Off-line cleaning device

Abstract

The utility model discloses an off-line cleaning device. The off-line cleaning device comprises a dispensing and stirring module, a skid-mounted module and a cleaning water backflow module. The dispensing and stirring module is configured to prepare cleaning water and convey the cleaning water to the skid-mounted module; the skid-mounted module is configured to feed cleaning water into the at least one electrodeionization module and collect reflux liquid output by the at least one electrodeionization module at the same time; the cleaning water backflow module is configured to monitor and control the flow of backflow liquid and collect the backflow liquid into the dispensing and stirring module. The problems of module blockage, water yield reduction, water inlet and outlet pressure difference rise and the like caused by the fact that pollutants such as organic matters, silicate and the like are easily accumulated in the electrodeionization module along with the prolonging of operation time in practical application are solved.

Description

Technical Field

[0001] The present application relates to the field of cleaning technology, and in particular to an off-line cleaning device. Background Art

[0002] With the continuous development of industrial technology and increasingly stringent environmental protection requirements, the demand for high-purity water has shown a significant growth trend in various fields, especially in the power, coal chemical and other industries. Although traditional ion exchange technology can effectively remove ionic impurities in water, it requires regular use of acid and alkali for resin regeneration, which not only increases operating costs, but also may produce waste liquid that is harmful to the environment. Therefore, it is particularly important to develop a new technology that does not require chemical regeneration, is easy to operate, and can efficiently produce ultrapure water.

[0003] Electrodesalination technology came into being, combining the advantages of electrodialysis and ion exchange technology. Through the action of the DC electric field, the ion exchanger is filled in the fresh water chamber of the electrodialyzer to achieve directional migration and removal of ions, thereby obtaining high-purity water. This technology does not require the use of acid and alkali for resin regeneration, reducing operating costs and also reducing environmental pollution.

[0004] In the boiler feed water treatment system of thermal power plants, electro-deionization technology has been widely used and has shown good performance. However, with the rapid development of the coal chemical industry, the water quality of coal chemical industry is usually poor, containing high organic matter, silicate and hardness and other impurities, which brings new challenges to the application of electro-deionization technology.

[0005] In actual applications, as the operation time increases, pollutants such as organic matter and silicates tend to accumulate inside the electro-deionization module, leading to problems such as module blockage, reduced water production, and increased inlet and outlet water pressure differences. This not only affects the normal operation of the system, but may also lead to subsequent system instability. Utility Model Content

[0006] The present application provides an off-line cleaning device, which solves the problem that in actual applications, as the operating time increases, pollutants such as organic matter and silicates are easily accumulated inside the electro-deionization module, leading to module blockage, decreased water production, and increased inlet and outlet water pressure differences.

[0007] The present application provides an offline cleaning device, comprising a dispensing and stirring module, a skid-mounted module and a cleaning water return module; the dispensing and stirring module is configured to prepare cleaning water and transport the cleaning water to the skid-mounted module; the skid-mounted module is configured to transport the cleaning water into at least one electric deionization module and collect the reflux liquid output by at least one electric deionization module; the cleaning water return module is configured to monitor and control the flow rate of the reflux liquid and collect the reflux liquid into the dispensing and stirring module.

[0008] In a possible implementation, the dosage and stirring module includes a cleaning water tank, a dosing port, a cleaning water pump, a reflux stirring pipeline, a safety filter and a cleaning water inlet main pipe; the dosing port is arranged at the top or side of the cleaning water tank; a vent pipe and a vent valve are arranged at the bottom of the cleaning water tank; the output end of the cleaning water tank is connected to the input end of the cleaning water pump through a pipeline; the output end of the cleaning water pump is respectively connected to the input end of the reflux stirring pipeline and the input end of the safety filter; the output end of the reflux stirring pipeline is connected to the cleaning water tank; the output end of the safety filter is connected to the skid-mounted module through the cleaning water inlet main pipe.

[0009] In a possible implementation, the skid-mounted module includes a first water inlet branch pipe and a second water inlet branch pipe; the output end of the cleaning water inlet main pipe is connected to the input end of the first water inlet branch pipe and the input end of the second water inlet branch pipe respectively; the output end of the first water inlet branch pipe is connected to the water inlet of the fresh water chamber of the electric deionization module, and the output end of the second water inlet branch pipe is connected to the water inlet of the concentrated water chamber of the electric deionization module.

[0010] In a possible implementation, the cleaning water reflux module includes a first reflux main pipe, a second reflux main pipe, a third reflux main pipe, a first reflux branch pipe, a second reflux branch pipe, and a third reflux branch pipe; the drain outlet of the fresh water chamber of the electric deionization module is connected to the input end of the first reflux main pipe through the first reflux branch pipe; the output end of the first reflux main pipe is connected to the cleaning water tank; the drain outlet of the concentrated water chamber of the electric deionization module is connected to the input end of the second reflux main pipe through the second reflux branch pipe; the output end of the second reflux main pipe is connected to the cleaning water tank; the drain outlet of the extreme water chamber of the electric deionization module is connected to the input end of the third reflux main pipe through the third reflux branch pipe; and the output end of the third reflux main pipe is connected to the cleaning water tank.

[0011] In a possible implementation, flow meters are provided on the first reflux branch pipe, the second reflux branch pipe, and the third reflux branch pipe.

[0012] In a possible implementation, the first reflux main pipe, the second reflux main pipe, and the third reflux main pipe are all provided with vent pipes and vent valves.

[0013] In a possible implementation, the number of the electric desalination modules matches the number of the first water inlet branch, the second water inlet branch, the first return branch, the second return branch, and the third return branch.

[0014] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0015] An offline cleaning device provided in an embodiment of the present application includes a dispensing and stirring module, a skid-mounted module and a cleaning water return module. The dispensing and stirring module is configured to prepare cleaning water and convey the cleaning water to the skid-mounted module. The skid-mounted module is configured to convey the cleaning water to at least one electric desalination module and collect the reflux liquid output by at least one electric desalination module. The cleaning water return module is configured to monitor and control the flow of the reflux liquid and collect the reflux liquid into the dispensing and stirring module. The problem that in actual applications, as the operating time increases, organic matter, silicate and other pollutants are easily accumulated inside the electric desalination module, resulting in module blockage, decreased water production and increased inlet and outlet water pressure differences is solved. This not only affects the normal operation of the system, but may also lead to instability in the subsequent system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of the structure of the off-line cleaning device provided in an embodiment of the present application.

[0018] Figure markings: 1-dosage mixing module; 11-cleaning water tank; 12-dosage port; 13-cleaning water pump; 14-reflux mixing pipeline; 15-safety filter; 16-cleaning water inlet main pipe; 2-skid mounted module; 21-first water inlet branch pipe; 22-second water inlet branch pipe; 3-cleaning water reflux module; 31-first reflux main pipe; 32-second reflux main pipe; 33-third reflux main pipe; 34-first reflux branch pipe; 35-second reflux branch pipe; 36-third reflux branch pipe; 4-electro-desalination module; 5-flow meter. DETAILED DESCRIPTION

[0019] In the description of the embodiments of the present application, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. The terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] Figure 1 A schematic diagram of the structure of an off-line cleaning device provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the off-line cleaning device includes a dispensing and stirring module 1, a skid-mounted module 2 and a cleaning water return module 3; the dispensing and stirring module 1 is configured to prepare cleaning water and transport the cleaning water to the skid-mounted module 2; the skid-mounted module 2 is configured to transport the cleaning water into at least one electric deionization module 4, and at the same time collect the reflux liquid output by at least one electric deionization module 4; the cleaning water return module 3 is configured to monitor and control the flow rate of the reflux liquid, and collect the reflux liquid into the dispensing and stirring module 1.

[0022] The electric deionization module 4 of the present application is an EDI module, which uses mixed ion exchange resin to adsorb anions and cations in the feed water. These adsorbed ions are removed through anion and cation exchange membranes respectively under the action of DC voltage. The fresh water chamber is the core part of the EDI module for producing high-purity water. It removes ions in water through a combination of ion exchange resin and ion exchange membrane to obtain pure water. The concentrated water chamber is located on both sides of the fresh water chamber and is separated from the fresh water chamber by an ion exchange membrane. Under the action of the electric field, ions pass through the exchange membrane from the fresh water chamber into the concentrated water chamber, thereby achieving ion removal. The pole water chamber is independent of the fresh water chamber and the concentrated water chamber in the EDI module, but they together constitute a complete electric deionization system. The electric field generated by the electrode in the pole water chamber provides a driving force for ion exchange in the fresh water chamber and the concentrated water chamber.

[0023] The dosage and mixing module 1 includes a cleaning water tank 11, a dosing port 12, a cleaning water pump 13, a reflux mixing pipeline 14, a safety filter 15 and a cleaning water inlet main pipe 16; the dosing port 12 is arranged at the top or side of the cleaning water tank 11; a vent pipe and a vent valve are arranged at the bottom of the cleaning water tank 11; the output end of the cleaning water tank 11 is connected to the input end of the cleaning water pump 13 through a pipeline; the output end of the cleaning water pump 13 is respectively connected to the input end of the reflux mixing pipeline 14 and the input end of the safety filter 15; the output end of the reflux mixing pipeline 14 is connected to the cleaning water tank 11; the output end of the safety filter 15 is connected to the skid-mounted module 2 through the cleaning water inlet main pipe 16.

[0024] Specifically, the cleaning water tank 11 is used to store and mix the cleaning liquid. It is usually made of corrosion-resistant materials to adapt to the corrosion of chemicals and water. The design of the dosing port 12 can have multiple solid sodium chloride, liquid sodium hydroxide and hydrochloric acid. The cleaning water pump 13 is responsible for extracting the cleaning liquid from the cleaning water tank 11 and transporting it to the reflux stirring pipeline 14 and the security filter 15 through a pipeline. At the same time, it can also provide sufficient pressure for the cleaning liquid to ensure that the cleaning liquid can smoothly reach the skid-mounted module 2. The reflux stirring pipeline 14 connects the output end of the cleaning water pump 13 and the cleaning water tank 11 to form a circulation loop. Through the reflux stirring pipeline 14, part of the cleaning liquid is pumped back to the cleaning water tank 11 and mixed with the cleaning liquid therein. This circulating stirring method helps to ensure the uniformity and stability of the cleaning liquid and improve the cleaning effect. The security filter 15 is used to filter impurities and particulate matter in the cleaning liquid, and ensure that the quality of the cleaning liquid transported to the skid-mounted module 2 meets the requirements to prevent impurities from damaging the electro-deionization module 4. The cleaning water inlet main pipe 16 is a pipe connecting the output end of the security filter 15 and the skid-mounted module 2. The cleaning liquid filtered by the security filter 15 is transported to the skid-mounted module 2 through the cleaning water inlet main pipe 16 for cleaning the electric desalination module 4. The cleaning water inlet main pipe 16 is usually made of corrosion-resistant materials to adapt to the chemical properties of the cleaning liquid. A vent pipe and a vent valve are provided at the bottom of the cleaning water tank 11 to discharge the residual cleaning liquid in the cleaning water tank 11 or to perform maintenance.

[0025] The skid-mounted module 2 includes a first water inlet branch pipe 21 and a second water inlet branch pipe 22; the output end of the cleaning water inlet main pipe 16 is connected to the input end of the first water inlet branch pipe 21 and the input end of the second water inlet branch pipe 22 respectively; the output end of the first water inlet branch pipe 21 is connected to the water inlet of the fresh water chamber of the electric deionization module 4, and the output end of the second water inlet branch pipe 22 is connected to the water inlet of the concentrated water chamber of the electric deionization module 4.

[0026] Specifically, flow control valves or regulating valves are installed on the first water inlet branch pipe 21 and the second water inlet branch pipe 22 to adjust the flow of the cleaning liquid entering the fresh water chamber and the concentrated water chamber according to actual needs. By accurately controlling the flow, it can be ensured that the cleaning liquid is evenly distributed in the fresh water chamber and the concentrated water chamber to achieve a better cleaning effect. In order to facilitate the connection and disconnection with the electric desalination module 4, the output ends of the first water inlet branch pipe 21 and the second water inlet branch pipe 22 usually adopt a quick connection design, such as a quick connector.

[0027] The cleaning water reflux module 3 includes a first reflux main pipe 31, a second reflux main pipe 32, a third reflux main pipe 33, a first reflux branch pipe 34, a second reflux branch pipe 35, and a third reflux branch pipe 36; the drain outlet of the fresh water chamber of the electric deionization module 4 is connected to the input end of the first reflux main pipe 31 through the first reflux branch pipe 34; the output end of the first reflux main pipe 31 is connected to the cleaning water tank 11; the drain outlet of the concentrated water chamber of the electric deionization module 4 is connected to the input end of the second reflux main pipe 32 through the second reflux branch pipe 35; the output end of the second reflux main pipe 32 is connected to the cleaning water tank 11; the drain outlet of the extreme water chamber of the electric deionization module 4 is connected to the input end of the third reflux main pipe 33 through the third reflux branch pipe 36; the output end of the third reflux main pipe 33 is connected to the cleaning water tank 11.

[0028] Specifically, during the cleaning process, the wastewater generated by the fresh water chamber, the concentrated water chamber and the extreme water chamber flows into the corresponding return main pipe through the corresponding return branch pipes. After the wastewater is collected in the return main pipe, it flows into the cleaning water tank 11 through the output end of the main pipe. The cleaning water tank 11 can be designed with an appropriate filtering or precipitation device to remove impurities or particulate matter in the wastewater to ensure the quality of the wastewater returned to the water tank. The return main pipe and branch pipe are usually made of corrosion-resistant materials, such as stainless steel or polymer plastics, to adapt to the chemical properties of the cleaning liquid and wastewater. In order to prevent corrosion and leakage, the connection of the pipeline usually adopts a connection method with good sealing performance, such as welding, flange connection or clamp connection. The function of the cleaning water return module 3 is to collect and recycle the wastewater generated during the cleaning process, and to realize the recycling of water resources by returning to the cleaning water tank 11. This not only helps to reduce the waste of water resources, but also reduces the cleaning cost and environmental burden. At the same time, by recycling wastewater and carrying out appropriate treatment, pollution and emissions to the environment can also be reduced.

[0029] It should be noted that the first reflux main pipe 31, the second reflux main pipe 32 and the third reflux main pipe 33 are all provided with vent valves and vent pipes. This arrangement can not only improve the safety of the equipment, but also facilitate maintenance, cleaning and emergency treatment. In an emergency, by quickly opening the vent valve, the liquid in the main pipe can be quickly emptied, thereby avoiding potential safety accidents. The first reflux branch pipe 34, the second reflux branch pipe 35 and the third reflux branch pipe 36 are all provided with flow meters 5. The flow meter 5 is designed to accurately monitor and control the flow rate of cleaning water flowing out of the fresh water chamber, the concentrated water chamber and the extreme water chamber. By monitoring the water flow of each branch pipe, it is also possible to promptly discover and solve possible flow imbalance problems to ensure that the cleaning effect of each part of the EDI module is consistent during the cleaning process.

[0030] Specifically, the number of the electric desalination modules 4 matches the number of the first water inlet branch 21, the second water inlet branch 22, the first return branch 34, the second return branch 35 and the third return branch 36. There can be multiple electric desalination modules 4. The number of specific electric desalination modules 4 can be appropriately increased or decreased according to the scale of the electric desalination system.

[0031] Further, in a specific cleaning operation process, chemical reagents are first added to the dosing port 12, and these chemical reagents are mixed with the dehydrogenated acid water in the cleaning water tank 11 to generate the required cleaning liquid. When the liquid in the cleaning water tank 11 is first pressurized by the cleaning water pump 13, the pressurized liquid then enters the reflux stirring tube for reflux stirring. This step is to ensure that the liquid in the cleaning water tank 11 can be fully mixed and uniform to avoid uneven concentration or component stratification. During the reflux stirring process, the liquid in the cleaning water tank 11 is gradually mixed and uniform. When the liquid in the cleaning water tank 11 is mixed and uniform, the valve to the security filter 15 can be opened. The security filter 15 is used to remove impurities and particulate matter in the liquid to ensure that the liquid supplied to the skid-mounted module 2 is clean. The clean liquid filtered by the security filter 15 enters the cleaning water inlet main pipe 16 of the skid-mounted module 2 through its output end. In this way, the skid-mounted module 2 can obtain clean cleaning liquid for subsequent cleaning of the electric desalination module 4. When the cleaning is completed, the generated waste liquid can be discharged into the downstream treatment system through the vent pipe of the cleaning water tank 11.

[0032] Furthermore, before any chemical cleaning is performed, the electro-deionization module 4 must first be regenerated. This process is intended to restore the performance of the electro-deionization module 4 in preparation for subsequent cleaning. Prepare a sodium chloride solution with a mass fraction of approximately 2% as the regeneration liquid. Evenly add the prepared sodium chloride solution into the cleaning water tank 11, turn on the cleaning water pump 13, and reflux and stir the pressurized sodium chloride solution through the reflux stirring pipeline 14 to ensure that the liquid in the cleaning water tank 11 is evenly mixed. The stirring time is usually 5 minutes. After the stirring is completed, allow the sodium chloride solution to circulate in the electro-deionization module 4 for regeneration. This process lasts for about 10 minutes.

[0033] When the regeneration treatment is completed, when the chemical reagent used is hydrochloric acid, the cleaning steps are as follows. 1. Prepare hydrochloric acid solution: prepare a hydrochloric acid solution with a mass fraction of about 1.8% (pH of about 1.5). 2. Add hydrochloric acid solution: Add the hydrochloric acid solution into the cleaning water tank 11 through the dosing port 12. 3. Cleaning process: Turn on the cleaning water pump 13 and let the hydrochloric acid solution circulate in the electric deionization module 4 for cleaning. The cleaning duration depends on the specific situation and is usually 30 to 60 minutes. 4. Rinse: After the cleaning is completed, rinse the electric deionization module 4 and the cleaning water tank 11 with desalted water for about 10 minutes.

[0034] When the chemical reagent used is sodium hydroxide, the cleaning steps are as follows. 1. Prepare sodium hydroxide solution: prepare a sodium hydroxide solution with a mass fraction of about 1% (pH of about 12.5). 2. Add sodium hydroxide solution: Add the sodium hydroxide solution into the cleaning water tank 11 through the dosing port 12. 3. Cleaning process: Start the cleaning water pump 13 and allow the sodium hydroxide solution to circulate and clean in the electro-deionization module 4. The cleaning duration depends on the specific situation and is usually 30 to 60 minutes. 4. Rinse: After the cleaning is completed, use desalted water to rinse the electro-deionization module 4 and the cleaning water tank 11 for about 10 minutes. After flushing until the pH of the produced water returns to 7-8, the cleaning is completed.

[0035] Specifically, during the regeneration, cleaning and flushing process of the electric desalination module 4, the water flow rate is a key parameter. The regeneration water, cleaning water or flushing water flow rate of a single electric desalination module 4 (including the concentrated water chamber and the fresh water chamber) is consistent with the flow rate of the normal operation of the electric desalination module 4, which is about 5-6m 3 / h.

[0036] Furthermore, the electro-deionization module 4 can be restored to rated performance after regeneration, single acid washing, single alkali washing or acid washing + alkali washing, and flushing. The electro-deionization module 4 restored to rated performance can quickly produce water after being quickly installed in the electro-deionization system, and the produced water can fully meet the boiler feed water quality requirements in the steam quality of thermal power generating units and steam power equipment (GB / T12145-2016). The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0037] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. An off-line cleaning device, characterized in that: It comprises a dispensing and stirring module (1), a skid-mounted module (2) and a cleaning water return module (3); The dispensing and stirring module (1) is configured to prepare cleaning water and transport the cleaning water to the skid-mounted module (2); The skid-mounted module (2) is configured to deliver cleaning water to at least one electric desalination module (4) and collect reflux liquid output by at least one electric desalination module (4); The cleaning water reflux module (3) is configured to monitor and control the flow rate of the reflux liquid, and collect the reflux liquid into the dispensing and stirring module (1).

2. The off-line cleaning device according to claim 1, characterized in that: The drug dispensing and stirring module (1) comprises a cleaning water tank (11), a drug adding port (12), a cleaning water pump (13), a reflux stirring pipeline (14), a safety filter (15) and a cleaning water inlet main pipe (16); The drug adding port (12) is arranged on the top or side of the cleaning water tank (11); The bottom of the cleaning water tank (11) is provided with a drain pipe and a drain valve; The output end of the cleaning water tank (11) is connected to the input end of the cleaning water pump (13) through a pipeline; The output end of the cleaning water pump (13) is respectively connected to the input end of the reflux stirring pipeline (14) and the input end of the security filter (15); The output end of the reflux stirring pipeline (14) is connected to the cleaning water tank (11); The output end of the security filter (15) is connected to the skid-mounted module (2) via a cleaning water inlet main pipe (16).

3. The off-line cleaning device according to claim 2, characterized in that: The skid-mounted module (2) comprises a first water inlet branch pipe (21) and a second water inlet branch pipe (22); The output end of the cleaning water inlet main pipe (16) is connected to the input end of the first water inlet branch pipe (21) and the input end of the second water inlet branch pipe (22) respectively; The output end of the first water inlet branch pipe (21) is in communication with the water inlet of the fresh water chamber of the electric deionization module (4), and the output end of the second water inlet branch pipe (22) is in communication with the water inlet of the concentrated water chamber of the electric deionization module (4).

4. The off-line cleaning device according to claim 3, characterized in that: The cleaning water reflux module (3) comprises a first reflux main pipe (31), a second reflux main pipe (32), a third reflux main pipe (33), a first reflux branch pipe (34), a second reflux branch pipe (35), and a third reflux branch pipe (36); The drain outlet of the fresh water chamber of the electric desalination module (4) is connected to the input end of the first return main pipe (31) through the first return branch pipe (34); The output end of the first reflux main pipe (31) is in communication with the cleaning water tank (11); The drain outlet of the concentrated water chamber of the electric desalination module (4) is connected to the input end of the second reflux main pipe (32) through the second reflux branch pipe (35); The output end of the second return main pipe (32) is in communication with the cleaning water tank (11); The drain outlet of the polar water chamber of the electric desalination module (4) is connected to the input end of the third reflux main pipe (33) through the third reflux branch pipe (36); The output end of the third reflux main pipe (33) is connected to the cleaning water tank (11).

5. The off-line cleaning device according to claim 4, characterized in that: The first reflux branch pipe (34), the second reflux branch pipe (35) and the third reflux branch pipe (36) are all provided with flow meters (5).

6. The off-line cleaning device according to claim 4, characterized in that: The first reflux main pipe (31), the second reflux main pipe (32) and the third reflux main pipe (33) are all provided with vent pipes and vent valves.

7. The off-line cleaning device according to claim 4, characterized in that: The number of the electric desalination modules (4) matches the number of the first water inlet branch pipe (21), the second water inlet branch pipe (22), the first return branch pipe (34), the second return branch pipe (35) and the third return branch pipe (36).

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