Repowering of Thermal Power 

Fully-Fired Combined Cycle Gene

HITACH

Tokyo, J

Chubu Electric Power Co.,

Inc. Nagoya, Japan

Takao Koike Yoshiki N

REP-1
TYPE OF COMBINED CYCLE

REPOWERING

FEEDWATER HEATING COMBINED CYCLEFULLY-FIRED COMBINED CYCLE

REQUIREMENTS

A) REDUCTION OF POWER GENERATING COST  

B) REDUCTION OF CARBON DIOXIDE EMISSIONS    

C) IMPROVEMENT OF EFFICIENCY OF EXISTING POWER PLANTS

SOLUTIONS

1. INTRODUCTION OF EXISTING POWER PLANT REPO

REP-2

HEAT RECOVERY COMBINED CYCLE 
Air

SYSTEMCONFIGURATION

IMPROVEMENT IN

PLANT EFFICIENCY Approx.(Relatively)

MODIFICATION

AND

NEW INSTALLATIONEQUIPMENT

Modification Items New Installation Equipments

Nil GT generating equipment

GT exhaust gas ductGT exhaust gas stackExhaust gas/feedwater heat exch

REMARKS 1.New equipments can be installed while the existing power plant in operat

2.Interconnection can be completed in less than eight weeks.

Exhaust gas/Feedwater HeatExchanger

GasTurbine

Addition

Pump

SteamTurbine

Feedwater Heater Co

Fuel

BoilerAirFuel

REP-3

1.1 FEEDWATER HEATING COMBINED CYCLE
SYSTEM

CONFIGURATION

IMPROVEMENT INPLANT EFFICIENCY Approx.10(Relatively)

MODIFICATIONANDNEW INSTALLATIONEQUIPMENT

Modification Items New Installation Equipments

Boiler GT generating equipment

GT exhaust gas ductGas feedwater heater

REMARKS Modification of the existing plant can be completed in less than six months.

* It depends on system configuration around the GT and Boiler show in the table of 

Additio

STACK

Pump

SteamTurbine

Feedwater Heater Co

BoilerFuel

Air

Gas FeedwaterHeater

GasTurbine

Fuel

REP-4

1.2 FULLY-FIRED COMBINED CYCLE
Item High temperature wind box GT exhaust gas cooler 

Heat recovery equipment of

GT exhaust gas Boiler Boiler evaporator Feed water heate

Configuration

Improvement of the thermal

efficiency(relatively)

*1)

 10

*1)

 10

*1

  

Modification of the boiler Largest Larger Smaller 

Remarks

Thermal analysis for the

interface between the boilerand wind box is required.

The wind box shall be

made of materials such as

low alloy steel or stainlesssteel.

Exhaust gas cooler

is designed as aboiler evaporator.

Bypass system

around the boilerevaporator is

required.

Bypass system

around the feed wsystem is required

Period of modification work Longer Longer Shorter 

*1)In case that gas turbine exhaust gas flow is Just matched to boiler combustion air required.

cooler

cooler

Boiler

Boiler



Exhaust gas

Exhaust gas

Boiler

D

HP heater 



 

REP-5

1.3 SYSTEM CONFIGURATION AROUND THE GT AND BOILE
1.4 PLANT EFFICIENCY IMPROVEMENT BY CONVERTING TO 

COMBINED CYCLE PLANT

EXISTING THERMAL FULLY-FIRED COMBINED CYCLE PLANT POWER PLANT

F2

E 2

E 1

Elecoutp

Boiler fuel

F1'

GT loss

GT fuel

Boiler loss Turbine loss Condenser

Boiler loss Turbine loss

Elecout

Condenser

Boiler fuel

F1

E1

Plant output

increase GT output



Plant

efficiency

improvement

Boiler fuel can be reduced by using GTexhaust gas as boiler input



'

REP-6
1.5 BASIC CONFIGURATION OF FULLY-FIRED COMBINED C





Gas turbine

2

Gas feedwater 

heater

A/H FDF

Low pressurefeedwaterheater

High pressure

feedwater heater

340

 100



Deaerator Boiler

Eco

LNG

LNG Air

540

600



Residual O

14

15%

Steam turbine

REP-7
Modification

1.6 BASIC ENGINEERING FOR FULLY-FIRED COMBINED CY

Item Basic engineering Consid

Increase of output

Improvement of

efficiency

Adoption of high efficiency gas turbineSelection of heat recovery typeSelection of gas turbine to match the

existing boiler

Utilization of gas turbine exEffective utilization of exhaIncrease of plant output is Plant efficiency improveme

Boiler exhaust gasCooling water for

condenser

Study on environmental regulation or

requirements

Exhaust gas flow rate from NOx from stack shall be leIncrease of cooling water f

Increase of temperature ris

Site area Compact arrangement Installation of gas turbine b

power plant

Modification

schedule

Shut-down period

Shorten the modification periodShorten the shut-down period

Construction work while th

in operation

Effective utilization of inspeShorten shut-down period

Gas turbineSteam turbinePlant operation

Gas turbine simple cycle operationSteam turbine independent operation is

required or not

Same operation flexibility as existing

thermal power plant

Gas turbine simple cycle o

-Low efficiency-Environmental issue

Depend on steam turbine oCombined cycle operation 

gas turbine

Existing equipment

Additional

equipment

Utilization of existing equipmentRemoval of existing equipmentAdditional equipments with gas turbine installation

Utilization of equipment foUtilization of existing stackRemoval of FDF, A/H etc.Addition of IDF, gas feedw

Environment Arrangement Schedule Operation Performance

REP-8
1.7 EXAMPLE OF SELECTION FOR GAS TURBINE TYPE

12001000

800600400200

500 2000

Plant output increase byconverting to fully-fired C/C

Approx.10

30%(at GT base operation)

Exhaust gas flow rate (



50Hz

1300

 class GT

		 class GT

1000MW

700MW

600MW

500MW

350MW

250MW

Plant output (MW)

50Hz60Hz

1GT

2GT

1GT

2GT

1GT

2GT

1GT

2GT

		 class 


		 class 


1100

 class GT

1300

 class GT

1000 2500 1500

REP-9

60Hz
2. EXPERIENCES IN JAPAN

Output (MW) Sup

GT ST Plant GT Bo

1 Tokyo Electric

Power Co., Inc.

Goi Unit No.6 ‘94/7 126 350 476 Hitachi Hit

2

Chubu ElectricPower Co., Inc.

Chita Unit No.6 ‘94/9 154 700 854 Hitachi Hit

3

Chubu ElectricPower Co., Inc.

Chita Daini

Unit No.1

‘94/9 154 700 854 Hitachi Hit

4

Chubu ElectricPower Co., Inc.

Chita Unit No.5 ‘95/6 154 700 854 Hitachi Hit

5

Chubu ElectricPower Co., Inc.

Chita Unit No.2 ‘95/8 154 375 529 Mitsubishi Mits

6

Power Co., Inc. Unit No.2

‘96/7 154 700 854 Toshiba I

7

Chubu ElectricPower Co., Inc.

Chita Unit No.1 ‘96/8 154 375 529 Mitsubishi Mits

Chubu Electric Chita Daini

No. Utility Plant name C/O 

REP-10
3. REPOWERING FOR CHITA POWER PLANT AND CH

POWER PLANT OF CHUBU ELECTRIC POWER Co., In3.1 LOCATION

CHITA POWER S

TOKYO

NAGOYA

OSAKA

CHITA DAINI POW

REP-11
3.2 MAIN SPECIFICATION

Before repowering After 

Chita Unit No.5,6 Chita Daini Unit No.1 Chita Unit No.5,6 

Plant output 700MW 8

Steam turbine output 700MW 7

Gas turbine output  1

Boiler  (Mod

Supercritical,

constant pressure

Supercritical,

sliding pressure

Supercritical,

constant pressure

once-through

reheat system

once-through

reheat system

once-through

reheat system

MCR 2300t/h 2150t/h 

Air supply system Forced Forced induced 

Fuel LNG 

Steam turbine  (Mo

Type TC4F-33.5 TC

Vacuum of Condenser 722mmHg 71

Gas turbine (New

Type Single-shaf

Model  

firing Temperature 

Fuel 

Commercial operation #5:1978.5 1983.9 #5:1995.6 

#6:1978.4 #6:1994.9

Item

Type

REP-12
3.3 SYSTEM CONFIGURATION

Gray areas indicate newly installed or modified sections.

BFP

HP IP



LP LP

Reheater



Boiler BFP-T

GRF LNG

De NOx

To condenser

	
 
 

No.1GFWH

No.2GFWH

AirAir

I

FDF

No.3 GFWH

Air LNG

Gas turbine(F7FA)

Low pressure

High pressure feed water heater

feed water heater

Fire ignition torch

Economizer

De NOx

A/H

A/H

Deaerator

REP-13
Item Feature

Feed water heating syste

Gas turbine exhaustgas heat recoverysystem

No.3 gas feed water heat

(newly installed)

(Gas turbine exhaust temp

about 600



350

)

Boiler exhaust gasheat recoverysystem

No.2 gas feed water heat

(newly installed)

No.1 gas feed water heat

(newly installed)

Boiler exhaust gas temp. (about 

Stack inlet gas temp. (about 1

Boiler bypass duct Newly installed (For plant start-up and

partial load operation)

Forced draft fan/air heater

Existing equipment

(Gas turbine exhaust gas flow

Boiler required air flow)

(Steam turbine independe

operation possible)

Induced draft fan Newly installed

(For adjustment of gas turb

exhaust draft)

REP-14

3.4 SYSTEM FEATURE
3.5 INSTALLATION AND TRIAL OPERATION SCHEDULE

Add F7FA gas turbine to existing 700MW thermal powRepowering to 854MW fully-fired combined cycle plantModification of repowering is completed with shut-dow

three(3) months

Construction schedule of repowering

(Example 

1992 1993 1994 

Boiler firing



11

Beginconstructionof GT house



1

GTon base



4



5



9

GT firing C/O

Commercial operation of 700MW plant Shut-down Trial operation Commer

REP-15



Boilershut-down

10
3.6 MODIFICATION OF BOILER

Heating surface area because steam flow reheater is increasefully-fired combined c

Example of Chita Unit No.6

Economizer outlet header

Increase of reheaterheating surface area

REP-16

The modification of necessary to introducbecause low O2 gais used as boiler coCatalyst and plate typbecause exhaust gconcentration is incrturbine.
3.7 MODIFICATION OF STEAM TURBINE PLANT

Further investigation for the modification of the condenser and circula

is required because the heat load of the condenser is increased due gas turbine

Item Chita Unit No.6 Chita 

IP and LP nozzle(newly exchanged) LP nozz

Steam turbine

(because of the increasing the IP/LP sectio

Gas turbine auxiliary

cooling water facility

Dry type radiator

(for gas turbine plant)

D

(for g

Condenser

Re -used

(cooling water flow not changed) (cooling w

Circulating water system

Condensate water system (operate stand-by equipment)

Boiler feed water pump(driven by steam turbine)

Re -used Re -used 

(operate 

Re -used 

REP-17
3.8 PLANT OPERATION

GAS TURBINE AND STEAM TURBINE LOAD

Gas turbine is started at 50% steam turbine load fro

view point of high efficiency operation

Gas turbine is operated as high load as possible

154

77

0

350 700

75%

Operating limitationbecause ofeconomizer steaming

Steam turbine load(MW)

Gas turbine load (MW)

REP-18
3.9 PLANT PERFORMANCE TEST RESULT

Item Chita Unit No.5 Chita Unit No.6 

Gas turbine output 154MW 154MW 

Plant efficiency Result 5.8% 5.0% 

improvement *1)

Target 3.7% 3.7% 

Plant efficiency (HHV)

Combined cycle operation

40.0% 40.1% 

Steam turbine independent operation

37.8% 38.2% 

Plant efficiency improvement shows the relative improved efficiency 

independent operation and combined cycle operation.

Plant efficiency (HHV)

REP-19
4. REDUCTION VALUE OF CARBON DIOXIDE EMIS

0.54

(kg-CO2/kW

[ - 32

]

0.58

(kg-CO2/kWh)

[ - 28

 ]

0.80

(kg-CO2/kWh)

[ Base ]

CO2 emission *1)2)per gross output

(kg-CO2/kWh)

Unit Gross Output 700MW 700MW 845MW 

Fuel Coal Fired LNG Fired LNG Fired 

Fully-FiredCombined Cy(AfterRepowering)

Conventional Conventional Type of Power Plant

AssumptionType of Power plant units are selected as typical exa

*1) CO2 emission = Energy Consumption x Carbon emission facto

x Fraction of Carbon Oxidised x 44/12

*2) Operating hour is 6100 hr/year ( 70% Capacity Factor )

REP-20