The Adapazarı and Gebze Power Plants

The InterGen-ENKA consortium, was awarded the right to build and operate the Adapazarı (770 MW), Gebze (1540 MW) power plants, by winning the BOO (Build Own and Operate) TEAS (the Turkish electrical authority) tender in 1997. The projects are governed by the Energy Sales Agreements (ESA), with durations of 20 years, including the development and construction time. This electricity will be the cheapest private electricity sold to the state in Turkey.

Over seven thousand workers have participated in the construction of the Gebze and Adapazari power plants at different times, with a peak labor crew of 2220. The InterGen-ENKA Consortium obtained all of the necessary financing for these power plants, with the government backing being a Treasury Guarantee in support of TEAŞ’s obligations to pay for the electricity sold under the ESA.

InterGen is a joint venture between Bechtel and The Royal Dutch/Shell Group of Companies. ENKA is a major Turkish conglomerate of companies, including the country’s largest construction company. The Turnkey Construction Contractor for the projects is the Bechtel-Enka Joint Venture; major equipment suppliers are General Electric (Gas Turbines), CMI of Belgium (Heat Recovery Steam Generators) and Alstom (Steam Turbines).

With the acquisition of InterGen’s shares, ENKA increased its shares to become the sole owner of the electricity generation companies on 1 December 2005.

Environmental Features of the Power Plants

Combined Cycle Power Plants are in wide demand throughout the world, because they are characterized by short construction times, low investment costs, high operating efficiencies and low exhaust emissions.

This type of power plants can reach fuel to electricity conversion efficiencies of 60% (compared with conventional coal plants, which can achieve approximately 40%), and at the same time have minimal environmental impacts.

The most important reason for this is the use of natural gas, which is a very clean fuel containing little or no sulfur, particulate matter and other unwanted ingredients.

The only significant emissions of combined cycle power plants, is nitrogen-oxides (NOx), which is formed by the reaction of atmospheric Nitrogen and Oxygen because of the high combustion temperature within the gas turbines. However, ENKA power plants makes use of a special General Electric technology called DLN (Dry Low NOx). With this combustion scheme, natural gas and air are pre-mixed before being sent into the burners. This allows us to control the air/natural gas content ratio, and thereby to control the amount of NOx formation. Also, our Heat Recovery Steam Generators are designed with 80-meter high stacks, in order to allow for quicker atmospheric dispersion at higher altitudes.

As a result of these factors, the emissions of our power plants fall well within the relevant limits stipulated by both the World Bank and Turkish Ministry of Environment. Our Heat Recovery Steam Generators (HRSGs) uses demineralized water, which is produced on site.

All of the by-products of this chemical process is treated along with the domestic wastewater of the plants, and then discharged into the Carksuyu River, in adherence to the relevant wastewater discharge limits. Also, special noise panels are placed around our gas turbines and silencers are used for the steam vent lines, to minimize the noise emissions from the plant.

Construction and Commercial Operation Time Frames

Construction of the Adapazarı and Gebze power plants started in March 2000 achieved commercial operation in October 2002.

System and Main Process Equipment

Our plants are typical combined cycle type power plants. Electricity is produced in two stages. The first stage occurs in the gas (or combustion) turbines, where the thermal expansion of the combustion of natural gas turns a shaft connected to a generator. The hot exhaust gases produced by this process are directed to the Heat Recovery Steam Generators (HRSGs), where the energy still contained in these gases is used to produce steam from water. Steam at the necessary pressure and temperature is then forwarded to the steam turbine, which turns a shaft coupled to another generator, producing the second stage electricity. Because two different thermodynamic “cycles” are utilized in parallel, these types of power plants are called “Combined Cycle” plants.

The utilized steam leaving the steam turbine must then be cooled and condensed into water, using the cooling system. Cold water is sprayed on to the steam in the condenser, turning it back into the liquid phase. This results in the collection of hot water at the bottom of the condenser. To be used again, this water must be cooled and is therefore sent to the cooling towers via large pumps. Our dry-type cooling towers work much like the radiator in an automobile. The only function of the 135-meter high, reinforced concrete structures is to generate a sufficiently high airflow through the coolers circumventing the towers. Water passing through these “Delta Coolers” is thereby cooled.

A very small portion of the water heading for the cooling towers is re-directed towards the HRSGs as feedwater, in order to produce steam by heating. The steam thus produced is then sent to the steam turbine, completing the cycle. In order to maximize efficiency, steam is produced in the boilers at three different pressure levels (low, intermediate and high). This enables us to extract the maximum heat possible out of the hot gases in the boilers.

Electricity is produced by the Steam Turbine Generator at 19 kV and by the Gas Turbine Generator at 15.75 kV. This must then be transformed up to 380 kV, before being fed into the national grid at three different connection points: Adapazarı Sub Station, Dokurcun-Temelli and Osmanca-Habipler energy transmission lines. A tie-line connecting the Gebze and Adapazarı plants allows for extra flexibility. The InterGen- ENKA consortium financed the construction of all of these transmission lines.

The diagram depicts a single “Block” consisting of two gas turbines, two HRSGs, one steam turbine, one condenser and one cooling tower. Our Gebze plant is made up of two Blocks and the Adapazarı plant contains just one. The Blocks work completely independent of each other, but do make use of some common facilities.