JP2008136935A - Selective treatment method of trifluoromethane, treatment unit and sample treatment system using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply, efficiently and selectively treating CHF<SB>3</SB>from a sample containing CHF<SB>3</SB>, a treatment unit and sample treatment system using it. <P>SOLUTION: In this CHF<SB>3</SB>treatment method using the selective adsorbing function of an adsorbent based on aluminum oxide, the CHF<SB>3</SB>-containing sample is treated in steps using at least two kinds of adsorbents and a reagent based on synthetic zeolite is used in a previous stage while a reagent based on aluminum oxide is used in a post stage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for selectively processing trifluoromethane, a processing unit, and a sample processing system using the processing unit.

In semiconductor manufacturing processes such as a plasma etching process, water, carbon dioxide (CO ₂ ), trifluoromethane (CHF ₃ ), fluorocarbon (FC) such as CF ₄ , C ₂ F ₆ , and C ₂ F ₄ are discharged as exhaust gas. The Among these, since CHF ₃ is one of the global warming gases, it needs to be decomposed and modified by various treatment methods and released to the atmosphere. In general, a combustion method or a plasma method is used as a technique for detoxifying these FCs including CHF ₃ . Also, a method for decomposing FC using microwaves has been proposed.
(1) The combustion method is a method in which a gas containing FC is burned at a high temperature, and the FC is converted to CO ₂ or hydrogen fluoride (HF) to be processed.
(2) The plasma method is a method in which corona discharge or silent discharge is used to decompose FC into other substances by discharge plasma. Specifically, a sample containing FC is exposed to corona discharge. A method of decomposing in the presence of a carrier gas having an ionization potential higher than that of FC to be decomposed has been proposed. The carrier gas contains oxygen, hydrogen or water (see, for example, Patent Document 1).
(3) The method for decomposing FC using microwaves is a method for decomposing FC by applying microwaves in an applicator to heat the magnetite and bringing the FC into contact with the magnetite in the heat generation state (for example, patents). Reference 2).

On the other hand, technologies for recovering FC have also been studied and several proposals have been made. For example, a collection technique using the following adsorbent has been proposed.
(4) Techniques for recovering perfluorocarbon, hydrofluorocarbon, etc. using activated carbon as an adsorbent have been disclosed (see, for example, Patent Document 3).
(5) A technique of an adsorption heat pump in which a refrigerant such as hydrofluorocarbon is adsorbed and desorbed on various adsorbents and used for a heat cycle is disclosed (for example, see Patent Document 4).

JP-A-8-323147 JP-A-6-293501 JP 2000-117052 A JP 2000-35256 A

However, application of the above processing method sometimes has the following problems.
(1) In the combustion method, nitrogen oxide (NOx) is also generated at the same time, and therefore further measures are required for the treatment of this NOx. Furthermore, since HF is also treated with water or the like, the treated water exhibits strong acidity, and thus neutralization is required. In addition, a large amount of air is used as a raw material gas for combustion, and a large amount of energy is required to increase the temperature of such a gas, and a large-scale mechanism is required for the treatment of exhaust gas at the outlet of the combustion apparatus.
(2) In the plasma method, since FC is decomposed by plasma, energy required for plasma generation is large. In addition, it is difficult to completely remove FC and the like, and there is a problem that the FC removal efficiency varies greatly depending on the FC concentration at the inlet, so that it is difficult to apply.
(3) The method for decomposing FC using microwaves has a problem that an expensive microwave generator is required and the reaction vessel is limited to a heat-resistant material that allows microwaves to permeate well. Some heat-resistant materials that transmit microwaves well are ceramics. However, these materials often deteriorate when they react with fluorine. Accordingly, there is another problem in industrially cheap and stable FC decomposition.
(4) When activated carbon is used as an adsorbent, it has been disclosed that CF ₄ , C ₂ F _{6 and the} like can be recovered, but removal and recovery of CHF ₃ are not disclosed and are unknown. Also, it is intended to recover the entire FC, and is not collected separately. In particular, when activated carbon is used as the adsorbent, CHF ₃ is selected from a sample containing CF ₄ , C ₂ F _6, etc. It has been impossible even in the demonstration of the present inventor to remove and collect automatically.
(5) The adsorption heat pump technology targets FC used as a refrigerant, does not require selective recovery with other components, and the concentration of FC is about 100%, which is low. It cannot be applied to technologies intended for selective removal and recovery of

As described above, there are various FC removal methods and recovery methods. However, selective removal and recovery of CHF ₃ is not focused on this point of view, and the level of selective removal and recovery is therefore not considered. Was incomplete. On the other hand, selective removal and recovery without affecting other FC components can also contribute to environmental conservation by recovery and reuse of other FC components or effective use of resources. Therefore, there has been a strong demand for selective removal of CHF ₃ from such a viewpoint.

An object of the present invention is to provide a technique for selectively removing and recovering CHF ₃ by a simple method, that is, FC comprising at least moisture, CO ₂ , CHF ₃ and a saturated bond (hereinafter referred to as “saturated FC”). ) Or an unsaturated FC (hereinafter referred to as “unsaturated FC”), a method, a processing unit, and a sample processing using the processing unit for processing CHF ₃ easily, efficiently and selectively. Is to provide a system.

  Here, “treatment” is a broad concept including chemical or physical removal or recovery from a sample, and reversible conversion to other substances, and is limited to removal and recovery. Is not to be done.

As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following selective processing method for CHF ₃ , a processing unit, and a sample processing system using the processing unit. The headline and the present invention have been completed.

  The present invention is a method for selectively treating trifluoromethane in a sample, and is characterized by utilizing a selective adsorption function of an adsorbent mainly composed of aluminum oxide.

As described above, in the process of selective removal and recovery of CHF ₃ , the conventional general FC removal method cannot be applied. As a result of verifying the selective treatment method of CHF ₃ by various physical or chemical techniques, the present inventor has found that an adsorbent mainly composed of aluminum oxide has a selective adsorption function, and FC and the like coexist. It was found that it can be applied to a sample.

That is, a method using physical adsorption is preferable for the recovery of CHF _{3. In} selecting a specific adsorbent, as will be described later, one of the adsorption isotherms is to grasp static adsorption characteristics. Based on this, the adsorption ability and selectivity of a specific substance for a specific adsorbent were verified. For various adsorbents including aluminum oxide, adsorption isotherms for various components including CHF ₃ were obtained. In addition to such static adsorption characteristics, (a) even if the static adsorption capacity is a large component, if the adsorption rate is slow, the dynamic adsorption amount becomes small, and (b) coexistence In the case where there are various components to be absorbed, the dynamic adsorption ability is reduced by competitive adsorption of other components, so the dynamic adsorption characteristics of a specific substance with respect to a specific adsorbent were verified. In the present invention, as a result of verification from several viewpoints as described above, the selective adsorption function for CHF _{3 in} a sample containing moisture, CO ₂ and FC such as CHF ₃ , CF ₄ , C ₂ F _6, etc. is oxidized. It has been demonstrated that aluminum is the best and has the selectivity to withstand practical use.

Further, by reversible physical adsorption of CHF ₃ by aluminum oxide, selective enrichment operations CHF ₃ by desorption of CHF ₃ from the adsorbent becomes possible became possible separate recovery of CHF _3. Therefore, it has become possible to provide a method for removing and recovering CHF ₃ simply, efficiently, and selectively.

The present invention is the above-described method for selectively treating trifluoromethane, wherein the sample contains at least moisture, carbon dioxide, trifluoromethane, and a fluorocarbon composed of other saturated or unsaturated bonds,
The adsorbent is characterized by using two or more kinds of adsorbents in stages, using a reagent mainly composed of synthetic zeolite in one of the preceding stages, and using a reagent mainly composed of aluminum oxide in the subsequent stage. To do.

Aluminum oxide,殆since it has a selectivity, moisture, be a sample, including CO ₂ and _{CF 4,} C 2 _{F 6,} etc. FC, the CHF ₃ to other coexisting components for CHF ₃ as an adsorbent It can be removed without any effect. However, the sample, since compared to the CHF ₃ may include water and CO ₂ several times to several tens times the concentration, can cause conflicts adsorption and CHF ₃ of aluminum oxide, in particular When recovering CHF ₃ , it is necessary to further remove such impurities from the gas desorbed from the adsorbent. In the present invention, a synthetic zeolite is provided as an adsorbent in the former stage to selectively remove moisture and CO ₂ , thereby preventing competitive adsorption with the aluminum oxide in the latter stage and further increasing the selective adsorption capacity of CHF _3. It became possible to increase. Therefore, CHF ₃ can be removed and recovered more efficiently and selectively.

  The present invention is a method for selectively treating trifluoromethane, wherein the adsorbent that has selectively adsorbed trifluoromethane by the treatment is desorbed by heating the trifluoromethane adsorbed, and then the trifluoromethane is adsorbed. Is recovered by condensing and liquefying at a temperature lower than its normal boiling point.

By utilizing selective adsorption function for CHF ₃ adsorbent that a main agent of aluminum oxide, and at the same time it is possible to remove the CHF ₃ in a sample efficiently and selectively, with high purity CHF ₃ adsorbent Can be occluded. However, as described above, when recovering CHF ₃ from a sample containing CHF ₃ at a low concentration of about 0.01 to 0.1%, since the sample contains impurities at substantially the same concentration, it is a one-step process. It is difficult to concentrate to CHF ₃ having a purity of more than 99% by a processing operation or the same type of multi-stage processing operation. In the present invention, in addition to the selective concentration by adsorption and desorption from the first stage adsorbent, the second stage condensation operation by low-temperature liquefaction condensation separation is performed for the first time. ₃ can be recovered efficiently and stably. The liquefaction temperature at this time is required to be −90 to −120 ° C., which is lower than −82.1 ° C. which is the standard boiling point of CHF ₃ . Here, −90 ° C. or lower is referred to as “low temperature”, and 99% or higher is referred to as “high purity”.

  The present invention is the above selective treatment method of trifluoromethane, characterized in that the desorption temperature of trifluoromethane adsorbed on the adsorbent is 250 ° C. or higher.

In the practice of CHF ₃ recovery, it is important how to selectively store the adsorbent in the adsorbent and how to efficiently desorb the adsorbed CHF ₃ at the same time. Depending on the adsorbent, the adsorption characteristics and desorption characteristics may differ greatly, and in the desorption of CHF ₃ , the specific optimum temperature has been verified in consideration of the need to add higher desorption energy. As described later, it has been proved that the desorption temperature is preferably 250 ° C. or higher. By ensuring these conditions, it became possible to recover CHF ₃ of high purity efficiently and stably in combination with the low-temperature condensation treatment in the subsequent stage.

The present invention is a trifluoromethane treatment unit filled with the adsorbent,
(1) A space provided inside the processing unit and having a sample introduction part and a sample delivery part,
(2) a heating part for heating the space part,
(3) a filling portion disposed in the center of the space portion and filled with an adsorbent;
(4) A guide part that divides the space part into two or more spaces in contact with the filling part, and partitions each part so as to be circulated.
(5) One end is connected to either the sample introduction part or the sample delivery part, and is spirally wound in the filling part, and the other end is disposed outside the filling part via the guide part. Flow path,
It is characterized by having.

In order to maintain the adsorption efficiency of CHF ₃ , it is preferable to perform the treatment under a low temperature condition (adsorption unit ambient atmosphere temperature or lower), and at the same time, how to eliminate the heat of adsorption is important. On the other hand, in order to maintain the CHF ₃ desorption efficiency, it is necessary to ensure a high temperature condition. Further, since most of the adsorbents are normally powder or fine particles, it is important how to ensure the adsorption and desorption conditions equally and efficiently. In order to ensure such a function, the present inventor inserted a spiral pipe line into the adsorbent packed bed, and configured a processing unit having a heat exchange function between the pipe line and the adsorbent. In addition, by introducing or deriving the sample from the space in contact with the packed bed partitioned by the guide section through the guide section to the packed bed, the heat exchange function can be effectively utilized and the function capable of contacting the adsorbent uniformly. It is possible to configure a processing unit having the same. In other words, during the adsorption treatment operation, the sample that has passed through the packed bed can be derived while taking heat of adsorption through the spiral conduit, and during the desorption treatment operation, the sample preheated by the spiral conduit is introduced into the packed bed. be able to. In addition, the sample can be uniformly contacted with the adsorbent by introducing the sample into the packed bed through the guide portion once diffused in the space in contact with the packed bed. By configuring such a processing unit having a heat exchange function and a diffusion function, CHF ₃ can be efficiently adsorbed, concentrated and desorbed.

The present invention is a sample processing system using the above processing unit,
(1) A processing operation for introducing a sample containing at least moisture, carbon dioxide, trifluoromethane and other saturated or unsaturated fluorocarbons into the processing unit and selectively adsorbing trifluoromethane, (2) Adsorption A treatment operation for desorbing the trifluoromethane, and (3) a treatment operation for recovering the trifluoromethane by condensing and liquefying the trifluoromethane under a temperature lower than its boiling point.

As described above, when high-purity CHF ₃ is collected from a sample containing CHF ₃ at a low concentration of about 0.01 to 0.1%, the sample contains almost the same concentration of impurities. It is difficult to concentrate to CHF ₃ having a high purity exceeding 99% even by an adsorption treatment operation having high properties. In the present invention, high-purity CHF ₃ is produced for the first time by performing a condensation operation by a low-temperature liquefaction condensation separation in addition to a selective adsorption treatment operation by an adsorbent and a selective concentration treatment operation by desorption from the adsorbent. It became possible to recover efficiently and stably. Thus, CHF ₃ in the sample can be adsorbed, concentrated, and desorbed more efficiently and selectively by utilizing the high functionality of the processing unit and combining with a higher concentration process.

As described above, according to the present invention, a sample containing CHF _3, a simple, efficient, and selective method for removing or recovering the CHF _3, the sample processing system using the processing unit and the processing unit Can be provided. In particular, it is possible to provide a technique for selectively removing or recovering CHF ₃ from a sample containing moisture, CO ₂ and FC, such as exhaust gas in a semiconductor manufacturing process, by a simple method. Further, the recovered and purified CHF ₃ can be used again in the semiconductor manufacturing process, and can contribute to the reduction of emission of CHF ₃ which is a global warming gas.

Hereinafter, embodiments of the present invention will be described.
The present invention is, for samples containing CHF _3, utilizing selective adsorption function of the adsorbent that a main agent of aluminum oxide, a method for selectively removing or recovering the CHF _3, the processing unit used in this and sample processing System.

Specifically, for example, CHF ₃ is selectively selected from a sample containing moisture, CO ₂ , CHF ₃ , CF ₄ , C ₂ F ₆ , C ₂ F ₄ , and the like, such as a semiconductor manufacturing process exhaust gas such as plasma etching. A processing unit and a sample processing system used for this method. However, in a semiconductor manufacturing process or the like, the concentration of CHF ₃ or other components or concentrations depends on whether the gas immediately after the process is used as a sample and the gas before or after the exhaust gas treatment (detoxification treatment). However, if the concentration is high, the system function can be used appropriately by diluting with an inert gas (preferably a gas that can be removed by this system) before introducing this system. can do.

Here, the reagent mainly composed of aluminum oxide (Al ₂ O ₃ ) is a commonly used α-alumina or γ-alumina (activated alumina) itself, aluminum oxide such as silica alumina or alumina ceramics. A compound containing a mixture or the like. It is also suitable to use a mixture of these compounds. Any shape, such as powder or granule, is acceptable, but considering the pressure loss of the processing gas and the processing load in the subsequent stage, the granule or the granule bound with the powder is preferable, and the surface area is increased to increase the adsorption activity. Is preferably ensured.

Below, the verification items regarding the selective adsorption function of the adsorbent and the selection of the adsorbent, the configuration of the CHF ₃ treatment unit that can make more efficient use of these adsorption characteristics, the adsorption efficiency and selectivity, and the use thereof will be described. The sample processing system that has been used will be described in detail.

<Understanding of selective adsorption function of adsorbent and selection of adsorbent>
In selecting the adsorbent, it is necessary to grasp the static adsorption characteristics and the dynamic adsorption characteristics of the adsorbent and the substance to be adsorbed. That is, as static adsorption characteristics, based on the adsorption isotherm, grasp the adsorption capacity and selectivity of a specific substance for a specific adsorbent, and as dynamic adsorption characteristics, a temperature close to the actual use conditions, The pressure and linear velocity can be set, and the adsorption ability and selectivity of the specific substance for the adsorbent at this time can be grasped.

(1) Grasping static adsorption characteristics In order to grasp the static adsorption characteristics of the adsorbent and the substance to be adsorbed, it is necessary to verify the adsorption isotherm for CHF ₃ . In general, six patterns are known as IUPAC adsorption isotherms (Pure Appl. Chem., 57, 603 (1985)) as illustrated in FIG. For a low concentration of CHF _{3 of} about 0.01 to 0.1% as in the present invention, the relative pressure is reduced as shown in (I), (II), (IV) or (VI) in FIG. An adsorbent having a large adsorption amount property even under low conditions is preferable. Since it is not a generally known substance such as moisture or CO ₂ , the adsorption characteristics of CHF _{3 on} each of adsorbents such as activated alumina, silica gel, synthetic zeolite, activated carbon and the like were compared.

Specifically, adsorption isotherms of CF ₄ , nitrogen (N ₂ ), CO ₂ , CHF ₃ , and oxygen (O ₂ ) with respect to activated alumina, synthetic zeolite (4A) and activated carbon are shown in FIGS.
(1-1) As shown in FIG. 2, the static adsorption characteristics of activated alumina with respect to various substances have selectivity for CO ₂ and CHF ₃ . The analysis and response to adsorption competition resulting from selectivity for CO ₂ will be described later.
(1-2) As shown in FIG. 3, the static adsorption characteristics of the synthetic zeolite (4A) for various substances had little selectivity for CHF ₃ .
(1-3) Similarly, as shown in FIG. 4, the static adsorption characteristics of activated carbon with respect to various substances have no selectivity for CHF ₃ .
(1-4) Similarly, silica gel was not selective for CHF ₃ (not shown).
(1-5) From the above, the selective adsorption function of activated alumina for CHF ₃ can be inferred from the static adsorption characteristics of the adsorbent.

(2) Grasping the dynamic adsorption characteristics To grasp the dynamic adsorption characteristics of the adsorbent and the adsorbed substance, the adsorption capacity and selectivity of CHF _{3 for} the adsorbent under conditions close to the actual use conditions. Need to be verified. In the following examples, demonstration results are shown for adsorbents such as activated alumina, silica gel, synthetic zeolite, and activated carbon.

[Example 1]
Actually, the dynamic adsorption characteristics of CHF ₃ were verified using the apparatus shown in FIG.
(A) Adsorption unit used A stainless steel adsorption cylinder having an inner diameter of 33 mm and a length of 150 mm was filled with bead-like activated alumina, silica gel, and synthetic zeolite (4A) having a diameter of about 2 mm, and the same adsorption cylinder was broken. The activated carbon was filled, and each processing unit 20 was obtained.
(B) the apparatus shown in experimental conditions (b-1) 5, sets the adsorption unit 20, an electric heater 20a attached to the adsorption unit 20, it is passed through the _{N 2} from the upper adsorption unit 20, the electric heaters 20a Then, the temperature of the adsorption unit 20 was raised to 250 ° C., and the temperature was maintained for 5 hours. After 5 hours passed, the electric heater 20a was turned off, and the adsorption units 20 were cooled in a state where N ₂ was circulated, and a regeneration operation for each adsorption unit 20 was performed.
(B-2) After regeneration, a standard gas 21 of 0.1% CHF ₃ / N ₂ balance is regulated by a pressure reducing valve 22 and flowed by a mass flow controller (manufactured by HORIBA STEC, model: SEC-4400MC-MK3) 23. The pressure was adjusted to 100 kPa using the compressor 24 and then introduced into each processing unit 20 maintained at an operating temperature of 300K.
(B-3) The gas concentration at the outlet of each adsorption unit 20 is measured by a Fourier transform infrared spectrometer (FT-IR, manufactured by MIDAC, model: M series) 25, and the breakthrough of CHF ₃ is monitored. Clarified the dynamic adsorption characteristics (adsorption amount) of various adsorbents.
(C) Experimental results The experimental results are shown in Table 1 below. It has been found that activated alumina has a very high dynamic adsorption capacity compared to other adsorbents.

(3) Selection of adsorbent As described above, activated alumina (aluminum oxide) has an excellent selective adsorption function for CHF ₃ in both aspects of static adsorption characteristics and dynamic adsorption characteristics. This was selected as the adsorbent.

(4) Temperature characteristics in regeneration treatment of aluminum oxide In order to secure a stable adsorption ability of the adsorbent (aluminum oxide) to CHF ₃ , a sufficient regeneration treatment of the adsorbent is required. In the regeneration process of the adsorbent, it is necessary to purge the adsorbent for a predetermined time as in [Example 1] and to maintain a high temperature state equal to or higher than the predetermined temperature during the purge. Therefore, it is necessary to grasp the temperature characteristic in the regeneration process of the adsorbent for CHF ₃ , that is, the dynamic adsorption characteristic after regeneration with respect to the regeneration process temperature. In the examples below, demonstration results for activated alumina are shown.

[Example 2]
(A) Adsorption unit used A stainless steel adsorption cylinder having an inner diameter of 33 mm and a length of 150 mm was filled with bead-like activated alumina having a diameter of about 2 mm.
(B) Experimental conditions (b-1) The regeneration processing operation of the processing unit 10 was performed. The adsorption unit 20 is set in the apparatus shown in FIG. 5, the electric heater 20a is attached to the adsorption unit 20, N ₂ is circulated through the adsorption unit 20, and the adsorption unit 20 is heated to a set temperature by the electric heater 20a. After that, the temperature was maintained for 5 hours. After 5 hours had passed, the electric heater 20a was turned off, and the adsorption unit 20 was cooled in a state where N ₂ was circulated. The set temperatures were 150 ° C., 200 ° C., 250 ° C., and 300 ° C.
(B-2) After regeneration, the standard gas 21 of 0.1% CHF ₃ / N ₂ balance is adjusted by the pressure reducing valve 22, the flow rate is adjusted by the mass flow controller 23 as in Example 1, and the compressor 24 is used. After adjusting the linear speed of 0.5 cm / sec and the pressure of 0.3 MPaG, it was introduced into the processing unit 20 maintained at an operating temperature of 300K.
(B-3) The gas concentration at the outlet of the adsorption unit 20 is measured by FT-IR25 as in Example 1, and the breakthrough of CHF ₃ is monitored to determine the dynamic adsorption characteristics of the adsorbent at each set temperature. Revealed.
(C) Experimental results The experimental results are shown in FIG. The adsorption treatment of 100% can be maintained for about several minutes at 150 ° C. regeneration treatment, and can be maintained for only about 10 minutes at 200 ° C., and can be maintained for about 20 minutes at 250 ° C. or more. Therefore, it was found that the adsorbent regeneration treatment temperature is preferably 250 ° C. or higher. In actual operation, the regeneration of the adsorbent means the desorption operation of the adsorbed CHF ₃ , that is, the recovery operation. Therefore, by setting the desorption temperature to 250 ° C. or higher, high desorption efficiency, that is, recovery efficiency is ensured. I found out that

<Processing unit of CHF ₃ >
The CHF ₃ processing unit (hereinafter referred to as “processing unit”) that uses aluminum oxide as an adsorbent is important in how to eliminate heat of adsorption while maintaining low temperature conditions to ensure CHF ₃ adsorption efficiency. Therefore, it is necessary to maintain and secure a high temperature state in order to secure the CHF ₃ desorption efficiency. In addition, since most of the adsorbents are normally in the form of granules or fine particles, it is important how to ensure adsorption and desorption conditions uniformly and efficiently. In order to ensure such a function, the processing unit according to the present invention is configured to have both the following heat exchange function and gas diffusion function.

Specifically, as illustrated in FIGS. 7A to 7D, a space portion 5 having a sample introduction portion 1 and a sample delivery portion 2 and provided with a packed layer 4 filled with an adsorbent 3 therein. In addition, a processing unit 10 having a heat exchange function was configured by inserting a spiral pipe (heat exchange channel) 6 into the packed bed 4. This makes it possible to release heat of adsorption by the sample gas in the forward direction (adsorption operation) and to preheat the purge gas in the reverse direction (purge operation). Further, the other end of the spiral duct 6 is disposed in the diffusing section 7a or 7b, and is distributed uniformly with the packed bed 4 through the guide section 8a or 8b that partitions the packed bed 4 so as to flow. A gas flow capable of contacting the adsorbent 3 can be formed. At this time, if necessary, it is also preferable to provide a filter in the guide portion 8a or 8b, or to configure the guide portion 8a or 8b itself with a material having a filter function such as a sintered material. In addition, an electric heater 9 for heating the processing unit 10 is provided around the space portion 5 and is used when the adsorbent is regenerated after the adsorption process or when the adsorbed CHF ₃ is collected.

FIG. 7A illustrates a case where an adsorption processing operation is performed. When a sample containing CHF ₃ is introduced from the sample introduction unit 1 of the processing unit 10, the sample is first buffered in the diffusion unit 7a, and then introduced into the packed layer 4 through the guide unit 8a and filled with oxidation. The CHF ₃ can be adsorbed by contact with the aluminum adsorbent 3. At this time, the packed bed 4 has a higher adsorption capability as the temperature is lower, and may condense when moisture is contained in the sample. Therefore, the packed bed 4 is adjusted to a temperature corresponding to the environmental temperature of the processing unit 10 or the sample conditions. It is preferable. The sample from which CHF ₃ has been removed is introduced into the diffusion part 7b via the guide part 8b, and is delivered from the sample delivery part 2 via the spiral conduit 6. At this time, the heat of adsorption generated in the packed bed 4 is transmitted to the sample through the spiral duct 6 and is delivered to the outside of the processing unit.

FIG. 7B illustrates a case where a desorption processing operation is performed. The processing unit 10 is heated by the electric heater 9 in a state where the introduction of the sample is stopped. As described later, the heating temperature is preferably 250 ° C. or higher. When the heating state is stabilized, a purge gas (for example, N ₂ ) is introduced from the sample delivery unit 2 of the processing unit 10. After flowing through the heat exchange flow path 6, the purge gas is buffered in the diffusion part 7b and introduced into the packed bed 4 through the guide part 8b. The purge gas preheated in the heat exchange flow path 6 is raised in temperature, and then contacted with the heated adsorbent _3, thereby efficiently desorbing the CHF ₃ adsorbed on the adsorbent 3. it can. A purge gas containing a high concentration of CHF ₃ is supplied from the sample introduction unit 1.

  Further, as shown in FIG. 7C, the sample introduction part 1 and the sample delivery part 2 are arranged in the same direction to facilitate the connection, and as shown in FIG. It is also possible to adopt a configuration capable of ensuring a high heat exchange function by forming the pipe line 6.

As described above, the processing unit 10 enables efficient processing operation of mass transfer such as adsorption, concentration, and desorption of CHF ₃ , release of heat of adsorption during the adsorption operation, and preheating of the purge gas during the purge operation. It enables efficient processing operations for energy transfer.

  The sample introduced into the processing unit 10 has a linear velocity of 0.1 to 2.0 cm / s, preferably 0.2 to 0.5 cm / s. Moreover, it is preferable that the pressure in the processing unit 10 keeps at least 0 MpaG and is higher. As for the material of the processing unit 10, a metal material such as a nickel material or a stainless material can be used, but a stainless material is preferable, and a stainless steel 316 material is more preferable.

Here, when put into practical use as a processing unit, it is processed stepwise using two or more kinds of adsorbents, a reagent mainly composed of synthetic zeolite is used in one of the front stages, and a reagent mainly composed of aluminum oxide in the subsequent stage. Is preferably used. Samples containing CHF ₃ may contain several times to several tens of times the concentration of moisture and CO ₂ , so even if the selectivity as an adsorbent is high, the presence of coexisting components exceeding it May cause competitive adsorption of aluminum oxide with CHF _3, and particularly when recovering CHF ₃ , it is necessary to further remove such impurities from the gas desorbed from the adsorbent. Therefore, by providing synthetic zeolite as a means for selectively removing moisture and CO ₂ , competitive adsorption with aluminum oxide can be prevented, and further, the selective adsorption capacity of CHF ₃ can be enhanced. Here, it is possible to make the synthetic zeolite in the former stage and the aluminum oxide in the latter stage as an integral processing unit. However, when selective recovery of CHF ₃ is performed, it is preferable in terms of processing operation to configure with separate processing units. .

<Sample processing system using the above processing unit>
The processing unit has a function of selectively and efficiently adsorbing and removing CHF ₃ from a sample in which various components coexist. Such a function is (1) not only detoxification of exhaust gas but also other useful components for recovering other components to a sample containing at least moisture, CO ₂ and FC, such as exhaust gas of a semiconductor manufacturing process. It becomes. Further, the CHF _3, which is thus adsorbed (2), by reversible physical adsorption, selective enrichment operations CHF ₃ by desorption of CHF ₃ from the adsorbent becomes possible, it becomes possible separate recovery of CHF ₃ . Hereinafter, these two functions in the sample processing system using the processing unit will be described in detail.

(1) for selective removal capabilities of selective removal capabilities CHF ₃ of CHF ₃ is specifically, aluminum oxide using the processing unit to the adsorbent, report on examples in the following three processing systems. Here, the first adsorbing means A1 for adsorbing and removing moisture and CO ₂ and CHF ₃ in the sample, the gas separating means A2 mainly comprising a gas separation membrane module for separating and removing saturated FC, and the second adsorbing and concentrating rare gas components. The adsorbing means A3 and the reaction means A4 filled with a reactive agent that reacts with the unsaturated FC are included. The first adsorbing means A1 has a case where a processing unit using a synthetic zeolite having a pore diameter of 4 mm or less is provided in the previous stage and the processing unit is provided in the subsequent stage.

Example 3
(A) Sample conditions As test gas, rare gas (Xe), moisture, CO ₂ is 0.3%, 3.1%, 0.3%, and FC is CF ₄ concentration 1000 ppm, CHF ₃ concentration 100 ppm, C ₂ F ₆ concentration 200 _ppm, a nitrogen balance gas of C 2 _{F 4} concentration 500 ppm, was set flow rate 25 slm.
(B) Sample processing system used in the experiment As illustrated in FIG. 8, moisture, CO ₂ and CHF ₃ are removed by the first adsorption means A1, and mainly saturated by the gas separation means A2 comprising a gas separation membrane module. FC is removed, and the rare gas component is concentrated and removed by the second adsorption means A3. The purified sample is further purified and discharged by some processing means. The sample composition at the inlet and outlet of the first adsorption means A1 at this time was measured. For the measurement, FT-IR (manufactured by MIDAC, model: M series, and Thermo-Nicolet, model: AVATAR) was used.
(C) Experimental results As shown in Table 2 below, CHF ₃ can be selectively removed without affecting other components such as CF ₄ , C ₂ F ₆ , and C ₂ F ₄ , and CO ₂ It was possible to remove to the detection limit level.

（単位：ｐｐｍ）

(Unit: ppm)

Example 4
(A) Sample conditions The test gas was set in the same manner as in Example 3 except that it did not contain moisture.
(B) Sample processing system used in the experiment As illustrated in FIG. 9, first, saturated FC is mainly removed by the gas separation means A2 including the gas separation membrane module, and then moisture and CO are removed by the first adsorption means A1. ₂ is removed, and the rare gas component is concentrated by the second adsorption means A3. The purified sample is further purified and discharged by some processing means. The sample composition at the inlet and outlet of the first adsorption means A1 at this time was measured. For the measurement, FT-IR was used as in Example 3.
(C) Experimental results As shown in Table 2 above, in the point that the concentration of CHF ₃ and CO ₂ is high and CF ₄ and C ₂ F ₆ have already been removed at the inlet of the first adsorption means A1. Although there was a difference from Example 3, CHF ₃ can be selectively removed without affecting other components of C ₂ F ₄ , and CO ₂ can also be removed to the detection limit level. It was.

Example 5
(A) Sample conditions The test gas was set in the same manner as in Example 3 except that it did not contain moisture and C ₂ F ₆ .
(B) Sample processing system used in the experiment As illustrated in FIG. 10, unsaturated FC is first removed by the reaction means A4 filled with the reactants, and then moisture and CO ₂ are removed by the first adsorption means A1. The CHF ₃ is removed, the saturated FC is mainly removed by the gas separation means A2 including the gas separation membrane module, and the rare gas component is concentrated by the second adsorption means A3. The purified sample is further purified and discharged by some processing means. The sample composition at the inlet and outlet of the first adsorption means A1 at this time was measured. For the measurement, FT-IR was used as in Example 3.
(C) Experimental Results As shown in Table 2 above, CHF ₃ could be selectively removed without affecting other components such as CF ₄ . In addition, moisture and CO ₂ could be removed to the detection limit level.

(2) for selective enrichment collection function of selective enrichment collection function CHF ₃ of CHF _3, after performing the selective adsorption treatment manipulation by the processing unit of the (1) by purging a processing unit in a heated state adsorption It can be configured by performing a treatment operation for desorbing the CHF ₃ and condensing and recovering the CHF ₃ under a low temperature condition.

Specifically, FIG. 11 illustrates a sample processing system for recovering CHF _{3 according} to the present invention. The gas desorbed from the processing unit 10 filled with activated alumina formed in the form of beads or pellets is similarly passed through the adsorption cylinder 11 filled with synthetic zeolite formed in the form of beads or pellets. Then, it is introduced into the condenser 12 cooled to a standard boiling point (−82.1 ° C.) or less of CHF ₃ using a cold heat source such as liquid nitrogen, and condensed and liquefied to be recovered. At this time, the activated alumina is a general one used for dehumidification and the like. Synthetic zeolite having a pore diameter of about 3 to 10 mm can be used, but preferably a pore diameter of about 4 mm is used. The condenser 12 can be made of an aluminum material, a copper material, a stainless steel material, or the like, but it is preferable to use an aluminum material having good thermal conductivity in order to liquefy gaseous CHF ₃ .

In addition, it is preferable that the processing unit 10 and the adsorption cylinder 11 perform initial regeneration of each adsorbent by circulating an inert gas such as N _{2 while} being heated by an electric heater or the like before use. The regeneration temperature at this time is preferably 250 ° C. or more as described above, and the regeneration time is 1 Hr or more, preferably 5 Hr or more. The linear velocity of the flowing inert gas is 1 cm / s or more, preferably 2 cm / s or more. It is preferable to prepare two or more processing units 10 and adsorption cylinders 11 so that continuous operation is possible.

Next, the operation will be described sequentially from the CHF ₃ adsorption treatment from the exhaust gas (sample) discharged from the semiconductor manufacturing process.
(2-1) The sample is introduced into the processing unit 10 with its flow rate and pressure adjusted by the mass flow controller 13 and the compressor 14. In the processing unit 10, CHF ₃ in the sample is mainly adsorbed. At this time, if moisture or CO ₂ is contained in the exhaust gas, these are also adsorbed, but other exhaust gas components are not adsorbed. The pressure of the processing unit 10 at this time is in the range of 0 to 0.9 MPaG, preferably 0.2 to 0.5 MPaG. Moreover, the linear velocity of the flowing gas is adjusted to 0.1 to 2.0 cm / s, preferably 0.5 to 1.0 cm / s.
(2-2) Before the CHF ₃ breaks through the processing unit 10, the other processing unit 10 is switched. Thereafter, the processing unit 10 on which the CHF ₃ is adsorbed is regenerated by heating with an inert gas and an electric heater. The heating temperature is 250 to 350 ° C.
(2-3) Next, the regeneration gas is introduced into the adsorption cylinder 11 with the flow rate and pressure adjusted by the mass flow controller 15 and the compressor 16. In the adsorption cylinder 11, moisture and CO ₂ in the regeneration gas are adsorbed and separated from the regeneration gas. The pressure of the adsorption cylinder 11 at this time is in the range of 0 to 0.9 MPaG, preferably 0.2 to 0.5 MPaG. Moreover, the linear velocity of the flowing gas is 0.1 to 2.0 cm / s, preferably 0.5 to 1.0 cm / s.
(2-4) The regeneration gas that has passed through the adsorption cylinder 11 is introduced into the condenser 12 cooled to -82.1 ° C or lower. Since this regeneration gas is composed of an inert gas and CHF ₃ , when introduced into the condenser 12, only CHF ₃ is liquefied and condensed, and the inert gas is discharged from the condenser 12. The liquefied and condensed CHF ₃ is purified by taking it out of the liquid phase.
(2-5) When regeneration of the processing unit 10 is completed, regeneration of the adsorption cylinder 11 is performed with an inert gas and an electric heater. The regeneration temperature at this time is 250 to 350 ° C.
(2-6) In this way, CHF ₃ discharged from the semiconductor manufacturing process can be recovered and purified by a simple operation, and the recovered and purified CHF ₃ can be used again in the semiconductor manufacturing process. Is possible.

  Next, specific examples of the following three sample processing systems using a processing unit using aluminum oxide as an adsorbent will be reported.

Example 6
As illustrated in FIG. 12, an experiment was performed using one processing unit 10.
(A) Used treatment unit A stainless steel adsorption cylinder having an inner diameter of 33 mm and a length of 150 mm was filled with bead-like activated alumina having a diameter of about 2 mm.
(B) Experimental condition (b-1) The regeneration processing operation of the processing unit 10 was performed in advance. N ₂ was passed through the processing unit 10 and the temperature was raised to 250 ° C., and then the temperature was maintained for 5 hours. Heating was stopped after 5 hours had elapsed, and the adsorption cylinder was cooled while N ₂ was circulated. Note that the N ₂ linear velocity at this time is 2.0 cm / s. Note that the temperature rise is preferably performed in two stages. That is, the first temperature rise was 100 ° C., and after reaching 100 ° C., the temperature was maintained for 1 hour or more, and then the second temperature rise was raised to 250 ° C.
(B-2) Next, the CHF ₃ adsorption processing operation to the processing unit 10 was performed. The flow rate and pressure were adjusted using the mass flow controller 13 and the compressor 14, and a standard gas 17 having a 0.1% CHF ₃ / N ₂ balance was introduced into the processing unit 10. The pressure of the processing unit 10 was adjusted to 0.3 MPaG, the linear velocity of the introduced gas was adjusted to 0.5 cm / s, and CHF ₃ was adsorbed.
(B-3) Thereafter, the supply of the standard gas was stopped, and the gas in the adsorption cylinder was released until the adsorption cylinder pressure became 0 MPaG. Although the release gas when this was measured by similar FT-IR as in Example 1, CHF ₃ concentration in the discharged gas was 1ppm or less.
(B-4) Next, the CHF ₃ desorption treatment operation was performed. The processing unit 10 was heated to 250 ° C. with an electric heater, and N ₂ gas was introduced into the processing unit 10.
(B-5) At the same time, a CHF ₃ condensation recovery treatment operation was performed. An aluminum condenser 12 having an internal volume of 0.3 L is previously cooled to −90 ° C. using liquid nitrogen. The N ₂ gas discharged from the processing unit 10 is introduced into the condenser 12, and CHF ₃ is liquefied. Note that the N ₂ gas linear velocity at this time is 1.0 cm / s.
(C) Experimental Results When the recovery and purification rate of CHF ₃ at this time was defined by [introduced CHF ₃ amount] / [liquefied CHF ₃ amount], it was 0.95 or more.

Example 7
As illustrated in FIG. 13, the adsorption cylinder 11 was placed between the processing unit 10 and the condenser 12 for experiments.
(A) Used treatment unit and adsorption cylinder The treatment unit 10 used is the same as in the above [Example 6], and the adsorption cylinder 11 is a stainless steel adsorption cylinder having an inner diameter of 33 mm and a length of 150 mm. Bead-shaped zeolite (pore diameter: 4 mm).
(B) Experimental conditions (b-1) Initial regeneration was performed in the same manner as in [Example 6] above.
(B-2) Next, the CHF ₃ adsorption processing operation to the processing unit 10 was performed. A sample having a composition of water, CO ₂ , CHF ₃ , CF ₄ , C ₂ F ₆ 0.1% / N ₂ balance was introduced into the processing unit 10. In the processing unit 10, CHF ₃ was adsorbed, and moisture and CO ₂ were adsorbed in addition to CHF ₃ .
(B-3) Next, the CHF ₃ desorption treatment operation was performed. The processing unit 10 was purged in the same manner as in [Example 6] above, and purge gas was introduced into the adsorption cylinder 11. This purge gas contains moisture, CO ₂ and CHF ₃ , and moisture and CO ₂ are adsorbed and removed in the adsorption cylinder 11.
(B-4) Thereafter, a CHF ₃ condensation and recovery treatment operation was performed. The gas discharged from the adsorption cylinder 11 is introduced into the cooled condenser 12, where CHF ₃ is liquefied.
(B-5) In the above operation, the pressure and linear velocity of the processing unit 10 and the adsorption cylinder 11 and the cooling temperature of the condenser 12 are the same as those in the first embodiment.
(C) Experimental result The recovery and purification rate of CHF ₃ at this time was 0.95 or more.

Example 8
In the same experiment as [Example 6] and [Example 7], the CHF ₃ concentration in the gas introduced into the processing unit 10 was changed to 0.01% and 1.0%. The results were equivalent to the results of [Example 6] and [Example 7] above.

As described above, according to the sample processing system, from a sample containing CHF _3, a simple, efficient, and have demonstrated that it is possible to selectively remove or recover the CHF _3.

As described above, the CHF ₃ selective processing unit and the sample processing system using the CHF ₃ according to the present invention, for example, remove CHF ₃ from a sample containing moisture, CO ₂ and various FCs in a semiconductor manufacturing process exhaust gas. The present invention is applicable not only when functionally removed or recovered, but also when recovering and purifying high-purity rare gases or specific other components.

Schematic showing the IUPAC adsorption isotherm. Schematic which illustrates the static adsorption characteristic with respect to various substances of activated alumina. Schematic which illustrates the static adsorption characteristic with respect to various substances of a synthetic zeolite (4A). Schematic which illustrates the static adsorption characteristic with respect to various substances of activated carbon. Schematic illustrating an apparatus for demonstrating the dynamic adsorption properties of CHF ₃ . Schematic illustrating the dynamic adsorption properties of CHF _3. Schematic illustrating the processing unit of CHF _{3 according to} the present invention. Schematic illustrating an apparatus for demonstrating the selective removal function of CHF ₃ . Schematic illustrating an apparatus for demonstrating the selective removal function of CHF ₃ . Schematic illustrating an apparatus for demonstrating the selective removal function of CHF ₃ . Schematic diagram illustrating a sample processing system for recovering CHF ₃ according to the present invention. Schematic which illustrates the sample processing system (Example 6) which concerns on this invention. Schematic which illustrates the sample processing system (Example 7) which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample introduction part 2 Sample delivery part 3 Adsorbent 4 Packing layer 5 Space part 6 Spiral pipe line (heat exchange flow path)
7a, 7b Diffusion section 8a, 8b Guide section 9 Electric heater 10 Processing unit 11 Adsorption cylinder 12 Condenser 13, 15 Mass flow controller 14, 16 Compressor 17 Standard gas

Claims (6)

  A method for selectively treating trifluoromethane in a sample, wherein the selective adsorption function of an adsorbent mainly composed of aluminum oxide is used. The sample contains at least moisture, carbon dioxide, trifluoromethane and other saturated or unsaturated fluorocarbons,
The adsorbent is characterized by using two or more kinds of adsorbents in stages, using a reagent mainly composed of synthetic zeolite in one of the preceding stages, and using a reagent mainly composed of aluminum oxide in the subsequent stage. The method for selectively treating trifluoromethane according to claim 1.   The adsorbent that has selectively adsorbed trifluoromethane by the treatment is recovered by desorbing the adsorbed trifluoromethane by heating, and then condensing and liquefying the trifluoromethane at a temperature lower than its normal boiling point. The method for selectively treating trifluoromethane according to claim 1 or 2, wherein:   The method for selectively treating trifluoromethane according to any one of claims 1 to 3, wherein a desorption temperature of trifluoromethane adsorbed on the adsorbent is 250 ° C or higher. A processing unit filled with the adsorbent according to any one of claims 1 to 4,
(1) A space provided inside the processing unit and having a sample introduction part and a sample delivery part,
(2) a heating part for heating the space part,
(3) a filling portion disposed in the center of the space portion and filled with an adsorbent;
(4) A guide part that divides the space part into two or more spaces in contact with the filling part, and partitions each part so as to be circulated.
(5) One end is connected to either the sample introduction part or the sample delivery part, and is spirally wound in the filling part, and the other end is disposed outside the filling part via the guide part. Flow path,
A processing unit for trifluoromethane, comprising: A sample processing system using the processing unit according to claim 5,
(1) A processing operation for introducing a sample containing at least water, carbon dioxide, trifluoromethane, and a fluorocarbon composed of other saturated or unsaturated bonds into the processing unit and selectively adsorbing trifluoromethane.
(2) Treatment operation for desorbing adsorbed trifluoromethane,
(3) A processing operation for recovering the trifluoromethane by condensing it under a condition lower than its boiling point.
A sample processing system comprising:

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