JPH06290896A - High frequency plasma heater and its operating method - Google Patents

Abstract

PURPOSE:To obtain a great quantity of ultra-high temperature gas without increasing the gas flow speed remarkably by omitting provision of any decompression device (vacuum pump or vacuum chamber), generating a plasma by high frequency electrodeless discharging at a normal pressure for obtaining large quantity of ultra-high temperature gas, and heightening the internal pressure of a plasma torch while the plasma is maintained. CONSTITUTION:A corona discharge electrode 11 is furnished on a plasma torch 2 so that a minute discharge is generated, and thereover a high frequency power is superposed by a microwave electric field converter 8 so that plasma is generated in the discharge part 1, and the supply gas pressure is boosted while the plasma generated condition is maintained, and thereby an ultra-high temperature gas is obtained. Accordingly a large quantity of ultra-high temperature gas with a high purity can be produced effectively at a lesser equipment cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency plasma heater and an operating method thereof, and more particularly to a high-frequency plasma heater capable of supplying high-purity high temperature gas and an operating method thereof.

[0002]

2. Description of the Related Art A high frequency plasma heater can heat a gas (including air) to an extremely high temperature (up to 10 ⁴ K) and is therefore used for development tests of heat resistant materials for space and research of ultra high temperature aerodynamics. Other practical applications include melting of metals, gasification of coal, decomposition and detoxification of CFCs and PCBs, which are stable substances using ultra-high temperature, and high-temperature treatment of industrial waste (“A SPACE -AGE FLAME FOR LYON.REVUE AEROSPAT
IAL. "Nov. 1992 No. 93.).

In the development of heat-resistant materials for space and the decomposition of CFCs and PCBs, oxygen molecules contained in the air are activated to atomic oxygen at ultra-high temperatures, and erosion tests of materials and CFCs and CFCs due to atomic oxygen are carried out. In order to promote the decomposition, it is necessary to bring a large amount of air to a supersonic temperature (-10 ⁴ K) for a long time. In particular, in the wind tunnel for development of heat resistant materials for space and research of ultra-high temperature aerodynamics, ultra-high temperature air that does not contain impurities
It is necessary to supply a large amount for a long time.

However, in normal combustion, the limit is about 3500 ° C., and it is difficult to obtain a gas having a temperature higher than that.

Therefore, in order to obtain such an ultrahigh temperature gas, conventionally, an arc plasma heater utilizing arc discharge has been used. An arc plasma heater is usually composed of a rod-shaped cathode electrode, which is connected to a DC power source, and a nozzle-shaped anode electrode that encloses the cathode electrode and flows a gas to be plasmatized inside. Is generated in between.

Due to the generated arc discharge, the gas ejected from the gap between the nozzles supplied to the anode is heated to an ultrahigh temperature and is ejected at a high speed by being restrained by the nozzle, and the ultrahigh temperature gas is directly used, or The gas heats the treated material.

[0007]

However, in the arc discharge, when the arc is generated, a part of the electrode is consumed and the constituent metal material of the electrode is mixed in the high temperature gas, so that an ultrahigh temperature gas of high purity is produced. It's difficult. Further, in the case of high-power arc discharge, the electrodes are heavily consumed, so that continuous operation for a long time is difficult, and the maintenance work is complicated accordingly. Further, the center temperature of the arc is as high as tens of thousands K, which causes a large radiation loss and lowers the thermal efficiency.

Further, in order to obtain ultrahigh temperature gas, fusion,
The high frequency plasma used in a CVD apparatus or an artificial diamond manufacturing apparatus can also be used.
However, since plasma is generated under reduced pressure, it is very difficult to generate a large amount of ultra-high temperature gas.

An object of the present invention is to provide a high-frequency plasma heater and a method of operating the same, which can supply a large amount of ultra-high temperature gas of high purity of about 10 ⁴ K for a long time.

[0010]

The above object is to supply a gas from one side, generate a plasma by heating the gas by electric discharge, and a plasma torch having a discharge part for maintaining the plasma, A high-frequency plasma heater having high-frequency power supply means for supplying power energy to plasma by high-frequency induction to the discharge part of the plasma torch, and plasma gas supply means for supplying gas to be plasmatized to the discharge part of the plasma torch. Since the high frequency discharge is started in the discharge part of the torch, plasma is generated between the plasma ignition means that generates auxiliary discharge in the discharge part and lowers the discharge start voltage, and the plasma generated in the discharge part of the plasma torch and its inner wall surface. In order to supply the gas to the inside of the plasma torch, the sheath gas is connected to the inside of the plasma torch and joined to the outer peripheral surface of the plasma torch. And road, further comprising a sheath gas supply means for supplying gas to the sheath gas supply passage, a plasma gas supply means may be accomplished by high-frequency plasma heater and supplying a plasma gas on the normal pressure.

Further, the above-mentioned object is, in a method of operating a high-frequency plasma heater having the above-mentioned means, a corona discharge or a creeping discharge at a gas pressure higher than normal pressure in a discharge part where a high frequency of a predetermined electric power is superposed. The plasma is started up, a gas at a predetermined pressure above the atmospheric pressure is flown to generate plasma, and while maintaining the generated plasma, the high-frequency power supply power is increased and the plasma gas supply pressure is increased sequentially. This can be achieved by a method of operating a high-frequency plasma heater, which is characterized in that the plasma is increased and maintained under a plasma gas supply pressure higher than that at plasma startup. Further, the above-mentioned object is to supply a gas from one side and generate a plasma when the gas is heated by an electric discharge, and further, in a plasma torch having a discharge part for maintaining the plasma, the gas is generated in the discharge part of the plasma torch. A plasma torch, characterized in that it has a sheath gas supply passage that is in communication with the inside of the plasma torch and is joined to a part of the outer peripheral surface for flowing gas between the plasma and the inner peripheral wall surface of the discharge part. This can be achieved by a plasma heater having the same.

[0012]

First, the principle of gas pressure and heating efficiency will be described. FIG. 1 is a graph showing the relationship between air temperature (horizontal axis) and enthalpy (vertical axis) for air at several pressures. As you can easily see from Figure 1,
When the air pressure is increased, the air temperature can be increased with a small enthalpy, and the heating efficiency is improved. For example, if you apply 4 kcal of heat to 1 gram of air at 20 atm,
The air temperature is about 7200 degrees K, but even if 4 kcal of heat is added to 1 gram of air at 0.01 atm, the air temperature is only about 5200 degrees K.

Therefore, according to the present invention, a large amount of ultra-high temperature air is efficiently generated by heating the gas pressure to be higher than atmospheric pressure.

Next, generation of high frequency plasma in the high pressure gas according to the present invention will be described. Generally, in order to generate an electric discharge in air (gas), as indicated by Paschen's method, the electric field strength of the electric discharge decreases in proportion to the gas pressure and reaches a minimum value at about 180 V / cm. The higher the electric field strength, the larger the electric field strength at the start of discharge. However, the electric field strength obtained by a practically used power supply for high-frequency plasma generation is about several hundred V / cm to several thousand V / cm, and with this value, discharge cannot be started in a gas at normal pressure.

Therefore, according to the present invention, a voltage of several thousand to tens of thousands of volts and several milliamperes or less is superimposed on the high frequency electric field applied to the discharge part in the plasma torch,
A small current flow path of ionized gas is generated by the discharge for plasma startup generated by applying the current. Then, the discharge start voltage of the discharge part suddenly drops to several tens of V /
cm or less. Therefore, a high-frequency current induced by a high-frequency electric field or magnetic field flows in the discharge part, ionization of gas proceeds, and high-frequency plasma grows. The plasma gas diffuses the ionized gas by thermal expansion to increase the heated volume of the gas. In this process, the plasma is maintained by balancing the heated volume of the gas, its temperature, and the applied high frequency power, which range is fairly wide.

The graph shown in FIG. 2 shows the result of calculation of the input power required to maintain the plasma for a torch of a certain size when the gas type and gas pressure are used as parameters. For example, when a high frequency power source with a frequency of 1 MHz is used, plasma can be maintained in the torch by applying an electric power of 50 to 60 KW or more with air of 1 atm, and with a high frequency power source of 10 MHz, 7 to 8 kW
With the above power, plasma can be maintained in air at 1 atm. The difference in plasma sustaining power due to these frequencies is mainly due to the difference in volume discharged in the gas.
That is, when the frequency becomes high, the effective discharge part is limited to the surface by the skin effect, so that the volume for heating and ionizing the gas decreases.

In the present invention, after the high-frequency plasma is generated in the gas at about normal pressure, the high-pressure gas above the normal pressure is applied by applying the high-frequency power above the level at which the plasma can be maintained to increase the gas pressure above the normal pressure. It heats and efficiently generates a large amount of ultra-high temperature air. Here, if the high-frequency input corresponding to the gas pressure is set as low as possible, the overall gas temperature will be low, and it is possible to prevent efficiency deterioration due to radiation loss such as arc discharge.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First, the structure of an embodiment of the plasma heater to which the present invention is applied will be described with reference to FIGS. 8 and 3, and two structural examples of the plasma torch in this plasma heater will be described with reference to FIGS. 4 and 5. After that, FIG.
The operating method will be described with reference to FIG. 7, and finally, another embodiment of the present invention will be described with reference to FIG.

First, an embodiment of the present invention will be described. In this embodiment, a corona discharge device is used as the plasma ignition means, and a magnetron for generating a microwave of 2.45 GHz is used as the high frequency power supply means as the high frequency power supply means.

FIG. 8 is a block diagram for explaining the outline of the apparatus in this embodiment. In FIG. 8, 2 is a plasma torch. This plasma torch 2 is an inner cylinder that forms a discharge part 1 that supplies gas to be plasmaized (hereinafter abbreviated as plasma gas) from one end and discharges it from the other end face, and forms and maintains plasma outside the end face. 3 and a cylindrical structure having a concentric axis with it and covering the discharge part 1, and flowing a gas that is not plasmatized (hereinafter abbreviated as sheath gas) between the inner surface of the part covering the discharge part 1 and the generated plasma. And a sheath gas supply path 5 capable of supplying a sheath gas from one of the outer cylinder 4 and the outer cylinder near the bottom of the outer cylinder 4 at right angles to each other.

Further, in FIG. 8, 6 is a high frequency power source for generating microwaves, 7 is a waveguide for introducing the generated microwaves to the vicinity of the plasma torch 2, and 8 is a microwave introduced by the waveguide 7. A microwave electric field converter for applying an electric field to the discharge unit 1, 9 is a plasma gas supply device capable of adjusting a supply pressure for supplying a plasma gas, 10 is a sheath gas supply device capable of adjusting a supply pressure for supplying a sheath gas,
Reference numeral 11 denotes a corona electrode attached to the tip of the outer cylinder 4 for generating corona discharge in order to start plasma in the discharge part 1, 12 denotes a high voltage generator for corona discharge for supplying a high voltage to the corona electrode 11, Reference numeral 13 is a plasma ignition gas supply device for supplying a monatomic gas such as argon so that discharge is facilitated when corona is generated, and reference numeral 14 is a plasma gas outlet. Here, the other corona electrode is arranged so as to sandwich the discharge part 1 so that the generated corona passes through the discharge part 1.
Since it depends on the detailed structure of the plasma torch, it will be described together with the following plasma torch structure examples.

In the present embodiment, the electric field of the microwave generated by the high frequency power source 6 and sent through the waveguide 7 is converted into several hundreds V / cm by the microwave electric field converter 8 to discharge the plasma torch 2. Added to Part 1.

Next, a monatomic gas having a low discharge starting voltage, for example, an argon gas is made to flow from the plasma ignition gas supply device 13 to the discharge part 1 through the sheath gas supply path 5, and at the same time, the corona electrode 11 and the other electrode. A voltage supplied from the high voltage generator 12 for corona discharge is applied to (not shown) to generate corona in the discharge unit 1.

When corona occurs, the high frequency discharge is started in the discharge section 1 by using it as a trigger. When the high frequency discharge is started, the plasma ignition gas supply means 13 is operated to stop the supply of the monatomic gas, and instead, the sheath gas and the plasma gas are supplied from the sheath gas supply device 10 and the plasma gas 9.

When the plasma gas is caused to flow in the discharge section 1, plasma is generated and maintained by the microwave discharge, and the plasma gas heated therein is discharged from the plasma gas outlet 14.

Since the sheath gas supplied to the inside of the outer cylinder 4 passes through the sheath gas supply passage 5 which is connected to the outer circumference of the outer cylinder 4 at a right angle and is joined thereto, first, the gap between the inner cylinder 3 and the outer cylinder 4 is made. Since the plasma moves between the plasma generated in the discharge part 1 and the inner surface of the outer cylinder 4 while rotating, it separates the plasma from the inner surface of the outer cylinder 4. Furthermore, since the sheath gas is not plasmatized, the temperature is low. Therefore, the sheath gas flows while swirling on the inner surface of the outer cylinder 4, thereby cooling the outer cylinder 4 and the corona electrode 11 attached thereto.

As the plasma gas, in addition to gases such as nitrogen and air, it is also possible to use a gas in which fine powder of a material to be heated at high temperature is mixed. As the sheath gas, the same gas as the plasma gas or a different gas can be used depending on the required high temperature gas condition.

In this embodiment, the inner cylinder 3 through which the plasma gas flows
Although only one is used, it is possible to combine several of them and arrange them in the outer cylinder 4 in order to increase the amount of plasma gas generated. FIG. 9 shows another embodiment of the plasma torch in which two inner cylinders 3 are combined. In FIG. 9, the plasma torch includes two inner cylinders 3 for ejecting plasma gas to the discharge part 1, an outer cylinder 2 for enclosing them, and a sheath gas supply path 5 for supplying sheath gas to the outer cylinder 2.
A microwave electric field converter 8 that supplies high-frequency power energy to the discharge unit 1.

Further, although corona discharge was used as the plasma ignition means, it is not limited to this. For example, a discharge can be generated in the discharge unit 1 on which a high frequency electric field is superposed,
Furthermore, if there is a cooling means (cooling with gas or water that has not been turned into plasma) for the electrode, another ignition method may be used. The cooling means is necessary for cooling the discharge electrode because it is heated directly by the generated plasma or indirectly by radiation.

Further, although the monatomic gas was used as the gas for starting the discharge, the plasma gas or the sheath gas can be used as it is from the time of plasma ignition by increasing the voltage supplied to the discharge electrode. On the contrary, the plasma can also be ignited by increasing the high-frequency electric field supplied by using the discharge starting gas. Further, a gas having a low discharge starting voltage and an independent small-sized auxiliary plasma torch which emits the gas into plasma by utilizing a high frequency electric field or magnetic field and discharges it to the discharge part 1 can also be used as the plasma ignition means.

Further, as the high frequency for supplying the electric power to the discharge section 1, the microwave is used in the present embodiment,
High frequencies in the so-called VHF band or UHF band from several MHz to several GHz can be used as well as microwaves.

The detailed operation method of this embodiment, such as maintaining the generated plasma and increasing the supply gas pressure, will be described below with reference to FIG.

FIG. 3 is a partially cutaway perspective view of this embodiment. The plasma heater of the present embodiment has the waveguide 7, the microwave electric field converter 8 and the corona electrode 11 shown in FIG. Here, the plasma torch 2 is arranged so that the discharge part 1 faces the opening at the center of the cylindrical microwave electric field converter 8, and the corona electrode 11 is attached to the tip part thereof. Further, 14 is an outlet of the generated plasma gas, 15 is a plasma gas supply port for supplying the plasma gas to the inner cylinder inside the plasma torch 2, and 16 is a sheath gas supply for supplying the sheath gas in a direction perpendicular to the flowing direction of the plasma gas. A port 17 is a microwave input port for introducing the microwave generated by the high frequency power source into the microwave electric field converter 8.

Next, a structural example of the plasma torch used in this embodiment will be described below.

FIG. 4 (a) is a detailed cross-sectional view of one structural example of the plasma torch schematically shown in FIG. 8, and FIG. 4 (b) is FIG. 4 (a) seen from the direction in which the plasma gas is supplied. ) A-
It is an A line sectional view. In FIG. 4, the plasma torch is
A nozzle shape having a double-barreled structure, in which plasma gas is supplied from the plasma gas inlet 20 and flows through the plasma gas flow path 22 to the discharge unit 1 to which a high frequency electric field is applied by the microwave electric field converter 8. Inner cylinder 3 having a discharge part 1
The outer cylinder 4 which covers the inner cylinder 3 and has a sheath gas flow path 23 for flowing the sheath gas in a gap between the inner cylinder 3 and the inner cylinder 3, and the sheath gas is supplied from the sheath gas inlet 21 to the sheath gas flow path 23, and the sheath gas is discharged while swirling in the sheath gas flow path 23. The sheath gas supply passage 5 is connected to the outer circumference of the outer cylinder 4 so as to be connected to the outer periphery of the outer cylinder 4 at a right angle to the traveling direction of the plasma gas flow so as to flow to the portion 1.

Further, in FIG. 4, in order to ignite the plasma, plasma ignition means for generating a corona in the discharge part 1 at a position indicated by a corona path 24 is, for example,
A corona electrode 11 mounted on a corona electrode support ring 18 at the tip of the outer cylinder 4 in the direction of plasma emission, a corona electrode 19 inserted in the center of the inner cylinder 3, and a high voltage applied to both electrodes. High voltage generator 1 for corona discharge
2 and.

The components of the plasma torch other than the corona electrodes 11 and 19 are made of, for example, thin quartz glass having high transparency. This is because high electrical insulation and heat resistance are required, and further, it is necessary to reduce the temperature difference between the inside and outside of the torch where plasma is generated to eliminate cracks.

In the plasma torch of this structural example, when a voltage of several thousands to tens of thousands V is applied to the corona electrodes 11 and 19 by the power supply device 12 for corona discharge with a current of several mA, the corona between the electrodes is increased. There is a corona pass 2 in the discharge part 1.
Fly like 4 The plasma gas to be turned into plasma is supplied from the plasma gas inlet 20, passes through the plasma gas flow path 22 in the inner cylinder 3, and flows into the discharge part 1. further,
Since a high frequency electric field is applied to the discharge section 1 by the microwave electric field converter 8, when the discharge start voltage of the discharge section 1 is rapidly lowered by the corona discharge, the high frequency current is concentrated and plasma is generated in the discharge section 1. Occur. After that, by gradually increasing the supply gas pressure and the electric power, a high temperature gas can be obtained at a gas pressure higher than normal pressure.

At this time, the sheath gas is injected from the sheath gas inlet 21 of the sheath gas supply passage 5 attached to the outer periphery of the torch. Therefore, the sheath gas passes through the sheath gas flow path 23 and flows in the direction of the discharge part 1 while swirling in the circumferential direction in the gap between the outer cylinder 4 and the inner cylinder 3. As a result, the plasma generated in the discharge part 1 spreads circumferentially inside the outer cylinder 4, but is surrounded by this sheath gas, so that the outer cylinder 4
It is isolated from the inner wall. The sheath gas also cools the outer cylinder 4 and the corona electrode 11.

Next, another structural example of the plasma torch according to the present embodiment will be described with reference to FIG. Figure 5 (a) shows
It is sectional drawing of one structural example of a plasma torch, FIG.5 (b)
FIG. 4 is a cross-sectional view of the plasma torch taken along the line AA as seen from the plasma gas supply side.

In FIG. 5 (a), all the constituent elements of the plasma torch are the same as those in FIG. 4 except for the joining position of the sheath gas supply passage attached to the outer circumference of the outer cylinder and the arrangement of the corona discharge electrode. is there.

In the plasma torch of this structural example, the corona electrode 11 located at the same position as in FIG. 4 is used as the corona discharge electrode.
And the conductor portion of the microwave electric field converter 8 is used as the other electrode, and a corona like the corona path 24 is generated in the discharge part 1. With this structure, the torch does not need to be provided with the other electrode, so that the structure of the torch is simplified. Further, the sheath gas supply passage 5 is joined to the outer cylinder 4 so that the central axis thereof and the central axis of the torch body are offset, as shown in FIG. In this structure,
The supplied sheath gas flows from the lower part of the plasma torch to the upper part while swirling in the sheath gas flow path 23 (counterclockwise in this example). Therefore, as compared with the plasma torch of FIG. 4, the swirling velocity of the sheath gas flow is high, the gas flow layer (sheath) formed by the sheath gas flow is more stable, and the generated plasma can be more completely discharged from the inner wall surface of the outer cylinder 4. Quarantine,
Furthermore, the wall surface of the outer cylinder 4 and the corona electrode 11 can be cooled more efficiently.

Next, the operating method of this embodiment will be described below with reference to FIG. FIG. 6 is a sectional view of this embodiment shown in FIG. 3, and the plasma torch shown in FIG. 4 is used.

First, a high frequency power source as a high frequency power generating means, for example, a magnetron (not shown) is operated,
A microwave having a predetermined power is supplied from the microwave inlet 17. At this time, since plasma is not generated, most of the supplied power is reflected.

Next, a plasma ignition gas supply device (not shown) is operated to supply a small amount of monatomic gas such as argon having a low discharge starting voltage to the discharge part 1 from the sheath gas inlet 16 or the plasma gas inlet 15. At the same time, a high voltage generator (not shown) for corona discharge applies a high voltage to the corona electrodes 11 and 19 to generate corona in the discharge part 1 like the corona path 24. Then, microwave discharge is generated from the generated corona path 24,
The supplied microwave power is absorbed by the monatomic gas, and the gas is heated.

Immediately after the microwave discharge is started, the supply of the monatomic gas is stopped and the gas to be heated or turned into plasma instead, for example, to obtain a normal high temperature gas, air or nitrogen gas ( (Hereinafter abbreviated as gas) is supplied from the plasma gas inlet 19. The sheath gas supplied from the sheath gas inlet 16 through the sheath gas supply passage 5 may be the same as or different from the plasma gas depending on the required gas conditions. However, the amount of gas supplied from the plasma gas inlet 15 is smaller than the amount supplied from the sheath gas inlet 16.

By flowing gas from the plasma gas inlet 15, the plasma is blown away. As a result, the generated plasma is prevented from being overheated by being concentrated in the central portion of the discharge part 1 by the pinch effect or retreating into the inside of the cylinder 3, so that the plasma is stably maintained and the temperature of the plasma torch 2 is maintained. Prevent the rise. The operations up to this point are carried out under normal pressure or at several atmospheric pressures.

Next, the plasma gas pressure and the sheath gas pressure to be supplied are increased while maintaining the plasma. At this time, the difference between the gas pressures supplied from the respective gas inlets 15 and 16 and the pressure outside the plasma torch 2 is limited to the pressure difference that the outer cylinder 4 can withstand.

In this embodiment, since the main constituent elements of the plasma torch 2 including the outer cylinder 4 are made of transparent quartz glass having a thickness of about several mm, a high pressure gas of about several tens of atmospheres is used. When supplying, as described in the following embodiments, the entire plasma heater is enclosed in a pressure tank, and the tank internal pressure is increased in proportion to the supply gas pressure. Further, the flow rate of gas to be turned into plasma is set so as to satisfy the following relationship.

Normally, in the gas supply device, the gas pressure and the gas flow rate have a certain proportional relationship. Further, in order to maintain a constant flow rate (Nl / min in atmospheric pressure) of gas plasma, a microwave having an electric power proportional to it is added (see FIG. 2) to heat the plasma to a certain temperature or higher. . Therefore, when the gas pressure of the gas supply device is increased, as shown in FIG. 1, so as to satisfy the entropy value which is a function of the temperature of the gas corresponding to the gas pressure,
The plasma can be maintained at high pressure by increasing the microwave power supplied.

For example, in this embodiment, a plasma torch having a diameter of 20 mm and having the structure shown in FIG.
It was observed that when the microwave of W was input, the plasma could be stably maintained even when the flow rate of the plasma gas (air) was changed in the range of about 15 Nl / min to at least 110 Nl / min.

Next, an embodiment of the plasma heater to which the high pressure supply gas according to the present invention can be used will be described with reference to FIG. FIG. 7 shows an example in which the plasma heater of the embodiment shown in FIG. 3 is housed in a high-pressure container having a pressure approximately equal to the supply gas pressure in order to reduce the difference between the internal and external pressures of the plasma torch. FIG.

In FIG. 7, reference numeral 26 is a cylindrical pressure tank capable of withstanding high pressure for containing the components such as the plasma torch 2 and the microwave electric field converter 8 shown in FIG. A plasma gas supply pipe 27 for supplying plasma gas from outside the tank 26 to the plasma torch 2 under pressure, and a sheath gas for supplying plasma gas to the plasma torch 2 from outside the pressure tank 26, as well as the pressure tank 2
A sheath gas supply pipe 28 for supplying gas for increasing the pressure of 6, a microwave input port 29 generated by a high frequency power generator (not shown) such as a magnetron, and a choke circuit for introducing the microwave. 30 having a waveguide
The gas is not passed through, but is emitted from the plasma torch 2 and the pressure partition wall 31 of the waveguide which is made of a material transparent to microwaves, such as alumina, and which is mounted on the pressure tank 26. In order to expand the plasma gas ejecting port 32 mounted on the pressure tank 26 for ejecting the plasma gas to the outside of the pressure tank 26 and the plasma gas ejected from the plasma gas ejecting port 32 at a high speed, Expansion nozzle mounting seat 33 and pressure tank 2
6 and an inspection port 34 for inspecting the plasma torch 2 located inside. Here, although not shown, similar to the embodiment shown in FIG. 1, the power supply device and the gas supply device of the connected corona discharge device, the power supply device to the magnetron, and the plasma gas and the sheath gas supply are provided. There is a device.

Here, the pressure tank 26 is maintained at an internal pressure approximately equal to the gas pressure supplied from the plasma gas supply pipe 27 and the sheath gas supply pipe 28, so that the inside of the plasma torch 2 through which the plasma gas and the sheath gas flow. And the pressure on the outside can be made almost equal.
Therefore, high-pressure plasma gas can be used for efficient heating, and for this reason, it is not necessary to use a material having a particularly high strength for the constituent elements of the plasma torch 2.

In order to maintain the pressure in the pressure tank 26, a simple method is to split the supplied sheath gas inside or outside the pressure tank and discharge one of them into the pressure tank.

In this embodiment, the sheath gas separates the generated plasma from the inside of the plasma torch 2, cools the inside, and is released into the pressure tank 26.
It is used to increase the gas pressure. The sheath gas and the plasma gas are the same gas and can be supplied from a single supply device, but it is also possible to separately provide the gas supply at substantially the same pressure for each device.

The structure of the plasma torch 2 in this embodiment may be any structure to which the present invention is applied, including the structure example shown in FIG. 4 or 5.

The operation of this embodiment will be described below with reference to FIG. First, the electric field of the microwave sent through the waveguide 30 and the waveguide pressure partition 31 is converted into several hundreds V / cm by the microwave electric field converter 8 and applied to the plasma torch 2. Next, a monatomic gas having a low discharge starting voltage, for example, argon gas, is supplied to the sheath gas supply passage 28.
Through the plasma torch 2 and through corona ignition means (not shown) to generate corona in the plasma torch 2.

When corona is generated, the high frequency discharge is started in the plasma torch 2 by using it as a trigger. When high frequency discharge is started, stop the supply of monatomic gas,
Instead, the sheath gas and the plasma gas are supplied from the respective supply pipes 27 and 28. When the plasma gas is flown into the plasma torch 2, the microwave discharge generated therein heats the gas to generate and maintain plasma. The heated plasma gas is discharged from the plasma gas ejection port 32 to the outside of the pressure tank 26.

Thereafter, while gradually maintaining the plasma, the pressure of the supplied plasma gas and the sheath gas and the high-frequency power can be increased to increase the pressure of the supplied plasma gas, thereby efficiently increasing the volume of the super gas. High temperature gas can be obtained.

INDUSTRIAL APPLICABILITY The present invention can be used for various thermal tests capable of obtaining a high-temperature and high-velocity gas flow, for example, development of heat-resistant materials and research on high-speed fluids. Since plasma-like oxygen heated to 10 ³ K to 10 ⁴ K can be generated, it can be used for decomposition of stable substances such as PCB and Freon, and treatment of waste at ultrahigh temperatures.

[0062]

According to the present invention, in order to maintain the high frequency plasma at a high pressure, a large amount of plasma gas at an ultra high temperature,
The gas can be stably generated without increasing the gas flow velocity in the plasma torch. Furthermore, since high-frequency plasma is generated at atmospheric pressure or higher, an exhaust device such as a vacuum pump for decompressing is unnecessary, and the cost of the device is reduced.

[0063]

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between temperature and gas enthalpy in air at several pressure values.

FIG. 2 shows a case where a gas having a specific flow velocity is flown into a plasma torch having a specific size to which the present invention is applied.
A graph showing high-frequency power and frequency capable of maintaining plasma with gas type and pressure as parameters.

FIG. 3 is a partially cutaway perspective view of an embodiment of a plasma heater to which the present invention is applied.

4A and 4B are cross-sectional views of the plasma torch of the embodiment of FIG. 3 to which the present invention is applied, in which FIG. Sectional drawing which expanded only the plasma torch part.

FIG. 5 is a cross-sectional view of the plasma torch in another structure example of the plasma torch to which the present invention is applied.
(B) is the sectional view on the AA line of the plasma torch.

6 is a structural cross-sectional view of a central portion in one embodiment of FIG. 3 to which the present invention is applied.

FIG. 7 is a partial cross-sectional perspective view of a plasma heater capable of increasing the gas supply pressure in the plasma torch and eliminating the pressure difference between the inside and the outside of the plasma torch, as another embodiment to which the present invention is applied.

FIG. 8 is a block diagram illustrating an embodiment of a plasma heater to which the present invention is applied.

FIG. 9 is a block diagram illustrating an embodiment of a plasma torch to which the present invention is applied.

[Explanation of symbols]

1 ... Discharging part, 2 ... Plasma torch, 3 ... Inner cylinder, 4
... Outer cylinder, 5 ... Sheath gas supply path, 6 ... High frequency power supply,
7 ... Waveguide, 8 ... Microwave electric field converter, 9 ... Plasma gas supply device, 10 ... Sheath gas supply device, 1
DESCRIPTION OF SYMBOLS 1 ... Corona electrode, 12 ... High voltage generator for corona discharge, 13 ... Gas supply device for plasma ignition, 14 ... Plasma gas outlet, 15 ... Plasma gas inlet, 16
… Sheath gas inlet, 17… Microwave input port, 1
8 ... Corona electrode support ring, 19 ... Corona electrode, 2
0 ... Plasma gas inlet, 21 ... Sheath gas inlet, 2
2 ... Plasma gas channel, 23 ... Sheath gas channel, 2
4 ... Corona pass, 25 ... Transducer opening, 26 ... Pressure tank, 27 ... Plasma gas supply pipe, 28 ... Sheath gas supply pipe, 29 ... Microwave input port, 30 ... Waveguide, 31 ... Waveguide pressure partition, 32 ... Plasma gas ejection port, 33 ... Expansion nozzle mounting seat, 34 ... Inspection port.

Claims (14)

[Claims] 1. A plasma torch having a discharge part for supplying a gas from one side and heating the gas by an electric discharge to maintain the plasma, and a high frequency induction to the discharge part of the plasma torch. In the high-frequency plasma heater having the high-frequency power supply means for supplying electric power energy to the plasma and the plasma gas supply means for supplying the gas to be plasmatized to the discharge part of the plasma torch, the high-frequency discharge is generated in the discharge part of the plasma torch. To start
In order to supply a gas between the plasma ignition means that generates an auxiliary discharge in the discharge part and lowers the discharge start voltage, and the plasma generated in the discharge part of the plasma torch and its inner peripheral wall surface, the plasma torch internal Further has a sheath gas supply path connected to the outer peripheral surface thereof and a sheath gas supply means for supplying gas to the sheath gas supply path. The plasma gas supply means supplies the plasma gas at a pressure higher than normal pressure. A high-frequency plasma heater characterized by: 2. A high frequency plasma heater according to claim 1, further comprising: a means for increasing / decreasing a supply pressure of plasma gas; and a means for increasing / decreasing an amount of high frequency power supplied. 3. The high frequency plasma heater according to claim 1, wherein the high frequency power supply means includes a high frequency electric field generator and a waveguide for guiding the generated high frequency to the discharge part. 4. The plasma ignition means according to any one of claims 1 to 3, comprising a gas supply device used for ignition, a pair of electrodes, and a high voltage generator for supplying a high voltage to them. A high-frequency plasma heater having a structure in which a pair of electrodes generate a corona discharge therebetween, and the corona discharge is arranged at a position passing through the discharge part of the plasma torch. 5. The high frequency plasma heater according to claim 3, wherein one electrode of the plasma ignition means is a conductor existing near the outside of the discharge portion of the plasma torch. 6. The high frequency plasma heater according to claim 4 or 5, wherein one electrode of the plasma ignition means is mounted at a position deviated from a discharge portion of the plasma torch where plasma is generated. 7. The method according to claim 1, wherein at least the constituent element of the plasma torch facing the generated plasma is made of a material having heat resistance and electric insulation. High frequency plasma heater. 8. The high frequency plasma heater according to claim 7, wherein the material having heat resistance and electrical insulation is transparent quartz glass. 9. The pressure container for accommodating the plasma torch and having a discharge port for the generated plasma, and the pressure difference between the inside and outside of the plasma torch within a predetermined range according to any one of claims 1 to 8. A high-frequency plasma heater, further comprising a pressurizing device for holding. 10. The method of operating a high frequency plasma heater according to claim 1, wherein the discharge part superposed with a high frequency of a predetermined electric power,
Plasma is activated at a gas pressure above atmospheric pressure, and a gas to be plasmatized at a predetermined pressure above atmospheric pressure is flown there.
The plasma is generated, and while maintaining the generated plasma, the supply power of the high frequency power is increased and the supply pressure of the gas to be turned into plasma is gradually increased to maintain the plasma under the gas supply pressure higher than that at the plasma startup. A method for operating a high frequency plasma heater, comprising: 11. A gas is supplied from one side, the gas is heated by electric discharge to generate plasma, and further,
In a plasma torch having a discharge part that maintains the plasma, a plasma torch for communicating gas between the plasma generated in the discharge part of the plasma torch and the inner peripheral wall surface of the discharge part, and an outer peripheral surface A plasma torch having a sheath gas supply path joined to a part of the plasma torch. 12. An electrode for corona discharge as a plasma ignition means, which is mounted on a part of an inner peripheral wall surface of a plasma torch on a plasma emission side of a discharge part so as to expose the electrode. The plasma torch, further comprising: a sheath gas supply path that supplies a gas that flows between an inner peripheral wall surface of the plasma torch and the plasma to cool the inner peripheral wall surface and the electrode. 13. The sheath gas supply passage according to claim 11, wherein the gas supplied into the plasma torch from the sheath gas supply passage is at an angle having a velocity component in a tangential direction of the inner periphery of the plasma torch when the inner periphery of the plasma torch flows. A plasma torch that is joined to the outer surface of the plasma torch. 14. The plasma torch according to claim 13, wherein the sheath gas supply passage is connected and connected at a position on a line where the central axis of the sheath gas does not intersect with the central axis of the plasma torch body.