A phosphorus-free circulating water composite scale and corrosion inhibitor and its application

Abstract

The present invention belongs to the technical field of scale and corrosion inhibition treatment for industrial circulating cooling water, and relates to a phosphorus-free composite scale and corrosion inhibitor for circulating water, its preparation method, and application. The composite scale and corrosion inhibitor comprises the following components by weight: 26-33% disodium cocoamphodipropionate, 8-10% sodium tartrate, 1-2% sodium thioglycolate, 0.1-0.2% concentrated hydrochloric acid, and 54.8-64.9% deionized water. The composite scale and corrosion inhibitor provided by the present invention not only has high scale inhibition performance, but also exhibits excellent corrosion inhibition performance in various circulating cooling water systems, exhibits broad-spectrum stability, and its key components are highly efficient and environmentally friendly, making it particularly suitable for use in industrial circulating cooling water systems.

Description

Technical Field

[0001] The invention relates to a phosphorus-free composite scale and corrosion inhibitor for circulating water and application thereof, belonging to the technical field of scale and corrosion inhibition treatment of industrial circulating cooling water. Background Art

[0002] Water is a precious natural resource used by humans for a range of industrial production activities. With the rapid development of modern industry, water consumption has skyrocketed. Industrial cooling water dominates this consumption, accounting for over 60% of total industrial water use. To conserve freshwater resources and reduce water consumption, circulating water is widely used instead of direct flow in industrial cooling water. This approach reduces industrial water supply by further increasing the concentration ratio of circulating water and reducing wastewater discharge.

[0003] Since the water in the cooling circulating water system contains a large amount of dissolved / suspended solids, organic matter and various dissolved gases, and the water is continuously concentrated during the long-term operation of the system, it has water quality characteristics such as high hardness, high alkalinity, and high organic matter. Therefore, in a circulating water system with high concentrations of various ions, coupled with long-term continuous operation in a high-temperature environment, over time, it will cause scaling deposition, microbial growth and severe corrosion in the circulating pipelines and related equipment (such as heat exchangers, lifting pumps, etc.), and eventually lead to perforation and leakage of the circulating pipelines, affecting the factory's safe production process and causing economic losses.

[0004] A wide variety of corrosion inhibition technologies are currently being used in industry, broadly categorized as process, physical, and chemical methods. Among these methods, chemical corrosion inhibition offers numerous advantages, including low cost and significant effectiveness, making it widely adopted both domestically and internationally. To address these issues, chemical corrosion inhibitors must be added to the cooling water system. These agents achieve excellent corrosion protection without altering the corrosive environment, while also indirectly improving the concentration ratio of the circulating water system and saving cooling water.

[0005] In terms of the types of corrosion inhibitors, commonly used corrosion inhibitors can be roughly divided into two categories based on the corrosion inhibition mechanism, namely anode-oxide film type corrosion inhibitors and cathode-precipitation film type corrosion inhibitors.

[0006] (1) Anodic-oxide film type corrosion inhibitor: This type of corrosion inhibitor achieves the purpose of corrosion inhibition by inhibiting the anodic process of the corrosion reaction. It is usually an inorganic strong oxidant that reacts with metal ions at the anode to form oxides or chloride oxides, that is, a dense oxide film is formed on the metal surface, which makes it passivated, thereby hindering the corrosion of the metal surface by the environmental water medium. Common corrosion inhibitors belonging to this type include chromates, molybdates, tungstates and borates (for details, see the Chinese patents with application publication numbers "CN1706759A" and "CN 102730848B"). When using this type of corrosion inhibitor, a very high concentration of the agent is required to passivate the entire metal anode surface. Once the corrosion inhibitor dosage is insufficient, pitting will occur in the passivated area. In addition, in actual engineering applications, except for chromates, which have strong oxidizing properties, the other types have weak oxidizing abilities and need to be oxygenated to form an oxide film on the metal surface, which increases the operating cost of the project to a certain extent.

[0007] (2) Cathode-precipitation film type corrosion inhibitor: This type of corrosion inhibitor relies on the cathode reaction products of the metal corrosion cell to form a film that prevents the cathode electrons on the metal surface from combining with other substances. Common cathode-precipitation film type corrosion inhibitors mainly include zinc carbonate, phosphate, calcium carbonate and hydroxide, etc. (see the Chinese patent application publication numbers "CN107973420B" and "CN114875394A" for details). They are formed by the reaction of zinc and calcium cations with carbonate, phosphate and hydroxide anions in water with the cathode area of the metal surface to precipitate into a film, and can also react with related ions in water. The reaction products are deposited at the cathode to form a film, which acts as a protective film. Compared with the anode-oxidation film type corrosion inhibitor film, the cathode-precipitation film type corrosion inhibitor film does not directly combine with the metal surface, so it is porous and has a poor corrosion inhibition effect. This type of film has weak adhesion to the metal, so it is not suitable for use in circulating cooling systems with high flow rates.

[0008] To sum up, in view of the shortcomings of the above-mentioned commonly used corrosion inhibitors, such as single function, large dosage, poor stability of corrosion inhibition effect and limited application scenarios, it is particularly important and imperative to develop a composite agent with dual functions of scale inhibition and corrosion inhibition, high efficiency, stability and environmental friendliness. Summary of the Invention

[0009] In order to overcome the above-mentioned deficiencies in the prior art, the present invention aims to provide a phosphorus-free composite scale and corrosion inhibitor for circulating water having both scale and corrosion inhibition functions and its application.

[0010] The composite scale and corrosion inhibitor provided by the present invention not only has high-efficiency scale inhibition performance, but also has excellent corrosion inhibition performance in various circulating cooling water systems, has broad-spectrum stability, and its key components are efficient and environmentally friendly, making it particularly suitable for application in industrial circulating cooling water systems.

[0011] The composition and compatibility of the phosphorus-free composite scale and corrosion inhibitor in the technical solution adopted by the present invention are as follows:

[0012]

[0013] Note: The proportions of the above agents are all in wt%.

[0014] Furthermore, the concentration of the concentrated hydrochloric acid is 35-37%.

[0015] The phosphorus-free scale and corrosion inhibitor in the present invention is a composite agent. The agent formula is creatively screened out through corrosion and scale inhibition experiments, and then the addition percentage of each single component in the above formula, that is, the optimal ratio concentration range, is determined through orthogonal experiments.

[0016] The pharmaceutical formulation of the present invention is miscible with water, has a density (20° C.) of about 1.14 to 1.22 g / mL, a total solid content of 35 to 46%, and a pH of the formulation stock solution of 8.0 to 8.5.

[0017] The present invention also provides a method for preparing the above-mentioned composite scale and corrosion inhibitor for circulating water, comprising the following steps:

[0018] Deionized water is added to a reaction vessel A, and a stirring device is started. Then, a disodium cocoamphodipropionate liquid is slowly added to the reaction vessel, and stirring is continued to make the mixed liquid uniform and clear; the reaction vessel A is transferred to a water bath, the water bath temperature is controlled at 75-85° C., and potassium sodium tartrate is added to the reaction vessel A, and stirring is continued in the water bath to obtain a solution A; concentrated hydrochloric acid is added to a reaction vessel B and stirred, and then sodium thioglycolate is added, stirring is continued and ultrasonic treatment is performed to obtain a solution B; and the solution B is added dropwise to the solution A using a dropper and stirred to obtain a phosphorus-free composite scale and corrosion inhibitor for circulating water.

[0019] Furthermore, the ultrasonic time is 30 minutes.

[0020] Furthermore, the water bath temperature was controlled at 80°C.

[0021] Furthermore, the method comprises the following steps:

[0022] Step 1: Add a certain amount of deionized water to reaction vessel A, start the stirring device, set and control the speed at 700-800 rpm, then slowly add disodium cocoamphodipropionate liquid to the reaction vessel, continue stirring for 10 minutes, and make the mixed solution uniform and clear;

[0023] Step 2: Transfer the reaction vessel A to a water bath, control the water bath temperature at 80°C, add a certain amount of potassium sodium tartrate solid powder to the reaction vessel A, adjust the speed to 900-1000 rpm, and continue stirring in the water bath for 30 minutes. The COO- of sodium tartrate and the COO- group of disodium cocoamphodipropionate form a synergistic effect, thereby improving the scale inhibition efficiency;

[0024] Step 3: Add concentrated hydrochloric acid to the reaction vessel B, stir, and add sodium thioglycolate, adjust the speed to 300-500 rpm, continue stirring for 10 minutes, and then ultrasonicate for 30 minutes. The resonance effect of ultrasound is conducive to the reaction of the lone pair electrons of S on the sodium thioglycolate-SH with the H3O provided by concentrated hydrochloric acid. + The combination produces a synergistic effect, which is beneficial to the stability of the corrosion inhibition film formed on the metal surface.

[0025] Step 4: Add the solution obtained in the third step dropwise into the solution obtained in the second step using a dropper, and stir for 24 hours to obtain the composite scale and corrosion inhibitor.

[0026] The present invention also provides the use of the phosphorus-free composite scale and corrosion inhibitor for circulating water in the scale and corrosion inhibition of industrial circulating cooling water system pipelines.

[0027] The present invention also provides a circulating water scale and corrosion inhibition method, which comprises adding the phosphorus-free circulating water composite scale and corrosion inhibitor into the circulating water.

[0028] Furthermore, the circulating water pipeline is made of carbon steel or aluminum.

[0029] Furthermore, the addition concentration of the phosphorus-free circulating water composite scale and corrosion inhibitor is greater than or equal to 5 ppm. When it is equal to 5 ppm, the corrosion inhibition efficiency of carbon steel material is greater than or equal to 90%, and the corrosion inhibition efficiency of aluminum-based material is greater than or equal to 95%.

[0030] Furthermore, when the phosphorus-free circulating water composite scale inhibitor is added at a concentration of 12.5 to 17.5 ppm, a passivation oxide film will be formed on the surface of the aluminum-based material, completely preventing corrosion of the aluminum surface. The corrosion inhibition efficiency of the aluminum-based material reaches 100%, i.e., there is no corrosion at all.

[0031] Beneficial effects

[0032] Key corrosion inhibitor component of the present invention is cocoyl amphoteric disodium dipropionate, different from anode-oxidation film type / cathode-precipitation film type corrosion inhibitor, this corrosion inhibiting component is adsorption type thin film corrosion inhibitor, its corrosion inhibition mechanism is that corrosion inhibiting component does not directly participate in the cathode and anode process of metal corrosion, by the special adsorption of the strong polar group on its molecular chain (-NH2 group of its molecular chain end, with stronger polarity, can be adsorbed by the free charge of metal surface), monomolecular film is formed on metal surface, the barrier layer of metal and aqueous phase interface is formed, or the potential barrier of material diffusion and reaction, thus stop or slow down the reaction of corresponding electrochemistry, play the corrosion inhibition to metal.Except molecular chain end-NH2 group and the adsorption effect of metal surface,-N (CH2CH2-)CH2CH2O-long molecular chain hydrophobic group plays certain covering shielding effect to metal surface and stretches diffusion on its surface, plays facilitation to suppressing metal corrosion reaction.

[0033] In addition, a small amount of sodium thioglycolate and concentrated hydrochloric acid additives are added to the formula of the present invention to improve the stability of the corrosion inhibition component by introducing H + and thiol groups, using the lone electron pairs of S and N in -SH and -NH2 to form H3O + The combined effect prevents the adsorption film of the corrosion inhibitor from desorption due to hydration, ensuring the long-term stability of the corrosion inhibition film.

[0034] The present invention introduces sodium tartrate as the corrosion inhibition component "disodium cocoylamphodipropionate + sodium thioglycolate" to further enhance the scale inhibition performance of the agent formula. 2+ Mg 2+ The chelating effect of cations and scale-forming anions (such as CO3 2- , PO4 3- and SiO3 2- The contact of the circulating water system with the water and the Ca in the circulating cooling water is greatly reduced. 2+ Mg 2+ The allowable concentration is relatively increased, that is, the solubility of calcium and magnesium salts is correspondingly increased, which indirectly solves the concentration rate problem of the circulating water system and saves cooling water to a certain extent.

[0035] Disodium cocoamphodipropionate, a key component in the formula of the present invention, has both corrosion and scale inhibition properties, is a natural substance, is easily degradable, highly efficient, and environmentally friendly. Sodium thioglycolate and concentrated hydrochloric acid are added to the formula to make the corrosion inhibition film more stable and uniform. Sodium tartrate added to the formula forms a synergistic effect with disodium cocoamphodipropionate, thereby significantly enhancing the static scale inhibition performance.

[0036] The agent provided by the present invention not only has high-efficiency scale inhibition and dispersibility, but also has excellent corrosion inhibition performance in various circulating cooling water systems and has broad-spectrum stability. Its key components are efficient and environmentally friendly, and are particularly suitable for application in industrial circulating cooling water circulation systems. When the addition concentration reaches a certain level, it will form a pre-film effect on the surface of the aluminum material, effectively preventing the corrosion of the aluminum-based material, and has a very good corrosion inhibition effect on aluminum pipelines. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific comparative examples. It should be understood that the following comparative examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0038] Comparative Example 1

[0039] This comparative example aims to examine the corrosion inhibition effect of each key component in the pharmaceutical formula on the metal coupon, thereby verifying the optimality of the pharmaceutical compatibility in the formula of the present invention.

[0040] In this comparative example, circulating cooling water from an electronics factory project was used as the test water sample, and 20# carbon steel coupons were used as the test objects. The effects of ① adding only a single scale inhibitor (sodium tartrate), ② adding only a single corrosion inhibitor (disodium cocoamphodipropionate), and ③ the formulation of the present invention at different addition concentrations on the corrosion rate and corrosion inhibition effect of the metal coupons were investigated (the test was conducted in accordance with the standard test of GB-T18175-2014 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotating Coupon Method", and the test time was 72 hours).

[0041] The important water quality indicators of the test water samples are summarized as follows:

[0042]

[0043]

[0044] The corrosion conditions and corrosion inhibition effect data of the above formulas on carbon steel coupons are summarized as follows:

[0045]

[0046] It can be clearly seen from the above table that at the same agent dosage concentration, the corrosion inhibition efficiency of the metal coupons is ③ the present invention formula > ② only adding a single corrosion inhibitor (disodium cocoylamphodipropionate) > ① only adding a single scale inhibitor (sodium tartrate), and the corrosion rate of the carbon steel coupons of the present invention formula can reach up to about 97%, which is much higher than ① only adding scale inhibitor formula (Y 缓蚀，MAX =70%) and ② only adding phosphorus corrosion inhibitor formula (Y 缓蚀，MAX=80%), further demonstrating that the composite scale and corrosion inhibitor formulation of the present invention is the optimal formulation with the best corrosion inhibition effect. For carbon steel, the present invention can achieve a corrosion inhibition efficiency of over 90% when the agent dosage concentration is only 5ppm.

[0047] Comparative Example 2

[0048] This comparative example is intended to investigate the effects of sodium thioglycolate and concentrated hydrochloric acid in the formula on the film-forming effect on the metal surface, thereby verifying whether the above two components promote the stability of the corrosion inhibition component.

[0049] This comparative example uses the circulating cooling water of a certain electronics factory project as the test water sample and 20# carbon steel coupons as the test objects to examine the appearance effects of the corrosion inhibition films formed by ① adding only sodium thioglycolate, ② adding only concentrated hydrochloric acid, and ③ the formulation of the present invention at different addition concentrations.

[0050] The important water quality indicators of the test water samples are summarized as follows:

[0051] Water quality indicators unit Measured value pH / 8.5 Conductivity μs / cm 4430 <![CDATA[Total alkalinity (calculated as CaCO3)]]> mg / L 1890 <![CDATA[Ca 2+ (Calculated by CaCO3) mg / L 700 <![CDATA[Mg 2+ (Calculated by CaCO3) mg / L 360 <![CDATA[Cl - ]]> mg / L 264 <![CDATA[SO4 2- ]]> mg / L 1288 COD mg / L 128

[0052] The corrosion inhibition efficiency data and corrosion inhibition film formation of the above formulas on carbon steel coupons are summarized as follows:

[0053]

[0054] As can be clearly seen from the table above, compared to formulations 1 and 2, the corrosion-inhibiting film formed on the metal coupon surface with the present formulation gradually evolves from a dotted pattern to a sheet-like pattern as the dosage concentration increases, ultimately forming a complete and uniform corrosion-inhibiting film that completely covers the originally clean and bright metal surface. This further demonstrates that the synergistic effect of sodium thioglycolate and concentrated hydrochloric acid is more conducive to the formation of a uniform and complete film than either component alone, promoting stable film formation.

[0055] Comparative Example 3

[0056] This comparative example aims to investigate the scale inhibition effect of disodium cocoamphodipropionate and sodium tartrate in the formula in water, so as to verify whether they have a synergistic scale inhibition effect.

[0057] This comparative example uses the static scale inhibition test method to examine the scale inhibition efficiency of the formula. The specific operation steps are as follows: Prepare Ca 2+ 160ppm CaCl2 solution and CO3 2- The content of Na2CO3 solution is 240ppm. In a conical flask, add 100ml Na2CO3 solution, 2-4ml of the target scale inhibition formula, and 100ml CaCl2 solution in sequence. Adjust the pH to 8-9, put it in a constant temperature shaker and shake it for 24-48h. Take the supernatant and filter it to measure Ca 2+The scale inhibition efficiency was calculated by measuring the concentration of the mixture. The scale inhibition formulas to be tested were ① only adding disodium cocoamphodipropionate, ② only adding sodium tartrate, and ③ the formula of the present invention.

[0058] The static antiscaling efficiency data of the above formulations are summarized as follows:

[0059]

[0060] It can be clearly seen from the above table that the average static scale inhibition efficiency of the formula of the present invention can be as high as 86.9%, which is much higher than the test data of formulas ① and ②. This further illustrates that the synergistic effect of disodium cocoamphodipropionate and sodium tartrate can achieve a better scale inhibition effect on water bodies.

[0061] Example 1

[0062] The rotating coupon corrosion test uses the circulating cooling water from an electronics factory project as the test water sample. The water quality indicators are summarized as follows:

[0063] Water quality indicators unit Measured value pH / 8.5 Conductivity μs / cm 4430 <![CDATA[Total alkalinity (calculated as CaCO3)]]> mg / L 1890 <![CDATA[Ca 2+ (Calculated by CaCO3) mg / L 700 <![CDATA[Mg 2+ (Calculated by CaCO3) mg / L 360 <![CDATA[Cl - ]]> mg / L 264 <![CDATA[SO4 2- ]]> mg / L 1288 COD mg / L 128

[0064] The test was conducted in accordance with GB-T18175-2014 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotating Coupon Method". The test material was 7573 aluminum sheet standard coupons. The test lasted 72 hours. The important data of the composite scale and corrosion inhibitor of the present invention, such as the dosage concentration, corrosion rate, and corrosion inhibition efficiency, are summarized in the following table:

[0065]

[0066] As shown in the table above, when the dosage concentration of the composite corrosion and scale inhibitor formula of the present invention is greater than 5ppm, its scale and corrosion inhibitor exhibits excellent corrosion inhibition effects, fully meeting the requirement of a carbon steel corrosion rate of <0.10mm / a, and its corrosion inhibition efficiency exceeds 90%. It is noteworthy that when the dosage concentration of the formula agent is between 12.5 and 17.5ppm, a negative corrosion rate and a corrosion inhibition efficiency exceeding 100% occur. This indicates that within the above dosage concentration range, this formula forms a passivating oxide film on the surface of the aluminum-based material (specifically, after the reaction is completed, the hanging piece increases in weight), completely preventing corrosion on the aluminum surface (i.e., there is no corrosion on the aluminum surface), and the corrosion inhibition efficiency can reach 100%.

[0067] In summary, for those skilled in the art, under the guidance of the concept and specific embodiments of this patent, some variations can be directly derived or associated from the disclosure of this patent and common sense. Ordinary technicians in this field will realize that other methods can also be used, or commonly known technologies in the prior art can be used as substitutes, as well as changes in parameters such as dosage, reaction time, or slightly beyond this range, etc., non-substantial changes can also be applied, and can achieve the functions and effects described in this patent. No further examples will be given to explain them in detail, and they all fall within the scope of protection of this patent.

Claims

1. A method for preparing a phosphorus-free composite scale and corrosion inhibitor for circulating water, characterized in that: The phosphorus-free circulating water composite scale and corrosion inhibitor comprises the following components in percentage by mass: 26-33% disodium cocoamphodipropionate, 8-10% sodium tartrate, 1-2% sodium thioglycolate, 0.1-0.2% concentrated hydrochloric acid, and 54.8-64.9% deionized water; The preparation method comprises the following steps: Deionized water is added to a reaction vessel A, and a stirring device is started. Then, a disodium cocoamphodipropionate liquid is slowly added to the reaction vessel, and stirring is continued to make the mixed liquid uniform and clear; the reaction vessel A is transferred to a water bath, the water bath temperature is controlled at 75-85° C., and potassium sodium tartrate is added to the reaction vessel A, and stirring is continued in the water bath to obtain a solution A; concentrated hydrochloric acid is added to a reaction vessel B and stirred, and then sodium thioglycolate is added, stirring is continued and ultrasonic treatment is performed to obtain a solution B; and the solution B is added dropwise to the solution A using a dropper and stirred to obtain a phosphorus-free composite scale and corrosion inhibitor for circulating water.

2. The method for preparing the phosphorus-free composite scale and corrosion inhibitor for circulating water according to claim 1, characterized in that: The concentration of the concentrated hydrochloric acid is 35-37%.

3. The method for preparing the phosphorus-free composite scale and corrosion inhibitor for circulating water according to claim 1, characterized in that: The ultrasonic time is 30 minutes.

4. The method for preparing the phosphorus-free composite scale and corrosion inhibitor for circulating water according to claim 1, characterized in that: The water bath temperature was controlled at 80°C.

5. A phosphorus-free composite scale and corrosion inhibitor for circulating water, characterized in that: Prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the phosphorus-free circulating water composite scale and corrosion inhibitor according to claim 5 in scale and corrosion inhibition of industrial circulating cooling water system pipelines.

7. A method for scale and corrosion inhibition of circulating water, characterized in that: Add the phosphorus-free composite scale and corrosion inhibitor for circulating water according to claim 5 into the circulating water.

8. The circulating water scale and corrosion inhibition method according to claim 7, characterized in that: The circulating water pipeline is made of carbon steel or aluminum-based material.

9. The circulating water scale and corrosion inhibition method according to claim 8, characterized in that: The addition concentration of the phosphorus-free circulating water composite scale inhibitor and corrosion inhibitor is greater than or equal to 5 ppm. When it is equal to 5 ppm, the corrosion inhibition efficiency of carbon steel material is greater than or equal to 90%, and the corrosion inhibition efficiency of aluminum-based material is greater than or equal to 95%.

10. The method for scale and corrosion inhibition of circulating water according to claim 8, characterized in that: When the phosphorus-free circulating water composite scale and corrosion inhibitor is added at a concentration of 12.5-17.5 ppm, the corrosion inhibition efficiency of the aluminum-based material reaches 100%.

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