A chemical cleaning agent for industrial recirculating cooling water systems

Abstract

The application discloses a chemical cleaning agent for an industrial circulating cooling water system, which is composed of the following components in mass fraction: phytic acid 22-25%, N-hydroxyethyl imino diacetic acid disodium salt 35-38%, beef tallow amine polyoxyethylene ether 3-5%, and water in remainder. The chemical cleaning agent can meet the cleaning requirements of oil removal, scale removal and rust removal of the system at the same time, has high cleaning efficiency, and the oil removal rate and rust removal rate can reach more than 90%, the scale removal rate after coupon cleaning is between 85+2%, and the chemical cleaning agent can also play a corrosion inhibition protection role on metal in the cleaning process, and will not cause secondary corrosion to the metal body.

Description

Technical Field

[0001] This invention relates to a chemical cleaning agent for industrial circulating cooling water systems. Background Technology

[0002] Before commissioning or during maintenance of an industrial circulating cooling water system, offline or online chemical cleaning is required for the system's pipelines, valves, and components (such as cooling towers and heat exchangers) to eliminate problems such as oil contamination, scaling, and rust, reduce the risk of corrosion from pollutants, extend the system's service life, and thus ensure the stable operation of the system and the efficiency of related processes.

[0003] Most chemical cleaning agents on the market currently only have a single cleaning function, such as conventional inorganic strong acid rust removers and scale removers, and alkaline surfactant degreasers. These single-function cleaning agents cannot address the complex conditions of actual system contamination and simultaneously meet the system's cleaning needs for degreasing, descaling, and rust removal. Furthermore, conventional cleaning agents are mostly formulated with strong acids or alkalis. If the cleaning time is not carefully controlled during the cleaning process, it can easily cause secondary corrosion problems such as pitting and perforation of the system's metal structure, posing a significant risk to the stable operation and maintenance of the system. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a chemical cleaning agent that can simultaneously meet the system's needs for degreasing, descaling, and rust removal, and has high cleaning efficiency without causing secondary corrosion to the metal body.

[0005] Technical solution: The chemical cleaning agent for industrial circulating cooling water systems described in this invention is composed of the following components by mass fraction: 22-25% phytic acid, 35-38% disodium N-hydroxyethyliminodiacetic acid, 3-5% tallow amine polyoxyethylene ether, and water as the balance.

[0006] The chemical cleaning agent is composed of the following components by mass fraction: 22% phytic acid, 35% disodium N-hydroxyethyliminodiacetic acid, 3% tallow amine polyoxyethylene ether, and 40% water.

[0007] In the aforementioned tallow amine polyoxyethylene ether, the tallow alkyl group is an aliphatic alkane group of C12 to C18 (C 12～18 H 25～37 -). Since the C18 tallow alkyl group has the best lipophilicity, C18 is preferred. 18 H 37 - As the alkyl group of tallow in this formula.

[0008] In the tallow amine polyoxyethylene ether, the degree of polymerization of ethoxy groups (n) is 9–20 (-[C2H5O]- n=9~20), to ensure that the polyoxyethylene group has good hydrophilicity. Since the polyoxyethylene group with n=15 has the best hydrophilicity and emulsifying properties, it is preferred to use -[C2H5O]-. 15 Polyoxyethylene groups are used in this formulation.

[0009] The degreasing, descaling, and rust-removing mechanism of the chemical cleaning agent of this invention is as follows:

[0010] H+ released from the phosphonic acid functional group in phytic acid molecules + First, the rust on the metal surface (a mixture mainly composed of Fe2O3 and Fe(OH)3) is dissolved in water to generate Fe. 3+ (See Equation 1) Subsequently, through the phosphonic acid functional groups (which become electronegative after losing hydrogen ions) attached to the C atoms of the cyclohexane structure in the phytic acid molecule, and Fe... 3+ The chelation-like effect and the cage-like structure formed by the six phosphonic acid functional groups capture Fe in water. 3+ It locks the rust stains firmly in the center of the phytic acid molecule, forming phytic acid iron complex precipitate, thereby removing the rust stains from the metal surface without increasing the color of the rust removal wastewater.

[0011] Fe2O3 / Fe(OH)3+H + →Fe 3+ +H2O(1)

[0012] Through the -N(CH2COO) in the disodium N-hydroxyethyliminodiacetic acid molecule - The unique pincer-like structure of the 2-group can continuously capture metal cations (such as Ca) in the scale. 2+ / Mg 2+ This forms a soluble metal chelate, and the -OH group in the N-hydroxyethyliminodiacetic acid disodium salt molecule has strong hydrophilicity, which can further enhance the dissolving ability of the metal chelate, thereby positively promoting the removal of scale; at the same time, the -N(CH2COO) group in the N-hydroxyethyliminodiacetic acid disodium salt molecule... - )2. The pincer-like functional groups can also continuously capture Fe from rust. 3+ Phytic acid, along with its hydroxyethyl hydrophilic group, can positively promote the dissolution of chelated iron, thus synergistically accelerating the dissolution and removal of rust from metal workpieces. Simultaneously, the cage-like structure of phytic acid molecules exhibits a cavitation effect, which, combined with its six negatively charged phosphonic acid functional groups in the "cage arms," ​​can remove Ca from scale. 2 + / Mg 2+ It is tightly locked at the molecular center of phytic acid, thereby promoting the dissolution of cations in the scale and synergistically improving the removal effect of scale on metal workpieces with disodium N-hydroxyethyliminodiacetic acid. Figure 2 As shown.

[0013] The tallow amine polyoxyethylene ether molecule contains extremely strong hydrophilic and lipophilic functional groups (of which the tallow alkyl group is a polar molecular group with strong lipophilicity; the polyoxyethylene group is a nonpolar molecular group with strong hydrophilicity), which can quickly dissolve and remove floating oil and heavy oil contaminants on metal surfaces, forming an oil-in-water emulsion. The N atom in the N-hydroxyethyliminodiacetic acid disodium salt molecule has a lone pair of electrons, and the oxygen atom in the ethoxy group of the tallow amine polyoxyethylene ether molecule also has a lone pair of electrons. Through the acidic atmosphere provided by phytic acid (i.e., H+), + This process allows the N and O atoms in both molecules to undergo heteroelectrochemical coordination adsorption, resulting in the coupling of the N-hydroxyethyliminodiacetic acid disodium salt molecule with the tallow amine polyoxyethylene ether molecule. The coupled molecule introduces a hydroxyethyl group into the polyoxyethylene group, significantly enhancing the hydrophilicity of the original tallow amine polyoxyethylene ether. This greatly improves the dispersion and emulsification of heavy oil in water, thereby effectively enhancing the removal of floating oil and heavy oil contaminants from metal surfaces. Figure 3 As shown in the schematic diagram of the coupling effect between tallow amine polyoxyethylene ether and disodium N-hydroxyethyliminodiacetic acid, it is evident that after adding disodium N-hydroxyethyliminodiacetic acid, the oil droplets in the water-in-oil emulsion are smaller, and the specific surface area in contact with water is larger. This indicates that the addition of disodium N-hydroxyethyliminodiacetic acid enhances the dispersion effect of oily molecules in water, i.e., improves the emulsification ability, thus making it easier to remove heavy oil from metal surfaces. Simultaneously, under acidic conditions, the secondary amine group (-NH-) on the tallow amine polyoxyethylene ether molecule can form Onium ions (Onium ions are formed by the lone pair electrons of the nitrogen atom on the secondary amine group interacting with H+ in the water). + The positively charged valence bonds formed can strongly adsorb onto the free negatively charged metal surface, creating an adsorbent corrosion-inhibiting protective layer on the metal surface. Combined with the tallow alkyl hydrophobic groups in its molecule, this prevents hydrated hydrogen ions from reaching the metal surface during rust / scaling, increasing the reaction barrier for metal corrosion and effectively preventing secondary corrosion of the metal itself (e.g., ...). Figure 4 (As shown).

[0014] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: The chemical cleaning agent of the present invention can simultaneously meet the cleaning needs of system degreasing + descaling + rust removal, and has high cleaning efficiency. The degreasing rate and rust removal rate can reach more than 90%, and the descaling rate after the plate cleaning is between 85±2%. Moreover, it can play a corrosion inhibitory protection role on the metal during the cleaning process and will not cause secondary corrosion to the metal body. Attached Figure Description

[0015] Figure 1 This is a diagram illustrating the interaction mechanism between phytic acid molecules and iron ions.

[0016] Figure 2This is a diagram illustrating the synergistic effect of disodium N-hydroxyethyliminodiacetic acid and phytic acid in rust / scale removal.

[0017] Figure 3 This is a diagram illustrating the synergistic degreasing mechanism between disodium N-hydroxyethyliminodiacetic acid and tallow amine polyoxyethylene ether.

[0018] Figure 4 This diagram illustrates the mechanism by which tallow amine polyoxyethylene ether provides corrosion inhibition and protection on metal surfaces.

[0019] Wherein, A is the molecular structure of phytic acid; B is the molecular structure of phytic acid iron complex precipitate; C is the molecular structure of disodium N-hydroxyethyliminodiacetic acid; D is the molecular structure of tallow amine polyoxyethylene ether; E is the coupling reaction between tallow amine polyoxyethylene ether and disodium N-hydroxyethyliminodiacetic acid; ① is the cage-like structure formed by phosphonic acid functional groups; ② is the electronegative phosphonic acid functional group after losing hydrogen ions; ③ is the hydrophilic hydroxyethyl functional group; ④ is -N(CH2COO) - )2. Clamping functional group, Me + Represents metal cations (Ca) 2+ Fe 3+ ); ⑤ represents the rust layer covering the metal surface (red represents rust, gray represents salt scale); ⑥ represents the synergistic effect of disodium N-hydroxyethyliminodiacetic acid and phytic acid, which positively promotes the removal of rust and salt scale; ⑦ represents tallow alkyl groups; ⑧ represents polyoxyethylene groups; ⑨ represents the Onium ionic structure (the double red dots represent the lone pair electrons of the N atom); ⑩ represents H + It exhibits a heterospatial coordination adsorption effect with the lone pairs of electrons of N and O atoms (the double red dots represent the lone pairs of electrons of O and N atoms). Detailed Implementation

[0020] Example 1

[0021] The chemical cleaning agent of the present invention is composed of the following components by mass fraction: 22% phytic acid, 35% disodium N-hydroxyethyliminodiacetic acid, 3% tallow amine polyoxyethylene ether, and 40% softened water;

[0022] Among them, tallow amine polyoxyethylene ether is obtained by catalytic polycondensation reaction of tallow alkylamine and ethylene oxide. The tallow alkyl group in the tallow amine polyoxyethylene ether molecule is selected as a C18 aliphatic alkane group, that is, C 18 H 37 - Group; the degree of polymerization of the ethoxy group in its molecule is selected as the polyoxyethylene group with n=15, i.e., -[C2H5O]- 15 Group.

[0023] The chemical cleaning agent of the present invention is obtained by adding the prescribed amounts of phytic acid, disodium N-hydroxyethyliminodiacetic acid and tallow amine polyoxyethylene ether to the prescribed amounts of water.

[0024] The chemical cleaning agent from Example 1 was applied to an industrial circulating cooling water system for cleaning tests.

[0025] The RO membrane effluent from the front-end process of an electronics factory was used as the water sample for cleaning tests. The water quality is shown below: This cleaning test was conducted using an RCC-III type rotating plate corrosion tester. 20# carbon steel plates were used as the test objects to examine and verify the degreasing, derusting, and descaling effects of the chemical cleaning agent of Example 1 on the metal plates. In the test, the chemical cleaning agent of Example 1 was added to a beaker containing the test water sample (15g of the cleaning agent of this invention was added to 1L of water, with a concentration of 15000ppm). Plates covered in machine oil, heavily rusted, and heavily scaled were suspended on the rotating stirring rod of the tester and immersed in the cleaning water. The test instrument was then started, causing the plates to continuously rotate and shear the water in the beaker, simulating the water flow scouring process during cleaning, and cleaning was performed continuously for 4–5 hours. After the cleaning test, the plates were removed and dried, and their weight before and after cleaning was measured to calculate the cleaning effect of the formula of this invention on the degreasing, descaling, and derusting of the plates. The surface condition of the plates after cleaning was also recorded to determine whether the formula of this invention caused secondary corrosion to the metal body.

[0026] The cleaning effect and related data of the above experiments are shown below:

[0027]

[0028] [Note: The above group numbers represent three parallel tests under the same test conditions, with m in each group of tests.] 挂 m is the initial weight of the mounting plate body. 前 m is the weight of the pads before cleaning. 后 Let the weight of the degreasing / rust removal / descaling cleaning pads be the weight after cleaning. Then the degreasing / rust removal / descaling (cleaning) rate ω = (m 前 -m 后 ) / (m 前 -m 挂 )*100%

[0029] The data from the three sets of parallel tests in the table above show that the degreasing and rust removal rates after cleaning the pads using the formula of this invention can reach over 90%, and the descaling rate is between 85±2%. This indicates that the formula of this invention is a composite cleaning agent with degreasing, rust removal, and descaling functions. Furthermore, no corrosion was observed on the surface of the carbon steel pads after cleaning; they exhibited a bright silver metallic luster, further demonstrating that the formula of this invention does not cause secondary corrosion of the steel and has a corrosion-inhibiting and protective effect on the metal.

[0030] Comparative Example 1

[0031] The RO membrane effluent from the front-end process of an electronics factory was used as the water sample for cleaning tests. The water quality is shown below: This cleaning test was conducted using an RCC-III type rotating decal corrosion tester, with 20# carbon steel decals as the test objects. During the test, formulations A, B, and the formulation of this invention were sequentially added to beakers containing test water samples. Three severely rusted decals were suspended on the rotating stirring rod of the tester and immersed in the cleaning water. The test instrument was then started, causing the decals to continuously rotate and shear the water in the beakers, simulating the water flow scouring process during cleaning, and the cleaning was performed continuously for 4–5 hours. After the cleaning test, the decals were retrieved and dried, and their weight before and after cleaning was measured to calculate the cleaning efficiency of each formulation in removing rust from the decals. Simultaneously, the surface condition of the decals after cleaning was recorded to determine whether each formulation caused secondary corrosion to the metal substrate.

[0032] The cleaning effect and related data of the above experiments are shown below:

[0033]

[0034]

[0035] [Note: The above group numbers represent three parallel tests under the same test conditions, with m in each group of tests.] 挂 m is the initial weight of the mounting plate body. 前 m is the weight of the pads before cleaning. 后 Let be the weight of the rust removal and cleaning plate after rust removal. Then the rust removal rate ω = (m 前 -m 后 ) / (m 前 -m 挂 )*100%

[0036] The data from the three sets of parallel experiments in the table above show that: compared with the formulation of this invention, formulation A, which does not contain disodium N-hydroxyethyliminodiacetate, only achieves a rust removal rate of 81-83% (<90%) after cleaning. Some speckled rust spots remain on the surface of the rust-removing plates, and the rust residue is finer. This indicates that disodium N-hydroxyethyliminodiacetate in this formulation can form a synergistic effect with phytic acid, enhancing the rust removal effect and positively promoting the precipitation of phytic acid-iron complex (forming flaky rust residue). Compared with the formulation of this invention, formulation B, which does not contain tallow amine polyoxyethylene ether, achieves a rust removal rate comparable to the formulation of this invention (>90%) after cleaning. However, the carbon steel rust-removing plates show corrosion after cleaning, with a dark gray-black surface. This indicates that without tallow amine polyoxyethylene ether, the phytic acid in the formulation will cause secondary corrosion to the carbon steel.

[0037] Comparative Example 2

[0038] The RO membrane effluent from the front-end process of an electronics factory was used as the water sample for cleaning tests. The water quality is shown below:

[0039]

[0040] This cleaning test was conducted using an RCC-III type rotating plate corrosion tester, with 20# carbon steel plates as the test objects. The effects of the presence or absence of N-hydroxyethyliminodiacetic acid disodium salt on the oil removal efficiency of heavy oil-contaminated plates and on the scale removal efficiency of plates with severe scaling were investigated and verified.

[0041] In the experiment, Formula A and the formula of this invention were added sequentially to beakers containing test water samples. Two feed plates heavily contaminated with heavy diesel oil and two feed plates with severe scaling were suspended on the rotating stirring rod of the aforementioned testing instrument and immersed in the cleaning water. The testing instrument was then started, causing the feed plates to continuously rotate and shear the water in the beakers, simulating the water flow scouring process during cleaning, and the cleaning was carried out continuously for 4-5 hours. After the cleaning test, the feed plates were removed and dried, and their weight before and after cleaning was measured to calculate the cleaning efficiency of each formula for degreasing and descaling the feed plates.

[0042] The cleaning effect and related data of the above experiments are shown below:

[0043]

[0044]

[0045] [Note: m in each of the above groups of experiments] 挂 m is the initial weight of the mounting plate body. 前 m is the weight of the pads before cleaning. 后 Let be the weight of the oil / stain removal after cleaning with the degreasing / stain removal pads. Then, the degreasing / stain removal rate ω = (m 前 -m 后 ) / (m 前 -m 挂 )*100%

[0046] The experimental data in the table above show that, compared with the formulation of this invention, formulation A, which does not contain disodium N-hydroxyethyliminodiacetate, only achieves an oil removal rate of 87% and a scale removal rate of 80% for heavily oil-contaminated feeders after cleaning, and a certain amount of oil and salt scale remains on the surface of the feeders. Furthermore, the effluent after oil removal is not emulsified. This proves that disodium N-hydroxyethyliminodiacetate can synergistically promote the emulsification of oils with tallow amine polyoxyethylene ether, and can also positively promote the dissolution of salt scale, thereby improving the efficiency of scale removal and oil removal.

[0047] Comparative Example 3

[0048] The RO membrane effluent from the front-end process of an electronics factory was used as the water sample for cleaning tests. The water quality is shown below:

[0049]

[0050] This cleaning test was conducted using an RCC-III type rotating plate corrosion tester. 20# carbon steel plates were used as the test objects. By changing the proportions of each component in the chemical cleaning agent formulation of Example 1, the effects of each formulation on the degreasing, derusting, and descaling effects of the metal plates were examined during the cleaning test. In the experiment, the modified formulations A and B, along with the formulation of Example 1, were added to beakers containing test water samples, respectively. Plates covered in machine oil, heavily rusted, and heavily scaled were suspended on the rotating stirring rod of the tester and immersed in the cleaning water. The test instrument was then started, causing the plates to continuously rotate and shear the water in the beakers, simulating the water flow scouring process during cleaning, and cleaning was performed continuously for 4–5 hours. After the cleaning test, the plates were retrieved and dried, and their weight before and after cleaning was measured to calculate the cleaning efficiency of each formulation for degreasing, descaling, and derusting. The corrosion status of the plate surface after cleaning with each formulation was also recorded.

[0051] The cleaning effect and related data of the above experiments are shown below:

[0052]

[0053] [Note: The above group numbers represent three parallel tests under the same test conditions, with m in each group of tests.] 挂 m is the initial weight of the mounting plate body. 前 m is the weight of the pads before cleaning. 后 Let the weight of the degreasing / rust removal / descaling cleaning pads be the weight after cleaning. Then the degreasing / rust removal / descaling (cleaning) rate ω = (m 前 -m 后 ) / (m 前 -m 挂 )*100%

[0054] The experimental data in the table above shows that, compared with the formulation of this invention, formulations A and B, by changing the proportions of the reagents, weakened the degreasing, derusting, and descaling effects on the feed plates (under formulations A and B, the degreasing / rusting efficiency of the feed plates was less than 90%, and the descaling efficiency was less than 80%). From the appearance of the feed plates after cleaning and the condition of the cleaning effluent, it is clear that formulations A and B cannot completely remove contaminants from the surface of the feed plates, and the emulsification state (for degreasing) and turbidity (for descaling) of the effluent are inferior to those of the formulation of this invention.

Claims

1. A chemical cleaning method for industrial circulating cooling water systems, characterized in that: The cleaning steps are as follows: adding a chemical cleaning agent to water to obtain a cleaning water body, wherein the concentration of the chemical cleaning agent in the cleaning water body is 15000ppm, immersing the carbon steel hanging plate in the cleaning water body, and continuously cleaning the carbon steel hanging plate under continuous rotation for 4-5 hours; wherein the chemical cleaning agent is composed of the following components by mass fraction: 22% phytic acid, 35% disodium N-hydroxyethyliminodiacetic acid, 3% tallow amine polyoxyethylene ether, and 40% water; wherein in the tallow amine polyoxyethylene ether, the tallow alkyl group is a C18 aliphatic alkane group; and the degree of polymerization n of the ethoxy group is 15.

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