JPH0427490A - Shutdown method for electrolytic treatment of water to be treated - Google Patents

Abstract

PURPOSE:To prevent the explosion of a gaseous mixture composed of generated gaseous hydrogen and gaseous oxygen at the time of shutdown and to safely treat water to be treated by shutting off a power source, then continuing the supply of the water to be treated to an electrolytic cell for a prescribed period of time at the time of stopping the treatment. CONSTITUTION:The supply of the water 19 to be treated is continued while the power supply for energizing both electrode terminals 3, 4 for power feeding is held shut off in the case of shutting down of the electrolytic treatment. This water is discharged together with the water to be treated to which the gaseous hydrogen is supplied in the electrolytic cell 2 to the outside of the electrolytic cell 2. The supply of the water 19 to be treated is stopped and the operation is completely stopped after the amt. of the gaseous hydrogen is sufficiently decreased or after the gaseous hydrogen does no longer exist. The presence of the gases contg. the gaseous hydrogen within the explosive limit in the electrolytic cell 2 after the shutdown is obviated in this way and the outbreak of the explosion does not longer arise in spite of the presence of an ignition source. The gaseous hydrogen within the explosive limit does not exist either at the time of restarting the operation of this electrolytic cell and, therefore, the explosion does not arise.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to electrolytic treatment of various types of water to be treated containing microorganisms to suppress various performance deteriorations caused by said microorganisms, or Regarding the method for stopping operations in electrolytic processing for electrolytic recovery of silver from aqueous solutions containing concentrated silver ions, more specifically, methods for stopping operations in electrolytic processing such as color development processing, bleaching processing, bleach-fixing processing, fixing processing, stabilization processing, water washing processing, etc. A fixed-bed tertiary system is used to process various types of water containing microorganisms, such as photographic processing solutions used in the processing of photographic light-sensitive materials, pool water, paper manufacturing washing water, heat exchanger cooling water, drinking water, fish farming water, and bathing water. By performing electrolytic treatment using the original electrode electrolytic cell, microorganisms in the water to be treated can be effectively sterilized or silver can be recovered. At the same time, when the operation is stopped due to the hydrogen gas and oxygen gas generated by the electrolytic treatment, This article relates to a method for preventing explosions when restarting operations.

(Prior Art) Many types of aqueous solutions and water alone in which other substances are not dissolved have been used for various purposes. In these aqueous solutions, if solutes provide adequate nutrients or if the temperature of the aqueous solution is relatively high, which is favorable for reproduction, microorganisms such as bacteria will proliferate and the microorganisms will deteriorate the performance of the aqueous solutions. It often occurs, floats in the processing equipment, accumulates, and impairs the functionality of the processing equipment.

For example, after image exposure of a photographic material, in the case of paper photosensitive material processing, the material is processed through color development, bleach-fixing, washing and/or stabilization, and then dried. In such photographic processing steps, various photographic processing solutions such as color developing solution, bleaching solution, bleach-fixing solution, fixing solution, stabilizing solution, and washing water are used. In order to provide an environment suitable for the growth of microorganisms, the microorganisms mixed in the photographic processing solution multiply, reducing the efficiency of processing the photosensitive material, and causing color unevenness in the resulting prints and contamination of images due to mold formation, etc. There is a drawback of doing so. Conventionally, the mainstream method for suppressing the deterioration of photographic processing solutions due to the proliferation of microorganisms has been to sterilize the microorganisms and activate their performance by adding an antifungal agent, but this method requires a large amount of antifungal agent to be added. In addition, the antifungal agent tends to remain in the photographic processing solution and the photosensitive material, which may have an adverse effect on the photosensitive material. Moreover, many of the above-mentioned antifungal agents cannot be said to be harmless to the human body, and it is difficult to use them unless they are regulated under various laws and regulations. Moreover, the antifungal agent selected in this way will develop antibacterial effects against the antifungal agent after a while, and the troublesome problem of selecting an antifungal agent against this antibacterial agent will arise again.

Furthermore, the popularity of swimming, which is the most common summer sport, remains undiminished and is enjoyed by people of all ages, and many pools are used in urban areas to enjoy swimming.

The pool water used for this pool is inhabited by many microorganisms such as bacteria that are harmful to the human body, and the pool water can cause diseases if it comes into direct contact with users' eyes or wounds. Chemicals such as sodium hypochlorite are added to the water to sterilize it in advance to prevent the spread of disease. However, chlorine-based reagents such as hypochlorous acid and liquid chlorine, which have a strong sterilization effect, are used as the above-mentioned chemicals, and the chlorine-based reagents themselves or their decomposed products are irritating, and the reagents do not produce sterilizing effects. However, the reagents cause side effects such as eye pain and skin irritation, which is a big problem, especially in the case of young children who have weak resistance. In addition, chlorine-based reagents cannot be used permanently because they decompose and must be added to the pool water every day. The cost is also a big burden.

Furthermore, with the progress of the information society in recent years, the demand for various types of paper, especially high-quality paper, is increasing. These papers are manufactured from papermaking pulp through various processes, and during these processes there is a step of washing the pulp before papermaking to wash away unnecessary components. Since the bulb is maintained at a moderate temperature and contains proper nutrients,
Microorganisms such as mold and bacteria easily breed, and if large amounts of mold and bacteria remain in the final product, performance deterioration such as discoloration of the paper will occur. Therefore, the large amount of washing water used in this washing process contains antifungal agents and bactericidal agents to prevent deterioration of the performance of the final product as much as possible.

However, with this method, not only does the cost of the anti-mold agent and bactericide increase, but also the anti-mold agent and bactericide remain in the product, causing performance deterioration that is different from the deterioration caused by mold and bacteria. The problem is that it can sometimes occur.

Furthermore, in recent years, with the increase in the number of buildings such as apartment complexes such as condominiums and buildings where many companies come together, the number of various types of heating and cooling equipment installed in these buildings has also increased dramatically. There is.

In condominiums, buildings, etc. in which a large number of such air-conditioning equipment are installed, a heat exchanger for cooling water of the air-conditioning equipment, such as a cooling tower, is usually installed on the roof of the building. If the cooling water of this heat exchanger equipment is continued to be used for a long period of time, microorganisms such as mold and bacteria will grow and precipitate on the heat exchange surface of the heat exchanger, deteriorating the heat exchange performance and causing microorganisms to form in clumps. This may cause the pipes to become clogged. In addition, large amounts of microbial waste may cause serious problems such as corrosion of pipes and equipment.

Furthermore, the amount of bath water used has increased due to the spread of home bathtubs and the hot spring boom in recent years, but this bath water has a liquid temperature of around 40°C, where microorganisms are most likely to breed, so it is not used for bathing. Even if you simply leave it in the bath, microorganisms will rapidly propagate and contaminate it, making it impossible to continue using it.If you repeatedly bathe, human body grime will become airborne, and this tendency will become more pronounced. The microorganisms that have grown are so small that they are difficult to remove through filtration, and the amount of microorganisms used is enormous, especially in public baths. Therefore, if contaminated bath water can be regenerated with a simple treatment process, it would significantly reduce costs. becomes possible.

Furthermore, in addition to the natural fish that breed in the sea and rivers as a variety of fish resources, farmed fish in fish farms have recently attracted attention.
Many farmed fish are supplied to the market. When raising these types of fish in aquaculture farms, in order to prevent negative effects such as microorganisms such as bacteria and mold contained in the fish farming water contaminating the fish or adhering to the fish and reducing their commercial value. A large amount of various chemicals such as bactericides and antifungal agents are added to the fish water to kill all or most of the microorganisms, and vitamin supplements and the like are added to minimize damage to fish caused by the chemicals. Large amounts of nutrients are administered to the fish and then fed. Therefore, compared to the amount of food, fish raised in aquaculture farms are often supplemented with various artificially administered drugs and vitamins, and fungicides and fungicides accumulate in the fish's bodies and are harmful to humans. Fish contaminated with various chemicals will be supplied to the market.

Also, like normal water, there is about 10 ppm of dissolved oxygen in fish farming water, and fish grow by ingesting this oxygen.

Furthermore, drinking water is water stored in a water source such as a reservoir, sterilized at a water purification plant, and then supplied to each home, restaurant, etc. through the water supply system. The sterilization of drinking water is generally performed by treating it with chlorine gas. Although chlorine treatment sterilizes drinking water relatively well, the residual chlorine may cause foreign substances to be mixed into the treated drinking water. The disadvantage is that the mellowness of natural water is lost due to the unpleasant feeling that occurs in water.

Drinking water is directly related to human health, and it is essential to sterilize the bacteria contained in it and prevent the growth of mold, that is, kill most or all of the microorganisms. Although chlorine-based sterilization methods are the mainstream, sterilization methods other than chlorine-based sterilization methods have been proposed to overcome the drawbacks of the chlorine method.

For example, methods have been proposed in which the drinking water is reformed by ozone addition treatment or activated carbon adsorption treatment, but if the drinking water to be treated is, for example, water from a water treatment plant, the disadvantage is that the amount of treatment becomes large. be. Furthermore, even if the water is treated at a water treatment plant, there is a problem that microorganisms will reproduce again before it reaches the faucet at the end.
At present, there is no method superior to chlorination. However, when sterilizing tap water in urban areas, the raw water, such as river water or lake water, is contaminated with various organic substances. This has the disadvantage of causing the generation of

In order to prevent these phenomena, conventionally, various chemicals such as antifungal agents and sedimentation inhibitors have been added to the water to be treated, and various filters have been installed in the pipes. It has been pointed out that residual chemicals have an adverse effect on the water to be treated and there are problems with the cost of using chemicals. Furthermore, there is a problem in that antibacterial effects against the added drug occur after a while, making it necessary to consider the next drug.

(Problems to be Solved by the Invention) The present applicant has proposed a method of electrochemically sterilizing microorganisms in water to be treated by solving these drawbacks (Patent Application No.
No. 326846).

In this method, a plurality of short cylindrical fixed bed electrodes made of, for example, a carbonaceous material are housed in a cylindrical body in the vertical direction, and electricity is applied while the water to be treated flows through the cylindrical body, so that the water to be treated is heated. This is a method of processing. In a normal electrolytic reaction, hydrogen gas and oxygen gas are produced by water electrolysis, and in electrolysis without a diaphragm, both gases are mixed and the mixed gas is taken out of the electrolytic cell and led to a storage tank or the like. In water electrolysis, hydrogen and oxygen:
A mixed gas of 1 is produced, and this proportion is 66.7% by volume, which is within the explosive limit of hydrogen gas of 4 to 75% by volume, and may ignite and explode due to the presence of static electricity.

When the operation of an electrolytic cell is stopped, explosions of the mixed gas, such as the generation of static electricity due to the impact caused by the interruption of the current, are likely to occur, and the operation cannot be stopped safely using conventional methods of stopping operation. There is. Furthermore, if the mixed gas remains in the electrolytic cell even when the electrolytic cell is restarted, ignition and explosion of the mixed gas is likely to occur when electricity is started.

(Purpose of the invention) The present invention is an object of the present invention to prevent explosions of a mixed gas of hydrogen gas and oxygen gas generated by water electrolysis in a fixed-bed bipolar electrolyzer when the operation is stopped, and to safely treat water to be treated. The purpose is to provide a method that allows you to do this.

(Means for Solving the Problems) The present invention provides a method for electrolytically treating water while supplying water to be treated to a fixed bed type three-dimensional electrode electrolyzer and generating a mixed gas of hydrogen gas and oxygen gas. This method of stopping operation is characterized in that, when stopping the operation, the supply of the water to be treated to the electrolytic cell is continued for a predetermined period of time after cutting off the power source.

The present invention will be explained in detail below.

The present invention supplies various types of water to be processed, such as photographic processing liquid, to a fixed bed type three-dimensional electrode electrolytic cell, and applies a DC or AC voltage to the electrolytic cell to generate hydrogen gas while being exposed to the photographic processing liquid, etc. A mixed gas of hydrogen gas and oxygen gas remaining in the electrolytic cell when the operation is stopped when sterilizing microorganisms in the treated water or recovering silver from the water to be treated is caused to flow through the electrolytic cell even after the operation is stopped. This is a method for stopping the operation of an electrolytic cell in which hydrogen gas having a concentration within the explosive limit is not present in the electrolytic cell until the electrolytic cell is taken out of the electrolytic cell together with the water to be treated and the operation is restarted.

Of the water to be treated, the photographic processing solution has an appropriate amount of nutrients such as salts and gelatin, and is maintained at an appropriate temperature. Similarly, water has the right amount of nutrients and the right temperature, making it the perfect environment for microorganisms to grow. Furthermore, bath water used in domestic bathtubs and public baths has a rating of 35 to 4, which is the most suitable for the growth of microorganisms.
Since the temperature is maintained at 5°C, a small amount of microorganisms can multiply to a large number in a short period of time. Water to be treated other than these photographic processing solutions etc. also comes into contact with an atmosphere containing microorganisms, and the microorganisms are taken into the water to be treated and propagate, resulting in the above-mentioned disadvantages.

When the water to be treated is supplied to a fixed bed type three-dimensional electrode electrolytic cell, microorganisms in the water to be treated come into contact with the anode and cathode of the electrolytic cell or the fixed bed and particles for forming a fixed bed, etc., which will be described later, due to liquid flow. It is thought that sterilization occurs when a substance undergoes a strong redox reaction on its surface or comes into contact with a high-potential electric current, weakening its activity and killing itself.

Therefore, in the treatment of water for the purpose of normal sterilization, it is sufficient for the microorganisms in the water to come into contact with voltage-applied electrodes, fixed beds, particles for forming fixed beds, etc., and a current is applied between the two electrodes. It is not essential to flow the water to cause a substantial electrolytic reaction accompanied by the generation of gases such as hydrogen and oxygen; rather, it is not necessary to cause a substantial electrolytic reaction to occur due to cost reasons and to avoid compositional changes in the water to be treated. Preferably, an electrical potential is applied to the electrode surface.

However, in practice, sterilization is often performed while generating a small amount of gas to confirm that sterilization is being carried out effectively, and in addition, for example, in the case of fish farming water, oxygen gas is actively generated. In some cases, it may be preferable to increase the dissolved oxygen concentration in the water to be treated. In the case of recovering silver from an aqueous solution, reduction of silver ions occurs on the surface of the cathode, and hydrogen gas is generated along with the reduction.

The method of the present invention is directed to a method of treating water to be treated that involves such gas generation.

In an electrolytic reaction using a normal diaphragmless electrolytic cell, a small amount of air is present in the electrolytic cell at the beginning of the electrolysis, and as the electrolysis continues, a mixed gas of hydrogen and oxygen that is generated gradually replaces the air and the air is removed. is discharged to the outside of the tank along with the electrolytic solution, and the inside of the electrolytic tank becomes almost only the above-mentioned mixed gas. The proportion of hydrogen in the mixed gas in this state is about 67% by volume, which is within the explosion limit. Therefore, when the power supply is cut off when the operation is stopped, the electrolytic cell is filled with a mixed gas within the explosion limit, and if there is a spark caused by static electricity or the like, it will ignite and explode. Further, even if the power supply is cut off and the current supply is stopped, gas generation often continues from the electrodes for a while. In the method of the present invention, even after the power supply is cut off and the electricity supply is stopped, the water to be treated continues to be supplied to the electrolytic cell, and the mixed gas in the electrolytic cell is almost completely discharged out of the electrolytic cell by the water to be treated. In this way, the mixed gas that can induce an explosion is prevented from being present in the electrolytic cell when the electrolytic cell is stopped until its operation is restarted.

If the supply of water to be treated is continued even after the power is cut off,
Not only does the amount of hydrogen gas in the electrolytic cell gradually decrease (hydrogen gas present in the pipes such as the water supply pipe and the water discharge pipe to be treated is also led to the storage tank, etc., causing an explosion in the pipes). Danger is avoided.

Note that when restarting the operation of an electrolytic cell that has been stopped by the method of the present invention, supply of water to be treated and energization may be started at the same time since there is no hydrogen gas within the explosive limit in the electrolytic cell. After starting the supply of water to be treated, if electricity is supplied, operation of the electrolytic cell can be started more safely.

The electrolytic potential in the method of the present invention is the potential at which gas generation occurs;
In other words, the anode potential is increased from +1.2■ to +2.0■ (vs, 5
HE), and the cathode potential was changed from -2,OV to -1,0■(v
s, 5HE).

The electrolytic cells used in the method of the present invention are fixed-bed three-dimensional electrode electrolytic cells, that is, fixed-bed monopolar electrolytic cells and fixed-bed bipolar electrolytic cells. Since the electrode has a large surface area, it is possible to increase the contact area between the electrode surface and the water to be treated such as photographic processing solution, which allows the device size to be reduced and the efficiency of electrochemical processing to be increased. It is advantageous in this respect.

The electrodes in the fixed bed three-dimensional electrode electrolytic cell used in the present invention generally include a three-dimensional electrode and a power supply electrode terminal,
The three-dimensional electrode has a shape according to the electrolytic cell to be used, and is made of a porous material through which the water to be treated can pass, such as granular, spherical, felt, woven cloth, porous block, etc. Made from carbon-based materials such as activated carbon, graphite, and carbon fiber, or from metal materials such as nickel, copper, stainless steel, iron, and titanium that have the same shape, and from materials coated with precious metals on these metal materials. The fixed bed may be a plurality of preferably granular, spherical, fibrous, felt, woven, porous block, or sponge-like dielectric materials.

These plurality of laminated fixed beds are preferably accommodated in a cylindrical electrolytic cell main body with both upper and lower ends open.

The main body is preferably made of an electrically insulating material that can withstand long-term use or reuse, and is particularly made of synthetic resins such as polyepichlorohydrin, polyvinyl methacrylate, polyethylene, polypropylene, polyvinyl chloride,
Polychlorinated ethylene, phenol-formaldehyde resin, etc. can be preferably used. Furthermore, it is more convenient to mold the fixed bed using a transparent or translucent material because it allows the wear state of the fixed bed to be visually checked.

The fixed bed is placed in a direct current or alternating current electric field, and a direct current or alternating current voltage is applied between power supply electrode terminals made of a porous plate such as a flat plate, an expanded mensch, or a part ole tiled plate installed at both ends. It is possible to provide a fixed bed type bipolar electrolytic cell that accommodates a three-dimensional electrode formed by polarizing the fixed bed and forming an anode and a cathode at one end and the other end of the fixed bed, respectively. A fixed-bed bipolar electrolytic cell can be obtained by alternately installing and electrically connecting three-dimensional materials that function as an anode or a cathode so as not to cause short circuits.

When using a fixed bed monopolar electrolytic cell, a fixed bed for anode polarization may be connected to the anode terminal for power supply, and a fixed bed for cathode polarization may be connected to the cathode terminal for power supply.

Examples of materials for the power supply anode terminal include carbon materials (activated carbon, charcoal, coke, coal, etc.), graphite materials (carbon fiber, carbon cloth, graphite, etc.), carbon composite materials (carbon and metal powder mixed and fired). activated carbon fiber nonwoven fabric (e.g. K E-1000 felt,
Toyobo Co., Ltd.) or materials that support platinum, palladium, nickel, etc., as well as dimensionally stable electrodes (platinum group oxide-coated titanium materials), platinum-coated titanium materials, nickel materials,
There are materials made of stainless steel, iron, etc.

The cathode terminal for power supply that faces the anode terminal for power supply and provides a negative DC voltage is made of, for example, platinum, stainless steel,
It can be formed from titanium, nickel, copper, Hastelloy, graphite, carbon material, mild steel, or a metal material coated with platinum group metal.

When using a carbon-based material such as activated carbon, graphite, or carbon fiber as the fixed bed and treating water while generating oxygen gas from the anode, the fixed bed is oxidized by the oxygen gas and dissolved as carbon dioxide gas. It becomes easier to do. In order to prevent this, a porous material that is usually used as an insoluble metal electrode is coated with a platinum group metal oxide such as iridium oxide or ruthenium oxide on a base material such as titanium on the anodically polarized side of the fixed bed. They may be placed in contact so that oxygen evolution occurs primarily on the porous material.

If there are gaps in the electrolytic cell through which the water to be treated flows, through which the liquid can flow without contacting the fixed bed, the treatment efficiency of the water to be treated will decrease. It is desirable to arrange the flow so that it does not short-circuit.

In addition, the flow rate of the water to be treated supplied to the electrolytic cell may be determined so that the water to be treated can efficiently contact the surface of the electrodes, etc. If the flow is completely laminar, there will be little lateral movement. Since contact with the fixed bed surface is reduced, it is preferable to create a turbulent flow state, particularly preferably a turbulent flow having a Reynolds number of 500 or more.

Even if the inside of the electrolytic cell is divided by a diaphragm to form an anode chamber and a cathode chamber, it is possible to conduct electricity without using a diaphragm. If the distance between the electrodes or the distance between the fixed bed and the power supply electrode terminal is to be narrowed, an electrically insulating material, for example, donut-shaped, and made of an organic polymer material, for example, which does not impede the flow of the water to be treated, is used to prevent short circuits. A mesh spacer can be inserted between the fixed beds and between the fixed bed and the power supply electrode terminal. In addition, when using a diaphragm, it is desirable to use a porous membrane, for example, one with an aperture ratio of 10% to 95%, preferably 20% to 80%, so as not to obstruct the movement of flowing water to be treated. The diaphragm must have micropores with a pore diameter that is at least large enough to allow the water to be treated to pass therethrough.

A treated water supply pipe and a treated water discharge pipe are connected to the electrolytic cell main body of such a fixed-bed bipolar or monopolar electrolytic cell. Although the installation location of the supply pipe and the discharge pipe is not particularly limited, the water to be treated is supplied to the three-dimensional electrode through one of the repowering electrode terminals, and the treated water is passed through the other electrode terminal for power supply. It is desirable that the treated water supply pipe and the treated water supply pipe are installed so that the water is taken out of the tank through the tank. Generally, a lid and a bottom plate are installed on the electrolytic cell body, and a treated water discharge pipe and a treated water supply pipe are installed through the lid and the bottom plate, respectively, so that the treated water flows through the electrolytic cell body from below. Preferably, it flows upwards.

In addition, in the electrolytic cell used in the method of the present invention, a leakage current occurs in the electrolytic cell, and the leakage current flows from the electrolytic cell through the water to be processed such as photographic processing solution and into other components, such as the photographic processing tank, and causes damage in the photographic processing tank. This may induce undesirable electrochemical reactions in the electrolytic bath, electrochemically corrode the walls of the photographic processing tank, and elute the wall material. The leakage current can be interrupted by installing a member having higher conductivity than the liquid to be treated in the inlet/outlet pipe of the electrolytic cell so that one end thereof can be grounded.

When used for example to sterilize microorganisms in photographic processing solutions, an electrolytic cell with such a configuration can be used for photographic processing such as a color developing tank, a bleaching tank, a bleach-fixing tank, a washing process tank, a stabilizing process tank, etc. Connecting to some or all of the tanks in the process, temporarily storing the photographic processing solution in each of the processing tanks in the storage tank, supplying the photographic processing solution in the storage tank to the electrolytic tank, and circulating it for processing. Even after the power is cut off when the operation is stopped, the supply of water to be treated is continued for a while, and the hydrogen gas in the electrolytic cell is discharged outside the electrolytic cell, reducing the amount of hydrogen gas in the electrolytic cell and preventing an explosion. Danger can be avoided.

Furthermore, the electrolytic cell used in the present invention can be installed close to a heat exchanger installed on the roof of a building or condominium, or close to a swimming pool, or at a key point in the paper manufacturing process, and can be installed near a fish farm or other important point in the paper manufacturing process. Installed near fishing ponds, etc., in the storage line of a water purification plant, or near the water faucets of homes and restaurants, and also near commercial baths such as public baths and hot springs, and domestic bathtubs. By installing this system, the water to be treated can be treated safely and efficiently without causing an explosion of hydrogen gas.

In order to avoid explosions during normal operation, an inert gas such as air may be introduced into the mixed gas discharged from the electrolytic cell together with the water to be treated, for example in the water supply pipe or storage tank, to generate hydrogen gas. can be diluted to bring it out of explosive limits.

Next, a preferred example of an electrolytic cell that can be used in the present invention will be described based on the accompanying drawings, but the electrolytic cell that can be used in the method of the present invention is not limited to this electrolytic cell.

FIG. 1 is a schematic longitudinal cross-sectional view showing an example of a fixed bed bipolar electrolytic cell that can be used as an electrolytic cell in the method of the present invention.

A mensch-shaped power feeding anode terminal 3 and a power feeding cathode terminal 4 are provided near the upper and lower ends of the cylindrical electrolytic cell body 2 having flanges 1 on the upper and lower sides, respectively.

A plurality of sponge-like or pumice-like fixed beds 5, in the illustrated example, are stacked between the two electrode terminals 3.4,
and four porous diaphragms or spacers 6 between the fixed beds 5 and between the fixed beds 5 and both electrode terminals 3.4.
is being held.

Each fixed bed 5 is in close contact with the inner wall of the electrolytic cell main body 2 so that the leakage flow of the photographic processing solution flowing between the fixed bed 5 and the side wall of the electrolytic cell main body 2 is reduced as much as possible without passing through the inside of the fixed bed 5. It is located in

On the upper flange 1 of the electrolytic cell body 2, a lid body 8 having an upwardly facing cylinder 7 formed in the center is placed, and the lid body 8 is folded laterally with the flange at the upper end of the cylinder 7. A filter 10 is held between the flange portions at the lower end of the bent water discharge pipe 9 to be treated. In the middle of the treated water discharge pipe 9, an auxiliary pipe 12 is provided with an inert gas inlet 11 facing the side so that each flange 13 contacts the flange 14 of the treated water discharge pipe 9. It has been inserted. The other end of the treated water discharge pipe 9 reaches into the storage tank 15 through the lid 16 of the storage tank 15. An inert gas introduction pipe 17 is inserted into the storage tank 15 through the lid 16, and the base end of the water supply pipe 180 is similarly connected to the lid 1.
The treated water 19 in the storage tank 15 is inserted through the
is in contact with The other end of the treated water supply pipe 18 is connected via a pump 20 to a circular hole 22 bored in the center lower surface of a bottom plate 21 installed so as to be in contact with the lower flange l of the electrolytic cell body 2. There is.

In the storage tank 15 of the electrolytic cell with a storage tank configured as described above, for example, washing water from a washing process in a photographic processing process is stored as water to be processed, and the pump 20 is operated to transfer the water to be processed. When water is supplied into the electrolytic cell main body 2 through the water supply pipe 18 and electricity is applied between the repowering electrode terminals 3 and 4, each of the fixed beds 5 is polarized with the lower surface being positively polarized and the upper surface being negatively polarized as shown in the figure. An electric potential is generated between the inside and the fixed bed 5, and the water to be treated flowing through the electrolytic cell comes into contact with the fixed bed 5 having this electric potential, and is subjected to reforming treatment such as sterilization of mold and bacteria contained therein. The water to be treated is taken out from the discharge pipe 9 of the electrolytic cell main body 2. At this time, solid impurities such as dead microorganisms generated during the sterilization process are filtered when passing through the filter 10 and circulated to the storage tank 15 as clear treated water. In this electrolytic treatment, hydrogen gas and oxygen gas are generated by water electrolysis on the fixed bed 5, and this mixed gas, which is composed of both gases and has a hydrogen concentration within the explosive limit, is mixed with the water to be treated into the water discharge pipe 9. The water is guided to the storage tank 15 through the.

At this time, the mixed gas may ignite and explode due to static electricity, but if a predetermined amount of inert gas such as air is introduced from the inert gas inlet 11 and inert gas inlet pipe 17, The proportion of hydrogen gas in the mixed gas in the water discharge pipe 9 and in the storage tank 15 is less than 4% by volume, which is outside the explosion limit, thereby making it possible to avoid the danger of hydrogen gas explosion. The gas pressure in the storage tank increases due to the introduction of the inert gas, but excess gas is removed from storage tank 1.
5 and the lid body 16, and the pressure inside the storage tank 15 is maintained almost constant.

When stopping the operation of this electrolytic treatment, the supply of water to be treated is continued while the power supply to the repowering electrode terminals 3 and 4 is cut off, and the hydrogen gas in the electrolytic cell 2 is supplied. The water to be treated is discharged to the outside of the electrolytic cell 2 together with the water to be treated, and after the amount of hydrogen gas is sufficiently reduced or hydrogen gas no longer exists, the supply of the water to be treated is stopped, and the operation is completely stopped.

As a result, there will be no gas containing hydrogen gas within the explosion limit in the electrolytic cell after the operation is stopped, and no explosion will occur even if an ignition source is present.

Similarly, when the electrolytic cell is restarted, an explosion will not occur because there is no hydrogen gas within the explosion limit.

The electrolytic cell shown in Figure 1 can be used not only for photographic processing solutions but also for other water to be treated, including the aforementioned pool water, for sterilization and silver recovery while avoiding the risk of explosion. It can be performed.

FIG. 2 shows another example of a bipolar fixed bed electrolytic cell that can be used in the present invention. A mesh-like insoluble metal material 13 is installed in close contact with the side to be positively polarized, and the auxiliary tube 12 is omitted.Since the other members are the same as in Fig. 1, they are given the same reference numerals and their explanations are omitted. do.

The fixed bed 5 to which a direct current or alternating current voltage is applied is most polarized at both ends thereof, and when accompanied by gas generation, gas generation occurs most intensely at both ends. Therefore, dissolution occurs fastest at the end of the fixed bed 5 facing the power supply cathode 4 where the polarization is strongest, that is, where oxygen gas is most intensely generated.

As shown in the figure, if the insoluble metal material 23 is installed in this part, the overvoltage of the insoluble metal material 23 is lower than the overvoltage of the carbon-based material forming the fixed bed 5, so that most of the oxygen gas is removed from the insoluble metal material 23. Since the fixed bed 5 hardly comes into contact with oxygen gas, the dissolution of the fixed bed 5 is effectively suppressed. Furthermore, the water to be treated that is supplied to the electrolytic cell 2 is treated and electrolytically sterilized in the same manner as in the case shown in Fig. 1, and when the power is cut off when the operation is stopped and the supply of the water to be treated is continued, the amount of hydrogen gas increases. There is no danger of explosion of hydrogen gas.

FIG. 3 shows another example of a bipolar fixed bed electrolytic cell that can be used in the present invention.

A cylindrical electrolytic cell main body 32 having flanges 31 on the upper and lower sides has a hole near its upper end and near its lower end, respectively.

A shoe-shaped power feeding cathode terminal 33 and a power feeding cathode terminal 34 are provided.

Between the repowering electrode terminals 33 and 34, there are a large number of fixed bed forming particles 35 made of a conductive material, such as a carbon-based material, and a smaller number of insulating particles made of, for example, synthetic resin than the fixed bed forming particles 35. 36 are mixed almost uniformly.

The insulating particles 36 have a function of preventing the power feeding anode terminal 33 and the power feeding cathode terminal 34 from being completely short-circuited.

A bottom plate 38 having a downward cylinder 37 formed in the center is connected to the lower surface of the flange 31 at the bottom of the electrolytic cell body 32.
A filter 40 is sandwiched between a flange portion at the lower end of the cylindrical body 37 and a flange portion at the upper end of the water supply pipe 39 .

A lid body 42 having an upwardly extending treated water discharge pipe 41 extending laterally on the central upper surface is installed on the upper flange 31. An auxiliary pipe 44 having an active gas inlet 43 connected thereto is inserted so that each flange 45 is brought into contact with a flange 46 of the water discharge pipe 41 . The other end of the water discharge pipe 41 reaches into the storage tank 47 through the lid 48 of the storage tank 47. The storage tank 47
Similarly, the base end of the water supply pipe 39 is connected to the lid 4.
The water to be treated 49 in the storage tank 47 is inserted through the
is in contact with The other end of the water supply pipe 39 to be treated is connected via a pump 50 to a circular hole 51 bored in the center lower surface of the bottom plate 38 installed so as to be in contact with the lower flange 3 of the electrolytic cell main body 32 mentioned above. has been done.

When electricity is supplied to the electrolytic cell having such a configuration while supplying water to be treated from the storage tank 47 through the water supply pipe 49, the particles 35 for forming a fixed bed are formed as in the case of FIGS. 1 and 2. After the water to be treated is polarized positively and negatively and the water to be treated is treated with gas generation in the polarized portion, the water to be treated is discharged together with the mixed gas of hydrogen and oxygen generated by the water discharge pipe 41.
The mixed gas is diluted by the inert gas introduced from the inert gas inlet 43 in the auxiliary pipe 44 of the treated water discharge pipe 41, and the hydrogen gas proportion becomes lower than the explosive limit. Since the fuel is circulated to the storage tank 47, an explosion within the storage tank 47 is prevented. Furthermore, when the operation of this electrolytic treatment is to be stopped, the supply of water to be treated is continued while the power supply flowing between the two power supply electrode terminals 33 and 34 is cut off, and the water to be treated is continued to be supplied.
The electrolytic cell 3 together with the water to be treated to which the hydrogen gas in 2 was supplied
2. Discharge the water to the outside to sufficiently reduce the amount of hydrogen gas, or stop supplying the water to be treated after hydrogen gas no longer exists.
Stop driving completely. As a result, there will be no gas containing hydrogen gas within the explosion limit in the electrolytic cell after the operation is stopped, and no explosion will occur even if an ignition source is present.

FIG. 4 illustrates a monopolar fixed bed electrolytic cell that can be used in the method of the present invention.

A mesoche-shaped power feeding anode terminal 63 and a power feeding cathode terminal 64 are provided near the top and bottom ends of the cylindrical electrolytic cell body 62 having flanges 61 on the top and bottom, respectively.

A diaphragm 6 is provided between the two power feeding electrode terminals 63 and 64.
A pair of fixed beds 66 made of conductive material, such as carbon fiber, formed into a felt shape are filled in the anode chamber and the cathode chamber, with the felt carbon fibers in the anode chamber and the cathode chamber respectively connected to the power feeding anode terminal. 63 and a power feeding cathode terminal 64, the fixed bed in the anode chamber is positively charged and the fixed bed in the cathode chamber is negatively charged.

A bottom plate 68 having a downward cylinder 67 formed in the center is connected to the lower surface of the flange 61 at the bottom of the electrolytic cell body 62.
A filter 70 is sandwiched between the flange portion at the lower end of the cylindrical body 67 and the flange portion at the upper end of the water supply pipe 69 . The filter 70 is made of a material with higher conductivity than the water to be treated and is grounded.

Further, a lid body 72 having an upward cylindrical body 71 formed in the center is connected to the upper surface of the flange 61 at the upper part of the electrolytic cell body 62, and the flange portion at the upper end of the cylinder body 71 and the treated water discharge pipe 73 are connected to each other. A filter 74 is held between the flange portions at the lower end. The treated water discharge pipe 73 extends laterally, is bent downward, and reaches into the storage tank 75 through the lid 76 of the storage tank 75.

The base end of the water supply pipe 69 to be treated is similarly inserted into the storage tank 75 through the lid body 76, and the water supply pipe 69 is inserted into the storage tank 75.
It is in contact with the water to be treated 77 inside. The treated water supply pipe 6
The other end of 9 is connected to the downward cylindrical body 67 via the pump 78 as described above.

The electrolytic cell 62 shown in FIG. 4, like the electrolytic cells shown in FIGS. 1 to 3, effectively treats the water to be treated and prevents the hydrogen gas remaining in the electrolytic cell from exploding. be done.

(Example) Examples of the treatment liquid modification treatment according to the method of the present invention will be described below, but the examples are not intended to limit the present invention.

In fact 1, we used an electrolytic cell identical to that shown in Figure 1, except that the low auxiliary pipe, storage tank, and pump were removed, to confirm the effect of diluting hydrogen gas by continuing to supply water to be treated. .

The electrolytic cell body is made of vinyl chloride and has a height of 100 m and an inner diameter of 50 m.
It has a cylindrical shape with a stopper flange, and inside the cylindrical body, three fixed bed electrodes made of carbon fiber electrode material with a diameter of 50 mm and a thickness of 10 mm are installed, with a porosity of 85%, a diameter of 5 degrees and a thickness. Inserted with four 1.5mm polyethylene resin diaphragms,
On the surface of the diaphragm at both the upper and lower ends, there is a platinum plate with a diameter of 48 m and a thickness of 1. The mesoche-like anode terminal and cathode terminal of hm+ were placed in contact with each other.

On the upper flange of the electrolytic cell body, a lid body with an upwardly facing cylinder with a diameter of 26 mm in the center was placed, and between the upwardly facing cylinder and the flange of the water discharge pipe to be treated, a diameter of 48 mm and a thickness of 3.0 mm was placed. A polypropylene fiber sintered filter with an average pore diameter of 5 μm and a porosity of 45% was sandwiched.

A 0.1 g/ff sodium hydroxide aqueous solution was supplied to this electrolytic cell at a rate of 21/min to perform water electrolysis through a temporary treatment.

During this electrolysis, the amount of foamy hydrogen gas per treated water 11 at the base end of the treated water discharge pipe at the electrolyzer outlet is 1.5 cc/l in terms of standard conditions, and the treated water is discharged. When an electric spark was brought close to the base end of the tube, it ignited.

In this state, the power supply to the electrolytic cell was stopped while the supply of water to be treated was continued, and the change over time in the amount of foamy hydrogen in the water discharge pipe was measured after the power supply was stopped. When an electric spark was brought close to the base end to check for ignition, the results shown in Table 1 were obtained.

From Table 1, when using the electrolytic cell of this example and supplying the water to be treated at the above flow rate, if the supply of the water to be treated is continued for 60 seconds after the power supply is stopped, the amount of foamy hydrogen in the electrolytic cell will be 1.
The surface weight is Occ/l, and it can be seen that below this value, ignition will not occur even if an electric spark is brought close.

(Effects of the Invention) The method of the present invention is an electrolyzer that continues to supply water to be treated to the electrolytic cell for a predetermined time even after the power is cut off when the operation is stopped when electrolytically treating water to be treated while generating gas. A method for stopping operation of a tank (Claim 1) A mixed gas consisting of hydrogen and oxygen generated by ordinary water electrolysis is within the explosion limit, so it may ignite and explode due to static electricity, creating a danger.

When the method of the present invention continues to supply the water to be treated to the electrolytic cell even after the power is cut off at the time of operation stoppage, the foamy mixed gas containing hydrogen gas in the electrolytic cell is discharged out of the electrolytic cell by the water to be treated. Explosion avoided. Furthermore, if the supply of the water to be treated is continued, not only the gas inside the electrolytic cell (the mixed gas in the pipes such as the water discharge pipe connected to the electrolytic cell) will also be discharged from the pipe by the water to be treated, and the gas will be discharged from the pipe. Therefore, when restarting operation of this electrolytic cell, even if electricity is immediately started, an explosion will not occur because there is hardly any hydrogen gas scattered in the electrolytic cell or piping.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are schematic sectional views each illustrating a fixed bed type three-dimensional electrode electrolytic cell that can be used in the method of the present invention. l ・ ・ 3 ・ ・ 4 ・ ・ 5 ・ ・ 7 ・ ・ 9 ・ ・ 11 ・ 13.14 16 ・ ・ 18 ・ 20 ・ 22 ・ 31 ・ 33 ・ ・ Flange 2... Electrolytic cell Main body, anode terminal for power supply, cathode terminal for power supply, fixed bed 6... Spacer, upward cylinder 8... Lid, treated water discharge pipe 10... Filter, inert gas inlet 12... Auxiliary pipe...Flange 15...Storage tank/lid 17...Inert gas introduction pipe/Water to be treated supply pipe 19...Water to be treated/Pump 21
... Bottom plate, circular hole 23 ... Insoluble metal material, flange 32 ... Electrolytic cell body, power supply anode terminal 34, 35, 37, 39, 41, 43, 45. 48・ 50・ 61・ 63・ 64・ 65・ 67・ 69・ 71・ 73・ 75・ 77・・・Cathode terminal for power supply・・Particles for forming a fixed bed 36・・Insulating particles・・Downward cylindrical body 38・...Bottom plate...Water supply pipe to be treated 40...Filter...Water discharge pipe to be treated 42...Cover body...Inert gas inlet 44...Auxiliary pipe 46...Flange 47... Storage tank...lid 49...Water to be treated...pump 51...circular hole...flange 62...electrolytic cell body...anode terminal for power supply...cathode terminal for power supply...diaphragm 66...・Fixed bed・Downward cylinder 68・Bottom plate・Water supply pipe 70・Filter・Upward cylinder 72・Cover body・Water discharge pipe 74・Filter・・Storage tank 76...Lid...Water to be treated

Claims (1)

[Claims] (1) In a method of supplying water to be treated to a fixed-bed three-dimensional electrode electrolytic cell and electrolytically treating it while generating a mixed gas of hydrogen gas and oxygen gas, when stopping the treatment, after cutting off the power supply, An operation shutdown method characterized by continuing to supply the water to be treated to the electrolytic cell for a predetermined period of time.