JP2015129345A - Electric insulation method for electrolysis system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric insulation method capable of shutting down an electrical conduction path easily, quickly and securely when energization to an electrolysis cell in an electrolysis system is stopped, so as to stop occurrence of inverse current as much as possible.SOLUTION: An electric insulation method for an electrolysis system uses an electrolysis system including an electrolysis cell 10 having at least: a cathode chamber 1 with a cathode attached; an anode chamber 2 with an anode attached; a barrier 3 partitioning the cathode chamber 1 and the anode chamber 2; and an electrolyte filled in the cathode chamber 1 and the anode chamber 2. When energization to the electrolysis cell 10 in an electrolysis system is stopped, the electrolyte is discharged from the cathode chamber 1 and the anode chamber 2 so that a liquid level of the electrolyte is lowered below a lowermost end of the electrolysis cell 10.

Description

  The present invention relates to an electrical insulation method for an electrolysis system. Specifically, it is an electrical insulation method for preventing the occurrence of a reverse current by interrupting a conductive path when energization to an electrolysis cell in an electrolysis system is stopped.

Hydrogen, for example, is very important as a raw material for chemical fertilizer, in addition to being used as a fuel in fuel cell vehicles, a turbine fuel in hydrogen power generation, a fuel such as city gas components, and the like.
Hydrogen can be produced, for example, by electrolysis of water. In particular, with the recent increase in environmental awareness, water electrolysis using renewable energy as a power source has attracted attention. An example of renewable energy is sunlight. Since a power generation system using sunlight has already been put into practical use and there are many commercial products, it is suitable as a power source for electrolysis.
However, a power generation system using renewable energy typified by sunlight has a large amount of power generation. For example, there is a significant difference in the amount of sunshine between clear and rainy days, and between daytime and nighttime, which greatly affects the amount of power generation.

When an electrolysis system that performs electrolysis of water is connected to, for example, a photovoltaic power generation system, sunlight is obtained, and when the electrolysis cell is energized, electrolysis of water is performed to obtain hydrogen as a product. be able to. However, for example, when sunlight is lost due to sunset and energization of the electrolysis cell is stopped, an electromotive force is generated in the electrolysis cell, and so-called “reverse current” is generated. When reverse current is generated in the electrolysis cell, for example, elution of the catalyst layer existing on the surface of the electrode (especially the negative electrode), cracking, peeling, degradation of electrode activity due to oxidation deterioration, etc., and associated increase in hydrogen overvoltage Will cause.
Therefore, when energization to the electrolysis cell is stopped, it is preferable to block the conductive path as soon as possible to prevent the generation of reverse current.
In this regard, Patent Document 1 proposes a method of obtaining insulation by replacing the electrolyte in the supply passage for supplying electrolyte to the cathode chamber and the anode chamber in the electrolysis system with gas.

JP 2014-95128 A

Specifically, the method of Patent Document 1 is a method of obtaining insulation by performing the replacement by blowing a gas (for example, air) into a supply flow channel installed in a looped state. However, in an ordinary electrolysis system, a plurality of electrolysis cells are often stacked in series. Therefore, the supply channel is also branched and installed in the number of electrolytic cells.
In the electrolysis system having such a configuration, when gas is blown into the supply channel, it is extremely difficult to replace the electrolyte solution quickly and completely without leakage in all of the plurality of loop-shaped supply channels. The electrolytic solution in the supply flow channel far from the gas blowing position remains partly without being replaced. Therefore, in the electrolytic cell to which the flow channel is connected, the concern about the occurrence of reverse current is not wiped out. .

The present invention has been made in view of the above situation.
Therefore, an object of the present invention is to prevent the occurrence of reverse current as much as possible by interrupting the conductive path easily, quickly and reliably when the energization to the electrolysis cell in the electrolysis system is stopped. It is an object of the present invention to provide an electrical insulation method.

The present inventors have intensively studied to achieve the above object. As a result, it was revealed that the known electrolysis system has a structural defect in preventing reverse current.
FIG. 1 shows a schematic diagram of a known electrolysis system.
The electrolysis system of FIG. 1 includes an electrolysis cell 10 having a cathode chamber 1, an anode chamber 2, a diaphragm 3, and an electrolyte (not shown), a cathode tank 11 connected to the cathode chamber 1, and the anode chamber. 2, and an anode tank 21 connected to 2. Each of the cathode tank 11 and the anode tank 21 also functions as a gas-liquid separation layer, and hydrogen (and oxygen or halogen), which is a product, is separated and recovered from the electrolytic solution by the function of these tanks. Further, FIG. 1 shows a pump 50 for liquid feeding.

In the electrolysis system of FIG. 1, when energization to the electrolysis cell 10 is stopped, the progress of electrolysis is stopped and an electromotive force is generated in the electrolysis cell 10. This electromotive force acts as a force that generates a current in the opposite direction to the energization of the electrolytic cell 10.
Here, the water level of the electrolyte is in the middle of the cathode tank and the anode tank. Accordingly, the pipes below these tanks are full of water, and a reverse current conductive path is prepared. When energization to the electrolysis cell is stopped in such a state, since the cathode chamber and the anode chamber of the electrolysis cell are conducting through the piping, a reverse current is generated, for example, causing deterioration of the cathode. It is.

Based on the above considerations, the present inventors have considered that the occurrence of reverse current can be avoided if the conductive path by the piping is interrupted when the energization to the electrolysis cell is stopped. The present invention is based on such consideration.
Therefore, the above objects of the present invention are achieved by the present invention summarized as follows:

[1] Electrolysis comprising at least a cathode chamber to which a cathode is attached, an anode chamber to which an anode is attached, a diaphragm partitioning the cathode chamber and the anode chamber, and an electrolyte filled in the cathode chamber and the anode chamber In an electrolysis system comprising a cell,
When energization to the electrolytic cell is stopped, the electrolytic solution is discharged from the cathode chamber and the anode chamber, and the liquid level of the electrolytic solution is lowered below the lowest end of the electrolytic cell, Electrical insulation method for electrolysis system.
[2] The electrolysis system further includes a drainage tank located below the cathode chamber and the anode chamber,
The electrical insulation method according to [1], wherein the electrolytic solution is discharged by moving the electrolytic solution in the cathode chamber and the anode chamber into the drainage tank.

[3] The electrical insulation method according to [2], wherein the electrolyte solution is discharged by moving the electrolyte solution in the cathode chamber and the anode chamber into the drainage tank under its own weight.
[4] The level of the electrolytic solution after discharging the electrolytic solution from the cathode chamber and the anode chamber is a confluence of flow paths for moving the electrolytic solution from the cathode chamber and the anolyte to the drainage tank. The electrical insulation method according to [2] or [3], which is in an upper part.
[5] The electrolysis system comprises:
A cathode gas-liquid separation chamber connected to the cathode chamber, having a gas-liquid separation capability but having substantially no liquid storage capability;
The anode gas-liquid separation chamber connected to the anode chamber, which has a gas-liquid separation capability but does not substantially have a liquid storage capability, and further includes an anode gas-liquid separation chamber according to any one of [1] to [4]. Electrical insulation method.

[6] After electrical insulation of the electrolysis system by the method according to any one of [1] to [5], when energization to the electrolysis cell is resumed, electrolysis is performed in the cathode chamber and the anode chamber. A method for resuming energization of an electrolysis system, characterized by refilling the liquid.
[7] At least
A cathode chamber to which a cathode is attached; an anode chamber to which an anode is attached; a diaphragm partitioning the cathode chamber and the anode chamber; and an electrolytic cell comprising an electrolyte filled in the cathode chamber and the anode chamber;
An electrolysis system comprising: the cathode chamber and a drainage tank located below the anode chamber.
[8] The electrolysis system according to [7], wherein the drainage tank includes pressure adjusting means for adjusting the pressure in the drainage tank.
[9] The electrolysis system according to [8], wherein the gas supplied to the drainage tank by the pressure adjusting unit when the pressure in the drainage tank is reduced is an inert gas.

According to the present invention, when energization to the electrolysis cell in the electrolysis system is stopped, it is possible to easily, quickly and surely cut off the conductive path and prevent the occurrence of reverse current as much as possible. An electrical isolation method is provided.
Since the method of the present invention can prevent the occurrence of reverse current when the amount of sunshine changes and the energization of the electrolysis cell is stopped, for example, in an electrolysis system connected to a photovoltaic power generation system, It becomes possible to suppress deterioration of the cathode with time as much as possible.

FIG. 1 is a schematic diagram for explaining a known electrolysis system. FIG. 2 is a schematic diagram for explaining an example of the electrolysis system of the present invention. FIG. 3 is a schematic diagram for explaining another example of the electrolysis system of the present invention.

The electrolysis system used in the present invention is at least:
A cathode chamber having a cathode, an anode chamber having an anode, a diaphragm partitioning the cathode chamber and the anode chamber, and an electrolytic cell comprising an electrolyte filled in the cathode chamber and the anode chamber;
Preferably, a drainage tank located below the cathode chamber and the anode chamber is further provided.
The electrolytic cell includes a cathode chamber having a cathode, an anode chamber having an anode, and a diaphragm partitioning the cathode chamber and the anode chamber. The cathode chamber and the anode chamber are arranged to face each other with a diaphragm interposed therebetween. Each of the cathode chamber and the anode chamber is filled with an electrolytic solution.
As the cathode, the anode, the diaphragm, and the electrolytic solution, known materials used in water electrolysis can be used without limitation. Specific examples are as follows, for example.

Examples of the cathode and the anode include soluble electrodes such as carbon electrodes, Al electrodes, Cu electrodes, Sn electrodes, and Pb electrodes;
Examples thereof include a metal plating electrode, a Pt / Ti electrode, a metal fired electrode, and an insoluble electrode such as an IrO ₂ / Ti electrode.
As the diaphragm, an ion exchange membrane is preferably used. For example, a cation exchange membrane having fluorine atoms can be exemplified.
Examples of the electrolytic solution include an alkali halide aqueous solution and an alkali hydroxide aqueous solution.
The electrolysis system in the present invention may have only one electrolysis cell as described above, or may have a cell stack structure in which two or more electrolysis cells are laminated. When the cell stack structure is adopted, it is preferable that each unit electrolysis cell is installed via the above-mentioned diaphragm, or a conductive path made of a conductive material is formed between each unit electrolysis cell. .

In the present invention, the cathode chamber and the anode chamber in the electrolytic cell are filled with an electrolytic solution when electrolysis is performed. The method of the present invention is characterized in that, when energization to the electrolytic cell is stopped, the electrolytic solution is discharged from the cathode chamber and the anode chamber, and the liquid level of the electrolytic solution is lowered below the lowest end of the electrolytic cell. To do. Even if the electrolytic solution is discharged from the cathode chamber and the anode chamber when energization to the electrolytic cell is stopped, if the liquid level of the electrolytic solution is higher than the lowest end of the electrolytic cell, the electrolytic solution functions as a conductive path. Therefore, the concern about the occurrence of reverse current cannot be eliminated. However, according to the method of the present invention, since the conductive path in the pipe is completely cut off, the reverse current does not flow even when the energization to the electrolysis cell is stopped.
There is no limitation on the method of discharging the electrolyte from the cathode chamber and the anode chamber. For example, it may be forcibly discharged by a liquid feed pump, or may be discharged using a drop due to its own weight. Preferably, discharging is performed by using a descent due to its own weight.

It is preferable that the electrolytic solution discharged from the cathode chamber and the anode chamber when the energization to the electrolysis cell is stopped is refilled in the cathode chamber and the anode chamber and subjected to electrolysis when the energization to the electrolysis cell is resumed. Therefore, it is preferable that the electrolytic system in the present invention has a drain tank for temporarily storing the discharged electrolytic solution and reusing it. Most preferably, the drainage tank is located below the cathode chamber and the anode chamber, and discharge of the electrolyte causes the electrolyte in the cathode chamber and the anode chamber to move into the drainage tank under its own weight. It is an aspect performed by this. In this case, it is convenient that the flow path for moving the electrolytic solution is emitted from each of the cathode chamber and the anolyte, merges in the middle, and reaches the drainage tank. It is preferable that the flow path is uniformly provided without providing a trap portion.
It is preferable that the liquid level of the electrolytic solution after the electrolytic solution is discharged from the cathode chamber and the anode chamber is higher than the junction of the flow paths for moving the electrolytic solution from the cathode chamber and the anode chamber. When the liquid level is lowered below the junction point, the cathode chamber and the anode chamber can flow in the gas phase. For this reason, hydrogen in the cathode chamber and oxygen in the anode chamber are mixed, and the purity of the product is lowered, and there is a possibility that an explosion gas composed of hydrogen and oxygen is formed.
The movement can be started, for example, by opening and closing a valve. This valve may be manually opened and closed, or may be an automatically controlled valve that opens and closes in conjunction with whether or not the electrolysis cell is energized.

The electrolytic system in the present invention aims to obtain hydrogen (and oxygen or halogen) as a product. Therefore, it is preferable to have gas-liquid separation means for separating and recovering hydrogen or the like generated in the vicinity of the electrode from the electrolytic solution.
In the known electrolysis system, the cathode tank and the anode tank are the gas-liquid separation means. However, as mentioned above, these tanks are filled with the electrolyte up to the middle thereof. Such an embodiment is not preferable in view of the rapidity when discharging the electrolytic solution from the cathode chamber and the anode chamber.
Therefore, in the present invention, it is preferable to provide a gas-liquid separation chamber that has gas-liquid separation ability but does not substantially have liquid storage ability, instead of these tanks. This gas-liquid separation chamber can be realized, for example, by providing a vertically elongated chamber above the cathode chamber and the anode chamber. The volume of the gas-liquid separation chamber is preferably 1,000 times or less, more preferably 1 to 100 times the volume of the cathode chamber and the anode chamber. The aspect ratio of the gas-liquid separation chamber is preferably about 10 to 1,000 as the ratio of the height (length) to the width of the chamber.

The gas-liquid separation chamber preferably includes a cathode gas-liquid separation chamber connected to the cathode chamber and an anode gas-liquid separation chamber connected to the anode chamber from the viewpoint of product purity.
By using the electrolysis system having the above-described configuration, when the energization to the electrolysis cell is stopped, the electrolyte solution can be quickly discharged from the cathode chamber and the anode chamber. Since no current flows, it is possible to prevent, for example, deterioration of the cathode as much as possible.
When energization of the electrolytic cell is resumed, the electrolytic solution can be continued by refilling the cathode chamber and the anode chamber with the electrolytic solution. The electrolyte solution refilled at this time may be a discharged electrolyte solution or a newly prepared electrolyte solution. Preferably, the previous liquid discharged into the drainage pump is reused. The refilling of the electrolytic solution into the cathode chamber and the anode chamber can be performed by, for example, a liquid feed pump.

The drainage tank receives the electrolytic solution when energization to the electrolysis cell is stopped, and discharges the electrolytic solution when energization to the electrolysis cell is resumed. At the time of receiving and discharging, the volume of the gas phase of the drainage tank varies. Therefore, it is preferable that the drainage tank is provided with a pressure adjusting means for adjusting the internal pressure so that the pressure in the drainage tank does not fluctuate with the acceptance / discharge.
As said pressure adjustment means, a water sealer, a valve, an accumulator etc., and these combinations can be illustrated, for example.
The water sealer is, for example, a vacuum sealer opened to the atmosphere in order to allow the gas phase gas pushed out of the drainage tank to escape to the atmosphere when the drainage tank receives the electrolyte,
A pressurizing water seal connected to the gas pipe to replenish the gas phase of the drainage tank when the drainage tank discharges the electrolyte;
May be combined.
As the valve, for example, when the drainage tank receives the electrolyte, and the pressure of the gas phase in the drainage tank rises above a predetermined pressure for smooth feeding, the gas phase part A pressure reducing valve having a function of releasing and decompressing the gas;
A pressurizing valve having a function of replenishing and pressurizing the gas phase portion when the drainage tank discharges the electrolytic solution and the gas phase portion pressure of the drainage tank decreases below a predetermined pressure; ,
May be combined.
Further, as the accumulator, in order to alleviate fluctuations in the volume of the gas phase part that occurs when the drainage tank receives the electrolyte and discharges the electrolyte, the accumulator is directly or via a valve in the gas phase of the tank. And a variable capacity gas tank (for example, a balloon) connected to each other.
As the gas supplied to the tank when the electrolytic solution is discharged from the drain tank, an inert gas (for example, nitrogen, helium, argon, etc.) is preferable. When supporting gas (for example, air) or flammable gas (for example, city gas) is used, these gases are mixed into the cathode chamber and the anode chamber and the purity of the product is impaired. When mixed into the chamber and when flammable gas is mixed into the anode chamber, there is no risk of squealing.

Hereinafter, the configuration of the electrolysis system of the present invention will be specifically described with reference to the drawings.
FIG. 2 shows a schematic diagram of an example of an electrolysis system preferably used in the present invention.
The electrolysis system of FIG. 2 includes an electrolysis cell 10 including a cathode chamber 1, an anode chamber 2, a diaphragm 3, and an electrolyte (not shown), a cathode gas-liquid separation chamber 12 connected to the cathode chamber 1, An anode gas-liquid separation chamber 22 connected to the anode chamber 2, a drainage tank 30, and a valve 40 are provided. Each of the cathode gas-liquid separation chamber 12 and the anode gas-liquid separation chamber 22 has an elongated shape, and is installed vertically above the cathode chamber 1 and the anode chamber 2. Since these gas-liquid separation chambers have gas-liquid separation capability, they contribute to increasing the purity of the product, but do not substantially have liquid storage capability, so that the electrolysis in the cathode chamber 1 and the anode chamber 2 is achieved. Contributes to the quick discharge of liquid. The drainage tank 30 is disposed below the cathode chamber 1 and the anode chamber 2. More specifically, the uppermost part of the drainage tank 30 is below the branch point of the supply flow path for supplying the electrolytic solution to the polar chamber and the anode chamber.

Since the valve 40 is installed between the electrolyte supply pipe and the drain tank 30, when the energization of the electrolytic cell 10 is stopped, the valve 40 is opened so that the electrolyte is caused by its own weight. The cathode chamber 1 and the anode chamber 2 can quickly move into the drainage tank 30. In this electrolysis system, since the liquid level after the electrolytic solution movement when the energization to the electrolytic cell 10 is stopped is lower than the cathode chamber 1 and the anode chamber 2 even in the highest case, After the liquid moves, the conductive path for the reverse current is not maintained. In addition, since the liquid level after the electrolyte is moved is above the junction of the flow path for moving the electrolyte from the cathode chamber 1 and the anode 2 to the drain tank 30, the cathode chamber 1 and anode There is no possibility that the chamber 2 can be circulated in the gas phase, and there is no risk of explosion.
Further, FIG. 2 shows a pump 50 for feeding liquid. With the function of the pump 50, the electrolytic solution moved into the drainage tank 30 when the energization of the electrolytic cell 10 is stopped can be refilled in the cathode chamber 1 and the anode chamber 2.

FIG. 3 shows a schematic diagram of another example of the electrolysis system preferably used in the present invention.
The electrolysis system of FIG. 3 is substantially the same as the electrolysis system of FIG. 2 except that a pressure adjustment comprising a pressurizing water seal 61 and a depressurization water seal 62 in the upper part (gas phase part) of the drainage tank 30 Means are provided. The water seal 61 for pressurization is preferably connected to an inert gas pipe via a pressure adjusting regulator (not shown). The depressurized water sealer 62 has a gas phase portion opened to the atmosphere.
When energization of the electrolysis cell 10 is stopped, the electrolyte moves from the cathode chamber 1 and the anode chamber 2 to the drainage tank 30 by opening the valve 40. At this time, the volume of the gas phase portion of the drainage tank 30 is reduced, and the pushed-out gas is released to the atmosphere through the sealing water in the decompression water sealer 62. On the other hand, when energization of the electrolytic cell 10 is resumed, the electrolytic solution is discharged from the drain tank 30 by the function of the pump 50 and refilled in the cathode chamber 1 and the anode chamber 2. At this time, although the volume of the gas phase portion of the drainage tank 30 increases at this time, the inert gas is supplied to the gas phase portion from the inert gas pipe through the sealing water in the pressurizing water seal 61. The

Due to the above-described action, the electrolysis system including the pressure adjusting means can maintain a constant pressure in the tank even when the drainage tank receives and discharges the electrolyte, thereby enabling stable operation. It becomes.
Furthermore, according to a preferred embodiment of the invention for maintaining the liquid level of the electrolyte above the junction of the electrolyte transfer flow path, the cathode chamber 1, the anode chamber 2, and the gas phase portion of the drain tank 30 Since the atmosphere and the inert gas pipe do not circulate in the gas phase, the high purity of the product is ensured and there is no risk of squealing.

DESCRIPTION OF SYMBOLS 1 Cathode chamber 2 Anode chamber 3 Diaphragm 10 Electrolytic cell 11 Cathode tank 21 Anode tank 12 Cathode gas-liquid separation chamber 22 Anode gas-liquid separation chamber 30 Drain tank 40 Valve 50 Liquid feed pump 60 Pressurized water seal 61 Depressurization water seal

Claims (9)

At least a cathode chamber to which a cathode is attached; an anode chamber to which an anode is attached; a diaphragm partitioning the cathode chamber and the anode chamber; and an electrolytic cell comprising an electrolyte filled in the cathode chamber and the anode chamber. In electrolysis system,
When energization to the electrolytic cell is stopped, the electrolytic solution is discharged from the cathode chamber and the anode chamber, and the liquid level of the electrolytic solution is lowered below the lowest end of the electrolytic cell, Electrical insulation method for electrolysis system. The electrolysis system further comprises a drainage tank located below the cathode chamber and the anode chamber;
The electrical insulation method according to claim 1, wherein the electrolytic solution is discharged by moving the electrolytic solution in the cathode chamber and the anode chamber into the drainage tank.   The electrical insulation method according to claim 2, wherein the electrolyte solution is discharged by moving the electrolyte solution in the cathode chamber and the anode chamber into the drainage tank under its own weight.   The liquid level of the electrolytic solution after discharging the electrolytic solution from the cathode chamber and the anode chamber is higher than the confluence of the flow path for moving the electrolytic solution from the cathode chamber and the anode material to the drainage tank. The electrical insulation method according to claim 2 or 3, wherein: The electrolysis system is
A cathode gas-liquid separation chamber connected to the cathode chamber, having a gas-liquid separation capability but having substantially no liquid storage capability;
The electrical insulation according to any one of claims 1 to 4, further comprising an anode gas-liquid separation chamber connected to the anode chamber, which has gas-liquid separation capability but does not substantially have liquid storage capability. Method.   After electrically insulating the electrolysis system by the method according to any one of claims 1 to 5, when the energization to the electrolysis cell is resumed, the cathode chamber and the anode chamber are refilled with an electrolyte. A method of resuming energization of an electrolysis system, characterized in that at least,
A cathode chamber to which a cathode is attached; an anode chamber to which an anode is attached; a diaphragm partitioning the cathode chamber and the anode chamber; and an electrolytic cell comprising an electrolyte filled in the cathode chamber and the anode chamber;
An electrolysis system comprising: the cathode chamber and a drainage tank located below the anode chamber.   The electrolysis system according to claim 7, wherein the drainage tank includes pressure adjusting means for adjusting the pressure in the drainage tank.   The electrolysis system according to claim 8, wherein the gas supplied to the drainage tank by the pressure adjusting means when the pressure in the drainage tank is reduced is an inert gas.

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