JPH0389499A - High-frequency induction plasma device - Google Patents

Abstract

PURPOSE:To efficiently feed a liquid organic halogen compound in plasma to be decomposed by feeding the carrier gas containing a steamed liquid material to a nozzle hole provided above a plasma torch, heating a cooling liquid of a nozzle, and feeding it to the nozzle section. CONSTITUTION:A nozzle 3 is formed near plasma P and heated at a high temperature. A cooling water passage 32 is provided in the nozzle 3, and a cooling liquid 38 from a cooling tank 36 is fed via a pump 39, a pipe 37 and a hole 34. The cooling liquid 38 is heated by a heater 40 and controlled at the temperature higher than the boiling point of the material sprayed into a plasma flame via a controller 42. The organic halogen compound steam such as fleon and trichlene contained in the carrier gas is maintained at the temperature that it is not returned to waterdrops, and it can be efficiently decomposed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an organic compound that uses a plasma reaction method that can efficiently decompose organic halogen compounds containing fluorine, chlorine, and bromine in organic compounds such as fluorocarbon gas and trichlorethylene. The present invention relates to a high frequency induction plasma device suitable for use in a method for decomposing halogen compounds.

(Prior art) Organic halogen compounds containing fluorine, chlorine, and bromine in organic compounds such as chlorofluorocarbon gas and trichlorethylene are
It is widely used in large quantities as a refrigerant, fire extinguisher, etc., and has great importance in industry.

However, these compounds are highly volatile, and many of those used in industry are released into the environment such as the air, water, and soil, resulting in the depletion of the ozone layer.

It has been pointed out that they have serious effects on the environment, such as the production of carcinogenic substances and mutagenic substances.

(Problems to be Solved by the Invention) Currently, when disposing of used organic halogen compounds, there is no suitable decomposition treatment method because their reactivity is extremely low.

The decomposition treatment methods that have been reported so far are mainly high-temperature combustion techniques. However, this method has extremely low energy efficiency as it burns organic halogen compounds together with a large amount of fuel such as hydrocarbons.
Because the fuel tank and combustion furnace are large, it is not possible to downsize the entire device. Furthermore, free halogens generated during combustion come into contact with the high-temperature furnace walls, resulting in severe corrosion of the furnace, especially when organic fluorine compounds are burned.

As a result of intensive research into a method that can easily decompose organic halogen compounds, the present inventors discovered a method that can easily decompose organic halogen compounds.

We have discovered a minute angle method using plasma generated by microwave induction heating or direct current heating. This method utilizes the phenomenon that substances are highly reactive under plasma conditions, and is based on the fact that difficult-to-decompose chemical substances such as organic halogen compounds can be decomposed in a short period of time. That is, in high-temperature plasma reaching 100,006 C or higher, almost all molecules are considered to be dissociated and decomposed into atomic states.

What should be considered in such a decomposition method using plasma is how to efficiently guide the liquid organic halogen compound into the plasma flame. That is, even if a liquid organic halogen compound is directly introduced into the plasma flame, the liquid organic halogen compound simply passes through the plasma flame and is not decomposed. Furthermore, if a liquid is directly introduced into a plasma flame, the state of the plasma will become unstable, and in extreme cases, the plasma will disappear.

The present invention was made in view of these points, and its purpose is to decompose organic halogen compounds such as chlorofluorocarbons and trichlene using a plasma reaction method that can decompose organic halogen compounds with high efficiency even at high concentrations. The object of the present invention is to realize a high-frequency induction plasma device suitable for carrying out a decomposition method, and in particular, to realize an apparatus that can efficiently supply a liquid organic halogen compound into plasma and decompose it.

(Means for Solving the Problems) A high-frequency induction plasma device based on the present invention includes a cylindrical tube, a gas supply nozzle, an RF coil wound around the tube, and a hole provided in the nozzle. a means for vaporizing a liquid substance to be ejected into the plasma formed in the tube and including it in a carrier gas; a means for guiding the carrier gas to the hole; a cooling liquid passage provided in the nozzle; and a cooling liquid. The present invention is characterized by comprising means for supplying a cooling liquid to the cooling liquid passage, and means for heating the cooling liquid supplied to the cooling liquid passage.

(Operation) In the present invention, a carrier gas containing a vaporized liquid substance is supplied to the hole of the nozzle provided at the upper part of the plasma torch. In addition, a cooling liquid is supplied to the nozzle to cool the nozzle heated by the plasma flame, but the nozzle is cooled too much by the cooling liquid and the carrier gas is also cooled, causing the vaporized liquid contained in the carrier gas to cool down. To prevent the material from turning back into water droplets, the coolant is heated and supplied to the nozzle.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. The attached drawings show a system for decomposing organic halogen compounds such as fluorocarbons using a high-frequency induction plasma device based on the present invention. The induction plasma torch 1 includes a cylindrical tube 2 made of an insulating material such as quartz. Ibff1 is provided by the gas supply nozzle 3 and the RF coil 4 wound around the tube 2 and the like. A ring-shaped groove 5 is bored in the gas supply nozzle 3, and a ring-shaped plate 6 is welded to the outside of the groove 5. A large number of micro holes 7 are bored in the ring-shaped plate 6, and one end of a hole 8 bored inside the nozzle 3 is connected to the groove 5. The other end of the hole 8 is connected to a tube 9 at the top of the nozzle 3 .

The pipe 9 is branched in the middle, and one end is introduced into the first container 10 and the other end is introduced into the second container 11.

A liquid organic halogen compound 12 such as chlorofluorocarbon 113 to be decomposed is placed in the first container 1o.

One end of the carrier gas supply pipe 13 is inserted into the organic halogen compound in the first container 1o. The other end of the carrier gas supply pipe 13 is connected to an argon gas source 15 via a flow controller 14 . Water 16 is placed in the second container 11, and one end of a carrier gas supply pipe 17 is inserted into the water 16. The other end of carrier gas supply pipe 17 is connected to argon gas source 15 via flow controller 18 .

One switching valve is provided in the middle of the pipe 9. One switching valve switches the gas from the first container 10 and the second container 11 and the gas from the argon gas source 20 and guides it to the hole 8 formed in the nozzle 3. The gas flow rate from the argon gas source 20 is controlled by the flow controller 2.
1.

An opening 22 is provided at the bottom of the cylindrical tube 2 constituting the plasma torch 1, and an exhaust pipe 23 is provided in the opening 22.
is connected. The exhaust pipe 23 has a cyclone 24 that traps powdery substances contained in the exhausted gas.
It is connected to the. The exhaust gas that has passed through the cyclone 24 is guided into a pipe 25, which is introduced into a container 27 containing an alkaline aqueous solution, such as potassium hydroxide (KOH) 26 inside. A discharge pipe 28 for internal gas is provided at the upper part of the container 27, and this discharge pipe 28 is connected to the lower part of a container 30 in which an alkaline solid such as calcium oxide (Cab) 29 is placed. At the top of the container 30, a discharge pipe 31 is provided for the gas that has passed between the two calcium oxides inside.

The nozzle 3 of the plasma torch 1 is provided with a ring-shaped hole 5 covered by a plate 6.
The nozzle 3 is further provided with a ring-shaped passage 32. The ring-shaped passage 32 is connected to a first hole 33 and a second hole 34 that are open to the outside at the top of the nozzle 3 . A pipe 35 is connected to the first hole 33 , and the other end of the pipe 35 reaches a cooling liquid tank 36 . A tube 37 is connected to the second hole 34 , and the other end of the tube 37 is pushed into a cooling liquid 38 in a cooling tank 36 . Three pumps are installed in the middle of the pipe 37, and the three pumps suck the coolant 38 in the cooling tank 36 and drain the pipe 37.
The cooling liquid is guided through the ring-shaped passage 32 provided in the nozzle 3. A heater 40 and a temperature detector 41 are placed in the cooling liquid 38 in the cooling tank 36 . Heater 4
0 is supplied with an appropriate current from the controller 42, and a temperature signal from the temperature detector 41 is supplied to the controller 42.

The operation of the device configured as described above will be explained as follows. In the initial state of the device, the switching valve 19 provided in the middle of the pipe 9 is operated to switch on the argon gas source 20.
argon gas is supplied into the groove 5 through the hole 8 of the nozzle 3.

By supplying argon gas to the groove 5, the argon gas becomes
It is ejected into the cylindrical tube 2 from a large number of microholes 7 provided in the plate 6. In this state, a high frequency is supplied to the RF coil 4, and the plasma P is ignited by an ignition mechanism not shown.

After that, switch one switching valve and switch the argon gas source 20.
Gases from the first container 10 and the second container 11 are supplied into the groove 5 through the hole 8 of the nozzle 3 instead of the argon gas from the argon gas. In the first container 10, an argon gas source 1 is added to the organic halogen compound solution 12 inside.
A carrier gas supply pipe 13 connected to 5 is inserted, and the pipe 13 is open into the organic halogen compound 12.
Argon gas is ejected from the end at an appropriate flow rate by the flow controller 14. As a result, the organic halogen compound is dissolved by bubbling argon gas.
The vapor is contained in the gas and discharged from the first container 10 into the pipe 9.

Further, in the second container 11, a carrier gas supply pipe 17 connected to the argon gas source 15 is inserted into the water 16 inside, and the pipe 1 opened into the water 16 is inserted into the second container 11.
From the end of 7, argon gas is ejected at an appropriate flow rate by a flow controller 18. As a result, water becomes steam and is contained in the gas due to the bubbling of the argon gas, and is discharged from the first container 11 into the pipe 9.

At a branch J in the middle of the pipe 9, argon gas containing the vapor of an organic compound and argon gas containing water vapor are mixed, and the mixed gas is introduced into the groove 5 through the hole 8 of the nozzle 3. be done. The mixed gas is ejected from the groove 5 into the tube 2 through a large number of micropores 7 provided in the plate 6.
Introduced into plasma flame F. At this time, the temperature of the plasma is 10,000 to 15,000 degrees, and the organic halogen compound and water introduced into the plasma flame F decompose with high efficiency due to the high temperature and undergo the chemical reaction shown below. do.

Trichlorofluoromethane (
When Freon-11...CCN5F) is decomposed in plasma, the following reaction occurs with water.

CCj! 3 F+2H20 = CO2+3 HCfI+ HF The exhaust gas containing the decomposed molecules is passed through the opening 2 at the bottom of the tube 2.
2, is led into a cyclone 24 through a discharge pipe 23. At this time, if there is less water than Freon-11, excess carbon will be produced, but fine powder such as carbon contained in the exhaust gas will be trapped within the cyclone 24. The gas that has passed through the cyclone 24 is introduced into the potassium hydroxide aqueous solution 26 inside the container 27 through the pipe 25. By passing exhaust gas through this solution 26, HCl2°H
Exhaust gas containing acids such as F is neutralized. The neutralized gas passes from the bottom of the container 27 through the exhaust pipe 28 to the container 30.
It is introduced into the interior and dehydrated by the two calcium oxides inside the container 30. The dehydrated gas is a stable compound with little impact on the environment and is released into the atmosphere as appropriate.

Here, since the plasma flame F is formed close to the nozzle 3, it is possible that the nozzle 3 is heated to a high temperature by the plasma flame and melts. Therefore, in this embodiment, a ring-shaped cooling water passage 32 is provided inside the nozzle 3.
A cooling liquid 38 such as water or oil is supplied to the cooling water passage 32 from a cooling tank 36. The cooling liquid 38 in the cooling tank 36 is sucked up by three pumps and sent to pipes 37. Coolant passage 32 through second hole 34
guided by. The coolant that has passed through the coolant passage 32 is returned to the cooling tank 36 through the first hole 33 and the pipe 35 .

In this way, the nozzle 3 is cooled and the nozzle 3 is prevented from being melted by the plasma flame F. However, if the nozzle 3 is cooled too much by the cooling liquid compared to the temperature of the organic halogen or water, the vaporized organic halogen compound or water that passes through the hole 8 and is supplied to the groove 5 returns to the state of water droplets. I end up. Even when the organic halogen compound and water in the form of water droplets are introduced into the plasma flame F, they simply pass through without being diffused into the flame, making it impossible to efficiently decompose the organic halogen compound. Therefore, in this embodiment, the pump 3
The coolant sucked up by the heater 40 is heated by the heater 40. When the substance ejected into the plasma flame F is fluorocarbon, the boiling point of fluorocarbon is not so high, so the temperature of the coolant is set to about 40°C to 50°C. The temperature of the coolant is measured by a temperature detector 41, and the temperature signal is supplied to a controller 42. The controller 42 controls the current supplied to the heater 4o to constantly maintain the temperature of the coolant 38 to the carrier gas. The temperature is maintained at such a level that the organic halogen compound vapor contained therein is not returned to the water droplets.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments. For example, one groove is provided in the nozzle of a torch, and argon gas and a carrier gas containing organic halogen compound vapor are alternately supplied to this groove by bubbling. In one case, argon gas and a carrier gas containing vapor of an organic halogen compound by bubbling may be switched and supplied, and in the other case, argon gas may be continuously supplied. In addition, in order to decompose organic halogen compounds, liquid organic halogen compounds are vaporized,
Although the present invention has been explained using an example of introducing it into plasma,
In addition to the purpose of decomposing organic halogen compounds, the present invention can also be applied to cases where other liquid substances are vaporized and introduced into plasma.

Furthermore, if a heater and a thermometer are provided inside the container containing the organic halogen compound and water, and the organic halogen compound and water are always kept at a temperature of about 30°C to 40°C, the temperature will be even higher. Evaporation can be promoted.

(Effects of the Invention) As explained above, according to the present invention, a carrier gas containing a vaporized wavy substance is supplied to the hole of the nozzle provided at the upper part of the plasma torch, and a cooling liquid for cooling the nozzle is supplied. Since the liquid substance is heated and supplied to the nozzle part, it is possible to efficiently diffuse the liquid substance into the plasma flame.In addition, if the nozzle is too cooled by the cooling liquid, the carrier gas is also cooled and the liquid substance is Contained vaporized liquid substances are also prevented from returning to water droplets.

[Brief explanation of drawings]

The accompanying drawings are diagrams showing an embodiment of an organic halogen compound decomposition system using a high frequency induction plasma device based on the present invention. 1...Torch 2...Pipe 3...Gas supply nozzle 4...RF coil 5...Groove
6... Plate 7... Microhole 8
...holes 9, 13. 17.25.28...Tube 10.
...First container 11...Second container 12...
Organic halogen compound 14.18.21...Flow controller 15...
Argon gas source 16...1 water...switching valve
20... Argon gas source 22... Opening
23... Exhaust pipe 24... Cyclone 26... Potassium hydroxide aqueous solution 27.30... Container 29... Calcium oxide 31... Discharge pipe 32... Passage 33.34...35 .3
7...Pipe 36...Cooling tank 38...Cooling liquid 3...Pump 40...Heater
41...Temperature detector 42...Controller Patent applicant: Agency of Industrial Science and Technology, Japan Electronics Co., Ltd.

Claims (1)

[Claims] A cylindrical tube, a gas supply nozzle, an RF coil wound around the tube, a hole provided in the nozzle, and vaporizing a liquid substance to be ejected into plasma formed in the tube,
means for containing the carrier gas, means for guiding the carrier gas to the hole, and a coolant passage provided in the nozzle;
A high frequency induced plasma apparatus comprising means for supplying a coolant to a coolant passage and means for heating the coolant supplied to the coolant passage.