Moisture removal device for alkali metal salt electrolyte

Abstract

The utility model provides a moisture removal device for alkali metal salt electrolyte, which comprises a nitrogen impurity removal box, a filtering tank and a water removal tank which are connected in sequence, the nitrogen impurity removal box is connected with a nitrogen supply tank, and the nitrogen impurity removal box is provided with a gas supply pipe connected with the bottom of the filtering tank and a gas return pipe connected with the top of the filtering tank. A feeding hopper is arranged at the top of the filtering tank, an impurity removal filtering cylinder for filtering electrolyte is arranged in the filtering tank, the upper part of the filtering cylinder is connected with the water removal tank through a feeding pipe, a first water absorption cylinder, a second water absorption cylinder and a lithiation molecular sieve layer are arranged in the water removal tank, and the feeding pipe is used for supplying the electrolyte to the first water absorption cylinder. According to the moisture removal device for the alkali metal salt electrolyte, provided by the utility model, nitrogen is fed into the filtering tank through the air feeding pipe, flows back into the nitrogen impurity removal box through the air return pipe, is filtered and then is used for filling the filtering tank, so that external air containing moisture is prevented from entering the filtering tank and the moisture removal tank, and the moisture removal efficiency is effectively improved by the moisture removal tank; and the quality of the electrolyte is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of alkali metal salt electrolyte treatment, and more specifically relates to a water removal device for alkali metal salt electrolyte. Background Art

[0002] As a new energy source, lithium batteries are increasingly being used in various fields. The electrolyte in lithium batteries is a carrier for ion transmission, which plays a role in conducting ions between the positive and negative electrodes of lithium batteries, enabling lithium-ion batteries to achieve high voltage, high specific energy, high cycle performance, etc.

[0003] Existing electrolytes are generally composed of high-purity organic solvents, electrolyte lithium salts, and necessary additives. The above raw materials need to be prepared under certain conditions and in a certain proportion. Since lithium battery electrolytes are highly sensitive to the presence of water, which has a great impact on the performance of the electrolyte, it is very important to remove a small amount of water from lithium battery electrolytes.

[0004] However, in the prior art, lithium battery electrolyte raw materials are generally passed through a dehydration sieve for dehydration. However, the above dehydration method absorbs moisture in the air during the process of passing the electrolyte raw materials, and cannot dehydrate the electrolyte system as a whole, resulting in a poor dehydration effect. Utility Model Content

[0005] The utility model aims to provide a water removal device for alkali metal salt electrolyte, which can effectively improve the water removal efficiency of the electrolyte and ensure the quality of the electrolyte.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the utility model is: to provide a moisture removal device for alkali metal salt electrolyte, comprising a nitrogen impurity removal box, a filter tank and a water removal tank connected in sequence, the nitrogen impurity removal box is connected to a nitrogen supply tank, the nitrogen impurity removal box is provided with an air supply pipe connected to the bottom of the filter tank and an air return pipe connected to the top of the filter tank, the filter tank is provided with a feed hopper on the top, and an impurity removal filter cylinder for filtering the electrolyte is provided inside, the upper part of the filter cylinder is connected to the water removal tank through a feed pipe, the water removal tank is provided with a first water absorption cylinder, a second water absorption cylinder surrounded by the outside of the water absorption cylinder and a lithiated molecular sieve layer arranged below the first water absorption cylinder and the second water absorption cylinder, and the feed pipe is used to supply electrolyte to the first water absorption cylinder.

[0007] In one possible implementation, a lower sealing plate is provided at the lower end of the first water absorption cylinder, and the lower sealing plate is connected to the middle of the top surface of the lithiated molecular sieve layer. A sealing ring plate is provided at the upper end of the second water absorption cylinder, and the sealing ring plate extends upward from the axis to the periphery and is used to cooperate with the lower sealing plate to guide the electrolyte to flow through the first water absorption cylinder, the second water absorption cylinder and the lithiated molecular sieve layer in sequence.

[0008] In a possible implementation, a separation sleeve is provided between the first water absorption cylinder and the second water absorption cylinder, a first support plate is provided between the second water absorption cylinder and the lithiated molecular sieve layer, a second support plate is provided at the bottom of the lithiated molecular sieve layer, and liquid holes are provided on the separation sleeve, the first support plate and the second support plate respectively.

[0009] In some embodiments, the peripheral wall of the second water absorption cylinder contacts the inner wall of the water removal tank, and the peripheral wall of the lithiated molecular sieve layer contacts the inner wall of the water removal tank.

[0010] In a possible implementation, a plurality of bosses protruding upward are provided on the second support plate, and the liquid passage hole is provided between two adjacent bosses.

[0011] In a possible implementation, the main axis of the water removal tank extends in the up-down direction, a discharge hopper is provided at the bottom of the water removal tank, a discharge pipe is connected below the discharge hopper, and a discharge valve is provided on the discharge pipe.

[0012] In some embodiments, the dewatering tank is further provided with a silica gel layer located below the lithiated molecular sieve layer and a third support plate for supporting the silica gel layer. The dewatering tank is embedded with a transparent display panel corresponding horizontally to the silica gel layer for observing the color of the silica gel layer. The third support plate is provided with a drainage hole running through from top to bottom.

[0013] In a possible implementation, the liquid inlet end of the feed pipe passes through the filter tank and extends to the outside of the filter tank, the liquid outlet end of the feed pipe is connected to the top of the filter cartridge, and a liquid pump is provided on the feed pipe.

[0014] In a possible implementation, the nitrogen impurity removal box includes a box body and an impurity adsorption layer and a water-absorbing molecular sieve layer arranged in the box body. The water-absorbing molecular sieve layer is arranged close to the air supply pipe, and the impurity adsorption layer is arranged close to the air return pipe.

[0015] In some embodiments, the outlet end of the air supply pipe extends into the electrolyte in the filter tank, and a control valve is provided between the nitrogen supply tank and the filter tank.

[0016] Compared with the prior art, the scheme shown in the embodiment of the present application is a moisture removal device for alkali metal salt electrolyte provided in the embodiment of the present application, in which nitrogen is sent into the filter tank through the air supply pipe, and refluxed into the nitrogen impurity removal box through the return pipe for filtration before being sent to the filter tank, so that the nitrogen fills the filter tank, thereby preventing external air containing moisture from entering the filter tank and the water removal tank when the feed hopper is feeding. The filter tank is used to filter out impurities in the electrolyte, and then the combined action of the first water absorption cylinder, the second water absorption cylinder and the lithiated molecular sieve layer is used to achieve the effect of removing moisture, thereby effectively improving the water removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 A schematic diagram of a partial cross-sectional structure of a moisture removal device for an alkali metal salt electrolyte provided by an embodiment of the utility model;

[0019] Figure 2 For the utility model embodiment Figure 1 The partially enlarged structural diagram of middle Ⅰ;

[0020] Figure 3 For the utility model embodiment Figure 1 Schematic diagram of the main cross-sectional structure of the middle filter tank.

[0021] Among them, the reference numerals in the figure are:

[0022] 1. Nitrogen impurity removal box; 11. Box body; 12. Impurity adsorption layer; 13. Water-absorbing molecular sieve layer; 14. Nitrogen supply tank; 15. Air supply pipe; 16. Air return pipe; 17. Control valve; 2. Filter tank; 21. Feed hopper; 22. Filter cylinder; 23. Feed pipe; 24. Liquid pump; 3. Water removal tank; 31. First water absorption cylinder; 32. Second water absorption cylinder; 33. Lithium molecular sieve layer; 34. Lower sealing plate; 35. Sealing ring plate; 36. Separation sleeve; 37. First support plate; 38. Second support plate; 381. Liquid passage hole; 382. Boss part; 39. Silica gel layer; 391. Third support plate; 392. Liquid discharge hole; 393. Transparent display board; 4. Discharge hopper; 41. Discharge pipe; 42. Discharge valve. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or indirectly on the other element. It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "back", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying 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 utility model. The terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "several" is two or more, unless otherwise clearly and specifically defined.

[0025] Please also read Figures 1 to 3 , the moisture removal device for alkali metal salt electrolyte provided by the utility model is now described. The moisture removal device for alkali metal salt electrolyte comprises a nitrogen impurity removal box 1, a filter tank 2 and a dewatering tank 3 connected in sequence, the nitrogen impurity removal box 1 is connected to a nitrogen supply tank 14, the nitrogen impurity removal box 1 is provided with an air supply pipe 15 connected to the bottom of the filter tank 2 and an air return pipe 16 connected to the top of the filter tank 2, the filter tank 2 is provided with a feed hopper 21 at the top, and an impurity removal filter cylinder 22 for filtering the electrolyte is provided inside, the upper part of the filter cylinder 22 is connected to the dewatering tank 3 through a feed pipe 23, the dewatering tank 3 is provided with a first water absorption cylinder 31, a second water absorption cylinder 32 arranged outside the water absorption cylinder, and a lithiated molecular sieve layer 33 arranged below the first water absorption cylinder 31 and the second water absorption cylinder 32, and the feed pipe 23 is used to supply electrolyte to the first water absorption cylinder 31.

[0026] The moisture removal device for alkali metal salt electrolyte provided in the present embodiment is compared with the prior art. In the moisture removal device for alkali metal salt electrolyte provided in the present embodiment, nitrogen is sent into the filter tank 2 through the air supply pipe 15, and is refluxed into the nitrogen impurity removal box 1 through the return pipe 16 for filtration and then sent to the filter tank 2, so that the nitrogen fills the filter tank 2, and prevents the external air containing moisture from entering the dewatering tank 3 through the filter tank 2 when the feed hopper 21 is feeding. The filter tank 2 is used to filter out impurities in the electrolyte, and then the combined action of the first water absorption cylinder 31, the second water absorption cylinder 32 and the lithiated molecular sieve layer 33 is used to achieve the effect of removing moisture, thereby effectively improving the moisture removal efficiency.

[0027] When it is first used, nitrogen is supplied to the filter tank 2 through the nitrogen supply tank 14 and the nitrogen impurity removal pipe. After the nitrogen fills the filter tank 2, the feed hopper 21 is used to load the material, so as to minimize the entry of air into the filter tank 2 and prevent the moisture in the air from affecting the electrolyte. In the subsequent normal use process, the nitrogen in the filter tank 2 can enter the nitrogen impurity removal box 1 through the return pipe 16 to filter out impurities and moisture, and then be re-sent to the filter tank 2. At this time, the nitrogen supply tank 14 can be closed or the nitrogen supply pipe can be used to supply nitrogen to the filter tank 2 at a small flow rate. The above method can form a nitrogen atmosphere protection, and try to avoid the mixing of air during the loading process, thereby preventing the water in the air from affecting the electrolyte.

[0028] In one possible implementation, please also refer to Figures 1 to 3 A lower sealing plate 34 is provided at the lower end of the first water absorption cylinder 31, and the lower sealing plate 34 is connected to the middle of the top surface of the lithiated molecular sieve layer 33. A sealing ring plate 35 is provided at the upper end of the second water absorption cylinder 32. The sealing ring plate 35 extends upward from the axis to the periphery and is used to cooperate with the lower sealing plate 34 to guide the electrolyte to flow through the first water absorption cylinder 31, the second water absorption cylinder 32 and the lithiated molecular sieve layer 33 in sequence.

[0029] In this embodiment, the sealing ring plate 35 is located at the top of the second water absorption cylinder 32 and is inclined downward from the periphery to the center, which can prevent the electrolyte fed by the feeding pipe 23 from directly entering the second water absorption cylinder 32, and allows the electrolyte to flow downward along the sealing ring plate 35 to enter the first water absorption cylinder 31. The lower sealing plate 34 at the lower end of the first water absorption cylinder 31 can prevent the electrolyte from directly entering the lithiated molecular sieve layer 33 downward, and allows the electrolyte to enter the second water absorption cylinder 32.

[0030] In one possible implementation, please also refer to Figures 1 to 3 A separation sleeve 36 is provided between the first water absorption cylinder 31 and the second water absorption cylinder 32, a first support plate 37 is provided between the second water absorption cylinder 32 and the lithiated molecular sieve layer 33, a second support plate 38 is provided at the bottom of the lithiated molecular sieve layer 33, and liquid holes 381 are respectively provided on the separation sleeve 36, the first support plate 37 and the second support plate 38.

[0031] In this embodiment, the first water absorption cylinder 31 adopts 3A water absorption molecular sieve. The pore size of the 3A molecular sieve is 3A (i.e. 0.3nm), which is mainly used to adsorb water and does not adsorb any molecules with a diameter greater than 3A. According to the industrial application characteristics, the molecular sieve has a fast adsorption speed, a high number of regeneration times, a high crushing strength and a high pollution resistance, which improves the utilization efficiency of the molecular sieve and prolongs the service life of the molecular sieve.

[0032] The second water absorption cylinder 32 adopts 4A molecular sieve, the pore size of 4A molecular sieve is 4A (ie 0.3nm), 4A molecular sieve is an alkali metal aluminosilicate, which can absorb water, ammonia, hydrogen sulfide, sulfur dioxide, carbon dioxide, and other molecules with a critical diameter not greater than 4A, and is widely used in the drying of gases and liquids.

[0033] The separation sleeve 36 between the first water absorption cylinder 31 and the second water absorption cylinder 32 effectively isolates the two, so that the dispersed water absorption particles can form a columnar or cylindrical water absorption structure, thereby avoiding mixing of water absorption materials of different particle sizes formed in the first water absorption cylinder 31 and the second water absorption cylinder 32.

[0034] The first support plate 37 arranged between the second water absorption cylinder 32 and the lithiated molecular sieve layer 33 can prevent the loss of the molecular sieve in the second molecular sieve layer, avoid the consumption of materials, and ensure its water absorption. The lithiated molecular sieve layer 33 is arranged at the bottom to reduce its water absorption load. The lithiated molecular sieve layer 33 can be adsorbed and exchanged with the metal ions in the electrolyte after dehydration, and fully utilizes it to remove the metal cations in the electrolyte, ensuring that a small amount of metal impurities can be completely removed. The third support plate 391 has the same function as the second support plate 38, which will not be repeated here. The setting of the liquid hole 381 can ensure that the electrolyte flows smoothly through the separation sleeve 36, the first support plate 37 and the second support plate 38, thereby realizing the dehydration and impurity removal process of the electrolyte.

[0035] In some embodiments, please refer to Figures 1 to 3 , the peripheral wall of the second water absorption cylinder 32 contacts the inner wall of the water removal tank 3, and the peripheral wall of the lithiated molecular sieve layer 33 contacts the inner wall of the water removal tank 3. The inner peripheral wall of the second water absorption cylinder 32 is limited by the separation sleeve 36, the top is limited by the sealing ring plate 35, the bottom is limited by the first support plate 37, and the periphery is limited by the inner wall of the water removal tank 3, finally forming the entire sleeve-shaped water absorption structure. The top of the lithiated molecular sieve layer 33 is limited by the lower sealing plate 34 and the first support plate 37, the bottom is limited by the second support plate 38, and the periphery is limited by the inner wall of the water removal tank 3, finally forming a columnar purification structure.

[0036] In one possible implementation, please also refer to Figures 1 to 3 The second support plate 38 is provided with a plurality of upwardly protruding bosses 382, ​​and the liquid passage hole 381 is provided between two adjacent bosses 382. The provision of the upper bosses can increase the unevenness of the top surface of the second support plate 38, so as to slow down the flow speed of the electrolyte and increase the turbulence performance of the falling electrolyte.

[0037] In one possible implementation, please also refer to Figures 1 to 3The main axis of the dewatering tank 3 extends in the up-down direction, and a discharge hopper 4 is provided at the bottom of the dewatering tank 3, and a discharge pipe 41 is connected below the discharge hopper 4, and a discharge valve 42 is provided on the discharge pipe 41. The discharge hopper 4 is used to receive the electrolyte after dewatering, and then the electrolyte is sent to the subsequent equipment through the discharge pipe 41. The discharge valve 42 on the discharge pipe 41 is convenient for controlling the flow of the electrolyte.

[0038] In some embodiments, please refer to Figures 1 to 3 The dewatering tank 3 is also provided with a silica gel layer 39 located below the lithiated molecular sieve layer 33 and a third support plate 391 for supporting the silica gel layer 39. A transparent display panel 393 corresponding to the level of the silica gel layer 39 for observing the color of the silica gel layer 39 is embedded in the dewatering tank 3. The third support plate 391 is provided with a drainage hole 392 which runs through from top to bottom.

[0039] In this embodiment, the silica gel layer 39 is used to detect whether the electrolyte passing through still contains moisture. If it contains moisture, the silica gel layer 39 will change color. At this time, the change of the silica gel layer 39 can be easily observed through the transparent display board 393, and then it can be determined whether the molecular sieves in the first water absorption cylinder 31 and the second water absorption cylinder 32 need to be replaced, so as to facilitate timely replacement to ensure the water discharge effect.

[0040] In one possible implementation, please also refer to Figures 1 to 3 The liquid inlet end of the feed pipe 23 passes through the filter tank 2 and extends to the outside of the filter tank 2. The liquid outlet end of the feed pipe 23 is connected to the top of the filter cartridge 22. A liquid pump 24 is provided on the feed pipe 23. After the electrolyte is removed from the filter cartridge 22, it is sent to the water removal tank 3 for water removal. When the electrolyte in the filter tank 2 is higher than the top surface of the filter cartridge 22, the feed pipe 23, under the action of the liquid pump 24, sends the electrolyte into the filter tank 2, ensuring the orderly delivery of the electrolyte.

[0041] In one possible implementation, please also refer to Figures 1 to 3 The nitrogen impurity removal box 1 includes a box body 11 and an impurity adsorption layer 12 and a water absorbing molecular sieve layer 13 arranged in the box body 11. The water absorbing molecular sieve layer 13 is arranged close to the air supply pipe 15, and the impurity adsorption layer 12 is arranged close to the air return pipe 16.

[0042] In this embodiment, the impurity adsorption layer 12 arranged in the box body 11 is used to adsorb impurities in the nitrogen, and the water-absorbing molecular sieve layer 13 is used to adsorb moisture in the nitrogen. The above structure mainly processes the nitrogen refluxed in the return pipe 16. For the nitrogen in the nitrogen supply tank 14, due to its high purity, it only needs to pass through the nitrogen impurity removal box 1, and the treatment effect is not obvious.

[0043] In some embodiments, please refer to Figures 1 to 3The outlet end of the air supply pipe 15 extends into the electrolyte of the filter tank 2, and a control valve 17 is provided between the nitrogen supply tank 14 and the filter tank 2. The control valve 17 is used to control the supply state of the nitrogen supply tank 14 into the filter tank 2. When the nitrogen in the filter tank 2 has squeezed out most of the air, the control valve 17 can be adjusted to reduce the nitrogen refluxed in the return pipe 16 and the nitrogen in the nitrogen supply tank 14 to flow back into the filter tank 2, thereby realizing the reciprocating circulation of nitrogen.

[0044] When the above-mentioned moisture removal device for alkali metal salt electrolyte is in use, nitrogen is sent into the filter tank 2 through the air supply pipe 15, and is refluxed to the nitrogen impurity removal box 1 through the return air pipe 16 for filtration and then sent to the filter tank 2, so that the nitrogen fills the filter tank 2, and prevents the external air containing moisture from entering the dewatering tank 3 through the filter tank 2 when the feed hopper 21 is feeding. The filter tank 2 is used to filter out impurities in the electrolyte, and then the combined action of the first water absorption cylinder 31, the second water absorption cylinder 32 and the lithiated molecular sieve layer 33 is used to achieve the effect of removing moisture, thereby effectively improving the moisture removal efficiency.

[0045] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. 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 present invention.

Claims

1. A water removal device for an alkali metal salt electrolyte, characterized in that: It comprises a nitrogen impurity removal box, a filter tank and a dewatering tank connected in sequence, wherein the nitrogen impurity removal box is connected to a nitrogen supply tank, the nitrogen impurity removal box is provided with an air supply pipe connected to the bottom of the filter tank and an air return pipe connected to the top of the filter tank, the top of the filter tank is provided with a feed hopper, and an impurity removal filter cylinder for filtering electrolyte is provided inside, the upper part of the filter cylinder is connected to the dewatering tank through a feed pipe, the dewatering tank is provided with a first water absorption cylinder, a second water absorption cylinder surrounded by the outside of the water absorption cylinder and a lithiated molecular sieve layer arranged below the first water absorption cylinder and the second water absorption cylinder, and the feed pipe is used to supply electrolyte to the first water absorption cylinder.

2. The water removal device for alkali metal salt electrolyte according to claim 1, characterized in that: A lower sealing plate is provided at the lower end of the first water absorption cylinder, and the lower sealing plate is connected to the middle of the top surface of the lithiated molecular sieve layer. A sealing ring plate is provided at the upper end of the second water absorption cylinder, and the sealing ring plate extends upward from the axis to the periphery and is used to cooperate with the lower sealing plate to guide the electrolyte to flow through the first water absorption cylinder, the second water absorption cylinder and the lithiated molecular sieve layer in sequence.

3. The water removal device for alkali metal salt electrolyte according to claim 2, characterized in that: A separation sleeve is provided between the first water absorption cylinder and the second water absorption cylinder, a first support plate is provided between the second water absorption cylinder and the lithiated molecular sieve layer, a second support plate is provided at the bottom of the lithiated molecular sieve layer, and liquid holes are respectively provided on the separation sleeve, the first support plate and the second support plate.

4. The water removal device for alkali metal salt electrolyte according to claim 3, characterized in that: The peripheral wall of the second water absorption cylinder contacts the inner wall of the water removal tank, and the peripheral wall of the lithiated molecular sieve layer contacts the inner wall of the water removal tank.

5. The water removal device for alkali metal salt electrolyte according to claim 3, characterized in that: The second support plate is provided with a plurality of bosses protruding upward, and the liquid passage hole is arranged between two adjacent bosses.

6. The water removal device for alkali metal salt electrolyte according to claim 2, characterized in that: The main axis of the dewatering tank extends in the up-down direction. A discharge hopper is provided at the bottom of the dewatering tank. A discharge pipe is connected below the discharge hopper. A discharge valve is provided on the discharge pipe.

7. The water removal device for alkali metal salt electrolyte according to claim 6, characterized in that: The dewatering tank is also provided with a silica gel layer located below the lithiated molecular sieve layer and a third support plate for supporting the silica gel layer. The dewatering tank is embedded with a transparent display panel corresponding horizontally to the silica gel layer for observing the color of the silica gel layer. The third support plate is provided with drainage holes that pass through from top to bottom.

8. The water removal device for alkali metal salt electrolyte according to any one of claims 1 to 7, characterized in that: The liquid inlet end of the feed pipe passes through the filter tank and extends to the outside of the filter tank. The liquid outlet end of the feed pipe is connected to the top of the filter cartridge. A liquid pump is provided on the feed pipe.

9. The water removal device for alkali metal salt electrolyte according to claim 8, characterized in that: The nitrogen impurity removal box includes a box body, an impurity adsorption layer and a water-absorbing molecular sieve layer arranged in the box body, the water-absorbing molecular sieve layer is arranged close to one side of the air supply pipe, and the impurity adsorption layer is arranged close to one side of the air return pipe.

10. The water removal device for alkali metal salt electrolyte according to claim 9, characterized in that: The outlet end of the air supply pipe extends into the electrolyte of the filter tank, and a control valve is provided between the nitrogen supply tank and the filter tank.

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