Once, when we were driving into the glorious city of Cheboksary, from the east, my wife noticed two huge towers standing along the highway. "What is this?" she asked. Since I absolutely did not want to show my ignorance to my wife, I dug a little into my memory and came out victorious: “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.” "Why?" Then I became 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 was lucky to get here on an excursion.
So what is CHP?
According to Wikipedia, CHP - short for combined heat and power plant - is a type of thermal station that produces not only electricity, but also a source of heat, in the form of steam or hot water.
I’ll tell you how everything works below, but here you can see a couple of simplified diagrams of the station’s operation.
So it all starts with water. Since water (and steam, as its derivative) at a thermal power plant is the main coolant, before it enters the boiler, it must first be prepared. In order to prevent scale from forming in boilers, at the first stage, the water must be softened, and at the second, it must be cleaned of all kinds of impurities and inclusions.
All this happens on the territory of the chemical workshop, in which all these containers and vessels are located.
Water is pumped by huge pumps.
The work of the workshop is controlled from here.
There are a lot of buttons around...
Sensors...
And also completely incomprehensible elements...
The quality of the water is checked in the laboratory. Everything is serious here...
The water obtained here will be called “Clean Water” in the future.
So, we've sorted out the water, now we need fuel. Usually it is gas, fuel oil or coal. At the Cheboksary CHPP-2, the main type of fuel is gas supplied through main gas pipeline Urengoy - Pomary - Uzhgorod. Many stations have a fuel preparation point. Here, natural gas, like water, is purified from mechanical impurities, hydrogen sulfide and carbon dioxide.
The thermal power plant is a strategic facility, operating 24 hours a day and 365 days a year. Therefore, here everywhere, and for everything, there is a reserve. Fuel is no exception. In case of absence natural gas, our station can run on fuel oil, which is stored in huge tanks located across the road.
Now we have Clean water and prepared fuel. The next point of our journey is the boiler-turbine shop.
It consists of two sections. The first contains boilers. No, not like that. The first contains BOILERS. To write differently, a hand doesn’t rise, each one is the size of a twelve-story building. There are five of them at CHPP-2 in total.
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 it “Clean 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.
In the second section of the boiler-turbine shop there are 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 purpose, 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 it looks like workplace duty officer
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 “Clean 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. She doesn't require any special training 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 pumping station 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 guide is the director of the branch in Mari El and Chuvashia of OJSC TGK-5, IES holding - Dobrov S.V.”
Together with the station director S.D. Stolyarov.
Without exaggeration, they are true professionals in their field.
CHP is a thermal power plant that not only produces electricity, but also provides heat to our homes in winter. Using the example of the Krasnoyarsk Thermal Power Plant, let’s see how almost any thermal power plant works.
There are 3 thermal power plants in Krasnoyarsk, the total electrical power of which is only 1146 MW (for comparison, our Novosibirsk CHPP 5 alone has a capacity of 1200 MW), but what was remarkable for me was Krasnoyarsk CHPP-3 because the station is new - not even a year has passed , as the first and so far only power unit was certified by the System Operator and put into commercial operation. Therefore, I was able to photograph the still dusty, beautiful station and learn a lot about the thermal power plant.
In this post, in addition to technical information about KrasTPP-3, I want to reveal the very principle of operation of almost any combined heat and power plant.
1.
Three chimneys, the height of the highest one is 275 m, the second highest is 180 m
The abbreviation CHP itself implies that the station generates not only electricity, but also heat (hot water, heating), and heat generation may even be a higher priority in our country, known for its harsh winters.
2.
The installed electrical capacity of Krasnoyarsk CHPP-3 is 208 MW, and the installed thermal capacity is 631.5 Gcal/h
In a simplified way, the operating principle of a thermal power plant can be described as follows:
It all starts with fuel. Coal, gas, peat, and oil shale can be used as fuel at different power plants. In our case it is brown coal grade B2 from the Borodino open-pit mine, located 162 km from the station. Coal is delivered by railway. Part of it is stored, the other part goes along conveyors to the power unit, where the coal itself is first crushed to dust and then fed into the combustion chamber - the steam boiler.
A steam boiler is a unit for producing steam at a pressure above atmospheric pressure from feed water continuously supplied to it. This happens due to the heat released during fuel combustion. The boiler itself looks quite impressive. At KrasCHETS-3, the height of the boiler is 78 meters (26-story building), and it weighs more than 7,000 tons.
6.
Steam boiler brand Ep-670, manufactured in Taganrog. Boiler capacity 670 tons of steam per hour
I borrowed a simplified diagram of a power plant steam boiler from the website energoworld.ru so that you can understand its structure 
1 - combustion chamber (furnace); 2 - horizontal gas duct; 3 - convective shaft; 4 - combustion screens; 5 - ceiling screens; 6 — drain pipes; 7 - drum; 8 – radiation-convective superheater; 9 — convective superheater; 10 - water economizer; 11 — air heater; 12 — blower fan; 13 — lower screen collectors; 14 - slag chest of drawers; 15 — cold crown; 16 - burners. The diagram does not show the ash collector and smoke exhauster.
7.
Top view
10.
The boiler drum is clearly visible. The drum is a cylindrical horizontal vessel having water and steam volumes, which are separated by a surface called the evaporation mirror.
Due to its high steam output, the boiler has developed heating surfaces, both evaporative and superheating. Its firebox is prismatic, quadrangular with natural circulation.
A few words about the principle of operation of the boiler:
Feed water enters the drum, passing through the economizer, and goes down through the drain pipes into the lower collectors of the pipe screens. Through these pipes, the water rises and, accordingly, heats up, since a torch burns inside the firebox. The water turns into a steam-water mixture, part of it goes into the remote cyclones and the other part back into the drum. In both cases, this mixture is divided into water and steam. The steam goes into the superheaters, and the water repeats its path.
11.
Cooled flue gases (approximately 130 degrees) exit the furnace into electric precipitators. In electric precipitators, gases are purified from ash, the ash is removed to an ash dump, and the purified flue gases escape into the atmosphere. The effective degree of flue gas purification is 99.7%.
The photo shows the same electrostatic precipitators.
Passing through superheaters, the steam is heated to a temperature of 545 degrees and enters the turbine, where under its pressure the turbine generator rotor rotates and, accordingly, electricity is generated. It should be noted that in condensing power plants (GRES) the water circulation system is completely closed. All steam passing through the turbine is cooled and condensed. Having turned into a liquid state again, the water is reused. But in the turbines of a thermal power plant, not all the steam enters the condenser. Steam extraction is carried out - production (use of hot steam in any production) and heating (hot water supply network). This makes CHP more economically profitable, but it has its drawbacks. The disadvantage of combined heat and power plants is that they must be built close to the end consumer. Laying heating mains costs a lot of money.
12.
Krasnoyarsk CHPP-3 uses a direct-flow technical water supply system, which makes it possible to abandon the use of cooling towers. That is, water for cooling the condenser and used in the boiler is taken directly from the Yenisei, but before that it undergoes purification and desalting. After use, the water is returned through the canal back to the Yenisei, passing through a dissipative release system (mixing heated water with cold water in order to reduce thermal pollution of the river)
14.
Turbogenerator
I hope I was able to clearly describe the operating principle of a thermal power plant. Now a little about KrasTPP-3 itself.
Construction of the station began back in 1981, but, as happens in Russia, due to the collapse of the USSR and crises, it was not possible to build a thermal power plant on time. From 1992 to 2012, the station worked as a boiler house - it heated water, but it learned to generate electricity only on March 1 of last year.
Krasnoyarsk CHPP-3 belongs to Yenisei TGC-13. The thermal power plant employs about 560 people. Currently, Krasnoyarsk CHPP-3 provides heat supply industrial enterprises and the housing and communal sector of the Sovetsky district of Krasnoyarsk - in particular, the Severny, Vzlyotka, Pokrovsky and Innokentyevsky microdistricts.
17.
19.
CPU
20.
There are also 4 hot water boilers at KrasTPP-3
21.
Peephole in the firebox
23.
And this photo was taken from the roof of the power unit. The large pipe has a height of 180m, the smaller one is the pipe of the starting boiler room.
24.
Transformers
25.
A 220 kV closed gas-insulated switchgear (GRUE) is used as a switchgear at KrasTPP-3.
26.
Inside the building
28.
General view of the switchgear
29.
That's all. Thank you for your attention
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 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 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 “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.
Interactive application “How CHP works”
The picture on the left is the Mosenergo power plant, where electricity and heat are generated for Moscow and the region. The most environmentally friendly fuel used is natural gas. At a thermal power plant, gas is supplied through a gas pipeline to a steam boiler. The gas burns in the boiler and heats the water.
To make the gas burn better, the boilers are equipped with draft mechanisms. Air is supplied to the boiler, which serves as an oxidizer during gas combustion. To reduce noise levels, the mechanisms are equipped with noise suppressors. The flue gases generated during fuel combustion are discharged into the chimney and dispersed into the atmosphere.
The hot gas rushes through the flue and heats the water passing through special boiler tubes. When heated, water turns into superheated steam, which enters the steam turbine. The steam enters the turbine and begins to rotate the turbine blades, which are connected to the generator rotor. Steam energy is converted into mechanical energy. In the generator, mechanical energy is converted into electrical energy, the rotor continues to rotate, creating an alternating electric current in the stator windings.
Through a step-up transformer and a step-down transformer substation, electricity is supplied to consumers via power lines. The steam exhausted in the turbine is sent to the condenser, where it turns into water and returns to the boiler. At a thermal power plant, water moves in a circle. Cooling towers are designed to cool water. CHP plants use fan and tower cooling towers. The water in cooling towers is cooled by atmospheric air. As a result, steam is released, which we see above the cooling tower in the form of clouds. The water in the cooling towers rises under pressure and falls like a waterfall into the front chamber, from where it flows back to the thermal power plant. To reduce droplet entrainment, cooling towers are equipped with water traps.
Water supply is provided from the Moscow River. In the chemical water treatment building, water is purified from mechanical impurities and supplied to groups of filters. In some, it is prepared to the level of purified water to feed the heating network, in others - to the level of demineralized water and is used to feed power units.
The cycle used for hot water supply and district heating is also closed. Part of the steam from steam turbine sent to water heaters. Next, the hot water is directed to heating points, where heat exchange occurs with water coming from houses.
Highly qualified Mosenergo specialists support the production process around the clock, providing the huge metropolis with electricity and heat.
How does a combined cycle power unit work?
The thermal part of power plants is discussed in sufficient detail in the course “General Energy”. However, here, in this course, it is advisable to return to the consideration of some issues of the thermal part. But this consideration must be made from the point of view of its influence on the electrical part of power plants.
2.1. Schemes of condensing power plants (CPS)
Feed water is also supplied to the boiler by the feed pump (PN). high temperature turns into steam. Thus, at the boiler output, live steam is obtained with the following parameters: p=3...30 MPa, t=400...650°C. Live steam is supplied to the steam turbine (T). Here, the steam energy is converted into mechanical energy of rotation of the turbine rotor. This energy is transferred to an electrical synchronous generator (G), where it is converted into electrical energy.
The exhaust steam from the turbine enters the condenser (K) (this is why these stations are called condensing stations), is cooled with cold water and condenses. The condensate is supplied by a condensate pump (CP) to the water treatment system (WTP), and then, after replenishing with chemically purified water (now called feed water), it is supplied to the boiler by the feed pump.
Sources of cold water, which is supplied to the condenser by a circulation pump (CP), can be a river, lake, artificial reservoir, as well as cooling towers and spray ponds. Passing the main part of the steam through the condenser leads to the fact that 60...70% of the thermal energy generated by the boiler is carried away by the circulating water.
Gaseous products of fuel combustion from the boiler are removed by smoke exhausters (DS) and released into the atmosphere through a chimney 100...250 m high (the tallest chimney with a height of 420 m is listed in the Guinness Book of Records), and solid particles are sent to the ash dump by the hydraulic ash removal system (GZU). .
All these devices and units (dust feeders, blower fans, smoke exhausters, feed pumps, etc.) designed to ensure the technological process and normal operation of the main equipment (boilers, turbines, generators) are called auxiliary mechanisms (S.N.). At block stations the mechanisms of S.N. They are divided into block ones, designed to ensure the operation of only one unit, and general station ones - for the operation of the station as a whole.
The main mechanisms of S.N. are:
– blower fan (DV) for supplying air to the boiler;
– a smoke exhauster (Ds) for the emission of gaseous (and largely solid suspended particles) fuel combustion products from the boiler into a chimney 100...250 m high (420 m in the Guinness Book);
– circulation pump (CP) for supplying cold circulating water to the condenser;
– condensate pump (KN) for pumping condensate from the condenser;
– feed pump (PN) to supply feed water to the boiler and to create the required pressure in the process circuit.
The power plant also uses other auxiliary mechanisms for fuel supply and fuel preparation, in the chemical water treatment and slag and ash removal systems, in control systems for various gate valves, taps and valves, etc. etc. All of them within this course It is not advisable to list them, but nevertheless we will consider most of them in the process of studying the material.
Mechanisms S.N. divided into responsible and irresponsible.
Responsible are those mechanisms whose short-term stop leads to an emergency shutdown or unloading of the main units of the station. A short-term interruption in the operation of non-critical auxiliary mechanisms does not lead to an immediate emergency stop of the main equipment. However, in order not to disrupt the technological cycle of electricity production, after a short period of time they must be put into operation again.
In the boiler room, the responsible mechanisms are smoke exhausters, blower fans, and dust feeders. Stopping the operation of smoke exhausters, blower fans and dust feeders leads to the extinguishing of the torch and stopping the steam boiler. The non-responsible ones include flushing and trap pumps of the hydraulic ash removal system (GZU), as well as electric precipitators.
Critical engine room machinery includes feed, circulation and condensate pumps, turbine and generator oil pumps, generator gas cooler lift pumps and generator shaft seal oil pumps. Irrelevant mechanisms include drain pumps of regenerative heaters, drainage pumps, and ejectors.
An important place in the station's technological cycle is occupied by feed pumps that supply feed water to steam boilers. The power of electric drives of high-pressure feed pumps reaches 40% (for gas-oil CPPs) of the total power of consumers of their own needs, i.e. several megawatts. Stopping feed pumps leads to emergency shutdown of steam boilers by technological protections. It is especially difficult for once-through boilers at block power plants to endure such a shutdown.
Disabling condensate and circulation pumps leads to disruption of the turbine vacuum and to their emergency shutdown.
Particularly critical auxiliary mechanisms, the shutdown of which can lead to damage to the main units, include oil pumps of the turbogenerator lubrication system and generator shaft seals. Failure to turn on the backup oil pumps during an emergency shutdown of the station with loss of auxiliary power can lead to disruption of the oil supply to the turbine and generator bearings and melting of their bearings. Therefore, the power supply for turbine oil pumps and generator shaft seals is backed up by batteries.
A special place at thermal power plants is occupied by fuel preparation and fuel supply mechanisms: crushers, coal grinding mills, mill fans, conveyors and conveyors for fuel supply and dust plant bunkers, loader cranes in a coal warehouse, car dumpers. A short-term stop of these mechanisms usually does not lead to disruption of the technological cycle for the production of electrical and thermal energy, and therefore these mechanisms can be classified as irresponsible. Indeed, there is always a supply of raw coal in the bunkers, and therefore stopping conveyors or coal crushing devices does not lead to a cessation of fuel supply to the combustion chambers. It is also possible to stop drum ball mills, since when they are used at power plants there are usually intermediate bunkers with a supply of coal dust designed for approximately two hours of boiler operation at rated output. When hammer mills are used, intermediate bunkers are usually not provided, but at least three mills are installed on each boiler. When one of them stops, the remaining ones provide at least 90% of productivity.
General station mechanisms include pumps for chemical water treatment and domestic water supply. Most of them can be classified as irresponsible consumers, since a short-term stop of chemical water treatment pumps should not lead to an emergency in the water supply to boiler units. An exception is pumps for supplying chemically purified water to the turbine compartment, since if the balance between their performance and feedwater consumption is disturbed, it is possible emergency at the station.
Mechanisms for general station purposes also include backup exciters, acid washing pumps, fire-fighting pumps (these mechanisms do not operate under normal operating conditions of the units), ventilation devices, air main compressors, crane facilities, workshops, battery chargers, open switchgear and combined auxiliary building. Most of these mechanisms can be classified as non-responsible. Some of the auxiliary mechanisms of the electrical part of the station are responsible: motor-generators of dust feeders and cooling fans of powerful transformers, which blow through oil coolers and forcefully circulate oil. When the generator operates on a backup exciter, the latter also belongs to the responsible mechanisms for its own needs.
As a rule, electric motors are used as drives for auxiliary mechanisms, and only at stations with higher-power units can steam turbines be used to reduce short-circuit currents in the auxiliary power supply system (this will be discussed below). To power electrical consumers S.N. At the stations, a S.N. power supply system is provided. with a special power source, which is usually a TSN transformer connected to the generator voltage.
The features of IES are as follows:
1) are built as close as possible to fuel deposits or electrical energy consumption;
2) the overwhelming majority of the generated electrical energy is supplied to high-voltage electrical networks (110...750 kV);
The first two points determine the purpose of condensing-type stations - power supply to regional networks (if the station is built in an area where electrical energy is consumed) and supply of power to the system (when constructing a station in places where fuel is produced).
3) operate according to a free (independent of heat consumers) electricity generation schedule - power can vary from the calculated maximum to the technological minimum (determined mainly by the stability of the flame combustion in the boiler);
4) low maneuverability - turning the turbines and loading the load from a cold state requires approximately 3...10 hours;
Points 3 and 4 determine the operating mode of such stations - they operate mainly in the base part of the system load schedule.
5) require more cooling water for supplying it to turbine condensers;
This feature determines the construction site of the station - near a reservoir with a sufficient amount of water.
6) have a relatively low efficiency - 30...40%.
1.2. CHP schemes
Combined heat and power plants are intended for the centralized supply of heat and electricity to industrial enterprises and cities. Therefore, unlike CES, CHP plants, in addition to electrical energy, produce heat in the form of steam or hot water for the needs of production, heating, ventilation and hot water supply. For these purposes, the thermal power plant has significant extractions of steam, partially exhausted in the turbine. With such a combined generation of electrical and thermal energy, significant fuel savings are achieved compared to separate power supply, i.e. generating electricity at CPPs and receiving heat from local boiler houses.
Turbines with one and two controlled steam extractions and condensers are most widely used at thermal power plants. Adjustable extractions make it possible to independently regulate heat supply and electricity generation within certain limits.
At partial thermal load, they can, if necessary, develop rated power by passing steam to the condensers. With large and constant steam consumption in technological processes Turbines with back pressure without condensers are also used. The operating power of such units is completely determined by the thermal load. The most widespread are units with a capacity of 50 MW and higher (up to 250 MW).
The mechanisms for auxiliary needs at CHP plants are similar to those at CPPs, but are supplemented with mechanisms that ensure the delivery of thermal energy to the consumer. These include: network pumps (SN), boiler condensate pumps, heating network feed pumps, return condensate pumps (RCP), and other mechanisms.
Combined generation of thermal and electrical energy significantly complicates technological scheme CHP also determines the dependence of electrical energy production on the heat consumer. 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. During periods when heat consumption is relatively 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 turbine and into the condensers. In addition, in order to avoid overheating of the tail section of the turbine, a certain amount of steam must be passed through it in all modes. At the same time, the efficiency of the power plant decreases. When the electrical load at the thermal power plant is reduced below the power of thermal consumption, the thermal energy necessary for consumers can be obtained using a reduction-cooling unit ROU, powered by live steam from the boiler.
Radius of action of powerful thermal power plants - supply hot water for heating - does not exceed 10 km. Suburban CHP plants transmit hot water at a higher initial temperature over a distance of up to 45 km. Steam for production processes at a pressure of 0.8...1.6 MPa it can be transmitted no further 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 the most big cities(Moscow, St. Petersburg) with a high load density, thermal power plants with a capacity of up to 1000...1500 MW are appropriate.
The features of the thermal power plant are as follows:
1) are built near thermal energy consumers;
2) usually operate on imported fuel (most thermal power plants use gas transported through gas pipelines);
3) most of the generated electricity is distributed to consumers in the nearby area (at generator or increased voltage);
4) operate according to a partially forced electricity generation schedule (i.e. the schedule depends on the heat consumer);
5) low maneuverability (like IES);
6) have a relatively high total efficiency (60...75% with significant steam extraction for production and domestic needs).
1.3. NPP diagrams
Atomic power stations– these are thermal stations that use the energy of nuclear reactions. The thermal energy released in the reactor during the fission reaction of uranium nuclei is removed from the core using a coolant that is pumped under pressure through the core. The most common coolant is water, which is thoroughly purified in inorganic filters.
Nuclear power plants are designed and constructed with reactors of various types using thermal or fast neutrons using a single-circuit, double-circuit or triple-circuit design. The equipment of the last circuit, which includes a turbine and a condenser, is similar to the equipment of thermal power plants. The first, radioactive circuit contains a reactor, a steam generator and a feed pump.
On nuclear power plants CIS are used nuclear reactors the following main types:
RBMK (high power reactor, channel) - thermal neutron reactor, water-graphite;
VVER (water-cooled power reactor) – thermal neutron reactor, vessel type;
BN (fast neutrons) is a fast neutron reactor with liquid metal sodium coolant.
The unit capacity of nuclear power units reached 1,500 MW. Currently, it is believed that the unit power of a nuclear power plant is limited not so much by technical considerations as by safety conditions in case of reactor accidents.
Water-cooled reactors can operate in water or steam mode. In the second case, steam is produced directly in the reactor core.
 |
| Rice. 2.6. Single-circuit diagram of a nuclear power plant |
A single-circuit scheme with a boiling water reactor and a graphite moderator of the RBMK-1000 type was used at the Leningrad NPP. The reactor operates in a block with two condensing turbines of the K-500-65/3000 type and two generators with a capacity of 500 MW. The boiling reactor is a steam generator and thus predetermines the possibility of using a single-circuit circuit. Initial parameters of saturated steam in front of the turbine: temperature 284°C, steam pressure 7.0 MPa. The single-circuit circuit is relatively simple, but radioactivity spreads to all elements of the unit, which complicates biological protection.
The three-circuit scheme is used at nuclear power plants with fast neutron reactors with sodium coolant of the BN-600 type. To prevent contact of radioactive sodium with water, a second circuit with non-radioactive sodium is constructed. Thus, the circuit turns out to be three-circuit. The BN-600 reactor operates in a unit with three K-200-130 condensing turbines with an initial steam pressure of 13 MPa and a temperature of 500°C.
The world's first industrial Obninsk nuclear power plant with a capacity of 5 MW was put into operation in the USSR on June 27, 1954. In 1956...1957. Nuclear power plant units were launched in England (Calder Hall with a capacity of 92 MW) and in the USA (Shippingport Nuclear Power Plant with a capacity of 60 MW). Subsequently, nuclear power plant construction programs began to be accelerated in England, the USA, Japan, France, Canada, Germany, Sweden and a number of other countries. It was assumed that by 2000, electricity generation from nuclear power plants in the world could reach 50% of total electricity generation. However, currently the pace of development nuclear energy in the world, due to a number of reasons, have decreased significantly.
The features of the nuclear power plant are as follows:
1) can be built in any geographical location, including hard-to-reach places;
2) in their mode they are autonomous from the series external factors;
3) require a small amount of fuel;
4) can work according to a free workload schedule;
5) sensitive to alternating conditions, especially nuclear power plants with fast neutron reactors; for this reason, and also taking into account the requirements for economical operation, the basic part of the power system load schedule is allocated for nuclear power plants (duration of use of the installed capacity 6500...7000 h/year);
6) lightly pollute the atmosphere; emissions of radioactive gases and aerosols are insignificant and do not exceed the values permissible by sanitary standards. In this regard, nuclear power plants are cleaner than thermal power plants.
1.4. Hydroelectric power station schemes
When constructing a hydroelectric power station, the following goals are usually pursued:
Electricity generation;
Improving conditions for navigation on the river;
Improving irrigation conditions for adjacent lands.
The power of a hydroelectric power station depends on the water flow through the turbine and the pressure (the difference in the levels of the upper and lower pools).
Units for each hydroelectric power station, as a rule, are designed individually, in relation to the characteristics of this hydroelectric power station.
For low pressures, run-of-river (Uglich and Rybinsk hydroelectric power stations) or combined (Volzhsky hydroelectric power stations named after V.I. Lenin and named after the XXII Congress of the CPSU) hydroelectric power stations are built, and for significant pressures (more than 30...35 m) - dam hydroelectric power stations (DneproGES, Bratsk hydroelectric power station). In mountainous areas, diversion hydroelectric power stations (Gyumush HPP, Farhad HPP) with high pressures and low flow rates are being built.
 |
| Rice. 6 |
Hydroelectric power plants usually have reservoirs that allow them to accumulate water and regulate its flow and, consequently, the operating power of the station so as to provide the most favorable mode for the energy system as a whole.
The regulatory process is as follows. For some time, when the load on the power system is low (or the natural inflow of water in the river is large), the hydroelectric power station consumes water in an amount less than the natural inflow. In this case, water accumulates in the reservoir, and the operating capacity of the station is relatively small. At other times, when the system load is high (or the water inflow is small), the hydroelectric power station consumes water in an amount exceeding the natural inflow. In this case, the water accumulated in the reservoir is consumed, and the operating capacity of the station increases to maximum. Depending on the volume of the reservoir, the regulation period, or the time required to fill and operate the reservoir, can be a day, a week, several months or more. During this time, the hydroelectric power station can consume a strictly defined amount of water, determined by natural inflow.
When a hydroelectric power station operates together with thermal power plants and nuclear power plants, the load of the power system is distributed between them so that, at a given water consumption during the period under review, the demand for electricity is met with minimal fuel consumption (or minimal costs for fuel) in the system. Experience in operating energy systems shows that during most of the year it is advisable to use hydroelectric power plants in peak mode. This means that during the day the operating power of a hydroelectric power station must vary within wide limits - from minimum during hours when the load on the power system is low to maximum during hours of the highest load on the system. With this use of hydroelectric power stations, the load of thermal stations is leveled and their operation becomes more economical.
During periods of flood, it is advisable to use hydroelectric power stations around the clock with an operating capacity close to maximum, and thus reduce idle water discharge through the dam.
The operation of hydroelectric power plants is characterized by frequent starts and stops of units, a rapid change in operating power from zero to nominal. Hydraulic turbines by their nature are adapted to this regime. For hydrogenerators, this mode is also acceptable, since, unlike steam turbine generators, the axial length of the hydrogenerator is relatively small and temperature deformations of the winding rods are less pronounced. The process of starting the hydraulic unit and gaining power is fully automated and requires only a few minutes.
The duration of use of the installed capacity of hydroelectric power plants is usually less than that of thermal power plants. It is 1500...3000 hours for peak stations and up to 5000...6000 hours for base stations. It is advisable to build hydroelectric power stations on mountain and semi-mountain rivers.
3-4. Mechanisms for auxiliary needs of hydroelectric power plants
Mechanisms for the auxiliary needs of hydroelectric power stations are divided into aggregate and general station ones according to their purpose.
The auxiliary aggregate mechanisms ensure the start, stop and normal operation of hydraulic generators and step-up power transformers associated with them in block diagrams. These include:
Oil pumps of the hydraulic turbine control system;
Cooling pumps and fans for power transformers;
Oil or water pumps of the unit lubrication system;
Direct water cooling pumps for generators;
Unit braking compressors;
Pumps for pumping water from the turbine cover;
Auxiliary devices for the generator excitation system;
Pathogens in self-excitation systems. Public ones include:
Pumps for pumping water out of spiral chambers and suction pipes;
Domestic water supply pumps;
Drainage pumps;
Devices for charging, heating and ventilation of batteries;
Cranes, lifting mechanisms dam gates, shields, suction pipe stoppers, debris-holding grates;
Outdoor switchgear compressors;
Heating, lighting and ventilation of premises and structures;
Heating devices for shutters, grilles and grooves.
With a centralized system for supplying units with compressed air, the station-wide compressors also include compressors for oil pressure units and unit braking.
The composition and power of electrical receivers for the auxiliary needs of hydroelectric power plants are influenced by climatic conditions: in a harsh climate, a significant (several thousand kilowatts) heating load appears on switches, oil tanks, oil-filled cable terminations, grilles, gates, grooves; In hot climates, these loads are absent, but energy consumption for equipment cooling, ventilation, and air conditioning increases.
At hydroelectric power plants, a relatively small proportion of auxiliary mechanisms operate continuously in a long-term mode. These include: pumps and cooling fans for generators and transformers; auxiliary devices of excitation systems; pumps for water or oil lubrication of bearings. These mechanisms are among the most critical and allow a power interruption for the duration of the automatic transfer of reserve (ATS). Pumps for technical water supply and electric heating devices also operate in continuous mode. The rest of the electrical receivers operate repeatedly, briefly, for a short time, or even only occasionally. Responsible mechanisms for own needs also include fire pumps, pumps for oil pressure installations, some drainage pumps, outdoor switchgear compressors, and closing mechanisms for pressure pipeline valves. These mechanisms allow a power interruption of up to several minutes without disrupting normal and safe work units. The remaining consumers of their own needs can be classified as irresponsible.
The oil pressure units of hydraulic units have a sufficient energy reserve to close the guide vane and brake the unit even in the event of an emergency loss of voltage in the auxiliary system. Therefore, to ensure the safety of equipment in the event of a loss of voltage at hydroelectric power stations, autonomous sources in the form of batteries and diesel generators are not required.
The unit power of auxiliary mechanisms ranges from units to hundreds of kilowatts. The most powerful mechanisms for own needs are technical water supply pumps, pumps for pumping water out of suction pipes, and some lifting mechanisms. At most hydroelectric power stations, with the exception of diversion-type hydroelectric power stations, consumers of their own needs are concentrated in a limited area, within the station building and dam.
Unlike thermal power plants, the auxiliary mechanisms of hydroelectric power plants do not require continuous regulation of productivity; Intermittent and short-term operating mode (oil pumps, compressors) is sufficient.
The features of the hydroelectric power station are as follows:
1) are built where there are water resources and conditions for construction, which usually does not coincide with the location of the electrical load;
2) most of the electrical energy is supplied to high-voltage electrical networks;
3) work on a flexible schedule (if there is a reservoir);
4) highly maneuverable (turning and gaining load takes approximately 3...5 minutes);
5) have high efficiency (up to 85%).
In terms of operating parameters, hydroelectric power plants have a number of advantages over thermal power plants. However, at present, thermal and nuclear power plants. The determining factors here are the size of capital investments and the time of construction of power plants. (There are data on specific capital investments, cost of electricity and construction time various types email stations).
The specific cost of hydroelectric power plants (RUB/MW) is higher than the specific cost of thermal power plants of the same capacity due to the larger volume construction work. The construction time of a hydroelectric power station is also longer. However, the cost of electricity is lower, since operating costs do not include the cost of fuel.
Pumped storage power plants.
The purpose of pumped storage power plants is to level out the daily load schedule of the electrical system and increase the efficiency of thermal power plants and nuclear power plants. During the hours of minimum system load, pumped storage power plant units operate in pumping mode, pumping water from the lower reservoir to the upper one and thereby increasing the load of thermal power plants and nuclear power plants. During the hours maximum load systems they operate in turbine mode, drawing water from the upper reservoir and thereby unloading thermal power plants and nuclear power plants from short-term peak loads. PSPP units are also used as rotating backup units and as synchronous compensators.
Peak pumped storage power plants are designed, as a rule, to operate in turbine mode for 4...6 hours per day. The duration of operation of a pumped storage power plant in pumping mode is 7...8 hours with a ratio of pumping to turbine power of 1.05...1.10. The annual use of pumped storage power plant capacity is 1000...1500 hours.
PSPPs are built in systems where there are no hydroelectric power stations or their capacity is insufficient to cover the load during peak hours. They are made from a number of blocks that produce energy in a high-voltage network and receive it from the network when operating in pump mode. The units are highly maneuverable and can be quickly transferred from pump mode to generator mode or to synchronous compensator mode. The efficiency of pumped storage power plants is 70...75%. They require a small number of maintenance personnel. Pumped storage power plants can be built where there are sources of water supply and local geological conditions allow the creation of a pressure reservoir.
1.4. Gas turbine units
1.7. Solar power plants.
Among solar power plants (solar power plants), two types of power plants can be distinguished - with a steam boiler and with silicon photocells. Such power plants have found application in a number of countries with a significant number of sunny days a year. According to published data, their efficiency can be increased to 20%.
1.8. Geothermal power plants use cheap energy from underground thermal springs.
Geothermal power plants operate in Iceland, New Zealand, Papua, New Guinea, the USA, and in Italy they provide about 6% of all electricity generated. In Russia (on Komchatka), the Pauzhetskaya geothermal power plant was built.
1.9. Tidal power plants with so-called capsule hydroelectric units are built where there is a significant difference in water levels during high and low tides. The most powerful TPP Rance was built in 1966 in France: its capacity is 240 MW. PPPs are being designed in the USA with a capacity of 1000 MW, in the UK with a capacity of 7260 MW, etc. In Russia, on the Kola Peninsula, where tides reach 10...13 m, in 1968 the first stage of the experimental Kislogubskaya TPP (2·0.4 MW) came into operation.
1.10. Magnetohydrodynamic power plants use the principle of current generation when a moving conductor passes through a magnetic field. Low-temperature plasma (about 2700 C) is used as a working fluid, which is formed during the combustion of organic fuel and the supply of special ionizing additives to the combustion chamber. The working fluid passing through the superconducting magnetic system creates a direct current, which is converted into alternating current with the help of inverter converters. The working fluid, after passing through the magnetic system, enters the steam turbine part of the power plant, consisting of a steam generator and a conventional condensing steam turbine. Currently, a 500 MW main MHD power unit has been built at the Ryazan State District Power Plant, which includes an MHD generator with a capacity of about 300 MW and a steam turbine unit with a capacity of 315 MW with a K-300-240 turbine. With an installed capacity of over 610 MW, the power output of the MHD power unit into the system is 500 MW due to significant energy consumption for its own needs in the MHD power unit. 
parts. The efficiency of MGD-500 exceeds 45%, specific fuel consumption is approximately 270 g/(kW*h). The main MHD power unit was designed to use natural gas; in the future it was planned to switch to solid fuel. However further development MHD installations were not developed due to the lack of materials capable of operating at such high temperatures.
Loading...
