The power unit is an almost autonomous part of a nuclear or non-nuclear thermal power plant , which is a technological complex for the production of electricity , including various equipment, such as a steam boiler or a nuclear reactor , a turbine , a turbine generator , a step-up transformer , auxiliary thermal and electrical equipment, steam lines and feedwater pipelines and other.
The layout of the power station of the power units is called block ; design solutions for implementing such a layout are called blocking . Its main need is to choose the thermal scheme of the power plant.
Block-type power plants lack connections between various steam-turbine plants in its composition. The principle of blocking applies both to the thermal and electrical circuits of a power plant, as well as to its construction part.
Block layout has a number of clear advantages over non-block, the latter is usually used only for non-nuclear power plants that do not have intermediate superheating of steam . NPPs are always built in block [1] [2] [3] [4] .
Content
Block Station Features
Non-nuclear thermal power plants according to the type of thermal scheme are divided into block and non-block (sectional, centralized, sectional-centralized). All nuclear power plants are block.
With the block scheme, all the main and auxiliary equipment of various steam-turbine plants as part of the station does not have technological connections between them. Common are only auxiliary lines serving for launching operations, supplying additional water and other purposes. With a non-block scheme ( TPP with cross-links ), steam from all steam boilers enters the common steam line , and from it is distributed to the turbines , so steam from all boilers can be used to power any turbine. The lines through which feed water is supplied to the boilers also have cross-links.
Block TPPs are cheaper than non-block TPPs, since this arrangement simplifies the piping layout and reduces the number of valves . It also simplifies the management of individual units, facilitates the automation of technological processes . At the same time, during operation, the operation of one unit does not affect the others. When expanding the power plant, subsequent units may have different power and technological parameters, which makes it possible with time to install more powerful equipment at higher parameters on the expandable station and thus increase the technical and economic parameters of the station. At the same time, the adjustment and development of new equipment will not affect the operation of already operating power units.
Locking is also used to reduce the master plan and the length of utilities . To do this, the main and auxiliary buildings and structures as closely as possible (according to technological capabilities) are assembled into separate large buildings. Thus, the density of construction of the industrial site increases and, as a result, the utilization rate of the territory increases and the amount of equipment is reduced, and the energy losses in it are reduced. Blocking structures also significantly improves the conditions for maintenance.
However, for normal operation of block TPPs, the reliability of their equipment must be significantly higher than on non-block ones, since there are no backup boilers in the units. At the block TPPs, it is impossible to use the so-called “hidden reserve”, which is widely used on non-block (when the possible boiler capacity exceeds the flow rate required for this turbine, some of the steam is transferred to another) [1] [2] [5] [6] .
Application
For steam turbine installations with intermediate superheating, the steam block scheme is almost the only possible, since the non-block one in this case will become extremely complicated.
Intermediate superheating of steam is usually used at large condensation power plants with an initial vapor pressure of more than 12.7 MPa (127 atmospheres) and combined heat and power plants with an initial pressure of 23.5 MPa, such stations are being built in blocks. Also built block all nuclear power plants .
Thermal power plants without regulated steam extraction with an initial pressure of less than 8.8 MPa and with variable steam extraction with an initial pressure of less than 12.7 MPa operate in cycles without intermediate superheating of steam, such stations are usually built non-block [1] [7] .
Monoblocks and Double Blocks
If the steam boiler of the TPP power unit supplies steam to one turbine, it is called a monoblock . In case of supplying the turbine with steam from two boilers - a double unit . The double-block scheme provides a slight increase in emergency backup capabilities. At the early stage of development of heat and power engineering , double-blocks were more often built, however, such a scheme did not justify itself economically and is currently hardly used; modern power units of thermal power plants, despite their large capacity, are being built as monobloc [8] [9] .
Dual power units are also used at NPPs - most of the NPPs with VVER-440 reactors had a common structure for two reactors , however they were only doubled in the construction part, the thermal and electrical circuits of such installations are monoblock. Since creating a powerful reactor for the parameters used at nuclear power plants is much simpler than a turbine, in the block with one reactor at many nuclear power plants built at the early stage of nuclear power development, 2-3 turbines were working. Modern nuclear power plants are built as monoblock with one turbine [1] [5] .
Notes
- ↑ 1 2 3 4 L.S. Sterman, S.A. Tevlin, A.T. Sharkov. Thermal and nuclear power plants / Ed. L.S. Sterman. - 2nd ed., Corr. and add. - M .: Energoizdat , 1982. - p. 25-26. - 456 s.
- ↑ 1 2 Under the general editorship of Corr. RAS E.V. Ametistova . Volume 1 edited by Prof. A.D. Trukhnia // Fundamentals of modern energy. In 2 volumes. - M .: Publishing House MPEI , 2008 .-- S. 36. - 472 p. - ISBN 978 5 383 00 162 2 .
- ↑ Block-turbine boiler - article from the Great Soviet Encyclopedia .
- ↑ Block thermal power station - article from the Great Soviet Encyclopedia .
- ↑ 1 2 L.M. Voronin. Features of the design and construction of nuclear power plants. - M .: Atomizdat , 1980. - P. 67-76. - 192 s.
- ↑ I.P. Kuptsov, Yu.R. Ioffe. Design and construction of thermal power plants. - 3rd ed., Pererab. and add. - M .: Energoatomizdat , 1985.- S. 42. - 408 p.
- ↑ V.D.Burov, E.V. Dorokhov, D.P.Elizarov, V.F. Liquid, E.T.Ilyin, G.P.Kiselev, V.M. Lavygin, V.D. Rozhnatovsky, A .S. Sedlov, S.G. Tishin, S.V. Tsanev. Thermal Power Plants / Ed. V.M. Lavygina, A.S. Sedlova, S.V. Tsaneva. - 3rd ed. - Publishing House MPEI , 2009. - P. 248. - 466 p. - ISBN 978 5 383 00404 3 .
- ↑ A.E. Geltman, D.M. Budnyatsky, L.E. Apatovsky. Block condensing power plants of high power (parameters and thermal circuits) / Ed. A.E. Geltman. - M. - L .: Energy , 1964. - P. 53-55. - 404 s.
- ↑ V.Ya.Ryzhkin. Thermal Power Plants / Ed. V.Ya.Girshfelda. - 3rd ed., Pererab. and add. - M .: Energoatomizdat , 1987. - P. 12-13. - 328 s.