JP2011179072A - Fluorine gas generation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorine gas generation device which can be stably electrolyzed. <P>SOLUTION: A fluorine gas generation device is provided with: an electrolytic cell 1 where a first gas space 11a into which a main raw gas containing fluorine gas generated in an anode 7 immersed in a molten salt as a principal ingredient is introduced and a second gas space 12a into which a by-produced gas containing gaseous hydrogen generated in a cathode 8 immersed in the molten salt as a principal ingredient is introduced, are separated and partitioned on the liquid level of the molten salt; a power source 9 for supplying current between the anode 7 and the cathode 8; a moisture concentration-measuring device 50 for measuring moisture concentration in the molten salt in the electrolytic cell 1; and a control device 60 for controlling the power source 9 so as to decrease the current supplied between the anode 7 and the cathode 8, when it is decided that the moisture concentration measured by the moisture concentration measuring device 50 is higher than a previously determined reference value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fluorine gas generator.

  As a conventional fluorine gas generation apparatus, an apparatus that uses an electrolytic cell and generates fluorine gas by electrolysis is known.

  Patent Document 1 includes an electrolytic bath for electrolyzing hydrogen fluoride in an electrolytic bath made of a molten salt containing hydrogen fluoride, and generates a product gas containing fluorine gas as a main component in the first gas phase portion on the anode side. In addition, a fluorine gas generation device that generates a by-product gas mainly containing hydrogen gas in a second gas phase portion on the cathode side is disclosed.

JP 2004-43885 A

  In the fluorine generator as described in Patent Document 1, a carbon electrode is usually used for the anode. From this, when electrolysis is performed in a state where the water concentration in the molten salt in the electrolytic bath is high, the surface of the electrode is oxidized by the reaction between the water in the molten salt and the carbon electrode. Since the oxidized electrode surface is unstable, it easily reacts with fluorine and may cause an anodic effect. When the anode effect occurs, stable electrolysis becomes difficult.

  This invention is made | formed in view of said problem, and it aims at providing the fluorine gas production | generation apparatus which can be electrolyzed stably.

  The present invention relates to a fluorine gas generating device that generates fluorine gas by electrolyzing hydrogen fluoride in a molten salt, the fluorine generated at an anode in which the molten salt is stored and immersed in the molten salt. The first gas chamber in which main gas mainly composed of gas is guided and the second chamber in which by-product gas mainly composed of hydrogen gas generated at the cathode immersed in the molten salt is guided are melted. An electrolytic cell separated on the surface of the salt solution, a power source for supplying current between the anode and the cathode, a moisture concentration measuring device for measuring the moisture concentration in the molten salt of the electrolytic cell, When it is determined that the moisture concentration measured by the moisture concentration measuring device is higher than a predetermined reference value, the power supply is controlled so that the current supplied between the anode and the cathode is reduced. And a control device.

  According to the present invention, when the control device determines that the moisture concentration in the molten salt is higher than a predetermined reference value, the power supply is configured so that the current supplied between the anode and the cathode is reduced. Therefore, generation of the anode effect is suppressed and stable electrolysis is possible.

1 is a system diagram showing a fluorine gas generation device according to an embodiment of the present invention. It is a block diagram which shows a control apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  With reference to FIG. 1, the fluorine gas production | generation apparatus 100 which concerns on embodiment of this invention is demonstrated.

  The fluorine gas generation device 100 generates fluorine gas by electrolysis and supplies the generated fluorine gas to the external device 4. The external device 4 is, for example, a semiconductor manufacturing device. In this case, fluorine gas is used as a cleaning gas, for example, in a semiconductor manufacturing process.

  The fluorine gas generation device 100 includes an electrolytic cell 1 that generates fluorine gas by electrolysis, a fluorine gas supply system 2 that supplies the fluorine gas generated from the electrolytic cell 1 to the external device 4, and the generation of fluorine gas. And a by-product gas processing system 3 for processing the generated by-product gas.

  First, the electrolytic cell 1 will be described.

  The electrolytic bath 1 stores a molten salt containing hydrogen fluoride (HF). In the present embodiment, a mixture (KF · 2HF) of hydrogen fluoride and potassium fluoride (KF) is used as the molten salt.

The inside of the electrolytic cell 1 is partitioned into an anode chamber 11 and a cathode chamber 12 by a partition wall 6 immersed in the molten salt. In the molten salt of the anode chamber 11 and the cathode chamber 12, the anode 7 and the cathode 8 are immersed, respectively. By supplying a current from the power source 9 between the anode 7 and the cathode 8, a main gas mainly composed of fluorine gas (F ₂ ) is generated at the anode 7, and hydrogen gas (H ₂ ) is generated at the cathode 8. By-product gas as a main component is generated. A carbon electrode is used for the anode 7, and soft iron, monel, or nickel is used for the cathode 8.

  On the surface of the molten salt solution in the electrolytic cell 1, a first gas chamber 11a into which fluorine gas generated at the anode 7 is guided, and a second gas chamber 12a into which hydrogen gas generated at the cathode 8 is guided. Are partitioned by the partition wall 6 so that the mutual gas cannot pass. As described above, the first air chamber 11a and the second air chamber 12a are completely separated by the partition wall 6 in order to prevent a reaction due to the contact of fluorine gas and hydrogen gas. On the other hand, the molten salt in the anode chamber 11 and the cathode chamber 12 is not separated by the partition wall 6 but communicates through the lower portion of the partition wall 6.

  Since the melting point of KF · 2HF is 71.7 ° C., the temperature of the molten salt is adjusted to 90 to 100 ° C. In each of the fluorine gas and the hydrogen gas generated from the anode 7 and the cathode 8 of the electrolytic cell 1, hydrogen fluoride is vaporized from the molten salt by the vapor pressure and mixed. As described above, each of the fluorine gas generated at the anode 7 and guided to the first air chamber 11a and the hydrogen gas generated at the cathode 8 and guided to the second air chamber 12a includes hydrogen fluoride gas. Yes.

  The electrolytic cell 1 is provided with a liquid level gauge 13 as a liquid level detector for detecting the liquid level of the stored molten salt. The liquid level gauge 13 detects the back pressure when the nitrogen gas having a constant flow rate is purged into the molten salt through the insertion tube 13a inserted into the electrolytic cell 1, and the liquid level gauge 13 detects the liquid pressure from the back pressure and the liquid specific gravity of the molten salt. It is a back pressure type liquid level gauge that detects the surface level.

  Next, the fluorine gas supply system 2 will be described.

  A first main passage 15 for supplying fluorine gas to the external device 4 is connected to the first air chamber 11a.

  The first main passage 15 is provided with a first pump 17 for deriving and transporting fluorine gas from the first air chamber 11a. As the first pump 17, a positive displacement pump such as a bellows pump or a diaphragm pump is used.

  A purification device 16 is provided upstream of the first pump 17 in the first main passage 15 to collect the hydrogen fluoride gas mixed in the main raw gas and purify the fluorine gas. The refining device 16 is a deep-cooling refining device that separates and removes hydrogen fluoride gas from fluorine gas using the difference in boiling point between fluorine and hydrogen fluoride. In addition, instead of the deep-cooling purification device, the purification device 16 is a device that separates and removes the hydrogen fluoride gas from the fluorine gas by adsorbing the hydrogen fluoride gas in the fluorine gas to an adsorbent such as sodium fluoride (NaF). May be used.

  A buffer tank 21 for storing the fluorine gas transferred by the first pump 17 is provided downstream of the first pump 17 in the first main passage 15. The fluorine gas stored in the buffer tank 21 is supplied to the external device 4.

  A flow meter 26 that detects the flow rate of fluorine gas supplied to the external device 4 is provided downstream of the buffer tank 21. The power source 9 controls the current value supplied between the anode 7 and the cathode 8 based on the detection result of the flow meter 26. Specifically, the amount of fluorine gas generated at the anode 7 is controlled so that the amount of fluorine gas supplied from the buffer tank 21 to the external device 4 is replenished to the buffer tank 21.

  In this way, the amount of fluorine gas generated at the anode 7 is controlled so as to supplement the amount of fluorine gas supplied to the external device 4, so that the internal pressure of the buffer tank 21 is maintained at a pressure higher than atmospheric pressure. Is done. On the other hand, since the external device 4 side where fluorine gas is used is atmospheric pressure, if the valve provided in the external device 4 is opened, the pressure difference between the buffer tank 21 and the external device 4 Fluorine gas is supplied from the buffer tank 21 to the external device 4.

  A shutoff valve 23 that switches between the flow and shutoff of the fluorine gas is provided upstream of the purification device 16 in the first main passage 15. The first main passage 15 is provided with a discharge passage 25 that branches from upstream of the shut-off valve 23 and discharges fluorine gas. The discharge passage 25 is provided with a discharge valve 24 for switching between discharge and shutoff of fluorine gas. An abatement part 27 is provided downstream of the discharge valve 24 in the discharge passage 25, and the fluorine gas discharged through the discharge passage 25 is rendered harmless by the abatement part 27 and released.

  Next, the byproduct gas processing system 3 will be described.

  A second main passage 30 for discharging hydrogen gas to the outside is connected to the second air chamber 12a.

  The second main passage 30 is provided with a second pump 31 for deriving and transporting hydrogen gas from the second air chamber 12a.

  An abatement part 34 is provided downstream of the second pump 31 in the second main passage 30, and the hydrogen gas transported by the second pump 31 is rendered harmless by the abatement part 34 and released.

  The fluorine gas generation device 100 also includes a raw material supply system 5 that supplies hydrogen fluoride, which is a raw material of fluorine gas, into the molten salt of the electrolytic cell 1. Below, the raw material supply system 5 is demonstrated.

  The electrolytic cell 1 is connected to a hydrogen fluoride supply source 40 in which hydrogen fluoride for replenishing the electrolytic cell 1 is stored through a raw material supply passage 41. Hydrogen fluoride stored in the hydrogen fluoride supply source 40 is supplied into the molten salt of the electrolytic cell 1 through the raw material supply passage 41.

  The raw material supply passage 41 is provided with a flow rate control valve 42 for controlling the supply flow rate of hydrogen fluoride. The flow rate control valve 42 controls the supply flow rate of hydrogen fluoride based on the detection result of the level gauge 13 so that the liquid level of the molten salt in the electrolytic cell 1 becomes a predetermined level. That is, the flow rate control valve 42 controls the supply flow rate of hydrogen fluoride so as to replenish hydrogen fluoride electrolyzed in the molten salt.

  The raw material supply passage 41 is connected to a carrier gas supply passage 46 that guides the carrier gas supplied from the carrier gas supply source 45 into the raw material supply passage 41. The carrier gas supply passage 46 is provided with a cutoff valve 47 for switching between supply and cutoff of the carrier gas. The carrier gas is an accompanying gas for introducing hydrogen fluoride into the molten salt, and nitrogen gas which is an inert gas is used. During operation of the fluorine gas generator 100, the shut-off valve 47 is basically open, and nitrogen gas is supplied into the molten salt in the cathode chamber 12 of the electrolytic cell 1. The nitrogen gas is hardly dissolved in the molten salt and is discharged from the second air chamber 12a through the byproduct gas processing system 3. Note that another inert gas such as argon gas or helium gas may be used as the carrier gas.

  Here, the molten salt in the electrolytic cell 1 contains a trace amount of water. This moisture is brought into the electrolytic cell 1 together with hydrogen fluoride supplied through the raw material supply passage 41, or is brought into the electrolytic cell 1 together with nitrogen gas supplied to the raw material supply passage 41 through the carrier gas supply passage 46. In other words, it is brought into the electrolytic cell 1 together with the nitrogen gas purged through the liquid level gauge 13. Further, the moisture contained in the molten salt includes the moisture mixed into the molten salt from the beginning, in addition to the moisture brought in during electrolysis. When electrolysis is performed in a state where the water concentration in the molten salt in the electrolytic cell 1 is high, the surface of the anode 7 is oxidized by the reaction between the water in the molten salt and the carbon electrode, so that the anode effect may occur. . Here, the anodic effect refers to a phenomenon in which the electrolysis voltage increases until electrolysis cannot be continued.

  As a countermeasure, the fluorine gas generation device 100 controls the generation and supply of fluorine gas based on the moisture concentration measurement device 50 that measures the moisture concentration in the molten salt of the electrolytic cell 1 and the measurement result of the moisture concentration measurement device 50. And a control device 60.

  The moisture concentration measuring device 50 measures the moisture concentration in the molten salt sampled through the sampling passage 51 connected to the electrolytic cell 1 and outputs the measurement result to the control device 60. Specifically, the moisture concentration measuring device 50 collects the sampled molten salt by pyrolyzing the sampled molten salt into potassium fluoride and hydrogen fluoride, and coagulating and collecting the hydrogen fluoride volatilized by the pyrolyzing step. The moisture concentration in the sampled molten salt is measured by performing the collecting step and the measuring step of measuring the moisture concentration in the hydrogen fluoride collected in the collecting step. In the measurement process, a Karl Fischer measurement device or an electrical conductivity measurement device is used.

  In addition, the measurement of the water concentration by the water concentration measuring device 50 may be performed all the time or may be performed every predetermined time.

  The control device 60 is configured by a microcomputer including a CPU, a ROM, and a RAM. As shown in FIG. 2, the control device 60 has a storage unit 61 that stores a reference value of the moisture concentration in the molten salt, and the moisture concentration in the molten salt that is a measurement result measured by the moisture concentration measuring device 50. The determination part 62 which determines whether it is higher than the reference value memorize | stored in the memory | storage part 61, and the instruction | command part 63 which outputs a command signal with respect to the power supply 9 based on the determination result by the determination part 62 are provided.

  The reference value stored in the storage unit 61 is a value determined in advance by performing an experiment or the like, and is determined from the viewpoint of preventing the anode effect, that is, protecting the anode 7. Specifically, 500 wt. Set to ppm.

When the moisture concentration in the molten salt is below the reference value, the command unit 63 outputs a command signal to the power source 9 so that the current supplied between the anode 7 and the cathode 8 is maintained. Driving is performed. On the other hand, when the water concentration in the molten salt is higher than the reference value, the anode effect may occur, so that the command unit 63 reduces the current supplied between the anode 7 and the cathode 8. In this manner, a command signal is output to the power source 9. Specifically, the current density of the current supplied between the anode 7 and the cathode 8 lowers the current to be in the range of 0.1~5.0A / dm ^2. Thereby, since electrolysis at the anode 7 is suppressed, generation of the anode effect is prevented.

In addition, when the water concentration in the molten salt is higher than the reference value, the moisture in the molten salt reacts with the generated fluorine to generate an impurity gas such as OF ₂ and the fluorine gas concentration decreases. Therefore, the command unit 63 outputs a command signal also to the shutoff valve 23 and the discharge valve 24 based on the determination result by the determination unit 62, and controls the supply of fluorine gas to the external device 4. Specifically, when the moisture concentration in the molten salt is below the reference value, the command unit 63 outputs a valve opening command to the shutoff valve 23 and a valve closing command to the discharge valve 24, and normal operation is performed. Done. As a result, the fluorine gas generated at the anode 7 is supplied to the external device 4 through the first main passage 15. On the other hand, when the water concentration in the molten salt is higher than the reference value, the command unit 63 outputs a valve closing command to the shutoff valve 23 and a valve opening command to the discharge valve 24. As a result, the fluorine gas generated at the anode 7 is discharged through the discharge passage 25 and detoxified, so that the fluorine gas containing the impurity gas can be prevented from being supplied to the external device 4.

  As the fluorine gas generated at the anode 7 is discharged, the moisture concentration in the molten salt decreases. When the moisture concentration in the molten salt becomes below the reference value, the command unit 63 sends a command signal to the power supply 9 so that the current supplied between the anode 7 and the cathode 8 increases. In addition to outputting, a valve opening command is output to the shutoff valve 23 and a valve closing command is output to the discharge valve 24 to return to normal operation.

  According to the above embodiment, there exist the effects shown below.

  When the fluorine gas generation device 100 determines that the moisture concentration measurement device 50 measures the moisture concentration in the molten salt and the measurement result of the moisture concentration measurement device 50 is higher than the reference value, the anode 7 and the cathode 8 And a control device 60 for controlling the power source 9 so that the current supplied during the period decreases. Therefore, even when the moisture concentration in the molten salt is high, the generation of the anode effect is prevented, so that stable electrolysis is possible.

  Furthermore, when the control device 60 determines that the measurement result of the moisture concentration measuring device 50 is higher than the reference value, the control device 60 controls the shut-off valve 23 to close and the discharge valve 24 to open, so that the anode The fluorine gas generated in 7 is not supplied to the external device 4 but is discharged through the discharge passage 25. Therefore, it is possible to prevent the fluorine gas containing the impurity gas from being supplied to the external device 4.

  Further, by discharging the fluorine gas generated in the anode 7 through the discharge passage 25, the moisture concentration in the molten salt of the electrolytic cell 1 is lowered, so that corrosion of the metal that is the material of the electrolytic cell 1 is prevented. Can do.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be applied to an apparatus that generates fluorine gas.

DESCRIPTION OF SYMBOLS 100 Fluorine gas production | generation apparatus 1 Electrolysis tank 2 Fluorine gas supply system 3 By-product gas processing system 4 External device 5 Raw material supply system 7 Anode 8 Cathode 13 Level gauge 15 First main passage 23 Shut-off valve 24 Drain valve 25 Drain passage 40 Hydrogen fluoride supply source 41 Raw material supply passage 50 Water concentration measuring device 51 Sampling passage 60 Control device 61 Storage unit 62 Determination unit 63 Command unit

Claims (2)

A fluorine gas generator that generates fluorine gas by electrolyzing hydrogen fluoride in a molten salt,
A first air chamber in which a main gas mainly composed of fluorine gas generated in an anode immersed in the molten salt is introduced and hydrogen generated in the cathode immersed in the molten salt. An electrolytic cell in which a second gas chamber into which a by-product gas containing a gas as a main component is guided is separated on the surface of the molten salt solution;
A power source for supplying a current between the anode and the cathode;
A moisture concentration measuring device for measuring the moisture concentration in the molten salt of the electrolytic cell;
When it is determined that the moisture concentration measured by the moisture concentration measuring device is higher than a predetermined reference value, the power supply is controlled so that the current supplied between the anode and the cathode is reduced. A control device,
A fluorine gas generation device comprising: A first main passage connected to the first air chamber for supplying main component gas to an external device;
A shut-off valve that is provided in the first main passage and switches between flow and shut-off of the main gas;
An exhaust passage provided for branching from the upstream of the shut-off valve in the first main passage, and for exhausting main raw gas;
A discharge valve provided in the exhaust passage for switching between discharge and shut-off of the main gas,
2. The control device according to claim 1, wherein when the moisture concentration in the molten salt is determined to be higher than the reference value, the control device closes the shut-off valve and opens the discharge valve. The fluorine gas production | generation apparatus of description.

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