What is a thermal power plant and what are the principles of TPP? The general definition of such objects sounds approximately as follows - these are power plants that are involved in the conversion of natural energy into electrical energy. Natural fuels are also used for these purposes.
The principle of TPP. Short description
Today, thermal power plants are most widely used . At such facilities, fossil fuels are burned , which release thermal energy. The goal of TPPs is to use this energy to get electrical energy.
The principle of TPP operation is the generation of not only electric energy, but also the production of thermal energy, which is also supplied to consumers in the form of hot water, for example. In addition, these energy facilities generate about 76% of all electricity. This widespread distribution is due to the fact that the availability of fossil fuels for the operation of the station is quite large. The second reason was that the transportation of fuel from the place of its extraction to the station itself is a fairly simple and streamlined operation. The principle of TPP operation is designed so that it is possible to use the spent heat of the working fluid for secondary supply to its consumer.
Separation of stations by type
It is worth noting that thermal stations can be divided into types depending on what type of energy they produce. If the principle of TPP operation is only in the production of electric energy (that is, thermal energy does not supply the consumer), then it is called condensation (IES).
Facilities intended for the production of electric energy, for the supply of steam, as well as the supply of hot water to the consumer, have steam instead of condensing turbines. Also, in such elements of the station there is an intermediate selection of steam or a backpressure device. The main advantage and principle of operation of a thermal power plant (CHP) of this type is that the exhaust steam is also used as a heat source and supplied to consumers. Thus, it is possible to reduce heat loss and the amount of cooling water.
Basic principles of TPP
Before proceeding to the consideration of the operating principle itself, it is necessary to understand which station is in question. The standard device of such objects includes a system such as intermediate steam overheating. It is necessary because the thermal efficiency of the circuit with the presence of intermediate overheating will be higher than in a system where it is absent. In simple words, the principle of operation of a thermal power plant having such a scheme will be much more effective with the same initial and final given parameters than without it. From all this we can conclude that the basis of the station is organic fuel and heated air.
Scheme of work
The principle of operation of TPPs is constructed as follows. The fuel material, as well as the oxidizing agent, the role of which is most often taken by heated air, is fed into the boiler furnace in a continuous stream. Substances such as coal, oil, fuel oil, gas, shale, peat can act as fuel. If we talk about the most common fuel in the Russian Federation, then it is coal dust. Further, the principle of operation of a thermal power plant is built in such a way that the heat that is generated by burning fuel heats the water in the steam boiler. As a result of heating, the liquid is converted to saturated steam, which through the steam outlet enters the steam turbine. The main purpose of this device at the station is to convert the energy of the incoming steam into mechanical energy.
All elements of the turbine that are able to move are closely connected with the shaft, as a result of which they rotate as a single mechanism. To make the shaft rotate, the kinetic energy of the steam is transferred to the rotor in a steam turbine.
The mechanical part of the station
The device and the principle of operation of the TPP in its mechanical part is associated with the operation of the rotor. The steam that comes from the turbine has a very high pressure and temperature. Because of this, high internal energy of the steam is created, which comes from the boiler into the nozzles of the turbine. Steam jets passing through the nozzle in a continuous stream, with a high speed, which is most often even higher than the sonic one, act on the turbine blades. These elements are rigidly fixed to the disk, which, in turn, is closely connected with the shaft. At this point in time, the mechanical energy of the steam is converted into the mechanical energy of the rotor turbines. More specifically, the principle of operation of thermal power plants, the mechanical effect affects the rotor of the turbogenerator. This is due to the fact that the shaft of a conventional rotor and generator are closely connected. And then there is a fairly well-known, simple and understandable process of converting mechanical energy into electrical energy in a device such as a generator.
Steam movement after the rotor
After the steam passes the turbine, its pressure and temperature drop significantly, and it enters the next part of the station - the condenser. Inside this element, the vapor turns back into liquid. To accomplish this task, there is cooling water inside the condenser, which enters there by means of pipes passing inside the walls of the device. After the steam is converted back to water, it is pumped out by a condensate pump and enters the next compartment, the deaerator. It is also important to note that the pumped water passes through regenerative heaters.
The main task of the deaerator is the removal of gases from the incoming water. Simultaneously with the cleaning operation, the liquid is heated in the same way as in regenerative heaters. For this purpose, heat of steam is used, which is taken from what follows in the turbine. The main purpose of the deaeration operation is to lower the oxygen and carbon dioxide content in the liquid to acceptable values. This helps to reduce the effect of corrosion on the paths through which water and steam are supplied.
Coal Stations
There is a high dependence of the principle of TPP operation on the type of fuel that is used. From a technological point of view, the most difficult substance to implement is coal. Despite this, raw materials are the main source of food at such facilities, the number of which is approximately 30% of the total share of stations. In addition, it is planned to increase the number of such facilities. It is also worth noting that the number of functional compartments required for the operation of the station is much larger than other types.
How do coal-fired TPPs work?
In order for the station to operate continuously, coal is constantly brought along the railway lines, which is unloaded using special unloading devices. Further, there are elements such as conveyor belts through which the unloaded coal is fed to the warehouse. Next, the fuel enters the crushing plant. If necessary, it is possible to bypass the process of supplying coal to the warehouse, and transfer it immediately to the crushers from unloading devices. After passing through this stage, the crushed raw material enters the raw coal bin. The next step is the delivery of material through feeders to pulverized coal mills. Next, coal dust, using a pneumatic transportation method, is fed into the coal dust bin. Passing this way, the substance bypasses such elements as a separator and a cyclone, and from the hopper it already enters through the feeders directly to the burners. The air passing through the cyclone is sucked in by the mill fan, after which it is fed into the combustion chamber of the boiler.
Further, the movement of gas is approximately as follows. The volatile substance formed in the furnace chamber passes sequentially to devices such as the gas ducts of the boiler installation, then, if an intermediate steam overheating system is used, gas is supplied to the primary and secondary superheater. In this compartment, as well as in the water economizer, the gas gives its heat to warm up the working fluid. Next, an element called an air superheater is installed. Here, the thermal energy of the gas is used to heat the incoming air. After passing through all these elements, the volatile substance passes into the ash collector, where it is cleaned of ash. After that, smoke pumps pull the gas out and release it into the atmosphere, using a gas pipe for this.
TPP and NPP
Quite often, the question arises of what is common between thermal and nuclear plants and whether there are similarities in the principles of operation of thermal power plants and nuclear power plants.
If we talk about their similarities, then there are several. Firstly, both of them are constructed in such a way that they use a natural resource that is fossil and excised for their work. In addition, it can be noted that both objects are aimed at generating not only electrical energy, but also thermal energy. The similarities in the operating principles also lie in the fact that TPPs and nuclear power plants have turbines and steam generators involved in the operation. Further there are only some differences. These include the fact that, for example, the cost of construction and electricity received from thermal power plants is much lower than from nuclear power plants. But, on the other hand, nuclear plants do not pollute the atmosphere until the waste is disposed of properly and there are no accidents. While TPPs, due to their operating principle, constantly emit harmful substances into the atmosphere.
Here lies the main difference in the operation of nuclear power plants and thermal power plants. If in thermal objects the thermal energy from burning fuel is most often transferred to water or converted into steam, then at nuclear plants energy is taken from the fission of uranium atoms. The resulting energy diverges to heat a wide variety of substances and water is rarely used here. In addition, all substances are in closed sealed circuits.
Heating
At some TPPs in their schemes, such a system can be provided that deals with the heating of the power plant itself, as well as the adjacent village, if any. To the network heaters of this installation, steam is taken from the turbine, and there is also a special line for condensate drainage. Water is supplied and discharged through a special pipeline system. The electric energy that will be generated in this way is diverted from the electric generator and transmitted to the consumer, passing through step-up transformers.
Basic equipment
If we talk about the main elements operated at thermal power plants, then these are boiler rooms, as well as turbine units paired with an electric generator and a capacitor. The main difference between the main equipment and the additional equipment is that it has standard parameters for its power, performance, steam parameters, as well as voltage and current strength, etc. It can also be noted that the type and number of main elements are selected depending on of what kind of power you need to get from one TPP, as well as from the mode of its operation. Animation of the principle of TPP operation can help to understand this issue in more detail.