The Allowable Water and Steam Chemistry Regimes for Supercritical Units have been identified along with maximum deviations during start up and commissioning. This presentation gives guidelines for contracting norms to avoid damages.It is for the EPC Contractors in charge of construction of these units to understand the risks associated and design organizational skills both in technical and commercial areas to avoid major delays and damages.

1. EPC Risk Management Paradigm
Start Up Chemistry
In Supercritical Power Generating Units
PRESENTED BY DR. HIMADRI BANERJI
EX CEO RELIANCE ENERGY
MD ECOURJA
TRUEVENTUS
Engineering, Procurement &
Construction (EPC) Senate
Date: September 23 - 24, 2013
Venue: Sofitel Bangkok Sukhumvit, Bangkok
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
1

2. EPC Risk Management Paradigm & Start Up Chemistry
In Supercritical Power Generating Units
1. INTRODUCTION
Most power stations today are going super critical due to the immense
advantages of efficiency and their potential of lowering emissions of
carbon dioxide.
However it is now being recognized that supercritical units pose
significant chemistry challenges during the start up and commissioning
regime with consequent financial risks to EPC Contractors, who hitherto
not aware or exposed to these risks have now to adapt quickly to a new
Risk Management paradigm
2. OBJECTIVE:
To understand the risks and challenges in start up and commissioning
of supercritical power generating units and take up proper risk
management and control measures
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
2

3. Supercritical Units: Efficiency Advantage
Improvements in the efficiency of pulverized coal (P.C.) fired boiler/steam
turbine power plants have been pursued since the introduction of P.C. fired
boilers in the 1920’s.
This led eventually in the late 1960’s to the introduction of supercritical
boilers operating at about 570 Deg C (1060qF) superheat/reheat
temperatures and 24 MPa (3400 psi) pressure for the steam.
Presently boilers with 300bar and 700 Deg C are being adopted for many of
the recent power plants.
Since at these pressures and temperatures there is no distinct differences
between the water and steam phases, no drums are required in the same.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
3

4. SUPERCRITICAL UNITS:
CONSTRUCTION FEATURES
Conventional steam
power plants operate at a
steam pressures in the
range of 170 bar and 565
Deg C.
These are Subcritical
power plants.
The new
generation of
power plants
operate at
pressures higher
than the critical
pressure.
These are
Supercritical
power plants.
The operating
pressures are in
the range of 230
to 265 bar. And
565 Deg C
The next generation of
power plants will
operate with Steam
Pressures in the range
of 300 bar and
630Temperatures 630700 Deg Centigrade.
These are the Ultra
Super Critical Power
Plants.
Dr. Himadri Banerji:Conference on EPC
Risk Management Bangkok 23-24 Sept
2013
4

5. SUPERCRITICAL UNITS:
CONSTRUCTION FEATURES
The lower part of the boiler furnace is arranged in a spiral
configuration such that the fluid path wraps around the boiler
as it travels up the furnace.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
5

6. SUPERCRITICAL UNITS:
MATERIALS OF CONSTRUCTION
Comparison of Allowable Stresses between Conventional and Advanced
Stainless Steel Tubes, Advanced CrMo Steel Pipes
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
6

7. 3.LEARNING
3.LEARNING THROUGH A CASE STUDY
SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
7

8. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Oxygenated Treatment OT of Supercritical Boilers
onceThe benefits from a once-through supercritical boiler on OT include:
doubleLowering overall corrosion rates by forming a protective, double-oxide
layer with a controlled amount of oxygen present in the condensate
[This protective layer is considered to be more stable than the oxide
layer formed using AVT(O) or AVT (R)]
Decreasing boiler chemical cleaning frequency due to reduced amounts
of iron transport and deposition
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
8

9. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Oxygenated Treatment OT of Supercritical Boilers
• Allowing quicker, cleaner start ups and reduced corrosion product
transport rates during cold and hot start ups
• Allowing boiler operation at lower pH with overall objective of
minimizing chemical costs
• Eliminating feeding, handling, and storage of oxygen scavenger
products
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
9

10. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Oxygenated Treatment OT of Supercritical Boilers
coalShows the pressure drop history of a coal-fired supercritical plant in Japan that
changed the water chemistry from AVT to OT in 1996.
After 7 years operation since the change, there has been no significant increase in
pressure drop.
This plant has not required acid cleaning since the change, and no future cleaning
is planned.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok
23-24 Sept 2013
10

11. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
all-ferrous metallurgy...no copper please
onceMost once-through supercritical boilers have been converted from previously
predominant AVT to OT, with new facilities almost exclusively using OT.
allThis chemistry change requires all-ferrous metallurgy in the feed water train,
copperand precludes copper or copper-based alloy feed water heat exchangers in
system design and bronze impellers in condensate pumps and valve trims in
the condensate system.
The other chemistry challenge requires that there be very high level of
cleanliness during construction of the entire piping and boiler tube system to
avoid silica from dust, iron from rust and other contaminants
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
11

12. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
all-ferrous metallurgy...no copper please
This is primarily the challenge to the engineering group of the EPC
contractor to ensure that this is strictly adhered..
Risk of contamination with copper and zinc in steels is very high.
The procurement group has to be aware and must use proper risk
mitigation.
Risks of contamination during fabrication and erection have to be
recognized by the construction teams.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
12

13. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES & RISKS
STARTUP CHALLENGE
In order to avoid corrosion in the ferrous materials in the water circuit, a
minimum alkalinity is to be maintained in the feed water (as measured
by pH).
cycle,
The startup and commissioning cycle, therefore include startup on All
Volatile Treatment(AVT) with quick conversion to OT( Oxygenated
Treatment) and this is the EPC turnkey contractor’s responsibility.
onceTo ensure efficient startup and commissioning of once-through
supercritical boilers, the EPC turnkey contractor must address these
chemistry issues and develop a practical approach to achieving steam
feedpurity and specified feed-water chemistry requirements.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
13

14. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES & RISKS
STARTUP CHALLENGE
The reducing environment (negative oxidation reduction potential [ORP]
present when operating on AVT(R) ESPECIALLY DURING STARTUP may
contribute to increased iron transport, subsequently increasing the
pressure drop through the boiler.
onceHence some once-through supercritical boiler manufacturers have
instituted penalties against the allowable pressure drop during initial
boiler performance testing, an additional complication that may impact
start up and commissioning activities including causing delays
These penalties are based on extended operation on all volatile treatment
reducing (AVT[R]) during start up and commissioning.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
14

15. SUPERCRITICAL UNITS:
EPC CONTRACTOR CHEMISTRY CHALLENGES & RISKS
STARTUP CHALLENGE
The major problem with this is however that we still do not
have a standard on penalties against pressure drop during
startstart-up based on models or analytics (risk management
principles)
Besides each unit is different from the other
As a result these pressure drop correction penalties will be
fervently debated by the EPC contractor during commissioning
and challenged by both owners and plant operators
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept
2013
15

16. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
WARRANTY IMPLICATIONS
Steam turbine suppliers are also setting limits, in the
equipment contract, on the number of hours a turbine
out-ofcan be operated with out-of-specification chemistry.
actionThese limits are typically listed in an action-level format
where minor chemistry excursions are allowable for
predetermined time periods without violating the
equipment warranty.
up—
Steam Purity Limits During Start up— EPC
OnceContractor Recommendation for Once-Through
Boilers...usually one week
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
16

17. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
During steam-side start up and commissioning, the EPC contractor is mostly
interested in main and reheat steam chemistry.
Table below lists EPRI recommendations for once-through boilers operating under
OT, including normal target value and action levels 1, 2, and 3.
Although recommendations listed in Table are
acceptable for targeted chemistry limits during
operation, EPC contractors would like to see the
following two columns added to this table:
• Allowable chemistry excursions during
hot start up
• Allowable chemistry excursions during
cold start up
Feed Water
Dr. Himadri Banerji:Conference
on EPC Risk Management
Bangkok 23-24 Sept 2013
17

18. What Are Action Levels 1, 2, 3
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
18

19. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Start up chemistry guidelines should primarily focus on main steam chemistry targets,
including
cation conductivity: it warns of salts and acids that may cause turbine corrosion
silica :
silicate scaling may contribute to turbine capacity and efficiency losses.
sodium: critical for avoiding corrosion because uncontrolled sodium hydroxide
concentrations are known to cause corrosion damage failures in boiler
tubes.
Targets for chlorides, sulphates, and organic compounds should be
deferred until the end of the commissioning cycle.
Degassed cation conductivity is the preferred conductivity to be
measured during commissioning since system air leaks are still being
discovered and sealed during the start up and commissioning phase.
The measurement of degassed cation conductivity will aid in
differentiating between air leaks and other contamination sources
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
19

20. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
The two most important parameters in Table are feed water
cation conductivity and pH.
Cation conductivity should be maintained below 0.15 µS/cm
during operation on OT. Normal pH range for feed water under
OT is 8.0 to 8.5.
The EPC contractor is challenged with controlling
pH when feed water cation conductivity increases to
concentration levels listed in Table , action levels 1,
2, and 3 (≤0.3 µS/cm, ≤0.6 µS/cm, >0.6 µS/cm,
respectively).
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
20

21. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
onceThe pH/conductivity relationship is crucial for oncethrough cycles on OT; thus, the EPC contractor
implements the chemistry control at its own risk.
Important issues to be addressed when implementing OT include:
• At what point during the start up and commissioning process should the chemistry
regime be switched from AVT to OT to prevent frequent switching back and forth
between a reducing and an oxidizing environment?
• What would be the “detrimental effects” of going from an oxidizing atmosphere to a
reducing (or close to reducing) atmosphere, for temporary periods?
• How can these “detrimental effects” be quantified and addressed during design and
equipment procurement?
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
21

22. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Stringent steam quality limits implemented by steam turbine
suppliers, boiler manufacturers have tightened limits on feed water
chemistry.
Yet EPC contractor requires standards to be relaxed during
commissioning to permit timely unit start up.
The challenge also is in determining the appropriate time to switch
from AVT to OT
Once cation conductivity levels are stable below 0.15 µS/cm,
EPRI recommends operation on OT with oxygen injection in a
pH range of 8.0 to 8.5. EPRI guidelines also state that oxygen injection
into feed water may continue with pH controlled between 9.2 and 9.6
and cation conductivity between 0.15 µS/cm and 0.3 µS/cm. However,
at cation conductivity levels greater than 0.3 µS/cm, EPRI recommends
that oxygen injection be terminated and AVT resumed. Upsets in
cation conductivity may lead to serious corrosion problems if oxygen
is continuously fed during upset conditions.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
22

23. Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
23

24. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Startup
Start up Steam Chemistry Limits
Guidelines on Feed Water Chemistry
Turbine Rolling Continued AVT(O)
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
24

25. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Turbine Rolling Continued
Balance of Commissioning Period Chemistry Limits
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
25

26. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Operation Guidelines with AVT R and AVT O
AVT(R) Feed water Chemistry Control Guidelines
AVT(O) Feed water Chemistry Control Guidelines
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
26

27. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Suggested Start up Feed water Chemistry
OnceGuidelines for Once-Through Cycles Without Deaerators
Practical start up chemistry guidelines should be established by
consensus among the turbine manufacturer, boiler manufacturer,
and EPC contractor early on in project development and outlined
in equipment contracts.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
27

28. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
ROLE OF CONDENSATE POLISHERS
DURING COMMISSIONING
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
28

29. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES & RISKS
STARTUP CHALLENGE
It must be recognized that no blowing down and adding fresh water
periodically during start up to flush off dirt and corrosion product and
dilute concentration of impurities carried into the system from the
feed water circuit is available as an operating intervention as in
conventional boilers to supercritical once through units.
Removal of such impurities during start up and commissioning of
supercritical units is done by full flow condensate polishers placed in
the feed water circuit which continuously keep removing the
impurities.
These polishers however need to be periodically taken off line as their
filtering ability get exhausted and need to be chemically regenerated
thus contributing significantly to increasing in the start up and
commissioning time and costs leading to major financial risks to the
EPC contractors.
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept 2013
29

30. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Impurities shaken loose during start up may cause a chemistry hold,
where plant load increases are temporarily halted until these impurities
are removed from the system.
onceFor a once-through supercritical boiler, impurities are removed
exclusively by condensate polishers subsequent to chemical cleaning
and boiler flush.
Once impurities are removed, the chemistry hold is lifted and the plant
is allowed to continue to ramp up to full load without exceeding
allowable boiler or turbine chemistry limits.
Dr. Himadri Banerji:Conference on EPC
Risk Management Bangkok 23-24 Sept
2013
30

31. SUMMARY
EPC Contractor Risk Management Responsibilities include that
onceChemistry limits are before, during and after once-through supercritical
boilers commissioning & besides,
• Control system component cleanliness during shop fabrication
• Control system component cleanliness during construction
start• Flush system components prior to start-up
• Implement stringent water quality requirements for hydro testing
• Perform boiler and feed water system chemical cleaning
• Flush system components thoroughly following chemical cleaning
• Perform steam blows to obtain steam cycle cleanliness
time• Implement time-based, progressively improving feed water and steam
chemistry targets
Dr. Himadri Banerji:Conference on EPC
Risk Management Bangkok 23-24 Sept
2013
31

32. SUMMARY
EPC Contractor Risk Management
Responsibilities
Before awarding a contract (boiler or turbine), the EPC contractor as a
turbine),
measure of contract risk mitigation should negotiate startup and
feedcommissioning feed-water quality and steam purity guidelines with
the boiler and turbine suppliers
to ensure that long-term warranties are not voided
longduring startup and commissioning activities and
opportunities of speeding up commissioning activities
are not missed.
In addition, industry standard steam purity guidelines for steam
turbine operation should be relaxed to the most practical limits
commissioning,
longfeasible during commissioning, while considering the owner’s longterm warranty interests.
Dr. Himadri Banerji:Conference on EPC
Risk Management Bangkok 23-24 Sept
2013
32

33. SUMMARY
EPC Contractor Risk Management
Responsibilities
Cycle chemistry-related equipment is operational and in good
condition, personnel are properly trained, and procedures are in
place for sampling, analysis and control of cycle chemistry
parameters,
Ensuring that all of the steps which must be taken to ensure the
entire cycle is as clean as possible so that the cycle chemistry can
quickly be brought within
recommended limits
Dr. Himadri Banerji:Conference on EPC
Risk Management Bangkok 23-24 Sept
2013
33

34. SUPERCRITICAL UNITS:
EPC CONTRACTOR’S CHEMISTRY CHALLENGES
Steam and Water Analysis System (SWAS) shall be furnished for continuous
monitoring and control of water and steam purity in the plant cycle
Dr. Himadri Banerji:Conference on EPC
Risk Management Bangkok 23-24 Sept
2013
34

35. THANK YOU
QUESTIONS PLEASE
Dr. Himadri Banerji:Conference on EPC Risk Management Bangkok 23-24 Sept
2013
35