A fluorine/fluoride gas generator which has an electrolyte made of mixed molten salt containing hydrogen fluoride in an electrolytic cell including an anode chamber and a cathode chamber, and generates a gas containing fluorine by electrolyzing the electrolyte, includes a raw material supply pipe for supplying an electrolysis raw material, reaching the inside of the electrolyte in the electrolytic cell, a normally-closed valve provided in the middle of the raw material supply pipe, and a bypass pipe provided with a normally-open valve, joining the raw material supply pipe on the downstream side from the normally-closed valve to a gas phase area of the electrolytic cell. Accordingly, the electrolyte is prevented from being suctioned into the raw material supply pipe in the fluorine/fluoride gas generator, and solidification of the electrolyte inside the raw material supply pipe can be prevented.

TECHNICAL FIELD

The present invention relates to a gas generator for generating a fluorine-based gas, having a raw material supply system, which can be safely stopped even in the case of emergency stop such as a sudden power cut.

BACKGROUND ART

Normally, a fluorine-based gas is generated by an electrolytic cell1of a fluorine/fluoride gas generator as shown in the schematic view ofFIG. 1. As the material of the electrolytic cell1, Ni, monel metal, and carbon steel, etc., are used. The inside of the electrolytic cell1is filled with potassium fluoride-hydrogen fluoride or ammonium fluoride-hydrogen fluoride mixed molten salt as an electrolyte2. The mixed molten salt to be used as the electrolyte2has a melting point higher than the ambient temperature, and the normal electrolytic cell1for generating fluorine-based gas has a heating device12(temperature adjusting means) such as a heater or a hot water pipe, etc., on its outer peripheral portion. The melting point of the mixed molten salt to be used for the electrolyte is, for example, approximately 70 degrees C. (KF-2HF) or approximately 50 degrees C. (NH4F-2HF)

The electrolytic cell1is divided into an anode chamber3and a cathode chamber4by a partition16made of monel metal or the like. By the electrolysis, as a result of applying a voltage between a carbon or nickel (hereinafter, referred to as Ni) anode51housed in the anode chamber3and an Ni cathode52housed in the cathode chamber4, a fluorine-based gas is generated in the anode chamber3side, and hydrogen gas is generated in the cathode chamber4side. The generated fluorine-based gas is exhausted from a fluorine-based gas exhaust port22, and the hydrogen gas generated in the cathode chamber4side is exhausted from a hydrogen gas exhaust port23. By the electrolysis, the electrolysis raw material is reduced. In the case of a potassium fluoride-hydrogen fluoride electrolyte, according to electrolysis, hydrogen fluoride (hereinafter, referred to as HF) is consumed and the electrolyte liquid level lowers. At this time, from a raw material gas supply port26extending from the outside of the electrolytic cell11to the inside of the electrolyte2of the cathode chamber, an HF gas as a raw material gas is directly supplied into the electrolyte2. HF has a boiling point of approximately 20 degrees C., and it is supplied in the form of gas to the gas generator, so that the raw material gas supply pipe25must be heated to approximately 35 to 40 degrees C., and it has a temperature adjusting means. Similarly, in the case of an ammonium fluoride-hydrogen fluoride electrolyte, when the liquid level lowers according to electrolysis, HF gas and NH3gas are directly supplied into the electrolyte2from the raw material gas supply pipe25extending from the outside of the electrolytic cell1into the electrolyte2of the cathode chamber and an ammonia (hereinafter, referred to as NH3) gas supply pipe with the same constitution as that of the HF gas supply pipe although this is not shown. The supply of the HF gas and NH3gas is interlocked with liquid level detection sensors5and6which monitor the height of the level of the electrolyte2so as to maintain a constant liquid level.

As the above-described gas generator, for example, one is disclosed in Patent document 1 listed below.

In the above-described fluorine/fluoride gas generator, when the supply of the raw material gas from the raw material gas supply pipe25is stopped due to emergency stop such as a sudden power cut, the raw material gas remaining in the pipe quickly dissolves into the electrolyte2, so that the inside of the raw material supply pipe25leading to the cathode chamber4is decompressed. The electrolyte2is low in viscosity in a molten state, and it is suctioned to the inside of the raw material gas supply pipe25via the raw material gas supply port26. The heating condition of the heater24attached to the raw material gas supply pipe25is 35 to 40 degrees C., and this is lower than the melting point of 50 to 70 degrees C. of the electrolyte2, so that the ingredients of the electrolyte2that have entered inside the raw material gas supply pipe25are cooled and solidified. The whole raw material gas supply pipe25clogged by the solidification of the ingredients of the electrolyte2must be replaced, however, this replacement is dangerous, and time and cost are necessary to recover the generator.

The melting point of potassium fluoride-hydrogen fluoride or ammonium fluoride-hydrogen fluoride mixed molten salt fluctuates according to the relative proportions of the ingredients. Particularly, mixed molten salt for an electrolyte to be generally used for generating fluorine is KF-2HF, and its melting point is 70 degrees C. In detail, the ratio of HF to KF in the electrolyte is controlled in the range of 1.9 to 2.3. Herein, at an HF concentration lower than a lower limit of KF-1.9HF, the melting point of the electrolyte suddenly rises and exceeds 100 degrees C. When the melting point is over the control capability of the gas generator, the molten state of the electrolyte cannot be maintained, and as a result, electrolysis cannot be performed, and the gas generator fails. At an HF concentration over an upper limit of KF-2.3HF, the melting point of the electrolyte lowers, however, the carbon-made anode collapses, and if HF increases, the gas generator corrodes. In both of these cases, stable gas supply cannot be performed. In consideration of these facts, to operate the gas generator without problems, stable supply of the raw material gas to the electrolyte must be continued.

As a method for solving the problem of clogging of the raw material gas supply pipe with the electrolyte in Patent document 1, for example, there is proposed a method described in Patent document 2 listed below. In detail, as shown inFIG. 2, the raw material gas supply pipe25is provided with a nitrogen gas supply pipe40and various members for controlling the flow in the nitrogen gas supply pipe40. First, nitrogen to be supplied to the nitrogen supply pipe40is adjusted in pressure by a decompression valve46, and temporarily stored in a nitrogen tank44through an automatic valve45. Nitrogen stored in the nitrogen tank44is adjusted in pressure again by a decompression valve43and adjusted in flow rate by a flowmeter42in the nitrogen supply pipe40, and then supplied to the raw material gas supply pipe25through an automatic valve41. As for operations in detail, first, when liquid level detection sensors5and6which are installed inside the electrolytic cell1and monitor the liquid level of the electrolyte2detect a liquid level lower than a reference, an automatic valve81opens and supplies the raw material gas to the raw material gas supply pipe25, and at this time, the automatic valve41does not open and nitrogen gas does not flow. When the liquid level detection sensors5and6which are installed inside the electrolytic cell1and monitor the liquid level of the electrolyte2detect a liquid level rise to the reference, the automatic valve81closes and the raw material gas inside the raw material gas supply pipe25is not supplied. At this time, when the raw material gas remains inside the raw material gas supply pipe25, it quickly dissolves into the electrolyte2, so that the inside of the raw material gas supply pipe25leading to the cathode chamber4is decompressed. The electrolyte2is low in viscosity in a molten state, and it is suctioned to the inside of the raw material gas supply pipe25via the raw material gas supply port26. The heating condition of the heater24attached to the raw material gas supply pipe25is 35 to 40 degrees C., and this is lower than the melting point of 50 to 70 degrees C. of the electrolyte2, so that a part of the electrolyte2that has entered inside the raw material gas supply pipe25is cooled and solidified. To prevent this suctioning of the electrolyte2, the automatic valve41is opened and nitrogen gas is supplied into the raw material gas supply pipe25to wash out all raw material gas remaining inside the raw material gas supply pipe25into the electrolyte2, whereby the inside of the raw material gas supply pipe25is cleaned.

Patent document 1: Published Japanese Translations of PCT International Publication for Patent Application No. 9-505853

Patent document 2: Japanese Patent Publication No. 3527735

DISCLOSURE OF INVENTION

Problem to be Solved by the Invention

In the gas generator which generates a fluorine-based gas, when the power is suddenly cut during supply of the raw material gas, or the pipe inside the gas generator is clogged, and, a person finds gas leakage or other abnormalities and operates an EMO (emergency stop) button that is not shown, or a sequencer determines the temperature, pressure, or liquid level as being abnormal to an extent equivalent to EMO, the gas generator may be emergency-stopped. In detail, (1) the power source (electricity) is cut off, (2) all automatic valves (inFIG. 2,45on the nitrogen gas supply pipe40,81on the raw material gas supply pipe25,89at the hydrogen gas exhaust port23,91at the fluorine gas exhaust port22, and other automatic valves in not-shown pipes leading to the generator) of the primary side and secondary side pipes of the gas generator ofFIG. 2are closed to cut gas connection to the outside so that the gas generator is sealed up. From this state, unless a person operates the gas generator to release the emergency stop state, the gas generator cannot be restored to a normal automatic operating state. The automatic valves mentioned herein are valves such as solenoid valves and air pressure values which are opened and closed in response to an electric signal from the outside or gas pressure.

At the time of this EMO, in the normal combination of only the nitrogen gas supply pipe40and the automatic valve41excluding the nitrogen tank44, the automatic valve45, and the decompression valve46ofFIG. 2, the nitrogen gas cannot be supplied to the raw material gas supply pipe25, and if the raw material gas remains inside the raw material gas supply pipe25, the raw material gas easily dissolves into the electrolyte2and the inside of the supply pipe is decompressed, and the electrolyte2is suctioned.

However, in the gas generator ofFIG. 2representatively described in Patent document 2, by using the gas pressure stored in the nitrogen tank44provided on the nitrogen gas supply pipe40, nitrogen is supplied for a predetermined time at a constant flow rate into the raw material gas supply pipe25to forcibly wash out the raw material gas inside the raw material gas supply pipe25to the electrolyte2, whereby suctioning and solidification of the electrolyte2to the inside of the raw material gas supply pipe25can be prevented.

However, in the gas generator ofFIG. 2, members including the nitrogen tank44and the decompression valve46, etc., are necessary on the nitrogen gas supply pipe40, and the piping becomes complicated.

At the time of EMO, nitrogen is forcibly supplied into the cathode chamber4, so that the inside of the cathode chamber4after EMO is pressurized and the liquid level in the electrolytic cell becomes imbalanced. When trying to recover the gas generator, due to this liquid level imbalance, abnormality detection and EMO are repeated, and nitrogen gas may be frequently introduced into the cathode chamber4from the nitrogen tank44.

These will be described by using detailed examples as follows. In the gas generator ofFIG. 2after EMO, the electrolytic cell1is sealed up for insulation from the outside. In this state, for example, when the nitrogen gas is allowed to flow for 30 minutes at 200 cc/min as a cleaning condition for the raw material supply pipe, a total of 6 liters of nitrogen per one EMO is compressed into the cathode chamber4. The size of the electrolytic cell1varies depending on the fluorine gas generating amount, however, as an example, when it is assumed that the electrolytic cell has a 100 A capacity and a space of approximately 60 liters is in the cathode chamber4, if 6 liters of nitrogen gas is compressed into the space, the pressure increases simply by 10 percent. Then, if this pressure difference causes the liquid level imbalance, and EMO occurs again for some reason, further imbalance of the liquid level is added, and the gas generator cannot be easily restarted.

The present invention was made in view of the above-described problems, and an object thereof is to provide a fluorine/fluoride gas generator which is improved in safety by preventing suctioning of electrolyte into the raw material supply pipe and solidification of the electrolyte by suppressing decompression inside the raw material supply pipe at the time of operation stop or stop of supply of a raw material such as HF or NH3, etc., due to abnormalities while the constitution of the gas generator is simple.

Means for Solving the Problems and Effects Thereof

The present invention relates to a gas generator which has an electrolyte made of mixed molten salt containing hydrogen fluoride or ammonium salt in an electrolytic cell including an anode chamber and a cathode chamber, and generates a fluorine-based gas (for example, fluorine or nitrogen trifluoride) by electrolyzing the electrolyte, equipped with a raw material supply system which includes a raw material supply pipe for supplying an electrolysis raw material, reaching the inside of the electrolyte in the electrolytic cell, a normally-closed valve provided in the middle of the raw material supply pipe, and a bypass pipe provided with a normally-open valve, joining the raw material supply pipe on the downstream side from the normally-closed valve to a gas phase area of the electrolytic cell. In the fluorine/fluoride gas generator of the present invention, it is preferable that the raw material supply pipe is provided on the cathode chamber side of the electrolytic cell. In the fluorine/fluoride gas generator of the present invention, it is preferable that even when the normally-closed valve of the raw material supply pipe is closed and the raw material supply is stopped, or when the gas generator is emergency-stopped during supply of the raw material, the normally-open valve opens to balance the pressure inside the raw material supply pipe and the pressure inside the electrolytic cell. The normally-closed valve mentioned herein means an automatic valve which is closed in a natural state, and opens in response to an electric signal from the outside or a gas pressure if necessary, and the normally-open valve means an automatic valve which is open in a natural state, and closes in response to an electric signal from the outside or a gas pressure if necessary.

With the above-described constitution, even when an abnormality occurs during supply of the raw material and the gas generator function stops and the supply of the raw material stops, the automatic valve of the bypass pipe opens concurrently, so that even if the raw material remaining inside the raw material supply pipe dissolves into the electrolyte and the inside of the raw material supply pipe is decompressed, the atmosphere gas immediately flows into the raw material supply pipe from the gas phase area of the electrolytic cell through the bypass pipe, so that the pressure inside the raw material supply pipe does not apparently decrease. Accordingly, with the simple constitution, even if an abnormality occurs during operation of the gas generator and the gas generator function stops, the pressure fluctuation inside the raw material supply pipe can be suppressed, and the pipe can be prevented from being clogged due to suctioning and solidification of the electrolyte into the raw material supply pipe.

In the present invention, it is preferable that a nitrogen gas supply pipe for supplying a nitrogen gas is further connected to the raw material supply pipe between the normally-closed valve of the raw material supply pipe and the normally-open valve of the bypass pipe.

With the above-described constitution, by always supplying a small amount of nitrogen gas into the raw material supply pipe, HF remaining inside the raw material supply pipe can be washed out, so that clogging of the pipe due to suctioning and solidification of the electrolyte into the raw material supply pipe can be further prevented.

Best Mode for Carrying Out the Invention

Hereinafter, an embodiment of the fluorine/fluoride gas generator of the present invention will be described. In the description given below of the embodiment, the portions similar to the portions of the gas generator described in Background Art above are attached with the same reference numerals, and description thereof may be omitted.

FIG. 3is a schematic view of a main portion of the fluorine gas generator of an embodiment of the present invention. InFIG. 3, the reference numeral1denotes an electrolytic cell,2denotes an electrolyte made of KF—HF mixed molten salt,3denotes an anode chamber, and4denotes a cathode chamber. The reference numeral5denotes a first liquid level detecting means for detecting a liquid level of the anode chamber. The reference numeral6denotes a second liquid level detecting means for detecting a liquid level of the cathode chamber. The reference numeral11denotes a temperature gauge for measuring the temperature of the electrolyte2, and12denotes a hot water jacket for heating and melting the electrolyte2on the outer periphery of the electrolytic cell1and a heating device (temperature adjusting means) leading to the hot water jacket. The reference numeral22denotes a generation port for fluorine gas generated from the anode chamber3, and inside this, an automatic valve91for shutting-off in the case of EMO is provided. The reference numeral23denotes a generation port for hydrogen gas generated from the cathode chamber4, and an automatic valve89for shutting-off in the case of EMO is provided ahead of it. The reference numeral25denotes a HF supply pipe for supplying HF to the electrolytic cell1. The reference numeral80denotes a bypass as a bypass pipe. The reference numeral81denotes an automatic valve disposed in the HF supply pipe,82denotes an automatic valve disposed in the bypass80, and83denotes a flowmeter which monitors a flow rate of HF passing through the HF supply pipe25. The reference numeral84denotes a pressure gauge for measuring the pressure of HF. The bypass80joins the raw material gas supply pipe25and the gas phase area of the cathode chamber4of the electrolytic cell1. The reference numeral14denotes a removing tower for removing HF from the hydrogen-HF mixed gas exhausted from the cathode chamber4. The removing tower14can be used at the front or the rear of the automatic valve89in the present invention. The reference numeral15denotes an HF removing tower which separates a fluorine gas by removing only HF from the fluorine-HF mixed gas exhausted from the anode chamber3. The HF removing tower15can be used at the front or the rear of the automatic valve91in this embodiment.

Further, although not shown, the gas generator is equipped with an HF supply stop detecting device (detecting means) which detects HF supply stop, and the automatic valve81, the automatic valve82, and the HF supply stop detecting device constitute an HF pipe clogging preventive means.

The electrolytic cell1is made of a metal such as Ni, monel metal, pure iron, or stainless steel, or an alloy. The electrolytic cell1is divided into an anode chamber3and a cathode chamber4by a partition16made of Ni or monel metal. In the anode chamber3, an anode51is disposed. In the cathode chamber4, a cathode52is provided. It is preferable that a low-polarizability carbon electrode is used for the anode. As the cathode, Ni or iron, etc., is preferably used.

The heating device12(temperature adjusting means) can detect the temperature measured by the temperature gauge11, and can adjust it to a desired electrolyte temperature. Accordingly, for example the electrolyte2can be heated to 85 to 90 degrees C. and maintained in a molten state. If it is difficult to control the temperature by only the hot water jacket, an electric heater may be complementarily used. It is also allowed that the electrolyte2is melted only by the electric heater if the heat capacity of the electric heater is the same.

In an upper cover17of the electrolytic cell1, a purge gas port from a gas pipe that is not shown as one of the pressure maintaining means for maintaining the insides of the anode chamber3and the cathode chamber4at the atmosphere pressure, a fluorine gas exhaust port22from which fluorine gas generated from the anode chamber3is exhausted, and a hydrogen gas exhaust port23for exhausting hydrogen gas generated from the cathode chamber4, are provided. The upper cover17is provided with a first liquid level detection sensor5and a second liquid level detection sensor6.

The raw material gas supply pipe25is connected to an HF supply source outside the gas generator, and extends from this connecting portion to the raw material gas supply port26disposed in the cathode chamber4of the electrolytic cell1. The raw material gas supply pipe25is covered with a temperature adjusting heater24for supplying HF in a gas phase, and is heated in the range of 35 to 40 degrees C. The raw material gas supply pipe25is provided with, in order from the upstream side to the downstream side, a manual valve66, a pressure gauge31, a pressure gauge34, a flowmeter83, the automatic valve81, and a pressure gauge84, and a bypass80is provided for the raw material gas supply pipe25between the automatic valve81and the pressure gauge84and communicates with the cathode chamber4, and in the middle of the bypass80, an automatic valve82is disposed. The pressure gauge84can be disposed at either the front or rear of the bypass pipe80as long as it is on the secondary side of the automatic valve81.

The automatic valve81opens so as to supply HF to the electrolyte2when the first liquid level detection sensor5and the second liquid level detection sensor6detect liquid level lowering of the electrolyte2. The automatic valve82opens and closes in conjunction with the HF supply stop detecting device not shown to balance the pressure inside the raw material gas supply pipe25with respect to the electrolytic cell1. The flowmeter83monitors the flow rate of HF supplied into the electrolytic cell1via the raw material gas supply pipe25.

Next, an operation for supplying HF to the electrolyte2at the time of normal operation of the gas generator of this embodiment will be described. According to electrolysis, as reaction within the electrolyte2progresses, a fluorine gas is obtained, and at the same time, HF in the electrolyte2is consumed. Consumption of the electrolyte2is detected by monitoring the liquid level lowering of the electrolyte2by the first liquid level detection sensor5and the second liquid level detection sensor6. When liquid level lowering of the electrolyte2is detected, the automatic valve81in the raw material gas supply pipe25opens to supply HF. The amount of HF supplied to the electrolyte2is measured by the flowmeter83. Then, when the electrolyte2increases to a regulated amount or more according to the supply of HF, this is detected by an HF supply stopping device that is not shown via the first liquid level detection sensor5and the second liquid level detection sensor6, and an operation for stopping the HF supply is performed. The manual valve66is left open, and the pressure gauges31,34, and84are provided for monitoring the HF distribution state by pressure.

Next, operations of the gas generator in the case of EMO will be described. In the gas generator, an EMO operation in the case where an abnormality occurs is performed when a power cut occurs or some abnormality occurs in the gas generator and a person finds this and operates the EMO (emergency stop) button, or in response to a command issued when a control device100detects an abnormality. In detail, all automatic valves (81in the raw material gas supply pipe25,41in the nitrogen supply pipe40,89in the hydrogen gas exhaust port23, and91in the fluorine gas exhaust port22inFIG. 3) of the gas generator are closed, and the automatic valve82in the bypass80is opened instead. Accordingly, when HF gas remains inside the raw material gas supply pipe25, even if the gas dissolves into the electrolyte2and causes decompression, the same pressure as in the cathode chamber4can be maintained by the bypass80. In addition, the pressure inside the raw material gas supply pipe25in this case can be monitored by the pressure gauge84.

After EMO-stop, it may take a long time to remove the cause of the EMO stop and secure safety, and after this, it is preferable that the gas generator is restarted as quickly as possible. In the conventional method, when the pipe is clogged, the members must be replaced, and when nitrogen gas is introduced into the raw material gas supply pipe25or the cathode chamber4, the pressure fluctuation must be eliminated and a secondary accident from pressurization must be considered.

In the present invention, in consideration of safety in the case of an emergency stop, it is preferable that the automatic valve81disposed in the raw material gas supply pipe25is a normally-closed type, and the automatic valve82disposed in the bypass80is a normally-open type. With this constitution, even in the case of an emergency stop that makes it impossible to secure a power source such as in the case of an earthquake or a power cut, the above-described operations as the gas generator can be automatically performed, so that decompression inside the raw material gas supply pipe25due to dissolving of the raw material gas (HF gas) inside the raw material gas supply pipe25into the electrolyte2and clogging due to backflow and solidification of the electrolyte2can be prevented, and imbalance of the liquid level in the electrolytic cell according to nitrogen gas introduction into the cathode chamber can also be prevented, so that the gas generator can be safely and stably stopped.

This embodiment brings about the following effect. That is, when the raw material gas supply to the gas generator is suddenly stopped, the raw material gas may remain inside the raw material gas supply pipe25, and thereafter, this raw material gas dissolves into the electrolyte2and the inside of the raw material gas supply pipe25tends to be decompressed. At this time, through the bypass80with the automatic valve82open, the atmosphere gas immediately flows into the raw material gas supply pipe25from the gas phase area of the cathode chamber4, so that the pressure inside the raw material gas supply pipe25is not apparently decompressed, and as a result, the raw material gas supply pipe25can be prevented from being clogged by backflow or solidification of the electrolyte2into the raw material gas supply pipe25. According to this raw material gas supply system, a gas generator which can prevent imbalance of the liquid level in the electrolytic cell1and backflow and solidification of the electrolyte2into the raw material gas supply pipe25with a simplified constitution than that of the conventional fluorine/fluoride gas generator can be provided.

In addition, the automatic valve82can be replaced with a check valve. When HF flows in the raw material gas supply pipe25, the valve closes and nothing flows into the bypass80. The function of the check valve is equivalent to that of the automatic valve as long as it can supply a gas which can compensate decompression caused by dissolving of HF into the electrolyte2when the HF supply to the raw material gas supply pipe25stops, to the raw material gas supply pipe25from the cathode chamber4through the bypass80.

According to this embodiment, operations in the case of EMO in the gas generator are definitely effective, however, measures after the HF supply operation stops are also effective. Specifically, in the gas generator of this embodiment, in the case of an emergency stop or supply stop of the raw material gas, even if the raw material gas remaining inside the raw material gas supply pipe25dissolves into the electrolyte2and the inside of the raw material gas supply pipe25tends to be decompressed, the atmosphere gas immediately flows into the raw material gas supply pipe25from the gas phase area of the cathode chamber4through the bypass, so that the pressure inside the raw material gas supply pipe25is not apparently decompressed, and as a result, the raw material gas supply pipe25can be prevented from being clogged by backflow or solidification of the electrolyte2into the raw material gas supply pipe25.

In this embodiment, the pipe40for supplying nitrogen gas into the raw material gas supply pipe25and members accompanying this pipe inFIG. 2can be omitted, so that the gas generator can be downsized in manufacturing. Further, to continue the operation, the nitrogen consumption can be reduced more than conventionally, and the number of members to be used in the gas generator is also reduced, so that the maintenance cost can be reduced accordingly.

The gas generator of the embodiment of the present invention is described above, however, the present invention is not limited to the above-described embodiment, and it can be varied within the scope of claims, for example, an NF3generator involving electrolysis of ammonium fluoride-hydrogen fluoride mixed molten salt is constituted by only adding an NH3supply pipe to the gas generator described above, and NH3also quickly dissolves into the electrolyte2similar to HF, so that the present invention can be used for preventing clogging of not only the raw material supply pipe but also the NH3supply pipe.

In addition, the raw material supply system of the present invention is definitely effective when HF or NH3is supplied in the form of gas, and, it is also effective when HF or NH3is supplied in the form of liquid.

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

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1is a schematic view of a main portion of a conventional gas generator;

FIG. 2is a schematic view of a main portion of another conventional gas generator; and

FIG. 3is a schematic view of a main portion of a gas generator of an embodiment of the present invention.

DESCRIPTION OF REFERENCE NUMERALS