Corrosion and scale inhibitor as well as preparation method and application thereof

Abstract

The invention provides a corrosion and scale inhibitor as well as a preparation method and application thereof, and relates to the technical field of chemical engineering. The corrosion and scale inhibitor is prepared from the following raw materials in percentage by mass: 7-12% of zinc sulfate, 8-12% of hydroxyethylidene diphosphonic acid, 8-15% of sulfonated terpolymer, 3-5% of methylbenzotriazole and the balance of water. The corrosion and scale inhibitor disclosed by the invention is simple in composition and low in cost, a remarkable scale inhibition effect can be realized only by adding 50ppm-70ppm of the corrosion and scale inhibitor into circulating cooling water, and the corrosion and scale inhibitor has a wide market application prospect.

Description

Technical Field

[0001] This invention provides a corrosion and scale inhibitor, its preparation method, and its application, belonging to the field of chemical technology, specifically relating to a corrosion and scale inhibitor. Background Art

[0002] Circulating cooling water systems are crucial for the safe, stable, long-term, and full-load operation of enterprise production facilities. Improving water treatment technology to achieve water and energy conservation, and extending equipment lifespan and operating cycles, are important ways to improve the overall economic benefits of an enterprise. During use, circulating cooling water undergoes continuous circulation and concentration, leading to an increase in its mineral content, which in turn causes scaling and corrosion in equipment pipelines. The presence of scale not only affects heat transfer efficiency but also causes under-deposit corrosion. Therefore, scale prevention treatment for circulating cooling water is extremely important.

[0003] Currently, in industrial circulating cooling water treatment, the addition of chemical agents is mostly used to control scale formation. For example, Chinese patent CN201810689747.0 discloses a corrosion and scale inhibitor for circulating cooling water, which includes 20-25 parts of polyepoxysuccinic acid, 12-16 parts of polyaspartic acid, 6-10 parts of starch, 10-15 parts of modified chitosan, 4-8 parts of mercaptobenzothiazole, 1-3 parts of surfactant, and 25-30 parts of water. The modified chitosan is mainly prepared by reacting chitosan with dimethylaminoethyl acrylate, and the degree of substitution of the modified chitosan is 60-85%. Although this scale inhibitor solves the environmental problems caused by phosphorus-containing agents in existing phosphorus-containing circulating cooling water and has good hydrolysis resistance, its high cost makes it difficult to popularize and promote in actual production. Therefore, providing an economical and efficient corrosion and scale inhibitor for circulating cooling water is currently a research hotspot. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a corrosion and scale inhibitor for circulating cooling water and its preparation method. The corrosion and scale inhibitor of the present invention is prepared using zinc sulfate, hydroxyethylidene diphosphonic acid, methylbenztriazole, a scale inhibitor dispersant, and water as raw materials. The corrosion and scale inhibitor of the present invention has a simple composition and low cost; only 50ppm to 70ppm needs to be added to the circulating cooling water to achieve a significant scale inhibition effect, and it has broad market application prospects.

[0005] The present invention is specifically implemented using the following technical solutions:

[0006] A corrosion and scale inhibitor, prepared from the following raw materials in the indicated weight percentages:

[0007] Zinc sulfate 10%,

[0008] Hydroxyethylidene diphosphonic acid 10%,

[0009] 10% sulfonated terpolymer

[0010] 4% methylbenztriazole

[0011] The rest is water.

[0012] Preferably, the scale inhibitor and dispersant of the present invention is carboxylic acid-sulfonated-nonionic terpolymer TH-3100.

[0013] The preparation method of the corrosion and scale inhibitor of the present invention is simple, requiring only that the raw materials be mixed evenly in proportion.

[0014] The application method of the corrosion and scale inhibitor of the present invention is to add the corrosion and scale inhibitor to the circulating cooling water for scale inhibition treatment, wherein the concentration of the corrosion and scale inhibitor in the circulating cooling water is 50ppm to 70ppm.

[0015] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0016] 1. The raw material composition of the corrosion and scale inhibitor of the present invention is simple, the raw material sources are wide, and the cost is low.

[0017] 2. The preparation method of the corrosion and scale inhibitor of the present invention is simple and easy to operate in industrial applications.

[0018] 3. The corrosion and scale inhibitor of this invention requires a small amount of material, which further reduces the cost of scale treatment for circulating cooling water.

[0019] 4. The corrosion and scale inhibitor of the present invention can significantly improve the scale inhibition of circulating cooling water without causing equipment corrosion. DETAILED DESCRIPTION

[0020] To make the purpose, technical solutions and advantages of the present invention more clear, the preferred embodiments of the present invention are further described in detail below with reference to the examples. Based on the examples in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] Comparative Example 1

[0022] A corrosion and scale inhibitor for circulating cooling water is composed of the following raw materials in weight percentages:

[0023] Hydroxyethylidene diphosphonic acid 15%,

[0024] 10% sulfonated terpolymer

[0025] 4% methyltriazole

[0026] The rest is water.

[0027] The corrosion and scale inhibitor prepared in Comparative Example 1 was used to inhibit scale formation in the circulating cooling water of a power plant. The initial state parameters of the circulating cooling water in the power plant are as follows:

[0028] pH 8.7, conductivity 1603 μS / cm, turbidity 5.1 NTU, calcium hardness 725.32 mg / L, total alkalinity 382.74 mg / L, chloride ion 354.57 mg / L, total iron 0.68 mg / L.

[0029] The water quality is of the scaling type. When the calcium hardness and alkalinity exceed 1100 mg / L, the risk of scaling increases. The chloride ion and total iron content in the circulating water is also high, which increases the tendency for corrosion.

[0030] The corrosion and scale inhibitor prepared in Comparative Example 1 was added to the circulating cooling water at a rate of 55 ppm / day. After six months of operation, the condenser was opened during maintenance. The condenser was found to be in good condition, with no scale on the surface. Minor pitting occurred on the carbon steel, while the copper surface was smooth and free of scale and corrosion. This indicates that the corrosion and scale inhibitor prepared in Comparative Example 1 did not have a significant corrosion inhibition effect on carbon steel.

[0031] The corrosion and scale inhibitor prepared in Comparative Example 1 was used for scale inhibition in the open-loop cooling water of a steel plant. The initial state parameters of the open-loop cooling water in the steel plant are as follows:

[0032] pH 8.56, conductivity 2653 μS / cm, turbidity 10.6 NTU, calcium hardness 563.2 mg / L, total alkalinity 532.63 mg / L, chloride ion 421.5 mg / L, total iron 0.76 mg / L.

[0033] The water quality is of the scaling type, with calcium hardness and alkalinity approaching 1100 mg / L, increasing the risk of scaling. The chloride ion and total iron content in the circulating water is also high, increasing the tendency for corrosion.

[0034] The corrosion and scale inhibitor prepared in Comparative Example 1 was added to the circulating cooling water at a rate of 60 ppm / day. After six months of operation, during which equipment such as the oil cooler was opened for maintenance, the heat exchange tubes were found to be in good condition, with no noticeable scale deposits on the surfaces. The carbon steel exhibited minor pitting corrosion, while the copper surface remained smooth and as good as new. This demonstrates that the corrosion and scale inhibitor prepared in Comparative Example 1 exhibits good scale and corrosion inhibition for copper, significant scale inhibition for carbon steel, and less pronounced corrosion inhibition.

[0035] Example 1

[0036] A corrosion and scale inhibitor for circulating cooling water is composed of the following raw materials in weight percentages:

[0037] Zinc sulfate 10%,

[0038] Hydroxyethylidene diphosphonic acid 10%,

[0039] 10% sulfonated terpolymer

[0040] 4% methyltriazole

[0041] The rest is water.

[0042] The corrosion and scale inhibitor prepared in Example 1 was used to inhibit scale in the circulating cooling water of a power plant. The initial parameters of the circulating cooling water were as follows: pH 8.7, conductivity 1603 μS / cm, turbidity 5.1 NTU, calcium hardness 725.32 mg / L, total alkalinity 382.74 mg / L, chloride ion 354.57 mg / L, and total iron 0.68 mg / L.

[0043] The corrosion and scale inhibitor prepared in Example 1 was added to the circulating cooling water at a dosage of 55 ppm / day. After one year of actual operation, the condenser was opened during maintenance and found to be in good condition with a smooth surface. No scale or pitting occurred on either the carbon steel or copper components.

[0044] The corrosion and scale inhibitor prepared in Example 1 was used to treat the steel plant's circulating cooling water for scale inhibition, wherein the initial parameters of the steel plant's circulating cooling water were as follows:

[0045] The water quality is characterized by a pH of 8.4, conductivity of 2300 μS / cm, turbidity of 15 NTU, calcium hardness of 310.00 mg / L, total alkalinity of 85 mg / L, chloride ion concentration of 830 mg / L, and total iron concentration of 0.94 mg / L. This water is typically corrosive, with high levels of chloride ions and total iron in the circulating water, indicating a significant risk of corrosion.

[0046] The steel plant adds corrosion and scale inhibitors at 55 ppm daily. After six months of actual operation, the total iron content remains at 0.85 mg / L, the corrosion rate of carbon steel pipelines is 0.067 mg / L, and there is no scale layer or micro-pitting corrosion on the pipelines.

[0047] During operation, the concentration of the corrosion and scale inhibitor was adjusted from 55 ppm to 70 ppm. After one year of actual operation, the total iron content remained at 0.50 mg / L, the corrosion rate of the carbon steel pipeline was 0.024 mg / L, and no scale or corrosion occurred on the pipeline.

[0048] I. The corrosion inhibition performance of the corrosion and scale inhibitor described in Example 1 of this invention was tested, as follows:

[0049] A. Experimental Methods

[0050] The corrosion inhibition performance was determined according to GB / T 18175-2000, "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Plating Method". The test piece was rotated in the original makeup water at a certain speed and temperature for a certain period of time. The corrosion rate was calculated based on the weight loss of the test piece.

[0051] B. Test conditions:

[0052] Water quality: circulating cooling water in a steel plant

[0053] Test water temperature: 45±1℃

[0054] Test speed: 98r / min (equivalent to 0.4m / s)

[0055] Ratio of test solution volume to test piece area: 23ml / cm 2

[0056] Test time: 72h

[0057] Test pieces: Type I test pieces conforming to HG3523-1985 standard, available in A3 carbon steel, brass, and stainless steel. The test pieces are treated according to HG3523-1985 method and then suspended in the makeup water. One test piece is used in each test sample cup.

[0058] C. Test results

[0059] Corrosion rate (mm / a) = 8760 × 10 × (W - W1) / (A × D × T) …………(1)

[0060] Where:

[0061] 8760 – the number of hours equivalent to one year, h / a;

[0062] 10——The number of millimeters equivalent to 1 cm, mm / cm;

[0063] W - the mass of the test piece before the test, g;

[0064] W1 - the mass of the test piece after the test, g;

[0065] A – Area of ​​the test piece, in cm² 2 , (Type 1 test piece A = 28cm 2 );

[0066] D – Density of the sample, g / cm³ 3 , (Carbon steel D = 7.85g / cm 3 Brass D = 8.50 g / cm 3 , stainless steel D = 7.90g / cm 3 );

[0067] T——Test time, h, (72h).

[0068] The average of the test results of the three test pieces is taken as the final result, which is listed as follows:

[0069] Ordinary carbon steel, stainless steel and brass were used as Type I test pieces in the experiment.

[0070] The raw water was the circulating cooling water from a steel mill's intercooler system. It had a pH of 8.4, a conductivity of 1000 μs / cm, a turbidity of 7.5 NTU, a calcium hardness of 380 mg / L, a total alkalinity of 120 mg / L, and a chloride ion concentration of 220 mg / L. Table 1 shows the corrosion inhibition performance of carbon steel, brass, and stainless steel in the circulating cooling water system of a steel mill's intercooler system, based on the amount of corrosion and scale inhibitor added in Example 1.

[0071] Table 1

[0072]

[0073] The raw water was circulating cooling water from a steel mill's direct cooling system. It had a pH of 8.2, conductivity of 2600 μs / cm, turbidity of 15 NTU, calcium hardness of 260.00 mg / L, total alkalinity of 71 mg / L, and chloride ion of 950 mg / L. Table 2 shows the corrosion inhibition performance of carbon steel, brass, and stainless steel in the circulating cooling water system of a steel mill's direct cooling system, based on the amount of corrosion and scale inhibitor added in Example 1.

[0074] Table 2

[0075]

[0076] The above tests demonstrate that the corrosion inhibitor is fully suitable for the requirements of circulating cooling water treatment, and the corrosion rate meets the standards specified in the "Design Code for Industrial Circulating Cooling Water Treatment".

[0077] II. The scale inhibition performance of the corrosion and scale inhibitor described in Example 1 of the present invention was tested, as follows:

[0078] The scale inhibition rate of calcium carbonate scale was tested according to GB / T 16632-2019 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method". A test solution was prepared using actual working water and the corrosion and scale inhibitor described in Example 1. Under heating conditions, calcium bicarbonate was accelerated to decompose into calcium carbonate. After reaching equilibrium, the calcium ion concentration in the test solution was measured. The higher the calcium ion concentration, the better the scale inhibition performance of the corrosion and scale inhibitor described in Example 1.

[0079] The corrosion and scale inhibitor sample solution described in Example 1: 1.00 mL contains 0.500 mg of water treatment agent (on a dry basis).

[0080] Actual operating condition water: Add 250 mL of actual operating condition water to a 500 mL volumetric flask, add a certain amount of corrosion and scale inhibitor sample solution using a pipette, and shake well. Dilute with water to the mark and shake well.

[0081] The scale inhibition performance of corrosion and scale inhibitors is expressed as η, with the value as a percentage, and is calculated using the following formula:

[0082] Where:

[0083] ρ2 — Calcium ions (Ca) in the test solution after adding corrosion and scale inhibitors 2+ The mass concentration is expressed in milligrams per milliliter (mg / mL).

[0084] ρ1—Calcium ions (Ca) in the blank test solution without corrosion and scale inhibitors. 2+ The mass concentration is expressed in milligrams per milliliter (mg / mL).

[0085] ρ——Calcium ions (Ca 2+ The mass concentration is expressed in milligrams per milliliter (mg / mL).

[0086] The raw water is circulating cooling water from an open-loop cooling system in a steel plant. It has a pH of 8.4, conductivity of 1000 μS / cm, turbidity of 7.5 NTU, calcium hardness of 380.00 mg / L, total alkalinity of 120 mg / L, and chloride ion concentration of 220 mg / L.

[0087] The corrosion and scale inhibitors of Example 1 were kept at 70℃ for 10 hours to test their calcium carbonate scale inhibition performance. The effect of the concentration of the corrosion and scale inhibitor in Example 1 on the calcium carbonate scale inhibition rate is shown in the table below:

[0088] Table 3

[0089] Experimental groups Corrosion and scale inhibitor concentration Scale inhibition rate / % 1 1mg / L 90.12 2 2mg / L 97.06 3 3mg / L 93.77

[0090] The above test shows that the corrosion and scale inhibitor described in Example 1 has good scale inhibition performance, and can still reach more than 90% at a relatively low concentration.

[0091] The raw water is circulating cooling water from a direct-cooling open system in a steel plant. It has a pH of 7.9, conductivity of 2500 μS / cm, turbidity of 5.5 NTU, calcium hardness of 420.0 mg / L, total alkalinity of 100.0 mg / L, and chloride ion concentration of 320 mg / L.

[0092] The corrosion and scale inhibitors of Example 1 were kept at 70℃ for 10 hours to test their calcium carbonate scale inhibition performance. The effect of the concentration of the corrosion and scale inhibitor in Example 1 on the calcium carbonate scale inhibition rate is shown in the table below:

[0093] Table 4

[0094] Experimental groups Corrosion and scale inhibitor concentration Scale inhibition rate / % 1 1mg / L 90.42 2 2mg / L 97.47 3 3mg / L 93.46

[0095] The above experiments show that the corrosion and scale inhibitor described in Example 1 has good scale inhibition performance, achieving over 90% inhibition even at low concentrations. The examples described above are some, but not all, of the embodiments of this invention. The detailed description of the embodiments of this invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

Claims

1. A corrosion and scale inhibitor, characterized in that: It is prepared from the following raw materials in percentage by weight: Zinc sulfate 7% to 12%, Hydroxyethylidene diphosphonic acid 8% to 12%, Sulfonated terpolymer 8-15%, Methylbenzotriazole 3-5%, The rest is water.

2. The corrosion and scale inhibitor according to claim 1, characterized in that: The scale inhibitor and dispersant is carboxylic acid-sulfonated-nonionic terpolymer TH-3100.

3. The method for preparing the corrosion and scale inhibitor according to any one of claims 1 to 2, characterized in that: The raw materials are uniformly mixed according to the proportion.

4. The use of the corrosion and scale inhibitor according to any one of claims 1 to 2, characterized in that: The corrosion and scale inhibitor is added into the circulating cooling water for corrosion and scale inhibition treatment.

5. The use according to claim 4, characterized in that The concentration of the corrosion and scale inhibitor in the circulating cooling water is 50ppm to 70ppm.

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