Modelling of Combined Cycle Powerplants with EBSILON Professional. Dr. Hans-Peter Wolf AGH Letniej Szkoły Energetyki 2018

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1 Modelling of Combined Cycle Powerplants with EBSILON Professional Dr. Hans-Peter Wolf

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 Modelling of Combined Cycle Power Plant with EBSILONProfessional 2

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) Modelling of Combined Cycle Power Plant with EBSILONProfessional 3

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) Modelling of Combined Cycle Power Plant with EBSILONProfessional 4

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 Modelling of Combined Cycle Power Plant with EBSILONProfessional 5

6 Exercise, Step 2, Explanations Alternative Procedure for configuration of components (if no heater outlet temperatures and Terminal Temperature Differences 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) Modelling of Combined Cycle Power Plant with EBSILONProfessional 6

7 Exercise, Step 3, 2-pressure HRSG - Splitting the turbine into HP and LP turbine - LP drum supplies steam to LP turbine Modelling of Combined Cycle Power Plant with EBSILONProfessional 7

8 Exercise, Step 4, 3-pressure HRSG - Splitting the turbine into HP-, IP- and LP-turbine Modelling of Combined Cycle Power Plant with EBSILONProfessional 8

9 Exercise, Step 4, 3-pressure HRSG in Ts-diagram X X < 0.9 Challenge: steam quality at LP turbine outlet too small (same with 1- and 2- pressure HRSG at same steam parameters) Modelling of Combined Cycle Power Plant with EBSILONProfessional 9

10 Exercise, Step 5, Reheat - Steam leaving HP turbine is heated again - As a consequence in Ts-diagram the turbine-expansion is shifted to the right (-> higher steam quality) Modelling of Combined Cycle Power Plant with EBSILONProfessional 10

11 Exercise, Step 5, 3-pressure HRSG with Reheat in Ts-diagram T < 540 C X ~0.9 Challenge: Heat in fluegas after superheater not sufficient to reach desired reheat temperature Modelling of Combined Cycle Power Plant with EBSILONProfessional 11

12 Exercise, Step 6, Splitting the superheater and reheater Splitting the superheater and reheater allows higher reheat steam temperature (because superheater 2 takes less heat from fluegas) A splitting of superheaters and reheaters into additional heaters is possible Modelling of Combined Cycle Power Plant with EBSILONProfessional 12

13 Exercise, Step 6, Splitting of Heaters in Ts-Diagram T = 540 C 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) Modelling of Combined Cycle Power Plant with EBSILONProfessional 13

14 Exercise, Step 7, Superheat of IP and LP steam By superheating IP and LP steam, exergy losses are reduced when mixing the steam Modelling of Combined Cycle Power Plant with EBSILONProfessional 14

15 Exercise, Step 7, Superheat of IP/LP steam in Ts-Diagram When mixing streams with similar temperature, the exergy losses are reduced Modelling of Combined Cycle Power Plant with EBSILONProfessional 15

16 3-pressure HRSG in QT-Diagram Significant difference in the slope dt/dq between fluegas side and water/steam side (because of high fluegas mass flow) But temperature differences (pinchpoints) are relatively small (compared to coal fired boilers) Modelling of Combined Cycle Power Plant with EBSILONProfessional 16

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 fluegas temperature is much higher) Higher exergy losses in boiler because of larger temperature differences in heat transfer Pinchpoint (at cold end ) Modelling of Combined Cycle Power Plant with EBSILONProfessional 17

18 Comparison: 1-pressure HRSG in QT-diagram In 1-pressure HRSG pinchpoint is located in the middle -> large difference between feedwater ínlet temperature and fluegas outlet temperature The location of the pinchpoint (-> evaporation pressure) determines the fluegas losses Pinchpoint ( in the middle ) Therefore: Evaporation at different pressure levels to reduce the fluegas outlet losses High fluegas outlet temperature and losss Modelling of Combined Cycle Power Plant with EBSILONProfessional 18

19 Exercise, Step 8, Water injections into SH and RH Both controllers control the injection massflows so, that the target steam temperature behind the heaters is maintained (i.e. not exceeded) The injections should be very small in the Design case (0.001 kg/s). The controllers should be active only in Off-Design Modelling of Combined Cycle Power Plant with EBSILONProfessional 19

20 Exercise, Step 9, Auxiliary burner In Off-design the controller sets the fuel flow to the auxiliary burner so, that the desired steam temperature is reached The auxiliary burner should be deactivated in Design case The controllers should be active only in Off-design Modelling of Combined Cycle Power Plant with EBSILONProfessional 20

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) Modelling of Combined Cycle Power Plant with EBSILONProfessional 21

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 Turbines from 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 can be created Modelling of Combined Cycle Power Plant with EBSILONProfessional 22

23 Exercise, Step 10, VTU GT-Lib for a particular gas turbine Consistent Reference Conditions Modelling of Combined Cycle Power Plant with EBSILONProfessional 23

24 Exercise, Step 10, VTU GT-Lib for a particular gas turbine The maximum loadcase for the auxiliary burner is encountered at low ambient 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 Modelling of Combined Cycle Power Plant with EBSILONProfessional 24

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 Modelling of Combined Cycle Power Plant with EBSILONProfessional 25

26 Exercise, Step 11, Auxiliary burner and Design case Because the fluegas massflow is increased (when operating the auxiliary burner), it is recommended to use the case with maximum firing of the auxiliary burner as the Design case for the HRSG : Define the case with maximum firing of auxiliary burner as the Design case for the complete plant Modelling of Combined Cycle Power Plant with EBSILONProfessional 26

27 Exercise, Step 11, auxiliary firing in QT-diagram Modelling of Combined Cycle Power Plant with EBSILONProfessional 27

28 Alternative heat-exchanger components component 20, drum Comp. 20 : drum, for the separate modelling of evaporator and drum Modelling of Combined Cycle Power Plant with EBSILONProfessional 28

29 Alternative heat-exchanger components comp. 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 the following additional options : When specifying the Alpha-values of fluegas and water/steam side, the component allows to calculate the heat-transfer area A and the heat transfer coefficient k For the Alpha-values of fluegas and water/steam side plausible values are recommended (-> Online help of comp.61) The Off-Design performance is calculated like the following 1/k = 1/ α i +1/α a α i/ α in = (M1/M1N)**EX12 α a /α an = (M3/M3N)**EX34 *( *(T34-T34N)) Modelling of Combined Cycle Power Plant with EBSILONProfessional 29

30 Alternative heat-exchanger components comp. 62, Duplex-heatexchanger Duplex-heatexchanger (as extension of comp.61) as combination of 2 heat-exchangers Modelling of Combined Cycle Power Plant with EBSILONProfessional 30

31 Alternative heat-exchanger components comp. 88 and 89, boiler heating surface Instead of the aforementioned heat-exchanger components also the so-called boiler components comp.88 ( Boiler: fluegas zone ) and comp.89 ( Boiler: bundle heating surface ) can be used. These components allow to calculate the heat-transfer taking into acount geometry and material data. The heat transfer coefficients (Alpha values) are calculated from geometry 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 heating surfaces 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 Modelling of Combined Cycle Power Plant with EBSILONProfessional 31

32 EbsWizard Assisted 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) Modelling of Combined Cycle Power Plant with EBSILONProfessional 32

33 EbsWizard Assisted creation of complete model Modifications of internal details of Macros is possible by editing the Macros Modelling of Combined Cycle Power Plant with EBSILONProfessional 33

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