JP2005205343A - Method for electrolytic antistaining treatment of liuquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the electrolytic antistaining treatment of a liquid capable of keeping a constant antistaining effect even in a large-sized cell over a long period of time. <P>SOLUTION: The potentials of negative and positive reaction electrodes 6 and 7 are detected by potential detecting electrodes 8 and 9 and the reaction in the reaction electrodes 6 and 7 is analyzed from the transition of the detected potentials to control the polarity switching timing of the anode and the cathode corresponding to an analytic result. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrolytic antifouling treatment method in which a liquid containing salt is antifouled by an electrochemical reaction between an anode and a cathode.

  When aquatic organisms are sterilized by an electrochemical reaction between an anode and a cathode, it is well known that the following halogen biodestruction (sterilization) generally occurs when water contains salt.

Cl ^- → Cl ₂ + 2e ^-
Cl ₂ + H ₂ O → HClO + HCl
HClO + H ₂ O → OCl ⁻ + H ₃ O

  Such a biodestructive effect is caused by the oxidation action of hypochlorite in a concentration of ppm level. Similarly, the release of certain harmful metal ions, such as Cu and Ag ions in a water stream, affects the growth of attached organic matter and inhibits its growth. Metal ions are effective at lower concentrations than hypochlorite, ie at the ppb level.

  Normally, metal ion separation requires a metal active electrode, whereas hypochlorite or ozone occurs on the inert anode surface. Also, in both cases, the biodestructive effect can be generated electrochemically by chemical addition means, or by a spare DC power source or other equivalent device.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2002-143859), an antifouling surface of an underwater structure is made of a corrosion-resistant metal material, and a counter electrode (electrode) is opposed to the antifouling surface in water, or further A reference electrode for providing a reference potential is disposed between the antifouling surface and the counter electrode, and a positive potential of +1.5 V vs. SCE or less and a negative potential of −0.1 to −10 V vs. are provided on the antifouling surface. In order to alternately apply periodically, positive and negative voltages are alternately applied between the antifouling surface and the counter electrode, and the negative potential application time t2 is longer than the positive potential application time t1 and periodically. An antifouling method for an underwater structure is disclosed in which antifouling surfaces are prevented from being corroded, aquatic organisms are prevented from adhering and sterilized by applying to the water.

  In the technique of Patent Document 1, it is necessary to apply a positive potential to sterilize the microorganisms in the water. On the other hand, the application of the positive potential accelerates the corrosion of the metal material. The positive and negative voltages are alternately applied between the positive electrode and the counter electrode, and the application time is set to t2> t1 at this time because the elution amount of Cr, Fe, etc. is further reduced, and the positive potential Is set to +1.5 V vs. SCE or less because if the positive potential exceeds this value, the amount of metal elution from the electrode increases and chlorine may be generated. .1 to -1.0V vs. SCE is that the negative potential is higher than -0.1V vs. SCE (small negative value), the effect of detachment of cells becomes insufficient, and the negative potential is- If it is lower than 1.0V vs. SCE (large negative value), hydrogen generation and the pH around the electrode This is because it may change.

  In Patent Document 2 (Japanese Patent Laid-Open No. 9-248554), a positive potential that does not cause decomposition of the electrolyte is applied directly or indirectly to the surface of the conductive substrate by applying it to the conductive substrate immersed in water. Sterilizing the aquatic cells that have come into contact, and applying a positive potential higher than the positive potential at which electrolyte decomposition does not occur, thereby aquatic organisms, some of them, sterilized aquatic organism cells and / or By combining the process of disinfecting and / or detaching destructive materials and organic substances with the process of detaching aquatic organism cells and scales attached to the conductive substrate by applying a negative potential, aquatic organism cells An antifouling method for disinfecting cells and detaching adhering cells and their degradation products from the surface of the conductive substrate that is the antifouling surface is disclosed.

  That is, the technique of Patent Document 2 is based on a three-stage potential application process, that is, the application of a positive potential for sterilization and a positive potential that does not cause decomposition of the electrolyte for further sterilization and desorption of organic substances. In addition, the application of a high positive potential and the application of a negative potential for detaching deposits from the surface of the conductive substrate that is the surface to be protected are performed while appropriately adjusting the potential application time.

The conventional technology including these conventional examples lacks consideration for the following problems.
(1) Excess generation and release of heat and gas (2) Generation of unnecessary reaction at the anode and change in reaction on the electrode surface due to change in electrode potential.
(3) Reduction of current in the cell due to inhibition of heteropolarity The cathodic reaction changes the pH of the surface and causes chemical deposition of various dissolved salts.

  By the way, in the electrolysis of a liquid containing salt, the following reaction occurs over time at the anode and the cathode. FIG. 1 shows a typical transition model of the electrochemical potential of each of the anode and cathode surfaces and the reaction at these surfaces, with reference to zero potential.

  As the main reaction of the first stage, metal dissolution occurs on the anode side, while oxygen reduction occurs on the cathode side, and chlorine is generated on the anode side as the main reaction of the second stage, whereas the cathode Chloride precipitates on the side, and as a main reaction in the third stage, oxygen is produced on the anode side while hydrogen is produced on the cathode side. And with this transition, deposition (scale) of precipitated chloride on the electrode surface increases, voltage loss increases, current flowing between the anode and cathode decreases, and the electrode itself deteriorates further. Also progress.

Since it becomes such an aspect in an anode and a cathode, the target antifouling effect attenuates with progress of time, and the antifouling effect over a long term cannot be expected. Antifouling treatment in a small-scale cell is a serious problem when it is not so much a problem but it is desired to maintain a certain antifouling effect for a long time in a large-scale cell.
JP 2002-143859 A JP-A-9-248554

  The present inventors perform control based on the above knowledge, that is, the reaction transition at the anode and the cathode and the degree thereof are correlated with the electrochemical potential on the surface of each electrode. Thus, the present invention has been devised that can maintain a certain antifouling effect for a long time even in a large-scale cell, and solves the above-mentioned problems.

  The present invention relates to an electrolytic antifouling treatment method for antifouling treatment of a salt-containing liquid by an electrochemical reaction between an anode and a cathode, wherein the potential of at least one of the anode and the cathode is detected by a potential detecting means, and the detection is performed. The reaction at the anode and the cathode is analyzed from the transition of the potential, and the polarity switching timing of the anode and the cathode is controlled according to the analysis result.

  The reaction transition as modeled in FIG. 1 occurs in contrast on the anode side and the cathode side, which is predicted by detecting the potential on the surface of each electrode, that is, the reaction at the anode and cathode is detected using the detected potential as a parameter. Since monitoring (analysis) can be performed, if the polarity switching timing of the anode and the cathode is controlled according to the analysis result, the reaction is reversed at both electrodes due to the polarity reversal of the electrodes, and the reversal timing is related to the change of the detection potential. Accordingly, adverse effects due to precipitation of chloride, excessive generation of gas and heat, etc. can be appropriately avoided, and the antifouling treatment can be performed efficiently over a long period of time.

  The polarity switching timing is a threshold at which the change rate of the detected potential detected by the potential detection means is determined as a trigger for polarity switching when the detection potential detected by the potential detection means exceeds a predetermined threshold. When the value exceeds, the polarity switching trigger may be used. Furthermore, the respective potentials of the anode and the cathode are detected by the respective potential detecting means, and when the potential of either one of them or the change rate of the detected potential exceeds a predetermined threshold, it may be used as a trigger for switching the polarity. Is possible.

  If the current flowing between the anode and the cathode is controlled in addition to the polarity switching as described above, precipitation of chloride can be reduced, and problems due to gas and heat can be appropriately avoided.

  As a specific application example, an anode and a cathode are installed in a ballast water tank of a hull, and the ballast water is subjected to an antifouling treatment.

  According to the present invention, the potential of at least one of the anode and the cathode is detected, and the reaction at the anode and the cathode is analyzed from the transition of the detected potential, that is, the reaction transition and the degree at the anode and the cathode are analyzed, Since the polarity switching timing of the anode and the cathode is controlled according to the analysis result, the reaction transition that occurs in each of the anode and the cathode is suppressed as shown in FIG. Can be wiped out. That is, adverse effects due to precipitation of chlorides, excessive generation of gas and heat, etc. can be appropriately avoided, and antifouling treatment can be performed efficiently over a long period of time.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a system configuration diagram showing an outline of the present invention, in which a reactor 3 is installed in a cell 2 containing a liquid 1 containing salt. This reactor 3 is connected to a control / power supply unit 5 outside the cell via a cable 4, and is supplied with power and controlled by the control / power supply unit 5. The cell 2 is a target for antifouling, and is, for example, a ballast water tank of a hull. In the case of a ballast water tank, a circulation pump is installed inside.

  In the reactor 3, the liquid 1 can enter. Inside the reactor, as shown in FIG. 3, two reaction electrodes 6 and 7 serving as negative and positive electrodes are arranged. The potential detection electrodes 8 and 9 are opposed to each of 7 as potential detection means for detecting the surface potential without contact. Positive and negative voltages are applied to the reaction electrodes 6 and 7 from the control / power supply unit 5, and are controlled by the control / power supply unit 5 as follows based on the detected potentials by the potential detection electrodes 8 and 9. The

  A computer is incorporated in the control / power supply unit 5, and when the potentials of the reaction electrodes 6 and 7 are detected by the potential detection electrodes 8 and 9, the detected potential is used as a parameter, and the anode and the cathode The reaction shown in FIG. 1 at the reaction electrodes 6 and 7 can be analyzed by computer. The control / power supply unit 5 alternately switches the polarities of the reaction electrodes 6 and 7 from the analysis result, controls the polarity switching timing, and further controls the current.

  The polarity switching timing is controlled by looking at the transition of the detection potential of one or both of the potential detection electrodes 8 and 9, and (1) when the detection potential exceeds a predetermined threshold as a trigger for polarity switching. (2) When the detection potential change rate exceeds a predetermined threshold, the polarity switching trigger may be used, and (3) When both the threshold values are exceeded, the polarity switching trigger may be used. . The timing chart is shown in FIG. 4. The switching at T1 time and T2 time (T1 ≠ T2) is in the case of (1) above, and the switching at T3 time (T1 ≠ T2 ≠ T3) is in the case of (2). Show.

  FIG. 5 is a control flowchart in the case of (1). After setting a threshold for the anode-side detection potential in step S1, the anode-side detection potential is captured in step S2, and in step S3, the detection potential is set to the threshold. In step S4, a polarity switching trigger is issued.

  FIG. 6 is a control flowchart in the case of (2). After setting a threshold for the rate of change of the detection potential on the cathode side in step S11, the detection potential on the cathode side is captured in step S12, and the detection is performed in step S13. The potential is stored, and the rate of change of the detection potential on the cathode side is calculated in step S14. In step S15, it is determined whether or not the rate of change exceeds the threshold value. If exceeded, a trigger for switching polarity is issued in step S16.

  The control / power supply unit 5 performs such polarity switching control on both reaction electrodes 6 and 7 from the transition of the detected potential and also controls the current.

  Although one embodiment of the present invention has been described above, the potential detection electrodes 8 and 9 may be provided only on one electrode side to detect the potential of only one of the electrodes. Instead of 9, a ready-made surface potential sensor or the like may be used. Furthermore, the potential of the reaction electrodes 6 and 7 was detected and the detected potential was controlled as a parameter. In addition to that, if the temperature, pH, etc. were detected by each sensor and the temperature, pH, etc. were also used as parameters, Therefore, more accurate control can be performed.

It is a graph which shows the typical transition model of the electrochemical potential of each electrode surface of an anode and a cathode, and reaction on these surfaces. 1 is a system configuration diagram showing an overview of the present invention. It is a schematic diagram which shows the electrode arrangement | positioning in the reactor shown in FIG. It is a timing chart which shows polarity switching control. It is a control flowchart in the case of setting a trigger for polarity switching when the detected potential exceeds a predetermined threshold value. It is a control flowchart in the case of setting a trigger for polarity switching when the change rate of the detected potential exceeds a predetermined threshold.

Explanation of symbols

1 Liquid 2 Cell 3 Reactor 4 Cable 5 Control / power supply unit 6/7 Reaction electrode 8/9 Potential detection electrode

Claims (6)

  An electrolytic antifouling treatment method for antifouling treatment of a liquid containing salt by an electrochemical reaction between an anode and a cathode, wherein the potential of at least one of the anode and the cathode is detected by a potential detection means, and the transition of the detected potential The reaction at the anode and the cathode is analyzed, and the polarity switching timing of the anode and the cathode is controlled according to the analysis result.   2. The liquid electrolytic antifouling treatment method according to claim 1, wherein when the detected potential detected by the potential detecting means exceeds a predetermined threshold value, the polarity switching is triggered.   2. The liquid electrolytic antifouling treatment method according to claim 1, wherein when the rate of change of the detected potential detected by the potential detecting means exceeds a predetermined threshold, the polarity switching is triggered.   The potential of each of the anode and the cathode is detected by each potential detecting means, and when the potential of either one of them or the change rate of the detected potential exceeds a predetermined threshold, the polarity switching is triggered. The liquid electrolytic antifouling treatment method according to claim 1.   The method for electrolytic antifouling treatment of liquid according to any one of claims 1 to 4, wherein the current flowing between the anode and the cathode is also controlled.   6. The method for electrolytic antifouling treatment of liquid according to claim 1, wherein the anode and the cathode are installed in a ballast water tank of the hull, and the ballast water is subjected to the antifouling treatment.

Images