Low-pressure cylinder zero-output operation system and method

Abstract

The invention belongs to the technical field of coal machines, and discloses a low-pressure cylinder zero-output operation system and method so as to reduce unnecessary operation of a low-pressure cylinder. The system comprises a steam turbine subsystem, a circulating water subsystem and a heat exchange subsystem, wherein the steam turbine subsystem, the circulating water subsystem and the heat exchange subsystem are interconnected and intercommunicated through pipelines; the steam turbine subsystem comprises an ultrahigh-pressure cylinder, a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, an auxiliary communicating pipe valve, a communicating pipe valve and a steam bypass valve, and the auxiliary communicating pipe valve, the communicating pipe valve and the steam bypass valve are used for controlling opening and closing of pipelines; a high-pressure cylinder steam extraction pipeline is arranged between the high-pressure cylinder and the heat exchange subsystem; the steam turbine subsystem extracts steam through the high-pressure cylinder, so that the steam enters the heat exchange subsystem to exchange heat with circulating water; when the medium-pressure cylinder normally operates, steam enters the low-pressure cylinder through the communicating pipe valve; during cylinder switching operation of the medium-pressure cylinder, a large part of steam enters the heat exchange subsystem through the auxiliary communication pipe valve and the steam bypass valve, and a small part of steam enters the low-pressure cylinder through the communication pipe valve to take away blast heat.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mining machinery, and in particular relates to a low-pressure cylinder zero-output operation system and method. Background Art

[0002] With the rapid growth of installed capacity of new energy sources such as wind power and photovoltaic power in my country, higher requirements are placed on the peak-shaving capacity of coal-fired power units. This trend not only marks the continuous optimization of my country's energy structure, but also poses unprecedented challenges to the peak-shaving capacity of traditional coal-fired power units. The instability and intermittent characteristics of new energy power generation require coal-fired power units to have more flexible and efficient peak-shaving capabilities to adapt to the rapid fluctuations of power grid load and ensure the stability and security of power supply. Against this background, low-pressure cylinder zero-output technology came into being and became an important innovation to improve the peak-shaving capacity of coal-fired power units. However, although low-pressure cylinder zero-output technology shows great application potential in theory, its application in practice faces many challenges. At present, the technology has been mainly explored and tested in small units, verifying its feasibility and some performance advantages. However, for large units, due to their complex structure and high operating parameters, the application difficulty and risk of low-pressure cylinder zero-output technology also increase, and large-scale practical application has not yet been achieved. Summary of the invention

[0003] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the objects of the present invention is to at least solve one or more of the above-mentioned problems in the prior art. In other words, one of the objects of the present invention is to provide a low-pressure cylinder zero-output operation system and method that meets one or more of the aforementioned needs, so as to reduce unnecessary operation of the low-pressure cylinder and thus improve the energy efficiency of the overall system.

[0004] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0005] In the first aspect, the present invention provides a low-pressure cylinder zero-output operation system, comprising a steam turbine subsystem, a circulating water subsystem and a heat exchange subsystem, wherein the steam turbine subsystem, the circulating water subsystem and the heat exchange subsystem are interconnected through pipelines; the steam turbine subsystem comprises an ultra-high-pressure cylinder, a high-pressure cylinder, a medium-pressure cylinder and a low-pressure cylinder, and also comprises an auxiliary connecting pipe valve, a connecting pipe valve and a steam bypass valve for controlling the opening and closing of the pipeline; a high-pressure cylinder extraction pipeline is arranged between the high-pressure cylinder and the heat exchange subsystem, and the steam turbine subsystem extracts steam through the high-pressure cylinder to allow steam to enter the heat exchange subsystem for heat exchange with circulating water; the medium-pressure cylinder allows steam to enter the low-pressure cylinder through the connecting pipe valve during normal operation; the medium-pressure cylinder allows a larger portion of steam to enter the heat exchange subsystem through the auxiliary connecting pipe valve and the steam bypass valve during cylinder cutting operation, and allows a smaller portion of steam to enter the low-pressure cylinder through the connecting pipe valve to take away the blast heat.

[0006] As a preferred solution, the circulating water subsystem includes a condenser, a condensate pump, a condensate pipeline, a condensate bypass, a low-pressure heater, a deaerator, a deaerator outlet pipeline, an electric pump, an electric pump outlet pipeline, a feed water pump, a feed water pump outlet pipeline, a feed water pump turbine, and an auxiliary steam manifold; the heat exchange subsystem includes a heat exchange tube, a heat exchange steam inlet branch, a heat exchange steam outlet branch, a heating user, a circulating water tank, a circulating water pump, and a heat pump; a pipeline to the condenser is arranged between the heat exchange tube and the condenser; a pipeline to the auxiliary steam manifold is arranged between the heat exchange tube and the auxiliary steam manifold; a return water pipeline is arranged between the condenser and the circulating water tank.

[0007] As a preferred solution, four low-pressure heaters are provided, namely a first low-pressure heater, a second low-pressure heater, a third low-pressure heater and a fourth low-pressure heater; an inlet water pipe to the deaerator is provided between the first low-pressure heater and the deaerator.

[0008] As a preferred solution, the circulation subsystem also includes a spare low-pressure heater and a spare low-pressure heater outlet pipe; the water in the steam generator hot well is divided into two paths through the condensate pump, one path enters the low-pressure heater, and the other path enters the spare low-pressure heater.

[0009] As a preferred solution, the circulation subsystem also includes a standby deaerator and a standby deaerator water outlet pipe; a standby deaerator water inlet pipe is arranged between the first low-pressure heater and the standby deaerator; the water in the low-pressure heater enters the deaerator during normal operation, and is divided into two paths to enter the deaerator and the standby deaerator respectively during cylinder cutting operation.

[0010] As a preferred solution, the circulation subsystem also includes a backup electric pump, a backup feed water pump, a backup feed water pump turbine, a first feed water pipe, a second feed water pipe, and a backup feed water pump outlet pipe; the backup electric pump is connected to the turbine subsystem through the first feed water pipe; the backup electric pump is connected to the heating user through the second feed water pipe.

[0011] In a second aspect, the present invention provides a method for zero-output operation of a low-pressure cylinder, which is based on the low-pressure cylinder zero-output operation system as described in the first aspect, and includes the following steps: during normal operation, operating the high-pressure cylinder to extract steam so that the steam enters the heat exchange subsystem from the high-pressure cylinder extraction pipe to exchange heat with circulating water, and operating the medium-pressure cylinder to discharge steam to the low-pressure cylinder through the pipe where the connecting pipe valve is located; during cylinder cutting operation, slowly closing the connecting pipe valve and opening the auxiliary connecting pipe valve and the steam bypass valve to allow a larger portion of the steam to enter the heat exchange subsystem, and allowing a smaller portion of the steam to enter the low-pressure cylinder to take away the blast heat.

[0012] As a preferred solution, it further includes the steps of: when the unit increases the load from a low load, slowly close the steam bypass valve, stop the steam in the pipeline to the auxiliary steam header, switch to heating with the standby motor-driven feed pump, reduce the amount of steam entering the standby low-pressure heater until the low-pressure heater gradually resumes normal operation.

[0013] As a preferred solution, it further includes the steps of: when operating with cylinder cutting, start the standby low-pressure heater and the standby deaerator so that the water in the low-pressure heater enters the deaerator and the standby deaerator respectively.

[0014] As a preferred solution, it further includes the steps of: when the motor-driven feed pump or the feed water pump fails, enable the standby motor-driven feed pump to assist in operation to prevent the unit from tripping.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] In a traditional steam turbine system under low load or specific operating modes, the low-pressure cylinder may continue to operate but with low efficiency, resulting in energy waste. Especially when it is necessary to increase the heating output and reduce the power output, it is difficult for the traditional steam turbine system to efficiently adjust the steam distribution. By adjusting the steam flow direction during cylinder cutting operation in the middle-pressure cylinder of the present invention, that is, controlling the steam flow direction through the auxiliary connecting pipe valve and the steam bypass valve, a larger part of the steam enters the heat exchange subsystem and a smaller part of the steam enters the low-pressure cylinder, which can more effectively utilize the steam energy for heat exchange, while reducing the unnecessary operation of the low-pressure cylinder, thereby improving the energy efficiency of the overall system. In addition, this adjustment can also help the system flexibly switch between power demand and heating demand, enhancing the flexibility and adaptability of the system.

[0017] Further or more detailed beneficial effects will be described in combination with specific embodiments in the specific implementation manners. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 It is a schematic structural diagram of a low-pressure cylinder zero output operation system provided by an embodiment of the present invention.

[0020] Reference numerals in the drawings:

[0021] 1. Ultra-high pressure cylinder; 2. High pressure cylinder; 2-1. High pressure cylinder extraction steam pipeline; 3. Intermediate pressure cylinder; 3-1. Auxiliary connecting pipe valve; 3-2. Connecting pipe valve; 3-3. Steam bypass valve; 4. Low pressure cylinder; 5. First low pressure heater; 5-1. Feed water pipeline to deaerator; 5-2. Feed water pipeline to standby deaerator; 6. Second low pressure heater; 7. Third low pressure heater; 8. Fourth low pressure heater; 9. Heat exchange tube; 9-1. Heat exchange inlet steam branch; 9-2. Heat exchange outlet steam branch; 10. Auxiliary steam header; 10-1. Pipeline to auxiliary steam header; 11. Condenser; 12. Condensate pump; 12-1. Condensate pipeline; 12-2. Condensate bypass; 13. Deaerator; 13-1. Deaerator outlet pipeline; 13-2. Outlet pipeline of standby low pressure heater; 13-3. Standby low pressure heater; 14. Standby deaerator; 14-1. Standby deaerator outlet pipeline; 15. Motor-driven feed pump; 15-1. Motor-driven feed pump outlet pipeline; 16. Feed water pump; 16-1. Feed water pump outlet pipeline; 17. Feed water turbine; 18. Standby motor-driven feed pump; 18-1. First feed water pipeline; 18-2. Second feed water pipeline; 19. Standby feed water pump; 19-1. Standby feed water pump outlet pipeline; 20. Standby feed water turbine; 21. Heat supply user; 22. Circulation water tank; 22-1. Circulation water pump; 22-2. Heat pump; 22-3. Pipeline to condenser; 22-4. Return water pipeline. Detailed implementation manners

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0023] In the following description, multiple embodiments of the present invention are provided. Replacements or combined combinations can be made between different embodiments. Therefore, the present invention can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present invention should also be considered to include embodiments containing one or more all other possible combinations of A, B, C, and D, although such an embodiment may not be explicitly described in the following content.

[0024] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes can be made to the functions and arrangements of the described elements without departing from the scope of the content of the present invention. Various processes or components can be appropriately omitted, substituted, or added to each example. For example, the described method can be executed in a different order from the described order, and various steps can be added, omitted, or combined. In addition, the features described in some examples can be combined into other examples.

[0025] Embodiment 1:

[0026] AsFigure 1 As shown in the figure, this embodiment provides a low-pressure cylinder zero-output operation system, including a steam turbine subsystem, a circulating water subsystem, and a heat exchange subsystem. The steam turbine subsystem, the circulating water subsystem, and the heat exchange subsystem are interconnected through pipelines; the steam turbine subsystem includes a ultra-high pressure cylinder 1, a high pressure cylinder 2, an intermediate pressure cylinder 3, and a low pressure cylinder 4, and also includes auxiliary connection pipe valves 3-1, connection pipe valves 3-2, and steam bypass valves 3-3 for controlling the opening and closing of pipelines; a high pressure cylinder extraction pipeline 2-1 is provided between the high pressure cylinder 2 and the heat exchange subsystem, and the steam turbine subsystem makes steam enter the heat exchange subsystem through the extraction of the high pressure cylinder 2 to exchange heat with the circulating water; when the intermediate pressure cylinder 3 is operating normally, steam enters the low pressure cylinder 4 through the connection pipe valve 3-2; when the intermediate pressure cylinder 3 is operating in the cut-cylinder mode, a larger part of the steam enters the heat exchange subsystem through the auxiliary connection pipe valve 3-1 and the steam bypass valve 3-3, and a smaller part of the steam enters the low pressure cylinder 4 through the connection pipe valve 3-2 to take away the blowing heat.

[0027] Specifically, this embodiment provides a preferred implementation manner. The circulating water subsystem includes a condenser 11, a condensate pump 12, a condensate pipeline 12-1, a condensate bypass 12-2, low-pressure heaters, a deaerator 13, a deaerator outlet pipeline 13-1, an electric pump 15, an electric pump outlet pipeline 15-1, a feed water pump 16, a feed water pump outlet pipeline 16-1, a feed water pump steam turbine 17, and an auxiliary steam header 10; the heat exchange subsystem includes heat exchange tubes 9, a heat exchange inlet branch 9-1, a heat exchange outlet branch 9-2, a heat supply user 21, a circulating water tank 22, a circulating water pump 22-1, and a heat pump 22-2; a pipeline 22-3 to the condenser is provided between the heat exchange tubes 9 and the condenser 11; a pipeline 10-1 to the auxiliary steam header is provided between the heat exchange tubes 9 and the auxiliary steam header 10; a return water pipeline 22-4 is provided between the condenser 11 and the circulating water tank 22.

[0028] Specifically, this embodiment provides a preferred implementation manner. Four low-pressure heaters are provided, namely a first low-pressure heater 5, a second low-pressure heater 6, a third low-pressure heater 7, and a fourth low-pressure heater 8; an inlet pipeline 5-1 to the deaerator is provided between the first low-pressure heater 5 and the deaerator 13.

[0029] Specifically, this embodiment provides a preferred implementation manner. The circulating subsystem further includes a standby low-pressure heater 13-3 and a standby low-pressure heater outlet pipeline 13-2; the water in the hot well of the steam condenser 11 is divided into two paths after passing through the condensate pump 12, one path enters the low-pressure heaters, and the other path enters the standby low-pressure heater 13-3.

[0030] Specifically, this embodiment provides a preferred implementation manner. The circulating subsystem further includes a standby deaerator 14 and a standby deaerator outlet pipe 14-1; a standby deaerator inlet pipe 5-2 is provided between the first low-pressure heater 5 and the standby deaerator 14; the water in the low-pressure heater enters the deaerator 13 during normal operation and is divided into two paths to enter the deaerator 13 and the standby deaerator 14 respectively during cylinder cutting operation.

[0031] Specifically, this embodiment provides a preferred implementation manner. The circulating subsystem further includes a standby motor-driven pump 18, a standby feed water pump 19, a standby feed water pump steam turbine 20, a first feed water pipe 18-1, a second feed water pipe 18-2, and a standby feed water pump outlet pipe 19-1; the standby motor-driven pump 18 is connected to the steam turbine subsystem through the first feed water pipe 18-1; the standby motor-driven pump 18 is connected to the heat supply user through the second feed water pipe 18-2.

[0032] The specific operation based on the above preferred implementation manner is as follows:

[0033] During normal operation, the extraction steam of the high-pressure cylinder 2 causes the steam to enter the heat exchange tube 9 through the high-pressure cylinder extraction steam pipe 2-1. The water in the circulating water tank 22 is divided into two paths by the circulating water pump 22-1. One path enters the condenser 11 for heat exchange, and the heat-exchanged water enters the circulating water tank 22 for cooling. The other path enters the heat exchange tube 9, is heated by the heat pump 22-2 after heat exchange, and then enters the heat supply user 21. The water in the hot well of the condenser 11 enters the first low-pressure heater 5, the second low-pressure heater 6, the third low-pressure heater 7, and the fourth low-pressure heater 8 through the condensate pump 12, and then enters the deaerator 5 through the deaerator inlet pipe 5-1. The water in the deaerator 5 enters the motor-driven pump 15 through the deaerator outlet pipe 13-1 at low load, and then is sent to the boiler after being heated at high pressure through the motor-driven pump outlet pipe 15-1; at high load, it enters the feed water pump 16 through the deaerator outlet pipe 13-1, and then is sent to the boiler after being heated at high pressure through the outlet pipe 16-1. The feed water pump 16 is driven by the feed water pump steam turbine 17. The steam of the intermediate-pressure cylinder 3 enters the low-pressure cylinder 4 through the pipeline where the connecting pipe valve 3-2 is located. At this time, both the auxiliary connecting pipe valve 3-1 and the steam bypass valve 3-3 are closed. The extraction steam of the intermediate-pressure cylinder 3 causes the steam to enter the first low-pressure heater 5 and the second low-pressure heater 6. The extraction steam of the low-pressure cylinder 4 causes the steam to enter the third low-pressure heater 7 and the fourth low-pressure heater 8.

[0034] During cylinder cutting operation, slowly close the connecting pipe valve 3-2, open the auxiliary connecting pipe valve 3-1 and keep it slightly open to ensure a small amount of steam enters the low-pressure cylinder 4. The steam takes away the blowing heat of the low-pressure cylinder 4 to prevent the blowing temperature from being too high. Cut off the high-pressure cylinder 2 so that steam is not extracted to the heat exchange tube 9, and the heat supply is switched to other systems. Open the valve of the steam bypass valve 3-3. At this time, the steam is divided into three paths. The first path of steam enters the heat exchange outlet steam branch 9-2 and then enters the standby low-pressure heater 13-3. The third low-pressure heater 7 and the fourth low-pressure heater 8 are cut off at this time because no steam enters. The water in the hot well of the condenser 11 passes through the condensate pump 12 and enters the standby low-pressure heater 13-3 from the condensate bypass 12-2. After entering the low-pressure heaters such as the second low-pressure heater 6 and the first low-pressure heater 5, it enters the deaerator 13 from the deaerator pipeline 5-1 and enters the standby deaerator 14 from the standby deaerator pipeline 5-2 respectively; the second path of steam enters the standby feed water turbine 20 from the pipeline 10-1 to the auxiliary steam header, driving the standby feed water pump 19 to work. The standby feed water pump 19 pumps out the water in the standby deaerator 14 and enters the feed water pump outlet pipeline 19-1 from the outlet pipeline 18-3 and finally sends it to the heat supply user 21 for heat supply; the third path of steam enters the heat exchange tube 9 from the heat exchange inlet steam branch 9-1. The steam after heat exchange enters the heat exchange inlet steam branch 9-2 and is discharged into the condenser 11. Among them, the standby electric pump 18 is in a shutdown state, and the water of the heat supply user 21 enters the circulating water tank 22 for cooling for water recycling.

[0035] When the unit increases the load at low load, slowly close the valve of the steam bypass valve 3-3 to stop the steam from flowing to the pipeline 10-1 to the auxiliary steam header. The standby steam turbine 20 shuts down and is switched to the standby electric pump 18. The water in the standby electric pump 18 enters the heat supply user 21 along the second feed water pipeline 18-2 for heat supply. The steam flow into the heat exchange inlet steam branch 9-1 and the standby low-pressure heater 13-3 decreases. Open the condensate pipeline 12-1, and then put the third low-pressure heater 7 and the fourth low-pressure heater 8 into use to reduce the water volume entering the standby deaerator 14 and increase the water volume entering the deaerator 13. As the load continues to increase, the valve of the steam bypass valve 3-3 closes, and the steam flow into the heat exchange inlet steam branch 9-1 and the standby low-pressure heater 13-3 stops. The circulating water enters the heat exchange tube 9 and then enters the heat pump 22-2 for heat supply. The electric pump 15 is deactivated and switched to the feed water pump 16 for operation.

[0036] In other states, for example, when the load is very high, if there is a large amount of water in the deaerator 14, heat can be supplied through the standby electric pump 18. If the feed water pump 16 malfunctions during operation, the electric pump 15 and the standby electric pump 18 can be used to maintain a stable load. If the electric pump 15 malfunctions during independent operation, the standby electric pump 18 is switched to the second feed water pipeline 18-1 for short-term water supply to prevent the unit from tripping, and at the same time, the feed water pump 16 is emergently started.

[0037] Embodiment 2:

[0038] This embodiment provides a method for zero output operation of a low-pressure cylinder. Based on the low-pressure cylinder zero output operation system described in Embodiment 1, it includes the steps of: during normal operation, operating the high-pressure cylinder 2 to extract steam so that the steam enters the heat exchange subsystem from the high-pressure cylinder steam extraction pipeline 2-1 for heat exchange with the circulating water, and operating the intermediate-pressure cylinder 3 to discharge steam through the pipeline where the connecting pipe valve 3-2 is located to the low-pressure cylinder 4; during cylinder switching operation, slowly closing the connecting pipe valve 3-2 and opening the auxiliary connecting pipe valve 3-1 and the steam bypass valve 3-3, so that a larger part of the steam enters the heat exchange subsystem and a smaller part of the steam enters the low-pressure cylinder 4 to carry away the blowing heat.

[0039] Specifically, this embodiment provides a preferred implementation manner, which further includes the steps of: when the unit increases the load at low load, slowly closing the steam bypass valve 3-3, stopping the steam to the auxiliary steam header pipeline 10-1, switching to heat supply by the standby electric pump 18, and reducing the amount of steam entering the standby low-pressure heater 13-3 until the low-pressure heater gradually resumes normal operation.

[0040] Specifically, this embodiment provides a preferred implementation manner, which further includes the steps of: during cylinder switching operation, starting the standby low-pressure heater 13-3 and the standby deaerator 14 so that the water in the low-pressure heater enters the deaerator 13 and the standby deaerator 14 respectively.

[0041] Specifically, this embodiment provides a preferred implementation manner, which further includes the steps of: when the electric pump 15 or the feed water pump 16 malfunctions, enabling the standby electric pump 18 to assist in operation to prevent the unit from tripping.

[0042] It should be noted that for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0043] In the above embodiments, the descriptions of the respective embodiments each have their own emphasis. For parts not elaborated in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0044] The foregoing are only exemplary embodiments of the present invention and should not be used to limit the scope of the present invention. That is, any equivalent changes and modifications made in accordance with the teachings of the present invention still fall within the scope of the present invention. After considering the specification and practicing the disclosure herein, those skilled in the art will readily conceive of other embodiments of the present invention. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not recorded in the present invention. The specification and embodiments are only regarded as exemplary, and the scope and spirit of the present invention are defined by the claims.

Claims

1. A low-pressure cylinder zero-output operation system, characterized in that: It includes a steam turbine subsystem, a circulating water subsystem and a heat exchange subsystem, wherein the steam turbine subsystem, the circulating water subsystem and the heat exchange subsystem are interconnected through pipelines; The steam turbine subsystem includes an ultra-high pressure cylinder, a high pressure cylinder, an intermediate pressure cylinder and a low pressure cylinder, and also includes an auxiliary connecting pipe valve, a connecting pipe valve and a steam bypass valve for controlling the opening and closing of the pipeline; A high-pressure cylinder steam extraction pipeline is provided between the high-pressure cylinder and the heat exchange subsystem, and the steam turbine subsystem extracts steam through the high-pressure cylinder so that steam enters the heat exchange subsystem to exchange heat with circulating water; During normal operation, the intermediate pressure cylinder allows steam to enter the low pressure cylinder through the connecting pipe valve; When the intermediate pressure cylinder is in cylinder cutting operation, a larger portion of steam enters the heat exchange subsystem through the auxiliary connecting pipe valve and the steam bypass valve, and a smaller portion of steam enters the low pressure cylinder through the connecting pipe valve to take away the blast heat.

2. A low-pressure cylinder zero-output operation system according to claim 1, characterized in that: The circulating water subsystem includes a condenser, a condensate pump, a condensate pipeline, a condensate bypass, a low-pressure heater, a deaerator, a deaerator outlet pipeline, an electric pump, an electric pump outlet pipeline, a feedwater pump, a feedwater pump outlet pipeline, a feedwater pump turbine, and an auxiliary steam header; The heat exchange subsystem includes a heat exchange tube, a heat exchange steam inlet branch, a heat exchange steam outlet branch, a heat supply user, a circulating water tank, a circulating water pump, and a heat pump; A pipeline to the condenser is provided between the heat exchange tube and the condenser; A pipeline to the auxiliary steam header is provided between the heat exchange tube and the auxiliary steam header; A return water pipeline is arranged between the condenser and the circulating water tank.

3. A low-pressure cylinder zero-output operation system according to claim 2, characterized in that: There are four low-pressure heaters, namely a first low-pressure heater, a second low-pressure heater, a third low-pressure heater and a fourth low-pressure heater; A water inlet pipe for the deaerator is arranged between the first low-pressure heater and the deaerator.

4. A low-pressure cylinder zero-output operation system according to claim 3, characterized in that: The circulation subsystem also includes a spare low-pressure heater and a spare low-pressure heater outlet pipe; The water in the hot well of the steam generator is divided into two paths through the condensate pump, one path enters the low-pressure heater, and the other path enters the standby low-pressure heater.

5. A low-pressure cylinder zero-output operation system according to claim 4, characterized in that: The circulation subsystem also includes a standby deaerator and a standby deaerator outlet pipe; A water inlet pipe for the standby deaerator is provided between the first low-pressure heater and the standby deaerator; The water in the low-pressure heater enters the deaerator during normal operation, and is divided into two paths during cylinder cutting operation to enter the deaerator and the standby deaerator respectively.

6. A low-pressure cylinder zero-output operation system according to claim 5, characterized in that: The circulation subsystem also includes a standby electric pump, a standby feedwater pump, a standby feedwater pump steam turbine, a first feedwater pipeline, a second feedwater pipeline, and a standby feedwater pump outlet pipeline; The standby electric pump is connected to the steam turbine subsystem through the first water supply pipeline; The standby electric pump is connected to the heating user through the second water supply pipeline.

7. A method for operating a low-pressure cylinder at zero output, characterized in that: Based on the low-pressure cylinder zero-output operation system as claimed in claim 6, the steps include: During normal operation, the high-pressure cylinder is operated to extract steam so that the steam enters the heat exchange subsystem from the high-pressure cylinder steam extraction pipeline to exchange heat with the circulating water, and the medium-pressure cylinder is operated to discharge steam to the low-pressure cylinder through the pipeline where the connecting pipe valve is located; During cylinder cutting operation, the connecting pipe valve is slowly closed and the auxiliary connecting pipe valve and the steam bypass valve are opened, so that a larger portion of steam enters the heat exchange subsystem and a smaller portion of steam enters the low-pressure cylinder to take away the blast heat.

8. A low-pressure cylinder zero-output operation method according to claim 7, characterized in that: Also includes the steps: When the unit increases its load from low load, slowly close the steam bypass valve, stop the steam to the auxiliary steam header pipeline, switch to the standby electric pump for heating, and reduce the amount of steam entering the standby low-pressure heater until the low-pressure heater gradually resumes normal operation.

9. A low-pressure cylinder zero-output operation method according to claim 8, characterized in that: Also includes the steps: When the cylinder is cut off, the standby low-pressure heater and the standby deaerator are started, so that the water in the low-pressure heater enters the deaerator and the standby deaerator respectively.

10. A low-pressure cylinder zero-output operation method according to claim 9, characterized in that: Also includes the steps: When the electric pump or the water supply pump fails, the standby electric pump is enabled to assist in operation to prevent the machine from tripping.

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