JPH0263549A - Process and apparatus for plasma reaction - Google Patents

Abstract

PURPOSE:To maintain high frequency induction plasma stably by irradiating a mixture of a reactant with plasma gas with laser light to excite and heat the reactant, then introducing the reactant into a top zone of the high frequency induction plasma. CONSTITUTION:A head part 1 of a plasma torch is arranged to above a plasma torch part 3 having a high frequency work coil 5 on the external periphery interposing thereby a part 2 to be irradiated with laser light, and a tip end of an introducing pipe 12 for the plasma gas and the reactant is arranged to the part 2 to be irradiated with laser light. The mixture of the reactant and the plasma gas is irradiated with laser light to excite and heat the reactant, then the product is introduced to a top zone of high frequency induction plasma. By this process, clean thermal plasma can be obtd., moreover, the plasma can be maintained stably and heating of a reactant to extremely high temp. has becomed possible.

Description

[Detailed Description of the Invention] [Field of Application] The present invention generates plasma stably by exciting and heating a reactant with a laser and introducing it into high-frequency induced plasma. The present invention relates to a plasma reaction method and apparatus that efficiently generate a reaction.

[Conventional technology and its problems]

In thermal plasma, not only the electrons but also the heavy particles have a high temperature.
The plasma is in thermal equilibrium, with a temperature of 5X103 to 2X
This is possible when the pressure is high (more than 0.5 atmospheres) and 10"K<. Therefore, the energy density of plasma is large and the material to be heated can be heated to high temperature in a short time. Take advantage of it.

It is used as a heat source for so-called high-temperature processing, such as chemical reactions that proceed only at high temperatures, and melting and refining of high-melting-point substances, and various uses are being investigated.

There are two ways to generate thermal plasma: arc discharge and high-frequency induction. In the arc discharge method, a cathode is applied to cause dielectric breakdown, and the gas is heated by induction. In the former,
Plasma with high kinetic energy can be obtained using an inexpensive power source,
Plasma can be easily obtained, but the electrodes (tungsten, carbon, etc.) may evaporate due to heat and mix into the DC plasma, contaminating the plasma. Furthermore, when reactants are injected together with the plasma gas, if these gases are corrosive, the electrodes will be corroded and mixed into the DC plasma. Therefore, clean plasma cannot be obtained. On the other hand, in the latter case, although the plasma density is lower than that of DC plasma generated by arc discharge, since it is electrodeless, clean plasma can be obtained and it is suitable for obtaining high-purity products. Furthermore, in the case of direct current plasma, the anode section is generally used as a nozzle and the plasma is blown out from there as a so-called plasma jet.
The ejection speed of the plasma is said to be supersonic. Therefore, it is said that there is a limit to the use of DC plasma when a certain amount of reaction time is required to control the reaction history and chemical reaction kinetics. On the other hand, in high-frequency induced plasma (R, F, plasma), the plasma gas flow rate is slower than in direct current plasma (z30+++/s), and a complete chemical reaction is expected within the plasma, making it possible to control the reaction history. However, since it is electrodeless, it is very sensitive to external disturbances, and the amount of reactants introduced is considerably limited, and if the supply rate exceeds a certain amount, the plasma quickly becomes unstable and disappears. .

Therefore, in order to maintain the reaction without impairing the stability of the plasma, it is necessary to prevent the temperature of the plasma from dropping rapidly and to prevent the flow of the plasma from being extremely disturbed.

Various attempts have been made to maintain the R, F, and plasma described above stably and use them as plasma reactors.

It is known that a vortex is generated at the top of the plasma due to magnetic pressure effects caused by R, F, electric and magnetic fields in the plasma, and research to date has shown that this vortex is deeply involved in the stability of the plasma. is revealed in. A torch that can inject a reactant without preventing the vortex flow above the plasma has been proposed. This torch can be roughly classified into the following three types.

The first torch is a torch that can inject a reactant from the tail flame part of the plasma or the work coil part without disturbing the upper plasma vortex. In this torch, the instability of the plasma due to injection is eliminated, but the temperature inside the plasma decreases due to the injection of the reactant.

Therefore, it cannot be said that the extremely high temperature of plasma is fully utilized. Rather than injecting into the plasma tail flame area.

Injecting from the gap between the work coils involves injecting into the sides of the plasma, which makes more efficient use of heat, but makes the structure of the torch more complicated.

In any case, since the injection is not from above the plasma, it cannot be said that ultra-high humidity is effectively utilized.

If a reactant is injected from the top of the plasma, the second torch will disturb the vortex, making the plasma unstable and extinguishing it. However, if energy is constantly supplied even after the plasma has disappeared, the second torch will ignite immediately. This method was developed based on the idea that plasma can be maintained even if the vortex is disturbed to some extent, and uses R, F, and a DC plasma jet placed above the plasma as energy supply sources. In this method, energy is supplied to the reactant and plasma gas by injecting the reactant into a DC plasma jet, and the DC plasma jet is ejected in the axial direction of the RoF plasma. As a result of our study, we found that in this method, the ejection direction of the DC plasma jet exactly matches the axial direction of R, F, and plasma, so the vortex is not disturbed (no vortex is generated on the central axis of R, F, and plasma. ). However, as mentioned above, in direct current plasma, the electrodes evaporate or corrode due to heat and mix into the thermal plasma, making it impossible to obtain clean thermal plasma and resulting in impurities being mixed into the reaction products. . Therefore, a product of high purity! It is not possible to make 32.

The third torch uses an RoF plasma torch instead of the DC plasma jet used in the second torch. In this method, R, F for energy supply
, the axis of the plasma torch and the axis of the R, F, plasma torch below it are on the same line.

The R, F, and plasma torches for energy supply have smaller plasma outputs than the R, F, and plasma torches located below them. This method does not use direct current plasma like the second torch, so clean plasma can be obtained.However, when the 5 reactants are injected from the top of the energy supply plasma torch, the vortex is disturbed and the plasma is extinguished. This also disturbs the R, F, and plasma vortices below it, extinguishing the plasma as well. Therefore, as a method of injecting the reactant, it is not possible to inject the reactant in the axial direction from above the plasma, so the extremely high temperature of the plasma is not fully utilized, and an efficient reaction cannot be expected.

R, F, and plasma are clean plasmas and are considered to be an excellent means for producing highly pure products, but a means for stably maintaining plasma and utilizing ultrahigh temperatures has not yet been found.

[Problem of invention]

An object of the present invention is to provide a plasma reaction method and apparatus that maintain R, F, and plasma stably and effectively utilize their ultrahigh temperatures.

[Means to solve the problem]

The inventors of the present invention, as a result of extensive research to solve these problems, have discovered a method in which a mixture of reactants and plasma gas is excited by laser light and then introduced into the upper part of the R, F, and frame ring plasmas. By doing this, clean plasma can be obtained.1. They also discovered that plasma can be maintained stably and ultra-high temperatures can be utilized, and based on this knowledge they have completed the present invention.

That is, the method of the present invention includes a step of irradiating R, F, and a reactant to be injected into the plasma with laser light to excite and heat it;
. (referred to as plasma laser reaction method and apparatus)
. The laser beam irradiation area is on the upper side of the R, F and plasma. The reactants are directed directly above the laser beam path. The reactant excited by the laser beam irradiation is injected into the center (in the axial direction) of the thermal plasma generated directly below the laser beam irradiation area, contacts the ultra-high temperature of R, F, and plasma, and is heated. Ru. Laser light does not contain impurities and can be excited and heated in a clean state, and uses clean plasma such as R, F, and plasma for heating, so it is suitable for manufacturing high-purity products. There is.

In the reaction to synthesize ceramic powders of Si and N, each of the reactants has 5i-H, C-H, and N-H, so C
A CO2 laser is preferably used because it efficiently absorbs O, laser light (wavelength 10,591.m). In addition, when using solid particles as a reactant, CO2 laser or Nd
: The reactant can be excited and heated by using a YAG laser (wavelength: 1.06 μm) or the like. In addition, various lasers (excimer laser, dye laser, etc.) can be used depending on the reactant. Directly below the laser irradiation area, there is a RoF plasma excited and induced by a work coil, and a reactant excited and heated by the laser beam is injected in the axial direction of this center to increase the stability of the R, F, and plasma. Utilizes ultra-high temperature to efficiently complete 9 reactions.

When producing a product from two or more reactants.

That is, in the case of A+B-DC (reactants A, B, product C), only one reactant A is irradiated with a laser, and the other reactant B is injected into R, F, and the tail flame of the plasma, and the reaction begins. It is also possible to obtain the reaction product C.

Next, the apparatus of the present invention will be described with reference to the accompanying drawings. In FIG. 1, the entire hybrid plasma laser reaction apparatus of the present invention includes a plasma torch head section 1, a laser irradiation section 2, R, F, a plasma torch section 3, It consists of a laser oscillation section 4 and a high frequency power supply section (not shown) connected to a work coil 5. The laser irradiation section 2, R, F, and plasma torch section 3 are made of double tubes made of heat-resistant and electrically insulating materials such as quartz glass and silicon nitride. In the outer tube 6, the laser beam inlet and outlet of the laser irradiation part are
Windows 7 and 8 through which the laser beam passes are provided (for example, KCQ or Zn5e for a CO□ laser, or silica glass for a YAG laser). The inner tube 9 is installed between the plasma torch head 1 and above the work coil 5, and a sheath gas 10 flows between the outer tube and the inner tube. This sheath gas uses the same gas as the plasma gas,
It flows in a spiral along the inner wall of the outer tube, protecting the outer tube from the heat of the thermal plasma, and creating an appropriate vortex to maintain the plasma stably.It is located between the inner tube and the outer tube. 4 to 6 provided on the plasma torch head to
It is fed through the hole 11 at the location.

At the center of the plasma torch head section 1, an introduction tube 12 for injecting plasma gas and reactants is installed, and next to it is a tungsten rod (or carbon rod) 1 for plasma ignition.
3 is placed, and can be pushed into the center of the work coil 5 during ignition, and can be pulled up after ignition. A cooling water pipe 14 is wound around the outer circumferential side of the upper end of the head portion l.

In the laser beam irradiation section 2, a laser oscillation device is placed outside a window 7, and the laser beam oscillated by the laser oscillation section 4 is narrowed down to an appropriate beam diameter by a lens 20, passes through the window 7, and is emitted by a plasma torch. The reactant injected from the tube 12 installed in the center of the head is irradiated. FIG. 2 shows a lateral sectional view of this laser irradiation section. A cooling gas introduction pipe 23 is provided so that cooling gas such as argon gas can be blown into the inside of the windows to protect the windows 7 and 8 from heat. The laser light that is not absorbed by the reactant exits through the window 8 on the exit side and is absorbed by the beam stopper 21. The mixture of reactants and plasma gas excited and heated by the laser beam generates a laser flame from the tip of the introduction tube 12, and is guided precisely to the axial center of the thermal plasma.

The reactants are then heated with plasma gas and converted to products.

In the R, F, plasma torch section 3, a work coil 5 is wound around the outside of an outer tube 6, and this work coil is connected to a high frequency power source. Plasma ignition involves first flowing plasma gas, inserting the tungsten rod in the torch head into the center of the work coil, turning on the power, and heating the tungsten rod using induction heating to generate plasma. After plasma ignition, pull up the tungsten rod. In addition, some of the reactants can be injected into the tail flame of the generated thermal plasma.
It is also possible to provide an injection tube 22 in the outer tube wall.

(Effect of the invention) In the present invention, 1. By injecting a reactant excited and heated by laser light into the upper part of the R, F, plasma, it is possible to obtain a clean thermal plasma, and
It becomes possible to maintain a stable plasma and heat reactants to extremely high temperatures. and.

The product obtained in the present invention is of high purity and does not contain impurities.

[Brief explanation of the drawing]

FIG. 1 is a detailed sectional view of the present invention. FIG. 2 is a lateral cross-sectional view of the laser irradiation section. 1... Plasma torch head section, 2... Laser irradiation section. 3...R, F, plasma torch section, 4...laser oscillation section, 5...work coil, 6...outer tube, 7,8...
...Window, 9...Inner pipe, 12...Pipe for introducing a mixture of plasma gas and reactant. Patent applicant: Kozo Iizuka, Director of the Agency of Industrial Science and Technology; Designated representative: Director of Hokkaido Industrial Development Testing Institute, Agency of Industrial Science and Technology; Fujitabe Gofuji

Claims (2)

[Claims] (1) A plasma reaction method characterized in that a mixture of a reactant and a plasma gas is irradiated with a laser beam to excite and heat the reactant, and then introduced into the upper part of a high-frequency induced plasma. (2) A plasma torch head section is disposed above the plasma torch section which has a high-frequency work coil on its outer periphery through a laser irradiation section, and the tip of a mixture introduction tube of plasma gas and reactant is connected to the laser irradiation section. A high-frequency induced plasma reaction device characterized by having a structure in which