JP2002355532A - Decomposition method of organic halogen compound and its equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decomposition method of organic halogen compound by means of plasma which efficiently decomposes organic halogen compounds such as from and trichloromethane. SOLUTION: This decomposition equipment of organic halogen compound which decomposes the organic halogen compounds by means of plasma is characterized in that it contains a microwave cavity for generating plasma, a container which stores alkali liquid for making reaction products harmless, a reactor of which the lower end part is opened and is arranged so as to be immersed in the alkali liquid, an electrical discharge tube which is disposed in such a manner that the lower end part of the electrical discharge tube reaches the inside of the reactor and the upper end part of the same penetrates the inner part of the microwave cavity and a plasma inducer which is disposed on the inside surface of the electric discharge tube. This decomposition method of organic halogen compound is performed by using the decomposition equipment thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for decomposing an organic halogen compound by plasma, and more particularly to a method and an apparatus for decomposing an organic halogen compound by plasma for efficiently decomposing an organic halogen compound such as chlorofluorocarbon and trichloromethane.

[0002]

2. Description of the Related Art Organic halogen compounds such as freon, trichloromethane, and halon containing fluorine, chlorine, and bromine in a molecule are widely used in a wide range of applications such as refrigerants, solvents, and digestives. Very important. However, due to their high volatility, many of these compounds are released untreated into the atmosphere, soil, water, and other environments without treatment, and currently produce carcinogens, deplete the ozone layer, and reduce global warming. It has been found that these compounds have a great adverse effect on the environment, and it is necessary to detoxify these organic halogen compounds from the viewpoint of environmental protection.

[0003] Conventionally, methods reported for treating organic halogen compounds mainly utilize a decomposition reaction at a high temperature. This treatment method is roughly classified into an incineration method and a plasma method.

In the incineration method, volatile organic halogen compounds are incinerated together with ordinary wastes such as resins. In order to burn in a waste incinerator, anti-corrosion measures are required as measures against hydrogen chloride, which is corrosive with strong acids. Further, since the combustion temperature is set differently from the combustion of ordinary resins, it is necessary to separately burn only these organic halogen compounds. In addition, since there are strict standards for the amount of hydrogen chloride, dioxin, and the like discharged from the incinerator, the amount of treatment cannot be increased unnecessarily in order to avoid factors such as unstable combustion temperature.

In the plasma method, a volatile organic halogen compound is allowed to react with water vapor in a plasma to decompose it into carbon dioxide, hydrogen chloride, and hydrogen fluoride as a dedicated decomposer for chlorofluorocarbon and the like. As a method for generating plasma, high-frequency discharge and DC arc discharge are used. Hereinafter, a conventional high-frequency discharge device will be described.

[0006] In the high frequency discharge, an electromagnetic wave having a frequency of 13.56 MHz derived from a power supply is used. First, a mixed gas is guided from a container to a reactor, and then a high-frequency current is applied to a coil wound around the reactor to convert the gas in the reactor into plasma. The gas reacted in the plasma is neutralized and rendered harmless by an alkaline aqueous solution, and is discharged from an exhaust duct.

However, this method has disadvantages in that it is difficult to reduce the size of the apparatus and that the processing cost is increased because argon gas is used. In addition, there is a problem that long-time continuous operation cannot be stably maintained. On the other hand, attempts have been made not to use argon, but there is a problem in equipment such that the reaction pressure condition for the decomposition of chlorofluorocarbon needs to be about １ ／ of the atmospheric pressure.

[0008] DC as another high-frequency discharge device
The device configuration of the arc discharge is configured such that the discharge unit is composed of a columnar cathode, a nozzle-shaped metal anode provided only around the cathode, and a DC power supply connected to the cathode and the anode. Have been. In the case of this device, as compared with the above-described high-frequency discharge type device, a reduced pressure atmosphere is not required,
A relatively small one with a high decomposability can be obtained. But,
Since the nozzle-shaped anode for generating the discharge is made of metal, both the anode and the cathode are susceptible to deterioration due to corrosion and erosion of the electrode surface due to corrosive gas generated by decomposition of chlorofluorocarbons, and a stable decomposition reaction for a long time Is difficult to realize.

In order to supply a gas to be decomposed such as chlorofluorocarbon after the generation of plasma without passing chlorofluorocarbon between the electrodes, argon or air is essential for maintaining the discharge. The use of air does not increase the running cost as compared with argon, but the gas temperature of the arc discharge is about 6000 K (Kelvi
On the n temperature scale (hereinafter simply referred to as K), it is obvious that a reaction between nitrogen and oxygen or the like causes generation of nitrogen oxides.
Therefore, there is a drawback in that a countermeasure for these reaction products is required.

[0010]

Since volatile organic halogen compounds such as chlorofluorocarbon and trichloromethane are originally very low in reactivity, there is no appropriate decomposition treatment method. A high-temperature combustion technique is one that can use the conventional technique as it is as a decomposition treatment method. In this method, since the organic halogen compound is burned together with a large amount of hydrocarbon fuel, the energy efficiency is low and the apparatus cannot be downsized. Also, in order to burn organic halogen compounds, etc., it is necessary to set the temperature higher than that of normal waste combustion,
It takes time to set and start the combustion temperature. Since the organic halogen compounds to be decomposed will be recovered and decomposed,
Low-cost and efficient decomposition cannot be performed.

On the other hand, as a conventional technique for shortening the start-up time, there is a plasma method using high-frequency discharge or arc discharge. In equipment using high-frequency discharge, effective argon gas is essential, and even if it becomes argon-less, a high decomposition rate can be obtained only under reduced pressure, and additional equipment such as vacuum pumps and hermetic structures are required. However, the use of expensive argon gas or air is not possible because organic halogenated compounds such as chlorofluorocarbons cannot be used as the gas to drive the discharge because the electrodes deteriorate due to the generation of corrosive gas. I have no choice. However, when air is used as a driving gas, nitrogen and oxygen react with each other in plasma heated to about 6000 K by arc discharge to generate nitrogen oxides. Accordingly, it is necessary to perform a new exhaust gas removal treatment.

In view of the above problems, the present inventors have devised a treatment method for efficiently decomposing waste gas such as an organic halogen compound contained in waste to efficiently detoxify harmful components. We studied diligently to develop a processing device that can improve the processing efficiency and operation efficiency of the entire device.
As a result, the inventors of the present invention effectively generate plasma by irradiating a microwave to a place where a specific plasma inducer is installed, and treat the harmful substances in exhaust gas with the plasma to solve such a problem. Was found to be resolved. The present invention has been completed from such a viewpoint.

[0013]

That is, the present invention provides a method in which a gas containing an organic halogen compound is passed through a flow path in which a plasma inducer is provided, and the plasma inducer is irradiated with microwaves. An object of the present invention is to provide a method for decomposing an organic halogen compound, which comprises generating plasma and decomposing an organic halogen compound. Here, the gas containing the organic halogen compound may be mixed with water vapor. Then, by spraying water or alkaline water into the plasma, the organic halogen compound can be decomposed more efficiently, and the product can be rendered harmless. As the carrier gas for the organic halogen gas, air can be used, but it is better to use an oxygen-nitrogen mixed gas with a reduced oxygen partial pressure so as not to generate nitrogen oxides. Is unnecessary, which is preferable.

The present invention also relates to an organic halogen compound decomposing apparatus for decomposing an organic halogen compound by plasma, comprising a microwave cavity for generating plasma, and an alkali solution for detoxifying a reaction product. , A reactor having an open lower end, the lower end being immersed in the alkaline solution, and a reactor having a lower end reaching the inside of the reactor and an upper end having the microwave cabinet. An object of the present invention is to provide an apparatus for decomposing an organic halogen compound, comprising: a discharge tube provided so as to penetrate the inside of a tee; and a plasma inducer provided on the inner surface of the discharge tube. Here, the plasma inducer has at least one inside of the microwave cavity.
In the embodiment provided above, at least one
The embodiment provided above, or the embodiment provided at least two or more on the inner surface of the discharge tube. When two or more plasma inducers are provided,
A mode in which the inside of the microwave cavity and the inside of the reactor are respectively installed can be suitably mentioned.

As the plasma inducer used in the present invention, for example, an SiC material can be used. In addition to a SiC sintered body, a graphite block, granular activated carbon, a perovskite oxide having high conductivity and the like can be mentioned.
Although the shape of the inducer is not particularly limited, for example, a block of about 2 to 3 mm square is filled, a porous body having pores of 10 to 30 mm, or a ring-shaped body having a width of about 1 to 10 mm is used. Can be used.

In a plasma state generated near the above-mentioned plasma inducer, a high gas temperature (2000-6000 K)
In addition, since the energy of electrons is high, the organic halogen compound is in a state in which a chlorine atom, a fluorine atom, and a hydrogen atom are easily dissociated. Therefore, in the present invention, the plasma inducer is irradiated with microwaves, and the gas containing the organic halogen compound flowing therethrough is efficiently plasma-treated. In the present invention, the whole gas can be turned into plasma by flowing a gas in which water vapor is added to an organic halogen compound.

In the present invention, there is no damage to the discharge part due to corrosiveness due to the conversion of the organic halogen compound into a plasma by the use of a microwave that does not require an electrode as in arc discharge. As a typical example, the decomposition reaction mechanism is considered to be CCl ₂ F ₂ + 2H ₂ O → 2HCl + 2HF + CO ₂ for Freon R12 (CCl ₂ F ₂ ) used as a refrigerant in an air conditioner or the like. The following reaction can be used. 2HCl + 2HF + 2Ca (OH) ₂ → CaCl ₂ +
CaF ₂ + 4H ₂ O Further, Freon 134a which is a halogen compound other than chlorine
The present invention is also effective for (CF ₃ CH ₂ F). An example of the reaction is shown below. CF ₃ CH ₂ F + 2H ₂ O → 4HF + CO ₂ + C Carbon (C) is converted to CO ₂ in the presence of oxygen or the like.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for decomposing an organic halogen compound according to the present invention will be described with reference to the accompanying drawings.
A specific embodiment will be described. FIG. 1 is a configuration diagram schematically showing an example of a decomposition apparatus suitable for carrying out the method of the present invention. The apparatus of the present embodiment is an apparatus for decomposing an organic halogen compound which decomposes an organic halogen compound by plasma, and includes a microwave cavity 25 for generating plasma and an alkali liquid for detoxifying a reaction product. A container 16 containing the container, a reactor 12 having an open lower end, the lower end being immersed in the alkaline solution, and a lower end reaching the inside of the reactor and an upper end being the microwave; It has a discharge tube 11 provided to penetrate the inside of the cavity, and a plasma inducer 1 provided on the inner surface of the discharge tube 11. In this apparatus, the discharge tube 1 is a flow path in which the plasma inducer 1 is installed.
A gas containing Freon gas 18 is circulated in the inside 1. Then, a microwave generated from the microwave oscillator 10 generates plasma in the cavity 15 and the discharge tube 11 through the coaxial waveguide converter 14 to decompose the organic halogen compound in the flowing gas. . As the wavelength of the microwave, for example, 2.45 GHz can be used. However, from the viewpoint of inducing the discharge efficiently, the wavelength is not limited to this wavelength, and the wavelength at which the discharge can be generated by acting on the inducer. Can be widely used. Also, the output is not limited, for example, 100 to 200
An oscillator of about 0 W can be used.

As shown in FIG. 2 (a), which is a detailed view of part A of FIG. 1, in the presence of the inducer 1 used in the present invention, when an external microwave is applied, plasma is generated. Is induced, and discharge is effectively generated inside even with extremely small electric power as compared with ordinary air, and discharge is intensively and locally generated inside the inside. As the inducer 1 here, for example, a graphite block, granular activated carbon, a SiC sintered body, a perovskite kite oxide having high conductivity, or the like is used. The shape of the inducer is not limited at all, and may be determined arbitrarily. From the viewpoint of effectively inducing plasma in the discharge tube 11 when a high-cost SiC material or the like is used, for example, a width of about 1 to 10 mm is used. A ring-shaped object having a degree can be used. Examples of the action of the plasma dielectric 1 include that an electric field is easily concentrated in shape, that electrons of a gas component are easily emitted because microwaves are easily absorbed, and that discharge is sustained. .

In the treatment method of the present invention, by uniformly introducing a decomposition aid such as water into the plasma, the plasma can be stabilized and the organic halogen compound can be treated. Specifically, the organic halogen compound can be effectively decomposed by mixing water vapor with the gas containing the organic halogen compound, spraying water, or the like. Also, by injecting alkaline water into the plasma,
Further, the product can be rendered harmless.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments.
In this example, a decomposition experiment of Freon 134a (CH ₂ CF ₄ ), which is relatively difficult to decompose among organic halogen compounds, is exemplified. The microwave uses a frequency of 2.45 GHz, and the discharge uses a coaxial waveguide type cavity.

(Embodiment 1) Referring to FIG. 16 in the figure
Is a quartz container containing an alkaline aqueous solution (calcium hydroxide) 13. In this vessel 16, a reactor 12 having an open lower end is disposed with its lower end immersed in the alkaline aqueous solution 13. Above the reactor 12, a quartz discharge tube 11 having an outer diameter of 12 mm and an inner diameter of 11 mm is erected with its lower end extending into the reactor 12. The reactor 12
A microwave coaxial waveguide type cavity 15 through which the upper side of the discharge tube 11 penetrates is disposed above. The cavity 15 has an inner diameter of the outer conductor of 40 mm and an outer diameter of the inner conductor of 1 mm.
At 0 mm, the gap length between the outer conductor and the inner conductor is 10 mm. The upper end side of the discharge tube 11 is penetrated and mounted inside the inner conductor of the coaxial waveguide converter 14 in the cavity 15. The microwave transmitter 10 is attached to one end of the cavity 15. The discharge tube 11 is connected via a pipe 21 to a container containing a chlorofluorocarbon gas 18 and a container containing a mixed gas 20 of oxygen and nitrogen.
An exhaust duct 22 is connected to an upper portion of the container 16.

As described above, the apparatus for decomposing an organic halogen compound according to the first embodiment includes a quartz container 16 containing an aqueous alkali solution 13 for detoxifying a reaction product, and It is configured to include a reactor 12 arranged in a state of being immersed in an aqueous solution 13, a microwave coaxial waveguide type cavity 15 for generating plasma, a discharge tube 11 for holding plasma, and the like. . And
The plasma inducer 1 is installed inside the discharge tube 11. For example, as shown in FIG. 2A showing details of a portion A in FIG. It is provided in the tee 15. FIG. 2 (b) showing details of a portion B in FIG.
May be provided below the discharge tube 11 and inside the microwave reactor 12. Further, two or more plasma inducers 1 may be provided inside the discharge tube 11, and in this case, one of the plasma inducers 1
A mode in which the plasma inducer 1 in 12 and the other is installed in the microwave cavity 15 is preferably mentioned.

The operation of the disassembly device having the above configuration is as follows. First, Freon 134a is supplied to the discharge tube 11 in the cavity at atmospheric pressure and a flow rate of 3.7 liter (l) / min (adjusted to 1 kg / h to be described later) while the microwave transmitter 10 supplies 2.45 GHz. Is introduced into the cavity 15 through the coaxial waveguide converter 14, and is discharged by the microwave electric field formed there. Here, when the plasma inducer 1 is provided in the cavity 15, it is possible to generate plasma with a small power. Further, as shown in FIG. 2, the plasma generation region can be further widened by disposing the plasma inducer 1 inside the discharge tube 11.

Next, the fluorocarbon gas 18 is decomposed by the generated discharge plasma in the discharge tube 11 or the reactor 12, passes through the alkaline aqueous solution 13, is detoxified, and the remaining gas including carbon dioxide gas and the like is removed. It was discharged from the exhaust duct 22.
The decomposition rate of CFCs was calculated from a gas chromatographic analysis of the CFC concentration with and without plasma by partially sampling the gas in the reactor 12. The experimental result of the decomposition rate measurement when the supplied amount of chlorofluorocarbon was 1 kg / h and the microwave power was used as a parameter was 99.99% at a decomposition energy of 1 kWh / kg-fluorocarbon. In this test, it was found that almost the same decomposition rate could be obtained by adjusting the microwave power even when argon, air, or the like was mixed in as an additive gas.

(Embodiment 2) Next, the trichloroethane gas 18 is decomposed in the discharge tube 11 or the reactor 12 by the generated discharge plasma, passes through the alkaline aqueous solution 13 and is subjected to detoxification treatment, carbon dioxide gas and the like. The remaining gas including was discharged from the exhaust duct 22. The decomposition rate of trichloroethane was calculated from a gas chromatographic analysis of the trichloroethane concentration with and without plasma by partially collecting the gas in the reactor 12. An experimental result of the decomposition rate measurement when the supply amount of trichloroethane was 1 kg / h and the microwave power was used as a parameter was that the decomposition rate was 99.99% at a decomposition energy of 1 kWh / kg-trichloroethane. In this test, it was found that almost the same decomposition rate could be obtained by adjusting the microwave power even when argon, air, or the like was mixed in as an additive gas.

[0027]

According to the present invention, it is possible to detoxify organic halogen compounds such as chlorofluorocarbons and trichloromethane in waste or exhaust gas at a high decomposition rate (99.99% or more). In addition, due to the action of the plasma inducer, the microwave can efficiently supply a large amount of energy to the gas containing the organic halogen compound efficiently, and can efficiently generate plasma. Furthermore, the size and cost of the device can be reduced because of its excellent controllability as an electromagnetic wave and the ability to use a mass-produced power supply.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a schematic configuration of a decomposition apparatus of the present invention.

FIG. 2 is an enlarged sectional view of a portion A and a portion B of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma inducer 10 Microwave oscillator 11 Discharge tube 12 Reactor 13 Alkaline aqueous solution 14 Coaxial waveguide converter 15 Microwave cavity 16 Container 17 Organic halogen (Freon etc.) container 18 Organic halogen (Freon etc.) gas 19 Oxygen- Nitrogen mixed gas container 20 Oxygen-nitrogen mixed gas 21 Piping 22 Exhaust duct

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07B 37/06 H05H 1/46 ZABB C07C 19/05 G21F 9/02 Z 19/08 B01D 53/34 134E H05H 1/46 ZAB 134B // G21F 9/02 134D (72) Minoru Tanno 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture, Mitsubishi Heavy Industries, Ltd. 1-14 Bunkyocho Nagasaki University Faculty of Engineering (72) Inventor Yasuhiro Shimizu 1-14 Bunkyocho Nagasaki City Nagasaki Pref. Nagasaki University Faculty of Engineering F-term (reference) 4D002 AA19 AA23 BA02 CA06 DA05 DA12 EA01 FA02 4G075 AA37 BA05 BD27 CA26 CA47 DA02 EB27 EB41 FB03 FB04 FB06 FC11 4H006 AA05 AC13 AC26 BA91 BA95

Claims (8)

[Claims] 1. A gas containing an organic halogen compound is passed through a flow path in which a plasma inducer is installed, and plasma is generated by irradiating the plasma inducer with microwaves to generate an organic halogen compound. A method for decomposing an organic halogen compound, comprising decomposing. 2. The method according to claim 1, wherein the gas containing the organic halogen compound is mixed with water vapor.
The method for decomposing an organic halogen compound according to the above. 3. The method for decomposing an organic halogen compound according to claim 1, wherein the organic halogen compound is decomposed by spraying water into the plasma. 4. The method for decomposing an organic halogen compound according to claim 1, wherein the organic halogen compound is decomposed by injecting alkaline water into the plasma, and the product is rendered harmless. 5. An apparatus for decomposing an organic halogen compound, which decomposes an organic halogen compound by plasma, comprising a microwave cavity for generating plasma and a container containing an alkali liquid for detoxifying a reaction product. When,
A reactor having an open lower end, the lower end being immersed in the alkaline solution, and a lower end reaching the inside of the reactor and an upper end penetrating through the inside of the microwave cavity. An organic halogen compound decomposing apparatus, comprising: a discharge tube provided in the discharge tube; and a plasma inducer provided on the inner surface of the discharge tube. 6. The organic halogen compound decomposer according to claim 5, wherein at least one or more of said plasma inducer is provided inside said microwave cavity. 7. The apparatus for decomposing an organic halogen compound according to claim 5, wherein at least one or more of the plasma inducers are provided in the reactor. 8. The apparatus for decomposing an organic halogen compound according to claim 5, wherein at least two or more of the plasma inducers are provided on the inner surface of the discharge tube.