Cleaning solution composition and method for cleaning scale

Abstract

The present invention provides a cleaning solution composition that exhibits broad cleaning performance against various scales with different components, and a method for cleaning scale. [Solution] A cleaning solution composition for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, wherein the cleaning solution composition comprises dimethyl sulfoxide, potassium hydroxide, and water, the content of dimethyl sulfoxide being 62 to 85% by mass based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water, and the content of potassium hydroxide being 5 to 30% by mass based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water.

Description

Technical Field

[0001] The present disclosure relates to a cleaning liquid composition for cleaning scale, and a method for cleaning scale using the cleaning liquid composition.

Background Art

[0002] It is known that cleaning liquid compositions containing acidic substances such as sulfuric acid, phosphoric acid and sulfamic acid, chelating agents such as citric acid and ethylenediaminetetraacetic acid, fluorides, or combinations thereof are used to remove scale adhering to the inside of pipes such as heat exchangers and drains, or inside facilities such as storage tanks and reaction tanks.

[0003] Patent Document 1 (Japanese Unexamined Patent Publication No. 2014-205758) describes a cleaning agent composition characterized by containing (A) dimethyl sulfoxide (DMSO) and (B) cyclodextrin.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In addition to salts such as Ca, Mg and Si, scale may contain other metal salts, organic substances, or components derived therefrom. When the components of scale differ, it is common to selectively use cleaning liquid compositions with different effective cleaning components. However, if the components contained in the scale adhering to the same pipe or facility change or the component ratio fluctuates, the scale may not be sufficiently cleaned. When different cleaning liquid compositions are selectively used for pipes and facilities in a factory, the costs related to the equipment and processes for waste liquid treatment of the cleaning liquid compositions may increase.

[0006] This disclosure provides a cleaning solution composition that exhibits broad cleaning performance against various scales with different components, and a method for cleaning scale. [Means for solving the problem]

[0007] The inventors completed the present invention by discovering that a composition containing dimethyl sulfoxide, potassium hydroxide, and water exhibits broad cleaning performance against various scales.

[0008] This disclosure includes the following aspects: [Aspect 1] A cleaning solution composition for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, The cleaning solution composition comprises dimethyl sulfoxide, potassium hydroxide, and water. The dimethyl sulfoxide content is 62-85% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. A cleaning solution composition in which the potassium hydroxide content is 5 to 30% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. [Aspect 2] The potassium hydroxide content is 5 to 25% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The cleaning solution composition according to embodiment 1, wherein the water content is 10 to 33% by mass based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. [Aspect 3] A cleaning solution composition for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, wherein the cleaning solution composition comprises potassium hydroxide, dimethyl sulfoxide, and water. [Aspect 4] The dimethyl sulfoxide content is 10 to 85% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The potassium hydroxide content is 5 to 30% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The water content is 10 to 60% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The cleaning solution composition according to embodiment 3. [Aspect 5] The cleaning solution composition according to any one of embodiments 1 to 4, wherein the scale further comprises a component derived from an organic substance. [Aspect 6] The cleaning solution composition according to any one of embodiments 1 to 5, wherein the scale further comprises at least one metal element selected from the group consisting of Al and Fe. [Aspect 7] A method for cleaning scale, comprising contacting the scale with a cleaning solution composition according to any one of embodiments 1 to 6, wherein the scale contains at least one element selected from the group consisting of Ca, Mg, and Si. [Aspect 8] The method according to embodiment 7, wherein the scale further comprises components derived from organic matter. [Aspect 9] The method according to embodiment 7 or 8, wherein the scale further comprises at least one metallic element selected from the group consisting of Al and Fe. [Aspect 10] The method according to any one of embodiments 7 to 9, wherein the cleaning solution composition is brought into contact with the scale in a turbulent state. [Aspect 11] The dimethyl sulfoxide is recovered by distilling the used cleaning solution composition, and The method according to any one of embodiments 7 to 10, comprising reusing the recovered dimethyl sulfoxide to prepare the cleaning solution composition. [Effects of the Invention]

[0009] This disclosure provides a cleaning solution composition that exhibits broad cleaning performance against various scales with different components, and a method for cleaning scales.

[0010] It should not be construed that the above description discloses all embodiments of the present invention and all advantages related to the present invention. [Mode for Carrying Out the Invention]

[0011] Hereinafter, the present invention will be described in more detail for the purpose of illustrating representative embodiments of the present invention, but the present invention is not limited to these embodiments.

[0012] In the present disclosure, "comprising" means that the cleaning liquid composition may contain other components in addition to dimethyl sulfoxide, potassium hydroxide, and water. In the present disclosure, "consisting essentially of" means that the cleaning liquid composition may contain other components in addition to dimethyl sulfoxide, potassium hydroxide, and water in an amount that does not impair the effects of the present invention, and the content of such other components is, for example, less than 1% by mass, less than 0.5% by mass, or less than 0.1% by mass based on the mass of the cleaning liquid composition. In the present disclosure, "consisting of" means that the cleaning liquid composition contains no other components in addition to dimethyl sulfoxide, potassium hydroxide, and water.

[0013] In the present disclosure, "scale" means solid aggregates formed by deposition or adhesion of components contained in a fluid that comes into contact with piping or equipment, or a fluid that flows through or stays inside the piping or equipment, on the surfaces of the piping or equipment, or structures, apparatuses, devices, instruments and the like disposed inside them. The scale includes, for example, poorly soluble salts of metals such as Ca, Mg, Si, Al, and Fe. Examples of poorly soluble salts include hydroxides, fluorides, carbonates, phosphates, or sulfates of Ca, Mg, Al, or Fe, and silicates such as calcium silicate and magnesium silicate. The scale may also contain components derived from organic substances, for example, hydrocarbon oils, coke-like carbon, bacteria, humic acid, or organic matter contained in wastewater or sewage from human activities.

[0014] [Cleaning Liquid Composition] A cleaning liquid composition according to one embodiment is for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, and comprises dimethyl sulfoxide (DMSO), potassium hydroxide (KOH), and water. The content of dimethyl sulfoxide is 62 to 85 mass% based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water, and the content of potassium hydroxide is 5 to 30 mass% based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water. By containing a combination of dimethyl sulfoxide and potassium hydroxide at a specific content, the cleaning liquid composition of this embodiment can exhibit high cleaning performance for scale containing at least one element selected from the group consisting of Ca, Mg, and Si.

[0015] In one embodiment, the scale further contains a component derived from an organic substance. Examples of such a component include hydrocarbon oils, coke-like carbon, bacteria, humic acid, and organic substances contained in wastewater or sewage from human activities. The cleaning liquid composition can exhibit high cleaning performance even for scale containing components derived from organic substances.

[0016] In one embodiment, the scale further contains at least one metal element selected from the group consisting of Al and Fe. The cleaning liquid composition can exhibit high cleaning performance even for scale containing Al or Fe.

[0017] Dimethyl sulfoxide is an organic solvent soluble in water and oil, and exhibits solubility in salts upon the addition of water. While most organic solvents show little to no solubility in salts, dimethyl sulfoxide's solubility in salts is advantageous for cleaning scales containing at least one element selected from the group consisting of Ca, Mg, and Si, and is also effective for cleaning scales containing Al or Fe. Dimethyl sulfoxide also acts as an organic solvent to effectively dissolve and remove components derived from organic substances in the scale. Because dimethyl sulfoxide is soluble in water, it can improve the wettability of the cleaning solution composition to water-containing scales, thereby maintaining good contact between the cleaning solution composition and the scale.

[0018] The freezing point of dimethyl sulfoxide is 19°C, which drops to 0°C when water is added. Therefore, the cleaning solution composition can be used at ambient temperatures above 0°C. The cleaning solution composition may also be used after being appropriately heated.

[0019] The dimethyl sulfoxide content is 62 to 85% by mass, preferably 62 to 80% by mass, and more preferably 65 to 80% by mass, based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water.

[0020] Potassium hydroxide dissolves in water, as described later, and is present in the cleaning solution composition as an aqueous potassium hydroxide solution. Because the aqueous potassium hydroxide solution is strongly alkaline, it is highly reactive and can, for example, promote the dissolution of salts in scale, or chemically react with the oxidized metal surface of piping or equipment to clean the metal surface. Potassium hydroxide can also dissolve or emulsify components with polar molecules among organic substances in the cleaning solution composition. High-concentration aqueous potassium hydroxide solutions have high penetration into the scale, and in some cases can peel the scale from the surface or break it down. In some embodiments, the scale is atomized in the aqueous layer containing potassium hydroxide. The atomized scale can be easily discharged from the piping or equipment system.

[0021] The potassium hydroxide content is 5 to 30% by mass, preferably 5 to 25% by mass, and more preferably 6 to 20% by mass, based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water.

[0022] Water dissolves the salts contained in the scale. Furthermore, the inclusion of water in the cleaning solution composition enhances its wettability to water-containing scale, thus maintaining good contact between the cleaning solution composition and the scale.

[0023] The water content is, for example, 8 to 33% by mass, preferably 10 to 33% by mass, and more preferably 14 to 29% by mass, based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water.

[0024] The cleaning solution composition may essentially consist of potassium hydroxide, dimethyl sulfoxide, and water.

[0025] One embodiment of the cleaning solution composition is for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, and comprises potassium hydroxide, dimethyl sulfoxide, and water.

[0026] In this embodiment, based on the total mass of dimethyl sulfoxide, potassium hydroxide, and water, preferably, the content of dimethyl sulfoxide is 10 to 85% by mass, the content of potassium hydroxide is 5 to 30% by mass, and the content of water is 10 to 60% by mass; more preferably, the content of dimethyl sulfoxide is 40 to 85% by mass, the content of potassium hydroxide is 5 to 25% by mass, and the content of water is 10 to 35% by mass; even more preferably, the content of dimethyl sulfoxide is 50 to 80% by mass, the content of potassium hydroxide is 6 to 25% by mass, and the content of water is 14 to 35% by mass.

[0027] The cleaning solution composition can be prepared by mixing dimethyl sulfoxide, potassium hydroxide, and water in the above-mentioned proportions. Since potassium hydroxide is hygroscopic, it is preferable to use an aqueous solution of an appropriate concentration (e.g., a 30% potassium hydroxide solution) rather than a solid. The order of mixing is not particularly limited, but for example, potassium hydroxide can be dissolved in water, and dimethyl sulfoxide can be added to the resulting aqueous potassium hydroxide solution. Mixing can be carried out by any known means.

[0028] When dimethyl sulfoxide and potassium hydroxide aqueous solution are mixed, the dimethyl sulfoxide and water separate into two layers. During this process, some of the water migrates to the dimethyl sulfoxide side, increasing the potassium hydroxide concentration in the aqueous layer. For example, when dimethyl sulfoxide and a 30% potassium hydroxide aqueous solution are mixed in a volume ratio of 8:2, the mass ratio becomes dimethyl sulfoxide:potassium hydroxide:water = 77:7:16. Through mixing, water is drawn from the potassium hydroxide aqueous solution to the dimethyl sulfoxide side, increasing the potassium hydroxide concentration in the aqueous layer to approximately 50%. This allows for a high cleaning effect by allowing the high-concentration potassium hydroxide aqueous layer to act on scale, while simultaneously ensuring the overall safety and ease of handling of the cleaning solution by dispersing the high-concentration potassium hydroxide aqueous solution within the dimethyl sulfoxide.

[0029] The cleaning solution composition separates into two layers when left to stand. The upper layer is an organic layer mainly containing dimethyl sulfoxide, and the lower layer is an aqueous layer mainly containing potassium hydroxide. Because dimethyl sulfoxide has a very high affinity for water, the water in the aqueous layer migrates to the organic layer. As the migration of water from the aqueous layer to the organic layer progresses, the flash point of the dimethyl sulfoxide in the organic layer (89°C, by the Tag closure method) disappears (the inventors have confirmed that the flash point disappears when water is present at approximately 13% by mass or more in a mixture of dimethyl sulfoxide and water), and the potassium hydroxide in the aqueous layer is concentrated to the maximum concentration that can maintain its solution state. At this time, for example, the potassium hydroxide concentration in the aqueous layer becomes 50-60% by mass, and the aqueous layer accounts for about 8-10% by volume of the total volume of the cleaning solution composition.

[0030] [How to clean scale] One embodiment of a scale cleaning method involves contacting the above-mentioned cleaning liquid composition with scale containing at least one element selected from the group consisting of Ca, Mg, and Si. By using the above-mentioned cleaning liquid composition, the scale can be effectively removed. Contact between the cleaning liquid composition and the scale can be carried out, for example, by circulating the cleaning liquid composition inside a pipe or equipment where scale has adhered to the internal surface. The cleaning liquid composition may also be brought into contact with the scale by spraying or injecting it towards the scale using a spray, jet nozzle, or the like.

[0031] It is preferable to bring the cleaning solution composition into contact with the scale in a turbulent flow state. This allows for more effective cleaning of the scale.

[0032] It is preferable to circulate the cleaning solution composition within the piping or equipment using a reciprocating pump with fluctuating pressure. This can promote the removal or crushing of scale.

[0033] Since the cleaning solution composition separates into two layers when left standing, it is preferable to disperse the heavier aqueous layer containing potassium hydroxide in droplet form throughout the entire cleaning solution composition before circulating the cleaning solution composition within the piping or equipment. Dispersion of the aqueous layer can be performed using a stirrer located outside the piping or equipment. Dispersion of the aqueous layer may also be performed inside the pump that supplies the cleaning solution composition within the piping or equipment.

[0034] In one embodiment, the scale further comprises components derived from organic substances. Examples of such components include hydrocarbon oils, coke-like carbon, bacteria, humic acid, and organic matter contained in wastewater or sewage from human activities. By using the above cleaning solution composition, scale containing components derived from organic substances can be effectively removed.

[0035] In one embodiment, the scale further comprises at least one metallic element selected from the group consisting of Al and Fe. By using the above cleaning solution composition, scale containing Al or Fe can be effectively removed.

[0036] One embodiment of the cleaning method includes recovering dimethyl sulfoxide by distilling the used cleaning solution composition, and preparing a cleaning solution composition by reusing the recovered dimethyl sulfoxide. By reusing dimethyl sulfoxide, the waste liquid generated by cleaning can be reduced. [Examples]

[0037] The following examples illustrate specific embodiments of the present disclosure, but the present invention is not limited thereto. All parts and percentages, including in the table, are by mass unless otherwise specified. Numerical values ​​include errors inherent to the measurement principle and measuring device. Numerical values, including those in the table, are shown with significant figures rounded to the usual degree.

[0038] Example 1 Dimethyl sulfoxide and a 30% aqueous potassium hydroxide solution were mixed to obtain the cleaning solution composition of Example 1, with a composition of dimethyl sulfoxide:potassium hydroxide:water = 77:7:16 (by mass).

[0039] Comparative Example 1 A 5% sulfamic acid aqueous solution was used as the cleaning solution composition in Comparative Example 1.

[0040] The cleaning performance of the cleaning solution compositions of Example 1 and Comparative Example 1 against the following three types of scales A, B, and C was evaluated using the following procedure.

[0041] A. Scale adhering to the cooling water side of the reactor condenser Scale A contained Ca, Mg, Si, and organic matter generated in the reactor, and was dissolved to approximately 45% by mass by a two-step washing process using a 5% hydrogen peroxide aqueous solution and a citric acid / ethylenediaminetetraacetic acid (EDTA) mixed aqueous solution. B. Scale adhering to the inner surface (metal base material side) of the drain pipe Scale B, which contains Ca, Mg, Si, Al, and Fe, was dissolved to approximately 40% by mass by a one-step washing with a sulfuric acid / fluoride mixture. C. Scale adhering to the cooling water side of the reaction vessel Scale C contains Ca, Mg, Si, and organic matter produced in the reactor.

[0042] Approximately 0.5 g of small pieces of scale A, B, and C were collected and placed in a vial. 15 mL of the washing solution composition of Example 1 or Comparative Example 1 was added to the vial and the lid was closed. For Example 1, the vial was shaken using a shaker (model NR-3, Taitec Co., Ltd.) at 23°C and 150 rpm for 15.7 hours to allow the washing solution composition to come into contact with the scale while being stirred. For Comparative Example 1, the vial was left to stand at 23°C for 15.7 hours. The results of visual observation of the scale condition are shown in Table 1.

[0043] [Table 1]

[0044] The cleaning solution composition of Example 1 showed solubility for scales A, B, and C, and changed the shape of scales B and C to either powder or mud. Therefore, the cleaning solution composition of Example 1 has higher cleaning ability compared to the cleaning solution composition of Comparative Example 1.

[0045] It will be apparent to those skilled in the art that the above embodiments and examples can be modified in various ways without departing from the basic principles of the present invention. It will also be apparent to those skilled in the art that various improvements and modifications of the present invention can be implemented without departing from the spirit and scope of the present invention.

Claims

1. A cleaning solution composition for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, The cleaning solution composition comprises dimethyl sulfoxide, potassium hydroxide, and water. The dimethyl sulfoxide content is 62 to 85% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. A cleaning solution composition in which the potassium hydroxide content is 5 to 30% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water.

2. The potassium hydroxide content is 5 to 25% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The cleaning solution composition according to claim 1, wherein the water content is 10 to 33% by mass based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water.

3. A cleaning solution composition for cleaning scale containing at least one element selected from the group consisting of Ca, Mg, and Si, wherein the cleaning solution composition comprises potassium hydroxide, dimethyl sulfoxide, and water.

4. The dimethyl sulfoxide content is 10 to 85% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The potassium hydroxide content is 5 to 30% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The water content is 10 to 60% by mass, based on the total mass of the dimethyl sulfoxide, potassium hydroxide, and water. The cleaning solution composition according to claim 3.

5. The cleaning solution composition according to any one of claims 1 to 4, wherein the scale further comprises a component derived from an organic substance.

6. The cleaning solution composition according to any one of claims 1 to 4, wherein the scale further comprises at least one metal element selected from the group consisting of Al and Fe.

7. A method for cleaning scale, comprising contacting the scale with a cleaning solution composition according to any one of claims 1 to 4, wherein the scale comprises at least one element selected from the group consisting of Ca, Mg, and Si.

8. The method according to claim 7, wherein the scale further comprises a component derived from an organic substance.

9. The method according to claim 7, wherein the scale further comprises at least one metallic element selected from the group consisting of Al and Fe.

10. The method according to claim 7, wherein the cleaning solution composition is brought into contact with the scale in a turbulent state.

11. The dimethyl sulfoxide is recovered by distilling the used cleaning solution composition, and The method according to claim 7, comprising reusing the recovered dimethyl sulfoxide to prepare the cleaning solution composition.

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