Schkopau lignite-fired power station. Leading-edge technology in harmony with nature

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1 Schkopau lignite-fired power station Leading-edge technology in harmony with nature b

2 2 New energy for a new age New energy means supplying millions of people with electricity around the clock. Reliably, efficiently, and responsibly. Conventional, coal-generated power is a key part of the energy supply system. At E.ON Kraftwerke, we re committed today to achieving a sustainable balance between the ecological and economic needs of tomorrow.

3 3 New energy across the country Headquartered in Hanover, E.ON Kraftwerke GmbH operates E.ON Energie AG s conventional thermal power stations. With some 5,600 employees at more than 30 locations, we produce over 50 billion kilowatt-hours of power annually. That s enough electricity to meet around 11 per cent of Germany s power requirements, making us the country s largest conventional generator. New energy from fossil fuels We generate most of our power by burning German coal, low-cost imported coal, and lignite from our own lignite deposits. We operate 17 hard-coal power stations and seven lignite-generating facilities with an aggregate installed capacity of approximately 10,300 megawatts. New energy on the banks of the Saale River With a net capacity of some 900 megawatts, the Schkopau lignite-fired power station is a major supplier of electricity in eastern Germany. As well as feeding electricity into the public grid, it supplies energy to a neighboring chemicals plant and to Germany s national rail carrier, Deutsche Bahn. Schkopau is co-owned by E.ON Kraftwerke and Saale Energie GmbH. The latter s 41.9 per cent stake is held by Minnesota-based NRG Energy Inc.

4 4 We rely on electricity nearly every hour of every day. It powers our appliances, heats our homes, and illuminates our living spaces. But electricity does more. It helps us turn ideas into reality. While there are many ways to generate electricity, there should only be one goal: to produce energy in the most responsible way possible. Just like we do at Schkopau. Powering up the future Supplying power reliably and safely requires precise coordination The generation of electricity has to be in perfect synch with the demand for electricity, which can fluctuate considerably throughout the day. That s why certain types of generating assets operate continuously and others only periodically. Unusually flexible for a lignitefired power station, Schkopau operates in three distinct load ranges as required by its three energy customers. It supplies the neighboring chemicals plant with base-load process steam and electricity; Deutsche Bahn with base and intermediate-load traction power at hertz; and the public transmission network with intermediate and peak-load electricity. Schkopau burns lignite from central Germany With both blocks at full load, the steam-generating boilers at Schkopau consume up to 20,000 tonnes of lignite a day. The lignite is sourced from the Profen open-cast mine, about 25 miles from the power station. It is stored in an interim storage facility that holds enough fuel to keep Schkopau operating continuously at full load for about three days. We re fired up about energy efficiency Before it s burned in the steam generator, raw lignite is dried and crushed to a fine powder in pulverizing mills to ensure optimum combustion. The mills then blow the lignite dust via burners into the steamgenerator combustion chamber, where it burns at about 1,150 C (2,102 F). Heat gets things going The combustion heat brings the feed water in the boiler s steel tubing to the boil. The steam generated is then further heated to 545 C (1,013 F) and fed under high pressure into a multistage turbine. The turbine is coupled to a generator. Like in a simple dynamo, the turbine s mechanical energy is converted into electric energy. The electricity, which has a voltage of 12 kilovolts, is converted by transformers to the required voltage and then fed directly into our customers supply networks.

5 5 The water merry-go-round As it passes through the turbine, the steam expands, resulting in a drop in pressure and temperature. The expanding steam is admitted to the condenser where it is transformed back into water. The water is then pumped back into the steam generator, where it is once more heated and turned into steam, completing the circuit. Some of the steam is drawn off and transmitted to the neighboring chemicals plant as steam heat. This process is known as cogeneration. The water that is removed from the cycle in the form of steam must be replaced with fresh water. Under control around the clock All processes in the power station everything from combustion to the production of steam and electricity are automated and controlled by numerous regulation and control circuits. The data from these circuits are monitored seven days a week, 24 hours a day by Schkopau s central control room. Functional diagram of the Schkopau power station Water-steam circuit Cooling-water circuit Flue gases Supply 1 Lignite bunker 2 Pulverizing mill 3 Forced-draft-fan air inlet 4 Air preheater 5 Water 6 Crushed limestone Process 7 Feedwater 8 Steam 9 Turbines 10 Generator 11 Transformers 12 Process steam 13 Condenser 14 Feedwater tank 15 Boiler feed-pump 16 Cooling water 17 Cooling tower Waste products 18 Coarse ash 19 Dust collection: electrostatic precipitator 20 Fly ash 21 Desulfurization: SO 2 scrubber 22 Gypsum dewatering 23 Gypsum for industrial applications 24 Reheater 25 Chimney stack

6 6 Schkopau clean power for the environment E.ON Kraftwerke systematically employs technology that helps protect the environment. We do this because generating electricity using fossil fuels like lignite also produces substances that, in high concentrations, can cause air pollution. The main air pollutants are nitrogen oxide, sulfur dioxide, carbon dioxide, and dust particles. Clean air in, clean air out The equipment needed to clean flue gas is capital-intensive. For a power station like Schkopau, the equipment costs about as much as it would to construct an entire chemicals factory. Despite the expense, we do everything we can to ensure that conventional power generation and environmental protection go hand in hand. Schkopau is a prime example of our commitment. Its comprehensive flue-gas cleaning systems are continually upgraded to ensure that they are always state-of-the-art. Environmentalprotection systems account for about 30 per cent of the cost of building a power station block. Added to this is the ongoing expense of operating and maintaining these systems. At Schkopau, flue gas gets the full treatment In the primary cleaning stage, flue gas is denitrified. Nitrogen is a naturally occurring part of the air we breathe and is present in lignite. It is only when lignite is burned that nitrogen combines with oxygen to form nitrogen oxide. At Schkopau, this oxidization process is significantly reduced via the use of low-emission combustion technology. Known as primary treatment, this process alone is sufficient to keep the amount of nitrogen oxide in the flue gas below government-mandated limits. Electrostatic precipitators remove dust from flue gas The secondary cleaning stage involves an electrostatic filter called a precipitator. The dust in flue gas is first given a negative electric charge. When the dust passes through the electric field inside the precipitator, it is deposited onto a positively charged collecting electrode. A vibrating mechanism then causes the dust particles to fall into an ash extractor. At Schkopau, this cleaning process is more than 99 per cent effective and keeps dust emissions well below statutory limits.

7 7 Our exhaust air has cleaned up its act Before flue gas is released into the atmosphere, it is first fed through the scrubbing towers of our state-of-theart desulfurization plant. Here, the sulfur dioxide present in the gas reacts with a mixture of liquid crushed limestone and oxygen to form gypsum. This process removes more than 95 per cent of the sulfur dioxide. Greater efficiency means less CO 2 The more efficient a power station is, the less lignite you have to burn to produce a kwh of power. This means lower CO 2 emissions and a healthier environment. That s why improving power plant efficiency is always a top priority for our engineers. Today, we can produce twice as much electricity from a kilogram of lignite as we could in Waste not, want not There are plenty of good uses for the residues from the flue-gas cleaning process. For example, coarse ash can be used in road construction; fly ash is used in the construction industry and for recultivating open-cast mining areas; and gypsum, once washed and dried, can be used by the construction industry. New energy requires committed employees At Schkopau, we re in the business of supplying electrical energy whenever it s needed. We can deliver on our promise because our skilled, experienced, and committed professionals know the systems they operate inside and out. That s something our customers can count on.

8 Key facts at a glance Net output capacity Commissioned Fuel Steam generator Steam output Number of pulverized coal/oil burners Live-steam pressure/temperature Reheater steam pressure/temperature Fuel consumption at full load Generator Power output Voltage Traction-electricity generator Power output Voltage Flue-gas cleaning Denitrification Dust collection Desulfurization System End product Chimney height Blocks A, B 450 MW each 1995/96 Lignite 2 x 1,360 t/h 2 x bar/545 C (1013 F) 70 bar/560 C (1040 F) 2 x 400 t/h 50 Hz 2 x 575 MVA 21 kv Hz 138 MVA 10.5 kv Primary treatment Electrostatic precipitator Wet cleaning, lime basis Gypsum 200 m (656 ft) MW: megawatt kv: kilovolt t/h: tonnes per hour MVA: megavolt-ampere Schkopau is worth a look We invite you to take a free tour of Schkopau. Find out about how a lignite-fired power plant works and see for yourself how we supply electric energy to Germany and Europe safely, economically, and responsibly. Kraftwerk Schkopau An der Bober Korbetha Germany T +49-(0) F +49-(0) Kraftwerk.Schkopau@eon-energie.com info@eon-kraftwerke.com NRG Energy Inc Nicollet Mall Suite 700 Minneapolis MN USA T F Berlin T +49-(0) F +49-(0) Publisher E.ON Kraftwerke GmbH Management Office/ Corporate Communications Tresckowstraße Hannover Germany Photographs Peter Hamel 8/02