Steam coaxial driving steam compression upgrading cascade high back pressure heat supply system

Abstract

The application discloses a kind of steam coaxial drive steam compression upgrading cascade high back pressure heating system, steam coaxial drive steam compression upgrading cascade high back pressure heating system includes backwater heating component, steam turbine low-pressure cylinder and air cooling island, backwater heating component includes first high back pressure condenser;Steam turbine low-pressure cylinder is connected with heating steam extraction pipeline, and steam turbine low-pressure cylinder is connected with first pipeline, and first pipeline is connected with first branch pipe and second branch pipe, and first branch pipe is communicated with first high back pressure condenser;Air cooling island is communicated with second branch pipe, and the outlet of air cooling island is connected with second pipeline, and the outlet of first high back pressure condenser is communicated with second pipeline, and second pipeline is communicated with steam turbine regenerative system to heat condensate water.The steam coaxial drive steam compression upgrading cascade high back pressure heating system of the application can recover waste heat of steam turbine low-pressure cylinder exhaust for heating, to realize the cascade utilization of energy.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation technology, and in particular to a cascade high back pressure heating system that uses steam coaxial drive for steam compression and upgrading. Background Technology

[0002] "Energy conservation and consumption reduction, heating system renovation, and flexibility renovation" are the main directions of coal-fired power plant renovation at present. That is, to continuously promote the ultra-low emission renovation of coal-fired power units and promote the replacement of coal heating (steam) with industrial waste heat, power plant waste heat, and clean energy.

[0003] To address the issue of high back pressure in power plant steam turbines during the summer, some power plants currently employ methods such as increasing the heat exchange area of ​​cooling towers to cool circulating water (i.e., peak cooling technology). This technology can effectively reduce steam turbine back pressure and increase the unit's power generation load, but it does not recover and utilize the heat from the exhaust steam. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a cascade high back pressure heating system driven by coaxial steam compression and upgrading, which can recover the waste heat of exhaust steam from the low-pressure cylinder of a steam turbine for heating, thereby realizing the cascade utilization of energy.

[0005] A cascade high back-pressure heating system for coaxial steam-driven steam compression and upgrading according to an embodiment of the present invention includes a return water heating assembly. Return water from the heating network is heated by the return water heating assembly and then flows back to the heating network. The return water heating assembly includes a first high back-pressure condenser; a low-pressure turbine cylinder connected to a heating extraction steam pipeline, through which low-pressure steam enters the low-pressure turbine cylinder to perform work; a first pipeline connected to the low-pressure turbine cylinder, which is connected to a first branch pipe and a second branch pipe, the first branch pipe being connected to the first high back-pressure condenser; and an air-cooled island connected to the second branch pipe, with a second pipeline connected to the outlet of the air-cooled island. The outlet of the first high back-pressure condenser is connected to the second pipeline, and the second pipeline is connected to the turbine regenerative system to heat the condensate.

[0006] According to an embodiment of the present invention, a cascade high back-pressure heating system for coaxial steam-driven steam compression and upgrading utilizes an air-cooled island to cool and condense the exhaust steam discharged from the low-pressure cylinder of the turbine into water, which is then connected to the turbine's regenerative system for boiler circulation, thus achieving water conservation in the power plant. Simultaneously, by installing a first high back-pressure condenser, the exhaust steam from the turbine's low-pressure cylinder enters the first high back-pressure condenser through a first branch pipe. The first high back-pressure condenser can recover the waste heat from the exhaust steam for heating, achieving cascaded energy utilization, thereby significantly reducing the unit's coal consumption for power generation and improving overall energy efficiency.

[0007] In some embodiments of the present invention, the first branch pipe is provided with a first control valve group for controlling the steam flow rate in the first branch pipe and the on / off state of the first branch pipe; and / or, the second branch pipe is provided with a second control valve group for controlling the steam flow rate in the second branch pipe and the on / off state of the second branch pipe.

[0008] In some embodiments of the present invention, the first high back pressure condenser is connected to the second pipeline through a first branch pipe, and a third control valve group is provided on the first branch pipe, the third control valve group being used to control the on / off state of the first branch pipe.

[0009] In some embodiments of the present invention, the cascade high back pressure heating system with steam coaxial drive for steam compression and upgrading further includes: a steam compressor, wherein the steam compressor is connected to the first pipeline through a third branch pipe, and the return water heating assembly further includes a compressor condenser, wherein the compressor condenser is connected to the steam compressor.

[0010] In some embodiments of the present invention, the cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading further includes: a small steam turbine, the inlet of which is connected to the heating extraction steam pipeline; a speed change gearbox is provided between the steam compressor and the small steam turbine, the small steam turbine driving the steam compressor through the speed change gearbox; the return water heating assembly further includes a second high back pressure condenser, the small steam turbine being connected to the second high back pressure condenser and the second pipeline; and an asynchronous motor, which is connected to the steam compressor, the asynchronous motor being switchable between generator mode and motor mode, and the asynchronous motor being connected to a four-quadrant frequency converter for adjusting the frequency of the asynchronous motor.

[0011] In some embodiments of the present invention, a third pipeline is connected between the small steam turbine and the second high back pressure condenser, and a fourth control valve group is provided on the third pipeline for controlling the on / off state of the third pipeline.

[0012] In some embodiments of the present invention, the second high back pressure condenser is connected to the second pipeline through a second branch pipe, and a fifth control valve group is provided on the second branch pipe for controlling the on / off state of the second branch pipe.

[0013] In some embodiments of the present invention, a fourth pipeline is connected between the steam compressor and the compressor condenser, and a sixth control valve group is provided on the fourth pipeline for controlling the on / off state of the fourth pipeline.

[0014] In some embodiments of the present invention, the compressor condenser is connected to the second pipeline via a third branch pipe, and a seventh control valve group is provided on the third branch pipe for controlling the on / off state of the third branch pipe; and / or, an eighth control valve group is provided on the third branch pipe for controlling the steam flow rate in the third branch pipe and the on / off state of the third branch pipe.

[0015] In some embodiments of the present invention, the cascade high back pressure heating system with steam coaxial drive for steam compression and upgrading further includes: a peak heater, which is located downstream of the return water heating component and connected to the heating extraction steam pipeline, for heating the return water of the heating network.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of a cascade high back pressure heating system that uses steam coaxial drive for steam compression and upgrading according to an embodiment of the present invention.

[0018] Figure label: 100. A cascade high back pressure heating system driven by coaxial steam compression and upgrading; 1. Return water heating assembly; 11. First high back pressure condenser; 12. Compressor condenser; 13. Second high back pressure condenser; 14. Heat network return water; 2. Low-pressure cylinder of steam turbine; 21. Heating extraction steam pipeline; 211. Seventh electric isolation valve; 212. Pneumatic check valve; 22. First pipeline; 221. First branch pipe; 2211. First control valve group; 2212. First electric butterfly valve; 222. Second branch pipe; 2221. Second control valve group; 2222. Second electric butterfly valve; 3. Air-cooled island; 31. Second pipeline; 311. First branch pipeline; 3111. Third control valve group; 3112. First electric isolation valve; 3113. Drain pump; 312. Second branch pipeline; 3121. Fifth control valve group; 3122. Third electric isolation valve; 3123. First check valve; 313. Third branch pipeline; 3131. Seventh control valve group; 3132. Fifth electric isolation valve; 3133. Second check valve; 314. Low-pressure heater; 315. Condensate pump; 316. Deaerator; 4. Steam compressor; 41. Third branch pipe; 411. Eighth control valve group; 412. Sixth electric isolation valve; 413. Electric regulating valve; 42. Fourth pipeline; 421. Sixth control valve group; 422. Fourth electric isolation valve; 5. Small steam turbine; 51. Third pipeline; 511. Fourth control valve group; 512. Second electric isolation valve; 6. Variable speed gearbox; 7. Asynchronous motor; 8. Four-quadrant frequency converter; 9. Peak heater. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The following description, with reference to the accompanying drawings, describes a cascade high back pressure heating system 100 based on an embodiment of the present invention, which utilizes a steam coaxial drive for steam compression and upgrading.

[0022] like Figure 1 As shown, the cascade high back pressure heating system 100 of the steam coaxial drive steam compression and upgrading according to an embodiment of the present invention includes a return water heating component 1, a steam turbine low-pressure cylinder 2, and an air-cooled island 3.

[0023] Specifically, the return water 14 of the heating network is heated by the return water heating component 1 and then flows back to the heating network, which can better meet the heating demand of the heating network. The return water heating component 1 includes a first high back pressure condenser 11, a low-pressure cylinder 2 of the steam turbine connected to a heating extraction steam pipe 21, and low-pressure steam from the steam turbine enters the low-pressure cylinder 2 of the steam turbine through the heating extraction steam pipe 21 to do work. The low-pressure cylinder 2 of the steam turbine is connected to a first pipe 22, which is connected to a first branch pipe 221 and a second branch pipe 222. The first branch pipe 221 is connected to the first high back pressure condenser 11. The exhaust steam discharged from the low-pressure cylinder 2 of the steam turbine enters the first high back pressure condenser 11 through the first branch pipe 221. The first high back pressure condenser 11 can recover the waste heat (cold source loss) of the exhaust steam from the low-pressure cylinder 2 of the steam turbine for heating, realizing the cascade utilization of energy, thereby significantly reducing the unit's coal consumption for power generation and improving the overall energy utilization efficiency.

[0024] like Figure 1 As shown, the air-cooled island 3 is connected to the second branch pipe 222, and the outlet of the air-cooled island 3 is connected to the second pipe 31. The outlet of the first high back-pressure condenser 11 is connected to the second pipe 31, and the second pipe 31 is connected to the turbine regenerative system to heat the condensate. The air-cooled island 3 can use air as the cooling medium to cool and condense the exhaust steam discharged from the low-pressure cylinder 2 of the turbine into water, which is then connected to the turbine regenerative system and can be used for boiler circulation. This is a key alternative technology for achieving water conservation in power plants.

[0025] Specifically, the working process of air-cooled island 3 can be summarized as "air cooling and steam condensation". First, the exhaust steam from the low-pressure cylinder 2 of the steam turbine, after completing its work, is guided into the heat dissipation fin bundle through a large exhaust pipe; then, a huge axial fan rotates, forcing a large amount of ambient air to flow over the surface of the heat dissipation fins, using the temperature difference between the air and the steam to remove heat; finally, the high-temperature exhaust steam is cooled and condensed into pure water at about 40-60°C, which is then treated and sent back to the boiler for recycling. Compared with traditional wet cooling towers, the water saving rate can reach more than 90%.

[0026] According to an embodiment of the present invention, the cascade high back pressure heating system 100 with steam coaxial drive for steam compression and upgrading, by setting up an air-cooled island 3 to cool and condense the exhaust steam discharged from the low-pressure cylinder 2 of the steam turbine into water, which is then connected to the steam turbine regenerative system and can be used for boiler circulation, thus achieving water conservation in the power plant; at the same time, by setting up a first high back pressure condenser 11, the exhaust steam from the low-pressure cylinder 2 of the steam turbine enters the first high back pressure condenser 11 through the first branch pipe 221. The first high back pressure condenser 11 can recover the waste heat of the exhaust steam from the low-pressure cylinder 2 of the steam turbine for heating, realizing cascade utilization of energy, thereby significantly reducing the unit's coal consumption for power generation and improving the overall energy utilization efficiency.

[0027] In some embodiments, such as Figure 1As shown, the condensate in the second pipeline 31 flows to the deaerator 316 via the low-pressure heater 314 and the condensate pump 315.

[0028] In some embodiments of the present invention, such as Figure 1 As shown, a first control valve assembly 2211 is provided on the first branch pipe 221 to control the steam flow rate in the first branch pipe 221 and the on / off state of the first branch pipe 221. By setting the first control valve assembly 2211, the on / off state of the first branch pipe 221 and the steam flow rate in the first branch pipe 221 can be controlled according to the heating demand of the heating network, thereby controlling the amount of steam in the first high back pressure condenser 11 to meet different usage requirements.

[0029] In this embodiment, the first control valve group 2211 includes a first electric butterfly valve 2212, which has a better effect on regulating the steam flow rate in the first branch pipe 221.

[0030] In some embodiments of the present invention, such as Figure 1 As shown, a second control valve assembly 2221 is provided on the second branch pipe 222 to control the steam flow rate in the second branch pipe 222 and the on / off state of the second branch pipe 222. By setting the second control valve assembly 2221, the on / off state of the second branch pipe 222 and the steam flow rate in the second branch pipe 222 can be controlled according to the heating demand of the heating network, thereby controlling the amount of steam entering the air-cooled island 3, which facilitates the control of the amount of steam flowing out of the low-pressure cylinder 2 of the steam turbine and meets different usage requirements.

[0031] In this embodiment, the second control valve group 2221 includes a second electric butterfly valve 2222, which has a better effect on regulating the steam flow rate in the second branch pipe 222.

[0032] In some embodiments of the present invention, such as Figure 1 As shown, the first high back-pressure condenser 11 and the second pipeline 31 are connected via a first branch pipe 311. By setting up the first branch pipe 311, the low-temperature steam condensate from the first high back-pressure condenser 11 after heating the return water 14 of the heating network can flow to the turbine regenerative system for boiler circulation. After utilizing the waste heat from the turbine's low-pressure cylinder 2, it can flow back to the turbine regenerative system, resulting in good water-saving performance in the heating system. A third control valve group 3111 is installed on the first branch pipe 311. The third control valve group 3111 is used to control the steam flow rate within the first branch pipe 311 and the on / off state of the first branch pipe 311. By setting up the third control valve group 3111, the on / off state of the first branch pipe 311 can be controlled according to the steam volume within the first high back-pressure condenser 11, meeting different usage requirements.

[0033] In this embodiment, the third control valve group 3111 includes a first electric isolation valve 3112 and a drain pump 3113. The first electric isolation valve 3112 can control the opening and closing of the first branch pipe 311, and the drain pump 3113 can pump the high-pressure condensate pump 315 in the first high back pressure condenser 11 to the second pipeline 31 to achieve sufficient flow of condensate.

[0034] In some embodiments of the present invention, such as Figure 1 As shown, the cascade high back pressure heating system 100 with steam coaxial drive for steam compression and upgrading also includes a steam compressor 4. The steam compressor 4 is connected to the first pipeline 22 through a third branch pipe 41. The steam compressor 4 can compress the exhaust steam discharged from the low-pressure cylinder 2 of the steam turbine. The return water heating assembly 1 also includes a compressor condenser 12. The compressor condenser 12 is connected to the steam compressor 4. The exhaust steam discharged from the low-pressure cylinder 2 of the steam turbine after compression by the steam compressor 4 can release heat in the compressor condenser 12. The compressor condenser 12 can heat the return water 14 of the heating network.

[0035] In some embodiments, the compressor condenser 12 can be located downstream of the first high back pressure condenser 11. After the heat network return water 14 is heated in the first high back pressure condenser 11, it is heated again in the compressor condenser 12 to meet the heating demand of the heat network and increase the heating capacity of the heat network.

[0036] In some embodiments of the present invention, such as Figure 1 As shown, the cascade high back pressure heating system 100, which uses coaxial steam to drive steam compression and upgrading, also includes a small steam turbine 5 and an asynchronous motor 7. The inlet of the small steam turbine 5 is connected to the heating extraction steam pipeline 21. A speed change gearbox 6 is provided between the steam compressor 4 and the small steam turbine 5. The small steam turbine 5 drives the steam compressor 4 through the speed change gearbox 6. The steam in the heating extraction steam pipeline 21 can drive the small steam turbine 5 to work, and then drive the steam compressor 4 to work through the speed change gearbox 6. This enables the steam compressor 4 to compress the steam flowing out of the low-pressure cylinder 2 of the steam turbine, thereby ensuring the heating effect of the compressor condenser 12 on the return water 14 of the heating network.

[0037] The return water heating assembly 1 also includes a second high back pressure condenser 13. The small steam turbine 5 is connected to the second high back pressure condenser 13 and the second pipeline 31. The exhaust steam discharged after the small steam turbine 5 starts working can release heat in the second high back pressure condenser 13. The second high back pressure condenser 13 can heat the return water 14 of the heating network.

[0038] In some embodiments, the second high back pressure condenser 13 can be located downstream of the compressor condenser 12 and the first high back pressure condenser 11. After the heat network return water 14 is heated in the first high back pressure condenser 11 and the compressor condenser 12, it is heated again in the second high back pressure condenser 13 to meet the heating demand of the heat network and increase the heating capacity of the heat network.

[0039] The asynchronous motor 7 is connected to the steam compressor 4. The asynchronous motor 7 can switch between generator mode and motor mode. The asynchronous motor 7 is connected to a four-quadrant frequency converter 8 to adjust the frequency of the asynchronous motor 7. When the small steam turbine 5 fails, the asynchronous motor 7 can drive the steam compressor 4 as a motor to compress the steam flowing out of the low-pressure cylinder 2 of the steam turbine. When the heating system is working normally, the asynchronous motor 7 can act as a generator to make full use of the excess power of the small steam turbine 5 and increase the working efficiency of the thermal power unit.

[0040] In some embodiments of the present invention, such as Figure 1 As shown, a third pipeline 51 connects the small steam turbine 5 and the second high back pressure condenser 13. A fourth control valve group 511 is installed on the third pipeline 51 to control the opening and closing of the third pipeline 51. By setting the fourth control valve group 511, the opening and closing of the third pipeline 51 can be controlled according to the residual heat in the small steam turbine 5 to meet different usage requirements.

[0041] In this embodiment, the fourth control valve group 511 includes a second electric isolation valve 512, which can control the opening and closing of the third pipeline 51.

[0042] In some embodiments of the present invention, such as Figure 1 As shown, the second high back pressure condenser 13 is connected to the second pipeline 31 via a second branch pipe 312. A fifth control valve group 3121 is provided on the second branch pipe 312 to control the on / off state of the second branch pipe 312. By setting the fifth control valve group 3121, the on / off state of the second branch pipe 312 can be controlled according to the steam volume in the second high back pressure condenser 13 to meet different usage requirements.

[0043] In this embodiment, the fifth control valve group 3121 includes a third electric isolation valve 3122 and a first check valve 3123. The third electric isolation valve 3122 can control the opening and closing of the second branch pipe 312, and the first check valve 3123 can prevent condensate from flowing backward in the second branch pipe 312, and can better guide the condensate of the second high back pressure condenser 13 to the second pipeline 31.

[0044] In some embodiments of the present invention, such as Figure 1 As shown, a fourth pipeline 42 connects the steam compressor 4 and the compressor condenser 12. A sixth control valve group 421 is installed on the fourth pipeline 42 to control the on / off state of the fourth pipeline 42. By setting the sixth control valve group 421, the on / off state of the fourth pipeline 42 can be controlled according to the remaining heat in the steam compressor 4 to meet different usage requirements.

[0045] In this embodiment, the sixth control valve group 421 includes a fourth electric isolation valve 422, which can control the opening and closing of the fourth pipeline 42.

[0046] In some embodiments of the present invention, such as Figure 1 As shown, the compressor condenser 12 is connected to the second pipeline 31 via a third branch pipe 313. A seventh control valve assembly 3131 is installed on the third branch pipe 313. This seventh control valve assembly 3131 controls the steam flow rate within the third branch pipe 313 and the on / off state of the third branch pipe 313. By installing the seventh control valve assembly 3131, the on / off state of the third branch pipe 313 can be controlled according to the steam quantity within the compressor condenser 12, thus meeting different usage requirements.

[0047] In this embodiment, the seventh control valve group 3131 includes a fifth electric isolation valve 3132 and a second check valve 3133. The fifth electric isolation valve 3132 can control the opening and closing of the third branch pipe 313, and the second check valve 3133 can prevent condensate from flowing backward in the third branch pipe 313, and can better guide the condensate of the compressor condenser 12 to the second pipeline 31.

[0048] In some embodiments of the present invention, such as Figure 1 As shown, an eighth control valve group 411 is provided on the third branch pipe 41 to control the steam flow rate in the third branch pipe 41 and the on / off state of the third branch pipe 41. By setting the eighth control valve group 411, the on / off state and flow rate of the third branch pipe 41 can be controlled according to the heating demand to meet different usage requirements.

[0049] In this embodiment, the eighth control valve group 411 includes a sixth electric isolation valve 412 and an electric regulating valve 413. The sixth electric isolation valve 412 can control the opening and closing of the third branch pipe 41, and the electric regulating valve 413 can regulate the steam flow rate in the third branch pipe 41.

[0050] In some embodiments of the present invention, such as Figure 1 As shown, the cascade high back pressure heating system 100, which uses steam coaxial drive for steam compression and upgrading, also includes a peak heater 9. The peak heater 9 is located downstream of the return water heating component 1 and is connected to the heating extraction steam pipe 21. It is used to heat the return water 14 of the heating network. It can further heat the return water 14 of the heating network to meet higher heating demands.

[0051] The following is for reference. Figure 1 The following detailed description of the steam coaxial-driven steam compression and upgrading cascade high back pressure heating system 100 of the present invention is intended to illustrate the invention in a specific embodiment. It should be understood that the following description is merely illustrative and should not be construed as limiting the invention.

[0052] A hot well is located downstream of the air-cooled island 3. During the heating season when the unit is operating at high back pressure, the exhaust steam from the low-pressure cylinder 2 of the turbine does not enter the air-cooled island 3 in principle. The second control valve group 2221 at the top of the air-cooled island 3 is closed, and the electric regulating valve 413 and the sixth electric isolation valve 412 in the eighth control valve group 411 are open. The first control valve group 2211 in the first branch pipe 221 is open, and the exhaust steam from the low-pressure cylinder 2 of the turbine flows to the steam compressor 4. After being compressed by the steam compressor 4, the exhaust steam passes through the fourth electric isolation valve 422 in the fourth pipeline 42 to the compressor condenser 12. The maximum pressure of the exhaust steam after compression can reach 45~50 kPa.

[0053] The return water 14 from the heating network is heated by the first high back-pressure condenser 11 and then enters the compressor condenser 12 for further heating. After being heated by the compressor condenser 12, the temperature of the return water 14 can reach about 80℃. The condensate released from the first high back-pressure condenser 11 returns to the hot well after passing through the first electric isolation valve 3112 and the drain pump 3113. Steam is led out from the heating extraction pipe 21 to the small steam turbine 5. A seventh electric isolation valve 211 and a pneumatic check valve 212 can be installed in between. The exhaust steam after the steam does work in the small steam turbine 5 has a pressure of 60~70 kPa. The exhaust steam enters the second high back-pressure condenser 13, where the heat of the exhaust steam is used to further heat the heating network circulating water. The temperature of the heating network circulating water at the outlet of the second high back-pressure condenser can reach 85~90℃, achieving a partial replacement of peak flow. After releasing heat, the exhaust steam becomes condensate and returns to the hot well after passing through the fifth control valve group 3121 and the seventh control valve group 3131.

[0054] In this system, a disengaged gearbox 6 is installed between the small steam turbine 5 and the steam compressor 4, and the small steam turbine 5, steam compressor 4, and asynchronous motor 7 are coaxially connected. During normal operation, the asynchronous motor 7 operates as a generator. Besides driving the steam compressor 4, the small steam turbine 5 also drives the generator, reducing the unit's power consumption. A four-quadrant frequency converter 8 is used to regulate the frequency of the asynchronous motor 7, enabling bidirectional energy flow between motoring and generating modes. If the small steam turbine 5 experiences a sudden failure, the asynchronous motor 7 switches from generator mode to motor mode, driving the steam compressor 4, thus improving the reliability of the steam compressor 4 and the cascade high back-pressure heating system. Simultaneously, this invention provides a method for operating and controlling the cascade high back-pressure heating system 100 under different heating demands, improving the unit's heating economy and operational flexibility. Through technological innovation, this invention achieves a comprehensive improvement in heating economy, system reliability, and operational flexibility, providing a safe and reliable solution for high back-pressure heating in thermal power units.

[0055] Taking a 330MW subcritical air-cooled unit as an example, when the unit's average load and winter heating demand are low, the seventh electric isolation valve 211, the pneumatic check valve 212, and the eighth control valve group 411 are opened, the small steam turbine 5 and the steam compressor 4 are started, and the second electric butterfly valve 2222 on the upper part of the air-cooled island 3 is gradually closed. In principle, the exhaust steam does not go to the air-cooled island 3. The heating network circulating water volume is 10,000 t / h, and the heating network circulating water return temperature is 50℃. Based on the unit's average load of 75%, when the heating demand is low, the exhaust steam is used to heat the heating network circulating water from the high back pressure condenser to 69℃. The steam compressor 4 compresses the exhaust steam to 50 kPa, and the compressor condenser 12 heats the heating network circulating water to 79℃. According to the heating demand, the steam inlet flow of the small steam turbine 5 is adjusted to about 100 t / h. The outlet water temperature at the second high back pressure condenser 13 is about 85℃, and the asynchronous motor 7 generates electricity, reducing the plant's power consumption. As heating demand increases, peak heaters 9 are gradually put into operation to further increase the temperature of the circulating water in the heating network.

[0056] When the small steam turbine 5 malfunctions, the seventh electric isolation valve 211 and the pneumatic check valve 212 are closed, the gearbox 6 is in clutch mode, and the asynchronous motor 7 switches from generator mode to motor mode, driven by plant power, which in turn drives the steam compressor 4. When the heating demand is low, the steam compressor 4 is used to compress the exhaust steam to 45~50 kPa, and the return water of the heating network is heated to about 14 to 80°C in the compressor condenser 12. When the heating demand is high (the heating network water temperature requirement is above 80°C), the peak heater 9 is activated to further increase the temperature.

[0057] Other configurations and operations of the cascade high back pressure heating system 100 with steam coaxial drive for steam compression and upgrading according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A cascade high back-pressure heating system with coaxial steam-driven steam compression and upgrading, characterized in that, include: The return water heating component heats the return water from the heating network before it flows back to the heating network. The return water heating component includes a first high back pressure condenser. The turbine low-pressure cylinder is connected to the heating extraction steam pipeline. The turbine low-pressure steam enters the turbine low-pressure cylinder through the heating extraction steam pipeline to do work. The turbine low-pressure cylinder is connected to a first pipeline. The first pipeline is connected to a first branch pipe and a second branch pipe. The first branch pipe is connected to the first high back pressure condenser. An air-cooled island is connected to the second branch pipe. A second pipeline is connected to the outlet of the air-cooled island. The outlet of the first high back-pressure condenser is connected to the second pipeline. The second pipeline is connected to the turbine regenerative system to heat the condensate.

2. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading as described in claim 1, characterized in that, The first branch pipe is equipped with a first control valve group, which is used to control the steam flow rate in the first branch pipe and the opening and closing of the first branch pipe; And / or, the second branch pipe is provided with a second control valve group for controlling the steam flow rate in the second branch pipe and the on / off state of the second branch pipe.

3. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading according to claim 2, characterized in that, The first high back pressure condenser is connected to the second pipeline through a first branch pipe. A third control valve group is provided on the first branch pipe, which is used to control the opening and closing of the first branch pipe.

4. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading according to claim 1, characterized in that, Also includes: The steam compressor is connected to the first pipeline via a third branch pipe. The return water heating assembly also includes a compressor condenser, which is connected to the steam compressor.

5. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading according to claim 4, characterized in that, Also includes: A small steam turbine, the inlet of which is connected to the heating extraction steam pipeline, a speed change gearbox is provided between the steam compressor and the small steam turbine, the small steam turbine drives the steam compressor through the speed change gearbox, the return water heating assembly also includes a second high back pressure condenser, the small steam turbine is connected to the second high back pressure condenser and the second pipeline; An asynchronous motor is connected to the steam compressor. The asynchronous motor can switch between generator mode and motor mode. The asynchronous motor is connected to a four-quadrant frequency converter for adjusting the frequency of the asynchronous motor.

6. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading according to claim 5, characterized in that, A third pipeline connects the small steam turbine to the second high back pressure condenser. A fourth control valve group is installed on the third pipeline to control the opening and closing of the third pipeline.

7. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading according to claim 5, characterized in that, The second high back pressure condenser is connected to the second pipeline through a second branch pipe. The second branch pipe is equipped with a fifth control valve group for controlling the opening and closing of the second branch pipe.

8. The cascade high back pressure heating system with steam coaxial drive for steam compression and upgrading according to claim 4, characterized in that, A fourth pipeline is connected between the steam compressor and the compressor condenser. A sixth control valve group is provided on the fourth pipeline to control the opening and closing of the fourth pipeline.

9. The cascade high back pressure heating system with steam coaxial drive for steam compression and upgrading according to claim 4, characterized in that, The compressor condenser is connected to the second pipeline through a third branch pipe. The third branch pipe is equipped with a seventh control valve group, which is used to control the opening and closing of the third branch pipe. And / or, the third branch pipe is provided with an eighth control valve group for controlling the steam flow rate in the third branch pipe and the on / off state of the third branch pipe.

10. The cascade high back pressure heating system with coaxial steam-driven steam compression and upgrading according to claim 4, characterized in that, Also includes: A peak heater is located downstream of the return water heating assembly and connected to the heating steam extraction pipeline, used to heat the return water of the heating network.

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