CN104108736B - The manufacture method of calcirm-fluoride and the manufacturing installation of calcirm-fluoride - Google Patents

Abstract

The invention provides a kind of manufacture method that is difficult to the better calcirm-fluoride of utilization ratio that produces the draining, the energy that contain sour composition. The manufacture method of described calcirm-fluoride, is characterized in that, possesses: heating process (K2), and this operation heats the gas that contains perfluoro-compound and water, and utilizes catalyst hydrolysis perfluoro-compound to generate the decomposition gas that contains sour gas; Heat exchange operation (K3), this operation is carried out heat exchange flowing into heating process (K2) containing between device portal exhaust and water and decomposition gas from heating process (K2) outflow before; And calcirm-fluoride generation operation (K4), this operation makes contained sour composition in the decomposition gas from heat exchange operation (K3) flows out react generation calcirm-fluoride with calcium salt.

Description

Calcium fluoride manufacturing method and calcium fluoride manufacturing apparatus

technical field

The present invention relates to, for example, a method for producing calcium fluoride in which calcium fluoride is produced by using a perfluoride as a raw material.

Background technique

For example, in the manufacturing process of a semiconductor device or a liquid crystal device, etching and cleaning may be performed in order to form a fine pattern. In this case, perfluorinated compounds are often used. In addition, perfluorinated compounds are generally stable and mostly harmless to the human body, so they are also used, for example, as refrigerants in air conditioners.

However, among these perfluorinated compounds, when released into the atmosphere, many perfluorinated compounds have a large impact on the global environment. That is, since it exists stably in the atmosphere for a long period of time and has a large global warming coefficient, it becomes a factor of global warming. In addition, as described above, perfluorinated compounds are generally relatively stable, and their influence often persists over a long period of time.

Therefore, in order not to affect the global environment, it is necessary to decompose the used perfluorinated compounds and release them into the atmosphere in a state harmless to the global environment.

In Patent Document 1, a method for decomposing fluorine-containing compounds is disclosed, that is, in the presence of water vapor, an air stream containing a fluorine compound containing only fluorine as a halogen is mixed with, for example, Al and Ni, Al and Zn, Al and Catalysts containing Al such as catalysts formed of Ti are contacted at about 200 to 800°C to convert fluorine in the gas stream to hydrogen fluoride.

In addition, Patent Document 2 discloses a perfluoride treatment device, which is characterized in that it includes: a perfluoride decomposition device, which is provided with a catalyst layer, is supplied with exhaust gas (exhaust gas) containing perfluoride, and decomposes the perfluoride fluoride; and an acidic substance removal device for removing a first reaction product produced by the reaction of an acidic substance and a Ca salt contained in the exhaust gas discharged from the perfluoride decomposition device.

prior art literature

Patent Document 1: Japanese Patent Laid-Open No. 2001-224926

Patent Document 2: Japanese Patent Laid-Open No. 2008-246485

Contents of the invention

Here, acid components such as HF may be contained in the decomposed gas generated by hydrolyzing perfluorinated compounds. Furthermore, it is desired to effectively utilize the acid component without discarding it.

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

Thus, according to the present invention, there is provided a method for producing calcium fluoride, which is characterized in that it includes a heating step of heating gas and water containing perfluoride, and using a catalyst to hydrolyze perfluoride to generate acid gas containing The decomposition gas of the heating process; the heat exchange process, which performs heat exchange between the gas containing perfluoride and water before flowing into the heating process, and the decomposition gas after flowing out from the heating process; and the calcium fluoride generation process, which makes the heat exchange process The acid component contained in the decomposed gas after the process flows out reacts with the calcium salt to form calcium fluoride.

Here, in the calcium fluoride generation step, it is preferable that the calcium salt is supplied from above, the generated calcium fluoride is discharged from below, and the decomposed gas is introduced from below and discharged from above.

In addition, it is preferable to further include a pretreatment step of pretreating the gas containing perfluoride before the heating step, and in the pretreatment step: a preheating step of heating the gas containing perfluoride to make the gas containing perfluoride evaporation of liquid water contained in the perfluorinated gas; and a solid content removal step of removing solid content from the perfluorinated gas from which the liquid water was evaporated in the preheating process.

Furthermore, it is preferable to further include an air introducing step for introducing air between the preheating step and the solid content removal step.

In addition, according to the present invention, there is provided a calcium fluoride production apparatus characterized by comprising: a heating unit for heating gas and water containing perfluoride, and using a catalyst to hydrolyze perfluoride to generate acid gas the decomposed gas; a heat exchange unit that exchanges heat between the gas containing perfluoride and water before flowing into the heating unit and the decomposed gas after flowing out from the heating unit; and a calcium fluoride generating unit that exchanges heat from the The acid component contained in the decomposed gas flowing out of the unit reacts with the calcium salt to form calcium fluoride.

Here, it is preferable to further include: a chemical supply unit that supplies calcium salt for reacting with the acid component from above the calcium fluoride production unit; and a chemical discharge unit that discharges the produced calcium salt from below the calcium fluoride production unit. Calcium fluoride, the decomposition gas introduced to the calcium fluoride production unit is introduced from the bottom of the calcium fluoride production unit, and is discharged from the top of the calcium fluoride production unit.

By including 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 less likely to generate waste water containing acid components and has better energy utilization efficiency.

In the calcium fluoride generation process, calcium salt is supplied from above, and the generated calcium fluoride is discharged from below, and the decomposed gas is introduced from below and discharged from above, thereby enabling easy replacement of calcium salt and generating Higher purity calcium fluoride.

By including the pretreatment step of the present invention, even if the perfluoride-containing gas contains moisture in addition to the perfluoride, it becomes difficult to cause clogging in the solid content removal step.

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

By including the heating unit, the heat exchange unit, and the calcium fluoride generating unit of the present invention, it is possible to provide a calcium fluoride manufacturing apparatus that hardly generates waste water containing acid components and has better energy utilization efficiency.

By including a chemical supply unit that supplies calcium salt from above the calcium fluoride production unit, and a chemical discharge unit that discharges the produced calcium fluoride from below the calcium fluoride production unit, the decomposed gas is discharged from the bottom of the calcium fluoride production unit. Introduce and discharge from above the calcium fluoride production unit, and adopt a simple system that uses gravity to drop, so that the calcium salt can be replaced and calcium fluoride with higher purity can be produced.

Description of drawings

FIG. 1 is a diagram illustrating an overall flow of a method for producing calcium fluoride according to the present embodiment.

Fig. 2 is a graph illustrating the relationship between the reaction temperature and the decomposition rate of perfluorinated compounds.

FIG. 3 is a diagram illustrating a schematic configuration of a calcium fluoride manufacturing apparatus according to the present embodiment.

FIG. 4 is a diagram showing each device constituting the calcium fluoride manufacturing apparatus of the present embodiment.

FIG. 5 is a flow chart illustrating the operation of the calcium fluoride manufacturing apparatus.

Explanation of reference signs

1... Calcium fluoride manufacturing device, 21... Pretreatment device, 22... Perfluoride decomposition device, 23... Calcium fluoride production device, 24... Control device, 211... Inlet heater, 212... Filter, 221... The first 1 heater, 222...second heater, 231...heat exchanger, 232...calcium fluoride generator, 233...ejector, 234...medicine supply device, 235...medicine discharge device, 236...HF concentration sensor, K1... Pretreatment process, K2...heating process, K3...heat exchange process, K4...calcium fluoride generation process, K5...post-treatment process.

detailed description

Hereinafter, modes for carrying out the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, Various deformation|transformation can be implemented within the range of the summary. In addition, the drawings used are for explaining this embodiment, and do not show actual size.

<Overall description of the production 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 method for producing calcium fluoride according to this embodiment includes a pretreatment step K1, a heating step K2, a heat exchange step K3, a calcium fluoride generation step K4, and a posttreatment step K5.

In the method for producing calcium fluoride according to this embodiment, a perfluoride is used as a raw material. This perfluorinated compound is contained in, for example, etching exhaust gas (etching exhaust gas) discharged from semiconductor manufacturing equipment that performs semiconductor manufacturing.

Semiconductor manufacturing equipment is equipped with: P-Si etcher for etching silicon as a semiconductor and polysilicon, oxide film etcher for etching oxide films such as silicon oxide (SiO ₂ ) as an insulating film, etching metal for use in wiring A dry etching (dry etching) device such as a metal etcher of a film, such as a reactive ion etching (RIE: ReactiveIonEtching) that uses a reactive etching gas in a processing chamber (process chamber: processchamber). ) device.

Etching gases used in P-Si etcher, oxide film etcher, and metal etcher are different, but the exhaust gas after performing dry etching by each device contains various perfluorinated gases caused by the etching gas. compound (hereinafter also referred to as PFC (perfluorocompound)). Examples of the perfluorinated compound include CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , C ₅ F ₈ , SF ₆ , CHF ₃ and the like. In addition, the exhausted gas containing perfluoride, that is, the etching exhaust gas, is discharged from the semiconductor manufacturing equipment through the collection pipe after toxic gases such as chlorine (Cl ₂ ) gas are removed by the toxic gas removal device. In this embodiment, the etching exhaust gas discharged outside the semiconductor manufacturing equipment is, for example, a gas containing 1% perfluoride or the like in 99% N ₂ (nitrogen) gas as a carrier gas. 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. In addition, the flow rate of the exhausted etching gas is, for example, 3000 L/min to 3500 L/min.

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

In the preheating step K11 , minute water droplets (mist) contained in the exhaust gas at the inlet of the apparatus are evaporated by preheating the exhaust gas at the inlet of the apparatus. Heating is performed using a heater or the like, and the temperature of the exhaust gas at the inlet of the apparatus is raised to, for example, 60°C. Thereby, it can suppress that a filter etc. are clogged with mist in the following solid content removal process K13.

In the air introduction step K12, air is introduced into the device inlet exhaust. In the heating step K2 performed after the pretreatment step K1, oxygen is sometimes required to suppress the generation of carbon monoxide, so air is mixed with the device inlet exhaust gas at this stage.

In the solid content removal step K13, fine particles that are solid content contained in the device inlet exhaust gas are removed by using a filter or the like. In semiconductor manufacturing equipment, fine particles such as silicon oxide that are chipped off during the above-mentioned dry etching are generated. And since these fine particles are mixed into the exhaust gas at the inlet of the apparatus, they are removed in advance in this step.

In addition, in the present embodiment, as will be described in detail later, the exhaust gas at the device inlet after the solid content removal step K13 is sent to the heat exchange step K3. Furthermore, in the heat exchange step K3, the device inlet exhaust gas is heated by heat exchange. Furthermore, water necessary for the reaction of decomposing perfluoride in the next heating process K2 at this time is added in a liquid state. This water is heated together with the device inlet exhaust gas in the heat exchange step K3, and becomes gaseous water vapor. It is then mixed with the plant inlet exhaust. In this embodiment, pure water is used as water. The amount of water added is an amount commensurate with the reaction formula described later, and is, for example, 350 mL/min. In addition, this water may be heated and added as water vapor in advance.

The heating step K2 is a step of heating the device inlet exhaust gas and water, and hydrolyzing the perfluorinated compound with a catalyst to generate a decomposition gas containing an acidic gas. The heating process K2 is provided with the 1st heating process K21 and the 2nd heating process K22.

In the first heating step K21, the exhaust gas at the inlet of the apparatus and the water added to become water vapor are heated. This heating is performed using a heater or the like. The exhaust gas at the device inlet after passing through the first heating step K21 becomes, for example, 450°C to 500°C.

In the second heating step K22, first, the device inlet exhaust gas and water vapor are further heated with a heater or the like. As a result, the device inlet exhaust gas is heated to, for example, 750°C. Then, the heated device inlet exhaust gas is decomposed by reacting with water (steam) mixed in the device inlet exhaust gas by a predetermined catalyst.

As the decomposition reaction at this time, the case of CF ₄ , CHF ₃ , C ₂ F ₆ and SF ₆ which are perfluorinated compounds 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), the perfluorinated compound turns into a decomposition gas containing HF (hydrogen fluoride) as an acid component by a hydrolysis reaction. In addition, in this case, HF can also be captured as acid gas contained in the decomposition gas.

Fig. 2 is a graph illustrating the relationship between the reaction temperature and the decomposition rate of perfluorinated compounds.

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 perfluoride contained in the etching exhaust gas. In addition, although it is not a perfluorinated compound, CO is also shown in the figure as a component contained in the gas discharged from semiconductor manufacturing equipment.

As shown in the figure, any component has a decomposition rate of approximately 100% at around 750°C, so by reacting at a temperature of 750°C, perfluoride and the like can be approximately removed.

In addition, as a catalyst, in the present embodiment, Al ₂ O ₃ (alumina) containing Zn (zinc), Ni (nickel), Ti (titanium), F (fluorine), Sn (tin), Co (Cobalt), Zr (zirconium), Ce (cerium), Si (silicon) and other oxide catalysts. More specifically, for example, a catalyst having a composition of 80% by weight of Al ₂ O ₃ (aluminum oxide) and 20% by weight of NiO (nickel oxide) can be used.

The heat exchange step K3 is arranged before and after the heating step K2, and performs heat exchange between the device inlet exhaust gas flowing into the heating step K2 and the decomposed gas flowing out of the heating step K2.

In the heat exchange step K3, heat is exchanged between the high-temperature decomposed gas discharged from the second heating step K22 and the aforementioned low-temperature device inlet exhaust gas before being introduced into the second heating step K22. This heat exchange is performed using a heat exchanger or the like. And thereby, while the temperature of the decomposed gas is lowered, the temperature of the exhaust gas at the device inlet before being introduced into the first heating step K21 is raised. In addition, as described above, the added water evaporates and becomes water vapor.

The temperature of the decomposed gas after passing through the heat exchange step K3 drops to about 300°C to 500°C, and the temperature of the exhaust gas at the inlet of the device after passing through the heat exchange step K3 rises to about 200°C to 300°C.

Calcium fluoride generating step K4 is a step of reacting the acid component contained in the decomposed gas flowing out from the heat exchanging step K3 with a calcium salt to generate calcium fluoride.

In the calcium fluoride production step K4, HF which is an acid component contained in the decomposed gas undergoes an adsorption reaction 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. In addition, the shape of the calcium salt may be powdery, but it is preferably a pellet molded into a cylindrical shape, a spherical shape, or the like from the viewpoint of ease of handling. In this embodiment, for example, CaCO ₃ : Ca(OH) ₂ =50% by weight to 80% by weight: 20% by weight to 50% by weight, a mixture of Ca(OH) ₂ and CaCO ₃ is used. In this case, formability is good, and pulverization can be suppressed when pelletized. In addition, in the present embodiment, this mixture is used as a cylindrical pellet having a diameter of the bottom surface of about 3 mm and a height of about 8 mm.

As an adsorption reaction at this time, a case where CaCO ₃ and/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)

It can be known from the above formulas (5) to (6) that HF reacts with calcium salt to generate CaF ₂ (calcium fluoride (fluorite)), CO ₂ (carbon dioxide) and H ₂ O (water).

In addition, at this time, the decomposed gas is introduced from below the device performing the calcium fluoride generating step K4 (for example, a calcium fluoride generating device 232 described later with reference to FIG. 4 ), and is discharged from above. Then, while the decomposed gas flows from the bottom to the top of the apparatus performing the calcium fluoride production step K4, reactions between HF and calcium salts as exemplified by the above formulas (5) to (6) occur to produce calcium fluoride. In addition, in this embodiment, it is preferable that the calcium salt is supplied from the upper side of the apparatus performing the calcium fluoride production step K4, and the produced calcium fluoride is discharged from the lower side.

The post-processing step K5 is a step of removing the solid content generated in the calcium fluoride generating step K4 and discharging the exhaust gas discharged from the calcium fluoride generating step K4 to the outside of the apparatus. The post-processing step K5 includes a solid content removal step K51 and an exhaust step K52.

In the calcium fluoride production step K4, powder of the calcium salt or the like may be generated when the calcium salt is replaced or the like. Therefore, in post-processing process K5, first, as solid content removal process K51, the solid content which is powder is removed using a filter etc. first. Then, after the solid content is removed, exhaust gas is discharged to the outside as an exhaust step K52. The exhaust gas discharged from the calcium fluoride production step K4 is, for example, about 200°C, but the exhaust gas discharged from the post-processing step K5 is, for example, 100°C or lower.

Calcium fluoride produced by the above-described process can be used in optical materials such as telescopes, zoom lenses, television cameras, infrared lenses, prisms, analysis equipment, window materials, and fluorine sources.

<Explanation of the configuration of the perfluoride treatment equipment>

Next, the calcium fluoride manufacturing apparatus for realizing the above-mentioned calcium fluoride manufacturing method is demonstrated in more detail.

FIG. 3 is a diagram illustrating a schematic configuration of a calcium fluoride manufacturing apparatus 1 according to the present embodiment.

As shown in the figure, the manufacturing device 1 of calcium fluoride is equipped with: a pretreatment device 21, which pretreats the introduced device inlet exhaust gas (etching exhaust gas); The perfluoride contained in the pretreated device inlet exhaust gas in 21 is decomposed; the calcium fluoride generation device 23, which makes the decomposed gas contained in the decomposed gas after decomposing perfluoride in the perfluoride decomposition device 22 HF (hydrogen fluoride) reacts with calcium salts to form calcium fluoride. Furthermore, the exhaust gas at the inlet of the processing device is treated with each of the above-mentioned devices to make it harmless, and then it is discharged outside the calcium fluoride manufacturing device 1 as exhaust gas.

FIG. 4 is a diagram showing each device constituting the calcium fluoride manufacturing apparatus 1 of the present embodiment.

As illustrated in FIG. 3 , the calcium fluoride manufacturing apparatus 1 mainly includes a pretreatment apparatus 21 , a perfluoride decomposition apparatus 22 , and a calcium fluoride generation apparatus 23 . In addition, as shown in the figure, the calcium fluoride manufacturing apparatus 1 includes a control device 24 , and performs control of various devices, valves (not shown), and the like included in the calcium fluoride manufacturing apparatus 1 .

The preprocessing device 21 is a device for performing the preprocessing step K1. The pretreatment device 21 includes an inlet heater 211 for preheating exhaust gas at the device inlet, and a filter 212 for removing fine particles.

The inlet heater 211 evaporates fine water droplets (mist) contained in the device inlet exhaust gas by preheating the device inlet exhaust gas. The inlet heater 211 is provided with a heater 211 a around a pipe through which exhaust gas at the inlet of the device passes. Furthermore, when the device inlet exhaust gas passes through the inlet heater 211, it is heated by the heater 211a, and is preheated to the temperature at which the mist evaporates. That is, the inlet heater 211 is a device for performing the preheating step K11.

The filter 212 removes fine particles that are solid components contained in the device inlet exhaust gas. That is, the filter 212 is a device for performing the solid content removal step K13. The filter 212 is not particularly limited as long as it is a filter capable of trapping fine particles while allowing exhaust gas to pass through the device inlet. For example, a mesh filter or the like can be used.

In addition, in this embodiment, air is introduced between the inlet heater 211 and the filter 212 . That is, this air introduction site becomes a site where the air introduction process K12 is performed.

In addition, thereafter, the device inlet exhaust gas that has passed through the filter 212 enters the heat exchanger 231 once. Then, by heat exchange in the heat exchanger 231, the device inlet exhaust gas is heated. Then, water necessary for the reaction of decomposing perfluoride in the subsequent perfluoride decomposing device 22 at this time is added in a liquid state as described above. This water is heated in the heat exchanger 231 together with the device inlet exhaust gas as described above, and turns into gaseous water vapor.

The perfluoride decomposition device 22 is a device for performing the heating step K2. In addition, the perfluoride decomposition device 22 is an example of heating means that heats exhaust gas and water at the device inlet, and hydrolyzes perfluoride with a catalyst to generate a decomposition gas containing an acidic gas. Moreover, the perfluoride decomposition apparatus 22 is equipped with two heaters, the 1st heater 221 and the 2nd heater 222.

In the first heater 221, a heater 221a is disposed inside, and the heater 221a heats the exhaust gas at the inlet of the device and the water added to the heat exchanger 231 to become water vapor. That is, the first heater 221 is a device for performing the first heating step K21. In the present embodiment, the first heater 221 is a horizontal heater in which the flow path of exhaust gas at the device inlet is horizontal.

The second heater 222 introduces the device inlet exhaust gas from above, and first further heats the device inlet exhaust gas and water vapor by the heater 222a provided inside. Then, the further heated device inlet exhaust gas reacts with water (water vapor) mixed in the device inlet exhaust gas in the catalyst layer 222b arranged below the second heater 222, and is decomposed. The catalyst layer 222 b is made of, for example, a catalyst comprising the aforementioned composition of 80% by weight of Al ₂ O ₃ (aluminum oxide) and 20% by weight of NiO (nickel oxide). That is, the second heater 222 is a device for performing the second heating step K22.

The decomposition reaction at this time is, for example, the reactions of the above formulas (1) to (4), and a decomposed gas containing HF is generated.

The decomposed gas containing HF after decomposing the perfluoride by the second heater 222 is discharged from the lower side of the second heater 222 and sent to the next calcium fluoride production device 23 .

The calcium fluoride generating device 23 is a device that performs the heat exchange step K3, the calcium fluoride generating step K4, and the post-processing step K5. Calcium fluoride generation device 23 is provided with: heat exchanger 231 as an example of heat exchange unit, it is arranged in the front stage and rear stage of first heater 221 and second heater 222, before flowing into first heater 221 Heat exchange is performed between the exhaust gas at the device inlet and the decomposed gas flowing out from the second heater 222; the calcium fluoride generating device 232, which is an example of a calcium fluoride generating unit, makes the decomposed gas flowing out from the heat exchanger 231 The acid component contained in the gas reacts with the calcium salt to generate calcium fluoride; and the exhaust device 233 as an example of the exhaust gas discharge unit discharges the exhaust gas after the acid component is dry removed by the calcium fluoride generating device 232 .

In addition, the calcium fluoride generating device 23 further includes: a drug supply device 234 as an example of a drug supply unit, which supplies calcium salt as a drug for reacting with HF from above the calcium fluoride generating device 232; The chemical discharge device 235 of an example of the unit, it discharges the calcium fluoride that has produced from below the calcium fluoride production device 232; concentration of HF contained in the exhaust gas; and a powder trap 237 disposed between the HF concentration sensor 236 and the ejector 233 and removing solid components generated in the calcium fluoride generating device 232 .

The heat exchanger 231 performs heat exchange between the high-temperature decomposition gas discharged from the second heater 222 and the aforementioned low-temperature device inlet exhaust gas before being introduced into the first heater 221 . That is, the heat exchanger 231 is a device for performing the heat exchange step K3. By utilizing the heat exchanger 231 , the temperature of the decomposed gas is lowered, and the temperature of the exhaust gas at the device inlet before being introduced into the first heater 221 is raised. In addition, as described above, the water added to the heat exchanger 231 evaporates and becomes water vapor.

The heat exchanger 231 is not particularly limited, and a plate-type heat exchanger or a shell-and-tube heat exchanger can be used. In a plate-type heat exchanger, two plates are alternately arranged to form a flow path between the plates to discharge the inlet of the device. The heat exchanger for the heat exchange of gas and decomposition gas, the shell-and-tube heat exchanger is a shell (cylinder) and a plurality of tubes (heat transfer tubes) that respectively flow through the device inlet exhaust gas and decomposition gas and communicate with each other A heat exchanger for exchanging heat. In addition, it may be a double-tube heat exchanger, that is, a double-tube structure, in which high-temperature decomposition gas flows through the inner tube, and low-temperature device inlet exhaust flows through the outer tube. In addition, the exhaust gas at the inlet of the device and the decomposition gas can flow in opposite directions or in parallel. In this embodiment, a double-pipe heat exchanger is used, and the exhaust gas at the device inlet and the decomposition gas flow in opposite directions.

Calcium fluoride generating device 232 is filled with chemical layer 232a containing calcium salt, decomposes HF contained in the gas, and removes it dry by adsorption reaction with the calcium salt, and generates calcium fluoride (CaF ₂ ) . That is, the calcium fluoride production device 232 is a device for performing the calcium fluoride production step K4. The adsorption reaction at this time is the reaction exemplified in the above formulas (5) to (6), and HF reacts with calcium salt to generate CaF ₂ (calcium fluoride (fluorite)), CO ₂ (carbon dioxide) and _H2O (water).

In addition, the decomposed gas is introduced from below the calcium fluoride generating device 232 and is discharged from above the calcium fluoride generating device 232 . Then, while the decomposed gas flows from below to above the calcium fluoride generating device 232 , reactions between HF and calcium salts as exemplified by the above equations (5) to (6) occur to generate calcium fluoride. Then, it is necessary to supply new calcium salt into the calcium fluoride generating device 232 while discharging the generated calcium fluoride from the calcium fluoride generating device 232 .

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

In the present embodiment, the HF concentration is monitored by the HF concentration sensor 236, and 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) and the like provided in the drug discharge device 235 are opened and closed to discharge a predetermined amount of generated calcium fluoride. In addition, after the generated calcium fluoride is discharged, a rotary valve (not shown) and the like provided in the drug supply device 234 are opened and closed to supply the discharged new calcium salt. In this manner, the calcium salts in the drug discharge device 235 are sequentially replaced. Furthermore, in this series of steps, the information related to the concentration of HF transmitted from the HF concentration sensor 236 is obtained by the control device 24, and when the concentration of HF reaches, for example, 100 ppm, the information is set in the medicine supply device 234 and/or The opening and closing control of the rotary valve in the drug discharge device 235 is automatically performed.

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

A compressed air pipe for inflowing compressed air is connected to the discharger 233 , and the compressed air is sucked and exhausted by negative pressure generated by flowing the compressed air at high speed, and discharged together with the compressed air to the outside of the calcium fluoride manufacturing apparatus 1 . As a result, the temperature of the exhaust gas is further lowered, and the exhaust gas is discharged.

Here, the powder trap 237 and the ejector 233 are devices for performing the post-processing step K5.

<Description of the operation of the calcium fluoride manufacturing apparatus 1>

FIG. 5 is a flowchart illustrating the operation of the calcium fluoride manufacturing apparatus 1 .

Hereinafter, the operation of the calcium fluoride manufacturing apparatus 1 will be described using FIGS. 4 and 5 .

First, the device inlet exhaust gas is preheated by the inlet heater 211 of the pretreatment device 21 (step 101 ). As a result, the mist contained in the exhaust gas at the inlet of the device evaporates.

Next, air is introduced into the preheated device inlet exhaust gas (step 102 ), and fine particles are removed by the filter 212 of the pretreatment device 21 (step 103 ).

Then, the device inlet exhaust gas is heated by heat exchange using the heat exchanger 231 (step 104 ). In addition, water necessary for the decomposition reaction of the perfluorinated compound at this time was added.

The device inlet exhaust gas passing 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 required for decomposition of perfluorinated compounds (step 106 ). Then, when passing through the catalyst layer 222b of the second heater 222, the perfluoride is decomposed, and the device inlet exhaust gas becomes a decomposed gas containing HF (step 107).

The decomposed gas enters the heat exchanger 231 again, where it exchanges heat with the aforementioned device inlet exhaust gas (step 108 ).

Then, the decomposed gas reacts with the calcium salt in the calcium fluoride generating device 232 , HF is removed dry-type, and calcium fluoride is generated (step 109 ). In addition, at this time, the control device 24 judges whether or not the HF concentration acquired by the HF concentration sensor 236 has reached a predetermined value or more (step 110 ). Then, when the value exceeds the predetermined value (YES in step 110 ), the medicine discharge device 235 and the medicine supply device 234 are operated to replace the calcium salt (step 111 ). In addition, when it is less than a predetermined value (No in step 110 ), the calcium salt is not replaced, and the process proceeds to the next step 112 .

The exhaust gas from which HF has been dry-removed is discharged to the outside of the calcium fluoride production apparatus 1 by the discharger 233 after the solid content is removed by the powder trap 237 (step 113 ).

The calcium fluoride production method and the calcium fluoride production apparatus 1 described in detail above have the following features.

(i) Since perfluoride is decomposed by the catalyst layer 222b, a large amount of etching exhaust gas can be treated, and the running cost can be reduced.

(ii) HF contained in the decomposed gas is dry-removed by an adsorption reaction with calcium salts, thereby preventing HF-containing wastewater from being produced in contrast to the conventional method of dissolving HF in water to remove HF. _In addition, the CaF generated after the adsorption reaction is harmless and easy to handle. Furthermore, CaF ₂ is a valuable substance because it becomes a raw material for producing HF. That is, CaF ₂ , which is a valuable substance, can be produced from etching exhaust gas which is harmful to the global environment.

(iii) By using the heat exchanger 231 to perform heat exchange between the device inlet exhaust gas and the decomposed gas, energy utilization efficiency increases. In addition, compared with the conventional method of cooling the decomposed gas with water, no drainage is generated. Therefore, the waste water treatment step is unnecessary, and the running cost of the calcium fluoride manufacturing apparatus 1 can be reduced.

(iv) By incorporating the drug supply device 234 arranged above the calcium fluoride generating device 232 and the drug layer 232a having the drug discharge device 235 below, it is possible to use a simple system that only opens the valve and falls by gravity. Replacement of calcium salts. In addition, in this embodiment, the decomposed gas is introduced from below and exhausted from above, and the HF concentration sensor 236 is installed to monitor the concentration of HF, thereby judging the replacement time of the calcium salt. Accordingly, the upper layer of the drug layer 232a is not discharged, but only the reacted calcium salt in the lower layer is discharged, so that the purity of the generated calcium fluoride is improved.

(v) In addition, in this embodiment, the concentration of HF is monitored by the HF concentration sensor 236 , and the calcium salt is replaced when the concentration of HF reaches a predetermined concentration or more. Thereby, HF can be more reliably removed from the decomposed gas, and it is possible to suppress the discharge of HF to the outside of the calcium perfluoride manufacturing apparatus 1 .

In addition, in the above-mentioned example, the case of treating perfluoride contained in the etching exhaust gas discharged from a semiconductor manufacturing plant was described, but of course it is not limited thereto. For example, it may be a case of treating perfluoride contained in etching exhaust gas and/or cleaning exhaust gas discharged from a liquid crystal manufacturing plant or the like.

Claims (4)

1. a manufacture method for calcirm-fluoride, is characterized in that, possesses:

Heating process, this operation adds the gas that contains perfluoro-compound and the water that becomes steamHeat, and utilize catalyst hydrolysis perfluoro-compound to generate the decomposition gas that contains sour gas;

Heat exchange operation, the gas that contains perfluoro-compound of this operation before flowing into described heating processAnd carry out heat exchange between water and the decomposition gas from this heating process flows out; And

Calcirm-fluoride generates operation, and this operation makes institute in the decomposition gas from described heat exchange operation flows outThe sour composition containing reacts with calcium salt and generates calcirm-fluoride,

Generate in operation at described calcirm-fluoride, according to generate the acid after outflow operation from described calcirm-fluorideThe concentration of composition, supplies with the described calcium salt that is used for the ormal weight reacting with sour composition from top, and fromThe described calcirm-fluoride of the ormal weight after generating is discharged in below,

Described decomposition gas imports from below, and discharges from top.

2. the manufacture method of calcirm-fluoride according to claim 1, is characterized in that,

Also possess pretreatment process, this operation before described heating process to containing the gas of perfluoro-compoundBody carries out pretreatment;

Described pretreatment process possesses:

Preheating procedure, this operation heats the gas that contains perfluoro-compound, makes to contain perfluoro-compoundGas in the water evaporation of contained liquid; With

Solid constituent is removed operation, and this operation is from utilizing described preheating procedure to make the water of liquid vaporizedThe gas that contains perfluoro-compound is removed solid constituent.

3. the manufacture method of calcirm-fluoride according to claim 2, is characterized in that, also possesses skyConductance enters operation, and this operation is removed importing sky between operation at described preheating procedure and described solid constituentGas.

4. a manufacturing installation for calcirm-fluoride, is characterized in that, possesses:

Heating unit, it heats the gas that contains perfluoro-compound and the water that becomes steam,And utilize catalyst hydrolysis perfluoro-compound to generate the decomposition gas that contains sour gas;

Heat exchange unit, its flow into the gas that contains perfluoro-compound before described heating unit andBetween water and the decomposition gas from this heating unit flows out, carry out heat exchange;

Calcirm-fluoride generation unit, it makes in the decomposition gas from described heat exchange unit flows out containedAcid composition reacts with calcium salt and generates calcirm-fluoride;

Medicament feed unit, the concentration of the sour composition of its basis from described calcirm-fluoride generation unit flows out,Supply with the described calcium of the ormal weight for reacting with sour composition from the top of described calcirm-fluoride generation unitSalt; With

Medicament deliverying unit, the ormal weight that generated is discharged in its below from this calcirm-fluoride generation unitDescribed calcirm-fluoride,

The decomposition gas importing to described calcirm-fluoride generation unit, from the below of this calcirm-fluoride generation unitImport, and discharge from the top of this calcirm-fluoride generation unit.