# GE Power Systems


# GE Combined-Cycle Product Line and Performance

D.L. Chase P.T. Kehoe GE Power Systems Schenectady, NY GER-3574G 

# g

## Contents

Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 STAG Product Line Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 STAG Product Line Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 STAG Power Generation Product Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 STAG Combined-Cycle Major Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Gas Turbines

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 HRSG

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Steam Turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0 Generators

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Controls

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Auxiliaries

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Plant Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Plant Arrangements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Installation

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Utility Load Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Thermal Energy and Power System Product Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Engineered Equipment Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Conclusion

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 List of Tables

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) i

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) ii

## Introduction The development during the past four decades of larger capacity gas turbine designs (50 MW to 380 MW) with increased specific power has led to the parallel development of highly-efficient and economical combined-cycle systems. The GE pre-engineered, combined cycle product line is designated STAGTM, which is an acronym for ST eam And Gas. Each STAG combined cycle system is an Engineered Equipment Package (EEP) consisting of GE gas turbines, steam turbines, generators, Heat Recovery Steam Generators (HRSGs) and controls. Themost efficient of these STAG systems is configured with the GE "H" model gas turbine and is scheduled for commercial operation by the year 2003. The “H” combined cycle will achieve 60 percent (LHV) thermal efficiency. The STAG EEP is an optimized and matched system of high technology power generation equipment, software, and services configuredfor convenient integration with the owner's auxiliaries and balance of plant equipment to form an economical power plant. This single sourcesupply of the EEP enables GE to provide guarantees of plant thermal and emission performance as well as warrant system operation.The product line spans a wide range of capabilities for both 50 and 60 Hz applications. A widerange of configurations is available with standard options that enable the systems to be adapted to suit the economic requirements of each application. The STAG combined-cycle product line includes two major categories:
■ Pre-engineered oil- or natural gas-fired systems for electric power generation
■ Pre-engineered building blocks for combined-cycle cogeneration systems and coal- or oil-fired integrated gasification combined-cycle (IGCC) power generation systems. Economical performance of function is the outstanding characteristic of STAG combined-cyclesystems. The features that contribute to economical power generation by STAG combinedcycle power generation systems are shown in Table 1 and those for thermal and power systems are presented in Table 2

.



## STAG Product Line DesignationsSystem designations that identify STAG combined-cycle product line configurations are defined in Table 3. This example defines the designation for the single-shaft and multi-shaft combined-cycle configurations. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 1 Table 1. STAG combined-cycle power generation system features

Table 2. STAG combined-cycle thermal energy and power system features • High Thermal Efficiency • Low Installed Cost • Fuel Flexibility – Wide Range of Gas and Liquid Fuels • Low Operation and Maintenance Cost • Operating Flexibility – Base, Mid-range, Daily Start • High Reliability • High Availability • Short Installation Time • High Efficiency in Small Capacity Increments

• High Thermal Efficiency • Low Installed Cost • Low Operation and Mainteance Costs - Steam Generation at Process Conditions - Extraction/Condensing Steam Turbine - Non-Condensing Turbine Exhausting to Process - Unfired/Fired HRSGs - Gas Turbine DLN/Steam Injection • High Power to Thermal Energy Ratio • High Reliability/Availability • Short Installation Time

## STAG Product Line Configurations The product line includes single-shaft and multi--shaft configurations. Simplified block diagrams of these configurations are presented in Figure 1 . The single-shaft STAG system consists of one gas turbine, one steam turbine, one generator, and one HRSG with the gas turbineand steam turbine coupled to the single generator in a tandem arrangement on a single shaft. Multi-shaft STAG systems have one or more gas turbine generators and HRSGs that supply steam through a common header to a separate, single steam turbine generator. Single- and multiple-pressure non-reheat steam cycles are applied to STAG systems equipped with GE gas turbines that have rating point exhaust gas temperatures of approximately 1000°F / 538°C or less. Selection of a single- or multiple-pressure steam cycle for a specificapplication is determined by economic evalua

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 2 GEN GT HRSG

GEN GT HRSG ST GEN HRSG

GT ST GEN


### S 2 0 7FA - MS

STAGTM Two GT Model Multi-Shaft GTs Series Configuration 

### S 1 0 7FA - SS
STAGTM One GT Model Single-Shaft GT Series Configuration

STAG IS A REGISTERED TRADEMARK OF GENERAL ELECTRIC(USA)
AND IS AN ACRONYM FOR STeam And Gas S107FA-SS S207FA-MS

Table 3. STAG combined-cycle system designations

GT19939 Figure 1. STAG system configurationstion, which considers plant-installed cost, fuel cost and quality, plant-duty cycle, and operating and maintenance cost. Multiple-pressure reheat steam cycles are applied to STAG systems with GE gas turbines that have rating point exhaust gas temperatures of approximately 1100°F / 593°C or greater. A generalized combined-cycle, electric power generation and thermal energy capability map is presented in Figure 2. This map is typical of a system supplying process steam at 150 psig/11.4 bars and utilizing a gas turbine with 100 MW rated output.

The vertical axis of Figure 2 with zero thermal energy shows the power and thermal efficiencyof combined cycles with unfired, supplementary-fired, and fully-fired steam cycles. The most efficient power generation cycles are those with unfired HRSGs having modular pre-engineered components. These unfired steam cycles are also the lowest in cost and are, therefore, applied in the STAG combined-cycle power generation product line. Supplementary-firedcombined-cycle systems are provided for customer specific applications in which the need for increased power offsets the corresponding reduction in thermal efficiency. The most efficient cycles for cogeneration applications are those with fully-fired HRSGs, as indicated by Figure 2, at maximum thermal energy output. The fully-fired HRSGs are high in cost because of their water wall construction and need for field erection. Also, fully-fired HRSGs may add to emission considerations as plant siting requirements are evaluated. The primary regions of interest for cogeneration, combined-cycle systems are those with unfired

and supplementary-fired steam cycles. These systems provide a wide range of thermal energy to electric power ratio, 0–12,000 Btu thermalenergy per kW (0–12,660 kJ per kW), and represent the range of thermal energy capability and power generation covered by the product line for cogeneration capability.



## STAG Power Generation Product Line The STAG power generation product line includes an array of steam cycle options, which 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 3 GT21520B Figure 2. Generalized combined-cycle performance capabilitysatisfies a wide range of fuels, fuel cost, duty cycle, and other economic considerations. Thisenables selection of a steam cycle for each application that suits specific economic and operational requirements. Steam cycles utilized in the STAG product line include:
■ Single-Pressure, Non-Reheat Heat Recovery Feedwater Heating. This steam cycle, shown in Figure 3, has an unfired HRSG with finned tube superheater, evaporator, and economizer sections. Energy is recovered from the exhaust gas by convective heat transfer. The HRSG schematic diagram is shown in Figure 4. This is the simplest steam cycle that can be applied in a combined cycle and it has been used extensively. It results in a low installed cost. Although it does not produce the highest combined-cycle thermal efficiency, it is a sound economic 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 4 GT16402A Figure 3. Single-pressure non-reheat cycle diagram

GT1640B

Figure 4. Single-pressure non-reheat HRSG diagramselection when fuel is inexpensive, when applied in peaking type service, or when burning ash-bearing fuel with high sulfur content. This steam cycle is utilized in the STAG product line primarily with GE gas turbines having a baseload exhaust gas temperature of approximately 1000°F / 538°C or less. The HRSG stack gas temperature with this steam cycle is approximately 340°F / 171°C.
■ Multiple-Pressure, Non-Reheat Heat Recovery / Feedwater Heating. Multipressure steam generation is used to maximize energy recovery from gas turbine exhaust. HRSG gas-side and steam-side temperature profiles for single- and multiple-pressure steam cycles are presented in Figures 5 and 6

. This illustrates that increasing the number of steam pressure levels reduces the exhaust gas andsteam/water energy difference. Twoor three-pressure steam cycles achievebetter efficiency than the singlepressure systems, but their installed cost is higher. They are the economic choice when fuel is expensive or if the duty cycle requires a high load factor. The three-pressure steam cycle is shown in Figure 7 and the HRSG schematic diagram is shown in Figure 8. This cycle is similar to the singlepressure cycle with the addition of thelow-pressure and intermediatepressure sections. Improved plant performance with multiple-pressure steam cycles results from additional heat transfer surface installed in theHRSG. The HRSG stack gas temperature is in the range of 200°F / 93°C to 260°F / 127°C.
■ Three-Pressure, Reheat Heat Recovery Feedwater Heating. The reheat steam cycle matches the characteristics of the “EC,” “F,” and “H” technology gas turbines. The higher exhaust gas temperature of 1100°F / 593°C or greater provides sufficient high temperature energy to the HRSG to make the reheat steam cycle practical. Fuel gas heating to approximately 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 5Temperature

Heat Transfer Economizer Evaporator Super Heater Pinch

Sub-cool Approach Typical Exhaust Gas Temperature Profile - One Pressure System

Figure 5. Typical exhaust gas/steam cycle temperature profile for single-pressure system

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 6 Heat TransferTemperature - °C HPS

RH HPS HPB

IPS
HPE LPS IPB IPE HPE LPB LPE Gas Turbine Exhaust Gas

Low Pressure High Pressure

Intermediate & Reheat Pressure

Figure 6. Typical exhaust gas/steam cycle temperature profile for three-pressure system

Bypass

Diverter Damper HRSG

Fuel

GT Gen ST Gen
Deaerating Cond.

Cond. Pump Legend Steam Water Air, Gas Fuel Figure 7. Three-pressure non-reheat cycle diagram

GT16405C Figure 8. Three-pressure non-reheat HRSG diagram365°F / 185°C, using water supplied from the HRSG IP economizer discharge, is also included with the “EC” and “F” technology gas turbines. This steam cycle is shown in Figure 9

. The HRSG schematic is presented in Figure 10

. The “H” platform gas turbines, configured with hot gas path components cooled with both a

closed-loop, steam-cooling system and an openloop, air-cooling system design, are designated as MS7001H and MS9001H. The reheat steam cycle utilized with these gas turbines is closely integrated with the gas turbine steam-cooling system. This integration provides additionalincentive to select single-shaft STAG configuration for these gas turbines. The steam cycle used with the S107H and S109H is shown in Figure 11 . The HRSG schematic is shown in Figure 12

. These STAG combined-cycle systems are themost efficient power generation systems currently available. The base configuration for the

STAG power generation combined-cycle product line is designed for high efficiency when firing natural gas or distillate fuel. A summary ofthe equipment and system configuration is presented in Table 4

. The 60 Hz STAG power generation product line ratings are presented in Table 5

. Table 6 shows the major equipment in each standard STAG system. The 50 Hz product line ratings are presented in Table 7 , and Table 8 shows the major equipment in each of these standard STAG systems. These ratings are presented for gas turbine base load operation with natural gasfuel. Nominal throttle and reheat steam conditions for the non-reheat and reheat STAG product lines are defined in Table 9

.

GE Power Systems ■ GER-3574G ■ (10/00) 7 

## GE Combined-Cycle Product Line and Performance

Figure 9. Three-pressure reheat cycle diagram

Figure 10. Three-pressure reheat HRSG diagram • Unfired, three-pressure steam cycle - Non-reheat for rated exhaust gas

temperature less than 1000°F/538°C - Reheat for rated exhaust gas temperature

higher than 1050°F/566°C and fuel heating - Heat recovery feedwater heating - Feedwater deaeration in condenser - Natural circulation HRSG evaporators • Gas turbine with Dry Low NO xcombustors • Once-through condenser cooling water system • Multi-shaft systems • Single-shaft systems

- Integrated equipment and control system

Table 4. STAG power generation combined-cycle base configurationThe STAG product line equipment and plant natural gas fuel ratings defined in Tables 5 and 7represent thermodynamic optimum performance that is expected to be the economic optimum configuration for baseload and mid-range dispatch using clean fuels costing about $2.50 per 10 6 Btu, HHV ($2.64 per 10 6 Kj, HHV). A wide array of options is available for the STAG power generation product line to suit specific economic criteria as well as the operating and installation preferences of the owner. Table 10 lists the most commonly-applied options in addition to the base configuration.Non-reheat steam cycles with one or two pressures and reheat steam cycles with two pressuresare also available for the STAG product-line systems. Typical performance variation for these optional steam cycles is presented in Table 11

. HRSGs with forced circulation evaporators are available to suit specific installation situations and owner preferences. Figure 13 shows a twopressure, non-reheat steam cycle with forced circulation HRSG.Systems can be provided with a deaerator integral to the HRSG that utilizes low-pressure evaporator energy to perform the feedwater deaeration at positive pressure at a small reduction in thermal efficiency. Those systems that include a 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 8 C oolin g Water C o o ling A ir C ooling S ystem To Stack

Air Gas Tu rb in e

Air Tre atment

Cond en sate Pu mp Fuel

IP H P H eat Recovery Steam Generator Fu el Heatin g System

Glan d S eal Cond en ser Deaerating Condenser G en erato r LP LP Attemp

Filte r

LEGE ND

Filter A

Filter B F eed water Pump

C on densate Filter Fuel Steam W ater Exhaust Air Steam Tu rb in e

Figure 11. STAG 107H/S109H cycle diagram

T O H P TU RB IN E T o Stack H e at Re c o v e ry Steam Generator

Atte mp

LEGEND Feedw ater Pump

FR OM C ON D ENSA TE PUM P

Fuel Steam Water Exhaust Air TO FUEL HEATING SY STE M TO COOLING AIR COOLING SYSTEM

FROM COOLING AIR COOLING SYSTEM

FROM GT E XHAUST

T O IP T UR B IN E TO LP TU RB IN E FR OM H P T UR B IN E

EXHAUST

T O G T C OO LIN G

Figure 12. HRSG schematic for S107H/S109Hlow-pressure economizer for high thermal efficiency will require material that resists corrosion because feedwater passing through this section may have a high oxygen concentration, and the external tube surface temperature maybe below the exhaust gas dew point temperature. Figure 14 shows a three-pressure nonreheat HRSG with integral deaerator.Fuel characteristics affect combined-cycle performance in a variety of ways. High hydrogen content in fuels such as natural gas results in high water content in the combustion products. Water has a higher heat content than air or othercombustion products, so fuels with high hydrogen content increase output and efficiency. Ashbearing fuels foul the gas turbine and HRSG;therefore, equipment and system design considerations that accept fouling reduce plant output and efficiency. Sulfur content in the fuel may require adjustment in the temperature of thestack gas and the water entering the HRSG economizer to prevent condensation of corrosive sul

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 9 Combined cycle Net Plant Net Plant Heat Rate(LHV) Thermal Designation Power (MW) Btu/ kWhr kJ/ kWhr Efficiency (%, LHV) S106B (4) 64.3 6960 7340 49.0 S206B (4) 130.7 6850 7230 49.8 S406B (4) 261.3 6850 7230 49.8 S106FA (5) 107.1 6440 6795 53.0 S206FA (5) 217.0 6355 6705 53.7 S107EA (4) 130.2 6800 7175 50.2 S207EA (4) 263.6 6700 7070 50.9 S107FA (5) 262.6 6090 6425 56.0 S207FA (5) 529.9 6040 6375 56.5 S107FB (5) 280.3 5950 6280 57.3 S207FB (5) 562.5 5940 6260 57.5 S107H (6) 400.0 5690 6000 60.0 Notes: 1. Site conditions =59 F, 14.7 psia, 60% RH (15 C, 1.013 bar) 2. Steam turbine exhaust pressure = 1.2 inches Hg,A (30.48 mm Hg,A) 3. Performance is net plant with allowance for equipment and plant auxiliaries including those associated with a once-through cooling water system 4. Three-pressure, non-reheat, heat-recovery feedwater heating steam cycle 5. Three-pressure, reheat, heat-recovery feedwater heating steam cycle with integrated fuel, gas-heating system 6. Three-pressure, reheat, heat-recovery feedwater heating steam cycle with integrated turbine steam- and air-cooling and fuel-heating systems

Table 5. 60 Hz STAG product line performance Thermal Efficiency (%, LHV)

Steam Turbine Gas Turbine HRSG Exhaust LSB Exhaust Designation No . Frame No. Type No. Inches mm Config.

• Heavy Duty GT
S106B 1 PG6581 B 1 Non-Reheat, Unfired 1 23 584 Axial S206B 2 PG6581 B 1 Non-Reheat, Unfired 1 33.5 851 Axial S406B 4 PG6581 B 2 Non-Reheat, Unfired 2 33.5 851 Down S106FA 1 PG6101 FA 1 Reheat, Unfired 1 30 762 Axial S206FA 2 PG6101 FA 1 Reheat, Unfired 2 30 762 Down S107EA 1 PG7121 EA 1 Non-Reheat, Unfired 1 33.5 851 Axial S207EA 2 PG7121 EA 2 Non-Reheat, Unfired 2 33.5 851 Down S107FA 1 PG7241 FA 1 Reheat, Unfired 2 30 762 Down S207FA 2 PG7241 FA 2 Reheat, Unfired 4 30 762 Down S107FB 1 PG7251 FB 1 Reheat, Unfired 2 30 762 Down S207FB 2 PG7251 FB 2 Reheat, Unfired 4 30 762 Down S107H 1 PG7001 H 1 Reheat, Unfired 2 40 1016 Down

Table 6. 60 Hz STAG product line equipmentfuric acid. The increased stack gas temperaturerequired by higher sulfur content decreases output and efficiency. Performance variation withfuel type (hydrogen, ash and sulfur content typical of each) is presented in Table 12

. The STAG product line includes gas turbines with Dry Low NO x (DLN) combustors that can operate with stack gas NO x emission concentration as low as 9 ppmvd at 15% oxygen (15.5 g/GJ) without water or steam injection, when operating on natural gas fuel. Water or steam injection may be required to meet NO x emission requirements when operating on distillate oil fuel. Also, gas turbines are available with conventional, diffusion flame combustors operating with water or steam injection to meet NO x emission limits. Table 13 presents stack gas NO x emissions from gas turbines in typical STAG combined cycle systems for operation with DLN or diffusion flame combustors with natural gas fuel. The effect of water- or steam-injection on NO x abatement and thermal performance is also presented. Selective catalytic reduction (SCR) is a stack gas NO x reduction system that uses ammonia to react with NO x over a catalyst that reduces NO x to nitrogen and water. These systems increase the plant installation and operating cost, but 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 10 Combined cycle Net Plant Net Plant Heat Rate (LHV) Thermal Designation Power (MW) Btu/kWhr kJ/kWhr Efficiency (%, LHV) S106B (4) 64.3 6950 7340 49.0 S206B (4) 130.7 6850 7230 49.8 S406B (5) 261.3 6850 7230 49.8 S106FA (5) 107.4 6420 6775 53.2 S206FA (4) 218.7 6305 6650 54.1 S109E (4) 189.2 6570 6935 52.0 S209E (4) 383.7 6480 6840 52.7 S109EC (5) 259.3 6315 6660 54.0 S209EC (5) 522.6 6270 6615 54.4 S109FA (5) 390.8 6020 6350 56.7 S209FA (5) 786.9 5980 6305 57.1 S109H (6) 480.0 5690 6000 60.0

Notes: 1. Site conditions = 59 F, 14.7 psia, 60% RH (15 C), 1.013 bar) 2. Steam turbine exhaust pressure = 1.2 Inches HgA (30.48 mm HgA) 3. Performance is net plant with allowance for equipment and plant auxiliaries including those associated with a once- through cooling water system 4. Three-pressure, non-reheat, heat recovery feedwater heating steam cycle 5. Three-pressure, reheat, heat-recovery feedwater healing steam cycle with integrated fuel gas heating system 6. Three-pressure, reheat, heat-recovery feedwater heating steam cycle with integrated turbine steam and air coolin g and fuel heating systems. Table 7. 50 Hz STAG product line performance

Steam Turbine Gas Turbine HRSG Exhaust LSB Exhaust Designation No. Frame No. Type No. Inches mm Config.

• Heavy Duty GT

S106B 1 PG6581 B 1 Non-Reheat, Unfired 1 17 432 Axial S206B 2 PG6581 B 1 Non-Reheat, Unfired 1 33.5 851 Axial S406B 4 PG6581 B 2 Non-Reheat, Unfired 2 33.5 851 Down S106FA 1 PG6101 FA 1 Reheat, Unfired 1 26 660 Axial S206FA 2 PG6101 FA 2 Reheat, Unfired 1 42 1066 Axial S109E 1 PG9171 E 1 Non-Reheat, Unfired 1 42 1066 Down S209E 2 PG9171 E 2 Non-Reheat, Unfired 2 42 1066 Down S109EC 1 PG9231 EC 1 Reheat, Unfired 1 42 1066 Down S209EC 2 PG9231 EC 2 Reheat, Unfired 2 42 1066 Down S109FA 1 PG9351 FA 1 Reheat, Unfired 2 33.5 851 Down S209FA 2 PG9351 FA 2 Reheat, Unfired 4 33.5 851 Down S109H 1 PG9001 H 1 Reheat, Unfired 2 42 1066 Down

Table 8. 50 Hz STAG product line equipmentthey can reduce NO x to less than 9 ppmvd at 15% oxygen (15.5 g/GJ) for all combined-cycle systems in the product line. The SCR catalyst typically operates in the 570°F/300°C to 750°F/400°C temperature range, so the catalyst is typically installed within the high-pressure evaporator as shown in Figure 15. The ammoniainjection grid is installed upstream of the evaporator where the gas temperature is below the temperature at which ammonia oxidizes to form NO x . This provides intimate mixing of the ammonia and NO x as the gas passes through the pre-evaporator section. Carbon monoxide (CO) emissions are low at gas turbine loads above 50%, typically less than 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 11 Heat Recovery Feedwater

Heater Steam Cycle Non-Reheat Three-Pressure Reheat Three-Pressure Steam Turbine Size (MW) ≤ 40 > 40 <60 ≥60 > 60
Throttle Pressure (psig) 820 960 1200 1400-1800 (Kg/cm 2 ,g) (58) (68) (84) (98)
Throttle Temperature ( ° F) 40 Approach to Gas Turbine 1000-1050 ( ° C) (22) Exhaust Gas Temperature (538-566)
Reheat Pressure (psig) -- -- -- 300-400 (Kg/cm 2 ,g) -- -- -- (21-28)
Reheat Temperature ( ° F) -- -- -- 1000-1050 ( ° C) -- -- -- (538-566)
IP Admission Pressure (psig) 100 120 155 300-400 (Kg/cm 2 ,g) (7) (8) (11) (21-28)
IP Admission Temperature (° F) 20 Approach to Exhaust Gas Temperature (° C) (11) Upstream of Superheater
LP Admission Pressure (psig) 25 25 25 40 (Kg/cm 2 ,g) (1.8) (1.8) (1.8) (2.8)
LP Admission Temperature (° F) 20 Approach to Exhaust Gas Temperature (° C) (11) Upstream of Superheater Table 9. STAG product line steam turbine throttle and admission steam conditions

STEAM CYCLE NO X CONTROL • Single pressure • Water injection • Two pressure • Steam injection

• Three pressure* • SCR (NO X and/or CO) • Reheat • Dry Low NOx combustion* • Non-reheat CONDENSER DEAERATION • Water cooled (once-through system)*

• Deaerating condenser* • Water cooled (evaporative cooling tower) • Deaerator/evaporator integral • Air-cooled condenser

with HRSG FUEL HRSG DESIGN • Natural gas*

• Natural circulation evaporators* • Distillate oil • Forced circulation evaporators • Ash bearing oil

• Unfired* • Low BTU coal and oil-derived gas • Supplementary fired • Multiple fuel systems

* Base configuration Table 10. Power generation combined-cycle product line system options

STAG 207EA

STEAM CYCLE NET PLANT OUTPUT (%) NET PLANT THERMAL EFFICIENCY (%) THREE PRESSURE, REHEAT +0.7 +0.7 THREE PRESSURE, NON-REHEAT BASE BASE TWO PRESSURE, NON-REHEAT -1.0 -1.0 SINGLE PRESSURE, NON-REHEAT -4.7 -4.7

STAG 107EA

STEAM CYCLE NET PLANT OUTPUT (%) NET PLANT THERMAL EFFICIENCY (%) THREE PRESSURE, REHEAT BASE BASE TWO PRESSURE, REHEAT -1.1 -1.1 THREE PRESSURE, NON-REHEAT -1.2 -1.2 TWO PRESSURE, NON-REHEAT -2.0 -2.0
Table 11. Performance variation with steam cycle5--25 ppmvd (9-43 g/GJ). Low CO emissions are the result of highly-efficient combustion. Catalytic CO emission abatement systems are also available, if required, for lower emission rates. The CO catalyst is installed in the exhaustgas path, typically upstream of the HRSG superheater. Options such as compressor inlet cooling,steam or water injection for power augmentation, HRSG supplementary firing and gas turbine peak load capabilities are available for combined-cycle plant power enhancements. They are generally applied primarily for peak period capacity additions. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 12 Figure 13. Two-pressure non-reheat steam cycle with forced circulation HRSG

GT21836A Figure 14. Three-pressure non-reheat HRSG with integral deaerator

STAG 209E

FUEL NET PLANT OUTPUT (%) NET PLANT THERMAL EFFICIENCY (%)

NATURAL GAS BASE BASE

DISTILLATE OIL -3.0 -2.1

RESIDUAL OIL -9.3 -7.6

NOTES 1. OPERATING POINT = BASE LOAD 2. TWO PRESSURE, NON-REHEAT RECOVERY FEEDWATER HEATING SYSTEM CYCLE Table 12. STAG combined-cycle performance variation with fuel characteristicsCompressor inlet cooling that uses evaporative cooling is an effective means of adding plant capacity for applications with high ambient air temperature and low relative humidity. An 85% effectiveness evaporative cooler is expected toincrease plant output by about 5% during operation at 90°F / 32°C and 30% relative humidity site conditions. Evaporative and mechanical chiller systems may be used to cool gas turbine inlet air to as low as 45°F / 7°C. These inlet cooling systems can achieve up to 11% capacity increase during operation at site conditions of 90°F / 32°C and 30% relative humidity. Evaporative cooling and chilling systems do not improve combined-cycleplant efficiency; however, they may provide economic peak power addition during warm summer periods.Supplementary firing of the HRSG can be utilized to increase steam turbine capability by as much as 100%. This will increase plant capacity by about 25%. Cogeneration of power and 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 13 Gas Turbine MS7001EA MS7001FA Combustion System DLN Diffusion Flame DLN Diffusion Flame NOx PMVD at 15% O2 (g/GJ) 9 (15.5) 160 (275) 42 (72) 25 (43) 9 (15.5) 212 (365) 42 (72) Diluent Injection Water/Fuel by Wt 0 0 0.81 - 1.04 - 0 0 0.89 -
Steam/Fuel by Wt 0 0 - 1.22 - 1.58 0 0 - 1.62

STAG Plant Performance Net Power ( ∆ %) Base Base +3.5 +1.0 +5.0 +1.1 Base Base +5.4 +2.8 Net Heat Rate ( ∆ %) Base Base +3.6 +2.1 +5.2 +3.4 Base Base +3.9 +3.1
Steam Cycle Non-Reheat, Three Pressure Reheat, Three Pressure Notes: 1. Site Conditions 59 ° F, 14.7 psia, 60% RH (15 ° C, 1.013 bars) 2. Fuel – Natural Gas
Table 13. Effect of NO x control on combined-cycle performance

GT122107B
Figure 15. Three-pressure reheat HRSG with SCRprocess energy is usually the incentive for HRSG supplementary firing; however, peaking capacity credits, or leveling fuel consumptionover the ambient temperature range to accommodate “take-or-pay” fuel contracts may also justify this option. The incremental efficiency for power produced by supplemental firing is in the 34–36% range based on the lower heating value of the fuel.
While gas turbine water or steam injection can be applied to enhance plant output as well as reduce NO x emissions, plant efficiency is degraded.
Gas turbine peak load capability is available with many gas turbine configurations and can add 3–10% combined-cycle plant capacity. This may be the most economic approach to small capacity additions for short periods of time because peak load operation significantly impacts gas turbine parts life and maintenance
cost. Table 14 summarizes the performanceimpact of these combined-cycle power enhancement options.
Combined-cycle systems can be integrated withgasification systems to form efficient coal- or oilfired power plants with outstanding environmental performance. The standard modules in the STAG combined-cycle product line can bereadily adapted to integrated gasification combined cycles (IGCCs).
Figure 16 shows a diagram of an advanced technology “H” platform combined-cycle IGCC system with oxygen-blown gasifier and integration of the air separation unit with the gas turbine.This advanced technology IGCC system promises to be an economical power generation system that can fire coal, petroleum coke, heavy residual oil and other solid or low-grade liquid fuels. The range of ratings for the advanced technology IGCC plants is as follows:

Net LHV IGCC Capacity Thermal Eff. Unit Frequency (Hz) Range (MW) Range (LHV)

STAG 107H 60 400-460 49-51 % STAG 109H 50 480-550 49-51%
The capacities and efficiencies are shown asranges because they vary with the type of gasifiers, gas clean-up systems, air and steam cycle integration, coal or other fuel analysis, and fuel moisture content. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 14 

### Typical Performance Impact Power Enhancement Option ∆Output ∆ Heat Rate Base Configuration Base Base Evaporative Cooling GT Inlet Air (85% Effective Cooler) +5.2% -

Chill GT Inlet Air to 45 ° F +10.7% +1.6% GT Peak Load +5.2% -1.0% GT Steam Injection (5% of GT Air Flow) +3.4% +4.2% GT Water Injection (2.9% of GT Air Flow) +5.9% +4.8% HRSG Supplementary Firing +28% +9% Notes: 1. Site Conditions = 90 ° F, 30% RH 2. Fuel = Natural Gas 3. Three Pressure, Reheat Steam Cycle
Table 14. STAG system power enhancement options

## STAG Combined-Cycle Major EquipmentThe major equipment for STAG combinedcycle electric power generation systems includesthe line of packaged gas turbine power generation units, unfired HRSGs, steam turbine-generators, and controls. This is a line of proven, reliable equipment with excellent performance characteristics for combined-cycle systems. This equipment includes gas turbine generators and steam turbine generators manufactured by GE as well as HRSGs and controls selected to form a coordinated combined-cycle system for each application. Features of the major equipmentthat are significant for efficient, reliable combined-cycle systems are presented in the following discussion.



## Gas Turbines The ratings of GE gas turbines applied in theSTAG combined-cycle product line are presented in Table 15

. Figure 17 shows a cross-section ofthe PG7121EA gas turbine typical of GE gas turbines with 2035°F / 1113°C firing temperature. The PG9171E gas turbine firing temperature is 2055°F / 1124°C. A cross-section of the PG9351 FA gas turbine is shown in Figure 18 , which is typical of the GE gas turbines with 2420°F / 1327°C firing temperature, including the PG7241FA. The next generation “FB” and “H” platform gasturbines are expected to be in commercial service in the first half of this decade. The cross-section of the “H” gas turbine is shown in Figure 19. This new machine features closed-loop steam cooling for the first and second stages of itsfour-stage turbine. In order to optimize performance at the 2600°F / 1426°C firing temperature, a higher-pressure ratio compressor derived from the GE CF680C2 aircraft engine is utilized. These gas turbines have the following features that uniquely suit them for combined-cycle applications:

■ The key performance characteristic of the gas turbine that influences combined-cycle performance is specific power. Specific power is the power produced by the gas turbine per unit of airflow (kW output per lb/sec of compressor airflow). Combined-cycle thermal efficiency 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 15 GT25099 Figure 16. Advanced technology IGCC systemincreases as gas turbine specific power increases, as shown in Figure 20. This figure shows that gas turbine firing temperature is the primary determinant of specific power. Improvements in combined-cycle thermal efficiency have developed primarily through the increases in gas 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 16 Heavy-Duty Output (kW) Frequency (Hz)
PG6581 B 42,100 50 and 60 PG6101 FA 70,140 50 and 60 PG7121 EA 85,400 60 PG7241 FA 171,700 60 PG9171 E 123,400 50 PG9231 EC 169,000 50 PG7251 FB 184,400 60 PG9351 FA 255,600 60 MS7001 H * 60 MS9001 H * 50

Notes: 1. Fuel = Natural Gas 2. Site Conditions = ISO Ambient 3. Operating Mode = Base Load, Simple Cycle *Single-Shaft STAG Combined Cycle Configuration Only Table 15. GE gas turbines applied to STAG product line

Figure 18. MS9001FA heavy-duty gas turbine Figure 17. MS7001EA heavy-duty gas turbineturbine firing temperature, which have resulted from the development of high-temperature / high strength materials, corrosion-resistant coatings, and improved cooling technology. Commercial development of combined cycles and improvements in combined-cycle efficiency have proceeded in parallel with advances in gas turbine technology.
■ STAG systems that utilize the “F” technology gas turbines achieve net thermal efficiencies of 53% (LHV) or greater. STAG systems that utilize “H” technology gas turbines achieve net thermal efficiencies of 58–60% (LHV). These gas turbines have a rated firing temperature of 2420°F / 1327°C and 2600°F / 1426°C, respectively. The “FA” technology turbine has a 15.5 pressure ratio, whereas the “H” technology turbine has a 23.0 pressure ratio. These designs provide the highest gas turbine specific power for this firing temperature. High specific power provides the lowest simple-cycle installed cost in addition to high combined-cycle efficiency.
■ The exhaust gas temperature range of 1000–1100°F / 538–566°C is uniquely suited to efficient combined cycles because it enables the transfer of heat from exhaust gas to the steam cycle to take place over a minimal temperature difference. This temperature range results in the maximum in thermodynamic availability while operating with highest temperature and highest efficiency steam cycles.
■ Multiple can-annular type combustors with film and impingement cooling meet the environmental requirements for applications throughout the world. They provide reliable operation at high firing temperatures while burning fuels that range from natural gas to residual oil.
■ Turbine materials, coatings and cooling systems enable reliable operation at high firing temperatures. This achieves high gas turbine specific power and high efficiency for combined-cycle systems. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 17 

### Features



# • Closed Loop Steam Cooling



# • 4-Stage Turbine



# • Compressor Scaled From Proven Design



# • Dry Low No x 

### Combustor GT25129 Figure 19. “H” gas turbine cross-section■ Most GE current product line gasturbines are configured with openloop cooling of the turbine hot gas path. Hot gas path components are in large part cooled by film cooling that uses air supplied from the compressor. This results in a significant exhaust gas steam temperature drop across the first stage nozzle, and requires significant “chargeable air” to cool the turbine stages. The temperature drop across the first stage nozzle and the chargeable cooling losses increase as turbine inlet temperature increases.
■ The advanced “H” platform gas turbine is configured with an integrated closed-loop steam-cooling system. The change in strategy to the closed-loop, steam-cooled system without film cooling allows higher turbine inlet temperatures to be achieved without increasing combustion temperature. This is because the temperature drop across the first stage nozzle is significantly reduced, as shown in Figure 21 . Gas turbine NO x emissions can then be maintained at low levels at increased turbine inlet temperature. Another important benefit of the integrated closed-loop, steam-cooling system is the elimination of “chargeable cooling air” for the first- and second-stage rotating and stationary airfoils. This results in two percentage points improvement in combined cycle thermal efficiency.
■ Factory packaging and containerized shipment of small parts achieve low installed cost and short installation time. ■ Reliable operation results from evolutionary design development that improves parts and components, a high-quality manufacturing program that includes operational factory testing of the gas turbine and accessory systems, follow-up service support by experienced installation and service personnel, and effective spare parts support. ■ Low maintenance costs are the result of the combination of the above features and a design to allow convenient access. These include borescope ports to permit inspection of key parts and components without dismantling the equipment.
■ The heavy-duty gas turbine product line has fuel flexibility provided by accessory systems, combustion systems, and turbine components, which enable utilization of a wide range of liquid and gaseous fuels. These include 150-400 Btu/scf (6520-16,850 kj/nm 3 ) gaseous fuels, including those derived from coal, coke, or heavy petroleum products, and liquid fuels including naphtha, light distillates, heavy distillates, crude oil and residual oil.



## HRSG HRSGs in the GE STAG product line are unfired and feature modular construction with finned-tube heat transfer surface and natural or forced-circulation evaporators. Figure 22 illustrates a natural circulation HRSG with modular construction. An installation showing two ofthese HRSGs operating with MS7001EA gas turbines is shown in Figure 23

. Figure 24 illustrates the modular-construction, forced-circulation HRSG, and Figure 25 shows an installation of 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (81000) 18this type HRSG in a STAG 107EA system.
Each gas turbine exhausts to an individual HRSG. For STAG systems with a MS6001B gas turbine, the standard gas ducting is designed so that two gas turbines exhaust to a single HRSG. These STAG systems are also available with oneHRSG per gas turbine. The HRSG and auxiliaries are designed for the specific operatingrequirements of the STAG combined cycle system. Design features include:

■ Exhaust gas bypass system to provide fast startup and shutdown and flexibility of operation for multi-shaft STAG systems. Exhaust gas bypass systems are not used with single-shaft STAG units.
■ Flexible tube support system to enable fast startup and load following

capability.
■ Low gas side pressure drop for optimum gas turbine performance.
■ Large, factory-tested modules that can be shipped to provide short 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 19 GT25454 Figure 20. Gas turbine performance thermodynamics

GT25134 Figure 21. Impact of stage-one nozzle cooling methodinstallation time and low construction
cost. ■ Fuel flexibility provided by the ability to operate reliably and efficiently, using exhaust gas from gas turbines that burn fuels ranging from natural gas to residual oil.


## Steam Turbine GE offers a complete line of steam turbines for combined-cycle applications. Two or more steam turbine selections are available for each STAG product line offering. Steam turbineswith different exhaust annulus areas are available to permit optimization to meet specific condenser cooling conditions. Steam turbines with large exhaust annulus areas are more expensive, but provide increased capability andmay be the most economic selection for applications with low steam turbine exhaust pressure. For applications in which steam turbineexhaust pressures are high, small exhaust annulus-area steam turbines provide comparable or higher capability and low cost, and therefore are the economic choice. Figure 26 illustrates 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 20 GT11717 Figure 22. Natural-circulation HRSG modular construction

Figure 23. Two natural-circulation HRSGs operating with MS7001EA gas turbinesthe performance difference for four last-stage buckets that are available for the STAG 107FAcombined cycle. Steam turbine last-stage bucket lengths for the STAG product line steam turbines range from 14.3 inches / 363 mm to 42 inches / 1067 mm.
Because there are no extractions for feedwater heating, and steam is generated and admitted to the turbine at three pressures, the flow at the exhaust is approximately 30% greater than the throttle flow. The turbine’s last stage generates up to 15% of the steam turbine output, so theefficiency of the turbine's last stage and the sizing of the exhaust annulus area are particularly important for combined-cycle applications. As with all modern GE steam turbine last-stage buckets, the continuously-coupled design is used for high efficiency and reliability. Continuously-coupled designs permit the use of many relatively slender blades with narrow, 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 21 GT00477C Figure 24. Forced-circulation HRSG modular construction

Figure 25. Forced-circulation HRSG with PG7111EA gas turbinesclosely-controlled flow passages, particularly in the critical high-velocity tip region. Covers reduce tip leakage losses, provide damping, and help to maintain control of the flow passage.Steam turbine designs for high exhaust pressure operation typical of those that are needed for air-cooled condenser operation at high ambient temperature are available. These steamturbine designs are capable of reliable and efficient operation at exhaust pressures up to 15 inches Hg,a/381mm Hg,a. Advanced 3D aero packages incorporate advanced vortex design, contoured inlet section sidewalls, and additional radial tip spill strips forsteam turbines larger than 80 MW, which contribute to maximum combined cycle thermodynamic efficiency. The STAG combined-cycle product line steam turbines include axial exhaust and downexhaust configurations. Axial exhaust is preferred for the single-flow steam turbines, typically applied in the small capacity STAG systems. Figure 27 shows a single-flow axial exhaust steam turbine.A line of reheat steam turbines designed specifically for combined-cycle service is available for STAG systems employing the “EC,” “F,” and “H” technology gas turbines. The single-shaft STAG 107FA, STAG 109FA and STAG 109H are designed as integrated machines with a solid turbine/generator coupling and a single-thrust bearing that includes common lubrication andhydraulic and control systems for both gas turbine and steam turbine. A two-flow reheat steam turbine is shown in Figure 28

.Steam turbines specially designed for combined-cycle service have features that include:
■ Assembled modules that can be shipped and assembled with a low profile installation that reduces installation time and cost. (Building cost, for indoor installation, also is reduced with the low profile design.)
■ Access for borescopic inspection of buckets and nozzles without removal of the turbine upper casing.
■ Fast startup and load-following capability provided by minimum shaft diameter in the vicinity of the first stage, large fillets between wheels and rotor, long coupling spans, vertical flexible plate support near the centerline with keys for maintenance of alignment, and off-shell valves with full-arc steam admission.

■ All main steam, cold reheat and hot reheat steam pipes connect to the lower half of the shell. This facilitates removal of the upper half shell for maintenance, and eliminates the need for bolted connections in a high temperature piping.
■ Sliding pressure operation with the control valves wide open. A control stage at the inlet is, therefore, not 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 22 Figure 26. STAG steam turbine last-stage bucket selectionrequired.
■ Applications at 1800 psig/124 bar,g use a single wall construction at the high-pressure stages as well as the reheat inlet. With 2400 psig/165 bar,g applications, a short inner shell encloses the early high-pressure stages. This reduces the load on the horizontal joint bolting and reduces the thickness of the shell flange.



## Generators Generators for the STAG combined-cycle product line gas turbines and steam turbines are factory assembled and tested. Air-cooled generators are standard for the smaller STAG systems using PG6581B, PG6101FA and PG7121EA gasturbines. They may be open-ventilated or totally enclosed water-to-air cooled. If open-ventilated, they are equipped with self-cleaning air filters for desert or other dusty or dirty environments, as shown in Figure 29 . Hydrogen-cooled generators are standard for the single-shaft andlarger multi-shaft STAG systems. The hydrogencooled generators can be cooled by plant-cool

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 23 GT24388 Figure 27. Non-reheat, single casing, axial exhaust steam turbine

Figure 28. Two-flow, reheat steam turbineing water or by ambient air with water-to-air heat exchangers. Figure 30 shows a typical packaged hydrogen cooled generator for gas turbine application.



## ControlsThe STAG combined-cycle plant has a distributed digital control system with a redundant data highway. The station operator consoles provide interactive color graphic displays of the overall STAG plant, with sufficient detail to enable the operator to conveniently operate the plant.The control systems for multi-shaft and singleshaft STAG combined-cycle system fundamentally follow the same principle objectives of simplicity, easy starting, automated operation andsuperior load following ability. All main components of the combined-cycle plant have individual control panels and interfaces that relay information and instructions to and from the plant operator through data highways to the operator console. The operator console will have a detailed graphic display with a high levelof detail that enables convenient and informative interaction with the plant as required. The single-shaft power train is a simple tandem arrangement that does not include an exhaust bypass system and is solidly coupled to one generator with a common overspeed protection device with less auxiliary equipment. Figures 31 and 32 show block diagrams for multi-shaft and single-shaft arrangements. The heat recovery combined cycle is a simple system with a minimum of control loops, as shown by the control diagram (Figure 33) for a single-pressure, multi-shaft STAG system. Thesimplicity of this system, coupled with wellestablished, automated operation of system components, enables effective automation of 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 24 Figure 29. Air-cooled generator with self-cleaning air filter

Figure 30. Typical packaged hydrogen-cooled generatorthe complete power plant. This minimizes the number of control room operators. Most STAG systems operate with only one control room operator and one roving operator. The multi-shaft STAG control is configured to enable automated startup and operation after remote manual starting of plant auxiliaries,remote manual operation of each major component, or operation of the gas turbine-generator units from local-control compartments. Thecontrol configuration enables maximum availability because the plant can be operated remotely with no additional control room operators. The equipment protection system is provided within the unit controls, so normal protection is maintained during all modes of operation, including local or remote manual operation. The single-shaft STAG unit control system is amicroprocessor-based controller that coordinates the operation of the components in eachintegrated combined-cycle unit and communicates with the plant control. Because of the simple steam cycle, the tandem coupling of the gas 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 25 Figure 31. Distributed control system for plant with multi-shaft STAG combined cycle

Figure 32. Distributed control system for plant with single-shaft STAG combined cycleand steam turbines to a single generator, and the elimination of the HRSG exhaust-gas,bypass system, the single-shaft STAG combinedcycle control is very simple. Starting, operation, and shutdown of individual units are automatic. Single-shaft STAG units are controlled by a localunit control system that is coupled to the central control room operator's console by a datahighway. One control room operator can operate one or more single-shaft STAG combinedcycle units with this type of control system and the aid of one local operator.



## Auxiliaries The STAG product line ratings are based on plants with once-through systems (seawater orriver water) for steam turbine condenser cooling. STAG combined-cycle configurations are also available for operation with a wide range ofowner-specified auxiliaries, including evaporative cooling towers and air-cooled condensers.Plant capability and efficiency with these systems is expected to be lower because steam turbine exhaust pressure and cooling system auxiliary power consumption are increased.


## Plant Operation Typical STAG plant performance variation with ambient air temperature is illustrated by theheat rate and power-output capability ambienttemperature effect curves in Figure 34. Low heat rate throughout the ambient-air-temperature range is typical of these plants. The low heatrate and increase in output as ambient temperature decreases are achieved by the gas turbinecharacteristics and optimum equipment matching. Gas turbine exhaust flow and temperature varywith ambient temperature and barometric pressure. Steam production and steam turbine output vary with the exhaust gas flow and temperature supply to the HRSG. Steam turbines areselected to suit specific application requirements. The steam turbines in the standard systems are sized so that their rated flow matches the steam production. Excellent part-load heat rate is achieved on multi--shaft systems or multiple single-shaft units by sequentially loading gas turbines to meet system requirements (Figure 35). Thiscurve also shows that the plant can operate efficiently following system load with all gas turbines operating. The heat rate increases only 1% at approximately 80% of rating. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 26 Figure 33. Multi-shaft STAG control diagramThe modulated, inlet guide vanes (IGV) on the gas turbine compressor contribute significantly to the excellent part-load performance. The inlet guide vanes are modulated to control air flow in the power plant between the “hash mark” and the point marked “B.” Varying the air flow maintains nearly constant gas turbine firing temperature so that the thermodynamic quality of the cycle remains essentially constant.The stack and condenser losses vary almost proportionally with output, so that the heat rate remains almost constant. At loads below thehash mark, the gas turbine operates with constant air flow, and firing temperature is reduced as load is reduced. Fast starting and loading is characteristic of STAG combined-cycle generation systems. This enables them to operate in mid-range, with daily start peaking service as well as baseload. Typically, STAG systems can achieve full load within one hour during a hot start and within approximately three hours for a cold start. Multi-shaft STAG systems allow the gas turbines to start independently of the steam cycle andprovide about 65% of the plant capability within 15–25 minutes, depending on the size of the gas turbine, for hot, warm, and cold starts, as illustrated in Figure 36. Single-shaft STAG systems are started and loaded to full capacity in about the same time period as the multi-shaft STAG systems. The startup sequence and load profile for the single-shaft systems differ because the gas and steam turbines are startedas a single integrated unit and not as two separate units. Single-shaft STAG startup is illustrated in Figure 37

. 

## Plant Arrangements The STAG combined-cycle equipment can be adapted to installation requirements demandedby varying climactic conditions, system configu

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 27 Figure 34. Combined-cycle, ambient air temperature effect curve

Figure 35. STAG 200 part-load performancerations and owner/operator preferences. The equipment is suitable for outdoor installations, semi-outdoor installations, or fully-enclosed installations. Plant arrangements have been designed for each STAG system.Plan views of STAG combined-cycle arrangements are shown in Figure 38 (multi-shaft, S406B), Figure 39 (multi-shaft, S207EA), Figure 40 (single-shaft S109E), Figure 41 (multi-shaft, S207FA), and Figure 42 (single-shaft, S107FA). An elevation of the single-shaft S107FA is shown in Figure 43

. Figure 44 shows the S107H and S109H plan and elevation views. The S107H provides about 58% increase in combined-cycle power output with only about 10% increase in footprint area. A 220 MW STAG 207E installation is shown in Figure 45

. Figure 46 presents a STAG 109FA combined cycle installation. Figure 47 shows a 4000 MW installation with eight STAG 107F and four STAG 207FA systems at one site. These arrangements have indoor turbine-generator

equipment and outdoor HRSGs. Figure 48shows a plant with two STAG multi-shaft combined-cycle units in an indoor installation. For outdoor installations, the standard gas turbine enclosures are weatherproof, and weatherproof lagging is available for the steam turbines. 

## Installation
The short installation time and low installation cost of STAG combined-cycle systems are keyfeatures contributing to economical power generation. This is due to factory packaging of all major components and containerized shipmentof small parts. In addition to low direct construction cost, the short installation time reduces interest payments during construction. The standard factory modules and standardized designs also reduce plant engineering time and
cost. The time from order to commercial operation for pre-engineered, standardized STAG designs is typically 24 months, not including permitting time. The multi-shaft STAG systems can be installed in two phases to reduce the time between order and initial power production. The gas turbines contribute 65% of the plant capacity. Typically, the gas turbine can be installed in less than 18 months to provide power generation while the steam system is being installed. Figure 49 is a typical two-phase multi-shaft STAG combined-cycle installation schedule. 

## Utility Load Growth Power generation economics can be enhanced by the installation of generation capacity in small increments as utility load grows. STAGcombined-cycle plants fit this economical pattern because efficient, low-cost plants are available in small blocks of generating capacity.Flexibility is also available with the pro-generation approach to capacity addition. Initial natural gas/distillate oil-fired, simple-cycle gas turbine installations can be converted to combinedcycle later, when power demands require capacity increases. Plot plan area for the steam cycle equipment and transmission line capability arethe main considerations during the initial com

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 28 GT08936B Figure 36. Multi-shaft STAG starting times

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 29 Figure 37. Single-shaft STAG starting times

Figure 38. STAG 406B combined-cycle plan

Figure 39. STAG 207EA combined-cycle plan

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 30 Heat Recovery Generator

Generator

Steam Turbine

Condenser Gas Turbine Figure 40. STAG 109E combined-cycle plan

Figure 41. STAG 207FA multi-shaft combined-cycle plan

Figure 42. Four-unit STAG 107FA combined-cycle plan

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 31 Figure 43. STAG 107FA single-shaft combined-cycle elevation

GT25050 Figure 44. Single-shaft S107H and S109H plan and elevation

Figure 45. STAG 207E installationmitment for simple-cycle gas turbines. Future conversion to coal-derived fuels also is anoption for dealing with the long-range uncertainties of conventional fuel availability and price.


## Thermal Energy and Power System Product Line The product line of thermal energy and powercombined-cycle systems (cogeneration and district heating systems) are designed with structured flexibility to provide a wide range of power and thermal energy capacities to suit varied application requirements. The most commonly supplied systems are:
■ Steam generation at process conditions with HRSG (no steam turbine)
- Unfired HRSG - Supplemental-fired HRSG
■ HRSG and non-condensing steam turbine exhausting to process - Unfired, one-pressure HRSG - Unfired, two-pressure HRSG - Supplemental-fired, one-pressure HRSG
■ HRSG with extraction/condensing steam turbine - Unfired, one-pressure HRSG - Unfired, two-pressure HRSG - Supplemental-fired, one-pressure HRSG The capabilities of the thermal energy and power systems are unique for each gas turbine frame size, as well as each set of process steam conditions for systems with both unfired process HRSGs and unfired HRSGs that have non-condensing steam turbines. The systems 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 32 Figure 46. Indoor S109FA installation

Figure 47. 4000 MW multi-shaft STAG installationwith fired HRSGs and condensing steam turbines provide extraordinary flexibility in both thermal energy and power generation capacity for each gas turbine frame size. The performance characteristics include thenet plant power, LHV heat content in fuel consumed, thermal energy in steam to process, and thermal efficiency and fuel charged to power (FCP). The thermal efficiency for these systems is calculated by the following equation:

η TH = 100 x (Q p + Q TE

) Q

F Symbols: η TH = Thermal efficiency - LHV (%) QF = LHV heat content of fuel consumption (Btu/hr, kJ/hr) Qp = Net power output (Btu/hr, kJ/hr) QTE = Thermal energy in process steam (Btu/hr, kJ/hr)
The fuel charged to power (FCP) is a useful parameter for comparing an integrated thermal energy and power system with separate systems generating the same power and thermal energy. For this comparison, the LHV heat content of fuel that would be consumed by a conventionalfired boiler in producing the same thermal energy is subtracted from the LHV heat consumptionof the integrated thermal energy and power system. The resulting FCP can then be compared with the heat rate of a separate power generation facility. This will assess the relative performanceof the integrated thermal energy and power system with separate thermal energy and powergeneration systems. FCP is calculated by the following equation:

FCP = 100 x (Q p - [Q TE

/ η

B ]) p Symbols: FCP = Fuel charged to power = LHV 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 33 Figure 48. Two 207FA multi-shaft combined-cycle installation

Figure 49. Typical multi-shaft, combined-cycle project schedule(Btu/kWH, kJ/hr) QF = LHV heat content of fuel consumption (Btu/hr, kJ/hr) QTE = Thermal energy in process steam (Btu/hr, kJ/hr) η B = LHV efficiency of fired boiler producing equivalent thermal energy (%) P = Net electrical output (kW)
Cycle diagrams for thermal energy and power combined cycle with steam generation at process conditions is presented in Figure 50

. These systems include generation of steam at process conditions. Figure 50 shows combinedcycle cogeneration systems that produceprocess steam with an unfired or supplementary-fired HRSG. HRSG design for supplementary firing provides the maximum process steam energy supply. Figure 51 shows combined-cycle cogeneration systems that are equipped with non-condensing steam turbines.Many variations of these systems can be furnished to satisfy specific process plant energy requirements, including:

■ Single automatic-extraction steam turbines to efficiently supply steam at two or three pressures.

■ Multi-pressure HRSGs to supply steam at multiple-pressure and temperature conditions. The most flexible thermal energy and power systems are those that include extraction condensing steam turbines. Simplified cycle diagrams for typical systems with single automatic extraction are shown in Figure 52. This system has the capability to operate at lower process steam demands while using the excess steam generation to produce power in the condensing section of the steam turbine. These systems can be furnished with double automatic extraction steam turbines and multiple-pressure HRSGs to satisfy specific process steam requirements.



## Engineered Equipment PackageThe GE Combined-Cycle Engineered Equipment Package (EEP) is a unique combination of equipment and services. It provides the owner with a plant performance guarantee and warranty of operation, and the ability to service the complete power generation system, as well as the capability to customize the plant design, auxiliaries, and structures. This is achieved byincluding in the GE scope the major combined

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 34 Figure 50. Cycle diagrams – thermal energy and power combined cycle with steam generation at process conditionscycle equipment that requires close coordination for assurance of meeting the performance and operating objectives. The equipment scope split between GE and the owner is shown in Table 16

.The services and software scope split is presented in Table 17 . Key elements in the GE EEP scope are the combined-cycle system design and the interface definition that enable the owner ,or the owner’s architect-engineer or engineerconstructor, to design the plant to meet project specific requirements. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 35 Figure 51. Cycle diagrams – thermal energy and power combined cycle with non-condensing steam turbine

Figure 52. Cycle diagrams – thermal energy and power combined cycle with extraction/condensing steam turbines

## ConclusionThe STAG combined-cycle product line, including power generation systems and thermal energy and power systems ranging from 60 MW to 750 MW, are efficient, low-cost systems that meet the environmental requirements of allcountries. The GE combined cycle EEP provides assurance of satisfying performance andoperating objectives while allowing a customized plant that incorporates the owner'spractices and preferences. The attractive economics, reliability, and operating flexibility of these systems recommend their consideration for all power generation applications. 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 36 GENERAL ELECTRIC

• GAS TURBINE(S)

• STEAM TURBINE(S)

• GENERATOR(S)

• HEAT RECOVERY STEAM GENERATOR(S)

• PLANT CONTROLS

OWNER

• MECHANICAL AUXILIARIES

• ELECTRICAL AUXILIARIES

• MAIN ELECTRICAL CONNECTIONS

• BALANCE OF PLANT

– FOUNDATIONS AND STRUCTURES

– SWITCHYARD

– FUEL HANDLING AND STORAGE

– PLANT COOLING SYSTEM

– CONSTRUCTION MATERIALS

– SITE PREPARATION MATERIALS

Table 16. Equipment scope split with engineered equipment package General Electric

• Plant performance and environmental guarantee

• Combined cycle system design and warranty

• Balance of plant equipment functional specifications

• Equipment interface drawings

• Steady state and dynamic interface definition

• Equipment operation and maintenance

• Operation and maintenance training

• Construction and operation per mit s upport

• Performance and environmental test support

Owner

• Construction and operation per mits

• Plant design

• Plant construction

• Plant start-up, co mmissioning and operation

• Performance and environmental testing

• Site preparation

• Project administration
Table 17. Services and software split with engineered equipment package

## List of Figures Figure 1. STAG system configurations Figure 2. Generalized combined-cycle performance capability Figure 3. Single-pressure non-reheat cycle diagram Figure 4. Single-pressure non-reheat HRSG diagram Figure 5. Typical exhaust gas/steam cycle temperature profile for single-pressure system Figure 6. Typical exhaust gas/steam cycle temperature profile for three-pressure system Figure 7. Three-pressure non-reheat cycle diagram Figure 8. Three-pressure non-reheat HRSG diagram Figure 9. Three-pressure reheat cycle diagram Figure 10. Three-pressure reheat HRSG diagram Figure 11. STAG 107H/109H cycle diagram Figure 12. HRSG schematic for S107H/S109H Figure 13. Two-pressure non-reheat steam cycle with forced circulation HRSG Figure 14. Three-pressure non-reheat HRSG with integral dearator Figure 15. Three-pressure reheat HRSG with SCR Figure 16. Advanced technology IGCC system Figure 17. MS7001EA heavy-duty gas turbine Figure 18. MS9001FA heavy-duty gas turbine Figure 19. “H” gas turbine cross-section Figure 20. Gas turbine performance thermodynamics Figure 21. Impact of stage-one nozzle cooling method Figure 22. Natural-circulation HRSG modular construction Figure 23. Two natural-circulation HRSGs operating with MS7001EA gas turbines Figure 24. Forced-circulation HRSG modular construction Figure 25. Forced-circulation HRSG with PG7111EA gas turbines Figure 26. STAG steam turbine last-stage bucket selection Figure 27. Non-reheat, single casing, axial exhaust steam turbine Figure 28. Two-flow, reheat steam turbine Figure 29. Air-cooled generator with self-cleaning air filter Figure 30. Typical packaged hydrogen-cooled generator Figure 31. Distributed control system for plant with multi-shaft STAG combined cycle Figure 32. Distributed control system for plant with single-shaft STAG combined cycle 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 37Figure 33. Multi-shaft STAG control diagram Figure 34. Combined-cycle, ambient air temperature effect curve Figure 35. STAG 200 part-load performance Figure 36. Multi-shaft STAG starting times Figure 37. Single-shaft STAG starting times Figure 38. STAG 406B combined-cycle plan Figure 39. STAG 207EA combined-cycle plan Figure 40. STAG 109E combined-cycle plan Figure 41. STAG 207FA multi-shaft combined-cycle plan Figure 42. Four-unit STAG 107FA combined-cycle plan Figure 43. STAG 107FA single-shaft combined-cycle elevation Figure 44. Single-shaft S107H and S109H plan and elevation Figure 45. STAG 207E installation Figure 46. S109FA indoor installation Figure 47. 4000 MW multi-shaft STAG installation Figure 48. Two 207FA multi-shaft combined-cycle installation Figure 49. Typical multi-shaft, combined-cycle project schedule Figure 50. Cycle diagrams - thermal energy and power combined cycle with steam generation at process conditions Figure 51. Cycle diagrams - thermal energy and power combined cycle with non-condensing steam turbine Figure 52. Cycle diagrams - thermal energy and power combined cycle with extraction/ condensing steam turbines 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 38

## List of Tables Table 1. STAG combined-cycle power generation system features Table 2. STAG combined-cycle thermal energy and power system features Table 3. STAG combined-cycle system designations Table 4. STAG power generation combined-cycle base configuration Table 5. 60 Hz STAG product line performance Table 6. 60 Hz STAG product line equipment Table 7. 50 Hz STAG product line performance Table 8. 50 Hz product line equipment Table 9. STAG product line nominal steam turbine throttle and admissions steam conditions Table 10. Power generation combined-cycle product line system options Table 11. Performance variation with steam cycle Table 12. STAG combined-cycle performance with fuel characteristics
Table 13. Effect of NO x control on combined-cycle performance Table 14. STAG system power enhancement options Table 15. GE gas turbines applied to STAG product line Table 16. Equipment scope split with engineered equipment package Table 17. Services and software scope split with engineered equipment package 

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 39

## GE Combined-Cycle Product Line and Performance

GE Power Systems ■ GER-3574G ■ (10/00) 40