REPOWERING OF PIACENZA STEAM POWER PLANT INTO A

STATE-OF-THE-ART COMBINED CYCLE POWER PLANT Giuseppe Monteforte, Edipower – Italy

Enrico Savoldi, Techint Cimi.Montubi – Italy

Summary Repowering of the existing Piacenza-Edipower steam turbine power plant with advanced technology gas turbines brings new useful life to this more than 30 years old power station. Combining steam and gas cycles results in increase of capacity, decrease in air-borne pollutant emissions and the efficiency is significantly improved. The economic benefits of this approach are so significant that utilities in Italy are at present converting many of existing gas/oil fired conventional old units into modern combined cycle. Extensive reuse of the existing components, as major goal of the rehabilitation program was very challenging both for the planning team and the EPC contractor as well. Condition of each component, piping, individual system and their suitability for further use have been thoroughly investigated and analysed. The tight constraints in terms of available extension of time and space for plant realization have been considered as additional matter of challenge. As the result of the tendering the Siemens - Fiat Engineering – Techint Consortium, with the V94.3A gas turbines, was selected for this project. This paper describes various technical challenges and their resolution in the planning phase of this repowering project. In particular are discussed: - the improvement of thermodynamic cycle; - the need for new suitable components, to be installed both in a green field and a brown

field area; - the adaptation of existing equipment and systems, for a complete integration in the future

plant; - the attention paid, during the planning of the realization phases, to the needs of a still

operating power plant. The final result is a mosaic of solutions leading to a modern power plant building approach, respectful of the very close local community and of the last environmental requirements. This positive scenario is finally supported by the fuel cost analysis based on the Plant efficiency consideration, carried on in the changing picture of the evolving Italian market, where new and old technologies operate contemporarily and in competition. Sommario L’utilizzo della tecnologia del ciclo combinato per il repowering dell’esistente impianto convenzionale a vapore di Piacenza Levante ha consentito di estendere la vita residua di questo impianto entrato in funzione più di 30 anni fa’. Il risultato della combinazione dei cicli a gas e a vapore ha consentito di incrementare la capacità produttiva dell’impianto, diminuirne le emissioni di inquinanti ed aumentarne significativamente l’efficienza di generazione.

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I benefici economici di questo approccio sono così evidenti che al giorno d’oggi molte Utilities in Italia stanno convertendo gli esistenti impianti convenzionali a olio/gas in moderni cicli combinati. L’estensivo riutilizzo dei componenti esistenti è stato l’obiettivo principale e più sfidante del programma di riabilitazione, sia per il team di pianificazione che per il Contrattista. Le condizioni di ciascun componente, del piping, dei vari sistemi e la loro adeguatezza per il futuro impiego sono state attentamente valutate ed analizzate. Gli stretti vincoli realizzativi, in termini di tempistiche e spazi a disposizione, hanno reso la materia ulteriormente impegnativa. Come risultato del bando di gara, il consorzio formato da Siemens – Techint – Fiatengineering è stato selezionato per l’esecuzione del progetto, con l’adozione della turbina a gas Siemens V94.3A. Questa memoria descrive le varie problematiche tecniche e la loro risoluzione affrontate nella fase di progettazione del repowering. In particolare vengono trattati i seguenti temi: - il miglioramento delle prestazioni termodinamiche; - la necessità dell’installazione di nuovi componenti adatti al futuro assetto, sia in aree

libere che occupate da apparecchi pre-esistenti; - l’adeguamento delle apparecchiature e dei sistemi esistenti per una completa integrazione

nel futuro assetto di impianto; - la cura prestata, durante la fasi di pianificazione e progettazione, alle necessità di una

centrale termica ancora a tutti gli effetti in produzione. Il risultato finale è stato un mosaico di soluzioni volte a promuovere un moderno approccio alla realizzazione di impianti, rispettoso della vicinissima comunità cittadina e degli ultimi requisiti in materia ambientale. Questo scenario già di per se’ positivo è stato alla fine supportato dai risultati dell’analisi economica del costo del combustibile, basato sulle nuove prestazioni di impianto, in una prospettiva in continua evoluzione del mercato energetico italiano, dove nuove e vecchie tecnologie operano contemporaneamente ed in competizione. Introduction Repowering existing steam power plants, typically 30 or more years old, with modern gas turbines brings not only new useful life to these plants, but also higher generating power output as well as significant higher efficiencies and lower air borne pollutant emissions. The repowered plant will have an efficiency in excess of 57% and will enable the plant to once again compete with other plants. Repowering quite often involves a change of fuel from heavy fuel oil or coal to natural gas which result in a much lower CO2 emission. Thus, the environment will also benefit from burning natural gas in these gas turbines, which will provide a benchmark for future power plants in this region in Italy and in similar industrial areas otherwise in the world as well. Edipower Profile Background - Before liberalisation, the Italian electricity market was a national monopoly with Enel

established in 1962 as the sole state-owned, vertically integrated electricity company (with the exception of auto producers and certain municipalities) and the sole importer and

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exporter of electricity to and from Italy. Tariffs were set by the Ministry of Industry in consultation with Enel.

- DECREE 79/99: this decree, issued on February 18, 1999 established a general regulatory framework for the Italian electricity industry to facilitate the gradual introduction of free competition in the power generation market and a class of end-users free to choose electricity suppliers (“Eligible Customers”) while maintaining a regulated monopoly structure for power transmission, distribution and sales to Non-Eligible Customers. The decree established, among the others, a limit of 50% on the share of the electricity generation/import market for any single company or group after 1 January 2003. As a consequence Enel was forced to sell 15GW grouped in three companies (“Gencos”).31st May 2002 Edipower S.p.A. purchases Eurogen S.p.A. (the biggest “GENCO”)

- 1st December 2002 Eurogen S.p.A. merged into Edipower S.p.A. - 8th August 2003 Refinancing Facilities signed - 3rd September 2003 Tolling Agreement / Hydro PPA signed - 12th September 2003 Refinancing Facilities funded Sharing

Figure 1 – Edipower share holders Overview Edipower is the largest private generator of electricity in Italy after ENEL Produzione (majority owned by the Italian Treasury).Nominal capacity (31.05.04) of 7,682 MW: - 6 thermal plants for a total of 6,900 MW. - 3 hydro bundles for a total 782 MW.

40.0 % 16.0 % 8.0 %16.0 % 10.0 % 5.0 % 5.0 %

50.0 % 20.0 % 10.0 % 20.0 % Off-Take Agreements

Market Risks

Operational Risks

40.0 % 16.0 % 8.0 %16.0 % 10.0 % 5.0 % 5.0 %

50.0 % 20.0 % 10.0 % 20.0 % Off-Take Agreements

Market Risks

Operational Risks

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Repowering Projects The Edipower conversion to CCGT program foresees important investments and involves the following thermal power stations: - SSeerrmmiiddee:: two of the four existing conventional oil fired units have been recently converted

in combined cycle (1200 MWe). - CChhiivvaassssoo:: the former power plant, fuelled by coal and oil, was dismantled and new natural

gas fired CCGT (1200 MWe) are under construction. The industrial operation is scheduled for the second half of 2004.

- TTuurrbbiiggoo:: it is planned a conversion of two oil/gas fired conventional units into a new natural gas fired CCGT (1200 MWe); other two oil/gas fired conventional units shall remain.

- PPiiaacceennzzaa:: object of the presentation. - BBrriinnddiissii:: it is planned a conversion of two coal fired conventional units into a new natural

gas fired CCGT (800 MWe); other two coal fired conventional units shall remain. - SS.. FFiilliippppoo ddeell MMeellaa:: a technical and economical study on the future assets of the power

plant is under evaluation. Piacenza Power Station Edipower decided in April 2003 to upgrade Unit #4 of Piacenza Thermal Power Plant from heavy fuel oil to a modern, peak load, combined cycle power plant and to increase the unit output from 320 MW to approximately 830 MW. The pre-qualified bidders were Enelpower (GE), Alstom and Siemens/Fiat Engineering/Techint.A very tight schedule for tendering activities was followed: less than 14 months from Publication on UE Official Gazette to Contract award. Economic considerations were mainly based on improving plant efficiency from currently approx. 34% to 57%, more than doubling of the generated output of Unit #4, switch from heavy oil to natural gas with subsequent reduction of maintenance costs. In order to maximize the generated output of the entire plant both units, Unit #4 and the identical Unit #3 will be maintained as much as possible in normal daily operation. Furthermore, a post firing skid was added to the scope of supply, thus enabling an increase of the combined cycle output by more than 35 MW, from 796 to 831 MW.

Table 1 – Existing Plant vs. new configuration performances

Net Power output (Mwe)

Net efficiency (%)

Total thermal Power (MWth)

NOx Emission (kg/h)

SOx Emission (kg/h)

PTS Emission (kg/h)

PZ- 3 312 38.9 802 170 340 42.5PZ-4 312 38.9 802 170 340 42.5

New CCGT - 1 400 56.3 710 64.2 / /New CCGT - 2 400 56.3 710 64.2 / /

Before re-powering 624 38.9 1604 340 680 85After re-powering 800 56.3 1421 128.4 / /

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Layout – Existing Plant and New Configuration

Figure 2a – Existing Plant

Figure 2b – Existing Plant and new configuration overview

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Investment value The total investment value may be mainly split in the following major items: - Owner activities : 4 millions Euro - EPC Contract : 230 millions Euro - Planning The scheduled construction time is about 2 years with a minimum outage period for the Unit #4 steam turbine.

Figure 3 – General project execution time schedule Repowering Project All the activities included in the repowering process could be resumed in the following categories: - Green field - Brown field – dismantled (and substituted) - Brown field – re-used - Performed by Edipower Green field - GT and Generator trains (Siemens supply) - Heat Recovery Steam Generators - Interconnecting piping - Closed Cycle Cooling Water System - GTG Step-up Transformers - Fuel Gas Treatment Station - Fire Fighting System - HVAC System - Plant Electrical Systems - Plant Control System

ID Nome attività Durata1 Start 587 g2 Bidding close 0 g3 new field 331 g4 site mobilization 0 g5 Boilers erection 192 g6 gas turbine erection 193 g7 steel structure erection 110 g89 Existing plant 115 g10 shut down unit 4 0 g11 Asbestos decontamination 25 g12 Demolition of existing equipment 16 g13 steam turbine revamping 73 g14 GIS installation 83 g15 Steam turbine generator 1st synchr 0 g16 PAC 0 g

23/09

01/03

21/01

01/0722/12

S2 S1 S2 S1 S2 S12° semestre 1° semestre 2° semestre 1° semestre 2° semestre 1° semestre

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Brown field dismantled (and substituted) - ST step-up transformer - 220 kV Gas Insulated Switchgear - Air compressorsBrown field re-used - Unit #4 Steam Turbine - Main Cooling Water System (Po river) - Demineralization Plant - Auxiliary Boiler - Approach: � mechanical, electrical and I&C survey;

� definition jointly with Plant Operators of the interventions; � check of the stored spare parts/equipment; � procurement of the necessary equipment.

Performed by Edipower - Preliminary demolitions and relocation, site area preparation - Condenser re-tubing - Waste water treatment plant refurbishment - Final demolitions Topics Extensive reuse of the existing power plant components, a major aspect of the project economics, is a significant challenge for the planning engineers and EPC contractor. It became apparent that it would be possible to increase plant efficiency still further by improving the existing steam turbine, generator and condenser. Major overhaul of the steam turbine, rewinding of the entire stator, major repairs of the condenser are thus expected to boost the current steam turboset efficiency. Plant Design Concept For achieving best performance at the specified ambient conditions, a triple-pressure, single-reheat cycle has been selected. The plant rated capacity at site conditions is 796 MW with a design efficiency of 57% at generator terminals having at its core two V94.3A gas turbines. The two advanced V94.3A gas turbines discharge their exhaust energy into two heat recovery steam generators (HRSG). These heat recovery steam generators supply main steam, reheat steam and low pressure steam to the existing reheat type steam turbine, which consists of one HP/IP cylinder with opposed steam flow and a single two-flow low pressure cylinder. This type of steam turbine, with condensers located underneath, aims at matching any requirements concerning plant layout and results in a cost effective redesign of the existing plant. The plant configuration selected is made up of a maximal number of standardized modules, the main modules being the gas turbines generator sets (CTG), two outdoor HRSG, as well as pre-designed, pre-engineered buildings or civil construction structures.

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Figure 4 - Thermodynamic configuration Main Components The specifications for the main components are as follows: 1. Gas turbine - Model V94.3A, single shaft, two bearings, 2 units - Output 260 MW - Efficiency 38% (based on LHV) at ISO conditions, simple cycle - Pressure ratio 17 - Exhaust flow 660 kg/s - Exhaust temperature 581 °C - Speed 3000 rpm - NOx emission 25 ppmvd (@15% O2) - CO emission 5 ppmvd (@15% O2) The V94.3A is of single-shaft construction with horizontally split casings, disk-type rotor with center tie bolt and radial Hirth serration, two outboard bearings, cold-end drive, axial exhaust diffuser. The 15-stage axial compressor with one variable IGV row and the 4-stage

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axial turbine designed to operate at an elevated firing temperature level without the need for an external cooling system were developed jointly by Pratt & Whitney and Siemens. The development, the experience gained and the appropriate modifications as well at different applications of this machine were presented in several publications. The gas turbines selected for Piacenza project will include the latest design upgrades introduced late 2002 and field validated at Mainz-Wiesbaden power plant. [Paper Becker- PowerGen 2004 Europe] 2. Heat recovery steam generator - Model horizontal, unfired, natural circulation, outdoor location - Type triple pressure, one reheat, 2 units - HP steam output 110 bar, 543 °C - Reheat output 32 bar, 542 °C - LP steam output 7 bar, 240 °C Much of the waste heat from gas turbine exhaust gas is recovered in unfired boilers, i.e. simple convection-type heat exchangers without radiating surfaces. In order to ensure rapid start-up and the best response to changes in load, drum-type boilers are used to allow true sliding-pressure operation. The HRSGs are designed as pre-engineered modules primarily for firing of the gas turbines on natural gas and have an internally insulated design. Duct firing system is provided. The HRSGs raise superheated steam at three different pressure levels in order to utilize thermodynamic gains from a triple-pressure steam turbine cycle. At part load, an attemperator operating on HP feedwater reduces the temperature of the high pressure (HP) steam. To optimize thermal economy, the condensate is passed through a flue-gas pre-heater to extract the remaining heat from the exhaust of the gas turbine before being dissipated into the atmosphere. 3. Steam turbine The existing steam turbine is a reaction type, two cylinders HP/IP, reheated, LP tandem compound, condensing exhaust. As result of the technical evaluation following modifications were decided: - HP valves: both the stop valves and the throttling valves (each one consisting of four

control valves operating in parallel) shall be revised; - HP section: general revision; - HRH combined valves: the right one shall be revised, the left one shall remain as it is; - Starting-up steam line: a steam pipe connecting the HP section of the turbine to the

condenser for a 15% flow shall be added; - By-pass dumpers: the two HRH and the LP by-pass dumpers shall be installed in the

condenser neck, from where the LP1 and LP2 preheaters shall be removed; - Condenser joints: the two joints connecting the four LP exhausts (two to each condenser)

shall be replaced with new ones; - Bleedings: the ST bleedings n. 1, 2, 3, 4, 6, 7 and 8 shall be definitely closed; - Boroscope control: the ST rotors shall be controlled by boroscope; - Control system: a control system integrated in the power plant DCS (distributed control

system) shall be provided; - Turbine drains: the system shall be revised; - General revision: a general revision of the ST, including valves, lubrication system, gland

system, oil cleaning system, control system, bolts (10% of each type added as spare), shall be provide.

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The choice to revamp the old steam turbine (instead to install a brend new one) bring some benefits to the power plant owner. - the old steam unit (Unit #4) can be operated during the erection of the new gas turbines,

recovery boilers and BOP utilities; - the thermal cycle structure (including turbine table and condensate cooling system) will

remain as it is with benefits in term of money, works, space needed and, in particular, the time in which the steam turbine will stay out of service is very short compared with a brend new installation (in this case 100 wd).

Operating modes Each module of the plant may be run in one of the following modes, assuring the maximum operation flexibility: - combined cycle without post firing - combined cycle with post firing The minimum start-up times of each module are approximately 160 minutes for a cold start (after a 4 days outage), 100 minutes for a warm start (after 48 hours outage) and 40 minutes for a hot start (after 8 hours outage). The plant is designed to also start the second gas turbine and its HRSG after having the first gas turbine in operation. This is made possible by having separate by-pass systems on both units and the use of isolation valves in the main, hot and cold reheat lines. Repowering solution comparison vs. possible alternatives The optimization of the above described intervention, both in terms of cost saving, trough the extensive reuse of the existing components, than in terms of technological application of the most recent solutions, led to a real profitable, self-supporting and environmental effective project. The key results are here below highlighted and compared with the relevant parameters of the alternative reference technologies available for the power production. Investment costs: � green field plant 360 Euro/kW

� repowering plant 280 Euro/kW Overall project schedule: � green field plant 46 (20+26) months (1)

� repowering plant 33 (6+26) months (1) (2) Environmental impact: � conventional plant 200 mg/Nm3 NOx 400 mg/Nm3 SOx 50 mg/Nm3 particulate

� repowering plant 50 mg/Nm3 NOx 0 mg/Nm3 SOx negligible mg/Nm3 particulate Land requirement: � green field plant 70,000 m2 � repowering plant 5,000 m2 (3) Efficiency: � conventional plant 38 %

� repowering plant 57 % Fuel cost: � conventional plant 44 Euro/MWh (4)

� repowering plant 30 Euro/MWh Notes: (1) the values between brackets mean development + realization times

(2) existing plant outage less than 12 months (3) new additional area (4) with 100% fuel gas

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Conclusions The benefits of repowering could be finally summarized by the followings key aspects:

1. lowering fuel cost (increased efficiency) 2. maximizing revenues (increased output) 3. reliable revenues and plant competitiveness (reliable and flexible generation of

electrical output) 4. minimizing invested capital (lifetime extension for equipment currently in service) 5. strategic and logistics assets (existing grid connection, cooling water, access to

existing infrastructure, permissions of regulatory agencies, fuel & power supply agreements, trained O&M personnel, administration)

6. reduction of environmental pollution (NOx, SOx, CO, CO2, particulates)