JP2001149771A - Microwave plasma device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave plasma device. SOLUTION: The microwave plasma device 10 having a reaction vessel 14 to house plasma 16 has a sensor 20 as a means to confirm that the plasma 16 is existed in the reaction vessel 14, so that the elimination of the plasma in the vessel is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microwave plasma device.

[0002]

2. Description of the Related Art Microwave-generated plasma is used not only for synthesizing new materials and surface engineering, but also for degreasing and cleaning in various industries such as machinery, electronics, and cleaning. Treatment of organic halogenated substances such as trichlorethylene, 1,1,1-trichloroethane, tetrachloroethylene, carbon tetrachloride, 1,1,2-trichloroethane and 1,2-dichloroethane, and product coating plants and solvent handling facilities ,
It is also used for detoxifying volatile organic substances in exhaust gas discharged from printing plants, automobile painting plants, gas stations, and the like.

Conventionally, a microwave plasma apparatus for generating plasma by microwaves has been known as one used for such an application. For example, Table 10-
No. 5,030,049 discloses a container for storing a plasma in which the plasma is confined within a certain volume so that once generated plasma does not dissipate, and means for radiating microwave energy to the container to generate plasma therein. A microwave plasma apparatus, comprising: means for generating the plasma; and output adjusting means for adjusting an output level of microwave energy to maintain the once generated plasma. I have.

In the microwave plasma apparatus as described above, it is necessary to apply energy to the plasma in order to maintain the plasma once generated, and the energy for maintaining the plasma is provided by the microwave.
In other words, increasing the microwave output increases the size of the plasma, decreasing the microwave output decreases the plasma, and decreasing the output further reduces the energy given by the microwave, causing the plasma to disappear. Resulting in. For this reason, in order to maintain the plasma, it is necessary to continuously irradiate a microwave having a certain output or more. From the viewpoint of maintaining this plasma,
The microwave irradiation is desirably continuous, but the irradiation can be performed in a pulse-like cycle as long as the off portion is not too long.

[0005]

Here, in order to operate the microwave plasma apparatus so as to maintain the plasma while reducing the energy input for generating the microwave, the output of the microwave is reduced as much as possible. It is preferable that the pulsed microwave energy is used.However, in such an operation, the plasma disappears compared to the case where the operation is performed by irradiating more microwaves than necessary. It's easy to do. If the plasma disappears in a case where volatile organic substances in the exhaust gas are being decomposed, a problem arises that the exhaust gas is released as it is and causes environmental pollution. Therefore, when the plasma disappears, it must be immediately reignited to generate the plasma. However, the above-described conventional microwave plasma apparatus has a configuration in which plasma is generated in the container of the apparatus, and thus has a problem in that the disappearance of plasma from outside cannot be detected. In addition, for example, there is a method of installing a volatile organic substance detection device after the microwave plasma device and indirectly knowing the disappearance of plasma by the detection device, but in this case, there is a problem that a time lag occurs until detection. there were.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a microwave plasma apparatus capable of maintaining plasma economically and efficiently. It is an object of the invention according to claim 2 to provide a microwave plasma device capable of maintaining plasma more economically and efficiently.

[0007]

According to a first aspect of the present invention, there is provided a microwave plasma apparatus having a reaction vessel containing a plasma, and having a means for confirming that plasma is present in the reaction vessel. A microwave plasma device is provided. According to a second aspect of the present invention, there is provided the microwave plasma apparatus according to the first aspect, wherein the means for confirming that plasma is present in the reaction vessel is an optical sensor, a UV sensor, or a temperature sensor. A microwave plasma device is provided.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a microwave plasma apparatus according to an embodiment of the present invention, which will be described below. The microwave plasma device 10 of FIG. 1 has a microwave source 11, which is connected to a microwave cavity 13 by a waveguide 12, and a container 14 is provided in the microwave cavity 13. When the microwave source 11 is switched on, a microwave field is generated in the microwave cavity 13, and a microwave field is also generated in the container 14 installed therein. The container 14 is provided with a gas inlet 17, and a gas containing a volatile organic substance is introduced into the container 14 through the gas inlet 17 and becomes a fuel of the plasma 16. The microwave power normally required to generate the plasma 16 is between 0.3 and 5 kW.

As shown in FIG. 1, the container 14 is preferably substantially spherical, but may have any shape as long as it can generate and maintain plasma. Also,
In FIG. 1, the container 14 is disposed in the microwave cavity 13, but the wall itself of the microwave cavity 13 is
4 can be configured. Container 1
In view of the high temperature of the plasma 16 in the container 4, the container wall is made of a heat-resistant material such as quartz.

[0010] The container 14 is also provided with an ignition port 18, and an electrode 19 is inserted through the ignition port 18 when generating plasma. The presence of the electrode 19 in the container 14 increases the intensity of the microwave field at a portion adjacent to the tip of the electrode 19, and discharge starts when the intensity of the microwave field in this region becomes sufficiently large. As a result, the gas around the electrode 19 is ionized, and the plasma 16 is formed and floats on the upper part in the container 14. After the plasma 16 is generated in the container 14, the electrode 19 is withdrawn from the container 14. As a result, the electrode 19 is removed from the field of the microwave, and distortion of the microwave is avoided, so that stable plasma 16 is generated. The electrode 19 is an elongated member having a sharp tip, and may be made of a conductive material. In the case of a metal electrode, the metal vaporized by plasma is coated in the container, so that the microwave field is reduced. It is undesired because it interferes. Therefore, from the viewpoint of not affecting the microwave field, carbon fibers are preferable as the electrode material.
The size of the plasma 16 in the container 14 depends on the microwave source 1
1 by changing the output level.
An exhaust port 15 is provided at the lower part of the container 14, and the gas after the volatile organic substance has reacted with the plasma is supplied to the exhaust port 15.
It is exhausted from.

According to another aspect of the invention, the generation of the plasma is achieved by reducing the pressure in the vessel using vacuum means. The pressure in the vessel is reduced until the pressure of the microwave energy is applied to the vessel to achieve a pressure such that the plasma spontaneously occurs. Gradually increase until atmospheric pressure or higher. While gradually increasing the pressure in the vessel, the plasma is forced into the upper region of the vessel and the plasma is maintained by adjusting the power level of the microwave energy.

The microwave plasma apparatus according to the present invention is provided with a means for confirming the presence of plasma. In the embodiment shown in FIG. Is provided with a sensor 20. The sensor 20 detects the plasma 16 in the container 14.
Since the plasma 16 emits visible light, UV, heat, and the like, it may be an optical sensor, a UV sensor, a temperature sensor, or the like that can detect such light.

In the embodiment shown in FIG. 1, the sensor 20 is disposed inside the container 14, but when the container is formed of a material having a light transmitting property such as quartz, an optical sensor,
The UV sensor and the like are arranged outside the container 14, and can detect light passing through the container and UV to confirm the presence or absence of plasma in the container. In another embodiment, a part of the container 14 is provided with a window formed of a light-transmitting material such as quartz,
An optical sensor, a UV sensor, or the like may be arranged outside the window portion of the container 14, and the presence or absence of plasma can be confirmed by detecting light and UV passing through the window. Further, in another embodiment, as shown in FIG.
The container 14 and the wall of the microwave cavity 13 are formed of a light-transmitting material such as quartz, or each has a light-transmitting window, so that the microwave cavity is 13 light sensor outside the wall, U
V sensor is arranged, the container 14 and the microwave cavity 1
The presence or absence of plasma can also be confirmed by detecting light, UV, etc. passing through the wall of No. 3.

As described above, it is also possible to arrange a temperature sensor outside the container 14 and outside the wall of the microwave cavity 13. In these cases, the wall of the container 14 and the wall of the microwave cavity 13 are formed. It does not need to be a light transmissive material. An optical sensor and a UV sensor are preferable because the disappearance of plasma can be detected without a time lag.

The sensor 20 is connected by a line 21 to control means 22. With this configuration, a signal indicating the presence or absence of plasma detected by the sensor 20 is sent to the control unit 22 through the line 21. As the control means 22, for example, a means for generating a plasma again when the plasma is extinguished upon receiving a signal indicating the presence or absence of the plasma can be employed. It becomes possible. Further, the control means 22 may be provided with a means for issuing a warning when no plasma is generated, in addition to the means for generating plasma again. Even so, a quick response to this is possible. Of course, the control means 22 is not limited to this, and various means such as a means for simply issuing a warning when the plasma has disappeared, a means for stopping the supply of the exhaust gas to the microwave plasma device 10, and the like. Can be adopted.

[0016]

As described above, according to the microwave plasma apparatus of the present invention, since the means for confirming that the plasma exists in the reaction vessel is provided, the microwave plasma apparatus can be compared with the conventional microwave plasma apparatus. When plasma is extinguished, re-ignition can be performed immediately, for example, so that quick response can be taken. In addition, since stable operation of the microwave plasma apparatus can be performed while reducing the power to be introduced into the apparatus, the plasma processing efficiency can be improved and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an embodiment of a microwave plasma device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Microwave plasma apparatus 20 Sensor 22 Control means

Claims (2)

[Claims] 1. A microwave plasma apparatus having a reaction vessel containing plasma, comprising: means for confirming that plasma is present in said reaction vessel. 2. The microwave plasma apparatus according to claim 1, wherein the means for confirming that plasma exists in the reaction vessel is an optical sensor, a UV sensor, or a temperature sensor. .