130 MWe Amercoeur coal veteran to be reborn as 420 MWe CCGT

Early in 2009, assuming the current project schedule is met, Electrabel’s Amercoeur 1, originally commissioned in 1968 as a coal fired station, and mothballed in 2000, will embark on a new life as a natural gas fired combined cycle plant (CCGT). The installed capacity will increase from 130 MWe to 420 MWe (net), with efficiency rising from 38% to 57%.

Key objectives of the 150 million euro project are to make maximum use of existing site facilities (including cooling system and cooling tower, steam turbine building and grid connections) and to allow more effective use of staff.

In comparison with a new-build CCGT a number of costs are avoided, there will also be O&M synergies with the remaining operating coal unit (127 MWe) at the site (as long as it remains operational, of course).

Another key part of the project will be provision of centralised control facilities at Amercoeur. This will allow operation of the repowered Amercoeur 1 and remote operation of the existing 350 MWe Saint Ghislain combined cycle unit, which is located in the same zone (Hainaut-Namur), from a single control room, allowing Electrabel to take advantage of “significant personnel synergies” between the two combined cycle units.

Overall, the repowering – which is being done under an EPCM contract between Tractebel Engineering and plant owner Electrabel (a fellow member of the Suez-Tractebel group) – will deliver a flexible mid-merit unit at an estimated cost around 30% below that of an equivalent greenfield project.

The notice to proceed for the Amercoeur repowering was given on 31 January 2007, and first firing of the repowered plant is scheduled for October 2008, with commercial operation due in April 2009.

Contracts awarded to date include:

• gas turbine and gas turbine generator – GE;

• steam turbine – Ansaldo;

• heat recovery steam generator – CMI;

• step-up transformers – Pauwels;

• DCS and remote operation systems – Cegelec;

• condenser – Alstom;

• cooling system – Hamon;

• building works – Lixon (concrete) and CSM (steel); and

• GT busbar and circuit breaker – Electrobudowa and Areva.

The gas turbine is a GE 9FB, and will be the first such machine in Electrabel’s fleet. Rated at 280 MWe, it will be manufactured at GE Energy’s Belfort facility in France. The gas turbine generator will be manufactured at GE’s Schenectady, NY, facility. Shipping of these items to site is scheduled for the first quarter of 2008. GE also has a multi-year maintenance agreement.

The heat recovery steam generator is of the three pressure level type, with reheat, and will be CMI’s first HRSG supplied to a 9FB project.

Fitting the foundations

The Ansaldo Energia steam turbine is rated at 150 MWe and will be coupled to the existing steam turbine generator. It is also necessary to re-use the existing foundation baseplate, so the footprint of the new steam turbine must be compatible with the existing foundations.

A three-cylinder configuration, making maximum use of standard modules from the Ansaldo Energia catalogue, has been selected, with the aim of reducing impacts on the existing foundations to the minimum. The main steam characteristics are:

• live steam pressure – 122.8 bar abs;

• live steam temperature – 565°C;

• reheat steam temperature – 565°C;

• condenser pressure – 0.055 bar abs.

To minimise impacts on civil works and to match the existing generator, the following basic ground rules have been followed: minimal removal of concrete parts from the turbine table; if absolutely necessary concrete can be added to the table; standard steam turbine modules to be employed, using “inner block” principle, with inner casing, rotor drum and blading unchanged and only the outer casing and rotor ends modified to accommodate generator and foundations; and use of an anchoring system compatible with the existing foundations (through-bolts and nuts).

The HP section is of fully standard configuration, while the IP outer casing is longer than standard to match the existing bearing span. Consequently the rotor ends, the parts outside the steam path, are also longer than standard.

Modifications to the existing deck will be required in order to accommodate a standard LP section (ie a standard LP outer casing) and to match the existing generator.

Overall the steam turbine strategy is designed to achieve the following goals: major reduction in civil works; use of a standard, well proven, steam path design; and significant reduction in the time schedule for the whole project.

Ansaldo’s steam turbine scope included a rotordynamic analysis, taking into account the modifications and including the existing generator, as well as supply and/or reconditioning of the steam turbine auxiliaries, including provision of new lube and control oil systems – again with the goal of minimising civil works – as well as new gland steam condenser plus associated valves and new low pressure steam admission valves.

Conserving the cooling tower

All the existing equipment is being removed from the cooling tower, ie the heat transfer media (asbestos cement), the water distribution system, the drift eliminator and the associated supports and accessories.

In other words, all that will remain of the original equipment will be the concrete, ie, shell, internal structure, basin and main water header.

The contracts for dismantling, asbestos removal and concrete repair, where required, have been awarded to a local contractor. This means a clean concrete structure will be handed over to Hamon for its work on site.

For new build, it is the thermal designer (Hamon) that typically defines the concrete structure required to match the cooling equipment. But in the Amercoeur 1 repowering case, it is the thermal design and equipment that must cope with the existing structure. The use of an old structure means obstructions and awkward dimensions when it comes to accommodating modern cooling technology.

However, the new design enables effective cooling for a heat load that is increased by 55%, This is achieved by using Cleanflow heat transfer media and the overlapping water sprayer concept.

The cooling tower will also be equipped with very high efficiency drift eliminators.

The Hamon scope in addition includes upgrading of the cooling water treatment system in order to reduce both make up and water blow down as well as to meet severe local restrictions on the use of the water from the adjacent canal.

Also, the presence of a private residence in the vicinity of the power plant has imposed particularly stringent noise level requirements. The cooling tower will be equipped with noise attenuators that will drastically reduce the noise generated by the “rain” inside the cooling tower (the water flow in the cooling tower is indeed such that in 10 minutes as much water is collected in the cooling tower basin as would be collected from one year of rain in the vicinity falling in an equivalent area).