Condenser pickling cleaning solution and preparation method thereof

Abstract

The invention provides a condenser pickling cleaning solution which is composed of the following components in percentage by mass: 3%-8% of sulfamic acid, 1%-4% of glycolic acid, 1%-4% of formic acid, 0.5%-2% of EDTA (Ethylene Diamine Tetraacetic Acid) disodium salt, 0.1%-0.5% of organic phosphonate, 0.05%-0.2% of zinc salt, 0.1%-0.5% of a copper corrosion inhibitor, 0.01%-0.1% of a nitrogen-containing surfactant, 0.05%-0.3% of a dispersing agent and the balance of water. By compounding sulfamic acid, glycolic acid and formic acid, iron scale and calcium scale are efficiently dissolved, and the corrosion rate is low. The organic phosphonate, the zinc salt and the copper corrosion inhibitor form an omnibearing metal protection system. The EDTA and the dispersing agent ensure stable dispersion of the dirt and the ions, so that secondary deposition and blockage are avoided, and safe and efficient cleaning is realized.

Description

Technical Field

[0001] This invention relates to the field of industrial cleaning agent technology, and in particular to a condenser acid cleaning solution and its preparation method. Background Technology

[0002] As a key component of a power plant's thermal system, the condenser's heat exchange efficiency directly impacts the overall economy and safety of the unit. During long-term operation, the inner walls of the condenser's stainless steel heat exchange tubes inevitably accumulate various types of fouling, primarily including calcium and magnesium carbonate scale from circulating water, corrosion products such as iron oxide, and silicate scale. The presence of these scale layers significantly reduces heat exchange efficiency, increases terminal temperature differences, leads to energy waste, and may induce under-deposit corrosion, threatening the safe operation of the equipment.

[0003] To ensure condenser performance, regular chemical cleaning is a necessary maintenance measure. Currently, for chemical cleaning of stainless steel equipment, the industry commonly uses inorganic acids (such as hydrochloric acid and nitric acid) or organic acids (such as citric acid) as the main cleaning agents. However, these cleaning solutions all have certain limitations. Chlorine-containing inorganic acids such as hydrochloric acid are extremely destructive to stainless steel, especially to the passivation film of stainless steel (such as 316L), easily causing pitting corrosion and stress corrosion cracking, posing a very high risk. Although nitric acid is an oxidizing acid, it produces toxic nitrogen oxides during operation, posing safety and environmental hazards. While organic acids such as citric acid are milder in corrosiveness, they have problems such as slow descaling speed, limited ability to dissolve calcium, magnesium, and silica scale, and the potential to produce insoluble ferric citrate precipitates under certain conditions, affecting the cleaning effect and potentially causing secondary pollution.

[0004] Furthermore, condenser systems typically contain copper components (such as tube sheets). Traditional pickling solutions dissolve copper ions during the cleaning process, causing a "copper plating" phenomenon on the steel surface, forming microscopic galvanic cells that accelerate the corrosion of the stainless steel substrate. Meanwhile, existing cleaning formulations often have limited functionality, failing to effectively target scale, iron deposits, and silica deposits simultaneously, and lacking comprehensive performance in inhibiting metal corrosion and preventing redeposition of fouling.

[0005] Therefore, developing a specialized pickling and cleaning solution for stainless steel that can efficiently dissolve various types of scale, has low corrosiveness, poses no environmental risks, and effectively prevents copper plating has become an urgent technical problem to be solved in this field.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a condenser acid cleaning fluid and its preparation method, which solves at least one of the problems mentioned in the background art.

[0008] A first aspect of the present invention provides a condenser pickling cleaning fluid, comprising the following components by mass percentage: Aminosulfonic acid 3%-8% Glycolic acid 1%-4% Formic acid 1%-4% Disodium EDTA 0.5%-2% Organophosphonates 0.1%-0.5% Zinc salts 0.05%-0.2% Copper corrosion inhibitor 0.1%-0.5% Nitrogen-containing surfactants 0.01%-0.1% Dispersant 0.05%-0.3% The remainder is water.

[0009] According to some embodiments, the zinc salt is one or a mixture of two of zinc nitrate and zinc sulfate; preferably, the organophosphonate is one or a mixture of two of hydroxyethylidene diphosphonic acid and aminotrimethylphosphonic acid.

[0010] According to some embodiments, the copper corrosion inhibitor is one or a mixture of two of benzotriazole and methylbenzotriazole.

[0011] According to some embodiments, the nitrogen-containing surfactant is one or a mixture of two of dodecyl dimethyl benzyl ammonium chloride and tetradecyl dimethyl benzyl ammonium chloride.

[0012] According to some embodiments, the dispersant is one or a mixture of two of sodium polyacrylate and hydrolyzed polymaleic anhydride.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned condenser acid cleaning solution, comprising the following steps: S1. Add the measured amount of water to the mixing vessel; S2. While stirring, add the measured zinc salt, organophosphonate, copper corrosion inhibitor, nitrogen-containing surfactant, and dispersant to the water in sequence, and stir until completely dissolved; S3. While continuously stirring, slowly add the measured amount of EDTA disodium salt to the solution obtained in step S2, and stir until completely dissolved; S4. Under continuous stirring and cooling, slowly add the measured amounts of aminosulfonic acid, glycolic acid and formic acid to the solution obtained in step S3 in sequence, and mix evenly to obtain the pickling cleaning solution.

[0014] According to some embodiments, in step S4, the temperature of the acid addition process is controlled to not exceed 40°C.

[0015] According to some embodiments, in step S4, the aminosulfonic acid, glycolic acid, and formic acid are added in solid form or in a high-concentration aqueous solution.

[0016] The third aspect of the present invention provides a method for cleaning a stainless steel condenser, especially a 316L stainless steel condenser, using the above-mentioned condenser pickling cleaning solution, wherein the cleaning temperature is 40℃-60℃ and the cleaning time is 4-8 hours.

[0017] According to some embodiments, during the cleaning process, the pH value of the cleaning solution is controlled within the range of 2.0-4.0; preferably, the flow rate of the cleaning solution during cleaning is 0.1-0.25 m / s.

[0018] The present invention has at least the following beneficial effects: This invention utilizes a multi-component complex acid system composed of aminosulfonic acid, glycolic acid, and formic acid. This synergistic effect achieves highly efficient and thorough dissolution of iron oxide and calcium carbonate scale, while maintaining low corrosivity and good safety. The formulation, incorporating organophosphonates, zinc salts, and a specialized copper corrosion inhibitor, constitutes a comprehensive metal protection system, effectively inhibiting corrosion of various materials such as carbon steel and copper pipes, significantly reducing the risk of equipment damage. Furthermore, the addition of EDTA and dispersants ensures the stable complexation and dispersion of dissolved scale and metal ions, effectively preventing secondary deposition and pipeline blockage. Overall, this cleaning solution achieves excellent cleaning results while ensuring operational safety and long-term equipment protection, laying a solid foundation for the smooth operation of the cleaned equipment. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the preparation method of condenser acid cleaning solution in an embodiment of the present invention. Detailed Implementation

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form includes the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] It should be noted that if the text uses terms such as "first" or "second", these terms are only used to distinguish similar objects and should not be interpreted as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data in the descriptions of "first" and "second" can be interchanged where appropriate.

[0024] Throughout the accompanying drawings, identical elements are represented by the same or similar reference numerals. Conventional structures or configurations may be omitted where they might cause confusion in understanding the invention. Furthermore, the shapes, dimensions, and positional relationships of the components in the drawings do not reflect actual size, scale, or actual positional relationships. Additionally, any reference symbols placed within parentheses in this invention should not be construed as limiting the scope of the invention.

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a condenser acid cleaning fluid, which is composed of the following components by mass percentage: Sulfamic acid 3%-8%, for example 3.5%, 4%, 5%, 6.5%, 7.8%, etc. Hydroxyacetic acid (GAA) 1%-4%, for example 1.4%, 2%, 2.6%, 3.5%, etc. Formic acid 1%-4%, for example 1.5%, 2%, 2.5%, 3.5%, etc. Disodium EDTA salt, 0.5%-2%, for example, 0.9%, 1.4%, 1.8%, etc. Organophosphonates, 0.1%-0.5%, for example, 0.2%, 0.4%, etc. Zinc salts are present at concentrations of 0.05%-0.2%, such as 0.08%, 0.12%, 0.15%, and 0.19%. Copper corrosion inhibitor 0.1%-0.5%, for example 0.2%, 0.4%, etc. Nitrogen-containing surfactants at 0.01%-0.1%, such as 0.05% or 0.08%. The dispersant concentration is 0.05%-0.3%, for example, 0.08%, 0.15%, 0.22%, 0.28%, etc. The remainder is water.

[0027] The condenser pickling solution in this invention utilizes the synergistic effect of multiple complex acids (sulfamic acid, glycolic acid, and formic acid) to efficiently dissolve calcium carbonate and iron oxide scale while exhibiting low corrosivity. The formulation, through the compounding of organophosphonates, zinc salts, and copper corrosion inhibitors, constructs a comprehensive corrosion inhibition system, providing excellent protection for carbon steel and copper tubes. EDTA and dispersants respectively complex metal ions and suspend solid particles, thoroughly preventing secondary deposition and clogging. This solution achieves a balance between high-efficiency cleaning, extremely low corrosion, and equipment safety, ensuring long-term stable operation of the condenser.

[0028] In some embodiments, the zinc salt is one or a mixture of zinc nitrate and zinc sulfate. In this invention, zinc salt is used as a cathodic corrosion inhibitor to rapidly form a Zn(OH)2 protective film in the cathodic region of the metal surface, inhibiting hydrogen evolution corrosion and effectively protecting the carbon steel substrate.

[0029] In some embodiments, the organophosphonate is one or a mixture of two of hydroxyethylidene diphosphonic acid and aminotrimethylphosphonic acid. The organophosphonate (HEDP / ATMP) inhibits scale formation through chelation and forms a protective film in the metal anodic region, working synergistically with zinc salts to reduce the overall corrosion rate.

[0030] In some embodiments, the copper corrosion inhibitor is one or a mixture of two of benzotriazole and methylbenzotriazole. The molecules of the copper corrosion inhibitor (BTA / TTA) can specifically adsorb onto the copper surface, thereby forming a dense protective film that effectively prevents acid from corroding copper and its alloys.

[0031] In some embodiments, the nitrogen-containing surfactant is one or a mixture of two of dodecyl dimethyl benzyl ammonium chloride and tetradecyl dimethyl benzyl ammonium chloride. Nitrogen-containing surfactants can significantly reduce the surface tension of cleaning fluids, enhancing their permeability and wettability, thereby helping acid solutions to quickly penetrate and remove scale.

[0032] In some embodiments, the dispersant is one or a mixture of two of sodium polyacrylate and hydrolyzed polymaleic anhydride. The dispersant (PAS / HPMA) can adsorb onto the stripped solid particles and stably suspend them in the solution through steric hindrance, thereby preventing secondary deposition and clogging.

[0033] This invention also provides a method for preparing the above-mentioned condenser acid cleaning solution, such as... Figure 1 As shown, it includes the following steps: S1. Add the measured amount of water to the mixing vessel; S2. While stirring, add the measured zinc salt, organophosphonate, copper corrosion inhibitor, nitrogen-containing surfactant, and dispersant to the water in sequence, and stir until completely dissolved; S3. While continuously stirring, slowly add the measured amount of EDTA disodium salt to the solution obtained in step S2, and stir until completely dissolved; S4. Under continuous stirring and cooling, slowly add the measured amounts of aminosulfonic acid, glycolic acid and formic acid to the solution obtained in step S3 in sequence, and mix evenly to obtain the pickling cleaning solution.

[0034] The preparation method of this invention is by no means a simple "mixing," but rather a refined process design based on profound electrochemical and solution chemistry principles. Through a scientific sequence of "first neutralizing the auxiliary agent, then adding the integrator, and finally adding acid under controlled temperature," it successfully integrates multiple chemicals with different functions and pH sensitivities into a stable, efficient, and safe system. This is the fundamental reason why this pickling cleaning solution can achieve both high-efficiency cleaning and low corrosivity.

[0035] To prevent the acid from reacting violently with the scale at an initial high concentration, generating a large amount of heat and acid mist, and to ensure safe operation and a gradual onset of action, in some embodiments, the temperature of the acid addition process is controlled to not exceed 40°C in step S4, such as room temperature, 30°C, or 35°C.

[0036] In some embodiments, in step S4, aminosulfonic acid, glycolic acid, and formic acid are added in solid form or in a high-concentration aqueous solution. Adding them in solid / high-concentration liquid form allows for precise dosing, facilitates rapid and uniform mixing during stirring, and avoids localized excessive concentrations that could cause instantaneous corrosion to the equipment.

[0037] Another aspect of the present invention provides a method for cleaning stainless steel condensers, particularly 316L stainless steel condensers, using the aforementioned condenser pickling cleaning solution. The cleaning temperature is 40℃-60℃, for example, 45℃, 52℃, 58℃, etc., and the cleaning time is 4-8 hours, for example, 4.5 hours, 5 hours, 6 hours, 6.6 hours, 7.2 hours, 7.8 hours, etc. Within this cleaning temperature range, the chemical reaction and penetration process can be significantly accelerated, improving the descaling efficiency, while ensuring that the corrosion rate of stainless steel is within a safe range, avoiding damage to the passivation film due to overheating.

[0038] In some embodiments, during the cleaning process, the pH value of the cleaning solution is controlled within the range of 2.0-4.0. This pH range maintains an optimal slightly acidic working environment. This pH range ensures sufficient acidity to dissolve scale while keeping the stainless steel in a stable passivated state, achieving "cleaning without corrosion".

[0039] In some embodiments, the flow rate of the cleaning fluid during cleaning is 0.1-0.25 m / s, for example, 0.15 m / s, 0.2 m / s, 0.24 m / s, etc. A suitable flow rate can effectively flush the equipment surface, remove detached scale and prevent dirt deposition from forming a "shielding effect"; at the same time, excessively high flow rates should be avoided to prevent further erosion and corrosion.

[0040] The technical solution of the present invention will be described in detail below through specific embodiments, but the present invention is not limited to the following embodiments.

[0041] The following examples are all prepared according to the preparation method of claim 6, and the temperature is controlled not to exceed 40°C in step S4.

[0042] Example 1 A condenser pickling cleaning fluid, the components and contents of which are as follows: Aminosulfonic acid: 5.5% Glycolic acid: 2.5% Formic acid: 2.5% Disodium EDTA: 1.2% Organophosphonates (hydroxyethylidene diphosphonic acid): 0.3% Zinc salt (zinc nitrate): 0.12% Copper corrosion inhibitor (benzotriazole): 0.3% Nitrogen-containing surfactant (dodecyl dimethyl benzyl ammonium chloride): 0.05% Dispersant (sodium polyacrylate): 0.15% Water: Balance (to 100%) Example 2 Aminosulfonic acid: 8% Glycolic acid: 3% Formic acid: 3% Disodium EDTA: 1.5% Organophosphonate (aminotrimethylphosphonic acid): 0.4% Zinc salt (zinc sulfate): 0.15% Copper corrosion inhibitor (methylbenzotriazole): 0.4% Nitrogen-containing surfactant (tetradecyl dimethyl benzyl ammonium chloride): 0.08% Dispersant (hydrolyzed polymaleic anhydride): 0.2% Water: Balance Example 3 Aminosulfonic acid: 3% Glycolic acid: 1% Formic acid: 1% Disodium EDTA: 0.5% Organophosphonates (hydroxyethylidene diphosphonic acid): 0.1% Zinc salt (zinc nitrate): 0.05% Copper corrosion inhibitor (benzotriazole): 0.1% Nitrogen-containing surfactant (dodecyl dimethyl benzyl ammonium chloride): 0.01% Dispersant (sodium polyacrylate): 0.05% Water: Balance Example 4 Aminosulfonic acid: 4% Glycolic acid: 4% / / Increasing the proportion of glycolic acid to better dissolve iron oxides Formic acid: 2% Disodium EDTA: 2% / / Increases the capacity of the integrator Organophosphonates (a mixture of hydroxyethylidene diphosphonic acid and aminotrimethylphosphonic acid): 0.35% Zinc salt (zinc nitrate): 0.18% Copper corrosion inhibitor (benzotriazole): 0.25% Nitrogen-containing surfactant: 0.06% Dispersant (mixture of sodium polyacrylate and hydrolyzed polymaleic anhydride): 0.25% Water: Balance Comparative Example 1 No zinc salts or organophosphonates were added; the rest of the components and contents were the same as in Example 1.

[0043] Comparative Example 2 No copper corrosion inhibitor was added; the rest of the components and contents were the same as in Example 1.

[0044] Comparative Example 3 No dispersant was added; the rest of the components and contents were the same as in Example 1.

[0045] Performance verification test 1. Experimental Materials and Methods Test piece: 316L stainless steel standard test piece (50mm × 25mm × 2mm), surface polished and cleaned according to standard.

[0046] Simulated cleaning solution: Take 2.5 L each of the cleaning solutions prepared in Examples 1-4 and Comparative Examples 1-3.

[0047] Test conditions: Temperature: 50℃ Time: 6 hours Flow rate: A magnetic stirrer was used to simulate a fluid state of 0.15 m / s. Initial pH: Adjust to 3.0 with dilute sulfuric acid or sodium hydroxide. Sample placement: Place one weighed (accurate to 0.1 mg) 316L sample into each beaker.

[0048] 2. Evaluation Indicators and Testing Methods The evaluation indicators and testing methods are shown in Table 1 below.

[0049] Table 1

[0050] 3. Comparison Table of Experimental Results The experimental results are shown in Table 2 below.

[0051] Table 2

[0052] As can be seen from Table 2, Comparative Example 1 proves that Zn 2+ The synergistic effect of / HEDP plays a key role. Comparative Example 2 demonstrates that BTA plays a key role in protecting Cu and preventing copper plating. Comparative Example 3 demonstrates that the dispersant plays a key role in maintaining the stability of dissolved ions.

[0053] Through the comparison of the above examples, comparative examples, and performance tests, the scientific validity and effectiveness of the condenser acid cleaning fluid formula can be systematically verified, and the irreplaceable role of each key component in the system can be clarified, thus providing solid data support for the practical application of the product.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A condenser pickling and cleaning fluid, characterized in that, It consists of the following components by mass percentage: Aminosulfonic acid 3%-8% Glycolic acid 1%-4% Formic acid 1%-4% Disodium EDTA 0.5%-2% Organophosphonates 0.1%-0.5% Zinc salts 0.05%-0.2% Copper corrosion inhibitor 0.1%-0.5% Nitrogen-containing surfactants 0.01%-0.1% Dispersant 0.05%-0.3% The remainder is water.

2. The condenser acid cleaning solution according to claim 1, characterized in that, The zinc salt is one or a mixture of two of zinc nitrate and zinc sulfate; Preferably, the organophosphonate is one or a mixture of two of hydroxyethylidene diphosphonic acid and aminotrimethylphosphonic acid.

3. The condenser acid cleaning solution according to claim 1 or 2, characterized in that, The copper corrosion inhibitor is one or a mixture of two of benzotriazole and methylbenzotriazole.

4. The condenser acid cleaning fluid according to any one of claims 1 to 3, characterized in that, The nitrogen-containing surfactant is one or a mixture of two of dodecyl dimethyl benzyl ammonium chloride and tetradecyl dimethyl benzyl ammonium chloride.

5. The condenser acid cleaning fluid according to any one of claims 1 to 4, characterized in that, The dispersant is one or a mixture of two of sodium polyacrylate and hydrolyzed polymaleic anhydride.

6. A method for preparing the condenser acid cleaning fluid according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Add the measured amount of water to the mixing vessel; S2. While stirring, add the measured zinc salt, organophosphonate, copper corrosion inhibitor, nitrogen-containing surfactant, and dispersant to the water in sequence, and stir until completely dissolved; S3. While continuously stirring, slowly add the measured amount of EDTA disodium salt to the solution obtained in step S2, and stir until completely dissolved; S4. Under continuous stirring and cooling, slowly add the measured amounts of aminosulfonic acid, glycolic acid and formic acid to the solution obtained in step S3 in sequence, and mix evenly to obtain the pickling cleaning solution.

7. The preparation method according to claim 6, characterized in that, In step S4, the temperature during the acid addition process is controlled to not exceed 40°C.

8. The preparation method according to claim 6 or 7, characterized in that, In step S4, the aminosulfonic acid, glycolic acid, and formic acid are added in solid form or in a high-concentration aqueous solution.

9. A method for cleaning a stainless steel condenser, particularly a 316L stainless steel condenser, using the condenser pickling solution according to any one of claims 1-5, characterized in that, The cleaning temperature is 40℃-60℃, and the cleaning time is 4-8 hours.

10. The cleaning method according to claim 9, characterized in that, During the cleaning process, the pH value of the cleaning solution should be controlled within the range of 2.0-4.0; Preferably, the flow rate of the cleaning fluid during cleaning is 0.1-0.25 m / s.

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