JP2008194674A - Gas treatment apparatus and gas treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas treating apparatus capable of thermally decomposing a gas to be treated without generating nitrogen oxides as by-products, by using an atmospheric pressure plasma using nitrogen as a working gas. <P>SOLUTION: The gas treating apparatus 10 solves the above problems by comprising: a reactor 22 which surrounds atmospheric pressure plasma P and the gas to be treated F supplied toward the atmospheric pressure plasma and which thermally decomposes the gas to be treated in it, and uses nitrogen gas as a working gas G; and by providind a cooling part 13 for cooling an exhaust gas R up to a temperature at least not producing the nitrogen oxides, to a plasma decomposer 12, in the state where oxygen and moisture are not mixing into the exhaust gas R containing the gas to be treated discharged from the plasma decomposer 12 and the working gas G. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and method for decomposing gas containing gas harmful to the human body, gas containing global warming gas, ozone layer depleting gas, particularly gas discharged from manufacturing processes such as semiconductors and liquid crystals.

In manufacturing processes of semiconductors and liquid crystals, various types of fluorine compound gases are used as cleaning gases and etching gases. Such fluorine compounds are referred to as “PFCs etc.”, and representative examples thereof include perfluorocarbons such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , and C ₅ F ₈ , CHF. _And hydrofluorcarbons such as ₃ and inorganic fluorine-containing compounds such as SF ₆ and NF ₃ .

Various types of PFCs used in manufacturing processes of semiconductors, liquid crystals, and the like include N ₂ and Ar used as a carrier gas and a purge gas, or O ₂ , H ₂ and NH ₃ used as an additive gas, It is discharged as an exhaust gas with such CH _4.

Here, the proportion of PFCs and the like in the exhaust gas is small compared to other gases such as N ₂ and Ar, but PFCs and the like have a global warming potential (GWP) of several thousand to several numbers compared to CO _2. Since the atmospheric life is as long as several thousand to several tens of thousands of years as compared with CO ₂ , even if it is discharged into the atmosphere in a small amount, the effect is enormous. Furthermore, it is known that perfluorocarbons typified by CF ₄ and C ₂ F ₆ are not easily decomposed because the C—F bond is stable (the bond energy is as large as 130 kcal / mol). For this reason, various technologies for removing used PFCs and the like from exhaust gas have been developed.

  FIG. 9 shows a technique for thermally decomposing and detoxifying a gas (hereinafter, simply referred to as “processing target gas”) containing such hard-to-decompose PFCs (hereinafter referred to as “processing target object”). As described above, the working gas G is fed between the electrodes 1a and 1b of the plasma torch 1, and a discharge voltage is applied between the electrodes 1a and 1b to eject the atmospheric pressure plasma P into the reactor 2, and this atmospheric pressure There has been proposed a plasma decomposing machine 3 that supplies a processing target gas F toward the plasma P to thermally decompose the processing target gas F (see, for example, Patent Document 1).

  In the plasma decomposing machine 3 using the atmospheric pressure plasma P, by using nitrogen gas as the working gas G, the temperature of the atmospheric pressure plasma P is approximately several thousand to several tens of thousands of degrees Celsius (in this case, the atmosphere of the atmospheric pressure plasma P) The temperature becomes several thousand degrees Celsius), and the gas to be treated, particularly the hardly-degradable gas to be treated F such as perfluorocarbon, can be instantly thermally decomposed and removed.

Then, the high-temperature exhaust gas R including the pyrolysis target gas F and the working gas G discharged from the plasma decomposing unit 3 is treated with water in a wet scrubber (not shown) connected immediately after the plasma decomposing unit 3. As a result, the dust contained in the exhaust gas R is removed and the exhaust gas R is cooled by the latent heat of evaporation of the water.
JP 2000-334294 A (FIG. 2)

  However, in the conventional technique as described above, nitrogen used as the working gas G and oxygen in the exhaust gas are combined to generate nitrogen oxide (NOx) called thermal NOx. In particular, when the exhaust gas R from the plasma decomposer 3 is passed through a wet scrubber at a high temperature, the water injected into the exhaust gas R is separated into hydrogen and oxygen by the heat of the exhaust gas R, and the oxygen is further converted into the working gas G Nitrogen oxide is generated by reacting with nitrogen. Of course, if the high-temperature working gas G comes into contact with the oxygen contained in the gas F to be treated in advance (the same is true for the oxygen contained in the water), all of them will lead to the generation of nitrogen oxides. By passing the wet scrubber, there is a problem that the oxygen concentration in the exhaust gas R increases rapidly, and the amount of nitrogen oxides generated becomes extremely large.

  For this reason, in this conventional thermal decomposition technique, nitrogen oxide must be further detoxified from the exhaust gas R in the post-process, which is very inefficient.

  The present invention has been developed in view of such problems of the prior art. Therefore, an object of the present invention is to use a plasma decomposing machine that uses nitrogen as a working gas, and to thermally decompose the gas to be processed more efficiently than the conventional example without generating by-product nitrogen oxides. An object of the present invention is to provide a gas processing apparatus that can perform this.

  According to the first aspect of the present invention, “the reactor 22 that surrounds the atmospheric pressure plasma P and the processing target gas F supplied toward the atmospheric pressure plasma P and thermally decomposes the processing target gas F therein is provided. Oxygen or moisture is not mixed in the plasma decomposer 12 using nitrogen gas as the working gas G, and the exhaust gas R including the processing target gas F and the working gas G after the thermal decomposition discharged from the plasma decomposer 12 In this state, the gas processing apparatus 10 "includes the cooling unit 13 that cools the exhaust gas R at least to a temperature at which nitrogen oxides are not generated.

  In the present invention, the processing target gas F including harmful gas, flammable gas, global warming gas, ozone layer depleting gas and the like is thermally decomposed by the high-temperature plasma flow of the working gas G (nitrogen gas) in the plasma decomposing machine 12. Further, the high temperature exhaust gas R including the processing target gas F and the working gas G discharged from the plasma decomposing unit 12 is discharged from the plasma decomposing unit 12, and then is cooled by the cooling unit 13 without coming into contact with oxygen or moisture. It is cooled to a temperature at which no oxide is formed. (Note that “oxygen or moisture” includes oxygen or moisture contained in the processing target gas F itself before the processing target gas F is supplied to the plasma decomposing unit 12, or the processing target gas F is atmospheric pressure plasma. This does not include oxygen or moisture added to the gas F to be treated until it is given to P.) Therefore, the chance of contact between high-temperature nitrogen and oxygen can be remarkably reduced, and nitrogen oxide by-products are produced. Can be minimized.

  The invention described in claim 2 relates to the gas processing apparatus 10 described in claim 1, characterized in that “the cooling unit 13 includes a heat exchanger 72”.

  In the present specification, the “heat exchanger” refers to a heat exchanger of a type in which the low temperature side medium and the high temperature side medium do not come into direct contact.

  The invention described in claim 3 relates to the gas processing apparatus 10 described in claim 1 or 2, “It is provided with a decomposition auxiliary agent supply unit 23 for supplying moisture as the decomposition auxiliary agent A to the gas F to be processed. It is characterized by that.

  In the present invention, moisture is supplied to the processing target gas F as the decomposition aid A, and the processing target in the processing target gas F is not only thermally decomposed by the heat of the atmospheric pressure plasma P, but also the water content. It can be decomposed more efficiently by reacting with hydrogen produced by the decomposition.

  The invention described in claim 4 relates to the gas processing apparatus 10 described in claim 1 or 2, “comprising a decomposition auxiliary agent supply unit 23 for supplying hydrogen or ammonia as the decomposition auxiliary agent A to the gas F to be processed. It is characterized by.

  In the present invention, hydrogen or ammonia is supplied to the processing target gas F as the decomposition aid A, and the processing target in the processing target gas F is not only thermally decomposed by the heat of the atmospheric pressure plasma P, Similarly to the invention described in claim 3, it can be decomposed more efficiently by reacting with hydrogen generated by decomposition of the hydrogen or ammonia.

  The invention described in claim 5 relates to the gas processing apparatus 10 according to claim 3 or 4, wherein “the decomposition auxiliary agent supply unit 23 includes a pipe 62 for supplying the decomposition auxiliary agent A to the processing target gas F; The flow rate adjusting means 66 for adjusting the flow rate of the decomposition aid A flowing through the pipe 62 and the flow rate signal of the decomposition aid A to the flow rate adjusting means 66 based on the flow rate signal S1 of the processing object in the processing target gas F. And a flow rate control means 69 for outputting S2. "

  According to the present invention, the flow rate of moisture, hydrogen or ammonia supplied to the processing target gas F as the decomposition aid A is the flow rate signal S1 of the processing target in the processing target gas F output from the semiconductor manufacturing apparatus or the like. Based on this, the flow rate control means 69 and the flow rate adjustment means 66 adjust the flow rate to be necessary for the decomposition of the processing object. Therefore, it can be avoided that the flow rate of the decomposition aid A is reduced with respect to the flow rate of the processing object and the decomposition efficiency of the processing target gas F is lowered. Further, when moisture is used as the decomposition aid A, excess moisture is generated by increasing the flow rate of moisture relative to the flow rate of the object to be treated, and oxygen derived from the excess moisture is contained in the reactor 22. It is also possible to avoid generation of nitrogen oxides (NOx) by reaction with the high temperature working gas G (nitrogen).

  The invention described in claim 6 relates to the gas processing apparatus 10 described in claim 5, “The reactor 22 has a double tube structure including an outer tube 46 and an inner tube 48 surrounding the atmospheric pressure plasma P. The outer pipe 46 is provided with a processing target gas introduction port 50 for introducing the processing target gas F into the space S between the outer pipe 46 and the inner pipe 48. A processing target gas supply port 52 for blowing the processing target gas F after flowing through S toward the atmospheric pressure plasma P is provided. "

  In the present invention, the reactor 22 has a double tube configuration, and the processing target gas F flows through the space S between the outer tube 46 and the inner tube 48 and then is sent to the atmospheric pressure plasma P. Be paid. For this reason, the heat in the reactor 22 is given to the processing target gas F flowing through the space S through the inner tube 48, and the processing target gas F to be supplied to the atmospheric pressure plasma P can be preheated. it can. Further, heat exchange is performed between the high temperature exhaust gas R and the processing target gas F having a temperature lower than that of the exhaust gas R, so that the processing target gas F to be supplied to the atmospheric pressure plasma P is preheated and the exhaust gas R is cooled. Can be executed simultaneously.

  The invention described in claim 7 relates to the gas processing device 10 described in claim 6, wherein “the decomposition aid A is in the space S between the outer tube 46 and the inner tube 48 or the gas supply port 52 to be processed. Supplied ".

  In the present invention, the decomposition aid A is fed to the space S between the outer tube 46 and the inner tube 48 or the processing object gas supply port 52, and before the processing object gas F is mixed with the high temperature working gas G. In addition, the decomposition aid A can be mixed with the processing target gas F. Therefore, for example, when water is used as the decomposition aid A, the decomposition reaction of the processing target gas F by the water can be started before the processing target gas F is mixed with the working gas G, and nitrogen oxide by-product is suppressed. Meanwhile, the decomposition efficiency of the processing target gas F can be increased.

  The invention described in claim 8 relates to the gas processing device 10 described in claim 6 or 7, wherein “the inlet scrubber 14 for washing the processing target gas F supplied to the plasma decomposing unit 12 with water and the cooling unit 13 are cooled. It has an outlet scrubber 15 for washing the exhaust gas R with water.

  According to the present invention, since the inlet scrubber 14 for washing the processing target gas F supplied to the gas processing apparatus 10 is provided, the solid component and the water-soluble component contained in the processing target gas F are processed. Can be removed in advance before being supplied to the plasma decomposer 12.

  Moreover, since the exit scrubber 15 for washing the exhaust gas R cooled by the cooling unit 13 with water is provided, the gas processing apparatus 10 as a cleaner exhaust gas R is removed by removing solid components and water-soluble components contained in the exhaust gas R. Can be discharged from. Further, the water that is washed by the outlet scrubber 15 is the exhaust gas R cooled by the cooling unit 13, that is, the exhaust gas R cooled to a temperature at which nitrogen oxides are not generated. There is no possibility that nitrogen oxides are undesirably by-produced by the derived oxygen.

  The invention described in claim 9 relates to the gas processing apparatus 10 described in claim 8, wherein the “inlet scrubber 14 is supplied to the water injection nozzle 102 for injecting water W toward the processing target gas F and the water injection nozzle 102. Based on the water supply device 104 that supplies the water W and the flow rate signal S1 of the processing target in the processing target gas F, when the flow rate of the processing target is zero, the water supply device 104 is stopped and the flow rate of the processing target And water supply control means 106 for operating the water supply device 104 when the value is greater than zero. "

  According to the present invention, the water supply device 104 that supplies water W to the water injection nozzle 102 of the inlet scrubber 14 is stopped by the water supply control means 106 when the flow rate of the processing object is zero. . For this reason, even though the object to be treated is zero, the water W injected by the inlet scrubber 14 is thermally decomposed in the reactor 22 by mixing the water W mixed in the object gas F into the water W. It is possible to avoid the generation of nitrogen oxides as a result of reaction between the derived oxygen and the high temperature working gas G.

  The invention described in claim 10 relates to the gas processing apparatus 10 according to any one of claims 6 to 9, wherein “the plasma decomposing machine 12 is a plasma that supplies atmospheric pressure plasma P generated therein to the reactor 22. It has a generating device 16 ”.

  In the present invention, the atmospheric pressure plasma P is generated inside the plasma generator 16 and then supplied into the reactor 22. On the other hand, the processing target gas F is given to the inside of the inner tube 48 through the processing target gas inlet 50 provided in the inner tube 48 of the reactor 22. That is, since the processing object gas F does not pass through the inside of the plasma generator 16, it is possible to avoid contact between the atmospheric pressure plasma P and the processing object gas F inside the plasma generator 16.

  Therefore, according to the present invention, the amount of nitrogen oxide by-products can be minimized. That is, the higher the temperature at which the atmospheric pressure plasma P and the processing target gas F containing oxygen are in contact with each other, the higher the possibility that nitrogen oxides are by-produced. Since the plasma generator 16 is provided separately from the reactor 22, the “part where the atmospheric pressure plasma P is generated” that is the highest temperature can be separated from the reactor 22 to which the processing target gas F is supplied. It is possible to prevent the processing target gas F containing oxygen from entering a portion that becomes high temperature.

  Further, since the processing target gas F does not pass through the plasma generator 16, there is no possibility that the electrodes 16 b and 16 c that generate the atmospheric pressure plasma P come into contact with the processing target gas F and corrode.

  The invention described in claim 11 relates to the gas processing apparatus 10 according to any one of claims 1 to 10, “The reactor 22 is provided with a temperature detection means 58 for detecting the temperature in the reactor 22. The plasma decomposing machine 12 is provided with mass flow rate control means 38 for controlling the amount of the working gas G supplied to the atmospheric pressure plasma P in accordance with the temperature detection value detected by the temperature detection means 58 ". It is a feature.

  By changing the supply amount of the working gas G, the atmospheric pressure plasma P can adjust its output (specifically, the ejection amount and temperature). Therefore, in the present invention, the temperature detection means 58 for detecting the temperature in the reactor 22 is provided, and the amount of the working gas G supplied to the atmospheric pressure plasma P according to the temperature detection value by the temperature detection means 58. Therefore, the output of the atmospheric pressure plasma P can be controlled so that the temperature in the reactor 22 becomes a predetermined value. That is, when the temperature in the reactor 22 becomes higher than a predetermined value, the supply amount of the working gas G is lowered to lower the output of the atmospheric pressure plasma P. Conversely, when the temperature in the reactor 22 becomes lower than the predetermined value. The supply amount of the working gas G can be increased to increase the output of the atmospheric pressure plasma P.

  For this reason, for example, if the temperature in the reactor 22 is set to a predetermined temperature (approximately 1300 ° C. or higher) at which the hardly decomposable perfluorocarbon can be easily pyrolyzed, the temperature is detected by the temperature detecting means 58. The mass flow rate control means 38 is operated according to the temperature in the reactor 22 and the amount of the working gas G supplied to the atmospheric pressure plasma P is increased or decreased, and the output of the atmospheric pressure plasma P is adjusted. As a result, the temperature in the reactor 22 is always maintained at the set temperature, and the processing target gas F can be reliably removed in the reactor 22. Further, since the reactor 22 is not constantly exposed to the ultra-high temperature heat generated when the output of the atmospheric pressure plasma P is maximized, the members are prevented from being damaged by the ultra-high temperature heat as much as possible. Can be made.

  According to the present invention, the high-temperature exhaust gas containing the working gas and the gas to be treated after pyrolysis is discharged from the plasma decomposing machine and then is in a state where it does not come into contact with oxygen or moisture in the cooling unit. Therefore, the opportunity of contact between nitrogen and oxygen having a high temperature can be significantly reduced, and the by-product of nitrogen oxides can be minimized.

  Moreover, according to the invention which concerns on Claim 3 and 4, decomposition | disassembly of process target gas can be made high, suppressing generation | occurrence | production of nitrogen oxides.

  Furthermore, according to the invention which concerns on Claim 6, since a reactor is comprised with a double tube and heat exchange is performed between the waste gas R and the process target gas F, the process target gas supplied to atmospheric pressure plasma is performed. Can be sufficiently preheated, and at the same time, the high-temperature exhaust gas after pyrolysis can be cooled. Therefore, it is possible to reduce the output of atmospheric pressure plasma, to reliably and efficiently thermally decompose the gas to be processed at a large flow rate, and to reduce the cooling burden on the exhaust gas cooling section after pyrolysis. can do.

  As described above, according to the present invention, it is possible to provide a gas processing apparatus capable of decomposing a gas to be processed while extremely reducing nitrogen oxide by-product.

  The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a configuration diagram showing an outline of a gas processing apparatus 10 according to the present embodiment. As shown in this figure, the gas processing apparatus 10 of this embodiment is generally composed of a plasma decomposing machine 12, a cooling unit 13, an inlet scrubber 14, and an outlet scrubber 15.

  The plasma decomposing machine 12 thermally decomposes the processing target gas F using the high-temperature atmospheric pressure plasma P. The plasma generating apparatus 16, the power supply unit 18, the working gas supply unit 20, the reactor 22, and the decomposition auxiliary agent. It consists of a feeding unit 23 and the like.

  The plasma generator 16 generates a high-temperature atmospheric pressure plasma P therein, and includes a short cylindrical torch body 16a made of a metal material such as brass and having both upper and lower surfaces opened. An anode 16b is connected to the tip of the torch body 16a, and a rod-like cathode 16c is attached inside the anode 16b.

  The anode 16b is a cylindrical nozzle made of a high melting point metal having high conductivity such as copper or tungsten and having a plasma generation chamber 16d recessed therein. A plasma ejection hole 16e for ejecting the atmospheric pressure plasma P generated in the plasma generation chamber 16d is provided in the center of the lower surface of the anode 16b, and a working gas supply port 16f is provided on the upper side of the anode 16b. It has been.

  The cathode 16c is composed of a main body portion made of a high melting point metal having high conductivity such as copper, and a tip portion made of tungsten mixed with thorium or lanthanum and having an outer diameter reduced to a spindle shape toward the tip. It is the comprised rod-shaped member. The tip of the cathode 16c is disposed in a plasma generation chamber 16d that is recessed in the anode 16b.

  An insulating material (not shown) such as tetrafluoroethylene resin or ceramic is interposed between the anode 16b and the cathode 16c so as not to energize (short-circuit) between them via the torch body 16a. ing. A cooling water passage (not shown) is provided inside the anode 16b and the cathode 16c so as to cool these members.

  The anode 16b and the cathode 16c configured as described above are connected to a power supply unit 18 that applies a predetermined discharge voltage to generate an arc between the anode 16b and the cathode 16c.

  The power supply unit 18 applies a predetermined discharge voltage to the above-described anode 16b and cathode 16c to generate a plasma arc. Specifically, as shown in FIG. After rectification and smoothing with a direct current filter 28 composed of a smoothing reactor 28a and a smoothing capacitor 28b, the direct current is converted into high frequency alternating current by an inverter 30 that performs high frequency switching with switching elements such as IGBTs and transistors, This high-frequency alternating current is transformed to a predetermined voltage by the transformer 32, rectified again by the rectifier 34, smoothed by the direct current filter 36 composed of the smoothing reactor 36a and the smoothing capacitor 36b, and supplied with direct current. A DC power supply device is suitable.

  The working gas feeding unit 20 (see FIG. 1) feeds nitrogen gas used as the working gas G into the plasma generation chamber 16d of the anode 16b, and a storage tank 20a for storing the working gas G, A working gas feed pipe 20b that communicates between the storage tank 20a and a working gas feed port 16f provided in the anode 16b is provided.

  Incidentally, in the plasma decomposing machine 12 of this embodiment, mass flow rate control means 38 is attached to the working gas supply pipe 20b. The mass flow rate control means 38 controls the amount of the working gas G fed into the plasma generation chamber 16d through the working gas feed pipe 20b. Specifically, as shown in FIG. 3, the mass flow rate of the working gas G flowing in the sensor pipe (not shown) is measured, and the measured value is output as a flow rate signal. The control valve 42 constituted by an electromagnetic valve for controlling the flow rate of the working gas G in the supply pipe 20b is compared with the flow rate signal of the flow rate sensor 40 and the flow rate setting signal L1 output from the temperature detecting means 58 described later. And a comparison control circuit 44 that outputs a control current to the control valve 42 so that they are equal to each other.

  As shown in FIG. 4, the reactor 22 has a main body 22 a composed of a double tube including an outer tube 46 and an inner tube 48. The outer tube 46 and the inner tube 48 constituting the main body 22a are straight tube members made of a corrosion-resistant metal material such as SUS304 or Hastelloy (registered trademark), and both longitudinal ends thereof are mutually connected. By connecting, a predetermined space S is formed between the outer tube 46 and the inner tube 48. The material constituting the main body 22a is preferably a metal material as described above in consideration of the thermal conductivity between the inner surface of the inner tube 48 and the space S. For example, the material 22F is corroded. When the corrosion resistance of the highly resistant and corrosion-resistant metal material is also affected, the main body 22a may be made of a material such as castable or ceramic. That is, the material constituting the main body 22a is not limited to a metal material.

  Further, a processing target gas inlet 50 for introducing the processing target gas F discharged from the semiconductor manufacturing apparatus or the like into the space S is provided at the lower portion of the outer tube 46 (that is, the end portion farthest from the plasma generator 16). A plurality of target gases F introduced into the space S are spirally blown toward the atmospheric pressure plasma P into the upper portion of the inner tube 48 (that is, the end closest to the plasma generator 16). The gas supply port 52 for processing is provided through (see FIG. 5). Therefore, the processing target gas F flows through the space S between the outer tube 46 and the inner tube 48 from the bottom to the top (that is, from the downstream side to the upstream side of the atmospheric pressure plasma P), and then the atmospheric pressure plasma. Will be sent to P.

  The main body 22a is provided with a step portion 54 at a position corresponding to the downstream end of the atmospheric pressure plasma P ejected inside, and in the portion L facing the atmospheric pressure plasma P above the step portion 54. The diameters of the outer tube 46 and the inner tube 48 are enlarged, and the inner surface of the inner tube 48 in the expanded diameter portion L is made of castable and has an outer diameter substantially equal to the inner diameter of the inner tube 48 in the expanded diameter portion L. A cylindrical fireproof wall 56 is inserted in a replaceable manner.

  The upper end of the reactor 22 is connected to the atmospheric pressure plasma P ejection side of the plasma generator 16, and an opening 22 b provided at the lower end of the reactor gas F and the working gas G decomposed in the reactor 22. It becomes the discharge end of the exhaust gas R containing.

  Further, in the reactor 22 surrounding the atmospheric pressure plasma P and the processing target gas F, a high temperature region heated by the high temperature atmospheric pressure plasma P is formed in the internal space. In this embodiment, a temperature detecting means 58 for detecting the temperature in the reactor 22 is attached to the reactor 22.

  As shown in FIG. 1, the temperature detection means 58 is attached so that the inner surface side and the outer surface side of the reactor 22 communicate with each other, and the gap between the inner surface of the reactor 22 and the atmospheric pressure plasma P (that is, the above-mentioned) The temperature detection signal L2 input from the thermocouple 58a is set in advance, and is electrically connected to the thermocouple 58a and the mass flow rate control means 38. The controller 58b outputs a predetermined signal (“flow rate setting signal L1” in the case of the present embodiment) to the mass flow rate control means 38 so as to coincide with the set temperature.

  As shown in FIG. 4, the decomposition auxiliary agent supply unit 23 is a unit for supplying moisture, which is the decomposition auxiliary agent A of the processing target gas F, to the reactor 22, and is attached to the inner surface of the outer tube 46. A nozzle 60 made of a metal such as SUS304, a pipe 62 for introducing the decomposition aid A to the nozzle 60, a flow meter 64 attached to the pipe 62, a nozzle 60 and a flow meter 64. A flow rate adjusting valve 66 as a flow rate adjusting means 66, a stop valve 68, and a flow rate adjusting valve 66, which are attached to the pipe between them, are electrically connected to each other and output from a semiconductor manufacturing apparatus (not shown). Based on the flow rate signal S1 of the processing object in the target gas F, a flow rate control means 69 that outputs a flow rate signal S2 in an amount necessary for the decomposition of the processing target object in the processing target gas F to the flow rate adjusting valve 66 is provided. It is. The “amount necessary for decomposing the processing object in the processing object gas F” means an amount in which all of the added water is used for decomposing the processing object.

  As shown in FIG. 1, the cooling unit 13 receives the high-temperature exhaust gas R discharged from the opening 22 b of the reactor 22, deprives the heat of the exhaust gas R, and at least reaches a temperature at which nitrogen oxides are not generated. In this embodiment, the exhaust gas introduction duct 70, the heat exchanger 72, and the exhaust gas discharge duct 74 are roughly configured.

  The exhaust gas introduction duct 70 is a duct having one end connected to the opening 22 b of the reactor 22 and the other end connected to the heat exchanger 72, and the inner surface thereof is lined with a refractory material 76. Of course, the refractory material 76 may be a laminated material of the refractory material and the heat insulating material. Further, as the material for the refractory material, a material having excellent heat resistance and wear resistance is selected according to the properties of the exhaust gas R.

  As shown in FIG. 6, the heat exchanger 72 faces a substantially rectangular parallelepiped casing 77 and a plurality of openings O provided on one surface (left side surface in FIG. 6) of the casing 77 and the surface. A plurality of heat transfer tubes 78 attached to the inside of the casing 77 so as to communicate with the opening O provided on the other surface (the right side surface in FIG. 6), and the casing 77 in a direction orthogonal to the heat transfer tubes 78. Cooling connected to the cooling water inlet hole 82 for introducing the cooling water C into the inside of the casing 77 provided in the plurality of plates 80 partitioning the inside and the casing 77 (the upper surface in FIG. 6 in this embodiment). A water introduction pipe 84 and a cooling water discharge pipe 88 respectively connected to a cooling water outlet hole 86 for discharging the cooling water C from the inside of the casing 77 are provided.

  The plurality of plates 80 have one end connected to the upper surface inside the casing 77 and the other end attached in a state of being separated from the lower surface inside the casing 77, and one end from the upper surface inside the casing 77. A plurality of plates 80b that are spaced apart and attached in a state where the other end is connected to the lower surface inside the casing 77 are arranged alternately.

  In this embodiment, Hastelloy is used for the heat transfer tube 78 in consideration of corrosion resistance. However, other materials may be used as long as they have corrosion resistance and heat resistance according to the properties of the exhaust gas R. It may be used. Moreover, the capability of the heat exchanger 72 should just cool the predetermined waste gas R to temperature lower than about 500 degreeC which is a nitrogen oxide production temperature minimum. At that time, it is preferable that the temperature of the exhaust gas R can be cooled (that is, rapidly cooled) in the shortest possible time.

  As shown in FIG. 1, the exhaust gas discharge duct 74 is a duct having one end connected to the heat exchanger 72 and the other end connected to the outlet scrubber 15. In the present embodiment, the inner surface of the exhaust gas discharge duct 74 is not lined with a refractory material, but the heat resistance and wear resistance depend on the temperature setting of the exhaust gas R discharged from the heat exchanger 72 and the properties of the exhaust gas R. It may be lined with an excellent fireproof material.

  In this manner, the cooling unit 13 can cool the exhaust gas R to a temperature at which nitrogen oxides are not generated without contact of oxygen or moisture with the exhaust gas R discharged from the plasma decomposer 12. (Note that “oxygen or moisture” includes oxygen or moisture contained in the processing target gas F itself before the processing target gas F is supplied to the plasma decomposing unit 12, or the processing target gas F is atmospheric pressure plasma. Oxygen or moisture added to the processing target gas F before being given to P is not included, for example, moisture added to the processing target gas F from the nozzle 60 is not included in the “oxygen or moisture”. )

  The inlet scrubber 14 is for washing and removing solid components and water-soluble components contained in the processing target gas F by spraying water W onto the processing target gas F supplied from a semiconductor manufacturing apparatus (not shown). An inlet duct 90 connected to a semiconductor manufacturing apparatus or the like, an outlet duct 92 that guides the processing target gas F after being washed to the processing target gas introduction port 50, an inlet scrubber body 94, and water W to the processing target gas F. Water spraying means 95 for spraying.

  The inlet scrubber main body 94 is a hollow columnar body that is erected in the vicinity of the plasma decomposing machine 12, and is provided with an inlet duct connection hole 96 to which an inlet duct 90 is connected at the lower portion thereof, and at the upper end thereof. An outlet duct connection hole 98 to which the outlet duct 92 is connected is provided. Further, the bottom of the inlet scrubber main body 94 is a water storage tank 100 for storing the water W injected by the water injection means 95.

  The water injection means 95 includes a water injection nozzle 102 that injects water W toward the processing target gas F, a water supply device 104 that supplies the water W to the water injection nozzle 102, and a water supply control means 106. Yes.

  The water injection nozzle 102 includes a spray nozzle 102a disposed inside the inlet scrubber body 94, a pipe 102b having one end penetrating the lower end side of the inlet scrubber body 94 and the other end connected to the spray nozzle 102a. The water storage tank 100 and the spray nozzle 102a are communicated with each other through a pipe 102b.

  The water supply device 104 is a pump for pumping the water W stored in the water storage tank 100 to the spray nozzle 102a, and is attached to the pipe 102b. The water supply device 104 receives the water W by the stop signal S3 from the water supply control means 106. The pumping is stopped, and the water W is pumped up by the operation signal S4.

  The water supply control means 106 is a means for outputting a stop signal S3 or an operation signal S4 to the water supply device 104. Specifically, the water supply control means 106 receives the flow rate signal S1 of the processing object in the processing target gas F, and receives the processing target object. When the flow rate is zero, a stop signal S3 is output to the water supply device 104, and when the flow rate of the processing object is greater than zero, an operation signal S4 of the water supply device 104 is output.

  The outlet duct 92 captures mist (particulate water W that has not been vaporized) contained in the processing target gas F discharged from the inlet scrubber body 94, and the mist flows undesirably into the reactor 22. A filter 107 for preventing this is attached.

  The outlet scrubber 15 is for removing solid components and water-soluble components contained in the exhaust gas R cooled by the cooling unit 13 with water, and the inlet duct 108 connected to the exhaust gas discharge duct 74 and the water after being washed with water. An outlet duct 110 that guides the exhaust gas R to the outside of the gas processing apparatus 10, an outlet scrubber main body 112, and water injection means 114 that sprays water W onto the exhaust gas R are provided.

  The outlet scrubber main body 112 is a hollow columnar body standing on the side of the plasma decomposing machine 12, and an inlet duct connection hole 116 to which the inlet duct 108 is connected is provided on the lower side thereof. An outlet duct connection hole 118 to which the outlet duct 110 is connected is provided on the upper end side portion. Moreover, the bottom part of the exit scrubber main body 112 serves as a water storage tank 120 for storing the water W injected by the water injection means 114.

  The water injection unit 114 includes a water injection nozzle 122 that injects water W toward the exhaust gas R, and a water supply device 124 that supplies the water W to the water injection nozzle 122.

  The water injection nozzle 122 includes a spray nozzle 122a disposed inside the outlet scrubber body 112, a pipe 122b having one end penetrating the lower end side of the outlet scrubber body 112 and the other end connected to the spray nozzle 122a. The water storage tank 120 and the spray nozzle 112a are communicated with each other via a pipe 122b.

  The water supply device 124 is a pump for pumping the water W stored in the water storage tank 120 to the spray nozzle 122a, and is attached to the pipe 122b.

  When detoxifying the processing target gas F using the gas processing apparatus 10 according to the present embodiment, first, the power source of the plasma decomposition machine 12 (not shown) is turned on, and the processing target gas F sets the set temperature of the controller 58b. The temperature detection means 58 set to a predetermined temperature that is easily thermally decomposed is operated, and the mass flow rate control means 38 is operated to feed the working gas G into the plasma generation chamber 16d. Further, the supply of the cooling water C to the cooling unit 13 and the water supply device 124 of the outlet scrubber 15 are operated to start water injection from the spray nozzle 122a.

  Subsequently, the power supply unit 18 is operated, and an atmospheric pressure plasma ignition switch (not shown) of the plasma decomposing machine 12 is turned on to apply a voltage between the electrodes 16b and 16c of the plasma generator 16, and the plasma ejection holes 16e. The atmospheric pressure plasma P is ejected from

  Here, when the temperature in the reactor 22 measured by the thermocouple 58a is lower than the set temperature, such as immediately after the atmospheric pressure plasma P is jetted, the controller 58b of the temperature detection means 58 compares the mass flow rate control means 38. A predetermined flow rate setting signal L1 is given to the control circuit 44 so as to increase the supply amount of the working gas G. Then, the flow rate setting signal L1 and the flow rate signal of the flow rate sensor 40 are compared in the comparison control circuit 44 so that both are equal to the control valve 42 from the comparison control circuit 44 (specifically, the working gas A predetermined control current is applied (to increase the feed amount of G). As a result, the control valve 42 is opened to increase the supply amount of the working gas G into the plasma generation chamber 16d, the output of the atmospheric pressure plasma P is increased, and the temperature in the reactor 22 is rapidly increased. become.

  Subsequently, when the temperature in the reactor 22 detected by the temperature detection means 58 reaches a predetermined set temperature, the processing target gas F is supplied to the inlet scrubber 14 from a semiconductor manufacturing apparatus or the like.

  Immediately before the supply of the processing target gas F to the inlet scrubber 14 is started, the flow rate signal S1 output to the water supply control means 106 becomes larger than zero, and the operation signal S4 is sent from the water supply control means 106 to the water supply device 104. Is output, and the water supply device 104 starts operating, whereby the water W stored in the water storage tank 100 is sprayed from the spray nozzle 102a.

  The processing target gas F washed with water by the inlet scrubber 14 is introduced into the reactor 22 through the outlet duct 92 and the processing target gas introduction port 50, and is supplied spirally so as to surround the atmospheric pressure plasma P. At the same time, the decomposition aid A is supplied from the nozzle 60 to the space S, and the decomposition of the processing target gas F is started (the function of the decomposition aid A will be described later).

  The exhaust gas R including the processing target gas F and the working gas G decomposed inside the inner pipe 48 is discharged from the opening 22b of the reactor 22, and then flows through the exhaust gas introduction duct 70 of the cooling unit 13 for heat exchange. It is introduced into the inside of the heat transfer tube 78 through an opening O provided on the side surface of the vessel 72. When the exhaust gas R passes through the heat transfer tube 78, the heat of the exhaust gas R is given to the cooling water C through the heat transfer tube 78. At this time, the cooling water C introduced from the cooling water inlet hole 82 meanders through the inside of the casing 77 partitioned by the plate 80 and then is discharged from the cooling water outlet hole 86. Therefore, according to the cooling unit 13 of the present embodiment, the opportunity for the cooling water C to come into contact with the heat transfer pipe 78 is increased, so that the exhaust gas R can be efficiently cooled.

  In this way, the exhaust gas R is cooled to at least a temperature at which nitrogen oxides are not generated, and then is exhausted from the heat exchanger 72 and supplied to the outlet scrubber 15 through the exhaust gas exhaust duct 74.

  The exhaust gas R given to the outlet scrubber 15 is washed with water W sprayed from the spray nozzle 122a, and then guided to the outside of the gas processing apparatus 10 through the outlet duct 110.

  According to the gas processing apparatus 10 of the present embodiment, the high temperature exhaust gas R including the processing target gas F and the working gas G discharged from the plasma decomposing machine 12 is discharged from the plasma decomposing machine 12, and then oxygen and moisture. Cooling to a temperature at which nitrogen oxides are not generated by the cooling unit 13 without contact with Therefore, there is no opportunity to combine nitrogen and oxygen having a high temperature, and the processing target gas F can be pyrolyzed without generating nitrogen oxide as a by-product.

  Further, as will be described in detail later, since moisture is supplied to the processing target gas F as the decomposition aid A, the processing target in the processing target gas F is simply thermally decomposed by the heat of the atmospheric pressure plasma P. Instead, it can be decomposed more efficiently by reacting with hydrogen contained in the moisture.

  The flow rate of moisture supplied as the decomposition aid A to the processing object gas F is based on the flow rate signal S1 of the processing object in the processing object gas F output from a semiconductor manufacturing apparatus or the like, and the flow rate control means 69 and The flow rate adjusting means 66 adjusts the flow rate necessary for the decomposition of the processing object. Therefore, it is possible to avoid a decrease in the decomposition efficiency of the processing target gas F due to a decrease in the flow rate of moisture relative to the flow rate of the processing target. Further, excess water is generated by increasing the flow rate of water relative to the flow rate of the object to be processed, and oxygen derived from the excess water reacts with the high-temperature working gas G (nitrogen) inside the reactor 22. Nitrogen oxide (NOx) can be avoided as a by-product.

  Further, according to the present embodiment, the reactor 22 is constituted by a double pipe, the processing target gas introduction port 50 is provided at the lower part of the outer pipe 46, and the processing target gas supply port is provided at the upper part of the inner pipe 48. 52 is provided, the processing target gas F is supplied to the atmospheric pressure plasma P after flowing through the space S between the outer tube 46 and the inner tube 48 from the bottom to the top. At this time, heat inside the reactor 22 is applied to the processing target gas F flowing through the space S via the inner pipe 48, and the processing target gas F fed to the atmospheric pressure plasma P is preheated. Specifically, when the set temperature in the reactor 22 is set to a predetermined temperature in the range of 1100 ° C. to 1300 ° C., the gas passes through the space S and is supplied from the processing object gas supply port 52 toward the atmospheric pressure plasma P. The temperature of the gas F to be processed can be raised to about 800 to 1000 ° C. Note that the positional relationship between the processing target gas introduction port 50 and the processing target gas supply port 52 is that the processing target gas F can flow through the space S and be sufficiently preheated. It is not restricted to an aspect, Another aspect may be sufficient.

  In addition, since a fire-resistant wall 56 made of castable is provided at a position facing the atmospheric pressure plasma P on the inner surface of the reactor 22, the thermal degradation of the reactor 22 due to the atmospheric pressure plasma P can be prevented and the durability of the reactor 22 can be prevented. In addition, it is possible to sufficiently exchange heat between the high-temperature exhaust gas R and the low-temperature processing target gas F on the downstream side of the refractory wall 56 of the reactor 22. Further, by providing the step portion 54 in the reactor 22, a turbulent flow is generated in the flow of the processing target gas F flowing through the space S between the outer tube 46 and the inner tube 48, and the residence time in the space S Therefore, it is possible to preheat the target gas F to be supplied to the atmospheric pressure plasma P more effectively. Furthermore, since the fire wall 56 is attached in a replaceable manner, even if the fire wall 56 is thermally deteriorated due to the heat of the atmospheric pressure plasma P, only this part needs to be replaced, and the stop time during maintenance can be shortened. The operating rate of the gas processing apparatus 10 can be improved.

  Further, since heat exchange is performed between the high temperature exhaust gas R and the low temperature processing target gas F, preheating of the processing target gas F supplied to the atmospheric pressure plasma P and cooling of the exhaust gas R can be performed simultaneously. it can. For this reason, it becomes possible to reduce the cooling burden of the exhaust gas R which the subsequent cooling unit 13 bears.

In addition, before the processing target gas F preheated in this way is introduced into the inner pipe 48 from the processing target gas supply port 52, the moisture (decomposition aid A) supplied from the nozzle 60 is the processing target gas. When added to F, the following reaction occurs.
[Chemical 1]
CF ₄ + 2H ₂ O → CO ₂ + 4HF
[Chemical 2]
SF ₆ + 3H ₂ O → SO ₃ + 6HF

  Here, since the water vapor as the decomposition aid A is supplied to the space S between the outer tube 46 and the inner tube 48, the water vapor is processed before the processing target gas F is mixed with the high temperature working gas G. F can be mixed. Therefore, the decomposition reaction of the processing target gas F with water vapor can be started before the processing target gas F is mixed with the working gas G, and the decomposition efficiency of the processing target gas F is increased while suppressing the by-production of nitrogen oxides. Can do.

That is, the gas F to be treated is preheated by receiving heat inside the reactor 22 by flowing through the space S between the outer tube 46 and the inner tube 48. When water vapor as decomposition aid A is added to this preheated gas F to be treated, the decomposition reactions shown in [Chemical Formula 1] and [Chemical Formula 2] occur almost simultaneously with the addition of water vapor. For this reason, when the processing target gas F is mixed with the working gas G, the oxygen contained in the water vapor reacts with the carbon and sulfur already contained in the processing target gas F and is chemically stable with CO ₂ and SO ₃ . Thus, it is possible to suppress the generation of nitrogen oxides due to the reaction of high-temperature nitrogen and oxygen contained in the working gas G. The same effect can be obtained even when the decomposition aid A is supplied to the processing object gas supply port 52.

In this embodiment, the nozzle 60 is made of a metal such as SUS304. As a result, when water is used as the decomposition aid A, the water supplied to the nozzle 60 flows outside the nozzle 60 when flowing through the nozzle 60, and heat from the preheated processing target gas F is flown. When it is discharged from the nozzle 60, it is vaporized into water vapor. Therefore, it is not necessary to provide a special device for vaporizing water as the decomposition aid A. Further, for example, the amount of water to be added when processing 0.5 L / min of CF ₄ is about 0.8 g / min (1 L / min in the case of water vapor). Since the amount of heat is small compared to the amount of heat of the processing target gas F preheated to about 800 to 1000 ° C., there is no problem even if the heat of the processing target gas F is used for the heat of vaporization of water.

  Moreover, since the gas processing apparatus 10 which concerns on a present Example is provided with the inlet scrubber 14 which flushes the process target gas F supplied to the gas process apparatus 10, the solid component contained in the process target gas F and water-soluble The sex component can be removed in advance before the gas F to be processed is supplied to the plasma decomposer 12. Further, the water supply device 104 that allows the water W to flow through the water injection nozzle 102 of the inlet scrubber 14 stops in response to the stop signal S3 from the water supply control means 106 when the flow rate of the processing object is zero. It has become. For this reason, even though the object to be treated is zero, the water W injected by the inlet scrubber 14 is thermally decomposed in the reactor 22 by mixing the water W mixed in the object gas F into the water W. It is possible to avoid the generation of nitrogen oxides as a result of reaction between the derived oxygen and the high temperature working gas G.

  Moreover, since the gas treatment apparatus 10 includes the outlet scrubber 15 for washing the exhaust gas R cooled by the cooling unit 13, the solid component and the water-soluble component contained in the exhaust gas R are removed, and the cleaner exhaust gas is removed. R can be discharged from the gas processing apparatus 10. In addition, since it is the waste gas cooled by the cooling unit, that is, the exhaust gas cooled to a temperature at which nitrogen oxides are not generated, oxygen discharged from water injected in the outlet scrubber is washed with water by the outlet scrubber. Therefore, there is no possibility that nitrogen oxides are undesirably by-produced. In addition, it is suitable to use the cooling water C with high temperature discharged | emitted from the cooling part 13 as water used with the said wet scrubber. This is because high temperature water has active molecular motion, and the spray efficiency of the exhaust gas R can be improved by spraying the water on the exhaust gas R.

  The atmospheric pressure plasma P is generated inside the plasma generator 16 and then supplied into the reactor 22. On the other hand, the processing target gas F is given to the inside of the inner tube 48 through the processing target gas inlet 50 provided in the inner tube 48 of the reactor 22. That is, since the processing object gas F does not pass through the inside of the plasma generator 16, it is possible to avoid contact between the atmospheric pressure plasma P and the processing object gas F inside the plasma generator 16.

  Therefore, according to the gas processing apparatus 10, the by-product amount of nitrogen oxides can be minimized. That is, the higher the temperature at which the atmospheric pressure plasma P and the processing target gas F containing oxygen are in contact with each other, the higher the possibility that nitrogen oxides are by-produced. Since the plasma generator 16 is provided separately from the reactor 22, the “part where the atmospheric pressure plasma P is generated” that is the highest temperature can be separated from the reactor 22 to which the processing target gas F is supplied. It is possible to prevent the processing target gas F containing oxygen from entering a portion that becomes high temperature.

  Further, since the processing target gas F does not pass through the plasma generator 16, there is no possibility that the electrodes 16 b and 16 c that generate the atmospheric pressure plasma P come into contact with the processing target gas F and corrode.

  Further, since the low-temperature decomposable process target gas F is decomposed simply by preheating the process target gas F, thermal energy is efficiently given to the hardly decomposable process target gas F such as perfluorocarbon. be able to. Therefore, even when the output of the atmospheric pressure plasma P is reduced and the temperature in the reactor 22 is set in the range of 1100 ° C. to 1300 ° C., the hardly decomposable target gas F can be sufficiently decomposed. In addition, it is possible to process the gas F to be processed with a large flow rate. Further, by reducing the output of the atmospheric pressure plasma P in this way, damage due to thermal deterioration of the plasma generator 16 and the reactor 22 can be delayed.

  Further, in the plasma decomposing machine 12 of this embodiment, the temperature in the reactor 22 is detected, and the amount of the working gas G to be supplied to the plasma generator 16 is increased or decreased according to the detected temperature value, so that the reactor 22 The output of the atmospheric pressure plasma P is controlled so that the temperature inside becomes a predetermined value. That is, when the temperature in the reactor 22 becomes higher than a predetermined value, the supply amount of the working gas G is reduced to lower the output of the atmospheric pressure plasma P. Conversely, when the temperature in the reactor 22 becomes lower than the predetermined value, the operation is started. The supply amount of the gas G is increased to increase the output of the atmospheric pressure plasma P.

  For this reason, the temperature in the reactor 22 becomes a predetermined temperature at which the hardly decomposable perfluorocarbon can be easily pyrolyzed (approximately 1300 ° C. or higher and does not damage the reactor 22) as described above. With this setting, the mass flow rate control means 38 is operated according to the temperature in the reactor 22 detected by the temperature detection means 58 to increase or decrease the supply amount of the working gas G, and the output of the atmospheric pressure plasma P is increased. Adjusted. As a result, the temperature in the reactor 22 is always maintained at the set temperature, and all types of PFCs and the like (treatment target) containing a hardly decomposable perfluorocarbon can be reliably removed in the reactor 22. . Further, since the plasma generator 16 and the reactor 22 are not constantly exposed to the extremely high temperature heat generated when the output of the atmospheric pressure plasma P is maximized, these members are damaged by the extremely high temperature heat. Can be delayed as much as possible.

  The target gas F was thermally decomposed using the gas processing apparatus 10 according to this example. As an operating condition of the gas processing apparatus 10, the temperature set value in the controller 58b of the temperature detecting means 58 was 1200 ° C. The DC voltage of the plasma was about 100V and the DC current was constant at 60A. As a result, the flow rate of nitrogen gas as the working gas G was about 20 L (liter) / min. Further, the cooling water C to the heat exchanger 72 was circulated at 20 ° C. at 10 L / min, and cooling was continued. Incidentally, the temperature of the exhaust gas R discharged from the heat exchanger 72 was 50 ° C.

In order to treat the processing target gas F containing 100 cc / min of CF ₄ in 80 L / min of nitrogen under such conditions, the decomposition treatment was performed by four methods.

First, the processing target gas F was processed without adding the decomposition aid A. At this time, the decomposition rate of CF ₄ was 90%, and the concentration of nitrogen oxides at the outlet of the heat exchanger 72 was less than 1 ppm, the detection limit for both NO and NO ₂ .

Next, 3 L / min of hydrogen gas as a decomposition aid A was added from the nozzle 60 to the gas F to be treated. The flow rate of hydrogen gas was checked by the flow meter 64 and the flow rate adjustment valve 66 was operated. At this time, the decomposition rate of CF ₄ was 99%, and the concentration of nitrogen oxides at the outlet of the heat exchanger 72 was less than 1 ppm, the detection limit for both NO and NO ₂ .

Further, ammonia gas 2 L / min was added to the processing target gas F from the nozzle 60 as the decomposition aid A. At that time, the decomposition rate of CF ₄ was 99%, and the concentration of nitrogen oxides at the outlet of the heat exchanger 72 was less than the detection limit of 1 ppm for both NO and NO ₂ .

Furthermore, 0.2 cc / min of water was supplied from the nozzle 60. At this time, the decomposition rate of CF ₄ was 99%, and the concentrations of nitrogen oxides at the outlet of the heat exchanger 72 were 20 ppm for NO and 1 ppm for NO ₂ .

  In the conventional technique (when a wet scrubber is connected immediately after the plasma decomposing machine 3), several thousand ppm of nitrogen oxide is generated. Therefore, according to the gas treatment apparatus 10 according to the present invention, nitrogen oxide is produced. It can be seen that the occurrence of can be extremely reduced.

  In the above-described embodiment, the example in which the heat exchanger 72 is used in the cooling unit 13 is described. However, the cooling unit 13 is configured so that at least nitrogen oxides are contained in the exhaust gas R in a state where oxygen or moisture is not mixed into the exhaust gas R. As long as it can cool to the temperature which does not produce | generate, it may be based on the other method of letting the waste gas R flow through the inner side of a long duct, and water-cooling the outer side of this duct, for example. Further, as the low temperature side medium in the cooling unit 13, water may be used as in the above-described embodiment (water cooling), or gas (air cooling) or oil (oil cooling) may be used.

  In the above-described embodiment, the case where the step portion 54 is provided at a predetermined position of the reactor 22 and the fireproof wall 56 is provided above the step portion 54 has been described. However, the reactor is not provided with such a step portion 54. The main body 22a of 22 may be a straight pipe, and the fire wall 56 may be provided on the entire inner peripheral surface or only on the upper side. However, when the refractory wall 56 is provided on the entire inner peripheral surface of the reactor 22, the preheating effect of the processing target gas F passing through the space S is reduced.

  In the above-described embodiment, the reactor 22 is configured as a double tube. However, the reactor 22 is a multiple tube (not shown) that is equal to or more than a triple tube, and the radial direction passes through the tube wall. The gas to be processed F flowing through the sealed spaces adjacent to each other flows counter-currently, and flows through the sealed space closest to the inside of the reactor 22 and the jet direction of the atmospheric pressure plasma P jetted into the reactor 22. The flow direction of the processing target gas F may be counterflowing. That is, the jet direction of the atmospheric pressure plasma P and the flow direction of the processing target gas F flowing through the sealed space of the double tube portion are counter-currently flown in the double tube portion closest to the inside of the reactor 22. As long as it has, the flow path of the process target gas F which flows through the outer side may be any. Note that, as described above, if multiple tubes of triple tubes or more are used, the heat dissipated to the outside through the tube wall of the reactor 22 can be used for preheating the processing target gas F more effectively.

  Further, in the above-described embodiment, as shown in FIG. 1, the case where the plasma generator 16 and the reactor 22 are arranged up and down to eject the atmospheric pressure plasma P in the vertical direction has been shown. 16 and the reactor 22 may be disposed in the horizontal direction, and the atmospheric pressure plasma P may be ejected in the horizontal direction.

  Further, in the present embodiment, an apparatus that uses DC arc discharge is used as an apparatus for generating atmospheric pressure plasma P. However, the apparatus is not limited to this as long as it can generate atmospheric pressure plasma P. Thermal plasma such as microwave plasma can be used.

  In addition, by adjusting the processing target gas F so as to be a reducing atmosphere during decomposition by the atmospheric pressure plasma P, the reaction between oxygen and nitrogen is suppressed, so that generation of nitrogen oxides is further suppressed. Can do.

Further, hydrogen or ammonia may be supplied as the decomposition aid A instead of moisture. When hydrogen or ammonia is supplied as decomposition aid A, the following reaction occurs.
[Chemical formula 3]
CF ₄ + 4H ₂ → CH ₄ + 4HF
[Chemical formula 4]
SF ₆ + 4H ₂ → H ₂ S + 6HF
[Chemical formula 5]
3CF ₄ + 8NH ₃ → 3CH ₄ + 4N ₂ + 12HF
[Chemical 6]
3SF ₆ + 8NH ₃ → 3H ₂ S + 4N ₂ + 18HF

  That is, when hydrogen or ammonia as the decomposition aid A is added to the preheated gas F to be processed, it is shown in [Chemical Formula 3] to [Chemical Formula 6] as compared with the case where the gas to be processed F is not preheated. Decomposition reaction is likely to occur. Further, even if hydrogen or ammonia is added, oxygen that causes generation of nitrogen oxides is not introduced into the reactor, and decomposition of the gas F to be processed can be performed without worrying about promoting by-product generation of nitrogen oxides. Efficiency can be increased.

  In addition, when the gas F that reacts with water is not included in the processing target gas F, the water added from the nozzle 60 can directly come into contact with the working gas G to cause generation of nitrogen oxides. Therefore, it is detected whether or not the gas F that reacts with water is contained in the processing target gas F, and when the gas is not contained, the stop valve 68 is closed to stop the addition of water, If it is included, the stop valve 68 may be opened to add water.

  Further, as the flow rate setting signal L1 to be supplied to the comparison control circuit 44 of the mass flow rate control means 38, a predetermined signal that makes the supply amount of the working gas G constant instead of the variable signal output by the temperature detection means 58 is used. In addition, as shown in FIG. 7, a power control means 126 for newly controlling the power output from the power supply unit 18 is provided, and a signal output from the temperature detection means 58 is supplied to the power control means 126 as a current switching signal. It may be.

  The power control means 126 is for varying the power output from the power supply unit 18 and includes a current detector 128 and a current setting means 130.

  The current detector 128 is constituted by a current transformer (CT) or the like, and detects the output current of the power supply unit 18 and outputs a predetermined voltage corresponding to the detected current value.

  As shown in FIG. 8, the current setting means 130 is composed of a variable reference voltage output means 132 (volume in this embodiment) and a comparison amplifier 134, and the voltage output from the current detector 128 and the reference The reference voltage output from the voltage output means 132 is compared and amplified by the comparison amplifier 134, and a predetermined current setting signal is output to the inverter 30 of the power supply unit 18, whereby the inverter 30 is variably operated. Here, the reference voltage output means 132 is automatically switched by a current switching signal given from the temperature detection means 58 via the wiring. Further, when a volume is used as the reference voltage output means 132, the variable operation of the inverter 30 by the current setting means 130 becomes mechanical control, but the current switching provided from the temperature detection means 58 as the reference voltage output means 132 is performed. A D / A module (not shown) that outputs a predetermined analog voltage based on the signal may be used, and the variable operation of the inverter 30 by the current setting means 130 may be linear continuous control.

  Further, a temperature detection means 58 for detecting the temperature in the reactor 22 is provided, and the working gas supply unit 20 has a working gas G to be fed into the plasma generation chamber 16d based on the temperature detection value detected by the temperature detection means 58. Is provided with mass flow rate control means 38 for controlling the amount of electric power, and the power supply unit 18 controls the amount of power supplied to the electrodes 16b and 16c of the plasma generator 16 based on the temperature detection value detected by the temperature detection means 58. Means 126 may be attached.

  Further, in this embodiment, the inlet scrubber 14 and the outlet scrubber 15 are provided separately, but the inlet scrubber main body 94 and the outlet scrubber main body 112 are erected on the upper part of one water storage tank to share the water storage tank. May be used. At this time, it goes without saying that a partition or the like must be provided so that the inside of the inlet scrubber body 94 and the inside of the outlet scrubber body 112 do not directly communicate with each other.

  In addition to the fluorinated compound, the present apparatus can be used to treat any gas as long as it can be thermally decomposed.

  Moreover, you may make it add the chemical | medical agent suitable for the water washing of the solid component and water-soluble component contained in the process target gas F to the water W injected in the entrance scrubber 14 or the exit scrubber 15. FIG.

It is a block diagram which shows the gas processing apparatus of one Example in this invention. It is a circuit diagram which shows the power supply unit of one Example in this invention. It is a block diagram which shows the mass flow control means of one Example in this invention. It is a block diagram which shows the plasma decomposition machine of one Example in this invention. It is the VV sectional view taken on the line in FIG. It is a block diagram which shows the heat exchanger main body of one Example in this invention. It is a figure which shows the Example provided with an electric power control means. It is a block diagram which shows the electric power control means of one Example in this invention. It is a figure which shows the conventional plasma decomposition machine.

Explanation of symbols

A ... Decomposition aid C ... Cooling water F ... Processing gas G ... Working gas L1 ... Flow rate setting signal L2 ... Temperature detection signal S1, S2 ... Flow rate signal S3 ... Stop signal S4 ... Actuation signal P ... Atmospheric pressure plasma R ... Exhaust gas DESCRIPTION OF SYMBOLS S ... Space 10 ... Gas processing apparatus 12 ... Plasma decomposition machine 13 ... Cooling part 14 ... Inlet scrubber 15 ... Outlet scrubber 16 ... Plasma generator 16a ... Torch body 16b ... Anode (electrode)
16c ... Cathode (electrode)
16d ... Plasma generation chamber 16e ... Plasma ejection hole 16f ... Working gas feed port 18 ... Power supply unit 20 ... Working gas feed unit 20a ... Storage tank 20b ... Working gas feed pipe 22 ... Reactor 23 ... Decomposition aid feed Unit 24 ... AC power supply 26 ... Rectifier 28 ... DC filter 30 ... Inverter 32 ... Transformer 34 ... Rectifier 36 ... DC filter 38 ... Mass flow control means 40 ... Flow sensor 42 ... Control valve 44 ... Comparison control circuit 46 ... Outer pipe 48 ... Inner pipe 50 ... Process target gas inlet 52 ... Process target gas supply port 54 ... Step part 56 ... Fireproof wall 58 ... Temperature detection means 58a ... Thermocouple 58b ... Controller 60 ... Nozzle 62 ... Piping 64 ... Flow meter 66 ... Flow rate adjustment means (flow rate adjustment valve)
68 ... Stop valve 69 ... Flow control means 70 ... Exhaust gas introduction duct 72 ... Heat exchanger 74 ... Exhaust gas discharge duct 76 ... Refractory material 77 ... Casing 78 ... Heat transfer pipe 80 ... Plate 82 ... Cooling water inlet hole 84 ... Cooling water inlet pipe 86 ... Cooling water outlet hole 88 ... Cooling water discharge pipe 90 ... Inlet duct 92 ... Outlet duct 94 ... Inlet scrubber body 95 ... Water injection means 96 ... Inlet duct connecting hole 98 ... Outlet duct connecting hole 100 ... Water storage tank 102 ... Water Spray nozzle 102a ... Spray nozzle 102b ... Pipe 104 ... Water supply device 106 ... Water supply control means 107 ... Filter 108 ... Inlet duct 110 ... Outlet duct 112 ... Outlet scrubber body 114 ... Water injection means 116 ... Inlet duct connection hole 118 ... Outlet Duct connection hole 120 ... Water storage tank 122 ... Water Spray nozzle 122a ... Spray nozzle 122b ... Pipe 124 ... Water supply device 126 ... Power control means 128 ... Current detector 130 ... Current setting means 132 ... Reference voltage output means 134 ... Comparison amplifier

Claims (13)

Plasma decomposition using a nitrogen gas as a working gas, having a reactor that surrounds the atmospheric pressure plasma and the gas to be processed supplied toward the atmospheric pressure plasma, and thermally decomposes the gas to be processed inside Cooling the exhaust gas to at least a temperature at which nitrogen oxides are not generated in a state where oxygen or moisture is not mixed in the exhaust gas containing the gas to be treated and the working gas after pyrolysis discharged from the plasma decomposition device A gas processing apparatus comprising a cooling unit.   The gas processing apparatus according to claim 1, wherein the cooling unit includes a heat exchanger.   The gas processing apparatus according to claim 1, further comprising a decomposition auxiliary agent supply unit that supplies moisture to the processing target gas as a decomposition auxiliary agent.   The gas processing apparatus according to claim 1, further comprising a decomposition auxiliary agent supply unit that supplies hydrogen or ammonia as a decomposition auxiliary agent to the gas to be processed.   The decomposition auxiliary agent supply unit includes a pipe for supplying the decomposition auxiliary agent to the processing target gas, a flow rate adjusting unit for adjusting a flow rate of the decomposition auxiliary agent flowing through the pipe, and the processing target gas. 4. A flow rate control means for outputting a flow rate signal of the decomposition aid corresponding to the flow rate of the processing object to the flow rate adjusting means based on a flow rate signal of the processing object inside. Or the gas processing apparatus of 4. The reactor has a double tube structure composed of an outer tube and an inner tube surrounding the atmospheric pressure plasma,
The outer pipe is provided with a processing target gas introduction port for introducing the processing target gas into a space between the outer pipe and the inner pipe.
6. The process pipe according to claim 5, wherein the inner pipe is provided with a process target gas supply port for blowing the process target gas after flowing through the space toward the atmospheric pressure plasma. Gas processing device.   The gas processing apparatus according to claim 6, wherein the decomposition aid is supplied to the space between the outer tube and the inner tube or the processing target gas supply port. 8. The apparatus according to claim 6, further comprising an inlet scrubber for washing the processing target gas supplied to the plasma decomposer, and an outlet scrubber for washing the exhaust gas cooled by the cooling unit. 9. Gas processing equipment.   The inlet scrubber includes a water injection nozzle that injects water toward the processing target gas, a water supply device that supplies the water to the water injection nozzle, and the flow rate signal of the processing target in the processing target gas. And a water supply control means for stopping the water supply device when the flow rate of the treatment object is zero and operating the water supply device when the flow rate of the treatment object is greater than zero. The gas processing apparatus according to claim 8, wherein the gas processing apparatus is characterized.   The gas processing apparatus according to any one of claims 6 to 9, wherein the plasma decomposing device includes a plasma generating device that supplies the atmospheric pressure plasma generated therein to the reactor. The reactor is provided with temperature detecting means for detecting the temperature in the reactor,
The plasma decomposing machine is provided with mass flow rate control means for controlling the amount of the working gas supplied to the atmospheric pressure plasma according to the temperature detection value detected by the temperature detection means. The gas treatment device according to any one of claims 1 to 10.   The gas processing apparatus according to claim 1, wherein the processing target gas is a fluorinated compound. Supplying a processing target gas to atmospheric pressure plasma using nitrogen gas as a working gas to thermally decompose the processing target gas;
A gas treatment method for cooling the exhaust gas to at least a temperature at which nitrogen oxides are not generated in a state in which oxygen and moisture are not mixed in the exhaust gas containing the gas to be treated and the working gas that has been thermally decomposed.