modernizzazione delle turbine a vapore allo scopo di ... · pdf filemodernizzazione delle...

Modernizzazione delle turbine a vapore allo

scopo di aumentare l’efficienza energetica e

la redditività degli investimenti

10 anni di modernizzazione dei turbogruppi in Italia

Alberto Torre

Steam Turbine Engineering

Verona, 7 Ottobre 2010

2

Introduction

In March 1999, a legislative decree (“Bersani Decree”) was issued for the liberalization of the Italian Energy market.

New players appeared in the Italian market installing new greenfieldpower plants based on high efficiency CCGT technology.

The owners of existing conventional plants has been forced to modernize the power plants in order to maximize their competitiveness in an open market.

The basic modernization concepts and some modernization activities on the existing Italian fleet are illustrated.

3

Power Generation market in Italy now

Renewables (hydro included) are relevant

(27%)

No nuclear energy is produced (all nuclear

power plants have been shut-down after

Chernobyl)

Most generation comes from conventional

thermal sources, production by coal is only

14%, the remaining is produced mainly by

natural gas (several installations of CCGT

plants) and oil.

Today the italian generation fleet is one of the most efficient in Europe.

Installed Capacity (2009)*

105 GW

Source: *Terna web site, **IEA analysis

Main characteristics

Average efficiency:

45%**

73%

21%

6%

Thermal plants Hydroelectric Renewables

Fuel mix

4

….and 10 years ago?

The context was quite different: like today Italy got the majority of its

electricity supply from conventional thermal sources, but the bulk was

oil-fired

14%

60%

26%

Before liberalization (2008)

Average efficiency:

<39%*

15%

37%

48%

Coal Gas Oil

Average efficiency:

45%**

Introduction of new CCGT Repowering of existing PP

Fuel mix

5

Italian Power Generation market: last 10 years

The last decade of the Italian Power Generation market has been

characterized by different factors which have modified radically the

characteristics of the turbogenerator fleet:

Liberalization

Environmental Impact

6

Liberalization

• Bersani Decree (1999) for the

restructuring and liberalization of the

Italian electricity sector

• Enel share of domestic market can not

be higher than 50% due to regulatory

constrains.

• Italian government forced Enel to sell

15,000MW of installed capacity.

• Different operators emerged as

significant players in the sector:

• installing new green field CCGT

power plants

• purchasing also the former Enel

assets

• A competitive market among players in

power generation

From monopoly…

…to a truly competitive context

1999 ...after 1999

7

Environmental impact

Climate has changed over the past century (average temperature increase)

Climate is expected to continue to change in the future

The Kyoto Protocol, adopted in 1997, contains legally binding comitments to reduce the anthropogenic GHG (GreenHouse Gas)

EU large combustion plant Directive 2001/80/CE defines specific emission limits (200/200/30 mg/Nm3) for SO2/Nox/Particulate

New investments over the next 20 years to meet the expected energy

demand and to replace the ageing infrastructure

8

Effects of the liberalisationM

AR

KE

T

Liberalization

(new operators)

Greenfield Plants

Investments in new Combined

Cycles (high overall efficiency,

>55%)

Existing old Plants

Modernisation of the old power

plants to become competitive

with the new CC

9

Green field plants

Before the liberalization process, the Italian fleet was not so advanced and

efficient as today (most of the Power Plants installed in the sixties and

seventies).

=

European energy target

New competitive scenario

+

Introduction of 400MW or 800 MW advanced gas fired CC plants

• High efficiency technology

• Reduced CO2 emissions

Greenfield Plants

10

Greenfield Plants

Greenfield Plants• High efficiency technology

• Reduced CO2 emissions

Scandale

Ferrara

Teverola

Sparanise

Rosignano

Ferrera

Leini

Ponti S.M.

Around 18,000MW(at the end of 2009)

EGL

Sorgenia

Rizziconi

Turano L.

Modugno

Aprilia

S.Severo

11

Installed capacity before liberalization

120/160 MW

240/350 MW

600/660 MW

Installed Capacity (1998)*

54 GW

25 units

60 units

17 units

Subcritical RH steam PP

Supplied by Ansaldo, F.Tosi, Rateau, BBC

Efficiency (overall) 34-36 %

Before

liberalisation

Subcritical RH steam PP

Supplied by Ansaldo, F.Tosi, Rateau

Efficiency (overall) 36-37%

Supercritical RH steam PP

Supplied by Ansaldo, F.Tosi

Efficiency (overall) 38-39%

PO

WE

R P

LA

NT

S

Source: *Terna web site

12

Aged fleet: modernisation strategy

In comparison to new greenfield power plants, the conversion/modernisation of existing power plants offers several

opportunities:

Reduction of the investment cost due to the extensive reuse of existingequipments, buildings, infrastructures, electrical substations, transmission lines

Reduction of environmental impact of the existing plant (designedaccording to old standards); this issue is often an important factor in promoting the acceptance of the project al local level

13


∆ Efficiency: up to 20%

160-320 MW Multifuel

PO

WE

R P

LA

NT

S

Conversion into Combined Cycles

(Repowering) to increase the efficiency as

new CCGT plants

Conversion to USC clean coal fired cycles

to increase the mixing of energy sources,

the efficiency and reduce the air pollution

Modernization of the turbines to increase

the power and the efficiency and reduce

CO2 emission.160-660 MW Coal fired

660 MW Multifuel



14

Modernization of existing old units

Existing old units •Modernisation activities

BrindisiFiumesanto (SS)

Turbigo (MI)

• Around 9000MW converted to CCPP

• Around 4500MW coal fired steam

turbines modernized

• Around 5000MW of large oil fired units

will be converted to USC cycles (clean

coal technology)

Eon

15

WHY REPOWERING ?

Conversion of existing Steam Power Plants into Combined Cycles by replacing

the fired Boiler with GT and HRSG is known as Repowering.

Repowering an existing steam Power Plant realizes a gain in efficiencyup to values of 56% and over.

Steam Cycle

XCombined Cycle

Repowering is the solution that best matches the optimization

goal of reduction of operating costs in an existing Power Plant.

Repowering

From Steam Cycle to Combined Cycle

16

Repowering


In a steam cycle unit

the overall Efficiency is about 36%

mSH=100%

mHRH=80%mLP=75%

mcond=60%

Flow diagram of a conventional RH steam power plant

17

In combined cycle, the overall Efficiency is higher than 56 %

10%

32.5%

Conversion of a conventional unit in C.C. (1+1 configuration)

2 - ST steam path could beoptimized; extraction pipes

blanked

1 - Steam Generator is replaced by

GT and HRSG, Feedwater

cycle is removed

3 - Condenser is maintained

mSH=30%

mHRH=40%

mcond=65%

Note (1): Mass flows % refer to original mass flow for each point of a subcritical 350 MW ST

Repowering


18

20

40

60

80

100

120

HP inlet RHT inlet LP inlet LP exhaust

Ste

am

flo

w to

ST

se

ctio

ns [%

]

Original

2+1

1+1

Repowering existing Power Plants causes a substantial modification of the

steam mass flow distribution across the different sections of the Turbine:

In the Steam Cycle the steam flow is reduced from HP inletto LP exhaust due to the bleeded steam for feedwater heaters

In the Combined Cycle the steam flow increases from HP inletto LP exhaust due to the addition of multiple level flows.

Steam flow distribution

before and after repowering

( ref. 320 MW ST )

Repowering

From Steam Cycle to CC - Reasons for retrofit

A partial or complete change of the old steam path in order to match the new operating

conditions permits to improve the Combined Cycle performance to a level comparable to

that of a new turbine

19

Steam ParametersLS pressure : 141 bar

HP inlet flow : 134 kg/s

SH/RH temperature : 538 / 538 °C

Exh. Pressure : 0.054 bar

Exh. Flow : 91 kg/s

Rating : 2 x 156 MW

• OEM: Franco Tosi (Westinghouse)

• Years of first operation: 1964, 1966.

• Reaction design.

• Tandem compound arrangement with a combined HP-IP section and a

double-flow LP section with 23” LSB

ITALY (P.TO CORSINI)

Original (Steam Cycle)

20

Steam ParametersLS pressure : 107 bar

HP inlet flow : 76.5 kg/s



Exh. Flow : 97 kg/s

Rating : 2 x 124 MW

From 2001, steam cycle repowered into 2 x ( 1+1 370 MW) combined cycle

using a AE94.3A Gas Turbine.

Complete replacement of LP inner block including:

· new inner casing and blade carriers

· new monoblock rotor

· modern 3D blading on front stages

· longer LS blade (33”) with 60% larger

exhaust area

Benefits: Improvement of 5.6 MW with reference to original design

Overall – Plant efficiency from 34% to 55%

ITALY (P.TO CORSINI)

Retrofit for CC conversion

21

Steam Parameters

LS pressure : 166.6 bar




Rating : 1 x 320 MW

• OEM: Ansaldo

• Years of first operation: 1970

• Tandem compound arrangement with a combined

HP-IP section and a two-flows LP section with 33.5” LSB

ITALY (Vado Ligure # 1) - Original (Steam Cycle)

22

• OEM: Ansaldo (impulse technology)


• Tandem compound arrangement with a combined

HP-IP section and a two-flows LP section with 33.5” LSB

Steam Parameters

LS pressure : 128 bar

HP inlet flow : 147 kg/s



Rating : 1 x 274 MW

• 2005, Conversion in C.C. 2+1 800 MW using two Ansaldo AE94.3A Gas Turbine

• Complete replacement of HP-IP section of up-to-date reaction type and materials suitable for increased

temperature

- New HP & IP stop and control valves directly connected to the outer casing

- Full-arc admission with elimination of control stage

- New rotor with 3D reaction blading and enhanced sealings

• New LP inner block (rotor, inner casing) with 43” LSB

Benefits: Increase of 12 MW with reference to the original design

Overall – Plant efficiency from 36% to 56%

ITALY (Vado Ligure # 1) - Retrofit for CC

23




PO

WE

R P

LA

NT

S



new CCGT plants






CO2 emission.160-660 MW Coal fired

660 MW Multifuel



24

The increasing of internal efficiency of an old steam turbine can be obtained

through the introduction of modern 3D blades and larger last stage blades.

Old design with shorter LSB’s and exhaust steam velocity over 300 [m/s]

have often high exhaust losses.

In the last decades, new materials

and new design methods

allowed the development

of large LSBs .

Efficiency increase on Coal Fired PP

A larger last stage blade will reduce

exhaust losses and convert them in

additional power output

25

Steam Parameters





Rating : 1 x 260 MW

• OEM: Rateau Schneider.


• Tandem compound arrangement with HP and IP separated

sections and double flow LP section with 34” LSB

ITALY (Sulcis # 2) – Original Coal Fired

Steam Cycle

26

• OEM: Rateau S. (impulse technology)


• Tandem compound arrangement with HP and IP separated

sections and double flow LP section with 33.5” LSB

• 2002, The modernisation of the Plant included:

Installation of a new CFB boiler with increased capacity

Replacement of old ST with a new Ansaldo steam turbine, reaction type, with a LP DF

(43”LSB)Benefit: - Increase of gross power output up to 345 MW

- Increase of gross efficiency up to 40%

- Significant CO2 emission reductions.

Steam Parameters





Rating : 1 x 345 MW

ITALY (Sulcis # 2) – Modernisation of the

Unit

27 27

Steam Parameters, STPPLS pressure: 167 bar

HP inlet flow: 293.4 kg/s

LS/RH temperature: 538/538°C

Exh. Pressure: 0.05 bar

Exh. Flow: 176.8 kg/s

Rating: 2 x 329.3 MW

Steam Turbine Retrofit

Fusina 3-4 / Italy

2006 / Replacement of LP inner block• LSB length: 43”

• Exhaust area: 9.6 m2

• Front stages: 3D optimized

• New rating: 336.8MW

BENEFITS: Power output: + 7.5 MW

Heat rate: - 42 kcal/kWh

OEM: Franco Tosi / Westinghouse

Years of first operation: 1974

28 28

Steam Turbine Retrofit

Brindisi Sud 4 x 660MW / Italy

BENEFITS: Power output: + 15.5 MW

Heat rate: - 43.4 kcal/kWh

Steam Parameters, STPPLS pressure: 242 bar

HP inlet flow: 581 kg/s

LS/RH temperature: 538/538°C

Exh. Pressure: 0.049 bar

Rating: 4 x 660 MW

Replacement of LP inner blocks• LSB length: 43”

• Exhaust area: 9.6 m2

• Front stages: 3D optimized

• New rating: 4 x 675 MW

OEM: Franco Tosi / Westinghouse

Years of first operation: 1991

29




PO

WE

R P

LA

NT

S



new CCGT plants






CO2 emission.

160-660 MW Coal fired

660 MW Multifuel



30

[%]

Evolution of cycle parameters

and their impact on overall plant efficiency

170 / 540 / 540

240 / 540 / 565

280/640/650

280/600/620

280/580/600

SC - Supercritical USC - UltraSupercriticalSubcritical

ΔHR

HR

201020001990198019701960

In development

COST 536

consolidatedconsolidated

in

operation

current

market

Efficiency increase on

Clean Coal Fired PP- USC application

The increasing of steam cycle parameters is the most promising way to improve the

efficiency of a modern coal fired Power Plant with low emissions.

7-8 %

31

• The old plant consisted of 4 x

660MW Ansaldo units, adopting an

oil fired supercritical cycle (250bar /

540°C / 540°C)

• The new plant consists of 3 x

660MW units, supplied by MHI,

adopting a clean coal ultra-

supercritical cycle (250bar/600°C/

610°C)

First unit start-up of commercial

operation: June 2009

Benefits:

• Efficiency gain from 40% to 45% => Δ 10%

• Emission SO2 ≤ 100mg/Nm3

• Emission Nox ≤ 100mg/Nm3

These values are about half of the limits stipulated in EU large combustion plant Directive

2001/80/CE.

Clean Coal Fired USC Conversion

Torrevaldaliga Nord 3 x 660MW / Italy

32

Conclusions

In these last ten years the italian power generation scenario deeply changed

The market liberalization forced the utilities to modernize the old power plants

to be competitive with new CCPP

On the old plant three basic strategies of intervention has been introduced to

gain efficiency:

• Repowering to combined cycle

• Modernization of existing coal fired power plants

• Conversion to clean coal USC of large power plants (660MW)

Example of modernizations have been illustrated, showing how a retrofit can

be attractive inside a modernization project

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