JP4378512B2 - Water treatment method and water treatment system for circulating water system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water treatment method and a water treatment system for a circulating water system. More specifically, a water treatment method capable of appropriately managing the water system operating conditions and water quality changes at any time while preventing the corrosion of pipes and other materials used in the circulating water system and the method. The present invention relates to an applied water treatment system.
[0002]
[Prior art]
Industrial water, seawater, lake water, river water, groundwater, etc. are used for process cooling at various steelworks, chemicals, petrochemicals and other factories, thermal power plants, and nuclear power plants, and for air conditioning at schools, hospitals, hotels and other buildings. It is used in large quantities as cooling water. Along with such increased use of cooling water, a cooling water system has been adopted in which a cooling tower is provided to circulate and reuse the water, and further, in order to save water, a highly concentrated operation is performed as much as possible. Is effectively used. Further, even in a system that uses a large amount of industrial water such as papermaking process water as manufacturing process water, the water is circulated as much as possible to save water for effective use.
[0003]
One of the obstacles in these circulating water systems is slime damage. Slime failure is a failure caused by microorganisms in the water, which causes a decrease in heat transfer efficiency in heat exchangers, poor water flow through pipes, etc., or corrosion. An inhibitor is added. As a slime inhibitor in a cooling water system, an oxidized slime inhibitor such as sodium hypochlorite is generally used.
[0004]
On the other hand, corrosion resistant materials such as stainless steel are generally widely used as materials for heat exchangers and piping in cooling water systems. However, in stainless steel, the passive film on the surface is lost at the welded seam, and local corrosion called pitting corrosion is likely to occur due to the anti-slime agent.
This failure causes various problems such as loss of resources and energy, increase in maintenance costs, and production stoppage in the factory, such as reduction in the service life of equipment and piping, breakage and reduction in thermal efficiency.
[0005]
[Problems to be solved by the invention]
In the circulating water system, the natural potential in the system may increase due to the addition of the slime inhibitor. At this time, if the passive film on the surface of piping or the like used in the circulating water system is torn and the chemically active metal surface (active part) is exposed to the circulating water system, the active part and other parts A battery is formed between the metal surface and local corrosion such as pitting corrosion and crevice corrosion is likely to occur in the active portion.
[0006]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a water treatment method and a water treatment system capable of responding to changes in operating conditions and water quality of a circulating water system as needed.
[0007]
[Means for Solving the Problems]
  According to this invention, the circulating water systemAntioxidant and non-oxidizing anti-slime agents are added individually as anti-slime agentsAnti-slime additive addition means,The metal material used in the water system as a sample electrodeA potential measuring means for measuring a natural potential in the system; and a slime measuring means for measuring a slime adhesion state in the system., SuNatural potential measured by potential measuring means when adding anti-slime agent by means of adding lime inhibitorAbout the sample electrodeControl the anti-slime additive so that it does not exceed the potential threshold as the pre-set corrosion gap repassivation potentialWhen the measured natural potential exceeds the potential threshold value and the slime measuring means confirms the adhesion of the slime, the slime inhibitor adding means is controlled and the oxidized slime is added. Add non-oxidizing anti-slime agent instead of inhibitorA water treatment method for a circulating water system is provided.
[0008]
  According to another aspect of the present invention, the circulating water systemAntioxidant and non-oxidizing anti-slime agents are added individually as anti-slime agentsAnti-slime additive addition means,The metal material used in the water system as a sample electrodeA potential measuring means for measuring a natural potential in the system; and a slime measuring means for measuring a slime adhesion state in the system;A control unit, the control unit,When adding the anti-slime agent by the anti-slime agent adding means, the natural potential measured by the electric potential measuring meansAbout the sample electrodeControl the anti-slime additive so that it does not exceed the potential threshold as the pre-set corrosion gap repassivation potentialWhen the measured natural potential exceeds the potential threshold value and the slime measuring means confirms the adhesion of the slime, the slime inhibitor adding means is controlled and the oxidized slime is added. Add non-oxidizing anti-slime agent instead of inhibitorThe water treatment system of the circulating water system characterized by this is provided.
[0009]
In the present invention, corrosion such as pitting corrosion and crevice corrosion occurring in a metal material used in a circulating water system such as circulating cooling water is likely to occur with an aqueous system to which a slime inhibitor is added. Focusing on the electrochemical corrosion that occurs between the piping material and the addition of the slime inhibitor so that the aqueous system does not become an environment in which the electrochemical corrosion occurs.
In this invention, the circulating water system is used for various processes such as steelmaking, chemical, petrochemical, etc., process cooling of thermal power, nuclear power plants, etc., air conditioning of schools, hospitals, hotels and other buildings, and manufacturing processes such as papermaking processes. Examples of the circulating water system used include tap water, industrial water, seawater, lake water, river water, and groundwater.
The metal material used in the circulating water system in this invention means a metal pipe material that forms a flow path for industrial water, specifically, copper, nickel, aluminum, titanium, or an alloy containing these. And stainless steel.
[0010]
A corrosion-resistant film (passive film) is formed on the surface of the metal either naturally or by electric polarization or immersion in a passivating solution. By removing the coating, it means a phenomenon that a chemically active metal surface is obtained. Examples of the treatment that causes such sensitization include heating at a temperature at which the passive film is oxidized or reduced, welding, and the like. On the metal surface subjected to the sensitization treatment, a battery is formed between the active metal surface from which the passive film has been removed and another metal surface, and corrosion such as pitting corrosion is likely to occur.
Among the above stainless steels, SUS304 stainless steel and SUS316 stainless steel, which are generally used as piping materials in the water system, are made of stainless steel by sensitization treatment such as welding that is locally exposed to a high temperature of about 700 ° C. The formed Cr (chromium) is deficient on the surface and becomes a chemically active metal surface.
The solution treatment of the metal material in the present invention is a heat treatment in which the heat-treated alloy is heated to an appropriate temperature that is equal to or higher than the solid solution limit temperature, and the alloy components are sufficiently dissolved, and then rapidly cooled to a supersaturated solid solution state. In the process of producing an alloy such as stainless steel as described above, it means an inevitable heat treatment. By such solution formation, the alloy becomes a solid solution having a mixed phase in which other substances are considered to have dissolved in the crystal phase.
On the metal surface that has undergone solution treatment, the dissolved oxygen is not sufficiently supplied at the contaminated portion or gap portion, so that the potential drops and shifts to the active state. The outside becomes a cathode and crevice corrosion is likely to occur, and if corrosion further progresses, it may lead to a through hole.
[0011]
As a slime inhibitor in this invention, a well-known slime inhibitor can be used. For example, organic nitrogen sulfur such as ozone, chlorine, hypochlorous acid or salts thereof, hydrogen peroxide, chlorine dioxide, radical type active oxygen and other antioxidative slime inhibitors, 3-isothiazolone compounds, S-triazine compounds, etc. Compounds, organic bromine compounds such as 2-bromo-2-nitropropane-1,3-diol, 2,2-dibromo-2-nitroethanol, organic nitrogen compounds such as quaternary ammonium compounds, sodium pyrithione, etc. Non-oxidizing slime inhibitors such as organic sulfur compounds and glutaraldehyde can be applied to the present invention.
[0012]
The natural potential in the present invention means a potential difference between the reference electrode and the sample electrode in water.
The potential measuring means in this invention includes a pitting potential test method based on “Method for measuring pitting corrosion potential of stainless steel” defined in JIS G0577, or “a corrosion clearance repassivation potential for stainless steel defined in JIS G0592. Examples thereof include those used in the repassivation potential test method based on the “measurement method”.
Crevice corrosion is more likely to occur than pitting corrosion. Therefore, especially when using a metal material that has been subjected to solution treatment in advance for the sample electrode, it is used in the repassivation potential test method as the potential measurement means described above. Is preferably adopted.
[0013]
The potential threshold in the present invention means the lower limit of the natural potential at which pitting corrosion or crevice corrosion occurs when the sample electrode is held at a constant potential for a long time. Therefore, in the present invention, it is preferable to control the aqueous potential so as not to exceed a preset potential threshold. However, even if the potential threshold is temporarily exceeded, the natural potential can be reduced in a short time. Since the occurrence of pitting corrosion or crevice corrosion can be prevented by returning to a normal value, the above-described potential threshold can be appropriately set depending on the circulating water system to be applied. In the present invention, the natural potential having the potential threshold is hereinafter referred to as pitting potential and corrosion gap repassivation potential.
By configuring the potential measuring means to measure the natural potential using the metal material used in the circulating water system as a sample electrode, the water system between the water system to which the anti-slime agent is added and the piping material that is susceptible to corrosion is used. Since the environment of electrochemical corrosion generated in the water system is simulated by the potential measuring means, it is possible to perform highly accurate monitoring corresponding to a sudden change in water quality in the water system.
Further, when the sample electrode is composed of two different sample electrodes, one is a metal material subjected to sensitization treatment and the other is a metal material subjected to solution treatment, the electrochemical system in the aqueous system It is possible to quickly and accurately grasp the tendency to shift to an environment in which excessive corrosion occurs.
[0014]
The slime measuring means in this invention includes an optical method for measuring the transmitted light intensity of the test water, a method for measuring the overall heat transfer coefficient of the heat exchanger, a method for measuring the slime volume of the pipe, and the inlet side and outlet of the pipe And a method of measuring the pressure difference on the side.
The slime inhibitor addition means comprises means for adding the oxidized slime inhibitor and the non-oxidized slime inhibitor individually or simultaneously to the circulating water system as the slime inhibitor, and the control unit is configured to control the natural potential in the system and / or Depending on the state of slime adhesion, the anti-slime inhibitor and the non-oxidized slime inhibitor are controlled individually or simultaneously so that the anti-slime additive is added to the circulating water system. Can be quickly suppressed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to the drawings. However, the scope of the present invention is not limited thereby.
FIG. 1 is a schematic view showing an embodiment of a circulating water system water treatment system according to the present invention.
[0016]
As shown in FIG. 1, the water treatment system 10 includes, for example, a water supply pipe 54 extending from the cooling water tank 51 to the heat exchanger 53 via the water supply pump 52, and the heat exchanger 53 to the cooling water tank 51 via the cooling tower 55. The present invention is applied to a circulating water system having a return pipe 56 that returns.
[0017]
This water treatment system 10 includes branch pipes 15, 16, and 17 that are branched from the water feed pipe 54 and arranged in parallel with the water feed pipe 54, and measuring units 1 that have respective sensors interposed in these branch pipes. And a tank 2 for storing the slime inhibitor, a pump 3 for adding the slime inhibitor stored in the tank 2 to the water system, and a control unit 4.
The measurement unit 1 includes sensors of a slime monitor 12, a potential monitor 13, and a residual chlorine concentration measuring instrument 14.
[0018]
As shown in the cross-sectional view of FIG. 2, the slime monitor 12 is interposed between the upstream opening end and the downstream opening end of the branch pipe 15 and has a measurement cell 22 having a rectangular tube-shaped measurement chamber 21 in the center. A light emitting unit 23 and a light receiving unit 24 which are arranged so as to sandwich the measurement cell 22 in a direction perpendicular to the axis of the measurement chamber 21, the openings at both ends of the measurement chamber 21, the upstream open end and the downstream of the branch pipe 15. It consists of nipples 26 and 27 that connect the side open ends.
The measurement cell 22 is formed of a transparent acrylic resin and is accommodated in a case (not shown) for shielding light from the outside.
The light emitting unit 23 includes an incandescent bulb such as a general bulb or a halogen bulb, a fluorescent lamp such as a bulb-type fluorescent lamp, an HID lamp such as a mercury lamp or a metal halide lamp, a semiconductor such as a light emitting diode (LED) or a semiconductor laser. Light emitting element, He-Ne laser or CO₂A gas laser such as a laser, a solid-state laser such as a liquid laser, a YAG laser, or the like is used.
As the light receiving unit 24, a photodiode, a phototransistor, a pin photodetector, an avalanche photodetector, or the like is used.
The slime monitor 12 is substantially the same as the water monitoring device disclosed in the previous application (Japanese Patent Laid-Open No. 2000-185276) filed by the applicant of the present invention, and thus detailed description thereof is omitted.
[0019]
As shown in the schematic diagram of FIG. 3, the potential monitor 13 is electrically connected to an electrode probe 32 having a reference electrode 31, a test tube 35 as a metal sample for corrosion testing, and the electrode probe 32 and the test tube 35. Potential measuring device 39.
[0020]
FIG. 4 is a cross-sectional view showing a state in which the potential monitor 13 is attached to the branch pipe 16.
As shown in FIG. 4, the electrode probe 32 is housed in an insulating resin case 34 so that the reference electrode 31 maintains insulation from the outside and the tip portion is exposed. The resin case 34 passes through the vicinity of the upstream opening end of the branch pipe 16 and is fixed to the branch pipe 16 while maintaining water tightness.
[0021]
The test tube 35 has the same outer diameter as the branch pipe 16, is located between the upstream opening end and the downstream opening end of the branch pipe 16, and the both end openings are in contact with the opening ends of the branch pipe 16. It is accommodated in the sleeve 36. The sleeve 36 has an inner diameter that fits closely to the outer diameter of the branch pipe 16, and covers the branch pipe 16 including the butted portions of the test tube 35 and the branch pipe 16. Both ends of the sleeve 36 and the branch pipe 16 are sealed between the sleeve 36 and the branch pipe 16 (or the test tube 35) according to the materials of the sleeve 36 and the branch pipe 16 in order to maintain watertightness.
[0022]
A part of the sleeve 36 is formed with a through hole 36 a for drawing out the lead wire 37 from the test tube 35. The base end of the lead wire 37 that is electrically connected to the test tube 35 in the through hole 36 a is connected to the sample electrode terminal of the potential measuring device 39. The base end of the reference electrode 31 is connected to the reference electrode terminal of the potential measuring device 39.
[0023]
The residual chlorine concentration measuring instrument 14 has a residual chlorine sensor (not shown) in which a known probe for measuring the residual chlorine amount is interposed in the branch pipe 17.
In addition, as shown in FIG. 1, the valves 61-64 can be arbitrarily arrange | positioned in piping of the measurement part 1 which has the said branch pipes 15-17.
[0024]
FIG. 5 is a block diagram showing the configuration of the water treatment system 10 of the present invention.
The water treatment system 10 includes a control unit 4 including a computer having a CPU, a ROM, a RAM, a timer, and the like.
The control unit 4 includes an interface 41 (for example, an amplifier, an AC, and an AC) that converts output signals from the light receiving unit 24 of the slime monitor 12, the potential measuring device 39 of the potential monitor 13, and the residual chlorine concentration measuring device 14 into predetermined measurement data. A DC / DC converter), an input unit 43 for inputting calculation conditions, calculation programs, and the like, a calculation unit 44 for calculating the calculation conditions and calculation program and the measurement data inputted from the input unit 43, and a liquid crystal display device A display unit 46 including a display device such as a display unit, a storage unit 42 that stores the measurement data and programs as information, and a display control unit 45 that displays information stored in the storage unit 42 on the display unit 46. .
[0025]
The storage unit 42 stores the input data in a writable / readable storage medium (for example, a memory card or a floppy disk).
The calculation unit 44 includes a comparison unit that compares a preset potential threshold value with the measurement result of the natural potential of the water system, and sets transmitted light that is set in advance based on the input calculation conditions and calculation program. The threshold values of the strength and pitting corrosion potential are compared with the measurement results in the water system, and the drive of the pump 3 is controlled based on the comparison results.
[0026]
An example of the water treatment method of the present invention using the water treatment system 10 will be described below based on the operation of the control unit 4.
First, an oil factory having a circulating water system shown in FIG. 1 was selected as a model plant. A test tube 35 was made of the same material as SUS304 stainless steel used as a piping material in the water system of the model plant.
Next, a pitting corrosion potential test (based on the “method for measuring pitting corrosion potential of stainless steel” defined in JIS G0577) is performed using the test tube 35 as a sample electrode. Was measured for the lower limit of the natural potential at which pitting corrosion occurred when held at a constant potential for a long time.
[0027]
For the test tube 35, a SUS304 stainless steel pipe having an outer diameter of 16 mm and a thickness of 1 mm was cut into a length of 100 mm, and subjected to a sensitization treatment at a heating temperature of 700 ° C. This sensitization treatment corresponds to a welded portion of SUS304 stainless steel used in the water system.
[0028]
Next, the measurement unit 1 of FIG. 1 was provided in the water system.
The measuring unit 1 branches branch pipes 15 to 17 made of rigid PVC pipe (outer diameter 16 mm, thickness 1 mm) from the water supply pipe 54, and the sensors (12, 13 and 14) are respectively connected to the branch pipes 15 to 17. Attached.
The potential monitor 13 has a sleeve 36 made of hard PVC covering the branch pipe 16 including the butted portions of both ends of the test tube 35 and the branch pipe 16 over a length of 150 mm, and the sleeve 36 and the branch pipe 16 are mutually connected. The contact surface of was sealed with an adhesive. As the reference electrode 31, an Ag / AgCl electrode was used.
As the potential measuring device 39, an electrometer [model HE-106] manufactured by Hokuto Denko Co., Ltd. was used.
[0029]
First, the circulating water system of FIG. 1 was operated for 130 hours with the valves 61 to 64 of the measuring unit 1 closed and the water treatment system 10 not operating.
Meanwhile, the components contained in the water collected from the water system were analyzed to determine a water treatment agent containing an appropriate slime inhibitor. In this example, 12% sodium hypochlorite from Nankai Chemical Industry was used.
Next, the valves 61 and 62 are opened, the slime monitor 12 is driven to accumulate a large amount of measurement data, and the accumulated measurement data is analyzed to maintain the transmitted light intensity at a predetermined value or higher (for example, 50% or higher). The driving conditions of the pump 3 were found out (this procedure is described in the above-mentioned Japanese Patent Application Laid-Open No. 2000-185276, so the description is omitted).
[0030]
The found driving conditions of the pump 3 and the threshold value of the pitting corrosion potential were input from the input unit 43 and set in the calculation unit 44. Based on the setting, the control unit 4 automatically adds an appropriate amount of water treatment chemical from the tank 2 to the water system based on the transmitted light intensity obtained from the light receiving unit 24 and measures obtained from the potential measuring device 39. When the potential reaches the threshold value of the pitting potential, if the pump 3 is in the driving state, the driving is stopped, and the pump 3 is driven until the measured potential returns to a normal value (below the threshold value of the pitting potential). A program for instructing the pump 3 to be limited is input.
The display unit 46 is configured to display the measured transmitted light intensity and residual chlorine concentration.
[0031]
130 hours after the start of the operation of the water system, the valves 63 and 64 were further opened, and water flow was started to the potential monitor 13 and the residual chlorine concentration measuring device 14. The water treatment chemical was prepared so that the amount of sodium hypochlorite added at the start of addition was 0.5 mg / L (the amount of chlorine was 0.2-1 mg / L). Further, the threshold value of the pitting potential was set to 45 mV vsAg / AgCl.
Changes in measured values of the natural potential, transmitted light intensity, and residual chlorine concentration until 330 hours have passed since the start of water flow are shown in the graphs of FIGS. 6 and 7.
[0032]
As shown in FIG. 6, after 180 hours from the start of operation, the measured values of the natural potential and the residual chlorine concentration temporarily exceeded the threshold value of the pitting potential and reached the danger zone. The natural potential could be immediately returned to the normal value by the control operation of the processing system 10. As a result, it became clear that pitting corrosion of the water-based piping can be prevented in advance. In addition, the natural potential is maintained at a substantially constant value except before and after reaching the danger zone, which indicates that the slime is properly controlled.
Further, as can be seen from FIGS. 6 and 7, in the water system, the measured values of the residual chlorine concentration and the natural potential are correlated by the control operation of the water treatment system 10, and the residual chlorine concentration and the transmitted light intensity are measured. The values are correlated. This is because the measurement of transmitted light intensity by the slime monitor 12 and the measurement of the natural potential by the potential measuring device 39 can prevent pitting corrosion and provide highly accurate slime control under the use of an anti-slime agent containing an oxidizing agent. It shows what is possible.
[0033]
As described above, the water treatment system 10 of the present invention includes the potential measuring device 39 that measures the natural potential using the test tube 35 made of a metal material used for the circulating water system as a sample electrode. The potential measuring device 39 simulates the environment of electrochemical corrosion that occurs between the water system to which the anti-slime agent composed of the agent is added and the piping material that is susceptible to corrosion. Therefore, highly accurate monitoring is possible in response to sudden water quality fluctuations in the water system.
Furthermore, by subjecting the test tube 35 to sensitization in advance, the electrochemical corrosion in the aqueous system can be accelerated, so that the tendency to shift to an environment in which the electrochemical corrosion in the aqueous system occurs is quickly observed. I can grasp it.
[0034]
[Other Embodiments]
In the above-described embodiment, the test tube 35 in which the metal material used in the circulating water system is previously sensitized is used as the sample electrode. However, in this embodiment, the test tube that has been subjected to the sensitizing process described above. The structure which uses 35 and the test tube which performed the solution treatment previously as each sample electrode is demonstrated.
[0035]
FIG. 8 is a diagram schematically showing an embodiment of a water treatment system having test tubes subjected to sensitization treatment and solution treatment.
As shown in FIG. 8, the water treatment system 50 has a potential monitor 18 provided with a test tube 35 subjected to sensitization and a test tube 65 subjected to solution treatment in the circulating water system of FIG. 1, This is a configuration in which a tank 5 for storing a non-oxidizing slime inhibitor and a pump 6 for adding the non-oxidizing slime inhibitor stored in the tank 5 to the aqueous system are added. Other than the above, the description is omitted because it is the same as that described in the above embodiment.
[0036]
9 and 10 are views corresponding to FIG. 3 and showing the arrangement of the sample electrodes in this embodiment.
As shown in FIG. 9, a test tube 35 that has been subjected to sensitization in advance and a test tube 65 that has been subjected to solution treatment in advance can be disposed in series with the branch pipe 16.
Further, as shown in FIG. 10, a test tube 35 that has been subjected to a sensitization process in advance and a test tube 65 that has been subjected to a solution treatment in advance can be disposed in parallel to the branch pipe 16.
[0037]
The test tube 35 subjected to the sensitization process and the potential monitor including the test tube 35 are the same as those described in the above embodiment.
By using this test tube 35 as a sample electrode, the corrosion gap repassivation potential test (based on “Method for measuring the corrosion gap repassivation potential of stainless steel” defined in JIS G0592) is used to remove the sensitizing treatment material. Threshold (E₁), That is, the lower limit value of the natural potential at which crevice corrosion occurs when a sample electrode made of a sensitizing treatment material is held at a constant potential for a long time is measured by one of the potential measuring devices 39 shown in FIGS.
The test tube 65 subjected to the solution treatment was made of SUS304 stainless steel in the same size and shape as the test tube 35 subjected to the sensitization treatment, and the corrosion gap repassivation potential test (as defined in JIS G0592). The threshold of the solution treatment material (E₂) That is, the lower limit value of the natural potential at which crevice corrosion occurs when the test tube 65 made of a solution-treated material is used as a sample electrode and the sample electrode is held at a constant potential for a long time is shown in FIG. 9 and FIG. Measure with the other of the potential measuring device 39.
[0038]
An example of the water treatment method of the present invention using the water treatment system 50 will be described below based on the operation of the control unit 4.
First, the driving conditions of the pump 3 and the pump 6 found in the same manner as in the above embodiment and the threshold value (E₁) And the solution treatment threshold (E₂) Is input from the input unit 43 and set in the calculation unit 44. Based on the setting, the control unit 4 automatically adds an appropriate amount of water treatment chemical from the tank 2 and the tank 5 to the water system based on the transmitted light intensity obtained from the light receiving unit 24, and each potential measuring device 39. A program for instructing each pump so as to limit the driving of the pump 3 and the pump 6 is input based on the measured potential obtained from the above.
Tank 2 contains 12% sodium hypochlorite as an oxidized slime inhibitor, and tank 5 contains 5-chloro-2-methyl-4-isothiazoline-3-one as a non-oxidized slime inhibitor. Each is stored.
[0039]
In the above program, (1) one of each natural potential measured after the start of operation of the water system is E₁And E₂If lower, an oxidation type slime inhibitor is added, and (2) one of the above natural potentials is E₁E higher₂If lower, the injection amount of the oxidation-type slime inhibitor is decreased, and (3) one of the natural potentials is E₂When it is higher, it is set to further lower the injection amount of the oxidation-type slime inhibitor, and the natural potential can be returned to the normal value by this setting.
Further, in (2) and (3), when the slime monitor 12 detects the occurrence of slime after reducing the injection amount of the oxidized slime inhibitor and before the natural potential returns to the normal value, The driving is stopped, and the pump 6 is driven so that the non-oxidized slime inhibitor stored in the tank 5 is added to the water system instead of the oxidized slime inhibitor.
Thereafter, the natural potential returns to a normal value, and when it is determined that the slime has disappeared based on the measured value of the slime monitor 12, the pump 3 is driven to return to the injection of the oxidized slime inhibitor.
[0040]
As described above, the branch pipe 16 is further branched and two potential monitors are installed in series or in parallel. The test tube 35 in one potential monitor is preliminarily sensitized and the test tube in the other potential monitor. 65 is subjected to a solution treatment, and a corrosion gap repassivation potential test (based on “corrosion gap measurement method for stainless steel” stipulated in JIS G0592) using each test tube as a sample electrode. By setting the threshold value, the tendency to shift to an environment where electrochemical corrosion occurs in the water system can be quickly and accurately grasped.
[0041]
【The invention's effect】
  In this invention, the natural potential of the water system is monitored in the circulating water system where the slime inhibitor is used, and the water system piping is used.ToSince the addition of the slime inhibitor is controlled so as not to exceed the potential at which crevice corrosion occurs,NoseCrevice corrosion can be prevented in advance.
  Optimal anti-fouling effect can be obtained by responding to changes in the operating status and water quality of the circulating water system at any time, reducing the service life of equipment and piping in the water system, loss of resources and energy such as damage and reduced thermal efficiency, and maintenance costs In addition to the increase, various problems such as production stoppage in the factory can be solved.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an embodiment of a circulating water treatment system according to the present invention.
FIG. 2 is a cross-sectional view of the slime monitor of FIG.
FIG. 3 is a diagram schematically showing the potential monitor of FIG. 1;
4 is a cross-sectional view showing a detailed configuration of the potential monitor of FIG. 2;
FIG. 5 is a control block diagram of the measurement unit in FIG. 1;
FIG. 6 is a graph showing changes in measured values of natural potential and residual chlorine concentration in a circulating water system to which the water treatment system of the present invention is applied.
FIG. 7 is a graph showing changes in measured values of transmitted light intensity and residual chlorine concentration in a circulating water system to which the water treatment system of the present invention is applied.
FIG. 8 is a diagram schematically showing another embodiment of the water treatment system of the circulating water system according to the present invention.
FIG. 9 is a view corresponding to FIG. 3 and showing a series arrangement of sample electrodes in another embodiment of the present invention.
FIG. 10 is a view corresponding to FIG. 3, showing a parallel arrangement of sample electrodes according to another embodiment of the present invention.
[Explanation of symbols]
1 Measurement unit
2 Anti-slime agent storage tank (medicine addition means)
3 Pump for adding oxidation type slime inhibitor (means for adding slime inhibitor)
4 Control unit
5 Anti-slime agent storage tank (medicine addition means)
6 Pump for adding non-oxidizing anti-slime agent (means for adding anti-slime agent)
10 Water treatment system
12 Slime monitor (slime measuring means)
13 Potential monitor (potential measurement means)
14 Residual chlorine concentration meter
18 Potential monitor (potential measurement means)
35 Test tube (sensitized sample electrode)
50 Water treatment system
65 Test tube (sample electrode subjected to solution treatment)

Claims (13)

Anti- slime agent adding means for individually adding an oxidized anti-slime agent and a non-oxidized anti-slime agent as anti-slime agents to the circulating water system, and a metal material used in the aqueous system as a sample electrode, comprising a potential measuring means for measuring the potential, and a slime measuring means for measuring a slime deposition conditions in the system, when adding slime preventing agent by scan lime inhibitor adding means, the natural potential measured by the potential measuring means The anti-slime additive is added by controlling the slime inhibitor addition means so that the corrosion threshold repassivation potential set in advance for the sample electrode does not exceed the potential threshold, and the measured natural potential is When the potential threshold is exceeded and slime adhesion is confirmed by the slime measuring means, the anti-slime additive adding means is controlled to control the oxidized type slurry. Water treatment method of the circulating water system, which comprises adding a non-oxidative slime preventing agent instead of the beam inhibitor. Anti- slime agent adding means for individually adding an oxidized anti-slime agent and a non-oxidized anti-slime agent as anti-slime agents to the circulating water system, and a metal material used in the aqueous system as a sample electrode, An electric potential measuring means for measuring an electric potential, a slime measuring means for measuring the slime adhesion state in the system, and a control unit, and the control unit measures the electric potential when adding the anti-slime agent by the anti-slime agent adding means. controlling slime preventing agent adding means so that the self-potential measured does not exceed the potential threshold as preset corrosion gap repassivation potential for the sample electrode by means the addition of oxidized slime preventing agent When the measured natural potential exceeds the potential threshold and slime adhesion is confirmed by the slime measuring means, Water treatment system of circulating water system, which comprises adding controlled in place of the oxidized slime preventing agent unoxidized form slime preventing agents. The water treatment system according to claim 2 , wherein the sample electrode is made of at least one metal material that has been subjected to sensitization or solution treatment in advance. The water treatment system according to claim 2 or 3 , wherein the metal material used in the circulating water system is any one of copper, nickel, aluminum, titanium, an alloy containing these, and stainless steel. The water treatment system according to any one of claims 2 to 4 , wherein the control unit includes a comparison unit that compares a preset potential threshold value with a measurement result of the natural potential in the system. Slime measuring means, a cylindrical measuring chamber comprising a part of the flow path of the circulating water system, from a light emitting portion and a light receiving portion Toka Ranaru claim 2 that sandwich the measuring chamber in the flow direction perpendicular Water 5 The water treatment system as described in any one of these. The water treatment system according to claim 2 , wherein the sample electrode is composed of two different sample electrodes, one of which is a metal material subjected to sensitization treatment and the other is a metal material subjected to solution treatment. A potential threshold is set in advance as a corrosion clearance re-immobilization potential for a sample electrode made of a metal material subjected to sensitization treatment and a sample electrode made of a metal material subjected to solution treatment. Anti-slime additive addition means to reduce the amount of oxidized anti-slime additive added when the measured natural potential exceeds the potential threshold set for a sample electrode made of a metal material subjected to sensitization treatment The potential threshold value set for the sample electrode made of a metal material subjected to solution treatment is controlled by the natural potential measured by the potential measuring means in a state where the amount of addition of the oxidation-type slime inhibitor is reduced. The water treatment system according to claim 7, wherein when it exceeds, the slime inhibitor addition means is controlled so as to further reduce the addition amount of the oxidized slime inhibitor. The water treatment method according to claim 1, wherein the sample electrode is made of at least one metal material that has been subjected to sensitization treatment or solution treatment in advance. The water treatment method according to claim 1 or 9, wherein the metal material used in the circulating water system is any one of copper, nickel, aluminum, titanium, an alloy containing these, and stainless steel. 10. The slime measuring means comprises a cylindrical measurement chamber that is a part of the flow path of the circulating water system, and a light emitting portion and a light receiving portion that are arranged with the measurement chamber sandwiched in a direction perpendicular to the flow of water. And the water treatment method according to any one of 10. The water treatment method according to claim 1, wherein the sample electrode is composed of two different sample electrodes, one of which is a metal material subjected to sensitization treatment and the other is a metal material subjected to solution treatment. A potential threshold is set in advance as a corrosion clearance re-immobilization potential for a sample electrode made of a metal material subjected to sensitization treatment and a sample electrode made of a metal material subjected to solution treatment. Anti-slime additive addition means to reduce the amount of oxidized anti-slime additive added when the measured natural potential exceeds the potential threshold set for a sample electrode made of a metal material subjected to sensitization treatment The potential threshold value set for the sample electrode made of a metal material subjected to solution treatment is controlled by the natural potential measured by the potential measuring means in a state where the amount of addition of the oxidation-type slime inhibitor is reduced. The water treatment method according to claim 12, wherein the anti-slime additive adding means is controlled so as to further reduce the addition amount of the oxidation-type anti-slime inhibitor when exceeding the limit.

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