Power plant steam water cycle improvement study report, CPU performance improvement report, Change of feed water treatment regime AVT(R) to AVT (O), Improvement in FAC, Reduction in Boiler chloride level,

1. Dr S. B. Das
Consultant (Chemistry)
A concise study report on steam water cycle
chemistry deviations of JITPL U#1 600 MW
unit, and corrective actions taken thereof for
sustainable chemistry operations

2. INTRODUCTION
• To minimize the metal release rate from structural materials.
• To minimize the probability of selective / localized forms of
corrosion.
• To minimize the deposition of corrosion products on heat
transfer surfaces.
• To avoid the formation of aggressive media, particularly local
aggressive environments under deposits.

3. ACTIONS
• Preventive measures : Cycle chemistry focusing on reduction
of corrosion product generation and deposition
• Control measures : Set up and performing regularly focusing
on maintaining cleanliness of the system
• Corrective measures : Removal of deposits / cruds from the
system by mechanical means and by chemical means

4. Comparison Of Running Steam Water Cycle
Chemistry Parameters
Date Time Condensate Feed Boiler Dr Pr CP
U
Load
Param pH Cond Silic
a
Fe pH Con
d
Silic
a
Fe pH Cond Silic
a
PO4 ACC Chlor
ide
12.08.21 20;00 9.1 4.5 8.0 12 9.1 4.6 18 10 9.4 13.0 27 1.1 5.0 298 176 2 555
13.08.21 08;00 9.1 4.8 7.0 11 9.1 4.7 22 10 9.7 19.2 18 2.0 3.0 300 179 2 550
23.11.21 12:00 9.3 6.8 8.0 5.0 9.3 6.9 7.0 6.7 9.3 8.0 28 0.1 0.6 58 176 2 565
24.11.21 12:00 9.3 6.7 7.0 4.0 9.3 6.7 7.0 6.8 9.3 7.7 24 0.2 0.7 32 183 2 568

5. The Cycle chemistry were managed with
following parameters before August 21
• Low Feed water pH 9.0-9.1 (9.1-9.6)
• High Phosphate (2.0-4.0) ppm
• Phosphate hide out
• High boiler chloride level (~ 300 ppb)
• High Boiler ACC (3.0-10.0)
• High Iron level ( more than 300 ppb during light up of the units)
• Higher Crud level

6. The Cycle chemistry were managed with
following parameters
• Two CPU vessels are always taken into service after synchronization
of unit (on an average after 4-5 hrs of synchronization) when
condensate sample iron level reached to 100 ppb
• Condensate iron after synchronisation of the unit was greater than
300 ppb on an average, during light up of the units
• Blow down is operated with Phosphate dosing
• Boiler make up started with Ammonia and hydrazine to maintain pH
and reducing conditions required for AVT(R).
• Phosphate hide out is exhibited

7. Corrective action No.1
• Increase of feed water pH 9.3-9.4
• IRON leaching in the feed water system through flow accelerated
corrosion is reduced by increasing feed water pH to 9.3-9.4.
Therefore, crud generation will reduce which are evident now.
• Due to reduced concentration of Iron in boiler drum, Chances of
formation of deposits of Fe (OH)3 , Fe(PO4) or Fe3(PO4)2 and other
mixed stoichiometric and non stoichiometric compounds will
automatically decrease.
• Therefore, threat of scale formation or underdeposit corrosion in the
boiler will reduce automatically.

8. Corrective action No.1
• To reduce IRON leaching feed water pH increased to 9.3-9.4
FIGURE 3. The dissolution of the carbon-steel matrix is a function of pH and temperature [1]

9. VARIATION OF IRON PICK UP WITH FEED WATER PH

10. FLOW ACCELERATED CORROSION

11. CORRECTIVE ACTION NO.2
• Performance of CPU enhanced through improved regeneration
system
• Reduction of CPU regeneration timing
• Open backwashed stopped,
• Reduction in DM water consumption
• Regeneration cycle time reduced through improvement in the
regeneration process.
• Boiler chloride level reduced

12. CRUD TRANSPORT DURING LIGHT UP OF UNITS

13. CORRECTIVE ACTION NO.3
• Three CPU vessels taken into service during light up of the units for
100% polishing of feed water.
• To reduce the crud level and Iron in the feed water system and to
clean the system ,
• Gradually Crud particles filtered and Fe2+ or Fe3+ ions are removed
through ion exchange and filtration in the CPU vessel.
• Feed water iron level reduced to < 10 ppb.
• Slowly boiler is cleaned
• Therefore, scaling and under deposit corrosion in the boiler is
prevented. Thereafter efficiency of the system is improving.

14. CORRECTIVE ACTION NO. 4
• Phosphate dosing in the Boiler reduced to 0.5 max from 4.0-5.0 ppm
to maintain pH and alkalinity in the boiler water.
• Boiler pH is maintained well with low level of Phosphate due to the
cleanliness of the system
• Hide out of phosphate phenamenon is less
• No threat of BTL due to huge chloride ion level.
• Boiler water ACC is maintained well within desired value <1.5 us/cm .
• No BTL due to chemistry.
• Sustainable maintenance of this chemical parameters will nullify the
requirement of early chemical cleaning in future

15. CPU performance improvement report
SN Parameters AUG 21 status April 22 status
1 CPU regeneration Regeneration carried out through open back wash Open back wash stopped,
2. Time of regeneration 6-7 days required for one regeneratioon 3-4 days required per regeneration
3. DM water consumption 1850 M3 DM water required Now approximately 1050 M3 of DM water required .
500-800 M3 of DM water saved
4. Output between regeneration
(OBR)
on an average 2,20,000 -2,50,000 M3 Now 2,50,000-2,80,000 M3 achieved.
5. Boiler chloride level Chloride concentration maintained <300 ppm
through CBD operations
Now without CBD blowdown Boiler Chloride level can
be maintained 20-30 ppb easily.
6 Boiler ACC Boiler ACC maintained <3.00 - 5.00 us/cm Now Boiler ACC maintained <1.5 us/cm easily,
Indicates highly effective cleanliness.
7. Condensate Iron level during light
up of the units
Condensate Iron level more than 300 ppb even
during synchronisation of the units.
Condensate Iron level less than 10 ppb.
Reduction in Fe level indicates FAC and Fe pick up
reduced.
8 Feed water Iron Maintained around 10 ppb improved <2ppb
9 Start up of the units Chemical parameters stabilisation time 11-12hrs. Chemical parameters stabilisation time 04-05 hrs. or
less.

16. Concluding Corrective action report
SN Before Aug 21 After Remarks
1 66% polishing done after 4-5 hrs of
Unit synchronization
100% polishing done since light up of
units
3 CPU vessels put into service during start up of
the units and one vessel taken out at the
DP 100 kg/cm2
2 66% polishing done after 4-5 hrs of
Unit synchronization
66% polishing continued after 7-8 hrs of
unit synchronisation.
2 CPU vessels kept in service when unit DP
reaches 100 kg/cm2
2. Feed water pH is maintained 9.0-9.1 Feed water pH is maintained 9.3-9.4 Iron pick up rate reduced
3. Boiler phosphate level maintained
1.0-4.0 ppm
Boiler phosphate level maintained less
than 0.5 ppm
Even at low PO4 Boiler pH is maintained
4. Boiler ACC maintained 5.0-10.0
us/cm
Boiler ACC maintained <1.5 us/cm Excellently clean
5. Boiler chloride level maintained
below 300 ppb
Chloride level reached 20-30 ppb Outstanding parameter
6 Phosphate hideout exhibited Phosphate hideout restricted due to
cleaniliness of the boiler
Indicates cleanliness
7. Condensate Iron level more than 300
ppb during synchronisation of the
units.
Condensate Iron level less than 10 ppb Reduction in Fe level indicates FAC and Fe pick
up reduced.

17. READY FOR AVT(O) CHEMISTRY OPERATION

18. BOTH THE UNITS PUT
INTO AVT (O)
OPERATION FROM
DATED 11.04.2022

19. PRECAUTIONS FOR SUSTAIBALE AVT (O)
CHEMISTRY OPERATIONS
• 100% condensate polishing should be done during cold start up of units
• Exhausted CPU should not be in service
• Two CPU vessels should always be in service to maintain purity of the feed
water system. To prevent BTF due to scale or under deposit corrosion
• Air in leakage (DO) should be controlled within 10 ppb (max)
• In AVT(O) operation Feed water pH should be maintained well above <9.2
prefereably 9.3 - 9.4 and feed water cation conductivity within <0.15 us/cm
• Phosphate concentration should be maintained within <0.5 ppm
• Boiler cation cation conductivity should be maintained within 1.5 us/cm

20. PRE AND POST TREATMENT CYCLE
CHEMISTRY PARAMETERS
• Feed water pH 9.0-9.1 Low Feed water pH 9.3-9.4
• High Phosphate (2.0-4.0) ppm Phosphate (0.5-0,1) ppm
• Phosphate hide out Phosphate hide out controlled
• Boiler chloride level (~ 300 ppb) Boiler chloride level < 50 ppb
• High Boiler ACC (3.0-5.0) Boiler ACC (0.5-1.5)
• Iron level (> 300 ppb during start up) Iron level (~ 30 ppb during start up)
• Feed water Iron level >10ppb Feed water iron level <3 ppb
• Crud level : High Crud level : Very less

21. ADVANTAGES

24. “CONSERVE WATER, CONSERVE LIFE”