Method for preventing damage to seawater cooling systems

Abstract

A method is provided that can suppress damage to a seawater cooling water system caused by marine organisms. [Solution] In one aspect, the present disclosure relates to a method for suppressing damage to a seawater cooling water system, the method comprising adding a monochloramine solution and hydrogen peroxide to seawater in the seawater cooling water system, adding the monochloramine solution so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and causing monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system by adding the monochloramine solution and hydrogen peroxide.

Description

[Technical Field]

[0001] The present disclosure relates to a method for inhibiting failure of a seawater cooling water system. [Background technology]

[0002] Seawater is used in large quantities as industrial cooling water, particularly for the condensers of thermal and nuclear power plants. Because seawater is home to a variety of organisms, large numbers of marine organisms, such as bivalves (e.g., mussels), barnacles, hydrozoans, and bryozoans, adhere to the walls and piping of seawater intake channels and heat exchangers, sometimes causing various problems in seawater cooling systems. Therefore, various countermeasures have been attempted to prevent the adhesion and proliferation of these organisms in seawater cooling systems.

[0003] Patent Document 1 discloses a method for suppressing the attachment of marine organisms to a seawater cooling water system by adding a monochloramine solution having a total residual chlorine concentration of 500 mg / L or more and 10,000 mg / L or less to the seawater in the seawater cooling water system, thereby adjusting the total residual chlorine concentration of the seawater to a concentration of 0.01 mg / L or more and 0.15 mg / L or less.

[0004] Patent Document 2 discloses a method for suppressing the adhesion of marine organisms to a seawater cooling water system by allowing bound halogen and hydrogen peroxide to coexist in seawater, in order to solve the problem that the combined addition of hydrogen peroxide and chlorine agents results in the consumption of both agents and insufficient effect. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6584948 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-058405 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 discloses that if the monochloramine concentration is less than 0.01 mg / L, the desired effect of inhibiting the adhesion of marine organisms is not achieved, and that if the monochloramine concentration exceeds 0.15 mg / L, there are concerns about the impact on marine resources. However, the present inventors have confirmed that even if a monochloramine solution is added so that the total residual chlorine concentration in seawater is 0.1 mg / L, damage to seawater cooling water systems caused by barnacles may not be sufficiently inhibited. Therefore, in order to actually inhibit damage to seawater cooling water systems using monochloramine alone, it is necessary to add a monochloramine solution at a higher concentration. However, as described in Patent Document 1, the safety standard concentration of ammonia nitrogen in seawater is 0.03 mg / L, and if the monochloramine solution is added at a high concentration, there are concerns that the increased ammonia nitrogen concentration in seawater may have an impact on marine resources.

[0007] In one aspect, the present disclosure provides a method capable of suppressing damage to seawater cooling water systems caused by marine organisms without excessively increasing ammonia nitrogen in seawater. [Means for solving the problem]

[0008] In one aspect, the present disclosure relates to a method for suppressing damage to a seawater cooling water system, the method comprising adding a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling water system, the monochloramine solution being added so that a total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and the addition of the monochloramine solution and hydrogen peroxide causes monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, damage to seawater cooling water systems caused by marine organisms can be suppressed without excessively increasing ammonia nitrogen in seawater. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the model waterway used in the examples. [Figure 2] FIG. 2 is a schematic diagram showing the model waterway used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The inventors have verified the technology described in Patent Document 1 and have confirmed that, as described above, even if a monochloramine solution is added to seawater so that the total residual chlorine concentration becomes 0.1 mg / L, the adhesion of bivalves and hydrozoans can be suppressed, but damage to seawater cooling systems caused by barnacles may not be sufficiently suppressed in some cases. Specifically, Patent Document 1 discloses that by producing a high-concentration monochloramine solution of 500 mg / L to 10,000 mg / L and adding this to seawater, monochloramine can be stably produced and maintained in the seawater, resulting in a sufficient effect of inhibiting the adhesion of marine organisms. However, as a result of testing by the present inventors, it was found that even when a high-concentration monochloramine solution was added to seawater, barnacle adhesion could not be sufficiently inhibited when the concentration of monochloramine added to the seawater (total residual chlorine concentration) was 0.1 mg / L.

[0012] The present applicant has proposed a method for preventing the adhesion of marine organisms to a seawater cooling water system and preventing corrosion of metal piping in the system by adding an effective amount of hydrogen peroxide or a hydrogen peroxide-supplying compound to prevent adhesion of marine organisms in the presence of ammonium ions at a concentration of 0.1 mg / L to 0.5 mg / L and a chlorine or bromine agent at a concentration of 0.7 to 1.2 moles, calculated as available chlorine or bromine per mole of ammonium ions (JP 2003-329389 A). This document also discloses that the addition of ammonium ions and a chlorine agent does not impair the effectiveness of preventing adhesion of marine organisms, and that the effectiveness of the examples in preventing adhesion of marine organisms is equivalent to that of a comparative example in which only hydrogen peroxide was added (paragraph

[0025] ). However, in the examples in this document, an ammonium chloride solution, a sodium hypochlorite solution, and hydrogen peroxide are directly added to a model waterway in that order. Therefore, if hydrogen peroxide is added before the ammonium ions and hypochlorous acid have sufficiently reacted, there is a possibility that monochloramine is not sufficiently produced.

[0013] In contrast, the method of the present disclosure adds a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling water system, and adds the monochloramine solution so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, thereby allowing monochloramine and hydrogen peroxide to coexist in the seawater, thereby achieving the excellent effect of suppressing damage to the seawater cooling water system caused by barnacles and the adhesion of hydrozoans to the seawater cooling water system, even with a low concentration of monochloramine, and in one or more embodiments, can preferably achieve the effect of being able to reduce the amount of hydrogen peroxide added (addition concentration). Furthermore, the method of the present disclosure can suppress damage to the seawater cooling water system caused by barnacles and adhesion of hydrozoans to the seawater cooling water system, without excessively increasing the ammonia nitrogen in the seawater, by adding a monochloramine solution to the seawater in the seawater cooling water system so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L.

[0014] Therefore, in one aspect, the present disclosure relates to a method for suppressing damage to a seawater cooling water system, the method comprising adding a monochloramine solution and hydrogen peroxide to seawater in the seawater cooling water system, the monochloramine solution being added so that a total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and the addition of the monochloramine solution and hydrogen peroxide causes monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system.

[0015] In this disclosure, "monochloramine" refers to a compound represented by NH2Cl (a compound in which one of the hydrogen atoms of ammonia is replaced with a chlorine atom). - +NH4 + →It is produced by reactions such as NH2Cl+H2O.

[0016] In this disclosure, "causing monochloramine and hydrogen peroxide to coexist in seawater of a seawater cooling water system" refers to causing monochloramine and hydrogen peroxide to coexist in seawater of a seawater cooling water system. Furthermore, when monochloramine is added to seawater, chloride ions and / or hydrogen ions in the monochloramine (NH2Cl) may be replaced with bromide ions in the seawater to produce monobromoamine (NH2Br) and / or monobromochloramine (NHBrCl). Therefore, in this disclosure, "causing monochloramine and hydrogen peroxide to coexist in seawater of a seawater cooling water system" may include causing monobromoamine (NH2Br) and / or monobromochloramine (NHBrCl) to coexist in seawater of a seawater cooling water system with hydrogen peroxide, which may be produced by adding monochloramine to seawater.

[0017] In one or more embodiments, "suppressing damage to a seawater cooling water system" in the present disclosure may include suppressing the growth of marine organisms in the seawater cooling water system and suppressing the attachment of marine organisms in the seawater cooling water system. Thus, in one or more embodiments, the method of the present disclosure includes suppressing the growth of marine organisms in the seawater cooling water system by causing monochloramine and hydrogen peroxide to coexist in seawater of the seawater cooling water system. In one or more embodiments, suppressing the growth of marine organisms in a seawater cooling water system includes suppressing the growth of barnacles in the seawater cooling water system.

[0018] In the present disclosure, a "seawater cooling water system" refers to a water system that uses seawater as cooling water. The seawater cooling water system is not particularly limited as long as it is equipment that forms a flow path through which seawater that can be used or has been used as cooling water flows, and in one or more embodiments, examples of the seawater cooling water system include a seawater intake channel, piping, a water conduit, a heat exchanger, a condenser, and a drainage channel. In one or more embodiments, examples of the seawater cooling water system include seawater cooling water systems in factories such as power plants, steel mills, and petrochemical plants.

[0019] In one or more embodiments, the method of the present disclosure can suppress the attachment of barnacles by adding a monochloramine solution to seawater so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and allowing the monochloramine and hydrogen peroxide to coexist in the seawater of a seawater cooling water system.

[0020] In the present disclosure, the "total residual chlorine concentration" refers to the combined value of the residual free chlorine concentration and the residual combined chlorine concentration. In one or more embodiments, the total residual chlorine concentration, residual free chlorine concentration, and residual combined chlorine concentration in seawater can be measured by the diethyl-p-phenylenediamine (DPD) method. The residual free chlorine concentration in this disclosure refers to the residual free chlorine concentration measured by the DPD method, and refers to the chlorine concentration measurement result (mg-Cl2 / L) after 30 seconds using the DPD (Free) reagent, which is a reagent for measuring free chlorine. The residual combined chlorine concentration in this disclosure refers to the value obtained by subtracting the chlorine concentration measurement result (mg-Cl2 / L) after 30 seconds using the DPD (Free) reagent, which is a reagent for measuring free chlorine, from the chlorine concentration measurement result (mg-Cl2 / L) after 120 seconds using the DPD (Total) reagent, which is a reagent for measuring total chlorine. Therefore, the total residual chlorine concentration in this disclosure can also be referred to as the chlorine concentration measurement result (mg-Cl2 / L) after 120 seconds using the DPD (Total) reagent, which is a reagent for measuring total chlorine.

[0021] The method of the present disclosure includes adding a monochloramine solution to seawater so that the monochloramine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and in one or more embodiments, may include adding the monochloramine solution to seawater so that the total residual chlorine concentration in the seawater is 0.01 mg / L or more, 0.015 mg / L or more, 0.02 mg / L or more, or 0.025 mg / L or more. Furthermore, in one or more embodiments, the method of the present disclosure may include adding the monochloramine solution to seawater so that the monochloramine concentration is 0.09 mg / L or less, 0.08 mg / L or less, 0.07 mg / L or less, or 0.06 mg / L or less.

[0022] In one or more embodiments, the monochloramine solution may be a high-concentration monochloramine solution, although the concentration of the monochloramine solution is not particularly limited. In one or more embodiments, the total residual chlorine concentration is 400 mg / L to 8000 mg / L, 700 mg / L to 7000 mg / L, or 800 mg / L to 6000 mg / L.

[0023] In one or more embodiments, the monochloramine solution can be prepared by mixing a hypochlorous acid compound and an ammonium compound. Examples of hypochlorous acid compounds include sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite. Examples of ammonium compounds include ammonium sulfate, ammonium bromide, ammonium chloride, ammonium sulfamate, ammonium bromide, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium nitrate. These compounds may be used alone or in combination of two or more. In one or more embodiments, the molar ratio of the hypochlorous acid compound to the ammonium compound is 1:1 to 1:2, 1:1.1 to 1:2, 1:1.2 to 1:2, 1:1.2 to 1:1.6, 1:1.2 to 1:1.5, or 1:1.2 to 1:1.4, expressed as the molar ratio of the total residual chlorine amount to nitrogen. In one or more embodiments, the monochloramine solution can be prepared by the methods described in Japanese Patent No. 4914146, Japanese Patent Application Laid-Open No. 2017-119245, Japanese Patent Application Laid-Open No. 2017-53054, etc.

[0024] In one or more embodiments, the monochloramine solution may be prepared by using a 5% by mass to 15% by mass aqueous solution of sodium hypochlorite and ammonium sulfate, and mixing these appropriately diluted aqueous solutions.

[0025] In one or more embodiments, the method of the present disclosure may include adding hydrogen peroxide to seawater so that the concentration of hydrogen peroxide in the seawater is 0.1 mg / L to 2 mg / L. In one or more embodiments, the concentration of hydrogen peroxide is 0.12 mg / L or more, 0.14 mg / L or more, 0.15 mg / L or more, 0.16 mg / L or more, or 0.17 mg / L or more, or 1.5 mg / L or less, 1.2 mg / L or less, 0.8 mg / L or less, 0.7 mg / mL or less, 0.6 mg / mL or less, 0.5 mg / mL or less, 0.4 mg / mL or less, or 0.35 mg / mL or less.

[0026] In one or more embodiments, the method of the present disclosure may include adding a monochloramine solution and hydrogen peroxide to seawater so that the ratio of the concentrations of total residual chlorine to hydrogen peroxide (total residual chlorine concentration (mg / L):hydrogen peroxide concentration (mg / L)) is 1:1 to 20, 1:1.5 to 15, or 1:2 to 10. In one or more embodiments, the method of the present disclosure may include adding hydrogen peroxide to seawater so that the concentration of hydrogen peroxide added to the seawater is 1 or more, 1.5 or more, 2 or more, 2.5 or more, or 3 or more times the concentration of monochloramine solution added to the seawater (total residual chlorine concentration).

[0027] In one or more embodiments, the daily addition time of the monochloramine solution and hydrogen peroxide is 12 hours or more and 24 hours or less, and preferably 14 hours or more, 16 hours or more, 18 hours or more, or 20 hours or more. In one or more embodiments, the addition of the monochloramine solution and hydrogen peroxide may be continuous or intermittent.

[0028] The order in which the monochloramine solution and hydrogen peroxide are added to seawater is not particularly limited, and in one or more embodiments, they may be added simultaneously, or hydrogen peroxide may be added after the addition of the monochloramine solution has begun, or the monochloramine solution may be added after the addition of hydrogen peroxide has begun.

[0029] In one or more embodiments, the location where the monochloramine and hydrogen peroxide are added may be a water intake channel, a piping or water conduit attached to a heat exchanger or condenser, an inlet of a heat exchanger, or an inlet of a condenser. In one or more embodiments, the locations where the monochloramine solution and hydrogen peroxide are added may be the same or different. When the monochloramine solution and hydrogen peroxide are added at different locations, the location where the hydrogen peroxide is added may be upstream or downstream of the location where the monochloramine solution is added. In one or more embodiments, the addition location may be one location or multiple locations.

[0030] The concentrations of monochloramine and hydrogen peroxide in the methods of the present disclosure can be measured by known methods.

[0031] The present disclosure further relates to one or more of the following embodiments. [1] A method for suppressing damage to a seawater cooling water system, comprising: adding a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling water system; The monochloramine solution is added so that the total residual chlorine concentration in the seawater becomes 0.005 mg / L to 0.1 mg / L, adding the monochloramine solution and hydrogen peroxide to cause monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system. [2] The method according to [1], which comprises adding hydrogen peroxide to the seawater so that the concentration of hydrogen peroxide becomes 0.1 mg / L to 2 mg / L. [3] The method according to [1] or [2], comprising suppressing the growth of marine organisms in the seawater cooling water system by allowing monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system. [4] The method according to any one of [1] to [3], comprising adding the monochloramine solution and the hydrogen peroxide for 12 hours or more per day.

[0032] Hereinafter, the present disclosure will be described in more detail using examples and comparative examples, but these are merely illustrative and the present disclosure is not limited to these. [Example]

[0033] [Method for measuring total residual chlorine concentration] The total residual chlorine concentration was measured using the diethyl-p-phenylenediamine (DPD) colorimetric method described in JIS K0101 "Testing methods for industrial water." [Method for measuring hydrogen peroxide concentration] The hydrogen peroxide concentration was measured by the enzymatic 4-aminoantipyrine colorimetric method.

[0034] [Evaluation test using a model waterway 1] The model waterway test equipment shown in Figure 1 was set up at a location facing Tokyo Bay, and tests were conducted. Unfiltered seawater (pH 8) was pumped using a submersible pump and fed into eight branched waterways (test areas) at a flow rate of 1 m3. 3 The water was passed through the channels at a flow rate of 100 / h for 76 days (April to June 2024), and the chemicals listed in Table 1 were added to each channel at the concentrations in seawater and for the daily addition times shown in Table 1 (Example 1, Comparative Examples 1 to 6, and blank). In each water channel (each test area) of the water channel test device, an acrylic column (inner diameter 64 mm x length 300 mm x thickness 2 mm, surface area: 602.88 cm) was installed for the investigation of attached organisms. 2 The column was cut in half to form a semicircle, and a mesh made of vinylon (PVA fiber) with a mesh size of 5 mm and a thread diameter of 1 mm was attached to the inner surface of one half, and then reshaped into a cylinder. After the water flow had stopped (76 days later), the marine organisms attached to the column were measured to evaluate its effectiveness in preventing the attachment of marine organisms. [Monochloramine] A highly concentrated monochloramine solution was prepared by using a metering pump to deliver appropriately diluted aqueous solutions of commercially available 12% sodium hypochlorite solution and ammonium sulfate, and mixing them in a tube just before the chemical addition point. The monochloramine solution was then added just before the acrylic column used to confirm the anti-adhesion effect, so as to achieve the concentration in seawater (total residual chlorine concentration) and daily addition time shown in Table 1. 〔hydrogen peroxide〕 Hydrogen peroxide was prepared by diluting a commercially available 35% hydrogen peroxide solution appropriately. The solution was added using a metering pump to the acrylic column used to confirm the adhesion prevention effect, upstream of the monochloramine addition point, so as to achieve the concentration in seawater and the daily addition time shown in Table 1. Monochloramine and hydrogen peroxide were added continuously for the daily addition times shown in Table 1.

[0035] [evaluation] (measurement of barnacles and bivalves) The collected columns were visually inspected for the presence or absence of barnacles and bivalves attached, and if attachment was confirmed, their body length was measured using a vernier caliper. The measurement results were evaluated as follows: "Good" if no attachment was observed, "Good" if all attached individuals were 2 mm or less, and "Poor" if attachment of individuals over 2 mm was observed. (Measuring the coverage of hydrozoans) The coverage rate (%) of hydroids was measured from the recovered column. After the water flow was completed, a 5 mm mesh net was pressed against the column, and the number of meshes on the coated and uncoated sides was counted. The coverage rate (%) of hydroids was measured based on the surface area of ​​the column (602.88 cm). 2 The coverage was calculated with the coverage being 100%. The calculation results were evaluated as follows: a coverage of less than 5% was evaluated as "Good", a coverage of 5 to 10% was evaluated as "Good", and a coverage of more than 10% was evaluated as "Poor". [Table 1]

[0036] In Comparative Example 2, where 0.05 mg / L of monochloramine solution was added, attachment of barnacles and bivalves was confirmed, and in Comparative Example 5, where 0.18 mg / L of hydrogen peroxide was added, attachment of barnacles, bivalves, and hydroids was confirmed. In contrast, in Example 1, attachment of barnacles, bivalves, and hydroids was not observed.

[0037] [Evaluation test 2 using a model waterway] A model waterway test device shown in Figure 2 was set up at a location in Wakayama Prefecture, and tests were conducted. Unfiltered seawater (pH 8) was pumped using a submersible pump into six branched waterways (test areas) at a flow rate of 1 m 3 Water was passed through the channels at a flow rate of 100 / h for 83 days (July to October 2024), and the chemicals listed in Table 2 were added to each channel at the concentrations in seawater and addition times per day shown in Table 2 (Example 2, Comparative Examples 7 to 10, and blank). In each water channel (each test area) of the water channel test device, an acrylic column (inner diameter 64 mm x length 300 mm x thickness 2 mm, surface area: 602.88 cm) was installed for the investigation of attached organisms.2 The column was cut in half to form a semicircle, and a mesh made of vinylon (PVA fiber) with a mesh size of 5 mm and a thread diameter of 1 mm was attached to the inner surface of one half, and then reshaped into a cylinder. After the water flow had stopped (83 days later), the marine organisms attached to the column were measured to evaluate its effectiveness in preventing the attachment of marine organisms. Monochloramine and hydrogen peroxide were added continuously for the daily addition times shown in Table 2. The evaluation was carried out in the same manner as in [Evaluation test 1 using a model waterway] above. The results are shown in Table 2 below.

[0038] [Table 2]

[0039] The sea area and time period in which the tests were conducted are different between [Evaluation Test 2 Using a Model Waterway] and [Evaluation Test 1 Using a Model Waterway]. However, in Example 2, as in Example 1, no attachment of barnacles, bivalves, or hydroids was observed. On the other hand, in Comparative Example 8, in which 0.15 mg / L of monochloramine solution was added, attachment of barnacles was confirmed, and in Comparative Example 10, in which 0.35 mg / L of hydrogen peroxide was added, attachment of barnacles, bivalves, and hydroids was confirmed.

Claims

1. A method for suppressing damage to a seawater cooling water system, comprising: adding a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling water system; The monochloramine solution is added to the seawater so that the total residual chlorine concentration in the seawater becomes 0.005 mg / L to 0.1 mg / L, Add hydrogen peroxide to the seawater so that the concentration is 0.1 mg / L to 2 mg / L; adding the monochloramine solution and hydrogen peroxide to cause monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system.

2. 2. The method of claim 1, comprising inhibiting the growth of marine organisms in the seawater cooling water system by providing monochloramine and hydrogen peroxide in seawater in the seawater cooling water system.

3. 2. The method according to claim 1, comprising preventing barnacle adhesion in the seawater cooling water system by causing monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling water system.

4. 4. The method of claim 1, further comprising adding the monochloramine solution and the hydrogen peroxide for at least 12 hours per day.

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