Condensate system

Study of schematics of Condensate system of 110 MW unit at NTPC Tanda.

1. CONDENSATE
SYSTEM
RAVI PAL SINGH
DUSHYANT SINGH
(GROUP-C)

2. LAYOUT
•CONDENSATE FLOW
•EXTRACTION STEAM AND DRIP FLOW
•CONDENSER
•CEP
•SJAE
•CSC & GSC
•LPH
•PARAMETERS CHART OF LP HEATERS
•START UP PROCEDURES
•SHUTDOWN PROCEDURES

3. CONDENSATE FLOW

5. CONDENSER

6. CONDENSER
•Functions
–Acts as a heat sink to complete the Rankine cycle
–Creates vacuum to provide a favorable back pressure
–Removes non condensable gases
–Serves as a drain receptacle
–Serves as a convenient site for providing feed water makeup
•Specifications
–Number Two nos.
–Each of condenser cooling area 3380 m2
–Quantity of cooling water 15400 m3/Hr. (330C)
–Steam flow 267t/hr
–No. of tubes in each condenser 6800
–Material of Tubes AL brass

7. WHY IMPERATIVE TO PROTECT
VACUUM IN CONDENSER
Sources :
–Condenser vacuum continuously compromised due to air
ingress because of vacuum
–Decomposition of water into hydrogen and oxygen due to
thermal and chemical reactions
Effects:
–Rise in backpressure hampers efficiency and work output
–Blanketing of tubes by non condensable gases further
hampers heat interaction, leading to further
deterioration of vacuum
–Corrosiveness of condensate increases as oxygen content
increases , detrimental especially to the boiler

8. Indicators of degraded performance:
–Degradation of vacuum reading
–Increased DO
–Increased TTD on shell side
–Measured increase in Heat Rate
Sites to check for air ingress:
–Vacuum breaker
–Diaphragm
–Turbine instrumentation lines
–LPHs drains and vents
–Manholes
–CEP seals
–HP flash tank


WHY IMPERATIVE TO PROTECT
VACUUM IN CONDENSER

9. –Increased wetness in last stages of LPT
–Under cooling of condensate causing less effective
regeneration
–APC of additional CW Pumps and CT fans

THE FLIP SIDE OF HIGH VACUUM

10. CEP
•Functions
–Flow in condensate cycle from Hot well to
Deaerator
–CEP discharge gives a provision for the following:
•Exhaust hood spray
•HP/LP bypass valve cooling
•LP bypass spray
•PRDS spray
•HP/LP dozing

11. CEP and Hotwell level
NPSH
•All pumps have a designed NPSH (Net Positive Suction Head) requirement for
their operation
Cavitation
•If the suction head is reduced (due to low hot well level) to a value such that
the net head at suction falls below atmospheric pressure at that temperature,
cavitation , in other words localized boiling of the working liquid is impending
•Localized vapourization occurs and bubbles move through the impeller at near
sonic velocities
•When these bubbles suddenly burst on collision with impeller, severe
vibrations and noise is observed
•Cavitation causes reduced pump capacity, metal removal, reduced flow, loss in
efficiency and noise.

12. CEP EMERGENCIES
–If CEP motor tripped reduce load to maintain deaerator
level, try starting standby CEP.
–If CEP tripped on hot well level low, increase hot well
level by immediately starting all CTP and take CEP in
service one by one.
–If CEP tripped on discharge pressure low (malfunctioning
of CDP-207 /208), manually operate their bypass valves
and take CEP in service one by one.
–If CEP rotating in reverse direction due to passing in NRV,
possible threat of pump seizure, immediately close
discharge valve.

13. SJAE
•An ejector has two inlets: one to
admit the motive fluid, usually
steam and the other to admit the
air to be evacuated or pumped
•Steam when passes through the
nozzle its velocity increases
creating a low pressure region in
the mixing chamber
•Air is sucked into this mixing
chamber because of this low
pressure.
•The mixture so obtained
undergoes increase in pressure as
it progresses through the diffuser
and finally reaches tube bunch

15. SJAE = SAVING IN POWER?
•Better energy conversion in SJAE(low grade
thermal energy) in comparison to vacuum
pumps (higher grade electrical energy).
•Drip formation in the condensing steam,
provides regenerative heat to the condensate.
•Absence of moving mechanical parts in SJAE
eliminates wear and tear of components.

16. CSC & GSC
CSC
Seal steam from last stage of the
labyrinth sealing is utilised for
regenerative heating of the
condensate
GSC
Seal steam from second last stage
of the labyrinth sealing of HP
front, rear and MP front is utilised
for regenerative heating of the
condensate

17. LP HEATER
















CONDENSATE INLET CONDENSATE OUTLET
EXTRACTION STEAM INLET
DRIP OUTLET

18. WHY LP HEATERS?
•Regenerative heating and thus overall
efficiency gain.(lead to ‘’Carnotization’’ of
Rankine cycle )
•Reduction in loading on LP turbine(design
criteria).
•Minimizing thermal effects in boiler.

19. DRIP IN LP HEATERS

20. PERFORMANCE OF LP HEATER
Tc1
Tc2
Th1
Th2
T Tc2
Tc1
Th1
Th2
If,

Th1= Steam inlet temperature
Th2= Drip temperature
Tc1= Condensate inlet temperature
Tc2= Condensate outlet temperature
P = Shell pressure of the heater
Tsat= Saturation temperature at shell pressure
ms = Steam flow rate
mc= Condensate flow rate

Then,

TTD = Tsat-Tc2
DCA = Th2-Tc1

21. PERFORMANCE OF LP HEATER
PARAMETER UNIT LPH-1 LPH-2 LPH-3 LPH-4 LPH-5
Bleed steam source
LPT 4th
stage
LPT 3rd
stage
LPT 1st
stage
MP
EXHAUST
MP 10TH
stage
Bleed steam pressure kg/cm2 0.208 0.442 0.959 2.240 5.180
Bleed steam temperature DEG C 60.500 79.000 146.000 219.000 311.000
Condensate flow T/hr 250 250 300 300 300
Condensate inlet
temperature
DEG C 67.000 72.800 114.270
Condensate outlet
temperature
DEG C 95.000 114.270 147.060
Saturation temperature DEG C 60.492 77.808 100.966 126.479 158.032
TTD DEG C 5.966 12.209 10.972
Drip temperature DEG C
DCA
?
? ?

22. LPH EMERGENCIES
•LPH out on drip level high
–Ensure all motorized valves and extraction NRVs
are closed.
–Check all drip valves are open.
–If heater level still rising, suspected tube leakage,
immediately isolate from condensate side.

23. HEATER DRAIN TANK
AND BOOSTER PUMP
•Condensate flow at low power pump
(compared to CEP) to meet the main
condensate flow requirement.
•Direct mixing of high energy drip (compared
to hot well) to condensate flow.

24. STARTUP PROCEDURES
•No PTWs are pending.
•Electrical supplies should be normal.
•CW to condenser charged.
•Suction valves of all CEPs and CBPs are open
•Equalizing valve to CEPs are opened
•Cooling lines of CEP and CBP are charged.
•Vents of LP heaters, HDT and GSC should be opened.
•Hot well level should be normal.
•Close discharge valve of 1
st
CEP.
•Give start command to 1
st
CEP and open discharge valve slowly.
•Close all the vents when continuous flow of water is observed.
•Now maintain hot well and deaerator level, if necessary take
successive CEPs in service.

25. SHUTDOWN PROCEDURES
•Ensure all extractions NRVs and motorized
valves are closed.
•Maintain hot well and deaerator level by
running of at least one CEP.
•In case of long shut down open vacuum
breaker and isolate PRDS.

26. THANK YOU