Method and device for controlling ph in closed cooling water system

Abstract

To provide a method and device for controlling pH in a closed cooling water system, capable of lowering the pH of closed cooling water with an elevated pH without replacing the water and increasing corrosive ions.SOLUTION: Water is supplied to a refrigerator 4 by a circulation pump 1 and pipes 2 and 3, and cold water from the refrigerator 4 is supplied to an air conditioner 7 by pipes 5 and 6 to cool the air around the air conditioner 7. The water whose temperature has been raised by the air conditioner 7 returns to the circulation pump 1 through a pipe 8. The pipe 6 is provided with a pH meter 12 and an addition device 13 for adding carbon dioxide gas. The pH meter 12 is disposed downstream of the addition device 13. The detection signal of the pH meter 12 is input to a controller 14. When the pH detected by the pH meter 12 is higher than a predetermined value, carbon dioxide gas is added from the addition device 13 into the pipe 6 in response to a control signal from the controller 14, thereby lowering the pH.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for controlling the pH of a closed cooling water system. [Background technology]

[0002] In a sealed cooling water system, the cooling water is circulated in a sealed state without any open parts to the atmosphere. This generally has the advantage that the cooling water (circulating water) is less likely to become dirty than in an open cooling water system, and maintenance frequency is reduced.

[0003] Methods for inhibiting corrosion of metallic materials in closed circulation cooling water systems, particularly iron, which is the main material, include those that utilize oxidation or precipitation type corrosion protection films and those that rely on deoxidation.

[0004] Corrosion inhibition methods using oxide films include those using at least one of nitrous acid, molybdic acid, tungstic acid, and their alkaline salts in combination with an alkali metal hydrogen carbonate (Patent Document 1). Corrosion inhibition methods using precipitation films include those using phosphates or zinc salts, and corrosion inhibition methods using deoxidation include those using hydrazine.

[0005] Patent Document 2 describes a method for inhibiting corrosion in a closed cooling water system, which comprises adding (a) one or more selected from the group consisting of erythorbic acid, ascorbic acid, and salts thereof, and (b) an alkali metal carbonate and / or an alkali metal hydrogen carbonate to a closed cooling water system equipped with iron-based and copper-based components. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 119788 [Patent Document 2] JP 2015-203121 A Summary of the Invention [Problem to be solved by the invention]

[0007] Even if the above-mentioned corrosion inhibitors are added, the pH of the closed cooling water system may increase, causing corrosion of metal components.

[0008] The causes of pH rise in closed cooling water systems are roughly divided into two categories. One is alkali (OH) caused by metal corrosion. - The other is the increase in pH due to the production of nitrite (NO2 - This is due to the gradual production of alkali when using a nitrile-based corrosion inhibitor.

[0009] If the pH of a closed cooling water system exceeds 10, the corrosion rate of metal components such as copper and iron will increase, shortening the equipment's lifespan, and the eluted metal ions will turn into sludge and clog the water system, reducing the cooling efficiency.

[0010] In closed cooling water systems, acid injection is one way to lower the pH level when it rises. However, when hydrochloric acid or sulfuric acid is injected, there is a problem that the increase in chloride ions and sulfate ions increases corrosiveness, so there are few examples of this being implemented.

[0011] Water replacement is often used as a measure to lower pH, but this has issues such as an increase in the amount of wastewater and the waste of cooling energy required to cool the replaced water back down to low temperature.

[0012] The present invention aims to provide a method and device for controlling pH in a closed cooling water system, which can lower the pH of closed cooling water with an elevated pH without replacing the water and without increasing corrosive ions. [Means for solving the problem]

[0013] The pH control method for a closed cooling water system of the present invention is a pH control method for a closed cooling water system for controlling the pH of the closed cooling water system, characterized in that when the pH of the closed cooling water system becomes higher than a predetermined value, at least one of carbon dioxide gas and carbonated water is added to the closed cooling water system.

[0014] In one embodiment of the method of the present invention, at least a part of the water-contacting members of the closed cooling water system is made of an iron-based or copper-based metal member.

[0015] In one embodiment of the method of the present invention, the sealed cooling water system includes a cooling means for cooling water to produce cold water, a heat exchange section through which cold water flows, a first water supply pipe for supplying the cold water from the cooling means to the heat exchange section, and a second water supply pipe for supplying water from the heat exchange section to the cooling means, and at least one of carbon dioxide gas and carbonated water is added to the water flowing through the first water supply pipe or the second water supply pipe.

[0016] In one aspect of the method of the present invention, at least one of the carbon dioxide gas and carbonated water is added to the water flowing through the first water supply pipe.

[0017] The pH control device for a closed cooling water system of the present invention has a means for measuring the pH of the closed cooling water system, and an addition means for adding at least one of carbon dioxide gas and carbonated water to the closed cooling water system when the detected pH of the measurement means becomes higher than a predetermined value.

[0018] In one embodiment of the device of the present invention, at least a part of the water-contacting members of the closed cooling water system is made of an iron-based or copper-based metal member.

[0019] In one embodiment of the device of the present invention, the sealed cooling water system includes a cooling means for cooling water to produce cold water, a heat exchange section through which cold water passes, a first water supply pipe for supplying the cold water from the cooling means to the heat exchange section, and a second water supply pipe for supplying water from the heat exchange section to the cooling means, and the adding means is provided in the first water supply pipe or the second water supply pipe.

[0020] In one aspect of the device of the present invention, the adding means is provided on the first water supply pipe. Effect of the Invention

[0021] According to the method and device for controlling pH in a closed cooling water system of the present invention, when the pH of the closed cooling water system becomes higher than a predetermined value, at least one of carbon dioxide gas and carbonated water is added to the closed cooling water system to lower the pH of the closed cooling water system. As a result, even if at least a part of the water-contacting members of the closed cooling water system is made of a metal member such as an iron-based, copper-based, or zinc-based member, the corrosion of the metal member is suppressed, and the equipment life is extended. In addition, the eluted metal ions are prevented from forming sludge and clogging the water system, improving the cooling efficiency.

[0022] In the present invention, at least one of carbon dioxide gas and carbonated water is used to lower the pH of the closed cooling water system, so that chloride ions and sulfate ions in the closed cooling water system do not increase, and thus there is no increase in corrosiveness due to these ions.

[0023] In the present invention, there is no need to replace the water in order to lower the pH of the closed cooling water system, so there is no increase in the amount of water used or discharged, and no cooling energy is required to convert the replaced water into low-temperature water. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a configuration diagram of a closed cooling water system for explaining a first embodiment. [Diagram 2] FIG. 11 is a configuration diagram of a closed cooling water system for explaining a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the drawings. Note that the embodiment described below is an example of a typical embodiment of the present invention, and the scope of the present invention should not be interpreted narrowly based on this embodiment.

[0026] Fig. 1 is a configuration diagram of a closed cooling water system for explaining a first embodiment. The closed cooling water system of this embodiment is not particularly limited as long as the equipment includes iron-based and copper-based members. Examples of such a closed cooling water system include a general factory reactor system, a steelworks cooling water system, a power generation or marine engine cooling water system, a general factory cooling water system, and a power plant bearing cooling water system.

[0027] In this closed cooling water system, water is sent to a chiller 4 via a circulation pump 1 and pipes 2 and 3, and cold water from the chiller 4 is sent to an air conditioner 7 via pipes 5 and 6 to cool the air around the air conditioner 7. The water heated in the air conditioner 7 returns to the circulation pump 1 via pipe 8.

[0028] In this embodiment, a bypass line consisting of a pipe 9, a bypass valve 10, and a pipe 11 is provided to bypass the chiller 4. The upstream end of the pipe 9 is connected to the connection point of the pipes 2 and 3, and the downstream end of the pipe 11 is connected to the connection point of the pipes 5 and 6. By opening the bypass valve 10, a part of the water from the circulating pump 1 flows through the bypass line. Note that a flow rate control valve is provided in the pipe 3 or 5, and by opening the bypass valve 10 and controlling the aperture of the flow rate control valve, the amount of water sent from the pump 1 to the chiller 4 can be controlled.

[0029] However, this bypass line may be omitted, and the amount of water sent to the refrigerator 4 may be controlled by controlling the circulation pump 1.

[0030] In this embodiment, the pipe 6 is provided with a pH meter 12 and an addition means 13 for adding carbon dioxide gas. The pH meter 12 is disposed downstream of the addition means 13. A detection signal from the pH meter 12 is input to a controller 14. When the detected pH by the pH meter 12 is higher than a predetermined value, carbon dioxide gas is added from the addition device 13 to the pipe 6 in response to a control signal from the controller 14. The added gas dissolves in the water in the pipe 6, thereby lowering the pH of the water. When the detected pH by the pH meter falls below the predetermined value, the addition of carbon dioxide gas from the addition device 13 is stopped.

[0031] The above-mentioned predetermined value is preferably 5 or more, particularly 6 or more, especially 7 or more, and 11 or less, particularly 10 or less, especially 9 or less at 25°C.

[0032] The pH measurement may be performed continuously or periodically at intervals, preferably at least 0.5 days, particularly at least 1 day, and more preferably at least 7 days, and at most 90 days, particularly preferably at most 60 days, and more preferably at most 30 days.

[0033] In this closed cooling water system, when the pH detected by the pH meter 12 becomes higher than a predetermined value, carbon dioxide gas is added to the closed cooling water system to keep the pH of the closed cooling water system at a predetermined value. This prevents corrosion of the metal members even if at least a part of the water-contacting members of the closed cooling water system is made of a metal member such as iron, copper, or zinc. This extends the life of the equipment. In addition, the eluted metal ions are prevented from forming sludge and clogging the water system, improving the cooling efficiency.

[0034] In this embodiment, the iron-based members include iron alloy members containing iron, such as carbon steel, in addition to iron members. The copper-based members include copper alloy members containing copper, such as brass, in addition to copper members. Specific parts in a closed cooling water system as the iron-based and copper-based members are not particularly limited, and examples thereof include pumps, piping, refrigerators, air conditioners, valves, and other machine parts.

[0035] In this embodiment, carbon dioxide gas is used to lower the pH of the closed cooling water system, so that chloride ions and sulfate ions in the closed cooling water system do not increase, and thus there is no increase in corrosiveness due to these.

[0036] In this embodiment, there is no need to replace the water to lower the pH of the closed cooling water system, so there is no increase in the amount of wastewater, and no cooling energy is required to turn the replaced water into low-temperature water.

[0037] In this embodiment, carbon dioxide gas is added to the low-temperature water from the refrigerator 4, so that the carbon dioxide gas dissolves efficiently in the water.

[0038] In the embodiment of FIG. 1, the pH meter 12 and the additive device 13 are provided in the pipe 6, but the pH meter 12 and the additive device 13 may be provided in the pipe 8. In the embodiment of FIG. 2, a branch / junction pipe 15 is provided which branches off from the pipe 6 and joins the pipe 6, and the pH meter 12 and the additive device 13 are provided in this branch / junction pipe 15. However, a branch / junction pipe 15 is provided which branches off from the pipe 8 and joins the pipe 8, and the pH meter 12 and the additive device 13 may be provided in this branch / junction pipe 15. The other configurations of FIG. 2 are the same as those of FIG. 1, and the same reference numerals denote the same parts. The embodiment of FIG. 2 also provides the same functions and effects as those of FIG. 1.

[0039] In each of the above embodiments, carbon dioxide gas is supplied as the adding device 13, but carbon dioxide gas may be added by dissolving it in the water of a closed cooling water system using a gas-permeable membrane that does not allow water to pass through but allows gas to pass through.

[0040] Also, carbon dioxide gas may be dissolved in water to produce carbonated water, which may then be added to the closed cooling water system. Both the carbon dioxide gas adding means and the carbonated water adding means may be provided.

[0041] 1 and 2, the refrigerator 4 is used, but a cooling heat exchanger may be used. Also, instead of the air conditioner 7, a heat exchanger other than an air conditioner may be used. [Explanation of symbols]

[0042] 1 Circulation pump 4. Refrigeration Machine 7 Air conditioner 12 pH meter 13 Addition equipment 14 Controller

Claims

1. A method for controlling the pH of a closed cooling water system, comprising: The method for controlling pH of a closed cooling water system includes adding at least one of carbon dioxide gas and carbonated water to the closed cooling water system when the pH of the closed cooling water system becomes higher than a predetermined value.

2. 2. The method for controlling pH in a closed cooling water system according to claim 1, wherein at least a part of said water-contacting members of said closed cooling water system is made of an iron-based or copper-based metal member.

3. The closed cooling water system comprises: A cooling means for cooling water to produce cold water; a heat exchange section through which cold water passes; a first water supply pipe for supplying cold water from the cooling means to the heat exchange section; a second water supply pipe for supplying water from the heat exchange unit to the cooling means; It has 3. The method for controlling pH in a closed cooling water system according to claim 1 or 2, further comprising the step of adding at least one of carbon dioxide gas and carbonated water to the water flowing through the first water supply pipe or the second water supply pipe.

4. 4. The method for controlling pH of a closed cooling water system according to claim 3, further comprising the step of adding at least one of carbon dioxide gas and carbonated water to the water flowing through the first water supply pipe.

5. A means for measuring the pH of a closed cooling water system; an adding means for adding at least one of carbon dioxide gas and carbonated water to the closed cooling water system when the detected pH value of the measuring means becomes higher than a predetermined value; A pH control device for a closed cooling water system having

6. 6. A pH control device for a closed cooling water system according to claim 5, wherein at least a part of said water-contacting members of said closed cooling water system is made of an iron-based or copper-based metal member.

7. The closed cooling water system comprises: A cooling means for cooling water to produce cold water; a heat exchange section through which cold water passes; a first water supply pipe for supplying cold water from the cooling means to the heat exchange section; a second water supply pipe for supplying water from the heat exchange unit to the cooling means; It has 7. A pH control device for a closed cooling water system according to claim 5 or 6, wherein the adding means is provided in the first water supply pipe or the second water supply pipe.

8. 8. The pH control device for a closed cooling water system according to claim 7, wherein said adding means is provided in said first water supply pipe.

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