JP3939542B2 - Exhaust gas treatment equipment - Google Patents

Description

【００３３】
表１から理解されるように、上記したセラミックフィルタ３１を使用し且つ一次処理ガス１１を過熱装置５により１００℃以上に加熱することにより、ＰＦＣガスを効果的に濃縮できることが確認された。
【００３４】
（実験２） 上記セラミックフィルタ３１をヘリウム雰囲気３５０℃で前処理し、ＣＨＦ₃：０．５気圧，Ｎ₂：０．５気圧の混合ガス（１００ｃｃ／ｍｉｎ）をガス導入室３４に導入して、ガス透過室３６から排出されるガスの流量を膜流量計により測定すると共に、当該ガスにおけるＣＨＦ₃濃度及びＮ₂濃度を夫々ガスクロマトグラフィーにより測定した。なお、実験１と同様に、混合ガスは大気圧，２００℃とし、ガス透過室３６は−０．０９ＭＰａに減圧した。そして、これらの測定値に基いて透過率＝透過量／（フィルタ面積×差圧×時間）からＣＨＦ₃及びＮ₂の透過率を求めた。さらに、ＣＨＦ₃の透過係数比（Ｎ₂の透過率／ＣＨＦ₃の透過率）を求めた。その結果は表２に示す通りであった。
【００３５】
【表２】

【００３６】
（実験３） 上記セラミックフィルタ３１をヘリウム雰囲気３５０℃で前処理し、ＳＦ₆：０．５気圧，Ｎ₂：０．５気圧の混合ガス（１００ｃｃ／ｍｉｎ）をガス導入室３４に導入して、ガス透過室３６から排出されるガスの流量を膜流量計により測定すると共に、当該ガスにおけるＳＦ₆濃度及びＮ₂濃度を夫々ガスクロマトグラフィーにより測定した。なお、実験１，２と同様に、混合ガスは大気圧，２００℃とし、ガス透過室３６は−０．０９ＭＰａに減圧した。そして、これらの測定値に基いて透過率＝透過量／（フィルタ面積×差圧×時間）からＳＦ₆及びＮ₂の透過率を求めた。さらに、ＳＦ₆の透過係数比（Ｎ₂の透過率／ＳＦ₆の透過率）を求めた。その結果は表３に示す通りであった。
【００３７】
【表３】

【００３８】
表２及び表３から明らかなように、セラミックフィルタ３１（分離膜３１ｂ）の細孔による透過率制御によりＮ₂ガスとＰＦＣガス（ＣＨＦ₃又はＳＦ₆）との分離において高い選択性を有することが確認された。
【００３９】
（実験４） 上記した無害化装置４におけるＣＦ₄濃度変化による分解効率への影響を確認した。すなわち、被燃焼ガス流路４４ｂから内筒４３にＮ₂，ＣＦ₄の混合ガスを導入させると共に、燃料ガス供給路４４ｃからプロパンガスを供給して、混合ガスを燃焼させた。そして、混合ガスの導入量を一定（５０Ｌ／ｍｉｎ）に保持した状態で、導入させる混合ガスのＣＦ₄濃度を０〜９％の範囲で変化させて、燃焼筒４１から排出される廃ガスのＣＦ₄濃度を測定した。導入させる混合ガス及び廃ガスのＣＦ₄濃度はＦＴＩＲ（フーリェ変換赤外分光計）で測定し、その測定値から分解率（（混合ガスのＣＦ₄濃度／廃ガスのＣＦ₄濃度）×１００）を求めた。その結果は図６に示す通りであった。
【００４０】
図６から明らかなように、上記構造の無害化装置４によれば、ＰＦＣガス濃度（ＣＦ₄濃度）に拘わらずほぼ一定の分解率を確保することができ、分離フィルタ装置３によるＰＦＣガスの濃縮に適した無害化処理（ＰＦＣガスの分解処理）を行い得ることが理解される。
【００４１】
（実験５） 実験４と同一の燃焼条件において、Ｎ₂，ＣＦ₄の混合ガスを上記無害化装置４で燃焼させた。そして、混合ガスにおけるＣＦ₄量を一定（１Ｌ／ｍｉｎ）としてＮ₂量を１００〜６００Ｌ／ｍｉｎの範囲で変化させつつ、実験４と同様にして分解率を求めた。その結果は図７に示す通りである。
【００４２】
ところで、実験１から理解されるように、上記した分離フィルタ装置３によるＮ₂，ＣＦ₄の混合ガスの分離能力つまりＮ₂の除去率は約２５％である（表１に示す如く、１％のＣＦ₄は約４％まで濃縮される）から、Ｎ₂量を６００Ｌ／ｍｉｎとする混合ガスを分離フィルタ装置３で処理するとすれば、無害化装置４に導入される混合ガスのＮ₂量は約１５０Ｌ／ｍｉｎに低減されることになるはずである。そして、図７から理解されるように、Ｎ₂量が約１５０Ｌ／ｍｉｎ以下であるときは、分解率が９８％で安定しているが、Ｎ₂量が増加するに従って分解率は急激に低下している。したがって、これらのことから、排ガスを分離フィルタ装置３により処理（ＰＦＣガスの濃縮）した上で無害化装置４による処理（ＰＦＣガスの燃焼）を行うことにより、排ガスをそのまま燃焼処理する場合に比して、極めて効率の良い無害化処理を行いうることが理解される。なお、図７に示す実験５の結果は、分離フィルタ装置３によるＰＦＣガスの濃縮度と無害化装置４による分解率との関係を間接的に示すものである。
【００４３】
（実験６） 上記した排ガス処理装置を使用して６００Ｌ／ｍｉｎの排ガス１を無害化処理して、無害化装置４から排出される廃ガスのＰＦＣ濃度を測定した。また、この排ガス処理装置の無害化装置４と同一構成をなす複数台の無害化装置を並列使用して、同一性状，流量の排ガス１を無害化処理した。その結果、無害化装置のみにより排ガス１を処理した場合、廃ガスのＰＦＣ濃度が排ガス処理装置を使用した場合と同等となるには、３台の無害化装置が必要であった。そして、排ガス処理装置を使用した場合の設置スペース、イニシャルコスト及びランニングコストは、夫々、３台の無害化装置を使用した場合の９０％、８０％及び５０％であった。このことから、本発明の排ガス処理装置によれば、設置スペース、イニシャルコスト及びランニングコストの低減を図りつつ良好なＰＦＣガスの無害化処理を行い得ることが理解される。
【００４４】
なお、本発明は上記した実施の形態に限定されるものではなく、本発明の基本原理を逸脱しない範囲において適宜に改良，変更することができる。例えば、無害化装置４として、特開平１１−３１９４８５号公報に開示される如く、二次処理ガスを加熱した上で触媒により分解させる触媒燃焼式のものを使用することができる。また、分離フィルタ装置３における分離膜３１ｂの水分吸着による性能低下を抑制する為には、図８に示す如く、過熱装置５の前段（上流側）に、水分を除去する為の冷凍式、加圧式、膜分離方式等による方式により、湿式スクラバー２を通過した一次処理ガス１１中の水分を予め除去する水分除去装置５１を設けておくことがより好ましい。なお、図８に示す排ガス処理における水分除去装置５１以外の構成は、上記した実施の形態における排ガス処理装置におけると同一である。また、本発明は、上記した如くバルクガス，ＰＦＣガスに加えて酸性ガス及びＳｉＯ₂微粉末が含まれる排ガスのみならず、酸性ガスを含まない排ガスやＳｉＯ₂微粉末を含まない排ガスを無害化処理する場合にも当然に適用することができる。
【００４５】
【発明の効果】
以上の説明からも容易に理解されるように、本発明の排ガス処理装置によれば、ＰＦＣガスを含む排ガスを冒頭で述べた問題を生じることなく効率良く経済的に無害化処理することができ、しかも排ガスに大量に含まれるバルクガスを効果的に回収，再利用することができる。
【図面の簡単な説明】
【図１】本発明に係る排ガス処理装置の実施の形態を示す系統図である。
【図２】分離フィルタ装置の一例を示す断面図である。
【図３】図２のIII −III 線に沿う要部の断面図である。
【図４】無害化装置の一例を示す断面図である。
【図５】図４の要部を拡大して示す詳細図である。
【図６】実験４で求めた分解率と濃度との関係を示す曲線図である。
【図７】実験５で求めた分解率と濃度との関係を示す曲線図である。
【図８】排ガス処理装置の変形例を示す図１相当の系統図である。
【符号の説明】
１…排ガス、２…スクラバー、３…分離フィルタ装置、４…無害化装置、５…過熱装置、６…バルクガス回収装置、７…排気路、８…一次処理ガス路、９…二次処理ガス路、１０…廃ガス路、１１…一次処理ガス、１２…バルクガス、１２ａ…バルクガス（精製バルクガス）、１２ｃ…不純物、１３…二次処理ガス、１４…廃ガス、２１…スプレー水、３１…セラミックフィルタ、３１ａ…多孔質支持体、３１ｂ…分離膜、３１ｃ…中間層、３４…ガス導入室、３５…ガス導出室、３６…ガス透過室、４１…燃焼筒、４２…外筒、４３…内筒、４４…燃焼バーナ、６１…バルクガス回収部、６２…バルクガス回収路、６３…バルクガス精製装置、６３ａ…活性炭、６３ｂ…セラミックフィルタ、６４…返戻路。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas treatment apparatus for detoxifying an exhaust gas discharged from a semiconductor manufacturing apparatus or the like and containing a bulk gas and a perfluoro compound gas (Per Fluoro Compound Gases).
[0002]
[Prior art]
In the semiconductor manufacturing apparatus, various perfluoro compound gases are used. For example, in the dry etching process, CF is used as an etching gas._FourIs used as a cleaning gas in the CVD process.₂F₆Etc. are used.
[0003]
Thus, the unreacted portion of the perfluoro compound gas is the N gas used as a carrier gas, a purge gas, etc.₂Along with a bulk gas such as Ar, He, etc., it is discharged as exhaust gas from the semiconductor manufacturing apparatus.
[0004]
By the way, the perfluoro compound gas contained in the exhaust gas is extremely small compared to the bulk gas and is harmless to the human body.₂The global warming potential is extremely large compared to the₂Against CF_FourIs 6500 times, C₂F₆Is 9200 times and SF₆Therefore, it is not preferable to discharge such exhaust gas to the atmosphere as it is.
[0005]
Therefore, conventionally, exhaust gas discharged from a semiconductor manufacturing apparatus is burned by a combustion apparatus, and perfluoro compound gas contained therein is detoxified by thermal decomposition.
[0006]
[Problems to be solved by the invention]
However, the exhaust gas contains a large amount of inert bulk gas such as nitrogen gas, so if the exhaust gas discharged from the semiconductor manufacturing equipment is burned as it is, the amount of fuel consumption increases and a combustion device is also required As a result of the increase in size, the running cost and initial cost have increased significantly.
[0007]
Moreover, although it is not a raw material gas necessary for the semiconductor manufacturing process like perfluoro compound gas, HF, SiF in the process_Four, SiHF_ThreeAcid gases such as these may be by-produced and contained in the exhaust gas. Therefore, when exhaust gas containing such acidic gas is introduced into the combustion apparatus, there is a possibility that the apparatus parts may be corroded, and there is a problem that the durability of the combustion apparatus is lowered.
[0008]
An object of the present invention is to provide an exhaust gas treatment apparatus capable of efficiently and effectively detoxifying exhaust gas discharged from a semiconductor manufacturing apparatus or the like without causing such problems.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the invention of claim 1 of the present application is an exhaust gas treatment apparatus for detoxifying exhaust gas containing bulk gas and perfluoro compound gas, which is a scrubber for pre-processing exhaust gas and exhaust gas that has passed through the scrubber. A separation filter device that separates and removes bulk gas from the primary treatment gas, and an exhaust gas that has passed through the separation filter device and is a bulk gasButA detoxification device that thermally decomposes and detoxifies the separated secondary treatment gas, and a bulk gas recovery device that recovers the bulk gas separated by the separation filter deviceAnd the bulk gas recovery device separates and purifies the perfluoro compound gas accompanying the bulk gas discharged from the separation filter device, and purifies the separated and removed perfluoro compound gas in the primary processing of the separation filter device. The basic configuration of the present invention is that a bulk gas purifier returning to the gas introduction side is provided.
[0010]
  SaidAs a bulk gas purification device, it accompanies the bulk gas discharged from the separation filter device.Perfluoro compound gasPermeating gas with smaller molecular diameter than perfluoro compound gasLetThose having a ceramic filter are used.
[0011]
  In addition, the separation filter device transmits gas with a smaller molecular diameter than perfluoro compound gas.LetIt is preferable to have a ceramic filter. As a ceramic filter, a filter comprising a ceramic porous support and a separation membrane made of an amorphous oxide containing Si and Zr having a large number of pores on at least one surface thereof is used. It is preferable to do. Such a ceramic filter is also used as a ceramic filter used in the above-described bulk gas purification apparatus.
[0012]
The scrubber also contains impurities other than bulk gas and perfluoro compound gas (for example, acidic gas such as HF or SiO₂In the case where fine solids such as fine powder and dust are contained, these are removed (pretreatment), and it is generally preferable to use a wet type. When such a wet scrubber is used, it is preferable to arrange a superheater that superheats the primary process gas in the primary process gas path from the scrubber to the separation filter device. As the superheater, it is preferable to use a heat exchanger that uses the waste heat of the detoxifying device as the main heat source.
[0013]
Further, as the detoxifying device, it is preferable to use a combustion type that burns and decomposes the secondary processing gas with a fuel burner or a catalytic combustion type that decomposes with a catalyst after heating the secondary processing gas. .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to FIGS.
[0015]
FIG. 1 shows an embodiment of an exhaust gas treatment apparatus according to the present invention. The exhaust gas treatment apparatus in this embodiment is for detoxifying exhaust gas 1 discharged from a semiconductor manufacturing process. A scrubber 2, a separation filter device 3, a detoxification device 4, a superheating device 5, and a bulk gas recovery device 6 are provided.
[0016]
The exhaust gas 1 discharged from the semiconductor manufacturing process is a large amount of bulk gas (N₂, Ar, He, etc.), a small amount of perfluoro compound gas (CF_Four, C₂F₆, C_ThreeF₈, C_FourF_TenPerfluorocarbons such as Perfluoro Carbon or CHF_Three, CH₂F₂, SF₆, NF_ThreeOrganic or inorganic fluorine compound gas such as "PFC gas") and acid gas (HF, SiF) by-produced in the semiconductor manufacturing process_Four, SiHF_ThreeEtc.).
[0017]
As shown in FIG. 1, the scrubber 2 is a wet type configured to spray water or alkaline water 21 onto the exhaust gas 1 introduced from the exhaust passage 7 of the semiconductor manufacturing apparatus. By contacting, the acidic gas contained in the exhaust gas 1 is dissolved and removed (when water is used as the spray water 21) or neutralized and removed (when alkaline water is used as the spray water 21). By the way, SiH as a reaction gas in the CVD apparatus._FourIs used, the exhaust gas 1 introduced into the scrubber 2 contains SiH._FourSiO, which is an oxide of₂In the piping system including the exhaust passage 7, dust may be mixed into the exhaust gas 1.₂) Is contained in the exhaust gas 1, such fine solids are also removed from the exhaust gas 1 by contact with the spray water 21. The primary processing gas 11 which is the exhaust gas from which the acid gas and the fine solid content have been removed is introduced from the scrubber 2 through the primary processing gas path 8 into the separation filter device 3.
[0018]
  As shown in FIG. 1, the separation filter device 3 separates and removes the bulk gas 12 from the primary processing gas 11 by a ceramic filter 31. As the ceramic filter 31, JP-A-2002001As disclosed in Japanese Patent No. -62241, an amorphous material containing Si and Zr having a large number of pores (average pore diameter of 2.5 to 10 mm) on at least one surface of a ceramic porous support. By depositing an oxide separation membrane and bringing the primary treatment gas into contact with one surface of the separation membrane, a bulk gas having a smaller molecular diameter than the PFC gas is selectively transmitted to the other surface of the separation membrane. What is configured as such is optimal. In this example, as shown in FIG. 2, the separation filter device 3 forms three chambers 34, 35, 36 partitioned by a pair of partition walls 32, 33 inside the device, and the partition walls 32, 33 have the above-mentioned A large number of cylindrical ceramic filters 31. The gas permeation chamber 36 formed between the partition walls 32 and 33 is maintained at a lower pressure than the gas introduction chamber 34 and the gas outlet chamber 35 on both sides thereof, and the primary processing gas path 8 is connected to the gas introduction chamber 34. ing. Each ceramic filter 31 has a cylindrical shape with an inner diameter of about 2 mm. As shown in FIG. 3, the ceramic filter 31 is formed on the outer peripheral surface or inner peripheral surface of a porous support 31a made of α-alumina ceramic in a cylindrical shape. After forming the air-permeable intermediate layer 31c made of γ-alumina ceramic, the separation membrane 31b is deposited.
[0019]
Thus, according to the separation filter device 3, the primary processing gas 11 introduced from the primary processing gas passage 8 into the introduction chamber 34 passes through the ceramic filters 31 and flows into the gas outlet chamber 35. The bulk gas 12 contained in the primary processing gas 11 permeates from the separation membrane 31b of each ceramic filter 31 to the gas permeation chamber 36 and is separated and removed. The secondary processing gas 13 which is the exhaust gas from which the bulk gas 12 has been separated and removed is introduced from the gas outlet chamber 35 into the detoxifying device via the secondary processing gas path 9.
[0020]
As shown in FIG. 1, the detoxifying device 4 is a combustion type that detoxifies the secondary processing gas 13 introduced from the secondary processing gas passage 9 by burning and pyrolyzing it with a combustion burner. In this example, as the detoxifying device 4, the one disclosed in Japanese Patent Laid-Open No. 2001-280629 is used. As shown in FIGS. 4 and 5, the detoxifying device 4 includes a combustion cylinder 41 including an outer cylinder 42 and an inner cylinder 43, a combustion burner 44 having an upper end attached to the center of the bottom of the inner cylinder 43, and an inner cylinder 43. And a combustion-supporting gas introduction path 45 for introducing the combustion-supporting gas 45a into the bottom side region. The inner cylinder 43 is formed by causing a plurality of cylindrical members 43a... To rise up and down with a slight gap 43b, and the secondary combustion air 46 introduced from the lower part of the outer cylinder 42 is between the inner and outer cylinders 42, 43. And is supplied to the inner cylinder 43 from the gap 43b. The combustion burner 44 forms a plurality of nozzle ports 44a that form an annular shape on the upper surface and are arranged in parallel at equal intervals. And a fuel gas supply path 44c that communicates with the nozzle ports 44a. The combustion gas channel 44 b is connected to the secondary processing gas channel 9 and introduces the secondary processing gas 13 that has passed through the separation filter device 3 into the inner cylinder 43. The fuel gas supply passage 44c uses a fuel gas (methane, propane, butane, ethylene, natural gas, city gas, or a mixed gas thereof) from a nozzle port group 44a that concentrically surrounds the opening of the combustion gas passage 44b. 44d) is ejected. The burner 44 is provided with an unillustrated igniter and ignites the fuel gas 44d ejected from the nozzle port 44a. The formation surface of the nozzle port 44a is inclined as shown in FIG. 5, and the flame 44e generated by the fuel gas 44d ejected from the nozzle port 44a is ejected from the combustion gas passage 44b (secondary processing gas). It is devised to be suitable for 13. In general, it is preferable to set the inclination angle β of the formation surface of the nozzle opening 44a to about 30 degrees in consideration of the stability of the flame 44e and the like. The combustion-supporting gas introduction passage 45 ejects the combustion-supporting gas 45a at a predetermined angle θ (usually 60 to 90 degrees) with respect to the ejection gas 13 from the combustion gas passage 44b. As the combustion-supporting gas 45a, a pressure higher than atmospheric pressure (usually 1.5 × 10^FiveCompressed air, compressed oxygen enriched air, and compressed oxygen.
[0021]
Thus, according to the detoxifying device 4, the secondary processing gas 13 introduced into the inner cylinder 43 from the combustion gas passage 44 b is combusted and pyrolyzed by the flame 44 e at 800 to 1500 ° C., and PFC gas The secondary processing gas 13 containing is rendered harmless. At this time, since the flame 44e is formed toward the secondary processing gas 13, the secondary processing gas 13 comes into direct contact with the flame 44e, and the secondary processing gas 13 is effectively burned. Furthermore, by supplying the combustion-supporting gas 45a at or above atmospheric pressure from the outer periphery of the flame 44e, the combustion of the flame 44e is promoted, and the flame-retardant PFC gas in the secondary treatment gas 13 is also reliably decomposed. . The combustion gas (waste gas) 14 is discharged from the upper exhaust port 41 a of the combustion cylinder 41 to the waste gas passage 10.
[0022]
As shown in FIG. 1, the superheater 5 is disposed in the primary processing gas path 8, superheats the primary processing gas 11 that has passed through the wet scrubber 2, and is included in the primary processing gas 11 by contact with the spray water 21. The water (water droplets) is evaporated and removed. That is, the superheater 5 evaporates water droplets into water vapor by heating the primary processing gas 11 to 100 ° C. or higher (generally, 100 to 500 ° C.). In this example, waste heat discharged from the detoxifying device 4 is used as the main heat source of the superheater 5. That is, the superheater 5 is composed of a heat exchanger provided in the waste gas passage 10 of the detoxification device 4 and is devised so that the primary treatment gas 11 is heated by heat exchange with the waste gas 14 (waste At the start of operation where heat recovery from the gas 14 cannot be performed, the primary processing gas 11 is overheated by an auxiliary heat source such as an electric heater). In addition, the superheater 5 vaporizes and removes water droplets that hinder the function (permeation function) of the ceramic filter 31 as described later, and does not dry the primary processing gas 11.
[0023]
As shown in FIG. 1, the bulk gas recovery device 6 is provided with a bulk gas recovery path 62 from the gas permeation chamber 36 of the separation filter device 3 to an appropriate bulk gas recovery unit 61, and the bulk gas 12 separated by the separation filter device 3 is transferred to the bulk gas. It is collected in the collection unit 61 and reused. Here, the bulk gas recovery unit 61 is an apparatus, a device, or a part thereof that should reuse the bulk gas 12. For example, when the bulk gas 12 is used as the purge gas of the detoxification device 4, the detoxification device 4 uses the bulk gas. It becomes the collection unit 61. By the way, the bulk gas 12 separated by the separation filter device 3 includes PFC gas, CO, CO₂, There is a possibility that impurities which are harmful to the reuse of bulk gas such as moisture are accompanied. Therefore, in the bulk gas recovery device 6, a bulk gas purification device 63 for separating and removing the impurities is disposed in the bulk gas recovery path 62. As the bulk gas purification device 63, for example, the above-mentioned impurities accompanying the bulk gas 12 discharged from the gas permeation chamber 36 of the separation filter device 3 are adsorbed and removed by activated carbon 63 a or a ceramic filter having the same structure as the ceramic filter 31 described above. What separates bulk gas and impurities, such as PFC gas, by 63b is used. That is, in the former, a pair of adsorption towers filled with activated carbon 63a is provided, and both adsorption towers are alternately switched between an adsorption process and a regeneration process (desorption process). Then, the bulk gas 12 is supplied from the separation device 3 to the adsorption tower in the adsorption process, and impurities contained therein are adsorbed and removed by the activated carbon 63a, and the bulk gas (purified bulk gas) 12a from which the impurities are removed is supplied to the bulk gas recovery unit 61. Supply. On the other hand, in the adsorption tower in the regeneration process, the impurities adsorbed on the activated carbon 63a are separated from the activated carbon 63a by supplying a purge gas and the like, and the impurities 12c are returned from the return path 64 to the primary processing gas path 8 to perform the primary treatment. The gas 11 is mixed. In the latter case, similarly to the separation filter device 3, the bulk gas (purified bulk gas) 12a that has permeated the ceramic filter 63b is supplied to the bulk gas recovery unit 61, and the impurity 12c that does not permeate the ceramic filter 63b is returned to the return path 64. To the primary processing gas path 8 and mixed with the primary processing gas 11. However, in the latter case, as in the separation filter device 3, there is a possibility that the PFC gas is accompanied by the bulk gas 12a that has passed through the ceramic filter 63b, although the amount is very small. Therefore, in order to purify the bulk gas 12 with higher accuracy, it is preferable to use the former activated carbon adsorption system as the bulk gas purification device 63. The return path 64 is connected to the upstream side portion of the superheater 5 in the primary processing gas path 8.
[0024]
According to the exhaust gas treatment apparatus configured as described above, the PFC gas contained in the exhaust gas 1 can be effectively detoxified, and the bulk gas contained in a large amount in the exhaust gas 1 can be effectively used.
[0025]
That is, the exhaust gas 1 is converted into acid gas and fine solids (SiO 2) by a wet scrubber 2.₂Etc.) and then introduced into the separation filter device 3 and the detoxifying device 4, each device without causing corrosion of the device parts due to acid gas and clogging of the ceramic filter 31 due to fine solids. Processing by 3 and 4 is performed satisfactorily.
[0026]
In addition, the primary processing gas 11 introduced into the separation filter device 3 is heated to 100 ° C. or more by the superheater 5 to vaporize water droplets generated by contact with the spray water 21. The permeation function by the filter 31 is not significantly deteriorated, and the bulk gas 12 is favorably separated. Moreover, since the primary processing gas 11 is heated to 100 ° C. or higher by the superheater 5, the gas permeation action in the ceramic filter 31 is effectively performed by the activation of the gas molecular motion. The degree of improvement in the gas permeation effect due to the activation of the molecular motion increases as the temperature of the primary processing gas 11 introduced into the separation filter device 3 increases. Therefore, it is preferable that the heating temperature of the primary processing gas 11 by the superheater 5 be as high as possible in the heat resistance range (generally about 100 to 500 ° C.) of the separation filter device 3. In addition, when an organic membrane filter whose heat resistance is inferior to that of a ceramic filter is used, such primary processing gas 11 cannot be overheated or heated, and the above-described effects cannot be achieved.
[0027]
Moreover, since the waste heat discharged | emitted from the harmless apparatus 4 is collect | recovered and utilized as a main heat source of the superheater 5, the running cost as the whole exhaust gas processing apparatus can be reduced.
[0028]
And since the exhaust gas 1 is introduced into the detoxification device 4 as the secondary treatment gas 13 obtained by concentrating the PFC gas with the separation filter device 3, the exhaust gas 1 in which the PFC gas is diluted with a large amount of bulk gas is used as it is. Compared with the case of introducing the fuel into the fuel cell 4, the fuel consumption required for the combustion decomposition of the PFC gas can be greatly reduced, the running cost can be reduced, and the detoxification processing device 4 can be downsized.
[0029]
Further, since the bulk gas 12 separated by the separation filter device 3 is further purified by the bulk gas purification device 63 and then recovered, the bulk gas contained in a large amount in the exhaust gas 1 can be effectively reused.
[0030]
By the way, the treatment effect of the exhaust gas 1 by the separation filter device 3 and the detoxification device 4 described above was confirmed by the following experiment.
[0031]
(Experiment 1) CF_Four: 1%, N₂: 99% of the mixed gas is introduced into the gas introduction chamber 34 of the separation filter device 3 under the conditions shown in Table 1, and the flow rate of the concentrated gas derived from the gas outlet chamber 35 and the CF_FourThe concentration was measured by a membrane flow meter and gas chromatography, and the bulk gas recovery rate was calculated. The mixed gas was at atmospheric pressure and 200 ° C., and the gas permeation chamber 36 was decompressed to −0.09 MPa. The results were as shown in Table 1.
[0032]
[Table 1]

[0033]
As understood from Table 1, it was confirmed that the PFC gas can be effectively concentrated by using the above-described ceramic filter 31 and heating the primary processing gas 11 to 100 ° C. or higher by the superheater 5.
[0034]
(Experiment 2) The ceramic filter 31 was pretreated in a helium atmosphere at 350 ° C., and CHF_Three: 0.5 atm, N₂: A 0.5 atm mixed gas (100 cc / min) is introduced into the gas introduction chamber 34, and the flow rate of the gas discharged from the gas permeation chamber 36 is measured with a membrane flow meter, and the CHF in the gas_ThreeConcentration and N₂Each concentration was measured by gas chromatography. As in Experiment 1, the mixed gas was at atmospheric pressure and 200 ° C., and the gas permeation chamber 36 was decompressed to −0.09 MPa. And based on these measured values, transmittance = transmission amount / (filter area × differential pressure × time) from CHF_ThreeAnd N₂The transmittance of was determined. In addition, CHF_ThreeTransmission coefficient ratio (N₂Transmittance / CHF_ThreeTransmittance). The results were as shown in Table 2.
[0035]
[Table 2]

[0036]
(Experiment 3) The ceramic filter 31 is pretreated in a helium atmosphere at 350 ° C.₆: 0.5 atm, N₂: 0.5 atm of mixed gas (100 cc / min) is introduced into the gas introduction chamber 34, and the flow rate of the gas discharged from the gas permeation chamber 36 is measured with a membrane flow meter, and SF in the gas is measured.₆Concentration and N₂Each concentration was measured by gas chromatography. As in Experiments 1 and 2, the mixed gas was at atmospheric pressure and 200 ° C., and the gas permeation chamber 36 was decompressed to −0.09 MPa. Then, based on these measured values, transmittance = transmission amount / (filter area × differential pressure × time) from SF₆And N₂The transmittance of was determined. In addition, SF₆Transmission coefficient ratio (N₂Transmittance / SF₆Transmittance). The results were as shown in Table 3.
[0037]
[Table 3]

[0038]
As is apparent from Tables 2 and 3, N is controlled by the transmittance control by the pores of the ceramic filter 31 (separation membrane 31b).₂Gas and PFC gas (CHF_ThreeOr SF₆It has been confirmed that it has high selectivity in the separation from).
[0039]
(Experiment 4) CF in the above detoxifying device 4_FourThe effect of degradation on concentration efficiency was confirmed. That is, N is transferred from the combustion gas passage 44b to the inner cylinder 43.₂, CF_FourIn addition, the propane gas was supplied from the fuel gas supply path 44c to burn the mixed gas. Then, the CF of the mixed gas to be introduced in a state where the introduction amount of the mixed gas is kept constant (50 L / min)._FourCF of waste gas discharged from the combustion cylinder 41 by changing the concentration in the range of 0 to 9%_FourConcentration was measured. CF of mixed gas and waste gas to be introduced_FourThe concentration is measured with FTIR (Fourier transform infrared spectrometer), and the decomposition rate ((CF of mixed gas)_FourConcentration / CF of waste gas_FourDensity) × 100). The result was as shown in FIG.
[0040]
As is apparent from FIG. 6, according to the detoxifying device 4 having the above structure, the PFC gas concentration (CF_FourIt is understood that a substantially constant decomposition rate can be ensured regardless of the concentration), and a detoxification process (PFC gas decomposition process) suitable for concentration of PFC gas by the separation filter device 3 can be performed.
[0041]
(Experiment 5) Under the same combustion conditions as Experiment 4, N₂, CF_FourThe mixed gas was burned by the detoxifying device 4. And CF in the mixed gas_FourN with constant amount (1 L / min)₂The decomposition rate was determined in the same manner as in Experiment 4 while changing the amount in the range of 100 to 600 L / min. The result is as shown in FIG.
[0042]
By the way, as understood from Experiment 1, N by the separation filter device 3 described above is used.₂, CF_FourThe separation capacity of the mixed gas, ie N₂The removal rate is about 25% (as shown in Table 1, 1% CF_FourIs concentrated to about 4%) to N₂If the mixed gas whose amount is 600 L / min is processed by the separation filter device 3, N of the mixed gas introduced into the detoxifying device 4₂The amount should be reduced to about 150 L / min. And as can be seen from FIG.₂When the amount is about 150 L / min or less, the decomposition rate is stable at 98%, but N₂As the amount increases, the decomposition rate decreases rapidly. Therefore, compared with the case where the exhaust gas is processed by the separation filter device 3 (concentration of the PFC gas) and then processed by the detoxifying device 4 (combustion of the PFC gas), the exhaust gas is combusted as it is. Thus, it is understood that extremely efficient detoxification processing can be performed. The results of Experiment 5 shown in FIG. 7 indirectly indicate the relationship between the concentration of PFC gas by the separation filter device 3 and the decomposition rate by the detoxification device 4.
[0043]
(Experiment 6) The above-described exhaust gas treatment apparatus was used to detoxify 600 L / min of exhaust gas 1, and the PFC concentration of waste gas discharged from the detoxification apparatus 4 was measured. Further, a plurality of detoxification devices having the same configuration as the detoxification device 4 of this exhaust gas treatment device were used in parallel to detoxify the exhaust gas 1 having the same property and flow rate. As a result, when the exhaust gas 1 is treated only by the detoxification device, three harmless devices are required for the PFC concentration of the waste gas to be equivalent to that when the exhaust gas treatment device is used. The installation space, initial cost, and running cost when using the exhaust gas treatment device were 90%, 80%, and 50%, respectively, when using three detoxification devices. From this, it is understood that according to the exhaust gas treatment apparatus of the present invention, it is possible to perform a good detoxification process of PFC gas while reducing the installation space, the initial cost and the running cost.
[0044]
It should be noted that the present invention is not limited to the above-described embodiment, and can be appropriately improved and changed without departing from the basic principle of the present invention. For example, as the detoxifying device 4, as disclosed in Japanese Patent Application Laid-Open No. 11-319485, a catalytic combustion type device in which the secondary processing gas is heated and decomposed with a catalyst can be used. In addition, in order to suppress the performance degradation due to moisture adsorption of the separation membrane 31b in the separation filter device 3, as shown in FIG. It is more preferable to provide a moisture removing device 51 that removes moisture in the primary processing gas 11 that has passed through the wet scrubber 2 in advance by a pressure method, a membrane separation method, or the like. The configuration other than the water removal device 51 in the exhaust gas treatment shown in FIG. 8 is the same as that in the exhaust gas treatment device in the above-described embodiment. In addition to the bulk gas and the PFC gas as described above, the present invention also includes an acidic gas and SiO 2₂Not only exhaust gas containing fine powder but also exhaust gas not containing acid gas and SiO₂Of course, the present invention can also be applied to the case of detoxifying exhaust gas that does not contain fine powder.
[0045]
【The invention's effect】
As can be easily understood from the above description, according to the exhaust gas treatment apparatus of the present invention, the exhaust gas containing PFC gas can be efficiently and economically detoxified without causing the problems described at the beginning. Moreover, bulk gas contained in a large amount in exhaust gas can be effectively recovered and reused.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of an exhaust gas treatment apparatus according to the present invention.
FIG. 2 is a cross-sectional view showing an example of a separation filter device.
3 is a cross-sectional view of a main part taken along line III-III in FIG.
FIG. 4 is a sectional view showing an example of a detoxifying device.
FIG. 5 is an enlarged detailed view showing a main part of FIG. 4;
6 is a curve diagram showing the relationship between the decomposition rate and concentration obtained in Experiment 4. FIG.
7 is a curve diagram showing the relationship between the decomposition rate and concentration obtained in Experiment 5. FIG.
FIG. 8 is a system diagram corresponding to FIG. 1 and showing a modification of the exhaust gas treatment apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Exhaust gas, 2 ... Scrubber, 3 ... Separation filter apparatus, 4 ... Detoxification device, 5 ... Superheater, 6 ... Bulk gas recovery device, 7 ... Exhaust path, 8 ... Primary process gas path, 9 ... Secondary process gas path DESCRIPTION OF SYMBOLS 10 ... Waste gas path, 11 ... Primary processing gas, 12 ... Bulk gas, 12a ... Bulk gas (purified bulk gas), 12c ... Impurity, 13 ... Secondary processing gas, 14 ... Waste gas, 21 ... Spray water, 31 ... Ceramic filter , 31a ... porous support, 31b ... separation membrane, 31c ... intermediate layer, 34 ... gas introduction chamber, 35 ... gas outlet chamber, 36 ... gas permeation chamber, 41 ... combustion cylinder, 42 ... outer cylinder, 43 ... inner cylinder 44 ... Combustion burner, 61 ... Bulk gas recovery section, 62 ... Bulk gas recovery path, 63 ... Bulk gas purifier, 63a ... Activated carbon, 63b ... Ceramic filter, 64 ... Return path.

Claims (8)

An exhaust gas treatment device for detoxifying exhaust gas containing bulk gas and perfluoro compound gas, a scrubber for pre-processing exhaust gas, a separation filter device for separating and removing bulk gas from primary treatment gas as exhaust gas that has passed through the scrubber, and separation A detoxification device that thermally decomposes and detoxifies the secondary processing gas from which the bulk gas has been separated and removed, and a bulk gas recovery device that recovers the bulk gas separated by the separation filter device ; The bulk gas recovery device separates and purifies the perfluoro compound gas accompanying the bulk gas discharged from the separation filter device, and purifies the separated perfluoro compound gas to the primary processing gas introduction side of the separation filter device. An exhaust gas treatment apparatus comprising a bulk gas purification apparatus for returning . The exhaust gas treatment device according to claim 1 , wherein the bulk gas purification device includes activated carbon for adsorbing and removing perfluoro compound gas accompanying the bulk gas discharged from the separation filter device. The exhaust gas treatment apparatus according to claim 1 , wherein the bulk gas purification apparatus includes a ceramic filter that allows a gas having a molecular diameter smaller than that of the perfluoro compound gas to pass therethrough. The exhaust gas treatment apparatus according to claim 1 , wherein the separation filter device includes a ceramic filter that allows a gas having a molecular diameter smaller than that of the perfluoro compound gas to pass therethrough. The ceramic filter, a porous support made of ceramic, has a configuration having a separation membrane made of an amorphous oxide containing Si and Zr having a large number of pores on at least one surface according claim 3 or exhaust gas treatment apparatus according to claim 4. The exhaust gas treatment apparatus according to claim 1 , wherein the scrubber is a wet type, and a superheater that superheats the primary treatment gas is disposed in the primary treatment gas path from the scrubber to the separation filter device. Overheating device, an exhaust gas processing device according to claim 6 which is a heat exchanger that utilizes waste heat of the detoxification unit as its primary heat source. Detoxification device, an exhaust gas according to the secondary processing gas to claim 1 which were of the catalytic combustion type to decompose the catalyst after having heated ones or secondary treatment gas of the combustion to be decomposed by burning the fuel burner Processing equipment.

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