JPH1187095A - Inductively coupled plasma device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make transmitting of a plasma flame possible to a processed object in a processing device, which is produced by high frequency inductively coupled, without generating a fouling in the device and efficiently. SOLUTION: In combustion processing applying irradiation of plasma flame 12, obtained by introducing plasma gas from a gas introducing part 4 on the inside of a discharge lamp 1 and flowing a high frequency current in a high frequency induction coil 2, to a processed object 20 consisting of powder graphite held as a fluidic layer by introducing oxygen to a diffusion chamber 16 of a furnace vessel 14 straitened by a straightening plate 15 to be made to flow upward, in an end part on the downstream of plasma gas of the discharge lamp 1, a plasma transport pipe 21 guiding plasma gas to the processed object 20 to consist of heat resistance material is incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an inductively coupled plasma apparatus which generates arc plasma using high frequency inductive coupling and supplies the generated arc plasma to a plasma processing apparatus for performing processing such as incineration and melting.

[0002]

2. Description of the Related Art An inductively coupled plasma apparatus is an apparatus in which a high-frequency induction coil is wound coaxially around a discharge tube, and a high-frequency current is applied to the high-frequency induction coil to convert the gas introduced into the discharge tube into plasma. FIG. 6 is a basic configuration diagram of a conventionally used inductively coupled plasma device. In FIG. 6, reference numeral 1 denotes a cylindrical discharge tube, which is usually formed using quartz which is an electrically insulating and heat-resistant material. As shown in the figure, the discharge tube 1 has a double tube structure of an inner tube 1a and an outer tube 1b. used. Reference numeral 2 denotes a high-frequency induction coil wound coaxially around the discharge tube 1 and is usually wound three to four turns.
Reference numeral 3 denotes a high-frequency power supply. At one end of the discharge tube 1,
A gas inlet 4 having a nozzle for blowing gas in the circumferential direction of the discharge tube 1 and a nozzle for blowing gas in the radial direction of the discharge tube 1 is provided, and a ground electrode 5 is further provided. The ground electrode 5 is of a water-cooled type, not shown, and is grounded to the earth side and capacitively coupled to the high-frequency induction coil 2.

In this configuration, first, as an ignition gas,
Helium gas supplied from a helium gas supply source 8 through a gas supply pipe 6 is introduced into the discharge tube 1 through a gas inlet 4 provided at the upper end, and an output voltage of a high frequency power supply 3 is applied to the high frequency induction coil 2. I do. The helium gas introduced into the discharge tube 1 is discharged by a capacitive coupling electric field formed between the high-frequency induction coil 2 and the ground electrode 5. In the discharge state, for example, an argon gas is introduced from the argon gas supply source 9 to maintain the discharge, subsequently, the introduction of the helium gas is stopped, and the concentration of the argon gas in the discharge tube 1 is increased to shift to arc plasma. . Thereafter, energy is supplied to the plasma by a high-frequency induction electric field generated by the high-frequency induction coil 2. This plasma is generally called an inductively coupled plasma. The resulting plasma depends on the strength and shape of the electric field and the gas flow.

[0004] Since the generated plasma is in a high temperature state of about 10,000 K, rapid thermal expansion occurs, and is ejected to the outside of the discharge tube 1 in a state generally called a plasma frame 12 (plasma flame). Spouting plasma frame 1
The length of 2 and the amount of heat involved depend on the temperature and the gas species. By using the plasma frame 12 that gushes out,
Particularly high-temperature heat treatment such as incineration and melting can be performed.

[0005]

As a method for using high-frequency inductively coupled plasma as a heat source for incineration / melting treatment, a method of introducing a plasma flame ejected from an inductively coupled plasma apparatus into a furnace of a processing apparatus and treating the object to be processed is described below. Is the most common method. The temperature of the plasma generated in the discharge tube of the inductively coupled plasma device is highest in the region where the high-frequency induction coil is wound, and the temperature of the plasma proceeds downstream from the region where the high-frequency induction coil is wound. descend. In particular, when a long discharge tube is used on the downstream side, the heat conduction loss to the discharge tube wall cooled for thermal protection increases, so that the temperature of the plasma drops rapidly. Further, even after the plasma is ejected from the discharge tube into the furnace of the plasma processing apparatus, the plasma gas is cooled by contact with the low-temperature atmosphere gas in the furnace, so that the plasma temperature further decreases. Therefore, in order to keep the temperature of the plasma gas high, it is desirable that the distance between the inductively coupled plasma apparatus for generating plasma and the object to be processed is set as small as possible.

However, when the inductively coupled plasma apparatus and the object to be treated are arranged in such a manner as to be close to each other, the discharge tube is contaminated by the scattering of the molten material to be treated and fly ash, and the electric insulation performance of the discharge tube is deteriorated. As a result, the induction electric field is shielded, the power is not absorbed by the plasma, and the discharge tube generates heat due to the induction heating, which may cause thermal stress destruction. When the plasma device is brought closer to the object,
Since heat is absorbed by radiation and heat transfer from the object to be processed, which has a high temperature of 1000 ° C. or more, if the distance is too close, the heat loss will increase and the efficiency will decrease. further,
If the distance between the inductively coupled plasma device and the object to be processed is limited, the degree of freedom in designing the plasma processing device is reduced, and for example, it is difficult to design the supply port of the object to be processed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to efficiently remove the heat of the plasma frame generated by the high-frequency inductive coupling from the plasma processing apparatus without causing contamination of the apparatus. An object of the present invention is to provide an inductively coupled plasma device capable of transmitting an object to an object.

[0008]

In order to achieve the above object, according to the present invention, there is provided a cylindrical discharge tube made of an electrically insulating and heat-resistant material cooled by a refrigerant, and a discharge tube wound around the discharge tube. It has a high-frequency induction coil and a plurality of gas inlets arranged at one end of the discharge tube, gas is introduced from the gas inlet into the discharge tube, a high-frequency current flows through the high-frequency induction coil, and the gas is turned into plasma. In an inductively coupled plasma apparatus for supplying the generated plasma gas to a plasma processing apparatus for processing an object to be processed using the plasma gas, (1) the discharge tube has an end on the downstream side of the plasma gas,
Guide the plasma gas to the object to be processed in the plasma processing apparatus,
A plasma transport tube made of a heat-resistant material is provided.

(2) In the inductively coupled plasma apparatus of the above (1), the diameter of the plasma transport tube is formed so as to decrease toward the downstream side of the plasma gas. Alternatively, it is formed so as to increase as it goes downstream of the plasma gas. (3) In the inductively-coupled plasma device of (1) or (2), the plasma transport tube is formed integrally with the discharge tube.

According to the above configuration (1), a high-frequency induction coil is wound, and a plasma transport pipe is arranged downstream of a region where plasma is generated.
The generated plasma is guided to the object through the inside of the plasma transport tube. Since the plasma transport tube is formed of a heat-resistant material and has no cooling means such as a discharge tube, the loss due to heat conduction of the plasma to the plasma transport tube is smaller than the loss due to heat conduction to the discharge tube. It will be greatly reduced. Furthermore, since the outlet of the plasma transport pipe is arranged close to the object to be processed, the heat generated by convection to the low-temperature atmosphere gas in the furnace is lower than in the case where the plasma flame is directly blown into the furnace of the plasma processing apparatus. The amount of transmission is also greatly reduced, and the plasma frame is irradiated onto the object to be processed while significantly suppressing heat loss. In addition, if the inductively coupled plasma apparatus of this method is used, the plasma is efficiently transported by the plasma transport pipe, and the plasma processing is performed by disposing the workpiece at a remote position where the plasma frame could not reach with the conventional apparatus. The apparatus can be configured, and can be applied to various plasma processing apparatuses. Furthermore, with this configuration, the distance between the discharge tube and the object to be processed is separated by the plasma transport tube, so that the discharge tube is prevented from being stained by scattering of the molten material to be processed and fly ash as conventionally seen, The deterioration of characteristics is suppressed.

Further, as described in (2) above, if the diameter of the plasma transport tube is formed so as to become smaller toward the downstream side of the plasma gas, the plasma frame is transported with a reduced diameter, so that the heat density is reduced. Plasma can be applied to the object to be processed. Further, if the diameter of the plasma transport tube is formed so as to increase toward the downstream side of the plasma gas, the plasma frame expands toward the outlet side, so that a plasma having a large irradiation area can be irradiated to the workpiece. .

The discharge tube provided with the cooling means is made of an electrically insulating and heat-resistant material, while the plasma transport tube is required to be a heat-resistant material. Therefore, as described in (3) above, even if the plasma transport tube is integrally formed using the same material as the discharge tube, and the plasma transport tube is not provided with a cooling means, the predetermined plasma frame can be used in the plasma apparatus. Is irradiated to the object to be processed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> FIG. 1 is a longitudinal sectional view showing a basic configuration of a first embodiment of a plasma processing apparatus incorporating an inductively coupled plasma apparatus according to the present invention. This plasma processing apparatus is an apparatus for performing incineration of graphite waste using inductively coupled plasma, and is a combination of a fluidized bed furnace and an inductively coupled plasma apparatus.

In FIG. 1, a furnace vessel 14 of a fluidized bed furnace having a vertically arranged central axis is constructed by mounting a refractory brick on the inner surface of a metal cylinder provided with a water cooling mechanism (not shown).
Inside the furnace vessel 14, there is provided a flow straightening plate 15 made of alumina foam, which straightens the flow of oxygen gas which plays two roles of fluidizing gas and combustion gas. On the upper part of the furnace container 14, the processing target 2 made of waste granular graphite is provided.
0, which supplies 0 to the rectifying plate 15,
A gas exhaust port 19 for exhausting exhaust gas is provided. A diffusion chamber having a gas supply port 18 for introducing oxygen gas is formed below the current plate 15 of the furnace vessel 14, and a discharge tube made of an electrically insulating and heat-resistant quartz material is further formed below the diffusion chamber. 1, an inductively-coupled plasma apparatus including a high-frequency induction coil 2 wound around a discharge tube 1 and a gas introduction unit 4 for introducing a plasma-generating gas into the discharge tube 1 is provided. In particular, in this embodiment, a plasma transport tube 21 made of a heat-resistant material, alumina, is incorporated at the downstream end of the plasma gas of the discharge tube 1 of the inductively coupled plasma device. The outlet is opened to the rectifying plate 15 on which the workpiece 20 is mounted.

In this configuration, the oxygen gas introduced from the gas supply port 18 into the diffusion chamber 16 is rectified by the rectifying plate 15 and flows upward, so that the processing object mounted on the rectifying plate 15 is processed. (Granular graphite) 20 is subjected to buoyancy to form a fluidized bed of granular graphite in balance with its own weight, and the fluidized bed is irradiated with a high-temperature plasma gas from an inductively coupled plasma apparatus to maintain a processing temperature at a predetermined temperature. By controlling the combustion reaction of granular graphite, incineration of graphite waste is performed.

FIG. 2 shows the temperature of the portion of the rectifying plate 15 corresponding to the graphite burning section under the two conditions of the inductively coupled plasma apparatus shown in FIG. FIG. 4 is a characteristic diagram showing the results of measuring and comparing. The horizontal axis in FIG. 2 is the flow rate of oxygen that plays the role of graphite fluidizing gas and combustion gas, and the flow rate of argon plasma gas is 90 (Nl / min). As shown by the white circles in the figure, when the plasma transport tube 21 is not incorporated, it can be seen that the temperature of the rectifying plate 15 decreases as the oxygen flow rate increases. This measurement result is obtained from the gas supply port 18.
This indicates that forced convection occurs inside the diffusion chamber 16 with an increase in the oxygen gas introduced, and the plasma frame 12 is cooled and its temperature is reduced. The heat generated does not contribute to the incineration of graphite, and eventually reaches the diffusion chamber 16.
Will be absorbed by the wall. According to the measurement results, when the flow rate of oxygen is 300 (Nl / min), the temperature of the rectifying plate section has dropped to 200 ° C, and it is impossible to burn graphite. On the other hand, as shown by the black circles in the figure, when the plasma transport tube 21 is incorporated, even if the flow rate of oxygen is increased, the temperature of the rectifying plate portion hardly decreases and is maintained at a high temperature. This is because the convection between the plasma frame and the oxygen gas is prevented by the plasma transport pipe 21 and
This indicates that the calorific value of the plasma flame is maintained up to around 5, and it can be seen that the incorporation of the plasma transport tube 21 can effectively contribute to the combustion of graphite without impairing the heat content of the plasma flame.

<Embodiment 2> FIG. 3 is a longitudinal sectional view showing a basic configuration of a second embodiment of a plasma processing apparatus incorporating the inductively coupled plasma apparatus of the present invention. The present plasma processing apparatus is an example of a melting apparatus using inductively coupled plasma, and is a configuration diagram of an apparatus that performs a melting process of incinerated ash using a melting furnace.

In FIG. 3, a furnace vessel 14A of a melting furnace body in which incinerated ash as an object to be treated 20A is melted,
The furnace container 14A is formed of a heat-insulating refractory. The furnace container 14A has a workpiece supply port 17A for introducing incinerated ash, a molten metal outlet 22 for allowing molten incinerated ash to flow out, and exhaust gas. A gas exhaust port 19A for exhaust is provided. Further, an inductively coupled plasma device including a discharge tube 1, a high frequency induction coil 2, and a gas introduction unit 4 made of quartz material is incorporated in the upper part of the furnace container 14A. A plasma transport tube 21A made of alumina is incorporated at the downstream end of the plasma gas of the discharge tube 1 of the plasma apparatus, and the opening at the tip is treated with the workpiece 20.
It is characterized in that it is arranged close to A.

In this configuration, the incinerated ash to be treated is supplied from the workpiece supply port 17A into the furnace vessel 14A, and is melted by the heat of the plasma frame 12A ejected from the upper inductively coupled plasma apparatus. You. The obtained melt is allowed to overflow from the melt tapping port 22 and is taken out, so that the object 20A inside the furnace container 14A is removed.
Is kept constant, and the incineration ash is continuously melted. In this configuration, since the plasma transport tube 21A is incorporated at the downstream end of the plasma gas of the discharge tube 1, similarly to the plasma transport duct 21 shown in the first embodiment, the plasma frame is composed of the furnace container 14A. Is guided to the processing object 20 without being affected by the atmosphere gas inside, the melting processing of the processing object is performed efficiently without causing a decrease in the calorific value of the plasma flame.

<Embodiment 3> FIG. 4 is a longitudinal sectional view showing a basic configuration of a third embodiment of a plasma processing apparatus incorporating the inductively coupled plasma apparatus of the present invention. This plasma processing apparatus is an example of a melting apparatus using inductively coupled plasma. The difference from the second embodiment shown in FIG. 3 lies in the plasma transport tubes 21A and 21B incorporated at the lower end of the discharge tube 1. In the second embodiment, the plasma transport pipe 21A is formed of a straight pipe having the same inner diameter, whereas the plasma transport pipe 21B of the third embodiment shown in FIG. It is characterized in that it is formed so as to become smaller as it goes. If the plasma transport tube 21B having this configuration is used, the plasma frame 12 generated by the inductively coupled plasma
B has a smaller diameter at the outlet portion, and is irradiated to the processing object 20B as plasma having a large heat density. Therefore, the melting device incorporating the inductively coupled plasma device of the present configuration is particularly advantageous when melting a high melting point material or the like.

<Embodiment 4> FIG. 5 is a longitudinal sectional view showing a basic configuration of a fourth embodiment of a plasma processing apparatus incorporating an inductively coupled plasma apparatus according to the present invention. This is an example, and is different from the second embodiment and the third embodiment in that the inner diameter of the plasma transport tube 21C installed at the lower end of the discharge tube 1 is increased as going to the outlet side. It is in. In this configuration, the plasma frame 12C generated by the inductively coupled plasma apparatus spreads on the outlet side and is irradiated onto a large area of the processing target 20C, so that the processing target having a large area is uniformly heated and processed. This is particularly advantageous if you want to.

In each of the first to fourth embodiments, the plasma transport tube made of alumina is provided in any of the embodiments. However, the material to be used is not limited to alumina. A heat-resistant ceramic material such as quartz or a high-melting metal material such as tungsten or molybdenum may be used as long as it is a heat-resistant material suitable for the atmosphere of the processing apparatus.

In the case where the plasma transport tube is formed using quartz, a discharge tube for generating a plasma flame is provided;
A plasma transport tube for transporting the generated plasma frame may be integrally formed. In this case, a cooling unit is provided in a part that functions as a discharge tube, but a part that functions as a plasma transport tube is configured without a cooling unit in order to suppress heat loss.

[0024]

As described above, according to the present invention, a cylindrical discharge tube made of an electrically insulating and heat-resistant material cooled by a refrigerant, a high-frequency induction coil wound around the discharge tube,
It has a plurality of gas inlets arranged at one end of the discharge tube, gas is introduced from the gas inlet into the discharge tube, a high-frequency current flows through a high-frequency induction coil, and the gas is turned into plasma.
In an inductively coupled plasma apparatus for supplying the generated plasma gas to a plasma processing apparatus for processing an object to be processed using the plasma gas, (1) the discharge tube has an end on the downstream side of the plasma gas,
Guide the plasma gas to the object to be processed in the plasma processing apparatus,
A plasma transport tube made of a heat-resistant material, for example, a heat-resistant ceramic material such as alumina or quartz, or a high-melting-point metal material such as tungsten or molybdenum is provided. And the plasma flame generated by the discharge tube can be irradiated to the object to be processed almost without being influenced by ambient conditions. The inductively-coupled plasma device capable of efficiently transferring the heat quantity to the object without causing contamination of the device is obtained.

(2) Further, in the inductively coupled plasma apparatus of the above (1), if the diameter of the plasma transport tube is formed so as to become smaller toward the downstream side of the plasma gas, a material having a high melting point or the like can be obtained. In particular, an inductively-coupled plasma apparatus that can efficiently transmit plasma having a high heat density to the object to be processed is obtained.

(3) Alternatively, if the plasma gas is formed so as to become larger toward the downstream side of the plasma gas, it is particularly effective for uniform heating of a large-area workpiece.
As a result, an inductively-coupled plasma device capable of efficiently transmitting a large-area uniform plasma to an object to be processed is obtained. (4) In the inductively-coupled plasma apparatus of (1), (2) or (3), if the plasma transport tube is formed integrally with the discharge tube, reliability can be improved by a single material. Therefore, it is suitable as an inductively coupled plasma apparatus capable of efficiently transmitting plasma to an object to be processed in a plasma processing apparatus having a high degree of freedom in design, since it can be formed in a low-cost and low-cost configuration.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a basic configuration of a first embodiment of a plasma processing apparatus incorporating an inductively coupled plasma apparatus of the present invention.

FIG. 2 is a characteristic diagram showing an effect of the plasma transport tube incorporated in the plasma processing apparatus of the first embodiment.

FIG. 3 is a longitudinal sectional view showing a basic configuration of a second embodiment of the plasma processing apparatus incorporating the inductively coupled plasma apparatus of the present invention.

FIG. 4 is a longitudinal sectional view showing a basic configuration of a third embodiment of the plasma processing apparatus incorporating the inductively coupled plasma apparatus of the present invention.

FIG. 5 is a longitudinal sectional view showing a basic configuration of a third embodiment of the plasma processing apparatus incorporating the inductively coupled plasma apparatus of the present invention.

FIG. 6 is a basic configuration diagram of a conventionally used inductively coupled plasma device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge tube 2 High frequency induction coil 4 Gas introduction part 12, 12A Plasma frame 12B, 12C Plasma frame 13 Plasma outlet 14, 14A Furnace container 15 Rectifier plate 16 Diffusion chamber 17, 17A Workpiece supply port 18 Gas supply port 19, 19A Gas exhaust port 20, 20A Workpiece 20B, 20C Workpiece 21, 21A Plasma transport duct 21B, 21C Plasma transport duct 22 Melt tapping port

Claims (5)

[Claims] 1. A cylindrical discharge tube made of an electrically insulating and heat-resistant material cooled by a refrigerant, a high-frequency induction coil wound around the discharge tube, and a plurality of gas introduction tubes disposed at one end of the discharge tube. A gas is introduced from the gas inlet into the discharge tube, a high-frequency current is passed through the high-frequency induction coil to convert the gas into plasma, and the generated plasma gas is processed using the plasma gas. In the inductively coupled plasma device to be supplied to the plasma processing apparatus, a plasma transport pipe made of a heat-resistant material, which guides the plasma gas to an object to be processed of the plasma processing apparatus, is provided at a downstream end of the plasma gas of the discharge tube. An inductively coupled plasma device, comprising: 2. The inductively coupled plasma apparatus according to claim 1, wherein the diameter of the plasma transport tube is formed so as to decrease toward the downstream side of the plasma gas. . 3. The inductively coupled plasma apparatus according to claim 1, wherein the diameter of the plasma transport tube is formed to increase toward the downstream side of the plasma gas. . 4. The inductively coupled plasma apparatus according to claim 1, wherein the heat-resistant material forming the plasma transport tube is a heat-resistant ceramic material such as alumina or quartz, or a high melting point metal such as tungsten or molybdenum. An inductively coupled plasma device characterized by being a material. 5. The inductively coupled plasma device according to claim 1, wherein said plasma transport tube is formed integrally with a discharge tube.