overiew of comb cycle rev 7.0_part 2
TRANSCRIPT
8/3/2019 Overiew of Comb Cycle Rev 7.0_Part 2
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Combined Cycle Power Generation
-An Introduction
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Combined Cycle Power Generation
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GTHRSG
+
ST
3%
MISC
LOSSES
100% FUEL
INPUT
OUTPUT30 %
67%
OUTPUT16 %
3% MISC
LOSSES
34%
CONDENSER
LOSSES
14% TO
STACK
Combined Cycle Heat Flow
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Fired ± Unfired HRSG
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District
heating andprocess heatfor industry.
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Classification
HRSG
DRUM TYPE
1/2/3 pr type
ONCE
THR OUGH
UNFIRED SUPPLEMENTRY FIRED
VER TICAL
Natural/ Forced Circulation
HOR IZONTA
N / F Circ.
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VERTICAL HRSG
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VERTICAL HRSG
Flue gas flow -vertical
Water/ steam flow inhorizontal finned tubes
Small foot print area
Added circulation
Good cycling capability
Replacement of tubeseasily possible
Easily access forinspections
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Horizontal HRSG
Flue gas flow-horizontal
Water/ steam flow invertical finned tubes
Large foot print area Natural circulation
In cycling duty problemsin superheater/ reheatersections.
Replacement of tubes notpossible
Access for inspections isdifficult
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Horizontal HRSG
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Horizontal HRSG
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Horizontal types require a 30 % larger footprint area.
More expansion joints are required in horizontal units.
Structural requirements are higher in vertical types.Horizontal types are more difficult for maintenance and
inspections.
Overall cost may be same in both types;
Horizontal Vs Vertical HRSG
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Typical two stage Combined Cycle
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Water ± Steam Path
CEP
HPBFP
LPBFPLP
Drum
LPCCpump
HPTurbine LP Turbine
&Condenser
HPDrum
HPCCpump
Cond.Preheater
LP ECO
HP ECO-I
LP EVA
LP SUP
HP ECO-II
HP EVA
HP SUP-I
HP SUP-II
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Types of Super heater
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Very popular for small gas
turbines and diesel engines.
Very compact design
Can be shipped totally
assembled.
Types of Evaporator
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This configuration has probably
been used for more years than any
of the others.
Has the advantage of the upper header being configured as the
steam separation drum.
Types of Evaporator
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Types of Evaporator
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Types of Evaporator
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Optimum Approach & Pinch Point
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Combined Cycle Parameters-PINCH POINT
Difference between flue gas and
water/steam temperature at evaporator
section
It is the minimum differential
temperature between gas and
water/steam in the Boiler
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Lower pinch point results in
linear rise in cycle efficiency
exponential rise in boiler heat transfer area
PINCH POINT
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PINCH POINT:Every 10°C decrease in Pinch Point, results in
HP steam flow increases by 4.6 %
Steam turbine output increases by 3.4 %
Heat rate improves by 20 kcal/kWHr
Efficiency improves by 0.52 %
Optimum 8-15 °C, with regard to Heat Transfer areaof Evaporator
Pinch point at Dadri (HP Ckt) is 11.6°C
(LP ckt) is 8.0 °C
Combined Cycle Parameters
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SINGLE PRESSURE NON REHEAT
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DOUBLE PRESSURE NON REHEAT CYCLE
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DUAL PRESSURE CC PLANT
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Dual Pressure Type
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TRIPLE PRESSURE CC PLANT
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TRIPLE PRESSURE CC PLANT
400MWi CCPP- Castejon (Spain)
Vertical gas path HRSG withnatural circulation and three levels
of pressure and reheat for a gas
turbine of 265MW in local
conditions.It was commissioned in 2002.
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Triple Pressure HRSG With SCR
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Tripple Pressure Type
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Triple Pressure Levels Reduces Irreversibility & Increasing Heat Transfer
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Higher approach point offers stability and compactdesign where as
Narrow approach point results in
Very large economiser surface area
Chances of steaming in economiser water hammer and
fluctuations in drum level
Dadri (HP Ckt) is 2°C
(LP ckt) is 2 °C
HRSG Parameters-Approach Point
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Pressure Stages in WHRB
Criteria : Maximum available Temperature at WHRB inlet
Provision of Supplementary firing in WHRB
Station owners own economic evaluation of
Heat rate,
Efficiency,
Power output,Extra investment,
Added O& M Cost
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Pressure Stages in WHRB
Output (%) Plant Eff. (%)
Single pr., Non reheat - 4.7 - 4.7
Two pr., Non reheat - 1.0 - 1.0
Three pr., Non reheat Base BaseThree pr., Reheat + 0.7 + 0.7
Limiting Factor:Saturation temperature at particular pressure
Possible degree of Superheat
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WHRB Steam Outlet Conditions
First stage Second Stage Third stage
bar 0C bar 0C bar 0C
Single Pr 40-60 450-520
Dual pr 60-100 480-520 5-15 200-250
Triple Pr 60-120 480-520 20-30 200-300 3-5 150-200
Heat Pick up in 3 Pr System
15-20 %
in Super htr/ Rehtr
60-70 % in Steaming 20-30 % in
heating water Originally this picture was super imposition of solar heating to that of HRSG
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Energy balance in diff scenario
Config GT
Output
GT
Losses
HRSG
Losses
Stack
losses
Condenser
losses
ST
Losses
ST
output
Singlepr.
37.6 0.5 0.2 11.4 29.9 0.3 20.1
Doublepr.
37.6 0.5 0.3 8.2 32.1 0.3 21.0
Triplepr.
37.6 0.5 0.3 8.2 32.0 0.3 21.1
Triple,reheat
37.6 0.5 0.3 8.6 31.0 0.3 21.7
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Temperature Profile
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SCR
Suitable temperature range 300 to 400 oC.
Segments having honeycomb patterns containing
catalyst is arranged within HRSG.
Ammonia slip is a concern, requires sophisticated
control system for controlling injection.
Excessive Size and Weight.
Costly as compared to primary methods.
Sensitive to fuels containing more than 1000 ppm of
sulfur.
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Principle of DeNOx thru¶ SCR
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Post Combustion Pollution Control
SCR: NOx is converted into nitrogenand water vapour by injectingammonia in presence of a catalyst.
SCONOx: Single catalyst for removal
of CO, NOx, VOCs, SO2 andrequires no chemical injection.
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Finned Tubes
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Module Concept
1 GT + 1 HRSG + 1 ST ]
2 *[ GT + HRSG ] + 1 ST ]
3 *[ GT + HRSG ] + 1 ST ]
4 *[ GT + HRSG ] + 1 ST ]
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2 GT + 1 ST
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2 * [2 GT + 1 ST]
Tamazunchale Combined Cycle Power Station (Mexico)
4 GE 7FA gas turbo-generator units [60
Hz, 183 MW each]
and 2 GE D11S
steam turbines.,totaling 1135 MW
in two modules.
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4 GT + 1 ST
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Single Shaft Arrangements
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Air
Air
Fuel
Fuel
Exhaust
gas
Exhaust
gas
GT-
1
GT-2
ST-
1
Steam
G
G
G
106 MW
106 MW
116MW
2 X 106 + 1 X 116 = 328 MW
Combined Cycle Module Configurations
HRS
G
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Combined Module Cycle Configurations
4 X (2 GT + 2 HRSG + 1 ST)
- Four(4)nos.multishaft CC Modules based on
conventional class gas turbine models.- The module shall consist of two (2) nos. Gas
Turbines, two (2) nos. HRSGs, and one (1) no.
Steam Turbine. Each Gas Turbine and Steam
Turbine would drive separate Electric
Generator.
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Air
Air
Fuel
Fuel
Exhaust
gas
Exhaust
gas
GT-
1
GT-2
ST-
1
Steam
G
G
G
255
MW
255
MW
276MW
2 X 255 + 1 X 276 = 786 MW
Combined Module Cycle Configurations
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Combined Cycle Module Configurations
2X (2 GT + 2 HRSG + 1 ST)
- Two nos. multishaft CC module based on
advanced (F/FA
) class GT model.- Each module shall consist of two (2) nos. Gas
Turbines, two (2) nos. HRSGs, and one (1) no.
Steam Turbine. Each GT and ST would drive
separate Generator.
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Exhaust
gas
Air
Fuel
Fuel
Exhaust
gasGT-
1
GT-
2 ST-
1
Stea
m
Air
Fuel
GT-
3
Air
Exhaust
gas
3 X 140 + 1 X 230=650 MW
Combined Cycle Module Configurations
G
G
G
G
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Combined Cycle Module Configurations
2X (3 GT + 3 HRSG + 1 ST)
- Two nos. multishaft CC module based on
conventional class gas turbine model.- Each module shall consist of three (3) nos. Gas
Turbines, three (3) nos.HRSGs, and one (1)
no. Steam Turbine. Each GT and ST would
drive separate Generator.
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250 MW GT + 140 MW ST = 390 MW
Combined Cycle Module ConfigurationsCombined Cycle Module Configurations
Configuration ± D
Single Shaft Module
G
Air
Exhaust
gas
Stea
mGas Turbine
Fuel
Steam Turbine
Si l Sh ft CC Pl t
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Single Shaft CC Plant
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Si l Sh ft Pl t A t
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Single Shaft ± Plant Arrangement
GT 188 MW
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Single Shaft Combined Cycle Plant
Simplified Plant design and operation
Lower initial investment
Unitized design means problems faced inmulti shaft configuration employing Triple
Pressure Reheat ST are absent.
GT ST G t C fi ti
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GT±ST±Generator Configuration
Axial steam turbine exhaust is notpossible
Steam turbine shares the cold endthrust / journal bearing of Gas Turbine
Auxiliary steam is required for coolingof steam turbine during startup
Outage of ST necessarily lads to outage of the
whole power train.
Gas Turbine is accessible formaintenance only after cool-down of complete power train.
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Single Shaft CC Units Don¶t Need
Main steam non return valves
Cold Reheat isolation valves
Cold Reheat Balancing valves
Reheater relief valves
Hot Reheat stop/ control valvesLow pressure Non return valves
Steam headers
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Single Shaft Unit Configuration
GT- Generator ² Clutch ² ST
GT ² ST ² Generator
GT G t Cl t h ST fi
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GT-Generator±Clutch±ST config.
y Steam turbine must be moved to remove andservice the generator Rotor.
y
Startup of gas Turbine is independent of Steam turbine
y SSS clutch allows load operation of Gas Turbinein case of outage of the ST
y Gas turbine and steam turbines have their ownthrust and journal bearings
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Cost Reduction in Single Shaft Unit results from:
Reduction in number of Electric generators,step up transformers, and high voltagefeeders.
Civil works ± Single building, Reducedbuilding height
Reduction in number of valves and lengthof piping.
Elimination of Bypass stack and diverterdamper.
Limitations of Single Shaft Units
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Limitations of Single Shaft Units
Need for higher starting power
Less Operating Flexibility ;
Option of phased construction and
commissioning not available.
Combined C cle Options
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Combined Cycle Options
STEAM CYCLE:
Single pressure
Two pressure
Three pressure
Reheat
Non-reheat
DEAERATION:
Deaerating condenser
Deaerator/evaporatorintegral with WHRB
HRSGDE
SIGN:
Natural circulationevaporator
Forced circulationevaporator
Unfired
Supplementary fired
NOx CONTROL:
Water Injection Steam Injection
SCR ( NOx and/or CO)
Dry Low NOx
Combustion
C bi d C l O i
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CO
NDE
NSE
R:
Water cooled (once through system)
Water cooled (evaporative cooling tower)
Air Cooled condenser)
FUEL:
Natural gas
Distillate oil
Ash bearing oil
Low Btu coal and oil-derived gas
Multiple fuel system
Combined Cycle Options
C t Di t ib ti f CC P Pl t
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(2GTs + 2HRSGs + 1ST)
Gas turbine, Aux equipment : 26 %HRSG + piping + auxiliary equipment: 17 %
Steam turbine + generator+piping+condenser: 21 %
Electric and supervisory equipment+transformer: 12 %Civil engineering: 6 %
Erection + supervision: 18 %
Cost Distribution for a CC Power Plant
Bypass Stack /
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Bypass Stack /
Waste Heat Recovery Systems
P E h t M th d
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It is Site specific and dependant on:
Site ambient temperature
Level of desired output enhancement
Anticipated Operational hours
Water availability
Structure of Power Purchase Agreement
Allowable plant emission
Owner¶s own economic evaluation factors
for plant output, heatrate, O& M costs.
Power Enhancement Methods
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Coal fired Vs Combined Cycle
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Coal fired Vs. Combined Cycle
0.6
0.4
0.55
0.73
0.46
0.35
0.65
1.37
0
0.2
0.4
0.6
0.8
1
1.2
1.4
C o s t o f I n s t a l l a t i o n
O & M C o s t
O & M S t a f f
F u e l R e q u i r e m e n t
L a n d r e q u i r e m e n t
W
a t e r R e q u i r e m e n t
G e s t a t i o n P e r i o d
P l a n t E f f i c e n c y
Thermal
Comb. Cycle
Comparison of Availability Reliability
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Comparison of Availability, Reliability
Availability = [Total Operating Hours ± Planned outage-Forced outage]/ Total Operating Hours
Reliability = [Total Operating Hours ± Forced outage]/ Total Operating Hours
Typical Figures
Plant types Availability Reliability
Gas turbine (gas) 88-95 97-99
Steam Turbine (coal) 82-89 94-97
Comb cycle (gas) 86-93 95-98
Nuclear 80-89 92-98
Diesel generator 90-95 96-98
Annexure
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Annexure
Performance Parameters
Annexure
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Annexure
Performance = Actual heat transfer / max possible (ASME PTC 4.4)
valuereferenceaboveinput energy sideGas
water Steambyabsorbed Energy Efficiency /!
possiblelossenergy sideGas Max
Gasbylost Energyess Effectiven !
Which is more ?
Efficiency or effectiveness and Why
Annexure
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Annexure
valuereferenceaboveinput energy sideGas
water Steambyabsorbed Energy Efficiency
/!
Annexure
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Annexure
hh
hh
possiblelossenergy sideGas MaxGasbylost Energyess Effectiven
gas gas
gas gas
in
out in
min
!!
h gasinis the HRSG inlet enthalpy condition for flue gas;
h gasoutis the HRSG outlet enthalpy condition for flue gas;
h gas minis the minimum possible HRSG outlet enthalpy condition for
flue gas;
= condensate temperature OR = actual gas temp ± pinch point± (approach point)*(gas temp
fall at eco/ water temp rise at eco)*correction factor of 1.15
8/3/2019 Overiew of Comb Cycle Rev 7.0_Part 2
http://slidepdf.com/reader/full/overiew-of-comb-cycle-rev-70part-2 80/80