WO2011129216A1

WO2011129216A1 - Fluorine gas generation device

Info

Publication number: WO2011129216A1
Application number: PCT/JP2011/058529
Authority: WO
Inventors: 章史八尾; 啓太中原; 達夫宮崎; 亜紀応菊池; 敦之徳永
Original assignee: セントラル硝子株式会社
Priority date: 2010-04-16
Filing date: 2011-04-04
Publication date: 2011-10-20
Also published as: JP5720112B2; JP2011225920A

Abstract

Disclosed is a fluorine gas generation device provided with: an electrolytic cell in which a first air chamber, into which fluorine gas generated at an anode is led, and a second air chamber, into which hydrogen gas generated at a cathode is led, are separated and partitioned above the surface of a molten salt; a first main passage for supplying the fluorine gas generated at the anode to an external device; a buffer tank for storing the fluorine gas; a pressure detector which detects the pressure of the buffer tank; a power supply which supplies electric current between the anode and the cathode; and a control device which controls the electric current supplied from the power supply between the anode and the cathode. The control device calculates an electric current value on the basis of the rate of the supply flow of fluorine gas to the external device and corrects the calculated electric current value on the basis of the detection result from the pressure detector.

Description

Fluorine gas generator

The present invention relates to a fluorine gas generator.

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

JP2004-43885A is equipped with an electrolytic cell that electrolyzes hydrogen fluoride in an electrolytic bath made of a molten salt containing hydrogen fluoride, and generates a product gas containing fluorine gas as the 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.

In the fluorine gas generator described in JP2004-43885A, the product gas is stored in the main buffer tank, and the pressure in the main buffer tank is measured with a pressure gauge. The measurement result of the pressure gauge is transmitted to the control member, and the control member controls the current source on and off based on the measurement result of the pressure gauge. Thus, the amount of product gas generated at the anode is controlled based on the pressure in the main buffer tank.

Thus, in the fluorine gas generator described in JP2004-43885A, the amount of product gas generated at the anode is controlled based on the pressure in the main buffer tank. For this reason, when the fluorine gas supply flow rate to the external device changes rapidly, the amount of fluorine gas generated at the anode cannot be controlled with good response. Therefore, the fluorine gas cannot be stably and automatically supplied to the external device.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fluorine gas generation device that can stably and automatically supply fluorine gas.

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, and a main passage connected to the first air chamber for supplying main raw gas generated at the anode of the electrolytic cell to an external device; A buffer tank provided in the main passage for storing main raw gas, a pressure detector for detecting the pressure of the buffer tank, and a power supply device for supplying a current between the anode and the cathode, Supplied between the anode and the cathode from the power supply device And a control device for controlling the current to be generated, wherein the control device calculates a current value based on a supply flow rate of main raw gas to the external device, and the calculated current value is detected by the pressure detector. Correct based on the results.
According to the present invention, the current value supplied between the anode and the cathode from the power supply device is calculated based on the flow rate of the main raw gas supplied from the buffer tank to the external device, and the calculated current value is Since correction is performed based on the pressure in the buffer tank, the main raw gas can be stably and automatically supplied to the external device.

FIG. 1 is a system diagram showing a fluorine gas generator according to an embodiment of the present invention. FIG. 2 is a flowchart showing the start-up procedure of the electrolytic cell. FIG. 3 is a flowchart showing a fluorine gas supply preparation procedure. FIG. 4 is a flowchart showing a fluorine gas supply procedure. FIG. 5 is a flowchart showing a fluorine gas supply stop procedure. FIG. 6 is a flowchart showing a procedure for stopping the electrolytic cell.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a fluorine gas generation apparatus 100 according to an embodiment of the present invention will be described.

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 that case, the fluorine gas is used as a cleaning gas in, for example, 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. The fluorine gas generation device 100 also includes a controller 10 as a control device that controls the operation of each device and each valve based on the detection result output from each meter. The controller 10 is configured by a microcomputer including a CPU, a ROM, and a RAM.

First, the electrolytic cell 1 will be described.

In the electrolytic cell 1, a molten salt containing hydrogen fluoride (HF) is stored. 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.

The temperature of the molten salt in the electrolytic cell 1 is adjusted by the temperature adjusting device 65 to 71.7 ° C. or higher, specifically 85 to 95 ° C., which is the melting point of KF · 2HF. The electrolytic cell 1 is provided with a thermometer 69 as a temperature detector for detecting the temperature of the molten salt. The detection result of the thermometer 69 is output to the controller 10.

The temperature adjusting device 65 includes a jacket 66 provided on the outer wall of the electrolytic cell 1, a tube (not shown) provided inside the electrolytic cell 1, and heating / cooling for circulating steam or cooling water through the jacket 66 and the tube. Device 67. When raising the temperature of the molten salt, steam is circulated from the heating / cooling device 67 to the jacket 66 and the tube, and when lowering the temperature of the molten salt, cooling water is circulated from the heating / cooling device 67 to the jacket 66 and the tube. To adjust the temperature. One of the jacket 66 and the tube may be provided. Further, instead of circulating steam or cooling water through the jacket 66 and the tube, a hot refrigerant such as silicone oil may be circulated. Furthermore, you may make it adjust the temperature of molten salt by providing heat exchangers, such as a heater and a capacitor | condenser, in the outer wall of the electrolytic cell 1. FIG.

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 14 as a liquid level detector for detecting the liquid level of the stored molten salt. The level gauge 14 detects a back pressure when nitrogen gas having a constant flow rate is purged into the molten salt through the insertion tube 14a inserted into the electrolytic cell 1, and the liquid level gauge 14 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. The detection result of the liquid level gauge 14 is output to the controller 10.

Further, the electrolytic cell 1 is provided with a first differential pressure gauge 20 as a differential pressure detector for detecting a pressure difference between the first air chamber 11a and the second air chamber 12a. The detection result of the first differential pressure gauge 20 is output to the controller 10.

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 as a transfer device for deriving and transferring 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. Connected to the first main passage 15 is a first return passage 18 that connects the discharge side and the suction side of the first pump 17. The first reflux passage 18 is provided with a first pressure adjusting valve 19 for returning the fluorine gas discharged from the first pump 17 to the suction side of the first pump 17.

A first pressure gauge 13 as a pressure detector for detecting the pressure in the first main passage 15 is provided upstream of the first pump 17 in the first main passage 15. The detection result of the first pressure gauge 13 is output to the controller 10.

The opening of the first pressure regulating valve 19 is controlled based on a signal output from the controller 10. Specifically, the controller 10 controls the opening degree of the first pressure regulating valve 19 so that the pressure detected by the first pressure gauge 13 is stored in the ROM and becomes a predetermined first set value.

In the first main passage 15, upstream of the first pressure gauge 13, an activation valve 70 that opens when the fluorine gas generation device 100 is activated and allows the flow of the fluorine gas generated at the anode 7 is provided. The start valve 70 is normally open during normal operation of the fluorine gas generator 100. The first main passage 15 is provided with a second differential pressure gauge 71 as a differential pressure detector that detects a pressure difference before and after the start valve 70 in the closed state. The detection result of the second differential pressure gauge 71 is output to the controller 10. The controller 10 opens the start valve 70 when the differential pressure detected by the second differential pressure gauge 71 is stored in the ROM and is within a predetermined setting range when the fluorine gas generator 100 is started. To control. Detailed control will be described later.

A branch passage 72 is connected upstream of the start valve 70 in the first main passage 15, and an abatement part 73 is provided at the downstream end of the branch passage 72. The branch passage 72 is provided with a first shut-off valve 74 that switches between the flow and shut-off of the fluorine gas. When the start valve 70 is closed and the first shut-off valve 74 is opened, the fluorine gas generated at the anode 7 is discharged through the branch passage 72, detoxified by the abatement part 73, and released.

In the first main passage 15, upstream of the first pump 17, a purification device 16 that collects hydrogen fluoride gas mixed in the fluorine gas and purifies the fluorine gas is provided. The purification device 16 includes two systems, a first purification device 16a and a second purification device 16b, which are provided in parallel. The first purification device 16a and the second purification device 16b are configured so that the gas passage portion 50 through which the fluorine gas passes and the hydrogen fluoride gas mixed in the fluorine gas solidify, while the fluorine gas passes through the gas passage portion 50. And a cooling device 51 that cools the gas passage portion 50 at a temperature not lower than the boiling point of fluorine and not higher than the melting point of hydrogen fluoride. Inlet valves 22a and 22b are provided upstream of the first purifier 16a and the second purifier 16b, respectively, and

outlet valves

23a and 23b are respectively provided downstream. The inlet valves 22a and 22b and the

outlet valves

23a and 23b are switched between open and closed so that the fluorine gas generated from the anode 7 passes through only one of the first purification device 16a and the second purification device 16b. That is, when one of the first refining device 16a and the second refining device 16b is in an operating state, the other is stopped or in a standby state.

The first main passage 15 is provided with a third differential pressure gauge 53 as a differential pressure detector that detects a pressure difference before and after the purifier 16. The detection result of the third differential pressure gauge 53 is output to the controller 10. When the differential pressure detected by the third differential pressure gauge 53 is stored in the ROM and reaches a predetermined set value, the controller 10 determines that the accumulated amount of hydrogen fluoride solidified in the gas passage 50 is a predetermined amount. Therefore, the opening and closing of the inlet valves 22a and 22b and the

outlet valves

23a and 23b are controlled to switch the operation of the purifier 16.

A buffer tank 21 for storing the fluorine gas transported 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. The buffer tank 21 is provided with a second pressure gauge 24 as a pressure detector for detecting the internal pressure. The detection result of the second pressure gauge 24 is output to the controller 10.

A flow meter 26 as a flow rate detector for detecting the flow rate of the fluorine gas supplied from the buffer tank 21 to the external device 4 is provided downstream of the buffer tank 21 in the first main passage 15. The detection result of the flow meter 26 is output to the controller 10.

A flow rate control valve 27 for adjusting the flow rate of the fluorine gas supplied to the external device 4 is provided downstream of the flow meter 26 in the first main passage 15. The opening degree of the flow control valve 27 is controlled based on a signal output from the controller 10. Specifically, the controller 10 controls the opening degree of the flow control valve 27 so that the flow rate of the fluorine gas detected by the flow meter 26 is stored in the ROM and becomes a predetermined target flow rate. A plurality of target flow rates are stored in the ROM of the controller 10. The target flow rate is a flow rate of fluorine gas required by the external device 4 and is changed by an operator who operates the fluorine gas generation device 100.

The controller 10 controls the current supplied from the power source 9 between the anode 7 and the cathode 8 based on the target flow rate of the fluorine gas. Specifically, a current value corresponding to the target flow rate is calculated, and the power source 9 is controlled so that the current value is energized between the anode 7 and the cathode 8. Thus, the amount of fluorine gas generated at the anode 7 is controlled so as to replenish the fluorine gas supplied from the buffer tank 21 to the external device 4.

Furthermore, the controller 10 corrects the current value calculated based on the target flow rate of the fluorine gas based on the detection result of the second pressure gauge 24. Specifically, when the pressure of the buffer tank 21 detected by the second pressure gauge 24 is larger than a predetermined setting range stored in the ROM, the calculated current value is corrected to be small, Further, when it is smaller than the set range, the calculated current value is corrected so as to increase. That is, the current value calculated based on the target flow rate of the fluorine gas is corrected so that the pressure of the buffer tank 21 is maintained within the set range (reference pressure). The setting range of the pressure in the buffer tank 21 is set to a pressure higher than the atmospheric pressure.

Thus, the fluorine gas supplied to the external device 4 is controlled to be replenished, and the internal pressure of the buffer tank 21 is controlled to a pressure higher than the atmospheric pressure. 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 second shutoff valve 28 for switching between supply and shutoff of fluorine gas to the external device 4 is provided downstream of the flow control valve 27 in the first main passage 15. A branch passage 55 is connected to the first main passage 15 upstream of the second shut-off valve 28, and an abatement part 56 is provided at the downstream end of the branch passage 55. The branch passage 55 is provided with a third shut-off valve 57 that switches between the flow and shut-off of the fluorine gas. When the second shut-off valve 28 is closed and the third shut-off valve 57 is open, the fluorine gas in the first main passage 15 is discharged through the branch passage 55, detoxified by the abatement part 56, 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 as a transfer device for deriving and transferring hydrogen gas from the second air chamber 12a. The second main passage 30 is connected to a second recirculation passage 32 that connects the discharge side and the suction side of the second pump 31. The second recirculation passage 32 is provided with a second pressure regulating valve 33 for returning the hydrogen gas discharged from the second pump 31 to the suction side of the second pump 31.

A third pressure gauge 35 as a pressure detector for detecting the pressure of the second main passage 30 is provided upstream of the second pump 31 in the second main passage 30. The detection result of the third pressure gauge 35 is output to the controller 10.

The opening of the second pressure regulating valve 33 is controlled based on a signal output from the controller 10. Specifically, the controller 10 controls the opening degree of the second pressure regulating valve 33 so that the pressure detected by the third pressure gauge 35 is stored in the ROM and becomes a predetermined second set value.

The 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 generator 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 raw material supply system 5 includes a hydrogen fluoride supply source 40 in which hydrogen fluoride for replenishing the electrolytic cell 1 is stored. The hydrogen fluoride supply source 40 and the electrolytic cell 1 are connected via 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 control valve 42 is controlled in opening degree based on a signal output from the controller 10. Specifically, the controller 10 controls the supply flow rate of hydrogen fluoride so that the liquid level of the molten salt detected by the level gauge 14 is stored in the ROM and becomes a predetermined level set in advance. 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 carrier gas supply passage 46 is connected to the raw material supply passage 41 to guide 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 a gas for introducing hydrogen fluoride into the molten salt of the electrolytic cell 1, and nitrogen gas which is an inert gas is used. When the fluorine gas generator 100 is in operation, the shut-off valve 47 is basically open, and nitrogen gas is supplied into the molten salt in the cathode chamber 12. 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.

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 nitrogen gas purged through the liquid level gauge 14. 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 due to the reaction between the water in the molten salt and the carbon electrode, and the anode effect may occur. The anode effect refers to a phenomenon in which the electrolysis voltage increases until electrolysis cannot be continued. Therefore, the electrolytic cell 1 is provided with a moisture concentration measuring device 59 that samples the molten salt through the sampling passage 58 and measures the moisture concentration in the molten salt. The Karl Fischer method is used to measure the moisture concentration by the moisture concentration measuring device 59.

Further, in the first main passage 15, gas concentration measurement is performed in which fluorine gas is sampled through the sampling passage 60 and the concentration of a reaction product such as OF ₂ produced by the reaction between fluorine and moisture in the molten salt is measured. A device 61 is provided. An infrared spectrophotometer is used for the gas concentration measuring device 61.

Only one of the moisture concentration measuring device 59 and the gas concentration measuring device 61 may be provided.

Next, automatic operation control of the fluorine gas generation device 100 executed by the controller 10 will be described with reference to FIGS.

In the stop state of the fluorine gas generation device 100, the first shut-off valve 74 is open, and the other start valves 70, inlet valves 22a and 22b,

outlet valves

23a and 23b, the second shut-off valve 28, and the second The three shutoff valve 57 is in a closed state.

First, the starting procedure of the electrolytic cell 1 will be described with reference to FIGS.

2 is started when the operator turns on the switch of the power source 9 of the electrolytic cell 1.

In step 1, the temperature adjusting device 65 is activated, and steam is supplied from the heating and cooling device 67 to the jacket 66 and the tube of the electrolytic cell 1. Thereby, the temperature of molten salt rises.

In step 2, it is determined whether or not the temperature of the molten salt has reached a predetermined temperature. If it is determined that the predetermined temperature has been reached, the process proceeds to step 3. The predetermined temperature is set to 80 ° C. at which the molten salt is in a dissolved state, for example. After the temperature of the molten salt reaches a predetermined temperature, the temperature of the molten salt is controlled to 85 to 95 ° C. by the heating and cooling device 67 based on the detection result of the thermometer 69.

In step 3, the molten salt liquid level control by the flow rate control valve 42 is started. Specifically, the controller 10 controls the opening degree of the flow rate control valve 42 based on the detection result of the liquid level gauge 14 so that the liquid level of the molten salt becomes a predetermined level, and supplies hydrogen fluoride. The flow rate of hydrogen fluoride supplied from 40 to the electrolytic cell 1 is adjusted. The predetermined level is set to a level higher than the lower end portion of the partition wall 6 and lower than a support (not shown) that supports the

electrodes

7 and 8.

In step 4, the moisture concentration in the molten salt is measured by the moisture concentration measuring device 59.

In step 5, it is determined whether or not the moisture concentration in the molten salt measured by the moisture concentration measuring device 59 is stored in the ROM and is equal to or lower than a predetermined reference concentration. When it is determined that the concentration is lower than the reference concentration, the start-up of the electrolytic cell 1 is completed. On the other hand, if it is determined that the reference density is exceeded, the process proceeds to step 6. The reference concentration is determined from the viewpoint of preventing the generation of the anode effect, that is, protecting the anode 7, for example, 500 wt. Set to ppm.

In step 6, a current of 0.5 to 5 A / dm ² is supplied from the power source 9 between the anode 7 and the cathode 8. As a result, fluorine gas is generated at the anode 7, and the fluorine gas is discharged from the first main passage 15 through the branch passage 72, detoxified by the abatement part 73, and released.

In Step 7, as in Step 6, it is determined whether or not the moisture concentration in the molten salt measured by the moisture concentration measuring device 59 is equal to or lower than the reference concentration. If it is determined that the density is not more than the reference density, the process proceeds to Step 8. The energization between the anode 7 and the cathode 8 is performed until the water concentration in the molten salt becomes equal to or lower than the reference concentration.

In step 8, the energization between the anode 7 and the cathode 8 is stopped.

As described above, the start-up of the electrolytic cell 1 is completed, and the electrolytic cell 1 enters a standby state in which current can be supplied between the anode 7 and the cathode 8.

Instead of measuring the moisture concentration in the molten salt by the moisture concentration measuring device 59, the gas concentration measuring device 61 may measure the concentration of the reaction product such as OF ₂ in the fluorine gas. In that case, after step 3 above, a current of 0.5 to 5 A / dm ² is supplied from the power source 9 between the anode 7 and the cathode 8, and the concentration of the reaction product in the fluorine gas generated from the anode 7 is increased. Measure. And when the density | concentration of a reaction product is below a reference | standard density | concentration, electricity supply between the anode 7 and the cathode 8 is stopped, and the electrolytic cell 1 will be in a standby state. On the other hand, when the concentration of the reaction product exceeds the reference concentration, the fluorine gas generated at the anode 7 is discharged through the branch passage 72, and when the concentration of the reaction product becomes lower than the reference concentration, The energization between the cathodes 8 is stopped.

Next, the fluorine gas supply preparation procedure will be described with reference to FIGS.

The fluorine gas supply preparation flow shown in FIG. 3 starts when the operator turns on the gas supply preparation switch.

In step 11, preliminary energization between the anode 7 and the cathode 8 is started. The current is stepped from 0 A / dm ² to 5 A / dm ² . As a result, fluorine gas is generated at the anode 7, and the fluorine gas is discharged from the first main passage 15 through the branch passage 72, detoxified by the abatement part 73, and released.

In step 12, the first pump 17 is started, and the pressure control of the first main passage 15 by the first pressure regulating valve 19 is started. Specifically, based on the detection result of the first pressure gauge 13, the controller 10 adjusts the first pressure so that the pressure on the upstream side of the first pump 17 in the first main passage 15 becomes the first set value. The opening degree of the valve 19 is controlled to adjust the flow rate of the fluorine gas recirculated through the first pressure regulating valve 19. The first set value is set to, for example, 100.5 to 102.0 kPa. When the detected pressure of the first pressure gauge 13 is smaller than the first set value, the opening of the first pressure regulating valve 19 is large so that the flow rate of fluorine gas recirculated to the suction side of the first pump 17 is increased. Is set. Further, when the detected pressure of the first pressure gauge 13 is larger than the first set value, the opening degree of the first pressure regulating valve 19 is set so that the flow rate of the fluorine gas returning to the suction side of the first pump 17 is reduced. Is set small. Here, when the detected pressure of the first pressure gauge 13 is smaller than the first set value, the fluorine gas in the buffer tank 21 moves to the first pump 17 side in the state where the fluorine gas is accumulated in the buffer tank 21. The gas flows backward and flows back through the first pressure regulating valve 19.

In step 13, the inlet and outlet valves of one system of the refiner 16 are opened. Here, the inlet valve 22a and the outlet valve 23a of the first purification device 16a are opened, and the first purification device 16a and the first pump 17 are connected.

In step 14, it is determined whether or not the pressure difference before and after the start valve 70 detected by the second differential pressure gauge 71 is within the set range. If it is determined that it is within the set range, the process proceeds to step 16. On the other hand, if it is determined that the set range is exceeded, the process proceeds to step 15.

In step 16, the start valve 70 is opened and the first shut-off valve 74 is closed, and the first air chamber 11a of the electrolytic cell 1 and the first pump 17 are connected. As a result, the fluorine gas generated at the anode 7 is conveyed by the first pump 17 and guided to the buffer tank 21.

In step 15, the first set value is changed so that the pressure difference before and after the start valve 70 detected by the second differential pressure gauge 71 is within the set range. Specifically, when the pressure upstream and downstream of the start valve 70 exceeds the set range because the pressure upstream of the start valve 70 is greater than the pressure downstream, the first pressure is set to increase the pressure downstream of the start valve 70. The set value is changed to a larger value. Thereby, the opening degree of the first pressure regulating valve 19 is increased, and the differential pressure across the start valve 70 is decreased. On the other hand, if the differential pressure across the start valve 70 exceeds the set range because the pressure upstream of the start valve 70 is lower than the downstream pressure, the first set value is set to reduce the pressure downstream of the start valve 70. Changed to a smaller value. Thereby, the opening degree of the 1st pressure regulation valve 19 becomes small, and the differential pressure before and behind the starting valve 70 becomes small. The change of the first set value is repeated until it is determined that the differential pressure across the start valve 70 is within the set range. And when it determines with it being in the setting range, it progresses to step 16 and the connection of the 1st air chamber 11a and the 1st pump 17 is performed as mentioned above. The setting range depends on the size of the electrolytic cell 1, but is set to 500 Pa, for example.

Thus, the opening of the starting valve 70, that is, the connection between the first air chamber 11a and the first pump 17 is performed when the differential pressure across the starting valve 70 is within the set range. Therefore, when the start valve 70 is opened, the fluorine gas in the first air chamber 11a is prevented from suddenly flowing downstream of the start valve 70, so that fluctuations in the liquid level of the anode chamber 11 are suppressed. . Therefore, the first air chamber 11a and the first pump 17 can be stably connected.

In step 17, the third shut-off valve 57 is opened, and the fluorine gas in the buffer tank 21 is discharged from the first main passage 15 through the branch passage 55, detoxified by the abatement part 56, and released.

In step 18, pressure control of the buffer tank 21 by the flow control valve 27 is started. Specifically, the controller 10 controls the opening degree of the flow control valve 27 based on the detection result of the second pressure gauge 24 so that the pressure of the buffer tank 21 is within a set range (reference pressure). The setting range is set to a range of 110 to 400 kPa, for example. Thus, in the fluorine gas supply preparation procedure, the flow rate control valve 27 performs pressure control of the buffer tank 21 instead of flow rate control of the fluorine gas.

This completes preparations for supplying fluorine gas. As a result, in the fluorine gas generation device 100, a necessary minimum current is passed between the anode 7 and the cathode 8, and the fluorine gas can be supplied to the external device 4.

Also in the by-product gas processing system 3, in order to stably connect the second air chamber 12 a and the second pump 31, the second air chamber 12 a and the second pump 31 are connected in the same manner as the fluorine gas supply system 2. An activation valve and a branch passage may be provided between them, and the same procedure as in

Steps

12, 14, 15, and 16 may be performed. Alternatively, the by-product gas processing system 3 may not be provided with the second pump 31, and the hydrogen gas generated at the cathode 8 may be directly discharged through the second main passage 30.

Next, the fluorine gas supply procedure and the control during normal operation of the fluorine gas generator 100 will be described with reference to FIGS.

The fluorine gas supply flow and normal operation control shown in FIG. 4 are started when the operator turns on the gas supply switch.

In step 21, the flow rate control valve 27 shifts from the pressure control of the buffer tank 21 to the flow rate control of the fluorine gas. Specifically, the controller 10 controls the opening degree of the flow rate control valve 27 so that the flow rate of the fluorine gas detected by the flow meter 26 becomes the target flow rate. Thereby, the fluorine gas flow rate detected by the flow meter 26 and the target flow rate substantially coincide.

In step 22, the current control between the anode 7 and the cathode 8 is changed from 5 A / dm ² constant control to control according to the fluorine gas supply flow rate to the external device 4. This control will be specifically described. There is a relationship of the following equation between the value of the current supplied between the anode 7 and the cathode 8 and the flow rate of the fluorine gas generated at the anode 7.

Here, assuming that the current efficiency is 95%, the flow rate of the fluorine gas can be obtained by the following formula.

The above equation (2) is stored in the ROM of the controller 10. The controller 10 calculates a current value corresponding to the target flow rate of the fluorine gas using the above equation (2), and controls the power source 9 so that the calculated current value is supplied between the anode 7 and the cathode 8. To do. As a result, fluorine gas corresponding to the flow rate of fluorine gas supplied to the external device 4 is generated at the anode 7.

In step 23, the second cutoff valve 28 is opened and the third cutoff valve 57 is closed. Thereby, the fluorine gas in the buffer tank 21 is supplied to the external device 4 and shifts to normal operation. Hereinafter, control of normal operation will be described.

In step 24, it is determined whether or not there is a change in the target flow rate of fluorine gas by the operator. If it is determined that there is a change in the target flow rate, the process proceeds to step 25, and the current value corresponding to the changed target flow rate is recalculated using the above equation (2). The recalculated current value is output to the power source 9, and the power source 9 supplies the recalculated current value between the anode 7 and the cathode 8. Here, when the recalculated current value is higher than the current current value of the power source 9, the current value supplied between the anode 7 and the cathode 8 is increased to the recalculated current value at a predetermined increase rate. Let On the other hand, when the recalculated current value is lower than the current current value of the power supply 9, the current value supplied between the anode 7 and the cathode 8 is lowered to the recalculated current value at a stretch.

The minimum current value is set as the current value supplied between the anode 7 and the cathode 8. The minimum current value is set to about 0.5 A / dm ² , for example. Therefore, even if the target flow rate is 0 L / min, the current value supplied between the anode 7 and the cathode 8 is controlled so as not to be lower than the minimum current value. However, when the flow rate of the fluorine gas detected by the flow meter 26 continues for 0 L / min for a certain period of time, the supply of fluorine gas (described later) is stopped (see FIG. 5).

In steps 22 and 25, it has been described that the current value corresponding to the target flow rate of fluorine gas is calculated using the above equation (2) as the current value supplied between the anode 7 and the cathode 8. However, as the current value supplied between the anode 7 and the cathode 8, the current value corresponding to the fluorine gas flow rate detected by the flow meter 26 may be calculated using the above equation (2). That is, the flow rate (L / min) of the above equation (2) may be calculated as the fluorine gas flow rate detected by the flow meter 26 instead of the target flow rate of fluorine gas. When the current value is calculated in this way, when the flow rate of the fluorine gas supplied to the external device 4 changes continuously, the flow rate of the fluorine gas generated at the electrode 7 is correspondingly changed. It becomes possible to control.

After the current value is recalculated in step 25, the process proceeds to step 26. If it is determined in step 24 that there is no change in the target flow rate, the process proceeds to step 26 without recalculating the current value. As described in Steps 22 and 25, since the current value supplied between the anode 7 and the cathode 8 is calculated based on the target flow rate of fluorine gas, the anode 7 supplies the current to the external device 4. Fluorine gas corresponding to the fluorine gas flow rate is generated. That is, since the fluorine gas supplied from the buffer tank 21 to the external device 4 is supplemented by the fluorine gas generated at the anode 7, theoretically, the pressure in the buffer tank 21 is always kept constant. become. However, since the current efficiency in the above equation (1) fluctuates in the range of about 85 to 99%, the flow rate of fluorine gas supplied from the buffer tank 21 to the external device 4 and the flow rate of fluorine gas generated at the anode 7 There may be a difference between In that case, the pressure in the buffer tank 21 varies without being kept constant.

Therefore, in step 26, it is determined whether or not the pressure in the buffer tank 21 detected by the second pressure gauge 24 is outside the set range. If it is determined that the current value is outside the set range, the process proceeds to step 27 where the current value supplied between the anode 7 and the cathode 8 is corrected. Specifically, when the pressure in the buffer tank 21 is larger than the set range, the current value calculated in step 22 or step 25 is corrected so as to be small. For example, it is corrected to about 90% of the calculated current value. On the other hand, when the pressure in the buffer tank 21 is smaller than the set range, the current value calculated in step 22 or step 25 is corrected so as to increase. For example, it is corrected to about 110% of the calculated current value. As described above, in step 27, the calculated current value is corrected based on the detection result of the second pressure gauge 24. That is, the calculated current value is based on a comparison between the detection result of the second pressure gauge 24 and the set range (reference pressure) so that the pressure of the buffer tank 21 is maintained within the set range (reference pressure). It is corrected. The setting range is set to a range of 110 to 400 kPa, for example.

After the current value is corrected in step 27, the process proceeds to step 28. On the other hand, if it is determined in step 26 that the pressure in the buffer tank 21 is not outside the set range, the process proceeds to step 28 without correcting the current value. The opening degree of the first pressure regulating valve 19 is controlled so that the pressure detected by the first pressure gauge 13 becomes the first set value, and the opening degree of the second pressure regulating valve 33 is detected by the third pressure gauge 35. The pressure is controlled to be the second set value. The first set value and the second set value are set so that the pressures in the first air chamber 11a and the second air chamber 12a are equal, that is, no pressure difference is generated between the two chambers. Therefore, basically, the pressure difference between the first air chamber 11a and the second air chamber 12a is controlled so as not to increase. However, when there is a difference between the actual pressure and the pressure indicated by the first pressure gauge 13 and the third pressure gauge 35 due to instrument error or the like, or from the first pressure gauge 13 or the third pressure gauge 35 to the electrolytic cell 1 When the pressure loss changes over time, the pressure difference between the first air chamber 11a and the second air chamber 12a may increase. The pressure difference between the first air chamber 11a and the second air chamber 12a greatly affects the difference in liquid level between the anode chamber 11 and the cathode chamber 12, and if the difference in liquid level between the two chambers increases, the first air chamber There is a possibility that the fluorine gas of 11a and the hydrogen gas of the second air chamber 12a come into contact with each other and react.

Therefore, in step 28, it is determined whether or not the pressure difference between the first air chamber 11a and the second air chamber 12a detected by the first differential pressure gauge 20 is outside the set range. If it is determined that the pressure is outside the set range, the process proceeds to step 29 where the pressure difference between the first air chamber 11a and the second air chamber 12a detected by the first differential pressure gauge 20 is stored in the ROM and set in a predetermined range. The first set value or the second set value is changed so that Specifically, when the pressure in the first air chamber 11a is larger than the pressure in the second air chamber 12a and the differential pressure between the two chambers exceeds the set range, the pressure in the first air chamber 11a is decreased. The first set value is changed to a small value as much as possible, or the second set value is changed to a large value so as to increase the pressure in the second air chamber 12a. Thereby, the opening degree of the 1st pressure regulation valve 19 becomes small, or the opening degree of the 2nd pressure regulation valve 33 becomes large, and the pressure difference of the 1st air chamber 11a and the 2nd air chamber 12a becomes small. On the other hand, when the pressure in the first air chamber 11a is smaller than the pressure in the second air chamber 12a and the differential pressure between the two chambers exceeds the set range, the pressure in the first air chamber 11a is increased to increase. The first set value is changed to a larger value, or the second set value is changed to a smaller value in order to reduce the pressure in the second air chamber 12a. Thereby, the opening degree of the 1st pressure regulation valve 19 becomes large, or the opening degree of the 2nd pressure regulation valve 33 becomes small, and the pressure difference of the 1st air chamber 11a and the 2nd air chamber 12a becomes small. Instead of this, both the first set value and the second set value may be changed simultaneously. That is, in step 29, at least one of the first set value and the second set value is changed. The change of the first set value and the second set value is repeated until it is determined that the differential pressure in both chambers is within the set range. And when it determines with it being in a setting range, it progresses to step 30. FIG. The setting range depends on the size of the electrolytic cell 1, but is set to 500 Pa, for example.

As described above, the pressure difference between the first air chamber 11a and the second air chamber 12a is controlled to be within the setting range by changing the first setting value and the second setting value. When there is a difference between the pressure indicated by the first pressure gauge 13 and the third pressure gauge 35 and the actual pressure, or the pressure loss from the first pressure gauge 13 and the third pressure gauge 35 to the electrolytic cell 1 has changed over time. Even in this case, a difference in the liquid level between the anode chamber 11 and the cathode chamber 12 is suppressed, and the liquid level control of the electrolytic cell 1 can be stably performed.

In the above step 28, the case where at least one of the first set value and the second set value is changed has been described. However, by changing only the first set value, the first air chamber 11a and the second air chamber 12a The pressure difference may be controlled to be within the set range.

The first pressure gauge 13 detects the pressure on the upstream side of the first pump 17 in the first main passage 15 and does not directly detect the pressure in the first air chamber 11a. Similarly, the third pressure gauge 35 detects the pressure upstream of the second pump 31 in the second main passage 30 and does not directly detect the pressure in the second air chamber 12a. Therefore, in order to eliminate the influence of the aging of the pressure loss from the first pressure gauge 13 and the third pressure gauge 35 to the electrolytic cell 1, the first air chamber 11 a is provided in each of the anode chamber 11 and the cathode chamber 12 of the electrolytic cell 1. And a pressure gauge that directly detects the pressure in the second air chamber 12a, and the first pressure adjustment valve 19 and the second pressure adjustment valve 33 so that the detection result of the pressure gauge becomes the first set value and the second set value. The degree of opening may be controlled. However, in this case as well, there may occur a difference between the pressure indicated by the pressure gauge and the actual pressure in the air chamber due to an instrument error or the like. Therefore, as in steps 28 and 29, the first air chamber 11a and the second air chamber 11 It is effective to change the first set value and the second set value so that the pressure difference with the chamber 12a is within the set range.

In step 30, it is determined whether or not the differential pressure across the purifier 16 detected by the third differential pressure gauge 53 has reached a set value. If it is determined that the set value has not been reached, the process returns to step 24. On the other hand, if it is determined that the set value has been reached, the process proceeds to step 31.

In step 31, it is determined that the accumulated amount of hydrogen fluoride solidified in the gas passage section 50 of the first purification device 16a has reached a predetermined amount, and the operation is switched from the first purification device 16a to the second purification device 16b. Is done. Specifically, after the inlet valve 22b and the outlet valve 23b of the second refining device 16b being stopped are opened, the operation is switched by closing the inlet valve 22a and the outlet valve 23a of the first refining device 16a that is in operation. Is done. After the operation switching of the purifier 16 is completed, the process returns to step 24.

During the normal operation, steps 24 to 31 are repeated.

Next, the procedure for stopping the supply of fluorine gas will be described with reference to FIGS.

The fluorine gas supply stop flow shown in FIG. 5 starts when the operator turns off the gas supply switch. Further, as described in step 24 above, when the fluorine gas flow rate detected by the flow meter 26 continues for a fixed time of 0 L / min, that is, the fluorine gas supply flow rate to the external device 4 is fixed for a fixed time of 0 L / min. Even when the state of min continues, the fluorine gas supply stop flow shown in FIG. 5 starts.

In step 41, the third cutoff valve 57 is opened and the second cutoff valve 28 is closed. Thereby, the supply of the fluorine gas to the external device is stopped, and the fluorine gas in the buffer tank 21 is discharged through the branch passage 55, detoxified by the abatement part 56, and released.

In step 42, the flow rate control valve 27 shifts from the flow rate control of the fluorine gas to the pressure control of the buffer tank 21. Specifically, the controller 10 controls the opening degree of the flow control valve 27 based on the detection result of the second pressure gauge 24 so that the pressure of the buffer tank 21 falls within the set range.

In step 43, the current value supplied between the anode 7 and the cathode 8 is reduced to 5 A / dm ² . If the flow of fluorine gas detected by the flow meter 26 continues to be 0 L / min for a certain period of time, this step 43 is skipped when the fluorine gas supply stop flow has progressed.

In step 44, the first shut-off valve 74 is opened and the start valve 70 is closed. Thereby, the fluorine gas produced | generated at the anode 7 is discharged | emitted through the branch channel | path 72, detoxified in the abatement part 73, and is discharge | released.

In step 45, energization between the anode 7 and the cathode 8 is stopped.

In step 46, the inlet valve 22b and the outlet valve 23b of the second refining device 16b in operation are closed, and the refining device 16 stops.

In step 47, the first pump 17 is stopped, and the pressure control of the first main passage 15 by the first pressure regulating valve 19 is stopped.

In step 48, the third shut-off valve 57 is closed, and the pressure control of the buffer tank 21 by the flow rate control valve 27 is stopped.

Thus, the supply stop of the fluorine gas is completed, and the electrolytic cell 1 is in a standby state.

Next, the procedure for stopping the electrolytic cell 1 will be described with reference to FIGS. The electrolytic cell 1 is stopped when the fluorine gas generator 100 is stopped for a long period of time.

The stop flow of the electrolytic cell 1 shown in FIG. 6 starts when the operator turns off the switch of the power source 9 of the electrolytic cell 1.

In step 51, the temperature adjusting device 65 is stopped, and the temperature control of the molten salt is stopped.

In step 52, the flow control valve 42 is closed, and the supply of hydrogen fluoride from the hydrogen fluoride supply source 40 to the electrolytic cell 1 is stopped. Thereby, the liquid level control of the molten salt is stopped.

In step 53, the measurement of the moisture concentration in the molten salt by the moisture concentration measuring device 59 is stopped. When the gas concentration measuring device 61 is used instead of the moisture concentration measuring device 59, the measurement of the concentration of the reaction product in the fluorine gas by the gas concentration measuring device 61 is stopped.

Thus, the stop of the electrolytic cell 1 is completed. Thereby, the stop of the fluorine gas production | generation apparatus 100 is completed.

According to the above embodiment, the following effects are obtained.

The current value supplied from the power source 9 between the anode 7 and the cathode 8 is calculated based on the flow rate of fluorine gas supplied from the buffer tank 21 to the external device 4, and the calculated current value is the pressure in the buffer tank 21. Therefore, fluorine gas can be stably and automatically supplied to the external device 4.

In addition, when the fluorine gas generation device 100 is started, the controller 10 changes the first set value so that the pressure difference detected by the second differential pressure gauge 71 is within a predetermined set range, and the pressure difference is set. When it falls within the range, the start valve 70 is opened. Thus, the start valve 70 is opened in a state where the pressure difference between the upstream and downstream is small, and the connection between the first air chamber 11a and the first pump 17 is performed. Therefore, fluctuations in the liquid level of the electrolytic cell 1 can be suppressed when the fluorine gas generator 100 is started.

Further, during the normal operation of the fluorine gas generation device 100, the controller 10 controls the opening of the first pressure regulating valve 19 so that the pressure detected by the first pressure gauge 13 becomes a predetermined first set value. In addition, the first set value or the second set value is changed so that the pressure difference between the first air chamber 11a and the second air chamber 12a detected by the first differential pressure gauge 20 is within a predetermined set range. To do. Therefore, an increase in the pressure difference between the first air chamber 11a and the second air chamber 12a is prevented, and the liquid level control of the electrolytic cell 1 can be performed stably.

As described above, in the fluorine gas generation device 100, the first main passage 15, the first air chamber 11a, and the second air are controlled in order to minimize the fluctuation in the liquid level of the electrolytic cell 1 during startup and normal operation. The pressure in the chamber 12a is controlled with high accuracy.

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.

For example, in FIG. 1, the controller 10 is illustrated for each device or valve. However, the detection result of each instrument is output to one controller, and the operation of each device and each valve is controlled by the one controller. Also good.

In the above-described embodiment, the case where the purification device 16 is a cryogenic purification device that separates and removes the hydrogen fluoride gas from the fluorine gas using the difference in boiling point between fluorine and hydrogen fluoride has been described. As the purification device 16, 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) instead of the cryogenic purification device is used. You may do it.

This application claims priority based on Japanese Patent Application No. 2010-95205 filed with the Japan Patent Office on April 16, 2010, the entire contents of which are incorporated herein by reference.

Claims

A fluorine gas generator that generates fluorine gas by electrolyzing hydrogen fluoride in a molten salt,
A first air chamber into which main gas mainly composed of fluorine gas generated at an anode immersed in molten salt is guided, and hydrogen gas generated at a cathode immersed in molten salt as a main component. An electrolytic cell in which a second gas chamber into which a by-product gas is guided is separated on the surface of the molten salt liquid,
A main passage connected to the first air chamber and for supplying main raw gas generated at the anode of the electrolytic cell to an external device;
A buffer tank provided in the main passage for storing main raw gas;
A pressure detector for detecting the pressure of the buffer tank;
A power supply device for supplying a current between the anode and the cathode;
A control device for controlling a current supplied between the anode and the cathode from the power supply device,
The control device calculates a current value based on a supply flow rate of main raw gas to the external device, and corrects the calculated current value based on a detection result of the pressure detector. Gas generator.
The fluorine gas generator according to claim 1,
The control device calculates a current value corresponding to a target flow rate of the main raw gas required by the external device, and calculates the calculated current value between a pressure detected by the pressure detector and a predetermined reference pressure. A fluorine gas generator that corrects based on the comparison.
The fluorine gas generator according to claim 1,
A flow rate detector that is provided in the main passage and detects a flow rate of main raw gas supplied from the buffer tank to the external device;
The control device calculates a current value corresponding to the flow rate of the main raw gas detected by the flow rate detector, and calculates the calculated current value from a pressure detected by the pressure detector and a predetermined reference pressure. Fluorine gas generator that corrects based on the comparison.
The fluorine gas generation device according to claim 2 or 3, wherein
The current value correction by the control device is a fluorine gas generation device that is performed so that the pressure of the buffer tank is maintained at the reference pressure.