JP2003136061A - Electrical water treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrical water treatment device which can prevent the deposition of scale on the surface of an electrode and scale trouble such as deterioration of an electric current value even in the case treating water containing components easily deposited as scale, such as hardness components, thereby maintaining a stable treatment over a long period of time, and to provide a scale component removing device which can efficiently remove the components easily deposited as the scale, such as the hardness components, only by electrical treatment without using chemicals. SOLUTION: This electrical treatment device treats water electrically by applying a direct current between a cathode 3 and an anode 2 disposed in an electrolytic cell 1. The electrical treatment device has a means by which the seed crystals of substances expected to be deposited on the surfaces of the electrodes 2, 3 or the their analogues are retained at least in the vicinity of the cathode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric treatment apparatus for electrically treating water in a water tank by passing a direct current between a cathode and an anode arranged in the water tank. The present invention relates to a water electric treatment device that solves the problem of scale adhesion to the electrode surface in such an electric treatment device.

[0002]

2. Description of the Related Art The following is an electric treatment apparatus for electrically treating water in a water tank by passing a direct current between a cathode and an anode arranged in the water tank. Electrolytic device that electrolyzes water to generate hydrogen and oxygen or ozone Sterilized water manufacturing device that electrolyzes salt water to generate free chlorine or hydrogen peroxide Ionized water manufacturing that electrolyzes water to produce ionic water Equipment Oxidative decomposition equipment that electrolyzes waste water to oxidize and decompose pollutants

In these electrical treatment apparatuses, when electrolysis is continued, hardness components (calcium ions, magnesium ions, etc.) mainly contained in water form hydroxides and adhere to the electrode surface as scales, resulting in a current value. And scale problems such as deterioration of electrolysis efficiency and electrolysis efficiency.

In a sterilizing water production apparatus which electrolyzes salt water to generate free chlorine, an operation of reversing the anode and the cathode is performed at regular intervals to prevent such scale. However, in order to perform the polarity reversal, it is necessary to make both electrode materials insoluble electrodes using expensive noble metal, and it is necessary to incorporate a control system for reversing the applied voltage, which makes the device expensive. There is a drawback that

Conventionally, as a method for removing hardness components in water, there are softening treatment using an ion exchange resin, a method combining pH adjustment and seed crystal addition, and the like. Preparation of chemicals (dissolution), because chemicals are needed and also for pH adjustment
It takes time to store, carry in, and manage inventory.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and does not generate scale even when treating water containing a component such as a hardness component that easily scales on the electrode surface. An object of the present invention is to provide an electrical treatment apparatus for water capable of stably continuing treatment.

The present invention also provides, without the use of chemicals,
An object of the present invention is to provide a scale component removing device capable of removing hardness components in water such as boiler feed water.

[0008]

An electrical treatment apparatus for water according to the present invention comprises a water tank, a cathode and an anode arranged in the water tank, and a direct current is applied between both electrodes to obtain In an electrical treatment device that electrically treats the water in the aquarium,
A means for causing a seed crystal of a substance which is expected to be deposited or a substance similar thereto to exist on the electrode surface at least in the vicinity of the cathode is characterized.

The presence of a substance which is expected to be deposited on the electrode surface or a substance similar thereto as a seed crystal causes the scale to deposit on the surface of this seed crystal instead of on the electrode surface. , Scale failure due to scaling on the electrode surface is prevented. Usually, the scale is a calcium ion in water that has moved to the cathode side that has become alkaline by the application of a direct current, hardness components such as magnesium ions are deposited on the cathode surface by forming a hydroxide, therefore, By allowing the seed crystal to exist in the vicinity of the cathode, a good scale preventing effect can be obtained.

The electric treatment apparatus of the present invention is suitable as various electrolyzers, but the hardness component in water is removed as a scale on the seed crystal surface to remove the hardness component from water such as boiler feed water. It is also effective as a scale component removing device. That is, the conditions are such that calcium ions and the like move around the cathode and the concentration thereof increases, and scales such as calcium carbonate are easily deposited. Therefore, the hardness component is removed by depositing these scales on the seed crystal near the cathode from the hardness component in water.
By using such a chemical-free scale component removing device as, for example, a pretreatment device of a softening device, it is possible to reduce the load of the ion exchange resin of the softening device and reduce the regeneration frequency and the amount of chemicals used. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

In the present invention, the substance (scale) expected to adhere to the electrode surface is usually calcium hydroxide, magnesium hydroxide or the like, and these particles can be used as seed crystals. Further, since even a sparingly soluble compound containing calcium or magnesium acts as a seed crystal, calcium carbonate, calcium sulfate, magnesium carbonate, magnesium calcium carbonate, or the like, or an ore containing these is also used as a seed crystal. You can also do it. These seed crystal substances may be used alone,
You may use 2 or more types together.

The grain size of the seed crystal varies depending on its existing form, but it is usually preferable that the grain size is about 0.1 to 3 mm.

The seed crystal has only to be present at least in the vicinity of the cathode, and its existing form is not particularly limited and may be arbitrary. For example, the following method can be adopted. Hold in suspension in the electrolytic cell. In this case, in order to prevent the seed crystal from flowing out into the electrolytic cell when the treated water is discharged, a seed crystal outflow prevention member such as a net that does not allow the seed crystal to pass through is provided at the treated water outlet of the electrolytic cell, or it has flowed out. It is preferable to provide means for separating the seed crystal from the treated water and circulating it in the electrolytic cell. The seed crystal is fixed to an arbitrary support material and held in the electrolytic cell.

As described above, the seed crystal does not have to exist in the entire area of the electrolytic cell, but may exist in the vicinity of the cathode.

Therefore, when the seed crystal is held in suspension in the electrolytic cell, for example, in order to allow the seed crystal to exist only in the vicinity of the cathode, a separator that is water-permeable on the cathode side of the electrolytic cell and does not pass the seed crystal, For example, the cathode chamber may be formed by partitioning with a porous plate such as a unglazed plate, paper, resin, etc., and seed crystals may be present in this cathode chamber.

As a method of fixing and holding the seed crystal on the support material, there is a method of fixing and holding the seed crystal on a sheet-shaped support material such as paper or resin by adhesion or polishing. In this case, by arranging this sheet-shaped support material in the vicinity of the cathode, the seed crystal can be made to exist in the vicinity of the cathode.

It is preferable that the seed crystal in the electrode tank is not in a stationary state but in a fluid state or a moving state. That is, when the seed crystal is in a stationary state, the seed crystals may be bonded to each other or the seed crystal and the electrode through a newly deposited scale, which may lead to scale failure, but the seed crystal is made to flow or move. As a result, such a problem can be prevented.

Therefore, in order to make the seed crystal flow, the seed crystal in the electrolytic cell or the cathode chamber of the electrolytic cell is made to flow by stirring by a stirrer or aeration by an air diffuser, or in order to make the seed crystal flow in a water stream. The crystals may be made to flow by a water flow of the water to be treated introduced into the electrolytic cell, preferably an upward flow, or the water in the tank may be circulated by a slurry pump provided inside or outside the electrolytic cell. When the seed crystal is made to flow by the water flow of the water to be treated, the seed crystal is made to flow together with the water to be treated, the seed crystal is added to the water to be treated introduced into the electrolytic cell, and the seed crystal is extracted from the treated water taken out from the electrolytic cell. Solid-liquid separation may be performed and returned to the introduction side of the water to be treated, or a fluidized bed of seed crystals may be formed in the electrolytic cell by upward flow of the water to be treated.

Alternatively, the electrode plate may be installed with a slight inclination, the seed crystal may be supplied from above the electrode plate, and the seed crystal may be moved downward along the inclined surface. In this case, the seed crystal precipitated below the electrode plate is moved upward and circulated by a slurry pump or the like.

As a method of moving the seed crystal fixed on the support material, there is a method of reciprocating or rotating the support material fixed on the seed crystal by an arbitrary method. For example, a method of fixing the upper end of the support material to a suspension member provided on the upper end of the cell wall of the electrolytic cell, and reciprocating the support material in the vicinity of the cathode by this suspension member, or attaching the support material to a roll, It is possible to adopt a method of rotating the.

The movement of the support material having such seed crystals fixed thereon,
Alternatively, the flow of the seed crystals in the above-mentioned suspended state does not have to be continuously performed at all times, and reflow or re-transfer is performed before the formation of a bridge due to scaling between the seed crystals or between the seed crystals and the electrode plate. You may perform intermittently at the intervals which can be made.

By the way, when the electrolysis is continued in the presence of the seed crystal as described above, scale components are deposited on the surface of the seed crystal, and the seed crystal is gradually coarsened. When the seed crystals are held in the electrolytic cell in a suspended state, the coarsened seed crystals will settle at the bottom of the vessel, so it is desirable to appropriately withdraw from the bottom of the vessel to discharge coarse particles. Therefore, for this purpose, a pit that serves as a seed crystal settling portion and a seed crystal discharge pipe with an on-off valve that communicates with this pit are provided at the bottom of the electrolytic cell, and coarse particles of the seed crystal are regularly or as needed. Is preferably extracted.
Alternatively, when the seed crystals are made to flow by a slurry pump, a seed crystal extraction pipe with an opening / closing valve is branched and provided in the seed crystal circulation pipe by the slurry pump, and periodically or when necessary, a circulation containing coarse particles of the seed crystals. You may make it extract a part of water.

The configuration of the electrical processing apparatus of the present invention will be described more specifically below with reference to the drawings.

1 (a) to 1 (c) are schematic sectional views showing an embodiment of the electrical processing apparatus of the present invention. In addition,
In FIGS. 1A to 1C, 1 is an electrolytic cell, 2 is an anode,
3 is a cathode, 4 is a direct current power source, and 5 is a seed crystal.

In the apparatus shown in FIG. 1A, a seed crystal 5 is introduced between an anode 2 and a cathode 3 facing each other in an electrolytic cell 1, and the seed crystal 5 is introduced into the electrolytic cell 1 to be treated. It is made to flow by the upward flow of water and aeration from the diffuser bulb 6.
A seed crystal outflow preventing member 7 such as a net for preventing the outflow of the seed crystals is provided at the outlet of the treated water.

The apparatus shown in FIG. 1 (b) causes the seed crystal 5 to flow by the upward flow of the water to be treated and the circulation by the pump 8. That is, the seed crystal 5 that settles in the electrolytic cell 1 is extracted from the bottom of the electrolytic cell 1 by the pump 8 and circulated in the upper part of the electrolytic cell 1, so that the seed crystal 5 is kept in a fluid state between the electrodes 2 and 3. . Even in this apparatus, an outflow prevention member 7 for preventing outflow of seed crystals is provided at the outlet of the treated water.

The apparatus of FIG. 1 (c) causes the seed crystal 5 to flow together with the water to be treated, and the seed crystal introduced into the electrolytic cell 1 together with the water to be treated rises in the electrolytic cell 1, After being taken out from the upper part of the electrolytic cell 1 together with the treated water, the solid-liquid separation device 9
The separated seed crystals are circulated on the introduction side of the water to be treated.

In any of the devices, the water to be treated is introduced from the lower part of the electrolytic cell 1 and the electrode 2,
Electrolyzed at 3. The electrolyzed water is discharged from the upper part of the tank. In this electrolysis treatment, the hardness component in the water to be treated is not deposited on the electrodes 2 and 3, but is deposited on the surface of the seed crystal 5 between the electrodes 2 and 3, so that scale failure is prevented.

The electroprocessing apparatus of the present invention is an electrolyzing apparatus for electrolyzing water to generate hydrogen and oxygen or ozone,
Sterilizing water production equipment that electrolyzes salt water to generate free chlorine or hydrogen peroxide, ion water production equipment that electrolyzes water to produce ionized water, oxidative decomposition that electrolyzes sewage to oxidatively decompose pollutants Although it is effective for various electric treatment devices such as equipment, it is also suitable as a scale component removal device for removing hardness components from water such as boiler feed water by precipitating hardness components in water as a scale on the seed crystal surface. Yes,
By using such a chemical-free scale component removing device as, for example, a pretreatment device of a softening device, it is possible to reduce the load of the ion exchange resin of the softening device and reduce the regeneration frequency and the amount of chemicals used. .

[0031]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1, Comparative Example 1 Electric conductivity: about 20 mS / m, hardness component concentration: about 50 m
In an electrolyzer that electrolyzes water of g / L (Ca hardness: 35 mg / L) in an electrolytic cell to generate free chlorine,
An experiment was conducted to confirm the scale prevention effect according to the present invention.

The structure of the electrolytic cell used is as shown in FIG. 1 (a), and the electrodes (anode, cathode) having a size of 50 mm × 150 mm × 1 mm, in which Pt is plated on Ti, are used. I was there. The distance between the electrodes was 10 mm, and the air was diffused at 50 mL / mm by the air diffuser 6 provided between the electrodes. The electrolytic cell has a capacity of 80 mL and the flow rate of water is 600 mL / h.
r.

In Example 1, calcium carbonate particles (particle size: 0.5 mm) as seed crystals 5 were placed in the electrolytic cell 1 and allowed to flow by aeration between the electrodes 2 and 3. Further, the outlet of the treated water was closed with a saran net so that the seed crystal 5 did not flow out of the electrolytic cell 1.

In Comparative Example 1, no seed crystal was used.

In both Example 1 and Comparative Example 1, a voltage of 15 V was applied, the initial current was 0.16 A, and the concentration of free chlorine in the treated water was 2.2 mg / L.

The changes over time in the current, the concentration of free chlorine in the treated water and the calcium hardness when the treatment was continued at a constant voltage of 15 V were examined, and the results are shown in Table 1.

Further, in order to investigate the adhesion of scale to the electrode surface, after the treatment was continued for 30 days, the electrode was washed with acid and the amount of calcium in the washing solution was measured. The results are shown in Table 1.

[0039]

[Table 1]

The following is clear from Table 1.

In Comparative Example 1 in which the seed crystal was not charged into the electrolytic cell, it was confirmed that a large amount of scale adhered to the electrode surface, and the current value decreased with time due to scale deposition on the electrode surface. Was observed, and the amount of free chlorine generated was also reduced.

On the other hand, in Example 1 in which the seed crystal was put in the electrolytic cell, the scale was prevented from being deposited on the electrode surface, and there was no problem in that the current value was lowered and the amount of free chlorine generated was lowered.

Moreover, in Example 1, the hardness component was also removed, so it was confirmed that the electrical treatment apparatus of the present invention is also effective as a scale component removal apparatus.

[0044]

As described in detail above, according to the electrical treatment apparatus for water of the present invention, even when water containing a component that easily scales, such as hardness component, is treated, the scale on the electrode surface can be reduced. It is possible to prevent scale failure such as precipitation and a decrease in current value due to the deposited scale, and to continue stable processing for a long period of time.

According to the present invention, there is also provided a scale component removing device which efficiently removes components such as hardness components in water which are likely to be scaled, without using chemicals, only by electrical treatment.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of an electrical processing apparatus of the present invention.

[Explanation of symbols]

1 electrolysis tank 2 anode 3 cathode 4 DC power supply 5 seed crystals 6 air diffuser 7 Seed crystal outflow prevention member 8 pumps 9 Solid-liquid separator

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01D 9/02 619 B01D 9/02 619A C02F 5/00 620 C02F 5/00 620B 5/02 5/02 B 5/06 5/06

Claims (3)

[Claims] 1. An electric treatment apparatus comprising a water tank, a cathode and an anode arranged in the water tank, and electrically treating the water in the water tank by passing a direct current between both electrodes. A device for electrically treating water, characterized in that a means for causing seed crystals of a substance which is expected to be deposited or a substance similar thereto to exist on the electrode surface is present at least in the vicinity of the cathode. 2. An electric water treatment apparatus according to claim 1, which is an electrolyzer. 3. The water electric treatment device according to claim 1, wherein the electric water treatment device is a scale component removing device.