How it's made, how it works, how it works. How does a thermal power plant (CHP) work? What fuel does the CHP plant use?

Thermal power plant is a power plant that generates electrical energy as a result of the conversion of thermal energy released during the combustion of organic fuel (Fig. E.1).

There are thermal steam turbine power plants (TPES), gas turbine power plants (GTPP) and combined cycle power plants (CGPP). Let's take a closer look at TPES.

Fig.D.1 TPP diagram

At TPES, thermal energy is used in a steam generator to produce high-pressure water steam, which drives a steam turbine rotor connected to an electric generator rotor. The fuel used at such thermal power plants is coal, fuel oil, natural gas, lignite (brown coal), peat, and shale. Their efficiency reaches 40%, power – 3 GW. TPES that have condensing turbines as a drive for electric generators and do not use the heat of exhaust steam to supply thermal energy to external consumers are called condensing power plants (the official name in the Russian Federation is the State District Electric Station, or GRES). State district power plants generate about 2/3 of the electricity produced at thermal power plants.

TPES equipped with heating turbines and releasing the heat of exhaust steam to industrial or municipal consumers are called combined heat and power plants (CHP); they generate about 1/3 of the electricity produced at thermal power plants.

There are four known types of coal. In order of increasing carbon content, and thus calorific value, these types are arranged as follows: peat, brown coal, bituminous (fat) coal or hard coal and anthracite. In the operation of thermal power plants, mainly the first two types are used.

Coal is not chemically pure carbon; it also contains inorganic material (brown coal contains up to 40% carbon), which remains after the combustion of coal in the form of ash. Coal may contain sulfur, sometimes as iron sulfide and sometimes as part of the organic components of coal. Coal usually contains arsenic, selenium, and radioactive elements. In fact, coal turns out to be the dirtiest of all fossil fuels.

When coal is burned, carbon dioxide, carbon monoxide, as well as large quantities of sulfur oxides, suspended particles and nitrogen oxides are formed. Sulfur oxides damage trees, various materials and have a harmful effect on people.

The particles released into the atmosphere when coal is burned in power plants are called "fly ash." Ash emissions are strictly controlled. About 10% of suspended particles actually enter the atmosphere.

A 1000 MW coal-fired power plant burns 4-5 million tons of coal per year.

Since there is no coal mining in the Altai Territory, we will assume that it is brought from other regions, and roads are built for this purpose, thereby changing the natural landscape.

APPENDIX E

The energy hidden in fossil fuels - coal, oil or natural gas - cannot be immediately obtained in the form of electricity. The fuel is first burned. The released heat heats the water and turns it into steam. The steam rotates the turbine, and the turbine rotates the generator rotor, which generates, i.e. produces, electric current.

This entire complex, multi-stage process can be observed at a thermal power plant (TPP), equipped with energy machines that convert the energy hidden in organic fuel (oil shale, coal, oil and its derivatives, natural gas) into electrical energy. The main parts of a thermal power plant are a boiler plant, a steam turbine and an electric generator.

Boiler installation - a set of devices for producing water steam under pressure. It consists of a firebox in which organic fuel is burned, a combustion chamber through which combustion products pass into the chimney, and a steam boiler in which water boils. The part of the boiler that comes into contact with the flame during heating is called the heating surface.

There are 3 types of boilers: smoke-fired, water-tube and once-through. Inside combustion boilers there is a series of tubes through which combustion products pass into the chimney. Numerous smoke tubes have a huge heating surface, as a result of which they make good use of fuel energy. The water in these boilers is between the smoke tubes.

In water-tube boilers, the opposite is true: water is released through the tubes, and hot gases are passed between the tubes. The main parts of the boiler are the firebox, boiling tubes, steam boiler and superheater. The steam formation process takes place in the boiling tubes. The steam generated in them enters the steam boiler, where it is collected in its upper part, above boiling water. From the steam boiler, steam passes into the superheater and is further heated there. Fuel is poured into this boiler through the door, and the air necessary for combustion of the fuel is supplied through another door into the ash pit. Hot gases rise upward and, bending around the partitions, follow the path indicated in the diagram for this article (see figure).

In once-through boilers, water is heated in long coil pipes.

Water is supplied to these pipes by a pump. Passing through the coil, it completely evaporates, and the resulting steam is overheated to the required temperature and then leaves the coils.

Boiler plants operating with intermediate superheating of steam are an integral part of an installation called a “boiler-turbine” power unit.

In the future, for example, to use coal from the Kansk-Achinsk basin, large thermal power plants with a capacity of up to 6400 MW with power units of 800 MW each will be built, where boiler plants will produce 2650 tons of steam per hour with a temperature of up to 565 ° C and a pressure of 25 MPa.

The boiler plant produces high-pressure steam, which goes to the steam turbine - the main engine of the thermal power plant. In the turbine, the steam expands, its pressure drops, and the latent energy is converted into mechanical energy. The steam turbine drives the rotor of a generator, which produces electric current.

In large cities, combined heat and power plants (CHPs) are most often built, and in areas with cheap fuel, condensing power plants (CPPs) are built.

A thermal power plant is a thermal power plant that produces not only electrical energy, but also heat in the form of hot water and steam. The steam leaving the steam turbine still contains a lot of thermal energy. At a thermal power plant, this heat is used in two ways: either the steam after the turbine is sent to the consumer and is not returned to the station, or it transfers heat in the heat exchanger to water, which is sent to the consumer, and the steam is returned back to the system. Therefore, the thermal power plant has a high efficiency, reaching 50-60%.

There are thermal power plants of heating and industrial types. Heating CHP plants heat residential and public buildings and supply them with hot water, while industrial CHP plants supply heat to industrial enterprises. Steam is transmitted from thermal power plants over distances of up to several kilometers, and hot water is transmitted over distances of up to 30 kilometers or more. As a result, thermal power plants are being built near large cities.

A huge amount of thermal energy is used for district heating or centralized heating of our apartments, schools, and institutions. Before the October Revolution, there was no centralized heating supply to houses. Houses were heated by stoves, which burned a lot of wood and coal. District heating in our country began in the first years of Soviet power, when, according to the GOELRO plan (1920), the construction of large thermal power plants began.

In recent years, the development of district heating in the USSR has been particularly rapid. The total capacity of thermal power plants in the early 1980s. exceeded 50 million kW.

But the main share of electricity generated by thermal power plants comes from condensing power plants (CPS). In our country they are more often called state district electric power plants (SDPPs). Unlike thermal power plants, where the heat of steam exhausted in a turbine is used to heat residential and industrial buildings, at CPPs, steam exhausted in engines (steam engines, turbines) is converted by condensers into water (condensate), which is sent back to the boilers for reuse. CPPs are built directly near water supply sources: lakes, rivers, seas. The heat removed from the power plant with cooling water is irretrievably lost. The efficiency of IES does not exceed 35-42%.

Wagons with finely crushed coal are delivered to the high overpass day and night according to a strict schedule. A special unloader tips the wagons and the fuel is poured into the bunker. The mills carefully grind it into fuel powder, and it flies into the furnace of the steam boiler along with the air. The flames tightly cover the bundles of tubes, in which the water boils. Water vapor is formed. Through pipes - steam lines - steam is directed to the turbine and hits the turbine rotor blades through nozzles. Having given energy to the rotor, the exhaust steam goes to the condenser, cools and turns into water. Pumps supply it back to the boiler. And the energy continues its movement from the turbine rotor to the generator rotor. In the generator its final transformation occurs: it becomes electricity. This is where the IES energy chain ends.

Unlike hydroelectric power stations, thermal power plants can be built anywhere, and thereby bring the sources of electricity closer to the consumer and distribute thermal power plants evenly throughout the economic regions of the country. The advantage of thermal power plants is that they operate on almost all types of organic fuel - coal, shale, liquid fuel, natural gas.

The largest condensing thermal power plants in the USSR include Reftinsk (Sverdlovsk region), Zaporozhye, Kostroma, Uglegorsk (Donetsk region). The power of each of them exceeds 3000 MW.

Our country is a pioneer in the construction of thermal power plants, the energy of which is provided by a nuclear reactor (see Nuclear power plant, Nuclear energy).

For the full functioning of industrial enterprises, to meet household needs and other needs of modern man, we all need electrical energy. Thermal power plants have been and remain a powerful source of electricity.

Due to the negative environmental impact of thermal power plants on the environment, as well as the threat of depletion of minerals used as fuel during the operation of thermal power plants, humanity is trying to reorient the energy sector to other - renewable heat sources. However, this process is complex and not as fast as we would like. Therefore, thermal power plants still supply most of the electricity needed by humanity.

PRINCIPLE OF OPERATION

To generate electricity, thermal power plants require fossil fuels, examples of which are oil, natural gas, and coal. To extract the energy hidden in these natural resources, they are burned. This combustion process releases heat, which is used to heat the water into steam. This steam acts on the turbine, causing it to rotate, which in turn drives an electric generator, which produces electric current.

TYPES OF TPP

By purpose, thermal power plants can be those that are intended primarily for the production of electricity (they are usually called CES - condensing power stations), and those that can release heat in large quantities for industrial or heating purposes to objects located at a relatively short distance ( CHP – combined heat and power plants). The same thermal power plants where steam is produced from the energy of fission of nuclear fuel are called nuclear power plants (NPPs).

TPP and ECOLOGY

When thermal power plants first began to be created and built, few people were concerned about the harm they caused to the environment during their operation. However, over time, the environmental factor has become of utmost importance in the development of thermal power plants. After all, now world organizations that monitor the state of the environment are placing strict and reasonable requirements for the environmental safety of thermal power plants. And therefore, engineers and scientists involved in thermal power research have faced many challenges to improve thermal power equipment.

First of all, it is necessary to equip thermal power plants with special filters, since during the operation of thermal power plants a huge amount of pollutants are released.

This includes sulfur dioxide, which causes acid rain. And nitrogen oxides are the culprits of smog and “components” of acid rain, which in high doses can have a detrimental effect on human health.

Also, as a result of the operation of thermal power plants, benzopyrene, hydrogen sulfide and heavy metals enter the environment, which are extremely dangerous in doses exceeding the maximum permissible concentration for both humans and other living organisms.

In addition, the operation of these power plants is accompanied by the formation of large amounts of ash, which, when released into the atmosphere, can cause respiratory diseases in people.

Therefore, it is very important to install high-quality filters at thermal power plants in order to minimize emissions of harmful substances into the air, as well as to apply a number of other measures to ensure the environmental safety of these enterprises.

FUTURE OF TPP

In order for thermal power plants to have a future, they need a sufficient supply of fuel necessary for their operation. According to rough estimates by experts, organic fuel should last for 100-150 years, but extracting it will become increasingly difficult due to the fact that it will be necessary to reach deep deposits.

Limited fuel reserves are a driving factor for the use of energy-saving technologies in thermal energy that allow saving resources.

Also, thermal power plants of the future must be as environmentally safe as possible. For this purpose, thermal power engineers around the world are developing systems to minimize the harm of thermal power plants.

The role of thermal power plants in providing humanity with electricity is as significant as in previous decades. Despite the harm caused to the environment by emissions produced by thermal power plants during their operation, it is not possible to abandon their use at the current level of development of alternative energy sectors. But there is an opportunity to give a new breath to thermal power engineering by intensifying efforts to improve old thermal power plants and to build new ones, designed taking into account new high standards of environmental safety.

Scheme of operation of a condensing power plant.

Slavyanskaya TPP. Ukraine, Donetsk region.

Boiler plant- a set of devices for producing water vapor under pressure. It consists of a firebox in which organic fuel is burned, a combustion chamber through which combustion products pass into the chimney, and a steam boiler in which water boils. The part of the boiler that comes into contact with the flame during heating is called the heating surface.

In water-tube boilers, the opposite is true: water is released through the tubes, and hot gases are passed between the tubes. The main parts of the boiler are the firebox, boiling tubes, steam boiler and superheater. The steam formation process takes place in the boiling tubes. The steam generated in them enters the steam boiler, where it is collected in its upper part, above boiling water. From the steam boiler, steam passes into the superheater and is further heated there. Fuel is poured into this boiler through the door, and the air necessary for combustion of the fuel is supplied through another door into the ash pit. Hot gases rise upward and, bending around the partitions, travel the path indicated in the diagram (see figure).

In once-through boilers, water is heated in long coil pipes. Water is supplied to these pipes by a pump. Passing through the coil, it completely evaporates, and the resulting steam is superheated to the required temperature and then exits the coils.

Boiler installations operating with intermediate superheating of steam are an integral part of the installation called power unit"boiler - turbine".

In large cities they most often build combined heat and power plants(CHP), and in areas with cheap fuel - condensing power plants(IES).

There are thermal power plants of heating and industrial types. Heating thermal power plants heat residential and public buildings and supply them with hot water, industrial ones supply heat to industrial enterprises. Steam is transmitted from thermal power plants over distances of up to several kilometers, and hot water is transmitted over distances of up to 30 kilometers or more. As a result, thermal power plants are being built near large cities.

Wagons with finely crushed coal are delivered to the high overpass day and night according to a strict schedule. A special unloader tips the wagons and the fuel is poured into the bunker. The mills carefully grind it into fuel powder, and it flies into the furnace of the steam boiler along with the air. The flames tightly cover the bundles of tubes, in which the water boils. Water vapor is formed. Through pipes - steam lines - steam is directed to the turbine and hits the turbine rotor blades through nozzles. Having given energy to the rotor, the exhaust steam goes to the condenser, cools and turns into water. Pumps supply it back to the boiler. And the energy continues its movement from the turbine rotor to the generator rotor. In the generator its final transformation takes place: it becomes electricity. This is where the IES energy chain ends.

The largest condensing thermal power plants in Russia include Reftinskaya (Sverdlovsk region), Zaporozhye (Ukraine), Kostroma, Uglegorskaya (Donetsk region, Ukraine). The power of each of them exceeds 3000 MW.

Our country is a pioneer in the construction of thermal power plants, powered by a nuclear reactor (see.

The main type of power plants in Russia are thermal power plants (CHP). These installations generate approximately 67% of Russia's electricity. Their placement is influenced by fuel and consumer factors. The most powerful power plants are located in places where fuel is produced. Thermal power plants using high-calorie, transportable fuel are aimed at consumers.

Thermal power plants use widely available fuel resources, are relatively freely located and are able to generate electricity without seasonal fluctuations. Their construction is carried out quickly and involves less labor and material costs. But TPP has significant drawbacks. They use non-renewable resources, have low efficiency (30-35%), and have an extremely negative impact on the environment. Thermal power plants around the world annually emit 200-250 million tons of ash and about 60 million tons of sulfur dioxide 6 into the atmosphere, and also absorb huge amounts of oxygen. It has been established that coal in microdoses almost always contains U 238, Th 232 and a radioactive carbon isotope. Most thermal power plants in Russia are not equipped with effective systems for purifying flue gases from sulfur and nitrogen oxides. Although installations running on natural gas are much cleaner environmentally than coal, shale and fuel oil plants, the installation of gas pipelines (especially in the northern regions) harms the environment.

Thermal power station is a complex of equipment and devices that convert fuel energy into electrical and (in general) thermal energy.

Thermal power plants are characterized by great diversity and can be classified according to various criteria.

1. According to the purpose and type of energy supplied, power plants are divided into regional and industrial.

District power plants are independent public power plants that serve all types of consumers in the region (industrial enterprises, transport, population, etc.). District condensing power plants, which generate mainly electricity, often retain their historical name - GRES (state district power plants). District power plants that produce electrical and thermal energy (in the form of steam or hot water) are called combined heat and power plants (CHP). CHP plants are installations for the combined production of electricity and heat. Their efficiency reaches 70% versus 30-35% for IES. CHP plants are tied to consumers, because The radius of heat transfer (steam, hot water) is 15-20 km. The maximum power of a CHP plant is less than that of a CPP.

As a rule, state district power plants and district thermal power plants have a capacity of more than 1 million kW.

Industrial power plants are power plants that supply thermal and electrical energy to specific production enterprises or their complex, for example a chemical production plant. Industrial power plants are part of the industrial enterprises they serve. Their capacity is determined by the needs of industrial enterprises for thermal and electrical energy and, as a rule, it is significantly less than that of district thermal power plants. Often industrial power plants operate on the general electrical network, but are not subordinate to the power system dispatcher. Only district power plants are considered below.

2. Based on the type of fuel used, thermal power plants are divided into power plants operating on organic fuel and nuclear fuel.

Thermal power plants running on fossil fuels are called condensing power plants (CPS). Nuclear fuel is used in nuclear power plants (NPPs). It is in this sense that this term will be used below, although thermal power plants, nuclear power plants, gas turbine power plants (GTPP), and combined cycle power plants (CGPP) are also thermal power plants operating on the principle of converting thermal energy into electrical energy.

The primary role among thermal installations is played by condensing power plants (CPS). They gravitate towards both fuel sources and consumers, and are therefore very widespread. The larger the IES, the further it can transmit electricity, i.e. As power increases, the influence of the fuel and energy factor increases.

Gaseous, liquid and solid fuels are used as organic fuel for thermal power plants. Focus on fuel bases occurs in the presence of cheap and non-transportable fuel resources (brown coals of the Kansk-Achinsk basin) or in the case of power plants using peat, shale and fuel oil (such CPPs are usually associated with oil refining centers). Most thermal power plants in Russia, especially in the European part, consume natural gas as the main fuel, and fuel oil as a backup fuel, using the latter, due to its high cost, only in extreme cases; Such thermal power plants are called gas-oil power plants. In many regions, mainly in the Asian part of Russia, the main fuel is thermal coal - low-calorie coal or high-calorie coal waste (anthracite coal - AS). Since before combustion such coals are ground in special mills to a dusty state, such thermal power plants are called pulverized coal.

3. Based on the type of thermal power plants used at thermal power plants to convert thermal energy into mechanical energy of rotation of the rotors of turbine units, steam turbine, gas turbine and combined cycle power plants are distinguished.

The basis of steam turbine power plants are steam turbine units (STU), which use the most complex, most powerful and extremely advanced energy machine - a steam turbine - to convert thermal energy into mechanical energy. PTU is the main element of thermal power plants, combined heat and power plants and nuclear power plants.

Gas turbine thermal power plants (GTPP) are equipped with gas turbine units (GTUs) running on gaseous or, in extreme cases, liquid (diesel) fuel. Since the temperature of the gases behind the gas turbine plant is quite high, they can be used to supply thermal energy to external consumers. Such power plants are called GTU-CHP. Currently, in Russia there is one gas turbine power plant (GRES-3 named after Klasson, Elektrogorsk, Moscow region) with a capacity of 600 MW and one gas turbine cogeneration plant (in the city of Elektrostal, Moscow region).

Combined-cycle thermal power plants are equipped with combined cycle gas turbine units (CCGTs), which are a combination of gas turbine units and steam turbine units, which allows for high efficiency. CCGT-CHP plants can be designed as condensing plants (CCP-CHP) and with thermal energy supply (CCP-CHP). In Russia there is only one operating CCGT-CHP (PGU-450T) with a capacity of 450 MW. The Nevinnomyssk State District Power Plant operates a PGU-170 power unit with a capacity of 170 MW, and at the South Thermal Power Plant of St. Petersburg there is a PGU-300 power unit with a capacity of 300 MW.

4. According to the technological scheme of steam pipelines, thermal power plants are divided into block thermal power plants and thermal power plants with cross connections.

Modular thermal power plants consist of separate, usually of the same type, power plants - power units. In the power unit, each boiler supplies steam only to its turbine, from which it returns after condensation only to its boiler. All powerful state district power plants and thermal power plants, which have the so-called intermediate superheating of steam, are built according to the block scheme. The operation of boilers and turbines at thermal power plants with cross connections is ensured differently: all boilers of the thermal power plant supply steam to one common steam line (collector) and all steam turbines of the thermal power plant are powered from it. According to this scheme, CESs without intermediate overheating and almost all CHP plants with subcritical initial steam parameters are built.

5. Based on the level of initial pressure, thermal power plants of subcritical pressure and supercritical pressure (SCP) are distinguished.

The critical pressure is 22.1 MPa (225.6 at). In the Russian heat and power industry, the initial parameters are standardized: thermal power plants and combined heat and power plants are built for subcritical pressure of 8.8 and 12.8 MPa (90 and 130 atm), and for SKD - 23.5 MPa (240 atm). TPPs with supercritical parameters, for technical reasons, are performed with intermediate overheating and according to a block diagram. Often thermal power plants or combined heat and power plants are built in several stages - in queues, the parameters of which are improved with the commissioning of each new phase.

Let's consider a typical condensing thermal power plant running on organic fuel (Fig. 3.1).

Rice. 3.1. Thermal balance of gas-oil and

pulverized coal (numbers in brackets) thermal power plant

Fuel is supplied to the boiler and to burn it, an oxidizer is supplied here - air containing oxygen. Air is taken from the atmosphere. Depending on the composition and heat of combustion, complete combustion of 1 kg of fuel requires 10–15 kg of air and, thus, air is also a natural “raw material” for the production of electricity, for the delivery of which to the combustion zone it is necessary to have powerful high-performance superchargers. As a result of the chemical combustion reaction, in which carbon C of the fuel is converted into oxides CO 2 and CO, hydrogen H 2 into water vapor H 2 O, sulfur S into oxides SO 2 and SO 3, etc., fuel combustion products are formed – a mixture of various high-temperature gases. It is the thermal energy of fuel combustion products that is the source of electricity generated by thermal power plants.

Next, inside the boiler, heat is transferred from the flue gases to the water moving inside the pipes. Unfortunately, not all the thermal energy released as a result of fuel combustion can be transferred to water for technical and economic reasons. The fuel combustion products (flue gases), cooled to a temperature of 130–160 °C, leave the thermal power plant through the chimney. The part of the heat carried away by flue gases, depending on the type of fuel used, operating mode and quality of operation, is 5–15%.

Part of the thermal energy remaining inside the boiler and transferred to the water ensures the formation of steam with high initial parameters. This steam is sent to a steam turbine. At the outlet of the turbine, a deep vacuum is maintained using a device called a condenser: the pressure behind the steam turbine is 3–8 kPa (recall that atmospheric pressure is at the level of 100 kPa). Therefore, steam, entering the turbine with high pressure, moves to the condenser, where the pressure is low, and expands. It is the expansion of steam that ensures the conversion of its potential energy into mechanical work. A steam turbine is designed in such a way that the expansion energy of steam is converted into rotation of its rotor. The turbine rotor is connected to the rotor of an electric generator, in the stator windings of which electrical energy is generated, which is the final useful product (good) of the operation of the thermal power plant.

The condenser, which not only provides low pressure behind the turbine but also causes the steam to condense (turn into water), requires large amounts of cold water to operate. This is the third type of “raw material” supplied to thermal power plants, and for the operation of thermal power plants it is no less important than fuel. Therefore, thermal power plants are built either near existing natural water sources (river, sea), or artificial sources are built (cooling pond, air cooling towers, etc.).

The main heat loss in thermal power plants occurs due to the transfer of condensation heat to cooling water, which then releases it to the environment. More than 50% of the heat supplied to the thermal power plant with fuel is lost with the heat of the cooling water. In addition, the result is thermal pollution of the environment.

Part of the thermal energy of the fuel is consumed inside the thermal power plant either in the form of heat (for example, to heat fuel oil supplied to the thermal power plant in a thick form in railway tanks) or in the form of electricity (for example, to drive electric motors for pumps for various purposes). This part of the losses is called own needs.

For normal operation of thermal power plants, in addition to “raw materials” (fuel, cooling water, air), a lot of other materials are required: oil for the operation of lubrication systems, regulation and protection of turbines, reagents (resins) for cleaning the working fluid, numerous repair materials.

Finally, powerful thermal power plants are serviced by a large number of personnel who provide ongoing operation, equipment maintenance, analysis of technical and economic indicators, supply, management, etc. Approximately, we can assume that 1 MW of installed capacity requires 1 person and, therefore, the staff of a powerful thermal power plant is several thousand people. Any condensing steam turbine power plant includes four required elements:

· an energy boiler, or simply a boiler, into which feed water is supplied under high pressure, fuel and atmospheric air for combustion. The combustion process takes place in the boiler furnace - the chemical energy of the fuel is converted into thermal and radiant energy. Feed water flows through a pipe system located inside the boiler. The burning fuel is a powerful source of heat, which is transferred to the feed water. The latter is heated to boiling point and evaporates. The resulting steam in the same boiler is overheated above the boiling point. This steam, with a temperature of 540°C and a pressure of 13–24 MPa, is supplied to a steam turbine through one or more pipelines;

· a turbine unit consisting of a steam turbine, an electric generator and an exciter. A steam turbine, in which steam is expanded to a very low pressure (about 20 times less than atmospheric pressure), converts the potential energy of compressed and heated steam into kinetic energy of rotation of the turbine rotor. The turbine drives an electric generator, which converts the kinetic energy of rotation of the generator rotor into electric current. An electric generator consists of a stator, in whose electrical windings a current is generated, and a rotor, which is a rotating electromagnet powered by an exciter;

· The condenser serves to condense the steam coming from the turbine and create a deep vacuum. This makes it possible to very significantly reduce the energy consumption for the subsequent compression of the resulting water and at the same time increase the efficiency of steam, i.e. get more power from the steam generated by the boiler;

· feed pump to supply feed water to the boiler and create high pressure in front of the turbine.

Thus, in the PTU, a continuous cycle of converting the chemical energy of burned fuel into electrical energy takes place over the working fluid.

In addition to the listed elements, a real STP additionally contains a large number of pumps, heat exchangers and other devices necessary to increase its efficiency. The technological process for producing electricity at a gas-fired thermal power plant is shown in Fig. 3.2.

The main elements of the power plant under consideration (Fig. 3.2) are a boiler plant that produces steam of high parameters; a turbine or steam turbine unit that converts the heat of steam into mechanical energy of rotation of the turbine rotor, and electrical devices (electric generator, transformer, etc.) that provide electricity generation.

The main element of a boiler installation is the boiler. Gas for boiler operation is supplied from a gas distribution station connected to the main gas pipeline (not shown in the figure) to gas distribution point (GDP) 1. Here its pressure is reduced to several atmospheres and it is supplied to the burners 2 located in the bottom of the boiler (such burners are called hearth burners).

Rice. 3.2. Technological process of electricity production at gas-fired thermal power plants

The boiler itself is a U-shaped structure with gas ducts of rectangular cross-section. Its left part is called the firebox. The inside of the firebox is free, and fuel, in this case gas, burns in it. To do this, a special blower 28 continuously supplies hot air to the burners, heated in the air heater 25. In Fig. Figure 3.2 shows a so-called rotating air heater, the heat-storing packing of which is heated by the exhaust flue gases in the first half of the revolution, and in the second half of the revolution it heats the air coming from the atmosphere. To increase the air temperature, recirculation is used: part of the flue gases leaving the boiler is used by a special recirculation fan 29 supplied to the main air and mixed with it. Hot air is mixed with gas and fed through the boiler burners into its firebox - the chamber in which the fuel burns. When burned, a torch is formed, which is a powerful source of radiant energy. Thus, when fuel burns, its chemical energy is converted into thermal and radiant energy of the torch.

The walls of the furnace are lined with screens 19 - pipes to which feed water is supplied from economizer 24. The diagram shows a so-called direct-flow boiler, in the screens of which feed water, passing through the boiler pipe system only once, is heated and evaporated, turning into dry saturated steam. Drum boilers are widely used, in the screens of which feed water is repeatedly circulated, and steam is separated from the boiler water in the drum.

The space behind the boiler firebox is quite densely filled with pipes, inside of which steam or water moves. From the outside, these pipes are washed by hot flue gases, which gradually cool down as they move towards chimney 26.

Dry saturated steam enters the main superheater, consisting of ceiling 20, screen 21 and convective 22 elements. In the main superheater, its temperature and therefore potential energy increases. The high-parameter steam obtained at the outlet of the convective superheater leaves the boiler and enters the steam turbine through a steam line.

A powerful steam turbine usually consists of several separate turbines - cylinders.

17 steam is supplied to the first cylinder - the high pressure cylinder (HPC) directly from the boiler, and therefore it has high parameters (for SKD turbines - 23.5 MPa, 540 °C, i.e. 240 at/540 °C). At the exit from the HPC, the steam pressure is 3–3.5 MPa (30–35 at), and the temperature is 300–340 °C. If the steam continued to expand in the turbine beyond these parameters to the pressure in the condenser, it would become so wet that long-term operation of the turbine would be impossible due to erosive wear of its parts in the last cylinder. Therefore, from the HPC, relatively cold steam returns back to the boiler into the so-called intermediate superheater 23. In it, the steam again comes under the influence of the hot gases of the boiler, its temperature rises to the initial one (540 ° C). The resulting steam is sent to the medium pressure cylinder (MPC) 16. After expansion in the MPC to a pressure of 0.2–0.3 MPa (2–3 at) the steam enters one or more identical low pressure cylinders (LPC) 15.

Thus, expanding in the turbine, the steam rotates its rotor, connected to the rotor of the electric generator 14, in the stator windings of which an electric current is generated. The transformer increases its voltage to reduce losses in power lines, transfers part of the generated energy to power the thermal power plant’s own needs, and releases the rest of the electricity into the power system.

Both the boiler and the turbine can only operate with very high quality feed water and steam, allowing only negligible impurities of other substances. In addition, the consumption of steam is enormous (for example, in a power unit of 1200 MW, more than 1 ton of water evaporates, passes through the turbine and condenses in 1 second). Therefore, normal operation of the power unit is possible only by creating a closed circulation cycle of the working fluid of high purity.

The steam leaving the turbine LPC enters condenser 12 - a heat exchanger, through the tubes of which cooling water continuously flows, supplied by circulation pump 9 from a river, reservoir or special cooling device (cooling tower).

A cooling tower is a reinforced concrete hollow exhaust tower (Fig. 3.3) up to 150 m high and an outlet diameter of 40–70 m, which creates gravity for air entering from below through air guide panels.

An irrigation (sprinkler) device is installed inside the cooling tower at a height of 10–20 m. The air moving upward causes some of the droplets (approximately 1.5–2%) to evaporate, thereby cooling the water coming from the condenser and heated in it. The cooled water is collected below in the pool, flows into the front chamber 10, and from there it is supplied to the condenser 12 by the circulation pump 9 (Fig. 3.2).

Rice. 3.3. Design of a cooling tower with natural draft

Rice. 3.4. Exterior view of the cooling tower

Along with circulating water, direct-flow water supply is used, in which cooling water enters the condenser from the river and is discharged into it downstream. The steam coming from the turbine into the annulus of the condenser condenses and flows down; The resulting condensate is supplied by a condensate pump 6 through a group of low-pressure regenerative heaters (LPH) 3 to the deaerator 8. In the LPH, the temperature of the condensate increases due to the heat of condensation of the steam taken from the turbine. This makes it possible to reduce fuel consumption in the boiler and increase the efficiency of the power plant. In deaerator 8, deaeration occurs—removal from the condensate of gases dissolved in it that disrupt the operation of the boiler. At the same time, the deaerator tank is a container for boiler feed water.

From the deaerator, feed water is supplied to a group of high-pressure heaters (HPH) by a feed pump 7 driven by an electric motor or a special steam turbine.

Regenerative heating of condensate in HDPE and HDPE is the main and very profitable way to increase the efficiency of thermal power plants. The steam, which expanded in the turbine from the inlet to the extraction pipeline, generated a certain power, and when it entered the regenerative heater, it transferred its condensation heat to the feed water (and not the cooling water!), increasing its temperature and thereby saving fuel consumption in the boiler. The temperature of the boiler feed water behind the HPH, i.e. before entering the boiler, is 240–280°C, depending on the initial parameters. This closes the technological steam-water cycle of converting the chemical energy of the fuel into the mechanical energy of rotation of the turbine rotor.