JP6097625B2 - Calcium fluoride manufacturing method and calcium fluoride manufacturing apparatus - Google Patents

Description

  The present invention relates to, for example, a method for producing calcium fluoride that produces calcium fluoride using perfluoride as a raw material.

For example, in the manufacturing process of a semiconductor device or a liquid crystal device, etching or cleaning may be performed to form a fine pattern. In this case, a perfluoride is often used. In addition, since perfluoride is generally stable and often harmless to the human body, it is also used, for example, as a refrigerant for air conditioners.
However, many of these perfluorides have a great impact on the global environment when released into the atmosphere. That is, since it exists stably in the atmosphere for a long time and has a large global warming potential, it can contribute to global warming. As described above, perfluoride is generally stable, and its influence often lasts for a long time.
Therefore, in order not to affect the global environment, it is necessary to decompose the used perfluoride and make it harmless to the global environment and release it into the atmosphere.

Patent Document 1 discloses a gas stream containing a fluorine compound containing only fluorine as a halogen, a catalyst containing Al, such as a catalyst made of Al and Ni, Al and Zn, and Al and Ti in the presence of water vapor. A method for decomposing a fluorine-containing compound is disclosed in which contact is made at about 200 to 800 ° C. to convert fluorine in a gas stream into hydrogen fluoride.
Further, Patent Document 2 includes a perfluoride decomposition apparatus that is provided with a catalyst layer and is supplied with exhaust gas containing perfluoride and decomposes perfluoride, and is included in exhaust gas discharged from the perfluoride decomposition apparatus. There is disclosed a perfluoride treatment apparatus comprising an acidic substance removing device for removing a first reaction product produced by reacting an acidic substance with a Ca salt.

JP 2001-224926 A JP 2008-246485 A

  Here, the cracked gas generated by hydrolyzing the perfluoride may contain an acid component such as HF. It is desirable to effectively use the acid component without discarding it.

  The present invention has been made in view of the above-mentioned problems of the prior art, and a method for producing calcium fluoride from this acid component by effectively using the acid component contained in the cracked gas without discarding it. The purpose is to provide.

  Thus, according to the present invention, a heating step of heating a gas and water containing perfluoride and hydrolyzing the perfluoride with a catalyst to generate a cracked gas containing an acidic gas, and a step before flowing into the heating step A heat exchange step for exchanging heat between the gas and water containing perfluoride and the cracked gas after flowing out of the heating step, and an acid component contained in the cracked gas after flowing out of the heat exchanging step as a calcium salt A method of producing calcium fluoride, comprising: a step of producing calcium fluoride by reacting with calcium fluoride.

Here, in the calcium fluoride production step, it is preferable that the calcium salt is supplied from above, the produced calcium fluoride is discharged from below, and the decomposition gas is introduced from below and discharged from above.
The method further includes a pretreatment step of pretreating a gas containing perfluoride before the heating step, and in the pretreatment step, the gas containing the perfluoride is heated to liquid water contained in the gas containing the perfluoride. It is preferable to include a preheating step for evaporating water and a solid content removing step for removing solid content from the gas containing perfluoride obtained by evaporating liquid water in the preheating step.
Furthermore, it is preferable to further include an air introduction step for introducing air between the preheating step and the solid content removal step.

  Further, according to the present invention, the heating means for heating the gas and water containing the perfluoride and hydrolyzing the perfluoride by the catalyst to generate a cracked gas containing the acid gas, and before the flow into the heating means A heat exchange means for exchanging heat between the perfluoride-containing gas and water and the cracked gas after flowing out of the heating means; and an acid component contained in the cracked gas after flowing out of the heat exchange means with calcium salt There is provided a calcium fluoride production device comprising a calcium fluoride production means for producing calcium fluoride by reaction.

  Here, a medicine supply means for supplying a calcium salt for reacting with the acid component from above the calcium fluoride production means, and a medicine discharge means for discharging the calcium fluoride produced from below the calcium fluoride production means are further provided. The cracked gas introduced into the calcium fluoride producing means is preferably introduced from below the calcium fluoride producing means and discharged from above the calcium fluoride producing means.

  By providing the heating step, the heat exchange step, and the calcium fluoride production step of the present invention, it is possible to provide a method for producing calcium fluoride that is unlikely to generate wastewater containing an acid component and that has better energy utilization efficiency.

  In the calcium fluoride production process, calcium salt is supplied from above and the produced calcium fluoride is discharged from below, and the decomposition gas is introduced from below and discharged from above to facilitate exchange of calcium salts. It is possible to produce calcium fluoride with higher purity.

  By providing the pretreatment process of the present invention, even if the gas containing perfluoride contains moisture in addition to perfluoride, blockage is less likely to occur in the solid content removal process.

  By further providing an air introduction step for introducing air between the preheating step and the solid content removal step, the production of carbon monoxide in the heating step can be suppressed.

  By providing the heating means, heat exchange means, and calcium fluoride generating means of the present invention, it is possible to provide an apparatus for producing calcium fluoride that is unlikely to generate wastewater containing an acid component and has better energy utilization efficiency.

  A chemical supply means for supplying calcium salt from above the calcium fluoride generating means and a chemical discharge means for discharging calcium fluoride generated from below the calcium fluoride generating means, and the decomposition gas is calcium fluoride generating means. Calcium fluoride can be exchanged with a simple system that is introduced from below and discharged from above the calcium fluoride generating means by using gravity, and the purity of calcium fluoride is higher. Can be generated.

It is the figure explaining the whole flow of the manufacturing method of the calcium fluoride of this Embodiment. It is a figure explaining the relationship between reaction temperature and the decomposition rate of perfluoride. It is the figure explaining schematic structure of the manufacturing apparatus of the calcium fluoride of this Embodiment. It is the figure which showed each apparatus which comprises the manufacturing apparatus of the calcium fluoride of this Embodiment. It is the flowchart explaining operation | movement of the manufacturing apparatus of a calcium fluoride.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. The drawings used are for explaining the present embodiment and do not represent the actual size.

<Overall description of the manufacturing method of calcium fluoride>
FIG. 1 is a diagram illustrating an overall flow of a method for producing calcium fluoride according to the present embodiment.
As shown in the figure, the manufacturing method of calcium fluoride of the present embodiment includes a pretreatment process K1, a heating process K2, a heat exchange process K3, a calcium fluoride production process K4, and a post-treatment process K5.

In the method for producing calcium fluoride of the present embodiment, perfluoride is used as a raw material. This perfluoride is contained in, for example, etching exhaust gas discharged from a semiconductor manufacturing facility that manufactures semiconductors.
In semiconductor manufacturing equipment, a P-Si etcher that etches silicon / polysilicon as a semiconductor, an oxide film etcher that etches an oxide film such as silicon oxide (SiO ₂ ) as an insulating film, and a metal film for use in wiring. This dry etching apparatus includes a dry etching apparatus such as a metal etcher for etching. For example, reactive ion etching (RIE) in which etching is performed using a reactive etching gas in a process chamber. Device.

Etching gases used for the P-Si etcher, oxide film etcher, metal etcher, and the like are different, but the gas exhausted after dry etching in each apparatus includes various perfluorides (hereinafter referred to as “perfluoride”) caused by this etching gas. , also referred to as PFC (perfluorocompound)) and CHF ₃ and the like. Examples of the perfluoride include CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , C ₅ F ₈ , and SF ₆ . The exhausted gas containing perfluoride, that is, the etching exhaust gas, is removed from the semiconductor manufacturing facility by the collection duct after the toxic gas such as chlorine (Cl ₂ ) gas is removed by the toxic gas abatement apparatus. In the present embodiment, the etching exhaust gas discharged outside the semiconductor manufacturing facility is, for example, a gas containing 99% N ₂ (nitrogen) gas as a carrier gas and 1% perfluoride. In the present embodiment, the perfluoride used as a raw material contained in the etching exhaust gas is preferably 1% or less with respect to the etching exhaust gas. Moreover, the flow volume of the etching exhaust gas discharged | emitted is 3000L / min-3500L / min, for example.

  The pretreatment process K1 is a process of pretreating the above-described etching exhaust gas (apparatus inlet exhaust gas). The pretreatment process K1 includes a preheating process K11, an air introduction process K12, and a solid content removal process K13.

In the preheating step K11, minute water droplets (mist) contained in the apparatus inlet exhaust gas are evaporated by preheating the apparatus inlet exhaust gas. Heating is performed by a heater or the like, and the temperature of the exhaust gas at the apparatus inlet rises to 60 ° C., for example. Thereby, it can suppress that a filter etc. obstruct | occludes with mist in the following solid content removal process K13.
In the air introduction process K12, air is introduced into the apparatus inlet exhaust gas. In the heating step K2 performed after the pretreatment step K1, oxygen may be required to suppress the formation of carbon monoxide, and therefore air is mixed with the apparatus inlet exhaust gas at this stage.
In the solid content removing step K13, fine particles as solid content contained in the exhaust gas at the inlet of the apparatus are removed by using a filter or the like. In a semiconductor manufacturing facility, fine particles such as silicon oxide scraped when performing the above-described dry etching are generated. Since the fine particles are mixed in the exhaust gas at the inlet of the apparatus, the removal is performed in advance in this step.

  Moreover, in this Embodiment, although mentioned later in detail, the apparatus inlet_port | entrance exhaust gas after the solid content removal process K13 is sent to the heat exchange process K3. In the heat exchange step K3, the apparatus inlet exhaust gas is heated by heat exchange. Further, at this time, in the next heating step K2, water necessary for the reaction for decomposing the perfluoride is added in a liquid state. This water is heated together with the exhaust gas at the inlet of the apparatus in the heat exchange step K3 to become gaseous water vapor. And it mixes with the apparatus inlet gas. In the present embodiment, pure water is used as water. The amount of water added is an amount commensurate with the reaction formula described below, and is, for example, 350 mL / min. The water may be heated in advance and added as water vapor.

  The heating step K2 is a step of heating the exhaust gas at the inlet of the apparatus and water, and hydrolyzing the perfluoride with a catalyst to generate a cracked gas containing an acidic gas. The heating process K2 includes a first heating process K21 and a second heating process K22.

In the first heating step K21, the exhaust gas at the inlet of the apparatus and the water that has been added to become water vapor are heated. This heating is performed by using a heater or the like. The apparatus inlet exhaust gas after passing through the first heating step K21 is, for example, 450 ° C to 500 ° C.
In the second heating step K22, the apparatus inlet exhaust gas and water vapor are further heated by a heater or the like. As a result, the exhaust gas at the inlet of the apparatus is heated to 750 ° C., for example. The heated apparatus inlet exhaust gas reacts with water (steam) mixed with the apparatus inlet exhaust gas by a predetermined catalyst and is decomposed.
As the decomposition reaction at this time, the case of CF ₄ , CHF ₃ , C ₂ F ₆ and SF ₆ as the perfluoride is taken as an example, and the reaction formula is shown below.

CF ₄ + 2H ₂ O → CO ₂ + 4HF (1)
CHF ₃ + (1/2) O ₂ + H ₂ O → CO ₂ + 3HF (2)
C ₂ F ₆ + 3H ₂ O + (1/2) O ₂ → 2CO ₂ + 6HF (3)
SF ₆ + 3H ₂ O → SO ₃ + 6HF (4)

  As can be seen from the above formulas (1) to (4), perfluoride becomes a cracked gas containing HF (hydrogen fluoride) which is an acid component by a hydrolysis reaction. In this case, HF can also be regarded as an acidic gas contained in the cracked gas.

FIG. 2 is a diagram illustrating the relationship between the reaction temperature and the decomposition rate of perfluoride.
Here, CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , C ₅ F ₈ , SF ₆ , and NF ₃ are exemplified as the perfluoride contained in the etching exhaust gas. Although not a perfluoride, CO is also shown as a component contained in the gas discharged from the semiconductor manufacturing facility.
As shown in the figure, since each component has a decomposition rate of almost 100% near 750 ° C., the reaction at a temperature of 750 ° C. can almost remove perfluoride and the like.

As the catalyst, in this embodiment, Al ₂ O ₃ (aluminum oxide), Zn (zinc), Ni (nickel), Ti (titanium), F (fluorine), Sn (tin), Co (cobalt), Those containing oxides such as Zr (zirconium), Ce (cerium), and Si (silicon) can be used. More specifically, for example, a composition comprising 80% by mass of Al ₂ O ₃ (aluminum oxide) and 20% by mass of NiO (nickel oxide) can be used.

  The heat exchange process K3 is a process of exchanging heat between the apparatus inlet exhaust gas before flowing into the heating process K2 and the cracked gas after flowing out from the heating process K2 arranged before and after the heating process K2.

In the heat exchange step K3, heat exchange is performed between the high-temperature cracked gas discharged from the second heating step K22 and the low-temperature apparatus inlet exhaust gas before being introduced into the first heating step K21. This heat exchange is performed by a heat exchanger or the like. As a result, the temperature of the cracked gas decreases, and the temperature of the exhaust gas at the apparatus inlet before being introduced into the first heating step K21 increases. Further, as described above, the added water evaporates to become water vapor.
The cracked gas after passing through the heat exchanging step K3 has a temperature lowered to about 300 ° C. to 500 ° C., and the exhaust gas at the apparatus inlet after passing through the heat exchanging step K3 rises to about 200 ° C. to 300 ° C. .

  The calcium fluoride production step K4 is a step of producing calcium fluoride by reacting an acid component contained in the cracked gas after flowing out of the heat exchange step K3 with a calcium salt.

In the calcium fluoride production step K4, HF, which is an acid component contained in the cracked gas, is adsorbed with a calcium salt to produce calcium fluoride. Here, CaCO ₃ (calcium carbonate), Ca (OH) ₂ (calcium hydroxide), CaO (calcium oxide), or the like can be used as the calcium salt. The shape of the calcium salt may be powder, but is preferably a pellet formed into a columnar shape or a spherical shape for ease of handling. In the present embodiment, for example, a mixture of Ca (OH) ₂ and CaCO ₃ and CaCO ₃ : Ca (OH) ₂ = 50% by mass to 80% by mass: 20% by mass to 50% by mass is used. To do. In this case, the moldability is good and pulverization can be suppressed when a pellet is formed. In the present embodiment, this mixture is used as a cylindrical pellet having a bottom diameter of about 3 mm and a height of about 8 mm.

As an adsorption reaction at this time, the case where CaCO ₃ or Ca (OH) ₂ is used as a calcium salt is taken as an example, and the reaction formula is shown below.

CaCO ₃ + 2HF → CaF ₂ + CO ₂ + H ₂ O (5)
Ca (OH) ₂ + 2HF → CaF ₂ + 2H ₂ O (6)

As can be seen from the above formulas (5) to (6), HF reacts with a calcium salt, and CaF ₂ (calcium fluoride (fluorite)), CO ₂ (carbon dioxide), and H ₂ O (water) become Arise.

  At this time, the cracked gas is introduced from below the apparatus (for example, a calcium fluoride producing apparatus 232 described later with reference to FIG. 4) that performs the calcium fluoride producing step K4 and discharged from above. While the cracked gas flows from the lower side to the upper side of the apparatus for performing the calcium fluoride production step K4, the reaction between HF and the calcium salt exemplified in the above formulas (5) to (6) occurs, Generate. In the present embodiment, it is preferable that the calcium salt is supplied from above the apparatus that performs the calcium fluoride production step K4, and the produced calcium fluoride is discharged from below.

The post-treatment process K5 is a process of removing the solid content generated in the calcium fluoride production process K4 and exhausting the exhaust gas discharged from the calcium fluoride production process K4 to the outside of the apparatus. The post-treatment process K5 includes a solid content removal process K51 and an exhaust process K52.
In the calcium fluoride production step K4, calcium salt powder or the like may be generated when the calcium salt is exchanged. Therefore, in the post-processing step K5, first, as the solid content removing step K51, the solid content that is powder is removed by using a filter or the like. And after removal of solid content, exhaust gas is discharged outside as an exhaust process K52. The exhaust gas discharged from the calcium fluoride production process K4 is, for example, about 200 ° C., but the exhaust gas discharged from the post-treatment process K5 is, for example, 100 ° C. or less.

  Calcium fluoride produced by the processes described above can be used for optical materials such as telephoto lenses, zoom lenses, television cameras, infrared lenses, prisms, analytical instruments, window materials, and fluorine sources.

<Description of configuration of perfluoride treatment apparatus>
Next, a calcium fluoride production apparatus for realizing the above-described calcium fluoride production method will be described in more detail.
FIG. 3 is a diagram illustrating a schematic configuration of the calcium fluoride production apparatus 1 according to the present embodiment.
As shown in the drawing, a calcium fluoride production apparatus 1 includes a pretreatment unit 21 that pretreats an introduced apparatus inlet exhaust gas (etching exhaust gas), and a superfluoride contained in the apparatus inlet exhaust gas pretreated by the pretreatment unit 21. Perfluoride decomposition unit 22 for decomposing fluoride, and HF (hydrogen fluoride) contained in the decomposition gas obtained by decomposing perfluoride by perfluoride decomposition unit 22 reacts with calcium salt to produce calcium fluoride. A calcium fluoride generating unit 23. Then, after the exhaust gas at the inlet of the apparatus is treated and detoxified by each of these units, it is discharged out of the calcium fluoride production apparatus 1 as exhaust gas.

FIG. 4 is a view showing each device constituting the calcium fluoride production apparatus 1 of the present embodiment.
As described with reference to FIG. 3, the calcium fluoride production apparatus 1 mainly includes a pretreatment unit 21, a perfluoride decomposition unit 22, and a calcium fluoride generation unit 23. As shown in the figure, the calcium fluoride production apparatus 1 includes a control unit 24, and controls each device and valves (not shown) provided in the calcium fluoride production apparatus 1.

The pretreatment unit 21 is a unit that performs the pretreatment step K1. The pretreatment unit 21 includes an inlet heater 211 for preheating the exhaust gas at the apparatus inlet and a filter 212 for removing fine particles.
The inlet heater 211 evaporates minute water droplets (mist) contained in the apparatus inlet exhaust gas by preheating the apparatus inlet exhaust gas. The inlet heater 211 includes a heater 211a around a pipe through which the apparatus inlet exhaust gas passes. The apparatus inlet exhaust gas is heated by the heater 211a when passing through the inlet heater 211, and is preheated to a temperature at which mist evaporates. That is, the inlet heater 211 is a device that performs the preheating step K11.

  The filter 212 removes fine particles as a solid content contained in the exhaust gas at the inlet of the apparatus. That is, the filter 212 is a device that performs the solid content removing step K13. The filter 212 is not particularly limited as long as it allows the exhaust gas at the inlet of the apparatus to pass therethrough and collects fine particles. For example, a mesh filter or the like can be used.

In this embodiment, air is introduced between the inlet heater 211 and the filter 212. That is, this air introduction location is a location where the air introduction process K12 is performed.
Thereafter, the exhaust gas at the inlet of the apparatus after passing through the filter 212 once enters the heat exchanger 231. The apparatus inlet exhaust gas is heated by heat exchange in the heat exchanger 231. As described above, at this time, water necessary for the reaction for decomposing the perfluoride is added in the liquid state in the next perfluoride decomposition unit 22. As described above, this water is heated together with the exhaust gas at the inlet of the apparatus in the heat exchanger 231 to become gaseous water vapor.

  The perfluoride decomposition unit 22 is a unit that performs the heating step K2. The perfluoride decomposition unit 22 is an example of a heating unit that heats the exhaust gas and water at the inlet of the apparatus, and hydrolyzes the perfluoride with a catalyst to generate a decomposition gas containing an acidic gas. The perfluoride decomposition unit 22 includes two heaters, a first heater 221 and a second heater 222.

  The first heater 221 has a heater 221a disposed therein, and the heater 221a heats the exhaust gas at the inlet of the apparatus and the water added to the heat exchanger 231 to become water vapor. That is, the 1st heater 221 becomes an apparatus which performs the 1st heating process K21. In the present embodiment, the first heater 221 is a horizontal heater in which the flow path of the apparatus inlet exhaust gas is in the horizontal direction.

The second heater 222 introduces apparatus inlet exhaust gas from above, and further heats the apparatus inlet exhaust gas and water vapor by a heater 222a provided therein. Further, the heated exhaust gas at the inlet of the apparatus reacts with the water (steam) mixed with the exhaust gas at the inlet of the apparatus in the catalyst layer 222b disposed below the second heater 222 and is decomposed. The catalyst layer 222b is made of, for example, a catalyst having a composition of 80% by mass of Al ₂ O ₃ (aluminum oxide) and 20% by mass of NiO (nickel oxide). That is, the second heater 222 is a device that performs the second heating step K22.
As the decomposition reaction at this time, for example, the reactions of the above formulas (1) to (4) are performed, and a decomposition gas containing HF is generated.

  The cracked gas containing HF after the perfluoride is decomposed by the second heater 222 is discharged from below the second heater 222 and sent to the next calcium fluoride generating unit 23.

  The calcium fluoride production unit 23 is a unit that performs a heat exchange process K3, a calcium fluoride production process K4, and a post-treatment process K5. The calcium fluoride generating unit 23 is disposed in the front stage and the rear stage of the first heater 221 and the second heater 222, and the exhaust gas from the apparatus before flowing into the first heater 221 and after flowing out from the second heater 222. A heat exchanger 231 which is an example of heat exchange means for exchanging heat with the cracked gas, and an acid component contained in the cracked gas after flowing out of the heat exchanger 231 reacts with calcium salt to generate calcium fluoride. A calcium fluoride generator 232 as an example of calcium fluoride generating means, and an ejector 233 as an example of an exhaust gas discharging means for discharging exhaust gas after the acid component has been dry-removed by the calcium fluoride generator 232; Is provided.

  The calcium fluoride generating unit 23 includes a drug supply device 234 that is an example of a drug supply unit that supplies calcium salt that is a drug for reacting with HF from above the calcium fluoride generation device 232, and a calcium fluoride generation device. An example of a medicine discharge device 235 which is an example of a medicine discharge means for discharging calcium fluoride generated from below 232 and an example of a concentration detection means for detecting the concentration of HF contained in exhaust gas flowing out from the calcium fluoride generation device 232 And a powder trap 237 that is disposed between the HF concentration sensor 236 and the ejector 233 and removes the solid content generated in the calcium fluoride generator 232.

  The heat exchanger 231 performs heat exchange between the high-temperature cracked gas discharged from the second heater 222 and the aforementioned low-temperature apparatus inlet exhaust gas before being introduced into the first heater 221. That is, the heat exchanger 231 is a device that performs the heat exchange step K3. While the temperature of the cracked gas is lowered from the heat exchanger 231, the temperature of the exhaust gas at the apparatus inlet before being introduced into the first heater 221 is raised. Further, as described above, the water added to the heat exchanger 231 evaporates to become water vapor.

  The heat exchanger 231 is not particularly limited, and two plate plates are alternately arranged, a flow path is formed between the plates, and a plate-type heat that exchanges heat between the apparatus inlet exhaust gas and the cracked gas. It is possible to use an exchanger, or a shell-and-tube type heat exchanger that exchanges heat between the shell exhaust gas and cracked gas through the shell (cylinder) and a number of tubes (heat transfer tubes). Moreover, it may be a double-pipe heat exchanger having a double-pipe structure in which a high-temperature cracked gas flows through the inner pipe and a low-temperature apparatus inlet exhaust gas flows through the outer pipe. Further, the apparatus inlet exhaust gas and the cracked gas may flow oppositely or may flow in parallel. In the present embodiment, a double-tube heat exchanger is used, and the apparatus inlet exhaust gas and the cracked gas are caused to flow opposite to each other.

The calcium fluoride generator 232 is filled with a drug layer 232a made of a calcium salt, and HF contained in the decomposition gas is dry-removed by an adsorption reaction with the calcium salt, and calcium fluoride. (CaF ₂ ) is generated. That is, the calcium fluoride production | generation apparatus 232 becomes an apparatus which performs the calcium fluoride production | generation process K4. The adsorption reaction at this time is the reaction exemplified in the above formulas (5) to (6), and HF reacts with a calcium salt to produce CaF ₂ (calcium fluoride (fluorite)), CO ₂ (carbon dioxide). ), And H ₂ O (water).

  The cracked gas is introduced from below the calcium fluoride generator 232 and discharged from above the calcium fluoride generator 232. While the cracked gas flows upward from below the calcium fluoride generator 232, the reaction between HF and the calcium salt exemplified in the above formulas (5) to (6) occurs and calcium fluoride is generated. . Then, it is necessary to discharge the generated calcium fluoride from the calcium fluoride generator 232 and supply a new calcium salt into the calcium fluoride generator 232.

  Therefore, in this embodiment, a drug supply device 234 that supplies a calcium salt to the calcium fluoride generation device 232 and a drug discharge device 235 that discharges the generated calcium fluoride from the calcium fluoride generation device 232 are provided.

  In the present embodiment, the HF concentration sensor 236 monitors the HF concentration. When the HF concentration reaches, for example, 100 ppm, it is determined that it is time to replace the calcium salt. Then, a rotary valve (not shown) provided in the medicine discharge device 235 is opened and closed to discharge a predetermined amount of generated calcium fluoride. Moreover, after discharging | emitting the produced | generated calcium fluoride, a rotary valve (not shown) etc. which were provided in the chemical | medical agent supply apparatus 234 are opened and closed, and the new calcium salt for the discharged | emitted is supplied. In this way, the calcium salts in the medicine discharge device 235 are sequentially replaced. In this series of procedures, the control unit 24 acquires information on the concentration of HF sent from the HF concentration sensor 236, and when the concentration of HF reaches, for example, 100 ppm, the medicine supply device 234 and the medicine discharge This is automatically performed by controlling opening and closing of a rotary valve provided in the device 235.

  The powder trap 237 is provided to remove calcium salt powder generated in the calcium fluoride generator 232 when the calcium salt is exchanged. As the powder trap 237, a metal mesh filter or the like can be used.

The ejector 233 is connected to a compressed air pipe through which compressed air flows. The exhaust gas is sucked by the negative pressure generated by flowing the compressed air at a high speed, and discharged together with the compressed air to the outside of the calcium fluoride manufacturing apparatus 1. To do. As a result, the exhaust gas is further discharged at a reduced temperature.
Here, the powder trap 237 and the ejector 233 are devices for performing the post-processing step K5.

<Description of Operation of Calcium Fluoride Production Apparatus 1>
FIG. 5 is a flowchart illustrating the operation of the calcium fluoride production apparatus 1.
Hereinafter, the operation of the calcium fluoride production apparatus 1 will be described with reference to FIGS. 4 and 5.
First, the apparatus inlet exhaust gas passes through the inlet heater 211 of the pretreatment unit 21 and is preheated (step 101). As a result, the mist contained in the exhaust gas at the inlet of the apparatus evaporates.
Next, air is introduced into the preheated apparatus inlet exhaust gas (step 102), and particulates are removed by the filter 212 of the pretreatment unit 21 (step 103).

The exhaust gas at the inlet of the apparatus is heated by heat exchange by the heat exchanger 231 (step 104). At this time, water necessary for the decomposition reaction of perfluoride is added.
The apparatus inlet exhaust gas that has passed through the heat exchanger 231 is first heated by the first heater 221 (step 105), and further heated by the second heater 222 to a temperature necessary for decomposition of perfluoride (step 105). 106). Then, the perfluoride is decomposed when passing through the catalyst layer 222b of the second heater 222, and the exhaust gas at the inlet of the apparatus becomes a decomposition gas containing HF (step 107).

  The cracked gas enters the heat exchanger 231 again, and exchanges heat with the above-described apparatus inlet exhaust gas (step 108).

  The cracked gas reacts with the calcium salt in the calcium fluoride generator 232, and HF is dry-removed and calcium fluoride is generated (step 109). At this time, the control unit 24 determines whether or not the HF concentration acquired by the HF concentration sensor 236 has become a predetermined value or more (step 110). And when it becomes more than a predetermined value (it is Yes at Step 110), medicine discharge device 235 and medicine supply device 234 are operated, and calcium salt is exchanged (Step 111). If it is less than the predetermined value (No in step 110), the calcium salt is not exchanged and the process proceeds to the next step 112.

  The exhaust gas from which HF has been dry removed is removed from the calcium fluoride production apparatus 1 by the ejector 233 after the solid content is removed by the powder trap 237 (step 112) (step 113).

The calcium fluoride manufacturing method and the calcium fluoride manufacturing apparatus 1 described in detail above have the following characteristics.
(I) Since the perfluoride is decomposed using the catalyst layer 222b, a large amount of etching exhaust gas can be treated and the operating cost can be reduced.
(ii) HF contained in the cracked gas is dry-removed by an adsorption reaction with a calcium salt, so that wastewater containing HF is not generated as compared with a conventional method of removing HF by dissolving HF in water. Moreover, CaF ₂ produced after the adsorption reaction is harmless and easy to handle. Further, CaF ₂ is a valuable material because it becomes a raw material for producing HF. That is, CaF ₂ which is a valuable material can be produced from etching exhaust gas harmful to the global environment.
(Iii) By using the heat exchanger 231 to exchange heat between the exhaust gas at the inlet of the apparatus and the cracked gas, the energy utilization efficiency increases. Moreover, compared with the conventional method of cooling the cracked gas with water, drainage does not occur. This eliminates the need for a wastewater treatment step and reduces the operating cost of the calcium fluoride production apparatus 1.
(iv) By incorporating the drug supply device 234 disposed above the calcium fluoride production device 232 and the drug layer 232a having the drug discharge device 235 below, it is possible to simply drop it using gravity by simply opening the valve. With a simple system, it is possible to exchange calcium salts. In this embodiment, the decomposition gas is introduced from below and exhausted from above, and the HF concentration sensor 236 is provided, and the HF concentration is monitored to determine the replacement timing of the calcium salt. As a result, the upper layer portion of the drug layer 232a is not discharged, and only the reacted calcium salt in the lower layer portion is discharged, so that the purity of the generated calcium fluoride is improved.
(v) In this embodiment, the HF concentration sensor 236 monitors the HF concentration, and when the HF concentration reaches a predetermined concentration or higher, the calcium salt is exchanged. Thereby, HF can be more reliably removed from the cracked gas, and the discharge of HF out of the calcium fluoride production apparatus 1 can be suppressed.

  In the above-described example, the case where the perfluoride contained in the etching exhaust gas discharged at the semiconductor manufacturing factory is treated has been described. However, the present invention is not limited to this. For example, it may be a case where perfluoride contained in etching exhaust gas or cleaning exhaust gas discharged from a liquid crystal manufacturing factory or the like is processed.

DESCRIPTION OF SYMBOLS 1 ... Calcium fluoride manufacturing apparatus, 21 ... Pretreatment unit, 22 ... Perfluoride decomposition unit, 23 ... Calcium fluoride production unit, 24 ... Control unit, 211 ... Inlet heater, 212 ... Filter, 221 ... 1st Heater, 222 ... second heater, 231 ... heat exchanger, 232 ... calcium fluoride generator, 233 ... ejector, 234 ... drug supply device, 235 ... drug discharge device, 236 ... HF concentration sensor, K1 ... pretreatment Step, K2 ... Heating step, K3 ... Heat exchange step, K4 ... Calcium fluoride production step, K5 ... Post-treatment step

Claims (5)

A heating step of heating a gas containing perfluoride and water and hydrolyzing the perfluoride with a catalyst to generate a decomposition gas containing an acid gas;
A heat exchanging step of exchanging heat between the gas and water containing perfluoride before flowing into the heating step and the cracked gas after flowing out of the heating step;
A calcium fluoride producing step of reacting an acid component contained in the cracked gas after flowing out of the heat exchange step with a calcium salt to produce calcium fluoride;
A pretreatment step of pretreating a gas containing perfluoride before the heating step;
Equipped with a,
In the pretreatment step,
A preheating step of heating a gas containing perfluoride to evaporate liquid water contained in the gas containing perfluoride;
A solid content removing step of removing solid content by a filter from a gas containing perfluoride in a state where liquid water is evaporated by the preheating step;
A method for producing calcium fluoride, comprising: In the calcium fluoride production step,
While supplying the calcium salt from above, discharge the calcium fluoride after generation from below,
The method for producing calcium fluoride according to claim 1, wherein the cracked gas is introduced from below and discharged from above. The method for producing calcium fluoride according to claim 1 or 2 , further comprising an air introduction step of introducing air between the preheating step and the solid content removal step. Heating means for heating a gas containing perfluoride and water, and hydrolyzing the perfluoride with a catalyst to generate a decomposition gas containing an acid gas;
Heat exchange means for exchanging heat between the gas and water containing perfluoride before flowing into the heating means and the cracked gas after flowing out from the heating means;
Calcium fluoride generating means for reacting an acid component contained in the cracked gas after flowing out of the heat exchange means with a calcium salt to generate calcium fluoride;
A pretreatment unit for pretreating a gas containing perfluoride before the heating means;
Equipped with a,
The pretreatment hand unit is
An inlet heater for heating a gas containing perfluoride and evaporating liquid water contained in the gas containing perfluoride;
A filter for removing solids from a gas containing perfluoride in a state where liquid water is evaporated by the inlet heater;
An apparatus for producing calcium fluoride, comprising: A drug supply means for supplying a calcium salt for reacting with an acid component from above the calcium fluoride generating means, and a drug discharge means for discharging calcium fluoride generated from below the calcium fluoride generating means. ,
5. The fluorination according to claim 4, wherein the cracked gas introduced into the calcium fluoride producing means is introduced from below the calcium fluoride producing means and discharged from above the calcium fluoride producing means. Calcium production equipment.

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