High and medium pressure combined heat supply system and operation method thereof

Abstract

The application provides a high-medium pressure combined heat supply system and a running method thereof, wherein the high-medium pressure combined heat supply system comprises a high pressure cylinder, a medium pressure cylinder, a high pressure heat supply switching system, a medium pressure heat supply switching system, a flexible flue gas reheating system and a steam reheating system. When the coal power frequently adjusts the peak, the application can effectively ensure the stability of the heat supply by flexibly switching the heat supply steam source. Moreover, the steam sources of the high pressure heat supply pipeline and the medium pressure heat supply pipeline are provided by the high pressure cylinder, which can avoid the problems of low efficiency of the medium pressure cylinder, low overall heat supply economy and waste of energy and resources caused by the conventional medium regulating valve throttling heat supply mode. Furthermore, the flexible flue gas reheating system can reasonably distribute the steam flow and appropriately input water spray cooling to improve the high pressure heat supply steam to the rated heat supply temperature, and realize the safe operation and non-disturbance switching of the heat supply and the pure condensing working condition.

Description

Technical Field

[0001] This invention relates to the field of combined heat and power (CHP), specifically to a high- and medium-pressure combined heating system and a method for operating such a system. Background Technology

[0002] With the introduction of the "dual carbon" target, my country's installed capacity of new energy power plants is rapidly increasing, and a new power system based on new energy will be gradually built. Thermal power units will also gradually shift from being the main power source to a deep peak-shaving power source. Combined heat and power (CHP) is an important means of efficient coal utilization, with significant advantages in energy conservation and emission reduction, and will become an important direction for the future transformation and development of thermal power units. CHP units provide heating for residential and industrial use. Residential heating systems include extraction steam heating, low-grade heat energy staged 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 generally adopts extraction steam (such as main steam, primary extraction, and reheat steam) desuperheating and pressure-reducing heating schemes.

[0003] For the higher-energy-level steam extraction (such as main steam) desuperheating and pressure-reducing heating schemes commonly used in industrial heating, the use of extraction points with higher pressure or temperature levels, followed by desuperheating and pressure reduction before supplying heat to users, results in large system losses and low heating economics, contradicting the energy-saving goals of national and corporate development. For heating schemes that extract steam from hot or cold reheat through intermediate control valves, under high-flow heating conditions, throttling of the intermediate control valves often leads to a reduction of more than 10% in the efficiency of the intermediate-pressure cylinder, resulting in low overall heating economics. As coal-fired power will shift from being the main power source to a supporting and regulating power source that emphasizes both electricity and power generation, the new power system places increasingly higher demands on the peak-shaving capacity of heating units. However, due to the current "heat-driven power generation" operation mode, the peak-shaving capacity of existing cogeneration units is limited, becoming one of the factors restricting the construction of the new power system.

[0004] In summary, existing heating solutions cannot be flexibly adjusted under conditions of high-flow heating and frequent peak shaving, resulting in limited electrical load of cogeneration units during heating operations. At the same time, conventional intermediate-pressure cylinder efficiency is reduced due to the throttling and regulation of the intermediate-pressure valve, leading to low overall heating economy and waste of energy and resources. Summary of the Invention

[0005] The purpose of this invention is to provide a high- and medium-pressure combined heating system and its operation method to solve the problem that existing heating schemes cannot be flexibly adjusted under high-flow heating conditions, resulting in low overall heating economy and waste of energy and resources.

[0006] To achieve the above objectives, embodiments of the present invention provide a combined high-pressure and medium-pressure heating system applied to a cogeneration unit. The system includes: a high-pressure cylinder, a medium-pressure cylinder, a flexible flue gas reheat system, a reheat steam system, a high-pressure heating header, a medium-pressure heating header, and a high-pressure heater. The exhaust end of the high-pressure cylinder is connected to the input end of the reheat steam system and the input end of the flexible flue gas reheat system, respectively. The input end of the reheat steam system is also connected to the exhaust end of the medium-pressure cylinder. The output end of the reheat steam system is connected to the input end of the high-pressure heater and the medium-pressure heating header, respectively. The output end of the flexible flue gas reheat system is connected to the steam inlet end of the medium-pressure cylinder and the high-pressure heating header, respectively.

[0007] The high-pressure cylinder is used to generate zero-extraction steam, single-extraction heating steam and cold reheat steam, and delivers the cold reheat steam to the flexible flue gas reheat system.

[0008] When the system is under high electrical load heating conditions, the high-pressure cylinder is also used to transport the first-stage heating steam to the flexible flue gas reheat system and the cold reheat steam to the reheat steam system; the intermediate-pressure cylinder is used to generate the third-stage steam and transport it to the reheat steam system; the flexible flue gas reheat system is used to heat the first-stage heating steam and then transport it to the high-pressure heating header, and to heat the cold reheat steam and then transport it to the intermediate-pressure cylinder; the reheat steam system is used to heat the cold reheat steam using the third-stage steam, and then transport the heated cold reheat steam to the intermediate-pressure heating header, and finally transport the cooled third-stage steam to the high-pressure heater;

[0009] When the system is operating under medium-load heating conditions, the high-pressure cylinder is also used to deliver zero-extraction steam to the flexible flue gas reheat system and cold reheat steam to the reheat steam system; the flexible flue gas reheat system is also used to deliver the zero-extraction steam to the high-pressure heating header after heating and to the medium-pressure cylinder after heating the cold reheat steam; the reheat steam system is also used to deliver the cold reheat steam to the medium-pressure heating header.

[0010] When the system is in a low electrical load heating condition, the high-pressure cylinder is also used to transport zero-extraction steam to the flexible flue gas reheat system and to transport first-extraction heating steam to the reheat steam system; the flexible flue gas reheat system is also used to transport the zero-extraction steam to the high-pressure heating header after heating it and to transport the cold reheat steam to the medium-pressure cylinder; the reheat steam system is also used to transport the first-extraction heating steam to the medium-pressure heating header after heating it.

[0011] When the system is in pure condensation mode, the flexible flue gas reheat system is also used to heat the cold resteam and deliver it to the intermediate pressure cylinder.

[0012] The system further includes: a high-pressure heating switching system and a medium-pressure heating switching system; the input end of the high-pressure heating switching system is connected to the zero-extraction exhaust end, the first-extraction heating exhaust end, and the cold reheating exhaust end of the high-pressure cylinder, respectively; the output end of the high-pressure heating switching system is connected to the input end of the flexible flue gas reheating system, the input end of the flexible flue gas reheating system is also connected to the cold reheating exhaust end of the high-pressure cylinder, the output end of the flexible flue gas reheating system is connected to the medium-pressure cylinder and the high-pressure heating header, the input end of the medium-pressure heating switching system is connected to the first-extraction heating exhaust end and the cold reheating exhaust end of the high-pressure cylinder, the output end of the medium-pressure heating switching system is connected to the input end of the reheat steam system, and the input end of the reheat steam system is also connected to the third-extraction exhaust end of the medium-pressure cylinder, reheating... The output of the steam system is connected to the input of the high-pressure heater and the medium-pressure heating header, respectively. When the system is under high electrical load heating conditions, the high-pressure cylinder delivers first-stage heating steam to the flexible flue gas reheat system through the high-pressure heating switching system, and delivers cold reheat steam to the reheat steam system through the medium-pressure heating switching system. When the system is under medium electrical load heating conditions, the high-pressure cylinder delivers zero-stage steam to the flexible flue gas reheat system through the high-pressure heating switching system, and delivers cold reheat steam to the reheat steam system through the medium-pressure heating switching system. When the system is under low electrical load heating conditions, the high-pressure cylinder delivers zero-stage steam to the flexible flue gas reheat system through the high-pressure heating switching system, and delivers first-stage heating steam to the reheat steam system through the medium-pressure heating switching system.

[0013] The high-pressure heating switching system includes: a zero-extraction to high-pressure heating pipeline, a first-extraction to high-pressure heating pipeline, and a cold reheat to the newly added low-temperature reheater pipeline; the input ends of the zero-extraction to high-pressure heating pipeline, the first-extraction to high-pressure heating pipeline, and the cold reheat to the newly added low-temperature reheater pipeline are respectively connected to the zero-extraction exhaust end, the first-extraction heating exhaust end, and the cold reheating exhaust end of the high-pressure cylinder;

[0014] The flexible flue gas reheat system includes: a cold reheat to the original low-temperature reheater pipeline, a new low-temperature reheating assembly, the original low-temperature reheating assembly, a final-stage reheating assembly, a high-pressure heating pipeline, and a new low-temperature reheater to the final-stage reheater pipeline. The input end of the cold reheat to the original low-temperature reheater pipeline is connected to the input end of the cold reheat to the new low-temperature reheater pipeline; the output end of the cold reheat to the original low-temperature reheater pipeline is connected to the input end of the original low-temperature reheating assembly; and the input end of the final-stage reheating assembly is connected to the output end of the original low-temperature reheating assembly and the new low-temperature reheater. The output end of the reheater to the final stage reheater pipeline is connected, the output end of the final stage reheat assembly is connected to the intermediate pressure cylinder, the output end of the newly added low temperature reheat assembly is connected to the input end of the newly added low temperature reheater to the final stage reheater pipeline and the input end of the high pressure heating pipeline, the input end of the newly added low temperature reheat assembly is connected to the output end of the zero-extraction to the high pressure heating pipeline, the output end of the first-extraction to the high pressure heating pipeline and the output end of the cold reheat to the newly added low temperature reheater pipeline, and the output end of the high pressure heating pipeline is connected to the high pressure heating header.

[0015] Optionally, the reheat system includes: a medium-pressure heating pipeline, a steam heat exchanger, a three-stage extraction pipeline to the steam heat exchanger, and a steam heat exchanger to the high-pressure heater pipeline;

[0016] The input end of the steam heat exchanger is connected to the output end of the medium-pressure heating switching system and the output end of the three-stage extraction to steam heat exchanger pipeline, respectively. The output end of the steam heat exchanger is connected to the input end of the steam heat exchanger to high-pressure heater pipeline and the input end of the medium-pressure heating pipeline. The input end of the three-stage extraction to steam heat exchanger pipeline is connected to the three-stage extraction exhaust end of the medium-pressure cylinder. The output end of the steam heat exchanger to high-pressure heater pipeline is connected to the input end of the high-pressure heater. The output end of the medium-pressure heating pipeline is connected to the medium-pressure heating header.

[0017] Optionally, the medium-pressure heating switching system includes: a pipeline drawn from the medium-pressure heating system and a pipeline drawn from the cold source to the medium-pressure heating system;

[0018] The input end of the first extraction to medium-pressure heating pipeline is connected to the first extraction heating exhaust end of the high-pressure cylinder, the input end of the cold reheat to medium-pressure heating pipeline is connected to the cold reheating exhaust end of the high-pressure cylinder, and the output ends of the first extraction to medium-pressure heating pipeline and the cold reheat to medium-pressure heating pipeline are both connected to the input end of the steam heat exchanger.

[0019] In a second aspect, embodiments of the present invention also provide a method for combined high- and medium-pressure heating, implemented based on the aforementioned combined high- and medium-pressure heating system, the method comprising:

[0020] When the system is operating under high electrical load heating conditions, close the zero-extraction to high-pressure heating pipeline, cold re-extraction to the newly added low-temperature reheater pipeline, first-extraction to medium-pressure heating pipeline, and the newly added low-temperature reheater to the final stage reheater pipeline; open the first-extraction to high-pressure heating pipeline, cold re-extraction to the original low-temperature reheater pipeline, cold re-extraction to medium-pressure heating pipeline, medium-pressure heating pipeline, third-extraction to steam heat exchanger pipeline, steam heat exchanger to high-pressure heater pipeline, and high-pressure heating pipeline.

[0021] When the system is operating under medium power load heating conditions, close the pipeline from the first extraction to the high-pressure heating pipeline, the cold reheat to the newly added low-temperature reheater pipeline, the first extraction to the medium-pressure heating pipeline, and the pipeline from the newly added low-temperature reheater to the final stage reheater; open the pipeline from the zero extraction to the high-pressure heating pipeline, the cold reheat to the original low-temperature reheater pipeline, the cold reheat to the medium-pressure heating pipeline, the medium-pressure heating pipeline, the third extraction to the steam heat exchanger pipeline, the steam heat exchanger to the high-pressure heater pipeline, and the high-pressure heating pipeline.

[0022] When the system is operating under low electrical load heating conditions, close the pipeline from the first extraction to the high-pressure heating pipeline, the cold reheat to the newly added low-temperature reheater pipeline, the cold reheat to the medium-pressure heating pipeline, and the pipeline from the newly added low-temperature reheater to the final stage reheater; open the pipeline from the zero extraction to the high-pressure heating pipeline, the first extraction to the medium-pressure heating pipeline, the cold reheat to the original low-temperature reheater pipeline, the medium-pressure heating pipeline, the third extraction to the steam heat exchanger pipeline, the steam heat exchanger to the high-pressure heater pipeline, and the high-pressure heating pipeline.

[0023] When the system is operating under pure condensation conditions, close the zero-extraction to high-pressure heating pipeline, the first-extraction to high-pressure heating pipeline, the first-extraction to medium-pressure heating pipeline, the cold re-extraction to medium-pressure heating pipeline, the medium-pressure heating pipeline, and the high-pressure heating pipeline. Open the cold re-extraction to the newly added low-temperature reheater pipeline, the cold re-extraction to the original low-temperature reheater pipeline, the third-extraction to the steam heat exchanger pipeline, the steam heat exchanger to the high-pressure heater pipeline, and the newly added low-temperature reheater to the final stage reheater pipeline.

[0024] In this embodiment of the invention, the high-pressure heating system supplies heat through a zero-extraction to high-pressure heating pipeline, a primary extraction to high-pressure heating pipeline, and a newly added low-temperature reheater pipeline. The medium-pressure heating system supplies heat through a primary extraction to medium-pressure heating pipeline and a cold reheat to medium-pressure heating pipeline. During frequent peak-shaving operation of coal-fired power plants, the stability of heating can be effectively ensured by flexibly switching the heating steam source. Moreover, the steam source for both high-pressure and medium-pressure heating pipelines is provided by the high-pressure cylinder, which avoids the problem of reduced efficiency of the medium-pressure cylinder caused by the conventional medium-pressure regulating valve throttling and regulation heating method, resulting in low overall heating economy and waste of energy and resources. Furthermore, the flexible flue gas reheat system, through reasonable allocation of steam flow and appropriate injection of water for desuperheating, can achieve safe operation and seamless switching between heating and pure condensation conditions while raising the high-pressure heating steam to the rated heating temperature.

[0025] 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

[0026] 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:

[0027] Figure 1 This is a schematic diagram of the operation of the high- and medium-pressure combined heating system provided in the first embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the operation of the high- and medium-pressure combined heating system provided in the second embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the operation of the high- and medium-pressure combined heating system provided in the third embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of the operation of the high- and medium-pressure combined heating system provided in the fourth embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures

[0032] 1. Add a new low-temperature reheater; 2. The original low-temperature reheater;

[0033] 3. Final stage reheater; 4. Steam heat exchanger;

[0034] P1, zero-level extraction to high-pressure heating pipeline; P2, one-level extraction to high-pressure heating pipeline;

[0035] P3, cold reheat to newly added low-temperature reheater pipeline; P4, extraction to medium-pressure heating pipeline;

[0036] P5, cold reheat to the original low-temperature reheater pipeline; P6, cold reheat to medium-pressure heating pipeline;

[0037] P7, medium-pressure heating pipeline; P8, three-stage extraction to steam heat exchanger pipeline;

[0038] P9, Steam heat exchanger to high-pressure heater pipeline; P10, High-pressure heating pipeline;

[0039] P11. Add piping from the low-temperature reheater to the final stage reheater;

[0040] T1, Zero-draw to high-pressure heating electric gate valve; N1, Zero-draw to high-pressure heating pneumatic check valve;

[0041] V1, Zero-draw to high-pressure heating rapid-closing flow regulating valve;

[0042] T2, one-way draw to high-pressure heating electric gate valve; N2, one-way draw to high-pressure heating pneumatic check valve;

[0043] V2, One-time draw to high-pressure heating quick-closing flow regulating valve;

[0044] T3, cold reheater with newly added low-temperature reheater electric gate valve;

[0045] N3, cold reheater with newly added low-temperature reheater pneumatic check valve;

[0046] V3, Cold Reheater Quick-Close Flow Control Valve for Newly Added Low-Temperature Reheater;

[0047] T4, One-way draw to medium-pressure heating electric gate valve; N4, One-way draw to medium-pressure heating pneumatic check valve;

[0048] V4, quick-closing flow regulating valve for medium-pressure heating; T5, electric gate valve for cold reheating to medium-pressure heating;

[0049] N5. Cold return to medium-pressure heating pneumatic check valve;

[0050] V5, Cold-to-medium-pressure heating quick-closing flow regulating valve; T6, High-pressure heating electric gate valve;

[0051] N6. High-pressure heating pneumatic check valve;

[0052] N7. Add a pneumatic check valve from the low-temperature reheater to the final stage reheater.

[0053] T7, Added electric gate valve from the low-temperature reheater to the final stage reheater; N8, High-pressure exhaust check valve;

[0054] T8, electric gate valve for three-stage extraction to steam heat exchanger;

[0055] T9, Electric gate valve from steam heat exchanger to high-pressure heater;

[0056] T10, medium-pressure heating electric gate valve. Detailed Implementation

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Reference Figure 1This invention provides a combined high- and medium-pressure heating system for use in cogeneration units. The system includes: a high-pressure cylinder, an intermediate-pressure cylinder, a flexible flue gas reheat system, a reheat steam system, a high-pressure heating header, an intermediate-pressure heating header, and a high-pressure heater. The exhaust end of the high-pressure cylinder is connected to the input ends of both the reheat steam system and the flexible flue gas reheat system. The input end of the reheat steam is also connected to the exhaust end of the third extraction section of the intermediate-pressure cylinder. The output end of the reheat steam system is connected to the input end of the high-pressure heater and the intermediate-pressure heating header. The output end of the flexible flue gas reheat system is connected to the steam inlet of the intermediate-pressure cylinder and the high-pressure heating header. The system is interconnected; the high-pressure cylinder generates zero-extraction steam, first-extraction heating steam, and cold reheat steam, and delivers the cold reheat steam to the flexible flue gas reheat system; when the system is under high electrical load heating conditions, the high-pressure cylinder also delivers first-extraction heating steam to the flexible flue gas reheat system and cold reheat steam to the reheat steam system; the intermediate-pressure cylinder generates third-extraction steam and delivers it to the reheat steam system; the flexible flue gas reheat system heats the first-extraction heating steam before delivering it to the high-pressure heating header, and heats the cold reheat steam before delivering it to the intermediate-pressure cylinder; the reheat steam system uses the third-extraction steam to heat the cold reheat steam. The heated cold reheat steam is delivered to the medium-pressure heating header, and the cooled triple-extraction steam is delivered to the high-pressure heater. When the high- and medium-pressure combined heating system is under medium-electricity load heating conditions, the high-pressure cylinder is also used to deliver zero-extraction steam to the flexible flue gas reheat system and cold reheat steam to the reheat steam system. The flexible flue gas reheat system is also used to deliver the heated zero-extraction steam to the high-pressure heating header and the heated cold reheat steam to the medium-pressure cylinder. The reheat steam system is also used to deliver cold reheat steam to the medium-pressure heating header. When the high- and medium-pressure combined heating system is under low-electricity load heating conditions... At the same time, the high-pressure cylinder is also used to transport zero-extraction steam to the flexible flue gas reheat system and to transport first-extraction heating steam to the reheat steam system; the flexible flue gas reheat system is also used to transport zero-extraction steam to the high-pressure heating header after heating and to transport cold reheat steam to the intermediate-pressure cylinder; the reheat steam system is also used to transport first-extraction heating steam to the intermediate-pressure heating header after heating; when the high-medium-high-pressure combined heating system is in pure condensation condition, the flexible flue gas reheat system is also used to transport cold reheat steam to the intermediate-pressure cylinder after heating; the high-medium-high-pressure combined heating system also includes: a high-pressure heating switching system and an intermediate-pressure heating switching system;The input terminals of the high-pressure heating switching system are connected to the zero-extraction exhaust terminal, the first-extraction heating exhaust terminal, and the cold reheating exhaust terminal of the high-pressure cylinder, respectively. The output terminal of the high-pressure heating switching system is connected to the input terminal of the flexible flue gas reheating system. The input terminal of the flexible flue gas reheating system is also connected to the cold reheating exhaust terminal of the high-pressure cylinder. The output terminal of the flexible flue gas reheating system is connected to the intermediate-pressure cylinder and the high-pressure heating header, respectively. The input terminals of the intermediate-pressure heating switching system are connected to the first-extraction heating exhaust terminal and the cold reheating exhaust terminal of the high-pressure cylinder, respectively. The output terminal of the intermediate-pressure heating switching system is connected to the input terminal of the reheat steam system. The input terminal of the reheat steam system is also connected to the third-extraction exhaust terminal of the intermediate-pressure cylinder. The output terminal of the reheat steam system is connected to the high-pressure heating... The input end of the heater is connected to the medium-pressure heating header. When the system is under high electrical load heating conditions, the high-pressure cylinder delivers first-stage extraction heating steam to the flexible flue gas reheat system via the high-pressure heating switching system, and delivers cold reheat steam to the reheat steam system via the medium-pressure heating switching system. When the system is under medium electrical load heating conditions, the high-pressure cylinder delivers zero-stage extraction steam to the flexible flue gas reheat system via the high-pressure heating switching system, and delivers cold reheat steam to the reheat steam system via the medium-pressure heating switching system. When the system is under low electrical load heating conditions, the high-pressure cylinder delivers zero-stage extraction steam to the flexible flue gas reheat system via the high-pressure heating switching system, and delivers first-stage extraction heating steam to the reheat steam system via the medium-pressure heating switching system. High-pressure heating switching... The system includes: a zero-extraction to high-pressure heating pipeline P1, a first-extraction to high-pressure heating pipeline P2, and a cold reheat to the newly added low-temperature reheater pipeline P3; the input ends of the zero-extraction to high-pressure heating pipeline P1, the first-extraction to high-pressure heating pipeline P2, and the cold reheat to the newly added low-temperature reheater pipeline P3 are respectively connected to the zero-extraction exhaust end, the first-extraction heating exhaust end, and the cold reheating exhaust end of the high-pressure cylinder; the flexible flue gas reheat system includes: a cold reheat to the original low-temperature reheater pipeline P5, a newly added low-temperature reheating component, the original low-temperature reheating component, the final stage reheating component, a high-pressure heating pipeline P10, and a newly added low-temperature reheater to the final stage reheater pipeline P11; the input end of the cold reheat to the original low-temperature reheater pipeline P5 is connected to the input end of the cold reheat to the newly added low-temperature reheater pipeline P3. The output of the cold reheat to the original low-temperature reheater pipeline P5 is connected to the input of the original low-temperature reheating assembly. The input of the final stage reheating assembly is connected to the output of the original low-temperature reheating assembly and the output of the new low-temperature reheater to final stage reheater pipeline P11. The output of the final stage reheating assembly is connected to the intermediate pressure cylinder. The output of the new low-temperature reheating assembly is connected to the input of the new low-temperature reheater to final stage reheater pipeline P11 and the input of the high-pressure heating pipeline P10. The input of the new low-temperature reheating assembly is connected to the output of the zero-extraction to high-pressure heating pipeline P1, the first-extraction to high-pressure heating pipeline P2, and the output of the cold reheat to the new low-temperature reheater pipeline P3. The output of the high-pressure heating pipeline P10 is connected to the high-pressure heating header.

[0061] In one embodiment, the high-pressure heating switching system further includes: a first valve control component, a second valve control component, and a third valve group control component. The first valve control component is disposed on the zero-extraction to high-pressure heating pipeline P1 and is used to control the flow rate of zero-extraction steam discharged from the zero-extraction exhaust end of the high-pressure cylinder to the flexible flue gas reheating system. The second valve control component is disposed on the first-extraction to high-pressure heating pipeline P2 and is used to control the flow rate of first-extraction heating steam discharged from the first-extraction heating exhaust end of the high-pressure cylinder to the flexible flue gas reheating system. The third valve control component is disposed on the cold reheat to newly added low-temperature reheater pipeline P3 and is used to control the flow rate of cold reheat steam discharged from the cold reheat exhaust end of the high-pressure cylinder to the flexible flue gas reheating system.

[0062] Specifically, refer to Figure 1 The first valve control assembly includes: an electric gate valve T1 for zero-pump to high-pressure heating, a pneumatic check valve N1 for zero-pump to high-pressure heating, and a quick-closing flow regulating valve V1 for zero-pump to high-pressure heating. All three are installed on the zero-pump to high-pressure heating pipeline P1. The electric gate valve T1 is located near the high-pressure cylinder, followed by the pneumatic check valve N1 and the quick-closing flow regulating valve V1. The second valve control assembly includes: an electric gate valve T2 for one-pump to high-pressure heating, a pneumatic check valve N2 for one-pump to high-pressure heating, and a quick-closing flow regulating valve V2 for one-pump to high-pressure heating. All three are installed on the one-pump to high-pressure heating pipeline P1. The heating pipeline P2 has an electric gate valve T2 for drawing to high-pressure heating located at one end near the high-pressure cylinder, followed by a pneumatic check valve N2 and a quick-closing flow regulating valve V2 for drawing to high-pressure heating. The third valve control assembly includes an electric gate valve T3 for cold reheating to the newly added low-temperature reheater, a pneumatic check valve N3 for cold reheating to the newly added low-temperature reheater, and a quick-closing flow regulating valve V3 for cold reheating to the newly added low-temperature reheater. The electric gate valve T3 for cold reheating to the newly added low-temperature reheater is located at one end near the high-pressure cylinder, followed by a pneumatic check valve N3 for cold reheating to the newly added low-temperature reheater and a quick-closing flow regulating valve V3 for cold reheating to the newly added low-temperature reheater.

[0063] In this embodiment, the on / off state of the heating pipeline is controlled by an electric gate valve to achieve flexible adjustment of the heating pipeline under frequent peak-shaving operation; the check valve ensures that the steam in the heating pipeline flows in a predetermined direction to prevent cooling or backflow, thus maintaining the stability of the system and avoiding the reduction in heating effect or damage to components caused by steam backflow; the opening degree of the flow regulating valve can be adjusted to achieve precise control and regulation of the heating pipeline, thereby improving its energy efficiency and heating quality.

[0064] In one embodiment, the flexible flue gas reheat system further includes a sixth valve control component and a seventh valve control component. The sixth valve control component is disposed on the high-pressure heating pipeline P10 and is used to control the flow rate of zero-extraction steam or one-extraction heating steam discharged from the new low-temperature reheating component to the high-pressure heating header. The seventh valve control component is disposed on the pipeline P11 from the new low-temperature reheater to the final reheater and is used to control the flow rate of cold reheat steam discharged from the new low-temperature reheating component to the final reheating component.

[0065] Specifically, refer to Figure 1 The sixth valve control component includes: a high-pressure heating electric gate valve T6 and a high-pressure heating pneumatic check valve N6, both of which are installed on the high-pressure heating pipeline P10. The high-pressure heating pneumatic check valve N6 is installed at the end closer to the high-pressure heating header, and the high-pressure heating electric gate valve T6 is installed at the end farther away from the high-pressure heating header. The seventh valve control component includes: a new low-temperature reheater to final stage reheater pneumatic check valve N7 and a new low-temperature reheater to final stage reheater electric gate valve T7, both of which are installed on the new low-temperature reheater to final stage reheater pipeline P11. The new low-temperature reheater to final stage reheater pneumatic check valve N7 is installed at the end closer to the final reheater inlet header, and the new low-temperature reheater to final stage reheater electric gate valve T7 is installed at the end farther away from the final reheater inlet header.

[0066] In this embodiment, the on / off state of the heating pipeline is controlled by an electric gate valve to achieve flexible adjustment of the heating pipeline under frequent peak-shaving operation; the check valve ensures that the steam in the heating pipeline flows in a predetermined direction to prevent cooling or backflow, thus maintaining the stability of the system and avoiding the reduction of heating effect or damage to the device caused by steam backflow.

[0067] In one embodiment, the medium-pressure heating switching system includes: a pump-to-medium-pressure heating pipeline P4 and a cold-to-medium-pressure heating pipeline P6; the input end of the pump-to-medium-pressure heating pipeline P4 is connected to the pump-to-heating exhaust end of the high-pressure cylinder, the input end of the cold-to-medium-pressure heating pipeline P6 is connected to the cold-to-exhaust end of the high-pressure cylinder, and the output ends of the pump-to-medium-pressure heating pipeline P4 and the cold-to-medium-pressure heating pipeline P6 are both connected to the input end of the steam heat exchanger 4.

[0068] In one embodiment, the medium-pressure heating switching system further includes a fourth valve control component and a fifth valve control component. The fourth valve control component is disposed on a first-extraction to medium-pressure heating pipeline P4 and is used to control the flow rate of first-extraction heating steam discharged from the first-extraction heating exhaust end of the high-pressure cylinder to the reheat steam system. The fifth valve control component is disposed on a cold reheat to medium-pressure heating pipeline P6 and is used to control the flow rate of cold reheat steam discharged from the cold reheat exhaust end of the high-pressure cylinder to the reheat steam system.

[0069] Specifically, refer to Figure 1 The fourth valve control component includes: a primary extraction to medium-pressure heating electric gate valve T4, a primary extraction to medium-pressure heating pneumatic check valve N4, and a primary extraction to medium-pressure heating quick-closing flow regulating valve V4. These three valves are sequentially installed on the primary extraction to medium-pressure heating pipeline P4 in the direction of conveying primary extraction heating steam output from the primary extraction heating exhaust end of the high-pressure cylinder. The fifth valve control component includes: a cold reheat to medium-pressure heating electric gate valve T5, a cold reheat to medium-pressure heating pneumatic check valve N5, and a cold reheat to medium-pressure heating quick-closing flow regulating valve V5. These three valves are sequentially installed on the cold reheat to medium-pressure heating pipeline P6 in the direction of conveying cold reheat steam.

[0070] In this embodiment, the on / off state of the heating pipeline is controlled by an electric gate valve to achieve flexible adjustment of the heating pipeline under frequent peak-shaving operation; the check valve ensures that the steam in the heating pipeline flows in a predetermined direction to prevent cooling or backflow, thus maintaining the stability of the system and avoiding the reduction in heating effect or damage to components caused by steam backflow; the opening degree of the flow regulating valve can be adjusted to achieve precise control and regulation of the heating pipeline, thereby improving its energy efficiency and heating quality.

[0071] In one embodiment, the reheat steam system includes: a medium-pressure heating pipeline P7, a steam heat exchanger 4, a three-stage extraction to steam heat exchanger pipeline P8, and a steam heat exchanger to high-pressure heater pipeline P9; the input end of the steam heat exchanger 4 is connected to the output end of the medium-pressure heating switching system and the output end of the three-stage extraction to steam heat exchanger pipeline P8, respectively; the output end of the steam heat exchanger 4 is connected to the input end of the steam heat exchanger to high-pressure heater pipeline P9 and the input end of the medium-pressure heating pipeline P7; the input end of the three-stage extraction to steam heat exchanger pipeline P8 is connected to the three-stage extraction exhaust end of the medium-pressure cylinder; the output end of the steam heat exchanger to high-pressure heater pipeline P9 is connected to the input end of the high-pressure heater; and the output end of the medium-pressure heating pipeline P7 is connected to the medium-pressure heating header.

[0072] In one embodiment, reference is made to Figure 1 The reheat steam system also includes: a third-stage extraction electric gate valve T8 to the steam heat exchanger, a steam heat exchanger to the high-pressure heater electric gate valve T9, and a medium-pressure heating electric gate valve T10. The third-stage extraction electric gate valve T8 is installed on the third-stage extraction to steam heat exchanger pipeline P8, the steam heat exchanger to high-pressure heater electric gate valve T9 is installed on the steam heat exchanger to high-pressure heater pipeline P9, and the medium-pressure heating electric gate valve T10 is installed on the medium-pressure heating pipeline P7. The third-stage extraction electric gate valve T8 is used to control the flow rate of the third-stage extraction steam discharged from the third-stage extraction exhaust end of the medium-pressure cylinder to the reheat steam system. The steam heat exchanger to high-pressure heater electric gate valve T9 is used to control the flow rate of the third-stage extraction steam discharged from the steam heat exchanger 4 to the high-pressure heater. The medium-pressure heating electric gate valve T10 is used to control the flow rate of the first-stage extraction heating steam or cold reheat steam discharged from the steam heat exchanger 4 to the medium-pressure heating header.

[0073] In this embodiment, electric gate valves are installed on the three-stage extraction to steam heat exchanger pipeline P8, the steam heat exchanger to high-pressure heater pipeline P9, and the medium-pressure heating pipeline P7 to control their on / off state, thereby increasing the flexibility of the heating system and improving its adjustability in the face of different operating conditions.

[0074] In one embodiment, the newly added cryogenic assembly includes a newly added emergency desuperheater, a newly added low-temperature re-inlet header, a newly added cryogenic reheater 1, a newly added low-temperature re-outlet header, and a newly added low-temperature re-outlet desuperheater connected in sequence; the original cryogenic assembly includes the original low-temperature re-inlet emergency desuperheater, the original low-temperature re-inlet header, the original cryogenic reheater 2, the original low-temperature re-outlet header, and the original low-temperature re-outlet desuperheater connected in sequence; the final stage reheat assembly includes the final re-inlet header, the final stage reheater 3, and the final re-outlet header connected in sequence; the input terminal of the newly added emergency desuperheater is connected to the output terminal of the zero-level to high-pressure heating pipeline P1 and the first-level to high-pressure pipeline P1, respectively. The output end of the heating pipeline P2 is connected to the output end of the cold reheat to the new low-temperature reheater pipeline P3. The output end of the new low-temperature reheat outlet desuperheater is connected to the input end of the new low-temperature reheater to the final stage reheater pipeline P11 and the input end of the high-pressure heating pipeline P10, respectively. The input end of the original low-temperature reheat inlet emergency desuperheater is connected to the output end of the cold reheat to the original low-temperature reheater pipeline P5. The input end of the final reheat inlet header is connected to the output end of the new low-temperature reheater to the final stage reheater pipeline P11 and the output end of the original low-temperature reheat outlet desuperheater, respectively. The output end of the final reheat outlet header is connected to the input end of the intermediate pressure cylinder.

[0075] In this embodiment, by adding an inlet emergency desuperheater, an outlet desuperheater, an inlet header, and an outlet header to both the newly added low-temperature reheater 1 and the original low-temperature reheater 2, the (emergency) desuperheater rapidly reduces the temperature when the equipment or system temperature rises above safety limits, preventing overheating and damage or dangerous situations. The inlet and outlet headers divert the heat transfer medium in the heating pipeline to the various pipes or heat exchanger units of the reheater, while the outlet header collects the reheated heat transfer medium and guides it to the next stage of the heating pipeline. These features ensure the rational distribution and smooth flow of the heat transfer medium within the reheater, improving reheating efficiency.

[0076] In one embodiment, a high-pressure backflow check valve N8 is installed on the cold reheat to the original low-temperature reheater pipeline P5. Compared with ordinary check valves, the high-pressure backflow check valve has a higher start-up pressure. It can withstand higher steam pressure and respond quickly to prevent backflow. The high-pressure backflow check valve has a larger flow channel design, which can accommodate a large flow of steam, ensuring the smooth operation of the system. Moreover, during operation, the high-pressure backflow check valve can reduce the pressure drop of the system and improve the system efficiency due to the smooth steam flow and low resistance.

[0077] It should be noted that the newly added low re-outlet desuperheater functions to ensure that the heating surface of the final reheater 3 does not exceed the temperature under pure condensing conditions, and to regulate the temperature of the high-pressure heating steam to the rated heating parameters under heating conditions.

[0078] In one embodiment, the original low-temperature reheater 2 has a reduced vertical heating surface area compared to the conventional design. The newly added low-temperature reheater 1 is installed in front of the vertical low-temperature superheater above the tail flue. The heat absorption reduced as a result is absorbed by the newly added low-temperature reheater 1. In order to take into account both extraction steam conditions and pure condensation conditions, in addition to using intermediate stage desuperheating water as a temperature control method, the heat exchange tube diameter of the final stage reheater 3 is reduced to increase the mass flow rate of the medium in the tube to enhance the tube cooling effect and prevent the risk of overheating caused by the reduction of steam flow in the final stage reheater 3 after a large amount of extraction steam is used for heating.

[0079] Understandably, valves and other devices are installed on each heating pipeline to control the flow of heat, allowing for flexible adjustments under different operating conditions and improving heating efficiency and energy utilization. In high-pressure heating, either the zero-extraction to high-pressure heating pipeline P1 or the first-extraction to high-pressure heating pipeline P2 can be connected. In medium-pressure heating, either the first-extraction to medium-pressure heating pipeline P4 or the cold re-extraction to medium-pressure heating pipeline P6 can be connected.

[0080] It should be noted that the zero-draw and one-draw of the high-pressure cylinder of the present invention have a large flow rate of steam extraction for heating. Under rated heating conditions, the total steam extraction volume for heating accounts for up to 30% of the steam inlet flow of the high-pressure cylinder.

[0081] Zero extraction steam refers to the first stage of steam extraction near the steam inlet of the high-pressure cylinder in a high-flow extraction high-pressure cylinder.

[0082] The first stage of steam extraction for heating refers to the first stage of steam extraction near the exhaust end of the high-pressure cylinder in the high-flow extraction high-pressure cylinder.

[0083] Cold resteam refers to steam discharged from the exhaust end of the high-pressure cylinder.

[0084] Three-stage steam extraction refers to the first stage of steam extraction in the intermediate-pressure cylinder, which is located near the steam inlet of the intermediate-pressure cylinder.

[0085] To facilitate better understanding, the working principle of a high- and medium-pressure combined heating system is explained in detail below:

[0086] 1. When the system is operating under high electrical load heating conditions, close the zero-extraction to high-pressure heating pipeline P1, the cold reheat to the new low-temperature reheater pipeline P3, the first extraction to medium-pressure heating pipeline P4, and the new low-temperature reheater to the final stage reheater pipeline P11. Open the first extraction to high-pressure heating pipeline P2, the cold reheat to the original low-temperature reheater pipeline P5, the cold reheat to medium-pressure heating pipeline P6, the medium-pressure heating pipeline P7, the third extraction to the steam heat exchanger pipeline P8, the steam heat exchanger to the high-pressure heater pipeline P9, and the high-pressure heating pipeline P10.

[0087] High-pressure heating steam process: The heating steam discharged from the high-pressure cylinder passes through the first pump to the high-pressure heating pipeline P2, the newly added low-temperature reheat component and the high-pressure heating pipeline P10 to supply heat to the high-pressure heating header.

[0088] Medium-pressure heating steam process: The cold reheat steam discharged from the high-pressure cylinder passes sequentially through the cold reheat to the original low-temperature reheater pipeline P5, the cold reheat to the medium-pressure heating pipeline P6, the steam heat exchanger 4, and the medium-pressure heating pipeline P7 to supply heat to the medium-pressure heating header; the three-stage extraction steam discharged from the medium-pressure cylinder passes sequentially through the three-stage extraction to the steam heat exchanger pipeline P8, the steam heat exchanger 4, and the steam heat exchanger to the high-pressure heater pipeline P9 to the input end of the high-pressure heater;

[0089] Cold reheat steam process: The cold reheat steam discharged from the high-pressure cylinder passes through the cold reheat to the original low-temperature reheater pipeline P5 and the original low-temperature reheat assembly in sequence before entering the final reheat assembly, and then enters the intermediate-pressure cylinder to do work.

[0090] 2. When the system is operating under intermediate electrical load heating conditions, close the first extraction to high pressure heating pipeline P2, the cold reheat to the new low temperature reheater pipeline P3, the first extraction to medium pressure heating pipeline P4, and the new low temperature reheater to the final stage reheater pipeline P11. Open the zero extraction to high pressure heating pipeline P1, the cold reheat to the original low temperature reheater pipeline P5, the cold reheat to medium pressure heating pipeline P6, the medium pressure heating pipeline P7, the third extraction to steam heat exchanger pipeline P8, the steam heat exchanger to high pressure heater pipeline P9, and the high pressure heating pipeline P10.

[0091] High-pressure heating steam process: The zero-extraction steam discharged from the high-pressure cylinder passes through the zero-extraction to the high-pressure heating pipeline P1, the newly added low-temperature reheat component and the high-pressure heating pipeline P10 to supply heat to the high-pressure heating header.

[0092] Medium-pressure heating steam process: The cold reheat steam discharged from the high-pressure cylinder passes through the cold reheat to the original low-temperature reheater pipeline P5, the cold reheat to the medium-pressure heating pipeline P6, the steam heat exchanger 4, and the medium-pressure heating pipeline P7 to supply heat to the medium-pressure heating header.

[0093] Cold reheat process: The cold reheat steam discharged from the high-pressure cylinder passes through the original low-temperature reheater pipeline P5 and the original low-temperature reheating assembly in sequence before entering the final reheating assembly, and then enters the intermediate-pressure cylinder to perform work.

[0094] 3. When the system is operating under low electrical load heating conditions, close the following pipelines: the first extraction to high pressure heating pipeline P2, the cold reheat to the new low temperature reheater pipeline P3, the cold reheat to medium pressure heating pipeline P6, and the new low temperature reheater to the final stage reheater pipeline P11. Open the following pipelines: the zero extraction to high pressure heating pipeline P1, the first extraction to medium pressure heating pipeline P4, the cold reheat to the original low temperature reheater pipeline P5, the medium pressure heating pipeline P7, the third extraction to the steam heat exchanger pipeline P8, the steam heat exchanger to the high pressure heater pipeline P9, and the high pressure heating pipeline P10.

[0095] High-pressure heating steam process: The zero-extraction steam discharged from the high-pressure cylinder passes through the zero-extraction to the high-pressure heating pipeline P1, the newly added low-temperature reheat component and the high-pressure heating pipeline P10 to supply heat to the high-pressure heating header.

[0096] Medium-pressure heating steam process: The heating steam discharged from the high-pressure cylinder passes through the medium-pressure heating pipeline P4, the steam heat exchanger 4 and the medium-pressure heating pipeline P7 to supply heat to the medium-pressure heating header.

[0097] Cold reheat process: The cold reheat steam discharged from the high-pressure cylinder passes through the original low-temperature reheater pipeline P5 and the original low-temperature reheating assembly in sequence before entering the final reheating assembly, and then enters the intermediate-pressure cylinder to perform work.

[0098] IV. When the system is operating under pure condensation conditions, close the zero-pressure heating pipeline P1, the first-pressure heating pipeline P2, the first-pressure heating pipeline P4, the cold reheat pipeline P6, the medium-pressure heating pipeline P7, and the high-pressure heating pipeline P10; and open the cold reheat pipeline P3 to the newly added low-temperature reheater, the cold reheat pipeline P5 to the original low-temperature reheater, the third-pressure heating pipeline P8 to the steam heat exchanger, the steam heat exchanger to the high-pressure heater pipeline P9, and the newly added low-temperature reheater to the final stage reheater pipeline P11.

[0099] Cold reheat steam process 1: The cold reheat steam discharged from the high-pressure cylinder passes through the cold reheat to the new low-temperature reheater pipeline P3, the new reheat heating component, and the new low-temperature reheater to the final stage reheater pipeline P11 before entering the final stage reheat component, and then enters the intermediate-pressure cylinder to do work.

[0100] Cold reheat process 2: The cold reheat steam discharged from the high-pressure cylinder passes through the original low-temperature reheater pipeline P5 and the original low-temperature reheating assembly in sequence before entering the final reheating assembly, and then enters the intermediate-pressure cylinder to perform work.

[0101] In this embodiment of the invention, the high-pressure heating system supplies heat through the zero-extraction to high-pressure heating pipeline P1 and the first-extraction to high-pressure heating pipeline P2, while the medium-pressure heating system supplies heat through the first-extraction to medium-pressure heating pipeline P4 and the cold reheat to medium-pressure heating pipeline P6. During frequent peak-shaving operation of coal-fired power plants, the stability of heating can be effectively ensured by flexibly switching the heating steam source. Furthermore, since the steam source for both high-pressure and medium-pressure heating pipelines is provided by the high-pressure cylinder, the problem of reduced efficiency of the medium-pressure cylinder caused by conventional medium-pressure regulating valve throttling heating methods, resulting in low overall heating economy and energy and resource waste, can be avoided. Moreover, the flexible flue gas reheat system, through reasonable allocation of steam flow and appropriate injection of water for desuperheating, can achieve safe operation and seamless switching between heating and pure condensation conditions while raising the high-pressure heating steam to the rated heating temperature.

[0102] Based on the same inventive concept, embodiments of the present invention also provide a high- and medium-pressure combined heating method, implemented based on the above-mentioned high- and medium-pressure combined heating system, the method comprising:

[0103] It should be noted that when the triangle inside the valve in the diagram that is in the same direction as its circuit is blank, it indicates that the valve is in the open state; when the triangle in the same direction as its circuit is filled with black, it indicates that the valve is in the closed state.

[0104] When the system is operating under high electrical load heating conditions, close the zero-extraction to high-pressure heating pipeline P1, the cold reheat to the newly added low-temperature reheater pipeline P3, the first extraction to medium-pressure heating pipeline P4, and the newly added low-temperature reheater to the final stage reheater pipeline P11; and open the first extraction to high-pressure heating pipeline P2, the cold reheat to the original low-temperature reheater pipeline P5, the cold reheat to medium-pressure heating pipeline P6, the medium-pressure heating pipeline P7, the third extraction to the steam heat exchanger pipeline P8, the steam heat exchanger to the high-pressure heater pipeline P9, and the high-pressure heating pipeline P10.

[0105] Specifically, refer to Figure 1 When the system is operating under high electrical load heating conditions, high-pressure heating steam is supplied by the primary extraction steam source, and medium-pressure heating steam is supplied by the cold reheat steam source. At the start of heating, open the high-pressure heating electric gate valve T6 and the high-pressure heating pneumatic check valve N6, and close the electric gate valve T7 from the new low-temperature reheater to the final reheater and the pneumatic check valve N7. Based on the principle of energy level matching, high-pressure heating preferentially uses primary extraction steam. At this time, open the electric gate valve T2 from primary extraction to high-pressure heating and the pneumatic check valve N2 from primary extraction to high-pressure heating, and use the rapid-closing flow regulating valve V from primary extraction to high-pressure heating. 2. Control the pressure of the high-pressure heating system to 4.1 MPa and the steam extraction flow rate; according to the principle of energy level matching, cold re-extraction steam is preferred for medium-pressure heating. Open the electric gate valve T5 for cold re-extraction to medium-pressure heating and the pneumatic check valve N5 for cold re-extraction to medium-pressure heating. Use the fast-closing flow regulating valve V5 for cold re-extraction to medium-pressure heating to control the pressure of the medium-pressure heating system to 2.3 MPa and the steam extraction flow rate; the steam from the third extraction enters the steam heat exchanger 4 through the third extraction to steam heat exchanger pipeline P8 to release heat, and enters the input end of the high-pressure heater through the steam heat exchanger to high-pressure heater pipeline P9 to improve energy utilization.

[0106] When facing high electrical load heating conditions, adjusting the high-pressure heating system to use extraction steam and the medium-pressure heating system to use cold extraction steam, and allocating heating pipelines according to energy levels, can achieve efficient utilization of heat energy. By distributing heat energy according to pressure and temperature levels, high-quality heat energy can be used efficiently, improving overall energy utilization efficiency, reducing energy consumption and emissions, and improving overall heating economy. Under the new situation of frequent peak-shaving operation of coal-fired power plants, the stability of heating supply can be effectively guaranteed by flexibly switching heating steam sources.

[0107] When the system is operating under medium power load heating conditions, close the first extraction to high pressure heating pipeline P2, the cold reheat to the new low temperature reheater pipeline P3, the first extraction to medium pressure heating pipeline P4, and the new low temperature reheater to the final stage reheater pipeline P11; open the zero extraction to high pressure heating pipeline P1, the cold reheat to the original low temperature reheater pipeline P5, the cold reheat to medium pressure heating pipeline P6, the medium pressure heating pipeline P7, the third extraction to steam heat exchanger pipeline P8, the steam heat exchanger to high pressure heater pipeline P9, and the high pressure heating pipeline P10.

[0108] Specifically, refer to Figure 2 When the heating system is operating under medium-pressure load conditions, the high-pressure heating steam is supplied by zero-pressure extraction and the medium-pressure heating steam is supplied by cold reheat. At this time, the electric gate valve T1 from zero-pressure extraction to high-pressure heating and the pneumatic check valve N1 from zero-pressure extraction to high-pressure heating are opened. The pressure of the high-pressure heating system and the extraction steam flow rate are controlled by the quick-closing flow regulating valve V1 from zero-pressure extraction to high-pressure heating. The electric gate valve T5 from cold reheat to medium-pressure heating and the pneumatic check valve N5 from cold reheat to medium-pressure heating are opened. The pressure of the medium-pressure heating system and the extraction steam flow rate are controlled by the quick-closing flow regulating valve V5 from cold reheat to medium-pressure heating.

[0109] When facing intermediate electrical load heating conditions, adjusting the high-pressure heating to use zero-extraction steam and the medium-pressure heating to use cold reheat steam, and allocating heating pipelines according to energy level, can achieve efficient utilization of heat energy. By distributing heat energy according to pressure and temperature levels, high-quality heat energy can be used efficiently, improving overall energy utilization efficiency, reducing energy consumption and emissions, and improving overall heating economy. Under the new situation of frequent peak-shaving operation of coal-fired power plants, the stability of heating can be effectively guaranteed by flexibly switching heating steam sources.

[0110] When the system is operating under low electrical load heating conditions, close the following pipelines: the first extraction to high pressure heating pipeline P2, the cold reheat to the new low temperature reheater pipeline P3, the cold reheat to medium pressure heating pipeline P6, and the new low temperature reheater to the final stage reheater pipeline P11. Open the following pipelines: zero extraction to high pressure heating pipeline P1, first extraction to medium pressure heating pipeline P4, cold reheat to the original low temperature reheater pipeline P5, medium pressure heating pipeline P7, third extraction to steam heat exchanger pipeline P8, steam heat exchanger to high pressure heater pipeline P9, and high pressure heating pipeline P10.

[0111] Specifically, refer to Figure 3When operating under low electrical load heating conditions, if the pressure of the high-pressure heating system's primary extraction valve is insufficient to meet the heating pressure, and the pressure of the medium-pressure heating system's secondary extraction valve is also insufficient, the high-pressure heating steam is adjusted to be supplied by the zero-pressure extraction valve, and the medium-pressure heating steam is supplied by the primary extraction valve. At this time, the electric gate valve T1 from the zero-pressure extraction valve to the high-pressure heating system and the pneumatic check valve N1 from the zero-pressure extraction valve to the high-pressure heating system are opened. The pressure of the high-pressure heating system and the extraction steam flow rate are controlled to 4.1 MPa using the rapid-closing flow regulating valve V1 from the zero-pressure extraction valve to the high-pressure heating system. At this time, the newly added low-temperature reheater 1 is operating in heating mode, heating the high-pressure heating steam source. The temperature of the high-pressure heating steam is controlled to 420℃ using the newly added low-temperature reheat outlet desuperheater for heating. The electric gate valve T4 from the primary extraction valve to the medium-pressure heating system and the pneumatic check valve N4 from the primary extraction valve to the medium-pressure heating system are opened. The heating flow rate and pressure are controlled using the rapid-closing flow regulating valve V4 from the primary extraction valve to the medium-pressure heating system. Under all load conditions, the temperature of the medium-pressure heating steam source is lower than the rated heating temperature of 320℃. The medium-pressure heating steam is heated to 320℃ by the three-extraction steam source through the steam heat exchanger 4 for heating. The steam heat exchanger 4 reduces the superheat of the three-extraction steam as a heat source by recovering the heat of the three-extraction steam, thereby reducing the heat loss in the internal heat release process of No. 3 high-pressure heater.

[0112] When facing low electrical load heating conditions, adjusting the high-pressure heating system to use zero-extraction steam and the medium-pressure heating system to use single-extraction steam, and allocating heating pipelines according to energy levels, can achieve efficient utilization of heat energy. By distributing heat energy according to pressure and temperature levels, high-quality heat energy can be used efficiently, improving overall energy utilization efficiency, reducing energy consumption and emissions, and improving overall heating economy. Under the new situation of frequent peak-shaving operation of coal-fired power plants, the stability of heating supply can be effectively guaranteed by flexibly switching heating steam sources.

[0113] When the system is operating under pure condensation conditions, close the zero-pressure heating pipeline P1, the first-pressure heating pipeline P2, the first-pressure heating pipeline P4, the cold reheat pipeline P6, the medium-pressure heating pipeline P7, and the high-pressure heating pipeline P10. Open the cold reheat pipeline P3 to the newly added low-temperature reheater, the cold reheat pipeline P5 to the original low-temperature reheater, the third-pressure heating pipeline P8 to the steam heat exchanger, the steam heat exchanger to the high-pressure heater pipeline P9, and the newly added low-temperature reheater to the final stage reheater pipeline P11.

[0114] Specifically, refer to Figure 4During pure condensing operation, the flexible flue gas reheat system operates the low-temperature reheater in two parts, allowing for seamless switching between heating and pure condensing modes. In heating mode, cold reheat steam only enters the original low-temperature reheater 2 for heating and does not enter the heating surface of the newly added low-temperature reheater 1. The heating surface of the newly added low-temperature reheater 1 is used to heat the high-pressure heating extraction steam at the high-pressure cylinder extraction point. Under this condition, the minimum high-pressure heating extraction steam flow rate is 50 t / h. A new emergency desuperheater is installed before the heating surface of the newly added low-temperature reheater 1 to prevent overheating. A new low-temperature reheat outlet desuperheater is installed after this heating surface to regulate the temperature of the high-pressure heating steam. The parameters are then adjusted accordingly. Steam enters the high-pressure heating header to supply steam to users; during pure condensing operation, part of the cold reheat steam enters the newly added low-temperature reheater 1 to cool the heating surface. After being heated, the steam enters the final reheat inlet header. The remaining cold reheat steam enters the original low-temperature reheater 2, is heated, and also enters the final reheat inlet header. The two streams of steam merge in the final reheat inlet header and enter the final reheater 3, and then enter the intermediate-pressure cylinder to do work. Under this condition, the newly added emergency desuperheater and the original low-temperature reheat inlet emergency desuperheater can ensure that the newly added low-temperature reheater 1 and the original low-temperature reheater 2 do not exceed the temperature. The newly added low-temperature reheat outlet desuperheater and the original low-temperature reheat outlet desuperheater can ensure that the final reheater 3 does not exceed the temperature.

[0115] To facilitate understanding of the present invention, a complete embodiment is provided below for illustration:

[0116] In one specific embodiment, a power plant's 2×670MW heating units were originally designed to carry more than 70% of their rated electrical load. Steam at 4.1MPa, 566℃, and 2×280.9t / h was drawn from the hot reheat pipeline and mixed with steam at 4.56MPa, 316℃, and 2×53.8t / h drawn from the cold reheat pipeline. The units only began closing the turbine's intermediate-pressure regulating valve when the electrical load fell below 630MW (94% of rated load) to meet the pressure requirements. After desuperheating, high-pressure steam at 4.1MPa, 420℃, and 2×241t / h was supplied externally. The mixed steam was then depressurized and desuperheated again to supply medium-pressure steam at 2.5MPa, 320℃, and 2×137t / h. Due to the adoption of a throttling and regulating heating method using a central regulating valve, the efficiency of the intermediate-pressure cylinder drops sharply as the valve opening decreases. This is particularly true under low-load, high-extraction steam conditions, where the efficiency falls below 80%, severely impacting the unit's economic efficiency. Furthermore, as the unit load decreases, the reduced efficiency of the intermediate-pressure cylinder caused by the throttling valve leads to a decrease or even negative growth in the unit's heat and coal consumption benefits from industrial steam extraction. Simultaneously, the original design required the unit to operate at over 70% of its rated electrical load, limiting its peak-shaving capacity. Considering the shortcomings of the original system in terms of peak-shaving flexibility and heating economy, this invention proposes a flexible high- and medium-pressure combined heating system suitable for peak-shaving conditions, based on high-flow-rate, high-efficiency high-pressure steam extraction technology. Under rated heating conditions, it provides 200 t / h of high-pressure heating steam (4.1 MPa, 420℃) and 140 t / h of medium-pressure heating steam (2.3 MPa, 320℃).

[0117] The economic analysis of the rated heating condition of this embodiment is shown in the table below:

[0118]

[0119] As shown in the table above, the flexible high- and medium-pressure combined heating system described in this invention, suitable for peak-shaving conditions, can meet the requirements of high-pressure heating at 4.1 MPa, 420℃, and 200 t / h, and medium-pressure heating at 2.3 MPa, 320℃, and 140 t / h when operating within the range of 48%-91% of the rated electrical load (323MW-612MW). The peak-shaving range is significantly wider than that of the original heating system (which requires operation at over 70% of the rated electrical load). Furthermore, it can achieve adjustable high-pressure heating from 50-340 t / h and adjustable medium-pressure heating from 0-340 t / h, resulting in high heating flexibility.

[0120] As shown in the table above, under rated heating conditions, the following method should be adopted in the range from 70%-80% of the rated electrical load to 91% of the rated electrical load: Figure 1The operating mode is as follows: First-stage extraction steam is used as the high-pressure heating steam source, and cold re-extraction steam is used as the medium-pressure heating steam source; within a load range from 60%-70% of the rated electrical load to 70%-80% of the rated electrical load, the following method is employed... Figure 2 The operating mode is as follows: zero-extraction steam is used as the high-pressure heating steam source, and cold re-extraction steam is used as the medium-pressure heating steam source; in a certain load range between 48% and 60%-70% of the rated electrical load, the following method is adopted. Figure 3 The operating mode shown is as follows: zero extraction steam is used as a high-pressure heating steam source, and one extraction steam is used as a medium-pressure heating steam source.

[0121] Based on the test data of the original heating system, the economic comparison analysis of the heating system of this invention and the original heating system is shown in the table below:

[0122]

[0123] Note: 1. Plant power consumption rate is taken as the average value of the test conditions, which is 4.5%; 2. Pipeline efficiency is taken as 99%; 3. Boiler efficiency is taken as the test value, which is 94%.

[0124] As shown in the table above, under the same heating conditions, the weighted average coal consumption for power generation of the heating system of this invention is reduced by 20.28 g / kWh compared with the original heating system (of which 14.00 g / kWh is due to the replacement of the unit with a high-efficiency cylinder and 6.28 g / kWh is due to the optimization of the heating method), with significant energy-saving and carbon reduction effects; at the same time, since the boiler reheater adopts flexible heating surface technology, it can realize seamless switching between heating and pure condensing conditions, and the system has high operational safety.

[0125] As can be seen from the examples above, this system can meet the heating demand under different peak-shaving conditions, and is a flexible and efficient high- and medium-pressure combined heating system.

[0126] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0127] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0128] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0129] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0130] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0131] In addition, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0132] 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.

[0133] 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 heating system, applied to a combined heat and power unit, characterized in that, The system includes: a high-pressure cylinder, an intermediate-pressure cylinder, a flexible flue gas reheating system, a reheat steam system, a high-pressure heating header, an intermediate-pressure heating header, and a high-pressure heater; the exhaust end of the high-pressure cylinder is connected to the input end of the reheat steam system and the input end of the flexible flue gas reheating system, respectively; the input end of the reheat steam system is also connected to the exhaust end of the three extraction stages of the intermediate-pressure cylinder; the output end of the reheat steam system is connected to the input end of the high-pressure heater and the intermediate-pressure heating header, respectively; and the output end of the flexible flue gas reheating system is connected to the steam inlet end of the intermediate-pressure cylinder and the high-pressure heating header, respectively. The high-pressure cylinder is used to generate zero-extraction steam, single-extraction heating steam and cold reheat steam, and delivers the cold reheat steam to the flexible flue gas reheat system. When the system is under high electrical load heating conditions, the high-pressure cylinder is also used to transport the first-stage heating steam to the flexible flue gas reheat system and the cold reheat steam to the reheat steam system; the intermediate-pressure cylinder is used to generate the third-stage steam and transport it to the reheat steam system; the flexible flue gas reheat system is used to heat the first-stage heating steam and then transport it to the high-pressure heating header, and to heat the cold reheat steam and then transport it to the intermediate-pressure cylinder; the reheat steam system is used to heat the cold reheat steam using the third-stage steam, and then transport the heated cold reheat steam to the intermediate-pressure heating header, and finally transport the cooled third-stage steam to the high-pressure heater; When the system is operating under medium-load heating conditions, the high-pressure cylinder is also used to deliver zero-extraction steam to the flexible flue gas reheat system and cold reheat steam to the reheat steam system; the flexible flue gas reheat system is also used to deliver the zero-extraction steam to the high-pressure heating header after heating and to the medium-pressure cylinder after heating the cold reheat steam; the reheat steam system is also used to deliver the cold reheat steam to the medium-pressure heating header. When the system is in a low electrical load heating condition, the high-pressure cylinder is also used to transport zero-extraction steam to the flexible flue gas reheat system and to transport first-extraction heating steam to the reheat steam system; the flexible flue gas reheat system is also used to transport the zero-extraction steam to the high-pressure heating header after heating it and to transport the cold reheat steam to the medium-pressure cylinder; the reheat steam system is also used to transport the first-extraction heating steam to the medium-pressure heating header after heating it. When the system is in pure condensation mode, the flexible flue gas reheat system is also used to heat the cold resteam and deliver it to the intermediate pressure cylinder. The system further includes: a high-pressure heating switching system and a medium-pressure heating switching system; the input end of the high-pressure heating switching system is connected to the zero-extraction exhaust end, the first-extraction heating exhaust end, and the cold reheating exhaust end of the high-pressure cylinder, respectively; the output end of the high-pressure heating switching system is connected to the input end of the flexible flue gas reheating system; the input end of the flexible flue gas reheating system is also connected to the cold reheating exhaust end of the high-pressure cylinder; the output end of the flexible flue gas reheating system is connected to the medium-pressure cylinder and the high-pressure heating header, respectively; the input end of the medium-pressure heating switching system is connected to the first-extraction heating exhaust end and the cold reheating exhaust end of the high-pressure cylinder, respectively; the output end of the medium-pressure heating switching system is connected to the input end of the reheat steam system; the input end of the reheat steam system is also connected to the third-extraction exhaust end of the medium-pressure cylinder. The output of the reheat steam system is connected to the input of the high-pressure heater and the medium-pressure heating header, respectively. When the system is under high electrical load heating conditions, the high-pressure cylinder delivers first-stage heating steam to the flexible flue gas reheat system through the high-pressure heating switching system, and delivers cold reheat steam to the reheat steam system through the medium-pressure heating switching system. When the system is under medium electrical load heating conditions, the high-pressure cylinder delivers zero-stage steam to the flexible flue gas reheat system through the high-pressure heating switching system, and delivers cold reheat steam to the reheat steam system through the medium-pressure heating switching system. When the system is under low electrical load heating conditions, the high-pressure cylinder delivers zero-stage steam to the flexible flue gas reheat system through the high-pressure heating switching system, and delivers first-stage heating steam to the reheat steam system through the medium-pressure heating switching system. The high-pressure heating switching system includes: zero-extraction to high-pressure heating pipeline (P1), first-extraction to high-pressure heating pipeline (P2), and cold reheat to newly added low-temperature reheater pipeline (P3); the input ends of the zero-extraction to high-pressure heating pipeline (P1), the first-extraction to high-pressure heating pipeline (P2), and the cold reheat to newly added low-temperature reheater pipeline (P3) are respectively connected to the zero-extraction exhaust end, the first-extraction heating exhaust end, and the cold reheating exhaust end of the high-pressure cylinder; The flexible flue gas reheat system includes: a cold reheat to the original low-temperature reheater pipeline (P5), a new low-temperature reheat assembly, the original low-temperature reheat assembly, a final stage reheat assembly, a high-pressure heating pipeline (P10), and a new low-temperature reheater to the final stage reheater pipeline (P11). The input end of the cold reheat to the original low-temperature reheater pipeline (P5) is connected to the input end of the cold reheat to the new low-temperature reheater pipeline (P3), the output end of the cold reheat to the original low-temperature reheater pipeline (P5) is connected to the input end of the original low-temperature reheat assembly, and the input end of the final stage reheat assembly is connected to the output end of the original low-temperature reheat assembly and the new low-temperature reheater to the final stage reheater pipeline. The output end of the final stage reheater pipeline (P11) is connected, the output end of the final stage reheat assembly is connected to the intermediate pressure cylinder, the output end of the newly added low temperature reheat assembly is connected to the input end of the newly added low temperature reheater to the final stage reheater pipeline (P11) and the input end of the high pressure heating pipeline (P10), respectively, the input end of the newly added low temperature reheat assembly is connected to the output end of the zero-extraction to high pressure heating pipeline (P1), the output end of the first extraction to high pressure heating pipeline (P2) and the output end of the cold reheat to the newly added low temperature reheater pipeline (P3), respectively, and the output end of the high pressure heating pipeline (P10) is connected to the high pressure heating header.

2. The high- and medium-pressure combined heating system according to claim 1, characterized in that, The reheat steam system includes: medium-pressure heating pipeline (P7), steam heat exchanger (4), three-stage extraction to steam heat exchanger pipeline (P8) and steam heat exchanger to high-pressure heater pipeline (P9). The input end of the steam heat exchanger (4) is connected to the output end of the medium-pressure heating switching system and the output end of the three-extraction to steam heat exchanger pipeline (P8), respectively. The output end of the steam heat exchanger (4) is connected to the input end of the steam heat exchanger to high-pressure heater pipeline (P9) and the input end of the medium-pressure heating pipeline (P7). The input end of the three-extraction to steam heat exchanger pipeline (P8) is connected to the three-extraction exhaust end of the medium-pressure cylinder. The output end of the steam heat exchanger to high-pressure heater pipeline (P9) is connected to the input end of the high-pressure heater. The output end of the medium-pressure heating pipeline (P7) is connected to the medium-pressure heating header.

3. The high- and medium-pressure combined heating system according to claim 2, characterized in that, The medium-pressure heating switching system includes: a cold-to-medium-pressure heating pipeline (P4) and a cold-to-medium-pressure heating pipeline (P6). The input end of the first extraction to medium-pressure heating pipeline (P4) is connected to the first extraction heating exhaust end of the high-pressure cylinder, the input end of the cold reheat to medium-pressure heating pipeline (P6) is connected to the cold reheating exhaust end of the high-pressure cylinder, and the output ends of the first extraction to medium-pressure heating pipeline (P4) and the cold reheat to medium-pressure heating pipeline (P6) are both connected to the input end of the steam heat exchanger (4).

4. A combined high- and medium-pressure heating method, implemented based on the combined high- and medium-pressure heating system described in claim 3, characterized in that, The method includes: When the system is operating under high electrical load heating conditions, close the zero-extraction to high-pressure heating pipeline (P1), cold reheat to the newly added low-temperature reheater pipeline (P3), first-extraction to medium-pressure heating pipeline (P4), and the newly added low-temperature reheater to the final stage reheater pipeline (P11). Open the first-extraction to high-pressure heating pipeline (P2), cold reheat to the original low-temperature reheater pipeline (P5), cold reheat to medium-pressure heating pipeline (P6), medium-pressure heating pipeline (P7), third-extraction to steam heat exchanger pipeline (P8), steam heat exchanger to high-pressure heater pipeline (P9), and high-pressure heating pipeline (P10). When the system is operating under medium power load heating conditions, close the first extraction to high pressure heating pipeline (P2), cold reheat to the newly added low temperature reheater pipeline (P3), first extraction to medium pressure heating pipeline (P4), and the newly added low temperature reheater to the final stage reheater pipeline (P11). Open the zero extraction to high pressure heating pipeline (P1), cold reheat to the original low temperature reheater pipeline (P5), cold reheat to medium pressure heating pipeline (P6), medium pressure heating pipeline (P7), third extraction to steam heat exchanger pipeline (P8), steam heat exchanger to high pressure heater pipeline (P9), and high pressure heating pipeline (P10). When the system is operating under low electrical load heating conditions, close the first extraction to high pressure heating pipeline (P2), cold reheat to the newly added low temperature reheater pipeline (P3), cold reheat to medium pressure heating pipeline (P6), and the newly added low temperature reheater to the final stage reheater pipeline (P11). Open the zero extraction to high pressure heating pipeline (P1), first extraction to medium pressure heating pipeline (P4), cold reheat to the original low temperature reheater pipeline (P5), medium pressure heating pipeline (P7), third extraction to steam heat exchanger pipeline (P8), steam heat exchanger to high pressure heater pipeline (P9), and high pressure heating pipeline (P10). When the system is operating under pure condensation conditions, close the zero-pressure heating pipeline to high-pressure heating pipeline (P1), the first-pressure heating pipeline to high-pressure heating pipeline (P2), the first-pressure heating pipeline to medium-pressure heating pipeline (P4), the cold reheat to medium-pressure heating pipeline (P6), the medium-pressure heating pipeline (P7), and the high-pressure heating pipeline (P10). Open the cold reheat to the new low-temperature reheater pipeline (P3), the cold reheat to the original low-temperature reheater pipeline (P5), the third-pressure heating pipeline to the steam heat exchanger pipeline (P8), the steam heat exchanger to the high-pressure heater pipeline (P9), and the new low-temperature reheater to the final stage reheater pipeline (P11).

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