Power (15-Aug-03)

Ilijan Combined-Cycle Power Plant, Southern Luzon, Philippines

Owned and operated by KEPCO Ilijan Corp.

The 1,200-MW Ilijan combined-cycle plant is truly a greenfield plant. It was literally carved out of the Philippine jungle by an international consortium of developers, engineers, and contractors. Obstacles that developers of plants in the U.S. often don't face—such as the absence of an existing transmission grid or natural gas pipeline nearby—had to be overcome by building those infrastructures from scratch. In addition, all the plant water has to be made from seawater, including NOx injection water. But for Ilijan, the end justified the means. The plant's first-year operating results are just in: over 96% availability and a minuscule 0.48% forced outage rate. Those numbers alone make this project a textbook study on "How to build a power plant against long odds."

In the mid-1990s, the Philippine government decided to develop the Camago-Malampaya gas fields in the Province of Palawan to foster growth of the economy of Southern Luzon. The project, offered for competitive international bidding by the Philippines' National Power Corp. (NPC) as a build-operate-transfer (BOT) scheme, was awarded to KEPCO on November 5, 1997. Simultaneously, KEPCO formed KEPCO Ilijan Corp. (KEILCO) to develop the project. Mitsubishi Corp. (MC), Mirant Corp., and Kyushu Electric Power Corp. joined the project in November 2001.

KEILCO contracted with United Engineers International Inc. (UEI) and Mitsubishi for the engineering and procurement phase and with Raytheon-Ebasco Overseas Ltd. (REOL) for the construction phase. Ground was broken on March 15, 1999, with the start of civil construction works. The plant entered commercial service on June 5, 2002.

The performance of the $710 million project over its first full year of commercial operation has been outstanding: availability of over 96%, and a forced outage rate of only 0.48%. Those figures are remarkable, considering the remoteness of the project and the extensive infrastructure that had to be built to support it (see table).

Ilijan combined-cycle project operational summary

Source: KEPCO Ilijan Corp.

Project overview

Ilijan, which is one of NPC's first natural gas–fired power plants, is located on a 60-acre site at Arenas Point, Barangay Ilijan, Batangas City, in Southern Luzon, Philippines (Figure 1). The plant, which is designed to be dispatched (Figure 2) and to operate at or near full load, consists of two 600-MW (nominal) power blocks. Each block consists of two Mitsubishi M501gas turbines with a nominal rating of 200 MW, two Babcock-Hitachi heat-recovery steam generators (HRSGs), and one Mitsubishi TC2F-40 steam turbine with a nominal rating of 242 MW. The plant is rated at 1,251 MW (net) on the high-voltage side of the main transformers. The gas turbines' primary fuel is natural gas, with diesel oil as a backup. The diesel is stored in three on-site storage tanks that are replenished through an offshore diesel fuel–unloading terminal.

1. Ilijan site.

The 1,200-MW Ilijan combined-cycle plant is located on a 60-acre site at Arenas Point, Barangay Ilijan, Batangas City, in southern Luzon, Philippines. The plant has two power blocks, each a 2 x 1 configuration based on the Mitsubishi 501G gas turbine. Source: KEPCO Ilijan Corp.

2. Controls.

Ilijan's instrumentation and control system helps plant operators run the plant safely, reliably, and economically. The integrated plant controls are based on the ABB Bailey distributed digital control system. Source: KEPCO Ilijan Corp.

NPC's 500-kV transmission line connects to the Luzon grid through the existing Tayabas-Dasmarinas line in Alaminos, Laguna, about 40 miles away. NPC supplies natural gas to Ilijan through a 300-mile undersea pipeline from the Camago-Malampaya field in Palawan to the Shell refinery in Tabangao. From there, the gas is transported through a 16-in-diameter onshore pipeline running 9 miles to the plant.

First G series turbine outside Japan

The Mitsubishi G series gas turbines (Figure 3) operate with a turbine inlet temperature of 2,730F and use steam to cool their combustor liners. The first (60-Hz) M501G gas turbine has been in commercial operation at Mitsubishi's in-house combined-cycle power plant in Takasago, Japan, since 1997. In 1999, two 50-Hz M701G gas turbines were put into commercial operation at Tohoku Electric Power Co.'s Higashi Niigata power plant.

3. First international installation.

The Mitsubishi G series gas turbines operate with a turbine inlet temperature of 2,730ºF and use steam to cool their combustor liners. This is the first 501G placed into commercial service outside Japan. The first 60-Hz 501G has been in commercial operation at Mitsubishi's in-house plant since 1997. In 1999, two 50-Hz M701G gas turbines were put into commercial operation at Tohoku Electric Power Co.'s Higashi Niigata power plant. Source: KEPCO Ilijan Corp.

According to Won-Kyung Sung, Ilijan's plant manager, "the technology feedback from Mitsubishi's Takasago Works greatly helped us enhance reliability during the early stages of commercial operation of the M501G machines at Ilijan. Significant improvements to the gas turbines' main fuel nozzles, combustion liners, first-stage nozzles and blades, and second-stage nozzles were made during commissioning and at the time of the gas turbine's first inspection. The blade passage temperature and mechanical vibration of all four GTs were maintained within satisfactory levels."

Cooling circuits for the turbine section are similar to those of the F series. They consist of a rotor cooling circuit and four stationary vane-cooling circuits. Rotor cooling air is provided with compressor discharge air extracted from the combustor shell. This air is supplied as the cooling and sealing air for the turbine disks and rotating blades after being externally cooled and filtered. Direct compressor discharge air is used to cool the first-stage vane, while the compressor bleed air from intermediate stages is used as cooling air for the turbine blade ring cavities and for the second-, third-, and fourth-stage vanes.

The DLN combustor in the MHI G gas turbines consists of a pilot nozzle, eight main fuel nozzles, air bypass valves, and a double-wall structure for basket and transitions. In the G combustor, the basket and transition are known as the combustor swirler assembly and combustor liner, respectively.

Inside the combustion chamber, the flame temperature of G combustors is between 2,700F and 2,900F. However, the combustor exit temperatures are different. The G gas turbine uses steam taken from the bottoming cycle for cooling the combustor liner. The Mitsubishi steam-cooled DLN combustor at Ilijan is the world's first demonstrated application of steam-cooled combustor technology.

Each turbine exhausts into a Babcock-Hitachi three-pressure reheat natural circulation HRSG with 2,200 psig/1,005F HP, 650 psig/1,055F IP, and 90 psig/490F LP steam conditions. Each of the two condensing steam turbines has sliding pressure main steam admission, one uncontrolled admission system, an HP/IP pressure casing, and an LP, double-flow casing with intermediate reheat, and appropriate instrumentation and controls. Intermediate steam and primary superheater outlet steam serve as a backup for GT combustor transition piece cooling and are returned to the hot reheat steam.

The turbines' emissions are managed with dry, low-NOx combustors while firing natural gas; water injection is added when firing diesel fuel. The plant cannot operate in simple-cycle mode because it has no bypass stack. However, the dumping of steam to the atmosphere and 100% steam bypassing of the condenser are integral to the plant's design and operating philosophy.

A desalination plant supplies Ilijan's water needs and uses a reverse osmosis (RO) system for domestic needs. Seawater is used for condenser cooling water. The seawater RO-type desalination system supplies the plant's service water, fire protection, potable water, and demin water requirements. The system has three, 33% capacity processing trains. During natural gas firing, one operates while the other two remain on standby. All three trains can be put into service when the plant burns diesel oil to supply adequate makeup demin water to the combustion turbines when water injection is used to control NOx emissions.

The water treatment system provides a continuous supply of the high-quality demin water required for plant makeup, gas turbine water injection for NOx control, and dilution water for chemical feed systems. Fresh water from the seawater desalination system is furnished to the water treatment system via a fire/service water storage tank. The water treatment system works in three stages: polishing reverse osmosis treatment, permeate break tank, and mixed demineralization. Ilijan has a 750,000-gallon demin water storage tank, a 1,250,000-gallon fire/service water storage tank, and a 330,000-gallon tank dedicated to fire protection.

Ilijan's stack emissions are monitored by a state-of-the-art continuous emission monitoring system. Meanwhile, the quality of the local watershed and coral reefs and the plant's noise and social impact are tracked by a quarterly monitoring scheme developed and administered by representatives of the community, the government, NPC, and KEILCO.

Obstacles overcome

Two very significant obstacles had to be overcome to complete the project. One is the plant's location, on an isolated seashore whose access roads are unpaved, in terrible condition, and impossible to transit during the rainy season. In addition, the site was often visited by heavy storms and typhoons that slowed construction and delayed the delivery of equipment and materials.

The second major obstacle was the financial weakness of the plant's contractors. Both UEI and REOL, affiliates of Washington Group International (WGI), were negatively affected during the middle phase of construction by WGI's financial crisis and subsequent filing for bankruptcy in May 2001. All the project participants paid a substantial cost for the delays until the bankruptcy court approved WGI's reorganization plan and funding in November 2001.

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