JP2010058063A - Decomposition treatment method, decomposition treatment agent, and decomposition treatment device of fluoride gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a decomposition treatment method and device of a fluoride gas, which can lower a decomposition treatment temperature of the fluoride gas. <P>SOLUTION: A reaction chamber 14 in which a decomposition treatment agent A consisting of calcium oxide, silicon, and an alkali metal halide is chambered is provided in a reaction container 10. A gas to be treated containing fluoride is supplied to the reaction chamber 14 and at the same time the fluoride is treated by decomposition on heating the reaction chamber to a predetermined temperature by an electric furnace 17 installed around the reaction container to discharge a treated gas. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a decomposition treatment method, a decomposition treatment agent, and a decomposition treatment apparatus for decomposing fluoride gas.

  Fluoride gas is widely used in industry, but some of them are pointed out as having a serious impact on the global environment. For example, it is known that perfluorocarbon (PFC) used as an etching gas or a cleaning gas in a semiconductor manufacturing process exhibits a high global warming potential and causes global warming as a greenhouse gas. Therefore, there is a trend in the semiconductor industry to reduce these PFC emissions, and development of a technology for decomposing PFC is required.

Conventionally, as a method for decomposing fluoride gas, a combustion method in which pyrolysis is performed in a baking furnace and a plasma method in which decomposition is performed by plasma are known. In addition, a processing technique as disclosed in Patent Document 1 is also known. The processing technique disclosed in Patent Document 1 is to decompose fluoride gas by bringing limestone or dolomite as a fluoride gas decomposition treatment agent into contact with fluoride gas at a high temperature.
JP 2001-79344 A

  However, the conventional decomposition methods have a problem that all methods must be processed at a high temperature. Specifically, a high temperature state of about 1300 ° C. in the combustion method, about 6000 ° C. in the plasma method, and 800 to 1400 ° C. is required in the method of Patent Document 1. For this reason, a processing apparatus capable of withstanding a high temperature state is required, resulting in an increase in processing cost.

  The present invention has been made in view of such conventional circumstances, and an object of the present invention is to provide a fluoride gas decomposition treatment method, a decomposition treatment agent, and a decomposition treatment apparatus that can lower the decomposition treatment temperature of fluoride gas. It is to provide.

  In order to achieve the above object, the method for decomposing a fluoride gas according to claim 1 is characterized in that the fluoride gas is heat-treated in the presence of calcium oxide, silicon and an alkali metal halide.

The invention of claim 2 is characterized in that, in the invention of claim 1, the silicon is blended in an amount of 0.7 to 3.0 molar equivalents relative to the calcium oxide.
The decomposition treatment agent for fluoride gas according to claim 3 is characterized by containing calcium oxide, silicon and an alkali metal halide.

The invention described in claim 4 is characterized in that, in the invention described in claim 3, the silicon is blended in an amount of 0.7 to 3.0 molar equivalents relative to the calcium oxide.
The apparatus for decomposing a fluoride gas according to claim 5 has a reaction chamber inside, an air supply port for sucking the fluoride gas into the reaction chamber, and a processing gas processed in the reaction chamber to the outside. An apparatus for decomposing fluoride gas comprising a reaction vessel provided with an exhaust port for discharging and a heating unit for heating the reaction chamber, wherein the reaction chamber contains calcium oxide, silicon and an alkali metal halide. In the decomposition treatment of the fluoride gas, the heating unit lowers the vapor pressure of the alkali metal generated from the alkali metal halide in the region on the exhaust port side in the reaction chamber. The reaction chamber can be heated while forming a low temperature zone for the purpose.

  The invention according to claim 6 is the invention according to claim 5, further comprising switching means for changing a position of the exhaust port in the reaction vessel, and as the position of the exhaust port is changed by the switching means, A heating part changes the formation position of the said low temperature zone to the area | region by the side of the said exhaust port after a position change.

  A seventh aspect of the invention is characterized in that, in the invention of the fifth or sixth aspect, a porous inorganic adsorbent is loaded in a portion on the exhaust port side in the reaction chamber.

  According to the fluoride gas decomposition treatment method, decomposition treatment agent, and decomposition treatment apparatus of the present invention, the fluoride gas decomposition treatment temperature can be lowered.

Hereinafter, embodiments of the decomposition treatment agent for fluoride gas embodying the present invention will be described in detail.
The decomposition treatment agent for fluoride gas of this embodiment contains calcium oxide, silicon, and alkali metal halide. Examples of the fluoride gas decomposed by the decomposition agent include chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), hydrofluorocarbon (HFC), perfluorocarbon (PFC) and other fluorocarbons, sulfur hexafluoride, Nitrogen trifluoride is mentioned.

  The alkali metal halide contained in the decomposition treatment agent is a salt composed of Group 1 alkali metal and Group 17 halogen in the periodic table. Examples of the alkali metal halide include lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, lithium chloride, sodium chloride, potassium chloride, and cesium chloride.

  Among alkali metal halides, potassium fluoride, cesium fluoride, potassium chloride, and cesium chloride are preferably used from the viewpoint of improving the decomposition rate with respect to fluoride gas under relatively low temperature conditions (about 600 to 800 ° C.). . Moreover, these alkali metal halides may be blended alone or in combination of two or more in the decomposition treatment agent.

  The mixing ratio of calcium oxide, silicon, and alkali metal halide contained in the decomposition treatment agent is, as a molar ratio, calcium oxide: silicon: alkali metal halide = 1: 0.5-4: 1-4. preferable. In particular, from the viewpoint of improving the duration of decomposition action on fluoride gas (inhibiting degradation of the decomposition treatment agent), it is preferable that silicon is blended in an amount of 0.7 to 3.0 molar equivalents relative to calcium oxide. More preferably, 0 to 2.0 molar equivalents are blended. In addition, in the range which does not impair the objective of this invention, other components, such as magnesium and chlorine, may be mix | blended in the decomposition processing agent.

  The shape of the decomposition treatment agent is not particularly limited, but a shape having a large surface area is preferable in order to increase the air permeability and the contact efficiency with the fluoride gas. For example, powder form, granular form (granular form, spherical form, cylindrical form), etc. are mentioned.

Next, a method for decomposing fluoride gas using the decomposition agent of the present embodiment will be described.
The decomposition treatment of fluoride gas is performed by heat-treating the fluoride gas in the presence of the decomposition treatment agent. Specifically, it is carried out by bringing the fluoride gas into contact with calcium oxide, silicon and alkali metal halide contained in the decomposition treatment agent under a high temperature condition. The temperature during the heat treatment is preferably in the range of 600 to 850 ° C, more preferably in the range of 700 to 800 ° C. For example, carbon tetrafluoride, which is considered to be most difficult to decompose among fluoride gases, can be almost completely decomposed at 750 ° C. When the temperature during the heat treatment is less than 600 ° C., it is difficult to sufficiently decompose the fluoride gas.

  Further, the fluoride gas to be decomposed may be in the state of fluoride gas alone, or may be in a state of being mixed in a base gas such as nitrogen, argon, oxygen, air, helium. At that time, the concentration of the fluoride gas is preferably 5.0% by volume or less, and more preferably 3.0% by volume or less from the viewpoint of processing efficiency. The contact time between the fluoride gas and the decomposition treatment agent varies depending on the decomposition treatment temperature, the type and concentration of the fluoride gas, etc., but is preferably 1 to 8 seconds, more preferably 2 to 5 seconds. preferable.

The overall reaction equation and elementary reaction equation of the decomposition reaction of fluoride gas that proceeds by bringing fluoride gas into contact with the decomposition treatment agent of the present embodiment are shown below (general equations (1) to (4)). Here, potassium fluoride (KF) is used as the alkali metal halide contained in the decomposition treatment agent, and carbon tetrafluoride (CF ₄ ) is used as the fluoride gas.

[Overall reaction formula]
4KF (s) + Si (s) + 2CaO (s) + CF ₄ (g)
→ 4KF (s) + 2CaF ₂ (s) + SiO ₂ (s) + C (s) (1)
[Element reaction formula]
4KF (s) + Si (s) → 4K (g) + SiF ₄ (g) (2)
SiF ₄ (g) + 2CaO (s) → 2CaF ₂ (s) + SiO ₂ (s) (3)
4K (g) + CF ₄ (g) → 4KF (s) + C (s) (4)
In the above reaction formulas, (s) indicates a solid and (g) indicates a gas.

As shown in the above reaction formulas, first, potassium fluoride (KF), which is an alkali metal halide, reacts with silicon (Si) to generate highly active potassium gas (K). Then, a potassium (K) gas generated, by a fluoride gas carbon tetrafluoride (CF ₄₎ is reacted, carbon tetrafluoride (CF ₄₎ is potassium fluoride (KF) and carbon (C ). Silicon tetrafluoride (SiF ₄ ) gas generated with the generation of potassium (K) gas reacts with calcium oxide (CaO), so that calcium difluoride (CaF ₂ ) and silicon dioxide (SiO _2). ). Then, potassium fluoride generated during decomposition process (KF) generates a silicon (Si) reacts again potassium gas (K) remaining, once again, decomposed carbon tetrafluoride (CF _4). Note that potassium fluoride (KF), calcium difluoride (CaF ₂ ), silicon dioxide (SiO ₂ ), and carbon (C), which are the final decomposition products, are all produced as solids.

Next, a decomposition apparatus 1 for decomposing fluoride gas using the decomposition method of the present embodiment will be described with reference to FIG.
The reaction vessel 10 is formed of a cylindrical tube portion 11 made of a material having corrosion resistance and heat resistance (for example, a metal material), and also made of a material having corrosion resistance and heat resistance, and closes both ends of the tube portion 11. It is comprised from a pair of cover parts 12 and 13. The lid parts 12 and 13 are respectively formed with a first supply / exhaust port 12a and a second supply / exhaust port 13a communicating with the reaction chamber 14 formed in the reaction vessel 10.

  A temperature sensor 15 for measuring the temperature in the reaction chamber 14 is disposed at both ends of the reaction chamber 14 in the reaction vessel 10, and a cartridge 16 filled with the decomposition treatment agent A in the center thereof. Is housed. The cartridge 16 is a hollow cylindrical member, and a plurality of holes (not shown) are formed on its wall surface to allow gas to pass inside and outside. The cartridge 16 accommodated in the reaction chamber is replaceable, and is configured so that it can be replaced with a new cartridge 16 when the ability to decompose fluoride gas decreases with use of the apparatus.

  An electric furnace 17 as a heating unit is disposed around the reaction vessel 10. The electric furnace 17 is configured to be heated in the axial direction of the reaction vessel 10 while locally changing the temperature in the reaction chamber 14. Specifically, while the electric furnace 17 is heating the reaction chamber 14 to a predetermined temperature, either the first supply / exhaust port 12a side or the second supply / exhaust port 13a side has a temperature higher than the predetermined temperature. It can heat so that it may become a low state (low-temperature state). Hereinafter, a local low temperature region formed in the reaction chamber 14 will be described as a low temperature zone T. The temperature sensor 15 and the electric furnace 17 are connected to a control unit (not shown), and the temperature state in the reaction chamber 14 is controlled by the control unit.

  Further, the first supply / exhaust port 12a and the second supply / exhaust port 13a formed in each of the lid portions 12 and 13 are processed through a switching unit 21 and a gas generation unit 22 which is a fluoride gas supply source and processed. Is connected to a discharge unit 23 for discharging the treated gas. The switching unit 21 is configured to be able to switch the connection state between the gas generation unit 22 and the discharge unit 23 and the first supply / discharge port 12a and the second supply / discharge port 13a. That is, a state where the gas generator 22 and the first supply / exhaust port 12a are connected and the discharge unit 23 and the second supply / exhaust port 13a are connected (see FIG. 1A), and the gas generator 22 and the second It is possible to switch the state (refer FIG.1 (b)) which connects the discharge part 23 and the 1st supply / exhaust port 12a while connecting the supply / exhaust port 13a.

  In the connection state shown in FIG. 1A, the first supply / discharge port 12a functions as an air supply port, and the second supply / discharge port 13a functions as an exhaust port. In the connection state shown in FIG. 1B, the first supply / exhaust port 12a functions as an exhaust port, and the second supply / exhaust port 13a functions as an air supply port. The switching unit 21 is connected to a control unit (not shown), and the control unit controls switching of the connection state between the gas generation unit 22 and the discharge unit 23 and the first supply / discharge port 12a and the second supply / discharge port 13a. Has been. In the present embodiment, the switching unit 21 functions as a switching unit.

  In addition, the decomposition processing apparatus 1 of the present embodiment is provided with a switching control unit that switches the heating state of the electric furnace 17 and the connection state of the switching unit 21 according to the temperature state in the reaction chamber 14. The switching control means includes a temperature sensor 15, an electric furnace 17, a switching unit 21, and a control unit (not shown). When the temperature of the low temperature zone T formed in the reaction chamber 14 exceeds a preset specified temperature, the control unit determines the connection state of the switching unit 21 when the gas generation unit 22 and the discharge unit 23 The connection state is switched from the state connected to the first supply / exhaust port 12a and the second supply / exhaust port 13a to the state connected to the second supply / exhaust port 13a and the first supply / exhaust port 12a, or vice versa. The switching unit 21 is controlled. At the same time, the control unit changes the formation position of the low temperature zone T from the first supply / exhaust port 12a side to the second supply / exhaust port 13a side or from the second supply / exhaust port 13a side to the first supply / exhaust port 12a side. The electric furnace 17 is controlled.

Next, the aspect which decomposes | disassembles fluoride gas using the decomposition processing apparatus 1 of this embodiment is demonstrated.
When using the decomposition processing apparatus 1 of the present embodiment, first, the interior of the reaction chamber 14 is heated to 600 to 850 ° C. by the electric furnace 17. At this time, as shown in FIG. 1A, the electric furnace 17 is controlled so that a low temperature zone T is formed in a region on the second supply / exhaust port 13 a side in the reaction chamber 14. The set temperature of the low temperature zone T varies depending on the type of alkali metal halide contained in the decomposition treatment agent, the pressure state in the reaction chamber 14, etc., but the vapor pressure of the alkali metal generated from the decomposition treatment agent is lowered. Temperature is set. For example, when the alkali metal generated from the decomposition treatment agent is lithium, the low temperature zone T is set to 500 to 1100 degrees, preferably 600 to 900 degrees. When the alkali metal generated from the decomposition treatment agent is sodium, the low temperature zone T is set to 300 to 800 degrees, preferably 400 to 600 degrees. When the alkali metal generated from the decomposition treatment agent is potassium, the low temperature zone T is set to 200 to 700 degrees, preferably 300 to 500 degrees. When the alkali metal generated from the decomposition treatment agent is cesium, the low temperature zone T is set to 100 to 600 degrees, preferably 200 to 400 degrees.

  After the inside of the reaction chamber 14 is heated to the set temperature, the control unit connects the first supply / discharge port 12a and the gas generation unit 22 and connects the second supply / discharge port 13a and the discharge unit 23. The switching unit 21 is controlled. That is, the first supply / discharge port 12a functions as an air supply port, and the second supply / discharge port 13a functions as an exhaust port.

  Then, the supply of fluoride gas from the gas generator 22 into the reaction chamber 14 is started. At that time, the fluorine gas is supplied into the reaction chamber 14 at a flow rate of about 1 to 8 seconds, preferably about 2 to 5 seconds. In the reaction chamber 14, the supplied fluoride gas and the decomposition treatment agent A in the cartridge 16 come into contact with each other, so that the fluoride gas is decomposed. The decomposed processing gas is quickly discharged to the discharge portion 23 through the second supply / discharge port 13a.

  At this time, in the reaction chamber 14, the alkali metal gas generated from the decomposition treatment agent A flows toward the downstream side, that is, the second supply / exhaust port 13 a functioning as an exhaust port, with the flow of the fluoride gas. To go. The alkali metal gas flowing into the second supply / exhaust port 13a is cooled in a low temperature zone T formed on the second supply / exhaust port 13a, becomes liquid or solid, and is collected in the reaction chamber 14. Is done. Thereby, it is suppressed that alkali metal gas flows out of reaction chamber 14 with processing gas.

  In addition, when a predetermined time has elapsed after the supply of the fluoride gas into the reaction chamber 14 is started, the temperature of the low temperature zone T rises due to a large amount of high-temperature alkali metal gas flowing into the low temperature zone T side. . And when the temperature of the low temperature zone T exceeds the preset specified temperature, the switching control means is operated to switch the heating state of the electric furnace 17 and the connection state of the switching unit 21 (from the state of FIG. 1A). FIG. 1 (b) state).

  Specifically, as shown in FIG. 1B, the control unit connects the second supply / discharge port 13a and the gas generation unit 22, and connects the first supply / discharge port 12a and the discharge unit 23. The switching unit 21 is controlled to do so. That is, the first supply / discharge port 12a functions as an air supply port, and the second supply / discharge port 13a functions as an exhaust port. As a result, the position of the exhaust port is changed from the lower end of the reaction vessel 10 (see FIG. 1A) to the upper end of the reaction vessel 10 (see FIG. 1B). At the same time, the control unit controls the electric furnace 17 so that the low temperature zone T is formed on the first supply / exhaust port 12a side that functions as an exhaust port after switching. By controlling the switching unit 21 and the electric furnace 17 in this way, the flow direction of the fluoride gas in the reaction chamber 14 is changed, and the formation position of the low temperature zone T is changed to the downstream side after the change. The Further, every time the temperature of the low temperature zone T exceeds the specified temperature, the switching means is operated to switch between the state shown in FIG. 1 (a) and the state shown in FIG. 1 (b). The specified temperature is set to the same temperature as the set temperature of the low temperature zone T or a temperature slightly higher than that.

Next, operational effects in the present embodiment will be described below.
(1) In the decomposition treatment method of this embodiment, a decomposition treatment agent containing calcium oxide, silicon, and an alkali metal halide is used. Thereby, the fluoride gas can be decomposed at a high decomposition rate under relatively low temperature heat treatment conditions of about 600 to 800 ° C. Therefore, a special processing apparatus capable of withstanding a high temperature state (for example, 1000 ° C. or higher) is not required, and the processing cost can be suppressed. Moreover, the early deterioration of the processing apparatus resulting from exposing the processing apparatus to a high temperature state can be suppressed, and the life of the processing apparatus can be extended.

  (2) Of calcium oxide, silicon and alkali metal halide contained in the decomposition treatment agent, when the mixing ratio of silicon is 1 to 2 molar equivalents with respect to calcium oxide, decomposition action on fluoride gas Can be prolonged.

  (3) According to the decomposition processing method of this embodiment, acidic gas such as hydrogen fluoride is not generated during the decomposition processing of fluoride gas, and an apparatus for processing acidic gas is unnecessary. In addition, according to the decomposition processing method of the present embodiment, all final decomposition products generated during the decomposition process of fluoride gas are generated as solids. Therefore, generation | occurrence | production of harmful gas etc. with a decomposition process is suppressed.

  (4) When the decomposition treatment of fluoride gas is performed using the decomposition treatment method of the present invention, the alkali metal gas generated from the decomposition treatment agent is discharged out of the system with the discharge of the decomposition treatment gas. Sometimes. Since the alkali metal gas is a substance having an action of directly decomposing the fluoride gas, the discharge of the alkali metal gas to the outside of the system causes a reduction in the decomposition treatment action and the like.

  For such a problem, in the decomposition treatment apparatus 1 of the present embodiment, the reaction chamber 14 is formed in the region on the exhaust port side in the reaction chamber 14 while forming the low temperature zone T in order to reduce the vapor pressure of the alkali metal. The electric furnace 17 is configured so that it can be heated. As a result, the alkali metal gas that has flowed to the exhaust port side together with the processing gas is cooled in the low temperature zone T formed on the exhaust port side and becomes solid or liquid. Therefore, the alkali metal gas is collected in the reaction chamber 14 and the discharge of the alkali metal gas to the outside of the reaction chamber 14 is suppressed.

  (5) The decomposition processing apparatus 1 of the present embodiment includes the switching unit 21 that changes the position of the exhaust port between the first supply / discharge port 12a and the second supply / discharge port 13a. Moreover, the electric furnace 17 provides the low temperature zone T on the first supply / exhaust port 12a side or the second supply / exhaust port 13a side that functions as an exhaust port after switching in accordance with the position change of the exhaust port by the switching unit 21. Controlled to form.

  When the fluoride gas is decomposed for a long period of time, the temperature in the low temperature zone T may increase with the discharge of the processing gas heated to a high temperature, and the alkali metal gas collection efficiency may decrease. Even in such a case, the discharge of the alkali metal gas to the outside of the reaction chamber 14 can be suppressed by changing the formation positions of the exhaust port and the low temperature zone T.

  (6) In the decomposition treatment apparatus 1 of the present embodiment, the control unit is configured to control the position change of the exhaust port and the formation position of the low temperature zone T according to the temperature state in the reaction chamber 14. As a result, when the temperature of the low temperature zone T exceeds a preset specified value, the formation positions of the exhaust port and the low temperature zone T are automatically changed. It is possible to continuously decompose a large amount of fluoride gas while suppressing the discharge of the gas to the outside of the reaction chamber 14.

In addition, this embodiment can also be changed and embodied as follows.
In the decomposition treatment apparatus 1 of the present embodiment, the low temperature zone T is formed only in the region on the exhaust port side in the reaction chamber 14, but if it is formed even in the region on the exhaust port side, In addition to the region, the low temperature zone T may be formed in another region in the reaction chamber 14.

  In the decomposition processing apparatus 1 of the present embodiment, the switching control unit is operated when the temperature of the low temperature zone T exceeds the specified temperature, but the operating condition of the switching control unit is not limited to this. For example, the switching control means may be operated every time a predetermined time elapses, or a fluoride gas or alkali metal gas detector is disposed in the vicinity of the exhaust port so that the fluoride gas or alkali metal gas is detected above a predetermined value. In this case, the switching control means may be operated. Further, the switching control means may be manually operated.

  In the decomposition processing apparatus 1 of the present embodiment, the switching control unit is configured to change both the position of the exhaust port and the formation position of the low temperature zone T, but only the position of the exhaust port is changed. It may be configured. In the case of such a configuration, for example, in the reaction chamber 14, the low temperature zone T is always formed in the entire peripheral region of the portion that can become the exhaust port, so that the position of the exhaust port and the formation of the low temperature zone T are formed. An effect similar to that of the configuration in which both of the positions are changed can be obtained.

  -It is good also as a structure which does not provide a switching control means. In this case, it is not necessary to provide the switching unit 21, and the first supply / discharge port 12a and the second supply / discharge port 13a may be directly connected to the gas generation unit 22 and the discharge unit 23, respectively. Moreover, what is necessary is just to comprise the electric furnace 17 so that the low temperature zone T may be formed only in the 2nd supply / exhaust port 13a side.

  -In the decomposition processing apparatus 1 of this embodiment, although the electric furnace 17 was employ | adopted as a heating part, the structure of a heating part is not restricted to this. For example, a combustion apparatus using gas or the like may be employed as the heating unit.

  -In the decomposition processing apparatus 1 of this embodiment, although the electric furnace 17 as a heating part has been arrange | positioned on the outer side of the reaction container 10, the arrangement position of the electric furnace 17 is not restricted to this. For example, the electric furnace 17 may be disposed in the reaction vessel 10 or in the reaction chamber 14.

  In the decomposition processing apparatus 1 of this embodiment, the decomposition treatment agent A is loaded in the cartridge 16 and the cartridge 16 is accommodated in the reaction chamber 14, but the loading method of the decomposition treatment agent A is limited to this. is not. For example, the decomposition treatment agent A may be directly loaded into the reaction chamber 14.

  In the reaction chamber 14, the porous inorganic adsorbent may be loaded or arranged in at least a portion (region) on the side used as the exhaust port of the first supply / exhaust port 12 a and the second supply / exhaust port 13 a. Good. Examples of the porous inorganic adsorbent include porous aluminum oxide (activated alumina) and porous zirconium oxide. When configured in this way, unreacted alkali metal gas can be captured by the porous inorganic adsorbent at the site on the exhaust port side in the reaction chamber 14, and the alkali metal gas can be trapped outside the reaction chamber 14. Emission can be suppressed more effectively. Thereby, the decomposition efficiency with respect to fluoride gas can be improved.

Next, the decomposition treatment agent of the above embodiment will be described more specifically with reference to examples and comparative examples.
In each test shown below, potassium fluoride is used as the alkali metal halide contained in the decomposition treatment agent of the present invention, and carbon tetrafluoride gas is used as the fluoride gas.

  First, the test apparatus used for each test is demonstrated based on FIG. A cylindrical SUS reaction vessel 32 is disposed inside an electric furnace 31 made of a magnetic tube. The reaction vessel 32 is filled with a decomposition treatment agent A as a test sample. The upstream end of the reaction vessel 32 is connected to a gas generator 34 as a fluoride gas supply source via a dehumidification column 33. And the downstream edge part of the reaction container 32 is connected to the discharge part 37 through the gas absorption bottle 35 and the water | moisture-content removal bottle 36 in order. The gas absorption bottle 35 is filled with ion-exchanged water for collecting unreacted alkali metal gas, and the water removal bottle 36 is filled with glass beads for removing moisture contained in the gas. Is filled.

  When this test apparatus is used, the reaction is performed by supplying the fluoride gas in the gas generation unit 34 into the reaction vessel 32 while the reaction vessel 32 is heated to a predetermined temperature by the electric furnace 31. The fluoride gas is decomposed in the container 32. The decomposed processing gas passes through the gas absorption bottle 35 and the moisture removal bottle 36 and is discharged to the discharge unit 37.

<Test on decomposition treatment action of decomposition treatment agent>
The decomposition treatment action of the decomposition treatment agent of the present invention on fluoride gas was evaluated. As a test sample of the decomposition treatment agent used in this test, potassium fluoride (manufactured by Junsei Chemical Co., Ltd.), calcium oxide (manufactured by Wako Pure Chemical Industries, Ltd.) and silicon (manufactured by Junsei Chemical Co., Ltd.) were blended at the blending ratio shown in Table 1. This was prepared as Example 1. Moreover, what contains only calcium oxide (made by Wako Pure Chemical Industries) was prepared, and this was made into the comparative example 1. In addition, the compounding ratio shown in Table 1 has shown the molar ratio.

  And Example 1 or the comparative example 1 was filled in the reaction container 32, and the decomposition process of carbon tetrafluoride was performed. In this test, the carbon tetrafluoride used was blended at a concentration of 3% by volume in nitrogen and supplied into the reaction vessel 32. The contact time between carbon tetrafluoride and the decomposition treatment agent was 4 seconds or 7 seconds. In addition, the temperature in the reaction container 32 at the time of a decomposition process was 600, 700, 800, 900 degreeC.

  Then, gas is sampled at a point X between the dehumidification column 33 and the reaction vessel 32 and a point Y downstream of the water removal bottle 36, and the concentration of carbon tetrafluoride contained in the collected gas is changed to four. The measurement was performed with a multipole gas chromatograph mass spectrometer (manufactured by Shimadzu Corporation). Based on the obtained measurement results, the decomposition rate of carbon tetrafluoride at each temperature in Example 1 and Comparative Example 1 was calculated. The result is shown in FIG.

  As shown in FIG. 3, Comparative Example 1 containing only calcium oxide as a decomposition treatment agent can decompose carbon tetrafluoride, but requires heat treatment at a high temperature of 800 ° C. or higher at that time. To do. On the other hand, it was confirmed that Example 1 can sufficiently decompose carbon tetrafluoride by heat treatment at a relatively low temperature of 600 to 800 ° C.

<Test on correlation between blending ratio of components contained in decomposition treatment agent and decomposition treatment action>
Examples in which the blending ratios of potassium fluoride, calcium oxide, and silicon contained in the decomposition treatment agent were different from each other were prepared. Table 2 shows the mixing ratio of each component in Examples 2 to 5. In addition, the compounding ratio shown in Table 2 has shown the molar ratio.

  And Example 2-5 was filled in the reaction container 32, and the decomposition process of carbon tetrafluoride was performed. In this test, carbon tetrafluoride was used which was blended in nitrogen at a concentration of about 3% by volume and introduced into the reaction vessel 32. The contact time between carbon tetrafluoride and the decomposition treatment agent was 4 seconds. The temperature in the reaction vessel 32 during the decomposition treatment was set to 700 ° C.

  Then, at each of the X point and the Y point, gas was sampled over time, and the concentration of carbon tetrafluoride contained in the collected gas was measured with a quadrupole gas chromatograph mass spectrometer. Based on the obtained measurement results, the amount of carbon tetrafluoride decomposed per unit time in Examples 2 to 5 with respect to the elapsed time was calculated. The result is shown in FIG.

  As shown in FIG. 4, in Example 3 where a large amount of silicon is blended, the amount of decomposition of carbon tetrafluoride per unit time is moderately lower than in Example 2 where each component is blended in approximately the same amount. Progressed. In Example 4 where a large amount of potassium fluoride was blended, the decrease in the amount of carbon tetrafluoride decomposed per unit time proceeded in substantially the same manner as in Example 2. In Example 5 in which a large amount of calcium oxide was blended, the amount of decomposition of carbon tetrafluoride per unit time rapidly proceeded as compared to Example 2. From these results, it is suggested that the mixing ratio of calcium oxide and silicon affects the duration of the decomposition treatment action. According to the above reaction formula (1), it is considered that 2 molar equivalents of calcium oxide are necessary for silicon. However, from the results of the examples, it was confirmed that, on the contrary, increasing the ratio of silicon is more suitable for extending the duration of the decomposition treatment action. Specifically, it was confirmed that 1 to 2 molar equivalents of silicon were added to calcium oxide, and more preferably 2 molar equivalents were added.

<Test on porous inorganic adsorbent>
A test device in which activated alumina is filled as a porous inorganic adsorbent at a downstream site in the reaction vessel 32 is prepared, and the decomposition treatment action of the decomposition treatment agent of the present invention on fluoride gas is evaluated using this test device. did. In the present test, Example 2 was used as a decomposition treatment agent, and carbon tetrafluoride was blended in nitrogen at a concentration of about 0.2 to 4.0% by volume. The temperature in the reaction vessel 32 during the decomposition treatment was 750 ° C., and the contact time between the carbon tetrafluoride and the decomposition treatment agent was 4 seconds.

  Then, at each of the X point and the Y point, gas was sampled over time, and the concentration of carbon tetrafluoride contained in the collected gas was measured with a quadrupole gas chromatograph mass spectrometer. The amount of carbon tetrafluoride decomposition per unit time is calculated based on the obtained measurement results, and the time until the carbon tetrafluoride decomposition amount per unit time starts to decrease is obtained. % Treatment time. Moreover, the same test was performed using the test apparatus which is not filled with the porous inorganic adsorbent, and this was used as a comparative control. FIG. 5 is a graph showing the relationship between the concentration of carbon tetrafluoride and the 100% processable time.

  As shown in FIG. 5, when the test apparatus filled with the porous inorganic adsorbent is used, the decomposition treatment agent 100 is compared with the case where the test apparatus not filled with the porous inorganic adsorbent is used. % Processable time was about twice as high. From this result, it was confirmed that the time during which the decomposition treatment action of the decomposition treatment agent can be exhibited 100% can be extended by filling the downstream portion in the reaction vessel 32 with the porous inorganic adsorbent. It was.

Next, a technical idea that can be grasped from the above embodiment will be described.
The reaction vessel has a first supply / exhaust port that serves both as an air supply / exhaust port and a second supply / exhaust port, and one of the first supply / exhaust port and the second supply / exhaust port is the supply unit. The function of each other can be switched so that the other becomes an exhaust port, and along with the switching of the functions of the first supply / exhaust port and the second supply / exhaust port by the switching means, An apparatus for decomposing fluoride gas, wherein the formation position of the low temperature zone is changed to a region on one side that functions as an exhaust port of the first supply port and the second supply port.

(A), (b) is a schematic sectional drawing which shows the decomposition processing apparatus of this embodiment. The schematic sectional drawing which shows a test apparatus. The graph which shows the change of the decomposition rate with respect to heat processing temperature. The graph which shows the change of the decomposition amount per unit time of the decomposition processing agent with respect to elapsed time. The graph which shows the change of the processing time of a decomposition processing agent with respect to the introduction density | concentration of carbon tetrafluoride gas in the presence or absence of a porous inorganic adsorption agent.

Explanation of symbols

  A ... Decomposition treatment agent, T ... Low temperature zone, 1 ... Decomposition treatment device, 10 ... Reaction vessel, 12a ... First supply / exhaust port, 13a ... Second supply / exhaust port, 14 ... Reaction chamber, 17 ... Electricity as heating unit Furnace, 21... Switching unit as switching means.

Claims (7)

A method for decomposing a fluoride gas, comprising heat-treating the fluoride gas in the presence of calcium oxide, silicon and an alkali metal halide. 2. The method for decomposing fluoride gas according to claim 1, wherein the silicon is blended in an amount of 0.7 to 3.0 molar equivalents relative to the calcium oxide. A fluoride gas decomposition treatment agent characterized by containing calcium oxide, silicon and an alkali metal halide. The decomposition treatment agent for fluoride gas according to claim 3, wherein the silicon is blended in an amount of 0.7 to 3.0 molar equivalents relative to the calcium oxide. A reaction vessel having a reaction chamber therein, an intake port for sucking fluoride gas into the reaction chamber, and an exhaust port for discharging the processing gas processed in the reaction chamber to the outside; and the reaction chamber An apparatus for decomposing fluoride gas comprising a heating section for heating
The reaction chamber is loaded with a decomposition treatment agent consisting of calcium oxide, silicon and alkali metal halide,
During the decomposition treatment of the fluoride gas, the heating unit forms a low-temperature zone for lowering the vapor pressure of the alkali metal generated from the alkali metal halide in the region on the exhaust port side in the reaction chamber. An apparatus for decomposing fluoride gas, wherein the reaction chamber can be heated. Comprising switching means for changing the position of the exhaust port in the reaction vessel;
The said heating part changes the formation position of the said low temperature zone in the area | region of the said exhaust port after a position change with the position change of the said exhaust port by this switching means. Fluoride gas decomposition treatment equipment. The fluoride gas decomposition treatment apparatus according to claim 5 or 6, wherein a porous inorganic adsorbent is loaded in a portion on the exhaust port side in the reaction chamber.

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