Tank cleaning method and cleaning liquid

Abstract

To provide a tank cleaning method and a cleaning liquid capable of increasing cleaning power for an inner surface of a tank while reducing the environmental load.SOLUTION: A tank cleaning method according to one embodiment is for cleaning an inner surface 2b of a tank 2. The tank cleaning method includes a step of generating a cleaning liquid E that contains caustic soda and fine bubbles, which are generated in water W by a bubble generation device 3b, and a step of supplying the cleaning liquid E to the inner surface 2b to clean the inner surface 2b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a tank cleaning method and cleaning solution. [Background technology]

[0002] Patent Document 1 describes a method for cleaning containers. In the method, fine bubbles (microbubbles) with a number-average or median diameter of 50 μm or less are generated in a cleaning solution to clean food or beverage containers. The cleaning solution contains a surfactant with an HLB (Hydrophile-Lipophile Balance) value of 12.3 to 16.0 and containing an ethoxy group.

[0003] Non-Patent Document 1 describes CIP (Cleaning in place), which is one of the tank cleaning methods. In CIP, cleaning is performed using a cleaning agent, and the cleaning agent used is an alkaline cleaning agent whose main component is caustic soda. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-247128 [Non-patent literature]

[0005] [Non-Patent Document 1] Brewers Association of Japan, Committee on International Technology (BCOJ), Basic Technology of Beer, March 15, 2002, pp. 112-117 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when cleaning tanks containing beer-taste beverages with a cleaning liquid, there is room for improvement in terms of the cleaning power for the tank's inner surface. Furthermore, as mentioned above, cleaning liquids containing caustic soda are sometimes used to clean tanks containing beer-taste beverages. If the concentration of caustic soda in the cleaning liquid is high, this can pose a problem of high environmental impact.

[0007] The present disclosure aims to provide a tank cleaning method and cleaning solution that can increase the cleaning power for the inner surface of a tank while reducing the environmental impact. [Means for solving the problem]

[0008] (1) A tank cleaning method according to the present disclosure is a method for cleaning the inner surface of a tank, and includes the steps of generating a cleaning solution containing caustic soda and fine bubbles generated in water by a bubble generator, and supplying the cleaning solution to the inner surface to clean the inner surface.

[0009] In this tank cleaning method, the cleaning liquid used to clean the inner surface of the tank contains caustic soda. The cleaning liquid containing caustic soda can remove yeast, proteins, and other substances derived from the beer-taste beverage that have adhered to the inner surface of the tank, thereby enhancing the cleaning power of the inner surface of the tank. The cleaning liquid contains fine bubbles, which are tiny bubbles generated in water by an air bubble generator. Cleaning the inner surface of the tank with the cleaning liquid containing fine bubbles allows the inner surface to be effectively cleaned and the amount of caustic soda to be reduced. This reduces the environmental impact.

[0010] (2) In the above (1), the step of generating a cleaning liquid may generate a cleaning liquid having a microbubble density of 100 million bubbles / mL or more. In this case, the high density of microbubbles in the cleaning liquid can further enhance the cleaning power for the inner surface of the tank.

[0011] (3) In the above (1) or (2), the step of producing a cleaning solution may produce a cleaning solution having a caustic soda concentration of less than 1%. In this case, the concentration of caustic soda in the cleaning solution is low, and the amount of caustic soda used can be reduced. Therefore, the environmental load can be reduced.

[0012] (4) In any of the above (1) to (3), the cleaning step may involve circulating a cleaning liquid in a circulation path connected to the tank to clean the inner surface. In this case, the cleaning liquid circulating in the circulation path flows along the inner surface of the tank, thereby preventing cavitation from occurring inside the tank. Therefore, the cleaning power for the inner surface of the tank can be further enhanced.

[0013] (5) In any of the above (1) to (4), the cleaning step may include a step of rinsing the inner surface, and a step of supplying a cleaning liquid to the inner surface after the rinsing step to perform a main cleaning of the inner surface. In the rinsing step, fine-bubble water containing fine bubbles and water may be supplied to the inner surface. In this case, fine-bubble water containing fine bubbles is used in rinsing the inner surface, which is performed before the main cleaning step. Therefore, the inner surface of the tank can be efficiently cleaned in the preliminary rinsing stage.

[0014] (6) In the above (5), the main cleaning step may include a pre-alkaline cleaning step in which a cleaning liquid is passed through a circulation path connected to the tank to clean the inner surface, and an alkaline cleaning step in which the cleaning liquid is passed through the circulation path after being discharged from the circulation path to clean the inner surface. In this case, by performing the alkaline cleaning step after the cleaning liquid is discharged from the circulation path, it is possible to more reliably prevent the occurrence of cavitation and further enhance the cleaning power for the inner surface.

[0015] (7) The cleaning liquid according to the present disclosure is a cleaning liquid for cleaning the inner surface of a tank. The cleaning liquid contains fine bubbles, which are tiny bubbles generated in water by a bubble generator, and caustic soda. Because this cleaning liquid contains caustic soda, it can remove yeast, proteins, and the like derived from beer-taste beverages that adhere to the inner surface of the tank by cleaning. Furthermore, the cleaning liquid contains fine bubbles, which are tiny bubbles generated in water by a bubble generator. This can enhance the cleaning power for the inner surface of the tank and reduce the amount of caustic soda used, thereby reducing the environmental impact. [Effects of the Invention]

[0016] According to the present disclosure, it is possible to increase the cleaning power for the inner surface of the tank and reduce the environmental impact. [Brief explanation of the drawings]

[0017] [Figure 1] 1A and 1B are diagrams schematically illustrating a tank cleaning method according to an embodiment of the present invention, a tank in which a cleaning liquid is used, and a bubble generating device. [Figure 2] 4 is a flowchart illustrating an example of steps in a tank cleaning method according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the tank cleaning method and cleaning solution according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are designated by the same reference numerals, and duplicate explanations will be omitted as appropriate. The drawings may be partially simplified or exaggerated to facilitate understanding, and the dimensional proportions and the like are not limited to those shown in the drawings.

[0019] First, a tank cleaning system as an example in which the tank cleaning method and cleaning solution according to this embodiment are used will be described. Fig. 1 is a diagram schematically showing a tank cleaning system 1 according to this embodiment. As shown in Fig. 1, the tank cleaning system 1 as an example has a tank 2 and a fine-bubble water generator 3.

[0020] For example, tank 2 is used when producing a beer-taste beverage. As an example, tank 2 is a tank used when fermenting and storing a beer-taste beverage. "Beer-taste beverage" includes beverages that have the taste of beer and beverages that give the drinker the sensation of drinking beer. Beer-taste beverages with an alcohol content of 1% or more are also called beer-taste alcoholic beverages.

[0021] A beer-taste beverage refers to a beverage that has a beer-like flavor. Examples of beer-taste beverages include, but are not limited to, those classified as beer, happoshu, and other sparkling alcoholic beverages as defined in Article 3 of the Liquor Tax Act (Act No. 6 of 1953). Beer-taste beverages also include beverages and soft drinks (e.g., non-alcoholic beer-taste beverages) that do not fall under the category of sparkling alcoholic beverages under the Liquor Tax Act. However, the beer-taste beverage according to this embodiment is not limited to the above examples.

[0022] A "tank" is a container for storing a fluid, including a liquid, and refers to a columnar, cylindrical, or box-shaped storage container. Tank 2 is, for example, a conical tank. In this case, it is possible to easily collect beer yeast. As an example, tank 2 may be a cylindrical conical tank. In this case, tank 2 is cylindrical, and the lower part of tank 2 is inverted cone shape.

[0023] For example, the tank 2 is cleaned by cleaning in place (CIP). The tank 2 is cleaned, for example, by supplying water and cleaning liquid E to the inner surface 2b of the tank 2. The cleaning liquid E cleans the inner surface 2b of the tank 2. The cleaning liquid E contains caustic soda (sodium hydroxide).

[0024] If cleaning solution E contains caustic soda, it can effectively remove yeast, proteins, and the like derived from the beer-taste beverage adhering to the inner surface 2b of the tank 2, thereby enhancing the cleaning power for the inner surface 2b of the tank 2. However, if cleaning solution E contains a large amount of caustic soda, there are concerns that the cost of the caustic soda will increase and that wastewater will have a greater environmental impact. Therefore, it is desirable to reduce the amount of caustic soda contained in cleaning solution E.

[0025] For example, a tank cleaning system 1 has a circulation path 4 including a tank 2. A fine-bubble water generator 3 is connected to the circulation path 4 via a water storage tank 7. When cleaning the tank 2, a cleaning liquid E is circulated in the circulation path 4 to clean the inner surface 2b. For example, the tank cleaning system 1 has a valve 5, a monitoring peephole 6, and a water storage tank 7 provided in the circulation path 4. The valve 5 opens and closes the circulation path 4. The monitoring peephole 6 is a window for viewing the flow of liquid passing through the inside of the circulation path 4. The water storage tank 7 stores either water W, which is process water, or fine-bubble water. Note that the tank cleaning system 1 does not necessarily have to have at least one of the valve 5, the monitoring peephole 6, and the water storage tank 7.

[0026] The micro-bubble water generator 3 includes a bubble generator 3b that generates micro-bubbles in the water W, and a micro-bubble water storage tank 3c that stores the micro-bubble water generated by generating micro-bubbles in the water W. For example, air A is supplied to the bubble generator 3b, and the bubble generator 3b generates micro-bubbles from the air A. In this embodiment, the micro-bubbles generated in the water W by the bubble generator 3b are used to clean the inner surface 2b of the tank 2.

[0027] For example, the above-mentioned fine bubble water is used to clean the inner surface 2b of the tank 2. "Fine bubble water" is water generated by, for example, generating fine bubbles in water W using a bubble generator 3b. In this embodiment, the "fine bubbles" are bubbles having a diameter of less than 1 μm. The size is, for example, the average diameter of the bubbles.

[0028] In this embodiment, "water" refers to water that is not generated by the bubble generator 3b generating microbubbles in the water W, and is distinguished from microbubble water. "Cleaning liquid" refers to a liquid used to clean the inner surface 2b of the tank 2, and contains microbubbles and caustic soda. "Cleaning liquid" refers to microbubble water that contains caustic soda. For example, microbubble water does not contain caustic soda.

[0029] For example, microbubbles do not rise to the surface in microbubble water and do not disappear for a long time. Microbubbles are, for example, not visible to the naked eye. Microbubbles have the effect of removing dirt by shock waves when the bubbles disappear, by potential adsorption, and by peeling and merging. By supplying microbubble water containing microbubbles to the inner surface 2b of the tank 2, the amount of caustic soda can be reduced while effectively cleaning the inner surface 2b. The microbubbles may be Ultra Fine Bubbles (registered trademark).

[0030] For example, the density of microbubbles in the microbubble water is 100 million / mL or more. In this embodiment, "density" refers to the number of microbubbles contained in 1 mL of the microbubble water. The density may be 200 million / mL or more, 300 million / mL or more, 500 million / mL or more, or 600 million / mL or more.

[0031] For example, the micro-bubble water generator 3 may have a circulation path including the air bubble generator 3b and the micro-bubble water storage tank 3c, and the air bubble generator 3b may generate micro-bubble water by repeatedly circulating the water W through this circulation path. As an example, if the water W is circulated through the circulation path 10 times while the air bubble generator 3b generates micro-bubbles, micro-bubble water with a density of over 1 billion bubbles / mL will be generated.

[0032] The higher the density of the microbubbles, the better the cleaning effect on the inner surface 2b. However, a density of 100 million bubbles / mL or more will provide a sufficient cleaning effect on the inner surface 2b. For example, the density of microbubbles in the microbubble water is 2 billion bubbles / mL or less. The density may be 1.5 billion bubbles / mL or less, or 1 billion bubbles / mL or less.

[0033] For example, the concentration of caustic soda in cleaning solution E is greater than 0% and less than 1%. The concentration of caustic soda may be 0.9% or less, 0.7% or less, or 0.5% or less. The lower the concentration of caustic soda, the lower the cost and environmental impact of cleaning solution E.

[0034] Next, an example of the steps of the tank cleaning method according to this embodiment will be described. The tank cleaning method according to this embodiment cleans the inner surface 2b of the tank 2. For example, a cleaning solution E containing caustic soda and fine bubbles, which are fine bubbles generated in water W by the bubble generator 3b, is generated (a step of generating a cleaning solution). More specifically, water W and air A are supplied to the bubble generator 3b, and the bubble generator 3b uses the air A to generate fine bubbles in the water W, thereby generating fine-bubble water. The generated fine-bubble water is stored, for example, in a water storage tank 7. For example, caustic soda is supplied to the fine-bubble water stored in the water storage tank 7 to generate the cleaning solution E.

[0035] Further, the inner surface 2b of the tank 2 is cleaned (inner surface cleaning step). FIG. 2 is a flowchart showing an example of the inner surface cleaning step. A specific example of the inner surface cleaning step will be described below with reference to FIGS. 1 and 2. First, the inner surface 2b of the tank 2 is pre-rinsed (step S1). In this embodiment, the pre-rinsing step S1 corresponds to the step of rinsing the inner surface.

[0036] In the pre-rinse, the inner surface 2b of the tank 2 is rinsed (the process of rinsing the inner surface). At this time, fine-bubble water containing fine bubbles and water W is supplied to the inner surface 2b. That is, a pre-rinse is performed in which fine-bubble water is flowed onto the inner surface 2b of the tank 2 to remove dirt from the inner surface 2b. For example, fine-bubble water generated by the fine-bubble water generator 3 is flowed onto the inner surface 2b to remove dirt from the inner surface 2b. Alternatively, dirt from the inner surface 2b may be removed by circulating the fine-bubble water through the circulation path 4 multiple times. For example, the cleaning solution E containing caustic soda is not used in the pre-rinse.

[0037] After the step of rinsing the inner surface (pre-rinse), a cleaning solution E containing caustic soda is supplied to the inner surface 2b to perform main cleaning of the inner surface 2b (main cleaning step). In this embodiment, the main cleaning step includes a pre-alkali cleaning step (step S2) and an alkali cleaning step (step S3) which will be described later.

[0038] In the pre-alkali cleaning step (step S2), for example, cleaning solution E is circulated through the circulation path 4 to clean the inner surface 2b. For example, the fine-bubble water generator 3 generates fine-bubble water with a fine-bubble density of 100 million or more / mL, and the cleaning solution E, which is fine-bubble water containing caustic soda to a caustic soda concentration of less than 1%, is supplied to the inner surface 2b. At this time, the caustic soda concentration in the cleaning solution E may be 0.3% or more and 0.5% or less. The cleaning solution E flows through the circulation path 4 multiple times to perform the pre-alkali cleaning step on the inner surface 2b. After the pre-alkali cleaning step, the cleaning solution E is discharged from the circulation path 4. Thereafter, the fine-bubble water not containing caustic soda may be circulated through the circulation path 4 to rinse the inner surface 2b.

[0039] After the pre-alkali cleaning step, an alkaline cleaning step is performed on the inner surface 2b of the tank 2 (step S3). In the alkaline cleaning step, first, as in the pre-alkali cleaning step, the cleaning solution E is circulated in the circulation path 4 to clean the inner surface 2b. Thereafter, the cleaning solution E is supplied to the inner surface 2b of the tank 2 and the cleaning solution E is discharged from the circulation path 4 to clean the inner surface 2b. After the cleaning of the inner surface 2b and the discharge of the cleaning solution E from the circulation path 4, the inner surface 2b may be rinsed, as in the pre-alkali cleaning step. After the pre-alkali cleaning step and alkaline cleaning step described above, the main cleaning of the inner surface 2b is completed.

[0040] After the main cleaning of the inner surface 2b, the inner surface 2b is rinsed (rinsing step, step S4). For example, in rinsing the inner surface 2b, water W that does not contain microbubbles is poured onto the inner surface 2b to rinse the inner surface 2b. Alternatively, in rinsing the inner surface 2b, water with microbubbles may be poured onto the inner surface 2b to rinse the inner surface 2b. Through the above steps, the series of steps for cleaning the inner surface 2b is completed.

[0041] Next, the effects obtained from the tank cleaning method and cleaning solution E according to this embodiment will be described. In the tank cleaning method and cleaning solution E according to this embodiment, the cleaning solution E used to clean the inner surface 2b of the tank 2 contains caustic soda. The cleaning solution E containing caustic soda can remove yeast, proteins, and the like derived from the beer-taste beverage that have adhered to the inner surface 2b of the tank 2 by cleaning, thereby enhancing the cleaning power for the inner surface 2b of the tank 2. The cleaning solution E contains fine bubbles, which are fine bubbles generated in the water W by the fine-bubble water generator 3. Cleaning the inner surface 2b of the tank 2 with the cleaning solution E containing fine bubbles allows the inner surface 2b to be effectively cleaned and the amount of caustic soda required to be reduced. This reduces the environmental impact.

[0042] According to this embodiment, the amount of caustic soda can be reduced, which contributes to Goal 12 of the Sustainable Development Goals (SDGs), "Ensure sustainable consumption and production patterns." Furthermore, according to this embodiment, the amount of caustic soda emissions can be reduced, which contributes to Goal 14 of the Sustainable Development Goals (SDGs), "Conserve and sustainably use the water below sea level."

[0043] In the step of producing the cleaning solution E, the cleaning solution E may have a microbubble density of 100 million bubbles / mL or more. In this case, the high density of the microbubbles in the cleaning solution E can further enhance the cleaning power for the inner surface 2b of the tank 2.

[0044] In the step of producing cleaning solution E, cleaning solution E having a caustic soda concentration of less than 1% may be produced. In this case, the concentration of caustic soda in cleaning solution E is low, and the amount of caustic soda used can be reduced. Therefore, the environmental load can be further reduced.

[0045] In the cleaning step, the inner surface 2b may be cleaned by circulating the cleaning liquid E in a circulation path 4 connected to the tank 2. In this case, the cleaning power of the tank 2 with respect to the inner surface 2b can be further enhanced.

[0046] The cleaning step may include a step of rinsing the inner surface 2b, and a step of supplying cleaning liquid E to the inner surface 2b after the step of rinsing the inner surface 2b to perform a main cleaning of the inner surface 2b. In the rinsing step, fine-bubble water containing fine bubbles and water may be supplied to the inner surface 2b. In this case, fine-bubble water containing fine bubbles is used to rinse the inner surface 2b before the main cleaning step. Therefore, the inner surface of the tank can be efficiently cleaned in the preliminary rinsing step, which further reduces the amount of caustic soda and other substances used, thereby further reducing the environmental impact.

[0047] This cleaning step may include a pre-alkaline cleaning step in which cleaning liquid E is caused to flow through the circulation path 4 connected to the tank 2 to clean the inner surface 2b, and an alkaline cleaning step in which cleaning liquid E is caused to flow through the circulation path 4 after the cleaning liquid E has been discharged from the circulation path 4 to clean the inner surface 2b. In this case, by performing the alkaline cleaning step after the cleaning liquid E has been discharged from the circulation path 4, for example, it is possible to prevent cavitation from occurring in a pump installed in the circulation path 4, thereby more reliably preventing the occurrence of cavitation and further enhancing the cleaning power for the inner surface 2b.

[0048] (Example) Next, examples of the tank cleaning method and cleaning liquid according to the present disclosure will be described. Note that the tank cleaning method and cleaning liquid according to the present disclosure are not limited to the contents of the following examples. In the examples, an experiment was conducted to verify the cleaning effect of the tank 2 using the tank cleaning system 1 described above. In the experiment, in each of the pre-rinse, main cleaning, and rinsing processes, water W, fine bubble water, or cleaning liquid E was flowed onto the inner surface 2b of the tank 2 to confirm whether dirt on the inner surface 2b could be removed.

[0049] The bubble generator 3b used was a DISSOLV02-PPU-012(D) (made by IDEC Corporation). Water W was passed (circulated) through the bubble generator 3b to generate fine bubbles in the water W, producing fine bubble water. The amount of fine bubble water produced by the bubble generator 3b was 10 L / min. The flow rate of air A to the bubble generator 3b was 0.3 L / min or more and 0.5 L / min or less, and the pressure of air A was 250 kPa or more and 350 kPa or less. Laser light was irradiated onto the fine bubble water, and the fine bubbles generated by scattered light were confirmed.

[0050] The cleaning effect on the inner surface 2b was confirmed by supplying cleaning liquid E, fine bubble water, and water W to the inner surface 2b of the tank 2 under the conditions of Examples 1 and 2 and Comparative Examples 1 and 2. The specifications of Examples 1 and 2 and Comparative Examples 1 and 2 are shown below. Example 1 A pre-rinse was performed by flowing fine bubble water onto the soiled inner surface 2b of tank 2, and then cleaning solution E was flowed onto the inner surface 2b of tank 2 to perform the main cleaning. The density of fine bubbles in the fine bubble water and cleaning solution E was 1 billion bubbles / mL, and the concentration of caustic soda in cleaning solution E was 0.5%, which is lower than in conventional cases. Water W was then flowed onto the inner surface 2b of tank 2 to rinse. Example 2 Fine bubble water was poured onto the soiled inner surface 2b of tank 2 to perform a pre-rinse, and then cleaning solution E was poured onto the inner surface 2b of tank 2 to perform the main cleaning. The density of fine bubbles in the fine bubble water and cleaning solution E was 100 million bubbles / mL, and the concentration of caustic soda in cleaning solution E was 0.5%. Water W was then poured onto the inner surface 2b of tank 2 to perform a rinse. (Comparative Example 1) A pre-rinse was performed by pouring process water W onto the inner surface 2b of the tank 2 where the dirt had adhered, and then main cleaning was performed by pouring water containing caustic soda onto the inner surface 2b of the tank 2. The concentration of caustic soda in this water was 3.0%. Then, water W was poured onto the inner surface 2b of the tank 2 to rinse it. (Comparative Example 2) Water W was poured onto the soiled inner surface 2b of the tank 2 to perform a pre-rinse, and then water containing caustic soda was poured onto the inner surface 2b of the tank 2 to perform the main cleaning. The concentration of caustic soda in this water was 0.5%. Water W was then poured onto the inner surface 2b of the tank 2 to rinse.

[0051] As an evaluation index of the organic matter removed from the inner surface 2b, the amount of organic matter contained in the pre-rinsed water was measured using a Lumitester (ATP wipe test). During the pre-rinse, water was circulated through the circulation path 4 for 30 minutes, after which a sample was taken and the amount of dissolved organic carbon contained in the water was measured using the Lumitester A3 method and COD (chemical oxygen demand). A visual inspection of the inside of tank 2 was also carried out. Furthermore, the water after the rinse was sampled and the total amount of organic matter contained in the water was measured using the Lumitester A3 method and TOC (total organic carbon).

[0052] The measurement results of the organic matter contained in the circulating water in the circulation path 4 after the pre-rinse are shown in Table 1 below. [Table 1] As shown in Table 1, after pre-rinsing, there was almost no difference in pH between the process water (Water W) and the fine-bubble water. The fine-bubble water showed higher values ​​for Lumitester and COD than Water W. This indicates that the fine-bubble water was able to remove more organic matter from the inner surface 2b than Water W during pre-rinsing.

[0053] Furthermore, the results of the experiments in which the above-mentioned evaluations were carried out for Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 2 below. [Table 2]

[0054] As shown in Table 2, in Examples 1 and 2, in which the inner surface 2b of the tank 2 was cleaned with cleaning solution E containing fine-bubble water and caustic soda, and in Comparative Example 1, in which the caustic soda concentration was 3.0%, the ATP and TOC values ​​were lower than in Comparative Example 2. This indicates that Examples 1, 2, and Comparative Example 1 were able to more effectively remove organic matter from the inner surface 2b of the tank 2 than Comparative Example 2. Furthermore, in Examples 1 and 2, the caustic soda concentration could be reduced from 3.0% to 0.5% while maintaining the same cleaning power as Comparative Example 1, thereby reducing the cost and environmental impact of caustic soda. Furthermore, in Example 2, in which the microbubble density was 100 million / mL, the ATP was higher than in Example 1 and Comparative Example 1, but the TOC was lower than in Example 1 and Comparative Example 1. From the above, it was found that Examples 1 and 2, which used fine-bubble water, were able to reduce the cost and environmental impact of caustic soda while exhibiting high cleaning power.

[0055] The above describes embodiments and examples of the tank cleaning method and cleaning solution according to the present disclosure. However, the tank cleaning method and cleaning solution according to the present disclosure are not limited to the above-described embodiments or examples, and may be modified within the scope of the gist described in the claims. In other words, the content and order of the steps of the tank cleaning method, the material of the cleaning solution, and the shape, size, material, number, and arrangement of each part of the tank cleaning system can be changed as appropriate within the scope of the above-described gist. [Explanation of symbols]

[0056] 1...tank cleaning system, 2...tank, 2b...inner surface, 3...fine bubble water generator, 3b...bubble generator, 3c...fine bubble water storage tank, 4...circulation path, 5...valve, 6...window, 7...water storage tank, A...air, E...cleaning liquid, W...water.

Claims

1. A tank cleaning method for cleaning the inner surface of a tank, comprising: A step of generating a cleaning solution containing fine bubbles, which are fine bubbles generated in water by the bubble generator, and caustic soda; supplying the cleaning liquid to the inner surface to clean the inner surface; Equipped with How to clean the tank.

2. In the step of generating the cleaning solution, the cleaning solution is generated so that the density of the microbubbles is 100 million / mL or more. The tank cleaning method according to claim 1.

3. In the step of generating the cleaning solution, the cleaning solution is generated having a caustic soda concentration of less than 1%. The tank cleaning method according to claim 1.

4. In the cleaning step, the cleaning liquid is circulated in a circulation path connected to the tank to clean the inner surface. The tank cleaning method according to any one of claims 1 to 3.

5. The washing step includes: rinsing the interior surface; a step of supplying the cleaning liquid to the inner surface after the step of rinsing the inner surface to perform main cleaning of the inner surface; It contains In the rinsing step, fine bubble water containing the fine bubbles and water is supplied to the inner surface. The tank cleaning method according to any one of claims 1 to 3.

6. The main cleaning step includes: a pre-alkali cleaning step of cleaning the inner surface by flowing the cleaning solution through a circulation path connected to the tank; an alkaline cleaning step of, after the cleaning liquid is discharged from the circulation path, flowing the cleaning liquid into the circulation path to clean the inner surface; Including, The tank cleaning method according to claim 5.

7. A cleaning liquid for cleaning the inner surface of a tank, The bubble generator includes fine bubbles, which are fine bubbles generated in water, and caustic soda. Cleaning solution.

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