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 combined production, at thermal power plants a fairly high efficiency is achieved, 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 radius of heat transfer (steam, hot water) is approximately 15 km. Suburban thermal power plants transmit hot water at a higher initial temperature over 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 a thermal power plant usually does not exceed 300-500 MW. Only in major cities, such as Moscow or St. Petersburg with a high heat load density, it makes 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 needs and parameters of the steam used in the production processes and for heating. Most Applications received 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, with design temperature air 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 energy system needs electrical power, the thermal power plant must switch to mixed mode, in which the supply of steam to parts increases low pressure turbines and condensers. At the same time, the efficiency of the power plant decreases.

Maximum electricity production by heating stations "on thermal consumption" is possible only when working together with powerful CPPs and HPPs, which take on a significant part of the load during hours of reduced heat consumption.

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

That's what a thermal power plant is. The definition of the concept is already familiar to you. But what features does this type of power plant have? 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 by-product, since the steam that is supplied to the heating systems first rotates the turbines of the generators. 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 recent 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 all the rest of the heat is often simply lost, dissipating in 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 the open option is used, then hot steam from 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

Can be used in solid, liquid and 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 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". Construction of this modern facility pursued several functions at once:

• Compensation severe shortage thermal energy, which prevented the intensification of the housing construction program.
• Increased reliability and energy efficiency the urban 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 an old collection of 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 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 it 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 1,150 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 gas 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, it is possible to heat water by burning almost all the garbage that a populated area produces. 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 also serve as desalination plants sea ​​water. This liquid is quite suitable for irrigation, for livestock farms and industrial enterprises. In a word, real technology of the future!

The operating principle of a combined heat and power plant (CHP) is based on unique property water vapor - to be a coolant. In a heated state, under pressure, it turns into a powerful source of energy that drives the turbines of thermal power plants (CHPs) - a legacy of the already distant era of steam.

The first thermal power plant was built in New York on Pearl Street (Manhattan) in 1882. A year later, St. Petersburg became the birthplace of the first Russian thermal station. Oddly enough, but even in our age high technology Thermal power plants have never found a full-fledged replacement: their share in the world energy sector is more than 60%.

And there is a simple explanation for this, which contains the advantages and disadvantages of thermal energy. Its “blood” is organic fuel - coal, fuel oil, oil shale, peat and natural gas are still relatively accessible, and their reserves are quite large.

The big disadvantage is that fuel combustion products cause serious harm environment. Yes, and the natural storehouse will one day be completely depleted, and thousands of thermal power plants will turn into rusting “monuments” of our civilization.

Operating principle

To begin with, it is worth defining the terms “CHP” and “CHP”. In simple terms, they are sisters. A “clean” thermal power plant - TPP is designed exclusively for the production of electricity. Its other name is “condensing power plant” - IES.

Combined heat and power plant - CHP - a type of thermal power plant. In addition to generating electricity, it supplies hot water to central system heating and for domestic needs.

The operation scheme of a thermal power plant is quite simple. Fuel and heated air - an oxidizer - simultaneously enter the furnace. The most common fuel at Russian thermal power plants is crushed coal. The heat from the combustion of coal dust turns the water entering the boiler into steam, which is then supplied under pressure to the steam turbine. A powerful flow of steam causes it to rotate, driving the generator rotor, which converts mechanical energy into electrical energy.

Next, the steam, which has already significantly lost its initial indicators - temperature and pressure - enters the condenser, where after a cold “water shower” it again becomes water. Then the condensate pump pumps it into the regenerative heaters and then into the deaerator. There, the water is freed from gases - oxygen and CO 2, which can cause corrosion. After this, the water is reheated from steam and fed back into the boiler.

Heat supply

Second, no less important function CHP – provision hot water(ferry) intended for systems central heating nearby settlements and domestic use. In special heaters, cold water is heated to 70 degrees in summer and 120 degrees in winter, after which it is supplied by network pumps to a common mixing chamber and then supplied to consumers through a heating main system. Water supplies at the thermal power plant are constantly replenished.

How do gas powered thermal power plants work?

Compared to coal-fired thermal power plants, thermal power plants with gas turbine units are much more compact and environmentally friendly. Suffice it to say that such a station does not need a steam boiler. A gas turbine unit is essentially the same turbojet aircraft engine, where, unlike it, the jet stream is not emitted into the atmosphere, but rotates the generator rotor. At the same time, emissions of combustion products are minimal.

New coal combustion technologies

The efficiency of modern thermal power plants is limited to 34%. The vast majority of thermal power plants still operate on coal, which can be explained quite simply - coal reserves on Earth are still enormous, so the share of thermal power plants in the total volume of electricity generated is about 25%.

The coal combustion process has remained virtually unchanged for many decades. However, new technologies have come here too.

Peculiarity this method consists in the fact that instead of air as an oxidizing agent when burning coal dust, the extracted from the air is used pure oxygen. As a result, a harmful impurity – NOx – is removed from the flue gases. The remaining harmful impurities are filtered out through several stages of purification. The CO 2 remaining at the outlet is pumped into containers under high pressure and is subject to burial at a depth of up to 1 km.

"oxyfuel capture" method

Here, too, when burning coal, pure oxygen is used as an oxidizing agent. Only in contrast to the previous method, at the moment of combustion, steam is formed, causing the turbine to rotate. Then ash and sulfur oxides are removed from the flue gases, cooling and condensation are performed. The remaining carbon dioxide under a pressure of 70 atmospheres is converted into a liquid state and placed underground.

Pre-combustion method

Coal is burned in the “normal” mode - in a boiler mixed with air. After this, ash and SO 2 - sulfur oxide are removed. Next, CO 2 is removed using a special liquid absorbent, after which it is disposed of by disposal.

Five of the most powerful thermal power plants in the world

The championship belongs to the Chinese thermal power plant Tuoketuo with a capacity of 6600 MW (5 power units x 1200 MW), occupying an area of ​​2.5 square meters. km. It is followed by its “compatriot” - the Taichung Thermal Power Plant with a capacity of 5824 MW. The top three is closed by the largest in Russia Surgutskaya GRES-2 - 5597.1 MW. In fourth place is the Polish Belchatow Thermal Power Plant - 5354 MW, and fifth is the Futtsu CCGT Power Plant (Japan) - a gas thermal power plant with a capacity of 5040 MW.

1 – electric generator; 2 – steam turbine; 3 – control panel; 4 – deaerator; 5 and 6 – bunkers; 7 – separator; 8 – cyclone; 9 – boiler; 10 – heating surface (heat exchanger); 11 – chimney; 12 – crushing room; 13 – warehouse reserve fuel; 14 – carriage; 15 – unloading device; 16 – conveyor; 17 – smoke exhauster; 18 – channel; 19 – ash catcher; 20 – fan; 21 – firebox; 22 – mill; 23 – pumping station; 24 – water source; 25 – circulation pump; 26 – regenerative heater high pressure; 27 – feed pump; 28 – capacitor; 29 – installation chemical cleaning water; 30 – step-up transformer; 31 – low pressure regenerative heater; 32 – condensate pump.

The diagram below shows the composition of the main equipment of a thermal power plant and the interconnection of its systems. Using this diagram, you can trace the general sequence of technological processes occurring at thermal power plants.

Designations on the TPP diagram:

1. Fuel economy;
2. fuel preparation;
3. intermediate superheater;
4. high pressure part (HPV or CVP);
5. low pressure part (LPP or LPC);
6. electric generator;
7. auxiliary transformer;
8. communication transformer;
9. main switchgear;
10. condensate pump;
11. circulation pump;
12. source of water supply (for example, river);
13. (PND);
14. water treatment plant (WPU);
15. thermal energy consumer;
16. return condensate pump;
17. deaerator;
18. feed pump;
19. (PVD);
20. slag removal;
21. ash dump;
22. smoke exhauster (DS);
23. chimney;
24. blower fan (DV);
25. ash catcher

Description of the TPP technological scheme:

Summarizing all of the above, we obtain the composition of a thermal power plant:

• fuel management and fuel preparation system;
• boiler installation: a combination of the boiler itself and auxiliary equipment;
• turbine installation: steam turbine and its auxiliary equipment;
• water treatment and condensate purification installation;
• technical water supply system;
• ash removal system (for thermal power plants operating on solid fuel);
• electrical equipment and electrical equipment control system.

Fuel facilities, depending on the type of fuel used at the station, include a receiving and unloading device, transport mechanisms, fuel storage for solid and liquid fuel, devices for preliminary fuel preparation (coal crushing plants). The fuel oil facility also includes pumps for pumping fuel oil, fuel oil heaters, and filters.

Preparation solid fuel for combustion consists of grinding and drying it in a dust preparation plant, and the preparation of fuel oil consists of heating it, cleaning it from mechanical impurities, and sometimes treating it with special additives. With gas fuel everything is simpler. Preparation of gas fuel comes down mainly to regulating the gas pressure in front of the boiler burners.

The air required for fuel combustion is supplied to the combustion space of the boiler by blower fans (AD). The products of fuel combustion - flue gases - are sucked off by smoke exhausters (DS) and discharged through chimneys into the atmosphere. A set of channels (air ducts and flues) and various elements of equipment through which air and flue gases pass forms the gas-air path of a thermal power plant (heating plant). The smoke exhausters, chimney and blower fans included in it make up a draft installation. In the fuel combustion zone, the non-combustible (mineral) impurities included in its composition undergo chemical and physical transformations and are partially removed from the boiler in the form of slag, and a significant part of them is carried away by flue gases in the form of small ash particles. To protect the atmospheric air from ash emissions, ash collectors are installed in front of smoke exhausters (to prevent their ash wear).

Slag and captured ash are usually removed hydraulically to ash dumps.

When burning fuel oil and gas, ash collectors are not installed.

When fuel is burned, chemically bound energy is converted into thermal energy. As a result, combustion products are formed, which in the heating surfaces of the boiler give off heat to the water and the steam generated from it.

The totality of equipment, its individual elements, and pipelines through which water and steam move form the station’s steam-water path.

In the boiler, the water is heated to saturation temperature, evaporates, and the saturated steam formed from the boiling boiler water is overheated. From the boiler, superheated steam is sent through pipelines to the turbine, where it is thermal energy turns into a mechanical one, transmitted to the turbine shaft. The steam exhausted in the turbine enters the condenser, transfers heat to the cooling water and condenses.

On modern thermal power plants and thermal power plants with units with a unit capacity of 200 MW and above use intermediate superheating of steam. In this case, the turbine has two parts: a high pressure part and a low pressure part. The steam exhausted in the high-pressure section of the turbine is sent to the intermediate superheater, where additional heat is supplied to it. Next, the steam returns to the turbine (to the low pressure part) and from it enters the condenser. Intermediate superheating of steam increases the efficiency of the turbine unit and increases the reliability of its operation.

The condensate is pumped out of the condenser by a condensation pump and, after passing through low-pressure heaters (LPH), enters the deaerator. Here it is heated by steam to a saturation temperature, while oxygen and carbon dioxide are released from it and removed into the atmosphere to prevent equipment corrosion. Deaerated water, called feedwater, is pumped through high-pressure heaters (HPH) into the boiler.

The condensate in the HDPE and deaerator, as well as the feed water in the HDPE, are heated by steam taken from the turbine. This heating method means returning (regenerating) heat to the cycle and is called regenerative heating. Thanks to it, the flow of steam into the condenser is reduced, and therefore the amount of heat transferred to the cooling water, which leads to an increase in the efficiency of the steam turbine plant.

The set of elements that provide cooling water to the condensers is called the technical water supply system. This includes: a water supply source (river, reservoir, cooling tower), circulation pump, inlet and outlet water pipes. In the condenser, approximately 55% of the heat of the steam entering the turbine is transferred to the cooled water; this part of the heat is not used to generate electricity and is wasted uselessly.

These losses are significantly reduced if partially exhausted steam is taken from the turbine and its heat is used for the technological needs of industrial enterprises or for heating water for heating and hot water supply. Thus, the station becomes a combined heat and power plant (CHP), providing combined generation of electrical and thermal energy. At thermal power plants, special turbines with steam extraction are installed - so-called cogeneration turbines. The steam condensate delivered to the heat consumer is returned to the thermal power plant by a return condensate pump.

At thermal power plants, there are internal losses of steam and condensate, due to the incomplete tightness of the steam-water path, as well as the unrecoverable consumption of steam and condensate for the technical needs of the station. They make up approximately 1 - 1.5% of total flow steam for turbines.

At thermal power plants there may also be external losses of steam and condensate associated with the supply of heat to industrial consumers. On average they are 35 - 50%. Internal and external losses of steam and condensate are replenished with additional water pre-treated in the water treatment plant.

Thus, boiler feed water is a mixture of turbine condensate and make-up water.

The electrical equipment of the station includes an electric generator, a communication transformer, a main switchgear, and a power supply system for the power plant's own mechanisms through an auxiliary transformer.

The control system collects and processes information about the progress technological process and condition of equipment, automatic and remote control of mechanisms and regulation of basic processes, automatic protection of equipment.

An electric power plant is a power plant used to convert natural energy into electrical energy. The type of power plant is determined primarily by the type of natural energy. The most widespread are thermal power plants (TPPs), which use thermal energy released by burning fossil fuels (coal, oil, gas, etc.). Thermal power plants generate about 76% of the electricity produced on our planet. This is due to the presence of fossil fuels in almost all areas of our planet; the possibility of transporting organic fuel from the extraction site to a power plant located near energy consumers; technical progress at thermal power plants, ensuring the construction of thermal power plants with high power; the possibility of using waste heat from the working fluid and supplying it to consumers, in addition to electrical energy, also thermal energy (with steam or hot water), etc. .

Basic principles of operation of thermal power plants (Appendix B). Let's consider the principles of operation of thermal power plants. Fuel and oxidizer, which is usually heated air, continuously flow into the boiler furnace (1). The fuel used is coal, peat, gas, oil shale or fuel oil. Most thermal power plants in our country use coal dust as fuel. Due to the heat generated as a result of fuel combustion, the water in the steam boiler is heated, evaporates, and the resulting saturated steam flows through a steam line into a steam turbine (2), designed to convert the thermal energy of steam into mechanical energy.

All moving parts of the turbine are rigidly connected to the shaft and rotate with it. In the turbine, the kinetic energy of the steam jets is transferred to the rotor as follows. Steam of high pressure and temperature, which has high internal energy, enters the nozzles (channels) of the turbine from the boiler. Jet of steam with high speed, often above the sound level, continuously flows out of the nozzles and enters the turbine blades mounted on a disk rigidly connected to the shaft. In this case, the mechanical energy of the steam flow is converted into mechanical energy of the turbine rotor, or more precisely, into the mechanical energy of the turbogenerator rotor, since the shafts of the turbine and electric generator (3) are interconnected. In an electric generator, mechanical energy is converted into electrical energy.

After steam turbine water vapor, already at low pressure and temperature, enters the condenser (4). Here, the steam, with the help of cooling water pumped through the tubes located inside the condenser, is converted into water, which is supplied to the deaerator (7) by a condensate pump (5) through regenerative heaters (6).

The deaerator is used to remove gases dissolved in it from water; at the same time, in it, just like in regenerative heaters, the feed water is heated by steam, taken for this purpose from the turbine outlet. Deaeration is carried out in order to bring the content of oxygen and carbon dioxide in it to acceptable values ​​and thereby reduce the rate of corrosion in water and steam paths.

Deaerated water is supplied to the boiler plant by a feed pump (8) through heaters (9). The condensate of the heating steam formed in the heaters (9) is passed in cascade into the deaerator, and the condensate of the heating steam of the heaters (6) is supplied by the drain pump (10) into the line through which the condensate from the condenser (4) flows.

The most difficult technically is the organization of the operation of coal-fired thermal power plants. At the same time, the share of such power plants in the domestic energy sector is high (~30%) and it is planned to increase it (Appendix D).

Fuel in railway cars (1) is supplied to unloading devices (2), from where it is sent to the warehouse (3) using belt conveyors (4), and from the warehouse the fuel is supplied to the crushing plant (5). It is possible to supply fuel to the crushing plant and directly from unloading devices. From the crushing plant, fuel flows into raw coal bunkers (6), and from there through feeders into pulverized coal mills (7). Coal dust is pneumatically transported through a separator (8) and a cyclone (9) to a coal dust hopper (10), and from there by feeders (11) to the burners. Air from the cyclone is sucked in by the mill fan (12) and supplied to the combustion chamber of the boiler (13).

The gases generated during combustion in the combustion chamber, after leaving it, pass sequentially through the gas ducts of the boiler installation, where in the steam superheater (primary and secondary, if a cycle with intermediate superheating of steam is carried out) and the water economizer they give off heat to the working fluid, and in the air heater - supplied to the steam boiler to air. Then, in ash collectors (15), the gases are purified from fly ash and released into the atmosphere through the chimney (17) by smoke exhausters (16).

Slag and ash falling under the combustion chamber, air heater and ash collectors are washed off with water and flow through channels to the bagger pumps (33), which pump them to ash dumps.

The air required for combustion is supplied to the air heaters of the steam boiler by a blower fan (14). Air is usually taken from the top of the boiler room and (for high-capacity steam boilers) from outside the boiler room.

Superheated steam from the steam boiler (13) enters the turbine (22).

Condensate from the turbine condenser (23) is supplied by condensate pumps (24) through low-pressure regenerative heaters (18) to the deaerator (20), and from there by feed pumps (21) through high-pressure heaters (19) to the boiler economizer.

In this scheme, the losses of steam and condensate are replenished with chemically demineralized water, which is supplied to the condensate line behind the turbine condenser.

Cooling water is supplied to the condenser from the receiving well (26) of the water supply circulation pumps(25). The heated water is discharged into a waste well (27) of the same source at a certain distance from the point of intake, sufficient to ensure that the heated water does not mix with the taken water. Devices for chemical treatment of make-up water are located in the chemical workshop (28).

The schemes may provide for a small network heating installation for district heating of the power plant and the adjacent village. Steam is supplied to the network heaters (29) of this installation from turbine extractions, and condensate is discharged through line (31). Network water is supplied to the heater and removed from it through pipelines (30).

The generated electrical energy is removed from the electrical generator to external consumers through step-up electrical transformers.

To supply electricity to electric motors, lighting devices and devices of the power plant, there is an auxiliary electrical switchgear (32).

Combined heat and power plant (CHP) is a type of thermal power plant that produces not only electricity, but is also a source of thermal energy in centralized systems heat supply (in the form of steam and hot water, including for providing hot water supply and heating of residential and industrial facilities). The main difference between a thermal power plant is the ability to take away part of the thermal energy of the steam after it has generated electrical energy. Depending on the type of steam turbine, there are various steam extractions that allow you to extract steam from it with different parameters. CHP turbines allow you to regulate the amount of extracted steam. The selected steam is condensed in network heaters and transfers its energy to network water, which is sent to peak water heating boilers and heating points. At thermal power plants it is possible to shut off thermal steam extraction. This makes it possible to operate the CHP plant according to two load schedules:

· electrical - the electrical load does not depend on the thermal load, or there is no thermal load at all (priority is the electrical load).

When constructing a thermal power plant, it is necessary to take into account the proximity of heat consumers in the form of hot water and steam, since heat transfer over long distances is not economically feasible.

CHP plants use solid, liquid or gaseous fuel. Due to the greater proximity of thermal power plants to populated areas, they use more valuable fuels that pollute the atmosphere less with solid emissions - fuel oil and gas. To protect the air basin from pollution by solid particles, ash collectors are used, and chimneys up to 200-250 m high are built to disperse solid particles, sulfur and nitrogen oxides in the atmosphere. Thermal power plants built near heat consumers are usually located at a considerable distance from water supply sources. Therefore, most thermal power plants use a circulating water supply system with artificial coolers - cooling towers. Direct-flow water supply at thermal power plants is rare.

At gas turbine thermal power plants, gas turbines are used to drive electric generators. Heat supply to consumers is carried out due to the heat taken from the cooling of air compressed by compressors gas turbine unit, and heat of gases exhausted in the turbine. Combined-cycle power plants (equipped with steam turbine and gas turbine units) and nuclear power plants can also operate as thermal power plants.

CHP is the main production link in the system district heating(Appendix D, E).