A multi-stage regenerative heating system for a thermal power plant

Abstract

The present application discloses a multi-stage regenerative heating system for a thermal power plant, belonging to the field of thermal power generation. A multi-stage regenerative heating system for a thermal power plant includes a steam turbine unit, which includes a high-pressure steam turbine cylinder, an intermediate-pressure steam turbine cylinder, and a low-pressure steam turbine cylinder connected in sequence; a generator, whose shaft is connected to the low-pressure rotor of the low-pressure steam turbine cylinder of the steam turbine; an air-cooled island, which is connected to the exhaust port of the low-pressure steam turbine cylinder of the steam turbine; a condensate system, which includes a condensate pump, and the inlet of the condensate pump is connected to the air-cooled island; a heat network circulating water system, which includes a heat network circulating water pump, the outlet of the heat network circulating water pump and the outlet of the condensate pump of the condensate system are jointly connected to a dual-cooling source low-pressure heater, and the two media are isolated from each other. The multi-stage regenerative heating system for a thermal power plant of the present application can greatly reduce the quality of the heat source steam and does not require an additional heat network heater.

Description

Technical Field

[0001] This application relates to the field of thermal power generation, and in particular, to a multi-stage regenerative heating system for a thermal power plant. Background Art

[0002] With the increase of China's urbanization rate, the demand for urban central heating has been increasing year by year. Under the background of the "dual carbon" goal and the construction of a new power system, cogeneration is an economically feasible, safe and reliable energy utilization method to meet the demand for central heating.

[0003] The inventors found that the current mainstream cogeneration technologies all have different defects during the research process, which are specifically as follows:

[0004] 1. Middle extraction steam heating method: A tee is installed on the medium and low pressure connecting pipe of the unit, and a medium and low pressure connecting pipe heating butterfly valve is installed after the tee to the inlet end of the low pressure cylinder to adjust the heating extraction steam. The other port of the tee is connected to the heat network heater to achieve cogeneration. However, the heating steam quality from the other port of the tee to the heat network heater is high, resulting in high heating energy consumption and poor energy-saving effect.

[0005] 2. Lithium bromide absorption heat pump method: Driven by some high-quality steam, the waste heat of the steam turbine exhaust steam is extracted by lithium bromide working medium to heat the heat network circulating water. There are not only problems such as the heating temperature of the heat network circulating water generally not exceeding 80°C, and the heating outlet temperature being inversely proportional to the COP, but also defects such as large initial investment, short system life, and complex operation and maintenance.

[0006] 3. High back-pressure heating method: When heating, the operating back pressure of the unit needs to be increased, and the heat network circulating water cools the exhaust steam of the low pressure cylinder of the steam turbine. When a higher heating temperature is required, the heat network heater at the heat network first station uses high-quality middle extraction steam to continue heating the heat network circulating water. However, it has high requirements for the unit's electrical load and heating heat load, and the operating back pressure of the unit in the heating season needs to be increased.

[0007] As can be seen from the above, it is urgent to provide a technical solution that can solve the problems of high heating energy consumption of middle extraction steam heating, large initial investment in lithium bromide heat pump transformation, and small heat network circulating water volume, which is not suitable for high back-pressure transformation. Summary of the Invention

[0008] In order to solve the problem of high heating energy consumption caused by the additional use of a heat network heater and the need to use high-quality steam, this application provides a multi-stage regenerative heating system for a thermal power plant.

[0009] A multi-stage regenerative heating system for a thermal power plant provided by this application adopts the following technical solutions:

[0010] A multi-stage regenerative heating system for a thermal power plant includes:

[0011] A steam turbine unit, which includes a high-pressure cylinder of the steam turbine, an intermediate-pressure cylinder of the steam turbine, and a low-pressure cylinder of the steam turbine connected in sequence;

[0012] A generator, whose shaft is connected to the low-pressure rotor of the low-pressure cylinder of the steam turbine;

[0013] An air-cooled island, which is connected to the exhaust port of the low-pressure cylinder of the steam turbine;

[0014] A condensate system, which includes a condensate pump, and the inlet of the condensate pump is connected to the air-cooled island;

[0015] A heat network circulating water system, which includes a heat network circulating water pump. The outlet of the heat network circulating water pump and the outlet of the condensate pump of the condensate system are jointly connected to at least one dual-cooling source low-pressure heater. The dual-cooling source low-pressure heater includes a dual-cooling source No. 7 low-pressure heater. The inlet of the dual-cooling source No. 7 low-pressure heater is connected to the extraction port of the low-pressure cylinder of the steam turbine. The medium entering the dual-cooling source No. 7 low-pressure heater from the heat network circulating water pump and the medium entering the dual-cooling source No. 7 low-pressure heater from the condensate pump of the condensate system are isolated from each other.

[0016] By adopting the above technical solution, the steam turbine unit drives the generator to generate electricity. At the same time, the exhaust steam coming out of the low-pressure cylinder of the steam turbine is condensed into condensate through the air-cooled island and enters the dual-cooling source low-pressure heater. The heat network circulating water also enters the dual-cooling source low-pressure heater. However, the condensate medium and the heat network circulating water medium do not mix. The steam coming out of the extraction port of the low-pressure cylinder of the steam turbine is input into the dual-cooling source No. 7 low-pressure heater to heat the condensate medium and the heat network circulating water medium. For the heat supply transformation, there is no need to set up an additional heat network heater. The steam with lower quality of the steam turbine can be used to heat the heat network circulating water to the heat user to complete the heat supply. The dual-cooling source low-pressure heater in this application can be a single-stage or multi-stage regenerative system, and thus a single-stage or multi-stage regenerative system is formed.

[0017] Optionally, the extraction ports include a seventh-stage extraction port, a sixth-stage extraction port, and a fifth-stage extraction port provided on the low-pressure cylinder of the steam turbine;

[0018] The dual-cooling source low-pressure heater further includes a dual-cooling source No. 6 low-pressure heater and a dual-cooling source No. 5 low-pressure heater;

[0019] The dual-cooling source No. 7 low-pressure heater is connected to the seventh-stage extraction port, the dual-cooling source No. 6 low-pressure heater is connected to the sixth-stage extraction port, and the dual-cooling source No. 5 low-pressure heater is connected to the fifth-stage extraction port; the dual-cooling source No. 7 low-pressure heater, the dual-cooling source No. 6 low-pressure heater, and the dual-cooling source No. 5 low-pressure heater have the same structure;

[0020] The double-cooling-source No. 6 low-pressure heater and the double-cooling-source No. 5 low-pressure heater are successively connected to the outlet side of the double-cooling-source No. 7 low-pressure heater, and the heat network circulating water successively passes through the double-cooling-source No. 7 low-pressure heater, the double-cooling-source No. 6 low-pressure heater and the double-cooling-source No. 5 low-pressure heater.

[0021] By adopting the above technical solution, using the original fifth, sixth and seventh stage extraction steam regeneration of the steam turbine to form a multi-stage regeneration system can meet the demand adjustment of the heat network circulating water temperature at different heating periods. For example, in the middle and late heating periods, when the heat user's demand for the supply water temperature of the heat network circulating water is still lower than the outlet temperature of the double-cooling-source No. 5 low-pressure heater, the double-cooling-source No. 5 low-pressure heater can be closed to make it not work, and the temperature of the heat network circulating water can be adjusted orderly.

[0022] Optionally, the double-cooling-source low-pressure heater further includes a double-cooling-source No. 4 low-pressure heater. The extraction steam port includes a fourth-stage extraction steam port provided on the intermediate pressure cylinder of the steam turbine. The fourth-stage extraction steam port is connected to the double-cooling-source No. 4 low-pressure heater. The double-cooling-source No. 4 low-pressure heater is connected to the outlet side of the double-cooling-source No. 5 low-pressure heater. The heat network circulating water passes through the double-cooling-source No. 4 low-pressure heater, and the double-cooling-source No. 4 low-pressure heater has the same structure as the double-cooling-source No. 7 low-pressure heater.

[0023] By adopting the above technical solution, using the original fourth, fifth, sixth and seventh stage extraction steam regeneration of the steam turbine to form a four-stage regeneration system, each double-cooling-source low-pressure heater can be switched on and off orderly, and the demand adjustment of the heat network circulating water temperature at different heating periods can be met. In the late heating period, when the heat user's demand for the supply water temperature of the heat network circulating water is lower than the outlet temperature of the double-cooling-source No. 4 low-pressure heater, the double-cooling-source No. 4 low-pressure heater can be closed to make it not work, and the temperature of the heat network circulating water can be adjusted again.

[0024] Optionally, a condensate and heat network circulating water switching inlet valve is provided on the inlet side of the double-cooling-source No. 7 low-pressure heater, and a condensate and heat network circulating water switching outlet valve is provided on the outlet side of the double-cooling-source No. 4 low-pressure heater.

[0025] By adopting the above technical solution, opening the condensate and heat network circulating water switching inlet valve and the condensate and heat network circulating water switching outlet valve can allow the condensate to enter and exit the condensate system, allow the heat network circulating water to enter and exit the heat network circulating water system, and enable both media to be heated by the double-cooling-source low-pressure heater.

[0026] Optionally, a No. 5 low-pressure heater circulating water bypass is provided on one side of the double-cooling-source No. 5 low-pressure heater. A No. 5 low-pressure heater circulating water bypass valve is provided on the No. 5 low-pressure heater circulating water bypass, and a No. 5 low-pressure heater circulating water inlet stop valve is provided on the inlet side of the double-cooling-source No. 5 low-pressure heater;

[0027] On one side of the double-cooling-source No. 4 low-pressure heater, there is a circulating water bypass for the No. 4 low-pressure heater. A circulating water bypass valve for the No. 4 low-pressure heater is arranged on the circulating water bypass of the No. 4 low-pressure heater. An inlet stop valve for the circulating water of the No. 4 low-pressure heater is arranged on the inlet side of the double-cooling-source No. 4 low-pressure heater.

[0028] By adopting the above technical solution, the inlet stop valve for the circulating water of the No. 4 low-pressure heater can be closed, and the circulating water bypass valve for the No. 4 low-pressure heater can be opened to allow the heat network circulating water to pass through this bypass; the inlet stop valve for the circulating water of the No. 5 low-pressure heater can be closed, and the circulating water bypass valve for the No. 5 low-pressure heater can be opened to allow the heat network circulating water to pass through this bypass. Furthermore, while several low-pressure heaters are closed to adjust the temperature of the heat network circulating water, the heat network circulating water can flow forward.

[0029] Optionally, each double-cooling-source low-pressure heater includes a shell. A condensate side tube group and a heat network circulating water side tube group are arranged in the shell. A steam inlet is arranged on the upper side of the shell, and a drain device is arranged on the lower side.

[0030] The condensate side tube group includes a condensate water inflow heat exchange tube bundle and a condensate water outflow heat exchange tube bundle connected at the ends. A condensate water to double-cooling-source heat exchanger inlet communicating with the condensate water inflow heat exchange tube bundle and a condensate water to double-cooling-source heat exchanger outlet communicating with the condensate water outflow heat exchange tube bundle are arranged on the shell.

[0031] The heat network circulating water side tube group includes a heat network circulating water inflow heat exchange tube bundle and a heat network circulating water outflow heat exchange tube bundle connected at the ends. A heat network circulating water to double-cooling-source heat exchanger inlet communicating with the heat network circulating water inflow heat exchange tube bundle and a heat network circulating water to double-cooling-source heat exchanger outlet communicating with the heat network circulating water outflow heat exchange tube bundle are arranged on the shell.

[0032] The steam inlet is close to the condensate water outflow heat exchange tube bundle and the heat network circulating water outflow heat exchange tube bundle, and the drain device is close to the condensate water inflow heat exchange tube bundle and the heat network circulating water inflow heat exchange tube bundle.

[0033] By adopting the above technical solution, the steam can heat the condensate water and the heat network circulating water simultaneously, and the three media will not mix. The temperature of the condensate water or the heat network circulating water is very low, forming a vacuum state. The steam entering from the upper side will condense and release heat after entering. The relatively cold condensate water and heat network circulating water are heated on the outlet side, and the condensed steam is discharged through the drain device.

[0034] Optionally, a seven-stage extraction steam regulating valve is arranged on the pipeline connecting the double-cooling-source No. 7 low-pressure heater to the seven-stage extraction steam port.

[0035] A six-stage extraction steam regulating valve is arranged on the pipeline connecting the double-cooling-source No. 6 low-pressure heater to the six-stage extraction steam port.

[0036] A five - stage extraction steam regulating valve is provided on the pipeline connecting the dual - cold - source No. 5 low - pressure heater to the five - stage extraction steam port;

[0037] A four - stage extraction steam regulating valve is provided on the pipeline connecting the dual - cold - source No. 4 low - pressure heater to the four - stage extraction steam port;

[0038] A steam supply butterfly valve for the medium - low pressure connection pipe of the steam turbine is provided on the pipeline connecting the medium - pressure cylinder and the low - pressure cylinder of the steam turbine;

[0039] An isolation valve for the exhaust steam from the low - pressure cylinder to the air - cooled island is provided on the pipeline connecting the air - cooled island to the exhaust steam port.

[0040] By adopting the above - mentioned technical solutions, setting the extraction steam regulating valve can adjust the amount of extraction steam, setting the steam supply butterfly valve can achieve pipeline connection, and setting the isolation valve can condense the exhaust steam.

[0041] Optionally, the connection of the condensate water flowing into the heat exchange tube bundle and the condensate water flowing out of the heat exchange tube bundle is symmetrically arranged with respect to the central longitudinal section of the shell, and the connection part between the two forms an arc; the connection of the heat network circulating water flowing into the heat exchange tube bundle and the heat network circulating water flowing out of the heat exchange tube bundle is symmetrically arranged with respect to the central longitudinal section of the shell, and the connection part between the two forms an arc.

[0042] By adopting the above - mentioned technical solutions, the isolation of the inlet and outlet of the heat exchange tube bundle can be achieved.

[0043] In summary, the present application includes at least one of the following beneficial technical effects:

[0044] 1. Utilize the original fourth, fifth, sixth, and seventh - stage extraction steam of the steam turbine for regenerative heating of the heat network circulating water.

[0045] 2. Adopt a four - stage regenerative system to significantly reduce the problem of high energy consumption in heating and supply, and can significantly reduce the quality of the heat source steam compared with the traditional heating method.

[0046] 3. During the heating period operation, the dual - cold - source low - pressure heater acts jointly on the corresponding condensate water and heat network circulating water, and the heat network circulating water can be heated by using the regenerative heat of the steam turbine and supplied to heat - demand users.

[0047] 4. Utilize the orderly switching of the No. 4 and No. 5 dual - cold - source low - pressure heaters to meet the demand adjustment of the temperature of the heat network circulating water at different heating periods.

[0048] 5. For the heating transformation, there is no need to additionally set up a heat network heater. During the non - heating period operation, the condensate water can be introduced into the heat network circulating water side of the dual - cold - source low - pressure heater, increasing the heat exchange area and reducing the terminal temperature difference of the low - pressure heater.

[0049] 6. The dual - cold low - pressure heater can heat the condensate water and the heat network circulating water simultaneously, and the two cooling - source media do not mix. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 FIG. 1 is a schematic diagram showing the overall structure of a multi-stage regenerative heating system for a thermal power plant according to the present application;

[0051] Figure 2 FIG. 2 is a schematic cross-sectional view of a dual-cooling-source low-pressure heater of a multi-stage regenerative heating system for a thermal power plant according to the present application;

[0052] Figure 3 FIG. 3 is a side view along line A-A in FIG. Figure 2 2.

[0053] DESCRIPTION OF REFERENCE NUMERALS

[0054] 1. Steam turbine unit; 11. High-pressure cylinder of steam turbine; 111. Main steam of steam turbine; 12. Intermediate-pressure cylinder of steam turbine; 121. Reheat steam of steam turbine; 122. Heat supply butterfly valve for intermediate-low pressure connecting pipe of steam turbine; 13. Low-pressure cylinder of steam turbine; 131. Isolation valve for exhaust steam from low-pressure cylinder to air-cooled island;

[0055] 2. Generator;

[0056] 3. Air-cooled island;

[0057] 4. Condensate system; 41. Condensate pump; 411. Switching inlet valve for condensate and heat network circulating water; 412. Switching outlet valve for condensate and heat network circulating water; 42. Dual-cooling-source No. 7 low-pressure heater; 421. Regulating valve for extraction steam of seventh stage; 43. Dual-cooling-source No. 6 low-pressure heater; 431. Regulating valve for extraction steam of sixth stage; 44. Dual-cooling-source No. 5 low-pressure heater; 441. Regulating valve for extraction steam of fifth stage; 442. Shut-off valve for inlet of circulating water of No. 5 low-pressure heater; 443. Bypass valve for circulating water of No. 5 low-pressure heater; 45. Dual-cooling-source No. 4 low-pressure heater; 451. Regulating valve for extraction steam of fourth stage; 452. Shut-off valve for inlet of circulating water of No. 4 low-pressure heater; 453. Bypass valve for circulating water of No. 4 low-pressure heater;

[0058] 5. Heat network circulating water system; 51. Heat network circulating water pump;

[0059] 6. Steam inlet; 71. Condensate flowing into heat exchange tube bundle; 72. Condensate flowing out of heat exchange tube bundle; 73. Inlet of condensate to dual-cooling-source heat exchanger; 74. Outlet of condensate to dual-cooling-source heat exchanger; 81. Heat network circulating water flowing into heat exchange tube bundle; 82. Heat network circulating water flowing out of heat exchange tube bundle; 83. Inlet of heat network circulating water to dual-cooling-source heat exchanger; 84. Outlet of heat network circulating water to dual-cooling-source heat exchanger; 9. Drainage device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] The present application will be further described in detail below with reference to the accompanying Figures 1-3 drawings.

[0061] An embodiment of the present application discloses a multi-stage regenerative heating system for a thermal power plant.

[0062] Referring to Figure 1 , a multi-stage regenerative heating system for a thermal power plant includes a steam turbine unit 1 and a generator 2. The steam turbine unit 1 includes a high-pressure steam turbine cylinder 11, an intermediate-pressure steam turbine cylinder 12, and a low-pressure steam turbine cylinder 13 connected in sequence. The connecting shaft of the low-pressure steam turbine cylinder 13 drives the generator 2 to generate electricity.

[0063] The main steam 111 of the steam turbine enters the high-pressure steam turbine cylinder 11. After the high-pressure steam turbine cylinder 11 completes work, the steam is continuously heated by a reheater. The reheated steam 121 of the steam turbine enters the intermediate-pressure steam turbine cylinder 12. One path of the steam in the intermediate-pressure steam turbine cylinder 12 enters the low-pressure steam turbine cylinder 13 through the heat supply butterfly valve 122 of the intermediate-low pressure connecting pipe of the steam turbine to continue working.

[0064] The exhaust port of the low-pressure steam turbine cylinder 13 is used for discharging the exhaust steam. The exhaust port is connected to an air-cooled island 3 for condensing the exhaust steam into condensed water. The air-cooled island 3 is connected to a condensate system 4. The condensate system 4 includes pipelines, a condensate pump 41 located on the pipeline, and a plurality of double-cooling-source low-pressure heaters with the same structure.

[0065] The condensate pump 41 is connected to the air-cooled island 3 to provide power for the condensed water condensed by the air-cooled island 3.

[0066] The double-cooling-source low-pressure heaters include a double-cooling-source seventh low-pressure heater 42, a double-cooling-source sixth low-pressure heater 43, a double-cooling-source fifth low-pressure heater 44, and a double-cooling-source fourth low-pressure heater 45 arranged in sequence on the pipeline starting from the outlet of the condensate pump 41.

[0067] The low-pressure steam turbine cylinder 13 is provided with a seventh-stage extraction port connected to the double-cooling-source seventh low-pressure heater 42, a sixth-stage extraction port connected to the double-cooling-source sixth low-pressure heater 43, and a fifth-stage extraction port connected to the double-cooling-source fifth low-pressure heater 44.

[0068] The intermediate-pressure steam turbine cylinder 12 is provided with a fourth-stage extraction port, and the double-cooling-source fourth low-pressure heater 45 is connected to the fourth-stage extraction port.

[0069] Among them, the steam quality of the fourth-stage extraction port is higher than that of the fifth-stage extraction port, the steam quality of the fifth-stage extraction port is higher than that of the sixth-stage extraction port, and the steam quality of the sixth-stage extraction port is higher than that of the seventh-stage extraction port.

[0070] The multi - stage regenerative heating system for a thermal power plant further includes a heat network circulating water system 5. The heat network circulating water system 5 includes pipelines and a heat network circulating water pump 51 located on the pipelines. Starting from the outlet of the heat network circulating water pump 51, the pipelines of the heat network circulating water system 5 are sequentially connected to the double - cold - source seventh - stage low - pressure heater 42, double - cold - source sixth - stage low - pressure heater 43, double - cold - source fifth - stage low - pressure heater 44, and double - cold - source fourth - stage low - pressure heater 45 in the condensate system 4. That is, each double - cold - source low - pressure heater can heat both the heat network circulating water and the condensate simultaneously, so additional heat network heaters do not need to be set up for the heating transformation.

[0071] The medium entering each double - cold - source low - pressure heater from the pipeline of the condensate system 4 and the medium entering each double - cold - source low - pressure heater from the pipeline of the heat network circulating water system 5 are isolated from each other, that is, the two do not mix.

[0072] Among them, the medium entering from the pipeline of the condensate system 4 is condensate, and the medium entering from the pipeline of the heat network circulating water system 5 is heat network circulating water or condensate.

[0073] The structures of each double - cold - source low - pressure heater are introduced in detail below.

[0074] Refer to Figure 2 and Figure 3 , Figure 3 which shows the placement state when the double - cold - source low - pressure heater is working. Each double - cold - source low - pressure heater includes a hollow shell. The shell can be any hollow structure such as a cylindrical shape or a columnar shape. In this embodiment, a cylinder is taken as an example. A condensate - side tube group and a heat - network - circulating - water - side tube group are arranged in the shell. A steam inlet 6 is arranged on the upper side of the shell, and a drainage device 9 for draining the water condensed from the steam is arranged on the lower side of the shell.

[0075] The condensate - side tube group includes a condensate - flowing - in heat - exchange tube bundle 71 located on the lower side of the shell and a condensate - flowing - out heat - exchange tube bundle 72 located on the upper side of the shell. A condensate - to - double - cold - source heat - exchanger inlet 73 connected to the condensate - flowing - in heat - exchange tube bundle 71 is arranged on the lower side of the shell, and a condensate - to - double - cold - source heat - exchanger outlet 74 connected to the condensate - flowing - out heat - exchange tube bundle 72 is arranged on the upper side.

[0076] Among them, a condensate - flowing - in heat - exchange tube bundle 71 and a condensate - flowing - out heat - exchange tube bundle 72 form a connected U - shaped tube. The condensate - side tube group includes multiple U - shaped tubes. The cross - section formed by the multiple U - shaped tubes is semi - circular, and the condensate - side tube group occupies half of the cavity of the shell.

[0077] The heat network circulating water side tube group includes a heat network circulating water inlet heat exchange tube bundle 81 located on the lower side of the housing and a heat network circulating water outlet heat exchange tube bundle 82 located on the upper side of the housing. A heat network circulating water to dual-cooling source heat exchanger inlet 83 communicating with the heat network circulating water inlet heat exchange tube bundle 81 is arranged on the lower side of the housing, and a heat network circulating water to dual-cooling source heat exchanger outlet 84 communicating with the heat network circulating water outlet heat exchange tube bundle 82 is arranged on the upper side.

[0078] The steam inlet 6 is close to the outlet of the condensate outflow heat exchange tube bundle 72, and the steam trap 9 is close to the inlet of the condensate inflow heat exchange tube bundle 71. The steam inlet 6 is close to the outlet of the heat network circulating water outlet heat exchange tube bundle 82, and the steam trap 9 is close to the inlet of the heat network circulating water inlet heat exchange tube bundle 81. Thus, it is possible to avoid the water condensed from the steam mixing with the steam under the action of gravity to form vibration. The temperature of the condensate or the heat network circulating water is very low, forming a vacuum state. When the steam enters, it condenses and releases heat, and can heat the condensate and the heat network circulating water.

[0079] Among them, a heat network circulating water inlet heat exchange tube bundle 81 and a heat network circulating water outlet heat exchange tube bundle 82 form a connected U-shaped tube. The heat network circulating water side tube group includes multiple U-shaped tubes. The cross-section formed by the multiple U-shaped tubes is semi-circular, and the heat network circulating water side tube group occupies the other half of the cavity of the housing.

[0080] Refer to Figure 1 and Figure 2 , a condensate and heat network circulating water switching inlet valve 411 is arranged on the inlet side of the dual-cooling source No. 7 low-pressure heater 42, and a condensate and heat network circulating water switching outlet valve 412 is arranged on the outlet side of the dual-cooling source No. 4 low-pressure heater 45.

[0081] In the non-heating season, the heat network circulating water system stops operating, and the condensate can operate in the condensate system 4. After being pressurized by the condensate pump 41, the condensate sequentially enters the dual-cooling source No. 7 low-pressure heater 42, the dual-cooling source No. 6 low-pressure heater 43, the dual-cooling source No. 5 low-pressure heater 44, and the dual-cooling source No. 4 low-pressure heater 45, and is heated and then enters the remaining regenerative system to be further heated.

[0082] In order to make full use of the heat exchange area of each dual-cooling-source low-pressure heater and reduce the heat transfer end difference of the low-pressure heater, when the heat network circulating water system is out of operation, condensate can also be connected to the heat network circulating water system 5. The condensate and heat network circulating water switching inlet valve 411 and the condensate and heat network circulating water switching outlet valve 412 are both opened. The condensate enters simultaneously from the condensate side system and the heat network circulating water side system of the dual-cooling-source low-pressure heater, and is heated successively by the dual-cooling-source No. 7 low-pressure heater 42, the dual-cooling-source No. 6 low-pressure heater 43, the dual-cooling-source No. 5 low-pressure heater 44, and the dual-cooling-source No. 4 low-pressure heater 45, and then enters the remaining regenerative system to be further heated. Since condensate enters both systems simultaneously, the heat exchange area is increased, so the heat transfer end difference of the dual-cooling-source low-pressure heater can be greatly reduced, and the energy consumption of the regenerative system can be reduced.

[0083] The dual-cooling-source No. 7 low-pressure heater 42 is connected to the seventh-stage extraction port through the seventh-stage extraction regulating valve 421; the dual-cooling-source No. 6 low-pressure heater 43 is connected to the sixth-stage extraction port through the sixth-stage extraction regulating valve 431; the dual-cooling-source No. 5 low-pressure heater 44 is connected to the fifth-stage extraction port through the fifth-stage extraction regulating valve 441; the dual-cooling-source No. 4 low-pressure heater 45 is connected to the fourth-stage extraction port through the fourth-stage extraction regulating valve 451.

[0084] The exhaust port of the low-pressure cylinder 13 of the steam turbine is connected to the air-cooled island 3 through the low-pressure cylinder exhaust to air-cooled island isolation valve 131.

[0085] A No. 5 low-pressure heater circulating water bypass is provided on one side of the dual-cooling-source No. 5 low-pressure heater 44. A No. 5 low-pressure heater circulating water bypass valve 443 is provided on this bypass. A No. 5 low-pressure heater circulating water inlet stop valve 442 is provided between the connection of the inlet side of the dual-cooling-source No. 5 low-pressure heater 44 and the inlet side of this bypass and the dual-cooling-source No. 6 low-pressure heater 43.

[0086] A No. 4 low-pressure heater circulating water bypass is provided on one side of the dual-cooling-source No. 4 low-pressure heater 45. A No. 4 low-pressure heater circulating water bypass valve 453 is provided on this bypass. A No. 4 low-pressure heater circulating water inlet stop valve 452 is provided between the connection of the inlet side of the dual-cooling-source No. 4 low-pressure heater 45 and the inlet side of this bypass and the dual-cooling-source No. 5 low-pressure heater 44.

[0087] Of course, the dual-cooling-source No. 6 low-pressure heater 43 can also be provided with a bypass, a bypass valve and a stop valve in the above manner, which will not be elaborated here.

[0088] During the heating season, both the condensate water and the heat network circulating water are put into operation. Among them, the condensate water is pressurized by the condensate pump 41 and then enters the double-cooling-source No. 7 low-pressure heater 42, double-cooling-source No. 6 low-pressure heater 43, double-cooling-source No. 5 low-pressure heater 44, and double-cooling-source No. 4 low-pressure heater 45 in sequence. After being heated, it enters the remaining regenerative system and continues to be heated. The heat network circulating water is pressurized by the heat network circulating water pump 51 and also enters the double-cooling-source No. 7 low-pressure heater 42, double-cooling-source No. 6 low-pressure heater 43, double-cooling-source No. 5 low-pressure heater 44, and double-cooling-source No. 4 low-pressure heater 45 in sequence. After being heated, it is transported to supply heat to users. The condensate water and the heat network circulating water entering both sides of each double-cooling-source low-pressure heater do not mix, operate independently, and there is no need to additionally set up a heat network heater.

[0089] At the end of the heating period, when the heat user's demand for the supply water temperature of the heat network circulating water is lower than the outlet temperature of the double-cooling-source No. 4 low-pressure heater 45, the inlet stop valve 452 of the circulating water of the No. 4 low-pressure heater can be closed, and the bypass valve 453 of the circulating water of the No. 4 low-pressure heater can be opened, so that the double-cooling-source No. 4 low-pressure heater 45 does not heat the heat network circulating water, in order to reduce the supply water temperature of the heat network circulating water; when the heat user's demand for the supply water temperature of the heat network circulating water is still lower than the outlet temperature of the double-cooling-source No. 5 low-pressure heater 44, the inlet stop valve 442 of the circulating water of the No. 5 low-pressure heater can be closed, and the bypass valve 443 of the circulating water of the No. 5 low-pressure heater can be opened, so that the double-cooling-source No. 5 low-pressure heater 44 does not heat the heat network circulating water, and the temperature of the heat network circulating water can be adjusted orderly.

[0090] The above are all preferred embodiments of this application. It does not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A multi-stage regenerative heating system for a thermal power plant, characterized in that: It includes: A steam turbine unit (1), which includes a steam turbine high-pressure cylinder (11), a steam turbine intermediate-pressure cylinder (12) and a steam turbine low-pressure cylinder (13) connected in sequence; A generator (2), the shaft of which is connected to the low-pressure rotor of the steam turbine low-pressure cylinder (13); An air-cooled island (3), which is connected to the exhaust port of the steam turbine low-pressure cylinder (13); A condensate system (4), which includes a condensate pump (41), and the inlet of the condensate pump (41) is connected to the air-cooled island (3); A heat network circulating water system (5), which includes a heat network circulating water pump (51), and the outlet of the heat network circulating water pump (51) and the outlet of the condensate pump (41) of the condensate system are jointly connected to at least one dual-cooling-source low-pressure heater. The dual-cooling-source low-pressure heater includes a dual-cooling-source No. 7 low-pressure heater (42), and the inlet of the dual-cooling-source No. 7 low-pressure heater (42) is connected to the extraction port of the steam turbine low-pressure cylinder (13). The medium entering the dual-cooling-source No. 7 low-pressure heater (42) from the heat network circulating water pump (51) and the medium entering the dual-cooling-source No. 7 low-pressure heater (42) from the condensate pump (41) of the condensate system are isolated from each other; The extraction ports include a seventh-stage extraction port, a sixth-stage extraction port and a fifth-stage extraction port provided on the steam turbine low-pressure cylinder (13); The dual-cooling-source low-pressure heater further includes a dual-cooling-source No. 6 low-pressure heater (43) and a dual-cooling-source No. 5 low-pressure heater (44); The dual-cooling-source No. 7 low-pressure heater (42) is connected to the seventh-stage extraction port, the dual-cooling-source No. 6 low-pressure heater (43) is connected to the sixth-stage extraction port, and the dual-cooling-source No. 5 low-pressure heater (44) is connected to the fifth-stage extraction port; the structures of the dual-cooling-source No. 7 low-pressure heater (42), the dual-cooling-source No. 6 low-pressure heater (43) and the dual-cooling-source No. 5 low-pressure heater (44) are the same; The dual-cooling-source No. 6 low-pressure heater (43) and the dual-cooling-source No. 5 low-pressure heater (44) are sequentially connected to the outlet side of the dual-cooling-source No. 7 low-pressure heater (42), and the heat network circulating water passes through the dual-cooling-source No. 7 low-pressure heater (42), the dual-cooling-source No. 6 low-pressure heater (43) and the dual-cooling-source No. 5 low-pressure heater (44) in sequence.

2. The multi-stage regenerative heating system for a thermal power plant according to claim 1, characterized in that: The dual-cooling-source low-pressure heater further includes a dual-cooling-source No. 4 low-pressure heater (45), the extraction port includes a fourth-stage extraction port provided on the steam turbine intermediate-pressure cylinder (12), the fourth-stage extraction port is connected to the dual-cooling-source No. 4 low-pressure heater (45), the dual-cooling-source No. 4 low-pressure heater (45) is connected to the outlet side of the dual-cooling-source No. 5 low-pressure heater (44), the heat network circulating water passes through the dual-cooling-source No. 4 low-pressure heater (45), and the structures of the dual-cooling-source No. 4 low-pressure heater (45) and the dual-cooling-source No. 7 low-pressure heater (42) are the same.

3. The multi-stage regenerative heating system for a thermal power plant according to claim 2, characterized in that: A condensate and heat network circulating water switching inlet valve (411) is provided at the inlet side of the dual-cooling-source No. 7 low-pressure heater (42), and a condensate and heat network circulating water switching outlet valve (412) is provided at the outlet side of the dual-cooling-source No. 4 low-pressure heater (45).

4. A multi-stage regenerative heating system for a thermal power plant according to claim 2, characterized in that: A No. 5 low-pressure heater circulating water bypass is provided on one side of the dual-cooling-source No. 5 low-pressure heater (44). A No. 5 low-pressure heater circulating water bypass valve (443) is provided on the No. 5 low-pressure heater circulating water bypass, and a No. 5 low-pressure heater circulating water inlet stop valve (442) is provided at the inlet side of the dual-cooling-source No. 5 low-pressure heater (44); A No. 4 low-pressure heater circulating water bypass is provided on one side of the dual-cooling-source No. 4 low-pressure heater (45). A No. 4 low-pressure heater circulating water bypass valve (453) is provided on the No. 4 low-pressure heater circulating water bypass, and a No. 4 low-pressure heater circulating water inlet stop valve (452) is provided at the inlet side of the dual-cooling-source No. 4 low-pressure heater (45).

5. A multi-stage regenerative heating system for a thermal power plant according to any one of claims 1 to 4, characterized in that: Each dual-cooling-source low-pressure heater includes a shell. A condensate side tube group and a heat network circulating water side tube group are arranged in the shell. A steam inlet (6) is provided on the upper side of the shell, and a drain device (9) is provided on the lower side; The condensate side tube group includes a condensate flow-in heat exchange tube bundle (71) and a condensate flow-out heat exchange tube bundle (72) connected at the ends. A condensate to dual-cooling-source heat exchanger inlet (73) communicating with the condensate flow-in heat exchange tube bundle (71) and a condensate to dual-cooling-source heat exchanger outlet (74) communicating with the condensate flow-out heat exchange tube bundle (72) are provided on the shell; The heat network circulating water side tube group includes a heat network circulating water flow-in heat exchange tube bundle (81) and a heat network circulating water flow-out heat exchange tube bundle (82) connected at the ends. A heat network circulating water to dual-cooling-source heat exchanger inlet (83) communicating with the heat network circulating water flow-in heat exchange tube bundle (81) and a heat network circulating water to dual-cooling-source heat exchanger outlet (84) communicating with the heat network circulating water flow-out heat exchange tube bundle (82) are provided on the shell; The steam inlet (6) is close to the condensate flow-out heat exchange tube bundle (72) and the heat network circulating water flow-out heat exchange tube bundle (82), and the drain device (9) is close to the condensate flow-in heat exchange tube bundle (71) and the heat network circulating water flow-in heat exchange tube bundle (81).

6. A multi-stage regenerative heating system for a thermal power plant according to any one of claims 2 to 4, characterized in that: A seven-stage extraction steam regulating valve (421) is provided on the pipeline connecting the dual-cooling-source No. 7 low-pressure heater (42) to the seven-stage extraction steam port; A six-stage extraction steam regulating valve (431) is provided on the pipeline connecting the dual-cooling-source No. 6 low-pressure heater (43) to the six-stage extraction steam port; A five-stage extraction steam regulating valve (441) is provided on the pipeline connecting the dual-cooling-source No. 5 low-pressure heater (44) to the five-stage extraction steam port; A four-stage extraction steam regulating valve (451) is provided on the pipeline connecting the double cold source low-pressure heater (45) to the four-stage extraction steam port; A steam turbine medium-low pressure connecting pipe heating butterfly valve (122) is provided on the pipeline connecting the medium-pressure cylinder (12) and the low-pressure cylinder (13) of the steam turbine; A low-pressure cylinder exhaust to air-cooled island isolation valve (131) is provided on the pipeline connecting the air-cooled island (3) to the exhaust port.

7. A multi-stage regenerative heating system for a thermal power plant according to claim 5, characterized in that: The condensate water flowing into the heat exchange tube bundle (71) and the condensate water flowing out of the heat exchange tube bundle (72) are symmetrically arranged with respect to the central longitudinal section of the housing, and the connection between the two forms an arc; the heat network circulating water flowing into the heat exchange tube bundle (81) and the heat network circulating water flowing out of the heat exchange tube bundle (82) are symmetrically arranged with respect to the central longitudinal section of the housing, and the connection between the two forms an arc.

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