High and medium pressure combined heat supply system based on back-pumping machine and operation method thereof

Abstract

The application provides a high and medium pressure combined heat supply system based on a back-draft machine and an operation method thereof, and belongs to the heat supply field. The system comprises a back-draft machine system, a flue gas reheating system and a high and medium pressure combined heat supply system. The application recycles the work capacity of the main steam by using the back-draft small steam turbine, recycles the flue gas heat of the boiler, and uses the back-draft steam after part work and the back-draft exhaust steam after complete work as the high and medium pressure heat supply steam sources, so that the high and medium pressure combined heat supply demand is met, the energy level matching heat supply is realized, the energy utilization rate is improved, the high and medium pressure combined heat supply is realized while power generation, the phenomenon that the energy level is not matched when the higher parameter steam is directly reduced in temperature and pressure for heat supply is avoided, the energy utilization efficiency is improved, the energy cascade utilization is realized, the feed water temperature is improved by the steam cooler system, and the efficiency of the Rankine cycle is improved.

Description

Technical Field

[0001] This invention relates to the field of heating, and more specifically to a high- and medium-pressure combined heating system based on a back-extraction fan and a method for operating such a system. Background Technology

[0002] Combined heat and power (CHP) has significant advantages in energy conservation and emission reduction due to its characteristics of "temperature matching and cascaded utilization," and is of great significance for promoting the clean and low-carbon transformation of the power industry. CHP units provide heating for both residential and industrial use. Residential heating systems include extraction steam heating, low-grade heat energy tiered heating, and heat pump waste heat recovery heating. Industrial heating, especially the high-parameter heating (2.3–6.0 MPa, 320–420℃) required by the chemical industry, currently commonly uses extraction steam (such as main steam, primary extraction, and reheat steam) with desuperheating and pressure reduction. However, the higher-level extraction steam desuperheating and pressure reduction heating schemes currently widely used in industrial heating result in energy level mismatch and waste due to the use of extraction steam from higher pressure or temperature points, followed by desuperheating and pressure reduction before supplying heat to users. This fails to truly achieve "temperature matching and cascaded utilization."

[0003] Faced with the demand for building a new power system, the proportion of new energy sources in the power generation system is rapidly increasing, and the utilization hours of thermal power units will continue to decrease, gradually shifting towards deep peak-shaving units. Ultra-wide load operation of thermal power units will become inevitable, and the resulting issues of unit safety and economy have become a key focus of the industry. Therefore, reducing plant power consumption while ensuring the safe and stable operation of units and equipment, and maximizing the economic benefits of power generation enterprises, has become a very important and urgent task.

[0004] Currently, large-scale hydropower and thermal power units (coal-fired / gas-fired units) are the main power sources for grid frequency regulation in my country's major regional power grids. Existing heating systems typically employ a main steam extraction heating scheme, which requires water spraying for cooling. Simultaneously, steam is extracted from extraction points with higher pressure or temperature ratings, and then further depressurized before being supplied to users. This results in energy level mismatch and waste, and the boiler's flue gas heat cannot be fully recovered and utilized, leading to low energy efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a high- and medium-pressure combined heating system based on a back-extraction fan and its operation method, so as to solve the problem of low energy utilization caused by mismatch in energy levels of existing heating systems and the inability to fully recover and utilize flue gas heat from boilers.

[0006] To achieve the above objectives, embodiments of the present invention provide a high- and medium-pressure combined heating system based on a back-extraction compressor, comprising:

[0007] The back-drawing machine system includes a generator and a back-drawing machine electrically connected to the generator. The back-drawing machine is connected to an external main steam source through a back-drawing machine steam inlet pipe. A back-drawing machine steam inlet regulating valve is installed on the back-drawing machine steam inlet pipe.

[0008] The flue gas reheat system includes a high-pressure reheat module and a medium-pressure reheat module. The high-pressure reheat module is connected to the back extractor through the back extractor steam extraction pipeline and is used to reheat the back extractor steam. The medium-pressure reheat module is connected to the back extractor through the back extractor exhaust steam pipeline and is used to reheat the back extractor exhaust steam.

[0009] A combined high-pressure and medium-pressure heating system includes a high-pressure steam cooler, a medium-pressure steam cooler, a high-pressure heating header, and a medium-pressure heating header. One end of the high-pressure steam cooler is connected to the steam outlet of the high-pressure heating reheat module via a high-pressure steam cooler inlet pipe, and the other end is connected to the high-pressure heating header. The steam inlet of the high-pressure heating reheat module is connected to the medium-pressure steam cooler via a third pipe. One end of the medium-pressure steam cooler is connected to the steam outlet of the medium-pressure heating reheat module via a medium-pressure steam cooler inlet pipe, and the other end is connected to the medium-pressure heating header. Both the medium-pressure steam cooler and the high-pressure steam cooler are connected to the main steam cooler feedwater line, which is connected to an external water source. The medium-pressure steam cooler is located close to the external water source.

[0010] Optionally, the high-pressure heating reheat module includes: a high-pressure heating reheater inlet steam header, a high-pressure heating reheater outlet steam header, and a high-pressure heating reheater.

[0011] The medium-pressure heating reheat module includes: a medium-pressure heating reheater inlet steam header, a medium-pressure heating reheater outlet steam header, and a medium-pressure heating reheater.

[0012] The back-extraction machine is connected to the inlet steam header of the high-pressure heating reheater through the back-extraction machine steam extraction pipeline. A back-extraction machine steam extraction regulating valve is installed on the back-extraction machine steam extraction pipeline. The back-extraction machine is connected to the inlet steam header of the medium-pressure heating reheater through the back-extraction machine steam exhaust pipeline. A back-extraction machine steam exhaust check valve is installed on the back-extraction machine steam exhaust pipeline.

[0013] The high-pressure steam cooler is connected to the outlet steam header of the high-pressure heating reheater via a high-pressure steam cooler inlet pipe. The inlet steam header of the high-pressure heating reheater is connected to the inlet steam pipe of the medium-pressure steam cooler via a third pipe. A high-pressure heating reheater inlet bypass valve is installed on the third pipe. A high-pressure steam cooler steam inlet valve is installed on the high-pressure steam cooler inlet pipe. A high-pressure steam cooler steam outlet valve is installed on the high-pressure heating pipe. The outlet steam header of the medium-pressure heating reheater is connected to the medium-pressure steam cooler via a medium-pressure steam cooler inlet pipe. A medium-pressure steam cooler outlet valve is installed on the medium-pressure steam cooler inlet pipe. The medium-pressure steam cooler has a steam inlet valve, and the medium-pressure steam cooler has a steam outlet valve on the medium-pressure heating pipeline. Both the medium-pressure steam cooler and the high-pressure steam cooler are connected to the main steam cooler water supply line. The main steam cooler water supply line is connected to an external water source. The medium-pressure steam cooler is located close to the external water source. The medium-pressure steam cooler has a water-side inlet three-way valve on its inlet side, and the high-pressure steam cooler has a water-side outlet valve on its outlet side. The high-pressure steam cooler water-side outlet valve is connected to the medium-pressure steam cooler water-side inlet three-way valve via a steam cooler water supply bypass.

[0014] Optionally, a high-pressure heating de-heating and pressure reducing valve is also provided on the high-pressure heating pipeline. The high-pressure heating de-heating and pressure reducing valve is connected to an external superheated de-heating water source through a high-pressure heating de-heating water pipeline. A high-pressure heating de-heating water regulating valve is provided on the high-pressure heating de-heating water pipeline.

[0015] The high-pressure auxiliary heating de-temperature and pressure reducing valve is connected to the high-pressure auxiliary heating de-temperature water pipeline through the high-pressure auxiliary heating de-temperature water pipeline, and the high-pressure auxiliary heating de-temperature water regulating valve is installed on the high-pressure auxiliary heating de-temperature water pipeline.

[0016] Optionally, a medium-pressure heating desuperheating and pressure reducing valve is also provided on the medium-pressure heating pipeline. The medium-pressure heating desuperheating and pressure reducing valve is connected to an external reheat desuperheating water source through a medium-pressure heating desuperheating water pipeline. A medium-pressure heating desuperheating water regulating valve is provided on the medium-pressure heating desuperheating water pipeline.

[0017] The medium-pressure auxiliary heating de-heating and pressure reducing valve is connected to the medium-pressure auxiliary heating de-heating water pipeline through the medium-pressure auxiliary heating de-heating water pipeline, and the medium-pressure auxiliary heating de-heating water regulating valve is installed on the medium-pressure auxiliary heating de-heating water pipeline.

[0018] Optionally, the flue gas reheating system further includes: a reheating module, a high-pressure cylinder, and an intermediate-pressure cylinder. The steam outlets of the reheating module and the high-pressure reheating module are connected through a first pipeline. The reheating module and the high-pressure cylinder are connected through a high-pressure cylinder exhaust pipeline. The intermediate-pressure reheating module and the high-pressure cylinder exhaust pipeline are connected through a second pipeline. The high-pressure cylinder is connected to an external main steam source through a main steam pipeline. The steam outlet of the reheating module is connected to the intermediate-pressure cylinder through a reheat steam pipeline.

[0019] A high-pressure auxiliary heating pipeline, one end of which is connected to the main steam pipeline and the other end of which is connected to the high-pressure heating header;

[0020] A medium-pressure auxiliary heating pipeline, one end of which is connected to the reheat steam pipeline and the other end of which is connected to the medium-pressure heating header.

[0021] Optionally, the reheating module includes: a reheat heater inlet steam header, a reheat heater, and a reheat heater outlet steam header. The reheat heater inlet steam header and the high-pressure reheater outlet steam header are connected via a first pipeline, and a high-pressure reheater outlet bypass valve is installed on the first pipeline. The reheat heater inlet steam header and the high-pressure cylinder are connected via a high-pressure cylinder exhaust pipeline, and a high-pressure cylinder exhaust shut-off valve is installed on the high-pressure cylinder exhaust pipeline. The medium-pressure reheater inlet steam header and the high-pressure cylinder exhaust pipeline are connected via a second pipeline, and a medium-pressure reheater inlet bypass valve is installed on the second pipeline. The reheat heater outlet steam header is connected to the medium-pressure cylinder via a reheat steam pipeline.

[0022] A high-pressure auxiliary heating regulating valve is installed at one end of the high-pressure auxiliary heating pipeline near the main steam pipeline, and a high-pressure auxiliary heating shut-off valve is installed at one end of the high-pressure auxiliary heating pipeline near the high-pressure heating header. A high-pressure auxiliary heating de-temperature and pressure reducing valve is installed between the high-pressure auxiliary heating shut-off valve and the high-pressure auxiliary heating regulating valve.

[0023] A medium-pressure auxiliary heating regulating valve is installed at one end of the medium-pressure auxiliary heating pipeline near the reheat steam pipeline, and a medium-pressure auxiliary heating shut-off valve is installed at one end of the medium-pressure auxiliary heating pipeline near the medium-pressure heating manifold. A medium-pressure auxiliary heating de-temperature and pressure reducing valve is installed between the medium-pressure auxiliary heating shut-off valve and the medium-pressure auxiliary heating regulating valve.

[0024] Optionally, both the high-pressure steam cooler and the medium-pressure steam cooler are surface heat exchangers, with steam arranged on the shell side and feedwater arranged on the tube side.

[0025] Optionally, the pump is coaxially connected to the generator, and the generator is connected to the high-voltage transformer or to an electrochemical energy storage device.

[0026] In a second aspect of the present invention, an operation method for a combined high- and medium-pressure heating system based on a back-extraction compressor is also provided, applied to the aforementioned combined high- and medium-pressure heating system based on a back-extraction compressor, the method comprising:

[0027] When the back-extraction machine is in operation, control the operation of the back-extraction machine and connect the back-extraction machine steam inlet pipeline, back-extraction machine steam extraction pipeline, high-pressure steam cooler steam inlet pipeline, high-pressure heating pipeline, high-pressure heating desuperheating water pipeline, back-extraction machine exhaust pipeline, medium-pressure steam cooler steam inlet pipeline, medium-pressure heating pipeline, and medium-pressure heating desuperheating water pipeline.

[0028] The high-pressure heating steam process is as follows: the steam from the main steam source passes through the steam inlet pipeline of the back extractor, the back extractor, the steam extraction pipeline of the back extractor, the high-pressure heating reheat module, the steam inlet pipeline of the high-pressure steam cooler, the high-pressure steam cooler, and the high-pressure heating pipeline before entering the high-pressure heating header.

[0029] The medium-pressure heating steam process is as follows: the steam from the main steam source passes through the steam inlet pipeline of the extraction back machine, the extraction back machine, the steam exhaust pipeline of the extraction back machine, the medium-pressure heating reheat module, the steam inlet pipeline of the medium-pressure steam cooler, the medium-pressure steam cooler, and the medium-pressure heating pipeline before entering the medium-pressure heating header.

[0030] In a third aspect of the present invention, an operation method for a combined high- and medium-pressure heating system based on a back-extraction compressor is also provided, applied to the aforementioned combined high- and medium-pressure heating system based on a back-extraction compressor, the method comprising:

[0031] When the back-extraction machine stops operating, control the back-extraction machine to stop operating, close the back-extraction machine steam inlet pipeline, back-extraction machine steam extraction pipeline, high-pressure steam cooler steam inlet pipeline, high-pressure heating pipeline, high-pressure heating desuperheating water pipeline, back-extraction machine exhaust pipeline, medium-pressure steam cooler steam inlet pipeline, medium-pressure heating pipeline, medium-pressure heating desuperheating water pipeline, and high-pressure cylinder exhaust pipeline, and open the first pipeline, second pipeline, and third pipeline, and the medium-pressure heating reheater and high-pressure heating reheater and reheat heater are connected in series;

[0032] The high-pressure heating steam process is as follows: the steam from the main steam source passes through the main steam pipeline and the high-pressure auxiliary heating pipeline in sequence before entering the high-pressure heating header.

[0033] The medium-pressure heating steam process is as follows: the steam from the main steam source passes through the main steam pipeline, the high-pressure cylinder, the high-pressure cylinder exhaust pipeline, the medium-pressure heating reheat module, the high-pressure heating reheat module, the reheat heating module, the reheat steam pipeline, and the medium-pressure auxiliary heating pipeline before entering the medium-pressure heating header.

[0034] The process of the medium-pressure heating reheat module, the high-pressure heating reheat module, and the reheating module operating in series is as follows: the steam from the main steam source passes through the main steam pipeline, the high-pressure cylinder, the high-pressure cylinder exhaust pipeline, the medium-pressure heating reheat module, the high-pressure heating reheat module, the reheating module, and the reheat steam pipeline before entering the medium-pressure cylinder.

[0035] In this embodiment of the invention, the steam generated by the main steam source is supplied to the high-pressure heating header after passing through the back extractor, high-pressure reheat module, and high-pressure steam cooler; the steam generated by the main steam source is supplied to the medium-pressure heating header after passing through the back extractor, medium-pressure reheat module, and medium-pressure steam cooler. This can simultaneously raise the temperature of high-pressure and medium-pressure heating steam to the rated value, achieving precise heating. The steam cooler system increases the feedwater temperature and improves the efficiency of the Rankine cycle. At the same time, by utilizing the back extractor to recover the work capacity of the main steam, the heat of the boiler flue gas is recovered. This achieves combined high-pressure and medium-pressure heating while generating electricity, avoiding the energy level mismatch phenomenon of directly reducing the temperature and pressure of higher-parameter steam for heating, improving energy utilization efficiency, and realizing the cascade utilization of energy.

[0036] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a schematic diagram of the pipeline of the high- and medium-pressure combined heating system based on the back-extraction machine of the present invention, under the operating state of the back-extraction machine in operation.

[0039] Figure 2 This is a schematic diagram of the pipeline in the high- and medium-pressure combined heating system based on the back-extraction machine of the present invention, with the back-extraction machine in a stopped operating state.

[0040] Explanation of reference numerals in the attached figures

[0041] P1, Main steam pipeline; P2, Steam inlet pipeline of the back extraction unit; P3, Steam extraction pipeline of the back extraction unit;

[0042] P4, High-pressure steam cooler inlet pipe; P5, High-pressure heating pipe;

[0043] P6, Exhaust pipe of the back exhaust fan; P7, Inlet pipe of the medium-pressure steam cooler;

[0044] P8, Medium-pressure heating pipeline; P9, Medium-pressure heating desuperheating water pipeline;

[0045] P10, Medium-pressure auxiliary heating and desuperheating water pipeline; P11, High-pressure heating and desuperheating water pipeline;

[0046] P12, High-pressure auxiliary heating desuperheating water pipeline; P13, Medium-pressure auxiliary heating pipeline;

[0047] P14, High-pressure auxiliary heating pipeline; P15, Reheat steam pipeline;

[0048] P16, High-pressure cylinder exhaust pipeline; P17, Steam cooler main water supply line;

[0049] P18, Steam cooler feedwater bypass; 1. Steam inlet regulating valve for back blower;

[0050] 2. Steam extraction regulating valve for the back-extraction unit; 3. Steam header at the inlet of the high-pressure reheater;

[0051] 4. High-pressure reheater inlet bypass valve; 5. Medium-pressure reheater inlet steam header;

[0052] 6. Steam header at the outlet of the reheat heater; 7. Steam header at the outlet of the high-pressure reheater;

[0053] 8. Steam header at the outlet of the medium-pressure reheater; 9. Steam header at the inlet of the reheat heater;

[0054] 10. High-pressure heating reheater outlet bypass valve; 11. High-pressure cylinder exhaust shut-off valve;

[0055] 12. Inlet bypass valve for medium-pressure reheater; 13. Steam inlet valve for high-pressure steam cooler;

[0056] 14. Water-side outlet valve of high-pressure steam cooler; 15. Steam outlet valve of high-pressure steam cooler;

[0057] 16. Steam inlet valve of medium-pressure steam cooler; 17. Steam outlet valve of medium-pressure steam cooler;

[0058] 18. Three-way valve for water side inlet of medium-pressure steam cooler; 19. High-pressure auxiliary heating regulating valve;

[0059] 20. High-pressure auxiliary heating desuperheating and pressure reducing valve; 21. High-pressure auxiliary heating shut-off valve;

[0060] 22. High-pressure auxiliary heating desuperheating water regulating valve; 23. High-pressure heating desuperheating water regulating valve;

[0061] 24. Medium-pressure heating desuperheating water regulating valve; 25. Medium-pressure auxiliary heating desuperheating water regulating valve;

[0062] 26. Medium-pressure heating desuperheating and pressure reducing valve; 27. Medium-pressure auxiliary heating regulating valve;

[0063] 28. Medium-pressure auxiliary heating desuperheating and pressure reducing valve; 29. ​​Medium-pressure auxiliary heating shut-off valve;

[0064] 30. High-pressure reheater; 31. Medium-pressure reheater; 32. Reheat heater;

[0065] 33. Exhaust check valve for back-extraction machine; 34. Exhaust shut-off valve for back-extraction machine;

[0066] 35. High-pressure heating desuperheating and pressure reducing valve; 40. First pipeline; 41. Second pipeline;

[0067] 42. Third pipeline; 43. Generator; 44. High-pressure steam cooler;

[0068] 45. Medium-pressure steam cooler; 46. High-pressure heating header; 47. Medium-pressure heating header;

[0069] 48. High-pressure cylinder; 49. Medium-pressure cylinder. Detailed Implementation

[0070] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0072] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0073] The term "substantially constitutes" used to describe a combination should include the identified element, component, part, or step, as well as other elements, components, parts, or steps that do not substantially affect the essential novel features of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, parts, or steps herein also contemplates embodiments substantially constituted by such elements, components, parts, or steps. The use of the term "may" herein is intended to indicate that any described attribute included by "may" is optional. Multiple elements, components, parts, or steps can be provided by a single integrated element, component, part, or step. Alternatively, a single integrated element, component, part, or step can be divided into multiple separate elements, components, parts, or steps. The use of "a" or "an" to describe an element, component, part, or step does not imply exclusion of other elements, components, parts, or steps.

[0074] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the pipeline in the high- and medium-pressure combined heating system based on the back-extraction machine of the present invention, under the condition of the back-extraction machine being put into operation.

[0075] This embodiment provides a combined high- and medium-pressure heating system based on a back-extraction steam extractor, comprising: a back-extraction steam extractor system, including a generator 43 and a back-extraction steam extractor electrically connected to the generator 43, the back-extraction steam extractor being connected to an external main steam source via a back-extraction steam extractor inlet pipe P2, and a back-extraction steam extractor inlet regulating valve 1 installed on the back-extraction steam extractor inlet pipe P2; a flue gas reheating system, including a high-pressure heating reheating module and a medium-pressure heating reheating module, the high-pressure heating reheating module being connected to the back-extraction steam extractor via a back-extraction steam extractor inlet pipe P3 and used for reheating the extracted steam of the back-extraction steam extractor, the medium-pressure heating reheating module being connected to the back-extraction steam extractor via a back-extraction steam extractor inlet pipe P6 and used for reheating the exhaust steam of the back-extraction steam extractor; and a combined high- and medium-pressure heating system, including a high-pressure steam cooler 44 and a medium-pressure steam cooler 45. The high-pressure heating header 46 and the medium-pressure heating header 47 are connected. One end of the high-pressure steam cooler 44 is connected to the steam outlet of the high-pressure heating reheat module through the high-pressure steam cooler inlet pipe P4, and the other end is connected to the high-pressure heating header 46. The steam inlet of the high-pressure heating reheat module is connected to the medium-pressure steam cooler 45 through the third pipe 42. One end of the medium-pressure steam cooler 45 is connected to the steam outlet of the medium-pressure heating reheat module through the medium-pressure steam cooler inlet pipe P7, and the other end is connected to the medium-pressure heating header 47. Both the medium-pressure steam cooler 45 and the high-pressure steam cooler 44 are connected to the main steam cooler feedwater line P17, which is connected to an external water source. The medium-pressure steam cooler 45 is located close to the external water source.

[0076] Specifically, both the high-pressure reheater 30 and the medium-pressure reheater 31 are located in the boiler. When the back-extraction machine is in normal operation, the high-pressure reheater 30 is cooled by the back-extraction machine steam extracted from the back-extraction machine in the back-extraction machine steam extraction pipeline P3; the medium-pressure reheater 31 is cooled by the back-extraction machine exhaust steam in the back-extraction machine exhaust pipeline P6. The steam generated by the main steam source is used for heating through the two lines respectively, thereby realizing the cascade utilization of energy.

[0077] It's important to note that in the diagram, the black state of a gate valve represents closed; the white state represents open. For regulating valves: a white triangle aligned with the pipe direction represents open; a black triangle aligned with the pipe direction represents closed.

[0078] In one embodiment, the high-pressure heating reheat module includes: a high-pressure heating reheater inlet steam header 3, a high-pressure heating reheater outlet steam header 7, and a high-pressure heating reheater 30; the medium-pressure heating reheat module includes: a medium-pressure heating reheater inlet steam header 5, a medium-pressure heating reheater outlet steam header 8, and a medium-pressure heating reheater 31; the back extraction unit is connected to the high-pressure heating reheater inlet steam header 3 via a back extraction unit extraction steam pipeline P3, and a back extraction unit extraction steam regulating valve 2 is installed on the back extraction unit extraction steam pipeline P3. The exhaust pipe P6 of the back-extraction machine is connected to the inlet steam header 5 of the medium-pressure reheater. A back-extraction machine exhaust check valve 33 is installed on the exhaust pipe P6. The high-pressure steam cooler 44 is connected to the outlet steam header 7 of the high-pressure reheater via the high-pressure steam cooler inlet pipe P4. The inlet steam header 3 of the high-pressure reheater is connected to the inlet steam pipe P7 of the medium-pressure steam cooler via a third pipe 42. A high-pressure reheater inlet bypass valve 4 is installed on the third pipe 42. The high-pressure steam cooler inlet steam pipe P4... A high-pressure steam cooler steam inlet valve 13 is installed on the high-pressure heating pipeline P5, and a high-pressure steam cooler steam outlet valve 15 is installed on the high-pressure heating pipeline P5. The steam header 8 at the outlet of the medium-pressure heating reheater is connected to the medium-pressure steam cooler 45 through the medium-pressure steam cooler inlet pipeline P7. A medium-pressure steam cooler steam inlet valve 16 is installed on the medium-pressure steam cooler inlet pipeline P7, and a medium-pressure steam cooler steam outlet valve 17 is installed on the medium-pressure heating pipeline P8. The medium-pressure steam cooler 45 and the high-pressure steam cooler 4... All 4 are connected to the main water supply line P17 of the steam cooler. The main water supply line P17 of the steam cooler is connected to an external water source. The medium-pressure steam cooler 45 is located near the external water source. The medium-pressure steam cooler 45 is equipped with a three-way valve 18 at the water inlet side. The high-pressure steam cooler 44 is equipped with a high-pressure steam cooler water outlet valve 14 at the water outlet side. The high-pressure steam cooler water outlet valve 14 is connected to the medium-pressure steam cooler water inlet three-way valve 18 through the steam cooler water supply bypass P18.

[0079] In this embodiment, the steam generated by the main steam source passes through the back extractor, high-pressure heating reheater 30, and high-pressure steam cooler 44 before being supplied to the high-pressure heating header 46; the steam generated by the main steam source passes through the back extractor, medium-pressure heating reheater 31, and medium-pressure steam cooler 45 before being supplied to the medium-pressure heating header 47. This system can simultaneously raise the temperature of high-pressure and medium-pressure heating steam to the rated value, achieving precise heating. The steam cooler system raises the feedwater temperature and improves the efficiency of the Rankine cycle. At the same time, by utilizing the back extractor to recover the work capacity of the main steam, the heat of the boiler flue gas is recovered. This achieves combined high-pressure and medium-pressure heating while generating electricity, avoiding the energy level mismatch phenomenon of directly reducing the temperature and pressure of higher-parameter steam for heating, improving energy utilization efficiency, and realizing the cascade utilization of energy.

[0080] Optionally, a high-pressure heating desuperheating and pressure reducing valve 35 is also installed on the high-pressure heating pipeline P5. The high-pressure heating desuperheating and pressure reducing valve 35 is connected to an external superheating and desuperheating water source through the high-pressure heating desuperheating water pipeline P11. A high-pressure heating desuperheating water regulating valve 23 is installed on the high-pressure auxiliary heating desuperheating and pressure reducing valve 20 is connected to the high-pressure heating desuperheating water pipeline P11 through the high-pressure auxiliary heating desuperheating water pipeline P12. A high-pressure auxiliary heating desuperheating water regulating valve 22 is installed on the high-pressure auxiliary heating desuperheating water pipeline P12.

[0081] In this embodiment, the high-pressure heating desuperheating water pipeline P11 injects superheated desuperheating water to reduce the high-temperature steam in the high-pressure heating pipeline P5 to the temperature required by the user before supplying it to the high-pressure heating manifold 46; the high-pressure heating desuperheating water regulating valve 23 adjusts the flow rate of the desuperheating water to achieve precise temperature control of the high-temperature steam in the high-pressure heating pipeline P5; at the same time, the high-pressure auxiliary heating desuperheating water pipeline P12 injects superheated desuperheating water to reduce the main steam in the high-pressure auxiliary heating pipeline P14 to the temperature required by the user before supplying it to the high-pressure heating manifold 46; the high-pressure auxiliary heating desuperheating water regulating valve 22 adjusts the flow rate of the desuperheating water to achieve precise temperature control of the main steam in the high-pressure auxiliary heating pipeline P14.

[0082] Optionally, a medium-pressure heating desuperheating and pressure reducing valve 26 is also installed on the medium-pressure heating pipeline P8. The medium-pressure heating desuperheating and pressure reducing valve 26 is connected to an external reheating and desuperheating water source through the medium-pressure heating desuperheating water pipeline P9. A medium-pressure heating desuperheating water regulating valve 24 is installed on the medium-pressure heating desuperheating water pipeline P9. A medium-pressure auxiliary heating desuperheating and pressure reducing valve 28 is connected to the medium-pressure heating desuperheating water pipeline P9 through the medium-pressure auxiliary heating desuperheating water pipeline P10. A medium-pressure auxiliary heating desuperheating water regulating valve 25 is installed on the medium-pressure auxiliary heating desuperheating water pipeline P10.

[0083] In this embodiment, the medium-pressure heating desuperheating water pipeline P9 injects reheat desuperheating water to reduce the high-temperature steam in the medium-pressure heating pipeline P8 to the temperature required by the user before supplying it to the medium-pressure heating manifold 46; the medium-pressure heating desuperheating water regulating valve 24 adjusts the flow rate of the desuperheating water to achieve precise temperature control of the high-temperature steam in the medium-pressure heating pipeline P8; at the same time, the medium-pressure auxiliary heating desuperheating water pipeline P10 injects reheat desuperheating water to reduce the reheated steam in the medium-pressure auxiliary heating pipeline P13 to the temperature required by the user before supplying it to the medium-pressure heating manifold 46; the medium-pressure auxiliary heating desuperheating water regulating valve 25 adjusts the flow rate of the desuperheating water to achieve precise temperature control of the reheated steam in the medium-pressure auxiliary heating pipeline P13.

[0084] Optionally, the flue gas reheat system further includes: a reheating module, a high-pressure cylinder 48, and an intermediate-pressure cylinder 49. The steam outlets of the reheating module and the high-pressure reheating module are connected through a first pipeline 40. The reheating module and the high-pressure cylinder 48 are connected through a high-pressure cylinder exhaust pipeline P16. The intermediate-pressure reheating module and the high-pressure cylinder exhaust pipeline P16 are connected through a second pipeline 41. The high-pressure cylinder 48 is connected to an external main steam source through a main steam pipeline P1. The steam outlet of the reheating module is connected to the intermediate-pressure cylinder 49 through a reheating steam pipeline P15. There are also a high-pressure auxiliary heating pipeline P14 and an intermediate-pressure auxiliary heating pipeline P13. One end of the high-pressure auxiliary heating pipeline P14 is connected to the main steam pipeline P1, and the other end is connected to the high-pressure heating header 46. One end of the intermediate-pressure auxiliary heating pipeline P13 is connected to the reheating steam pipeline P15, and the other end is connected to the intermediate-pressure heating header 47.

[0085] Specifically, when the steam extraction unit stops operating, the following valves are closed: the pipelines originally connected to the steam extraction unit inlet, the steam extraction pipeline P3, the steam extraction pipeline P6, the steam inlet regulating valve 1, the steam extraction regulating valve 2, the steam exhaust check valve 33, and the steam exhaust shut-off valve 34. Simultaneously, the valves on the high-pressure steam cooler inlet pipeline P4, the medium-pressure steam cooler inlet pipeline P7, the high-pressure steam cooler steam inlet valve 13, and the medium-pressure steam cooler steam inlet valve 16 are closed. The valves on the high-pressure heating pipeline P5 and the medium-pressure heating pipeline P8 are also closed. The steam outlet valve 15 of the high-pressure steam cooler, the high-pressure heating desuperheating and pressure reducing valve 35, the steam outlet valve 17 of the medium-pressure steam cooler, and the medium-pressure heating desuperheating and pressure reducing valve 26 are closed. One main steam source supplies heat to the high-pressure heating header 46 through the high-pressure auxiliary heating pipeline P14, and the other source enters the high-pressure cylinder 48 from the main steam pipeline P1. Then, it operates in series with the medium-pressure heating reheater 31, the high-pressure heating reheater 30, and the reheat heater 32. Finally, it supplies heat to the medium-pressure heating header 47 through the medium-pressure auxiliary heating pipeline P13, ensuring the stable operation of the heating system.

[0086] In this embodiment, if the back-extraction machine malfunctions or stops operating for other reasons, and the operating mode is not changed, the high-pressure heating reheater 30 and the medium-pressure heating reheater 31 will dry-burn due to insufficient cooling. Therefore, it is necessary to connect the medium-pressure heating reheater 31 in series with the high-pressure heating reheater 30 and the reheat heater 32, and use the high-pressure cylinder exhaust steam in the high-pressure cylinder exhaust pipe P16 to cool the high-pressure heating reheater 30 and the medium-pressure heating reheater 31, preventing dry-burning of the high-pressure heating reheater 30 and the medium-pressure heating reheater 31, thus improving the safety of the system.

[0087] Optionally, the reheating module includes: a reheat heater inlet steam header 9, a reheat heater 32, and a reheat heater outlet steam header 6. The reheat heater inlet steam header 9 and the high-pressure reheater outlet steam header 7 are connected via a first pipeline 40, on which a high-pressure reheater outlet bypass valve 10 is installed. The reheat heater inlet steam header 9 and the high-pressure cylinder 48 are connected via a high-pressure cylinder exhaust pipeline P16, on which a high-pressure cylinder exhaust shut-off valve 11 is installed. The medium-pressure reheater inlet steam header 5 and the high-pressure cylinder exhaust pipeline P16 are connected via a second pipeline 41, on which a medium-pressure reheater inlet bypass valve 12 is installed. The reheat heater outlet steam header 6 is connected via a reheat steam pipeline P16. 15 is connected to the medium-pressure cylinder 49; a high-pressure auxiliary heating regulating valve 19 is installed at one end of the high-pressure auxiliary heating pipeline P14 near the main steam pipeline P1, and a high-pressure auxiliary heating shut-off valve 21 is installed at one end of the high-pressure auxiliary heating pipeline P14 near the high-pressure heating header 46; a high-pressure auxiliary heating desuperheating and pressure reducing valve 20 is installed between the high-pressure auxiliary heating shut-off valve 21 and the high-pressure auxiliary heating regulating valve 19; a medium-pressure auxiliary heating regulating valve 27 is installed at one end of the medium-pressure auxiliary heating pipeline P13 near the reheat steam pipeline P15, and a medium-pressure auxiliary heating shut-off valve 29 is installed at one end of the medium-pressure auxiliary heating pipeline P13 near the medium-pressure heating header 47; a medium-pressure auxiliary heating desuperheating and pressure reducing valve 28 is installed between the medium-pressure auxiliary heating shut-off valve 29 and the medium-pressure auxiliary heating regulating valve 27.

[0088] In this embodiment, by configuring the reheating module as a reheat heater inlet steam header 9, a reheat heater 32, and a reheat heater outlet steam header 6, it can be connected in series with the medium-pressure reheater 31 and the high-pressure reheater 30, thereby improving the safety of the system.

[0089] Optionally, both the high-pressure steam cooler 44 and the medium-pressure steam cooler 45 are surface heat exchangers, with steam arranged on the shell side and feedwater arranged on the tube side.

[0090] In this embodiment, the surface heat exchanger has the advantages of compact equipment, small machine room footprint, closed-loop circulation of cold and heat sources without pollution, and convenient operation and management. The steam is located in the shell side of the heat exchanger and can be cooled by water in the pipes.

[0091] Optionally, the pumping unit is coaxially connected to the generator 43, which is connected to the high-voltage transformer or to an electrochemical energy storage device.

[0092] In this embodiment, the electricity generated by the pump can be sent to the high-voltage transformer to reduce the plant's power consumption rate; or it can be used for electrochemical energy storage to participate in grid frequency regulation, which not only improves energy utilization but also benefits the environment.

[0093] Based on the same inventive concept, please refer to Figure 1 The present invention also provides an operation method for a high- and medium-pressure combined heating system based on a back-extraction fan, applicable to the aforementioned high- and medium-pressure combined heating system based on a back-extraction fan, the method comprising:

[0094] When the back-extraction machine is in operation, control the operation of the back-extraction machine and connect the back-extraction machine steam inlet pipeline, back-extraction machine steam extraction pipeline, high-pressure steam cooler steam inlet pipeline, high-pressure heating pipeline, high-pressure heating desuperheating water pipeline, back-extraction machine exhaust pipeline, medium-pressure steam cooler steam inlet pipeline, medium-pressure heating pipeline, and medium-pressure heating desuperheating water pipeline.

[0095] The high-pressure heating steam process is as follows: the steam from the main steam source passes through the steam inlet pipeline of the back extractor, the back extractor, the steam extraction pipeline of the back extractor, the high-pressure heating reheat module, the steam inlet pipeline of the high-pressure steam cooler, the high-pressure steam cooler, and the high-pressure heating pipeline before entering the high-pressure heating header.

[0096] The medium-pressure heating steam process is as follows: the steam from the main steam source passes through the steam inlet pipeline of the extraction back machine, the extraction back machine, the steam exhaust pipeline of the extraction back machine, the medium-pressure heating reheat module, the steam inlet pipeline of the medium-pressure steam cooler, the medium-pressure steam cooler, and the medium-pressure heating pipeline before entering the medium-pressure heating header.

[0097] Understandably, the specific structure of the high- and medium-pressure combined heating system based on the back-extraction machine refers to the above embodiments. Since the operation method of this high- and medium-pressure combined heating system based on the back-extraction machine adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0098] Reference Figure 2 , Figure 2 This is a schematic diagram of the pipeline in the high- and medium-pressure combined heating system based on the back-extraction machine of the present invention, with the back-extraction machine in a stopped operating state.

[0099] Based on the same inventive concept, the present invention also provides an operation method for a high- and medium-pressure combined heating system based on a back-extraction compressor, applicable to the aforementioned high- and medium-pressure combined heating system based on a back-extraction compressor, the method comprising:

[0100] When the back-extraction machine stops operating, control the back-extraction machine to stop operating, close the back-extraction machine steam inlet pipeline, back-extraction machine steam extraction pipeline, high-pressure steam cooler steam inlet pipeline, high-pressure heating pipeline, high-pressure heating desuperheating water pipeline, back-extraction machine exhaust pipeline, medium-pressure steam cooler steam inlet pipeline, medium-pressure heating pipeline, medium-pressure heating desuperheating water pipeline, and high-pressure cylinder exhaust pipeline, and open the first pipeline, second pipeline, and third pipeline, and the medium-pressure heating reheater and high-pressure heating reheater and reheat heater are connected in series;

[0101] The high-pressure heating steam process is as follows: the steam from the main steam source passes through the main steam pipeline and the high-pressure auxiliary heating pipeline in sequence before entering the high-pressure heating header.

[0102] The medium-pressure heating steam process is as follows: the steam from the main steam source passes through the main steam pipeline, the high-pressure cylinder, the high-pressure cylinder exhaust pipeline, the medium-pressure heating reheat module, the high-pressure heating reheat module, the reheat heating module, the reheat steam pipeline, and the medium-pressure auxiliary heating pipeline before entering the medium-pressure heating header.

[0103] The process of the medium-pressure heating reheat module, the high-pressure heating reheat module, and the reheating module operating in series is as follows: the steam from the main steam source passes through the main steam pipeline, the high-pressure cylinder, the high-pressure cylinder exhaust pipeline, the medium-pressure heating reheat module, the high-pressure heating reheat module, the reheating module, the reheat steam pipeline, and the medium-pressure auxiliary heating pipeline before entering the medium-pressure cylinder.

[0104] Understandably, the specific structure of the high- and medium-pressure combined heating system based on the back-extraction machine refers to the above embodiments. Since the operation method of this high- and medium-pressure combined heating system based on the back-extraction machine adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0105] To facilitate understanding of the technical solution of the present invention, a specific embodiment is given below:

[0106] Taking a supercritical 670MW unit as an example, the technical boundary parameters are as follows: pipeline efficiency is 99%, boiler efficiency is 94.5%, and plant power consumption is 4.5%. The operating data under different main steam flow conditions are shown in the table below:

[0107] As can be seen from the data in operating condition 5 in the table, when the main steam flow rate is 367t / h (20% THA), the standard coal consumption rate for power supply is only 301.59g / kWh, indicating that the heating system is economically efficient.

[0108] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A high and medium pressure combined heat supply system based on a back-pumping machine, characterized in that, The utility model relates to a back pressure turbine system, a flue gas reheating system and a high-medium pressure combined heating system. The back pressure turbine system comprises a generator and a back pressure turbine electrically connected with the generator, the back pressure turbine is communicated with an external main steam source through a back pressure turbine inlet steam pipeline, and a back pressure turbine inlet steam regulating valve is arranged on the back pressure turbine inlet steam pipeline. The flue gas reheating system comprises a high-pressure heating reheating module and a medium-pressure heating reheating module, the high-pressure heating reheating module is communicated with the back pressure turbine through a back pressure turbine steam extraction pipeline and is used for reheating steam extracted by the back pressure turbine, and the medium-pressure heating reheating module is communicated with the back pressure turbine through a back pressure turbine exhaust steam pipeline and is used for reheating exhaust steam of the back pressure turbine. The high-medium pressure combined heating system comprises a high-pressure steam cooler, a medium-pressure steam cooler, a high-pressure heating header and a medium-pressure heating header, one end of the high-pressure steam cooler is communicated with an outlet of the high-pressure heating reheating module through a high-pressure steam cooler inlet steam pipeline, the other end is communicated with the high-pressure heating header, an inlet of the high-pressure heating reheating module is communicated with the medium-pressure steam cooler through a third pipeline, one end of the medium-pressure steam cooler is communicated with an outlet of the medium-pressure heating reheating module through a medium-pressure steam cooler inlet steam pipeline, and the other end is communicated with the medium-pressure heating header; the medium-pressure steam cooler and the high-pressure steam cooler are both communicated with a steam cooler feedwater main line, the steam cooler feedwater main line is communicated with an external water source, and the medium-pressure steam cooler is arranged close to the external water source. The high-pressure heating reheating module comprises a high-pressure heating reheating device, and the medium-pressure heating reheating module comprises a medium-pressure heating reheating device; when the back pressure turbine is normally put into operation, the high-pressure heating reheating device is cooled by back pressure turbine steam in the back pressure turbine steam extraction pipeline, and the medium-pressure heating reheating device is cooled by back pressure turbine exhaust steam in the back pressure turbine exhaust steam pipeline.

2. The back-flushing based high and medium pressure combined heat supply system according to claim 1, characterized in that, The high-pressure heating reheating module comprises a high-pressure heating reheating device inlet steam header and a high-pressure heating reheating device outlet steam header. The medium-pressure heating reheating module comprises a medium-pressure heating reheating device inlet steam header and a medium-pressure heating reheating device outlet steam header. The back pressure turbine is communicated with the high-pressure heating reheating device inlet steam header through a back pressure turbine steam extraction pipeline, a back pressure turbine steam extraction regulating valve is arranged on the back pressure turbine steam extraction pipeline, the back pressure turbine is communicated with the medium-pressure heating reheating device inlet steam header through a back pressure turbine exhaust steam pipeline, and a back pressure turbine exhaust steam check valve is arranged on the back pressure turbine exhaust steam pipeline. The high-pressure steam cooler is communicated with the high-pressure heat supply reheater outlet steam header through a high-pressure steam cooler inlet pipe, the high-pressure heat supply reheater inlet steam header is communicated with the medium-pressure steam cooler inlet pipe through a third pipe, a high-pressure heat supply reheater inlet bypass valve is arranged on the third pipe, a high-pressure steam cooler steam inlet valve is arranged on the high-pressure steam cooler inlet pipe, a high-pressure steam cooler steam outlet valve is arranged on the high-pressure heat supply pipe, the medium-pressure heat supply reheater outlet steam header is communicated with the medium-pressure steam cooler through a medium-pressure steam cooler inlet pipe, a medium-pressure steam cooler steam inlet valve is arranged on the medium-pressure steam cooler inlet pipe, a medium-pressure steam cooler steam outlet valve is arranged on the medium-pressure heat supply pipe, the medium-pressure steam cooler and the high-pressure steam cooler are communicated with a steam cooler feed water main line, the steam cooler feed water main line is communicated with an external water source, the medium-pressure steam cooler is arranged close to the external water source, a medium-pressure steam cooler water side inlet three-way valve is arranged on the water inlet side of the medium-pressure steam cooler, a high-pressure steam cooler water side outlet valve is arranged on the water outlet side of the high-pressure steam cooler, and the high-pressure steam cooler water side outlet valve is communicated with the medium-pressure steam cooler water side inlet three-way valve through a steam cooler feed water bypass.

3. The back-flushing based high and medium pressure combined heat supply system according to claim 1, characterized in that, A high-pressure heat supply temperature and pressure reducing valve is further arranged on the high-pressure heat supply pipe, the high-pressure heat supply temperature and pressure reducing valve is communicated with an external superheated temperature reducing water source through a high-pressure heat supply temperature reducing water pipe, and a high-pressure heat supply temperature reducing water regulating valve is arranged on the high-pressure heat supply temperature reducing water pipe. A high-pressure auxiliary heat supply temperature and pressure reducing valve is communicated with the high-pressure heat supply temperature reducing water pipe through a high-pressure auxiliary heat supply temperature reducing water pipe, and a high-pressure auxiliary heat supply temperature reducing water regulating valve is arranged on the high-pressure auxiliary heat supply temperature reducing water pipe.

4. The back-flashing based high and medium pressure combined heat supply system according to claim 3, characterized in that, A medium-pressure heat supply temperature and pressure reducing valve is further arranged on the medium-pressure heat supply pipe, the medium-pressure heat supply temperature and pressure reducing valve is communicated with an external reheated temperature reducing water source through a medium-pressure heat supply temperature reducing water pipe, and a medium-pressure heat supply temperature reducing water regulating valve is arranged on the medium-pressure heat supply temperature reducing water pipe. A medium-pressure auxiliary heat supply temperature and pressure reducing valve is communicated with the medium-pressure heat supply temperature reducing water pipe through a medium-pressure auxiliary heat supply temperature reducing water pipe, and a medium-pressure auxiliary heat supply temperature reducing water regulating valve is arranged on the medium-pressure auxiliary heat supply temperature reducing water pipe.

5. The back-flashing based high and medium pressure combined heat supply system according to claim 1, characterized in that, The flue gas reheating system further comprises a reheating heating module, a high-pressure cylinder and a medium-pressure cylinder, the reheating heating module and the steam outlet of the high-pressure heat supply reheating module are communicated through a first pipe, the reheating heating module and the high-pressure cylinder are communicated through a high-pressure cylinder exhaust pipe, the medium-pressure heat supply reheating module and the high-pressure cylinder exhaust pipe are communicated through a second pipe, the high-pressure cylinder is communicated with an external main steam source through a main steam pipe, the steam outlet of the reheating heating module is communicated with the medium-pressure cylinder through a reheated steam pipe; A high-pressure auxiliary heat supply pipe, one end of the high-pressure auxiliary heat supply pipe is communicated with the main steam pipe, and the other end is communicated with the high-pressure heat supply header; A medium-pressure auxiliary heat supply pipe, one end of the medium-pressure auxiliary heat supply pipe is communicated with the reheated steam pipe, and the other end is communicated with the medium-pressure heat supply header.

6. The back-flashing based high and medium pressure combined heat supply system according to claim 5, characterized in that, The reheating heating module comprises a reheating heater inlet steam header, a reheating heater, a reheating heater outlet steam header, the reheating heater inlet steam header and the high-pressure heating reheater outlet steam header are communicated through a first pipeline, a high-pressure heating reheater outlet bypass valve is arranged on the first pipeline, the reheating heater inlet steam header and the high-pressure cylinder are communicated through a high-pressure cylinder exhaust pipeline, a high-pressure cylinder exhaust stop valve is arranged on the high-pressure cylinder exhaust pipeline, the medium-pressure heating reheater inlet steam header and the high-pressure cylinder exhaust pipeline are communicated through a second pipeline, a medium-pressure heating reheater inlet bypass valve is arranged on the second pipeline, and the reheating heater outlet steam header is communicated with the medium-pressure cylinder through a reheating steam pipeline. A high-pressure auxiliary heating regulating valve is arranged on one end of the high-pressure auxiliary heating pipeline close to the main steam pipeline, a high-pressure auxiliary heating stop valve is arranged on one end of the high-pressure auxiliary heating pipeline close to the high-pressure heating header, and a high-pressure auxiliary heating temperature and pressure reducing valve is arranged between the high-pressure auxiliary heating stop valve and the high-pressure auxiliary heating regulating valve. A medium-pressure auxiliary heating regulating valve is arranged on one end of the medium-pressure auxiliary heating pipeline close to the reheating steam pipeline, a medium-pressure auxiliary heating stop valve is arranged on one end of the medium-pressure auxiliary heating pipeline close to the medium-pressure heating header, and a medium-pressure auxiliary heating temperature and pressure reducing valve is arranged between the medium-pressure auxiliary heating stop valve and the medium-pressure auxiliary heating regulating valve.

7. The back-flushing machine based high and medium pressure combined heat supply system according to any one of claims 1-6, characterized in that, The high-pressure steam cooler and the medium-pressure steam cooler are both surface heat exchangers, steam is arranged in the shell side of the heat exchanger, and feed water is arranged in the tube side of the heat exchanger.

8. The back-flushing based high and medium pressure combined heat supply system according to any one of claims 1-6, characterized in that, The back-pumping machine is coaxially connected with the generator, and the generator is connected with a high-voltage transformer or an electrochemical energy storage device.

9. The operation method of the high and medium pressure combined heat supply system based on the back-draft machine, applied to the high and medium pressure combined heat supply system based on the back-draft machine of claim 1, characterized in that, The method comprises the following steps: In the working condition that the back-pumping machine is in operation, the back-pumping machine is controlled to operate, the back-pumping machine steam inlet pipeline, the back-pumping machine steam extraction pipeline, the high-pressure steam cooler steam inlet pipeline, the high-pressure heating pipeline, the high-pressure heating temperature reducing water pipeline, the back-pumping machine steam exhaust pipeline, the medium-pressure steam cooler steam inlet pipeline, the medium-pressure heating pipeline and the medium-pressure heating temperature reducing water pipeline are turned on, and the first pipeline, the second pipeline and the third pipeline are turned off. The high-pressure heating steam flow process is as follows: steam of the main steam source enters the high-pressure heating header through the back-pumping machine steam inlet pipeline, the back-pumping machine, the back-pumping machine steam extraction pipeline, the high-pressure heating reheating module, the high-pressure steam cooler steam inlet pipeline, the high-pressure steam cooler and the high-pressure heating pipeline in sequence. The medium-pressure heating steam flow process is as follows: steam of the main steam source enters the medium-pressure heating header through the back-pumping machine steam inlet pipeline, the back-pumping machine, the back-pumping machine steam exhaust pipeline, the medium-pressure heating reheating module, the medium-pressure steam cooler steam inlet pipeline, the medium-pressure steam cooler and the medium-pressure heating pipeline in sequence.

10. The operation method of the high and medium pressure combined heat supply system based on the back-draft machine, applied to the high and medium pressure combined heat supply system based on the back-draft machine of claim 5, characterized in that, The method comprises the following steps: In the working condition that the back-pumping machine is stopped, the back-pumping machine is controlled to be stopped, the back-pumping machine steam inlet pipeline, the back-pumping machine steam extraction pipeline, the high-pressure steam cooler steam inlet pipeline, the high-pressure heating pipeline, the high-pressure heating temperature reducing water pipeline, the back-pumping machine steam exhaust pipeline, the medium-pressure steam cooler steam inlet pipeline, the medium-pressure heating pipeline, the medium-pressure heating temperature reducing water pipeline and the high-pressure cylinder exhaust pipeline are closed, the first pipeline, the second pipeline and the third pipeline are turned on, and the medium-pressure heating reheater, the high-pressure heating reheater and the reheating heater are connected in series and operated. The high-pressure heat supply steam process is that steam from a main steam source enters a high-pressure heat supply header through a main steam pipeline and a high-pressure auxiliary heat supply pipeline in sequence; The medium-pressure heat supply steam process is that steam from the main steam source enters a medium-pressure heat supply header through a main steam pipeline, a high-pressure cylinder, a high-pressure cylinder exhaust pipeline, a medium-pressure heat supply reheating module, a high-pressure heat supply reheating module, a reheating heating module, a reheated steam pipeline and a medium-pressure auxiliary heat supply pipeline in sequence; The process of the medium-pressure heat supply reheating module, the high-pressure heat supply reheating module and the reheating heating module operating in series is that steam from the main steam source enters a medium-pressure cylinder through a main steam pipeline, a high-pressure cylinder, a high-pressure cylinder exhaust pipeline, a medium-pressure heat supply reheating module, a high-pressure heat supply reheating module, a reheating heating module and a reheated steam pipeline in sequence.

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