Scale and corrosion inhibitors for bypass hardening industrial circulating cooling water systems

Abstract

This invention discloses a scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system. This scale and corrosion inhibitor is added to the circulating cooling water and enters the bypass hardening pipeline of the system without interfering with the chemical precipitant added in the bypass hardening pipeline. The scale and corrosion inhibitor includes a scale inhibitor component, which includes component A and 2-phospho-1,2,4-tricarboxylate butane. Component A is prepared by reacting polysuccinimide and 2-acrylamide-2-methylpropanesulfonic acid in a solvent system composed of N,N-dimethylformamide and water, reacting at a constant temperature of 40–80°C, followed by the addition of sodium hydroxide for continued reaction. The scale and corrosion inhibitor of this invention not only has excellent scale and corrosion inhibition performance for circulating cooling water, but its most significant advantage is that it does not interfere with the chemical precipitant added in the bypass hardening pipeline for removing scale-forming ions. This achieves efficient scale removal in the bypass while avoiding the loss of the scale and corrosion inhibitor, allowing the circulating cooling water to retain its superior scale and corrosion inhibition properties for reuse after descaling. This ensures the safe operation of the circulating cooling water system and, under the premise of safe operation, achieves "zero discharge" of the system and effective control of operating costs.

Description

Technical Field

[0001] This invention relates to the field of scale and corrosion inhibitors for circulating cooling water, and particularly to a scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system. Background Technology

[0002] Circulating cooling water, also known as circulating water, is a major category of industrial water use. With increasing water scarcity, restrictions on circulating water usage are becoming increasingly stringent. To conserve circulating water in cooling systems, people are increasing the concentration ratio and reducing wastewater discharge. A common method to increase the concentration ratio is to add scale inhibitors. Scale inhibitors not only control scale but also, to some extent, control corrosion products, slime, and sludge. Adding a small amount of scale inhibitor can control a large amount of scale-forming substances. However, scale inhibitors have limitations in increasing the concentration ratio of circulating water. With increasingly stringent environmental requirements, the goal of "zero discharge" for industrial water use has been established. Therefore, to achieve this "zero discharge" standard, a bypass hardening process has been developed to overcome the limitations of scale inhibitors on the concentration ratio. This involves drawing out a portion of the water from the circulating water system and using chemical precipitation to remove scale-forming ions, thus meeting the water quality requirements of the circulating water system and further increasing the concentration ratio, achieving "zero discharge" by only replenishing water and not discharging wastewater. However, during the operation of the bypass hardening circulating cooling water system, it was found that the scale inhibitors and the chemical precipitants used in the bypass hardening pipeline (commonly used chemical precipitants include sodium carbonate and sodium hydroxide used in the double alkali hardening process; flocculants such as polyaluminum chloride and polyferric sulfate can also be used to further increase the precipitate flocs) have contradictory mechanisms of action. The scale inhibitors enrich scale-forming ions in the water, preventing crystallization and scale formation in the circulating water system, while the chemical precipitants disrupt the stable balance between scale-forming ions, promoting their crystallization. Therefore, the commonly used scale inhibitors added to the circulating water will interfere with the chemical precipitants added to the hardening bypass.

[0003] Specifically, scale inhibition is generally achieved through the following three methods:

[0004] (1) Lattice distortion: Inorganic scale (such as calcium carbonate) crystals grow according to a certain lattice arrangement, resulting in dense and relatively strong crystals. When water contains scale inhibitors such as polycarboxylic acids or organic phosphate esters, the scale inhibitor's groups have a resistance to metal ions (such as Ca). 2+ The chelating ability of ions interferes with the crystallization of inorganic scale, causing the crystal lattice to become distorted and irregular crystals. This is the effect of lattice distortion. Lattice distortion transforms hard scale into amorphous soft scale. This type of scale does not easily grow into crystals, has a large number of voids in the scale layer, and has poor adhesion between the crystals. It is easily washed away by water flow and can be discharged with sewage.

[0005] (2) Complexation and solubilization: Agents such as polyphosphates, organophosphates, or polycarboxylic acids can capture calcium and magnesium ions in water to form stable complexes. This is essentially equivalent to reducing the concentration of calcium and magnesium ions in the water, i.e., reducing the concentration of calcium and magnesium ions. 2+ This increases the chance of calcium carbonate combining with CO to form CaCO3. In other words, it increases the permissible concentration of calcium and magnesium ions in water, thus increasing the solubility of calcium and magnesium salts. The complexation and solubilization effect can stabilize more calcium carbonate in water, preventing precipitation.

[0006] (3) Coagulation and Dispersion: Anionic scale inhibitors (such as polycarboxylic acids) dissociate into negative ions in water, which can adsorb the microcrystals of scale-forming salts (such as calcium carbonate). First, the microcrystals form an electric double layer, and then adsorb onto the molecular chains of the negative ions, making the microcrystals negatively charged. Since multiple microcrystals on the molecular chains carry the same charge, they repel each other and cannot form large crystals, making it difficult for scale-forming salts to deposit on the metal heat transfer surface to form a scale layer. The negative ions of anionic scale inhibitors have both a coagulating effect on microcrystals and can disperse them throughout the water system, making them evenly dispersed. This coagulation and dispersion effect keeps the scale-forming salt microcrystals stably suspended in the water, effectively reducing the chance of microcrystals colliding, growing, forming crystal nuclei, and then precipitating, allowing the water to accommodate more scale-forming salts.

[0007] The scale inhibitors mentioned above that utilize lattice distortion or coagulation and dispersion effects can enable circulating water to achieve a high concentration ratio during operation. However, the enrichment of scale ions through complexation and solubilization has limited effect on increasing the concentration ratio and often fails to meet operational requirements.

[0008] When circulating water with added scale inhibitors undergoes bypass hardening treatment, if a scale inhibitor with lattice distortion effect is used, the distortion of the scale-forming lattice in the water significantly increases the difficulty of scale crystallization, directly reducing the bypass hardening effect. If a scale inhibitor with coagulation and dispersion effect is used, in order to break the balance between scale particles and promote scale crystallization, the added chemical precipitant often neutralizes the scale inhibition effect and decomposes the scale inhibitor. This not only increases the amount of chemical precipitant used, but also requires a large amount of scale inhibitor to be added after bypass hardening to ensure the continued safe operation of the circulating water, significantly increasing the cost of chemical usage. Scale inhibitors that utilize complexation and solubilization effects, such as commonly used polyphosphates, organophosphates, or polycarboxylic acids, also interfere with chemical precipitants. While removing calcium and magnesium, chemical precipitants also remove or exacerbate the decomposition of scale inhibitors, affecting the water quality treatment effect of the circulating water, increasing operating costs, and making it difficult to achieve the expected operating effect of the circulating water.

[0009] Based on this, we developed a scale and corrosion inhibitor specifically for bypass hardening circulating cooling water systems, so that the scale and corrosion inhibition and bypass chemical precipitation effects do not interfere with each other. This is of great significance for zero-discharge operation of circulating water, as well as for reducing operating costs and ensuring safe and efficient operation. Summary of the Invention

[0010] To address the problem of interference between scale inhibition and bypass chemical precipitation in current bypass-type hardening circulating cooling water systems, which affects the operation of the circulating water, this invention provides a scale and corrosion inhibitor specifically designed for bypass-type hardening industrial circulating cooling water systems. The scale inhibition effect of this inhibitor does not interfere with the chemical precipitation effect of the bypass-type hardening pipeline, and the scale-inhibiting components of the inhibitor do not consume each other with the chemical precipitant. This improves the quality of the circulating water and achieves "zero discharge" for the system.

[0011] The scale and corrosion inhibitor for the bypass hardening industrial circulating cooling water system of the present invention is added to the circulating cooling water, usually in the cooling tower, and enters the bypass hardening pipeline of the system with the circulating cooling water, without interfering with the chemical precipitant added in the bypass hardening pipeline.

[0012] The scale inhibitor and corrosion inhibitor includes a scale inhibitor component, which includes component A and 2-phospho-1,2,4-tricarboxylate butane (PBTCA). Component A is prepared by reacting the reactants polysuccinimide and 2-acrylamide-2-methylpropanesulfonic acid in a solvent system composed of N,N-dimethylformamide and water, reacting at a constant temperature of 40-80°C, and then adding sodium hydroxide for continued reaction.

[0013] This invention utilizes component A, which contains both strong and weak acid functional groups (obtained by reacting polysuccinimide with 2-acrylamide-2-methylpropanesulfonic acid), to form a scale inhibitor component in combination with 2-phospho-1,2,4-tricarboxylate butane (PBTCA). Due to the special structure of component A, it can fully dissolve and effectively stabilize PBTCA in the circulating water system, efficiently inhibiting the formation of calcium carbonate and calcium phosphate scale. During the bypass hardening process, it can significantly reduce the mutual interference between PBTCA and chemical precipitants. When chemical precipitants are added, the colloids destabilize and form micro-aggregates due to the action of the precipitants, and the precipitated calcium salts, magnesium salts, and other micro-suspended matter agglomerate into large flocs, achieving bypass hardening. Component A and PBTCA in the circulating water after hardening are unaffected and continue to work synergistically to exert a scale inhibition effect after returning to the circulating water system.

[0014] Regarding scale inhibition, the weak acid group—carboxylic acid group—in component A exhibits strong adsorption of scale-forming ions such as calcium and magnesium, inhibiting the crystal growth of slightly soluble salts. The strong acid group—sulfonic acid group—maintains slight ionic characteristics, effectively preventing the formation of insoluble polymer calcium gel and dispersing particulate matter, thus demonstrating scale inhibition and dispersion properties. Based on the scale inhibition effect of component A, synergistic effect with PBTCA significantly improves scale inhibition capacity. Furthermore, because the sulfonic acid group is insensitive to salt and possesses good temperature and salt resistance, component A can maintain excellent scale inhibition performance in high-salt environments.

[0015] As a limitation of the above technical solution, the specific preparation of component A is as follows:

[0016] a. Preparation raw materials: 5-10 parts of polysuccinimide, 0.2-3 parts of 2-acrylamide-2-methylpropanesulfonic acid, 30-100 parts of N,N-dimethylformamide, 30-100 parts of deionized water, 1-10 parts of sodium hydroxide, and 500-1500 parts of anhydrous ethanol.

[0017] b. Preparation steps: Dissolve polysuccinimide in N,N-dimethylformamide, add deionized water and mix well, then add 2-acrylamide-2-methylpropanesulfonic acid. Under stirring, heat the reaction solution to 40-80℃ and react for 1.5-5 hours. Then add sodium hydroxide dropwise over 2 hours to maintain the pH of the reaction system at 8.5-10. Keep the temperature for 1 hour, stop the reaction, add anhydrous ethanol for precipitation, filter, and then vacuum dry at 40-80℃ to obtain a white to brownish-yellow solid, which is component A.

[0018] As a limitation of the above technical solution, the raw materials for preparing component A include: 5-10 parts of polysuccinimide, 2-3 parts of 2-acrylamide-2-methylpropanesulfonic acid, 50-80 parts of N,N-dimethylformamide, 50-80 parts of deionized water, and 3-8 parts of sodium hydroxide.

[0019] As a limitation of the above technical solution, the solid content of component A is greater than 85%, and the pH value of the 10 g / L aqueous solution is 8.5 to 10.5.

[0020] Further restrictions are placed on the raw materials and preparation methods for component A to ensure its scale inhibition performance and chemical stability. Component A works synergistically with PBTCA to enhance the scale inhibition effect on circulating water, increase the concentration ratio of circulating water, and greatly reduce the mutual interference between PBTCA and chemical precipitants, thus ensuring the safe and efficient operation of circulating water.

[0021] As a limitation of the above technical solution, the mass ratio of component A and 2-phospho-1,2,4-tricarboxylate butane in the scale inhibitor component is 1 to 3:1.

[0022] As a limitation of the above technical solution, the scale and corrosion inhibitor further includes a corrosion inhibitor component, a pH adjuster, and deionized water, wherein the corrosion inhibitor component includes at least one of azole corrosion inhibitors and zinc salts; the pH adjuster is selected from at least one of sulfuric acid, citric acid, aminosulfonic acid, sodium hydroxide, and sodium carbonate; the azole corrosion inhibitor is selected from at least one of benzotriazole, methylbenzotriazole, and mercaptobenzothiazole; and the zinc salt is selected from at least one of zinc sulfate monohydrate, zinc sulfate heptahydrate, and zinc chloride.

[0023] The scale and corrosion inhibitor of this invention primarily functions to disperse and inhibit scale. During the concentration process of circulating water, the hardness, alkalinity, and pH value all increase, increasing the tendency for scaling and reducing the tendency for corrosion. In other words, the circulating water mainly relies on its own properties to form a self-limiting protective film for corrosion inhibition. When copper and carbon steel are present in the system, azole corrosion inhibitors are added primarily to inhibit the corrosion of copper equipment, and zinc salts are added primarily to inhibit the corrosion of carbon steel equipment. Component A possesses zinc-stabilizing properties; when combined with the zinc salt corrosion inhibitor, it prevents the zinc salt from precipitating from the system, maintaining a certain concentration of zinc ions to prevent rapid deposition and loss of corrosion inhibition effectiveness, thereby significantly increasing the corrosion inhibition effect. The formulation of this application is suitable for scaling-prone water, with operating pH values ​​mostly at the natural pH range, typically between 8.0 and 9.5. It allows for relatively high calcium content and alkalinity in the water and has a higher tolerance for calcium hardness.

[0024] As a limitation of the above technical solution, the scale and corrosion inhibitor comprises the following raw material components in parts by weight:

[0025] Component A 5-10 parts, 2-phospho-1,2,4-tricarboxylate butane 5-10 parts, azole corrosion inhibitor 0-5 parts, zinc salt 1-20 parts, pH adjuster 0.1-5 parts, deionized water 30-50 parts.

[0026] Further refine the formulation of the scale and corrosion inhibitor by limiting the corrosion inhibitor and other components, and optimize its scale and corrosion inhibition performance. Component A, combined with other components such as PBTCA, azole corrosion inhibitors, and zinc salts, can inhibit scale and corrosion in equipment and pipelines, and maintain normal equipment operation.

[0027] As a limitation of the above technical solution, the scale and corrosion inhibitor is prepared by the following method:

[0028] After mixing component A with deionized water, add a pH adjuster to adjust the pH to 2.0–5.0. Then slowly add 2-phospho-1,2,4-tricarboxylate butane, azole corrosion inhibitor, and zinc salt. Stir for 30–90 minutes at a stirring speed of 75–90 r / min to obtain a uniform scale and corrosion inhibitor.

[0029] The preparation of the scale and corrosion inhibitor of the present invention involves adjusting component A to a suitable pH value and then mixing it sequentially with PBTCA and the corrosion inhibitor, which makes it easier to dissolve and yields a scale and corrosion inhibitor that does not interfere with chemical precipitants, has excellent scale and corrosion inhibition effects, and significantly increases the concentration ratio of circulating water.

[0030] As a limitation of the above technical solution, the scale and corrosion inhibitor is added to the circulating cooling water system at a rate of 50-200 ppm, and the scale inhibition rate is ≥95%.

[0031] This invention relates to a scale and corrosion inhibitor specifically for bypass hardening circulating cooling water systems. It not only exhibits excellent scale and corrosion inhibition performance for circulating water, but its most significant advantage lies in its non-interference with chemical precipitants that remove scale-forming ions in bypass hardening pipelines. This achieves efficient scale removal while avoiding the loss of the scale and corrosion inhibitor, ensuring the safe operation of the circulating water system. Component A in the scale inhibitor component dissociates in water, and its sulfonic acid groups adsorb microcrystals of scale-forming salts (such as calcium carbonate). First, the microcrystals form an electric double layer, then adsorb onto the molecular chain of component A, making the microcrystals negatively charged. Because multiple microcrystals on the molecular chain carry the same charge, they repel each other and cannot form large crystals, making it difficult for scale-forming salts to deposit on the metal heat transfer surface to form a scale layer. The sulfonic acid groups both coagulate the microcrystals and disperse them throughout the water system, ensuring a uniform dispersion. Component A, when combined with PBTCA, effectively inhibits the growth of metal ions (such as Ca2+). 2+ The chelating ability of the agent is significantly improved, interfering with the crystallization of inorganic scale. Hard scale is transformed into amorphous soft scale, which is less prone to crystal growth. The scale layer contains a large number of voids and has poor adhesion. The above-mentioned coagulation and dispersion effects keep the scale-forming salt microcrystals stably suspended in the water, reducing the chance of microcrystal collision, growth, crystal nucleation, and precipitation, allowing the water to accommodate more scale-forming salts. In addition, and most importantly, the scale inhibitor and corrosion inhibitor of this invention do not interfere with the bypass chemical precipitation. When a chemical precipitant is added to the circulating water during the bypass hardening process, the ion concentration in the circulating water increases, and the thickness of the diffusion layer decreases. When two colloidal particles approach each other, due to the reduced diffusion layer thickness and lower potential, the mutual repulsion force decreases accordingly, allowing the colloidal particles to quickly coagulate into clusters and precipitate to achieve hardening removal. At the same time, the scale inhibitor component remains stable and continues to exert its scale inhibition effect on the circulating water as it returns to the cooling system from the bypass hardening pipeline.

[0032] The scale and corrosion inhibitor of this invention has good chemical and thermal stability, which can meet the scale and corrosion inhibition requirements of circulating cooling water systems. At the same time, it does not interfere with chemical precipitants that remove scale-forming ions, so that the circulating water still maintains effective scale and corrosion inhibition performance after hardening, ensuring the continuous safe operation of the circulating cooling water system and improving the quality of circulating water. It is of great significance for zero-discharge operation of circulating water, as well as operating costs and operating effects. Attached Figure Description

[0033] Figure 1 The first row, from left to right, shows photos of the corrosion inhibition performance test results of the scale and corrosion inhibitors of Examples 1-3; the second row, from left to right, shows photos of the corrosion inhibition performance test results of the scale and corrosion inhibitors of Examples 1-3 after standing for 90 days.

[0034] Figure 2From left to right, the following are comparative photos of the working water sample, the working water sample with the scale and corrosion inhibitor of Example 1 added, and the working water sample with the scale and corrosion inhibitor of Example 1 added and then the chemical precipitant added.

[0035] Figure 3 Comparative photographs showing the experimental results of the scale and corrosion inhibitors in Example 1 and Comparative Example 1 on their resistance to interference from chemical precipitants;

[0036] Figure 4 Comparative photographs showing the experimental results of the scale and corrosion inhibitors in Example 1 and Comparative Example 2 on their resistance to interference from chemical precipitants;

[0037] Figure 5 Comparative photographs showing the experimental results of the scale and corrosion inhibitors in Example 1 and Comparative Example 4 on their resistance to interference from chemical precipitants. Detailed Implementation

[0038] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The raw materials used in the following examples and comparative examples are all typical products purchased from the market.

[0040] Example

[0041] This embodiment relates to the scale and corrosion inhibitor of the present invention and its preparation. The raw material components of each embodiment are shown in Table 1.

[0042] Table 1. Raw material composition table for each embodiment

[0043]

[0044] Component A in the raw material is prepared by the following method:

[0045] a. Weigh the raw materials: 10g polysuccinimide, 0.5g 2-acrylamide-2-methylpropanesulfonic acid, 30g N,N-dimethylformamide, 50g deionized water, 3g sodium hydroxide and 500g anhydrous ethanol;

[0046] b. After fully dissolving polysuccinimide in N,N-dimethylformamide, transfer it to a reactor. Add 50g of deionized water to the reactor, then add 2-acrylamide-2-methylpropanesulfonic acid to the reactor. After mixing evenly, heat the reaction solution to 70℃ and react for 1.5-2 hours. Then, add sodium hydroxide dropwise over 2 hours. Adjust the pH to 9, maintain the temperature for 1 hour, and stop the reaction. Add an appropriate amount of anhydrous ethanol for precipitation, filter, and then vacuum dry in a constant temperature drying oven at 50±5℃ to obtain a white to brownish-yellow solid, which is component A. The solid content of component A is 85%, and the pH of a 10g / L aqueous solution is 8.5-10.5.

[0047] The amount of raw materials for component A can be appropriately adjusted within the range of 5-10 parts of polysuccinimide, 0.2-3 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 30-100 parts of N,N-dimethylformamide.

[0048] To prepare the scale and corrosion inhibitor, mix component A with deionized water according to the formula amount, add pH adjuster to adjust the pH to a suitable value (pH ≤ 5.0 for a 1% aqueous solution of scale and corrosion inhibitor), and then slowly add PBTCA, azole corrosion inhibitor and zinc salt in sequence. Stir for 90 minutes at a stirring speed of 75-90 r / min and room temperature to obtain a uniformly mixed scale and corrosion inhibitor.

[0049] The appearance characteristics of each scale and corrosion inhibitor are shown in Table 2 below.

[0050] Table 2. Appearance of scale and corrosion inhibitors in each embodiment

[0051]

[0052] The scale inhibition performance of each scale inhibitor and corrosion inhibitor was determined according to GB / T 16632-2019 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method" and the corrosion inhibition performance was determined according to GB / T 18175-2014 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Coating Method". A 168-hour rotating coating test at room temperature with a speed of 75 r / min was conducted. The coating results are shown in […]. Figure 1 .

[0053] Stability tests were conducted on each scale and corrosion inhibitor. Samples of each inhibitor were left at room temperature for 90 days to observe for stratification and precipitation. The scale inhibition and corrosion inhibition performance of the samples after storage were then measured. The results are shown in the attached sample table. Figure 1 By comparing the samples before and after placement, the stability of the scale and corrosion inhibitor of the present invention was determined.

[0054] The above test results are shown in Table 3 below:

[0055] Table 3. Scale inhibition, corrosion inhibition performance and stability of the scale and corrosion inhibitors in each embodiment.

[0056]

[0057] As can be seen from the results in the table above, the scale and corrosion inhibitor of the present invention exhibits satisfactory scale and corrosion inhibition performance, with a scale inhibition rate ≥95% and an annual average corrosion rate not exceeding 0.035 mm / a, meeting the standard requirements of a scale inhibition rate ≥95% and an annual average corrosion rate ≤0.075 mm / a; and it has good stability, with its appearance and scale and corrosion inhibition performance remaining stable after being placed at room temperature for 90 days.

[0058] The scale and corrosion inhibitors of each embodiment were subjected to chemical precipitant interference and stability tests. A fixed amount of actual operating water (i.e., on-site circulating water sample) was taken, and 20 ppm of each embodiment's scale and corrosion inhibitor was added, followed by the addition of an appropriate amount of chemical precipitant (sodium carbonate and sodium hydroxide were used in this experiment) to ensure that the calcium ion concentration in the water sample was less than 30 ppm. The water sample was then allowed to stand, and the supernatant was used to determine its scale inhibition and corrosion inhibition performance. Table 4 below shows the test results after adding the scale and corrosion inhibitor of Example 1. (See attached figures.) Figure 2 The experimental phenomena observed after adding the scale and corrosion inhibitor from Example 1 are shown.

[0059] Table 4. Resistance of the scale and corrosion inhibitor in Example 1 to interference from chemical precipitants.

[0060]

[0061] As can be seen from the results in the table above, the addition of the scale and corrosion inhibitor of this invention to the circulating water, followed by the addition of a chemical precipitant, can still effectively remove calcium ions from the water and form obvious flocs that settle down. The scale inhibition and corrosion inhibition performance of the supernatant are basically consistent with the performance of the sample before the addition of the chemical precipitant, with no significant decrease. Therefore, it can be determined that the scale and corrosion inhibitor of this invention does not affect the hardening effect after passing through the hardening removal section, and the scale and corrosion inhibitor will not be lost or damaged.

[0062] Comparative Example 1

[0063] A commonly used scale and corrosion inhibitor is described below, along with its formulation and preparation method.

[0064] Add 500g of deionized water and a pH adjuster (about 10g of commercially available sulfuric acid) to adjust the pH to a suitable value (pH ≤ 5.0 for a 1% aqueous solution of scale and corrosion inhibitor). Then slowly add 50g of PBTCA, 10g of azole corrosion inhibitor BTA, and 30g of zinc sulfate heptahydrate. Stir for 90 minutes at a stirring speed of 75-90 r / min and room temperature to obtain a uniformly mixed scale and corrosion inhibitor.

[0065] Comparative Example 2

[0066] This comparative example uses a common chelating agent, ethylenediaminetetraacetic acid tetrasodium, combined with PBTCA to form a scale and corrosion inhibitor. The specific formulation and preparation are as follows.

[0067] Mix 100g of tetrasodium ethylenediaminetetraacetate (EDTA tetrasodium) with 500g of deionized water until homogeneous. Add a pH adjuster (approximately 10g of commercially available sulfuric acid) to adjust the pH to a suitable value (pH ≤ 5.0 for a 1% aqueous solution of scale and corrosion inhibitor). Then slowly add 50g of PBTCA, 10g of azole corrosion inhibitor, and 30g of zinc sulfate heptahydrate. Stir for 90 minutes at room temperature with a stirring speed of 75-90 r / min to obtain a homogeneous scale and corrosion inhibitor.

[0068] Comparative Example 3

[0069] This comparative example uses component A (same as in the example) combined with other organophosphonate scale inhibitors instead of PBTCA to form a scale and corrosion inhibitor. The specific formulation and preparation are as follows.

[0070] Mix 100g of component A with 500g of deionized water until homogeneous. Add a pH adjuster (about 10g of commercially available sulfuric acid) to adjust the pH to a suitable value (pH ≤ 5.0 for a 1% aqueous solution of scale and corrosion inhibitor). Then slowly add 50g of HEDP, 10g of azole corrosion inhibitor, and 30g of zinc sulfate heptahydrate. Stir for 90 minutes at a stirring speed of 75-90 r / min and room temperature to obtain a homogeneous scale and corrosion inhibitor.

[0071] Comparative Example 4

[0072] This comparative example uses a simple mixture of polyaspartic acid and 2-acrylamide-2-methylpropanesulfonic acid, which is then combined with PBTCA and corrosion inhibitors to form a scale and corrosion inhibitor. The specific formulation and preparation are as follows.

[0073] Mix 95.23g of polyaspartic acid with 4.76g of 2-acrylamide-2-methylpropanesulfonic acid and stir until homogeneous. Add 500g of deionized water and mix until homogeneous. Add pH adjuster (about 10g of commercially available sulfuric acid) to adjust the pH to a suitable value (pH ≤ 5.0 for a 1% aqueous solution of scale and corrosion inhibitor). Then slowly add 50g of PBTCA, 10g of azole corrosion inhibitor, and 30g of zinc sulfate heptahydrate. Stir for 90 minutes at a stirring speed of 75-90r / min and room temperature to obtain a homogeneous scale and corrosion inhibitor.

[0074] The scale and corrosion inhibitors in the above comparative examples were tested to determine whether they interfered with each other, and the scale inhibition and corrosion inhibition performance of each scale and corrosion inhibitor after the addition of chemical precipitants was also examined. The results are shown in Table 5 and the appendix. Figures 3-5 .

[0075] Table 5. Comparison of the anti-interference performance of scale and corrosion inhibitors against chemical precipitants in each comparative example with that in the examples.

[0076]

[0077] As can be seen from the results in the table above, neither commonly used scale and corrosion inhibitors nor those with simple optimization can meet the requirements for resisting interference from chemical precipitants. The scale and corrosion inhibitor of this invention makes a breakthrough in this regard, thereby ensuring the safe and efficient operation of the bypass hardening circulating cooling water.

[0078] In summary, the scale and corrosion inhibitor of the present invention, through the compounding of specially formulated component A and PBTCA with corrosion inhibitor components, achieves excellent scale and corrosion inhibition performance for circulating water, while also ensuring that it does not interfere with chemical precipitants that remove scale-forming ions. This enables efficient scale removal in bypass hardened pipelines while avoiding the loss of scale and corrosion inhibitors, ensuring the safe operation of the circulating water system, achieving "zero discharge" of the system and effective control of operating costs.

Claims

1. A scale and corrosion inhibitor for a bypass-type hardening industrial circulating cooling water system, characterized in that: The scale and corrosion inhibitor is added to the circulating cooling water and enters the bypass hardening pipeline of the system along with the circulating cooling water, without interfering with the chemical precipitant added in the bypass hardening pipeline; The scale inhibitor and corrosion inhibitor includes a scale inhibitor component, which includes component A and 2-phospho-1,2,4-tricarboxylic acid butane. Component A is prepared by reacting the reaction raw materials polysuccinimide and 2-acrylamide-2-methylpropanesulfonic acid in a solvent system composed of N,N-dimethylformamide and water, reacting at a constant temperature of 40~80℃, and then adding sodium hydroxide for continuous reaction. The specific preparation of component A is as follows: a. Preparation raw materials: 5-10 parts of polysuccinimide, 0.2-3 parts of 2-acrylamide-2-methylpropanesulfonic acid, 30-100 parts of N,N-dimethylformamide, 30-100 parts of deionized water, 1-10 parts of sodium hydroxide, and 500-1500 parts of anhydrous ethanol; b. Preparation steps: Dissolve polysuccinimide in N,N-dimethylformamide, add deionized water and mix well, then add 2-acrylamide-2-methylpropanesulfonic acid. Under stirring, heat the reaction solution to 40~80℃ and react for 1.5~5h. Then add sodium hydroxide dropwise over 2h to maintain the pH of the reaction system at 8.5~10. Keep warm for 1h, stop the reaction, add anhydrous ethanol for precipitation, filter, and then vacuum dry at 40~80℃ to obtain a white to brownish-yellow solid, which is component A. The scale and corrosion inhibitor also includes corrosion inhibitors, pH adjusters and deionized water, wherein the corrosion inhibitors include azole corrosion inhibitors and zinc salts.

2. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to claim 1, characterized in that, The raw materials for preparing component A include: 5-10 parts of polysuccinimide, 2-3 parts of 2-acrylamide-2-methylpropanesulfonic acid, 50-80 parts of N,N-dimethylformamide, 50-80 parts of deionized water, and 3-8 parts of sodium hydroxide.

3. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to claim 1, characterized in that: The solid content of component A is greater than 85%, and the pH value of a 10 g / L aqueous solution is 8.5 to 10.

5.

4. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to claim 1, characterized in that: The mass ratio of component A and 2-phospho-1,2,4-tricarboxylate butane in the scale inhibitor component is 1~3:

1.

5. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to claim 1, characterized in that: The pH adjuster is selected from at least one of sulfuric acid, citric acid, aminosulfonic acid, sodium hydroxide, and sodium carbonate; The azole corrosion inhibitor is selected from at least one of benzotriazole, methylbenzotriazole, and mercaptobenzothiazole; The zinc salt is selected from at least one of zinc sulfate monohydrate, zinc sulfate heptahydrate, and zinc chloride.

6. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to claim 5, characterized in that, The scale and corrosion inhibitor comprises the following raw material components in parts by weight: Component A 5-10 parts, 2-phospho-1,2,4-tricarboxylate butane 5-10 parts, azole corrosion inhibitor 0-5 parts, zinc salt 1-20 parts, pH adjuster 0.1-5 parts, deionized water 30-50 parts.

7. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to claim 6, characterized in that, The scale and corrosion inhibitor is prepared by the following method: After mixing component A with deionized water, add a pH adjuster to adjust the pH to 2.0~5.0, then slowly add 2-phospho-1,2,4-tricarboxylate butane, azole corrosion inhibitor, and zinc salt. Stir for 30~90 min at a stirring speed of 75~90 r / min to obtain a uniform scale and corrosion inhibitor.

8. The scale and corrosion inhibitor for a bypass hardening industrial circulating cooling water system according to any one of claims 1 to 7, characterized in that: The scale and corrosion inhibitor is added to the circulating cooling water system at a rate of 50-200 ppm, with a scale inhibition rate of ≥95%.

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