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Modelling of Combined Cycle Powerplantswith EBSILON®Professional
Dr. Hans-Peter Wolf
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 2
Stepwise introduction into modelling of gas turbine process and heat recovery boiler (HRSG)
• Gas turbine process using individual components
• HRSG 1-pressure
• HRSG 2-pressure
• HRSG 3-pressure
• Reheat
• Separation of superheat and reheat
• HRSG and steam turbine in Ts – diagram
• Superheat of IP and LP steam
• HRSG in QT - diagram
• Water injections
• Auxiliary burner
• VTU Gas turbine library for a particular gas turbine
• Alternative heat exchanger components
• EbsWizard
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 3
Exercise, Step 1 Modelling of Gasturbine
Modelling of gasturbine with Ebsilon-components
- compressor (comp. 24)
- Combustion chamber (comp. 22)
- Turbine (comp. 23)
(detailled Modelling using VTU Gasturbine library -> Exercise, Step 10)
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 4
Exercise, Step 2, Adding a HRSG (1-pressure)
Modelling of HRSG with components
- Heat exchanger (comp. 26) for superheater and economizer
- Evaporator with drum (comp. 70)AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 5
Exercise, Step 2, Explanations
The recommended procedure for configuration of components :
• Superheater :- Specification of steam outlet temperature (measurement)
- FTYPHX = „Superheater“- FSPECD = „both cold stream and one hot stream temperature“
• Evaporator (with drum) :- FSPECD = „specification of pinchpoint PINPN“
- PINPN = 5K (default value)
- FTAPPN = „by specification value TAPPN“
- TAPPN = 3K (default value)
• Economizer :- FTYPHX = „Economizer“
- FSPECD = „both cold stream and one hot stream temperature“
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 6
Exercise, Step 2, Explanations
Alternative Procedure for configuration of components(if no heater outlet temperatures and Terminal TemperatureDifferences are known):
• Superheater :- FSPECD = „Effectiveness Method“- EFF = 0.8 (default value)
• Evaporator (with drum) :- FSPECD = „Effectiveness given as EFF“
- EFF = 0.96 (recommended value)
- FTAPPN = „T1 given externally“
• Economizer :- FSPECD = „Effectiveness Method“- EFF = 0.8 (default value)
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 7
Exercise, Step 3, 2-pressure HRSG
- Splitting the turbine into HP and LP turbine
- LP drum supplies steam to LP turbine
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 8
Exercise, Step 4, 3-pressure HRSG
- Splitting the turbine into HP-, IP- and LP-turbine
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 9
Exercise, Step 4, 3-pressure HRSG in Ts-diagram
Challenge: steam quality at LP turbine outlet too small(same with 1- and 2- pressure HRSG at same steam parameters)
XX < 0.9
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 10
Exercise, Step 5, Reheat
- Steam leaving HP turbine is heated again
- As a consequence in Ts-diagram the turbine-expansion isshifted to the right (-> higher steam quality)
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 11
Exercise, Step 5, 3-pressure HRSG with Reheat in Ts-diagram
Challenge: Heat in fluegas after superheater not sufficient toreach desired reheat temperature
X ~0.9
T < 540 °C
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 12
Exercise, Step 6, Splitting the superheater and reheater
Splitting the superheater and reheater allows higher reheat steamtemperature (because superheater 2 takes less heat from fluegas) A splitting of superheaters and reheaters into additional heaters is possible
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 13
Exercise, Step 6, Splitting of Heaters in Ts-Diagram
The desired reheat temperature (540 °C) can be rreached.
When mixing steam into cold reheat and before LP-turbine, there are significant
temperature differences (-> exergy loss)
T = 540 °C
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 14
Exercise, Step 7, Superheat of IP and LP steam
By superheating IP and LP steam, exergy losses are reducedwhen mixing the steam
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 15
Exercise, Step 7, Superheat of IP/LP steam in Ts-Diagram
When mixing streams with similar temperature, the exergy losses are reduced
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 16
3-pressure HRSG in QT-Diagram
Significant difference in the „slope“ dT/dQbetween fluegas side and water/steam side(because of high fluegas mass flow)
But temperature differences(pinchpoints) are relatively small(compared to coal fired boilers)
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 17
Comparison to coal-fired boiler: coal fired boiler in QT-Diagram
In coal fired boilers (at same thermal power) significantly lower fluegas flow (because fluegastemperature is much higher)
Higher exergy losses in boiler becauseof larger temperature differences in heattransfer
Pinchpoint
(at „cold end“)
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 18
Comparison: 1-pressure HRSG in QT-diagram
In 1-pressure HRSG pinchpoint is located „in the middle“-> large difference between feedwater ínlet temperatureand fluegas outlet temperature
The location of the pinchpoint (-> evaporationpressure) determines the fluegas losses
Pinchpoint
(„in the middle“)
High fluegas outlet
temperature and
losss
Therefore: Evaporation at different pressure levels toreduce the fluegas outlet losses
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 19
Exercise, Step 8, Water injections into SH and RH
The injections should be very small in the Design case (0.001 kg/s).
The controllers should be active only in Off-Design
Both controllers control theinjection massflows so, thatthe target steam temperaturebehind the heaters ismaintained (i.e. not exceeded)
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 20
Exercise, Step 9, Auxiliary burner
The auxiliary burner should be deactivated in Design case
The controllers should be active only in Off-design
In Off-design the controller setsthe fuel flow to the auxiliaryburner so, that the desiredsteam temperature is reached
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 21
Exercise, Step 10, VTU GT-Lib for realistic GT data
Replace individual Ebsilon components of the GT with comp. 106,
Select a proper gas turbine (for example Siemens SGT5-3000E)AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 22
Exercise, Step 10, VTU GT-Lib for a particular gas turbine
Calculates realistic results using manufacturers data
New Gasturbine Data
Meanwhile (GT-Lib Version 5) more than 600 Turbinesfrom 13 manufacturers
(Alstom, Ansaldo, Capstone, Centrax, GE, Hitachi, Kawasaki, MAN, Mitsubishi, OPRA, Rolls-Royce, Siemens, Solar Turbines)
if required by the customer, datasets for additional turbines canbe created
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 23
Exercise, Step 10, VTU GT-Lib for a particular gas turbine
Consistent
Reference Conditions
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 24
Exercise, Step 10, VTU GT-Lib for a particular gas turbine
The maximum loadcase for the auxiliary burner is encountered at lowambient temperatures, because then the fluegas temperature is low
Correction curve for fluegas outlet temperature as function of ambient temperature for
Siemens „SGT5-3000E (41MAC) Oil“
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 25
Exercise, Step 10, VTU GT-Lib for a particular gas turbine
Also in Off-design there is a drop in fluegas temperature
Correction curve for fluegas outlet temperature as function of ambient temperature for
Siemens „SGT5-3000E (41MAC) Oil“
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 26
Exercise, Step 11, Auxiliary burner and Design case
Because the fluegas massflow is increased (when operating theauxiliary burner), it is recommended to use the case with maximumfiring of the auxiliary burner as the Design case for the HRSG :
• Define the case with maximum firing of auxiliary burner as theDesign case for the complete plant
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 27
Exercise, Step 11, auxiliary firing in QT-diagram
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 28
Alternative heat-exchanger componentscomponent 20, drum
Comp. 20 : drum, for the separate modelling of evaporator anddrum
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 29
Alternative heat-exchanger componentscomp. 61, heat-exchanger with exponents
This heat-exchanger can be uses as alternative to comp.26
The specification values are the same like in comp. 26 with thefollowing additional options :
When specifying the Alpha-values of fluegas and water/steam side, the component allows to calculate the heat-transfer area A and theheat transfer coefficient k
For the Alpha-values of fluegas and water/steam side plausible valuesare recommended (-> Online help of comp.61)
The Off-Design performance is calculated like the following
• 1/k = 1/ αi+1/αa
• αi/ αiN = (M1/M1N)**EX12
• αa/αaN = (M3/M3N)**EX34 *(1.-0005*(T34-T34N))
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 30
Alternative heat-exchanger componentscomp. 62, Duplex-heatexchanger
Duplex-heatexchanger (as extension of comp.61) as combinationof 2 heat-exchangers
AGH Letniej Szkoły Energetyki 2018
Modelling of Combined Cycle Power Plant with EBSILONProfessional 31
Alternative heat-exchanger componentscomp. 88 and 89, boiler heating surface
Instead of the aforementioned heat-exchanger components also theso-called „boiler components“ comp.88 („Boiler: fluegas zone“) andcomp.89 („Boiler: bundle heating surface“) can be used.
These components allow to calculate the heat-transfer taking intoacount geometry and material data.
The heat transfer coefficients (Alpha values) are calculated fromgeometry and material data according to VDI Wärmeatlas Mb4 (there is an English edition, the „VDI heat atlas“)
Also a heat-transfer by radiation between neighbouring heatingsurfaces is taken into account by these components
Remark: only since Ebsilon Rel.11 Patch 4 correct calculation according to VDI
Wärmeatlas. Earlier there were some simplified calculations
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 32
EbsWizardAssisted creation of complete model
The EbsWizard allows to create a model of a GT + HRSG + water/steam-cycle in very short time (5 minutes)
(prerequiste: VTU GT-Lib)
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Modelling of Combined Cycle Power Plant with EBSILONProfessional 33
EbsWizardAssisted creation of complete model
Modifications of internal details of Macros is possible by editing the Macros
AGH Letniej Szkoły Energetyki 2018