JP6993157B2 - How to make fluorite - Google Patents

Description

The present invention relates to a method for producing fluorite.

Calcium fluoride (fluorite (CaF ₂ )) has various uses depending on its purity. Since high-purity fluorite has a low refractive index and low dispersibility, it is mainly traded at a high price for optical raw materials such as fluorite lenses and glass additions.

Conventionally, such high-purity fluorite produced from mines has been used. However, from the viewpoint of quality stability and certainty of acquisition route, it is required to synthetically produce high-purity fluorite.

Here, a technique relating to a method for producing a calcium fluoride crucible made of a sintered body of calcium fluoride powder is disclosed in Japanese Patent Application Laid-Open No. 2004-123417 (Patent Document 1).

Japanese Unexamined Patent Publication No. 2004-123417

In the technique disclosed in Patent Document 1, a calcium salt and hydrofluoric acid are reacted in water to synthesize calcium fluoride, and the obtained calcium fluoride is dried into a powder and then calcium fluoride. The powder is press-molded into a pot shape. Here, when hydrofluoric acid is dissolved in water when the calcium salt and hydrofluoric acid are reacted, hydrofluoric acid is generated. Since such hydrofluoric acid is extremely corrosive, it corrodes metal parts, for example, the inner wall of the reactor. Then, a large amount of corroded metal impurities, that is, metal contamination, is generated in the obtained fluorite. As a result, the purity of the obtained fluorite will be low. In particular, in the synthesis of fluorite used for the above-mentioned optical raw materials, it is required to efficiently produce high-purity fluorite containing as little metal impurities as possible.

An object of the present invention is to provide a method for producing fluorite capable of efficiently producing high-purity fluorite.

A method for producing fluorite according to the present invention comprises at least an inner wall of a calcium compound containing at least one selected from the group consisting of carbonates, nitrates, sulfates, oxalates, hydroxides, and oxides of calcium. A process of arranging a part in a reactor made of metal and a raw material gas containing hydrogen fluoride are introduced into the reactor while maintaining the inner wall at a temperature of 110 ° C. or higher to react the calcium compound and the raw material gas. Includes the process of obtaining calcium by allowing it to grow.

According to the method for producing fluorite having such a structure, a calcium compound is placed in a reactor in which at least a part of the inner wall is made of metal, and hydrogen fluoride is produced while maintaining the inner wall at a temperature of 110 ° C. or higher. It is decided to introduce the contained raw material gas and react the calcium compound with the raw material gas to obtain fluorite. Here, when water is generated as a reaction product or when water is contained in the reaction system, for example, the raw material gas, the inner wall of the reactor is maintained at 110 ° C. or higher, so that the water is a liquid. It will exist in a gaseous state. Then, the possibility that hydrogen fluoride is dissolved in liquid water to generate hydrofluoric acid can be greatly reduced. Therefore, the corrosion of the inner wall of the reactor due to hydrofluoric acid is suppressed, and the possibility that the fluorite synthesized by the reaction between the calcium compound and the raw material gas contains metal impurities due to the corrosion of the inner wall is greatly reduced. be able to. Further, since the corrosion of the inner wall of the reactor is suppressed, the life of the reactor can be extended. As a result, according to such a method for producing fluorite, high-purity fluorite can be efficiently produced.

The high-purity fluorite produced by the above-mentioned method for producing fluorite means that the ratio of CaF ₂ (calcium fluoride) to the whole is 99.95% by mass or more. For high-purity fluorite, for example, the content ratio of each metal element such as Fe (iron), Cr (chromium), and Ni (nickel) contained as a metal element is 100 mass ppm or less. The raw material gas containing hydrogen fluoride preferably contains as little halogen element as possible. Further, with respect to the fluorite produced by the above-mentioned method for producing fluorite, the possibility of containing metal impurities due to the corrosion of the inner wall of the reactor is greatly reduced to obtain high-purity fluorite. Therefore, regarding the calcium compound that is the raw material of fluorite, the content ratio of each metal element such as Fe, Cr, and Ni is less than the target value of the content ratio of fluorite to be finally obtained, specifically, for example. It is necessary to prepare a calcium compound having a content ratio of Fe, Cr, and Ni of 50 mass ppm or less, preferably 20 ppm or less, and more preferably 10 ppm or less of the calcium compound as a raw material. Similarly, as the raw material gas, one having a small content ratio of each metal element such as Fe, Cr, and Ni, or one having no content ratio is used.

The method for producing fluorite may further include a step of replacing the gas in the reactor from which the fluorite is obtained with at least one of non-corrosive gas and air. By doing so, after the reaction is completed and fluorite is obtained, the inner wall of the reactor may be corroded by the raw material gas remaining unutilized in the reaction, and metal corrosive substances may be generated in the reactor. Can be reduced. Therefore, for example, when producing fluorite using a repeating reactor, high-purity fluorite can be efficiently produced.

Here, in the present specification, "at least one of non-corrosive gas and air" means a simple substance of non-corrosive gas, a simple substance of air, and a mixture of non-corrosive gas and air in a predetermined ratio. It is a concept that includes a mixed gas. Further, in the present specification, the "non-corrosive gas" refers to a gas that does not react with piping materials such as SUS, calcium raw materials, and fluorite at about 110 to 200 ° C., and is specifically referred to as a non-corrosive gas. For example, nitrogen gas, argon gas, helium gas, or other inert gas can be used.

The reactor may be connected to a preheating unit that heats the raw material gas to 110 ° C. or higher before introducing the raw material gas into the reactor. By doing so, the temperature of the raw material gas can be set to 110 ° C. or higher by the preheating unit before the raw material gas is introduced into the reactor. Therefore, since the temperature of 110 ° C. or higher can be secured immediately after the raw material gas is introduced into the reactor, even if water is generated as a reaction product, the water is gasified by heating at 110 ° C. or higher by the preheating unit. That is, it can be made into water vapor, and the possibility that hydrofluoric acid produced by dissolving hydrogen fluoride in liquid water can be reduced.

A discharge member for discharging the gas in the reactor is connected to the reactor, and the discharge member may be maintained at a temperature of 110 ° C. or higher. By doing so, it is possible to reduce the possibility that hydrofluoric acid is generated in the discharge member even when the gas in the reactor is discharged, and it is possible to suppress the corrosion of the discharge member due to hydrofluoric acid. In particular, when the discharge member includes a metal pipe, corrosion of the metal pipe can be suppressed, and the life of the equipment can be extended.

The above-mentioned step of arranging may include a step of replacing the gas in the discharge member with at least one of non-corrosive gas and air. By doing so, it is possible to more reliably suppress the corrosion of the discharge member.

An introduction member for introducing the raw material gas into the reactor via the preheating unit is connected to the reactor, and the introduction member may be maintained at a temperature of 110 ° C. or higher. By doing so, when the raw material gas is introduced into the reactor, the temperature of the raw material gas can be maintained at 110 ° C. or higher, and the raw material gas can be introduced into the reactor. In this case, even if water is contained in the raw material gas, the water in the raw material gas exists in a gaseous state because the introduction member is maintained at a temperature of 110 ° C. or higher. Then, it is possible to reduce the possibility that hydrogen fluoride is dissolved in water as a liquid to generate hydrofluoric acid, and it is possible to suppress corrosion due to hydrofluoric acid on the inner wall of the reactor and the like.

The replacement step may include a step of replacing the gas in the introduction member with at least one of non-corrosive gas and air. By doing so, it is possible to more reliably suppress the corrosion of the introduced member. Therefore, higher purity fluorite can be surely obtained.

The raw material gas may contain exhaust gas. Such exhaust gas is treated as waste in, for example, a semiconductor manufacturing apparatus, and is relatively inexpensive as a fluorine raw material. Therefore, by doing so, it is possible to efficiently produce high-purity fluorite at a lower cost. In this case, since the introduction member is maintained at a temperature of 110 ° C. or higher, the water contained in the exhaust gas exists in a gaseous state instead of a liquid state. Therefore, it is possible to reduce the possibility of hydrofluoric acid being generated, reduce the corrosion caused by hydrofluoric acid, and efficiently produce high-purity fluorite.

In the process of obtaining the fluorite, after the process of introducing the raw material gas into the reactor and distributing the raw material gas and the process of distributing the raw material gas, the introduction of the raw material gas is stopped and the raw material gas is introduced into the reactor. It may include a step of encapsulation. By doing so, the reaction can be promoted by effectively using the enclosed raw material gas, especially from the middle of the reaction, and the cost can be further reduced.

The material of the inner wall of the reactor may be stainless steel. As described above, the material of the inner wall of the reactor is made of a metal having good corrosion resistance, and the possibility that corrosive substances are contained in the synthesized fluorite can be reduced. Therefore, higher purity fluorite can be produced.

The calcium compound may be configured to be in the form of powder. By doing so, the calcium compound as a solid in the so-called gas-solid reaction and the raw material gas as a gas can be efficiently brought into contact with each other. Therefore, the synthesis of fluorite can be efficiently promoted, and the fluorite can be efficiently produced.

According to the method for producing fluorite having such a structure, high-purity fluorite can be efficiently produced.

It is a figure which shows typically an example of the manufacturing apparatus used in the manufacturing method of fluorite which concerns on one Embodiment of this invention. It is a flowchart which shows the typical process in the manufacturing method of the fluorite which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference numbers, and the description thereof will not be repeated.

FIG. 1 is a diagram schematically showing an example of an apparatus for producing fluorite used in the method for producing fluorite according to an embodiment of the present invention. With reference to FIG. 1, the fluorite manufacturing apparatus 11 used in the fluorite manufacturing method according to the embodiment of the present invention supplies HF (hydrogen fluoride gas) which is a gas containing fluorine as a raw material gas. Hydrogen fluoride gas supply device 12, purge air supply device 13 that supplies air for purging (exhaust), calcium carbonate supply unit 14 that supplies calcium carbonate as a calcium compound, calcium carbonate and hydrogen fluoride gas. The reactor 15 that reacts with, the fluorite take-out unit 16 that takes out the fluorite obtained by the reaction of calcium carbonate and hydrogen fluoride gas in the reactor 15, and the gas generated by the reaction and not used for the reaction. It includes an exhaust gas treatment device 17 for treating unreacted gas. These components are connected by pipes or the like. The HF gas supply device 12 stores the HF gas to be supplied to the reactor 15. The purging air supply device 13 stores purging air to be supplied to the reactor 15. The calcium carbonate supply unit 14 stores calcium carbonate to be supplied to the reactor 15.

In the above-mentioned fluorite production apparatus 11, fluorite (CaF) is reacted with hydrogen fluoride (HF) gas, which is a raw material gas, and calcium carbonate (CaCO ₃ ), which is a carbonate of calcium which is a calcium compound. ₂ ) is obtained. This reaction is a so-called ki-solid reaction. The main reaction formula in this case is as follows, and water (H ₂ O) is produced as a reaction product.

2HF + CaCO ₃ → CaF ₂ + H ₂ O + CO ₂

Here, the exhaust gas is used in the HF gas supply device 12. That is, the HF gas supply device 12 supplies the exhaust gas as a raw material gas containing HF. Exhaust gas is treated as waste in, for example, a semiconductor manufacturing apparatus, and is relatively inexpensive as a fluorine raw material. Such exhaust gas contains, for example, water in advance. In the following, the exhaust gas supplied by the HF gas supply device 12 is simply referred to as a raw material gas or an HF gas.

A first pipe 21 as an introduction member for introducing HF gas into the reactor 15 is connected between the HF gas supply device 12 and the reactor 15. That is, the HF gas supply device 12 and the reactor 15 are connected by the first pipe 21. The first pipe 21 is a so-called tubular member, through which HF gas can pass. The first pipe 21 is made of stainless steel typified by SUS304 or the like. Other examples of the material of the first pipe 21 include iron, copper, brass, nickel, Hastelloy (registered trademark) and Inconel (registered trademark) having strong corrosion resistance. Further, in FIG. 1, the first pipe 21 is indicated by a simple arrow.

A valve for adjusting the inflow amount of HF gas to be introduced into the reactor 15 in the middle of the first pipe 21, that is, in the middle of the flow path of the HF gas from the HF gas supply device 12 to the reactor 15. The first valve 22 is provided.

In the first pipe 21, a first heating unit 23 for heating the HF gas supplied from the HF gas supply device 12 is provided between the HF gas supply device 12 and the first valve 22. The HF gas supplied from the HF gas supply device 12 is heated to a temperature of 110 ° C. or higher by the first heating unit 23. In this case, specifically, for example, the HF gas is heated to 120 ° C.

The first pipe 21 is covered with a heater 24 from the position where the first heating unit 23 is provided to the first valve 22. The temperature of the first pipe 21 as an introduction member is maintained at a temperature of 110 ° C. or higher by the heater 24. In this case, the first pipe 21 is maintained at a temperature of 120 ° C. by the heater 24. Therefore, the HF gas heated to a temperature of 120 ° C. by the first heating unit 23 is introduced into the reactor 15 while basically maintaining the temperature of 120 ° C. when passing through the first pipe 21. Will be done. The heater 24 is shown by a thick line in FIG.

In the first pipe 21, a preheating unit 30 is provided between the first valve 22 and the reactor 15. That is, the reactor 15 is connected to the first pipe 21 as an introduction member for introducing the raw material gas into the reactor 15 via the preheating unit 30. With such a configuration, it is possible to secure a temperature of 110 ° C. or higher immediately after the raw material gas is introduced into the reactor 15. In this case, specifically, the raw material gas can be heated to 120 ° C. and the raw material gas can be introduced into the reactor 15 from the first pipe 21. The raw material gas is heated to 120 ° C. by the first heating unit 23, and the temperature of the raw material gas passing through the first pipe 21 maintained at 120 ° C. by the heater 24 is lower than 120 ° C. Even if there is, the preheating unit 30 can more reliably introduce it at 110 ° C. or higher before it is introduced into the reactor 15.

The purging air supply device 13 is connected to the first pipe 21. Specifically, in the first pipe 21, on the upstream side of the first valve 22, that is, in the middle of the side of the first pipe 21 where the HF gas supply device 12 is located from the first valve 22. The first pipe 21 is connected so as to branch off. In the first pipe 21, a second heating unit 25 for heating the purging air supplied from the purging air supply device 13 is provided between the purging air supply device 13 and the first valve 22. Has been done. The purging air supplied from the purging air supply device 13 is heated to a temperature of 110 ° C. or higher by the second heating unit 25. In this case, specifically, for example, the purging air is heated to 120 ° C. In the first pipe 21, the heater 24 covers from the position where the second heating portion 25 is provided to the branch 26. Therefore, the purging air heated to a temperature of 120 ° C. by the second heating unit 25 is introduced into the reactor 15 while maintaining the temperature of 120 ° C. when passing through the first pipe 21. To.

The calcium carbonate supply unit 14 is provided on the upper part of the reactor 15. The calcium carbonate supply unit 14 is composed of a container 27 having a predetermined shape and a rotating body 28 provided at the lower part of the container 27. The powdered calcium carbonate 29 required for the reaction is stored in the container 27. An opening is provided in the lower part of the container 27, and the calcium carbonate supply unit 14 causes the rotating body 28 to rotate to drop a predetermined amount of calcium carbonate 29 stored in the container 27, and carbonic acid in the reactor 15. Calcium 29 can be supplied.

Here, with respect to the calcium carbonate 29 as a raw material supplied by the calcium carbonate supply unit 14, one having a small content ratio of metal impurities is stored in the calcium carbonate supply unit 14 from the viewpoint of obtaining high-purity fluorite. Specifically, for example, Fe, Cr, and Ni contained in calcium carbonate 29, which is a raw material, each have a mass of 50 mass ppm or less. The same applies to the case where other calcium compounds described later are used.

A part of the container 27 and the rotating body 28 of the calcium carbonate supply unit 14 are covered with the heater 24. The temperature of these portions is also maintained at 120 ° C. by the heater 24. That is, the calcium carbonate 29 is heated by the heater 24 to some extent before the supply to the reactor 15.

The reactor 15 has a conical shape and is arranged so that the top is located on the lower side. The entire reactor 15, including the inner wall 31, is made of metal. Specifically, the reactor 15 is made of stainless steel such as SUS. Inside the reactor 15, a cavity 32 used for the reaction is provided, and calcium carbonate 29, which is a calcium compound, is first supplied and arranged in the region of the cavity 32. The reactor 15 has a sealable configuration. The reactor 15 is provided with a stirring rod 33 for stirring the calcium carbonate 29 supplied therein. The stirring rod 33 is provided with a support portion 35 which is attached to a part of a lid portion 34 located on the upper side of the reactor 15 to support the rotational movement of the stirring rod 33, and the support portion 35 is centered on rotation. As shown by the arrow 36 in FIG. 1, the inside of the cavity 32 of the reactor 15 can be rotated. The calcium carbonate 29 arranged in the reactor 15 can be agitated by rotating the stirring rod 33 at a predetermined speed, and the reaction can be promoted by the agitation by the stirring rod 33.

The reactor 15 has a configuration in which the entire reactor 15 is covered with the heater 24. That is, the entire reactor 15 can be maintained at a temperature of 110 ° C. or higher by the heater 24. In this case, the entire reactor 15 is maintained at a temperature of 120 ° C. by the heater 24.

The first pipe 21 is connected to the reactor 15 as described above. Specifically, the first pipe 21 is on the lower side of the reactor 15, and in the first pipe 21 in the region where the calcium carbonate 29 is located when the calcium carbonate 29 is arranged in the reactor 15. It is connected so that the opening of the raw material gas is located. By providing the opening of the first pipe 21 at such a position, the HF gas and the calcium carbonate 29 can be brought into contact with each other more efficiently to promote the reaction.

The bottom of the reactor 15, that is, the top of the conical reactor 15, is provided with a fluorite take-out portion 16 for taking out the fluorite obtained by the reaction in the reactor 15. The fluorite take-out unit 16 is composed of a container 38 for storing the fluorite 37 obtained by the reaction and a rotating body 39 provided on the upper portion of the container 38. The fluorite take-out unit 16 can discharge the fluorite 37 accumulated at the bottom of the reactor 15 from the reactor 15 and take it out into the container 38 by rotating the rotating body 39 after the reaction is completed.

A part of the container 38 and the rotating body 39 of the fluorite take-out portion 16 are covered with the heater 24. The temperature of these portions is also maintained at 120 ° C. by the heater 24.

The exhaust gas treatment device 17 can treat a gas generated by the reaction of calcium carbonate 29 and hydrogen fluoride gas, in this case mainly carbon dioxide and steam, or unreacted gas not used in the reaction. Specifically, it can be detoxified while adjusting the temperature of the exhaust gas or the like generated by the reaction. The detoxified gas is discharged by the exhaust gas treatment device 17.

The exhaust gas treatment device 17 is connected to the reactor 15 by a second pipe 41 as a discharge member. The second pipe 41 is also made of stainless steel. Further, regarding the second pipe 41, the inflow of the exhaust gas to be flowed into the exhaust gas treatment device 17 is also in the middle of the second pipe 41, that is, in the middle of the gas flow path from the reactor 15 to the exhaust gas treatment device 17. A second valve 42 is provided as a valve for adjusting the amount and the like.

The second pipe 41 is covered by the heater 24 from the position where the reactor 15 is provided to the second valve 42. The temperature of the second pipe 41 as a discharge member is maintained at a temperature of 110 ° C. or higher by the heater 24. In this case, the second pipe 41 is maintained at a temperature of 120 ° C. by the heater 24. Therefore, the exhaust gas generated by the reaction passes through the second pipe 41 while maintaining the temperature of 120 ° C. until the position where the second valve 42 is provided.

That is, the heater 24 is a part of the first pipe 21, a first valve 22, a first heating part 23, a second heating part 25, a part of the calcium carbonate supply part 14, and the whole reactor 15. It is configured to cover a part of the fluorite take-out part 16, a part of the second pipe 41, and the second valve 42. The heater 24 keeps the first pipe 21 and the like at 120 ° C.

Here, a method for producing fluorite when producing fluorite using the above-mentioned fluorite producing apparatus 11 will be described. FIG. 2 is a flowchart showing a typical process in the method for producing fluorite according to the embodiment of the present invention.

At the same time, with reference to FIG. 2, first, a predetermined amount of calcium carbonate is charged into the reactor 15 from the calcium carbonate supply unit 14 (in FIG. 2, step S11, hereinafter, “step” is omitted). In this case, the calcium carbonate 29 is charged while controlling the rotation of the rotating body 28 provided in the calcium carbonate supply unit 14. In this way, the calcium carbonate 29 is placed in the reactor 15.

Next, the added calcium carbonate 29 is heated (S12). In this case, the entire reactor 15 is heated by the heater 24 provided so as to cover the reactor 15, and the calcium carbonate 29 is heated. Here, the calcium carbonate 29 in the reactor 15 is heated to 120 ° C.

After heating the calcium carbonate 29 to 120 ° C., the raw material gas is introduced into the reactor 15 while maintaining the calcium carbonate 29 at a temperature of 120 ° C. (S13). In this case, the raw material gas introduced from the first pipe 21 is maintained at a temperature of 120 ° C. That is, in this case, both the calcium carbonate 29 and the raw material gas are mixed while being maintained at a temperature of 120 ° C.

Then, the calcium carbonate 29 is stirred while rotating the stirring rod 33 in the reactor 15, and the reaction based on the above reaction formula is advanced. That is, fluorite is synthesized by a gas-solid reaction with calcium carbonate 29 and a raw material gas.

Here, with respect to the raw material gas to be introduced, the raw material gas is circulated in the reactor 15 until the middle of the reaction, and the raw material gas is sealed in the reactor 15 from the middle of the reaction. That is, the raw material gas is introduced into the reactor 15 to circulate the raw material gas, and after the raw material gas is circulated, the introduction of the raw material gas is stopped and the raw material gas is sealed in the reactor 15. Specifically, when the total reaction amount is 100%, the reaction is carried out while the raw material gas is circulated in the reactor 15 from the beginning to the reaction amount of 50%, and the reaction is completed after the 50% reaction has elapsed. Until then, the reaction is carried out with the raw material gas sealed in the reactor 15. That is, from the beginning until the reaction amount is 50%, the supply of the raw material gas from the HF gas supply device 12 into the reactor 15 is continued with the first valve 22 open. In this case, the second valve 42 is also left open so that the inside of the reactor 15 is circulated by the raw material gas. When the reaction amount reaches 50%, the reactor 15 is sealed with both the first valve 22 and the second valve 42 closed, and the raw material gas is sealed in the reactor 15 to carry out the reaction. Proceed.

After the reaction is completed, purging air is supplied from the purging air supply device 13 into the reactor 15 into the reactor 15 to perform purging (exhaust) in the reactor 15 (S14). That is, the first valve 22 and the second valve 42 are opened again, and the remaining raw material gas and the gas generated by the reaction in the reactor 15 in which the fluorite 37 is obtained are replaced with air for purging.

After that, the rotating body 39 provided in the fluorite taking-out section 16 is rotated, and the fluorite 37 collected at the bottom of the reactor 15 is taken out into the container 38 provided in the fluorite taking-out section 16 to obtain the fluorite 37. (S15). In addition, when the fluorite 37 is continuously manufactured, after the fluorite 37 manufactured by the fluorite taking-out unit 16 is collected, the work is performed again by returning to S11. Such work is performed by so-called batch processing.

According to such a method for producing fluorite 37, calcium carbonate 29 is arranged in a reactor 15 in which the inner wall 31 is made of metal, and the inner wall 31 is maintained at 120 ° C., which is a temperature of 110 ° C. or higher, as a raw material. HF gas as a gas is introduced to react calcium carbonate 29 with HF gas to obtain fluorite 37. Here, the exhaust gas containing water is used as the raw material gas, and water is generated as the reaction product. However, since the inner wall 31 of the reactor 15 is maintained at 120 ° C., which is 110 ° C. or higher, water exists in a gaseous state rather than a liquid state. Then, the possibility that hydrogen fluoride is dissolved in liquid water to generate hydrofluoric acid can be greatly reduced. Therefore, the fluorite 37 synthesized by the reaction between the calcium carbonate 29 and the HF gas by suppressing the corrosion of the inner wall 31 of the reactor 15 by hydrofluoric acid contains metal impurities caused by the corrosion of the inner wall 31. The risk can be greatly reduced. Further, since the corrosion of the inner wall 31 of the reactor 15 is suppressed, the life of the reactor 15 can be extended. As a result, according to such a method for producing fluorite 37, high-purity fluorite 37 can be efficiently produced.

In the above embodiment, since the raw material gas is heated by the preheating unit, the raw material gas is supplied in a high temperature immediately before the raw material gas is supplied to the reactor 15 to surely generate hydrofluoric acid. Can be suppressed.

Further, in the above embodiment, since the HF gas supply device 12 supplies the exhaust gas, it is possible to efficiently produce the high-purity fluorite 37 at a lower cost. In this case, the exhaust gas is heated by the first heating unit 23, and the first pipe 21 as an introduction member is maintained at a temperature of 110 ° C. or higher. Therefore, the water contained in the exhaust gas is not liquid. It will exist in the state of gas without. Therefore, it is possible to reduce the possibility that hydrofluoric acid is generated, reduce the corrosion caused by hydrofluoric acid, and efficiently produce high-purity fluorite 37.

Further, in the above embodiment, since the raw material gas is circulated in the reactor 15 until the middle of the reaction and the raw material gas is sealed in the reactor 15 from the middle of the reaction, particularly from the middle of the reaction. Can proceed with the reaction by effectively using the enclosed raw material gas. Therefore, the enclosed raw material gas can be efficiently used to further reduce the cost.

Since the second pipe 41 and the second valve 42 as discharge members are also maintained at a temperature of 110 ° C. or higher, hydrofluoric acid is also generated when the gas in the reactor 15 is discharged. It is possible to reduce the risk of hydrofluoric acid in the second pipe 41 and the second valve 42. In particular, when the second pipe 41 is made of metal, corrosion of the metal pipe can be suppressed, and the life of the equipment can be extended.

Here, in the above embodiment, hydrogen fluoride gas is supplied by an HF gas supply device as a raw material gas containing fluorine, but the present invention is not limited to this, and a fluorocarbon destruction device which is a device for destroying fluorocarbons is used. The gas prepared and destroyed by the fluorocarbon destruction device may be supplied as a raw material gas containing hydrogen fluoride.

Further, the second pipe 41 and the second valve 42 may be replaced with air. That is, in the replacement step, the gas in the second pipe 41 and the second valve 42 may be replaced with air. By doing so, it is possible to more reliably suppress the corrosion of the second pipe 41 and the second valve 42.

In the above embodiment, calcium carbonate, which is a carbonate of calcium, is used as the calcium compound, but the present invention is not limited to this. For example, a calcium sulfate such as CaSO ₄ , a calcium hydrate such as CaC ₂ O ₄ , a calcium hydroxide such as Ca (OH) ₂ , a calcium oxide such as CaO, or the like may be used, and the calcium compound may be calcium. It may be configured to contain at least one selected from the group consisting of calcium carbonate, nitrate, sulfate, oxalate, hydroxide, and oxide. Further, the properties of the calcium compound used are not limited to powder, and may be, for example, pellets or granules.

Further, in the above embodiment, the gas is purged with air, that is, air is used as the replacement gas, but the present invention is not limited to this, and the above-mentioned non-corrosive gas may be used as the replacement gas. It may be used as a gas for replacing a mixed gas in which a non-corrosive gas and air are mixed. As the non-corrosive gas, for example, nitrogen gas, argon gas, helium gas, or other inert gas can be used as described above.

In the above embodiment, the first heating unit 23, the second heating unit 25, the heater 24 covering the introduction member, and the preheating unit are provided, but the present invention is not limited to this, and some of them are provided. Alternatively, it may be configured not to provide all of them. For example, the first heating unit 23 and the second heating unit 25 are omitted. By doing so, it is possible to simplify the equipment.

Further, in the above embodiment, the exhaust gas is supplied as the raw material gas, but the present invention is not limited to this, and high-purity hydrogen fluoride gas may be used as the raw material gas. In this case, for example, when the water content in the hydrogen fluoride gas is extremely low, it becomes less necessary to consider the water content before the reaction, and the heater 24 in the first pipe 21 may be replaced with a smaller one. , The heater 24 itself can be omitted.

In the above embodiment, the step of obtaining the fluorite is a step of introducing the raw material gas into the reactor 15 and distributing it, and after the step of distributing the raw material gas, the introduction of the raw material gas is stopped and the raw material gas is reacted. Although it is decided to include the step of encapsulating in the vessel 15, the process is not limited to this, and the raw material gas may be continuously introduced into the reactor 15 until the reaction is completed, or the raw material may be introduced over several cycles. It may be possible to distribute the gas and fill the raw material gas.

Further, the step of replacing the gas in the reactor 15 in which the fluorite 37 is obtained may be omitted if necessary.

In the above embodiment, the inner wall 31 of the reactor 15 is made of metal, but the present invention is not limited to this, and the inner wall 31 of the reactor 15 is partially made of metal and is not limited to this. The portion may be made of a material other than metal. That is, at least a part of the inner wall 31 of the reactor 15 may be made of metal. In this case, a material other than stainless steel may be used as the metal.

Further, in the above embodiment, the first pipe 21 and the second pipe 41 are made of stainless steel, but the present invention is not limited to this, and the first pipe 21 and the second pipe 41 may be made of other metals. Further, the first pipe 21 and the second pipe 41 may be configured by a material other than metal.

In the above embodiment, 120 ° C. is adopted as the temperature of 110 ° C. or higher for the temperature of the inner wall 31 and the like of the reactor 15, but the temperature is not limited to this, and for example, 150 ° C. may be adopted. Further, a temperature between 110 ° C. and 200 ° C., particularly a temperature between 120 ° C. and 150 ° C. may be adopted.

Hereinafter, Examples and Comparative Examples will be described. The metal content was confirmed using the method for producing fluorite according to the embodiment of the present invention. The test method was as follows. Approximately 1 g of calcium carbonate (CaCO ₃ ) was prepared and set in a tubular reactor (internal volume 20 ml) made of SUS304. Then, in a state where the reactor was heated to a predetermined temperature in a constant temperature bath, 100% by mass of HF gas was circulated at a flow rate of 100 ccm (cc / minutes) for 5 minutes. The flow rate of HF gas flowing at a flow rate of 100 ccm for 5 minutes is such that 1 g of calcium carbonate can react with CaF ₂ in its entirety. However, under this condition, only about 50% by mass reacts, and the rest is exhausted.

Then, after the HF gas was circulated, the valves before and after the reactor were closed to fill the HF gas. This state was maintained for several hours in order to contribute almost all of the encapsulated HF gas to the reaction. In this case, the reactor is filled with HF gas, water generated by the reaction, and carbon dioxide gas.

After encapsulation, the fluorite (CaF ₂ ) obtained by the reaction was taken out, and the content ratio of each element such as Fe, Cr, and Ni contained in the fluorite was analyzed. Specifically, the entire amount of the obtained fluorite was decomposed with an acid and analyzed by ICP. Such experiments were performed under constant temperature bath temperatures of 80 ° C, 100 ° C, 120 ° C, and 150 ° C, respectively. The results are shown in Table 1. Comparative examples are for 80 ° C. and 100 ° C., and Examples are for 120 ° C. and 150 ° C. The content ratio before the treatment, that is, the content ratio of the components of each metal element at the raw material stage is also shown.

With reference to Table 1, when the temperature is 80 ° C., the Fe content is 3930 mass ppm, which is a very large content. Further, the Cr content is 1417 mass ppm and the Ni content is 807 mass ppm, which are very high. And even in the case of 100 ° C., the content ratio of each element is basically about the same. That is, in the case of 80 ° C. and the case of 100 ° C., the content ratios of Fe, Cr and Ni are very large. On the other hand, at 120 ° C., the Fe content is 45 mass ppm, the Cr content is 10 mass ppm, and the Ni content is 8 mass ppm, which can be understood to be very small. Further, at 150 ° C., the Fe content is 14 mass ppm, the Cr content is 1 mass ppm, and the Ni content is 1 mass ppm, which can be understood to be extremely small. That is, if the inner wall of the reactor is 110 ° C. or higher, metal contamination can be made very small, and high-purity fluorite can be produced.

It should be understood that the embodiments disclosed here are exemplary in all respects and are not restrictive in any way. The scope of the present invention is defined by the scope of claims, not the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The method for producing fluorite of the present invention may be particularly advantageously applied when efficient production of high-purity fluorite is required.

11 Fluorite production equipment, 12 HF gas supply equipment, 13 purge air supply equipment, 14 calcium carbonate supply unit, 15 reactor, 16 fluorite extraction unit, 17 exhaust gas treatment equipment, 21 first piping, 22 first Valve, 23 1st heating part, 24 heater, 25 2nd heating part, 26 branches, 27,38 container, 28,39 rotating body, 29 calcium carbonate, 30 preheating part, 31 inner wall, 32 cavity, 33 Stirring rod, 34 lid, 35 support, 36 arrow, 37 fluorite, 41 second pipe, 42 second valve.

Claims (9)

A calcium compound containing at least one selected from the group consisting of carbonates, nitrates, sulfates, oxalates, hydroxides, and oxides of calcium is placed in a reactor in which at least a portion of the inner wall is made of metal. Process and
Including a step of introducing a raw material gas containing hydrogen fluoride into the reactor and reacting the calcium compound with the raw material gas to obtain fluorite while maintaining the inner wall at a temperature of 110 ° C. or higher. fruit,
In the first pipe connecting the gas supply device for supplying the raw material gas and the reactor, a first valve is provided between the gas supply device and the reactor.
A first heating unit is provided between the gas supply device and the first valve.
A preheating section is provided between the first valve and the reactor.
The raw material gas is heated to 110 ° C. or higher in the preheating section.
How to make fluorite. The method for producing fluorite according to claim 1, further comprising a step of replacing the gas in the reactor from which the fluorite is obtained with at least one of non-corrosive gas and air. A discharge member for discharging the gas in the reactor is connected to the reactor.
The method for producing fluorite according to claim 2 , wherein the discharge member is maintained at a temperature of 110 ° C. or higher. The method for producing fluorite according to claim 3 , wherein the replacement step comprises a step of replacing the gas in the discharge member with at least one of non-corrosive gas and air. The method for producing fluorite according to claim 2 , wherein the replacement step comprises a step of replacing the gas in the first pipe with at least one of non-corrosive gas and air. The method for producing fluorite according to claim 4 or 5 , wherein the raw material gas contains exhaust gas. In the step of obtaining the fluorite, after the step of introducing the raw material gas into the reactor and circulating the raw material gas and the step of circulating the raw material gas, the introduction of the raw material gas is stopped and the raw material is distributed. The method for producing a fluorite according to any one of claims 1 to 6 , which comprises a step of encapsulating the gas in the reactor. The method for producing fluorite according to any one of claims 1 to 7 , wherein the material of the inner wall of the reactor is stainless steel. The method for producing fluorite according to any one of claims 1 to 8 , wherein the calcium compound is in the form of powder.

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