A citric acid chemical cleaning anti-settling agent

Abstract

The application discloses a citric acid chemical cleaning anti-settling agent and belongs to the technical field of chemical cleaning. The anti-settling agent comprises 3.0-10.0% of dispersant, 3.0-10.0% of masking agent, 3.0-5.0% of cosolvent, 0.1-1.0% of surfactant and desalted water. The temperature reduction of the cleaning liquid in the top row process accelerates the generation and deposition of the precipitate. In the top row process, the anti-settling agent is added into the desalted water, so that the generation and deposition of the precipitate can be prevented, the cleaning effect is ensured, and the heat exchange tube blockage accident can be avoided.

Description

Technical Field

[0001] This invention belongs to the field of chemical cleaning technology, specifically relating to a citric acid chemical cleaning agent to prevent sedimentation. Background Technology

[0002] Citric acid is a commonly used chemical cleaning agent, possessing advantages such as strong scale-dissolving ability, low corrosion rate, absence of chloride ions, and easy high-temperature decomposition of cleaning residues. It is widely used in the chemical cleaning of industrial equipment such as power plant boilers. During chemical cleaning, citric acid reacts with iron oxides to easily form ferrous citrate precipitate. Therefore, in existing citric acid chemical cleaning processes, ammonia is usually added to the citric acid solution to adjust the pH to 3.5–4.0 to partially address the citric acid precipitation problem. However, when using high-concentration citric acid to clean equipment with high scale levels and low water volume, precipitation still occurs. Ferrous citrate precipitate is adhesive and easily adsorbs onto the cleaned metal surface, severely affecting cleaning quality and even causing accidents such as heat exchanger tube blockage.

[0003] In the later stages of citric acid chemical cleaning, when the iron ion concentration in the cleaning solution approaches or exceeds the critical concentration, posing a risk of precipitation or when precipitation has already occurred, acid draining is usually necessary. Due to the requirements of the citric acid chemical cleaning process, acid draining is often carried out using a demineralized water top drain method. Because the temperature of the demineralized water (20–60℃) is much lower than the citric acid cleaning temperature (85–95℃), the temperature drop of the cleaning solution during top draining promotes the formation and deposition of precipitates. During top draining, an anti-precipitant is added to the demineralized water to prevent the formation and deposition of precipitates, avoid heat exchange tube blockage accidents, and also has a good dissolving effect on ferrous citrate that has already deposited. Summary of the Invention

[0004] The purpose of this invention is to provide a citric acid chemical cleaning anti-precipitant, which can effectively prevent the formation and deposition of ferrous citrate precipitate during citric acid chemical cleaning, and at the same time has a good dissolving effect on ferrous citrate that has already been deposited.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention is to provide a citric acid chemical cleaning anti-precipitation agent, comprising, by mass percentage: 3.0% to 10.0% of a dispersant, 3.0% to 10.0% of a masking agent, 3.0% to 5.0% of a co-solvent, 0.1% to 1.0% of a surfactant, and the balance being demineralized water.

[0007] As a further improvement of the present invention, the dispersant comprises 30% to 70% polyaspartic acid and 30% to 70% polymaleic anhydride.

[0008] As a further improvement of the present invention, the masking agent includes one or more of hydroxyethylidene diphosphonic acid, diethylenetriaminepentamethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, aminotriacetic acid, and diethylenetriaminepentaacetic acid.

[0009] As a further improvement of the present invention, the co-solvent comprises 30% to 40% EDTA ammonium salt, 30% to 40% ammonium citrate salt, and 20% to 60% ammonia.

[0010] As a further improvement of the present invention, the surfactant includes one or more of polyoxyethylene fatty alcohol ethers, alkylphenol polyoxyethylene ethers, and alkanolamides.

[0011] As a further improvement of the present invention, by mass percentage, it comprises: 5.0 to 10.0% dispersant, 5.0 to 10.0% masking agent, 3.0 to 5.0% cosolvent, 0.5 to 1% surfactant, and the balance being demineralized water.

[0012] As a further improvement of the present invention, by mass percentage, it comprises: 3.0 to 5.0% dispersant, 3.0 to 5.0% masking agent, 3.0 to 4.0% cosolvent, 0.1 to 0.5% surfactant, and the balance being demineralized water.

[0013] A second aspect of the present invention is to provide a method for using a citric acid chemical cleaning and anti-precipitation agent, comprising the following steps:

[0014] In the later stages of citric acid chemical cleaning, when the iron ion concentration in the cleaning solution approaches or exceeds the critical concentration, demineralized water is often used to drain the acid. During the acid draining process, citric acid chemical cleaning anti-precipitation agent is added to the demineralized water.

[0015] As a further improvement of the present invention, the concentration of the added citric acid chemical cleaning anti-precipitation agent is 1% to 10%.

[0016] As a further improvement of the present invention, the temperature at which the citric acid chemical cleaning anti-precipitation agent is added is 20–95°C.

[0017] The technical solution provided by this invention has the following beneficial effects:

[0018] The anti-precipitation agent of this invention comprises a dispersant, a masking agent, a co-solvent, a surfactant, and demineralized water. The dispersant, as a key component, prevents the contact and aggregation between ferrous citrate crystals, inhibiting crystal deposition and adhesion to the cleaned surface to form ferrous citrate deposits. The masking agent is mainly used to mask Fe in the solution. 2+ Fe 3+The co-solvent is mainly used to dissolve ferrous citrate deposits already deposited on the metal surface being cleaned. The surfactant is mainly used to reduce the contact angle between the solution and the ferrous citrate deposits, promoting the penetration of the co-solvent into the interior of the deposits and facilitating their dissolution. In the later stages of citric acid chemical cleaning, when the iron ion concentration in the cleaning solution approaches or exceeds the critical concentration, there is a risk of precipitation, or precipitation has already occurred; in such cases, acid drainage is usually required. This anti-precipitant can inhibit the formation and deposition of ferrous citrate precipitates, and also has a good dissolving effect on existing ferrous citrate precipitates, preventing accidents such as heat exchanger tube blockage. It can be used under conditions of high ferric ion content, high temperature, acidity, or alkalinity, solving the problems of low efficiency and easy deactivation of traditional anti-precipitants under high ferric ion content and high temperature conditions. It is also adaptable to acidic and alkaline conditions, making it widely applicable. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0024] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple.

[0025] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0026] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0027] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0028] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0030] The first objective of this invention is to provide a citric acid chemical cleaning anti-precipitation agent, comprising, by mass percentage: 3.0% to 10.0% dispersant, 3.0% to 10.0% masking agent, 3.0% to 5.0% cosolvent, 0.1% to 1.0% surfactant, and the balance being deionized water.

[0031] The dispersant is used to prevent the contact and aggregation between ferrous citrate crystals, inhibit the deposition of crystals and their adhesion to the cleaned surface, and is composed of 30% to 70% polyaspartic acid (PASP) and 30% to 70% polymaleic anhydride (HPMA).

[0032] The masking agent is mainly used to mask Fe in the solution. 2+ Fe 3+ It is composed of one or more of hydroxyethylidene diphosphonic acid (HEDPA), diethylenetriaminepentamethylenephosphonic acid (DTPMP), ethylenediaminetetramethylenephosphonic acid (EDTMPS), aminotriacetic acid (NTA), and diethylenetriaminepentaacetic acid (DTPA).

[0033] The surfactant described herein is used to reduce the contact angle between the solution and the ferrous citrate deposit, promote the penetration of the co-solvent into the interior of the ferrous citrate deposit, and promote the dissolution of the deposit. It is composed of one or more of polyoxyethylene fatty alcohol ether, alkylphenol polyoxyethylene ether, and alkanolamide.

[0034] The co-solvent is mainly used to dissolve ferrous citrate deposits that have been deposited on the surface of the cleaned metal, and includes 30%–40% EDTA ammonium salt, 30%–40% ammonium citrate salt, and 20%–60% ammonia.

[0035] The principle of this invention is as follows: the dispersant, as a key component, prevents the contact and aggregation between ferrous citrate crystals, inhibits crystal deposition and adhesion to the cleaned surface, forming ferrous citrate deposits. The masking agent is mainly used to mask Fe in the solution. 2+ Fe 3+ Co-solvents are primarily used to dissolve ferrous citrate deposits already deposited on the metal surface being cleaned. Surfactants are mainly used to reduce the contact angle between the solution and the ferrous citrate deposits, promoting the penetration of the co-solvent into the interior of the ferrous citrate deposits and facilitating their dissolution.

[0036] As a specific embodiment, the citric acid chemical cleaning anti-precipitation agent, by mass percentage, comprises: 5.0–10.0% dispersant, 5.0–10.0% masking agent, 2–5.0% co-solvent, 0.5–1% surfactant, and the balance being demineralized water.

[0037] This invention also provides a method for using a citric acid chemical cleaning and anti-precipitation agent, comprising the following steps:

[0038] In the later stages of citric acid chemical cleaning, when the iron ion concentration in the cleaning solution approaches or exceeds the critical concentration, demineralized water is often used to drain the acid. During the acid draining process, citric acid chemical cleaning anti-precipitation agent is added to the demineralized water.

[0039] Citric acid chemical cleaning and anti-settling agent, its concentration is 1% to 10%, and its operating temperature is 20 to 95℃.

[0040] Due to the requirements of citric acid chemical cleaning processes, acid discharge is mostly carried out using demineralized water top discharge. Since the temperature of the demineralized water (20–60℃) is much lower than the citric acid cleaning temperature (85–95℃), the temperature drop of the cleaning solution during top discharge accelerates the formation and deposition of precipitates. During top discharge, an anti-precipitant is added to the demineralized water to prevent the formation and deposition of precipitates, ensuring the cleaning effect and avoiding heat exchange tube blockage accidents.

[0041] The present invention will be further described in detail below with reference to specific embodiments.

[0042] Example 1:

[0043] An 8% citric acid chemical cleaning solution was prepared, and the pH value was adjusted to 3.5 with ammonia. A metal tube containing ferric oxide scale was placed in the solution, and the temperature was raised to 95°C. After static soaking for 20 hours, the total iron content in the cleaning solution reached 12000 mg / L, which exceeded the critical concentration for ferrous citrate precipitation. Some ferrous citrate had been deposited on the surface of the tube, and the deposits continued to increase.

[0044] Add 3% citric acid chemical cleaning anti-precipitant to the above cleaning solution. The anti-precipitant consists of 10.0% dispersant, 10.0% masking agent, 5.0% co-solvent, 0.3% surfactant, and 74.7% demineralized water by weight. The dispersant consists of 60% polyaspartic acid (PASP) and 40% polymaleic anhydride (HPMA); the masking agent is diethylenetriaminepentamethylenephosphonic acid (DTPMP). The co-solvent consists of 30% EDTA diammonium salt, 40% triammonium citrate, and 30% ammonia. The surfactant is polyoxyethylene fatty alcohol ether.

[0045] After adding the anti-precipitant, the sample was allowed to stand for 1 hour, and the deposits on the surface dissolved without further precipitation. After standing for 24 hours, the solution remained clear, with no precipitation observed.

[0046] Example 2:

[0047] An 8% citric acid chemical cleaning solution was prepared, and the pH value was adjusted to 3.0 with ammonia. A metal tube containing ferric oxide scale was placed in the solution, and the temperature was raised to 95°C. After static soaking for 16 hours, the total iron content in the cleaning solution reached 8000 mg / L, which exceeded the critical concentration for ferrous citrate precipitation. Some ferrous citrate had been deposited on the surface of the tube, and the deposits continued to increase.

[0048] Add 4% citric acid chemical cleaning anti-precipitant to the above cleaning solution. The anti-precipitant consists of 10.0% dispersant, 5.0% masking agent, 5.0% co-solvent, 0.3% surfactant, and 79.7% demineralized water by weight. The dispersant consists of 50% polyaspartic acid (PASP) and 50% polymaleic anhydride (HPMA); the masking agent consists of 20% hydroxyethylidene diphosphonic acid (HEDPA) and 80% diethylenetriaminepentamethylenephosphonic acid (DTPMP). The co-solvent consists of 40% EDTA diammonium salt, 30% triammonium citrate, and 30% ammonia. The surfactant is polyoxyethylene fatty alcohol ether.

[0049] After adding the anti-precipitant, the sample was allowed to stand for 1 hour, and the deposits on the surface dissolved without further precipitation. After standing for 24 hours, the solution remained clear, with no precipitation observed.

[0050] Example 3:

[0051] The metal pipe section with a large amount of ferrous citrate deposited and causing blockage was placed in a 10% citric acid chemical cleaning anti-precipitation solution at 95°C. The pH of the solution was adjusted to 10.0 (simulating the quality of rinsing water after citric acid chemical cleaning). After standing for 2 hours, all the ferrous citrate deposited in the metal pipe dissolved. After standing for another 24 hours, no further precipitation was observed.

[0052] The aforementioned citric acid chemical cleaning anti-precipitant consists of 10.0% by weight of dispersant, 10.0% by weight of masking agent, 5.0% by weight of co-solvent, 1.0% by weight of surfactant, and 74.0% by weight of deionized water. The dispersant comprises 30% polyaspartic acid (PASP) and 70% polymaleic anhydride (HPMA); the masking agent comprises 40% ethylenediaminetetramethylenephosphonic acid (EDTMPS) and 60% aminotriacetic acid (NTA). The co-solvent comprises 40% EDTA diammonium salt, 30% triammonium citrate, and 30% ammonia. The surfactant is polyoxyethylene fatty alcohol ether.

[0053] Example 4:

[0054] An 8% citric acid chemical cleaning solution was prepared, and the pH value was adjusted to 3.5 with ammonia. A metal tube containing ferric oxide scale was placed in the solution, and the temperature was raised to 90°C. After static soaking for 20 hours, the total iron content in the cleaning solution reached 10,000 mg / L, which exceeded the critical concentration for ferrous citrate precipitation. Some ferrous citrate had been deposited on the surface of the tube, and the deposits continued to increase.

[0055] Add 5% citric acid chemical cleaning anti-precipitant to the above cleaning solution. The anti-precipitant consists of 3.0% dispersant, 3.0% masking agent, 4.0% co-solvent, 0.2% surfactant, and 89.8% demineralized water by weight. The dispersant consists of 30% polyaspartic acid (PASP) and 70% polymaleic anhydride (HPMA); the masking agent is diethylenetriaminepentamethylenephosphonic acid (DTPMP). The co-solvent consists of 35% EDTA diammonium salt, 30% triammonium citrate, and 60% ammonia. The surfactant is polyoxyethylene fatty alcohol ether.

[0056] After adding the anti-precipitant, the sample was allowed to stand for 1 hour, and the deposits on the surface dissolved without further precipitation. After standing for 24 hours, the solution remained clear, with no precipitation observed.

[0057] Example 5:

[0058] A 9% citric acid chemical cleaning solution was prepared, and the pH value was adjusted to 3.4 with ammonia. The metal tube sample containing ferric oxide scale was placed in the solution, heated to 93°C, and statically soaked for 19 hours. The total iron content in the cleaning solution reached 9000 mg / L, which exceeded the critical concentration for ferrous citrate precipitation. Some ferrous citrate had been deposited on the surface of the tube sample, and the deposits continued to increase.

[0059] Add 1% citric acid chemical cleaning anti-precipitant to the above cleaning solution. The anti-precipitant consists of 8.0% dispersant, 8.0% masking agent, 3.0% co-solvent, 1.0% surfactant, and 80.0% demineralized water by weight. The dispersant consists of 70% polyaspartic acid (PASP) and 30% polymaleic anhydride (HPMA); the masking agent is hydroxyethylidene diphosphonic acid. The co-solvent consists of 35% EDTA diammonium salt, 35% triammonium citrate, and 30% ammonia. The surfactant is polyoxyethylene fatty alcohol ether.

[0060] After adding the anti-precipitant, the sample was allowed to stand for 1 hour, and the deposits on the surface dissolved without further precipitation. After standing for 24 hours, the solution remained clear, with no precipitation observed.

[0061] Example 6:

[0062] The metal pipe section with a large amount of ferrous citrate deposited and causing blockage was placed in a 6% citric acid chemical cleaning anti-precipitation solution at 95°C. The pH of the solution was adjusted to 10.0 (simulating the quality of rinsing water after citric acid chemical cleaning). After standing for 2 hours, all the ferrous citrate deposited in the metal pipe dissolved. After standing for another 24 hours, no further precipitation was observed.

[0063] The aforementioned citric acid chemical cleaning anti-precipitant consists of 6.0% by weight of dispersant, 4.0% by weight of masking agent, 3.5% by weight of co-solvent, 0.5% by weight of surfactant, and 86.0% by weight of deionized water. The dispersant comprises 60% polyaspartic acid (PASP) and 40% polymaleic anhydride (HPMA); the masking agent comprises 65% ethylenediaminetetramethylenephosphonic acid and 35% diethylenetriaminepentaacetic acid. The co-solvent comprises 35% EDTA diammonium salt, 38% triammonium citrate, and 37% ammonia. The surfactant is polyoxyethylene fatty alcohol ether.

[0064] All articles and references disclosed herein, including patent applications and publications, are incorporated herein by reference for various purposes. The term “substantially constitutes…” used to describe a combination should include the identified elements, components, parts, or steps, as well as other elements, components, parts, or steps that do not substantially affect the essential novelty of the combination. The use of the terms “comprising” or “including” to describe combinations of elements, components, parts, or steps herein also contemplates embodiments substantially constituted by such elements, components, parts, or steps. The use of the term “may” herein is intended to indicate that any described attribute included by “may” is optional.

[0065] Multiple elements, components, parts, or steps can be provided by a single integrated element, component, part, or step. Alternatively, a single integrated element, component, part, or step can be divided into multiple separate elements, components, parts, or steps. The use of "a" or "an" to describe an element, component, part, or step does not imply the exclusion of other elements, components, parts, or steps.

[0066] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A citric acid chemical cleaning and anti-precipitation agent, characterized in that, It consists of the following components by mass percentage: 3.0%~10.0% dispersant, 3.0%~10.0% masking agent, 3.0%~5.0% cosolvent, 0.1%~1.0% surfactant and the balance being demineralized water; The dispersant is composed of 30%~70% polyaspartic acid and 30%~70% polymaleic anhydride; The cosolvent consists of 30%~40% EDTA ammonium salt, 30%~40% ammonium citrate salt and 20%~37% ammonia.

2. The citric acid chemical cleaning and anti-precipitation agent according to claim 1, characterized in that: The masking agent includes one or more of hydroxyethylidene diphosphonic acid, diethylenetriaminepentamethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, aminotriacetic acid, and diethylenetriaminepentaacetic acid.

3. The citric acid chemical cleaning and anti-precipitation agent according to claim 1, characterized in that: The surfactant includes one or more of polyoxyethylene fatty alcohol ethers, alkylphenol polyoxyethylene ethers, and alkanolamides.

4. The citric acid chemical cleaning and anti-precipitation agent according to claim 1, characterized in that, By mass percentage, it consists of the following components: 5.0% to 10.0% dispersant, 5.0% to 10.0% masking agent, 3.0% to 5.0% cosolvent, 0.5% to 1% surfactant, and the balance being demineralized water.

5. The citric acid chemical cleaning and anti-precipitation agent according to claim 1, characterized in that, By mass percentage, it consists of the following components: 3.0% to 5.0% dispersant, 3.0% to 5.0% masking agent, 3.0% to 4.0% cosolvent, 0.1% to 0.5% surfactant, and the balance being demineralized water.

6. A method of using a citric acid chemical cleaning and anti-precipitation agent according to any one of claims 1 to 5, characterized in that, Includes the following steps: In the later stage of citric acid chemical cleaning, when the iron ion concentration in the cleaning solution approaches or exceeds the critical concentration, the acid is discharged by top discharge of demineralized water. During the acid discharge process, the citric acid chemical cleaning anti-precipitation agent according to any one of claims 1 to 5 is added to the demineralized water.

7. The method of using a citric acid chemical cleaning and anti-precipitation agent according to claim 6, characterized in that: The concentration of citric acid chemical cleaning anti-precipitant added is 1%~10%.

8. The method of using a citric acid chemical cleaning and anti-precipitation agent according to claim 6, characterized in that: The temperature for adding citric acid chemical cleaning and anti-settling agent is 20~95℃.