Closed water system flushing method and closed water system

Abstract

The invention relates to the technical field of closed water systems, in particular to a closed water system flushing method and a closed water system. The method comprises the steps that the closed water system is filled with a flushing medium, and then the flushing medium is discharged; the closed water system is filled with the flushing medium again, and then the flushing medium circulates in the closed water system; the flushing medium is discharged, the turbidity of the discharged flushing medium is detected, and if the turbidity of the flushing medium is smaller than or equal to the preset turbidity, flushing of the closed water system is completed. According to the closed water system flushing method, the mode that static flushing and discharging are combined with closed circulating flushing is adopted, the filter screen is adopted for conducting circulating filtration on the flushing medium in the closed circulating flushing process, the flushing flexibility of the closed water system is achieved, and the flushing efficiency is improved. The invention further provides the closed water system, the closed water system adopts the closed water system flushing method, flushing of the closed water system is met, and meanwhile the influence on formal equipment is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of closed water systems, and in particular to a closed water system flushing method and a closed water system. Background Art

[0002] The closed-loop cooling water system of the steam turbine plant (referred to as the closed water system) provides cooling water required for the normal operation of the units for the auxiliary equipment in the plant, and transfers the absorbed heat to the outlet of the cooling water system. During the construction of the steam turbine plant, the closed cooling water system must be installed and handed over for commissioning first. After completing the relevant commissioning tests, it must be able to provide cooling water for the auxiliary equipment in the steam turbine plant, ensuring the implementation of relevant commissioning activities for the auxiliary equipment and the normal operation of related systems.

[0003] After the installation and commissioning of the closed water system, it needs to be flushed to ensure the cleanliness of the system, thereby ensuring the smooth progress of the commissioning work and the safe and stable operation of the system. In order to meet the cleanliness requirements and minimize the impact on the formal equipment, the closed water system adopts a large number of temporary devices during the flushing stage, including temporary short-circuiting of the plate heat exchanger, temporary short-circuiting of the regulating valve, and temporary flushing filter screens to support the closed-loop operation of the closed water system and achieve circulating filtration and flushing. However, flushing only relies on the closed water system circulating filtration method, the flushing method is single and the flushing efficiency is low. Therefore, a closed water system flushing method is urgently needed. Summary of the invention

[0004] The purpose of the present invention is to provide a closed water system flushing method to improve flushing efficiency.

[0005] Another object of the present invention is to provide a closed water system that meets the flushing needs of the closed water system while reducing the impact on formal equipment.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A closed water system flushing method, wherein a filter screen is provided in the closed water system, and the closed water system flushing method comprises:

[0008] S1. Filling the closed water system with a flushing medium, and then discharging the flushing medium;

[0009] S2, filling the closed water system with the flushing medium again, and then circulating the flushing medium in the closed water system for a first preset time;

[0010] S3. Discharge the flushing medium and detect the turbidity of the discharged flushing medium. If the turbidity of the flushing medium is less than or equal to the preset turbidity, the flushing of the closed water system is completed. If the turbidity of the flushing medium is greater than the preset turbidity, repeat steps S2-S3.

[0011] As an optional technical solution, isolation valves are provided upstream and downstream of the filter screen;

[0012] In step S2, when the flushing medium circulates inside the closed water system, the pressure difference between the upstream and downstream sides of the filter is monitored. If the pressure difference is greater than the preset pressure difference, the isolation valves upstream and downstream of the filter are closed, and then the flushing medium is introduced into the downstream side of the filter, the filter is backwashed with the flushing medium, and the sewage on the upstream side of the filter is discharged from the closed water system. If the pressure difference is less than or equal to the preset pressure difference, the flushing medium is kept circulating inside the closed water system.

[0013] As an optional technical solution, the closed water system includes a main circuit and a plurality of parallel branches, the plurality of branches are connected to the main circuit, each of the branches is provided with a closed water pump and the filter, the closed water pump is used to circulate the flushing medium inside the closed water system, the filter is located at the inlet side of the closed water pump, and each of the branches is provided with the isolation valve on the upstream side of the filter and the outlet side of the closed water pump;

[0014] In step S2, the isolation valve on any one of the multiple branches is opened to allow the flushing medium to circulate inside the closed water system. When the pressure difference is greater than the preset pressure difference, the isolation valve on the branch is closed to backwash the filter of the branch. At the same time, the isolation valve on any one of the remaining branches is opened to keep the flushing medium circulating inside the closed water system.

[0015] As an optional technical solution, the closed water system further comprises a plate heat exchanger, and a temporary short-circuit pipe of the plate heat exchanger is connected between the inlet end and the outlet end of the plate heat exchanger;

[0016] In step S2, the flushing medium in the temporary short-circuit pipe of the plate heat exchanger is introduced into the downstream side of the filter screen.

[0017] As an optional technical solution, in step S2, after the flushing medium circulates inside the closed water system for a second preset time, the closed water system is replenished and drained simultaneously, and the flushing medium is kept circulating inside the closed water system, and the first preset time is greater than the second preset time.

[0018] As an optional technical solution, the closed water system is provided with a water replenishment isolation valve and a sewage discharge valve. The water replenishment isolation valve is used to control the on-off of water inlet to the closed water system, and the sewage discharge valve is used to control the on-off of drainage of the closed water system. When the closed water system is replenished and drained at the same time, the opening of the water replenishment isolation valve and the sewage discharge valve is adjusted in real time to keep the water replenishment amount and the drainage amount in dynamic balance.

[0019] As an optional technical solution, when the water replenishment amount is greater than the drainage amount, the opening of the water replenishment isolation valve is reduced or the opening of the sewage valve is increased; when the water replenishment amount is less than the drainage amount, the opening of the water replenishment isolation valve is increased or the opening of the sewage valve is reduced.

[0020] As an optional technical solution, in step S1, the closed water system is filled with a flushing medium, and then the flushing medium is discharged, and the process is repeated a set number of times.

[0021] As an optional technical solution, the flushing medium is desalted water.

[0022] The present invention also adopts the following technical solutions:

[0023] A closed water system adopts the closed water system flushing method described in any of the above schemes.

[0024] Beneficial effects of the present invention:

[0025] The present invention provides a closed water system flushing method, the method comprising: filling the closed water system with a flushing medium, and then discharging the flushing medium; filling the closed water system with the flushing medium again, and then circulating the flushing medium in the closed water system for a first preset time; discharging the flushing medium and detecting the turbidity of the discharged flushing medium, if the turbidity of the flushing medium is less than or equal to the preset turbidity, the flushing of the closed water system is completed, if the turbidity of the flushing medium is greater than the preset turbidity, the closed water system continues to be circulated and flushed. The closed water system flushing method adopts a combination of static flushing and closed cycle flushing, and uses a filter to circulate and filter the flushing medium during the closed cycle flushing process. Compared with the flushing mode of a single closed cycle filtration, the flexibility of flushing of the closed water system is achieved and the flushing efficiency is improved.

[0026] The present invention also provides a closed water system, which adopts the above-mentioned closed water system flushing method to meet the flushing needs of the closed water system while reducing the impact on formal equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of a closed water system flushing method provided by an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of a closed water system provided by an embodiment of the present invention.

[0029] In the figure:

[0030] 1. Closed expansion water tank; 2. Closed water pump; 3. Filter; 4. Closed water supply main pipe; 5. Closed water return main pipe; 6. Plate heat exchanger; 7. Cooling water user heat exchanger; 8. Temperature and air conditioning valve group;

[0031] 10. Flushing medium delivery pipeline; 20. Temporary short-circuit pipeline of water supply regulating valve; 30. Temporary short-circuit pipeline of plate heat exchanger; 40. Temporary short-circuit pipeline of cooling water user heat exchanger; 50. Temporary short-circuit pipeline of temperature control regulating valve group; 60. Sewage pipeline; 70. Backwash pipeline; 80. Drainage pipeline;

[0032] 100. Water supply isolation valve; 200. Drain valve. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0034] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0037] Combine the following Figure 1-Figure 2 The technical solution of the present invention is further illustrated through specific implementation methods.

[0038] During the construction of the steam turbine plant, after the installation is completed and the commissioning is completed, the closed water system needs to be flushed to ensure the cleanliness of the system, so as to ensure the smooth progress of the commissioning work and the safe and stable operation of the system. In order to achieve the flushing of the closed water system and minimize the impact on the formal equipment, the embodiment of the present invention provides a closed water system, which includes a closed expansion water tank 1, a closed water pump 2, a plate heat exchanger 6, a cooling water user heat exchanger 7 and a temperature control valve group 8, as well as temporary devices such as a temporary short-circuit pipe 20 for the water supply regulating valve, a temporary short-circuit pipe 30 for the plate heat exchanger, a temporary short-circuit pipe 40 for the cooling water user heat exchanger, and a temporary short-circuit pipe 50 for the temperature control valve group.

[0039] In detail, the temporary short-circuit pipe 20 of the water supply regulating valve is connected to both sides of the water supply regulating valve, the temporary short-circuit pipe 30 of the plate heat exchanger is connected between the inlet end and the outlet end of the plate heat exchanger 6, the temporary short-circuit pipe 40 of the cooling water user heat exchanger is connected between the inlet end and the outlet end of the cooling water user heat exchanger 7, and the temporary short-circuit pipe 50 of the temperature control valve group is connected between the inlet end and the outlet end of the temperature control valve group 8.

[0040] Furthermore, if Figure 2As shown, the inlet of the closed expansion water tank 1 is connected to the flushing medium delivery pipeline 10, and a water supply isolation valve 100 is arranged on the flushing medium delivery pipeline 10. The water supply isolation valve 100 is used to control the on-off of water inlet of the closed water system. The water supply regulating valve temporary short-circuit pipeline 20 is provided with a water supply regulating valve. When the closed expansion water tank 1 is at a low water level, the water supply regulating valve can automatically open to replenish water for the closed expansion water tank 1, so that the water level in the closed expansion water tank 1 is always at a constant liquid level; the outlet of the closed expansion water tank 1 is connected to the inlet of the closed water pump 2, and the inlet end of the closed water pump 2 is also provided with a filter The filter screen 3 can filter the flushing medium; the outlet of the closed water pump 2 is connected to the temporary short-circuit pipe 30 of the plate heat exchanger, the temporary short-circuit pipe 30 of the plate heat exchanger is connected to the closed water supply main pipe 4, the closed water supply main pipe 4 is connected to the temporary short-circuit pipe 40 of the cooling water user heat exchanger, the temporary short-circuit pipe 40 of the cooling water user heat exchanger is connected to the temporary short-circuit pipe 50 of the temperature control valve group, the temporary short-circuit pipe 50 of the temperature control valve group is connected to the closed water return main pipe 5, and the closed water return main pipe 5 is connected to the inlet of the closed water pump 2, so as to form a circulation loop inside the closed water system. The temporary short-circuit pipe 30 of the plate heat exchanger is provided with a sewage pipe 60, which is used to discharge the sewage inside the closed water system, and the sewage pipe 60 is provided with a sewage valve 200, which is used to control the on and off of the drainage of the closed water system.

[0041] Among them, the closed expansion water tank 1 can balance the water volume and pressure inside the system to maintain stable operation of the system. The closed expansion water tank 1 is set at the highest point of the closed water system. The closed expansion water tank 1 is a prior art and will not be described in detail here.

[0042] Based on the above closed water system, the present invention also provides a closed water system flushing method, which comprises the following steps:

[0043] S1. Fill the closed water system with flushing medium, and then discharge the flushing medium;

[0044] Specifically, the drain valve 200 is first closed, the water supply isolation valve 100 is opened, and the flushing medium is introduced into the closed water system; then the water supply isolation valve 100 is closed, the drain valve 200 is opened, and the flushing medium in the closed water system is discharged.

[0045] S2, filling the closed water system with the flushing medium again, and then circulating the flushing medium in the closed water system for a first preset time;

[0046] Specifically, the drain valve 200 is closed, the water replenishment isolation valve 100 is opened, and the closed water system is refilled with the flushing medium; the closed water pump 2 is started to circulate the flushing medium inside the closed water system for a first preset time, and the filter 3 circulates and filters the flushing medium inside the closed water system.

[0047] S3, discharge the flushing medium and detect the turbidity of the discharged flushing medium. If the turbidity of the flushing medium is less than or equal to the preset turbidity, the flushing of the closed water system is completed. If the turbidity of the flushing medium is greater than the preset turbidity, repeat steps S2-S3.

[0048] Specifically, after the flushing medium circulates in the closed water system for the first preset time, the flushing medium is discharged, and the turbidity of the discharged water is detected by a turbidity meter. In this embodiment, if the turbidity is less than or equal to 3NTU, it can be determined that the flushing of the closed water system is completed. The specific value of the turbidity can be set according to the actual working conditions and is not specifically limited here. The turbidity meter is a prior art and is not described in detail here. The first preset time is set according to the actual flushing conditions, and the specific value is not specifically limited here.

[0049] In detail, during the flushing process of the closed water system, static flushing is first performed, that is, the internal pipes of the closed water system are connected, ensuring that the drain valve 200 is in a closed state, opening the water supply isolation valve 100, and filling the closed water system with flushing medium through the flushing medium delivery pipeline 10 and the closed expansion water tank 1, and then closing the water supply isolation valve 100, opening the drain valve 200, and discharging the flushing medium inside the closed water system through the drain pipe 60, and foreign matter such as mud and sand inside the closed water system is discharged along with the flushing medium, thereby realizing static flushing of the closed water system. Among them, the drain pipe 60 is located at the lowest point of the closed water system, and the system can be discharged by using the gravitational potential energy of the flushing medium itself. The discharged water can be discharged to an outdoor sewage well or to an indoor sewage pool, and can be discharged according to the actual pipeline layout. Then close the drain valve 200, open the water replenishment isolation valve 100 again, fill the closed water system with flushing medium again, start the closed water pump 2, and the flushing medium in the closed water system circulates under the action of the closed water pump 2. The potential energy and large flow provided by the closed water pump 2 are used, and the flushing medium in the closed water system is circulated and filtered through the filter 3 at the inlet end of the closed water pump 2 to achieve closed-loop flushing of the closed water system. After the closed-loop flushing, the flushing medium is discharged, the turbidity of the discharged flushing medium is detected, and it is determined whether the flushing of the closed water system is completed based on the turbidity. After the flushing of the closed water system is completed, the temporarily short-circuited pipes are removed, and the closed water system can be put into use.

[0050] The closed water system flushing method adopts a combination of static flushing and closed-loop flushing, and uses a filter 3 to circulate and filter the flushing medium during the closed-loop flushing process. Compared with the flushing mode of a single closed-loop filtration, the flushing flexibility of the closed water system is achieved and the flushing efficiency is improved.

[0051] In this embodiment, the flushing medium is desalted water, which can better absorb foreign matter such as mud and rust inside the closed water system, thereby improving the flushing effect.

[0052] Furthermore, in step S1, the closed water system is filled with a flushing medium, and then the flushing medium is discharged, and the set number of times is repeated. Specifically, in step S1, the cleanliness of the discharged flushing medium is observed. If the drainage is relatively clear and there is no obvious fine sand-like substance, step S2 is executed; if the drainage is relatively turbid and there is a lot of muddy and sandy substances, the drain valve 200 is closed again, and the water replenishment isolation valve 100 is opened, and step S1 is repeated until the drainage is relatively clear. Generally, 3-5 static flushings can discharge mud and other foreign matter inside the closed water system. This embodiment does not specifically limit the specific number of static flushings, and the operation can be carried out according to actual conditions. It should be noted that the cleanliness of the discharged flushing medium in step S1 can be judged visually. If there is no obvious fine sand-like substance in the drainage, step S2 can be entered.

[0053] In order to clean the filter screen 3 at the inlet end of the closed water pump 2, in step S2, when the flushing medium circulates inside the closed water system, the pressure difference between the upstream and downstream sides of the filter screen 3 is monitored. If the pressure difference is greater than the preset pressure difference, the isolation valves upstream and downstream of the filter screen 3 are closed, and then the flushing medium is introduced into the downstream side of the filter screen 3, the filter screen 3 is backwashed with the flushing medium, and the sewage on the upstream side of the filter screen 3 is discharged from the closed water system. If the pressure difference is less than or equal to the preset pressure difference, the flushing medium is kept circulating inside the closed water system.

[0054] In this embodiment, a differential pressure gauge is provided on the installation pipeline of the filter 3, and the differential pressure gauge is used to monitor the pressure difference between the upstream and downstream sides of the filter 3. When the pressure difference is greater than 30 kPa, it can be determined that the filter 3 intercepts too many impurities and the flow capacity is significantly reduced. At this time, the closed water pump 2 is stopped, and the isolation valves upstream and downstream of the filter 3 are closed. Then, the flushing medium is introduced into the downstream side of the filter 3 to achieve backwashing of the filter 3, and the sewage on the upstream side of the filter 3 is discharged from the closed water system. When the drainage is clear and there are no obvious impurities, it indicates that the filter 3 has been cleaned and the closed water pump 2 can be put into use. By backwashing the filter 3, the filter 3 at the inlet end of the closed water pump 2 can be cleaned without disassembling the filter 3, which effectively reduces manpower input and improves work efficiency. It should be noted that the specific values ​​of the preset pressure difference on the upstream and downstream sides of the filter 3 can be set according to the use conditions, and no specific restrictions are made here.

[0055] In order to ensure the continuous and stable operation of the closed water system, the closed water system includes a main road and multiple parallel branches, and the multiple branches are connected to the main road. A closed water pump 2 and a filter 3 are provided on each branch. The closed water pump 2 is used to circulate the flushing medium inside the closed water system. The filter 3 is located on the inlet side of the closed water pump 2. Each branch is provided with an isolation valve on the upstream side of the filter 3 and the outlet side of the closed water pump 2. In step S2, the isolation valve on any one of the multiple branches is opened to allow the flushing medium to circulate inside the closed water system. Multiple parallel roads are set. When the pressure difference between the upstream and downstream sides of the filter 3 is greater than the preset pressure difference, the isolation valve on the branch is closed, and the filter 3 of the branch is backwashed. At the same time, the isolation valve on any one of the remaining branches is opened to keep the flushing medium circulating inside the closed water system. This setting ensures the normal operation of the closed water system and improves the flushing efficiency.

[0056] In this embodiment, three branches are provided, and the three branches are connected to the main road. Correspondingly, three closed water pumps 2 are provided, and a filter screen 3 is provided at the inlet end of each closed water pump 2. The number of branches can be set according to the use requirements, and is not specifically limited here.

[0057] Furthermore, in step S2, the flushing medium in the temporary short-circuit pipe 30 of the plate heat exchanger is introduced into the downstream side of the filter screen 3. The temporary short-circuit pipe 30 of the plate heat exchanger is connected with a backwash pipe 70. When the filter screen 3 intercepts too many impurities and the flow capacity is significantly reduced, the backwash pipe 70 is connected to backwash the filter screen 3, and water is taken from the temporary short-circuit pipe 30 of the plate heat exchanger, which facilitates the removal of the backwash pipe 70 after the subsequent closed water system is put into use.

[0058] In this embodiment, the closed water system is further provided with a drainage pipe 80 , which is located at the upstream side of the filter screen 3 , and the sewage used for backwashing the filter screen 3 is discharged from the closed water system through the drainage pipe 80 .

[0059] Furthermore, in step S2, after the flushing medium circulates in the closed water system for a second preset time, the closed water system is replenished and drained at the same time, and the flushing medium is kept circulating in the closed water system, and the first preset time is greater than the second preset time. In detail, during the closed circulation flushing stage, without affecting the closed water pump 2 and the closed water system circulation operation, the water replenishment isolation valve 100 and the sewage valve 200 are opened at the same time, while replenishing the system with water and draining the system, and using the potential energy and large flow provided by the closed water pump 2, foreign matter such as rust and welding slag is discharged from the system through the sewage valve 200, so as to achieve dynamic flushing of the closed water system, which can effectively reduce the frequency of blockage of the filter 3 and improve the flushing efficiency. It should be noted that in this embodiment, the second preset time is 30 minutes, that is, after the flushing medium circulates in the closed water system for 30 minutes, the closed water system is replenished and drained at the same time.

[0060] Furthermore, when the closed water system is replenished and drained at the same time, the opening of the water replenishment isolation valve 100 and the sewage discharge valve 200 is adjusted in real time to maintain a dynamic balance between the replenishment amount and the drainage amount. When the replenishment amount is greater than the drainage amount, the opening of the water replenishment isolation valve 100 is reduced or the opening of the sewage discharge valve 200 is increased; when the replenishment amount is less than the drainage amount, the opening of the water replenishment isolation valve 100 is increased or the opening of the sewage discharge valve 200 is reduced.

[0061] Specifically, when the closed water system is replenished and drained at the same time, the opening of the water replenishment isolation valve 100 and the sewage valve 200 needs to be manually adjusted to maintain the balance between the replenishment amount and the drainage amount, to ensure the water loading amount of the entire closed water system, and then to ensure the normal operation of the closed water pump 2 and the closed water system. In this embodiment, the capacity of the closed expansion water tank 1 is 20t, and the maximum liquid level is 4000mm. When the replenishment amount is slightly greater than the drainage amount, the water level in the closed expansion water tank 1 will rise slowly. When the water level reaches the high liquid level of 3500mm, the opening of the water replenishment isolation valve 100 is slightly adjusted or the opening of the sewage valve 200 is slightly increased, so that the drainage amount is slightly greater than the replenishment amount, and the water level in the closed expansion water tank 1 slowly decreases; when the water level reaches the low liquid level of 1500mm, the opening of the water replenishment isolation valve 100 is increased or the opening of the sewage valve 200 is reduced to make the water level rise, and this is repeated to maintain the dynamic balance of the water level.

[0062] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A closed water system flushing method, characterized in that: A filter screen (3) is provided in the closed water system, and the closed water system flushing method comprises: S1. Filling the closed water system with a flushing medium, and then discharging the flushing medium; S2, filling the closed water system with the flushing medium again, and then circulating the flushing medium in the closed water system for a first preset time; S3. Discharge the flushing medium and detect the turbidity of the discharged flushing medium. If the turbidity of the flushing medium is less than or equal to the preset turbidity, the flushing of the closed water system is completed. If the turbidity of the flushing medium is greater than the preset turbidity, repeat steps S2-S3.

2. The closed water system flushing method according to claim 1, characterized in that: Isolation valves are provided upstream and downstream of the filter screen (3); In step S2, when the flushing medium circulates inside the closed water system, the pressure difference between the upstream side and the downstream side of the filter (3) is monitored. If the pressure difference is greater than a preset pressure difference, the isolation valves upstream and downstream of the filter (3) are closed, and then the flushing medium is introduced into the downstream side of the filter (3). The filter (3) is backwashed using the flushing medium, and the sewage on the upstream side of the filter (3) is discharged from the closed water system. If the pressure difference is less than or equal to the preset pressure difference, the flushing medium is kept circulating inside the closed water system.

3. The closed water system flushing method according to claim 2, characterized in that: The closed water system comprises a main circuit and a plurality of parallel branch circuits, wherein the plurality of branch circuits are all connected to the main circuit, and each of the branch circuits is provided with a closed water pump (2) and a filter screen (3). The closed water pump (2) is used to circulate the flushing medium inside the closed water system, and the filter screen (3) is located at the inlet side of the closed water pump (2). Each of the branch circuits is provided with an isolation valve at the upstream side of the filter screen (3) and at the outlet side of the closed water pump (2); In step S2, the isolation valve on any one of the multiple branches is opened to allow the flushing medium to circulate inside the closed water system. When the pressure difference is greater than the preset pressure difference, the isolation valve on the branch is closed to backwash the filter (3) of the branch. At the same time, the isolation valve on any one of the remaining branches is opened to allow the flushing medium to continue circulating inside the closed water system.

4. The closed water system flushing method according to claim 2, characterized in that: The closed water system further comprises a plate heat exchanger (6), wherein a temporary short-circuit pipe (30) of the plate heat exchanger is connected between the inlet end and the outlet end of the plate heat exchanger (6); In step S2, the flushing medium in the temporary short-circuit pipe (30) of the plate heat exchanger is introduced into the downstream side of the filter screen (3).

5. The closed water system flushing method according to claim 1, characterized in that: In step S2, after the flushing medium circulates in the closed water system for a second preset time, the closed water system is replenished and drained simultaneously, and the flushing medium is kept circulating in the closed water system, and the first preset time is greater than the second preset time.

6. The closed water system flushing method according to claim 5, characterized in that: The closed water system is provided with a water replenishment isolation valve (100) and a sewage discharge valve (200). The water replenishment isolation valve (100) is used to control the on-off of water inflow into the closed water system, and the sewage discharge valve (200) is used to control the on-off of drainage of the closed water system. When the closed water system is replenished and drained at the same time, the openings of the water replenishment isolation valve (100) and the sewage discharge valve (200) are adjusted in real time to keep the water replenishment amount and the drainage amount in dynamic balance.

7. The closed water system flushing method according to claim 6, characterized in that: When the water replenishment amount is greater than the drainage amount, the opening of the water replenishment isolation valve (100) is reduced or the opening of the sewage discharge valve (200) is increased; when the water replenishment amount is less than the drainage amount, the opening of the water replenishment isolation valve (100) is increased or the opening of the sewage discharge valve (200) is reduced.

8. The closed water system flushing method according to any one of claims 1 to 7, characterized in that: In step S1, the closed water system is filled with a flushing medium, and then the flushing medium is discharged, and the process is repeated for a set number of times.

9. The closed water system flushing method according to any one of claims 1 to 7, characterized in that: The flushing medium is deionized water.

10. Closed water system, characterized in that: A closed water system flushing method as described in any one of claims 1 to 9 is adopted.

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