAL MILLS PULVERIZED THE
COAL INTO 75 µ SIZE
VARIOUS SIZED COAL
20 mm SIZE

32. FUEL SYSTEM
COAL HANDLING
PLANT
CRUSHER
HOUSE
CONVEYOR BELT
COAL BUNKERS
COAL MILLS PULVERIZED THE
COAL INTO 75 µ SIZE
COAL SAMPLES
COLLECTED FROM
COAL FEEDER S FOR
DETAILED ANALYSIS
(PROXIMATE
ANALYSIS & GCV)

33. PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR

34. PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
Coal sample
sampling point for
MILL FINENESS

35. PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
MILL FINENESS
+50 3.00%
-100
-200 70%

36. PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
Oxygen % in flue gas
>4% for efficient
combustion of fuel

37. Bottom Ash Hopper
COAL MILL
Bottom Ash Hopper
Samples for determination of
combustibles in bottom ash

38. Bottom Ash Hopper
COAL MILL
Combustibles in bottom ash <3.00%
Combustibles in Fly ash <1.00%
ESPs
SAMPLING POINT FOR
FLY ASH ANALYSIS

39. 16 April 2015 PMI Revision 00 39

40. GENERATOR CHEMISTRY

41. Basic Generator Theory

42. GENERATOR PARTS
STATOR OF GENERATOR
ROTOR WINDING & ROTOR

43. GENERATOR PARTS

44. GENERATOR INTERNALS COOLING
STATOR COOLED BY PRIMARY WATER

45. GENERATOR INTERNALS COOLING
ROTOR COOLED BY HYDROGEN GAS
HYDROGEN PURITY MAINTAINED >97%

46. GENERATOR INTERNALS COOLING
LOWER FLAMABILITY LIMIT OF H2 4% H2 IN AIR
UPPER FLAMABILITY LIMIT OF H2 74% H2 IN AIR

47. PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
ALKALIZER
IONEXCHANGER
GENERATOR WINDING
EXPANSION TANK

48. PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
In Case Of Low PH
(6.0-8.0) & High DO
(<100ppb)
Protective Layer
formed in Winding is
CuO
EXPANSION TANK

49. PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
In Case Of High DO
(Without alkalizer)
Control limits are
pH 6.0-8.0
K <1.5 µs/cm
Cu <20ppb
Fe <20 ppb
EXPANSION TANK

50. PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
ALKALIZER
IONEXCHANGER
In Case Of High PH
(8.5-9.0) & Low DO
(<10 ppb)
Protective Layer
formed in Winding is
Cu2O
EXPANSION TANK

51. PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
ALKALIZER
IONEXCHANGER
In Case Of High DO
(With alkalizer)
Control limits are
pH 8.5-9.0
K <2.2 µs/cm
Cu <20ppb
Fe <20 ppb
EXPANSION TANK