WO2021131579A1

WO2021131579A1 - Fluorine gas production method and fluorine gas production apparatus

Info

Publication number: WO2021131579A1
Application number: PCT/JP2020/045093
Authority: WO
Inventors: 慎也小黒; 陽介福地; 小林　浩
Original assignee: 昭和電工株式会社
Priority date: 2019-12-27
Filing date: 2020-12-03
Publication date: 2021-07-01
Also published as: KR20220065825A; TW202136584A; CN113874553A; CN113874553B; JPWO2021131579A1; US20220275523A1; TWI755972B; EP4083264A1

Abstract

Provided is a fluorine gas production method whereby it becomes possible to prevent the clogging of a pipe or a valve by mists. A fluorine gas is produced by a method comprising: an electrolysis step of carrying out the electrolysis of an electrolyte solution in an electrolysis tank; a water concentration measurement step of measuring the water concentration in the electrolyte solution at a time point of the electrolysis; and a gas feeding step of feeding a fluid generated in the electrolysis tank upon the electrolysis of the electrolyte solution from the inside of the electrolysis tank to the outside of the electrolysis tank through a flow passage. In the gas feeding step, a flow passage through which the fluid is to be flown is switched to another one depending on the water concentration in the electrolyte solution which is measured in the water concentration measurement step, in such a manner that the fluid is fed to a first flow passage through which the fluid can be fed from the inside of the electrolysis tank to a first outside zone when the water concentration in the electrolyte solution which is measured in the water concentration measurement step is equal to or less than a preset reference value, while the fluid is fed to a second flow passage through which the fluid can be fed from the inside of the electrolysis tank to a second outside zone when the water concentration is larger than the preset reference value. The preset reference value is a numerical value falling within the range of 0.1 to 0.8% by mass inclusive.

Description

Fluorine gas production method and fluorine gas production equipment

The present invention relates to a method for producing fluorine gas and a fluorine gas production apparatus.

Fluorine gas can be synthesized (electrolytic synthesis) by electrolyzing an electrolytic solution containing hydrogen fluoride and metal fluoride. Since mist (for example, mist of electrolytic solution) is generated together with fluorine gas by electrolysis of the electrolytic solution, the mist accompanies the fluorine gas sent out from the electrolytic cell. The mist that accompanies the fluorine gas becomes powder, which may block the pipes and valves used to supply the fluorine gas. Therefore, the operation for producing the fluorine gas may have to be interrupted or stopped, which hinders the continuous operation in the production of the fluorine gas by the electrolytic method.
In order to suppress blockage of pipes and valves by mist, Patent Document 1 discloses a technique of heating fluorine gas accompanied by mist or a pipe through which the gas passes to a temperature equal to or higher than the melting point of an electrolytic solution. Further, Patent Document 2 discloses a gas generating apparatus having a gas diffusion portion which is a space for roughly removing mist and a filler accommodating portion for accommodating a filler for adsorbing mist.

Japanese Patent Gazette No. 5584904 Japanese Patent Gazette No. 5919824

However, there has been a demand for a technique capable of more effectively suppressing blockage of pipes and valves due to mist.
An object of the present invention is to provide a method for producing fluorine gas and a fluorine gas production apparatus capable of suppressing clogging of pipes and valves due to mist.

In order to solve the above problems, one aspect of the present invention is as follows [1] to [5].
[1] A method for producing fluorine gas, which produces fluorine gas by electrolyzing an electrolytic solution containing hydrogen fluoride and metal fluoride.
The electrolysis step of performing the electrolysis in the electrolytic cell and
A water concentration measuring step of measuring the water concentration in the electrolytic solution at the time of the electrolysis, and a water concentration measuring step.
An air supply step of sending a fluid generated inside the electrolytic cell during electrolysis of the electrolytic cell from the inside of the electrolytic cell to the outside via a flow path, and
With
In the air supply step, the flow path through which the fluid flows is switched according to the water concentration in the electrolytic solution measured in the water concentration measuring step, and the water content in the electrolytic solution measured in the water concentration measuring step is switched. When the concentration is equal to or less than the preset reference value, the fluid is sent to the first flow path for sending the fluid from the inside of the electrolytic cell to the first outside, and is larger than the preset reference value. In this case, the fluid is sent to the second flow path that sends the fluid from the inside of the electrolytic cell to the second outside.
The method for producing fluorine gas, wherein the preset reference value is a numerical value within the range of 0.1% by mass or more and 0.8% by mass or less.

[2] The method for producing fluorine gas according to [1], wherein the metal fluoride is a fluoride of at least one metal selected from potassium, cesium, rubidium, and lithium.
[3] The anode used in the electrolysis is a carbonaceous electrode formed of at least one carbon material selected from diamond, diamond-like carbon, amorphous carbon, graphite, and glassy carbon [1] or [2]. ] The method for producing fluorine gas described in.
[4] The electrolytic cell has a structure in which bubbles generated at the anode or cathode used in the electrolysis rise vertically in the electrolytic solution and reach the liquid level of the electrolytic solution [1] to The method for producing a fluorine gas according to any one of [3].

[5] A fluorine gas production apparatus for producing fluorine gas by electrolyzing an electrolytic solution containing hydrogen fluoride and metal fluoride.
An electrolytic cell that houses the electrolyte and is electrolyzed.
A water concentration measuring unit that measures the water concentration in the electrolytic solution in the electrolytic cell during the electrolysis, and a water concentration measuring unit.
A flow path for sending the fluid generated inside the electrolytic cell during electrolysis of the electrolytic cell from the inside of the electrolytic cell to the outside,
With
The flow path has a first flow path for sending the fluid from the inside of the electrolytic cell to the first outside, and a second flow path for sending the fluid from the inside of the electrolytic cell to the second outside. It has a flow path switching unit that switches the flow path through which the fluid flows to the first flow path or the second flow path according to the water concentration in the electrolytic solution measured by the water concentration measuring unit.
When the water concentration in the electrolytic solution measured by the water concentration measuring unit is equal to or less than a preset reference value, the flow path switching unit is connected to the first flow path from the inside of the electrolytic cell. When the fluid is sent and is larger than the preset reference value, the fluid is sent from the inside of the electrolytic cell to the second flow path.
The fluorine gas production apparatus whose preset reference value is a numerical value within the range of 0.1% by mass or more and 0.8% by mass or less.

According to the present invention, when an electrolytic solution containing hydrogen fluoride and metal fluoride is electrolyzed to produce fluorine gas, clogging of pipes and valves due to mist can be suppressed.

It is a schematic diagram explaining an example of the light scattering detector used as the average particle diameter measuring part in the fluorine gas production apparatus which concerns on one Embodiment of this invention. It is the schematic explaining an example of the fluorine gas production apparatus which concerns on one Embodiment of this invention. It is a schematic diagram explaining an example of the mist removing apparatus used as the mist removing part in the fluorine gas production apparatus of FIG. It is the schematic explaining the 1st modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 2nd modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 3rd modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 4th modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 5th modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 6th modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 7th modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 8th modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the 9th modification of the fluorine gas production apparatus of FIG. It is the schematic explaining the tenth modification example of the fluorine gas production apparatus of FIG. In Reference Example 1, it is a graph which shows the particle size distribution of the mist contained in the fluid generated at an anode. In Reference Example 1, it is a graph which shows the correlation between the average particle diameter of mist, and the amount of mist generated at an anode. In Reference Example 1, it is a graph which shows the relationship between the average particle diameter of mist and the water concentration in an electrolytic solution.

An embodiment of the present invention will be described below. It should be noted that the present embodiment shows an example of the present invention, and the present invention is not limited to the present embodiment. In addition, various changes or improvements can be added to the present embodiment, and the modified or improved forms may be included in the present invention.
The present inventors have diligently studied the mist that causes clogging of pipes and valves in the electrolytic synthesis of fluorine gas. The "mist" in the present invention refers to liquid fine particles or solid fine particles generated together with fluorine gas in an electrolytic cell by electrolysis of an electrolytic solution. Specifically, fine particles of the electrolytic solution, solid fine particles in which the fine particles of the electrolytic cell have undergone phase change, and members constituting the electrolytic cell (metal forming the electrolytic cell, packing for the electrolytic cell, carbon electrode, etc.) and fluorine. It is a solid fine particle produced by the reaction of gas.

The present inventors measured the average particle size of the mist contained in the fluid generated inside the electrolytic cell during the electrolysis of the electrolytic solution, and confirmed that the average particle size of the mist changed with time. In addition, as a result of diligent studies, it was found that there is a correlation between the average particle size of mist and the water concentration in the electrolytic solution during electrolysis. We found that there was a correlation with the likelihood. Then, by devising a flow path for sending the fluid generated inside the electrolytic cell according to the water concentration in the electrolytic solution during electrolysis, clogging of piping and valves can be suppressed, and fluorine gas can be suppressed. We have found that it is possible to reduce the frequency of interruptions and suspensions of the operation of manufacturing the above-mentioned products, and have completed the present invention. An embodiment of the present invention will be described below.

The method for producing fluorine gas of the present embodiment is a method for producing fluorine gas by electrolyzing an electrolytic solution containing hydrogen fluoride and metal fluoride, and electrolyzing in the electrolytic tank. The electrolysis step, the water concentration measurement step of measuring the water concentration in the electrolytic solution during electrolysis, and the fluid generated inside the electrolytic tank during electrolysis of the electrolytic solution are sent from the inside of the electrolytic tank to the outside via a flow path. It is equipped with an air supply process.

In the air supply process, the flow path through which the fluid flows is switched according to the water concentration in the electrolytic solution measured in the water concentration measuring process. That is, when the water concentration in the electrolytic solution measured in the water concentration measuring step is equal to or less than a preset reference value, the fluid is sent to the first flow path that sends the fluid from the inside of the electrolytic cell to the first outside. When the fluid is fed and is larger than the preset reference value, the fluid is fed from the inside of the electrolytic cell to the second flow path for feeding the fluid to the second outside. The preset reference value is a value within the range of 0.1% by mass or more and 0.8% by mass or less.

Further, the fluorine gas production apparatus of the present embodiment is a fluorine gas production apparatus that electrolyzes an electrolytic solution containing hydrogen fluoride and metal fluoride to produce fluorine gas, and accommodates the electrolytic solution for electrolysis. The electrolytic tank that is performed, the water concentration measuring unit that measures the water concentration in the electrolytic solution in the electrolytic tank during electrolysis, and the fluid generated inside the electrolytic tank during electrolysis of the electrolytic solution are transferred from the inside to the outside of the electrolytic tank. It is equipped with a flow path for sending.

The flow path has a first flow path for sending a fluid from the inside of the electrolytic cell to the first outside, and a second flow path for sending the fluid from the inside of the electrolytic cell to the second outside. Further, this flow path has a flow path switching unit that switches the flow path through which the fluid flows to the first flow path or the second flow path according to the water concentration in the electrolytic solution measured by the water concentration measuring unit. There is.
When the water concentration in the electrolytic solution measured by the water concentration measuring unit is equal to or less than the preset reference value, the flow path switching unit sends fluid from the inside of the electrolytic cell to the first flow path and sets it in advance. If it is larger than the set reference value, the fluid is sent from the inside of the electrolytic cell to the second flow path. The preset reference value is a value within the range of 0.1% by mass or more and 0.8% by mass or less.

In the fluorine gas production method and the fluorine gas production apparatus of the present embodiment, the flow path through which the fluid flows is switched to the first flow path or the second flow path according to the water concentration in the electrolytic solution during electrolysis. As a result, the flow path is switched to the first flow path or the second flow path according to the average particle size of the mist, and the flow path is less likely to be blocked by the mist. Therefore, in the fluorine gas production method and the fluorine gas production apparatus of the present embodiment, when the electrolytic solution containing hydrogen fluoride and metal fluoride is electrolyzed to produce fluorine gas, the pipes and valves are blocked by mist. Can be suppressed. Therefore, the frequency of interruption and stop of the operation of producing the fluorine gas can be reduced, and continuous operation can be easily performed. Therefore, fluorine gas can be economically produced.

In the method for producing fluorine gas and the apparatus for producing fluorine gas of the present embodiment, the water concentration in the electrolytic solution may be measured with respect to the electrolytic solution in the anode chamber in which the anode is arranged, or the cathode may be used. This may be performed on the electrolytic solution in the arranged cathode chamber. Further, the measurement of the water concentration in the electrolytic solution may be carried out at all times during electrolysis, may be carried out periodically at regular intervals, or may be carried out irregularly at any time. Further, although the first flow path and the second flow path are different flow paths, the first outer flow path and the second outer flow path may be different places or the same place.

Here, an example of the fluorine gas production method and the fluorine gas production apparatus of the present embodiment is shown. The first flow path is a flow path for sending a fluid from the inside of the electrolytic cell to a fluorine gas sorting unit that sorts and extracts fluorine gas from the fluid via a mist removing unit that removes mist from the fluid. The second flow path is a flow path for sending the fluid from the inside of the electrolytic cell to the fluorine gas sorting part without passing through the mist removing part. That is, when the water concentration in the electrolytic solution is equal to or less than the preset reference value, the fluid is sent to the mist removing unit provided in the first flow path, and when it is larger than the preset reference value, the fluid is sent. , The fluid is not sent to the mist remover. In this example, the fluorine gas sorting unit corresponds to the first outside and the second outside, and the first outside and the second outside are the same place, but the first outside and the second outside are the same. The outside may be another place.

The second flow path has a blockage suppression mechanism that suppresses blockage of the second flow path by mist. The blockage suppressing mechanism is not particularly limited as long as it can suppress blockage of the second flow path by mist, and examples thereof include the following. That is, a large-diameter pipe, an inclined pipe, a rotating screw, and an air flow generator can be exemplified, and these may be used in combination.
More specifically, by forming at least a part of the second flow path with a pipe having a diameter larger than that of the first flow path, it is possible to suppress blockage of the second flow path by mist. Further, by forming at least a part of the second flow path with a pipe that is inclined with respect to the horizontal direction and extends in the direction of descending from the upstream side to the downstream side, the second flow path is blocked by mist. Can be suppressed.

Further, by installing a rotary screw that sends the mist accumulated inside the second flow path to the upstream side or the downstream side inside the second flow path, it is possible to suppress the blockage of the second flow path by the mist. .. Further, by providing an airflow generator for increasing the flow velocity of the fluid flowing in the second flow path in the second flow path, it is possible to suppress blockage of the second flow path by mist. A mist removing portion other than the mist removing portion provided in the first flow path may be provided in the second flow path as a clogging suppressing mechanism.

The first flow path is less likely to be blocked by the mist because the mist is removed from the fluid by the mist removing portion, and the second flow path is less likely to be blocked by the mist because the blockage suppressing mechanism is provided. Therefore, in the fluorine gas production method and the fluorine gas production apparatus of the present embodiment, when the electrolytic solution containing hydrogen fluoride and metal fluoride is electrolyzed to produce fluorine gas, the pipes and valves are blocked by mist. Can be suppressed. Even if the mist removing part and the blockage suppressing mechanism are not provided, the pipes and valves using the mist can be connected by simply switching the flow path through which the fluid flows to another flow path (first flow path or second flow path). Although the effect of suppressing obstruction is achieved, the above effect is superior when a mist removing portion and an obstruction suppressing mechanism are provided.

Hereinafter, the method for producing fluorine gas and the fluorine gas production apparatus of the present embodiment will be described in more detail.
[Electrolytic cell]
The mode of the electrolytic cell is not particularly limited, and any electrolytic cell can be used as long as the electrolytic solution containing hydrogen fluoride and metal fluoride can be electrolyzed to generate fluorine gas.
Normally, the inside of the electrolytic cell is divided into an anode chamber in which an anode is arranged and a cathode chamber in which a cathode is arranged by a partition member such as a partition wall, and fluorine gas generated at the anode and hydrogen gas generated at the cathode are generated. Is not mixed.

As the anode, for example, a carbonaceous electrode formed of a carbon material such as diamond, diamond-like carbon, amorphous carbon, graphite, glassy carbon, or amorphous carbon can be used. Further, as the anode, in addition to the above carbon material, for example, a metal electrode formed of a metal such as nickel or Monel (trademark) can be used. As the cathode, for example, a metal electrode made of a metal such as iron, copper, nickel, or Monel ™ can be used.

The electrolytic solution contains hydrogen fluoride and metal fluoride, and the type of the metal fluoride is not particularly limited, but is a fluoride of at least one metal selected from potassium, cesium, rubidium, and lithium. It is preferable to have. When the electrolytic solution contains cesium or rubidium, the specific gravity of the electrolytic solution becomes large, so that the amount of mist generated during electrolysis is suppressed.

As the electrolytic solution, for example, a mixed molten salt of hydrogen fluoride (HF) and potassium fluoride (KF) can be used. The molar ratio of hydrogen fluoride to potassium fluoride in the mixed molten salt of hydrogen fluoride and potassium fluoride can be, for example, hydrogen fluoride: potassium fluoride = 1.5 to 2.5: 1. When hydrogen fluoride: potassium fluoride = 2: 1, KF and 2HF are typical electrolytic solutions, and the melting point of this mixed molten salt is about 72 ° C. Since this electrolytic solution is corrosive, it is preferable that the part in contact with the electrolytic solution, such as the inner surface of the electrolytic cell, is made of a metal such as iron, nickel, or Monel ™.

At the time of electrolysis of the electrolytic solution, a DC current is applied to the anode and the cathode, a gas containing fluorine gas is generated at the anode, and a gas containing hydrogen gas is generated at the cathode. Further, since hydrogen fluoride in the electrolytic solution has a vapor pressure, hydrogen fluoride is accompanied by the gases generated at the anode and the cathode, respectively. Further, in the production of fluorine gas by electrolysis of the electrolytic solution, the gas generated by the electrolysis contains the mist of the electrolytic solution. Therefore, the gas phase portion of the electrolytic cell is composed of a gas generated by electrolysis, hydrogen fluoride, and a mist of an electrolytic solution. Therefore, what is sent out from the inside of the electrolytic cell is composed of a gas generated by electrolysis, hydrogen fluoride, and a mist of an electrolytic solution, which is referred to as a "fluid" in the present invention.

Since hydrogen fluoride in the electrolytic solution is consumed as the electrolysis progresses, a pipe for continuously or intermittently supplying hydrogen fluoride to the electrolytic cell for replenishment may be connected to the electrolytic cell. .. Hydrogen fluoride may be supplied to the cathode chamber side of the electrolytic cell or to the anode chamber side.
The main reasons why mist is generated during electrolysis of the electrolytic solution are as follows. The temperature of the electrolytic solution at the time of electrolysis is adjusted to, for example, 80 to 100 ° C. Since the melting point of KF ・ 2HF is 71.7 ° C., the electrolytic solution is in a liquid state when adjusted to the above temperature. Gas bubbles generated at both electrodes of the electrolytic cell rise in the electrolytic solution and burst at the liquid level of the electrolytic solution. At this time, a part of the electrolytic solution is released into the gas phase.

Since the temperature of the gas phase is lower than the melting point of the electrolytic solution, the released electrolytic solution undergoes a phase change to a state like a very fine powder. This powder is considered to be a mixture of potassium fluoride and hydrogen fluoride, KF · nHF. This powder rides on the flow of other generated gas and becomes mist, forming a fluid generated in the electrolytic cell. It is difficult to effectively remove such mist by ordinary measures such as installing a filter because of its adhesiveness.

Although the amount generated is small, fine powder of the organic compound may be generated as mist due to the reaction between the carbonic electrode which is the anode and the fluorine gas generated by electrolysis. More specifically, contact resistance is often generated in the portion where the current is supplied to the carbonaceous electrode, and Joule heat may cause the temperature to be higher than the temperature of the electrolytic solution. Therefore, the soot-like organic compound CFx may be generated as a mist by the reaction between the carbon forming the carbonaceous electrode and the fluorine gas.

It is preferable that the electrolytic cell has a structure in which air bubbles generated at the anode or cathode used in electrolysis rise vertically in the electrolytic solution and reach the liquid level of the electrolytic solution. If the structure is such that the bubbles do not easily rise in the electrolytic solution in the vertical direction and rise in the direction inclined with respect to the vertical direction, a plurality of bubbles are likely to aggregate to generate large bubbles. As a result, large bubbles reach the liquid surface of the electrolytic solution and burst, so that the amount of mist generated tends to increase. If the structure is such that bubbles can reach the liquid level of the electrolytic solution if they rise vertically in the electrolytic solution, small bubbles will reach the liquid surface of the electrolytic solution and burst, so that mist is generated. The amount tends to be small.

[Average particle size measuring unit]
The fluorine gas production apparatus of the present embodiment may include an average particle size measuring unit for measuring the average particle size of mist contained in the fluid, and the average particle size measuring unit uses a light scattering method to measure the average particle size. It may be composed of a light scattering detector for measuring. The light scattering detector is preferable as an average particle size measuring unit because it can measure the average particle size of mist in the fluid flowing through the flow path while continuously operating the fluorine gas production apparatus.

An example of a light scattering detector will be described with reference to FIG. The light scattering detector of FIG. 1 is a light scattering detector that can be used as an average particle size measuring unit in the fluorine gas production apparatus of the present embodiment (for example, the fluorine gas production apparatus of FIGS. 2 and 4 to 13 described later). is there. That is, when the electrolytic solution containing hydrogen fluoride and metal fluoride is electrolyzed inside the electrolytic cell of the fluorine gas production apparatus to produce fluorine gas, the mist contained in the fluid generated inside the electrolytic cell It is a light scattering detector that measures the average particle size.
A light scattering detector may be connected to a fluorine gas production device, and a fluid may be sent from the inside of the electrolytic tank to the light scattering detector to measure the average particle size of the mist, or the light scattering detector and the fluorine gas production device may be used. Instead of connecting, the fluid may be taken out from the inside of the electrolytic tank and introduced into a light scattering detector to measure the average particle size of the mist.

In the light scattering detector of FIG. 1, the sample chamber 1 accommodating the fluid F, the light source 2 that irradiates the fluid F in the sample chamber 1 with the light L for light scattering measurement, and the light L for light scattering measurement are in the fluid F. The scattered light detection unit 3 that detects the scattered light S generated by being scattered by the mist M of the above, the transparent window 4A that is installed in the sample chamber 1 and comes into contact with the fluid F and transmits the light L for light scattering measurement, and the sample chamber. It is provided with a transparent window 4B which is installed in 1 and comes into contact with the fluid F and allows scattered light S to pass through. The

transparent windows

4A and 4B are _{at least selected from diamond, calcium fluoride (CaF 2} ), potassium fluoride (KF), silver fluoride (AgF), barium fluoride (BaF ₂ ), and potassium bromide (KBr). It is formed by one species.

The light L for light scattering measurement (for example, laser light) emitted from the light source 2 passes through the focusing lens 6 and the transparent window 4A of the sample chamber 1 and enters the sample chamber 1, and the fluid F housed in the sample chamber 1 enters the sample chamber 1. Is irradiated to. At this time, if a substance that reflects light such as mist M is present in the fluid F, the light L for light scattering measurement is reflected and scattered. A part of the scattered light S generated by the light L for light scattering measurement scattered by the mist M is taken out from the sample chamber 1 through the transparent window 4B of the sample chamber 1, and is taken out from the sample chamber 1 to the condenser lens 7 and the aperture 8. Enters the scattered light detection unit 3 via. At this time, the average particle size of the mist M can be known from the information obtained from the scattered light S. The average particle size obtained here is the number average particle size. As the scattered light detection unit 3, for example, an aerosol spectral meter welas (registered trademark) digital 2000 manufactured by PALAS can be used.

The

transparent windows

4A and 4B come into contact with the fluid F, but since the fluid F contains highly reactive fluorine gas, it is necessary to form the

transparent windows

4A and 4B with a material that is not easily corroded by the fluorine gas. Examples of the material forming the

transparent windows

4A and 4B include at least one selected from diamond, calcium fluoride, potassium fluoride, silver fluoride, barium fluoride, and potassium bromide. If the

transparent windows

4A and 4B are made of the above materials, deterioration due to contact with the fluid F can be suppressed.

Further, a coating made of the above-mentioned material coated on the surface of glass such as quartz can also be used as the

transparent windows

4A and 4B. Since the portion in contact with the fluid F is coated with a film made of the above-mentioned material, deterioration due to contact with the fluid F can be suppressed while suppressing the cost. The

transparent windows

4A and 4B may be a laminate in which the surface in contact with the fluid F is formed of the above material and the other portion is formed of ordinary glass such as quartz.
The material of the light scattering detector other than the

transparent windows

4A and 4B is not particularly limited as long as it is a material having corrosion resistance to fluorine gas. For example, Monel (trademark) which is a copper-nickel alloy. ), Hastelloy ™, stainless steel and other metal materials are preferred.

[Average particle size of mist and water concentration in electrolyte]
The present inventors measured the average particle size of mist generated during the production of fluorine gas by electrolysis of an electrolytic solution using a light scattering detector. An example of the result will be described. Electrolysis is started after replacing the anode of the fluorine gas production equipment with a new anode or filling the electrolytic cell with a new electrolyte, and the average particles of mist in the fluid generated at the anode for a certain period immediately after the start of electrolysis. The diameter was measured. As a result, the average particle size of the mist was 0.5 to 2.0 μm. After that, when the electrolysis was continued and a sufficient time had passed, the electrolysis began to stabilize, and the average particle size of the mist in the fluid during this stable electrolysis was about 0.2 μm.
In this way, a mist having a relatively large particle size is generated from immediately after the start of electrolysis to the time of stable electrolysis. When a fluid containing a large mist immediately after the start of electrolysis flows in a pipe or valve, the mist is adsorbed on the inner surface of the pipe or valve, and the pipe or valve is likely to be blocked.

On the other hand, during stable electrolysis, the particle size of the mist generated is relatively small. Since such a small mist is unlikely to cause sedimentation or accumulation in a fluid, it can flow stably through pipes and valves. Therefore, during stable electrolysis, the fluid composed of mist and gas generated at the electrodes is relatively unlikely to cause clogging of pipes and valves. The time from immediately after the start of electrolysis to the time of stable electrolysis is usually 25 hours or more and 200 hours or less. Further, from immediately after the start of electrolysis to the time of stable electrolysis, it is necessary to energize approximately 40 kAh or more per 1000 L of the electrolytic solution.

In addition, the present inventors have found that there is a close relationship between the average particle size of mist and the water concentration in the electrolytic solution. Usually, the water concentration in the electrolytic solution is large at the start of electrolysis and shows a value larger than 1.0% by mass. The average particle size of the mist at this time is larger than 0.4 μm. After that, as the electrolysis is continued, the water concentration in the electrolytic solution decreases, and when it becomes 0.3% by mass or less, the average particle size of the mist becomes 0.4 μm or less.

In this way, since there is a correlation between the average particle size of the mist and the water concentration in the electrolytic solution, the water concentration in the electrolytic solution is measured instead of the average particle size of the mist during electrolysis, and the measurement result is obtained. It can be used for switching the flow path. That is, if the water concentration in the electrolytic solution is measured at a predetermined timing during electrolysis, the flow path through which the fluid generated by electrolysis flows can be appropriately switched according to the measurement result. ..

The transition of the water concentration in the electrolytic solution decreases depending on the magnitude of the current value and the amount of energization (the product of the current value and the electrolysis time). The larger the current value, the faster the decrease in water concentration, but when a carbonic electrode that causes the anode effect that the voltage of the anode rises sharply is used for the anode, the current density of the anode is higher than ^{0.1 A / cm 2.} It will be electrolyzed with a small value. The water concentration may be lowered with a constant current density, or the water concentration may be lowered while gradually increasing the current density.

Based on these findings, the present inventors have invented the above-mentioned fluorine gas production method and fluorine gas production apparatus having a structure capable of switching the flow path through which the fluid flows according to the water concentration in the electrolytic solution during electrolysis. did. The fluorine gas production apparatus of this embodiment has a first flow path and a second flow path, and is used for transporting a fluid from the two flow paths by using a flow path switching unit (for example, a switching valve). The flow path may be selected.

Alternatively, the fluorine gas production apparatus of the present embodiment has two flow paths and a moving replacement mechanism for moving and replacing the electrolytic cell, and a flow used for transporting a fluid from the two flow paths. The flow path may be switched by selecting a path and moving and connecting the electrolytic cell in the vicinity of the flow path.
Since it has a first flow path and a second flow path as described above, even while one flow path is blocked and cleaned, the other flow path is opened to continue the fluorine gas production apparatus. You can drive.

In the study by the present inventors, mist having a relatively large average particle size is generated from immediately after the start of electrolysis to the time of stable electrolysis. At this time, the fluid is sent to the second flow path having the clogging suppressing mechanism. You may. When time elapses and stable electrolysis is performed, mist having a relatively small average particle size is generated. Therefore, at this time, the flow path may be switched so as to send the fluid to the first flow path having the mist removing portion.

Such switching of the flow path is performed according to the measured water concentration in the electrolytic solution, but the flow path is switched based on a preset reference value. Appropriate reference values for the average particle size of the mist generated at the anode vary from device to device, but are, for example, 0.1 μm or more and 1.0 μm or less, preferably 0.2 μm or more and 0.8 μm or less, and more preferably 0. It is 4 μm.
Therefore, from the correlation between the average particle size of the mist and the water concentration in the electrolytic solution, an appropriate reference value for the water concentration in the electrolytic solution is 0.1% by mass or more and 0.8% by mass or less, preferably 0. .2% by mass or more and 0.6% by mass or less, more preferably 0.3% by mass. When the water concentration in the electrolytic solution is higher than the reference value, the fluid can be sent to the second flow path, and when it is equal to or less than the reference value, the fluid can be sent to the first flow path.

The water concentration in the electrolytic solution can be measured by, for example, the Karl Fischer method. Alternatively, the concentration of water in the electrolytic solution can be determined by heating the electrolytic solution to, for example, 250 ° C. or higher and 400 ° C. or lower, and measuring the amount of water in the generated gas by, for example, infrared spectroscopy. Since the solid electrolyte is hardly dissolved in the detection solution used in the Carl Fisher method, another solvent for dissolving the solid electrolyte is required, but a solvent having a large solubility in the solid electrolyte is required. Is almost nonexistent. Therefore, it is difficult to dissolve a large amount of solid electrolyte solution for Karl Fischer analysis. Therefore, the Karl Fischer method is suitable for analysis of a solid electrolyte solution having a high water content. On the other hand, the method of heating a solid electrolyte and measuring the amount of water in the generated gas requires a longer analysis time than the Karl Fischer method, but it can determine the water concentration in the electrolyte. It can be analyzed accurately.

In the fluid generated at the cathode (main component is hydrogen gas), for example, 20 to 50 μg per unit volume (1 liter) (calculated assuming that the specific gravity of mist is 1.0 g / mL). It contains powder, the average particle size of this powder is about 0.1 μm, and it has a distribution of ± 0.05 μm.

In the fluid generated at the cathode, no significant difference was observed in the particle size distribution of the generated powder depending on the water concentration in the electrolytic solution. The mist contained in the fluid generated at the cathode has a smaller average particle size than the mist contained in the fluid generated at the anode, so that the mist contained in the fluid generated at the anode is smaller than the mist contained in the fluid generated at the anode. Is unlikely to occur. Therefore, the mist contained in the fluid generated at the cathode may be removed from the fluid by using an appropriate removal method.

An example of the fluorine gas production apparatus of this embodiment will be described in detail with reference to FIG. The fluorine gas production apparatus of FIG. 2 is an example in which two electrolytic cells are provided, but the number of electrolytic cells may be one or three or more, for example, 10 to 15. You may.
The fluorine gas production apparatus shown in FIG. 2 includes

electrolytic cells

11 and 11 in which the electrolytic cell 10 is housed and electrolyzed, an anode 13 arranged inside the electrolytic cell 11 and immersed in the electrolytic cell 10. It is provided with a cathode 15 which is arranged inside the electrolytic cell 11 and is immersed in the electrolytic solution 10 and is arranged so as to face the anode 13.

The inside of the electrolytic cell 11 is divided into an anode chamber 22 and a cathode chamber 24 by a partition wall 17 extending vertically downward from the ceiling surface inside the electrolytic cell 11 and having its lower end immersed in the electrolytic solution 10. The anode 13 is arranged in the anode chamber 22, and the cathode 15 is arranged in the cathode chamber 24. However, the space on the liquid surface of the electrolytic solution 10 is separated into a space inside the anode chamber 22 and a space inside the cathode chamber 24 by the partition wall 17, and the portion of the electrolytic solution 10 on the upper side of the lower end of the partition wall 17. However, the portion of the electrolytic solution 10 below the lower end of the partition wall 17 is not directly separated by the partition wall 17 and is continuous.

Further, the fluorine gas production apparatus shown in FIG. 2 includes a water concentration measuring unit 36 for measuring the water concentration in the electrolytic solution 10 in the electrolytic solution 10 when the electrolytic solution 10 is electrolyzed, and an electrolytic tank when the electrolytic solution 10 is electrolyzed. The first average particle size measuring unit 31 for measuring the average particle size of the mist contained in the fluid generated inside the eleven, the first mist removing unit 32 for removing the mist from the fluid, and the fluorine gas are selected from the fluid. It includes a fluorine gas sorting unit (not shown) for taking out, and a flow path for sending the fluid from the inside of the electrolytic tank 11 to the fluorine gas sorting unit.

Further, this flow path is a first flow path for sending a fluid from the inside of the electrolytic cell 11 to the fluorine gas sorting unit via the first mist removing unit 32, and an electrolytic cell without passing through the first mist removing unit 32. It has a second flow path for sending a fluid from the inside of the eleven to the fluorine gas sorting unit. Further, this flow path has a flow path switching unit that switches the flow path through which the fluid flows to the first flow path or the second flow path according to the water concentration in the electrolytic solution 10 measured by the water concentration measuring unit 36. doing. That is, a flow path switching portion is provided in the middle of the flow path extending from the electrolytic cell 11, and the flow path through which the fluid flows can be changed by the flow path switching portion.

When the water concentration in the electrolytic solution 10 measured by the water concentration measuring unit 36 is equal to or less than a preset reference value, the flow path switching unit transfers a fluid from the inside of the electrolytic cell 11 to the first flow path. If the value is larger than the preset reference value, the fluid is sent from the inside of the electrolytic cell 11 to the second flow path. The second flow path has a blockage suppression mechanism that suppresses blockage due to mist in the second flow path.

That is, when the water concentration in the electrolytic solution 10 is equal to or lower than the reference value, the fluid is sent to the first flow path in which the electrolytic cell 11 and the fluorine gas sorting unit are connected and the first mist removing unit 32 is provided. When the water concentration in the electrolytic solution 10 is higher than the reference value, the fluid is sent to the second flow path which connects the electrolytic cell 11 and the fluorine gas sorting unit and is provided with the clogging suppressing mechanism.
As the water concentration measuring unit 36, for example, a Karl Fischer water content measuring device can be used.

As the first mist removing unit 32, for example, a mist removing device capable of removing mist having an average particle diameter of 0.4 μm or less from the fluid is used. The type of mist removing device, that is, the method for removing mist is not particularly limited, but since the average particle size of mist is small, for example, an electrostatic precipitator, a venturi scrubber, or a filter is used as the mist removing device. be able to.

Among the above mist removing devices, it is preferable to use the mist removing device shown in FIG. The mist removing device shown in FIG. 3 is a scrubber type mist removing device that uses liquid hydrogen fluoride as a circulating fluid. The mist removing device shown in FIG. 3 can efficiently remove mist having an average particle diameter of 0.4 μm or less from the fluid. Further, although liquid hydrogen fluoride is used as the circulating fluid, it is preferable to cool the circulating fluid in order to reduce the concentration of hydrogen fluoride in the fluorine gas. Therefore, the hydrogen fluoride in the fluorine gas is controlled by controlling the cooling temperature. The concentration can be adjusted.

The fluorine gas production apparatus shown in FIG. 2 will be described in more detail. The first pipe 41 that sends the fluid generated in the anode chamber 22 of the electrolytic cell 11 (hereinafter, also referred to as “anode gas”) to the outside communicates the electrolytic cell 11 and the

fourth pipe

44, 2 The anodic gas sent out from the two

electrolytic cells

11 and 11 is sent to the fourth pipe 44 by the first pipe 41 and mixed. The main component of the anode gas is fluorine gas, and the subcomponents are mist, hydrogen fluoride, carbon tetrafluoride, oxygen gas, and water.

The fourth pipe 44 is connected to the first mist removing unit 32, and the anodic gas is sent to the first mist removing unit 32 by the fourth pipe 44, so that the mist and hydrogen fluoride in the anodic gas are removed from the first mist. The part 32 removes the anodic gas from the anodic gas. The anodic gas from which mist and hydrogen fluoride have been removed is sent from the first mist removing unit 32 to a fluorine gas sorting unit (not shown) by a sixth pipe 46 connected to the first mist removing unit 32. .. Then, the fluorine gas sorting unit sorts and takes out the fluorine gas from the anode gas.

An eighth pipe 48 is connected to the first mist removing unit 32, and liquid hydrogen fluoride, which is a circulating liquid, is supplied to the first mist removing unit 32 by the eighth pipe 48. .. Further, a ninth pipe 49 is connected to the first mist removing unit 32. The ninth pipe 49 is connected to the

electrolytic cells

11 and 11 via the third pipe 43, and is used by the first mist removing unit 32 to remove the mist, and is a circulating liquid (liquid hydrogen fluoride) containing the mist. Is returned from the first mist removing unit 32 to the

electrolytic cells

11 and 11.

The cathode chamber 24 of the electrolytic cell 11 is the same as the anode chamber 22. That is, the second pipe 42 that sends the fluid generated in the cathode chamber 24 of the electrolytic cell 11 (hereinafter, also referred to as “cathode gas”) to the outside communicates the electrolytic cell 11 and the fifth pipe 45. The cathode gas sent out from the two

electrolytic cells

11 and 11 is sent to the fifth pipe 45 by the second pipe 42 and mixed. The main component of the cathode gas is hydrogen gas, and the subcomponents are mist, hydrogen fluoride, and water.

Cathode gas contains fine mist and 5 to 10% by volume of hydrogen fluoride, so it is not preferable to discharge it to the atmosphere as it is. Therefore, the fifth pipe 45 is connected to the second mist removing unit 33, the cathode gas is sent to the second mist removing unit 33 by the fifth pipe 45, and the mist and hydrogen fluoride in the cathode gas are the second mist. It is designed to be removed from the cathode gas by the removing unit 33. The cathode gas from which the mist and hydrogen fluoride have been removed is discharged to the atmosphere from the second mist removing unit 33 by the seventh pipe 47 connected to the second mist removing unit 33. The type of the second mist removing unit 33, that is, the method of removing the mist is not particularly limited, but a scrubber type mist removing device using an alkaline aqueous solution as a circulating solution can be used.

The pipe diameter and installation direction (meaning the direction in which the pipe extends, for example, the vertical direction and the horizontal direction) of the first pipe 41, the second pipe 42, the fourth pipe 44, and the fifth pipe 45 are not particularly limited. Although not, the first pipe 41 and the second pipe 42 are installed so as to extend in the vertical direction from the electrolytic tank 11, and the flow velocity of the fluid flowing through the first pipe 41 and the second pipe 42 is 30 cm / sec in the standard state. It is preferable that the pipe diameter is as follows. Then, even if the mist contained in the fluid falls due to its own weight, the mist settles in the electrolytic cell 11, so that the inside of the first pipe 41 and the second pipe 42 is less likely to be blocked by the powder.
Further, when the fourth pipe 44 and the fifth pipe 45 are installed so as to extend along the horizontal direction and the flow velocity of the fluid flowing through the fourth pipe 44 and the fifth pipe 45 is the first pipe 41 and the second pipe 42. It is preferable to set the pipe diameter so as to be about 1 to 10 times faster than the above.

Further, a second bypass pipe 52 for sending the anode gas to the outside of the electrolytic cell 11 is provided separately from the first pipe 41. That is, the second bypass pipe 52 communicates the electrolytic cell 11 and the first bypass pipe 51, and the anode gas sent out from the two

electrolytic cells

11 and 11 is transmitted by the second bypass pipe 52 to the first bypass pipe 51. It is sent to and mixed. Further, the anodic gas is sent out to a fluorine gas sorting unit (not shown) by the first bypass pipe 51. Then, the fluorine gas sorting unit sorts and takes out the fluorine gas from the anode gas. The fluorine gas sorting unit connected to the first bypass pipe 51 and the fluorine gas sorting unit connected to the sixth pipe 46 may be the same or different.

The pipe diameter and installation direction of the second bypass pipe 52 are not particularly limited, but the second bypass pipe 52 is installed so as to extend from the electrolytic cell 11 in the vertical direction, and the fluid flowing through the second bypass pipe 52. It is preferable to set the pipe diameter so that the flow velocity of the above is 30 cm / sec or less in the standard state.

Further, the first bypass pipe 51 is installed so as to extend along the horizontal direction. The first bypass pipe 51 has a pipe diameter larger than that of the fourth pipe 44, and the pipe diameter of the first bypass pipe 51 is such that the first bypass pipe 51 is blocked due to the accumulation of powder. The size is such that it is unlikely to occur. Since the first bypass pipe 51 is a pipe having a diameter larger than that of the fourth pipe 44, a blockage suppressing mechanism is configured.
The pipe diameter of the first bypass pipe 51 is preferably 1.0 times more than 3.2 times or less than that of the fourth pipe 44, and more preferably 1.05 times or more and 1.5 times or less. That is, the flow path cross-sectional area of the first bypass pipe 51 is preferably 10 times or less that of the fourth pipe 44.

As can be seen from the above description, the first pipe 41 and the fourth pipe 44 form the first flow path, and the first bypass pipe 51 and the second bypass pipe 52 form the second flow path. .. A blockage suppressing mechanism is provided in the first bypass pipe 51 that constitutes the second flow path.

Next, the flow path switching unit will be described. A first piping valve 61 is installed in each of the first piping 41. Then, by switching the first piping valve 61 to the open state or the closed state, it is possible to control whether or not the anode gas can be supplied from the electrolytic cell 11 to the first mist removing unit 32. Further, a bypass valve 62 is installed in each of the second bypass pipes 52. Then, by switching the bypass valve 62 to the open state or the closed state, it is possible to control whether or not the anode gas can be supplied from the electrolytic cell 11 to the first bypass pipe 51.

Further, a water concentration measuring unit 36 is installed in the electrolytic cell 11, and the electrolytic solution 10 in the electrolytic cell 11 is introduced into the water concentration measuring unit 36 to measure the water concentration in the electrolytic cell 10 at the time of electrolysis. You can do it. The electrolytic solution 10 for measuring the water concentration may be the electrolytic solution 10 on the anode chamber 22 side or the electrolytic solution 10 on the cathode chamber 24 side.

Further, in detail, the first average particle size is measured between the electrolytic cell 11 and the first mist removing portion 32, which is an intermediate portion of the fourth pipe 44 and downstream of the connecting portion with the first pipe 41. The section 31 is installed. Then, the first average particle size measuring unit 31 measures the average particle size of the mist contained in the anode gas flowing through the fourth pipe 44. Further, by analyzing the fluorine gas and the nitrogen gas contained in the anode gas after measuring the average particle size of the mist, the current efficiency in the production of the fluorine gas can be measured.

A similar second average particle size measuring unit 34 is installed in the middle portion of the first bypass pipe 51 and on the downstream side of the connecting portion with the second bypass pipe 52 to measure the second average particle size. The unit 34 measures the average particle size of the mist contained in the anode gas flowing through the first bypass pipe 51. However, the fluorine gas production apparatus shown in FIG. 2 does not have to include the first average particle size measuring unit 31 and the second average particle size measuring unit 34.

The water concentration measuring unit 36 measures the water concentration in the electrolytic cell 10 in the electrolytic cell 11, and if the measurement result is larger than the preset reference value, the bypass valve 62 is opened and the anode gas is used. It is sent from the electrolytic cell 11 to the first bypass pipe 51, and the first pipe valve 61 is closed to prevent the anode gas from being sent to the fourth pipe 44 and the first mist removing unit 32. That is, the anode gas is sent to the second flow path.

On the other hand, when the measurement result is equal to or less than the preset reference value, the first pipe valve 61 is opened, the anode gas is sent to the fourth pipe 44 and the first mist removing unit 32, and the bypass valve 62 is opened. In the closed state, the anode gas is prevented from being sent from the electrolytic cell 11 to the first bypass pipe 51. That is, the anode gas is sent to the first flow path.
As can be seen from the above description, the first piping valve 61 and the bypass valve 62 constitute the above-mentioned flow path switching portion.

As described above, by operating the fluorine gas production apparatus while switching the flow path according to the water concentration in the electrolytic solution 10 at the time of electrolysis, the fluorine gas production apparatus is smoothly continuously suppressed while suppressing clogging of piping and valves due to mist. Can drive. Therefore, according to the fluorine gas production apparatus shown in FIG. 2, fluorine gas can be economically produced.

For example, a plurality of pipes on which a filter is installed may be prepared as a mist removing unit, and electrolysis may be performed while changing the filter as appropriate.
Further, it is preferable to determine the period during which the filter should be frequently replaced and the period during which the filter does not need to be replaced based on the measurement of the water concentration in the electrolytic solution 10 at the time of electrolysis. Then, if the switching frequency of the piping through which the fluid flows is appropriately adjusted based on the above determination, the operation of the fluorine gas production apparatus can be efficiently and continuously performed.

Next, a modified example of the fluorine gas production apparatus shown in FIG. 2 will be described.
[First modification]
The first modification will be described with reference to FIG. In the fluorine gas production apparatus shown in FIG. 2, the second bypass pipe 52 connects the electrolytic cell 11 and the first bypass pipe 51, whereas in the fluorine gas production apparatus of the first modification shown in FIG. The second bypass pipe 52 connects the first pipe 41 and the first bypass pipe 51. Since the configuration of the fluorine gas production apparatus of the first modification is almost the same as that of the fluorine gas production apparatus of FIG. 2 except for the above points, the description of the same parts will be omitted.

[Second modification]
The second modification will be described with reference to FIG. The fluorine gas production apparatus of the second modification shown in FIG. 5 is an example including one electrolytic cell 11. The first average particle size measuring unit 31 is provided not in the fourth pipe 44 but in the first pipe 41, and is provided on the upstream side of the first pipe valve 61. Further, the second bypass pipe 52 is not provided, and the first bypass pipe 51 is directly connected to the electrolytic cell 11 without passing through the second bypass pipe 52.

Since the first bypass pipe 51 has a larger diameter than the fourth pipe 44, it functions as a blockage suppressing mechanism. Further, for example, by providing a space for collecting mist at the downstream end of the first bypass pipe 51, the effect of suppressing blockage can be further increased. As the space for collecting mist, for example, the downstream end portion of the first bypass pipe 51 is formed to have a pipe diameter larger than the central portion in the installation direction (for example, a pipe diameter four times or more the central portion in the installation direction). Examples thereof include a space in which the downstream end portion of the first bypass pipe 51 is formed in a container-like shape, and the space for collecting mist can suppress the blockage of the first bypass pipe 51. This is aimed at the effect of preventing blockage due to the large cross-sectional area of the flow path and the effect of preventing blockage by utilizing the gravity drop of mist due to the decrease in the linear velocity of gas flow.
Further, the bypass valve 62 is provided in the third bypass pipe 53 that connects the first bypass pipe 51 and the fluorine gas sorting unit (not shown). Since the configuration of the fluorine gas production apparatus of the second modification is almost the same as that of the fluorine gas production apparatus of FIG. 2 except for the above points, the description of the same parts will be omitted.

[Third modification example]
A third modification will be described with reference to FIG. In the fluorine gas production apparatus of the third modification, the first average particle size measuring unit 31 is provided in the electrolytic cell 11, and the anode gas inside the electrolytic cell 11 is directly connected to the first average particle size measuring unit 31. Introduced in, the average particle size of mist has been measured. The fluorine gas production apparatus of the third modification does not have the second average particle size measuring unit 34. Since the configuration of the fluorine gas production apparatus of the third modification is almost the same as that of the fluorine gas production apparatus of the second modification except for the above points, the description of the same parts will be omitted.

[Fourth modification]
A fourth modification will be described with reference to FIG. 7. The fluorine gas production apparatus of the fourth modification is an example in which the clogging suppressing mechanism is different from that of the second modification shown in FIG. In the fluorine gas production apparatus of the second modification, the first bypass pipe 51 was installed so as to extend along the horizontal direction, but in the fluorine gas production apparatus of the fourth modification, the first bypass pipe 51 Is inclined with respect to the horizontal direction and extends in a direction descending from the upstream side to the downstream side. This inclination suppresses the accumulation of powder inside the first bypass pipe 51. The larger the slope, the greater the effect of suppressing the accumulation of powder.

The inclination angle of the first bypass pipe 51 is preferably 30 degrees or more, and more preferably 40 degrees or more and 60 degrees or less in the range where the depression angle from the horizontal plane is smaller than 90 degrees. If the first bypass pipe 51 is likely to be blocked, hammering the inclined first bypass pipe 51 makes it easier for the deposits inside the first bypass pipe 51 to move, so that the blockage can be avoided. it can.
Since the configuration of the fluorine gas production apparatus of the fourth modification is almost the same as that of the fluorine gas production apparatus of the second modification except for the above points, the description of the same parts will be omitted.

[Fifth variant]
A fifth modification will be described with reference to FIG. The fluorine gas production apparatus of the fifth modification is an example in which the clogging suppressing mechanism is different from that of the third modification shown in FIG. In the fluorine gas production apparatus of the third modification, the first bypass pipe 51 was installed so as to extend along the horizontal direction, but in the fluorine gas production apparatus of the fifth modification, the first bypass pipe 51 Is inclined with respect to the horizontal direction and extends in a direction descending from the upstream side to the downstream side. This inclination suppresses the accumulation of powder inside the first bypass pipe 51. The preferable inclination angle of the first bypass pipe 51 is the same as in the case of the fourth modification. Since the configuration of the fluorine gas production apparatus of the fifth modification is almost the same as that of the fluorine gas production apparatus of the third modification except for the above points, the description of the same parts will be omitted.

[6th modification]
A sixth modification will be described with reference to FIG. The fluorine gas production apparatus of the sixth modification is an example in which the structure of the electrolytic cell 11 is different from that of the second modification shown in FIG. The electrolytic cell 11 has one anode 13 and two

cathodes

15 and 15, and is divided into one anode chamber 22 and one cathode chamber 24 by a tubular partition wall 17 surrounding one anode 13. Has been done. The anode chamber 22 is formed so as to extend above the upper surface of the electrolytic cell 11, and the first bypass pipe 51 is connected to the upper end portion of the anode chamber 22 of the electrolytic cell 11. Since the configuration of the fluorine gas production apparatus of the sixth modification is almost the same as that of the fluorine gas production apparatus of the second modification except for the above points, the description of the same parts will be omitted.

[7th modification]
A seventh modification will be described with reference to FIG. The fluorine gas production apparatus of the seventh modification is an example in which the structure of the first bypass pipe 51 is different from that of the sixth modification shown in FIG. That is, in the fluorine gas production apparatus of the 7th modification, the 1st bypass pipe 51 is inclined with respect to the horizontal direction and is inclined from the upstream side to the downstream side as in the 4th modification and the 5th modification. It extends in the direction of descending. The preferable inclination angle of the first bypass pipe 51 is the same as in the case of the fourth modification. Since the configuration of the fluorine gas production apparatus of the seventh modification is almost the same as that of the fluorine gas production apparatus of the sixth modification except for the above points, the description of the same parts will be omitted.

[8th modification]
An eighth modification will be described with reference to FIG. The fluorine gas production apparatus of the eighth modification is an example in which the clogging suppressing mechanism is different from that of the second modification shown in FIG. In the fluorine gas production apparatus of the eighth modification, the rotary screw 71 constituting the blockage suppressing mechanism is installed inside the first bypass pipe 51. The rotating screw 71 is installed with its rotating shaft parallel to the longitudinal direction of the first bypass pipe 51.
Then, by rotating the rotary screw 71 by the motor 72, the mist accumulated inside the first bypass pipe 51 can be sent to the upstream side or the downstream side. As a result, the powder is prevented from accumulating inside the first bypass pipe 51. Since the configuration of the fluorine gas production apparatus of the eighth modification is almost the same as that of the fluorine gas production apparatus of the second modification except for the above points, the description of the same parts will be omitted.

[9th modification]
A ninth modification will be described with reference to FIG. The fluorine gas production apparatus of the ninth modification is an example in which the clogging suppressing mechanism is different from that of the second modification shown in FIG. In the fluorine gas production apparatus of the ninth modification, the airflow generator 73 constituting the blockage suppression mechanism is installed in the first bypass pipe 51. The airflow generator 73 sends an airflow (for example, an airflow of nitrogen gas) from the upstream side to the downstream side of the first bypass pipe 51 to increase the flow velocity of the anode gas flowing in the first bypass pipe 51. As a result, the powder is prevented from accumulating inside the first bypass pipe 51.

At this time, the preferable flow velocity of the anode gas flowing in the first bypass pipe 51 is 1 m / sec or more and 10 m / sec or less. It is possible to increase the flow velocity to more than 10 m / sec, but in that case, the pressure loss due to the piping resistance in the first bypass pipe 51 becomes large, and the pressure in the anode chamber 22 of the electrolytic cell 11 becomes high. It is preferable that the pressure in the anode chamber 22 and the pressure in the cathode chamber 24 are about the same, but if the difference between the pressure in the anode chamber 22 and the pressure in the cathode chamber 24 becomes too large, the anode gas becomes a partition wall. If it exceeds 17, it flows into the cathode chamber 24, and a reaction between the fluorine gas and the hydrogen gas occurs, which may hinder the generation of the fluorine gas.
Since the configuration of the fluorine gas production apparatus of the ninth modification is almost the same as that of the fluorine gas production apparatus of the second modification except for the above points, the description of the same parts will be omitted.

[10th modification]
A tenth modification will be described with reference to FIG. In the fluorine gas production apparatus of the tenth modification, the first average particle size measuring unit 31 is provided in the electrolytic cell 11, and the anode gas inside the electrolytic cell 11 is directly connected to the first average particle size measuring unit 31. Introduced in, the average particle size of mist has been measured. The fluorine gas production apparatus of the tenth modification does not have the second average particle size measuring unit 34. Since the configuration of the fluorine gas production apparatus of the tenth modification is almost the same as that of the fluorine gas production apparatus of the ninth modification shown in FIG. 12 except for the above points, the description of the same part will be omitted.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
[Reference Example 1]
Fluorine gas was produced by electrolyzing the electrolytic solution. As the electrolytic solution, a mixed molten salt (560 L) of 434 kg of hydrogen fluoride and 630 kg of potassium fluoride was used. An amorphous carbon electrode (width 30 cm, length 45 cm, thickness 7 cm) manufactured by SGL Carbon Co., Ltd. was used as the anode, and 16 anodes were installed in the electrolytic cell. In addition, a punching plate manufactured by Monel (trademark) was used as a cathode and installed in an electrolytic cell. Two cathodes face one anode, and the total area of the portion of one anode facing the cathode is 1736 cm ² .

The electrolysis temperature was controlled to 85 to 95 ° C. First, the electrolyte temperature was set to 85 ° C., a DC current of 1000 A was applied at a ^{current density of 0.036 A / cm 2, and electrolysis was started.} The water concentration in the electrolytic solution at this time was 1.0% by mass. The water concentration was measured by the Karl Fischer titer analysis method.
Electrolysis was started under the above conditions, and a small plosive sound was observed in the vicinity of the anode in the anode chamber for 10 hours immediately after the start of electrolysis. It is probable that this plosive sound was generated due to the reaction between the generated fluorine gas and the water content in the electrolytic solution.

The fluid generated at the anode in this state was sampled when it was sent out from the anode chamber of the electrolytic cell, and the mist contained in the fluid was analyzed. As a result, 5.0 to 9.0 mg of powder (calculated assuming that the specific gravity of the mist is 1.0 g / mL. The same applies to the following) is contained in 1 L of the fluid generated at the anode. The average particle size of this powder was 1.0 to 2.0 μm. When this powder was observed with an optical microscope, the powder having a shape like a hollow inside a sphere was mainly observed. The current efficiency of fluorine gas generation at this time was 0 to 15%.

Furthermore, when electrolysis was continued up to 30 mAh with the amount of electricity supplied, the frequency of plosive noise inside the anode chamber was reduced. The water concentration in the electrolytic solution at this time was 0.7% by mass. Further, the fluid generated at the anode in this state was collected when it was sent out from the anode chamber of the electrolytic cell, and the mist contained in the fluid was analyzed. As a result, 0.4 to 1.0 mg of mist was contained in 1 L of the fluid generated at the anode, and the average particle size of this mist was 0.5 to 0.7 μm. Further, the current efficiency of fluorine gas generation at this time was 15 to 55%. The stage of electrolysis from the start of electrolysis to this point is referred to as "step (1)".

Further, the electrolysis of the electrolytic solution was continued following the step (1). Then, hydrogen fluoride is consumed and the level of the electrolytic solution is lowered. Therefore, hydrogen fluoride was appropriately replenished from the hydrogen fluoride tank to the electrolytic cell. The water concentration in the supplemented hydrogen fluoride is 500 mass ppm or less.
Further, when the electrolysis was continued and the energization amount became 60 mAh, the average particle size of the mist contained in the fluid generated at the anode became 0.36 μm (that is, 0.4 μm or less). At this point, no plosives were generated inside the anode chamber. The water concentration in the electrolytic solution at this time was 0.2% by mass (that is, 0.3% by mass or less). Further, the current efficiency of fluorine gas generation at this time was 65%. The stage of electrolysis from the end of step (1) to this point is referred to as "step (2)".

Further, the current was increased to 3500 A and the current density was increased to 0.126 A / cm ^2, and the electrolysis of the electrolytic solution was continued in the step (2). The fluid generated at the anode in this state was sampled when it was sent out from the anode chamber of the electrolytic cell, and the mist contained in the fluid was analyzed. As a result, 0.03 to 0.06 mg of powder was contained in 1 L of the fluid generated at the anode, and the average particle size of this powder was about 0.2 μm (0.15 to 0.25 μm). The diameter had a distribution of about 0.1-0.5 μm. FIG. 14 shows the measurement results of the particle size distribution of this powder. Further, the current efficiency of fluorine gas generation at this time was 94%. The water concentration in the electrolytic solution at this time was less than 0.2% by mass. The stage of electrolysis from the end of step (2) to this point is referred to as a "stable stage".

Table 1 summarizes the contents of the electrolysis of Reference Example 1 performed as described above. Table 1 shows the current, the elapsed electrolysis time, the amount of energization, the water concentration in the electrolytic solution, the mass of mist contained in 1 L of the fluid generated at the anode (denoted as "anode gas" in Table 1), and the mist. Along with the average particle size and current efficiency of, the amount of fluid (containing fluorine gas, oxygen gas, and mist) generated at the anode, the amount of mist generated at the anode, the strength of the bursting sound, and the fluid generated at the cathode. The water concentration inside (indicated as "water concentration in the cathode gas" in Table 1) is also shown.

Further, FIG. 15 shows a graph showing the relationship between the average particle size of mist and the amount of mist generated at the anode. From the graph of FIG. 15, it can be seen that there is a correlation between the average particle size of mist and the amount of mist generated at the anode. The larger the amount of mist generated, the more likely it is that the pipes and valves will be blocked. If mist with an average particle size larger than 0.4 μm is generated, the amount of mist generated will increase and will be deposited by the action of gravity. Therefore, it can be said that the relationship shown in the graph of FIG. 15 represents the correlation between the average particle size of the mist and the likelihood of clogging of pipes and valves.
Further, FIG. 16 shows a graph showing the relationship between the average particle size of the mist and the water concentration in the electrolytic solution. The larger the average particle size of the mist, the more likely it is that the pipes and valves will be clogged. Therefore, the relationship shown in the graph of FIG. 16 shows the correlation between the water concentration in the electrolyte and the likelihood of clogging of the pipes and valves. It can be said that.

[Example 1]
The same electrolysis as in Reference Example 1 was performed using the fluorine gas production apparatus shown in FIG. In the electrolysis of the step (1), the fluid generated at the anode was circulated via the second bypass pipe, the bypass valve, and the first bypass pipe. After the electrolysis of the step (1) was completed, the electrolysis was temporarily stopped, and the inside of the fluorine gas production apparatus was inspected. As a result, although mist was accumulated in the first bypass pipe, the pipe was not blocked because the diameter of the pipe was increased.

Since the electrolysis was performed in the stage (2) when the average particle size of the mist was 0.4 μm or less (the water concentration in the electrolytic solution was 0.2% by mass, which is 0.3% by mass or less of the reference value), it was generated at the anode. The fluid was circulated via the first pipe, the first pipe valve, the fourth pipe, and the first mist removing section. No mist was accumulated or blocked in the first pipe, the first pipe valve, and the fourth pipe, and the fluid generated at the anode was supplied to the first mist removing part, so that the mist was removed in the first mist removing part. The first mist removing part was a scrubber type removing part for removing fine particles such as mist by spraying liquid hydrogen fluoride, and the mist removing rate was 98% or more.

[Comparative Example 1]
In the electrolysis of the step (1), the same as in the first embodiment except that the fluid generated at the anode is circulated via the first pipe, the first pipe valve, the fourth pipe, and the first mist removing part. Electrolysis was performed.
During the electrolysis of step (1), the measured value of the pressure gauge on the anode side among the pressure gauges attached to the anode side and the cathode side of the electrolytic cell gradually increased, and the differential pressure from the pressure on the cathode side became 90 mmH ₂ O. Therefore, electrolysis was stopped. The reasons for the suspension are as follows. Since the vertical length (immersion depth) of the part of the partition wall in the electrolytic cell that was immersed in the electrolytic solution was 5 cm, when the pressure on the anode side was about 100 mmH ₂ O higher than the pressure on the cathode side, the anode side The level of the electrolyte is lower than the lower end of the partition. As a result, the fluorine gas gets over the partition wall and mixes with the hydrogen gas on the cathode side, causing a rapid reaction between the fluorine gas and the hydrogen gas, which is extremely dangerous.

After purging the inside of the system with nitrogen gas, etc., the inside of the 1st pipe, 1st pipe valve, and 4th pipe was inspected. As a result, the 1st pipe was a pipe extending in the vertical direction, so there was no blockage. There was a small amount of powder adhering to the first piping valve, and the piping on the downstream side of the first piping valve, that is, the inlet portion to the fourth piping was blocked by the powder. There was also powder accumulation on the 4th pipe, but the amount was not enough to block the pipe.

1 ... Sample room 2 ... Light source 3 ... Scattered

light detector

4A, 4B ... Transparent window 10 ... Electrolyte 11 ... Electrolyte tank 13 ... Anosome 15 ... Cathode 22 ... Adenator chamber 24 ... Cathode chamber 31 ... 1st average particle size measuring unit 32 ... 1st mist removing unit 33 ... 2nd mist removing unit 34 ... 2nd average particle size measuring unit Part 36 ... Moisture concentration measurement part 41 ... 1st pipe 42 ... 2nd pipe 43 ... 3rd pipe 44 ... 4th pipe 45 ... 5th pipe 46 ... 6th Piping 47 ... 7th piping 48 ... 8th piping 49 ... 9th piping 51 ... 1st bypass piping 52 ... 2nd bypass piping 61 ... 1st piping valve 62 ... Bypass valve F ・・・ Fluid L ・・・ Light for light scattering measurement M ・・・ Mist S ・・・ Scattered light

Claims

A method for producing fluorine gas, which is a method for producing fluorine gas by electrolyzing an electrolytic solution containing hydrogen fluoride and metal fluoride.
The electrolysis step of performing the electrolysis in the electrolytic cell and
A water concentration measuring step of measuring the water concentration in the electrolytic solution at the time of the electrolysis, and a water concentration measuring step.
An air supply step of sending a fluid generated inside the electrolytic cell during electrolysis of the electrolytic cell from the inside of the electrolytic cell to the outside via a flow path, and
With
In the air supply step, the flow path through which the fluid flows is switched according to the water concentration in the electrolytic solution measured in the water concentration measuring step, and the water content in the electrolytic solution measured in the water concentration measuring step is switched. When the concentration is equal to or less than the preset reference value, the fluid is sent to the first flow path for sending the fluid from the inside of the electrolytic cell to the first outside, and is larger than the preset reference value. In this case, the fluid is sent to the second flow path that sends the fluid from the inside of the electrolytic cell to the second outside.
The method for producing fluorine gas, wherein the preset reference value is a numerical value within the range of 0.1% by mass or more and 0.8% by mass or less.
The method for producing fluorine gas according to claim 1, wherein the metal fluoride is a fluoride of at least one metal selected from potassium, cesium, rubidium, and lithium.
The invention according to claim 1 or 2, wherein the anode used in the electrolysis is a carbonaceous electrode formed of at least one carbon material selected from diamond, diamond-like carbon, amorphous carbon, graphite, and glassy carbon. Fluorine gas production method.
The electrolytic cell has a structure in which bubbles generated at the anode or cathode used in the electrolysis rise vertically in the electrolytic solution and reach the liquid level of the electrolytic solution. The method for producing fluorine gas according to item 1.
A fluorine gas production device that electrolyzes an electrolytic solution containing hydrogen fluoride and metal fluoride to produce fluorine gas.
An electrolytic cell that houses the electrolyte and is electrolyzed.
A water concentration measuring unit that measures the water concentration in the electrolytic solution in the electrolytic cell during the electrolysis, and a water concentration measuring unit.
A flow path for sending the fluid generated inside the electrolytic cell during electrolysis of the electrolytic cell from the inside of the electrolytic cell to the outside,
With
The flow path has a first flow path for sending the fluid from the inside of the electrolytic cell to the first outside, and a second flow path for sending the fluid from the inside of the electrolytic cell to the second outside. It has a flow path switching unit that switches the flow path through which the fluid flows to the first flow path or the second flow path according to the water concentration in the electrolytic solution measured by the water concentration measuring unit.
When the water concentration in the electrolytic solution measured by the water concentration measuring unit is equal to or less than a preset reference value, the flow path switching unit is connected to the first flow path from the inside of the electrolytic cell. When the fluid is sent and is larger than the preset reference value, the fluid is sent from the inside of the electrolytic cell to the second flow path.
The fluorine gas production apparatus whose preset reference value is a numerical value within the range of 0.1% by mass or more and 0.8% by mass or less.