COMBINED GAS AND STEAM POWER PLANT

The Combined Gas and Steam Power Plant (COGAS) at the Gallileïstraat in Rotterdam officially came into operation on December 9, 1988. The COGAS is one of the power plants which is owned worldwide by E.ON and is responsible for the delivery of district heat to Rotterdam/Capelle aan den IIssel, Leiden and The Hague. In addition to that the COGAS unit at the Gallileïstraat delivers electricity to the public grid and heat to Rotterdam and Capelle aan den IJssel The construction of the unit started in April 1986 on the foundations of an old Coal Power Plant which was in operation from 1934 to 1975.

The delivery of electricity started on September 1st, 1988. On September 30, 1988 the COGAS at the Gallileïstraat took over the heat delivery from the plant in Schiedam, which officially closed down on January 1st, 1990.

Steam and Gas
The COGAS consists of three gas turbines (which run on natural gas) �?and one steam turbine. The hot exhaust gasses of the gas turbines are being led to the central heating boiler, where the gas is used for the production of steam and also to heat the water of the district heating. If necessary, extra burners can supply extra heat. The steam is driving the steam turbine and it will still be hot enough to bring the water of the district heating to the right temperature. To make this happen the low pressure area of the steam turbine will be disconnected, as a result of which no heat can be discharged through the cooling water.

Because of the application of district heating about 80 percent of the added energy (in the form of natural gas) can be transformed into electricity and heat. This kind of installation has an electricity yield of 45 % against a 40% yield rendered by a conventional installation without the combination steam and gas turbines.

Electricity
The generators, which are connected to the gas and steam turbines, can generate electricity. The total net electrical power of the plant is 219 MW, which is divided over one steam turbine generator of 74 MW and three gas turbine generators of each 49 MW. Two machine transformers �?each one has a generator attached to it - will bring the voltage generator from 11.500 volt to150.000 volt. Next, the electricity will be distributed to the coupled network in the 150.000 volt Marconistraat station.

District Heating
The steam from the steam turbine is still hot enough to heat the water of the District Heating. This process takes place in the “heat exchangers�?of the plant. The steam is being led through the heat exchangers and conveys its heat to the water of the district heating circuit. The water runs via pipe bundles through the exchangers. The thermal power (heat power) of the District Heating is max. 260 MW, which is 80% more than the capacity of the old power plant Schiehaven, the former provider of heat to the District Heating.

Hot Water Circuit
The heated water for the District Heating can be pumped directly into the hot water circuit or stored into two buffer tanks, which have a volume of 12.500 cubic meters each. The capacity of these buffer tanks function as a backup when the COGAS is not heating any water. In that case the hot water from the circuit will be led to the city where again the heat will be conveyed via the converters to the hot water circuit of the houses where it will be used to heat the tap water as well.

Start-Stop Unit
Tennet (The Utility Cooperative) in Arnhem determines on a daily basis which power plants have to deliver electricity and which don’t. In this process the price, stoked fuel and yield of the power plant play an important role. This procedure stimulatescheap production of energy. Some power plants, such as the E.ON Coal Power Plant Maasvlakte in Rotterdam, operate most economically if they are in production nonstop. Other plants are more fitted to be started up if more electricity is needed, or stopped if the demand declines. The STOGAS unit in the Gallileïstraat is such a Start-Stop Unit.

Central Control Panel
The “Process Guard�? the Central Control Panel of the COGAS regulates the production of energy and the heat delivery to the District Heating. A lot of attention has been given to the automation and security of the installations and the registration of glitches. The Central Control Panel has a 24 hour shift. This means about 20 people (3 employees for every 8 hour shift). Maintenance and management personnel are not included in this number.

Environmentally Friendly Installation
The COGAS unit of the power plant in the Gallileïstraat is an environmentally friendly installation. Vital to the image of the power plant Gallileïstraat is the stack that emits the flue gasses. Because of its height of 125 m �?which is 25 m higher than the height required by the building permit �?the flue gasses are being discharged above the Europoint building located next to the power plant. No discharge of flue gas takes place whilst stoking natural gas and the percentage of sulphur in flue gasses is insignificantly small. Special burners of the gas turbines give a low emission of Nitrogen Oxyde (NOx). Finally, the District Heating uses less fossil fuel than the free-standing conventional heating systems in dwellings. Just this fact in itself means less stress on the environment.

General Information

Gas Turbines

Steam Turbine
supplier : ASEA Brown Boveri B.V.
number : 1
power : 73.5 MW only when
generating electricity,
57.2 MW with 148.6
MWth for district heating
(low pressure area of the
turbine disconnected)
low pressure area
steam turbine : can be disconnected during
operation
number of district
heating condensers : 2
pipe material head
condenser : titanium

Generators
supplier : ASEA Brown Boveri B.V.
manufacture : Holec (ABB-Licence)
nominal : gas turbine generators 55 MW
power : steam turbine generator 77 MW
pressure : 11.5 kV + 10%
cos phi : steam turbine generator
0.9 indicative
gas turbine generator
0.8 indicative
cooling : air, with air/water heat
exchangers
Machine Transformers
supplier : Smit Transformatoren B.V.
power : 1x85.5/56.6/142 MVA
1x56.5/56.5/56.6/113.2 MVA
pressure : 11.5/11.5/160 kV
Generator Switches
supplier : ASEA Brown Boveri B.V.
power : steam turbine generator
24 kV/6300 A
gas turbine generators
17.5 kV/3600 A