Cleaning method of ozone tank, texturing process of solar cell and ozone cleaning device

Abstract

The invention provides a cleaning method of an ozone tank, a texturing process of a solar cell and an ozone cleaning device. In the first aspect, the cleaning method of the ozone tank comprises the following steps: an alkali soaking tank step: carrying out circulating cleaning on an ozone tank body for a first preset duration by adopting a sodium hydroxide hot alkali washing solution, and discharging the sodium hydroxide hot alkali washing solution after the cleaning is finished to remove silicon powder accumulated in the ozone tank, the temperature of the sodium hydroxide hot alkali washing solution being 50-70 DEG C; and an acid tank soaking step: after the alkali tank soaking step is finished, adding a hydrochloric acid stock solution, a hydrogen peroxide stock solution and water into the ozone tank body to form a pickling solution, and soaking the tank with the pickling solution at the preset temperature for a second preset duration. And the effect of cleaning the silicon wafer by ozone water is ensured, secondary texturing is avoided, and a high-quality solar cell is ensured to be subsequently prepared.

Description

Technical Field

[0001] The present application relates to the technical field of solar cell preparation, and in particular to an ozone tank cleaning method, a solar cell texturing process and an ozone cleaning device. Background Art

[0002] Reworked solar cells often appear in the process of solar cell production, which requires secondary texturing. The quality of reworked solar cells after secondary texturing is poor, and the cell efficiency of reworked cells is at least 0.05% lower than that of normal cells. It is urgent to avoid secondary texturing and reworked solar cells in the process of solar cell production. Summary of the invention

[0003] The first aspect of the present application provides a method for cleaning an ozone tank, comprising:

[0004] In the alkaline bath step, the ozone tank body is cyclically cleaned for a first preset time using a sodium hydroxide hot alkaline cleaning solution, and the hot sodium hydroxide cleaning solution is discharged after the cleaning is completed to remove the silicon powder accumulated in the ozone tank. The temperature of the hot sodium hydroxide cleaning solution is 50° C. to 70° C.;

[0005] Acid soaking tank step: after the alkaline soaking tank step, hydrochloric acid stock solution, hydrogen peroxide stock solution and water are added to the ozone tank body to form an acid washing solution, and the sodium hydroxide hot alkaline washing solution is used to soak the tank at a preset temperature for a second preset time.

[0006] In some optional embodiments of the first aspect of the present application,

[0007] In the alkaline bubble tank step, sodium hydroxide stock solution and hot water are respectively added into the ozone tank body to form a sodium hydroxide hot alkaline washing solution, and the temperature of the hot water is greater than the temperature of the sodium hydroxide hot alkaline washing solution.

[0008] In some optional embodiments of the first aspect of the present application, the mass percentage concentration of sodium hydroxide in the sodium hydroxide hot alkaline washing solution is in the range of 5% to 10%.

[0009] In some optional embodiments of the first aspect of the present application, the volume of the ozone tank is greater than or equal to the volume of the hot alkaline washing solution of sodium hydroxide.

[0010] In some optional embodiments of the first aspect of the present application, the volume ratio of the sodium hydroxide stock solution to the ozone tank is 4:305.

[0011] In some optional embodiments of the first aspect of the present application, the mass percentage concentration of the sodium hydroxide stock solution is 48±1%.

[0012] In some optional embodiments of the first aspect of the present application, the first preset time length is 10 minutes to 20 minutes.

[0013] In some optional embodiments of the first aspect of the present application, in the acid soaking tank step, the second preset time length is greater than or equal to 2 hours.

[0014] In some optional embodiments of the first aspect of the present application, the volume ratio of hydrochloric acid stock solution, hydrogen peroxide stock solution and water is 2:2:57.

[0015] In some optional embodiments of the first aspect of the present application, in the pickling solution, the mass percentage concentration of hydrochloric acid is 1% to 2%, and the mass percentage concentration of hydrogen peroxide is 0.8% to 1.5%.

[0016] In some optional embodiments of the first aspect of the present application, the mass percentage concentration of the hydrochloric acid stock solution is 37±1%; the mass percentage concentration of the hydrogen peroxide stock solution is 30% to 32%.

[0017] In some optional embodiments of the first aspect of the present application, the preset temperature is 25±10°C.

[0018] A second aspect of the present application provides a texturing process for solar cells. The texturing process for solar cells uses an ozone tank cleaning method according to any one of claims 1 to 8 to clean an ozone tank, wherein the ozone tank is used to pass ozone water to clean silicon wafers.

[0019] The third aspect of the present application is an ozone cleaning device, which is used to clean silicon wafers in a texturing process, comprising:

[0020] The ozone tank body is cleaned by the ozone tank cleaning method according to any one of claims 1 to 8 before the ozone water is introduced;

[0021] An ozone water delivery device, comprising an ozone generator, an ozone water inlet pipe and an ozone water outlet pipe, the ozone water delivery device being used for reciprocatingly cyclically delivering the ozone water between the ozone tank and the ozone transmitter;

[0022] Liquid transportation piping system, including:

[0023] A liquid medicine inlet tube group, comprising a hydrochloric acid inlet tube, a sodium hydroxide inlet tube, and a hydrogen peroxide inlet tube;

[0024] The water inlet pipe group includes a cold water inlet pipe and a hot water inlet pipe.

[0025] In some optional embodiments of the third aspect of the present application, in the ozone tank body, the liquid inlet of each liquid inlet pipe in the liquid inlet pipe group is arranged higher than the water inlet of each water inlet pipe in the water inlet pipe group.

[0026] In some optional embodiments of the third aspect of the present application, one end of the ozone water inlet pipe is connected to the top of the ozone generator, and the other end of the ozone water inlet pipe is connected to the bottom of the ozone tank.

[0027] One end of the ozone water outlet pipe is connected to the bottom of the ozone tank body, and the other end is connected to the bottom of the ozone generator. In the ozone tank body, the outlet of the ozone water outlet pipe is lower than the inlet of the ozone water inlet pipe.

[0028] The ozone tank cleaning method provided in the first aspect of the present application is that the alkaline bubble tank step is performed first, and the silicon powder remaining in the ozone tank body is reacted with a hot sodium hydroxide alkaline washing liquid to generate Na2SiO3 which is more soluble in water than silicon powder Si, and the silicon powder residue is removed by discharging the alkaline washing waste liquid containing Na2SiO3 after the reaction, wherein the principle of removing silicon powder can refer to the chemical equation of the reaction between silicon and sodium hydroxide: Si+2NaOH+H2O=Na2SiO3+2H2↑. At room temperature, the solubility of Na2SiO3 is about 100g / L. However, as the temperature rises, the solubility of Na2SiO3 will also increase. For example, at 50°C, the solubility of Na2SiO3 can reach 220g / L. Considering the improvement of silicon powder removal efficiency and quality and ensuring the smooth discharge of Na2SiO3 after the reaction, a hot sodium hydroxide alkaline washing liquid with a higher temperature is selected. The subsequent acid bubble tank step can neutralize the excess residual sodium hydroxide by adding hydrochloric acid, so that the ozone tank that cleans the silicon powder is weakly acidic, so that when ozone is subsequently introduced into the ozone tank, the ozone tank can dissolve ozone under weak acidity, and the ozone reaches the set ozone concentration value, ensuring the effect of ozone water cleaning silicon wafers, avoiding secondary texturing, and ensuring the subsequent preparation of high-quality solar cells. The texturing process provided in the second aspect of the present application ensures the success rate of single texturing, avoids the impact of secondary texturing on the quality of solar cells, and improves the production efficiency and quality of batteries. The ozone cleaning device provided in the third aspect of the present application achieves efficient removal of silicon powder in the ozone tank body without increasing the equipment cost and the space occupied by the equipment, reduces safety hazards during equipment operation, and improves the production efficiency of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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 or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a three-dimensional structural schematic diagram of an embodiment of an ozone cleaning device according to the third aspect of the present application.

[0031] Description of reference numerals:

[0032] Ozone cleaning device-1;

[0033] Ozone tank-11;

[0034] Ozone generator-2; ozone water inlet pipe-21; ozone water outlet pipe-22;

[0035] Hydrochloric acid inlet pipe-3; sodium hydroxide inlet pipe-4; hydrogen peroxide inlet pipe-5; cold water inlet pipe-6; hot water inlet pipe-7. DETAILED DESCRIPTION

[0036] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. 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 the present application.

[0037] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application 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 limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0038] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, 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 the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0039] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0040] The inventors discovered in in-depth research that the low efficiency of solar cells in the current preparation process often requires secondary rework and texturing. The further reason is that: in the current texturing process, ozone needs to be used in the ozone tank to clean silicon wafers. When the ozone concentration in the ozone tank rises slowly and / or the ozone water circulation abnormality caused by silicon powder residue affects the texturing effect, it is easy to rework solar cells that need secondary texturing, affecting the quality of the solar cells and the efficiency of the cells. The frequent abnormalities of the ozone tank before texturing are caused by the presence of silicon powder residue under the general bubble tank method, which makes it difficult to remove the silicon powder. Silicon powder back-blocks the ozone generator pipe, causing the ozone concentration in the ozone tank to rise slowly, and the silicon wafers cannot be effectively cleaned.

[0041] In view of this, this application is filed.

[0042] The first aspect of the present application provides a method for cleaning an ozone tank, comprising:

[0043] In the alkaline bath step, the ozone tank body is cyclically cleaned for a first preset time using a sodium hydroxide hot alkaline cleaning solution, and the alkaline cleaning waste liquid is discharged after the cleaning is completed to remove the silicon powder accumulated in the ozone tank. The temperature of the sodium hydroxide hot alkaline cleaning solution is 50° C. to 70° C.;

[0044] Acid soaking tank step: after the alkaline soaking tank step, hydrochloric acid stock solution, hydrogen peroxide stock solution and water are added to the ozone tank body to form an acid wash solution, and the acid wash solution is soaked in the tank at a preset temperature for a second preset time.

[0045] The ozone tank cleaning method provided in the first aspect of the present application is that the alkaline bubble tank step is performed first, and the silicon powder remaining in the ozone tank body is reacted with a hot sodium hydroxide alkaline washing liquid to generate Na2SiO3 which is more soluble in water than silicon powder Si, and the silicon powder residue is removed by discharging the alkaline washing waste liquid containing Na2SiO3 after the reaction, wherein the principle of removing silicon powder can refer to the chemical equation of the reaction between silicon and sodium hydroxide: Si+2NaOH+H2O=Na2SiO3+2H2↑. At room temperature, the solubility of Na2SiO3 is about 100g / L. However, as the temperature rises, the solubility of Na2SiO3 will also increase. For example, at 50°C, the solubility of Na2SiO3 can reach 220g / L. Considering the improvement of silicon powder removal efficiency and quality and ensuring the smooth discharge of Na2SiO3 after the reaction, a hot sodium hydroxide alkaline washing liquid with a higher temperature is selected. In the subsequent acid bubble tank step, hydrochloric acid can be added to neutralize excess residual sodium hydroxide, so that the ozone tank that cleans the silicon powder is weakly acidic, so that when ozone is subsequently introduced into the ozone tank, the ozone tank can dissolve the ozone under weak acidity, and the ozone reaches the set ozone concentration value, thereby ensuring the effect of ozone water cleaning silicon wafers, avoiding secondary texturing, and ensuring the subsequent preparation of high-quality solar cells.

[0046] In some optional embodiments of the first aspect of the present application, in the alkaline bubble tank step, sodium hydroxide stock solution and hot water are respectively added to the ozone tank body to form a sodium hydroxide hot alkaline washing solution, and the temperature of the hot water is greater than the temperature of the sodium hydroxide hot alkaline washing solution.

[0047] In some optional embodiments of the first aspect of the present application, the mass percentage concentration of sodium hydroxide in the sodium hydroxide hot alkaline washing solution is in the range of 5% to 10%.

[0048] In some optional embodiments of the first aspect of the present application, the volume of the ozone tank is greater than or equal to the volume of the hot alkaline washing solution of sodium hydroxide.

[0049] In some optional embodiments of the first aspect of the present application, the volume ratio of the sodium hydroxide stock solution to the ozone tank body is 4:305. In some specific examples, the sodium hydroxide stock solution is added to the ozone tank body according to the volume ratio of the sodium hydroxide stock solution to the ozone tank body, and the remaining space of the ozone tank body is supplemented with hot water.

[0050] In some optional embodiments of the first aspect of the present application, the mass percentage concentration of the sodium hydroxide stock solution is 48±1%.

[0051] In some optional embodiments of the first aspect of the present application, the first preset time is 10 minutes to 20 minutes. In these embodiments, the cyclic cleaning refers to pumping the sodium hydroxide hot alkaline washing liquid out of the tank body through a liquid pump and returning it to the tank body to complete a cycle, so that the silicon powder and the sodium hydroxide can fully react and the silicon powder can be removed more thoroughly.

[0052] In some optional embodiments of the first aspect of the present application, in the acid soaking tank step, the second preset time length is greater than or equal to 2 hours.

[0053] In some optional embodiments of the first aspect of the present application, the volume ratio of hydrochloric acid stock solution, hydrogen peroxide stock solution and water is 2:2:57.

[0054] In some optional embodiments of the first aspect of the present application, in the pickling solution, the mass percentage concentration of hydrochloric acid is 1% to 2%, and the mass percentage concentration of hydrogen peroxide is 0.8% to 1.5%. In these embodiments, the pickling solution mainly washes metal ions in the ozone tank, and then neutralizes the sodium hydroxide residue in the sodium hydroxide bubble tank, and then provides ozone water to wash the silicon wafer in the texturing process. The state of the tank is an acid environment, and then the water extracted from the ozone tank to the ozone generator is acidic, which ensures the solubility of ozone in the pickling solution, ensures the quality of the cleaned silicon wafer and avoids secondary texturing.

[0055] In some optional embodiments of the first aspect of the present application, the preset temperature is 25±10°C.

[0056] The second aspect of the present application provides a texturing process for solar cells. The texturing process for solar cells uses the ozone tank cleaning method provided in the first aspect of the present application to clean the ozone tank, which is used to pass ozone water to clean silicon wafers.

[0057] The third aspect of the present application provides an ozone cleaning device 1, which is used to clean silicon wafers in a texturing process, and includes:

[0058] The ozone tank body 11 is cleaned by the ozone tank cleaning method provided in the first aspect of the present application before the ozone water is introduced;

[0059] The ozone water delivery device comprises an ozone generator 2, an ozone water inlet pipe 2 and an ozone water outlet pipe 22, wherein one end of the ozone water inlet pipe 2 is connected to the top of the ozone generator 2, and the other end of the ozone water inlet pipe 2 is connected to the bottom of the ozone tank 11.

[0060] One end of the ozone water outlet pipe 22 is connected to the bottom of the ozone tank body 11, and the other end is connected to the bottom of the ozone generator 2. In the ozone tank body 11, the outlet of the ozone water outlet pipe 22 is lower than the inlet of the ozone water inlet pipe 2.

[0061] Liquid transportation piping system, including:

[0062] A liquid medicine inlet pipe group, comprising a hydrochloric acid inlet pipe 3, a sodium hydroxide inlet pipe 4, and a hydrogen peroxide inlet pipe 5;

[0063] The water inlet pipe group includes a cold water inlet pipe 6 and a hot water inlet pipe 7.

[0064] In some optional embodiments of the third aspect of the present application, in the ozone tank body 11, the liquid inlet of each liquid inlet pipe in the liquid liquid inlet pipe group is higher than the liquid inlet of each liquid inlet pipe in the water inlet pipe group. In these embodiments, the position arrangement of the liquid inlet of each liquid inlet pipe and the liquid inlet of each liquid inlet pipe is more conducive to mixing and diluting various drug stock solutions with water to form a target washing solution (including sodium hydroxide hot alkaline washing solution and sodium hydroxide hot alkaline washing solution) when cleaning the ozone tank body 11, and also avoids high-concentration drug stock solutions from corroding the ozone tank body 11, thereby ensuring the service life of the ozone tank body 11.

[0065] In some embodiments, the sodium hydroxide inlet pipe 4 and the hot water inlet pipe 7 use PFV pipes, and pneumatic valves are used as control pipeline switch valves on the sodium hydroxide inlet pipe 4 and the hot water inlet pipe 7. The pneumatic valve is connected to the compressed air valve, and the compressed air valve can be individually controlled in the operation interface to adjust the air supply pressure to control the opening and closing of the pneumatic valve.

[0066] In these embodiments, the sodium hydroxide stock solution and hot water are respectively input into the ozone tank 11 through the sodium hydroxide liquid inlet pipe 4 and the hot water inlet pipe 7 to mix and form a sodium hydroxide hot alkaline washing solution, thereby avoiding the need to add a liquid mixing device to the original equipment and reducing space occupancy.

[0067] The ozone generator 2 generates ozone, which is dissolved in the acidic water input into the ozone transmitter through the ozone water outlet pipe 22 to form ozone water. The ozone water flows back to the ozone tank through the ozone water inlet pipe 2, and the cycle repeats.

[0068] Alkali bubble tank step: when cleaning the ozone tank, first open the sodium hydroxide liquid inlet pipe 4 and the hot water inlet pipe 7, and close the other liquid inlet pipes and water inlet pipes, and form a sodium hydroxide hot alkali washing liquid in the ozone tank body according to a preset volume ratio to complete the above-mentioned alkaline bubble tank step. In some specific examples, 8L of sodium hydroxide is added to the ozone tank with a volume of 610L, and the rest is supplemented with hot water to form a sodium hydroxide hot alkali washing liquid. The ozone tank body 11 is circulated and cleaned for 10min using the sodium hydroxide hot alkali washing liquid. After the cleaning is completed, the alkali washing waste liquid is discharged to remove the silicon powder accumulated in the ozone tank. The temperature of the sodium hydroxide hot alkali washing liquid is 50°C to 70°C.

[0069] Acid soaking tank step: After the alkaline soaking tank step, add hydrochloric acid stock solution, hydrogen peroxide stock solution and water to the ozone tank body 11 to form a pickling solution, and use the pickling solution to soak at a preset temperature for a second preset time. The mass percentage concentration of the hydrochloric acid stock solution is 37±1%; the mass percentage concentration of the hydrogen peroxide stock solution is 30%-32%. The mass percentage concentration of hydrogen peroxide in the pickling solution is 0.8%-1.5%, and the mass percentage concentration of hydrochloric acid is 1%-2%. The volume ratio of hydrochloric acid stock solution, hydrogen peroxide stock solution and water is 2:2:57 to prepare a soaking tank acid pickling solution, and the soaking time is ≥2 hours.

[0070] In the first aspect of the present application, a cleaning method for an ozone tank is designed that is suitable for use in the solar cell manufacturing process; this method can be used to improve the slow rise of ozone concentration in the ozone tank before texturing, and solve the circulation abnormality caused by residual silicon powder in the ozone tank before cleaning; this method can be used to avoid abnormal ozone concentration in the ozone tank when cleaning silicon wafers before texturing, and abnormal circulation caused by abnormal cell products being transmitted to the downstream, affecting the quality of the battery. Through this design, production capacity can be increased, the number of reworked pieces can be reduced, and overall efficiency can be improved. The texturing process provided in the second aspect of the present application ensures a single texturing success rate, avoids the impact of secondary texturing on the quality of solar cells, and improves battery production efficiency and quality. The ozone cleaning device 1 provided in the third aspect of the present application, on the basis of not much increasing the equipment cost and the space occupied by the equipment, realizes efficient removal of silicon powder in the ozone tank body 11, reduces safety hazards during equipment operation, and improves the production efficiency of solar cells.

[0071] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for cleaning an ozone tank, characterized in that: include: In the alkaline bath step, the ozone tank body is cyclically cleaned for a first preset time using a sodium hydroxide hot alkaline cleaning solution, and the hot sodium hydroxide cleaning solution is discharged after the cleaning is completed to remove the silicon powder accumulated in the ozone tank, and the temperature of the hot sodium hydroxide cleaning solution is 50° C. to 70° C.; Acid bubble tank step: after the alkaline bubble tank step, hydrochloric acid stock solution, hydrogen peroxide stock solution and water are added to the ozone tank body to form an acid wash solution, and the acid wash solution is used to bubble the tank at a preset temperature for a second preset time.

2. The ozone tank cleaning method according to claim 1, characterized in that: In the alkaline bubble tank step, sodium hydroxide stock solution and hot water are respectively added into the ozone tank body to form the sodium hydroxide hot alkaline washing solution, and the temperature of the hot water is greater than the temperature of the sodium hydroxide hot alkaline washing solution.

3. The ozone tank cleaning method according to claim 2, characterized in that: The mass percentage concentration of sodium hydroxide in the sodium hydroxide hot alkaline washing solution is in the range of 5% to 10%; Preferably, the volume of the ozone tank is greater than or equal to the volume of the sodium hydroxide hot alkaline washing solution; Preferably, the volume ratio of the sodium hydroxide stock solution to the ozone tank is 4:305; Preferably, the mass percentage concentration of the sodium hydroxide stock solution is 48±1%.

4. The ozone tank cleaning method according to claim 1, characterized in that: The first preset time length is 10 minutes to 20 minutes.

5. The ozone tank cleaning method according to claim 1, characterized in that: In the acid soaking tank step, the second preset time length is greater than or equal to 2 hours.

6. The ozone tank cleaning method according to claim 1, characterized in that: The volume ratio of the hydrochloric acid stock solution, the hydrogen peroxide stock solution and the water is 2:2:

57.

7. The ozone tank cleaning method according to claim 1, characterized in that: In the pickling solution, the mass percentage concentration of hydrochloric acid is 1% to 2%, and the mass percentage concentration of hydrogen peroxide is 0.8% to 1.5%; Preferably, the mass percentage concentration of the hydrochloric acid stock solution is 37±1%; the mass percentage concentration of the hydrogen peroxide stock solution is 30%-32%.

8. The ozone tank cleaning method according to claim 1, characterized in that: The preset temperature is 25±10°C.

9. A texturing process for solar cells, characterized in that: The texturing process of the solar cell adopts the ozone tank cleaning method according to any one of claims 1 to 8 to clean the ozone tank, and the ozone tank is used to pass ozone water to clean the silicon wafer.

10. An ozone cleaning device, characterized in that: The ozone cleaning device is used to clean silicon wafers in the texturing process, and includes: The ozone tank body is cleaned by the ozone tank cleaning method according to any one of claims 1 to 8 before the ozone water is introduced; An ozone water delivery device, comprising an ozone generator, an ozone water inlet pipe and an ozone water outlet pipe, the ozone water delivery device being used for reciprocatingly cyclically delivering the ozone water between the ozone tank and the ozone transmitter; Liquid transportation piping system, including: A liquid medicine inlet tube group, comprising a hydrochloric acid inlet tube, a sodium hydroxide inlet tube, and a hydrogen peroxide inlet tube; A water inlet pipe group, including a cold water inlet pipe and a hot water inlet pipe; Preferably, in the ozone tank body, the liquid inlet of each liquid inlet pipe in the liquid inlet pipe group is higher than the water inlet of each water inlet pipe in the water inlet pipe group; Preferably, one end of the ozone water inlet pipe is connected to the top of the ozone generator, and the other end of the ozone water inlet pipe is connected to the bottom of the ozone tank. One end of the ozone water outlet pipe is connected to the bottom of the ozone tank body, and the other end is connected to the bottom of the ozone generator. In the ozone tank body, the outlet of the ozone water outlet pipe is lower than the inlet of the ozone water inlet pipe.

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