moncalieri plant gt i t

M O N C A L I E R I P L A N T3RD G T

w w w . i r e n e n e r g i a . i t

Iren Energia is the company in the Iren Group whose core

businesses are the production and distribution of electri-

city, the production and distribution of thermal energy for

district heating and the provision of technological services.

Iren Energia constantly pursues its objectives, which are qua-

lity, reliability, sustainable development, energy efficiency

and a close relationship with the areas in which it operates.

The 3rd GT is part of the Moncalieri cogeneration plant, which,

together with the Torino Nord plant, supplies Turin’s district

heating system.

The plant is made up of two combined-cycle cogenera-

tion units (2nd GT and 3rd GT), with an overall electrical

capacity of 800 MW and thermal capacity of 520 MW in

cogeneration mode, and a 141 MW supplementary and

back-up plant.

The heat produced by the cogenerators provides district

heating for a total volume of 55 million cubic metres,

making Turin the city with the largest district heating sy-

stem in Italy.

Iren Energia S.p.A.Corso Svizzera, 9510143 Torino - ItalyTel. +39 011 5549 111Fax +39 011 53 83 13

Combined-cycle operationISO conditions on site

• Net electrical power 383 MW

• Efficiency 57%

Combined-cycle and cogeneration operation ISO conditions on site

• Thermal power 260 MW

• Efficiency 87%

TEST DATA

3rd GT of the Cogeneration Plant

GAP MP BP 3~

Functional diagram

Steam generator with three pressure levels pressure (bar) capacity (Kg/s) temperature (°C)

• AP 104 74 550

• MP 28 87,4 560

• BP 3,5 9,63 250

Heat exchangers for district heating

• Inlet temperature 70°C

• Outlet temperature 120°C

Gas turbine

• Capacity 260 MW

• Fuel natural gas

Steam turbine

• Capacity 138 MW

water-cooled condenser

heating system.

back-up plant.

stem in Italy.

• Efficiency 57%

• Efficiency 87%

TEST DATA

GAP MP BP 3~

Functional diagram

• AP 104 74 550

• MP 28 87,4 560

• BP 3,5 9,63 250

Gas turbine

• Capacity 260 MW

Steam turbine

• Capacity 138 MW

heating system.

back-up plant.

stem in Italy.

• Efficiency 57%

• Efficiency 87%

TEST DATA

GAP MP BP 3~

Functional diagram

• AP 104 74 550

• MP 28 87,4 560

• BP 3,5 9,63 250

Gas turbine

• Capacity 260 MW

Steam turbine

• Capacity 138 MW

3rd GT of theCogeneration Plant

Operating conditions

The plant will provide optimum perfor-

mance under the following main ope-

rating conditions:

• Gas turbine with continuous nominal

load, steam turbine in electricity only

mode without extraction of steam for

the district heating network;

load, steam turbine in cogeneration

mode with maximum extraction of

steam for district heating network;

load, steam turbine out of order, ma-

ximum extraction of steam from by-

pass system for district heating net-

• Gas turbine continuous nominal load,

steam turbine out of order without

extraction of steam from bypass sy-

stem for district heating network.

The plant will, in any case, operate un-

der all the intermediate conditions in-

dicated in the graph above.

Functional characteristics

The functions of the thermoelectric po-

wer plant include:

• Production of electricity and heat for

district heating;

• Operation under partial loads above

the minimum technical level to allow

use of these loads;

• Operation of the unit from the central

control room without any need for

any local actions;

• Protection of all mechanical compo-

nents against faults or failures (for

example, in case of gas turbine or ste-

am turbine cut-out);

• Operation in a single cycle with by-

pass to the condenser for a limited

period of time.

The 3rd GT of the Moncalieri plant with

its capacity of 400 MWe was desig-

ned using the very latest technologies

for the simultaneous production of

electricity and heat. The unit, with its

thermal capacity of 260 MWt, together

with the upgraded 2nd GT, constitutes

the main source of heat for the Turin

district heating system, one of the lar-

gest in Europe.

The plant provides the district heating

system with water at a temperature of

120 °C, dispatched by the pumping sy-

stem to the end user devices through

the vast underground pipe network.

The 3rd GT, designed to guarantee the

maximum efficiency and minimum

environmental impact currently avai-

lable, is made up principally of:

• Gas turbine that generates more

than 260 MW of electricity under ISO

conditions with an efficiency of over

• Heat recovery steam generator, with

three pressure levels, fed with hot

exhaust gas from the gas turbine

(660 kg/s at a temperature of almost

600°C), without a smoke bypass flue;

• Condensation steam turbine with a

capacity of about 138 MWe and re-

gulated extraction of steam at a low

pressure for the production of heat

for the district heating network;

• Tube nest condensation system, co-

oled by the water coming from the

off-take canal of the river Po (about

7,000 kg/s);

• Heat production system for the di-

strict heating network (260 MWt) in

the form of water superheated to

120°C, whose operation is based on

the extraction of steam at a low pres-

sure and temperature from the steam

turbine and/or by-pass system;

• Unit heater-based heat dissipation

system with a capacity of about

340 MWt, at an ambient temperatu-

re of 30°C, for cooling the superhea-

ted district heating water, which may

be used by the 2nd and 3rd GTs, if the

water flow from the off-take canal is

insufficient;

In electricity mode, the 3rd GT reaches

a total efficiency of over 57%.

In cogeneration mode, its overall effi-

ciency is 87%.

The gas turbine

The turbine (fed with natural gas) is a

single-shaft machine with a 15-stage

air compression section (final pressure

17 bars) combined with a 4-stage tur-

bine section.

The turbine’s hollow shaft, of the type

with blade holding rings, ensures short

start-up times (34 minutes from rest to

full load) due to the low thermal inertia

and adapts rapidly to variations in the

demand for power with an upward po-

wer gradient of 13 MW/min.

The blades of the turbine, subjected to

extreme stress, are air-cooled internal-

ly and protected externally by a cushion

of cooling air blown in through laser-

drilled holes.

Adjustable direction blades at the inlet

of the compressor enable the extracted

air flow rate to be adapted to the power

of the machine so as to allow the ma-

ximum exhaust gas temperature possi-

ble and thus optimum steam conditions

also in the partial load range.

The steam generator

The heat recovery steam generator

has the following characteristics:

• Three pressure levels;

• Degassing tower built into the cylin-

drical low-pressure body;

• High efficiency thermal design with

small-diameter tubes and tabs den-

sely arranged in a quincunx confor-

mation;

• Natural circulation, based on bro-

ad-diameter cylindrical bodies with

high-efficiency separators and high

circulation stability in the evapora-

tion circuits;

• “Hanging” support to allow free

downward expansion of the heat

exchange elements;

• Cold wall closure (insulated internal-

ly) with structure and reinforcements

welded externally;

• Fully welded pressurized parts;

• Completely drainable heat exchange

elements.

The steam turbine

The condensation steam turbine is

made up of separate high, medium

and low pressure turbine sections.

The high pressure turbine section has

a barrel-shaped body. The fixed sup-

port is situated between the HP and

MP turbine sections.

The LP turbine section has a dual-flow

design.

The internal casing of the LP section is

connected to the casing of the MP sec-

tion by connecting rods to reduce the

necessary play (thermal expansion).

The turbine blades provide three-di-

mensional flow optimization.

The HP and MP valves are compact,

combined valves (regulation and quick

stop valve form a unit). The steam

flows towards the bottom of the con-

denser situated below the turbine.

Steam for the district heating system

can be extracted from two steam

taps on the medium pressure turbi-

ne section.

1800 20 40 60 80 100 120 140 160 180 200 220 240 260

Thermal power (MW )

TG 100% TG 75% TG 60%

Operating range at an ambient T of 15°C

Cogeneration plants

Supplementary and back-up plants

MONCALIERI

POLYTECHNIC

MIRAFIORI NORD

TORINO NORD

District heated area

rating conditions:

wer plant include:

district heating;

use of these loads;

any local actions;

period of time.

gest in Europe.

7,000 kg/s);

insufficient;

ciency is 87%.

The gas turbine

bine section.

drilled holes.

The steam generator

mation;

tion circuits;

exchange elements;

welded externally;

elements.

The steam turbine

design.

ne section.

1800 20 40 60 80 100 120 140 160 180 200 220 240 260

Thermal power (MW )

TG 100% TG 75% TG 60%

Cogeneration plants

MONCALIERI

POLYTECHNIC

MIRAFIORI NORD

TORINO NORD

rating conditions:

wer plant include:

district heating;

use of these loads;

any local actions;

period of time.

gest in Europe.

7,000 kg/s);

insufficient;

ciency is 87%.

The gas turbine

bine section.

drilled holes.

The steam generator

mation;

tion circuits;

exchange elements;

welded externally;

elements.

The steam turbine

design.

ne section.

1800 20 40 60 80 100 120 140 160 180 200 220 240 260

Thermal power (MW )

TG 100% TG 75% TG 60%

Cogeneration plants

MONCALIERI

POLYTECHNIC

MIRAFIORI NORD

TORINO NORD

rating conditions:

wer plant include:

district heating;

use of these loads;

any local actions;

period of time.

gest in Europe.

7,000 kg/s);

insufficient;

ciency is 87%.

The gas turbine

bine section.

drilled holes.

The steam generator

mation;

tion circuits;

exchange elements;

welded externally;

elements.

The steam turbine

design.

ne section.

1800 20 40 60 80 100 120 140 160 180 200 220 240 260

Thermal power (MW )

TG 100% TG 75% TG 60%

Cogeneration plants

MONCALIERI

POLYTECHNIC

MIRAFIORI NORD

TORINO NORD

heating system.

back-up plant.

stem in Italy.

• Efficiency 57%

• Efficiency 87%

TEST DATA

GAP MP BP 3~

Functional diagram

• AP 104 74 550

• MP 28 87,4 560

• BP 3,5 9,63 250

Gas turbine

• Capacity 260 MW

Steam turbine

• Capacity 138 MW

moncalieri plant gt i t

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