By Siân Green

The Jebel Ali complex in Dubai is to be further expanded with the addition of a new power plant and desalination facility – K2. The 860 MW, 40 million g/day facility will start operating later this year, helping to secure the economic future of the region

In mid-2000, the Dubai Electricity and Water Authority (DEWA) awarded a contract for the phase two development of the Jebel Ali K power and desalination plant to a consortium comprising Enelpower and Fisia Italimpianti of Italy. The new unit will start up in mid-2002, and is scheduled to be completed by mid-2003.

Jebel Ali K2 is the latest addition to the Jebel Ali power and desalination complex which is located 50 km from Dubai in the United Arab Emirates. The complex has a combined electrical capacity of almost 2000 MW and a desalination capacity of 530 000 m3/day (115 million gallons/day), and the K2 facility will add a further 860 MW of power and 182 000 m3/day (40 million g/day).

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Jebel Ali K2 is a $650 million project and is 100 per cent owned by DEWA. It will consist of three gas turbines, three heat recovery steam generators (HRSGs), two steam turbines and three desalination units.

The purpose of the project is to expand the capacity of Dubai’s current facilities to meet the projected increase in demand for water and power for the domestic and future industrial sectors of the economy. Economic growth in the UAE in 2001 is estimated to have reached four per cent, and with some 70 per cent of the country’s non-oil trade concentrated in Dubai, demand for water and power in the Emirate is projected to grow rapidly over the next few years.

Due to projected demand growth, in addition to developing Jebel Ali K2, DEWA is also repowering the Jebel Ali D power and desalination plant and is planning to add station L at Jebel Ali in two phases. It recently took on Lahmeyer International as project consultants. Station L phase I is likely to be a 700 MW, 318 000 m3/day (70 million g/day) plant, and phase II could double this capacity. Phase I is scheduled to be completed in late 2005.

Turnkey scope

Working with consultants Fichtner, DEWA selected Fisia Italimpianti and Enelpower to be the main engineering, procurement and construction (EPC) contractors for Jebel Ali K2 in July 2000. The two Italian companies won the contract against competition from companies such as Hanjung, Sumitomo Corporation and Sidem.

Figure 1. Jebel Ali K2 power and desalination facility. The power plant will have a net output of 800 MW and will supply steam to both the K1 and K2 desalination plants
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The consortium’s scope is to develop the power and desalination plant on a turnkey basis in 32 months, and the project is currently running on schedule. Fisia Italiampianti’s main responsibility is the supply and commissioning of the desalination plant.

In March 2001, Siemens announced that it had been selected by the Italian consortium to supply the main equipment for the K2 power plant as well as the instrumentation and control (I&C) system for the entire K2 facility. Under its f500 million ($136 million) contract, Siemens Power Generation (PG) will supply three gas turbines, two steam turbines and the I&C equipment for the plant. Siemens Power Transmission and Distribution group will provide the high voltage switchgear for the plant.

According to Giampiero Valenti, S&P engineering director at Enelpower, Siemens PG won the contract in different stages: it was selected by Enelpower to be the gas turbine equipment and I&C DCS system supplier in Enelpower’s bid proposal, but had to compete with other manufacturers to supply the steam turbine equipment.

Other subcontractors to Enelpower include Six Construct, which is carrying out the main civil works under a $21.8 million contract, Alstom Power Boilers Italia, and Murray & Roberts, which is constructing the control building under a $3 million contract.

Advanced technology

The Jebel Ali K2 power plant will have a net output of approximately 800 MW and will supply steam to the K2 desalination facility as well as the existing K1 desalination plant, which consists of two units with a total capacity of 91 000 m3/day (20 million g/day).

At the heart of the K2 power plant are three Siemens V94.3A gas turbine generators each rated at 190 MW at site conditions (250 MW ISO). The V94.3A is a single shaft machine of a single casing design with a low-NOx combustion system. It has an ISO inlet temperature of 1230°C and its 15-stage axial-flow compressor develops a pressure ratio of 17:1.

The annular walk-in combustion chamber is equipped with 24 hybrid burners and ceramic combustion chamber tiles, and the machine develops an exhaust mass flow of 650 kg/s and an exhaust temperature of 585°C at ISO conditions.

Each gas turbine at Jebel Ali K2 will exhaust to a single pressure, natural circulation, horizontal path HRSG supplied by Alstom Power Boilers Italia. These HRSGs are equipped with supplementary firing and will supply around 133 kg/s of high pressure steam at 67.5 bar and 539°C to the two steam turbines.

Siemens will supply the two steam turbines to the project. Each will be a back pressure-type machine rated at 150 MW. From the steam turbines, steam will pass to the desalination units at 2.3 bar and 133°C. The two K1 evaporators will receive steam at a rate of 128 kg/s while the three K2 evaporators will receive around 261 kg/s of steam, depending on the power plant’s mode of operation.

Figure 3. Siemens Power Transmission and Distribution Group is supplying the high voltage switchgear to the K2 power plant, while Siemens Power Generation will supply the main power generating equipment and a complete I&C system for the whole power and desalination facility
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Siemens will also supply a complete Teleperm XP I&C system for the power and desalination plant.

MSF desalination

The Jebel Ali K2 desalination plant will be designed, supplied, constructed and commissioned by Fisia Italimpianti and will consist of three identical units producing a total of 182 000 m3/day (40 million g/day) of desalinated water. The units are cross-flow multi-stage flash evaporators of the brine recycle type.

Multi stage flash evaporation is a widely-used method for producing desalinated water in large quantities. The process is based on the principle that the amount of energy that can be stored in water at its boiling point falls as the pressure falls. Thus when hot seawater at its boiling point flows into a vessel at a lower pressure, the excess energy is released resulting in ‘flashing’, i.e. liberating vapour.

This vapour is then cooled and distillate is obtained, and the brine continues into a series of further chambers, each with a progressively lower pressure.

The desalination plant consists of three main parts: the brine heater, the heat recovery section and the heat rejection section. Steam extracted from the steam turbines passes into the brine heater where the brine is heated to boiling point.

Seawater is passed through a heat rejection section and then to the heat recovery section, which consists of cooling tube bundles and a series of flash chambers arranged in successively lower pressure conditions. The hot brine releases vapour as it flows through each flashing chamber in the heat recovery and heat rejection sections. Brine flowing through the cooling tubes recovers the heat from the condensing distillate and flows to the brine heater where it is further heated.

Condensed vapour is collected in trays as distillate. From here, it is passed to a water treatment plant where it is treated so that it is fit for human consumption.

The Jebel Ali K2 desalination plant will consist of 17 recovery stages and two reject stages. The tube bundle length is 23 m.

Each unit has a nominal capacity of 60 460 m3/day (13.3 million g/day) of distillate, or a maximum of 66 070 m3/day (15 million g/day) at a top brine temperature of 108°C and a salt water temperature of 30°C. The performance ratio of the plant will be 8.5 with a top brine temperature ranging between 88-112°C and a salt water temperature range of 16-36°C. The K2 desalination plant will consume around 34 MW of power, equating to a specific power consumption of 4.2 kW/t of distillate produced.

On schedule

Jebel Ali K2 will operate as a baseload plant on natural gas. Its electricity output will be fed into the DEWA grid.

Currently all civil works at the site are complete. The first gas turbine has been installed and the second gas turbine unit is due to arrive on site early in 2002. The project is on schedule or start-up later this year.