An Aerial View of the Ledvice New Source

The new power source in Ledvice – the most state-of-the-art traditional power station in Central Europe – has been erected on the site of the existing Ledvice coal power station. It offers unique views due to its position between the Central Bohemian Uplands (Ceske stredohori) and the eastern foothills of the Ore Mountains (Krusne hory). It is visitors to the 140-meter tall lookout point on the tallest industrial structure in the Czech Republic who will appreciate the views the most. Nevertheless, our virtual tour will enable a much wider public to enjoy a similar experience, especially those interested in industrial tourism.

From Volcanoes to the Ore Mountains

The conical massif of Milešovka (837m a.s.l.), considered to be the windiest mountain in the Czech Republic, will attract your attention some 10 kilometers eastward. There is a meteorological station and a lookout tower with a restaurant at the top of this former volcano.

In the southern direction, past the former spa town of Bílina, you will find another landscape dominant – the 539-meter high Bořeň, considered to be the biggest phonolite rock surface formation in Central Europe. The most prominent feature of Bílina itself is a chateau, which was reconstructed into its present appearance in the 17th century. The historical center of the town, and the St. Peter and Paul church with its remarkable Gothic and Renaissance elements, are like a magnet for tourists.

Southwest of the Ledvice power source, you will find the Bílina brown coal mines, past which you can discern the silhouette of the refinery in Záluží u Mostu.

The northwestern horizon reveals the ridges of the Ore Mountains some 15 kilometers away, specifically the area of Klíny, Loučná (956 m a.s.l.) and Bouřňák (869 m a.s.l.).

On the contrary, on the northeast side the land descends towards the lowlands around Teplice, a major Central European spa town with several remarkable spa houses boasting notable architectural designs. In the immediate vicinity of the town, you can visit the former mining town of Krupka, where you will find the longest suspended cableway in Central Europe.

Facing the Power Station

The power stations located in North Bohemia have long been a stable pillar of the Czech energy mix. Their current upgrading or even complete new construction is a part of the CEZ Group’s strategic plan to increase efficiency despite the ever lower quality of coal extracted from the nearby mines, all that in combination with adoption of the toughest environmental measures and observing other regulations from Czech and European authorities.

CEZ Group’s Power Source Renewal Project

The CEZ Group’s power generation strategy is based on creating a diversified production mix. This means developing nuclear projects wherever possible, building gas-fired power stations, investing in coal-fired power stations (which enjoy a significant cost advantage), but also erecting renewable sources and investing in the environment. Projects in the Czech Republic are primarily implemented in North Bohemia.

Another traditional power station that is included in the CEZ Group’s power station renewal and construction programme is the Ledvice Power Station, where a new, highly environmental-friendly, supercritical unit has been built with an installed capacity of 660 MWe and nearly 43% efficiency. The unit was built by ŠKODA PRAHA INVEST, s.r.o.

Ledvice Power Station

Originally, the Ledvice power station had five units, built in 1966 – 1969, with Unit 1 having an installed capacity of 200 MW and Units 2 through 5 having 110 MW each.

Units 1 and 5 were shut down in the 1990s, Units 2 and 3 were equipped with flue-gas desulfurization systems in the mid-1990s, Unit 4 went through a major reconstruction – the original granulation boiler was replaced with a fluidized bed combustion system in 1998, and the turbine was replaced in 2007, with the new one being optimized for heat generation although its capacity stayed at 110 MW. Units 3 and 4 were taken out of operation in 2013 and 2015, respectively.

Presently, it is only the 110 MW_el Unit 4 that is in operation, together with the new Unit 6 with an installed capacity of 660MW_el.

A newly erected gas boiler station with a steam generation capacity of 160 t/hr is now used as a back-up source.

Apart from generating power, the Ledvice power station also supplies heat to customers in the nearby municipalities, and by means of ČEZ Teplárenská a.s. it supplies heat in the form of steam to the cities of Teplice and Bílina, and in the form of hot water to the town of Ledvice as well. The combined generation of power and heat in one cycle, referred to as co-generation, reduces fuel consumption per unit of energy produced, which also helps the environment.

The total annual amount of heat supplied to customers is approx. 1,000 TJ, with the maximum capacity currently being some 150 MWt. The installed capacity allows up to 270 MWe to be supplied to heat systems. Therefore, the power station has a considerable performance buffer that allows other customers to be connected (e.g., the town of Duchcov) and the volumes supplied to existing customers to be increased. The benefit of supplying heat from a power station are reasonable and competitive prices as well as supply stability in terms of operational availability and price.

Building a New Source in the Ledvice Power Station – the NZ660MW Project

The decision to build this state-of-the-art power-generation unit, the most modern one in the Czech Republic, was made in 2006 when the Construction Plan was approved.

The New Source was designed to meet the current state of the art in technology as well as strict technical, financial and environmental parameters.

These requirements led to a decision to use supercritical pressure and superheated steam temperature of 600 °C and reheated steam temperature of 610 °C.

The value of the installed electrical capacity – 660 MW – was determined as an intersection of the production technology selectable parameters (supercritical steam parameters and high unit performance to increase energy efficiency), usable deposits of coal useful for energy production in the Bílina surface mine during the planned unit service life, space available on the site of the Ledvice power station (LPS), and the installed capacity values from the viewpoint of ensuring reliable operation of the power transmission system in the Czech Republic.

Due to the space constraints in the location of the LPS, preparing a construction site for the New Source was very complicated and time-consuming. First, common technologies had to be re-built and re-launched to secure operation of the existing units, which were originally located where the new unit was to be erected.

This primarily included a chemical water treatment station, coaling feeding facility, coal storage, but also a rainwater pump station, gas control station and a new office building. This work was performed in 2007 and 2008.

The actual construction of the new source started in 2009; the general structure was handed over to the boiler and turbine suppliers, ready for installation of the core technologies – the boiler room and the machine room - in the spring of 2010. The boiler pressure test was conducted in May 2013, and the generator was connected to the grid for the first time in July 2014.

How Is Electricity Generated?

In principal, the new unit of the Ledvice power station generates power using the same system as the existing units, yet with significantly higher steam parameters (a temperature of 600 °C compared to 540 °C, a pressure of 27 MPa compared to 12.8 MPa in the old units), which makes it possible to achieve a considerably higher efficiency and, thus, a lower fuel consumption per kilowatt-hour generated (up by more than 20%).

When brown coal is burned in steam generators, the energy chemically bound in the fuel is transformed to thermal energy. This energy is used to evaporate water under high pressure and at high temperatures. The steam generated in this manner then drives the turbine. The connected generator transforms the rotational energy of the turbine shaft into electrical energy. After passing through the turbine, the steam flows into a condenser where it condenses, and the condensed water is then gradually re-heated in regeneration heaters and then pumped back to the boiler as feedwater. The condensation heat from the condenser is taken away by means of cooling water into the cooling tower – there the water gets cooled and is then pumped back to the condenser.

The combustion processes happening during power and heat generation have secondary energy products – slag and flue cinder are formed from the ash in the fuel, and plaster stone (gypsum) is formed during the desulfurization process. These products, provided that technological and statutory requirements are fulfilled, become input materials for subsequent processing and production, which can be used mainly in construction and in reclaiming and recultivating exploited parts of the Bílina surface mine.

Central Control Room

The Control Room staff control most of the equipment and facilities of the Ledvice New Source. It is from here that commands are given for each of the power plant sections. More than 10 specialists work here in peak hours.

Boiler Room – Floor ±0.00m

Ventilator Mill

The ventilator mill pulverizes the coal and blows the fine dust into the boiler. There are 8 such mills in total, 7 of which run at full power and can process up to 550 tons of coal per hour – that is in the case of the worst foreseen grade of coal with a heating value of 10.5 GJ/t; if the nominal heating value is 11.5 GJ/t, the capacity is 442 tons of coal per hour.

Air Ventilator

The combustion air required for the combustion process is fed in by an axial ventilator. The air volume is regulated by tilting the rotary wheel blades; at full speed the ventilator can feed in up to 20 m³ of air per second.

Boiler Room

The 660 MW unit boiler is the biggest power plant boiler in the Czech Republic. The boiler itself is 132 meters tall, while the boiler room facility including the adjacent staircase towers is over 143 meters tall, which makes it the tallest building in the Czech Republic.

How Fuel is Converted into Thermal Energy

Brown coal is transported from a raw coal storage facility on conveyor belts into ventilator mill driers. There it is first dehumidified (the water content in raw fuel is around 25%) using hot flue gases sucked in by the mill from the upper section of the boiler combustion chamber. The mill crushes the coal into a fine dust, blows it into the coal burners of the boiler, where it burns in the combustion chamber (it has a cross-section of 20 by 20 meters, with the chamber being over 75 meters tall).

The combustion process is controlled so that at any point in time, the combustion air is supplied into the boiler in the right proportion to the fuel; the right air-to-fuel ratio ensures already in this phase that the formation of nitrogen oxides (NOx) is minimized. This approach, without the use of additional catalysts, makes it possible to meet the statutory emission limit for nitrogen oxides (NOx), which is set at 200 milligrams per cubic meter of flue gases.

On the heating surfaces of the boiler (combustion chamber walls formed of tube membranes, tube bundles of the superheaters and re-heaters and of the water heater), the hot flue gases are gradually cooled down from a temperature of more than 1200 °C, and subsequently they still give off some of the heat to the combustion air. After the ash is separated in an electrostatic separator, the last portion of the usable heat is rendered in the flue gas exchanger, where flue gas is cooled down from 170 °C to some 130 °C.

Machine Room

The largest room in the whole power station is its machine room – a hall with dimensions equal to those of an ice-skating arena. A turbine with a power generator represent the most prominent elements in the machine room; on the lower floors you can see primarily condensers, condensate pumps, vacuum pumps, low-pressure condensate heaters and high-pressure feedwater heaters.

Turbo Set

Steam Turbine

The turbine is the biggest of its kind in the Czech Republic. The turbines used in the 1000 MW units in the Temelín power plant do have a greater installed capacity and they are bigger, too, but they operate with significantly lower steam parameters. In any case, the machine dimensions are astonishing – the total length of the turbo set including the generator and the exciter is 53 meters, the diameter of the last rotary wheel of the low-pressure parts is nearly 4 meters, with the blades of this section being over one meter long. The turbine consists of four sections: separate high-pressure and medium-pressure sections and two low-pressure sections. There are two condensers located under the latter sections.

The steam entering the high-pressure section has a temperature of 600 °C and a pressure of 27.2 MPa, but exits the same section at 5 MPa and 356 °C and returns to the boiler to be heated up to 610 °C again. The steam then re-enters the turbine, this time the medium-pressure section and then the two low-pressure sections, where it expands up to a deep vacuum.

Generator

The rotational energy of the turbine shaft is converted into electrical energy in the coupled generator. Electrical energy is generated by means of induction in a magnetic field formed between the generator rotor and the generator stator. It revolves at a constant speed of 3,000 revs/min, which ensures a standard frequency of 50 Hz and a voltage of 21 kV, which is then transformed and supplied to the 400 kV VHV transmission system.

Condensers

To achieve the maximum efficiency, it is necessary to ensure that the steam expansion in the turbine is as long as possible, i.e., faces the lowest counter-pressure possible. This is ensured by means of condensers – there are two of them, one under each of the low-pressure turbine sections. They are connected in series on the side of the cooling water; therefore, the operating pressures in them are a little different. This also adds a tenth of a percent to the overall efficiency. There is a deep vacuum in the condensers during operation – at the nominal output power, the pressure in them is just 35 or 42 mbar, respectively, which is just some 3.5 or 4.2% of atmospheric pressure. Three liquid ring pumps are used to create a vacuum when the unit is started up and to suck out air that seeps into the vacuum system through air leakages during operation.

The latent heat of the condensing steam is taken away by the cooling water that flows through stainless steel tubes. To achieve the largest cooling area, there are 20,000 such tubes in each of the condensers, which renders a total heat exchange surface area of 28,000 m², i.e., 2.8 hectares!

Space Under Condensers

In order to dissipate the condensation heat of the steam coming out of the turbine, we need to run 15 m³/s of cooling water through the condenser, the temperature of which rises by 10 °C.

The cooling water is supplied and drained through a steel pipe with an interior anti-corrosion coating, with a section of the route between the cooling water pumping station and the machine room laid underground. The pipeline diameter is 2.8 meters, and the pipeline branches out upon entry in the condenser (both condensers have two parallel sections), and the branches then unite again at the exit; both parallel routes have a diameter of 2 meters.

To illustrate: The average annual flow in the nearest river – the Bílina – is around 12.4 m³/s; the thermal power dissipated from the condenser would heat the river water up by 12 °C.

Feed Pumps

The feed pumps are used to transport the feedwater to the boiler. They are installed in a separate machine room. There are three of them in total, with just two needed to facilitate the full output power of the unit, the third one being for redundancy purposes.

The pumps are driven by electric motors with a maximum output power of 16 MW. Their revolving is regulated by a hydraulic coupling with a regulation range from 800 to 5050 revs/min. This allows the volume of feedwater flowing into the boiler to be regulated from some 120 t/hour at a pressure of 7 MPa up to a maximum of 1,050 t/hour at a pressure of 35 MPa.

Electrostatic Separators

A greater portion of the ash contained in the burned coal is so fine that the flowing flue gases carry it out of the boiler. Therefore, an ash separator has been installed behind the boiler, which reduces the ash content from some 70 g/Nm³ of flue gases to a mere 50 mg/Nm³. In absolute terms, this represents a reduction from 118 t/hr to 85 kg/hr; the separator efficiency is thus more than 99.9%.

The separator uses electrostatic separation technology, i.e., the ash particles are charged with an electrostatic charge, which causes them to deposit on electrodes, from which they are automatically shaken off. The separated ash falls into hoppers under the electrodes, and from there it is pneumatically conveyed to silos.

Desulphurization

The main harmful pollutants formed during coal combustion include fly ash, sulfur dioxide formed from the sulfur contained in the fuel, and nitrogen oxides (NOx), which are formed from both the nitrogen contained in the combustion air and the nitrogen contained in the coal. Imperfect combustion may also lead to the formation of carbon monoxide. The formation of NOx and carbon monoxide is minimized already during the combustion process, while the fly ash is to a great extent removed in the electrostatic separators.

Sulfur dioxide is removed in a desulfurization facility by means of wet limestone washing – the mutual reaction of pulverized limestone, sulfur dioxide and added oxidization air produces calcium sulfate (gypsum), water and carbon dioxide. This reaction happens in the absorber, a cylindrical vessel with a diameter of 17 meters and a height of 47 meters. The calcium-gypsum suspension circulation is ensured by a total of 5 process pumps – the material pumped by each of them is conveyed into one of the five levels of showers that sprinkle the suspension in very small droplets. The flue gases enter the absorber from the bottom and then pass through the showers, where sulfur dioxide is “washed” out of them, including the last residues of fly ash. The cleansed flue gases, now at a temperature of just 70 °C, leave the absorber through a laminated pipe with a diameter of 8 meters to the cooling tower, where the upward draught, multiplied by the heat brought in by the cooling water, pushes it up high into the atmosphere.

The rising flue gases contain no more than 20 mg/Nm³, of fly ash and a maximum of 150 mg/Nm³ of SO₂.

The gypsum produced can be dehumidified, deposited in a repository, from where it can be loaded into wagons or trucks to be sold as “energy gypsum”. A great portion of this material is used to make “cast granulate”, which is used to give a shape to the internal dump site of the Bílina surface mine.

Cast Granulate Pumping Station

The new source operation creates a considerable quantity of energy by-products (EBPs), i.e., solid residues after coal combustion and flue gas cleansing. These can either be directly sold as construction materials (gypsum, fly ash) or used, when mixed together with added lime and water, to make a construction input material referred to as ‘cast granulate’, which special pumps convey back to the mine, where it is used to shape the exploited areas of the mine before their reclaiming.

Cooling Tower

The cooling tower is used to cool the water that was heated in the condenser. It is a cooling tower with a natural draught of cooling air. Despite the high efficiency of the unit, the heat dissipated in the cooling tower represents approximately half of the boiler thermal power, which also determines the cooling tower dimensions – its base has a diameter of 108 meters, and the tower is 140 meters tall. More than 52,000 cubic meters of water constantly flow through it every hour, which is sprinkled as small droplets over the entire cross-section of the tower at a height of some 12 meters and then collected in a pool under the tower. From there the main cooling pumps (2 pumps, each with a flow capacity of up to 30 000 m³/hr) pump the water back to the condenser.

The cooling water is cooled down by 10 °C in the tower. A portion of the dissipated heat warms up the air drawn upward through the tower, but a greater portion is the latent heat of water that evaporates in the tower – this can be up to 900 m³/hr when running at full power. The evaporation causes the density of the water circulating in the circuit to increase; therefore, a portion of the water needs to be taken away as blowdown. The total quantity of water that needs to be replenished due to evaporation and blowdown losses can be up to 1,200 cubic meters per hour.

Letting the Power Out

Transformers

The generator produces electricity at a voltage of 22 kV, which is increased to 400 kV in block transformers (three single-phase transformers). Apart from the output transformers, there is a 110 kV back-up transformer, used to supply power to the shut-down power plant unit when the 400 kV line is disconnected.

Opposite the transformers there is an output terminal array with disconnectors, to which a new 400 kV transmission line is connected that connects the new unit to the transmission system.

Coaling

The coal feeding process ensures that energy coal is conveyed from the Ledvice coal treatment facility to the existing Unit B4 and also to the newly built 660 MWe unit (B6).

The construction of the new coaling facility was completed in two phases – Phase I included all the facilities and equipment required for the operation of Unit B4 and the soon-to-be-closed Units B2 and B3, including facilities shared for operation of the Ledvice New Source. The common facilities include a coal dump with a capacity of some 70,000 tons of coal together with the related conveyor belt routes to the dump site and from the dump site to the power station units.

In Phase II of the coaling facility construction, the conveyor belt routes to the new 660 MWe source were built. Belt conveyors (that is the blue bridge on tall supports that rises from right to left to the boiler room building) are used to fill the operating coal storage sections in the B6 boiler room.

Coal can be fed into both Unit B4 and the new Unit B6 either directly from the Bílina mine or from the dump, with the quantity of coal in the dump being sufficient for approximately one week of Unit B6 operation.

Information Center – Ground Floor

The Ledvice power station has a modern information center that allows its visitors to become acquainted with the past, present and the future of traditional power generation. They can find information there about the power station itself as well as about the CEZ Group, energy sector developments, and the closest municipalities and region where the new source is located.

As part of the tours, you can also walk up to the top of the tallest building in the Czech Republic (150 meters tall), which offers attractive views of the surrounding landscape. From there you can also see the lowest point in our country – currently just some 10 meters above the level of the North Sea. The point is at the bottom of the nearby Bílina surface mine.

The Information Center in Ledvice is open to the public from Monday to Friday, always from 7 a.m. to 3 p.m. (excluding public holidays). Larger groups may book a visit in advance by telephone on 411 102 313 or by e-mail at: infocentrum.ele@cez.cz. The Information Center was built as a part of the comprehensive programme of upgrading and renewing coal-fired power stations and of the construction of the Ledvice New Source. The power station renewal programme will further improve the environment in North Bohemia.

Where can you find us?

Ledvice Power Station Information Center
ČEZ, a. s. – Ledvice Power Station
Bílina, č.p. 141
418 48 BÍLINA

Tel.: +420 411 10 2313
E-mail: infocentrum.ele@cez.cz

Information Center – Floor 1

In the virtual and interactive world of the Information Center, you can easily walk through virtually the entire power station. Everyone can use a simple joystick and immerse themselves in a large 3D screen and see right away how the power station looks from the inside. You can walk past the turbine, inspect the desulfurization facility, boiler room and other technology sections. There is of course also an audio panel that allows you to experience the sounds of the cooling tower, turbine, electrical separators and other power station technologies. Another point of interest is the online measuring of a living tree’s photosynthesis and the reclaiming process.

Several more or less difficult tests are available for anyone to check their knowledge of traditional power generation, regardless of whether they already knew something before coming to the Information Center or gained it right there.

Information Center – 3D Cinema

Visitors to the Ledvice Information Center can also watch a 3D film about the creation of space, including the origin of the Earth and its evolutionary development. Just put on 3D glasses and sit down in the comfortable chairs of the 3D cinema. Everyone can thus learn when dinosaurs roamed through clubmosses and horsetails, what fate they encountered, and what it all led to.

Of course, the result was coal, yet it still took many centuries for the first coal-fired power station to be built, to be followed by numerous others. The parting sequence of illuminated cities will not leave anyone in doubt that they find themselves in the right place – in the foreground of the Ledvice Power Station, which operates a new, modern, highly environmentally-friendly source of electricity.

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