Combined cycle gas steam turbine power plants

302 Pages·2005·3.99 MB·English

&
COMBINED-CYCLE GAS STEAM
TURBINE POWER PLANTS
Second Edition

Contents
List of Figures and Tables .......................................................... vi
1. Introduction .................................................................................. 1
2. The Electricity Market .................................................................. 5
3. Thermodynamic Principles of the Combined-Cycle Plant ........35
4. Combined-Cycle Concepts ....................................................... .47
5. Applications of Combined-Cycles ............................................ 125
6. Components .............................................................................. 155
7. Control and Automation .......................................................... 189
8. Operating and Part Load Behavior .......................................... 203
9. Environmental Considerations .................................................. 219
10. Developmental Trends .............................................................. 231
11. Some Typical Combined-Cycle Plants .................................... 241
12. Conclusion ................................................................................ 265
13. Appendices ................................................................................ 269
Conversions .............................................................................. 270
Calculation of the Operating Performance of
Combined-Cycle Installations .................................................. 271
Symbols and Indicies Used ...................................................... 280
Bibliography ............................................................................ 281
Index ........................................................................................ 288
List of Figures and Tables
1-1 Simplified Flow Diagram of a Combined-Cycle .................... 3
2-1 Market Development Order Volumes .................................. 10
2-2 Comparison of Different Turnkey Power Plants
in Terms of Specific Price and Output ................................ 15
2-3 The Cost Percentage of the Different Plant Areas for
a Typical 400 MW Turnkey Combined-Cycle Plant.. ..........16
2-4 Net Efficiencies for GT, CC, ST (Coal Fired),
Nuclear and Diesel Power plants ........................................ 18
2-5 The Cost of Fuels .................................................................. 21
2-6 Variable Operating and Maintenance Costs for Various
Power plants of Different Sizes. Fuel costs not included ...22
2-7 Fixed Operating and Maintenance Costs for
Various Power plants of Different Sizes............................... 23
2-8 Construction Time for various Power Plants
(From 'Notice To Proceed' to 'Commercial Operation') ....26
2-9 Dependence of the Cost of Electricity on the
Equivalent Utilization Time (100 MW) ................................ 27
2-10 Dependence of the Cost of Electricity on the
Equivalent Utilization Time (400 MW) ................................ 28
2-11 Dependence of the Cost of Electricity on the
Equivalent Utilization Time 0,000 MW).............................. 29
2-12 Dependence of Cost of Electricity on the
Annuity Factor (4,000 hr/annum) ........................................ 30
2-13 Dependence of Cost of Electricity on the
Annuity Factor (7,500 hr/annum) ........................................ 31
2-14 Dependence of Cost of Electricity on the Cost of Fuel.. ....32
3-1 Temperature/Entropy Diagrams for Various Cycles ............38
3-2a The Efficiency of a Simple Cycle Gas Turbine with
Singl~ Stage Combustion as a Function of Turbine Inlet
Temperature (TIT) & the Turbine Exhaust Temperature ....42
Figures and Tables vii
3-2b The Efficiency of a Combined-Cycle with a Single
Stage Combustion Gas Turbine as a Function of
the Turbine Inlet Temperature (TIT) and the
Turbine Exhaust Temperature .............................................. 43
3-3a The Efficiency of a Simple Cycle Gas Turbine with
Sequential Combustion as a Function of the Turbine
Inlet Temperature (TIT) and the Turbine Exhaust
Temperature .......................................................................... 44
3-3b The Efficiency of a Combined-Cycle with a Sequential
Combustion Gas Turbine as a Function of the Turbine
Inlet Temperature (TIT) and the Turbine Exhaust
Temperature .......................................................................... 45
4-1 Energy/Temperature Diagram for an Idealized
Heat Exchanger .................................................................... 49
4-2 Flow Diagram of a Single Pressure Cycle............................ 51
4-3 Energy/Temperature Diagram for a Single
Pressure HRSG ...................................................................... 52
4-4 Heat Balance for a Single Pressure Cycle........................... .53
4-5 Energy Flow Diagram for the Single Pressure
Combined-Cycle Plant .......................................................... 54
4-6 Effect of Live Steam Pressure on Steam Turbine
Output, Steam Turbine Exhaust Moisture Content
and HRSG Efficiency for a Single Pressure Cycle ............. .55
4-7 Energy/Temperature Diagram of a Single Pressure
HRSG with Live Steam Pressures of 40 and 105 bar ..........56
4-8 Effect of Live Steam Pressure on Condenser Waste
Heat at Constant Vacuum .................................................... 57
4-9 Effect of Live Steam Temperature on Steam Turbine
Output, HRSG Efficiency and Steam Turbine Exhaust
Moisture Content for a Single Pressure Cycle at 105
bar Live Steam Pressure ........................................................ 58
4-10 Effect of Pinch Point on Relative Steam Turbine
Output and Relative HRSG Heating Surface ...................... 59
4-11 Influence of HRSG Back Pressure on Combined-Cycle
Output and Efficiency, GT Output and Efficiency
and HRSG Surface ................................................................ 61
viii Figures and Tables
4-12 Effect of Feedwater Temperature on Steam Turbine
Output and HRSG Efficiency for Cycles with One
Stage of Preheating .............................................................. 62
4-13 Energy/Temperature Diagram for a Single
Pressure HRSG ...................................................................... 63
4-14 Energy/Temperature Diagram for a Conventional
Steam Generator ..................................... ·..················· ..········.64
4-15 Flow Diagram of a Single Pressure Cycle with LP
Preheating Loop for High-Sulphur Fields ............................ 66
4-16 Effect of Live Steam Pressure and Feedwater
Temperature on Available Heat Compared to
Required Heat in Preheating Loop ...................................... 67
4-17 Heat Balance for a Single Pressure Cycle with
LPPreheating Loop .............................................................. 68
4-18 Energy/Temperature Diagram for a Single Pressure
HRSG with LPEvaporator Preheating Loop ........................ 69
4-19 Flow Diagram of a Dual Pressure Cycle for
High Sulfur Fuels .................................. ··········..·..················ .70
4-20 Effect of Feedwater Temperature and Number of
Preheating Stages on Steam Turbine Output of a
Dual Pressure Cycle ........................................... ······..···········71
4-21 Flow Diagram of a Dual Pressure Cycle for Low
Sulfur Fuels ............................................ ·················· ..············72
4-22 Heat Balance for a Dual Pressure Cycle with Low
Sulfur FueL.......................................... ·································· .73
4-23 Energy Flow Diagram for the Dual Pressure
Combined-Cycle Plant .......................................................... 74
4-24 Energy/Temperature Diagram for a Dual
Pressure HRSG ...................................................................... 75
4-25 Effect of HP and LPPressure on Steam Turbine
Output and Exhaust Moisture Content for a Dual
Pressure Cycle ...................................................................... 78
4-26 Effect of LPPressure on HRSG Efficiency for a
Dual Pressure Cycle ............................................ ·..···············79
Figures and Tables ix
4-27 Effect of LPand HP Steam Temperatures on
Steam Turbine Output for a Dual Pressure Cycle ..............80
4-28 Effect of HP and LPEvaporator Pinch Point on
Steam Turbine Output and Relative HRSG Surface
for a Dual Pressure Cycle .................................................... 81
4-29 Flow Diagram of a Triple Pressure Cycle ............................ 82
4-30 Heat Balance for a Triple Pressure Cycle ............................ 83
4-31 Energy/Temperature Diagram for a Triple
Pressure HRSG ...................................................................... 84
4-32 Energy Flow Diagram for the Triple Pressure
Combined-Cycle plant .......................................................... 85
4-33 Steam Turbine Output and Exhaust Moisture
Content versus HP and IP Pressure for Triple
Pressure Cycle at Constant LP Pressure (5 bar) .................. 86
4-34 Effect of LPPressure on Steam Turbine Output
and Relative HRSG Surface for Triple Pressure
Cycle at Constant HP 005 bar) and IP (25 bar) ................87
4-35 Live Steam Temperature Optimization for a
Triple Pressure Cycle ............................................................ 88
4-36 Temperature/Entropy Diagram Showing the
Effect of "Mild Reheat" on the Steam Turbine
Expansion Line ...................................................................... 89
4-37 Effect of HP and IP Evaporator Pinch Points
on Steam Turbine Output and Relative HRSG
Surface for a Triple Pressure Cycle with Constant
LPPinch Point ...................................................................... 90
4-38 Flow Diagram of a Triple Pressure Reheat Cycle ..............91
4-39 Heat Balance for a Triple Pressure Reheat Cycle................92
4-40 Temperature/Entropy Diagram Showing the Effect of
Full Reheat on the Steam Turbine Expansion Line ............93
4-41 Energy Flow Diagram for the Triple Pressure Reheat
Combined-Cycle plant .......................................................... 93
4-42 Energy/Temperature Diagram for a Triple Pressure
Reheat HRSG ........................................................................ 94
x Figures and Tables
Steam Turbine Output and HRSG Surface versus
4-43
HP and Reheat Pressure for a Triple Pressure
Reheat Cycle at Constant HP (S68QC) and
Reheat (S68 C) Temperature ................................................ 94
Q
Steam Turbine Output versus HP Steam and Reheat
4-44
Temperature for a Triple Pressure Reheat Cycle at
Constant HP (120 bar), IP (30 bar) and LP(S bar)
Pressure .................................................................................. 96
Flow Diagram of a High Pressure Reheat Cycle
4-45
with an HP Once Through HRSG and a
Drum Type LP Section .......................................................... 97
Heat Balance for a Dual Pressure Reheat Cycle
4-46
with a Once Through HRSG ................................................ 98
Energy/Temperature Diagram for 647QC(A), 7S0QC(B)
4-47
and 1000 C(C) Exhaust Gas Temperature Entering
Q
1
the HRSG......................................... ·········..·················· ...·...· 00
Effect of Temperature after Supplementary Firing
4-48
on Power Output and Efficiency Relative to that of
a Single Pressure Cycle ...................................................... 101
Heat Balance for a Single Pressure Cycle with
4-49
Supplementary Firing .......................... ················· ...............102
Selection of a Combined-Cycle Concept ........................... ·1OS
4-50
Entropy/Temperature Diagram for a Gas Turbine
4-51
Process at Two Different Ambient Air Temperatures ......108
Relative Efficiency of Gas Turbine, Steam Process
4-52
and Combined-Cycle as a Function of the
Air Temperature at Constant Vacuum ................................ 109
Relative Power Output of Gas Turbine, Steam
4-53
Turbine and Combined-Cycle as a Function of
Air Temperature at Constant Vacuum ...................... ·....·....110
Relative Power Output of Gas Turbine, Steam
4-54
Turbine and Combined-Cycle and Relative Air
Pressure versus Elevation Above Sea Level .................. ···.111
Relative Power Output and Efficiency of Gas
4-55
T\lrbine and Combined-Cycle versus Relative
Humidity at Constant Vacuum ................ ·············· ..···········.112
Figures and Tables xi
4-56 Effect of Water and Steam Injection on Relative
Combined-Cycle Power Output and Efficiency
versus the Water or Steam/Fuel Ratio................................ 114
4-57 Effect of Condenser Pressure on Steam
Turbine Output .................................................................... 117
4-58 Temperature of Cooling Medium versus Condenser
Pressure for Direct Cooling, Wet Cooling Tower
and Air Cooled Condenser ................................................ 118
4-59 Flow Diagram to Show Fuel Preheating ............................ 119
4-60 Steam Turbine Output and HRSG Efficiency versus
Gas Turbine Exhaust Temperature for a Single
Pressure Cycle...................................................................... 121
4-61 Ratio of Steam Turbine Output of a Dual Pressure
to that of a Single Pressure Cycle as a Function of
Gas Turbine Exhaust Temperature .................................... 122
4-62 Indicative Relative Price versus Performance of
Different Combined-Cycles based on a 178 MW
Class Gas Turbine with an Exhaust Gas Temperature
of 647°C (1197°F) ................................................................ 123
4-63 Indicative Relative Price versus Performance of
Different Combined-Cycles based on a 178 MW
Class Gas Turbine with an Exhaust Gas Temperature
of 525°C(977°F) .................................................................. 124
5-1 Simplified Flow Diagram of a Cogeneration Cycle
with a Back Pressure Turbine ............................................ 128
5-2 Flow Diagram of a Cogeneration Cycle with an
Extraction/Condensing Steam Turbine ............................ 129
5-3 Flow Diagram of a Cogeneration Cycle with no
Steam Turbine ...................................................................... 130
5-4 Heat Balance for a Single Pressure Cogeneration
Cycle with Supplementary Firing ...................................... 131
5-5 Effect of Process Steam Pressure on Relative Combined-
Cycle Power Output and Power Coefficient for a Single
Pressure Cycle with 750°C Supplementary Firing ............132
Figures and Tables xiii
6-7 Once-Through HRSG with a Drum Type LPSection ........169
6-8 Supplementary Fired Heat Recovery Steam Generator ....174
6-9 Cross Section of a 140 MW Reheat Steam Turbine
with a Separate HP Turbine and a Combined IP/LP
Turbine with Axial Exhaust ................................................ 180
6-10 Cross Section of a Two Casing Steam Turbine
with Geared HP Turbine .................................................... 181
6-11 Cut-away Drawing of an Air Cooled Generator for
use in Combined-Cycle Power plant.. ................................ 182
Single Line Diagram ............................................................ 183
6-12
Hierarchic Levels of Automation ........................................ 185
6-13
6-14 Standard Layout for a Modern Combined-Cycle
Power Plant Control Room ................................................ 186
7-1 Principle Diagram for a Combined-Cycle Load
Control System .................................................................... 192
7-2 Typical Combined Cycle Droop Characteristic .................. 193
7-3 Closed Control Loops in a Combined-Cycle Plant.. ..........195
7-4 Start-up Curve for a 250 MW Class Combined-
Cycle after 8 h Standstill .................................................... 201
7-5 Start-up Curve for a 250 MW Class Combined-
Cycle after 60 h Standstill .................................................. 201
7-6 Start-up Curve for a 250 MW Class Combined-
Cycle after 120 h Standstill ................................................ 202
Combined-Cycle Shut Down Curve.................................... 202
7-7
Effect of Vacuum on Combined-Cycle Efficiency..............208
8-1
Effect of Frequency on Relative Combined-Cycle
8-2
Output and Efficiency for Continuous Full Load
Operation ............................................................................ 209
Part Load Efficiency of Gas Turbine and
8-3
Combined-Cycle .................................................................. 211