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Apparatus for generating fluorine gas

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Apparatus for generating fluorine gas


[Solving means] A fluorine gas generating system characterized by including a purification apparatus 20 for adsorbing and removing hydrogen fluoride vaporized from a molten salt of an electrolysis tank 1 and mixed in fluorine gas generated at an anode 7, in which the purification apparatus 20 includes a cylindrical member through which main-product gas containing fluorine gas generated in the electrolysis tank 1 flows, a temperature regulator for regulating temperature of the cylindrical member, and an adsorbent holder disposed inside the cylindrical member, the adsorbent holder being disposed to form an aperture for securing a flow passage of the main-product gas inside the cylindrical member. [Object] To provide a fluorine gas generating system which can stably supply high purity fluorine gas while preventing blockade of a purification apparatus for adsorbing and removing hydrogen fluoride.

Browse recent Central Glass Company, Limited patents - Ube-shi, JP
Inventors: Tatsuo Miyazaki, Akifumi Yao, Takuya Kita
USPTO Applicaton #: #20120318665 - Class: 2042431 (USPTO) - 12/20/12 - Class 204 
Chemistry: Electrical And Wave Energy > Apparatus >Electrolytic >Cells >Fused Bath

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The Patent Description & Claims data below is from USPTO Patent Application 20120318665, Apparatus for generating fluorine gas.

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TECHNICAL FIELD

This invention relates to a fluorine gas generating system for generating fluorine gas.

BACKGROUND TECHNIQUE

Hitherto the following fluorine gas generating system has been known: The fluorine gas generating system includes an electrolysis tank in which hydrogen fluoride is electrolyzed in an electrolysis bath including a molten salt containing hydrogen fluoride so that a main-product gas whose main component is fluorine gas is generated at an anode side while a by-product gas whose main component is hydrogen gas is generated at a cathode side.

In the fluorine gas generating system of this kind, hydrogen fluoride gas vaporized from the molten salt is mixed in fluorine gas generated at the anode of the electrolysis tank. Therefore, in order to separate hydrogen fluoride gas from gas generated at the anode so as to purify fluorine gas, a purification apparatus having a treatment cylinder filled with adsorbent such as sodium fluoride (Nan or the like is provided.

Fluorine and hydrogen gases generated from the electrolysis tank contain hydrogen fluoride vaporized from the molten salt contained in the electrolysis tank and mist components of the molten salt itself. These components cause deterioration of the adsorbent. Particularly with hydrogen fluoride having a high concentration, the adsorbent near a treatment cylinder inlet may make its expansion or fusion, thereby resulting in clogging of the adsorbent. When such clogging arises, flow of gas is suppressed thereby causing a blockade, which is problematic.

As a technique for solving this problem, Patent Citation 1 discloses such a technique that a separating means is provided to form a space between a gas introduction opening and adsorbent in a purification apparatus filled with the adsorbent such as sodium fluoride (NaF) or the like, in which liquid drops of the mist components are released and settled within this space, thus forming a configuration in which the adsorbent and the liquid drops of the mist components are hard to contact with each other, thereby suppressing clogging of the adsorbent and reducing the frequency of maintenance of the purification apparatus.

PRIOR ART CITATIONS Patent Citation

Patent Citation 1: Japanese Patent Provisional Publication No. 2009-215588

SUMMARY

OF THE INVENTION Problems to be Solved by Invention

However, in case that the fluorine gas generating system is operated for a long time or in case that the flow rate of generated gas is large, the amount of hydrogen fluoride gas and mist components contacting with the adsorbent increases with the prolonged operation time of the system or the increased amount of the gas and mist components. Therefore, in a configuration using the purification apparatus which is compactly filled with the adsorbent as described in Patent Citation 1, if clogging of the adsorbent once arises, flow path for gas cannot be secured so as to block the purification apparatus, thus interrupting a continuous operation of the fluorine gas generating system, which is problematic.

Thus, it is difficult to completely prevent blockade inside the purification apparatus with a configuration of being compactly filled with adsorbent for adsorbing hydrogen fluoride in a purification apparatus for adsorbing and removing hydrogen fluoride contained in fluorine gas and hydrogen gas generated in an electrolysis tank of a conventional fluorine gas generating system.

The present invention has been made in view of the above problems and has an object to provide a fluorine gas generating system which can stably supply high purity fluorine gas while preventing blockade of a purification apparatus for adsorbing and removing hydrogen fluoride.

The present inventors have made eager studies in order to solve the above-discussed problems. As a result, they have found to be able to stably supply high purity fluorine gas while preventing blockade within a purification apparatus by providing an adsorbent holder inside a cylindrical member disposed in the purification apparatus for adsorbing and removing hydrogen fluoride and allowing gas generated in an electrolysis tank to flow therethrough, and further by disposing this adsorbent holder in such a manner as to form an aperture for securing a gas flow passage for gas flowing through the inside of the cylindrical member, in an inside space of the cylindrical member, and reached the present invention.

That is, the present invention is a fluorine gas generating system for generating fluorine gas by electrolyzing hydrogen fluoride in a molten salt containing hydrogen fluoride, characterized by comprising: an electrolysis tank in which hydrogen fluoride is electrolyzed in an electrolysis bath including the molten salt containing hydrogen fluoride to generate a main-product gas whose main component is fluorine gas at an anode side and a by-product gas whose main component is hydrogen gas at a cathode side; and a purification apparatus in which hydrogen fluoride mixed in the main-product gas is removed by an adsorbent, wherein the purification apparatus includes a cylindrical member through which the main-product gas passes, a temperature regulator for regulating a temperature of the cylindrical member, and an adsorbent holder disposed inside the cylindrical member, the adsorbent holder being disposed to form an aperture for securing a flow passage of the main-product gas inside the cylindrical member.

Additionally, the present invention is a fluorine gas generating system characterized in that the adsorbent holder includes plural or more adsorbent holders disposed to meander the flow passage of the main-product gas.

Additionally, the present invention is a fluorine gas generating system characterized in that the adsorbent holder is a tray-like member, the tray-like member including a bottom plate section formed with a cutout section for allowing gas to flow therethrough, an outer periphery side wall section disposed standing at outer periphery of the bottom plate section except for the cutout section, and a cutout side wall section disposed standing at a cutout section side of the bottom plate section, and an upper end opening section of a main body of the tray-like member, and in that the outer periphery side wall section is disposed to internally contact with inner wall of the cylindrical member.

Additionally, the present invention is a fluorine gas generating system characterized in that the bottom plate section is formed with a through-hole.

Additionally, the present invention is a fluorine gas generating system characterized in that the adsorbent holder includes plural or more adsorbent holders disposed separate from each other in the cylindrical member, wherein a distance between the tray-like member and the adjacent tray-like member is not less than ⅕ of inner diameter of the cylindrical member and less than the inner diameter of the cylindrical member.

Additionally, the present invention is a fluorine gas generating system characterized in that an area of the bottom plate section formed with the cutout section is not less than 50% and not more than 95% of an area of an inner diameter section of the cylindrical member.

Effects of the Invention

According to the present invention, an aperture which is not filled with the adsorbent is formed inside the cylindrical member disposed in the purification apparatus and allowing gas generated in the electrolysis tank to flow therethrough, so as to provide a configuration for always securing a gas flow passage. Accordingly, the present invention can provide a fluorine gas generating system which can stably supply high purity fluorine gas without causing blockade even in case that a part of the adsorbent makes its clogging.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a fluorine gas generating system according to an embodiment of the present invention;

FIG. 2 is a diagrammatic illustration of a purification apparatus according to the embodiment of the present invention;

FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2;

FIG. 4 is a view showing an example of a tray-like member according to the embodiment of the present invention; and

FIG. 5 is a diagrammatic illustration of an experimental apparatus with which a purification performance test of a purification apparatus applicable to the embodiment of the present invention was carried out.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be discussed with reference to drawings. A fluorine gas generating system 100 according to the embodiment of the present invention will be discussed with reference to FIG. 1.

The fluorine gas generating system 100 is configured to generate fluorine gas by electrolysis and supply the generated fluorine gas to an outside apparatus 4. The outside apparatus 4 is, for example, a semiconductor production equipment, in which fluorine gas is used, for example, as cleaning gas in a production process for semiconductor.

The fluorine gas generating system 100 includes an electrolysis tank 1 for generating fluorine gas under electrolysis, a fluorine gas supply system 2 for supplying the outside apparatus 4 with fluorine gas generated from the electrolysis tank 1, and a by-product gas treating system 3 for treating by-product gas generated with generation of fluorine gas.

First, the electrolysis tank 1 will be discussed. A molten salt containing hydrogen fluoride (HF) is stored in the electrolysis tank 1. In this embodiment, a mixture of hydrogen fluoride and potassium fluoride (KF) is used as the molten salt.

The inside of the electrolysis tank 1 is divided into an anode chamber 11 and a cathode chamber 12 by a dividing wall 6 dipped in the molten salt. An anode 7 and a cathode 8 are dipped respectively in the molten salt of the anode chamber 11 and the molten salt of the cathode chamber 12. By supplying electric current to between the anode 7 and the cathode 8 from an electric power source 9, a main-product gas whose main component is fluorine gas (F2) is generated at the anode 7 while a by-product gas whose main component is hydrogen gas (H2) is generated at the cathode 8. A carbon electrode is used as the anode 7 while soft metal, Monel or nickel is used as the cathode 8.

A first gas chamber 11a to which fluorine gas generated at the anode 7 is introduced and a second gas chamber 12a to which hydrogen gas generated at the cathode 8 is introduced are divided on the liquid surface of the molten salt in the electrolysis tank 1 in such a manner that each gas is prevented from transferring between the gas chamber 11a and the gas chamber 12a. Thus, the first gas chamber 11a and the second gas chamber 12 are completely separated from each other by the dividing wall 6 in order to prevent fluorine gas and hydrogen gas from reacting with each other under mixing and contacting with each other. In contrast, the molten salt in the anode chamber 11 and the molten salt in the cathode chamber 12 are not separated from each other by the dividing wall 6 so as to be communicated with each other through the lower side of the dividing wall 6.

Since the melting point of KF•2HF is 71.7° C., the temperature of the molten salt is adjusted at 91 to 93° C. Hydrogen fluoride vaporizes from the molten salt by an amount corresponding to a vapor pressure and mixed into each of fluorine gas and hydrogen gas which are respectively generated at the anode 7 and the cathode 8 of the electrolysis tank 1. Thus, fluorine gas is contained in each of fluorine gas generated at the anode 7 and introduced into the first gas chamber 11a and hydrogen gas generated at the cathode 8 and introduced into the second gas chamber 12a.

Next, the fluorine gas supply system 2 will be discussed. A first main passage 15 is connected to the first gas chamber 11a to supply fluorine gas to the outside apparatus 4.

A first pump 17 is disposed in the first main passage 15 to introduce fluorine gas outside the first chamber 11a and convey fluorine gas. A displacement pump such as a bellows pump, a diaphragm pump or the like is used as the first pump 17. A purification apparatus 20 is disposed in a part of the first main passage 15 upstream of the first pump 17 to trap hydrogen fluoride mixed in fluorine gas so as to purify fluorine gas. The purification apparatus 20 will be discussed in detail after.

Next, the by-product gas treatment system 3 will be discussed. A second main passage 30 is connected to the second gas chamber 12a to discharge hydrogen gas to outside.

A second pump 31 is disposed in the second main passage 30 to introduce hydrogen gas outside the second gas chamber 12a and convey hydrogen gas. A de-toxifying section 34 is disposed in a part of the second main passage 30 downstream of the second pump 31 so that hydrogen gas conveyed by the second pump 31 is made harmless by the de-toxifying section 34 and released.

The fluorine gas generating system 100 includes a raw material supply system 5 to supply and supplement hydrogen fluoride as a raw material of fluorine gas into the molten salt in the electrolysis tank 1. Hereinafter, the raw material supply system 5 will be discussed.

The electrolysis tank 1 is connected through a raw material supply passage 41 to a hydrogen fluoride supply source for storing hydrogen fluoride to be supplemented to the electrolysis tank 1. Hydrogen fluoride stored in the hydrogen fluoride supply source 40 is supplied into the molten salt in the electrolysis tank 1 through the raw material supply passage 41.

Additionally, a carrier gas supply passage 46 is connected to the raw material supply passage 41 to introduce a carrier gas supplied from a carrier gas supply source 45 into the raw material supply passage 41. The carrier gas is a gas for introduce hydrogen fluoride into the molten salt, in which nitrogen gas which is an inert gas is used as the carrier gas. Nitrogen gas is supplied into the molten salt in the cathode chamber 12 and discharged from the second gas chamber 12a through the second main passage 30, in which nitrogen hardly dissolves in the molten salt.

Next, the purification apparatus 20 will be discussed. The purification apparatus 20 is an apparatus for allowing hydrogen fluoride mixed in fluorine gas to be adsorbed to an adsorbent such as sodium fluoride (NaF) or the like thereby to remove hydrogen fluoride mixed in fluorine gas.

An inlet line 51a for introducing fluorine gas generated at the anode 7 and an outlet line 52a for introducing fluorine gas outside the purification apparatus 20 are connected to the purification apparatus 20. Additionally, the purification apparatus 20 includes a cylindrical member 31a through which fluorine gas passes, and an adsorbent holder is disposed inside the cylindrical member 31a to hold the adsorbent for adsorbing hydrogen fluoride.

The cylindrical member referred to here represents a container for accommodating thereinside the adsorbent for adsorbing hydrogen fluoride, for allowing fluorine gas generated from the electrolysis tank 1 to pass therethrough and for adsorbing and removing hydrogen fluoride in fluorine gas, in which the shape of the cylindrical member is not particularly limited. The material of the cylindrical member is preferably one having a resistance characteristics to fluorine gas and hydrogen fluoride gas, for example, alloy or metal such as stainless steel, Monel, nickel or the like.

Many porous beads formed of sodium fluoride (NaF) are used as the adsorbent. The adsorbing ability of sodium fluoride changes according to temperature, and therefore a heater 41a is disposed around the cylindrical member 31a so as to serve as a temperature regulator for regulating the temperature inside the cylindrical member 31a.

The temperature regulator is not particularly limited as far as it can regulate the temperature inside the cylindrical member. For example, a heating or cooling device using a heater, steam heating, heating medium or cooling medium may be used.

Chemical to be used as the adsorbent is preferably alkali metal fluoride such as NaF, KF, RbF, CsF or the like, in which NaF is particularly preferable.

The adsorbent holder is disposed to form an aperture for securing a gas flow passage inside the cylindrical member 31a. By this, even in case that a part of the adsorbent makes its clogging, blockade does not occur structurally thereby allowing gas to flow.



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stats Patent Info
Application #
US 20120318665 A1
Publish Date
12/20/2012
Document #
13574177
File Date
02/24/2011
USPTO Class
2042431
Other USPTO Classes
International Class
/
Drawings
6



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