Method for preventing malfunctions in seawater cooling systems

Abstract

This invention provides a method that can suppress damage to seawater cooling systems caused by marine organisms. [Solution] In one aspect, the present disclosure relates to a method for suppressing malfunctions in a seawater cooling system, comprising adding a monochloramine solution and hydrogen peroxide to the seawater of the seawater cooling system, wherein the monochloramine solution is added so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and the method involves allowing monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling system by adding the monochloramine solution and hydrogen peroxide.

Description

Technical Field

[0001] The present disclosure relates to a method for suppressing failures in a seawater cooling water system.

Background Art

[0002] Seawater is widely used as industrial cooling water, especially as cooling water for condensers in thermal power plants and nuclear power plants. Since various organisms inhabit seawater, a large amount of marine biological species such as bivalves like Mytilus edulis, barnacles, hydroids, and scale insects adhere to the walls of seawater intake channels, inside pipes, and inside heat exchangers. As a result, various failures may occur in the seawater cooling water system. For this reason, various countermeasures have been attempted for the purpose of suppressing the adhesion and reproduction of these organisms to the seawater cooling system.

[0003] Patent Document 1 discloses a method for suppressing the adhesion of marine organisms to a seawater cooling water system by adding a monochloramine solution with 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 so that the total residual chlorine concentration of the seawater is 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 coexisting combined halogen and hydrogen peroxide in seawater in order to solve problems such as both agents being consumed and not exerting a sufficient effect in the combined addition method of a hydrogen peroxide agent and a chlorine agent.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 discloses that if the added concentration of monochloramine is less than 0.01 mg / L, the desired effect of suppressing marine organism attachment is not achieved, and if it exceeds 0.15 mg / L, there are concerns about the impact on fishery resources. However, the present inventors have confirmed that even when a monochloramine solution is added to bring the total residual chlorine concentration of seawater to 0.1 mg / L, damage to the seawater cooling water system by barnacles may not be sufficiently suppressed. Therefore, in order to actually suppress damage to the seawater cooling water system using only monochloramine, it is necessary to add a monochloramine solution to a higher concentration. However, as described in Patent Document 1, the safe standard concentration of ammonia nitrogen in seawater is 0.03 mg / L, and if the concentration of monochloramine solution added is high, there are concerns about the impact on fishery resources due to the increase in the ammonia nitrogen concentration in seawater.

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

[0008] This disclosure relates to a method for suppressing malfunctions in a seawater cooling system, comprising adding a monochloramine solution and hydrogen peroxide to the seawater of the seawater cooling system, wherein the monochloramine solution is added so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and the method involves creating a coexistence of monochloramine and hydrogen peroxide in the seawater of the seawater cooling system by adding the monochloramine solution and hydrogen peroxide. [Effects of the Invention]

[0009] According to this disclosure, in one embodiment, it is possible to suppress damage to the seawater cooling system caused by marine organisms without excessively increasing ammonia nitrogen in seawater. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the model waterway used in the example. [Figure 2] Figure 2 is a schematic diagram showing the model waterway used in the example. [Modes for carrying out the invention]

[0011] The present inventors have verified the technology described in Patent Document 1 and have confirmed that, as described above, even when a monochloramine solution is added to seawater so that the total residual chlorine concentration is 0.1 mg / L, the attachment of bivalves and hydroids can be suppressed, but damage to the seawater cooling system caused by barnacles may not be sufficiently suppressed. Specifically, Patent Document 1 discloses that by producing a high-concentration monochloramine solution of 500 mg / L to 10,000 mg / L and adding it to seawater, monochloramine can be stably produced and maintained in the seawater, resulting in a sufficient inhibitory effect on the attachment of marine organisms. However, as a result of the inventor's verification, it was found that even when a high-concentration monochloramine solution is added to seawater, if the concentration of monochloramine added to the seawater (total residual chlorine concentration) is 0.1 mg / L, the attachment of barnacles cannot be sufficiently suppressed.

[0012] The applicant has proposed a method to prevent the attachment of marine organisms to a seawater cooling water system and to prevent corrosion of metal piping present in the seawater cooling water system by adding an effective amount of hydrogen peroxide or hydrogen peroxide supply compound to the presence of ammonium ions at a concentration of 0.1 mg / L to 0.5 mg / L and a chlorine agent or bromine agent at a concentration of 0.7 moles to 1.2 moles per mole of ammonium ions (calculated as available chlorine or bromine), and the attachment of marine organisms to a seawater cooling water system. (Japanese Patent Publication No. 2003-329389). The same document also discloses that the effect of preventing the attachment of marine organisms is not inhibited by the addition of ammonium ions and chlorine agents, and that the effect of preventing the attachment of marine organisms in the examples is equivalent to that of the comparative example in which only hydrogen peroxide was added (paragraph

[0025] ). However, in the examples of the same document, aqueous ammonium chloride solution, aqueous sodium hypochlorite solution, and hydrogen peroxide are directly added to the model water channel in this order. Therefore, if hydrogen peroxide is added before the ammonium ions and hypochlorous acid have reacted sufficiently, it is possible that monochloramine is not produced in sufficient quantities.

[0013] In contrast, the method of this disclosure involves adding a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling system, and adding 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. This method exhibits the excellent effect of suppressing damage to the seawater cooling system caused by barnacles and the attachment of hydroids to the seawater cooling system, even at low concentrations of monochloramine. In one or more embodiments, it is preferable that the amount (concentration) of hydrogen peroxide added can be reduced. Furthermore, the method disclosed herein can suppress damage to the seawater cooling system caused by barnacles and the attachment of hydroids to the seawater cooling system without excessively increasing the ammonia nitrogen in the seawater, by adding a monochloramine solution to the seawater of the seawater cooling system so that the total residual chlorine concentration relative to the seawater is 0.005 mg / L to 0.1 mg / L.

[0014] Therefore, in one aspect, this disclosure relates to a method for suppressing malfunctions in a seawater cooling system, comprising adding a monochloramine solution and hydrogen peroxide to the seawater of the seawater cooling system, wherein the monochloramine solution is added so that the total residual chlorine concentration in the seawater is 0.005 mg / L to 0.1 mg / L, and the method includes allowing monochloramine and hydrogen peroxide to coexist in the seawater of the seawater cooling system by adding the monochloramine solution and hydrogen peroxide.

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

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

[0017] In the present disclosure, "suppressing the failure of the seawater cooling water system" may include, in one or more embodiments, suppressing the growth of marine organisms in the seawater cooling water system and suppressing the adhesion of marine organisms in the seawater cooling water system. Therefore, the method of the present disclosure includes, in one or more embodiments, suppressing the growth of marine organisms in the seawater cooling water system by coexisting monochloramine and hydrogen peroxide in the seawater of the seawater cooling water system. Suppressing the growth of marine organisms in the seawater cooling water system may include, in one or more embodiments, suppressing the growth of barnacles in the seawater cooling water system.

[0018] The "seawater cooling water system" in the present disclosure 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 a facility that forms a flow path through which seawater that can be used or has been used as cooling water circulates. In one or more embodiments, examples include a seawater intake channel, a pipe, a water conduit, a heat exchanger, a condenser, and a drainage channel. The seawater cooling water system may include, in one or more embodiments, the seawater cooling water system in factories such as power plants, steel mills, and petrochemical plants.

[0019] The method of the present disclosure can, in one or more embodiments, suppress the adhesion of barnacles by adding a monochloramine solution to seawater so that the total residual chlorine concentration with respect to seawater becomes 0.005 mg / L to 0.1 mg / L and coexisting monochloramine and hydrogen peroxide in the seawater of the seawater cooling water system.

[0020] In the present disclosure, the "total residual chlorine concentration" refers to the value obtained by combining the residual free chlorine concentration and the residual combined chlorine concentration. 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 in one or more embodiments. In this disclosure, the residual free chlorine concentration refers to the residual free chlorine concentration measured by the DPD method, specifically the chlorine concentration measurement result (mg-Cl2 / L) after 30 seconds using the DPD(Free) reagent, which is a reagent for measuring free chlorine. In this disclosure, the residual bound chlorine concentration 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 said to be 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 such that the concentration of monochloramine in the seawater is such that the total residual chlorine concentration in the seawater is between 0.005 mg / L and 0.1 mg / L, and in one or more embodiments, the method may include adding the monochloramine solution to seawater such that the concentration 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 such that the 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, which are not particularly limited, a high-concentration monochloramine solution may be used. The concentration of the monochloramine solution is not particularly limited, but 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] A monochloramine solution can be prepared in one or more embodiments by mixing a hypochlorite compound and an ammonium compound. Examples of hypochlorite compounds in one or more embodiments include sodium hypochlorite, potassium hypochlorite, and calcium hypochlorite. Examples of ammonium compounds in one or more embodiments include ammonium sulfate, ammonium bromide, ammonium chloride, ammonium sulfamate, ammonium bromide, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium nitrate. These may be used individually or in combination of two or more. The molar ratio of the hypochlorite compound to the ammonium compound is, in one or more embodiments, 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, as the molar ratio of total residual chlorine to nitrogen. Monochloramine solutions can be prepared in one or more embodiments by methods described in Japanese Patent No. 4914146, Japanese Unexamined Patent Publication No. 2017-119245, and Japanese Unexamined Patent Publication No. 2017-53054, etc.

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

[0025] In one or more embodiments, the method of this disclosure may include adding hydrogen peroxide to seawater so that the concentration of hydrogen peroxide in 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 in such a ratio of total residual chlorine to hydrogen peroxide concentrations (total residual chlorine concentration (mg / L): hydrogen peroxide concentration (mg / L)) as 1:1 to 20, 1:1.5 to 15, or 1:2 to 10. In one or more embodiments, the method of this disclosure may include adding hydrogen peroxide to seawater such that the concentration of hydrogen peroxide added to 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 seawater (total residual chlorine concentration).

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

[0028] The order in which the monochloramine solution and hydrogen peroxide are added to the seawater is not particularly limited. 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 locations where monochloramine and hydrogen peroxide are added include the intake channel, piping or water conduits attached to the heat exchanger or condenser, the inlet of the heat exchanger, or the inlet of the condenser. In one or more embodiments, the locations where the monochloramine solution and hydrogen peroxide are added may be the same or different. If the locations where the monochloramine solution and hydrogen peroxide are added are different, the hydrogen peroxide addition location may be upstream or downstream of the monochloramine solution addition location. In one or more embodiments, the addition site may be one location or multiple locations.

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

[0031] This disclosure further relates to one or more embodiments described below. [1] A method for suppressing problems in a seawater cooling system, This involves adding a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling system. The monochloramine solution is added to the seawater so that the total residual chlorine concentration is 0.005 mg / L to 0.1 mg / L. A method comprising adding the monochloramine solution and hydrogen peroxide to the seawater of the seawater cooling system to cause monochloramine and hydrogen peroxide to coexist. [2] The method according to [1], comprising adding hydrogen peroxide to the seawater at a concentration of 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 system by having monochloramine and hydrogen peroxide coexist in the seawater of the seawater cooling 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] The present disclosure will be described in further detail below using examples and comparative examples, but these are illustrative examples and the disclosure is not limited thereto. [Examples]

[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 "Test Methods for Industrial Water". [Method for measuring hydrogen peroxide concentration] The hydrogen peroxide concentration was measured using an enzyme-based 4-aminoantipyrine colorimetric method.

[0034] [Evaluation test using a model waterway 1] A model waterway test apparatus, as shown in Figure 1, was set up at a certain location facing Tokyo Bay, and tests were conducted. Unfiltered seawater (pH 8), pumped up using a submersible pump, was fed into eight branched waterways (test sections) at a flow rate of 1 m³. 3 Water was passed through the channels in a single pass at a rate of / h for 76 days (April to June 2024), and the chemicals listed in Table 1 were added to each channel according to the concentrations in the seawater and the daily addition time shown in Table 1 (Example 1, Comparative Examples 1-6, and Blank). Within each channel (each test section) of the waterway testing apparatus, there are acrylic columns (inner diameter 64 mm x length 300 mm x thickness 2 mm, surface area: 602.88 cm²) for the purpose of investigating attached organisms. 2 A cylindrical shape was created by splitting a column in half to form a semicircle, attaching a 5mm mesh size, 1mm thread diameter vinylon (PVA fiber) mesh to the inner surface of one half, and then reshaping it into a cylinder. After the water flow was completed (after 76 days), the marine organisms attached to the column were measured to evaluate the effectiveness of preventing marine organism attachment. [Monochrome] A high-concentration monochloramine solution was prepared by appropriately diluting commercially available 12% sodium hypochlorite solution and ammonium sulfate aqueous solutions, respectively, using a metering pump, and mixing them in a tube before the drug addition point. This solution was then added to the acrylic column used to confirm the anti-fouling effect, so that the concentration in the seawater (total residual chlorine concentration) and the daily addition time were as shown in Table 1. 〔hydrogen peroxide〕 Hydrogen peroxide was added using a metering pump to an aqueous solution of a commercially available 35% hydrogen peroxide solution, appropriately diluted, before the acrylic column used to confirm the anti-fouling effect, and upstream of the monochloramine addition point, at the concentrations in seawater and the daily addition time shown in Table 1. Monochloramine and hydrogen peroxide were added continuously to 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 to them. If attachment was confirmed, their body length was measured using calipers. Based on the measurement results, each was evaluated as follows: "○" if no attachment was observed, "△" if all attached individuals were 2 mm or less, and "×" if individuals larger than 2 mm were found. (Measurement of hydroid coverage) The hydroid coverage percentage (%) was measured from the recovered column. The hydroid coverage percentage (%) was determined by pressing a 5 mm mesh net against the column after water flow and counting the number of meshes on the covered and uncovered surfaces, based on the column's surface area of ​​602.88 cm². 2 The coverage rate was calculated with the value set to 100%. Based on the calculation results, the following evaluations were made: "○" for coverage rate less than 5%, "△" for coverage rate between 5% and 10%, and "×" for coverage rate greater than 10%. [Table 1]

[0036] In Comparative Example 2, where 0.05 mg / L of monochloramine solution was added, the attachment of barnacles and bivalves was observed. In Comparative Example 5, where 0.18 mg / L of hydrogen peroxide was added, the attachment of barnacles, bivalves, and hydroids was observed. In contrast, no attachment of barnacles, bivalves, or hydroids was observed in Example 1.

[0037] [Evaluation test using a model waterway 2] A model waterway test apparatus, as shown in Figure 2, was set up at a certain location in Wakayama Prefecture, and tests were conducted. Unfiltered seawater (pH 8), pumped up using a submersible pump, was fed into six separate waterways (test sections) at a flow rate of 1 m³. 3 Water was passed through the channels in a single pass at a rate of / h for 83 days (July to October 2024), and the chemicals listed in Table 2 were added to each channel according to the concentrations in the seawater and the daily addition time shown in Table 2 (Example 2, Comparative Examples 7-10, and Blank). Within each channel (each test section) of the waterway testing apparatus, there are acrylic columns (inner diameter 64 mm x length 300 mm x thickness 2 mm, surface area: 602.88 cm²) for the purpose of investigating attached organisms.2 A cylindrical shape was created by splitting a column in half to form a semicircle, attaching a 5mm mesh size, 1mm thread diameter vinylon (PVA fiber) mesh to the inner surface of one half, and then reshaping it into a cylinder. After the water flow was completed (after 83 days), the marine organisms attached to the column were measured to evaluate the effectiveness of preventing marine organism attachment. Monochloramine and hydrogen peroxide were added continuously to the daily addition times shown in Table 2. The evaluation was conducted in the same manner as in the above [Evaluation Test 1 using a Model Channel]. The results are shown in Table 2 below.

[0038] [Table 2]

[0039] The sea area and timing of the tests differed between [Evaluation Test 2 using a Model Channel] and [Evaluation Test 1 using a Model Channel]. However, in Example 2, similar to Example 1, no attachment of barnacles, bivalves, or hydroids was observed. On the other hand, in Comparative Example 8, where 0.15 mg / L of monochloramine solution was added, barnacle attachment was confirmed, and in Comparative Example 10, where 0.35 mg / L of hydrogen peroxide was added, attachment of barnacles, bivalves, and hydroids was confirmed.

Claims

1. A method for suppressing problems in a seawater cooling system, This involves adding a monochloramine solution and hydrogen peroxide to seawater in a seawater cooling system. The monochloramine solution is added to the seawater so that the total residual chlorine concentration is between 0.005 mg / L and 0.1 mg / L. A method comprising adding the monochloramine solution and hydrogen peroxide to the seawater of the seawater cooling system to cause monochloramine and hydrogen peroxide to coexist.

2. The method according to claim 1, comprising adding hydrogen peroxide to the seawater so that its concentration is between 0.1 mg / L and 2 mg / L.

3. The method according to claim 1, comprising suppressing the growth of marine organisms in the seawater cooling system by coexisting monochloramine and hydrogen peroxide in the seawater of the seawater cooling system.

4. The method according to any one of claims 1 to 3, comprising adding the monochloramine solution and the hydrogen peroxide for 12 hours or more per day.

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