CHP is a reliable source of energy production. TES - what is it? TPP and CHP: differences
The blades of the impellers are clearly visible in this steam turbine.
A thermal power plant (CHP) uses the energy released by burning fossil fuels - coal, oil and natural gas - to turn water into high-pressure steam. This steam, which has a pressure of about 240 kilograms per square centimeter and a temperature of 524°C (1000°F), drives a turbine. The turbine spins a giant magnet inside a generator that generates electricity.
Modern thermal power plants convert about 40 percent of the heat released during the combustion of fuel into electricity, the rest is discharged into the environment. In Europe, many thermal power plants use waste heat to heat nearby homes and businesses. The combined generation of heat and electricity increases the energy efficiency of the power plant by up to 80 percent.
Steam turbine plant with electric generator
A typical steam turbine contains two groups of blades. High-pressure steam coming directly from the boiler enters the flow path of the turbine and rotates the impellers with the first group of blades. Then the steam is heated in the superheater and again enters the turbine flow path to rotate the impellers with the second group of blades, which operate at a lower steam pressure.
Sectional view
A typical generator in a thermal power plant (CHP) is driven directly by a steam turbine that rotates at 3,000 revolutions per minute. In generators of this type, the magnet, which is also called the rotor, rotates, and the windings (stator) are stationary. The cooling system prevents the generator from overheating.
Steam power generation
In a thermal power plant, the fuel is burned in a boiler to form a high-temperature flame. Water passes through the tubes through the flame, heats up and turns into high pressure steam. The steam drives the turbine, producing mechanical energy, which the generator converts into electricity. After leaving the turbine, the steam enters the condenser, where it washes the tubes with cold running water, and as a result turns back into a liquid.
Oil, coal or gas boiler
Inside the boiler
The boiler is filled with intricately curved tubes through which heated water passes. The complex configuration of the tubes allows you to significantly increase the amount of heat transferred to the water and, due to this, produce much more steam.
The principle of operation of a combined heat and power plant (CHP) is based on the unique property of water vapor - to be a heat carrier. When heated, under pressure, it turns into a powerful source of energy that sets in motion the turbines of thermal power plants (TPPs) - a legacy of such a distant era of steam.
The first thermal power plant was built in New York on Pearl Street (Manhattan) in 1882. St. Petersburg became the birthplace of the first Russian thermal station, a year later. Strange as it may seem, but even in our age of high technologies, thermal power plants have not been found to be a full-fledged replacement: their share in the world energy sector is more than 60%.
And there is a simple explanation for this, which contains the advantages and disadvantages of thermal energy. Its "blood" - organic fuel - coal, fuel oil, oil shale, peat and natural gas are still relatively available, and their reserves are quite large.
The big disadvantage is that the products of fuel combustion cause serious harm to the environment. Yes, and the natural pantry one day will finally be depleted, and thousands of thermal power plants will turn into rusting "monuments" of our civilization.
Principle of operation
To begin with, it is worth deciding on the terms "CHP" and "TPP". To put it simply, they are sisters. A "clean" thermal power plant - TPP is designed exclusively for the production of electricity. Its other name is "condensing power plant" - IES.
Combined heat and power plant - CHP - a type of thermal power plant. It, in addition to generating electricity, supplies hot water to the central heating system and for domestic needs.
The scheme of operation of the CHP is quite simple. The furnace simultaneously receives fuel and heated air - an oxidizing agent. The most common fuel at Russian thermal power plants is pulverized coal. The heat from the combustion of coal dust turns the water entering the boiler into steam, which is then fed under pressure to the steam turbine. A powerful steam flow makes it rotate, setting in motion the generator rotor, which converts mechanical energy into electrical energy.
Further, the steam, which has already significantly lost its initial indicators - temperature and pressure - enters the condenser, where after a cold "water shower" it again becomes water. Then the condensate pump pumps it to the regenerative heaters and then to the deaerator. There, water is freed from gases - oxygen and CO 2, which can cause corrosion. After that, the water is again heated by steam and fed back into the boiler.
Heat supply
The second, no less important function of the CHPP is to provide hot water (steam) intended for central heating systems of nearby settlements and domestic use. In special heaters, cold water is heated to 70 degrees in summer and 120 degrees in winter, after which it is supplied to the common mixing chamber by network pumps and then goes to consumers through the heating main system. Water supplies at the thermal power plant are constantly replenished.
How gas-fired thermal power plants work
Compared to coal-fired CHPs, CHPs with gas turbines are much more compact and environmentally friendly. Suffice it to say that such a station does not need a steam boiler. A gas turbine plant is essentially the same turbojet aircraft engine, where, unlike it, the jet stream is not emitted into the atmosphere, but rotates the generator rotor. At the same time, emissions of combustion products are minimal.
New coal combustion technologies
The efficiency of modern CHPs is limited to 34%. The vast majority of thermal power plants still operate on coal, which can be explained quite simply - coal reserves on Earth are still huge, so the share of thermal power plants in the total amount of electricity generated is about 25%.
The process of burning coal for many decades remains virtually unchanged. However, new technologies have also come here.
The peculiarity of this method is that instead of air, pure oxygen released from the air is used as an oxidizing agent during the combustion of coal dust. As a result, a harmful impurity - NOx - is removed from the flue gases. The remaining harmful impurities are filtered out in the process of several stages of purification. The remaining CO 2 at the outlet is pumped into tanks under high pressure and is subject to burial at a depth of up to 1 km.
"oxyfuel capture" method
Here, too, when burning coal, pure oxygen is used as an oxidizing agent. Only in contrast to the previous method, at the moment of combustion, steam is formed, which drives the turbine into rotation. Ash and sulfur oxides are then removed from the flue gases, cooling and condensation are carried out. The remaining carbon dioxide under a pressure of 70 atmospheres is converted into a liquid state and placed underground.
"pre-combustion" method
Coal is burned in the "normal" mode - in a boiler mixed with air. After that, ash and SO 2 - sulfur oxide are removed. Next, CO 2 is removed using a special liquid absorbent, after which it is disposed of by landfill.
The five most powerful thermal power plants in the world
The championship belongs to the Chinese Tuoketuo thermal power plant with a capacity of 6600 MW (5 en / unit x 1200 MW), occupying an area of 2.5 square meters. km. She is followed by her "compatriot" - Taichung TPP with a capacity of 5824 MW. The top three is closed by Russia's largest Surgutskaya GRES-2 - 5597.1 MW. In fourth place is the Polish Belchatow TPP - 5354 MW, and the fifth - Futtsu CCGT Power Plant (Japan) - a gas-fired TPP with a capacity of 5040 MW.
A power station is a power plant that converts natural energy into electrical energy. The most common are thermal power plants (TPPs) that use thermal energy released during the combustion of fossil fuels (solid, liquid and gaseous).
Thermal power plants generate about 76% of the electricity produced on our planet. This is due to the presence of fossil fuels in almost all areas of our planet; the possibility of transporting organic fuel from the place of production to the power plant located near energy consumers; technical progress at thermal power plants, which ensures the construction of high-capacity thermal power plants; the possibility of using the waste heat of the working fluid and supplying consumers, in addition to electrical, also thermal energy (with steam or hot water), etc.
A high technical level of the energy sector can only be ensured with a harmonious structure of generating capacities: the energy system should include both nuclear power plants that produce cheap electricity, but with serious restrictions on the range and rate of load change, and thermal power plants that supply heat and electricity, the amount of which depends on the needs for heat, and powerful steam turbine power units operating on heavy fuels, and mobile autonomous gas turbines covering short-term load peaks.
1.1 Types of TES and their features.
On fig. 1 shows the classification of thermal power plants running on fossil fuels.
Fig.1. Types of thermal power plants on organic fuel.
Fig.2 Schematic diagram of thermal power plant
1 - steam boiler; 2 - turbine; 3 - electric generator; 4 - capacitor; 5 - condensate pump; 6 – low pressure heaters; 7 - deaerator; 8 - feed pump; 9 – high pressure heaters; 10 - drainage pump.
A thermal power plant is a complex of equipment and devices that convert fuel energy into electrical and (generally) thermal energy.
Thermal power plants are characterized by great diversity and can be classified according to various criteria.
According to the purpose and type of supplied energy, power plants are divided into regional and industrial.
District power plants are independent public power plants that serve all types of district consumers (industrial enterprises, transport, population, etc.). District condensing power plants, which produce mainly electricity, often retain their historical name - GRES (state district power plants). District power plants that produce electricity and heat (in the form of steam or hot water) are called combined heat and power plants (CHP). As a rule, state district power plants and regional thermal power plants have a capacity of more than 1 million kW.
Industrial power plants are power plants that supply heat and electricity to specific industrial enterprises or their complex, for example, a plant for the production of chemical products. Industrial power plants are part of the industrial enterprises they serve. Their capacity is determined by the needs of industrial enterprises for heat and electricity and, as a rule, it is significantly less than that of district thermal power plants. Often, industrial power plants operate on a common electrical network, but are not subordinate to the power system manager.
According to the type of fuel used, thermal power plants are divided into power plants operating on organic fuel and nuclear fuel.
For condensing power plants operating on fossil fuels, at a time when there were no nuclear power plants (NPPs), the name thermal (TPP - thermal power plant) has historically developed. It is in this sense that this term will be used below, although CHPPs, NPPs, gas turbine power plants (GTPPs), and combined-cycle power plants (CCPPs) are also thermal power plants operating on the principle of converting thermal energy into electrical energy.
Gaseous, liquid and solid fuels are used as fossil fuels for thermal power plants. Most TPPs in Russia, especially in the European part, consume natural gas as the main fuel, and fuel oil as a reserve fuel, using the latter only in extreme cases due to its high cost; such thermal power plants are called oil-fired. In many regions, mainly in the Asian part of Russia, the main fuel is thermal coal - low-calorie coal or waste from the extraction of high-calorie coal (anthracite sludge - ASh). Since such coals are ground in special mills to a pulverized state before burning, such thermal power plants are called pulverized coal.
According to 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 plants (STP), 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, thermal power plants and nuclear power plants.
PTU, which have condensing turbines as a drive for electric generators and do not use the heat of the exhaust steam to supply thermal energy to external consumers, are called condensing power plants. PTU equipped with heating turbines and giving off the heat of the exhaust steam to industrial or domestic consumers are called combined heat and power plants (CHP).
Gas turbine thermal power plants (GTPPs) are equipped with gas turbine units (GTUs) operating on gaseous or, in extreme cases, liquid (diesel) fuel. Since the temperature of the gases downstream of the gas turbine is quite high, they can be used to supply thermal energy to an external consumer. Such power plants are called GTU-CHP. Currently, there is one GTPP operating in Russia (GRES-3 named after Klasson, Elektrogorsk, Moscow Region) with a capacity of 600 MW and one GTU-CHPP (in Elektrostal, Moscow Region).
A traditional modern gas turbine plant (GTU) is a combination of an air compressor, a combustion chamber and a gas turbine, as well as auxiliary systems that ensure its operation. The combination of a gas turbine and an electric generator is called a gas turbine unit.
Combined-cycle thermal power plants are equipped with combined-cycle plants (CCGT), which are a combination of GTP and STP, which allows for high efficiency. CCGT-TPPs can be condensing (CCGT-CES) and with heat output (CCGT-CHP). At present, four new CCGT-CHPPs are operating in Russia (Severo-Zapadnaya CHPP of St. Petersburg, Kaliningradskaya, CHPP-27 of OAO Mosenergo and Sochinskaya), and a combined heat and power plant has also been built at the Tyumenskaya CHPP. In 2007 Ivanovskaya CCGT-IES was put into operation.
Block TPPs consist of separate, as a rule, the same type of power plants - power units. In the power unit, each boiler supplies steam only for its own turbine, from which it returns after condensation only to its own boiler. According to the block scheme, all powerful state district power plants and thermal power plants are built, which have the so-called intermediate superheating of steam. The operation of boilers and turbines at TPPs with cross-links is provided differently: all boilers of TPPs supply steam to one common steam pipeline (collector) and all steam turbines of TPPs are fed from it. According to this scheme, CPPs are built without intermediate overheating and almost all CHPPs are built for subcritical initial steam parameters.
According to the level of initial pressure, TPPs of subcritical pressure, supercritical pressure (SKP) and super-supercritical parameters (SSCP) are distinguished.
Critical pressure is 22.1 MPa (225.6 atm). In the Russian thermal power industry, the initial parameters are standardized: thermal power plants and thermal 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). Thermal power plants for supercritical parameters, for technical reasons, are installed with reheat and according to the block scheme. The super-supercritical parameters conditionally include pressure over 24 MPa (up to 35 MPa) and temperature over 5600C (up to 6200C), the use of which requires new materials and new equipment designs. Often, thermal power plants or CHPPs for different levels of parameters are built in several stages - in queues, the parameters of which increase with the introduction of each new queue.
combined heat and power plant
The simplest schemes of combined heat and power plants with various turbines and various steam release schemes
a - a turbine with back pressure and steam extraction, heat release - according to an open scheme;
b - condensing turbine with steam extraction, heat supply - according to open and closed schemes;
PC - steam boiler;
PP - superheater;
PT - steam turbine;
G - electric generator;
K - capacitor;
P - regulated production steam extraction for the technological needs of the industry;
T - adjustable heat extraction for heating;
TP - heat consumer;
FROM - heating load;
KN and PN - condensate and feed pumps;
LDPE and HDPE - high and low pressure heaters;
D - deaerator;
PB - feed water tank;
SP - network heater;
CH - network pump.
Thermal power plant (CHP)- a thermal power plant that produces not only electrical energy, but also heat supplied to consumers in the form of steam and hot water. The use for practical purposes of the waste heat of engines rotating electric generators is a distinctive feature of CHP and is called district heating. The combined production of two types of energy contributes to a more economical use of fuel compared to the separate generation of electricity at condensing power plants (GRES in the USSR) and thermal energy at local boiler plants. The replacement of local boiler houses, which use fuel irrationally and pollute the atmosphere of cities and towns, with a centralized heating system contributes not only to significant fuel savings, but also to an increase in the purity of the air basin, and an improvement in the sanitary condition of populated areas.
Description
The initial source of energy at CHPs is organic fuel (at steam turbine and gas turbine CHPs) or nuclear fuel (at nuclear CHPs). Fossil-fuelled steam turbine CHP plants are predominantly used, which, along with condensing power plants, are the main type of thermal steam turbine power plants (TPES). There are industrial type CHP plants - for supplying heat to industrial enterprises, and heating type - for heating residential and public buildings, as well as for supplying them with hot water. Heat from industrial thermal power plants is transferred over a distance of up to several kilometers (mainly in the form of steam heat), from heating plants - over a distance of up to 20-30 km (in the form of hot water heat).
- Coal fired power plant in England
Heating turbines
The main equipment of steam turbine CHP plants are turbine units that convert the energy of the working substance (steam) into electrical energy, and boiler units that produce steam for turbines. The turbine set includes a steam turbine and a synchronous generator. Steam turbines used in CHP plants are called combined heat and power turbines (CTs). Among them, TTs are distinguished: with a back pressure, usually equal to 0.7-1.5 MN / m 2 (installed at thermal power plants supplying industrial enterprises with steam); with condensation and steam extraction under pressure 0.7-1.5 MN/m 2 (for industrial consumers) and 0.05-0.25 MN/m 2 (for domestic consumers); with condensation and steam extraction (heating) under pressure 0.05-0.25 MN/m2.
Waste heat from backpressure CTs can be fully utilized. However, the electric power developed by such turbines depends directly on the magnitude of the heat load, and in the absence of the latter (as, for example, happens in the summer at heating CHP plants), they do not generate electric power. Therefore, CTs with backpressure are used only if there is a sufficiently uniform heat load provided for the entire duration of the operation of the CHP (that is, mainly at industrial CHPs).
For heat pumps with condensation and steam extraction, only extraction steam is used to supply heat to consumers, and the heat of the condensing steam flow is given off in the condenser to the cooling water and is lost. To reduce heat losses, such CTs should work most of the time according to the "thermal" schedule, that is, with a minimum "ventilation" passage of steam into the condenser. CTs with condensation and steam extraction are predominantly used at CHPPs as universal ones in terms of possible operating modes. Their use allows you to adjust the thermal and electrical loads almost independently; in a particular case, with reduced thermal loads or in their absence, the CHP plant can operate according to the "electric" schedule, with the necessary, full or almost full electrical power.
Power of cogeneration turbine units
The electric power of cogeneration turbine units (unlike condensing units) is preferably chosen not according to a given power scale, but according to the amount of fresh steam consumed by them. Thus, R-100 turbine units with backpressure, PT-135 with industrial and heating extractions, and T-175 with heating extraction have the same fresh steam consumption (about 750 t/h), but different electric power (respectively 100, 135 and 175 MW) . Boilers generating steam for such turbines have the same capacity (about 800 t/h). Such unification makes it possible to use turbine units of various types with the same thermal equipment of boilers and turbines at one CHPP. In the USSR, the boiler units used to work at TPPs for various purposes were also unified. Thus, boilers with a steam capacity of 1000 t/h are used to supply steam to both 300 MW condensing turbines and the largest 250 MW HPs in the world.
Fresh steam pressure at CHPPs is accepted in the USSR as ~ 13-14 MN/m 2 (mainly) and ~ 24-25 MN/m 2 (at the largest thermal power units - with a capacity of 250 MW). At CHPPs with a steam pressure of 13-14 MN/m 2 , in contrast to GRESs, there is no intermediate superheating of steam, since at such CHPPs it does not provide such significant technical and economic advantages as at GRESs. Power units with a capacity of 250 MW at CHPPs with a heating load are performed with intermediate steam superheating.
The heat load at heating CHP plants is uneven throughout the year. In order to reduce the cost of the main power equipment, part of the heat (40-50%) during periods of increased load is supplied to consumers from peak hot water boilers. The share of heat released by the main power equipment at the highest load determines the value of the CHP heat supply coefficient (usually equal to 0.5-0.6). In a similar way, it is possible to cover the peaks of the thermal (steam) industrial load (about 10-20% of the maximum) with peak steam
Once, when we were driving into the glorious city of Cheboksary, from the east, my wife noticed two huge towers standing along the highway. "And what is it?" she asked. Since I absolutely did not want to show my ignorance to my wife, I dug a little in my memory and gave out a victorious one: “These are cooling towers, don’t you know?”. She was a little embarrassed: “What are they for?” “Well, something to cool there, it seems.” "And what?". Then I was embarrassed, because I did not know at all how to get out further.
Maybe this question has remained forever in the memory without an answer, but miracles do happen. A few months after this incident, I see a post in my friend feed about the recruitment of bloggers who want to visit the Cheboksary CHPP-2, the same one that we saw from the road. Having to drastically change all your plans, it would be unforgivable to miss such a chance!
So what is CHP?
This is the heart of the CHP plant, and here the main action takes place. The gas entering the boiler burns out, releasing a crazy amount of energy. This is where Pure Water comes in. 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 "Pure steam" because it is formed from prepared water.
In addition to steam, we also have exhaust at the exit. At maximum power, all five boilers consume almost 60 cubic meters of natural gas per second! To remove the products of combustion, a non-childish "smoke" pipe is needed. And there is one 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 is a slightly smaller pipe. Reserve again.
If the CHP plant is coal-fired, additional exhaust treatment is required. But in our case, this is not required, since natural gas is used as fuel.
In the second section of the boiler and turbine shop there are installations that generate electricity.
Four of them are installed in the engine room of the Cheboksary CHPP-2, with a total capacity of 460 MW (megawatts). It is here that superheated steam from the boiler room is supplied. He, under huge pressure, is sent to the turbine blades, forcing 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 here is what the turbine rotor looks like.
Sensors and gauges are everywhere.
Both turbines and boilers can be stopped instantly in case of an emergency. For this, there are special valves that can shut off the supply of steam or fuel in a fraction of a second.
Interestingly, is there such a thing as an industrial landscape, or an industrial portrait? It has its own beauty.
There is a terrible noise in the room, and in order to hear a neighbor, you have to strain your hearing a lot. Besides, 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 CHP plant, there are too many hot pipes.
Most of the time, the workshop is empty, people appear here once every two hours, during a round. And the operation of the equipment is controlled from the Main Control Board (Group Control Panels for Boilers and Turbines).
This is what the duty station looks like.
There are hundreds of buttons around.
And dozens of sensors.
Some are mechanical and some are electronic.
This is our excursion, and people are working.
In total, after the boiler and turbine shop, at the output we have electricity and steam that has partially cooled down and lost part of its pressure. With electricity, it seems to be easier. At the output from different generators, the voltage can be from 10 to 18 kV (kilovolt). With the help of block transformers, it rises to 110 kV, and then electricity can be transmitted over long distances using power lines (power lines).
It is unprofitable to release the remaining “Clean Steam” to the side. Since it is formed from "Pure Water", the production of which is a rather complicated and costly process, it is more expedient to cool it and return it 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 can be easily sold to third-party consumers.
In general, it is in this way that we get heat and electricity into our homes, having the usual comfort and coziness.
Oh yes. Why are cooling towers needed anyway?
It turns out everything is very simple. In order to cool the remaining "Pure steam", before a new supply to the boiler, all the same heat exchangers are used. It is cooled with the help of technical water, at CHPP-2 it is taken directly from the Volga. It does not require any special training and can also be reused. After passing through the heat exchanger, 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 oncoming air flow created by the fans. And in ejection cooling towers, water is sprayed using special nozzles. In any case, the main cooling occurs due to the evaporation of a small part of the water. The cooled water leaves the cooling towers through a special channel, after which, with the help of a pumping station, it is sent for reuse.
In a word, cooling towers are needed to cool the water that cools the steam that works in the boiler-turbine system.
All work of the CHP is controlled from the Main Control Panel.
There is an attendant here at all times.
All events are logged.
Don't feed me bread, let me take pictures of the buttons and sensors...
On this, almost everything. In conclusion, there are a few photos of the station.
This is an old, no longer working pipe. Most likely it will be taken down soon.
There is a lot of propaganda at the enterprise.
They are proud of their employees here.
And their achievements.
It doesn't seem right...
It remains to add that, as in a joke - “I don’t know who these bloggers are, but their guide is the director of the branch in Mari El and Chuvashia of OAO TGC-5, IES of the holding - Dobrov S.V.”
Together with the station director S.D. Stolyarov.
Without exaggeration, they are true professionals in their field.
And of course, many thanks to Irina Romanova, representing the press service of the company, for the perfectly organized tour.