What is it and what are the operating principles of thermal power plants? The general definition of such objects sounds approximately as follows - these are power plants that process natural energy into electrical energy. Fuel of natural origin is also used for these purposes.
The operating principle of thermal power plants. Short description
Today, it is precisely at such facilities that combustion is most widespread that releases thermal energy. The task of thermal power plants is to use this energy to produce electrical energy.
The operating principle of thermal power plants is not only the generation but also the production of thermal energy, which is also supplied to consumers in the form of hot water, for example. In addition, these energy facilities generate about 76% of all electricity. This widespread use is due to the fact that the availability of fossil fuels for the operation of the station is quite high. The second reason was that transporting fuel from the place of its extraction to the station itself is a fairly simple and streamlined operation. The operating principle of thermal power plants is designed in such a way that it is possible to use the waste heat of the working fluid for its secondary supply to the consumer.
Separation of stations by type
It is worth noting that thermal stations can be divided into types depending on what kind they produce. If the principle of operation of a thermal power plant is only to produce electrical energy (that is, it does not supply thermal energy to the consumer), then it is called condensing power plant (CES).
Facilities intended for the production of electrical energy, for the supply of steam, as well as the supply of hot water to the consumer, have steam turbines instead of condensing turbines. Also in such elements of the station there is an intermediate steam extraction or a backpressure device. The main advantage and operating principle of this type of thermal power plant (CHP) is that waste steam is also used as a heat source and supplied to consumers. This reduces heat loss and the amount of cooling water.
Basic operating principles of thermal power plants
Before moving on to considering the principle of operation itself, it is necessary to understand what kind of station we are talking about. The standard design of such facilities includes a system such as intermediate superheating of steam. It is necessary because the thermal efficiency of a circuit with intermediate superheating will be higher than in a system without it. In simple words, the operating principle of a thermal power plant with such a scheme will be much more efficient with the same initial and final specified parameters than without it. From all this we can conclude that the basis of the station’s operation is organic fuel and heated air.
Scheme of work
The operating principle of the thermal power plant is constructed as follows. The fuel material, as well as the oxidizer, whose role is most often played by heated air, is supplied in a continuous flow into the boiler furnace. Substances such as coal, oil, fuel oil, gas, shale, and peat can act as fuel. If we talk about the most common fuel in the territory Russian Federation, then it is coal dust. Further, the operating principle of thermal power plants is constructed in such a way that the heat generated by burning fuel heats the water in the steam boiler. As a result of heating, the liquid is converted into saturated steam, which enters the steam turbine through the steam outlet. The main purpose of this device at the station is to convert the energy of the incoming steam into mechanical energy.
All elements of the turbine that can move are closely connected to the shaft, as a result of which they rotate as a single mechanism. To make the shaft rotate, a steam turbine uses a transmission kinetic energy couple to the rotor.
Mechanical part of the station operation
The design and principle of operation of a thermal power plant in its mechanical part is associated with the operation of the rotor. The steam that comes from the turbine has very high pressure and temperature. Because of this, high internal energy of steam is created, which flows from the boiler into the turbine nozzles. Jets of steam, passing through the nozzle in a continuous flow, at high speed, which is often even higher than sound speed, act on the turbine blades. These elements are rigidly fixed to the disk, which, in turn, is closely connected to the shaft. At this point in time, the mechanical energy of the steam is converted into the mechanical energy of the rotor turbines. If we talk more precisely about the principle of operation of thermal power plants, then the mechanical impact affects the rotor of the turbogenerator. This is due to the fact that the shaft of a conventional rotor and generator are tightly coupled to each other. And then there is a fairly well-known, simple and understandable process of converting mechanical energy into electrical energy in a device such as a generator.
Steam movement after the rotor
After the water vapor passes the turbine, its pressure and temperature drop significantly, and it enters the next part of the station - the condenser. Inside this element, the vapor is converted back into liquid. To perform this task, there is cooling water inside the condenser, which is supplied there through pipes running inside the walls of the device. After the steam is converted back into water, it is pumped out by a condensate pump and enters the next compartment - the deaerator. It is also important to note that the pumped water passes through regenerative heaters.
The main task of the deaerator is to remove gases from the incoming water. Simultaneously with the cleaning operation, the liquid is heated in the same way as in regenerative heaters. For this purpose, the heat of the steam is used, which is taken from what goes into the turbine. The main purpose of the deaeration operation is to reduce the oxygen and carbon dioxide content in the liquid to acceptable values. This helps reduce the rate of corrosion on the paths through which water and steam are supplied.
Coal stations
There is a high dependence of the operating principle of thermal power plants on the type of fuel used. From a technological point of view, the most difficult substance to implement is coal. Despite this, raw materials are the main source of power at such facilities, the number of which is approximately 30% of the total share of stations. In addition, it is planned to increase the number of such objects. It is also worth noting that the number of functional compartments required for the operation of the station is much greater than that of other types.
How do thermal power plants run on coal fuel?
In order for the station to operate continuously, railway tracks Coal is constantly brought in, which is unloaded using special unloading devices. Then there are elements such as through which unloaded coal is supplied to the warehouse. Next, the fuel enters the crushing plant. If necessary, it is possible to bypass the process of delivering coal to the warehouse and transfer it directly to the crushers from unloading devices. After passing this stage, the crushed raw materials enter the raw coal bunker. The next step is to supply the material through feeders to the pulverized coal mills. Next, the coal dust, using a pneumatic transportation method, is fed into the coal dust bunker. Along this path, the substance bypasses elements such as a separator and a cyclone, and from the hopper it already flows through the feeders directly to the burners. The air passing through the cyclone is sucked in by the mill fan and then fed into the combustion chamber of the boiler.
Further, the gas movement looks approximately as follows. The volatile substance formed in the chamber of the combustion boiler passes sequentially through such devices as the gas ducts of the boiler plant, then, if a steam reheat system is used, the gas is supplied to the primary and secondary superheater. In this compartment, as well as in the water economizer, the gas gives up its heat to heat the working fluid. Next, an element called an air superheater is installed. Here the thermal energy of the gas is used to heat the incoming air. After going through all these elements, volatile substance goes to the ash collector, where it is cleaned of ash. After this, smoke pumps draw the gas out and release it into the atmosphere using a gas pipe.
Thermal power plants and nuclear power plants
Quite often the question arises about what is common between thermal power plants and whether there are similarities in the operating principles of thermal power plants and nuclear power plants.
If we talk about their similarities, there are several of them. Firstly, both of them are built in such a way that they use natural resource, being a fossil and excised. In addition, it can be noted that both objects are aimed at generating not only electrical energy, but also thermal energy. The similarities in operating principles also lie in the fact that thermal power plants and nuclear power plants have turbines and steam generators involved in the operation process. Further there are only some differences. These include the fact that, for example, the cost of construction and electricity obtained from thermal power plants is much lower than from nuclear power plants. But, on the other hand, nuclear power plants do not pollute the atmosphere as long as the waste is disposed of correctly and no accidents occur. While thermal power plants, due to their operating principle, constantly emit harmful substances into the atmosphere.
Here lies the main difference in the operation of nuclear power plants and thermal power plants. If in thermal facilities the thermal energy from fuel combustion is most often transferred to water or converted into steam, then at nuclear power plants the energy is taken from the fission of uranium atoms. The resulting energy is used to heat a variety of substances and water is used here quite rarely. In addition, all substances are contained in closed, sealed circuits.
District heating
At some thermal power plants, their design may include a system that handles heating of the power plant itself, as well as the adjacent village, if there is one. To the network heaters of this installation, steam is taken from the turbine, and there is also a special line for condensate removal. Water is supplied and discharged through special system pipeline. The electrical energy that will be generated in this way is removed from the electrical generator and transmitted to the consumer, passing through step-up transformers.
Basic equipment
If we talk about the main elements operated at thermal power plants, these are boiler houses, as well as turbine units paired with an electric generator and a capacitor. The main difference between the main equipment and the additional equipment is that it has standard parameters in terms of its power, productivity, steam parameters, as well as voltage and current, etc. It can also be noted that the type and number of main elements are selected depending on how much power needs to be obtained from one thermal power plant, as well as its operating mode. An animation of the operating principle of thermal power plants can help to understand this issue in more detail.
March 23rd, 2013
Once, when we were driving into the glorious city of Cheboksary, from the east, my wife noticed two huge towers standing along the highway. "And what is it?" - she asked. Since I absolutely did not want to show my wife my ignorance, I dug a little into my memory and came out victoriously: “These are cooling towers, don’t you know?” She was a little confused: “What are they for?” “Well, there’s something there to cool, it seems.” "And what?". Then I got embarrassed because I didn’t know how to get out of it any further.
This question may remain forever in the memory without an answer, but miracles happen. A few months after this incident, I see a post in my friend feed z_alexey about the recruitment of bloggers who want to visit the Cheboksary CHPP-2, the same one that we saw from the road. You have to suddenly change all your plans; missing such a chance would be unforgivable!
So what is CHP?
This is the heart of the power plant and where most of the action takes place. The gas entering the boiler burns, releasing a crazy amount of energy. “Clean water” is also supplied here. After heating, it turns into steam, more precisely into superheated steam, having an outlet temperature of 560 degrees and a pressure of 140 atmospheres. We will also call him " Pure steam", because it is formed from prepared water.
In addition to steam, we also have exhaust at the exit. At maximum power, all five boilers consume almost 60 cubic meters of natural gas per second! To remove combustion products, you need a non-childish “smoke” pipe. And there is one like this too.
The pipe can be seen from almost any area of the city, given the height of 250 meters. I suspect that this is the tallest building in Cheboksary.
Nearby there is a slightly smaller pipe. Reserve again.
If the thermal power plant operates on coal, additional exhaust cleaning is necessary. But in our case this is not required, since natural gas is used as fuel.
The second section of the boiler-turbine shop contains installations that generate electricity.
There are four of them installed in the turbine hall of the Cheboksary CHPP-2, with a total capacity of 460 MW (megawatt). This is where superheated steam from the boiler room is supplied. It is directed under enormous pressure onto the turbine blades, causing the thirty-ton rotor to rotate at a speed of 3000 rpm.
The installation consists of two parts: the turbine itself, and a generator that generates electricity.
And this is what the turbine rotor looks like.
Sensors and pressure gauges are everywhere.
Both turbines and boilers can be stopped instantly in case of an emergency. For this, there are special valves that can shut off the supply of steam or fuel in a fraction of a second.
I wonder if there is such a thing as an industrial landscape, or an industrial portrait? There is beauty here.
There is terrible noise in the room, and in order to hear your neighbor you have to strain your ears. Plus it's very hot. I want to take off my helmet and strip down to my T-shirt, but I can’t do that. For safety reasons, short-sleeved clothing is prohibited at the thermal power plant; there are too many hot pipes.
Most of the time the workshop is empty; people appear here once every two hours, during their rounds. And the operation of the equipment is controlled from the Main Control Panel (Group Control Panels for Boilers and Turbines).
This is what the duty officer's workplace looks like.
There are hundreds of buttons around.
And dozens of sensors.
Some are mechanical, some are electronic.
This is our excursion, and people are working.
In total, after the boiler-turbine shop, at the output we have electricity and steam that has partially cooled and lost some of its pressure. Electricity seems to be easier. The output voltage from different generators can be from 10 to 18 kV (kilovolts). With the help of block transformers, it increases to 110 kV, and then electricity can be transmitted over long distances using power lines (power lines).
It is not profitable to release the remaining “Pure Steam” to the side. Since it is formed from " Clean water", the production of which is a rather complex and costly process, it is more expedient to cool it and return it back to the boiler. So in a vicious circle. But with its help, and with the help of heat exchangers, you can heat water or produce secondary steam, which you can safely sell to third-party consumers.
In general, this is exactly how you and I get heat and electricity into our homes, having the usual comfort and coziness.
Oh yes. But why are cooling towers needed anyway?
It turns out everything is very simple. To cool the remaining “Clean Steam” before re-supplying it to the boiler, the same heat exchangers are used. It is cooled using technical water; at CHPP-2 it is taken directly from the Volga. It does not require any special preparation and can also be reused. After passing through the heat exchanger, the process water is heated and goes to the cooling towers. There it flows down in a thin film or falls down in the form of drops and is cooled by the counter flow of air created by fans. And in ejection cooling towers, water is sprayed using special nozzles. In any case, the main cooling occurs due to the evaporation of a small part of the water. The cooled water leaves the cooling towers through a special channel, after which, with the help of a pumping station, it is sent for reuse.
In a word, cooling towers are needed to cool the water, which cools the steam operating in the boiler-turbine system.
All work of the thermal power plant is controlled from the Main Control Panel.
There is always a duty officer here.
All events are logged.
Don't feed me bread, let me take a picture of the buttons and sensors...
That's almost all. Finally, there are a few photos of the station left.
This is an old pipe that is no longer working. Most likely it will be demolished soon.
There is a lot of agitation at the enterprise.
They are proud of their employees here.
And their achievements.
It seems that it was not in vain...
It remains to add that, as in the joke - “I don’t know who these bloggers are, but their tour guide is the director of the branch in Mari El and Chuvashia of TGC-5 OJSC, IES holding - Dobrov S.V.”
Together with the station director S.D. Stolyarov.
Without exaggeration, they are true professionals in their field.
And of course, thanks a lot Irina Romanova, representing the company’s press service, for a perfectly organized tour.
Supplying the population with heat and electricity is one of the main tasks of the state. In addition, without electricity generation it is impossible to imagine a developed manufacturing and processing industry, without which the country’s economy cannot exist in principle.
One of the ways to solve the problem of energy shortage is the construction of thermal power plants. The definition of this term is quite simple: this is the so-called combined heat and power plant, which is one of the most common types of thermal power plants. In our country, they are very common, since they run on organic fossil fuel (coal), the characteristics of which have very modest requirements.
Peculiarities
This is what a thermal power plant is. The definition of the concept is already familiar to you. But what features does it have? this variety power plants? It’s no coincidence that they are placed in a separate category!?
The fact is that they generate not only electricity, but also heat, which is supplied to consumers in the form of hot water and steam. It should be noted that electricity is a by-product, since the steam that is supplied to heating systems first rotates the generator turbines. Combining two enterprises (boiler house and power plant) is good because it can significantly reduce fuel consumption.
However, this also leads to a rather insignificant “distribution area” of thermal power plants. The explanation is simple: since the station supplies not only electricity, which can be transported thousands of kilometers with minimal losses, but also heated coolant, they cannot be located at a significant distance from a populated area. It is not surprising that almost all thermal power plants are built in close proximity to cities, whose residents they heat and light.
Ecological significance
Due to the fact that during the construction of such a power plant it is possible to get rid of many old city boiler houses, which play an extremely negative role in the ecological condition of the area (huge amounts of soot), the cleanliness of the air in the city can sometimes be increased by an order of magnitude. In addition, new thermal power plants make it possible to eliminate waste from city landfills.
The latest cleaning equipment makes it possible to effectively purify emissions, and the energy efficiency of such a solution is extremely high. Thus, the energy release from burning a ton of oil is identical to the volume that is released when recycling two tons of plastic. And this “good” will be enough for decades to come!
Most often, the construction of thermal power plants involves the use of fossil fuels, as we have already discussed above. However, in last years It is planned to create which will be installed in hard-to-reach regions of the Far North. Since the delivery of fuel there is extremely difficult, nuclear energy is the only reliable and constant source of energy.
What are they?
There are thermal power plants (photos of which are in the article) industrial and “household”, heating. As you can easily guess from the name, industrial power plants provide electricity and heat to large manufacturing enterprises.
They are often built during the construction of the plant, forming a single infrastructure together with it. Accordingly, “domestic” varieties are being built near the city’s residential neighborhoods. In industrial applications it is transmitted in the form of hot steam (no more than 4-5 km), in the case of heating - using hot water (20-30 km).
Information about station equipment
The main equipment of these enterprises are turbine units, which convert mechanical energy into electricity, and boilers, responsible for generating steam that rotates the flywheels of generators. The turbine unit includes both the turbine itself and a synchronous generator. Pipes with a back pressure of 0.7-1.5 Mn/m2 are installed at those thermal power plants that supply heat and energy to industrial facilities. Models with a pressure of 0.05-0.25 Mn/m2 are used to supply household consumers.
Efficiency issues
In principle, all generated heat can be fully utilized. But the amount of electricity generated at a thermal power plant (you already know the definition of this term) directly depends on the heat load. Simply put, in the spring-summer period its production decreases almost to zero. Thus, backpressure installations are used only to supply industrial facilities whose consumption is more or less uniform throughout the entire period.
Condensing type units
In this case, only the so-called “bleeding steam” is used to supply consumers with heat, and the rest of the heat is often simply lost, dissipating in the environment. To reduce energy losses, such CHP plants must operate with minimal heat release to the condensing unit.
However, since the times of the USSR, such stations have been built in which a hybrid mode is structurally provided: they can operate like conventional condensing thermal power plants, but their turbine generator is fully capable of operating in backpressure mode.
Universal varieties
It is not surprising that it is steam condensation installations that have become most widespread due to their versatility. Thus, only they make it possible to practically independently regulate the electrical and thermal load. Even if no heat load is expected at all (in the case of a particularly hot summer), the population will be supplied with electricity according to the previous schedule (Zapadnaya CHPP in St. Petersburg).
“Thermal” types of CHP
As you can already understand, heat production at such power plants is extremely uneven throughout the year. Ideally, about 50% of hot water or steam is used to heat consumers, and the rest of the coolant is used to generate electricity. This is exactly how the South-West CHPP works in the Northern capital.
Heat release in most cases is carried out according to two schemes. If an open option is used, then hot steam from the turbines goes directly to consumers. If a closed operating scheme was chosen, the coolant is supplied after passing through the heat exchangers. The choice of scheme is determined based on many factors. First of all, the distance from the object provided with heat and electricity, the number of population and the season are taken into account. Thus, the Yugo-Zapadnaya CHPP in St. Petersburg operates according to a closed scheme, as it provides greater efficiency.
Characteristics of the fuel used
Solid, liquid and can be used. Since thermal power plants are often built in close proximity to large settlements and cities, it is often necessary to use quite valuable types of it, gas and fuel oil. The use of coal and garbage as such in our country is quite limited, since not all stations have modern, effective air purification equipment installed.
To clean the exhaust from installations, special particle traps are used. To disperse solid particles sufficiently high layers atmosphere, they build pipes 200-250 meters high. As a rule, all combined heat and power plants (CHPs) are located at a fairly large distance from water supply sources (rivers and reservoirs). Therefore, artificial systems are used that include cooling towers. Direct-flow water supply is extremely rare, under very specific conditions.
Features of gas stations
Gas-fired thermal power plants stand apart. Heat supply to consumers is carried out not only from the energy that is generated during combustion, but also from the recovery of heat from the gases that are generated. The efficiency of such installations is extremely high. In some cases, nuclear power plants can also be used as thermal power plants. This is especially common in some Arab countries.
There, these stations play two roles at once: they provide the population with electricity and technical water, since they simultaneously perform functions. Now let’s look at the main thermal power plants in our country and neighboring countries.
Yugo-Zapadnaya, St. Petersburg
In our country, the Western Thermal Power Plant, which is located in St. Petersburg, is famous. Registered as OJSC "Yugo-Zapadnaya CHPP". The construction of this modern facility served several functions:
- Compensation for the severe shortage of thermal energy, which prevented the intensification of the housing construction program.
- Increasing the reliability and energy efficiency of the city system as a whole, since it was precisely this aspect that St. Petersburg had problems with. The thermal power plant allowed us to partially solve this problem.
But this station is also known for being one of the first in Russia to meet the strictest environmental requirements. The city government has allocated an area of more than 20 hectares for the new enterprise. The fact is that the reserve area remaining from the Kirovsky district was allocated for construction. In those parts there was old collection ash from CHPP-14, and therefore the area was not suitable for housing construction, but it was extremely well located.
The launch took place at the end of 2010, and almost the entire city leadership was present at the ceremony. Two newest automatic boiler installations were put into operation.
Murmansk
The city of Murmansk is known as the base of our fleet on the Baltic Sea. But it is also characterized by extreme severity of climatic conditions, which imposes certain requirements on its energy system. It is not surprising that the Murmansk Thermal Power Plant is in many ways a completely unique technical facility, even on a national scale.
It was put into operation back in 1934, and since then has continued to regularly supply city residents with heat and electricity. However, in the first five years, the Murmansk CHPP was an ordinary power plant. The first 1150 meters of the heating main were laid only in 1939. The point is the neglected Nizhne-Tulomskaya hydroelectric power station, which almost completely covered the city’s electricity needs, and therefore it became possible to free up part of the thermal output for heating city houses.
The station is characterized by the fact that it operates in a balanced mode all year round, since its thermal and “energy” output is approximately equal. However, in the conditions of the polar night, the thermal power plant at some peak moments begins to use most of the fuel specifically to generate electricity.
Novopolotsk station, Belarus
The design and construction of this facility began in August 1957. The new Novopolotsk CHPP was supposed to solve the issue of not only heating the city, but also providing electricity to the oil refinery being built in the same area. In March 1958, the project was finally signed, approved and approved.
The first stage was put into operation in 1966. The second was launched in 1977. At the same time, the Novopolotsk CHPP was modernized for the first time, its peak power was increased to 505 MW, and a little later the third stage of construction was launched, completed in 1982. In 1994, the station was converted to liquefied natural gas.
To date, about 50 million US dollars have already been invested in the modernization of the enterprise. Thanks to such an impressive cash injection, the enterprise was not only completely converted to gas, but also received a huge amount of completely new equipment that will allow the station to serve for decades.
conclusions
Oddly enough, today it is the outdated thermal power plants that are truly universal and promising stations. Using modern neutralizers and filters, you can heat water by burning almost all the garbage that produces locality. This achieves a triple benefit:
- Landfills are unloaded and cleared.
- The city receives cheap electricity.
- The heating problem is being solved.
In addition, in coastal areas it is quite possible to build thermal power plants, which will simultaneously serve as desalinators of sea water. This liquid is quite suitable for irrigation, for livestock farms and industrial enterprises. In a word, real technology of the future!
Combined heat and power production
Combined heat and power (CHP), also called cogeneration, is the process of producing electrical and thermal energy simultaneously. This means that the heat generated to produce electricity is recovered and used. The production process at a thermal power plant can be based on the use of steam or gas turbines, or internal combustion engines. The primary source for energy production can be a wide range of fuels, including biomass, waste and fossil fuels, as well as geothermal or solar energy.
Finland is a leading country in the use of cogeneration
The amount of energy Finland saves annually using cogeneration sources is equal to more than 10 percent of all primary energy used in the country, or 20 percent of Finland's fossil fuel consumption. Approximately one third of the electricity used in Finland comes from CHP. Industrial CHP and district heating plants respectively account for 45 and 55 percent of the combined production system. Industry uses more than half of all electricity consumed in Finland, and almost 40 percent of this is produced by combined heat and power plants. Depending on annual climate change, almost 75 - 80 percent of district heating energy is produced in CHP plants.
Widely used for many decades
Finland's per capita energy consumption is the highest among OECD countries. This is due to the large share of energy-intensive industries such as pulp and paper in the Finnish economy. As a result, the economical use and reliable distribution of energy has always been given special attention in Finland. The geographical and climatic features of the country provided the basis for the development of CHP in district heating. The efficiency of energy production is an essential factor, since the annual heat demand and the number of hours of energy use are high.
History of the use of industrial thermal power plants
Combined energy production in industry is the result of the need to produce heat for its own needs.
The first industrial thermal power plants in Finland were built already in the early 20s and 30s. CHP plants were chosen because they were the most reliable and economical way to produce electricity. Local energy sources were often used as a starting point.
Industrial backpressure CHP plants mainly use liquid alkaline waste generated during the production of cellulose as fuel. Black lye solution is suitable for burning due to the organic wood residues it contains. The pulp and paper industries are not the only industries that use their waste for incineration in thermal power plants. Metallurgical and chemical industry, also produce waste that can be converted into heat and electricity through the cogeneration process.
District heating as partcogeneration
Due to the country's northern location, district heating is a natural choice for Finland. Plans for organizing a centralized heating system were implemented after World War II. The cogeneration of thermal and electrical energy was carried out using wood waste produced
wood industry, this has proven to be an effective concept for producing energy while preserving the environment. Thus, the Finnish district heating system was based on the CHP principle from the very beginning.
Approximately half of the buildings in Finland are connected to centralized system heat supply. In the most major cities, this figure exceeds 90 percent. Most office and public buildings in the country are also connected to a centralized heating system. CHP plants provide approximately three-quarters of the heat consumed annually. If we compare the separate production of electrical and thermal energy, cogeneration allows us to save approximately a third of fuel. Most heat-producing companies belong to municipalities, but the share of private enterprises is constantly increasing.
District heating provides the necessary heat load for CHP plants, and this provides great potential for the use of renewable energy sources such as biofuels and waste. The European Union's goal of doubling the share of cogeneration in energy production cannot be achieved without further development of this area. Therefore, district heating must be recognized important topic on the European energy policy agenda.
CHP for a centralized systemcooling
If we talk about centralized heating, cooling of buildings can also occur using thermal energy. During the winter months, high temperatures are used to heat the rooms, but during the summer, little heat is required. This excess heat can be used to produce cold in a room air conditioning system.
District cooling systems exist today in only three Finnish cities, but the prospects are promising. Today, the centralized cooling system in Helsinki is the largest in Finland. Thirty percent of the cold is obtained from cold sea water, through simple heat exchangers.
The use of CHP allows you to produce energy in the most cost-effective wayby
The main task of a CHP plant is to produce energy in the most cost-effective way. Therefore, combined heat and power production should be cheaper than alternative methods. Profitability various options production must be previously estimated for the full period of operation of the power plant. CHP usually requires more investment than conventional power generation technologies, but it uses less fuel.
As a result, CHP plants are cheaper to operate than power plants of similar capacity. The heat produced by CHP can be used both for centralized heating of residential areas and for industrial needs. Transferring heat over long distances is expensive. Therefore, it is better to build thermal power plants close to populated areas and industrial facilities where thermal energy will be used.
High efficiency
CHP plants make maximum use of the energy of burning fuel, producing electricity and heat with minimal losses. Their efficiency reaches 80 - 90 percent. While conventional condensing power plants achieve an efficiency of 35 - 40 percent.
High fault tolerance
CHP plants have high level fault tolerance, allowing you not to interrupt the energy production process. At the same time, CHP plants are highly automated, thus minimizing the number of personnel required and reducing operating and maintenance costs.
Electricity and heat production can be easily matched to consumption levels, which can change very quickly. The reliability of the district heating system in Finland during the heating season is 99.98 percent.
On average, heat supply for an individual customer during the heating season is interrupted only once every six
Wide range of fuels used
CHP can use a wide range of fuels, including low-calorie and moist fuels such as industrial waste and biofuels. The optimal combination of different types of fuel is determined for each thermal power plant separately, depending on the local fuel situation. Typical fuels used are natural gas, coal, industrial gases, peat and other renewable resources (eg industrial wood waste, municipal waste and wood chips). Fuel oil is used in small quantities, usually as a backlight for other fuels.
Traditionally, the use of biofuels in cogeneration is associated with technological processes in the forest industry. For many reasons, CHP plants are ideal for using biofuels. Because their heating value is low and transportation is expensive, they tend to be local fuels.
Efficient energy production causes less harmnature
High efficiency and low emissions in the cogeneration process, the most environmentally friendly way to produce energy. Modern thermal power plants use effective methods combustion of fuel to reduce emissions of nitrogen oxides.
Reducing the amount of fuel burned to produce energy reduces the negative impact on the environment. For example, the amount of carbon dioxide released when burning fossil fuels decreases depending on the amount of fuel used. The same thing happens with pollutants such as sulfur and nitrogen oxides.
A study of air quality in Finland's largest cities shows that sulfur emissions have dropped significantly and this is a direct result of the use of cogeneration technology and district heating.
All the advantages of using CHP, in terms of impact on environment, have been realized over the past few years. Despite this, the economic side of the matter plays a decisive role when deciding on the construction of one or another type of energy source. Therefore, the cost of energy produced in the cogeneration process must be competitive compared to other energy sources.
CHP and district heating are supported by authorities because they are powerful tools for reducing carbon dioxide emissions. The goal of Finland's energy strategy is to bring carbon dioxide emissions into line with the Kyoto Protocol, which states that by 2010, emissions should be reduced to 1990 levels. Thanks to a centralized heating system and combined heat and power plants, in 2004 Finland reduced carbon dioxide emissions into the atmosphere by 8 million tons. Which is equal to approximately three quarters of the planned annual emissions reduction in accordance with the Kyoto Protocol.
Wide range of CHP applications
Evolution of CHP technology, in this moment, goes in the direction of decreasing power. Small sources allow for large quantities
use local fuels, such as wood and other renewable types, and abandon secondary energy sources from natural fossil fuels.
Fuel pre-drying technologies can increase the heat output of the cogeneration process. Other modern combustion technologies, such as gasification or positive pressure combustion, which increase electricity production in CHP plants, are currently at the development stage. All this is done so that small thermal power plants can be competitive.
Improving electricity production technology will lead to increased heat production. Combined cycle technology based on gasification of solid fuels can lead to interesting results. In this case, the gas can be used in gas turbine, and the generated heat will work in a steam turbine. In this case, the ratio of electricity and heat produced could be 1:1, now it is 0.5.
Enormous market potential exists for the use of cogeneration to generate energy from various waste materials.
Finnish energy policy and thermal power plants
Finland's energy policy is based on three pillars: energy, economy and environment. Sustainable and secure energy supply, competitive energy prices and minimization of negative environmental impact, in accordance with international obligations. The main and most important factor influencing energy policy is international cooperation in the field of reducing greenhouse gas emissions. Among other factors influencing energy policy, it is necessary to highlight the need to prevent environmental disasters and adapting economic activity to the principles of sustainable development.
Cogeneration has always played a major role in Finland's energy policy and will remain a major part of it in the future. The combined cycle is effective way production of heat and electricity. It promotes the development of local renewable energy sources. All these points mean only one thing - CHP is a huge contribution to reducing greenhouse gas emissions.
In accordance with the decision of the Government, for an uninterrupted and safe energy supply, it is necessary to ensure energy production based on several types of fuel supplied from various sources. The goal is to create a flexible, decentralized and balanced energy system in the future. For its part, the Government continues to provide all the conditions for the creation of such a system, and focuses on energy produced in its country, in other words, on renewable energy resources and biofuels.
The government will continue to support the combined cycle of heat and electricity production in the future. A prerequisite for decisions regarding energy sources is that heat consumption should be most efficiently linked to the cogeneration process. Sufficient attention should also be paid to the technical and economic aspects. The high status of the cogeneration process is determined by the fact that the overall efficiency of energy sources is an important factor in the area of allocated quotas for harmful emissions. By investing in the continued development of technology, it is possible to be fully equipped to meet the point in the future when obligations to reduce greenhouse gas emissions become very stringent. In addition to technology, development focuses on the entire chain of operation, delivery and trade. Renewable energy and energy efficiency remain important sectors. Constant and intensive investments will contribute to the development and implementation of new, cost-effective solutions for the cogeneration process, industrial energy production, small-scale energy and efficient use of energy.
Government investments will mainly be directed to projects introducing new energy technologies, on the one hand, and associated with special technological risks associated with the demonstration nature of these projects.
Highly efficient combined cycle technology
CompanyHelsinkiEnergy
Thanks to its advanced gas combustion technology, the Vuosaari district power plant in Helsinki is one of the most efficient and cleanest. They use combined cycle technology, in which two processes are combined - gas and steam turbine. If we compare the traditional energy production scheme with the combined cycle technology, then in the second case, we have higher efficiency in the production of electricity and, accordingly, a higher electricity output, in proportion to the thermal energy produced.
In the combined cycle process, Vuosaari CHP achieves an efficiency of over 90 percent, meaning less than 10 percent of the energy produced is lost. If we talk about energy losses, then most often these are thermal losses. Heat is lost through flue gases, coolant, and the production process itself.
Electricity production - 630 MW
Heat production - 580 MW
Fuel - natural gas 650-800 million m3/g
Small CHP plants with gasification process
CompanyKokemä enLampoOy
The first small thermal power plants operating using Novel technology, gasification of fuel in the layer, were built in 2004. The station is equipped with a complete gas purification process chain, consisting of a gas reforming unit, a filter and an acid-base scrubber to remove residual nitrogen compounds. Three 0.6 MW gas turbines and one gas boiler for heat recovery are used to produce electricity.
The Novel gasifier is a new development, its operating principle is based on the supply of fuel under pressure, this method makes it possible to use fibrous biofuels with low bulk density. The gasifier can use a wide range of biological wastes with moisture content ranging from 0 to 55 percent and particle sizes ranging from sawdust to large wood chips.
Electricity production – 1.8 MW
Heat production – 4.3 MW
Thermal power of the fuel dryer is 429 kW
Fuel storage capacity – 7.2 MW
An integrated approach to achieve profitability
CompanyVapoOy
The construction of the thermal power plant, expansion and modernization of the pellet production facility in Ilomantsi was completed in November 2005. The thermal power plant was equipped with a boiler for combustion in a “fluidized bed”. The modernization of the production of fuel pellets consisted of the construction of a new raw material receiver, dryer, third line for the production of pellets, a conveyor system and a bunker. The thermal power plant, pellet production and dryer are controlled from one control room. Milled peat and wood are used as fuel. Fuel consumption is approximately 75 GW per year.
Fuel storage capacity – 23 MW
Heat production for heating supply. – 8 MW
From coal to biofuels
Porvoon Energia Oy company
The Tolkkinen thermal power plant was converted from coal to biomass. The company wanted to kill two birds with one stone - reduce coal consumption and reduce the burden on the environment. The chain grate boiler was replaced by a fluidized bed boiler in 2000. This provided a good opportunity to use Various types wood and wood waste as fuel. At the same time, the air supply, flue gas exhaust, ash collection, fuel supply, control devices and automation systems were modernized. A scrubber for waste heat recovery, which can increase the plant's efficiency by more than 7 MW, will be completed in 2006.
Fuel storage capacity – 54 MW
Steam production – 46 MW
Electricity production 7 MW
Heat production – 25 MW
Energy for pulp and paper mill and heat supply system
CompanyKyminVoimaOy
The Kymin Voima CHP plant is owned by Pohjolan Voima Oy and Kouvolan Seudun Sahko Oy. It is located at the UPM Kymi pulp and paper mill; the thermal power plant uses fluidized bed combustion technology. It produces energy both for the technological process and for centralized systems
heat supply to the cities of Kouvola and Kuusankoski. The following fuels are used: tree bark, logging waste, sludge, peat, gas and fuel oil. Fuel consumption is approximately 2,100 GW/year.
Electricity production – 76 MW
Process steam – 125 MWth
Process heat production – 15 MWth
Heat production for heating supply. – 40 MWth
CHPForssaburns only wood
CompanyVapoOy
Forssa Bio Power Plant is the first CHP plant in Finland (1996) in a district heating system using only wood as fuel. For industrial needs, wood fuel was widely used before. The combustion process takes place in a “fluidized bed”. This technology allows the use of almost all other available fuels. The main type of fuel is wood processing industry waste. For example, sawdust and bark, along with logging waste and construction waste. When burning wood, there are no sulfur emissions, and emissions of nitrogen oxides are insignificant.
Electricity production – 17 MW
Heat production for heating supply. – 48 MW
Flexible technology
CompanyOyAhlholmensKraftAb
CHP AK2 is owned by Oy Ahlholmens Kraft Ab. The heat source is flexible in operation, so regardless of the volume of electricity generated, heat is produced in the amount that is needed at the moment. The efficiency of the installation when producing heat is more than 80%, therefore, production does not harm the environment. Heat is supplied to the city of Pietarsaari and to the UPM pulp and paper mill.
The main types of fuel are coal and different kinds biofuels. Such as: tree bark, wood chips, other forest industry waste and peat.
Electricity production – 240 MW
Process steam – 100 MW
Heat production for heating supply. – 60 MW
Purpose of combined heat and power plants. Schematic diagram of a thermal power plant
CHP (combined heat and power plants)- designed for centralized supply of heat and electricity to consumers. Their difference from IES is that they use the heat of steam exhausted in turbines for the needs of production, heating, ventilation and hot water supply. Due to this combination of electricity and heat generation, significant fuel savings are achieved in comparison with separate energy supply (electricity generation at CPPs and thermal energy at local boiler houses). Thanks to this method of combined production, CHP plants achieve a fairly high efficiency, reaching up to 70%. Therefore, CHP plants have become widespread in areas and cities with high heat consumption. The maximum power of a CHP plant is less than that of a CPP.
CHP plants are tied to consumers, because The radius of heat transfer (steam, hot water) is approximately 15 km. Suburban thermal power plants transmit hot water at a higher initial temperature for a distance of up to 30 km. Steam for production needs with a pressure of 0.8-1.6 MPa can be transmitted over a distance of no more than 2-3 km. With an average heat load density, the power of thermal power plants usually does not exceed 300-500 MW. Only in large cities such as Moscow or St. Petersburg with a high heat load density does it make sense to build stations with a capacity of up to 1000-1500 MW.
The power of the thermal power plant and the type of turbogenerator are selected in accordance with the heat requirements and parameters of the steam used in production processes and for heating. The most widely used are turbines with one and two adjustable steam extractions and condensers (see figure). Adjustable selections allow you to regulate the production of heat and electricity.
The CHP mode - daily and seasonal - is determined mainly by heat consumption. The station operates most economically if its electrical power matches the heat output. In this case, a minimum amount of steam enters the condensers. In winter, when the demand for heat is maximum, at the design air temperature during operating hours of industrial enterprises, the load of CHP generators is close to the nominal one. During periods when heat consumption is low, for example in summer, as well as in winter when the air temperature is higher than the design temperature and at night, the electric power of the thermal power plant corresponding to heat consumption decreases. If the power system needs electrical power, the thermal power plant must switch to mixed mode, which increases the flow of steam into the low pressure part of the turbines and into the condensers. At the same time, the efficiency of the power plant decreases.
Maximum electricity production by heating stations "at heat consumption"is only possible with working together with powerful CPPs and HPPs, which take on a significant part of the load during hours of reduced heat consumption.
