Santa Rita hits the mark

Roger Fox, First Gas Power Corporation, Philippines, Friedrich Heimann, Siemens Power Generation Asia Pacific, Malaysia

Figure 1. Santa Rita is one of three combined cycle independent power projects that will use Malampaya gas
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In August 2000, Siemens Power Generation Group (KWU) handed over the 1000 MW Santa Rita power plant to operating company First Gas Power. The plant is now the largest and most technologically advanced power plant in the Philippines, and represents a major step forward in achieving the country’s energy policy aims.

The Philippines has made shifting from a heavy reliance on imported oil to indigenous fuel a major goal. In addition, its electricity demand is expected to grow by up to nine per cent per year until 2009, necessitating the installation of up to 10 000 MW of new power generation capacity. These two factors are fuelling the exploitation of the Malampaya-Camango natural gas field, as well as an associated boom in natural gas-fired electricity development.

The Philippines is keen to increase the use of natural gas in its economy largely due to the environmental advantages. It is by far the cleanest of all fossil fuels, burning without emitting smoke, dust or ash. Its use will also contribute significantly to the Philippines’ economy due to royalties paid to the government.

The increase in power demand in the Philippines will be satisfied largely by Santa Rita and two other combined cycle power plants currently under development, all of which will use gas from the Malampaya field. Gas from Malampaya will fire the three facilities – with a combined capacity of 2700 MW – for the next 20 years, and could replace as much as 50 per cent of the oil that the Philippines currently imports for power generation. Two of the plants alone – Santa Rita and San Lorenzo – can supply about 20-30 per cent of the country’s equivalent petroleum requirement.

Figure 2. The project’s ownership structure and key contractual agreements
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The Malampaya-Camango field, located off the Philippine island of Palawan, holds natural gas reserves of 762 billion m3, and remains the Philippines’ only significant hydrocarbons discovery. Estimates show that commercial production of these reserves will trim the country’s annual oil bill by $250-$600 million, depending on world crude prices. This represents a substantial savings in foreign exchange. The Philippine government likewise expects revenues of about $5-8 billion over a 20 to 25 year period from its share of the gas.

The Santa Rita project

The Santa Rita power plant has been developed by First Gas Power Corporation (FGPC), a wholly owned subsidiary of First Gas Holdings Corp., which itself is jointly owned by First Philippines Holdings Corp., BG plc, and Meralco Pension Fund.

FGPC was established in 1995 to pursue opportunities in the Philippines’ emerging natural gas sector, in particular, the development of power plants using natural gas from the Malampaya field. It initially signed a power purchase agreement (PPA) with Philippine utility Meralco in March 1995 for the sale of power from a 450 MW plant. However, following revised projections of the increase in electricity demand by Meralco, the plans were adjusted and the two companies signed a 25-year PPA for a 1000 MW plant.

Natural gas from the Malampaya field is not expected to be available until September 2001, and so Santa Rita is currently operating on condensate fuel supplied by Enron Capital and Trade Resources Inter Corp. under a liquid fuel purchase contract.

On December 16 1996, FGPC awarded the engineering, procurement and construction contract (EPC) for Santa Rita to a consortium consisting of Siemens AG and Siemens Power Generation Asia Pacific Sdn Bhd. In the EPC selection process, FGPC screened 42 potential contractors and eventually narrowed this down to eight companies to which an invitation to tender package was issued.

The EPC contract is a fixed price, turnkey contract obligating the contractor to construct the power station, related fuel receiving and storage facilities and related transmission line and facility upgrades. Siemens Power Operations Inc., as operator, will operate and maintain the plant for an initial term of six years.

First Gas Holdings Corporation and BG plc have provided the 25 per cent equity portion of the $1.390 billion capital expenditure required for the Santa Rita and San Lorenzo power projects, both of which are being developed by FGPC. The remaining 75 per cent has been financed through borrowings from domestic and foreign financial institutions. Of the loans, 90 per cent has been foreign sourced, and they carry an average tenure of 10-12 years.

In September 1997, FGPC completed a $680 million financing package, thus setting the stage for the full implementation of Santa Rita.

Construction underway

The scope of work undertaken by Siemens comprised the design, engineering and supply, construction, testing and commissioning of plant and equipment. The plant consists of two blocks, or four single shaft units, with a nominal capacity of 1000 MW.

FGPC acquired a 35 ha site in Santa Rita in the Province of Batangas as the site for the project. The cost of acquiring the land was $7.1 million. The site, formerly agricultural land, sits along the coast of Batangas Bay. Prior to back-filling, the site area had to be stripped of humus, mud and plants. A total of 420 000 m3 of fill was needed to achieve the new ground level for the power station.

A few weeks after financial close was achieved, construction work started on the Santa Rita combined cycle power plant on 17 November 1997. Site preparation for the project was a particular challenge. Due to the existence of very soft and loose soil conditions in the superficial layers, pile foundations had to be provided for almost every structure. The whole plant now rests on 5200 pre-cast and pre-stressed concrete piles of between 12 m and 17 m in length – around 2000 more piles than were originally planned.

Two intake concrete structures for the cooling water are located as an offshore construction approximately 200m from the shoreline at the sea bed contour line of -15m. Two intake GRP lines, designed as gravity pipes with a nominal diameter 2500mm, carry cooling water from these structures to the pump house. The pipes were prefabricated onshore, placed and connected together by special offshore equipment under water in a dredged pipe trench.

Figure 3. A tanker unloading at the Santa Rita site in the Philippines
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For unloading the liquid fuel from sea-going vessels, which range between 20 000 to 100 000 DWT, a jetty has been constructed which is a unique feature.

For receiving the untreated fuel from the tanker and delivering it to the fuel treatment plant, five tanks are available with a total capacity of 143 100 m3. Two more tanks have been installed with a total capacity of 13 400 m3 to store the treated fuel from the fuel treatment plant and also to store the return fuel from the turbines.

In the plant layout design, special care was taken to ensure the provision of short paths, dismantling and lay-down areas for overhaul operations and good accessibility to buildings and components for maintenance. During initial construction, the heaviest pieces, i.e. pre-assembled gas turbine and generator, were transported by special trailer and hydraulically lowered to the foundation. The steam turbine and condenser were delivered in pre-assembled parts and were erected on site.

The turbine building is founded on reinforced concrete foundations with the above mentioned piles. The foundations for the gas and steam turbines and the buildings are separated from each other by means of a construction joint. The overhead travelling cranes in the turbine buildings are designed for a lifting capacity, which is sufficient for the heaviest single load to be lifted during maintenance and overhauls.

Each of the four units comprises one gas turbine, one high pressure/intermediate pressure/low pressure (HP/IP/LP) steam turbine, one generator, one synchronous clutch between the steam turbine and generator, one heat recovery steam generator (HRSG), one generator transformer and all associated equipment. In this single shaft arrangement there are no bypass stacks and the plant is designed for base load operation.

The gas turbine burners are operating initially with liquid fuel, namely gasoil (distillate), condensate and naphtha. When gas becomes available, natural gas will become the primary fuel source for the plant and liquid fuel will become the back up.

The V84.3A gas turbine machines installed in Santa Rita are particularly suitable for combined cycle operation due to the provision of variable inlet guide vanes (IGV) in the compressor section. These can be modulated to control the gas mass flow through the gas turbine, ensuring that the gas turbine exhaust temperature (and hence the HRSG inlet temperature) is held virtually constant in the gas turbine load range of 50-100 per cent.

The hybrid burner ring (HBR) combustion system is equipped with a ring combustor with 24 hybrid burners. The design ensures concentric gas and air paths throughout the length of the machine, thus involving a minimum pressure drop. The installed hybrid burners achieve dry low NOx control with minimal CO emissions by means of premix combustion in the upper load range using fuel gas. The hybrid burners permit both diffusion and premix burning with both gaseous and liquid fuels. In case of diffusion burning, water injection for thermal NOx suppression is provided. The premix operation of the gas turbine burners reduces NOx emissions to less than the specified guaranteed value of 86 ng/J for gas and 130 ng/J heat input on liquid fuel.

The pressure build up at the HRSG is controlled by the provision of steam bypass stations and surplus steam not accepted by the steam turbine is led to the condenser. It is therefore not necessary to restrict the output of the gas turbine and the HRSG until the steam turbine can accept the full flow of steam and the bypass stations are closed. Therefore short start-up times are achievable and less steam is dumped to the atmosphere.

The most economic start-up is achieved by temperature controlled start-up as the exhaust gas flows completely through the HRSG. Due to the single-shaft design, simple fully automatic start-up and loading to any pre-selected load is possible, as is short run-down time due to the ability of the gas turbine compressor to act as a brake on the entire single-shaft machine.

The synchronous clutch installed between generator and steam turbine gives the advantage of high flexibility, low start-up power requirements, the possibility of simple cycle operation without a bypass stack, and the possibility of independent turning operation.

Maximizing benefits

The well proven state-of-the-art Teleperm XP system employing centralised monitoring and supervision provides a high level of automation for each combined cycle module in order to maximize the benefit of high efficiency on base load operation.

Figure 4. The funding commitments of the two plants
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A 230 kV outdoor switchyard on the plant site and a 35 km long high voltage overhead transmission line to the Calaca outdoor substation operated by the National Power Corporation (NPC) is part of the package. From Calaca the power is being exported to Meralco, which serves the Manila conurbation.

Cooling requirements for the station are met by a direct seawater cooling system, and fresh water is provided by deep wells on site.

To generate emergency power and power for black start of one unit in case of a voltage loss in the external grid, two independent diesel sets are provided.

Santa Rita meets the environmental performance standards set by the Department of Environment and Natual Resources:

  • Continuous noise at any site boundary: sound power level must be less than 60 dB(A)
  • NOx for liquid fuel: less than 130 ng/J
  • NOx for gas fuel: less than 86 ng/J

Final stages

The first gas turbine arrived on site in December 1998 and was lifted onto its foundation while mechanical erection had already started.

Siemens decided to incorporate in the Santa Rita gas turbines, lessons learned and experience gained in other projects and test bed programmes. All four units of the V84.3A gas turbines for Santa Rita were therefore dismantled so that modifications could be made.

Commissioning started as soon as the systems and the unit auxiliary power units had been energized. Before starting test runs with the entire plant, the individual systems with their components were tested and commissioned carefully. Activities were carried out stepwise and were performed in five phases:

  • Commissioning of components and individual systems
  • Commissioning of system groups and operation with turning gear
  • Commissioning of system groups including. bypass operation
  • Power operation
  • Reliability run and performance testing

After completion of the performance tests and a net dependable capacity test, Block 1 immediately entered commercial operation on 11 June 2000 while commercial operation for Block 2 started on 17 August 2000. As widely reported, the project was delayed for some six months and the contractual differences arising from this are still to be resolved.

Click here to enlarge image

The reliability runs for both units were completed with all three liquid fuels, and the plant achieved its specified guarantees. The results of the tests performed on Block 1 in May 2000 and on Block 2 in August 2000 are shown in Table 1.

Since handing over the plant to the client, the plant has been operated by Siemens Power Operations Inc., and has been running with 100 per cent reliability and availability.

Further steps

Siemens KWU recently received a follow-up contract from FGP Corp. for the construction of the 500 MW San Lorenzo power plant, which will also use gas from Malampaya. The San Lorenzo plant will be built adjacent to Santa Rita, and the two power plants will have a common control room, water treatment plant and tank farm. Piling activities at San Lorenzo have already started.

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