Taweelah B plant takes shape

“It was the biggest in the world and people were very cautious during the design and development phases”, added Andrianne, the manager responsible for Taweelah at Brussels-based Tractebel Energy Engineering. “In the event, everything went smoothly”.

He was speaking at the mid-point of the project’s two-year guarantee period, which ends next July, during which a Tractebel team is monitoring the project’s performance on behalf of the client, Abu Dhabi’s Water and Electricity department (WED).

Taweelah B has six 150MW gas-fired generation units and six MSF desalination units each with a capacity of 45,000m³/d. Under a contract signed in 1992, the project was built by a consortium headed by Germany’s ABB Kraftwerke.

The steam turbines and generators were supplied by Kraftwerke ABB and the boilers by Babcock-Lentjes Kraftwerkstechnik, also of Germany. Italy’s ABB SAE Sadelmi was responsible for design and installation, and Frankfurt-based Hartmann & Braun for instrumentation and control systems. The giant distillers were supplied by Italy’s Italimpianti.

The scheme was commissioned in stages, between mid-1995 and mid-1997. At its peak, the on-site workforce numbered 9000. Tractebel now has an on-site team of about 10 engineers, compared with a peak of 70 during construction.

The designs for the giant distillers were based on those of 36,000m³/d units installed at Abu Dhabi’s Umm al Nar desalination scheme in the 1980s. The specifications required them to operate between 65% and 127% of design capacity. The units’ sheer scale and their high degree of operational flexibility demanded significant developments in material technology and process control. To eliminate the possibility of corrosion, for example, the heat exchanger tubes are made of titanium and a high-grade copper-nickel alloy.

As in other Gulf states, water demand in Abu Dhabi is growing rapidly. Despite official efforts to persuade the approximately 1M residents to conserve water, they consume an average of almost 400l/d. Seawater desalination has offered the only means of averting shortages. Most of Taweelah B’s water output is piped 140km to the inland oasis city of Al Ain. Power demand, meanwhile, is expanding at about 10%/year.

Taweelah B is not the first station at Taweelah, and it will not be the last. Taweelah A, built in the 1980s, has three 85MW gas turbines and a capacity of 127,000m³/d of water. Plans are advanced for a third Taweelah complex, designated A-2.

Tractebel has already played a part in the development of the A-2 scheme, and it could soon be even more centrally involved. Designs for the project were completed last year by Tractebel Energy Engineering under a contract awarded at a time when the scheme was intended to be in the public sector. In mid-1997, however, Abu Dhabi’s WED decided to opt for a BOO scheme instead.

Another Tractebel group company, Electricity and Gas International (EGI), in association with Total of France, is one of three bidders which in July was shortlisted for the scheme. The others are CMS Energy and Enron, both of the US.

The scheme will comprise a co-generation plant with a capacity of 480-580MW and an MSF desalination plant with a capacity of 227,000m³/d.

Andrianne stressed, however, that the final specifications of Taweelah A-2 had yet to be fixed. “Nothing has yet been finalised. No contract has been signed, and no-one knows what the precise specifications will be”.

The Abu Dhabi Privatisation Committee for the Water and Electricity Sector, which is overseeing the scheme, hopes to select the final contractor in the autumn. The successful bidder will take a 40% stake in a new Abu Dhabi-based utility. The other 60% will initially be held by the government. 70% of the station’s capacity is scheduled for commissioning by April 2001.

Tractebel in the Middle East and North Africa

Tractebel Energy Engineering is a division of Tractebel Engineering which is one of Europe’s largest design, consultancy and project management concerns. The Brussels-based Tractebel group as a whole is a diversified multi-national involved in the electricity, gas, engineering and environmental services businesses. It had 1996 revenues of $11.2Bn.

In addition to its role at Taweelah B, Tractebel Engineering has worked on smaller desalination schemes elsewhere in Abu Dhabi, and also in the emirates of Fujairah, Ras al Khaimah and Ajman. In the early 1980s Tractebel designed the second phase of the Yanbu desalination plant in Saudi Arabia, and the firm designed the pipeline from Yanbu to the city of Medina.

Tractebel has also been successful in north west Africa – the Arab Maghreb. In Libya the company was consultant for a 22,500m³/d MSF desalination plant in the capital, Tripoli, and for the water intake and a 100,000m³/d MSF desalination plant at a thermal power station in Libya’s second city of Benghazi. Amongst Tractebel’s biggest projects this decade has been a 22,500m³/d RO plant to serve the Gabes region of Tunisia.