JP2009191362A - Apparatus for molten salt electrolysis and method for producing fluorine gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for molten salt electrolysis, which can be stably operated with extended life, by controlling the concentration of produced fluorine gas such that the fluorine gas does not react with moisture, oxygen gas and OF<SB>2</SB>in an electrolysis bath, and a method for producing fluorine gas. <P>SOLUTION: The apparatus for molten salt electrolysis includes an electrolysis tank 1 which forms the electrolysis bath 2 comprising a mixed molten salt containing hydrogen fluoride and is divided into an anode chamber 3 in which an anode 51 is disposed and a cathode chamber 4 in which a cathode 52 is disposed, an inert gas feeding means 91 which feeds inert gas to the electrolysis tank 1, a measuring means which measures the amount of fluorine gas produced in the electrolysis tank 1 and a control means which controls the concentration of the fluorine gas such that it is diluted at least two-fold by the inert gas feeding means 91, based on the amount of the fluorine gas measured by the measuring means. The method for producing fluorine gas includes electrolyzing the mixed molten salt containing hydrogen fluoride in the electrolysis tank 1 to produce the fluorine gas and diluting the fluorine gas in the electrolysis tank 1 at least two-fold with inert gas. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a molten salt electrolysis apparatus capable of generating fluorine gas and hydrogen gas, and a method for generating fluorine gas.

  There are known molten salt electrolyzers that can generate fluorine gas and hydrogen gas, and methods for generating fluorine gas, as disclosed in Patent Documents 1 to 3 below. Briefly described, Patent Document 1 discloses a gas generator and an electric current thereof for generating fluorine or fluoride gas by electrolysis using a carbon electrode as an anode in an electrolytic bath made of a mixed molten salt containing hydrogen fluoride. A control method that measures the voltage fluctuation range between the cathode and the anode when a constant current is applied to the gas generator, and applies the current while varying the input current amount according to the voltage fluctuation range. .

Patent Document 2 is an F ₂ gas generator that generates F ₂ gas by electrolyzing an electrolytic bath composed of KF · 2HF, a preparation system for preparing KF or KF · HF into KF · 2HF, An HF supply system that supplies HF to the electrolytic bath and the preparation system; and an F ₂ gas generation system that generates F ₂ gas by electrolyzing KF · 2HF prepared by the preparation system. It is what. In Patent Document 2, a F ₂ gas generating method of by electrolyzing an electrolytic bath comprising a KF · 2HF generate F ₂ gas, the moisture removal means for removing moisture in the KF or KF · HF In the preparation system for preparing the attached KF or KF · HF to KF · 2HF, the KF or KF · HF is heated or degassed in a vacuum or an inert gas atmosphere for a predetermined time, and then the vacuum or inert gas. Cooling to room temperature under an atmosphere, and then supplying vaporized HF from the HF supply system into the preparation system to react the KF or KF · HF with the HF in the preparation system, A method is disclosed in which 2HF is generated, KF · 2HF is supplied to an electrolytic cell of an F ₂ gas generation system, and then electrolyzed to generate F ₂ gas having a low oxygen concentration.

  The thing of patent document 3 is the control apparatus of the molten salt electrolysis tank which makes the state which melt | dissolves the solid electrolytic bath accommodated in the electrolysis tank automatically, and can electrolyze, Comprising: By the detector provided in the electrolysis tank It has a detection means for detecting a change in the state of the electrolytic cell, and an adjustment means for adjusting the electrolytic bath liquid surface to a state capable of electrolysis after the detection means is implemented. Patent Document 3 discloses a method for controlling a molten salt electrolytic cell in which a solid electrolytic bath accommodated in an electrolytic cell is melted and automatically electrolyzed, and includes a detector provided in the electrolytic cell. Is disclosed that includes a detection step of detecting a change in the state of the electrolytic cell and an adjustment step of adjusting the electrolytic bath liquid level to a state capable of electrolysis after the detection step.

Japanese Patent No. 3569277 Japanese Patent No. 3569279 JP 2005-48279 A

However, in the apparatuses and methods of Patent Documents 1 to 3, the concentration of the generated fluorine gas reacts with the moisture, oxygen gas, or OF _{2 in the} electrolytic bath, and the electrolytic cell is subjected to an impact during the reaction. In some cases, the components themselves or the parts provided in the electrolytic cell are deformed. If such deformation occurs many times, there is a possibility of causing a failure of the apparatus. Therefore, conventionally, it has been necessary to periodically stop the operation of the apparatus at relatively short intervals and perform maintenance such as failure check or parts replacement.

The present invention has been made to solve the above problems, and suppresses the concentration of the generated fluorine gas from reacting with moisture, oxygen gas, or OF ₂ in the electrolytic bath, and an electrolytic cell. As a result, an object of the present invention is to provide a molten salt electrolysis apparatus capable of extending the life of the apparatus and enabling more stable operation, and a method for generating fluorine gas.

(1) The molten salt electrolysis apparatus of the present invention forms an electrolytic bath made of a mixed molten salt containing hydrogen fluoride, and is separated into an anode chamber provided with an anode and a cathode chamber provided with a cathode. A molten salt electrolysis apparatus provided with a tank, wherein an inert gas supply means for supplying an inert gas into the electrolytic tank, a measuring means for measuring the amount of fluorine gas generated in the electrolytic tank, and the measuring means And a control unit that controls the inert gas supply unit to dilute the fluorine gas twice or more from the value of the fluorine gas amount obtained in (1). Examples of the inert gas include a gas that does not react with fluorine or a gas that has low reactivity with fluorine.

According to the configuration of (1) above, it is possible to suppress the concentration of the generated fluorine gas from reacting with moisture, oxygen gas, or OF ₂ in the electrolytic bath, thereby extending the lifetime of the electrolytic cell and the apparatus, and more A molten salt electrolysis apparatus capable of stable operation can be provided.

(2) In the molten salt electrolysis apparatus of the present invention, the apparatus includes a current application unit that applies a current between the anode and the cathode, and the amount of current applied at the beginning of electrolysis using the current application unit is as follows: The surface area effective for electrolysis on the anode is preferably smaller than 0.5 A / dm ² .

  According to the configuration of the above (2), since an appropriate amount of current is applied in preliminary electrolysis, it can be efficiently dehydrated from the electrolytic bath, and the generation of the anode effect and polarization can be further suppressed than in the past. It is possible to provide a molten salt electrolysis apparatus suitable for longer-term operation.

(3) In the molten salt electrolysis apparatus of the present invention, it is preferable that the current application means can increase the amount of current to be applied from the initial amount of electrolysis. More preferably, the applied current amount is gradually increased when the current amount is increased from the initial current amount.

  According to the configuration of (3) above, it is possible to efficiently dehydrate from the electrolytic bath.

(4) The method for generating fluorine gas of the present invention is a method for generating fluorine gas by electrolyzing a mixed molten salt containing hydrogen fluoride in an electrolytic cell, wherein the fluorine gas in the electrolytic cell is It is diluted more than twice with an inert gas.

According to the configuration of (4), since the generated fluorine can be diluted, it is possible to suppress the concentration of the fluorine gas from reacting with moisture, oxygen gas, or OF ₂ in the electrolytic bath. Can do. Therefore, if the method of the above configuration (3) is used in the molten salt electrolysis apparatus, it is possible to prevent the electrolytic cell itself or the components provided in the electrolytic cell from being deformed and failing due to the impact during the reaction. Therefore, it is possible to provide a molten salt electrolyzer capable of more stable operation while extending the electrolytic cell and thus the device life.

(5) In the fluorine gas generation method of the present invention, the electrolytic cell forms an electrolytic bath made of a mixed molten salt containing hydrogen fluoride, an anode chamber provided with an anode, and a cathode provided with a cathode. The amount of current applied between the anode and the cathode at the beginning of electrolysis is less than 0.5 A / dm ^{2 with} respect to the surface area effective for electrolysis on the anode. It is preferable.

  When the method (5) is used in a molten salt electrolysis apparatus, the generation of the anode effect and polarization can be further suppressed as compared with the conventional case, and a fluorine gas generation apparatus suitable for longer-term operation can be obtained.

(6) In the method for generating fluorine gas of the present invention, it is preferable that the amount of current applied is increased after making it smaller than 0.5 A / dm ^{2 at the} beginning of electrolysis. More preferably, the applied current amount is gradually increased when the current amount is increased from the initial current amount.

  According to the configuration of (6) above, it is possible to efficiently dehydrate from the electrolytic bath.

  According to the molten salt electrolysis apparatus and the fluorine gas generation method of the present invention, the life of the electrolytic cell and thus the molten salt electrolysis apparatus is extended, and stable operation of the apparatus becomes possible.

It is a schematic diagram of the principal part of the molten salt electrolysis apparatus which concerns on embodiment of this invention. According to a second embodiment of the present invention, the amount of current applied to the one between the anode and the cathode (the current amount) is a graph showing the relationship between the order of dehydrated electrolytic bath (concentration of O _2).

  Hereinafter, a molten salt electrolysis apparatus according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram of a main part of a molten salt electrolysis apparatus according to an embodiment of the present invention.

  In FIG. 1, 1 is an electrolytic cell, 2 is an electrolytic bath made of a KF-HF mixed molten salt, 3 is an anode chamber, and 4 is a cathode chamber. Reference numeral 5 denotes first liquid level detecting means for detecting the liquid level height of the anode chamber. 6 is a second liquid level detecting means for detecting the liquid level height of the cathode chamber.

  The electrolytic cell 1 is made of a metal or alloy such as Ni, Monel, pure iron, stainless steel or the like, and can be heated by a hot water jacket 13 provided around and a hot water heating device 12 connected to the hot water jacket 13. It can be done. The electrolytic cell 1 is separated into an anode chamber 3 and a cathode chamber 4 by a partition wall 16 made of Ni or Monel. An anode 51 is disposed in the anode chamber 3. The cathode chamber 4 is provided with a cathode 52. The anode 51 can be a low polarizable carbon electrode. As the cathode 52, Ni or the like can be used.

Further, a power source 53 (current application means) is electrically connected to the anode 51 and the cathode 52 so that an arbitrary amount of current can be applied between the anode 51 and the cathode 52. Although not shown, the power source 53 has power amount measuring means that can measure the amount of power. The power amount is measured by the power amount measuring means, and the amount of fluorine gas generated in the anode chamber 3 is measured. It can be calculated (estimated) by a calculation means (such as a computer equipped with a calculation program). Note that the measuring means for measuring the amount of fluorine gas generated in the electrolytic cell includes the power amount measuring means and the calculating means. Here, the amount of current applied at one time using the power source 53 is 0.5 A / dm ² or less with respect to the surface area effective for electrolysis on the anode 51 (apparent surface area (electrode size as it is)).

  The upper lid 17 of the electrolytic cell 1 has a purge gas inlet / outlet from a gas line (not shown) which is one of pressure maintaining means for maintaining the anode chamber 3 and the cathode chamber 4 at atmospheric pressure, and fluorine gas generated from the anode chamber 3. A generating port 22 and a generating port 23 for hydrogen gas generated from the cathode chamber 4 are provided. These generating ports 22 and 23 are provided with bent tubes made of a material resistant to fluorine gas such as stainless steel and hastelloy, and splashes from the anode chamber 3 and the cathode chamber 4 are generated in the gas line. Intrusions are suppressed. Further, the upper lid 17 has an HF inlet 25 from an HF supply line 24 for supplying HF when the liquid level of the electrolytic bath 2 is lowered, a first liquid level detecting means 5 and a second liquid level detecting means. 6 and are provided

  The HF supply line 24 is connected to an HF supply source outside the fluorine gas generator, and extends from the connection portion to a connection portion with the HF introduction port 25 arranged in the electrolytic cell 1. In the vicinity of the electrolytic cell 1, an automatic valve 81, a flow meter 83, an automatic valve 82, and a pressure gauge 84 are arranged in order from the upstream side to the downstream side in the HF supply line 24. The automatic valve 81 opens and closes in conjunction with the HF supply stop detection device to cut off the supply of HF to the electrolytic cell 1. The flow meter 83 monitors the flow rate of HF supplied to the electrolytic cell 1 via the HF supply line. The automatic valve 82 detects the decrease in the liquid level of the electrolytic bath by the first liquid level detecting means and the second liquid level detecting means, and opens and closes so as to supply HF to the electrolytic bath. The pressure gauge 84 measures the pressure of HF in the HF supply line 24. The HF supply line 24 is covered with a temperature adjusting heater for preventing HF liquefaction. Here, the automatic valve is a valve that is opened and closed by an external signal, such as an electromagnetic valve.

  Reference numeral 91 denotes an inert gas supply line that supplies an inert gas to the HF supply line 24 or the anode chamber 3, and the inert gas supply lines 91a and 91b that are separately connected to two locations of the HF supply line 24 from the middle. The inert gas supply line 91c connected to the anode chamber 3 is branched into three. More specifically, the inert gas supply lines 91a and 91b include an upstream connection portion between the automatic valve 81 disposed on the HF supply line 24 and the HF supply line 24 between the flow meter 83 and an automatic valve. 82 and a downstream connection portion of the HF supply line 24 between the pressure gauge 84 and the pressure gauge 84, respectively. Reference numeral 92 denotes an inert gas storage tank that supplies an inert gas to the inert gas supply line 91, and is placed on a load cell (weighing scale) that measures the amount of the inert gas used. 72 is an automatic valve disposed on the inert gas supply line 91c, 73 is an automatic valve disposed near the upstream side connection portion on the inert gas supply line 91a, and 74 is on the inert gas supply line 91b. It is an automatic valve arranged near the downstream connection part. 86 is disposed upstream of the automatic valve 72 in the inert gas supply line 91c. In this embodiment, a gas that does not react with fluorine (for example, a rare gas) or a gas that has low reactivity with fluorine can be used as the inert gas.

  The inert gas storage tank 92 having the pressure gauge 33 is always supplied with an inert gas from an inert gas supply source (not shown) via a manual valve 65, a pressure gauge 32, and a check valve 75. From the output side of the inert gas storage tank, a stable inert gas is always supplied to the inert gas supply line 91 at a constant pressure.

A detoxification tower 14 detoxifies HF from the mixed gas of hydrogen and HF discharged from the cathode chamber 4, and is connected to the gas generating port 23 through the automatic valve 8. Reference numeral 15 denotes an HF abatement tower that detoxifies HF from the mixed gas of F ₂ and HF discharged from the anode chamber 3 and discharges fluorine gas, and is connected to the gas generating port 22 via the automatic valve 7. Has been.

  Further, as not shown, an HF supply stop detection device (detection means) for detecting the supply stop of HF and a control for controlling the supply amount of the inert gas from the inert gas supply line 91 by controlling the automatic valve 72. Means (for example, a computer loaded with a predetermined program). The inert gas supply line 91, the inert gas storage tank 92, the automatic valve 73, the automatic valve 82, the automatic valve 74, and the HF supply stop detection device constitute an inert gas replacement means. The line having the inert gas storage tank 92 and the normal inert gas supply line 91 can be provided separately, or the inert gas storage tank 92 can be provided on the same supply line. It is preferable to provide a pressure gauge and a pressure reducing valve on the line.

  Next, the operation of the fluorine gas generator according to this embodiment will be described.

(Operation of supplying HF to the electrolytic bath during normal operation)
As the reaction in the electrolytic bath proceeds by electrolysis, fluorine gas is obtained and at the same time the electrolytic bath is consumed. The consumption of the electrolytic bath is detected by monitoring the decrease in the electrolytic bath liquid level by the first liquid level detecting means 5 and the second liquid level detecting means 6. When the consumption of the specified amount of the electrolytic bath is detected, the operation of supplying HF is performed. Specifically, the automatic valve 73 disposed on the inert gas supply line 91 connected to the upstream connection portion of the HF supply line 24 is closed, and the automatic valve 81 and automatic valve disposed on the HF supply line are closed. 82, the automatic valve 74 arranged on the inert gas supply line 91 connected to the downstream connection portion of the HF supply line 24 is opened. As a result, the inert gas having a constant pressure supplied from the inert gas storage tank 92 flows downstream from the automatic valve 82 in the HF supply line 24 from the downstream connection portion between the HF supply line 24 and the inert gas supply line 91. Supplied to the side. The inert gas supplied to the HF supply line 24 becomes a carrier gas and supplies HF in the HF supply line to the electrolytic bath. The amount of HF supplied to the electrolytic bath is measured by a flow meter 83.

  When the electrolytic bath rises by a specified amount by supplying HF, the HF supply stop device detects the HF supply stop device via the first liquid level detection means 5 and the second liquid level detection means 6, and the HF supply stop operation is performed. Specifically, the automatic valve 81 is closed to cut off the supply of HF, the automatic valve 82 and the automatic valve 73 are opened, and the automatic valve 74 is closed, so that the upstream of the HF supply line 24 and the inert gas supply line 91 is upstream. A constant pressure inert gas supplied from an inert gas storage tank 92 is supplied to the downstream side of the automatic valve 81 in the HF supply line 24 from the side connection portion, and the HF downstream of the automatic valve 81 is inactive. Replaced with gas. Thereby, all the HF remaining in the HF supply line 24 can be sent out to the electrolytic cell 1 and the pressure in the line can be maintained. Further, the inert gas that is always supplied to the electrolytic cell 1 is discharged from the gas generating port 23 together with the generated hydrogen.

(Supplying HF to the electrolytic bath of the fluorine gas generator in an emergency)
In an emergency of the fluorine gas generator, the supply of HF is stopped by the HF supply stop device. Specifically, the automatic valve 81 is closed to cut off the supply of HF, the automatic valve 82 and the automatic valve 73 are opened, and the automatic valve 74 is closed, so that the upstream of the HF supply line 24 and the inert gas supply line 91 is upstream. A constant pressure inert gas supplied from an inert gas storage tank 92 is supplied to the downstream side of the automatic valve 81 in the HF supply line 24 from the side connection portion, and the HF downstream of the automatic valve 81 is inactive. Replaced with gas. Thereby, all the HF remaining in the HF supply line 24 can be sent out to the electrolytic cell 1. Even when the supply of the inert gas from the inert gas supply source is shut off, the HF remaining in the HF supply line 24 is sent to the electrolytic cell 1 to the inert gas storage tank 92, and the HF in the line is converted into the inert gas. A sufficient amount of inert gas is stored for replacement.

  As described above, the fluorine gas generation device according to the present embodiment acts as a carrier gas for HF by supplying an inert gas to the HF supply line, and also closes the automatic valve 81 when HF supply is stopped or in an emergency. HF in the HF supply line on the downstream side is replaced with an inert gas.

(Operation to dilute fluorine gas in anode chamber 3 using inert gas)
First, the amount of electric power applied to the molten salt is measured by the power amount measuring means in the power source 53 to estimate the amount of fluorine gas generated in the anode chamber 3. Next, a control means (not shown) controls the automatic valve 72 from the estimated value of the amount of fluorine gas generated, adjusts the inert gas flow rate in the inert gas supply line 91c, Dilute more than twice. At this time, if the flow rate is adjusted while measuring the introduction amount of the inert gas (nitrogen gas) from the inert gas supply line 91c to the anode chamber 3 by the flow meter 86 of the inert gas supply line 91c, the flow rate is adjusted efficiently. It can be adjusted accurately. Further, the adjustment may be performed while adjusting the amount of electric power applied to the molten salt in the power source 53 to adjust the generation amount of the fluorine gas. A series of these operations can be performed by the control means.

According to the above configuration, the concentration of the generated fluorine gas and the moisture, oxygen gas, or OF ₂ in the electrolytic bath 2 is prevented from reacting with each other. A molten salt electrolyzer capable of operation can be provided.

In addition, since an appropriate amount of current is applied in the preliminary electrolysis of 0.5 A / dm ² or less with respect to the surface area effective for electrolysis on the anode 51, dehydration can be efficiently performed from the electrolytic bath, and the anode effect and polarization can be achieved. Can be further suppressed than before, and a molten salt electrolysis apparatus suitable for longer-term operation can be provided.

Example 1
Whether a molten salt electrolysis apparatus having the same configuration as that of the above-described embodiment is manufactured, and in this apparatus, the concentration of the generated fluorine gas and the moisture, oxygen gas, or OF ₂ in the electrolytic bath is suppressed from reacting. I verified it. Specifically, it was verified whether or not the electrolytic cell was deformed depending on the concentration to be diluted, and the clogging frequency due to the electrolytic bath scattered by the impact during reaction of the piping at the electrolytic cell outlet. The electrolytic cell outlet piping is about 50 to 65 ° C., considerably lower than the electrolytic bath temperature of 80 to 90 ° C., and further lower than the melting point (70 ° C.) of the electrolytic bath components. For this reason, when an electrolytic bath component scatters in this vicinity, there is a high risk of solidification and clogging of piping. The results are shown in Table 1 below.

  From Table 1 above, it can be seen that by diluting the generated fluorine gas more than twice, deformation of the electrolytic cell and clogging of the piping can be suppressed.

(Example 2)
Next, when dehydrating the electrolytic bath, the amount of current applied at a time between the anode and the cathode in the electrolytic cell was set to 0.5 A / dm ² or less with respect to the surface area effective for electrolysis on the anode. In this case, the relationship between the current amount (energization amount) and the degree of dehydration (O ₂ concentration) of the electrolytic bath was verified. The result is shown in the graph of FIG. In FIG. 2, series 1 was energized at a constant 0.5 A / dm ² , and series 2 was changed over time from 0.1 → 0.3 → 0.5 (unit: A / dm ² ). In this case, series 3 shows a case where power is supplied at a constant 0.3 A / dm ² .

From FIG. 2, in the series 1, the fluorine gas generated in the electrolytic cell and the water in the bath are not sufficiently reacted. Since the amount of fluorine gas generated is proportional to the current density, increasing the current value is thought to increase the probability that the fluorine gas bubbles will come into contact with the electrolytic bath per unit time. It is presumed that there is an appropriate current density for efficiently reacting the electrolytic bath of the entire electrolytic cell because it only goes up to adhere to the electrode and does not diffuse. For this reason, it can be seen that in Series 1, since the generation of the fluorine gas is too much, the bubble rises too quickly, and as a result, the bath and the fluorine gas cannot be sufficiently contacted, and the dehydration is performed slowly. It can be seen that the amount of current applied at the beginning of electrolysis is less than 0.5 mA / cm ² , and in the series 2 in which the current value is increased stepwise, dehydration is most efficiently performed. In series 3, the fluorine gas generated in the electrolytic cell can react with moisture in the bath more efficiently than series 1, but since it has a constant current density, dehydration proceeds more than series 2. In spite of the fact that the anodic effect did not occur, the electrolysis was carried out with the current value kept low after that, and as a result, it was found that a large amount of energization was required.

  The present invention can be changed in design without departing from the scope of the claims, and is not limited to the above-described embodiments and examples.

  By utilizing the present invention, the life of the molten salt electrolysis apparatus can be extended. In addition, the apparatus can be operated stably.

DESCRIPTION OF SYMBOLS 1 Electrolysis tank 2 Electrolytic bath 3 Anode chamber 4 Cathode chamber 5 1st liquid level detection means 6 2nd liquid level detection means 7 and 8 Automatic valve 12 Hot water heating apparatus 14 and 15 HF removal tower 16 Partition walls 22 and 23 Gas generating port 24 HF supply line 25 HF introduction ports 31 to 34, 84 Pressure gauge 51 Anode 52 Cathode 65, 66 Manual valve 72, 73, 74, 81, 82 Automatic valve 83, 85 Flow meter 91 Inert gas supply line 92 Inert gas Storage tank

Claims (6)

A molten salt electrolyzer comprising an electrolytic bath formed of a mixed molten salt containing hydrogen fluoride and separated into an anode chamber provided with an anode and a cathode chamber provided with a cathode,
An inert gas supply means for supplying an inert gas into the electrolytic cell;
Measuring means for measuring the amount of fluorine gas generated in the electrolytic cell;
And a control means for controlling the fluorine gas to be diluted more than twice by the inert gas supply means from the value of the fluorine gas amount obtained by the measuring means. apparatus. Comprising a current application means for applying a current between the anode and the cathode;
^2. The molten salt electrolysis according to claim 1, wherein an amount of current applied at the beginning of electrolysis using the current application unit is smaller than 0.5 A / dm ^{2 with} respect to a surface area effective for electrolysis on the anode. apparatus.   The molten salt electrolysis apparatus according to claim 2, wherein the current application unit is capable of increasing the amount of current to be applied from an initial amount of electrolysis. A method for generating fluorine gas by electrolyzing a mixed molten salt containing hydrogen fluoride in an electrolytic cell,
A method for generating fluorine gas, wherein the fluorine gas in the electrolytic cell is diluted with an inert gas at least twice. The electrolytic cell is an electrolytic bath made of a mixed molten salt containing hydrogen fluoride and separated into an anode chamber provided with an anode and a cathode chamber provided with a cathode,
The amount of current applied at the beginning of electrolysis between the anode and the cathode is made smaller than 0.5 A / dm ^{2 with} respect to the surface area effective for electrolysis on the anode. Of generating fluorine gas. 6. The method for generating fluorine gas according to claim 5, wherein the applied current amount is increased after being made smaller than 0.5 A / dm ^{2 at the} beginning of electrolysis.

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