JP2004113981A - Water treatment method and water treatment system for circulating water system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water treatment method and water treatment system capable of dealing with any time the operating condition of a circulating water system and the water quality thereof. <P>SOLUTION: The water treatment system is characterized by being provided with a slime preventive agent adding means for adding a slime preventive agent to the circulating water system, a potential measuring means for measuring the spontaneous potential of the water system, and a control section for controlling the slime preventive agent adding means in such a manner that the spontaneous potential measured by the potential measuring value does not exceed the potential threshold preset in accordance with this when the slime preventive agent is added to the slime by the slime preventive agent adding means according to the slime deposition condition measured by the slime measuring means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circulating water water treatment method and a water treatment system. More specifically, a water treatment method and a water treatment method that can perform appropriate management at any time in response to changes in the operating conditions and water quality of the water system while preventing corrosion of materials such as piping used in the circulating water system. The applied water treatment system.
[0002]
[Prior art]
Industrial water, seawater, lake water, river water, groundwater, etc. are used for process cooling in factories, thermal power plants, nuclear power plants, etc. for steelmaking, chemicals, petrochemicals, etc., and for air conditioning in schools, hospitals, hotels and other buildings. It is used in large quantities as cooling water. Along with such an increase in the use of cooling water, a cooling tower is provided to provide a cooling tower to circulate and reuse water, and to save water, a cooling water system that performs a high concentration operation as much as possible is adopted. Is being used effectively. Further, even in a system that uses a large amount of industrial water such as papermaking process water as the production process water, the water is circulated as much as possible to save water, and the water is effectively used.
[0003]
One of the obstacles in these circulating water systems is slime disorders. Slime damage is caused by microorganisms in the water, which causes a decrease in heat transfer efficiency in the heat exchanger, poor water flow in pipes, or corrosion. An inhibitor has been added. As the slime inhibitor in the 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 pipes in a cooling water system. However, in stainless steel, the passivation film on the surface of the welded joint is lost, and local corrosion called pitting corrosion is easily caused by the slime inhibitor.
This obstruction causes various problems, such as a loss of resources and energy, an increase in maintenance costs, and a stoppage of production in a factory, such as a reduction in the service life of equipment and piping, breakage and a decrease in thermal efficiency.
[0005]
[Problems to be solved by the invention]
In the above circulating water system, the natural potential in the system may increase due to the addition of the slime inhibitor. At this time, if the passivation film on the surface of a pipe or the like used in the circulating water system is broken and the chemically active metal surface (active portion) is exposed to the circulating water system, the active portion and other active portions are exposed. A battery is formed between the battery and the metal surface, and local corrosion such as pitting 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 a change in the operating state of the circulating water system and water quality at any time.
[0007]
[Means for Solving the Problems]
According to the present invention, a slime inhibitor adding means for adding a slime inhibitor to the circulating water system, a potential measuring means for measuring a spontaneous potential in the system, and a slime measuring means for measuring a slime adhesion state in the system. When the slime inhibitor is added by the slime inhibitor adding means based on the slime adhesion state measured by the slime measuring means, a potential threshold set in advance based on the spontaneous potential measured by the potential measuring means. A water treatment method for a circulating water system is provided, wherein the means for adding a slime inhibitor is controlled so as not to exceed the value.
[0008]
According to another aspect of the present invention, a slime inhibitor adding means for adding a slime inhibitor to a circulating water system, a potential measuring means for measuring a spontaneous potential in the system, and a slime adhesion state in the system are measured. A slime measuring means and a potential preset based on the spontaneous potential measured by the potential measuring means when adding the slime preventing agent by the slime preventing agent adding means according to the slime adhesion state measured by the slime measuring means. A control section for controlling the slime inhibitor adding means so as not to exceed the threshold value.
[0009]
The present invention relates to pitting corrosion and crevice corrosion occurring in metal materials used in a circulating water system such as a circulating cooling water, and corrosion such as crevice corrosion is easily generated with a water system to which a slime inhibitor is added. The present invention focuses on electrochemical corrosion occurring between piping materials and controls the addition of a slime inhibitor so that the aqueous system does not provide an environment in which the electrochemical corrosion occurs.
The circulating water system in the present invention is used for processes such as steel mills, chemicals, petrochemicals, and various other factories and thermal power plants, nuclear power plants, etc., air conditioning of schools, hospitals, hotels, and other buildings, and manufacturing processes such as papermaking processes. The circulating water system used includes tap water, industrial water, seawater, lake water, river water, and groundwater.
The metal material used in the circulating water system in the present invention means a metal piping material forming a flow path of industrial water, specifically, copper, nickel, aluminum, titanium or an alloy containing these. , Stainless steel and the like.
[0010]
On the surface of the metal, a corrosion-resistant film (passive film) is formed naturally or by immersion in an electric polarization or passivation solution. It means a phenomenon that the removal of the coating results in a chemically active metal surface. 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 passivation 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 a sensitization treatment such as welding locally exposed to a high temperature of about 700 ° C. Cr (chromium) to be formed is depleted on the surface, resulting in a chemically active metal surface.
The solution treatment of the metal material in the present invention is a heat treatment in which a heat-treated alloy is heated to an appropriate temperature equal to or higher than the solid solution limit temperature to sufficiently dissolve the alloy components, and then rapidly cooled to a supersaturated solid solution state, that is, This means an unavoidable heat treatment in the process of manufacturing an alloy such as stainless steel described above. By such solution, the alloy becomes a solid solution having a mixed phase in which another substance is considered to be dissolved in the crystal phase.
On the solution-treated metal surface, the dissolved oxygen is not sufficiently supplied in the contaminated areas and gaps, so the potential drops and the state shifts to the active state. Outside becomes a cathode, and crevice corrosion is apt to occur, and further corrosion may lead to through holes.
[0011]
As the slime inhibitor in the present invention, a known slime inhibitor can be used. For example, oxidized slime inhibitors such as ozone, chlorine, hypochlorous acid or salts thereof, hydrogen peroxide, chlorine dioxide, radical active oxygen, and organic nitrogen sulfur such as 3-isothiazolone-based compounds and S-triazine-based compounds. Compounds, organic bromo 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 self potential in the present invention means a potential difference between a reference electrode and a sample electrode in water.
As the potential measuring means in the present invention, the pitting potential test method based on the “method for measuring pitting potential of stainless steel” specified in JIS G0577, or the “corrosion crevice re-passivation potential of stainless steel” specified in JIS G0592 Used for the re-passivation potential test method based on the "measurement method".
Since crevice corrosion is more likely to occur than pitting corrosion, particularly when using a metal material that has been subjected to a solution treatment beforehand as a sample electrode, the one used in the re-passivation potential test method as the above potential measurement means It is preferred to employ
[0013]
The potential threshold value in the present invention means a lower limit value of a natural potential at which pitting or crevice corrosion occurs when a sample electrode is held at a constant potential for a long time. Therefore, in the present invention, it is preferable to control the potential of the aqueous system so as not to exceed the preset potential threshold. Is returned to the normal value, thereby preventing the occurrence of pitting corrosion and crevice corrosion. Therefore, the above potential threshold can be appropriately set depending on the circulating water system to be applied. In the present invention, the spontaneous potential having the above potential threshold is hereinafter referred to as a pitting potential and a corrosion crevice re-passivation potential.
The potential measuring means is configured to measure a spontaneous potential using a metal material used in the circulating water system as a sample electrode, so that the water system to which the slime inhibitor is added and the piping material that is likely to corrode are used. Since the environment of electrochemical corrosion occurring in the water system is simulated by the potential measuring means, highly accurate monitoring can be performed in response to a sudden change in water quality in the water system.
Further, when the sample electrode is composed of two different sample electrodes, one of which is a metal material subjected to a sensitization treatment and the other is a metal material subjected to a solution treatment, the electrochemical The tendency to shift to an environment where severe corrosion occurs can be grasped quickly and with high accuracy.
[0014]
As the slime measuring means in the present invention, there are 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, an inlet and an outlet of the pipe. And a method of measuring the pressure difference on the side.
The means for adding a slime inhibitor comprises means for adding an oxidized slime inhibitor and a non-oxidized slime inhibitor individually or simultaneously to the circulating water system as a slime inhibitor, and the control unit comprises a natural potential and / or Depending on the slime adhesion status, the slime inhibitor addition means is controlled so that the oxidized slime inhibitor and the non-oxidized slime inhibitor are separately or simultaneously added to the circulating water system. Can be suppressed promptly.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, but the scope of the present invention is not limited thereby.
FIG. 1 is a schematic view showing one embodiment of a circulating water treatment system of the present invention.
[0016]
As shown in FIG. 1, the water treatment system 10 includes, for example, a water supply pipe 54 from a cooling water tank 51 to a heat exchanger 53 via a water supply pump 52, and a cooling water tank 51 from the heat exchanger 53 via a cooling tower 55. The present invention is applied to a circulating water system having a return pipe 56 for returning.
[0017]
The water treatment system 10 includes branch pipes 15, 16, 17, each of which is branched from a water supply pipe 54 and arranged in parallel with the water supply pipe 54, and a measuring unit 1 having respective sensors provided in these branch pipes. And a tank 2 for storing a slime inhibitor, a pump 3 for adding the slime inhibitor stored in the tank 2 to the water system, and a controller 4.
The measurement unit 1 has sensors of a slime monitor 12, a potential monitor 13, and a residual chlorine concentration measuring device 14.
[0018]
As shown in the cross-sectional view of FIG. 2, the slime monitor 12 is provided between the upstream open end and the downstream open end of the branch pipe 15, and has a square measurement chamber 21 at the center. A light-emitting unit 23 and a light-receiving unit 24 that are opposed to each other so as to sandwich the measurement cell 22 in a direction perpendicular to the axis of the measurement chamber 21, the respective openings at both ends of the measurement chamber 21, the upstream opening end of the branch pipe 15, and the downstream. Nipples 26 and 27 connecting the side opening ends.
The measurement cell 22 is formed of a transparent acrylic resin, and is housed in a case (not shown) for shielding light from the outside.
The light emitting section 23 includes an incandescent lamp such as a general light bulb or a halogen lamp, a fluorescent lamp such as a bulb-type fluorescent lamp, an HID lamp such as a mercury lamp or a metal halide lamp, and a semiconductor such as a light emitting diode (LED) or a semiconductor laser. Light emitting device, He-Ne laser or CO₂A gas laser such as a laser, a liquid laser, a solid-state laser such as 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 earlier application of the present applicant (Japanese Patent Application Laid-Open No. 2000-185276), and a detailed description thereof will be 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 a corrosion test, and the electrode probe 32 and the test tube 35. And a potential measuring device 39.
[0020]
FIG. 4 is a cross-sectional view showing a state where 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 such that the reference electrode 31 retains insulation from the outside and the distal end is exposed. The resin case 34 penetrates the vicinity of the upstream opening end of the branch pipe 16 and is fixed to the branch pipe 16 while maintaining watertightness.
[0021]
The test tube 35 has the same outer diameter as the branch pipe 16, is located between the upstream open end and the downstream open end of the branch pipe 16, and has both ends opened against the above-mentioned open ends of the branch pipe 16. It is housed in a sleeve 36. The sleeve 36 has an inside diameter that closely fits the outside diameter of the branch tube 16, and covers the branch tube 16 including the abutting portions of the test tube 35 and the branch tube 16. Both ends of the sleeve 36 and the branch pipe 16 are sealed according to the respective materials of the sleeve 36 and the branch pipe 16 (or the test tube 35) in order to maintain water tightness.
[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 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. Further, a base end of the reference electrode 31 is connected to a reference electrode terminal of the potential measuring device 39.
[0023]
The residual chlorine concentration measuring device 14 has a residual chlorine sensor (not shown) in which a known probe for measuring the residual chlorine amount is provided in the branch pipe 17.
In addition, as shown in FIG. 1, valves 61 to 64 can be arbitrarily arranged in the piping of the measuring section 1 having the branch pipes 15 to 17 described above.
[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 has a control unit 4 including a computer having a CPU, a ROM, a RAM, a timer, and the like.
The control unit 4 converts an output signal from the light receiving unit 24 of the slime monitor 12, the potential measuring device 39 of the potential monitor 13 and the output signal from the residual chlorine concentration measuring device 14 into predetermined measurement data. / DC converter, etc.), an input unit 43 for inputting calculation conditions, a calculation program, and the like; a calculation unit 44 for calculating the calculation conditions, the calculation program, and the measurement data input from the input unit 43; And the like, a storage unit 42 for storing the measurement data, the program, and the like as information, and a display control unit 45 for displaying the 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 has a comparison unit that compares a preset potential threshold value with the measurement result of the natural potential of the water system, and based on the input calculation conditions and calculation program, sets the transmitted light The threshold values of the strength and the pitting potential are compared with the measurement results of the water system, and the driving 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 this model plant.
Next, a pitting potential test (based on the “method for measuring pitting potential of stainless steel” specified in JIS G0577) is performed using the test tube 35 as a sample electrode, and the threshold value of the pitting potential, that is, the sample electrode is measured. Was held at a constant potential for a long time, and the lower limit of the spontaneous potential at which pitting occurred was measured.
[0027]
The test tube 35 was obtained by cutting a SUS304 stainless steel pipe having an outer diameter of 16 mm and a thickness of 1 mm into a length of 100 mm, and performing a sensitization treatment at a heating temperature of 700 ° C. This sensitization treatment corresponds to the welded portion of SUS304 stainless steel used in the water system.
[0028]
Next, the measuring unit 1 of FIG. 1 was provided in the water system.
The measuring unit 1 branches branch pipes 15 to 17 formed of hard PVC pipes (outside diameter 16 mm, thickness 1 mm) from the water supply pipe 54, and attaches the sensors (12, 13 and 14) to the respective branch pipes 15 to 17 respectively. Attached.
The potential monitor 13 shows that the sleeve 36 made of hard PVC covers the branch tube 16 including the abutting portions of both ends of the test tube 35 and the branch tube 16 over a length of 150 mm, and the sleeve 36 and the branch tube 16 are connected to each other. Was sealed with an adhesive. An Ag / AgCl electrode was used as the reference electrode 31.
As the potential measuring device 39, an electrometer [model HE-106] manufactured by Hokuto Denko KK 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.
In the meantime, the components contained in the water collected from the water system were analyzed to determine the water treatment agent containing an appropriate slime inhibitor. In this example, 12% sodium hypochlorite of Nankai Chemical Industry Co., Ltd. was used.
Next, the valves 61 and 62 are opened, the slime monitor 12 is driven to accumulate a large number of measurement data, and the accumulated measurement data is analyzed to maintain the transmitted light intensity at a predetermined value or more (for example, 50% or more). (This procedure is described in the above-mentioned Japanese Patent Application Laid-Open No. 2000-185276, and the description is omitted).
[0030]
The found driving conditions of the pump 3 and the threshold value of the pitting potential were input from the input unit 43 and set in the calculation unit 44. According to the setting, the control unit 4 automatically adds an appropriate amount of the 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 the measurement 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 the normal value (below the threshold value of the pitting potential). A program for instructing the pump 3 to limit the pressure was 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 to the potential monitor 13 and the residual chlorine concentration measuring device 14 was started. The water treatment agent was prepared so that the amount of sodium hypochlorite added at the start of the addition was 0.5 mg / L (the amount of chlorine was 0.2 to 1 mg / L). The threshold value of the pitting potential was set at 45 mV vs Ag / AgCl.
The graphs of FIG. 6 and FIG. 7 show 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 passage.
[0032]
As shown in FIG. 6, after a lapse of 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 a dangerous area. By the control operation of the processing system 10, the natural potential could be immediately returned to the normal value. Thereby, it became clear that pitting corrosion of the water system piping could be prevented beforehand. Except before and after the dangerous area is reached, the spontaneous potential changes at a substantially constant value, which indicates that the slime is being properly controlled.
Further, as can be seen from FIGS. 6 and 7, in the water system, due to the control operation of the water treatment system 10, each measurement value of the residual chlorine concentration and the self potential is correlated, and each measurement of the residual chlorine concentration and the transmitted light intensity is performed. The values are correlated. This is because the measurement of the transmitted light intensity by the slime monitor 12 and the measurement of the spontaneous potential by the potential measuring device 39 enable the prevention of pitting corrosion and the highly accurate slime control under the use of the slime inhibitor containing the oxidizing agent. Indicates what is possible.
[0033]
As described above, the water treatment system 10 of the present invention is provided with the potential measuring device 39 for measuring the natural potential using the test tube 35 made of a metal material used for the circulating water system as a sample electrode. An electrochemical corrosion environment generated between a water system to which a slime inhibitor made of a chemical agent is added and a piping material in which corrosion is likely to occur is simulated by the potential measuring device 39. Therefore, highly accurate monitoring can be performed in response to sudden fluctuations in water quality in the water system.
Further, by subjecting the test tube 35 to a sensitization process in advance, the electrochemical corrosion in the aqueous system can be accelerated. Therefore, the tendency to shift to an environment in which electrochemical corrosion occurs in the aqueous system is promptly reduced. I can figure it out.
[0034]
[Other embodiments]
In the above-described embodiment, the test tube 35 in which the metal material used for the circulating water system has been subjected to the sensitization treatment in advance is used as the sample electrode. In this embodiment, the test tube in which the above-described sensitization treatment has been performed is used. A configuration in which 35 and a test tube that has been subjected to a solution treatment in advance are used as respective sample electrodes will be described.
[0035]
FIG. 8 is a diagram schematically showing an embodiment of a water treatment system having test tubes subjected to a sensitization treatment and a solution treatment.
As shown in FIG. 8, the water treatment system 50 attaches the potential monitor 18 having the test tube 35 subjected to the sensitization treatment and the test tube 65 subjected to the solution treatment to the circulating water system in FIG. A tank 5 for storing a non-oxidizing slime inhibitor and a pump 6 for adding the non-oxidizing slime preventing agent stored in the tank 5 to the water system are added. Except for the above, the configuration is the same as that described in the above embodiment, and thus the description is omitted.
[0036]
9 and 10 are views corresponding to FIG. 3 and show the arrangement of the sample electrodes in this embodiment.
As shown in FIG. 9, 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 arranged in series with the branch tube 16.
Further, as shown in FIG. 10, a test tube 35 which has been subjected to a sensitization process in advance and a test tube 65 which has been subjected to a solution treatment in advance can be arranged in parallel to the branch pipe 16.
[0037]
The test tube 35 subjected to the sensitization process and the potential monitor provided with the test tube 35 are the same as those described in the above embodiment.
Using this test tube 35 as a sample electrode, a corrosion clearance re-passivation potential test (based on “method for measuring corrosion clearance re-passivation potential of stainless steel” specified in JIS G0592) is performed to remove the sensitized material. Threshold (E₁),That is, the lower limit of the natural potential at which crevice corrosion occurs when the sample electrode made of the sensitizing material is held at a constant potential for a long time is measured by one of the potential measuring devices 39 shown in FIGS. 9 and 10.
The test tube 65 subjected to the solution treatment is made of SUS304 stainless steel in the same size and shape as the test tube 35 subjected to the sensitization treatment, and subjected to a re-passivation test for corrosion crevice (specified by JIS G0592). The method for measuring the re-passivation potential of the corrosion clearance of stainless steel ”).₂9) and 10) show the lower limit of the natural potential at which crevice corrosion occurs when this sample electrode is held at a constant potential for a long time using a test tube 65 made of a solution treatment material as a sample electrode. The potential is measured by the other of the potential measuring instruments 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 pumps 3 and 6 found in the same manner as in the above embodiment and the threshold value (E₁) And the solution treatment material threshold (E₂) Is input from the input unit 43 and set in the calculation unit 44. According to the setting, the control unit 4 automatically adds an appropriate amount of the 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 controls each potential measuring device 39. A program for instructing each pump to limit the driving of the pump 3 and the pump 6 based on the measured potential obtained from is input.
The tank 2 contains 12% sodium hypochlorite as an oxidized slime inhibitor, and the tank 5 contains 5-chloro-2-methyl-4-isothiazolin-3-one as a non-oxidized slime inhibitor. Each is stored.
[0039]
The above program is based on (1) one of the respective self-potentials measured after the start of operation of the water system.₁And E₂If it is lower, an oxidized slime inhibitor is added, and (2) one of the above natural potentials is E₁Higher E₂If it is lower, the injection amount of the oxidized slime inhibitor is reduced, and (3) one of the above-mentioned natural potentials is E.₂When it is higher, the injection amount of the oxidized slime inhibitor is set to be further reduced, and the natural potential can be returned to a normal value by this setting.
Further, in (2) and (3), after the injection amount of the oxidized slime inhibitor was reduced and before the slime monitor 12 detected the generation of slime before the natural potential returned to the normal value, the pump 3 was turned on. The driving is stopped, and the pump 6 is driven so that the non-oxidizing slime inhibitor stored in the tank 5 is added to the water system instead of the oxidizing slime preventing agent.
Thereafter, when the natural potential returns to the normal value and it is determined that the slime has disappeared based on the measurement 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 tube 16 is further branched, and two potential monitors are installed in series or in parallel. The test tube 35 in one potential monitor is subjected to a sensitization process in advance, and the test tube in the other potential monitor is tested. The sample 65 was subjected to a solution treatment, and each test tube was used as a sample electrode to conduct a re-passivation test for corrosion clearance (based on “Method for measuring corrosion clearance of stainless steel” specified in JIS G0592). 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 the present invention, in the circulating water system in which the slime inhibitor is used, the natural potential of the water system is monitored, and the slime prevention is performed so as not to exceed the potential at which pitting or crevice corrosion occurs in the water piping. Since the addition of the agent is controlled, pitting corrosion and crevice corrosion of the piping can be prevented beforehand.
Optimal contamination prevention effect can be obtained at any time in response to changes in the operating conditions of the circulating water system and changes in water quality. In addition to the increase in the number of products, various problems such as the suspension of production at a factory can be solved.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an embodiment of a circulating water-based 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;
FIG. 4 is a sectional view showing a detailed configuration of the potential monitor of FIG. 2;
FIG. 5 is a control block diagram of a measurement unit in FIG. 1;
FIG. 6 is a graph showing transitions of measured values of a natural potential and a 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 transitions of 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 circulating water-based water treatment system according to the present invention.
FIG. 9 is a view corresponding to FIG. 3 and showing a serial arrangement of sample electrodes according to 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 section
2) Slime inhibitor storage tank (means for adding chemicals)
3) Pump for adding oxidized slime inhibitor (means for adding slime inhibitor)
4 Control unit
5 Slime inhibitor storage tank (means for adding chemicals)
6) Pump for adding non-oxidizing slime inhibitor (means for adding slime inhibitor)
10 Water treatment system
12 slime monitor (slime measuring means)
13 potential monitor (potential measurement means)
14 Residual chlorine concentration measuring instrument
18 ° potential monitor (potential measuring means)
35 test tube (sensitized sample electrode)
50 water treatment system
65 test tube (solution treated sample electrode)

Claims (9)

A slime measuring means comprising: a slime preventing agent adding means for adding a slime preventing agent to a circulating water system; a potential measuring means for measuring a spontaneous potential in the system; and a slime measuring means for measuring a slime adhesion state in the system. When the slime inhibitor is added by the slime inhibitor adding means based on the slime adhesion state measured by the above, so as not to exceed a potential threshold set in advance based on the spontaneous potential measured by the potential measuring means. A method for treating a circulating water system, comprising controlling means for adding a slime inhibitor. Slime inhibitor adding means for adding a slime inhibitor to the circulating water system, potential measuring means for measuring the spontaneous potential in the system, slime measuring means for measuring the slime adhesion state in the system, and slime measuring means When the slime inhibitor is added by the slime inhibitor adding means according to the slime adhesion state, the slime is added so as not to exceed a preset potential threshold based on the spontaneous potential measured by the potential measuring means. A circulating water-based water treatment system, comprising: a control unit that controls the inhibitor addition means. The water treatment system according to claim 2, wherein the potential measuring means measures a natural potential using a metal material used in the circulating water system as a sample electrode. The water treatment system according to claim 3, wherein the sample electrode is made of at least one of a metal material that has been subjected to a sensitization treatment or a solution treatment in advance. The water treatment system according to claim 3 or 4, wherein the metal material used in the circulating water system is any of copper, nickel, aluminum, titanium, an alloy containing these, and stainless steel. The water treatment system according to any one of claims 2 to 5, wherein the control unit includes a comparison unit configured to compare a preset potential threshold value with a measurement result of the self potential in the system. The slime measuring means is a cylindrical measuring chamber that becomes a part of the flow path of the circulating water system, a light emitting unit and a light receiving unit that are arranged across the measuring chamber in a direction perpendicular to the flow of water, and an electric signal from the light receiving unit. The water treatment system according to any one of claims 2 to 5, comprising: a control unit for performing arithmetic processing on the slime inhibitor as measurement data to control the slime inhibitor adding means. 4. The water treatment system according to claim 3, wherein the sample electrode comprises two different sample electrodes, one of which is a sensitized metal material and the other is a solution-treated metal material. The means for adding a slime inhibitor includes means for individually adding an oxidized slime inhibitor and a non-oxidized slime inhibitor as a slime inhibitor to a circulating water system, and the control unit includes a natural potential in the system and / or The water treatment system according to claim 2, wherein the slime inhibitor adding means is controlled so that each of the oxidized slime inhibitor and the non-oxidized slime inhibitor is individually added to the circulating water system according to the slime adhesion state.

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