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The first unit of the old Turbigo West thermal power plant with a capacity of 35 MW was commissioned in 1928.
In year 1937, the Isarco-Turin powerline, the first European 220 kV line,connected to the Turbigo sub-station, was commissoned.
In the '60s, the old plant was dismantled and new 70 MW and 75 MW units were erected and commissioned in 1960 and 1964 respectively.
The establishment of the Enel Company led to the erection and commissioning of the following units: one 250 MW unit in 1967 and three units in 1970, one of which with a capacity of 320 MW and the other two of 330 MW.
The Ministry of Industry acknowledged the Enel’s request to carry out the revamping and environmental compatibility works and released the decrees dated June 30, 1990 and October 28, 1993. Each steam unit was coupled with a 125 MW gas turbine unit.
At the end of 2005, Edipower was authorized for the environmental re-qualification of the plant, with the transformation of sections 2 and 4 into the combined cycle. The re-qualification project envisages 2 phases divided as described here below:
Phase I:
- removal from service of section 4, with the exception of the steam turbine and the condensor;
- retirement and demolition of the four existing turbogas turbines;
- installation of an 850 MWe combined cycle consisting of two new gas turbines of 264 MWe each, associated with the steam turbine of the existing section 4;
- maintenance of the steam sections 1, 2 and 3, run in isolated set-up.
Phase II:
- removal from service of section 2, with the exception of the steam turbine and the condensor;
- demolition of the two disused chimneys of steam sections 1 and 2;
- installation of a combined cycle of approximately 430 MWe consisting of a new 264 MWe gas turbine associated with the steam turbine of the existing section 2;
- maintenance of the steam sections 1 and 3, run in isolated set-up.
Phase 1 is approaching completion and module 4 is terminating the commissioning phase.
The preliminary activities of modifying the construction site on Section 2 in relation to Phase 2 began in June 2008.
 TECHNICAL OUTLOOK
The power plant occupies an area of 56 hectares situated on the right bank of the Naviglio Grande canal, in northwest Lombardy, lying in the territories of the Municipalities of Turbigo and Robecchetto, in the province of Milan.
At present, it consists of 3 conventional thermoelectric sections operating by oil/gas in service (sections 1, 2, and 3) and a module (module 4) with a combined cycle operating by gas.
The outputs of the sections/modules are:
- section 1 - 250 MW
- section 2 - 320 MW
- section 3 - 330 MW
- module 4 - 850 MW
The power plant is connected with the 380 kV national grid by means of an armoured substation.
TECHNICAL DESCRIPTION
Conventional thermal units
STEAM GENERATORS
Unit 1
- type: forced circulation
- burners : front wall
- steam generation : 840 t/h
- steam pressure: SH/RH 208/44 Ata
- steam temperature: SH/RH 538°C
Unit 2
- type: forced circulation
- burners: front/rear wall
- steam generation: 1,050 t/h
- steam pressure: SH/RH 176/38 Ata
- steam temperature: SH/RH 538°C
Unit 3
- type : cylindrical drum, controlled circulation
- burners: tangential-fired
- steam generation: 1,050 t/h
- steam pressure: SH/RH 176/38 Ata
- steam temperature: SH/RH 538°C.
STEAM TURBINES
The turbine converts the thermal energy of the boiler generated steam into mechanical energy that is available as driving torque at the turbine shaft.
The turbine consists of high, medium and low pressure stages and makes the generator to rotate. The steam flowing through the turbine is discharged into the condenser. The power rating output is as follows:
Unit 1
Unit 2
Unit 3
GENERATORS
The generator converts the turbine mechanical energy into electric energy.
The voltage rating in the steam units ranges from 15 kV to 20 kV. Cooling occurs by water and hydrogen forced circulation.
CONDENSERS
The condenser uses water from Naviglio Grande channel to condense steam from the steam turbine
The gas turbine combined cycle
GAS TURBINES
Both gas turbines (GT) of the combined cycle have a 270 MWe capacity each.
Each gas turbine includes the axial air compressor feeding the air needed for combustion and cooling of the machine hot parts. Burners are of low NOx type to reduce emissions to the limits set forth by the laws in force.
The thermal energy from combustion is converted into mechanical energy in the gas turbine and then in electric energy via the coupled generator.
The flue gas leaving the gas turbines is conveyed to the heat recovery steam generators for steam generation and then discharged to the stack.
HEAT RECOVERY STEAM GENERATORS
The Heat Recovery Steam Generators (HRSG) are surface heat exchangers that use the thermal energy of the gas turbine flue gas to generate steam to operate the steam turbine.
STEAM TURBINES
The main technical specifications are as follows:
- Type: 4 cylinder, impulse-reaction
- Capacity : 340 MW
- Steam pressure: SH 171 Ata
- Steam pressure: RH 45 Ata
- Steam temperature: SH 538°C
- Steam temperature: RH 538°C
- Pressure at discharge: 0,050 Ata
GENERATORS
The two generators coupled to the gas turbines are of 3-phase, closed loop air cooled type.
A third alternator (coupled to the steam turbine) is 3-phase, mixed cooling type (closed loop hydrogen environment and closed loop deionized water cooling for stator windings).
MAIN TRANSFORMERS
Each generator is connected to its main transformer, which will raise voltage up to 380 KV in order to allow supply of the generated electricity to the transmission grid.
CONDENSERS
The condenser is surface, horizontal tube single flow type. The Naviglio Grande channel water flows through the tubes. Steam from the turbine low pressure stages condensates when it comes in contact with the tubes, and the water is collected in the hot well and fed back to the HRSGs by the extraction pumps after a physico-chemical filtration process.
FUELS
The combined cycle is natural gas fired only. The conventional thermal units can also use low sulphur content fuel oil. Oil is supplied through oil pipeline or tank trucks and stored in the fuel storage yard. The natural gas is supplied via gas pipeline.
The Turbigo Power Plant is equipped with the following systems to minimize emissions to air:
- unit 3: "low NOx" combustion systems to reduce the nitrogen oxide emissions (NOx);
- unit 1 and 2: catalytic denitrification systems (DeNOx) to reduce nitrogen oxide emissions (NOx);
- unit 1, 2 and 3: electrostatic filters (PE) to reduce particulate emissions.
Emissions to air of nitrogen oxides (NOx), sulphur dioxide (SO2), particulate and carbon monoxide (CO) are continuously monitored and recorded via an Emission Monitoring System (SME); the recorded values are transmitted to the relevant control authority every six months.
Immissions to ground of sulphur dioxide (SO2) and nitrogen oxides (NOx) are detected by an Air Quality Detection System (AQDS) consisting of 5 measuring workstations located in the municipalities of Turbigo, Castano Primo, Cuggiono, Galliate and Robecchetto con Induno. The measuring instrumentation was additionally implemented in the frame of the revamping project. The measuring workstations of Turbigo, Castano Primo and Robecchetto are also fitted with total particulate analyzers. The recorded data is made available to the relevant control authority.
The waste waters (acid/alkaline, oily, biological) are treated in a purposely designed plant (ITAR, Waste Water Treatment Plant, and deoling basins) and continuously tested before the discharge.
The sewage waters are directly conveyed to the municipal sewage system.
All activities that interact or may interact with the environment are managed in accordance with the ruling environmental laws and the available state–of-the-art techniques.
The Environmental Management System implemented in the power plant was certified in September 2000 according to the UNI EN ISO Std. 14001.
To foster the ongoing improvement of the environmental performances and the information to the public the management of the Turbigo Power Plant has voluntarily adopted the EU Ecomanagement and Audit Scheme (EMAS) and obtained the registration in March 21, 2001 with the number I-000051
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