TW201441158A - Calcium fluoride manufacturing method and calcium fluoride manufacturing device - Google Patents

Abstract

The present invention provides a calcium fluoride manufacturing method for inhibiting the generation of acid-containing drainage so as to enhance energy utilization efficiency. The calcium fluoride manufacturing method is characterized by comprising: a heating process (K2) for heating exhaust gas and water at the device inlet and using catalyst to hydrolyze perfluoride so as to generate acid-containing decomposed gas; a heat exchange process (K3) for performing the heat exchange between exhaust gas and water at the device inlet before flowing into the heating process (K2) and the decomposed gas flowing out of the heating process (K2); and a calcium fluoride generation process (K4) for generating calcium fluoride by reacting acid contained in the decomposed gas flowing out of the heat exchange process (K3) with calcium salt.

Description

Method for producing calcium fluoride and device for producing calcium fluoride

The present invention relates to a method for producing calcium fluoride which produces calcium fluoride using a perfluorinated material as a raw material, and the like.

For example, in a manufacturing process of a semiconductor device and a liquid crystal device, etching and cleaning are performed in order to form a fine pattern. At this time, the use of perfluorinated compounds is mostly the case. Further, perfluorinated materials are generally stable and harmless to the human body, and others are used, for example, in refrigerants for air conditioners.

However, most of these perfluorinated substances, once released into the atmosphere, will have a serious impact on the global environment. In other words, since it has a property of being stably present in the atmosphere for a long period of time and having a large global warming coefficient, it is one of the causes of global warming. Moreover, as described above, perfluorinated compounds are generally stable, and their effects are sustained for a long period of time.

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

Patent Document 1 discloses a method for decomposing a fluorine-containing compound, which is a gas containing a fluorine compound containing only fluorine as a halogen. The flow is contacted with a catalyst at a temperature of about 200 to 800 ° C in the presence of water vapor. The catalyst is an Al-containing catalyst composed of Al, Ni, Al, and Zn, Al, and Ti to convert fluorine in the gas stream. Hydrogen fluoride.

Further, Patent Document 2 discloses a perfluorinated material processing apparatus comprising: a perfluorination decomposition apparatus provided with a catalyst layer and supplied with a perfluorinated exhaust gas to decompose perfluorinated substances; The acid removal device removes the first reaction product generated by the reaction between the acidic substance contained in the exhaust gas discharged from the perfluorination decomposition apparatus and the Ca salt.

[prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-224926

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-246485

Among them, the decomposition gas generated by the hydrolysis of the perfluorinated compound sometimes contains an acid component such as HF. Therefore, it is desirable to effectively utilize the acid component without being discarded.

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

According to the present invention, there is provided a method for producing calcium fluoride, comprising: a heating process of heating a gas containing perfluorinated water and water, and hydrolyzing a perfluorinated product by a catalyst; a decomposition gas containing an acid gas; a heat exchange process is performed between the perfluorinated gas and water before flowing into the heating process and the decomposition gas flowing out of the heating process; and a calcium fluoride production process, The acid component contained in the decomposition gas discharged from the heat exchange process is reacted with a calcium salt to produce calcium fluoride.

Among them, it is preferred that in the calcium fluoride production process, the calcium salt is supplied from above and the calcium fluoride after the generation is discharged from below, and the decomposition gas system is introduced from below and discharged from above.

Further, it is preferable to further provide a pretreatment process for pretreating a gas containing perfluorinated acid before the heating process, and the pretreatment process includes: a preheating process for heating a gas containing perfluorinated acid to contain perfluorocarbon The water of the liquid contained in the gas of the compound is evaporated; and the solid component removal process removes the solid component from the perfluorinated gas after the liquid water is evaporated by the preheating process.

Further preferably, an air introduction process for introducing air between the preheating process and the solid component removing process is further provided.

Moreover, according to the present invention, there is provided a device for producing calcium fluoride, comprising: heating means for heating a gas containing perfluorinated matter and water, and hydrolyzing a perfluorinated product by a catalyst to produce a content a decomposition gas of an acid gas; a heat exchange means, which is a gas containing perfluorinated water flowing into the heating means and flowing out from the heating means The heat exchange between the decomposition gases is performed, and the calcium fluoride generation means reacts the calcium component contained in the decomposition gas after flowing out from the heat exchange means with the calcium salt to produce calcium fluoride.

Preferably, the method further includes: 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 discharging means for discharging fluorine generated from the lower portion of the calcium fluoride generating means Calcium; a decomposition gas system introduced into a calcium fluoride generating means is introduced from below the calcium fluoride generating means, and is discharged from above the calcium fluoride generating means.

By providing the heating process, the heat exchange process, and the calcium fluoride production process of the present invention, it is difficult to produce drainage containing an acid component, and a method for producing calcium fluoride having better energy utilization efficiency can be provided.

In the calcium fluoride production process, the calcium salt is supplied from above and the calcium fluoride after the generation is discharged from below, and the decomposition gas system is introduced from below and discharged from above, so that the exchange of calcium salts can be easily performed, and the purity can be made higher. Calcium fluoride.

According to the pretreatment process of the present invention, even if the perfluorinated gas contains moisture in addition to the perfluorinated product, clogging is less likely to occur in the solid component removal process.

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

By providing the heating means, the heat exchange means, and the calcium fluoride generating means of the present invention, the drainage containing the acid component is less likely to occur, and the apparatus for producing calcium fluoride having better energy utilization efficiency can be provided.

The method for supplying a drug is to supply a calcium salt from above the calcium fluoride generating means; and the means for discharging the drug, which discharges calcium fluoride generated from the lower portion of the calcium fluoride generating means; and the decomposition gas system to generate a calcium fluoride The lower portion is introduced and discharged from the upper portion of the calcium fluoride generating means, and the calcium salt can be exchanged by such a simple system in which gravity is dropped, and calcium fluoride having higher purity can be produced.

1‧‧‧Manufacture of calcium fluoride

21‧‧‧Pre-processing unit

22‧‧‧Perfluorinated decomposition unit

23‧‧‧calcium fluoride generating unit

24‧‧‧Control unit

211‧‧‧Inlet heater

212‧‧‧Filter

221‧‧‧1st heater

222‧‧‧2nd heater

231‧‧‧ heat exchanger

232‧‧‧calcium fluoride generating device

233‧‧‧Injector

234‧‧‧Pharmaceutical supply device

235‧‧‧Drug discharge device

236‧‧‧HF concentration detector

K1‧‧‧Pre-treatment process

K2‧‧‧heating process

K3‧‧‧Heat exchange process

K4‧‧‧ Calcium fluoride production process

K5‧‧‧ Post-treatment process

Fig. 1 is an explanatory view showing the overall flow of a method for producing calcium fluoride according to the present embodiment.

Fig. 2 is an explanatory diagram showing the relationship between the reaction temperature and the decomposition rate of perfluorinated compound.

Fig. 3 is an explanatory view showing a schematic configuration of a calcium fluoride production apparatus of the present embodiment.

Fig. 4 is a schematic view showing the respective devices constituting the apparatus for producing calcium fluoride of the present embodiment.

Fig. 5 is a flow chart for explaining the operation of the apparatus for producing calcium fluoride.

Hereinafter, embodiments of the present invention will be described in detail. In addition, The present invention is not limited to the following embodiments, and various modifications can be made without departing from the spirit and scope of the invention. Moreover, the drawings used are for explaining the present embodiment and do not represent actual sizes.

<Overall explanation of the method for producing calcium fluoride>

Fig. 1 is an explanatory view showing the 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 the present embodiment is composed of 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 according to the present embodiment, a perfluorinated compound is used as a raw material. The perfluorinated material is contained, for example, in an etched exhaust gas discharged from a semiconductor manufacturing facility that performs semiconductor manufacturing.

The semiconductor manufacturing equipment includes a dry etching (dry etching) device for etching an oxide film such as a P-Si etchant of a semiconductor, a ruthenium oxide (SiO ₂ ) such as an etched insulating film, and a etched semiconductor. A film etcher and a metal etcher for etching a metal film for wiring, the dry etching device is, for example, a reactive ion etching (RIE) device that performs etching using a reactive etching gas in a process chamber. .

The etching gases used in the P-Si etcher, the oxide film etcher, the metal etcher, and the like are different, but after the dry etching of each device, the exhaust gas contains various perfluorinated substances derived from the etching gas (hereinafter, also referred to as PFC (perfluorocompound)). The perfluorinated compound is exemplified by 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. Further, the perfluorinated exhaust gas, that is, the exhaust gas is etched, and the toxic gas such as chlorine (Cl ₂ ) gas is removed by a toxic gas detoxification device, and then discharged to the outside of the semiconductor manufacturing equipment by the collecting duct. The etching exhaust gas discharged to the outside of the semiconductor manufacturing equipment in the present embodiment is, for example, a gas containing 1% perfluorinated matter such as 99% N ₂ (nitrogen) gas as a carrier gas. In the present embodiment, the perfluorinated material used as the raw material contained in the etching exhaust gas is preferably 1% or less with respect to the etching exhaust gas. Further, the flow rate of the discharged etching exhaust gas is, for example, 3000 L/min to 3500 L/min.

The pretreatment process K1 is a process for pre-treating the above-described etching exhaust gas (device inlet exhaust). The pretreatment process K1 has a preheating process K11, an air introduction process K12, and a solid component removal process K13.

In the preheating process K11, the inlet venting of the apparatus is caused by preheating to evaporate minute water droplets (fogs) contained in the inlet venting of the apparatus. The heating is performed by a heater or the like, and the temperature of the inlet and outlet of the apparatus rises, for example, to 60 °C. Thereby, in the subsequent solid component removal process K13, it is possible to suppress clogging due to fog or the like by a filter or the like.

In the air introduction process K12, air is introduced into the exhaust gas of the device inlet. The heating process K2 performed after the pretreatment process K1 has a situation in which oxygen for suppressing the generation of carbon monoxide is required, so that air is mixed with the device inlet exhaust gas at this stage.

The solid component removal process K13 removes fine particles which are solid components contained in the exhaust gas of the apparatus by using a filter or the like. In the semiconductor manufacturing equipment, bismuth oxide and the like which are eliminated during the above dry etching are generated. particle. Further, since the fine particles are mixed into the inlet of the apparatus, the removal is performed in advance in this process.

Further, as will be described in detail later, the apparatus inlet exhaust system after the solid component removal process K13 in the present embodiment is transferred to the heat exchange process K3. Then, at the heat exchange process K3, the device inlet exhaust gas is heated by heat exchange. Further, at this time, water required for the reaction for decomposing the perfluorinated acid in the next heating process K2 is added in a liquid state. This water is heated in the heat exchange process K3 together with the inlet venting of the apparatus to become water vapor of the gas. Moreover, it is mixed with the device inlet exhaust. In the present embodiment, pure water is used as the water system. The amount of water added is an amount corresponding to the reaction formula described later, for example, 350 mL/min. Further, the water may be previously heated and added as steam.

The heating process K2 is a process in which the inlet vent gas and water of the apparatus are heated, and the perfluorinated product is hydrolyzed by a catalyst to generate a decomposition gas containing an acid gas. The heating process K2 includes a first heating process K21 and a second heating process K22.

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

In the second heating process K22, first, the device inlet exhaust gas and steam are further heated by a heater or the like. Thereby, the device inlet exhaust is heated, for example, to 750 °C. Moreover, the heated inlet and outlet of the device are reacted with water (water vapor) mixed with the inlet of the device by a predetermined catalyst. solution.

As a decomposition reaction at this time, a case where perfluorinated compounds are CF ₄ , CHF ₃ , C ₂ F ₆ and SF ₆ is taken as an example, and the following reaction formula is shown.

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)

From the above formulas (1) to (4), it is understood that the perfluorinated compound is converted into a decomposition gas containing an acid component HF (hydrogen fluoride) by a hydrolysis reaction. Further, HF in this case can be used as an acid gas contained in the decomposition gas.

Fig. 2 is an explanatory diagram showing the relationship between the reaction temperature and the decomposition rate of perfluorinated compound.

Here, as the perfluorinated compound contained in the etching exhaust gas, 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. Further, although it is not a perfluorinated product, CO in the components contained in the gas discharged from the semiconductor manufacturing equipment is also shown.

As shown in the figure, any component has a decomposition rate of approximately 100% at around 750 ° C so that it can react at a temperature of 750 ° C to substantially remove perfluorinated materials.

Further, as the catalyst, in the present embodiment, it is possible to use Zn (zinc), Ni (nickel), Ti (titanium), F (fluorine), Sn (tin), and Co in Al ₂ O ₃ (alumina). Cobalt), Zr (zirconium), Ce (铈), Si (矽) and other oxides. More specifically, for example, a composition of 80% by weight of Al ₂ O ₃ (alumina) and 20% by weight of NiO (nickel oxide) can be used.

The heat exchange process K3 is a process in which heat exchange is performed between the device inlet exhaust gas before the inflow of the heating process K2 and the decomposition gas flowing out from the heating process K2 in the front and rear stages of the heating process K2.

In the heat exchange process K3, heat exchange is performed between the pyrolysis gas discharged from the second heating process K22 and the inlet and exhaust gas of the low temperature device before being introduced into the first heating process K21. This heat exchange is performed by a heat exchanger or the like. Further, by this, the temperature of the decomposition gas is lowered and the temperature of the inlet of the apparatus before the introduction of the first heating process K21 is increased. Further, as described above, the added water evaporates into water vapor.

The temperature of the decomposition gas after the heat exchange process K3 is lowered to about 300 ° C to 500 ° C, and the temperature of the inlet of the device after the heat exchange process K3 is raised to about 200 ° C to 300 ° C.

The calcium fluoride production process K4 is a process in which an acid component contained in a decomposition gas discharged from the heat exchange process K3 reacts with a calcium salt to produce calcium fluoride.

In the calcium fluoride production process K4, the acid component HF contained in the decomposition gas generates calcium fluoride by adsorption reaction with a calcium salt. Here, as the calcium salt, CaCO ₃ (calcium carbonate), Ca(OH) ₂ (calcium hydroxide), CaO (calcium oxide), or the like can be used. Further, the shape of the calcium salt may be a powder, but it is preferably formed into a cylindrical shape or a spherical shape in terms of ease of handling. In the present embodiment, for example, a mixture of Ca(OH) ₂ and CaCO ₃ is used, and CaCO ₃ : Ca(OH) ₂ = 50% by mass to 80% by mass: 20% by mass to 50% by mass is used. In this case, the formability is good, and when it is used as a pellet, pulverization can be suppressed. Further, in the present embodiment, the mixture is used as a cylindrical particle having a diameter of about 3 mm on the bottom surface and a height of about 8 mm.

The adsorption reaction at this time is exemplified by the case where CaCO ₃ or Ca(OH) ₂ is used as the calcium salt, and the following reaction formula is shown.

CaCO ₃ +2HF→CaF ₂ +CO ₂ +H ₂ O...(5)

Ca(OH) ₂ +2HF→CaF ₂ +2H ₂ O...(6)

From the above formulas (5) to (6), it is understood that the HF system reacts with a calcium salt to produce CaF ₂ (calcium fluoride (fluorite)), CO ₂ (carbon dioxide), and H ₂ O (water).

At this time, the decomposition gas system is introduced from below the apparatus for performing the calcium fluoride production process K4 (for example, the calcium fluoride production device 232 described later in FIG. 4), and is discharged from above. Further, during the decomposition gas system flowing upward from the lower side of the apparatus for performing the calcium fluoride production process K4, the reaction of HF and the calcium salt exemplified in the above formulas (5) to (6) produces calcium fluoride. Further, in the present embodiment, it is preferable that the calcium salt is supplied from above the apparatus for performing the calcium fluoride generating process K4, and the calcium fluoride after the formation is discharged from below.

Post-treatment process K5 is removed in the calcium fluoride production process K4 The generated solid component, and the exhaust gas discharged from the calcium fluoride generating process K4 is discharged to the outside of the apparatus. The post-treatment process K5 has a solid component removal process K51 and an exhaust process K52.

In the calcium fluoride production process K4, a calcium salt powder or the like may be generated during the exchange of calcium salts or the like. Therefore, in the post-treatment process K5, the process K51 is first removed by a solid component, and the powder solid component is removed using a filter or the like. Then, after the solid component is removed, the exhaust gas is discharged to the outside by the exhaust gas process K52. The exhaust gas discharged from the calcium fluoride generating 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 lower.

The calcium fluoride produced by the above-described process can be used for optical materials such as telescopes, zoom lenses, television cameras, infrared lenses, enamels, analytical machines, window materials, and fluorine sources.

<Description of Configuration of Perfluorinated Processing Apparatus>

Next, a device for producing calcium fluoride for realizing the above-described method for producing calcium fluoride will be further described in detail.

Fig. 3 is an explanatory view showing a schematic configuration of a calcium fluoride production apparatus 1 of the present embodiment.

As shown in the figure, the calcium fluoride manufacturing apparatus 1 includes a pretreatment unit 21 for pre-treating the introduced device inlet exhaust (etching exhaust gas), and a perfluorination decomposition unit 22 for decomposing by the pre-processing unit 21 a perfluorinated product contained in the inlet vent of the device after pretreatment; and a calcium fluoride generating unit 23 which is decomposed by the perfluorination decomposition unit 22 The HF (hydrogen fluoride) contained in the decomposition gas reacts with the calcium salt to produce calcium fluoride. Then, the inlet and exhaust of the treatment device are detoxified by the respective units, and then discharged as exhaust gas to the outside of the manufacturing apparatus 1 of calcium fluoride.

Fig. 4 is a schematic view showing the respective devices constituting the calcium fluoride production apparatus 1 of the present embodiment.

As described in FIG. 3, the calcium fluoride production apparatus 1 mainly includes a pretreatment unit 21, a perfluorination decomposition unit 22, and a calcium fluoride generation unit 23. Moreover, as shown in the figure, the calcium fluoride manufacturing apparatus 1 is equipped with the control unit 24, and controls each apparatus, valve (not shown), etc. which are equipped with the calcium fluoride manufacturing apparatus 1.

The pre-processing unit 21 is a unit that performs the pre-processing process K1. The pre-processing unit 21 includes an inlet heater 211 that performs preheating of the inlet and outlet of the apparatus, and a filter 212 that removes fine particles.

The inlet heater 211 evaporates minute water droplets (foils) contained in the inlet vent of the apparatus by preheating the exhaust gas of the apparatus. The inlet heater 211 is provided with a heater 211a around the pipe through which the exhaust gas of the device passes. Further, the device inlet exhaust is heated by the heater 211a when passing through the inlet heater 211, and is preheated to a temperature at which the mist evaporates. That is, the inlet heater 211 serves as a means for performing the preheating process K11.

The filter 212 performs the removal of fine particles as a solid component contained in the exhaust gas of the apparatus. That is, the filter 212 is used as a means for performing the solid component removal process K13. The filter 212 is not particularly limited as long as it can exhaust the device inlet and collect fine particles, and for example, a mesh filter or the like can be used.

Further, in the present embodiment, air is introduced between the inlet heater 211 and the filter 212. That is, the air introduction portion serves as a portion where the air introduction process K12 is performed.

Then, the exhaust gas passing through the device inlet after the filter 212 enters the heat exchanger 231. Then, the device inlet exhaust gas is heated by heat exchange of the heat exchanger 231. As described above, at this time, water required for the reaction for decomposing the perfluorinated compound in the next perfluorination unit 22 is added in a liquid state. This water system is heated as a gas vapor of the gas in the heat exchanger 231 together with the inlet and exhaust of the apparatus as described above.

The perfluorination decomposition unit 22 is a unit that performs the heating process K2. Further, the perfluorination unit 22 is an example of a heating means for generating a decomposition gas containing an acid gas by heating the inlet vent gas and water of the apparatus and hydrolyzing the perfluorinated product by a catalyst. Further, the perfluorination unit 22 includes two heaters of the first heater 221 and the second heater 222.

The first heater 221 is internally provided with a heater 221a, and the heater 221a heats the inlet of the apparatus and the water which is added by the heat exchanger 231 to become steam. That is, the first heater 221 is a device that performs the first heating process K21. In the present embodiment, the first heater 221 forms a horizontal heater in the horizontal direction in the flow path of the inlet and outlet of the device.

The second heater 222 introduces the exhaust gas from the inlet of the apparatus, and firstly heats the inlet and the steam of the apparatus by the heater 222a provided therein. Further, the heated device inlet exhaust gas is decomposed by the catalyst layer 222b disposed under the second heater 222 and reacted with water (water vapor) mixed at the inlet of the device. The catalyst layer 222b is composed of, for example, a catalyst composed of 80% by mass of the above Al ₂ O ₃ (alumina) and 20% by mass of NiO (nickel oxide). That is, the second heater 222 is used as a device for performing the second heating process K22.

As the decomposition reaction at this time, for example, the reaction of the above formula (1) to (4) is formed, and a decomposition gas containing HF is generated.

The decomposition gas system containing HF after decomposing the perfluorinated product by the second heater 222 is discharged from the lower side of the second heater 222 and sent to the next calcium fluoride generating unit 23.

The calcium fluoride generating 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 includes a heat exchanger 231 which is disposed in the front stage and the rear stage of the first heater 221 and the second heater 222, and the apparatus inlet exhaust gas before flowing into the first heater 221 and from the second An example of a heat exchange means for exchanging heat between the decomposition gases after the heater 222 flows out; the calcium fluoride generator 232 reacts with the calcium salt in the decomposition gas contained in the decomposition gas from the heat exchanger 231. An example of the means for generating calcium fluoride to produce calcium fluoride; and the ejector 233 is an example of an exhaust gas discharge means for discharging the exhaust gas after the acid component is dry-removed by the calcium fluoride generating means 232.

Further, the calcium fluoride generating unit 23 further includes a drug supply device 234, which is an example of a drug supply means for supplying a calcium salt of a drug for reacting with HF from above the calcium fluoride generating device 232, and a drug discharging device 235 The fluorine generated from the lower portion of the calcium fluoride generating device 232 is discharged An example of the means for detecting the release of calcium by the calcium; the HF concentration detector 236 is an example of a concentration detecting means for detecting the concentration of HF contained in the exhaust gas flowing out of the calcium fluoride generating means 232; and a powder trap 237 is disposed between the HF concentration detector 236 and the ejector 233 to remove solid components generated by the calcium fluoride generating device 232.

The heat exchanger 231 exchanges heat between the pyrolysis gas discharged from the second heater 222 and the inlet and exhaust of the low temperature device before being introduced into the first heater 221. That is, the heat exchanger 231 is a device that performs the heat exchange process K3. The temperature of the decomposition gas is lowered by the heat exchanger 231, and the temperature of the inlet of the apparatus before the introduction of the first heater 221 is raised. Further, as described above, the water added to the heat exchanger 231 evaporates into water vapor.

The heat exchanger 231 is not particularly limited, and a plate type heat exchanger in which two sheets are alternately arranged and a flow path is formed between the plates to exchange heat between the device inlet exhaust gas and the decomposition gas can be used; Among the casing (cylinder) and the plurality of branch pipe members (heat transfer pipes), a casing and a tube-type heat exchanger that allow the device inlet exhaust gas and the decomposition gas to pass through, respectively, exchange heat with each other. Further, it may be a double tube heat exchanger, which is a double tube structure in which a high-temperature decomposition gas flows through the inner tube, and a low-temperature device inlet exhaust gas flows through the outer tube. Further, the device inlet exhaust gas and the decomposition gas may flow in opposite directions or may flow in parallel. In the present embodiment, the double inlet heat exchanger is used to make the device inlet exhaust gas and the decomposition gas flow in opposite directions.

The calcium fluoride generating device 232 is internally filled with a chemical layer 232a composed of a calcium salt, and the HF contained in the decomposition gas is dry-removed in a manner of performing adsorption reaction with the calcium salt, and calcium fluoride (CaF ₂ ) is produced. . That is, the calcium fluoride generating device 232 is used as a device for performing the calcium fluoride generating process K4. The adsorption reaction at this time is a reaction exemplified in the above formula (5) to (6), and the HF system reacts with a calcium salt to produce CaF ₂ (calcium fluoride (fluorite)), CO ₂ (carbon dioxide), and H _{2 .} O (water).

Further, the decomposition gas system is introduced from below the calcium fluoride generating device 232 and discharged from above the calcium fluoride generating device 232. Further, during the period in which the decomposition gas system flows upward from the lower side of the calcium fluoride generating device 232, calcium fluoride is generated by the reaction of HF and the calcium salt exemplified in the above formulas (5) to (6). Moreover, the calcium fluoride produced must be discharged from the calcium fluoride generating device 232 and a new calcium salt is supplied into the calcium fluoride generating device 232.

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

In the present embodiment, the concentration of HF is monitored by the HF concentration detector 236, and when the concentration of HF reaches, for example, 100 ppm, it is determined that the calcium salt is replaced. Further, opening and closing of a rotary valve (not shown) or the like provided in the medicine discharge device 235 is performed, and a predetermined amount of calcium fluoride which has been generated is discharged. Moreover, after the calcium fluoride which has already been produced is discharged, opening and closing of a rotary valve (not shown) or the like provided in the drug supply device 234 is performed, and a new amount of calcium salt is dispensed. In this manner, the calcium salt in the drug discharge device 235 is sequentially changed. Further, the control unit 24 obtains information on the HF concentration sent from the HF concentration detector 236, and the HF concentration reaches, for example, 100 ppm. At this time, the series of programs are automatically performed so as to perform opening and closing control of the rotary valve provided in the medicine supply device 234 or the medicine discharge device 235.

The powder trap 237 is provided to remove the powder of the calcium salt generated by the calcium fluoride generating device 232 or the like in the case of replacement of the calcium salt. As the powder trap 237, a metal mesh filter or the like can be used.

A compressed air pipe through which compressed air flows in is connected to the ejector 233, and the exhaust gas is sucked by the negative pressure generated by the compressed air at a high speed, and is discharged together with the compressed air to the outside of the manufacturing apparatus 1 of the perfluoromonic acid. Thereby, the exhaust gas is further lowered in temperature and discharged.

Here, the powder trap 237 and the ejector 233 are used as means for performing the post-treatment process K5.

<Description of Operation of Calcium Fluoride Manufacturing Apparatus 1>

Fig. 5 is a flow chart for explaining the operation of the apparatus 1 for producing calcium fluoride.

Hereinafter, the operation of the apparatus for producing calcium fluoride 1 will be described using Figs. 4 and 5 .

First, the device inlet exhaust gas passes through the inlet heater 211 of the pre-processing unit 21 and is preheated (step 101). Thereby, the mist contained in the exhaust gas of the apparatus inlet is evaporated.

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

Moreover, the device inlet exhaust is heated by heat exchange by the heat exchanger 231 (step 104). Also, at this time, the addition of perfluorinated components Solve the water needed for the reaction.

The exhaust gas passing through the apparatus inlet of 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 the perfluorinated product (step 106). Further, when the catalyst layer 222b of the second heater 222 is decomposed, the perfluorination is decomposed, and the device inlet exhaust gas becomes a decomposition gas containing HF (step 107).

The decomposed gas enters the heat exchanger 231 again, and performs heat exchange with the inlet exhaust of the apparatus (step 108).

Further, the decomposition gas system is reacted with the calcium salt in the calcium fluoride generating device 232, and the HF is dry-removed and calcium fluoride is produced (step 109). Moreover, at this time, the control unit 24 determines whether or not the HF concentration acquired by the HF concentration detector 236 has reached a predetermined value or more (step 110). When the predetermined value or more is reached (Yes in step 110), the medicine discharge device 235 and the medicine supply device 234 are operated to replace the calcium salt (step 111). Moreover, when the predetermined value is not reached (No in Step 110), the replacement of the calcium salt is not performed, and the process proceeds to the next step 112.

The exhaust gas after the HF dry removal is removed by the powder trap 237 (step 112), and is discharged to the outside of the calcium fluoride production apparatus 1 by the ejector 233 (step 113).

The method for producing calcium fluoride described above and the apparatus for producing calcium fluoride 1 have the following features.

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

(ii) A method of removing HF by dissolving HF in water to remove HF by a method in which HF and a calcium salt contained in the decomposition gas are reacted by dry reaction, and HF-containing drainage is not generated. Further, CaF ₂ produced after the adsorption reaction is harmless and easy to handle. Further, since CaF ₂ is a raw material for producing HF, it is a valuable substance. That is, the valuable substance CaF ₂ can be produced from an etched exhaust gas which is harmful to the global environment.

(iii) The energy utilization efficiency can be improved by heat exchange between the device inlet exhaust gas and the decomposition gas by the heat exchanger 231. Further, no drainage is generated as compared with the conventional method in which the decomposition gas is cooled by water. Therefore, the operation cost of the manufacturing apparatus 1 of calcium fluoride can be reduced without requiring a drain treatment step.

(iv) The group is provided with the drug supply device 234 provided above the calcium fluoride generating device 232 and the drug layer 232a having the drug discharging device 235 underneath, and can be dropped by gravity as long as the valve is opened, and the system can be carried out by such a simple system. Replacement of calcium salts. In the present embodiment, the decomposition gas is introduced from below, and is exhausted from above, and the HF concentration detector 236 is provided to determine the replacement period of the calcium salt so as to monitor the HF concentration. Thereby, 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 calcium fluoride produced can be improved.

(v) In the present embodiment, the HF concentration detector 236 monitors the concentration of HF, and when the concentration of HF reaches a predetermined concentration or higher, the calcium salt is exchanged. Thereby, HF can be more reliably removed from the decomposition gas, and it is possible to suppress the HF from being discharged to the outside of the manufacturing apparatus 1 of calcium fluoride.

Moreover, the above examples illustrate the discharge at a semiconductor manufacturing plant. The treatment of the perfluorination contained in the exhaust gas is etched, but it is of course not limited thereto. For example, it may be a treatment of etched exhaust gas discharged from a liquid crystal manufacturing plant or the like, or a perfluorinated product contained in the exhaust gas.

K1‧‧‧Pre-treatment process

K11‧‧‧Preheating process

K12‧‧‧Air introduction process

K13‧‧‧Solid component removal process

K2‧‧‧heating process

K21‧‧‧1st heating process

K22‧‧‧2nd heating process

K3‧‧‧Heat exchange process

K4‧‧‧ Calcium fluoride production process

K5‧‧‧ Post-treatment process

K51‧‧‧Solid component removal process

K52‧‧‧Exhaust process

Claims (6)

A method for producing calcium fluoride, comprising: a heating process of heating a gas containing perfluorinated water and water, and hydrolyzing a perfluorinated product by a catalyst to generate a decomposition gas containing an acid gas; The exchange process is performed by performing heat exchange between the perfluorinated gas and water before flowing into the heating process and the decomposition gas flowing out from the heating process; and the calcium fluoride generating process is performed from the heat exchange process described above. The acid component contained in the decomposition gas after the outflow reacts with the calcium salt to produce calcium fluoride. The method for producing calcium fluoride according to the first aspect of the invention, wherein the calcium fluoride is produced from the above, and the calcium salt is supplied from above, and the calcium fluoride after the generation is discharged from the lower side, and the decomposition gas system is introduced from below. And discharged from the top. The method for producing calcium fluoride according to claim 1 or 2, further comprising a pretreatment process for pretreating a gas containing perfluorinated acid before the heating process, wherein the pretreatment process comprises: a preheating process Heating a gas containing perfluorinated material to evaporate water of a liquid contained in a perfluorinated gas; and a solid component removing process for purifying the liquid from the liquid by evaporation of the liquid by the preheating process The gas of the compound removes the solid component. A method for producing calcium fluoride according to item 3 of the patent application, Further, an air introduction process for introducing air between the preheating process and the solid component removing process is further provided. A device for producing calcium fluoride, comprising: a heating means for heating a gas containing perfluorinated matter and water, and hydrolyzing a perfluorinated product by a catalyst to generate a decomposition gas containing an acid gas; The exchange means is a heat exchange between a perfluorinated gas and water which flows before the heating means and a decomposition gas which flows out from the heating means, and a calcium fluoride generating means for the heat exchange means The acid component contained in the decomposition gas after the effluent reacts with the calcium salt to produce calcium fluoride. The apparatus for producing calcium fluoride according to the fifth aspect of the invention, further 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 discharging means The calcium fluoride generated from the lower portion of the calcium fluoride generating means is discharged, and the decomposition gas introduced into the calcium fluoride generating means is introduced from below the calcium fluoride generating means, and from above the calcium fluoride generating means discharge.