Composition for reducing corrosivity of demineralized water in circulating water system and method for reducing corrosivity of demineralized water in circulating water system

Abstract

The invention relates to a composition for reducing the corrosivity of demineralized water in a circulating water system and a method for reducing the corrosivity of the demineralized water in the circulating water system. The composition contains an alkaline substance and hydrogen peroxide; the weight ratio of the alkaline substance to the hydrogen peroxide in the composition is 1: (2-50). The composition disclosed by the invention can still effectively reduce the corrosion rate of carbon steel when demineralized water is not subjected to deoxidization treatment, the operation process is simple, and the operation cost is relatively low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water treatment, in particular, to a composition for reducing the corrosiveness of desalted water in a circulating water system and a method for reducing the corrosiveness of desalted water in a circulating water system. BACKGROUND

[0002] Desalted water is mostly used as makeup water for closed circulating water systems in chemical, metallurgical, petroleum, and power industries, and can also be used in boiler systems. Although the desalted water is free of salts, it still contains dissolved oxygen. Studies have shown that dissolved oxygen is reduced on the cathode of a metal (1 / 2O2+ H2O + 2e→ 2OH - ), thereby accelerating the oxidation reaction of the metal on the anode (Fe - 2e→ Fe 2+ ), and thus accelerating the corrosion of the metal. Therefore, the dissolved oxygen in the desalted water still has a significant impact on the corrosion of the closed system, and the main treatment method for oxygen corrosion is deoxygenation or addition of corrosion inhibitors.

[0003] The commonly used deoxygenation methods currently include physical methods and chemical methods. The physical methods include thermal deoxygenation, vacuum deoxygenation, and stripping deoxygenation, and the physical deoxygenation methods have the disadvantage of incomplete deoxygenation, and generally need to be combined with chemical deoxygenation methods to remove residual oxygen. The chemical deoxygenation methods include chemical deoxygenation and resin deoxygenation, and the commonly used deoxygenating agents mainly include sodium sulfite, hydrazine, acetone oxime, and erythorbic acid. The chemical deoxygenating agents can achieve complete deoxygenation, but also have certain limitations. For example, hydrazine is toxic, and many enterprises are limiting or no longer using it; acetone oxime has strong reducing properties, and when desalted water is used as makeup water, ammonia must be added to maintain the pH value of the feed water at 8.5-9.5.

[0004] If deoxygenation is not performed, the corrosion rate of the system can also be reduced by adding an oxygen corrosion-resistant corrosion inhibitor.

[0005] For example, CN105036363A discloses a composite corrosion inhibitor suitable for desalted water and a preparation method thereof, and the components and mass fractions thereof are as follows: sodium silicate 25-35 parts, trisodium phosphate 20-30 parts, sodium molybdate 1-5 parts, polyacrylic acid with a concentration of 30% 1-10 parts, benzotriazole 0.1-1.5 parts, triethanolamine 1-5 parts, and deionized water 100-200 parts.

[0006] CN101928075A discloses a corrosion inhibitor for a closed circulating cooling water system and a preparation method thereof, and the corrosion inhibitor contains the following components in percentage by weight: molybdate 1%-5%, alkyl alcohol amine 5%-20%, deoxygenating agent 1%-3%, copper protective agent 0.5%-1.5%, and the balance is water.

[0007] CN101125713A discloses a liquid type corrosion inhibitor special for closed circulating water system, and relates to its application and preparation method. The corrosion inhibitor contains the following components and weight percentage contents: borax 5.5%-10%, caustic soda 1.0%-3.0%, silicate 3.5%-4.2%, nitrite 6.4%-12.4%, 2-mercaptobenzothiazole 0.1%-1.0%, and the rest is water.

[0008] The compositions of the corrosion inhibitors disclosed in the above prior art are mainly phosphorus series and nitrite substances. The use of phosphorus series agents increases the phosphorus content of the effluent water, leading to water eutrophication. Nitrite entering the human body can oxidize hemoglobin into methemoglobin, destroying the oxygen-carrying capacity of hemoglobin and causing harm to the human body, so its use is also limited. Non-phosphorus and non-nitrite corrosion inhibitors, such as molybdate and tungstate, are more studied, but the cost of such substances is relatively high, so their use is also limited. There are also other non-phosphorus and non-nitrite corrosion inhibitor formulations in the prior art, but they often contain multiple components, are complex in composition, and have relatively high cost. Moreover, the corrosion inhibitors in the prior art are usually only suitable for corrosion inhibition of low-temperature closed systems with a temperature below 80°C, and have poor corrosion inhibition effect on high-temperature closed systems with a temperature above 80°C. SUMMARY

[0009] The purpose of the present disclosure is to provide a composition for reducing the corrosion of desalted water in a circulating water system and a method for reducing the corrosion of desalted water in a circulating water system, which can effectively reduce the corrosion rate of carbon steel when the desalted water is not subjected to oxygen removal treatment, and the method process is simple and has low operating cost.

[0010] To achieve the above purpose, the present disclosure provides a composition for reducing the corrosion of desalted water in a circulating water system, which contains an alkaline substance and hydrogen peroxide.

[0011] The weight ratio of the alkaline substance and the hydrogen peroxide in the composition is 1:(2-50).

[0012] Optionally, the weight ratio of the alkaline substance and the hydrogen peroxide in the composition is 1:(3-30), more preferably 1:(5-20).

[0013] Optionally, the alkaline substance is selected from one or more of inorganic alkali, organic alkali, and strong alkali weak acid salt.

[0014] Preferably, the inorganic alkali is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water; the organic alkali is selected from one or more of ethanolamine, ethylenediamine, and triethylamine; and the strong alkali weak acid salt is selected from sodium carbonate and / or sodium bicarbonate.

[0015] The second aspect of the present disclosure provides a method for reducing the corrosiveness of desalted water in a circulating water system, the method comprising: sequentially adding an alkaline substance and hydrogen peroxide into the desalted water.

[0016] Optionally, the amount of the alkaline substance is 5-50 mg, preferably 10-40 mg, and more preferably 20-30 mg, and the amount of the hydrogen peroxide is 100-400 mg, preferably 150-350 mg, and more preferably 200-300 mg, per 1 L of the desalted water.

[0017] Optionally, the alkaline substance is selected from one or more of inorganic bases, organic bases, and strong base weak acid salts.

[0018] Preferably, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water; the organic base is selected from one or more of ethanolamine, ethylenediamine, and triethylamine; and the strong base weak acid salt is selected from sodium carbonate and / or sodium bicarbonate.

[0019] Optionally, the sequential addition of the alkaline substance and the hydrogen peroxide into the desalted water is performed in a closed system at 25-200°C.

[0020] Optionally, the sequential addition of the alkaline substance and the hydrogen peroxide into the desalted water is performed in a closed system at 120-200°C.

[0021] Optionally, the pH of the desalted water after the addition of the alkaline substance and the hydrogen peroxide is 8 or higher, and preferably 9-11.

[0022] The method further comprises: after the sequential addition of the alkaline substance and the hydrogen peroxide into the desalted water, adding a corrosion inhibitor.

[0023] The corrosion inhibitor is selected from one or more of sodium gluconate, citric acid, ascorbic acid, and phosphoric acid, and the amount of the corrosion inhibitor is 2-20 mg per 1 L of the desalted water.

[0024] Optionally, the desalted water has a dissolved oxygen concentration of 2-10 mg / L, a pH of 8-10, and a conductivity of less than 10 μS / cm.

[0025] The composition and method of the present disclosure have the following advantages:

[0026] (1) The method of the present disclosure does not require the removal of dissolved oxygen in the desalted water in advance, i.e., no oxygen removal pretreatment or oxygen removal agent is needed, and the method is simple and easy to implement.

[0027] (2) The alkaline substance and the hydrogen peroxide used in the composition and method of the present disclosure are non-toxic and low in cost.

[0028] (3) The composition and method of the present disclosure are suitable for reducing the corrosiveness of desalted water in a high-temperature closed system.

[0029] Other features and advantages of the present disclosure will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, which together with the detailed description, serve to explain the present disclosure. In the drawings:

[0031] Figure 1 is an XPS spectrum of the test piece after the test in Example 1 of the present disclosure.

[0032] Figure 2 is an XPS spectrum of a brand-new 20# carbon steel standard corrosion test piece. DETAILED DESCRIPTION

[0033] The following detailed description of the present disclosure is provided. It should be understood that the detailed description described herein is merely intended to illustrate and explain the present disclosure, and is not intended to limit the present disclosure.

[0034] The first aspect of the present disclosure provides a composition for reducing the corrosiveness of desalted water in a circulating water system, the composition containing an alkaline substance and hydrogen peroxide; the weight ratio of the content of the alkaline substance and the hydrogen peroxide in the composition is 1:(2-50).

[0035] The composition of the present disclosure can effectively reduce the corrosiveness of desalted water in a circulating water system, without the need for prior removal of dissolved oxygen in the desalted water, and is easy to use.

[0036] In a preferred embodiment of the present disclosure, the weight ratio of the content of the alkaline substance and the hydrogen peroxide in the composition is 1:(3-30), more preferably 1:(5-20). The composition with this composition has a more optimal effect of reducing the corrosiveness of desalted water in a circulating water system.

[0037] According to the present disclosure, the alkaline substance can be known to those skilled in the art, and in an embodiment, the alkaline substance is selected from one or more of an organic base, an inorganic base, and a strong base weak acid salt; preferably, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water; the organic base is selected from one or more of ethanolamine, ethylenediamine, and triethylamine; and the strong base weak acid salt is selected from sodium carbonate and / or sodium bicarbonate.

[0038] The second aspect of the present disclosure provides a method for reducing the corrosiveness of desalted water in a circulating water system, the method comprising: sequentially adding an alkaline substance and hydrogen peroxide to the desalted water.

[0039] The inventors of the present disclosure have surprisingly found that by sequentially adding a basic substance and hydrogen peroxide into desalted water, an oxide film can be formed on the surface of carbon steel and other materials in a circulating water system, thereby effectively reducing the corrosiveness of the desalted water to the circulating water system, and the method does not require prior removal of dissolved oxygen in the desalted water, is simple and easy to implement, and has low cost.

[0040] According to the present disclosure, the amount of the basic substance can be varied within a wide range, and in one specific embodiment, the amount of the basic substance is 5-50 mg, preferably 10-40 mg, and more preferably 20-30 mg, per 1 L of desalted water. Within the above amount range, the amount of the basic substance is suitable to make the method of the present disclosure have a more optimal effect of reducing the corrosiveness of the desalted water.

[0041] According to the present disclosure, the amount of hydrogen peroxide can be varied within a wide range, and in one specific embodiment, the amount of hydrogen peroxide is 100-400 mg, preferably 150-350 mg, and more preferably 200-300 mg, per 1 L of desalted water. Within the above amount range, the amount of hydrogen peroxide is suitable to make the method of the present disclosure have a more optimal effect of reducing the corrosiveness of the desalted water.

[0042] According to the present disclosure, the basic substance can be known to those skilled in the art, and in one embodiment, the basic substance is selected from one or more of inorganic bases, organic bases, and strong base weak acid salts; preferably, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water; the organic base is selected from one or more of ethanolamine, ethylenediamine, and triethylamine; and the strong base weak acid salt is selected from sodium carbonate and / or sodium bicarbonate.

[0043] In one specific embodiment of the present disclosure, the sequential addition of the basic substance and hydrogen peroxide into the desalted water includes sequentially adding the basic substance and the hydrogen peroxide into the desalted water in a closed system at 25-200°C. Preferably, in a closed system at 120-200°C. The method of the present disclosure is more advantageous for forming an oxide film when used in a circulating water system under the above high-temperature closed conditions, and can more effectively reduce the corrosiveness of the desalted water.

[0044] In one specific embodiment of the present disclosure, the pH of the desalted water after the addition of the basic substance and hydrogen peroxide is 8 or higher, and preferably 9-11.

[0045] According to the present disclosure, the method further comprises: after sequentially adding the alkaline substance and the hydrogen peroxide into the desalted water, adding a corrosion inhibitor to further improve the effect of reducing the corrosiveness of the desalted water. The corrosion inhibitor can be known to those skilled in the art, for example, can be selected from one or more of sodium gluconate, citric acid, ascorbic acid and phosphoric acid. In a specific embodiment, the amount of the corrosion inhibitor used is 2-20 mg, preferably 5-10 mg, relative to 1 L of desalted water.

[0046] According to the present disclosure, the method of the present disclosure is particularly suitable for desalted water with a dissolved oxygen concentration of 2-10 mg / L, a pH value of 8-10 and a conductivity of less than 10 μS / cm, and has a good effect of reducing the corrosiveness of the desalted water.

[0047] The present disclosure will be further illustrated by examples below, but the present disclosure is not limited in any way by the examples.

[0048] The desalted water used in all examples and comparative examples is desalted water of the same quality from a certain petrochemical enterprise, with an initial dissolved oxygen concentration of 8 mg / L, a pH value of 8.5 and a conductivity of 6.3 μS / cm. Nitrogen gas is used to blow the desalted water to obtain desalted water with different dissolved oxygen concentrations before the test.

[0049] The corrosion material used in the following examples and comparative examples is a 20# carbon steel standard corrosion test piece, and the carbon steel corrosion rate is calculated by continuous operation for 15 days. According to the standard requirements of Q / SH 0628.2-2014 “Water Management Technical Requirements Part 2: Circulating Water”, the treatment effect of circulating water in chemical enterprises should meet: the carbon steel corrosion rate is ≤0.075 mm / a.

[0050] Example 1

[0051] Before the test, the desalted water is blown by nitrogen gas to have a dissolved oxygen concentration of 4 mg / L, 20 mg / L of sodium hydroxide is added into the desalted water, and after stirring, 200 mg / L of hydrogen peroxide is added into the desalted water. At this time, the pH value of the desalted water is 10.12, the test temperature is 120°C, and the test is started. The test results are shown in Table 1, and the same below.

[0052] At the same time, the test piece after the test of the present example and a brand new 20# carbon steel standard corrosion test piece are subjected to XPS analysis, and the XPS spectra are shown in Figure 1 and Figure 2 The element analysis results show that the content of iron element on the surface of the test piece after treatment is reduced, and the content of oxygen element is increased, which indicates that an oxide film is generated on the surface of the test piece after the treatment by the method of the present disclosure, which protects the carbon steel test piece, thereby effectively reducing the corrosiveness of the desalted water.

[0053] Example 2

[0054] The dissolved oxygen concentration of the desalted water is 8 mg / L without any treatment. The sodium hydroxide is added to the desalted water at a concentration of 30 mg / L, and then the hydrogen peroxide is added to the desalted water at a concentration of 300 mg / L after stirring. At this time, the pH value of the desalted water is 10.34, and the test temperature is 160°C.

[0055] Example 3

[0056] The dissolved oxygen concentration of the desalted water is 6 mg / L by nitrogen blowing before the test. The sodium hydroxide is added to the desalted water at a concentration of 25 mg / L, and then the hydrogen peroxide is added to the desalted water at a concentration of 250 mg / L after stirring. At this time, the pH value of the desalted water is 10.25, and the test temperature is 200°C.

[0057] Example 4

[0058] The dissolved oxygen concentration of the desalted water is 2 mg / L by nitrogen blowing before the test. The sodium hydroxide is added to the desalted water at a concentration of 10 mg / L, and then the hydrogen peroxide is added to the desalted water at a concentration of 150 mg / L after stirring. At this time, the pH value of the desalted water is 9.63, and the test temperature is 40°C.

[0059] Example 5

[0060] The dissolved oxygen concentration of the desalted water is 4 mg / L by nitrogen blowing before the test. The sodium hydroxide is added to the desalted water at a concentration of 40 mg / L, and then the hydrogen peroxide is added to the desalted water at a concentration of 350 mg / L after stirring. At this time, the pH value of the desalted water is 10.39, and the test temperature is 80°C.

[0061] Example 6

[0062] The dissolved oxygen concentration of the desalted water is 4 mg / L by nitrogen blowing before the test. The sodium hydroxide is added to the desalted water at a concentration of 20 mg / L, and then the hydrogen peroxide is added to the desalted water at a concentration of 200 mg / L, and sodium gluconate and citric acid are added to the desalted water at a concentration of 5 mg / L after stirring. At this time, the pH value of the desalted water is 10.07, and the test temperature is 120°C.

[0063] Example 7

[0064] The dissolved oxygen concentration of the desalted water is 4 mg / L by nitrogen blowing before the test. The sodium bicarbonate is added to the desalted water at a concentration of 20 mg / L, and then the hydrogen peroxide is added to the desalted water at a concentration of 200 mg / L after stirring. At this time, the pH value of the desalted water is 9.85, and the test temperature is 120°C.

[0065] Example 8

[0066] The test is carried out by the same method as in Example 1, except that the amount of sodium hydroxide is 35 mg / L, and the amount of hydrogen peroxide is 150 mg / L. The pH value of the desalted water after adding the sodium hydroxide and the hydrogen peroxide is 10.53.

[0067] Example 9

[0068] The test was carried out by using the same method as in Example 1, except that the amount of sodium hydroxide was 50 mg / L and the amount of hydrogen peroxide was 130 mg / L, and the pH value of the desalted water after adding sodium hydroxide and hydrogen peroxide was 10.78.

[0069] Example 10

[0070] The test was carried out by using the same method as in Example 1, except that the test temperature was 100°C.

[0071] Example 11

[0072] The desalted water was purged by nitrogen to make the dissolved oxygen concentration 4 mg / L before the test, and then 10 mg / L of sodium hydroxide was added to the desalted water, and after stirring, 50 mg / L of hydrogen peroxide was added, at which time the pH value of the desalted water was 9.63, and the test temperature was 120°C.

[0073] Example 12

[0074] The desalted water was purged by nitrogen to make the dissolved oxygen concentration 6 mg / L before the test, and then 3 mg / L of sodium hydroxide was added to the desalted water, and after stirring, 150 mg / L of hydrogen peroxide was added, at which time the pH value of the desalted water was 8.67, and the test temperature was 120°C.

[0075] Comparative Example 1

[0076] The desalted water was purged by nitrogen to make the dissolved oxygen concentration 4 mg / L before the test, and then 200 mg / L of hydrogen peroxide was added to the desalted water, and after stirring, 20 mg / L of sodium hydroxide was added, at which time the pH value of the desalted water was 10.10, and the test temperature was 120°C.

[0077] Comparative Example 2

[0078] The desalted water was purged by nitrogen to make the dissolved oxygen concentration 4 mg / L before the test, and then a solution of hydrogen peroxide and sodium hydroxide was added to the desalted water, the concentrations of hydrogen peroxide and sodium hydroxide in the desalted water being 200 mg / L and 20 mg / L, respectively, at which time the pH value of the desalted water was 10.23, and the test temperature was 120°C.

[0079] Comparative Example 3

[0080] (1) 28 parts of sodium silicate was dissolved in 60 parts (40% of the total water) of water, heated to 45°C, and stirred at a speed of 210 rpm for 0.5 h to prepare solution A;

[0081] (2) Weigh 27 parts of trisodium phosphate by mass and dissolve it in 60 parts (40% of the total water volume) of water. Heat the solution to 45°C and stir at 210 rpm for 0.5 h to prepare solution B.

[0082] (3) Weigh 2.5 parts of sodium molybdate and 0.5 parts of benzotriazole according to the mass fraction, dissolve them in the remaining 30 parts of water, and add them to the reaction vessel. Heat the mixture to 50°C and stir at 120 rpm. Then add solution A and solution B at the same time. Weigh 3 parts of polyacrylic acid and 4 parts of triethanolamine according to the mass fraction, continue to keep warm and stir for 1.5 hours. After mixing, let it stand and cool to obtain composite corrosion inhibitor 1#.

[0083] Before the test, the dissolved oxygen concentration of the demineralized water was purged with nitrogen to 2 mg / L. The composite corrosion inhibitor #1 was added to the demineralized water at a concentration of 100 mg / L and the test temperature was 120℃.

[0084] Table 1

[0085]

[0086]

[0087] As can be seen from the above, the compositions and methods disclosed herein can effectively reduce the corrosiveness of demineralized water, and are particularly suitable for reducing the corrosiveness of demineralized water in high-temperature sealing systems.

[0088] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0090] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A composition for reducing the corrosiveness of desalted water in a circulating water system, the composition comprising an alkaline substance and hydrogen peroxide. The weight ratio of the alkaline substance to the hydrogen peroxide in the composition is 1:(2-50).

2. The composition of claim 1, wherein, The weight ratio of the alkaline substance to the hydrogen peroxide in the composition is 1:(3-30), more preferably 1:(5-20).

3. The composition of claim 1, wherein, The alkaline substance is selected from one or more of inorganic bases, organic bases and strong base weak acid salts. Preferably, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water; the organic base is selected from one or more of ethanolamine, ethylenediamine and triethylamine; and the strong base weak acid salt is selected from sodium carbonate and / or sodium bicarbonate.

4. A method for reducing the corrosivity of desalinated water in a recirculating water system, the method comprising: The alkaline substance and the hydrogen peroxide are sequentially added to the desalted water.

5. The method of claim 4, wherein, The amount of the alkaline substance is 5-50 mg, preferably 10-40 mg, more preferably 20-30 mg, and the amount of the hydrogen peroxide is 100-400 mg, preferably 150-350 mg, more preferably 200-300 mg, per 1 L of the desalted water.

6. The method of claim 4, wherein, The alkaline substance is selected from one or more of inorganic bases, organic bases and strong base weak acid salts. Preferably, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water; the organic base is selected from one or more of ethanolamine, ethylenediamine and triethylamine; and the strong base weak acid salt is selected from sodium carbonate and / or sodium bicarbonate.

7. The method of claim 4, wherein, The sequential addition of the alkaline substance and the hydrogen peroxide to the desalted water includes sequentially adding the alkaline substance and the hydrogen peroxide to the desalted water in a closed system at 25-200°C.

8. The method of claim 7, wherein, The sequential addition of the alkaline substance and the hydrogen peroxide to the desalted water includes sequentially adding the alkaline substance and the hydrogen peroxide to the desalted water in a closed system at 120-200°C.

9. The method of claim 4, wherein, The pH of the desalted water after the addition of the alkaline substance and the hydrogen peroxide is 8 or higher, preferably 9-11.

10. The method of claim 4, wherein, The method further comprises adding a corrosion inhibitor after the sequential addition of the alkaline substance and the hydrogen peroxide to the desalted water. The corrosion inhibitor is selected from one or more of sodium gluconate, citric acid, ascorbic acid and phosphoric acid, and the amount of the corrosion inhibitor is 2-20 mg per 1 L of the desalted water.

11. The method of claim 4, wherein, The desalted water has a dissolved oxygen concentration of 2-10 mg / L, a pH of 8-10 and a conductivity of less than 10 μS / cm.

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